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The Ignitor tokamak nuclear fusion research project is one of the most ambitious initiatives undertaken under the long-term scientific cooperation program between the Russian Federation and the Italian Republic. Currently, negotiations are underway to develop the engineering design of the Ignitor tokamak to be sited at JSC SRC TRINITI (Troitsk Institute for Innovation and Fusion Research) in Troitsk, Moscow. The Ignitor tokamak differs essentially from other tokamaks currently under development. It will have an ultra-powerful magnetic field of 13 T, in which a powerful plasma current of 11 MA will flow at a pulse discharge of about 10 s. The fusion reaction will be ignited mainly by ohmic heating. On the basis of the inspection of practically all the basic components of the energy and supporting infrastructure of the TRINITI Strong-Field Tokamak (SFT) experimental test facility, including steady-state and pulsed power supply systems, vacuum, cryogenic, and fuel systems, and diagnostic equipment, as well as on the analysis of the technical requirements for the tokamak support systems, the proposals for modernizing the TRINITI SFT experimental test facility for the implementation of the Ignitor Project were developed.

In 2015, the development of the conceptual design of IGNITOR, a Russian–Italian experimental thermonuclear tokamak, was completed, and the parameters of all the systems, including the fuel system, were determined. In this work, an integrated design of arrangement of all the tritium-containing gas and secondary water streams expected in the operation of the IGNITOR tokamak was proposed on the basis of analyzing the designs of the fuel cycles of the large thermonuclear facilities JET, TFTR, and ITER. This design includes the storage of deuterium and tritium in a system of gas cylinders at a pressure of 0.4 MPa, the purification of the exhaust gas mixture from the plasma chamber using a “hot getter,” the separation of the deuterium–tritium isotope mixture by displacement gas chromatography, the purification of the process gas and air streams in a wet scrubber, and the detritiation of the water streams by chemical isotope exchange of hydrogen with water. The main technical parameters of equipment in the proposed design were estimated.

A fusion reactor is an artificial sun created under laboratory conditions of high temperature and pressure to produce inexhaustible energy. When two nuclei of hydrogen isotopes are forced to fuse, under high temperature and high pressure, the reaction produces huge amount of energy and the heavier atoms of helium. The tokamak concept for magnetic confinement of plasma in a fusion reactor made the use of superconducting magnets most attractive and a natural choice. This chapter gives an account of the fusion process, the Lawson-Criterion for realizing ‘ignition’, different methods of plasma confinement and the superiority of tokamak concept. In a tokamak plasma is confined in a torus by an axial field generated by a set of toroidal coils distributed around the torus and a poloidal field generated by a set of poloidal coils. A high field central solenoid induces current in the plasma to heat it to high temperature through ramping of the field. This current in turn also produces poloidal field. We discuss the superconducting magnet systems built for most important fusion reactors so far, namely, T-7 of Russia, Tore Supra of France, JT-60 SA of Japan, KSTAR of Korea, EAST of China and SST-1 of India. The magnet systems of ITER, has been discussed in greater details. Two tokamaks, namely, TFTR of USA and JET at Culham UK both using normal magnets have also been included for they had many firsts and the data collected from them contributed significantly to the design of ITER. Two more futuristic reactors, the stellarator W7-X being built in Germany and IGNITOR an Italian–Russian joint fusion reactor being built in Russia have also been included towards the end of the chapter.

In the framework of fusion energy research based on magnetic confinement, pulsed high-field tokamaks such as Alcator and FTU have made significant scientific contributions, while several others have been designed to reach ignition, but not built yet (IGNITOR, FIRE). Equivalent stellarator concepts, however, have barely been explored. The present study aims at filling this gap by: (1) performing an initial exploration of parameters relevant to ignition and of the difficulties for a high-field stellarator approach, and, (2) proposing a preliminary high-field stellarator concept for physics studies of burning plasmas and, possibly, ignition. To minimize costs, the device is pulsed, adopts resistive coils and has no blankets. Scaling laws are used to estimate the minimum field needed for ignition, fusion power and other plasma parameters. Analytical expressions and finite-element calculations are used to estimate approximate heat loads on the divertors, coil power consumption, and mechanical stresses as functions of the plasma volume, under wide-ranging parameters. Based on these studies, and on assumptions on the enhancement-factor of the energy confinement time and the achievable plasma beta, it is estimated that a stellarator of magnetic field B ~ 10 T and 30 m3 plasma volume could approach or reach ignition, without encountering unsurmountable thermal or mechanical difficulties. The preliminary conceptual device is characterised by massive copper coils of variable cross-section, detachable periods, and a lithium wall and divertor.

CANDOR is a high-field advanced fusion fuel cycle experiment based on Ignitor, but with larger dimensions and higher fusion power: it is a feasibility study of a high-field Deuterium-Helium-3 (D3He) experiment of larger dimensions and higher fusion power than Ignitor, still based on the core Ignitor technologies. Results of investigations on the feasibility of D3He burning and side neutrons production in D3He plasmas and specifically in CANDOR show that, with the initial use of DT triggering, the need for an intense auxiliary heating would be considerably alleviated. The total released 14 MeV neutron energy during the 16-second burning sums to about 210 MJ. DT and DD neutron currents incoming in the CANDOR plasma chamber wall and the Neutron Wall Loads have been computed. D3He ignition could be studied in CANDOR, with modest and conservative developments of the present technology. CANDOR has a low neutron wall loading, softer neutron spectrum, low radiation damage, and - consequently - lower neutr...

The poloidal current induced in the tokamak wall during fast transient events is analytically evaluated. The analysis is based on the electromagnetic relations coupled with plasma equilibrium equations. The derived formulas describe the consequences of both thermal and current quenches. In the final form, they give explicit dependence of the wall current on the plasma pressure and current. A comparison with numerical results of Villone et al. [F. Villone, G. Ramogida, G. Rubinacci, Fusion Eng. Des. 93, 57 (2015)] for IGNITOR is performed. Our analysis confirms the importance of the effects described there. The estimates show that the disruption-induced poloidal currents in the wall should be necessarily taken into account in the studies of disruptions and disruption mitigation in ITER.

We report on shadowgraphic measurements showing the first space- and time-resolved snapshots of ultraintense laser pulse-generated fast electrons propagating through a solid target. A remarkable result is the formation of highly collimated jets ( $l20\ensuremath{-}\ensuremath{\mu}\mathrm{m}$) traveling at the velocity of light and extending up to 1 mm. This feature clearly indicates a magnetically assisted regime of electron transport, of critical interest for the fast ignitor scheme. Along with these jets, we detect a slower ( $\ensuremath{\approx}c/2$) and broader (up to 1 mm) ionization front consistent with collisional hot electron energy transport.

Guided compression offers an attractive route to explore some of the physics issues of hot electron heating and transport in the fast ignition route to inertial confinement fusion, whilst avoiding the difficulties associated with establishing the stability of the channel formation pulse. X-ray images are presented that show that the guided foil remains hydrodynamically stable during the acceleration phase, which is confirmed by two-dimensional simulations. An integrated conical compression/fast electron heating experiment is presented that confirms that this approach deserves detailed study. © 2000 American Institute of Physics.

In a tokamak plasma, reaching the critical energy balance for ignition, for which the gain factor Q = energy output/energy input = \(\infty \), or even the \(Q \sim 40-50\) value needed for reactor operation, is a very challenging task—for example, a plasma temperature of the order of hundreds of million degrees is needed, a value much higher than the core temperature of the sun. The help that can come from a fusion cross section enhancement due to the appropriate polarization of the reacting nuclei could be instrumental in achieving the goal. Two works carried out in the 80s have provided insight on the effective ability of a spin-polarized D–T thermonuclear plasma to preserve the polarization status of the fuel nuclei (Kulsrud et al., Phys Rev Lett, 49:1248, 1982, [1], and Coppi et al., Phys Rev Lett 51:892, 1983, [2]). The conclusions are both encouraging and cautious. While Kulsrud’s work shows that many of the potential mechanisms for depolarization are weak, Coppi’s work points out that the presence of energetic alpha particles, products of the D–T fusion reaction, could generate collective modes able to depolarize the fuel. In the present contribution, we review the arguments and the main results of the two above-mentioned papers, while contextualizing them to present-day tokamak devices. In particular, we consider plasma regimes characteristic of ITER and IGNITOR, two tokamaks under construction and in advanced state of design, respectively, and which represent different approaches to magnetic fusion research. The depolarization rates estimated for these two devices indicate that polarization may not be maintained long enough for fusion reactions to occur, unless ion cyclotron resonances provide an effective damping mechanism for the excited modes. Only a targeted experimental campaign could provide a final answer on the feasibility of polarized fusion in tokamaks.

An in depth understanding of the collective modes that can be excited in a wide range of high-energy plasmas is necessary to advance nuclear fusion research in parallel with other fields that include space and astrophysics in particular. Important achievements are shown to have resulted from implementing programs based on this reality, maintaining a tight connection with different areas of investigations. This involves the undertaking of a plurality of experimental approaches aimed at understanding the physics of fusion burning plasmas. At present, the most advanced among these is the Ignitor experiment involving international cooperation, that is designed to investigate burning plasma regimes near ignition for the first time.

The effects of Hot Electrons (HEs) generated by the nonlinear Laser-Plasma Interaction (LPI) on the dynamics of Shock Ignition Inertial Confinement Fusion targets are investigated. The coupling between the laser beam, plasma dynamics and hot electron generation and propagation is described with a radiative hydrodynamics code using an inline model based on Paraxial Complex Geometrical Optics [Colaitis et al., Phys. Rev. E 92, 041101 (2015)]. Two targets are considered: the pure-DT HiPER target and a CH-DT design with baseline spike powers of the order of 200–300 TW. In both cases, accounting for the LPI-generated HEs leads to non-igniting targets when using the baseline spike powers. While HEs are found to increase the ignitor shock pressure, they also preheat the bulk of the imploding shell, notably causing its expansion and contamination of the hotspot with the dense shell material before the time of shock convergence. The associated increase in hotspot mass (i) increases the ignitor shock pressure required to ignite the fusion reactions and (ii) significantly increases the power losses through Bremsstrahlung X-ray radiation, thus rapidly cooling the hotspot. These effects are less prominent for the CH-DT target where the plastic ablator shields the lower energy LPI-HE spectrum. Simulations using higher laser spike powers of 500 TW suggest that the CH-DT capsule marginally ignites, with an ignition window width significantly smaller than without LPI-HEs, and with three quarters of the baseline target yield. The latter effect arises from the relation between the shock launching time and the shell areal density, which becomes relevant in presence of a LPI-HE preheating.

The foreseen future expansion of nuclear power would involve a solution to burn the long half-life transuranics (TRU) in the spent nuclear fuel discharged from LWRs. Moreover, high-energy neutrons can be very useful for many processes. The study addresses the development of a tokamak neutron source for a hybrid fission-fusion demonstration experimental device, using Ignitor-based technologies. Ignitor is a proposed compact high magnetic field tokamak, aimed at reaching ignition in DT plasmas. A revision of its operating parameters, in order to act a as a suitable neutron source in a hybrid device, is discussed, and a new operating scenario is proposed. Features of the tokamak neutron source are illustrated and preliminary results are discussed. A two phase project is described, in order to test an Ignitor-based neutron source and then implement an experimental device for demonstration of technical feasibility of TRU transmutation

The European High Power laser Energy Research (HiPER) project aims at demonstrating the feasibility of high gain inertial confinement fusion (ICF) using the fast ignitor approach. A baseline target has been recently developed by Atzeni et al. [Phys. Plasmas 14, 052702 (2007)]. The radiative transport have a minor effect on the peak areal density but decreased by 20% the peak density. We have found that with 95 kJ of absorbed laser energy one can assemble the fuel with a peak density around 500 g/cm3 and a peak areal density of 1.2 g/cm2. This implies a total target gain of about 60.

Design development of continuous-wave 240 GHz gyrotron and 300 GHz gyrotrons with output power about 200–1000 kW for fusion research at advanced plasmas with intense magnetic field is presented. Main goal of such gyrotrons is application for EC complexes of IGNITOR and DEMO tokamaks. This paper includes task motivation and existing technical basis, results of calculation, design, technical requirements and pre-prototype experimental tests for main subsystems of gyrotron.

The present paper reports a detailed analysis of disruptions in the IGNITOR tokamak. Two different numerical models are used (one axisymmetric, the other three-dimensional), in order to validate the results and to highlight specific effects due to different assumptions. The results show a good agreement between the two codes, when similar assumptions are made, and highlight the potential significance of three-dimensional effects. © 2015 Elsevier B.V.

A high-energy petawatt laser, OMEGA EP, is currently under construction at the University of Rochester's Laboratory for Laser Energetics. Integrated into the existing OMEGA laser, it will support three major areas of research: (a) backlighting of high-energy-density plasmas, (b) integrated fast ignition experiments, and (c) high-intensity physics. The laser will provide two beams combined collinearly and coaxially with short pulses (~1 to 100 ps) and high energy (2.6 kJ at 10 ps). Cone-in-shell fuel-assembly experiments and simulations of short-pulse heated cryogenic targets are being performed in preparation for cryogenic integrated fast ignitor experiments on OMEGA EP.

This paper introduces the next generation of fast ignition research facilities now under construction and describes in detail the Japanese project Fast Ignition Realization Experiment (FIREX-I) and its proposed follow-up, FIREX-II. Both the facilities and their scientific objectives are presented. FIREX-I and the other two facilities described in subsequent papers-OMEGA EP at the University of Rochester and the Z-Petawatt at Sandia National Laboratories-will conduct proof-of-principle experiments for the fast ignitor concept. The facilities consist of two components: a long-pulse (τ >ns) driver capable of compressing and assembling the fusion fuel and a separate petawatt-class laser for heating. For the FIREX project, the present status of the construction of the 10-kJ-level, high-energy petawatt Laser for Fusion Experiment is reported, and the theoretical basis for high-density plasma heating with an ∼10-kJ, 10-ps petawatt laser is discussed to show how this heating pulse is predicted to achieve the plasma parameters required for the fast ignition. The required petawatt spot size, the tolerable carbon fraction in the proposed D-T-loaded foam cryogenic target, appropriate heating laser pulse shape, and the required electron stopping range are explored. The theoretical analysis includes the use of Fokker-Planck simulation to describe the heating of the dense plasma by relativistic electrons created in the petawatt laser-plasma interactions. This modeling indicates that if 30% of the 10-kJ petawatt laser energy is coupled by relativistic electrons into D-T plasmas compressed to 100 to 200 g/cm 3 , the plasmas will be subsequently heated to 5 keV and fusion gains, defined as fusion energy produced divided by the total incident (compression and heating) laser energy, as high as 0.1 can result.

In recent fast ignitor research, neutron measurements have become increasingly important not only to understand the ultraintense laser-plasma interaction physics associated with ion acceleration and energy transport processes in dense plasmas but also the characterization of the plasma temperature in integrated experiments, as summarized in this paper. New technologies that are relevant to the next-generation integrated fast ignition experiments are also reviewed. These will become increasingly important in the next few years as second-generation multikilojoule petawatt facilities come online and the detection environment becomes increasingly hostile, particularly if, as anticipated, the generated neutron fluxes begin to approach energy breakeven conditions.

Pulsed-power machines can deliver large electrical energies to Z-pinches, which efficiently convert this energy into X-rays that can indirectly drive capsule implosions to obtain high-fusion fuel (D-T) densities. Presently, the Z machine generates 1.0 to 1.8 MJ of soft X-rays radiated from various Z-pinch loads. This output should be roughly doubled when Z is upgraded to ZR in 2006, making ZR an excellent machine to compress materials for fast ignition studies. The Z-Beamlet Laser (ZBL) has been installed adjacent to Z and is currently being used for X-ray backlighting. Presently, ZBL delivers up to 2 TW of 2ω (526-nm-wavelength) light in pulses up to 1 ns long. Chirped-pulsed amplification is being added to the ZBL, which will increase the power a thousandfold enabling integrated fast ignitor experiments to be performed on the ZR facility beginning in 2007. Numerical simulations and analytic scaling, which have been performed to design such experiments, are presented in this paper.

The effects of transverse temperature distribution on the Weibel instability in a laser produced plasma are studied analytically by using a three dimensional waterbag model. It is found that the purely transverse Weibel instability can be stabilized for the case in which the electron beam has a more symmetric transverse temperature distribution. This analytical expectation is supported by our two dimensional particle-in-cell simulations.

The acceleration of ions by ultra-intense lasers has attracted great attention due to the unique properties and the unmatched intensities of the ion beams. In the early days the prospects for applications were already studied, and first experiments have identified some of the areas where laser accelerated ions can contribute to the ongoing inertial confinement fusion (ICF) research. In addition to the idea of laser driven proton fast ignition (PFI) and its use as a novel diagnostic tool for radiography the strong dependence on the electron transport in the target was found to be helpful in investigating the energy transport by electrons in fast ignitor scenarios. More recently an additional idea has been presented to use laser accelerated ion beams as the next generation ion sources, and taking advantage of the luminosity of the beams, to develop a test bed for heavy ion beam driven inertial confinement fusion physics. We review our recent experiments and simulations relevant to ICF research presenting a possible scenario for PFI as well as the prospects for next generation ion sources.

Integrated fast-ignition experiments on the combined OMEGA/OMEGA EP laser systems have been simulated with the multidimensional hydrodynamic code DRACO. The OMEGA laser system provides up to 30 kJ of compression energy, and OMEGA EP will provide two short-pulse beams, each with energies up to 2.6 kJ. In the electron transport model included in DRACO, the relativistic electrons are introduced at the pole of a two-dimensional (2D) simulation and transported in a straight line toward the target core. The electron's energy is calculated from the laser irradiance using a semi-empirical formula. An OMEGA cryogenic DT target designed to reach a one-dimensional fuel ρR of 0.5 g cm−2 has been simulated in 2D, with and without non-uniformities, to assess the sensitivity to energy, timing, and irradiance of the Gaussian fast-ignitor beam. For the uniform case, the neutron yield is predicted to be in excess of 1015 (compared to ~1014 without an ignitor beam) over a synchronization range of ~80 ps. Implosions with the ignitor beam show little decrease in the neutron yield with increasing inner-ice non-uniformity, in contrast to implosions without the ignitor beam, which show a significant decrease in neutron yield with increasing non-uniformity.

Some preliminary views are presented to the topic “Fast High Density Plasma Blocks Driven by Picosecond Terawatt Lasers” of the UWS-International Workshop 1–4 December 2004 in Sydney, Australia, underlining the motivation to explain the difference between the relativistic and the subrelativistic effects of ps-laser pulse interaction with plasma at powers above TW. This refers to specifically selected experimental and theoretical presentations at the workshop containing results for explaining the differences but also the important applications for studies on the fast ignitor scheme for application on nuclear fusion energy. One of the aims with relativistic proton beams is to realize conditions of spark ignition, while the subrelativistic case implies the generation of fast plasma blocks eventually with the possibility to ignite a fusion flame in uncompressed solid DT fuel for a power station with high efficiency.

A totally new ignition scheme is proposed, in which the compressed DT main fuel is ignited by impact collision of another fraction of separately imploded DT fuel, which is accelerated in the hollow conical target to hyper-velocities in the order of 10 8 cm/s. Its kinetic energy is directly converted into thermal energy corresponding to temperatures >5 keV on the collision with the main fuel, and this self-heated portion plays the role of ignitor. The ignitor shell is irradiated typically by nsec-pulses at intensities >10 15 W/cm 2 and laser wavelength of 0.35 μm to exert ablation pressures >100 Mbar. A preliminary two-dimensional hydrodynamic simulation shows substantial heating of the compressed core. The impact-shell acceleration and consequent working windows for the beam and target parameters are addressed based on a rocket model. Simple physics, high-energy coupling efficiency, low cost, not needing a PW laser, and affordability of investigation in laboratories under rather well-established physical understanding and experimental know-how are considered to be the notable advantages of the present scheme.

This paper reports the results of a series of experiments on laser generated ions using the 100 TW laser at the ‘Laboratiore pour l’Utilisation des Lasers Intenses (LULI)’ at the Ecole Polythechnique in Palaiseau, France, and the 30 TW ‘Trident’ facility at Los Alamos National Laboratories in New Mexico, USA. It shows the importance of the ‘Target Normal Sheath Acceleration’ process (TNSA) for short pulse laser generated ion beams and its connection to the influence of target properties on the ion beam quality. It is shown that TNSA-generated protons form an ion beam with superior beam quality, following versatile spatial beam shaping approaches. These insights are set into perspective for a fast ignitor scenario based on short pulse laser generated protons.

Preamble Laser induced beams of protons, neutrons and gamma rays using short pulse lasers is currently important principally because of the potential applications e.g. isotope production, transmutation studies, laser induced fission, heavy ion fusion reactions, neutron production and radiography, fast ignitor and spallation studies of neutrons. Although the Strathclyde group in collaboration with teams from Imperial College and the Rutherford Appleton Laboratory have been at the forefront of many of these applications this presentation only deals with laser induced PET isotope production and laser transmutation studies. These two applications will be dealt with in separate sections.

The concept of the fast ignitor for laser fusion has led to some modifications in applying petawatt-picosecond (PW-ps) laser-produced high intensity particle beams to ignite deuterium-tritium (DT) fuel. Some very anomalous measurements of ion emission from targets irradiated by picosecond laser pulses led to the development of a skin depth interaction scheme where a defined control of prepulses is necessary. Based on these experimental facts, we have applied a one-dimensional two-fluid hydrodynamic code to understand how the nonlinear ponderomotive force generates two plasma blocks, one moving against the laser light (ablation) and the other moving into the target. This compressed block produces an ion current density of above 10$^{11}$ A cm$^{-2}$ and an ion energy of about 100 keV. This may be a rather promising option to use PW-ps laser pulses for igniting fusion in solid density DT fuel, realizing very high gain controlled fusion reactions.

Computations are to be performed using the laser driven inertial fusion energy option based on volume ignition with the natural adiabatic self-similarity compression and expansion hydrodynamics [1]. The numerical work includes the establishing of a multi-branch reaction code to be used for simultaneous fusion reactions of D-D, D-T D-He3 and mutual nuclear reaction products. This will permit the studies of neutron lean reactions as well as tritium-rich cases. The D-T reactions will stress the recent new results on one step laser fusion [2] as an alternative to the two-step fast ignitor scheme whose difficulties with new physics phenomena at petawatt laser interaction are more and more evident [3].

From a Hamiltonian analysis, a Vlasov‐Maxwell model was developed to study the interaction of intense laser pulse in plasma conditions relevant to the fast ignitor concept. We report here the first observation of self‐sustained kinetic electron nonlinear waves driven by high‐intensity laser pulse in a moderately underdense or overdense plasma.

The technical challenges and motivations for high-energy, short-pulse generation with the National Ignition Facility (NIF) and possibly other large-scale Nd : glass lasers are reviewed. High-energy short-pulse generation (multi-kilojoule, picosecond pulses) will be possible via the adaptation of chirped pulse amplification laser techniques on NIF. Development of metre-scale, high-efficiency, high-damage-threshold final optics is a key technical challenge. In addition, deployment of high energy petawatt (HEPW) pulses on NIF is constrained by existing laser infrastructure and requires new, compact compressor designs and short-pulse, fibre-based, seed-laser systems. The key motivations for HEPW pulses on NIF is briefly outlined and includes high-energy, x-ray radiography, proton beam radiography, proton isochoric heating and tests of the fast ignitor concept for inertial confinement fusion.

By using an axicon lens in conjunction with the ignitor-heater scheme, a 1.2-cm-long high-quality plasma waveguide is generated efficiently, which can extend the range of laser-plasma interaction much beyond the limit of Rayleigh range

The GLF23 and multi-mode core transport models are used along with models for the H-mode pedestal to predict the fusion performance for the International Thermonuclear Experimental Reactor, Fusion Ignition Research Experiment, and IGNITOR tokamak designs. Simulations using combinations of core and pedestal models have also been compared with experimental data for H-mode profiles in DIII-D, JET, and Alcator C-Mod. Power-independent (ballooning mode limit) and power-dependent pedestal scalings lead to very different predictions when used with the core models. Although the two drift-wave transport models reproduce the core profiles in a wide variety of tokamak discharges, they differ in their projections to burning plasma experiments for the same pedestal parameters. Differences in the core transport models in their response to the ion temperature gradient (i.e. their stiffness) and impact of the power dependence of the H-mode pedestal on fusion performance predictions are discussed.

Fusion power predictions are presented using the GLF23 drift-wave transport model for several next-step tokamak designs including ITER, FIRE, and IGNITOR. The GLF23 model has been renormalized using recent gyrokinetic simulations and a database of nearly 50 H-mode discharges from three different tokamaks. The renormalization reduces the ion temperature gradient/trapped electron mode (ITG/TEM)-driven transport by a factor of 3.7 while electron temperature gradient (ETG) mode transport is increased by a factor of 4.8 with respect to the original model. Using the renormed model, the fusion power performance is uniformly assessed, and the pedestal requirements are summarized for each device. The renormed model is still quite stiff and yields somewhat more optimistic predictions for next-step burning plasma experiments. The consequences of stiff transport in the plasma core are discussed. A fusion fit formula is derived whereby the GLF23 results follow a universal stiff model curve for the normalized fusion power versus pedestal temperature.

Models for the height of the pedestal at the edge of H-mode plasmas (Onjun T et al 2002 Phys. Plasmas 9 5018) are used together with the Multi-Mode core transport model (Bateman G et al 1998 Phys. Plasmas 5 1793) in the BALDUR integrated predictive modelling code to predict the performance of the ITER (Aymar A et al 2002 Plasma Phys. Control. Fusion 44 519), FIRE (Meade D M et al 2001 Fusion Technol. 39 336), and IGNITOR (Coppi B et al 2001 Nucl. Fusion 41 1253) fusion reactor designs. The simulation protocol used in this paper is tested by comparing predicted temperature and density profiles against experimental data from 33 H-mode discharges in the JET (Rebut P H et al 1985 Nucl. Fusion 25 1011) and DIII-D (Luxon J L et al 1985 Fusion Technol. 8 441) tokamaks. The sensitivities of the predictions are evaluated for the burning plasma experimental designs by using variations of the pedestal temperature model that are one standard deviation above and below the standard model. Simulations of the fusion reactor designs are carried out for scans in which the plasma density and auxiliary heating power are varied.

Compression of plasmas with laser pulses in the 10-kJ range produced densities in the range of 1000 times that of the solid state, where however the temperatures within a few hundred eV were rather low. This induced the fast ignitor scheme for central or peripheral deposition of some 10-kJ ps laser pulses on conventional $n_{\rm s}$-precompressed DT plasma of 3000 times solid-state density. We present results where the ps ignition is avoided and only a single-event conventional compression is used. Following our computations of volume ignition and the excellent agreement with measured highest fusion gains of volume compression, we found conditions where compression to 5000 times that of the solid state and by using laser pulses of 10 MJ produce volume ignition with temperatures between 400 and 800 eV only for high-gain volume ignition.

The transport and net loss of cyclotron radiation for burning plasmas represented by the ITER, FIRE and IGNITOR designs are assessed using the CYTRAN radiation transport code. Although cyclotron ra...

The use of high-intensity lasers to cause ignition in inertial confinement fusion is presented, with emphasis on current experimental programs and physical concepts that are at the forefront of the field. In particular, we highlight the issues of fast electron transport through dense materials, an essential element of the “Fast Ignitor” concept.

The stability of α-particle driven shear Alfven eigenmodes (AE) for nominal burning plasma (BP) parameters in the proposed international tokamak experimental reactor (ITER), fusion ignition research experiment (FIRE) and IGNITOR tokamaks is studied. JET plasma, where fusion αs were generated in tritium experiments, is also studied to compare the numerical predictions with the existing experiments. An analytic assessment of toroidal AE (TAE) stability is first presented, where the α-particle β due to the fusion reaction rate and electron drag is simply and accurately estimated in plasmas with central temperature in the range of 7–20 keV. In this assessment the hot particle drive is balanced against ion-Landau damping of the background deuterons, and electron collision effects and stability boundaries are determined. Then two numerical studies of AE instability are presented. In one, the HIgh-n STability (HINST) code is used to predict the instabilities of low and moderately high frequency Alfven modes. HINST computes the non-perturbative solutions of the AE including effects of ion finite Larmor radius, orbit width, trapped electrons etc. The stability calculations are repeated using the global code NOVAK. We show that for these plasmas the spectrum of the least stable AE modes is at medium-/high-n numbers. In HINST, TAEs are locally unstable due to the α pressure gradient in all the devices under consideration except IGNITOR. However, NOVAK calculations show that the global mode structure enhances the damping mechanisms and produces stability for the nominal FIRE proposal and near-marginal stability for the nominal ITER proposal. NBI ions produce a strong stabilizing effect for JET. However, in ITER, the beam energies needed to penetrate to the core must be high (~1 MeV) so that a diamagnetic drift frequency comparable to that of α-particles is produced by the beam ions which induces a destabilizing effect. A serious question remains whether the perturbation theory used in NOVAK overestimates the stability predictions, so that it is premature to conclude that the nominal operation of all three BP proposals without neutral beam injection are stable (or marginally stable) to AEs.

Current ramping to achieve reversed shear confinement enhancement and peaked density profiles are important for achieving ignition conditions in the high-field tokamak IGNITOR [Coppi et al., Phys. Scri. 45, 112 (1992)]. Previous transport simulations used either fixed density profiles or obtained flat density profiles leading to a conclusion that a mechanism for peaking the density profile is required for ignition. In this paper an enhanced particle confinement regime that produces ignition before the sawtooth activity begins is explored. It is shown that fast current ramping is a general scheme leading to density profile peaking. In these simulations, peaked density profiles result from the formation of internal transport barrier due to reversed magnetic shear, which is produced by controlled plasma current and volume-averaged density ramping. Such a programmed Ohmic heating scheme is demonstrated to be an effective approach to achieve ignition of a deuterium-tritium plasma.

Fusion alpha parameters are calculated for tokamaks with high DT fusion rates using the TRANSP plasma analysis code. Parameters include the fast alpha density nα, fast alpha pressure normalized to magnetic field energy βα, and its normalized gradient −R×∇(βα). The plasma conditions are taken from the plasmas in TFTR and JET with the highest DT fusion rates, and from plasmas in the proposed IGNITOR, FIRE, and ITER-FEAT tokamaks.

The growth rate for the purely transverse Weibel instability is determined from relativistic kinetic theory using a waterbag distribution function in the momenta perpendicular to the main propagation direction of the beam. A parametric study is presented for conditions relevant to the fast ignitor. It is shown that for expected parameters the purely transverse Weibel instability will be significantly suppressed or even eliminated due to the transverse energy spread or emittance.

100 TW light from the Petawatt Module (PWM) laser illuminated a preimploded spherical deuterated polystyrene(CD) shell target. The DD neutron yield increased from 2.5×105–106. Analysis indicates that hundreds of keV deuterons, generated around the critical density, collide with cold fuel deuterons and play the leading role in the enhancement of the neutron yield. A two-dimensional particle-in-cell (2D PIC) simulation predicted well the deuteron spectrum. A 60 TW laser was used for MeV proton emissions and megagauss magnetic fields generation on the rear surface of a Poly p-xylene(C8H8) plane target. The 2D PIC simulation explained well the results. The PWM laser was upgraded to one PW, making it the world biggest Petawatt laser (PW laser). An optically parametric chirped amplification was introduced in the front end. The pulse was synchronized to the GEKKO XII imploding beams to within 10 ps.

Two experiments have been performed to investigate heating by high-intensity laser-generated electrons, in the context of studies of the fast ignitor approach to inertial confinement fusion (ICF). A new spectrometer and layered targets have been used to detect Kα emission from aluminum heated by a fast electron beam. Results show that a temperature of about 40 eV is reached in solid density aluminum up to a depth of about 100 μm.

An independent assessment of the physics of Ignitor is presented. Ignitor is a physics demonstration experiment with the main goal of achieving thermonuclear ignition, defined as the regime where fusion alpha heating compensates for all forms of energy losses. Simulations show that a pulse of alpha particle power of up to 10-20 MW is produced for a period of more than a few seconds. Crucial issues are the production of peaked density profiles on a timescale of several energy confinement times, the control of current penetration for the optimization of ohmic heating and sawtooth avoidance. The presence of a 10-20 MW ICRF system and the operation of a high speed pellet injector are considered essential to provide added flexibility in order to counter unexpected, adverse plasma behaviour.

Modern high-power lasers can generate extreme states of matter that are relevant to astrophysics, equation-of-state studies and fusion energy research. Laser-driven implosions of spherical polymer shells have, for example, achieved an increase in density of 1,000 times relative to the solid state. A new laser technology ‘ultra-intense’ laser is now opening a new ground of the laser fusion research, which is called as fast ignition. During the last several years, we have extensively studied elementary physics relevant to the fast ignitor. Based on these results, we have succeeded enforced heating of imploded plasmas with a 100 TW laser as the first demonstration of this new approach. The experimental result implies the future possibility of breakeven and ignition with significantly small laser energies. This new approach provides a route toefficientfusionenergy production.

A new concept of radial passive and active press, to replace the previous axial design is presented in this paper. This solution reduces the stresses in the components concerned and at the same time it improves the assembly, operation and maintenance of the machine.

The physics element relevant to the fast ignitor in inertial confinement fusion has been extensively studied. Laser-hole boring with enormous photon pressures into overcritical densities was experimentally proved by density measurements with XUV laser probing. Ultra-intense laser interactions at a relativistic parameter regime were studied with a 50-TW glass laser system and a 100-TW glass laser system synchronized with a long pulse laser system. In the study of relativistic laser beam propagation in a 100-μm scale-length plasma, a special propagation mode (super-penetration mode) was observed, where the beam propagated into overdense regions close to the solid target surface. At the super-penetration mode, 20% of the laser energy converted to energetic electrons toward the target inside, while the coupling efficiency was 40% without the long scale-length plasmas. The high-density energetic electron transport and heating of solid material was also studied, indicating beamlike propagation of the energetic electrons in the solid target and effective heating of solid density ions with the electrons. Based on these basic experimental results, the heating of imploded plasma by short-pulse-laser light with three different ways of injecting the heating pulse has been studied.

A model has been developed which is capable to describe in a self-consistent way plasma dynamics in the center and edge regions of fusion reactor. The core plasma is treated in the frame of 1-D radial transport model whereas a 1-D analytical model along magnetic field lines for plasma and impurity transport outside the last closed magnetic surface (LCMS) is applied. The model is suitable to fast scans of the parameter space of the tokamak type reactor and has been used to investigate operation regimes of the high-field IGNITOR experiment.