A high power iodine photodissociation laser(IPL) amplifier system of 1GW is designed and developed. The amplifier system consists of an oscillator, two pre-amplifiers, and a main amplifier. The output characteristics of the amplifier system are examined with $TEM_00$ mode. The gas pressure of laser medium, $i-C_3F_7I$, of the oscillator, the first pre-amplifier, and the second pre-amplifier are fixed to 80, 100, and 60 torr, respectively. The maximum output energy of the main amplifier is measured to be 12.7J for the pressure of 40torr, and the operating voltage of 24kV. The conversion efficiency of stored electrical energy to laser energy is 0.26%. The pulse width of the main amplifier output is found to be 13.3ns for 50ns output pulse of the oscillator, and the maximum output power of the entire amplifier system is 0.96GW.
The emission characteristics of the x-ray from the plasma produced by this 0.96GW IPL beam are investigated. The size of the plasma is measured to be 165, 199, 206, and 337㎛ for the focussing lenses with focal length f'=6, 10, 14, and 25cm, respectively. The relative intensity of the x-ray is more intense for the target with higher atomic number and for the lens with shorter focal length. The spectral intensity distribution of the x-ray from the laser plasma is examined by x-ray diffraction experiment using a convex curved mica (2d=19.84$À$) crystal spectrometer. For the Ti target and laser intensity of $2.87×10^12W/㎠$ the experiment gives the result that there is no significant line spectrum in continuous spectrum in continuous spectrum.
The plasma electron temperature is determined by numerically fitting the theoretical curve to the normalized experimental data obtained from the exposed x-ray film. It is obtained as 0.57, 0.51, 0.49, 0.43, and 0.35keV for Al, Ti, Fe, Cu, and Mo target, respectively at the laser intensity of $2.87×10^12W/㎠$.
The reflection of the laser beam backscattered from the plasma through the focussing lens is measured to be 4.7% for Al and 12.0% for Mo target. The FWHM of reflected laser pulse from the plasma is decreased by 1.5ns for Al and 4.5ns for Mo.
For the purpose of comparison with laser plasma, the Mather type dense plasma focus(DPF) unit(50μF,20kV) is developed and its electrical characteristics are examined. The time delay before the DPF occurs is 5.85μs for the Ar gas pressure of 0.3torr and the capacitor charging voltage of 18kV, then the plasma sheath velocity is $4.27×10^6cm/s$.
