Investigation of system for external injection of H⁻ ion beam on cyclotrons
The article presents results of experimental studies carried out at an installation (“SVITS”) simulating a system for external injection of H⁻ions with the beam current of up to 2 mA and energy up to 30 keV for cyclotrons. The beam characteristics (current, current density distribution over cross-se...
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| Zitieren: | Investigation of system for external injection of H⁻ ion beam on cyclotrons / O.L. Veresov, S.V. Grigorenko, A.P. Strokach, S.Yu. Udovichenko, S.S. Tsygankov, Yu.V. Zuev // Вопросы атомной науки и техники. — 2004. — № 2. — С. 60-63. — Бібліогр.: 8 назв. — англ. |
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irk-123456789-793302015-04-01T03:01:52Z Investigation of system for external injection of H⁻ ion beam on cyclotrons Veresov, O.L. Grigorenko, S.V. Strokach, A.P. Udovichenko, S.Yu. Tsygankov, S.S. Zuev, Yu.V. Элементы ускорителей The article presents results of experimental studies carried out at an installation (“SVITS”) simulating a system for external injection of H⁻ions with the beam current of up to 2 mA and energy up to 30 keV for cyclotrons. The beam characteristics (current, current density distribution over cross-section, phase diagrams) as well as gas pressure were measured in three points along the beam axis. The influence of the compensation and de-compensation of the beam space charge on the beam dynamics in the plasma produced under beam transportation was studied. Приводяться результати експериментальних досліджень, виконаних на установці, що моделює систему зовнішньої інжекції Н⁻ зі струмом пучка до 2 мА й енергією до 30 кеВ для циклотрону. Вимір характеристик пучка (струму, розподілу густини струму по перетині, фазових діаграм), а також тиску газу провадиться в трьох точках уздовж осі пучка. Відзначено вплив на динаміку пучка в інжекторі ефекту компенсації власного просторового заряду пучка іонами плазми, що напрацьовується при русі пучка в залишковому газі. Приводятся результаты экспериментальных исследований, выполненных на установке, моделирующей систему внешней инжекции Н⁻ с током пучка до 2 мА и энергией до 30 кэВ для циклотрона. Измерение характеристик пучка (тока, распределения плотности тока по сечению, фазовых диаграмм), а также давления газа производится в трех точках вдоль оси пучка. Отмечено влияние на динамику пучка в инжекторе эффекта компенсации собственного пространственного заряда пучка ионами плазмы, нарабатываемой при движении пучка в остаточном газе. 2004 Article Investigation of system for external injection of H⁻ ion beam on cyclotrons / O.L. Veresov, S.V. Grigorenko, A.P. Strokach, S.Yu. Udovichenko, S.S. Tsygankov, Yu.V. Zuev // Вопросы атомной науки и техники. — 2004. — № 2. — С. 60-63. — Бібліогр.: 8 назв. — англ. 1562-6016 PACS: 29.20.Hm, 29.25.Ni http://dspace.nbuv.gov.ua/handle/123456789/79330 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Элементы ускорителей Элементы ускорителей |
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Элементы ускорителей Элементы ускорителей Veresov, O.L. Grigorenko, S.V. Strokach, A.P. Udovichenko, S.Yu. Tsygankov, S.S. Zuev, Yu.V. Investigation of system for external injection of H⁻ ion beam on cyclotrons Вопросы атомной науки и техники |
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The article presents results of experimental studies carried out at an installation (“SVITS”) simulating a system for external injection of H⁻ions with the beam current of up to 2 mA and energy up to 30 keV for cyclotrons. The beam characteristics (current, current density distribution over cross-section, phase diagrams) as well as gas pressure were measured in three points along the beam axis. The influence of the compensation and de-compensation of the beam space charge on the beam dynamics in the plasma produced under beam transportation was studied. |
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Article |
| author |
Veresov, O.L. Grigorenko, S.V. Strokach, A.P. Udovichenko, S.Yu. Tsygankov, S.S. Zuev, Yu.V. |
| author_facet |
Veresov, O.L. Grigorenko, S.V. Strokach, A.P. Udovichenko, S.Yu. Tsygankov, S.S. Zuev, Yu.V. |
| author_sort |
Veresov, O.L. |
| title |
Investigation of system for external injection of H⁻ ion beam on cyclotrons |
| title_short |
Investigation of system for external injection of H⁻ ion beam on cyclotrons |
| title_full |
Investigation of system for external injection of H⁻ ion beam on cyclotrons |
| title_fullStr |
Investigation of system for external injection of H⁻ ion beam on cyclotrons |
| title_full_unstemmed |
Investigation of system for external injection of H⁻ ion beam on cyclotrons |
| title_sort |
investigation of system for external injection of h⁻ ion beam on cyclotrons |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2004 |
| topic_facet |
Элементы ускорителей |
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http://dspace.nbuv.gov.ua/handle/123456789/79330 |
| citation_txt |
Investigation of system for external injection of H⁻ ion beam on cyclotrons / O.L. Veresov, S.V. Grigorenko, A.P. Strokach, S.Yu. Udovichenko, S.S. Tsygankov, Yu.V. Zuev // Вопросы атомной науки и техники. — 2004. — № 2. — С. 60-63. — Бібліогр.: 8 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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| first_indexed |
2025-07-06T03:24:41Z |
| last_indexed |
2025-07-06T03:24:41Z |
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| fulltext |
INVESTIGATION OF SYSTEM FOR EXTERNAL
INJECTION OF H-ION BEAM ON CYCLOTRONS
O.L.Veresov, S.V.Grigorenko, A.P.Strokach, S.Yu.Udovichenko, S.S.Tsygankov, Yu.V. Zuev
The Scientific Research Institute of Electrophysical Apparatus, Scientific Production Complex
of Linear Accelerators and Cyclotrons, Saint-Petersburg, Russia,
E-mail: npkluts@niiefa.spb.su
The article presents results of experimental studies carried out at an installation (“SVITS”) simulating a system
for external injection of H-ions with the beam current of up to 2 mA and energy up to 30 keV for cyclotrons. The
beam characteristics (current, current density distribution over cross-section, phase diagrams) as well as gas pressure
were measured in three points along the beam axis. The influence of the compensation and de-compensation of the
beam space charge on the beam dynamics in the plasma produced under beam transportation was studied.
PACS: 29.20.Hm, 29.25.Ni
INTRODUCTION
The system for external injection of negative H- ions
into a cyclotron-type accelerator is intended for forming
a beam with a current of more than 1mA and energy of
10-30 keV and its transport for a distance of several me-
ters. The system contains: a plasma source of ions, elec-
trostatic beam-forming optics, a beam-transportation
channel with elements of magnet focusing system and
an inflector required to bend the beam to the cyclotron
median plane.
The “SVITS” installation (the system of H- beam ex-
ternal injection into cyclotron) was constructed at the
D.V. Efremov Institute, NIIEFA in the middle 90-ies. [1
]. The facility is intended for try-out and optimization of
separate elements of the external injection system and
production of output H- beam with specified parameters
optimal for injection to the central area of cyclotron.
The problem of negative ion beam transportation un-
der gas leaking from the ion source to the transportation
channel is highly topical but it is rather far from being
solved. There is a series of works on this problem [2-5].
Collective processes causing excitation of a spectrum of
plasma oscillations result in heating of fast ions and dy-
namic de-compensation of the space beam charge. The
effect of strong de-compensation of negative ion beam
with a current density of 50 mA/cm2 was discovered by
the authors [6]. In ref. [5] is suggested a theoretical
model describing the process of dynamic de-compensa-
tion of space charge of ion beam due to developing ion
beam-plasma instability; analytic expressions for plas-
ma ion density and stationary electric field distribution
in partially compensated beam are obtained. Numerical
solution of the equation of beam motion in self electric
field and external magnetic field allowed us to deter-
mine the effect of plasma charged particles on the trans-
portation of the 30 mA, 30 keV negative ion beam
through the cyclotron injector (ref. [5]).
This report presents results of numerical simulation
of ion beam dynamics in the channel of external injec-
tion in comparison with results obtained on the
“SVITS” installation with the H-beam of ≈1.5 mA and
energies of 12 and 24 keV.
EXPERIMENTAL EQUIPMENT
Fig.1 presents a schematic of the “SVITS” installa-
tion.
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PROBLEMS OF ATOMIC SIENCE AND TECHNOLOGY. 2004. № 2.
Series: Nuclear Physics Investigations (43), p.60-63.60
mailto:npkluts@niiefa.spb.su
Fig.1. Schematic of the “SVITS” installation: 1-ion source; 2-vacuum chamber; 3-vacuum gate valve;
4-turbomolecular pump (750 l/s); 5-solenoid magnetic lens; 6- beam emittance, current and current density distri-
bution sensor; 7--“pepper-pot” current collector; 8-bellows; 9-ion channel; 10-diagnostic chamber of ion beam;
11-capacity probe
The “cusp”-type volume-plasma ion source (1) with
transverse magnetic filter is described in ref. [7]. At dis-
charge current of 20 A this source (with the emission
electrode aperture 5mm in diameter) produced an H- ion
beam with a current of more than 2 mA, energy of
30 keV and normalized emittance of 0.3 π mm mrad.
The 80 mm long solenoidal magnetic lens (5) provides
maximum induction of axial magnetic field up to 0.4 T.
The emittance scanner (6) also functions as a beam
total current meter and meter of radial current density
distribution. The method of the beam emittance determi-
nation is based on measuring the divergence of elemen-
tary sheet beams cut off from the main beam with a nar-
row slit diaphragm. The measurements being complet-
ed, the emittance scanner sensor is removed out of the
beam.
The “pepper-pot” type current collector (7) is fixed
in vacuum chambers for the period of the beam align-
ment. Behind the current collector, there is placed a
quartz glass, which provides visual information about
the beam structure and sizes.
The chamber of ion beam diagnostics (10) is located
at the output of the ion channel. It is equipped with a
moving sensor, which serves to measure the beam total
current, current density distribution over the radius and
beam emittance.
The capacitive probe (11), of the design similar to
that in [6], serves to measure the potential distribution in
the beam cross-section.
All vacuum chambers, including the diagnostic
chamber, are equipped with vacuum pressure gauges.
RESULTS OF MEASUREMENTS
AND CALCULATIONS
When measuring the beam characteristics, we kept
constant the operating mode of the ion source with the
following parameters: discharge current-15 A; discharge
voltage-100 V; extraction voltage-2.8 kV; current of ex-
tracting electrode-50mA, H2 pressure in the source-10-2
torr, pressure in the first chamber- 1.2×10–4 torr, pres-
sure in the second chamber-3.5×10-5 torr, pressure in the
diagnostic chamber-4.0×10-5 torr.
The beam parameters in the first chamber were mea-
sured to form a beam with matched phase volume at the
magnetic lens input. In this case at an energy of Wb=24
kev the current of H-beam was Ib=1.7 mA, radius-Rb=7
mm, divergence–R’=20 mrad and normalized emit-
tance-εn=0.32 π mm·mrad.
Fig.2 (“a” and “b”) demonstrate measured distribu-
tions of current density and diagrams of the beam emit-
tance in the second chamber for two versions:
1) Wb=24 keV, Ib=1.5 mA, induction in the center of the
lens - Bmax=0.26 T; 2) Wb=12 keV, Ib=1.35 mA,
Bmax=0.18 T. In the second case the beam was initially
accelerated up to 19 keV and then decelerated down to
12 keV. The lens field induction was chosen in such a
way as to minimize the beam sizes at the system output.
In ref. [5] we obtained an expression for critical gas
density at which the de-compensation of the ion beam
occurs. In this expression transverse ion-plasma oscilla-
tions were taken into account: ngs ≈ vs/3σivbxb, where: vb
and xb are the beam longitudinal velocity and beam
transverse dimension, respectively, σi is the cross-sec-
tion of a gas molecule ionized with a beam ion,
vs=(Te/mi)1/2 is the ion sound velocity.
-3 -2 -1 0 1 2 3
0
1
2
3
4
5
J H
-,
µA
/m
m2
R, cm
E
b
=12 keV
E
b
=24 keV
Fig.2a. Distribution of the beam current density
in the second chamber
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PROBLEMS OF ATOMIC SIENCE AND TECHNOLOGY. 2004. № 2.
Series: Nuclear Physics Investigations (43), p.60-63.61
-2 -1 0 1 2
-15
-10
-5
0
5
10
15
R
',
m
ra
d.
R, cm
Eb=12 keV
Eb=24 keV
Fig.2b. Diagram of the beam emittance
in the second chamber
Values of H2 critical pressure, which can be derived
from this expression, are: 8.4×10–5 torr (for 24 keV) and
6×10–5 torr (for 12 keV). Thus, in compliance with the
theory, conditions for de-compensation of the beam
space discharge in the second vacuum chamber are pro-
vided in both the cases. However, increment and ampli-
tude of oscillations are rather small and the degree of
de-compensation is close to zero due to large (∼2cm) ra-
dius of the beam. Further, as the beam moves to the di-
agnostic chamber, the beam radius is decreased and
negative potential near the beam axis should be in-
creased due to larger amplitude of plasma transverse ion
oscillations and larger ejection of positive ions to the
walls of the ion guide. Under these conditions the mode
of the space charge weak overcompensation is main-
tained at the beam periphery. In [8] the positively and
negatively charged areas in the H-beam cross-section at
ng < ngc were experimentally discovered.
Fig.3 (a,d) demonstrate calculated beam trajectories
for two versions: Wb=24 keV, Ib=1.5 mA, Bmax=0.26 T,
εn=0.4 π mm mrad. 2) Wb=12 keV, Ib=1.35 mA,
Bmax=0.18 T, εn=0.25 π mm mrad. Envelopes calculated
in the approximation of uniformly charged beam with a
de-compensation degree of 0.0, 0.1 and 0.2 are also
shown on the same figures.
Fig.3 (b,e) shows calculated diagrams of emittance
at the system output for versions1 and 2, respectively.
Fig.3 (c,f) shows photos of the beam cross-section in
the diagnostic chamber for the same two versions.
a) (ver. 1) b) (ver. 1) c) (ver. 1)
d) (ver. 2) e) (ver. 2)
f) (ver. 2)
Fig.3(a,d). Calculated beam trajecto-
ries and envelopes with different de-
compensation degree
Fig.3(b,e). Calculated diagram of
beam emittance at the injector out-
put
Fig.3(c,f).Photos of the beam
at the injector output.
In the calculations we assumed that the beam space
charge was fully compensated at the section from the
ion source to the emittance scanner in the second cham-
ber. Trajectories (z=0) were started from this emittance
scanner and ended in the diagnostic chamber (the drift
part was 163 cm long). 300 trajectories were involved in
the calculation. Initial distribution of particles in the 4-
dimensional phase space was specified uniform. In the
point z=0, the amplitude of plasma potential oscillations
was assumed to be 1 V.
From Fig.3 it is seen that for the version with
Wb=24 keV the de-compensation effect is rather weak
and at a given emittance practically is not seen. With
twice reduction of the beam energy (Wb=12 keV) and
with constant current magnitude, the de-compensation
effect is appreciably heightened. Distribution of
particles over the beam cross-section at the output of the
system becomes non-uniform. The effective emittance
is more than 1.5 times increased.
Results of probe measurements in the second cham-
ber at beam energy of 12 keV have demonstrated the
62
following. The ne/ni ratio (where ne, ni are the electron
and ion concentrations in plasma), obtained as a result
of the analysis of probe characteristics, was in the range
of (2-5)·10–3. Such a low concentration of electrons is
indicative of the de-compensated state of the beam. Po-
tential fluctuations with an amplitude of 0.2-0.5 V and
frequency of∼ϖpi (ϖpi is the Langmuir frequency of
ions) were observed in the beam. Floating potential of
the capacitive probe on the beam axis was 0.45 V.
When the probe is moved from the beam axis to the
chamber wall, its potential smoothly rises up to 0.82 V
and then drops. The potential has its maximum at a dis-
tance of 1.7 cm from the axis that corresponds to the
beam effective radius. With 1.5 times higher induction
of the magnetic field of the lens, the beam effective ra-
dius is reduced to 0.5 cm. In this case the potential on
the beam axis is 0.68 V and the potential on the beam
radius is 1,3 V, respectively. The capacitive probe po-
tential is higher than that of the beam by an average en-
ergy of secondary electrons knocked out of the probe
under the beam action. If the probe is made of tungsten
with 0,5% of Tho, the average energy of secondary
electrons is lower than 1 eV. Thus, in the area near the
beam axis, the potential is minimum and can acquire
negative values. On the beam periphery, weak overcom-
pensation of the space charge and positive potential are
observed.
CONCLUSIONS
The experimentally obtained results confirm that
compensation and partial de-compensation of the space
charge of the beam of negative ions occurs under gas
leaking to the transportation channel from the ion
source. These results agree with experimental data of
other authors[6-8] as well as with analytical studies of
potential distribution in a partially de-compensated
beam [5].
The dynamics of the beam moving under plasma ion
oscillations was calculated by the method of large parti-
cles by solving the motion equation. The results were
compared with the results obtained by the method of en-
velopes with different degrees of compensation.
Differences in the beam dynamics of these two mod-
els have been observed, which are due to non-linear
character of the stationary electric field distribution over
the beam radius in the first case.
Experimentally found positively and negatively
charged areas in the cross-section of H- beam affect its
dynamics and results in an increase of its effective emit-
tance.
We should note that in a low current beam (Ib≤
1 mA) the effect of the space charge de-compensation
and changes in the beam dynamics are weak. With high-
er beam current, they will have increased their impor-
tance.
The carried out investigations are aimed at the con-
struction of H- ion injector for new-generation cy-
clotrons intended for production of medical isotopes
nowadays designed in the D.V. Efremov Institute, NI-
IEFA.
REFERENCES
1. Yu.V.Afanasiev, M.F.Vorogushin, S.V. Grig-
orenko, A.P. Strokach // Theses of 8th Conference
on Applied Charged Particle Accelerators in
Medicine and Industry. St.Petersburg. 1995, p.150.
2. S.Yu. Udovichenko // ZhTF. 1995, № 4, p.31-39 (in
Russian).
3. N.G. Vaganov, V.P. Sidorov, S.Yu. Udovchenko //
VANT. Series “Thermonuclear Fusion”. 1955, №4,
p.36-39.
4. S.Yu.Udovichenko // ZhTF. 1994, № 8, p.104-112
(in Russian).
5. S.V. Grigorenko, S.Yu. Udovichenko // ZhTF.
2003, № 7, p.119-124.
6. M.D. Gabovich, D.G. Dzhabbarov, A.P. Naida //
Pisjma v ZHETF. 1979, v.29, № 9, p. 536-539 (in
Russian).
7. Yu.V. Afanasiev, O.L. Veresov, S.V. Grigorenko,
A.P. Strokach, S.Yu. Udovichenko // Proceedings
of 10thMeeting on Applied Charged Particle Accel-
erators in Medicine and Industry. St.Petersburg,
2001.
8. V.P. Goretsky, A.P. Naida // Fizika Plasmy. 1985,
v.11, № 4, p.394-399 (in Russian).
ИССЛЕДОВАНИЕ СИСТЕМЫ ВНЕШНЕЙ ИНЖЕКЦИИ ПУЧКА ИОНОВ Н- ДЛЯ ЦИКЛОТРОНА
О.Л. Вересов, С.В. Григоренко, Ю.В. Зуев, А.П. Строкач, С.Ю. Удовиченко, С.С. Цыганков
Приводятся результаты экспериментальных исследований, выполненных на установке, моделирующей
систему внешней инжекции Н- с током пучка до 2 мА и энергией до 30 кэВ для циклотрона. Измерение ха-
рактеристик пучка (тока, распределения плотности тока по сечению, фазовых диаграмм), а также давления
газа производится в трех точках вдоль оси пучка. Отмечено влияние на динамику пучка в инжекторе эффек-
та компенсации собственного пространственного заряда пучка ионами плазмы, нарабатываемой при движе-
нии пучка в остаточном газе.
ДОСЛІДЖЕННЯ СИСТЕМИ ЗОВНІШНЬОЇ ІНЖЕКЦІЇ ПУЧКА ІОНІВ Н- ДЛЯ ЦИКЛОТРОНУ
О.Л. Вересов, С.В. Григоренко, Ю.В. Зуєв, А.П. Строкач, С.Ю. Удовиченко, С.С. Циганков
Приводяться результати експериментальних досліджень, виконаних на установці, що моделює систему
зовнішньої інжекції Н- зі струмом пучка до 2 мА й енергією до 30 кеВ для циклотрону. Вимір характеристик
пучка (струму, розподілу густини струму по перетині, фазових діаграм), а також тиску газу провадиться в
___________________________________________________________
PROBLEMS OF ATOMIC SIENCE AND TECHNOLOGY. 2004. № 2.
Series: Nuclear Physics Investigations (43), p.60-63.63
трьох точках уздовж осі пучка. Відзначено вплив на динаміку пучка в інжекторі ефекту компенсації
власного просторового заряду пучка іонами плазми, що напрацьовується при русі пучка в залишковому газі.
64
Introduction
Experimental equipment
Results of Measurements
and Calculations
ConclusionS
|