Fig. 11-1 Performance of the superconducting cavity test stand

Fig. 11-2 Electric properties of a single-cell cavity

Two kinds of superconducting accelerators have been operated at the JAERI Tokai Establishment. One is an accelerator for the free electron laser, which accelerates electrons up to the velocity of light, and the other is the tandem-booster for heavy ion acceleration. Now a third more technically challenging device is planned for the Tokai Establishment. We are pursuing the development of a large-scale superconducting proton linear accelerator. The operating parameters of the superconducting accelerator, which are 1.5 GeV and 8 MW, have no precedent in the world. Since the proton velocity varies in the course of acceleration, eight kinds of cavities will be arrayed to match the velocity; about 300 cavities in total will be manufactured and arrayed in a straight line. However, since a very high-intensity electric field can be produced in the cavities, the linear accelerator will be only about 800 m in total length. The superconducting cavities are made of niobium and cooled to ultra-low temperatures during operation. Since a need to develop many of the technological items in the manufacturing process is anticipated, research and development is now being conducted using a test stand. In initial testing, a high-intensity electric field of 18 MV/m was obtained at 2 K in a single-cavity test.

Reference N. Ito et al., Development of Superconducting Cavity for the High Intensity Proton Linac in JAERI, Proc. 18th Int. Linear Accelerator Conf., Aug. 26-30, 1996, Geneva, 671 (1996).

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