Linear accelerator of the injector of the synchrotron radiation facility SKIF (SRF SKIF) was assembled in Koltsovo in the end 2024. It is the beginning part of the accelerator complex where the electron beam is formed. After the acceleration up to the energy of 200 MeV the beam is transported to the booster synchrotron. The linear accelerator (linac) consists of the electron source based on the radiofrequency (RF) gun, the bunching channel with the bunching preaccelerator and five regular accelerating structures. Three 50 MW klystrons with the operating frequency of 2856 MHz feed the accelerating structures. Two of the klystrons were developed and manufactured at the Budker Institute of Nuclear Physics of Siberian Branch of Russian Academy of Sciences (BINP SB RAS) in house, while the remaining one was purchased. During the linac operation, maximum values of the RF power in waveguides were achieved. The transverse dynamics of the bunched electron beam was tuned in a single-bunch mode. Using the mechanical waveguide phase shifters, the accelerating field phases were chosen, which provided the required beam energy. Achieved parameters of the linac beam allowed us to proceed to the work with the linac–booster transport channel and the booster synchrotron itself. The article describes the linac launching process together with its current operation status and the achieved beam parameters.

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 radiation damping time is a crucial parameter that depends on the overall magnetic structure of the accelerator. Accurate measurement of this damping time can provide insights into the fidelity of the accelerator model by allowing for a comparison with calculated damping time values. In this study, we present a series of measurements of radiation damping times at the VEPP-4M and VEPP-2000 collider at BINP. In order to determine the damping time, we recorded the transverse beam profile using a digital camera. The results includes study of the damping times at revolution frequencies and different energies of the beams.

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.

Introduction:To ensure the safety and efficacy of precise proton therapy, real-time and non-intrusive monitoring of the clinical beam position is essential. However, in cyclotron-based proton therapy facilities, clinical proton beams with low repetition frequency and exceptionally low intensity due to the Energy Selection Systems (ESS), pose considerable challenges for accurate online beam diagnostics. Conventional non-interceptive beam diagnostic devices lack the sensitivity required to detect such weak beams with sufficient precision. Methods:This paper presents an innovative solution to this challenge: an off-centerrectangular cavity Beam Position Monitor (BPM) with dielectric loading. This novel design achieves remarkable position sensitivity while maintaining compact transverse dimensions of 500×250×100 mm. Results:A prototype of this cavity has been fabricated and tested offline. Experimental results demonstrate that, within the clinical treatment energy range, the BPM achieves minimum beam position measurement sensitivities of 0.49 nV/mm at 70 MeV and 17.12 nV/mm at 230 MeV. In addition to enabling online beam position monitoring without disturbing the beam path, which ensures real-time beam orbit feedback correction with submillimeter stability (± 0.5 mm). Discussion:In addition to monitoring beam positions for precise control of the beam orbit, the BPMs could serve additional functions to enhance proton therapy-such as enabling beam energy verification through the phase of the BPM signal.

A new high precision measurement of the Y(1S)-meson rest mass is being carried out at the VEPP-4M collider using the KEDR detector. The resonant depolarization method with the laser polarimeter has been employed for the absolute calibration of the beam energy. In the paper resent status of the experiment is discussed.

The paper presents a design of an autocorrelator manufactured to measure the duration of infrared picosecond pulses of radiation from the 3rd laser of the Novosibirsk Free Electron Laser facility, as well as the results of testing the autocorrelator when measuring the duration of picosecond pulses in the visible range. The results and future plans for future experiments using developed autocorrelator

Using strong electromagnetic fields generated by lasers to interact with electrons for precise diagnosis and manipulation of electron beams represents a recent focal point in accelerator technology. This approach surpasses the limitations of conventional RF technology, such as low electric field gradients and timing jitters, effectively enhancing the accuracy of ultrafast electron beam diagnostics and manipulations. As demands for precision continue to rise, the precise diagnosis of crucial parameters of ultrafast electron beams remains challenging. This study delves into the electromagnetic behavior of THz-driven devices and proposes an all-optical method utilizing single-cycle THz radiation to compress and characterize a 3 MeV electron beam. Particle tracking simulations demonstrate an astonishing compression effect, reducing the bunch length from 54.0 fs to 4.3 fs, and achieving sub-femtosecond bunch length measurement resolution. Moreover, when combined with an orthogonal THz streak camera, this method shows even greater potential in multi-bunch scenarios.

The linear accelerator of the Siberian Circular Photon Source is being developed at Budker Institute of Nuclear Physics of the Siberian Branch of the Russian Academy of Sciences (BINP SB RAS). The test accelerator facility with the RF gun, the bunching system, the pre-accelerator and the first regular accelerating structuresoperates at Budker Institute of Nuclear Physics. The aim of work at this facility is to demonstrate the performance of the basic system of the linear accelerator, including the accelerating structures. This paper presents the first accelerating structures for the linear accelerator of the SKIF injector produced at BINP SB RAS.

The Siberian ring source of photons (SKIF) is a new 3 GeV fourth-generation synchrotronlight source being developed by the Budker Institute of Nuclear Physics (BINP). A beam lossmonitoring system is necessary to ensure its reliable commissioning and operation. Two typesof beam loss monitors will be installed in the SKIF: 5 fiber-based Cherenkov beam loss monitors(CBLMs) for the linac and transfer lines and 128 scintillator-based beam loss monitors (SBLMs) forthe storage ring. Sophisticated electronic equipment is employed to use these monitors in differentmodes of SKIF operation. The paper describes the design of the SKIF beam loss monitoring systembased on numerical simulations and experimental studies

This paper describes investigation of scintillator P43 coating for large area screens intended for preliminary beam diagnostics in the Collector Ring (Facility for Antiproton and Ion Research in Europe). We used two appropriate coating techniques: detonation spraying and electrophoresis. The article contains short descriptions of the Collector Ring, screen coating techniques, light output (with application of electron welding), and vacuum tests. We also applied SEM to check the structure and chemical composition of pure P43 powder and scintillation screen samples, prepared by detonation spraying and electrophoresis coating techniques. As a result, we observed poor P43 light output after detonation spraying (the reason is a change in the chemical composition of P43) and poor ruby and alumina light output in comparison with P43 in the case of the electrophoresis technique. Improving of the electrophoresis technique enabled us to reach good adhesion and vacuum properties without decrease in the light yield.

Bunch trains consisting of ultrashort picosecond-spaced microbunches have potential applications in generating pulsed, tunable, narrow-band radiation sources in the THz region via coherent Smith-Purcell radiation (cSPr). However, the electrons in each microbunch experience longitudinal space-charge field, blurring the periodicity of the bunch train. There has been an increasing interest in manipulating each microbunch individually, and therefore significantly improving radiation intensity and bandwidth. The commonly used RF cavities (with nanosecond working period) cannot match the picosecond bunch spacing and, fail to compress each bunch individually. This paper proposes a novel method to simultaneously compress each microbunch in a picosecond-spaced bunch train using a THz-driven resonator with a customizable working frequency. A multi-pulse drives the THz-driven resonator to compensate for the field decay in the THz-driven resonator and preserve the well-defined periodicity of the bunch train. We demonstrate a resonating field with an amplitude fluctuation within±20%, which can be utilized to compress up to ten microbunches simultaneously.

The new fourth-generation synchrotron light source SKIF is under development in Novosibirsk, Russia. It consists of a 3 GeV electron storage ring with extremely low emittance, a booster synchrotron, and a linear accelerator. The paper discusses essential aspects of the design of the 200 MeV linear accelerator for SKIF, its main characteristics, and parameters in different operation modes. Description of the linac systems is presented.

Using the 1.32 pb(-1) statistics collected at the J/psi peak with the KEDR detector at the VEPP-4M e(+)e(-) collider, we measured the branching fractions of J/psi meson decays to the final states 2(pi(+)pi(-))pi(0), K+K- pi(+)pi(-)pi(0), 2(pi(+)pi(-)) and K+K- pi(+)pi(-). The results obtained for the decays J/psi -> 2(pi(+)pi(-))pi(0), J/psi -> K+K- pi(+)pi(-)pi(0) contradict the measurements performed by other groups in the last century, but agree well with recent results of BABAR and BESIII collaborations.

This Letter reports the observation of WWW production and a measurement of its cross section using 139 fb^{-1} of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. Events with two same-sign leptons (electrons or muons) and at least two jets, as well as events with three charged leptons, are selected. A multivariate technique is then used to discriminate between signal and background events. Events from WWW production are observed with a significance of 8.0 standard deviations, where the expectation is 5.4 standard deviations. The inclusive WWW production cross section is measured to be 820±100 (stat)±80 (syst) fb, approximately 2.6 standard deviations from the predicted cross section of 511±18 fb calculated at next-to-leading-order QCD and leading-order electroweak accuracy.

As the injector of the new fourth-generation SKIF synchrotron light source at the BINP SB RAS (Novosibirsk, Russia), the linear accelerator will provide a 200 MeV electron beam. A precise measurement of the beam is very important for the control of the linac and even the entire light source. A set of diagnostic instruments for tuning the linac and measuring the beam parameters starting from the electron RF gun to the output of accelerator has been designed. The instrumentation should cover the dynamic diagnostic range of 0.6 to 200 MeV and a beam duration from the initial 100 ps to 3 ps at the output of the accelerator. The set includes eight fluorescent screens to measure beam transverse size, two Cherenkov probes and RF-cavity sensors to record beam duration, a dipole magnetic spectrometer to measure energy and energy spread, a Faraday cup (FC) and fast current transformers (FCTs) to measure beam charge current, and beam position monitors (BPMs) to check the beam position. This paper aims to give an overview of the beam instrumentation and briefly describes the design and parameters of each diagnostic system. The results of numerical and dynamics simulations of some of the instruments are briefed. Possible scenarios of linac tuning are discussed.

The orientation of molecules is essential to study molecular angle-differential properties such as ionization and scattering cross-sections in material physics and chemistry. Ultrafast electron diffraction (UED) facilities offer effective ways to explore the ultrafast dynamics of orientated molecules. Generally, the orientation of molecules is generated by a strong dc-field. However, the presence of a strong field may influence detection outcome. Field-free orientation of molecules is preferable, avoiding the disadvantages of traditional dc-field excitation. This paper proposes a practical and versatile method for field-free molecular orientation using the co-rotating two-color circularly polarized ultrafast laser pulses, and the orientation of the molecules can be controlled by the relative phase of the two-color laser fields. We also performed our simulation in CO molecules with the Born-Oppenheimer and rigid rotor approximations, and the light-molecule interaction Hamiltonian is given by the low-order perturbation theory.

Streak cameras based on THz-driven split-ring resonator (SRR) are recently proposed to achieve electron bunchlengthmeasurement with femtosecond resolution due to the available GV/m level streaking field. However, to apply the SRRtothe streaking experiment, the SRR needs to have a relatively large gap to accommodate the beamto traverse. Alargergap leads to higher electromagnetic power radiation, which requires high exciting THz power to compensate powerradiation to achieve a strong streaking field. The maximum stored energy in the gap is determined by the availableexciting THz power. If a single THz pulse drives the SRR, the achievable streaking field is not enough for highresolution because of the radiation diluting the stored energy. This paper proposes a novel method to illuminate theSRRwith multipulse, which can accumulate the energy stored in the gap to compensate the electromagnetic radiationuntil saturation and consequently enhance the resonance to a much higher peak field. We explore the effects of drivingpulseswith various intervals and obtain an optimal field enhancement factor up to 47 with the THz field strength of 1MV/m. The particle tracking simulation indicates that the multipulse-driven method can achieve the temporal resolution of 0.4fswith the central frequencies of SRR at 0.3 THz.

The first measurement of longitudinal decorrelations of harmonic flow amplitudes v_{n} for n=2-4 in Xe+Xe collisions at sqrt[s_{NN}]=5.44  TeV is obtained using 3  μb^{-1} of data with the ATLAS detector at the LHC. The decorrelation signal for v_{3} and v_{4} is found to be nearly independent of collision centrality and transverse momentum (p_{T}) requirements on final-state particles, but for v_{2} a strong centrality and p_{T} dependence is seen. When compared with the results from Pb+Pb collisions at sqrt[s_{NN}]=5.02  TeV, the longitudinal decorrelation signal in midcentral Xe+Xe collisions is found to be larger for v_{2}, but smaller for v_{3}. Current hydrodynamic models reproduce the ratios of the v_{n} measured in Xe+Xe collisions to those in Pb+Pb collisions but fail to describe the magnitudes and trends of the ratios of longitudinal flow decorrelations between Xe+Xe and Pb+Pb. The results on the system-size dependence provide new insights and an important lever arm to separate effects of the longitudinal structure of the initial state from other early and late time effects in heavy-ion collisions.

VEPP-4M is an electron positron collider equipped with the universal KEDR detector for HEP experiments in the beam energy range from 1 GeV to 6 GeV. A unique feature of VEPP-4M is the high precision beam energy calibration by resonant polarization technique which allows conducting of interesting experiments despite the low luminosity of the collider. Recently we have started new luminosity acquisition run above 2 GeV. The hadron cross section was measured from 2.3 GeV to 3.5 GeV has been done. The luminosity run for gamma-gamma physics has been started. The luminosity at ψ(1S)-meson has been obtained. For the beam energy calibration the laser polarimeter is used. The paper discusses recent results from VEPP-4M collider.