Top-up operation at SPring-8

Japan Synchrotron Radiation Research Institute (JASRI)

[simulation results] Simulation results of the stored beam oscillation induced in the horizontal plane by using the ideal half-sine field shape.
Accelerator Division (Director, Noritaka Kumagai) of JASRI (Director-General, Akira Kira) successfully started the top-up operation of the SPring-8 storage ring. In the top-up operation, beam is injected with short intervals during user beamtime, and the current stored in the storage ring is kept constant. In the conventional operation, on the other hand, the stored current decayed with time and during beam injections, user experiments were interrupted due to beam orbit instabilities. Therefore, we were hard-pressed to come up with improvement measures.

[experimental results] Experimental results for performance of the bump leakage suppression.
The top-up operation realized at SPring-8 provides the solutions to the above problems. Moreover, this operation has unique and innovative features such as (1) a perturbation-free beam injection scheme, (2) minimum injection beam loss, (3) a high purity singlebunch beam. The SPring-8 top-up operation is, in a sense, an 'ideal top-up operation' which many light source facilities around the world have pursued.

This success of the top-up operation is expected to make the following improvements: (1) The time-averaged brilliance is increased by a factor of two. (2) Thermal stability of the X-ray optics is attained by stabilizing the stored beam current with a deviation of less than 0.1%, and accuracy of experimental data is improved. (3) A new filling pattern with a high bunch current is made available, which was not available in the conventional operation due to the extremely short beam lifetime. This will pave the way for new SR experiments with intense pulsed X-ray. The top-up operation was introduced on May 20, 2004 to user beamtime and users have great hopes for this new operation.

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Kenji Tsuda