E. Caselli

CsTb2F7: an efficient radioluminescent material for fiberoptic radiation detection

In this article, the feasibility of using CsTb2F7 crystals as scintillating detectors to build radioluminescent fiberoptic dosimetry (FOD) probes has been investigated for the first time. The radioluminescence (RL) efficiency of this compound has been found to be more than twice as high as that of commercial Al2O3:C detectors under excitation with gamma radiation from a 60Co source. Additionally, the intensity of the RL signal shows no dependence on the accumulated dose. Both RL and photoluminescence spectra are nearly identical, showing emission bands at 490 and 550 nm and a minor band at 600 nm, which are compatible with the characteristic emission of Tb3+. In accordance with these results, stoichiometric terbium fluoride seems to be a promising material for use as an RL sensor for FOD in radiation medicine.

A Procedure for Calculation of the Density of States of Wide-Gap Semiconductors and Dielectrics by Means of the Recursion Method

The recursion method allows to calculate the density of states for electrons in solids from a continued fraction. Since only a finite number of coefficients can be computed, the truncation of the continued fraction requires a procedure to approximate the effect of the uncalculated coefficients. Different procedures have been propounded. When they are applied to crystals having a wide gap this often shows up as a minimum of the density of states, which renders the method unappropiate to find the width of a gap and the energy of impurities and defects relative to the band edges. In this paper a procedure based on the method due to Nex [9] to find the integrated density of states is reported that yields better results than the usual ways of concluding the continued fraction.

Characterization of new materials for fiberoptic dosimetry

In this work we have investigated the radioluminescence (RL) characteristics of three materials (Mg2SiO4:Tb, CsY2F7:Tb and KMgF3:Sm) in order to determine whether they can be used as real time dosimeters in the the framework the fiberoptic dosimetry (FOD) technique. This technique is based on the use of scintillating materials coupled to the end of an optical fiber, which collects the light emitted by the scintillator during irradiation. Since usually the intensity of the emitted light is proportional to the dose-rate, the technique provides a reliable measuring method, which can be employed in radiotherapy treatments.