We avaluate the contribution of electron scattering on the rear wall of a windowless gaseous tritium source in the Troitsk nu-mass setup. There is a finite probability for them to scatter, return back and reach the detector. A such additional component distorts the measured electron spectrum. We calculate the scattering on the rear side of the vacuum pipe by the GEANT4 simulation and trace the electrons back through the magnetic fields to the spectrometer and registration system. The contribution is a few orders of magnitude smaller compared to the original spectrum at the end of the beta-spectrum of 18.6 keV but reaches 2% at 11 keV. Taking into account this rear wall scattering we can fit well the measured spectrum in search for a sterile neutrino component in the tritium beta decay.

A well-known problem of multi-stage laser systems is deviations of radiation from a given direction during its transmission between sections. To automatically correct the radiation direction, an auto-tuning system has been developed based on piezoelectric actuators with feedback through a four-section photodiode. It is demonstrated that the developed system operates reliably at low disturbance frequencies. At the same time, there is an upper frequency, above which the system does not process disturbances.

The work is devoted to the development, fabrication and analysis of broadband W / Si multilayer mirrors for a broadband monochromator, calculated for the spectral range of 7-10 keV. The possibility of using the stacking approach to obtain multilayer mirrors with a reflection coefficient of about 30% and a spectral bandwidth Delta E/E of about 20% is shown. The results of measurements of the angular and spectral reflection curves of the mirror obtained on a laboratory diffractometer and on a synchrotron in Novosibirsk are presented. Keywords: hard X-ray range, monochromator, synchrotron radiation, broadband mirrors, stack structures, multilayer X-ray mirrors.

Synchrotron radiation incident on a block of multilayer X-ray mirrors of a two-mirror monochromator heats a silicon substrate, which leads to thermal deformation and an increase in the angular error of the surface shape. The work examines the heating of a block of multilayer X-ray mirrors by a synchrotron beam with a power of up to 200 W with an energy in the range of 8–36 keV at grazing angles of incidence in the range of 0.5°–1.3°. Using SolidWorks software, the silicon-substrate parameters for mirrors with grooves on the end surface are calculated at which the root-mean-square deviation of the angular error of the substrate’s surface shape is about 1 μrad for a grazing angle of 1.3°, and for smaller angles it is less than 1 μrad. Heat is removed from the substrate surface by water using copper radiators. Reducing the beam aperture at the monochromator output makes it possible to obtain rays reflected from the surface of mirrors, which has a standard deviation of the surface shape of an order of 0.5 μrad, while maintaining 88

A brief description of the concept of a soft X-ray microscope for the Nanoscope station, which is planned to be installed at the SKIF fourth-generation synchrotron, is given. The microscope is designed to study the structure of cells and dynamic processes in them with nanometer spatial resolution. It will use a unique absorption contrast of ~15 between carbon-containing structures and water in the spectral range of the water window, λ = 2.3–4.3 nm, which eliminates the need for contrasting and the use of fluorophores and minimizes the doses of ionizing radiation absorbed in the samples to obtain high-quality 3D images. The scanning and projection schemes of the microscope, their main technical characteristics, including the calculated spectra and parameters of the undulator source are presented, and an estimate of the absorbed doses depending on the resolution is obtained. The main advantage of the proposed concept lies in the use of an objective lens of high-aperture multilayer X-ray mirrors, which makes it possible to clearly visualize the focal section of the sample. Technically simple axial tomography will also be used to reconstruct the three-dimensional structure of frozen or dried samples. In the scanning scheme, due to a low dose of radiation, it will be possible to study living plant cells with a resolution of up to 10 nm, animals with a resolution of up to 80 nm, and cryofixed samples with a resolution of up to 5 nm. In the projection scheme, due to simultaneous observation of the entire focal XY section, the time for obtaining three-dimensional images is significantly reduced, but due to a large dose, it will be oriented mainly on the study of fixed samples.

We present the conceptual design of a universal materials-research beamline based on the undulator of a fourth-generation synchrotron-radiation source. The distinctive feature of the beamline is its capability to work with both spectrally narrow (Δ E / E ~ 10 –4 ) and relatively broad, high-intensity radiation beams (5 × 10 –2 ). The optical scheme enables rapid switching between diffraction, radiographic, and spectroscopic experimental methods while keeping the beam’s position fixed on the test sample and varying the spot size of the radiation from 100 nm to 1 mm.

A project of an X-ray monochromator for the «SKIF» synchrotron based on two flat mirrors with multilayer reflective coatings is reported. The concept of the monochromator is based on the absence of precision mechanical systems and feedthroughs in vacuum, which significantly reduces mirror surface contamination and increases scanning accuracy. In addition, the overall structure of the device is greatly simplified in this way, which in turn leads to a significant reduction in the total cost and labor for manufacturing. The grazing angle of incidence of radiation on the mirrors in the process of scanning by photon energy varies within 0.5-1.3º. The length of the mirrors is 120 mm, the assumed size of the input beam is 1×1 mm2. A wide operating energy range, 8-36 keV, is achieved through the use of 3 strip-mirrors with coatings of different chemical composition, namely: Mo/B4C, W/B4C and Cr/Be. The article presents the X-ray optical scheme, the expected reflection coefficients and spectral selectivity of the monochromator, the results of the calculation of thermally induced surface deformations and the corresponding slope errors of the first mirror.

A project of an X-ray monochromator for the "SKIF" synchrotron based on two flat mirrors with multilayer reflective coatings is reported. The concept of the monochromator is based on the absence of precision mechanical systems and feedthroughs in vacuum, which significantly reduces mirror surface contamination and increases scanning accuracy. In addition, the overall structure of the device is greatly simplified in this way, which in turn leads to a significant reduction in the total cost and labor for manufacturing. The grazing angle of incidence of radiation on the mirrors in the process of scanning by photon energy varies within 0.5-1.3 o . The length of the mirrors is 120 mm, the assumed size of the input beam is 1x1 mm 2 . A wide operating energy range, 8-36 keV, is achieved through the use of 3 strip-mirrors with coatings of different chemical composition, namely: Mo/B4C, W/B4C and Cr/Be. The article presents the X-ray optical scheme, the expected reflection coefficients and spectral selectivity of the monochromator, the results of the calculation of thermally induced surface deformations and the corresponding slope errors of the first mirror. Keywords: synchrotron radiation, multilayer mirror, monochromator, surface.

The work is devoted to the development, fabrication and analysis of broadband W / Si multilayer mirrors for a broadband monochromator, calculated for the spectral range of 7–10 keV. The possibility of using the stacking approach to obtain multilayer mirrors with a reflection coefficient of about 30% and a spectral bandwidth ΔE / E of about 20% is shown. The results of measurements of the angular and spectral reflection curves of the mirror obtained on a laboratory diffractometer and on a synchrotron in Novosibirsk are presented.

The paper presents the results from a study of the interaction of Lamb waves with inhomogeneities in composite plates. It was found that waves of this type are diffracted by inhomogeneities, such as hole and localized mass load of the surface. A method for detecting and localizing inhomogeneities by comparing the distribution of the wave field amplitudes over the plate surface before and after the appearance of inhomogeneities is proposed and tested experimentally. The article was prepared based on materials in a report at the Third All-Russian Acoustics Conference (September 21–25, 2020, St. Petersburg).

The paper briefly describes the concept of scanning transmission X-ray microscopy (STXM) and the Nanoscope station, which is planned to be installed on the 4th generation SKIF synchrotron. The microscope is designed to study the internal structure of cells and dynamic processes in them with nanometer spatial resolution. The microscope uses a unique absorption contrast between proteins and water, in the region of 15, in the spectral range of the "water window", λ=2.3 - 4.3 nm, which eliminates the need for contrasting and fluorophores, and minimizes the doses absorbed in the samples necessary for obtaining high-quality 3D images. The article presents an X-ray optical diagram of a microscope, its main technical characteristics and an estimate of absorbed doses depending on the resolution.

The results of the numerical simulation and experimental study of an entirely piezoceramic cylindrical resonator to generate sonoluminescence are presented. The data on the origin and study of single- and multibubble sonoluminescence in a water–air system are presented. It is shown that in a piezoelectric resonator sonoluminescence occurs under electric voltages, whose values of are one order of magnitude less than in resonators of other types.

Creation of localized NV center ensembles, produced by irradiation of CVD diamond with nitrogen doped delta-layer with 200 keV electron beam and the subsequent annealing is demonstrated. Results of optical measurements of activated areas at different irradiation doses are presented. Issues concerning defect formation in diamond lattice during the electron beam impact are discussed.

AbstractCreation of localized NV center ensembles, produced by irradiation of CVD diamond with nitrogen doped delta-layer with 200 keV electron beam and the subsequent annealing is demonstrated. Results of optical measurements of activated areas at different irradiation doses are presented. Issues concerning defect formation in diamond lattice during the electron beam impact are discussed.

The paper presents the results of theoretical analysis and numerical modeling of physical processes occurring in microwave discharge supported in two intersecting wave beams in H2–CH4 gas mixture. The transformation rules are defined that allow transferring the results of self-consistent solution of system of equations describing the state of microwave discharge for selected parameters (gas pressure, microwave radiation power and frequency, reactor and wave beams geometry) to other parameters. The following parameters ranges are considered: the medium gas pressure range (100–600 Torr), the radiation power from 1 to 30 kW and radiation frequencies from 10 to 60 GHz. The results of numerical simulation confirm the proposed approach and allow comparing the energy efficiency of the systems in terms of their practical application. The optimal parameters for diamond deposition in the considered plasma-chemical reactor in given range are discussed. The limits of applicability of the microwave discharge model and the proposed transformation rules are discussed.

The long-term stability of the counting and spectrometric characteristics of a fused silica proportional counter has been investigated to assess its applicability to search for an admixture of sterile neutrinos. The results of continuous measurements of the K-peak position in the spectrum of deposited energies from decay of 37Ar traces in a counter filled with CO2 are presented. It is shown that the gas amplification remained stable within 0.1% during 1 month of continuous measurements at an initial isotope activity of approximately 100 Bq. This estimate of the stability of a fused silica counter is 5 times better than the values published earlier.

This work describes an investigation of electron scattering on molecular hydrogen and deuterium measured by “Troitsk nu-mass” group. The results of this work are essential for further investigation of the tritium beta-spectrum in search for active and sterile neutrinos in “Troitsk nu-mass” and KATRIN experiments as well as astrophysical problems. Electrons were generated by the electron gun with a narrow emission spectrum (less than 0.3 eV) at the electron energies of 14, 17, 18.7, 19 and 25 keV. The relative resolution of spectrometer in these measurements was 8.3 × 10–5.