Status and upgrade of the compact SR ring 'HiSOR'

'HiSOR' is a compact synchrotron light source constructed at Hiroshima Synchrotron Radiation Center, Hiroshima University in 1996. The ring has two 180deg degree bending magnets, which generate 2.7 T magnetic field and the 700-MeV electron beam circulates at the radius 0.87 m. This racetrack-type ring has two undulators, linear and helical, in each the straight section. HiSOR is a VUV-ring having 1.4 nm critical wavelength. At the beginning, it started the operation at 100 mA stored current. After some improvements and tuning in 2000, the current increased to 200 mA. Now, we are on the next step to accumulate 300 mA, which is the primary specification. There are two main modifications, one is the upgrade of the control system, and the other replacing the RF cavity with new one to suppress undesirable HOM's. In addition, we are installing a Randau cavity for tuning flexibility. (author)