A double parallel-plate electrostatic analyzer for Tara endloss studies

The authors report on an endloss spectrograph designed and being fabricated for the Tara tandem mirror. This spectrograph is a double parallel-plate electrostatic analyzer about 60 cm in length with a 30 deg. entrance angle; the high voltage plate is a transparent wire cloth grid which allows higher energy particles to pass through for detection on a symmetric ground plane. The analyzer has three detection planes: first, the normal focal plane for low energy detection at high resolution (100eV to 4keV); second, the entrance grounded plate for mid energies (4 to 6keV); and third, the symmetric ground plane for coarse resolution at higher energies (8 to 20keV). This spectroscope will be able to measure simultaneously the endloss potential cutoff and ions from the neutral beams: in conjunction with a loss cone neutral beam source, the resolution is sufficient (60eV) to measure the plasma potential