Electron detectors for vacuum pressure rise diagnostics at RHIC

Abstract

In the RHIC 2001 run, an unexpected vacuum pressure rise versus bunch increasing currents was observed in both gold and proton operations. This pressure increase due to molecular desorption is suspected to be induced mainly by electron multipacting, but other causes may coexist, such as ion desorption due to halo scraping. In order to get a reliable diagnostic of the phenomenon electron detectors have been installed along the RHIC ring. In this report we describe results measured by the electron detectors with energy filters during the RHIC 2002/2003 run. [4] P. He et al. Calibration of RHIC Electron Detector. In these proceedings. [5] U. Iriso-Ariz et al. Electron cloud and pressure rise sirnulations for RHIC. In these proceedings.

Improvement of RHIC warm beam vacuum for high intensity operation

“…The solenoids have been energized during the machine studies in 2003. Significant reduction in both the electron signal and the pressure rise has been observed [5,7].…”

Electron cloud and pressure rise simulations for RHIC

“…In order to determine the proper values of SEY,,, and R, we could fit the growth and decay times from both simulations and experimental data and compare the results. However, the experimental data comes from an AC coupled signal with a low frequency cut off, flO,=300kHz [4]. Therefore, the signal needs to be treated before fitting when slow dynamics (<300kHz) play a role, as they did for fill # 3460.…”

“…We also compare the simulation results with data when a solenoidal field is applied to suppress the effect. The experimental results are based on the electron detector in [4]. The direct output provided by this detector is a voltage, which can be converted to a current into the wall (Iwall) with a large uncertainty (factors ~3 are possible [4]).…”

“…The experimental results are based on the electron detector in [4]. The direct output provided by this detector is a voltage, which can be converted to a current into the wall (Iwall) with a large uncertainty (factors ~3 are possible [4]). Despite this large error, it has been decided to show the experimental observations in terms of Iwall, expressed in ($).…”