1 ©2001 by The Japan Society of Plasma Science and Nuclear Fusion Research J. Plasma Fusion Res. SERIES, Vol. 4 (2001) 000–000 Increase of Hot Initial Plasma Energy Content in the End System of AM BAL-M During Hydrogen Puffing AKHMETOV Timour * , BEKHER Sergei, DAVYDENKO Vladimir, KRIVENKO Aleksandr, MURAVIEV Maksim, REVA Vladimir and SOKOLOV Vladimir Budker Institute of Nuclear Physics, Prospect Lavrentieva 11, Novosibirsk, 630090, Russia (Received: 00 XXXXX 2001 / Accepted: 00 XXX 2001) Abstract At the end system of the completely axisymmetric mirror trap AMBAL-M the experiments on creation and study of a hot initial plasma have been performed. In the experiments a gas-box was used for hydrogen supply into the hot startup plasma in the mirror trap to increase the plasma density. The hot initial plasma in the trap was produced by the trapping of a plasma stream with developed electrostatic turbulence generated by a gas-discharge source located outside the entrance throat. It was found that in addition to the increase in the plasma density by a factor of 2–3, hydrogen puffing resulted in an unexpected nearly twofold diamagnetism increase. The gas puffing did not reduce the electron temperature in the trap. Essential for explanation of the observed effect is the fact that with the gas puffing the measured plasma potential in the trap increased. The increase in the plasma potential enhanced the trapping of the ion flow entering the trap and increased the average energy of the electron flow entering the trap. It was found that with the increasing hydrogen puffing rate plasma parameters in the trap were saturated. Keywords: magnetic mirror trap, plasma confinement, heating, gas puffing * Corresponding author’s e-mail: akhmetov@inp.nsk.su 1. Introduction The ambipolar magnetic mirror trap AMBAL-M [1-3] is a completely axisymmetric machine, and experimental investigations performed at it are of fundamental importance for a future thermonuclear reactor. Investigations at AMBAL-M are divided into two stages. Since 1993 the experiments at the end system (Fig. 1) consisting of a simple mirror trap and semicusp have been carried out. In this system, a hot initial plasma was obtained using a gas-discharge plasma source located outside a magnetic throat. Thermal insulation in the entrance throat and electron heating in the mirror trap by the axial current flowing along the plasma were studied. Consistent accumulation of fast ions in the mirror trap plasma during pulse Fig. 1 Top view of the magnetic system and vacuum chamber of the end system of AMBAL-M. Magnetic field line starting from the plasma source (z = –375, r = 6 cm) is shown. Below is given the magnetic field profile at the axis.