Micro Ion Spectrometer for Fusion Plasmas Boundary Measurements

As magnetically confined plasmas progress towards ignition and very long pulse experiments, the physics of the pedestal and diverter regions have become increasingly important. Measurements of electron density, electron temperature, fluctuation levels, impurity content in the plasma edge, and heat loads on plasma facing components in the diverter are readily obtained with a variety of diagnostics. However, there is a critical need to measure the low energy ions at the edge of the plasma. The energy spectra of the ions determines the rates of sputtering and erosion of the plasma facing surfaces. The focus of this proposal is the direct, spatially resolved measurement of the energy spectra of ions in the edge of a tokamak plasma using in-situ plasma spectrometers that are easily replaced and require minimal resources. The ion spectra in the edge is not easily determined spectroscopically and must be measured in situ since the ions are confined by the strong magnetic fields of the tokamak. There are essentially three elements in any plasma ion energy spectrometer: a collimating structure that defines the viewing geometry of the instrument and, ideally, provides partial or complete shielding of the instrument from light; an energy per charge or energy per mass resolving analyzer; and a particle detector. By combining advances in lithography, high contrast etching, and particle detectors, we have designed improvements to each element to develop a compact plasma spectrometer concept.