ABSTRACT
Nano-CaF2, prepared by the co-precipitation method, was annealed under different annealing conditions to improve its thermoluminescence (TL) characteristics. Different annealing parameters, such as temperature (400-700°C), duration (1-4 h) and environment (vacuum and air), were explored. The effect on TL sensitivity, peak position (Tm) and full-width at half-maximum (FWHM) with respect to the different annealing conditions are discussed as they are the measure of crystallinity of the material. Annealing temperature of 500°C with annealing duration of two and a half hours in vacuum provided the highest luminescence response (i.e. maximum sensitivity, minimum peak temperature and FWHM). Wide detectable dose range (5 mGy to 2 kGy), absence of thermal quenching and sufficient activation energy (1.04 eV) of this phosphor make it suitable for dosimetric applications.
Subject(s)
Calcium Fluoride/chemistry , Luminescence , Nanostructures/chemistry , Temperature , Thermoluminescent Dosimetry/methods , Dose-Response Relationship, Drug , X-Ray DiffractionABSTRACT
A new compact light-emitting diode (LED) sun photometer, in which a LED is used as a spectrally selective photodetector as well as a nonlinear feedback element in the operational amplifier, has been developed. The output voltage that is proportional to the logarithm of the incident solar intensity permits the direct measurement of atmospheric optical depths in selected spectral bands. Measurements made over Ahmedabad, India, show good agreement, within a few percent, of optical depths derived with a LED as a photodetector in a linear mode and with a LED as both a photodetector and a feedback element in an operational amplifier in log mode. The optical depths are also found to compare well with those obtained simultaneously with a conventional filter photometer.
ABSTRACT
A backscatter Nd:YAG laser radar, the first of this type in India to our knowledge, was developed at the Physical Research Laboratory, Ahmedabad (23° N, 72.5° E), for middle atmospheric studies. The system has been operational since April 1992. The system details and sample results on the Mt. Pinatubo volcanic aerosol layer and its decay as observed over this tropical site are presented and discussed. The future augmentation of the system and planned activities are also outlined.
