Instruments and Experimental Techniques最新文献

A two-dimensional scintillation hodoscope assembled using FEU-85 domestic photomultiplier tubes and highly sensitive shapers, which are developed and manufactured at Logunov Institute for High Energy Physics (IHEP), is presented. The design features are shown and its characteristics are given when operating as the part of an experimental setup in the beam channel 14 of the U-70 accelerator complex.

We present the results on the created semiconductor source of spin-polarized electrons and spin detector, as well as the concept of their integration into the dissociative electron attachment (DEA) spectroscopy with consideration for the necessary values of electron-beam parameters, at which the resonant scattering and dissociative attachment are observed. The design of a setup for studying the resonant scattering of spin-polarized electrons by the DEA spectroscopy method is described, which will allow for studies of the intramolecular dynamics of isolated negative ions. The main goal of the design and fabrication of the setup is to make it possible to study the interaction of spin-polarized electrons with chiral molecules, which will provide the experimental verification of the Vester–Ulbricht hypothesis on the origin of biological homochirality. In addition to this fundamental issue, the expected results of the proposed experiment are important for promising areas of spintronics and for the establishment of molecular mechanisms of various biological effects of enantiomers of pharmaceuticals.

A system for reading photoluminescent screens with memory is presented that allows obtaining images with a higher spatial resolution compared to industrial scanners. It has been experimentally determined that, in the range of 6–25 keV, the spatial resolution of the created readout system does not depend on the quantum energy and is δ = 13 ± 2 μm.

The phosphor screen made of 1-mm-thick Chromox alumina ceramic has been used to measure the current density distribution over the cross section of an intense pulsed low-energy electron beam. The properties of the screen with deposited gold coatings 30 and 300 nm thick have been investigated. The 30-nm-thick coating is characterized by a high conductivity at a good transparency (~5%) that is sufficient for studying fluorescence. As a result, it is possible to visualize a two-dimensional picture of the beam current distribution with a high spatial resolution. However, it is shown that such a coating has a limited stability against the beam with a current of ≥1.5 A (>0.6 A/cm²), an energy of 15 keV, and a duration of 1 ms. The 300-nm-thick coating is much more stable, but is non-transparent to fluorescence radiation, so an image is recorded from the backside of the scintillator plate. Using this approach, it is possible to obtain an image of the beam footprint, but with a lower spatial resolution.

A multicathode counter is designed to search for cold, dark matter, presumably composed of dark photons, by detecting single electrons emitted from the surface of the metal cathode of the counter during the conversion of dark photons on its surface. The counter design allows for the efficient discrimination of the background from an ambient radioactivity and the electron thermal emission by subtracting the count rate measured in the blocking potential configuration. The paper provides a detailed description of the design of a multicathode counter.

The operating principles and practical design of the elements of the created experimental stand of a tracking adaptive optics system for the formation and correction of turbulent distortions of laser radiation are described. The stand allows for the emulation of atmospheric turbulence with the ability to replay it to configure the adaptive system, correct distortions caused by atmospheric turbulence, and also correct the general slopes of the wave front. The results of tests of a mirror developed by Tip–Tilt as part of a tracking adaptive optics system are presented.

In this study, we investigated the influence of biasing and Resonant Helical Magnetic Field (RHF) on plasma current, ion saturation (({{I}_{{{text{sat}}}}})), and the gradient of floating potential ((nabla {{V}_{f}})) using the Multi-Directional Langmuir Probe (MDLP) at the plasma edge in IR-T1 tokamak. The experiment was conducted in three scenarios: only biasing, only RHF, and biasing with RHF (biasing voltage fixed at V = 250 V on plasma edge, RHF with L = 2 and L = 3) were applied to the plasma. Biasing with RHF resulted in an increase in plasma current (19–21 kA), enhanced plasma confinement time (33–34 ms), and reduced plasma resistance. Simultaneously applying biasing and RHF led to an increase in plasma energy compared to the situation with no biasing and RHF ({{I}_{{{text{sat}}}}}) decreased by 25% in biasing, 5% in RHF, and 40% in biasing with RHF. (nabla {{V}_{f}}) fluctuations decreased by 3, 2, and 4%, respectively. Applying biasing with RHF reduced the cross-correlation between (nabla {{V}_{f}}) and ({{I}_{{{text{sat}}}}}), increasing their phase difference. Empirical Mode Decomposition (EMD) revealed that biasing with RHF decreased the overall average of Intrinsic Mode Functions (IMFs) amplitude for (nabla {{V}_{f}}) and ({{I}_{{{text{sat}}}}}) compared to the absence of biasing with RHF.

Two methods for measuring the penetration depth of the surface plasmon polariton (SPP) field using quasi-monochromatic terahertz radiation from the Novosibirsk free electron laser (λ = 141 μm) are proposed and tested: a probe method with modulation of the radiation by a shutter or modulation of the diffracting fraction of the SPP field by oscillations of a probe embedded in it and a screening method that records the intensity of SPPs that have passed under a metal screen. In both methods, to reduce the proportion of parasitic illumination from volumetric waves, it is proposed to use a fracture of the sample surface or conversion elements (radiation to SPP and back) of cylindrical shape. The results of experiments on assessing the depth of penetration of the SPP field into the air by both methods are consistent with each other. The advantages and disadvantages of these methods, as well as the conditions for their application when working with samples containing and not containing a dielectric coating, are identified.

The linear accelerator (linac) with a mass-to-charge ratio of A/Z = 8, an energy of 4 MeV/n and a current of 10 mA is under develop at the National Research Center Kurchatov Institute. The linac consists of an accelerator with radio frequency quadrupole (RFQ) operating at a frequency of 40 MHz and two accelerating structures with drift tubes DTL₁ and DTL₂ operating at frequencies of 80 and 160 MHz, respectively. It is assumed that the electrodes of the RFQ accelerator will be with offset magnetic coupling windows. The total length of the RFQ accelerator will be approximately 11 m.

With the advent of new neutron sources for boron neutron capture therapy (BNCT) based on accelerators, it became necessary to create an independent system for monitoring the particle flux during patient irradiation. The results presented in this article showed that the proposed system based on a scintillator–optical fiber–silicon photomultiplier, using three different sensors, made it possible to measure the neutron flux, as well as to estimate the dose induced by gamma radiation. The use of two types of polystyrene scintillators: SC-301 and boron-enriched SC-331 manufactured by Logunov Institute for High Energy Physics (IHEP), National Research Center Kurchatov Institute, Protvino, makes it possible to estimate the contribution of neutrons, and the application of an additional sensor without a scintillator makes it possible to estimate the contribution to the signal from the Cherenkov radiation generated in the optical fiber. The implemented system for detecting optical signals based on silicon photomultipliers has a high quantum efficiency and the counting mode of operation of the readout electronics made it possible to achieve an intrinsic noise level of the order of several tens of hertz.