Penning-type H⁻ ion source with metal hydride cathode in pulsating regime
The features of H⁻ ion emission from gas-feed-free Penning-type ion source with metal hydride cathode have been studied in pulsating regime. The metal hydride cathode provided local injection of hydrogen in activated state and impacts on Penning discharge ability to emit H⁻ ions in the longitudinal...
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| Cite this: | Penning-type H⁻ ion source with metal hydride cathode in pulsating regime / I. Sereda, Ya. Hrechko, N. Azarenkov // Problems of Atomic Science and Technology. — 2023. — № 4. — С. 126-128. — Бібліогр.: 12 назв. — англ. |
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Sereda, I. Hrechko, Ya. Azarenkov, N. 2023-12-11T12:35:27Z 2023-12-11T12:35:27Z 2023 Penning-type H⁻ ion source with metal hydride cathode in pulsating regime / I. Sereda, Ya. Hrechko, N. Azarenkov // Problems of Atomic Science and Technology. — 2023. — № 4. — С. 126-128. — Бібліогр.: 12 назв. — англ. 1562-6016 PACS: 29.25.Ni DOI: https://doi.org/10.46813/2023-139-146-126 https://nasplib.isofts.kiev.ua/handle/123456789/196189 The features of H⁻ ion emission from gas-feed-free Penning-type ion source with metal hydride cathode have been studied in pulsating regime. The metal hydride cathode provided local injection of hydrogen in activated state and impacts on Penning discharge ability to emit H⁻ ions in the longitudinal direction. For stimulation of pre-excited hydrogen desorption from metal hydride the voltage pulse (4.5 kV, τ ≈ 15 μs) was performed against the background constant voltage of 6 kV on the anode of the discharge. The H⁻ ion current of about 0.2 mA was obtained. Досліджено особливості емісії іонів H⁻ джерела іонів пеннінгівського типу з металогідридним катодом у пульсуючому режимі. Металогідридний катод забезпечував локальну інжекцію водню в активованому стані та впливав на здатність пеннінгівського розряду емітувати іони H⁻ у поздовжньому напрямку. Для стимуляції десорбції попередньо збудженого водню з гідриду металу до анода розряду підводили імпульс напруги (4,5 кВ, τ ≈ 15 мкс) на фоні постійної напруги 6 кВ. Отримано струм іонів H⁻ близько 0,2 мА. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Problems of Atomic Science and Technology Gas discharge, plasma-beam discharge and their applications Penning-type H⁻ ion source with metal hydride cathode in pulsating regime Джерело іонів H⁻ пеннінгівського типу з металогідридним катодом у пульсуючому режимі Article published earlier |
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Penning-type H⁻ ion source with metal hydride cathode in pulsating regime |
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Penning-type H⁻ ion source with metal hydride cathode in pulsating regime Sereda, I. Hrechko, Ya. Azarenkov, N. Gas discharge, plasma-beam discharge and their applications |
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Penning-type H⁻ ion source with metal hydride cathode in pulsating regime |
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Penning-type H⁻ ion source with metal hydride cathode in pulsating regime |
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Penning-type H⁻ ion source with metal hydride cathode in pulsating regime |
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Penning-type H⁻ ion source with metal hydride cathode in pulsating regime |
| title_sort |
penning-type h⁻ ion source with metal hydride cathode in pulsating regime |
| author |
Sereda, I. Hrechko, Ya. Azarenkov, N. |
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Sereda, I. Hrechko, Ya. Azarenkov, N. |
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Gas discharge, plasma-beam discharge and their applications |
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Gas discharge, plasma-beam discharge and their applications |
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2023 |
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English |
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Problems of Atomic Science and Technology |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Джерело іонів H⁻ пеннінгівського типу з металогідридним катодом у пульсуючому режимі |
| description |
The features of H⁻ ion emission from gas-feed-free Penning-type ion source with metal hydride cathode have been studied in pulsating regime. The metal hydride cathode provided local injection of hydrogen in activated state and impacts on Penning discharge ability to emit H⁻ ions in the longitudinal direction. For stimulation of pre-excited hydrogen desorption from metal hydride the voltage pulse (4.5 kV, τ ≈ 15 μs) was performed against the background constant voltage of 6 kV on the anode of the discharge. The H⁻ ion current of about 0.2 mA was obtained.
Досліджено особливості емісії іонів H⁻ джерела іонів пеннінгівського типу з металогідридним катодом у пульсуючому режимі. Металогідридний катод забезпечував локальну інжекцію водню в активованому стані та впливав на здатність пеннінгівського розряду емітувати іони H⁻ у поздовжньому напрямку. Для стимуляції десорбції попередньо збудженого водню з гідриду металу до анода розряду підводили імпульс напруги (4,5 кВ, τ ≈ 15 мкс) на фоні постійної напруги 6 кВ. Отримано струм іонів H⁻ близько 0,2 мА.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/196189 |
| citation_txt |
Penning-type H⁻ ion source with metal hydride cathode in pulsating regime / I. Sereda, Ya. Hrechko, N. Azarenkov // Problems of Atomic Science and Technology. — 2023. — № 4. — С. 126-128. — Бібліогр.: 12 назв. — англ. |
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| first_indexed |
2025-11-25T22:49:29Z |
| last_indexed |
2025-11-25T22:49:29Z |
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| fulltext |
126 ISSN 1562-6016. Problems of Atomic Science and Technology. 2023. № 4(146)
https://doi.org/10.46813/2023-139-146-126
PENNING-TYPE H
–
ION SOURCE WITH METAL HYDRIDE CATHODE
IN PULSATING REGIME
I. Sereda
1
, Ya. Hrechko
1
, N. Azarenkov
1,2
1
V.N. Karazin Kharkiv National University, Kharkiv, Ukraine;
2
National Science Center “Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine
E-mail: igorsereda@karazin.ua
The features of H
–
ion emission from gas-feed-free Penning-type ion source with metal hydride cathode have
been studied in pulsating regime. The metal hydride cathode provided local injection of hydrogen in activated state
and impacts on Penning discharge ability to emit H
–
ions in the longitudinal direction. For stimulation of pre-excited
hydrogen desorption from metal hydride the voltage pulse (4.5 kV, τ ≈ 15 µs) was performed against the background
constant voltage of 6 kV on the anode of the discharge. The H
–
ion current of about 0.2 mA was obtained.
PACS: 29.25.Ni
INTRODUCTION
The independence of neutralization efficiency at
high beam energy determines the main fields of H
–
ions
application for the production of neutral beam for fusion
[1] and medical radionuclides in cyclotrons [2]. The
construction of H
–
sources is usually based on two well-
known physical mechanisms [3]. It is the direct for-
mation of H
–
ions in plasma, when highly rovibrational-
ly excited molecules H2* produced with fast electrons,
dissociate after colliding with slow electrons. The re-
sulting current of H
–
ions is determined by the flow of
neutral hydrogen and is limited by the destruction pro-
cesses of negative ions, when the pressure in cold plas-
ma rises more than 0.1 Pa [4]. Next one is the produc-
tion of H
–
ions on the plasma electrode surface covered
with cesium [5]. It gives much greater intensity of H
–
current, but cesium leakage to the acceleration zone can
cause a breakdown. So, the search for material for effi-
cient cesium-free ion source operation is currently the
great challenge [6].
Metal hydride application as a plasma electrode mate-
rial is known to increase the production of negative hy-
drogen ions due to H2* molecules activation at the metal
hydride surface, which then can be easily converted to H
–
ions by dissociative electron attachment [8]. Previously
we reported about successful application of metal hydride
cathode in Penning negative ion source [7], where we
obtained the H
–
current of 5 µA at a power input of 10 W.
For further increase of source performance, the uptake
rate of pre-excited hydrogen molecules from the cathode
should be raised. The purpose of this paper is to increase
the yield of H
–
ions by the pulsating regime implementa-
tion followed by the stimulation of pre-excited hydro-
gen desorption from metal hydride due to the current of
charged particles impact from plasma.
1. EXPERIMENTAL SETUP
The scheme of a Penning cell used as an ion source
is shown in Fig. 1. Hydrogen plasma is generated be-
tween a metal hydride cathode (1), a copper cathode (5)
and a tube-shaped anode (4) with a longitudinal magnet-
ic field Hzo0 = 0…0.1 T. The specified dimensions of the
cell were chosen experimentally for the stable operation
of the discharge without break-downs. The metal hy-
dride cathode was produced from hydride-forming alloy
Zr50V50 with the hydrogen amount absorbed by the ma-
terial on the level of 190 cm
3
/g at atmospheric pressure
and room temperature. Temperature stabilization of
metal hydride at a level which is lower than the temper-
ature of thermal destruction of hydride phase ensures
activated hydrogen H2* uptake mainly by ion-stimulated
processes from the surface of metal hydride locally to
the cathode region.
z,c
m
0 1 2 3 4 5 6 7 8 9
Hz0
4 8
5 7
6
2
1
9
z water
Icol 3 1
kΩ
+Ugrid
IAC
Hzo0
Hcoil
20 MΩ 20 kΩ 12 Ω 10 kΩ
+U0
UDC 4.7 pF 16 µF 4.7 nF + - ignition
100 pF Ud
UAC
Fig. 1. The scheme of a Penning-type ion source:
1 – metal hydride cathode; 2 – cathode-holder;
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
Hydrogen activation changes the Penning discharge
properties and a flow of negatively charged particles
together with positive ions starts yielding along the ex-
ternal magnetic field through an aperture in the cathode
(5). The separation of negative ions H
–
from electrons
and positive ions is performed by electromagnetic filter,
which consists of a grid (6) for positive ions retarding, a
magnetic coil (8) to divert electrons, a collector of di-
verted electrons (7) and a collector of extracted axial
beam of H
–
ions (9). The coil (8) creates a reverse mag-
netic field Hcoil. The required values of the resulting
field Hz0 and grid potential (Ugrid = 1.65 kV) in the filter
is calculated from the analysis of electrons and H
–
ions
ISSN 1562-6016. Problems of Atomic Science and Technology. 2023. № 4(146) 127
trajectories by numerical solution of a motion equation
in axially symmetric electric and magnetic fields [7].
The grid (6) in addition to the retarding function for
positive ions accelerates electrons and H
–
ions to ap-
proximately the same energy followed by the successful
separation in the magnetic field Hz0 of the filter.
The discharge operation is ensured by applying a
positive potential to the anode. The electrical circuit
provides the supply of pulse voltage of 4.5 kV against
the background voltage Ud of 6 kV. The residual pres-
sure in the vacuum chamber was 0.2 mPa.
2. RESULTS AND DISCUSSION
The ability of Penning source with metal hydride
cathode of emitting negative particles in longitudinal
direction was described in [7]. It occurs at low pressure,
high magnetic field and discharge voltage, when a field-
free plasma region is formed along the axis, containing
electrons oscillating between the cathodes. Discharge
voltage drops in the region of negative space charge
layer close to an anode [10]. The cathode layer may still
present, but with low voltage drop. H
–
ions are formed
close to the metal hydride cathode due to the dissocia-
tive attachment of slow electrons (2…4 eV) to pre-
excited hydrogen molecules H2*, which are desorbed
from metal hydride due to ion-stimulated mechanism
under the influence of ion current from plasma [8]. The
ion current determines the rate of desorption and the
equilibrium pressure in the discharge volume [11]. So,
the easiest way of improving the efficiency of H
–
pro-
duction is to intensify the desorption rate by the increas-
ing of ion current from plasma [3].
To implement this idea, we used pulsating regime of
gas-feed-free Penning type H
–
ion source with metal
hydride cathode, when the voltage pulse of 4.5 kV was
performed against the background constant voltage of
6 kV on the anode. In case of only pulse regime, the
only surface of metal hydride works. And after several
pulses, when the stored in surface layer hydrogen has
been evacuated, the efficiency of H
–
production drops.
In pulsating regime, due to the energy transfer from
background continuous discharge, hydrogen releases
from thicker surface layer or even from the whole vol-
ume of metal hydride.
The oscillograms of discharge voltage Ud, pulse dis-
charge current Id and H
–
current are shown in Fig. 2.
The distortion of the Id curve especially in the beginning
of the pulse is a consequence of the application of Sa-
vitzky-Golay smoothing method. However, despite the
distortion, it is clearly seen the coincidence of Id and H
–
current peaks at t ~ 10 µs, which pointed on the intensi-
fication of activated hydrogen desorption and the in-
creasing of H
–
production efficiency.
0 10µ 20µ 30µ 40µ 50µ 60µ
-60
-40
-20
0
20
40
H
--
c
u
rr
en
t,
m
A
t, sec
Hzo0 = 0,05 T
UMH = 0 V
0 10µ 20µ 30µ 40µ 50µ 60µ
6
8
10
Ud
U
d
,
k
V
-10
-8
-6
-4
-2
0
2
4
6
I d
,
m
A
Id
0 10µ 20µ 30µ 40µ 50µ 60µ
-100
-50
0
H
--
c
u
rr
en
t,
m
A
t, sec
Hzo0 = 0,07 T
UMH = 0 V
0 10µ 20µ 30µ 40µ 50µ 60µ
6
8
10
Ud
U
d
,
k
V
-4
0
4
8
12
I d
,
m
A
Id
0 10µ 20µ 30µ 40µ 50µ 60µ
-80
-60
-40
-20
0
20
H
--
c
u
rr
en
t,
m
A
t, sec
Hzo0 = 0,09 T
UMH = 0 V
0 10µ 20µ 30µ 40µ 50µ 60µ
6
8
10
Ud
U
d
,
k
V
-4
0
4
8
12
I d
,
m
A
Id
Fig. 2. The oscillograms of discharge voltage Ud pulse discharge current Id and H
–
current at P = 0.2 mPa
A strong dependence of the H
–
current on external
magnetic field can be explained by the discharge transi-
tion to another mode, when the increase of pressure dur-
ing a pulse leads to a jump of the voltage drop from the
anode layer to the cathode and makes it difficult for
negative particles of escaping along the axis [12]. But
according to the estimations performed in [12] high
magnetic field suppresses the discharge transition and
the maximum values of H
–
current is observed only for
high magnetic field Hzo0 = 0.07…0.1 T.
Sufficient enhance of negative current output can be
achieved by the supply of negative potential on metal
hydride cathode UMH. Due to central field-free plasma
region negative particles are additionally pushed out. A
positive electrical bias on the cathode-reflector did not
lead to any significant result, which testifies to the crea-
tion of H
–
ions near the metal hydride cathode followed
by the pushing them out by electrical bias. Fig. 3 shows
the dependence of the value of H
–
current on UMH at
different external magnetic field Hzo0 in constant regime
of discharge operation at Ud of 6 kV.
20 40 60 80 100 120 140 160 180 200
-10
-8
-6
-4
-2
H
- c
u
rr
en
t
in
c
o
n
st
an
t
re
g
im
e,
m
A
Hzo0 = 0.09 T
Hzo0 = 0.07 T
Hzo0 = 0.05 T
-UMH , V
Fig. 3. The dependence of H
–
current on UMH
in constant regime Ud = 6 kV
Fig. 4 represents the same, but when the pulse volt-
age of 4.5 kV was supplied against the background Ud
of 6 kV.
128 ISSN 1562-6016. Problems of Atomic Science and Technology. 2023. № 4(146)
20 40 60 80 100 120 140 160 180 200
-240
-220
-200
-180
-160
-140
-120
-100
-80
-60
-40
-20
H
- c
u
rr
en
t
in
p
u
ls
e
re
g
im
e,
m
A
Hzo0 = 0.09 T
Hzo0 = 0.07 T
Hzo0 = 0.05 T
-UMH , V
Fig. 4. The dependence of H
–
current on UMH
in pulsating regime (Ud = 6 kV + 4.5 kV in pulse)
In both cases, there is a general trend of increasing
the H
–
current from the UMH value of about -60 V with
following decline after -120 V. This behavior is deter-
mined by the temperature of plasma electrons (Te),
which have Boltzmann distribution and are slowed
down in the cathode layer [9].
According to the calculations performed in [9], the
higher values of Te, the closer the reflection point of
plasma electrons to the cathode surface and higher val-
ues of UMH is needed for efficient formation and ejec-
tion of H
–
ions.
Reaching the maximum of H
–
current at certain UMH
is due to the competitive processes of H
–
ion production
and destruction, because increasing of UMH pushes the
formation area of H
–
ions away from the surface, and Te
increasing reduces the cross section of H
–
ion formation.
CONCLUSIONS
The efficient production of H
–
ions occurs due to the
dissociative attachment of thermal electrons to activated
hydrogen molecules desorbed from metal hydride cath-
ode. Negative electrical bias of metal hydride cathode
contributes to a more efficient output of negative ions
along the axis of the Penning cell. The value of electri-
cal bias is determined by the temperature of plasma
electrons ejected from anode layer on the cathodes.
When it takes -100 V, the current of H
–
ions reaches the
maximum value of about 0.2 mA. High magnetic field
suppresses the potential redistribution in the cell and the
maximum values of H
–
current is observed only for high
magnetic field Hzo0 = 0.07…0.1 T, when field-free
plasma region is formed along the axis.
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mean free path and its possible implications // Se-
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Article received 15.05.2023
ДЖЕРЕЛО ІОНІВ H
–
ПЕННІНГІВСЬКОГО ТИПУ З МЕТАЛОГІДРИДНИМ КАТОДОМ
У ПУЛЬСУЮЧОМУ РЕЖИМІ
І. Середа, Я. Гречко, М. Азарєнков
Досліджено особливості емісії іонів Н
–
джерела іонів пеннінгівського типу з металогідридним катодом у
пульсуючому режимі. Металогідридний катод забезпечував локальну інжекцію водню в активованому стані
та впливав на здатність пеннінгівського розряду емітувати іони H
–
у поздовжньому напрямку. Для стимуля-
ції десорбції попередньо збудженого водню з гідриду металу до анода розряду підводили імпульс напруги
(4,5 кВ, τ ≈ 15 мкс) на фоні постійної напруги 6 кВ. Отримано струм іонів H
–
близько 0,2 мА.
|