Improvement of beam transport and target station of technological linac “EPOS”
To increase the reliability of operation and simplify the precise tuning of the beam it is proposed to upgrade the output part of the accelerator “EPOS” NSC KIPT that operates in the range of electron energies 25…35 MeV and beam power up to 12 kW. An additional collimator, beam profile scanner and a...
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nasplib_isofts_kiev_ua-123456789-1945562025-02-09T10:29:19Z Improvement of beam transport and target station of technological linac “EPOS” Вдосконалення тракту проводки пучку і мішеневого комплексу технологічного ЛПЕ “ЕПОС” Усовершенствование тракта проводки пучка и мишенного комплекса технологического ЛУЭ “ЭПОС” Dronov, R.N. Reprintsev, L.V. Tatanov, V.I. Application of accelerators in radiation technologies To increase the reliability of operation and simplify the precise tuning of the beam it is proposed to upgrade the output part of the accelerator “EPOS” NSC KIPT that operates in the range of electron energies 25…35 MeV and beam power up to 12 kW. An additional collimator, beam profile scanner and a wide aperture beam current monitor is offered to install. It is also proposed to upgrade the target station, which will improve the quality of irradiation and improve working conditions for personnel. Для підвищення надійності роботи і спрощення точного проведення пучка пропонується модернізувати вихідну частину прискорювача “ЕПОС” ННЦ ХФТІ, що працює в діапазоні енергій електронів 25…35 МеВ і потужності пучка до 12 кВт. Пропонується установка додаткового коліматора, сканера профілю пучка та широкоапертурного монітора струму пучка. Також пропонується модернізувати мішеневі пристрої, що підвищить якість опромінювання і поліпшить умови роботи персоналу. Для повышения надёжности работы и упрощения точной проводки пучка предлагается модернизировать выходной тракт ускорителя “ЭПОС” ННЦ ХФТИ, который работает в диапазоне энергий электронов 25…35 МэВ и мощности пучка до 12 кВт. Предлагается установка дополнительного коллиматора, сканера профиля пучка и широкоапертурного монитора тока пучка. Также предлагается модернизировать мишенные устройства, что повысит качество облучения и улучшит условия работы персонала. We are profoundly grateful to the late Leonid M'yakushko for very useful advices and encouragement during the early stage of this work. 2020 Article Improvement of beam transport and target station of technological linac “EPOS” / R.N. Dronov, L.V. Reprintsev, V.I. Tatanov // Problems of atomic science and tecnology. — 2020. — № 3. — С. 172-176. — Бібліогр.: 5 назв. — англ. 1562-6016 PACS: 29.20.Ej, 29.27.-a https://nasplib.isofts.kiev.ua/handle/123456789/194556 en Вопросы атомной науки и техники application/pdf Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Application of accelerators in radiation technologies Application of accelerators in radiation technologies |
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Application of accelerators in radiation technologies Application of accelerators in radiation technologies Dronov, R.N. Reprintsev, L.V. Tatanov, V.I. Improvement of beam transport and target station of technological linac “EPOS” Вопросы атомной науки и техники |
| description |
To increase the reliability of operation and simplify the precise tuning of the beam it is proposed to upgrade the output part of the accelerator “EPOS” NSC KIPT that operates in the range of electron energies 25…35 MeV and beam power up to 12 kW. An additional collimator, beam profile scanner and a wide aperture beam current monitor is offered to install. It is also proposed to upgrade the target station, which will improve the quality of irradiation and improve working conditions for personnel. |
| format |
Article |
| author |
Dronov, R.N. Reprintsev, L.V. Tatanov, V.I. |
| author_facet |
Dronov, R.N. Reprintsev, L.V. Tatanov, V.I. |
| author_sort |
Dronov, R.N. |
| title |
Improvement of beam transport and target station of technological linac “EPOS” |
| title_short |
Improvement of beam transport and target station of technological linac “EPOS” |
| title_full |
Improvement of beam transport and target station of technological linac “EPOS” |
| title_fullStr |
Improvement of beam transport and target station of technological linac “EPOS” |
| title_full_unstemmed |
Improvement of beam transport and target station of technological linac “EPOS” |
| title_sort |
improvement of beam transport and target station of technological linac “epos” |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2020 |
| topic_facet |
Application of accelerators in radiation technologies |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/194556 |
| citation_txt |
Improvement of beam transport and target station of technological linac “EPOS” / R.N. Dronov, L.V. Reprintsev, V.I. Tatanov // Problems of atomic science and tecnology. — 2020. — № 3. — С. 172-176. — Бібліогр.: 5 назв. — англ. |
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Вопросы атомной науки и техники |
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| fulltext |
ISSN 1562-6016. ВАНТ. 2020. №3(127) 172
IMPROVEMENT OF BEAM TRANSPORT AND TARGET STATION
OF TECHNOLOGICAL LINAC "EPOS"
R.N. Dronov, L.V. Reprintsev, V.I. Tatanov
National Science Center “Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine
E-mail: romandronov@kipt.kharkov.ua
To increase the reliability of operation and simplify the precise tuning of the beam it is proposed to upgrade the
output part of the accelerator "EPOS" NSC KIPT that operates in the range of electron energies 25…35 MeV and
beam power up to 12 kW. An additional collimator, beam profile scanner and a wide aperture beam current monitor
is offered to install. It is also proposed to upgrade the target station, which will improve the quality of irradiation and
improve working conditions for personnel.
PACS: 29.20.Ej, 29.27.-a
INTRODUCTION
The EPOS accelerator of the NSC KIPT operates in
the range of electron energies of 25…35 MeV and beam
power up to 12 kW and is currently used for different
irradiation programs. Some of radiation technologies
require that low energy electrons with energy below
17 MeV must be prevented from getting on the targets
which being irradiated. To meet this requirement, the
"energy filter" system [1] was installed on this accelera-
tor (Fig. 1).
Fig. 1. “Energy filter” system.
Beam travels from right to left
The energy filter consists of dipole magnet [2] with
constant magnetic field and collimator. Low-energy
electrons were planned to be removed by deflecting it
downward with the bending magnet and further dumped
on the copper water-cooled Collimator-1 (Fig. 2).
Fig. 2. Output part of "EPOS" accelerator [1]
Nevertheless, in some modes of accelerator’s opera-
tion, part of the electrons with low-energy hit the walls
of linac’s drift part and caused vacuum condition to
worsen beyond the acceptable operational range. That
was the main reason for modernization.
1. GEOMETRICAL DESCRIPTION
OF ELECTRON MOTION
Trajectories of motion of electrons with different en-
ergies were drawn based on equations
sin l
, (1)
410 (MeV) (cm)
3 (G)
E
Н
, (2)
+ =
2 1 cos
l l
, (3)
where E total energy of the accelerated electron;
H induction of magnetic field in the gap of the mag-
net; ρ radius of the trajectory of the central particle of
the beam in the magnet; l effective length of the mag-
net, taking into account the boundary effects; φ angle
of inclination at the output, beam input is normal.
Fig. 3. Scheme of electron passage through a magnet
with parallel faces [3]
Because in our case the angle << 1, so when draw-
ing the trajectory of electrons with different energies, it
was assumed that they start from the center of the mag-
net as shown in Fig. 3. As it follows from (3) in the
cases when << 1, the distance between the begin-
ning of geometrical drawing and the center of the mag-
net is relatively small value:
2
:
2 4
l
.
Table shows the geometric parameters of the trajec-
tory of an electron of nominal energy when passing
through a deflecting magnet.
ISSN 1562-6016. ВАНТ. 2020. №3(127) 173
Parameters of the particles used for calculations
E, МеV H, G ρ, cm l, cm φ, rad φ, grad
32.5 310 350 13.44 0.0384 2.2
Fig. 4 shows the output part of the accelerator after
the deflecting magnet with possible variants of elec-
tron’s travel.
Fig. 4. Scheme of electrons passing through the output part of accelerator
Depending on the energy, the trajectories of elec-
trons are grouped in a three differently colored areas on
the scheme that roughly resemble sectors.
The green sector is filled with electron trajectories
with energy in the range of 20…32 MeV. All electrons
from the green sector pass freely through the aperture in
Collimator-1 and subsequently hit the target during
various irradiation programs.
The electrons moving within the yellow sector have
energies in the range of 11…20 MeV and fall to the
surface of the copper water-cooled Collimator-1. In
some modes of accelerator’s operation, electrons with
energy lower than 11 MeV appear. Possible trajectories
of such electrons are located within the red-colored sec-
tor. The total power of electrons that appear and move
within the red sector and ultimately hit the walls of the
vacuum chamber is significant. Power density of the
beam is high enough and sufficient to deteriorate the
vacuum conditions in the accelerator beyond the opera-
tional range and even to damage the drift line com-
pletely breaking the vacuum, which already took place
in the past.
Fig. 5. Proposed configuration of the output part of accelerator
To eliminate the situations in which low-energy
electrons hit the wall of the transmission line and dete-
riorate or break the vacuum, it is suggested to install an
additional Collimator-2 (Fig. 5). The Collimator-2 is
proposed to be water-cooled with an expanded heat ab-
sorption area and decreased electron collision angle up
to 25…35.
Fig. 6 shows the proposed Сollimator-2 design, ex-
isting Collimator-1 and highlights the difference.
Fig. 6. Comparison of collimator configurations:
left offered Collimator-2 (2=25; L2=85 mm);
right existing Collimator-1 (1=85; L1=55 mm)
ISSN 1562-6016. ВАНТ. 2020. №3(127) 174
2. BEAM CURRENT TRAVEL CONTROL
2.1. WIDE-APERTURE CURRENT MONITOR
OF PULSE ELECTRON BEAM
At least two current monitors are required to control
current through the energy filter channel, which includes
a collimator to intercept part of the beam. The current
and beam position monitor located at the entrance to the
channel (see Fig. 2) controls the parameters of the beam
of the "EPOS" accelerator and is an integral part of beam
diagnostics system. It is impossible to position the out-
put monitor directly after the oval collimator because of
the high radiation load and due to the lack of sufficient
space for its installation.
Fig. 7. Wide-aperture current monitor.
Top simplified monitor design;
bottom dimensions of the core
Therefore, it is suggested to place the output monitor
after the vacuum window of the scan horn (see Fig. 5).
Vertical size of the part of output window where scanned
beam crosses it, is as large as 200 mm, therefore the aper-
ture of the monitor is made 26050 mm (HW).
The magneto-induction type monitor (Fig. 7) in-
cludes a core (pos. 5) wound with a 100 μm thick per-
malloy ribbon. Structurally, it is embedded in an alumi-
num clamp (pos. 3) and secured to the plate (pos. 4).
The latter is attached to the outlet flange of the scan
horn. Two windings (pos. 1; 6), together with the cali-
bration coils, are located on the end portions of the core
and insulated with a fiberglass tape. Terminals are made
using special ceramic insulators (pos. 2).
Main parameters of a monitor:
- Number of coils: W = 100; inductance L = 50 mH;
specific capacity of each winding C = 200 pF.
- Core cross section S = 2.5 cm2; length of magnetic
force line l = 65 cm.
- Aperture (HW) 26050 mm; overall dimensions:
28075 mm.
- Pulse tilt: U/U1% with 100 termination and
pulse duration =3.5 μs; raise time: e50 ns.
- Magnetic permeability of the core: =104.
- Beam current monitor response: U/I = 1V/A.
The signals from both windings are fed to the ADC
inputs and processed by the computer. The sum of the
signals gives the value of the beam current in the pulse.
The difference of the signals divided by their sum gives
the instantaneous position of the beam’s center and the
sweep deflection angle. In this way, energy control and
beam interlocking can be performed without scanning.
2.2. INNER BEAM PROFILE STEPPING
SCANNER
To control the profile of a beam in front of the oval
outlet Collimator-1 (see Fig. 5), an internal beam profile
stepping scanner is planned to be installed. This scanner
is a modification of the previously developed scan-
ner [4] shown in Fig. 8.
Fig. 8. Prototype Inner Beam Profile Stepping Scanner
The moving frame of prototype scanner contains
three differently oriented tubular probes (pos. 1) with
45 angular spacingf between them. Such probe ar-
rangement was initially used to scan the profile of an
ellipse-shaped beam (pos. 2) with ellipse axes tilted to
the horizon.
Specifications of prototype scanner:
Probe travel 82.5 mm
Number of steps per full travel 175
Step rate 25 s-1
Linear step of probe’s movement 0.47 mm
Duration of three measurements 7 s
Probe speed 12 mm/s
Linear backlash of a probe 0.25 mm
Aperture 30 mm
Probe material Ni
Probe diameter 1.5 mm
The thickness of the probe’s wall 50 μm
Permissible probe temperature 800°С
Max. operating temperature 500°С
Cooling time (500…200°C) 20 s
Max. output signal (RL = 75 ) 225 mV
Number of probes 3
Parameters of the beam used in the calculations:
Beam current 0.6 А
Beam pulse duration 4 μs
Pulse repetition rate 100 Hz
Conditional beam diameter 7.5 mm.
The inner beam profile stepping scanner is intended
for scanning the beam core profile and measuring full
charge of the deflected beam. Unlike prototype scanner
[4], the new inner beam stepping scanner will use a
modified moving frame that is shown in Fig. 9. This
moving frame contains two different probes. The planar
probe (pos. 1) is made of titanium plate (50 μm thick)
and tubular one (pos. 2) is nickel tube 1.5 mm in diame-
ter with 50 μm wall thickness. Delta-electrons from
these two probes form the scanner’s signal.
ISSN 1562-6016. ВАНТ. 2020. №3(127) 175
Fig. 9. Technical drawing of moving frame of inner
beam stepping scanner with planar and tubular probes
Carbon rod 0.5 mm in diameter may be used as a
possible substitute for tubular probe made of nickel and
further development and testing of this option is under-
way.
3. LOW ACTIVATION TARGET STATION
The target station, which presently installed at
"EPOS" linac is intended for irradiation of different
bulk materials with scanned electron beam. Materials to
be irradiated are usually placed in series of specially
designed cartridges. To avoid overheating of the sam-
ples during irradiation, water spraying is used.
The distribution of scanned electrons on the target is
non-uniform; this leads to the necessity of shifting the
cartridges periodically in course of irradiation. The set
of total six vertical cartridges (similar to those shown in
Fig. 11) is divided into two parts. Left and right parts
with three cartridges in each then shift horizontally to
take each other’s place to compensate for uneven elec-
tron irradiation. At present the shifting is performed
manually, which results in increased processing time.
To improve both the working conditions and the
quality of the irradiation procedure, a new target station
(Fig. 10) is proposed as the second stage of reconstruc-
tion.
Fig. 10. Target station with front cover removed
Newly developed target station features cartridge
shifting device (see Fig. 11) which remotely shifts the
cartridges in mid run, thus saving time and reducing
operational costs. Shifting is performed by alternated
90 degrees turn of hinged cartridge holder with the
counterweight. The result of shifting is seen in Fig. 11
with all cartridges numbered. Remote cartridge shifting
reduces personnel exposure and shortens the time
needed for radiation treatment.
Fig. 11. Six cartridges mounted on remotely
operated hinged holder:
left – initial position; right – shifted position
An aluminum alloy AD31 will be the main structural
material for manufacturing this target station. As de-
scribed in [5], this aluminum alloy is more attractive in
terms of induced activation level comparing to previ-
ously used duralumin and stainless steel, which improve
personnel safety too.
CONCLUSIONS
1. The proposed modification of the output part of
the "EPOS" accelerator allows eliminating the disadvan-
tages of the "energy filter" system such as vacuum dete-
rioration or even breaking and radiation contamination
of equipment. Installing a step scanner will allow us to
control the low energy "tail" of the energy spectrum,
making tuning of accelerator easier.
2. Installation of a wide-aperture current monitor
will guarantee continuous operational measurement of
beam current and instantaneous position of the beam
immediately after the vacuum window. This will allow
us to monitor the sweep angle and the energy of the
electrons and instantly interlock the beam if these pa-
rameters fall outside the operational range.
3. Usage of developed target station will shorten
treatment time, reduce operational costs and improve
personnel safety.
ACKNOWLEDGEMENT
We are profoundly grateful to the late Leonid M'ya-
kushko for very useful advices and encouragement dur-
ing the early stage of this work.
REFERENCES
1. V.N. Boriskin, I.S. Guk, A.N. Dovbnya, et al. Energy
filter system for the accelerator "EPOS" // Problems
of Atomic Science and Technology. Series “Nuclear
Physics Investigations”. 2012, № 3, p. 39-43.
2. I.S. Guk, A.N. Dovbnja, S.G. Kononenko, et al. The
dipole magnet of the energy filter for accelerator
"EPOS"// Problems of Atomic Science and Technol-
ogy. Series “Nuclear Physics Investigations”. 2012,
№ 3, p. 67-69.
3. A. Bendford. Transportirovka puchkov zaryazhen-
nyx chastic. M.: “Atomizdat”, 1969 (in Russian).
ISSN 1562-6016. ВАНТ. 2020. №3(127) 176
4. R.N. Dronov, L.K. Myakushko, L.V. Reprintsev,
V.A. Shendrik. A stepping scanner of internal beam
profile of the technological electron linac // Book of
abstracts XIX International Workshop on Charged
Particle Accelerators. Sept. 12-18, 2005, Ukraine,
p. 89.
5. Ye.Z. Biller, R.N. Dronov, V.F. Zhiglo. Low activa-
tion target handling station for photonuclear isotope
production on electron linac // Book of abstracts
XXIII International Workshop on Charged Particle
Accelerators. Sept. 8-14, 2013, Ukraine, p. 160-161.
Article received 24.01.2020
УСОВЕРШЕНСТВОВАНИЕ ТРАКТА ПРОВОДКИ ПУЧКА И МИШЕННОГО КОМПЛЕКСА
ТЕХНОЛОГИЧЕСКОГО ЛУЭ “ЭПОС“
Р.Н. Дронов, Л.В. Репринцев, В.И. Татанов
Для повышения надёжности работы и упрощения точной проводки пучка предлагается модернизировать
выходной тракт ускорителя “ЭПОС“ ННЦ ХФТИ, который работает в диапазоне энергий электронов
25…35 МэВ и мощности пучка до 12 кВт. Предлагается установка дополнительного коллиматора, сканера
профиля пучка и широкоапертурного монитора тока пучка. Также предлагается модернизировать мишенные
устройства, что повысит качество облучения и улучшит условия работы персонала.
ВДОСКОНАЛЕННЯ ТРАКТУ ПРОВОДКИ ПУЧКУ І МІШЕНЕВОГО КОМПЛЕКСУ
ТЕХНОЛОГІЧНОГО ЛПЕ “ЕПОС“
Р.М. Дронов, Л.В. Репринцев, В.І. Татанов
Для підвищення надійності роботи і спрощення точного проведення пучка пропонується модернізувати
вихідну частину прискорювача “ЕПОС“ ННЦ ХФТІ, що працює в діапазоні енергій електронів 25…35 МеВ і
потужності пучка до 12 кВт. Пропонується установка додаткового коліматора, сканера профілю пучка та
широкоапертурного монітора струму пучка. Також пропонується модернізувати мішеневі пристрої, що під-
вищить якість опромінювання і поліпшить умови роботи персоналу.
|