Calibration: Perform the following procedure at three-month intervals. (Calibrate the HV indication of the PRS-1 used prior to probe calculation.): 1. 2. Inspect and clean or repair the probe face and connector es necessary. af the mylar is removed, allow several hours for photomultiplier (PM) tube stabilization before proceeding.) Run an alpha plateau using a "medium" or "hot" 239py or 2414m standard. Start at 800 volts and take reading every 50 volts. Use the 1-minute sealer range. The operating voltage will be located on the flat portion of the curve and should be at least 75 volts higher than the knee of the curve. 3. Run a 30-minute background check at the operating voltage. If the background is greater than 1 cpm, decontaminate the probe face. 4. Check that the beta response (R,-Rp) at the operating voltage is not more 5. than 1 epm using the procedure: a. Determine Rg, (source + background qpin) over a 30-minute interval (6 five-minute measurements) using a "hot" 90sr-y source. b. Determine Ry, (background epm) over a 30-minute interval (6 five-minute measurements) in the same geometry that R, was determined. Using a "medium" 239py or 24l1Am standard compute probe efficiency and calibration factor. Use the 1-minute scaler range. Assume a 2n counting geometry so that efficiency and calibration factor will be epm/epm. (Eff. = epm/(source dpm/2).) 6. List the operating voltage, efficiency and calibration factor on the calibration label. (C.F. = 1/eff.) RASP-1 General: The RASP-1 alpha scintillation probe uses a cartridge type replaceable detector and a shock-mounted PM tube to provide a survey instrument more rugged than the AC-3 probe. Due to its smaller active face area, the RASP-1 is a less sensitive survey detector, but is useful in confined areas or where an AC-3 probe might be damaged. Calibration: Perform the same procedure as the AC-3 except start the plateau at 700 volts. The ealibration interval is three months. SPA-1 General: The SPA-1 is a windowless alpha scintillation probe with a built-in sample holder. It is designed to count small diameter swipe papers. It is useful for monitoring nose swipes and for removable contamination, Calibration: At three-month intervals perform the same procedure as the AC-3 except start the plateau at 700 volts (use 239py standard). A-29-4