Cs-137 Benchtop Irradiator
The NRL benchtop irradiator is used for research and development and for educational activities. These activities may include:
- Observation of radiation effects on materials and devices.
- Inducement of radiation effects in materials and devices, with subsequent investigation and/or utilization of the effects.
- Demonstration of operation of radiation detectors, and their behavior in high-dose gamma radiation fields.
No irradiation of explosive, flammable, or corrosive materials, or of food destined for human consumption is allowed.
Experiments or samples are put in a shielded drawer for insertion into the irradiation area, and the drawer has through-tubes that allow wires to be run out of the irradiator for in-situ measurements during the irradiation. The space for sample irradiations is 7.75 inch in length by 3.75 inch in diameter.
Because a common use for the benchtop irradiator has been irradiation of electronics parts for radiation damage testing, a filter box has been designed and built using the guidance in ASTM E1249-10, 'Standard Practice for Minimizing Dosimetry Errors in Radiation Hardness Testing of Silicon Electronic Devices Using Co-60 Sources', in order to minimize low energy photon absorbed-dose enhancement effects. The board size to fit in the filter box is 2 inch wide by up to 5.5 inch long, and parts should not be mounted within 1/8 inch of any of the board edges.
Per nucleide.org, cesium-137 has a half-life of 30.1 years, and its decay results in the emission of a 662-keV gamma 85.0% of the time. (Cs-137 decays by beta minus emission to the ground state of Ba-137 [5.6%] and to the 662-keV isomeric level of Ba-137 [94.4%], which has a half-life of 2.55 min. Isomeric Ba-137 emits a 662 keV gamma 90.0% of the time.)
The approximate dose rate in silicon at the peak location is: