SENSITIVITY OF $beta$ COUNTERS TO THE $gamma$ AND CONVERSION SPECTRA OF CERTAIN $alpha$ EMITTERS

Technical Report · Sat Jun 01 00:00:00 EDT 1963

OSTI ID:4702194

O'Connor, L P; Large, R S

The alpha emitters Am/sup 243/, Np/sup 237/, and Pa/sup 231/ are commonly used as tracers or for calibration purposes in BETA counting. High proportions of their-disintegrations lead to excited states of the daughter nuclei which are deactivated by gamma emission associated with conversion electrons and x rays. As all of these will be detected by BETA counters, the appropriate corrections have to be determined. Pure fractions of the alpha emitters from which the radioactive daughters were separated by chemical methods were counted in Geiger-Mueller and BETA proportional counters. The purity of the sources was checked by observing the growth of the daughters with a gamma spectrometer. Absorption curves were also plotted. From the results, counter sensitivities at optimum absorber thicknesses were determined for the three nuclides. The results for Am/sup 243/ were corrected for the known growth of Np/ sup 239/ during the time interval between chemical separation and counting. Results, expressed as counts per 100 alpha disintegrations, were obtained with a source-to-counter geometry of approximately 0.36 snd at a total absorber thickness of 10 mg/cm/sup 2/. The counts obtained appeared to be due largely to low-energy x rays in the conversion spectra or to low-energy gamma radiations when present. The differences in sensitivity between proportional and Geiger- Mueller counters are attributed to different gas fillings. Experimental results for Am/sup 241/ and Pu/sup 239/ were also included for comparative purposes. (auth)

• Research Organization: United Kingdom Atomic Energy Authority. Weapons Group. Atomic Weapons Research Establishment, Aldermaston, Berks, England
• NSA Number: NSA-17-029191
• OSTI ID: 4702194
• Report Number(s): AWRE-O-29/63
• Resource Relation: Other Information: Orig. Receipt Date: 31-DEC-63
• Country of Publication: United Kingdom
• Language: English

Related Subjects

INSTRUMENTS AND INSTRUMENTATION
ABSORPTION
ALPHA PARTICLES
AMERICIUM 243
BETA PARTICLES
COUNTERS
DECAY
ELECTRONS
FISSION PRODUCTS
GAMMA RADIATION
GAMMA SPECTROMETERS
GASES
GEIGER-MUELLER COUNTERS
ISOTOPE SEPARATION
NEPTUNIUM 237
PROPORTIONAL COUNTERS
PROTACTINIUM 231
RADIOCHEMISTRY
SENSITIVITY
SPECTRA
STANDARDS
THICKNESS
TRACER TECHNIQUES
X RADIATION