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
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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
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
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,
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.