Horizontal, vertical, and radial high-energy particle distribution measurement system in Large Helical Device

Abstract

A horizontal, vertical, and radial high-energy particle distribution measurement system, which consists of the time-of-flight neutral particle analyzer (TOF-NPA), the silicon detector neutral particle analyzer (SD-NPA), and pellet charge exchange (PCX) analyzers, is successfully installed in the Large Helical Device (LHD). In a horizontal scan, it is interesting to measure the pitch angle distribution and to investigate the loss cone feature obtained by it. The pitch angle distribution from 40° to 100° can be obtained by horizontal scanning of the TOF-NPA during a long discharge of over 100 s sustained by the NBI2 (coinjection) at the magnetic axis of 3.6 m. With a vertical scan, the heating deposition profile of the ion cyclotron resonance heating (ICH) has been discussed. The deposition profile can be obtained by the vertical scan of the SD-NPA. The region where the high-energy particle is generated agrees with the location of the resonance layer of the ICH. Similar results can be obtained by the PCX measurement, which gives radial information of the high-energy particle distribution in a short discharge.