High local ionization density effects in X-ray excitations deduced from optical stimulation of trapped charge in Al2O3 : C

作者：Jain M^*; Botter Jensen L; Thomsen K J

来源：Journal of Physics: Condensed Matter , 2007, 19(11): 116201.

DOI：10.1088/0953-8984/19/11/116201

X- rays are used extensively in luminescence studies. Recent studies have shown a strong sample and material dependence in the response of the optically stimulated luminescence ( OSL) signal to x- rays, which cannot be accounted for by differences in the photoelectric cross- sections of these materials. In this paper we give direct experimental evidence for a high local ionization density caused during low energy x- ray interactions; this is similar to the effect produced by high LET ( linear energy transfer) radiations such as protons. This effect is deduced on the basis of optical stimulation of trapped charge in carbon doped aluminium oxide ( Al2O3: C) after exposure to different radiations (Sr-90/Y-90 beta, proton, Cs-137 gamma and x- rays), and making a comparative analysis of the changes in the initial OSL decay rates. The sensitive parameter. ( the decay constant) is > 100% larger for irradiations carried out with x- rays in comparison to that for low LET radiation such as beta particles.
We further show that the nature of the increase in lambda with dose, lambda( D), is a saturating exponential function plus a constant (lambda(0)), and that both lambda (D) and lambda(0) are unique for a given radiation type or more specifically its LET. Such behaviour is explained by superimposition of OSL from several first- order traps or by the presence of a competing trap in Al2O3: C. The understanding of x- ray interaction with OSL traps presented here explains the x- ray dose rate calibration problem in different materials, and opens up the area of studying ionization density effects in low energy x- ray interactions using the OSL of Al2O3: C.

• 出版日期2007-3-21