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.

PRELIMINARY STUDIES OF RADIATION COUPLING BETWEEN REMOTE SOFT-X-RAY LASER-AMPLIFIERS

Coupling of a soft X-ray laser beam with a relaying concave mirror in a sequentially pumped amplifier geometry using the Ne-like Ge system has been studied experimentally. Preliminary observations indicate an increase in the spatial coherence of the amplified relayed beam. In addition, near-field imaging of one of the amplifier plasmas shows a double-lobed intensity pattern of the emergent beam indicating refractive guiding of the amplified beam with components both normal and tangential to the target surface.

COHERENCE AND DOUBLE-PASS AMPLIFICATION IN GE SOFT-X-RAY LASER

From measurements of spatial coherence and beam divergence of Ge soft x-ray laser at a far field, the x-ray laser beam has been characterized as a partially coherent Gaussian beam. Double-pass amplification will improve spatial and temporal coherence, spectral brightness and efficiency. Close to 100% geometrical coupling efficiency has been obtained in double pass amplification in Ge. Transient loss of feedback is attributed to mirror structure damage within the build-up time of the x-ray laser. Prospect for generation of coherent x-ray laser beam is discussed.

COLLISION PUMPED SOFT-X-RAY LASERS - PROGRESS AT RAL

Recent developments and progress on collision pumped soft X-ray lasers using the VULCAN glass laser at Rutherford-Appleton Laboratory are presented. This includes saturated output operation of a double target germanium system within a low Fresnel number half-cavity, measurement of the spatial coherence of the output beam in the above and other geometries, use of the beam to demonstrate almost-equal-to 0.15 mum spatial resolution in a full-field microscope and initial studies of other Ne-like and Ni-like systems. Future directions, in the light of new developments of VULCAN facilities, are outlined.

MEASUREMENT OF THE PHOTO-PUMP STRENGTH OF THE 3D-5F TRANSITIONS IN THE AUTOMATICALLY LINE MATCHED NI-LIKE SM PHOTOPUMPED X-RAY LASER

The photo-pump strengths of both the ((3 (d) over bar(4))(0)(3d(6))(0))(0)-(((3 (d) over bar(3))(3/2)(3d(6))(0))(3/2)(5 (f) over bar)(5/2))(1) and the ((3 (d) over bar(4))(0)(3d(6))0)0-(((3 (d) over bar(4))(0)(3d(5))(5/2))(5/2)(5f)(7/2))(1) transitions in Ni-like Sm34+ have been measured to be 2.0 x 10(-4) and 2.4 x 10(-4) photons/mode respectively. The implications of the measurement are briefly discussed in a comparison of the merits of automatically line matched photo-pump scheme to those of the collisional excitation Ni-like Sm+34 scheme.

PROPERTIES OF AN EXPLODING FOIL NEON-LIKE GERMANIUM SOFT-X-RAY LASER

We describe the properties of the exploding foil neon-like germanium soft X-ray lasers having wavelengths of 19-28 nm and gain length product of more than 10. The measured X-ray intensity of lasing lines from an exploding foil target has been explained with the results of the plasma hydrodynamic code from the viewpoint of suitable condition of electron density and temperature for creating population inversion.

AN INJECTOR AMPLIFIER DOUBLE TARGET CONFIGURATION FOR THE NE-LIKE GE X-RAY LASER SCHEME

The XUV lasing output from one germanium slab target has been efficiently coupled into, and further amplified in, a second plasma produced by irradiation of a similar target from the opposite direction. The operation of such a double target was shown to be strongly dependent on the distance by which the two target surfaces were displaced. The line brightness peaked for a surface displacement of approximately 200-mu-m and it was observed that the pointing direction of one output beam could be controlled by the surface separation in an asymmetric geometry. Gain length products of approximately 16 with estimated output powers close to the megawatt level were achieved on both the 23.2 and 23.6 nm J=2-1 transitions for an optimised target configuration. Maximum effective coupling efficiencies of the individual outputs from double targets, comprising 2.2 and 1.4 cm length components, approached 100% for beams propagating from the shorter to the longer target.

COLLISIONALLY EXCITED X-RAY LASER SCHEMES - PROGRESS AT RUTHERFORD APPLETON LABORATORY

Characteristics of the 3p-3s amplified spontaneous emission from Ne-like Ge plasma columns, generated by ablation from massive targets, have been studied in detail. In particular, the gain coefficients of the J = 2-1 lines at 23.2 and 23.6 nm have been measured as a function of incident intensity for a 1.05-mu-m wavelength pump laser beam. For 100-mu-m wide stripe targets and a fixed energy pump laser the maximum gain length product is achieved at an irradiance of