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Wijethunga SAK, Mamun MA, Suleiman R, Hernandez-Garcia C, Bullard B, Delayen JR, Grames J, Krafft GA, Palacios-Serrano G, Poelker M. Improving the electrostatic design of the Jefferson Lab 300 kV DC photogun. Rev Sci Instrum 2022; 93:073303. [PMID: 35922315 DOI: 10.1063/5.0091134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Accepted: 05/23/2022] [Indexed: 06/15/2023]
Abstract
The 300 kV DC high voltage photogun at Jefferson Lab was redesigned to deliver electron beams with a much higher bunch charge and improved beam properties. The original design provided only a modest longitudinal electric field (Ez) at the photocathode, which limited the achievable extracted bunch charge. To reach the bunch charge goal of approximately few nC with 75 ps full-width at half-maximum Gaussian laser pulse width, the existing DC high voltage photogun electrodes and anode-cathode gap were modified to increase Ez at the photocathode. In addition, the anode aperture was spatially shifted with respect to the beamline longitudinal axis to minimize the beam deflection introduced by the non-symmetric nature of the inverted insulator photogun design. We present the electrostatic design of the original photogun and the modified photogun and beam dynamics simulations that predict vastly improved performance. We also quantify the impact of the photocathode recess on beam quality, where recess describes the actual location of the photocathode inside the photogun cathode electrode relative to the intended location. A photocathode unintentionally recessed/misplaced by sub-millimeter distance can significantly impact the downstream beam size.
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Affiliation(s)
| | - M A Mamun
- Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
| | - R Suleiman
- Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
| | - C Hernandez-Garcia
- Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
| | - B Bullard
- Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
| | - J R Delayen
- Old Dominion University, Norfolk, Virginia 23529, USA
| | - J Grames
- Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
| | - G A Krafft
- Old Dominion University, Norfolk, Virginia 23529, USA
| | - G Palacios-Serrano
- Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
| | - M Poelker
- Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
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Wang E, Litvinenko VN, Pinayev I, Gaowei M, Skaritka J, Belomestnykh S, Ben-Zvi I, Brutus JC, Jing Y, Biswas J, Ma J, Narayan G, Petrushina I, Rahman O, Xin T, Rao T, Severino F, Shih K, Smith K, Wang G, Wu Y. Long lifetime of bialkali photocathodes operating in high gradient superconducting radio frequency gun. Sci Rep 2021; 11:4477. [PMID: 33627743 PMCID: PMC7904862 DOI: 10.1038/s41598-021-83997-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 02/08/2021] [Indexed: 11/09/2022] Open
Abstract
High brightness, high charge electron beams are critical for a number of advanced accelerator applications. The initial emittance of the electron beam, which is determined by the mean transverse energy (MTE) and laser spot size, is one of the most important parameters determining the beam quality. The bialkali photocathodes illuminated by a visible laser have the advantages of high quantum efficiency (QE) and low MTE. Furthermore, Superconducting Radio Frequency (SRF) guns can operate in the continuous wave (CW) mode at high accelerating gradients, e.g. with significant reduction of the laser spot size at the photocathode. Combining the bialkali photocathode with the SRF gun enables generation of high charge, high brightness, and possibly high average current electron beams. However, integrating the high QE semiconductor photocathode into the SRF guns has been challenging. In this article, we report on the development of bialkali photocathodes for successful operation in the SRF gun with months-long lifetime while delivering CW beams with nano-coulomb charge per bunch. This achievement opens a new era for high charge, high brightness CW electron beams.
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Affiliation(s)
- E Wang
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.
| | - V N Litvinenko
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.,Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - I Pinayev
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - M Gaowei
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - J Skaritka
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - S Belomestnykh
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA.,Fermi National Accelerator Laboratory, Batavia, IL, 60510, USA
| | - I Ben-Zvi
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.,Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - J C Brutus
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Y Jing
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.,Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - J Biswas
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - J Ma
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - G Narayan
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - I Petrushina
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.,Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - O Rahman
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - T Xin
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
| | - T Rao
- Instrumentation Division, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - F Severino
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - K Shih
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - K Smith
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - G Wang
- Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.,Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Y Wu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
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