Experimental Studies On Gas-Puff Z-Pinch Plasma

Being considered as one of the possible plasma sources for realizing controlled thermonuclear fusion and being used as a pulsed intense soft x-ray source or neutron source, Z-pinch plasma is being intensively studied in the world at present. This dissertation describes the construction of a small-scale Z-pinch device and Z-pinch plasma diagnostics.This dissertation stresses the experimental studies on Z-pinch plasma diagnostics and radiation characteristic. We have finished four items of work: (1) Constructing a small-scale Z-pinch device; (2) Measuring the total photon energy of Z-pinch plasma with thermopiles; (3) Developing a three-frame Mach-Zehnder interferometer for studing the plasma implosion within a single shot of Z-pinch discharge; (4) Analyzing the energy spectra of ion beams emitted from neon Z-pinch plasma with a compact Thomson spectrometer. The last two items of work are innovative in the research on gas-puff Z-pinch device in china and abroad. Results from our studies are shown below: (1) The Z-pinch device is powered by a capacitor bank of 16μF charged to a voltage of 22.5 kV. The discharge current reaches its peak value of 210 kA with a rise time of 2.4μs. working gas neon is injected into the discharge chamber with a supersonic nozzle. (2) The maximum total photon energy measured with thermopiles is about 766 J for a "good shot". A "good shot" here means a deeper dip on the dI/dt signal, the time derivative of Z-pinch current.(3) As shown on the interferograms, at the final pinch phase, the average electron density is about and the imploding velocity of plasma is 9106cm/s. The final pinch instant time tp is determined from the dip on the dI/dt signal. By increasing the mass of the injected neon the instant tp can be changed from 1.2μs to 2.4μs. A "good shot" is often obtained when tp is in the range from 1.2μs to 2.0μs. The reason may lies in the fact that a longer tp allows plasma instabilities to be fullydeveloped. A uniform and symmetric imploding plasma shell shown on the interferogram usually leads to a "good shot", otherwise a "bad shot". Plasma instabilities appearing as bubbles or shearing in the pinched plasma column are observed on the interferograms. (4) From the picture of parabolas produced by ion beams bombarding on a CR-39 plastic target, Ne+, Ne2+, Ne3+, and Ne4+ are easily determined. The tracks from higher ionized neon ions may also be found. The highest energy of Ne+ ions produced in "good shot" is calculated to be 1.28 MeV. And an ion energy spectrum moves toward the direction of lower energy within a bad shot.