• H. Toki, K. Sato
  RCNP, Osaka

The ordinary electric circuits produce and receive electromagnetic noise. The noise is a problem for stable operation of synchrotron accelerators. We do not know the origin of the noise generation due to the lack of electric circuit theory, which takes into account the noise sources. The proper treatment of electric circuit together with noise requires a proper knowledge of multiconductor transmission-line theory. We have developed a new multiconductor transmission-line theory in which we are able to describe the performance of multiconductor transmission-line system*. In this theory, it is essential to use the coefficients of potential instead of capacities and the introduction of the normal and common modes. After understanding the multiconductor transmission-line theory, we propose the introduction of the middle line (three lines) and symmetric arrangements of electric loads**. The use of this concept made the J-PARC MR successful in operation.

* H. Toki and K. Sato, J. Phys. Soc. Jpn 78 (2009) 094201.
** K. Sato and H. Toki, Nucl. Inst. Methods A565 (2006) 351.

• J. Watanabe, S. Kimura, K. Sato
  Toshiba, Yokohama
• T. Asaka, H. Ego, H. Hanaki
  JASRI/SPring-8, Hyogo-ken

TOSHIBA is manufacturing the L-band acceleration system for the SPring-8 Joint Project for XFEL. We have developed a new type duct-shaped SiC dummy load for its power distribution system. The load terminates a WR650 waveguide and can absorb the maximum mean power of 10kW. In order to reduce VSWR less than 1.1 in the frequency range of 1.428GHz, we shaped the SiC absorber into a 35cm long tapered cylinder and mounted matching stubs in the waveguide near the inlet of the load. The SiC absorber was fit into a cylindrical copper with efficient water-cooling channels. The design and manufacture and the low-power tests of our original dummy load are described in this paper.