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The BIBA (Busan Ion Beam Accelerator) is a compact linear accelerator facility using the 28 GHz ECRIS (Electron Cyclotron Resonance Ion Source) at the KBSI (Korea Basic Science Institute). The superconducting magnets of the 28 GHz ECRIS produce high magnetic fields for strong confinement of plasmas in an ion source chamber. For stable operation of the superconducting magnets, performance of cryostat system is very essential. However, the cryostat system produces significant quantities of the heating due to conduction from room temperature. In addition, part of the X-ray radiation produced by the collisions of the electrons within the ion source chamber is absorbed by the cold mass of the superconducting magnet, leading to an additional heat load in the cryostat system. In this paper, a study on the performance of the cryostat system for 28 GHz ECRIS is performed to improve the cooling efficiency of the cryostat system.

Analytical and numerical analyses for predicting the mechanical responses of BCC and FCC lattice structures under compressive loading were performed and verified by comparing them to experimental data. The analytical and numerical results are in excellent correlation, while the error between the experimental and numerical results is about 5.8 ~ 15.3 %, which was caused by the inconsistent lattice strut diameter and the material elastic modulus. The measured lattice strut diameter is smaller than the designed diameter by thermal shrinkage, so the thermal shrinkage should be taken into the lattice structure design in additive manufacturing processes. Based on the same analytical and numerical techniques, a parametric investigation of the elastic moduli of BCC and FCC lattice unit cells with respect to the strut aspect ratio, specific density and strut angle was performed. Finally, the elastic moduli of multi-cell BCC and FCC lattice structures with the same density were investigated by varying the number of rows and columns of lattice unit cells in both unconstrained and constrained boundary conditions. As the strut aspect ratio, density and angle increase, the elastic moduli of both BCC and FCC lattice increase. FCC elastic modulus is higher than that of BCC lattice with respect to the strut aspect ratio, density and angle, while BCC elastic modulus could be found to be higher than of FCC lattice for a constrained boundary condition.

Currently, the 28 GHz ECRIS (electron cyclotron resonance ion source) was developed to produce a high-current heavy-ion beam at the KBSI (Korea Basic Science Institute). The high-voltage platform of the 28 GHz ECRIS is essential to deliver an ion beam to the next acceleration stage. The high-voltage platform was designed considering dielectric characteristics in order to ensure electrical safety. In this paper, a study on the dielectric characteristics of GFRP (glass- fiber-reinforced plastic) is performed to determine the thickness of the GFRP cylindrical shell located between the plasma chamber and the warm bore of the superconducting magnet cryostat. The dielectric experiments on a GFRP cylindrical shell were conducted under a DC voltage. Sphere-to-plane electrode systems were used to examine the dielectric characteristics. Also, the relationship between the dielectric characteristics of the GFRP cylindrical shell and the distribution of the electric field intensity was calculated and analyzed by using FEM (Finite Elements Method) simulations.

The design of a beam dump for the energy range less than 20 MeV is reported. The beam dump was developed for the beam extraction commissioning stage of the Korea Basic Science Institute’s( KBSI’s) heavy ion facility. At present, the downstream section design of the diagnostic chamber of the beam line was completed, as has the fabrication of a radio-frequency quadrupole(RFQ) section. We are now performing frequency tuning for optimization. For reduction and elimination of the generated beam, the beam dump will be located downstream of the diagnostic beam line, and the beam dump was designed to withstand a heavy-ion beam energy of less than 20 MeV. The PHITS code and ANSYS steady-state thermal analysis were adapted for simulating the heat transfer and determining the numbers and types of secondary particles produced by bombardment of the beam’s dump material, respectively.

The application of cement asphalt mortar (CAM) in modern high-speed railways has been gaining attention due to its combined merits between asphalt and cement hydration product characteristics. To promote sustainable development, it is promising to utilize by-products in the making of new CAM instead of using only cement. In this research, the cement content was partly replaced by fly ash or ground-granulated blast furnace (GGBS) slag to achieve this objective. Then, laboratory experiments were conducted to determine the effect of these admixtures on the fresh and hardened characteristics of CAM. The test results revealed that the CAM mixture with slag received better fresh properties compared to the controlled mixture. However, the poor pozzolanic property of these by-product materials may lead to the low strength development. Meanwhile, although the mixture with fly ash suffered from slow strength establishment compared to the control mix at an early age, the strength of this condition increases dramatically after 28 days. Based on the findings, the application of appropriate fly ash content in the CAM mixture will not only provide ideal workable time and mixing stability but also ensure the required strength for the design target. This combination also serves as a cost-effective and environmental solution.

A SiC crystal mixed with 4H-, 6H-, and 15R-SiC polytypes and their wetting properties were characterized using precisely dispensed de-ionized (DI) water drops. Contact angles of a DI water drop on SiC surfaces were quantitatively determined by analyzing the sideview image of a DI water drop in contact with the SiC substrate with mixed polytypes using image analysis software. The contact angle measurements showed that the contact angle for the Si-face (0001) was approximately 4o ∼ 8o greater than that for the C-face (000-1) regardless of polytype. The surface roughness of both Si-face and C-face was measured using atomic force microscopy and confirmed to be nearly identical. Due to the difference in surface energy of polarity of SiC basal planes, the contact angle measured from the Si-face (0001) after native oxide removal showed significant decrease and it recovered over time by room temperature oxidation in air. In contrast, the contact angle measured from the C-face (000-1) after native oxide removal, showed significant decrease and it was maintained, even after room temperature oxidation for 24 h in air. We found that there is correlation between the wetting property of SiC polytypes of 4H-, 6H-, and 15 R and a difference in their surface potential energy corresponding to the hexagonality of each SiC polytype determined by the atomic arrangement.

A gyrotron is used as a microwave power source in an electron-cyclotron-resonance (ECR) ion source system. In order to test the gyrotron, which operates at a frequency of 28 GHz in the continuous-wave (CW) mode, the Korea Basic Science Institute (KBSI) developed a water load that absorbed up to 10 kW of power. The water load consists of an aluminum jacket, a quartz window, and a waveguide. A distilled water flow of 13 L/min, sealed with the quartz window, is used as the absorbent. At 28 GHz, the S11 parameter and the voltage standing-wave ratio (VSWR) of the water load design were calculated to be less than −30 dB and 1.05, respectively. In practical experiments, the increase in the water’s temperature was approximately 10 °C at the highest power.

The effects of water back-flushing period (filtration time, FT) and time (BT) and polypropylene (PP) beads concentration were investigated in hybrid process of seven-channel ceramic microfiltration and PP beads coated with titanium dioxide (TiO2) photocatalyst for advanced drinking water treatment. Instead of natural organic matters (NOM) and fine inorganic particles in natural water source, modified solution was prepared with humic acid and kaolin. As results of the effect of water back-flushing condition, FT 2 min and BT 10 s were the most effective to reduce membrane fouling and to maintain high permeate flux, and the highest total permeate volume (VT) could be acquired at FT 2 min and BT 10 s in our experimental range. Thus, the optimal condition for the hybrid water treatment process would be FT 2 min and BT 10 s. The final permeate flux (J) and total permeate volumes (VT) were the maximum at 40 g/L after 180 min’s operation. Also, the treatment efficiencies of turbidity and humic acid were t...

The 28 GHz superconducting electron cyclotron resonance (ECR) ion source has been developed to produce a high current heavy ion for the linear accelerator at KBSI (Korea Basic Science Institute). The objective of this study is to generate fast neutrons with a proton target via a p(Li,n)Be reaction. The design and fabrication of the essential components of the ECR ion source, which include a superconducting magnet with a liquid helium re-condensed cryostat and a 10 kW high-power microwave, were completed. The waveguide components were connected with a plasma chamber including a gas supply system. The plasma chamber was inserted into the warm bore of the superconducting magnet. A high voltage system was also installed for the ion beam extraction. After the installation of the ECR ion source, we reported the results for ECR plasma ignition at ECRIS 2014 in Russia. Following plasma ignition, we successfully extracted multi-charged ions and obtained the first results in terms of ion beam spectra from various species. This was verified by a beam diagnostic system for a low energy beam transport system. In this article, we present the first results and report on the current status of the KBSI accelerator project.

The installation of the 28 GHz electron cyclotron resonance ion source (ECRIS) ion implantation beamline was recently completed at the Korea Basic Science Institute. The apparatus contains a beam monitoring system and a sample holder for the ion implantation process. The new implantation system can function as a multipurpose tool since it can implant a variety of ions, ranging hydrogen to uranium, into different materials with precise control and with implantation areas as large as 1-10 mm(2). The implantation chamber was designed to measure the beam properties with a diagnostic system as well as to perform ion implantation with an in situ system including a mass spectrometer. This advanced implantation system can be employed in novel applications, including the production of a variety of new materials such as metals, polymers, and ceramics and the irradiation testing and fabrication of structural and functional materials to be used in future nuclear fusion reactors. In this investigation, the first nitrogen ion implantation experiments were conducted using the new system. The 28 GHz ECRIS implanted low-energy, multi-charged nitrogen ions into copper, zinc, and cobalt substrates, and the ion implantation depth profiles were obtained. SRIM 2013 code was used to calculate the profiles under identical conditions, and the experimental and simulation results are presented and compared in this report. The depths and ranges of the ion distributions in the experimental and simulation results agree closely and demonstrate that the new system will enable the treatment of various substrates for advanced materials research.

The Korea Basic Science Institute (KBSI) has been developing a heavy ion accelerator system to accelerate high current, multi-charge state ions produced by a 28 GHz superconducting electron cyclotron ion source. A beam analyzing system as a part of the low energy beam transport apparatus was developed to select charged particles with desirable charge states from the ion beams. The desired species of ion, which is generated and extracted from the ECR ion source including various ion particles, can be selected by 90° dipole electromagnet. Due to the non-symmetrical structure in the coil as well as the non-linear permeability of the yoke material coil, a three dimensional analysis was carried out to confirm the design parameters. In this paper, we present the experimental results obtained as result of an analysis of KBSI accelerator. The effectiveness of beam selection was confirmed during the test of the analyzing system by injecting an ion beam from an ECR ion source.

The influence of current distribution on the transport current loss in vertically stacked high-Tc superconductor (HTS) tapes was evaluated. AC loss was analyzed as a function of current distribution by introducing a current distribution parameter through a numerical method (finite element analysis). AC loss under non-uniform current distribution is always higher than that for a uniformly distributed transport current in a conductor. Although the effect of non-uniformity is relatively insignificant in low transport current, AC loss increases substantially in high transport current regions as non-uniformity is enlarged. The results verify that non-uniform current distribution causes extra loss by examining the cross-sectional view of current densities in stacked conductor.

The ceramic microfiltration system with periodic N2-back-flushing was operated for treating paper wastewater discharged from a company making toilet papers by recycling milk or juice cartons. Two kinds of alumina membranes with 7 channels used here for recycling paper wastewater. The optimal N2 filtration time for HC04 membrane with 0.4μm pore size was lower value of 4min than 16min for HC10 with 1.0μm pore size at fixed back-flushing time 40s, trans-membrane pressure 1.0kgf/cm2 and back-flushing pressure 5.0kgf/cm2. From the results of TMP effect at fixed filtration time and back-flushing time, the lower TMP was better on membrane fouling because high TMP could make easily membrane cake and fouling inside membrane structure. However, we could acquire the highest volume of total permeate for the reason that TMP was driving force in our filtration system to treat paper wastewater. Then the permeate water of low turbidity was acquired in our microfiltration system using multichannels ceramic membranes, and the treated water could be reused in paper process.

Styryl dyes 7a–e having diheteryl moiety were synthesized and used as an emitter material in organic electroluminescent (EL) devices. The device structure of indium-tin oxide(ITO)/poly(3,4-ethylenedioxythiophene)(PEDOT)/ N , N ′-diphenyl- N , N ′-di(m-tolyl)benzidine(TPD)/styryl dye/Al was employed. The EL device with dye 7a exhibited red light with a maximum luminance 3745 nW/cm 2 at 11 V.

We report the fabrication of a magnesium diboride (MgB2) coil and evaluate its persistent-mode operation in a system cooled by a cryocooler with solid nitrogen (SN2) as a cooling medium. The main purpose of SN2 was to increase enthalpy of the cold mass. For this work, an in situ processed carbon-doped MgB2 wire was used. The coil was wound on a stainless steel former in a single layer (22 turns), with an inner diameter of 109 mm and height of 20 mm without any insulation. The two ends of the coil were then joined to make a persistent-current switch to obtain the persistent-current mode. After a heat treatment, the whole coil was installed in the SN2 chamber. During operation, the resultant total circuit resistance was estimated to be

Cryostat performance is essential for the stable operation of a superconducting magnet. A closed-cycle liquid helium cryostat was adopted for use for a superconducting electron cyclotron resonance (ECR) ion source by recondensing liquid helium vapor. The goal was to maintain the liquid helium filled reservoir at a constant level without transferring any liquid helium during the normal operation of the ECR ion source. To accomplish this, Gifford-McMahon (GM) refrigerators, which have two cold heads, were installed on the top of the cryostat. The cooling power of the GM cryocooler is 1.5 W at the second stage and 50 W at the first stage. Each stage was connected to the liquid helium reservoir, a radiation shield including high-Tc current lead, and related items. Before commissioning the ECR ion source, a preliminary evaluation of the recondensation performance was carried out with the magnet in partial operation. The design of the cryostat, its fabrication, and the experimental results are reported.

It is generally assumed that large amounts of x-rays are emitted from the ion source of an Electron Cyclotron Resonance (ECR) instrument. The total amount of x-rays should be strictly limited to avoid the extra heat load to the cryostat of the superconducting ECR ion source, since they are partly absorbed by the cold mass into the cryostat. A simulation of x-ray shielding was carried out to determine the effective thickness of the x-ray shield needed via the use of Geant4. X-ray spectra of the 10 GHz Nanogan ECR ion source were measured as a function of the thickness variation in the x-ray shield. The experimental results were compared with Geant4 results to verify the effectiveness of the x-ray shield. Based on the validity in the case of the 10 GHz ECR ion source, the x-ray shielding results are presented by assuming the spectral temperature of the 28 GHz ECR ion source.

A superconducting magnet for use in an electron cyclotron resonance ion source was developed at the Korea Basic Science Institute. The superconducting magnet is comprised of three solenoids and a hexapole magnet. According to the design value, the solenoid magnets can generate a mirror field, resulting in axial magnetic fields of 3.6 T at the injection area and 2.2 T at the extraction region. A radial field strength of 2.1 T can also be achieved by hexapole magnet on the plasma chamber wall. NbTi superconducting wire was used in the winding process following appropriate techniques for magnet structure. The final assembly of the each magnet involved it being vertically inserted into the cryostat to cool down the temperature using liquid helium. The performance of each solenoid and hexapole magnet was separately verified experimentally. The construction of the superconducting coil, the entire magnet assembly for performance testing and experimental results are reported herein.

We propose two methods to predict the AC transport current losses of MgB2 superconducting wires with respect to various operating currents (Itr) and temperatures (T). Firstly, the transport current loss was estimated by a numerical method (finite element analysis). In order to consider the highly nonlinear behavior of the superconducting properties according to magnetic flux density (B) at each temperature, the measured Jc - B - T characteristics were used in the calculation. The numerical results were compared with these of conventional Norris theory and showed quite good coincidence. A second method to predict the transport current loss at various temperatures, which used a loss at a specific temperature and the critical current data, is suggested. We deduce a formula for the prediction of the loss by a simple analogy through normalization, which performs excellently. The comparison of the transport current loss values calculated using the two methods is addressed.

The effect of light illumination on the electronic transport in hydrogenated amorphous silicon-sulfur alloys (a-SiSx:H) has been investigated at various temperatures. The light-induced effects were monitored using photoconductivity and dark conductivity measurements, including subgap defect density by the constant photocurrent method. The light-induced changes in the dark conductivity, as illumination temperature increases, reveal a transition from normal to inverse Staebler–Wronski (S–W) behavior at a critical temperature (Tc) that decreases with increasing sulfur concentration. On the other hand, the changes in the photoconductivity reveal normal S–W behavior at all the observed temperatures, but those are significantly reduced with increasing temperature and sulfur concentration. Correlation between subgap defect density and photoconductivity indicates that the defects created at temperatures higher than Tc act as inefficient recombination centers as compared with those created at temperatures lower th...