Development of NSC KIPT nuclear microprobe
Development of the microanalysis methods is stimulated by investigations of actual materials. Their properties depend not only on an atomic structure, but also on imperfections of this structure, phase composition, areas of impurity accumulation, various kinds of microinclusions etc. Characteristic...
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 1999 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
1999
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| Цитувати: | Development of NSC KIPT nuclear microprobe / V.N. Bondarenko, A.V. Goncharov, V.Ya. Kolot // Вопросы атомной науки и техники. — 1999. — № 4. — С. 98-101. — Бібліогр.: 23 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859648308065075200 |
|---|---|
| author | Bondarenko, V.N. Goncharov, A.V. Kolot, V.Ya. |
| author_facet | Bondarenko, V.N. Goncharov, A.V. Kolot, V.Ya. |
| citation_txt | Development of NSC KIPT nuclear microprobe / V.N. Bondarenko, A.V. Goncharov, V.Ya. Kolot // Вопросы атомной науки и техники. — 1999. — № 4. — С. 98-101. — Бібліогр.: 23 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | Development of the microanalysis methods is stimulated by investigations of actual materials. Their properties depend not only on an atomic structure, but also on imperfections of this structure, phase composition, areas of impurity accumulation, various kinds of microinclusions etc. Characteristic sizes of these objects are usually ranged from a few parts of micron to several tens of micron. So, there is need for methods which provide the analysis of chemical elements in samples with the corresponding level of spatial resolution.
|
| first_indexed | 2025-12-07T13:30:06Z |
| format | Article |
| fulltext |
DEVELOPMENT OF NSC KIPT NUCLEAR MICROPROBE
V.N. Bondarenko, A.V. Goncharov, V.Ya. Kolot
NSC KIPT, Kharkov, Ukraine
Development of the microanalysis methods is
stimulated by investigations of actual materials. Their
properties depend not only on an atomic structure, but
also on imperfections of this structure, phase
composition, areas of impurity accumulation, various
kinds of microinclusions etc. Characteristic sizes of
these objects are usually ranged from a few parts of
micron to several tens of micron. So, there is need for
methods which provide the analysis of chemical
elements in samples with the corresponding level of
spatial resolution.
In the development of semiconductor materials
and materials for microelectronics, in laser engineering,
in the production of various kinds of composite
materials and alloys with multiphase structure, and also
in investigations of geological objects and biological
systems on microlevel, the progress would be
impossible without use of microanalysis methods.
A part of these methods is used mainly in the
surface analysis (X-ray spectroscopy, Auger-electron
spectroscopy, spectroscopy of scattered slow ions,
mass-spectrometry of secondary ions), because the
thickness of an analyzable layer in these methods is
insignificant (0.0005-0.01 microns). An application of
these methods to volume analysis using layers
sputtering leads to an essential deterioration of depth
resolution because of sputtering non-uniformity.
It is necessary to notice that the sample-
destructive methods are often undesirable, since after
their application the sample becomes unsuitable for
other researches, and a preparation of the samples is a
laborious procedure. Besides, some samples are unique
(such as samples of cosmic origin substance, objects of
archaeology etc.).
For studies of chemical elements distribution
over a volume are more widely used the microanalysis
methods which provide the greater depth of the analysis.
The laser mass-spectroscopy is used frequently among
destructive methods of analysis. The most popular
nondestructive methods are the electron probe
microanalysis (EPMA) and analysis by means of the
nuclear microprobe (NM).
In EPMA an excitation of X-rays is produced by
an electron beam of energy 10…100 keV. As the
electron beam disperses during penetration into sample,
the lateral resolution at the surface ranges usually from
0.5 to 5 microns for the given method, in spite of the
fact that an initial beam diameter can be by 2-3 order of
magnitude less [1]. The limit of mass concentration
determination is about 0.5% for the X-ray spectrometers
with energy dispersion and ∼ 0.1% for ones with wave
dispersion [1]. The sensitivity of the method is limited
by a high level of bremsstrahlung accompanying the
electron energy dissipation. This method is widely used
despite of its low trace element detection limits because
it is embodied in rather compact commercially available
devices.
The first NM was constructed by Cookson in
1970 [2]. In this microprobe 3 MeV proton beam was
focussed to a diameter of a few microns by means of
quadruplet of quadrupole lenses ("Russian quadruplet").
The NM has the following advantages in
comparison to the electron microprobe: 1) the spatial
resolution is practically determined only by diameter of
the focussed beam on a sample because the beam of
protons or other accelerated ions with energies of a few
MeV scatters weakly in a sample; 2) the NM allows to
carry out investigations in parallel by several nuclear
analysis methods (NAM) which is well-known as
quantitative methods for a long time [4,5]; 3) the limit
of impurity determination by means of induced X-rays
registration (PIXE-method) is by several order less than
that for the electron microprobe, because the NM has
the low bremsstrahlung background; 4) it is capable to
analyze elements with A=1-14 by means of nuclear
reaction (PIGE, NRA), while it is a rather complicated
problem for the standard electron microprobe; 5) it is
possible to carry out the analysis of layers and structures
along depth of a sample by means of Rutherford
backscattering (RBS).
Unfortunately, the NM did not become a serial
device and it will hardly become that in the near future.
The reason is that NM is bound to an accelerator (as a
rule, to an electrostatic one, because this type of
accelerators has the best energy stability). The
accelerator-microprobe complex is a rather expensive
facility and it requires large areas for its arrangement
(sometimes a separate building.).
So, there is the tendency to develop the NM
using available accelerators and existing experimental
areas. As a rule, such complexes are developed in the
research centers and large university labs.
In 1995 there were about 30 high energy NM
with the beam energies exceeding 1 MeV in the world
[6]. At some facilities a submicron spatial resolution for
a high microbeam current (100 pA) was achieved [6-8].
The scanning transmission ion microscope (STIM),
based on the NM [9, 10], was developed and a
resolution of 0.05 µm was achieved [11]. In STIM the
beam currents are low and each ion passed through a
sample is recorded.
Thus, the NM practically has no competitors
among other non-destructive techniques, both in the
detection sensitivity and in the range of analyzable
elements, for performing microanalysis with a
resolution from submicron values to a few tens of
micron.
In NSC KIPT the activities on the NM
development were started in the middle of eighties. The
calculations of the beam formation system, the
parameters of NM and examples of investigations
performed with the NM are discussed below.
The scheme of ion beam formation system is
given in the Fig.1. The accelerated ion beam, collimated
by a pair of diaphragms, passes through the focussing
system and hits a sample. The focussing system based
on magnetic quadrupole lens doublet was chosen. The
doublet of lenses is the simplest system of strong
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98
focusing, that is important for adjusting and running the
system in a routine operation. Besides, a doublet of
lenses ensures the highest ion currents, as compared to a
triplet and a quadruplet, at the given length of system,
the lens geometry and the size of the focussed beam on
the target [12].
The disadvantage of doublet consist in different
values of the demagnification coefficients Mx
-1and My
-1
in two orthogonal planes. However, it can be
compensated by the proper choice of the sizes of
rectangular diaphragms (object and angular).
Let’s dwell on some aspects of the executed
calculation and assume that Z is the longitudinal axis of
the lens, XZ and YZ are, accordingly, the focusing and
defocusing planes of the quadrupole lens, q and p are,
accordingly, the charge and the momentum of a beam
particle. Then the particle trajectory in the field of the
lens is described by the following system of two
nonlinear differential equations for coordinates of a
particle in the transverse plane, x(z) and y(z) (see, for
example, [12]):
=−++++−
=−+++++
0]''')'1[(''1''
0]''')'1[(''1''
222
222
zyx
zxy
BxByxByyx
pc
qy
ByByxBxyx
pc
qx
where c is the speed of light, Bx, By, Bz are the
components of magnetic field of lenses..
The following approaches to the trajectory
calculation are possible: 1) calculation in linear
approximation, when all nonlinear terms in these
equations and in the expression for a lens field are
omitted; 2) calculation using a 3-rd order expansion of
these equations by entrance coordinates x0
, y0 and slope
angles x0
’, y0
’ (the values of coefficients are obtained in
works [13, 14]); 3) numerical integration of the system
of nonlinear equations.
To ensure the maximum precision in calculations
we used the last approach. The terms up to 6-th order in
the field expansion were taken into account. They
appear as the result of a substitution of an ideal
hyperbolic shape of the “working” surface of poles with
more technological – cylindrical [15] and a breakage of
the “working” surface [16].
The decreasing of the field gradient G(z) near the
face ends (fringing field) was described by a bell-shaped
function [17]. Three components of the fringing fields
were defined using Taylor expansion in terms of x and
y, where expansion coefficients are expressed through
G(z) and its derivatives.
Chromatic factor was determined by varying
input particle energy.
Thus, the developed codes took into account
practically all significant types of aberrations: а)
chromatic; b) aberrations due to the finite angular size
of the beam (the special case is the spherical
aberration); c) fringe aberrations, caused by the axial
field components near the face ends of lenses; d)
aberrations, arising from the non-linearity of lens field.
These codes allow to compute both the total effect of all
aberrations, and contributions of separate aberrations to
the beam size and the shape of the focussed beam on a
target.
The main goal of calculation of the beam
forming system is to ensure the maximal phase space
and, as a result, the maximal beam intensity for the
given size of the beam on a target. Since some
parameters of the system can not be optimized
proceeding only from the requirement of phase volume
maximality. So, for example, it is desirable distance a
(see, Fig. 1) be more longer, but it limits by size of
workroom, where installation is supposed to dispose.
On other hand, distance b should be minimum, but it is
necessary to leave space before the target for
arrangement of detectors. Energy E of particles and its
relative instability dE/E also are objective parameters of
the accelerator.
Fig.1.The NM ion beam formation system on base of
magnetic lenses doublet. 1-object diaphragm,
2 - angular diaphragm, 3-4 - lenses, 5 - target,
a - distance between object diaphragm and 1-st lens,
l - effective length of lens, s-distance between lenses,
b - distance between 2-nd lens and target. The envelope
of beam in horizontal and vertical planes is showed.
If these parameters and the parameters of lenses
are set then it is possible to achieve a maximum phase
space by varying the sizes of collimator diaphragms.
The program of optimization of the diaphragm
parameters (4 parameters) with 2 constraints imposed
on these parameters (the fixed sizes of the beam on a
target in x- and y- directions).
Taking into account the layout of ESU-4,5
accelerator, its energy stability and the space required
for placing detectors in front of the target, the following
parameters for calculation were selected: a =2500 mm,
b=100 mm, dE/E = 0,05 %. The calculation was
executed for a “classic” version of doublet (s=l) and
proton energy of 2 MeV, (the energy can be increased
up to 3,5 MeV). The calculations were executed for a
wide range of values of lens effective length.
As the result of these calculations the optimal
value of 50 mm for the lens effective length was
obtained. For this effective length and the value of lens
aperture radius of 6,5 mm it is possible to focus the
beam if the field induction at the pole does not exceed
0,4 T (such value is far from saturation and is easy
provided).
Following step was determination of installation
tolerances of poles in lenses at their assembly. For this
purpose the aberrations of system, arising from the
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98
poles displacement were investigated [18]. It was shown
that the errors in pole installation of 5 µm lead to
decreasing the sizes of collimator diaphragms., and,
consequently, to a loss of beam intensity in 2 - 3 times
if the beam spot size at the target is kept within 1×1 µ
m2.
Indispensable alignment element of a doublet is
rotation of lenses and their displacement in the plane
transversal to the beam axis. The effect of these
manipulations on field distribution in the focusing
system was studied in ref. [19]. The expression for
disturbed field distribution from this work we used for
calculation of distortion of focused beam spot on target.
It was shown that the rotation misalignment of lenses
along the longitudinal axis 0.05 mrad decreases the
beam intensity in 2-3 times. The requirements for the
lens rotation around of transverse axes and their
displacement in the transverse plane are not so critical.
The detailed description of the calculation of ion
optical system and the optimization of its parameters
can be found elsewhere [20-22].
Let's stay briefly on the parameters of lenses,
which were designed and manufactured for the NM. As
it was mentioned above, the effective length of lenses
constitutes 50 mm and the radius of the aperture is 6,5
mm. The poles of lenses are manufactured from a high
quality iron-cobalt alloy 49КФ with saturation field
reaching 2.4 – 2.5 Т. The tips of poles have cylindrical
shape (the cylinder radius is 6.5×1.12=7,28 mm
according to the recommendations given in ref. [15], the
width of cylindrical part of a pole equals to10.29 mm).
The total of pole width is 20 mm. The cylindrical
surface is ganged to the lateral face of a pole by a plane,
the corner between this plane and the pole axis
constitutes 300. The end faces of poles are flat. The
number of turns in each of 4 pole windings are 380.
The lens yoke is manufactured from a high
quality iron and it has the shape of an empty cylinder
(the external radius - 240 mm, the internal radius - 220
mm, the height - 55 mm). Each lens is mounted at the
tuning table which allows to displace the lens in
horizontal and vertical directions with a step of 10 µm
and to rotate the lens around of the longitudinal axis
with a step of 0.03 mrad.
Unfortunately, manufacturing the NM units
coincided in time with an essential cutting of financing
for this project. Nevertheless, the activities aimed at
developing the NM in NSC KIPT were not stopped
completely. It was decided to create the non-stationary
version of NM, which could be installed at ESU-4,5
accelerator for the period of performing measurements
and removed after their accomplishment.
In this version the focusing system developed for
the NM is used. The beam line, collimator, the system
of beam current monitoring, the vacuum system and the
irradiation chamber of the existing NAM facility are
also used (see Fig. 2).
Fig.2. The general view of NM.
The short ion beam line of 12 mm diameter
placed between poles of the doublet lenses connects the
NAM chamber to the NM target chamber (the NM
chamber incorporates a goniometer with three
translation and one rotation degrees). The goniometer
can move a sample with ∼1 µm step. The doublet and
the target chamber are mounted on the alignment table.
The beam and a sample are visually observed through
the window by means of the optical microscope with
magnification х100. The nuclear analysis methods
PIXE, PIGE, NRA, RBS are used. Parameters of NM
are presented in the Table 1.
A series of analytical investigations, using this
facility, was carried out. In particular, an impurity
composition of synthetic diamonds (200-330 microns)
was defined [23], the investigations of some composite
materials were also carried out.
Table 1
Distance between object diaphragm and 1-st lens of doublet, mm 3310
Distance between lenses, mm 50
Distance between 2-nd lens and target, mm 165
Effective length of lens, mm 50
Excitation of 1-st lens (ϕ1) 0,58987
Excitation of 2-nd lens (ϕ2) 0,72285
Demagnification coefficient in horizontal plane (Mx
-1) 6,6
Demagnification coefficient in vertical plane (My
-1) 30,9
Beam sizes of microprobe, µm2 5×3
Proton energy, MeV 2,4
Maximal proton energy, MeV 3,5
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98
0 200 400 600 800 1000 1200
0,000
0,002
0,004
0,006
0,008
0,010
0,012
0,014
0,016
0,018
0,020
coating - substrate interface
Surfase
Co
nc
en
tra
tio
n
(w
t.%
)
Distance from surface ( µ m)
Fig.3.The depth profile of fluorine in W CVD coating.
For example, the depth profile of fluorine in W
CVD coating on the W substrate is presented in fig.3.
This profile was obtained by PIGE technique using the
reaction 19F(p,p′γ). In the region of coating-substrate
boundary an increase in fluorine concentration one
order of magnitude is observed. Such information can
be useful for technology perfecting, because often
fluorine can be a harm impurity.
The NM of NSC KIPT is the first and the only
one in Ukraine. Now by means of NM the analytical
investigations are carried out in cooperation with NSC
department of solid state physics and materials and
other organizations.
The work on further improving the NM
parameters and perfecting its systems will be prolonged.
Now the plan of the arrangement of the stationary NM
is considered.
REFERENCES
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p.1752.
20. Bondarenko V.N., Goncharov A.V., // Proceedings
of coference on microanalysis by ions beams (Kharkov,
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pechati, 1991, p.263. (in Russian)
21. Bondarenko V.N., Goncharov A.V. // Ibidem, p.271.
22. Bondarenko V.N.,Goncharov A.V.,Grizay V.N.,
Kolot V.Ya., Storizhko V.E. // Ibid., p. 74.
23. V.Ya.Kolot, V.N.Bondarenko, A.V.Goncharov.
Some applications of nuclear microanalysis methods in
NSC KIPT. // Proceedings of ХI conference on
electrostatic accelerators. Obninsk, PEI, 1996, p.92.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. № 4.
Серия: Ядерно-физические исследования (35), с. 98-101.
98
|
| id | nasplib_isofts_kiev_ua-123456789-81507 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T13:30:06Z |
| publishDate | 1999 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Bondarenko, V.N. Goncharov, A.V. Kolot, V.Ya. 2015-05-17T15:40:43Z 2015-05-17T15:40:43Z 1999 Development of NSC KIPT nuclear microprobe / V.N. Bondarenko, A.V. Goncharov, V.Ya. Kolot // Вопросы атомной науки и техники. — 1999. — № 4. — С. 98-101. — Бібліогр.: 23 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/81507 Development of the microanalysis methods is stimulated by investigations of actual materials. Their properties depend not only on an atomic structure, but also on imperfections of this structure, phase composition, areas of impurity accumulation, various kinds of microinclusions etc. Characteristic sizes of these objects are usually ranged from a few parts of micron to several tens of micron. So, there is need for methods which provide the analysis of chemical elements in samples with the corresponding level of spatial resolution. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Development of NSC KIPT nuclear microprobe Разработка и создание ядерного микрозонда в ННЦ ХФТИ Article published earlier |
| spellingShingle | Development of NSC KIPT nuclear microprobe Bondarenko, V.N. Goncharov, A.V. Kolot, V.Ya. |
| title | Development of NSC KIPT nuclear microprobe |
| title_alt | Разработка и создание ядерного микрозонда в ННЦ ХФТИ |
| title_full | Development of NSC KIPT nuclear microprobe |
| title_fullStr | Development of NSC KIPT nuclear microprobe |
| title_full_unstemmed | Development of NSC KIPT nuclear microprobe |
| title_short | Development of NSC KIPT nuclear microprobe |
| title_sort | development of nsc kipt nuclear microprobe |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/81507 |
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