2D beam dynamics simulation in linear mode LPWA channel with pre-modulation stage
Laser plasma wakefield acceleration (LPWA) is one of most popular novel methods of acceleration. The acceleration process differs significantly for linear LPWA mode and bubble (non-linear) modes. The LPWA has two serous disadvantages as very high energy spread and low part of electrons trapped into...
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irk-123456789-1118052017-01-15T03:03:23Z 2D beam dynamics simulation in linear mode LPWA channel with pre-modulation stage Polozov, S.M. Новые и нестандартные ускорительные технологии Laser plasma wakefield acceleration (LPWA) is one of most popular novel methods of acceleration. The acceleration process differs significantly for linear LPWA mode and bubble (non-linear) modes. The LPWA has two serous disadvantages as very high energy spread and low part of electrons trapped into acceleration. The energy spectrum better than 10% does not observed anyone in simulations or experiments without of especial plasma density distribution. Such simulations and first experiments was done for bubble mode with different injection methods as varying of plasma density into bunching sub-stage, pondermotive injection, etc. But linear mode LPWA is also very interesting to design a compact hundreds-MeV accelerator. 2D beam dynamics in linear mode LPWA is discussed in this report. The waveguide and klystron type beam pre-modulation schemes are studied. The simulation shows that the klystron type pre-modulation can to gives the energy spectrum better than 1.5% for 200…300 MeV beam and to achieve the capturing coefficient 70…80%. Прискорення електронів у плазмовому каналі, утвореному при впливі лазерного випромінювання, є в цей час одним з найбільш досліджуваних нових методів прискорення. Процес прискорення розрізняється для двох випадків: лінійного та нелінійного («бульбашкового») режимів. Однак прискорення в плазмовому каналі має два суттєвих недоліки – широкий спектр енергії пучка на виході і низький коефіцієнт захоплення електронів у режим прискорення. Проведені моделювання та експерименти показують, що без застосування спеціальних методів передмодуляціі пучка не може бути отриманий спектр краще 10%. Для нелінійного режиму розроблено кілька таких методів і проведено перші експерименти. Лінійний режим прискорення може бути дуже перспективним для створення компактного прискорювача електронів у діапазоні енергій сотні мегаелектронвольт. Розглянута двовимірна динаміка пучка в каналі з передгрупувателем хвилеводного і клістронного типів. Моделювання показує, що при використанні групувателя клістронного типу можна отримати спектр пучка вже 1,5% при енергії електронів 200…300 МеВ і коефіцієнті захоплення 70…80%. Ускорение электронов в плазменном канале, образованном при воздействии лазерного излучения, является в настоящее время одним из наиболее исследуемых новых методов ускорения. Процесс ускорения различается для двух случаев: линейного и нелинейного («пузырькового») режимов. Однако ускорение в плазменном канале имеет два существенных недостатка – широкий спектр энергии пучка на выходе и низкий коэффициент захвата электронов в режим ускорения. Проведенные моделирование и эксперименты показывают, что без применения специальных методов предмодуляции пучка не может быть получен спектр лучше 10%. Для нелинейного режима разработано несколько таких методов и проведены первые эксперименты. Линейный режим ускорения может быть очень перспективен для создания компактного ускорителя электронов в диапазоне энергий сотни мегаэлектронвольт. Рассмотрена двумерная динамика пучка в канале с предгуппирователем волноводного и клистронного типов. Моделирование показывает, что при использовании группирователя клистронного типа можно получить спектр пучка уже 1,5% при энергии электронов 200…300 МэВ и коэффициенте захвата 70…80%. 2013 Article 2D beam dynamics simulation in linear mode LPWA channel with pre-modulation stage / S.M. Polozov // Вопросы атомной науки и техники. — 2013. — № 6. — С. 29-34. — Бібліогр.: 20 назв. — англ. 1562-6016 PACS: 29.17.w, 29.27.Bd http://dspace.nbuv.gov.ua/handle/123456789/111805 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Новые и нестандартные ускорительные технологии Новые и нестандартные ускорительные технологии |
| spellingShingle |
Новые и нестандартные ускорительные технологии Новые и нестандартные ускорительные технологии Polozov, S.M. 2D beam dynamics simulation in linear mode LPWA channel with pre-modulation stage Вопросы атомной науки и техники |
| description |
Laser plasma wakefield acceleration (LPWA) is one of most popular novel methods of acceleration. The acceleration process differs significantly for linear LPWA mode and bubble (non-linear) modes. The LPWA has two serous disadvantages as very high energy spread and low part of electrons trapped into acceleration. The energy spectrum better than 10% does not observed anyone in simulations or experiments without of especial plasma density distribution. Such simulations and first experiments was done for bubble mode with different injection methods as varying of plasma density into bunching sub-stage, pondermotive injection, etc. But linear mode LPWA is also very interesting to design a compact hundreds-MeV accelerator. 2D beam dynamics in linear mode LPWA is discussed in this report. The waveguide and klystron type beam pre-modulation schemes are studied. The simulation shows that the klystron type pre-modulation can to gives the energy spectrum better than 1.5% for 200…300 MeV beam and to achieve the capturing coefficient 70…80%. |
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Article |
| author |
Polozov, S.M. |
| author_facet |
Polozov, S.M. |
| author_sort |
Polozov, S.M. |
| title |
2D beam dynamics simulation in linear mode LPWA channel with pre-modulation stage |
| title_short |
2D beam dynamics simulation in linear mode LPWA channel with pre-modulation stage |
| title_full |
2D beam dynamics simulation in linear mode LPWA channel with pre-modulation stage |
| title_fullStr |
2D beam dynamics simulation in linear mode LPWA channel with pre-modulation stage |
| title_full_unstemmed |
2D beam dynamics simulation in linear mode LPWA channel with pre-modulation stage |
| title_sort |
2d beam dynamics simulation in linear mode lpwa channel with pre-modulation stage |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2013 |
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Новые и нестандартные ускорительные технологии |
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http://dspace.nbuv.gov.ua/handle/123456789/111805 |
| citation_txt |
2D beam dynamics simulation in linear mode LPWA channel with pre-modulation stage / S.M. Polozov // Вопросы атомной науки и техники. — 2013. — № 6. — С. 29-34. — Бібліогр.: 20 назв. — англ. |
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| fulltext |
ISSN 1562-6016. ВАНТ. 2013. №6(88) 29
NOVEL AND ADVANCED ACCELERATION TECHNIQUES
2D BEAM DYNAMICS SIMULATION IN LINEAR MODE LPWA
CHANNEL WITH PRE-MODULATION STAGE
S.M. Polozov
National Research Nuclear University “Moscow Engineering Physics Institute”, Moscow, Russia
E-mail: smpolozov@mephi.ru
Laser plasma wakefield acceleration (LPWA) is one of most popular novel methods of acceleration. The accel-
eration process differs significantly for linear LPWA mode and bubble (non-linear) modes. The LPWA has two se-
rous disadvantages as very high energy spread and low part of electrons trapped into acceleration. The energy spec-
trum better than 10% does not observed anyone in simulations or experiments without of especial plasma density
distribution. Such simulations and first experiments was done for bubble mode with different injection methods as
varying of plasma density into bunching sub-stage, pondermotive injection, etc. But linear mode LPWA is also very
interesting to design a compact hundreds-MeV accelerator. 2D beam dynamics in linear mode LPWA is discussed in
this report. The waveguide and klystron type beam pre-modulation schemes are studied. The simulation shows that
the klystron type pre-modulation can to gives the energy spectrum better than 1.5% for 200…300 MeV beam and to
achieve the capturing coefficient 70…80%.
PACS: 29.17.w, 29.27.Bd
INTRODUCTION
One of the main directions in accelerator technolo-
gy, known as the energy frontier, is the development
towards higher energies. However, the accelerating gra-
dient in both room temperature and superconducting
accelerating structures is limited by the discharge ef-
fects and processes on the surface. Even with the best of
today’s RF technology, the scale of future high-energy
accelerators sets to tens of kilometers in length, and the
fabrication costs are high in both cases. Compact medi-
um energy facilities would also be enabled by higher
acceleration rate to the benefit of smaller laboratories
and universities.
A number of ideas for increasing the rate of the en-
ergy gain have been discussed in the last few decades.
The idea of electrons acceleration in a modulated plas-
ma channel was proposed by Ya.B. Feinberg in the
1950’s [1]. Possible schemes for the plasma wakefield
acceleration (PWA) differing in ways of modulating the
plasma channel were developed later. The first one uses
a high energy (tens of GeV) beam of particles to form a
plasma wave and accelerate a fraction of the injected
particles or a probe beam [2]. Another method is the
laser plasma wakefield acceleration (LPWA) [3], in
which a laser pulse is used to create a plasma wave. The
modulation period of the accelerating field (the wake-
field) is Lw=λw/2=πc/ p, were c is the speed of light in
vacuum, p=(4πen0/m)1/2 is the plasma frequency, e end
m are the elementary charge and mass, and n0 is the
electron density in plasma. Using two lasers with close
frequencies ( p~ ) was also suggested for enhanc-
ing the accelerating gradient even further.
The advantage of the PWA technique vs. conven-
tional accelerators is obvious: the accelerating gradient
in a plasma channel can reach hundreds of GeV/m and
hence the accelerator can be very compact. The idea is
very popular at present and a number of international
collaborations are working on analytical and experi-
mental demonstration of LPWA. Large scale projects
based on LPWA are being discussed now.
However, the step from a novel acceleration tech-
nique to routinely operating facilities has not been made
yet. LPWA has two serious disadvantages: a very high
energy spread of the accelerated electrons and only a
small fraction of electrons is captured into the process
of acceleration. An energy spectrum better than 10%
has not been demonstrated either in simulations or ex-
perimentally without special methods of beam injection
or pre-modulation [4 - 7]. A beam with such a wide en-
ergy spread can not be used for the majority of applica-
tions including medical and particle physics as the beam
can not be transported efficiently. It should be noted that
this problem does not apply to beam driven PWA, in
which the modulated channel is produced by previously
accelerated electrons, and the modulation period is
equal to the bunching period [2].
1. BEAM ACCELERATION IN LPWA
AND METHODS FOR IMPROVING
THE ENERGY SPREAD
Considering LPWA, two regimes are distinguished:
the underdense plasma, in which lpl ar 2// 2
0
22 ,
(quasi linear regime) and the non-linear regime with
lpl ar 2// 2
0
22 . Here rl is the laser spot size,
a0=eA/W0 normalized laser intensity, 2/12
0 )2/1( al .
The electron beam dynamics is different in the two re-
gimes. The theory of the laser-plasma interaction and
acceleration in the plasma channel are discussed in [8 -
10].
Both regimes, however, experience the high energy
spread and low capturing. Conventional accelerators
experienced similar problems in the past, where they
were solved by bunching the beams using klystron or
waveguide type bunchers, and later producing short
bunches with photocathodes. Making a bunch shorter
than the accelerating field modulation period Lw in a
plasma channel does not seem to be viable. However,
pre-modulation (bunching) of the electron beam can still
be used as discussed below.
ISSN 1562-6016. ВАНТ. 2013. №6(88) 30
A few methods for improving the energy spread in
the non-linear regime have been proposed. The first is to
use two plasma stages with constant but not equal plas-
ma densities and a transient stage with varying density
between them for the beam modulation [11]. An energy
spectrum better than 3% for a 1 GeV beam has been
numerically and in experiment has demonstrated a low
energy spectrum < ± 3% [12] for a similar distribution
of the plasma density (decreasing in the first stage and
constant in the second one).
A ponderomotive injection using two synchronized
laser pulses was proposed in [13]. Two lasers can also
excite a beat wave in the plasma, which is then used for
capturing of the shot bunch [14]. With a third laser
pulse this method can produce “cooled” electron beams
[15]. The method of controlled electron self-injection in
wave breaking regime has been also proposed [16], and
an energy spread of ± 3% has been demonstrated exper-
imentally.
These methods improve the energy spread to about
3% for a 1 GeV beam. Still, this number is too high for
many applications. The electron capturing efficiency
also remains problematic. All the methods described
above apply to the non-linear or wave breaking regimes.
However, the linear LPWA mode is also interesting for
practical use. The rate of the energy gain can still be
very high, while the laser power requirements are com-
paratively moderate, meaning that compact, laboratory
scale facilities could be designed for accelerating elec-
tron beams to hundreds of MeV.
2. PRE-MODULATION SCHEMES
IN LINEAR LPWA MODE
Two possible schemes of beam pre-modulation n
linear LPWA mode were proposed [17 - 18].
In the first the bunching scheme similar to wave-
guide buncher in conventional RF lnac was studied. The
plasma channel is divided into two stages. The plasma
density slowly decreases in the first, pre-modulation
stage, and is constant in the second, the main accelerat-
ing stage. The following assumptions are made: the
beam is injected externally, the amplitude of the electric
field does not vary on the scale of the time of flight, the
plasma is cold, linear and collisionless, and the space
charge field of the injected electrons is much lower than
the plasma.
The beam dynamics was studied studied analytically
in a way similar to how it is done for electron RF linacs
and simulated numerically in 1D approach. Functions
)(p and )(E describe dependencies of the plasma
frequency and accelerating field on the longitudinal
coordinate lz /2 . A variable similar to the wave
velocity in a conventional accelerator is introduced
1/2
2ˆ( ) 1 ( )v p
, where ˆ ( ) ( ) / 2p p l c is the
normalized plasma frequency and λl laser wavelength.
Hamiltonian formalism was applied to the above
equations for studying the beam-wave system and the
standard energy balance equation written and injection
conditions were analyzed analytically.
In contrast to conventional RF accelerators, the
phase velocity and amplitude of the accelerating field
are not independent variables, but functions of the
plasma electron density )(0n and are related as
emcE p / . Therefore, optimizing the parameters of
the plasma channel is a complex problem in LPWA.
The linearity condition for the plasma wave can be ex-
pressed as 00 kEkE , and hence
the amplitude of the accelerating field only depends on
the longitudinal coordinate. Here k describes the
plasma wave number in the longitudinal direction.
It was shown by means of analytical study and 1D
numerical simulation that the beam can be modulated
efficiently, the bunch has the minimal phase spread and
more than half of electrons are captured. The resulting
energy spread is 4% with the capturing coefficient
reaching 40…45% front-to-end. But these results do not
match well with the analytical study and single particle
simulations.
Thus the other beam pre-modulation method was
discussed [18]. This scheme is similar to the multigap
klystron buncher of conventional RF linac and based on
a number of short plasma sub-stages (several l long
each) separated by drift gaps. The plasma density distri-
bution in the sub-stages can be simulated using standard
functions (step, Gauss, etc.). The step function was cho-
sen for the simulation. The distribution was expanded
into series. Changing the number of terms in the series
allows for shape adjustment of the plasma density pro-
file. The dimensionless accelerating field distribution in
the bunching part is shown in Fig. 1. The phase size
and energy spread / after pre-modulation stage
with are necessary for an efficient capturing into main
stage and further acceleration can be achieved with elec-
tric field amplitude in bunching stage
)0(/)( EE b =0.85 and a low value of the accel-
erating field in the bunching part ˆ( 0)e =0.009,
0
ˆ( ) ( ) / 2le eE W , (E=2.75∙1010 V/m,
n(ξ=0)=8∙1016 cm-3) for an injection energy
Win=10 MeV/m. The beam is accelerated in the main
plasma stage with ˆ( 0)e =0.033, lz 1000
(E=1∙1011 V/m, n(ξ=0)=1.1∙1018 cm-3, laser beam inten-
sity I0 ≈ 1.2∙1015 W/cm-2). It has Δγ/γ 4% at the output
while accelerating from 12 to 110 MeV.
Fig. 1. Accelerating field distribution in bunching part
linear mode LPWA with pre-modulation scheme
consisting of a number of short plasma
sub-stages separated by drift gaps
ISSN 1562-6016. ВАНТ. 2013. №6(88) 31
3. 2D BEAM DYNAMICS SIMULATION
The equations of motion for an electron in a plasma
channel in 2D Cauchy form then are:
2
2 2
1/2
2
d
ˆ( )exp( ( / ) )sin ,
d
d
,
d
d
ˆ( )(2 / )exp( ( / ) )cos ,
d
d
,
d
d
ˆ1 ( ) 1,
d
z l
z
r
z l l
r
z p
e p
e p p
(1)
where lr /2 is the normalized transverse coordi-
nate, ll a /2 is the normalized laser spot size, p
is the degree in transverse plasma density distribution
and γ Lorentz factor.
New BEAMDULAC-LWA2D code [19, 20] version
was designed to study the beam dynamics in LPWA
channel. The 2D simulation shows that the results of 1D
study are all correct. The simulations were done with the
following beam and channel parameters: an injection
energy before pre-modulation stages Win=10 MeV/m,
beam injection size 50 µm and transverse emittance
1π mm∙mrad, injection energy spread 10%,
Fig. 2. Results of 2D electrons dynamics simulation for beam after pre-modulation (1st stem), for z = 1000 l
(2nd stem), z = 1000 l (3
rd), z = 2000 l (last stem) are sown (top to bottom): particles distribution in conventional
(γ, φ) and (βr, r [m]) phase planes and in non-conventional (γ, r) and (r, φ) planes, phase spectrum, total energy
spectrum and energy spectrum near peak energy (only for the accelerating stage). Injection distributions are plotted
by red points and lines, distribution after pre-modulation by blue and output by black
ISSN 1562-6016. ВАНТ. 2013. №6(88) 32
number of pre-modulation stage 8, total pre-modulation
length 240 µm, maximal electric field amplitude for pre-
bunching stages decreases from 2.5∙109 to 2.15∙109 V/m,
laser spot size 100 µm, electric field amplitude for min
accelerating stage E=1.0∙1010 V/m. The results of simu-
lation are presented in Fig. 2 for beam after pre-
modulation (1st stem), for z =1000 l (2nd stem),
z =1000 l (3
rd), z =2000 l (last stem). The peak energies
are 120, 210 and 400 MeV respectively. In Fig. 2 are
sown (top to bottom): particles distribution in conven-
tional (γ, φ) and (βr, r [m]) phase planes and in non-
conventional (γ, r) and (r, φ) planes, phase spectrum,
total energy spectrum and energy spectrum near peak
energy (only for the accelerating stage). Injection distri-
butions are plotted by red points and lines, distribution
after pre-modulation by blue and output by black.
It is clear that the electrons are effectively bunched
and captured into acceleration in the main stage. The
spectrum is lower than 3% and decreases with energy.
The part of electrons is decapturing of acceleration and
part of electrons having maximal energy decreases from
70% for 120 MeV to 40…45% for 400 MeV. But such
dependence is typical for conventional RF linac also.
The possible way of decaptured electrons separation
is very interesting. It is clear that uncaptured electrons
are transported in the accelerating plasma channel with-
out of the acceleration but the transverse motion of hun-
dreds-MeV electrons is very slow and such particles not
achieve the channel boundary. But they are transporting
having higher readies comparatively captured electrons.
The easy diaphragm can be effective used to separate
uncaptured and decaptured electrons.
Fig. 3. The results of simulation taking into account plasma density distribution errors are shown (left to right):
plasma density distribution, particles distribution in (γ, φ) and (βr, r [m]) phase planes after pre-modulation stages,
particles distribution in (γ, φ) and (βr, r [m]) phase planes and energy spectrum after main accelerating channel.
The figures (top to bottom) are calculated without error of plasma density distribution and taking into account er-
rors for plasma stages forms, stages length and both of them. Injection distributions are plotted by red points and
lines, distribution after pre-modulation by blue and output by black
ISSN 1562-6016. ВАНТ. 2013. №6(88) 33
4. SIMULATION OF “REAL” PLASMA
DENSITY DISTRIBUTIONS
It is obvious that the all previous simulations were
done for “ideal” plasma density distribution in sugges-
tion that necessary for effective pre-modulation distribu-
tion can be realized on practice. Thus the distribution
errors influence to the beam dynamics should be dis-
cussed.
The BEAMDULAC-LWA2D code was modified
and pseudo-random error solver was applied in the
code. This solver allows doing the pseudo-random cor-
rection for plasma stages length, centre of the stem posi-
tion and density distribution. The correction can be
made for each stem independently. But the error of each
parameters (and plasma density in each point) will ran-
domize only in user defined limits. Such pseudo-random
approach allows to define the limiting conditions for
plasma density distribution quality and to discuss the
possibility of these distributions experimental realiza-
tion possibility.
The results of simulation are shown in Fig. 3 (left to
right): plasma density distribution, particles distribution
in (γ, φ) and (βr, r [m]) phase planes after pre-
modulation stages, particles distribution in (γ, r) and
(r, φ) phase planes and energy spectrum after main ac-
celerating channel. The figures (top to bottom) are cal-
culated without error of plasma density distribution and
taking into account errors for plasma stages forms, stag-
es length and both of them. It is clear that the random-
ized errors influence is not sufficient for stage form er-
rors up to 20%. But the stage length error influenced
more sufficiently and plasma stems should be posi-
tioned not poorly than 10%. These results are confirms
by simulation done taking into account both errors: 10%
length error and 20% form error gives very serious de-
viation of particle distributions in phase spaces and of
the spectrum.
CONCLUSIONS
The basic idea of klystron-like beam pre-modulation
for linear mode laser plasma wake-field acceleration
was discussed. The idea is directed to beam pre-
modulation using shot low density plasma stages with
gaps between of them. Such idea is similar to known
method of multi-gap klystron.
The new code version BEAMDULAC-LWA2D was
developed to study the 2D electrons dynamics both in
pre-modulation stage and main acceleration stage. It
was shown that the beam can be effectively bunched,
captured into acceleration in the main stage and acceler-
ated up to hundreds of MeV. The energy spread is not
higher than 3% for 100 MeV beams which is much low-
er than for other LPWA bunching schemes.
The capturing coefficient is high also and it is
achieved up to 70…75%. Later some electrons lose
from the acceleration but half of external injected beam
can be accelerated up to 400…500 MeV. This result is
also much better than for other known bunching
schemes.
Tolerances of plasma density distributions were also
studied.
Using pseudo-random solver added to BEAMDULAC-
LWA2D was shown that the maximal deviation of
plasma density should not exceed than 20 % of the ana-
lytically defined function. But the tolerance of plasma
stem length should not exceed 10 %. Such plasma den-
sity distributions can be realized in the experiment by
plasma filled capillary or a supersonic gas jet.
The simulation taking into account the beam-plasma
interactions and self-fields is planned to do in future.
The laser intensity attenuation due to plasma excitation
should be also discussed.
This work is supported in part by the Ministry of
Science and Education of Russian Federation under
contract No. 14.516.11.0084.
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p. 1084.
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v. 43 (4), p. 267.
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Article received 10.09.2013
http://www.nature.com/nphys/journal/v7/n11/full/nphys2071.html#auth-1
ISSN 1562-6016. ВАНТ. 2013. №6(88) 34
МОДЕЛИРОВАНИЕ ДВУМЕРНОЙ ДИНАМИКИ ПУЧКА В КАНАЛЕ ЛАЗЕРНО-ПЛАЗМЕННОГО
УСКОРИТЕЛЯ, РАБОТАЮЩЕГО В ЛИНЕЙНОМ РЕЖИМЕ С ПРЕДГРУППИРОВАТЕЛЕМ
С.М. Полозов
Ускорение электронов в плазменном канале, образованном при воздействии лазерного излучения, являет-
ся в настоящее время одним из наиболее исследуемых новых методов ускорения. Процесс ускорения разли-
чается для двух случаев: линейного и нелинейного («пузырькового») режимов. Однако ускорение в плаз-
менном канале имеет два существенных недостатка – широкий спектр энергии пучка на выходе и низкий
коэффициент захвата электронов в режим ускорения. Проведенные моделирование и эксперименты показы-
вают, что без применения специальных методов предмодуляции пучка не может быть получен спектр лучше
10%. Для нелинейного режима разработано несколько таких методов и проведены первые эксперименты.
Линейный режим ускорения может быть очень перспективен для создания компактного ускорителя элек-
тронов в диапазоне энергий сотни мегаэлектронвольт. Рассмотрена двумерная динамика пучка в канале с
предгуппирователем волноводного и клистронного типов. Моделирование показывает, что при использова-
нии группирователя клистронного типа можно получить спектр пучка уже 1,5% при энергии электронов
200…300 МэВ и коэффициенте захвата 70…80%.
МОДЕЛЮВАННЯ ДВОВИМІРНОЇ ДИНАМІКИ ПУЧКА В КАНАЛІ ЛАЗЕРНО-ПЛАЗМОВОГО
ПРИСКОРЮВАЧА, ЩО ПРАЦЮЄ В ЛІНІЙНОМУ РЕЖИМІ З ПЕРЕДГРУПУВАТЕЛЕМ
С.М. Полозов
Прискорення електронів у плазмовому каналі, утвореному при впливі лазерного випромінювання, є в цей
час одним з найбільш досліджуваних нових методів прискорення. Процес прискорення розрізняється для
двох випадків: лінійного та нелінійного («бульбашкового») режимів. Однак прискорення в плазмовому ка-
налі має два суттєвих недоліки – широкий спектр енергії пучка на виході і низький коефіцієнт захоплення
електронів у режим прискорення. Проведені моделювання та експерименти показують, що без застосування
спеціальних методів передмодуляціі пучка не може бути отриманий спектр краще 10%. Для нелінійного ре-
жиму розроблено кілька таких методів і проведено перші експерименти. Лінійний режим прискорення може
бути дуже перспективним для створення компактного прискорювача електронів у діапазоні енергій сотні
мегаелектронвольт. Розглянута двовимірна динаміка пучка в каналі з передгрупувателем хвилеводного і
клістронного типів. Моделювання показує, що при використанні групувателя клістронного типу можна
отримати спектр пучка вже 1,5% при енергії електронів 200…300 МеВ і коефіцієнті захоплення 70…80%.
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