Pinzhong Fan

Stigmatic grazing-incidence flat-field grating spectrograph

A stigmatic grazing-incidence flat-field grating spectrograph was developed. The spectrograph consisted of a variable line-spacing concave grating and a grazing-incidence collecting optics composed of a cylindrical mirror and a spherical mirror. Using this spectrograph, we have obtained soft x-ray spectra of line-focused laser plasmas with good spatial resolution along the normal of the target surface over the entire wavelength range covered by the spectrograph.

A simple in situ calibration technique for soft x‐ray film

A simple valid in situ relative intensity calibration technique for soft x‐ray film is described. This is based on film exposure measurements of the uniform line‐shaped distributed soft x‐ray monochromatic irradiation transmitted through a step‐wedge absorption filter. Fitting the calibration data with Henke’s semiempirical equation for thick‐emulsion film, the characteristic curves for Shanghai 5F soft x‐ray film without supercoat (SIOM‐5FW) have been obtained in the wavelength region from 50 to 80 A.

Space‐ and time‐resolved investigation of short wavelength x‐ray laser in Li‐like Ca ions

We have demonstrated the soft x‐ray amplification for lithium‐like Ca17+ 4f‐3d transition at 57.7 A with 900 ps, 1.05 μm drive laser pulse. The spatial distribution of the gain coefficient and temporal history of the lasing line emissions were also obtained.

Spatial uniformity and its time evolution of linear laser plasmas

The effect of laser illumination conditions on the uniformity of the linear laser plasmas produced is investigated with time-integrated and time-resolved soft x-ray diagnostics. Evident nonuniformities along the line focus resulting from nonuniform laser intensity distributions have been observed with a conventional simple line-focusing technique. Specifically, the nonuniformity of higher charge-state ions is more remarkable than that of lower ones. A uniform linear plasma can be obtained with a new line-focusing technique that produces uniform laser illumination. Nonuniformities under uniform laser illumination are found to occur primarily in the laser heating period. Further development of time-matched and spatial uniform line-focused laser illumination will produce more uniform linear plasmas.

Studies of Recombination X-Ray-Laser Gain and Gain-Medium Uniformity

The time evolution of the uniformity of the line-shaped X-ray-laser gain medium and the spatial characteristics of the recombination X-ray-laser gains of the Li-like ions are studied using long (∼900 ps) and short (∼100 ps) laser pulses.

Spot-focused laser-plasma toward large-scale, line-shaped, uniform monochromatic soft x-ray source

A simple way to obtain a large-scale, line-shape, uniform monochromatic soft x-ray source is described. Spot-focused laser-plasma of various materials serve as an original source, then a dispersion system (consisting of pre-optics and a flat-field concave grating) transforms the abundant line emission point source into a series of monochromatic line-shaped sources located on the spectrum focal plane of the concave grating. The intensity uniformity along the longitudinal direction and the monochromaticity of this kind of line source are treated carefully in this paper.

An alternative method for gain determination of recombination X-ray lasers

Abstract An improved method was proposed for gain determination of recombination X-ray lasers. The axial line intensity ratio of the lasing emission to an optically thin spontaneous emission is used to overcome the intensity fluctuations caused by shot-to-shot randomness in laser conditions. With this method, the gain of the Li-like Si 4f-3d lasers at 13.0 nm was measured, which is in agreement with theoretical simulations.

Space resolved spectrograph for laser induced plasma diagnostics

The detailed characteristic of a stigmatic grazing incidence grating spectrograph was investigated by a ray-tracing and spectroscopic experiments. As an example of application, some new physical result on the comparison of long-pulse and short-pulse laser driven recombining plasma are described.

Emission from line‐focused laser‐heated multi‐groove target

Line‐shaped plasma was produced by ablating plasma from multi‐groove Aluminum surface of a groove period of 100 μm, on which the direction of groove (50 μm in depth and 50 μm in width) is perpendicular to the focal line of 1.05 μm 120 ps (FWHM) heating laser. Comparison with the results of flat‐slab target, different spatial profiles of electron density and temperature and line emission intensity were found. Enhancement of on‐axis emission of candidate lasing line of Al10+which maybe originate from enhanced GL value were observed.

Comparison of the exposure characteristics of soft-x-ray film SIOFM-5FW with Kodak 101-05 and Ilford Q-plates

In identical exposure and processing conditions, we compare the exposure characteristics of soft-x-ray film, SIOFM-5FW, with Kodak101-05 and Ilford Q-plates in the soft-x-ray and extreme UV region below 100 nm, using D-19 and Phenisol developers. The experimental results show that for radiation greater than 10 nm, the response of SIOFM-5FW lies between the Kodak101-05 and the Ilford Q-plates but is closer to the former. For radiation of less than 10 nm, the SIOFM-5FW is more sensitive than the Kodak101-05 plate, with a higher saturated optical density, a higher dynamic range, and an obvious carbon K absorption edge structure in the spectra obtained. The effects of the two developers used on the exposure characteristics are discussed.