Influence of saturation degree of metal-hydride cathode on characteristics of penning type ion source of hydrogen
The experimental examinations of Penning type plasma source of hydrogen ions using metal-hydride cathode was carried out. The discharge characteristics, radial distributions of plasma parameters were measured in a gap between the anode and the metal-hydride cathode for different degree of hydrogen s...
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| Дата: | 2003 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2003
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| Цитувати: | Influence of saturation degree of metal-hydride cathode on characteristics of penning type ion source of hydrogen / V.N. Borisko, Ye.V. Klochko, I.N. Sereda // Вопросы атомной науки и техники. — 2003. — № 4. — С. 217-220. — Бібліогр.: 8 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859665544876130304 |
|---|---|
| author | Borisko, V.N. Klochko, Ye.V. Sereda, I.N. |
| author_facet | Borisko, V.N. Klochko, Ye.V. Sereda, I.N. |
| citation_txt | Influence of saturation degree of metal-hydride cathode on characteristics of penning type ion source of hydrogen / V.N. Borisko, Ye.V. Klochko, I.N. Sereda // Вопросы атомной науки и техники. — 2003. — № 4. — С. 217-220. — Бібліогр.: 8 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | The experimental examinations of Penning type plasma source of hydrogen ions using metal-hydride cathode was carried out. The discharge characteristics, radial distributions of plasma parameters were measured in a gap between the anode and the metal-hydride cathode for different degree of hydrogen saturation of the cathode material. The plasma parameters and voltage drop on the discharge was shown to be depended on the degree of saturation with hydrogen of the metal-hydride cathode. Plasma density on the axis of the system was established to be increased in accordance to the increase of the initial hydrogen saturation of the metal-hydride cathode. This phenomenon is explained by the increase of a desorption intensity of hydrogen from the central part of the surface of the metal-hydride cathode.
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| first_indexed | 2025-11-30T11:04:07Z |
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UDK 533.9
INFLUENCE OF SATURATION DEGREE OF METAL-HYDRIDE
CATHODE ON CHARACTERISTICS OF PENNING TYPE ION SOURCE
OF HYDROGEN
V.N. Borisko, Ye.V. Klochko*, I.N. Sereda
Kharkov National University, 61077, Kharkov, Svobody Sq., 4, Ukraine
e-mail: borisko@pht.univer.kharkov.ua
*A.N.Podgorny Institute of Mechanical Engineering Problems of National Academy of
Sciences of Ukraine, 61046, Kharkov, Ukraine
The experimental examinations of Penning type plasma source of hydrogen ions using metal-hydride cathode
was carried out. The discharge characteristics, radial distributions of plasma parameters were measured in a gap
between the anode and the metal-hydride cathode for different degree of hydrogen saturation of the cathode
material. The plasma parameters and voltage drop on the discharge was shown to be depended on the degree of
saturation with hydrogen of the metal-hydride cathode. Plasma density on the axis of the system was established to
be increased in accordance to the increase of the initial hydrogen saturation of the metal-hydride cathode. This
phenomenon is explained by the increase of a desorption intensity of hydrogen from the central part of the surface of
the metal-hydride cathode.
1. INTRODUCTION
The analysis of existing opportunities of utilization
of metal-hydrides in systems of gas feeding of hydrogen
isotopes of vacuum-plasma devices has shown that the
combination of hydrogen-sorptive and thermalphysics
properties of hydrides (reversible getters of hydrogen)
allows us to realize the fundamentally new schemes of
adjustable "interior" filling of the plasma-generating gas
[1]. According to this scheme the metal-hydride source
of hydrogen on the basis of hydrogen saturated getter
material is used as constructive units of devices-
consumers. Such schemes have a number of advantages
in comparison with traditional systems of gas feeding.
In this case the immediate interaction of the metal-
hydride surface with the hydrogen plasma is realized,
which improves technical characteristics of a metal-
hydride source of hydrogen and a vacuum-plasma
device as a whole [2]. However, the mechanism of the
interaction of the reversible hydrogen sorbents with the
plasma of the gas discharge has not been investigated
thoroughly. There are no data concerning the influence
of the degree of hydrogen saturation of such materials
on the parameters of the discharges using metal-hydride
electrodes and on the characteristics of the plasma of
ion sources, which was created on this basis.
The purpose of this work is the examination of the
influence of the degree of hydrogen saturation of a
hydride-forming material on the basis of Zr50V50 alloy
on the discharge characteristics and on the emissive
properties of Penning type plasma ion sources.
2. EXPERIMENT
The experiments were carried out on an installation
that is shown schematically in a fig. 1. The installation
includes a gas-discharge chamber (1), a system of
making an exterior magnetic field (2), diagnostic
equipment, a system of a discharge supply (3), a
monitoring system of pressure (4), a system of working
gas feeding (5) and a system of a vacuum pumping-out
(6). The electrodes of the reflective discharge were
located inside the quartz cylinder. The anode (7) of the
gas-discharge system was made from stainless steel and
represented the hollow cylinder 3,2 cm in diameter and
3,0 cm in length. The metal-hydride cathode (8) was
performed in a form of a disk electrode with a diameter
of 20 mm and a width of 4 mm from Zr50V50 getter alloy
saturated with hydrogen. It was pressed with copper
binding powder. The content of a copper filer formed 40
% from the mass of hydride. The maximum amount of
the accumulated hydrogen in such electrode was
2,5 dm3 at standard conditions. In our experiments
metal-hydride cathodes were used with the maximum
initial degree of hydrogen saturation (the concentration
of hydrogen in hydride corresponded to an atomic rating
«hydrogen/metal» like H/M = 1,4), as well as with 50 %
initial degree of hydrogen saturation (H/M = 0,7). The
second cathode (9) was made from stainless steel. In
verifying experiments two cathodes from stainless steel
were used. The total length of a Penning cell was 7 cm.
The residual pressure in a vacuum chamber did not
exceed 3·10-6 torr. The range of changes of an exterior
Fig.1. The scheme of experimental device for
examination of the reflective discharge using metal-
hydride cathode
2
56
1
4
7
3
8
mA
mA
10
119
T , 0 C
( H / M ) 0 = 0 . 7
1 0 9 0 C
dX/
dT
(cm
3 H
2
at S
TP/
mi
n)
2 2 1 0 C
5 1 4 0 C
5 8 6 0 C
1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0 8 0 0 9 0 0
0 . 0 0
0 .5 0
1 .0 0
1 .5 0
2 .0 0
2 .5 0
( H / M ) 0 = 1 .4
dX
/d
T
(c
m
3 H
2
at
S
TP
/
m
in
)
Fig.2. The thermal desorption spectrum of hydrogen
from ZrV
2
H
x
samples with various initial
concentrations of hydrogen
magnetic field was from 0,05 up to 0,1 Tl, and voltage
drop on the discharge was from 1 up to 3,5 kV during
the experiments. Hydrogen was used as plasma-forming
gas which moved from metal-hydride unit of exterior
feeding. Using of metal-hydride unit provided high
purity (not worse than 99,99 %) of filling hydrogen. The
working pressure of hydrogen in a vacuum chamber
varied from 5·10-5 torr up to 10-4 torr.
The radial profiles of plasma parameters were
measured by Lengmuir probes (11). The probes were
settled in the same plane in the middle of the gap
between the anode and the metal-hydride cathode. They
also were located in different distances from an axial
axis of the discharge cell. The energy distributions of
ions were investigated by a multigrid energy analyzer
(10). The energy analyzer was located in the distance of
5 mm behind a hole in the centre of the cathode (8)
(fig. 1). The diameter of the hole in the cathode was
3 mm. The aperture of the energy analyzer was selected
in such a way that the collector excepted only those ions
that had a ratio of v||/v⊥ >> 1 between longitudinal and
cross velocities.
3. RESULTS AND DISCUSSION
3.1 HYDROGEN-SORPTIVE
CHARACTERISTICS OF A HYDRIDE-FORMING
ALLOY
The saturation with hydrogen and measurement of
getter capacity of the hydride-forming alloy Zr50V50 was
carried out according to the method of Siverts [3]. The
specific saturation of such reversible sorbent of
hydrogen was from 210 up to 235 cm3 per 1 gram of
initial alloy at standard conditions. It corresponds to the
stochiometric composition of a hydride (ZrH2+ZrV2Hx)
where the x=3,34 – 4,12 with an atomic ratio
H/M = 1,34 – 1,50. The dynamics of the given metal-
hydride decomposition was explored using a method of
thermal desorption spectroscopy [4]. The measuring of
the dependence between the velocity of hydrogen
desorption in a pumped out vacuum chamber on the
temperature of a metal-hydride sample was carried out
under the linear law of the temperature increase
dependant on time (fig.2). In the given figure the spectra
of the thermal desorption of hydrogen from
hydrogenated sample of the alloy are given at different
degrees of their saturation, which corresponded to initial
values H/M = 1.4 (100 % saturation) and H/M = 0,7
(50 % saturation). The desorption of hydrogen of a
completely saturated sample is seen to be carried out
immediately turning on the pumping-out. It loses about
0,3 H/M (45 – 50 cm3 per 1 gram of hydrogen at
standard conditions). The thermal desorption of
hydrogen in the range from a room temperature up to
400 0C flows practically with a steady speed with a
broad peak of gassing in the field of 2000 C. The further
growth of the temperature results in the increase of the
intensity of gassing with the obviously pronounced peak
at T=5860 C. The obtained results are qualitatively
agreed with the data of the operations [4, 5]. The first
stage of the gassing the authors explain by
decomposition of intermetallic hydride ZrV2Hx, and the
second one they explain by decomposition of a hydride
of zirconium. For a sample with a degree of saturation
H/M = 0,7 (stochiometric composition ZrH2+ZrV2H0,60)
the intensity of desorption of hydrogen from an
intermetallic phase is inappreciable and the main part of
hydrogen is evolved from a phase of ZrH2 in the range
of temperature from 4000 C up to 6500 C.
3.2. CURRENT-VOLTAGE CHARACTERISTICS
AND PARAMETERS OF PLASMA OF THE
REFLECTIVE DISCHARGE USING METAL-
HYDRIDE CATHODE
Typical current-voltage characteristics of the
reflective discharge using metal-hydride cathode are
given in fig.3. One can see in the figure at identical
exterior parameters the heightened voltage drop on the
discharge using metal-hydride cathode is observed.
While hydrogen generates from the metal-hydride
electrode, the drop of voltage on the discharge
diminishes and tends to the typical value for cathodes
1.0 1.5 2.0 2.5 3.0 3.5
0
1
2
3
4
5
6
I,
m
A
U, kV
Stainless-steel
Mh, H/M=0.7
Mh, H/M=1.4
p=8*10-5 torr
H=600 Oe
Fig. 3 The current-voltage characteristics of the
reflective discharge
Fig.4. The radial distribution of plasma density
in the reflective discharge
-0,8 -0,6 -0,4 -0,2 0,0 0,2 0,4 0,6 0,8
0
5
10
15
20
25
n
* 1
0 9
c
m
- 3
*R, cm
Stainless-steel
Mh, H/M=0.4
Mh, H/M=1.7
p=1*10-4 torr
H=600 Oe
U=2,5 kV
which is made from materials that do not form hydrides
(in our experiments the cathode made from stainless
steel was used). The obtained result is agreed with the
data of the operation [6]. The authors explain this effect
by dissociative attachment of low-energy electrons to
hydrogen molecules, which is desorbed from the surface
of metal-hydride in vibrationally excited state. As a
result of this process the negative ion formation of
hydrogen H– near the cathode of the discharge takes
place. It leads to the reduction of the electron
concentration and prevents from the propagation of the
electron avalanches. Consequently in order to maintain
the discharge the higher voltage drop is necessary.
While hydrogen generates from the metal-hydride
cathode the intensity of desorption of vibrationally-
exited molecules of hydrogen is reduced. As the
consequence of this the contribution of the process of
dissociative attachment into losing of electrons near the
cathode of the discharge decreases. It is the reason for
the rise of the electron concentration and diminution of
voltage drop on the discharge.
The increase of working gas pressure leads to
approaching of the current-voltage characteristics of the
discharge using metal-hydride cathodes with different
initial degrees of saturation. In this case collision rate
increases and the mean-lifetime of negative ions in the
discharge diminishes [7]. Besides it also results in
reduction of lifetime of vibrationally excited state of
desorbed hydrogen molecules and decrease of capture
frequency of low-energy electrons near the cathode of
the discharge. Therefore it is observed a voltage
reduction on the discharge while the hydrogen pressure
increases in the gas-discharge cell even in case of
complete initial hydrogen saturation of the cathode
(H/M=1,4).
The typical radial distributions of plasma densities,
which were measured for different values of initial
hydrogen saturation of cathodes, are represented in fig.
4. It can be seen that comparing these dependencies the
considerable increase of the plasma density on the
discharge axis is observed in case of the cathode with
the maximum of initial degree of hydrogen saturation
(H/M=1,4). While concentration of hydrogen in the
metal-hydride cathode decreases the plasma density on
the discharge axis reduces and the shape of a
distribution curve approaches to the radial distribution,
which is typical for the discharge with the cathode that
is made from materials that do not form hydrides.
It is possible to explain obtained feature of plasma
density distribution in the discharge using metal-hydride
cathode by character of current density distribution of
ions bombarding the cathode. The radial distribution of
current density of ions falling into cathodes of reflective
discharge is well known to have the pronounced
maximum on an axis of the system. Taking into
consideration the conditions of our experiments the
hydrogen desorption from the metal-hydride is caused
by ion bombardment, the greatest intensity of desorption
will be observed from central area of the surface of the
metal-hydride cathode. As a result the stream of the
hydrogen having major density in paraxial area of the
discharge is formed. While hydrogen generates from
metal-hydride, the intensity of paraxial stream of
hydrogen is reduced, and the radial distribution of
plasma density approaches to the shape typical for
materials that do not form hydrides. As the material of
the cathode is a reversible getter of hydrogen the partly
saturated electrode under ions bombardment of its
surface will sorb hydrogen as well. It may be presumed
to explain inappreciable reducing of plasma density for
partially saturated metal-hydride cathode (Н/М=0,7) in
comparison with the cathode from materials that do not
form hydrides (fig. 4).
For the purpose of ascertaining this assumption the
measurements of energies distribution of hydrogen ions
bombarding the central area of the metal-hydride
cathode (fig. 5) were carried out. As one can see from
the dependencies that have been demonstrated the
degree of initial saturation influences the most probable
energy of paraxial group of ions falling into the metal-
hydride cathode. The reduction of initial hydrogen
saturation of metal-hydride leads to the increase of the
most probable energy of ions and to diminution of a
maximum of energy distribution curve of ions falling
into the collector of an energy analyzer. Such behavior
of energy distribution of ions is caused by the following
0 50 100 150 200 250 300
0,00
0,25
0,50
0,75
1,00
C
on
ve
nt
io
na
l u
ni
ts
U, eV
Mh, H/M=0.7
Mh, H/M=1.4
p=5*10-5 torr
H=600 Oe
U
d
=2.5 kV
I
d
=1mA
Fig.5. The energy distribution of the paraxial ion
group in the reflective discharge
reasons. In our experiments the aperture of the energy
analyzer was chosen in such a way that only those ions
that moved almost in parallel with the axes of the
system fell on the collector. The collisions of paraxial
group of ions with molecules of hydrogen stream
desorbed from the cathode lead to the loss of ion
energy. Therefore leftward bias (fig. 5) of a maximum
of energy distribution of ions is observed while initial
hydrogen saturation of the metal-hydride cathode
increases. On the other hand, the rise of the plasma
density on a discharge axis caused by a paraxial stream
of the desorbed hydrogen leads to the increase of ion
current falling into a collector of an energy analyzer as
well. As a result the observed character of changes in
the energy distribution of paraxial group of ions of
plasma is determined by the stream of hydrogen that is
desorbed from the metal-hydride cathode.
4. CONCLUSION
The experimental examination of the influence of a
degree of hydrogen saturation of a hydride-forming
getter material on the basis of Zr50V50 alloy on the
discharge performances and parameters of plasma of the
reflective discharge are carried out. The use of the
metal-hydride cathode is shown to be led to the essential
change of both exterior parameters of the discharge and
parameters of plasma. The dependencies of plasma
density and energy distribution of ions in paraxial field
of the discharge on a degree of hydrogen saturation of
the metal-hydride cathode are investigated. The
dependencies of plasma parameters of the discharge on
a degree of hydrogen saturation of the metal-hydride
cathode is established to be determined by the paraxial
stream of hydrogen that is desorbed from the surface of
this electrode under ion bombardment.
REFERENCES
1. Yu.F. Shmal'ko, V.V. Solovey and M.V. Lototsky.
Use of hydrides in systems for supplying vacuum
physical-energy installations // Hydrogen Energy
Progress X. Proc. 10-th Word Hydrogen Energy
Conf. (Cocoa Beach, Florida, U.S.A., 20 – 24 June,
1994). – Ed. by D.L.Block, T.N.Veziroglu. – Int.
Association for Hydrogen Energy, 1994, vol.2,
p.1311–1319.
2. Ye.V. Klochko, M.V. Lototsky, V.V. Popov, Yu.F.
Shmal'ko, V.N. Borysko. Investigation of plasma
interaction with metal hydride. //Int. J. Hydrogen
Energy. – 1999, vol.24, p.169–174.
3. G. Sandrock. Hydrogen – metal systems. //
Hydrogen Energy System. Production and
Utilization of Hydrogen and Future Aspects, ed. by
Y.Yürüm, Kluwer Academic Publ., 1995, p.135–
166
4. A. Stern, A. Resnik and D. Shaltiel. Thermal
Desorption Spectra of Hydrogen in HfV2Hx and
ZrV2Hx //J. Less-Common Met. – 1982, vol. 88,
p.431-440.
5. V.A. Yartis, I.Yu. Zavaliy, M.V. Lototsky,
I.I. Bulik, P.B. Novosad, Yu.F. Shmalko. The
material on the basis of Zr-V-Fe alloys as a
effective sorbents of hydrogen //Phys.-chem.
mechanics of materials. – 1991, vol.27, №2, p.26-
35. (in Russian).
6. Yu.F. Shmalko, V.M. Borisko, Ye.V. Klochko,
M.V. Lototsky, V.V. Solovey. About vibration
exiting of hydrogen molecules that are desorbed
from metal-hydrides. // Repor of NAS of Ukraine,
2000, № 11, p.91–95(in Russian).
7. H. Massey. Negative ions. М.: Мir, 1979. (in
Russian).
8. O.K. Kurbatov. The energy and angular
distributions of ions falling into the different parts
of cathode in a high voltage Penning discharge.
//JTF 1966, vol. 36(9), p.1665–1668. (in Russian)
|
| id | nasplib_isofts_kiev_ua-123456789-111157 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-30T11:04:07Z |
| publishDate | 2003 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Borisko, V.N. Klochko, Ye.V. Sereda, I.N. 2017-01-08T16:40:45Z 2017-01-08T16:40:45Z 2003 Influence of saturation degree of metal-hydride cathode on characteristics of penning type ion source of hydrogen / V.N. Borisko, Ye.V. Klochko, I.N. Sereda // Вопросы атомной науки и техники. — 2003. — № 4. — С. 217-220. — Бібліогр.: 8 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/111157 533.9 The experimental examinations of Penning type plasma source of hydrogen ions using metal-hydride cathode was carried out. The discharge characteristics, radial distributions of plasma parameters were measured in a gap between the anode and the metal-hydride cathode for different degree of hydrogen saturation of the cathode material. The plasma parameters and voltage drop on the discharge was shown to be depended on the degree of saturation with hydrogen of the metal-hydride cathode. Plasma density on the axis of the system was established to be increased in accordance to the increase of the initial hydrogen saturation of the metal-hydride cathode. This phenomenon is explained by the increase of a desorption intensity of hydrogen from the central part of the surface of the metal-hydride cathode. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Газовый разряд, ППР и их применения Influence of saturation degree of metal-hydride cathode on characteristics of penning type ion source of hydrogen Article published earlier |
| spellingShingle | Influence of saturation degree of metal-hydride cathode on characteristics of penning type ion source of hydrogen Borisko, V.N. Klochko, Ye.V. Sereda, I.N. Газовый разряд, ППР и их применения |
| title | Influence of saturation degree of metal-hydride cathode on characteristics of penning type ion source of hydrogen |
| title_full | Influence of saturation degree of metal-hydride cathode on characteristics of penning type ion source of hydrogen |
| title_fullStr | Influence of saturation degree of metal-hydride cathode on characteristics of penning type ion source of hydrogen |
| title_full_unstemmed | Influence of saturation degree of metal-hydride cathode on characteristics of penning type ion source of hydrogen |
| title_short | Influence of saturation degree of metal-hydride cathode on characteristics of penning type ion source of hydrogen |
| title_sort | influence of saturation degree of metal-hydride cathode on characteristics of penning type ion source of hydrogen |
| topic | Газовый разряд, ППР и их применения |
| topic_facet | Газовый разряд, ППР и их применения |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/111157 |
| work_keys_str_mv | AT boriskovn influenceofsaturationdegreeofmetalhydridecathodeoncharacteristicsofpenningtypeionsourceofhydrogen AT klochkoyev influenceofsaturationdegreeofmetalhydridecathodeoncharacteristicsofpenningtypeionsourceofhydrogen AT seredain influenceofsaturationdegreeofmetalhydridecathodeoncharacteristicsofpenningtypeionsourceofhydrogen |