Lasing in visible and ultraviolet regions in an optical klystron installed on the VEPP‐3 storage ring (invited)

Since 1979, experiments on the storage ring VEPP‐3 with an optical klystron (OK) have been performed at the INP Academy of Sciences of the USSR. In 1979, 1981, and 1983, three different OK magnetic systems based on SmCo permanent magnets undulators were installed at the VEPP‐3 straight section at 6300‐A wavelength. The following gains per pass have been obtained: 0.5% in 1980, 1% in 1982, and 2%–2.5% in 1984. In late 1985, we decided to improve the storage ring VEPP‐3 and develop a dc bypass, a special straight section dedicated for OK operation. The bypass allowed us to install an OK magnetic system of 7.8 m length and significantly increase the gain per pass in March of 1988. The bypass was installed at the storage ring VEPP‐3 on 3 June 1988. We obtained lasing in the red and yellow light spectral range from 5800 to 6900 A with 5%–10% gain per pass. After changing mirrors for new ones with minimum losses at 4150 A, lasing in the violet and near UV spectral range with 3%–6% gain per pass from 4500 to 3750 A was obtained on 8 July. All work is being carried out at an energy of 350 MeV. Threshold currents for lasing are 1–10 mA depending on the optical cavity mirror conditions. The maximum current is 80 mA at present. A set of measurements on studying lasing in various conditions is underway.