Neutrino capture by r-process waiting-point nuclei

We use the Quasiparticle Random Phase Approximation to include the effects of low-lying Gamow-Teller and first forbidden strength in neutrino capture by very neutron-rich nuclei with N = 50, 82, or 126. For electron neutrinos in what is currently considered the most likely r-process site the capture cross sections are two or more times previous estimates. We briefly discuss the reliability of our calculations and their implications for nucleosynthesis.Comment: 9 pages, 4 figure

Fuel-Air Mixing In A Turbulent Coannular Pipe Flow Measured Using Laser Absorption With Genetic Algorithm-Based Tomographic Reconstruction And Modeled With LES

This research aims at improving the knowledge base of fuel-air mixing through measurements and modeling. The measurements are from an improved tomographic reconstruction method that is relatively easy to accomplish. A novel aspect of this research is the use of tomography for generating the RMS of fuel concentration. Measurements of fuel concentration for a mixing field were tomographically reconstructed from time resolved line of sight laser absorption measurements. The modeling is done using large eddy simulations (LES). LES predictions were compared to measurements of the mean and RMS of fuel concentration. The LES model predicted time-averaged radial fuel concentration profiles to within 5%, and overpredicted the RMS of fuel concentration slightly, predicting the trends correctly

Orbital-based Scenario for Magnetic Structure of Neptunium Compounds

In order to understand a crucial role of orbital degree of freedom in the magnetic structure of recently synthesized neptunium compounds NpTGa_5 (T=Fe, Co, and Ni), we propose to discuss the magnetic phase of an effective two-orbital model, which has been constructed based on a j-j coupling scheme to explain the magnetic structure of uranium compounds UTGa_5. By analyzing the model with the use of numerical technique such as exact diagonalization, we obtain the phase diagram including several kinds of magnetic states. An orbital-based scenario is discussed to understand the change in the magnetic structure among C-, A-, and G-type antiferromagnetic phases, experimentally observed in NpFeGa_5, NpCoGa_5, and NpNiGa_5.Comment: 18 pages, 8 figures, to appear in New Journal of Physic

Power exhaust concepts and divertor designs for Japanese and European DEMO fusion reactors

Concepts of the power exhaust and divertor design have been developed, with a high priority in the pre-conceptual design phase of the Japan-Europe broader approach DEMO design activity (BA DDA). Common critical issues are the large power exhaust and its fraction in the main plasma and divertor by the radiative cooling (P radtot/P heat 0.8). Different exhaust concepts in the main plasma and divertor have been developed for Japanese (JA) and European (EU) DEMOs. JA proposed a conventional closed divertor geometry to challenge large P sep/R p handling of 30-35 MW m-1 in order to maintain the radiation fraction in the main plasma at the ITER-level (f radmain = P radmain/P heat ∼ 0.4) and higher plasma performance. EU challenged both increasing f radmain to ∼0.65 and handling the ITER-level P sep/R p in the open divertor geometry. Power exhaust simulations have been performed by SONIC (JA) and SOLPS5.1 (EU) with corresponding P sep = 250-300 MW and 150-200 MW, respectively. Both results showed that large divertor radiation fraction (P raddiv/P sep 0.8) was required to reduce both peak q target (10 MW m-2) and T e,idiv. In addition, the JA divertor performance with EU-reference P sep of 150 MW showed benefit of the closed geometry to reduce the peak q target and T e,idiv near the separatrix, and to produce the partial detachment. Integrated designs of the water cooled divertor target, cassette and coolant pipe routing have been developed in both EU and JA, based on the tungsten (W) monoblock concept with Cu-alloy pipe. For year-long operation, DEMO-specific risks such as radiation embrittlement of Cu-interlayers and Cu-alloy cooling pipe were recognized, and both foresee higher water temperature (130 °C-200 °C) compared to that for ITER. At the same time, several improved technologies of high heat flux components have been developed in EU, and different heat sink design, i.e. Cu-alloy cooling pipes for targets and RAFM steel ones for the baffle, dome and cassette, was proposed in JA. The two approaches provide important case-studies of the DEMO divertor, and will significantly contribute to both DEMO designs

Measurement of tau polarization in e+ e- annihilation at sqrt{s}=58 GeV

The polarization of tau leptons in the reaction e+ e- --> tau+ tau- has been measured using a e+e- collider, TRISTAN, at the center-of-mass energy of 58 GeV. From the kinematical distributions of daughter particles in tau --> e nu nu-bar, mu nu nu-bar, rho nu or pi(K) nu decays, the average polarization of tau- and its forward-backward asymmetry have been evaluated to be 0.012 +- 0.058 and 0.029 +- 0.057, respectively.Comment: 18 pages, 5 figure