Physics and engineering design studies on the Large Helical Device

Perpendicular and tangential angularly resolved multi-sight neutral particle analyzer system in LHD

The particle loss in a helical plasma can be found by measuring the angular distribution of the energetic neutral particles using the angularly resolved multi-sightline neutral particle analyzer (ARMS). In ARMS, the AXUV detector with 20 segments usually used as UV monitor is utilized as the particle detector. Two ARMSs, which are installed with perpendicular and tangential views are operated for measuring the real time neutral particle distribution and investigating the particle loss.

Pellet charge exchange helium measurement using neutral particle analyzer in large helical device

It is very important to investigate the confinement of alpha particles, which will be produced by nuclear reactions in ITER and fusion reactors. The pellet charge exchange (PCX) measurement is one of the most powerful methods because it can directly provide the profile of the alpha particle energy spectra in a plasma. In the large helical device, PCX using tracer encapsulated solid pellet (TESPEL) has been tried in many hydrogen and helium plasmas, including helium accelerated by using the cyclotron resonance heating. In the PCX, we use the compact neutral particle analyzer without simultaneous mass separation ability. The helium particle measurement can be achieved by the application of voltage in the condenser plate. The scattering of hydrogen particle is carefully considered during the estimation of the helium amount. The radial helium profiles can also be obtained by comparing four TESPEL injection shots with/without higher harmonic fast wave heating and at applied plate voltages for He or H, respectively.