The operation of Thick Gaseous Electron Multipliers (THGEM) in Ne and Ne/CH 4 mixtures, features high multiplication factors at relatively low operation potentials, in both single-and double-THGEM configurations. We present some systematic data measured with UV-photons and soft x-rays, in various Ne mixtures. It includes gain dependence on hole diameter and gas purity, photoelectron extraction efficiency from CsI photocathodes into the gas, long-term gain stability and pulse rise-time. Position resolution of a 100x100 mm 2 X-ray imaging detector is presented. Possible applications are discussed.

Italy) (4) Interdisciplinary Centre for Nanostructured Materials and Interfaces (CIMaINa), Milano (Italy) (5) Fondazione IRCCS "Istituto Nazionale dei Tumori", Milano (Italy)

Ferrous sulphate gel analysed by relaxation time measurements with NMR imaging is considered a useful dosimeter for 3D determinations of absorbed dose. A protocol for the gel preparation with agarose SeaPlaque that leads to a dosimeter with very high dose sensitivity is described. The dose-response curve slope is about 0.2 s(-1) Gy(-1) and the G factor turns out to be approximately 185 ions per 100 eV of absorbed energy. A method for making the measurements and analysing the results that brings about good result reproducibility is suggested. A thorough experimental study of the dependence of the dosimeter response on the elapsed time from preparation to irradiation and from irradiation to NMR measurement has revealed good reproducibility. The above characteristic of the gel system is very interesting, because it shows the possibility of utilizing the dosimeter for absolute dose determinations with satisfactory reliability.

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