The developed elastic scintillators based on polymethylphenylsiloxane rubber are characterized by an elevated light output and a low toxicity. The increase of their light output is achieved by raising the content of phenyl chains, varying the chemical structure of luminescent additions and using isopropylnaphthalene. This high-boiling solvent introduced into the scintillation siloxane compositions is confined within siloxane matrix after the hardening of the rubber.

Prior work has shown that there is a correlation between trap densities and scintillation efficiency of cerium-activated, lithium-aluminosilicate glasses. Raman spectroscopy has strongly suggested that phase separation may be playing an important role in governing the scintillation efficiency. In this study, we relate the thermoluminescence glow-curve data and microstructural analysis for a compositional series. The thermoluminescence data provide information about the traps in the neighborhood of the activator (Ce3+). The microscopy and crystallization of the glasses provide direct evidence of activator partitioning.

Pacific Northwest Laboratory (PNL) has fabricated cerium-activated lithium silicate scintillating fibers via a hot-downdraw process. These fibers, which, as produced, typically have a transmission length (e−1 length) of greater than 2 meters, are found to undergo aging when subjected to room air. The aging, which is complete in a few weeks, reduces the transmission length to the order of 0.5 meter. Because of the high alkali content of the glass (on the order of 20-30 mole % lithia), we have attributed this aging to aqueous corrosion at the polymer cladding/glass interface. Changes in transmission with chemical treatment of the surface support the corrosion model. Fiber transmission performance has been preserved by modifying the hot-downdraw to a double crucible to produce glass-on-glass waveguides.

A family of low melting temperature tin fluorophosphate glasses that can incorporate certain organic compounds has been under investigation. The glasses are comprised principally of SnF2, SnO, and P2O5; the addition of small amounts (< 5%) of Pb improves chemical durability. These materials are dense, reasonably water durable, and easily fabricated. Photoluminescence properties of glasses doped with pyrene, POPOP, stilbene 420 and several other organic molecules were studied. All of the doped glasses exhibited intense photoluminescence. Pyrene doped glass was found to have monomer-triplet and dimer-excimer pyrene species present, depending on the dopant concentration. Scintillation properties of the glasses were also investigated. Generally a very fast (~1 ns or less) but weak luminescence was observed. Results of these studies suggest that higher concentrations of the dyes must be incorporated into the glass and more efficient energy transfer from the glass host to the organic fluor must be attained for these materials to be useful as fast scintillators.

In the quest for low cost scintillators to equip the very large electromagnetic calorimeters for future High Energy Physics experiments, scintillating glasses can offer an attractive alternative to crystals. The expected production price is indeed supposed to be reduced as compared to crystals, especially for very large volumes. An intense R&D effort has been made by the Crystal Clear collaboration to develop heavy scintillating fluoride glasses in close collaboration with the industry. Results will be shown on the fluorescence and scintillation properties as well as on the radiation resistance of different types of fluoride glasses. Ideas about possible improvement of present performances will also be given.

Reflectivity and fluorescence excitation spectra and fluorescence decays of CeF3 and LaF3:Ce have been recorded and analyzed in the VUV range up to 120 eV and in the X-ray region using the synchrotron radiation. Dominant mechanisms are identified in various regions of excitation, leading to different shapes of the excitation spectra and typical profiles of the decay curves. Strong difference in the light yield of fluorides and oxides are shown and discussed in terms of relative energies of levels of cerium and of the valence and conduction bands of the solid compounds.

The time-resolved luminescence spectra and decay kinetics of BaF2, BGO, and CeF3, were measured with the dissector technique using X-ray synchrotron radiation (SR)of different spectral composition from wiggler mounted at VEPP-3 storage ring (Novosibirsk).

Two effects of X-ray excitation energy on the luminescence parameters were observed: modifications of the emission spectrum and acceleration of decay kinetics. Under the excitation by soft X-ray SR the 220 nm emission band for BaF2 is broadened, whereas shorter wavelength part of CeF3 and BGO emission spectra increases. For luminescence decay of excitons and crossluminescence the degree of the deviation from the single exponential law depends on the photon energies and increases under soft X-ray excitation as well. These effects are supposed to be due to the interaction of electronic excitations created after the relaxation of deep core holes.

Fast intrinsic luminescence was observed for Cdl2, and CsPbCl3 under X-ray SR excitation. 500 nm band of Cdl2 has characteristic time τ=4.6 ns, whereas 420 nm band of CsPbCl3 shows very fast decay with τ=0.2 ns.

The Auger decay of a core hole results in appearance of several strongly correlated excitations. This excited region strongly polarizes the lattice and thus the defect creation is possible. In all cases the core hole causes the strong local perturbation of electronic and lattice subsystems. The creation of such excited region with mutual relaxation of correlated electrons and holes can result in the increase of the efficiency of energy transfer to activators, acceleration of the luminescence kinetics, and the appearance of radiation-induced luminescence centers.

The studies of the dependence of the optical properties of various scintillators on intrinsic structural defects have been reviewed. The greater part of the review is devoted to the defects introduced by plastic deformation. A wide range of variations in the light output, spectral distribution, kinetics and other properties has been observed. These defects can be induced during crystal growth, annealing, processing, etc. The proper regulation of the superstructure of intrinsic defects can ensure the production of high quality scintillators having required properties.

The connection of lead fluoride luminescence properties with its structural characteristics has been studied. Single crystals of the cubic and orthorombic phases, cubic and orthorombic powders, pressure compacted orthorombic ceramics, plastically deformed crystals were used. The photo- and X-ray excited luminescence spectra have been investigated. The experimental results have shown that the room temperature luminescence of lead fluoride can be accounted for local light emitting centers which are produced by the intrinsic structural defects in the orthorombic lead fluoride.

The spectral characteristics for cubic and orthorhombic lead fluoride excited by light with energies of 5–2.5 eV, X-ray, and α-particles were studied. It is shown that the room temperature luminescence in orthorhombic lead fluoride is connected with resonance excitations of some luminescence centers. Possible models of the centers responsible for this phenomenon are proposed.

An extremely dense single crystal of PbF2 with the orthorhombic structure is an attractive material for use as a scintillator. Its luminescence properties are quite different from those of the currently well-known cubic PbF2 crystal. The spectroscopic study of orthorhombic and cubic monocrystals of PbF2 as well as of crystals of mixed structure containing both the orthorhombic and cubic phases is presented in the paper. The orthorhombic PbF2 luminescence contains a visual part with the rapid kinetics (≈100 ns) at temperatures near 100 K.

A series of BaF2 crystals doped with 10% mole fraction of each rare earth element has been grown, and the effect of these dopants on the slow luminescence (due to anionic self trapped excitons) and fast luminescence (due to core-valence transitions) has been studied. While significant suppression was observed for both components, the best dopants for suppressing the slow component of barium fluoride (up to 25-50%) while maintaining the luminosity of the fast component are La, Y, and Lu. The luminescence of Ba0.9Eu0.1F2.1 is almost entirely fast (>90%), but with low light output. For two rare earth dopants (La and Gd), the effect of slow and fast component suppression was studied as a function of concentration (Ba1-xRxF2+x with x≦0.5 for R=La and x≦0.3 for R=Gd). The suppression is non-linear with dopant concentration, with the relative degree of slow component suppression correlated with the melting point of these samples.

A mechanism of scintillations based on sensitisation of radiating centres luminescence by Pb2+ ions is proposed for PbWO4 crystals.

Fast UV-luminescence of CsI has been studied by time resolved luminescent spectroscopy. Experimental data support the conclusion that the high temperature (150–500 K) fast UV-luminescence arises from the trapping of free excitons in sites perturbed by lattice defects.

Data about fast luminescence of natural and synthetic diamonds are presented. Analysis of the luminescence spectra and the kinetics of both the luminescence and pulse conductivity leads to the conclusion that these processes are determined by the band electron lifetime.

The spectra and kinetics of the fast luminescence and optical absorption of Bismuth Germanate (BGO) after excitation by single high-power nanosecond and subnanosecond electron pulses were studied. The short-lived optical absorption of the center responsible for BGO scintillations is assigned. The cause for the low scintillation yield in BGO is discussed in comparison with analogous measurements in crystalline and amorphous silicon dioxide. The ultrafast (decay time < 50 ps) luminescence is observed and it is concluded that it can be connected to intraband transitions.

Two kinds of luminescence (excitonic luminescence and excitonic molecule luminescence) were investigated for solid solutions AgBr1-xClx after pulsed electron beam and N2 laser irradiation. Careful theoretical treatment of a set of experimental excitonic luminescence kinetics is presented. It is shown that the effective activation energy of Agoi migration is a linear function of the composition x. The narrow peak of the excitonic molecule luminescence shifts from 2.66ev in pure AgBr towards higher energies as x increases.

The temperature stability of NaI(T1) scintillators is studied for crystals with various Tl+ impurity content. It is shown that supersaturation of the T1+ ions and regulation of solid solution decomposition increase the light output at elevated temperatures. An explanation of this phenomenon is proposed.

We have modified our previous fast analog technique to determine the luminescence decay times of scintillators following an excitation with a Sr90 β3-source. In the original technique [1], the sample was excited with a nitrogen-pumped dye laser, and the fluorescence pulses (consisting of typically 50 to 1000 photons) were detected by a multi-channel plate photomultiplier tube (MCP-PMT). The output from the MCP-PMT was directed to a fast waveform digitizer triggered externally by the exciting laser. In the modified technique, the digitizer acquires the fluorescence decay in the internal trigger mode, as no corresponding external trigger pulse is available from the Sr90 source. For efficient light collection from scintillators, an ellipsoidal mirror assembly has been tested. The fluorescence decays are acquired as multi-photon pulses and are subsequently corrected for the temporal instrument response by using a deconvolution technique. The overall time resolution of the technique is about 100 ps. The fluorescence decay time obtained using this technique for a commercial scintillator (SCSN-81) agrees well with literature. We also discuss our results on new epoxy-polymer based scintillators prepared in our laboratory. The primary motivation for this work was development of new scintillators with shorter fluorescence decay times for high collision rate experiments.