Study Of Plasma Stabilization And Lower-Hybrid Wave Heating Mechanism In KMAX Tandem Mirror

Axial Symmetrical tandem mirror in combination with kinetic stabilizer is considered to poccess many advantages over the traditional mirrors which largely feature the minimum magnetic field structure.The symmetrical design can remove the neoclassical transport,hence,improve the overall confinement.The axial confinement,similar to other mirrors,relies on a potential barrier in the plug cell to reflect the escaped ions back to the central mirror.To establish such potential barrier,electron heating and neutral beams have been applied in the plug cells to raise the electron temperature and the density.The improvement of axial confinement has been observed in different tandem mirrors.This dissertation concerns the lower hybrid wave heating(LHWH)method to heat up the plasma in plug cells on the basis of RF waves heating plasma in magnetic confinement devices..This method can improve the axial confinement of the device by increasing the plasma potential of the plug cell.Two sets of 13.56MHz-40kW lower-hybrid heating system were assembeled in the plug cells on KMAX device,respectively.To simplify engineering burden,single loop antenna is used in the dissertation.The coupling between antenna and plasma plays a very important role in LHWH.A phased multiple-loop antenna can be applied well to LHWH.The heating research requires both stable plasma platform and plasma with specific density distribution.This paper aims to improve the work of LHWH on KMAX device.In view of the plasma conditions required for LHWH,this paper realizes the stabilization of plasma.At the same time,The LHWH system and the diagnostics system are built on KMAX device.In order to design a better antenna,PML antenna is applied in our experiment.the 2D PIC simulation framework for LHWs launched by phased array antenna in nonuniform plasma is applied to linear device.The reliability and accuracy of the program for cold plasma wave dispersion relation and propagation can be well verified by theoretical calculation.The LHW excited by single and double loop antenna are simulated in magnetic mirror with non-uniform density and magnetic field.These provide theoretical and technical support for LHWH experiment in magnetic mirror device.The main research research results are as follows.The diagnostics device for the measurement of plasma parameters in KMAX device has been developed.The interchange-flute mode can be stabilized by rotating magnetic field(RMF),cusp magnetic field and 750kHz and 800kHz RF field.Meanwhile,the radial confinement was increased about 10 times.The central density of 2×1017m-3 for LHWH is achieved well by magnetic field adjustment or modification of plasma gun.The LHWH system with power source,power meter,current and voltage probe,vacuum electrode and the single loop antenna is completed.The PML antenna with two,three,and four loops is investigated in the exciting m=0 HW plasma by changing the antenna wavenumber spectra.The detailed analysis of wave trajectory and kz spectrum over time for antenna phasing ??=0 shows that the wave packet radially penetrate to plasma center as a fast wave with high kz spectrum and gradually convert into slow wave and achieve resonance near LHR layer.Besides,the slow wave excited by phased array antenna directly cannot propagate for kz<k?,C in this case.The LHW excited by single loop and loop antenna in magnetic mirror is simulated well.The results showed that the energy is deposited near the LHR layers as expected in this case.As the electric field component EX excited in plasma is strongest,the temperature components of Tix(ions mainly accelerated by Ex q)and Tey have obvious improvement while the other components of temperature are still at the noise level which is good guide to the experiment.