Electron Beam Diameter Research Articles

Xenotime-(Y) from granitic pegmatites of the Monatsitovaya mine, Aduisky massif, Middle Urals (chemical composition and age)

The relevance of the work is due to the need to improve the chemical dating method as applied to high-uranium and high-thorium accessory minerals, which are difficult to study using isotopic research methods. The purpose of the work is to study the chemical composition of accessory xenotime from granite pegmatites of the Monatsitovaya mine (western part of the Aduisky massif) and determine its age. Research methodology. A quantitative analysis of the chemical composition of monazite was performed on a CAMECA SX 100 electron probe microanalyzer (IGG Ural Branch RAS, Ekaterinburg). Measurement conditions: accelerating voltage 15 kV, current 250 nA, electron beam diameter 2 μm. The pressure in the sample chamber is 2 × 10–4 Pa. The spectra were obtained on inclined wave spectrometers, the intensity measurements were carried out along the analytical lines: Y Lα, Si Kα, (TAP crystal analyzer), U Mβ, Pb Mα, Ca Kα, Th Mα, P Kα (PET), Yb Lα, Dy Lα, Er Lα, Gd Lα, Lu Lα, Sm Lβ (LiF). The overlap of peaks of spectral lines was taken into account, which is extremely important in the quantitative determination of lead content (the Y Lγ2,3 и Th Mζ1,2 lines are superimposed on the analytical Pb Mα line). The pulse accumulation time at the peaks of analytical lines was twice as long as for the background and was 60 s for Th, 40 s for U and Pb, and 10 s for other elements. When conducting research, linear experimental design was used to vary the time of measuring the intensities of the Mβ line of uranium, Mα lines of thorium and lead. The calculated detection limits are 345 ppm for U, 283 ppm for Th, 65 ppm for Pb, 205 ppm for Y. Results. It has been established that xenotime belongs to the yttrium variety and is characterized by an increased content of uranium (UO2 up to 8.8 wt. %) and thorium (ThO2 up to 4.5 wt. %). According to the results of chemical dating (based on 32 analyses), xenotime-(Y) shows a weighted average age of 276 ± 7 Ma (MSWD = 0.54). When constructing the dependence (ThO2 +UO2 eq) – PbO, the points fall on one isochron. Calculating the age using the isochron slope angle gave a dating of 276 ± 12 million years (MSWD = 0.94). Conclusions. The obtained age values for the xenotime are in good agreement with the dating of the pegmatoid granites of the Krutikhinsky massif, which is located on the western contact of the Aduisky granite massif and relatively close to the Monatsitovaya mine. It is quite possible that some pegmatites in the western part of the Aduisky massif were formed as a result of the formation of the Krutikhinsky massif.

Lossless Monochromator in an Ultrafast Electron Microscope Using Near-Field THz Radiation.

The ability to form monoenergetic electron beams is vital for high-resolution electron spectroscopy and imaging. Such capabilities are commonly achieved using an electron monochromator, which energy filters a dispersed electron beam, thus reducing the electron flux to yield down to meV energy resolution. This reduction in flux hinders the use of monochromators in many applications, such as ultrafast transmission electron microscopes (UTEMs). Here, we develop and demonstrate a mechanism for electron energy monochromation that does not reduce the flux-a lossless monochromator. The mechanism is based on the interaction of free-electron pulses with single-cycle THz near fields, created by nonlinear conversion of an optical laser pulse near the electron beam path inside a UTEM. Our experiment reduces the electron energy spread by a factor of up to 2.9 without compromising the beam flux. Moreover, as the electron-THz interaction takes place over an extended region of many tens of microns in free space, the realized technique is highly robust-granting uniform monochromation over a wide area, larger than the electron beam diameter. We further demonstrate the wide tunability of our method by monochromating the electron beam at multiple primary electron energies from 60 to 200keV, studying the effect of various electron and THz parameters on its performance. Our findings have direct applications in the fast-growing field of ultrafast electron microscopy, allowing time- and energy-resolved studies of exciton physics, phononic vibrational resonances, charge transport effects, and optical excitations in the mid IR to the far IR.

Monazite from lithium-bearing pegmatites of the Lipovskoye vein field, Middle Urals (composition and chemical dating)

The relevance of the research is due to the need to improve the method of chemical dating as applied to high-thorium accessory minerals, which are difficult to study by isotope research methods. Purpose of the research is to study the chemical composition of monazite from lithium-bearing granite pegmatites of the Lipovskoye vein field and to determine their age. Research methodology. The quantitative analysis of the chemical composition of monazite was performed on a CAMECA SX 100 electron probe microanalyzer (IGG UB RAS, Ekaterinburg). Measurement conditions: accelerating voltage 15 kV, current strength 250 nA, electron beam diameter 2 μm. The pressure in the sample chamber is 2 ⋅ 10–4 Pa. The spectra were obtained on tilted wave spectrometers, the intensity was measured using analytical lines: Th Ma, U Mb, Pb Ma, Y La, Si Ka, Ca Ka, P Ka, Ce La, La La, Pr Lb, Nd La, Sm Lb, Dy La, Gd Lb. Standard samples: ThO2 , UO2 , Pb2 P2 O7 , diopside, synthetic rare-earth phosphates. The intensity measurement time at the peak for Th is 180 s, U is 100 s, and Pb is 500 s (240 s on one and simultaneously 260 s on another spectrometer), for Y and Si 20 s each, for the other elements 10 s; on the background – two times less. The detection limits for Th, U, and Pb in monazite are 290, 350, and 64 ppm, respectively. The oxygen content was determined under the assumption of the stoichiometry of the composition. Results. It has been established that monazite belongs to the cerium variety and is characterized by high contents of thorium (ThO2 up to 23.6 wt. %) and uranium (UO2 up to 2.5 wt. %). At the same time, cheralite-type isomorphism is realized in phosphate. In a closed Th–U–Pb-system (β = 0.92–0.97), according to the results of chemical dating (according to 20 analyses), monazite-(Ce) shows a weighted average age of 243 ± 7 Ma. When plotting the dependence (ThO2 + UO2 eq) – PbO, the points fall on one isochrone. Calculation of the age from the slope of the isochron gave a dating of 242 ± 17 Ma, MSWD = 0.21, probability = 1.00. Conclusion. It has been established that accessory monazite from lithium-bearing granitic pegmatites of the Lipovskoye vein field (Middle Urals) is of Triassic age. Apparently, this dating shows the time of the secondary transformation of lithium-bearing granitic pegmatites, which are often tectonized, and in some places even boudinaged.

Tungstates of the Boyovskoye tungsten deposit (Southern Urals)

The relevance of the work is due to the need for a mineralogical study of tungsten deposits in the Ural region, which have been mined since the end of the 19th century. The purpose of the work is the diagnostics and detailed description of tungstates from the Boyovskoye tungsten deposit located on the border of the Chelyabinsk and Sverdlovsk regions in the Southern Urals. Analytical studies were carried out in the Laboratory of Physical and Chemical Research Methods of the Institute of Geology and Geochemistry, UB RAS, Ekaterinburg. The chemical composition of minerals was analyzed in polished sections on a CAMECA SX 100 microanalyzer. Measurement conditions: accelerating voltage 15 kV, current 150 nA, electron beam diameter 2 μm. The pressure in the sample chamber is 2 ⋅ 10–4 Pa. The spectra were obtained on tilted wave spectrometers; the intensity was measured from analytical lines. Standard samples: scheelite, wolframite, galena, rutile and chromite. Raman spectra of minerals were obtained using a LabRam HR Evolution spectrometer (Horiba Scientific). A red laser, 532 nm, was used for analysis. As a result of the work, new data on the chemical composition of hubnerite and scheelite were obtained and their Raman spectra were presented. For the first time for the Boyovskoye tungsten deposit, a reliable diagnosis and description of lead tungstate – stolzite was made. The mineral was found in samples with veined quartz in association with muscovite, fluorite, hubnerite and scheelite. It fills cracks and voids in hubnerite, rarely overgrows scheelite or fills cracks in scheelite. It is a later mineral in relation to hubnerite and scheelite. Its chemical composition contains impurities of manganese, calcium, iron and titanium. The stolzite found by us is a mineral of the oxidation zone and, most likely, was formed due to the weathering of wolframite and galena, which is also present in quartz veins.

Investigation of the Acceleration and Deceleration Performance of the New Geometrical Shapes of the Three Electrode

Electrostatic lenses are established using billed electrodes with cylinder bores which are exactly organized on a line of symmetry. In this paper, four designs of three-element cylindrical electrostatic lenses in the acceleration and deceleration mode with different geometrical shapes were created to prove how the operational characteristics of the lenses are affected by the electrode geometry according to potentials, the electron beam diameter in the image plane, kinetic energy, velocity, and acceleration before and after the electron beam passes through each of the four lenses. The best lens is chosen from the four lenses based on its optical performance. It has been found that the lens with the concave outer electrode surface has the best optical performance as an accelerating lens, and the lens with the concave inner electrode surface has the best optical performance as a decelerating lens. It was discovered that the geometry of the electrodes plays a major role in minimizing the beam electron diameter at the image plane and in accelerating and decelerating the electron beam. The calculations are carried out by using the SIMION8.0 and SL Tools Programs package.

Geochronology of plagioclasite veins from the Lipovskoye pegmatite field (Middle Urals)

The relevance of the research is due to the need to improve the method of chemical dating as applied to high-thorium and high-uranium accessory minerals, which are difficult to date by isotopic research methods. The purpose of the research is to study the chemical composition of monazite and uraninite from plagioclasite veins of the Lipovskoye pegmatite field and to determine their age. Research Methodology: quantitative analysis of the chemical composition of monazite and uraninite was performed on an X-ray spectral electron probe microanalyzer CAMECA SX 100. Measurement conditions: accelerating voltage 15 kV, current strength 250 nА, electron beam diameter 2 µm. Sample chamber pressure 2 ∙ 10–4 Pa. The spectra were obtained on tilted wave spectrometers, the intensity was measured using analytical lines: Th Ma, U Mb, Pb Ma, Y La, Si Ka, Ca Ka, P Ka, Ce La, La La, Pr Lb, Nd La, Sm Lb, Dy La, Gd Lb. Age calculation was carried out according to well-known methods of foreign authors in addition to their own developments. Results. According to the chemical composition, monazite belongs to the cerium variety and is characterized by high contents of ThO2 up to 13,4 wt. %, UO2 up tо 0,8 wt. % and PbO up to 0,18 wt. %. According to chemical dating, monazite-(Ce) gives an age of 266 ± 17 Ma. In undeformed plagioclasites, uraninite contains impurities of ThO2 up to 11,6 wt. % and PbO up to 3,0 wt. %, its calculated age is 258 ± 3 Ma. In tectonized plagioclasites, uraninite is characterized by impurities of ThO2 from 26 up to 45 wt. % and PbO up to 2,4 wt. %. According to chemical dating data, two ages are calculated in these uraninites: 255 ± 10 Ma in the central part of the grains, and 244 ± 4 Ma in the marginal parts of the grains. Conclusions. Microprobe data on the composition of these minerals have been obtained, and the complex geochronology of these rocks has been established by chemical dating. These plagioclasite bodies were formed after the Middle Permian quartz-potassium feldspar (topaz-beryl) granitic pegmatites, widely developed within the Lipovskoye field, and later underwent superimposed changes twice in the Upper Permian and Triassic times.

The Effect of Operation Modes on the Electron Beam Diameter in Condenser Magnetic Lenses System

The effect of operation modes of condensing magnetic lenses has been investigated to determining the total demagnification and the diameter of the electron beam coming out of it. The cross-over point inside the electron gun is considered as the object (do) with a diameters ranges of (10 – 100 µm) to find out the optical efficiency of the double lens condensing system and its ability to forming a high précising image of the 1st real image formed inside electron gun of thermal emission that acts as an actual source of electron beam. The following modes; (weak- weak), (weak- strong), (strong- strong), and (strong- weak); denoted as (#1, #2, #3, #4 respectively); have been studied. The best value for the total demagnification and the diameter of the electron beam has been obtained in the mode of (strong- strong; #3); where the parameters were: (dMt = 1014.199), (d2 = 49.3 nm), while the worst value has been achieved in the mode (weak- weak; #1) (dMt = 31.56267), (d2 = 1584.15 nm). It is found that by increasing the demagnification of the first condenser lens, the demagnification of the final real image produced by the double lens system has been positively affected. It is found that the relationships that obtained between the demagnification and the current density can be used as a calibration curve to obtain the required total demagnification for the electronic beam diameter for any mode according to the purpose of the desired application.

Impact of the Power-Dependent Beam Diameter during Electron Beam Additive Manufacturing: A Case Study with γ-TiAl

The development of process parameters for electron beam powder bed fusion (PBF-EB) is usually made with simple geometries and uniform scan lengths. The transfer to complex parts with various scan lengths can be achieved by adapting beam parameters such as beam power and scan speed. Under ideal conditions, this adaption results in a constant energy input into the powder bed despite of the local scan length. However, numerous PBF-EB machines show deviations from the ideal situation because the beam diameter is subject to significant changes if the beam power is changed. This study aims to demonstrate typical scaling issues when applying process parameters to scan lengths up to 45 mm using a fourth generation γ-TiAl alloy. Line energy, area energy, return time, and lateral velocity are kept constant during the additive manufacturing process by adjusting beam power and beam velocity to various scan lengths. Samples produced in this way are examined by light microscopy regarding lateral melt pool extension, melt pool depth, porosity, and microstructure. The process-induced aluminum evaporation is measured by electron probe microanalysis. The experiments reveal undesired changes in melt pool geometry, gas porosity, and aluminum evaporation by increasing the beam power. In detail, beam widening is identified as the reason for the change in melt pool dimensions and microstructure. This finding is supported by numerical calculations from a semi-analytic heat conduction model. This study demonstrates that in-depth knowledge of the electron beam diameter is required to thoroughly control the PBF-EB process, especially when scaling process parameters from simply shaped geometries to complex parts with various scan lengths.

Effect of Gradient Doping on Charge Collection Efficiency of EBCMOS Devices

We investigated the effect of different gradient doping methods on the charge collection efficiency of the electron multiplication layer of EBCMOS devices. Exponential doping of the electron multiplication layer can form a built-in electric field in the electron multiplication layer that is favorable for photoelectron transport, so exponential doping instead of uniform doping in the electron multiplication layer of EBCMOS can effectively improve the charge collection efficiency. It is shown that exponential heavy doping on the side of the electron multiplication layer near the dead layer and exponential light doping on the side near the depletion region can improve the built-in electric field structure and increase the lifetime of the multiplied electrons, thereby improving the charge collection efficiency of EBCMOS. The optimized device achieves a charge collection efficiency of 94.48% at an incident electron energy of 4 keV, an electron beam diameter of 20 nm, a dead layer thickness of 60 nm, and a P-type silicon epitaxial layer thickness of 10 μm.

The Relationship Between the Emitter Position and the Wehnelt Cylinder Aperture Radius of the Thermionic Electron Gun

This paper includesfinding a mathematical relationship between the distance from the emitter to the width of the Wehnelt cylinder bore and the diameter of that bore, by studying the effect and correlation of these two parameterson the quality of the electron beam. A group of electron guns with identical and variable geometric parameters were designed for the values ​​of the Wehnelt cylinder aperture radius for each case from the emitter site, which represents the distance from the emitter head to the Wehnelt cylinder aperture. As well as the calculation of the electron beam diameter and the brightness and emittance, as the mathematical relationship between these two parameters was found to be linear.

Methods and algorithm for calculating the focal parameters of a hollow conical electron beam in high-voltage glow discharge electron guns with a focusing magnetic lens

The algorithm is considered for calculating the focal distance of a hollow conical electron beam generated by high-voltage glow discharge electron guns with magnetic focusing of the beam in the drift region, as well as a method for calculating the diameter of the focal ring and its thickness for such a beam. The proposed algorithm is based on the theory of electron drift in the field of a focusing magnetic lens and is designed using the methods of discrete mathematics and the minimax analysis. The obtained simulation results made it possible to establish the influence of the magnetic lens current on the focal diameter of a hollow conical electron beam and on its focal ring thickness. It is shown that the change in the focal parameters of a hollow conical electron beam can be effectively provided through the regulation of the magnetic lens current.

Field emission property of multi-cathode electron sources with vertically aligned CNT arrays

Carbon nanotube (CNT)-based cold cathode has been used as an efficient electron emitter owing to its high electrical conductivity and unique structural feature of high aspect ratio. However, conventional CNT-based cold cathode with diode electrode configuration restricts the applicable range of the CNT cold cathode. Here, we present the systematic investigation of electron beam property and I–V characteristic of various CNT-based multi-emitter system for advanced electron emitting devices capable of large areal applications. Single emitter island, consisting of well-defined N × N CNT strands, shows high maximum current value, low turn-on voltage and large electron beam diameter with increase of N value. For the multi-emitter system consisting multi-islands, a critical pitch size of multi-emitter system is found to obtain separated electron beam for each island without significant interference between electrons departing from each island.

Analytical and numerical methods for calculation the deep of penetration the welding seam formed by the electron beam generated by glow discarge electron guns

The article is devoted to the problem of defining the focal diameter of electron beam, formed by the glow discharge electron guns, as well as the necessary pressure in the gun chamber for realising the welding process. Taking into account, that glow discharge electron guns are widely used in industry for welding of different metals, and that for providing the high quality of welding joints estimation of energetic parameters in beam focus is very important, proposed methods are very important for effective elaboration and designing of the novel glow discharge electron guns constructions for specific technological operations. With known focal beam deameter and thermodinamic parameters of welding details material the deep of penetration of welding seam, as well as the necessary pressure in discharge chamber have been estimatied. Two proposed methods are generally based on the analytical solving of explite equation and on numeracal solving of sophisticated non-linear equation. Obtained simulation results with and without taking into account the spsace charge of own beam electrons are also given

Non-thermal liquid-to-solid Si conversion induced by electron beam irradiation

A liquid precursor for the semiconductor, Si, called liquid Si (liq-Si), was synthesized. Although liq-Si is converted to semiconducting Si by heating at 400 °C, herein, we demonstrate liquid-to-solid Si conversion without heating using liquid-phase electron beam-induced deposition. This technique realizes the direct deposition of semiconducting Si by irradiating liq-Si with an electron beam. Specifically, at electron beam (diameter, ∼50 nm) irradiation, a Si deposit with a diameter of approximately 240 nm was obtained. It is expected that the application of this developed method will enable the production of high-resolution Si nanostructures and grant access to previously inaccessible devices.

ТЕОРЕТИЧНЕ ОЦІНЮВАННЯ РОБОЧОГО ТИСКУ ГАРМАТ ВИСОКОВОЛЬТНОГО ТЛІЮЧОГО РОЗРЯДУ ДЛЯВИКОРИСТАННЯ В ЕЛЕКТРОННО-ПРОМЕНЕВІЙ ТЕХНОЛОГІЇ ЗВАРЮВАННЯ МЕТАЛЕВИХ ВИРОБІВ

У статті проведений порівняльний аналіз методів аналітичного та чисельного розрахунку глибини зварювального шва металевих виробів за умови здійснення зварювання у низькому вакуумі електронним пучком, який формується гарматою високовольтного тліючого розряду. Показано, що хоча аналітичний метод розрахунку є простим та зручним, але, у разі його використання, розрахункові залежності правильно відображають динаміку зміни глибини шва лише у разі малих тисків та високої прискорювальної напруги. У даному випадку проблема забезпечення точності та адекватності аналітичних розрахунків за простими співвідношеннями насамперед пов’язана з тим, що не враховується залежність діаметра електронного пучка в фокусі від його струму. Запропонований чисельний метод розрахунку дозволяє оцінювати глибину шва в значно більш широкому діапазоні робочих тисків електронної гармати. Для розрахунку глибини зварювального шва були використані відомі прості аналітичні залежності, які дозволяють обчислити глибину проплавлення металу залежно від його термодинамічних властивостей, а також геометричних та енергетичних параметрів електронного пучка. Як параметри пучка розглядалися прискорювальна напруга, струм пучка та його фокальний діаметр. Для проведення аналітичних та чисельних оцінок були окремо враховані існуючи аналітичні залежності фокального діаметру електронного пучка від його струму, а також залежність струму електронної гармати високовольтного тліючого розряду від тиску у розрядній камері. Чисельні розрахунки проводились через аналіз функціональної залежності, в яку входили глибина зварювального шва та тиск газу у розрядній камері гармати як явні параметри, та через пошук нульового значення цієї функції шляхом розв’язування відповідного нелінійного рівняння. Аналіз поведінки функції у заданому інтервалі значень тиску та глибини зварювального шва показав, що така постановка задачі є цілком коректною з математичної точки зору. У статті наведені результати тестових аналітичних та чисельних розрахунків залежності глибини зварювального шва від тиску гелію в розрядній камері гармати, отримані для виробів із титану, та проведений аналіз отриманих розрахункових результатів.

Chemical composition and age of monazite-(Ce) in granitoids of the crystalline basement from the South Yamal

The relevance of the work is due to the need to improve the method of chemical dating as applied to high-thorium accessory minerals, which are difficult to date by isotope research methods. Purpose of the work: study of the chemical composition of accessory monazite from granitoids of the crystalline basement of the South Yamal and determination of its age. Research methodology: quantitative analysis of the chemical composition of monazite was carried out using X-ray spectral electron probe microanalyzer CAMECA SX 100 (electron beam diameter from 1 μm, BSE, SE, Cat modes, determination of elements from beryllium to uranium). The spectra were obtained with the help of inclined wave spectrometers, the intensity was measured using analytical lines: Th Ma, U Mb, Pb Ma, Y La, Si Ka, Ca Ka, P Ka, Ce La, La La, Pr Lb, Nd La, Sm Lb, Dy La, Gd Lb. The age calculation was carried out according to the well-known methods of foreign authors in addition to some developments of the author. Results. The chemical composition of monazite makes it possible to classify it as a cerium variety, the content of radiogenic components varies greatly (in wt.%): ThO2 – 5.37–16.31, UO2 – 0.40–0.81, PbO – 0.08–0,19. There are significant concentrations of SiO2 (up to 3.5 wt.%), Y2 O3 (up to 1.8 wt.%) and CaO (up to 1.2 wt.%). It turns out that monazite implements hattonite (Th4+(U4+)+Si4+ → REE3++P5+) and cheralite (Th4+(U4+)+Ca2+(Sr2+,Ba2+,Pb2+) → 2REE3+) isomorphism types. The decent content of lead and high crystallinity of the substance makes it possible to use this mineral as a geochronometer mineral. Conclusions. New data on the chemical composition of monazite have been obtained, and the late Permian age of granitoids has been determined by microprobe dating. The values of the point U–Th–Pb ages of monazite together give a weighted average age of 256 ± 10 Ma (MSWD = 0.15) and an isochron of 254 ± 19 Ma (MSWD = 0.28), which almost ideally coincides with the results of isotopic U–Pb zircon dating from the same rock, 254 ± 3 Ma.

Electron-beam broadening in electron microscopy by solving the electron transport equation

Scanning transmission electron microscopy (STEM) and scanning electron microscopy (SEM) are prominent techniques for the structural characterization of materials. STEM in particular provides high spatial resolution down to the sub-angstrom range. The spatial resolution in STEM and SEM is ultimately limited by the electron-beam diameter provided by the microscope's electron optical system. However, the resolution is frequently degraded by the interaction between electron and matter leading to beam broadening, which depends on the thickness of the analyzed sample. Numerous models are available to calculate beam broadening. However, most of them neglect the energy loss of the electrons and large-angle scattering. These restrictions severely limit the applicability of the approaches for large sample thicknesses in STEM and SEM. In this work, we address beam broadening in a more general way. We numerically solve the electron transport equation without any simplifications, and take into account energy loss along the electron path. For this purpose, we developed the software package CeTE (Computation of electron Transport Equation). We determine beam broadening, energy deposition, and the interaction volume of the scattered electrons in homogeneous matter. The calculated spatial and angular distributions of electrons are not limited to forward scattering and small sample thicknesses. We focus on low electron energies of 30 keV and below, where beam broadening is particularly pronounced. These electron energies are typical for SEM and STEM in scanning electron microscopes.

Measuring the diameter of electron beam by rotating slit disc

A device for analysing the shape of the electron beam in electron beam welding apparatus has been developed. Experiments has been done with the device. The beam size at different focusing currents and constant beam current has been measured. The performance of the device is shown.

Computer Simulation of the Angular Distribution of Electrons and Bremsstrahlung Photons in Tantalum Converter

The present work is dedicated to study of the possibilities of improving the production method of 11C and 18F medical isotopes using a linear electron accelerator. Experimental studies of 11C and 18F isotopes production by the photonuclear technique were carried out in [1]. Various targets were irradiated by bremsstrahlung photons following by measurements targets’ activities. This experimental research has been carried out in the energy range from 10 to 40 MeV. The current work studies an angular distribution of bremsstrahlung photons in order to estimate the possibilities of producing maximum achievable levels of medical isotopes 18F and 11С activities. The angular distribution of bremsstrahlung photons is an important property of the irradiation stand which contains an assembly of targets. This important property allows designing necessary changes in the target assembly setup used to produce medical isotopes. The research presented in the current work was done as a computer simulation. The computer software package ‘KIPT’ was developed in С++ programming language, using the Geant4 toolkit in order to obtain the angular distribution of bremsstrahlung photons. Experimental setup materials as well as structural elements positions were defined in the DetectorConstruction class of our program. The parameters of an electron beam were defined in the PrimaryGeneratorAction class. The electron beam diameter was defined as 8 mm, energy Ее=36.7 MeV, corresponding to the real experiment carried out at the “Accelerator” Science and Research Establishment of Kharkiv Institute of Physics and Technology [1]. Models of physical processes occurring while the electron beam crosses the target assembly were defined in the PhysicsList class. All classes and modules necessary for the analysis of simulation results were included to our program together with visualization modules. Visualization modules use the OpenGL graphics library and the Qt5 software to represent the relative position of experimental setup parts and to visualize particle trajectories. As a result of this work, the angular distributions were obtained for the beam of electrons and bremsstrahlung photons directly before the target. This result will allow target assembly parameter optimization for optimal production of medical isotopes by the photonuclear technique.

Compact Electron Gun for High-Voltage Electron Cooling Systems

One way to increase the efficiency of electron cooling is to increase the electron density in the beam reference frame. As a rule, with an increase in the energy of the cooled ion beam, they reduce its size; therefore, the electron current density can be increased by reducing the diameter of the electron beam and preserving its total current. This paper describes two versions of an electron gun for high-voltage electron cooling systems with flat and convex cathodes, in each of which the electron gun is capable of producing a beam with a diameter of up to 1 cm and a current about 1 A.