IPAC2016 - Classification: 02 Photon Sources and Electron Accelerators / T02 Electron Sources

Paper	Title	Page
TUOCA02	APEX Phase-II Commissioning Results at the Lawrence Berkeley National Laboratory	1041
	F. Sannibale, J.A. Doyle, J. Feng, D. Filippetto, G.L. Harris, M.J. Johnson, T.D. Kramasz, D. Leitner, C.E. Mitchell, J.R. Nasiatka, H.A. Padmore, H.J. Qian, H. Rasool, J.W. Staples, S.P. Virostek, R.P. Wells, M.S. Zolotorev LBNL, Berkeley, California, USA S.M. Gierman, R.K. Li, J.F. Schmerge, T. Vecchione, F. Zhou SLAC, Menlo Park, California, USA C. Pagani, D. Sertore INFN/LASA, Segrate (MI), Italy
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 Science needs in the last decade have been pushing the accelerator community to the development of high repetition rates (MHz/GHz-class) linac-based schemes capable of generating high brightness electron beams. Examples include X-ray FELs; ERLs for light source, electron cooling and IR to EUV FEL applications; inverse Compton scattering X-ray or gamma sources; and ultrafast electron diffraction and microscopy. The high repetition rate requirement has profound implications on the technology choice for most of the accelerator parts, and in particular for the electron gun. The successful performance of the GHz room-temperature RF photo-injectors running at rates <~ 100 Hz, cannot be scaled up to higher rates because of the excessive heat load that those regimes would impose on the gun cavity. In response to this gun need, we have developed at Berkeley the VHF-Gun, a lower-frequency room-temperature RF photo-gun capable of CW operation and optimized for the performance required by MHz-class X-ray FELs. The Advanced Photo-injector EXperiment (APEX) was funded and built for demonstrating the VHF gun performance, and the results of its last phase of commissioning are presented.
	Slides TUOCA02 [12.015 MB]
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THPMY017	A Comparison of Surface Properties of Metallic Thin Film Photocathodes	3691
	S. Mistry, M.D. Cropper Loughborough University, Leicestershre, United Kingdom A.N. Hannah, L.B. Jones, K.J. Middleman, B.L. Militsyn, T.C.Q. Noakes, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	In this work physical vapour deposition magnetron sputtering has been employed to deposit metallic thin films onto Cu, Mo and Si substrates. The use of metallic thin films offers several advantages: (i) metal photocathodes present a fast response time and a relative insensitivity to the vacuum environment (ii) metallic thin films when prepared and transferred in vacuum can offer smoother and cleaner cathode surfaces. The photocathodes developed here will ultimately be used to drive NCRF guns such as that used in VELA and the proposed CLARA light source test facility. The samples grown on Si substrates were used to investigate the morphology and thickness of the film. The samples grown onto Cu and Mo substrates were analysed and tested as photocathodes in a surface characterisation chamber, where X-Ray photoelectron spectroscopy was employed to determine surface chemistry and a Kelvin probe apparatus used to determine work function. QE measurements were enabled using a 266 nm UV laser.
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THPOW001	Design of a 4.6-Cell RF Gun for the PHIL accelerator at LAL	3922
	P. Chen, C. Bruni, S. Chancé, L. Garolfi, A. Gonnin, P. Lepercq, T. Vinatier LAL, Orsay, France
	A photo-injector with 4.6-cell and resonate frequency of 2.998 GHz has been designed and studied to replace the 2.5-cell RF gun + booster association. The cavity iris shape and dimensions were simulated systematically to optimize the shunt impedance. In this study, electron beam reaches to 9.7 MeV with a moderate peak accelerat-ing gradient of 80 MV/m. Considering a beam charge of 1 nC/bunch, average transverse emittance of ~ 5.9 πmm mrad and energy spread of ~ 0.8% can be obtained at the exit of the gun. The RF input power is only 10.2 MW due to the high shunt impedance. Asymmetry of the electric field due to the coupling port has also been studied using 3D codes for RF and beam dynamics calculations. We will present the RF design and beam calculations results.
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THPOW002	Electromagnetic, Thermal, and Structural Analysis of a THOMX RF Gun Using ANSYS	3925
	M. El Khaldi, J. Bonis, A. Camara, L. Garolfi, A. Gonnin LAL, Orsay, France
	Photocathode RF guns are used in the first stage of electron beam generation and acceleration. The RF gun of THOMX is a 2.5 cell standing wave copper cavity with resonance frequency of 2998.55 MHz at 30 °C under vacuum. The metal photocathode such as copper or magnesium is inserted into the backplane of the cavity. Due to high repetition rates up to 50 Hz with the average dissipated power into the internal surfaces up to 1.5 kW, causing a heating and deformation of the cavity shape. Therefore, the cooling system of the device has to be well designed to take under control the deformations of the structure, providing a temperature increase as small and uniform as possible. For this purpose a fully coupled electromagnetic-thermal-structural finite element analysis on this gun has been performed with Ansys workbench. Numerical results show that the gun could operate at 3 μs RF pulse length and 50 Hz repetition rate with an average dissipated power of 1.5 kW. The gun average temperature is around 30 °C while the incoming water temperature is around 24°C. Internal speed of water is 2.5 m/s which corresponds to 15 l/min for the incoming water. The total pressure drop is around 0.4 bar
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THPOW003	Highlights on Metallic Photocathodes Used in SRF Gun	3928
	R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate HZDR, Dresden, Germany P.N. Lu, H. Vennekate TU Dresden, Dresden, Germany
	For the accelerator-based light sources and the electron colliders, the development of photoinjectors has become a key technology. Especially for the superconducting radio frequency cavity based injector (SRF Gun), the searching for better photocathodes is always a principal technical challenge. To use metallic photocathodes for ELBE SRF Gun is the primary choice to prevent cavity contamination. In this contribution, we will report the investigation of Magnesium (Mg) in ELBE SRF gun, including laser cleaning treatment and the measurement on quantum efficiency, Schottky effect, dark current and damage threshold. The work is supported by the European Community under the FP7 programme (EuCARD-2 and LA3NET) and by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1.
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THPOW004	Pulse Response Measurements of NEA Photocathodes at Different Laser Wavelengths	3931
	M.A. Dehn, K. Aulenbacher, V. Bechthold IKP, Mainz, Germany
	For high average electron beam currents the length of the electron bunches must match the acceptance of the accelerator. At Johannes Gutenberg-University Mainz we are able to measure the longitudinal pulse response of NEA photocathodes (GaAs) under photo excitation of different wavelengths. A time resolution of < 2 ps at a beam energy of 100 keV is achieved, furthermore, a high dynamic range allows to investigate long ranging tails of the response (longitudinal halo). This serves to identify the best possible operation mode for high current photo sources.
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THPOW005	A Study of CsK2Sb Multi-alkali Photocathode by Ultraviolet Photoelectron Spectroscopy at UVSOR	3934
SUPSS022	use link to see paper's listing under its alternate paper code
	M. Urano, M. Kuriki, K. Negishi HU/AdSM, Higashi-Hiroshima, Japan T. Konomi, Y. Seimiya, N. Yamamoto KEK, Ibaraki, Japan
	Photocathode is one of the most important components in the next-generation accelerators, especially based on linear accelerators. Photocathode performance depends not only on electronic state in its bulk material but also on the surface condition. CsK2Sb multi-alkali photocathode is a candidate for the high brightness electron source because of its high quantum efficiency by green laser and its high robustness. We have carried out an UPS (UV Photoelectron Spectroscopy) experiment at UVSOR facility, synchrotron radiation light source in Aichi Japan. We have compared the UPS spectra among several samples, each one has a different quantum efficiency, and try to find physics which decide photocathode's performance. In this case, we focused some characters correlated to the quantum efficiency. I'm going to present a result of this analysis.
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THPOW006	A Study of Operational Lifetime of CsK2Sb Photo-cathode	3938
	A. Yokota, R. Kaku, M. Kuriki, K. Negishi, M. Urano HU/AdSM, Higashi-Hiroshima, Japan Y. Seimiya KEK, Ibaraki, Japan
	A high performance electron beam generated with a laser photo-cathode is one of the most important pieces in the advanced accelerator. Because the CsK2Sb photo-cathode is robust with more than 10 % quantum efficiency (QE) by green laser (532nm), it is considered to be the best candidates of the cathode for Energy Recovery Lin-ac (ERL) and Free Electron Laser (FEL) requiring a high brightness beam. We developed a system to evaporate the cathode as a thin film in vacuum to study the cathode performance. The cathode operational lifetime regarding not only on time, but also extracted charge density was studied. We found the lifetime is long enough for practical use in an accelerator.
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THPOW007	Cs2Te Photocathode Response Time Measurements and Femtosecond Comb Electron Beam Generation as a Milestone Towards Pre-Bunched Thz Fel Realization	3941
	A. Aryshev, Y. Honda, K. Lekomtsev, M. Shevelev, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	Funding: Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan and JSPS KAKENHI: 23226020 and 24654076 Currently there is a rapidly growing demand to increase the brightness of electron beams generated by conventional RF guns as well as to decrease the cost of the injector accelerator system for many research facilities worldwide. To address this demand we investigate one of the most important parameter of the high Q.E. conventional semiconductor Cs2Te photocathode, its response time. It sets the principle limitation for generated bunch length and hence maximum achievable beam brightness of electron diffraction and pre-bunched THz FEL facility's injectors. The experimental investigation was done at KEK: LUCX facility. The Cs2Te photocathode response time better than 250 fs was demonstrated. The generation of 4 micro-bunch comb electron beam with variable time separation as a crucial technology for pre-bunched THz FEL realization was achieved.
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THPOW008	DC Photoemission Gun Upgrade at the Compact ERL	3944
	N. Nishimori, R. Hajima, R. Nagai JAEA, Ibaraki-ken, Japan Y. Honda, T. Miyajima, T. Uchiyama, M. Yamamoto KEK, Ibaraki, Japan M. Mori JAEA/Kansai, Kyoto, Japan
	Funding: This work is partially supported by a JSPS Grant-in-Aid for Scientific Research in Japan (15H03594). The DC photoemission gun at the compact ERL (cERL) has stably provided beam for ERL commissioning and laser Compton scattering experiments since April 2013. The operational voltage has however been limited to 390 kV due to failures of two segments out of the ten segmented insulator. In order to recover 500 kV operation, we installed an additional two segmented insulator on the existing ten segmented insulator during summer shutdown in 2015. The details of the gun upgrade and the operational experience of the upgraded cERL gun will be presented.
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THPOW009	Optimal Design of a Photocathode Electron Gun with High-brightness and High-repetition Rate Based on Genetic Algorithm	3947
	Zh. X. Tang, X.M. Yang, W.Q. Zhang DICP, Dalian, People's Republic of China Y.J. Pei, Y. Yu USTC/NSRL, Hefei, Anhui, People's Republic of China
	A low RF frequency of normal conducting photocathode gun with high-brightness and high-repetition rate is designed as an electron source of the Next Generation Light Source (NGLS). In order to optimize the performance of the gun, a genetic multi-objective algorithm has been used. A genetic algorithm is used because of the inherent complexity of the large number of parameters of the cavity geometry available for optimization. On the other hand, the multiplicity of requirements on the beam, which include beam emittance, beam pulse length, energy chirp, as well as pulse shape and peak current, leads to a multi-objective approach for the optimization technique. In this paper, we present the status of the optimization simulations, using the SUPERFISH and PERMELA particle-in-cell code.
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THPOW010	Study on Characteristics of Asymmetric Centre Iris of Photocathode Microwave Electron Gun	3951
	Zh. X. Tang, X.M. Yang, W.Q. Zhang DICP, Dalian, People's Republic of China Y.J. Pei USTC/NSRL, Hefei, Anhui, People's Republic of China
	The characteristics of asymmetric iris between first cell and second cell of 1.6 cell photocathode gun are studied. For π-mode, the RF radial field of two sides of the iris is non anti-symmetric. Thus, the RF transverse force at the iris is not negligible. In this paper, we present the status of the optimization simulations, using the SUPERFISH and PARMELA particle-in-cell code. Numerical results of beam dynamics show that it can improve the emittance at the exit of the gun.
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THPOW011	The Measurement System of the Electron Gun with Double-anode Structure	3954
	F.L. Shang, J. Li, L. Shang USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: National Natural Science Foundation of China(11175181); National Natural Science Foundation of China(10875116) The double-anode structure with an intermediate electrode has been proposed to overcome the strong space-charge force on the cathode and improve the transverse focusing, which make the goal of high perveance and high compression ratio achieved. This gun plays a key role as the external injecting electron source of the independently-tunable-cells (ITC) RF gun. In order to understand the quality of the beam, a measurement system has been designed. The papers present the measurement system and the result of the test.
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THPOW015	Study of the Performance of Cs2Te Cathodes in the PHIN RF Photoinjector using Long Pulse Trains	3960
	C. Heßler, E. Chevallay, S. Döbert, V. Fedosseev, F. Friebel, I. Martini, M. Martyanov, H. Neupert, V. Nistor, M. Taborelli CERN, Geneva, Switzerland
	The drive beam of CLIC requires unusually high peak and average currents which is challenging for the electron source. As an alternative to the thermionic electron gun foreseen in the baseline design, a photoinjector option is under study at CERN using the PHIN photoinjector, which was designed for a bunch charge of 2.3 nC and 1200 ns train length. During operation with nominal train length in 2014, a large pressure increase in the vacuum system, attributed to a heating of the Faraday cup, caused a degradation of the photocathode. To overcome this problem a vacuum window has been installed to separate the Faraday cup from the rest of the vacuum system. In addition the train length has been further increased to 1600 ns to advance the beam parameters towards CLIC requirements. In this paper recent improved photocathode lifetime measurements carried out under these new conditions will be presented and compared with earlier measurements. Furthermore, the utilized Cs2Te cathode has been analyzed with X-ray Photoelectron Spectroscopy (XPS) before and after its usage in PHIN to get a better understanding of photocathode surface deterioration effects, which will also be discussed.
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THPOW016	Transverse Energy Spread Measurements from GaAs Photocathodes at Variable Wavelengths	3964
	T.C.Q. Noakes, R. Beech, L.B. Jones, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom H.E. Scheibler, A.S. Terekhov ISP, Novosibirsk, Russia
	The transverse energy spread spectrometer (TESS) is an instrument specially developed at Daresbury Laboratory to measure the intrinsic transverse and longitudinal energy distributions from photocathode materials. Early work on the instrument has focussed on its use for the characterisation of GaAs photocathodes such as those commonly used in DC photoinjectors. More recently work has been conducted to extend the range of materials which can be evaluated using this apparatus, in particular by incorporating a monochromated white light source. New results are presented using the white light source to measure the energy spread of a GaAs photocathode across a range of different wavelengths to evaluate how this changes with excess energy.
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THPOW017	VELA Photoinjector Cavity RF Investigations	3968
	L.S. Cowie, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom J.A. Mitchell Lancaster University, Lancaster, United Kingdom M.D. Roper STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	One of two ALPHA-X photocathode gun cavities, designed and fabricated at the Laboratoire de l'Accélérateur Linéaire, has been in operation on the VELA electron accelerator at Daresbury Laboratory since first beam in April 2013. In this time the maximum beam momentum recorded is 5.06 MeV/c. An investigation of the cavity has been performed with the aim of reconciling the expected momentum of over 6 MeV/c with the measured momentum. RF and beam simulation results are presented along with low power RF measurements of the cavity. One source of momentum loss, the flatness of the cathode face, is identified and rectified.
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THPOW018	Simulations of Field Emitted Dark Current Dynamics in DC Photoinjectors	3971
	P.J. Tipping, J.W. McKenzie, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Field emission is a concern in injectors with DC photoelectron guns because of the constant generation of dark current, which is accelerated down the beam line and can deteriorate the photoemitted bunch quality and lead to hardware damage. Simulations were carried out on the co-propagation of a field emitted, dark current halo and a photoemitted bunch in a typical 350 kV gun as used in an ERL or FEL injector, followed by a single cell buncher cavity. The photoemitted bunch repelled the halo longitudinally, leaving the area in the centre of the bunch with very low dark current, surrounded by two peaks of relatively high current at the front and back of the bunch. The peaks in current occur at all levels of dark current and were about 3.5 times the amplitude of the undisturbed dark current. The buncher caused the dark current to overcompress, forming a 'ghost' pulse an order of magnitude larger than the initial level of dark current, in front of the photoemitted bunch.
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THPOW019	Beam Characterisation and Machine Developments at VELA	3975
	D. Angal-Kalinin, A.D. Brynes, F. Jackson, S.P. Jamison, J.K. Jones, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, T.C.Q. Noakes, M.D. Roper, Y.M. Saveliev, D.J. Scott, R.J. Smith, E.W. Snedden, 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 C.S. Edmonds, F. Jackson, S.P. Jamison, J.K. Jones, J.W. McKenzie, B.D. Muratori, Y.M. Saveliev, D.J. Scott, C.P. Topping, P.H. Williams, A. Wolski Cockcroft Institute, Warrington, Cheshire, United Kingdom
	An overview is presented of developments on VELA (Versatile Electron Linear Accelerator), an RF photo-injector with two user stations at Daresbury Laboratory. Numerous commissioning, machine development, beam characterisation and user experiments have been completed in the past year. A new beamline and a dedicated multiuser station have been commissioned and the first experiments performed. A number of measures have been taken to improve the stability of machine by mitigating a phase drift, laser beam transport drift and a coherent ~1 Hz beam oscillation. The 6D phase space of the electron beam has been characterised through quad scans, transverse tomography and with a transverse deflecting cavity.
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THPOW020	S-Band Photoinjector Investigations by Multiobjective Genetic Optimizer	3979
	H.J. Qian, D. Filippetto, F. Sannibale LBNL, Berkeley, California, USA
	Photoinjectors has witnessed great progress in the past few decades, with low duty cycle high gradient guns, such as normal conducting S/L band gun, pushing the peak beam brightness frontier, and CW guns, such as DC gun, SRF gun and VHF gun, pushing the average beam brightness frontier. Due to different degrees of complexity, pulsed high gradient photoinjectors are usually optimized by manual scans, while CW photoinjectors are optimized by multi-objective genetic optimizers. In this paper, a multi-objective genetic optimizer is used to revisit S-band photoinjector beam brightness optimizations, showing a trade-off between peak current and transverse emittance, with the optimized injector layout depending on bunch charge and peak current. For 200 pC case, the final beam core brightness at injector exit is close to cathode maximum brightness in the 'cigar beam' regime. Assuming a thermal emittance of 0.5 μm/mm and a beam charge of 200 pC, about 90 nm slice emittance at 20 A peak current is achieved.
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THPOW021	Generation of Homogeneous and Patterned Electron Beams using a Microlens Array Laser-Shaping Technique	3983
SUPSS020	use link to see paper's listing under its alternate paper code
	A. Halavanau, P. Piot Northern Illinois University, DeKalb, Illinois, USA D.R. Edstrom, P. Piot, J. Ruan, J.K. Santucci Fermilab, Batavia, Illinois, USA W. Gai, G. Ha, J.G. Power, E.E. Wisniewski ANL, Argonne, Illinois, USA G. Ha POSTECH, Pohang, Kyungbuk, Republic of Korea G. Qiang TUB, Beijing, People's Republic of China
	Funding: Northern Illinois University - US DOE contract No. DE-SC0011831. Fermilab - US DOE contract No. DE-AC02-07CH11359. The Argonne wakefield facility - US DOE contract No. DE-AC02-06CH11357. In photocathodes the achievable electron-beam parameters are controlled by the laser used to trigger the photoemission process. Non-ideal laser distribution hampers the final beam quality. Laser inhomogeneities, for instance, can be "amplified" by space-charge force and result in fragmented electron beams. To overcome this limitation laser shaping methods are routinely employed. In the present paper we demonstrate the use of simple microlens arrays to dramatically improve the transverse uniformity. We also show that this arrangement can be used to produce transversely-patterned electron beams. Our experiments are carried out at the Argonne Wakefield Accelerator facility.
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THPOW023	Intrinsic Emittance Reduction in Transmission Mode Photocathodes	3987
SUPSS021	use link to see paper's listing under its alternate paper code
	H. Lee, I.V. Bazarov, L. Cultrera Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	High quantum efficiency (QE) and low emittance electron beams provided by multi-alkali photocathodes make them of great interest for next generation high brightness photoinjectors. Spicer's three-step model well describe the photoemission process, however, some photocathode characteristics such as their thickness have not been completely exploited to further improve the brightness of the generated electron beam. In this work, we report on the emittance and QE of a multi-alkali photocathode grown onto glass substrate operated in transmission and reflection modes at different photon energies. We observed a 20% reduction on the intrinsic emittance from the reflection to the transmission mode operation. This observation can be explained by inelastic electron-phonon scattering events experienced by electrons during their transit towards the cathode surface. This scattering will expect the further emittance reduction than the no scattering at the cryo-temperatures.
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THPOW025	Photocathode Growth and Characterization Advances at Cornell University	3990
	L. Cultrera, A.C. Bartnik, I.V. Bazarov, B.M. Dunham, C.M. Gulliford, H. Lee, R.A. Lipton, T.P. Moore Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Alkali-antimonides based photocathodes have demonstrated outstanding performance in high brightness electron beam production suitable for a wide range of applications such as FELs, ERLs and UED and for use in photomultiplier devices with picosecond resolution aimed at photon counting application in medicine and High Energy Physics. The photocathode laboratory at Cornell University is dedicated to studying the growth procedures and characterizing the properties in a wide range of photocathodes materials. Different experimental arrangements and alkali metal sources have been successfully explored to date to synthesize photosensitive materials. Recent work on commissioning a new growth chamber equipped with effusion cells loaded with pure metal allowing uniform deposition over large area substrates resulted on successful growth of photocathodes with extended sensitivity in the IR part of the spectrum and high efficiency alkali antimonides containing Rb metal. This and other advances aimed at demonstrating superior photocathodes will be presented.
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THPOW026	LLNL X-band RF Gun Results	3993
	R.A. Marsh, G.G. Anderson, C.P.J. Barty, D.J. Gibson LLNL, Livermore, California, USA Y. Hwang UCI, Irvine, California, USA
	Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 An X-band test station and Inverse Compton Scattering (ICS) x-ray source has been built and commissioned at LLNL. The electron beam source is a unique 5.59 cell RF photoinjector, which will be described in detail, including: quantum efficiency, emittance measurements, energy spread and jitter, final focus spot size and stability, laser profile and final transport, and consistency with expectations based on beam dynamics simulations.
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THPOW028	Automated Design for Standing Wave Electron Photoguns: TOPGUN RF Design	3999
	A.D. Cahill UCLA, Los Angeles, California, USA M. Dal Forno, V.A. Dolgashev SLAC, Menlo Park, California, USA
	Funding: DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515 Systematic design of RF photoguns involves multiple RF simulations in conjunction with beam dynamic simulations. RF simulations include tuning gun frequency, matching the gun to the feeding RF circuit, balancing the on axis electric fields between gun cells, minimizing surface electric and magnetic fields and power consumption, and optimizing separation of resonant mode frequencies. We created a tool that allows this multiple parameter optimization to be done automatically. We used SUPERFISH to accomplish the RF simulations. We present an example of the rf photogun TOPGUN design using these tools.
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FRXBB01	Achieved Performance of an All X-band Photo-injector	4253
	C. Limborg, C. Adolphsen, M.P. Dunning, R.K. Jobe, H. Li, D.J. McCormick, T.O. Raubenheimer, T. Vecchione, A.R. Vrielink, F.Y. Wang, S.P. Weathersby SLAC, Menlo Park, California, USA
	Funding: Work funded by DOE/SU Contract DE-AC02-76-SF00515 Building more compact accelerators to deliver high brightness electron beams for the generation of high flux, highly coherent radiation is a priority for the photon science community. A relatively straightforward reduction in footprint can be achieved by using high-gradient X-Band (11.4 GHz) RF technology. This talk presents the all X-band photo-injector facility at SLAC, covering the benefits of using this technology and highlighting the performance achieved.
	Slides FRXBB01 [40.418 MB]
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Paper

Title

Page

APEX Phase-II Commissioning Results at the Lawrence Berkeley National Laboratory

1041

F. Sannibale, J.A. Doyle, J. Feng, D. Filippetto, G.L. Harris, M.J. Johnson, T.D. Kramasz, D. Leitner, C.E. Mitchell, J.R. Nasiatka, H.A. Padmore, H.J. Qian, H. Rasool, J.W. Staples, S.P. Virostek, R.P. Wells, M.S. Zolotorev
LBNL, Berkeley, California, USA
S.M. Gierman, R.K. Li, J.F. Schmerge, T. Vecchione, F. Zhou
SLAC, Menlo Park, California, USA
C. Pagani, D. Sertore
INFN/LASA, Segrate (MI), Italy

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
Science needs in the last decade have been pushing the accelerator community to the development of high repetition rates (MHz/GHz-class) linac-based schemes capable of generating high brightness electron beams. Examples include X-ray FELs; ERLs for light source, electron cooling and IR to EUV FEL applications; inverse Compton scattering X-ray or gamma sources; and ultrafast electron diffraction and microscopy. The high repetition rate requirement has profound implications on the technology choice for most of the accelerator parts, and in particular for the electron gun. The successful performance of the GHz room-temperature RF photo-injectors running at rates <~ 100 Hz, cannot be scaled up to higher rates because of the excessive heat load that those regimes would impose on the gun cavity. In response to this gun need, we have developed at Berkeley the VHF-Gun, a lower-frequency room-temperature RF photo-gun capable of CW operation and optimized for the performance required by MHz-class X-ray FELs. The Advanced Photo-injector EXperiment (APEX) was funded and built for demonstrating the VHF gun performance, and the results of its last phase of commissioning are presented.

Slides TUOCA02 [12.015 MB]

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THPMY017

A Comparison of Surface Properties of Metallic Thin Film Photocathodes

3691

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

In this work physical vapour deposition magnetron sputtering has been employed to deposit metallic thin films onto Cu, Mo and Si substrates. The use of metallic thin films offers several advantages: (i) metal photocathodes present a fast response time and a relative insensitivity to the vacuum environment (ii) metallic thin films when prepared and transferred in vacuum can offer smoother and cleaner cathode surfaces. The photocathodes developed here will ultimately be used to drive NCRF guns such as that used in VELA and the proposed CLARA light source test facility. The samples grown on Si substrates were used to investigate the morphology and thickness of the film. The samples grown onto Cu and Mo substrates were analysed and tested as photocathodes in a surface characterisation chamber, where X-Ray photoelectron spectroscopy was employed to determine surface chemistry and a Kelvin probe apparatus used to determine work function. QE measurements were enabled using a 266 nm UV laser.

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THPOW001

Design of a 4.6-Cell RF Gun for the PHIL accelerator at LAL

3922

P. Chen, C. Bruni, S. Chancé, L. Garolfi, A. Gonnin, P. Lepercq, T. Vinatier
LAL, Orsay, France

A photo-injector with 4.6-cell and resonate frequency of 2.998 GHz has been designed and studied to replace the 2.5-cell RF gun + booster association. The cavity iris shape and dimensions were simulated systematically to optimize the shunt impedance. In this study, electron beam reaches to 9.7 MeV with a moderate peak accelerat-ing gradient of 80 MV/m. Considering a beam charge of 1 nC/bunch, average transverse emittance of ~ 5.9 πmm mrad and energy spread of ~ 0.8% can be obtained at the exit of the gun. The RF input power is only 10.2 MW due to the high shunt impedance. Asymmetry of the electric field due to the coupling port has also been studied using 3D codes for RF and beam dynamics calculations. We will present the RF design and beam calculations results.

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THPOW002

Electromagnetic, Thermal, and Structural Analysis of a THOMX RF Gun Using ANSYS

3925

M. El Khaldi, J. Bonis, A. Camara, L. Garolfi, A. Gonnin
LAL, Orsay, France

Photocathode RF guns are used in the first stage of electron beam generation and acceleration. The RF gun of THOMX is a 2.5 cell standing wave copper cavity with resonance frequency of 2998.55 MHz at 30 °C under vacuum. The metal photocathode such as copper or magnesium is inserted into the backplane of the cavity. Due to high repetition rates up to 50 Hz with the average dissipated power into the internal surfaces up to 1.5 kW, causing a heating and deformation of the cavity shape. Therefore, the cooling system of the device has to be well designed to take under control the deformations of the structure, providing a temperature increase as small and uniform as possible. For this purpose a fully coupled electromagnetic-thermal-structural finite element analysis on this gun has been performed with Ansys workbench. Numerical results show that the gun could operate at 3 μs RF pulse length and 50 Hz repetition rate with an average dissipated power of 1.5 kW. The gun average temperature is around 30 °C while the incoming water temperature is around 24°C. Internal speed of water is 2.5 m/s which corresponds to 15 l/min for the incoming water. The total pressure drop is around 0.4 bar

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THPOW003

Highlights on Metallic Photocathodes Used in SRF Gun

3928

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

For the accelerator-based light sources and the electron colliders, the development of photoinjectors has become a key technology. Especially for the superconducting radio frequency cavity based injector (SRF Gun), the searching for better photocathodes is always a principal technical challenge. To use metallic photocathodes for ELBE SRF Gun is the primary choice to prevent cavity contamination. In this contribution, we will report the investigation of Magnesium (Mg) in ELBE SRF gun, including laser cleaning treatment and the measurement on quantum efficiency, Schottky effect, dark current and damage threshold.
The work is supported by the European Community under the FP7 programme (EuCARD-2 and LA3NET) and by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1.

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THPOW004

Pulse Response Measurements of NEA Photocathodes at Different Laser Wavelengths

3931

M.A. Dehn, K. Aulenbacher, V. Bechthold
IKP, Mainz, Germany

For high average electron beam currents the length of the electron bunches must match the acceptance of the accelerator. At Johannes Gutenberg-University Mainz we are able to measure the longitudinal pulse response of NEA photocathodes (GaAs) under photo excitation of different wavelengths. A time resolution of < 2 ps at a beam energy of 100 keV is achieved, furthermore, a high dynamic range allows to investigate long ranging tails of the response (longitudinal halo). This serves to identify the best possible operation mode for high current photo sources.

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THPOW005

A Study of CsK2Sb Multi-alkali Photocathode by Ultraviolet Photoelectron Spectroscopy at UVSOR

3934

SUPSS022

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M. Urano, M. Kuriki, K. Negishi
HU/AdSM, Higashi-Hiroshima, Japan
T. Konomi, Y. Seimiya, N. Yamamoto
KEK, Ibaraki, Japan

Photocathode is one of the most important components in the next-generation accelerators, especially based on linear accelerators. Photocathode performance depends not only on electronic state in its bulk material but also on the surface condition. CsK2Sb multi-alkali photocathode is a candidate for the high brightness electron source because of its high quantum efficiency by green laser and its high robustness. We have carried out an UPS (UV Photoelectron Spectroscopy) experiment at UVSOR facility, synchrotron radiation light source in Aichi Japan. We have compared the UPS spectra among several samples, each one has a different quantum efficiency, and try to find physics which decide photocathode's performance. In this case, we focused some characters correlated to the quantum efficiency. I'm going to present a result of this analysis.

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THPOW006

A Study of Operational Lifetime of CsK2Sb Photo-cathode

3938

A. Yokota, R. Kaku, M. Kuriki, K. Negishi, M. Urano
HU/AdSM, Higashi-Hiroshima, Japan
Y. Seimiya
KEK, Ibaraki, Japan

A high performance electron beam generated with a laser photo-cathode is one of the most important pieces in the advanced accelerator. Because the CsK2Sb photo-cathode is robust with more than 10 % quantum efficiency (QE) by green laser (532nm), it is considered to be the best candidates of the cathode for Energy Recovery Lin-ac (ERL) and Free Electron Laser (FEL) requiring a high brightness beam. We developed a system to evaporate the cathode as a thin film in vacuum to study the cathode performance. The cathode operational lifetime regarding not only on time, but also extracted charge density was studied. We found the lifetime is long enough for practical use in an accelerator.

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THPOW007

Cs2Te Photocathode Response Time Measurements and Femtosecond Comb Electron Beam Generation as a Milestone Towards Pre-Bunched Thz Fel Realization

3941

A. Aryshev, Y. Honda, K. Lekomtsev, M. Shevelev, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

Funding: Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan and JSPS KAKENHI: 23226020 and 24654076
Currently there is a rapidly growing demand to increase the brightness of electron beams generated by conventional RF guns as well as to decrease the cost of the injector accelerator system for many research facilities worldwide. To address this demand we investigate one of the most important parameter of the high Q.E. conventional semiconductor Cs2Te photocathode, its response time. It sets the principle limitation for generated bunch length and hence maximum achievable beam brightness of electron diffraction and pre-bunched THz FEL facility's injectors. The experimental investigation was done at KEK: LUCX facility. The Cs2Te photocathode response time better than 250 fs was demonstrated. The generation of 4 micro-bunch comb electron beam with variable time separation as a crucial technology for pre-bunched THz FEL realization was achieved.

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THPOW008

DC Photoemission Gun Upgrade at the Compact ERL

3944

N. Nishimori, R. Hajima, R. Nagai
JAEA, Ibaraki-ken, Japan
Y. Honda, T. Miyajima, T. Uchiyama, M. Yamamoto
KEK, Ibaraki, Japan
M. Mori
JAEA/Kansai, Kyoto, Japan

Funding: This work is partially supported by a JSPS Grant-in-Aid for Scientific Research in Japan (15H03594).
The DC photoemission gun at the compact ERL (cERL) has stably provided beam for ERL commissioning and laser Compton scattering experiments since April 2013. The operational voltage has however been limited to 390 kV due to failures of two segments out of the ten segmented insulator. In order to recover 500 kV operation, we installed an additional two segmented insulator on the existing ten segmented insulator during summer shutdown in 2015. The details of the gun upgrade and the operational experience of the upgraded cERL gun will be presented.

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THPOW009

Optimal Design of a Photocathode Electron Gun with High-brightness and High-repetition Rate Based on Genetic Algorithm

3947

Zh. X. Tang, X.M. Yang, W.Q. Zhang
DICP, Dalian, People's Republic of China
Y.J. Pei, Y. Yu
USTC/NSRL, Hefei, Anhui, People's Republic of China

A low RF frequency of normal conducting photocathode gun with high-brightness and high-repetition rate is designed as an electron source of the Next Generation Light Source (NGLS). In order to optimize the performance of the gun, a genetic multi-objective algorithm has been used. A genetic algorithm is used because of the inherent complexity of the large number of parameters of the cavity geometry available for optimization. On the other hand, the multiplicity of requirements on the beam, which include beam emittance, beam pulse length, energy chirp, as well as pulse shape and peak current, leads to a multi-objective approach for the optimization technique. In this paper, we present the status of the optimization simulations, using the SUPERFISH and PERMELA particle-in-cell code.

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THPOW010

Study on Characteristics of Asymmetric Centre Iris of Photocathode Microwave Electron Gun

3951

Zh. X. Tang, X.M. Yang, W.Q. Zhang
DICP, Dalian, People's Republic of China
Y.J. Pei
USTC/NSRL, Hefei, Anhui, People's Republic of China

The characteristics of asymmetric iris between first cell and second cell of 1.6 cell photocathode gun are studied. For π-mode, the RF radial field of two sides of the iris is non anti-symmetric. Thus, the RF transverse force at the iris is not negligible. In this paper, we present the status of the optimization simulations, using the SUPERFISH and PARMELA particle-in-cell code. Numerical results of beam dynamics show that it can improve the emittance at the exit of the gun.

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THPOW011

The Measurement System of the Electron Gun with Double-anode Structure

3954

F.L. Shang, J. Li, L. Shang
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: National Natural Science Foundation of China(11175181); National Natural Science Foundation of China(10875116)
The double-anode structure with an intermediate electrode has been proposed to overcome the strong space-charge force on the cathode and improve the transverse focusing, which make the goal of high perveance and high compression ratio achieved. This gun plays a key role as the external injecting electron source of the independently-tunable-cells (ITC) RF gun. In order to understand the quality of the beam, a measurement system has been designed. The papers present the measurement system and the result of the test.

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THPOW015

Study of the Performance of Cs2Te Cathodes in the PHIN RF Photoinjector using Long Pulse Trains

3960

C. Heßler, E. Chevallay, S. Döbert, V. Fedosseev, F. Friebel, I. Martini, M. Martyanov, H. Neupert, V. Nistor, M. Taborelli
CERN, Geneva, Switzerland

The drive beam of CLIC requires unusually high peak and average currents which is challenging for the electron source. As an alternative to the thermionic electron gun foreseen in the baseline design, a photoinjector option is under study at CERN using the PHIN photoinjector, which was designed for a bunch charge of 2.3 nC and 1200 ns train length. During operation with nominal train length in 2014, a large pressure increase in the vacuum system, attributed to a heating of the Faraday cup, caused a degradation of the photocathode. To overcome this problem a vacuum window has been installed to separate the Faraday cup from the rest of the vacuum system. In addition the train length has been further increased to 1600 ns to advance the beam parameters towards CLIC requirements. In this paper recent improved photocathode lifetime measurements carried out under these new conditions will be presented and compared with earlier measurements. Furthermore, the utilized Cs2Te cathode has been analyzed with X-ray Photoelectron Spectroscopy (XPS) before and after its usage in PHIN to get a better understanding of photocathode surface deterioration effects, which will also be discussed.

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THPOW016

Transverse Energy Spread Measurements from GaAs Photocathodes at Variable Wavelengths

3964

T.C.Q. Noakes, R. Beech, L.B. Jones, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
H.E. Scheibler, A.S. Terekhov
ISP, Novosibirsk, Russia

The transverse energy spread spectrometer (TESS) is an instrument specially developed at Daresbury Laboratory to measure the intrinsic transverse and longitudinal energy distributions from photocathode materials. Early work on the instrument has focussed on its use for the characterisation of GaAs photocathodes such as those commonly used in DC photoinjectors. More recently work has been conducted to extend the range of materials which can be evaluated using this apparatus, in particular by incorporating a monochromated white light source. New results are presented using the white light source to measure the energy spread of a GaAs photocathode across a range of different wavelengths to evaluate how this changes with excess energy.

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THPOW017

VELA Photoinjector Cavity RF Investigations

3968

L.S. Cowie, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
J.A. Mitchell
Lancaster University, Lancaster, United Kingdom
M.D. Roper
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

One of two ALPHA-X photocathode gun cavities, designed and fabricated at the Laboratoire de l'Accélérateur Linéaire, has been in operation on the VELA electron accelerator at Daresbury Laboratory since first beam in April 2013. In this time the maximum beam momentum recorded is 5.06 MeV/c. An investigation of the cavity has been performed with the aim of reconciling the expected momentum of over 6 MeV/c with the measured momentum. RF and beam simulation results are presented along with low power RF measurements of the cavity. One source of momentum loss, the flatness of the cathode face, is identified and rectified.

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THPOW018

Simulations of Field Emitted Dark Current Dynamics in DC Photoinjectors

3971

P.J. Tipping, J.W. McKenzie, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Field emission is a concern in injectors with DC photoelectron guns because of the constant generation of dark current, which is accelerated down the beam line and can deteriorate the photoemitted bunch quality and lead to hardware damage. Simulations were carried out on the co-propagation of a field emitted, dark current halo and a photoemitted bunch in a typical 350 kV gun as used in an ERL or FEL injector, followed by a single cell buncher cavity. The photoemitted bunch repelled the halo longitudinally, leaving the area in the centre of the bunch with very low dark current, surrounded by two peaks of relatively high current at the front and back of the bunch. The peaks in current occur at all levels of dark current and were about 3.5 times the amplitude of the undisturbed dark current. The buncher caused the dark current to overcompress, forming a 'ghost' pulse an order of magnitude larger than the initial level of dark current, in front of the photoemitted bunch.

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THPOW019

Beam Characterisation and Machine Developments at VELA

3975

D. Angal-Kalinin, A.D. Brynes, F. Jackson, S.P. Jamison, J.K. Jones, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, T.C.Q. Noakes, M.D. Roper, Y.M. Saveliev, D.J. Scott, R.J. Smith, E.W. Snedden, 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
C.S. Edmonds, F. Jackson, S.P. Jamison, J.K. Jones, J.W. McKenzie, B.D. Muratori, Y.M. Saveliev, D.J. Scott, C.P. Topping, P.H. Williams, A. Wolski
Cockcroft Institute, Warrington, Cheshire, United Kingdom

An overview is presented of developments on VELA (Versatile Electron Linear Accelerator), an RF photo-injector with two user stations at Daresbury Laboratory. Numerous commissioning, machine development, beam characterisation and user experiments have been completed in the past year. A new beamline and a dedicated multiuser station have been commissioned and the first experiments performed. A number of measures have been taken to improve the stability of machine by mitigating a phase drift, laser beam transport drift and a coherent ~1 Hz beam oscillation. The 6D phase space of the electron beam has been characterised through quad scans, transverse tomography and with a transverse deflecting cavity.

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THPOW020

S-Band Photoinjector Investigations by Multiobjective Genetic Optimizer

3979

H.J. Qian, D. Filippetto, F. Sannibale
LBNL, Berkeley, California, USA

Photoinjectors has witnessed great progress in the past few decades, with low duty cycle high gradient guns, such as normal conducting S/L band gun, pushing the peak beam brightness frontier, and CW guns, such as DC gun, SRF gun and VHF gun, pushing the average beam brightness frontier. Due to different degrees of complexity, pulsed high gradient photoinjectors are usually optimized by manual scans, while CW photoinjectors are optimized by multi-objective genetic optimizers. In this paper, a multi-objective genetic optimizer is used to revisit S-band photoinjector beam brightness optimizations, showing a trade-off between peak current and transverse emittance, with the optimized injector layout depending on bunch charge and peak current. For 200 pC case, the final beam core brightness at injector exit is close to cathode maximum brightness in the 'cigar beam' regime. Assuming a thermal emittance of 0.5 μm/mm and a beam charge of 200 pC, about 90 nm slice emittance at 20 A peak current is achieved.

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THPOW021

Generation of Homogeneous and Patterned Electron Beams using a Microlens Array Laser-Shaping Technique

3983

SUPSS020

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A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
D.R. Edstrom, P. Piot, J. Ruan, J.K. Santucci
Fermilab, Batavia, Illinois, USA
W. Gai, G. Ha, J.G. Power, E.E. Wisniewski
ANL, Argonne, Illinois, USA
G. Ha
POSTECH, Pohang, Kyungbuk, Republic of Korea
G. Qiang
TUB, Beijing, People's Republic of China

Funding: Northern Illinois University - US DOE contract No. DE-SC0011831. Fermilab - US DOE contract No. DE-AC02-07CH11359. The Argonne wakefield facility - US DOE contract No. DE-AC02-06CH11357.
In photocathodes the achievable electron-beam parameters are controlled by the laser used to trigger the photoemission process. Non-ideal laser distribution hampers the final beam quality. Laser inhomogeneities, for instance, can be "amplified" by space-charge force and result in fragmented electron beams. To overcome this limitation laser shaping methods are routinely employed. In the present paper we demonstrate the use of simple microlens arrays to dramatically improve the transverse uniformity. We also show that this arrangement can be used to produce transversely-patterned electron beams. Our experiments are carried out at the Argonne Wakefield Accelerator facility.

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THPOW023

Intrinsic Emittance Reduction in Transmission Mode Photocathodes

3987

SUPSS021

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H. Lee, I.V. Bazarov, L. Cultrera
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

High quantum efficiency (QE) and low emittance electron beams provided by multi-alkali photocathodes make them of great interest for next generation high brightness photoinjectors. Spicer's three-step model well describe the photoemission process, however, some photocathode characteristics such as their thickness have not been completely exploited to further improve the brightness of the generated electron beam. In this work, we report on the emittance and QE of a multi-alkali photocathode grown onto glass substrate operated in transmission and reflection modes at different photon energies. We observed a 20% reduction on the intrinsic emittance from the reflection to the transmission mode operation. This observation can be explained by inelastic electron-phonon scattering events experienced by electrons during their transit towards the cathode surface. This scattering will expect the further emittance reduction than the no scattering at the cryo-temperatures.

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THPOW025

Photocathode Growth and Characterization Advances at Cornell University

3990

L. Cultrera, A.C. Bartnik, I.V. Bazarov, B.M. Dunham, C.M. Gulliford, H. Lee, R.A. Lipton, T.P. Moore
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Alkali-antimonides based photocathodes have demonstrated outstanding performance in high brightness electron beam production suitable for a wide range of applications such as FELs, ERLs and UED and for use in photomultiplier devices with picosecond resolution aimed at photon counting application in medicine and High Energy Physics. The photocathode laboratory at Cornell University is dedicated to studying the growth procedures and characterizing the properties in a wide range of photocathodes materials. Different experimental arrangements and alkali metal sources have been successfully explored to date to synthesize photosensitive materials. Recent work on commissioning a new growth chamber equipped with effusion cells loaded with pure metal allowing uniform deposition over large area substrates resulted on successful growth of photocathodes with extended sensitivity in the IR part of the spectrum and high efficiency alkali antimonides containing Rb metal. This and other advances aimed at demonstrating superior photocathodes will be presented.

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THPOW026

LLNL X-band RF Gun Results

3993

R.A. Marsh, G.G. Anderson, C.P.J. Barty, D.J. Gibson
LLNL, Livermore, California, USA
Y. Hwang
UCI, Irvine, California, USA

Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344
An X-band test station and Inverse Compton Scattering (ICS) x-ray source has been built and commissioned at LLNL. The electron beam source is a unique 5.59 cell RF photoinjector, which will be described in detail, including: quantum efficiency, emittance measurements, energy spread and jitter, final focus spot size and stability, laser profile and final transport, and consistency with expectations based on beam dynamics simulations.

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THPOW028

Automated Design for Standing Wave Electron Photoguns: TOPGUN RF Design

3999

A.D. Cahill
UCLA, Los Angeles, California, USA
M. Dal Forno, V.A. Dolgashev
SLAC, Menlo Park, California, USA

Funding: DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515
Systematic design of RF photoguns involves multiple RF simulations in conjunction with beam dynamic simulations. RF simulations include tuning gun frequency, matching the gun to the feeding RF circuit, balancing the on axis electric fields between gun cells, minimizing surface electric and magnetic fields and power consumption, and optimizing separation of resonant mode frequencies. We created a tool that allows this multiple parameter optimization to be done automatically. We used SUPERFISH to accomplish the RF simulations. We present an example of the rf photogun TOPGUN design using these tools.

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FRXBB01

Achieved Performance of an All X-band Photo-injector

4253

C. Limborg, C. Adolphsen, M.P. Dunning, R.K. Jobe, H. Li, D.J. McCormick, T.O. Raubenheimer, T. Vecchione, A.R. Vrielink, F.Y. Wang, S.P. Weathersby
SLAC, Menlo Park, California, USA

Funding: Work funded by DOE/SU Contract DE-AC02-76-SF00515
Building more compact accelerators to deliver high brightness electron beams for the generation of high flux, highly coherent radiation is a priority for the photon science community. A relatively straightforward reduction in footprint can be achieved by using high-gradient X-Band (11.4 GHz) RF technology. This talk presents the all X-band photo-injector facility at SLAC, covering the benefits of using this technology and highlighting the performance achieved.

Slides FRXBB01 [40.418 MB]

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