D-MICROGEIGER: A MICROFABRICATED BETA-PARTICLE DETECTOR WITH DUAL CAVITIES FOR ENERGY SPECTROSCOPY

ABSTRACT This paper reports on micromachined Geiger counters fabricated from stacks of glass and Si wafers. As a beta particle passes through, a bias applied between two enclosed electrodes generates electron cascades in the gas between them. This results in a current pulse or "count". A single die of 2 cm 2 had 6 independent chambers ranging in size from 8X8 mm 2 to 1X3 mm 2 . Helium and neon, which have different voltage bias requirements, were separately evaluated as background gases. In tests the device was found to detect incident beta particles from a Uranium-238, and calibrated 90 Sr, 60 Co, and 204 Tl sources, of 0.1-1 µCurie strength. In the D-microGeiger incident beta particles pass through two independent cavities that are separated by a glass barrier, which provides calibrated energy absorption. By comparing the counts in the two cavities, information about the energy of the radiation is determined. This provides an inherent ability to discern the chemical nature of the isotope, not just the presence of radiation