Gas Puffing into the AMBAL-M Solenoid Plasma

The central solenoid of AMBAL-M was filled with a turbulent plasma stream generated by a source located outside the entrance magnetic throat, the plasma ~0.4 m in diameter, with density ~1.510¹³ cm^-3, electron temperature ~50 eV and ion energy ~200 eV was obtained.

Additional hydrogen puffing allowed plasma density increase. The plasma with a cold component from ionized gas and charge exchange ions was heated by electrostatic oscillations produced by the working source. At optimized gas puffing the plasma density was increased to 510¹³ cm^-3 without substantial reduction of the ion temperature. No big differences in plasma properties were found between gas puffing through a gas-box and a ceramic tube.

The plasma density increment was shown to depend only on the total amount of the injected gas. The experimental optimization was made for different values of solenoid magnetic field taking the diamagnetism into account.

Neutral hydrogen distribution in the solenoid vacuum chamber and recycling rate were estimated from data of fast inverse magnetron gauges constructed in BINP.