This issue of Laser and Particle Beams contains the papers submitted for publication by participants of the 14th International Heavy Ion Inertial Fusion (HIF) Symposium held in Moscow, May 26–31, 2002. This conference was organized by State Research Center of Russian Federation, Institute for Theoretical and Experimental Physics, Moscow, under the auspices of the International Atomic Energy Agency, Beam Plasma and Inertial Fusion Section of the European Physical Society, and Accelerator Council of Russian Academy of Science. The symposium was supported by the Ministry of Atomic Energy of Russian Federation, Russian Academy of Science, Russian Foundation for Basic Research, International Science, and Technology Center, and by GSI Darmstadt.

Significant experimental and theoretical progress has been made in the U.S. heavy ion fusion program on high-current sources, transport, and focusing. Currents over 200 mA have been transported through a matching section and 10 half-lattice periods with electric quadrupoles. An experiment shows control of high-beam current with an aperture, while avoiding secondary electrons. New theory and simulations of the neutralization of intense beam space charge with plasma in various focusing chamber configurations predict that near-emittance-limited beam focal spot sizes can be obtained even with beam perveance (ratio of beam space potential to ion energy) >10× higher than in earlier HIF focusing experiments. Progress in a new focusing experiment with plasma neutralization up to 10−3 perveance, and designs for a next-step experiment to study beam brightness evolution from source to target are described.

This article presents analytical and simulation studies of intense heavy ion beam propagation, including the injection, acceleration, transport and compression phases, and beam transport and focusing in background plasma in the target chamber. Analytical theory and simulations that support the High Current Experiment (HCX), the Neutralized Transport Experiment (NTX), and the advanced injector development program, are being used to provide a basic understanding of the nonlinear beam dynamics and collective processes, and to develop design concepts for the next-step Integrated Beam Experiment (IBX), an Integrated Research Experiment (IRE), and a heavy ion fusion driver. Three-dimensional nonlinear perturbative simulations have been applied to collective instabilities driven by beam temperature anisotropy, and to two-stream interactions between the beam ions and any unwanted background electrons; three-dimensional particle-in-cell simulations of the 2-MV electrostatic quadrupole (ESQ) injector have clarified the influence of pulse rise time; analytical studies and simulations of the drift compression process have been carried out; syntheses of a four-dimensional particle distribution function from phase-space projections have been developed; and studies of the generation and trapping of stray electrons in the beam self-fields have been performed. Particle-in-cell simulations, involving preformed plasma, are being used to study the influence of charge and current neutralization on the focusing of the ion beam in NTX and in a fusion chamber.

The construction of the Terawatt Accumulator (TWAC) facility is nearly completed at the ITEP in Moscow. All the major milestones have been successfully passed with a beam of carbon ions, except for the final result (the high power beam accumulation), which is on the way. The beam of C4+ ions delivered by the laser ion source is accelerated up to the energy of 300 MeV/amu by two steps—in the linear injector I3 and in the booster synchrotron UK. The accelerated beam is extracted from the UK ring and transferred to the U10 accumulator ring. Non-Liouvillian stripping technique (C4+ ⇒ C6+) is applied for stacking of C6+ batches into the accumulator ring U10. First experiments with extracted beam of ions have started in 2002. Status of the TWAC components, current results of activities aiming at mastering the ion beam stacking technique, and outlook for the TWAC advance are presented.

This paper presents two-dimensional numerical simulations of heating of matter with intense heavy ion beams. It has been shown that it is very advantageous to irradiate the target with two different beams simultaneously, a main high intensity bunched beam of a heavy element like uranium and an unbunched low intensity beam of a lighter element like argon. The main beam is used to heat the target while the second beam is used as a diagnostic tool.

Influence of the shape of the focal spot on compression and heating of matter has also been studied using an elliptic focal spot with an ellipticity of 1.5 (semimajor axis is along y-axis and is 1.5 times the semiminor axis which is along x-axis). It has been found that the temporal behavior of the development of density, pressure, and temperature profiles along different directions is quite different, which is not the case with a circular focal spot.

By the interaction of intense (1010 particles/500 ns) relativistic (∼300 MeV/amu) heavy ion beams with solid targets, large volumes (several cubic millimeters) of strongly coupled plasmas are produced at solid-state densities and temperatures of up to 1 eV, with relevance for equation-of-state (EOS) studies of matter at high energy density and heavy ion-beam-driven inertial confinement fusion (ICF). The time and space profile of the ion beams, focused by the plasma lens to diameters of a minimum of 0.5 mm in order to obtain specific energy depositions of up to about 4 kJ/g, were measured to calculate the energy deposition in the target. In the present work, the plasmas created by ion beam interaction with cryogenic gas crystals and metallic targets are studied, among other methods, by backlighting shadowgraphy and electrical conductivity measurements. The experiments are coupled with two-dimensional hydrodynamic simulations.

Progress in heavy ion target design over the past few years has focused on relaxing the target requirements for the driver and for target fabrication. We have designed a plastic (CH) ablator capsule that is easier to fabricate and fill than the beryllium ablator we previously used. In addition, two-dimensional Rayleigh–Taylor instability calculations indicate that this capsule can tolerate ablator surface finishes up to 10 times rougher than the NIF specification. We have also explored the trade-off between surface roughness and yield as a method for finding the optimum capsule. We have also designed two new hohlraums: a “hybrid” target and a large-angle, distributed radiator target. The hybrid target allows a beam spot radius of almost 5 mm while giving gain of 55 from 6.7 MJ of beam energy in integrated Lasnex calculations. To achieve the required symmetry with the large beam spot, internal shields were used in the target to control the P2 and P4 asymmetry. The large-angle, distributed radiator target is a variation on the distributed radiator target that allows large beam entrance angles (up to 24°). Integrated calculations have produced 340 MJ from 6.2 MJ of beam energy in a design that is not quite optimal, In addition, we have done a simple scaling to understand the peak ion beam power required to compress fuel for fast ignition using a short pulse laser.

A possibility is analyzed to use direct drive cylindrical targets in the fast ignition mode irradiated by beams of nearly relativistic heavy ions with long ranges in matter. The minimum beam energy required to compress the DT fuel in a 1-cm-long target to (ρR)DT = 0.5 g/cm2, ρDT = 100 g/cm3 is found to lie in the range 10–15 MJ. Ignition and axial burn propagation is achieved with a 0.2-ns, 0.4-MJ pulse of 100-GeV heavy ions. Thermonuclear energy gains in the range 50–150 appear to be possible.

The so-called fast ignition mode is one way to ignite the thermonuclear fuel in systems of inertial fusion and decrease of the necessary energy of the driver. In the present work the second stage of the process—the heating, the thermonuclear burning initiation under the influence of a powerful ion pulse, and distribution of the burning all over the rest of the cylindrical system—is studied. The main purpose of the presented calculations was to determine the threshold of the fast ignition of the cylindrical DT cord by a heavy ion beam.

The characteristics of a fast ignition heavy ion fusion (FIHIF) power plant are preliminarily evaluated. The reactor chamber consists of two sections: The upper smaller part is the microexplosion section proper; the lower bigger part is the condensation section, in which sprayed jets of coolant are injected. The first surface of the blanket is of generally accepted wetted porous design. The coolant is lithium-lead eutectic with an initial surface temperature of 820 K. The mass of the evaporated coolant just after the explosion is evaluated as 4 kg. Computation of neutronics results in blanket energy deposition with maximum density of the order of 108 J/m3 at the first wall. The heat conversion system consisting of three coolant loops provides a net efficiency of the FIHIF power plant of 0.37.

An overview of the various design choices to be made for a two-dimensional numerical code to simulate heavy ion targets is given. We discuss such issues as the grid structure, rezoning techniques, and the inclusion of material properties to various degrees. This is followed by a brief discussion of the open codes being used in the European heavy ion fusion community with characteristic samples of their application.

We have developed an analytical model for the implosion of a heavy ion beam driven multilayered cylindrical target. The target consists of a thick metallic shell, typically made of lead which is filled with a low density material, for example frozen hydrogen, and it is axially irradiated with a heavy ion beam with an annular focal spot. The model describes the expansion of the absorption region, the implosion of the pusher, the trajectories of the incident and reflected shocks and the final quasi-isentropic compression. The model is expected to be very helpful to optimize detailed simulations of such problems which are of close relevance to the GSI plasma physics experimental program, planned for the future upgraded accelerator facilities.

For the intense beams in heavy ion fusion accelerators, details of the beam distribution as it emerges from the source region can determine the beam behavior well downstream. This occurs because collective space-charge modes excited as the beam is born remain undamped for many focusing periods. Traditional studies of the source region in particle beam systems have emphasized the behavior of averaged beam characteristics, such as total current, rms beam size, or emittance, rather than the details of the full beam distribution function that are necessary to predict the excitation of the collective modes. Simulations of the beam in the source region and comparisons to experimental measurements at Lawrence Berkeley National Laboratory and the University of Maryland are presented to illustrate some of the complexity in beam characteristics that has been uncovered as increased attention has been devoted to developing a detailed understanding of the source region. Also discussed are methods of using the simulations to infer characteristics of the beam distribution that can be difficult to measure directly.

The High Current Experiment (HCX) is being assembled at Lawrence Berkeley National Laboratory as part of the U.S. program to explore heavy ion beam transport at a scale representative of the low-energy end of an induction linac driver for fusion energy production. The primary mission of this experiment is to investigate aperture fill factors acceptable for the transport of space-charge dominated heavy ion beams at high space-charge intensity (line-charge density ∼ 0.2 μC/m) over long pulse durations (>4 μs). This machine will test transport issues at a driver-relevant scale resulting from nonlinear space-charge effects and collective modes, beam centroid alignment and beam steering, matching, image charges, halo, lost-particle induced electron effects, and longitudinal bunch control. We present the first experimental results carried out with the coasting K+ ion beam transported through the first 10 electrostatic transport quadrupoles and associated diagnostics. Later phases of the experiment will include more electrostatic lattice periods to allow more sensitive tests of emittance growth, and also magnetic quadrupoles to explore similar issues in magnetic channels with a full driver scale beam.

For the High Current Beam Transport Experiment (HCX) at Lawrence Berkeley National Laboratory, an injector is required to deliver up to 1.8 MV of 0.6 A K+ beam with an emittance of ≈1 π-mm-mrad. We have successfully operated a 10-cm-diameter surface ionization source together with an electrostatic quadrupole (ESQ) accelerator to meet these requirements. The pulse length is ≈4 μs, firing at once every 10–15 s. By optimizing the extraction diode and the ESQ voltages, we have obtained an output beam with good current density uniformity, except for a small increase near the beam edge. Characterization of the beam emerging from the injector included measurements of the intensity profile, beam imaging, and transverse phase space. These data along with comparison to computer simulations provide the knowledge base for designing and understanding future HCX experiments.

The beam dynamics design of the low energy DTL section of a fusion driver linac based on the IH-structure is presented. The acceleration of a 209Bi1+ beam by an IH-DTL operated at 27 MHz (54 MHz) is investigated for two specific injection energies at 60 A keV and at 200 A keV, respectively. Both cases are optimized separately, with the goal to find out the maximum achievable acceleration gradient, beam current, as well as the most attractive field strength range of the quadrupole lenses. Calculations are performed on one beamlet, but the results can be applied to build up multibeam cavities. H-mode cavities are very well suited for this purpose and provide high acceleration efficiency, especially at low particle velocity. In addition, the “Combined 0° structure” (“Kombinierte Null Grad Struktur–KONUS”) beam dynamics concept allows grouping into modular units consisting of short, simple rf cavities and of multiaperture quadrupole triplet lenses located in the intertank sections.

A new efficient injection method from a laser ion source to a Radio Frequency Quadropole (RFQ) was proposed and is being tested in RIKEN, Japan. A laser plasma is induced just before the entrance of the RFQ and is injected directly into the RFQ channel. Using an existing RFQ, first verification tests have been completed successfully. Finally, the preliminary specifications for the first RFQ dedicated to the new injection scheme are presented.

In this article, we present the results of the laser ion source (LIS) for heavy ion high charge state Institute of Theoretical and Experimental Physics terawatt accumulator facility. This LIS is a duty ion source of C+4 for the injector. The main parameters of CO2 laser, vacuum target chamber, ion beam high voltage extraction system, and low energy beam transport line are shown. The stability of the LIS operation is discussed and measured ion beam parameters (ion current, pulse duration, emittance) for different charge states are presented. After the upgrading of the laser cavity, high voltage capacitors, and spark gaps and the installation of a new catalyst regenerator system, the CO2 laser became much more stable and allows long term operation. LIS works about 1 × 106 shots without intervention.

The main goal of the Tera Watt A Cumulator project (Institute for Theoretical and Experimental Physics, Moscow) is accumulation in the storage ring of an intense ion beam, its longitudinal compression and the use of the extracted beam for plasma experiments. However, beam parameters at the target are decreased because of extreme transverse heating and growth of the beam momentum spread due to intrabeam scattering. These effects can be suppressed by application of the electron cooling system (ECS). Design study of ECS has been performed in the Joint Institute for Nuclear Research. The design project and characteristics of the system are described, as well as analysis of the accumulation kinetics in the presence of the cooling system. Design work has shown that because of the small length of the straight section (2.35 m), the effective length of the cooling system is small (about 55–60 cm). Nevertheless, for long accumulation times (>100 s), the system allows us to significantly improve the beam parameters at the target (specific energy, specific power, and so on) and to suppress the beam losses by an order of magnitude.

Two distinct issues of recent concern for ion–plasma interactions are investigated. First, the subtle connection between quantum and classical ion stopping is clarified by varying the space dimension. Then we evaluate the range of thermonuclear αS′ in dense plasmas simultaneously magnetized and compressed.