OR Research
Curriculum Vitae

Research Interests - Reuven Chen

My work consists of different aspects of thermally stimulated processes in solids, in particular thermoluminescence (TL) as well as on optically stimulated luminescence (OSL) and phosphorescence. In addition to the experimental study of TL in several materials, a number of basic processes associated with TL and OSL have been investigated theoretically. An important phenomenon studied both experimentally and theoretically has been the non-linear, usually superlinear, dose dependence of TL occurring in some materials. Also has been studied the sensitization of TL by irradiation of a sample followed by thermal annealing, anomalous fading and a new explanation has been given to the extremely high values of activation energy and frequency factor found in LiF and some other materials. Another work deals with the dose-rate effect of the excitation of TL, which has been observed in some materials, and is of importance in TL dating.

The method of Optically Stimulated Luminescence (OSL), which sometimes replaces TL in dosimetry and dating, has also been studied. The superlinear dose dependence observed in annealed quartz samples has now been given a theoretical explanation. Also has been studied the dose-rate effect of OSL. A distinction is made between pulsed OSL and cw OSL. It has been shown that when retrapping is a significant factor, pulsed OSL can be expected to be superlinearly dependent on the dose even when only one trapping state and one kind of recombination center are involved. The integral of emitted OSL light over a very long stimulating illumination can be superlinearly dose dependent only in the presence of competing states.

More recently, I have been studying the time decay of phosphorescence and of OSL. It has been found that in many cases these phenomena obey a stretched-exponential decay law, a behavior, which is quite ubiquitous in many other relaxation phenomena. I have also been studying the theories behind a number of some experimental results associated with TL and OSL. These include the nonmonotonic dose dependence of TL and of OSL, the latter in particular in the dosimetric material Al2O3:C. The effects associated with competition during excitation and during readout have been explained. Thermal-activation curves (TACs) have also been modeled as well as thermal transfer in OSL of quartz. Effects of pulse annealing and dating protocols for quartz based on thermally transferred OSL (TT-OSL) have been simulated by numerical solution of the relevant sets of differential equations. The technique of LM-OSL has been critically studied by theoretical and numerical methods. In work unpublished yet, two phenomena have been studied, namely the concentration quenching of TL and the two-stage thermal stimulation of TL which under certain circumstances may lead to anomalous stability of the TL signal.

In an entirely different area, Operations Research, I have published a number of papers concerning location problems with Euclidean distances. A number of new algorithms have been presented concerning single and multiple facility location in the plane.