[en] Issues with coupling efficiency, beam illumination symmetry and Rayleigh Taylor (RT) instability are discussed for spherical heavy-ion-beam-driven targets with and without hohlraums. Efficient coupling of heavy ion beams to compress direct-drive inertial fusion targets without hohlraums is found to require ion range increasing several-fold during the drive pulse. One-dimensional implosion calculations using the LASNEX ICF target physics code shows the ion range increasing four-fold during the drive pulse to keep ion energy deposition following closely behind the imploding ablation front, resulting in high coupling efficiencies (shell kinetic energy/incident beam energy of 16 to 18%). Ways to increase beam ion range while mitigating Rayleigh-Taylor instabilities are discussed for future work

[en] In December 1998, LBNL Director Charles Shank and LLNL Director Bruce Tarter signed a Memorandum of Agreement to create the Heavy-Ion Fusion Virtual National Laboratory (HIF-VNL) with the purpose of improving the efficiency and productivity of heavy ion research through coordination of the two laboratories' efforts under one technical director. In 1999, PPPL Director Robert Goldston signed the VNL MOA for PPPL's heavy-ion fusion group to join the VNL. LBNL and LLNL each contribute about 45% of the $10.6 M/yr trilab VNL effort, and PPPL contributes currently about 10% of the VNL effort. The three labs carry out collaborative experiments, theory and simulations of a variety of intense beam scientific issues described below. The tri-lab HIF VNL program is part of the DOE Office of Fusion Energy Sciences (OFES) fusion program. A short description of the four major tasks areas of HIF-VNL research is given in the next section. The task areas are: High Current Experiment, Final Focus/Chamber Transport, Source/Injector/Low Energy Beam Transport (LEBT), and Theory/Simulation. As a result of the internal review, more detailed reviews of the designs, costs and schedules for some of the tasks have been completed, which will provide more precision in the scheduled completion dates of tasks. The process for the ongoing engineering reviews and governance for the future management of tasks is described in section 3. A description of the major milestones and scientific deliverables for flat guidance budgets are given in section 4. Section 5 describes needs for enabling technology development for future experiments that require incremental funding

[en] Recent heavy ion fusion target studies show that it is possible to achieve ignition with direct drive and energy gain larger than 100 at 1MJ. To realize these advanced, high-gain schemes based on direct drive, it is necessary to develop a reliable beam smoothing technique to mitigate instabilities and facilitate uniform deposition on the target. The dynamics of the beam centroid can be explored as a possible beam smoothing technique to achieve a uniform illumination over a suitably chosen region of the target. The basic idea of this technique is to induce an oscillatory motion of the centroid for each transverse slice of the beam in such a way that the centroids of different slices strike different locations on the target. The centroid dynamics is controlled by a set of biased electrical plates called 'wobblers'. Using a model based on moments of the Vlasov-Maxwell equations, we show that the wobbler deflection force acts only on the centroid motion, and that the envelope dynamics are independent of the wobbler fields. If the conducting wall is far away from the beam, then the envelope dynamics and centroid dynamics are completely decoupled. This is a preferred situation for the beam wobbling technique, because the wobbler system can be designed to generate the desired centroid motion on the target without considering its effects on the envelope and emittance. A conceptual design of the wobbler system for a heavy ion fusion driver is briefly summarized.

[en] The centroid and envelope dynamics of a high-intensity charged particle beam are investigated as a beam smoothing technique to achieve uniform illumination over a suitably chosen region of the target for applications to ion-beam-driven high energy density physics and heavy ion fusion. The motion of the beam centroid projected onto the target follows a smooth pattern to achieve the desired illumination, for improved stability properties during the beam-target interaction. The centroid dynamics is controlled by an oscillating 'wobbler', a set of electrically-biased plates driven by RF voltage.

[en] Highly ionized plasmas are being used as a medium for charge neutralizing heavy ion beams in order to focus the ion beam to a small spot size. A radio frequency (RF) plasma source has been built at the Princeton Plasma Physics Laboratory (PPPL) in support of the joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization with plasma. The goal is to operate the source at pressures ∼ 10^-5 Torr at full ionization. The initial operation of the source has been at pressures of 10^-4-10^-1 Torr and electron densities in the range of 10⁸-10¹¹ cm^-3. Recently, pulsed operation of the source has enabled operation at pressures in the 10^-6 Torr range with densities of 10¹¹ cm^-3. Near 100% ionization has been achieved. The source has been integrated with the NTX facility and experiments have begun

[en] Plasmas are employed as a source of unbound electrons for charge neutralizing heavy ion beams to allow them to focus to a small spot size. Calculations suggest that plasma at a density of 1-100 times the ion beam density and at a length ∼ 0.1-1 m would be suitable. To produce one-meter plasma, large-volume plasma sources based upon ferroelectric ceramics are being developed. These sources have the advantage of being able to increase the length of the plasma and operate at low neutral pressures. The source utilizes the ferroelectric ceramic BaTiO₃ to form metal plasma. The drift tube inner surface of the Neutralized Drift Compression Experiment (NDCX) will be covered with ceramic, and high voltage (∼ 1-5 kV) applied between the drift tube and the front surface of the ceramic by placing a wire grid on the front surface. A prototype ferroelectric source 20 cm long has produced plasma densities of 5 x 10¹¹ cm^-3. The source was integrated into the previous Neutralized Transport Experiment (NTX), and successfully charge neutralized the K⁺ ion beam. Presently, the one-meter source is being fabricated. The source is being characterized and will be integrated into NDCX for charge neutralization experiments

[en] The HYDRA radiation-hydrodynamics code [M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001)] is used to explore one-sided axial target illumination with annular and solid-profile uranium ion beams at 60 GeV to compress and ignite deuterium-tritium fuel filling the volume of metal cases with cross sections in the shape of an ''X'' (X-target). Quasi-three-dimensional, spherical fuel compression of the fuel toward the X-vertex on axis is obtained by controlling the geometry of the case, the timing, power, and radii of three annuli of ion beams for compression, and the hydroeffects of those beams heating the case as well as the fuel. Scaling projections suggest that this target may be capable of assembling large fuel masses resulting in high fusion yields at modest drive energies. Initial two-dimensional calculations have achieved fuel compression ratios of up to 150X solid density, with an areal density ρR of about 1 g/cm². At these currently modest fuel densities, fast ignition pulses of 3 MJ, 60 GeV, 50 ps, and radius of 300 μm are injected through a hole in the X-case on axis to further heat the fuel to propagating burn conditions. The resulting burn waves are observed to propagate throughout the tamped fuel mass, with fusion yields of about 300 MJ. Tamping is found to be important, but radiation drive to be unimportant, to the fuel compression. Rayleigh-Taylor instability mix is found to have a minor impact on ignition and subsequent fuel burn-up.

[en] The centroid and envelope dynamics of a high-intensity charged-particle beam are investigated as a beam smoothing technique to achieve uniform illumination over a suitably chosen region of the target for applications to ion-beam-driven high energy density physics and heavy ion fusion. The motion of the beam centroid projected onto the target follows a smooth pattern to achieve the desired illumination, for improved stability properties during the beam-target interaction. The centroid dynamics is controlled by an oscillating 'wobbler', a set of electrically biased plates driven by rf voltage.

[en] Research has been initiated in the U.S. Virtual Laboratory for Technology on IFE chamber and target technologies. The critical issues, and the approaches taken to address these issues, are discussed

[en] A few % wobbling-beam illumination nonuniformity is realized in heavy ion inertial confinement fusion (HIF) by a spiraling beam axis motion. So far the wobbling heavy ion beam (HIB) illumination was proposed to realize a uniform implosion in HIF. However, the initial imprint of the wobbling HIBs introduces a large unacceptable energy deposition nonuniformity. In the wobbling HIBs illumination, the illumination nonuniformity oscillates in time and space. The oscillating-HIB energy deposition may contribute to the reduction of the HIBs' illumination nonuniformity. The wobbling HIBs can be generated in HIB accelerators and the oscillating frequency may be several 100 MHz ∼ 1 GHz. Three-dimensional HIBs illumination computations presented here show that the few % wobbling HIBs illumination nonuniformity oscillates successfully with the same wobbling HIBs frequency. (author)