Focusing of ion beams by permanent magnet plasma lens
This work was supported by the Science and Technology Center in Ukraine under Project #1596.
Збережено в:
| Дата: | 2002 |
|---|---|
| Автори: | , , , , , |
| Формат: | Стаття |
| Мова: | English |
| Опубліковано: |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2002
|
| Назва видання: | Вопросы атомной науки и техники |
| Теми: | |
| Онлайн доступ: | https://nasplib.isofts.kiev.ua/handle/123456789/80302 |
| Теги: |
Додати тег
Немає тегів, Будьте першим, хто поставить тег для цього запису!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Focusing of ion beams by permanent magnet plasma lens / I. Protsenko, A. Goncharov, V. Gorshkov, S. Gubarev, I. Litovko, I. Brown // Вопросы атомной науки и техники. — 2002. — № 4. — С. 138-140. — Бібліогр.: 5 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
nasplib_isofts_kiev_ua-123456789-80302 |
|---|---|
| record_format |
dspace |
| spelling |
nasplib_isofts_kiev_ua-123456789-803022025-02-09T13:46:16Z Focusing of ion beams by permanent magnet plasma lens Protsenko, I. Goncharov, A. Gorshkov, V. Gubarev, S. Litovko, I. Brown, I. Plasma electronics This work was supported by the Science and Technology Center in Ukraine under Project #1596. 2002 Article Focusing of ion beams by permanent magnet plasma lens / I. Protsenko, A. Goncharov, V. Gorshkov, S. Gubarev, I. Litovko, I. Brown // Вопросы атомной науки и техники. — 2002. — № 4. — С. 138-140. — Бібліогр.: 5 назв. — англ. 1562-6016 PACS: 52.59.-f; 52.40.Mj https://nasplib.isofts.kiev.ua/handle/123456789/80302 en Вопросы атомной науки и техники application/pdf Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| topic |
Plasma electronics Plasma electronics |
| spellingShingle |
Plasma electronics Plasma electronics Protsenko, I. Goncharov, A. Gorshkov, V. Gubarev, S. Litovko, I. Brown, I. Focusing of ion beams by permanent magnet plasma lens Вопросы атомной науки и техники |
| description |
This work was supported by the Science and Technology Center in Ukraine under Project #1596. |
| format |
Article |
| author |
Protsenko, I. Goncharov, A. Gorshkov, V. Gubarev, S. Litovko, I. Brown, I. |
| author_facet |
Protsenko, I. Goncharov, A. Gorshkov, V. Gubarev, S. Litovko, I. Brown, I. |
| author_sort |
Protsenko, I. |
| title |
Focusing of ion beams by permanent magnet plasma lens |
| title_short |
Focusing of ion beams by permanent magnet plasma lens |
| title_full |
Focusing of ion beams by permanent magnet plasma lens |
| title_fullStr |
Focusing of ion beams by permanent magnet plasma lens |
| title_full_unstemmed |
Focusing of ion beams by permanent magnet plasma lens |
| title_sort |
focusing of ion beams by permanent magnet plasma lens |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2002 |
| topic_facet |
Plasma electronics |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/80302 |
| citation_txt |
Focusing of ion beams by permanent magnet plasma lens / I. Protsenko, A. Goncharov, V. Gorshkov, S. Gubarev, I. Litovko, I. Brown // Вопросы атомной науки и техники. — 2002. — № 4. — С. 138-140. — Бібліогр.: 5 назв. — англ. |
| series |
Вопросы атомной науки и техники |
| work_keys_str_mv |
AT protsenkoi focusingofionbeamsbypermanentmagnetplasmalens AT goncharova focusingofionbeamsbypermanentmagnetplasmalens AT gorshkovv focusingofionbeamsbypermanentmagnetplasmalens AT gubarevs focusingofionbeamsbypermanentmagnetplasmalens AT litovkoi focusingofionbeamsbypermanentmagnetplasmalens AT browni focusingofionbeamsbypermanentmagnetplasmalens |
| first_indexed |
2025-11-26T11:36:57Z |
| last_indexed |
2025-11-26T11:36:57Z |
| _version_ |
1849852723616284672 |
| fulltext |
FOCUSING OF ION BEAMS BY PERMANENT MAGNET PLASMA LENS
I. Protsenko, A. Goncharov , V. Gorshkov, S. Gubarev, I. Litovko
Institute of Physics NASU, 46, pr. Nauki, Kiev, 01650, Ukraine
I. Brown
Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
PACS: 52.59.-f; 52.40.Mj
1. INTRODUCTION
The electrostatic plasma lens (PL) is based on the
introduction of controlled electric fields and
equipotentialization of magnetic field lines within the lens
volume. Moderate energy, large area, high current, heavy
ion beams can be focussed in this way, as has been well
demonstrated in a series of experiments carried out at
Kiev and at Berkeley in recent years [1-4]. The lens used
in these experiments employed a magnetic field that was
established by conventional current-driven
electromagnetic coils. In these experiments we noted an
increase in the focussed ion beam current density for
specific low magnetic field strengths. This suggested to us
the possibility of a plasma lens based on the use of
permanent magnets.
The first experimental investigations of the focusing
properties of a PL based on permanent magnets for
establishing the required magnetic field configuration
were carried out collaboratively both at the IP NASU
(Kiev) and at the LBNL (Berkeley). This work has been
reported [5].
Here we describe some further investigations of
the focusing properties of a simple and compact PL based
on the use of small permanent magnets.
2. EXPERIMENTAL CONDITIONS AND
APPROACH
Experiments were carried out at Kiev using the set-
up described in detail in [1] and at Berkeley described in
[4]. For ion beam creation we use a two-chamber
MEVVA ion source with grid anode and three-electrode
multi-aperture accel-decel ion optical system. Both
sources operate in a repetitively-pulsed mode and produce
moderate energy, low-divergence, broad, heavy metal ion
beams with primary parameters as follows. Kiev − beam
duration τ = 100 µs, beam extraction voltage Uacc ≤ 25
kV, total current Ib ≤ 800 mA, initial beam diameter ∅ =
5.5 cm, ion species Cu, distance d from ion source
extractor to mid-plane of the PL ~ 30 cm. Berkeley − τ =
250 µs, Uacc ≤ 50 kV, Ib ≤ 200 mA, initial ∅ = 6 and
10 cm for two different extraction systems, ion species Bi,
Pb, Ta, Nb, Mg, Cu, and C, distance d = 34 cm. The basic
parameters of the lenses used were as follows. Kiev −
input aperture D = 7.4 cm, length L = 14 cm, number of
electrostatic electrodes N = 13; the electrodes were fed
via an RC-divider that provided fixed electrode potentials
for the duration of the ion beam, and the highest potential
(UL) applied to the central electrode was + 4.7 kV; the
maximum strength of the magnetic field formed by the
permanent Fe-Nd-B magnets at the center of the lens was
B = 360 G. Berkeley − D = 10 cm, L = 15 cm, N = 11;
the electrodes were fed by a 110 kΩ resistive voltage
divider; UL ≤ +10 kV, B = 300 G. The magnetic field
shape required for each PL and the corresponding
disposition of magnets need to establish the magnetic
field were determined by computer simulation and
experimental tests. The magnetic field strength B could be
varied by changing the number of magnets used and also
by employing iron pieces to shunt a part of the magnetic
field, allowing the field strength to be changed by
increments of 17 G.
Radially movable Langmuir probes were used for
measurement of the plasma in the lens volume and in the
beam drift space. Ib and Jb were measured by an axially-
movable sectioned collector (at Kiev) and by a radially-
movable, magnetically-suppressed Faraday cup with
entrance aperture 3 mm (at Berkeley), located at a
distance ~30 cm from the lens mid-plane. The base
pressure in the vacuum chamber was less than 1 x 10 -5
Torr, allowing formation of plasma within the PL volume
by the ion beam itself and by secondary electron emission
electrons from the lens electrodes.
3. RESULTS AND DISCUSSIONS
In work [5] preliminary to that described here,
we investigated the cases of a copper ion beam with initial
beam diameter 5.5cm (Kiev) and a tantalum ion beam
with initial diameter 6cm (Berkeley). Note that the input
aperture of the Berkeley PL was 10cm. Here we describe
some experimental results obtained for large area ion
beams with initial diameter 10cm.
The experiments show that for a large area ion
beam with initial beam diameter equal to the input
aperture of the PL, the focusing properties are more
distinct. The maximum compression for the tantalum ion
beam was a factor of 5-7 for the optimal lens potential
distribution, for the case of beam with initial diameter 6
cm. At the same time for the case of tantalum beam with
diameter 10 cm, the maximum beam compression at the
PL focus was approximately a factor of 20, with and
current density up to 32 mA/cm2. Note that similar results
were obtained for a copper ion beam on the Kiev set-up,
where the compression was a factor 15-25 depending on
the total ion beam current passing through the lens (see
[5] for details). Note also that similar results were
observed when beams of this type were focussed using a
PL with conventional current-driven coils [4].
The experimental results depend on the particular
externally-applied potential distribution along the lens
electrodes. The optimal distribution minimizes lens
spherical aberrations, as established empirically for a PL
138 Problems of Atomic Science and Technology. 2002. № 4. Series: Plasma Physics (7). P. 138-140
with an input aperture of 10 cm, and as shown in Fig. 1
(curve 2). One can see that this distribution differs
significantly from the theoretical optimum distribution
obtained by plasma optic principles.
Focusing of different ion beams species (Bi, Pb,
Ta, Nb, Mg, Cu, C) was investigated. Better results were
obtained for the case of the heavy ion beams Bi, Pb, and
Ta. In Fig. 2 one can see good bismuth beam compression
for the case of the optimal distribution. Fig.3 show that
the radial profile of the focused Bi ion beam depends on
the PL operation, for case of electrode potential
distribution corresponding to Fig. 1 (2). Note that the
maximum ion beam compression for Bi was up to a factor
of 30, and the low-noise focused beam current density
was up to 45mA/cm2.
These results and experimental conditions were used
for computer simulation of the processes of formation of
the plasma medium within the electrostatic high current
PL. One can see some of these results in Figs. 4 to 6.
Analysis of these data show the formation within the PL
volume of layered electron structures (Fig. 4) owing to
finite width of the ring lens electrodes. This means that
the presence of spherical aberrations restricted the
maximum compression of the focussed ion beam. This is
confirmed by Fig. 6, which models ion beam focusing for
the experimental conditions presented here. The
maximum compression obtained by computer simulation
is in the range 35-150x. This value depends markedly on
the collector radius, the lens potential distribution, and the
width of the ring electrodes, in good accordance with
experimental results.
4. CONCLUDING REMARKS
The experimental results and the computer simulation
results described here both indicate good prospects for the
use of the permanent-magnet electrostatic plasma lens for
manipulating high current, moderate energy, large area,
heavy ion beams. The simple design, robust construction,
the need for only a single power supply, and the high
efficiency are all attractive advantages of the PL based on
139
0 10 20 30 40 50 60
0,0
0,2
0,4
0,6
0,8
1,0
2
1
U/UL
z, mm
Fig. 1. The optimal PL electrode potential
distribution.
1-theoretical U(R,z)∼B(0,z); 2-experimental
Fig.2. Oscillograms of bismuth beam current measured
by an on-axis Faraday cup, for the case of maximum
compression and the experimental optimal PL potential
distribution. Beam accelerating voltage Uacc = 34kV,
UL=7.7kV, B=300G. Upper trace – ion source arc
current (200A/cm); middle trace – ion beam current
density for cases PL on; lower trace - PL-off. Vertical
scale: 14mA/cm2 per cm. Horizontal scale: 50µs/cm.
Fig. 3. Radial ion beam current density profile at the
Faraday cup location.
the use of permanent magnets rather than of conventional
current-driven coils. At this stage of the investigations,
this plasma-optical device could be used, for example, in
particle accelerator beam lines and for high dose ion
implantation. Further experimental and theoretical efforts
are needed on forming an optimized PL without spherical
aberrations, in part by optimization of the magnetic field
configuration in the low magnetic field range.
This work was supported by the Science and Technology
Center in Ukraine under Project #1596.
REFERENCES
[1] A.Goncharov, A.Dobrovolsky, I. Protsenko, V.Kaluh, I.Onishchenko
and I.Brown,
Rev. Sci. Instrum., 69(2), 1135 (1998).
[2] A.Goncharov, S.Gubarev, A.Dobrovolsky, I.Protsenko, I.Litovko
and I.Brown, IEEE Trans. Plasma Sci., 27(4), 1068 (1999).
[3] A.Goncharov, I.Protsenko, , G. Yushkov and I.Brown, Appl.Phys.
Lett., 75(7), 911 (1999)
[4] A. Goncharov, I.Protsenko , G. Yushkov and
I. Brown, IEEE Trans. Plasma Sci., 28(6), 2238 (2000).
-40 -30 -20 -10 0 10
-4
-2
0
2
4
r
z
Fig. 6. Ion beam particle trajectories for the case of Fig. 4(a)
0 10 20 30 40 50
0,0
0,5
1,0
1,5
2,0
2,5
3,0
2
1
ρ e
mmr,
a
0 10 20 30 40 50
0
1
2
3
4
5
6
7 U(z=0,r), kV
mmr,
b
Fig.5. Radial distribution of (a) electron space charge,
and (b) potential, at the lens mid-plane. Solid lines - for
the
case of Fig. 4(a); dotted lines - for the case of Fig. 4(b).
Horizontal line in (a) - ion space charge background
0 2 4 6
-6 -4 -2 0 2 4 6
0,0
2,5
5,0
r
z
a
0 2 4 6
-6 -4 -2 0 2 4 6
0,0
2,5
5,0
r
z
b
Fig. 4. Electron space charge distribution in the PL
volume for the two lens potential distributions
shown in Fig.1.
(a) theoretical; (b) experimental. The background
ion space charge is 0.43 CGSE units /cm3.
Shaded areas – electron space charge density
86.0≥eρ CGSE units /cm3.
[5] A.Goncharov, V.Gorshkov, S.Gubarev, A.Dobrovosky, I.Protsenko
and I.Brown ,
Rev. Sci. Instrum., 73(2), 1001 (2002).
141
I. Protsenko, A. Goncharov , V. Gorshkov, S. Gubarev, I. Litovko
REFERENCES
|