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A dosimeter-on-a-chip (DoseChip) comprised of a tissue-equivalent scintillator coupled to a solid-state photomultiplier
(SSPM) built using CMOS (complementary metal-oxide semiconductor) technology represents an ideal technology for a
space-worthy, real-time solar-particle monitor for astronauts. It provides a tissue-equivalent response to the relevant
energies and types of radiation for Low-Earth Orbit (LEO) and interplanetary space flight to the moon or Mars. The
DoseChip will complement the existing Crew Passive Dosimeters by providing real-time dosimetry and as an alarming
monitor for solar particle events (SPEs).[1]
A prototype of the DoseChip, comprised of a 3 x 3 x 3 mm3 cube of BC-430 plastic scintillator coupled to a 2000-pixel
SSPM, has successfully demonstrated response to protons at the NASA Space Radiation Laboratory (NSRL) at
Brookhaven National Laboratory and at the HIMAC facility in Japan. The dynamic range of the dose has been verified
over four orders of magnitude for particles with LET ranging from 0.2 keV/μm to 200 keV/μm, which includes 1-GeV
protons to 420-MeV/n Fe nuclei.
To exploit the benefits of the CMOS SSPM, we have developed our first autonomous prototype using the DoseChip. An
analog circuit is used to process the signals from the SSPM, and an on-board microprocessor is used to digitize and store
the pulse height information. Power is distributed over the device from a single dual voltage supply through various
regulators and boost converters to appropriate supply voltages to each of the components.
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