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Johns, Paul M.

Publications and source records attributed to Johns, Paul M..

Materials for Gamma Radiation Sensors

Sensors used for spectroscopic measurements of gamma radiation are most often scintillator or semiconductor materials. An overview is provided in this chapter on the materials and development techniques used in producing spectroscopic gamma radiation sensors. Challenges that prevent a perfect sensor are discussed along with the reasons why some sensor materials are ubiquitous despite their performance limitations. The types of sensors commonly used as detectors are discussed along with their key physical properties and electronic characteristics. Materials commonly utilized in radiation detectors are then reviewed to highlight how sensor materials have advanced since the earliest gamma detectors were developed

Johns, Paul M.↗

Multilateral Testing Workshop on Relocatable Portal Monitors

The procurement and deployment of radiation detection equipment is a multi-faceted challenge across the globe. Knowledge sharing of the testing methods used to evaluate equipment for deployment scenarios helps improve the understanding of deployed systems by the global community. The United States Department of Energy’s Nuclear Smuggling Detection and Deterrence Office (NSDD) performed a series of characterization measurements in 2019, focused on radiation detection systems that could function as relocatable portal monitors. The capstone activity for this project was a multilateral and cross-disciplinary workshop demonstrating, performing, and refining the techniques used in the characterization measurements with International Atomic Energy Agency (IAEA) and global partners. A group of technical experts including representatives from nine countries, the IAEA, and NSDD gathered at Sandia National Laboratories in Albuquerque, NM during September of 2019 for the Operational and Performance Testing and Evaluation of Relocatable Portals Workshop. Over the course of a week, the group discussed the necessity for and process of developing operational and performance requirements, challenges related to deploying radiation detection systems for the countries in attendance, use cases for deploying relocatable radiation detection equipment, and considerations related to testing equipment for appropriate deployment scenarios. All participants were given the opportunity to have hands-on experience with eleven relocatable systems in executing a limited scope characterization test comprised of six test scenarios. At the conclusion of testing, participants reviewed and presented their findings, and the group as a whole compared and contrasted their experiences. Suggested revisions to the test methods and ideas for further collaborations were discussed. This report discusses the logistical and planning considerations for bringing together experts across disciplines in a multilateral workshop on testing of radiation detectors, as well as presenting the testing methods performed, results, and paths forward. Success of workshops related to technical knowledge transfer and improvement of test methods is key to global technical and scientific support of radiation detection deployments.

Erchinger, Jennifer L.↗

Nuclear Interdiction Through Relocatable Detectors

The NNSA Office of Nuclear Smuggling Detection and Deterrence (NSDD) has investigated a set of minimal-infrastructure radiation detection systems as alternatives to fixed Radiation Portal Monitors (RPMs) for nuclear interdiction applications. These versatile and relocatable systems can improve nuclear security in missions or locations that do not warrant or support a standard fixed radiation detection system. Over 2019, a variety of relocatable detectors were characterized at the Interdiction Technologies Integration Laboratory at Pacific Northwest National Laboratory (PNNL). Evaluated detectors were diverse in their size and capabilities, ranging from backpack-sized systems to lane-spanning cargo scanning portals. Both spectroscopic and non-spectroscopic pedestrian and vehicle detection systems were characterized against uranium and plutonium sources. Signatures from the sources were modulated by both shielding and distance to quantify the performance of the relocatable systems as signal strength was decreased. Findings showed that relocatable spectroscopic detectors with isotope identification capabilities could reduce nuisance alarm rates compared to conventional fixed installation, gross-counting, radiation portal monitors. In vehicle scanning applications, detection ability generally trended with detection volume, regardless of spectral capability. In pedestrian scanning applications, several smaller backpack-sized detector systems were found to be more sensitive to detecting material than pedestrian portal monitors. The results of this characterization effort have helped inform the deployment of versatile equipment to improve nuclear security missions.

relocatable detectors, Nuclear Security↗