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Low-emittance thermionic-gun-based injector for a compact free-electron laser

Takao Asaka, Hiroyasu Ego, Hirohumi Hanaki, Toru Hara, Taichi Hasegawa, Teruaki Hasegawa, Takahiro Inagaki, Toshiaki Kobayashi, Chikara Kondo, Hirokazu Maesaka, Shinichi Matsubara, Sakuo Matsui, Takashi Ohshima, Yuji Otake, Tatsuyuki Sakurai, Shinsuke Suzuki, Yasuyuki Tajiri, Shinichiro Tanaka, Kazuaki Togawa, and Hitoshi Tanaka
Phys. Rev. Accel. Beams 20, 080702 – Published 14 August 2017

Abstract

A low-emittance thermionic-gun-based injector was developed for the x-ray free-electron laser (XFEL) facility known as the SPring-8 angstrom compact free-electron laser (SACLA). The thermionic-gun-based system has the advantages of maintainability, reliability, and stability over a photocathode radio-frequency (rf) gun because of its robust thermionic cathode. The basic performance of the injector prototype was confirmed at the SPring-8 compact self-amplified spontaneous emission source (SCSS) test accelerator, where stable FEL generation in an extreme ultraviolet wavelength range was demonstrated. The essential XFEL innovation is the achievement of a constant beam peak current of 3–4 kA, which is 10 times higher than that generated by the SCSS test accelerator, while maintaining a normalized-slice emittance below 1 mm mrad. Thus, the following five modifications were applied to the SACLA injector: (i) a nonlinear energy chirp correction; (ii) the optimization of the rf acceleration frequency; (iii) rf system stabilization; (iv) nondestructive beam monitoring; and (v) a geomagnetic field correction. The SACLA injector successfully achieved the target beam performance, which shows that a thermionic-gun-based injector is applicable to an XFEL accelerator system. This paper gives an overview of the SACLA injector and describes the physical and technical details, together with the electron beam performance obtained in the beam commissioning.

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  • Received 28 December 2016

DOI:https://doi.org/10.1103/PhysRevAccelBeams.20.080702

Published 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 Society

Physics Subject Headings (PhySH)

  1. Research Areas
Accelerators & Beams

Authors & Affiliations

Takao Asaka1, Hiroyasu Ego1,2, Hirohumi Hanaki2, Toru Hara1, Taichi Hasegawa3, Teruaki Hasegawa1, Takahiro Inagaki1, Toshiaki Kobayashi2, Chikara Kondo1, Hirokazu Maesaka1, Shinichi Matsubara2, Sakuo Matsui1, Takashi Ohshima1, Yuji Otake1, Tatsuyuki Sakurai2, Shinsuke Suzuki2, Yasuyuki Tajiri3, Shinichiro Tanaka3, Kazuaki Togawa1, and Hitoshi Tanaka1

  • 1RIKEN SPring-8 Center, Kouto 1-1-1 Sayo, Hyogo 679-5148, Japan
  • 2Japan Synchrotron Radiation Research Institute (JASRI), Kouto 1-1-1 Sayo, Hyogo 679-5198, Japan
  • 3SPring-8 Service Company Limited, Kouto 1-20-5, Shingu-cho, Tatsuno, Hyogo 679-5165, Japan

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Issue

Vol. 20, Iss. 8 — August 2017

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