Yaolin Li

Preparation of Y-Ba-Cu-O high Tc superconducting thin films by plasma-assisted organometallic chemical vapor deposition

Thin films of the high Tc superconducting Y‐Ba‐Cu metal oxide have been prepared for the first time by plasma‐assisted organometallic chemical vapor deposition using β‐diketonate chelates of Y, Ba, and Cu, Y(C11H19O2)3, Ba(C11H19O2)2, and Cu(C11H19O2)2 as starting materials, followed by post‐annealing under a reduced pressure of oxygen stream. X‐ray diffraction spectra indicate that the films deposited on the yttria‐stabilized zirconia (YSZ) substrate have a significant preferential orientation of the crystallite c axis being perpendicular to the substrate surface. Four‐probe resistivity measurements reveal the temperature of the onset of superconductivity at 91.6 K and zero resistance by 78.5 K.

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.

Time and space resolved studies of recombination x-ray lasers

Abstract A novel experimental technique of time- and space-resolved X-ray diagnostics has been developed by coupling a stigmatic flatfield grating spectrometer to a soft X-ray streak camera to study the dynamics of recombination X-ray lasers. Time and space characteristics of Li-like Si X-ray lasers have been investigated and some interesting results have been obtained. Preliminary results with CaF2 target are given.

Investigation of soft X-ray spectra from laser plasma by using a transmission grating spectrometer

With the help of the transmission grating spectrometer (PTGS), we have obtained the real emission spectra of several elements. The band structures of the soft x-ray spectra from laser produced plasmas are extensively studied as the function of atomic number and laser intensity. Finally, the PTGS space-resolved spectra from the laser heated half-cylindrically grooved target show that this kind of semi-closed geometry is a promising candidate for x-ray laser targets.

Recent progress in recombination X-ray laser research at Shanghai Institute of Optics and Fine Mechanics

In this paper, the results of the X-ray laser gain experiments of Li-like K and Ca ions, conducted recently at LF12 Laser Facility of SIOFM with KCl and CaF2 slab targets, will be presented. Also presented will be the space-resolved time history of ASE emission in the Li-like X-ray lasers and the in-situ calibration for the X-ray film used in the experiments.

Intense laser source for X-ray laser research and laser-plasma study

For the X-ray laser researching toward shorter wave length, we set up compact short pulse laser facility with high intensive output at the variable pulsewidth from 20 ps to 2.5 ns. Occupying a table smaller than 10 m2 and with output of 2.5 J in 20 ps this facility is reported with the emphasis on the use of X-ray lasers research and laser-plasma study.

Theoretical calculation of soft X-ray laser gains for Li-like Ca ions

By the calculation of the 4f-3d line gains of Li-like Ca ions, which varied with electronic densities, temperatures and abundances, we found the plasma conditions on which the 4f-3d gain could be produced. Then, we calculated the gains which varied with time and space, under the plasma parameters which were calculated with self-similar model in cylindrical geometry.

Soft x-ray emission characteristics from laser plasma sources

Atomic number and laser intensity dependences of laser plasma soft-x-ray (SXR) emissions are presented, and the nonuniformities of line-shaped plasma SXR emission are studied with time- and spectrum- resolving. The SXR emissions of the half-cylindrical-shell target are investigated aiming at producing a more available plasma condition for x-ray lasering.