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Micro-pulling down (μ-PD) method allows to prepare single crystals quickly and relatively inexpensively. Since it is a melt growth and taking into account segregation phenomena, the μ-PD method allows also to obtain single crystals characterized by dopant concentration gradients. Especially, taking the advantage of the grown crystal high aspect ratio, it allows to prepare crystalline samples with variable and wide range concentrations of dopants. These samples can help in understanding the correlation between dopant concentration and luminescence properties.

A radioluminescent (RL) dosimeter based on cerium-doped silica optical fibre was recently developed by means of the sol-gel and powder-in-tube techniques. The detector, already tested with both soft X-rays and more energetic photon beams used in conventional radiation therapy and in stereotactic radiosurgery, showed interesting and promising properties. A feasibility study for the use of the doped fibre in proton therapy is here presented. The measurements were performed at the proton therapy facility of the Paul Scherrer Institute (PSI) using a 138 MeV scanned proton pencil beam. The preliminary results showed a good sensitivity of the RL dosimeter to proton beams and a satisfactory reproducibility of the response (better than 0.5%) following repeated irradiations under the same experimental conditions. A linear dose response of the signal was observed in the investigated range (0.1-10 Gy) and, moreover, the stem effect proved to be negligible. The characteristic of the system to enable a real-time measurement of the dose rate was exploited for time-resolving different spot scanning sequences. Finally, the detector was used for assessing the depth dose curve in water: by comparing the curve obtained with the doped fibre with the corresponding one measured with a standard ionization chamber, a quenching effect in the order of 12% in the region of the Bragg peak was observed, as consequence of the decrease of the scintillation efficiency with increasing the Linear Energy Transfer (LET) of protons. © 2009 Elsevier Ltd. All rights reserved.

Photon beams produced by a cobalt-60 Unit and a 6 MV linear accelerator equipped with stereotactic collimators were used to investigate some dosimetric properties of a radioluminescent dosimeter based on a Ce-doped optical fibre. The stability of the signal with increasing the irradiation time, enabled a reliable and real-time measurement of the dose rate. The methods, recently developed, of optical coupling, light collection and signal processing allowed to achieve a satisfactory signal to noise ratio, a good reproducibility and a linear dose-response. The punctual dimension of the doped fibre diameter was exploited in the characterization of stereotactic fields, providing results in agreement with those obtained using a micro-ionization chamber. © 2008 Elsevier Ltd. All rights reserved.

A set of terbium-doped silicate glasses densified up to 1050 °C was prepared by the sol-gel method. A broad range of dopant concentrations (0.001-10 mol%) was considered together with an undoped sample as a reference. The effects of a high-temperature (1600-1800 °C) post-densification rapid thermal treatment (RTT) on the luminescence properties of the samples were investigated. RTT enhances the scintillating efficiency of the samples increasing the radio-luminescence intensity up to two orders of magnitude. The relevant effects induced by RTT on radio- and photo-luminescence spectra (RL, PL) and on PL decay curves indicate the occurrence of modifications of the surroundings of Tb3 + luminescence centres. © 2007 Elsevier Ltd. All rights reserved.

LiCaAlF6 (LiCAF) crystals doped with two different ions (europium and lead) have been investigated as potential new dosimetric materials. The stability of thermally stimulated luminescence (TSL) glow peaks in LiCAF:Eu was evaluated by means of the initial rise technique. The decay times at room temperature of the traps related to the dosimetric glow peaks were found to range between 40 and 2 × 104 years confirming the good dosimetric characteristics of this crystal. The glow curve of LiCAF:Pb is dominated by a peak at approximately 300 °C emitting in the UV region ( 3P0,1-1S0 transition of Pb 2+) superimposed to a very broad structure at lower temperature (20-200 °C) featuring recombination at an intrinsic defect centre. The anomalous behavior of the low temperature structure during thermal cleaning procedures prevented any reliable numerical analysis of the TSL glow peak at 300 °C. © 2009 Elsevier Ltd. All rights reserved.