Present status of a 500 MeV compact electron storage ring for UV FEL experiments

Abstract We have constructed a racetrack-type compact electron storage ring “NIJI-IV” for UV FEL experiments. The ring has a hexagonal configuration with a circumference 29.6 m. consisting of the two-cell structure of the triple-bend achromat lattice. The length of the straight section is 7.25 m in which a 6.3 m insertion device can be installed. A stored current higher than 200 mA is expected. The first storage of electrons was achieved on February 15, 1991, with an injection energy of 270 MeV. At present, a stored current higher than 70 mA with a lifetime of 20 to 30 min is obtained at full bunch operation (the harmonic number is sixteen).