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September 22, 2010

Next-generation light source gets boost from powerful new analysis technique

A new analysis technique for the design and optimization of beam optics has successfully been used to model the group behavior of electron beams over a linear accelerator, paving the way for its use at linear accelerator based light source facilities around the world. The technique contributes to improved operation of the X-ray Free-Electron Laser (XFEL) under construction at the RIKEN SPring-8 synchrotron radiation facility (Fig. 1), whose intense beams will open a unique window onto the minuscule structure of molecules and the rapid reaction of chemical species.

RIKEN SPring-8

Despite its key importance to all fields of science, the world of atoms and molecules exists beyond the reach of traditional observation techniques, holding back progress in research on everything from molecular biology to nanotechnology.

The new XFEL at RIKEN, Japan's flagship research institute, will shed first-ever light on this hidden world, delivering radiation one billion times brighter and with pulses one thousand times shorter than existing X-ray sources such as SPring-8. The XFEL facility will be only the second laser of its kind in the world when it opens in 2011.

Obtaining a stable XFEL beam, however, is not an easy task. To do so, the transverse distribution of electrons ejected from the XFEL's linear accelerator must be carefully calibrated each time conditions change to match the configuration of magnets (undulators) where X-ray laser radiation is emitted (Fig. 2). In experiments with a small test accelerator, researchers performed this calibration by directly measuring the laser intensity, but the full-sized XFEL is too complicated for this approach to work.

The new technique, developed at RIKEN and the Japan Synchrotron Radiation Research Institute (JASRI), solves this problem by rapidly and precisely computing the effect of changes in optics using information on electron beam distributions after full bunch compression (Fig. 3). By doing so, the technique plays a key role in ensuring the successful operation of the XFEL, whose intense beams promise to herald a new era of scientific exploration and discovery.

Reference

  • Toru Hara, Kazuaki Togawa and Hitoshi Tanaka. Transverse envelope analysis for accelerating relativistic electron beams in a linear accelerator as a photon source. Nuclear Instruments and Methods in Physics Research Section A, 17 September 2010. DOI: 10.1016/j.nima.2010.09.035

Contact

Hitoshi Tanaka
Beam Commissioning Team
XFEL Project Head Office
Tel/Fax: +81-(0)791-58-2862

Jens Wilkinson
RIKEN Global Relations and Research Coordination Office
Tel: +81-(0)48-462-1225 / Fax: +81-(0)48-463-3687
Email: pr@riken.jp

Aerial photo of the SPring-8 campus

Figure 1: Aerial photo of the SPring -8 campus

The long structure extending diagonally to the bottom-left is the X-ray Free-Electron Laser (XFEL). To its right is the storage ring of the SPring-8 synchrotron.

Matching an electron beam transverse distribution to focusing system of an undulator beamline

Figure 2: Matching an electron beam transverse distribution to focusing system of an undulator beamline

Schematic illustration of beam transverse distribution control using the developed "accelerator model"

Figure 3: Schematic illustration of beam transverse distribution control using the developed "accelerator model"