Li Haibing

The Plasma Channel Evolution Characteristics of Pulsed Flashlamps Working in an Array

This work is devoted to the study of plasma channel evolution characteristics in pulsed xenon flashlamps working in an array. Influencing factors on the plasma channel evolution process are studied, including pre-ionization pulse and neighbor flashlamps. It has been found that neighbor flashlamps affect the plasma channel by shaping the electric potential distribution, rather than by Lorentz force. Branching is observed in the plasma channels of the flashlamps in the middle of the array. Inconsistency also exists in the plasma channels of these flashlamps in different tests. The branching and inconsistency are both caused by the unique electric field distribution in these flashlamps. Besides, the pre-ionization pulse can help the main pulse plasma channel to develop more smoothly and faster, which will weaken the shock wave and benefit the mechanical strength of the flashlamp.

Thermal damage mechanism of pulsed xenon lamp silica envelope during high-power discharge

To improve reliability of pulsed xenon lamps in optical amplifier of inertial confinement fusion(ICF) facility, high power xenon lamps were tested with the power modules similar to NIF facility in US. Though operating at a relatively safe energy loading factor of 0.2 or so, unexpected behavior of some lamps was observed while peak power value of discharge pulse was higher than 300 mega watts. Milky white participants appear in the inner surface of the quartz envelope opposite to metallic reflector inside amplifier. Scanning electron microscopy and X-ray photoelectron spectroscopy data demonstrate that the chemical composition of whitish participant is SiO2. To understand the thermal damage mechanism of lamp envelope, the plasma channel profiles are captured by a high speed CCD camera. Photographs indicate that the existence of metallic reflector beside silica envelope results in uneven distribution of plasma. The temperature is higher in the region with high plasma density. This leads to local evaporation of silica glass and the whitening of quartz envelope. The results are helpful to optimize the design of discharge circuit of power module and reflector of amplifier of ICF facility.

Influence of preionization on irradiation characteristics of pulsed xenon lamp

Summary form only given. High power xenon flashlamps are mainly used in laser inertial confinement fusion facility as the optical pump source. The preionization technique was used to fire the xenon flashlamps and to improve the radiant efficiency and gain of amplifier. It is difficult to find papers describing characteristics and mechanism of preionization. This work is devoted to study the characteristics of preionization and its mechanism during main discharge of high power xenon flashlamps. In experiments, electrical parameters of discharge are recorded by high voltage probe and rogowski coils. The radiation energy of flashlamps was obtained by a pyroelectric energy meter. The plasma channel profiles were captured by a high speed CCD camera. In addition, the spectral distribution in a flash was acquired by a spectrometer with CCD as detector. With proper time interval between preionization and main discharge, the radiant efficiency of flashlamps will increase by 3.8%~5.1%. While the interval is less than period of prepulse, the main capacitor will discharge the preionization circuit and the current through it oscillates badly. Meantime the radiant efficiency will decrease by more than 10%. Spectroscopy results indicate that the preionization pulse will improve the spectral distribution of flashlamp during main discharge. With preionization discharge, the blue shift of spectral distribution curve will be reduced, and it can improve the gain of amplifier.

New Development on High Power Optical Pump Source

High power flashlamp is mainly used in inertial confinement fusion research as the optical pump source for solid-state lasers, and its performance will decide the device design and stability. Many research work have done and some aspects such as material and sealing techniques have made breakthrough.