The effects of multi-pulse irradiation on X-ray laser media

Multipulse irradiation with 100 ps pulses of stripe Germanium targets is shown to enhance by up to several orders-of-magnitude the output of Ne-like Ge lasing on the J = 0-1 line at 196 Angstrom compared to single pulse pumping. Various pre-pulse and multipulse configurations have been experimentally investigated for irradiances of approximate to 4 x 10(13) W/cm(2) with a 1.06 mu m wavelength pumping laser. The ionisation balance measured by a KeV crystal spectrometer (KAP crystal) has been found to not affect the X-ray laser output. Good agreement between the experimental results and a fluid code incorporating atomic physics, gain and X-ray beam ray tracing is obtained. The code results show that the enhanced X-ray laser output is produced by multipulse irradiation reducing the electron density gradients in the gain region and simultaneously increasing the gain region spatial size. These changes reduce the effect of refraction on the X-ray laser beam propagation.

Saturated output of a Ge XXIII x-ray laser at 19.6 nm

We report on measurements of the saturated single frequency output of a Ge XXIII x-ray laser on the J=0-->1 transition at 19.6 nm from a refraction compensating double target driven by 150 J of energy from 75-ps Nd-glass laser pulses. The 19.6-nm line completely dominated the laser output. The output energy was measured to be 0.9 mJ in a beam of 6.6x30 mrad(2) divergence, corresponding to a conversion efficiency of 6 x 10(-6).

Spectroscopic characterization of prepulsed x-ray laser plasmas

Through the use of time-integrated space-resolved keV spectroscopy, we investigate line plasmas showing gain in Ne-like nickel, copper, and zinc for irradiation using the prepulse technique. The experiments were conducted at 1.06 mu m with the prepulse to main pulse intensity contrast ranging from 10(-6) to 10(-2). The effect of the prepulses on the plasma conditions is inferred through spectroscopic line ratio diagnostics for the electron temperature, the Ne-like ground-state density, and the lateral size of the Ne-like region. It is observed that neither the value of the electronic temperature nor its spatially resolved profile along the linear focus axis varies significantly with the prepulse level, contrary to the lateral width and the density of the Ne-like region in the plasma, which are seen to increase. These results explain, at least in part, why prepulsed x-ray lasers show such high gain and brightness.

High-gain x-ray lasing at 11.1 nm in sodiumlike copper driven by a 20-J, 2-ps Nd:glass laser

Evidence of high gain pumped by recombination has been observed in the 5g-4f transition at 11.1 nn in sodiumlike copper ions with use of a 20-J 2-ps Nd:glass laser system. The time- and space-integrated gain coefficient was 8.8 +/- 1.4 cm(-1), indicating a single-transit amplification of similar to 60 times. This experiment has shown that 2 ps is the optimum pulse duration to drive the sodiumlike copper recombination x-ray lasing at 11.1 nm. (C) 1996 Optical Society of America

Characteristics of rapidly recombining plasmas suitable for high-gain X-ray laser action

Recombining plasmas produced by picosecond laser pulses are characterized by measuring ratio of intensities of resonance lines of H- and He-like ions in the plasmas. It is found that the rapidly recombining plasmas produced by picosecond laser pulses are suitable for high-gain operation.

Collisional exitation soft X-ray laser at 23.6 nm in a laser-produced cylindrical target

We have tested soft X-ray lasing in neon-like germanium with cylindrical targets where wave guiding and plasma confinement may affect lasing. An intense soft X-ray laser beam of 0.05 MW peak power and a narrow beam divergence (8 mrad) was produced at 23.6 nm with a 4 cm long straight cylindrical target of 0.72 mm inner diameter. Bending the cylindrical target to form a toroidal shape increased the lasing intensity by a factor of 3 accompanied with reduction of the beam divergence from 8 to 6 mrad.

EFFECT OF WEAK PREPULSES ON COLLISIONAL X-RAY LASER PLASMAS

Through the use of time-integrated space-resolved keV spectroscopy, we characterize line plasmas showing gain in Ne-like Zn with prepulsed irradiation to explain the enhanced performances of x-ray lasers using the prepulse technique. It is observed that the value of the electron temperature does not vary significantly with prepulse level, nor does its spatially resolved profile along the line. The lateral width and density of the Ne-like region in the plasma are seen to increase with the prepulse level. (C) 1995 Optical Society of America

LASING PROPERTIES OF THE J = 0-1 AND THE J = 2-1 LINES OF A NEON-LIKE GERMANIUM SOFT-X-RAY LASER

Lasing properties of a collisional-excitation Ne-like Ge soft-x-ray laser have been studied with exploding-foil, single-slab, and double-slab targets under identical pumping conditions. Experimental results for the angular intensity distributions and the temporal variations of the lasing intensities are examined with a hydrodynamic code and ray-trace calculations. The observed angular distribution are well reproduced by these analyses, and it is found that the effective gain regions are located on the high-density side of the expected gain regions. It is shown that the observed lasing intensity of the J = 0 to J = 1 line is strongly correlated with the temporal change of the calculated electron temperature for both the slab and the exploding-foil targets.