DEVELOPMENT OF A NEW DEVICE FOR TRIGGERING A LINEAR ELECTRON ACCELERATOR “ALMAZ-2”

A new device for triggering of the linear accelerator of electrons has been developed and tested. The circuit de-vice consists of a master generator forming rectangular pulses with a duration of 1…2 μs with a front of about 50 ns and a repetition rate of 1 to 5 pps, and three channels generating pulses with a delay relative to the pulses of master generator, which can be adjusted from 0.1 up to 10 μs.

Linear Electron Beam Assisted Roll-to-Roll in-Vacuum Flexographic Patterning for Flexible Thermoelectric Generators

In this work, we investigated the use of in-line linear electron beam irradiation (LEB) surface treatment integrated into a commercially compatible roll-to-roll (R2R) processing line, as a single fluorocarbon cleaning step, following flexography oil masking used to pattern layers for devices. Thermoelectric generators (TEGs) were selected as the flexible electronic device demonstrator; a green renewable energy harvester ideal for powering wearable technologies. BiTe/BiSbTe-based flexible TEGs (f-TEGs) were fabricated using in-line oil patterned aluminium electrodes, followed by a 600 W LEB cleaning step, in which the duration was optimised. A BiTe/BiSbTe f-TEG using an oil-patterned electrode and a 15 min LEB clean (to remove oil prior to BiTe/BiSbTe deposition) showed similar Seebeck and output power (S~0.19 mV K−1 and p = 0.02 nW at ΔT = 20 K) compared to that of an oil-free reference f-TEG, demonstrating the success of using the LEB as a cleaning step to prevent any remaining oil interfering with the subsequent active material deposition. Device lifetimes were investigated, with electrode/thermoelectric interface degradation attributed to an aluminium/fluorine reaction, originating from the fluorine-rich masking oil. A BiTe/GeTe f-TEG using an oil-patterned/LEB clean, exceeded the lifetime of the comparable BiTe/BiSbTe f-TEG, highlighting the importance of deposited material reactivities with the additives from the masking oil, in this case fluorine. This work therefore demonstrates (i) full device architectures within an R2R system using vacuum flexography oil patterned electrodes; (ii) an enabling Electron beam cleansing step for removal of oil remnants; and (iii) that careful selection of masking oils is needed for the materials used when flexographic patterning during R2R.

High frequency power supply to improve operation stability of linear electron accelerator

The use of linear electron accelerators in medicine and industry is explained by the simplicity of the input and output of accelerated electrons and adjusting the energy and dose rate, as well as the high dose rate of bremsstrahlung. The purpose of this work is to increase the stability of their work. A standing wave accelerator containing a high-frequency generator, a phase shifter, a waveguide bridge, a high-frequency load, and an accelerating system of two accelerating sections is equipped with two waveguide tees. Their inputs are connected to the output arms of the waveguide bridge, and the first and second output arms of each tee are connected to the first and last accelerating cells of each section, respectively. In this system, due to the introduction of several elements that do not require large costs for manufacturing and tuning, a significantly greater frequency separation of the operating mode of oscillations from neighboring ones is ensured, or even a single-frequency excitation mode is implemented, which makes it possible to significantly increase the stability of the accelerator operation. This technique can be used to increase the stability of operation in the design and calculation of linear accelerators of electrons with a standing wave.

Control of spectral characteristics of the medical accelerator on the basis of comparison of mass weaking coefficients of different materials

Background. Radiation protection of patients undergoing radiation therapy using linear electron accelerators is based on ensuring the constancy of the equipment parameters set during commissioning. Therefore, studying the possibility of operational assessment of the spectrum characteristics consistency of the generated bremsstrahlung is a priority along with standard dosimetric parameter control procedures. Primarily, this refers to specifying the average measured energy of bremsstrahlung which provides an impartial assessment of the constancy of the whole wave path of the accelerator. However, there is no special diagnostic equipment to determine this parameter. At the same time, the literature data represent a growing interest in the use of CdTe sensors for the analysis of high-energy radiation, including the ones in medical accelerators. Purpose – developing and testing special diagnostic equipment based on semiconductor CdTe sensors, which would implement the assessment of the average measured energy of bremsstrahlung of the medical accelerator 6 MeV via comparing the mass attenuation coefficients in lead and aluminum. Materials and Methods. The paper deals with experimental evaluation of the Varian Clinac 600C linear accelerator (USA) spectrum characteristics carried out at Radiation Oncology Department of State Organization «Grigoriev Institute for Medical Radiology and Oncology of the National Academy of Medical Sciences of Ukraine» via determining the average measured energy of bremsstrahlung. The assessment of the average measured energy of the bremsstrahlung of the accelerator was performed based on comparing two mass attenuation coefficients of radiation with materials having significantly different atomic numbers, i.e. Al and Pb. The assessment of the mass attenuation coefficients was performed on the basis of measuring the average amplitudes of CdTe signals of the sensor, operating in the pulse mode in conjunction with a 16-bit ADC. Pulses of bremsstrahlung from the linear accelerator were recorded by a peak detector for 10 seconds of measurement by the hardware-software complex at 400 monitor units by CdTe sensor with aluminum and lead absorber. The study was performed at a distance of «source-surface» 100 cm with an area of the irradiation field of 20x20 cm. The spectral energy profile of the generated field of bremsstrahlung was studied. Results. The developed equipment was tested by CdTe sensor, which was created taking into account the energy sensitivity of the sensor itself as well as the spectraltemporal characteristics of the pulsed radiation of the accelerator. The approach dealing with assessing the average measured energy of bremsstrahlung of the linear electron accelerator, based on the dependence of the attenuation of radiation by the absorber layer on the radiation energy, has been experimentally confirmed. The theoretical dependence of the average measured energy of bremsstrahlung of the linear accelerator on the ratio of the mass attenuation coefficients of lead and aluminum has been obtained. The energy range from 0.1 to 6 MeV corresponds to the ratio of mass absorption coefficients of lead to aluminum, varying nonlinearly from 33.8 to 1.639. The average measured energy of the linear accelerator of 0.8 MeV corresponds to a mass coefficient ratio of about 1.23 for these materials. The assessed absolute error (from the set value during commissioning the linear accelerator) of the specified measured average energy of bremsstrahlung is up to 12.5% (0.72 MeV), corresponding to the ratio of mass attenuation coefficients – 1.340. Conclusions. The special diagnostic equipment for recording the spectrum characteristics of the Varian Clinac 600C linear accelerator (USA) based on semiconductor CdTe sensors, which along with 16-bit ADC make it possible to estimate the average measured energy of bremsstrahlung via comparing mass attenuation coefficients in Al and Pb has been substantiated and reduced to practice. The assessment of mass attenuation coefficients is carried out based on measuring the average amplitudes of pulses of СdTe sensors operating in a pulse mode.

The Physiological Functionality of PGR5/PGRL1-Dependent Cyclic Electron Transport in Sustaining Photosynthesis

The cyclic electron transport (CET), after the linear electron transport (LET), is another important electron transport pathway during the light reactions of photosynthesis. The proton gradient regulation 5 (PGR5)/PRG5-like photosynthetic phenotype 1 (PGRL1) and the NADH dehydrogenase-like complex pathways are linked to the CET. Recently, the regulation of CET around photosystem I (PSI) has been recognized as crucial for photosynthesis and plant growth. Here, we summarized the main biochemical processes of the PGR5/PGRL1-dependent CET pathway and its physiological significance in protecting the photosystem II and PSI, ATP/NADPH ratio maintenance, and regulating the transitions between LET and CET in order to optimize photosynthesis when encountering unfavorable conditions. A better understanding of the PGR5/PGRL1-mediated CET during photosynthesis might provide novel strategies for improving crop yield in a world facing more extreme weather events with multiple stresses affecting the plants.

IMPROVED FAST PROTECTION SYSTEM AT HIGH-VOLTAGE GAS BREAKDOWNS FOR INDUSTRIAL ELECTRON ACCELERATORS

The article considers the ways to improve the protection system of linear electron accelerators ELV-1 and ELV-2 series on the basis of modern integrated and semiconductor component base. The proposed circuit solutions allowed turning off the facility power in case of gas electrical insulation breakdowns in the fast mode, that makes it impossible to work in an emergency. In order to improve the quality of control over the accelerator operation and additional informing an operator, capability of the proposed system to display information on the operator's computer monitor has been realized.

AFFECT OF ULTRASHORT ELECTRON BEAMS ON THE ESCHERICHEA COLI SURVIVAL

The paper represents the study of ultrashort electron beams impact on some Escherichia coliK-12strains with different radiosensitivity. The charged particle beams generated by ultrashort bunch accelerators differ by short duration of particle direct exposure, relatively long intervals between bunches and by high values of instantaneous dose rates. Because of these characteristics, the nature of ultrashort beams impact on biological objects may sufficiently differ from conventional sources of radiation. As a source of ultrashort beams linear electron accellerator AREAL of SichrotronResearcinstitut CANDLE (Yerevan, Armenia) was used. The dependence of E.coli cells survival from electron bunches repetition rate and irradiation media was investigated. It is shown that the dose dependence of the survival degree of microorganisms has a qualitatively different unusual concave shape. Such behavior of the survival curves does not depend on the ionic composition of the irradiation medium as well as on the time of preliminary incubation of microorganisms in this medium. To explain the observed phenomenon, it was assumed that the compensatory capacity of the irradiated object increases with an increase of the irradiation dose.The proposed mathematical model described well the behavior of the survival curves. It is assumed that this change of the compensatory capacity may be determined by oxygen.