The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
D A Gates - One of the best experts on this subject based on the ideXlab platform.
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taming the plasma material interface with the snowflake divertor in nstx
Nuclear Fusion, 2011Co-Authors: V Soukhanovskii, J W Ahn, R E Bell, D A Gates, S P Gerhardt, R Kaita, Egemen Kolemen, B P Leblanc, R Maingi, M A MakowskiAbstract:Steady-state handling of divertor heat flux is a critical issue for ITER and future conventional and spherical tokamaks with compact high-power density divertors. A novel 'snowflake' divertor (SFD) configuration was theoretically predicted to have significant magnetic geometry benefits for divertor heat flux mitigation, such as an increased plasma-wetted area and a higher divertor volume available for volumetric power and momentum loss processes, as compared with the standard divertor. Both a significant divertor peak heat flux reduction and impurity screening have been achieved simultaneously with core H-mode confinement in discharges with the SFD using only a minimal set of poloidal Field Coils.
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plasma shape control on the national spherical torus experiment nstx using real time equilibrium reconstruction
Nuclear Fusion, 2006Co-Authors: D A Gates, J R Ferron, M G Bell, T Gibney, R D Johnson, R Marsala, D Mastrovito, J E Menard, D Mueller, B G PenaflorAbstract:Plasma shape control using real-time equilibrium reconstruction has been implemented on the National Spherical Torus Experiment (NSTX). The rtEFIT code originally developed for use on DIII-D was adapted for use on NSTX. The real-time equilibria provide calculations of the flux at points on the plasma boundary, which are used as input to a shape control algorithm known as isoflux control. The flux at the desired boundary location is compared with a reference flux value, and this flux error is used as the basic feedback quantity for the poloidal Field Coils on NSTX. The hardware that comprises the control system is described, as well as the software infrastructure. Examples of precise boundary control are also presented.
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plasma shape control on the national spherical torus experiment nstx using real time equilibrium reconstruction
Other Information: PBD: 15 Apr 2005, 2005Co-Authors: D A Gates, J R Ferron, M G Bell, T Gibney, R D Johnson, R Marsala, D Mastrovito, J E Menard, D Mueller, B G PenaflorAbstract:Plasma shape control using real-time equilibrium reconstruction has been implemented on the National Spherical Torus Experiment (NSTX). The rtEFIT code originally developed for use on DIII-D was adapted for use on NSTX. The real-time equilibria provide calculations of the flux at points on the plasma boundary, which is used as input to a shape control algorithm known as isoflux control. The flux at the desired boundary location is compared to a reference flux value, and this flux error is used as the basic feedback quantity for the poloidal-Field Coils on NSTX. The hardware that comprises the control system is described, as well as the software infrastructure. Examples of precise boundary control are also presented.
B G Penaflor - One of the best experts on this subject based on the ideXlab platform.
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plasma shape control on the national spherical torus experiment nstx using real time equilibrium reconstruction
Nuclear Fusion, 2006Co-Authors: D A Gates, J R Ferron, M G Bell, T Gibney, R D Johnson, R Marsala, D Mastrovito, J E Menard, D Mueller, B G PenaflorAbstract:Plasma shape control using real-time equilibrium reconstruction has been implemented on the National Spherical Torus Experiment (NSTX). The rtEFIT code originally developed for use on DIII-D was adapted for use on NSTX. The real-time equilibria provide calculations of the flux at points on the plasma boundary, which are used as input to a shape control algorithm known as isoflux control. The flux at the desired boundary location is compared with a reference flux value, and this flux error is used as the basic feedback quantity for the poloidal Field Coils on NSTX. The hardware that comprises the control system is described, as well as the software infrastructure. Examples of precise boundary control are also presented.
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plasma shape control on the national spherical torus experiment nstx using real time equilibrium reconstruction
Other Information: PBD: 15 Apr 2005, 2005Co-Authors: D A Gates, J R Ferron, M G Bell, T Gibney, R D Johnson, R Marsala, D Mastrovito, J E Menard, D Mueller, B G PenaflorAbstract:Plasma shape control using real-time equilibrium reconstruction has been implemented on the National Spherical Torus Experiment (NSTX). The rtEFIT code originally developed for use on DIII-D was adapted for use on NSTX. The real-time equilibria provide calculations of the flux at points on the plasma boundary, which is used as input to a shape control algorithm known as isoflux control. The flux at the desired boundary location is compared to a reference flux value, and this flux error is used as the basic feedback quantity for the poloidal-Field Coils on NSTX. The hardware that comprises the control system is described, as well as the software infrastructure. Examples of precise boundary control are also presented.
M Oshikiri - One of the best experts on this subject based on the ideXlab platform.
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cable twist pitch variation in hbox nb _ 3 hbox sn conductors for iter toroidal Field Coils in japan
IEEE Transactions on Applied Superconductivity, 2013Co-Authors: Y Takahashi, K. Hamada, K Kawano, Y Nabara, Yoshihiko Nunoya, T Isono, K Matsui, T Hemmi, N Koizumi, M OshikiriAbstract:In March 2010, the Japan Atomic Energy Agency (JAEA) was the first to start the mass production of toroidal Field (TF) conductors among the six parties who were procuring TF conductors in the International Thermonuclear Experimental Reactor project. The height and width of the TF Coils are 14 m and 9 m, respectively. The conductor is a cable-in-conduit conductor with an operating current of 68 kA. A circular multistage superconducting cable is inserted into a circular stainless steel jacket with a thickness of 2 mm. A total of 900 Nb3Sn strands and 522 copper strands are cabled around the central spiral and then wrapped with stainless steel tape whose thickness is 0.1 mm. The superconducting cables are inserted into the jacket assembled using the automatic butt Tungsten Inert Gas welding technique. Cable insertion is one of the key technologies in the jacketing process because the gap between the inner surface of the jacket and the outer diameter of the superconducting cable is only 2 mm in diameter. It was observed that the cabling pitch of the destructive sample is longer than the original pitch at cabling. JAEA carried out the tensile tests of the cable and the measurement of the cable rotation during the insertion to investigate the cause of the elongation. The cause of elongation was clarified, and the results are described in this paper.
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technology development and mass production of nb3sn conductors for iter toroidal Field Coils in japan
Nuclear Fusion, 2011Co-Authors: Y Takahashi, K. Hamada, K Kawano, Y Nabara, Yoshihiko Nunoya, T Isono, K Matsui, T Hemmi, N Koizumi, M OshikiriAbstract:The design and manufacture of Nb3Sn conductors for ITER toroidal Field (TF) Coils have many technical challenges. Although it was demonstrated in the ITER model coil project that the conductors have a sufficiently high performance and the engineering design is valid, unexpected issues arose. Through both theoretical and experimental efforts improved conductors were developed. The Japan Atomic Energy Agency started to procure improved conductors for TF Coils as part of the ITER project. Because the required tonnage of Nb3Sn strands is quite large compared with past experience and the required superconducting performance is higher than that of the model Coils, quality control techniques are very important for the successful manufacture of the strands. Approximately 60?ton of Nb3Sn strands have been successfully completed under a severe quality control regimen and all strands meet ITER specifications. This paper summarizes the technical developments leading to the first successful mass production of ITER TF conductors.
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performance of japanese hbox nb _ 3 hbox sn conductors for iter toroidal Field Coils
IEEE Transactions on Applied Superconductivity, 2008Co-Authors: Y Takahashi, Y Nabara, Yoshihiko Nunoya, T Isono, K Matsui, T Hemmi, N Koizumi, Y Uno, M Oshikiri, K OkunoAbstract:The cable-in-conduit conductors for the ITER TF Coils are fabricated using the latest high performance strands. The strands made by bronze and internal-tin methods are used for the conductors with a void fraction of 29% and 33%, respectively. Superconducting performance of the conductors was measured at the operating condition of the TF Coils. The measured current sharing temperatures Tcs are 6.3-6.6 K for the bronze and 5.6-6.1 K for the internal-tin. The Tcs of the conductor with void fraction of 29% is 0.1-0.3 K higher than the conductor with a void fraction of 33%. It is shown from the results that the strain on the cable is between 0.7% and 0.75% and the n-values are between 4 and 6, much smaller than the n-values of strands.
Y Takahashi - One of the best experts on this subject based on the ideXlab platform.
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cable twist pitch variation in hbox nb _ 3 hbox sn conductors for iter toroidal Field Coils in japan
IEEE Transactions on Applied Superconductivity, 2013Co-Authors: Y Takahashi, K. Hamada, K Kawano, Y Nabara, Yoshihiko Nunoya, T Isono, K Matsui, T Hemmi, N Koizumi, M OshikiriAbstract:In March 2010, the Japan Atomic Energy Agency (JAEA) was the first to start the mass production of toroidal Field (TF) conductors among the six parties who were procuring TF conductors in the International Thermonuclear Experimental Reactor project. The height and width of the TF Coils are 14 m and 9 m, respectively. The conductor is a cable-in-conduit conductor with an operating current of 68 kA. A circular multistage superconducting cable is inserted into a circular stainless steel jacket with a thickness of 2 mm. A total of 900 Nb3Sn strands and 522 copper strands are cabled around the central spiral and then wrapped with stainless steel tape whose thickness is 0.1 mm. The superconducting cables are inserted into the jacket assembled using the automatic butt Tungsten Inert Gas welding technique. Cable insertion is one of the key technologies in the jacketing process because the gap between the inner surface of the jacket and the outer diameter of the superconducting cable is only 2 mm in diameter. It was observed that the cabling pitch of the destructive sample is longer than the original pitch at cabling. JAEA carried out the tensile tests of the cable and the measurement of the cable rotation during the insertion to investigate the cause of the elongation. The cause of elongation was clarified, and the results are described in this paper.
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examination of japanese mass produced rm nb _ 3 rm sn conductors for iter toroidal Field Coils
IEEE Transactions on Applied Superconductivity, 2012Co-Authors: Y Nabara, K. Hamada, K Kawano, Yoshihiko Nunoya, T Isono, Y Takahashi, K Matsui, T Hemmi, N Koizumi, N EbisawaAbstract:The performances of six Nb3Sn conductors for the ITER Toroidal Field Coils were tested. Four of them showed similar degradation rates of their current sharing temperatures Tcs over 1,000 electromagnetic cycles. By contrast, two of them showed sharp Tcs degradations at 50 cycles, after which their slopes became similar to those of the other four conductors. These two cables seemed to shrink under high magnetic Fields during the first 50 cycles, which caused the sharp Tcs degradation. This shrinkage might arise from a decline in cable rigidity due to, for example, the deformation of strands or the breakage of the Nb3Sn filaments. The four mass-produced conductors had roughly the same AC loss before cycling. After 1,000 cycles, the AC losses of all the conductors decreased markedly to less than half of those before cycling, and the values became approximately the same. After the test campaign, the destructive inspection of two of the conductors made it clear that the conductor had shrunk by about 520 ppm under the high magnetic Field during the test. It was also clarified that some strands were visibly deformed under the high magnetic Field, whereas those under the low magnetic Field did not look distorted. This plastic deformation of the strands could be one of the major reasons for the Tcs degradation with cyclic operation.
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technology development and mass production of nb3sn conductors for iter toroidal Field Coils in japan
Nuclear Fusion, 2011Co-Authors: Y Takahashi, K. Hamada, K Kawano, Y Nabara, Yoshihiko Nunoya, T Isono, K Matsui, T Hemmi, N Koizumi, M OshikiriAbstract:The design and manufacture of Nb3Sn conductors for ITER toroidal Field (TF) Coils have many technical challenges. Although it was demonstrated in the ITER model coil project that the conductors have a sufficiently high performance and the engineering design is valid, unexpected issues arose. Through both theoretical and experimental efforts improved conductors were developed. The Japan Atomic Energy Agency started to procure improved conductors for TF Coils as part of the ITER project. Because the required tonnage of Nb3Sn strands is quite large compared with past experience and the required superconducting performance is higher than that of the model Coils, quality control techniques are very important for the successful manufacture of the strands. Approximately 60?ton of Nb3Sn strands have been successfully completed under a severe quality control regimen and all strands meet ITER specifications. This paper summarizes the technical developments leading to the first successful mass production of ITER TF conductors.
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performance of japanese hbox nb _ 3 hbox sn conductors for iter toroidal Field Coils
IEEE Transactions on Applied Superconductivity, 2008Co-Authors: Y Takahashi, Y Nabara, Yoshihiko Nunoya, T Isono, K Matsui, T Hemmi, N Koizumi, Y Uno, M Oshikiri, K OkunoAbstract:The cable-in-conduit conductors for the ITER TF Coils are fabricated using the latest high performance strands. The strands made by bronze and internal-tin methods are used for the conductors with a void fraction of 29% and 33%, respectively. Superconducting performance of the conductors was measured at the operating condition of the TF Coils. The measured current sharing temperatures Tcs are 6.3-6.6 K for the bronze and 5.6-6.1 K for the internal-tin. The Tcs of the conductor with void fraction of 29% is 0.1-0.3 K higher than the conductor with a void fraction of 33%. It is shown from the results that the strain on the cable is between 0.7% and 0.75% and the n-values are between 4 and 6, much smaller than the n-values of strands.
H W Weijers - One of the best experts on this subject based on the ideXlab platform.
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electromagnetic modeling of rebco high Field Coils by the h formulation
Superconductor Science and Technology, 2015Co-Authors: Jing Xia, Hongyu Bai, Andrew V Gavrilin, Youhe Zhou, H W WeijersAbstract:In this paper, we employ the anisotropic bulk approximation to successfully implement the electromagnetic modeling of superconducting Coils wound with rare-earth-barium-copper-oxide (REBCO) tapes based on the H-formulation, in which the Field-dependent critical current density and highly nonlinear characteristic are considered. The total number of turns in the stacks of REBCO pancake Coils is up to several thousand. We validate the anisotropic bulk model by comparing the ac loss of a small four-pancake coil between the bulk model and the original model which takes the actual thickness of the superconducting layer into account. Then, the anisotropic bulk model is used to investigate the self-Field problem of the REBCO prototype Coils of the National High Magnetic Field Laboratory all-superconducting magnet. The Field and current density distributions are obtained, and an obvious shielding effect is observed at the top and bottom of the Coils. The ac losses in the first and second cycles are calculated. The former is crucial to the design of the cooling system and the latter relates to the routine consumption of the liquid helium. It is found that the ac loss in the first cycle is 2.6 times as large as that in the second cycle. We also study the ac loss dependences on some key parameters (the critical current, n-value and ramp rate of the applied current). It is found that both in the first and second cycles, the ac loss increases with decreasing critical current. Moreover, the influence of the n-value on the ac loss is negligible. In addition, the ac loss decreases logarithmically with increasing ramp rate. However, the average power loss increases linearly with increasing ramp rate. We also compare some analytical estimates with the simulation result for the ac loss of the dual prototype Coils. It is found that the results of Bean's slab model are closer to the simulation result. The presented model is a useful tool to help us understand electromagnetic behavior and ac losses in REBCO high Field Coils. It also provides a basis to analyze the mechanical characteristics in the Coils in the future.
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progress in the development of a superconducting 32 t magnet with rebco high Field Coils
IEEE Transactions on Applied Superconductivity, 2014Co-Authors: H W Weijers, W D Markiewicz, Adam Voran, W R Sheppard, P D Noyes, Scott Gundlach, B Jarvis, Z L Johnson, Jun Lu, Hom KandelAbstract:The design and development of a 32 T, 32 mm cold bore superconducting magnet with high Field REBCO inner Coils are underway at the NHMFL. The two nested REBCO Coils that form the high Field section are dry wound, with uninsulated conductor and insulated stainless steel cowind reinforcement. Active quench protection uses distributed protection heaters. As part of the development activity, prototype Coils of the two REBCO Coils with full scale radial dimensions and final design features, but with reduced axial length are being constructed. The first of these prototype Coils was tested in a 15 T resistive background Field magnet. The coil has inner and outer winding diameters of 40 mm and 140 mm, respectively, and consists of six double pancakes with a total conductor length of roughly 900 m. The construction of this prototype coil is described, including the protection heaters. Coil test results are reported including coil critical current, coil ramping characteristics, thermal stability, joint, and terminal resistance with Field cycling. The corresponding operating stress in the windings is calculated. Importantly, the performance characteristics of the protection heaters will be measured including activation time.
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progress in the development of a superconducting 32 t magnet with rebco high Field Coils
IEEE Transactions on Applied Superconductivity, 2014Co-Authors: H W Weijers, W D Markiewicz, Adam Voran, W R Sheppard, P D Noyes, Scott Gundlach, B Jarvis, Z L Johnson, Hom Kandel, Hongyu BaiAbstract:The design and development of a 32 T, 32 mm cold bore superconducting magnet with high Field REBCO inner Coils are underway at the NHMFL. The two nested REBCO Coils that form the high Field section are dry wound, with uninsulated conductor and insulated stainless steel cowind reinforcement. Active quench protection uses distributed protection heaters. As part of the development activity, prototype Coils of the two REBCO Coils with full scale radial dimensions and final design features, but with reduced axial length are being constructed. The first of these prototype Coils was tested in a 15 T resistive background Field magnet. The coil has inner and outer winding diameters of 40 mm and 140 mm, respectively, and consists of six double pancakes with a total conductor length of roughly 900 m. The construction of this prototype coil is described, including the protection heaters. Coil test results are reported including coil critical current, coil ramping characteristics, thermal stability, joint, and terminal resistance with Field cycling. The corresponding operating stress in the windings is calculated. Importantly, the performance characteristics of the protection heaters will be measured including activation time.
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design of a superconducting 32 t magnet with rebco high Field Coils
IEEE Transactions on Applied Superconductivity, 2012Co-Authors: W D Markiewicz, Andrew V Gavrilin, H W Weijers, D C Larbalestier, Adam Voran, K W Pickard, W R Sheppard, J Jaroszynski, R P Walsh, P D NoyesAbstract:The design and fabrication of a 32 T, 32 mm cold bore superconducting magnet with high Field REBCO inner Coils is underway at the NHMFL. In support of the design, conductor characterization measurements have been made including critical current as a function of Field, Field orientation, temperature, and strain on conductors and joints. Various conductor and turn insulation systems were examined. The selected coil fabrication method for the 32 T magnet is pancake wind, dry wind Coils with sol-gel insulation on a stainless steel co-wind. Quench protection of the REBCO Coils by distributed heaters is under development. Small REBCO Coils have been made and tested in a 20 T background Field to demonstrate performance of the technology. The design of the 32 T magnet is described, including coil configuration and conductor lengths, fraction of critical current, selection of conductor copper content for protection, and stress in the windings.