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Title: Convenient counter for measuring alpha activity of smear and air samples

Abstract

A counting system has been designed to overcome the difficulties encountered when using silicon surface-barrier diodes for the measurement of spectra of short lived alpha -emitters. The system operates at atmospheric pressure with the source placed a minimum distance from the detector. Although this technique allows rapid measurement of the samples and avoids the other problems of measurement in a vacuum, it results in energy loss of the alpha particles in the air between the source and the detector. The distance cannot be decreased much below 5 mm due to the geometry of the diode and a 5.4 MeV alpha particle will lose about 270 keV in traversing this much air at 760 torr and 20 deg C. However, by flowing He through the chamber, the energy lost by a 6.4 MeV alpha particle was reduced to about 80 keV. Using helium also reduced the nonlinearity in the energy response of the system caused by the variation of stopping power with energy. Measurements of a /sup 239/Pu source made in vacuum, air and helium are compared. Frequent use of the system for a period of a year has demonstrated its stability, resolution and efficiency. One of the principal uses hasmore » been the measurement of the /sup 222/Rn from decay of its daughters. Also the system has been employed to measure thoron (/sup 220/Rn) in thorium processing operations, from the daughters trapped on a membrane air filter. In these applications, the vacuum method is both unduly time-consuming and capable of dislodging the alpha-containing dust particles from the filter. (UK)« less

Authors:
; ; ;
Publication Date:
Research Org.:
Oak Ridge National Lab., TN
OSTI Identifier:
4393940
NSA Number:
NSA-29-010254
Resource Type:
Journal Article
Journal Name:
Health Phys., v. 26, no. 1, pp. 114-116
Additional Journal Information:
Other Information: Orig. Receipt Date: 30-JUN-74; Bib. Info. Source: UK (United Kingdom (sent to DOE from))
Country of Publication:
United Kingdom
Language:
English
Subject:
N46130* -Instrumentation-Radiation Detection Instruments- Nuclear Spectroscopic Instrumentation; *ALPHA SOURCES- RADIOMETRIC ANALYSIS; *ALPHA SPECTROMETERS- SI SEMICONDUCTOR DETECTORS; AIR FILTERS; ALPHA DETECTION; ALPHA SPECTRA; ALPHA SPECTROSCOPY; ENERGY LOSSES; HELIUM; MEDIUM PRESSURE; MEV RANGE 01-10; PLUTONIUM 239; RADON 220; RADON 222; STOPPING POWER; SURFACE BARRIER DETECTORS

Citation Formats

Perdue, P T, Shinpaugh, W H, Thorngate, J H, and Auxier, J A. Convenient counter for measuring alpha activity of smear and air samples. United Kingdom: N. p., 1974. Web.
Perdue, P T, Shinpaugh, W H, Thorngate, J H, & Auxier, J A. Convenient counter for measuring alpha activity of smear and air samples. United Kingdom.
Perdue, P T, Shinpaugh, W H, Thorngate, J H, and Auxier, J A. Tue . "Convenient counter for measuring alpha activity of smear and air samples". United Kingdom.
@article{osti_4393940,
title = {Convenient counter for measuring alpha activity of smear and air samples},
author = {Perdue, P T and Shinpaugh, W H and Thorngate, J H and Auxier, J A},
abstractNote = {A counting system has been designed to overcome the difficulties encountered when using silicon surface-barrier diodes for the measurement of spectra of short lived alpha -emitters. The system operates at atmospheric pressure with the source placed a minimum distance from the detector. Although this technique allows rapid measurement of the samples and avoids the other problems of measurement in a vacuum, it results in energy loss of the alpha particles in the air between the source and the detector. The distance cannot be decreased much below 5 mm due to the geometry of the diode and a 5.4 MeV alpha particle will lose about 270 keV in traversing this much air at 760 torr and 20 deg C. However, by flowing He through the chamber, the energy lost by a 6.4 MeV alpha particle was reduced to about 80 keV. Using helium also reduced the nonlinearity in the energy response of the system caused by the variation of stopping power with energy. Measurements of a /sup 239/Pu source made in vacuum, air and helium are compared. Frequent use of the system for a period of a year has demonstrated its stability, resolution and efficiency. One of the principal uses has been the measurement of the /sup 222/Rn from decay of its daughters. Also the system has been employed to measure thoron (/sup 220/Rn) in thorium processing operations, from the daughters trapped on a membrane air filter. In these applications, the vacuum method is both unduly time-consuming and capable of dislodging the alpha-containing dust particles from the filter. (UK)},
doi = {},
url = {https://www.osti.gov/biblio/4393940}, journal = {Health Phys., v. 26, no. 1, pp. 114-116},
number = ,
volume = ,
place = {United Kingdom},
year = {1974},
month = {1}
}