Development of negative ion source with combined discharge
The results of investigation of emission productivity of negative particles source with combined discharge are presented. A cylindrical beam of negative hydrogen ions with density about 5 A/cm² on source emission aperture is obtained. The full beam current values are up to 200 mA for negative hydrog...
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irk-123456789-1122072017-01-19T03:02:16Z Development of negative ion source with combined discharge Goretskii, V.P. Dobrovolskiy, A.M. Приложения и технологии The results of investigation of emission productivity of negative particles source with combined discharge are presented. A cylindrical beam of negative hydrogen ions with density about 5 A/cm² on source emission aperture is obtained. The full beam current values are up to 200 mA for negative hydrogen ions and up to 1.5 A for electrons with high divergence after source. The source has simple design and produces stable discharge with low level of oscillation. Представлено результати досліджень емісійних особливостей імпульсного джерела негативно заряджених часток з комбінованим типом розряду. Отримано циліндричний пучок негативних іонів водню з густиною 5 А/см² на емісійній апертурі джерела. Загальний струм негативних іонів водню досягає 200 мА, а електронів – 1,5 А, але має значне розходження на виході з джерела. Джерело має просту конструкцію та стабільні характеристики розряду з низьким рівнем коливань. Представлены результаты исследований эмиссионных особенностей источника отрицательно заряженных частиц с комбинированным типом разряда. Получен циллиндрический пучок отрицательных ионов водорода с плотностью 5 А/см² на эмиссионной апертуре источника. Полный ток отрицательных ионов водорода достигает 200 мА, а электронов – 1,5 А, но имеет значительную расходимость на выходе источника. Источник имеет простую конструкцию и стабильные характеристики разряда с низким уровнем колебаний. 2015 Article Development of negative ion source with combined discharge / V.P. Goretskii, A.M. Dobrovolskiy // Вопросы атомной науки и техники. — 2015. — № 4. — С. 315-318. — Бібліогр.: 7 назв. — англ. 1562-6016 PACS: 29.25.Ni, 41.75.Cn, 41.85.Ar http://dspace.nbuv.gov.ua/handle/123456789/112207 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Приложения и технологии Приложения и технологии |
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Приложения и технологии Приложения и технологии Goretskii, V.P. Dobrovolskiy, A.M. Development of negative ion source with combined discharge Вопросы атомной науки и техники |
| description |
The results of investigation of emission productivity of negative particles source with combined discharge are presented. A cylindrical beam of negative hydrogen ions with density about 5 A/cm² on source emission aperture is obtained. The full beam current values are up to 200 mA for negative hydrogen ions and up to 1.5 A for electrons with high divergence after source. The source has simple design and produces stable discharge with low level of oscillation. |
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Article |
| author |
Goretskii, V.P. Dobrovolskiy, A.M. |
| author_facet |
Goretskii, V.P. Dobrovolskiy, A.M. |
| author_sort |
Goretskii, V.P. |
| title |
Development of negative ion source with combined discharge |
| title_short |
Development of negative ion source with combined discharge |
| title_full |
Development of negative ion source with combined discharge |
| title_fullStr |
Development of negative ion source with combined discharge |
| title_full_unstemmed |
Development of negative ion source with combined discharge |
| title_sort |
development of negative ion source with combined discharge |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2015 |
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Приложения и технологии |
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| citation_txt |
Development of negative ion source with combined discharge / V.P. Goretskii, A.M. Dobrovolskiy // Вопросы атомной науки и техники. — 2015. — № 4. — С. 315-318. — Бібліогр.: 7 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-07-08T03:32:29Z |
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2025-07-08T03:32:29Z |
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1837048056874270720 |
| fulltext |
ISSN 1562-6016. ВАНТ. 2015. №4(98) 315
DEVELOPMENT OF NEGATIVE ION SOURCE WITH COMBINED
DISCHARGE
V.P. Goretskii, A.M. Dobrovolskiy
Institute of Physics NASU, Kiev, Ukraine
E-mail: gorets@iop.kiev.ua
The results of investigation of emission productivity of negative particles source with combined discharge are
presented. A cylindrical beam of negative hydrogen ions with density about 5 A/cm2 on source emission aperture is
obtained. The full beam current values are up to 200 mA for negative hydrogen ions and up to 1.5 A for electrons
with high divergence after source. The source has simple design and produces stable discharge with low level of
oscillation.
PACS: 29.25.Ni, 41.75.Cn, 41.85.Ar
INTRODUCTION
Researches devoted to creation of hydrogen negative
ion sources continue for several last decades [1]. These
sources are widely used in physical experiments on con-
trolled fusion and in some practical applications, such as
neutron generators for medicine. The main attention of
the researches is now drawn to development of powerful
sources capable of generation of pulsed current with
values about tens kA. However, the necessity in im-
provement of characteristics of moderate power sources
still remains. The main efforts are directed to improve-
ment of the beam emittance and the source economy.
The present work is targeted to investigation of emis-
sion features of hydrogen negative ions or electron
source of cylindrical beam operating in pulse-periodical
mode with combined discharge.
1. APPROACH
Early we present the investigation of productivity of
two variants of negative particles source – the first with
a discharge in crossed fields only, and the second with
additional hollow cathode type discharge. It was shown
that presence of additional discharge significantly im-
proves emission capability of the source [2]. From a
source with combined discharge we register negative
ion current about 5 mA at distance of 50 cm from the
source by collector with 10 cm diameter. Here we pre-
sent results of investigations of emission capability of
advanced model of the source with combined discharge.
In design of our source we use experience of other au-
thors [1, 3-7]. The main features of the source were de-
scribed in [2]. Here we made the minor changes in dis-
charge chamber design and changed the emission hole
diameter. We explain increasing of negative ion current
by influence of the second discharge. So in advanced
model of the source we improve exchange capability
between discharges chambers. Also, we increase emis-
sion of the source as a whole.
2. EXPERIMENTAL SETUP
Experimental setup consisted from studied gas dis-
charge based Н- ion source placed in vacuum chamber at
pressure of 3⋅10-5 Torr. The discharge was ignited after
hydrogen supply to the source channel by means of
pulsed valve. Cesium adding to the discharge was done
by its extraction from cesium dichromate tablets during
the source heating by electric discharge. Hydrogen sup-
ply valve and the source electrodes were powered by
pulsed electric supply modules. High voltage power
source of VS-50-50 type was used for the beam extrac-
tion and acceleration up to more than 10 keV energy. The
beam was investigated by means of collectors described
below. Signal from the collectors was supplied to oscillo-
scope input for determining current values of negatively
charged particle beam. Main task of the investigations
was determining the value of extracted Н- ion beam cur-
rent immediately at output aperture of the source. Be-
sides, transport characteristics of obtained beams were
studied. Due to that, two setups for determining the beam
parameters were used.
Fig. 1. Scheme of H-ion beam current measurement at
50 cm distance from the source: 1 – source of H-ions;
2 – magnetic shield; 3 – electromagnet poles; 4 – beam
of H- ions; 5 – collector for the current measurement
Fig. 2. Scheme of hydrogen negative ion beam current
measurement at 8 cm distance from the source aper-
ture: 1-5 – collectors for measurement of the beam
current components; 6 – beam of hydrogen negative
ions; 7 – extracting electrode of the source;
8 – anode of the source
The first setup for measurements of negative particle
beam parameters at 50 cm distance from the source is
shown schematically in Fig. 1. The beam current was
measured by collector having 10 cm diameter, which
determined the value corresponding to beam propagation
within a cone having angle of about 12°.
mailto:gorets@iop.kiev.ua
ISSN 1562-6016. ВАНТ. 2015. №4(98) 316
Fig. 2 exhibits scheme of measurements of the beam
parameters at 8 cm distance from output aperture of the
source. Measuring device in this case consisted from
5 collectors. The first collector was bulk metal plate.
The second, third, fourth and fifth ones were apertures
with diameters of 2, 4, 6 and 8 cm, respectively.
The fifth collector was limited by a cylinder with
equal potential having 10 cm diameter and 4 cm length.
At that, both total current of negatively charged par-
ticles including electrons, and Н- ion beam current could
be measured. For separation of the particles, weak
transverse magnetic field could be applied in vicinity of
emission slit, which deflected electron flow to electro-
magnet poles.
The source exterior is shown in Fig. 3. The source
was assembled between two flanges separated by isola-
tor. The right side flange was mounted to vacuum cham-
ber of the setup. Cathode system of the source was
mounted at the left side flange. One can see electric pow-
er supply connectors and gas feed tube at external side of
the flange. The right side flange was at ground potential.
It held the elements of extracting system. The left side
flange with the source cabinet in operation regime was at
negative potential of about 10 kV.
Fig. 3. Picture of negative ion source
One can understand operation principle of the source
by consideration of its schematic drawing in Fig. 4.
Fig. 4. Schematic drawing of Н- ion source
Number 1 denotes gas valve for hydrogen feed. The
feed was done in pulsed mode 1.5 ms prior to the source
discharge ignition. 2 and 5 are steel magnetic cores,
which together with ring-shaped magnet 3 served for
creation of magnetic field with about 1 kGs strength in
the gap between anode 7 and cathode 4. It enabled igni-
tion in this gap the discharge with crossed electric and
magnetic field. The anode was separated from the cath-
ode by ceramic isolator 6. Emission hole with 4 mm
diameter was located in anode insert made of molyb-
denum in washer 7. Elements from 1 to 7 were mounted
at external flange. Extracting electrode 8 was assembled
on the front flange. Accelerating potential was applied
to electrode of the anode 7 relatively to grounded elec-
trode 8. As it was shown by the experiments, in cham-
ber 9 at voltage supply to electrodes 4 and 7 additional
discharge was ignited, which influenced essentially on
emission features of the source. The discharge glowed
in the cathode electrode cavity. We consider it as one of
hollow cathode type [2]. Thus, two types of the dis-
charges coexist in the source. These are hollow cathode
discharge located inside the source, and the discharge in
crossed fields near emission slit.
3. EXPERIMENTAL RESULTS
Two types of negatively charged particles – elec-
trons and negative ions are extracted from the source
with hydrogen as working gas. Taking into account con-
siderable difference in masses of the particles, one can
easily separate their flows by means of magnetic field.
Behavior of the current value at magnetic field strength
variation enables conclusion about portion of H- current
in the beam, and determination of possibility of the
source use for production of H- ion beams.
0 20 40 60 80 100120140160180
0
5
10
15
20
25
C
ol
le
ct
or
c
ur
re
nt
(m
A
)
Magnetic field (Gs)
Fig. 5. Dependence of current of negatively charged
particles to remote collector on magnetic field strength
Earlier in [2] measurements of current on collector
with 10 cm diameter located at 50 cm distance from the
source (cone with 12o angle) were performed. Plot of
dependencies of negative particle current to the collec-
tor on magnetic field strength is presented in Fig. 5. One
can see that at the field strength higher than 10 Gs the
dependencies become weakly exhibited. This was con-
sidered as complete electron beam deflection. At that,
current of heavy negatively charged particles flows to
the collector. In our case these particles can be only
hydrogen negative ions. The measurements have shown
that the current of hydrogen negative ions is 5 mA. At
that, emission slit had 2 mm diameter. In subsequent
experiments, with emission slit diameter increase to
4 mm, we succeeded in enhancement of H- ion current
value at remote collector up to 20 mA. For determining
peculiarities of negative particle flow from the source,
collector shown in Fig. 2 was used. It enabled both
measurement of total current from the source, and de-
termining angular distribution of the current density.
Fig. 6 shows the total current corresponding to over-
all beam propagation cone (total beam current) depend-
ing on a deflecting magnetic field strength.
One can see similarity with behavior shown in
Fig. 7. Particularly, sharp maximum of the current at
zero magnetic field changes to slow decrease of current
on collector with magnetic field strength growth. How-
ISSN 1562-6016. ВАНТ. 2015. №4(98) 317
ever, unlike the case of previous plot, one can’t see sharp
bend of the curve, and visible decrease of the current is
observed only at the field strength of about 100 Gs, which
is essentially bigger than in previous case.
0 50 100 150 200 250 300 350 400
0
200
400
600
800
1000
1200
1400
To
ta
l b
ea
m
c
ur
re
nt
(m
A)
Magnetic field (Gs)
Discharge current 100A
Discharge current 50A
Discharge current 30A
Fig. 6. Total current of negatively charged particles of
the beam on collectors 1-4 (see Fig. 2) depending on
magnetic field strength for three different values of dis-
charge current in the source
It is explained by fact that at short distance larger
deflection angle of the beam electrons is required, as
compared to that at long distance. And this requires re-
spective magnetic field strength increase. Namely, at the
field of about 150 Gs, Larmor radius of electrons having
10 keV energy becomes equal to 4 cm, which prevents
their coming to collectors 1-4. Thus, one can expect that
in such case we measure only H- ion current value. One
can see that at discharge current of 100 A negative ion
current value may exceed 200 mA. But this is a value
for the current which propagates within cone having
angle of about 50°. As well, one can see that the dis-
charge current decrease, that is the decrease of supplied
power, causes diminishing of extracted current value.
The beam current suitable for subsequent acceleration
can be determined from the next plot, which presents
dependencies of current of negative particles on the first
collector which receives particles propagating within a
cone having about 14o value which is close to that ob-
tained at remote distance. By extrapolation of ranges of
slow decrease to the point with zero magnetic field
strength, one can see that respective H- current value
should be about 50 mA.
0 50 100 150 200 250 300 350 400
0
50
100
150
200
250
300
350
B
ea
m
c
ur
re
nt
o
n
1c
ol
le
ct
or
(m
A
)
Magnetic field (Gs)
Discharge current 100A
Discharge current 50A
Discharge current 30A
Fig. 7. Dependencies of current of negatively charged
particles on 1 collector on magnetic field strength for
three different values of discharge current in the source
Below in Fig. 8 values of current density on collec-
tors at different magnetic field strength are presented.
As in previous measurements, the beam energy was
10 keV. Discharge current in the source was 100 A.
Each collector accepted the beam to a ring of 1 cm
width. Since current receiving ring radius measured in
centimeters coincides with the collector number, the
plot also presents radial distribution of current at the
collector plane.
One can see that maximum value of the beam cur-
rent is observed in the center for both light and heavy
negatively charged particles. Nevertheless, the beam
periphery also possesses high enough density, which
confirms strong angular divergence of the beam.
Zero magnetic field
Magnetic field 34Gs
Magnetic field 100Gs
Magnetic field 340Gs
1 2 3 4
0
10
20
30
40
50
60
70
80
90
Cu
rre
nt
d
en
si
ty
(m
A/
cm
2 )
Collector number
Fig. 8. Radial distributions of current density
of negatively charged particles for different values
of deflecting field
For increasing the source efficiency, further efforts
on improvement of the beam extraction system are re-
quired.
CONCLUSIONS
We consider that essential increase of hydrogen neg-
ative beam current extracted from studied source with
axial symmetry is due to plasma density growth at the
expense of additional discharge in the source channel
and decrease of Н- loss rate owing to their decay at col-
lisions with electrons resulted from cooling of the elec-
trons during their drift through near-anode region of
magnetic field. Further modernization of the design, and
increase of the source emission hole square enabled
increase of H- ion current from the source up to 20 mA
under the same transport conditions, as in [2]. Radial
dependencies of H- current density obtained by means
of sectioned collector at 8 cm distance from the source
show that total H- current exceeds 200 mA value near
the source. H- current density at the source aperture
reaches the value of about 5 A/cm2, which can give evi-
dence to significant role of surface-plasma processes in
Н- creation due to cesium presence in the source dis-
charge. However, the beam possesses large value of the
scattering cone of about 50o. Although the current den-
sity maximum is observed at the axis, the current densi-
ty decrease rate along the radius is slow enough. Thus,
just less than a half of total Н-current comes to central
collector (propagation cone angle of about 14o). Strong
beam divergence in the studied source is probably due
to complexity of Pierce geometry obeying for extracting
gap at large dimension of extracting slit in the source.
The last circumstance implies use of the source in a tan-
dem with additional focusing device. Activities aimed to
this task are performed. As well, the measurements have
ISSN 1562-6016. ВАНТ. 2015. №4(98) 318
shown that negative ion beam current value at its propa-
gation for 50 cm (propagation cone angle of 12°) de-
creases from about 50 mA at the source aperture down
to 20 mA at remote collector. The last fact can be ex-
plained by a process of electron loss by H- ions at their
collisions with particles of the gas flow, which is inher-
ent to gas discharge sources of H- negative ions. Ac-
complished researches have shown that pulsed dis-
charge of combined type [2] with 100 V voltage and
current values from several tens up to hundreds amperes
is steadily ignited in the proposed source. At that, rela-
tion oscillations which can occur in some other types of
H- sources did not exist in our case.
Thus, one can state that highly efficient source of in-
tense H- ion beams of moderate energy is proposed.
Improvement of extracting system at the source aperture
is required.
REFERENCES
1. P. Moehs et al. Negative Hydrogen Ion Sources for
Accelerators // IEEE Trans. Pl. Sci. 2005, v. 33,
№ 6, p. 1786-1798.
2. V.P. Goretskii, A.M. Dobrovolskiy. Peculiarities of
Hydrogen Negative Ion Beams Extraktion Axially
Symmetric Source with Crossed Fields // Problems
of Atomic Science and Technology. Series “Plasma
Physics”. 2015, № 1, p. 73-76.
3. E.M. Oks. Plasma Cathode Electron Sources: Phys-
ics, Technology, Applications / Tomsk State Univer-
sity of Radio Electronics and Control Systems.
4. Yu.I. Belchenko, G.I. Dimov, V.G. Dudnikov. Pro-
duction of an intensive beam of H-ions from dis-
charge in crossed fielfs // JTF. 1973, v. 43, p. 1720-
1725.
5. Y.V. Kursanov, P.A. Litvinov, V.A. Baturin. H-
Source with the Volume Plasma Formation” // 10th
Intern, Symp. on Production and Neutralization of
Negative Ion and Beams. Kiev, 2004.
6. V.P. Goretskii, A.V. Ryabtsev, et al. Comparative
emission characteristics of hydrogen negative ion
source with Cs and without Cs” // JTF. 1999, v. 69,
p.102-109.
7. M. Bacal, A.M. Brunettau, M. Nachman. Negative
ion production in hydrogen plasmas confined by a
multicusp magnetic field // Journal of Applied Phys-
ics. 1984, v. 55, p. 15-24.
Article received 26.05.2015
УСОВЕРШЕНСТВОВАНИЕ ИСТОЧНИКА ОТРИЦАТЕЛЬНЫХ ИОНОВ
С КОМБИНИРОВАННЫМ РАЗРЯДОМ
В.П. Горецкий, А.М. Добровольский
Представлены результаты исследований эмиссионных особенностей источника отрицательно заряжен-
ных частиц с комбинированным типом разряда. Получен циллиндрический пучок отрицательных ионов во-
дорода с плотностью 5 А/см2 на эмиссионной апертуре источника. Полный ток отрицательных ионов водо-
рода достигает 200 мА, а электронов – 1,5 А, но имеет значительную расходимость на выходе источника.
Источник имеет простую конструкцию и стабильные характеристики разряда с низким уровнем колебаний.
ВДОСКОНАЛЕННЯ ДЖЕРЕЛА НЕГАТИВНИХ ІОНІВ З КОМБІНОВАНИМ РОЗРЯДОМ
В.П. Горецький, А.М. Добровольський
Представлено результати досліджень емісійних особливостей імпульсного джерела негативно зарядже-
них часток з комбінованим типом розряду. Отримано циліндричний пучок негативних іонів водню з густи-
ною 5 А/см2 на емісійній апертурі джерела. Загальний струм негативних іонів водню досягає 200 мА, а елек-
тронів – 1,5 А, але має значне розходження на виході з джерела. Джерело має просту конструкцію та стабі-
льні характеристики розряду з низьким рівнем коливань.
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