Sc-46 Spot Irradiator
A spot irradiator is also located at the NRL. It makes use of a source collimator to enable in-situ radiation-damage testing of an electronic device while minimizing the dose received by other devices nearby on the test board. The irradiator uses scandium-46 created in the reactor from irradiation of Sc-45. Sc-46 decays with an 84-day half-life, emitting 1120 keV and 889 keV gammas. These gamma are hard enough for useful electronics damage testing such that they can act as a surrogate gamma emitter for Co-60 that can be tailored for use in enhanced-low-dose-rate-sensitivity (ELDRS) testing. The Sc-46 sources can be activated for dose rates in the range of 1 -10 mrad (Si)/s, which is the typical desired range for ELDRS radiation damage testing of electronics.
Note that the test cavity is 7 inch wide by 9 inch deep. The slots that hold the phenolic support piece are 1/8 inch high and 1/4 inch wide. Therefore, the support piece should be 7.4 inch wide by no more than 8.9 inch deep and less than 1/8 inch high. The circuit board on which the parts are mounted can have dimensions up to 6.9 inch wide by 8.9 inch deep, but the area of the board on which parts are mounted should be kept to 6 inch wide by 8 inch deep.
The figure below shows the approximate falloff of dose rate with distance from the center spot.