Terahertz (THz) radiation has gained attention due to technological advancements, but its biological effects remain unclear. We investigated the impact of 2.3 THz radiation on SK-MEL-28 cells using metabolomic and gene network analysis. Forty metabolites, primarily related to purine, pyrimidine synthesis and breakdown pathways, were significantly altered post-irradiation. Lipids, such as ceramides and phosphatidylcholines, were also affected. Gene network reconstruction and analysis identified key regulators of the enzymes involved in biosynthesis and degradation of significantly altered metabolites. Mitochondrial membrane components, such as the respiratory chain complex, the proton-transporting ATP synthase complex, and components of lipid rafts reacted to THz radiation. We propose that THz radiation induces reversible disruption of the lipid raft macromolecular structure, thereby altering mitochondrial molecule transport while maintaining protein integrity, which explains the high cell survival rate. Our findings enhance the understanding of THz biological effects and emphasize the role of membrane components in the cellular response to THz radiation.

We present an overview of recent and upcoming enhancements to the optical electron beam diagnostics stations at the Novosibirsk Free Electron Laser (FEL) facility. These diagnostic stations are designed to measure key beam parameters, including beam energy spread, length and emittance, at the third FEL of Novosibirsk FEL. Currently, the stations for measuring electron beam energy spread and undulator radiation spectrum are in the commissioning phase, with initial results already obtained. The new optical diagnostics are essential for the precise tuning of the magnet system used in electron outcoupling experiments. This paper provides a comprehensive overview of the new diagnostic systems, discusses the preliminary measurement results of beam parameters, and outlines the experiments planned for the near future.

The Novosibirsk Free Electron Laser (NovoFEL) is a facility that consists of three free electron laser (FEL) systems installed on different parts of the Energy Recovery Linac (ERL). These three FELs share the same acceleration system, which enables the generation of high average electron current, typically around 10 mA. Precise measurement of the electron beam parameters is essential for monitoring the performance of the accelerator and tuning its operating modes. One of the most important parameters is the length of the electron bunch, as it directly affects the efficiency of the laser radiation generation process. This paper presents the results of experiments conducted to study the behavior of the longitudinal beam size in various Novosibirsk FEL lasers. For these experiments, we used Cherenkov radiation produced by a beam of electrons passing through a thin aerogel plate. The resulting flash of radiation was captured by a streak camera, allowing us to determine the longitudinal size of the electron beam. The results of the study on the dependence of the longitudinal beam size on various accelerator parameters are presented.

A conventional derivation of motion equations in mechanics and field equations in field theory is based on the principle of least action with a proper Lagrangian. With a time-independent Lagrangian, a function of coordinates and velocities that is called energy is constant. This paper presents an alternative approach, namely derivation of a general form of equations of motion that keep the system energy, expressed as a function of generalized coordinates and corresponding velocities, constant. These are Lagrange equations with addition of gyroscopic forces. The important fact, that the energy is defined as the function on the tangent bundle of configuration manifold, is used explicitly for the derivation. The Lagrangian is derived from a known energy function. A development of generalized Hamilton and Lagrange equations without the use of variational principles is proposed. The use of new technique is applied to derivation of some equations.

A derivation of the time-dependent Schrödinger equation from the time-independent one is considered. Instead of time, the coordinate of an additional degree of freedom, the clock, is introduced into the original time-independent Schrödinger equation. It is shown that the standard time-dependent Schrödinger equation can be obtained for the semiclassical clock only. For elucidation of the physical meaning of the equation obtained in this way, various types of clocks are discussed. In addition, the corresponding equation for the density matrix and formulas for the mean values of operators are derived.

Energy-recovery linacs (ERLs) have been emphasised by the recent (2020) update of the European Strategy for Particle Physics as one of the most promising technologies for the accelerator base of future high-energy physics. The current paper has been written as a base document to support and specify details of the recently published European roadmap for the development of energy-recovery linacs. The paper summarises the previous achievements on ERLs and the status of the field and its basic technology items. The main possible future contributions and applications of ERLs to particle and nuclear physics as well as industrial developments are presented. The paper includes a vision for the further future, beyond 2030, as well as a comparative data base for the main existing and forthcoming ERL facilities. A series of continuous innovations, such as on intense electron sources or high-quality superconducting cavity technology, will massively contribute to the development of accelerator physics at large. Industrial applications are potentially revolutionary and may carry the development of ERLs much further, establishing another shining example of the impact of particle physics on society and its technical foundation with a special view on sustaining nature.

The deflection of charged particles is an intuitive way to visualize an electromagnetic oscillation of coherent light. Here, we present a real-time ultrafast oscilloscope for time-frozen visualization of a terahertz (THz) optical wave by probing light-driven motion of relativistic electrons. We found the unique condition of subwavelength metal slit waveguide for preserving the distortion-free optical waveform during its propagation. Momentary stamping of the wave, transversely travelling inside a metal slit, on an ultrashort wide electron bunch enables the single-shot recording of an ultrafast optical waveform. As a proof-of-concept experiment, we successfully demonstrated to capture the entire field oscillation of a THz pulse with a sampling rate of 75.7 TS/s. Owing to the use of transversely-wide and longitudinally-short electron bunch and transversely travelling wave, the proposed “single-shot oscilloscope” will open up new avenue for developing the real-time petahertz (PHz) metrology.

In this study we demonstrated that exposure of Escherichia coli ( E. coli ) to terahertz (THz) radiation resulted in a change in the activities of the tdcABCDEFGR and matA–F genes (signs of cell aggregation), gene yjjQ (signs of suppression of cell motility), dicABCF , FtsZ , and minCDE genes (signs of suppression of cell division), sfmACDHF genes (signs of adhesin synthesis), yjbEFGH and gfcA genes (signs of cell envelope stabilization). Moreover, THz radiation induced E. coli csg operon genes of amyloid biosynthesis. Electron microscopy revealed that the irradiated bacteria underwent increased aggregation; 20% of them formed bundle-like structures consisting of two to four pili clumped together. This could be the result of changes in the adhesive properties of the pili. We also found aberrations in cell wall structure in the middle part of the bacterial cell; these aberrations impaired the cell at the initial stages of division and resulted in accumulation of long rod-like cells. Overall, THz radiation was shown to have adverse effects on bacterial populations resulting in cells with abnormal morphology.

One of the aims of new circular collider projects is further increase in their luminosity. A high electromagnetic field of space charge at the meeting points limits the achievable current densities and consequently the luminosity. Non- linear focusing compensation in a storage ring done by the opposite-charge beam circulating in another storage ring was proposed and tested many years ago. Ya. S. Derbenev has shown that such a scheme suffers from tune shifts of coherent betatron oscillations, which move betatron frequencies toward the nearest integer or half-integer resonance. In this paper, the collider based on electron energy recovery linac (ERL) and "figure-8" positron storage ring with beams of equal currents is considered. Positrons are circulating in a two-loop storage ring (positron-positron collider), and electron- electron collider uses ERL, as in original Tigner's proposal. Thus, a collision of four bunches and space-charge compensation in a multi-bunch mode can be ensured. The mathematical and numerical analysis of this configuration is presented.

Due to strong sextupole corrections, the vertical dynamic aperture of a low-emittance storage ring is rather small. Therefore, in-vacuum short-period undulators can provide a sufficiently high field. In particular, a significant electrostatic field value can be obtained near electrodes. To eliminate the field emission, the high-field surfaces should be at a positive electric potential. In this paper, we consider the feasibility of an undulator using a comb of such electrodes. It is worth noting that a variable-period design may be rather simple for electrostatic undulators.

Free electron laser based on multi-turn microtron-recuperator is currently operates at Novosibirsk. Whole facility is a coherent radiation source with ability of wavelength tuning in adequately wide range. The main parameters of radiation (wavelength and radiation power) are depends on electron beam parameters – its energy, average current, movement trajectory. The system of magnetic elements, in turn, appear to be a main instrument to control over beam movement trajectory. The structure, main parameters of this system, abilities of magnetic elements control system are described in this article.

Differential proteomic analysis of the total E.coli protein after exposure to terahertz (THz) radiation was performed. Glutamine synthetase was one of the proteins overexpressed in response to THz radiation. E.coli/pGlnA-GFP biosensor based on the promoter of the glnA gene and the GFP protein was constructed and there was demonstrated that it could detect THz radiation. Such a method of design of biosensors which includes cell irradiation, omics analysis of differential expression of genes, the definition of the most pronounced gene can be used for any region of the electromagnetic spectrum.

The experimental observation of femtosecond dynamics in atoms and molecules by stroboscopic technologies utilizing x ray or electron flashes has attracted much attention and has rapidly developed. We propose a feasible ultrafast electron diffraction (UED) technology with high brightness and a sub-10 fs temporal resolution. We previously demonstrated a UED system with an overall temporal resolution of 31 fs by using an RF photoelectron gun and a 90° achromatic bending structure. This UED structure enabled a bunch duration of 25 fs and a low timing jitter of less than 10 fs while maintaining a high bunch charge of 0.6 pC. In this paper, we demonstrate a simple way to further compress the electron bunch duration to sub-10 fs based on installing an energy filter in the dispersion section of the achromatic bend. The energy filter removes the electrons belonging to nonlinear parts of the phase space. Through numerical simulations, we demonstrate that the electron bunches can be compressed, at the sample position, to a 6.2 fs (rms) duration for a 100 fC charge. This result suggests that the energy filtering approach is more viable and effective than complicated beam-shaping techniques that commonly handle the nonlinear distribution of the electron beam. Furthermore, a gas-filled hollow core fiber compressor and a Ti:sapphire amplifier are used to implement pump laser pulses of less than 5 fs (rms). Thus, we could present the full simulation results of a sub-10 fs UED, and we believe that it will be one of the technical prototypes to challenge the sub-fs time resolution.

Most contemporary storage rings operate in the multibunch mode. In this case, the transverse dynamics in the presence of feedback may be complicated. Indeed, generally, the amplified signal of beam position monitor kicks all circulating bunches. In this paper, the stability of such system with many degrees of freedom is considered. Damping times are estimated for the simplest cases.

A new normal-conducting, CW, thermocathode RF gun has been developed and tested recently at Budker Institute of Nuclear Physics. Providing an average current of up to 100 mA, this device will be used to upgrade the injector of the Novosibirsk FEL facility. Simulation of beam dynamics in the RF gun and its beamline was performed, the space-charge forces taken into account. Comparison of the simulation results and experimental measurements is presented in this paper.

In this article, we propose methods for the generation of surface plasmon polaritons (SPPs), both carrying orbital angular momentum, and conventional ones, using vortex Bessel beams, and also investigate the propagation of SPPs along flat and cylindrical conductors. The possibility of their practical application is discussed and the first experimental results are presented.

A review of experiments in the field of photonics and plasmonics, recently performed with the Novosibirsk free electron laser (NovoFEL) is given. Parameters of NovoFEL radiation and user workstations are described. Considerable attention was paid to the development and testing of quasi-optical elements designed for this range and to methods for the formation of powerful beams of terahertz radiation with a given mode composition. The use of terahertz radiation in the spectroscopy of gases and semiconductors, in generation and study of surface plasmon polaritons, as well as the use of the latter for the study of surfaces and in communication applications is described.

Polarized photon beams provide a unique experimental tool for the study of various polarization-dependent physical processes. Here, we report the experimental demonstration of full polarization control of an oscillator free-electron laser (FEL) using helical undulators of opposite helicities. Using two helical undulator magnets of opposite helicities and a buncher magnet in between, we have generated a linearly polarized FEL beam with any desirable polarization direction. With the development of a high-precision FEL polarimeter, we are able to optimize the highly polarized FEL beams in visible wavelengths and measure the polarization with high accuracy, demonstrating linear polarization ${P}_{\mathrm{lin}}g0.99$ on the routine basis and with the maximum polarization reaching ${P}_{\mathrm{lin}}=0.998$. In this paper, we describe the FEL configuration, experimental setup, and related beam diagnostics, including the newly developed high-precision FEL polarimeter. We report our experimental approaches to generate, tune up, and characterize the polarization controllable FEL beams and share a new insight into how high-degree polarization is realized based upon our investigation of the temporal structure of the FEL beam. This FEL polarization control technique has been used successfully to generate a polarization controllable Compton $\ensuremath{\gamma}$-ray beam for nuclear physics experiments.

A new variable period undulator of unique design was developed and built recently at Budker INP. It will replace the electromagnetic undulator in use now on the second FEL of the Novosibirsk FEL facility. As a result, the FEL tunability range will be substantially extended. In this paper, we present the results of measurements of the undulator magnetic field for different periods and discuss ways to reduce the field errors, which include sorting of magnets, weakening of undulator edge poles, and using of steering coils.

Ultrafast Electron Diffraction (UED) system, using an electron bunch of the duration with less than 100 fs and of the energy with 3 MeV, has been developed as a tool probing the ultrafast dynamics in pump–probe experiments. To keep the temporal and transverse characteristics of the electron bunch for the time-resolved electron diffraction, the bunch charge is limited to be the pico-Coulomb or less. S-band transverse deflecting cavity working on TM120 mode is designed, fabricated, and installed in the UED system to measure directly the fs-scaled pulse duration of low-energy and low-charge electron bunches. We describe the design and the expected performance of a single-cell RF deflector. For the electron beam of 3 MeV in energy and 1.88 pC in charge, we could measure the bunch duration of 69 fs and the timing jitter of 62 fs, both in rms.