Electric Control of Spin Helicity in a Magnetic Ferroelectric

Magnetic ferroelectrics or multiferroics, which are currently extensively explored, may provide a good arena to realize a novel magnetoelectric function. Here we demonstrate the genuine electric control of the spiral magnetic structure in one of such magnetic ferroelectrics, TbMnO3. A spin-polarized neutron scattering experiment clearly shows that the spin helicity, clockwise or counter-clockwise, is controlled by the direction of spontaneous polarization and hence by the polarity of the small cooling electric field.Comment: 4 pages, 3 figure

MPS simulation of spreading behavior of molten material

Spreading behavior with solidification is important phenomenon for the assessment of containment integrity and managing the severe accident in nuclear power plants. Existing codes such as CORFLOW use empirical equations for analyzing spreading behavior. Moving particle semi-implicit (MPS) method which calculates free surface without empirical equations is suitable for analyzing the solidification behavior of fluid with large deformation. MPS calculation models have been developed for the spreading analysis and deal with calculating thermal field, buoyancy, solid-liquid phase transition and temperature dependency of viscosity. The code was improved to calculate radiation heat transfer in three dimensions and high viscosity materials, and to control numerical instability. The FARO L26S and ECOKATS-V1 experiments were analyzed and showed good agreements with the experimental results in terms of final position of melt spread. Water Spreading Test by Theofanous and SPREAD test using stainless steel melt, were analyzed and compared with the results by SAMPSON code. Both analyses agreed with the experiments. The MPS method will be useful for computer experiments with various physical property of corium. It is expected to improve severe accident analysis code

Monolithic Ge:Ga Detector Development for SAFARI

We describe the current status and the prospect for the development of monolithic Ge:Ga array detector for SAFARI. Our goal is to develop a 64x64 array for the 45 -- 110 um band, on the basis of existing technologies to make 3x20 monolithic arrays for the AKARI satellite. For the AKARI detector we have achieved a responsivity of 10 A/W and a read-out noise limited NEP (noise equivalent power) of 10^-17 W/rHz. We plan to develop the detector for SAFARI with technical improvements; significantly reduced read-out noise with newly developed cold read-out electronics, mitigated spectral fringes as well as optical cross-talks with a multi-layer antireflection coat. Since most of the elemental technologies to fabricate the detector are flight-proven, high technical readiness levels (TRLs) should be achieved for fabricating the detector with the above mentioned technical demonstrations. We demonstrate some of these elemental technologies showing results of measurements for test coatings and prototype arrays.Comment: To appear in Proc. Workshop "The Space Infrared Telescope for Cosmology & Astrophysics: Revealing the Origins of Planets and Galaxies". Eds. A.M. Heras, B. Swinyard, K. Isaak, and J.R. Goicoeche