Electron gun for technological linear accelerator
The work is purposed to the design of diode electron gun for powerful technologic electron linac and to experimental investigations of the beam parameters at the gun exit. The gun feature is the quick cathode replacement. This is very impotent for operating of the accelerator. The gun optics and bea...
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| Published in: | Вопросы атомной науки и техники |
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| Date: | 2000 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2000
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| Cite this: | Electron gun for technological linear accelerator / I.V. Khodak, V.A. Kushnir, V.V. Mitrochenko, S.A. Perezhogin, D.L. Stepin, L.M. Zavada, V.F. Zhiglo // Вопросы атомной науки и техники. — 2000. — № 2. — С. 86-88. — Бібліогр.: 6 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859811857935630336 |
|---|---|
| author | Khodak, I.V. Kushnir, V.A. Mitrochenko, V.V. Perezhogin, S.A. Stepin, D.L. Zavada, L.M. Zhiglo, V.F. |
| author_facet | Khodak, I.V. Kushnir, V.A. Mitrochenko, V.V. Perezhogin, S.A. Stepin, D.L. Zavada, L.M. Zhiglo, V.F. |
| citation_txt | Electron gun for technological linear accelerator / I.V. Khodak, V.A. Kushnir, V.V. Mitrochenko, S.A. Perezhogin, D.L. Stepin, L.M. Zavada, V.F. Zhiglo // Вопросы атомной науки и техники. — 2000. — № 2. — С. 86-88. — Бібліогр.: 6 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | The work is purposed to the design of diode electron gun for powerful technologic electron linac and to experimental investigations of the beam parameters at the gun exit. The gun feature is the quick cathode replacement. This is very impotent for operating of the accelerator. The gun optics and beam parameters were calculated using the EGUN code. Beam parameters were investigated as at the special test stand so as a component of the linac injector. The gun produces the beam current of 2 A at the anode voltage 25 kV. Measured beam parameters correspond to calculated results.
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| first_indexed | 2025-12-07T15:19:37Z |
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ELECTRON GUN FOR TECHNOLOGICAL LINEAR ACCELERATOR
I.V. Khodak, V.A. Kushnir, V.V. Mitrochenko, S.A. Perezhogin, D.L. Stepin, L.M. Zavada,
V.F. Zhiglo
National Science Center "Kharkov Institute of Physics and Technology",
"ACCELERATOR" R&D Production Establishment, Kharkov, Ukraine
The work is purposed to the design of diode electron gun for powerful technologic electron linac and to
experimental investigations of the beam parameters at the gun exit. The gun feature is the quick cathode
replacement. This is very impotent for operating of the accelerator. The gun optics and beam parameters were
calculated using the EGUN code. Beam parameters were investigated as at the special test stand so as a component
of the linac injector. The gun produces the beam current of 2 A at the anode voltage 25 kV. Measured beam
parameters correspond to calculated results.
PACS: 41.85
1. INTRODUCTION
In the general case any technological electron
accelerator has to comply with following requirements:
- compactness;
- low power consumption;
- operation and service flexibility;
- long-time beam supply.
The last one is defined by a beam source quality.
Modern linear technological electron accelerators,
generally, are assembled with one accelerating structure
and low-voltage electron source. This comes from one
simple reason. Application of low-voltage electron
sources permits an accelerator to be more compact and
adaptable to technological processes. The linear
accelerator facility KUT [1] that is applied for
technological purposes represents such class of
accelerators. It includes following main subsystems:
injector system, disk-loaded accelerating structure, beam
scanning and extraction system and feedback systems.
The injector system [2] uses a low-voltage diode
electron gun. The injector also includes: buncher,
accelerating cavity, two axial-symmetric lenses and
beam current monitor. It is capable to produce electron
beam with energy of 0.5 to 0.6 MeV at the exit.
One of units determining the accelerator long-term
operation is an electron gun. An idealized electron gun
for a technologic accelerator has to meet high cathode
emission capability, low filament power and good
accessibility. The present paper is purposed to
experimental investigations of a low-voltage electron
gun for technological accelerators.
2. ELECTRON GUN DESIGN
Initial parameters used to design the electron gun for
the technologic accelerator are defined, in particular, by
performances of the injector, which the gun will operate
in. In this context the gun was designed to injectors
similar to the KUT injector. Taking into account the
injector operating experience the gun has to be able to
produce a beam pulse current about 2 A at the anode
voltage 25 kV. Besides, for optimal beam transit
through the focusing and bunching systems of the
injector and reducing the space charge force influence
on electron bunch shaping it is necessary to provide
certain beam performances at the injector input. In
particular, beam waist should to be sited a near the
injector input and beam size in the waist should be about
7 mm. It is desirable that the particle density should be
increased to the beam circumscription.
From the technological point of view the gun should
be sufficiently compact and provide a short time for
maintenance in the accelerator facility. It is assumed
here the cathode replacement. Obviously, some gun
details have to correspond to structural details of the
injector. Investigations showed that the required beam
parameters could be obtained by using the input injector
flange as an anode. This materially simplifies the gun
design and makes it possible for short-term
maintenance.
Gun optic calculations and electron beam simulations
were carried out with using the EGUN code [3]. The
cathode lifetime depends, in particular, on the cathode
load value. Therefore, a flat cathode with 14 mm a
diameter was chosen. This gives a rather low value of
the cathode load (about 1.5 A/cm2). Calculations of the
focusing electrode geometry were paid great attention
because of the specifying beam parameters.
0 100 200 300 400 500 600
0
50
100
150
200
250
300
350
400
450
Fig. 1. EGUN simulation.
Simulation results showed that the gun could
produce electron beam with specified parameters. Beam
current density at the gun exit increases with beam
radius increasing because of aberration of the gun optic
86 ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2000, № 2.
Серия: Ядерно-физические исследования (36), с. 86-88.
system. The calculated normalized beam emittance (4σ)
is 31 π mm mrad. Fig. 1 demonstrates the gun electron-
optic system geometry and particle traces simulation.
Being based on simulation results the gun assembly
was designed. Structurally it represents a high-voltage
insulator 3 (see Fig. 2) having flange junction 4 to join
with anode 5. Flange junction 1,2 of the cathode-heating
unit with the insulator makes it possible for the cathode
6 replacement without focusing electrode displacing. In
this procedure the cathode-heating unit design ensures
the required cathode position relative to the focusing
electrode. Having the supplementary cathode-heating
unit the procedure of the cathode replacement can be
time minimized up to several minutes. The emitter
replacement in the cathode-heating unit can feather be
done independently of operating of the accelerator. Such
design of the cathode-heating unit makes it possible, if
necessary, changing of the gun electron-optic system.
Fig. 2. Gun Assembly.
The flat dispenser tungsten emitter with barium-
aluminate impregnation and surface cover with the Os-
Ir-Al film [4] is used as a cathode. The last one enables
to decrease the cathode temperature that increases its
lifetime. The feature of such a cathode is the low
filament power. The gun design makes it possible using
of BaNi cathodes [5], which have more low operating
temperature.
3. EXPERIMENTAL LAYOUT
Experimental tests were carried out at the special test
setup. The gun was fed from the modulator which was
similar to the modulator KUT equipped with. It provides
high voltage and filament voltage smooth tuning in
limits of 11 – 25 kV and 1.5 – 8 V, respectively. The
high voltage pulse duration is adjusted from 1 to 4 µs
with the pulse repetition rate from 1 to 300 p.p.s. The
modulator has a high-voltage divider and a beam current
transformer to control the high-voltage pulse magnitude
and cathode current, respectively. The section movable
beam monitor was designed for measurements of the
transverse beam distribution and the beam emittance. It
consists of 32 copper strips having thickness of
0.25 mm. The strips are placed perpendicular to the
beam axis and are insulated by mica strips having
thickness of 0.25 mm. Thus, the strip arrangement
period is up 0.5 mm. For measurements of beam
distribution and beam size in different cross sections the
monitor movement is provided along the beam axis in
wide limits. The monitor position is controlled accurate
to 0.1 mm. During tests the signals from monitor were
measured with a multichanell data processing system
[6]. The section beam monitor is connected with the
system via the electronic switchbox. The data processing
system has A/D converters with 50 ns time resolution
what enables one to indicate pulse signals quite
accurate.
Oilless vacuum system enables to keep vacuum at
the 10-6 torr that is one order less of critical value, which
the cathode poisoning can occur.
4. TEST RESULTS
The designed gun was tested in two steps. During the
first step there was investigated the operation of the gun
electron-optic system, its ability to produce the electron
beam with required parameters. The behavior of anode
current with anode voltage and the beam spatial
distribution were measured at different distances of the
monitor from the anode plane. These measurements
were carried out in one pulse per second repetition rate
mode with the high-voltage pulse duration 4 µs.
Results of the gun current-voltage characteristic
measurements confirm the electron emission presence
which follows the "3/2" law. This points at the sufficient
emission capacity of the cathode. As Fig. 3 indicates this
is correct at the maximum monitor position (l=99 mm)
from the cathode plane. At the minimum monitor
position (l=17 mm) from the cathode plane some
displacement to the linearity is observed. This is
explained by distortions of electric field distribution in
the gun caused by the beam monitor close position. This
hypothesis was confirmed by computer simulation.
1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4 2 6 2 8 3 0
0 . 4
0 . 6
0 . 8
1
1 . 2
1 . 4
1 . 6
1 . 8
2
2 . 2
U, (kV)
I,
(
A
)
l = 1 7 m
m
l = 4 5 m
m
l = 9 9 m
m
Fig. 3. Volt-current dependences.
Fig. 4 indicates integral transverse beam profile
measured at the position l=17 mm and processed by the
data processing system. Such transverse profile features
a beam the density of which increases to the
circumference. This corresponds to calculated results.
87
0 1 0 20 30
0
1 00 0
2 00 0
3 00 0
4 00 0
5 00 0
S t r i p n um be r
S
tr
ip
c
ur
re
nt
, a
rb
. u
ni
ts
Fig. 4. Beam profile.
The possibility to measure the beam profile in three
different positions made it possible experimental
defining of the emittance. The beam divergence and its
emittance measurements showed well computing and
experiment coordination. This follows from the beam
envelope graph processed in Cartesian coordinates
(Fig. 5). Solid line is the envelope calculated from the
particle traces simulation. Dash line is the experimental
one processed by the data processing system. According
to calculated and experimental results the beam
crossover position is at 30 cm from the cathode plane.
0 2 0 4 0 6 0 8 0
0
1
2
3
4
5
6
7
Z, (mm)
X
, (
m
m
)
e x p .
Fig. 5. Beam envelope.
The gun as a component of the injector was tested
during the second step. The electron beam transit
through the injector and the gun working capacity
depending on repetition rate was investigated. The
injector had following operating mode: anode voltage –
25 kV, pulse current – 2 A, high-voltage pulse duration
– 4 µs and repetition frequency up to 300 p.p.s. The
volt-ampere characteristics were measured using the
passive beam current transformer with the transform
coefficient 0.5 A/V. The test results indicates the gun
volt-ampere dependence agrees in fact with the line
l=99 mm (see Fig. 3). A sensible change in the gun
operating was not observed with repetition frequency
increasing. The electron beam transit through the
injector is 93% and does not change in fact with the
repetition frequency increasing. The main experimental
parameters of the gun are summarized in Table.
Gun parameters
Parameter Calc. Exp.
Anode voltage, kV 25 25
Current, A 1,98 1.7 – 2
Perveance, A/A3/2⋅10-6 0,51 0,42 – 0,52
Size in crossover, mm 7.1 7.5
εn , π⋅mm mrad 31 30
5. CONCLUSION
Thus, as a result of the research work and
experimental tests a new electron gun design for
technologic electron accelerators was developed. The
electron gun prototype passed tests to satisfaction and
can operate in linear electron accelerators applied for
technologic purposes.
REFERENCES
1.N.I. Aizatsky et. al. KUT-industrial technological
accelerator // Proceedings of XIV Workshop on
charged particles accelerators, Protvino, 1994, v. 4,
p. 259-263 (in Russian).
2.N.I. Aizatsky et al. Experimental Studies on an
Injector Complex with RF-Bunching and Pre-
Accelerator System // Proc. of the Int. Workshop on
e+e− Sources and Pre-Accelerators for Linear
Colliders, Schwerin, 1994.
3.W.B. Herrmannsfeldt. EGUN: Electron Optics
Program, Stanford Lin. Acc. C-r, SLAC-PUB-6729,
1994.
4.A.B. Kiselev Cathodes and cathode units for long-
term electron devices, Electronic Engineering
Reviews, Ser. 1 RF- Engineering, v. 11(1684),
Moscow CSRI (Electronics), 1992 (in Russian).
5.Yu.V. Alekseev et. al. Preprint SIIEPhA, P-b-0753
- L.:1987 (in Russian).
6.V.A. Kushnir et al.Information Measurement
System for Laser Injector Complex (LIC)//VANT,
Series: Nuclear Physics Research, 1997,
v. 4,5(31,32), p. 78 (in Russian).
88
3. EXPERIMENTAL LAYOUT
Gun parameters
|
| id | nasplib_isofts_kiev_ua-123456789-82284 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T15:19:37Z |
| publishDate | 2000 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Khodak, I.V. Kushnir, V.A. Mitrochenko, V.V. Perezhogin, S.A. Stepin, D.L. Zavada, L.M. Zhiglo, V.F. 2015-05-27T13:25:40Z 2015-05-27T13:25:40Z 2000 Electron gun for technological linear accelerator / I.V. Khodak, V.A. Kushnir, V.V. Mitrochenko, S.A. Perezhogin, D.L. Stepin, L.M. Zavada, V.F. Zhiglo // Вопросы атомной науки и техники. — 2000. — № 2. — С. 86-88. — Бібліогр.: 6 назв. — англ. 1562-6016 PACS: 41.85 https://nasplib.isofts.kiev.ua/handle/123456789/82284 The work is purposed to the design of diode electron gun for powerful technologic electron linac and to experimental investigations of the beam parameters at the gun exit. The gun feature is the quick cathode replacement. This is very impotent for operating of the accelerator. The gun optics and beam parameters were calculated using the EGUN code. Beam parameters were investigated as at the special test stand so as a component of the linac injector. The gun produces the beam current of 2 A at the anode voltage 25 kV. Measured beam parameters correspond to calculated results. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Тheory and technics of particle acceleration Electron gun for technological linear accelerator Article published earlier |
| spellingShingle | Electron gun for technological linear accelerator Khodak, I.V. Kushnir, V.A. Mitrochenko, V.V. Perezhogin, S.A. Stepin, D.L. Zavada, L.M. Zhiglo, V.F. Тheory and technics of particle acceleration |
| title | Electron gun for technological linear accelerator |
| title_full | Electron gun for technological linear accelerator |
| title_fullStr | Electron gun for technological linear accelerator |
| title_full_unstemmed | Electron gun for technological linear accelerator |
| title_short | Electron gun for technological linear accelerator |
| title_sort | electron gun for technological linear accelerator |
| topic | Тheory and technics of particle acceleration |
| topic_facet | Тheory and technics of particle acceleration |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/82284 |
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