SOFT-X-RAY EMISSION PRODUCED BY A SUBPICOSECOND LASER IN A SINGLE-PULSE AND DOUBLE-PULSE SCHEME

The interaction of a high-contrast, 400 fs, 5x10(17) W/cm(2) laser pul se with a preformed tantalum plasma produced in a double-pulse configu ration is investigated. The x-ray emission characteristics are studied for different time delays between the two laser pulses. A time-resolv ed transmission grating spectrometer is used to measure the x-ray conv ersion efficiency and emission duration in the 0.2-1.2 keV energy rang e. Our results show that it is possible to increase the x-ray source c onversion efficiency by an order of magnitude simply by optimizing the delay between the laser pulses. To give an overview of the performanc es available from such laser-plasma x-ray sources, these results are c ompared those obtained with a single laser pulse in different interact ion regimes. (C) 1997 American Institute of Physics.