Peculiarities of hydrogen negative ion beams extraction from axially symmetric source with crossed fields
A comparison of emission features of axially symmetric H⁻ ion source with magnetron discharge and H⁻ source which incorporates additional hollow cathode discharge in series with main one is presented. It is shown that in the last case concentration of H⁻ ions in a region of emission hole of the sour...
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Goretskii, V.P. Dobrovolskiy, A.M. 2015-05-25T05:43:56Z 2015-05-25T05:43:56Z 2015 Peculiarities of hydrogen negative ion beams extraction from axially symmetric source with crossed fields / V.P. Goretskii, A.M. Dobrovolskiy // Вопросы атомной науки и техники. — 2015. — № 1. — С. 73-76. — Бібліогр.: 6 назв. — англ. 1562-6016 PACS: 29.25.Ni, 41.75.Cn, 41.85.Ar https://nasplib.isofts.kiev.ua/handle/123456789/82092 A comparison of emission features of axially symmetric H⁻ ion source with magnetron discharge and H⁻ source which incorporates additional hollow cathode discharge in series with main one is presented. It is shown that in the last case concentration of H⁻ ions in a region of emission hole of the source essentially increases. H⁻ ion current from the source with additional discharge increases by an order of magnitude. Additional plasma drift from assisting discharge and cooling of electrons at their passing through magnetic field region are considered as the reasons of determined growth of concentration of negative ions. H⁻ current density value of 150 mA/cm2 on emission aperture of ion source is reached. Приводится сравнение эмиссионных свойств источника ионов Н⁻ с осевой симметрией с магнетронным разрядом и источника Н⁻, в котором последовательно с основным дополнительно горит разряд типа «полый катод». Показано, что в последнем случае существенно возрастает концентрация ионов Н⁻ в области эмиссионного отверстия источника. Ток ионов Н⁻ из источника с дополнительным разрядом увеличивается на порядок величины. В качестве причин обнаруженного увеличения концентрации отрицательных ионов рассматриваются дополнительный дрейф плазмы из области вспомогательного разряда и охлаждение электронов при прохождении области с магнитным полем. Достигнутая величина плотности тока Н⁻ в пересчете на эмиссионную апертуру источника составила не менее 150 мА/см², что в полтора раза превышает ранее полученные результаты. Наведено порівняння емісійних властивостей джерела іонів Н⁻ з симетрією навколо oсі з магнетронним розрядом із джерелом Н⁻, в якому додатково до основного запалюється розряд типу «порожнистий катод». Показано, що в останньому випадку значно зростає концентрація іонів Н⁻ в області емісійного отвору джерела. Струм іонів Н⁻ iз джерела з додатковим розрядом збільшується на порядок величини. В якості причин виявленого збільшення концентрації негативних іонів розглядається додатковий дрейф плазми з області допоміжного розряду та охолодження електронів при проходженні області з магнітним полем. Досягнута величина густини струму іонів Н⁻ у перерахунку на емісійну апертуру джерела становить не менше ніж 150 мА/см², що в півтора рази перевершує попередні результати. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Фундаментальная физика плазмы Peculiarities of hydrogen negative ion beams extraction from axially symmetric source with crossed fields Особенности извлечения пучков отрицательных ионов водорода из осесимметричного источника со скрещенными полями Особливості витягування пучків негативних іонів водню з вісесиметричного джерела зі схрещеними полями Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| title |
Peculiarities of hydrogen negative ion beams extraction from axially symmetric source with crossed fields |
| spellingShingle |
Peculiarities of hydrogen negative ion beams extraction from axially symmetric source with crossed fields Goretskii, V.P. Dobrovolskiy, A.M. Фундаментальная физика плазмы |
| title_short |
Peculiarities of hydrogen negative ion beams extraction from axially symmetric source with crossed fields |
| title_full |
Peculiarities of hydrogen negative ion beams extraction from axially symmetric source with crossed fields |
| title_fullStr |
Peculiarities of hydrogen negative ion beams extraction from axially symmetric source with crossed fields |
| title_full_unstemmed |
Peculiarities of hydrogen negative ion beams extraction from axially symmetric source with crossed fields |
| title_sort |
peculiarities of hydrogen negative ion beams extraction from axially symmetric source with crossed fields |
| author |
Goretskii, V.P. Dobrovolskiy, A.M. |
| author_facet |
Goretskii, V.P. Dobrovolskiy, A.M. |
| topic |
Фундаментальная физика плазмы |
| topic_facet |
Фундаментальная физика плазмы |
| publishDate |
2015 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Особенности извлечения пучков отрицательных ионов водорода из осесимметричного источника со скрещенными полями Особливості витягування пучків негативних іонів водню з вісесиметричного джерела зі схрещеними полями |
| description |
A comparison of emission features of axially symmetric H⁻ ion source with magnetron discharge and H⁻ source which incorporates additional hollow cathode discharge in series with main one is presented. It is shown that in the last case concentration of H⁻ ions in a region of emission hole of the source essentially increases. H⁻ ion current from the source with additional discharge increases by an order of magnitude. Additional plasma drift from assisting discharge and cooling of electrons at their passing through magnetic field region are considered as the reasons of determined growth of concentration of negative ions. H⁻ current density value of 150 mA/cm2 on emission aperture of ion source is reached.
Приводится сравнение эмиссионных свойств источника ионов Н⁻ с осевой симметрией с магнетронным разрядом и источника Н⁻, в котором последовательно с основным дополнительно горит разряд типа «полый катод». Показано, что в последнем случае существенно возрастает концентрация ионов Н⁻ в области эмиссионного отверстия источника. Ток ионов Н⁻ из источника с дополнительным разрядом увеличивается на порядок величины. В качестве причин обнаруженного увеличения концентрации отрицательных ионов рассматриваются дополнительный дрейф плазмы из области вспомогательного разряда и охлаждение электронов при прохождении области с магнитным полем. Достигнутая величина плотности тока Н⁻ в пересчете на эмиссионную апертуру источника составила не менее 150 мА/см², что в полтора раза превышает ранее полученные результаты.
Наведено порівняння емісійних властивостей джерела іонів Н⁻ з симетрією навколо oсі з магнетронним розрядом із джерелом Н⁻, в якому додатково до основного запалюється розряд типу «порожнистий катод». Показано, що в останньому випадку значно зростає концентрація іонів Н⁻ в області емісійного отвору джерела. Струм іонів Н⁻ iз джерела з додатковим розрядом збільшується на порядок величини. В якості причин виявленого збільшення концентрації негативних іонів розглядається додатковий дрейф плазми з області допоміжного розряду та охолодження електронів при проходженні області з магнітним полем. Досягнута величина густини струму іонів Н⁻ у перерахунку на емісійну апертуру джерела становить не менше ніж 150 мА/см², що в півтора рази перевершує попередні результати.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/82092 |
| citation_txt |
Peculiarities of hydrogen negative ion beams extraction from axially symmetric source with crossed fields / V.P. Goretskii, A.M. Dobrovolskiy // Вопросы атомной науки и техники. — 2015. — № 1. — С. 73-76. — Бібліогр.: 6 назв. — англ. |
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2025-11-26T11:37:23Z |
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| fulltext |
ISSN 1562-6016. ВАНТ. 2015. №1(95)
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2015, № 1. Series: Plasma Physics (21), p. 73-76. 73
PECULIARITIES OF HYDROGEN NEGATIVE ION BEAMS
EXTRACTION FROM AXIALLY SYMMETRIC SOURCE WITH
CROSSED FIELDS
V.P. Goretskii, A.M. Dobrovolskiy
Institute of Physics, NAS of Ukraine, Kiev, Ukraine
E-mail: gorets@iop.kiev.ua
A comparison of emission features of axially symmetric H
-
ion source with magnetron discharge and H
-
source
which incorporates additional hollow cathode discharge in series with main one is presented. It is shown that in the
last case concentration of H
-
ions in a region of emission hole of the source essentially increases. H
-
ion current from
the source with additional discharge increases by an order of magnitude. Additional plasma drift from assisting
discharge and cooling of electrons at their passing through magnetic field region are considered as the reasons of
determined growth of concentration of negative ions. H
-
current density value of 150 mA/cm
2
on emission aperture
of ion source is reached.
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
controlled 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 values of tens kA. However, the necessity in
improvement of characteristics of moderate power
sources still remains. The main efforts are directed to
improvement of the beam emittance and the source
economy. The present work is targeted to investigation
of emission features of hydrogen negative ion source
with axial symmetry operating in pulse-periodical
mode.
1. APROACH
The source with axial symmetry and cylindrical
beam extraction along the axis was selected as a work
model due to optimum correspondence to the
requirements of focusing system operation. For such
kind of the source, it is important to have the plasma
low temperature and high enough density in the
emission region. The last can be achieved by means of
separation of the plasma generation zone from that of
extraction of negative ions. Plasma cooling with
simultaneous increase of its density can be realized at
the expense of diffusion of converging plasma flow
across magnetic field, or by obtaining hydrogen plasma
in additional discharge and providing its flow and
accumulation in the region of H
-
ion formation and
extraction. Version of combining two these options is
interesting as well. For study of the influence of
additional discharge on the efficiency of extraction of
H
-
ions from the source, two versions of its design were
researched. The hollow cathode discharge was selected
as additional one. It has been shown that the efficiency
of extraction of hydrogen negative ions in the last case
essentially increases, and the extracted electron current
(Ie) to H
-
current ratio Г=(Ie/I
-
H) is considerably
improved. Hypotheses on the reasons of negative ion
current growth in the source with additional discharge
are proposed.
2. EXPERIMENTAL SETUP
We took into consideration an experience of
construction of electron beam sources with gas discharge
and axial symmetry [1-4] at designing of the negative
ion source Particularly, discharge parameters of the
source were chosen close to those described in [3],
however, they were realized in axially symmetric
geometry. As well as in [4], the discharge in crossed
electric and magnetic field was selected as the main one.
Experimental setup consisted from H
-
ion source, pulsed
valve for hydrogen supply, pulsed power supply modules
for the valve and the source discharge.
Fig. 1. Scheme of measurements of negative particle
beam current from the source:
1 negative ion source; 2 magnetic shield;
3 solenoid poles; 4 beam of negatively charged
particles; 5 collector for the beam current
measurements
For extraction and acceleration of the beam, high
voltage was used which enable acceleration the
extracted beam up to energy values of above 10 kV.
Fig. 1 shows scheme of experiment on transport and
measurement of negative particle beam parameters.
The current value was measured by the current
collector having 10 cm diameter at a distance of 50 cm
74 ISSN 1562-6016. ВАНТ. 2015. №1(95)
from the emission plane. At that, both the overall
current of negatively charged particles, and H
-
ion
beam current could be measured. Thus, the weak
magnetic field was turned on in vicinity of extracting
hole to remove the electron flow from beam.
The source exterior is shown in Fig. 2. The ion
source has 17 cm diameter and 7 cm length. The
source housing under the cathode potential is mounted
inside isolator at the flange from external side of
which electric power connectors and gas supply valve
tube are seen. The front flange separated from the rear
one by isolator and is under the ground potential.
Fig. 2. General view of negative ion source
Fig. 3. Schemes of the two versions of H
-
ion source:
.
a Source with magnetron discharge; b source with
additional hollow cathode discharge
At grounded flange elements of extracting systems
are mounted. In operation regime the rear flange with
the source is under negative potential of about 10 kV.
One can understand operation principle of the source
from its schematic drawing in Fig. 3. The figure
presents two versions of the source. Gas valve for
hydrogen feed is marked as 1. The feed was done in
pulsed way, in advance of 1.5 s to turning on the
source discharge pulse. The discharge was ignited
between the electrodes 7 (anode) and 4 (cathode) in
crossed electric and magnetic fields. The magnetic field
of about 1 kGs strength was formed between the
magnetic conductor poles 2 and 5 by means of ring
magnet 3. The anode was separated from the cathode by
ceramic isolator 6. Emission hole with 2 mm diameter
are located in the anode insertion from molybdenum in
washer 7. Elements marked from 1 to 7 were assembled
at the rear flange. Extracting electrode 8 was assembled
at the front flange. Accelerating potential was supplied
to anode electrode 7 relatively to grounded electrode 8.
All said above regards to both source versions a) and b).
The difference of version b) was the presence of
chamber 9. As it was shown by the experiments, at
supply of the discharge voltage between electrodes 4
and 7, an additional discharge was ignited in the
chamber which provided essential influence on emission
features of the source. This discharge was glowing in a
region where magnetic field was shielded. We name this
discharge as the hollow cathode discharge.
3. RESULTS
Pulsed discharge was ignited by supply of the
discharger voltage to electrodes 7 and 4 after hydrogen
feed in presence of cesium vapor. Fig. 4 shows current-
voltage characteristics of the discharge in the source
with magnetron discharge, as well as in one with
additional hollow cathode discharge.
a
b
Fig. 4. Characteristics of the discharge glow in the
source with hydrogen: a − Source with magnetron
discharge; b − Source with additional hollow cathode
discharge
One can see that the discharge characteristics are
close enough in both cases. At that, in the source with
additional discharge the voltage is somewhat lower with
the same current values. Measurements of negative
particle current from the source was performed at the
discharge current of 100 A. The discharge pulse had
500 s duration. Repetition rate was ~ 2 Hz. It was
determined that negative ion current from the source
ISSN 1562-6016. ВАНТ. 2015. №1(95) 75
with hollow cathode comprised 5 mA, whereas the
current in the first version of the source was an order of
magnitude less. Fig. 5 presents the dependence of
negative particle current from the source with hollow
cathode measured at the collector on the strength of
transverse magnetic field applied across the beam
behind emission slit of the source. One can see that at
the field increase up to 5 Gs negative particle current
drastically decreases from 25 to 5 mA. We explain this
behavior by the electron flow cutoff.
.
Fig. 5. Dependence of negative particle current onto the
collector on deflecting magnetic field strength
In subsequent, the current remains unchanged up to
the field strength of 40 Gs and exhibits noticeable
decrease already at the field strength of about 200 Gs.
This part shows behavior of H
-
ion flow in the magnetic
field. Results of negative particle current measurements
are presented in Table.
The beam current on collector
Magnetron source
Magnetron source
with hollow
cathode
(IH-)mA 0,5 mA 5 mA
(Ie)mA 5,5 mA 20 mA
Ie/IH- 11 4
Note that in the case with assisting discharge the
efficiency of negative ion extraction in the emission slit
region considerably increases. As well, one can see that
in this case negative ion portion in the negative plasma
component is essentially higher.
4. DISCUSSION
By comparison of the measurement results for
current values extracted from two versions of the
sources of negative particles, one can see that presence
of additional chamber with hollow cathode discharge
results in an increase of concentrations of both negative
ions and electrons and, consequently, overall plasma
density in the region of emission hole. The most
probable reason of that is the plasma drift from
additional discharge region along magnetic field at the
source axis. Increase of plasma concentration in the
emission region results in the growth of formation rate
of H
-
negative ions in the processes of recharging of
positive ions at the anode surface in vicinity of the
emission region and negative ions formation in the
plasma volume due to processes of dissociative
attachment of electrons to vibrationally excited
hydrogen molecules [3, 5, 6]. At the same time, one can
expect cooling the plasma electrons at the drift from
assisting discharge region through a zone of
concentrated magnetic field. It in turn may essentially
reduce the rate of negative ions destruction in a process
of their collisions with electrons. We mentioned only
the main processes responsible for negative ions
existence in hydrogen plasma of the source. Other
processes are possible as well. Particularly, efficient gas
blocking is possible during the discharge glow in the
source with combined discharge. It may essentially
reduce NI beam destruction on the gas stream at the exit
from the source. For now, one can resume that
mentioned processes for considered type of the source
require further detailed studies.
CONCLUSIONS
Accomplished experiments with axially symmetric
Н
-
source with magnetron discharge have shown that
introduction of additional discharge of hollow cathode
type into the source enables essential increase of
extracted current of hydrogen negative ions. H
-
current
density value about 150 mA/cm
2
on emission aperture is
reached. It can be explained by the plasma density
increase in emission region of the source. The last
should lead to increase of the rate of formation of
hydrogen negative ions in this region due to reactions of
recharging of positive ions at the anode surface, and
also due to volume processes of negative ions
formation. One can also assume that the negative ions
disappearance rate decreases due to lowering electron
temperature in this region. The last is confirmed by an
increase of contribution of negative ions current to
overall current of the beam extracted from the source
with additional hollow cathode discharge.
REFERENCES
1. P. Moehs et al. Negative Hydrogen Ion Sources for
Accelerators // IEEE Trans. On Pl. Sci. December 2005,
v. 33, № 6, p. 1786-1798.
2. E.M. Oks. Plasma Cathode Electron Sources:
Physics, Technology, Applications / Tomsk State
University of Radio Electronics and Control Systems,
Tomsk-2005.
3. Yu.I. Belchenko, G.I. Dimov, V.G.. Dudnikov.
Production of an intensive beam of H-ions from
discharge in crossed fielfs // JTF. 1973, v. 43, p. 1720-
1725.
4. Y.V. Kursanov, P.A. Litvinov, V.A. Baturin. H-Source
with the Volume Plasma Formation”//10
th
International
Symposium on Production and Neutralization of
Negative Ion and Beams. Kiev 14-17 September 2004.
74 ISSN 1562-6016. ВАНТ. 2015. №1(95)
5. 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.
6. M. Bacal, A.M. Brunettau, M. Nachman. Negative
ion production in hydrogen plasmas confined by a
multicusp magnetic field // Journal of Applied Physics.
1984, v. 55, p. 15-24.
Article received 02.12.2014
ОСОБЕННОСТИ ИЗВЛЕЧЕНИЯ ПУЧКОВ ОТРИЦАТЕЛЬНЫХ ИОНОВ ВОДОРОДА
ИЗ ОСЕСИММЕТРИЧНОГО ИСТОЧНИКА СО СКРЕЩЕННЫМИ ПОЛЯМИ
В.П. Горецкий, А.Н. Добровольский
Приводится сравнение эмиссионных свойств источника ионов Н
-
с осевой симметрией с магнетронным
разрядом и источника Н
-
, в котором последовательно с основным дополнительно горит разряд типа «полый
катод». Показано, что в последнем случае существенно возрастает концентрация ионов Н
-
в области
эмиссионного отверстия источника. Ток ионов Н
-
из источника с дополнительным разрядом увеличивается
на порядок величины. В качестве причин обнаруженного увеличения концентрации отрицательных ионов
рассматриваются дополнительный дрейф плазмы из области вспомогательного разряда и охлаждение
электронов при прохождении области с магнитным полем. Достигнутая величина плотности тока Н
-
в
пересчете на эмиссионную апертуру источника составила не менее 150 мА/см
2
, что в полтора раза
превышает ранее полученные результаты.
ОСОБЛИВОСТІ ВИТЯГУВАННЯ ПУЧКІВ НЕГАТИВНИХ ІОНІВ ВОДНЮ
З ВІСЕСИМЕТРИЧНОГО ДЖЕРЕЛА ЗІ СХРЕЩЕНИМИ ПОЛЯМИ
В.П. Горецький, А.М. Добровольський
.
Наведено порівняння емісійних властивостей джерела іонів Н
-
з симетрією навколо oсі з магнетронним
розрядом із джерелом Н
-
, в якому додатково до основного запалюється розряд типу «порожнистий катод».
Показано, що в останньому випадку значно зростає концентрація іонів Н
-
в області емісійного отвору
джерела. Струм іонів Н
-
iз джерела з додатковим розрядом збільшується на порядок величини. В якості
причин виявленого збільшення концентрації негативних іонів розглядається додатковий дрейф плазми з
області допоміжного розряду та охолодження електронів при проходженні області з магнітним полем.
Досягнута величина густини струму іонів Н
-
у перерахунку на емісійну апертуру джерела становить не
менше ніж 150 мА/см
2
, що в півтора рази перевершує попередні результати.
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