beam-loading

Paper	Title	Other Keywords	Page
MOPC119	Low-Output-Impedance RF System for the ISIS Second Harmonic Cavity	impedance, synchrotron, controls, acceleration	343
	Y. Irie, S. Fukumoto, K. Muto, A. Takagi KEK, Ibaraki D. Bayley, I. S.K. Gardner, A. Seville, J. W.G. Thomason STFC/RAL/ISIS, Chilton, Didcot, Oxon J. C. Dooling, D. Horan, R. Kustom, M. E. Middendorf ANL, Argonne, Illinois T. Oki Tsukuba University, Ibaraki
	Low-output-impedance RF system for the second harmonic cavity in the ISIS synchrotron has been developed by the collaboration between Argonne National Laboratory, US, KEK, Japan and Rutherford Appleton Laboratory, UK. Low output impedance is realized by the feedback from plate output to grid input of the final triode amplifier, resulting in less than 30 Ω over the frequency range of interest. Precise control of the second harmonic voltage can then be realized without considering beam loading effects. Beam test scenario in the ISIS synchrotron is discussed.
TUPC113	Beam Energy Compensation by RF Amplitude Control for Thermionic RF Gun and Linac Based Mid-infrared FEL	controls, gun, klystron, electron	1329
	H. Zen, T. Kii, R. Kinjo, K. Masuda, H. Ohgaki, S. Sasaki, T. Shiiyama Kyoto IAE, Kyoto
	Institute of Advanced Energy, Kyoto University has constructed a mid-infrared FEL facility which consists of a thermionic RF gun, a traveling-wave type accelerating tube and a halbach type undulator. The electron beam quality is critical for lasing FEL. However, we found that the beam energy after the accelerator tube decreased from 25 to 23.5 MeV (around 6%) during macro-pulse duration (~4μsec), because.the beam current increases from 65 to 120 mA during the macro-pulse due to the backbombardment effect in the RF gun. To compensate the energy drop and to minimize the energy spread over the macro-pulse, the amplitude of RF power fed to the tube was controlled. Since a precise micro-bunch interval required to build up the FEL, the RF phase was also controlled. As the result, the energy spread of the electron beam was greatly reduced from 6 to 0.8% in FWHM which was same with micro-pulse energy spread (~0.8%). The phase stability during macro-pulse was also improved from 10 to less than 2 degree.
TUPC144	Digital Low Level RF System for SOLEIL	feedback, simulation, controls, synchrotron	1407
	P. Marchand, M. D. Diop, F. Ribeiro, R. Sreedharan SOLEIL, Gif-sur-Yvette M. Luong, O. Piquet CEA, Gif-sur-Yvette
	In the SOLEIL storage ring, two cryomodules, each containing a pair of 352 MHz superconducting cavities, will provide the maximum power of 560, required at the nominal energy of 2.75 GeV with the full beam current of 500 mA. Presently, an analogue Low Level RF system is successfully operating to control the amplitude and phase of the accelerating voltage. A fast digital FPGA based I-Q feedback is currently under development. The digital I-Q loop is realised with a HERON IO2 FPGA module using a Virtex II with 1M gates. The performance of the digital LLRF system has been evaluated using a Matlab-Simulink based simulation tool taking into account different features (loop delays, bandwidth limitation, extra power budget). The hardware design is described and the first experimental results are reported.
TUPP048	Collective Effects in the EMMA Non-scaling FFAG	space-charge, acceleration, emittance, simulation	1652
	S. Machida, D. J. Kelliher STFC/RAL/ASTeC, Chilton, Didcot, Oxon J. S. Berg BNL, Upton, Long Island, New York S. R. Koscielniak TRIUMF, Vancouver
	EMMA is an electron machine to study beam dynamics in a linear nonscaling FFAG. We wish to verify that the behavior predicted by the theory and simulation is correct. In particular, we will study, with large emittance beams, a novel accelerating mode outside an rf bucket, and the effects of crossing "resonances." In EMMA, some collective effects become a concern even though the beam stays in the ring for only 10 to 20 turns. We report studies of direct and image space charge, beam loading, and other collective effects with a tracking simulation. Space charge effects, already potentially significant in EMMA, are enhanced by the fact that the beam passes through the beam pipe off-center. There is some possibility of a negative mass instability for some operation modes. We will show several 3D simulation results for space charge and beam loading effects and pure longitudinal simulation for the negative mass instability.
TUPP059	Study of Controlled Longitudinal Emittance Blow-up for High Intensity LHC Beams in the CERN SPS	emittance, synchrotron, damping, quadrupole	1676
	G. Papotti, T. Bohl, T. P.R. Linnecar, E. N. Shaposhnikova, J. Tuckmantel CERN, Geneva
	Preventive longitudinal emittance blow-up, in addition to a fourth harmonic Landau damping RF system, is required to keep the LHC beam in the SPS stable up to extraction. The beam is blown-up in a controlled way during the acceleration ramp by using band-limited phase noise targeted to act inside the synchrotron frequency spread, which is itself modified both by the second RF system and by intensity effects (beam loading and others). For a high intensity beam these latter effects can lead to a non-uniform emittance blow-up and even loss of stability for certain bunches in the batch. In this paper we present studies of the emittance blow-up achieved with high intensity beams under different conditions of both RF and noise parameters.
THYG02	Results from the CLIC Test Facility CTF3 and Update on the CLIC Design	linac, acceleration, electron, luminosity	2912
	G. Geschonke CERN, Geneva
	The CLIC Test Facility CTF3 is being built and commissioned in stages. Up to now the facility consists of an electron linac, a magnetic chicane for changing bunch length, the Delay Loop and the Combiner Ring. Recent experience and commissioning results will be presented together with plans for the next steps which should lead to feasibility demonstration of CLIC technology by the year 2010. The CLIC design has been reviewed in detail. The resulting changes in parameters will be presented.
	Slides