Measurement of neutral gas pressure in the D-module of GAMMA 10/PDX by using ASDEX type fast ionization gauge

In a large tandem mirror device GAMMA 10/PDX, divertor plasmas are simulated by irradiating the end-loss plasma flux of high ion temperature (Ti = 100~400 eV) to the V-shaped tungsten target in the divertor simulation experimental module (D-module) placed inside the large vacuum chamber of GAMMA 10/PDX end-cell. The V-shaped target is enclosed by rectangular box in order to achieve high gas pressure localized around the target plate. For the radiation cooling of the irradiating plasma flux, gases such as hydrogen or argon are injected to the D-module.\nIn order to measure the local gas pressure inside the D-module, An ASDEX type fast ionization gauge was mounted directly to the D-module. The gauge was absolutely calibrated for hydrogen and argon gas by comparing the gauge output current with gas pressure monitored by capacitance manometers (Baratron gauges). Then, increase of the gauge sensitivity due to the magnetic field was investigated in the actual magnetic field of the GAMMA 10/PDX. Typical gas pressure during a detached plasma experiments were measured to be 0.1~10 Pa. The degree of plasma detachment evaluated from the reduction of heat flux was enhanced as the gas pressure increases. Gas pressure in the D-module drastically increased during plasma discharge. Gas compression effect by plasma flow is considered to be the cause of the pressure increase. Detailed results and discussions will be presented in the presentation.第21回高温プラズマ計測に関する国際会