pimiПриборы и методы измеренийDevices and Methods of Measurements2220-95062414-0473BNTU10.21122/2220-9506-2020-11-1-42-52pimi-638Research ArticleМетоды измерений, контроля, диагностикиMethods of measurements, monitoring, diagnosticsРасчёт эмиттанса пучка отрицательных ионовNegative Ion Beam Emittance CalculationsТурекМ.TurekM.

Адрес для переписки:  Marcin Turek – Institute of Physics,Maria Curie-Sklodowska University in Lublin, pl. M.Curie-Sklodowskiej 1, 20-031 Lublin, Poland.    e-mail: mturek@kft.umcs.lublin.pl

Address for correspondence: Marcin Turek – Institute of Physics,Maria Curie-Sklodowska University in Lublin, pl. M.Curie-Sklodowskiej 1, 20-031 Lublin, Poland.    e-mail: mturek@kft.umcs.lublin.pl

mturek@kft.umcs.lublin.plВенгерекП.WęgierekP.

ул. Надбыстрицкая 38A, г. Люблин 20-618,

Nadbystrzycka str., 38A, Lublin 20-618, Poland

Университет имени Марии Кюри-Склодовской в ЛюблинеПольшаMaria Curie-Sklodowska University in LublinPolandЛюблинский технический университетПольшаLublin University of TechnologyPoland2020170320201114252Copyright © Турек М., Венгерек П., 20202020Турек М., Венгерек П.Turek M., Węgierek P.Данная работа распространяется под лицензией Creative Commons Attribution 4.0.This work is licensed under a Creative Commons Attribution 4.0 License.https://pimi.bntu.by/jour/article/view/638

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.

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.

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The authors declare that there are no conflicts of interest present.