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Localised ion temperature measurements can only be performed with special electric probes where the electron component of the current is kept off from the collector. In a strong magnetic field the effect can be utilised that the electron gyro-radius is much smaller than that of the ions. This method was developed by Katsumata and Okazaki (Japan J. Appl. Phys. 6, 123 (1967)). We have used a so-called tunnel probe (which consists of a conductive tunnel, terminated by an isolated back plate) by adding a diaphragm in front. Thereby the tunnel is prevented from incident electrons at any potential of both electrodes. By sweeping the potential across the tunnel, the perpendicular ion temperature can be inferred. By segmenting the tunnel axially in two parts also the parallel ion temperature can be determined. When the electrodes are biased to ion saturation, the ratio between the ion currents, which reach the first and the second segment, respectively, is a measure for the parallel ion temperature. The dependence of the ratio of the currents has to be determined by a PIC simulation.

The angular distribution of electrons emitted from AlAl2O3Au sandwich cathodes was measured at various voltages and temperatures between 80 and 300 °K. The distributions obtained are all highly non-isotropic and consist of a maximum in the normal direction and a temperature dependent background. This background is approximately isotropic at low voltages, at high voltages it forms two new maxima. It is supposed that this behaviour may be caused by the influence of phonons and traps in the dielectric layer. Die Winkelverteilung der aus AlAl2O3Au Sandwich-Kathoden emittierten Elektronen wurde bei Temperaturen zwischen 80 und 300 °K fur verschiedene Spannungen gemessen. Alle gewonnenen Verteilungen sind stark anisotrop. Sie bestehen aus einem Maximum in senkrechter Richtung und aus einem temperaturabhangigen Untergrund. Dieser Untergrund ist bei niedrigen Spannungen angenahert isotrop, bei hoheren Spannungen entstehen zwei neue Maxima. Es wird angenommen, das dieses Verhalten durch den Einflus von Phononen und Elektronenhaftstellen in der dielektrischen Schicht verursacht wird.