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The 5th Asia Summer School and Symposium
on Laser-plasma Acceleration and Radiation
Aug. 16~20, 2010
Shanghai, China
Organized by
State Key Laboratory of High Field Laser Physics, Shanghai Institute
of Optics and Fine Mechanics, Chinese Academy of Sciences
Sponsored by
National Nature Science Foundation of China
Chinese Academy of Sciences
APRI, Gwangju Institute of Science and Technology
2
Committees
International Curriculum and Program (ICP) Committee
Parshotam Dass Gupta, Raja Ramanna Centre for Advanced Technology, India
Hyyong Suk, Gwangju Institute of Science and Technology, Korea
Yen-Chieh Huang, National Tsinghua University, Taiwan
Kazuhisa Nakajima, KEK High Energy Accelerator Research Organization, Japan
Shigeo Kawata, Utsunomiya University, Japan
Baifei Shen, Shanghai Institute of Optics and Fine Mechanics, CAS, China
Zheng-Ming Sheng, Shanghai Jiao Tong University, China
Jyhpyng Wang, Academic Sinica, China Taiwan
Local Organizers
Shanghai Institute of Optics and Fine Mechanics, CAS, China
Baifei Shen
Xiaomei Zhang
Shuyan Zhang
Liangliang Ji
Jiancai Xu
Wenpeng Wang
3
CONTENT CONTENT ............................................................................................................................ 3
AGENDA .............................................................................................................................. 5
PROGRAM .......................................................................................................................... 7
Laser science ....................................................................................................................... 9
PIC simulation of LWFA and capillary discharge .............................................................. 10
Basic issues on laser-plasma acceleration for novel versatile applications...................... 11
Charged particle beam physics in laser-plasma acceleration ........................................... 12
Concepts of laser plasma acceleration ............................................................................. 13
Plasma based acceleration at UCLA: theory, simulation and experiment ........................ 14
Advanced simulation tools for laser-plasma acceleration ................................................. 15
Stability improvement of laser-accelerated electron beam and its control........................ 16
Laser driven plasma wakefield accelerators and radiation sources ................................. 17
Experiments and Diagnostics on Laser Particle Acceleration ........................................... 18
Generation of fast electrons in the intense laser-plasma interactions .............................. 19
Laser ion acceleration in laser-foil interaction ................................................................... 20
Energetic ion generation by high contrast lasers irradiated on nanometer-foils ............... 21
Particle acceleration by circularly polarized lasers ............................................................ 22
Stable proton beam acceleration in two-ion-specie regime dominated by the laser
radiation pressure .............................................................................................................. 23
High harmonic x-ray sources ............................................................................................. 24
Overview of high power THz sources from laser-plasma interaction ................................ 25
Relativistic electrodynamics, synchrotron and undulator radiation ................................... 26
An introduction to particle accelerators ............................................................................. 27
An introduction to beam dynamics .................................................................................... 28
THz region accelerator including beam driven dielectric acceleration .............................. 29
Analytical method for laser plasma interaction .................................................................. 30
Recent progress in laser wakefield acceleration experiments .......................................... 31
Electron Bow-wave injection in laser wake field acceleration ........................................... 32
Efficient energy coupling into nanolayed target by intense short-pulse laser ................... 33
4
Enhancement of electron injection using two auxiliary interfering-pulses in LWFA .......... 34
Electron acceleration in wake bubble by ultraintense laser interacting with plasma ........ 35
Electron-positron pair creation in time-dependent external fields ..................................... 36
Comparison of ion acceleration from ultra-short intense laser interactions with thin foil and
small dense target ............................................................................................................. 37
Interferometric technique for measurement of capillary plasma density ........................... 38
Detection of the terahertz radiation emitted from laser-induced plasmas by using the
electro-optic sampling method ........................................................................................... 39
Overloading Effect of Energetic Electrons on Wakefield in Bubble Regime ..................... 40
Photodissociation of nitrobenzene and o-nitrotoluene at 266 nm: a new photoproduct of
OH ...................................................................................................................................... 41
Raman amplification of ultrashort laser pulses in plasma ................................................. 42
Quasi-monoenergetic proton acceleration from double layer targets irradiated by intense
laser pulse .......................................................................................................................... 43
Comparison between classical and quantum treatment of harmonic generation by
relativistic electrons in strong laser fields .......................................................................... 44
Simulation study of self-injection and density-ramping-injection in LWFA based on typical
100 TW laser facilities by OOPIC ...................................................................................... 45
Vacuum laser-driven electron acceleration by Airy beams ............................................... 46
Ion jet generation in the ultra-intense laser interactions with rear-side concave target .... 47
Generation of low density plasma channels and optical guiding in plasma waveguides . 48
Interaction of ultraintense and ultrashort laser pulse with overdense plasma target ........ 49
High charged electrons generation by dual laser pulses .................................................. 50
Numerical research on evaporation of target bombarded by pulsed ion beam ................ 51
Generation of tens of GeV quasi-monoenergetic proton beams from a moving double
layer formed by ultraintense lasers at intensity 1021–1023 W cm−2 .................................... 52
Ultra-intense single attosecond pulse generated from circularly-polarized laser interacting
with overdense plasma ...................................................................................................... 53
Self-generated magnetic fields in the relativistic laser-plasma interaction ....................... 54
High resolution emittance and energy spread measurements of 80- 135 MeV electron
beams from a laser driven plasma wakefield accelerator on the ALPHA-X beam line..... 55
Ultrafast pulse-train laser leading to desktop intense THz free-electron laser ................. 56
5
AGENDA
Aug. 15, 2010 Sunday
13:00~20:00 Registration Lounge 1st Floor
Aug. 16, 2010 Monday
8:30~9:30 Registration Lounge 1st Floor
9:30~10:00 Opening Remark
Conference room 2nd Floor 10:00~11:00 Session I
11:00~11:30 Group photo and coffee break
11:30~12:30 Session I
12:30~13:30 Lunch 1st Floor
13:30~15:30 Session II
Conference room 2nd Floor 15:30~16:00 Coffee break
16:00~18:00 Session II
18:30~20:00 Dinner 1st Floor
Aug. 17, 2010 Tuesday
9:00~11:00 Session III
Conference room 2nd Floor 11:00~11:30 Coffee break
11:30~12:30 Session III
12:30~13:30 Lunch 1st Floor
13:30~15:30 Session IV
Conference room 2nd Floor 15:30~16:00 Coffee break
16:00~18:00 Session IV
18:30~20:00 Dinner 1st Floor
Aug. 18, 2010 Wednesday
9:00~11:00 Session V
Conference room 2nd Floor 11:00~11:30 Coffee break
11:30~12:30 Session V
12:30~13:30 Lunch 1st Floor
13:30~15:30 Session VI
Conference room 2nd Floor 15:30~16:00 Coffee break
16:00~18:00 Session VI
18:30~20:00 Dinner 1st Floor
Aug. 19, 2010 Thursday
6
9:00~11:00 Session VII
Conference room 2nd Floor 11:00~11:30 Coffee break
11:30~12:30 Session VII
12:30~13:30 Lunch 1st Floor
13:30~15:00 Session VIII Conference room 2 nd Floor
15:00~16:50 Lab. tour SIOM
17:00~18:00 Coffee break and Poster 2 nd Floor
18:30~20:30 Banquet 1st Floor
Aug. 20, 2010 Friday
7:30~17:30 EXPO 2010 Waiting for the notice
7
PROGRAM
Invited lectures: 60 minutes
Invited talks: 30 minutes or 15 minutes
Aug. 16
Session I Chairman: Hyyong Suk
10:00~11:00 Laser science (Invited lecture) Prof. Leng
11:30~12:30 PIC simulation of LWFA and capillary discharge
(Invited lecture) Prof. Hur
Session II Chairman: Dino Jaroszynski
13:30~14:30 Basic issues on laser-plasma acceleration for
novel versatile applications (Invited lecture) Prof. Nakajima
14:30~15:30 Charged-particle beam physics in laser-plasma
acceleration (Invited lecture) Prof. Suk
16:00~17:00 Concepts of Laser Plasma (Invited lecture) Prof. Huang
17:00~18:00 Plasma based acceleration at UCLA: theory,
simulation and experimentn (Invited lecture) Dr. Lu
Aug. 17
Session III Chairman: Shigeo Kawata
9:00~10:00 Advanced simulation tools for laser-plasma
acceleration (Invited lecture) Dr. Cowan
10:00~11:00 Stability improvement of laser-accelerated
electron beam and its control (Invited lecture) Dr. Kotaki
11:30~12:30 Laser-driven plasma wakefield accelerators and
radiation sources (Invited lecture) Prof. Jaroszynski
Session IV Chairman: Hideyuki Kotaki
13:30~14:30 Experimental study on laser particles
acceleration (Invited lecture) Prof. Gu
14:30~15:30 Generation of fast electrons in the intense
laser-plasma interactions (Invited lecture) Prof. Li
16:00~17:00 Laser ion acceleration in lase-foil interaction
(Invited lecture) Prof. Kawata
17:00~17:30 Energetic ion generation by high contrast laser
irradiated on nanometer-foil (Invited talk) Prof. Yan
17:30~17:45 Particle acceleration by circularly polarized
lasers (Invited talk) Dr. Wang
17:45~18:00 Stable proton beam acceleration in
two-ion-specie regime dominated by the laser Dr. TongpuYu
8
radiation pressure (Invited talk)
Aug. 18
Session V Chairman: Helmut Wiedemann
9:00~11:00 High harmonic X-ray sources (Invited lecture) Prof. Nam
11:30~12:30 High power THz sources from relativistic laser
plasmas (Invited lecture) Prof. Sheng
Session VI Chairman: Zhengming Sheng
13:30~15:30
Relativistic electrodynamics,
synchrotron-radiation and undulator radiation
(Invited lecture)
Prof. Wiedemann
16:00~18:00
An introduction to particle accelerators,
historical review and basic physics (Invited
lecture) Prof. Zhang
An introduction to beam dynamics (Invited
lecture)
Aug. 19
Session VII Chairman: Chang Hee Nam
9:00~10:00 THz region accelerator including beam driven
dielectric acceleration (Invited lecture) Prof. Yoshida
10:00~11:00 Analytical method for laser plasma interaction
(Invited lecture) Prof. Wei Yu
11:30~12:00 Recent progress in laser wakefield acceleration
experiments (Invited talk) Dr. Hafz
12:00~12:30 Electron bow-wave Injection in laser wake field
acceleration (Invited talk) Prof. Ma
Session VIII Chairman: Wei Yu
13:30~14:00 Efficient laser energy coupling bynanolayered
target (Invited talk) Prof. Cao
14:00~14:30
Enhancement of electron injection using two
auxiliary interfering-pulses in LWFA (Invited
talk)
Prof. Yin
14:30~15:00
Electron acceleration in wake bubble by
ultraintense laser interacting with plasma
(Invited talk)
Prof. Xie
9
Laser science
Yuxin Leng
(SIOM, CAS, China)
10
PIC simulation of LWFA and capillary discharge
Min Sup Hur
KERI, Korea
11
Basic issues on laser-plasma acceleration for novel versatile
applications
Kazuhisa Nakajima
High Energy Accelerator Research Organization, Oho, Tsukuba, Ibaraki 305-0801 Japan
Department of Physics, Shanghai Jiao Tong University, 200240, China
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 percent energy spread. On the other
hand, laser-driven production of GeV-class high-quality ion beams such as protons and
carbon ions is underdeveloped, harnessing development of Petawatt-class ultra-intense
lasers with high-quality and ultra-thin foil targets. 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.
In this lecture, basic issues on laser-driven plasma particle accelerators including
electron- and ion-acceleration are reviewed from the aspects of injection or particle
generation, acceleration process, resultant beam properties such as energy, energy
spread, emittance, bunch length and charge, strictly determined by acceleration
mechanism or laser-plasma interaction such as the bubble mechanism for electrons and
radiation pressure acceleration for ions. Based on currently vital researches on laser
plasma accelerators, we conceive novel versatile tools for broad scientific fields ranging
from basic researches to medical and industrial applications in conjunction with the recent
cutting-edge technology.
12
Charged particle beam physics in laser-plasma acceleration
Hyyong Suk
APRI, Gwangju Institute of Science and Technology Gwangju, 500-712 Rebuplic of Korea
In laser-driven plasma acceleration, intense high-energy charged-particle beams are
generated by strong laser-plasma interactions. Such beams are quite unique in several
points of view compared with those from RF-based conventional accelerators, and
dynamics of charged particle beams is an interesting and important subject in
laser-plasma acceleration. In this lecture, some details of the beam dynamics in
laser-plasma acceleration are presented, which will be helpful for graduate students and
young scientists.
13
Concepts of laser plasma acceleration
Yen-Chieh Huang
Department of Electrical Engineering, National Tsinghua University,
Hsinchu 30013, Taiwan China
This lecture is to quickly introduce the ABC of pulsed laser, plasma, and laser plasma. So,
sit back, relax, and enjoy the simplicity of its content.
14
Plasma based acceleration at UCLA: theory, simulation and
experiment
Wei Lu
University of California, Los Angeles (UCLA)
The field of Plasma based acceleration (LWFA and PWFA) has experienced amazing
development lately. During the past decade, Researchers at UCLA and their collaborators
have achieved many important progresses on theory, simulation and experiment in both
LWFA and PWFA. In this lecture, I will describe some of these progress that I have
actively engaged in and try to give my personal view of this field. On theory part, the topics
I will cover include the nonlinear wake excitation in the blowout regime, beam loading,
hosing instability, multi-dimensional injection (self and controlled) and phenomenological
framework and scaling of LWFA in the blowout regime. On simulation part, the topics I will
cover include the full scale 3D modeling of LWFA for GeV to 100GeV stage by large scale
parallel PIC simulations in both lab frame and in a Lorentz boosted frame. On experiment
part, the topics I will cover include both PWFA and LWFA. For PWFA, a series of
successful experiments at SLAC will be discussed, including an experiment that
demonstrated energy doubling of the 42GeV electron beam. For LWFA, a series of
experiments at UCLA and LLNL will be discussed, including short pulse laser self-guiding,
injection threshold, ionization induced injection and GeV level electron beam generation in
the self-guided blowout regime with both self and ionization induced injection.
15
Advanced simulation tools for laser-plasma acceleration
Benjamin M. Cowan1, David L. Bruhwiler1, John R. Cary1,2, Estelle Cormier-Michel1,3, Eric
Esarey3, Cameron G. R. Geddes3, Peter Messmer1, and Kevin Paul1
1 Tech-X Corporation, Boulder, Colorado 80303, USA
2 University of Colorado, Boulder, Colorado 80309, USA
3 Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
As the field of laser wakefield acceleration makes rapid progress, improved computational
methods are essential to understanding the physics of the latest designs and further
developing the technology. We present an overview of recent advances in computational
algorithms for laser-plasma acceleration. The use of higher-order particles in
particle-in-cell (PIC) simulations has been shown to significantly reduce numerical
noise. To simulate meter-scale stages, several algorithms have been developed,
including operating in a Lorentz-boosted frame, scaling simulation parameters, and
reduced models which remove the need to resolve the fast laser oscillations. Such
algorithms can achieve over 5 orders of magnitude speedup over conventional PIC
simulations. Finally, we discuss computation on emerging architectures, such as
graphics processing units, which can further speed simulations by two orders of
magnitude.
Work supported by U. S. Department of Energy, Office of Science, Office of High Energy
Physics grants DE-SC0000840 (SBIR), DE-FC02-07ER41499 (ComPASS SciDAC), and
DE-AC02-05CH11231 (LBNL), and by Tech-X Corporation.
16
Stability improvement of laser-accelerated electron beam and its
control
Hideyuki Kotaki
Japan Atomic Energy Agency
Laser wakefield acceleration (LWFA) is regarded as a basis for the next-generation of
charged particle accelerators. In experiments, it has been demonstrated that LWFA is
capable of generating electron bunches with high quality: quasi-monoenergetic, low in
emittance, and a very short duration of the order of ten femtoseconds. Such femtosecond
bunches can be used to measure ultrafast phenomena. In applications of the laser
accelerated electron beam, it is necessary to generate a stable electron beam and to
control the electron beam.
In order to improve the stability and to control the electron beam, some methods are
proposed. The proposed methods are colliding injection [1], ionization-stage control [2],
etc. The colliding injection uses multiple laser pulses. A driver pulse produces a wake
wave to accelerate electrons. Colliding laser pulses injects plasma electrons into the wake
excited by the driver pulse. We can separate the wake wave excitation and the electron
injection. The separation makes possible to improve the electron-beam stability and to
control the electron beam. The ionization-stage control by using high-Z gases makes a
long channel due to cascade ionization. The long channel improves the stability of the
electron beam pointing.
Experimentally, we have improved the electron beam stability by the optical injection and
the ionization-stage control. In my lecture, I will present the improvement of the electron
beam stability, and its control of the direction and the profile.
Reference
1. E. Esarey et al., PRL 79, 2682 (1997); H. Kotaki et al., PoP 9, 1392 (2002); J. Faure
et al., Nature 444, 737 (2006); H. Kotaki et al., PRL 102, 211083 (2009).
2. M. Mori, et al., Phys. Rev. ST-AB 12, 082801 (2009).
17
Laser driven plasma wakefield accelerators and radiation sources
D. A. Jaroszynski
University of Strathclyde, Physics Department, John Anderson Building
107 Rottenrow, Glasgow, G4 0NG, Scotland, UK
In this lecture we will present progress towards producing an ultra-compact laser driven
plasma wakefield accelerator and applying it as an ultra-short pulse X-ray radiation source.
We will discuss how the state-of-the-art before 2004, where electron beams were
produced with 100% energy spreads, has been completely transformed by pioneering
developments that have culminating in wakefield accelerators routinely producing very
high quality electron beams with energies from 50 MeV to more than 1 GeV. An
overview of the basic physical processes of plasma wakefild acceleration will be given and
we will examine how the transverse forces in the plasma bubble produced by the laser
pulse cause oscillation of the electrons and result in the emission of brilliant X-ray pulses.
We will also present an overview of applications of wakefield accelerators.
18
Experiments and Diagnostics on Laser Particle Acceleration
Gu Yuqiu
National Key Laboratory of Laser Fusion,
Laser Fusion Research Center, CAEP, Mianyan, 621900
Abstract: Laser particle acceleration, as an observable phenomenon of ultra intense laser
interacting with targets, is a fast increasing research field for its potential applications.
Many theories and computer simulations were developed for describing laser particle
acceleration and laser interacting with matter. Experiments and diagnostics are more
important from another point of view, since practice is the sole criterion for testing truth. In
this report, the experiments on electron acceleration and proton acceleration on SILEX-I
were introduced and the diagnostics used in the experiments were described in details.
19
Generation of fast electrons in the intense laser-plasma
interactions
Yutong Li
Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
Email: [email protected]
In the interaction of a high intensity relativistic laser pulse with a solid foil, a large number
of electrons can be accelerated to very high energies, forming so-called fast electrons.
Some of the fast electrons are ejected backward from the interaction region into the
vacuum in front of the target. The others transport into the overdense plasma and cold
target region and, finally, part of them escape from the rear target surface. The fast
electrons are of significance for fast ignition in inertial confined fusion, high-energy ion
generation, x-ray emission, etc. In this lecture the dependence of the fast electron beams
on the experimental conditions of the laser and plasmas, such as intensity, polarization,
incident angle, scale length of the preplasma, as well as the possible ways to control the
emission direction of fast electrons will be discussed.
Funding supported by the National Nature Science Foundation of China (Grant Nos. 10925421,
10734130), National Basic Research Program of China (973 Program) (Grant No.
2007CB815101) and the National High-Tech ICF program.
20
Laser ion acceleration in laser-foil interaction
Shigeo Kawata
Utsunomya University, 321-8585 Utsunomiya Japan.
In this lecture key issues relating to laser ion acceleration are summarized and explained with
detail examples. Intense short-pulse lasers are now available in actual experiments. The laser
has opened a new world in laser particle acceleration, radiation generation, etc. In laser
thin-foil interaction first electrons are expelled or accelerated by the laser strong field, and form
a strong electric field or a large current in the foil depending on the thin foil density and the
foil-parameter values. The high-energy-electron current or motion is sustained for the laser
pulse length or a longer period than the laser pulse. During the period ions are gradually
accelerated by the electric field, created by the high-energy electrons or the time-dependent
strong magnetic field. In the laser ion acceleration the following key issues are included: ion
species control, ion energy control, ion divergence reduction, ion beam pulse shape control,
energy spectrum control, laser-ion energy convergence enhancement, ion beam temperature
control, ion particle number increase, etc.
In the lecture the attendees are requested to propose or discuss new ideas to improve the ion
beam quality or to propose new directions for the laser ion acceleration. New solutions are
very welcome to solve the issues.
Funding supported by JSPS, MEXT, CORE (Center for Optical Research and Education) and
ILE / Osaka university, Japan.
The Author would like to extend his acknowledgements to colleagues and friends, including Dr.
Y.Y. Ma, Dr. W.M. Wang, Prof. Z.M. Sheng, Prof. Y.T. Li, Dr. Q. Kong, Dr. P.X. Wang, Prof. J.
Limpouch, Dr. O. Klimo, Prof. A.A. Andreev, Dr. K. takahashi, Dr. D. Barada and Dr. D. Satoh.
21
Energetic ion generation by high contrast lasers irradiated
on nanometer-foils
X.Q.Yan
State Key Lab. of Nuclear Physics & Technology, PKU, Beijing 100871, China
Max Planck for Quantum Optics (MPQ), Garching B. Muenchen, 85748, Germany
Ultrahigh-intensity lasers can produce accelerating fields of TV/m, surpassing those in
conventional accelerators for ions by few orders of magnitude. Remarkable progress has
been made in producing laser-driven ultra-bright MeV proton and ion beams in a very
compact fashion compared to conventional RF accelerators. These beams have been
produced up to several MeV per nucleon with outstanding properties in terms of
transverse emittance and current, but typically suffer from exponential energy
distributions.
A new mechanism for laser-driven ion acceleration was proposed, where particles gain
energy directly from the Radiation Pressure Acceleration or Phase Stable Acceleration
(RPA / PSA). By choosing the laser intensity, target thickness, and density such that the
radiation pressure equals the restoring force given by the charge separation field, the ions
can be bunched in a phase-stable way and efficiently accelerated to a higher energy. In
proof of principle experiments quasi-monoenergetic peaks for C6+ at ~30 MeV were
observed by MPQ/MBI/LANL/PKU group and C6+ at >500 MeV (exponential) was
observed at LANL/MPQ. Furthermore at LANL also quasi-monoenergetic protons at
~40MeV were generated from nm thin diamond-like carbon foils. Theoretical study shows
that the required medical proton/carbon beams (200MeV for proton and 400MeV/u for
Carbon) can be generated from hydrogen/carbon foil (sub micron) in a laser intensity of
~1021/1022W/cm2.
Funding supported by NSFC (10935002)
22
Particle acceleration by circularly polarized lasers
W.-M. Wang1,2, Z.-M. Sheng 1,3, S. Kawata2, Y.-T. Li1, L.-M. Chen1, J. Zhang1,3 1Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing
100190, China 2Graduate School of Engineering, Utsunomiya University, 7-1-2 Yohtoh, Utsunomiya 321-8585,
Japan 3Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, China
The first part is concerned with the electron acceleration by a circularly polarized laser
pulse. Our analytical and simulation investigations show that future ultra-short 1022-1025
Wcm-2 laser pulses offer the possibility of producing ultra-short monoenergetic electron beams in the GeV-TeV level by direct laser ponderomotive force acceleration (LPFA) in
distances of millimeters to about one meter. A scheme is proposed that a thin solid foil
and a thick solid foil are placed on the laser axis, where the thin foil supplies the electron
source for LPFA and the thick foil reflects the laser away while allows the accelerated
electrons to go through. By optimizing the distance between the foils, one can obtain the maximum electron beam energy. This scheme is demonstrated by particle-in-cell
simulations. In such laser regime, LPFA has the larger acceleration field and can produce
higher energy electron beams than laser wakefield acceleration (LWFA).
Such laser can also be used to accelerate ions. The acceleration of protons by the radiation pressure of a circularly polarized laser pulse with the intensity up to 1021 Wcm-2
from a double-layer or multi-ion-mixed thin foil is investigated by two-dimensional
particle-in-cell simulations, where the double-layer foil is composed of a heavy ion layer
and a proton layer. It is found that the radiation pressure acceleration can be classified
into three regimes according to the laser intensity due to the different critical intensities for laser transparency with different ion species. When the laser intensity is moderately high,
the laser pushes the electrons neither so slowly nor so quickly that the protons can catch
up with the electrons, while the heavy ions cannot. Therefore, the protons can be
accelerated efficiently. The proton beam generated from the double-layer foil has better
quality and higher energy than from a pure proton foil with the same areal electron density. When the intensity is relatively low, the protons and heavy ions are accelerated together,
which is not favorable to the proton acceleration. When the intensity is relatively high,
neither the heavy ions nor the protons can be accelerated efficiently due to the laser
transparency through the target.
23
Stable proton beam acceleration in two-ion-specie regime
dominated by the laser radiation pressure
Tongpu Yu
Institut fuer Theoretische Physik I, HHUD, 40225 Duesseldorf, Germany
Recently, with the rapid development of laser technology, one of the most straightforward
acceleration mechanisms, radiation pressure acceleration (RPA) is being re-visited. By
using multi-dimensional particle-in-cell simulations, we investigate the proton acceleration
dominated by the RPA in a two-ion-specie ultra-thin foil. In this two-ion-specie regime, the
lighter protons are initially separated from the heavier carbon ions due to their higher
charge-to-mass ratio Z/m. The laser pulse is well-defined so that it doesn’t penetrate the
carbon ion layer. The Rayleigh-Taylor-like (RT) instability seeded at the very early stage
then only degrades the acceleration of the carbon ions which act as a ”cushion” for the
lighter protons. In the absence of proton-RT instability, the produced high quality
mono-energetic proton beams can be well collimated even after the laser-foil interaction
concludes.
24
High harmonic x-ray sources
Chang Hee Nam
Department of Physics and Coherent X-ray Research Center, KAIST, Daejeon 305-701, Korea
Gaseous atoms, exposed to an intense femtosecond laser field, are periodically
modulated by the laser electric field and emit very high-order harmonics of the laser
frequency. The high harmonics possess unique properties of superb spatial coherence
and ultrashort duration reaching the attosecond range. In this lecture the physical picture
of high harmonic generation processes will be given first, and the characteristics of high
harmonics and applications to x-ray interferometry and to attosecond pulse generation will
then be explained.
25
Overview of high power THz sources from laser-plasma interaction
Z.M. Sheng
Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, China
Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Email: [email protected]
The high intensity laser-plasma can be a radiation source covering ultra-broad spectrum
ranging from terahertz (THz) radiation to MeV gamma ray. In this talk, I will present an
overview of recent experimental, theoretical and numerical studies on THz emission from
laser-plasma interaction. Particular attention will be paid on the progress made in our
group.
Experimental investigation of strong THz wave generation by laser interacting with solid
targets has been conducted. It is found that such emission is in p-polarization and its
energy scales linearly with the incident laser energy. The emission shows very board
spectrum such as 20THz. It is attributed to the plasma currents associated with the hot
electrons produced by the laser pulse.
In a theoretical study, it is found that high power THz emission can be produced by the
residual currents as a laser pulse passing through a gas or plasma target. The residual
currents can be produced by field ionization process or by a dc/ac bias field applied over
tenuous plasma, which is produced by a laser pulse. The current can be converted
efficiently into electromagnetic (EM) emission at the plasma frequency p with its
amplitude and polarization determined by the bias. The initial phase of the EM waves can
be controlled by the triggering time of the bias and therefore circularly/elliptically polarized
EM waves can be obtained by applying two bias fields perpendicular to each other. An
analytical model is presented and confirmed by particle-in-cell (PIC) simulation.
In another theoretical study, we clarify THz radiation mechanism from a plasma filament
formed by an intense femtosecond laser pulse based upon 2D PIC simulation. The
nonuniform plasma density of the filament formed by field ionization and the electron
motion driven by the laser ponderomotive force can result in a nonvanishing radiating
current for the THz radiation. This current is mainly located within the pulse and the first
cycle of the wakefield of the laser pulse. As the laser pulse propagates, a single-cycle and
radially polarized THz pulse is constructively built up forward.
26
Relativistic electrodynamics, synchrotron and undulator radiation
Helmut Wiedemann
Stanford University
In this lecture, we discuss the emission of electromagnetic radiation from relativistic
electron beams. Starting with fundamental rules determining the possibility to emit
electromagnetic radiation from charged particles, we derive the radiation power from
dipole oscillations of electrons. Applications of four-vectors will define the emission
geometry and relativistic Doppler effect which together with the Lorentz contraction plays
an important role in the final radiation spectrum. Transforming that to the laboratory
system we are ready to derive the spectrum of synchrotron radiation. Special insertion
devices like wavelength shifters, undulators and wiggler magnets have been developed to
control the radiation properties without affecting the electron beam in the storage ring.
Undulator magnets emit quasi monochromatic radiation in a line spectrum, while radiation
from wiggler magnets produces a more and more dense line spectrum overlapping at high
harmonics into a continuous spectrum similar to that of a bending magnet.
27
An introduction to particle accelerators
Chuang Zhang
Institute of High Energy Physics, CAS, Beijing 100049, China
The human’s curiosity on the universe has always been the driven force behind the
development of telescopes and microscopes. As a type of powerful microscope, particle
accelerators play an important role in discovery on the micro-world, which provide a major
stimulus for research into the constituents and nature of matter. Traced to its three roots,
the history of accelerators is a continuous upgrade towards higher energy, better
performance and wider application. Innovative ideas, new methods, and new technologies
emerge in endlessly. Historical evolution, innovative ideas and prospective in accelerator
developments are briefly reviewed in this lecture.
The outline of the lecture is as follows:
From telescope to microscope
Historical evolution of accelerators
Frontiers of modern accelerators
Future science and accelerators
Summary
28
An introduction to beam dynamics
Chuang Zhang
Institute of High Energy Physics, CAS, Beijing 100049, China
Beam dynamics is the study of particle beams, their motion in environments, involving
external electro-magnetic fields and their interactions, including the interaction of beams
with matters, of beams with beams, and of particle beams with radiation. Evolving from
concepts and ideas derived from classical mechanics, electromagnetism, statistical
physics, and quantum physics. The study of beams is opening up a very rich field, with
new effects being discovered and new types of beams with novel characteristics being
realized. Basic knowledge of the beam physics is briefly introduced in this lecture for the
students who are preparing to work in the field of laser-plasma acceleration and radiation.
The outline of the lecture is as follows:
Basic Concepts
Transverse Motion
Longitudinal Motion
Collective Effects
Lepton and Hadron
29
THz region accelerator including beam driven dielectric
acceleration
Mitsuhiro Yoshida
High Energy Accelerator Research Organization (KEK) in Japan
Higher frequency electromagnetic wave can make much higher energy density that leads
very high electric field. The electric field is expected to increase linear to the frequency.
The terahertz (THz) region accelerator is growing to become a moderate frequency region
to accelerate the recent low emittance and short bunch electron beam. For example, the
transverse beam size can be easily focused under 10 micron using the low emittance
beam and the bunch length can be compressed under 100 fs using a photo cathode or a
bunch compressor. Thus the transverse and longitudinal beam size becomes enough
small to capture inside the stable phase space.
However such a THz region accelerator is not currently established since the THz source
is limited and some additional solution is required to avoid the wakefield and the surface
breakdown.
In this lecture, some candidates of the THz accelerator, its sources and simulation
methods are presented.
30
Analytical method for laser plasma interaction
Wei Yu
(SIOM, CAS, China)
31
Recent progress in laser wakefield acceleration experiments
Nasr A. M. Hafz
APRI, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
Relativistic electron beam generation through the excitation of large-amplitude plasma waves by high-power ultrashort laser pulses has gained a lot of attention in the past few years. Such an acceleration regime is known as the laser wakefield accelerator (LWFA) [1]. In 2004 a breakthrough in LWFA research has led, for the first time, to the generation of high-quality quasimonoenergetic electron beams [2-4]. Since then, several important results have been reported in this field [5-7]. With the emergence of compact PW-class and PW laser systems around the world, a new era for the LWFA research has started [8-9]. By using PW-class lasers, laser-driven plasma acceleration is foreseen to produce multi- GeV electron beams in the near future. One of the main goals for future LWFA research would be achieving electron energy frontiers relevant to high-energy physics applications [10]. However, there are other motivations for laser-driven electron beam acceleration research. For example, electron beams from laser-driven plasma (shortened here as EBLP)
produced by using 10−20 TW laser systems are very useful from the application point of view [11]. EBLP are unique in their characteristics as they have a small divergence of a few mrad and an
extremely-short bunch length of ≈ 40 fs [12] or shorter. Those characteristics are essential for compact high brightness light source applications such as free-electron lasers and synchrotrons [13-14]. In addition, EBLP are naturally synchronized with the driving laser pulse, thus allowing
jitter−less timing for pump-probe experiments and laser-electron collisions for Thomson scattering X-ray applications. Furthermore, high flux EBLP in the 20 MeV-range have been used in table-top photonuclear physics and radiation chemistry experiments [15-16]. In this talk, I am going to review the recent progress of LWFA in key laboratories worldwide and present recent results from my laboratory [17].
Reference
1. T. Tajima and J. Dawson, Phys. Rev. Lett. 43 (1979) 267. 2. S. P. D. Mangles et al., Nature, 431, (2004) 535. 3. C. G. R. Geddes, et al., Nature, 431, (2004) 538. 4. J. Faure et al., Nature 431 (2004) 541. 5. J. Faure et al., Nature 444 (2006) 737. 6. W. Leemans et al., Nature Phys. 2 (2006) 696. 7. Nasr A. M. Hafz et al., Nat. Photonics 2 (2008) 571. 8. S. Kneip et al., Phys. Rev. Lett. 103 (2009) 035002. 9. D. H. Froula et al., Phys. Rev. Lett. 103 (2009) 215006. 10. S. F. Martins et al., Nat. Phys. 6 (2010) 311. 11. Compact 10−20 TW laser systems are affordable to many university-scale laboratories
worldwide. 12. 12 A. D. Debus et al., Phys. Rev. Lett. 104 (2010) 084802. 13. H.-P. Schlenvoigt et al., Nat. Phys. 4 (2008) 130. 14. Matthias Fuchs et al., Nat. Phys. 5 (2009) 826. 15. A. Giulietti etal., Phys. Rev. Lett. 101 (2008) 105002. 16. Beata Brozek-Pluska et al., Rad. Phys. & Chem. 72 (2005) 149. 17. Nasr A. M. Hafz et al., Accepted 2010.
32
Electron Bow-wave injection in laser wake field acceleration
Y. Y. Ma1,2,3 S. Kawata3 Y. Q. Gu2 Z. M. Sheng4 M. Y. Yu5 H. J. Liu2 H. B. Zhuo6 W. M. Wang3,7
Y. Yin1 K. Takahashi3 X. H. Yang1 C. L. Tian1 and F. Q. Shao1
1. Department of Physics, National University of Defense Technology, Changsha 410073, China
2. Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621000, China
3. Center for Optical Research and Education, Graduate School of Engineering, Utsunomiya University,
7-1-2 Yohtoh, Utsunomiya 321-8585, Japan
4. Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, China
5 Institute for Fusion Theory and Simulation, Department of Physics, Zhejiang University, Hangzhou
310027, China
6. College of Computer Science, National University of Defense Technology, Changsha 410073, China
7. Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
A new regime of strong electron injection named electron bow-wave injection (EBWI) in
laser wakefield acceleration of electrons is investigated using particle-in-cell simulation. In
contrast to the known injection regimes, here the dense trapped electrons in a strong
electron bow wave (EBW) excited behind the primary bubble contribute most to the
injected, trapped, and accelerated electrons in the bubble. EBWI operates at higher laser
intensities than that of the normal self injection (NSI) of the electrons from the bubble
periphery. Even with EBWI for lower laser intensities, the number of the bubble-trapped
electrons is much larger than that from NSI. In this regime the electrons in the intense
electron bow waves behind the first bubble catch up with the bubble tail and enter into it.
The number of the bubble-trapped electrons can thus be much enhanced. It is shown that
the trapped-electron charge can reach 0.27 nC in 180μm. A simple analytical model of the
condition for EBWI is proposed, which is in good agreement with the simulation results.
The EBWI scheme is robust and controllable and should be useful for efficient generation
of collimated high energy electrons. Funding supported by the National Natural Science Foundation of China (grants 10976031,
10935002, and 10835003) and the National Basic Research Program of China (grants
2007CB815105 and 2008CB717806). Y. Y. Ma acknowledges the support of the JSPS and
CORE of Utsunomiya University, Japan
33
Efficient energy coupling into nanolayed target by intense
short-pulse laser
Lihua Cao
Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Center for Applied Physics and Technology, Peking University, Beijing, 100871, China
The introduction of a target with nanolayered front can reduce the reflection and increase
energy coupling of an intense short laser pulse into it. The electrons within the skin depth
on the target surfaces are accelerated to relativistic velocities and then propagate forward
with most of the absorbed laser energy along the surfaces of the layers. The two
dimensional particle-in-cell (PIC) simulations show that more laser energy goes into
kinetic energy of hot electrons respected to the planar target. The energy absorption
decreases a little both for too lower and higher laser intensity. It is ascribed to the
weakening of the electric and magnetic fields associated with smaller hot
electron jet, shorter relativistic skin length at lower intensity and the corruption of
layer structure at higher intensity. The manipulation of the properties of the hot
electrons is discussed by matching the parameters of nanolayered target and laser pulse.
34
Enhancement of electron injection using two auxiliary
interfering-pulses in LWFA
Z. Y. Ge1 Y. Yin1* H. Xu2, 3 Y. Y. Ma1, 3 H. B. Zhuo2 and F. Q. Shao1
1 Department of Physics, National University of Defense Technology, Changsha 410073,
China
2 National Laboratory of Parallel and Distributed Processing, National University of Defense
Technology, Changsha 410073, China
3 Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621000,
China
An interfering-pulses auxiliary laser wake-led acceleration (IPA-LWFA) scheme has been
pro-posed and examined by particle-in-cell (PIC) simulations. In this scheme, two
low-intensity long pulses are interfering in the plasma before the main pump pulse arrival.
The plasma density is modulated in the interfering ¯eld of the auxiliary pulses and the
electrons are heated slightly. Enhancement of electron injection has been demonstrated
compared with the LWFA. It is shown that the IPA-LWFA works well for the main pump
pulse with moderate intensity I < 1021W=cm2. When the pump pulse is extremely intense,
the energy distribution of electrons is broadened although the number of injected
electrons increases.
35
Electron acceleration in wake bubble by ultraintense laser
interacting with plasma
Bai-Song Xie and Hai-Cheng Wu
College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 China
Email: [email protected]
Modification of fields and shape of bubble from electrons which go into the bubble interior
from the bubble front is theoretically studied by three different models - the
phenomenological theory from Kostyukov et al. [Phys. Plasmas 11, 5256 (2004)], a model
with an elliptic boundary condition and the consistent dynamic model from Lu et al.[ Phys.
Plasmas 13, 056709 (2006)]. The results from these three models are the same: the
electrons in the bubble go backward with a speed close to the velocity of light in vacuum,
the slops of the transverse fields are reduced by these electrons, and the ratio of the
radius of longitudinal to transverse of the bubble is decreased; the slop of the longitudinal
electric field is hardly changed because the decrease of the radius’ ratio compensates the
weakening of the field by the electrons. The theoretical results of field and bubble shape in
modification would agree better with the particle-in-cell simulations.
A way of optimizing the electron acceleration in the wake bubble - a quasi phase-stable
acceleration scheme - is also presented. This way is achieved by adding a capillary-like
dense-plasma wall with an inner radius of between the initial lateral radius and maximum
lateral radius of the bubble in the path of the laser pulse. With the wall, the bubble shape
is transversely controlled and longitudinally shrunk. The advantages of this scheme are as
follows: (i) The shrink of the bubble sheath would tailor some of the injected electron
bunch and suppress further electron self-injection, this results in a more monoenergetic
electron bunch; (ii) The accelerated electron bunch almost always stays close to the
bottom of the bubble that leads to larger average accelerating gradient and overcomes the
limit of dephasing to a certain degree; (iii) This scheme does not need increase the
density of the plasma and the depletion rate of the laser, however, it does produce a
larger gradient of accelerating field. Therefore, in this scheme, the electron bunch is
accelerated to much higher energy, meanwhile, it has narrower energy spread.
36
Electron-positron pair creation in time-dependent external fields
Na Ren, Jia-xiang Wang
State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal
University, Shanghai, 200062 China
We investigate electron-positron pair production from vacuum for time-dependent laser
pulses. It has been found that, in order to have prominent pair productions, we not only
require that the electric field intensity should be higher than the Schwinger threshold, but
also require that the pulse duration should be longer than a threshold. The former
condition guarantees that the electron in the negative energy state could gain enough
energy to jump onto a positive-energy state in Compton time. The latter is related to
momentum requirement for the transition. In particular, we show that the probability of the
created electron-positron pairs depends on the laser frequency, the pulse length, and the
carrier phase. This observation could help in the design of laser pulses to optimize the
experimental signature of Schwinger pair production.
Funding supported by Shanghai Shuguang Project Grant personnel issues(06sg27); Shanghai
Pujiang Talent Project Grant subject (07pj14036); National Natural Science Foundation of
topics (10974056).
37
Comparison of ion acceleration from ultra-short intense laser
interactions with thin foil and small dense target
Youwei Tian
College of Science, Nanjing University of Posts and Telecommunications,
Nanjing 210003, China
The generation of highly directional beam of ions with energies in the MeV range through
the interaction of high-intensity laser radiation with solid targets, gas jets, and clusters has
been the subject of great significance due to recent research in high-field laser interaction
physics by experiments and particle-in-cell (PIC) simulations. Laser-driven energetic ion
beam generation has a promising application in hadron cancer therapy, as well as in
controlled nuclear fusion and particle injectors. In a number of experimental and
theoretical publications, the laser-driven ion beam generation with energies in the range of
few MeV to several tens of MeV has been reported.
The comparative efficiency and beam characteristics of high-energy ions generated from
the interaction of a petawatt laser pulse with thin foil target and a small solid-density
plasma bunch target have been studied by particle-in-cell simulation under identical
conditions. It is shown that thin foil and small solid dense target of micrometer size can be
efficiently accelerated when irradiated by a laser pulse of intensity21 210 /W cm> . Using
direct beam measurements, we find that small solid dense target acceleration produces
higher energy particles with smaller divergence and a higher efficiency compared to thin
foil target acceleration. The merits of small solid target acceleration can be exploited for
potential applications such as its role as ignitor for fast ignition (FI) in inertial confinement
fusion (ICF).
This work has been supported by the National Natural Sciences Foundation of China under
Grant No. 10947170/A05, and Foundation of NJUPT under Grant Nos. NY207151 and
NY207006.
38
Interferometric technique for measurement of capillary plasma
density
Dong K. Jang, Do G. Jang, Min-Seok Kim, Seong Y. Oh1), and Hyyong Suk
Graduate Program of Photonics and Applied Physics, Gwangju Institute of Science and
Technology, Gwangju 500-712, Republic of Korea
1)Advanced Photonics Research Institute, Gwangju Institute of Science and Technology,
Gwangju 500-712, Republic of Korea
LWFA (laser wake field acceleration) has been extensively studied to achieve high energy
electron beams in a short distance compared to conventional accelerators. Recently a
pre-ionized plasma capillary apparatus has been utilized in order to accelerate electrons
up to Gev level, avoiding the rapid laser divergence due to diffraction. Such an optical
phenomenon can be avoided with the so-called ‘optical guiding’, where the laser beam
can propagate a long distance due to the parabolic density profile. In this case,
divergence of the laser beam can be compensated by the focusing effect from the
parabolic density profile. The plasma column in the capillary changes very rapidly in time,
so knowing the density profile dynamics is very important. Shadowgraphy and
interferometry are good techniques to measure the temporal and spatial electron density.
We built a Mach-Zehnder interferometer to investigate the plasma dynamics in the
capillary and some results are shown in this presentation.
39
Detection of the terahertz radiation emitted from laser-induced
plasmas by using the electro-optic sampling method
Do-Geun Jang, Jin-Ju Kim, and Hyyong Suk
Graduate Program of Photonics and Applied Physics, Gwangju Institute of Science and
Technology, Gwangju 500-712, Republic of Korea
THz radiation based on laser-induced plasma was first demonstrated by Hamster et al,
and the THz pulse emission process in air has been studied by a few people so far. When
an intense laser pulse is focused in air, it produces a plasma and it propagates through it.
In this case, the electrons in the plasma oscillate at the frequency of ,
where is the density of electrons, is the electric charge, is the mass of the
electron, and is the permittivity of the free space. In the density region of 1016 – 1018
cm-3, the plasma frequency is sub-1012 Hz range and we are interested in this range. In
our research group at GIST, we are going to generate THz pulses from an ionized air
plasma using an intense laser beam. We are also interested in application of the THz
emission for diagnostics of the plasma. For this research we are going to use a
Ti:sapphire laser system consisting of an oscillator and a regenerative amplifier. The laser
pulse will be focused in air by means of a parabolic mirror and the air pressure will be
controlled in the gas cell to investigate the relation between the THz spectrum and the
plasma density, which can give a way for plasma diagnostics. For the THz detection
system, the produced THz pulses from the plasma will be measured by the electro-optic
sampling(EOS) method in time-domain. In this presentation, we will show the on-going
experiment for THz generation and detection from the laser-induced plasmas.
40
Overloading Effect of Energetic Electrons on Wakefield in Bubble
Regime
Jiancai Xu, Baifei Shen, Xiaomei Zhang, Meng Wen, Liangliang Ji, Wenpeng Wang,
Yahong Yu
State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine
Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
Overloading effects of a high-charge self-injected electron bunch on bubble wakefield
have been studied in the bubble regime. After many electrons has been trapped by the
bubble, the wakefield is strongly modified and prevents further injection of background
electrons. These effects are directly observed in two-dimensional particle-in-cell
simulations, and are explained by one-dimensional wake theory. In order to obtain much
more energetic electrons, it is suggested to use a decreasing density profile of the plasma
in the electron acceleration process.
41
Photodissociation of nitrobenzene and o-nitrotoluene at 266 nm: a
new photoproduct of OH
Xian-Fang Yue1,2, Hai-Ran Feng1, Jie Cheng1
1 Department of Physics and Information Engineering, Jining University, Qufu 273155, China
2 State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics,
Chinese Academy of Sciences, Dalian 116023, China
Photodissociation of nitrobenzene and o-nitrotoluene has been investigated in the gas
phase at room temperature at 266 nm. The OH fragment was firstly observed in the
photodissociation of nitrobenzene. The internal state distribution of the nascent OH from
the photodissociation of nitrobenzene and o-nitrotoluene were measured using the
one-photon laser induced fluorescence (LIF) technique. It was found that the OH fragment
was vibrationally cold and their rotational state distributions showed Boltzmann behavior.
Preferential populations of the 2Π3/2 spin-orbit state and the Π+ Λ-doublet state were
observed for the two molecules. One possible dissociation mechanism involving the
intramolecular hydrogen transfer from the benzene ring to the nitro group was proposed
for the OH fragment pathway. To examine the nature of the potential energy surfaces, we
performed the density functional theory (DFT) calculations for the hydrogen transfer and
dissociation processes on both T1 and S0 states.
Funding supported by National Natural Science Foundation of China (No.10947103), the
Foundation for Outstanding Young Scientist in Shandong Province (No.2008BS01017), and
the Young Funding of Jining University (No.2009QNKJ02).
42
Raman amplification of ultrashort laser pulses in plasma
X. Yang G. Vieux E. Brunetti J. Farmer B. Ersfeld D.A. Jaroszynski
University of Strathclyde, Dept of Physics, 107 Rottenrow, Glasgow UK
Raman backscattering (RBS) in plasma is an attractive source of intense, ultrashort laser
pulses which has the potential to bring in a new generation of laser amplifiers. Capitalizing
on the advantages of plasmas, which can withstand extremely high power densities and
can offer high efficiencies over short distances, Raman amplification in plasma could lead
to significant reductions in both size and cost of high power laser systems.
We are investigating chirped laser pulse amplification through RBS in the linear and
nonlinear regimes, with experiments aiming to develop an effective way to transfer energy
from a long pump pulse to a resonant counter-propagating short probe pulse. Current
results show a peak spectral gain of 2200%, with an energy increase of 500%.
Funding supported by University of Strathclyde
43
Quasi-monoenergetic proton acceleration from double layer targets
irradiated by intense laser pulse
L. G. Huang, A. L. Lei*, Y. Bai, Wei Yu and M.Y. Yu
Shanghai Institute of Optics and Fine Mechanics, CAS, Shanghai 201800, China
Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027, China
*E-mail: lal @siom.ac.cn
Abstract: In recent ten years, laser-ion acceleration has been studied with a great interest
worldwide. Double layer targets (DLT) consisting of a high-Z layer and a low-Z
hydrogen-rich layer was first proposed by Ueshima et al. to obtain higher-energy protons
relative to a single layer target. Bulanov et al. and Esirkepov et al. found in a particle in cell
simulation that high-quality, i.e., monoenergetic, intense ion beam could be achieved with
DLT. Schwoerer et al. experimentally demonstrated laser acceleration of protons with a
quasi-monoenergetic peak distribution using DLT. In this paper, an improved DLT is
proposed to enhance monoenergetic proton acceleration with higher peak energy
compared to the conventional DLT. The shape of improved DLT is shown in Fig.1(b). The
front layer of the both DLTs is made of Au2+ ions and the rear is a thin proton patch. When
the intense laser pulse irradiates onto the two DLTs, one sees that the laser absorption
and the hot electron temperature are both higher in the case of the improved target. As a
result, the protons can be accelerated more efficiently by the rear-surface electrostatic
sheath field. As shown in Fig.1(c), the proton
energy spectra show a higher peak energy
~77.1MeV with the improved DLT while the
peak energy of the reference target is
57.2MeV.
FIG.1. Shape of the (a) conventional DLT; (b)
improved DLT; and (c) energy spectra of the
improved DLT and conventional DLT at t=42T.
44
Comparison between classical and quantum treatment of harmonic
generation by relativistic electrons in strong laser fields
A.K. Li and J. X. Wang
Department of Physics, East China Normal University, Shanghai
We consider relativistic harmonic generation by scatting of circularly and a linearly
polarized laser field from free electron. We investigate in detail the relation between the
photon spectrum calculated through classical and quantum theory for several scattering
configurations by both analytical and numerical methods. We found that when the effects
of radiation reaction on the electron motion are significant, the difference between QED
and classical results are also large.
45
Simulation study of self-injection and density-ramping-injection in
LWFA based on typical 100 TW laser facilities by OOPIC
LI Dazhang1 GAO Jie2 ZhU Xiongwei3 HE An4
1Institute of High Energy Physics, Chinese Academy of Science
One of the most important advanced acceleration concepts is laser plasma acceleration.
The amplitude of the accelerating electric fields generated from Laser WakeField
Accelerators (LWFA) may beyond 100 GV/m, which is more than 1000 times higher than
traditional radio frequency accelerating structures. We do 2-D simulations based on
typical 100TW laser facilities by OOPIC. At first, we fix the laser parameters and do
explicit plasma density scanning to find a matched plasma density as in a real LWFA
experiment. And then in order to solve the problems during self-injection, we give
theoretical and simulation results of density-ramping-injection (DRI) methods. It is shown
that the number of captured electrons is 10 times larger in DRI than in normal
self-injection process and the energy and absolute energy spread of the bunch doesn’t
change a lot.
Funding supported by NSFC (10525525, 10775154) and Knowledge Innovation Funds of
IHEP, CAS (H75452A0U2).
46
Vacuum laser-driven electron acceleration by Airy beams
Jian-Xing Li1, Wei-Ping Zang1, 2, Jian-Guo Tian1, 2
1Photonics Center, School of Physics, Nankai University, Tianjin 300071, China
2The Key Laboratory of Weak Light Nonlinear Photonics, Ministry of Education, Teda Applied
Physics School, Nankai University, Tianjin 3000457, China
Due to the invention of the chirped pulse amplification (CPA) technique, laser acceleration
in vacuum has been an active research area in recent years. Laser-driven electron
acceleration relies on the large laser intensity that can be achieved by focusing laser
beams down to spot sizes in the order of wavelength. However, a shortcoming of many of
these schemes is that the interaction length over which the high intensity can be sustained
is relatively short due to transverse spreading (diffraction). Therefore, electron
acceleration by quasi-diffraction-free beams, Bessel beam, has attracted widespread
attentions.
Another known diffraction-free beam is Airy wave packets, first predicted by Berry and
Balazs within the context of quantum mechanics. This intriguing class of beams was only
recently predicted and realized in optical domain. Its key features are transversely
accelerating and diffraction-free during propagation. Unlike other-diffracting beams, the
Airy beam does not result from conical superposition, is possible even in one-dimension,
and is highly asymmetric. Airy beams have been used in optical micromanipulation. In this
poster we present the first use of the Airy beam in vacuum electron acceleration. The
characteristics of acceleration and non-diffraction of Airy beam in one dimensional
configuration lead to the formation of a long “asymmetric field channel” (AFC) along the
propagation axis. Electron senses a continual acceleration phase in AFC, so 1D Airy
beam is more appreciable to the accelerating of electron than other diffraction and
diffraction-free beams. Moreover, the injection energy of electron plays an important role
in determining the final energy gain. An initial fast electron can be captured by AFC, and a
slow electron could be captured or reflected.
Funding supported by the Natural Science Foundation of China (grant 60678025), Chinese
National Key Basic Research Special Fund (2006CB921703), Program for New Century
Excellent Talents in University, and 111 Project (B07013).
47
Ion jet generation in the ultra-intense laser interactions with
rear-side concave target
Bin Liu1,2 Hua Zhang1,3 Li-Bin Fu1,3 Yu-Qiu Gu4 Bao-Han Zhang4 Ming-Ping Liu5
Bai-Song Xie6 Jie Liu1,3 Xian-Tu He1,3
1Center for Applied Physics and Technology, Peking University, Beijing, 100084, China
2Graduate School, China Academy of Engineering Physics, Beijing 100088, China
3Institute of Applied Physics and Computational Mathematics, Beijing, 100088, China
4Fusion Research Center, Chinese Academy of Engineering Physics, Mianyang, China
5School of Information Engineering, Nanchang University, Nanchang, China
6College of Nuclear Science and technology, Beijing Normal University, Beijing 100875, China
The ion jet generation from the interaction of an ultraintense laser pulse and a rear-side
concave target is investigated analytically using a simple fluid model. We find that the ion
expanding surface at the rear-side is distorted due to a strong charge-separation field, and
that this distortion becomes dramatic with a singular cusp shown on the central axis at a
critical time. The variation of the transverse ion velocity and the relative ion density
diverge on the cusp, signaling the emergence of an on-axis ion jet. We have obtained
analytical expressions for the critical time and the maximum velocity of the ion jet, and
suggested an optimum shape for generating a collimated energetic ion jet. The above
theoretical analysis has been verified by particle-in-cell (PIC) numerical simulations.
Funding supported by the National Fundamental Research Programme of China (Contact
Nos.2007CB815103,2007CB814800), the National Natural Science Foundation of China
(Contact Nos. 10725521, 10875015, 10834008), and the Foundation of CAEP (Contact No.
2006Z0202).
48
Generation of low density plasma channels and optical guiding in
plasma waveguides
Mingwei Liu1,2, Aihua Deng1, Jiancai Xu1, Changquan Xia1, Cheng Wang1, Jiansheng Liu1,
Baifei Shen1, Ruxin Li1, Zhizhan Xu1
1State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine
Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
2School of Physics, Hunan University of Science and Technology, Xiangtan Hunan, 411201,
China
A technique is developed to trigger ablative capillary discharges transversely by a laser
pulse. This transverse laser ignition method has several advantages over previous
techniques employing a laser pulse collinear with the capillary, including increased
capillary lifetime and simpler arrangement of the igniting and the driving pulses for
laser-wakefield acceleration. Using this technique long plasma channels (waveguides) are
produced with low jitter. An off-axis incident model is presented to analyze the influence of
beam pointing fluctuation on the propagation properties of intense laser beams in such
kinds of waveguides. Optical guiding of a 200TW laser pulse over 3-cm in plasma
waveguides is also demonstrated in experiments.
Funding supported by the National Natural Science Foundation (Grant Nos.10734080 and
10834008), the National Basic Research Program of China (Grant No. 2006CB806000), the
Chinese Academy of Sciences, the Shanghai Commission of Science and Technology (Grant
Nos. 06DZ22015 and 0652nm005), and the Hunan Provincial Natural Science Foundation of
China (Grant No. 09JJ3012).
49
Interaction of ultraintense and ultrashort laser pulse with overdense
plasma target
Shixia Luan Wei Yu
Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, 201800,
Shanghai, China
A simple but comprehensive 2-dimensional analytical model for laser and overdense
plasma interaction during the normal incidence by a ultrashort and ultraintense Gaussian
laser pulse with a finite spot size on a solid-density plasma is proposed. Hole punching by
the laser pulse is a key feature in this process, which induces strong spatial charge
separation and plays an crucial role for the occurrence of linear mode conversion (both for
circularly and linearly polarized laser pulse) and J B× heating (only for linearly polarized
laser pulse). It is also found that the depth of the hole increases with higher laser intensity
50
High charged electrons generation by dual laser pulses1
Meng Wen1 ,2 ,3 Baifei Shen2
1 Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai,
China
2 IHIP, Peking University, Beijing China
3 Institute of Photonics & Photon-Technology, North-West University, Xi’an China
Large amount of energetic electrons generated in laser wake fields driven by dual parallel
laser pulses is investigated with three-dimensional (3D) PIC simulation. By adjusting the
distance between the pulses, bubbles with different structure are formed, which results in
different injection efficiency. Compared with the single pulse case, the charge of the
energetic electrons can be doubled when the distance between two pulses is large
enough. A characteristic distance between the pulses is obtained, above which the total
amount of the energetic electrons increases linearly by applying more laser pulses. There
is no limit for the charge increase in our scheme, as long as the plasma is wide enough so
that more pulses can be applied.
Funding supported by the National Natural Science Foundation of China (Project 60921004
and 10834008), the Program of Shanghai Subject Chief Scientist (09XD1404300), Shanghai
Natural Science Foundation (10ZR1433800) and the 973 program (No. 2006CB806004)
51
Numerical research on evaporation of target bombarded by pulsed
ion beam
Wu Di1 Gong Ye2 Liu Jin-Yuan2 Wang Xiao-Gang2 Liu Yue2 Ma Teng-Cai2
1 Collge of Physical Science and Technology, Dalian University, Dalian 116622, China
2 Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Dalian
University of Technology, Dalian 116024, China
To discuss the mechanism of plasma transport in vacuum, the ejection model of
hydrodynamic equations related to the ablation shape of the target has been established
by using the ablation results as initial conditions of plasma formed by high intensity pulsed
ion beam irradiation. The spatial and temporal evolution profiles of plasma pressure, mass
density and velocity are calculated. The plasma transport is faster based on our model
than vertical one, and the formation of film relates to the distance between target and
substrate can be well explained according to our ejection model.
Funding supported by the National Natural Science Foundation of China (Grant No.
10975026).
52
Generation of tens of GeV quasi-monoenergetic proton beams
from a moving double layer formed by ultraintense lasers at
intensity 1021–1023 W cm−2
Lu-Le Yu1, Han Xu2, Wei-Min Wang1, Zheng-Ming Sheng1,3,5, Bai-Fei Shen4, Wei Yu4 and Jie
Zhang1,3
1 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, CAS, Beijing
100190, People’s Republic of China
2 School of Computer Science, National University of Defence Technology, Changsha 410073,
Weimin Wang China
3 Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, China
4 Shanghai Institute of Optics and Fine Mechanics, CAS, Shanghai 201800, China
We present a scheme for proton acceleration from a moving double layer formed by an
ultraintense circularly polarized laser pulse with intensity1021–1023 Wcm−2 irradiated on a
combination target. The target is composed of a thin overdense proton-rich foil located at
the front followed by an underdense gas region behind with an effective Z/A ratio of the
order of 1/3. When the areal density of the thin foil is small enough, the protons together
with electrons in the thin overdense foil can be pre-accelerated under the laser irradiation.
As the laser pulse passes through the thin foil and propagates in the underdense gas
region, it excites high-amplitude electrostatic fields moving at a high speed, which appear
like a moving double layer. The pre-accelerated protons can get trapped and accelerated
in the moving double layer and tens of GeV quasi-monoenergetic proton beams are
achieved, provided the laser intensity and plasma density are properly chosen, as
demonstrated by one-dimensional (1D) and 2D particlein-cell (PIC) simulations.
Funding supported by NSFC (grant numbers 10935002, 10734130 and 60621063),the
National High-Tech ICF Committee of China and the National Basic Research Program of
China (grant numbers 2007CB815101 and 2007CB815105).
53
Ultra-intense single attosecond pulse generated from
circularly-polarized laser interacting with overdense plasma
Liangliang Ji, Baifei Shen, Xiaomei Zhang, Meng Wen, Changquan Xia, Wenpeng Wang,
Jiancai Xu, and Yahong Yu
State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine
Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
Ultra-intense high order harmonics and furthermore attosecond pulses can be generated
by relativistic linearly polarized laser pulse interacting with overdense target, which has
previously been demonstrated theoretically and experimentally. However, with linearly
polarized lasers, there would be a train of attosecond pulses which is difficult for
applications. By particle-in-cell simulations and analysis, we propose that employing a
circularly polarized pulse a single attosecond pulse is generated by itself and no
post-treatments are required. This method is much more convenient than previous
proposals to isolate pulse from the pulse train by linearly polarized lasers. We give the
analytical mode and it describes the simulation results very well. Parameter relationship
shows that using a single-cycle 21 210 W/cm circularly polarized laser, a single 36as
attosecond pulse with peak intensity of 21 26.3 10 W/cm× is generated. Two dimensional
simulation shows that the proposal is also efficient in multi-dimension geometries.
54
Self-generated magnetic fields in the relativistic laser-plasma
interaction
A. Abudurexiti
Physics Department, Xinjiang University, Urumqi , 830046
Strong magnetic fields can be generated when an intense laser pulse interacts with
plasma. The spontaneous magnetic fields as large as several mega-Gauss have been
directly measured in the blowoff plasma in front and rear of solid targets ,and attributed to
a mechanism that occurs when the plasma density gradient n∇ and temperature gradient
T∇ are not collinear, These magnetic fields, which can become strong enough to
significantly affect transport, are attributed to nonlocal effects that are missing in the
standard, local theories .In this paper ,The self-generated magnetic field by a relativistic
laser pulse irradiated on a thin plasma target at the perpendicular incidence is
investigated using a two dimensional particle-in cell simulation.
55
High resolution emittance and energy spread measurements of
80- 135 MeV electron beams from a laser driven plasma wakefield
accelerator on the ALPHA-X beam line
G. Manahan E. Brunetti R. P. Shanks M. P. Anania S. Cipiccia R. T. L. Burgess R.
Issac M. R. Islam B. Ersfeld G. H. Welsh S. M. Wiggins and D. A. Jaroszynski
Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK
The normalised transverse emittance characterises the quality of an electron beam
generated from the laser-plasma wakefield accelerator (LWFA). Brightness, parallelism
and focusability are all functions of the emittance. Here, we present a high-resolution
single shot method of measuring the transverse emittance of a 125 MeV electron beam
generated from a LWFA using a pepper-pot mask. An average normalised emittance of
around 1 mm mrad was measured, which is comparable to that of a conventional
accelerator. We also show high resolution measurements of the energy spread
determined using a magnetic dipole spectrometer.
Funding supported by U.K. EPSRC and the Scottish Universities Physics Alliance.
56
Ultrafast pulse-train laser leading to desktop intense THz
free-electron laser
Yen-Chieh Huanga, Kuei-Feng Honga, Yen-Yin Lina, An-Chung Chiangb, Chiahsian Chena a Department of Electrical Engineering, b Nuclear Science and Technology Development
Center, National Tsinghua University, Hsinchu 30013, Taiwan
We report the development of a high-power THz pulse train laser to drive an electron
photoinjector, which in turn drives a single-pass free electron laser to generate fully
tunable, coherent, intense THz radiation in a desktop dimension. In this work, we
engineer a TW-power, THz pulse train laser and further encode the laser pulse structure
to an electron beam through a photocathode electron accelerator. Such an electron beam,
carrying the coherence of the laser, is ideal for generating high-brightness electron
radiation at frequencies that can not be reached by a solid-state laser.
This work is supported by National Tsinghua University under project code 98N2534E1 and by
National Science Council under Contract NSC 99-2112-M-007 -013 -MY3.
