E. Michael Campbell

Ignition and high gain with ultrapowerful lasers

Ultrahigh intensity lasers can potentially be used in conjunction with conventional fusion lasers to ignite inertial confinement fusion (ICF) capsules with a total energy of a few tens of kilojoules of laser light, and can possibly lead to high gain with as little as 100 kJ. A scheme is proposed with three phases. First, a capsule is imploded as in the conventional approach to inertial fusion to assemble a high‐density fuel configuration. Second, a hole is bored through the capsule corona composed of ablated material, as the critical density is pushed close to the high‐density core of the capsule by the ponderomotive force associated with high‐intensity laser light. Finally, the fuel is ignited by suprathermal electrons, produced in the high‐intensity laser–plasma interactions, which then propagate from critical density to this high‐density core. This new scheme also drastically reduces the difficulty of the implosion, and thereby allows lower quality fabrication and less stringent beam quality and symmet...

Progress toward Ignition and Burn Propagation in Inertial Confinement Fusion

For the past four decades, scientists throughout the world have pursued the dream of controlled thermonuclear fusion. The attraction of this goal is the enormous energy that is potentially available in fusion fuels and the view of fusion as a safe, clean energy source. The fusion reaction with the highest cross section uses the deuterium and tritium isotopes of hydrogen, and D‐T would be the fuel of choice for the first generation of fusion reactors. (See the article by J. Geoffrey Cordey, Robert J. Goldston and Ronald R. Parker, January, page 22.)

Demonstration of X-ray Holography with an X-ray Laser

An x-ray hologram was made by means of an x-ray laser and a laser-quality near normal incidence x-ray mirror. The high brightness and large coherence lengths of x-ray lasers now offer the potential for in vitro three-dimensional high-resolution holographic images of dynamically varying biological microstructures.

The National Ignition Facility - applications for inertial fusion energy and high-energy-density science

Over the past several decades, significant and steady progress has been made in the development of fusion energy and its associated technology and in the understanding of the physics of high-temperature plasmas. While the demonstration of net fusion energy (fusion energy production exceeding that required to heat and confine the plasma) remains a task for the next millennia and while challenges remain, this progress has significantly increased confidence that the ultimate goal of societally acceptable (e.g. cost, safety, environmental considerations including waste disposal) central power production can be achieved. This progress has been shared by the two principal approaches to controlled thermonuclear fusion--magnetic confinement (MFE) and inertial confinement (ICF). ICF, the focus of this article, is complementary and symbiotic to MFE. As shown, ICF invokes spherical implosion of the fuel to achieve high density, pressures, and temperatures, inertially confining the plasma for times sufficient long (t {approx} 10{sup -10} sec) that {approx} 30% of the fuel undergoes thermonuclear fusion.

Half- and three-halves harmonic measurements from laser-produced plasmas

Spectral measurements of the 3/2 harmonic emissions from 1.06 μm irradiated disk targets, and the 1/2 harmonic emissions from 0.53 μm irradiations, are presented. The splitting of the double‐peaked spectra show a distinct target Z dependence, for constant laser irradiation parameters. Possible generation mechanisms in terms of the two‐plasmon decay instability are discussed.

Characteristics of lateral and axial transport in laser irradiations of layered‐disk targets at 1.06 and 0.35 μm wavelengths

Results and analysis are presented for Be‐on‐Al disk target irradiations at 1.06 and 0.35 μm laser wavelengths with 600–700 psec pulses, 240 μm spot diameter, and 1×1014 W/cm2 absorbed intensity. Absorptions of 32%–39% (1.06 μm) and 90% (0.35 μm) are largely due to inverse bremsstrahlung. The hard x‐ray spectra indicate low hot‐electron fractions of 10−2 (1.06 μm) and 10−4 (0.35 μm). Backreflected light shows strong hot spots for 0.35 μm irradiations. Multiple absolute and relative x‐ray measurements are compared with one‐ and two‐dimensional computer hydrodynamics calculations. Only weak indications of lateral transport are found and limits are set from x‐ray imaging and spectral data from targets with and without a surrounding Ti shield. Axial transport appears strongly inhibited at 1.06 μm and mildly inhibited at 0.35 μm wavelength. Measured shock‐wave transit times and velocities imply ablation pressures of 7 Mbar (1.06 μm) and 11 Mbar (0.35 μm).

Fast Ignition: Overview and Background

Abstract Fast ignition is an approach to inertial fusion in which precompressed fuel is ignited with an external heat source. This arrangement can, in principle, lead to higher gains than conventional ignition produced by stagnation of convergent flows. In addition, because ignition is separate from the implosion in fast ignition, hydrodynamic mix has less opportunity to quench ignition than in the conventional process. This paper introduces some of the basic ideas of fast ignition: ignition requirements, gain curves based on simple energetic models, and integrated gain models including hohlraum and implosion physics. Because possible gains in this approach are so large, it is possible to examine the use of fuels with small tritium fractions, the so-called “advanced fuels.” In addition, the historical background of this field is discussed.

Exploding‐pusher‐tamper areal density measurement by neutron activation

Neutron activation of 28Si nuclei was used to measure the areal density ρΔR of a silicate‐glass tamper of a laser‐driven exploding‐pusher target. The values found were in good agreement with complex computer codes and an empirically based scaling model. This is the first demonstration of a technique that will be used in diagnosing the compression of high‐density inertial confinement fusion targets.

Measurement of DT neutron‐induced activity in glass‐microshell laser fusion targets

Laser fusion targets consisting of DT gas contained in Teflon‐coated glass microshells produce 14.1‐MeV neutrons that can interact with the 28Si nuclei in the glass to produce radioactive 28Al. Using a very efficient collection‐detection scheme that could detect the decay of 10% of the 28Al created, we identified these nuclei by their 1.78‐MeV γ ray, which decayed with a 2.2‐min half‐life. From the number of 28Al nuclei created and the neutron yield the compressed glass areal density was found to be 0.0059 g/cm2.

Fast ignition inertial fusion : An introduction and preview

Abstract The motivation for the fast ignition inertial fusion concept is presented as well as a brief synopsis of the papers contained within this dedicated issue. The papers cover a comprehensive view of the fast ignition inertial fusion field at the close of 2005, including both the present status and the future research that will exploit the next generation of facilities now under construction to investigate this emerging field of science and technology.