LINAC2012 - List of Keywords (impedance)

Paper	Title	Other Keywords	Page
SUPB035	RF Photoinjector and Radiating Structure for High-power THz Radiation Source	radiation, coupling, electron, vacuum	86
	S.M. Polozov, T.V. Bondarenko MEPhI, Moscow, Russia Y.A. Bashmakov LPI, Moscow, Russia
	Sources of high-power electromagnetic radiation in THz band are becoming promising as a new method of a low activation introscopy. Research and development of accelerating RF photoinjector and radiating system for THz radiation source are reported. The photoinjector is based on disk loaded waveguide (DLW). Two different designs of accelerating structures were modeled: widespread 1.6 cell of DLW structure and travelling wave resonator structure. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics and electric field distribution for all models were acquired. Results of picoseconds photoelectron beam dynamics in modeled structures are reported. Design of decelerating structures exciting Cherenkov radiation are based on corrugated metal channel and metal channel coated with dielectric. Analysis of radiation intensity and frequency band are presented.

MOPLB05	Applications of Compact Dielectric-Based Accelerators	coupling, multipactoring, wakefield, electron	150
	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
	Important progress on the development of dielectric based accelerators has been made experimentally and theoretically in the past few years. One advantage of dielectric accelerators over the metallic counterparts is its compact size, which may attract some applications in industrial or medical accelerators. In this article, we discuss the design and technologies of dielectric based accelerators toward these needs.

MOPB007	Study of Microbunching Instabilitity in the Linac of the Shanghai Soft X-Ray Free Electron Laser Facility	linac, FEL, simulation, electron	189
	D. Huang, Q. Gu, M. Zhang SINAP, Shanghai, People's Republic of China
	The microbunching instability in the LINAC of a FEL facility has always been an issue which may degrade the quality of the electron beam. As the result, the whole facility may not be working properly. Shanghai soft X-ray FEL project (SXFEL), which is planned to start construction by the end of 2012, will be the first X-ray FEL facility in China. In this article, detailed study will be given based on the physical design of the facility to gain better understanding and control over the possible microbunching instability in SXFEL, which is critical to the success of the project. Moreover, the contribution of the possible plasma effects to the instability will also be studied by modifying the physical model of the longitudinal space charge (LSC) impedance.

MOPB021	Bunch-by-bunch Phase Modulation for Linac Beam-loading Compensation	beam-loading, linac, injection, bunching	216
	G. Huang, D. Jia, K. Jin, H. Lin, Weishi, Zhou. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China Y. Liu USTC, Hefei, Anhui, People's Republic of China
	Funding: supported by NSFC-CAS Joint Fund, contract no. 11079034 If the linac is loaded by a high current, long pulse multi-bunch beam, the energy of the beam drops with time during the pulse. The bunch phase modulation method is introduced to compensate the beam loading. In this method the beam phase in the RF accelerating filed is changed bunch-by-bunch, the beam energy gain in the RF filed gradually grows up, which cancels the drop due to beam loading. The relationship between the beam phase distribution and the linac parameters is calculated in this paper.

MOPB022	RF Characteristic Studies on the Whole Accelerating Structure for the BEPCII Linear Accelerator	linac, simulation, vacuum, electromagnetic-fields	219
	S. Pei, M. Hou, X. Li, J.R. Zhang IHEP, Beijing, People's Republic of China B.L. Wang SINAP, Shanghai, People's Republic of China
	An accelerating structure is one device to boost the particle energy. 2856 MHz 3 m long travelling wave disk-loaded accelerating structure is applied in BEPCII linac, its RF characteristics are mainly determined by the 84 regular cells located between the input and output couplers. Input and output couplers need to be included when the whole structure RF characteristics are simulated before fabrication; otherwise it would be difficult to obtain the travelling wave fields excited in the whole structure. If the real 3D couplers are modelled during the design process, a large amount of computer resources and time need to be used. However, if the redesigned azimuth symmetric coupler is used to replace the real 3D one during the simulation process, much less computer resources and time are required. With this method proposed here, the simulation results agree well with the theoretically calculated and experimentally measured ones. *peisl@ihep.ac.cn

MOPB043	Detailed Analysis of the Long-Range Wakefield in the Baseline Design of the CLIC Main Linac	wakefield, damping, HOM, factory	270
	V.F. Khan, A. Grudiev CERN, Geneva, Switzerland
	The baseline design for the accelerating structure of the CLIC main linac relies on strong damping of transverse higher order modes (HOMs). Each accelerating cell is equipped with four damping waveguides that enables HOM energy to propagate to damping loads. Most of the HOMs decay exponentially with a Q-factor of about 10 however, there are modes with higher Q-factors. Though the amplitude of the high Q modes is nearly two orders of magnitude smaller than the dominating lowest dipole mode, their cumulative effect over the entire bunch train may be significant and dilute the beam emittance to unacceptable level. In this paper we report on an accurate calculation of the long-range wakefield and its overall effect on beam dynamics. We also discuss possible measures to minimise its effect in a tapered structure.

MOPB047	Applications of Compact Dielectric Based Accelerators	coupling, multipactoring, wakefield, electron	279
	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
	Important progress on the development of dielectric based accelerators has been made experimentally and theoretically in the past few years. One advantage of dielectric accelerators over the metallic counterparts is its compact size, which may attract some applications in industrial or medical accelerators. In this article, we discuss the design and technologies of dielectric based accelerators toward these needs.

MOPB060	RF Surface Impedance Characterization of Potential New Materials for SRF-based Accelerators	niobium, SRF, cavity, superconductivity	312
	B. P. Xiao, G.V. Eremeev, H.L. Phillips, C.E. Reece JLAB, Newport News, Virginia, USA M.J. Kelley, B. P. Xiao The College of William and Mary, Williamsburg, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. In the development of new superconducting materials for possible use in SRF-based accelerators, it is useful to work with small candidate samples rather than complete resonant cavities. The recently commissioned Jefferson Lab rf Surface Impedance Characterization (SIC) system* can presently characterize the central region of 50 mm diameter disk samples of various materials from 2 to 40 K exposed to RF magnetic fields up to 14 mT at 7.4 GHz. We report the measurement results from bulk Nb, thin film Nb on Cu and sapphire substrates, and thin film MgB₂ on sapphire substrate provided by colleagues at JLab and Temple University. We also report on efforts to extend the operating range to higher fields. * B.P. Xiao, et al., RSI, 2011. 82: p. 056104

MOPB081	Travelling Wave Accelerating Structures with a Large Phase Advance	acceleration, electron, linac, proton	363
	V.V. Paramonov RAS/INR, Moscow, Russia
	The electrons acceleration is considered in higher pass bands of TM01 wave for disk loaded waveguide, resulting in the possibility of traveling wave accelerating structures with an operating field phase advance between 180 – 1260 degrees per cell. With an appropriate shape optimization and some additional elements in cells proposed traveling wave structures have small transverse dimensions and high RF efficiency of standing wave operation. Examples of proposed structures together with RF and dispersion properties are presented.

MOPB082	RF Parameters of the TE - Type Deflecting Structure for S-Band Frequency Range	ion, multipole, linac, heavy-ion	366
	V.V. Paramonov, L.V. Kravchuk RAS/INR, Moscow, Russia K. Flöttmann DESY, Hamburg, Germany
	Funding: in part RBFR N 12-02-0654-a Effective compact deflecting structure* has been proposed for L-band frequency range preferably. RF parameters of this structure considered for S-band frequency range both for traveling and standing wave operation. * -V. Paramonov, L. Kravchuk, INR, S. Korepanov. Effective Standing Wave RF Structure for Particle Beam Deflector. Proc. 2006 Linac Conference, p. 649

TUPB001	The Fine Structure of the Zone of Particle Interaction with a Finite Length Periodic Structure	wakefield, simulation, diagnostics, emittance	473
	V.V. Paramonov RAS/INR, Moscow, Russia
	The periodic constant impedance deflecting structures are widely used for a special beam diagnostic in FEL facilities. The method, based on frequency domain approach, was developed to estimate long range wake fields structure parameters in a wide frequency range. It is shown, that regardless to number of cells in the structure, at each passband to the zone of particle effective interaction with the structure belongs several, at least three modes. The usual time domain simulations provide the total estimation for loss factor or kick factor values and modes separation in the time domain approach requires enormous simulations.

TUPB009	C-Band Accelerating Structure Development and Tests for the SwissFEL	controls, klystron, FEL, linac	492
	R. Zennaro, J. Alex, H. Blumer, M. Bopp, A. Citterio, T. Kleeb, L. Paly, J.-Y. Raguin PSI, Villigen, Switzerland
	SwissFEL requires a 5.8 GeV beam provided by a C-band linac consisting of 104 two-meter accelerating structures. Each structure is of the constant gradient type and is composed of 113 cups. The cup shape is double-rounded to increase the quality factor. No tuning feature is implemented. For this reason ultra-precise turning is exploited. A strong R&D program has been launched on structure fabrication, which will be followed by a future technology transfer to a commercial company. The program includes the production and test of short structures that can be brazed in the existing PSI vacuum oven and will be completed with the production of the full two-meter prototype once the new full scale brazing oven, presently under construction, is operational. The status of the R&D program, including the production and power test results of the first two test structures, is reported here.

TUPB011	The Swiss FEL S-Band Accelerating Structure: RF Design	accelerating-gradient, linac, gun, FEL	498
	J.-Y. Raguin PSI, Villigen, Switzerland
	The Swiss FEL accelerator concept consists of a 450 MeV S-band injector Linac at 2998.8 GHz followed by the main linac at the C-band frequency aiming at a final energy of 5.8 GeV. The injector has six four-meter long S-band accelerating structures that shall operate with gradients up to 20 MV/m and with a 100 Hz repetition rate. Each structure has 122 cells, including the two coupler cells and operates with a 2π/3 phase advance. The design presented is such that the average dissipated RF power is constant over the whole length of the structure. The cells consist of cups and the cell irises have an elliptical profile to minimize the peak surface electric field. The coupler cells are of the double-feed type with a racetrack cross-section to cancel the dipolar components of the fields and to minimize its quadrupolar components.

TUPB012	The Swiss FEL C-Band Accelerating Structure: RF Design and Thermal Analysis	accelerating-gradient, linac, klystron, FEL	501
	J.-Y. Raguin, M. Bopp PSI, Villigen, Switzerland
	The Swiss FEL accelerator concept consists of a 450 MeV S-band injector linac followed by the main linac in C-band aiming at a final energy of 5.8 GeV. The two-meter long C-band accelerating structures have 113 cells, including the two coupler cells, and operate with a 2π/3 phase advance. The structure is of the constant-gradient type with rounded wall cells and has an average iris radius of 6.44 mm, a radius compatible with the impact of the short-range wakefields on the whole linac beam dynamics. The cell irises have an elliptical profile to minimize the peak surface electric fields and the coupler cells are of the J-type. We report here on the RF design of the structure, as well as on its thermal analysis, to target operational conditions with an accelerating gradient of about 28 MV/m and a repetition rate of 100 Hz.

TUPB021	Study of Plasma Effect in Longitudinal Space Charge Induced Microbunching Instability	plasma, electron, linac, space-charge	522
	D. Huang, Q. Gu SINAP, Shanghai, People's Republic of China K.Y. Ng Fermilab, Batavia, USA
	The longitudinal space charge (LSC) plays an important role in introducing the microbunching instability in the LINAC of a free electron laser (FEL) facility. The current model of LSC impedance [1] derived from the fundamental electromagnetic theory [2] is widely used to explain the growth of the microbunching instability [3]. However, in the case of highly bright relativistic electron beams, the plasma effect starts to play a role. In this article, the basic model of LSC impedance including the plasma effect is built , and the modifications to the microbunching instability based on the new model are discussed in various conditions. [1] Marco Venturini, Phys Rev. ST Accel. Beams 11, 034401 (2008) [2] J. D. Jackson, Classical Electrodynamics (Wiley, 1999) [3] Z. Huang, et. al., Phys, Rev. ST Accel. Beams 7, 074401 (2004)

TUPB036	Design of Re-Buncher Cavity for Heavy-ion LINAC in IMP	cavity, DTL, simulation, linac	558
	L.P. Sun, X. Du, Y. He, A. Shi, C. Zhang, Z.L. Zhang IMP, Lanzhou, People's Republic of China
	A re-buncher with spiral arms for a heavy ion linear accelerator named as SSC-LNAC at HIRFL (the heavy ion research facility of Lanzhou) has been constructed. The re-buncher, which is used for beam longitudinal modulation and match between the RFQ and DTL, is designed to be operated in continuous wave (CW) mode at the Medium-Energy Beam-Transport (MEBT) line to maintain the beam intensity and quality. Because of the longitudinal space limitation, the re-buncher has to be very compact and will be built with four gaps. We determined the key parameters of the re-buncher cavity from the simulations using Microwave Studio software, such as the resonant frequency, the quality factor Q and the shunt impedance. The detailed design of a 53.667 MHz spiral cavity and measurement results of its prototype will be presented.

TUPB060	Multipacting Suppression Modeling for Half Wave Resonator and RF Coupler*	simulation, cavity, electron, cryomodule	612
	Z. Zheng, A. Facco, Z. Liu, J. Popielarski, K. Saito, J. Wei, Y. Xu, Y. Zhang FRIB, East Lansing, Michigan, USA Z. Zheng TUB, Beijing, People's Republic of China
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 In prototype cryomodule test of Facility of Rare Isotope Beam (FRIB) β=0.53 half-wave-resonators (HWRs) severe multipacting barriers, prevented RF measurement at the full field specified. The multipacting could not be removed by several hours of RF conditioning. To better understand and to eliminate multipacting, physics models and CST simulations have been developed for both cavity and RF coupler. The simulations have good agreement with the multipacting discovered in coupler and cavity testing. Proposed cavity and coupler geometric optimizations are discussed in this paper.

TUPB091	176 MHz Solid State Microwave Generator Design	linac, simulation, scattering, resonance	672
	A.Yu. Smirnov, E.V. Ivanov, A.A. Krasnov, K.I. Nikolskiy, N.V. Tikhomirova Siemens Research Center, Moscow,, Russia O. Heid, T.J.S. Hughes Siemens AG, Erlangen, Germany
	This paper concerns the R&D work upon design of a compact RF amplifier to be used for superconducting CW cavities. The machine under development will operate at 176 MHz with output power of 25 kW in continuous wave regime. It consists of 50 push-pull PCB modules (approx. 500W output power each), connected in parallel to several radial filter rings, which both allow class-F operation and combine the power from the modules, delivering it to a single 50 Ω coax cable. The CST simulations ad the design of 324 MHz test prototype are presented.

TUPB095	Design of Coupler for Direct Coupled Amplifier to Drift Tube Linac Cavities of the Injector RILAC2 for RIKEN RI Beam Factory	cavity, DTL, coupling, linac	684
	K. Suda, S. Arai, Y. Chiba, O. Kamigaito, M. Kase, H. Okuno, N. Sakamoto, Y. Watanabe, K. Yamada RIKEN Nishina Center, Wako, Japan
	A new linac RILAC2 was constructed at RIKEN RI Beam Factory as an injector for very heavy ions such as uranium and xenon of a high mass to charge ratio m/q ∼ 7, but high intensity ions can be extracted from an ion source. Three drift tube linac cavities, operate in continuous wave mode at 36.5 MHz, have been designed and built. In order to reduce an installation area, and to save a construction cost, we adopted a direct coupling method for a power amplifier without using a long transmission line. A complicated design procedure was performed in order to take into account a change of resonant frequency of the cavity caused by a capacitance of a power tube used in the amplifier. A design of the coupler, as well as the cavity was performed using a three-dimensional electromagnetic calculation code, CST Microwave Studio (MWS). The measured input impedance seen from the amplifier (700 – 1100 Ω) was reproduced well by the calculation of MWS. Also, in order to examine MWS, a case of a coupling with 50 Ω were calculated. The coupling conditions obtained by MWS were compared with the measurement and a calculation with a lumped circuit model.

TUPB102	Design and Performances of Phase Monitor in J-PARC Linac	linac, acceleration, pick-up, vacuum	699
	A. Miura JAEA/J-PARC, Tokai-mura, Japan Z. Igarashi, T. Miyao KEK, Ibaraki, Japan
	J-PARC linac employs a fast current transformer (FCT) as a beam phase monitor to calculate the beam energy by time-of-flight method. We have installed and used 61 FCTs in the current beam line. Because the phase measurements at additional 41 points in the future ACS sections are required for the energy upgrade project with adding 21 ACS (Annular Coupled Structure) cavities, we stared the design and fabrication of FCTs as the phase measurement devices. In addition, J-PARC linac employs the 4-stripline beam position monitors (BPMs) for the beam position measurement. It has been considered that the signals from striplines of BPM would be useful for a phase measurement. A phase measurement using a BPM has been successfully conducted. In order to evaluate the performances of the FCT, the signal sensitivity and cut-off frequency of newly fabricated FCT are measured. Also, these data of the BPM are also measured to be compared with the data of FCT. Based on the results of the comparing both measurements, the superiority of both monitors for beam phase measurement is discussed.

TH1A03	Superconducting Spoke Cavities for Electron and High-Velocity Proton Linacs	cavity, linac, SRF, electron	758
	J.R. Delayen ODU, Norfolk, Virginia, USA
	Spoke resonantors are currently under development for many proton machines but these structures are also considered for high beta electron linacs as well. These structures compare well to traditional elliptical cavities.
	Slides TH1A03 [3.570 MB]

THPB025	325 MHz CW Room Temperature High Power Bunching Cavity for the China ADS MEBT1	cavity, bunching, vacuum, resonance	903
	S. Pei, X. Li, H.F. Ouyang, J.R. Zhang IHEP, Beijing, People's Republic of China
	Two room temperature high power bunching cavities are required to be located in the ADS MEBT1 section. Double re–entrant nose cone geometry has been adopted as the type of the bunching cavity for its simplicity, higher shunt impedance and lower risk of multipacting. SUPERFISH is used to optimize the internal dimensions of the bunching cavity, then the RF–thermal–structural–RF coupled analysis were carried out in ANSYS to obtain the preliminary mechanical design, the layout of the cooling channels is optimized to suppress the frequency shift as much as possible. The cavity was specially designed to have the capability to withstand the 1 atm air pressure effect. In addition, the main dimensions of the coupler and tuner are also estimated. *peisl@ihep.ac.cn

THPB074	RF Photoinjector and Radiating Structure for High-power THz Radiation Source	radiation, coupling, electron, vacuum	1005
	S.M. Polozov, T.V. Bondarenko MEPhI, Moscow, Russia Y.A. Bashmakov LPI, Moscow, Russia
	Sources of high-power electromagnetic radiation in THz band are becoming promising as a new method of a low activation introscopy. Research and development of accelerating RF photoinjector and radiating system for THz radiation source are reported. The photoinjector is based on disk loaded waveguide (DLW). Two different designs of accelerating structures were modeled: widespread 1.6 cell of DLW structure and travelling wave resonator structure. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics and electric field distribution for all models were acquired. Results of picoseconds photoelectron beam dynamics in modeled structures are reported. Design of decelerating structures exciting Cherenkov radiation are based on corrugated metal channel and metal channel coated with dielectric. Analysis of radiation intensity and frequency band are presented.

Paper

Title

Other Keywords

Page

SUPB035

RF Photoinjector and Radiating Structure for High-power THz Radiation Source

radiation, coupling, electron, vacuum

86

S.M. Polozov, T.V. Bondarenko
MEPhI, Moscow, Russia
Y.A. Bashmakov
LPI, Moscow, Russia

Sources of high-power electromagnetic radiation in THz band are becoming promising as a new method of a low activation introscopy. Research and development of accelerating RF photoinjector and radiating system for THz radiation source are reported. The photoinjector is based on disk loaded waveguide (DLW). Two different designs of accelerating structures were modeled: widespread 1.6 cell of DLW structure and travelling wave resonator structure. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics and electric field distribution for all models were acquired. Results of picoseconds photoelectron beam dynamics in modeled structures are reported. Design of decelerating structures exciting Cherenkov radiation are based on corrugated metal channel and metal channel coated with dielectric. Analysis of radiation intensity and frequency band are presented.

MOPLB05

Applications of Compact Dielectric-Based Accelerators

coupling, multipactoring, wakefield, electron

150

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

Important progress on the development of dielectric based accelerators has been made experimentally and theoretically in the past few years. One advantage of dielectric accelerators over the metallic counterparts is its compact size, which may attract some applications in industrial or medical accelerators. In this article, we discuss the design and technologies of dielectric based accelerators toward these needs.

MOPB007

Study of Microbunching Instabilitity in the Linac of the Shanghai Soft X-Ray Free Electron Laser Facility

linac, FEL, simulation, electron

189

D. Huang, Q. Gu, M. Zhang
SINAP, Shanghai, People's Republic of China

The microbunching instability in the LINAC of a FEL facility has always been an issue which may degrade the quality of the electron beam. As the result, the whole facility may not be working properly. Shanghai soft X-ray FEL project (SXFEL), which is planned to start construction by the end of 2012, will be the first X-ray FEL facility in China. In this article, detailed study will be given based on the physical design of the facility to gain better understanding and control over the possible microbunching instability in SXFEL, which is critical to the success of the project. Moreover, the contribution of the possible plasma effects to the instability will also be studied by modifying the physical model of the longitudinal space charge (LSC) impedance.

MOPB021

Bunch-by-bunch Phase Modulation for Linac Beam-loading Compensation

beam-loading, linac, injection, bunching

216

G. Huang, D. Jia, K. Jin, H. Lin, Weishi, Zhou. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China
Y. Liu
USTC, Hefei, Anhui, People's Republic of China

Funding: supported by NSFC-CAS Joint Fund, contract no. 11079034
If the linac is loaded by a high current, long pulse multi-bunch beam, the energy of the beam drops with time during the pulse. The bunch phase modulation method is introduced to compensate the beam loading. In this method the beam phase in the RF accelerating filed is changed bunch-by-bunch, the beam energy gain in the RF filed gradually grows up, which cancels the drop due to beam loading. The relationship between the beam phase distribution and the linac parameters is calculated in this paper.

MOPB022

RF Characteristic Studies on the Whole Accelerating Structure for the BEPCII Linear Accelerator

linac, simulation, vacuum, electromagnetic-fields

219

S. Pei, M. Hou, X. Li, J.R. Zhang
IHEP, Beijing, People's Republic of China
B.L. Wang
SINAP, Shanghai, People's Republic of China

An accelerating structure is one device to boost the particle energy. 2856 MHz 3 m long travelling wave disk-loaded accelerating structure is applied in BEPCII linac, its RF characteristics are mainly determined by the 84 regular cells located between the input and output couplers. Input and output couplers need to be included when the whole structure RF characteristics are simulated before fabrication; otherwise it would be difficult to obtain the travelling wave fields excited in the whole structure. If the real 3D couplers are modelled during the design process, a large amount of computer resources and time need to be used. However, if the redesigned azimuth symmetric coupler is used to replace the real 3D one during the simulation process, much less computer resources and time are required. With this method proposed here, the simulation results agree well with the theoretically calculated and experimentally measured ones.
*peisl@ihep.ac.cn

MOPB043

Detailed Analysis of the Long-Range Wakefield in the Baseline Design of the CLIC Main Linac

wakefield, damping, HOM, factory

270

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

The baseline design for the accelerating structure of the CLIC main linac relies on strong damping of transverse higher order modes (HOMs). Each accelerating cell is equipped with four damping waveguides that enables HOM energy to propagate to damping loads. Most of the HOMs decay exponentially with a Q-factor of about 10 however, there are modes with higher Q-factors. Though the amplitude of the high Q modes is nearly two orders of magnitude smaller than the dominating lowest dipole mode, their cumulative effect over the entire bunch train may be significant and dilute the beam emittance to unacceptable level. In this paper we report on an accurate calculation of the long-range wakefield and its overall effect on beam dynamics. We also discuss possible measures to minimise its effect in a tapered structure.

MOPB047

Applications of Compact Dielectric Based Accelerators

coupling, multipactoring, wakefield, electron

279

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

Important progress on the development of dielectric based accelerators has been made experimentally and theoretically in the past few years. One advantage of dielectric accelerators over the metallic counterparts is its compact size, which may attract some applications in industrial or medical accelerators. In this article, we discuss the design and technologies of dielectric based accelerators toward these needs.

MOPB060

RF Surface Impedance Characterization of Potential New Materials for SRF-based Accelerators

niobium, SRF, cavity, superconductivity

312

B. P. Xiao, G.V. Eremeev, H.L. Phillips, C.E. Reece
JLAB, Newport News, Virginia, USA
M.J. Kelley, B. P. Xiao
The College of William and Mary, Williamsburg, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In the development of new superconducting materials for possible use in SRF-based accelerators, it is useful to work with small candidate samples rather than complete resonant cavities. The recently commissioned Jefferson Lab rf Surface Impedance Characterization (SIC) system* can presently characterize the central region of 50 mm diameter disk samples of various materials from 2 to 40 K exposed to RF magnetic fields up to 14 mT at 7.4 GHz. We report the measurement results from bulk Nb, thin film Nb on Cu and sapphire substrates, and thin film MgB₂ on sapphire substrate provided by colleagues at JLab and Temple University. We also report on efforts to extend the operating range to higher fields.
* B.P. Xiao, et al., RSI, 2011. 82: p. 056104

MOPB081

Travelling Wave Accelerating Structures with a Large Phase Advance

acceleration, electron, linac, proton

363

V.V. Paramonov
RAS/INR, Moscow, Russia

The electrons acceleration is considered in higher pass bands of TM01 wave for disk loaded waveguide, resulting in the possibility of traveling wave accelerating structures with an operating field phase advance between 180 – 1260 degrees per cell. With an appropriate shape optimization and some additional elements in cells proposed traveling wave structures have small transverse dimensions and high RF efficiency of standing wave operation. Examples of proposed structures together with RF and dispersion properties are presented.

MOPB082

RF Parameters of the TE - Type Deflecting Structure for S-Band Frequency Range

ion, multipole, linac, heavy-ion

366

V.V. Paramonov, L.V. Kravchuk
RAS/INR, Moscow, Russia
K. Flöttmann
DESY, Hamburg, Germany

Funding: in part RBFR N 12-02-0654-a
Effective compact deflecting structure* has been proposed for L-band frequency range preferably. RF parameters of this structure considered for S-band frequency range both for traveling and standing wave operation.
* -V. Paramonov, L. Kravchuk, INR, S. Korepanov. Effective Standing Wave RF Structure for Particle Beam Deflector. Proc. 2006 Linac Conference, p. 649

TUPB001

The Fine Structure of the Zone of Particle Interaction with a Finite Length Periodic Structure

wakefield, simulation, diagnostics, emittance

473

V.V. Paramonov
RAS/INR, Moscow, Russia

The periodic constant impedance deflecting structures are widely used for a special beam diagnostic in FEL facilities. The method, based on frequency domain approach, was developed to estimate long range wake fields structure parameters in a wide frequency range. It is shown, that regardless to number of cells in the structure, at each passband to the zone of particle effective interaction with the structure belongs several, at least three modes. The usual time domain simulations provide the total estimation for loss factor or kick factor values and modes separation in the time domain approach requires enormous simulations.

TUPB009

C-Band Accelerating Structure Development and Tests for the SwissFEL

controls, klystron, FEL, linac

492

R. Zennaro, J. Alex, H. Blumer, M. Bopp, A. Citterio, T. Kleeb, L. Paly, J.-Y. Raguin
PSI, Villigen, Switzerland

SwissFEL requires a 5.8 GeV beam provided by a C-band linac consisting of 104 two-meter accelerating structures. Each structure is of the constant gradient type and is composed of 113 cups. The cup shape is double-rounded to increase the quality factor. No tuning feature is implemented. For this reason ultra-precise turning is exploited. A strong R&D program has been launched on structure fabrication, which will be followed by a future technology transfer to a commercial company. The program includes the production and test of short structures that can be brazed in the existing PSI vacuum oven and will be completed with the production of the full two-meter prototype once the new full scale brazing oven, presently under construction, is operational. The status of the R&D program, including the production and power test results of the first two test structures, is reported here.

TUPB011

The Swiss FEL S-Band Accelerating Structure: RF Design

accelerating-gradient, linac, gun, FEL

498

J.-Y. Raguin
PSI, Villigen, Switzerland

The Swiss FEL accelerator concept consists of a 450 MeV S-band injector Linac at 2998.8 GHz followed by the main linac at the C-band frequency aiming at a final energy of 5.8 GeV. The injector has six four-meter long S-band accelerating structures that shall operate with gradients up to 20 MV/m and with a 100 Hz repetition rate. Each structure has 122 cells, including the two coupler cells and operates with a 2π/3 phase advance. The design presented is such that the average dissipated RF power is constant over the whole length of the structure. The cells consist of cups and the cell irises have an elliptical profile to minimize the peak surface electric field. The coupler cells are of the double-feed type with a racetrack cross-section to cancel the dipolar components of the fields and to minimize its quadrupolar components.

TUPB012

The Swiss FEL C-Band Accelerating Structure: RF Design and Thermal Analysis

accelerating-gradient, linac, klystron, FEL

501

J.-Y. Raguin, M. Bopp
PSI, Villigen, Switzerland

The Swiss FEL accelerator concept consists of a 450 MeV S-band injector linac followed by the main linac in C-band aiming at a final energy of 5.8 GeV. The two-meter long C-band accelerating structures have 113 cells, including the two coupler cells, and operate with a 2π/3 phase advance. The structure is of the constant-gradient type with rounded wall cells and has an average iris radius of 6.44 mm, a radius compatible with the impact of the short-range wakefields on the whole linac beam dynamics. The cell irises have an elliptical profile to minimize the peak surface electric fields and the coupler cells are of the J-type. We report here on the RF design of the structure, as well as on its thermal analysis, to target operational conditions with an accelerating gradient of about 28 MV/m and a repetition rate of 100 Hz.

TUPB021

Study of Plasma Effect in Longitudinal Space Charge Induced Microbunching Instability

plasma, electron, linac, space-charge

522

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

The longitudinal space charge (LSC) plays an important role in introducing the microbunching instability in the LINAC of a free electron laser (FEL) facility. The current model of LSC impedance [1] derived from the fundamental electromagnetic theory [2] is widely used to explain the growth of the microbunching instability [3]. However, in the case of highly bright relativistic electron beams, the plasma effect starts to play a role. In this article, the basic model of LSC impedance including the plasma effect is built , and the modifications to the microbunching instability based on the new model are discussed in various conditions.
[1] Marco Venturini, Phys Rev. ST Accel. Beams 11, 034401 (2008)
[2] J. D. Jackson, Classical Electrodynamics (Wiley, 1999)
[3] Z. Huang, et. al., Phys, Rev. ST Accel. Beams 7, 074401 (2004)

TUPB036

Design of Re-Buncher Cavity for Heavy-ion LINAC in IMP

cavity, DTL, simulation, linac

558

L.P. Sun, X. Du, Y. He, A. Shi, C. Zhang, Z.L. Zhang
IMP, Lanzhou, People's Republic of China

A re-buncher with spiral arms for a heavy ion linear accelerator named as SSC-LNAC at HIRFL (the heavy ion research facility of Lanzhou) has been constructed. The re-buncher, which is used for beam longitudinal modulation and match between the RFQ and DTL, is designed to be operated in continuous wave (CW) mode at the Medium-Energy Beam-Transport (MEBT) line to maintain the beam intensity and quality. Because of the longitudinal space limitation, the re-buncher has to be very compact and will be built with four gaps. We determined the key parameters of the re-buncher cavity from the simulations using Microwave Studio software, such as the resonant frequency, the quality factor Q and the shunt impedance. The detailed design of a 53.667 MHz spiral cavity and measurement results of its prototype will be presented.

TUPB060

Multipacting Suppression Modeling for Half Wave Resonator and RF Coupler*

simulation, cavity, electron, cryomodule

612

Z. Zheng, A. Facco, Z. Liu, J. Popielarski, K. Saito, J. Wei, Y. Xu, Y. Zhang
FRIB, East Lansing, Michigan, USA
Z. Zheng
TUB, Beijing, People's Republic of China

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
In prototype cryomodule test of Facility of Rare Isotope Beam (FRIB) β=0.53 half-wave-resonators (HWRs) severe multipacting barriers, prevented RF measurement at the full field specified. The multipacting could not be removed by several hours of RF conditioning. To better understand and to eliminate multipacting, physics models and CST simulations have been developed for both cavity and RF coupler. The simulations have good agreement with the multipacting discovered in coupler and cavity testing. Proposed cavity and coupler geometric optimizations are discussed in this paper.

TUPB091

176 MHz Solid State Microwave Generator Design

linac, simulation, scattering, resonance

672

A.Yu. Smirnov, E.V. Ivanov, A.A. Krasnov, K.I. Nikolskiy, N.V. Tikhomirova
Siemens Research Center, Moscow,, Russia
O. Heid, T.J.S. Hughes
Siemens AG, Erlangen, Germany

This paper concerns the R&D work upon design of a compact RF amplifier to be used for superconducting CW cavities. The machine under development will operate at 176 MHz with output power of 25 kW in continuous wave regime. It consists of 50 push-pull PCB modules (approx. 500W output power each), connected in parallel to several radial filter rings, which both allow class-F operation and combine the power from the modules, delivering it to a single 50 Ω coax cable. The CST simulations ad the design of 324 MHz test prototype are presented.

TUPB095

Design of Coupler for Direct Coupled Amplifier to Drift Tube Linac Cavities of the Injector RILAC2 for RIKEN RI Beam Factory

cavity, DTL, coupling, linac

684

K. Suda, S. Arai, Y. Chiba, O. Kamigaito, M. Kase, H. Okuno, N. Sakamoto, Y. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan

A new linac RILAC2 was constructed at RIKEN RI Beam Factory as an injector for very heavy ions such as uranium and xenon of a high mass to charge ratio m/q ∼ 7, but high intensity ions can be extracted from an ion source. Three drift tube linac cavities, operate in continuous wave mode at 36.5 MHz, have been designed and built. In order to reduce an installation area, and to save a construction cost, we adopted a direct coupling method for a power amplifier without using a long transmission line. A complicated design procedure was performed in order to take into account a change of resonant frequency of the cavity caused by a capacitance of a power tube used in the amplifier. A design of the coupler, as well as the cavity was performed using a three-dimensional electromagnetic calculation code, CST Microwave Studio (MWS). The measured input impedance seen from the amplifier (700 – 1100 Ω) was reproduced well by the calculation of MWS. Also, in order to examine MWS, a case of a coupling with 50 Ω were calculated. The coupling conditions obtained by MWS were compared with the measurement and a calculation with a lumped circuit model.

TUPB102

Design and Performances of Phase Monitor in J-PARC Linac

linac, acceleration, pick-up, vacuum

699

A. Miura
JAEA/J-PARC, Tokai-mura, Japan
Z. Igarashi, T. Miyao
KEK, Ibaraki, Japan

J-PARC linac employs a fast current transformer (FCT) as a beam phase monitor to calculate the beam energy by time-of-flight method. We have installed and used 61 FCTs in the current beam line. Because the phase measurements at additional 41 points in the future ACS sections are required for the energy upgrade project with adding 21 ACS (Annular Coupled Structure) cavities, we stared the design and fabrication of FCTs as the phase measurement devices. In addition, J-PARC linac employs the 4-stripline beam position monitors (BPMs) for the beam position measurement. It has been considered that the signals from striplines of BPM would be useful for a phase measurement. A phase measurement using a BPM has been successfully conducted. In order to evaluate the performances of the FCT, the signal sensitivity and cut-off frequency of newly fabricated FCT are measured. Also, these data of the BPM are also measured to be compared with the data of FCT. Based on the results of the comparing both measurements, the superiority of both monitors for beam phase measurement is discussed.

TH1A03

Superconducting Spoke Cavities for Electron and High-Velocity Proton Linacs

cavity, linac, SRF, electron

758

J.R. Delayen
ODU, Norfolk, Virginia, USA

Spoke resonantors are currently under development for many proton machines but these structures are also considered for high beta electron linacs as well. These structures compare well to traditional elliptical cavities.

Slides TH1A03 [3.570 MB]

THPB025

325 MHz CW Room Temperature High Power Bunching Cavity for the China ADS MEBT1

cavity, bunching, vacuum, resonance

903

S. Pei, X. Li, H.F. Ouyang, J.R. Zhang
IHEP, Beijing, People's Republic of China

Two room temperature high power bunching cavities are required to be located in the ADS MEBT1 section. Double re–entrant nose cone geometry has been adopted as the type of the bunching cavity for its simplicity, higher shunt impedance and lower risk of multipacting. SUPERFISH is used to optimize the internal dimensions of the bunching cavity, then the RF–thermal–structural–RF coupled analysis were carried out in ANSYS to obtain the preliminary mechanical design, the layout of the cooling channels is optimized to suppress the frequency shift as much as possible. The cavity was specially designed to have the capability to withstand the 1 atm air pressure effect. In addition, the main dimensions of the coupler and tuner are also estimated.
*peisl@ihep.ac.cn

THPB074

RF Photoinjector and Radiating Structure for High-power THz Radiation Source

radiation, coupling, electron, vacuum

1005

S.M. Polozov, T.V. Bondarenko
MEPhI, Moscow, Russia
Y.A. Bashmakov
LPI, Moscow, Russia

Sources of high-power electromagnetic radiation in THz band are becoming promising as a new method of a low activation introscopy. Research and development of accelerating RF photoinjector and radiating system for THz radiation source are reported. The photoinjector is based on disk loaded waveguide (DLW). Two different designs of accelerating structures were modeled: widespread 1.6 cell of DLW structure and travelling wave resonator structure. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics and electric field distribution for all models were acquired. Results of picoseconds photoelectron beam dynamics in modeled structures are reported. Design of decelerating structures exciting Cherenkov radiation are based on corrugated metal channel and metal channel coated with dielectric. Analysis of radiation intensity and frequency band are presented.