Accuracy of time measurements with a QUASAR-370G hybrid vacuum photodetector in Cherenkov detectors of extensive air showers

The accuracy of time measurements in the Cherenkov detectors of extensive air showers, based on QUASAR-370G hybrid vacuum photodetectors with a large-area hemispherical photocathode, is estimated. The dependence of the time measurement error on the amplitude of the output pulses from the photodetector and the light background of the night sky is determined.     

A method for automatic tuning and stabilization of the energy threshold in scintillation detectors

A method is proposed for automatic tuning and stabilization of the energy threshold in scintillation detectors by maintaining the constancy of the average detector counting rate from ?? rays of natural radiation background or cosmic rays. Stabilization is automatically performed by controlling the photodetector supply voltage, which makes it possible to stabilize the detector threshold with an error of 0.73?C2.40%, depending on the used circuitry. The stabilization electronics for scintillation detectors with avalanche multipixel photodiodes and photomultipliers is described. A circuit ensuring the increased precision of threshold stabilization is also proposed.     

Calculation of absolute values of the spectral energy density of polychromatic radiation

A method for calculating absolute values of the spectral distribution of the radiant energy of a polychromatic source is described for the case in which the spectral distribution of the radiant energy is recorded in relative units, and the time dependence of a current pulse of a photodetector the spectral sensitivity of which is known in absolute units is measured. The expression for the time-averaged spectral density of the radiation power for the pulse-periodic operation of a radiant source is given.     

Construction of a multichannel filter for detecting point targets in the image formed by a matrix photodetector

A new approach is proposed to construct a multichannel filter for detecting small-size targets in images recorded by a matrix photodetector. For estimating the pulse response of each channel of the filter, the set of experimentally obtained images of targets having different locations with respect to photodetector cells is divided into several subsets, which are used as reference elements in calculating the pulse response of the filter. Experimental data are presented, which demonstrate appreciable reduction of the probability of missing the targets in images subjected to processing with a filter constructed by the proposed method.     

Submillimeter matrix photosensitive device on PbSnTe : In films

Principles of operation of large-scale photodetector arrays for image visualization in a submillimeter spectral range are considered. Parameters of a thermal picture produced on an intermediate screen by a submillimeter component of radiation of an object with a temperature of about 300 K are estimated. Photodetector array parameters required for registration of the intermediate screen radiation are analyzed. The possibility of creating large-scale photodetector arrays on PbSnTe : In films for imaging objects with a room temperature without additional submillimeter illumination is shown.     

Solar-blind UV flame detector based on natural diamond

We consider the properties and use of a natural-diamond-based photodetector sensitive in a wavelength range of λ < 300 nm for detecting gas-burner flame with a temperature of 1900 K. In the region of maximum sensitivity (λ = 210 nm), the current responsivity of the photodetector is 2 A/W. The possibility of flame detection is based on the fact that nonequilibrium flame radiation intensity in the region of maximum sensitivity of the photodetector is six orders of magnitude greater than the intensity of the equilibrium (thermal) emission.     

Calibration of photodetectors in IR microscopes

Operation of a photodetector in an infrared microscope has a number of features preventing the application of calibration methods known for thermal imaging devices. A differential method of calibration is proposed which gives an opportunity to consider the nonlinearity of the transfer characteristics of the photodetector reading unit and electronic path and the variation of the background radiation flux.     

Development of a diagnostic technique based on Cherenkov effect for measurements of fast electrons in fusion devices

A diagnostic technique based on the Cherenkov effect is proposed for detection and characterization of fast (super-thermal and runaway) electrons in fusion devices. The detectors of Cherenkov radiation have been specially designed for measurements in the ISTTOK tokamak. Properties of several materials have been studied to determine the most appropriate one to be used as a radiator of Cherenkov emission in the detector. This technique has enabled the detection of energetic electrons (70 keV and higher) and the determination of their spatial and temporal variations in the ISTTOK discharges. Measurement of hard x-ray emission has also been carried out in experiments for validation of the measuring capabilities of the Cherenkov-type detector and a high correlation was found between the data of both diagnostics. A reasonable agreement was found between experimental data and the results of numerical modeling of the runaway electron generation in ISTTOK.     

A radiation foil bolometer for measuring the energy losses of fast Z-pinches

A radiation foil bolometer intended for measuring radiation-energy fluxes and plasma flows in high-power pulsed plasma X-ray sources is studied. In the bolometer, the radiation or ion-flow energy is absorbed by a 13-μm-thick niobium foil preliminarily heated to T ≈ 1900 K by a quasi-constant current lasting 2 s. Radiation from the foil was fed through an 8-m-long light guide to a semiconductor photodetector. The sensitivity of the instrument obtained from the results of calibrations is 0.56 J/V cm². The time resolution of this technique (∼2.5 μs) is determined by the foil heating time. In experiments with megaampere Z-pinches, the time resolution attained allows detection of the radiation energy independently of the energy of expanding plasma flows. In this case, the photoelectric effect from X-rays and the conductivity of expanding plasma do not affect the operation of the radiation bolometer. The working capacity of the bolometer was demonstrated at the Angara-5-1 facility in experiments with high-current Z-pinches with a radiation output energy of 50–100 kJ/pulse. The measurements performed have shown that the energy flux density of plasma expanding in the direction perpendicular to the pinch axis is at most 5% of the energy flux density of soft X-rays.     

Determining the energy spectrum of a charged particle beam using Cherenkov radiation in the deceleration system

A technique for monitoring the energy and the spectrum width of an electron beam in industrial and medical accelerators using Cherenkov radiation in the deceleration system is described. A mathematical model is constructed, and the spectra and the structure of the radiation field in the microwave region are calculated. In mathematical simulation, particular emphasis was placed on the physical aspects playing an important role in practical application of the proposed technique. A layout of the experimental setup and a procedure for reconstructing the energy spectrum are proposed.     

The photomultiplier tubes in the light sensor of an orbital detector for studying the fluorescent radiation of extensive air showers

The characteristics of the photomultiplier tube used in a photodetector of fluorescent radiation and the arrangement of its power supply and control systems are described. The photodetector is used to observe extensive air showers from near-Earth orbit under varying conditions of the night sky background.Translated from Pribory i Tekhnika Eksperimenta, No. 1, 2005, pp. 108–111.Original Russian Text Copyright © 2004 by Garipov, Khrenov, Lubsandorzhiev, Belyanchenko, Smolitskiy, Salazar, Fokitis.     

A Nanographite Film-Based Fast Response Detector for Intense Laser Radiation

A simple high-speed photodetector of high-power laser radiation, based on the optical rectification effect, is described. It operates without an external power source. A nanographite film deposited onto a silicon substrate using the plasmochemical deposition technique and having two conducting surface electrodes is used as the photodetector’s photosensitive element. The performance of this device was demonstrated by detecting pulsed laser radiation in a spectral range of 0.266–1.9 µm using the second, third, and fourth harmonics of radiation from an YAG : Nd³⁺ laser with passive Q-switching and radiation from light oscillators based on stimulated Raman scattering in compressed hydrogen. It was shown that the photodetector sensitivity is proportional to the optical radiation frequency and its response time is shorter than 0.5 ns.__________Translated from Pribory i Tekhnika Eksperimenta, No. 3, 2005, pp. 84–89.Original Russian Text Copyright © 2005 by Mikheev, Zonov, Obraztsov, Svirko, Volkov.     

Ultrabroad-band tomography of remote objects

A method for restoring the images of remote objects with the system??s instrument function in ultrabroad-band (UBB) pulse sounding is considered. The system is a synthetic-aperture radar combined with a parabolic reflector. The aperture was synthesized via UBB scanning with a transceiver over the near-focus plane of a parabolic rereflector. Such a scheme allows the boundary of the maximum offset of a sounded object to be displaced at a distance equal to 2?C3 diameters of the parabolic reflector. An additional advantage of the system that contains a parabolic reflector (rereflector) consists in the possibility of focusing radiation to a specified remote spatial region. In support of the validity of this method, we represent the results of numerical and physical modeling.     

A Position-Sensitive Photodetector for Studying the Spatial–Time Radiation Intensity Distribution in a Laser Beam

A position-sensitive nine-sectional photodetector for studying the spatial–time distribution of the radiation intensity in a laser beam is described. The photodetector was developed according to the technology used in the production of silicon surface-barrier detectors of nuclei fission fragments. Its sensitivity at a wavelength of 1.06 m is 0.1 A/W, and the mutual interference of its sections is within 10%. The device was used in studies of the spatial–time evolution of the optical characteristics of an active medium based on an uranium-containing liquid during nuclear pumping on a pulsed reactor.     

A photomultiplier tube for a NT-200 deep-underwater neutrino telescope

A fast, high-sensitive photomultiplier tube (PMT) with a 25-mm diameter bialkali photocathode is being developed to be used as part of a KBA3AP-370 hybrid photodetector. Its linearity is ∼ 150 mA. The rise time of an anode current pulse is ∼ 2 ns. The transit time difference of photoelectrons originating from different points of the photocathode does not exceed 1 ns. Deceased.     

快速光谱光度计的研制

基于多通道技术和脉冲照明光源,采用自扫描光电二极管阵列(SPD)作为光电探测器,研制成快速的光谱光度计。经过精密的波长定标和光谱反射比定标,在专用PC计算机控制下结合软件功能,实现对物体表面色的快速高精度测量。     

Spectral pyrometry of objects with unknown emissivities in a temperature range of 400–1200 K

A spectrometer with a photodetector array, which consists of 512 InGaAs-based pixels and is sensitive to IR radiation at wavelengths of 0.9–2.5 μm, is described. It allows registering of thermal-radiation spectra of objects with unknown emissivities and calculation of their temperatures near 400 and 500–600 K at storage times of 100–500 and 10 ms, respectively.     

The FLINT setup for studying cumulative processes with photon production

A setup is developed at the Institute for Theoretical and Experimental Physics for studying cumulative processes in hA and AA interactions with photon and π ⁰-meson production in the central region of rapidities at high transverse momenta. Lead glass calorimeters and a charged particle rejection system are the main components of the setup. A fast trigger for a high-energy cumulative particle, based on detection of Cherenkov radiation in the lead glasses, is realized in the setup.     

Optimal evaluation of radiometric signal intensity for the count-time radiation recording mode

An unbiased asymptotically efficient estimate of the radiometric signal intensity that takes the unprolonged ??dead time?? of the hardware into account was obtained using the maximum likelihood method for the case of the count-time radiation recording mode that is used in radiometric testing systems.