Experimental procedure. To carry out one or another type of studies on the effects of solar radiation and the experimental determination of the effectiveness of solar energy concentrators, you need, above all, a source of radiation which spectrum is close to the sun spectrum in outer space or near the Earth’s surface. Therefore, one of the most important components of system test stations is a solar simulator. As is known, considerable remoteness of Sun from Earth leads to the fact that solar rays incident on the objects in cosmic space or on the Earth’s surface in parallel, while the artificial radiation sources are located at relatively short distances from the surface of the test product. Solar simulator (SS) designed to simulate solar radiation. An important requirement of the SS is its minimum impact on the simulation of temperature and humidity regimes in the measuring chamber. SS includes light sources (lamps), forming optical devices (FOD), devices for radiation input into the chamber, reflecting mirror systems, power supplies for lamps, filters, measuring and control devices for simulator and its individual systems, as well as other auxiliary systems. The luminescent properties of the samples were tested using the newly developed experimental installation, LUMEN. The installation (Figure 2) provides ample opportunities for research in the field of fluorescent UV-visible spectroscopy with energy resolution at different temperatures.
Fig. 2. LUMEN laboratory installation
Figure 3 shows the scheme of optical measurements using LUMEN installation. The installation was mounted using standard serial equipment has been collected on the basis of equipment from serial production and two monochromators. To excite luminescence, a primary monochromator was used. In order to eliminate higher orders of diffraction gratings, quartz or LiF filters were arranged on the output window of the primary monochromator. Optical scheme of the primary monochromator provided UV radiation spot size 2 х 0.15 мм2 on the sample. The second monochromator was used for the registration of luminescence in UV and visible spectral regions. At the exit of the monochromator, a solar-blind photomultiplier was arranged to measure luminescence spectra. LUMEN installation operations, regimes of temperature and measurement range selection, were computer controlled, and processing of luminescence spectra was carried using special software.
Fig.3 The scheme of LUMEN experimental installation.
As a light source, DKsEL 1000-5 ultra-high pressure xenon lamp was used. For this xenon lamp, a high-aperture illuminator was specially made from KU quartz glass. The power of the xenon lamp radiation spectrum (240 nm to 360 nm) was 1,000 kW. The samples under investigation were placed within the working chamber on a copper crystal holder of a blow nitrogen cryostat that provided high vacuum not worse than 2·10– 6 Torr to guarantee the needed purity of the crystal surface at low temperature experiments.
The registration system made it possible to measure the luminescence spectra in different spectral points at the selective photoexcitation to 3.5 eV, as well as the luminescence spectra within the range of 1.2 -3.5 eV.
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