[en] The thermal design of a breeding blanket for the Korean Fusion Demonstration reactor (K-DEMO) is evaluated using the Multidimensional Analysis of Reactor Safety (MARS-KS) code in this study. The MARS-KS code has advantages in simulating transient 2-phase flow over the Computational Fluid Dynamics (CFD) codes. In order to confirm the prediction ability of the code for the present blanket system, the calculation results in steady-state normal operation condition were compared with the CFD predictions. The results of MARS-KS calculation and CFD prediction are in good agreement. Afterwards, 2 kinds of transient simulation for conceptual problems were carried out so as to show the applicability of MARS-KS for transient or accidental conditions: one is a reduction of the coolant flow rate followed by a pump failure event and the other is a vertical displacement event which is specific to fusion reactor as being the result of plasma instabilities. (authors)

[en] Highlights: → CdS NCs are formed by e-beam irradiation of CdCl₂ + MPA aqueous solution. → CdS molecules are released from Cd²⁺ - MPA complex by energetic electrons. → Only QDs are formed under a MPA-rich condition. → NRs and QDs are formed under a cadmium-rich condition. - Abstract: We investigated a simple route for synthesizing CdS nanocrystals (NCs) via irradiation of a CdCl₂ + mercaptopropionic acid (MPA) aqueous solution with a 10-MeV electron beam without using any additional sulfur precursors or stabilizers. When the concentration of the MPA was fixed to 2.5 mM, the morphology and optical properties of the NCs were changed by varying the CdCl₂ concentration. Based on transmission electron microscopy (TEM) imaging, a 0.4 mM concentration of CdCl₂ (the-MPA rich case) created only spherical quantum dots (QDs) with an average diameter of 6.6 nm. When the concentration of CdCl₂ was increased to 5 mM (the cadmium-rich case), nanorods with an average diameter of 5.3 nm and an average aspect ratio of 8.2 were formed along with QDs with diameter of 4.9 nm. The crystalline structures of the NCs were verified to be hexagonal.

[en] The Center for Underground Physics (CUP) of the Institute for Basic Science (IBS) is searching for the neutrinoless double-beta decay ($0\mathrm{\nu <!--\; ??\; -->}\mathrm{\beta <!--\; ??\; -->}\mathrm{\beta <!--\; ??\; -->}$) of ${}^{100}$Mo in the molybdate crystals of the AMoRE experiment. The experiment requires pure scintillation crystals to minimize internal backgrounds that can affect the $0\mathrm{\nu <!--\; ??\; -->}\mathrm{\beta <!--\; ??\; -->}\mathrm{\beta <!--\; ??\; -->}$ signal. For the last few years, we have been growing and studying Li${}_2$MoO${}_4$ crystals in a clean-environment facility to minimize external contamination during the crystal growth. Before growing Li${}_2^{100}$MoO${}_4$ crystal, we have studied Li₂^natMoO${}_4$ crystal growth by a conventional Czochralski (CZ) grower. We grew a few different kinds of Li₂^natMO${}_4$crystals using different raw materials in a campaign to minimize impurities. We prepared the fused Al${}_2$O${}_3$ refractories for the growth of ingots. Purities of the grown crystals were measured with high purity germanium detectors and by inductively coupled plasma mass spectrometry. The results show that the Li${}_2$MoO${}_4$ crystal has purity levels suitable for rare-event experiments. In this study, we present the growth of Li${}_2$MoO${}_4$ crystals at CUP and their purities.

[en] We studied the development of spatial pulse diagnostic apparatus with magnetic sensor array using giant magnetoresistance (GMR)/spin valves (SV). Magnetic field distributions for the permanent magnet of 10 arrays using the finite element method (FEM) in a sensing surface were simulated. The characteristics of GMR/SV sensor array consisted of the boundary limit of the sensing magnetic fields and the sensitivity of ΔMR/ΔH below 20 Oe and 1%/Oe, respectively

[en] We report structural, magnetic and electronic structure study of Mn doped TiO₂ thin films grown using pulsed laser deposition method. The films were characterized using X-ray diffraction (XRD), dc magnetization, X-ray magnetic circular dichroism (XMCD) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy measurements. XRD results indicate that films exhibit single phase nature with rutile structure and exclude the secondary phase related to Mn metal cluster or any oxide phase of Mn. Magnetization studies reveal that both the films (3% and 5% Mn doped TiO₂) exhibit room temperature ferromagnetism and saturation magnetization increases with increase in concentration of Mn doping. The spectral features of XMCD at Mn L_3,2 edge show that Mn²⁺ ions contribute to the ferromagnetism. NEXAFS spectra measured at O K edge show a strong hybridization between Mn, Ti 3d and O 2p orbitals. NEXAFS spectra measured at Mn and Ti L_3,2 edge show that Mn exist in +2 valence state, whereas, Ti is in +4 state in Mn doped TiO₂ films.

[en] The Advanced Molybdenum-based Rare process Experiment (AMoRE) in its second phase will search for neutrinoless double-beta ($0\nu \beta \beta$) decay of ¹⁰⁰Mo in 200 kg of molybdate crystals. To achieve the zero-background level in the energy range of the double-beta decay Q-value of ¹⁰⁰Mo, the radioactive contamination levels in AMoRE crystals should be low. Enriched molybdenum trioxide powder, ${}^{\mathrm{100Enr}}$MoO₃, enriched to 95.73% abundance of the ¹⁰⁰Mo isotope is used to grow the AMoRE crystals. A shielded array of fourteen high-purity germanium detectors with 70% relative efficiency each was used for the measurement of background activities in a sample of 9.6-kg powder. The detector system named the CAGe located at the Yangyang underground laboratory was designed for measuring low levels of radioactivity from natural radioisotopes or cosmogenic nuclides such as ²²⁸Ac, ²²⁸Th, ²²⁶Ra, ⁸⁸Y, and ⁴⁰K. The activities of ²²⁸Ac and ²²⁸Th in the powder sample were 0.88 $\pm$ 0.13 and 0.669 $\pm$ 0.089 mBq/kg, respectively. The activity of ²²⁶Ra was measured to be 1.19 $\pm$ 0.42 mBq/kg. The activity of ⁸⁸Y was 0.101 $\pm$ 0.016 mBq/kg. The activity of ⁴⁰K was found as 36.0 $\pm$ 4.1 mBq/kg.

[en] Searches for new physics push experiments to look for increasingly rare interactions. As a result, detectors require increasing sensitivity and specificity, and materials must be screened for naturally occurring, background-producing radioactivity. Furthermore, the detectors used for screening must approach the sensitivities of the physics-search detectors themselves, thus motivating iterative development of detectors capable of both physics searches and background screening. We report on the design, installation, and performance of a novel, low-background, fourteen-element high-purity germanium detector named the CAGe (CUP Array of Germanium), installed at the Yangyang underground laboratory in Korea.

[en] Si(100)/Mo(30nm)/Nd_xFe_92-xB₈(800nm)/Mo(30nm) (x=14, 20, 30) films are prepared by RF magnetron sputtering at room temperature. As-deposited films are amorphous materials. The crystallization temperature of the Nd₂Fe₁₄B phase decreases from 575deg. C to 500deg. C with increase of x from 14 to 20-30. The optimum annealing temperature with 30min annealing time is 650 deg. C, 625 deg. C and 600 deg. C for x=14, 20 and 30, respectively, and the x=20 film has the largest energy product of 18MGOe

[en] The effects of the cooling rate (speeds of wheel surface v=15-30m/s in steps of 5m/s) and composition 0=< x=<1 on the magnetic properties and microstructure of Nd₁₂Fe_71.4-xCo₁₀B_6.6Ga_x ribbons were studied. The coercivity H_c increases from 12 to 17kOe when x increases from 0 to 1. The best magnetic properties of the ribbon after annealing were H_c=17kOe, M_r/M_s=0.8 (BH)_max=18MGOe with optimum cooper wheel speed of 25m/s and x=0.6