Schwoerer / Magill / Beleites Lasers and Nuclei

Applications of Ultrahigh Intensity Lasers in Nuclear Science
1. Auflage 2006
ISBN: 978-3-540-30272-8
Verlag: Springer
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, Band 694, 287 Seiten, eBook

Reihe: Lecture Notes in Physics

Lasers and Nuclei describes the generation of high-energy-particle radiation with high-intensity lasers and its application to nuclear science. A basic introduction to laser--matter interaction at high fields is complemented by detailed presentations of state of the art laser particle acceleration and elementary laser nuclear experiments. The text also discusses future applications of lasers in nuclear science, for example in nuclear astrophysics, isotope generation, nuclear fuel physics and proton and neutron imaging.

Zielgruppe

Research

Autoren/Hrsg.

Schwoerer, Heinrich

Magill, Joseph

Beleites, Burgard

Inhaltsverzeichnis

Fundamentals and Equipment.- The Nuclear Era of Laser Interactions: New Milestones in the History of Power Compression.- High-Intensity Laser–Matter Interaction.- Laser-Triggered Nuclear Reactions.- POLARIS: An All Diode-Pumped Ultrahigh Peak Power Laser for High Repetition Rates.- The Megajoule Laser – A High-Energy-Density Physics Facility.- Sources.- Electron and Proton Beams Produced by Ultrashort Laser Pulses.- Laser-Driven Ion Acceleration and Nuclear Activation.- Pulsed Neutron Sources with Tabletop Laser-Accelerated Protons.- Transmutation.- Laser Transmutation of Nuclear Materials.- High-brightness ?-Ray Generation for Nuclear Transmutation.- Potential Role of Lasers for Sustainable Fission Energy Production and Transmutation of Nuclear Waste.- High-Power Laser Production of PET Isotopes.- Nuclear Science.- Nuclear Physics with High-Intensity Lasers.- Nuclear Physics with Laser Compton ?-Rays.- Status of Neutron Imaging.

Leseproben

3 Laser-Triggered Nuclear Reactions (p. 25-26)

F. Ewald
Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität Jena
Max-Wien-Platz 1, 07743 Jena

3.1 Introduction

Nearly 30 ago, laser physicists dreamed of the laser as a particle accelerator [1]. With the acceleration of electrons, protons, and ions up to energies of several tens of MeV by the interaction of an intense laser pulse with matter, this dream has become reality within the last ten years. Today, highly intense laser systems drive microscopic accelerators. Nuclear reactions are induced by the accelerated particles. This article intends to outline the unique properties of laser-based particle and bremsstrahlung sources, and the diversity of new ideas that arise from the combination of lasers and nuclear physics.

Triggering nuclear reactions by a laser is done indirectly by accelerating electrons to relativistic velocities during the interaction of a very intense laser pulse with a laser-generated plasma. These electrons give rise to the generation of energetic bremsstrahlung, when they are stopped in a target of high atomic number. They can as well be used to accelerate protons or heavier ions to several tens of MeV. Those bremsstrahlung photons, protons, and ions with energies in the typical range of the nuclear giant dipole resonances of about a few to several tens of MeV may then induce nuclear reactions, such as fission, the emission of photoneutrons, or proton-induced emission of nucleons. To induce one of these reactions, a certain energy threshold – the activation energy of the reaction – must be exceeded.

Since the .rst demonstration experiments, nuclear reactions were used for the spectral characterization of laser-accelerated electrons and protons as well as bremsstrahlung [2, 3, 4, 5]. A whole series of classical known nuclear reactions has been shown to be feasible with lasers, such as photo-induced .ssion [6, 7], proton- and ion-induced reactions [5, 8, 9], or deuterium fusion [10, 11, 12, 13, 14]. Recently the cross section of the (ã,n)-reaction of 129I was measured in laser-based experiments [15, 16, 17].

This last step from the pure observation of nuclear reactions to the measurement of nuclear parameters is of importance regarding the small size of nowaday’s high-intensity laser systems compared to large accelerator facilities. It is a .rst step to a possible joint future of nuclear and laser physics. Nevertheless, all probable future applications of laser-induced nuclear reactions would need to have properties that are not covered by classical nuclear physics. Otherwise, they would stay a diagnostics tool for laser–plasma physicists. The striking properties of a laser as driving device for nuclear reactions are its small tabletop size, the possibility to switch very fast from one accelerated particle to another as well as the ultrashort duration of these particle and bremsstrahlung pulses.

3.2 Laser–Matter Interaction

The basis of all laser-triggered nuclear reactions is the acceleration of particles such as electrons, protons, and ions as well as the generation of high-energy bremsstrahlung photons by the interaction of very intense laser pulses incident on matter. The mechanisms of particle acceleration change sensitively with the target material and chemical phase. The choice of target material in conjunction with the laser parameters is important for the control of plasma conditions and therewith for the control of optimum particle acceleration.

Gaseous targets and underdense plasmas are suited best for the acceleration of electrons to energies of several tens of MeV [18, 19, 20, 21]. Thin solid targets, in contrary, are used to accelerate protons and ions [5, 22, 23, 24]. Deuterium fusion reactions have been realized with both heavy water droplets and deuterium-doped plastic [10, 12, 14]. Therefore, but without being exhaustive, the different acceleration mechanisms of electrons, protons, and ions that are important for the production of energetic electrons, protons, and photons are outlined in this section.