9 research outputs found
Measurements of self-field and voltage for the REBCO stacked tapes assembled in rigid structure (STARS) conductor at 77 K
The measurements of self-fields and voltages for the stacked tapes assembled in rigid structure (STARS) conductor were carried out when the conductor immersed in liquid nitrogen was energized. In the measurements, a 3 m straight line shaped STARS conductor, which is composed of 45 REBCO tapes (15 tapes × 3 rows) embedded in a copper stabilizer, was used as a conductor sample. The measurement results indicate that the ramp rate at the conductor excitation and the one-time thermal cycle of the conductor do not affect the self-fields but the voltages.
The current center position in the conductor cross-section during the conductor excitation was analyzed from the measurement results of the self-fields. The current center position always maintains the same position in the middle of the cross-section during the excitation. The analysis indicates that the current distribution of the STARS conductor is stable during the excitation. In addition, two-dimensional magnetic field calculations were conducted using the various models for the cross-sectional configuration of the STARS conductor. As a result, the calculation results agree with the measurement results regarding the self-fields.journal articl
Characteristics and causes of voltage observed at the current feeder of high-temperature superconducting WISE conductor
ORCID 0000-0002-3541-6298The HTS (high-temperature superconducting) conductor is a feasible candidate for constructing magnets for next-generation fusion devices because of its higher critical current in a high magnetic field. A new concept of the HTS-WISE (Wound and Impregnated Stacked Elastic tapes) conductor has been studied aiming to apply the fusion reactor magnet. Here, the WISE-U conductor is composed of stacked thirty REBCO tapes (10 mm width, 65 μm thickness, Ic = 370 A @77 K, s.f.) wrapped by a stainless-steel coil tube which is inserted into the metal pipe. The 4 m-long REBCO tapes are folded with a radius of curvature of 35 mm in a hairpin-like structure. A low-melting-point metal U-Alloy 60 whose melting point is 60°C is poured into the pipe for impregnation to make the non-insulation conductor. The REBCO tapes and the current feeder made of oxygen-free copper were also impregnated with the U-Alloy 60 to connect. This fabrication method has the advantage of being easier to fabricate than the technique of connecting each tape using indium foil. The energization test results showed that a maximum current value of 16.9 kA was recorded at B = 5 T and T = 30 K, however, a burnout occurred in the current feeder before the critical current was determined. Then, the improved WISE conductor has been designed and tested which showed a maximum of 19kA was reached in the self-field and 20K. However, burnout still occurred in the current feeder section. In those experiments, the superconducting section has not been damaged at all. If this burnout had been avoided, a higher current-carrying capacity could have been obtained. Identifying the cause of burnout and improving the current feeder is required.journal articl
Stable operation characteristics and perspectives of the large-current HTS STARS conductor
ORCID 0000-0002-4489-8241The High-Temperature Superconducting (HTS) magnet option has been explored for fusion reactors as well as for next-generation fusion experimental devices. The Stacked Tapes Assembled in Rigid Structure (STARS) conductor uses HTS tapes with simple stacking without twisting and transposition. A practically applicable STARS conductor is presently being developed with an operating current of 18 kA at 20 K temperature and ~15 T magnetic field. The conductor is required to have a high current density of 80 A/mm2. For the second stage of the conductor development, internal electrical insulation is applied between the copper stabilizer casing and the outer stainless-steel jacket, and a 6-m conductor sample was fabricated in a solenoid coil shape with a 600-mm diameter and three turns. The coiled sample was tested in 8 T, 20 K using a facility equipped with a maximum 13-T, 700-mm bore solenoid coil. Excitation up to the rated current of 18 kA was successfully attained with stable operation. The characteristics of the conductor observed during the excitation test are discussed.journal articl
核融合科学研究所 核融合工学研究プロジェクト 全体報告書
On the basis of the outstanding progress in high-density and high-temperature plasma experiments in the Large Helical Device (LHD) at National Institute for Fusion Science (NIFS), the conceptual design studies on the LHD-type helical fusion reactor, the FFHR series, have been conducted since 1993. In order to strongly promote this research activity in parallel with the acceleration of the related technological R&D for reactor components, the Fusion Engineering Research Project (FERP) was launched at NIFS in FY2010. The FERP consists of 13 tasks and 44 sub-tasks, each strongly assisted by domestic and international collaborations.
The reactor design studies have focused on FFHR-d1, the demo-class reactor having a major radius of 15.6 m, which is four times larger than that of LHD. The similar heliotron magnetic configuration is employed to ensure steady-state operation with 3 GW self-ignited fusion power generation. The design activity has proceeded with the staged program, named “round,” that defines iterative working. The first round is to determine the basic core plasma parameters, the second is to compose all of the three-dimensional designs, the third focuses on construction and maintenance schemes, and the fourth is dedicated to passive safety. Since 2015, a multi-path strategy has been taken to include various options in the design, with FFHR-d1A as the base option. As a remarkable achievement of the reactor design, the Direct Profile Extrapolation (DPE) method is included in the helical systems code, HELIOSCOPE, in order to predict the confinement capability. The radial-build was successfully fixed and the neutronics calculation was carried out for the determined three-dimensional structure. The cost evaluation is also being conducted using these outcomes.
The related R&D works in FERP are categorized into five key subjects: (1) large-scale superconducting (SC) magnet, (2) long-life liquid blanket, (3) low-activation structural materials, (4) high heat & particle-flux control, and (5) tritium and safety. Using the remarkable achievements of the related R&D works, the engineering design of FFHR-d1 defines the basic option and challenging option. While the basic option is an extension of the ITER technology, the challenging option includes innovative ideas from the following three purposes: (1) to overcome the difficulties related with the construction and maintenance of three-dimensionally complicated large structures, (2) to enhance the passive safety, and (3) to improve plant efficiency.
For the superconducting magnet, the high-temperature superconductor (HTS) using ReBCO tapes is considered as an alternative (challenging) option to the cable-in-conduit conductor using low-temperature superconducting Nb3Sn strands. One of the purposes for selecting the HTS is to facilitate the three-dimensional winding of the helical coils by connecting prefabricated segmented conductors. A mechanical lap joint technique with low joint resistance has been developed and a 3 m-long short-sample conductor has successfully achieved 100 kA- current at a magnetic field of 5 T and temperature of 20 K. Further tests will be carried out in the world-largest 13 T, 700-mm bore superconducting magnet facility.
For the tritium breeding blanket, we have chosen, as a challenging option, the liquid blanket with molten salt FLiNaBe from the viewpoint of passive safety. To increase the hydrogen solubility, an innovative idea to include powders of titanium was also proposed. An increase of hydrogen solubility over five orders of magnitude has been confirmed in an experiment, which makes the tritium permeation barrier less necessary for the coating on the walls of cooling pipes. The “Oroshhi-2” testing facility was constructed as a platform for international collaborations, having
a twin-loop for testing both molten-salt (FLiNaK) and liquid metal (LiPb) under the perpendicular magnetic field of 3 T, the world’s largest for this purpose. For the structural material of blankets, a dissimilar bonding technique has been developed to join the vanadium alloy, NIFS-HEAT2, and a nickel alloy.
For the helical built-in divertor, the diverter tiles could be placed at the backside of the blankets where the incident neutron flux is sufficiently reduced by an order of magnitude. It is thus expected that a copper-alloy could be used for cooling pipes under the bonded tungsten tile, since the maximum neutron fluence is limited to be lower than the allowable limit of ~1 dpa for copper within the operation period. We note that the peak heat flux on the helical divertor is expected to reach or exceed ~20 MW/m² because of the non-uniform strike point distributions, and effective removal of this heat flux is a concern. The maintenance scheme for the full-helical divertor is also a critical issue. To solve these problems, a new concept of liquid divertor has been proposed as a unique idea. Ten units of molten-tin shower jets (falls) are proposed to be installed on the inboard side of the torus to intersect the ergodic layer. It is considered that the vertical flow of tin jets could be stabilized using an internal flow resistance such as wires, chains, and tapes imbedded. In case the liquid divertor actually works, the full-helical divertor would become less necessary, though it should still be situated at the rear. Neutral particles are expected to be efficiently evacuated through the gaps between liquid metal showers.
The mission of the NIFS FERP is to establish the scientific and technological basis that demonstrates the engineering feasibility of the helical fusion reactor and to promote the entire fusion engineering research toward the realization of fusion reactors in the mid-21st century. The progress of the NIFS FERP during the second six-year mid-term period in Japan for FY2010-2015 is overviewed in this full report. The numerical targets for the major components, which are the SC magnet, the in-vessel components, and the blanket, were compiled in FY2016,and its summary is also added in this report.research repor
Gene delivery into mouse retinal ganglion cells by in utero electroporation-2
<p><b>Copyright information:</b></p><p>Taken from "Gene delivery into mouse retinal ganglion cells by in utero electroporation"</p><p>http://www.biomedcentral.com/1471-213X/7/103</p><p>BMC Developmental Biology 2007;7():103-103.</p><p>Published online 17 Sep 2007</p><p>PMCID:PMC2080638.</p><p></p> after electroporation many growth cones from targeted RGCs are observed at the optic chiasm. (C) Retinal axons are seen in the optic tract three days after electroporation. (D) In newborn animals electroporated at E13, individual retinal axons expressing GFP project into the superior colliculus. (E) Higher magnification of (D) showing individual axons within the superior colliculus. (F) The location of the axons from targeted cells can be detected in the LGN of frontal brain sections of P8 animals after electroporation at E13. (G) Higher magnification of (F) shows the precise location of individual axons. (H) RGC axons electroporated at E13 in the retina terminate in the superior colliculus at P8 (arrow). (I) A frontal section through the superior colliculus of the same animal shown in (H). Od, optic disc; on, optic nerve; md, midline; ot, optic tract; sc, superior colliculus; dLGN, dorsal lateral geniculate nucleus; vLGN, ventral lateral geniculate nucleus; ic, inferior colliculus; cb, cerebellum. Scale bars: 100 μm in E; 200 μm in A, B, C, F, G, I and 500 μm in D, H
Gene delivery into mouse retinal ganglion cells by in utero electroporation-5
<p><b>Copyright information:</b></p><p>Taken from "Gene delivery into mouse retinal ganglion cells by in utero electroporation"</p><p>http://www.biomedcentral.com/1471-213X/7/103</p><p>BMC Developmental Biology 2007;7():103-103.</p><p>Published online 17 Sep 2007</p><p>PMCID:PMC2080638.</p><p></p>ount of DNA is injected into the embryo's eye through the uterine wall (left), and then electric pulses are passed using paddle electrodes. The result is the delivery of DNA to a subset of retinal cells (right). Only when the positive electrode was located on the injected eye was the electroporation successful. (B) Retinal section of an E16 embryo electroporated at E13. GFP expressing cells can be detected in the central part of the retina (arrows), surrounding the optic disc; scale bar: 200 μm. (C, D, E) Flattened whole mounts of E16 retinas electroporated at E13 after injection of different volumes of GFP-plasmid solution (0.2 μl, 0.5 μl and 1 μl respectively of a 1 μg/μl DNA solution) show the increase in the number cells targeted in the central retina (cells in the dashed circle). Scale bar: 500 μm
Gene delivery into mouse retinal ganglion cells by in utero electroporation-1
<p><b>Copyright information:</b></p><p>Taken from "Gene delivery into mouse retinal ganglion cells by in utero electroporation"</p><p>http://www.biomedcentral.com/1471-213X/7/103</p><p>BMC Developmental Biology 2007;7():103-103.</p><p>Published online 17 Sep 2007</p><p>PMCID:PMC2080638.</p><p></p> and sacrificed at E14, E16 or E18. Left panels show retinal sections from electroporated embryos incubated with anti-Islet1/2 antibodies to detect post-mitotic RGCs. Middle panels show targeted cells in the same retinal sections. Note that axons projecting to the inner layer can already be visualized in panel B at E14. Right panels show the merged images. At E16 GFP-positive cells are located closer to the inner layer (labelled by Islet 1/2, red) and a few double-labelled cells are observed (white arrows). At E18 the majority of the electroporated cells are located in the inner retinal layer and many of them are positive for Islet1/2. Scale bar: 20 μm. (J) Diagram showing the retrograde labelling paradigm. Dextran-rhodamine is applied at E17 in the optic tract (red) contralateral to the retina that was electroporated at E13 (green). The typical distribution of dextran-labelled cells and axons in the contralateral retina at E17 are shown (red), together with the GFP targeted cells that were electroporated at E13. (K) Retinal section electroporated at E13 (green cells) and retrogradely labelled with dextran-rhodamine (red cells). In all of the merged images, the double/labelled cells are yellow and they are indicated by white arrows. Scale bar: 100 μm (L-N) High magnification of the boxed area in K. Scale bar: 25 μm INL, Inner layer; VZ, ventricular zone
Gene delivery into mouse retinal ganglion cells by in utero electroporation-3
<p><b>Copyright information:</b></p><p>Taken from "Gene delivery into mouse retinal ganglion cells by in utero electroporation"</p><p>http://www.biomedcentral.com/1471-213X/7/103</p><p>BMC Developmental Biology 2007;7():103-103.</p><p>Published online 17 Sep 2007</p><p>PMCID:PMC2080638.</p><p></p>acrificed at P0 or P8. Retinal sections from electroporated embryos were incubated with anti-Calbindin (A-D) or anti-Brn3a (E-L) antibodies to identify horizontal cells and post-mitotic RGCs, respectively. (A-C) Calbindin staining on electroporated retinal sections at P0. (A) Shows the electroporated cell population at P0. Note that the vast majority of electroporated cells are distributed between the RGC and INL retinal layers but also, infrequent GFP labelled cells can be observed in the VZ. (B) Calbindin staining performed on electroporated retinal sections (C) Co-localization of calbindin and GFP (yellow cells) in a single cell located deep in the ventricular zone. A few amacrine cells are also positive for calbindin in the INL. Scale bar: 50 μm. (D) Higher magnification of a single cell in the ventricular zone that was electroporated at E13 and stained for calbindin at P0 indicating that it is a horizontal cell. Scale bar: 25 μm. (E-G) Sections of P0 retinas that were electroporated at E13, and stained for Brn3a. Scale bar: 50 μm. (I-K) Staining of electroporated retinal sections with the anti-Brn3a antibody at P8 when RGCs have reached their final location at the retinal surface. Note that the majority of GFP expressing cells located at the RGC layer co-localize with Brn3a (yellow cells), indicating that they are RGCs. Scale bar: 100 μm. High-magnification of GFP-expressing RGCs double-labelled with anti-Brn3a at P0 (H) and P8 (L). Scale bar: 25 μm RGC, retinal ganglion cell layer; INL, internal nuclear layer; VZ, ventricular zone