b'Novel Methods to Produce anNew production methods for argon-37 standards improve global capabilities for Argon-37 Standard establishing evidence of unsanctioned underground nuclear detonations.T he purpose of this research was to produce a measurable quantity of radioactive argon-37 (37Ar) through photonuclear production methods. The detection of 37Ar above background levels uniquely and clearly indicates the underground detonation of a nuclear device. Fission neutrons generated from a nuclear blast interact with calcium present in rocks and soil in the underground TOTAL APPROVED AMOUNT:environment. The interaction of these fission neutrons with calcium-40 (40Ca) $700,592 over 3 years produces 37Ar, through a 40Ca(neutron, alpha) 37Ar reaction. The gas then seeps PROJECT NUMBER:through the underground environment to the surface for detection by on-site 18A12-076 inspectors. Inspections are performed to aid in the regulation of nuclear non-proliferation treaties, such as the Comprehensive Nuclear-Test-Ban treaty. 37Ars PRINCIPAL INVESTIGATOR:half-life of approximately 35 days means that detection is possible long after the Edna Crdenas detonation, making its identification valuable during on-site inspections.CO-INVESTIGATORS: Successful production of 37Ar on a small scale would provide proof-of-principle Ariana Foley, INL leading to opportunities for yet-to-be realized large scale sample production. An Brian Bucher, INL 37Ar standard would give on-site inspectors the ability to calibrate their detectors Jacob Brookhart, INL and measure detector efficiency, thus providing higher accuracy in quantifying Jessica Ward, INL detected 37Ar. An 37Ar standard would also provide authentic samples to test novel Mathew Snow, INL detectors and improve models predicting the diffusion of 37Ar in an underground Troy Robinson, INL environment. Current research into the production of 37Ar utilizes neutrons generated Jon Stoner, Idaho Accelerator Center from nuclear reactors on samples containing 40Ca. The research in this project studied COLLABORATOR: photonuclear production of 37Ar through photon bombardment on potassium-39, Idaho Accelerator Center 40Ca, and 38Ar using electron linear accelerators. Linear accelerators are more readily available than nuclear reactors used for experiments and have a wide range of power output, allowing for the optimization of 37Ar production and potentially providing a novel production pathway. This project advanced research in security solutions that prevent, detect, and counter nuclear and radiological threats.Fission neutrons interacting with the calcium in rocks and soil generate37 Ar at a nuclear detonation site. The 37Ar seeps to the surface where it can be detected by sensors.110'