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- H. Hanaki, T. Asaka, H. Ego, H. Kimura, T. Kobayashi, S. Suzuki
JASRI/SPring-8, Hyogo-ken
- T. Hara, A. Higashiya, T. Inagaki, N. Kumagai, H. Maesaka, Y. Otake, T. Shintake, H. Tanaka, K. Togawa
RIKEN/SPring-8, Hyogo
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The SPring-8 X-FEL based on the SASE process has been developed to generate X-rays of 0.1 nm by the combination of an 8 GeV high gradient linac (400 m) and a mini-gap undulator of in-vacuum type (90 m). The design goals of the slice beam emittance and peak current at the end of the linac are 1 π mm mrad and 3 kA, respectively. The injector of the linac generates an electron beam of 1 nC, accelerates it up to 30 MeV, and compresses its bunch length down to 20 ps step by step. The injector has been designed on the basis of the SCSS test accelerator. We adopted the following keys to toward the goals:- A 500 kV thermionic gun (CeB6) without a control grid ejecting a beam holding the low rms emittance of 1.1 π mm mrad,
- a beam deflector downstream gating the beam to form a bunch of a 1 ns length,
- multi-stage RF structures (238, 476 and 1428 MHz) bunching and accelerating the beam gradually to maintain the initial emittance, and
- extra RF cavities of 1428 and 5712 MHz linearizing the energy chirp of the beam bunch to achieve the bunch compression resulting the required peak current.
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