E-PARALLEL-TO-B ENERGY-MASS SPECTROGRAPH FOR MEASUREMENT OF IONS AND NEUTRAL ATOMS

Real-time measurement of plasma composition and energy is an important diagnostic in fusion experiments. The Thomson parabola spectrograph d escribed here utilizes an electric field parallel to a magnetic field (E parallel to B) and a two-dimensional imaging detector to uniquely i dentify the energy-per-charge and mass-per-charge distributions of pla sma ions. An ultrathin foil can be inserted in front of the E parallel to B filter to convert neutral atoms to ions, which are subsequently analyzed using the E parallel to B filter. Since helium exiting an ult rathin foil does not form a negative ion and hydrogen isotopes do, thi s spectrograph allows unique identification of tritium ions and neutra ls even in the presence of a large background of He-3. (C) 1997 Americ an Institute of Physics.