Environmental Sensors and Subsystems

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Microdischarge-Based Radiation Detectors Utilizing Stacked Electrode Arrays in a TO-5 Package
Christine K. Eun and Yogesh B. Gianchandani
(a) Device concept. The detector comprises a stacked arrangement of multi-electrode stainless steel elements (i.e., anode and cathode) and a glass insulator, assembled within a commercial TO-5 package base. Gamma radiation interacts with the metal layers, which releases photoelectrons into the biased gap. These charged particles trigger avalanche within the biased gap, leading to wireless signaling. (b) Photograph of assembled device.
(a) Device concept. The detector comprises a stacked arrangement of multi-electrode stainless steel elements (i.e., anode and cathode) and a glass insulator, assembled within a commercial TO-5 package base. Gamma radiation interacts with the metal layers, which releases photoelectrons into the biased gap. These charged particles trigger avalanche within the biased gap, leading to wireless signaling. (b) Photograph of assembled device.

Motivation: We have developed a wireless gas-based beta/gamma radiation detector that uses an arrayed electrode structure to demonstrate a scalable path for increasing detection efficiency. During operation, gas microdischarges, initiated by incident radiation, can transmit wideband wireless signals. Wireless-enabled radiation sensors are envisioned for use in rapidly-deployable, mobile networks.

Device Concept & Results: The detector comprises a stacked arrangement of multi-electrode stainless steel elements (i.e., anode and cathode) and a glass insulator, assembled within a commercial TO-5 package base (Fig. 1). Each electrode is an array of 3 or 4 ‘linked’ elements.The spacer maintains a 200 µm-wide gap between electrode layers. Gamma radiation interacts with the metal layers, which releases photoelectrons into the biased gap. These charged particles trigger current avalanche and wireless signaling. The components are manufactured by commercial micromachining methods. The detector diameter and height are 9 and 9.6 mm, respectively, and its weight is 1.01 g. With a 99 µCi Cs-137 source, the detector provides >78 cpm to a hardwired interface at a source-detector distance of 30.5 cm. Receiver operating characteristics (ROC) have been shown to improve with longer integration time. The estimated intrinsic detection efficiency (i.e., with the background rate subtracted) is 3.49%. Portable power modules have been developed for this effort.

Updated 03/07/2012