Density and lifetime measurements in the KEMP II electromagnetic trap

Abstract

The temporal evolution of the electron density in a repetitively-pulsed electromagnetic trap has been measured. The plasma is produced by ionization of a background gas by a pulsed electron beam. The plasma density is measured by a microwave interferometer (8 GHz), and the particle lifetime by the density decay after the interruption of the beam pulse. These measurements show that reasonably dense plasmas (~4 × 1011 cm−3 cm−3) can be confined for the order of a millisecond. Apparently the effect of residual ionization becomes important in the decay phase, due to the high electron energies (~2000 eV).