Improvement of ESR dosimetry for thermal neutron beams through the addition of gadolinium

Abstract

In this paper, the addition of gadolinium is proposed as a useful tool to enhance the electron spin resonance (ESR) sensitivity of organic compounds to thermal neutrons. The target of this work is the detection, through the ESR technique, of the thermal neutron fluence in a mixed field of photons and neutrons. Gadolinium was chosen because it has a very high capture cross section to thermal neutrons; its nuclear reaction with thermal neutrons induces complex inner shell transitions that generate, besides other particles, Auger electrons, which in turn release their energy in the neighborhood (only several nanometers) of the place of reaction. Gadolinium was added to two organic molecules: alanine and ammonium tartrate. The main result obtained was a greater neutron sensitivity for dosimeters with gadolinium than for those without gadolinium for both organic molecules used. Since a dosimeter pair is required to discriminate between the two components of a mixed field, we studied the response of each dosimeter pair irradiated in a mixed field. Through a blind test we verified the usefulness of this dosimetric system and we obtained an estimate of the fluence in the mixed field with a relative uncertainty of 3%, when the pair composed of an alanine dosimeter and a dosimeter with alanine and gadolinium is used.

ESR response of watch glasses to proton beams

“…Various materials have been studied by means of ESR technique for dosimetric purposes, such as alanine, ammonium tartrate and tooth enamel [9][10][11][12][13][14][15].…”

The Effect of Gadolinium on the ESR Response of Alanine and Ammonium Tartrate Exposed to Thermal Neutrons

“…Once this response is known, it is possible to create a dosimetric system that can discriminate the neutron component from the ␥-ray component (32,33). Since our approach could be applied to any mixed (n, ␥) radiation field with any neutron and photon contributions, to obtain a good estimation of the photon dose, it is necessary that the absorption and scattering properties of the pellets for photons simulate as nearly as possible those of soft tissue or other reference materials such as water, etc.…”

ESR dosimeter material properties of phenols compound exposed to radiotherapeutic electron beams

“…The tested materials (organic and inorganic) include ammonium tartrate, ammonium formate, taurine, potassium tartrate hemihydrate, lithium formate, dithionates, strontium carbonate, sodium tartrate dehydrate and strontium sulfate, hydroxyapatite, glass and some others [42][43][44][45][46][47][48][49][50][51][52][53][54]. Another methods followed to increase the sensitivity to various types of ionizing radiations is the addition of dopants such as gold, gadolinium, silver in small concentrations (to avoid the loss of tissue equivalence) [55][56][57][58][59][60][61][62][63].…”