Modulation of negatively charged particle flux from penning discharge with metal hydride cathode
The features of modulation of negatively charged particle flux extracted along the magnetic field from Penning discharge with metal hydride cathode have been investigated. The separation of negative ions from coextracted electrons was performed by an electromagnetic filter with efficiency not worse...
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Sereda, I. Hrechko, Ya. Azarenkov, M. 2023-12-09T10:02:37Z 2023-12-09T10:02:37Z 2023 Modulation of negatively charged particle flux from penning discharge with metal hydride cathode / I. Sereda, Ya. Hrechko, M. Azarenkov // Problems of Atomic Science and Technology. — 2023. — № 1. — С. 71-73. — Бібліогр.: 9 назв. — англ. 1562-6016 PACS: 52.80.Sm DOI: https://doi.org/10.46813/2023-143-071 https://nasplib.isofts.kiev.ua/handle/123456789/196032 The features of modulation of negatively charged particle flux extracted along the magnetic field from Penning discharge with metal hydride cathode have been investigated. The separation of negative ions from coextracted electrons was performed by an electromagnetic filter with efficiency not worse than 90%. It is shown that electrons in the extracted flow are deeply modulated with the frequency of the diocotron instability of the anode layer, while negative ions are not. An increase in the interelectrode distance and anode length resulted in a more pronounced expression of this effect due to the minimization of the influence of the magnetic field of the filter on the discharge. Досліджено особливості модуляції потоку негативно заряджених частинок, витягнутих уздовж магнітного поля з розряду Пенінга з металогідридним катодом. Відділення негативних іонів від спільно витягнутих електронів проводилося електромагнітним фільтром з ефективністю не гірше, ніж 90%. Показано, що електрони у вилученому потоці глибоко модулюються на частоті діокотронної нестабільності анодного шару, а негативні іони − ні. Збільшення міжелектродної відстані та довжини анода призвело до більшого вираження цього ефекту за рахунок мінімізації впливу електромагнітного фільтра на розряд. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Problems of Atomic Science and Technology Low temperature plasma and plasma technologies Modulation of negatively charged particle flux from penning discharge with metal hydride cathode Модуляція потоку негативно заряджених частинок з розряду пенинга з металогідридним катодом Article published earlier |
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Modulation of negatively charged particle flux from penning discharge with metal hydride cathode |
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Modulation of negatively charged particle flux from penning discharge with metal hydride cathode Sereda, I. Hrechko, Ya. Azarenkov, M. Low temperature plasma and plasma technologies |
| title_short |
Modulation of negatively charged particle flux from penning discharge with metal hydride cathode |
| title_full |
Modulation of negatively charged particle flux from penning discharge with metal hydride cathode |
| title_fullStr |
Modulation of negatively charged particle flux from penning discharge with metal hydride cathode |
| title_full_unstemmed |
Modulation of negatively charged particle flux from penning discharge with metal hydride cathode |
| title_sort |
modulation of negatively charged particle flux from penning discharge with metal hydride cathode |
| author |
Sereda, I. Hrechko, Ya. Azarenkov, M. |
| author_facet |
Sereda, I. Hrechko, Ya. Azarenkov, M. |
| topic |
Low temperature plasma and plasma technologies |
| topic_facet |
Low temperature plasma and plasma technologies |
| publishDate |
2023 |
| language |
English |
| container_title |
Problems of Atomic Science and Technology |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Article |
| title_alt |
Модуляція потоку негативно заряджених частинок з розряду пенинга з металогідридним катодом |
| description |
The features of modulation of negatively charged particle flux extracted along the magnetic field from Penning discharge with metal hydride cathode have been investigated. The separation of negative ions from coextracted electrons was performed by an electromagnetic filter with efficiency not worse than 90%. It is shown that electrons in the extracted flow are deeply modulated with the frequency of the diocotron instability of the anode layer, while negative ions are not. An increase in the interelectrode distance and anode length resulted in a more pronounced expression of this effect due to the minimization of the influence of the magnetic field of the filter on the discharge.
Досліджено особливості модуляції потоку негативно заряджених частинок, витягнутих уздовж магнітного поля з розряду Пенінга з металогідридним катодом. Відділення негативних іонів від спільно витягнутих електронів проводилося електромагнітним фільтром з ефективністю не гірше, ніж 90%. Показано, що електрони у вилученому потоці глибоко модулюються на частоті діокотронної нестабільності анодного шару, а негативні іони − ні. Збільшення міжелектродної відстані та довжини анода призвело до більшого вираження цього ефекту за рахунок мінімізації впливу електромагнітного фільтра на розряд.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/196032 |
| citation_txt |
Modulation of negatively charged particle flux from penning discharge with metal hydride cathode / I. Sereda, Ya. Hrechko, M. Azarenkov // Problems of Atomic Science and Technology. — 2023. — № 1. — С. 71-73. — Бібліогр.: 9 назв. — англ. |
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2025-11-24T16:51:35Z |
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2025-11-24T16:51:35Z |
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| fulltext |
ISSN 1562-6016. Problems of Atomic Science and Technology. 2023. №1(143).
Series: Plasma Physics (29), p. 71-73. 71
https://doi.org/10.46813/2023-143-071
MODULATION OF NEGATIVELY CHARGED PARTICLE FLUX FROM
PENNING DISCHARGE WITH METAL HYDRIDE CATHODE
I. Sereda1, Ya. Hrechko1, M. Azarenkov1,2
1V.N. Karazin Kharkiv National University, Kharkiv, Ukraine;
2National Science Center “Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine
E-mail: igorsereda@karazin.ua
The features of modulation of negatively charged particle flux extracted along the magnetic field from Penning
discharge with metal hydride cathode have been investigated. The separation of negative ions from coextracted
electrons was performed by an electromagnetic filter with efficiency not worse than 90 %. It is shown that electrons
in the extracted flow are deeply modulated with the frequency of the diocotron instability of the anode layer, while
negative ions are not. An increase in the interelectrode distance and anode length resulted in a more pronounced
expression of this effect due to the minimization of the influence of the magnetic field of the filter on the discharge.
PACS: 52.80.Sm
INTRODUCTION
Due to the neutralization efficiency, that remains
acceptable at higher kinetic energy, negative hydrogen
(H–) ions are widely used for injection into high power
proton accelerator facilities for fusion [1], and for
production of medical radionuclides [2]. The initial
beam of negative ions is usually produced by two well-
known mechanisms: the process at the plasma surface
boundary and the process in the plasma volume [3].
Cesium deposition on the plasma electrode surface is
usually used in surface plasma sources that significant
intensify the H– beam [4]. But it causes cesium leakage
to the acceleration zone leading to operational risks. In
the second case, H– ions are formed directly in the
plasma volume by the mechanism of dissociative
attachment of low-energy electrons to rovibrationally
excited molecules of hydrogen. The current of H– beam
from volume sources keeps much low intensity, then
from surface plasma sources, but they are more reliable
and environmentally friendly (cesium free).
Source operation with metal hydride cathode is
known to increase the production of H– ions [5]. The
stored hydrogen is chemically bounded and released in
an atomic state at the required rate under the discharge
current impact. Highly rovibrationally excited
molecules H2* are formed by the recombination of H-
atoms at the metal hydride surface, which then can be
easily converted to H– by dissociative electron
attachment [6].
Previously we reported about successful application
of metal hydride cathode in Penning negative ion source
[5]. The extraction of negatively charged particles are
performed along the magnetic field followed by the
separation of H– ions by electromagnetic filter. But
there are about 10% electrons in the registered H–
current despite the successful separation in general [7].
These are axial electrons, which are weakly affected the
transverse component of magnetic field of the filter.
The purpose of this paper is to study the modulation
of extracted current of negatively charged particles in
order to find the way to improve separation
performance.
1. EXPERIMENTAL SETUP
A schematic illustration of the experimental
apparatus is shown in Fig. 1. The discharge cell consists
of a water-cooled metal hydride cathode 1, a tubular
anode 4 and a copper cathode 5, which are placed in an
external uniform longitudinal magnetic field Hzo0 =
0…0.1 T. The metal hydride cathode was produced
from hydride-forming alloy Zr50V50 using the standard
method of metal hydride preparation includes its
melting, activation and filling with hydrogen. The
hydrogen amount which is absorbed by hydride material
was ~ 190 cm3/g at atmospheric pressure and room
temperature. Since the process of the alloy uptake with
hydrogen is accompanied by the crystal lattice
destruction, the obtained hydride powder was mixed
with a cooper binder and then pressed in a disk 2 cm in
diameter with the thickness of 0.4 cm.
IAC
+Ugrid
1
4
5
6
7
8
9
Icol
z
Hz0
Hzo0
z,cm 0 1 2 3 4 5 6 7 8 9
Hcoil
water
2
3
+ −
100 pF Ud
UAC
16 µF
4.7 pF 4.7 nF
20 MΩ 20 kΩ
12 Ω 10 kΩ
1 kΩ
Fig. 1. The schematic illustration of the Penning type
H– ion source: 1 – metal hydride cathode;
2 – cathode-holder with water-cool;
3 – thermocouple; 4 – anode; 5 – copper cathode with
an aperture; 6 – reflecting grid;
7 – electrons collector; 8 – filter magnetic coil;
9 – H– ion collector; Hzo0 – main axial Penning
magnetic field (Hzo0 = 0…0.1 T);
Hcoil – reverse magnetic field of the filter
Due to the water-cool of metal hydride its
temperature was not exceed 20 0С, that much lower than
the temperature of thermal destruction of hydride
phases. Therefore, H2* desorption is determined only by
72 ISSN 1562-6016. Problems of Atomic Science and Technology. 2023. №1(143)
a discharge current and is provided mainly by ion-
stimulated processes from the surface of metal hydride.
A flow of negatively charged particles including
negative ions and electrons along with positive ions was
registered along the external magnetic field through an
aperture in the cathode 5. The separation of H– ions was
performed by electromagnetic filter. It includes a grid 6
for positive ions retarding, a magnetic coil 8 to divert
electrons, a collector of diverted electrons 7 and a
collector of extracted axial beam of H– ions 9.
The coil 8 creates a reverse magnetic field Hcoil
between the cathode 5 and the collector 9, so that the
resulting field Hz0 in the gap is enough to divert
electrons on the collector 7. The required values of the
field Hz0 and grid potential in the filter were calculated
from the analysis of electrons and H– ions trajectories
by numerical solution of a motion equation in axially
symmetric electric and magnetic fields [7].
The discharge operation is ensured by positive
potential Ud application to the anode. The cathodes have
ground potential.
All studies were carried out only on hydrogen
desorbed from metal hydride cathode under the ion
current impact from discharge plasma without external
gas injection at residual pressure of 210-6 Torr.
2. RESULTS AND DISCUSSION
A voltage applied to the anode is concentrated in
anode layer region of negative space charge, forming
approximately radial component of electric field. The
central plasma is almost field-free, where the electrons
oscillate between cathode layers. The creation of H–
ions takes place near the metal hydride cathode
followed by the ejection in longitudinal direction.
Previously we analyzed the behavior of H– current
depending on plasma electron temperature Te [8]. The
main conclusion was the more Te, the closer electron
reflects from the metal hydride cathode. But revealed in
[9] existence of electrons groups with different energy
leads to a discrepancy between the experimental data
and the calculated ones. The groups of electrons with
different energies appear due to heating on the
instability of the anode layer.
The characteristic dependence of the oscillation
frequency, measured on the anode with spectrum
analyzer, on the magnetic field 1/f ~ H indicates on a
diocotron type instability (Fig. 2). Oscillation amplitude
A (in relative units) behaves non-linearly and is
characterized by large values in the range of magnetic
fields from 0.06 to 0.083 T.
The region to 0.05 T was not considered, since no
sufficient yield of negative ions was observed here [5].
The study of H– ion beam modulation was
performed with an oscilloscope, connected to the H– ion
collector 9 (see Fig. 1) of the electromagnetic filter. The
spectra were taken with oscilloscope in the spectrum
analyser mode using Hanning method (Figs. 3, 4).
The figures represent the obtained results, where the
change in the main harmonic of the signal was
evaluated. The screenshots of the oscilloscope screen
are given for the magnetic field, where the modulation
suppression effect is the most efficient.
0,04 0,06 0,08 0,10
0,010
0,015
0,020
0,025
1
/f
,
M
H
z-1
Hzo0 , T
0
20
40
60
80
A
,
re
la
ti
v
e
u
n
it
s
Fig. 2. The dependence of frequency and arbitrary
amplitude of oscillation in anode layer on magnetic
field at Ud = 5 kV, Id = 0.8 mA, P = 510-6 Torr
0,0 0,2 0,4 0,6 0,8 1,0 1,2
0
5
10
15
20
25
30
35
40
45
50
55
60
65
A
,
m
V
Hzo0 / Hz0
Hzo0 = 0.07 T
Hzo0 = 0.08 T
Hzo0 = 0.09 T
Hzo0 = 0.1 T
Hzo0 = 0.07 T
P = 2*10-6 Torr, Ud = 5 kV, Short cell
Fig. 3. The oscillograms and the dependence of
arbitrary amplitude of oscillation of extracted negative
current on Hzo0/Hz0 in case of short cell
When resulting magnetic field Hz0 in the gap of
electromagnetic filter is equal to the main axial Penning
magnetic field Hzo0, the axial electrons are diverted and
do not fall on H– ion collector [5]. So, a decrease of the
oscillation amplitude in Fig. 3 can be associated with
the modulation of the electron flow. Incomplete
suppression of oscillations is due to the fact that a part
of the near-axis electrons, which is weakly sensitive to
the action of the transverse component of the magnetic
field, passes to the H– ion collector. According to [5],
their part is about 10 % of the total number of electrons.
However, the effects associated with the diffusion of
electrons across the magnetic field, as well as possible
electromagnetic pickups, are not taken into account
here.
Nonetheless, one can also see the correlation
between the intensity of oscillations in the anode layer
and the suppression efficiency. The oscillation
amplitude in the anode layer is non-linear (see Fig. 2)
and possess large values for magnetic fields from 0.06
P = 2∙10-6 Torr,
ISSN 1562-6016. Problems of Atomic Science and Technology. 2023. №1(143) 73
to 0.083 T. It is in this range the most pronounced effect
of suppression of the intensity of oscillations is
appeared.
0,0 0,2 0,4 0,6 0,8 1,0 1,2
0
5
10
15
20
25
30
35
40
45
50
55
60
65
A
,
m
V
Hzo0 / Hz0
Hzo0 = 0.07 T
Hzo0 = 0.08 T
Hzo0 = 0.09 T
Hzo0 = 0.1 T
Hzo0 = 0.08 T
P = 2*10-6 Torr, Ud = 5 kV, Long cell
Fig. 4. The oscillograms and the dependence of
arbitrary amplitude of oscillation of extracted negative
current on Hzo0 / Hz0 in case of long cell
Increasing the distance between cathodes and anode
from 0.4 to 1 cm makes the suppression effect clearer,
obviously, due to the decrease of the influence of the
filter on the discharge plasma.
CONCLUSIONS
Hydrogen desorption in activated state from metal
hydride cathode, caused by ion bombardment of the
surface, leads to intensification of H– ions formation and
ejection them in longitudinal direction together with
electrons, which have got different energies due to
heating on the instability of the anode layer. Thereby
electrons in the extracted flow of negative particles are
deeply modulated with the frequency of the diocotron
instability of the anode layer, while negative ions are
not. An increase in the interelectrode distance and anode
length resulted in a more pronounced expression of this
effect due to the minimization of the influence of the
magnetic field of the filter on the discharge.
The effect of the modulation of extracted electron
current can open the way for improving the separation
performance.
REFERENCES
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Physics design of the injector source for ITER neutral
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2. P.W. Schmor. Review of Cyclotrons for the
Production of Radioactive Isotopes for Medical and
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3. M. Bacal, M. Wada. Negative hydrogen ion
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4. V. Dudnikov. Thirty years of surface plasma sources
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2002, v. 73, p. 992-994.
5. I. Sereda, A. Tseluyko, N. Azarenkov, D. Ryab-
chikov, Ya. Hrechko. Effect of metal-hydride hydrogen
activation on longitudinal yield of negative ions from
PIG // Int. J. Hydrogen Energy. 2017, v. 42, p. 21866-
21870.
6. C. Schermann, F. Pichou, M. Landau, I. C̆adez̆,
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7. I. Sereda, Ya. Hrechko, Ie. Babenko, A. Kashaba.
Peculiarities of electromagnetic filter operation in
penning source with metal hydride cathode // Problems
of Atomic Science and Technology. Series “Plasma
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8. I. Sereda, A. Tseluyko, D. Ryabchikov, Ya. Hrechko,
N. Azarenkov. The increasing of H– current from
Penning ion source with electrically biased metal
hydride cathode // Vacuum. 2019, v. 162, p. 163-167.
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Article received 21.11.2022
МОДУЛЯЦІЯ ПОТОКУ НЕГАТИВНО ЗАРЯДЖЕНИХ ЧАСТИНОК З РОЗРЯДУ ПЕНИНГА
З МЕТАЛОГІДРИДНИМ КАТОДОМ
І. Середа, Я. Гречко, М. Азарєнков
Досліджено особливості модуляції потоку негативно заряджених частинок, витягнутих уздовж
магнітного поля з розряду Пенінга з металогідридним катодом. Відділення негативних іонів від спільно
витягнутих електронів проводилося електромагнітним фільтром з ефективністю не гірше, ніж 90 %.
Показано, що електрони у вилученому потоці глибоко модулюються на частоті діокотронної нестабільності
анодного шару, а негативні іони − ні. Збільшення міжелектродної відстані та довжини анода призвело до
більшого вираження цього ефекту за рахунок мінімізації впливу електромагнітного фільтра на розряд.
P = 2∙10-6 Torr,
|