Two beam proton accelerator for electronuclear industry (plutonium conversion)
A concept of a linear proton accelerator with excited by electron beam RF cavities is discussed. This accelerator with parameters of a second proton beam equaled to 1 GeV, 10-30 mA can be used for the new type of electronuclear installations and weapon plutonium conversion.
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 2000 |
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| Мова: | Англійська |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2000
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| Цитувати: | Two beam proton accelerator for electronuclear industry (plutonium conversion) / G.V. Dolbilov // Вопросы атомной науки и техники. — 2000. — № 2. — С. 107-110. — Бібліогр.: 10 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860060465681399808 |
|---|---|
| author | Dolbilov, G.V. |
| author_facet | Dolbilov, G.V. |
| citation_txt | Two beam proton accelerator for electronuclear industry (plutonium conversion) / G.V. Dolbilov // Вопросы атомной науки и техники. — 2000. — № 2. — С. 107-110. — Бібліогр.: 10 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | A concept of a linear proton accelerator with excited by electron beam RF cavities is discussed. This accelerator with parameters of a second proton beam equaled to 1 GeV, 10-30 mA can be used for the new type of electronuclear installations and weapon plutonium conversion.
|
| first_indexed | 2025-12-07T17:04:15Z |
| format | Article |
| fulltext |
TWO BEAM PROTON ACCELERATOR
FOR ELECTRONUCLEAR INDUSTRY (PLUTONIUM CONVERSION)
G.V. Dolbilov
Joint Institute for Nuclear Research, Dubna, 141980 Moscow reg. Russia, dol@sunse.jinr.ru
A concept of a linear proton accelerator with excited by electron beam RF cavities is discussed. This accelerator
with parameters of a second proton beam equaled to 1 GeV, 10-30 mA can be used for the new type of electronucle-
ar installations and weapon plutonium conversion.
1. INTRODUCTION
In electronuclear installations a flux of neutrons gen-
erated by the ~1 GeV proton beam keeps up a reaction
of a heavy nucleus fission [1]. An energy produced by
the protons is increased in some ten times and the elec-
tronuclear reactor represents itself as an energy amplifi-
er [2]. From energy point of view a proton accelerator is
an energy converter from a power line to RF oscillations
and then to an accelerated proton beam. An efficiency of
the each conversion is a very important parameter. At
present a superconducting proton accelerator looks up
most perspective one for the electronuclear installations
[3]. In such the accelerator the conversion efficiency of
the RF energy into the proton energy is practically equal
to 1, and the total efficiency is about to 60%, which de-
pends on the efficiency of RF stations converting a ki-
netic energy of electrons to the RF energy.
Electron beams can be used for an excitation of su-
perconducting cavities of the accelerator directly, with-
out their using in amplifiers of the RF stations. Here-
with, if a reacceleration of the electrons by external
fields is used, the efficiency of the conversion of their
kinetic energy into the proton energy can be close to 1.
The excitation of an accelerating structure by the
electron beam (the two beam method of the accelera-
tion) can be used in “room temperature” accelerators.
However a significant growth of a ion beam load of the
cavities need be increased to reduce a relative value of a
energy loss in the accelerating structure cavities. There-
fore “room temperature” accelerator should operate in a
pulse regime.
The electrodynamic structure of the as superconduct-
ing so “room temperature” two beam accelerator fulfills
two functions. It is the buncher of the primary exciting
electron beam and accelerating structure of the sec-
ondary ion beam [4-7].
2. EXCITATION OF ACCELERATING
FIELDS BY ELECTRON BEAM
For an effective conversion of the electron beam en-
ergy into the energy of the ion beam, the solution of 3
principal points are needed:
• longitudinal stability of the driving electron
bunch;
• amplitude of the RF field excited by the
electron beam;
• synchronism of the accelerated protons and
excited RF fields.
2.1 LONGITUDINAL STABILITY OF THE
ELECTRON BUNCHES
A bunching of the electrons in exciting the cavities
of the proton accelerating structure is provided by the
excited RF field similar the multi-cavity klystron bunch-
er. The buncher frequency is slightly less than the fre-
quency of the unloaded cavities of the accelerator and
the cavities have almost pure inductive impedance, so
the bunches of the driving electron beam pass the cavity
at zero phase of RF field. As a result of a phase shift be-
tween the excited voltage and the electron bunches the
longitudinal stability is provided (Fig. 1).
To verify the possibility of the stationary bunches
existence a computer simulations have been performed.
The results of the simulations of the Ie=430 A,
Ue=500 kV electron beam bunching and exciting of
14 GHz cavities of the electrodynamic structure are
shown on Fig. 2.
Fig. 1. Time diagrams of the RF voltage and the
electron and ion beam currents.
The computer simulations have shown that there is
the optimum matching regime when the longitudinal di-
mension of bunches are matched with the electrodynam-
ic structure of the accelerator and the oscillation ampli-
tude of the electron bunch dimensions have a minimal
value. In this matching regime the 430 A, 500 keV elec-
tron beam excite the ~1 MV voltage in the cavities
(Fig. 2). The average proton accelerating gradient is de-
termined by number of the cavities per unit of length.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2000, № 2.
Серия: Ядерно-физические исследования (36), с. 107-110.
107
Fig. 2. Phase trajectories of electrons. Matching of
the electron bunch dimensions and electrodynamic
structure parameters. RF voltage amplitudes in the
cavities (kV) - right column of parameters.
The “DISKLY v.3.5” computer program have been
used for the calculation and matching of the phase tra-
jectories. This program have been developed at the Bud-
ker Institute of Nuclear Physics (Protvino, Novosibirsk)
for calculations of powerful multi-cavity klystrons.
2.2 AMPLITUDE OF RF FIELDS
From the law of conservation of energy
P P Pe i loss= + ,
where Pe - average power of the driving beam which is
spent to excite the cavity, Pi - average power which is
taken to accelerate the proton beam, Ploss - power lost in
the cavity, it results that the magnitude of the cavity
voltage excited by electron beam is equal to
U R
I
Ii
e
i=
+
−2
1
0 2
( )
ξ
.
Here I e - average electron beam current, I i - average
proton beam current, ξ = 2 0Q
f
f
∆
- relative detuning
of the frequencies of the cavity and bunching electron
beam, R0 and Q0 - shunt impedance and quality factor
of the unloaded cavity.
The shunt impedance of the superconducting cavities
is some ten GOhm, therefore there it is not a problem to
excite the very high RF voltage. Maximum accelerating
gradients will be limited by critical fields of the super-
conducting cavities.
The use of the “room temperature” cavities requires
a choice of a compromise between a wish to have the
maximum accelerating gradient and maximum efficiency
of the electron beam energy conversion into the energy
of the ion beam.
2.3. CONDITION OF SYNCHRONISM FOR THE
PROTONS AND EXCITING RF FIELDS
The condition of synchronism for the protons and
exciting RF field is realized when [4-7]:
1 1
β β
λ
i e
k
L
= ± ,
L - period of the accelerating structure, λ- wave length,
βi and βe - relative velocity of protons and electrons, k -
integer. This condition is consequence of the equality:
∆ ∆ϕ ϕ πi e k = ± 2 ,
where −∆ ei,ϕ a proton and electron transit phase
of the accelerating structure period. Synchronism is pos-
sible when the electron and ion beams move as in the
same so in the opposite directions.
3. SUPERCONDUCTING VARIANT OF TWO
BEAM PROTON ACCELERATOR
There is possibility to construct some variants of the
two beam accelerator:
• Variant using a reacceleration of the elec-
tron beam to recover the electron energy
loss. (counter-propagating electron and ion
beams), Fig. 3,a.
• Variant without a reacceleration of the elec-
tron beam. The kinetic energy of the elec-
tron beam is almost wholly used to excite
the cavity (counter-propagating electron
and ion beams), Fig. 3,b.
• Accelerator using a reacceleration of the
electrons to provide an equality of the elec-
tron and ion velocities. In this case the ex-
cited RF fields and ions are always phased
and the dependence of the structure period
upon the ion velocity is absent, Fig. 3,c.
It is assumed that a remainder of the electron beam
kinetic energy is recuperated.
Fig. 3. Schemes of the superconducting two beam
accelerator.
In the first variant (a), the velocity and energy elec-
trons are close to constant. The ratio of the energies
spent by the electrons and gained by the ions depends on
the relative detuning magnitude of the cavities ξ . The
magnitude of the relative detuning can be about to 103 -
104.
108
For superconducting accelerator
21 ξ+
= iU
eU ,
I Ie i= +1 2ξ ,
and to accelerate the ions up to 1 GeV the total potential
of induction modules should be equal to 0.1 - 1.0 MeV.
At 30 mA current of the ion beam the electron beam
current should be equal to 300 - 30 A. The induction
modules and itself proton accelerator operate in the
pulse regime. The low reaccelerating gradient and mag-
nitude of the induction core voltage allow one to use the
transistor variant of the modulators. Cheap and reliable
modulator is composed of the DC voltage source and
transistor bridge circuit. The output voltage of the mod-
ulator is a square wave (“meander”). The efficiency of
the energy conversion from the power line to the elec-
tron beam is up to 90-95%. The total length of the in-
duction modules depends on the used ferromagnetic ma-
terial (metglas ~20 m/MV, ferrite ~50 m/MV).
The cost of induction accelerator is estimated to be
0.1-1 million USD (depend on the total energy and type
of the ferromagnetic material).
In the second variant (b) the electron gun generates
the direct current beam. The initial electron beam power
slightly larger the final proton beam power. For the
1 GeV, 30 mA proton accelerator the parameters of the
electron beam would be following: energy ~ 1 MeV,
current ~ 30 A. This gun can be constructed on the base
of the industrial accelerator for EB-technologies [8].
This variant allows using the lower current, 20-10 A,
but higher energy, 1.5-3 MeV, beams. In this case, for a
generation of the direct current beam the two induction
accelerators are required. These accelerators should op-
erate at the opposite phase regime of the square waves.
After the addition of the beams the direct current would
be got.
The approximate cost of the electron beam units is
~1-3 million USD. The efficiency of the energy conver-
sion from the power line to the electron beam is ~85-95%.
In the variant (c) the protons and electrons move
with the same value and direction of the velocities. It al-
lows choosing the period of the electrodynamic struc-
ture, which is more optimum to achieve the maximum
ion accelerating gradient and focusing of the electron
and ion beams. The cost and efficiency of the electron
part of the accelerator is the same as the variant (a).
Further analysis and experimental tests will allow
one to choose the most optimum variant of the super-
conducting two beam accelerator.
4. “ROOM TEMPERATURE” VARIANT
OF THE PROTON ACCELERATOR
There is principal possibility to use the “room tem-
perature” cavity in the two beam accelerator of the pro-
tons. In this case, to increase the efficiency of the energy
conversion from the electron beam into the proton beam
it is necessary to increase the load of the cavities by the
proton beam (to increase the proton beam current).
Therefore the “room temperature” accelerator is the
pulsed machine.
Let the energy conversion efficiency from the elec-
trons into the ions be equal to η, then the voltage of the
cavity induced by the electron beam can be written as:
U
R I e= −
+
2 1
1
0
2
( )η
ξ
.
The average current of the electron and ion beams
and the conversion efficiency of their energy are associ-
ated by the ratio:
21 ξ
η
+
= eI
iI .
The average accelerating gradient, E U L= , of the
accelerating structure with cylindrical cavities and the
period of the structure L i e= +− −λ β β( )1 1 is equal to
E
I e=
−
+
⋅ ⋅
1
1 2
0η
ξ
ρ
π δ
Ψ ,
where πεµρ 120000 == - wave-forming resis-
tance of free space, δ - skin-layer,
Ψ = + + −( )
1 1 2
0
1
β β
π
i e
h
L j ,
h- accelerating gap, j0 2 4= . - first root of the Bessel
function J 0 .
For accelerating structure based on copper cavities
Ψ⋅⋅
+
−⋅⋅=
λξ
η eI
E
21
17101.3 .
At energies of the electron and ion beams in regions
eUi = 100-1000 MeV,
eUe = 100-1000 keV,
and h/L=0.25 we have Ψ=0.2−0.35.
The average deaccelerating gradient of this structure
for driving electrons is equal to
E
E
e =
+1 2ξ
.
4.1 AVERAGE ACCELERATING GRADIENT
The average accelerating electric field strength of the
two beam accelerator with the copper cavities and
λ = 01. m is
.
21
1710)4.30.2( eIE ⋅
+
−⋅⋅−=
ξ
η
If parameters of the electron beam is the same as the
powerful klystron beam parameters:
Ie = 500 A, Ue = 500 keV,
and the ratio of the accelerating ions and deaccelerating
electrons fields of the cavities is
U U e = − =1 1002ξ ,
the average electric field strength will be equal to
E≈20 -30 MV/m.
Herewith the efficiency of the conversion of the elec-
tron kinetic energy into the energy of the accelerating
protons will achieve 80% (η=0.8).
109
4.2 INTENSITY OF THE PROTON AND ELEC-
TRON BEAMS
At the average electron beam current of the mi-
cropulse equaled 500 A to achieve the 80% efficiency of
the beam energy conversion the average proton beam
current should be increased up to
I
I
Ai
e=
+
=η
ξ1
4
2
The generation of the 4 A pulsed proton beams is the
rather difficult problem. Possible ways of its solution are
the use of the ion beam compression technique or MV
voltage proton gun.
4.3 SCHEME OF THE “ROOM TEMPERA-
TURE” PROTON ACCELERATOR
The main part of the accelerator (0.1-1 GeV) has the
900 MeV total accelerating potential. At above regime
of the two beam accelerator the total deaccelerating
electron potential will be equal to ~9 MeV. Therefore, if
the electron gun voltage is ~500 kV more than 20 this
guns are required.
If to assume that 300 keV of the 500 keV electron
kinetic energy is converted into the RF energy of the
loaded cavities, then total number of the proton acceler-
ating modules with autonomous electron guns will be
30. After passing the module the 200 keV electron beam
is injected into the recuperator of the kinetic energy.
A scheme of the proton accelerator composed of the
autonomous accelerating modules with the energy
equaled some ten MeV is showed on Fig. 4. The voltage
of the electron gun is egualed to U=U1+U2, where U1 -
deaccelerated electrons voltage of the module, U2 - volt-
age of the recuperator.
Fig. 4. Scheme of the “room temperature” proton
accelerator with the excited by electron beam cavities.
U1 - deaccelerated electrons voltage of the module, U2 -
voltage of the recuperator. Cathodes of the electron
guns have a hole on the axis to pass the proton beam.
The cost of the “room temperature” variant of the
two beam accelerator of protons is significantly lower
because the superconducting cavities, cryogenic system
and RF station are absent. The “room temperature” ac-
celerator is more reliable and its maintenance is cheaper.
In this variant the requirement on the electron loss value
is significantly lower because a water-cooling of accel-
erator systems is used.
To make the electron guns simpler and cheaper it is
assumed the use of the high voltage sources developed
by V.E. Balakin team for the VLEPP klystron. DC volt-
age (1MV [9]) is used in this variant of the electron
source. A pulsed regime of an operation is realized by
means of an employment of the electron gun with a grid
control [9]. Analogously VLEPP the high voltage coaxi-
al feeder is laid along the proton accelerator and the
electron guns of the autonomous modules is connected
to a branch of this feeder (Fig. 4).
The powerful klystron technique of the beam focus-
ing can be used to focus the electron beam of the two
beam accelerator. In our opinion, most preferable focus-
ing system is the system based on a permanent magnets,
which is developed by V. Balakin team (Budker INP,
Protvino, Novosibirsk) for the VLEPP linear collider
klystron [9,10].
The problem of the recuperation is less worked up.
The rough estimations of the recuperation efficiency
give the value > 0.9, and the total accelerator efficiency
is ~70%. If the recuperation is absent the total efficiency
from the power line is ~50%.
REFERENCE
1. V.N. Mikhailov. JINR Rapid Communication.
1996. No 6(80)- 96, Dubna, p. 17.
2. C. Rubia, P. Mandrilon, P. Fietier. Proc. of 4th
EPAC, London. 1994, p. 270-272.
3. B.P. Murin. II Seminar in Memory of V.P. Sarant-
sev. Dubna, 1997, p. 43-45.
4. G.V. Dolbilov. High Current Linacs at JINR and
Perspective of Their Application for Acceleration of
Ions. AIP Conf. Proc. 480, “Space Charge Beam
Physics for Heavy Ion Fusion”, Sainta, Japan, 1998,
p. 85-98.
5. G.V. Dolbilov. Electrodynamic Structure of Two
Beam Accelerator. Proc. of International University
Conference on “Electronics and Radiophysics of Ul-
tre-High Frequencies”, St. Petersburg, Russia, 1999,
p. 443-446.
6. G.V. Dolbilov. Two Beam LIA. III Seminar in
Memory of V.P. Sarantsev, Dubna, 1999 (to be
publ.).
7. G.V. Dolbilov. Two Beam Induction Linear
Collider. Proc. of the 7th EPAC, Viena, 2000, in
Joint Accel. Conf. Website, THP4B15, http://ac -
celconf . web.cern.ch /accelconf/e00.
8. Yu.I. Golubenko et al. Accelerators of Electrons
EVL-series: Status, Application, Development. Na-
tional Scientific Center Russian Federation. Budker
INP, INP 97-7, Novosibirsk, 1997.
9. V.E. Balakin et al. High Power Sources for
VLEPP. AIP Conf. Proc. 337, “Pulsed RF Sources
for Linear Collider”, Montauk, USA, 1994, p. 118-
121.
10. G.V. Dolbilov, V.E. Balakin et al. A concept of a
Wide Aperture Klystron with RF Absorbing Drift
Tubes for Linear Colliders // Nucl. Inst. and Meth-
ods in Physics Research. 1996, v. A383, p. 318-324.
110
1. Introduction
2. Excitation of accelerating fields by electron beam
2.3. Condition of synchronism for the protons and exciting RF fields
3. Superconducting variant of two beam proton accelerator
4. “Room temperature” variant of the proton accelerator
4.1 Average accelerating gradient
4.2 Intensity of the proton and electron beams
4.3 Scheme of the “room temperature” proton accelerator
Reference
|
| id | nasplib_isofts_kiev_ua-123456789-82277 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T17:04:15Z |
| publishDate | 2000 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Dolbilov, G.V. 2015-05-27T13:06:02Z 2015-05-27T13:06:02Z 2000 Two beam proton accelerator for electronuclear industry (plutonium conversion) / G.V. Dolbilov // Вопросы атомной науки и техники. — 2000. — № 2. — С. 107-110. — Бібліогр.: 10 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/82277 A concept of a linear proton accelerator with excited by electron beam RF cavities is discussed. This accelerator with parameters of a second proton beam equaled to 1 GeV, 10-30 mA can be used for the new type of electronuclear installations and weapon plutonium conversion. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Тheory and technics of particle acceleration Two beam proton accelerator for electronuclear industry (plutonium conversion) Двухпучковый линейный ускоритель протонов для электроядерной энергетики (конверсия плутония) Article published earlier |
| spellingShingle | Two beam proton accelerator for electronuclear industry (plutonium conversion) Dolbilov, G.V. Тheory and technics of particle acceleration |
| title | Two beam proton accelerator for electronuclear industry (plutonium conversion) |
| title_alt | Двухпучковый линейный ускоритель протонов для электроядерной энергетики (конверсия плутония) |
| title_full | Two beam proton accelerator for electronuclear industry (plutonium conversion) |
| title_fullStr | Two beam proton accelerator for electronuclear industry (plutonium conversion) |
| title_full_unstemmed | Two beam proton accelerator for electronuclear industry (plutonium conversion) |
| title_short | Two beam proton accelerator for electronuclear industry (plutonium conversion) |
| title_sort | two beam proton accelerator for electronuclear industry (plutonium conversion) |
| topic | Тheory and technics of particle acceleration |
| topic_facet | Тheory and technics of particle acceleration |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/82277 |
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