Radio-frequency plugging of a high density plasma

Abstract

Mirror end loss can be suppressed by applying an rf field at the mirror throat through low impedance coils. This method is verified to be effective for a high density plasma up to 10¹⁴ cm⁻³. Experimental results show that the rf field strength required for the plugging is dependent on the plasma density. The dependence differs according to the geometry of the coil. The mechanism of giving the density dependence is theoretically clarified for each coil. Particularly, it is shown that the electric field induced in the direction of the static magnetic field is intrinsic for the result of type‐III coil where its efficiency for rf plugging is insensitive to the plasma density.