• A. Xiao, M. Borland, X.W. Dong
  ANL, Argonne

Beam scattering effects, including intra-beam scattering (IBS) and Touschek scattering, may become an issue for linac-based 4th-generation light sources, such as X-ray free-electron lasers (FELs) and energy recovery linacs (ERLs), as the electron density inside the bunch is very high. In this paper, we describe simulation tools for modeling beam-scattering effects that were recently developed at the Advanced Photon Source (APS). We also demonstrate their application to a possible ERL-based APS upgrade. The beam loss issue due to the Touschek scattering effect is addressed through momentum aperture optimization. The consequences of IBS for brightness, FEL gain, and other figures of merit are also discussed. Calculations are performed using a particle distribution generated by an optimized high-brightness injector simulation.

• M. Ikegami
  KEK, Ibaraki
• T. Morishita, H. Sako
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• G.B. Shen
  BNL, Upton, Long Island, New York

The beam commissioning of J-PARC linac has been performed since November 2006, and we are now in a transitional phase from an initial commissioning stage to a stage where we seek more stable operation with higher beam power. In the beam commissioning, the modeling is important to understand the underlying physics of the experimental data obtained by beam monitors. As the J-PARC is a high-intensity proton accelerator facility, the beam is subject to strong space-charge effects. In addition, mitigation of the beam loss is critically important to avoid excess radio-activation of the accelerator components. Therefore, an accurate Particle-In-Cell simulation code plays an essential role in the beam commissioning, especially in mapping out our course in the beam commissioning planning. For this purpose, we have been using IMPACT code in J-PARC linac. In this paper, we review the simulation studies performed for J-PARC linac trying to understand the experimental results in the course of the beam commissioning efforts.

• J.J. Yang
  TUB, Beijing
• J.J. Yang, H.J. Yao, T.J. Zhang
  CIAE, Beijing

A high intensity compact cyclotron, CYCIAE-100, is selected as the driving accelerator for Beijing Radioactive Ion-beam Facility (BRIF). At present the physics design of this machine has been accomplished. This paper gives a brief review of the general designs of this machine. For further intensity upgrade of this compact machine in the future, it is crucial to carry out in-depth study on the self fields effects including the contributions of single bunch space charge and the interaction of many radially neighboring bunches. In order to include the neighboring bunch effects fully self-consistently in compact cyclotrons, a new physical model is established for the first time and implemented in the parallel PIC code OPAL-CYCL. After that, the impact of the single bunch space charge and neighboring bunches on the beam dynamics in CYCIAE-100 for different intensity levels are studied by the simulations using the new model.

• B.G. Pine, D.J. Adams, C.M. Warsop, R.E. Williamson
  STFC/RAL/ISIS, Chilton, Didcot, Oxon

ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Presently, it runs at beam powers of ~0.2 MW, with upgrades in place to supply increased powers for the new Second Target Station. Studies are also under way for major upgrades in the megawatt regime. Underpinning this programme of operations and upgrades is a study of the high intensity effects that impose the limitations on beam power. Spallation is driven by a 50 Hz rapid cycling synchrotron, characterized by high space charge and fast ramping acceleration. High intensity effects are of particular importance as they drive beam loss, but are poorly understood analytically. This paper reviews development of the space charge charge code Set.