Lithium ion source of thermionic emission type

In this paper, the ion emission characteristics of a lithium ion source and its ion beam are explained. The ion source was made as a beam source for the neutral particle beam probe method. The ion emitter (beta-eucryptite) was coated on a platinum plate, and heated by a tungsten heater. The emitted ion current was measured as the functions of anode and grid voltages. Following the results of this measurement, further experiments were carried out at the grid voltage of 0 V for the anode voltage less than 100V and at the grid voltage between -10V and -40V for the anode voltage more than 200V. The relation between ion current and anode voltage was measured at various anode temperature. The current saturated above some anode voltage. The saturation current depends on the temperature. The results of measurement were not in agreement with those of the theoretical analysis. The life of the ion source was also measured. The experiment on the production of lithium ion beam was performed with this ion source. The beam profile was observed with a movable probe at the beam energy of 3 KeV. The full width at half maximum was 8mm, and the beam current measured by a Faraday cup was 100 μ A. The analysis of elements in the beam was made by a magnetic mass spectrometer. The ions included in the beam were mostly lithium ions, and the proportion of other elements (23Na+, 39K+, and 41K+) was about 0.5%. (Kato, T.)