Position Sensitive Alpha Counter for RASA Filter Screening

78017S Verification instruments are required to assure that nations adhere to their promises not to develop or test nuclear weapons. To address this need, the DOE's Pacific Northwest National Laboratory has developed a Radionuclide Aerosol Sampler/Analyzer (RASA) that extracts sub-micron particulates of nuclear debris from the atmosphere by filtering 20,000 cubic meters of air per day. If nuclear debris is detected, the protocol specifies that the filter be divided into an archival piece plus two pieces to be sent to Certified Laboratories for confirmatory test. The difficulty with this protocol is that if the number of debris fragments is small, it is difficult to assure that all three pieces are representative. This project will develop technology to provide this assurance. The technique is based on the fact that fission fragments are strong alpha particle emitters. A recently developed ultra-low-background alpha counter will be expanded to image the ionization tracks produced by alpha particles and thereby locate the fission fragments from which the alpha particles emanate. In Phase I, an existing detector will be outfitted with a modified anode and existing electronics. The modified detector will be used to capture data from an alpha source, and algorithms will be developed to identify the alpha particle ionization tracks. As a proof of principle, at least 1 cm FWHM spatial resolution will be demonstrated, and a commercially viable instrument will be designed. This effort will lay the groundwork for Phase II, in which a counter will be developed that can locate fission fragments on RASA filters with a spatial resolution of 5 mm FWHM or better. Commercial Applications and Other Benefits as described by the awardee: Applications for the proposed technology fall into three broad areas: (1) support for the network of RASA detectors that is being deployed worldwide; (2) support for DOE ultra-low background detector programs (e.g. Majorana) where large numbers of detector parts must be screened for low alpha emissivity; and (3) use in environmental and remediation measurements where the detector's spatial resolution would allow a large number of low level samples to be counted in parallel.