On the beam probe

The measuring method with beam probe is introduced. The method is used for the measurement of plasma parameters such as the time variation and the spatial variation of electron density, ion density, electron temperature, and plasma potential. This method of measurement can be carried out without any disturbance to plasma and spatial distribution is relatively good. Neutral beam can pass across magnetic field. Attenuation of beam injected into plasma will give informations on the plasma. The beam is produced in an ion source, is neutralized in a gas cell, and injected into a plasma system. The beam is attenuated, comes out from the system, and stripped in a gas cell for analysis. The measurement was made with BSG-IA system, and the value of ion density multiplied by path length was 1 x 1015 cm-2. For the measurement of higher temperature region, potassium ion is used. At first, the effective cross-section of charge exchange for potassium was measured. The results are shown in comparison with the results with a Langmuir probe and others. The measurement of electron temperature in turbulent heating was made by using argon beam. Experiments with beam probes made in foreign country are introduced. (Kato, T.)