First measurements of plasma parameters in an expander of a mirror trap with sub-fusion plasma parameters are reported. Potential drop near the end plates of the expander appears to be much lower than the electron temperature in the center of the trap. Characteristic energy of electrons in the expander region is also substantially lower than the electron temperature in the confinement plasma. Variation of the magnetic field expansion ratio K between 30 and 160 does not influence the main parameters of the confinement plasma. Electron temperatures of the confinement plasma of about 700 eV were achieved at K = 30.

Abstract. The paper includes a brief overview of previous researches on the stabilization of MHD instabilities, study of micro-instabilities, and demonstration a tangible increase of the electron temperature with application of auxiliary ECR heating. A review of the results of recent researches related to application of microwave radiation for plasma generation, and plasma heating in the GDT device is presented. The paper summarizes also recent results of researches that oriented on study of expander physics.

A two-color infrared interferometer has been developed for the investigation of high-density weakly ionized tantalum plasma in x-ray complexes based on linear induction accelerators (1.6 kA electron beam current, 4.6 MeV energy, and 100 ns pulse duration). Simultaneous probing at two different wavelengths makes it possible to independently measure the density of neutral and electron components. The interferometer uses wavelength values of 1.064 µm (Nd:YAG laser) and 10.6 µm (CO2 laser). To attenuate the effect of sample beam refraction in inhomogeneous plasma, the interferometer used a refraction suppression scheme composed of spherical mirrors focusing the object beam into the region occupied by the plasma. In addition, the power of the sample beam transmitted through the plasma was controlled in order to analyze whether there was a distortion of the interference pattern because of strong sample beam refraction and absorption in the plasma cloud. To calibrate the initial phase shift of the probe radiation, a movable mirror mounted on a piezoelectric element and oscillating according to a harmonic law with amplitude greater than the laser wavelengths was used. In initial experiments, the parameters of target plasma registered by this interferometer are as follows: the linear density of neutrals reached 1.5 · 1017 cm−2, and the degree of ionization was of the order of 10−2. The target plasma expansion velocity is determined as ∼6 km/s.

Abstract. The paper presents first results of investigations on processes take place in expander of mirror trap where subfusion plasma is confined. It is shown that plasma parameters remain constant at magnetic field expansion ratio decreasing down to K = 30. Potential drop in Debye layer near the end plate for expansion ratios K > 30 appeared to be much lower than electron temperature in the center of the mirror as well as characteristic energy of electrons trapped in the expander region.