A miniature, low-power, solid-state detector for ionizing radiation was developed for use in more locations, and requiring less space and lower power than current technology. An accepted way of counting high-energy charged particles common in space radiation is to detect the light produced when the particles strike a scintillator material.
Scintillator detectors are required that can be used as part of, or in addition to, a space-radiation-detector system. The detectors are required for trigger and veto (rejection) roles in data acquisition. The detectors allow for placement over a surface area that conforms to the internal geometry of a larger system, able to round corners, filling odd geometries, and fit into a compact volume using minimum power. A novel miniature paddle counter was developed to function as part of, or in addition to, the space radiation system. This miniature paddle counter uses a small piece of scintillator and a low-voltage, UV-sensitive, wide-bandgap photodiode as the photodetector, rather than a large, bulky scintillator connected to a fragile, high-voltage PMT (photomultiplier tube), and eliminates the need for a wave shifter.
Energetic ions striking the scintillator cause faint, weak light pulses that are detected by fast, efficient photodetectors; in this case, a GaP photodiode. The photodiode generates current proportional to the amount of light incident upon it. In the present embodiment, the photodiode is connected to a charge-sensitive preamplifier that gives a voltage output proportional to the total integrated charge of the pulse from the photodiode. A current pulse detector reads current pulses from the photodiode, which are recorded by computer.
The primary unique feature is the use of a UV-sensitive photodiode with the scintillator such that a wave shifter is not required between the scintillator and the photodetector. Use of wide-bandgap detectors does not require the temperature regulation required by Si photodiodes, which lends this configuration to more robust operation in space without the additional need for a temperature compensation system. Other unique features are the small size and the use of solid-state detectors that allow the detector to be used in a wider variety of applications such as space missions where small size, light weight, and low power consumption are necessary.
This work was done by Susan Y. Wrbanek, John D. Wrbanek, and Gustave C. Fralick of Glenn Research Center.
Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steven Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-19171-1.