Formation of MeV energy ion beams with high current density for materials micro-irradiation

A numerical analysis has been performed for the optimum configuration of a probe-forming system based on magnetic quadrupole lens multiplets in a nuclear scanning microprobe intended for irradiations of micron-size areas. The current densities expressed via the reduced collimated acceptance were cal...

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Hauptverfasser: Romanenko, A.V., Ponomarev, A.G., Miroshnichenko, V.I.
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spelling Romanenko, A.V.
Ponomarev, A.G.
Miroshnichenko, V.I.
2017-01-15T14:47:28Z
2017-01-15T14:47:28Z
2013
Formation of MeV energy ion beams with high current density for materials micro-irradiation / A.V. Romanenko, A.G. Ponomarev, V.I. Miroshnichenko // Вопросы атомной науки и техники. — 2013. — № 4. — С. 30-33. — Бібліогр.: 15 назв. — англ.
1562-6016
PACS: 29.17.-q
https://nasplib.isofts.kiev.ua/handle/123456789/111902
A numerical analysis has been performed for the optimum configuration of a probe-forming system based on magnetic quadrupole lens multiplets in a nuclear scanning microprobe intended for irradiations of micron-size areas. The current densities expressed via the reduced collimated acceptance were calculated as function of the spot dimensions for working distances ranging from 4 to 24 cm. Consideration is being given to the advantages of the doublet of magnetic quadrupole lenses as a probe-forming system.
Проведено теоретичний чисельний аналіз оптимальної конфігурації зондоформуючої системи на базі мультиплетів магнітних квадрупольних лінз у ядерному скануючому мікрозонді для задач опромінення мікроскопічних областей матеріалів. Знайденo залежності густини струму, вираженні через приведений колімований аксептанс, від розмірів плями на мішені для робочих відстаней у діапазоні 4…24 см. Показано перевагу використання в якості зондоформуючої системи дублету магнітних квадрупольних лінз.
Проведен теоретический численный анализ оптимальной конфигурации зондоформирующей системы на базе мультиплетов магнитных квадрупольных линз в ядерном сканирующем микрозонде для задач облучения микроскопических областей материалов. Найдены зависимости плотности тока, выраженные через приведенный коллимированный аксептанс, от размеров пятна на мишени для рабочих расстояний в диапазоне 4…24 см. Показано преимущество использования в качестве зондоформирующей системы дублета магнитных квадрупольных линз.
en
Національний науковий центр «Харківський фізико-технічний інститут» НАН України
Вопросы атомной науки и техники
Нерелятивистская электроника
Formation of MeV energy ion beams with high current density for materials micro-irradiation
Формування йонних пучків МеВ-них енергій з високою густиною струму для мікроопромінення матеріалів
Формирование ионных пучков ФэВ-ных энергий с высокой плотностью тока для микрооблучения материалов
Article
published earlier
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
title Formation of MeV energy ion beams with high current density for materials micro-irradiation
spellingShingle Formation of MeV energy ion beams with high current density for materials micro-irradiation
Romanenko, A.V.
Ponomarev, A.G.
Miroshnichenko, V.I.
Нерелятивистская электроника
title_short Formation of MeV energy ion beams with high current density for materials micro-irradiation
title_full Formation of MeV energy ion beams with high current density for materials micro-irradiation
title_fullStr Formation of MeV energy ion beams with high current density for materials micro-irradiation
title_full_unstemmed Formation of MeV energy ion beams with high current density for materials micro-irradiation
title_sort formation of mev energy ion beams with high current density for materials micro-irradiation
author Romanenko, A.V.
Ponomarev, A.G.
Miroshnichenko, V.I.
author_facet Romanenko, A.V.
Ponomarev, A.G.
Miroshnichenko, V.I.
topic Нерелятивистская электроника
topic_facet Нерелятивистская электроника
publishDate 2013
language English
container_title Вопросы атомной науки и техники
publisher Національний науковий центр «Харківський фізико-технічний інститут» НАН України
format Article
title_alt Формування йонних пучків МеВ-них енергій з високою густиною струму для мікроопромінення матеріалів
Формирование ионных пучков ФэВ-ных энергий с высокой плотностью тока для микрооблучения материалов
description A numerical analysis has been performed for the optimum configuration of a probe-forming system based on magnetic quadrupole lens multiplets in a nuclear scanning microprobe intended for irradiations of micron-size areas. The current densities expressed via the reduced collimated acceptance were calculated as function of the spot dimensions for working distances ranging from 4 to 24 cm. Consideration is being given to the advantages of the doublet of magnetic quadrupole lenses as a probe-forming system. Проведено теоретичний чисельний аналіз оптимальної конфігурації зондоформуючої системи на базі мультиплетів магнітних квадрупольних лінз у ядерному скануючому мікрозонді для задач опромінення мікроскопічних областей матеріалів. Знайденo залежності густини струму, вираженні через приведений колімований аксептанс, від розмірів плями на мішені для робочих відстаней у діапазоні 4…24 см. Показано перевагу використання в якості зондоформуючої системи дублету магнітних квадрупольних лінз. Проведен теоретический численный анализ оптимальной конфигурации зондоформирующей системы на базе мультиплетов магнитных квадрупольных линз в ядерном сканирующем микрозонде для задач облучения микроскопических областей материалов. Найдены зависимости плотности тока, выраженные через приведенный коллимированный аксептанс, от размеров пятна на мишени для рабочих расстояний в диапазоне 4…24 см. Показано преимущество использования в качестве зондоформирующей системы дублета магнитных квадрупольных линз.
issn 1562-6016
url https://nasplib.isofts.kiev.ua/handle/123456789/111902
citation_txt Formation of MeV energy ion beams with high current density for materials micro-irradiation / A.V. Romanenko, A.G. Ponomarev, V.I. Miroshnichenko // Вопросы атомной науки и техники. — 2013. — № 4. — С. 30-33. — Бібліогр.: 15 назв. — англ.
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fulltext ISSN 1562-6016. ВАНТ. 2013. №4(86) 30 FORMATION OF MeV ENERGY ION BEAMS WITH HIGH CURRENT DENSITY FOR MATERIALS MICRO-IRRADIATION A.V. Romanenko, A.G. Ponomarev, V.I. Miroshnichenko Institute of Applied Physics, National Academy of Sciences of Ukraine, Sumy, Ukraine E-mail: romanenko@ipflab.sumy.ua A numerical analysis has been performed for the optimum configuration of a probe-forming system based on magnetic quadrupole lens multiplets in a nuclear scanning microprobe intended for irradiations of micron-size areas. The current densities expressed via the reduced collimated acceptance were calculated as function of the spot di- mensions for working distances ranging from 4 to 24 cm. Consideration is being given to the advantages of the dou- blet of magnetic quadrupole lenses as a probe-forming system. PACS: 29.17.-q INTRODUCTION Ion microprobes for MeV-energies find wide appli- cation not only in the investigations into material prop- erties, but also in ion-beam material modification. The use of focused proton beams in ion-beam lithography makes it possible to create 3D micro- and nanostruc- tures [1, 2, 3]. Micro-irradiations with ions can be help- ful in making masks [3], studying modified optical properties of quartz glasses [4, 5], and examining the effects of ionizing radiation on a material [6]. The prob- lem of current concern is the application of micro- irradiations to the determination of the radiation resis- tance of materials. Microprobe techniques combined with a possibility of high ion dose irradiation permit experiments to be performed in-situ. As a result, the impurity migration at the grain boundaries can be de- termined in the course of irradiation. A deterring factor here is that it is not reasonable to build up high radiation doses by means of simple collimated microbeams since in this case the current density at the target is rather small (10-2 A/m2) [7]. To increase it to desired values, in ion microprobes use is made of active focusing elements based on multiplets of magnetic quadrupole lenses (MQL) permitting an ion beam to be focused into a spot of micron size with the current density at the target of about 102 A/m2. However, it is to be noted that in doing so one is faced with a problem of keeping the spot size unchanged as the beam energy is varied [8]. As was shown in Ref. [9], with the increasing probe spot size in a submicron interval the current density increases. This property is typical of probe-forming systems (PFS) with a number of lenses from 3 to 6. Yet, so far this depend- ence has not been thoroughly investigated, so the aim of the present paper is to consider different PFS versions used to obtain the maximum current density. 1. METHODS OF ANALYSIS OF ION-OPTIC PROPERTIES A system of steady trajectory motion equations de- scribing the evolution of the phase set of beam particles in the active elements under the influence of electric and magnetic fields can be written in the general vector form as follows ),,,,,( 0 δψEBFψ qp ds d = , ψ(s0)= ψ0 , (1) where ψ(s)=(x(s), y(s), x´(s), y´(s),δ(s))T are the steady phase coordinates of the beam particles, p0=p0(s) and q are the average momentum and charge of a beam parti- cle, respectively, В=В(x,y,s) and E=E(x,y,s) are the vec- tor distributions of the magnetic and electric field, re- spectively, in the beam transport region, and δ = δ(s) = (p-p0)/p0 is the relative momentum deviation of each particle, р=p(s), from its average value, p0. In the general case, Eqs. (1) are nonlinear fundamen- tal equations in the optics of charged particle beams. Methods of solving these equations are presented in many papers, the best known being the method of ma- trizants [10 - 12] based on the representation of an infi- nite-dimensional space of phase momenta, in which a system of nonlinear differential equations (1) in a five- dimensional steady phase space can be approximated by a system of linear differential equations. The space of phase momenta is determined by a set of linear- independent power functions xi(s)yj(s)x´k(s)y´l(s)δm(s). A solution for the nonlinear differential problem (1) is sought for as a nonlinear dependence of the ion coor- dinates in the target plane (zt) on initial phase coordi- nates in the object collimator plane (z0) 14 1 14 , 1 ( ) ( ) ( , ) , ( ) ( ) ( , ) t x t xj t xj j t x t yj t yj j x z F z A z Q y z F z A z Q = = = = ⋅ = = ⋅ ∑ ∑ τ τ (2) where 3 2 2 3 2 1...14 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 0 0 0 0 0 0 0 0 0 0 0 0 { }| { , , , , , , , , , , , , , }, xj jQ x x x x x x x x x x x y x y y x y x y x y y x y δ δ= ′ ′ ′ ′ ′= ′ ′ ′ ′ ′ ′ ′ 3 2 2 3 2 1...14 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 0 0 0 0 0 0 0 0 0 0 0 0 { }| { , , , , , , , , , , , , , }, yj jQ y y y y y y y y y y y x y x x y x y x y x x y x δ δ= ′ ′ ′ ′ ′= ′ ′ ′ ′ ′ ′ ′ yyxx DADA == 11 , are the PFS demagnification coef- ficients, yyxx fAfA == 22 , are the astigmatism coefficients, 3 ,2 ,, =jAA yjxj are the chromatic aberration coeffi- cients, 14,...,4 ,, =jAA yjxj are the third-order geometric aber- ration coefficients, },,...,,,...,{ 11 gaaGG NN=τ is the vector of parame- ters which influence the beam formation in the quadru- pole PFS, Gi and ai are the magnetic field gradient and the geometric position of the i th magnetic quadrupole lens in the PFS, respectively, g is the PFS working dis- tance. ISSN 1562-6016. ВАНТ. 2013. №4(86) 31 The PFS quality criterion follows from actual ex- perimental requirements. The number of interactions between the beam particles and the target atoms is di- rectly related to the number of particles reaching the target spot per unit time. Thus, a physically sensible criterion of the PFS quality is the value of current I at the target spot of given dimensions [13]. However, in calculations use is mostly made of the acceptance den- sity rather than of the current density. Since the current I ≈ bεT, where b, ε, T are the nor- malized brightness, emittance, and energy of the beam particles, respectively, and the maximum emittance pro- vided by the PFS is, by definition, the PFS acceptance, εmax= A, then, considering that the particle energy is always known a priori, and brightness is a characteristic of the ion source and the accelerating structure, which remains constant while the beam is being focused, we can express the maximum current density at the spot of square shape with a side d via a reduced collimated PFS acceptance as max(J)= A·b/d2. Here the reduced collimated PFS acceptance is de- termined by the maximum phase space produced by the object and angular collimators, which, using the PFS, is transformed in the target plane into a phase space shaped as a square with a side d. The method of calculating the acceptance with the beam focussed into a spot of prescribed size is imple- mented in the MaxBEmit numerical code [13]. The method is formulated for a PFS whose ion-optic pa- rameters are known. The probe spot size d is also pre- scribed. 2. PFS PARAMETERS The present work has been performed with PFS’s based on doublet-, triplet-, and distributed “Russian quadruplet” MQL’s (lenses are arranged in doublets which are spaced 80 cm apart along the axis of the sys- tem) with parameters used in the real nuclear scanning microprobe of the IAP NAS Ukraine [14]. It is assumed that the angular collimator plane is positioned at the entrance to the first MQL (а0 = а1, Fig. 1). Fig. 1. A schematic representation of the PFS with MQL multiplets. a0 – collimator separation; a1-aN – drift gaps; l1-lN – effective lens lengths; g – working distance; L – total system length All PFS’s have the following fixed parameters: total length L = 4 m, effective lens lengths l1= 7.141 cm and l2 = 5.067 cm, lens separation a=3.94 cm, and lens aper- ture radius R = 0.65 cm. The working distance, g was varied from 4 to 24 cm by varying the object distance, a0, (separation between the collimators). The calcula- tions were performed for a 1 MeV proton beam with the maximum energy spread δmax=10-3. The PFS ion-optic properties such as the demagnification coefficients (Ta- ble), aberrations, and magnetic inductions at the lens poles were obtained with the help of a ProbeForm nu- merical code [9]. PFS Demagnification Coefficients Doublet Oxford-type triplet Distributed “Russian quadruplet” g, cm Dx Dy Dx Dy Dx Dy 4 -10 -98 139 -25 178 178 8 -9 -62 81 -21 100 100 12 -8 -44 54 -17 63 63 16 -7 -33 -40 -14 44 44 20 -6 -27 31 -13 32 32 24 -6 -22 25 -11 24 24 3. RESULTS Calculations done for a PFS based on MQL multi- plets are shown in Fig. 2 as the reduced collimated ac- ceptance plotted vs the spot size for varied working dis- tances. As can be seen in Figs. 2,b and c, the density of the reduced acceptance for the triplet-based and the dis- tributed “Russian quadruplet”-based PFS, has pro- nounced peaks whose magnitude depends on the work- ing distance. For the doublet-based PFS (see Fig. 2,a) the maxima of the reduced acceptance density were not found since starting from the spot size of 130 µm, 1 MeV proton beam envelopes extend beyond the beam line dimensions which are closely related to the MQL aperture size at their location (Fig. 3,a). Beam envelopes for the other two PFS’s presented in Figs. 3,b and c, demonstrate that the beam line dimensions are not a critical factor, limiting their maximum reduced accep- tance density. It is also evident in Fig. 2 that the use of the PFS based on the distributed “Russian quadruplet” for irra- diation purposes does not seem reasonable from the viewpoint of the desired rate of dose accumulation since the highest current density in this PFS is only half as large as that of the triplet-based PFS and about one-third that of the doublet-based PFS. A general tendency to be observed for all PFS versions examined is that with a small spot size the most advantageous is a system with a small working distance. If a PFS is examined only in terms of the maximum current density, ignoring the spot size, one would see that the best parameters for the dou- blet-based and the triplet-based PFS are achievable with the working distances in the range from 8 to 12 cm. It is, however, not possible to obtain such parameters for the distributed “Russian quadruplet” because its reduced acceptance density increases steadily with the working distance. The doublet-based PFS characterized by great- er acceptances as compared with other compact multi- plets [15] have turned out to be more suitable for micro- irradiation purposes. ISSN 1562-6016. ВАНТ. 2013. №4(86) 32 0 20 40 60 80 100 120 140 0 50 100 150 200 250 300 350 A /d 2 , m ra d2 Beam size, mkm 1 2 3 4 5 6 a 0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 A /d 2 , m ra d2 Beam size, mkm 1 2 3 4 5 6 b 0 20 40 60 80 100 120 140 10 20 30 40 50 60 70 80 A /d 2 , m ra d2 Beam size, mkm 1 2 3 4 5 6 c Fig. 2. The reduced acceptance density versus the spot size for various working distances in the PFS based on the a) MQL doublet; b) MQL triplet; c) distributed “Russian quadruplet”. The working distances are denoted by numbers: 1 – 4 cm; 2 – 8 cm; 3 – 12 cm; 4 – 16 cm: 5 – 20 cm; 6 – 24 cm CONCLUSIONS PFS versions based on MQL multiplets have been analyzed in terms of the highest attainable current den- sity at the target expressed via the reduced collimated acceptance. A PFS type has been identified which is most advantageous for micro-irradiation applications. The current densities were calculated as function of the working distance and spot size. The highest current den- sity for MQL doublet-based PFS is shown to be limited by the beam line dimensions. The results obtained will be used in further investigations with the nuclear scan- ning microprobe at the Institute of Applied Physics, National Academy of Sciences of Ukraine. 0 1 2 3 4 -2 -1 0 1 2 3 4 5 6 x, y, m m L, m Y X a 0 1 2 3 4 -3 -2 -1 0 1 2 3 x, y, m m L, m Y X b 0 1 2 3 4 -3 -2 -1 0 1 2 3 x, y, m m L,m Y X c Fig. 3. Proton beam envelopes for the PFS based on the a) MQL doublet with a working distance g=12 cm and a spot side d=130 µm; b) MQL triplet with g=24 cm and d=140 µm; c) distributed “Russian quadruplet” with g=24 cm and d=140 µm. Shown diagrammatically are MQL’s with dimensions given to scale and with a sign of the effective lens field polarity. A dashed line represents the beam line boundary REFERENCES 1. M.B.H. Breese, G.W. Grime, F. Watt. MeV ion beam lithography of PMMA // Nucl. Instr.and Meth. In Phys. Res. B. 1993, v. 77, p. 169-174. 2. G.A. Glass, B. Rout, A.D. Dymnikov, et al. High energy focused ion beam lithography using P-beam writing // Nucl. Instr. and Meth. In Phys. Res. B. 2005, v. 241, p. 397-401. 3. V. Auzelyte, M. Elfman, P. Kristiansson. Fabrica- tion of phosphor micro-grids using proton beam li- thography // Nucl. Instr. and Meth. In Phys. Res. B. 2006, v. 242, p. 253-256. ISSN 1562-6016. ВАНТ. 2013. №4(86) 33 4. H. Nishikawa, M. Murai, T. Nakamura, et al. Modi- fication of structural and optical properties of silica glass induced by ion microbeam // Surface and Coatings Technology. 2007, v. 201, p. 8185-8189. 5. M Hattori, Y Ohki, M. Fujimaki. Characterization of refractive index changes of silica glass induced by ion microbeam // Nucl. Instr. and Meth. In Phys. Res. B. 2003, v. 210, p. 272-276. 6. S.P. Dooley, D.N. Jamieson, S. Prawer. He+ and H+ microbeam damage, swelling and annealing in dia- mond // Nucl. Instr. and Meth. In Phys. Res. B. 1993, v. 77, p. 484-491. 7. A.A. Ponomarev, V.I. Miroshnichenko, A.G. Po- nomarev. Influence of the beam current density dis- tribution on the spatial resolution of a nuclear mi- croprobe // Nucl. Instr. and Meth. In Phys. Res. B. 2009, v. 267, p. 2041-2045. 8. A.V. Romanenko, A.G. Ponomarev. The Effect of Hysteresis of Magnetic Quadrupole Lenses on Beam Focusing with varied Beam Energy in a Scanning Nuclear Microprobe // Pis’ma v ZhTF. 2013, v. 39, № 7, p. 1-8 (in Russian). 9. A.G. Ponomarev, K.I. Melnik, V.I. Miroshnichenko. Parametric multiplets of magnetic quadupole lenses: application prospects for probe-forming systems of nuclear microprobe // Nucl. Instr. and Meth. In Phys. Res. B. 2005, v. 231, p .86-93. 10. A.D. Dymnikov, G.M. Osetinsky. 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Program for Optimizing Proton Microprobe Entrance Collimator Dimensions to Produce Beams with Maximum Phase Volume // Proceedings of IId All-Union. Conf. “Ion Beam Mi- croanalysis”: 11-13 Oct. 1988, Kharkov-Sumy, 1991, p. 271-275 (in Russian). Article received 05.04.2013. ФОРМИРОВАНИЕ ИОННЫХ ПУЧКОВ МэВ-НЫХ ЭНЕРГИЙ С ВЫСОКОЙ ПЛОТНОСТЬЮ ТОКА ДЛЯ МИКРООБЛУЧЕНИЯ МАТЕРИАЛОВ А.В. Романенко, А.Г. Пономарев, В.И. Мирошниченко Проведен теоретический численный анализ оптимальной конфигурации зондоформирующей системы на базе мультиплетов магнитных квадрупольных линз в ядерном сканирующем микрозонде для задач облу- чения микроскопических областей материалов. Найдены зависимости плотности тока, выраженные через приведенный коллимированный аксептанс, от размеров пятна на мишени для рабочих расстояний в диапа- зоне 4…24 см. Показано преимущество использования в качестве зондоформирующей системы дублета магнитных квадрупольных линз. ФОРМУВАННЯ ЙОННИХ ПУЧКІВ МеВ-НИХ ЕНЕРГІЙ З ВИСОКОЮ ГУСТИНОЮ СТРУМУ ДЛЯ МІКРООПРОМІНЕННЯ МАТЕРІАЛІВ О.В. Романенко, О.Г. Пономарьов, В.І. Мирошніченко Проведено теоретичний чисельний аналіз оптимальної конфігурації зондоформуючої системи на базі му- льтиплетів магнітних квадрупольних лінз у ядерному скануючому мікрозонді для задач опромінення мікро- скопічних областей матеріалів. Знайденo залежності густини струму, вираженні через приведений колімова- ний аксептанс, від розмірів плями на мішені для робочих відстаней у діапазоні 4…24 см. Показано перевагу використання в якості зондоформуючої системи дублету магнітних квадрупольних лінз.