The Polarized Electron Source for the International Collider (ILC) Project

Abstract

The ILC project will be the next large high energy physics tool that will use polarized electrons (and positrons). For this machine spin physics will play an important role. The polarized electron source design is based on electron injectors built for the Stanford Linear Collider (polarized) and Tesla Test Facility (un-polarized). The ILC polarized electron source will provide a 5GeV spin polarized electron beam for injection into the ILC damping ring. Although most ILC machine parameters have been achieved by the SLC or TTF source, features of both must be integrated into one design. The bunch train structure presents unique challenges to the source laser drive system. A suitable laser system has not yet been demonstrated and is part of the ongoing R&D program for ILC at SLAC. Furthermore, ILC injector R&D incorporates photocathode development, increasing available polarization, and improving operational properties in gun vacuum systems. Another important area of research and development is advancing the design of DC and RF electron gun technology for polarized sources. This presentation presents the current status of the design and outlines aspects of the relevant R&D program carried out within the ILC community.

Automated Activation Procedure for GaAs Photocathodes at Photo-CATCH*

“…High-current electron beams with a high degree of spin-polarization are in demand for a multitude of state-of-the-art particle accelerator applications such as energy-recovery linacs (ERLs [1,2]), positron sources [3,4] and colliders [5][6][7]. Direct-current (DC) high-voltage (HV) photoemission guns using negative electron affinity (NEA) gallium arsenide (GaAs) photocathodes are currently the best available source to provide these required beam parameters.…”

Cryogenic GaAs cathode development for improved lifetime

“…Photo-guns with semiconductor photo-cathodes like GaAs provide a source for high-current, low emittance electron beams necessary for ERL experiments [1], positron production [2], or future colliders in general [3]. For highly polarized beams a negative-electron affinity (NEA) coating of the cathode is essential for photo emission.…”

Lifetime Measurements of GaAs photocathodes at the Upgraded Injector Test Facility at Jefferson Lab*

“…Electron sources providing a high degree of polarization and high beam current are in demand for a multitude of accelerator applications, such as energy-recovery linacs (ERLs [1,2]), positron sources [3], colliders [4] and electron cooling at high-energy storage rings [5]. Promising candidates are based on state-of-the-art dircet-current (DC) high-voltage (HV) photo-emission guns, using photo-cathodes based on the III-V semiconductor gallium arsenide (GaAs).…”