Lin Zunqi

Temporal and spectral features of the 3'2 ω0 spatial fine structure in laser irradiated planar targets

Both temporally and Spectrally resolved fine structures of 90° lateral 3/2ω0 harmo-nic emission were experimentally observed. The existence of 3/2ω0 harmonic filaments isattributed to the 3/2ω0 harmonic radiation emitted from neighborhood of the bottom ofmoving filament, about nc/4 away from it. The double hump structure with intensered hump of laterally emitted 3/2ω0 spectrum can also be explained by Doppler correc-tion besides the thermal correction due to fast moving TPD process occuring in the unstable filaments. Estimation of both red and blue shifts using our simple model is wellconsistent with experimental results. Experiments showed that the 3/2ω0 emission wasobviously suppressed by using broad band laser owing to more uniform illumination on the target surface and broad band effect. These may be promissing for superhot electron suppression.

Resonance absorption initiated by self-focusing filamentation

A theoretical model for resonance absorption initiated by self-focusing filamenta-tion is proposed on the base of experiments of the 2ω0 time resolved spectrum and recent experiments of 3ω0/2 filamentation, as well as slow ion emission. A number of aspects of previously obtained experimental results may well be explained.

The fine structure of the 2ω0 time resolved spectrum in laser plasmas

Time resolved spectrum with both high temporal resolution (∼10 psec) and spectral resolution (∼0.6 A) of the 2ω0 harmonic emission scattered at 90° to the laser axis are presented in this paper. It is shown experimentally that the primary and secondary peaks of the 2ω0 harmonic are actually composed of many fine and bright fringes with intervals of about 1.5∼3 A for each, the values of which are in close relation to the atomic weight. Finally, analyses and discussions of these are given.

The influence of laser frequency bandwidth on the time and space resolved structures of the 2ω0 harmonic generation

Reported here are 2ω0 harmonic space and time resolved structures taken by a streak camera at an angle of 90° with respect to the laser optical axis. The evident differences, as shown between the broadband and narrowband laser shooting, are analyzed using the theory of plasma soliton generation. The results obtained are consistent with other experiments.

Tending to Saturated Gain of Soft X-Ray Laser at 23.2 and 23.6Nm

We proposed a design named “Four-Target Series Coupling” to work, on soft x-ray laser in Ne-like Ge plasma. The total length for four targets is up to 5.6cm. The gain length product (GL) for small signal is up to about 18 for both lines at 23.2 and 23.6nm , and the effective GL is 16.4 and 15.7 for these two lines respectively. These two lines are obviously tending to saturation. The divergence of X-ray laser beam is about 3 ˜ 4 mrad. Before experiments, we developed a series of codes to simulate these experiments, got the parameters about the distance and angle between the targets in order to get best coupling.

Laser-imploding dynamics of glass microballoons by multi-frame X-ray shadowgraphy

X-ray shadowgraphs at four distinct times for each implosion of the glass microballoon illuminated by high power laser have been obtain. Ultilizing the anomalous scattering of the backlighting x-rays by judiciously selecting the photon energies, the motion of the innerwall of the imploding glass microballoon can be directly diagnosed.

Study of laser-imploded glass shelis by multi-frame x-ray shadowgraphy

We present preliminary studies of the laser-imploded glass microballons by our newly developed multi-frame x-ray shadowgraphy which is in good agreement with our simulation calculation. The study shows that uniform illumination is an important factor for good implosions.