Design and test of 704 MHz and 2.1 GHz normal conducting cavities for low energy RHIC electron cooler

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The Low Energy RHIC electron Cooling (LEReC) project at Brookhaven National Laboratory recently demonstrated for the first time cooling of hadron bunches with radio-frequency (rf) accelerated electron bunches. LEReC uses a high-voltage photoemission electron gun with stringent requirements for beam current, beam quality, and stability. The electron gun has a photocathode with a high-power fiber laser, and a novel cathode production, transport, and exchange system. It has been demonstrated that the high-voltage photoemission gun can continually produce a high-current electron beam with a beam quality suitable for electron cooling. We describe the operational experience with the LEReC dc photoemission gun in RHIC and discuss the important aspects needed to achieve the required beam current, beam quality, and stability.

Section: B the Lerec Acceleratormentioning

confidence: 99%

Stable operation of a high-voltage high-current dc photoemission gun for the bunched beam electron cooler in RHIC

Gu¹,

Altinbas²,

Badea³

et al. 2020

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“…The LEReC accelerator [16], shown in Fig. 1, consists of a 400 keV photo-gun [17] followed by a 704 MHz superconducting rf accelerating cavity (SRF Booster) [18], which accelerates the beam to 1.6-2.6 MeV. The photocathode is illuminated by a green 704 MHz laser modulated with the 9 MHz frequency to match the frequency of RHIC ions.…”

Section: Lerec Acceleratormentioning

confidence: 99%

Accurate setting of electron energy for demonstration of first hadron beam cooling with rf-accelerated electron bunches

Seletskiy

Blaskiewicz

Drees

et al. 2019

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The world's first electron cooling based on the rf acceleration of electron bunches was experimentally demonstrated at the Low Energy RHIC Electron Cooler (LEReC) at Brookhaven National Laboratory. The critical step in obtaining cooling of the Au ions in the collider with this new approach was matching the electron and ion relativistic γ-factors with a relative error of less than 5 × 10 −4. Since the electron beam kinetic energy was just 1.6 MeV, it was required to set the absolute energy of electrons with an accuracy better than 0.8 keV. The method of setting electron energy in conventional coolers was unsuitable for LEReC and a new technique had to be developed. In this paper we describe our experience with measuring the electron beam energy at LEReC and precisely matching electron and ion γ-factors, which resulted in demonstration of the cooling.

“…Design and commissioning of the rf cavities are described in Refs. [15][16][17][18][19][20]. 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].…”

Section: Introductionmentioning

confidence: 99%

High-brightness electron beams for linac-based bunched beam electron cooling

Kayran¹,

Altinbas²,

Bruno³

et al. 2020

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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.