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beam-loading

Paper Title Other Keywords Page
MOP002 A High Phase Advance Damped and Detuned Structure for the Main Linacs of CLIC dipole, wakefield, coupling, HOM 49
 
  • R.M. Jones, A. D'Elia, V.F. Khan
    UMAN, Manchester
  • A. Grudiev, W. Wuensch, R. Zennaro
    CERN, Geneva
 
 

We report on the suppression of long-range wakefields in the main linacs of the CLIC collider. The wakefield is damped using a combination of detuning the frequencies of beam-excited higher order modes and by light damping, through slot-coupled manifolds. This unique accelerator, in the process of being fabricated, will be the first structure to demonstrate wakefield damping and the ability to sustain high accelerating gradients for CLIC. This serves as an alternative to the baseline CLIC design, which at present relies entirely on heavy damping. Detailed simulations are presented, on both the optimised surface fields resulting from the monopole mode, and from wakefield damping of the dipole modes. Preparations for the fabrication of a structure, suitable for high power testing, are also discussed. This design takes into account practical mechanical engineering issues and is the result of several optimisations since the original CLICDDS proposal[*].


*V.F. Khan and R.M. Jones, Presented at Particle Accelerator Conference (PAC 09), Vancouver, BC, Canada, 4-8 May 2009.

 
MOP021 Compensation of Transient Beam-Loading in the CLIC Main Linac linac, impedance, coupling, injection 94
 
  • A. Grudiev, A. Cappelletti, O. Kononenko
    CERN, Geneva
 
 

Compensating transient beam loading to maintain a 0.01% relative beam energy spread is a key issue for the CLIC two-beam acceleration technique. The combination of short pulses, narrow bandwidth rf components and the limited number of rf pulse shaping 'knobs' given by the drive beam generation scheme makes meeting this specification challenging. A dedicated model, which takes into account all stages of drive beam generation, including the delay loop and combiner rings, the single-bunch response of the power generation structure (PETS), the RF waveguide network transfer function and dispersive properties of the accelerating structure has been developed. The drive beam phase switching delays, resulting rf pulse shape, loaded and unloaded voltages and finally the energy spread are presented.

 
MOP035 Transient Beam Loading Compensation in L-band Traveling-wave Accelerating Structure with Intense Electron Beam electron, injection, klystron, gun 133
 
  • S.H. Kim, M.-H. Cho, S.D. Jang, W. Namkung, S.J. Park, H.R. Yang
    POSTECH, Pohang, Kyungbuk
  • K.H. Chung, K. Lee
    KAPRA, Cheorwon
  • J.-S. Oh
    NFRI, Daejon
  • Y.G. Son
    PAL, Pohang, Kyungbuk
 
 

An intense L-band electron linac is now being commissioned at ACEP (Advanced Center for Electron-beam Processing in Cheorwon, Korea) for irradiation applications. It is capable of producing 10-MeV electron beams with the 30-kW average beam power. The constant-impedance accelerating structure is operated under fully-beam-loaded condition with the RF power of peak 25 MW and the beam current of 1.45 A. The total attenuation coefficient of the structure is 0.17 and the RF filling time is 0.9 μs along the 2.3-m accelerating structure. To suppress the energy spread due to the transient beam loading effect, we consider three methods: modulating the beam current amplitude, modulating the RF amplitude, and adjusting the beam injection time. In this paper, we calculate the transient beam energy numerically for the above cases. We also propose the actual compensation method.

 
MOP087 Beam Test of Chopped Beam Loading Compensation for the J-PARC Linac 400-MeV Upgrade cavity, linac, controls, LLRF 256
 
  • T. Kobayashi
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • M. Ikegami
    KEK, Ibaraki
 
 

The function of the chopped beam loading compensation was implemented into the digital feedback/feed-forward control system of the J-PARC Linac LLRF system to stabilize the ACS cavity fields for the 400-MeV upgrade. The beam test of the chopped beam loading compensation was performed with the present 324-MHz cavity sysmte. Consequently the chopped beam loading was successfully compensated and that this system is valid.

 
THP110 Generation of Long Bunch Train using RF Gun gun, linac, cavity, laser 992
 
  • A. Deshpande
    Sokendai, Ibaraki
  • S. Araki, M.K. Fukuda, N. Terunuma, J. Urakawa
    KEK, Ibaraki
  • K. Sakaue, M. Washio
    RISE, Tokyo
 
 

At Laser Undulator Compact X-ray Source (LUCX) facility at KEK, we have developed a RF gun with increased mode separation. Using this RF gun we have successfully generated a bunch train of 300 bunches per train with 160 nC total charge and with peak to peak energy difference less than 0.85% at 5.2 MeV. We plan to generate and accelerate 8000 bunches per train with 0.5 nC per bunch. These bunches will then collide in the collision chamber with laser pulses to produce soft x-ray. After successful results from above work, we take next step and are now designing and fabricating a new 3.5 cell RF gun and a high gradient standing wave linac to achieve 50 MeV beam with 8000-bunches per train. This compact source will be used for future research. This paper details achieved results with existing gun for generation of long bunch train and lists out proposed activity.