First lasings at 0.27-0.37 mu m and 0.51-0.63 mu m using an S-band electron linac with a thermionic gun

First lasings at 0.27-0.37 mu m and 0.51-0.63 mu m were achieved by using a 2.68 m long undulator and a 6.72 m long optical cavity installed in the 165 MeV beam line of the FELI S-band linac with a thermionic triode gun. The strong-focusing, short-bunching process in the injector and 24 mu s stable RF pulses allowed lasing at 0.27 mu m in spite of a small signal gain of near 6%. The observed peak and average powers are 1.8 MW and 4 mW at 0.35 mu m and 4.7 MW and 14 mW at 0.6 mu m at the upstream cavity mirror.