A Microdischarge-Based Neutron Radiation Detector Utilizing a Stacked Arrangement of Micromachined Steel Electrodes With Gadolinium Film for Neutron Conversion

Microfabricated detectors can be used to provide first alert information about the presence of radiation sources. This paper describes a micromachined neutron detector that operates in the Geiger-Muller regime. It utilizes electrodes that are lithographically micromachined from 50-μm thick stainless steel #304 foil. The cathode is coated with a 2.9-μm thick layer of Gd on one side to convert thermal neutrons into fast electrons and gamma rays, which are then detected by ionization of the fill gas (Ar). Three electrodes are stacked in a cathode-anode-cathode arrangement, separated by 70-μm thick Kapton spacers, and assembled within a commercial TO-5 package. The detector diameter and height are 9 and 9.6 mm and it weighs 0.97 g. Detector performance is characterized using a 90 μCi
²⁵²
Cf neutron source placed at a distance of 10 cm from the detector. Using Pb blocks between the source and detector to block gamma rays, the typical detector response at 285 V bias is ~8.7 counts per minute (cpm), with background radiation count of 1.2 cpm. The typical dead time is 5.3 ms. Compared with commercial devices which operate at >900 V, have detector volumes of 2000-100000 mm
³
and can only detect a subset of radiation types (i.e., beta particles, gamma rays, and neutrons), this device offers lower operating voltages smaller volume and the ability to detect all three types of radiation.