Recent progress on laser plasma accelerators and applications for compact high-quality particle beam and radiation sources
Recent progress in laser-driven plasma-based electron accelerators is overviewed in theoretical and experimental aspects. In particular, basic acceleration physics called as a bubble mechanism is highlighted to show recent achievements of laser plasma accelerator technologies that produce high-energ...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2010
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| Cite this: | Recent progress on laser plasma accelerators and applications for compact high-quality particle beam and radiation sources / K. Nakajima // Вопросы атомной науки и техники. — 2010. — № 6. — С. 68-72. — Бібліогр.: 28 назв. — англ. |
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| citation_txt | Recent progress on laser plasma accelerators and applications for compact high-quality particle beam and radiation sources / K. Nakajima // Вопросы атомной науки и техники. — 2010. — № 6. — С. 68-72. — Бібліогр.: 28 назв. — англ. |
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| description | Recent progress in laser-driven plasma-based electron accelerators is overviewed in theoretical and experimental aspects. In particular, basic acceleration physics called as a bubble mechanism is highlighted to show recent achievements of laser plasma accelerator technologies that produce high-energy, high-quality stable beams required for compact particle beam and radiation sources.
Приведен обзор нынешнего прогресса в теоретических и экспериментальных исследованиях электронных ускорителей, основанных на лазерно-плазменном взаимодействии. В частности, фундаментальная физика ускорения, называемая механизмом «пузыря», выдвигается на первый план для демонстрации последних достижений лазерно-плазменных ускорительных технологий получения высококачественных стабильных пучков высокой энергии, требуемых для компактных источников пучков и излучения.
Приведено огляд нинішнього прогресу в теоретичних і експериментальних дослідженнях електронних прискорювачів, заснованих на лазерно-плазмовій взаємодії. Зокрема, фундаментальна фізика прискорення, що називається механізмом «пузиря», висувається на перший план для демонстрації останніх досягнень лазерно-плазмових прискорювальних технологій отримання високоякісних стабільних пучків високої енергії, які потребуються для компактних джерел пучків і випромінювання.
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RECENT PROGRESS ON LASER PLASMA ACCELERATORS
AND APPLICATIONS FOR COMPACT HIGH-QUALITY
PARTICLE BEAM AND RADIATION SOURCES
K. Nakajima
High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0081 Japan;
Shanghai Jiao Tong University, 800 Dongchuan Rd., Shanghai 200240, P. R. China
E-mail: nakajima@post.kek.jp
Recent progress in laser-driven plasma-based electron accelerators is overviewed in theoretical and experimental
aspects. In particular, basic acceleration physics called as a bubble mechanism is highlighted to show recent
achievements of laser plasma accelerator technologies that produce high-energy, high-quality stable beams required for
compact particle beam and radiation sources.
PACS: 41.75Jv, 52.38kd, 52.50Jm
1. INTRODUCTION
In this decade, worldwide experimental and theoretical
researches on laser-plasma accelerators have brought
about great progress in high-energy high-quality electron
beams of the order of GeV-class energy and a few %
energy spread [1-6]. These high-energy high-quality
particle beams make it possible to open the door for a
wide range of applications in research, and medical and
industrial uses.
Here recent progress in laser-driven plasma particle
accelerators is overviewed in terms of particle beam
parameters such as energy, energy spread, emittance,
bunch length and charge, strictly determined by
acceleration mechanism such as the bubble mechanism in
electron acceleration.
Although there is no practical application to date,
developed are various applications of laser plasma
accelerators such as a compact THz or coherent X-ray
radiation source and radiation therapy driven by laser-
accelerated electrons [7]. On the other hand, a promising
application project of laser-driven proton and ion beams
to the future hadron therapy is implemented worldwide.
In the future laser-plasma accelerators may come into
being as a novel versatile tool for developing fields such
as space science where a compact and cost-effective tool
is required as well as inherent application to the energy-
frontier particle accelerator.
2. LASER WAKEFIELD ACCELERATOR
2.1. LINEAR WAKEFIELD ACCELERATION
In underdense plasma an ultraintense laser pulse excites
a large-amplitude plasma wave with frequency
ωp = (4πe2ne/mec2)1/2 and electric field on the order of
~ ne
1/2 V/cm for the electron rest mass mec2 and plasma
density ne cm-3 due to the ponderomotive force expelling
plasma electrons out of the laser pulse and the space
charge force of immovable plasma ions restoring expelled
electrons on the back of the ion column remaining behind
the laser pulse. Since the phase velocity of the plasma
wave is approximately equal to the group velocity of the
laser pulse vg/c = (1- ωp
2/ω0
2)1/2 ~1 for the laser frequency
ω0 and the accelerating field of ~ 1 GeV/cm for the
plasma density ~ 1018 cm-3, electrons trapped into the
plasma wave are likely to be accelerated up to ~ 1 GeV
energy in a 1 cm plasma. More accurately in the linear
regime for the normalized laser intensity
( ) 2122182
0 mWcm/1085.0 μλ −= Ia ≲1,
where I is the laser intensity and λ = 2πc/ω0 the laser
wavelength, the energy gain[8] is given by
( )( ) ( ) GeV,cm10mTW35
3.1
13-182
0
2
0
2
−−≈
=
e
ece
nrP
nnacmE
μ
for the peak laser power P TW focused onto the spot
radius r0 μm, assuming that the plasma wave is efficiently
excited at λp ~ cτL for the pulse duration τL, and that
electrons are accelerated over the dephasing length given
by Ldp ~ λp(ωp
2/ω0
2) = λp(nc/ne), where nc = π/(reλ2) ⋍
1.115×1021 cm-3 (λ/μm)-2 is the cutoff density, re = e2/mec2
the classical electron radius. The accelerated electrons
overrun the accelerating field toward the decelerating
field beyond the dephasing length.
2.2. QUASI-MONOENERGETIC ACCELERATION
IN THE BUBBLE REGIME
The leading experiments [9-11] that successfully
demonstrated the production of quasi-monoenergetic
electron beams with narrow energy spread have been
elucidated in terms of self-injection and acceleration
mechanism in the bubble regime [12,13]. In these
experiments, electrons are self-injected into a nonlinear
wake, referred to as a “bubble”, i.e. a cavity void of
plasma electrons consisting of a spherical ion column
surrounded with a narrow electron sheath, formed behind
the laser pulse instead of a periodic plasma wave in the
linear regime. As analogous to a conventional RF cavity
inside which electromagnetic energy is resonantly
confined at the matched frequency to accelerate externally
injected particles, inducing a current flow in a skin depth
of a metal surface, plasma electrons radially expelled by
the radiation pressure of the laser form a sheath with
thickness of the order of the plasma skin depth c/ωp
outside the ion sphere remaining “unshielded” behind the
laser pulse moving at relativistic velocity so that the
cavity shape should be determined by balancing the
Lorentz force of the ion sphere exerted on the electron
sheath with the ponderomotive force of the laser pulse.
68 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2010. № 6.
Series: Plasma Physics (16), p. 68-72.
This estimates the bubble radius RB matched to the laser
spot radius w0 , approximately as 00 2 awkRk pBp ≈≈ ,
for which a best spherical shape of the bubble is created.
This condition is reformulated as a0 ≃ 2(P/Pc)1/3, where
Pc = 17(ω0/ωp)2 GW is the critical power for the
relativistic self-focusing [13].
The electromagnetic fields inside the bubble is obtained
from the wake field potential of the ion sphere moving at
the velocity vB as
( ) ( ) 2,2 rkcmeEkcmeE pperppez −=−= ωξω ,
where ξ =z-vBt is the coordinate in the moving frame of
the bubble and r the radial coordinate with respect to the
laser propagation axis [12]. One can see that the
maximum accelerating field is given by
e|Ez|max = (1/2)mec2kp
2RB at the back of the bubble and the
focusing force is acting on an electron inside the bubble.
Assuming the bubble phase velocity is given by vB ~
vg-vetch~c[1-(1/2+1)(ωp/ω0)2], where vetch ~c(ωp/ω0)2 is the
velocity at which the laser front etches back due to the
local pump depletion, the dephasing length leads to
Ldp ~ c/(c-vB)RB ~ (2/3) (ω0/ωp)2RB = (2/3) (n
69
B c/ne)RB.
Hence the electron injected at the back of the bubble can
be accelerated up to the energy
( )
e
c
e
p
Bpedpz n
n
acmRkcmLEeE 0
2
2
022
max 3
2
6
1
2
1
≈⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
≈≈
ω
ω .
Using the matched bubble radius condition, the energy
gain is approximately given by
3231
2
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
≈
e
c
r
e n
n
P
PcmE ,
where Pr = me
2c5/e2 = 8.72 GW [14].
The 2D or 3D particle-in-cell simulations confirm that
quasi-monoenergetic electron beams are produced due to
self-injection of plasma electrons at the back of the
bubble from the electron sheath outside the ion sphere as
the laser intensity increases to the injection threshold. As
expelled electrons flowing the sheath are initially
decelerated backward in a front half of the bubble and
then accelerated in a back half of it toward the
propagation axis by the accelerating and focusing forces
of the bubble ions, their trajectories concentrate at the
back of the bubble to form a strong local density peak in
the electron sheath and a spiky accelerating field.
Eventually the electron is trapped into the bubble when its
velocity reaches the group velocity vg of the laser pulse.
Theoretical analysis on the trapping threshold gives kpRB
≥ 21/2γg = (2nc/ne)1/2, where γg = [1- (vg /c)2 ]-1/2 [15]. This
trapping condition leads to a0 ≥ nc/2ne, while the trapping
cross section σ ≃ (2π/kp
3d)(ln kpRB/81/2)-1 [12] with the
sheath width d imposes kpRB ≥ 2.8, i.e. a0 ≥ 2 for the
matched bubble radius. Once an electron bunch is trapped
in the bubble, loading of trapped electrons reduces the
wakefield amplitude below the trapping threshold and
stops further injection. Consequently the trapped electrons
undergo acceleration and bunching process within a
separatrix on the phase space of the bubble wakefield.
This is a simple scenario for producing high-quality
monoenergetic electron beams in the bubble regime.
However, in most of laser-plasma experiments
aforementioned conditions and scenarios are not always
fulfilled.
In the experiment for the plasma density
ne = (1…2)× 1019 cm-3, observation of the self-injection
threshold on the normalized laser intensity gives ath = 3.2
after accounting for self-focusing and self-compression
that occur during laser pulse propagation in the plasma. In
terms of the laser peak power P/Pc = (π2/8)a0
2(w0/λp)2, the
self-injection threshold for the power (P/Pc )th ≈ 12.6 as
the laser spot size reduces to the plasma wavelength due
to the relativistic self-focusing [16]. In the experiment at
ne = (3…5)×1018 cm-3, the self-injection threshold is
(P/Pc )th = 3, corresponding to ath =1.6 [17]. Our 2-D PIC
simulations on the self-injection threshold show that for
the uniform density plasma such as a gas jet or a gas cell
of ne =(1.7…5)×1018 cm-3, the self-injection occurs at
a0 ≥3.6 and for the preformed plasma channel such as
discharge capillary of the plasma density ne = 2×1018 cm-3
with the density depth Δnch/ne = 0.3, the threshold is
ath ∼ 2.8.
2.3. CONTROLLED INJECTIONS
For many applications of laser wakefield accelerators,
stability and controllability of the beam performance such
as the energy, the energy spread, the emittance and the
charge are indispensable as well as compact and robust
features of the system. In contrast to the conventional
accelerators composed of various complex-functioned
systems, the performance of laser plasma accelerators is
strongly correlated to the injection mechanism of electron
beams as well as the laser performance. To date, the
external injection into laser wakefields from the
conventional RF injector [18] or the staging concept,
which is conceivable on the analogy of the high-energy
RF accelerators, has not been always successful for
generating intense high-quality electron beams that could
be useful for applications. Hence, besides the self-
injection, the optical injection scheme with two colliding
pulses and the enhanced self-injection by ionization are
highlighted.
The optical injection scheme for manipulating electron
beams in a phase space of laser wakefield acceleration
with fs-synchronization and MeV-energy response utilize
an injection pulse split from the same drive pulse with fs
duration, crossing the drive pulse at some angle in the
plasma. When crossing each other, the phase space of
wakefields excited by the drive pulse overlaps with the
phase space of beat waves generated by mixing the drive
pulse and the injection pulse. As a result, the
ponderomotive force of the beat wave boosts plasma
electrons and locally injects them into the separatrix of
the wakefields. In the case of head-on collision of two
counter-propagating laser pulses at the angle of 180°, the
ponderomotive force Fbw ≈ (1/γ)mec2k0a0a1sin(2k0x) of the
injection beat wave oscillating with the wavelength λ0/2
locally accelerates the plasma electrons to be injected into
the wakefield bucket, where k0 = 2π/λ0 is the laser wave
number, a0, and a1 the intensity of the drive pulse and the
injection pulse, respectively, and γ the Lorentz factor of
the plasma electron, i.e. γ ∼ 1 for the cold plasma. On the
contrary to the self-injection with a single drive pulse, this
force is independently controllable by changing the
injection pulse intensity and/or its polarization with
respect to that of the drive pulse as well as the injection
position, where two pulses collides. Therefore the energy
and the charge can be controlled within some extent,
associating with evolution of the energy spread due to the
beam loading and the injection volume of the phase space.
These effects are successfully demonstrated with good
stability by the experiments carried out below the self-
injection threshold of the drive pulse intensity. The
experiment of [19] with a0 = 1.3, a1 = 0.4 and the pulse
duration of 30 fs for both pulses shows an almost linear
control of the monoenergetic beam energy from 50 MeV
to 250 MeV by changing the colliding position over the
2-mm gas jet at the plasma density of ne = 7.5 × 1018 cm-3,
consequently changing the acceleration length in the
average accelerating field of Ez = 270 GV/m, which is
close to an estimate of the wave breaking field for the
cold plasma, Ewb ≈ 0.96ne
1/2 ~ 263 GV/m. The experiment
of [20] demonstrates the colliding optical injection at the
crossing angle of 135°in the 1-mm gas jet with a0 = 0.6
(Pdrive = 3 TW), a1 = 0.1 (Pinj = 0.14 TW) and 70 fs pulse
duration, resulting in the energy E =15 MeV and the
energy spread ΔE/E =7.8% at ne = 3.95×1019 cm-3 free
from the self-injection as well as the head-on colliding
injection at 180° with a0 = 1.2 (Pdrive = 10 TW), a1 = 0.2
(Pinj = 0.6 TW) and 40 fs pulse duration, resulting in the
energy E =134 MeV and the energy spread ΔE/E =3.5% at
ne=1 × 1019 cm-3. These experiments suggest a very
compact system of the electron beam source including the
laser and the accelerator on a table-top size with high
quality and high stability.
2.4. IONIZATION INDUCED TRAPPING
A technique for controlling the injection into a tiny
phase volume of the bubble is based on the use of
chemical structure of plasma species, i.e. a mixture of
gases with the different ionization potential rather than a
uniform plasma of a single species. A mechanism of the
ionization-induced trapping is elucidated by the fact that
likely trapped are a number of electrons that are produced
from impurity of gas with a large difference of the
ionization potential between the outer shell electrons and
the inner shell ones such as nitrogen, of which two K-
shell electrons are ionized by the optical field ionization
over the threshold intensity IBS ≈ 1019 W/cm2 (the
ionization potential of 552 eV for N6+ and the ionization
potential of 667 eV for N7+), whereas L-shell electrons
are ionized below the intensity of IBS < 1017 W/cm2 (the
ionization potential of 98 eV for N5+) and can be
considered preionized in the leading front of the laser
pulse before the bubble formation. Hence the inner shell
electrons are produced only near the peak intensity of the
laser pulse, which is located near the bubble centre on the
propagation axis, where the wake potential is a maximum
and the expelling ponderomotive force of the laser pulse
is a minimum. Contrary to preionized free electrons,
whose trajectories move along a narrow sheath with
radius RB outside the bubble, the ionized electrons emitted
from the inner shell move close to the bubble axis toward
the back of the bubble where the wake potential is a
minimum and are eventually trapped into the wakefield
when electrons gain a sufficient kinetic energy required
for trapping. This mechanism occurs at as the low
intensity as the optical field ionization threshold for the
inner shell electrons of impurity gas and significantly
increases the trapped charge. As trapping occurs close to
the bubble axis, amplitudes of the betatron oscillation
after trapping decrease compared to the self-injection
from the electron sheath. Recent experiments [21,22]
support the ionization induced trapping mechanism that
reduces the self-injection threshold to P/Pc ~ 1.4 (a0 ~
1.6) for ne ~ 1.4× 1019 cm-3, 9:1 He:N2 gas mixture,
increases 4~5 times the charge for ne ~ 2×1019 cm-3,
1.2% N2 98.8% He gas mixture with the 30 TW, 30 fs
laser pulse, and produces significantly collimated electron
beams. Evidence of the ionization induced electron
trapping has been observed in the laser plasma
acceleration experiments with ablative capillary made of
acrylic resin with length of 4 cm and the capillary
diameter of 500 μm. The experiment of ref. [3] shows the
production of electron beams of 560 MeV for 24 TW
(a0 ~1.7), ne≈1.9×1018 cm-3 and 190 MeV for P = 16 TW
(a0 ~1.4), ne ≈ 2.7 × 1018 cm-3, respectively. In the
experiment with the 3 cm capillary made of polyethylene
with the diameter of 400 μm, however, no electron has
been produced at 35 TW (a0 ~1.6), ne≈(1…3) ×1018 cm-3
[23]. This fact suggests that for the acrylic resin
composed of C:O:H = 4:2:7 (CH2COOC2H5) the injection
is assisted by the ionization induced trapping for the
outer shell electrons of oxygen, whereas for the
polyethylene composed of C:O:H =1:0:2 (-[CH2]n-) the
injection depends only on the self-injection of free
electrons ionized by the capillary discharge and/or the
optical field of the laser pulse because of no oxygen.
2.5. BEAM LOADING EFFECTS
The trapped electrons inside the bubble generate
electromagnetic fields and modify the bubble wakefields.
As a result, the trailing electron bunch undergoes less
accelerated field that limits the charge and produces
energy spread. A thorough measurement of the beam
loading has been made by the use of the colliding optical
injection with the pump pulse intensity a0 = 1.5, varying
the injection pulse intensity from a1 = 0.1 to 0.4 to control
the injected charge. As a result of analyzing the measured
energy shift consisting of the beam loading and the
injection volume effects, the beam loading field per
charge is deduced as 0.8 (GV/m)/pC at ne ≈ 5.7 ×
× 1018 cm-3[24]. The analysis of the beam loading in the
bubble regime gives the energy absorbed per unit length
of the beam is given as
( )4
316 cm10047.0
nC1 Bp
epe
ss Rk
ncm
eEQ −
≈
ω
,
where Qs is the total charge and Es the accelerating
wakefield at the phase position where the bunch charge
starts, assuming the density distribution of the bunch
charge has a trapezoidal shape so that the energy spread
inside the bunch is minimized [25]. This equation implies
70
the trade-off between the total charge that can be
accelerated and the accelerating gradient, i.e. the
accelerated energy. With kpRB ≃ 2 a0
1/2, the charge is
proportional to 1/ne
1/2.
Recent experiments on laser plasma acceleration
successfully demonstrated GeV-class quasimonoenergetic
electron beams from laser wakefield accelerators by the
use of a cm-scale gas jet or a capillary plasma waveguide.
Table 1 summarizes the parameters of GeV-class electron
beams and the experimental condition on the laser and the
plasma demonstrated by the recent laser plasma
experiments.
Table 1. Recent GeV-class laser wakefield acceleration
experiment
Laser and plasma Electron beam Ref.
P = 40 TW, τ = 37 fs
a0 = 1.4
ne = 4.3×1018 cm-3
33 mm gas-fill capillary
E = 1 GeV
ΔE/E = 2.5 % (rms)
Divergence = 1.6 mrad
Charge = 35 pC
[1]
P = 18 TW, τ = 42 fs
a0 = 0.84
ne = 8.4×1018 cm-3
15 mm gas-fill capillary
E = 0.5 GeV
ΔE/E = 2.5 % (FWHM)
Divergence = 0.3 mrad
Charge > 0.3 pC
[2]
P = 24 TW, τ = 27 fs
a0
n = 1.9×10
= 1.7
e
4 cm ablative capillary
18 cm-3
E = 0.56 GeV
ΔE/E = 2.5 % (rms)
Divergence = 1.6 mrad
Charge > 10 fC
[3]
P = 32 TW, τ = 80 fs
a0 = 0.8
ne = 1.8×1018 cm-3
3 cm gas-fill capillary
E = 0.52 GeV
ΔE/E = 5 % (FWHM)
Divergence = 5.4 mrad
Charge = 70 pC
[4]
P = 180 TW, τ = 55 fs
a0 = 3.9
ne = 5.7×1018 cm-3
8 mm gas jet
E = 0.8 GeV
ΔE/E = 12 % (FWHM)
Divergence = 3.6 mrad
Charge = 90 pC av.
[5]
P = 65 TW, τ = 60 fs
a0
n
= 2.8
e = 3×1018 cm-3
8 mm gas jet
E = 0.72 GeV
ΔE/E = 14 % (FWHM)
Divergence = 2.9 mrad
Charge = 100 pC
[6]
71
3. APPLICATIONS TOWARD TABLE-TOP
SOFT X-RAY FEL
It is prospectively conceivable that a compact source
producing high-energy high-quality electron beams from
laser plasma accelerators are an essential tool for many
applications, such as THz and X-ray synchrotron radiation
sources and a unique medical therapy as well as inherent
high-energy accelerators for basic sciences. In particular
the present achievements of the laser wakefield
accelerator performance on the beam properties such as
the GeV-class energy, the 1%-level energy spread, a few
πmm-mrad emittance, the 100 pC-level charge and a few
fs bunch length, and good stability and controllability of
the beam production allow us to downsize a large-scale
X-ray synchrotron radiation source and FEL to a table-top
scale including laser drivers and radiation shields as
shown in the Figure. The undulator radiation from laser-
plasma accelerated electron beams are first demonstrated
at the wavelength of λrad = 740 nm and the estimated peak
brilliance of the order of 6.5×1016 photons/s/mrad2/mm2
/0.1% bandwidth driven by the electron beam from a
2-mm-gas jet with E = 64 MeV, ΔE/E = 5.5% (FWHM)
and total charge 28 pC [26]. The soft X-ray undulator
radiation is successfully demonstrated at the wavelength
λrad = 18 nm and the estimated peak brilliance of the order
of ~ 1.3×1017 photons/s/mrad2/mm2/0.1% bandwidth
radiated by electrons with E = 207 MeV, ΔE/E = 6%
(FWHM) and total charge 30 pC from a 15-mm-
hydrogen-fill gas cell driven by the 20 TW 37 fs laser
pulse at the plasma density ne = 8×1018 cm-3 [27]. These
experiments show the tunability of the radiation
wavelength with respect to the electron beam energy
γ=E/mec2 as λrad = (λu/2hγ2)(1+(K2/2)), where λu is the
undulator period, h the harmonic order and
K = 0.93λu[cm]B B0[T] the undulator parameter with the
magnetic field B0B .
A concept of table-top soft X-ray FEL
Table 2. A design of table-top soft X-ray FEL
ELECTRON BEAM PARAMETERS
Beam energy Eb = 243 MeV
Peak beam current Ib = 10 kA
energy spread (rms) σE/Eb = 0.4%
Pulse duration τb = 10fs
Normalized emittance εn = 7 πmm mrad
UNDULATOR PARAMETERS
Undulator period λu = 5 mm
Strength parameter K = 0.465
Undulatot length Lu = 1.1 m
X-RAY PARAMETERS
Wavelength λrad = 13.5 nm (Ex = 92 eV)
FEL saturation power Px = 10 GW
With extremely small energy spread and peak current
high enough to generate self-amplified spontaneous
emission so-called SASE, a photon flux of the undulator
radiation could be amplified by several orders of
magnitude to levels of brilliance similar to current large-
scale X-ray FELs [28]. As an example, a design of the
table-top soft X-ray FEL is shown in Table 2. In order to
show feasibility of this soft X-ray FEL, we made the 2D
PIC simulation of a capillary laser wakefield accelerator
72
with the laser intensity a0 = 2, the spot radius r0 = 20 μm,
the plasma density ne=2×1018 cm-3, the channel density
depth Δnch/ne =0.3, and the pulse duration τL =38 fs. The
simulation results show the electron beam energy Eb =
260 MeV, the rms energy spread σE/Eb = 0.5%, the
normalized emittance εn = 2.1 πmm mrad, the pulse
duration τb ~ 1.9 fs and the peak current Ib=10.5 kA.
These electron beam parameters indicate a distinct
possibility of the table-top soft X-ray FEL with the
capillary laser wakefield accelerator driven by 54 TW
laser and a 1.1-m long undulator with 5-mm period and
the 1-Tesla magnetic field.
CONCLUSIONS
Recent progress and achievements in laser-plasma
accelerators are overviewed from the aspects on the
bubble mechanism, the self-injection, the control and the
beam loading to lead accelerated-electron beams to the
high-energy and high-quality performance as compact
particle and radiation sources. As an example of
applications, the design of the table-top soft X-ray FEL
that generates coherent radiations at the wavelength of
13.5 nm is presented.
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Article received 13.09.10
НОВЫЙ ПРОГРЕСС В РАЗРАБОТКЕ ЛАЗЕРНО-ПЛАЗМЕННЫХ УСКОРИТЕЛЕЙ И ИХ ПРИМЕНЕНИИ
ДЛЯ СОЗДАНИЯ КОМПАКТНЫХ ВЫСОКОКАЧЕСТВЕННЫХ ИСТОЧНИКОВ ПУЧКОВ И ИЗЛУЧЕНИЯ
К. Накаджима
Приведен обзор нынешнего прогресса в теоретических и экспериментальных исследованиях электронных
ускорителей, основанных на лазерно-плазменном взаимодействии. В частности, фундаментальная физика
ускорения, называемая механизмом «пузыря», выдвигается на первый план для демонстрации последних
достижений лазерно-плазменных ускорительных технологий получения высококачественных стабильных
пучков высокой энергии, требуемых для компактных источников пучков и излучения.
НОВИЙ ПРОГРЕС В РОЗРОБЦІ ЛАЗЕРНО-ПЛАЗМОВИХ ПРИСКОРЮВАЧІВ І ЇХ ЗАСТОСУВАННІ
ДЛЯ СТВОРЕННЯ КОМПАКТНИХ ВИСОКОЯКІСНИХ ДЖЕРЕЛ ПУЧКІВ І ВИПРОМІНЮВАННЯ
К. Накаджіма
Приведено огляд нинішнього прогресу в теоретичних і експериментальних дослідженнях електронних
прискорювачів, заснованих на лазерно-плазмовій взаємодії. Зокрема, фундаментальна фізика прискорення, що
називається механізмом «пузиря», висувається на перший план для демонстрації останніх досягнень лазерно-
плазмових прискорювальних технологій отримання високоякісних стабільних пучків високої енергії, які
потребуються для компактних джерел пучків і випромінювання.
1. INTRODUCTION
2. LASER WAKEFIELD ACCELERATOR
2.2. QUASI-MONOENERGETIC ACCELERATION IN THE BUBBLE REGIME
2.3. CONTROLLED INJECTIONS
2.4. IONIZATION INDUCED TRAPPING
2.5. BEAM LOADING EFFECTS
3. APPLICATIONS TOWARD TABLE-TOP SOFT X-RAY FEL
With extremely small energy spread and peak current high enough to generate self-amplified spontaneous emission so-called SASE, a photon flux of the undulator radiation could be amplified by several orders of magnitude to levels of brilliance similar to current large-scale X-ray FELs [28]. As an example, a design of the table-top soft X-ray FEL is shown in Table 2. In order to show feasibility of this soft X-ray FEL, we made the 2D PIC simulation of a capillary laser wakefield accelerator with the laser intensity a0 = 2, the spot radius r0 = 20 m, the plasma density ne=2×1018 cm-3, the channel density depth nch/ne =0.3, and the pulse duration L =38 fs. The simulation results show the electron beam energy Eb = 260 MeV, the rms energy spread E/Eb = 0.5%, the normalized emittance n = 2.1 mm mrad, the pulse duration b ~ 1.9 fs and the peak current Ib=10.5 kA. These electron beam parameters indicate a distinct possibility of the table-top soft X-ray FEL with the capillary laser wakefield accelerator driven by 54 TW laser and a 1.1-m long undulator with 5-mm period and the 1-Tesla magnetic field.
CONCLUSIONS
REFERENCES
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| id | nasplib_isofts_kiev_ua-123456789-17461 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T17:48:49Z |
| publishDate | 2010 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Nakajima, K. 2011-02-26T21:05:35Z 2011-02-26T21:05:35Z 2010 Recent progress on laser plasma accelerators and applications for compact high-quality particle beam and radiation sources / K. Nakajima // Вопросы атомной науки и техники. — 2010. — № 6. — С. 68-72. — Бібліогр.: 28 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/17461 Recent progress in laser-driven plasma-based electron accelerators is overviewed in theoretical and experimental aspects. In particular, basic acceleration physics called as a bubble mechanism is highlighted to show recent achievements of laser plasma accelerator technologies that produce high-energy, high-quality stable beams required for compact particle beam and radiation sources. Приведен обзор нынешнего прогресса в теоретических и экспериментальных исследованиях электронных ускорителей, основанных на лазерно-плазменном взаимодействии. В частности, фундаментальная физика ускорения, называемая механизмом «пузыря», выдвигается на первый план для демонстрации последних достижений лазерно-плазменных ускорительных технологий получения высококачественных стабильных пучков высокой энергии, требуемых для компактных источников пучков и излучения. Приведено огляд нинішнього прогресу в теоретичних і експериментальних дослідженнях електронних прискорювачів, заснованих на лазерно-плазмовій взаємодії. Зокрема, фундаментальна фізика прискорення, що називається механізмом «пузиря», висувається на перший план для демонстрації останніх досягнень лазерно-плазмових прискорювальних технологій отримання високоякісних стабільних пучків високої енергії, які потребуються для компактних джерел пучків і випромінювання. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Фундаментальная физика плазмы Recent progress on laser plasma accelerators and applications for compact high-quality particle beam and radiation sources Новый прогресс в разработке лазерно-плазменных ускорителей и их применении для создания компактных высококачественных источников пучков и излучения Новий прогрес в розробці лазерно-плазмових прискорювачів і їх застосуванні для створення компактних високоякісних джерел пучків і випромінювання Article published earlier |
| spellingShingle | Recent progress on laser plasma accelerators and applications for compact high-quality particle beam and radiation sources Nakajima, K. Фундаментальная физика плазмы |
| title | Recent progress on laser plasma accelerators and applications for compact high-quality particle beam and radiation sources |
| title_alt | Новый прогресс в разработке лазерно-плазменных ускорителей и их применении для создания компактных высококачественных источников пучков и излучения Новий прогрес в розробці лазерно-плазмових прискорювачів і їх застосуванні для створення компактних високоякісних джерел пучків і випромінювання |
| title_full | Recent progress on laser plasma accelerators and applications for compact high-quality particle beam and radiation sources |
| title_fullStr | Recent progress on laser plasma accelerators and applications for compact high-quality particle beam and radiation sources |
| title_full_unstemmed | Recent progress on laser plasma accelerators and applications for compact high-quality particle beam and radiation sources |
| title_short | Recent progress on laser plasma accelerators and applications for compact high-quality particle beam and radiation sources |
| title_sort | recent progress on laser plasma accelerators and applications for compact high-quality particle beam and radiation sources |
| topic | Фундаментальная физика плазмы |
| topic_facet | Фундаментальная физика плазмы |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/17461 |
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