An Investigation of Radiological Risk in Test Dwelling through Experimental and Simulation Approaches

389-400Study of radon, thoron and their progeny are important from radiological point of view. This work is towards their prediction, measurement, decay behavior, estimation of associated factors and effective dose for different room conditions (open and closed). The levels are measured experimentally using active monitors, dosimeters and deposition-based progeny sensors. Radon is found uniformly distributed for the open room condition while thoron shows complex behavior. A decrease in radon concentration is found through prediction and measurement for open room condition with increase of homogeneity. The solid radon progenies got distributed uniformly in the closed room. Total equilibrium equivalent concentration (EEC) for thoron is found comparatively more for the open room condition, EEC (unattached) found more for the closed environment, while for radon both are higher for closed room condition. The gas levels along with distribution are found to be affected by the vent ambiance. The average of unattached factors is estimated to be fRn (0.1) for open, (0.2) for closed while fT (0.1) for open, (0.3) for closed room. Comparison of measurement and simulation approach shows reasonable matching of the results and validation of the simulation code. Different doses and conversion factors are also estimated and found within the recommended limits

In-induced stable ordering of stepped Si(553) surface

The growth mechanism and adsorbate-induced surface morphology of metal atoms on semi conducting surfaces crucially determines the electronic and physicochemical properties of thesemetal/ semiconductor systems. In this study, we investigate the kinetically controlled growth of indium( In) atoms on the high index stepped Si(553)-7 x 7 surface and the thermal stability of various novel-Ininduced superstructural phases formed during adsorption/desorption process. Auger electron spectroscopy analysis reveals that In adsorption at room temperature (RT) and at 350 degrees C, with a controlled incident flux of 0.0016 ML/s, proceeds in the Stranski-Krastanov growth mode where two dimensional( 2D)/three dimensional (3D) islands are formed on top of two complete monolayers. At higher substrate temperature up to 450 degrees C, the growth of In atoms occurs in the form of islands on the bare Si(553) surface, and In coverage is limited to the sub-monolayer regime. During the thermal desorption of the RT grown In/Si(553) system, the In clusters rearrange themselves and an unusual "cluster to layer" transformation occurs on top of the stable monolayer. In situ low energy electron diffraction analysis during adsorption and desorption shows the development of various coverage and temperature dependent Ininduced superstructural phases on Si(553) surface, such as: (8 x 2) after annealing at 520 degrees C with coverage 0.5 ML, (8 x 4) after annealing at 580 degrees C (similar to 1 ML coverage) and (553)-7 x 1 + (111)-root 3 x root 3-R30 degrees at 0.3 ML (630 degrees C). These adsorbate-induced superstructural phases could potentially be utilized as templates for pattern assisted growth of various exotic 1D/2D structures for optoelectronics and photovoltaic applications