Erdong Wang

K2CsSb Cathode Development

K2CsSb is an attractive photocathode for high current applications. With a quantum efficiency of >4% at 532 nm and >10% at 355 nm, it is the only cathode to have demonstrated an average current of 35 mA in an accelerator environment. We describe ongoing cathode development work for the energy recovery linac being constructed at BNL. Several cathodes have been created on both copper and stainless steel substrates, and their spatial uniformity and spectral response have been characterized. Preliminary lifetime measurements have been performed at high average current densities (>1 mA/mm2).

Conceptual design of a Polarized Electron Ion Collider at Brookhaven National Laboratory

To facilitate the SAC 2015 Long Range Plan for Nuclear Science: a high-energy high-luminosity polarized Electron-Ion Collider (EIC) as the highest priority for new facility construction following the completion of FRIB. Brookhaven National Laboratory (BNL) is proposing to build a high luminosity electron-hadron collider called e-RHIC which incorporates a new electron synchrotron with the existing Relativistic Heavy Ion Collider (RHIC). A low risk conventional technology based design is being adopted for the majority of the accelerator components. The e-RHIC electron source will produce a highly polarized beam current of up to 50 mA with > 80% polarization at an energy of up to 18 GeV with a luminosity > 1034 cm-2s-1. The prototype e-RHIC beam source is currently under development at BNL and Stony Brook University. This paper presents a conceptual design of the e-RHIC machine, how polarized beam will enhance the physics program and plans to address the remaining challenges associated with the construction of e-RHIC. In order to construct a future electron ion collider with high luminosity, a high average current and high bunch charge polarized electron source is under development at Brookhaven National Laboratory. We present the R&D plan for achieving the required charge and current in the polarized eRHIC gun.. The plan involves developing a large single cathode gun to generate 5.3 nC and 6 mA polarized electrons beam. We report the progress of large cathode prototype gun development, the beam line design and plan for measuring gun charge lifetime for high bunch charge, high current operation.

Record Performance of SRF Gun with CsK2Sb Photocathode

High-gradient CW photo-injectors operating at high accelerating gradients promise to revolutionize many sciences and applications. They can establish the basis for super-bright monochromatic X-ray and gamma-ray sources, high luminosity hadron colliders, nuclearwaste transmutation or a new generation of microchip production. In this paper we report on our operation of a superconducting RF electron gun with a record-high accelerating gradient at the CsK2Sb photocathode (i.e. ~ 20 MV/m) generating a record-high bunch charge (i.e., 2 nC). We briefly describe the system and then detail our experimental results. INTRODUCTION The coherent electron cooling experiment (CeC PoP) [1, 2] is expected to demonstrate cooling of a single hadron bunch in RHIC. A superconducting RF gun operating at 112 MHz frequencies generates the electron beam. 500MHz normal conducting cavities provide energy chirp for ballistic compression of the beam. 704-MHz superconducting cavity will accelerate beam to the final energy. The electron beam merges with the hadron beam and after cooling process is steered to a dump. The FEL-like structure enhances the electron-hadron interaction. The electron beam parameters are shown in the Table 1. Table 1: Parameters of the Electron Beam