Ultrafast hybrid nanocomposite scintillators: A review

In recent years, demand for scintillation detectors with high time resolution (better than 100 ps) has emerged in high-energy physics and medical imaging applications. In particular, time of flight positron emission tomography (TOF-PET) can greatly benefit from increasing time resolution of scintillators, which leads to the increase of signal-to-noise ratio, decrease of patient dose, and achievement of the superior spatial resolution of PET images. Currently, extensive research of various types of materials is carried out to achieve the best time resolution. In this review, the recent progress of various approaches is summarized and scintillation compounds with the best temporal characteristics are first reviewed. The review presents the physical processes causing fast luminescence in inorganic and organic materials. Special attention is paid to nanocomposites which belong to a new perspective class of scintillating materials, consisting of a plastic matrix, inorganic nanocrystalline fillers, and organic or inorganic luminescence activators and shifters. The main features and functions of all parts of existing and prospective nanocomposite scintillators are also discussed. A number of currently created and investigated nanocomposite materials with various compounds and structures are reviewed. © 2021 Elsevier B.V.Eesti Teadusagentuur, ETAg: PRG111, PRG629; European Regional Development Fund, ERDF: 2014-2020.4.01.15–0011, TK141Authors thank Minobrnauki project FEUZ-2020-0059 and Estonian Research Council (grants PRG629 and PRG111 ) for financial support. Authors are also grateful for partial support from the European Regional Development Fund (DoRA Pluss program) and the ERDF funding in Estonia granted to the Center of Excellence TK141 “ Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelectronics ” (project No. 2014-2020.4.01.15–0011 )

THE CONTROL UNIT OF THE PULSE CATHODOLUMINESCENT ANALYZER

The control unit is designed for the pulse electron beam and luminescent analyzer (“KLAVI-R” equipment) in order to realize the strobe mode which should improve the capabilities of luminescent measurements.Работа выполнена при финансовой поддержке Минобрнауки РФ (стипендия Президента РФ - 2015) и УрФУ (грант молодым ученым - кандидатам наук)

Radioluminescence properties of nanocomposite scintillators with BaF 2 fillers

In this paper, studies of the luminescence properties of nanocrystalline BaF 2 samples synthesized by laser ablation and pulse electron beam evaporation method are presented. The measurements of X-ray excited luminescence (XEL) showed the dependence between luminescence intensity and the shape of the spectrum on the morphology and particle size. Also, studies of X-ray excited luminescence, decay curves and optical transmittance for nanocomposite materials containing BaF 2 nanopowder are presented. Barium fluoride nanopowder, obtained by pulsed electron beam evaporation method is characterized by a lower intensity than the initial microcrystalline powder, but at the same time, XEL spectrum of the nanocomposite material with this nanocrystalline filler is more intense, then that for nanocomposite material with initial powder. © Published under licence by IOP Publishing Ltd

New Debris Disks Around Nearby Main Sequence Stars: Impact on The Direct Detection of Planets

Using the MIPS instrument on the Spitzer telescope, we have searched for infrared excesses around a sample of 82 stars, mostly F, G, and K main-sequence field stars, along with a small number of nearby M stars. These stars were selected for their suitability for future observations by a variety of planet-finding techniques. These observations provide information on the asteroidal and cometary material orbiting these stars - data that can be correlated with any planets that may eventually be found. We have found significant excess 70um emission toward 12 stars. Combined with an earlier study, we find an overall 70um excess detection rate of $13 \pm 3$% for mature cool stars. Unlike the trend for planets to be found preferentially toward stars with high metallicity, the incidence of debris disks is uncorrelated with metallicity. By newly identifying 4 of these stars as having weak 24um excesses (fluxes $\sim$10% above the stellar photosphere), we confirm a trend found in earlier studies wherein a weak 24um excess is associated with a strong 70um excess. Interestingly, we find no evidence for debris disks around 23 stars cooler than K1, a result that is bolstered by a lack of excess around any of the 38 K1-M6 stars in 2 companion surveys. One motivation for this study is the fact that strong zodiacal emission can make it hard or impossible to detect planets directly with future observatories like the {\it Terrestrial Planet Finder (TPF)}. The observations reported here exclude a few stars with very high levels of emission, $>$1,000 times the emission of our zodiacal cloud, from direct planet searches. For the remainder of the sample, we set relatively high limits on dust emission from asteroid belt counterparts

Monochromatic optical cherenkov radiation of moderately relativistic lons in radiators with frequency dispersion

Optical Cherenkov radiation of moderately relativistic ions in a CVD-diamond plate with frequency dispersion is considere

Evolution of the Velocity Ellipsoids in the Thin Disk of the Galaxy and the Radial Migration of Stars

Data from the revised Geneva--Copenhagen catalog are used to study the influence of radial migration of stars on the age dependences of parameters of the velocity ellipsoids for nearby stars in the thin disk of the Galaxy, assuming that the mean radii of the stellar orbits remain constant. It is demonstrated that precisely the radial migration of stars, together with the negative metallicity gradient in the thin disk,are responsible for the observed negative correlation between the metallicities and angular momenta of nearby stars, while the angular momenta of stars that were born at the same Galactocentric distances do not depend on either age or metallicity. (abridged)Comment: Astronomy Reports, Vol. 86 No. 9, P.1117-1126 (2009

Optimization of a Method of Searching the Best Approximation for an Observed Molecular Spectra

Since the increasing a number of observational data we need to simplify a process of its interpretation. For optimize the procedure for searching such set of physical parameters that best describes the observed molecular spectrum, we created a program for comparing model and observable spectra based on the χ2 method. Moreover we can connect to the program various methods of model spectra formation, for example, RADEX, and conduct comparison of the methods.С увеличением количества данных наблюдений возрастает необходимость в упрощении процесса их интерпретации. Для оптимизации процедуры поиска набора физических параметров, наилучшим образом описывающего наблюдаемый молекулярный спектр, была создана программа, позволяющая наглядно сопоставлять модельные и наблюдаемые спектры на основе метода χ2. Кроме того, в программу можно подключать различные программы, формирующие модельные спектры, например RADEX, и проводить сравнение методов.Работа поддержана Министерством науки РФ, базовая часть госзадания, РК № AAAA-A17-117030310283-7, и Правительством РФ, контракт № 02.A03.21.0006, постановление № 211

Coherent Cherenkov radiation as an intense THz source

Diffraction and Cherenkov radiation of relativistic electrons from a dielectric target has been proposed as mechanism for production of intense terahertz (THz) radiation. The use of an extremely short high-energy electron beam of a 4th generation light source (X-ray free electron laser) appears to be very promising. A moderate power from the electron beam can be extracted and converted into THz radiation with nearly zero absorption losses. The initial experiment on THz observation will be performed at CLARA/VELA FEL test facility in the UK to demonstrate the principle to a wider community and to develop the radiator prototype. In this paper, we present our theoretical predictions (based on the approach of polarization currents), which provides the basis for interpreting the future experimental measurements. We will also present our hardware design and discuss a plan of the future experiment