Vol 83, No 2 (2019)

A description is given of the SRXFA synchrotron radiation station on the VEPP-4M storage ring at the Siberian Synchrotron and Terahertz Radiation Center. The station is intended to develop and implement SRXFA technology in the hard X-ray photon (40–120 keV) range. The main parameters of the station are given, along with its layout, its monochromatic system, and its detector. The X-ray fluorescence spectrum obtained at the SRXFA station on the VEPP-4M storage ring at an excitation energy of 112 keV is presented. Results obtained at the station on the minimum detection limits for rare-earth elements are presented.

It is planned to construct a network of national sources of synchrotron radiation with extremely low emittance in Russia in the near future, known as the SSRS-4 (Fourth Generation Specialized Source of Synchrotron Radiation program). In this work, modern and promising methods for using synchrotron radiation are described from the viewpoint of insertion devices for generating synchrotron radiation.

A technological station for synchrotron radiation (referred to below as the TSSR) is created on Channel 1 of synchrotron radiation (SR) output on the VEPP-4M storage ring. The new station is designed for practical study of the basics of synchrotron research conducted by university students. The modular construction of the station allows us to change its equipment, test different research techniques and new equipment, and perform some auxiliary experiments. The design of the station, the radiation characteristics relative to other active SR stations, and the main training programs are described.

A design for a planar FEL operating in the terahertz frequency range at the multimegawatt power level is being jointly developed at the ELMI accelerator by the Budker Institute of Nuclear Physics and the Institute of Applied Physics. The FEL oscillator is driven by parallel intense sheet electron beams of moderately relativistic energy, and transitions to the above frequency range via a two-stage cascade scheme. The first beam generates a powerful millimeter pump wave, which then travels through special waveguides to the parallel channel and is scattered by the second beam into a wave of terahertz radiation. Various possible arrangements of the FEL scheme are discussed, and results from their simulation are presented. The results from cold tests of the FEL’s electrodynamic system are reported.

Tomographic reconstruction by integral means preserves the prior information of a reconstructed image. It is difficult to reconstruct high-quality CT images by integral means if the measured parameters or object properties do not satisfy the requirements of the model used in reconstruction (few angles of rotation, angles that are not homogeneously distributed, the object containing regions critically different in absorption at the probing energy). Algebraic approaches are time-consuming. However, they allow consideration of the prior information of a setup or image. Results are prevented from a laboratory tomographic experiment on a test object. A highly absorbing inclusion is placed inside the object. A polychromatic beam is used. Results obtained using integral and algebraic reconstructions are compared. The reconstruction procedure is described in detail for the latter. The algebraic approach uses information on the presence of a highly absorbing region.

A simple technique is proposed to modulate the output radiation power in a free-electron laser (FEL) oscillator that allows the average radiation power to be adjusted smoothly, and short (as brief as 35 μs) radiation macrobunches to be obtained. It is based on the periodic shift of the electron bunch phase with respect to that of an FEL radiation bunch stored in the optical cavity, resulting in lasing suppression. The phase shift frequency required to suppress lasing is relatively low and does not change the electron bunch repetition rate appreciably. A computer-based test bench is created to demonstrate the feasibility of the proposed technique. The test bench contains standard CAMAC blocks: a G0609 modulator timer and a G0601 clock generator. The electron bunch phase is shifted via programmable skipping of the reference frequency periods used to start the current modulator in the electron gun. The skipping is controlled by a computer program operating in the real-time mode. The clock generator is used to send synchronization signals to the radiation user’s equipment. The test bench is tested via EPR spectroscopy with a temporal resolution that allows the duration of the generated macrobunches to be estimated.

The dosimetry system at the FEL facility registers the dose rates in workrooms and in the accelerator hall. The collected information is stored in the database, and the data is visualized in real time. The sensors installed in the accelerator hall are used for monitoring both radiation levels and beam losses on the walls of the vacuum chamber of the FEL’s transport tracks.

A scheme of electron radiation output is proposed to solve the problem of overheating of the optical resonator mirrors in free-electron lasers (FEL) with high average radiation power. Such a structure acts on the electron beam, which is initially grouped in the first section of the undulator due to interaction with the mode of the optical resonator. In subsequent sections, it rotates at a small angle relative to the optical axis while maintaining its grouping, and its coherent radiation goes beyond the limits of the resonator mode. The electron outcoupling system is installed on the last of the three lasers of the Novosibirsk FEL. It consists of three undulators, two quadrupoles, and dipole correctors located between them. There are thus two possible configurations, as the electron beam can be rotated in both the second and third undulator. Preliminary estimates of the radiation power are considered. Different configurations of the electron radiation output system of the Novosibirsk FEL are compared.

The problem of calculating the electromagnetic field of directional radiation passing through a system of amplitude-phase masks arises in many studies. This work describes the WaveThruMasks software package written for planning and analyzing experiments on the terahertz radiation of the Novosibirsk free electron laser. An example is given of using the package to analyze the results from experimental studies of the diffraction of Bessel beams with orbital momentum on two-dimensional gratings.

Bottom sediments from Lake Kucherlinskoe that contain finely-laminated layers are studied using micro-XRF on synchrotron radiation beams from the VEPP-3 storage ring. Samples with visible layers are prepared as solid specimens impregnated with epoxy. The procedure for preparing the samples preserves the original structure and composition of the sediment. Scanning X-ray fluorescence microanalysis of the samples is performed on an experimental setup at the joint usage center of the Institute of Nuclear Physics, Siberian Synchrotron and Terahertz Radiation Center. Scan profiles with increments of 100 and 200 µm are obtained that contain data on the distribution of over 20 rock-forming and microelements. The experimental material is used to confirm the annual nature of the observed layering of sediments, estimate the rate of sedimentation, and construct a lithological and geochemical model of the sedimentation process.

The article describes the magnetic system modernization of the wiggler installed at the ELETTRA storage ring in 2002. This work was made in Budker Institute of Nuclear Physycs SB RAS in 2017. Modernization touched, mainly, changes in the parameters of superconducting coils.

Acousto-optic (AO) interaction in optically isotropic media is studied. Vector differential equations are obtained that describe the Raman–Nath diffraction of light on ultrasound in an absorbing medium. Particular emphasis is placed upon light-beam divergency caused by its transverse restriction.

The thickness and structure of scintillation screens are of paramount importance in X-ray microscopy. A scintillator should be fairly thick in order to maximize the conversion of X-ray quanta to the visible range. At the same time, scattering of light in scintillators considerably reduces the spatial resolution of X-ray images. To improve resolution, the CsI:Tl layer can be structured as a matrix of micropixels to inhibit the spread of light to neighboring cells. In this work, radiation-induced ablation of CsI:Tl with the use of synchrotron radiation is examined as a new way of structuring for scintillation screens.

A study is made of morphological changes that occur in the M. Wistar skeletal muscles as a result of tissue damage by focused radiation of the first stage of the Novosibirsk free electron laser. Samples are studied via optical and electron microscopy. The aim of the study is to determine the impact of powerful terahertz radiation and the damage to tissue, compared to CO₂ laser radiation. A detailed morphological description and possible causes of tissue damage are given.