The Experts below are selected from a list of 99 Experts worldwide ranked by ideXlab platform
Kyekyoon Kim - One of the best experts on this subject based on the ideXlab platform.
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Study of a transaugmented two-stage small circular-bore railgun for injection of hypervelocity hydrogen pellets as a fusion Reactor Refueling mechanism
IEEE Transactions on Magnetics, 1997Co-Authors: M.w. Tompkins, J. Zhang, M.a. Anderson, Qichen Feng, Kyekyoon KimAbstract:Injection of hypervelocity hydrogen pellets has become widely accepted as the most effective means of Refueling magnetically confined fusion Reactors. Pellet velocities on the order of 10 km/s are desired and hydrogen pellet erosion during acceleration must be minimized. It is important to maintain uniform bore surfaces during repetitive shots, implying that, if a railgun is to be used to accelerate the pellets, damage to the sidewalls and rails of the railgun due to local heating must be limited. In order to reduce the amount of power dissipated within the bore and increase the propulsive force generated by the plasma-arc armature while minimizing losses due to pellet, rail, and sidewall ablation, we have employed a magnetic field transaugmentation mechanism consisting of a two-turn pulsed electromagnet. The two-stage gun consists of a light-gas gun which accelerates a 4- to 5-mg pellet to a speed around 1.2 km/s and injects it into the plasma-arc armature railgun. Currently, we have achieved a final output velocity for a hydrogen pellet of 2.11 km/s with a time-averaged acceleration of 4850 km/s/sup 2/ using a 58-cm railgun pulsed with a peak rail current of 9.2 kA and 28.0 kA of transaugmentation current. This paper will present a description of our hydrogen-pellet-injector railgun system, a discussion of the data on hydrogen pellet acceleration, and projections for future systems.
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Development and implementation of a rail current optimization program
IEEE Transactions on Magnetics, 1997Co-Authors: T.l. King, Kyekyoon Kim, J. Zhang, M.w. Tompkins, M.a. Anderson, R. Dharamshi, Qichen FengAbstract:Efforts are underway to automate the operation of a railgun hydrogen pellet injector for fusion Reactor Refueling. A plasma armature is employed to avoid the friction produced by a sliding metal armature and, in particular, to prevent high-Z impurities from entering the tokamak. High currents are used to achieve high accelerations, resulting in high plasma temperatures. Consequently, the plasma armature ablates and accumulates material from the pellet and gun barrel. This increases inertial and viscous drag, lowering acceleration. A railgun model has been developed to compute the acceleration in the presence of these losses. The model suggests that, depending on the rail and insulator materials used, there is a point of diminishing returns. Namely, for a given current, there is an acceleration time beyond which little or no increase in pellet speed is produced. The optimal pulse width was determined by identifying the time at which the acceleration decreased to zero. In order to quantify these losses, the ablation coefficient, /spl alpha/, and drag coefficient, C/sub d/, must be determined. These coefficients are estimated based on the pellet acceleration. The sensitivity of acceleration to /spl alpha/ and C/sub d/ has been calculated using the model. Once /spl alpha/ and C/sub d/ have been determined, their values are applied to the model to compute the appropriate current pulse width. An optimization program was written in LabVIEW software to carry out this procedure. This program was then integrated into the existing code used to operate the railgun system. Preliminary results obtained after test firing the gun indicate that the program computes reasonable values for /spl alpha/ and C/sub d/ and calculates realistic pulse widths.
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Acceleration of solid hydrogen pellet using augmented railgun for magnetic fusion Reactor Refueling
IEEE Transactions on Magnetics, 1995Co-Authors: J. Zhang, Kyekyoon Kim, T.l. KingAbstract:A 1.2 m long electromagnetic railgun with separate augmentation was designed, fabricated, and tested for the purpose of injecting hypervelocity hydrogen pellets into magnetic fusion devices for Refueling. A compact configuration of two pairs of coaxial rails insulated by thin Kapton films was employed. Two pulse-forming networks were used to separately control the duration, amplitude, and overlap of the current pulses. Copper sulphate resistors were employed as impedance-matching resistors and bank short resistors. The magnetic field inside the gun bore boosted by the high current on the gun augmentation rails, which in turn increased the J/spl times/B force without increasing the armature current, resulting in less ablation of the gun bore and pellet. Higher acceleration was achieved due to reduced inertial and viscous drag. Using a 1.2 m augmented railgun, hydrogen pellet velocities in excess of 2.5 km/s were achieved. Hydrogen pellet accelerations as high as 4.4/spl times/10/sup 6/ m/s/sup 2/ were achieved at a railgun current of 13.5 kA while the acceleration obtained on a conventional railgun was 2.2/spl times/10/sup 6/ m/s/sup 2/ at 14.1 kA. Computer simulations have been performed using the finite element code MSC/EMES to analyze the current density, magnetic field, Lorentz force, and inductance gradient of the conventional and augmented railguns. >
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Controls and diagnostics on a fuseless railgun for solid hydrogen pellet acceleration
IEEE Transactions on Magnetics, 1993Co-Authors: T.l. King, J. Zhang, R.g. Haywood, W.c. Manns, Kyekyoon KimAbstract:A two-stage railgun system has been built, incorporating several controls and diagnostics, some including unique features to account for the fact that the projectile is a frozen hydrogen pellet for fusion Reactor Refueling. A timing circuit has been developed to monitor projectile breech and muzzle velocities and to automatically trigger a sequence of events critical for effective plasma armature railgun operation. This circuit can initiate electrical breakdown of the propellant gas directly behind an incoming projectile, thus enabling fuseless operation. It also triggers a streak camera and a flashlamp for photographing the arc and the outgoing projectile, respectively. The automatic timing circuit is expandable and has been extended to incorporate a trigger for transaugmentation. The timing circuit is immune to mistriggering due to electromagnetic interference or fragmentation of the fragile hydrogen pellets. >
T.l. King - One of the best experts on this subject based on the ideXlab platform.
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Development and implementation of a rail current optimization program
IEEE Transactions on Magnetics, 1997Co-Authors: T.l. King, Kyekyoon Kim, J. Zhang, M.w. Tompkins, M.a. Anderson, R. Dharamshi, Qichen FengAbstract:Efforts are underway to automate the operation of a railgun hydrogen pellet injector for fusion Reactor Refueling. A plasma armature is employed to avoid the friction produced by a sliding metal armature and, in particular, to prevent high-Z impurities from entering the tokamak. High currents are used to achieve high accelerations, resulting in high plasma temperatures. Consequently, the plasma armature ablates and accumulates material from the pellet and gun barrel. This increases inertial and viscous drag, lowering acceleration. A railgun model has been developed to compute the acceleration in the presence of these losses. The model suggests that, depending on the rail and insulator materials used, there is a point of diminishing returns. Namely, for a given current, there is an acceleration time beyond which little or no increase in pellet speed is produced. The optimal pulse width was determined by identifying the time at which the acceleration decreased to zero. In order to quantify these losses, the ablation coefficient, /spl alpha/, and drag coefficient, C/sub d/, must be determined. These coefficients are estimated based on the pellet acceleration. The sensitivity of acceleration to /spl alpha/ and C/sub d/ has been calculated using the model. Once /spl alpha/ and C/sub d/ have been determined, their values are applied to the model to compute the appropriate current pulse width. An optimization program was written in LabVIEW software to carry out this procedure. This program was then integrated into the existing code used to operate the railgun system. Preliminary results obtained after test firing the gun indicate that the program computes reasonable values for /spl alpha/ and C/sub d/ and calculates realistic pulse widths.
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Acceleration of solid hydrogen pellet using augmented railgun for magnetic fusion Reactor Refueling
IEEE Transactions on Magnetics, 1995Co-Authors: J. Zhang, Kyekyoon Kim, T.l. KingAbstract:A 1.2 m long electromagnetic railgun with separate augmentation was designed, fabricated, and tested for the purpose of injecting hypervelocity hydrogen pellets into magnetic fusion devices for Refueling. A compact configuration of two pairs of coaxial rails insulated by thin Kapton films was employed. Two pulse-forming networks were used to separately control the duration, amplitude, and overlap of the current pulses. Copper sulphate resistors were employed as impedance-matching resistors and bank short resistors. The magnetic field inside the gun bore boosted by the high current on the gun augmentation rails, which in turn increased the J/spl times/B force without increasing the armature current, resulting in less ablation of the gun bore and pellet. Higher acceleration was achieved due to reduced inertial and viscous drag. Using a 1.2 m augmented railgun, hydrogen pellet velocities in excess of 2.5 km/s were achieved. Hydrogen pellet accelerations as high as 4.4/spl times/10/sup 6/ m/s/sup 2/ were achieved at a railgun current of 13.5 kA while the acceleration obtained on a conventional railgun was 2.2/spl times/10/sup 6/ m/s/sup 2/ at 14.1 kA. Computer simulations have been performed using the finite element code MSC/EMES to analyze the current density, magnetic field, Lorentz force, and inductance gradient of the conventional and augmented railguns. >
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Controls and diagnostics on a fuseless railgun for solid hydrogen pellet acceleration
IEEE Transactions on Magnetics, 1993Co-Authors: T.l. King, J. Zhang, R.g. Haywood, W.c. Manns, Kyekyoon KimAbstract:A two-stage railgun system has been built, incorporating several controls and diagnostics, some including unique features to account for the fact that the projectile is a frozen hydrogen pellet for fusion Reactor Refueling. A timing circuit has been developed to monitor projectile breech and muzzle velocities and to automatically trigger a sequence of events critical for effective plasma armature railgun operation. This circuit can initiate electrical breakdown of the propellant gas directly behind an incoming projectile, thus enabling fuseless operation. It also triggers a streak camera and a flashlamp for photographing the arc and the outgoing projectile, respectively. The automatic timing circuit is expandable and has been extended to incorporate a trigger for transaugmentation. The timing circuit is immune to mistriggering due to electromagnetic interference or fragmentation of the fragile hydrogen pellets. >
J. Zhang - One of the best experts on this subject based on the ideXlab platform.
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Study of a transaugmented two-stage small circular-bore railgun for injection of hypervelocity hydrogen pellets as a fusion Reactor Refueling mechanism
IEEE Transactions on Magnetics, 1997Co-Authors: M.w. Tompkins, J. Zhang, M.a. Anderson, Qichen Feng, Kyekyoon KimAbstract:Injection of hypervelocity hydrogen pellets has become widely accepted as the most effective means of Refueling magnetically confined fusion Reactors. Pellet velocities on the order of 10 km/s are desired and hydrogen pellet erosion during acceleration must be minimized. It is important to maintain uniform bore surfaces during repetitive shots, implying that, if a railgun is to be used to accelerate the pellets, damage to the sidewalls and rails of the railgun due to local heating must be limited. In order to reduce the amount of power dissipated within the bore and increase the propulsive force generated by the plasma-arc armature while minimizing losses due to pellet, rail, and sidewall ablation, we have employed a magnetic field transaugmentation mechanism consisting of a two-turn pulsed electromagnet. The two-stage gun consists of a light-gas gun which accelerates a 4- to 5-mg pellet to a speed around 1.2 km/s and injects it into the plasma-arc armature railgun. Currently, we have achieved a final output velocity for a hydrogen pellet of 2.11 km/s with a time-averaged acceleration of 4850 km/s/sup 2/ using a 58-cm railgun pulsed with a peak rail current of 9.2 kA and 28.0 kA of transaugmentation current. This paper will present a description of our hydrogen-pellet-injector railgun system, a discussion of the data on hydrogen pellet acceleration, and projections for future systems.
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Development and implementation of a rail current optimization program
IEEE Transactions on Magnetics, 1997Co-Authors: T.l. King, Kyekyoon Kim, J. Zhang, M.w. Tompkins, M.a. Anderson, R. Dharamshi, Qichen FengAbstract:Efforts are underway to automate the operation of a railgun hydrogen pellet injector for fusion Reactor Refueling. A plasma armature is employed to avoid the friction produced by a sliding metal armature and, in particular, to prevent high-Z impurities from entering the tokamak. High currents are used to achieve high accelerations, resulting in high plasma temperatures. Consequently, the plasma armature ablates and accumulates material from the pellet and gun barrel. This increases inertial and viscous drag, lowering acceleration. A railgun model has been developed to compute the acceleration in the presence of these losses. The model suggests that, depending on the rail and insulator materials used, there is a point of diminishing returns. Namely, for a given current, there is an acceleration time beyond which little or no increase in pellet speed is produced. The optimal pulse width was determined by identifying the time at which the acceleration decreased to zero. In order to quantify these losses, the ablation coefficient, /spl alpha/, and drag coefficient, C/sub d/, must be determined. These coefficients are estimated based on the pellet acceleration. The sensitivity of acceleration to /spl alpha/ and C/sub d/ has been calculated using the model. Once /spl alpha/ and C/sub d/ have been determined, their values are applied to the model to compute the appropriate current pulse width. An optimization program was written in LabVIEW software to carry out this procedure. This program was then integrated into the existing code used to operate the railgun system. Preliminary results obtained after test firing the gun indicate that the program computes reasonable values for /spl alpha/ and C/sub d/ and calculates realistic pulse widths.
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Acceleration of solid hydrogen pellet using augmented railgun for magnetic fusion Reactor Refueling
IEEE Transactions on Magnetics, 1995Co-Authors: J. Zhang, Kyekyoon Kim, T.l. KingAbstract:A 1.2 m long electromagnetic railgun with separate augmentation was designed, fabricated, and tested for the purpose of injecting hypervelocity hydrogen pellets into magnetic fusion devices for Refueling. A compact configuration of two pairs of coaxial rails insulated by thin Kapton films was employed. Two pulse-forming networks were used to separately control the duration, amplitude, and overlap of the current pulses. Copper sulphate resistors were employed as impedance-matching resistors and bank short resistors. The magnetic field inside the gun bore boosted by the high current on the gun augmentation rails, which in turn increased the J/spl times/B force without increasing the armature current, resulting in less ablation of the gun bore and pellet. Higher acceleration was achieved due to reduced inertial and viscous drag. Using a 1.2 m augmented railgun, hydrogen pellet velocities in excess of 2.5 km/s were achieved. Hydrogen pellet accelerations as high as 4.4/spl times/10/sup 6/ m/s/sup 2/ were achieved at a railgun current of 13.5 kA while the acceleration obtained on a conventional railgun was 2.2/spl times/10/sup 6/ m/s/sup 2/ at 14.1 kA. Computer simulations have been performed using the finite element code MSC/EMES to analyze the current density, magnetic field, Lorentz force, and inductance gradient of the conventional and augmented railguns. >
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Controls and diagnostics on a fuseless railgun for solid hydrogen pellet acceleration
IEEE Transactions on Magnetics, 1993Co-Authors: T.l. King, J. Zhang, R.g. Haywood, W.c. Manns, Kyekyoon KimAbstract:A two-stage railgun system has been built, incorporating several controls and diagnostics, some including unique features to account for the fact that the projectile is a frozen hydrogen pellet for fusion Reactor Refueling. A timing circuit has been developed to monitor projectile breech and muzzle velocities and to automatically trigger a sequence of events critical for effective plasma armature railgun operation. This circuit can initiate electrical breakdown of the propellant gas directly behind an incoming projectile, thus enabling fuseless operation. It also triggers a streak camera and a flashlamp for photographing the arc and the outgoing projectile, respectively. The automatic timing circuit is expandable and has been extended to incorporate a trigger for transaugmentation. The timing circuit is immune to mistriggering due to electromagnetic interference or fragmentation of the fragile hydrogen pellets. >
D.a. Gantt - One of the best experts on this subject based on the ideXlab platform.
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Fast Flux Test Facility final safety analysis report. Amendment 73
1993Co-Authors: D.a. GanttAbstract:This report provides Final Safety Analysis Report (FSAR) Amendment 73 for incorporation into the Fast Flux Test Facility (FFTR) FSAR set. This page change incorporates Engineering Change Notices (ECNs) issued subsequent to Amendment 72 and approved for incorparoration before May 6, 1993. These changes include: Chapter 3, design criteria structures, equipment, and systems; chapter 5B, Reactor coolant system; chapter 7, instrumentation and control systems; chapter 9, auxiliary systems; chapter 11, Reactor Refueling system; chapter 12, radiation protection and waste management; chapter 13, conduct of operations; chapter 17, technical specifications; chapter 20, FFTF criticality specifications; appendix C, local fuel failure events; and appendix Fl, operation at 680{degrees}F inlet temperature.
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Fast Flux Test Facility final safety analysis report. Amendment 72
1992Co-Authors: D.a. GanttAbstract:This document provides the Final Safety Analysis Report (FSAR) Amendment 72 for incorporation into the Fast Flux Test Facility (FFTF) FSAR set. This amendment change incorporates Engineering Change Notices issued subsequent to Amendment 71 and approved for incorporation before June 24, 1992. These include changes in: Chapter 2, Site Characteristics; Chapter 3, Design Criteria Structures, Equipment, and Systems; Chapter 5B, Reactor Coolant System; Chapter 7, Instrumentation and Control Systems; Chapter 8, Electrical Systems - The description of the Class 1E, 125 Vdc systems is updated for the higher capacity of the newly installed, replacement batteries; Chapter 9, Auxiliary Systems - The description of the inert cell NASA systems is corrected to list the correct number of spare sample points; Chapter 11, Reactor Refueling System; Chapter 12, Radiation Protection and Waste Management; Chapter 13, Conduct of Operations; Chapter 16, Quality Assurance; Chapter 17, Technical Specifications; Chapter 19, FFTF Fire Specifications for Fire Detection, Alarm, and Protection Systems; Chapter 20, FFTF Criticality Specifications; and Appendix B, Primary Piping Integrity Evaluation.
Qichen Feng - One of the best experts on this subject based on the ideXlab platform.
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Study of a transaugmented two-stage small circular-bore railgun for injection of hypervelocity hydrogen pellets as a fusion Reactor Refueling mechanism
IEEE Transactions on Magnetics, 1997Co-Authors: M.w. Tompkins, J. Zhang, M.a. Anderson, Qichen Feng, Kyekyoon KimAbstract:Injection of hypervelocity hydrogen pellets has become widely accepted as the most effective means of Refueling magnetically confined fusion Reactors. Pellet velocities on the order of 10 km/s are desired and hydrogen pellet erosion during acceleration must be minimized. It is important to maintain uniform bore surfaces during repetitive shots, implying that, if a railgun is to be used to accelerate the pellets, damage to the sidewalls and rails of the railgun due to local heating must be limited. In order to reduce the amount of power dissipated within the bore and increase the propulsive force generated by the plasma-arc armature while minimizing losses due to pellet, rail, and sidewall ablation, we have employed a magnetic field transaugmentation mechanism consisting of a two-turn pulsed electromagnet. The two-stage gun consists of a light-gas gun which accelerates a 4- to 5-mg pellet to a speed around 1.2 km/s and injects it into the plasma-arc armature railgun. Currently, we have achieved a final output velocity for a hydrogen pellet of 2.11 km/s with a time-averaged acceleration of 4850 km/s/sup 2/ using a 58-cm railgun pulsed with a peak rail current of 9.2 kA and 28.0 kA of transaugmentation current. This paper will present a description of our hydrogen-pellet-injector railgun system, a discussion of the data on hydrogen pellet acceleration, and projections for future systems.
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Development and implementation of a rail current optimization program
IEEE Transactions on Magnetics, 1997Co-Authors: T.l. King, Kyekyoon Kim, J. Zhang, M.w. Tompkins, M.a. Anderson, R. Dharamshi, Qichen FengAbstract:Efforts are underway to automate the operation of a railgun hydrogen pellet injector for fusion Reactor Refueling. A plasma armature is employed to avoid the friction produced by a sliding metal armature and, in particular, to prevent high-Z impurities from entering the tokamak. High currents are used to achieve high accelerations, resulting in high plasma temperatures. Consequently, the plasma armature ablates and accumulates material from the pellet and gun barrel. This increases inertial and viscous drag, lowering acceleration. A railgun model has been developed to compute the acceleration in the presence of these losses. The model suggests that, depending on the rail and insulator materials used, there is a point of diminishing returns. Namely, for a given current, there is an acceleration time beyond which little or no increase in pellet speed is produced. The optimal pulse width was determined by identifying the time at which the acceleration decreased to zero. In order to quantify these losses, the ablation coefficient, /spl alpha/, and drag coefficient, C/sub d/, must be determined. These coefficients are estimated based on the pellet acceleration. The sensitivity of acceleration to /spl alpha/ and C/sub d/ has been calculated using the model. Once /spl alpha/ and C/sub d/ have been determined, their values are applied to the model to compute the appropriate current pulse width. An optimization program was written in LabVIEW software to carry out this procedure. This program was then integrated into the existing code used to operate the railgun system. Preliminary results obtained after test firing the gun indicate that the program computes reasonable values for /spl alpha/ and C/sub d/ and calculates realistic pulse widths.
