| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2006: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2005: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
The negative ion temperature is one of the most important parameters of hydrogen negative sources, since it affects the beam optics and determines the lower limit of negative ion beam divergence. To understand the physical mechanism which dominates the H-velocity distribution and H-temperature (average kinetic energy) inside the source, numerical modeling of H-production, transport and destruction processes has been done.
In order to calculate H-production profile, a three dimensional (3D) Monte Carlo code for neutrals (hydrogen molecules and atoms) has been developed. The code takes into account the various important reactions for H- production. As for the H-transport and destruction, a 3-D Monte Carlo code has been also developed. Momentum and energy relaxation processes by Coulomb collisions with back ground H^+ ions are taken into account as well as the destruction reactions with back ground H+ and electrons. These two codes are applied to the analysis of the H- velocity distribution in the large H-source "Camembert III" under the typical low pressure conditions (gas pressure 〜a several mTorr, discharge voltage〜50V). The numerical results qualitatively reproduce the experimental observation, i.e., two energy groups of H-ions : hot (〜1eV) and cold (〜1eV) H-ions are present. Coulomb collisions play an important for the formation of cold H-ions, while the acceleration by the plasma potential is responsible for the formation of hot H-ions.
In addition, 1D PIC modeling of the measurement of H-ion temperature by two-laser photodetachment technique has been done. It is shown that the ambipolar potential formed by the laser shot affects the measurement, and H-temperature deduced by two-laser photodetachment technique tends to be larger than the actual temperature in high H-ion density regime.
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