Abstract
A high-current high-brightness electron accelerator for low-energy RHIC electron cooling (LEReC) was successfully commissioned at Brookhaven National Laboratory. The LEReC accelerator includes a dc photoemission gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a superconducting rf booster cavity, and a set of normal conducting rf cavities to provide enough flexibility to tune the beam in the longitudinal phase space. Cooling with nonmagnetized rf accelerated electron beams requires longitudinal corrections to obtain a small momentum spread while preserving the transverse emittances. Electron beams with kinetic energies of 1.6 and 2.0 MeV with a beam quality suitable for cooling were successfully propagated through 100 m of beam lines, including dispersion sections, maintained through both cooling sections in RHIC and used for cooling ions in both RHIC rings simultaneously. The beam quality suitable for cooling RHIC beams was achieved in 2018, which led to the first experimental demonstration of bunched beam electron cooling of hadron beams in 2019.7 MoreReceived 22 November 2019Accepted 23 January 2020DOI:https://doi.org/10.1103/PhysRevAccelBeams.23.021003Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeam coolingBeam opticsHigh intensity beam dynamicsAccelerators & Beams
Highlights
A new, state-of-the-art, electron accelerator for cooling of low-energy RHIC ion beams (LEReC) was built and commissioned at Brookhaven National Laboratory (BNL) [1]
The highest-energy electron cooling using a dc electron beam was demonstrated at Fermi National Accelerator Laboratory (FNAL) [6]
The low-energy RHIC electron cooling (LEReC) accelerator includes a photocathode dc gun with a high-power laser system, magnets, beam diagnostics, a superconducting rf (SRF) booster cavity, and a set of normal conducting rf cavities to provide enough flexibility to tune the beam in the longitudinal phase space
Summary
A new, state-of-the-art, electron accelerator for cooling of low-energy RHIC ion beams (LEReC) was built and commissioned at Brookhaven National Laboratory (BNL) [1]. The 350–400 keV electron beam from the gun is transported to a 704 MHz SRF booster cavity, where electron bunches are accelerated off crest to produce an energy chirp, and to a 2.1 GHz third-harmonic normal conductive “linearizing” cavity. The optics of the entire transport line has been designed and optimized to deliver electron bunches of different energies with an electron beam quality suitable for cooling [21]. In the 76 kHz mode, the train repetition frequency is matched with the RHIC revolution frequency at the RHIC operational energy Each ion bunch interacts with the electrons in the cooling section
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