[en] With 180MJ/mg, antiprotons offer the highest stored energy per unit mass of any known entity. We investigate the use of antiprotons to promote fast ignition in an ICF capsule and seek high gains with only modest compression of the main fuel. Unlike standard fast ignition where the ignition energy is supplied by an energetic, short pulse laser, the energy here is supplied through the ionization energy deposited when antiprotons annihilate at the center of a compressed fuel capsule. In the first of two candidate fast ignition schemes, the antiproton package is delivered by a low energy external ion beam. In the second, ''autocatalytic'' scheme, the antiprotons are pre-emplaced at the center of the capsule prior to compression. In both schemes, we estimate that approximately3x10¹³ antiprotons are required to initiate fast ignition in a typical ICF capsule and show that incorporation of a thin, heavy metal shell is desirable to enhance energy deposition in the igniter zone. In addition to obviating the need for a second energetic fast laser and vulnerable final optics, this scheme would achieve central without reliance on laser channeling through halo plasma or houlrahm debris. However, in addition to the unknowns involved in the storage and manipulation of antiprotons at low energy, the other large uncertainty for the practicality of such a scheme is the ultimate efficiency of antiproton production in, an external, optimized facility

[en] A miniature neutron spectrometer with minimal flux perturbation and a quasi-idealised response has been designed and developed for use in LiF benchmark experiments. The equipment has been used for the accurate determination of the absolute neutron spectra from 0.4 to 16 MeV within the LiF benchmark and has enabled the minimum accuracy requirements of existing neutron transport codes to be determined. Results are compared with theoretical predictions for several spatial coordinates, enabling discrepancies in current evaluated cross section data for ⁶Li, ⁷Li and ¹⁹F to be isolated. (U.K.)

[en] A comprehensive theoretical study has been performed on the reduction of the electrical breakdown potential of liquid and gaseous helium under neutron and gamma radiation. Extension of the conventional Townsend breakdown theory indicates that radiation fields at the superconducting magnets of a typical fusion reactor are potentially capable of significantly reducing currently established (i.e., unirradiated) helium breakdown voltages. Emphasis is given to the implications of these results including future deployment choices of magnet cryogenic methods (e.g., pool-boiling versus forced-flow), the possible impact on magnet shielding requirements and the analogous situation for radiation-induced electrical breakdown in fusion RF transmission systems

[en] This testimony to the subcommittee on Energy and the Environment of the U.S. House of Representatives's Committee on Science pushes for about 25% of the fusion budget to go to alternative fusion concepts. These concepts are: low density magnetic confinement, inertial confinement fusion, high density magnetic confinement, and non- thermonuclear and miscellaneous programs. Various aspects of each of these concepts are outlined

[en] Nuclear fission can meet humanity's disparate requirements for carbon-free energy throughout this century and for millennia to come - not only for electricity but also as a source of hydrogen for transportation fuels and a heat source for desalination. However, most countries are not pursuing fission as an option for future energy and global climate needs. One paramount reason is diminished public acceptance over concerns of waste disposal. We would also add 'fuel resources' as a major future concern, because fission is not sustainable in the long term with the present 'once-through' fuel that utilizes less than 1% of the mined uranium and consigns its fertile potential to a permanent waste repository. Accordingly, global scale fission will become attainable (i.e., doable) if and when an integrated solution to this overall 'fuel-cycle' problem is realized. It is the back-end of the fuel cycle - i.e., the need for permanent storage of spent fuel and high-level waste - that has become the focus of much of the criticism. In particular, the construction and implementation of permanent waste repositories such as Yucca Mountain is becoming increasingly problematic from a financial and political perspective. The major shortcoming of these conventional repositories is that they must accommodate the whole spent fuel output from once-through fuel cycles. They are thus burdened with very large masses of material but where less than 1% is long-term, hazardous waste and where only a small fraction of the potential nuclear energy has been extracted. Second, such facilities must ensure integrity of waste containment for tens of thousands of years. Given that anything more than a few hundred years hence is unknowable and wholly unpredictable as far as future civilizations are concerned, public perception is that such facilities cannot be guaranteed to be absolutely secure for their envisaged lifetimes of tens of millennia.

[en] Probably the single largest advantage of the inertial route to fusion energy (IFE) is the perception that its power plant embodiments could achieve acceptable capacity factors. This is a result of its relative simplicity, the decoupling of the driver and reactor chamber, and the potential to employ thick liquid walls. We examine these issues in terms of the complexity, reliability, maintainability and, therefore, availability of both magnetic and inertial fusion power plants and compare these factors with corresponding scheduled and unscheduled outage data from present day fission experience. We stress that, given the simple nature of a fission core, the vast majority of unplanned outages in fission plants are due to failures outside the reactor vessel itself Given we must be prepared for similar outages in the analogous plant external to a fusion power core, this puts severe demands on the reliability required of the fusion core itself. We indicate that such requirements can probably be met for IFE plants. We recommend that this advantage be promoted by performing a quantitative reliability and availability study for a representative IFE power plant and suggest that databases are probably adequate for this task

[en] Four potential radiation problem areas were identified as follows: (1) Resistivity degradations in the ceramic insulation under instantaneous neutron and gamma absorbed dose-rates. (2) Mechanical and structural degradations in the ceramic insulation under long-term neutron fluences. (3) Radiolytic dissociation of the coolant water leading to corrosion product formation. (4) Resistivity increases in the MZC copper conductor due to radiation damage and neutron-induced transmutations

[en] Under neutron and/or gamma absorbed dose-rates typical of fusion reactor conditions, common ceramic insulators such as Al₂O₃, MgO, MgAl₂O₃, etc., exhibit a significant instantaneous decrease in their dc resistivity. Ceramic insulators in lightly shielded normal-conducting magnets, direct convertors and first wall applications are shown to be the most affected. Depending on conductor design, magnet location, absorbed dose-rate and applied voltages, it is demonstrated that the resulting leakage currents in the ceramic material are potentially capable of producing significant Joule heating rates which may lead to thermal runaway and subsequent insulator destruction. The theoretical background for this effect is presented and the rather sparse experimental data base reviewed. Recommendations are given for computing worst case radiation-induced conductivity increases as a function of absorbed dose rate. The possible ameliorating influences of long term fluence damage are then discussed. The practical consequences of ceramic resistivity degradation are quantitatively assessed by consideration of resulting leakage current Joule heating in the extruded conductor of a typical normal-conducting magnet. Relationships are derived to compute dose-rate-dependent leakage currents and Joule heating rates as a function of several magnet parameters

[en] One rather discouraging feature of our conventional approaches to fusion energy is that they do not appear to lend themselves to a small reactor for developmental purposes. This is in contrast with the normal evolution of a new technology which typically proceeds to a full scale commercial plant via a set of graduated steps. Accordingly' several concepts concerned with dense plasma fusion systems are being studied theoretically and experimentally. A common aspect is that they employ: (a) high to very high plasma densities (∼10¹⁶cm^-3 to ∼10²⁶cm^-3) and (b) magnetic fields. If they could be shown to be viable at high fusion Q, they could conceivably lead to compact and inexpensive commercial reactors. At least, their compactness suggests that both proof of principle experiments and development costs will be relatively inexpensive compared with the present conventional approaches. In this paper, the following concepts are considered: (1) The staged Z-pinch, (2) Liner implosion of closed-field-line configurations, (3) Magnetic ''fast'' ignition of inertial fusion targets, (4) The continuous flow Z-pinch

[en] We describe a neutralized-beam intense neutron source (NBINS) as a relevant application of fusion technology for the type of high-current ion sources and neutral beamlines now being developed for heating and fueling of magnetic-fusion-energy confinement systems. This near-term application would support parallel development of highly reliable steady-state higher-voltage neutral D₀ and T₀ beams and provide a relatively inexpensive source of fusion neutrons for materials testing at up to reactor-like wall conditions. Beam-target examples described incude a 50-A mixed D-T total (ions plus neutrals) space-charge-neutralized beam at 120 keV incident on a liquid Li drive-in target, or a 50-A T₀ + T⁺ space-charge-neutralized beam incident on either a LiD or gas D² target with calculated 14-MeV neutron yields of 2 x 10₁₅/s, 7 x 10₁₅/s, or 1.6 x 10₁₆/s, respectively. The severe local heat loading on the target surface is expected to limit the allowed beam focus and minimum target size to greater than or equal to 25 cm₂