• P. Mercère, R. Bachelard, M.-E. Couprie, M. Idir
  SOLEIL, Gif-sur-Yvette
• S. Bucourt, G. Dovillaire, X. Levecq
  Imagine Optic, Orsay
• O.V. Chubar
  BNL, Upton, Long Island, New York
• J. Gautier, G. Lambert, P. Zeitoun
  LOA, Palaiseau
• T. Hara, A. Higashiya, T. Ishikawa, M. Nagasono, M. Yabashi
  RIKEN/SPring-8, Hyogo
• H. Kimura, H. Ohashi
  JASRI/SPring-8, Hyogo-ken

The VUV Self-Amplified Spontaneous Emission of the SPring-8 Compact SASE Source (SCSS) Test Accelerator is characterized at different stages of amplification up to saturation [1]. Experimental measurements are performed by use of a VUV Hartmann wavefront sensor. This kind of sensor gives access to both intensity and phase profiles of the incoming beam. We characterize the mode selection when approaching the saturation regime of the FEL. Optical quality of the saturated SASE radiation is measured to be better than Lambda/5 PV and Lambda/22 rms (Lambda = 61.5 nm) depending on the machine optimization. Moreover, pointing of the beam as well as spatial structure, size and position of the source are retrieved and their shot-to-shot fluctuations investigated. Analytical [2] and numerical calculations [3], using SRW and GENESIS codes, show good agreement with the experimental measurements. All these elements are of crucial importance for a better understanding and optimization of the FEL and of course for user applications requiring a stable focused beam on their samples. We are grateful to the SCSS Test Accelerator Operation Group at RIKEN for continuous support in the course of the studies

[1] R. Bachelard et al., "Wavefront and Transverse Structure of the FEL Self-Amplified Spontaneous Emission", to be submitted
[2] M. Xie, NIMA 445, 59(2000)
[3] O. Chubar et al., Proc. EPAC-98, 1177(1998)

Slides

• H. Tanaka, T. Fukui, T. Hara, N. Hosoda, T. Inagaki, S.I. Inoue, T. Ishikawa, H. Kitamura, C. Kondo, N. Kumagai, H. Maesaka, M. Nagasono, T. Ohshima, Y. Otake, T. Sakurai, T. Shintake, K. Shirasawa, T. Tanaka, K. Togawa, K. Tono, M. Yabashi
  RIKEN/SPring-8, Hyogo
• T. Hasegawa, Y. Kano, T. Morinaga, H. Ohashi, Y. Tajiri, S. Takahashi, S. Tanaka, T. Togashi, M. Yamaga, R. Yamamoto
  JASRI/SPring-8, Hyogo-ken

Stable SASE FEL has been routinely used for user experiments since May 2008 at the SCSS test accelerator, which was constructed to perform a proof-of-principle experiment towards realization of a compact and high performance XFEL facility. In FY2008, a beam time of 840 hr (95 days) was provided to 11 research groups with a downtime rate of ~4%, a pulse energy of ~30μJ and an intensity fluctuation of ~10% in STD. A feature of our stable operation is power-saturated SASE FEL kept over a full operation period

1. in spite of a day-by-day operation,
2. without a complicated beam feedback control, and
3. without hard maintenance.

Slides