No 4 (2023)

A cryogenic source of polarized deuterium atoms is described. This source is used in the experiment on measuring the analyzing powers in the deuteron photodisintegration reaction at the VEPP-3 electron storage ring at the Budker Institute of Nuclear Physics. The efficiency has been measured for atomic transitions to a specified energy state in the medium field transition (MFT) unit, in the strong field transition (SFT) unit, and for joint operation of these units. A Lamb shift polarimeter was used in the measurements. The measured efficiency of the units is over 90%. The procedure for determining the background in the polarimeter is presented. The use of pumping in the ionizer chamber is expected to significantly reduce the background signal.

A new compact time-of-flight neutron detector is being planned for the identification and energy measurement of neutrons produced in nucleus-nucleus interactions at energies up to 4 AGeV at the BM@N experiment, located at the Nuclotron (Joint Institute for Nuclear Research, Dubna, Russia). This detector will be used to measure neutron yields and azimuthal flows, which should be sensitive to the equation of state of dense nuclear matter, as shown in various theoretical models It is proposed to use plastic scintillators produced at JINR and IFTP and silicon photomultipliers with a sensitive area of 6 × 6 mm2 for photon registration, one for each scintillation cell. To achieve the required neutron energy resolution (of the order of several percent) in the energy range up to 4 GeV, the time resolution of scintillation detectors should be 100−150 ps. The concept of a time-of-flight neutron detector is discussed. The results of measurements of the light yield and time resolution of several scintillation detector specimens of various sizes and two types of silicon photomultipliers are presented.

A high-resolution scintillating fiber hodoscope comprising multi-anode photomultiplier tubes is presented. The technologies for manufacturing fiber bundles and mounting them into the detector housing are described in detail. The functional diagram of the anode-signal discriminator and the characteristics of the hodoscope operating as the part of an experimental setup at the beamline 14 of the U-70 accelerator complex are presented.

Amplifiers of the buildup signal of piezo emitters in the hardware of a hydroacoustic research complex are described. They are designed to amplify short-term signals with amplitude, frequency, and phase modulation at a frequency of 1 MHz. A feature of the linear signal amplifier with amplitude modulation is the use of an amplifier with current feedback, which is characterized by high speed properties. A feature of a switch signal amplifier with a constant amplitude (frequency and phase modulation) is the use of optocouplers in the control pulse shaper circuit of the output MOSFETs (metal–oxide–semiconductor field effect transistor), which ensured the symmetry of the pulses. The high duty cycle of the amplified signals made it possible to avoid the need for special heat sinks and to perform a simple and compact implementation of the circuits. The gain of the linear amplifier was 18 dB, the maximum amplitude of the output signal was 80 V, and the gain of the switch amplifier and switch signal amplitude were 26 dB and 200 V, respectively. Specific circuit solutions are given.

Two types of switches for high-power current pulses with an operating voltage of 24 kV based on blocks of series-connected shock-ionized dynistors are described. The switching processes of these switches are considered, and the results of their comparative study are presented. The possibility of efficient switching of nanosecond current pulses with an amplitude of 6 kA and a rise rate of 150 A/ns is shown. The prospects for increasing the switched power are determined.

The energy characteristics of a high-current electron gun with a radially converging beam have been studied. The cathode unit of the gun consisted of one or two ring sections with an inner diameter of 8 cm, each of which included 18 resistively decoupled arc plasma sources initiated by discharges over the dielectric surface. It is shown that electrostatic shielding that prevents the liberation of electrons and ultraviolet radiation from cathode and anode plasmas to the space behind the cathode decreases the probability of the breakdown development along the resistors of arc plasma sources and increases the beam pulse energy released in the anode approximately two times. In the case of two-sectioned cathode unit, the width of the beam autograph on the anode (melting trace) was ~7 cm at an axial distance between the centers of the sections of 4 cm.

The results of the development of a two-frequency resonator operating at frequencies of 4.95 and 7.1 MHz, which correspond to the frequencies of hyperfine transitions of the ground state of a nitrogen-vacancy color center in diamond, are presented. The efficiency of the resonator has been demonstrated via observation of Rabi oscillations. With a resonator input power of 0.3 W, the amplitude of the alternating magnetic field was 1.6 and 1 mT for field frequencies of 4.95 and 7.1 MHz, respectively.

A method of multiangle scanning for measuring the cross-sectional beam intensity distribution has been developed. This method is based on reconstructing the beam profiles obtained at different angles in a plane perpendicular to the beam axis. To efficiently implement the multiangle scanning method, it is necessary to find the optimal number of projections, i.e., such a number for which the measurement result remains reliable with a minimum measurement time. A numerical simulation provided the development of a technique for finding the optimal number of projections, and it was shown that the optimal number is ten if the errors due to operation of units of the experimental setup are disregarded. To eliminate this error, multiangle X-ray beam scanning was carried out and its intensity distributions in the cross section were reconstructed with different numbers of projections. The developed technique was used to determine the optimal number of projections for this experimental setup, which were 18.

The work describes an updated magnetometer based on the ponderomotive principle in which specially used hemispherical pole pieces create an inhomogeneous magnetic field with zones of virtually constant values of the magnetic gradient (MG) and/or the magnetic force factor (MFF) in the vicinities of the extrema of the coordinate dependences of the MG and MFF. These zones (MGconst and MFFconst) are fixed in the magnetometer by limiters in the form of controllable (laser) markers and have individual values of the coordinates of their conditional centers xextr and lengths ∆x with a permissible error of changes in the MG and MFF data within such zones. It is shown that, at various mutual distances between the hemispherical pole pieces with the diameter D, the MFFconst zone is located almost a third closer to the center-to-center line of the hemispheres (according to xextr/D) in comparison with the MGconst zone and is less extended (according to Δx/D) to the same extent.

Information on the characteristics of separationless three-phase oil–water–gas flowmeters of horizontal orientation is presented, probably, for the first time; it is related to the optimization of their design based on experimental studies of single-isotope and dual-isotope gamma densitometers (GD) and a combined conical narrowing device (ND), which consists of two sequentially installed cones of various dimensions. The experiments were carried out on both real oil–gas–salt water mixtures at a TUV SUD NEL test bench (Glasgow) and with model exxsol–gas–fresh water flows at the GET195-2011 standard of multiphase flows at the All-Russia Research Institute for Flow Metering (Kazan) using typical flowmeters with a nominal diameter of DN 100. It is shown that it is advisable to install a γ-densitometer in a cross section with an intermediate diameter of D = 70 mm, use a cone of 70/50 mm as the measuring ND, and use a cone of 100/70 mm to preaccelerate the flow in order to reduce the variety of flow regimes of two-phase and three-phase flows in the measuring ND and in the flow part of the γ-densitometer. This significantly improves the characteristics of the prototype flowmeter. Some of the obtained characteristics are compared with those of the well-known Vx Schlumberger vertical analogue, and designs of variants of an advanced horizontal three-phase flowmeter are presented, which also make it possible to increase its service life and raise the operating pressure.