Том 62, № 4 (2019)

An integral method is described for processing xenon used as a working medium in the RED-100 two-phase emission detector constructed in the NRNU MEPhI to study the process of elastic coherent neutrino scattering off atomic nuclei. The developed technology for purifying xenon and the detector has made it possible to increase the lifetime of quasi-free electrons in the 205-kg liquid xenon from ≤0.1 to ≥400 μs in fields of 50−500 V/cm. The entire procedure takes approximately 1000 h. The method can be used to process working media for new-generation two-phase emission detectors designed to conduct basic research, in particular, searching for dark matter in the form of weakly interacting massive particles, detecting boron solar neutrinos, and searching for neutrinoless double-beta decay.

The results of testing a prototype of a surface-barrier detector of charged particles based on single-crystal epitaxial layers of diamond are presented. Diamond films with p-type conduction with a boron concentration of (4–8) × 10¹⁴ cm^–3 65 μm thick were grown using gas-phase deposition on heavily doped diamond substrates grown at high pressure and high temperature. A 17 mm² Schottky barrier was formed by sputtering Pt with a thickness of 30 nm. When irradiated from the ²³⁸Pu α-source (the 5.499 keV line) a detector with an external bias of 90 V demonstrated a charge collection efficiency close to 100% and a FWHM high energy resolution of 0.56%. The obtained energy resolution is at the level of standard silicon detectors.

The numerical step-by-step and combined shift methods for correction and reconstruction of experimental data presented as a set of superposed pulse responses of the measuring system are considered. These methods are effective for different types of superposition functions and make it possible not only to correct the data with various distortions in the course of measurements, but also to reconstruct the system response from a shorter initiating pulse, which means an improvement in the resolution of the measuring system. Comparative analysis of the proposed methods is presented and the inaccuracies of reconstruction with different types of superposition function, as well as different volumes of experimental data and noise levels in them. The possibility is considered of using these methods for renewal of multidimensional images or objects in them smudged by shifts or distorted by the Gaussian function. Examples of experimental-data reconstruction and image renewal are presented.

An autonomous multichannel generator of optical sync pulses is described. The interval between sync pulses of this generator can be set with a step of 250 ns. The maximum delay between sync pulses is 262 ms. Programming of the delay can be carried out both from the control panel located on the generator and from a personal computer. The generator is completely autonomous. The estimated operating time without replacement of batteries is 20 years.

The current source of the IP-2500 type is intended to feed the SP-41 magnet, one of the key elements in the beamline for transporting the charged-particle beam to the experimental zone of the BM@N facility (baryonic matter at the Nuclotron) at the NICA collider complex that is created at the Joint Institute for Nuclear Research (Dubna). The inductance of the magnet is 2.3 H, and its active resistance is 0.0896 Ω. The source is used for powering the SP-41 magnet with a current of 2500 A and a relative accuracy of 10⁻⁴.

An automated apparatus is presented that allows a user to measure the mass spectrum or velocity map images of photofragments during tuning of the dye-laser radiation wavelength and its second harmonic, which interact with an investigated substance in a molecular beam. The NI LabVIEW environment was used for automation. The apparatus was successfully tested when studying the resonant ionization of oxygen molecules. The automation software makes it possible to extend the possibilities of measuring spectral dependences by creating additional modules without modifying the existing program code.

The design and characteristics of resistively decoupled multi-emitter explosive-emission cathodes intended for high-current plasma-filled diodes are presented. The integral glow of the emission-center plasma, the energy-density distribution over the cross section of a nonrelativistic high-current electron beam, which is formed in the plasma-filled diode, and the operation lifetime of the cathode were studied. The best results were obtained for a cathode based on TVO-1 resistors, whose wire outputs serve as emitters.

The characteristics of the electron beam generated by a subnanosecond accelerator with double sharpening in the voltage-pulse shaping circuit have been recorded. The duration of the electron-beam current pulse was 240–270 ps, the current amplitude was approximately 1.5 kА, and the maximum electron energy was approximately 0.95 MeV. The pulse-response characteristics of SPPD29k and SPPD29-02 X-ray semiconductor detectors were determined: their full widths at the half-maximum τ_0.5 were approximately 320±30 and 450±30 ps, respectively.

A temporal 4-step polarization phase-shifting technique for digital speckle pattern interferometry (DSPI) with one fixed and two rotatable polarizers is proposed. The fixed polarizer is used to filter out the reflected object beam in one polarization direction, and the two rotatable polarizers are used to perform the 4 times phase shifts. The Jones derivation illustrates the object surface phase distribution can be derived from the 4 speckle pattern interferograms, which are bright, gloomy, bright, and gloomy successively. The experiment shows that the proposed temporal polarization phase-shifting technique is able to extract the phase change caused by a tiny out-of-plane displacement. Unlike the PZT-driven phase-shifting, the polarization phase-shifting in this method is stable and accurate in the long term.

An instrument for recording photoinduced-absorption spectra using the pump–probe method with femtosecond time resolution is described, in which a regenerative amplifier based on a chromium-doped forsterite crystal with a fundamental harmonic of 1240 nm is used as the laser system. Two optical schemes with pumping at a wavelength of 620 nm and a wavelength of 413 nm that are described in detail allow measurements in the spectral range of 280–1000 nm. The time resolution of the system is 250 fs.

A multichannel spectroheliograph (SHG) based on an Alta U16M (4096 × 4096) high-performance cooled CCD camera has been created for studying the active regions and flares on the Sun in the wavelength range of 0.32–1.10 μm with a very low noise level. The SHG is intended for use in the ATB-1 solar tower telescope at the Solar Physics Department of the SAI. This will make it possible to obtain tomographic sections and record the field of plasma-flows rates at different levels in the chromosphere of the Sun.

A drive is described that provides the rotation of a water-cooled rod at a speed of 0.2–30 rpm and its translation to a vacuum of up to 1 × 10^–6 Torr through a distance of 400 mm at a speed of 0.05–100 mm/min. The positioning accuracy is ±0.2 mm over the entire distance of the displacement. The transmitted load is approximately 100 kg. High accuracy and a wide range of rotational and translational speeds of the rod are provided by digital servomotors and a kinematic scheme of the drive, which eliminates the occurrence of bending moments on ball slideways and ball-screw assemblies. The reliable sealing of the rod is achieved using a plate bellows with a great stroke and a magnetic–liquid vacuum feed-trough to rotate the rod.

A laboratory technology for manufacturing iridium–yttrium cathodes, which are totally or locally coated with yttria, was developed. A technique for determining the emissivity on the iridium surface was proposed and its value was determined: 0.6 at a wavelength of 665 nm. The work function of such film cathodes was determined: eφ = 3.4 eV. The temperature range of the cathode operation under the conditions of a medium vacuum was established, and it was shown that this operation is efficient only for Т ≥ 1600 K. A physical model for describing this process is proposed. The high thermal stability of yttria-based cathodes, which can withstand heating at Т = 2500 K for hours without degradation, is shown.

The characteristics of four different photomultiplier tubes (PMTs) that can be used for photoemission spectroscopy analysis of radiation and, in particular, for temperature measurements, are presented. The integral color temperature is determined by the ratio of two responses of a photoemissive device, which correspond to the entire photoelectron flux from the spectral sensitivity region of the photocathode, and by the current limited by the decelerating field or separated by the energy in the field of an electrostatic lens. The modulation of the electron beam instead of the light beam with a frequency of up to 1 MHz makes it possible to obtain a time resolution of 1 μs in a temperature measurement. The method error due to emissive capacity is ~0.3% for most materials in the temperature range of 1200–3300 K, which is much smaller than the error in measuring the brightness or color temperature. The instrumental error depends on the design of the electron-optical system of the entrance chamber in a PMT and on the layout of data acquisition and processing and may be 2–6%. The conversion parameter is (2–15) × 10^–3 K^–1. The described PMTs can be used to measure the temperature dynamics in fast high-temperature processes.