Probabilités d'émission photonique des principales raies gamma émises par les descendants du radon-222

摘要

There has been increasing interest over recent years in methods for measuring the activity of 222Rn (T↓(1 2)= 3.8 d). Among these methods. gamma-ray spectrometry would appear to be advantageous because the radionuclide activity can be measured directly without special preparation. Although ↑(222)Rn is not a gamma-ray emitter, the activity of this radionuclide can be derived from measurements of the daughters in equilibrium. To obtain accurate results by gamma-ray spectrometry, more precise nuclear data are needed. The photon emission probabilities of the main gamma-rays have been measured using two calibrated germanium detectors and four bulbs filled with a↑(222)Rn standard gas. The activity of the gas was accurately determined by an absolute measurement method based on counting in a defined solid angle the alpha particles emitted by radon condensed on a cold point. Efficiency responses were determined from a calibration using several standard point sources and two bulbs filled with ↑(133)Ba and↑ (152)Eu standard solutions : corrections factors were applied for the differences in geometry. An extensive number of gamma-ray emission probabilities were determined as given in detail in the main text.