Articles

The 1st Asian workshop on Generation and Application of High-Order Harmonics was held during Feb. 23-25, 2005 at KAIST, Daejeon, Korea. The workshop was organized to provide a forum for graduate students, junior and senior scientists from Asian countries, as a part of activities of the Asian Intense Laser Network.

The number of participants was 58, among which 13 were from Japan and China. The workshop was supported by the Div. of Quantum Electronics of Optical Society of Korea, Div. of Optics & Quantum Electronics of Korean Physical Society, Advanced Photonics Research Institute at Gwangju Institute of Science and Technology, Korea-China Optical Technology Research Center at Korea Atomic Energy Research Institute, and Coherent X-ray Research Center at KAIST.

Three groups, one in the US at Berkeley, lead by W. Leemans1, one in England, lead by K. Krushelnick2 and one in France, lead by V. Malka3, have experimentally produced a monoenergetic electron beam using a short and intense laser pulse. This “dream beam” as it is called in the scientific journal, Nature, open new perspectives in the domain of accelerators.

Using the interaction of ultraintense lasers with plasmas is an elegant and efficient way to produce beam of electrons. The first motivation, as proposed by Tajima and Dawson 25 ago4, was to demonstrate that we are able to reduce the size of accelerators, which tend to be gigantic and very expensive.

Our laser-based accelerator is incredibly smaller than conventional accelerators. At LOA, for example, we are producing 170 +/- 20 MeV high quality electrons beam in a length of only 3 mm long (versus several tens of meters for conventional accelerators with similar energies). Previously, it was impossible to control the injection of electrons in the plasma wave, as a consequence electron beams produced by laser had 100 % energy spread. The improvement of the beam quality obtained by the three groups (divergence, energy spread, duration) will open new perspectives in many fields as diverse as medicine, biology and chemistry.

Those properties are well adapted to accelerate electrons to even higher energies, while still keeping a high quality beam. We are hoping to reach 1 GeV in the near future with a compact device. This would be the energy range required for synchrotron light sources.

[1] C. G. R. Geddes et al., Nature 431, 2004
[2] S. P. D. Mangles et al. , Nature 431, 2004
[3] J. Faure et al ., Nature 431, 2004
[4] T. Tajima and J. Dawson, Phys. Rev. Lett. 43 (1979).

By Victor Malka LOA, ENSTA, CNRS, Ecole Polytechnique, Contact : victor.malka@ensta.fr

(This article has been published in "Science" in May 1994)

Introduction

The application of the chriped - pulse amplification technique to solid-state lasers combined with the availability of broad - bandwidth materials has made possible the development of small-scale terawatt and now even petawatt (1000-terawatt) laser systems. The laser technology used to produce these intense pulses and examples of new phenomena resulting from the application of these systems to atomic and plasma physics are described.

Conclusion

The development of terawatt, and soon petawatt, lasers based on CPA has led to new opportunities in the interaction of intense laser radiation with matter. This article has foused on enabling laser technology and introduced the application of these sources to atomic and plasma physics. Continuing laser development to produce both high-energy (kilojoule), low-repetition-rate systems and low-energy (millijoule) high-repition-rate (kilohertz) systems will further expand the application of these powerful new laser sources.

Article Overview

• A method of laser amplification in the mid-1980s has enabled a new generation of tabletop lasers that produce very brief pulses of extremely intense lights
• Lights of such high intensity interacts with matter in new ways, directly propelling electrons to nearly the speed of light in femtoseconds. The lasers can accelerate particles at 10,000 times the rate of standard accelerators.
• Potential applications include high-resolution medical imaging, inexpensive precision radiation therapy, nuclear fusion, and research in numerous subfields of physics.

Article Summary

By stretching, amplifying and then compressing laser pulses, one can reach petawatt powers, gigagauss magnetic fields, terabar light pressures and 10²² m/s² electron acceleration.

Broad Contents

• Evolution of laser peak power
• Chipped pulse amplification
• Pulse generation and characterization
• Ultrahigh-intensity applications
• Electron acceleration
  Self-focusing, harmonic generation
  ICF fast ignitor
  Astrophysics
  Quantum electrodynamics
• References

The attached presentation touches on the ongoing research at the Rutherford Appletown Laboratory (RAL) on radiological protection.

The contents of this presentation include:

• RAL Petawatt Target Area
• Primary Radiation Emission (γ,p,n)
• Shielding
• Activation
• High Repetition Facilities
• Conclusion

The conclusions drawn in this presentation cover the following areas:

• Radiological impact of primary gamma,p,n doses are getting understood
• Primary activation at RAL from p,(x)n reactions
• Ongoing investigations into neutron activation at other facilities
• Primary shielding in the forward direction for high energy photons
• Secondary shielding to protect from lower energies and scattered radiation