A determination of the gamma-ray emission of radium

Abstract

,-ray emission of radi um (roentgen s per m illi gram-hour at 1 centimeter) have been ma de by m eans of a graphite cavity ionization c ha mber. An au xi liary experi mental examination of th e stopping-power correction fo r t he non-air-equi:a lcn ce of.the cavity wall is a lso described . The r esult ing average valu e fot' t he -y-ray emlSSlOn of radIUm (enc losed in an 0.5-millimet er platinum capsule) is 8.26 ± 0.05 roentgen s p er mi ll igra m-hollr at 1 centime ter, whi ch is based upon the concluslOnt.hat the stoppmg-power data of Bakkcr and SegJ'c are con sistent with t he res ults of the a uxliJary expenment.

Cavity ionization as a function of wall material

“…The agreement between this theory and the experimental results otherwise is not very exact, although it generally seems to be an improvem ent upon the other theory, particularly at small separations. Recent ionization measurements by Greening [2], by Whyte [3], and by Attix and Ritz [1], also confirm that the modified cavity theory gives improved agreement and predicts closely the …”

“…In table 7 are listed the values of (l /s) obtained from this theory, based upon the same mean-excitation potentials (1) and density-effect data as were used before. Table 5 has again been used to weight (l /s) by the electron-energy flux at each (mean) energy, To present in a material.…”

“…'Note that tbe filtration data gh 'eu for 150 kv in this reforenee are in error, according to private COlTI1TIunication with the authors. 1 The inherent filtra tion of the X-ray tube was equivalent to 3-mm A!. 2 A s det.ermined from attelluation measuremen ts in copper.…”

“…It was found that, for wall separations as great as 1 cm, there was a negligible difference in ionization collected whether the rings were operated at the potential of the highvoltage wall or at ground potential, indicating no field-distorting effect. Glancing angle attenuation (1) of the ,),-rays striking the rings was checked by also constructing rings of 1-cm depth but with a cone shape to allow the rays to strike the inner-ring surface at a 45° angle rather than a glancing angle, resulting in much less attenuation.…”

Intercomparison of National Roentgen and Gamma Ray Exposure-Dose Standards

“…( , 1959b. The graphite cavity chamber used for the cobalt 60 and cesium 137 gamma ray beam calibrations is described by ATTIX and RITZ (1957) and the corrections are discussed by WYCKOFF (1960). (The stopping power corrections used for these calibrations are those labeled 'Bakker and Segrt' in the paper mentioned here.…”