1ST LASING OF THE NIJI-IV STORAGE-RING FREE-ELECTRON LASER

The first lasing at around 590 nm of a free-electron laser (FEL) in th e storage ring NIJI-IV was achieved on August 18, 1992, though just ab ove threshold, The NIJI-IV is a racetrack-type ring dedicated to FEL, which was completed in December 1990. Though the ring is compact, it h as two 7.25-m straight sections. The electron beam was stacked for the first time in February 1991. After a 6.3-m optical klystron was insta lled in one of the straight sections, FEL related experiments were sta rted at the end of April this year, and oscillation experiments have b een carried out since the beginning of August. The electron-beam energ y during the lasing was about 240 MeV, and the current was 1.1-0.2 mA/ bunch. The laser wavelength ranged from 594.5 to 588.7 nm, and the ban dwidth was below 0.4 nm.