Journal of the Korean Physical Society

Using the soft X-ray magnetic circular dichroism (XMCD) technique, we investigated the magnetic states of the Sm 4f and the Mn 3d moments in a Néel N-type ferrimagnet, SmMnO3, which exhibits a striking magnetocapacitive effect around the compensation temperature (Tcomp ≈ 9.4 K). The XMCD results show that the Sm 4f and the Mn 3d moments were always aligned antiparallel to each other and that, upon sweeping a magnetic field, the angular momenta of Sm 4f and Mn 3d were simultaneously reversed at the field where the magnetocapacitive effect was observed. This indicates that the magnetocapacitive effect of SmMnO3 is induced by a simultaneous reversal of Sm 4f and Mn 3d angular momenta, i.e., magnetization reversal. We discuss a plausible origin of the magnetocapacitive effect in terms of the p-d hybridization mechanism.

Trong nghiên cứu này, các bộ phim composite Li-Cu2O được trưởng thành trên các chất nền oxit thiếc được dop fluor (FTO) bằng phương pháp lắng đọng điện hóa. Một lượng lithium (Li) khác nhau đã được thêm vào để phát triển các bộ phim composite Li-Cu2O. Chúng tôi đã phân tích hình thái, cấu trúc, mật độ dòng photô và độ ổn định ánh sáng của các bộ phim composite Li-Cu2O bằng cách sử dụng các biện pháp khác nhau như kính hiển vi điện tử quét phát xạ trường (FE-SEM), nhiễu xạ tia X (XRD) và các phép đo với điện trở kế/ điện áp kế. Kết quả cho thấy, tỷ lệ cường độ đỉnh XRD Cu2O (111)/ LiO (011) cao nhất được thu được cho mẫu chứa 10% trọng lượng, mẫu này cũng có giá trị mật độ dòng photô cao nhất là -5.00 mA/cm2. Giá trị mật độ dòng photô cao nhất cho mẫu 10% trọng lượng lớn gấp khoảng 5 lần so với mẫu 0% trọng lượng. Như kết quả này cho thấy, chúng tôi nhận thấy việc thêm Li có thể cải thiện các giá trị dòng photô của các bộ phim composite Li-Cu2O.

The Korea Multipurpose Accelerator Complex has been developing a 300-kV test stand for a 1-MV electrostatic accelerator ion source. The ion source and accelerating tube will be installed in a high-pressure vessel. The ion source in the high-pressure vessel is required to have a high reliability. The test stand has been proposed and developed to confirm the stable operating conditions of the ion source. The ion source will be tested at the test stand to verify the long-time operating conditions. The test stand comprises a 300-kV high-voltage terminal, a battery for the ion-source power, a 60-Hz inverter, 200-MHz radio-frequency power supply, a 5-kV extraction power supply, a 300-kV accelerating tube, and a vacuum system. The results of the 300-kV high-voltage terminal tests are presented in this paper.

We describe our experimental apparatus for generating quantum degenerate gases of bosonic 174Yb and fermionic 173Yb atoms. We use a Zeeman slower to generate a slow atomic beam and collect atoms in a magneto-optical trap formed by 556-nm laser beams without frequency modulations. Laser-cooled ytterbium atoms are transferred to a crossed optical dipole trap and evaporatively cooled to quantum degeneracy. Our system generates a Bose-Einstein condensate containing over 6 × 104 174Yb atoms or a degenerate Fermi gas of about 7 × 104 173Yb atoms at T/T F =0.8(1), where T F is the Fermi temperature of the gas. We highlight the high performance of the Zeeman slower and the home-made frequency-doubling systems for 399-nm and 556-nm lasers.

Distribution of a high-stability clock signal is an important topic for many applications. Recently, optical frequency comb transfer through outdoor atmosphere has become a valuable tool for the clock distribution due to its versatility. To extend the benefits of comb-based open-air clock distribution, one-way radiofrequency (RF) transfer with a single optical frequency comb is an attractive approach due to its simplicity and broad application span. Here, we transfer an L-band RF signal across 820-m-scale outdoor beam path with a single optical frequency comb. We measured the absolute phase noise of the transferred RF signal, and analyzed it with Kolmogorov’s f −8/3 power law and Taylor’s hypothesis of frozen turbulence. We also show that the residual-phase noise of the transferred RF signal can be suppressed to the femtosecond regime by a delay-locked loop. Our results may benefit remote ranging at km-range, inter-building clock distribution, and optical communication through aerial drones.

High-energy physics (HEP) experiments have employed many new types of scintillators. Specifically, bismuth germanate, thallium-doped cesium iodide, and lead tungstate (PbWO4, PWO) have been used for the L3 experiment; CLEO II, Belle and BES-III; and CMS, respectively. PWO has particularly beneficial properties, such as high density, fast decay time, short radiation length and radiation hardness. In this study, we tested the PWO crystals at low temperatures to determine their applicability in future calorimeters. Various crystals from the Proton Antiproton Annihilations at Darmstadt (PANDA) experiment in Giessen, the Bogoroditsk Techno-Chemical Plant (BTCP) in Russia and by Shanghai Institute of Ceramics, Chinese Academy of Sciences (SICCAS) in China were investigated. We studied the scintillation properties of PWO crystals, such as their X-ray luminescence, relative light yields, absolute light yields, energy resolutions, decay times and longitudinal uniformities of their light yields. In addition, we measured the temperature dependences of the light yields and decay times by using a 137Cs γ-ray source. The emission spectra of the PWO crystals consisted of a broad band from 350 nm to 700 nm, and the peak emission wavelength in each spectrum was 420 nm. The emission spectra of the PWO crystals from SICCAS were slightly shifted to longer wavelengths compared with those of the crystals from the other institutions.

Here, we report a polyol method to prepare monodispersed FeCo alloy particles with Pt seeds added in the production of nanoparticles. The prepared samples were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and magnetic measurements. Structural studies revealed that the FeCo nanoparticles had a body-centered cubic (BCC) structure. FE-SEM analysis demonstrated a sphere morphology for the FeCo alloy particles. The size of the FeCo nanoparticles could be well tuned by changing the number of Pt-seed partices in the FeCo alloy. The magnetic properties of the FeCo alloys were investigated as a function of the Pt-seed concentration and temperature. The saturation magnetization and coercivity of the FeCo nanoparticles were found to depend on the molar ratio of Fe/Co, as well as the number of Pt-seeds, and increased with increasing FeCo concentration. A higher value of the saturation magnetization, 218 emu/g, was obtained for the 0.07-M concentration of FeCo alloy. In the process of producing an FeCo alloy powder by heterogeneous nucleation, a powder having minute sizes could be produced under the experimental conditions of a Pt-seed-added temperature of 90 °C and a Pt/FeCo mole ratio of 8 × 10−5, and showed far superior properties.

We designed a 20-MV S-band traveling-wave deflecting structure to measure the bunch length of the electron beams for the PAL-XFEL. Since the start of commissioning of all RF systems of the PAL-XFEL on 12 April 2016, two out of three fabricated structures are currently being operated; one each in the hard X-ray and the soft X-ray branches. These deflecting structures were carefully tuned by using a 4-m-long nodal phase scanner in a precisely temperature and humidity controlled cleanroom considering the phase predictions calculated using RF field solvers. We carried out RF conditioning and beam commissioning with highly-stable high-power S-band RF systems and an EPICS-based control system. We briefly present our design of S-band deflecting structure and discuss the test results, including the results of the RF and the beam measurements.

A computational method for predicting and analyzing the cumulative effect of ionizing radiation in space is presented, taking into account the presence of the charged particles from the Sun and Earth together with the cosmic rays precipitating toward the vicinity of Earth. The method first integrates the population of charged particles along the trajectories of the instrument in space and then transports the charged particles across the shielding material. A novel method of interfacing a sophisticated mechanical design from computer-aided design (CAD) tools is introduced to geometrically model the shielding distribution of the orbiting instrument. The cumulative effect of ionizing radiation across the shielding distribution is then calculated based on the ray-tracing method and on a Monte Carlo simulation with Geant4. A description of this computational method is provided along with results for a representative example often encountered in the development of orbiting space instruments.