Improved Pellet Charge Exchange Measurements in Large Helical Device

The pellet charge exchange technique (PCX), which is a combination of the compact neutral particle analyzerand an impurity pellet, is a unique method to observe the radial energetic particle distribution. There are notonly charge exchange reactions between the hydrogen in the pellet and a proton, but also between the partiallyionized carbon in the pellet and the proton. The neutralization factor from energetic ion to neutral particle couldbe deduced from the electron temperature and the electron density of the pellet cloud. The radial profiles ofenergetic particle distribution were measured and compared in various ion cyclotron resonance heating (ICH)plasmas. The energetic particle flux significantly increased at the resonance layer created by the ICH. PCXprovides more precise information about the resonance layer than conventional neutral particle diagnostics

Helium Ion Observation during 3rd Harmonic Ion Cyclotron Heating in Large Helical Device

In higher harmonic ion cyclotron resonance heating using the fast wave, a helium resonance layer appears near the plasma core. It is very important to detect the helium ions to investigate the confinement of α particles, which are produced by a nuclear reaction in ITER or a fusion reactor. In Large Helical Device (LHD), we attempt to observe the charge-exchange helium particles using a compact neutral particle analyzer (CNPA). Helium acceleration below 5 keV can be confirmed by comparing the signal ratio of helium in adjusted plate voltages of the CNPA to that of hydrogen. Successful helium measurement in LHD will lead to the development of α particle measurement