IPAC2015 - List of Keywords (gun)

Paper	Title	Other Keywords	Page
MOPWA029	Investigations of the Space-Charge-Limited Emission in the L-Band E-Xfel Photoinjector at Desy-Pitz	simulation, space-charge, cathode, electron	162
	Y. Chen, H. De Gersem, E. Gjonaj, A.V. Tsakanian, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany C. Hernandez-Garcia JLab, Newport News, Virginia, USA M. Krasilnikov, F. Stephan DESY Zeuthen, Zeuthen, Germany
	Funding: work supported by DESY Hamburg and Zeuthen Sites This paper discusses the numerical modelling of electron bunch emission for an L-band normal conducting RF photogun. The main objective is clarifying the discrepancies between measurements and simulations performed for the European X-ray Free Electron Laser (E-XFEL) injector at DESY-PITZ. An iterative beam dynamics simulation procedure is proposed for the calculation of the total extracted bunch charge under the assumption that the emission source operates at the space-charge limit of the gun. This algorithm has been implemented in the three-dimensional full electromagnetic PIC Solver of the CST Particle Studio (CST-PS). Simulation results are in good agreements with measurements for a series of operation parameters. Further comparisons with a conventional Poisson-solver-based (PSB) tracking algorithm demonstrates the great significance of transient electromagnetic field effects for the beam dynamics in high brightness electron sources. Computer Simulation Technology AG, http://www.cst.com/
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA029
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MOPJE006	Electron Gun Longitudinal Jitter: Simulation and Analysis	electron, timing, linac, simulation	297
	M.S. Liu, Y.L. Chi, S. Pei, Y.F. Sui IHEP, Bejing, People's Republic of China
	The beam longitudinal jitter is fatal not only for the electron beam performance but also for the positron yield in routine operation of the Beijing Electron Positron Collider II (BEPCII) linear accelerator (Linac). Practically, longitudinal jitter has been observed many times which decreased the beam performance. We simulated the electron gun longitudinal jitter effect by PARMELA software in bunch capture process and analyzed its results about beam performance including average energy, energy spread, emittance and longitudinal phase of reference particle. We adjusted the electron gun trigger time during one cycle without changing other parameters. The percentage difference between maximum and minimum of average energy, energy spread, emittance and longitudinal phase of reference particle was 11.3%, 42%, 98% and 6.4%, respectively. It is observed and analyzed that gun trigger time longitudinal jitter is fatal for maintaining good beam performance. This analysis also gives a salutary lesson to any other longitudinal jitter which can affect the beam bunching in pre-injector .
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE006
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MOPMA043	Longitudinal Bunch Shaping at Picosecond Scales using Alpha-BBO Crystals at the Advanced Superconducting Test Accelerator	electron, laser, linac, space-charge	643
	B. Beaudoin UMD, College Park, Maryland, USA D.R. Edstrom, A.H. Lumpkin, J. Ruan, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA
	Funding: This works is supported by the University Research Association, Inc. Operated by the Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy The Integrable Optics Test Accelerator (IOTA) electron injector at Fermilab will enable a broad range of experiments at a national laboratory in order to study and develop solutions to the limitations that prevent the propagation of high intensity beams at picosecond lengths. One of the most significant complications towards increasing short-beam intensity is space-charge, especially in the vicinity of the gun. A few applications that require a longitudinally shaped electron beam at high intensities are for, the generation of THz waves and dielectric wakefields, each of which will encounter the effects of longitudinal space-charge. This paper investigates the effects of longitudinal space-charge on alpha-BBO UV laser shaped electron bunches in the vicinity of the 1½cell 1.3 GHz cylindrically symmetric RF photocathode gun.
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MOPHA006	A Slow RF-Laser Feedback for PHIL Photoinjector	laser, feedback, electron, controls	784
	N. ElKamchi, V. Chaumat, V. Soskov LAL, Orsay, France
	PHIL is an electron beam accelerator at LAL. It produces low energy (E<5 MeV) and high current (1 nC/bunch) electrons bunch at a repetition frequency of 5Hz. The stability of the beam charge at PHIL is a key issue for the succeful operation of the physic experiences that use the machine. At PHIL, the beam charge is quite stable, but we often note a slow charge drift on long duration experiences. Two ICTs, and a back-end electronics are used to monitor the stability of the beam charge, with an accuracy of about 1pC. Several types of jitter can impact the stability of the beam charge. The fluctuations of the RF power or the RF-laser relative phase drift could have significant influence, due to temperature variations that produce cables dilataion, and electronic components overheating. To correct the phase drift, we describe a method based on a slow analog-digital feedback loop between the RF wave in the gun (3 GHz) and the synchronisation signal of the laser (75MHz). It allows to maintain the jitter between the laser pulse and the RF wave stable at a very low value. As a result, the electron beam charge is maintained at a stable level, to meet the requirements of the users.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPHA006
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MOPHA028	Operation of Normal Conducting RF Guns with MicroTCA.4	LLRF, cavity, feedback, operation	841
	M. Hoffmann, V. Ayvazyan, J. Branlard, L. Butkowski, M.K. Grecki, U. Mavrič, M. Omet, S. Pfeiffer, H. Schlarb, Ch. Schmidt DESY, Hamburg, Germany W. Fornal, R. Rybaniec Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland A. Piotrowski FastLogic Sp. z o.o., Łódź, Poland
	During the last half year, the MicroTCA.4 based single cavity LLRF control system was installed and commissioned at several normal conducting facilities at DESY (FLASH RF gun, REGAE, PITZ RF gun, and XFEL RF gun). First tests during the last year show promising results in optimizing the system for high speed digital LLRF feedbacks, i.e. reducing system latency, increasing the internal controller processing speed, testing new control schemes, and optimizing controller parameters. In this contribution we will present results and gained experience from the commissioning phase and the first time period of real operation.
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MOPHA033	Physical Parameter Identification of Cross-Coupled Gun and Buncher Cavity at REGAE	resonance, cavity, coupling, higher-order-mode	857
	A.S. Nawaz, H. Werner TUHH, Hamburg, Germany M. Hoffmann, S. Pfeiffer, H. Schlarb DESY, Hamburg, Germany
	A reasonable description of the system dynamics is one of the key elements to achieve high performance control for accelerating modules. This paper depicts the system identification of a cross-coupled pair of cavities for the Relativistic Electron Gun for Atomic Exploration - REGAE. Two normal conducting copper cavities driven by a single RF source accelerate and compress a low charge electron bunch with sub 10 fs length at a repetition rate up to 50 Hz. It is shown how the model parameters of the cavities and the attached radio frequency subsystem are identified from data generated at the REGAE facility.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPHA033
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MOPTY002	Bunch Length Measurement of Femtosecond Electron Beam by Monitoring Coherent Transition Radiation	electron, detector, radiation, linac	940
	I. Nozawa, M. Gohdo, K. Kan, T. Kondoh, A. Ogata, J. Yang, Y. Yoshida ISIR, Osaka, Japan
	Ultrashort electron bunches with durations of femtoseconds and attoseconds are essential for time-resolved measurements, including pulse radiolysis and ultrafast electron microscopy. However, generation of the ultrashort electron bunches is commonly difficult because of bunch length growth due to space charge effect, nonlinear momentum dispersion and so on. Several bunch length measurement methods for the ultrashort electron beams have also been considered so far, which have not been established yet. In this study, the femtosecond electron beams were generated using a laser photocathode radio-frequency gun linac and a magnetic bunch compressor. The bunch length measurement was carried out using a Michelson interferometer based on monitoring coherent transition radiation (CTR), which is characterized by square modulus of the Fourier transform of the longitudinal bunch distribution. Analyzing the experimentally obtained interferograms of CTR, the electron beams with the average duration of 5 fs were generated and measured successfully at the condition of bunch charge of 1 pC. Consideration of the longitudinal bunch shapes was also carried out using the Kramers-Kronig relation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPTY002
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MOPTY015	Beam Compression Dynamics and Associated Measurement Methods in Superconducting THz Source	controls, simulation, space-charge, electron	969
	Z. Zhou, Y.-C. Du, W.-H. Huang TUB, Beijing, People's Republic of China
	To ensure the quality of high brightness electron beams needed by the terahertz FEL facility at China academy of engineering physics(CAEP), which aims to obtain 100 to 300 terahertz light, a feed-back control system is required to monitor the amplitude and phase jittering by measuring beam arrival time as well as bunch length at the site of the beam position monitor(BPM). In this paper, we make an idealized model of injector section and deduce analytic expressions of bunch arrival time and bunch length. In consideration of the space charge effect on bunch lengthening, bunch arrival time and bunch length as a function of DC gun voltage, buncher field amplitude and buncher phase is carefully calibrated by means of particle in cell (PIC) simulation. With the time and space resolution of the BPM, the control accuracy of phase is estimated to be 0.01 degree, while the amplitude is 0.04%.
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MOPTY023	Beam Diagnostic of the LINAC for the Compact High-Performance THz-FEL	linac, FEL, emittance, target	987
	T. Hu, Q.S. Chen, K.F. Liu, B. Qin, P. Tan, Y.Q. Xiong, J. Yang HUST, Wuhan, People's Republic of China W. Chen Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China J. Liu, Y.J. Pei, Z.X. Tang USTC/NSRL, Hefei, Anhui, People's Republic of China Z.M. Wang Chinagray, Hefei, Anhui, People's Republic of China
	With the aim to obtain short-pulse bunches with high peak current for a terahertz radiation source, an FEL-based LINAC is employed in HUST THz-FEL, and the LINAC consists of an EC-ITC RF gun, a disk-loaed waveguide structure with a constant gradient and collinear absorbing loads with focusing coils surrounded and so on. To achieve a balance between compactness and high performance, beam diagnostic system should be simple and high-precision. So that a cost-effective measurement scheme for the high-brightness beam extracted by the LINAC is needed. This paper will describe the beam line and beam diagnostic system of the LINAC in the HUST THz-FEL in detail and give corresponding assembly scheme. In addition, online monitor system is introduced.
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MOPWI005	Emittance and Optics Measurements on the Versatile Electron Linear Accelerator at Daresbury Laboratory	space-charge, quadrupole, emittance, coupling	1153
	C.P. Topping, D.J. Scott, A. Wolski Cockcroft Institute, Warrington, Cheshire, United Kingdom S.D. Barrett, C.P. Topping, A. Wolski The University of Liverpool, Liverpool, United Kingdom B.L. Militsyn, D.J. Scott STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	The Versatile Electron Linear Accelerator (VELA) is a facility designed to provide a high quality electron beam for accelerator systems development, as well as industrial and scientific applications. Currently, the RF gun can deliver short (of order a few ps) bunches with charge in excess of 250 pC at up to 5.0 MeV/c beam momentum. Measurement of the beam emittance and optics in the section immediately following the gun is a key step in tuning both the gun and the downstream beamlines for optimum beam quality. We report the results of measurements (taking account of coupling and space charge) indicating normalised emittances of order 0.5 μm at low bunch charge.
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MOPWI028	Initial Experimental Results of a Machine Learning-Based Temperature Control System for an RF Gun	controls, cavity, monitoring, network	1217
	A.L. Edelen, S. Biedron, S.V. Milton CSU, Fort Collins, Colorado, USA B.E. Chase, D.J. Crawford, N. Eddy, D.R. Edstrom, E.R. Harms, J. Ruan, J.K. Santucci, P. Stabile Fermilab, Batavia, Illinois, USA
	Colorado State University (CSU) and Fermi National Accelerator Laboratory (Fermilab) have been developing a control system to regulate the resonant frequency of an RF electron gun. As part of this effort, we present experimental results for a benchmark temperature controller that combines a machine learning-based model and a predictive control algorithm for improved settling time, overshoot, and disturbance rejection relative to conventional techniques. Such improvements have implications for machine up-time and management of reflected power. This work is part of an on-going effort to develop adaptive, machine learning-based tools specifically to address control challenges found in particle accelerator systems.
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MOPWI032	Analysis of Primary Stripper Foils at SNS by an Electron Beam Foil Test Stand	electron, proton, operation, experiment	1230
	E.P. Barrowclough, C.S. Feigerle University of Tennessee, Knoxville, Tennessee, USA C.F. Luck, M.A. Plum, R.W. Shaw, L.L. Wilson ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. Diamond foils are used at the Spallation Neutron Source (SNS) as the primary strippers of hydride ions. A nanocrystalline diamond film, typically 17x45 mm with an aerial density of 0.35 mg/cm², is deposited on a corrugated silicon substrate by plasma-assisted chemical vapor deposition. After growth, 30 mm of the silicon substrate is etched away, leaving a freestanding diamond foil with a silicon handle that can be inserted into SNS for operation. An electron beam test facility was constructed to study stripper foil degradation and impact on foil lifetime. The electron beam capabilities include: current up to 5 mA, focused spot size of 0.30 mm², and rastering in the x- and y-directions. A 30 keV and 1.6 mA/mm² electron beam deposits the same power density on a diamond foil as a 1.4 MW beam on SNS target. Rastering of the electron beam can expose a similar area of the foil as SNS beams. Experiments were conducted using the foil test stand to study: foil flutter and lifetime; effects of corrugation patterns, aerial densities, crystal size (micro vs. nano), and boron doping; temperature distributions and film emissivity; and conversion rate of nanocrystalline diamond into graphite.
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TUYB1	Progress of SuperKEKB	emittance, positron, electron, linac	1291
	T. Miura, T. Abe, T. Adachi, K. Akai, M. Akemoto, A. Akiyama, D.A. Arakawa, Y. Arakida, Y. Arimoto, M. Arinaga, K. Ebihara, K. Egawa, A. Enomoto, J.W. Flanagan, S. Fukuda, H. Fukuma, Y. Funakoshi, K. Furukawa, T. Furuya, K. Hara, T. Higo, H. Hisamatsu, H. Honma, T. Honma, R. Ichimiya, N. Iida, H. Iinuma, H. Ikeda, M. Ikeda, T. Ishibashi, H. Ishii, M. Iwasaki, A. Kabe, T. Kageyama, H. Kaji, K. Kakihara, S. Kamada, T. Kamitani, S. Kanaeda, K. Kanazawa, H. Katagiri, S. Kato, S. Kazama, M. Kikuchi, T. Kobayashi, H. Koiso, Y. Kojima, M. Kurashina, K. Marutsuka, M. Masuzawa, S. Matsumoto, T. Matsumoto, H. Matsushita, S. Michizono, K. Mikawa, T. Mimashi, F. Miyahara, K. Mori, T. Mori, A. Morita, Y. Morita, H. Nakai, H. Nakajima, T.T. Nakamura, K. Nakanishi, K. Nakao, H. Nakayama, T. Natsui, M. Nishiwaki, J.-I. Odagiri, Y. Ogawa, K. Ohmi, Y. Ohnishi, S. Ohsawa, Y. Ohsawa, N. Ohuchi, K. Oide, T. Oki, M. Ono, H. Sakai, Y. Sakamoto, S. Sasaki, M. Sato, M. Satoh, K. Shibata, T. Shidara, M. Shirai, A. Shirakawa, M. Suetake, Y. Suetsugu, R. Sugahara, H. Sugimoto, T. Suwada, S. Takasaki, T. Takatomi, T. Takenaka, Y. Takeuchi, M. Tanaka, M. Tawada, S. Terui, M. Tobiyama, N. Tokuda, K. Tsuchiya, X. Wang, K. Watanabe, H. Yamaoka, Y. Yano, K. Yokoyama, Ma. Yoshida, M. Yoshida, S.I. Yoshimoto, K. Yoshino, R. Zhang, D. Zhou, X. Zhou, Z.G. Zong KEK, Ibaraki, Japan D. Satoh TIT, Tokyo, Japan
	This presentation will cover the status of the installation and the injector commissioning status of SuperKEKB. The IR optics and design with very low β^* of less than 1 mm will be discussed.
	Slides TUYB1 [6.588 MB]
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TUAD3	LLRF Commissioning of the European XFEL RF Gun and Its First Linac RF Station	LLRF, linac, cryomodule, electronics	1377
	J. Branlard, G. Ayvazyan, V. Ayvazyan, L. Butkowski, M.K. Grecki, M. Hoffmann, F. Ludwig, U. Mavrič, M. Omet, S. Pfeiffer, K.P. Przygoda, H. Schlarb, Ch. Schmidt, H.C. Weddig, B.Y. Yang DESY, Hamburg, Germany S. Bou Habib, K. Czuba, M. Grzegrzółka, E. Janas, K. Oliwa, J. Piekarski, K.T. Pozniak, I. Rutkowski, R. Rybaniec, D. Sikora, W. Wierba, L.Z. Zembala, M. Żukociński Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland W. Cichalewski, D.R. Makowski, A. Mielczarek, P. Perek TUL-DMCS, Łódź, Poland A. Piotrowski FastLogic Sp. z o.o., Łódź, Poland
	The European X-ray free electron laser (XFEL) at the Deutsches Elektronen-Synchrotron (DESY), Hamburg Germany is in its construction phase. Approximately a third of the super-conductive cryomodules have been produced and tested. The RF gun is installed since 2013; periods of commissioning are regularly scheduled between installation phases of the rest of the injector. The first linac, L1, consisting of 4 cryomodules powered by one 10 MW klystron is installed and being commissioned. This contribution reports on the installation and preparation work of the low-level radio frequency system (LLRF) to perform the commissioning of the XFEL first components. The commissioning plans, schedule and first results are presented.
	Slides TUAD3 [14.016 MB]
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TUPWA009	50 MeV Electron Linac with a RF Gun and a Thermoionic Cathode	linac, cavity, focusing, cathode	1413
	A.S. Setty, A.S. Chauchat, D. Fasse, D. Jousse, P. Sirot Thales Communications & Security (TCS), Gennevilliers Cedex, France
	The low energy part of our pre injectors is made up of a 90 kV DC themoionic trioode gun, followed by a 500 MHz sub harmonic prebuncher and a 3 GHz prebuncher. We propose a new design for a 50 MeV linac with a RF gun . this study will compare the beam dynamics simulations for the new design and for our previous pre injectors. A. Setty et al. "Study of a RF gun with a Thermoionic Cathode", Proceeding IPAC 2014, Germany, Dresden, June 2014.
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TUPWA018	Progress Report of the Berlin Energy Recovery Project BERLinPro	SRF, booster, cavity, electron	1438
	M. Abo-Bakr, W. Anders, K.B. Bürkmann-Gehrlein, A. Burrill, A.B. Büchel, P. Echevarria, A. Frahm, H.-W. Glock, A. Jankowiak, C. Kalus, T. Kamps, G. Klemz, J. Knobloch, J. Kolbe, J. Kühn, O. Kugeler, B.C. Kuske, P. Kuske, A.N. Matveenko, A. Meseck, R. Müller, A. Neumann, N. Ohm, K. Ott, E. Panofski, F. Pflocksch, D. Pflückhahn, J. Rahn, J. Rudolph, M. Schmeißer, O. Schüler, J. Völker HZB, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association The Helmholtz Zentrum Berlin is constructing the Energy Recovery Linac Project BERLinPro on its site in Berlin Adlershof. The project is intended to expand the required accelerator physics and technology knowledge mandatory for the design, construction and operation of future synchrotron light sources. The project goal is the generation of a high current (100 mA), high brilliance (norm. emittance below 1 mm mrad) cw electron beamat 2~ps rms bunch duration or below. The planning phase of the project is completed and the design phase of most of the components is finished. Many of them have already been ordered. After some delay the construction of the building has started in February 2015. The status of the various subprojects as well as a summary of current and future activities will be given. Major project milestones and details of the project time line will be finally introduced.
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TUPWA023	A Step Closer to the CW High Brilliant Beam with the ELBE SRF-Gun-II	SRF, cavity, cathode, electron	1456
	R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate HZDR, Dresden, Germany
	In order to achieve the CW electron beam with a high average current up to 1 mA and a very low emittance of 1 μm, an improved superconducting photo-injector (ELBE SRF-Gun-II) has been installed and commissioned at HZDR since 2014. This new gun replaces the first 3.5-cell SRF gun (SRF-Gun-I) at the SC Linac ELBE. The RF performance of the niobium cavity has been evaluated, the beam parameters for low charge bunches have been measured, and the first beam has been guided into the ELBE beam line. The results agree with the simulation very well. The photocathode transfer system has been installed for the first high current beam test planned in 2015. However, the unexpected strong degradation on the cavity and also on the photocathode was found soon after the first photocathode exchange. In this contribution the results of the SRF-Gun-II commissioning and the latest experiment will be presented in detail.
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TUPWA028	Simulation Results of the Beam Transport of Ultra-Short Electron Bunches in Existing Beam Transfer Lines to Sinbad	linac, optics, electron, synchrotron	1466
	U. Dorda, R.W. Aßmann, K. Flöttmann, B. Marchetti, Y.C. Nie, J. Zhu DESY, Hamburg, Germany
	SINBAD, the upcoming accelerator R&D facility at DESY, will host multiple independent experiments on the production and acceleration of ultra-short bunches including plasma wakefield experiments. As a possible later upgrade the option to transport higher energy electrons (up to 800 MeV) or positrons (up to 400 MeV) from the existing DESY Linac 2 to the facility is studied. Though existing a possible connection using e.g. a part of the DESY synchrotron as a transfer line and other currently unused transfer-line, these machines were not designed for the desired longitudinal bunch compression and high peak current required by e.g. beam driven plasma wake-field experiments. Simulation results illustrate the modifications to the current layout that would have to be implemented and the corresponding achievable beam parameters are given.
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TUPWA032	Progress in the Injector Upgrade of the LINAC II at DESY	electron, linac, simulation, solenoid	1479
	Y.C. Nie, M. Hüning, C. Liebig, M. Schmitz DESY, Hamburg, Germany
	A new injection system is under development for the LINAC II at DESY to improve the reliability of the machine and mitigate the radiological problem due to electron losses at energy of hundreds of MeV. It consists of a 100 kV triode DC gun, a 2.998 GHz pre-buncher, a novel 2.998 GHz hybrid buncher, and the dedicated beam transport and diagnostic elements. As the key components, the pre-buncher and the hybrid buncher realize a two-stage velocity bunching process including the ballistic bunching and the phase space rotation. Therefore, they produce a certain number of well-bunched 5 MeV micro-bunches from the input 2 ns-50 ns electron pulse for the downstream LINAC II. The overall upgrade plan, developments of the critical components, as well as the latest beam test results will be reported.
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TUPWA042	Status of the Accelerator Physics Test Facility FLUTE	electron, linac, diagnostics, laser	1506
	M.J. Nasse, A. Bernhard, I. Birkel, A. Borysenko, A. Böhm, S. Hillenbrand, N. Hiller, S. Höninger, S. Marsching, A.-S. Müller, R. Rossmanith, R. Ruprecht, M. Schuh, M. Schwarz, B. Smit, S. Walther, M. Weber, P. Wesolowski KIT, Karlsruhe, Germany R.W. Aßmann, M. Felber, K. Flöttmann, C. Gerth, M. Hoffmann, P. Peier, H. Schlarb, B. Steffen DESY, Hamburg, Germany R. Ischebeck, B. Keil, V. Schlott, L. Stingelin PSI, Villigen PSI, Switzerland
	A new compact versatile linear accelerator named FLUTE (Ferninfrarot Linac Und Test Experiment) is currently under construction at the Karlsruhe Institute of Technology (KIT). It will serve as an accelerator test facility and allow conducting a variety of accelerator physics studies. In addition, it will be used to generate intense, ultra-short THz pulses for photon science experiments. FLUTE consists of a ~7 MeV photo-injector gun, a ~41 MeV S-band linac and a D-shaped chicane to compress bunches to a few femtoseconds. This contribution presents an overview of the project status and the accompanying simulation studies.
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TUPWA046	Facility Upgrade at PITZ and First Operation Results	laser, plasma, operation, electron	1518
	A. Oppelt, P. Boonpornprasert, A. Donat, J.D. Good, M. Groß, H. Huck, I.I. Isaev, L. Jachmann, D.K. Kalantaryan, M. Khojoyan, W. Köhler, G. Koss, G. Kourkafas, M. Krasilnikov, O. Lishilin, D. Malyutin, J. Meissner, D. Melkumyan, M. Otevřel, M. Penno, B. Petrosyan, S. Philipp, M. Pohl, Y. Renier, T. Rublack, B. Schöneich, J. Schultze, F. Stephan, F. Tonisch, G. Trowitzsch, G. Vashchenko, R.W. Wenndorff DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria M. A. Bakr Assiut University, Assiut, Egypt C. Hernandez-Garcia JLab, Newport News, Virginia, USA G. Pathak Uni HH, Hamburg, Germany D. Richter HZB, Berlin, Germany
	The Photo Injector Test facility at DESY, Zeuthen site (PITZ), develops, optimizes and characterizes high brightness electron sources for free electron lasers like FLASH and the European XFEL. In the last year, the facility was significantly upgraded by the installation of a new normal conducting radio- frequency (RF) gun cavity with its new waveguide system for the RF feed, which should allow stable and reliable gun operation, as required for the European XFEL. Other relevant additions include beamline modifications for improving the electron beam transport through the PITZ accelerator, extending the beam-based measurement capabilities, and preparing the installation of a plasma cell. Furthermore, the laser hutch was re-arranged in order to be able to house an additional, new photo cathode drive laser system which should be able to produce 3D ellipsoidal laser pulses to further improve the electron beam quality. This paper describes in detail the aforementioned facility upgrades and reports on the first operation experience with the new gun setup.
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TUPWA056	New Gun Implementation and Performance of the DAΦNE LINAC	linac, cathode, electron, operation	1546
	B. Buonomo, L.G. Foggetta, G. Piermarini INFN/LNF, Frascati (Roma), Italy
	A new electron gun system has been developed for DAΦNE LINAC, and put into operation since January 2014. Several elements of the system were upgraded, including a new grid pulser, an improved bias voltage system and a renewed cathode socket. The new LINAC gun has now a wider range of parameters, i.e. the emission pulse length spans from 1.4ns up to 40ns, while the better control of the grid and bias voltage allows a maximum peak current of 5A with a pulse repetition rate of 50 Hz. This paper describes the details of the pulser, the power supply, the socket, all the service components of the upgraded gun and its integration in the main LINAC control system. A report on the performance of the LINAC with the new gun will follow.
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TUPWA058	Study of a C-band Harmonic RF System to Optimize the RF Bunch Compression Process of the SPARC Beam	cavity, linac, experiment, emittance	1552
	A. Gallo, D. Alesini, M. Bellaveglia, M. Ferrario INFN/LNF, Frascati (Roma), Italy A. Bacci, V. Petrillo, A.R. Rossi, L. Serafini Istituto Nazionale di Fisica Nucleare, Milano, Italy F. Cardelli, L. Piersanti INFN-Roma1, Rome, Italy B. Marchetti DESY, Hamburg, Germany M. Rossetti Conti Universita' degli Studi di Milano & INFN, Milano, Italy
	The SPARC linac at the INFN Frascati Labs is a high brilliance electron source with a wide scientific program including production of THz and Thomson backscattering radiation, FEL studies and plasma wave acceleration experiments. The linac is based on S-band RF and consists in an RF Gun followed by 3 accelerating structures, while an energy upgrade based on 2 C-band accelerating structures is ready to be implemented. Short bunches are ordinarily produced by using the linear RF bunch compression concept. A harmonic RF structure interposed between the Gun and the 1st accelerating structure can be used to optimize the RF compression by a longitudinal phase space pre-correction, allowing to reach shorter bunches, a much more uniform current distribution and in general to control better the whole compression process. Here we report the results of numerical studies on the SPARC bunch compression optimization through the use of a harmonic cavity, and the design of a C-band RF system to implement it. The proposed system consists in a multi-cell SW cavity powered by a moderate portion of the total RF power spilled from the C-band power plant already installed for the linac energy upgrade.
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TUPWA065	Generation of Multi-bunch Beam with Beam Loading Compensation by Using RF Amplitude Modulation in Laser Undulator Compact X-ray (LUCX)	cavity, electron, laser, booster	1576
	M.K. Fukuda, S. Araki, Y. Honda, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan K. Sakaue, M. Washio RISE, Tokyo, Japan
	We have developed a compact X-ray source based on inverse Compton scattering between an electron beam and a laser pulse stacked in an optical cavity at Laser Undulator Compact X-ray (LUCX) accelerator in KEK. The accelerator consists of a 3.6 cell photo-cathode rf-gun, a 12cell standing wave accelerating structure and a 4-mirror planar optical cavity. Our aim is to obtain a clear X-ray image in a shorter period of times and the target flux of X-ray is 1.7x10⁷ photons/pulse with 10% bandwidth at present. To achieve this target, it is necessary to increase the intensity of an electron beam to 500nC/pulse with 1000 bunches at 30 MeV. Presently, we have achieved the generation of 24MeV beam with total charge of 600nC in 1000bunches with beam-loading compensation by using the delta T method and the amplitude modulation of RF pulse. The bunch-by-bunch energy difference is within 1.3% peak to peak. We will report the results of the multi-bunch beam generation and acceleration in this accelerator. This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
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TUPWA068	Simulation Study of Beam Halo and Loss for KEK Compact ERL	simulation, cavity, laser, electron	1587
	O. Tanaka, T. Miyajima, N. Nakamura, S. Sakanaka, M. Shimada KEK, Ibaraki, Japan
	At the KEK Compact ERL (cERL) designed to operate at high-brilliance and high-current electron beams, the maximum averaged current was recorded at 6.5 muA for the beam energy of 20 MeV on March 2014 and should be increased up to 10 mA in a step-by-step manner in a few years. In order to increase the beam current by reducing the beam loss, we need to know the mechanism of the beam loss. For this purpose we investigate beam halo originated from characteristics and imperfections of an electron gun system, using the tracking code GPT (General Particle Tracer). The beam halo can be lost by the beam-pipe apertures and the collimators in the cERL beam line. In this paper, we will present the simulation results including the beam halo formation and the beam loss distribution along the beam line.
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TUPWA071	Improvements of the Laser System for RF-Gun at SuperKEKB Injector	laser, electron, operation, cryogenics	1598
	R. Zhang, T. Natsui, Y. Ogawa, M. Yoshida, X. Zhou KEK, Ibaraki, Japan
	For realizing higher charge and low emittance electron and positron beams in SuperKEKB, we have been making improvements in laser system for RF-gun. The difficulty in controlling thermomechanical distortions has been one of the most important factors for preserving high laser conversion efficiency of infrared-to-ultraviolet and operating at higher repetition rate. We demonstrated that efficient removal of waste heat can be realized by adopting Yb:YAG and copper bonding composite via Au-Sn solder. On the other hand, we proposed the novel design of the cascade laser configuration. Base on this, we can improve the quantum efficiency by utilizing other Yb ions doped crystals as active medium which are pumped by 1035 nm Yb:YAG laser. Excellent thermal management and high charge beams have been achieved by improvements of these two aspects. Additionally, in order to employ high duty ratio pump system and realize laser operation at high repetition rate, we investigated the laser operation in cryogenic environment. A perspective towards the next step experiment is also presented in this paper.
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TUPJE003	Quasi-Traveling Wave RF Gun and Beam Commissioning for SuperKEKB	laser, cathode, emittance, cavity	1610
	T. Natsui The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan Y. Ogawa, M. Yoshida, X. Zhou KEK, Ibaraki, Japan
	We are developing a new RF gun for SuperKEKB. High charge low emittance electron and positron beams are required for SuperKEKB. We will generate 7.0 GeV electron beam at 5 nC 20 mm-mrad by J-linac. In this linac, a photo cathode S-band RF gun will be used as the electron beam source. For this reason, we are developing an advanced RF gun which has two side coupled standing wave field. We call it quasi-traveling wave side couple RF gun. This gun has a strong focusing field at the cathode and the acceleration field distribution also has a focusing effect. This RF gun has been installed in the KEK J-linac. Beam commissioning with the RF gun is in progress.
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TUPJE009	Study on Frequency Multiplier of a Pulsed Laser Repetition using an Optical Cavity	laser, cavity, electron, cathode	1629
	T. Kobayashi Waseda University, Tokyo, Japan
	We have been studying a compact electron accelerator based on an S-band Cs-Te photo-cathode rf gun at Waseda University. The system is using S-band rf of 2856MHz. When a repetition of the electron bunch is integral multiple of rf, it enables a lot of electron bunch acceleration for the rf gun. The repetition of the electron bunch generated by a photo-cathode rf gun depends on the oscillating frequency of the pulsed mode-locked laser. We have been developing a mode-locked Yb-doped fiber laser based on Non-Linear Polarization Rotation (NLPR). However, its repetition is limited by the fiber length to produce NLPR. Therefore, we have started to develop the external optical cavity which is multiplier of a pulsed laser repetition. It would enable the rf gun to generate high-dose electron beam in a very short time. In this conference, we will report design of the external optical cavity to multiply the pulsed laser repetition, the experimental results of the frequency multiplying of a mode-locked Yb-doped fiber laser, and the future prospects. Work supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
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TUPJE010	Study of Cs-Te Photocathode for RF Electron Gun	electron, vacuum, radiation, scattering	1632
	S. Matsuzaki, M. Nishida, K. Sakaue, M. Washio Waseda University, Tokyo, Japan H. Iijima Tokyo University of Science, Tokyo, Japan
	At Waseda University, we have been studying high quality electron beam with an rf electron gun. In recent accelerator study and application researches, high quality electron beam are strongly required. Photocathode is a key component to generate higher quality electron beam. Cs-Te photocathode shows high quantum efficiency (Q.E.) (~10%) and has long life time (~several months). From 2013, we built a photocathode evaporation chamber and started photocathode study. In this study, our purpose is to clarify their property and to establish an ideal evaporation recipe. We succeeded in producing high quality Cs-Te photocathode, and electron beam generated by our Cs-Te photocathode shows high charge (4.6nC/bunch) and high Q.E. (1.74%) in our rf electron gun. Furthermore, we found a Q.E. recovery after Cs deposition process and it causes higher Q.E. than usual due to, we believe, Cs deposition quantity or Cs deposition speed. Thus we are now surveying the optimum Cs evaporation parameters. In this conference, we will report a detail of our photocathode development system, the latest progress of optimization study of Cs-Te photocathode and future plans. Work supported by Cooperative and Supporting Program for Researches and Educations in Universities and NEDO(New Energy and Industrial Technology Development Organization.
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TUPJE014	An X-Band Linac with Tunable Beam Energy	linac, electron, simulation, software	1644
	L. Zhang, H.B. Chen, Y.-C. Du, Q.X. Jin, J. Shi, C.-X. Tang, P. Wang, Z. Zhang TUB, Beijing, People's Republic of China
	The low-energy X-band linac has a wide application in medical imaging. In this paper, an X-band linac is designed to produce beam energy between 0.5MeV and 1.5MeV, and the output beam energy is continuously adjustable within this range. Two sections of linacs are combined and powered by a single microwave source. During the experiment, we can tune the RF phase and amplitude of the second section of the linac, the electron beam can see either acceleration or deceleration, which tunes the output energy. This paper presented the production of the whole linac system, as well as the measurement of the continuously-adjustable beam energy.
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TUPJE017	The Generation of Highly Intense THz Radiation based on Smith-Purcell Radiation	radiation, electron, factory, cathode	1654
	Y.F. Xu, Z.G. He, Q.K. Jia, W.W. Li USTC/NSRL, Hefei, Anhui, People's Republic of China
	A photocathode RF gun can generate trains of THz subpicosecond electron bunches by illuminating the cathode with trains of laser pulses. Let this electron bunches passes close to the surface of a lamellar grating, THz radiation will be emitted, which is the so-called Smith-Purcell Radiation (SPR). If the lamellar grating has a narrow groove, this radiation will be narrow-band. By choosing suitable parameter, the SPR frequency can be resonant with the electron bunches frequency, and then generate high intense, narrow band THz radiation.
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TUPJE039	Recent Results on the Performance of Cs3Sb Photocathodes in the PHIN RF-Gun	cathode, laser, vacuum, operation	1699
	C. Heßler, E. Chevallay, S. Döbert, V. Fedosseev, I. Martini, M. Martyanov CERN, Geneva, Switzerland
	For the CLIC drive beam a photoinjector option is under study at CERN as an alternative to the thermionic electron gun in the CLIC baseline design. The CLIC drive beam requires a high bunch charge of 8.4 nC and 0.14 ms long trains with 2 ns bunch spacing, which is challenging for a photoinjector. In particular the required long and high intensity laser pulses cause a degradation of the beam quality during the frequency conversion process, which generates the ultra-violet laser beam needed for standard Cs2Te photocathodes. To overcome this issue Cs3Sb cathodes sensitive to green light have been studied at the high-charge PHIN photoinjector since a few years. In this paper recent measurements of fundamental properties of Cs3Sb photocathodes such as quantum efficiency, cathode lifetime and dark current from summer 2014 will be presented, and compared with previous measurements and with the performance of Cs2Te photocathodes.
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TUPJE040	Surface Characterization at CERN of Photocathodes for Photoinjector Applications	cathode, laser, electron, operation	1703
	I. Martini, E. Chevallay, V. Fedosseev, C. Heßler, H. Neupert, V. Nistor, M. Taborelli CERN, Geneva, Switzerland
	R&D on photocathodes takes place at CERN within the CLIC (Compact Linear Collider) project. Photocathodes are produced as thin films on Oxygen Free copper substrate using a co-deposition technique, and characterized in a dedicated laboratory with a DC photo-electron gun. A new UHV carrier vessel compatible with CERN’s XPS (X-ray Photoelectron Spectroscopy) analysis equipment has been commissioned and is used to transport photocathodes from the production laboratory to perform a systematic study of different compounds used as photoemissive materials. In this paper photocathodes used in a RF photoinjector will be characterized and the correlation of their surface properties with their performance will be investigated.
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TUPJE041	Progress on a Compact Accelerator Design for a Compton Light Source	dipole, linac, space-charge, solenoid	1706
	K.E. Deitrick, J.R. Delayen, B.R.P. Gamage, G.A. Krafft, T. Satogata ODU, Norfolk, Virginia, USA
	A compact Compton light source using an electron linear accelerator is in design at the Center for Accelerator Science at Old Dominion University and Jefferson Lab. We report on the current design, including beam properties through the entire system based on a full end-to-end simulation, compare current specifications to design goals, and target areas for improvement.
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TUPJE052	Bunch Compression in the Driver Linac for the Proposed NSRRC VUV FEL	electron, linac, optics, FEL	1738
	N.Y. Huang, W.K. Lau, A.P. Lee NSRRC, Hsinchu, Taiwan A. Chao, K. Fang, M.-H. Wang, J. Wu SLAC, Menlo Park, California, USA
	A bunch compressor is designed for the S-band driver linac system of the proposed NSRRC VUV free electron laser (FEL). Instead of using a more conventional rf harmonic linearizer, one main feature of this compressor is to use electron linearization optics to correct the nonlinearity in the energy-time correlation of the electron bunch longitudinal phase space. The strategy of compressor design will be discussed by an analytical calculation and particle tracking simulation. The beam dynamics which include the collective instabilities such as the space charge effects, the wake fields and the coherent synchrotron radiation (CSR) effects are discussed.
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TUPJE056	VELA Machine Development and Beam Characterisation	cavity, cathode, electron, klystron	1752
	D.J. Scott, D. Angal-Kalinin, A.D. Brynes, F. Jackson, J.K. Jones, A. Kalinin, S.L. Mathisen, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, T.C.Q. Noakes, L.K. Rudge, E. Sneddon, M. Surman, R. Valizadeh, A.E. Wheelhouse, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S.D. Barrett, C.P. Topping, A. Wolski The University of Liverpool, Liverpool, United Kingdom A. Lyapin JAI, Egham, Surrey, United Kingdom M.D. Roper STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom C.P. Topping, A. Wolski Cockcroft Institute, Warrington, Cheshire, United Kingdom E. Yamakawa Royal Holloway, University of London, Surrey, United Kingdom
	Recent developments on the VELA (Versatile Electron Linear Accelerator) RF photo-injector at Daresbury Laboratory are presented. These are three-fold; commissioning/installation, characterising and providing beam to users. Measurements for characterising the dark current (DC), 4-D transverse emittance, lattice functions and photoinjector stability are presented. User beam set ups to provide beam for electron diffraction and Cavity Beam Position Monitor development are summarised.
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TUPJE058	Preparation of Polycrystalline and Thin Film Metal Photocathodes for Normal Conducting RF Guns	cathode, electron, experiment, cavity	1759
	S. Mistry, M.D. Cropper Loughborough University, Leicestershre, United Kingdom A.N. Hannah, K.J. Middleman, B.L. Militsyn, T.C.Q. Noakes, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	A comparison of quantum efficiency (QE) and work function (wf) measurements of polycrystalline and thin film metal photocathodes for use in NCRF guns, similar to the S-band gun under development for CLARA project at Daresbury, are reported. Cu and Nb thin films were grown onto a Si substrate by magnetron sputtering and subsequently were prepared by annealing and Ar ion sputtering. To determine the surface chemistry, x-ray photoelectron spectroscopy was employed. QE measurements were enabled using a UV laser source giving 266 nm light. Wf measurements were carried out using a kelvin probe and ultraviolet photoelectron spectroscopy. Annealing the Cu thin film to 250°C yielded a QE of 1.2E-4; one order of magnitude higher than the QE for sputter cleaned and post annealed polycrystalline Cu. The optimum QE measurement for Nb thin film was 2.6·10^-4, which was found to be comparable to the results obtained for cleaned bulk Nb. Analysis of XPS data of these metals suggest surface composition and surface chemistry are main contributing factors to the QE and WF.
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TUPMA010	Development of a Field-Emission Type S-band RF-Gun System for High Brightness Electron Source Applications	cathode, electron, emittance, vacuum	1856
	Y.-M. Shin Northern Illinois University, DeKalb, Illinois, USA N. Barov Far-Tech, Inc., San Diego, California, USA A.T. Green Northern Illinois Univerity, Dekalb, Illinois, USA
	Electron beams emitted from a cold cathode are thermally stable and mono-energetic with a small phase-space volume. We have been developing a field-emission type RF-gun system for high brightness electron source applications, including electron scattering/diffraction and tunable coherent X-ray/THz generation. The system consists of a single-gap gun-cavity and an S-band klystron/modulator capable of powering the gun with up to 5.5 MW peak (PRR = 1 Hz, duration = 2.5 μs). The designed gun built with the symmetrised side-couplers has surface field on the cathode ranging 50 – 100 MV/m with 1.3 – 1.7 MW klystron-power and 1.2 field ratio (HFSS). ASTRA simulations also indicate that the gun produces the beam with transverse emittances of less than 1 mm-mrad with 10 – 20 pC bunch charge at 500 keV beam energy. Under the gun operating condition, particle tracking/PIC simulations (CST) show that a single-tip CNT field-emitter* produces short pulsed bunches (~ 1/10 RF-cycle) with small emittance ( 0.01 mm-mrad) and high peak current density ( 10,000 kA/cm²). After the gun is fully installed and commissioned, a CNT-tip cathode will be tested with RF-field emission. * N. De Jonge, J.-M. Bonard, Phil. Trans. R. Soc. Lond. A 362, 2239 (2004) ** G. S. Bocharov, and A. V. Eletskii, Nanomaterials 3, 393 (2013)
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TUPMA018	An Improved Analytic Model of Electron Back-Bombardment in Thermionic Cathode RF Guns	simulation, electron, cathode, cavity	1872
	J.P. Edelen, S. Biedron, J.R. Harris, S.V. Milton CSU, Fort Collins, Colorado, USA J.W. Lewellen LANL, Los Alamos, New Mexico, USA
	This paper describes work done at Colorado State University to improve upon the recent theory developed to predict the back-bombardment power in single-cell thermionic-cathode electron guns. The previous theory used a square-wave approximation of the time varying field to solve for the total kinetic energy deposited on the cathode due to the back-bombarded electrons. In addition the transit time factor was added as a correction to compensate for the non-sinusoidal field. By solving for the back-bombardment power using a sinusoidal field, the transit time factor can be removed and therefore a better overall model is produced. These alterations continue to accurately predict how back-bombardment varies as a function of the gun parameters and provides improvement when compared to the existing theory.
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TUPMA025	X-Band RF Photoinjector for Laser Compton X-Ray and Gamma-Ray Sources	laser, electron, emittance, dipole	1891
	R.A. Marsh, G.G. Anderson, S.G. Anderson, C.P.J. Barty, D.J. Gibson LLNL, Livermore, California, USA
	Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Extremely bright narrow bandwidth gamma-ray sources are expanding the application of accelerator technology and light sources in new directions. An X-band test station has been commissioned at LLNL to develop multi-bunch electron beams. This multi-bunch mode will have stringent requirements for the electron bunch properties including low emittance and energy spread, but across multiple bunches. The test station is a unique facility featuring a 200 MV/m 5.59 cell X-band photogun powered by a SLAC XL4 klystron driven by a Scandinova solid-state modulator. This paper focuses on its current status including the generation and initial characterization of first electron beam. Design and installation of the inverse-Compton scattering interaction region and upgrade paths will be discussed along with future applications.
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TUPMA047	Multipacting-free Quarter-wavelength Choke Joint Design for BNL SRF	cathode, SRF, cavity, electron	1935
	W. Xu, S.A. Belomestnykh, I. Ben-Zvi, C.J. Liaw, G.T. McIntyre, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, D. Weiss, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA
	The BNL SRF gun cavity was operated well at CW mode up to 2 MV. However, the performance suffered due to multipacting in the quarter-wavelength choke-joint. A new multipacting-free cathode stalk was designed and will be conditioned. This paper will describes RF and thermal design of new cathode stalk and conditioning results. This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
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TUPMA048	Experimental and Simulational Result of Multipactors in 112 MHz QWR Injector	electron, cavity, cathode, simulation	1938
	T. Xin Stony Brook University, Stony Brook, USA S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, V. Litvinenko, I. Pinayev, J. Skaritka, Q. Wu, B. P. Xiao BNL, Upton, Long Island, New York, USA
	Funding: This work was carried out at Brookhaven Science Associates, LLC under Contracts No. DE-AC02-98CH10886 and at Stony Brook University under grant DE-SC0005713 with the U.S. DOE. The first RF commissioning of 112 MHz QWR superconducting electron gun was done in late 2014. The coaxial Fundamental Power Coupler (FPC) and Cathode Stalk (stalk) were install and tested for the first time. During this experiment, we observed several multipacting barriers at varied gun voltage levels. The simulation work was done within the same range. The comparison between the experimental observation and the simulation results are presented in this paper. The observations during the test are consisted with the simulation predictions. We were able to overcome most of the multipacting barriers and reach 1.7 MV gun voltage under pulsed mode after several round of conditioning processes.
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TUPMA049	First Beam Commissioning at BNL ERL SRF Gun	cathode, SRF, electron, cavity	1941
	W. Xu, Z. Altinbas, S.A. Belomestnykh, I. Ben-Zvi, S. Deonarine, D.M. Gassner, H. Hahn, L.R. Hammons, T. Hayes, J.P. Jamilkowski, P. K. Kankiya, D. Kayran, N. Laloudakis, R.F. Lambiase, V. Litvinenko, L. Masi, G.T. McIntyre, K. Mernick, T.A. Miller, G. Narayan, D. Phillips, V. Ptitsyn, T. Rao, T. Seda, F. Severino, B. Sheehy, K.S. Smith, A.N. Steszyn, T.N. Tallerico, R. Than, J.E. Tuozzolo, E. Wang, D. Weiss, M. Wilinski, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, V. Ptitsyn Stony Brook University, Stony Brook, USA
	Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. The 704 MHz superconducting RF gun successfully generated the first photoemission beam on Nov. 17 2014. This paper will report the latest results of SRF beam commissioning, including the SRF cavity performance, cathode QE measurements, and beam parameter measurements. The beam commissioning setup is described in the paper as well.
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TUPHA003	Sputter Growth of Alkali Antimonide Photocathodes: An in Operando Materials Analysis	cathode, target, emittance, radiation	1965
	J. Smedley, K. Attenkofer, M. Gaowei, J. Sinsheimer, J. Walsh BNL, Upton, Long Island, New York, USA H. Bhandari Radiation Monitoring Devices, Watertown, USA Z. Ding, E.M. Muller SBU, Stony Brook, New York, USA H.J. Frisch Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA H.A. Padmore, S.G. Schubert, J.J. Wong LBNL, Berkeley, California, USA
	Funding: Work supported by U.S. DoE, under KC0407-ALSJNT-I0013 and SBIR grant # DE-SC0009540. NSLS was supported by DOE DE-AC02-98CH10886, CHESS is supported by NSF & NIH/NIGMS via NSF DMR-1332208 Alkali antimonide photocathodes are a strong contender for the cathode of choice for next-generation photon sources such as LCLS II or the XFEL. These materials have already found extensive use in photodetectors and image intensifiers. However, only recently have modern synchrotron techniques enabled a systematic study of the formation chemistry of these materials. Such analysis has led to the understanding that these materials are inherently rough when grown through traditional sequential deposition; this roughness has a detrimental impact on the intrinsic emittance of the emitted beam. Sputter deposition may provide a path to achieving a far smoother photocathode, while maintaining adequate quantum efficiency. We report on the creation and vacuum transport of a K2CsSb sputter target, and its use to create an ultra-smooth (sub nm roughness) cathode with a 2% quantum efficiency at 532 nm.
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TUPTY083	Conceptual MEIC Electron Ring Injection Scheme using CEBAF as a Full Energy Injector	injection, electron, linac, operation	2232
	J. Guo, F. Lin, R.A. Rimmer, H. Wang, S. Wang, Y. Zhang JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 The Medium-energy Electron-Ion Collider (MEIC) proposed by Jefferson Lab is planning to use the newly upgraded 12 GeV CEBAF 1497 MHz SRF CW recirculating linac as a full-energy injector for the electron collider ring. The electron collider ring is proposed to reuse the 476MHz PEP-II RF system to achieve high installed voltage and high beam power. The MEIC electron injection requires 3-10 (or 12) GeV beam in 3-4μs long bunch trains with low duty factor and high peak current, resulting in strong transient beam loading for the CEBAF. In this paper, we propose an injection scheme that can match the two systems’ frequencies with acceptable injection time, and also address the transient beam loading issue in CEBAF. The scheme is compatible with future upgrade to 952.6 MHz SRF system in the electron ring.
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TUPWI008	RF Gun Based Ultrafast Electron Microscopy	electron, emittance, cavity, cathode	2259
	J. Yang, K. Tanimura, Y. Yoshida ISIR, Osaka, Japan J. Urakawa KEK, Ibaraki, Japan
	Ultrafast electron microscopy (UEM) would be a powerful tool for the direct visualization of structural dynamic processes in matter. The resolutions of the observation on femtosecond time scales over sub-nanometer (even atomic) spatial dimensions have long been a goal in science. To achieve such resolutions, we have designed and constructed a femtosecond time-resolved relativistic-energy electron microscopy using a photocathode radio-frequency (RF) electron gun (RF based UEM). The RF gun has successfully generated a high-brightness electron beam with bunch length of 100 fs and emittance of 0.2 mm-mrad, which are essential beam parameters for the achievement of nm-fs space-time resolution in the microscopy. Both the static measurements of both relativistic-energy electron diffraction and image have been succeeded. In this presentation, the activities on RF based UEM are introduced. The requirements and limitations of the beam parameters are reviewed. The concept and design of RF based UEM are reported. Finally, some demonstrations of the relativistic-energy UEM images are reported.
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TUPWI010	Development of a Pulse Radiolysis System by Ultra-fast Super Continuum Probe at Waseda University	laser, polarization, electron, cathode	2265
	Y. Ito Waseda University, Tokyo, Japan Y. Hosaka, K. Sakaue, M. Washio RISE, Tokyo, Japan
	We have been studying the pulse radiolysis using photo-cathode rf gun at Waseda Univ. Pulse radiolysis is one of the powerful methods to trace early chemical reactions by ionizing radiation. In pulse radiolysis, the probe light absorption, which produced by active species formed by electron beam of rf gun, is measured at each wavelength and made possible to trace reactions. Therefore, we have used the super continuum (SC) light for the probe light. The SC light has a broad spectrum and is generated by nonlinear optical effect caused by injecting picosecond laser to photonic crystal fiber. However, the resulting SC light was unstable because its peak intensity was not enough. We need to use a femtosecond pulsed laser which is expected to be stronger peak intensity than a picosecond laser. We have developed a mode-locked Yb-doped fiber laser based on Non-Linear Polarization Rotation as a femtosecond pulsed laser and the chirped pulse amplification system which will be able to amplify the femtosecond pulse. In this conference, we will report the performance of the SC light using this fiber laser system, recent results of pulse radiolysis experiments and the future plans. Work supported by NEDO(New Energy and Industrial Technology Development Organization).
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TUPWI017	Single-shot Multi-MeV Ultrafast Electron Diffraction on VELA at Daresbury Laboratory	electron, FEL, scattering, experiment	2278
	L.K. Rudge, D. Angal-Kalinin, J.A. Clarke, F. Jackson, J.K. Jones, A. Kalinin, S.L. Mathisen, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, T.C.Q. Noakes, Y.M. Saveliev, D.J. Scott, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom P. Aden, R.J. Cash, D.M.P. Holland, M.D. Roper STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom P.D. Lane, D.A. Wann University of York, York, United Kingdom M. Surman STFC/DL/SRD, Warrington, Cheshire, United Kingdom J.G. Underwood UCL, London, United Kingdom
	Funding: This work was funded by STFC Accelerator based Ultrafast Electron Diffraction (UED) is a technique for obtaining static structures and for studying sub-100 fs dynamic structural changes on the atomic scale. In this paper we present the first electron diffraction results obtained from the VELA accelerator in 2014. The accelerator was operated to provide typically 4MeV/c electron bunches. Diffraction patterns were observed with <<1 pC transported to the detection screen. Single shot and multi-shot accumulated diffraction data are presented from single crystal and polycrystalline samples, including Au, Al, Pt and C. Contamination of the diffraction pattern with dark current contributions is an issue. A variable size aperture directly in front of the sample offers some mitigation, but at the expense of reduced charge contributing to the diffraction pattern. We discuss future developments for electron diffraction on VELA including further beam optimization, measurement of bunch length with a newly installed Transverse Deflecting Cavity, and the planned developments for pump-probe studies.
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TUPWI042	Initial Results from Streaked Low-energy Ultra-fast Electron Diffraction System	electron, simulation, diagnostics, experiment	2339
	J.J. Hartzell, R.B. Agustsson, S. Boucher, L. Faillace, A.V. Smirnov RadiaBeam, Santa Monica, California, USA P. Musumeci, E.W. Threlkeld UCLA, Los Angeles, USA
	RadiaBeam, in collaboration with UCLA, is developing an inexpensive, low-energy, ultra-fast, streaked electron diffraction (S-UED) system which allows one to reconstruct a single ultrafast event with a single pulse of electrons using and RF deflector. The high-frequency (GHz), high voltage, phase-locked RF field in the deflector enables temporal resolution of atomic events as fine as sub-100 fs. In this paper, we present an overview of the system being developed and the initial experimental results. We also discuss the challenges based on our design of a UED system that incorporates a novel, high-resolution dielectric-loaded RF deflector and a solid-state X-band amplifier.
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WEYC1	Technical Challenges of the LCLS-II	undulator, linac, electron, cavity	2434
	T.O. Raubenheimer SLAC, Menlo Park, California, USA
	The LCLS-II will be a CW X-ray FEL upgrade to the existing LCLS X-ray FEL at the SLAC National Accelerator Laboratory (SLAC). This paper describes the overall layout and the technical challenges that the upgrade project faces.
	Slides WEYC1 [4.446 MB]
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WEBB1	Plans for Deployment of Hollow Electron Lenses at the LHC for Enhanced Beam Collimation	electron, collimation, solenoid, operation	2462
	S. Redaelli, A. Bertarelli, R. Bruce, D. Perini, A. Rossi, B. Salvachua CERN, Geneva, Switzerland G. Stancari, A. Valishev Fermilab, Batavia, Illinois, USA
	Hollow electron lenses are considered as a possible mean to improve the LHC beam collimation system, providing an active control of halo diffusion rates and suppressing the population of transverse halos. After a very successful experience at the Tevatron, a conceptual design of a hollow e-lens optimized for the LHC was produced. Recent further studies have led to a mature preliminary technical design. In this paper, possible scenarios for the deployment of this technology at the LHC are elaborated in the context of the scheduled LHC long shutdowns until the full implementation of the HL-LHC upgrade in 2023. Possible setups of electron beam test stands at CERN and synergies with other relevant electron beam programmes outside CERN are also discussed.
	Slides WEBB1 [3.216 MB]
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WEAD2	Experimental Results of Carbon NanoTube Cathodes inside RF Environment	cathode, electron, emittance, laser	2475
	L. Faillace, S. Boucher, J.J. Hartzell, A.Y. Murokh RadiaBeam, Santa Monica, California, USA D. Mihalcea, P. Piot, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA H. Panuganti Northern Illinois University, DeKalb, Illinois, USA
	Funding: Work supported by US DOE SBIR grant # DE-SC0004459 Carbon Nano Tubes (CNT’s) as field-emitters have been investigated for more than two decades and can produce relatively low emittance electron beams for a given cathode size. Unlike thermionic cathodes, CNT cathodes are able to produce electrons at room temperature and relatively low electric field (a few MV/m). In collaboration with FermiLab, we have recently tested CNT cathodes both with DC and RF fields. We observed a beam current close to 1A with a ~1cm² CNT cathode inside an L-band RF gun. Steady operation was obtained up to 650 mA and the measured current vs. surface field plot showed perfect agreement with the Fowler-Nordheim distribution.
	Slides WEAD2 [10.445 MB]
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WEAD3	Quantum Efficiency Improvement of Polarized Electron Source using Strain Compensated Super Lattice Photocathode	electron, laser, polarization, collider	2479
	N. Yamamoto, M. Hosaka, A. Mano, T. Miyauchi, Y. Takashima, Y. Takeda Nagoya University, Nagoya, Japan X.J. Jin, M. Yamamoto KEK, Ibaraki, Japan
	Polarized electron beam is essential for future electron-positron colliders and electron-ion colliders. Improving the quantum efficiency is an important subject to realize those proposed applications. Recently we have developed the strain compensated superlattice (SL) photocathode. In the strain compensated SLs, the equivalent compressive and tensile strains introduced in the well and barrier SL layers so that strain relaxation is effectively suppressed with increasing the SL layer thickness and high crystal quality can be expected. In this study, we fabricated the GaAs/GaAsP strain compensated SLs with the thickness up to 90-pair SL layers. Up to now, the electron spin polarization of 92 % and the quantum efficiency of 1.6 % were simultaneously achieved from 24-pair sample. In the presentation, we show the effect of the superlattice thickness on the photocathode performances and discuss the photocathode physics.
	Slides WEAD3 [3.064 MB]
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WEPWA014	Low Temperature Properties of 20 K Cooled Test Cavity for C-band 2.6-cell Photocathode RF Gun	cavity, experiment, cryogenics, resonance	2519
	T. Tanaka, M. Inagaki, K. Nakao, K. Nogami, T. Sakai LEBRA, Funabashi, Japan M.K. Fukuda, T. Takatomi, J. Urakawa, M. Yoshida KEK, Ibaraki, Japan D. Satoh TIT, Tokyo, Japan T.S. Shintomi Nihon University, Tokyo, Japan
	Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). A cryogenic C-band 2.6-cell photocathode RF gun, which operates at 20 K, is under development at Nihon University for future possibility of use in a compact linac-driven X-ray source. The cavity material is 6N8 high purity copper, the RRR of which being expected to be higher than 3000. A 2.6-cell pi-mode test cavity was fabricated for investigation of the properties under low temperature of 20 K. Ultraprecision machining and diffusion bonding of the cavity were carried out in KEK. The operating frequency of the RF gun cavity is 5712 MHz. The machining dimensions of the test cavity were determined by taking into account the contraction of copper from room temperature to 20 K by approximately 0.33 %. The resonant frequency observed at around 21 K was 5711.761 MHz, which is 185 kHz higher than the expected value that was deduced from the resonant frequency obtained at 23.5 degree C in vacuum and the linear expansion coefficient data for OFC copper by NIST. The unloaded Q-value of 64500 obtained at 21 K is in agreement with the SUPERFISH calculation when the surface resistance of the RRR=3000 copper was specified with taking the anomalous skin effect into account. T. Tanaka et al., Proceedings of IPAC2014, 658-660, http://accelconf.web.cern.ch/AccelConf /IPAC2014/papers/mopri030.pdf ** http://cryogenics.nist.gov/MPropsMAY/OFHC%20Copper/OFHC_Copper_rev.htm
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WEPWA015	RF Input Coupler for 20 K Cooled C-band 2.6-cell Photocathode RF Gun	cavity, simulation, resonance, network	2522
	T. Tanaka, M. Inagaki, K. Nakao, K. Nogami, T. Sakai LEBRA, Funabashi, Japan M.K. Fukuda, T. Takatomi, J. Urakawa, M. Yoshida KEK, Ibaraki, Japan D. Satoh TIT, Tokyo, Japan T.S. Shintomi Nihon University, Tokyo, Japan
	Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). For future use in a compact linac-driven X-ray source, a cryo-cooled C-band photocathode RF gun is under development. The RF experiment on the basic 2.6-cell test cavity has shown that the unloaded Q-value of the cavity at 20 K can be explained by the surface resistance based on the anomalous skin effect. Since the cavity was intended for preliminary experiments of the low temperature RF properties, a new test cavity with an RF input coupler has been designed. The basic structure of the accelerating cells has not been changed from the previous cavity. Avoiding an element with a low cooling efficiency such as the inner electrode in a coaxial coupler, a simpler cylindrical input coupler has been designed. The coupler consists of a cylindrical TM01 mode waveguide and a mode converter from a rectangular TE10 mode, with both elements placed on the accelerating axis. The structure and the dimensions of the coupler have been determined using the 3-D simulation code CST Studio so that the resonant frequency of the whole system and the coupling coefficient of the coupler meet the specifications of the RF gun. The new test cavity will be completed early in 2015 at KEK. T. Tanaka et al., Proceedings of IPAC2014, 658-660, http://accelconf.web.cern.ch/AccelConf /IPAC2014/papers/mopri030.pdf
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WEPWA024	Development of a C-band RF Gun with a Coniferous-tree-type Carbon Nanostructure Field Emission Cathode	cavity, cathode, electron, radiation	2545
	Y. Taira, H. Kato, R. Kuroda, H. Toyokawa AIST, Tsukuba, Ibaraki, Japan
	A C-band RF gun for compact radiation sources such as a high energy x-ray and a terahertz radiation is developed at AIST, which is designed to work at the frequency of 5.3 GHz. A coniferous-tree-type carbon nanostructure (CCNS) is used for a field emission cathode in the C-band RF gun. A graphene sheet composed of carbon has a coniferous form, and the tip has a nanometer-size tubular structure that becomes thicker on the substrate side. Owing to this configuration, the CCNS has a large field enhancement factor, and is considered to be more stable in high electric fields than Carbon nanotubes. We have fabricated the C-band RF gun of the single cell cavity. Emission current depending on the electric field strength on the CCNS cathode surface was measured. When the electric field strength was 30 MV/m, the total charge per a macro pulse was 30 nC. After applying a stronger electric field, a decline of the field enhancement factor was observed. We will present the experimental result of the field emission measurement of the CCNS and the simulation result of a beam trajectory using a C-band RF gun of a multi cell cavity. Y. Taira et al., Nucl. Instr. and Meth. Phys. Res. B 331 (2014) 27. ** R. Suzuki, Synthesiology 2 (3) (2009) 221.
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WEPWA052	RF Conditioning of the Photo-Cathode RF Gun at the Advanced Photon Source - NWA RF Measurements	detector, cathode, linac, vacuum	2621
	T.L. Smith, N.P. DiMonte, A. Nassiri, Y.-E. Sun, A. Zholents ANL, Argonne, Illinois, USA
	Funding: Work supported by U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357 A new S-band photo-cathode (PC) gun was recently installed and RF conditioned at the Advanced Photon Source (APS) Injector Test-stand (ITS) at Argonne National Lab (ANL). The APS PC gun is a LCLS type gun fabricated at SLAC [1]. The PC gun was delivered to the APS in October 2013 and installed in the APS ITS in December 2013. At ANL, we developed a new method of fast detection and mitigation of the gun’s internal arcs during the RF conditioning process to protect the gun from arc damage and to RF condition more efficiently. Here, we report the results of RF measurements for the PC gun and an Auto-Restart method for high power RF conditioning.
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WEPWA070	Considerations for an Efficient Terahertz-driven Electron Gun	electron, acceleration, laser, controls	2664
	F. Lemery, P. Piot Northern Illinois University, DeKalb, Illinois, USA P. Piot Fermilab, Batavia, Illinois, USA
	We investigate a dispersion-controlled-acceleration scheme of low-energy electrons to mitigate phase slipping using a tapered dielectric lined waveguide (DLW). Our approach matches the velocity of an electron being accelerated in a slab-symmetric structure in a constant electric field. We also present first experimental results of a THz pulse propagating in a slab-symmetric DLW.
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WEPJE019	Simulations of Field-Emission Electron Beams from CNT Cathodes in RF Photoinjectors	cathode, electron, simulation, emittance	2711
	D. Mihalcea, H. Panuganti, P. Piot Northern Illinois University, DeKalb, Illinois, USA L. Faillace RadiaBeam, Santa Monica, California, USA P. Piot, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA
	Average field emission currents of up to 700 mA were produced by Carbon Nano Tube (CNT) cathodes in a 1.3 GHz RF gun at Fermilab High Brightness Electron Source Lab. (HBESL). The CNT cathodes were manufactured at Xintek and tested under DC conditions at RadiaBeam. The electron beam intensity as well as the other beam properties are directly related to the time-dependent electric field at the cathode and the geometry of the RF gun. This report focuses on simulations of the electron beam generated through field-emission and the results are compared with experimental measurements. These simulations were performed with the time-dependent Particle In Cell (PIC) code WARP.
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WEPJE023	Cathode Performance during Two Beam Operation of the High Current High Polarization Electron Gun for eRHIC	cathode, electron, vacuum, operation	2720
	O.H. Rahman Stony Brook University, Stony Brook, USA M.A. Ackeret, J.R. Pietz Transfer Engineering and Manufacturing, Inc, Fremont, California, USA I. Ben-Zvi, C. Degen, D.M. Gassner, R.F. Lambiase, A.I. Pikin, T. Rao, B. Sheehy, J. Skaritka, E. Wang BNL, Upton, Long Island, New York, USA E. Dobrin, R.C. Miller, K.A. Thompson, C. Yeckel Stangenes Industries, Palo Alto, California, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Two electron beams from two activated bulk GaAs photocathodes were successfully combined during the recent beam test of the High Current High Polarization Electron gun for eRHIC. The beam test took place at Stangenes Industries in Palo Alto, CA, where the cathodes were placed in radially opposite locations inside the high voltage shroud. No significant cross talking between the cathodes were found for the pertinent vacuum and low average current operation, which is very promising towards combining multiple beams for higher average current. This paper describes the cathode preparation, transport and cathode performance in the gun for the combining test, including the QE and lifetimes of the photocathodes at various steps of the experiment.
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WEPJE033	The Progress of Funnelling Gun High Voltage Condition and Beam Test	cathode, electron, high-voltage, radiation	2735
	E. Wang, I. Ben-Zvi, D.M. Gassner, R.F. Lambiase, W. Meng, A.I. Pikin, T. Rao, B. Sheehy, J. Skaritka BNL, Upton, Long Island, New York, USA M.A. Ackeret, J.R. Pietz Transfer Engineering and Manufacturing, Inc, Fremont, California, USA E. Dobrin, R.C. Miller, K.A. Thompson, C. Yeckel Stangenes Industries, Palo Alto, California, USA O.H. Rahman Stony Brook University, Stony Brook, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. A prototype of a high average current polarized electron funneling gun as an eRHIC injector has been built at BNL. The gun was assembled and tested at Stangenes Incorporated. Two beams were generated from GaAs photocathodes and combined by a switched combiner field. We observed the combined beams on a YAG crystal and measured the photocurrent by a Faraday cup. The gun has been shipped to Stony Brook University and is being tested there. In this paper we will describe the major components of the gun and recent beam test results. High voltage conditioning is discussed as well.
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WEPMA011	First Horizontal Test Results of the HZB SRF Photoinjector for BERLinPro	cavity, SRF, operation, cryomodule	2768
	A. Burrill, W. Anders, A. Frahm, J. Knobloch, A. Neumann HZB, Berlin, Germany G. Ciovati, W.A. Clemens, P. Kneisel, L. Turlington JLab, Newport News, Virginia, USA
	The BERLinPro project, a small superconducting RF (SRF) c.w. energy recovery linac (ERL) is being built at Helmholtz-Zentrum Berlin in order to develop the technology required for operation of a high current, 100 mA, 50 MeV ERL. The electron source for the accelerator is a 1.4 cell SRF photoinjector fitted with a multi-alkali photocathode. As part of the HZB photoinjector development program three different SRF photoinjectors will be fabricated and tested. The photoinjector described herein is the second cavity that has been fabricated, and the first photoinjector designed for use with a multi-alkali photocathode. The photoinjector has been built and tested at JLab and subsequently shipped to HZB for testing in the horizontal test cryostat HoBiCaT prior to installation in the photoinjector cryomodule. This cryomodule will be used to measure the photocathode operation in a dedicated experiment called GunLab, the precursor to installation in the BERLinPro hall. This paper will report on the final results of the cavity installed in the helium vessel in the vertical testing dewar at Jefferson Lab as well as the first horizontal test in HoBiCaT
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WEPMA031	Timing Jitter Studies for sub-fs Electron Bunch Generation at SINBAD	laser, electron, simulation, acceleration	2826
	J. Zhu, R.W. Aßmann, U. Dorda, J. Grebenyuk, B. Marchetti DESY, Hamburg, Germany
	Generation of ultra-short electron bunches with a few femtoseconds arrival-time jitter is the major challenge in plasma acceleration with external injection. Meanwhile, peak current stability is also one of the crucial factors for user experiments when the electron bunch is used for free-electron laser (FEL) generation. ARES (Accelerator Research Experiment at SINBAD) will consist of a compact S-band normal-conducting photo-injector providing ultra-short electron bunches of 100 MeV. We present bunch arrival-time jitter studies for two different compression schemes, velocity bunching and magnetic compression with a slit, at ARES with start-to-end simulations. Contributions from various jitter sources are quantified.
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WEPMA036	Double-Cell Notch Filter for SRF Gun Investigations	cathode, SRF, cavity, simulation	2838
	E.N. Zaplatin FZJ, Jülich, Germany A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA J. Knobloch, A. Neumann HZB, Berlin, Germany V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Some projects of SRF guns apply the design where the cathode can be easily and quickly removed. One of the disadvantages of this design is the RF power leakage from the accelerating gun cavity cells to the cathode housing that results in the excessive cathode heating. To minimize the RF power leak different kinds of choke filters are used to protect the cathode structure. These choke filters represent resonant circuits with a zero input impedance and installed at the entrance of the cathode structure that shunt the cathode housing. Still, since the choke filter frequency shift under working conditions is bigger than its bandwidth a filter tuning during assembly only in the warm stage seems insufficient and requires also fine-tuning during operation. To eliminate the problems of the choke filter fine-tuning and hence ensure its stability during operation, a combination of the resonance choke elements can be implemented. In the paper we demonstrate advantages of the double-cell notch filter using BERLinPro SRF gun cavity as an example with its simple design modifications.
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WEPMA044	25 Hz, Sub-mJ Ytterbium Laser Source of RF Gun for SuperKEKB Linac	laser, cavity, polarization, electron	2862
	X. Zhou, T. Natsui, Y. Ogawa, M. Yoshida, R. Zhang KEK, Ibaraki, Japan
	For injector linac of SuperKEKB project, the 5 nC electron beams with double-bunch is expected to be generated in the photocathode RF gun. For the repetition rate of electrum beam, the optional of 2 Hz, 5 Hz, 25 Hz and 50 Hz are requested. Although, more than 5 nC electron with single-bunch has been generated in the 2 Hz and 5 Hz, when the repetition rate increases to 25 Hz, the condition of the laser amplifier system such as the thermal lens effect is changed seriously. To correspond to 25 Hz repetition rate, the ytterbium-doped laser system was reformed. An AuSu (80:20) heat-dissipating solder is employed to reduce the thermal lens effect. Because of the damage threshold limitation of the thin-disk crystal and optical mirrors, Some improvement were performed to increase the quality of the pulses rather than the amplify power, which cause the SHG conversion efficiency is up to 60% and 30% with 2ω and 4ω respectively. More than 3 nC electron beam is obtained with 25 Hz.
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WEPMN012	Cathode Stalk Optimization for a 325 MHz Superconducting QWR Electron Gun	cathode, cavity, electron, impedance	2940
	P.L. Fan, Y.M. Li, L. Lin, K.X. Liu, S.W. Quan, F. Zhu PKU, Beijing, People's Republic of China
	Funding: Work supported by National Basic Research Project (No. 2011CB808302) The structure of cathode stalk is very important for the performance of a superconducting QWR (Quarter Wave Resonator) gun. With improper design, RF power dissipation on the surface of cathode stalk and its surrounding tube can lead to a serious decrease of quality factor for superconducting QWR injector. We present here an optimized design of the cathode stalk for the 325 MHz superconducting QWR gun and special considerations are taken to minimize the power dissipation. The details of microwave simulation, beam dynamic simulation of the cavity with cathode stalks in different length, diameter and position are presented in this paper.
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WEPMN015	Dark Current Imaging Experiment in an L-band RF Gun	cathode, solenoid, electron, experiment	2952
	J.H. Shao, H.B. Chen, J. Shi, D. Wang TUB, Beijing, People's Republic of China S.P. Antipov, S.V. Baryshev, C.-J. Jing, J.Q. Qiu Euclid TechLabs, LLC, Solon, Ohio, USA M.E. Conde, D.S. Doran, W. Gai, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski ANL, Argonne, Illinois, USA F.Y. Wang, L. Xiao SLAC, Menlo Park, California, USA
	The localized high electric field enhancement or low work function is the trigger for strong field emission, which however has yet been well experimentally studied. Using an L-band photocathode gun test stand at Argonne Wakefield Accelerator Facility (AWA), we’ve constructed an imaging beam line to observe field emission current from predefined emitters on cathode. Preliminary experiment results are present. Future plan is discussed.
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WEPMN016	Observation of Dark Current Dependence on Stored Energy in an L-Band RF Gun	cathode, solenoid, experiment, simulation	2956
	J.H. Shao, H.B. Chen, J. Shi, D. Wang TUB, Beijing, People's Republic of China S.P. Antipov, S.V. Baryshev, C.-J. Jing, J.Q. Qiu Euclid TechLabs, LLC, Solon, Ohio, USA M.E. Conde, D.S. Doran, W. Gai, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski ANL, Argonne, Illinois, USA F.Y. Wang, L. Xiao SLAC, Menlo Park, California, USA
	A pin cathode has been installed into an L-band photocathode gun to study the influence of stored energy on field emission. The stored energy was varied by tuning the recess of the cathode in order to have the same E-field on the cathode tip. We have observed 5 times difference of dark current level at the same E-field, while by varying the stored energy by three fold. Dynamics study reveals the difference is not caused by transmission, but by emission process itself. We'll present experiment results and discuss possible mechanisms about the phenomena.
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WEPMN018	Measurement of Cell-Cell Coupling Coefficient in Photocathode RF Gun	coupling, simulation, laser, cathode	2963
	P. Wang, H.B. Chen, Q. Gao, J. Shi, L. Zhang TUB, Beijing, People's Republic of China
	A photocathode RF gun is under cold rest in Tsinghua University. We measured the single cavity frequency and the cell-cell coupling coefficient by the detuning method with high accuracy. We use a simplified model to illustrate the whole process of the measurement. The data obtained in the cold test seem to accord with that from the model very well.
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WEPMN021	Design and Research of Secondary Electron Emission Test Equipment with Low Electron Energy	electron, vacuum, ion, accumulation	2970
	Y.H. Xu, L. Fan, Y.Z. Hong, X.T. Pei, J. Wang, Y. Wang, W. Wei, B. Zhang USTC/NSRL, Hefei, Anhui, People's Republic of China
	In particle accelerators, the secondary electrons resulting from the interaction between particles and vacuum chamber have a great impact on beam quality. Especially for positron, proton and heavy ion accelerators, massive electrons lead to electron cloud, which affects the stability, energy, emittance and beam life adversely. We have studied the secondary electron emission (SEE) of metal used for accelerators. A secondary electron emission measurement system with low electron energy has been designed and used to measure the SEE yield of metal and non-evaporable getter materials. With the equipment, we have obtained the characteristic of the SEE yield of stainless steel and oxygen free copper (OFC).
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WEPMN034	Electron Emission from Surface Roughness on Cavity in Low Temperature	electron, radiation, cavity, vacuum	3003
	H. Kim, H.J. Cha, S. Choi, W.K. Kim, G.-T. Park IBS, Daejeon, Republic of Korea Y. Chang Hanshin University, Kyungki, Republic of Korea
	Electron emission phenomenon from surface roughness on cavity is investigated. The distribution of the electric field from the surface roughness can be obtained on cavity surface. The field emission is calculated from the electric field distribution. The generalized electron emission from electric field and temperature effect is also calculated on the surface roughness of the cavity.
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WEPTY013	Cs2Te Photocathode Performance in the AWA High-charge High-gradient Drive Gun	laser, cathode, wakefield, space-charge	3283
	E.E. Wisniewski, S.P. Antipov, M.E. Conde, D.S. Doran, W. Gai, C.-J. Jing, W. Liu, J.G. Power, C. Whiteford ANL, Argonne, Illinois, USA S.P. Antipov, C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA
	Funding: U.S. Dept of Energy Office of Science under contract number DE-AC02-06CH11357 The unique high-charge L-band, 1.3 GHz, 1.5 cell gun for the new 75 MeV drive beam is in operation at the Argonne Wakefield Accelerator (AWA) facility (see M.E. Conde, this proceedings.) The high-field (> 80 MV/m) photoinjector has a large area, high QE Cesium telluride photocathode (diameter > 30 mm). The photocathode, a crucial component of the upgraded facility, is fabricated on-site. The photoinjector generates high-charge, short pulse, single bunches (Q > 100 nC) and long bunch-trains (Q > 600 nC) for wakefield experiments. The performance of the photocathode for the AWA drive gun is detailed. Quantum efficiency (QE) measurements indicate long, stable photocathode lifetime under demanding conditions.
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WEPTY025	LBNF Hadron Absorber: Mechanical Design and Analysis for 2.4MW Operation	operation, hadron, shielding, target	3318
	B.D. Hartsell, K. Anderson, J. Hylen, V.I. Sidorov, S. Tariq Fermilab, Batavia, Illinois, USA
	Fermilab’s Long-Baseline Neutrino Facility (LBNF) requires an absorber, essentially a large beam dump consisting of actively cooled aluminum and steel blocks, at the end of the decay pipe to stop leftover beam particles and provide radiation protection to people and groundwater. At LBNF’s final beam power of 2.4 MW and assuming the worst case condition of a 204 m long helium filled decay pipe, the absorber is required to handle a heat load of about 750 kW. This results in significant thermal management challenges which have been mitigated by the addition of an aluminum ‘spoiler’ and ‘sculpting’ the central portion of the aluminum core blocks. These thermal effects induce structural stresses which can lead to fatigue and creep considerations. Various accident conditions are considered and safety systems are planned to monitor operation and any accident pulses. Results from these thermal and structural analyses will be presented as well as the mechanical design of the absorber. The design allows each of the core blocks to be remotely removed and replaced if necessary. A shielded remote handling structure is incorporated to hold the hadron monitor when it is removed from the beam.
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WEPTY056	Novel High Power Sources for the Physics of Ionospheric Modification	cathode, simulation, electron, impedance	3398
	B. Beaudoin, T.M. Antonsen, I. Haber, T.W. Koeth, A.H. Narayan, G.S. Nusinovich, K.J. Ruisard UMD, College Park, Maryland, USA J. Rodgers Naval Research Laboratory (NRL), Washington, USA
	Funding: This work is supported by the Air Force Office of Scientific Research under grant FA95501410019. The ionosphere plays a controlling role in the performance of critical civilian and DoD systems including the ELF-ULF communications. The objective of Ionospheric Modification is to control triggered processes to improve the performance of trans-ionospheric C3I systems and develop new applications that take advantage of the ionosphere as an active plasma medium. A key instrument is the Ionospheric Heater, a powerful HF transmitter that modifies the properties of the ionospheric plasma by modulating the electron temperature at preselected altitudes. A major reason for the development of a mobile source is that it would allow investigators to conduct the needed research at different latitudes without building permanent installations. As part of a MURI, UMD will develop a powerful RF source utilizing IOT technology in class-D amplifier mode. This technology was chosen because it has the potential to operate at very high efficiency. Some of the technical challenges presented in this paper will include a gun design that minimizes intercepted current, a compact tunable cavity, an efficient modulator system capable of modulating a high power beam and output couplers to feed the antennas.
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WEPWI024	Vacuum Characterization and Improvement for the Jefferson Lab Polarized Electron Source	ion, electron, vacuum, background	3540
	M.L. Stutzman, P.A. Adderley, M. Poelker JLab, Newport News, Virginia, USA M.A. Mamun Old Dominion University, Norfolk, Virginia, USA
	Operating the JLab polarized electron source with high reliability and long lifetime requires vacuum near the XHV level (<=1x10^-12 Torr). This paper describes ongoing vacuum research at Jefferson Lab including characterization of outgassing rates for surface coatings and heat treatments, ultimate pressure measurements, investigation of pumping including an XHV cryopump, and characterization of ionization gauges in this pressure regime.
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WEPWI033	Effects of Plasma Processing on Secondary Electron Yield of Niobium Samples	electron, plasma, cavity, vacuum	3558
	M. Basovic, S. Popović, M. Tomovic, L. Vušković ODU, Norfolk, Virginia, USA F. Čučkov, A. Samolov University of Massachusetts Boston, Boston, Massachusetts, USA
	Impurities deposited on the surface of Nb during both the forming and welding of accelerator cavities add to the imperfections of the sheet metal, which then affects the overall performance of the cavities. This leads to a drop in the Q factor and limits the maximum acceleration gradient achievable per unit length of the cavities. The performance can be improved either by adjusting the fabrication and preparation parameters, or by mitigating the effects of fabrication and preparation techniques used. We have developed the experimental setup to determine Secondary Electron Yield (SEY) from the surface of Nb samples. Our aim is to show the effect of plasma processing on the SEY of Nb. The setup measures the secondary electron energy distribution at various incident angles as measured between the electron beam and the surface of the sample. The goal is to determine the SEY on non-treated and plasma treated surface of electron beam welded samples. Here we describe the experimental setup, plasma treatment device, and fabrication and processing of the Nb samples.
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WEPWI049	Commissioning of the 112 MHz SRF Gun and 500 MHz Bunching Cavities for the CeC PoP Linac	SRF, bunching, experiment, electron	3597
	S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, V. Litvinenko, G. Narayan, P. Orfin, I. Pinayev, T. Rao, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, Q. Wu, B. P. Xiao, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, T. Xin Stony Brook University, Stony Brook, USA P.A. McIntosh, A.J. Moss, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE. The Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL includes a short electron linac. During Phase I a 112 MHz superconducting RF photoemission gun and two 500 MHz normal conducting bunching cavities were installed and commissioned. The paper describes the Phase I linac layout and presents commissioning results for the cavities and associated RF, cryogenic and other sub-systems.
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WEPWI050	SRF and RF Systems for LEReC Linac	cavity, SRF, electron, booster	3600
	S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, A.V. Fedotov, G.T. McIntyre, S. Polizzo, K.S. Smith, R. Than, J.E. Tuozzolo, Q. Wu, B. P. Xiao, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE. The Low Energy RHIC electron Cooling (LEReC) is under development at BNL to improve RHIC luminosity at low energies. It will consist of a short electron linac and two cooling sections, one for blue and one for yellow beams. For the first stage of the project, LEReC-1, we will to install a 704 MHz superconducting RF cavity and two normal conducting cavities operating at 704 MHz and 2.1 GHz. The SRF cavity will boost the electron beam energy up to 2 MeV. The warm cavities will be used to correct the energy spread introduced in the SRF cavity. The paper describes layouts of the SRF and RF systems, their parameters and status.
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Paper

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MOPWA029

Investigations of the Space-Charge-Limited Emission in the L-Band E-Xfel Photoinjector at Desy-Pitz

simulation, space-charge, cathode, electron

162

Y. Chen, H. De Gersem, E. Gjonaj, A.V. Tsakanian, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany
C. Hernandez-Garcia
JLab, Newport News, Virginia, USA
M. Krasilnikov, F. Stephan
DESY Zeuthen, Zeuthen, Germany

Funding: work supported by DESY Hamburg and Zeuthen Sites
This paper discusses the numerical modelling of electron bunch emission for an L-band normal conducting RF photogun. The main objective is clarifying the discrepancies between measurements and simulations performed for the European X-ray Free Electron Laser (E-XFEL) injector at DESY-PITZ. An iterative beam dynamics simulation procedure is proposed for the calculation of the total extracted bunch charge under the assumption that the emission source operates at the space-charge limit of the gun. This algorithm has been implemented in the three-dimensional full electromagnetic PIC Solver of the CST Particle Studio (CST-PS)*. Simulation results are in good agreements with measurements for a series of operation parameters. Further comparisons with a conventional Poisson-solver-based (PSB) tracking algorithm demonstrates the great significance of transient electromagnetic field effects for the beam dynamics in high brightness electron sources.
* Computer Simulation Technology AG, http://www.cst.com/

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MOPJE006

Electron Gun Longitudinal Jitter: Simulation and Analysis

electron, timing, linac, simulation

297

M.S. Liu, Y.L. Chi, S. Pei, Y.F. Sui
IHEP, Bejing, People's Republic of China

The beam longitudinal jitter is fatal not only for the electron beam performance but also for the positron yield in routine operation of the Beijing Electron Positron Collider II (BEPCII) linear accelerator (Linac). Practically, longitudinal jitter has been observed many times which decreased the beam performance. We simulated the electron gun longitudinal jitter effect by PARMELA software in bunch capture process and analyzed its results about beam performance including average energy, energy spread, emittance and longitudinal phase of reference particle. We adjusted the electron gun trigger time during one cycle without changing other parameters. The percentage difference between maximum and minimum of average energy, energy spread, emittance and longitudinal phase of reference particle was 11.3%, 42%, 98% and 6.4%, respectively. It is observed and analyzed that gun trigger time longitudinal jitter is fatal for maintaining good beam performance. This analysis also gives a salutary lesson to any other longitudinal jitter which can affect the beam bunching in pre-injector .

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MOPMA043

Longitudinal Bunch Shaping at Picosecond Scales using Alpha-BBO Crystals at the Advanced Superconducting Test Accelerator

electron, laser, linac, space-charge

643

B. Beaudoin
UMD, College Park, Maryland, USA
D.R. Edstrom, A.H. Lumpkin, J. Ruan, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA

Funding: This works is supported by the University Research Association, Inc. Operated by the Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
The Integrable Optics Test Accelerator (IOTA) electron injector at Fermilab will enable a broad range of experiments at a national laboratory in order to study and develop solutions to the limitations that prevent the propagation of high intensity beams at picosecond lengths. One of the most significant complications towards increasing short-beam intensity is space-charge, especially in the vicinity of the gun. A few applications that require a longitudinally shaped electron beam at high intensities are for, the generation of THz waves and dielectric wakefields, each of which will encounter the effects of longitudinal space-charge. This paper investigates the effects of longitudinal space-charge on alpha-BBO UV laser shaped electron bunches in the vicinity of the 1½cell 1.3 GHz cylindrically symmetric RF photocathode gun.

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MOPHA006

A Slow RF-Laser Feedback for PHIL Photoinjector

laser, feedback, electron, controls

784

N. ElKamchi, V. Chaumat, V. Soskov
LAL, Orsay, France

PHIL is an electron beam accelerator at LAL. It produces low energy (E<5 MeV) and high current (1 nC/bunch) electrons bunch at a repetition frequency of 5Hz. The stability of the beam charge at PHIL is a key issue for the succeful operation of the physic experiences that use the machine. At PHIL, the beam charge is quite stable, but we often note a slow charge drift on long duration experiences. Two ICTs, and a back-end electronics are used to monitor the stability of the beam charge, with an accuracy of about 1pC. Several types of jitter can impact the stability of the beam charge. The fluctuations of the RF power or the RF-laser relative phase drift could have significant influence, due to temperature variations that produce cables dilataion, and electronic components overheating. To correct the phase drift, we describe a method based on a slow analog-digital feedback loop between the RF wave in the gun (3 GHz) and the synchronisation signal of the laser (75MHz). It allows to maintain the jitter between the laser pulse and the RF wave stable at a very low value. As a result, the electron beam charge is maintained at a stable level, to meet the requirements of the users.

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MOPHA028

Operation of Normal Conducting RF Guns with MicroTCA.4

LLRF, cavity, feedback, operation

841

M. Hoffmann, V. Ayvazyan, J. Branlard, L. Butkowski, M.K. Grecki, U. Mavrič, M. Omet, S. Pfeiffer, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany
W. Fornal, R. Rybaniec
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
A. Piotrowski
FastLogic Sp. z o.o., Łódź, Poland

During the last half year, the MicroTCA.4 based single cavity LLRF control system was installed and commissioned at several normal conducting facilities at DESY (FLASH RF gun, REGAE, PITZ RF gun, and XFEL RF gun). First tests during the last year show promising results in optimizing the system for high speed digital LLRF feedbacks, i.e. reducing system latency, increasing the internal controller processing speed, testing new control schemes, and optimizing controller parameters. In this contribution we will present results and gained experience from the commissioning phase and the first time period of real operation.

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MOPHA033

Physical Parameter Identification of Cross-Coupled Gun and Buncher Cavity at REGAE

resonance, cavity, coupling, higher-order-mode

857

A.S. Nawaz, H. Werner
TUHH, Hamburg, Germany
M. Hoffmann, S. Pfeiffer, H. Schlarb
DESY, Hamburg, Germany

A reasonable description of the system dynamics is one of the key elements to achieve high performance control for accelerating modules. This paper depicts the system identification of a cross-coupled pair of cavities for the Relativistic Electron Gun for Atomic Exploration - REGAE. Two normal conducting copper cavities driven by a single RF source accelerate and compress a low charge electron bunch with sub 10 fs length at a repetition rate up to 50 Hz. It is shown how the model parameters of the cavities and the attached radio frequency subsystem are identified from data generated at the REGAE facility.

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MOPTY002

Bunch Length Measurement of Femtosecond Electron Beam by Monitoring Coherent Transition Radiation

electron, detector, radiation, linac

940

I. Nozawa, M. Gohdo, K. Kan, T. Kondoh, A. Ogata, J. Yang, Y. Yoshida
ISIR, Osaka, Japan

Ultrashort electron bunches with durations of femtoseconds and attoseconds are essential for time-resolved measurements, including pulse radiolysis and ultrafast electron microscopy. However, generation of the ultrashort electron bunches is commonly difficult because of bunch length growth due to space charge effect, nonlinear momentum dispersion and so on. Several bunch length measurement methods for the ultrashort electron beams have also been considered so far, which have not been established yet. In this study, the femtosecond electron beams were generated using a laser photocathode radio-frequency gun linac and a magnetic bunch compressor. The bunch length measurement was carried out using a Michelson interferometer based on monitoring coherent transition radiation (CTR), which is characterized by square modulus of the Fourier transform of the longitudinal bunch distribution. Analyzing the experimentally obtained interferograms of CTR, the electron beams with the average duration of 5 fs were generated and measured successfully at the condition of bunch charge of 1 pC. Consideration of the longitudinal bunch shapes was also carried out using the Kramers-Kronig relation.

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MOPTY015

Beam Compression Dynamics and Associated Measurement Methods in Superconducting THz Source

controls, simulation, space-charge, electron

969

Z. Zhou, Y.-C. Du, W.-H. Huang
TUB, Beijing, People's Republic of China

To ensure the quality of high brightness electron beams needed by the terahertz FEL facility at China academy of engineering physics(CAEP), which aims to obtain 100 to 300 terahertz light, a feed-back control system is required to monitor the amplitude and phase jittering by measuring beam arrival time as well as bunch length at the site of the beam position monitor(BPM). In this paper, we make an idealized model of injector section and deduce analytic expressions of bunch arrival time and bunch length. In consideration of the space charge effect on bunch lengthening, bunch arrival time and bunch length as a function of DC gun voltage, buncher field amplitude and buncher phase is carefully calibrated by means of particle in cell (PIC) simulation. With the time and space resolution of the BPM, the control accuracy of phase is estimated to be 0.01 degree, while the amplitude is 0.04%.

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MOPTY023

Beam Diagnostic of the LINAC for the Compact High-Performance THz-FEL

linac, FEL, emittance, target

987

T. Hu, Q.S. Chen, K.F. Liu, B. Qin, P. Tan, Y.Q. Xiong, J. Yang
HUST, Wuhan, People's Republic of China
W. Chen
Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China
J. Liu, Y.J. Pei, Z.X. Tang
USTC/NSRL, Hefei, Anhui, People's Republic of China
Z.M. Wang
Chinagray, Hefei, Anhui, People's Republic of China

With the aim to obtain short-pulse bunches with high peak current for a terahertz radiation source, an FEL-based LINAC is employed in HUST THz-FEL, and the LINAC consists of an EC-ITC RF gun, a disk-loaed waveguide structure with a constant gradient and collinear absorbing loads with focusing coils surrounded and so on. To achieve a balance between compactness and high performance, beam diagnostic system should be simple and high-precision. So that a cost-effective measurement scheme for the high-brightness beam extracted by the LINAC is needed. This paper will describe the beam line and beam diagnostic system of the LINAC in the HUST THz-FEL in detail and give corresponding assembly scheme. In addition, online monitor system is introduced.

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MOPWI005

Emittance and Optics Measurements on the Versatile Electron Linear Accelerator at Daresbury Laboratory

space-charge, quadrupole, emittance, coupling

1153

C.P. Topping, D.J. Scott, A. Wolski
Cockcroft Institute, Warrington, Cheshire, United Kingdom
S.D. Barrett, C.P. Topping, A. Wolski
The University of Liverpool, Liverpool, United Kingdom
B.L. Militsyn, D.J. Scott
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The Versatile Electron Linear Accelerator (VELA) is a facility designed to provide a high quality electron beam for accelerator systems development, as well as industrial and scientific applications. Currently, the RF gun can deliver short (of order a few ps) bunches with charge in excess of 250 pC at up to 5.0 MeV/c beam momentum. Measurement of the beam emittance and optics in the section immediately following the gun is a key step in tuning both the gun and the downstream beamlines for optimum beam quality. We report the results of measurements (taking account of coupling and space charge) indicating normalised emittances of order 0.5 μm at low bunch charge.

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MOPWI028

Initial Experimental Results of a Machine Learning-Based Temperature Control System for an RF Gun

controls, cavity, monitoring, network

1217

A.L. Edelen, S. Biedron, S.V. Milton
CSU, Fort Collins, Colorado, USA
B.E. Chase, D.J. Crawford, N. Eddy, D.R. Edstrom, E.R. Harms, J. Ruan, J.K. Santucci, P. Stabile
Fermilab, Batavia, Illinois, USA

Colorado State University (CSU) and Fermi National Accelerator Laboratory (Fermilab) have been developing a control system to regulate the resonant frequency of an RF electron gun. As part of this effort, we present experimental results for a benchmark temperature controller that combines a machine learning-based model and a predictive control algorithm for improved settling time, overshoot, and disturbance rejection relative to conventional techniques. Such improvements have implications for machine up-time and management of reflected power. This work is part of an on-going effort to develop adaptive, machine learning-based tools specifically to address control challenges found in particle accelerator systems.

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MOPWI032

Analysis of Primary Stripper Foils at SNS by an Electron Beam Foil Test Stand

electron, proton, operation, experiment

1230

E.P. Barrowclough, C.S. Feigerle
University of Tennessee, Knoxville, Tennessee, USA
C.F. Luck, M.A. Plum, R.W. Shaw, L.L. Wilson
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
Diamond foils are used at the Spallation Neutron Source (SNS) as the primary strippers of hydride ions. A nanocrystalline diamond film, typically 17x45 mm with an aerial density of 0.35 mg/cm², is deposited on a corrugated silicon substrate by plasma-assisted chemical vapor deposition. After growth, 30 mm of the silicon substrate is etched away, leaving a freestanding diamond foil with a silicon handle that can be inserted into SNS for operation. An electron beam test facility was constructed to study stripper foil degradation and impact on foil lifetime. The electron beam capabilities include: current up to 5 mA, focused spot size of 0.30 mm², and rastering in the x- and y-directions. A 30 keV and 1.6 mA/mm² electron beam deposits the same power density on a diamond foil as a 1.4 MW beam on SNS target. Rastering of the electron beam can expose a similar area of the foil as SNS beams. Experiments were conducted using the foil test stand to study: foil flutter and lifetime; effects of corrugation patterns, aerial densities, crystal size (micro vs. nano), and boron doping; temperature distributions and film emissivity; and conversion rate of nanocrystalline diamond into graphite.

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TUYB1

Progress of SuperKEKB

emittance, positron, electron, linac

1291

T. Miura, T. Abe, T. Adachi, K. Akai, M. Akemoto, A. Akiyama, D.A. Arakawa, Y. Arakida, Y. Arimoto, M. Arinaga, K. Ebihara, K. Egawa, A. Enomoto, J.W. Flanagan, S. Fukuda, H. Fukuma, Y. Funakoshi, K. Furukawa, T. Furuya, K. Hara, T. Higo, H. Hisamatsu, H. Honma, T. Honma, R. Ichimiya, N. Iida, H. Iinuma, H. Ikeda, M. Ikeda, T. Ishibashi, H. Ishii, M. Iwasaki, A. Kabe, T. Kageyama, H. Kaji, K. Kakihara, S. Kamada, T. Kamitani, S. Kanaeda, K. Kanazawa, H. Katagiri, S. Kato, S. Kazama, M. Kikuchi, T. Kobayashi, H. Koiso, Y. Kojima, M. Kurashina, K. Marutsuka, M. Masuzawa, S. Matsumoto, T. Matsumoto, H. Matsushita, S. Michizono, K. Mikawa, T. Mimashi, F. Miyahara, K. Mori, T. Mori, A. Morita, Y. Morita, H. Nakai, H. Nakajima, T.T. Nakamura, K. Nakanishi, K. Nakao, H. Nakayama, T. Natsui, M. Nishiwaki, J.-I. Odagiri, Y. Ogawa, K. Ohmi, Y. Ohnishi, S. Ohsawa, Y. Ohsawa, N. Ohuchi, K. Oide, T. Oki, M. Ono, H. Sakai, Y. Sakamoto, S. Sasaki, M. Sato, M. Satoh, K. Shibata, T. Shidara, M. Shirai, A. Shirakawa, M. Suetake, Y. Suetsugu, R. Sugahara, H. Sugimoto, T. Suwada, S. Takasaki, T. Takatomi, T. Takenaka, Y. Takeuchi, M. Tanaka, M. Tawada, S. Terui, M. Tobiyama, N. Tokuda, K. Tsuchiya, X. Wang, K. Watanabe, H. Yamaoka, Y. Yano, K. Yokoyama, Ma. Yoshida, M. Yoshida, S.I. Yoshimoto, K. Yoshino, R. Zhang, D. Zhou, X. Zhou, Z.G. Zong
KEK, Ibaraki, Japan
D. Satoh
TIT, Tokyo, Japan

This presentation will cover the status of the installation and the injector commissioning status of SuperKEKB. The IR optics and design with very low β^* of less than 1 mm will be discussed.

Slides TUYB1 [6.588 MB]

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TUAD3

LLRF Commissioning of the European XFEL RF Gun and Its First Linac RF Station

LLRF, linac, cryomodule, electronics

1377

J. Branlard, G. Ayvazyan, V. Ayvazyan, L. Butkowski, M.K. Grecki, M. Hoffmann, F. Ludwig, U. Mavrič, M. Omet, S. Pfeiffer, K.P. Przygoda, H. Schlarb, Ch. Schmidt, H.C. Weddig, B.Y. Yang
DESY, Hamburg, Germany
S. Bou Habib, K. Czuba, M. Grzegrzółka, E. Janas, K. Oliwa, J. Piekarski, K.T. Pozniak, I. Rutkowski, R. Rybaniec, D. Sikora, W. Wierba, L.Z. Zembala, M. Żukociński
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
W. Cichalewski, D.R. Makowski, A. Mielczarek, P. Perek
TUL-DMCS, Łódź, Poland
A. Piotrowski
FastLogic Sp. z o.o., Łódź, Poland

The European X-ray free electron laser (XFEL) at the Deutsches Elektronen-Synchrotron (DESY), Hamburg Germany is in its construction phase. Approximately a third of the super-conductive cryomodules have been produced and tested. The RF gun is installed since 2013; periods of commissioning are regularly scheduled between installation phases of the rest of the injector. The first linac, L1, consisting of 4 cryomodules powered by one 10 MW klystron is installed and being commissioned. This contribution reports on the installation and preparation work of the low-level radio frequency system (LLRF) to perform the commissioning of the XFEL first components. The commissioning plans, schedule and first results are presented.

Slides TUAD3 [14.016 MB]

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TUPWA009

50 MeV Electron Linac with a RF Gun and a Thermoionic Cathode

linac, cavity, focusing, cathode

1413

A.S. Setty, A.S. Chauchat, D. Fasse, D. Jousse, P. Sirot
Thales Communications & Security (TCS), Gennevilliers Cedex, France

The low energy part of our pre injectors is made up of a 90 kV DC themoionic trioode gun, followed by a 500 MHz sub harmonic prebuncher and a 3 GHz prebuncher. We propose a new design for a 50 MeV linac with a RF gun *. this study will compare the beam dynamics simulations for the new design and for our previous pre injectors.
* A. Setty et al. "Study of a RF gun with a Thermoionic Cathode", Proceeding IPAC 2014, Germany, Dresden, June 2014.

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TUPWA018

Progress Report of the Berlin Energy Recovery Project BERLinPro

SRF, booster, cavity, electron

1438

M. Abo-Bakr, W. Anders, K.B. Bürkmann-Gehrlein, A. Burrill, A.B. Büchel, P. Echevarria, A. Frahm, H.-W. Glock, A. Jankowiak, C. Kalus, T. Kamps, G. Klemz, J. Knobloch, J. Kolbe, J. Kühn, O. Kugeler, B.C. Kuske, P. Kuske, A.N. Matveenko, A. Meseck, R. Müller, A. Neumann, N. Ohm, K. Ott, E. Panofski, F. Pflocksch, D. Pflückhahn, J. Rahn, J. Rudolph, M. Schmeißer, O. Schüler, J. Völker
HZB, Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association
The Helmholtz Zentrum Berlin is constructing the Energy Recovery Linac Project BERLinPro on its site in Berlin Adlershof. The project is intended to expand the required accelerator physics and technology knowledge mandatory for the design, construction and operation of future synchrotron light sources. The project goal is the generation of a high current (100 mA), high brilliance (norm. emittance below 1 mm mrad) cw electron beamat 2~ps rms bunch duration or below. The planning phase of the project is completed and the design phase of most of the components is finished. Many of them have already been ordered. After some delay the construction of the building has started in February 2015. The status of the various subprojects as well as a summary of current and future activities will be given. Major project milestones and details of the project time line will be finally introduced.

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TUPWA023

A Step Closer to the CW High Brilliant Beam with the ELBE SRF-Gun-II

SRF, cavity, cathode, electron

1456

R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate
HZDR, Dresden, Germany

In order to achieve the CW electron beam with a high average current up to 1 mA and a very low emittance of 1 μm, an improved superconducting photo-injector (ELBE SRF-Gun-II) has been installed and commissioned at HZDR since 2014. This new gun replaces the first 3.5-cell SRF gun (SRF-Gun-I) at the SC Linac ELBE. The RF performance of the niobium cavity has been evaluated, the beam parameters for low charge bunches have been measured, and the first beam has been guided into the ELBE beam line. The results agree with the simulation very well. The photocathode transfer system has been installed for the first high current beam test planned in 2015. However, the unexpected strong degradation on the cavity and also on the photocathode was found soon after the first photocathode exchange. In this contribution the results of the SRF-Gun-II commissioning and the latest experiment will be presented in detail.

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TUPWA028

Simulation Results of the Beam Transport of Ultra-Short Electron Bunches in Existing Beam Transfer Lines to Sinbad

linac, optics, electron, synchrotron

1466

U. Dorda, R.W. Aßmann, K. Flöttmann, B. Marchetti, Y.C. Nie, J. Zhu
DESY, Hamburg, Germany

SINBAD, the upcoming accelerator R&D facility at DESY, will host multiple independent experiments on the production and acceleration of ultra-short bunches including plasma wakefield experiments. As a possible later upgrade the option to transport higher energy electrons (up to 800 MeV) or positrons (up to 400 MeV) from the existing DESY Linac 2 to the facility is studied. Though existing a possible connection using e.g. a part of the DESY synchrotron as a transfer line and other currently unused transfer-line, these machines were not designed for the desired longitudinal bunch compression and high peak current required by e.g. beam driven plasma wake-field experiments. Simulation results illustrate the modifications to the current layout that would have to be implemented and the corresponding achievable beam parameters are given.

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TUPWA032

Progress in the Injector Upgrade of the LINAC II at DESY

electron, linac, simulation, solenoid

1479

Y.C. Nie, M. Hüning, C. Liebig, M. Schmitz
DESY, Hamburg, Germany

A new injection system is under development for the LINAC II at DESY to improve the reliability of the machine and mitigate the radiological problem due to electron losses at energy of hundreds of MeV. It consists of a 100 kV triode DC gun, a 2.998 GHz pre-buncher, a novel 2.998 GHz hybrid buncher, and the dedicated beam transport and diagnostic elements. As the key components, the pre-buncher and the hybrid buncher realize a two-stage velocity bunching process including the ballistic bunching and the phase space rotation. Therefore, they produce a certain number of well-bunched 5 MeV micro-bunches from the input 2 ns-50 ns electron pulse for the downstream LINAC II. The overall upgrade plan, developments of the critical components, as well as the latest beam test results will be reported.

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TUPWA042

Status of the Accelerator Physics Test Facility FLUTE

electron, linac, diagnostics, laser

1506

M.J. Nasse, A. Bernhard, I. Birkel, A. Borysenko, A. Böhm, S. Hillenbrand, N. Hiller, S. Höninger, S. Marsching, A.-S. Müller, R. Rossmanith, R. Ruprecht, M. Schuh, M. Schwarz, B. Smit, S. Walther, M. Weber, P. Wesolowski
KIT, Karlsruhe, Germany
R.W. Aßmann, M. Felber, K. Flöttmann, C. Gerth, M. Hoffmann, P. Peier, H. Schlarb, B. Steffen
DESY, Hamburg, Germany
R. Ischebeck, B. Keil, V. Schlott, L. Stingelin
PSI, Villigen PSI, Switzerland

A new compact versatile linear accelerator named FLUTE (Ferninfrarot Linac Und Test Experiment) is currently under construction at the Karlsruhe Institute of Technology (KIT). It will serve as an accelerator test facility and allow conducting a variety of accelerator physics studies. In addition, it will be used to generate intense, ultra-short THz pulses for photon science experiments. FLUTE consists of a ~7 MeV photo-injector gun, a ~41 MeV S-band linac and a D-shaped chicane to compress bunches to a few femtoseconds. This contribution presents an overview of the project status and the accompanying simulation studies.

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TUPWA046

Facility Upgrade at PITZ and First Operation Results

laser, plasma, operation, electron

1518

A. Oppelt, P. Boonpornprasert, A. Donat, J.D. Good, M. Groß, H. Huck, I.I. Isaev, L. Jachmann, D.K. Kalantaryan, M. Khojoyan, W. Köhler, G. Koss, G. Kourkafas, M. Krasilnikov, O. Lishilin, D. Malyutin, J. Meissner, D. Melkumyan, M. Otevřel, M. Penno, B. Petrosyan, S. Philipp, M. Pohl, Y. Renier, T. Rublack, B. Schöneich, J. Schultze, F. Stephan, F. Tonisch, G. Trowitzsch, G. Vashchenko, R.W. Wenndorff
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
M. A. Bakr
Assiut University, Assiut, Egypt
C. Hernandez-Garcia
JLab, Newport News, Virginia, USA
G. Pathak
Uni HH, Hamburg, Germany
D. Richter
HZB, Berlin, Germany

The Photo Injector Test facility at DESY, Zeuthen site (PITZ), develops, optimizes and characterizes high brightness electron sources for free electron lasers like FLASH and the European XFEL. In the last year, the facility was significantly upgraded by the installation of a new normal conducting radio- frequency (RF) gun cavity with its new waveguide system for the RF feed, which should allow stable and reliable gun operation, as required for the European XFEL. Other relevant additions include beamline modifications for improving the electron beam transport through the PITZ accelerator, extending the beam-based measurement capabilities, and preparing the installation of a plasma cell. Furthermore, the laser hutch was re-arranged in order to be able to house an additional, new photo cathode drive laser system which should be able to produce 3D ellipsoidal laser pulses to further improve the electron beam quality. This paper describes in detail the aforementioned facility upgrades and reports on the first operation experience with the new gun setup.

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TUPWA056

New Gun Implementation and Performance of the DAΦNE LINAC

linac, cathode, electron, operation

1546

B. Buonomo, L.G. Foggetta, G. Piermarini
INFN/LNF, Frascati (Roma), Italy

A new electron gun system has been developed for DAΦNE LINAC, and put into operation since January 2014. Several elements of the system were upgraded, including a new grid pulser, an improved bias voltage system and a renewed cathode socket. The new LINAC gun has now a wider range of parameters, i.e. the emission pulse length spans from 1.4ns up to 40ns, while the better control of the grid and bias voltage allows a maximum peak current of 5A with a pulse repetition rate of 50 Hz. This paper describes the details of the pulser, the power supply, the socket, all the service components of the upgraded gun and its integration in the main LINAC control system. A report on the performance of the LINAC with the new gun will follow.

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TUPWA058

Study of a C-band Harmonic RF System to Optimize the RF Bunch Compression Process of the SPARC Beam

cavity, linac, experiment, emittance

1552

A. Gallo, D. Alesini, M. Bellaveglia, M. Ferrario
INFN/LNF, Frascati (Roma), Italy
A. Bacci, V. Petrillo, A.R. Rossi, L. Serafini
Istituto Nazionale di Fisica Nucleare, Milano, Italy
F. Cardelli, L. Piersanti
INFN-Roma1, Rome, Italy
B. Marchetti
DESY, Hamburg, Germany
M. Rossetti Conti
Universita' degli Studi di Milano & INFN, Milano, Italy

The SPARC linac at the INFN Frascati Labs is a high brilliance electron source with a wide scientific program including production of THz and Thomson backscattering radiation, FEL studies and plasma wave acceleration experiments. The linac is based on S-band RF and consists in an RF Gun followed by 3 accelerating structures, while an energy upgrade based on 2 C-band accelerating structures is ready to be implemented. Short bunches are ordinarily produced by using the linear RF bunch compression concept. A harmonic RF structure interposed between the Gun and the 1st accelerating structure can be used to optimize the RF compression by a longitudinal phase space pre-correction, allowing to reach shorter bunches, a much more uniform current distribution and in general to control better the whole compression process. Here we report the results of numerical studies on the SPARC bunch compression optimization through the use of a harmonic cavity, and the design of a C-band RF system to implement it. The proposed system consists in a multi-cell SW cavity powered by a moderate portion of the total RF power spilled from the C-band power plant already installed for the linac energy upgrade.

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TUPWA065

Generation of Multi-bunch Beam with Beam Loading Compensation by Using RF Amplitude Modulation in Laser Undulator Compact X-ray (LUCX)

cavity, electron, laser, booster

1576

M.K. Fukuda, S. Araki, Y. Honda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
K. Sakaue, M. Washio
RISE, Tokyo, Japan

We have developed a compact X-ray source based on inverse Compton scattering between an electron beam and a laser pulse stacked in an optical cavity at Laser Undulator Compact X-ray (LUCX) accelerator in KEK. The accelerator consists of a 3.6 cell photo-cathode rf-gun, a 12cell standing wave accelerating structure and a 4-mirror planar optical cavity. Our aim is to obtain a clear X-ray image in a shorter period of times and the target flux of X-ray is 1.7x10⁷ photons/pulse with 10% bandwidth at present. To achieve this target, it is necessary to increase the intensity of an electron beam to 500nC/pulse with 1000 bunches at 30 MeV. Presently, we have achieved the generation of 24MeV beam with total charge of 600nC in 1000bunches with beam-loading compensation by using the delta T method and the amplitude modulation of RF pulse. The bunch-by-bunch energy difference is within 1.3% peak to peak. We will report the results of the multi-bunch beam generation and acceleration in this accelerator.
This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

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TUPWA068

Simulation Study of Beam Halo and Loss for KEK Compact ERL

simulation, cavity, laser, electron

1587

O. Tanaka, T. Miyajima, N. Nakamura, S. Sakanaka, M. Shimada
KEK, Ibaraki, Japan

At the KEK Compact ERL (cERL) designed to operate at high-brilliance and high-current electron beams, the maximum averaged current was recorded at 6.5 muA for the beam energy of 20 MeV on March 2014 and should be increased up to 10 mA in a step-by-step manner in a few years. In order to increase the beam current by reducing the beam loss, we need to know the mechanism of the beam loss. For this purpose we investigate beam halo originated from characteristics and imperfections of an electron gun system, using the tracking code GPT (General Particle Tracer). The beam halo can be lost by the beam-pipe apertures and the collimators in the cERL beam line. In this paper, we will present the simulation results including the beam halo formation and the beam loss distribution along the beam line.

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TUPWA071

Improvements of the Laser System for RF-Gun at SuperKEKB Injector

laser, electron, operation, cryogenics

1598

R. Zhang, T. Natsui, Y. Ogawa, M. Yoshida, X. Zhou
KEK, Ibaraki, Japan

For realizing higher charge and low emittance electron and positron beams in SuperKEKB, we have been making improvements in laser system for RF-gun. The difficulty in controlling thermomechanical distortions has been one of the most important factors for preserving high laser conversion efficiency of infrared-to-ultraviolet and operating at higher repetition rate. We demonstrated that efficient removal of waste heat can be realized by adopting Yb:YAG and copper bonding composite via Au-Sn solder. On the other hand, we proposed the novel design of the cascade laser configuration. Base on this, we can improve the quantum efficiency by utilizing other Yb ions doped crystals as active medium which are pumped by 1035 nm Yb:YAG laser. Excellent thermal management and high charge beams have been achieved by improvements of these two aspects. Additionally, in order to employ high duty ratio pump system and realize laser operation at high repetition rate, we investigated the laser operation in cryogenic environment. A perspective towards the next step experiment is also presented in this paper.

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TUPJE003

Quasi-Traveling Wave RF Gun and Beam Commissioning for SuperKEKB

laser, cathode, emittance, cavity

1610

T. Natsui
The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan
Y. Ogawa, M. Yoshida, X. Zhou
KEK, Ibaraki, Japan

We are developing a new RF gun for SuperKEKB. High charge low emittance electron and positron beams are required for SuperKEKB. We will generate 7.0 GeV electron beam at 5 nC 20 mm-mrad by J-linac. In this linac, a photo cathode S-band RF gun will be used as the electron beam source. For this reason, we are developing an advanced RF gun which has two side coupled standing wave field. We call it quasi-traveling wave side couple RF gun. This gun has a strong focusing field at the cathode and the acceleration field distribution also has a focusing effect. This RF gun has been installed in the KEK J-linac. Beam commissioning with the RF gun is in progress.

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TUPJE009

Study on Frequency Multiplier of a Pulsed Laser Repetition using an Optical Cavity

laser, cavity, electron, cathode

1629

T. Kobayashi
Waseda University, Tokyo, Japan

We have been studying a compact electron accelerator based on an S-band Cs-Te photo-cathode rf gun at Waseda University. The system is using S-band rf of 2856MHz. When a repetition of the electron bunch is integral multiple of rf, it enables a lot of electron bunch acceleration for the rf gun. The repetition of the electron bunch generated by a photo-cathode rf gun depends on the oscillating frequency of the pulsed mode-locked laser. We have been developing a mode-locked Yb-doped fiber laser based on Non-Linear Polarization Rotation (NLPR). However, its repetition is limited by the fiber length to produce NLPR. Therefore, we have started to develop the external optical cavity which is multiplier of a pulsed laser repetition. It would enable the rf gun to generate high-dose electron beam in a very short time. In this conference, we will report design of the external optical cavity to multiply the pulsed laser repetition, the experimental results of the frequency multiplying of a mode-locked Yb-doped fiber laser, and the future prospects.
Work supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

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TUPJE010

Study of Cs-Te Photocathode for RF Electron Gun

electron, vacuum, radiation, scattering

1632

S. Matsuzaki, M. Nishida, K. Sakaue, M. Washio
Waseda University, Tokyo, Japan
H. Iijima
Tokyo University of Science, Tokyo, Japan

At Waseda University, we have been studying high quality electron beam with an rf electron gun. In recent accelerator study and application researches, high quality electron beam are strongly required. Photocathode is a key component to generate higher quality electron beam. Cs-Te photocathode shows high quantum efficiency (Q.E.) (~10%) and has long life time (~several months). From 2013, we built a photocathode evaporation chamber and started photocathode study. In this study, our purpose is to clarify their property and to establish an ideal evaporation recipe. We succeeded in producing high quality Cs-Te photocathode, and electron beam generated by our Cs-Te photocathode shows high charge (4.6nC/bunch) and high Q.E. (1.74%) in our rf electron gun. Furthermore, we found a Q.E. recovery after Cs deposition process and it causes higher Q.E. than usual due to, we believe, Cs deposition quantity or Cs deposition speed. Thus we are now surveying the optimum Cs evaporation parameters. In this conference, we will report a detail of our photocathode development system, the latest progress of optimization study of Cs-Te photocathode and future plans.
Work supported by Cooperative and Supporting Program for Researches and Educations in Universities and NEDO(New Energy and Industrial Technology Development Organization.

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TUPJE014

An X-Band Linac with Tunable Beam Energy

linac, electron, simulation, software

1644

L. Zhang, H.B. Chen, Y.-C. Du, Q.X. Jin, J. Shi, C.-X. Tang, P. Wang, Z. Zhang
TUB, Beijing, People's Republic of China

The low-energy X-band linac has a wide application in medical imaging. In this paper, an X-band linac is designed to produce beam energy between 0.5MeV and 1.5MeV, and the output beam energy is continuously adjustable within this range. Two sections of linacs are combined and powered by a single microwave source. During the experiment, we can tune the RF phase and amplitude of the second section of the linac, the electron beam can see either acceleration or deceleration, which tunes the output energy. This paper presented the production of the whole linac system, as well as the measurement of the continuously-adjustable beam energy.

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TUPJE017

The Generation of Highly Intense THz Radiation based on Smith-Purcell Radiation

radiation, electron, factory, cathode

1654

Y.F. Xu, Z.G. He, Q.K. Jia, W.W. Li
USTC/NSRL, Hefei, Anhui, People's Republic of China

A photocathode RF gun can generate trains of THz subpicosecond electron bunches by illuminating the cathode with trains of laser pulses. Let this electron bunches passes close to the surface of a lamellar grating, THz radiation will be emitted, which is the so-called Smith-Purcell Radiation (SPR). If the lamellar grating has a narrow groove, this radiation will be narrow-band. By choosing suitable parameter, the SPR frequency can be resonant with the electron bunches frequency, and then generate high intense, narrow band THz radiation.

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TUPJE039

Recent Results on the Performance of Cs3Sb Photocathodes in the PHIN RF-Gun

cathode, laser, vacuum, operation

1699

C. Heßler, E. Chevallay, S. Döbert, V. Fedosseev, I. Martini, M. Martyanov
CERN, Geneva, Switzerland

For the CLIC drive beam a photoinjector option is under study at CERN as an alternative to the thermionic electron gun in the CLIC baseline design. The CLIC drive beam requires a high bunch charge of 8.4 nC and 0.14 ms long trains with 2 ns bunch spacing, which is challenging for a photoinjector. In particular the required long and high intensity laser pulses cause a degradation of the beam quality during the frequency conversion process, which generates the ultra-violet laser beam needed for standard Cs2Te photocathodes. To overcome this issue Cs3Sb cathodes sensitive to green light have been studied at the high-charge PHIN photoinjector since a few years. In this paper recent measurements of fundamental properties of Cs3Sb photocathodes such as quantum efficiency, cathode lifetime and dark current from summer 2014 will be presented, and compared with previous measurements and with the performance of Cs2Te photocathodes.

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TUPJE040

Surface Characterization at CERN of Photocathodes for Photoinjector Applications

cathode, laser, electron, operation

1703

I. Martini, E. Chevallay, V. Fedosseev, C. Heßler, H. Neupert, V. Nistor, M. Taborelli
CERN, Geneva, Switzerland

R&D on photocathodes takes place at CERN within the CLIC (Compact Linear Collider) project. Photocathodes are produced as thin films on Oxygen Free copper substrate using a co-deposition technique, and characterized in a dedicated laboratory with a DC photo-electron gun. A new UHV carrier vessel compatible with CERN’s XPS (X-ray Photoelectron Spectroscopy) analysis equipment has been commissioned and is used to transport photocathodes from the production laboratory to perform a systematic study of different compounds used as photoemissive materials. In this paper photocathodes used in a RF photoinjector will be characterized and the correlation of their surface properties with their performance will be investigated.

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TUPJE041

Progress on a Compact Accelerator Design for a Compton Light Source

dipole, linac, space-charge, solenoid

1706

K.E. Deitrick, J.R. Delayen, B.R.P. Gamage, G.A. Krafft, T. Satogata
ODU, Norfolk, Virginia, USA

A compact Compton light source using an electron linear accelerator is in design at the Center for Accelerator Science at Old Dominion University and Jefferson Lab. We report on the current design, including beam properties through the entire system based on a full end-to-end simulation, compare current specifications to design goals, and target areas for improvement.

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TUPJE052

Bunch Compression in the Driver Linac for the Proposed NSRRC VUV FEL

electron, linac, optics, FEL

1738

N.Y. Huang, W.K. Lau, A.P. Lee
NSRRC, Hsinchu, Taiwan
A. Chao, K. Fang, M.-H. Wang, J. Wu
SLAC, Menlo Park, California, USA

A bunch compressor is designed for the S-band driver linac system of the proposed NSRRC VUV free electron laser (FEL). Instead of using a more conventional rf harmonic linearizer, one main feature of this compressor is to use electron linearization optics to correct the nonlinearity in the energy-time correlation of the electron bunch longitudinal phase space. The strategy of compressor design will be discussed by an analytical calculation and particle tracking simulation. The beam dynamics which include the collective instabilities such as the space charge effects, the wake fields and the coherent synchrotron radiation (CSR) effects are discussed.

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TUPJE056

VELA Machine Development and Beam Characterisation

cavity, cathode, electron, klystron

1752

D.J. Scott, D. Angal-Kalinin, A.D. Brynes, F. Jackson, J.K. Jones, A. Kalinin, S.L. Mathisen, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, T.C.Q. Noakes, L.K. Rudge, E. Sneddon, M. Surman, R. Valizadeh, A.E. Wheelhouse, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S.D. Barrett, C.P. Topping, A. Wolski
The University of Liverpool, Liverpool, United Kingdom
A. Lyapin
JAI, Egham, Surrey, United Kingdom
M.D. Roper
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
C.P. Topping, A. Wolski
Cockcroft Institute, Warrington, Cheshire, United Kingdom
E. Yamakawa
Royal Holloway, University of London, Surrey, United Kingdom

Recent developments on the VELA (Versatile Electron Linear Accelerator) RF photo-injector at Daresbury Laboratory are presented. These are three-fold; commissioning/installation, characterising and providing beam to users. Measurements for characterising the dark current (DC), 4-D transverse emittance, lattice functions and photoinjector stability are presented. User beam set ups to provide beam for electron diffraction and Cavity Beam Position Monitor development are summarised.

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TUPJE058

Preparation of Polycrystalline and Thin Film Metal Photocathodes for Normal Conducting RF Guns

cathode, electron, experiment, cavity

1759

S. Mistry, M.D. Cropper
Loughborough University, Leicestershre, United Kingdom
A.N. Hannah, K.J. Middleman, B.L. Militsyn, T.C.Q. Noakes, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

A comparison of quantum efficiency (QE) and work function (wf) measurements of polycrystalline and thin film metal photocathodes for use in NCRF guns, similar to the S-band gun under development for CLARA project at Daresbury, are reported. Cu and Nb thin films were grown onto a Si substrate by magnetron sputtering and subsequently were prepared by annealing and Ar ion sputtering. To determine the surface chemistry, x-ray photoelectron spectroscopy was employed. QE measurements were enabled using a UV laser source giving 266 nm light. Wf measurements were carried out using a kelvin probe and ultraviolet photoelectron spectroscopy. Annealing the Cu thin film to 250°C yielded a QE of 1.2E-4; one order of magnitude higher than the QE for sputter cleaned and post annealed polycrystalline Cu. The optimum QE measurement for Nb thin film was 2.6·10^-4, which was found to be comparable to the results obtained for cleaned bulk Nb. Analysis of XPS data of these metals suggest surface composition and surface chemistry are main contributing factors to the QE and WF.

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TUPMA010

Development of a Field-Emission Type S-band RF-Gun System for High Brightness Electron Source Applications

cathode, electron, emittance, vacuum

1856

Y.-M. Shin
Northern Illinois University, DeKalb, Illinois, USA
N. Barov
Far-Tech, Inc., San Diego, California, USA
A.T. Green
Northern Illinois Univerity, Dekalb, Illinois, USA

Electron beams emitted from a cold cathode are thermally stable and mono-energetic with a small phase-space volume*. We have been developing a field-emission type RF-gun system for high brightness electron source applications, including electron scattering/diffraction and tunable coherent X-ray/THz generation. The system consists of a single-gap gun-cavity and an S-band klystron/modulator capable of powering the gun with up to 5.5 MW peak (PRR = 1 Hz, duration = 2.5 μs). The designed gun built with the symmetrised side-couplers has surface field on the cathode ranging 50 – 100 MV/m with 1.3 – 1.7 MW klystron-power and 1.2 field ratio (HFSS). ASTRA simulations also indicate that the gun produces the beam with transverse emittances of less than 1 mm-mrad with 10 – 20 pC bunch charge at 500 keV beam energy. Under the gun operating condition, particle tracking/PIC simulations (CST) show that a single-tip CNT field-emitter** produces short pulsed bunches (~ 1/10 RF-cycle) with small emittance ( 0.01 mm-mrad) and high peak current density ( 10,000 kA/cm²). After the gun is fully installed and commissioned, a CNT-tip cathode will be tested with RF-field emission.
* N. De Jonge, J.-M. Bonard, Phil. Trans. R. Soc. Lond. A 362, 2239 (2004)
** G. S. Bocharov, and A. V. Eletskii, Nanomaterials 3, 393 (2013)

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TUPMA018

An Improved Analytic Model of Electron Back-Bombardment in Thermionic Cathode RF Guns

simulation, electron, cathode, cavity

1872

J.P. Edelen, S. Biedron, J.R. Harris, S.V. Milton
CSU, Fort Collins, Colorado, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA

This paper describes work done at Colorado State University to improve upon the recent theory developed to predict the back-bombardment power in single-cell thermionic-cathode electron guns. The previous theory used a square-wave approximation of the time varying field to solve for the total kinetic energy deposited on the cathode due to the back-bombarded electrons. In addition the transit time factor was added as a correction to compensate for the non-sinusoidal field. By solving for the back-bombardment power using a sinusoidal field, the transit time factor can be removed and therefore a better overall model is produced. These alterations continue to accurately predict how back-bombardment varies as a function of the gun parameters and provides improvement when compared to the existing theory.

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TUPMA025

X-Band RF Photoinjector for Laser Compton X-Ray and Gamma-Ray Sources

laser, electron, emittance, dipole

1891

R.A. Marsh, G.G. Anderson, S.G. Anderson, C.P.J. Barty, D.J. Gibson
LLNL, Livermore, California, USA

Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Extremely bright narrow bandwidth gamma-ray sources are expanding the application of accelerator technology and light sources in new directions. An X-band test station has been commissioned at LLNL to develop multi-bunch electron beams. This multi-bunch mode will have stringent requirements for the electron bunch properties including low emittance and energy spread, but across multiple bunches. The test station is a unique facility featuring a 200 MV/m 5.59 cell X-band photogun powered by a SLAC XL4 klystron driven by a Scandinova solid-state modulator. This paper focuses on its current status including the generation and initial characterization of first electron beam. Design and installation of the inverse-Compton scattering interaction region and upgrade paths will be discussed along with future applications.

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TUPMA047

Multipacting-free Quarter-wavelength Choke Joint Design for BNL SRF

cathode, SRF, cavity, electron

1935

W. Xu, S.A. Belomestnykh, I. Ben-Zvi, C.J. Liaw, G.T. McIntyre, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, D. Weiss, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA

The BNL SRF gun cavity was operated well at CW mode up to 2 MV. However, the performance suffered due to multipacting in the quarter-wavelength choke-joint. A new multipacting-free cathode stalk was designed and will be conditioned. This paper will describes RF and thermal design of new cathode stalk and conditioning results.
This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.

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TUPMA048

Experimental and Simulational Result of Multipactors in 112 MHz QWR Injector

electron, cavity, cathode, simulation

1938

T. Xin
Stony Brook University, Stony Brook, USA
S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, V. Litvinenko, I. Pinayev, J. Skaritka, Q. Wu, B. P. Xiao
BNL, Upton, Long Island, New York, USA

Funding: This work was carried out at Brookhaven Science Associates, LLC under Contracts No. DE-AC02-98CH10886 and at Stony Brook University under grant DE-SC0005713 with the U.S. DOE.
The first RF commissioning of 112 MHz QWR superconducting electron gun was done in late 2014. The coaxial Fundamental Power Coupler (FPC) and Cathode Stalk (stalk) were install and tested for the first time. During this experiment, we observed several multipacting barriers at varied gun voltage levels. The simulation work was done within the same range. The comparison between the experimental observation and the simulation results are presented in this paper. The observations during the test are consisted with the simulation predictions. We were able to overcome most of the multipacting barriers and reach 1.7 MV gun voltage under pulsed mode after several round of conditioning processes.

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TUPMA049

First Beam Commissioning at BNL ERL SRF Gun

cathode, SRF, electron, cavity

1941

W. Xu, Z. Altinbas, S.A. Belomestnykh, I. Ben-Zvi, S. Deonarine, D.M. Gassner, H. Hahn, L.R. Hammons, T. Hayes, J.P. Jamilkowski, P. K. Kankiya, D. Kayran, N. Laloudakis, R.F. Lambiase, V. Litvinenko, L. Masi, G.T. McIntyre, K. Mernick, T.A. Miller, G. Narayan, D. Phillips, V. Ptitsyn, T. Rao, T. Seda, F. Severino, B. Sheehy, K.S. Smith, A.N. Steszyn, T.N. Tallerico, R. Than, J.E. Tuozzolo, E. Wang, D. Weiss, M. Wilinski, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, V. Ptitsyn
Stony Brook University, Stony Brook, USA

Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The 704 MHz superconducting RF gun successfully generated the first photoemission beam on Nov. 17 2014. This paper will report the latest results of SRF beam commissioning, including the SRF cavity performance, cathode QE measurements, and beam parameter measurements. The beam commissioning setup is described in the paper as well.

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TUPHA003

Sputter Growth of Alkali Antimonide Photocathodes: An in Operando Materials Analysis

cathode, target, emittance, radiation

1965

J. Smedley, K. Attenkofer, M. Gaowei, J. Sinsheimer, J. Walsh
BNL, Upton, Long Island, New York, USA
H. Bhandari
Radiation Monitoring Devices, Watertown, USA
Z. Ding, E.M. Muller
SBU, Stony Brook, New York, USA
H.J. Frisch
Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
H.A. Padmore, S.G. Schubert, J.J. Wong
LBNL, Berkeley, California, USA

Funding: Work supported by U.S. DoE, under KC0407-ALSJNT-I0013 and SBIR grant # DE-SC0009540. NSLS was supported by DOE DE-AC02-98CH10886, CHESS is supported by NSF & NIH/NIGMS via NSF DMR-1332208
Alkali antimonide photocathodes are a strong contender for the cathode of choice for next-generation photon sources such as LCLS II or the XFEL. These materials have already found extensive use in photodetectors and image intensifiers. However, only recently have modern synchrotron techniques enabled a systematic study of the formation chemistry of these materials. Such analysis has led to the understanding that these materials are inherently rough when grown through traditional sequential deposition; this roughness has a detrimental impact on the intrinsic emittance of the emitted beam. Sputter deposition may provide a path to achieving a far smoother photocathode, while maintaining adequate quantum efficiency. We report on the creation and vacuum transport of a K2CsSb sputter target, and its use to create an ultra-smooth (sub nm roughness) cathode with a 2% quantum efficiency at 532 nm.

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TUPTY083

Conceptual MEIC Electron Ring Injection Scheme using CEBAF as a Full Energy Injector

injection, electron, linac, operation

2232

J. Guo, F. Lin, R.A. Rimmer, H. Wang, S. Wang, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The Medium-energy Electron-Ion Collider (MEIC) proposed by Jefferson Lab is planning to use the newly upgraded 12 GeV CEBAF 1497 MHz SRF CW recirculating linac as a full-energy injector for the electron collider ring. The electron collider ring is proposed to reuse the 476MHz PEP-II RF system to achieve high installed voltage and high beam power. The MEIC electron injection requires 3-10 (or 12) GeV beam in 3-4μs long bunch trains with low duty factor and high peak current, resulting in strong transient beam loading for the CEBAF. In this paper, we propose an injection scheme that can match the two systems’ frequencies with acceptable injection time, and also address the transient beam loading issue in CEBAF. The scheme is compatible with future upgrade to 952.6 MHz SRF system in the electron ring.

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TUPWI008

RF Gun Based Ultrafast Electron Microscopy

electron, emittance, cavity, cathode

2259

J. Yang, K. Tanimura, Y. Yoshida
ISIR, Osaka, Japan
J. Urakawa
KEK, Ibaraki, Japan

Ultrafast electron microscopy (UEM) would be a powerful tool for the direct visualization of structural dynamic processes in matter. The resolutions of the observation on femtosecond time scales over sub-nanometer (even atomic) spatial dimensions have long been a goal in science. To achieve such resolutions, we have designed and constructed a femtosecond time-resolved relativistic-energy electron microscopy using a photocathode radio-frequency (RF) electron gun (RF based UEM). The RF gun has successfully generated a high-brightness electron beam with bunch length of 100 fs and emittance of 0.2 mm-mrad, which are essential beam parameters for the achievement of nm-fs space-time resolution in the microscopy. Both the static measurements of both relativistic-energy electron diffraction and image have been succeeded. In this presentation, the activities on RF based UEM are introduced. The requirements and limitations of the beam parameters are reviewed. The concept and design of RF based UEM are reported. Finally, some demonstrations of the relativistic-energy UEM images are reported.

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TUPWI010

Development of a Pulse Radiolysis System by Ultra-fast Super Continuum Probe at Waseda University

laser, polarization, electron, cathode

2265

Y. Ito
Waseda University, Tokyo, Japan
Y. Hosaka, K. Sakaue, M. Washio
RISE, Tokyo, Japan

We have been studying the pulse radiolysis using photo-cathode rf gun at Waseda Univ. Pulse radiolysis is one of the powerful methods to trace early chemical reactions by ionizing radiation. In pulse radiolysis, the probe light absorption, which produced by active species formed by electron beam of rf gun, is measured at each wavelength and made possible to trace reactions. Therefore, we have used the super continuum (SC) light for the probe light. The SC light has a broad spectrum and is generated by nonlinear optical effect caused by injecting picosecond laser to photonic crystal fiber. However, the resulting SC light was unstable because its peak intensity was not enough. We need to use a femtosecond pulsed laser which is expected to be stronger peak intensity than a picosecond laser. We have developed a mode-locked Yb-doped fiber laser based on Non-Linear Polarization Rotation as a femtosecond pulsed laser and the chirped pulse amplification system which will be able to amplify the femtosecond pulse. In this conference, we will report the performance of the SC light using this fiber laser system, recent results of pulse radiolysis experiments and the future plans.
Work supported by NEDO(New Energy and Industrial Technology Development Organization).

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TUPWI017

Single-shot Multi-MeV Ultrafast Electron Diffraction on VELA at Daresbury Laboratory

electron, FEL, scattering, experiment

2278

L.K. Rudge, D. Angal-Kalinin, J.A. Clarke, F. Jackson, J.K. Jones, A. Kalinin, S.L. Mathisen, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, T.C.Q. Noakes, Y.M. Saveliev, D.J. Scott, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
P. Aden, R.J. Cash, D.M.P. Holland, M.D. Roper
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
P.D. Lane, D.A. Wann
University of York, York, United Kingdom
M. Surman
STFC/DL/SRD, Warrington, Cheshire, United Kingdom
J.G. Underwood
UCL, London, United Kingdom

Funding: This work was funded by STFC
Accelerator based Ultrafast Electron Diffraction (UED) is a technique for obtaining static structures and for studying sub-100 fs dynamic structural changes on the atomic scale. In this paper we present the first electron diffraction results obtained from the VELA accelerator in 2014. The accelerator was operated to provide typically 4MeV/c electron bunches. Diffraction patterns were observed with <<1 pC transported to the detection screen. Single shot and multi-shot accumulated diffraction data are presented from single crystal and polycrystalline samples, including Au, Al, Pt and C. Contamination of the diffraction pattern with dark current contributions is an issue. A variable size aperture directly in front of the sample offers some mitigation, but at the expense of reduced charge contributing to the diffraction pattern. We discuss future developments for electron diffraction on VELA including further beam optimization, measurement of bunch length with a newly installed Transverse Deflecting Cavity, and the planned developments for pump-probe studies.

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TUPWI042

Initial Results from Streaked Low-energy Ultra-fast Electron Diffraction System

electron, simulation, diagnostics, experiment

2339

J.J. Hartzell, R.B. Agustsson, S. Boucher, L. Faillace, A.V. Smirnov
RadiaBeam, Santa Monica, California, USA
P. Musumeci, E.W. Threlkeld
UCLA, Los Angeles, USA

RadiaBeam, in collaboration with UCLA, is developing an inexpensive, low-energy, ultra-fast, streaked electron diffraction (S-UED) system which allows one to reconstruct a single ultrafast event with a single pulse of electrons using and RF deflector. The high-frequency (GHz), high voltage, phase-locked RF field in the deflector enables temporal resolution of atomic events as fine as sub-100 fs. In this paper, we present an overview of the system being developed and the initial experimental results. We also discuss the challenges based on our design of a UED system that incorporates a novel, high-resolution dielectric-loaded RF deflector and a solid-state X-band amplifier.

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WEYC1

Technical Challenges of the LCLS-II

undulator, linac, electron, cavity

2434

T.O. Raubenheimer
SLAC, Menlo Park, California, USA

The LCLS-II will be a CW X-ray FEL upgrade to the existing LCLS X-ray FEL at the SLAC National Accelerator Laboratory (SLAC). This paper describes the overall layout and the technical challenges that the upgrade project faces.

Slides WEYC1 [4.446 MB]

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WEBB1

Plans for Deployment of Hollow Electron Lenses at the LHC for Enhanced Beam Collimation

electron, collimation, solenoid, operation

2462

S. Redaelli, A. Bertarelli, R. Bruce, D. Perini, A. Rossi, B. Salvachua
CERN, Geneva, Switzerland
G. Stancari, A. Valishev
Fermilab, Batavia, Illinois, USA

Hollow electron lenses are considered as a possible mean to improve the LHC beam collimation system, providing an active control of halo diffusion rates and suppressing the population of transverse halos. After a very successful experience at the Tevatron, a conceptual design of a hollow e-lens optimized for the LHC was produced. Recent further studies have led to a mature preliminary technical design. In this paper, possible scenarios for the deployment of this technology at the LHC are elaborated in the context of the scheduled LHC long shutdowns until the full implementation of the HL-LHC upgrade in 2023. Possible setups of electron beam test stands at CERN and synergies with other relevant electron beam programmes outside CERN are also discussed.

Slides WEBB1 [3.216 MB]

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WEAD2

Experimental Results of Carbon NanoTube Cathodes inside RF Environment

cathode, electron, emittance, laser

2475

L. Faillace, S. Boucher, J.J. Hartzell, A.Y. Murokh
RadiaBeam, Santa Monica, California, USA
D. Mihalcea, P. Piot, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA
H. Panuganti
Northern Illinois University, DeKalb, Illinois, USA

Funding: Work supported by US DOE SBIR grant # DE-SC0004459
Carbon Nano Tubes (CNT’s) as field-emitters have been investigated for more than two decades and can produce relatively low emittance electron beams for a given cathode size. Unlike thermionic cathodes, CNT cathodes are able to produce electrons at room temperature and relatively low electric field (a few MV/m). In collaboration with FermiLab, we have recently tested CNT cathodes both with DC and RF fields. We observed a beam current close to 1A with a ~1cm² CNT cathode inside an L-band RF gun. Steady operation was obtained up to 650 mA and the measured current vs. surface field plot showed perfect agreement with the Fowler-Nordheim distribution.

Slides WEAD2 [10.445 MB]

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WEAD3

Quantum Efficiency Improvement of Polarized Electron Source using Strain Compensated Super Lattice Photocathode

electron, laser, polarization, collider

2479

N. Yamamoto, M. Hosaka, A. Mano, T. Miyauchi, Y. Takashima, Y. Takeda
Nagoya University, Nagoya, Japan
X.J. Jin, M. Yamamoto
KEK, Ibaraki, Japan

Polarized electron beam is essential for future electron-positron colliders and electron-ion colliders. Improving the quantum efficiency is an important subject to realize those proposed applications. Recently we have developed the strain compensated superlattice (SL) photocathode. In the strain compensated SLs, the equivalent compressive and tensile strains introduced in the well and barrier SL layers so that strain relaxation is effectively suppressed with increasing the SL layer thickness and high crystal quality can be expected. In this study, we fabricated the GaAs/GaAsP strain compensated SLs with the thickness up to 90-pair SL layers. Up to now, the electron spin polarization of 92 % and the quantum efficiency of 1.6 % were simultaneously achieved from 24-pair sample. In the presentation, we show the effect of the superlattice thickness on the photocathode performances and discuss the photocathode physics.

Slides WEAD3 [3.064 MB]

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WEPWA014

Low Temperature Properties of 20 K Cooled Test Cavity for C-band 2.6-cell Photocathode RF Gun

cavity, experiment, cryogenics, resonance

2519

T. Tanaka, M. Inagaki, K. Nakao, K. Nogami, T. Sakai
LEBRA, Funabashi, Japan
M.K. Fukuda, T. Takatomi, J. Urakawa, M. Yoshida
KEK, Ibaraki, Japan
D. Satoh
TIT, Tokyo, Japan
T.S. Shintomi
Nihon University, Tokyo, Japan

Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
A cryogenic C-band 2.6-cell photocathode RF gun, which operates at 20 K, is under development at Nihon University for future possibility of use in a compact linac-driven X-ray source. The cavity material is 6N8 high purity copper, the RRR of which being expected to be higher than 3000. A 2.6-cell pi-mode test cavity was fabricated for investigation of the properties under low temperature of 20 K*. Ultraprecision machining and diffusion bonding of the cavity were carried out in KEK. The operating frequency of the RF gun cavity is 5712 MHz. The machining dimensions of the test cavity were determined by taking into account the contraction of copper from room temperature to 20 K by approximately 0.33 %. The resonant frequency observed at around 21 K was 5711.761 MHz, which is 185 kHz higher than the expected value that was deduced from the resonant frequency obtained at 23.5 degree C in vacuum and the linear expansion coefficient data for OFC copper by NIST**. The unloaded Q-value of 64500 obtained at 21 K is in agreement with the SUPERFISH calculation when the surface resistance of the RRR=3000 copper was specified with taking the anomalous skin effect into account.
* T. Tanaka et al., Proceedings of IPAC2014, 658-660, http://accelconf.web.cern.ch/AccelConf
/IPAC2014/papers/mopri030.pdf
** http://cryogenics.nist.gov/MPropsMAY/OFHC%20Copper/OFHC_Copper_rev.htm

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WEPWA015

RF Input Coupler for 20 K Cooled C-band 2.6-cell Photocathode RF Gun

cavity, simulation, resonance, network

2522

T. Tanaka, M. Inagaki, K. Nakao, K. Nogami, T. Sakai
LEBRA, Funabashi, Japan
M.K. Fukuda, T. Takatomi, J. Urakawa, M. Yoshida
KEK, Ibaraki, Japan
D. Satoh
TIT, Tokyo, Japan
T.S. Shintomi
Nihon University, Tokyo, Japan

Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
For future use in a compact linac-driven X-ray source, a cryo-cooled C-band photocathode RF gun is under development. The RF experiment on the basic 2.6-cell test cavity has shown that the unloaded Q-value of the cavity at 20 K can be explained by the surface resistance based on the anomalous skin effect. Since the cavity was intended for preliminary experiments of the low temperature RF properties*, a new test cavity with an RF input coupler has been designed. The basic structure of the accelerating cells has not been changed from the previous cavity. Avoiding an element with a low cooling efficiency such as the inner electrode in a coaxial coupler, a simpler cylindrical input coupler has been designed. The coupler consists of a cylindrical TM01 mode waveguide and a mode converter from a rectangular TE10 mode, with both elements placed on the accelerating axis. The structure and the dimensions of the coupler have been determined using the 3-D simulation code CST Studio so that the resonant frequency of the whole system and the coupling coefficient of the coupler meet the specifications of the RF gun. The new test cavity will be completed early in 2015 at KEK.
* T. Tanaka et al., Proceedings of IPAC2014, 658-660, http://accelconf.web.cern.ch/AccelConf
/IPAC2014/papers/mopri030.pdf

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WEPWA024

Development of a C-band RF Gun with a Coniferous-tree-type Carbon Nanostructure Field Emission Cathode

cavity, cathode, electron, radiation

2545

Y. Taira, H. Kato, R. Kuroda, H. Toyokawa
AIST, Tsukuba, Ibaraki, Japan

A C-band RF gun for compact radiation sources such as a high energy x-ray and a terahertz radiation is developed at AIST, which is designed to work at the frequency of 5.3 GHz*. A coniferous-tree-type carbon nanostructure (CCNS) is used for a field emission cathode in the C-band RF gun. A graphene sheet composed of carbon has a coniferous form, and the tip has a nanometer-size tubular structure that becomes thicker on the substrate side**. Owing to this configuration, the CCNS has a large field enhancement factor, and is considered to be more stable in high electric fields than Carbon nanotubes. We have fabricated the C-band RF gun of the single cell cavity. Emission current depending on the electric field strength on the CCNS cathode surface was measured. When the electric field strength was 30 MV/m, the total charge per a macro pulse was 30 nC. After applying a stronger electric field, a decline of the field enhancement factor was observed. We will present the experimental result of the field emission measurement of the CCNS and the simulation result of a beam trajectory using a C-band RF gun of a multi cell cavity.
* Y. Taira et al., Nucl. Instr. and Meth. Phys. Res. B 331 (2014) 27.
** R. Suzuki, Synthesiology 2 (3) (2009) 221.

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WEPWA052

RF Conditioning of the Photo-Cathode RF Gun at the Advanced Photon Source - NWA RF Measurements

detector, cathode, linac, vacuum

2621

T.L. Smith, N.P. DiMonte, A. Nassiri, Y.-E. Sun, A. Zholents
ANL, Argonne, Illinois, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357
A new S-band photo-cathode (PC) gun was recently installed and RF conditioned at the Advanced Photon Source (APS) Injector Test-stand (ITS) at Argonne National Lab (ANL). The APS PC gun is a LCLS type gun fabricated at SLAC [1]. The PC gun was delivered to the APS in October 2013 and installed in the APS ITS in December 2013. At ANL, we developed a new method of fast detection and mitigation of the gun’s internal arcs during the RF conditioning process to protect the gun from arc damage and to RF condition more efficiently. Here, we report the results of RF measurements for the PC gun and an Auto-Restart method for high power RF conditioning.

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WEPWA070

Considerations for an Efficient Terahertz-driven Electron Gun

electron, acceleration, laser, controls

2664

F. Lemery, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA

We investigate a dispersion-controlled-acceleration scheme of low-energy electrons to mitigate phase slipping using a tapered dielectric lined waveguide (DLW). Our approach matches the velocity of an electron being accelerated in a slab-symmetric structure in a constant electric field. We also present first experimental results of a THz pulse propagating in a slab-symmetric DLW.

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WEPJE019

Simulations of Field-Emission Electron Beams from CNT Cathodes in RF Photoinjectors

cathode, electron, simulation, emittance

2711

D. Mihalcea, H. Panuganti, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
L. Faillace
RadiaBeam, Santa Monica, California, USA
P. Piot, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA

Average field emission currents of up to 700 mA were produced by Carbon Nano Tube (CNT) cathodes in a 1.3 GHz RF gun at Fermilab High Brightness Electron Source Lab. (HBESL). The CNT cathodes were manufactured at Xintek and tested under DC conditions at RadiaBeam. The electron beam intensity as well as the other beam properties are directly related to the time-dependent electric field at the cathode and the geometry of the RF gun. This report focuses on simulations of the electron beam generated through field-emission and the results are compared with experimental measurements. These simulations were performed with the time-dependent Particle In Cell (PIC) code WARP.

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WEPJE023

Cathode Performance during Two Beam Operation of the High Current High Polarization Electron Gun for eRHIC

cathode, electron, vacuum, operation

2720

O.H. Rahman
Stony Brook University, Stony Brook, USA
M.A. Ackeret, J.R. Pietz
Transfer Engineering and Manufacturing, Inc, Fremont, California, USA
I. Ben-Zvi, C. Degen, D.M. Gassner, R.F. Lambiase, A.I. Pikin, T. Rao, B. Sheehy, J. Skaritka, E. Wang
BNL, Upton, Long Island, New York, USA
E. Dobrin, R.C. Miller, K.A. Thompson, C. Yeckel
Stangenes Industries, Palo Alto, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Two electron beams from two activated bulk GaAs photocathodes were successfully combined during the recent beam test of the High Current High Polarization Electron gun for eRHIC. The beam test took place at Stangenes Industries in Palo Alto, CA, where the cathodes were placed in radially opposite locations inside the high voltage shroud. No significant cross talking between the cathodes were found for the pertinent vacuum and low average current operation, which is very promising towards combining multiple beams for higher average current. This paper describes the cathode preparation, transport and cathode performance in the gun for the combining test, including the QE and lifetimes of the photocathodes at various steps of the experiment.

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WEPJE033

The Progress of Funnelling Gun High Voltage Condition and Beam Test

cathode, electron, high-voltage, radiation

2735

E. Wang, I. Ben-Zvi, D.M. Gassner, R.F. Lambiase, W. Meng, A.I. Pikin, T. Rao, B. Sheehy, J. Skaritka
BNL, Upton, Long Island, New York, USA
M.A. Ackeret, J.R. Pietz
Transfer Engineering and Manufacturing, Inc, Fremont, California, USA
E. Dobrin, R.C. Miller, K.A. Thompson, C. Yeckel
Stangenes Industries, Palo Alto, California, USA
O.H. Rahman
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A prototype of a high average current polarized electron funneling gun as an eRHIC injector has been built at BNL. The gun was assembled and tested at Stangenes Incorporated. Two beams were generated from GaAs photocathodes and combined by a switched combiner field. We observed the combined beams on a YAG crystal and measured the photocurrent by a Faraday cup. The gun has been shipped to Stony Brook University and is being tested there. In this paper we will describe the major components of the gun and recent beam test results. High voltage conditioning is discussed as well.

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WEPMA011

First Horizontal Test Results of the HZB SRF Photoinjector for BERLinPro

cavity, SRF, operation, cryomodule

2768

A. Burrill, W. Anders, A. Frahm, J. Knobloch, A. Neumann
HZB, Berlin, Germany
G. Ciovati, W.A. Clemens, P. Kneisel, L. Turlington
JLab, Newport News, Virginia, USA

The BERLinPro project, a small superconducting RF (SRF) c.w. energy recovery linac (ERL) is being built at Helmholtz-Zentrum Berlin in order to develop the technology required for operation of a high current, 100 mA, 50 MeV ERL. The electron source for the accelerator is a 1.4 cell SRF photoinjector fitted with a multi-alkali photocathode. As part of the HZB photoinjector development program three different SRF photoinjectors will be fabricated and tested. The photoinjector described herein is the second cavity that has been fabricated, and the first photoinjector designed for use with a multi-alkali photocathode. The photoinjector has been built and tested at JLab and subsequently shipped to HZB for testing in the horizontal test cryostat HoBiCaT prior to installation in the photoinjector cryomodule. This cryomodule will be used to measure the photocathode operation in a dedicated experiment called GunLab, the precursor to installation in the BERLinPro hall. This paper will report on the final results of the cavity installed in the helium vessel in the vertical testing dewar at Jefferson Lab as well as the first horizontal test in HoBiCaT

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WEPMA031

Timing Jitter Studies for sub-fs Electron Bunch Generation at SINBAD

laser, electron, simulation, acceleration

2826

J. Zhu, R.W. Aßmann, U. Dorda, J. Grebenyuk, B. Marchetti
DESY, Hamburg, Germany

Generation of ultra-short electron bunches with a few femtoseconds arrival-time jitter is the major challenge in plasma acceleration with external injection. Meanwhile, peak current stability is also one of the crucial factors for user experiments when the electron bunch is used for free-electron laser (FEL) generation. ARES (Accelerator Research Experiment at SINBAD) will consist of a compact S-band normal-conducting photo-injector providing ultra-short electron bunches of 100 MeV. We present bunch arrival-time jitter studies for two different compression schemes, velocity bunching and magnetic compression with a slit, at ARES with start-to-end simulations. Contributions from various jitter sources are quantified.

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WEPMA036

Double-Cell Notch Filter for SRF Gun Investigations

cathode, SRF, cavity, simulation

2838

E.N. Zaplatin
FZJ, Jülich, Germany
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
J. Knobloch, A. Neumann
HZB, Berlin, Germany
V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Some projects of SRF guns apply the design where the cathode can be easily and quickly removed. One of the disadvantages of this design is the RF power leakage from the accelerating gun cavity cells to the cathode housing that results in the excessive cathode heating. To minimize the RF power leak different kinds of choke filters are used to protect the cathode structure. These choke filters represent resonant circuits with a zero input impedance and installed at the entrance of the cathode structure that shunt the cathode housing. Still, since the choke filter frequency shift under working conditions is bigger than its bandwidth a filter tuning during assembly only in the warm stage seems insufficient and requires also fine-tuning during operation. To eliminate the problems of the choke filter fine-tuning and hence ensure its stability during operation, a combination of the resonance choke elements can be implemented. In the paper we demonstrate advantages of the double-cell notch filter using BERLinPro SRF gun cavity as an example with its simple design modifications.

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WEPMA044

25 Hz, Sub-mJ Ytterbium Laser Source of RF Gun for SuperKEKB Linac

laser, cavity, polarization, electron

2862

X. Zhou, T. Natsui, Y. Ogawa, M. Yoshida, R. Zhang
KEK, Ibaraki, Japan

For injector linac of SuperKEKB project, the 5 nC electron beams with double-bunch is expected to be generated in the photocathode RF gun. For the repetition rate of electrum beam, the optional of 2 Hz, 5 Hz, 25 Hz and 50 Hz are requested. Although, more than 5 nC electron with single-bunch has been generated in the 2 Hz and 5 Hz, when the repetition rate increases to 25 Hz, the condition of the laser amplifier system such as the thermal lens effect is changed seriously. To correspond to 25 Hz repetition rate, the ytterbium-doped laser system was reformed. An AuSu (80:20) heat-dissipating solder is employed to reduce the thermal lens effect. Because of the damage threshold limitation of the thin-disk crystal and optical mirrors, Some improvement were performed to increase the quality of the pulses rather than the amplify power, which cause the SHG conversion efficiency is up to 60% and 30% with 2ω and 4ω respectively. More than 3 nC electron beam is obtained with 25 Hz.

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WEPMN012

Cathode Stalk Optimization for a 325 MHz Superconducting QWR Electron Gun

cathode, cavity, electron, impedance

2940

P.L. Fan, Y.M. Li, L. Lin, K.X. Liu, S.W. Quan, F. Zhu
PKU, Beijing, People's Republic of China

Funding: Work supported by National Basic Research Project (No. 2011CB808302)
The structure of cathode stalk is very important for the performance of a superconducting QWR (Quarter Wave Resonator) gun. With improper design, RF power dissipation on the surface of cathode stalk and its surrounding tube can lead to a serious decrease of quality factor for superconducting QWR injector. We present here an optimized design of the cathode stalk for the 325 MHz superconducting QWR gun and special considerations are taken to minimize the power dissipation. The details of microwave simulation, beam dynamic simulation of the cavity with cathode stalks in different length, diameter and position are presented in this paper.

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WEPMN015

Dark Current Imaging Experiment in an L-band RF Gun

cathode, solenoid, electron, experiment

2952

J.H. Shao, H.B. Chen, J. Shi, D. Wang
TUB, Beijing, People's Republic of China
S.P. Antipov, S.V. Baryshev, C.-J. Jing, J.Q. Qiu
Euclid TechLabs, LLC, Solon, Ohio, USA
M.E. Conde, D.S. Doran, W. Gai, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Argonne, Illinois, USA
F.Y. Wang, L. Xiao
SLAC, Menlo Park, California, USA

The localized high electric field enhancement or low work function is the trigger for strong field emission, which however has yet been well experimentally studied. Using an L-band photocathode gun test stand at Argonne Wakefield Accelerator Facility (AWA), we’ve constructed an imaging beam line to observe field emission current from predefined emitters on cathode. Preliminary experiment results are present. Future plan is discussed.

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WEPMN016

Observation of Dark Current Dependence on Stored Energy in an L-Band RF Gun

cathode, solenoid, experiment, simulation

2956

J.H. Shao, H.B. Chen, J. Shi, D. Wang
TUB, Beijing, People's Republic of China
S.P. Antipov, S.V. Baryshev, C.-J. Jing, J.Q. Qiu
Euclid TechLabs, LLC, Solon, Ohio, USA
M.E. Conde, D.S. Doran, W. Gai, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Argonne, Illinois, USA
F.Y. Wang, L. Xiao
SLAC, Menlo Park, California, USA

A pin cathode has been installed into an L-band photocathode gun to study the influence of stored energy on field emission. The stored energy was varied by tuning the recess of the cathode in order to have the same E-field on the cathode tip. We have observed 5 times difference of dark current level at the same E-field, while by varying the stored energy by three fold. Dynamics study reveals the difference is not caused by transmission, but by emission process itself. We'll present experiment results and discuss possible mechanisms about the phenomena.

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WEPMN018

Measurement of Cell-Cell Coupling Coefficient in Photocathode RF Gun

coupling, simulation, laser, cathode

2963

P. Wang, H.B. Chen, Q. Gao, J. Shi, L. Zhang
TUB, Beijing, People's Republic of China

A photocathode RF gun is under cold rest in Tsinghua University. We measured the single cavity frequency and the cell-cell coupling coefficient by the detuning method with high accuracy. We use a simplified model to illustrate the whole process of the measurement. The data obtained in the cold test seem to accord with that from the model very well.

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WEPMN021

Design and Research of Secondary Electron Emission Test Equipment with Low Electron Energy

electron, vacuum, ion, accumulation

2970

Y.H. Xu, L. Fan, Y.Z. Hong, X.T. Pei, J. Wang, Y. Wang, W. Wei, B. Zhang
USTC/NSRL, Hefei, Anhui, People's Republic of China

In particle accelerators, the secondary electrons resulting from the interaction between particles and vacuum chamber have a great impact on beam quality. Especially for positron, proton and heavy ion accelerators, massive electrons lead to electron cloud, which affects the stability, energy, emittance and beam life adversely. We have studied the secondary electron emission (SEE) of metal used for accelerators. A secondary electron emission measurement system with low electron energy has been designed and used to measure the SEE yield of metal and non-evaporable getter materials. With the equipment, we have obtained the characteristic of the SEE yield of stainless steel and oxygen free copper (OFC).

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WEPMN034

Electron Emission from Surface Roughness on Cavity in Low Temperature

electron, radiation, cavity, vacuum

3003

H. Kim, H.J. Cha, S. Choi, W.K. Kim, G.-T. Park
IBS, Daejeon, Republic of Korea
Y. Chang
Hanshin University, Kyungki, Republic of Korea

Electron emission phenomenon from surface roughness on cavity is investigated. The distribution of the electric field from the surface roughness can be obtained on cavity surface. The field emission is calculated from the electric field distribution. The generalized electron emission from electric field and temperature effect is also calculated on the surface roughness of the cavity.

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WEPTY013

Cs2Te Photocathode Performance in the AWA High-charge High-gradient Drive Gun

laser, cathode, wakefield, space-charge

3283

E.E. Wisniewski, S.P. Antipov, M.E. Conde, D.S. Doran, W. Gai, C.-J. Jing, W. Liu, J.G. Power, C. Whiteford
ANL, Argonne, Illinois, USA
S.P. Antipov, C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: U.S. Dept of Energy Office of Science under contract number DE-AC02-06CH11357
The unique high-charge L-band, 1.3 GHz, 1.5 cell gun for the new 75 MeV drive beam is in operation at the Argonne Wakefield Accelerator (AWA) facility (see M.E. Conde, this proceedings.) The high-field (> 80 MV/m) photoinjector has a large area, high QE Cesium telluride photocathode (diameter > 30 mm). The photocathode, a crucial component of the upgraded facility, is fabricated on-site. The photoinjector generates high-charge, short pulse, single bunches (Q > 100 nC) and long bunch-trains (Q > 600 nC) for wakefield experiments. The performance of the photocathode for the AWA drive gun is detailed. Quantum efficiency (QE) measurements indicate long, stable photocathode lifetime under demanding conditions.

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WEPTY025

LBNF Hadron Absorber: Mechanical Design and Analysis for 2.4MW Operation

operation, hadron, shielding, target

3318

B.D. Hartsell, K. Anderson, J. Hylen, V.I. Sidorov, S. Tariq
Fermilab, Batavia, Illinois, USA

Fermilab’s Long-Baseline Neutrino Facility (LBNF) requires an absorber, essentially a large beam dump consisting of actively cooled aluminum and steel blocks, at the end of the decay pipe to stop leftover beam particles and provide radiation protection to people and groundwater. At LBNF’s final beam power of 2.4 MW and assuming the worst case condition of a 204 m long helium filled decay pipe, the absorber is required to handle a heat load of about 750 kW. This results in significant thermal management challenges which have been mitigated by the addition of an aluminum ‘spoiler’ and ‘sculpting’ the central portion of the aluminum core blocks. These thermal effects induce structural stresses which can lead to fatigue and creep considerations. Various accident conditions are considered and safety systems are planned to monitor operation and any accident pulses. Results from these thermal and structural analyses will be presented as well as the mechanical design of the absorber. The design allows each of the core blocks to be remotely removed and replaced if necessary. A shielded remote handling structure is incorporated to hold the hadron monitor when it is removed from the beam.

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WEPTY056

Novel High Power Sources for the Physics of Ionospheric Modification

cathode, simulation, electron, impedance

3398

B. Beaudoin, T.M. Antonsen, I. Haber, T.W. Koeth, A.H. Narayan, G.S. Nusinovich, K.J. Ruisard
UMD, College Park, Maryland, USA
J. Rodgers
Naval Research Laboratory (NRL), Washington, USA

Funding: This work is supported by the Air Force Office of Scientific Research under grant FA95501410019.
The ionosphere plays a controlling role in the performance of critical civilian and DoD systems including the ELF-ULF communications. The objective of Ionospheric Modification is to control triggered processes to improve the performance of trans-ionospheric C3I systems and develop new applications that take advantage of the ionosphere as an active plasma medium. A key instrument is the Ionospheric Heater, a powerful HF transmitter that modifies the properties of the ionospheric plasma by modulating the electron temperature at preselected altitudes. A major reason for the development of a mobile source is that it would allow investigators to conduct the needed research at different latitudes without building permanent installations. As part of a MURI, UMD will develop a powerful RF source utilizing IOT technology in class-D amplifier mode. This technology was chosen because it has the potential to operate at very high efficiency. Some of the technical challenges presented in this paper will include a gun design that minimizes intercepted current, a compact tunable cavity, an efficient modulator system capable of modulating a high power beam and output couplers to feed the antennas.

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WEPWI024

Vacuum Characterization and Improvement for the Jefferson Lab Polarized Electron Source

ion, electron, vacuum, background

3540

M.L. Stutzman, P.A. Adderley, M. Poelker
JLab, Newport News, Virginia, USA
M.A. Mamun
Old Dominion University, Norfolk, Virginia, USA

Operating the JLab polarized electron source with high reliability and long lifetime requires vacuum near the XHV level (<=1x10^-12 Torr). This paper describes ongoing vacuum research at Jefferson Lab including characterization of outgassing rates for surface coatings and heat treatments, ultimate pressure measurements, investigation of pumping including an XHV cryopump, and characterization of ionization gauges in this pressure regime.

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WEPWI033

Effects of Plasma Processing on Secondary Electron Yield of Niobium Samples

electron, plasma, cavity, vacuum

3558

M. Basovic, S. Popović, M. Tomovic, L. Vušković
ODU, Norfolk, Virginia, USA
F. Čučkov, A. Samolov
University of Massachusetts Boston, Boston, Massachusetts, USA

Impurities deposited on the surface of Nb during both the forming and welding of accelerator cavities add to the imperfections of the sheet metal, which then affects the overall performance of the cavities. This leads to a drop in the Q factor and limits the maximum acceleration gradient achievable per unit length of the cavities. The performance can be improved either by adjusting the fabrication and preparation parameters, or by mitigating the effects of fabrication and preparation techniques used. We have developed the experimental setup to determine Secondary Electron Yield (SEY) from the surface of Nb samples. Our aim is to show the effect of plasma processing on the SEY of Nb. The setup measures the secondary electron energy distribution at various incident angles as measured between the electron beam and the surface of the sample. The goal is to determine the SEY on non-treated and plasma treated surface of electron beam welded samples. Here we describe the experimental setup, plasma treatment device, and fabrication and processing of the Nb samples.

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WEPWI049

Commissioning of the 112 MHz SRF Gun and 500 MHz Bunching Cavities for the CeC PoP Linac

SRF, bunching, experiment, electron

3597

S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, V. Litvinenko, G. Narayan, P. Orfin, I. Pinayev, T. Rao, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, Q. Wu, B. P. Xiao, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, T. Xin
Stony Brook University, Stony Brook, USA
P.A. McIntosh, A.J. Moss, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL includes a short electron linac. During Phase I a 112 MHz superconducting RF photoemission gun and two 500 MHz normal conducting bunching cavities were installed and commissioned. The paper describes the Phase I linac layout and presents commissioning results for the cavities and associated RF, cryogenic and other sub-systems.

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WEPWI050

SRF and RF Systems for LEReC Linac

cavity, SRF, electron, booster

3600

S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, A.V. Fedotov, G.T. McIntyre, S. Polizzo, K.S. Smith, R. Than, J.E. Tuozzolo, Q. Wu, B. P. Xiao, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The Low Energy RHIC electron Cooling (LEReC) is under development at BNL to improve RHIC luminosity at low energies. It will consist of a short electron linac and two cooling sections, one for blue and one for yellow beams. For the first stage of the project, LEReC-1, we will to install a 704 MHz superconducting RF cavity and two normal conducting cavities operating at 704 MHz and 2.1 GHz. The SRF cavity will boost the electron beam energy up to 2 MeV. The warm cavities will be used to correct the energy spread introduced in the SRF cavity. The paper describes layouts of the SRF and RF systems, their parameters and status.

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