IPAC2013 - List of Keywords (bunching)

Paper	Title	Other Keywords	Page
MOPME073	Measurement of Schottky-like Signals from Linac Bunched Hadron Beams for Momentum Spread Evaluation	linac, cavity, synchrotron, pick-up	649
	P. Kowina, P. Forck, R. Singh GSI, Darmstadt, Germany F. Caspers CERN, Geneva, Switzerland R. Singh TEMF, TU Darmstadt, Darmstadt, Germany
	We present a novel method for the measurement of Linac beam parameters in the longitudinal phase space. The longitudinal momentum spread can be evaluated by means of Schottky type signal analysis of bunched beams. There is a close similarity between a repetitive Linac bunch train and a circulating beam with a single short batch in a large machine like the LHC. A dedicated longitudinal cavity pick-up was used in the Linac where resonance frequency and Q-value were carefully selected in order to get an optimum compromise between the unavoidable coherent signal and the desired incoherent part of the beam spectrum. A time domain gating similar to the 4.8 GHz LHC Schottky front-end is applied. As a cross-check of the validity of the interpretation in terms of momentum spread, the Linac beam is analyzed in the downstream synchrotron using standard Schottky methods. In principle, this approach can be understood as an extension of Schottky analysis for circular machines with a perfect “mixing” between subsequent bunch trains. This contribution describes the test set-up and discusses the results of the measurements with a heavy ion beam.

MOPWO071	Coherent Electron Cooling: Status of Single-Pass Simulations	electron, simulation, FEL, ion	1049
	B.T. Schwartz, G.I. Bell, I.V. Pogorelov, S.D. Webb Tech-X, Boulder, Colorado, USA D.L. Bruhwiler CIPS, Boulder, Colorado, USA Y. Hao, V. Litvinenko, G. Wang BNL, Upton, Long Island, New York, USA S. Reiche PSI, Villigen PSI, Switzerland
	Funding: US DOE Office of Science. Contracts DE-FC02-07ER41499, DE-FG02-08ER85182, DE-AC02-05CH11231. Advances in nuclear physics depend on experiments that employ relativistic hadron accelerators with dramatically increased luminosity. Current methods of increasing hadron beam luminosity include stochastic cooling and electron cooling; however, these approaches face serious difficulties at the high intensities and high energies proposed for eRHIC . Coherent electron cooling promises to cool hadron beams at a much faster rate. A single pass of an ion through a coherent electron cooler involves the ion's modulating the charge density of a copropagating electron beam, amplification of the modulated electron beam in a free-electron laser, and energy correction of the ion in the kicker section. Numerical simulations of these three components are underway, using the parallel Vorpal framework and Genesis 1.3, with careful coupling between the two codes. Here we present validations of two components of the simulations: Adding bunching to an electron beam at the start of an FEL, and the time-dependent charge density modulation in the kicker. http://www.bnl.gov/cad/eRHIC/ ** V.N. Litvinenko and Y.S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009).

TUODB101	Studies on An S-band Bunching System with Hybrid Buncher	linac, cavity, electron, gun	1120
	S. Pei, O. Xiao IHEP, Beijing, People's Republic of China
	Generally, a standard bunching system is composed by a SW pre-buncher, a TW buncher and a standard accelerating section. However, there is one way to simplify the whole system to some extent by using the hybrid buncher, which is a combined structure of the SW pre-buncher and the TW buncher. Here the beam dynamics studies on an S-band bunching system with hybrid buncher is presented, simulation results shows that similar beam performance can be obtained at the linac exit by using this kind of bunching system rather than the standard one. In the meantime, the structure design of the hybrid buncher is also described. Furthermore, the standard accelerating section can also be integrated with the hybrid buncher, this can further simplify the bunching system and lower the construction cost.
	Slides TUODB101 [22.120 MB]

TUPEA028	Echo-enabled Harmonic Generation based on Hefei Storage Ring	FEL, electron, laser, storage-ring	1208
	H.T. Li, W.W. Gao, Q.K. Jia, L. Wang USTC/NSRL, Hefei, Anhui, People's Republic of China
	Echo-Enabled Harmonic Generation (EEHG) has been proposed and experimently demonstrated recently. In this paper, we numerically investigate the possibility of operating EEHG based on Hefei storage ring, which has a short circumference and a small momentum compaction factor. The difference to other similar reserch is that we use the whole ring as the first dispersive section and an optical klystron as the second one.

TUPFI040	Experimental Verification of the CLIC Two-Beam Acceleration Technology in CTF3	linac, acceleration, feedback, collider	1436
	P. Skowroński, A. Andersson, J. Barranco, B. Constance, R. Corsini, S. Döbert, A. Dubrovskiy, W. Farabolini, E. Ikarios, R.L. Lillestøl, T. Persson, F. Tecker CERN, Geneva, Switzerland W. Farabolini CEA/DSM/IRFU, France E. Ikarios National Technical University of Athens, Athens, Greece M. Jacewicz, A. Palaia, R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden R.L. Lillestøl University of Oslo, Oslo, Norway T. Persson Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden
	The Compact Linear Collider (CLIC) International Collaboration is pursuing an extensive R&D program towards a multi-TeV electron-positron collider. In particular, the development of two beam acceleration technology is the focus of the CLIC test facility CTF3. In this paper we summarize the most recent results obtained at CTF3: the results of the studies on the drive beam generation are presented, the achieved two beam acceleration performance is reported and the measured break-down rates and related observations are summarized. The stability of deceleration process performed over 13 subsequent modules and the comparison of the obtained results with the theoretical expectations are discussed. We also outline and discuss the future experimental program.

TUPME019	Simulation for Control of Longitudinal Beam Emittance in J-PARC MR	emittance, injection, simulation, acceleration	1610
	M. Yamamoto, M. Nomura, A. Schnase, T. Shimada, F. Tamura JAEA/J-PARC, Tokai-mura, Japan E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, K. Takata, M. Toda, M. Yoshii KEK, Ibaraki, Japan
	The J-PARC MR receives a high intensity beam from the RCS. The designed longitudinal emittance of the RCS is 5 eVs, whereas the MR rf bucket has enough margin to accept up to 10 eVs. Although the RCS emittance can be increased by using PM method and a large emittance is desirable to increase the bunching factor and to avoid instability, it is difficult to receive such large emittance beam in the MR because of the MR kicker performance. We have performed the particle tracking simulation of longitudinal emittance control for enlarging the beam emittance by PM method and for keeping the bunching factor high using 2nd harmonic rf during the MR injection period.

TUPME047	Sub-Harmonic Bunching System of CLIC Drive Beam Injector	space-charge, collider, klystron, acceleration	1670
	S. Sanaye Hajari, S. Döbert, S. Döbert, H. Shaker CERN, Geneva, Switzerland S. Sanaye Hajari, H. Shaker IPM, Tehran, Iran
	In the Compact Linear Collider (CLIC) the RF power for the acceleration of the Main Beam is extracted from a high-current Drive Beam that runs parallel with the main linac. The sub-harmonic bunching system of the drive beam injector has been studied in detail and optimized. The model consists of a thermionic gun, three travelling wave sub-harmonic bunchers followed by a tapered travelling wave buncher. The simulation of the beam dynamics has been carried out with PARMELA with the goal of optimizing the overall bunching process and in particular capturing particles as much as possible in the buncher acceptance and decreasing the satellite population.

TUPME053	General Beam Loading Compensation in a Traveling Wave Structure	beam-loading, linac, electron, storage-ring	1688
	H. Shaker, S. Döbert CERN, Geneva, Switzerland H. Shaker IPM, Tehran, Iran
	The well-known beam loading in a traveling wave structure is in fact a resistive beam loading which bunches travel on the crest. This type of beam loading could be compensated by increasing RF feed power. But generally, bunches could travel on each phase. General beam loading compensation is well-known for a single cell cavity and it is done by changing the RF feed power and detuning the structure together. In this paper, the concept of detuning for a TW structure will be shown and the evolution of fundamental mode beam-induced field will be derived and finally, it will be shown how to compensate beam loading by changing the phase velocity in comparison to the beam velocity.

TUPWA039	Identification of the SPS Impedance at 1.4 GHz	impedance, optics, simulation, resonance	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.

TUPWO019	A Local Achromatic Design of C-ADS MEBT2	emittance, linac, controls, cavity	1922
	H. Geng, Z. Guo, Z. Li, C. Meng, S. Pei, J.Y. Tang IHEP, Beijing, People's Republic of China
	The accelerator of China Accelerator Driven Sub-critical system consists of two injectors to ensure its high reliability. The Medium Energy Beam Transport line-2 is an essential part of the accelerator to transport and match the beam from either injector to the main linac. This paper presents a local achromatic design, which uses four bending magnets, for CADS MEBT2. It is found that both transverse and longitudinal emittance growths can be well controlled below 15% from MEBT2 entrance to the exit of the following superconducting spoke-021 section. The beam dynamics of MEBT2 will be discussed and the multi-particle tracking results will also be shown.

WEPEA019	Status of the J-PARC MA Loaded RF Systems	cavity, impedance, injection, proton	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.

THOBB103	THz Electron-pulse-train Dynamics in a MeV Photo-injector	electron, acceleration, cathode, laser	3109
	F.H. Chao, C.H. Chen, Y.-C. Huang NTHU, Hsinchu, Taiwan P.J. Chou NSRRC, Hsinchu, Taiwan
	A conventional free electron laser (FEL) is bulky and expensive. In order to quickly build up the FEL power in a short undulator, a laser technology has been proposed to generate a pre-bunched electron pulse-train with a THz bunching frequency from a photoinjector. The bunching factor* of an accelerated pulse-train beam is influenced by the beam radius, initial bunching frequency, space charge force, acceleration gradient, and acceleration phase in an accelerator. For a given RF accelerator and initial beam parameters, there is a limitation on the maximally attainable bunching factor and bunching frequency for the accelerated pulse-train beam. This paper presents a theoretical analysis for the bunching factor and bunching frequency of an accelerated pulse-train beam subject to nominal initial beam conditions in a photoinjector. The theoretical analysis is compared with the simulation results from the simulation code, PARMELA. To obtain an output bunching factor larger than 0.5%, our simulation study indicates that the maximum bunching frequency at the cathode is 25 THz for a 150 A beam current under a peak acceleration field of 80 MV/m. * Y.C. Huang, C.H. Chen, A.P. Lee, W.K. Lau, S.G. Liu, NIM, A, 637, S1–S6 (2011). ** Y.C Huang, Appl. Phys. Lett., 96, 231503 (2010).
	Slides THOBB103 [3.076 MB]

THOAB203	100 MeV/100kW Electron Linear Accelerator Driver of the NSC KIPT Neutron Source	electron, target, neutron, gun	3121
	A.Y. Zelinsky, N. Ayzatsky, O. Bezditko, I.M. Karnaukhov, V.A. Kushnir, V. Mitrochenco NSC/KIPT, Kharkov, Ukraine Y.L. Chi, X.W. Dai, C.D. Deng, M. Hou, X.C. Kong, R.L. Liu, W.B. Liu, C. Ma, G. Pei, S. Pei, H. Song, S. Wang, J.B. Zhao, Z.S. Zhou IHEP, Beijing, People's Republic of China Y. Gohar ANL, Argonne, USA
	In NSC KIPT, Kharkov, Ukraine a neutron source based on a subcritical assembly driven by a 100MeV/100kW electron linear accelerator will be constructed. This neutron source is an USA (ANL)-Ukraine (KIPT) Joint project, and its Accelerator will be designed and constructed by Institute of High Energy Physics (IHEP), China. The design and construction of such a Accelerator with high average beam current and low beam power losses is a technical challenging task. In the paper, the main accelerator features and current status are under discussion.
	Slides THOAB203 [8.585 MB]

THPEA004	Precise Verification of Phase and Amplitude Calibration by means of a Debunching Experiment in SIS18	target, controls, cavity, injection	3155
	U. Hartel, H. Klingbeil TEMF, TU Darmstadt, Darmstadt, Germany J. Grieser, D.E.M. Lens TU Darmstadt, RTR, Darmstadt, Germany H. Klingbeil, U. Laier, K.-P. Ningel, S. Schäfer, B. Zipfel GSI, Darmstadt, Germany
	Funding: Work supported by the GSI Helmholtzzentrum für Schwerionenforschung GmbH Several new rf cavity systems have to be realized for the FAIR synchrotrons and for the upgrade of the existing GSI synchrotron SIS18. For this purpose, a completely new low-level rf system architecture* has been developed, which is now used in SIS18 operation. Closed-loop control systems stabilize the amplitude and the phase of the rf gap voltages. Due to component imperfections the transmission and the detection of the actual values lead to systematic errors without countermeasures. These errors prohibit the operation of the rf systems over the whole amplitude and frequency range within the required accuracy. To compensate the inevitable errors, the target values provided by the central control system are modified by so-called calibration electronics*** modules. The calibration curves can be measured without the beam, but the desired beam behaviour has to be verified by experiments. For this purpose, a debunching scenario was selected as a SIS18 beam experiment that proved to be very sensitive to inaccuracies. In this contribution the results of this experiment are presented, showing for the first time at GSI by beam observation that the accuracy requirements are met based on predefined calibration curves. * “FAIR - Baseline Technical Report,” Volume 2, Accelerator and Scientific Infrastructure, (2006). Klingbeil et al.: Phys. Rev. ST Accel. Beams 14, 102802, 2011. * S. Schaefer et al., “Use of FPGA-based Configurable Electronics to Calibrate Cavities,” THPEA003, these proceedings.

THPWA001	Design of X-Band Medical Linear Accelerator with Multiple RF Feeds and RF Phase Focusing	focusing, linac, cavity, impedance	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.

THPWA030	Design and Prototype Test of C-band Standing-wave Accelerating Structure to Enhance RF Phase Focusing	electron, focusing, coupling, simulation	3690
	H. Yang, M.-H. Cho, W. Namkung, S.-G. Shin POSTECH, Pohang, Kyungbuk, Republic of Korea S.H. Kim ANL, Argonne, USA J.-S. Oh NFRI, Daejon, Republic of Korea
	Funding: This research was financially supported by the MOTIV, KIAT and Dongnam Institute for Regional Program Evaluation through the Leading Industry Development for Economic Region A C-band standing-wave accelerator for X-ray and electron beam sources of medical radiotherapy is designed and being fabricated. The accelerator system is to be operated in two modes, using the X-ray and electron beams. Because of the energy loss in electron mode, the accelerator is capable of producing 6-MeV, 100-mA electron beams with peak 2-MW RF power, and 7.5-MeV, 20 mA electron beams with peak 2.5-MW RF power. The beam radius at the end of column was < 0.5 mm without focusing magnets in PARMELA simulations, because the bunching cells are designed to enhance the RF phase focusing. Each cavity in the bunching and normal cells was designed by the MWS code to maximize the effective shunt impedance with 3.8% inter-cell coupling in normal cells. The dimensions of normal cells were determined by the low power RF test of prototype cells with 5711.06-MHz resonant frequency and 3.5% inter-cell coupling. In this paper, we present details of the accelerator design and prototype test.

THPWO076	Design Study for 10 MHz Beam Frequency of Post-accelerated RIBs at HIE-ISOLDE	rfq, emittance, linac, solenoid	3933
	M.A. Fraser, R. Calaga, I.-B. Magdau CERN, Geneva, Switzerland
	An increased bunch spacing of approximately 100 ns is requested by several research groups targeting experimental physics at HIE-ISOLDE. A design study testing the feasibility of retrofitting the existing 101.28 MHz REX (Radioactive ion beam EXperiment) RFQ with a sub-harmonic external pre-buncher at the ISOLDE radioactive nuclear beam facility has been carried out as a means of decreasing the beam frequency by a factor of 10. The proposed scheme for the 10 MHz bunch repetition frequency is presented and its performance assessed with beam dynamics simulations. The opportunity to reduce the longitudinal emittance formed in the RFQ is discussed along with the options for chopping the satellite bunches populated in the bunching process.

Paper

Title

Other Keywords

Page

MOPME073

Measurement of Schottky-like Signals from Linac Bunched Hadron Beams for Momentum Spread Evaluation

linac, cavity, synchrotron, pick-up

649

P. Kowina, P. Forck, R. Singh
GSI, Darmstadt, Germany
F. Caspers
CERN, Geneva, Switzerland
R. Singh
TEMF, TU Darmstadt, Darmstadt, Germany

We present a novel method for the measurement of Linac beam parameters in the longitudinal phase space. The longitudinal momentum spread can be evaluated by means of Schottky type signal analysis of bunched beams. There is a close similarity between a repetitive Linac bunch train and a circulating beam with a single short batch in a large machine like the LHC. A dedicated longitudinal cavity pick-up was used in the Linac where resonance frequency and Q-value were carefully selected in order to get an optimum compromise between the unavoidable coherent signal and the desired incoherent part of the beam spectrum. A time domain gating similar to the 4.8 GHz LHC Schottky front-end is applied. As a cross-check of the validity of the interpretation in terms of momentum spread, the Linac beam is analyzed in the downstream synchrotron using standard Schottky methods. In principle, this approach can be understood as an extension of Schottky analysis for circular machines with a perfect “mixing” between subsequent bunch trains. This contribution describes the test set-up and discusses the results of the measurements with a heavy ion beam.

MOPWO071

Coherent Electron Cooling: Status of Single-Pass Simulations

electron, simulation, FEL, ion

1049

B.T. Schwartz, G.I. Bell, I.V. Pogorelov, S.D. Webb
Tech-X, Boulder, Colorado, USA
D.L. Bruhwiler
CIPS, Boulder, Colorado, USA
Y. Hao, V. Litvinenko, G. Wang
BNL, Upton, Long Island, New York, USA
S. Reiche
PSI, Villigen PSI, Switzerland

Funding: US DOE Office of Science. Contracts DE-FC02-07ER41499, DE-FG02-08ER85182, DE-AC02-05CH11231.
Advances in nuclear physics depend on experiments that employ relativistic hadron accelerators with dramatically increased luminosity. Current methods of increasing hadron beam luminosity include stochastic cooling and electron cooling; however, these approaches face serious difficulties at the high intensities and high energies proposed for eRHIC *. Coherent electron cooling promises to cool hadron beams at a much faster rate**. A single pass of an ion through a coherent electron cooler involves the ion's modulating the charge density of a copropagating electron beam, amplification of the modulated electron beam in a free-electron laser, and energy correction of the ion in the kicker section. Numerical simulations of these three components are underway, using the parallel Vorpal framework and Genesis 1.3, with careful coupling between the two codes. Here we present validations of two components of the simulations: Adding bunching to an electron beam at the start of an FEL, and the time-dependent charge density modulation in the kicker.
* http://www.bnl.gov/cad/eRHIC/
** V.N. Litvinenko and Y.S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009).

TUODB101

Studies on An S-band Bunching System with Hybrid Buncher

linac, cavity, electron, gun

1120

S. Pei, O. Xiao
IHEP, Beijing, People's Republic of China

Generally, a standard bunching system is composed by a SW pre-buncher, a TW buncher and a standard accelerating section. However, there is one way to simplify the whole system to some extent by using the hybrid buncher, which is a combined structure of the SW pre-buncher and the TW buncher. Here the beam dynamics studies on an S-band bunching system with hybrid buncher is presented, simulation results shows that similar beam performance can be obtained at the linac exit by using this kind of bunching system rather than the standard one. In the meantime, the structure design of the hybrid buncher is also described. Furthermore, the standard accelerating section can also be integrated with the hybrid buncher, this can further simplify the bunching system and lower the construction cost.

Slides TUODB101 [22.120 MB]

TUPEA028

Echo-enabled Harmonic Generation based on Hefei Storage Ring

FEL, electron, laser, storage-ring

1208

H.T. Li, W.W. Gao, Q.K. Jia, L. Wang
USTC/NSRL, Hefei, Anhui, People's Republic of China

Echo-Enabled Harmonic Generation (EEHG) has been proposed and experimently demonstrated recently. In this paper, we numerically investigate the possibility of operating EEHG based on Hefei storage ring, which has a short circumference and a small momentum compaction factor. The difference to other similar reserch is that we use the whole ring as the first dispersive section and an optical klystron as the second one.

TUPFI040

Experimental Verification of the CLIC Two-Beam Acceleration Technology in CTF3

linac, acceleration, feedback, collider

1436

P. Skowroński, A. Andersson, J. Barranco, B. Constance, R. Corsini, S. Döbert, A. Dubrovskiy, W. Farabolini, E. Ikarios, R.L. Lillestøl, T. Persson, F. Tecker
CERN, Geneva, Switzerland
W. Farabolini
CEA/DSM/IRFU, France
E. Ikarios
National Technical University of Athens, Athens, Greece
M. Jacewicz, A. Palaia, R.J.M.Y. Ruber
Uppsala University, Uppsala, Sweden
R.L. Lillestøl
University of Oslo, Oslo, Norway
T. Persson
Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden

The Compact Linear Collider (CLIC) International Collaboration is pursuing an extensive R&D program towards a multi-TeV electron-positron collider. In particular, the development of two beam acceleration technology is the focus of the CLIC test facility CTF3. In this paper we summarize the most recent results obtained at CTF3: the results of the studies on the drive beam generation are presented, the achieved two beam acceleration performance is reported and the measured break-down rates and related observations are summarized. The stability of deceleration process performed over 13 subsequent modules and the comparison of the obtained results with the theoretical expectations are discussed. We also outline and discuss the future experimental program.

TUPME019

Simulation for Control of Longitudinal Beam Emittance in J-PARC MR

emittance, injection, simulation, acceleration

1610

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

The J-PARC MR receives a high intensity beam from the RCS. The designed longitudinal emittance of the RCS is 5 eVs, whereas the MR rf bucket has enough margin to accept up to 10 eVs. Although the RCS emittance can be increased by using PM method and a large emittance is desirable to increase the bunching factor and to avoid instability, it is difficult to receive such large emittance beam in the MR because of the MR kicker performance. We have performed the particle tracking simulation of longitudinal emittance control for enlarging the beam emittance by PM method and for keeping the bunching factor high using 2nd harmonic rf during the MR injection period.

TUPME047

Sub-Harmonic Bunching System of CLIC Drive Beam Injector

space-charge, collider, klystron, acceleration

1670

S. Sanaye Hajari, S. Döbert, S. Döbert, H. Shaker
CERN, Geneva, Switzerland
S. Sanaye Hajari, H. Shaker
IPM, Tehran, Iran

In the Compact Linear Collider (CLIC) the RF power for the acceleration of the Main Beam is extracted from a high-current Drive Beam that runs parallel with the main linac. The sub-harmonic bunching system of the drive beam injector has been studied in detail and optimized. The model consists of a thermionic gun, three travelling wave sub-harmonic bunchers followed by a tapered travelling wave buncher. The simulation of the beam dynamics has been carried out with PARMELA with the goal of optimizing the overall bunching process and in particular capturing particles as much as possible in the buncher acceptance and decreasing the satellite population.

TUPME053

General Beam Loading Compensation in a Traveling Wave Structure

beam-loading, linac, electron, storage-ring

1688

H. Shaker, S. Döbert
CERN, Geneva, Switzerland
H. Shaker
IPM, Tehran, Iran

The well-known beam loading in a traveling wave structure is in fact a resistive beam loading which bunches travel on the crest. This type of beam loading could be compensated by increasing RF feed power. But generally, bunches could travel on each phase. General beam loading compensation is well-known for a single cell cavity and it is done by changing the RF feed power and detuning the structure together. In this paper, the concept of detuning for a TW structure will be shown and the evolution of fundamental mode beam-induced field will be derived and finally, it will be shown how to compensate beam loading by changing the phase velocity in comparison to the beam velocity.

TUPWA039

Identification of the SPS Impedance at 1.4 GHz

impedance, optics, simulation, resonance

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.

TUPWO019

A Local Achromatic Design of C-ADS MEBT2

emittance, linac, controls, cavity

1922

H. Geng, Z. Guo, Z. Li, C. Meng, S. Pei, J.Y. Tang
IHEP, Beijing, People's Republic of China

The accelerator of China Accelerator Driven Sub-critical system consists of two injectors to ensure its high reliability. The Medium Energy Beam Transport line-2 is an essential part of the accelerator to transport and match the beam from either injector to the main linac. This paper presents a local achromatic design, which uses four bending magnets, for CADS MEBT2. It is found that both transverse and longitudinal emittance growths can be well controlled below 15% from MEBT2 entrance to the exit of the following superconducting spoke-021 section. The beam dynamics of MEBT2 will be discussed and the multi-particle tracking results will also be shown.

WEPEA019

Status of the J-PARC MA Loaded RF Systems

cavity, impedance, injection, proton

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.

THOBB103

THz Electron-pulse-train Dynamics in a MeV Photo-injector

electron, acceleration, cathode, laser

3109

F.H. Chao, C.H. Chen, Y.-C. Huang
NTHU, Hsinchu, Taiwan
P.J. Chou
NSRRC, Hsinchu, Taiwan

A conventional free electron laser (FEL) is bulky and expensive. In order to quickly build up the FEL power in a short undulator, a laser technology has been proposed to generate a pre-bunched electron pulse-train with a THz bunching frequency from a photoinjector*. The bunching factor** of an accelerated pulse-train beam is influenced by the beam radius, initial bunching frequency, space charge force, acceleration gradient, and acceleration phase in an accelerator. For a given RF accelerator and initial beam parameters, there is a limitation on the maximally attainable bunching factor and bunching frequency for the accelerated pulse-train beam. This paper presents a theoretical analysis for the bunching factor and bunching frequency of an accelerated pulse-train beam subject to nominal initial beam conditions in a photoinjector. The theoretical analysis is compared with the simulation results from the simulation code, PARMELA. To obtain an output bunching factor larger than 0.5%, our simulation study indicates that the maximum bunching frequency at the cathode is 25 THz for a 150 A beam current under a peak acceleration field of 80 MV/m.
* Y.C. Huang, C.H. Chen, A.P. Lee, W.K. Lau, S.G. Liu, NIM, A, 637, S1–S6 (2011).
** Y.C Huang, Appl. Phys. Lett., 96, 231503 (2010).

Slides THOBB103 [3.076 MB]

THOAB203

100 MeV/100kW Electron Linear Accelerator Driver of the NSC KIPT Neutron Source

electron, target, neutron, gun

3121

A.Y. Zelinsky, N. Ayzatsky, O. Bezditko, I.M. Karnaukhov, V.A. Kushnir, V. Mitrochenco
NSC/KIPT, Kharkov, Ukraine
Y.L. Chi, X.W. Dai, C.D. Deng, M. Hou, X.C. Kong, R.L. Liu, W.B. Liu, C. Ma, G. Pei, S. Pei, H. Song, S. Wang, J.B. Zhao, Z.S. Zhou
IHEP, Beijing, People's Republic of China
Y. Gohar
ANL, Argonne, USA

In NSC KIPT, Kharkov, Ukraine a neutron source based on a subcritical assembly driven by a 100MeV/100kW electron linear accelerator will be constructed. This neutron source is an USA (ANL)-Ukraine (KIPT) Joint project, and its Accelerator will be designed and constructed by Institute of High Energy Physics (IHEP), China. The design and construction of such a Accelerator with high average beam current and low beam power losses is a technical challenging task. In the paper, the main accelerator features and current status are under discussion.

Slides THOAB203 [8.585 MB]

THPEA004

Precise Verification of Phase and Amplitude Calibration by means of a Debunching Experiment in SIS18

target, controls, cavity, injection

3155

U. Hartel, H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany
J. Grieser, D.E.M. Lens
TU Darmstadt, RTR, Darmstadt, Germany
H. Klingbeil, U. Laier, K.-P. Ningel, S. Schäfer, B. Zipfel
GSI, Darmstadt, Germany

Funding: Work supported by the GSI Helmholtzzentrum für Schwerionenforschung GmbH
Several new rf cavity systems have to be realized for the FAIR synchrotrons and for the upgrade of the existing GSI synchrotron SIS18*. For this purpose, a completely new low-level rf system architecture** has been developed, which is now used in SIS18 operation. Closed-loop control systems stabilize the amplitude and the phase of the rf gap voltages. Due to component imperfections the transmission and the detection of the actual values lead to systematic errors without countermeasures. These errors prohibit the operation of the rf systems over the whole amplitude and frequency range within the required accuracy. To compensate the inevitable errors, the target values provided by the central control system are modified by so-called calibration electronics*** modules. The calibration curves can be measured without the beam, but the desired beam behaviour has to be verified by experiments. For this purpose, a debunching scenario was selected as a SIS18 beam experiment that proved to be very sensitive to inaccuracies. In this contribution the results of this experiment are presented, showing for the first time at GSI by beam observation that the accuracy requirements are met based on predefined calibration curves.
* “FAIR - Baseline Technical Report,” Volume 2, Accelerator and Scientific Infrastructure, (2006).
** Klingbeil et al.: Phys. Rev. ST Accel. Beams 14, 102802, 2011.
*** S. Schaefer et al., “Use of FPGA-based Configurable Electronics to Calibrate Cavities,” THPEA003, these proceedings.

THPWA001

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

focusing, linac, cavity, impedance

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.

THPWA030

Design and Prototype Test of C-band Standing-wave Accelerating Structure to Enhance RF Phase Focusing

electron, focusing, coupling, simulation

3690

H. Yang, M.-H. Cho, W. Namkung, S.-G. Shin
POSTECH, Pohang, Kyungbuk, Republic of Korea
S.H. Kim
ANL, Argonne, USA
J.-S. Oh
NFRI, Daejon, Republic of Korea

Funding: This research was financially supported by the MOTIV, KIAT and Dongnam Institute for Regional Program Evaluation through the Leading Industry Development for Economic Region
A C-band standing-wave accelerator for X-ray and electron beam sources of medical radiotherapy is designed and being fabricated. The accelerator system is to be operated in two modes, using the X-ray and electron beams. Because of the energy loss in electron mode, the accelerator is capable of producing 6-MeV, 100-mA electron beams with peak 2-MW RF power, and 7.5-MeV, 20 mA electron beams with peak 2.5-MW RF power. The beam radius at the end of column was < 0.5 mm without focusing magnets in PARMELA simulations, because the bunching cells are designed to enhance the RF phase focusing. Each cavity in the bunching and normal cells was designed by the MWS code to maximize the effective shunt impedance with 3.8% inter-cell coupling in normal cells. The dimensions of normal cells were determined by the low power RF test of prototype cells with 5711.06-MHz resonant frequency and 3.5% inter-cell coupling. In this paper, we present details of the accelerator design and prototype test.

THPWO076

Design Study for 10 MHz Beam Frequency of Post-accelerated RIBs at HIE-ISOLDE

rfq, emittance, linac, solenoid

3933

M.A. Fraser, R. Calaga, I.-B. Magdau
CERN, Geneva, Switzerland

An increased bunch spacing of approximately 100 ns is requested by several research groups targeting experimental physics at HIE-ISOLDE. A design study testing the feasibility of retrofitting the existing 101.28 MHz REX (Radioactive ion beam EXperiment) RFQ with a sub-harmonic external pre-buncher at the ISOLDE radioactive nuclear beam facility has been carried out as a means of decreasing the beam frequency by a factor of 10. The proposed scheme for the 10 MHz bunch repetition frequency is presented and its performance assessed with beam dynamics simulations. The opportunity to reduce the longitudinal emittance formed in the RFQ is discussed along with the options for chopping the satellite bunches populated in the bunching process.