No abstract available

[en] Energy recovery from sewage sludge waste treatment is examined critically to establish whether it can become a commercially viable proposition. Biogas-fired combined heat and power (CHP) plants using methane from sewage are assessed in terms of economic viability. Without inclusion in the United Kingdom's Non-Fossil Fuel Obligation subsidy, biogas-fired CHP plants are shown not to be economically viable. High maintenance costs are identified as a factor leading to the failure of these schemes. (UK)

[en] The Edge Simulation Laboratory (ESL) is a project to develop a gyrokinetic code for MFE edge plasmas based on continuum (Eulerian) techniques. ESL is a base-program activity of OFES, with an allied algorithm research activity funded by the OASCR base math program. ESL OFES funds directly support about 0.8 FTE of career staff at LLNL, a postdoc and a small fraction of an FTE at GA, and a graduate student at UCSD. In addition the allied OASCR program funds about 1/2 FTE each in the computations directorates at LBNL and LLNL. OFES ESL funding for LLNL and UCSD began in fall 2005, while funding for GA and the math team began about a year ago. ESL's continuum approach is a complement to the PIC-based methods of the CPES Project, and was selected (1) because of concerns about noise issues associated with PIC in the high-density-contrast environment of the edge pedestal, (2) to be able to exploit advanced numerical methods developed for fluid codes, and (3) to build upon the successes of core continuum gyrokinetic codes such as GYRO, GS2 and GENE. The ESL project presently has three components: TEMPEST, a full-f, full-geometry (single-null divertor, or arbitrary-shape closed flux surfaces) code in E, μ (energy, magnetic-moment) coordinates; EGK, a simple-geometry rapid-prototype code, presently of; and the math component, which is developing and implementing algorithms for a next-generation code. Progress would be accelerated if we could find funding for a fourth, computer science, component, which would develop software infrastructure, provide user support, and address needs for data handing and analysis. We summarize the status and plans for the three funded activities

[en] In a number of plasmas of practical interest, including the scrape-off layer of a tokamak with a divertor or toroidal limiter, some gas discharge devices, and in the vicinity of spacecraft, magnetic field lines intersect bounding surfaces at shallow angles. Under these circumstances a number of interesting and important effects arise. Drifts can compete with parallel flows in establishing the boundary conditions for plasma mass-flow and current (sheath current-voltage characteristics). We derive the mass-flow constraints including both poloidal and radial drifts, review the current boundary conditions, and survey the consequences, including along-field density and heat-flux asymmetries, convection created by a wavy surface, generation of electric fields and surface currents associated with shadows from surface structures, and modification of instability growth

No abstract available

[en] It is shown that, in a finite beta plasma, there may exist sheath driven modes whose amplitude decreases exponentially with the distance from the divertor plate. The modes are sensitive to the radial tilt of the divertor plate. The short-wavelength branch of the instability, with the cross-field wavelength Dof order of a few ion gyroradii, is present in the case of a ''positive'' tilt of the divertor plate, whereas the long-wavelength branch, with D of order of 10 or so gyroradii is unstable for the opposite sign of the tilt. The parallel e-folding length becomes less than the distance from the plate to the X point (thereby making the mode insensitive to the processes near the X-point and the upper scrape-off layer) at the plasma betas exceeding (2-3) · 10^-4. A detailed analysis of the dispersion relations is provided. The features of the modes that can be used for their experimental identification are discussed. It is pointed out that the analog of these modes may also exist in linear plasma devices with shaped end electrodes

[en] It is possible to use a nuclear fusion reactor, of a somewhat less technologically challenging design than that contemplated purely for the generation of electricity, by employing fusion-derived neutrons to drive useful nuclear reactions. One device based on this concept is called the fusion hybrid reactor, or, perhaps more explicitly, the fusion-fission hybrid reactor. Neutrons from a fusion core would react with fertile and fissible material in a blanket surrounding the core, with the consequent creation of both fissile material for conventional nuclear reactor fuel and heat for generating electricity. Another such device, called the tritium-breeding fusion reactor, would breed tritium by reaction with lithium targets around the core. This report examines future circumstances in which these reactors might be needed and advantageous. Based on their technical, economic, and social aspects, it discusses the program content and pace at which these applications ought to be pursued. 46 refs., 35 figs., 31 tabs

[en] In this paper, theory is developed to describe (SOL) broadening by inducing convective cells through divertor plate biasing in a tokamak. The theory is applied to the Mega-Ampere Spherical Tokamak (MAST), where such experiments are planned in the near future. Criteria are derived for achieving strong broadening and for exciting shear-flow turbulence in the SOL, and these criteria are shown to be attainable in practice. It is also shown that the magnetic shear present in the vicinity of the X-point is likely to confine the potential perturbations to the divertor region below the X-point, leaving the part of the SOL that is in direct contact with the core plasma intact. The current created in the SOL by the biasing and the associated heating power are also calculated and are found to be modest. (author)

[en] An instability driven by an electron temperature gradient in combination with sheath boundary conditions at a divertor plate is considered. It is shown that there exists a mode localized between the divertor plate and the x point. Further propagation of the mode is terminated by a strong shear near the x point. A ''heuristic'' boundary condition at the control surface situated somewhat below the x point is suggested. The mode manifests a strong dependence on the radial tilt of the divertor plate, thereby providing some degree of control over the plasma transport in the divertor leg. Estimates of the diffusion coefficient show that it may reach the Bohm value

[en] The surface of a divertor plate has usually a certain degree of ''roughness.'' Depending on the material and the exposure time, the size of surface features may range from submicrons to a fraction of a millimeter, covering a range of spatial scales from well below the electron gyroradius, ρ_e to significantly above the ion gyroradius, ρ_i. The plasma approaches the divertor plate along a magnetic field which forms a shallow angle, α << 1, with the plate surface. Under such circumstances, a significant ''shadowing'' effect takes place, with only a small part of the surface being accessible to the plasma particles. A methodology is presented that allows one to find the fraction (ε_e and ε_i) of the surface geometrically accessible for the electrons and the ions. At small α, ε_e,i are typically small, meaning a strong local enhancement of heat and particle fluxes. In a broad range of parameters, ε_e, is also much smaller than ε_i. As the surface features are usually greater than the Debye radius, this leads to the formation of an ambipolar potential which causes reflection of part of the ions from the surface. The resulting albedo of the divertor plate for the plasma ions can be as high as 50%. Gradual diffusion of the plasma electrons into the zones reflecting the ions, reduces ambipolar fields and brings the ion albedo back to very small values. We present estimates of the time scales governing the neutralization process. This time scale shows itself up in the sheath boundary conditions for non-steady-state perturbations. The effect of surface roughness on secondary electron emission is discussed and it is shown that, depending on the surface structure, it may be smaller or greater than for a perfectly flat plate. We consider modifications of the sheath current-voltage characteristics by particle drifts. The presence of reflected ions reduces the ion diamagnetic current in the ion sub-sheath and significantly changes the ion response. This, in turn, affects sheath-controlled instabilities, which are sensitive to the tilt of the magnetic field