Plastic Electrical System Design In High Power Laser Device

The inertial confinement fusion (ICF) is one approach to realizing controllednuclear fusion. It is the process that the laser heats the target pellet instantly and thegenerated inertia recoil causes high temperature and high pressure, which leads tonuclear fusion occur. The prerequisite of implementing ICF experiment is that theablation pressure resulting from the laser pulse irradiating on the pellet must increasewith certain rules. Therefore, high-quality targeting laser pulse shape system isrequired.The arbitrary electrical waveform generator is based on Gallium-Arsenide FieldEffect Transistor (GaAs FET) set which has a good ability of on-off switching andgenerating voltage-controlled current. The ultra-narrow pulse triggers the GaAs FETsand multiple negative pulses are generated. The different time delay for each pulse isintroduced by transmitting it through analog time delay wire. Finally we have amicro-strip line to couple the pulses and get the overlapped pulse shape. The gate biason FET determines the magnitude of pulse, so we can get the arbitrary pulse byoverlapping the multiple pulses with various magnitudes and time delays. In thetriggering circuit, the tapered line technology is applied for compensating propagationloss of the trigger pulse, which makes the pulse amplitude invariant.For changing the waveform of the shaping electrical pulse, we design an electriccontrol system. Use serial communication function of LabVIEW to realize that thehost computer transfers data with lower computer---LPC2136. The lower computerreceives33channels voltage set from the host and then dominates corresponding DAperformance to generate analogy voltage via RS-232protocol to control GaAs on-offstate. Thus, an arbitrary waveform electrical pulse with10ns width is obtained. All thetask scheduling and resource allocation are administrated by embodied real timeoperation system---COS-II kernel. In this project, with only one DA chip the designedscanning and the output voltage keeping circuit can reduce the design cost and enhance the utilization efficiency of the resource.The testing resulting demonstrate that the designed generator generates a pulsewaveform with amplitude between0and5V, duration less than10ns,330pstime-domain adjustment and a square pulse with rising edge471ps, falling edge428ps. And the electrical pulse trigger jitter (peak to peak) is about28ps and RMS valueis about4.38ps which guarantees the output stability of the laser pulse. We inject theshaping electrical pulse into the semiconductor laser, and the ideal waveform ofshaped laser pulse is obtained. The shaped laser pulse can be taken as a seed resourcefor high-power laser and the experiment results agree well with our anticipation.