R. Than

Design of a high-bunch-charge 112-MHz superconducting RF photoemission electron source

High-bunch-charge photoemission electron-sources operating in a continuous wave (CW) mode are required for many advanced applications of particle accelerators, such as electron coolers for hadron beams, electron-ion colliders, and free-electron lasers. Superconducting RF (SRF) has several advantages over other electron-gun technologies in CW mode as it offers higher acceleration rate and potentially can generate higher bunch charges and average beam currents. A 112 MHz SRF electron photoinjector (gun) was developed at Brookhaven National Laboratory to produce high-brightness and high-bunch-charge bunches for the coherent electron cooling proof-of-principle experiment. The gun utilizes a quarter-wave resonator geometry for assuring beam dynamics and uses high quantum efficiency multi-alkali photocathodes for generating electrons.

Progress of 650 MHz SRF Cavity for eRHIC SRF Linac

A high-current, well-damped 5-cell 647 MHz cavity was designed for ERL-Ring based eRHIC. Two prototype cavities were contracted to RI Research Instruments GmbH: one copper cavity with detachable beampipes for HOM damping study, and one niobium cavity for performance study. The performance study includes high-Q study for ERL-Ring eRHIC design and high gradient study for Ring-Ring eRHIC design. This paper will present the preliminary results of the HOM study, progress on Nb cavity fabrication and preparation for vertical test.

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

Cryogenic systems for proof of the principle experiment of coherent electron cooling at RHIC

The Coherent electron Cooling (CeC) Proof of Principle (PoP) experiment is proposed to be installed in the Relativistic Heavy Ion Collider (RHIC) to demonstrate proton and ion beam cooling with this new technique that may increase the beam luminosity in certain cases, by as much as tenfold. Within the scope of this project, a 112 MHz, 2MeV Superconducting Radio Frequency (SRF) electron gun and a 704 MHz 20MeV 5-cell SRF cavity will be installed at IP2 in the RHIC ring. The superconducting RF electron gun will be cooled in a liquid helium bath at 4.4 K. The 704 MHz 5-cell SRF cavity will be cooled in a super-fluid helium bath at 2.0 K. This paper discusses the cryogenic systems designed for both cavities. For the 112 MHz cavity cryogenic system, a condenser/boiler heat exchanger is used to isolate the cavity helium bath from pressure pulses and microphonics noise sources. For the 704 MHz 5-cell SRF cavity, a heat exchanger is also used to isolate the SRF cavity helium bath from noise sources in the sub-atmospheric pumping system operating at room temperature. Detailed designs, thermal analyses and discussions for both systems will be presented in this paper.

The Relativistic Heavy Ion Collider (RHIC) cryogenic system at Brookhaven National Laboratory: Review of the modifications and upgrades since 2002 and planned improvements.

Brookhaven National Laboratory continues its multi-year program to improve the operational efficiency, reliability, and stability of the cryogenic system, which also resulted in an improved beam availability of the Relativistic Heavy Ion Collider (RHIC). This paper summarizes the work and changes made after each phase over the past four years to the present, as well as proposed future improvements. Power usage dropped from an initial 9.4 MW to the present 5.1 MW and is expected to drop below 5 MW after the completion of the remaining proposed improvements. The work proceeded in phases, balancing the Colliders schedule of operation, time required for the modifications and budget constraints. The main changes include process control, compressor oil removal and management, elimination of the use of cold compressors and two liquid-helium storage tanks, insulation of the third liquid-helium storage tank, compressor-bypass flow reduction and the addition of a load turbine (Joule-Thomson expander) with associat...