Low transverse emittance electron bunches from two-color laser-ionization injection

A method is proposed to generate low emittance electron bunches from two color laser pulses in a laser-plasma accelerator. A two-region gas structure is used, containing a short region of a high-Z gas (e.g., krypton) for ionization injection, followed by a longer region of a low-Z gas for post-acceleration. A long-laser-wavelength (e.g., 5 micron) pump pulse excites plasma wake without triggering the inner-shell electron ionization of the high-Z gas due to low electric fields. A short-laser-wavelength (e.g., 0.4 micron) injection pulse, located at a trapping phase of the wake, ionizes the inner-shell electrons of the high-Z gas, resulting in ionization-induced trapping. Compared with a single-pulse ionization injection, this scheme offers an order of magnitude smaller residual transverse momentum of the electron bunch, which is a result of the smaller vector potential amplitude of the injection pulse

Swarm of ultra-high intensity attosecond pulses from laser-plasma interaction

We report on the realistic scheme of intense X-rays and γ-radiation generation in a laser interaction with thin foils. It is based on the relativistic mirror concept, i.e., a flying thin plasma slab interacts with a counterpropagating laser pulse, reflecting part of it in the form of an intense ultra-short electromagnetic pulse having an up-shifted frequency. A series of relativistic mirrors is generated in the interaction of the intense laser with a thin foil target as the pulse tears off and accelerates thin electron layers. A counterpropagating pulse is reflected by these flying layers in the form of a swarm of ultra-short pulses resulting in a significant energy gain of the reflected radiation due to the momentum transfer from flying layers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85400/1/jpconf10_244_022029.pd

Studies and research design in medicine

Adequate design is an essential condition for conducting a successful study. This review describes the most common types of research design in medicine. We discuss the differences between different types of observational and interventional studies, their advantages and limitations providing examples for each study design. The concept of bias and its potential sources in different studies are covered. We suggest the most suitable approaches to study design for different research objectives and outline approaches to data presentation. During the last decades, several guidelines for conducting and reporting different types of research were proposed and they are also covered in this manuscript

Generation of GeV protons from 1 PW laser interaction with near critical density targets

The propagation of ultra intense laser pulses through matter is connected with the generation of strong moving magnetic fields in the propagation channel as well as the formation of a thin ion filament along the axis of the channel. Upon exiting the plasma the magnetic field displaces the electrons at the back of the target, generating a quasistatic electric field that accelerates and collimates ions from the filament. Two-dimensional Particle-in-Cell simulations show that a 1 PW laser pulse tightly focused on a near-critical density target is able to accelerate protons up to an energy of 1.3 GeV. Scaling laws and optimal conditions for proton acceleration are established considering the energy depletion of the laser pulse.Comment: 26 pages, 8 figure

ГАЗОХРОМАТОГРАФИЧЕСКОЕ ОПРЕДЕЛЕНИЕ ФТОРИД-ХЛОРИДОВ КРЕМНИЯ SiСlnF4-n (n = 0 ÷ 4), ПОЛУЧЕННЫХ ПО РЕАКЦИИ ТЕТРАФТОРИДА КРЕМНИЯ С ХЛОРИДОМ АЛЮМИНИЯ(III)

It is for the first time that the method of gas chromatography was used for the determination of silicon fluoride-chlorides SiСlnF4-n (n = 0 ÷ 4) which are the initial, intermediate and final substances while producing silicon tetrachloride from silicon tetrachloride and aluminum chloride (III). The analysis of samples taken during this reaction was carried out using the "Tsvet - 800" gas chromatographer. The samples were injected into the instrument using a vacuum dosing system. To separate the components, a chromatographic column made of molybdenum glass with a length of 5 m and an internal diameter of 3 mm was used. It was filled with a Chromatone N-AW-HMDS (grain size 0.250-0.315 mm) with 15% methylsilicon elastoplastic E-301. The registration of silicon fluoride-chlorides was implemented using a thermal conductivity detector. The identification of SiF4 and SiCl4 in the mixture was conducted by comparing the times of holding the chromatographic peaks with the times of holding these individual substances. The times of holding not available for SiClF3, SiCl2F2, SiCl3F in the individual states were determined using the dependence of the logarithm of the corrected holding time on their molecular mass. The concentrations of silicon fluoride-chlorides were determined using the internal normalization method. The data were obtained on the changes in the concentrations of these substances during the synthesis of silicon tetrachloride. The confirmation of the correctness of the analysis results was made using the method of varying the size of the sample.Key words:  silicon fluoride-chlorides, gas chromatography, identification, calibration factor, correctness(Russian) DOI: http://dx.doi.org/10.15826/analitika.2019.23.4.011Т.G. Sorochkina, О.Yu. Chernova, О.Yu. Troshin, А.Yu. Sozin, А.D. Bulanov, А.А. Ermakov  G.G. Devyatykh Institute of Chemistry of High-Purity Substances of the Russian Academy of Sciences, ul. Tropinina 49, Nizhny Novgorod, 603950, Russian FederationВпервые с использованием метода газовой хроматографии проведено определение фторид-хлоридов кремния SiСlnF4-n(n = 0 ÷ 4), являющихся исходными, промежуточными и конечными веществами при получении тетрахлорида кремния из тетрафторида кремния и хлорида алюминия(III). Анализ проб, отобранных в процессе протекания данной реакции, проводили с использованием газового хроматографа «Цвет–800». Их ввод в прибор осуществляли с помощью вакуумируемой системы дозирования. Для разделения компонентов применяли насадочную хроматографическую колонку из молибденового стекла длиной 5 м и внутренним диаметром 3 мм, заполненную хроматоном N-AW-HMDS (размер зерна 0.250-0.315 мм) с 15 % метилсиликонового эластомера Е-301. Регистрацию фторид-хлоридов кремния осуществляли с использованием детектора по теплопроводности. Идентификацию SiF4 и SiCl4 в смеси проводили сравнением времен удерживания хроматографических пиков со временами удерживания соответствующих индивидуальных веществ. Времена удерживания веществ, отсутствующих у нас в индивидуальном состоянии SiClF3, SiCl2F2 и SiCl3F, оценивали с использованием зависимости логарифма исправленного времени удерживания от их молекулярной массы. Определение концентраций фторид-хлоридов кремния выполнено с использованием метода внутренней нормировки. Получены данные по изменению концентраций этих веществ в процессе синтеза тетрахлорида кремния. Подтверждение правильности результатов анализа выполнено с использованием метода варьирования величины пробы.Ключевые слова: фторид-хлориды кремния, газовая хроматография, идентификация, калибровочный коэффициент, правильностьDOI: http://dx.doi.org/10.15826/analitika.2019.23.4.01

Nonlinear relativistic optics in the single cycle, single wavelength regime and kilohertz repetition rate

Pulses of few optical cycles, focused on one wavelength with relativistic intensities can be produced at a kilohertz repetition rate. By properly choosing the plasma and laser parameters, relativistic nonlinear effects, such as channeling and electron and ion acceleration to tens of megaelectronvolts are demonstrated. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87926/2/138_1.pd

Accelerating Protons to Therapeutic Energies with Ultra-Intense Ultra-Clean and Ultra-Short Laser Pulses

Proton acceleration by high-intensity laser pulses from ultra-thin foils for hadron therapy is discussed. With the improvement of the laser intensity contrast ratio to 10-11 achieved on Hercules laser at the University of Michigan, it became possible to attain laser-solid interactions at intensities up to 1022 W/cm2 that allows an efficient regime of laser-driven ion acceleration from submicron foils. Particle-In-Cell (PIC) computer simulations of proton acceleration in the Directed Coulomb explosion regime from ultra-thin double-layer (heavy ions / light ions) foils of different thicknesses were performed under the anticipated experimental conditions for Hercules laser with pulse energies from 3 to 15 J, pulse duration of 30 fs at full width half maximum (FWHM), focused to a spot size of 0.8 microns (FWHM). In this regime heavy ions expand predominantly in the direction of laser pulse propagation enhancing the longitudinal charge separation electric field that accelerates light ions. The dependence of the maximum proton energy on the foil thickness has been found and the laser pulse characteristics have been matched with the thickness of the target to ensure the most efficient acceleration. Moreover the proton spectrum demonstrates a peaked structure at high energies, which is required for radiation therapy. 2D PIC simulations show that a 150-500 TW laser pulse is able to accelerate protons up to 100-220 MeV energies.Comment: 26 pages, 6 figure

ПРИМЕНЕНИЕ ВНУТРЕННЕГО СТАНДАРТА ПРИ ИЗОТОПНОМ АНАЛИЗЕ ВЫСОКООБОГАЩЕННОГО “КРЕМНИЯ-28” МЕТОДОМ МАСС-СПЕКТРОМЕТРИИ ВЫСОКОГО РАЗРЕШЕНИЯ С ИНДУКТИВНО СВЯЗАННОЙ ПЛАЗМОЙ

 In order to study the isotopic effects in semiconductor materials, single crystals of high chemical and isotopic purity are required. The reliability of the obtained data on the magnitude and the direction of isotopic shifts depends on the accuracy of determining the concentration of all stable isotopes. In the isotopic analysis of enriched “silicon-28” with a high degree of enrichment ( 99.99%), it is necessary to determine the impurities of 29Si and 30Si isotopes at the level of 10-3 ¸ 10-5 at. %. At this concentration level, these isotopes can be considered as impurities. It is difficult to achieve high measurement accuracy with simultaneous registration of the main and “impurity” isotopes in such a wide range of concentrations. The registration of analytical signals of silicon isotopes must be carried out in the solutions with different matrix concentrations. The use of the solutions with the high concentration of the matrix element requires the introduction of corrections for matrix noise and the drift of the instrument sensitivity during the measurement. It is possible to reduce the influence of the irreversible non-spectral interference and sensitivity drift by using the method of internal standardization. The inconsistency of the literature data on the selection criteria for the internal standard required studying the behavior of the signals of the “candidates for the internal standard” for the ELEMENT 2 single-collector high-resolution inductively coupled plasma mass spectrometer on the matrix element concentration and the nature of the solvent, as well as on the solution nebulizing time. Accounting for the irreversible non-spectral matrix noise and instrumental drift in isotopic analysis of enriched “silicon-28” and initial 28SiF4 by inductively coupled plasma mass spectrometry had allowed us to reduce by 3-5 times the random component and by more than an order of magnitude the systematic component of the measurement error in comparison with the external standard method. This made it possible to carry out, with sufficient accuracy, the operational control of the isotopic composition of enriched “silicon-28”, both in the form of silicon tetrafluoride and polycrystalline silicon obtained from it, using a single serial device in the range of isotopic concentrations 0.0001–99.999%.Key words: high-resolution inductively coupled plasma mass spectrometry, isotope analysis, isotopically enriched silicon, internal standard DOI: http://dx.doi.org/10.15826/analitika.2021.25.2.009P.A. Otopkova, A.M. Potapov, A.I. Suchkov, A.D. Bulanov, A.Yu. Lashkov G.G. Devyatykh Institute of Chemistry of High-Purity Substances of the Russian Academy of Sciences (IChHPS RAS), 49 Tropinina St., Nizhny Novgorod, 603951, Russian FederationДля изучения изотопических эффектов в полупроводниковых материалах требуются монокристаллы с высокой химической и изотопной чистотой. Надежность полученных данных о величине и направлении изотопических сдвигов зависит от точности определения концентрации всех стабильных изотопов. При изотопном анализе обогащенного “кремния-28” с высокой степенью обогащения (более 99.99 %) необходимо определять примеси изотопов 29Si и 30Si на уровне 10-3 ¸ 10-5 ат. %. На таком уровне концентраций указанные изотопы можно рассматривать как примеси. Достижение высокой точности измерений при одновременной регистрации основного и “примесных” изотопов в таком широком интервале концентраций затруднительно. Регистрацию аналитических сигналов изотопов кремния приходится проводить на растворах с разной концентрацией матрицы. Использование растворов с высокой концентрацией матричного элемента требует введения поправок на матричные помехи и дрейф чувствительности прибора в процессе измерения. Снизить влияние необратимых неспектральных помех и дрейфа чувствительности можно при использовании метода внутренней стандартизации. Противоречивость литературных данных о критериях выбора внутреннего стандарта потребовала исследования поведения сигналов элементов “кандидатов во внутренний стандарт“ для одноколлекторного масс-спектрометра высокого разрешения с индуктивно связанной плазмой ELEMENT 2 от концентрации матричного элемента и природы растворителя, а также от времени распыления раствора. Учет необратимых неспектральных матричных помех и аппаратного дрейфа при изотопном анализе обогащенного “кремния-28” и исходного 28SiF4 методом масс-спектрометрии с индуктивно связанной плазмой позволил снизить в 3-5 раз случайную составляющую и более чем на порядок систематическую составляющую погрешности измерения по сравнению с методом внешнего стандарта. Это позволило проводить с достаточной точностью оперативный контроль изотопного состава обогащенного “кремния-28”, как в виде тетрафторида кремния, так и получаемого из него поликристаллического кремния с помощью одного серийного прибора в интервале изотопных концентраций 0.0001–99.999 ат. %.Ключевые слова: масс-спектрометрия высокого разрешения с индуктивно связанной плазмой, изотопный анализ, изотопнообогащенный кремний, внутренний стандартDOI: http://dx.doi.org/10.15826/analitika.2021.25.2.00