The Neutron Scattering Laboratory at Serpong is equipped with three diffractometers: a powder diffractometer (PD), a four circle diffractometer/texture diffractometer (FCD/TD) and a high resolution powder diffractometer (HRPD). The powder diffractometer (PD) was the first instrument installed (1987) by JICA/Japan and is situated in the reactor experimental hall (XHR) of the multi-purpose reactor (RSG) GA Siwabessy. The two others were installed in 1992 under phase III of the Sumitomo project, together with other neutron scattering instruments. In 1995 the PD instrument was modified to allow for residual stress measurements (RSM) in collaboration with the Japan Atomic Energy Research Institute (JAERI). The detailed activities of this instrument are explained in elsewhere in this issue. High resolution powder diffractometerThe high resolution powder diffractometer (HRPD) is a versatile diffractometer to study both crystallographic and magnetic structures of powder samples. Since X-ray diffraction is rather insensitive to light atoms such as hydrogen and oxygen, neutron diffraction is indispensable for the structure determination of materials containing such light elements. Furthermore, neutrons have an inherent magnetic moment that enables probing many kinds of magnetic structures ranging from colinear-commensurate to incommensurate configurations.The high resolution powder diffractometer (HRPD) is installed at the second neutron guide (NG2) in the neutron guide hall (NGH) about 71 meters away from the reactor core. It consists of a monochromator, collimators, a sample table, and a multicounter system. The monochromator drum has three exits corresponding to three different take-off angles: 2θ M = 41.5°, 89°, and 130°. At present the instrument is set for 2θ M = 89°. Figures 1 and 2 show the instrument and the schematic diagram of HRPD, respectively.At the beginning, a pyrolitic graphite PG(004) focusing monochromator system comprised of five PG(004) single crystals provided a focused neutron beam having a wavelength of 2.352 Å. Although two PG(002) filters had been inserted in front of the sample with the consequence of reducing the beam intensity, higher order peaks were still apparent in the diffraction pattern, which confused the analysis. Later on, to overcome this problem, a hot pressed germanium single crystal replaced the PG monochromator [1] under a bilateral cooperation between JAERI and BATAN. The Ge(331) single crystal was pressed up to 70 kgcm −2 during heating at 850°C for one hour to increase the mosaic spread. Although the Ge(331) Figure 1. The HRPD instrument.Figure 2. Schematic diagram of HRPD.
The fibrillation mechanism of insulin in acid solution has been studied by small angle X-ray scattering (SAXS). It was observed that insulin monomer unfolded in both conditions. Furthermore, in zinc free solution, insulin tend to aggregate on heating start in the first 5 min. The fibrillation through aggregation process continues until 30 min on heating. The similar phenomenon occurs in the presence of zinc ions. The SAXS data suggest that the presence of zinc ions prevent the long cylindrical fibril at the beginning of heating. However, after 20 min heating, the large cylindrical fibril of insulin formed in both conditions.
Apoferritin is a complex protein potential for drug delivery application. The advantage of apoferritin lies in its core-shell structure, its nano size, and its pH-sensitivity. This study was aimed to characterize the structure of apoferritin due to the pH alteration effect in a solution using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). Both DLS and SANS can observe protein size in solution near its physiological condition. The results show that apoferritin possesses a core-shell structure with a diameter of around 12–13 nm at pH 7. The dissociation of apoferritin occurs at pH 1.9. The SANS data shows the apoferritin at pH 1.9 was dissociated into the smaller oligomer. The structure of this smaller oligomer has a different configuration than the configuration of apoferritin subunits at pH 7. It can cause the failure of reassembly of apoferritin if the apoferritin is neutralized back to pH 7 after dissociation from pH 1.9.
STUDY OF CERIA STABILIZED ZIRCONIA MICROSPHERES MORPHOLOGY BY SMALL-ANGLE SCATTERING AND MICROSCOPY. Ceria stabilized zirconia microspheres of about 500 microns were prepared by external gelation. The morphology in nano and micro scale of the microsphere was evaluated. The nanostructure of CSZ microsphere after drying was studied by small angle neutron and x-ray scattering (SANS and SAXS). In this state, the existing of the mixture of ceria oxide and zirconia oxide was observed inside the polymer matrix. The roundness and surface properties of the CSZ microsphere were observed under the optical microscopy (OM) and scanning electron microscopy (SEM). The data showed their good size uniformity, smooth surface, but also the imperfect phase of the gelation.
Testing and evaluation of velocity selector control system of small angle neutron scattering (SANS) spectrometer has been done. It applied a unit of speed control variable AC, Optidrive Invertek Drives. This system is designed to be manually controlled and computerized. To control the Optidrive in manual mode, it can be done by keypad on the unit. The Optidrives can be controlled using computer by connecting the unit into a computer via USB port and OptiTools Studio software. Optidrive Invertek Drives need alternative current (AC) voltage one phase 220 volt with three phase out 220 volt. This out voltage is used as voltage source for moving the motor of disk in SANS neutron velocity selector. The speed of the disk in SANS neutron velocity selector is changed by adjusting the frequency from the Optidrive Invertek Drives. The numbers of speed of the disk determine the neutron wavelength passed through SANS neutron velocity selector. It is observed that every increasing frequency of 1 Hz, it will increase the disk speed by 59.929 rpm. The calibration that has been done for this system using silver behenate, obtain wavelength of the neutrons dependent to the disk speed. They are 3.10, 3.09, 3.41, 3.76, 4.23, 4.71, and 5.39 Å for disk speed 6500, 6000, 5500, 5000, 4500, 4000, and 3500 rpm respectively.
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