In a recent report, the National Academies of Science, Engineering, and Medicine (NASEM) recommends that “the United States should start a national program of accompanying research and technology leading to the construction of a compact pilot plant that produces electricity from fusion at the lowest possible capital cost.” It is generally acknowledged that a decarbonization of the world’s energy system is unavoidable to combat climate change. While an exothermic chemical reaction such as the combustion of fossil fuels produces an energy of <1 eV per molecule, a nuclear fusion reaction is an attractive alternative as it releases 10 million times more energy. To date, considerable effort has been devoted to research involving the fusion between the nuclei of the two heavy isotopes of hydrogen: deuterium (D) and tritium (T). However, the main roadblock for the adoption of this technology is the need to heat the fuel to temperatures in the order of 50 million Kelvin and to keep it stable under extreme pressure conditions. Recent results show that this difficulty can be overcome by utilizing the nonthermal radiation pressure that can be generated via chirped-pulse amplifier laser systems and can trigger the fusion of hydrogen and boron-11 nuclei, producing clean energy in the form of kinetic alpha particles, thus sidestepping nuclear radiation problems due to the aneutronic nature of the process.
Numerical investigations on high energy proton beam interaction with high density Boron plasma allows to simulate conditions concerning the alpha production from recent experimental measurements . The experiments measure the alpha production due to p11B nuclear fusion reactions when a laser-driven high energy proton beam interacts with Boron plasma produced by laser beam interaction with solid Boron. The alpha production and consequently the efficiency of the process depends on the initial proton beam energy, proton beam density, the Boron plasma density and temperature, and their temporal evolution. The main advantage for the p11B nuclear fusion reaction is the production of three alphas with total energy of 8.9 MeV, which could enhance the alpha heating effect and improve the alpha production. This particular effect is termed in the international literature as the alpha avalanche effect. Numerical results using a multi-fluid, global particle and energy balance, code shows the alpha production efficiency as a function of the initial energy of the proton beam, the Boron plasma density, the initial Boron plasma temperature and the temporal evolution of the plasma parameters. The simulations enable us to determine the interaction conditions (proton beam – B plasma) for which the alpha heating effect becomes important.
The nuclear reaction of hydrogen (protons) with the boron isotope 11 (HB11) is aneutronic avoiding the production of dangerous neutrons in contrast to any other fusion but it is extremely difficult at thermal equilibrium plasma conditions. There are alternative schemes without thermal equilibrium, e.g. the Tri Alpha reversed magnetic field (RMF) confinement and others, however, the only historical first measurements of HB11 fusion were with lasers interacting with high density plasmas using non-thermal direct conversion of laser energy into ultrahigh acceleration of plasma blocks to avoid the thermal problems. Combining these long studied mechanisms with recently measured ultrahigh magnetic fields for trapping the reacting plasma arrives at a very compact design of an environmentally clean reactor for profitable low cost energy using present technologies.
This book is an important reference work for the field of high-intensity and high-plasma-density laser–plasma interaction. It summarizes past advances and opens insights into the future. The book covers the essentials from a single particle to dense fluids, and from computational physics to applications for fusion energy or hadron cancer therapy. In addition, it contains clear explanations of the theory of electrodynamics, laser-driven hydrodynamics, Maxwell’s stress tensor and Lorentz force, complex refractive index, and relativistic effects in plasmas. Beyond these classical aspects, the book indicates where quantum and classical theory converge.
Topics new to this edition include: an introduction to the ponderomotive potential and an overview of related phenomena, including hydrodynamic derivation of nonlinear forces; Richard Feynman and the nonlinearity principle; application of ultrahigh plasma block acceleration for electrons above GeV energy; extremely dense ion blocks for non-thermal picosecond ignition of fusion; and the very first approach to economical power generation using boron fusion with complete exclusion of nuclear radiation problems.
The burning process of high density (about 1018cm-3), high temperature (tens to hundreds of keV) plasma trapped by a high mirror-like magnetic field in a Compact Magnetic Fusion (CMF) device is numerically investigated.. The initial high density and high temperature plasma in the CMF device is produced by ultrashort high intensity laser beam interaction with clusters or thin foils, and two fuels, D-T and p-11B are studied. The spatio-temporal evolution of D-T and p-11B plasmas, the production of alphas, the generated electric fields and the high external applied magnetic field are described by a 1-D multifluid code. The initial values for the plasma densities, temperatures and external applied magnetic field (about 100 T) correspond to high β plasmas. The main objectives of the numerical simulations are: to study the plasma trapping, the neutron and alpha production for both fuels, and compare the effect of the external applied magnetic field on the nuclear burning efficiency for the two fuels.. The comparisons and the advantages for each fuel will be presented. The proposed CMF device and the potential operation of the device within the ELI-NP pillar will be discussed.
An alternative way may be possible for igniting solid density hydrogen-11B (HB11) fuel. The use of >petawatt-ps laser pulses from the non-thermal ignition based on ultrahigh acceleration of plasma blocks by the nonlinear (ponderomotive) force, has to be combined with the measured ultrahigh magnetic fields in the 10 kilotesla range for cylindrical trapping. The evaluation of measured alpha particles from HB11 reactions arrives at the conclusion that apart from the usual binary nuclear reactions, secondary reactions by an avalanche multiplication may cause the high gains, even much higher than from deuterium tritium fusion. This may be leading to a concept of clean economic power generation.
A fundamental difference between interaction of laser pulses of less than picosecond duration and power in the range of and above Petawatt appears in contrast to pulses of nanosecond duration. This is due to the basic property that the long pulse interaction is based on thermal effects with inefficient delays of chaotic microscopic thermal motion while the short pulses avoid these complications and the interacting plasma reacts as a macroscopic collective known from atomic physics. Optical energy is converted into mechanical motion with high efficiency and nearly no thermal losses. These developments cover a long history of laser developments leading now into a new era of nonlinear physics combined with quantum properties. One of the applications is laser driven fusion energy
Laser ignition of fusion (LIF) of light nuclei for fusion reactions for producing energy (LIFE) by using very
powerful laser pulses with duration in the range of picoseconds is the aim of fast ignition where HiPER is one
of the options. Special attention is given to the ultrahigh acceleration of plasma blocks about which option
results are reported including an alternative scheme for avoiding lateral energy losses. Examples of relativistic
accelerations are evaluated for HiPER and LIFE applications.
When crossing an electron beam in vacuum with an optical (laser) beam with standing waves, an interaction was
redicted known as Kapitz-Dirac effect where the electrons are diffracted at the nodes of the optical field. After
the final success of an experiment was reported (Freimund et al. 2001) confirming this classical kind of laser
interaction with free electrons, the generalization of this effect (Schwarz-Hora effect) in the presence of a target
or medium in the crossing area of the beams is re-considered as a basic non-resonance nonlinear quantum
interaction process. The proof is based on a discovery of Peierls and of repeated later measurements agreeing
with a quantum threshold for which the theory was elaborated initially. This is confirmed also in connectnion
with the quantum theory of 1/f noise. Other aspects for electron acceleration of electrons by lasers may be
interesting up to PeV energy using laser pulses of femtosecond (fs) duration and powers from Petawatt (PW) to
Exawatt and Zetawatt.
Interaction of TW-ps laser with plasma results in a skin layer mechanism for nonlinear (ponderomotive) force driven two dimensional plasma blocks (pistons) if a very high contrast ratio is provided for suppression of relativistic self-focusing. This Skin layer acceleration (SLA) [1] results in space charge neutral plasma blocks with ion current densities larger than 1010 Amp/cm2 [1-3]. Using Ions in the MeV range results in 1000 times higher proton or DT current densities [3] than the proton fast igniter [4] is using and may result in better conditions of this fast ignitor scheme. Using ballistic focusing of the generated plasma blocks and a short time thermal expansion of these blocks for increasing their thickness while keeping the high ion current densities, results in conditions favourable for this option of fast ignition of a fusion target. Some details of the interaction processes are still to be analysed but the solutions studies to date are most encouraging.
Conversion of n- into p-conducting silicon by electron bombardment was first observed with subthreshold intense electron beams of 75 keV energy and confirmed later by several groups. These results received attention again in view of microelectronics and nanotechnology with respect to the shorter than optical focusing conditions for electrons. In order to continue these studies with subthreshold defect generation we report on experiments with optical detection of the changes as observed before in silicon together with the changes from n- into p- conductivity. Further interest is in production of very low cost solar cells from conducting polymers like polyacetylene and avoiding chemical methods leading to formation of highly aggressive waste. The near band gap generation of defects by electron irradiation has been detected in optical absorption spectra. We aim to analyze the stability of the generated defects in view of crystal defects or dangling bond generation in the semiconductors.
It is being clarified why the observations of plane wave geometry interaction within the skin depth of a laser irradiated target are very unique exceptions from the broad stream of the usual experiments of laser plasma interaction. This permits a much more simplified description by plane wave interaction theory for laser pulses of about ps or shorter duration and powers above TW and simplifies computations in contrast to the usual cases with relativistic self-focusing. After establishing theoretically and experimentally the generation of highly directed plasma blocks with ion current densities above 1010 A/cm2 moving against the laser light or into the target, applications for laser fusion, and a completely new improvement of ion sources for the next generation of accelerators are discussed.
The studies of laser ablation have lead to a new theory of nuclei, endothermic nuclei generation and quark-gluon plasmas. The surface of ablated plasma expanding into vacuum after high power laser irradiation of targets, contains an electric double layer having the thickness of the Debye length. This led to the discovery of surface tension of plasmas and to the internal dynamic electric fields in all inhomogeneous plasmas. The surface causes stabilization by short length surface waves smoothing the expanding plasma plume. Generalizing this to the degenerate electrons in a metal with the Fermi energy instead of the temperature, resulted in the surface tension of metals in agreement with measurements. Taking then the Fermi energy in the Debye length for nucleons results in a theory of nuclei with stable confinement of protons and neutrons just at the well known nuclear density, and in the Debye length equal to Hofstadter's decay of the nuclear surface. Increasing the nuclear density by a factor of 6 leads to the change of the Fermi energy into its relativistic branch where no surface energy is possible and the particle mass is not defined, permitting the quark-gluon plasma. Expansion of this higher density at the big band or in a supernova results in nucleation and element generation. The Boltzmann equilibrium permits the synthesis of nuclei even in the endothermic range limited to about uranium.
Plasma emission or ablation from laser-irradiated targets shows very complicated properties. One novelty was observed at irradiation of neodymium glass laser pulses of ps duration and TW power if there was a very strong suppression of prepulses by a contrast ratio of about 108 until 100 ps before the main pulse arrived. The emitted ion maximum energy was more than 50 times below the values observed in all the comparable numerous experiments. The other anomaly is that the number of the fast ions did not change when the laser intensity varied by a factor 30. This permitted a separation of the usual effects of self-focusing and permitted an analysis fully based on simplified plane geometry as a skin layer interaction mechanism. The consequence is that plasma blocks are accelerated by the nonlinear (ponderomotive) force with ion current densities above 1010 A/cm2. This provides basically new aspects for laser fusion using uncompressed solid DT fuel and a new kind of x-ray laser process may be possible.
The experiment of Badziak et al has shown that irradiation of copper by 1.5 ps laser pulses produced 50 times lower maximum ion energies than the 22 MeV expected after relativistic self focusing from laser pulses of about ns duration. This discrepancy was confirmed in the following reported experiments specifically designed for this clarification, where MeV Au+30 maximum ion energies needed 400 times higher intensity with ps pulses than with 0.5 ns pulses. Comparing the theory for generating the fastest ions by relativistic self focusing and of the second fastest group by a quiver-collision model, we arrived at the conclusion that the mentioned ps-TW-generated ions are not following these usual theories but that a skin depth model with exclusion of relativistic self focusing explains the experiments. The essential importance is the suppression of the prepulse. We conclude how the experiment by Norreys et al. with the highest ever reported fusion gains may be increased to fusion reactor conditions if our results of prepulse control and suppression of relativistic self focusing would be applied following our skin layer interaction model. This extends the fast ignitor to the nonlinear-force block ignition without plasma precompression.
The investigations of nonthermal processes in laser-produced plasmas are not yet complete, especially with regard to the ion acceleration in the plasma generated by high-energy short-wavelengths lasers. This contribution presents the results of studies of fast ion emission from plasma generated using a short wavelength (438 nm), high-energy (up to 250 J in 400 p5 pulse) iodine laser PALS at the Joint Research Laboratory PALS ASCR in Prague, Czech Republic. The properties of highly charged ion streams were investigated by ion diagnostic methods: ion collectors and solid state track detectors as well as a cylindrical electrostatic energy analyzer. Attention was paid to the determination of ion energy and comparison of the energies and abundance of different ion groups. The presented results shown the existence of highly charged ions with z <40 (measured z, =57 forTa) and with energies higher then 20 MeV in a far expansion zone. Ion current densities up to tens of mA/cm2 at a distance of 1 m from the target were obtained. On the basis of the ion diagnostic investigations the existence of nonthermal and nonlinear accelerating processes was demonstrated for the plasma produced by a high-energy short-wavelength laser pulse.
A new type of MeV ion generation at laser-plasma interaction has been measured based on the observation [1] that ps neodymium glass laser pulses of about TW and higher power do not produce the relativistic self-focusing based very high ion energies but more than 50 times lower energies. On top the strange observation was reported [fl that the number of the emitted fast ions did not change at variation of the laser focus intensity by a factor 30. This can be explained by the effect that without an inadiating prepulse, a pui plane gcmetnc skin layer interaction mechathsm occurs [2]. Neither relativistic self-focusing is possible nor the process of thermalization of quiver energy by quantum modified collisions. Following our conclusions about the difficulties for the fast ignitor concept of laser fi.ision [3], we can explain how these mechanisms can be used for studying the self-sustained fusion combustion waves [4] as known from the spark ignition at laser fusion. We further expect an improvement of the conditions for the experiments [5]with the highest laser fusion gains ever reported where even no pre-compression of the ftision plasma was necessary.
Laser generated electron-positron pair production is under discussion in the literature form 1969 and large numbers of positrons have been measured since a few years. For electron-positron pair production in vacuum due to vacuum polarization as predicted by Heisenberg 1934, again much higher laser intensities around 1028W/cm2 are necessary which may be available within a number of years. For these cases the similar electron acceleration by gravitation near black holes at Hawking-Unruh radiation have been discussed since 1985 by McDonald. These conditions are considered in view of the earlier work on pair production, change of statistics for electrons at relativistic black body radiation and an Einstein-recoil mechanism with a consequence of a physical foundation of the fine structure constant.
The new principle of nonlinearity requesting a much higher degree of accuracy of all physical presumptions for the treatment, can be demonstrated ideally by the field of acceleration of electrons by lasers in vacuum. Initially the net energy conversion from electromagnetic radiation to electrons, e.g. by lasers in vacuum, was considered to be impossible based on the fact that plane-wave and phase symmetric wave packets can never transfer energy to electrons apart from Thomson or Compton scattering or the Kapitza-Dirac effect. The nonlinear nature of the electrodynamic forces of the fields to the electrons, expressed as nonlinear forces including ponderomotion or the Lorentz force, however, does permit an energy transfer if the conditions of plane waves in favor of beams and/or the phase symmetry are broken. The result in electron acceleration is now well understood as 'free wave acceleration', as 'ponderomotive scattering', as 'violent acceleration' or as 'vacuum beat wave acceleration'. The basic understanding of these phenomenon, however, relates to an accuracy principle of nonlinearity for explaining numerous discrepancies on the way to the mentioned achievement of 'vacuum laser acceleration'. From mathematically designed beam conditions, an absolute maximum of electron energy per laser interaction has been established. Numerical results strongly depend on the accuracy of the used laser fields for which examples are presented and finally tested by a criterion of the absolute maximum.
For the use of laser ablation from solid materials, laser intensities I in the range of few orders of magnitudes above or below 1010 Watts/cm2 are of interest. Though these are of a modest magnitude it is known from the very beginning of laser plasma interaction studies that the ablation process mostly is not following the simple gasdynamic (thermokinetic) heating and hydrodynamic plasma mechanisms but that most complicated phenomena appear which are in the focus of research since their first observations in 1962 by Linlor and Honig. A number of basically new nonlinear mechanisms were discovered including the nonlinear (ponderomotive) force, emission of different groups of plasma where the fast ions show a separation by energy linearly increasing on their ion charge number Z, ponderomotive and relativistic self focusing, generation of higher harmonics in the backscattered radiation, double layer and surface tension effects, parametric instabilities and a stochastic pulsation of the interaction within some ten picoseconds. This all seems to have a threshold of about 1 MW laser power at least if beams of up to 100 wavelength diameter are being used. For the applications of the ablation mechanisms it may well be that further anomalous mechanisms may be discovered with the very wide beams. In order to simulate the awareness of these complexities, this paper is presenting a new and updated synopsis on the anomalous nonlinear mechanisms whose knowledge seems to be settled at present.
KEYWORDS: Plasma, Fusion energy, Picosecond phenomena, Laser welding, Laser energy, Solid state physics, Solid state lasers, Ions, High power lasers, Information operations
Laser fusion has achieved the level today that the physical mechanisms for an economic production (at the costs of light water reactors) of energy has been confirmed, based on underground tests using 10 MJ laser pulses. This scheme is based on conversion of the laser radiation into x rays for smoothing, called hohlraum or indirect drive, and on central spark ignition. The authors present an improvement of this scheme by the following two advancements: (a) More efficient direct drive. The long misunderstood 10 psec pulsating laser- plasma interaction, which cannot be dominated by stimulated Raman nor Brillouin scattering as confirmed experimentally by P.R. Drake and C. Labaune et at., is now understood from a very detailed computation showing how the laser radiation causes partial standing waves in the corona and spatial density ripple, followed by reflection far out at very low density (as measured by Maddever and Luther-Davies), with subsequent hydrodynamic decay of the ripples, repeated penetration of the light through the corona, standing ware generation etc., within 10 to 20 psec. (b) Use of volume ignition of ICF pellets. The mechanisms of self heat by charged fusion reaction products permit a very transparent computation of optimized fusion gains where the strongly lowered initial temperatures and the strong heating of the pellets after volume ignition result in fusion gains beyond 1000 for the not too high compression of DT.
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