Electrostatic Energy Analyzer and Gas Stripping Cell to Measure Ion Temperature in the PFRC-2

We describe a diagnostic to analyze the energy distribution of neutrals exiting RMF_o-heated PFRC-2 plasmas. Energetic escaping neutrals, sourced primarily by charge exchange reactions of cold neutrals with energetic ions, first pass through a gas (H₂) stripping cell, becoming partially ionized. The ions formed then enter a 90° curved-plate electrostatic ion energy analyzer (IEA), and those of the selected energy strike a Channeltron electron multiplier. The IEA is predicted to have a resolution of approximately 5%. To obtain a better estimate of the energy resolution, the IEA will be calibrated with an ion beam of known energy. The ionization efficiency of the stripping cell is predicted to be below 10% for H₂ gas. Although the efficiency varies with the energy of incoming neutrals, this variation should not greatly influence our measured values of ion temperature. The RMF_o heating mechanism is predicted to produce energy distributions unequal in the directions parallel and anti-parallel to the plasma current. Modeling the two energy distributions is being performed with a Hamiltonian single-particle code.