Miniature Imaging Plasma Spectrometer: A New Approach with Large Geometric Factor and Wide Field of View

New advances in Silicon technology micro-fabrication enable a new miniature imaging plasma spectrometer with sensitivity per unit mass (units of cm{^2}-steradkg) 10 to 100 times that of conventional spectrometers, depending on the application. In our design, micro-miniature spectrometer elements, laid out in a 2-dimensional array, allow a high ratio of sensitive area to array base area. Ions (or electrons) are energy selected in an array of parallel plate electrostatic deflectors after passing a collimator array defining the field of view (direction and angular divergence). The transmitted particles are detected on a micro-channel plate electron multiplier. A voltage applied to the deflectors controls the selected energy. The collimator and energy analyzer arrays are micro-machined in silicon and packaged together with the micro-channel plate and a charge pre-amplifier array. In a typical design, a 1cm x 1cm pixel base may have about 50 energy selector slots with 0.275 cm{^2} total aperture. High collimator transmission of about 80% gives an effective aperture of about 0.22 cm{^2} (22% of array base area). Corresponding power reductions are achieved with recent ASIC designs for charge-amplifier-discriminator arrays. This paper describes how the need for focusing energy analyzers is eliminated by the high open area ratios and small channel diameters now available for collimator arrays; this enables high sensitivity per unit mass of detector. The new concept allows multiple viewing angles from a flat collection (tiling) of spectrometer elements. Each collection forms a pixel with unique viewing angle. Many pixels can be placed above a single micro-channel plate detector base with anodes and an amplifier array in one-to-one correspondence with the pixels above. A flat module consisting of any number of tiled pixels may be assembled to define a specific application. Overall thickness is 3 to 10 mm and practical pixel fields of view are 1 to 5 degrees and can be aimed in any direction in space. For example, 72 pixels (5 degrees) provide 360 degree coverage with about 200 gm of mass and 200 milliwatts of power. This approach also offers static imaging over a full 4Pi steradian field of view.