• Journal of Magnetics
• /
• v.2 no.3
• /
• pp.72-75
• /
• 1997

The temperature dependent saturation magnetization curve of amorphous Fe67 Co18B14Si1, alloy was measured using a SQUID magnetometer and vibrating sample magnetometer from 5 K up to 800 K. Inelastic neutron neutron scattering measurements also have been used to study the long wavelength spin dynamics of this high Tc amorphous ferromagnetic alloy. The magnon dispersion curve exhibit the conventional quadratic relationship E = D (T) q2 + $\Delta$, typical of an iso=obtained from a low temperature magnetization curve, which was consistent with the value obtained from the analysis oif inelastic neutron scattering data after consideration of its temperature dependence.

• Proceedings of the Korean Nuclear Society Conference
• /
• 2005.10a
• /
• pp.783-784
• /
• 2005

• Proceedings of the Korean Nuclear Society Conference
• /
• 2005.10a
• /
• pp.785-786
• /
• 2005

• Nuclear Engineering and Technology
• /
• v.38 no.5
• /
• pp.433-436
• /
• 2006

The implementation of multiplexing techniques combined with advances in neutron optics make the neutron three-axis spectrometers (TAS) an efficient tool to map inelastic response from single crystals over momentum transfer ranges comparable to the size of a single Brillouin zone. Thanks to recent progress in polarization techniques such experiments can be combined relatively easily with neutron polarization analysis, which does not only provide unambiguous separation of response corresponding to structural and magnetic degrees of freedom, but permits a quantitative analysis of the magnetic response anisotropy, often of crucial importance to test theoretical predictions. In the forthcoming decade we therefore expect a further development of the complementary use, rather than competition, of the reactor-based TAS's with time-of-flight (TOF) instruments for single crystal spectroscopy at the existing (ISIS) as well as at the newly built (SNS, J-PARK) pulsed sources.

• Nuclear Engineering and Technology
• /
• v.38 no.3
• /
• pp.201-210
• /
• 2006

This article presents a brief overview of an important area of neutron scattering: the general principles and techniques of elastic, quasielastic and inelastic scattering from a system composed predominately of incoherent scatterers. The methodology is then applied to the study of water, specifically when it is confined in nanometer-scale environments. The confined water exhibits uniquely anomalous properties in the supercooled state. It also nourishes biological functions, and supports essential chemical reactions in living systems. We focus on recent investigations of water encapsulated in nanoporous silica and carbon nanotubes, hydrated water in proteins and water or hydroxyl species incorporated in nanostructured minerals. Through these scientific examples, we demonstrate the advantages derived from the high sensitivity of incoherent neutron spectroscopy to hydrogen atom motions and hydrogen-bond dynamics, aided by rigorous data interpretation method using molecular dynamics simulations or theoretical modelling. This enables us to probe the inter-/intramolecular vibrations and relaxation/diffusion processes of water molecules in a complex environment.

• Nuclear Engineering and Technology
• /
• v.55 no.4
• /
• pp.1280-1286
• /
• 2023

MgF₂ as a moderator material has been extensively used in the beam shaping assembly (BSA) that plays an important role in the boron neutron capture therapy (BNCT). Regarded as important for applications, the thermal neutron scattering data of MgF₂ were calculated, based on the phonon expansion model. The structural properties of MgF₂ were researched by the VASP code based on the ab-initio methods. The PHONOPY code was employed to calculate the phonon density of states. Furthermore, the NJOY code was used to calculate the thermal neutron scattering data of MgF₂. The calculated inelastic cross sections plus absorption cross sections are in agreement with the available experimental data. The neutron transport in the BSA has been simulated by using a hybrid Monte-Carlo-Deterministic code NECP-MCX. The results indicated that compared with the calculation of the free gas model, the thermal neutron flux and epithermal neutron flux at the BSA exit port calculated by using the thermal neutron scattering data of MgF₂ were reduced by 27.7% and 8.2%, respectively.

• Journal of the Korean Magnetics Society
• /
• v.22 no.3
• /
• pp.103-108
• /
• 2012

Having a de Broglie wavelength of a few ${\AA}$ with its corresponding energies in the range of a few to a few hundreds meV, neutrons are ideally suited for the studies of structure and dynamics in condensed matter research. Neutron scattering has been developed over the past 60 years or so and become a very mature and established experimental technique in the very broad range of material sciences. In this short introductory article, we have explained its working principles and provided few selected examples of application.

• Nuclear Engineering and Technology
• /
• v.53 no.2
• /
• pp.423-429
• /
• 2021

The investigation of the utilization of enriched ²⁰⁸Pb as a coolant to enhance the performance of a long-life fast reactor with a Modified CANDLE (Constant Axial shape of Neutron flux, nuclide densities, and power shape During Life of Energy production) burnup scheme has performed. The analyzes were performed on a reactor with thermal power of 800 MegaWatt Thermal (MWTh) with a refueling process every 15 years. Uranium Nitride (enriched ¹⁵N), ²⁰⁸Pb, and High-Cr martensitic steel HT-9 were employed as fuel, coolant, and cladding materials, respectively. One of the Pb-nat isotopes, ²⁰⁸Pb, has the smallest neutron capture cross-section (0.23 mb) among other liquid metal coolants. Furthermore, the neutron-producing cross-section (n, 2n) of ²⁰⁸Pb is larger than sodium (Na). On the other hand, the inelastic scattering energy threshold of ²⁰⁸Pb is the highest among Na, ^natPb, and Bi. The small inelastic scattering cross-section of ²⁰⁸Pb can harden the neutron energy spectrum. Therefore, ²⁰⁸Pb is a better neutron multiplier than any other liquid metal coolant. The excess neutrons cause more production than consumption of ²³⁹Pu. Hence, it can reduce the initial fuel loading of the reactor. The selective photoreaction process was developing to obtain enriched ²⁰⁸Pb. The neutronic was calculated using SRAC and JENDL 4.0 as a nuclear data library. We obtained that the modified CANDLE reactor with enriched ²⁰⁸Pb as coolant and reflector has the highest k-eff among all reactors. Meanwhile, the ^natPb cooled reactor has the lowest k-eff. Thus, the utilization of the enriched ²⁰⁸Pb as the coolant can reduce reactor initial fuel loading. Moreover, the enriched ²⁰⁸Pb-cooled reactor has the smallest power peaking factor among all reactors. Therefore, the enriched ²⁰⁸Pb can enhance the performance of a long-life Modified CANDLE fast reactor.

• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1998.06a
• /
• pp.39-43
• /
• 1998

Single crystals of{{{{ { Zn}_{ 1-x} {Mn }_{x }{Te} }}}} with x=0.3-0.6 were prepared by the standard Bridgeman method. Diffuse neutron diffraction intensities due to the short range magnetic ordering is found in the vicinities of 1 1/2 0 reciprocal point and its equivalent point, indicating that the magnetic correlation of the clusters is the type III antiferromangetic one do the F-type Bravais class crystals, being identical with that of {{{{{ Cd}_{ 1-x} {Mn }_{x }Te }}}}. Neutron inelastic scattering measure-ment has been performed for {{{{{ Zn}_{ 0.6} { Mn}_{ 0.4}Te }}}} sample using the cold neutron spectrometer. AGNES. High resolution measurement with the energy resolution of {{{{ TRIANGLE E= +- .01meV}}}} was carried out in the temperature range from 10K to the ambient. Critical scattering, closely related with the spin glass transition, has been observed for the first time in this semimagnetic semi-conductor. The critical scattering is observed at temperatures in the vicinity of the spin glass transition temperature, 17K. The scattering is observed as a kind of quasielastic scattering in the reciprocal range where the elastic magnetic diffuse scattering has been observed, e.g., 11/20 reciprocal point, indicating the spin fluctuation has dynamic components in this material. Photoconductivity has been discovered below 150K in {{{{{ Zn}_{ 0.4} {Mn }_{0.6 } Te}}}}. The electric AC conductivity has been increased dramatically under the laser light with the wave lengths of {{{{ lambda =6328,5145 and4880 }}}}$\AA$ ,respectively. After the light was darkened, the conductivity was reduced to the original level after about 2000 seconds at 50K, being above the spin glass transition temperature. This phenomenon is the typical persistent photoconductivity; PPC which was similarly found in {{{{ { Zn}_{ 1-x} { Mn}_{x} Te}}}}.

• Nuclear Engineering and Technology
• /
• v.5 no.4
• /
• pp.265-278
• /
• 1973

The incoherent neutron scattering cross section of molecular liquids is analyzed using a damping function model for correlation functions of molecular translations and rotations. The present approach is different from recent works in that the scattering function is evaluated directly, not through the intermediate scattering function. The damping fuction is determined from a simple relation between its long-wavelength limit and the generalized frequency distribution function, and translation-rotation couplings are assumed to be neglected. A physical model is used for the translational motions of center-of-mass of a molecule, including properly its short-time and long-time behaviors. A simple model for the rotational motions is suggested which relates the damping function to the Fourier transform of the dipole correlation function, or equivalently, the infrared vibrational absorption spectrum. Theoretical absolute scattering intensities are computed for liquid methane and shown to be in satisfactory agreement with both thermal and cold neutron measurements.