Evaluation of the radon interference on the performance of the portable monitoring air pump for radioactive aerosols (MARE).

A compact portable aerosol sampling and measurement device was developed at Jozef Stefan Institute (JSI). A CeBr3 scintillation detector is positioned centrally within a concertinaed filter assembly. It provides continuous and via network communications on-line monitoring of low levels of airborne radioactive particulates. The evaluation of the response of the device to the natural background at controlled conditions with elevated radon concentrations, performed at the National Institute of Ionizing Radiation Metrology of ENEA, is presented.

Compact radioactive aerosol monitoring device for early warning networks.

In the frame of the European metrological research project MetroERM, a compact portable aerosol sampling and measurement device was developed at Jozef Stefan Institute. The system incorporates a CeBr3 scintillation detector positioned centrally within a concertinaed filter assembly and an improved high flow rate air pump. It provides continuous on-line low level airborne radioactive particulate monitoring for field station use via 3G network communications. The calibration of the device was performed at National Physical Laboratory (NPL) with filters, spiked with a certified mixed nuclide solution. Additionally first tests were performed in an environment with an elevated radon concentration.

Wide view supertwisted nematic liquid-crystal light shutter.

We present a novel concept of a wide viewing angle liquid-crystal display (LCD) light shutter, taking advantage of the highly symmetric 180 degrees -twisted liquid-crystal (LC) configuration and the light propagation starting with a single mode. In a specific case of the high voltage driven LCD light shutter, the resulting very high overall symmetry allows for the efficient angular compensation of the light attenuation in the optically closed state using just a simple, specifically tuned, negative-birefringent c-plate retarder. The latter can be adapted to compensate for the positive optical birefringence of the homeotropically aligned LC molecules as well as also for a great deal of the angular dependence of the crossed polarizers. We show that the additional partial compensation of the angular dependence of the crossed polarizers can be explained by a combined effect of the positive birefringence of the homeotropically aligned LC molecules, negative-birefringence c-plate retarder, and an in-plane residual positive birefringence (a-plate) of the boundary layers of the LC molecules.