ORBIT ANALYZER PROBES FOR THE MEASUREMENT OF PLASMA TEMPERATURES

Abstract

An investigation is presented of two different probes, of the magnetic analyzer type, in which the magnetic field used for analysis of the particle orbits is also present in the plasma. Both probes employ a current collector whose distance from the aperture plane is adjustable. One probe (the charge-selective probe) collects charged particles of one sign, while theother (the charge-insensitive probe) collects particles of both signs. Assuming a Maxwell–Boltzmann distribution of electrons, the current collection characteristics are calculated for each probe. The use of these current characteristics for the measurement of the electron temperature is discussed. A procedure is also given for obtaining the mean electron velocity perpendicular to the magnetic field in the case of a non-Maxwellian velocity distribution. Finally, methods for measuring the ion temperature are presented for the special case of a small Debye length compared with the ion Larmor radius.