Some phosphor materials, when previously exposed to radiation, have the property of emitting light when heated. This phenomenon, called thermally stimulated luminescence or thermoluminescence (TL), is used to measure the amount of radiation (dose) to which a material has been exposed, if the amount of light emitted (thermoluminescent emission) is proportional to the exposure dose. Dosimetry refers to the measurement of radiation dose, and the phenomenom of TL is the basis of the TL dosimetry, which since it was proposed by Farrington Daniels in the 1950s remained as the most widely used dosimetric technique [1, 2].
A Risø TL/OSL model TL/OSL-DA-20 unit equipped with a 90Sr beta radiation source was used to perform beta irradiations and the TL measurements. All irradiations were accomplished using a 5 Gy/min dose rate at room temperature ( 295 K (22 °C)). The TL readouts were carried out under N2 atmosphere using a heating rate of 5 K/s. Figure 1 show a simplified diagram and a picture of the TL measurement system.
To characterize the structure, Raman spectroscopy was carried out using a Dilor micro-Raman spectrometer with a 20 mW, 632 nm He-Ne laser equipped with a confocal microscope. The PLICVD system use small micro-doses of liquid precursors the precise micro-doses of such solution are injected through a computer-driven system into the evaporation zone, where they instantly evaporate (flash evaporation), so there is no time for chemical changes of the precursor.
Nanodiamond films growth from tequila using the PLICVD technique are promising for the development of high dose detectors and dosimeters. The technique assures good reproducibility of samples synthesis. The characteristic glow curves display emission in the interval from 200 to 250 °C, which is considered very suitable to guarantee both, thermal stability to avoid TL fading under storage, and non interference of the TL signal and the black body radiation.
Thursday, December 01, 2011
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