Fusion materials science at reactor 14-MeV neutron fluxes: upgrading RTNS targets into the multi-megawatt/m/sup 2/ regime

The Rotating Target Neutron Source-II (RTNS-II) facility is the most intense continuous source of 14-MeV neutrons in the world. It is used to study the effects of fast neutrons on materials, to determine their suitability for use in fusion reactors. In RTNS-II, a water-cooled rotating target coated with titanium tritide is bombarded with deuterons. A small fraction of the incident deuterons fuse with the tritons in the target, producing 14.3-MeV neutrons. At present the neutron flux is substantially less than what a fusion test reactor would generate. This report examines the possibilities for upgrading RTNS targets to produce reactor-level neutron fluxes (or more). It is shown that the existing targets are operating near their thermal limit. However, modifications in target design and operating conditions are possible which could reasonably support up to a 30-fold increase in peak neutron flux (approx. 3 x 10/sup 14/ neutrons/cm/sup 2/-sec, or 6 MW/m/sup 2/). The irradiated volume could also be increased, if desired. It seems likely that with some research and experimentation with palladium underlayers, target cladding/overcoating, and/or in-situ retritiding, an acceptable target lifetime can still be achieved at this greatly upgraded neutron flux. The proposed target modifications consist of a number of significant incremental improvements on the existing system, rather than one large breakthrough. Some of them could be implemented rapidly (time scale of less than a year); others would require somewhat more research (time scale of 2 or 3 years, depending on funding and staffing levels, and difficulties encountered). Each change can be independently omitted should technological difficulties arise. As such the overall RTNS upgrade process would be low-risk and high-payoff

Thermal Modeling and Management of Liquid-Cooled 3D Stacked Architectures Ay¸se Kıvılcım Co¸skun 1,JoséL.Ayala 2,

Abstract. 3D stacked architectures are getting increasingly attractive as they improve yield, reduce interconnect power and latency, and enable integrating layers manufactured with different technologies on the same chip. However, 3D integration results in higher temperatures following the increase in thermal resistances. This chapter discusses thermal modeling and management of 3D systems with a particular focus on liquid cooling, which has emerged as a promising solution for addressing the high temperatures in 3D systems. We first introduce a framework that is capable of detailed thermal modeling of the interlayer structure containing microchannels and through-silicon-vias (TSVs). For energy-efficient liquid cooling, we describe a controller to adjust the liquid flow rate to meet the current chip temperature. We also discuss job scheduling techniques for balancing the temperature across the 3D system to maximize the cooling efficiency and to improve reliability.

Analysis of streamwise conduction in forced convection of microchannels using fin approach

The effects induced by streamwise conduction on the thermal characteristics of forced convection for single-phase liquid flow in rectangular microchannel heat sinks under imposed constant wall temperature have been studied. By employing the fin approach in the first law of analysis, models with and without streamwise conduction term in the energy equation were developed for hydrodynamically and thermally fully-developed flow under local thermal non-equilibrium for the solid and fluid phases. These two models were solved to obtain closed form analytical solutions for the fluid and solid temperature distributions and the analysis emphasized details of the variations induced by the streamwise conduction on the fluid temperature distributions. The effects of the Peclet number, aspect ratio, and thermal conductivity ratio on the thermal characteristics of forced convection in microchannel heat sinks were analyzed and discussed. This study reveals the conditions under which the effect of streamwise conduction is significant and should not be neglected in the forced convective heat transfer analysis of microchannel heat sinks

A Lattice Boltzmann kinetic model for microflow and heat transfer

10.1007/s10955-005-8413-zJournal of Statistical Physics1211-2239-25