Two types of experiments with a gas-box mounted in the mirror trap of the end system AMBAL-M between the central plane and the exit throat have been performed during the last year. In the experiments of the first type the gas-box was used for generation of a quasistationary hot plasma using input of RF-power at a frequency near the ion cyclotron. The RF-power up to 0.5 MW was introduced into the plasma by means of a Nagoya-III antenna located in a transition region between the mirror trap and the semicusp. At optimized hydrogen puffing into the gas-box, the plasma with the density ~4·1012 cm−3, electron temperature ~100 eV, ion temperature ~400 eV, and duration up to 120 ms was obtained in the mirror trap.

In experiments of the second type the gas-box was used for hydrogen supply into the hot initial plasma in the mirror trap with the purpose to increase its density. The hot initial plasma in the trap is maintained owing to the trapping from a plasma stream with the developed electrostatic turbulence generated by a gas-discharge source located before the entrance throat. It was found that in addition to the plasma density increase by a factor of 2–3, hydrogen puffing leads to an unexpected diamagnetism increase by a factor of 2. Measurements showed that the gas puffing does not reduce the electron temperature in the trap. Essential for explanation of the observed effect is the fact that at the gas puffing the measured plasma potential in the trap increases. The increase of the plasma potential enhances the trapping of the ion flow entering the trap and increases the average energy of the electron flow entering the trap.

Preparation of an experiment on creation and study of a dense and hot plasma in the central solenoid of the completely axisymmetric ambipolar trap is underway. To perform this experiment, the finished part of the central solenoid will be attached to the carefully studied end system. The hot plasma will be produced by a gas-discharge plasma source located before the solenoid throat. Additional enhancement of the plasma parameters will be achieved using RF-power input and hydrogen puffing. As a result of the experiment, an MHD stable 6 m long plasma with the diameter ~30 cm, density 1013 cm−3, ion temperature of hundreds of electronvolts, electron temperature above 100 eV will be obtained in the central solenoid. Magnitudes of transverse particle and energy losses from the obtained hot collisionless plasma will be determined as well, and substantial reduction of longitudinal plasma losses from the solenoid will be provided owing to creation of an ambipolar potential in the mirror trap plasma. At the initial stage of the solenoid filling the ion distribution function over longitudinal velocities will have two peaks and experimental investigation of the corresponding microinstability is possible.