BNL, Upton, Long Island, New York
JINR, Dubna, Moscow Region
Standard models of the intra-beam scattering (IBS) are based on the growth of the rms beam parameters for a Gaussian beam distribution. However, in many situations distribution can significantly deviate from Gaussian which requires accurate treatment of IBS. Our original interest in this problem was motivated for the need to have accurate description of beam evolution due to IBS while distribution is strongly affected by external electron cooling force [1]. A variety of models with various degrees of approximation were implemented in BETACOOL in the past to address this topic [2]. A more complete treatment based on the friction coefficient and full 3-D diffusion tensor was introduced in BETACOOL at the end of 2007 under the name “local IBS” [3]. Such a model allowed us calculation of IBS for arbitrary beam distributions. Numerical benchmarking of this local IBS model and its comparison with other models was reported before. Here, after briefly describing the model and its limitations, we present its comparison with available experimental data.
[1] A. Fedotov et al., Proc. of PAC05 (Knoxville, TN), p. 4263.
[2] http://betacool.jinr.ru; A. Sidorin et al., NIM A 558, p. 325 (2006).
[3] BNL BETACOOL development report, December 2007.
BNL, Upton, Long Island, New York
There is a strong interest in heavy-ion collisions at the center of mass energies of 5-20 GeV/nucleon. This physics program is motivated by a search of the QCD phase transition critical point. Such low-energy operations started at Relativistic Heavy Ion Collider (RHIC) in 2010. The defining limitation in luminosity improvement for this program is expected to be due to the space charge. For RHIC, we are interested in rather long beam lifetime, which sets limitation on an allowable space-charge tune shift. An additional complication comes from the fact that ion beams are colliding, which requires careful consideration of the interplay of direct space-charge and beam-beam effects. We started to explore these beam dynamics effects in RHIC Accelerator Physics Experiments (APEX) in 2009 with proton beams. The experiments continued in 2010 with Au ion beams. This paper summarizes our findings and observations.
