Prestripping section of the MILAC accelerator based on the principle of alternating-phase focusing with the moving bunch center
The main task facing the personnel of the linear accelerator of multicharged ions (MILAC) at the NSC KIPT was carrying out the fundamental investigations in the field of nuclear physics and material engineering.
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
1999
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| Cite this: | Prestripping section of the MILAC accelerator based on the principle of alternating-phase focusing with the moving bunch center / V.A. Bomko, Yu.P. Mazalov, Yu.V. Meleshkova, A.F. Kobetz, B.I. Rudyak // Вопросы атомной науки и техники. — 1999. — № 3. — С. 11-13. — Бібліогр.: 17 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860233329554489344 |
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| author | Bomko, V.A. Mazalov, Yu.P. Meleshkova, Yu.V. Kobetz, A.F. Rudyak, B.I. |
| author_facet | Bomko, V.A. Mazalov, Yu.P. Meleshkova, Yu.V. Kobetz, A.F. Rudyak, B.I. |
| citation_txt | Prestripping section of the MILAC accelerator based on the principle of alternating-phase focusing with the moving bunch center / V.A. Bomko, Yu.P. Mazalov, Yu.V. Meleshkova, A.F. Kobetz, B.I. Rudyak // Вопросы атомной науки и техники. — 1999. — № 3. — С. 11-13. — Бібліогр.: 17 назв. — англ. |
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| container_title | Вопросы атомной науки и техники |
| description | The main task facing the personnel of the linear accelerator of multicharged ions (MILAC) at the NSC KIPT was carrying out the fundamental investigations in the field of nuclear physics and material engineering.
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| first_indexed | 2025-12-07T18:22:49Z |
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PRESTRIPPING SECTION OF THE MILAC ACCELERATOR BASED ON
THE PRINCIPLE OF ALTERNATING–PHASE FOCUSING WITH THE
MOVING BUNCH CENTER
V.A.Bomko, Yu.P.Mazalov, Yu.V.Meleshkova, A.F.Kobetz, B.I.Rudyak
NSC KIPT, Kharkov, Ukraine
INTRODUCTION
The main task facing the personnel of the
linear accelerator of multicharged ions (MILAC) at the
NSC KIPT was carrying out the fundamental
investigations in the field of nuclear physics and
material engineering. Since its construction [1] it was
somewhat improved, and in 1989 it was completely
redesigned on the basis of the effective accelerating
structure of the interdigital type excited at H111 wave [2,
3, 4]. Other systems were replaced by the systems
upgraded on the basis of the latest achievement
technologies of RF-power systems, sources of
multicharged ions, high-voltage equipment and modern
systems of the beam control and diagnostics.
The MILAC consists of two parts, prestripping
section (PSS) and poststripping main section (MS),
designed for the energy of 0.975 and 8.5 MeV/u,
respectively. The average intensity of the current at the
output of the sections is (1012÷1010) and (1011÷109)
particles/s for 14N, 20Ne, 40Ar etc. The PSS is designed
for acceleration of ions with the mass-to-charge ratio
A/q=15, and MS is designed for A/q=5. In recent years
it became necessary to adapt the accelerator to applied
research. Among them the most promising is
organization of the track membrane production and
radionuclide production. The parameters of MILAC
provide a possibility to solve both problems profitably.
However, the requirements for beams of heavy ions are
rather different. For the track membrane production it is
necessary to have masses of ions as high as possible and
of moderate intensity, but the radionuclide production
requires only light ions (protons, deuterons, helium ions
(3He, 4He) with the beam current as high as possible
(from 100 to 1000 µA). It is hardly possible to design an
accelerator combining the two requirements. The
bottleneck is found to be the prestripping section. At the
present time it is possible to use it for the track
membrane production with use of 40Ar ions accelerated
to 1 MeV/u. However, to organize the commercial
production of the membranes with unique properties
(sterilizing effect) heavier ions (96Mo, 184W) are
required. In that case the existing PSS must be replaced
by that designed for acceleration of ions with higher
A/q. The results of calculation of the new PSS designed
for acceleration of the intense beams of light ions are
presented in the report [5] of this Workshop.
At the present time the personnel of the
Department of the Linear Accelerator of multicharged
ions are developing a new PSS. It is designed for
acceleration of ions with the A/q=32 (PSS-32) which
will provide a possibility to increase the current of the
accelerated ions in an order, and to extend considerably
the range of the atomic masses. Ions with this A/q ratio
are the most intense component of the source of ions of
metals [6]. Besides these ions it will be possible to
accelerate other ions for which A/q =32, Cu2+, Kr3+,
Xe3+, W6+, U7+ for example, and so on. The ions
accelerated at the PSS-32 to 0.975 MeV/u, after
stripping at the solid target will be accelerated at MS
section of MILAC to the energy of 8.5 MeV/u.
Optimization of the PSS-32 parameters is necessary to
develop convenient, cheap, and efficient accelerator
having improved beam parameters.
The new PSS-32 is based on two important
innovations: i) the accelerating structure of the
interdigital type is used, adequate on three parameter –
compactness (large operating wavelength), high
acceleration rate, shunt impedance [4, 7, 8]; ii) radial-
phase beam stability is provided by alternating-phase
focusing with bunch moving center (APF with the
BMC). In the paper the different aspects of beam
dynamics in PSS-32 are discussed.
1. THE METHOD OF THE APF WITH THE BMC
M.L.Good [9] and Ya.B.Fainberg [10]
proposed the principle of alternating-phase focusing
early in 50s. In succeeding years it was improved
[11,12].
The version of the alternating-phase focusing
with the bunch moving center was discussed earlier
[13,14]. Its distinctive feature is the mismatch between
the center of the bunch of accelerated particles and
synchronous particle both in energy and in phase. In the
course of acceleration the bunch moves relative to the
synchronous particle. The idea of the mismatch between
the synchronous phase and phase of the bunch center
was discussed earlier and was used in the designs of the
heavy ion linear accelerators [15, 16, 17]. However, due
to the fact that the zero phase (ϕs=0) was chosen as
synchronous, both longitudinal and transverse capture
are small, therefore the radial stability is achieved
mainly by use of quadrupole triplets alternating with the
regions of the accelerating structure, and the phase
capture did not exceed 30o.
The version of the APF with the BMC under
discussion is based on the periodical shift of the bunch
from the region of negative phases to the region of
positive phases, and conversely, with the constant
excess of bunch center energy over the synchronous
particle energy both in positive and in negative phases.
As a result, at every region of the structure all of the
bunch move in the direction of the smaller phases in the
(∆W, ϕ) plane, where ∆W is deviation in the energy of
the bunch particles relative to the synchronous particle
energy, ϕ is the phase of the bunch particles. That
allows to enhance the focusing and bunching action of
the RF-fields. The continuous distortion of the phase
portrait of the bunch and shifting of the particles relative
to the bunch center is accompanied by the attenuation of
the phase oscillations of particles. The best compromise
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. №3.
Серия: Ядерно-физические исследования (34), с. 11-13.
11
between the conflicting requirements for the radial and
phase stability is achieved by selecting the region of
phase shift, the number of accelerating cells along
focusing and bunching regions, and by the excess of
bunch center energy over synchronous particle energy.
2. BEAM DYNAMICS
As a result of the optimum selection of each of
the three degree of freedom the accelerating structure is
obtained, the parameters of which are presented in the
Table. The beam dynamics is a complicated process of
maintenance of the phase-radial stability of bunches
during acceleration.
Parameters of the PSS-32 accelerator
Input energy of ions, keV 14
Output energy of ions, keV 655
Mass-to-charge ratio, A/q 32
Operating frequency, MHz 23,7
Electric field in gaps MV/m 9,5
Length of accelerating structure, m 6
Number of drift tubes 47
Aperture of drift tubes, mm 16-24
Synchr. phase of bunching regions, deg. - 40
Synchr. phase of focusing regions, deg. + 40
Number of bunching regions 6
Number of focusing regions 6
Acceleration rate, MeV/m 3,2
Longitudinal capture, deg. 100
Longitudinal output bunch deg 18
Longitudinal acceptance, π⋅(keV/u)mrad 777
Radial acceptance, mm.mrad 491
Normalized radial acceptance, π.mm.mrad 0,87
In Fig.1 the combined diagram of phase and
energy parameters of the particle dynamics along the
PSS-32 is presented. On the abscissa the sequence
numbers of the cells grouped in 12 regions (6 bunching
and 6 focusing regions) are given. On the ordinate phase
characteristics is at the left, and energy parameters is at
the right (total energy of the synchronous particle (Ws)
and shift in energy of the bunch center relative to the
synchronous particle energy (∆W). As one can see from
the Fig.1, the initial acceleration with bunching takes
place when the phase is large in modulus (- 70o). At the
following bunching regions the phase is equal to – 40o,
at the focusing regions it is equal to +40o. The phase of
the bunch center at the following bunching regions does
not change considerably being, in average, several
degrees above the synchronous phase. At the same time
the significant shift of the phase of the bunch center
occurs during its moving along the focusing regions.
First, the center of the bunch enters a center of the
focusing gap at large positive phase that results in
significant focusing. Further the center of the beam
moves to the smaller phases. Its average value at the
focusing regions varies from 44o to 20o. Therefore, the
high acceleration rate is conserved. The excess of the
energy of the bunch center over the energy of the
synchronous particle varies from 2 keV/u at the input of
the bunching sections to 1 keV/u at the output. For the
focusing sections this value varies in the wider limits
and as a more complicated function.
`
Fig.1. Phase and energy beam dynamic along POS-32.
ϕs-synchronous phase, ϕbc-beam center phase,
Ws- synchronous particle energy, ∆W=Wbc-Ws
Fig.2. Injection beam separatrix POS-32
Fig.3. Phase portrait at output 7th and 8th regions.
Fig.4. Particle radial trajectory of POS-32
The separatrix that determines the capture of
the injected beam to stable acceleration is presented in
Fig.2. The portraits of the beams at the focusing and
bunching regions combined in the common scale are
given in Fig.3. The radial trajectory of particles for
theinput radii of 1, 2, 3, and 4mm with the angular
discrepancy of 6, 3, 0, -3, -3 mrad are given in Fig.4.
The trajectories of the stable radial motion correspond
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. №3.
Серия: Ядерно-физические исследования (34), с. 11-13.
11
∆W,keV/u
ϕ
ϕо
40302010 0
20500
-50
50
0
∆W,
keV/uW
s
n
ϕ
s
ϕ
bc W
s
∆W
approximately to the normalized emittance of the ion
beam of 0.2 π.mm mrad at the input. The total
normalized acceptance is POS-32 0.87 π.mm. mrad.
RESULTS
As indicated in the Table, we were able to meet
the demands for adequate compact accelerating
structure using the method of APF with the BMC. With
the acceleration rate of 3.2 MeV/m at the 6m length the
gain in energy of 650 keV/u was achieved (the total gain
in energy is 20.8 MeV).
The demands on radial-phase stability were
fulfilled using by using RF-field without
complementary focusing device. The longitudinal
capture was 100o. Further optimization of the
parameters will give a possibility to increase the capture
up to 120-140o. The normalized radial acceptance
(0.87 π.mm.mrad) is of the order of magnitude of that as
in RFQ at the considerably higher acceleration rate, and
the prestripping section is simple in construction.
REFERENCES
1. L.I.Bolotin, et al. International Conf. On High Energy
Accelerators and Instr. CERN, Geneva, 1959, p. 643.
2. V.A.Bomko, B.I.Rudyak, G.M.Skoromny,
N.A.Khiznyak, Trudu IX Vsesoyusnogo Soveshchania
po Uskoritelyam Zaryazenych Chastits, Dubna,1985,
v.1, P.68 (in Russian).
3. V.A.Bomko, A.F.Kobetz, Ju.P.Mazalov, B.I.Rudyak,
Ukrainsky Physichesky Zurnal. 1988, v.43. P.1144.
4. V.A.Bomko, A.F.Kobetz, Ju.P.Mazalov, B.I.Rudyak.
Review of Scientific Instruments, 1998, v.69, N 10,
p.3537-3540.
5. V.A.Bomko, A.F.Kobetz, Ju.P.Mazalov et al. // VANT,
1999, # 4 (35). P. 27.
6. V.A.Batalin, Yu.N.Volkov, T.B.Kulevoy, S.V.Petrenko
«Vacuum-dicharged source of metal ions» Preprint
ITEP 91-37, Moskva, 1991, 28 p.
7. V.A.Bomko, E.I.Revutsky. Zhurnal Technicheskoy
Physiky, 1964, v.24, N7, p.1259.
8. V.A.Bomko, A.F.Dyachenko, A.F.Kobetz, B.I.Rudyak.
Issledovanye structur dlya uskoryenya tyazeluch ionov
- М.: TsNII Atominform, 1988, 26 p. (in Russian).
9. М .L Good, Phis. Rev. 1953, 538.
10. Ya.B.Fainberg. Proc. Symposium on High Energy
Accelerators and Hion Phisic, ERN, Geneva, 1956, p.
91.
11. V.V.Кushin. Аtomnaya Energia. v. 29, N2 (1970),
p.123.
12. V.G.Papkovich, N.А.Khiznyak, N.G.Shulika.
Vopr.At.Nauki i Techn. Ser.: Technika
Fis.Experimenta, iss2(2), Kharkov, 1978, p.51.
13. V.A.Bomko, Ju.P.Mazalov, Ju.V Meleshkova. 16
Soveshchanie po uskoritelyam zariazhenhych chastitz,
Protvino, 1996, v.2, p.50.
14. V.A.Bomko, Ju.P. Mazalov, Ju.V. Meleshkova. 16
Soveshchanie po uskoriteliam zaryazenych chastitz.
Protvino, 1998, v.2, p.123.
15. E.Nolte et al. Nucl. Instr.&Methods, 1979, 158, 311.
16. U.Ratzinger. The New GSI Prestripper Linac for High
Current Heavy Ion Beams, Proc. of the Linac - 96,
Geneva, 1996, v.1, pp. 288-292.
17. P.Lapostolle. IEEE Trans. on Nuclear Science, 1983,
pp 1957-1961.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. №3.
Серия: Ядерно-физические исследования (34), с. 11-13.
11
REFERENCES
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| id | nasplib_isofts_kiev_ua-123456789-81146 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T18:22:49Z |
| publishDate | 1999 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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| spelling | Bomko, V.A. Mazalov, Yu.P. Meleshkova, Yu.V. Kobetz, A.F. Rudyak, B.I. 2015-05-11T18:12:42Z 2015-05-11T18:12:42Z 1999 Prestripping section of the MILAC accelerator based on the principle of alternating-phase focusing with the moving bunch center / V.A. Bomko, Yu.P. Mazalov, Yu.V. Meleshkova, A.F. Kobetz, B.I. Rudyak // Вопросы атомной науки и техники. — 1999. — № 3. — С. 11-13. — Бібліогр.: 17 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/81146 The main task facing the personnel of the linear accelerator of multicharged ions (MILAC) at the NSC KIPT was carrying out the fundamental investigations in the field of nuclear physics and material engineering. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Prestripping section of the MILAC accelerator based on the principle of alternating-phase focusing with the moving bunch center Предобдирочный участок ускорения лумзи на базе ПФФ с ПЦС Article published earlier |
| spellingShingle | Prestripping section of the MILAC accelerator based on the principle of alternating-phase focusing with the moving bunch center Bomko, V.A. Mazalov, Yu.P. Meleshkova, Yu.V. Kobetz, A.F. Rudyak, B.I. |
| title | Prestripping section of the MILAC accelerator based on the principle of alternating-phase focusing with the moving bunch center |
| title_alt | Предобдирочный участок ускорения лумзи на базе ПФФ с ПЦС |
| title_full | Prestripping section of the MILAC accelerator based on the principle of alternating-phase focusing with the moving bunch center |
| title_fullStr | Prestripping section of the MILAC accelerator based on the principle of alternating-phase focusing with the moving bunch center |
| title_full_unstemmed | Prestripping section of the MILAC accelerator based on the principle of alternating-phase focusing with the moving bunch center |
| title_short | Prestripping section of the MILAC accelerator based on the principle of alternating-phase focusing with the moving bunch center |
| title_sort | prestripping section of the milac accelerator based on the principle of alternating-phase focusing with the moving bunch center |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/81146 |
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