Improving ion collection in a personnel monitor for alpha contamination

A second-generation prototype personnel monitor for alpha contamination based on long-range alpha detection (LRAD) technology has been constructed and tested. Monitoring personnel for alpha contamination via LRAD has potential advantages compared with traditional methods, such as hand frisking. These advantages include reduced chance for human error, the ability to detect contamination in less accessible places on the person, and lower cost. A detection limit of 50 Bq (3000 decays per minute or 3000 dpm) was realized in a first-generation prototype. To improve ion collection in a second-generation prototype, a 1:8 scaled-model was constructed to investigate airflow. Model results provided significant input to the design of the second-generation prototype personnel monitor. Improvements in airflow have been realized, resulting in improved sensitivities. This improvement, along with reduced signal noise, has resulted in a lower detection limit of 7 Bq (400 dpm).