Light collection in the scintillation counter with a volume of 1.5 m<Superscript>3</Superscript> and quasi-mirror reflection

Collection of light in a counter with mirror reflection from relief (nonflat) surfaces and with a high transparency of the liquid scintillator was investigated. Based on results of measurements and simulation of light collection, the dependence of light collection coefficient K on the relief of reflecting surfaces and the scintillator transparency was obtained using the Monte Carlo method. The light collection coefficient was K=(30.9+1.1)×10^s-3, and the resolution of the distribution function for the K value over the counter volume was η ≈12%.     

Low-cost and effective organic scintillators

Test results of the optical and scintillation properties of low-cost scintillators based on widely produced oil-refinery products are presented. Under excitation with high-energy particles, the best speciments of the scintillators showed luminescence decay times of 6.3–8.9 ns and light outputs of 80–90% that of a benchmark polystyrene scintillator containing 2% pTP+0.05% POPOP.     

Determination of the <Superscript>14</Superscript>C Concentration in a Liquid Scintillator for a Neutrino Detector

A setup has been developed for studying ultralow ¹⁴C concentrations in liquid scintillator samples for a large neutrino detector. The setup is located at the low-background underground laboratory of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) at a depth of 4900 m of water equivalent. The ¹⁴C concentrations in a liquid scintillator based on linear alkyl benzene, the background counting rates, and the spectra of particle energies deposited in the technological scintillator sample have been measured. The ratio ¹⁴C/¹²C = (1.41 ± 0.12) × 10^–16 has been obtained. A model of the γ-ray background has been developed, with which it is possible to extract the energy spectrum of 14C and reduce the systematic uncertainty of measurements.     

A Nd-loaded liquid organic scintillator for the experiment aimed at measuring double β decay

A new Nd-loaded liquid organic scintillator based on pseudocumene (PC) solvent was developed for the experiment aimed at searching for 0νββ decay of a ¹⁵⁰Nd nucleus. The optical characteristics of the scintillator were measured for several Nd concentrations. The measurements taken using two modules 1 and 2 m in length have made it possible to determine the effective attenuation length of the PC scintillator containing Nd (6.5 g/L). It was demonstrated that the scintillator characteristics remained unaltered over 1 year. The content of radioactive contaminants was analyzed, and the sensitivity of the experiment to effective Majorana neutrino mass 〈m _ν〉 ∼ 0.05–0.10 eV was estimated for a detector containing a 12-ton scintillator.     

Measurements of nonstationary temperatures by the spectral pyrometry method

Recording of a sequence of thermal-radiation spectra allows determination of a nonstationary temperature T(t) without using the data on the emissivity of an object. For a КЭФ-4.5 silicon single crystal heated with radiation from a continuous-wave Nd:YAG laser (λ = 1.064 μm), sequences of hundreds of emission spectra in wavelength ranges of λ = 350–760 nm and λ = 650–1000 nm were recorded at a signal storage time of a CCD array of τ = 15–35 ms and a frequency of recording spectra of f ≈ 30–66 Hz. The spectra were automatically processed, and the dependences of the crystal temperature on the time after the irradiation onset were obtained in the range T ≈ 1100–1450 K.     

A time-of-flight measurement system for the HADES wide-aperture dielectron spectrometer

The HADES spectrometer and a time-of-flight detector based on long-sized (50–250 cm) scintillation counters are described. The detector is designed for identification of electrons, pions, and protons with momenta of 0.1–1.5 GeV/c at a flight distance of 220–250 cm. The operating conditions are analyzed, and the requirements to the detector and counter design are formulated. The design of the counters and their arrangement in the spectrometer are considered. The results of experimental studies of such characteristics of long counters as the light attenuation length in a scintillator and temporal and spatial resolutions, dependeing on the location of the point of the particle’s hit on the counter, are presented. Analysis of the data has shown that the main factor determining the spatial resolution of long counters is the quality of the polishing of the side faces of the scintillators, which determines the effective (averaged over the scintillator side surfaces) coefficient of total internal reflectionR. It is shown that, forR>-0.99, it is quite possible to achieve temporal and spatial resolutions of 100 ns and 2–3 cm, respectively, for scintillators with a length of up to 250 cm and a cross section of 1–20 cm². Foreign and Russian photomultipliers were used in the counters.     

Laser NIR lifetime spectrometer with nanosecond time resolution

A laser lifetime spectrometer (fluorometer) for recording the luminescence kinetics in the range 950–1400 nm with a time resolution of 1 ns is described. The performance capabilities of the facility are demonstrated by an example of studying the near-IR luminescence of molecular singlet oxygen ¹O₂. The fluorometer allows measurements of quenched luminescence of ¹O₂ with a quantum yield of up to 6 × 10⁻⁹.     

Energy dependence of the relative light output of YAlO<Subscript>3</Subscript>:Ce,Y<Subscript>2</Subscript>SiO<Subscript>5</Subscript>:Ce,and YPO<Subscript>4</Subscript>:Ce scintillators

The nonlinear dependence of the relative light output on the energy deposited in single-crystal scintillation materials YAlO₃:Ce (YAP:Ce), Y₂SiO₅:Ce (YSO:Ce), and YPO₄:Ce (YPO:Ce) has been studied. The investigations have been conducted under quasi-monochromatic X-ray excitation in the energy range of 9.5–100 keV. In addition to the standard technique for measuring the nonproportional scintillator response based on the dependence of the full-energy peak position on the energy of incident radiation, a method is proposed for measuring the light output by X-ray fluorescence peaks. Using this method for YAP:Ce, it is possible to investigate the nonlinear dependence of the light output on the photon energy in the energy range of 2–40 keV. Along with this method, the K-dip spectroscopy method has been proposed and tested by measuring the dependence of the relative light output on the electron energy in the range of 0.1–80.0 keV. The processes resulting in the loss of the scintillation material efficiency at a high ionization density are considered.     

CdTe-based detectors for recording X-ray pulses with a subnanosecond resolution

Characteristics and manufacturing methods of semiconductor detectors made of pressed cadmium telluride are given. The sensitivity of the detectors is ∼(1–5) × 10⁻¹⁹ A cm² s/quantum. SPPD29k and SPPD29-02 detectors are calibrated by subnanosecond X-ray pulses generated by the СПИН-2 accelerator. The measured pulse durations are τ_0.5 = 0.29 and 0.47 ns, respectively. The X-ray pulse shape of the APCA accelerator is recorded.     

A TEA CO2 laser with a peak radiation power of 100 MW

A high-power pulse-periodic TEA CO₂ laser is used as a component of a long-range mobile differential absorption lidar. In order to reach the ultimate peak generation power, a system for laser excitation with a supply voltage of ±40 kV and efficient preionization was developed, allowing the laser to operate at high pressures of gas mixtures of various compositions. Energy, time, and spatial characteristics of laser radiation were studied. Laser pulses with an energy of >10 J and FWHM duration of ≈30 ns were obtained. The ultimate peak laser radiation power is 100 MW, and the maximum efficiency with respect to the discharge-consumed energy is 12.6%.     

A Wideband spectrometer for NMR studies

The design of a wideband decimeter-wave (200–900 MHz) spectrometer with a magnetic induction of up to ∼10 T is described. This spectrometer is intended for studying electronic-nuclear oscillations in antiferromagnets at low temperatures (4.2−1.3 K). Critical field H _c = 2.5 ± 0.3 T of a reorientation transition in a noncollinear antiferromagnet Mn₃Al₂Ge₃O₁₂ at temperature T ≈ 1.3 K was determined from a ⁵⁵Mn²⁺ NMR spectrum.     

A single crystal of YALO3: Ce3+ as a fast scintillator in SEM

A new single-crystal scintillator intended for applications in a scanning electron microscope (SEM) is presented. It is a single-crystal disc of yttrium aluminium perovskite activated by trivalent cerium free of traces of Fe ions. The single crystals of YAlO₃: Ce³⁺ (YAP: Ce³⁺) were prepared by the Czochralski method in a reducing atmosphere of Ar and H₂ with an excess amount of Y³⁺ ions. Effective methods of purification and purity control of the raw material are described. The highest achievable concentration of Ce³⁺ ions in as grown crystals amounted to 0.3 wt%, concentration in the melt was 8–9 times higher. The best properties were found with samples of the maximum possible concentration of Ce³⁺. Compared with the previous aluminate Y₃ Al₅ O₁₂: Ce³⁺ (YAG: Ce³⁺) these samples showed higher efficiency, a shorter decay time of luminescence (40 ns) and an emission band in a more advantageous spectral region (378 nm). Because of high resistance to radiation damage, high chemical resistance and applicability to ultra-high vacuum it is also suitable for detection of other kinds of ionizing radiation.     

A Streak-Camera Monitor for Hard X Rays

The instrument is designed on the basis of a fast scintillator and a high-speed image-converter tube for hard X and rays (10 keV). Using a scintillator, it is possible to obtain an almost constant spectral response over an energy range of 40–1000 keV. The time resolution of the camera is governed by the luminescence decay time in the scintillator and may go as high as 100–150 ps. The instrument is used at the ISKRA-5 facility to detect pulses of hard X rays.     

A Gas-Discharge Source of Quasi-monochromatic Ultrasoft X-rays

The results of a study of radiation characteristics of a high-current pinch discharge of the plasma-focus type in the region of soft and ultrasoft X-rays are presented. Experiments were performed at a moderate energy of discharges in a mixture of H₂ and Ne. It was shown that a comparatively narrow spectrum region of the generated radiation, which corresponds to the line emission of lithium-like ions Ne⁷⁺ with an average effective quantum energy E _eff 0.16 keV, can be selected. The Ne⁷⁺ emission fluence was (0.2–1.0) × 10¹² quant/cm² per pulse with a duration _0.5 = 40–100 ns. The results obtained demonstrate the feasibility of using such discharges in laboratories as pulse sources of quasi-monochromatic ultrasoft X-rays.     

A transition radiation detector based on thin inorganic scintillators

The possibility of designing a prototype of the scintillation transition radiation detector (Sci-TRD) based on a thin (～200 μm) inorganic scintillator has been investigated. Vacuum and silicon photomultipliers have been used in the measurements with inorganic scintillator samples based on LuBO₃:Ce and wavelength shifting fibers. The light collection coefficient has been measured for scintillator prototypes under exposure to X rays, and the quantity of photoelectrons has been experimentally determined by irradiating the Sci-TRD working substance with a ²⁴¹Am X ray source. The electron-hadron rejection ratio of the proposed Sci-TRD is expected to be ～30.     

A high-energy YAG: Nd<Superscript>3+</Superscript> laser with a phase conjugation in an optical fiber

An optical scheme and design of a YAG:Nd³⁺ frequency laser with a two-pass amplifier and a mirror with the phase conjugation by the stimulated Brillouin scattering in an optical fiber is described. The maximal radiation energy is 1000 mJ at a 1.064-μm fundamental wavelength and 500, 200, and 20 mJ at the second, fourth, and fifth harmonics, respectively, when the divergence is ∼5 × 10⁻⁴ rad and the pulse duration is 4.5 ns.     

Effect of electron trapping centers on electrical and photoelectric properties of PbSnTe : In

Results of experimental studies presenting data on the effect of electron trapping centers on the properties of Pb_1−x Sn _x Te: In with x ≈0.24–0.29 at temperatures below 20 K are described. A model is developed that consistently explains a number of phenomena in Pb_1−x Sn _x Te: In solid solutions, including current-voltage characteristics in the absence of light resulting from the injection from contacts and space-charge limited current when electrons are captured in traps distributed in energy in the bandgap, photoelectric phenomena in the infrared and terahertz spectral ranges, features of galvanomagnetic phenomena, and fluctuations and autooscillations of current in the absence or presence of light.     

Use of <Superscript>44</Superscript>Ti in the time-differential γγ perturbed-angular- correlation method for studying condensed matter

The principal aspects of ⁴⁴Ti application in time-differential γγ perturbed-angular-correlation method (TDPAC) for studying condensed matter are discussed. In the presented spectrometer modification, the efficiency of ⁴⁴Ti application can be considerably increased by using thin NaI scintillator crystals. Promising techniques for ⁴⁴Ti production and a method for synthesizing samples are described. Examples of TDPAC studies of titanium (rutile TiO₂) and scandium (Sc₂O₃) oxide samples are shown.     

Scintillation γ spectrometers for use at nuclear power plants (review)

In this review, it is shown that out of the 300 scintillators synthesized to date only LaBr₃:Ce, CeBr₃, YAlO₃: Ce, and CsI:Tl crystals with the corresponding silicon photosensors (SiPSs) can be used as detectors in industrial γ-ray spectrometers intended for nuclear power plants. They are superior in their energy resolution and their resistance to mechanical and electromagnetic effects to spectrometers used today with a NaI:Tl crystal and a photomultiplier tube (PMT). A p–i–n photodiode (PD), an avalanche photodiode (APD), and a silicon photomultiplier (SiPM) are promising SiPSs. The properties of various assemblies of listed scintillators and photosensors are analyzed. A PD matches well with any scintillator. A spectrometer does not require LED stabilization of the scale, but its noise level must be reduced by selective PD cooling and the use of a light guide for coupling a massive scintillator and a SiPS with a small area of its sensitive surface. A spectrometer with an APD does not require photosensor cooling; however, LED stabilization of its energy scale is necessary. Application of an SiPM can rule out the use of a light concentrator (which is important for large CsI:Tl scintillators) and selective cooling, but this introduces nonlinearity at a short decay time and a high light yield in the scintillator (LaBr₃:Ce and CeBr₃) and also calls for an LED stabilization system for the spectrometer. The prospects for the development and application of new scintillation γ-ray spectrometers are discussed in this review.     

An indium-loaded organic liquid scintillator for solar neutrino detection

An organic liquid In-loaded scintillator based on a salt of carboxylic (2-methyl valeric) acid was developed. At an In loading of ∼50 g/l, the scintillator characteristics were as follows: the light yield was 9000 photons/MeV, and the attenuation length was ∼1.5 m. Operation of a 1-m-long optical module used as a detector prototype was demonstrated. The scintillator stability was tested under low-background conditions of an underground laboratory.