R&D towards cooling of the RHIC Collider

Abstract

We introduce the R&D program for electron-cooling of the Relativistic Heavy Ion Collider (RHIC). This electron cooler is designed to cool 100 GeVInucleon bunchedbeam ion collider at storage energy using 54 MeV electrons. The electron source will be an RF photocathode gun. The accelerator will be a superconducting energy recovery linac. The frequency of the accelerator is set at 703.75 MHz. The maximum bunch frequency is 28.15 MHz, with bunch charge of 10 nC. The R&D program has the following components: The photoinjector, the superconducting linac, start-to-end 'beam dynamics with magnetized electrons, electron cooling calculations and development of a large superconducting solenoid.

Cold electron beams from cryocooled, alkali antimonide photocathodes

“…The quest for photocathodes that generate electron beams with increased brightness to drive x-ray free electron lasers (FEL) [1], energy recovery linacs (ERL) [2], electron cooling of hadron beams [3], inverse Compton scattering [4], and ultrafast electron diffraction (UED) [5] experiments has recently received much attention from the scientific community, resulting in a stronger interaction between accelerator and solid state physicists trying to identify suitable materials with improved performance for future accelerators and novel applications [6].…”

“…For high current (∼100 mA) applications, like ERL's [2] and electron cooling [3], QE's of a few percent or more in the visible range of the spectrum are needed in order to maintain the average laser power within a few tens of Watts [2]. However, for most other applications such as single pass FEL's or UED setups, where the current requirement is in the 100 μA range or lower [1] and/or the maximum charge per bunch extracted should be kept small enough to avoid space charge emittance degradation QE in the 10 −5 range in the visible or UV light is acceptable.…”

Ultrabright and Ultrafast III–V Semiconductor Photocathodes

“…These sources enable applications such as ultrafast electron diffraction (UED) [2], inverse compton scattering [3], electron cooling of hadron beams [4], polarized electron beams for colliders, and modern light sources based on freeelectron lasers [5] or energy recovery linacs [6].…”

Review and demonstration of ultra-low-emittance photocathode measurements

“…The increased electron beam brightness from photocathodes enhances the performance of accelerators and enables new applications [1][2][3][4] such as Free electron Lasers (FELs), Energy Recovery Linacs (ERLs), and ultra-fast electron diffraction (UED). 5 Properties like quantum efficiency (QE), mean transverse energy (MTE) or intrinsic emittance, response time, and robustness are important figures of merit to determine the photocathode performance.…”