High-current Electron Accelerator Research Articles

Simulation of Secondary X-Ray of Sterilization Setup Based on High-Current Pulse Electron Accelerator SINUS-320

Simulation of Secondary X-Ray of Sterilization Setup Based on High-Current Pulse Electron Accelerator SINUS-320

Fabrication and rejuvenation of high quantum efficiency caesium telluride photocathodes for high brightness and high average current photoinjectors

With their high quantum efficiency (QE) and excellent photoemissive properties, cesium telluride (Cs-Te) photocathodes are the current workhorse in the high average current electron accelerators around the globe. Their ability to generate high brightness and high charge electron beams has opened the doorway to numerous applications, including fundamental particle physics research, radiation therapy, high-energy physics experiments, and high repetition rate free-electron lasers (FELs). Their long-term performance is critical. In this work, we analyze the systematic production and rejuvenation of photocathodes via thermal evaporation and deposition techniques (both sequential and co-deposition), showing excellent values of QE exceeding 20% using deep ultraviolet illumination (λ=262–266 nm). To extend the photocathode lifetime, the rejuvenation process is performed via multilayer thin-film co-deposition, demonstrating the feasibility of reliably recovering the initial QE even after air exposure. We evaluated their final performance in both high gradient dc and rf gun setups and obtained consistent results of QE and lifetimes. The technique can be used at the gun level, which significantly extends the sustained accelerator operation without major interventions. These approaches significantly enhance the robustness and performance of Cs-Te photoinjectors and represent a significant advancement for reliable high average current electron accelerators and FELs. Published by the American Physical Society 2024

High voltage dc gun for high intensity polarized electron source

The high intensity polarized electron source is a critical component for future nuclear physics facilities. The Electron Ion Collider (EIC) requires a polarized electron gun with higher voltage and higher bunch charge compared to any existing polarized electron source. At Brookhaven National Laboratory, we have built an inverted high voltage direct current (HVDC) photoemission gun with a large cathode size. We report on the performances of GaAs photocathodes in a high gradient with up to a 16 nC bunch charge. The measurements were performed at a stable operating gap voltage of 300 kV - demonstrating outstanding lifetime, and robustness. We observed obvious lifetime enhancement by biasing the anode. The gun also integrated a cathode cooling system for potential application on high current electron sources. The various novel features implemented and demonstrated in this polarized HVDC gun open the door towards future high intensity-high average current electron accelerator facilities.

RADIATION STIMULATION OF THE CATALYTIC ACTIVITY OF ZIRCONIUM DIOXIDE NANOPARTICLES DURING THE CONVERSION OF HYDROCARBONS

The comparison of the catalytic activity of the initial and activated by bremsstrahlung -radiation on a high-current electron accelerator of zirconium dioxide nanoparticles on the nature of the conversion of ethanol. The used -activation parameters contributed to the formation of a more perfect crystal structure of ZrO2 nanoparticles. It was shown that when using -activated ZrO2 nanoparticles as a catalyst, the yield of hydrocarbon products during the conversion of ethanol was several times higher than the yield of the same products in the case of using the initial ZrO2 nanoparticles. The mechanism of such a conversion of ethanol can be associated with the synergism of large ionization losses of Auger electrons and the effect of highly reactive products involved in heterogeneous catalysis.

Experimental proof test of CW mode RF modulated grid-controlled thermionic electron gun

A CW mode RF modulated grid-controlled thermionic electron gun was proposed by Institute of Modern Physics (IMP), Chinese Academy of Sciences (CAS) for some high average current electron accelerators requirements. The RF modulated grid-controlled thermionic electron gun was selected for these purposes due to its simplicity and cost savings. The experimental proof test of this type electron gun was conducted. The RF power supply at 107.5 MHz for the grid modulation can be adjusted from 10 W to 70 W. The RF power is coupled into the gun of grid-cathode through a RF&DC modulator. The electromagnetic field and RF simulation of the modulator is presented here. The gun structure and the beam dynamics design are also shown in the paper. The cathode assembly and the electron guns are tested on a 10 kV test bench for beam characterization. The CW mode 107.5 MHz electron beam obtained from the proof test, which is important for future high average current electron injectors development.

ИССЛЕДОВАНИЕ ФАКТОРОВ, СПОСОБСТВУЮЩИХ НЕCАНКЦИОНИРОВАННОМУ ИНИЦИИРОВАНИЮ ЭНЕРГОНАСЫЩЕННЫХ МАТЕРИАЛОВ

The results of experimental studies on the initiation of compositions containing energy-saturated materials by high-current electron beams and electrodischarge plasma are presented. Experimental studies simulate the effects on energy-saturated materials of electromagnetic fields of natural and man-made origin. The threshold voltage of the electrical breakdown of the compositions during a high-voltage electric discharge was determined and the possibility of initiation of the compositions by high-current electron beams of nanosecond duration using a pulsed high-current electron accelerator GKVI-300 was studied. Four compositions were selected as objects of study: a composition based on potassium picrate, a composition containing ammonium perchlorate, a composition based on lead minium with zirconium and colloxylin additives, and ballistite composition SBK-3. It is shown in the work that the initiation of compositions by a high-current electron beam is potentially possible only for compositions with low ignition temperatures, ignition of compositions with high ignition temperatures is possible due to the introduction of a powdery nanoscale additive, particles of which have specific heat less than particles of an energy-saturated material, and ignition of ammonium perchlorate is possible only if the particles of the additive have lower thermal conductivity than the particles of perchlorate ammonium.

HYPERBOLIC FIELDS. SEARCH EXPERIMENTS WITH A VACUUM DIODE

The article describes experiments carried out on the high-current pulsed electron accelerator Terek-2. The experiments, in their main features, reproduce the results obtained earlier in the Proton-21 laboratory. The incentive to carry out the experimental studies described in the article was an attempt to experimentally confirm the idea of a “hyperbolic lens” described in [1].

High-brightness electron beams for linac-based bunched beam electron cooling

A high-current high-brightness electron accelerator for low-energy RHIC electron cooling (LEReC) was successfully commissioned at Brookhaven National Laboratory. The LEReC accelerator includes a dc photoemission gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a superconducting rf booster cavity, and a set of normal conducting rf cavities to provide enough flexibility to tune the beam in the longitudinal phase space. Cooling with nonmagnetized rf accelerated electron beams requires longitudinal corrections to obtain a small momentum spread while preserving the transverse emittances. Electron beams with kinetic energies of 1.6 and 2.0 MeV with a beam quality suitable for cooling were successfully propagated through 100 m of beam lines, including dispersion sections, maintained through both cooling sections in RHIC and used for cooling ions in both RHIC rings simultaneously. The beam quality suitable for cooling RHIC beams was achieved in 2018, which led to the first experimental demonstration of bunched beam electron cooling of hadron beams in 2019.7 MoreReceived 22 November 2019Accepted 23 January 2020DOI:https://doi.org/10.1103/PhysRevAccelBeams.23.021003Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeam coolingBeam opticsHigh intensity beam dynamicsAccelerators & Beams

Radiological Protection Policy Aspects concerning the Design and Operation Modus of Medium Energy (< 1 GeV) or High Current (> 25 MeV, = 1 kA) Electron Accelerators Facilities

Radiation Protection in major research-facilities includes several aspects concerning their planning, the hazard-sources, the environmental protection and the general safety. The present paper includes a concise presentation of the approach to the radiation protection policies proposed for the Athens Race Track Microtron (250 MeV, 550 mA) and the Heraclion Modified Betatron Accelerator (25 MeV, 1 kA).

High-Current Pulsed-Repetitive Electron Accelerator “Sinus-320”: Formation and Diagnostics of a Wide-Aperture Beam

A wide-aperture (16 cm × 27 cm) source of e-beams for sterilization of plastic packages based on a“SINUS- 320” high-current accelerator with 450 keV energy, 9 kA current, 12 ns pulse duration, and repetition rate up to 100 Hz is described. A metal-dielectric cathode forms e-beam by explosive emission during a few nanoseconds of the voltage pulse. A high degree of e-beam uniformity can be achieved because of a large number of triple points (~800) and of electron scattering in a foil and in a 3 cm air layer for characteristic electron free paths in air up to half a meter.

SMALL-SIZE DIRECT-ACTION ELECTRON ACCELERATOR WITH A HIGH-EFFICIENCY NANOSECOND PLASMA-CURRENT SWITCH

The paper presents the results of a study undertaken to determine operating modes for a small-size direct-action electron accelerator with a high-efficiency nanosecond plasma-current switch (PCS). The investigations have shown that using PCS as a base it is possible to develop small-size nanosecond pulsed high-current electron accelerators with a voltage pulse sharpening coefficient of about 12, beam (flow) electron energy of 300…400 keV and current of 100 kA for pulse duration of 30 ns. The ways for improving the PCS and accelerator operating parameter stability, increasing the switching current and maximum accessible switching frequency are proposed.

Сильноточный имульсно-периодический ускоритель электронов «SINUS-320»: формирование и диагностика широкоапертурного пучка

Сильноточный имульсно-периодический ускоритель электронов «SINUS-320»: формирование и диагностика широкоапертурного пучка

Investigation of the level of DNA double-strand breaks and mechanisms of cell death under irradiation of lung cancer and melanoma cells with ultra-high dose rate photon radiation

Research into the effects of radiation delivered at ultrahigh dose rates > 1 × 107 Gy/min to biological objects is a new promising area of radiobiology. The unique characteristics of the high-current nanosecond electron accelerator Mir-M enable its use in medical and biological research, specifically in the experiments aimed at investigating the effect of therapeutic doses at a dose rate up to 100 MGy/s. In this work we study the effects of ultrahigh dose rate photon radiation on human lung carcinoma (A549) and melanoma (MelMtp-x) cells lines and compare them with those of the therapeutic gamma unit Rokus-AM. We show that ultrahigh dose rates induce more significant damage in the studied cell lines at doses between 2 and 7 Gy, radioresistant melanoma being more sensitive to photon radiation delivered at ultrahigh dose rates.

A high-current nanosecond electron accelerator MIR-M for biomedical research

A high-current electron accelerator MIR-M for biomedical studies of the reaction of healthy and tumor tissues, as well as cell cultures, exposed to X-ray radiation with high dose rate – up to 100 MGy/s at absorbed doses of 0.5 to 20 Gy in the single pulse, was developed and constructed. The main parameters of the accelerator are as follows: accelerating voltage – up to 800 kV, peak current – up to 50 kA, e-beam pulse duration – ≈80 ns. The design and parameters of the main systems of the accelerator together with the methods of measurements and first results of a comparative analysis of the effects of irradiation in vivo and in vitro using therapeutic devices and accelerator MIR-M are presented and discussed.

Registration of over-accelerated electrons in a high-current picoseconds accelerator

A high-voltage (U = 280 keV) high-current (I = 5 kA) electron accelerator with a beam duration of 200 ps was investigated. The luminescent method showed that the beam diameter in the uniform pinching mode is about a micrometer, therewith the beam contains electrons with an energy exceeding 400 keV.

Magnetic Sweep of a Relativistic Electron Beam into a Rectangular Raster

The design of a magnetic sweep unit that provides a combination of two linear (with respect to time) sweeps of the relativistic electron beam and the radiation field of the accelerated electron beam swept into a rectangular raster and scattered by an air layer when approaching the target have been considered. Expressions for the distribution of absorbed dose over the whole exposed surface have been obtained taking into account the real distribution of beam current density. The considered expressions for the distribution function of absorbed dose can be used as a foundation for the calculations of magnetic sweep units for radiochemical equipment with high-current industrial electron accelerators, in particular, with escape of a focused beam of accelerated electrons into the atmosphere.

Collective “overacceleration” of electrons in a pinched picosecond electron beam

The extreme operating mode of a high-voltage (U = 280 keV) high-current (I = 5 kA) electron accelerator with a beam duration of 200 ps is investigated. The luminescent method shows that the beam diameter in the uniform pinching mode is about a micrometer, and the beam contains electrons with an energy exceeding 400 keV. The analysis of the bremsstrahlung X-ray spectrum of the beam electrons shows that in this mode, a significant part of the spectrum lies in the energy range >300 keV, with the energy of quanta in the “tail” of the spectrum exceeding 500 keV.

Two-Wave Cherenkov Oscillator With Moderately Oversized Slow-Wave Structure

This paper describes a new design of a relativistic Cherenkov oscillator with strong modulation of the e-beam current at the input of two-sectioned slow-wave structure, as well as numerical and experimental results on generation of few gigawatt-level $X$ -band pulses with pulse duration of up to 35 ns. Due to special phase shift between two sections and electrodynamic coupling between $E_{01}$ surface wave and $E_{02}$ volume mode, the first one is locked at the upper boundary of the passband and the second one gains more transparency. An electron beam can interact simultaneously with two waves with higher power conversion efficiencies, which in simulations amount up to 47% and 30% for high (~4 T) and low (~1 T) guiding magnetic fields, correspondingly. The tests of the geometry optimized in simulations were performed on the base of SINUS-7 high-current electron accelerator in the diode voltage range of 400–850 kV and current from 7 to 16 kA. The repeated and full-pulsewidth generation of about 1.5-GW microwave power is achieved only in the low magnetic field. The pulse shortening and the mode competition took place in the strong magnetic field. The results are considered as preliminary for creation of the efficient relativistic millimeter-wave oscillators at magnetic fields below the cyclotron resonance.

Extremely High Peak Power Obtained at 29 GHZ Microwave Pulse Generation

The paper presents research results on enhancing the peak power of microwave pulses with sub- and nanosecond length using a backward-wave oscillator (BWO) operating at 29 GHz frequency and possessing a reproducible phase structure. Experiments are conducted in two modes on a high-current electron accelerator with the required electron beam power. In the first (superradiation) mode, which utilizes the elongated slow-wave structure, the BWO peak power is 3 GW at 180 ns pulse duration (full width at halfmaximum, FWHM). In the second (quasi-stationary) mode, the BWO peak power reaches 600 MW at ~2 ns pulse duration (FWHM). The phase spread from pulse to pulse can vary from units to several tens of percent in a nanosecond pulse mode. The experiments do not show any influence of microwave breakdown on the BWO power generation and radiation pulse duration.

A high-current subnanosecond electron accelerator with a gas-filled former

A subnanosecond electron accelerator prototype based on the ARSA small-size accelerator with a gas-filled former (nitrogen ~4 MPa) has been developed and studied. The operation principle of the former involves charging of a short storage line and its discharge to a stepped line with an accelerating tube that generates electrons. The recorded electron-beam current pulse length was t0.5 = 0.3 ns, the current amplitude was at least 1.5 kA, and the maximum electron energy was ~850 keV.