Electron cloud measurements and simulations for the Brookhaven Relativistic Heavy Ion Collider

Abstract

Intense ion beams in the Brookhaven Relativistic Ion Collider lead to a rise in the vacuum pressure. Electron clouds can contribute to such a process. To measure electron cloud densities the coherent tune shift along the bunch train was observed with different bunch spacings and intensities. From the measured coherent tune shifts, electron cloud densities are computed and compared with densities obtained in electron cloud simulations.

Electron Cloud Phase Transitions

“…In contrast the electron cloud at IP12 decays smoothly over about 10 minutes, until it turns off at about 16:16. There is an unexplained knee in the rate at which the IP12 cloud decays, at about 16:08. dcct meas wcm meas 3 Simulation results showing second order transitions Figure 6 shows the results of an investigation of the electron cloud phase transition using the simulation CSEC [2]. While the simulation conditions and parameters are somewhat similar to those in the RHIC observations, there are significant differences.…”

Numerical simulation of the generation of secondary electrons in the High Current Experiment

“…Electron effects presently limit the performance of many ion accelerators [1][2][3]. One source of these electrons is electrons emitted from collisions between beam ions and the beam pipe walls.…”

Use of maps in the exploration of electron cloud parameter space

“…Figure 4 shows the result of three attempts in injecting three different bunch patterns: (3,16,4), (3,12,8), and (3,14,6). Even though pressure rises are detected for the first two cases and not for the third one, (see pressure rise at the blue section in Fig.…”

“…The electron density per beam pipe meter (ρ) as a function of time grows exponentially until the space charge due to the electrons themselves produces a saturation level. In this case, the code used is CSEC (Cylindrical Symmetric Electron Cloud simulation) [12]. The red line shows CSEC output, while the grey circles mark the average electron density between the passage of two bunches, no matter if they are full bunches or empty.…”