Расчёт эмиттанса пучка отрицательных ионов

Computer simulations are commonly used to support design and optimisation of powerful negative ion sources for the needs of future thermonuclear reactors like e. g. ITER. The aim of the paper was to study changes of produced beam quality (described by its emittance and brightness) with the geometry of the extraction system as well as extraction voltage.A two-dimensional Particle-in-Cell (PIC) method based code was applied to model Hions and electrons extraction from the ion source plasma chamber through the opening with bevelled surface. The root-meansquare emittance of the extracted beam was calculated according to Chasman and Lapostolle approach. Ion beam phase space portraits were also presented to enrich the discussion.Growth of ion (electron) beam emittance was observed both with the increasing radius of the extraction opening and the inclination of its bevelled surfaces. This degradation of beam quality is partially balanced by increasing extracted Hion current. On the other hand, increasing length of the extraction channel improves the beam quality.It was demonstrated that for wider extraction opening the Hion beam consist of two parts coming form the two different regions of the chamber. According to calculated beam brightness the optimal wall inclination was found to be near 26o in the studied case. The decrease of the beam emittance saturates for larger channel length values. In the considered case the optimal channel length was h = 1.7 mm. The evolution of ion beam emittance and brightness shows that the best beam quality is achieved for extraction voltages between 0.5 kV and 2 kV.Компьютерное моделирование находит широкое применение в разработке и оптимизации мощных источников отрицательных ионов для будущих термоядерных реакторов, в частности, ITER. Целью настоящей работы являлось изучение изменений качества генерируемого пучка (характеризуемого параметрами эмиттанса и яркости) в зависимости от геометрии вытяжной системы и выходного напряжения.Для моделирования извлечения ионов Hи электронов из плазменной камеры источника ионов через канал со скошенной поверхностью использовался двумерный метод частиц в ячейке (PIC). Среднеквадратическое значение эмиттанса извлечённого пучка рассчитывалось на основе подхода Часмана и Лапостолле. Дополнительно приводятся ионно-лучевые фазовые пространственные изображения ионного пучка.Рост эмиттанса ионного (электронного) пучка наблюдался при увеличении как радиуса вытяжного канала, так и наклона его скошенной поверхности. Данное ухудшение качества пучка частично компенсируется увеличением ионным током H-. С другой стороны, увеличение длины вытяжного канала повышает качество пучка.Показано, что в случае большей ширины вытяжного канала пучок ионов Hвключает в себя две составляющих, исходящих из двух различных областей камеры. Из результатов расчёта яркости пучка следует, что оптимальный угол наклона стенки канала для рассматриваемого случая составляет 26o. Уменьшение эмиттанса пучка достигает насыщения при бόльших значениях длины канала. В рассмотренном случае оптимальная длина канала составила h = 1,7 мм. Эволюция эмиттанса и яркости ионного пучка показывает, что наилучшее качество пучка достигается при выходных напряжениях от 0,5 кВ до 2 кВ

Analysis of the Influence of Deposition Conditions on the Structure of the Coating Nb-Al-N

Nanocomposite Nb-Al-N films prepared by magnetron sputtering have been studied. It has been found that, in the films, there are two stable crystalline structural states, namely, NbNz and B1-Nb1 – xAlxNyO1 – y, and an amorphous like component related to aluminum oxynitride upon reactive magnetron sputtering. The substructure characteristics are sensitive to the current supplied to an Al target and related to the Knoop nanohardness and hardness, which change within in the ranges of 29-33.5 and 46-48 GPa, respectively. Ab initio calculations for the NbNz and Nb2AlN phases and NbN / AlN heterostructures have been performed to interpret the obtained results for the first time

Analysis of the Influence of Deposition Conditions on the Structure of the Coating Nb-Al-N

Nanocomposite Nb-Al-N films prepared by magnetron sputtering have been studied. It has been found that, in the films, there are two stable crystalline structural states, namely, NbNz and B1-Nb1 – xAlxNyO1 – y, and an amorphous like component related to aluminum oxynitride upon reactive magnetron sputtering. The substructure characteristics are sensitive to the current supplied to an Al target and related to the Knoop nanohardness and hardness, which change within in the ranges of 29-33.5 and 46-48 GPa, respectively. Ab initio calculations for the NbNz and Nb2AlN phases and NbN / AlN heterostructures have been performed to interpret the obtained results for the first time

Yuri Popov — as we remember him

Dr. Yuri Popov, born 5 March 1936, passed away 16 November 2016. Upon graduation from the Entomology Department of Moscow State University, he joined the Arthropoda Lab of the Paleontological Institute, where he studied fossil and living true bugs and their kin and became a major expert in that area. He was a man of many talents and had lots of friends all over the world. The few flashbacks collected here are but a small tribute to his memory

Influence of Temperature on Electrical Parameters of GaAs in the Aspect of Applications in Photovoltaics

The article describes the results of the research on thermal stability of electrical parameters of n-type gallium arsenide doped with tellurium, defected by ion implantation, measured at the operating temperature ranging from 77 K to 373 K. The aim of the work is to investigate the character of changes in the values of such electrical parameters as resistivity, capacity and loss tangent of the tested GaAs samples, exposed to different thermal conditions. Temperature dependences analyzed in the paper could be taken as a basis to formulate general speculations concerning potential applications of the tested material as a substrate in the process of photovoltaic cells production. The phenomenon of conversion of solar energy into electricity is strongly connected with electrical properties of photovoltaic cell substrate material and its internal structure. Moreover, the efficiency of photoconversion is affected by such factors as charge carrier lifetime distribution and diffusion length in the base material. Therefore, it is necessary to confirm what is the character of the influence of operating temperature on the electrical parameters of GaAs and what modification could be introduced in the material in order to increase the efficiency of photoconversion

Jump Mechanism of Electric Conduction in n-Type Silicon Implanted with Ne++Ne^{++} Neon Ions

The article presents the results of research on alternating-current electrical conduction in phosphorus-doped silicon, strongly defected by the implantation of $Ne^{++}$ neon ions. An analysis of electrical properties recorded at the annealing temperature of $T_{a}$ = 373 K and affected by the changes of testing temperature ranging from 253 K to 368 K as well as frequency from 50 Hz to 5 MHz has been discussed. The obtained results have confirmed the occurrence of two conduction mechanisms in strongly defected semiconductors: the band conduction mechanism that is characteristic of low frequency values and the jump conduction one that corresponds to higher frequencies

Changes in the Activation Energy of Radiation Defects in Strongly Defected Silicon Depending on the Type and Concentration of Dopant

The article presents the outcome of the research on alternating-current electric conduction in silicon doped with boron, phosphorus, and antimony of resistivities ρ=0.01 Ω cm and ρ=10 Ω cm, strongly defected by the implantation of $Ne^{+}$ ions (D=1.5 × $10^{14}$ $cm^{-2}$, E=100 keV). On the basis of results obtained for samples annealed at the temperature $T_{a}$=598 K and measured at the testing temperature $T_{p}$=298 K and frequency f=1 MHz it was possible to carry out an analysis of mechanisms of electric conduction depending on the type and concentration of dopant. Obtained results confirmed the occurrence of hopping conductivity mechanism in strongly defected semiconductors, which is typical for high frequency values

Research on Thermal Stability of Electrical Parameters of Silicon Used in PV Cells Production Process

Considering the results of recent research, it is possible to state that the problem of thermal stability of electrical parameters of silicon is very important in the context of efficiency of commonly used photovoltaic cells. Subsequent investigations confirmed that the efficiency of photovoltaic cells is strongly influenced by active defects of silicon crystal lattice. Those defects, arising in the process of photovoltaic cells base material preparation, are responsible for changes in the values of conductivity and activation energy of the tested material. Taking this into consideration, it is reasonable to carry out research oriented at experimental verification of the influence of both operating temperature on the electrical parameters of silicon and annealing temperature on the distribution of radiation defects in the silicon substrate used in the production of photovoltaic cells. The main purpose of this work is a comparative analysis of dependences of electrical parameters of silicon on temperature. The article presents the results of the research on resistivity and capacity of silicon samples (doped with boron and phosphorus) whose structure was modified by the ion implantation process

Research on Mechanisms of Electric Conduction in the p-Type Silicon Implanted with Ne+Ne^{+} Ions

The article presents the results of research on alternating-current electric conduction in boron-doped silicon (ρ = 10 Ω cm), strongly defected by the implantation of $Ne^{+}$ ions (D = $1.5 \times 10^{14} cm^{-2}$, E = 100 keV). The analysis of changes in electrical characteristics recorded at the sample annealing temperature of $T_{a}$ = 373 K has been presented, concerning the influence of the testing temperature ranging from 253 K to 368 K as well as the frequency from 50 Hz to 5 MHz. The obtained results have confirmed the occurrence of two electric conduction mechanisms in strongly defected semiconductors, such as the band conduction mechanism that is characteristic of low frequency values and the jump conduction one that corresponds to higher frequencies

Application of Ion Implantation for Intermediate Energy Levels Formation in the Silicon-Based Structures Dedicated for Photovoltaic Purposes

The main aim of the research was to verify if it is possible to create the intermediate energy levels in silicon by means of ion implantation as well as to confirm whether the intermediate band could arise. The tests covered recording of conductance and capacitance of antimony-doped silicon, implanted with Ne⁺ ions. As a result, it was possible to identify a single deep level in the sample and determine its location in the band gap by estimating the value of activation energy