A NEW TARGET CONFIGURATION PRODUCING AN EFFECTIVE POPULATION-INVERSION AT ENERGY-LEVELS OF MG XI 1S3P AND 1S4P

A microtube target with lateral jet nozzle has recently been developed. Strong population inversion was observed along the whole jet nozzle between the energy level of MgXI 1s3p and that of 1s4p while the average laser irradiance was around 3. 5 multiplied by 10**1**3 W cm** minus **2 on the inner wall of the microtube targets. A corresponding average electron temperature of 470-520 eV and density of 2 multiplied by 10**2**0 cm** minus **3 at the inversion area of the plasma medium was measured. Possible mechanisms of the population inversion under the average high temperature condition have been analysed.