IPAC2013 - List of Keywords (impedance)

Paper	Title	Other Keywords	Page
MOPEA059	The Optimization of Transverse Stripline Kicker	kicker, simulation, vacuum, insertion	214
	H.P. Hsueh, C.-C. Chang, Y.P. Chang, J.-R. Chen, Y.T. Cheng, G.-Y. Hsiung, Y.C. Yang NSRRC, Hsinchu, Taiwan J.-R. Chen National Tsing Hua University, Hsinchu, Taiwan
	The construction of a new 3 GeV synchrotron facility, Taiwan Photon Source, is ongoing. It is required to install stripline kickers to suppress instability generated by mismatch between injection kickers or imperfect installation of vacuum components all around. First, the design philosophy will be described for transverse stripline kickers. HFSS electromagnetic simulation software is used to optimize all structure parameters like electrode dimensions, electrode distance from vacuum chambers etc. to make transverse stripline kicker working more efficiently and effectively. All simulation results will be presented in this paper and all structure dimension choices will be discussed and the final prototype structure dimensions will be selected from the discussion.

MOPFI047	Analysis and Design of Matching Unit for a RF Driven Plasma Source for Fusion Purpose	plasma, ion, ion-source, neutral-beams	389
	H.K. Yue Huazhong University of Science and Technology(HUST), Wuhan, People's Republic of China D.Z. Chen, M. Fan, J. Huang, D. Li, X.F. Li, K.F. Liu, C.R. Wan, C. Zhou HUST, Wuhan, People's Republic of China
	A RF driven plasma exciter for producing negative ions, aiming for heating and current drive neutral beam injectors for fusion applications, is in developing in Huazhong University of Science and Technology (HUST). In order to couple the maximum RF power to the source, the matching unit is designed to match the impedance of the source to that of the RF coaxial line. Firstly, a FEM model was built to estimate the equivalent circuit parameters of the source. Numerical predictions were compared with a small experimental setup to verify the accuracy of the fem model. Based on the numerical results, the RF coil and the matching components were carefully designed. Finally, the matching circuit for the source is developed and tested. Experimental results will be presented in the full paper.

MOPFI052	A New Lead Ion Injection System for the CERN SPS with 50 ns Rise Time	injection, kicker, ion, septum	398
	B. Goddard, O. Aberle, J. Borburgh, E. Carlier, K. Cornelis, L. Ducimetière, L.K. Jensen, T. Kramer, D. Manglunki, A. Mereghetti, V. Mertens, D. Nisbet, B. Salvant, L. Sermeus CERN, Geneva, Switzerland
	The LHC High Luminosity upgrade project includes a performance upgrade for heavy ions. One of the present performance limitations is the rise time of the SPS injection kicker system, which imposes a spacing of at least 220 ns between injected bunch trains at the operational rigidity. A reduction of this rise time to 50 ns for lead ions is requested as part of the suite of measures needed to increase the present design performance by a factor three. A new injection system based on a fast pulsed septum and a fast kicker has been proposed to fulfil this rise time requirement, and to meet all the constraints associated with the existing high intensity proton injection in the same region. This paper describes the concept and the required equipment parameters, and explores the implications of such a system for SPS operation.

MOPME015	Numerical Wakefield Calculations for Electro-optical Measurements	simulation, wakefield, laser, storage-ring	503
	B. Kehrer, A. Borysenko, E. Hertle, N. Hiller, V. Judin, S. Marsching, A.-S. Müller, M.J. Nasse, M. Schuh KIT, Karlsruhe, Germany
	Funding: This project is funded by the Federal Ministry of Education and Research under the contract number 05K10VKC The technique of electro-optical measurements allows precise and single-shot measurements of the bunch length and shape. The installation of such a near-field setup changes the impedance of the storage ring and the corresponding effects have to be studied carefully. One possibility is to use numerical codes for simulating the wakefields induced by the setup. Such simulations has been done using the wakefield solver implemented in the CST Studio Suite. In this paper we present the simulation results together with first measurements.

MOPME023	ORBIT Beam Simulation Progress in the 3-GeV Rapid Cycling Synchrotron of J-PARC	simulation, lattice, injection, synchrotron	521
	P.K. Saha, H. Harada, H. Hotchi, Y. Shobuda, M. Yamamoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan J.A. Holmes ORNL, Oak Ridge, Tennessee, USA S. Kato Tohoku University, Graduate School of Science, Sendai, Japan
	We have made a numerous progress for beam simulation in the 3-GeV RCS (Rapid Cycling Synchrotron) of J-PARC (Japan Proton Accelerator Research Complex) by using 3-D particle tracking code, ORBIT. Namely, the TEAPOT lattice file used for ORBIT tracking has been made to give exactly same results to that with SAD model used for the RCS beam commissioning. In addition, time dependent lattice functions of the injection chicane magnets and similar other time dependent lattice imperfections, which are already found to have significant influences on the beam losses in the real machine have also been successfully introduced. At present, time dependent transverse and longitudinal impedances are going to be introduced. That should prove the ORBIT code much more matured for beam simulations in synchrotrons. Latest beam simulation results illustrating these new realistic features are presented.

MOPME041	Design and Calculation of the Stripline Beam Position Monitor for HLS II Storage Ring	quadrupole, coupling, simulation, storage-ring	562
	F.F. Wu, C. Cheng, W.B. Li, P. Lu, T.J. Ma, B.G. Sun, H. Xu, Y.L. Yang, Z.R. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: Supported by the National Science Foundation of China (10875117, 11005105, 11175173) According to the requirements of HLS II upgraded, in order to acquire the non-intercepting measurement of beam position and quadrupole component, a new stripline beam position monitor (BPM) was designed for storage ring. The BPM parameters were optimized to acquire impedence matching with characteristic impedance of the external transmission lines and the coupling coefficients between the electrodes were calculated. According to the difference/sum and log-ratio methods, the horizontal and vertical sensitivities, mapping figures and fitting polynomials wered acquired. The results showed that sensitivities using log-ratio method were bigger than those using difference/sum method. The sum signal was also simulated when beam displacement varied from (0 mm, 0 mm) to (5 mm, 5 mm), the result showed that the variation of normalized sum signal was no more than ±6%. The gaussian weighted method of a two-dimensional grid structure was used to simulate the gaussian bunch and simulate the beam transverse quadrupole component changing with position (x, y), the result showed that the beam transverse quadrupole component changed linearly with position combination (x2-y2).

MOPME044	A Novel Type of Forward Coupler Slotted Stripline Pickup Electrode for CSRe Stochastic Cooling	pick-up, vacuum, kicker, simulation	571
	J.X. Wu, X.J. Hu, M. Li, J.W. Xia, J.C. Yang, Y. Zhang, G. Zhu IMP, Lanzhou, People's Republic of China F. Caspers CERN, Geneva, Switzerland
	A novel type of slotted or perforated strip-line pick-up or kicker electrode structure for CSRe stochastic cooling for non relativistic particle beams with b=v/c values around 0.7 is presented. This slotted structure is to be used as a forward coupler with the output signal taken from the downstream end and has a rather large relative bandwidth of several octaves. The electrode structure and pickup tank, as well as the beam test result will be presented in this paper.

MOPME046	Preliminary Experimental Results of Axial B-dot Measuring Beam Tilt	high-voltage, coupling, simulation, dipole	577
	X. He, Q. Li, C. Ma, J. Pang, L. Zhao CAEP/IFP, Mainyang, Sichuan, People's Republic of China
	Funding: This work is under the support of NSFC project No. 11175166 Beam monitors sensitive to the beam's azimuthal B-dot field (sometimes referred as B-dots) are widly used to measure the displacement of beam centroid, as the beam generates a dipole term of the azimuthal magnetic field. The authors have pointd out that the similar B-dots sensitive to axial magnetic field can be used to measure the beam tilt directly in earlier work. A monitor which consists of four azimuthal B-dots and four axial B-dos is designed and fabricated. The monitor was tested on a coaxial calibration stand, which has a character resistance of 50 Ohm. Two position tuners are installed on the calibration stand, to adjust the position and the tilt of the inner conductor. Experiments show that the axial B-dot monitor can be successfully used to measure the tilt of the inner conductor directly.

MOPME059	R&D of a Beam Position Monitor for RISP	linac, ion, heavy-ion, pick-up	607
	E.-S. Kim KNU, Deagu, Republic of Korea A. Heo Kyungpook National University, Daegu, Republic of Korea H.K. Park CHEP, Daegu, Republic of Korea
	We have investigated on the R&D of stripline beam position monitor for the heavy-ion accelearator at Korea. We present the detailed design and fabrications on the beam position monitor in superconducting linac that the beam is accelerated to 200 MeV/u.

MOPWA004	Development of a Non-inductive Ceramic Resistor	kicker, injection, pulsed-power, power-supply	669
	T. Sugimoto, K. Fan, K. Ishii, H. Matsumoto KEK, Ibaraki, Japan K. Abe Hitachi Haramachi Electronics Co. Ltd., Hitachishi, Ibaraki, Japan S. Fukuoka University of Tsukuba, Graduate School of Pure and Applied Sciences,, Tsukuba, Ibaraki, Japan
	Non-inductive ceramic resistors, based on alumina and carbon, are used for impedance matching in the circuit of the J-PARC main ring injection kicker system. The kickers were installed in December 2011, and have been in operation successfully since then. However, discharges at the edge of the ceramic bulk were observed after several weeks’ operation, which increase resistance from O(100) to O(1M). Investigation indicates that poor contact with the rough surface of the ceramic bulk due to irregular shaped spots causes micro-gaps, which trigger the discharge. In order to improve the contact, one type of brazing technology has been experimentally applied to one resistor. Another resistor had an annealed thin copper plate inserted, and both resistors were tested and compared. In this paper, we will describe details of the development of the resistors and give future prospects.

MOPWA005	Development of a Feedback Control System for Resonant Power Supplies in the J-PARC 3-GeV Synchrotron	controls, power-supply, feedback, quadrupole	672
	Y. Watanabe JAEA, Ibaraki-ken, Japan N. Tani JAEA/J-PARC, Tokai-mura, Japan
	In the J-PARC 3-GeV Synchrotron, dipole magnets and seven families of quadrupole magnets are excited with a DC-biased 25 Hz sinusoidal waveforms using an individual resonant circuits. This paper proposed a feedback system to improve the amplitude and phase stability, specially against variation of capacitance caused by temperature characteristics in the resonant circuits. The control system has been successfully demonstrated and achieved amplitude and phase stability under ±0.005% and ±0.5 uS, respectively.

MOPWA009	Development of a Fast Compensation Kicker System for J-PARC Main-ring Injection	kicker, injection, simulation, power-supply	684
	S. Fukuoka University of Tsukuba, Graduate School of Pure and Applied Sciences,, Tsukuba, Ibaraki, Japan K. Fan, K. Ishii, H. Matsumoto, T. Sugimoto KEK, Ibaraki, Japan
	Injection system of J-PARC main ring employs four lumped kickers to deflect the incoming beam. The residual field caused by tail and reflection of excitation current increases the closed beam orbit leading to particle loss in high power operation. A correction method using a fast kicker system to compensate the remaining angle is being developed. Doe to the narrow bunch spacing, transmission line kicker is selected to satisfy requirements of fast rise and fall time. The kicker magnet uses ceramic capacitors instead of parallel metal plates to make the magnet compact and reduce the stray inductance. Capacitors are installed in vacuum chamber. A very thin core is used to reduce distributed inductance. A bandwidth is calculated as 160 MHz. A Marx generator using FET switches has been studied, which is able to produce fast rise and fall time as 50 ns. Any pulse shape is generated by choosing switches to fire. A prototype magnet and a power supply have been fabricated for parameters test. In this paper, we will report the details of the system design, analyze the measurement results and give future prospects.

MOPWA018	CW-type HV Power Supply of 50 Hz and its Application in Accelerator Power Supply	high-voltage, electron, power-supply, damping	699
	Z.-F. He, D.M. Li, Y.H. Liu, S.L. Wang, J.-L. Zhang, Y.-T. Zhang SINAP, Shanghai, People's Republic of China
	Funding: The Knowledge Innovation Program of Chinese Academy of Sciences 　　The high-voltage power supply is an integral part of accelerator technology, as its stable and reliable output is an important guarantee for accelerator properly working. In a number of engineering practice of accelerator design and construction, we tried to use the Cockcroft-Walton (CW) type of power supply driven by 50 Hz and got success. It is of simple structure, low cost, easy maintenance, and high efficiency. This report describes the technical difficulties and the solutions in the CW-type power supply driven by 50 Hz. It also gives an introduction of the latest design of 800 kV/30 mA electron accelerator, which is being assembled at SINAP. Recent work has shown that it is an option to choose 50 Hz driven power system when it is more lenient on the voltage ripple but needed to be as high as possible on the energy conversion efficiency.

MOPWA022	A 500 kV Pulser with Fast Risetime for EMP Simulation	high-voltage, simulation, pulsed-power, laser	708
	W. Jia, W.Q. Chen, J.N. Li, J.P. Tang, L.S. Xie, Y.Z. Xie, G.W. Zhang NINT, Xi'an, People's Republic of China
	A fast risetime generator with 500kV rated output voltage for the electromagnetic pulse ( EMP ) effects experiment is fabricated. It mainly consists of a low inductance Marx ge nerator, a compact independent-sealed peaking capacitor, an output switch, and a small quantity of gas-sealed insulated containers. Compared with other similar pulsers mentioned in IEC 61000-4-32, the insulated containers of the generator are independent of each other in gas-sealed structure, and its number is les s than that of other pulsers. It can be used to drive a guided wave antenna directly to produce an electromagnetic environment, which conformed with the new standard for high-altitude nuclear explosion electromagnetic pulse (HEMP) developed by IEC. Output voltage produced by the generator in demo-load state can reach to 600kV. And, risetime of the waveform is 1.2ns, pulse width (FWHM) being 32ns. When the generator driving a 10m guided-wave antenna, an output voltage with a risetime of no more than 2.7ns and a FWHM of 30ns is achieved.

MOPWA030	Upgrade of the LHC Injection Kicker Magnets	vacuum, kicker, injection, electron	729
	M.J. Barnes, P. Adraktas, V. Baglin, G. Bregliozzi, S. Calatroni, F. Caspers, H.A. Day, L. Ducimetière, M. Garlaschè, V. Gomes Namora, J.M. Jimenez, N. Magnin, V. Mertens, E. Métral, B. Salvant, M. Taborelli, J.A. Uythoven, W.J.M. Weterings CERN, Geneva, Switzerland
	The two LHC injection kicker systems, comprising 4 magnets per ring, produce a kick of 1.3 T.m with a rise-time of less than 900 ns and a flattop ripple of less than ±0.5%. A beam screen is placed in the aperture of each magnet, to provide a path for the image current of the high intensity LHC beam and screen the ferrite yoke against wake fields. The screen consists of a ceramic tube with conductors in the inner wall. The initially implemented beam screen ensured a low rate of electrical breakdowns while providing an adequate beam coupling impedance. Operation with increasingly higher intensity beams, stable for many hours at a time, now results in substantial heating of the ferrite yoke, sometimes requiring cool down over several hours before the LHC can be refilled. During the long shutdown in 2013/2014 all 8 kicker magnets will be upgraded with an improved beam screen and an increased emissivity of the vacuum tank. In addition equipment adjacent to the injection kickers and various vacuum components will also be modified to help reduce the vacuum pressure in the kickers during high-intensity operation. This paper discusses the upgrades as well as their preparation and planning.

MOPWA031	Beam Induced Ferrite Heating of the LHC Injection Kickers and Proposals for Improved Cooling	vacuum, kicker, injection, simulation	732
	M.J. Barnes, S. Calatroni, F. Caspers, L. Ducimetière, M. Garlaschè, V. Gomes Namora, V. Mertens, Z.K. Sobiech, M. Taborelli, J.A. Uythoven, W.J.M. Weterings CERN, Geneva, Switzerland H.A. Day UMAN, Manchester, United Kingdom
	The two LHC injection kicker systems produce a kick of 1.3 T.m with a flattop duration variable up to 7860 ns, and rise and fall times of less than 900 ns and 3000 ns, respectively. A beam screen is placed in the aperture of each magnet, which consists of a ceramic tube with conductors in the inner wall. The conductors provide a path for the beam image current and screen the ferrite yoke against wake fields. Recent LHC operation, with high intensity beam stable for many hours, resulted in significant heating of both the ferrite yoke and beam impedance reduction ferrites. For one kicker magnet the ferrite yoke approached its Curie temperature. As a result of a long thermal time-constant the ferrites can require several hours to cool enough to re-inject beam, thus limiting the availability of the LHC. Thermal measurement data has been analysed, a thermal model developed and emissivity measurements carried out. The effects of various measures to improve the ferrite cooling have been simulated, including an improved emissivity of the vacuum tank and active cooling on the outside of the tank.

MOPWA032	Reduction of Surface Flashover of the Beam Screen of the LHC Injection Kickers	kicker, injection, vacuum, simulation	735
	M.J. Barnes, P. Adraktas, S. Calatroni, F. Caspers, L. Ducimetière, V. Gomes Namora, V. Mertens, R. Noulibos, M. Taborelli, B. Teissandier, J.A. Uythoven, W.J.M. Weterings CERN, Geneva, Switzerland
	The LHC injection kicker magnets include beam screens to shield the ferrite yokes against wake fields resulting from the high intensity beam. The screening is provided by conductors lodged in the inner wall of a ceramic support tube. Operation with increasingly higher bunch intensity, and narrow bunches, now requires improved ferrite screening. This will be implemented by additional conductors; however the good high-voltage behaviour of the kicker magnets must not be compromised by the supplementary screening. Extensive studies and optimisations have been carried out, to better satisfy the often conflicting requirements for low beam coupling impedance, fast magnetic field rise-time, high vacuum and good high voltage behaviour. A new configuration is proposed which reduces significantly the electric field associated with the screen conductors and the secondary electron yield of the surface of the ceramic tube. Results of high voltage test results are also presented.

MOPWA033	Modelling of Parasitic Inductances of a High Precision Inductive Adder for CLIC	kicker, damping, coupling, emittance	738
	J. Holma, M.J. Barnes CERN, Geneva, Switzerland S.J. Ovaska Aalto University, School of Science and Technology, Aalto, Finland
	The CLIC study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC pre-damping rings and damping rings will produce, through synchrotron radiation, ultra-low emittance beam with high bunch charge. To avoid beam emittance increase, the damping ring kicker systems must provide extremely flat, high-voltage, pulses. The specifications for the extraction kickers of the DRs are particularly demanding: the flat-top of the pulses must be ±12.5 kV with a combined ripple and droop of not more than ±0.02 % (±2.5 V). An inductive adder is a very promising approach to meeting the specifications. However, the output impedance of the inductive adder needs to be well matched to the system impedance. The primary leakage inductance, which cannot be computed accurately analytically, has a significant effect upon the output impedance of the inductive adder. This paper presents predictions, obtained by modelling the 3D geometry of the adder structure and printed circuit boards using the FastHenry code, for primary leakage inductance.

MOPWA042	The Leakage Current Induced by Stray Capacitance in the Pulse Magnet System	kicker, booster, high-voltage, injection	762
	C.S. Chen, C.K. Chan, K.H. Hsu, Y.-H. Liu, C.S. Yang NSRRC, Hsinchu, Taiwan
	A huge amount of current must be provided during the nominal operation of the pulse magnet system in TPS (Taiwan Photon Source). It comes with all kinds of electromagnetic noises, including radiated and conducted EMI (electromagnetic interferences). The primary object of this article is to clarify the paths of induced EMI, especially by means of capacitance induction. Furthermore, some geometrical suggestions which had been tested are listed in this paper as the guidelines of the pulse magnet design. According to the measurement, proper distance and surface area lead to sufficient insulation and reduce the leakage current under the expected value.

MOPWO003	Multibunch Tracking Code Development to Account for Passive Landau Cavities	cavity, electron, damping, radiation	885
	M. Klein, R. Nagaoka SOLEIL, Gif-sur-Yvette, France
	The MAX IV 3 GeV storage ring will achieve an ultra-low horizontal emittance of 0.24 nm rad by using a multibend achromat lattice. Passive harmonic cavities are introduced to relax the Touschek-lifetime and intrabeam scattering issues as well as fight collective beam instabilities via Landau damping. Since instabilities occur during injection, when the passive harmonic cavity potential is also time varying, it became important to simulate this transient process. The most promising approach was considered to be multibunch tracking which also allows for an arbitrary filling pattern. Since every bunch is represented by numerous macroparticles, internal motions as well as microstructures in the charge distribution can be followed.

MOPWO007	Numerical Calculation of Electromagnetic Fields in Acceleration Cavities Under Precise Consideration of Coupler Structures	dipole, cavity, electromagnetic-fields, resonance	897
	C. Liu, W. Ackermann, W.F.O. Müller, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: Work supported by BMBF under contract 05H12RD5 The acceleration with superconducting radio frequency cavities requires dedicated couplers to transfer energy from the radio frequency source to the beam. Simultaneously, higher order mode couplers are installed to effectively suppress parasitic modes. Therefore, the numerical eigenmode analysis based on real-valued variables is no longer suitable to describe the dissipative acceleration structure. At the Computational Electromagnetics Laboratory (TEMF) a robust parallel eigenmode solver to calculate the eigenmodes in the lossy acceleration structure is available. This eigenmode solver is based on complex-valued finite element analysis and utilizes basis functions up to the second order on curved tetrahedral elements to enable the high precision elliptical cavity simulations. The eigenmode solver has been applied to the TESLA 1.3 GHz accelerating cavity to determine the resonance frequency, the quality factor and the corresponding field distribution for all 192 eigenmodes up to the 5th dipole passband (3.12 GHz).

MOPWO022	Design and Manufacturing Description of the Prototype Striplines for the Extraction Kicker of the CLIC Damping Rings	kicker, extraction, damping, vacuum	930
	C. Belver-Aguilar, A. Faus-Golfe IFIC, Valencia, Spain M.J. Barnes CERN, Geneva, Switzerland J. Gómez Trinos Vacuum Projects, Paterna, Spain D. Gutiérrez Arribas Trinos Vacuum Projects, S.L., Paterna - Valencia, Spain F. Toral CIEMAT, Madrid, Spain
	The Pre-Damping Rings (PDRs) and Damping Rings (DRs) of CLIC are needed to reduce the beam emittances to the small values required for the main linacs. The injection and extraction, from the PDRs and DRs, are carried out by kicker systems. In order to achieve both low beam coupling impedance and reasonable broadband impedance matching to the electrical circuit, striplines have been chosen for the kicker elements. The design of the stripline kicker was previously carried out by modelling the striplines with simulation codes such as HFSS, Quickfield and CST Particle Studio. In order to have a complete analysis of the striplines, the effect of electrodes supports and coaxial feedthroughs have been studied in detail. In this paper, electromagnetic analyses of the complete striplines, including fabrication tolerances, are reported. Furthermore, a new idea for impedance matching is presented.

TUODB201	Recent Progress on the Development of a High Gradient RF System using High Impedance Magnetic Alloy, FT3L	cavity, acceleration, synchrotron, controls	1152
	C. Ohmori, K. Hara, K. Hasegawa, M. Toda, M. Yoshii KEK, Ibaraki, Japan M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan
	An upgrade project of J-PARC MR (Main Ring) includes developments of high gradient RF cavities and magnet power supplies for high repetition rate. A dedicated production system for high impedance magnetic alloy (FT3L) cores was assembled in J-PARC. This setup demonstrated that we can produce material with two times higher muQf product compared to the cores used for present cavities. And, the new results also show up to 20% higher impedance than the 2011 production with the former setup. In this summer, the system will be used for mass production of 200 FT3L cores for J-PARC MR. The cores produced in 2011 are already used for standard machine operation. The operation experience shows that the power loss in the cores was reduced significantly as expected. The scenario describing the upgrade plan of MR and the cavity replacements is reported. By the replacement plan, the total acceleration voltage will be almost doubled, while the number of RF stations remains the same.
	Slides TUODB201 [5.105 MB]

TUODB203	Dual Chip in Single Module Solid-State Power Amplifier Design for Compact Transmitter Architecture	insertion, storage-ring, booster, linac	1158
	T.-C. Yu, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Y.-H. Lin, Z.L. Liu, C.H. Lo, M.H. Tsai, Ch. Wang, T.-T. Yang, M.-S. Yeh NSRRC, Hsinchu, Taiwan
	At present, the high power solid-state technique transmitter design are composed of hundreds parallel combined single chip for hundreds Watts power modules to achieve enough output power. Although the large numbers can bring high redundancy during system operation, the power hungry of next generation RF system of accelerator would need much more modules to reach its power requirement. Huge amount of power modules would bring the complexity and difficulty in power combining, system construction, management and maintenance. To overcome this problem, upgrading the power level of a single module could be the solution. Besides depending on the power level growing with technology advancement in semiconductor industry, a circuit level solution to combine dual chip in advance in a single PCB board is proposed to produce twice power as single chip. Such feasible solution can overcome the over-complexity of future several-hundreds kW solid-state transmitter design.
	Slides TUODB203 [2.337 MB]

TUPEA035	Plasma Effect in the Longitudinal Space Charge Induced Microbunching Instability	plasma, electron, space-charge, background	1220
	D. Huang, Q. Gu SINAP, Shanghai, People's Republic of China K.Y. Ng Fermilab, Batavia, USA
	Funding: National Science Foundation of China (NSFC), grant No. 11275253, and US DOE, contract DE-FG02-92ER40747. In many cases, the longitudinal space charge (LSC) is a dominant factor to bring in the microbunching instability in the LINAC of a Free-Electron-Laser (FEL) facility. The current model of LSC impedance* derived from the fundamental electromagnetic theor is widely used to explain the physics of the LSC-induced microbunching instability. However, in the case of highly bright electron beams, the plasma effect starts to play a role. In this paper, the basic model of the LSC impedance including the plasma effect is built up by solving the Vlasov and Poisson equations in 6 dimensional phase space, and the investigation is done to study the modification to the gain of the instability based on the model. The solutions indicate that the gain does not only depend on the spatial information of the beam, but also on the velocity (momentum) and time information. The comparison of the gains of the microbunching instability in the LINAC of Shanghai soft X-ray Free Electron Laser Facility (SXFEL) computed by various methods is also given and the discrepancy is illustrated. Marco Venturini, Phys. Rev. ST Accel. Beams 11, 034401 (2008) J. D. Jackson, Classical Electrodynamics (Wiley, 1999) * Z. Huang, et. al., Phys, Rev. ST Accel. Beams 7, 074401 (2004)

TUPEA075	Passively Driving X-band Structures to Achieve Higher Beam Energies	electron, linac, laser, gun	1304
	S. Biedron, S.V. Milton, N. Sipahi, T. Sipahi CSU, Fort Collins, Colorado, USA
	Particle accelerators at X-band frequencies have gradients of around 100 MV/m. This technology permits more compact accelerators. One of our aims at the Colorado State University Accelerator Laboratory is to adapt this technology to our L-band (1.3 GHz) accelerator system to increase our overall beam energy; however, we would like to do this in a passive manner, i.e. one that does not require investment in an expensive, custom, high-power klystron system. In this paper we explore using the beam from our L-band 6 MeV photoinjector to power an x-band structure tuned to the 9th harmonic of our L-band system, 11.7 GHz. Electron bunches will be generated at a repetition rate of 81.25 MHz and passed through a high shunt impedance x-band accelerating structure where they will resonantly excite the fundamental field. We will optimize the system to create the highest accelerating potential within this structure. Once the peak gradient is achieved we will send a single electron bunch through the system at a phase that places it on the crest of the X-band accelerating wave thereby increasing the electron bunch energy by some amount without need for additional external power sources.

TUPFI033	Colliding During the Squeeze and β* Leveling in the LHC	luminosity, collider, controls, optics	1415
	X. Buffat EPFL, Lausanne, Switzerland W. Herr, M. Lamont, T. Pieloni, S. Redaelli, J. Wenninger CERN, Geneva, Switzerland
	While more challenging operationally, bringing the beams into collisions during the β squeeze rather than after presents some advantages. The large tune spread arising from the non-linearity of head-on beam-beam interactions can damp impedance-driven instabilities much more efficiently than external non-linearity such as octupoles presently used in operation. Moreover, colliding during the squeeze allows to level the luminosity, optimizing the pile-up in the experiments without changing the longitudinal distribution of collisions. Operational issues are discussed and experimental results from the LHC are presented.

TUPFI034	Observations of Two-beam Instabilities during the 2012 LHC Physics Run	octupole, damping, betatron, luminosity	1418
	T. Pieloni EPFL, Lausanne, Switzerland G. Arduini, X. Buffat, R. Giachino, W. Herr, M. Lamont, N. Mounet, E. Métral, G. Papotti, B. Salvant, J. Wenninger CERN, Geneva, Switzerland S.M. White BNL, Upton, Long Island, New York, USA
	During the 2012 run coherent beam instabilities have been observed in the LHC at 4 TeV, during the betatron squeeze and in collision for special filling patterns. Several studies to characterize these instabilities have been carried out during operation and in special dedicated experiments. In this paper we summarize the observations collected for different machine parameters and the present understanding of the origin of these instabilities.

TUPFI036	Observation of Beam Instabilities with Very Tight Collimation	damping, collimation, proton, octupole	1424
	H. Burkhardt, N. Mounet, T. Pieloni CERN, Geneva, Switzerland
	We report about the observation of instabilities in the LHC in special runs with high β^* and very tight collimation down to 2 σ which increases the transverse impedance significantly. The losses appeared primarily on the highest intensity, non-colliding bunches which can be interpreted as evidence for insufficient Landau damping. We describe the beam conditions, observations and possible explanations for the observed effects.

TUPFI063	Electromagnetic Coupling between High Intensity LHC Beams and the Synchrotron Radiation Monitor Light Extraction System	simulation, resonance, extraction, synchrotron	1493
	F. Roncarolo, W. Andreazza, A. Bertarelli, E. Bravin, F. Caspers, M. Garlaschè, A. Goldblatt, J-J. Gras, O.R. Jones, T. Lefèvre, E. Métral, A.A. Nosych, B. Salvant, G. Trad, R. Veness, C. Vollinger, M. Wendt CERN, Geneva, Switzerland
	The CERN LHC is equipped with two Synchrotron Radiation Monitor systems used to characterise transverse and longitudinal beam distributions. Since the end of the 2011 LHC run the light extraction system, based on a retractable mirror, has suffered deformation and mechanical failure that is correlated to the increase in beam intensity. Temperature probes have associated these observations to a strong heating of the mirror support with a dependence on the longitudinal bunch length and shape, indicating the origin as electromagnetic coupling between the beam and the structure. This paper combines all this information with the aim of characterising and improving the system in view of its upgrade during the current LHC shutdown. Beam-based observations are presented along with electromagnetic and thermomechanical simulations and complemented by laboratory measurements, including the study of the RF properties of different mirror bulk and coating materials.

TUPME017	Validation of the Microwave Instability in the Damping Ring of SuperKEKB using VFP Solver	damping, simulation, wakefield, synchrotron	1604
	L. Wang SLAC, Menlo Park, California, USA H. Ikeda, K. Ohmi, K. Oide, D. Zhou KEK, Ibaraki, Japan
	Microwave instability driven by CSR impedance in the damping ring of Super-KEKB is a concern due to its high bunch current. To understand the beam dynamics, we simulate the microwave instability using Vlasov-Fokker-Planck (VFP) solver. The longitudinal wake potential is calculated as a sum of the contributions due to vacuum chamber components distributed around the ring, including geometry wake field and CSR wake. To improve the accuracy of the simulation of microwave instability, the coherent synchrotron radiation impedance is calculated to very high frequency to get more accurate wake field with a short bunch. The CSR wake is much larger than the geometry wake. The threshold is just above the design current and saw-tooth type of instability is found above the threshold.

TUPME032	Update on Beam Induced RF Heating in the LHC	injection, kicker, proton, simulation	1646
	B. Salvant, O. Aberle, G. Arduini, R.W. Aßmann, V. Baglin, M.J. Barnes, W. Bartmann, P. Baudrenghien, O.E. Berrig, A. Bertarelli, C. Bracco, E. Bravin, G. Bregliozzi, R. Bruce, F. Carra, F. Caspers, G. Cattenoz, S.D. Claudet, H.A. Day, M. Deile, J. Esteban Müller, P. Fassnacht, M. Garlaschè, L. Gentini, B. Goddard, A. Grudiev, B. Henrist, S. Jakobsen, O.R. Jones, O. Kononenko, G. Lanza, L. Lari, T. Mastoridis, V. Mertens, N. Mounet, E. Métral, A.A. Nosych, J.L. Nougaret, S. Persichelli, A.M. Piguiet, S. Redaelli, F. Roncarolo, G. Rumolo, B. Salvachua, M. Sapinski, R. Schmidt, E.N. Shaposhnikova, L.J. Tavian, M.A. Timmins, J.A. Uythoven, A. Vidal, J. Wenninger, D. Wollmann, M. Zerlauth CERN, Geneva, Switzerland H.A. Day UMAN, Manchester, United Kingdom L. Lari IFIC, Valencia, Spain
	Since June 2011, the rapid increase of the luminosity performance of the LHC has come at the expense of increased temperature and pressure readings on specific near-beam LHC equipment. In some cases, this beam induced heating has caused delays whilie equipment cools down, beam dumps and even degradation of these devices. This contribution gathers the observations of beam induced heating attributable to beam coupling impedance, their current level of understanding and possible actions that are planned to be implemented during the long shutdown in 2013-2014.

TUPME033	Evaluation of the Beam Coupling Impedance of New beam Screen Designs for the LHC Injection Kicker Magnets	kicker, coupling, injection, resonance	1649
	H.A. Day UMAN, Manchester, United Kingdom M.J. Barnes, F. Caspers, E. Métral, B. Salvant CERN, Geneva, Switzerland R.M. Jones Cockcroft Institute, Warrington, Cheshire, United Kingdom
	The LHC injection kicker magnets (MKIs) have experienced a significant degree of beam induced heating since the beginning of the 2011 due to the increasing intensity stored in the LHC, for long periods of time, and the relatively large broadband impedance of the installed kicker magnets. In this paper we show the sources of impedance in the MKIs, especially the effect that the beam screen dimensions have on the impedance. We show how these alter the power loss, and present an improved beam screen design that improves shielding on the magnet, whilst further improving electrical breakdown.

TUPWA005	Study of Collective Beam Instabilities for the MAX IV 3 GeV Ring	simulation, vacuum, damping, wakefield	1730
	M. Klein, R. Nagaoka SOLEIL, Gif-sur-Yvette, France G. Skripka, P.F. Tavares, E.J. Wallén MAX-lab, Lund, Sweden
	The present paper reports on a systematic simulation study made on the collective beam instability in the MAX IV 3 GeV ring. We study both single and multibunch instabilities in the longitudinal plane. Specifically, we focus on the microwave instabilities which are considered to be particularly dangerous for MAX IV, in view of its small effective radius of aperture (b_eff < 11 mm), the high intensity (500 mA) and the low emittance (0.24 nm.rad) nature of the circulating beam. Single and multibunch tracking are performed using wake fields that were numerically obtained using GdfidL for the ensemble of the vacuum components. A special effort was made to include dynamically the effect of harmonic cavities that lengthen the bunch and introduce Landau damping, whose details are described in the companion paper . The study aims to confirm the effectiveness of storing long bunches in the 100 MHz RF system, where tune spreads are further increased by the harmonic cavities, in order to fight against collective instabilities. M. Klein and R. Nagaoka "Multibunch Tracking Code Development to Account for Passive Landau Cavities", these proceedings

TUPWA008	Computation of Wakefields for an In-vacuum Undulator at PETRA III	vacuum, undulator, wakefield, simulation	1736
	E. Gjonaj, L. Lünzer, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany R. Wanzenberg DESY, Hamburg, Germany
	Funding: Work supported by DESY, Hamburg, Germany At DESY the installation of an in-vacuum undulator at the synchrotron radiation facility PETRA III is under consideration. The moveable magnet array of the undulator is installed inside the vacuum chamber to achieve shorter wavelength synchrotron radiation. A thin metal foil covers the magnet structure to mitigate resistive wall wakefields. Moveable tapered transitions connect the magnet structure and the adjacent vacuum duct to reduce the geometric wakefields. Nevertheless these moveable tapered transitions contribute significantly to the impedance budget of PETRA III. The computer codes MAFIA, CST-Studio and PBCI have been used to calculate the longitudinal and transverse wakefields. The results for the loss and kick parameters are presented and compared to the corresponding parameters for a standard undulator section.

TUPWA009	Bunch by Bunch Intra-Bunch Feedback System for Curing Transverse Beam Instabilities at the J-PARC MR	feedback, injection, kicker, betatron	1739
	O. A. Konstantinova, Y.H. Chin, Y. Kurimoto, T. Obina, M. Okada, K. Takata, M. Tobiyama, T. Toyama KEK, Ibaraki, Japan Y. Shobuda JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	At the J-PARC Main Ring (MR), transverse instabilities have been observed during the injection and at the onset of acceleration with large particle losses. The present bunch by bunch feedback system, operating in a narrowband mode, has been effectively suppressing these instabilities, allowing the beam power to reach 230kW with only 400W of particle losses. The observed beam signals show that bunches are still executing complicated intra-bunch oscillations even if the narrowband feedback system is on, though they are not imposing significant particle losses at present. The new and more advanced broadband feedback system has been developed for control of the intra-bunch oscillations and further reduction of particle losses. The elaborate analysis code has been also developed on the MATLAB platform to analyse effects of the broadband feedback system on intra-bunch oscillations. This paper describes the development of these advanced instruments and presents the analysis of the latest beam test results using the MATLAB code.

TUPWA010	A Trial to Reduce the Kicker Impedance of 3-GeV RCS in J-PARC	kicker, resonance, acceleration, status	1742
	Y. Shobuda, N. Hayashi, T. Takayanagi JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan Y. Irie KEK, Ibaraki, Japan T. Toyama J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	At 3GeV RCS in J-PARC, the kicker impedance has been considered to be the dominant source to cause the beam instability. Recently, experimental studies demonstrate that the beam instability is suppressed by reducing the kicker impedance. In this report, a trial to reduce the kicker impedance is reported.

TUPWA014	The Status of Coupling Impedance Measurement for the CSNS/RCS Extraction Kicker Prototype*	kicker, coupling, simulation, extraction	1754
	L. Huang, Y. Li, R.H. Liu, Y.D. Liu, S. Wang, O. Xiao IHEP, Beijing, People's Republic of China
	Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) is a high intensity proton accelerator, with average beam power of 100kW. In order to high intensity beam operation, the beam coupling impedance of the extracted kickers must be controlled. Longitudinal and transverse impedance of extracted kicker prototype with power supply had been roughly measured by coaxial-wire and dual-wire methods respectively. At the same time, impedance of window has been analyzed theoretically and simulated based on CST PARTICLE STUDIO.

TUPWA015	The Study of Bunch Lengthening in Electron Storage Ring	synchrotron, storage-ring, luminosity, electron	1757
	Y. Li, L. Wang, Y. Zhang IHEP, Beijing, People's Republic of China
	The bunch length of electron storage ring of BEPCII was measured repeatedly during steady synchronous mode and streak camera was calibrated well. From the bench lengthening , the coupling impedance of the whole ring was estimated, which was according with theoretic impedance budget . Meanwhile, the small ap optics for improving the luminosity was feasible in collision mode form synchronous result .

TUPWA023	Design of the Tuning System for the He⁺ Coupled RFQ-SFRFQ Cavity	cavity, rfq, simulation, linac	1775
	W.L. Xia, J.E. Chen, S.L. Gao, Z.Y. Guo, Y.R. Lu, S.X. Peng, Z. Wang, X.Q. Yan, J. Zhao, K. Zhu PKU, Beijing, People's Republic of China
	Funding: Supported by NSFC 10905003, 11079001, 91026012 Corresponding author: wangzhi@pku.edu.cn The CRS (coupled RFQ-SFRFQ) cavity is a new type linac that couples traditional RFQ (radio frequency quadrupole) and SFRFQ (separated function RFQ) electrodes into a single cavity. The overall design of the CRS cavity has been completed and the linac is being manufactured currently. In this paper, we aimed to design a frequency tuning system for the CRS cavity, which will be used to explore the electromagnetic field distribution between RFQ and SFRFQ sections in the cavity. The frequency range, variation of Q value, power consumption and electric field distribution were investigated. Based on the beam dynamic program SFRFQDYNv1.0, we analysed the beam transmission properties of the cavity under the unbalanced electric field distribution. The optimized parameters of the tuning system were obtained.

TUPWA030	Impedances Calculations of Bellows in HLS II Storage Ring	wakefield, storage-ring, shielding, coupling	1784
	Q. Zhang, W. Li, L. Wang USTC/NSRL, Hefei, Anhui, People's Republic of China
	The upgrade project of Hefei Lighe Source storage ring is carrying on.In this project,a new Bellows, in which shielding is provided by sprung fingers which can slide along the beam screen,is installed at the accelerator interaction area In order to reduce this impedance to an acceptable value. The contributions of Bellows to short range wakefields and broadband impedance were calculated numerically by Mafia code .

TUPWA038	Equilibrium Bunch Density Distribution with Passive Harmonic Cavities in the MAX IV 3 GeV Storage Ring	cavity, storage-ring, emittance, damping	1790
	P.F. Tavares, Å. Andersson, A. Hansson MAX-lab, Lund, Sweden
	The MAX IV storage rings will use third harmonic cavities operated passively to lengthen the bunches and alleviate collective instabilities. These cavities are an essential ingredient in the MAX IV design concept and are required for achieving the final design goals in terms of stored current, beam emittance and beam lifetime. This paper reports on fully self-consistent calculations of the longitudinal bunch density distribution in the MAX IV 3 GeV storage ring, which indicate that up to a factor 5 increase in RMS bunch length is achievable with a purely passive system.

TUPWA039	Identification of the SPS Impedance at 1.4 GHz	optics, simulation, resonance, bunching	1793
	T. Argyropoulos, T. Bohl, H. Damerau, J. Esteban Müller, E.N. Shaposhnikova, H. Timko CERN, Geneva, Switzerland
	In the SPS spectrum measurements of very long single bunches were used in the past to identify sources of longitudinal microwave instability. Shielding of the identified objects significantly improved the beam stability. However, longitudinal instabilities are still one of the limitations for high intensity LHC beams in the SPS. Recently the same measurement technique was used again, revealing a strong high frequency resonance. During the slow de-bunching with the RF switched off, the presence of different resonant impedances leads to a line density modulation at the resonant frequencies. Longitudinal profiles of bunches of various intensities were acquired. For sufficiently high intensities their spectra show a fast growing and strong modulation at 1.4 GHz. Measurements using two transverse optics with different transition energy are compared. Reproducing the measurements with numerical simulations, including the known SPS longitudinal impedances, allowed the parameter range of this unknown source to be determined. Possible candidates as impedance sources in the SPS ring are investigated.

TUPWA040	Loss of Landau Damping for Inductive Impedance in a Double RF System	damping, emittance, synchrotron, simulation	1796
	T. Argyropoulos, E.N. Shaposhnikova CERN, Geneva, Switzerland A.V. Burov Fermilab, Batavia, USA
	In this paper the thresholds of the loss of Landau damping due to the presence of inductive impedance in a single and double harmonic RF systems are determined, both from calculations and particle simulations. High harmonic RF system, operating in bunch lengthening mode is used in many accelerators with space charge or inductive impedance to reduce the peak line density or stabilize the beam. An analytical approach, based on emerging of the discrete Van Kampen modes, shows that improved stability in a double RF system can be achieved only below some critical value of longitudinal emittance. Above this threshold, a phase shift of more than 15 degrees between the two RF components is proven to stabilize the bunch. These results, confirmed also by particle simulations, are able to explain now observations during the ppbar operation of the SPS. The thresholds in bunch shortening mode as well as in a single RF case are compared with this regime.

TUPWA042	Lessons Learned and Mitigation Measures for the CERN LHC Equipment with RF Fingers	resonance, vacuum, damping, simulation	1802
	E. Métral, O. Aberle, R.W. Aßmann, V. Baglin, M.J. Barnes, O.E. Berrig, A. Bertarelli, G. Bregliozzi, S. Calatroni, F. Carra, F. Caspers, H.A. Day, M. Ferro-Luzzi, M.A. Gallilee, C. Garion, M. Garlaschè, A. Grudiev, J.M. Jimenez, O.R. Jones, O. Kononenko, R. Losito, J.L. Nougaret, V. Parma, S. Redaelli, B. Salvant, P.M. Strubin, R. Veness, C. Vollinger, W.J.M. Weterings CERN, Geneva, Switzerland
	Beam-induced RF heating has been observed in several LHC components when the bunch/beam intensity was increased and/or the bunch length reduced. In particular eight bellows, out of the ten double-bellows modules present in the machine in 2011, were found with the spring, which should keep the RF fingers in good electrical contact with the central insert, broken. Following these observations, the designs of all the components of the LHC equipped with RF fingers have been reviewed. The lessons learnt and mitigation measures are presented in this paper.

TUPWA043	Impedance Studies for VMTSA Module of LHC Equipped with RF Fingers	simulation, resonance, factory	1805
	O. Kononenko, F. Caspers, A. Grudiev, E. Métral, B. Salvant CERN, Geneva, Switzerland
	During 2011 run of LHC it was found that beam-induced heating causes many issues for accelerator components. Particularly some of the double-bellow modules, called VMTSA modules, were found to have deformed RF fingers and a broken spring which ensured good contact between them and a central insert. Impedance studies have been performed for different types of nonconformities and benchmarked against measurements. It was found that even a small gap between the fingers and a central insert could be fatal for the VMTSA operation. Results of this study were an input for the further thermal analysis.

TUPWA047	Collimator Impedance Measurements in the LHC	simulation, optics, proton, collimation	1817
	N. Mounet, R. Bruce, E. Métral, S. Redaelli, B. Salvachua, B. Salvant, G. Valentino CERN, Geneva, Switzerland
	The collimation system of the LHC is one of the largest impedance contributors of the machine, in particular for its imaginary part. To evaluate the collimator impedance and its evolution with integrated luminosity, several measurement campaigns were performed along the year 2012, in which collimator jaws were moved back-and-forth leading to significant tune shifts for a nominal intensity bunch in the machine. These observations are compared to the results from HEADTAIL simulations with the impedance model in its current state of development.

TUPWA049	Short High-Intensity Bunches for Plasma Wakefield Experiment AWAKE in the CERN SPS	optics, emittance, proton, plasma	1820
	H. Timko, T. Argyropoulos, H. Bartosik, T. Bohl, J. Esteban Müller, E.N. Shaposhnikova CERN, Geneva, Switzerland A.V. Petrenko BINP SB RAS, Novosibirsk, Russia
	Obtaining the shortest possible bunch length in combination with the smallest transverse emittances and highest bunch intensity – this is the wish list of the proton-bunch driven, plasma wakefield acceleration experiment AWAKE currently under feasibility study at CERN. A few measurement sessions were conducted to determine the achievable bunch properties and their reproducibility. To obtain a short bunch length, the bunches were rotated in longitudinal phase space using the maximum available RF voltage prior to extraction. Measurements were carried out in two optics with different transition energies. The main performance limitation is longitudinal beam instability that develops during the acceleration ramp. With lower transition energy, beam stability is improved, but the bucket area is smaller for the same voltage. Based on the results obtained, we shall discuss the choice of optics, the impact of longitudinal instabilities, the importance of reproducibility, as well as options for improving the bunch parameters.

TUPWA052	Loss Factor and Impedance Analysis for the Diamond Storage Ring	storage-ring, vacuum, wiggler, simulation	1826
	R. Bartolini, R.T. Fielder, C.A. Thomas Diamond, Oxfordshire, United Kingdom
	Diamond Light Source is investigating the possibility of increasing the storage ring operating current above the nominal 300 mA. A campaign of measurements and simulations has been carried out in order to understand the extent of the parasitic energy loss and characterise the most important items which build up the machine impedance. In this paper we report on the most recent measurements of the longitudinal loss factor and the present status of the impedance database with an initial comparison between the two.

TUPWA057	Effects of Transient CSR Wakefields on Microbunching in a Bunch Compressor	wakefield, lattice, radiation, FEL	1832
	C.E. Mitchell, J. Qiang LBNL, Berkeley, California, USA
	Funding: Supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The standard analytical model of CSR-induced microbunching in a bunch compressor chicane makes use of a steady-state 1-D model of the longitudinal CSR interaction. This model is numerically generalized to include the effects of transient CSR wakefields due to bend entry and exit, as well as CSR that is generated in upstream bends and propagates across one or more lattice elements before interacting with the beam. The resulting linear integral equation for CSR-induced microbunching is solved numerically for the second bunch compressor of a proposed Next Generation Light Source.

TUPWA071	Studies of Resistive Wall Heating at JLAB FEL	FEL, wiggler, resonance, electron	1868
	R. Li, S.V. Benson JLAB, Newport News, Virginia, USA
	Funding: Work supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. When the JLAB FEL is under CW operation, it had been observed that temperature rises over the wiggler vacuum chamber, presumably as the result of the power deposition on the resistive wall of the wiggler chamber. Previous analyses have been done on the resistive wall impedance for various cases, such as DC, AC, and anomalous skin effects. Here we report an investigation on the beam kinetic energy losses for each of these cases. This study includes the non-ultrarelativistic effect on resistive wall loss, for both round pipe and parallel plates. We will present the comparison of our results with the measured data obtained during CW operation of the JLAB FEL. Other possible factors contributing to the measured heating will also be discussed. K. Bane and G. Stupakov, SLAC-PUB-10707, 2004.

TUPWA074	Studies of Ion Beam Instabilities for Low Energy RHIC Operations with Electron Cooling	ion, electron, simulation, emittance	1871
	G. Wang, M. Blaskiewicz, V. Litvinenko BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Electron cooling has the potential to compensate the emittance growth of the circulating ion beam due to intra-beam scattering at low energy. A test of electron cooling for RHIC low energy operations has been planned at IP2. Apart from the wakefield from the environment, the coherent interaction between the electron beam and ion beam could also play a role for the instability threshold. This work presents studies of ion beam stabilities in presence of coherent electron-ion interactions for the planned low energy RHIC electron-cooling test using the simulation code TRANFT.

WEOAB102	CSR-driven Longitudinal Single Bunch Instability Thresholds	synchrotron, resonance, damping, electron	2041
	P. Kuske BESSY GmbH, Berlin, Germany
	According to Bane, et al.* threshold currents should follow a quite simple scaling law. More detailed theoretical results for the underlying shielded CSR-interaction have been performed for BESSY-II and the MLS and will be presented in comparison with observations at these storage rings. It is found that there are parameter regions where the instability is weak and thus thresholds depend on damping time and synchrotron tune. Theoretical findings are in surprisingly good agreement with most of the observed instability features. * K.L. Bane, et al., Phys. Rev. ST-AB 13, 104402 (2010)
	Slides WEOAB102 [0.779 MB]

WEPWA006	Beam Heat Load Measurements with COLDDIAG at the Diamond Light Source	electron, synchrotron, synchrotron-radiation, radiation	2135
	S. Gerstl, S. Casalbuoni, A.W. Grau, T. Holubek, D. Saez de Jauregui, R. Voutta KIT, Eggenstein-Leopoldshafen, Germany R. Bartolini, M.P. Cox, E.C. Longhi, G. Rehm, J.C. Schouten, R.P. Walker Diamond, Oxfordshire, United Kingdom M. Migliorati, B. Spataro INFN/LNF, Frascati (Roma), Italy
	Understanding the heat load from an electron beam is still an open issue for the cryogenic design of superconducting insertion devices. COLDDIAG, a cold vacuum chamber for diagnostics was designed and built specially for this purpose. With the equipped instrumentation, which covers temperature sensors, pressure gauges, mass spectrometers as well as retarding field analyzers it is possible to measure the beam heat load, total pressure, and gas content as well as the net flux and energy of particles hitting the chamber walls. Following a failure after its first installation in November 2011, COLDDIAG was subsequently reinstalled in the Diamond storage ring in August 2012. We report on the preliminary results that have been obtained since then.

WEPWA080	Development of a Compact Insertion Device for Coherent Sub-mm Generation	radiation, linac, laser, wakefield	2295
	A.V. Smirnov, R.B. Agustsson, S. Boucher, T.J. Grandsaert, J.J. Hartzell, M. Ruelas, S. Storms RadiaBeam, Santa Monica, USA A. Andrews, B.L. Berls, C.F. Eckman, K. Folkman, A.W. Hunt, Y. Kim, A.E. Knowles-Swingle, C. O'Neill, M. Smith IAC, Pocatello, IDAHO, USA P. Buaphad, Y. Kim ISU, Pocatello, Idaho, USA
	Funding: Department of Energy Contracts DE- SC-FOA-0000760 and DE-FG02-07ER84877 A novel design of resonant Cherenkov wakefield extractor that produced a ~0.9 mm wavelength radiation is presented. The experiment was performed at Idaho Accelerator Center (IAC) using specially upgraded 1.3 GHz 44 MeV linac facility. Specifics of the radiator performance and design are outlined including low-energy beam interaction with non-circular geometry. Some elements of the design may have certain potential for future compact mm-sub-mm-wave sources.

WEPWO048	Investigation of a Ridge-loaded Waveguide Structure for CLIC X-band Crab Cavity	cavity, damping, HOM, beam-loading	2411
	V.F. Khan, R. Calaga, A. Grudiev CERN, Geneva, Switzerland
	In conventional crab cavities the TM11 mode is used to deflect the beam. In a linear collider such as CLIC, it is necessary to damp all the other modes, namely the accelerating i.e. lower order mode (LOM), same order mode (SOM) and higher order modes (HOMs). In addition to this, as the TM11 mode is not the fundamental mode, it is generally not excited with the highest shunt impedance. This necessitates damping of the high shunt impedance modes to acceptable level. Here we report on the investigation of an alternative design of the X-band crab cavity for CLIC based on ridge-loaded waveguide. In this type of cavity, the deflecting mode is the fundamental mode and has the maximum shunt impedance. However, the geometry of the cavity is chosen to optimise the ratio of group velocity to shunt impedance to minimise the effect of beam loading. The other modes are excited above the crabbing mode and are damped using wave-guides. Another advantage of this type of cavity is, unlike the conventional TM11 mode cavities, the e.m. surface fields do not peak at the iris. This provides ample margin to optimise the cavity geometry and reach the desired field distribution.

WEPWO077	Rf System Requirements for JLab’s MEIC Collider Ring	ion, cavity, electron, SRF	2477
	S. Wang, R. Li, R.A. Rimmer, H. 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, consists of a series of accelerators [1]. At the top energy are the electron and ion collider rings. For the ion ring, it accelerates five long ion bunches to colliding energy and rebunches ions into a train of very short bunches before colliding. A set of low frequency RF system is needed for the long ion bunch energy ramping. Another set of high frequency RF cavities is needed to rebunch ions. For the electron ring, superconducting RF (SRF) cavities are needed to compensate the synchrotron radiation energy loss. The impedance of the SRF cavities must be low enough to keep the high current electron beam stable. The preliminary design requirements of these RF cavities are presented. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.

WEPEA011	Bursting Patterns of Coherent Synchrotron Radiation in the ANKA Storage Ring	radiation, simulation, electron, synchrotron	2516
	M. Schwarz, V. Judin, A.-S. Müller KIT, Karlsruhe, Germany M. Klein SOLEIL, Gif-sur-Yvette, France
	We report measurements of bursting patterns of coherent synchrotron radiation (CSR) for a wide range of single bunch currents at the ANKA storage ring. The radiation was detected with a fast THz detector, a Hot Electron Bolometer, and its signal acquired with both a spectrum analyzer and an external sampling oscilloscope. Both analysis methods consistently show the onset of bursting at a threshold current with the appearance of strong high frequency bands with higher harmonics in the several 10th of kHz range. For currents higher than twice the threshold value an abrupt change in the bursting pattern occurs. These results are compared with different numerical models solving the one-dimensional Vlasov-Fokker-Planck equation.

WEPEA019	Status of the J-PARC MA Loaded RF Systems	cavity, injection, proton, bunching	2537
	M. Yoshii, E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, K. Takata, M. Toda KEK, Tokai, Ibaraki, Japan M. Nomura, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan A. Schnase GSI, Darmstadt, Germany
	Japan proton accelerator complex operates two cascaded synchrotrons, 3GeV RCS and 50GeV MR. The high electric field gradient magnetic alloy (MA) loaded cavities are used in both synchrotrons. The RF systems have no tuning control loop and the direct digital synthesis based fully digital low level RF guarantees the stable and reproducible proton acceleration. The feed-forward systems using the circulating beam current signals works efficiently to compensate the heavy beam induced voltage. In RCS, 11 RF systems are operating in a dual harmonic mode since December 2008. The longitudinal RF control based on the particle tracking performed effectively and the equivalent beam power of 530 kW was successfully demonstrated. The 260kW operation for the neutron users started in October 2012. In MR synchrotron, the 9th RF system was newly installed and became available as a 2nd harmonic RF system in November 2012. A 30 GeV proton of 200 kW beam power has been delivered to the T2K neutrino beam experiment with 2.48 sec repetition cycle. This paper summarizes the operation details and the status and features of the J-PARC RF systems.

WEPEA020	Commissioning of Beam Loading Compensation System in the J-PARC MR	beam-loading, cavity, injection, extraction	2540
	F. Tamura, M. Nomura, A. Schnase, T. Shimada, M. Yamamoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan K. Hara, K. Hasegawa, C. Ohmori, M. Toda, M. Yoshii KEK, Tokai, Ibaraki, Japan
	Beam loading compensation is indispensable to accelerate high intensity proton beams in the J-PARC MR. The MA-loaded rf cavities in the MR are driven by the single harmonic (h=9) rf signals, while the cavity frequency response covers also the neighbor harmonics (h=8, 10). The wake voltage induced by the beam consists of the three harmonics (h=8, 9, 10). We employ the rf feedforward method to compensate the beam loading of these harmonics. The full-digital feedforward system was developed for the MR. We have successfully commissioned the feedforward patterns for all of eight cavities by using high intensity beams with 1.0·10¹⁴ ppp. We present the commissioning results. The impedance seen by the beam is reduced and the longitudinal oscillations due to the beam loading are reduced. By the beam loading compensation, high power beam operation at the beam power of 200 kW has been achieved.

WEPFI002	Acceptance Tests for the Spiral2 SC Linac RF Power Systems	cavity, linac, insertion, controls	2702
	M. Di Giacomo GANIL, Caen, France
	Funding: This activity received founds from the EuCard RF Tech program The Spiral2 SC linac uses solid state amplifiers ranging from 2,5 to 19 kW and external circulators to drive normal and superconducting cavities at 88.0525 MHz. The project has no manpower for in house development and all power devices are ordered to commercial companies. Robust acceptance tests have therefore been defined to check reliability with respect to our application. The papers describes the tests procedure and results on our first units.

WEPFI005	Simulations and RF Measurements of the Fundamental and Higher Order Modes of the ThomX 500 MHz Cavity	cavity, HOM, feedback, controls	2711
	M. El Khaldi, I.V. Drebot, P. Lepercq, R. Marie, B. Mercier, T. Roulet, A. Variola, F. Wicek LAL, Orsay, France H.D. Dias, M.D. Diop, M.E. El Ajjouri, R. Lopes, A. Loulergue, P. Marchand, F. Ribeiro, R. Sreedharan SOLEIL, Gif-sur-Yvette, France
	The RF system of the ThomX* storage ring consists in a 500 MHz single cell copper cavity of the ELETTRA type, powered with a 50 kW CW solid state amplifier, and the associated Low Level RF feedback and control loops. The low operating energy of 50 – 70 MeV makes the impedances of the cavity higher order modes (HOMs) particularly critical for the beam stability. Their parasitic effects on the beam can be cured by HOM frequency shifting techniques, based on a fine temperature tuning and a dedicated plunger. A typical cavity temperature stability of ± 0.05°C within a range from 35 up to 80 °C can be achieved by a precise control of its water cooling temperature. On the other hand, the tuning of the cavity fundamental mode is achieved by changing its axial length by means of a mechanical tuner. In order to insure a fine control of the HOM frequencies, a good knowledge of their characteristics is mandatory. The main parameters of the fundamental and of the HOMs up to 4 GHz have been calculated using the HFSS and CST MWS codes. Preliminary measurements results have been obtained and show a good agreement with the simulations. * A.Variola, “The ThomX Project”, Proceedings of IPAC2011, San Sebastián, Spain

WEPFI012	Conceptual Design of ILSF RF System	cavity, HOM, LLRF, storage-ring	2723
	Kh.S. Sarhadi, H. Ajam, H. Azizi, M. Fereidani, M. Jafarzadeh, S. Pirani, J. Rahighi, R. Safian, A. Shahverdi ILSF, Tehran, Iran
	The Iranian Light Source Facility (ILSF) RF system, consisting of RF cavities, power sources and low-level RF systems, is conceptually designed in accordance with the requirements of ILSF 3GeV storage ring. To achieve the desired 400mA beam current, utilization of the existing HOM-damped cavities is explored and RF system parameters are compared based on the usage of each cavity. Moreover, the choice of solid state amplifier as the RF power source is presented with its available power and structure. This paper, furthermore, explains the conceptual design and functionality of the selected digital LLRF system.

WEPFI021	Influence of Core Winding Tension and Ribbon Quality on the MA Core RF Characteristics	synchrotron, vacuum, factory, cavity	2747
	M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan K. Hara, K. Hasegawa, C. Ohmori, M. Toda, M. Yoshii KEK, Tokai, Ibaraki, Japan
	J-PARC 3 GeV Rapid Cycling Synchrotron (RCS) and Main Ring (MR) employ RF cavities loaded with Magnetic Alloy (MA) cores to generate a high field gradient. To achieve the high field gradient, the core shunt impedance is a key parameter. We found during the development of MA cores for RCS RF cavities that the core shunt impedance was increased by lowering a core winding tension. We lowered the core winding tension in order to improve the electrical insulation between MA ribbon layers. The lower winding tension reduced the core filling factor that is defined as the volume ratio of MA ribbons and geometrical dimensions. The core shunt impedance might be reduced according to the core filling factor reduction. We discuss the reason why the lower winding tension increased the core shunt impedance. We also report the influence of the ribbon quality variation on the MA core RF characteristics.

WEPFI027	The Measurement of the Ferrite Rings for the Mass Production RF Cavity of CSNS RCS	cavity, LLRF, resonance, booster	2762
	H. Shi, W.L. Huang, B. Jiang, X. Li, W. Long, W.Y. Song, H. Sun, J.Y. Tang, C.L. Xie, C.L. Zhang, W. Zhang IHEP, Beijing, People's Republic of China
	The Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) will install 8 ferrite-loaded coaxial resonant cavities. The construction and measurement of prototype cavity have been finished. Based on the existing experiences, the small inner diameter (ID) rings T500/250/25-4M2 (mm) have been adopted for the mass production RF cavity, and the test results have shown that such rings can bear more RF magnetic flux density and have lower power loss. The characteristics of 60 small ID rings have been measured with two-ring test system, and we figured out that the rings have good consistence and the shunt impedance of all rings is above 100 Ω.

WEPFI031	Development of an X-Band Metallic Power Extractor for the Argonne Wakefield Accelerator	damping, extraction, simulation, cavity	2771
	J. Shi, H.B. Chen, Q. Gao, X.W. Wu, Y. Yang, H. Zha TUB, Beijing, People's Republic of China W. Gai, C.-J. Jing ANL, Argonne, USA
	An X-band (11.7GHz) power extractor has been developed for RF power generation at Argonne Wakefield Accelerator (AWA). The structure is a 2pi/3-mode disk-loaded structure with group velocity of 22% of the speed of light and a total length of about 300mm. It is build with copper disks brazed together. This note presents the design and the fabrication of this structure, as well as the RF measurement results.

WEPFI038	R&D of New C-band Accelerating Structure for SXFEL Facility	FEL, cavity, wakefield, linac	2785
	W. Fang, Q. Gu, Z.T. Zhao SINAP, Shanghai, People's Republic of China L. Chen, X. Sheng BVERI, Beijing, People's Republic of China D.C. Tong TUB, Beijing, People's Republic of China
	C-band high gradient accelerating structure is crucial technology for Shanghai Soft X-ray FEL facility. Based on the prototype, the optimized C-band accelerating structure is proposed, and the experimental model is ready for high power test. In this paper, optimization design and some experiment results are presented, also design, fabrication and cold test of experimental model are introduced.

WEPFI039	New X-band Deflecting Cavity Design for Ultra-short Bunch Length Measure of FEL at SINAP	cavity, simulation, electron, FEL	2788
	J.H. Tan, W. Fang, Q. Gu, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	For the development of Free Electron Lasers (FEL) at SINAP, ultra-short bunch is the crucial requirement for excellent lasing performance. It’s big challenge for deflecting cavity to measure the length of ultra-short bunch, and higher deflecting gradient is required for higher measurement resolution. X-band travelling wave deflecting structure has features of higher deflecting voltage and compact structure, which is good performance at ultra-short bunch length measuring. In this paper, a new X-band deflecting structure was designed, operated at HEM11- 2π/3 mode. For suppressing the polarization of deflection plane of the HEM11 mode, two symmetrical caves are added on the cavity wall to separate two polarized modes. More details of design and simulation results are presented in this paper.

WEPFI045	PAL-XFEL Accelerating Structures	linac, klystron, electron, emittance	2806
	H.-S. Lee, H. Heo, J.Y. Huang, W.H. Hwang, S.D. Jang, Y.D. Joo, H.-S. Kang, I.S. Ko, S.S. Park, Y.J. Park PAL, Pohang, Kyungbuk, Republic of Korea I.S. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea H. Matsumoto KEK, Ibaraki, Japan S.J. Noh, K.M. Oh Vitzrotech Co., Ltd., Ansan City, Kyunggi-Do, Republic of Korea
	We need 172 accelerating structures for the PAL-XFEL 10 GeV main linac. It takes long time for these structures to be delivered. So we are trying to find suppliers of the accelerating structures. First, we made an order of 40 accelerating structures to Mitsubishi Heavy Industry (MHI), which have Quasi-type couplers to reduce the quadruple and sextuple components of the electric field in the coupling cavity. And Research Instruments (RI) has fabricated a 3m long race type accelerating structure for PAL-XFEL. Also, Vitzrotech which is a domestic company and IHEP in China are under developing accelerating structures for PAL-XFEL respectively. We will describe the current status of accelerating structures and high power test results of the newly developed structures in this paper.

WEPFI058	Breakdown Localization Studies on the SwissFEL C-band Test Structures	background, linac, coupling, factory	2824
	J. Klavins, S. Dementjevs, F. Le Pimpec, L. Stingelin, M. Wohlmuther, R. Zennaro PSI, Villigen PSI, Switzerland N.C. Shipman CERN, Geneva, Switzerland
	The SwissFEL main linac will consist of 10⁴ C-band structures with a nominal accelerating gradient of 28MV/m. First power tests were performed on short constant impedance test-structures composed of eleven double-rounded cups. In order to localize breakdowns, two or three acoustic emission sensors were installed on the test-structures. In order to localize breakdowns we have analyzed, in addition to acoustic measurements, the delay and phase of the rf power signals. Parasitic, acoustic noise emitted from the loads of the structure complicated the data interpretation and necessitated appropriate processing of the acoustic signals. The Goals of the experiments were to identify design and manufacturing errors of the structures. The results indicate that breakdowns occur mostly at the input power coupler, as also confirmed by vacuum-events at the same location. The experiments show that the linac test-structures fulfill the requirements in breakdown probability. Moreover developing a detection system based on acoustic emission sensors for breakdown localization for our C-band structure seems reasonable given the results obtained.

WEPFI060	Planar Balun Design with Advanced Heat Dissipation Structure for kW Level Solid-state Amplifier Module Development	coupling, controls, storage-ring, klystron	2830
	T.-C. Yu, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Y.-H. Lin, Z.L. Liu, C.H. Lo, M.H. Tsai, Ch. Wang, T.-T. Yang, M.-S. Yeh NSRRC, Hsinchu, Taiwan
	The power level of solid-state amplifier is continuously growing for advanced accelerator application as the RF power source. Huge amount of solid-state power amplifier (SSPA) modules can contribute several hundreds of kW RF power with high redundancy and reliability. However, with the increasing desire of RF power of single RF station, too much power modules would adversely cause larger area occupation and higher maintenance cost and complexity. Therefore, with the advancement of the RF power on single SSPA, the overall system design and configuration would become much simple and compact. However, the increasing RF of single SSPA would also bring the thermal problem at its chip as well as the output power combining balun. In this paper, kW range SSPA is developed with the novel planar balun structure with good thermal expansion property. With such new planar balun design, the SSPA can operate stably with above 1kW output RF power.

WEPFI062	Precise Cavity Tuning System of a Low Output-impedance Second-harmonic Cavity at ISIS	cavity, resonance, cathode, beam-loading	2836
	Y. Irie, S. Fukumoto, K. Muto, H. Nakanishi KEK, Ibaraki, Japan D.B. Allen, D. Bayley, N.E. Farthing, I.S.K. Gardner, R.J. Mathieson, A. Seville, J.W.G. Thomason STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom J.C. Dooling, D. Horan, R. Kustom, M.E. Middendorf ANL, Argonne, USA
	A very low output-impedance (~35ohms) second-harmonic cavity system is being developed for high intensity proton accelerators. The final amplifier is comprised of a grounded cathode scheme with a feedback loop from anode to grid. Due to the Miller effect, the grid voltage waveform is seriously distorted even if only a few percent of sub-harmonic or higher harmonic are mixed in the generator current. Such distortion is much enhanced by the beam loading. In order to eliminate the effect of this distortion upon the phase detector used to achieve precise cavity tuning, a swept bandpass filter was applied to the grid voltage at the phase detector input. Filter design details and the result of high power tests are reported.

WEPFI090	An X-band Dielectric-based Wakefield Power Extractor	wakefield, simulation, damping, vacuum	2908
	C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow Euclid TechLabs, LLC, Solon, Ohio, USA M.E. Conde, W. Gai, J.G. Power ANL, Argonne, USA V.A. Dolgashev, J.R. Lewandowski, S.G. Tantawi, S.P. Weathersby SLAC, Menlo Park, California, USA I. Syratchev CERN, Geneva, Switzerland
	Funding: US DoE SBIR Phase II project under Contract#DE-SC0004322 An X-band dielectric-based wakefield power extractor is under development to function as a high power rf source primarily for Two Beam Accelerator applications. A low surface electric field to gradient ratio and low fabrication cost are two main advantages of the dielectric-loaded accelerating/decelerating structure. We have designed a 12 GHz dielectric-based power extractor that has similar performance parameters to the CLIC PETS (23 mm beam channel, 240 ns pulse duration, 135 MW output per structure) using the CLIC drive beam. In order to study potential rf breakdown issues, as a first step we built a 11.424 GHz dielectric-based power extractor scaled from the 12 GHz design. A high power rf test will be conducted using the SLAC 11.424 GHz high power rf source in Dec. 2012. Results of the high power testing will be reported. Meanwhile, the 12 GHz fully featured dielectric power extractor is also under construction; construction progress and bench tests will be discussed.

WEPME061	A Wideband Slotted Kicker Design for SPS Transverse Intra-bunch Feedback	kicker, feedback, coupling, simulation	3073
	J.M. Cesaratto, J.D. Fox, C.H. Rivetta SLAC, Menlo Park, California, USA D. Alesini, A. Drago, A. Gallo, F. Marcellini, M. Zobov INFN/LNF, Frascati (Roma), Italy S. De Santis LBNL, Berkeley, California, USA W. Höfle CERN, Geneva, Switzerland
	Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP) and by the EU FP7 HiLumi LHC - Grant Agreement 284404. Control and mitigation of transverse beam instabilities caused by electron cloud and TMCI will be essential for the SPS to meet the beam intensity demands for the HL-LHC upgrade. A wideband intra-bunch feedback method is in development, based on a 4 GS/s data acquisition and processing, and with a back end frequency structure extending to 1 GHz. A slotted type kicker, similar to those used for stochastic cooling, has been considered as the terminal element of the feedback chain. It offers the most promising deflecting structure characteristics to meet the system requirements in terms of bandwidth, shunt impedance, and beam coupling impedance. Different types of slotted structures have been explored and simulated, including a ridged waveguide and coaxial type waveguide. In this paper we present our findings and the conceptual design of a vertical SPS wideband kicker consistent with the stay clear, vacuum, frequency band coverage, and peak shunt impedance requirements.

THOBB102	Beam Coupling Impedance Localization Technique Validation and Measurements in the CERN Machines	kicker, quadrupole, lattice, betatron	3106
	N. Biancacci, G. Arduini, T. Argyropoulos, H. Bartosik, R. Calaga, K. Cornelis, S.S. Gilardoni, N. Mounet, E. Métral, Y. Papaphilippou, S. Persichelli, G. Rumolo, B. Salvant, G. Sterbini, R. Tomás, R. Wasef CERN, Geneva, Switzerland M. Migliorati, L. Palumbo URLS, Rome, Italy
	The beam coupling impedance could lead to limitations in beam brightness and quality, and therefore it needs accurate quantification and continuous monitoring in order to detect and mitigate high impedance sources. In the CERN machines, for example, kickers and collimators are expected to be the main contributors to the total imaginary part of the transverse impedance. In order to detect the other sources, a beam based measurement was developed: from the variation of betatron phase beating with intensity, it is possible to detect the locations of main impedance sources. In this work we present the application of the method with beam measurements in the CERN PS, SPS and LHC.
	Slides THOBB102 [7.224 MB]

THPFI014	Bellows with a New RF Shield Made of Metal Braid for High Intensity Proton Accelerators	vacuum, background, synchrotron, coupling	3321
	N. Ogiwara, J. Kamiya, M. Kinsho, Y. Shobuda JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan O. Koizumi Sun-Tech limited, Kobe, Japan
	In the 3 GeV-RCS (Rapid cycling Synchrotron) in J-PARC (Japan Accelerator Research Complex) project, large-scale hydro-formed bellows were developed to adjust the gap between the ceramic ducts and/or between the ceramic ducts and the transport ducts. They have been equipped with a newly developed RF shield, because the usual beryllium-copper spring finger contacts were found to be very hard (roughly 1000 N/mm) owing to the large size. This contact is made of Ti braid, which consists of wires with a diameter of 0.3 mm. This RF contact is a kind of basket (with two ports) made with the braids. Because of the spring effect, the contact can change shape easily. In addition, the contact can easily connect the different cross sections in a smooth fashion. Furthermore, this structure is almost free from the dust generation, which is one of the most troublesome problems for the usual spring finger contacts. This time, we have constructed reserve bellows with the RF shield made of SUS 316L wires to improve the reliability of user operation. The outline of the bellows will be presented, especially laying emphasis on the mechanical function of the RF shield.

THPFI057	Development of Vacuum Chamber in Low Z Material	vacuum, radiation, background, coupling	3421
	C. Garion, P. Costa Pinto, M.A. Gallilee, J. Perez Espinos CERN, Geneva, Switzerland
	Highly transparent vacuum chambers are more and more required in high energy particle physics. In particular, vacuum chambers in the experiments should be as transparent as possible to minimize the background to the detectors while reducing also the material activation. Beryllium is, so far, the most performing material for this application, but it presents some drawbacks such as brittleness, manufacturing issues, toxic hazard, high cost and low availability. A development work to obtain alternative material to the beryllium with similar performance is being carried out at CERN. Three categories have been defined and considered: raw bulk material, material and structural composites. Main requirements are the vacuum compatibility: leak tightness, low outgassing rate, temperature resistance (in the range 200-230 °C), transparency, and mechanical stiffness and strength. Carbon is the element with the lowest atomic number after beryllium and that is appropriate for this application. Therefore carbon based materials have been considered in a variety of options. In this paper, several technologies are presented and discussed. Results of preliminary tests on samples are also shown.

THPWA001	Design of X-Band Medical Linear Accelerator with Multiple RF Feeds and RF Phase Focusing	focusing, linac, cavity, bunching	3627
	Y. N. Nour El-Din, T.M. Abuelfadl Cairo University, Giza, Egypt
	Funding: Work supported by the Egyptian Science and Technology Development Fund (STDF) No. 953. A design of 6 MeV X-band 9.3 GHz medical linear accelerator is presented. It is composed of four separate clusters of accelerating cavities, where a coherent RF excitation is provided separately to each cluster. The use of multiple accelerating sections with multiple RF feeds permits the use of inexpensive RF sources. The first cluster is Alternate Phase Focusing (APF) RF cavities, providing radial and longitudinal beam focusing without the use of heavy and bulky magnets or solenoids. The three other clusters used for acceleration are composed of multiple standing wave sections operating in the Pi-mode. Each section has been designed and optimized for high shunt impedance by means of 2D SUPERFISH code and 3D CST code. A two dimensional code, named PTCC, was developed to facilitate design and analysis of the different parts of the accelerating structure.

THPWA022	An 800kV 30mA Line-Frequency Cockcroft-Walton Dc Generator Using Gas Insulated Transformer for Radiation Application	high-voltage, electron, power-supply, radiation	3675
	Y.H. Liu, H.L. Guo, Z.-F. He, D.M. Li, M.X. Li, W.G. Shi, H.J. Su, S.L. Wang, Y.J. Yang, J.L. Zhang, Y.-T. Zhang SINAP, Shanghai, People's Republic of China
	The design and construction of a line-frequency 800 kV Cockcroft-Walton DC generator using gas insulated transformers are described, as well as the motive to develop it into radiation application. Several features are underlined, preliminary test results of the prototype presented and some problems encountered discussed.

THPWO018	Power Tests of the 325 MHz 4-ROD RFQ Prototype	rfq, cavity, pick-up, simulation	3800
	B. Koubek, H. Podlech, A. Schempp, J.S. Schmidt IAP, Frankfurt am Main, Germany
	For the FAIR project of GSI as part of the proton linac a 325 MHz RFQ with an output energy of 3 MeV is planned. Simulations that have lead to a prototype of a 4-Rod Radio Frequency Quadrupole (RFQ) have been done. The RF parameters have been verified with the prototype. Power tests of this 6 stem copper RFQ should now verify parameters like shunt impedance, electrode voltage and give answers of how much power the structure can sustain.

THPWO032	Progress of Injection Energy Upgrade Project for J-PARC RCS	injection, power-supply, septum, linac	3833
	N. Hayashi, H. Harada, K. Horino, H. Hotchi, J. Kamiya, M. Kinsho, P.K. Saha, Y. Shobuda, T. Takayanagi, N. Tani, T. Togashi, T. Ueno, M. Watanabe, Y. Watanabe, K. Yamamoto, M. Yamamoto, Y. Yamazaki, M. Yoshimoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan Y. Irie KEK, Ibaraki, Japan T. Toyama J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	The injection energy of the J-PARC RCS will be upgraded in 2013. New power supplies for the shift bump magnet system will be installed. Some of other systems, upgrade of the painting bump power supplies and pulse steering systems, are already installed and tested or used for the nominal operation. The paper reports the progress of injection energy upgrade project.

Paper

Title

Other Keywords

Page

MOPEA059

The Optimization of Transverse Stripline Kicker

kicker, simulation, vacuum, insertion

214

H.P. Hsueh, C.-C. Chang, Y.P. Chang, J.-R. Chen, Y.T. Cheng, G.-Y. Hsiung, Y.C. Yang
NSRRC, Hsinchu, Taiwan
J.-R. Chen
National Tsing Hua University, Hsinchu, Taiwan

The construction of a new 3 GeV synchrotron facility, Taiwan Photon Source, is ongoing. It is required to install stripline kickers to suppress instability generated by mismatch between injection kickers or imperfect installation of vacuum components all around. First, the design philosophy will be described for transverse stripline kickers. HFSS electromagnetic simulation software is used to optimize all structure parameters like electrode dimensions, electrode distance from vacuum chambers etc. to make transverse stripline kicker working more efficiently and effectively. All simulation results will be presented in this paper and all structure dimension choices will be discussed and the final prototype structure dimensions will be selected from the discussion.

MOPFI047

Analysis and Design of Matching Unit for a RF Driven Plasma Source for Fusion Purpose

plasma, ion, ion-source, neutral-beams

389

H.K. Yue
Huazhong University of Science and Technology(HUST), Wuhan, People's Republic of China
D.Z. Chen, M. Fan, J. Huang, D. Li, X.F. Li, K.F. Liu, C.R. Wan, C. Zhou
HUST, Wuhan, People's Republic of China

A RF driven plasma exciter for producing negative ions, aiming for heating and current drive neutral beam injectors for fusion applications, is in developing in Huazhong University of Science and Technology (HUST). In order to couple the maximum RF power to the source, the matching unit is designed to match the impedance of the source to that of the RF coaxial line. Firstly, a FEM model was built to estimate the equivalent circuit parameters of the source. Numerical predictions were compared with a small experimental setup to verify the accuracy of the fem model. Based on the numerical results, the RF coil and the matching components were carefully designed. Finally, the matching circuit for the source is developed and tested. Experimental results will be presented in the full paper.

MOPFI052

A New Lead Ion Injection System for the CERN SPS with 50 ns Rise Time

injection, kicker, ion, septum

398

B. Goddard, O. Aberle, J. Borburgh, E. Carlier, K. Cornelis, L. Ducimetière, L.K. Jensen, T. Kramer, D. Manglunki, A. Mereghetti, V. Mertens, D. Nisbet, B. Salvant, L. Sermeus
CERN, Geneva, Switzerland

The LHC High Luminosity upgrade project includes a performance upgrade for heavy ions. One of the present performance limitations is the rise time of the SPS injection kicker system, which imposes a spacing of at least 220 ns between injected bunch trains at the operational rigidity. A reduction of this rise time to 50 ns for lead ions is requested as part of the suite of measures needed to increase the present design performance by a factor three. A new injection system based on a fast pulsed septum and a fast kicker has been proposed to fulfil this rise time requirement, and to meet all the constraints associated with the existing high intensity proton injection in the same region. This paper describes the concept and the required equipment parameters, and explores the implications of such a system for SPS operation.

MOPME015

Numerical Wakefield Calculations for Electro-optical Measurements

simulation, wakefield, laser, storage-ring

503

B. Kehrer, A. Borysenko, E. Hertle, N. Hiller, V. Judin, S. Marsching, A.-S. Müller, M.J. Nasse, M. Schuh
KIT, Karlsruhe, Germany

Funding: This project is funded by the Federal Ministry of Education and Research under the contract number 05K10VKC
The technique of electro-optical measurements allows precise and single-shot measurements of the bunch length and shape. The installation of such a near-field setup changes the impedance of the storage ring and the corresponding effects have to be studied carefully. One possibility is to use numerical codes for simulating the wakefields induced by the setup. Such simulations has been done using the wakefield solver implemented in the CST Studio Suite. In this paper we present the simulation results together with first measurements.

MOPME023

ORBIT Beam Simulation Progress in the 3-GeV Rapid Cycling Synchrotron of J-PARC

simulation, lattice, injection, synchrotron

521

P.K. Saha, H. Harada, H. Hotchi, Y. Shobuda, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
J.A. Holmes
ORNL, Oak Ridge, Tennessee, USA
S. Kato
Tohoku University, Graduate School of Science, Sendai, Japan

We have made a numerous progress for beam simulation in the 3-GeV RCS (Rapid Cycling Synchrotron) of J-PARC (Japan Proton Accelerator Research Complex) by using 3-D particle tracking code, ORBIT. Namely, the TEAPOT lattice file used for ORBIT tracking has been made to give exactly same results to that with SAD model used for the RCS beam commissioning. In addition, time dependent lattice functions of the injection chicane magnets and similar other time dependent lattice imperfections, which are already found to have significant influences on the beam losses in the real machine have also been successfully introduced. At present, time dependent transverse and longitudinal impedances are going to be introduced. That should prove the ORBIT code much more matured for beam simulations in synchrotrons. Latest beam simulation results illustrating these new realistic features are presented.

MOPME041

Design and Calculation of the Stripline Beam Position Monitor for HLS II Storage Ring

quadrupole, coupling, simulation, storage-ring

562

F.F. Wu, C. Cheng, W.B. Li, P. Lu, T.J. Ma, B.G. Sun, H. Xu, Y.L. Yang, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: Supported by the National Science Foundation of China (10875117, 11005105, 11175173)
According to the requirements of HLS II upgraded, in order to acquire the non-intercepting measurement of beam position and quadrupole component, a new stripline beam position monitor (BPM) was designed for storage ring. The BPM parameters were optimized to acquire impedence matching with characteristic impedance of the external transmission lines and the coupling coefficients between the electrodes were calculated. According to the difference/sum and log-ratio methods, the horizontal and vertical sensitivities, mapping figures and fitting polynomials wered acquired. The results showed that sensitivities using log-ratio method were bigger than those using difference/sum method. The sum signal was also simulated when beam displacement varied from (0 mm, 0 mm) to (5 mm, 5 mm), the result showed that the variation of normalized sum signal was no more than ±6%. The gaussian weighted method of a two-dimensional grid structure was used to simulate the gaussian bunch and simulate the beam transverse quadrupole component changing with position (x, y), the result showed that the beam transverse quadrupole component changed linearly with position combination (x2-y2).

MOPME044

A Novel Type of Forward Coupler Slotted Stripline Pickup Electrode for CSRe Stochastic Cooling

pick-up, vacuum, kicker, simulation

571

J.X. Wu, X.J. Hu, M. Li, J.W. Xia, J.C. Yang, Y. Zhang, G. Zhu
IMP, Lanzhou, People's Republic of China
F. Caspers
CERN, Geneva, Switzerland

A novel type of slotted or perforated strip-line pick-up or kicker electrode structure for CSRe stochastic cooling for non relativistic particle beams with b=v/c values around 0.7 is presented. This slotted structure is to be used as a forward coupler with the output signal taken from the downstream end and has a rather large relative bandwidth of several octaves. The electrode structure and pickup tank, as well as the beam test result will be presented in this paper.

MOPME046

Preliminary Experimental Results of Axial B-dot Measuring Beam Tilt

high-voltage, coupling, simulation, dipole

577

X. He, Q. Li, C. Ma, J. Pang, L. Zhao
CAEP/IFP, Mainyang, Sichuan, People's Republic of China

Funding: This work is under the support of NSFC project No. 11175166
Beam monitors sensitive to the beam's azimuthal B-dot field (sometimes referred as B-dots) are widly used to measure the displacement of beam centroid, as the beam generates a dipole term of the azimuthal magnetic field. The authors have pointd out that the similar B-dots sensitive to axial magnetic field can be used to measure the beam tilt directly in earlier work. A monitor which consists of four azimuthal B-dots and four axial B-dos is designed and fabricated. The monitor was tested on a coaxial calibration stand, which has a character resistance of 50 Ohm. Two position tuners are installed on the calibration stand, to adjust the position and the tilt of the inner conductor. Experiments show that the axial B-dot monitor can be successfully used to measure the tilt of the inner conductor directly.

MOPME059

R&D of a Beam Position Monitor for RISP

linac, ion, heavy-ion, pick-up

607

E.-S. Kim
KNU, Deagu, Republic of Korea
A. Heo
Kyungpook National University, Daegu, Republic of Korea
H.K. Park
CHEP, Daegu, Republic of Korea

We have investigated on the R&D of stripline beam position monitor for the heavy-ion accelearator at Korea. We present the detailed design and fabrications on the beam position monitor in superconducting linac that the beam is accelerated to 200 MeV/u.

MOPWA004

Development of a Non-inductive Ceramic Resistor

kicker, injection, pulsed-power, power-supply

669

T. Sugimoto, K. Fan, K. Ishii, H. Matsumoto
KEK, Ibaraki, Japan
K. Abe
Hitachi Haramachi Electronics Co. Ltd., Hitachishi, Ibaraki, Japan
S. Fukuoka
University of Tsukuba, Graduate School of Pure and Applied Sciences,, Tsukuba, Ibaraki, Japan

Non-inductive ceramic resistors, based on alumina and carbon, are used for impedance matching in the circuit of the J-PARC main ring injection kicker system. The kickers were installed in December 2011, and have been in operation successfully since then. However, discharges at the edge of the ceramic bulk were observed after several weeks’ operation, which increase resistance from O(100) to O(1M). Investigation indicates that poor contact with the rough surface of the ceramic bulk due to irregular shaped spots causes micro-gaps, which trigger the discharge. In order to improve the contact, one type of brazing technology has been experimentally applied to one resistor. Another resistor had an annealed thin copper plate inserted, and both resistors were tested and compared. In this paper, we will describe details of the development of the resistors and give future prospects.

MOPWA005

Development of a Feedback Control System for Resonant Power Supplies in the J-PARC 3-GeV Synchrotron

controls, power-supply, feedback, quadrupole

672

Y. Watanabe
JAEA, Ibaraki-ken, Japan
N. Tani
JAEA/J-PARC, Tokai-mura, Japan

In the J-PARC 3-GeV Synchrotron, dipole magnets and seven families of quadrupole magnets are excited with a DC-biased 25 Hz sinusoidal waveforms using an individual resonant circuits. This paper proposed a feedback system to improve the amplitude and phase stability, specially against variation of capacitance caused by temperature characteristics in the resonant circuits. The control system has been successfully demonstrated and achieved amplitude and phase stability under ±0.005% and ±0.5 uS, respectively.

MOPWA009

Development of a Fast Compensation Kicker System for J-PARC Main-ring Injection

kicker, injection, simulation, power-supply

684

S. Fukuoka
University of Tsukuba, Graduate School of Pure and Applied Sciences,, Tsukuba, Ibaraki, Japan
K. Fan, K. Ishii, H. Matsumoto, T. Sugimoto
KEK, Ibaraki, Japan

Injection system of J-PARC main ring employs four lumped kickers to deflect the incoming beam. The residual field caused by tail and reflection of excitation current increases the closed beam orbit leading to particle loss in high power operation. A correction method using a fast kicker system to compensate the remaining angle is being developed. Doe to the narrow bunch spacing, transmission line kicker is selected to satisfy requirements of fast rise and fall time. The kicker magnet uses ceramic capacitors instead of parallel metal plates to make the magnet compact and reduce the stray inductance. Capacitors are installed in vacuum chamber. A very thin core is used to reduce distributed inductance. A bandwidth is calculated as 160 MHz. A Marx generator using FET switches has been studied, which is able to produce fast rise and fall time as 50 ns. Any pulse shape is generated by choosing switches to fire. A prototype magnet and a power supply have been fabricated for parameters test. In this paper, we will report the details of the system design, analyze the measurement results and give future prospects.

MOPWA018

CW-type HV Power Supply of 50 Hz and its Application in Accelerator Power Supply

high-voltage, electron, power-supply, damping

699

Z.-F. He, D.M. Li, Y.H. Liu, S.L. Wang, J.-L. Zhang, Y.-T. Zhang
SINAP, Shanghai, People's Republic of China

Funding: The Knowledge Innovation Program of Chinese Academy of Sciences
　　The high-voltage power supply is an integral part of accelerator technology, as its stable and reliable output is an important guarantee for accelerator properly working. In a number of engineering practice of accelerator design and construction, we tried to use the Cockcroft-Walton (CW) type of power supply driven by 50 Hz and got success. It is of simple structure, low cost, easy maintenance, and high efficiency. This report describes the technical difficulties and the solutions in the CW-type power supply driven by 50 Hz. It also gives an introduction of the latest design of 800 kV/30 mA electron accelerator, which is being assembled at SINAP. Recent work has shown that it is an option to choose 50 Hz driven power system when it is more lenient on the voltage ripple but needed to be as high as possible on the energy conversion efficiency.

MOPWA022

A 500 kV Pulser with Fast Risetime for EMP Simulation

high-voltage, simulation, pulsed-power, laser

708

W. Jia, W.Q. Chen, J.N. Li, J.P. Tang, L.S. Xie, Y.Z. Xie, G.W. Zhang
NINT, Xi'an, People's Republic of China

A fast risetime generator with 500kV rated output voltage for the electromagnetic pulse ( EMP ) effects experiment is fabricated. It mainly consists of a low inductance Marx ge nerator, a compact independent-sealed peaking capacitor, an output switch, and a small quantity of gas-sealed insulated containers. Compared with other similar pulsers mentioned in IEC 61000-4-32, the insulated containers of the generator are independent of each other in gas-sealed structure, and its number is les s than that of other pulsers. It can be used to drive a guided wave antenna directly to produce an electromagnetic environment, which conformed with the new standard for high-altitude nuclear explosion electromagnetic pulse (HEMP) developed by IEC. Output voltage produced by the generator in demo-load state can reach to 600kV. And, risetime of the waveform is 1.2ns, pulse width (FWHM) being 32ns. When the generator driving a 10m guided-wave antenna, an output voltage with a risetime of no more than 2.7ns and a FWHM of 30ns is achieved.

MOPWA030

Upgrade of the LHC Injection Kicker Magnets

vacuum, kicker, injection, electron

729

M.J. Barnes, P. Adraktas, V. Baglin, G. Bregliozzi, S. Calatroni, F. Caspers, H.A. Day, L. Ducimetière, M. Garlaschè, V. Gomes Namora, J.M. Jimenez, N. Magnin, V. Mertens, E. Métral, B. Salvant, M. Taborelli, J.A. Uythoven, W.J.M. Weterings
CERN, Geneva, Switzerland

The two LHC injection kicker systems, comprising 4 magnets per ring, produce a kick of 1.3 T.m with a rise-time of less than 900 ns and a flattop ripple of less than ±0.5%. A beam screen is placed in the aperture of each magnet, to provide a path for the image current of the high intensity LHC beam and screen the ferrite yoke against wake fields. The screen consists of a ceramic tube with conductors in the inner wall. The initially implemented beam screen ensured a low rate of electrical breakdowns while providing an adequate beam coupling impedance. Operation with increasingly higher intensity beams, stable for many hours at a time, now results in substantial heating of the ferrite yoke, sometimes requiring cool down over several hours before the LHC can be refilled. During the long shutdown in 2013/2014 all 8 kicker magnets will be upgraded with an improved beam screen and an increased emissivity of the vacuum tank. In addition equipment adjacent to the injection kickers and various vacuum components will also be modified to help reduce the vacuum pressure in the kickers during high-intensity operation. This paper discusses the upgrades as well as their preparation and planning.

MOPWA031

Beam Induced Ferrite Heating of the LHC Injection Kickers and Proposals for Improved Cooling

vacuum, kicker, injection, simulation

732

M.J. Barnes, S. Calatroni, F. Caspers, L. Ducimetière, M. Garlaschè, V. Gomes Namora, V. Mertens, Z.K. Sobiech, M. Taborelli, J.A. Uythoven, W.J.M. Weterings
CERN, Geneva, Switzerland
H.A. Day
UMAN, Manchester, United Kingdom

The two LHC injection kicker systems produce a kick of 1.3 T.m with a flattop duration variable up to 7860 ns, and rise and fall times of less than 900 ns and 3000 ns, respectively. A beam screen is placed in the aperture of each magnet, which consists of a ceramic tube with conductors in the inner wall. The conductors provide a path for the beam image current and screen the ferrite yoke against wake fields. Recent LHC operation, with high intensity beam stable for many hours, resulted in significant heating of both the ferrite yoke and beam impedance reduction ferrites. For one kicker magnet the ferrite yoke approached its Curie temperature. As a result of a long thermal time-constant the ferrites can require several hours to cool enough to re-inject beam, thus limiting the availability of the LHC. Thermal measurement data has been analysed, a thermal model developed and emissivity measurements carried out. The effects of various measures to improve the ferrite cooling have been simulated, including an improved emissivity of the vacuum tank and active cooling on the outside of the tank.

MOPWA032

Reduction of Surface Flashover of the Beam Screen of the LHC Injection Kickers

kicker, injection, vacuum, simulation

735

M.J. Barnes, P. Adraktas, S. Calatroni, F. Caspers, L. Ducimetière, V. Gomes Namora, V. Mertens, R. Noulibos, M. Taborelli, B. Teissandier, J.A. Uythoven, W.J.M. Weterings
CERN, Geneva, Switzerland

The LHC injection kicker magnets include beam screens to shield the ferrite yokes against wake fields resulting from the high intensity beam. The screening is provided by conductors lodged in the inner wall of a ceramic support tube. Operation with increasingly higher bunch intensity, and narrow bunches, now requires improved ferrite screening. This will be implemented by additional conductors; however the good high-voltage behaviour of the kicker magnets must not be compromised by the supplementary screening. Extensive studies and optimisations have been carried out, to better satisfy the often conflicting requirements for low beam coupling impedance, fast magnetic field rise-time, high vacuum and good high voltage behaviour. A new configuration is proposed which reduces significantly the electric field associated with the screen conductors and the secondary electron yield of the surface of the ceramic tube. Results of high voltage test results are also presented.

MOPWA033

Modelling of Parasitic Inductances of a High Precision Inductive Adder for CLIC

kicker, damping, coupling, emittance

738

J. Holma, M.J. Barnes
CERN, Geneva, Switzerland
S.J. Ovaska
Aalto University, School of Science and Technology, Aalto, Finland

The CLIC study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC pre-damping rings and damping rings will produce, through synchrotron radiation, ultra-low emittance beam with high bunch charge. To avoid beam emittance increase, the damping ring kicker systems must provide extremely flat, high-voltage, pulses. The specifications for the extraction kickers of the DRs are particularly demanding: the flat-top of the pulses must be ±12.5 kV with a combined ripple and droop of not more than ±0.02 % (±2.5 V). An inductive adder is a very promising approach to meeting the specifications. However, the output impedance of the inductive adder needs to be well matched to the system impedance. The primary leakage inductance, which cannot be computed accurately analytically, has a significant effect upon the output impedance of the inductive adder. This paper presents predictions, obtained by modelling the 3D geometry of the adder structure and printed circuit boards using the FastHenry code, for primary leakage inductance.

MOPWA042

The Leakage Current Induced by Stray Capacitance in the Pulse Magnet System

kicker, booster, high-voltage, injection

762

C.S. Chen, C.K. Chan, K.H. Hsu, Y.-H. Liu, C.S. Yang
NSRRC, Hsinchu, Taiwan

A huge amount of current must be provided during the nominal operation of the pulse magnet system in TPS (Taiwan Photon Source). It comes with all kinds of electromagnetic noises, including radiated and conducted EMI (electromagnetic interferences). The primary object of this article is to clarify the paths of induced EMI, especially by means of capacitance induction. Furthermore, some geometrical suggestions which had been tested are listed in this paper as the guidelines of the pulse magnet design. According to the measurement, proper distance and surface area lead to sufficient insulation and reduce the leakage current under the expected value.

MOPWO003

Multibunch Tracking Code Development to Account for Passive Landau Cavities

cavity, electron, damping, radiation

885

M. Klein, R. Nagaoka
SOLEIL, Gif-sur-Yvette, France

The MAX IV 3 GeV storage ring will achieve an ultra-low horizontal emittance of 0.24 nm rad by using a multibend achromat lattice. Passive harmonic cavities are introduced to relax the Touschek-lifetime and intrabeam scattering issues as well as fight collective beam instabilities via Landau damping. Since instabilities occur during injection, when the passive harmonic cavity potential is also time varying, it became important to simulate this transient process. The most promising approach was considered to be multibunch tracking which also allows for an arbitrary filling pattern. Since every bunch is represented by numerous macroparticles, internal motions as well as microstructures in the charge distribution can be followed.

MOPWO007

Numerical Calculation of Electromagnetic Fields in Acceleration Cavities Under Precise Consideration of Coupler Structures

dipole, cavity, electromagnetic-fields, resonance

897

C. Liu, W. Ackermann, W.F.O. Müller, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: Work supported by BMBF under contract 05H12RD5
The acceleration with superconducting radio frequency cavities requires dedicated couplers to transfer energy from the radio frequency source to the beam. Simultaneously, higher order mode couplers are installed to effectively suppress parasitic modes. Therefore, the numerical eigenmode analysis based on real-valued variables is no longer suitable to describe the dissipative acceleration structure. At the Computational Electromagnetics Laboratory (TEMF) a robust parallel eigenmode solver to calculate the eigenmodes in the lossy acceleration structure is available. This eigenmode solver is based on complex-valued finite element analysis and utilizes basis functions up to the second order on curved tetrahedral elements to enable the high precision elliptical cavity simulations. The eigenmode solver has been applied to the TESLA 1.3 GHz accelerating cavity to determine the resonance frequency, the quality factor and the corresponding field distribution for all 192 eigenmodes up to the 5th dipole passband (3.12 GHz).

MOPWO022

Design and Manufacturing Description of the Prototype Striplines for the Extraction Kicker of the CLIC Damping Rings

kicker, extraction, damping, vacuum

930

C. Belver-Aguilar, A. Faus-Golfe
IFIC, Valencia, Spain
M.J. Barnes
CERN, Geneva, Switzerland
J. Gómez
Trinos Vacuum Projects, Paterna, Spain
D. Gutiérrez Arribas
Trinos Vacuum Projects, S.L., Paterna - Valencia, Spain
F. Toral
CIEMAT, Madrid, Spain

The Pre-Damping Rings (PDRs) and Damping Rings (DRs) of CLIC are needed to reduce the beam emittances to the small values required for the main linacs. The injection and extraction, from the PDRs and DRs, are carried out by kicker systems. In order to achieve both low beam coupling impedance and reasonable broadband impedance matching to the electrical circuit, striplines have been chosen for the kicker elements. The design of the stripline kicker was previously carried out by modelling the striplines with simulation codes such as HFSS, Quickfield and CST Particle Studio. In order to have a complete analysis of the striplines, the effect of electrodes supports and coaxial feedthroughs have been studied in detail. In this paper, electromagnetic analyses of the complete striplines, including fabrication tolerances, are reported. Furthermore, a new idea for impedance matching is presented.

TUODB201

Recent Progress on the Development of a High Gradient RF System using High Impedance Magnetic Alloy, FT3L

cavity, acceleration, synchrotron, controls

1152

C. Ohmori, K. Hara, K. Hasegawa, M. Toda, M. Yoshii
KEK, Ibaraki, Japan
M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto
JAEA/J-PARC, Tokai-mura, Japan

An upgrade project of J-PARC MR (Main Ring) includes developments of high gradient RF cavities and magnet power supplies for high repetition rate. A dedicated production system for high impedance magnetic alloy (FT3L) cores was assembled in J-PARC. This setup demonstrated that we can produce material with two times higher muQf product compared to the cores used for present cavities. And, the new results also show up to 20% higher impedance than the 2011 production with the former setup. In this summer, the system will be used for mass production of 200 FT3L cores for J-PARC MR. The cores produced in 2011 are already used for standard machine operation. The operation experience shows that the power loss in the cores was reduced significantly as expected. The scenario describing the upgrade plan of MR and the cavity replacements is reported. By the replacement plan, the total acceleration voltage will be almost doubled, while the number of RF stations remains the same.

Slides TUODB201 [5.105 MB]

TUODB203

Dual Chip in Single Module Solid-State Power Amplifier Design for Compact Transmitter Architecture

insertion, storage-ring, booster, linac

1158

T.-C. Yu, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Y.-H. Lin, Z.L. Liu, C.H. Lo, M.H. Tsai, Ch. Wang, T.-T. Yang, M.-S. Yeh
NSRRC, Hsinchu, Taiwan

At present, the high power solid-state technique transmitter design are composed of hundreds parallel combined single chip for hundreds Watts power modules to achieve enough output power. Although the large numbers can bring high redundancy during system operation, the power hungry of next generation RF system of accelerator would need much more modules to reach its power requirement. Huge amount of power modules would bring the complexity and difficulty in power combining, system construction, management and maintenance. To overcome this problem, upgrading the power level of a single module could be the solution. Besides depending on the power level growing with technology advancement in semiconductor industry, a circuit level solution to combine dual chip in advance in a single PCB board is proposed to produce twice power as single chip. Such feasible solution can overcome the over-complexity of future several-hundreds kW solid-state transmitter design.

Slides TUODB203 [2.337 MB]

TUPEA035

Plasma Effect in the Longitudinal Space Charge Induced Microbunching Instability

plasma, electron, space-charge, background

1220

D. Huang, Q. Gu
SINAP, Shanghai, People's Republic of China
K.Y. Ng
Fermilab, Batavia, USA

Funding: National Science Foundation of China (NSFC), grant No. 11275253, and US DOE, contract DE-FG02-92ER40747.
In many cases, the longitudinal space charge (LSC) is a dominant factor to bring in the microbunching instability in the LINAC of a Free-Electron-Laser (FEL) facility. The current model of LSC impedance* derived from the fundamental electromagnetic theor** is widely used to explain the physics of the LSC-induced microbunching instability***. However, in the case of highly bright electron beams, the plasma effect starts to play a role. In this paper, the basic model of the LSC impedance including the plasma effect is built up by solving the Vlasov and Poisson equations in 6 dimensional phase space, and the investigation is done to study the modification to the gain of the instability based on the model. The solutions indicate that the gain does not only depend on the spatial information of the beam, but also on the velocity (momentum) and time information. The comparison of the gains of the microbunching instability in the LINAC of Shanghai soft X-ray Free Electron Laser Facility (SXFEL) computed by various methods is also given and the discrepancy is illustrated.
* Marco Venturini, Phys. Rev. ST Accel. Beams 11, 034401 (2008)
** J. D. Jackson, Classical Electrodynamics (Wiley, 1999)
*** Z. Huang, et. al., Phys, Rev. ST Accel. Beams 7, 074401 (2004)

TUPEA075

Passively Driving X-band Structures to Achieve Higher Beam Energies

electron, linac, laser, gun

1304

S. Biedron, S.V. Milton, N. Sipahi, T. Sipahi
CSU, Fort Collins, Colorado, USA

Particle accelerators at X-band frequencies have gradients of around 100 MV/m. This technology permits more compact accelerators. One of our aims at the Colorado State University Accelerator Laboratory is to adapt this technology to our L-band (1.3 GHz) accelerator system to increase our overall beam energy; however, we would like to do this in a passive manner, i.e. one that does not require investment in an expensive, custom, high-power klystron system. In this paper we explore using the beam from our L-band 6 MeV photoinjector to power an x-band structure tuned to the 9th harmonic of our L-band system, 11.7 GHz. Electron bunches will be generated at a repetition rate of 81.25 MHz and passed through a high shunt impedance x-band accelerating structure where they will resonantly excite the fundamental field. We will optimize the system to create the highest accelerating potential within this structure. Once the peak gradient is achieved we will send a single electron bunch through the system at a phase that places it on the crest of the X-band accelerating wave thereby increasing the electron bunch energy by some amount without need for additional external power sources.

TUPFI033

Colliding During the Squeeze and β* Leveling in the LHC

luminosity, collider, controls, optics

1415

X. Buffat
EPFL, Lausanne, Switzerland
W. Herr, M. Lamont, T. Pieloni, S. Redaelli, J. Wenninger
CERN, Geneva, Switzerland

While more challenging operationally, bringing the beams into collisions during the β squeeze rather than after presents some advantages. The large tune spread arising from the non-linearity of head-on beam-beam interactions can damp impedance-driven instabilities much more efficiently than external non-linearity such as octupoles presently used in operation. Moreover, colliding during the squeeze allows to level the luminosity, optimizing the pile-up in the experiments without changing the longitudinal distribution of collisions. Operational issues are discussed and experimental results from the LHC are presented.

TUPFI034

Observations of Two-beam Instabilities during the 2012 LHC Physics Run

octupole, damping, betatron, luminosity

1418

T. Pieloni
EPFL, Lausanne, Switzerland
G. Arduini, X. Buffat, R. Giachino, W. Herr, M. Lamont, N. Mounet, E. Métral, G. Papotti, B. Salvant, J. Wenninger
CERN, Geneva, Switzerland
S.M. White
BNL, Upton, Long Island, New York, USA

During the 2012 run coherent beam instabilities have been observed in the LHC at 4 TeV, during the betatron squeeze and in collision for special filling patterns. Several studies to characterize these instabilities have been carried out during operation and in special dedicated experiments. In this paper we summarize the observations collected for different machine parameters and the present understanding of the origin of these instabilities.

TUPFI036

Observation of Beam Instabilities with Very Tight Collimation

damping, collimation, proton, octupole

1424

H. Burkhardt, N. Mounet, T. Pieloni
CERN, Geneva, Switzerland

We report about the observation of instabilities in the LHC in special runs with high β^* and very tight collimation down to 2 σ which increases the transverse impedance significantly. The losses appeared primarily on the highest intensity, non-colliding bunches which can be interpreted as evidence for insufficient Landau damping. We describe the beam conditions, observations and possible explanations for the observed effects.

TUPFI063

Electromagnetic Coupling between High Intensity LHC Beams and the Synchrotron Radiation Monitor Light Extraction System

simulation, resonance, extraction, synchrotron

1493

F. Roncarolo, W. Andreazza, A. Bertarelli, E. Bravin, F. Caspers, M. Garlaschè, A. Goldblatt, J-J. Gras, O.R. Jones, T. Lefèvre, E. Métral, A.A. Nosych, B. Salvant, G. Trad, R. Veness, C. Vollinger, M. Wendt
CERN, Geneva, Switzerland

The CERN LHC is equipped with two Synchrotron Radiation Monitor systems used to characterise transverse and longitudinal beam distributions. Since the end of the 2011 LHC run the light extraction system, based on a retractable mirror, has suffered deformation and mechanical failure that is correlated to the increase in beam intensity. Temperature probes have associated these observations to a strong heating of the mirror support with a dependence on the longitudinal bunch length and shape, indicating the origin as electromagnetic coupling between the beam and the structure. This paper combines all this information with the aim of characterising and improving the system in view of its upgrade during the current LHC shutdown. Beam-based observations are presented along with electromagnetic and thermomechanical simulations and complemented by laboratory measurements, including the study of the RF properties of different mirror bulk and coating materials.

TUPME017

Validation of the Microwave Instability in the Damping Ring of SuperKEKB using VFP Solver

damping, simulation, wakefield, synchrotron

1604

L. Wang
SLAC, Menlo Park, California, USA
H. Ikeda, K. Ohmi, K. Oide, D. Zhou
KEK, Ibaraki, Japan

Microwave instability driven by CSR impedance in the damping ring of Super-KEKB is a concern due to its high bunch current. To understand the beam dynamics, we simulate the microwave instability using Vlasov-Fokker-Planck (VFP) solver. The longitudinal wake potential is calculated as a sum of the contributions due to vacuum chamber components distributed around the ring, including geometry wake field and CSR wake. To improve the accuracy of the simulation of microwave instability, the coherent synchrotron radiation impedance is calculated to very high frequency to get more accurate wake field with a short bunch. The CSR wake is much larger than the geometry wake. The threshold is just above the design current and saw-tooth type of instability is found above the threshold.

TUPME032

Update on Beam Induced RF Heating in the LHC

injection, kicker, proton, simulation

1646

B. Salvant, O. Aberle, G. Arduini, R.W. Aßmann, V. Baglin, M.J. Barnes, W. Bartmann, P. Baudrenghien, O.E. Berrig, A. Bertarelli, C. Bracco, E. Bravin, G. Bregliozzi, R. Bruce, F. Carra, F. Caspers, G. Cattenoz, S.D. Claudet, H.A. Day, M. Deile, J. Esteban Müller, P. Fassnacht, M. Garlaschè, L. Gentini, B. Goddard, A. Grudiev, B. Henrist, S. Jakobsen, O.R. Jones, O. Kononenko, G. Lanza, L. Lari, T. Mastoridis, V. Mertens, N. Mounet, E. Métral, A.A. Nosych, J.L. Nougaret, S. Persichelli, A.M. Piguiet, S. Redaelli, F. Roncarolo, G. Rumolo, B. Salvachua, M. Sapinski, R. Schmidt, E.N. Shaposhnikova, L.J. Tavian, M.A. Timmins, J.A. Uythoven, A. Vidal, J. Wenninger, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland
H.A. Day
UMAN, Manchester, United Kingdom
L. Lari
IFIC, Valencia, Spain

Since June 2011, the rapid increase of the luminosity performance of the LHC has come at the expense of increased temperature and pressure readings on specific near-beam LHC equipment. In some cases, this beam induced heating has caused delays whilie equipment cools down, beam dumps and even degradation of these devices. This contribution gathers the observations of beam induced heating attributable to beam coupling impedance, their current level of understanding and possible actions that are planned to be implemented during the long shutdown in 2013-2014.

TUPME033

Evaluation of the Beam Coupling Impedance of New beam Screen Designs for the LHC Injection Kicker Magnets

kicker, coupling, injection, resonance

1649

H.A. Day
UMAN, Manchester, United Kingdom
M.J. Barnes, F. Caspers, E. Métral, B. Salvant
CERN, Geneva, Switzerland
R.M. Jones
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The LHC injection kicker magnets (MKIs) have experienced a significant degree of beam induced heating since the beginning of the 2011 due to the increasing intensity stored in the LHC, for long periods of time, and the relatively large broadband impedance of the installed kicker magnets. In this paper we show the sources of impedance in the MKIs, especially the effect that the beam screen dimensions have on the impedance. We show how these alter the power loss, and present an improved beam screen design that improves shielding on the magnet, whilst further improving electrical breakdown.

TUPWA005

Study of Collective Beam Instabilities for the MAX IV 3 GeV Ring

simulation, vacuum, damping, wakefield

1730

M. Klein, R. Nagaoka
SOLEIL, Gif-sur-Yvette, France
G. Skripka, P.F. Tavares, E.J. Wallén
MAX-lab, Lund, Sweden

The present paper reports on a systematic simulation study made on the collective beam instability in the MAX IV 3 GeV ring. We study both single and multibunch instabilities in the longitudinal plane. Specifically, we focus on the microwave instabilities which are considered to be particularly dangerous for MAX IV, in view of its small effective radius of aperture (b_eff < 11 mm), the high intensity (500 mA) and the low emittance (0.24 nm.rad) nature of the circulating beam. Single and multibunch tracking are performed using wake fields that were numerically obtained using GdfidL for the ensemble of the vacuum components. A special effort was made to include dynamically the effect of harmonic cavities that lengthen the bunch and introduce Landau damping, whose details are described in the companion paper *. The study aims to confirm the effectiveness of storing long bunches in the 100 MHz RF system, where tune spreads are further increased by the harmonic cavities, in order to fight against collective instabilities.
* M. Klein and R. Nagaoka "Multibunch Tracking Code Development to Account for Passive Landau Cavities", these proceedings

TUPWA008

Computation of Wakefields for an In-vacuum Undulator at PETRA III

vacuum, undulator, wakefield, simulation

1736

E. Gjonaj, L. Lünzer, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany
R. Wanzenberg
DESY, Hamburg, Germany

Funding: Work supported by DESY, Hamburg, Germany
At DESY the installation of an in-vacuum undulator at the synchrotron radiation facility PETRA III is under consideration. The moveable magnet array of the undulator is installed inside the vacuum chamber to achieve shorter wavelength synchrotron radiation. A thin metal foil covers the magnet structure to mitigate resistive wall wakefields. Moveable tapered transitions connect the magnet structure and the adjacent vacuum duct to reduce the geometric wakefields. Nevertheless these moveable tapered transitions contribute significantly to the impedance budget of PETRA III. The computer codes MAFIA, CST-Studio and PBCI have been used to calculate the longitudinal and transverse wakefields. The results for the loss and kick parameters are presented and compared to the corresponding parameters for a standard undulator section.

TUPWA009

Bunch by Bunch Intra-Bunch Feedback System for Curing Transverse Beam Instabilities at the J-PARC MR

feedback, injection, kicker, betatron

1739

O. A. Konstantinova, Y.H. Chin, Y. Kurimoto, T. Obina, M. Okada, K. Takata, M. Tobiyama, T. Toyama
KEK, Ibaraki, Japan
Y. Shobuda
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

At the J-PARC Main Ring (MR), transverse instabilities have been observed during the injection and at the onset of acceleration with large particle losses. The present bunch by bunch feedback system, operating in a narrowband mode, has been effectively suppressing these instabilities, allowing the beam power to reach 230kW with only 400W of particle losses. The observed beam signals show that bunches are still executing complicated intra-bunch oscillations even if the narrowband feedback system is on, though they are not imposing significant particle losses at present. The new and more advanced broadband feedback system has been developed for control of the intra-bunch oscillations and further reduction of particle losses. The elaborate analysis code has been also developed on the MATLAB platform to analyse effects of the broadband feedback system on intra-bunch oscillations. This paper describes the development of these advanced instruments and presents the analysis of the latest beam test results using the MATLAB code.

TUPWA010

A Trial to Reduce the Kicker Impedance of 3-GeV RCS in J-PARC

kicker, resonance, acceleration, status

1742

Y. Shobuda, N. Hayashi, T. Takayanagi
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
Y. Irie
KEK, Ibaraki, Japan
T. Toyama
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

At 3GeV RCS in J-PARC, the kicker impedance has been considered to be the dominant source to cause the beam instability. Recently, experimental studies demonstrate that the beam instability is suppressed by reducing the kicker impedance. In this report, a trial to reduce the kicker impedance is reported.

TUPWA014

The Status of Coupling Impedance Measurement for the CSNS/RCS Extraction Kicker Prototype*

kicker, coupling, simulation, extraction

1754

L. Huang, Y. Li, R.H. Liu, Y.D. Liu, S. Wang, O. Xiao
IHEP, Beijing, People's Republic of China

Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) is a high intensity proton accelerator, with average beam power of 100kW. In order to high intensity beam operation, the beam coupling impedance of the extracted kickers must be controlled. Longitudinal and transverse impedance of extracted kicker prototype with power supply had been roughly measured by coaxial-wire and dual-wire methods respectively. At the same time, impedance of window has been analyzed theoretically and simulated based on CST PARTICLE STUDIO.

TUPWA015

The Study of Bunch Lengthening in Electron Storage Ring

synchrotron, storage-ring, luminosity, electron

1757

Y. Li, L. Wang, Y. Zhang
IHEP, Beijing, People's Republic of China

The bunch length of electron storage ring of BEPCII was measured repeatedly during steady synchronous mode and streak camera was calibrated well. From the bench lengthening , the coupling impedance of the whole ring was estimated, which was according with theoretic impedance budget . Meanwhile, the small ap optics for improving the luminosity was feasible in collision mode form synchronous result .

TUPWA023

Design of the Tuning System for the He⁺ Coupled RFQ-SFRFQ Cavity

cavity, rfq, simulation, linac

1775

W.L. Xia, J.E. Chen, S.L. Gao, Z.Y. Guo, Y.R. Lu, S.X. Peng, Z. Wang, X.Q. Yan, J. Zhao, K. Zhu
PKU, Beijing, People's Republic of China

Funding: Supported by NSFC 10905003, 11079001, 91026012 Corresponding author: wangzhi@pku.edu.cn
The CRS (coupled RFQ-SFRFQ) cavity is a new type linac that couples traditional RFQ (radio frequency quadrupole) and SFRFQ (separated function RFQ) electrodes into a single cavity. The overall design of the CRS cavity has been completed and the linac is being manufactured currently. In this paper, we aimed to design a frequency tuning system for the CRS cavity, which will be used to explore the electromagnetic field distribution between RFQ and SFRFQ sections in the cavity. The frequency range, variation of Q value, power consumption and electric field distribution were investigated. Based on the beam dynamic program SFRFQDYNv1.0, we analysed the beam transmission properties of the cavity under the unbalanced electric field distribution. The optimized parameters of the tuning system were obtained.

TUPWA030

Impedances Calculations of Bellows in HLS II Storage Ring

wakefield, storage-ring, shielding, coupling

1784

Q. Zhang, W. Li, L. Wang
USTC/NSRL, Hefei, Anhui, People's Republic of China

The upgrade project of Hefei Lighe Source storage ring is carrying on.In this project,a new Bellows, in which shielding is provided by sprung fingers which can slide along the beam screen,is installed at the accelerator interaction area In order to reduce this impedance to an acceptable value. The contributions of Bellows to short range wakefields and broadband impedance were calculated numerically by Mafia code .

TUPWA038

Equilibrium Bunch Density Distribution with Passive Harmonic Cavities in the MAX IV 3 GeV Storage Ring

cavity, storage-ring, emittance, damping

1790

P.F. Tavares, Å. Andersson, A. Hansson
MAX-lab, Lund, Sweden

The MAX IV storage rings will use third harmonic cavities operated passively to lengthen the bunches and alleviate collective instabilities. These cavities are an essential ingredient in the MAX IV design concept and are required for achieving the final design goals in terms of stored current, beam emittance and beam lifetime. This paper reports on fully self-consistent calculations of the longitudinal bunch density distribution in the MAX IV 3 GeV storage ring, which indicate that up to a factor 5 increase in RMS bunch length is achievable with a purely passive system.

TUPWA039

Identification of the SPS Impedance at 1.4 GHz

optics, simulation, resonance, bunching

1793

T. Argyropoulos, T. Bohl, H. Damerau, J. Esteban Müller, E.N. Shaposhnikova, H. Timko
CERN, Geneva, Switzerland

In the SPS spectrum measurements of very long single bunches were used in the past to identify sources of longitudinal microwave instability. Shielding of the identified objects significantly improved the beam stability. However, longitudinal instabilities are still one of the limitations for high intensity LHC beams in the SPS. Recently the same measurement technique was used again, revealing a strong high frequency resonance. During the slow de-bunching with the RF switched off, the presence of different resonant impedances leads to a line density modulation at the resonant frequencies. Longitudinal profiles of bunches of various intensities were acquired. For sufficiently high intensities their spectra show a fast growing and strong modulation at 1.4 GHz. Measurements using two transverse optics with different transition energy are compared. Reproducing the measurements with numerical simulations, including the known SPS longitudinal impedances, allowed the parameter range of this unknown source to be determined. Possible candidates as impedance sources in the SPS ring are investigated.

TUPWA040

Loss of Landau Damping for Inductive Impedance in a Double RF System

damping, emittance, synchrotron, simulation

1796

T. Argyropoulos, E.N. Shaposhnikova
CERN, Geneva, Switzerland
A.V. Burov
Fermilab, Batavia, USA

In this paper the thresholds of the loss of Landau damping due to the presence of inductive impedance in a single and double harmonic RF systems are determined, both from calculations and particle simulations. High harmonic RF system, operating in bunch lengthening mode is used in many accelerators with space charge or inductive impedance to reduce the peak line density or stabilize the beam. An analytical approach, based on emerging of the discrete Van Kampen modes, shows that improved stability in a double RF system can be achieved only below some critical value of longitudinal emittance. Above this threshold, a phase shift of more than 15 degrees between the two RF components is proven to stabilize the bunch. These results, confirmed also by particle simulations, are able to explain now observations during the ppbar operation of the SPS. The thresholds in bunch shortening mode as well as in a single RF case are compared with this regime.

TUPWA042

Lessons Learned and Mitigation Measures for the CERN LHC Equipment with RF Fingers

resonance, vacuum, damping, simulation

1802

E. Métral, O. Aberle, R.W. Aßmann, V. Baglin, M.J. Barnes, O.E. Berrig, A. Bertarelli, G. Bregliozzi, S. Calatroni, F. Carra, F. Caspers, H.A. Day, M. Ferro-Luzzi, M.A. Gallilee, C. Garion, M. Garlaschè, A. Grudiev, J.M. Jimenez, O.R. Jones, O. Kononenko, R. Losito, J.L. Nougaret, V. Parma, S. Redaelli, B. Salvant, P.M. Strubin, R. Veness, C. Vollinger, W.J.M. Weterings
CERN, Geneva, Switzerland

Beam-induced RF heating has been observed in several LHC components when the bunch/beam intensity was increased and/or the bunch length reduced. In particular eight bellows, out of the ten double-bellows modules present in the machine in 2011, were found with the spring, which should keep the RF fingers in good electrical contact with the central insert, broken. Following these observations, the designs of all the components of the LHC equipped with RF fingers have been reviewed. The lessons learnt and mitigation measures are presented in this paper.

TUPWA043

Impedance Studies for VMTSA Module of LHC Equipped with RF Fingers

simulation, resonance, factory

1805

O. Kononenko, F. Caspers, A. Grudiev, E. Métral, B. Salvant
CERN, Geneva, Switzerland

During 2011 run of LHC it was found that beam-induced heating causes many issues for accelerator components. Particularly some of the double-bellow modules, called VMTSA modules, were found to have deformed RF fingers and a broken spring which ensured good contact between them and a central insert. Impedance studies have been performed for different types of nonconformities and benchmarked against measurements. It was found that even a small gap between the fingers and a central insert could be fatal for the VMTSA operation. Results of this study were an input for the further thermal analysis.

TUPWA047

Collimator Impedance Measurements in the LHC

simulation, optics, proton, collimation

1817

N. Mounet, R. Bruce, E. Métral, S. Redaelli, B. Salvachua, B. Salvant, G. Valentino
CERN, Geneva, Switzerland

The collimation system of the LHC is one of the largest impedance contributors of the machine, in particular for its imaginary part. To evaluate the collimator impedance and its evolution with integrated luminosity, several measurement campaigns were performed along the year 2012, in which collimator jaws were moved back-and-forth leading to significant tune shifts for a nominal intensity bunch in the machine. These observations are compared to the results from HEADTAIL simulations with the impedance model in its current state of development.

TUPWA049

Short High-Intensity Bunches for Plasma Wakefield Experiment AWAKE in the CERN SPS

optics, emittance, proton, plasma

1820

H. Timko, T. Argyropoulos, H. Bartosik, T. Bohl, J. Esteban Müller, E.N. Shaposhnikova
CERN, Geneva, Switzerland
A.V. Petrenko
BINP SB RAS, Novosibirsk, Russia

Obtaining the shortest possible bunch length in combination with the smallest transverse emittances and highest bunch intensity – this is the wish list of the proton-bunch driven, plasma wakefield acceleration experiment AWAKE currently under feasibility study at CERN. A few measurement sessions were conducted to determine the achievable bunch properties and their reproducibility. To obtain a short bunch length, the bunches were rotated in longitudinal phase space using the maximum available RF voltage prior to extraction. Measurements were carried out in two optics with different transition energies. The main performance limitation is longitudinal beam instability that develops during the acceleration ramp. With lower transition energy, beam stability is improved, but the bucket area is smaller for the same voltage. Based on the results obtained, we shall discuss the choice of optics, the impact of longitudinal instabilities, the importance of reproducibility, as well as options for improving the bunch parameters.

TUPWA052

Loss Factor and Impedance Analysis for the Diamond Storage Ring

storage-ring, vacuum, wiggler, simulation

1826

R. Bartolini, R.T. Fielder, C.A. Thomas
Diamond, Oxfordshire, United Kingdom

Diamond Light Source is investigating the possibility of increasing the storage ring operating current above the nominal 300 mA. A campaign of measurements and simulations has been carried out in order to understand the extent of the parasitic energy loss and characterise the most important items which build up the machine impedance. In this paper we report on the most recent measurements of the longitudinal loss factor and the present status of the impedance database with an initial comparison between the two.

TUPWA057

Effects of Transient CSR Wakefields on Microbunching in a Bunch Compressor

wakefield, lattice, radiation, FEL

1832

C.E. Mitchell, J. Qiang
LBNL, Berkeley, California, USA

Funding: Supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The standard analytical model of CSR-induced microbunching in a bunch compressor chicane makes use of a steady-state 1-D model of the longitudinal CSR interaction. This model is numerically generalized to include the effects of transient CSR wakefields due to bend entry and exit, as well as CSR that is generated in upstream bends and propagates across one or more lattice elements before interacting with the beam. The resulting linear integral equation for CSR-induced microbunching is solved numerically for the second bunch compressor of a proposed Next Generation Light Source.

TUPWA071

Studies of Resistive Wall Heating at JLAB FEL

FEL, wiggler, resonance, electron

1868

R. Li, S.V. Benson
JLAB, Newport News, Virginia, USA

Funding: Work supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
When the JLAB FEL is under CW operation, it had been observed that temperature rises over the wiggler vacuum chamber, presumably as the result of the power deposition on the resistive wall of the wiggler chamber. Previous analyses have been done on the resistive wall impedance for various cases, such as DC, AC, and anomalous skin effects*. Here we report an investigation on the beam kinetic energy losses for each of these cases. This study includes the non-ultrarelativistic effect on resistive wall loss, for both round pipe and parallel plates. We will present the comparison of our results with the measured data obtained during CW operation of the JLAB FEL. Other possible factors contributing to the measured heating will also be discussed.
* K. Bane and G. Stupakov, SLAC-PUB-10707, 2004.

TUPWA074

Studies of Ion Beam Instabilities for Low Energy RHIC Operations with Electron Cooling

ion, electron, simulation, emittance

1871

G. Wang, M. Blaskiewicz, V. Litvinenko
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Electron cooling has the potential to compensate the emittance growth of the circulating ion beam due to intra-beam scattering at low energy. A test of electron cooling for RHIC low energy operations has been planned at IP2. Apart from the wakefield from the environment, the coherent interaction between the electron beam and ion beam could also play a role for the instability threshold. This work presents studies of ion beam stabilities in presence of coherent electron-ion interactions for the planned low energy RHIC electron-cooling test using the simulation code TRANFT.

WEOAB102

CSR-driven Longitudinal Single Bunch Instability Thresholds

synchrotron, resonance, damping, electron

2041

P. Kuske
BESSY GmbH, Berlin, Germany

According to Bane, et al.* threshold currents should follow a quite simple scaling law. More detailed theoretical results for the underlying shielded CSR-interaction have been performed for BESSY-II and the MLS and will be presented in comparison with observations at these storage rings. It is found that there are parameter regions where the instability is weak and thus thresholds depend on damping time and synchrotron tune. Theoretical findings are in surprisingly good agreement with most of the observed instability features.
* K.L. Bane, et al., Phys. Rev. ST-AB 13, 104402 (2010)

Slides WEOAB102 [0.779 MB]

WEPWA006

Beam Heat Load Measurements with COLDDIAG at the Diamond Light Source

electron, synchrotron, synchrotron-radiation, radiation

2135

S. Gerstl, S. Casalbuoni, A.W. Grau, T. Holubek, D. Saez de Jauregui, R. Voutta
KIT, Eggenstein-Leopoldshafen, Germany
R. Bartolini, M.P. Cox, E.C. Longhi, G. Rehm, J.C. Schouten, R.P. Walker
Diamond, Oxfordshire, United Kingdom
M. Migliorati, B. Spataro
INFN/LNF, Frascati (Roma), Italy

Understanding the heat load from an electron beam is still an open issue for the cryogenic design of superconducting insertion devices. COLDDIAG, a cold vacuum chamber for diagnostics was designed and built specially for this purpose. With the equipped instrumentation, which covers temperature sensors, pressure gauges, mass spectrometers as well as retarding field analyzers it is possible to measure the beam heat load, total pressure, and gas content as well as the net flux and energy of particles hitting the chamber walls. Following a failure after its first installation in November 2011, COLDDIAG was subsequently reinstalled in the Diamond storage ring in August 2012. We report on the preliminary results that have been obtained since then.

WEPWA080

Development of a Compact Insertion Device for Coherent Sub-mm Generation

radiation, linac, laser, wakefield

2295

A.V. Smirnov, R.B. Agustsson, S. Boucher, T.J. Grandsaert, J.J. Hartzell, M. Ruelas, S. Storms
RadiaBeam, Santa Monica, USA
A. Andrews, B.L. Berls, C.F. Eckman, K. Folkman, A.W. Hunt, Y. Kim, A.E. Knowles-Swingle, C. O'Neill, M. Smith
IAC, Pocatello, IDAHO, USA
P. Buaphad, Y. Kim
ISU, Pocatello, Idaho, USA

Funding: Department of Energy Contracts DE- SC-FOA-0000760 and DE-FG02-07ER84877
A novel design of resonant Cherenkov wakefield extractor that produced a ~0.9 mm wavelength radiation is presented. The experiment was performed at Idaho Accelerator Center (IAC) using specially upgraded 1.3 GHz 44 MeV linac facility. Specifics of the radiator performance and design are outlined including low-energy beam interaction with non-circular geometry. Some elements of the design may have certain potential for future compact mm-sub-mm-wave sources.

WEPWO048

Investigation of a Ridge-loaded Waveguide Structure for CLIC X-band Crab Cavity

cavity, damping, HOM, beam-loading

2411

V.F. Khan, R. Calaga, A. Grudiev
CERN, Geneva, Switzerland

In conventional crab cavities the TM11 mode is used to deflect the beam. In a linear collider such as CLIC, it is necessary to damp all the other modes, namely the accelerating i.e. lower order mode (LOM), same order mode (SOM) and higher order modes (HOMs). In addition to this, as the TM11 mode is not the fundamental mode, it is generally not excited with the highest shunt impedance. This necessitates damping of the high shunt impedance modes to acceptable level. Here we report on the investigation of an alternative design of the X-band crab cavity for CLIC based on ridge-loaded waveguide. In this type of cavity, the deflecting mode is the fundamental mode and has the maximum shunt impedance. However, the geometry of the cavity is chosen to optimise the ratio of group velocity to shunt impedance to minimise the effect of beam loading. The other modes are excited above the crabbing mode and are damped using wave-guides. Another advantage of this type of cavity is, unlike the conventional TM11 mode cavities, the e.m. surface fields do not peak at the iris. This provides ample margin to optimise the cavity geometry and reach the desired field distribution.

WEPWO077

Rf System Requirements for JLab’s MEIC Collider Ring

ion, cavity, electron, SRF

2477

S. Wang, R. Li, R.A. Rimmer, H. 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, consists of a series of accelerators [1]. At the top energy are the electron and ion collider rings. For the ion ring, it accelerates five long ion bunches to colliding energy and rebunches ions into a train of very short bunches before colliding. A set of low frequency RF system is needed for the long ion bunch energy ramping. Another set of high frequency RF cavities is needed to rebunch ions. For the electron ring, superconducting RF (SRF) cavities are needed to compensate the synchrotron radiation energy loss. The impedance of the SRF cavities must be low enough to keep the high current electron beam stable. The preliminary design requirements of these RF cavities are presented.
The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.

WEPEA011

Bursting Patterns of Coherent Synchrotron Radiation in the ANKA Storage Ring

radiation, simulation, electron, synchrotron

2516

M. Schwarz, V. Judin, A.-S. Müller
KIT, Karlsruhe, Germany
M. Klein
SOLEIL, Gif-sur-Yvette, France

We report measurements of bursting patterns of coherent synchrotron radiation (CSR) for a wide range of single bunch currents at the ANKA storage ring. The radiation was detected with a fast THz detector, a Hot Electron Bolometer, and its signal acquired with both a spectrum analyzer and an external sampling oscilloscope. Both analysis methods consistently show the onset of bursting at a threshold current with the appearance of strong high frequency bands with higher harmonics in the several 10th of kHz range. For currents higher than twice the threshold value an abrupt change in the bursting pattern occurs. These results are compared with different numerical models solving the one-dimensional Vlasov-Fokker-Planck equation.

WEPEA019

Status of the J-PARC MA Loaded RF Systems

cavity, injection, proton, bunching

2537

M. Yoshii, E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, K. Takata, M. Toda
KEK, Tokai, Ibaraki, Japan
M. Nomura, T. Shimada, F. Tamura, M. Yamamoto
JAEA/J-PARC, Tokai-mura, Japan
A. Schnase
GSI, Darmstadt, Germany

Japan proton accelerator complex operates two cascaded synchrotrons, 3GeV RCS and 50GeV MR. The high electric field gradient magnetic alloy (MA) loaded cavities are used in both synchrotrons. The RF systems have no tuning control loop and the direct digital synthesis based fully digital low level RF guarantees the stable and reproducible proton acceleration. The feed-forward systems using the circulating beam current signals works efficiently to compensate the heavy beam induced voltage. In RCS, 11 RF systems are operating in a dual harmonic mode since December 2008. The longitudinal RF control based on the particle tracking performed effectively and the equivalent beam power of 530 kW was successfully demonstrated. The 260kW operation for the neutron users started in October 2012. In MR synchrotron, the 9th RF system was newly installed and became available as a 2nd harmonic RF system in November 2012. A 30 GeV proton of 200 kW beam power has been delivered to the T2K neutrino beam experiment with 2.48 sec repetition cycle. This paper summarizes the operation details and the status and features of the J-PARC RF systems.

WEPEA020

Commissioning of Beam Loading Compensation System in the J-PARC MR

beam-loading, cavity, injection, extraction

2540

F. Tamura, M. Nomura, A. Schnase, T. Shimada, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
K. Hara, K. Hasegawa, C. Ohmori, M. Toda, M. Yoshii
KEK, Tokai, Ibaraki, Japan

Beam loading compensation is indispensable to accelerate high intensity proton beams in the J-PARC MR. The MA-loaded rf cavities in the MR are driven by the single harmonic (h=9) rf signals, while the cavity frequency response covers also the neighbor harmonics (h=8, 10). The wake voltage induced by the beam consists of the three harmonics (h=8, 9, 10). We employ the rf feedforward method to compensate the beam loading of these harmonics. The full-digital feedforward system was developed for the MR. We have successfully commissioned the feedforward patterns for all of eight cavities by using high intensity beams with 1.0·10¹⁴ ppp. We present the commissioning results. The impedance seen by the beam is reduced and the longitudinal oscillations due to the beam loading are reduced. By the beam loading compensation, high power beam operation at the beam power of 200 kW has been achieved.

WEPFI002

Acceptance Tests for the Spiral2 SC Linac RF Power Systems

cavity, linac, insertion, controls

2702

M. Di Giacomo
GANIL, Caen, France

Funding: This activity received founds from the EuCard RF Tech program
The Spiral2 SC linac uses solid state amplifiers ranging from 2,5 to 19 kW and external circulators to drive normal and superconducting cavities at 88.0525 MHz. The project has no manpower for in house development and all power devices are ordered to commercial companies. Robust acceptance tests have therefore been defined to check reliability with respect to our application. The papers describes the tests procedure and results on our first units.

WEPFI005

Simulations and RF Measurements of the Fundamental and Higher Order Modes of the ThomX 500 MHz Cavity

cavity, HOM, feedback, controls

2711

M. El Khaldi, I.V. Drebot, P. Lepercq, R. Marie, B. Mercier, T. Roulet, A. Variola, F. Wicek
LAL, Orsay, France
H.D. Dias, M.D. Diop, M.E. El Ajjouri, R. Lopes, A. Loulergue, P. Marchand, F. Ribeiro, R. Sreedharan
SOLEIL, Gif-sur-Yvette, France

The RF system of the ThomX* storage ring consists in a 500 MHz single cell copper cavity of the ELETTRA type, powered with a 50 kW CW solid state amplifier, and the associated Low Level RF feedback and control loops. The low operating energy of 50 – 70 MeV makes the impedances of the cavity higher order modes (HOMs) particularly critical for the beam stability. Their parasitic effects on the beam can be cured by HOM frequency shifting techniques, based on a fine temperature tuning and a dedicated plunger. A typical cavity temperature stability of ± 0.05°C within a range from 35 up to 80 °C can be achieved by a precise control of its water cooling temperature. On the other hand, the tuning of the cavity fundamental mode is achieved by changing its axial length by means of a mechanical tuner. In order to insure a fine control of the HOM frequencies, a good knowledge of their characteristics is mandatory. The main parameters of the fundamental and of the HOMs up to 4 GHz have been calculated using the HFSS and CST MWS codes. Preliminary measurements results have been obtained and show a good agreement with the simulations.
* A.Variola, “The ThomX Project”, Proceedings of IPAC2011, San Sebastián, Spain

WEPFI012

Conceptual Design of ILSF RF System

cavity, HOM, LLRF, storage-ring

2723

Kh.S. Sarhadi, H. Ajam, H. Azizi, M. Fereidani, M. Jafarzadeh, S. Pirani, J. Rahighi, R. Safian, A. Shahverdi
ILSF, Tehran, Iran

The Iranian Light Source Facility (ILSF) RF system, consisting of RF cavities, power sources and low-level RF systems, is conceptually designed in accordance with the requirements of ILSF 3GeV storage ring. To achieve the desired 400mA beam current, utilization of the existing HOM-damped cavities is explored and RF system parameters are compared based on the usage of each cavity. Moreover, the choice of solid state amplifier as the RF power source is presented with its available power and structure. This paper, furthermore, explains the conceptual design and functionality of the selected digital LLRF system.

WEPFI021

Influence of Core Winding Tension and Ribbon Quality on the MA Core RF Characteristics

synchrotron, vacuum, factory, cavity

2747

M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto
JAEA/J-PARC, Tokai-mura, Japan
K. Hara, K. Hasegawa, C. Ohmori, M. Toda, M. Yoshii
KEK, Tokai, Ibaraki, Japan

J-PARC 3 GeV Rapid Cycling Synchrotron (RCS) and Main Ring (MR) employ RF cavities loaded with Magnetic Alloy (MA) cores to generate a high field gradient. To achieve the high field gradient, the core shunt impedance is a key parameter. We found during the development of MA cores for RCS RF cavities that the core shunt impedance was increased by lowering a core winding tension. We lowered the core winding tension in order to improve the electrical insulation between MA ribbon layers. The lower winding tension reduced the core filling factor that is defined as the volume ratio of MA ribbons and geometrical dimensions. The core shunt impedance might be reduced according to the core filling factor reduction. We discuss the reason why the lower winding tension increased the core shunt impedance. We also report the influence of the ribbon quality variation on the MA core RF characteristics.

WEPFI027

The Measurement of the Ferrite Rings for the Mass Production RF Cavity of CSNS RCS

cavity, LLRF, resonance, booster

2762

H. Shi, W.L. Huang, B. Jiang, X. Li, W. Long, W.Y. Song, H. Sun, J.Y. Tang, C.L. Xie, C.L. Zhang, W. Zhang
IHEP, Beijing, People's Republic of China

The Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) will install 8 ferrite-loaded coaxial resonant cavities. The construction and measurement of prototype cavity have been finished. Based on the existing experiences, the small inner diameter (ID) rings T500/250/25-4M2 (mm) have been adopted for the mass production RF cavity, and the test results have shown that such rings can bear more RF magnetic flux density and have lower power loss. The characteristics of 60 small ID rings have been measured with two-ring test system, and we figured out that the rings have good consistence and the shunt impedance of all rings is above 100 Ω.

WEPFI031

Development of an X-Band Metallic Power Extractor for the Argonne Wakefield Accelerator

damping, extraction, simulation, cavity

2771

J. Shi, H.B. Chen, Q. Gao, X.W. Wu, Y. Yang, H. Zha
TUB, Beijing, People's Republic of China
W. Gai, C.-J. Jing
ANL, Argonne, USA

An X-band (11.7GHz) power extractor has been developed for RF power generation at Argonne Wakefield Accelerator (AWA). The structure is a 2pi/3-mode disk-loaded structure with group velocity of 22% of the speed of light and a total length of about 300mm. It is build with copper disks brazed together. This note presents the design and the fabrication of this structure, as well as the RF measurement results.

WEPFI038

R&D of New C-band Accelerating Structure for SXFEL Facility

FEL, cavity, wakefield, linac

2785

W. Fang, Q. Gu, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
L. Chen, X. Sheng
BVERI, Beijing, People's Republic of China
D.C. Tong
TUB, Beijing, People's Republic of China

C-band high gradient accelerating structure is crucial technology for Shanghai Soft X-ray FEL facility. Based on the prototype, the optimized C-band accelerating structure is proposed, and the experimental model is ready for high power test. In this paper, optimization design and some experiment results are presented, also design, fabrication and cold test of experimental model are introduced.

WEPFI039

New X-band Deflecting Cavity Design for Ultra-short Bunch Length Measure of FEL at SINAP

cavity, simulation, electron, FEL

2788

J.H. Tan, W. Fang, Q. Gu, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

For the development of Free Electron Lasers (FEL) at SINAP, ultra-short bunch is the crucial requirement for excellent lasing performance. It’s big challenge for deflecting cavity to measure the length of ultra-short bunch, and higher deflecting gradient is required for higher measurement resolution. X-band travelling wave deflecting structure has features of higher deflecting voltage and compact structure, which is good performance at ultra-short bunch length measuring. In this paper, a new X-band deflecting structure was designed, operated at HEM11- 2π/3 mode. For suppressing the polarization of deflection plane of the HEM11 mode, two symmetrical caves are added on the cavity wall to separate two polarized modes. More details of design and simulation results are presented in this paper.

WEPFI045

PAL-XFEL Accelerating Structures

linac, klystron, electron, emittance

2806

H.-S. Lee, H. Heo, J.Y. Huang, W.H. Hwang, S.D. Jang, Y.D. Joo, H.-S. Kang, I.S. Ko, S.S. Park, Y.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea
I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea
H. Matsumoto
KEK, Ibaraki, Japan
S.J. Noh, K.M. Oh
Vitzrotech Co., Ltd., Ansan City, Kyunggi-Do, Republic of Korea

We need 172 accelerating structures for the PAL-XFEL 10 GeV main linac. It takes long time for these structures to be delivered. So we are trying to find suppliers of the accelerating structures. First, we made an order of 40 accelerating structures to Mitsubishi Heavy Industry (MHI), which have Quasi-type couplers to reduce the quadruple and sextuple components of the electric field in the coupling cavity. And Research Instruments (RI) has fabricated a 3m long race type accelerating structure for PAL-XFEL. Also, Vitzrotech which is a domestic company and IHEP in China are under developing accelerating structures for PAL-XFEL respectively. We will describe the current status of accelerating structures and high power test results of the newly developed structures in this paper.

WEPFI058

Breakdown Localization Studies on the SwissFEL C-band Test Structures

background, linac, coupling, factory

2824

J. Klavins, S. Dementjevs, F. Le Pimpec, L. Stingelin, M. Wohlmuther, R. Zennaro
PSI, Villigen PSI, Switzerland
N.C. Shipman
CERN, Geneva, Switzerland

The SwissFEL main linac will consist of 10⁴ C-band structures with a nominal accelerating gradient of 28MV/m. First power tests were performed on short constant impedance test-structures composed of eleven double-rounded cups. In order to localize breakdowns, two or three acoustic emission sensors were installed on the test-structures. In order to localize breakdowns we have analyzed, in addition to acoustic measurements, the delay and phase of the rf power signals. Parasitic, acoustic noise emitted from the loads of the structure complicated the data interpretation and necessitated appropriate processing of the acoustic signals. The Goals of the experiments were to identify design and manufacturing errors of the structures. The results indicate that breakdowns occur mostly at the input power coupler, as also confirmed by vacuum-events at the same location. The experiments show that the linac test-structures fulfill the requirements in breakdown probability. Moreover developing a detection system based on acoustic emission sensors for breakdown localization for our C-band structure seems reasonable given the results obtained.

WEPFI060

Planar Balun Design with Advanced Heat Dissipation Structure for kW Level Solid-state Amplifier Module Development

coupling, controls, storage-ring, klystron

2830

T.-C. Yu, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Y.-H. Lin, Z.L. Liu, C.H. Lo, M.H. Tsai, Ch. Wang, T.-T. Yang, M.-S. Yeh
NSRRC, Hsinchu, Taiwan

The power level of solid-state amplifier is continuously growing for advanced accelerator application as the RF power source. Huge amount of solid-state power amplifier (SSPA) modules can contribute several hundreds of kW RF power with high redundancy and reliability. However, with the increasing desire of RF power of single RF station, too much power modules would adversely cause larger area occupation and higher maintenance cost and complexity. Therefore, with the advancement of the RF power on single SSPA, the overall system design and configuration would become much simple and compact. However, the increasing RF of single SSPA would also bring the thermal problem at its chip as well as the output power combining balun. In this paper, kW range SSPA is developed with the novel planar balun structure with good thermal expansion property. With such new planar balun design, the SSPA can operate stably with above 1kW output RF power.

WEPFI062

Precise Cavity Tuning System of a Low Output-impedance Second-harmonic Cavity at ISIS

cavity, resonance, cathode, beam-loading

2836

Y. Irie, S. Fukumoto, K. Muto, H. Nakanishi
KEK, Ibaraki, Japan
D.B. Allen, D. Bayley, N.E. Farthing, I.S.K. Gardner, R.J. Mathieson, A. Seville, J.W.G. Thomason
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
J.C. Dooling, D. Horan, R. Kustom, M.E. Middendorf
ANL, Argonne, USA

A very low output-impedance (~35ohms) second-harmonic cavity system is being developed for high intensity proton accelerators. The final amplifier is comprised of a grounded cathode scheme with a feedback loop from anode to grid. Due to the Miller effect, the grid voltage waveform is seriously distorted even if only a few percent of sub-harmonic or higher harmonic are mixed in the generator current. Such distortion is much enhanced by the beam loading. In order to eliminate the effect of this distortion upon the phase detector used to achieve precise cavity tuning, a swept bandpass filter was applied to the grid voltage at the phase detector input. Filter design details and the result of high power tests are reported.

WEPFI090

An X-band Dielectric-based Wakefield Power Extractor

wakefield, simulation, damping, vacuum

2908

C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow
Euclid TechLabs, LLC, Solon, Ohio, USA
M.E. Conde, W. Gai, J.G. Power
ANL, Argonne, USA
V.A. Dolgashev, J.R. Lewandowski, S.G. Tantawi, S.P. Weathersby
SLAC, Menlo Park, California, USA
I. Syratchev
CERN, Geneva, Switzerland

Funding: US DoE SBIR Phase II project under Contract#DE-SC0004322
An X-band dielectric-based wakefield power extractor is under development to function as a high power rf source primarily for Two Beam Accelerator applications. A low surface electric field to gradient ratio and low fabrication cost are two main advantages of the dielectric-loaded accelerating/decelerating structure. We have designed a 12 GHz dielectric-based power extractor that has similar performance parameters to the CLIC PETS (23 mm beam channel, 240 ns pulse duration, 135 MW output per structure) using the CLIC drive beam. In order to study potential rf breakdown issues, as a first step we built a 11.424 GHz dielectric-based power extractor scaled from the 12 GHz design. A high power rf test will be conducted using the SLAC 11.424 GHz high power rf source in Dec. 2012. Results of the high power testing will be reported. Meanwhile, the 12 GHz fully featured dielectric power extractor is also under construction; construction progress and bench tests will be discussed.

WEPME061

A Wideband Slotted Kicker Design for SPS Transverse Intra-bunch Feedback

kicker, feedback, coupling, simulation

3073

J.M. Cesaratto, J.D. Fox, C.H. Rivetta
SLAC, Menlo Park, California, USA
D. Alesini, A. Drago, A. Gallo, F. Marcellini, M. Zobov
INFN/LNF, Frascati (Roma), Italy
S. De Santis
LBNL, Berkeley, California, USA
W. Höfle
CERN, Geneva, Switzerland

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP) and by the EU FP7 HiLumi LHC - Grant Agreement 284404.
Control and mitigation of transverse beam instabilities caused by electron cloud and TMCI will be essential for the SPS to meet the beam intensity demands for the HL-LHC upgrade. A wideband intra-bunch feedback method is in development, based on a 4 GS/s data acquisition and processing, and with a back end frequency structure extending to 1 GHz. A slotted type kicker, similar to those used for stochastic cooling, has been considered as the terminal element of the feedback chain. It offers the most promising deflecting structure characteristics to meet the system requirements in terms of bandwidth, shunt impedance, and beam coupling impedance. Different types of slotted structures have been explored and simulated, including a ridged waveguide and coaxial type waveguide. In this paper we present our findings and the conceptual design of a vertical SPS wideband kicker consistent with the stay clear, vacuum, frequency band coverage, and peak shunt impedance requirements.

THOBB102

Beam Coupling Impedance Localization Technique Validation and Measurements in the CERN Machines

kicker, quadrupole, lattice, betatron

3106

N. Biancacci, G. Arduini, T. Argyropoulos, H. Bartosik, R. Calaga, K. Cornelis, S.S. Gilardoni, N. Mounet, E. Métral, Y. Papaphilippou, S. Persichelli, G. Rumolo, B. Salvant, G. Sterbini, R. Tomás, R. Wasef
CERN, Geneva, Switzerland
M. Migliorati, L. Palumbo
URLS, Rome, Italy

The beam coupling impedance could lead to limitations in beam brightness and quality, and therefore it needs accurate quantification and continuous monitoring in order to detect and mitigate high impedance sources. In the CERN machines, for example, kickers and collimators are expected to be the main contributors to the total imaginary part of the transverse impedance. In order to detect the other sources, a beam based measurement was developed: from the variation of betatron phase beating with intensity, it is possible to detect the locations of main impedance sources. In this work we present the application of the method with beam measurements in the CERN PS, SPS and LHC.

Slides THOBB102 [7.224 MB]

THPFI014

Bellows with a New RF Shield Made of Metal Braid for High Intensity Proton Accelerators

vacuum, background, synchrotron, coupling

3321

N. Ogiwara, J. Kamiya, M. Kinsho, Y. Shobuda
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
O. Koizumi
Sun-Tech limited, Kobe, Japan

In the 3 GeV-RCS (Rapid cycling Synchrotron) in J-PARC (Japan Accelerator Research Complex) project, large-scale hydro-formed bellows were developed to adjust the gap between the ceramic ducts and/or between the ceramic ducts and the transport ducts. They have been equipped with a newly developed RF shield, because the usual beryllium-copper spring finger contacts were found to be very hard (roughly 1000 N/mm) owing to the large size. This contact is made of Ti braid, which consists of wires with a diameter of 0.3 mm. This RF contact is a kind of basket (with two ports) made with the braids. Because of the spring effect, the contact can change shape easily. In addition, the contact can easily connect the different cross sections in a smooth fashion. Furthermore, this structure is almost free from the dust generation, which is one of the most troublesome problems for the usual spring finger contacts. This time, we have constructed reserve bellows with the RF shield made of SUS 316L wires to improve the reliability of user operation. The outline of the bellows will be presented, especially laying emphasis on the mechanical function of the RF shield.

THPFI057

Development of Vacuum Chamber in Low Z Material

vacuum, radiation, background, coupling

3421

C. Garion, P. Costa Pinto, M.A. Gallilee, J. Perez Espinos
CERN, Geneva, Switzerland

Highly transparent vacuum chambers are more and more required in high energy particle physics. In particular, vacuum chambers in the experiments should be as transparent as possible to minimize the background to the detectors while reducing also the material activation. Beryllium is, so far, the most performing material for this application, but it presents some drawbacks such as brittleness, manufacturing issues, toxic hazard, high cost and low availability. A development work to obtain alternative material to the beryllium with similar performance is being carried out at CERN. Three categories have been defined and considered: raw bulk material, material and structural composites. Main requirements are the vacuum compatibility: leak tightness, low outgassing rate, temperature resistance (in the range 200-230 °C), transparency, and mechanical stiffness and strength. Carbon is the element with the lowest atomic number after beryllium and that is appropriate for this application. Therefore carbon based materials have been considered in a variety of options. In this paper, several technologies are presented and discussed. Results of preliminary tests on samples are also shown.

THPWA001

Design of X-Band Medical Linear Accelerator with Multiple RF Feeds and RF Phase Focusing

focusing, linac, cavity, bunching

3627

Y. N. Nour El-Din, T.M. Abuelfadl
Cairo University, Giza, Egypt

Funding: Work supported by the Egyptian Science and Technology Development Fund (STDF) No. 953.
A design of 6 MeV X-band 9.3 GHz medical linear accelerator is presented. It is composed of four separate clusters of accelerating cavities, where a coherent RF excitation is provided separately to each cluster. The use of multiple accelerating sections with multiple RF feeds permits the use of inexpensive RF sources. The first cluster is Alternate Phase Focusing (APF) RF cavities, providing radial and longitudinal beam focusing without the use of heavy and bulky magnets or solenoids. The three other clusters used for acceleration are composed of multiple standing wave sections operating in the Pi-mode. Each section has been designed and optimized for high shunt impedance by means of 2D SUPERFISH code and 3D CST code. A two dimensional code, named PTCC, was developed to facilitate design and analysis of the different parts of the accelerating structure.

THPWA022

An 800kV 30mA Line-Frequency Cockcroft-Walton Dc Generator Using Gas Insulated Transformer for Radiation Application

high-voltage, electron, power-supply, radiation

3675

Y.H. Liu, H.L. Guo, Z.-F. He, D.M. Li, M.X. Li, W.G. Shi, H.J. Su, S.L. Wang, Y.J. Yang, J.L. Zhang, Y.-T. Zhang
SINAP, Shanghai, People's Republic of China

The design and construction of a line-frequency 800 kV Cockcroft-Walton DC generator using gas insulated transformers are described, as well as the motive to develop it into radiation application. Several features are underlined, preliminary test results of the prototype presented and some problems encountered discussed.

THPWO018

Power Tests of the 325 MHz 4-ROD RFQ Prototype

rfq, cavity, pick-up, simulation

3800

B. Koubek, H. Podlech, A. Schempp, J.S. Schmidt
IAP, Frankfurt am Main, Germany

For the FAIR project of GSI as part of the proton linac a 325 MHz RFQ with an output energy of 3 MeV is planned. Simulations that have lead to a prototype of a 4-Rod Radio Frequency Quadrupole (RFQ) have been done. The RF parameters have been verified with the prototype. Power tests of this 6 stem copper RFQ should now verify parameters like shunt impedance, electrode voltage and give answers of how much power the structure can sustain.

THPWO032

Progress of Injection Energy Upgrade Project for J-PARC RCS

injection, power-supply, septum, linac

3833

N. Hayashi, H. Harada, K. Horino, H. Hotchi, J. Kamiya, M. Kinsho, P.K. Saha, Y. Shobuda, T. Takayanagi, N. Tani, T. Togashi, T. Ueno, M. Watanabe, Y. Watanabe, K. Yamamoto, M. Yamamoto, Y. Yamazaki, M. Yoshimoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
Y. Irie
KEK, Ibaraki, Japan
T. Toyama
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

The injection energy of the J-PARC RCS will be upgraded in 2013. New power supplies for the shift bump magnet system will be installed. Some of other systems, upgrade of the painting bump power supplies and pulse steering systems, are already installed and tested or used for the nominal operation. The paper reports the progress of injection energy upgrade project.