Laser Plasma Interferometry Experiment Diagnostic Studies

The mechanism of the laser plasma beginning are summarized, and basicprinciple of optic diagnosis of plasma characteristic are analyzed by using the opticalshadowing photography and the Mach-zehnder interference method to conduct theresearch of the plasma evolutionary process and the plasma nature.Optical shadowgraphic method is used to study the spatial shape and theevolution of laser-target plasma. The experimental result indicates that the inflationspeed of the plasma is supersonic, and can achieve 10 6 cm/s, the expansion process istwo-dimensional, moreover along with time passing, the inflation speed graduallyreduces to the sound speed, and the inflation speed of the plasma also tends to be thesame in each direction, as a result the inflation wavefront gradually becomesspherical.The laser plasma Mach-Zehnder interference system based on detecting lightdelay and the real-time register system composed by CCD, oscillograph, energymeter and computer are established. Plasma interferograms at different time and underdifferent laser energy are obtained, and by Matlab programs, the interferogram isprocessed automatically, such as the stripe filter, enhancement, binary, thinning, thinpatching pick-up of the image and the displacement quantity computation. Then therefractive index of the plasma can be gained. Using the relation of the refractive indexand plasma important parameter, like the electron density, the density of plasma, thedensity of neutral particle, the ionicity, the temperature, the pressure and so on, thediagnoses of plasma character is accomplished. The experimental results indicatedthat the plasma electron density can achieve10¹⁹cm^-3, such density is higher incentre compared with that of fringe. The plasma electron density reduces gradually asthe time passing. The plasma temperature can reach 9400K.