The Model 240 Alpha-Beta Floor and Wall Monitor allows a user to quickly survey large areas for alpha-beta contamination. Compatible with either gas-proportional or scintillation detectors, the Model 240 cart comes in a floor-style only version, or a version that supports both floor and wall monitoring. Detector-to-surface spacing is adjustable and detectors are positioned for no “dead” zones when scanning. Gas proportional models come with a gas regulator, flowmeters, and gas lines, but a P-10 gas bottle is not included. The cart also provides two holders for spare detectors, to provide for replacement if a detector becomes damaged.
Utilizing an array of detectors instead of a single detector provides several advantages: 1) smaller detectors have lower backgrounds and thus lower minimum detectable activity (MDA); 2) smaller detectors allow the user to pinpoint the contamination; and 3) smaller detectors make it easier to maintain and replace fragile metallized polyester windows necessary for alpha detection.
The array of detectors is connected to an electronics box, which has a USB connection to a laptop. The electronics has 12 separate detector boards, each with its own settable high voltage, lower and upper thresholds, and alpha-beta count channels. The laptop display makes it easy to view all 12 detectors simultaneously, and provides setup wizards to help with establishing operating points for the detectors.
The system initially measures radiation background from the detector array, allowing the operator to see net counts during scanning. While scanning, a rolling average is checked on all 24 channels (12 each, alpha and beta) every half-second, and a momentary audible and visual alarm activates if any alarm points are exceeded. Measurements are also automatically logged to a file for subsequent reports.
