Browsing by Subject "IGNITEX"

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Description of Pulsed Homopolar Generator Technologies for a Fusion Ignition Experiment
(American Nuclear Society, 1991-05) Walls, W.A.; Gully, J.H.; Weldon, W.F.; Woodson, H.H.
The concept for a single-turn tokamak experiment IGNITEX 1 makes possible the realization of a controlled, self-sustained fusion reaction in the near term with relative simplicity and low cost. The IGNITEX tokamak utilizes low-impedance toroidal field (TF) and poloidal field (PF) magnet systems which induce the high-level fields and currents required for fusion ignition. These magnet systems require power supplies that can meet strict operational conditions. Homopolar generators (HPGs) are well suited for operation of a single-turn tokamak because they are inherently high current, low voltage machines which can kinetically store all the energy required for a pulsed discharge. The energy storage is accomplished in a compact manner by using high speed composite flywheel technology and provides the added advantage of keeping electrical grid power requirements very low. Finally, since HPGs are simple de machines, their cost is low and rectifier systems are not necessary. In this paper, the HPG technologies to be utilized in a fusion ignition experiment are described. The various components, materials, and design considerations for the HPG current-collection systems are reviewed, including rotor slip ring, brushes, and actuators. Design, fabrication, and assembly techniques for the lightweight, composite, energy-storage flywheel are given. The status of these HPG technologies relative to IGNITEX power supply requirements are reviewed. The modes of operation of the TF and PF magnet systems are analyzed. Questions of reliability of operation, maintenance, and cost evaluation are also addressed. Finally, the construction and testing of a full-scale prototype IGNITEX HPG power supply module is proposed.
Design of a homopolar generator power supply system for the IGNITEX experiment
(1987-10) Walls, W.A.; Weldon, W.F; Woodson, H.H; Driga, M.D; Gully, J.H.
Pulsed homopolar generator (HPG) power supplies are well suited for driving the single-turn coils of the Ignitex fusion experiment[1] because they are inherently low voltage DC machines capable of high output currents. Basic operation of an HPG is voltage generation across a conductive disk or drum rotating in 1 steady magnetic field. An electrical load is connected across the generated voltage through two sets of sliding electrical contacts or brushes. As pulsed energy stores, kinetic energy of the disk (rotor) is converted into an electrical pulse by the interaction of the armature current with the excitation field. For the Ignitex experiment, a total of 14.6 GJ are required for the 10 s total pulse length, 12 GJ for the toroidal field excitation and 2.6 GJ for the poloidal field coils. The toroidal field supply is composed of 12, one GJ modules each rated at 12.5 MA output current and an open circuit voltage of 30 V. Five generators are used to drive the poloidal fieldcoils. They have stored energies between 40 and 700 MJ each and output ratings from 8 HA at 60 V to 750 kA at 150 v. Pulse shaping for all the generators is accomplished by actively controlling the HPG excitation field during the discharge. Operation of the poloidal field system uses an underdamped coil/generator circuit to >ring> the total current from 22 to -15.7 MA. The Ignitex HPG power supplies use a combination of iron-core machine technology and relatively new composite energy storage flywheel developments. Ironcore HPG technology provides adequate voltage generation and extensively developed current collection techniques which can be used. For the 1 GJ machines, the brushes operate at a 200 11/s slip speed and a current density of 1.25 kA/cm2. These are below state of the art performance levels for pulsed HPGs. Composite flywheel technology allows the 1 GJ modules to be built compact enough to be placed close to the Ignitex coil system and provides a significant cost savings over steel flywheel energy storage. Flywheels for the generators are fiberglass/epoxy composite rims with 3.75 m outer diameters and 1 m axial lengths.
Design of a Homopolar Generator Power Supply System for the Ignitex Experiment
(1989-10) Walls, W. A.; Gully, J.H; Weldon, W.F; Woodson, H.H.
The fusion ignition experiment IGNITEX [l] is based on the concept of a tokomak operating at very high magnetic fields. The toroidal field (TF) and the poloidal field (PF) magnet systems are made of single turn coils which provide the capability to produce very high magnetic fields (20 T) and induce very high plasma currents (12 MA). These magnet systems have very low impedances which impose rather strict constraints on the power supply system in terms of energy (12 GJ), current (150 MA), voltage (10 V), and pulse length (10 V). In addition, the power supply system should comply with the general IGNITEX emphasis on simplicity, reliability, and low cost. A set of homopolar generators (HPGs) can meet these requirements. The characteristics of the HPGs for the proposed TF and PF magnet systems, materials, fabrication procedures, and technologies to be employed in the construction of the generators are described. A preliminary mode of operation for the generators and associated circuit schemes are given. Auxiliary systems needed for operation of the system are described and estimates for the grid power requirements for the IGNITEX facility are obtained and analyzed. A modular approach for the design and construction of small and large versions of the IGNITEX experiment is presented. Although no generator exists that meets the requirements of the IGNITEX experiment, the technologies needed for it have been demonstrated. The construction and operation of a full size, 1 GJ, HPG module for the IGNITEX demonstration baa been proposed. The technological basis, objectives, schedule, and coats of the demonstration program are presented. This represents the second element of the Ignition Technology Demonstration (ITD) program associated with the IGNITEX project (the first element of the ITD program is presented in companion papers by M. Werst, [2] and K. T. Hsieh, [3] at this Symposium).
Design of a Prototype 20 Tesla, Single Turn, Toroidal Field Coil for the Fusion Ignition Experiment (IGNITEX)
(1989-10) Werst, M. D.; Brunson, G. W; Hsieh, K. T; Sledge, R. L; Weldon, W. F.
The electromagnetic design of the fusion ignition experiment (IGNITEX)[l] combines unconventional pulsed power and magnet technologies. The experiment should produce an ignited plasma in a relatively simple and low cost way.[2,3) The proposed IGNITEX toroidal field (TF) coil is a 20 T, single tum, toroidal magnet powered by homopolar generators (HPGs). In order to demonstrate the magnet technologies, the Center for Electromechanics at The University of Texas at Austin (CEM-UT) is building a 0.06 scale prototype toroidal field coil to be powered by an existing 60 MJ, 9-MA, HPG power supply. This element of the Ignition Technology Demonstration (ITD) program is funded by the Texas Advanced Technology Program and the Texas Atomic Energy Research Foundation.
Electromechanical Analysis of a Prototype 20 Tesla, Single Turn Toroidal Field Coil for Ignitex
(1989-10) Hsieh, K. T.; Driga, M. D; Weldon, W. F; Werst, M. D.
The fusion ignition experiment (IGNITEX) device is a single turn coil tokamak designed to produce and control an ignited plasma using ohmic heating alone. The proposed high strength toroidal field (TF) magnet operates at a magnetic field onaxis of 20 T, using homopolar generators (HPGs). In this paper, the electromechanical analysis of a scaled down prototype (0.06 scale in linear dimensions) of the IGNITEX TF' magnet is presented. The objective of the Ignition Technology Demonstration (ITD) program is to design, build, and test the operation of a single turn, 20 T, TF coil, powered by an existing HPG power supply system. Unlike conventional TF coils that use multiple turns of the conductor, the single turn coil eliminates the need for tum-to-turn insulation; therefore, better utilizing the available area for stress and thermal management. Precooling of' the coil to liquid-nitrogen temperature permits the magnet to operate in a wider temperature regime without exceeding material properties. Scaling relationships presented in this paper show that temperatures and stresses of a scaled-down coil and their relative distribution will approximate predicted levels of the full-scale IGNITEX device. A finite element program (TEXCOR) which solves a set of coupled electrical circuit, magnetic diffusion, and thermal diffusion equations with temperature dependent properties was developed. TEXCOR provides temperatures and magnetic body force densities for stress analysis of the magnet structure. The effect of flatness tolerance stackups in the TF coil assembly is discussed and methods to characterize and minimize the negative effect of nonideal conditions are given. Generator fault scenarios are also addressed. The analysis results presented in this paper show the feasibility of a single turn, 20 T, TF magnet powered by HPGs. This work is sponsored by the Texas Advanced Technology Program and the Texas Atomic Energy Research Foundation.
Electromechanical Analysis of the Technology Demonstrator for the Ignitex Fusion Device
(1989-03) Driga, M. D.; Hsieh, K. T.; Weldon, W. F.; Werst, M. D.
The Texas Ignition Experiment (IGNITEX) device is a single turn coil tokamak designed to produce and control an ignited plasma using ohmic heating alone. The proposed high strength magnet system operates at a magnetic field on-axis of 20 T, using homopolar generators (HPGs), which meet the power supply requirements (150 MA, 10 V) inexpensively. In this paper, the electromechanical analysis of a scaled down prototype (1/10 scale in linear dimensions) of the IGNITEX toroidal field (TF) magnet is presented. The primary goal of the IGNITEX Technology Demonstrator (ITD) is to prove the operation of a single turn, 20 T, toroidal field coil powered by a homopolar generator power supply system of 60 MJ, 9 MA, current operating at the Center for Electromechanics. The University of Texas at Austin (CEM-UT). In order to simulate the actual operating conditions of the full-scale device, the ITD coil will be precooled at liquid nitrogen temperature and driven by the six homopolar generators in parallel. Scaling relationships have shown that electromagnetic loading mechanical and thermal loading of the coil and their relative distribution will approximate well predicted levels of the full-scale IGNITEX device.
Electromechanical and Thermomechanical Stress Analysis of the Toroidal Field Magnet System in Single Turn Ignition Tokamaks
(American Nuclear Society, 1991-05) Hsieh, K.T.; Weldon, W.F.; Werst, M. D.; Montalvo, E.; Carrera, R.
The Texas fusion ignition experiment (IGNITEX) device is a 20 T single turn coil tokamak designed to produce and control an ignited plasma using ohmic heating alone. As a baseline design, IGNITEX has a 1.5 m major radius and operates at a toroidal field (TF) of 20 T on-axis. The small version of IGNITEX (R = 1.2 m) represents the smallest, low cost experiment that can produce fusion ignition under the saturated Neo-Alcator energy confinement scaling. The large version of IGNITEX (R = 2.1 m) represents the smallest experiment that can produce fusion ignition using the most pessimistic extrapolation of the Goldston scaling in L-mode. The Ignition Technology Demonstration (ITD) program was initiated to design, build, and test the operation of a single turn, 20 T, TF coil powered by an existing 9 MA, HPG power supply system. The ITD TF coil is a 0.06 scale of the IGNITEX and is now operating at the Center for Electromechanics at The University of Texas at Austin (CEM-UT). Data from the ITD experiment is used to confirm the complex computer model utilized for the IGNITEX design and analysis. In this paper, feasibility of the TF magnets is evaluated based on the electromechanical and thermomechanical considerations.
Fusion Ignition Experiment
(1986-10) Carrera, R.; Montalvo, E; Weldon, W. F; Woodson, H. H; Gully, J. H; Walls, W. A; Driga, M. D; Wu, A. Y; Hsieh, K. T.
Fusion Ignition Experiment (IGNITEX)
(1988-04) Carrera, R.; Driga, M. D; Gully, J. H; Hallock, G; Hertel, N; Hsieh, K. T; Walls, W. A; Weldon, W. F; Woodson, H. H; Wu, A. Y; Montalvo, E; Ordonez, C; et. al.
Fusion Ignition Experiment (IGNITEX)
(1987-04) Carrera, R.; Driga, M. D; Gully, J. H; Hsieh, K. T; Montalvo, E; Ordonez, C; Walls, W. A; Weldon, W. F; Woodson, H. H; Wu, A. Y; Rosenbluth, M. N.
Fusion Ignition Experiment (IGNITEX)
(1987-10) Carrera, R.; Driga, M. D; Gully, J. H; Hsieh, K. T; Montalvo, E; Ordonez, C; Rosenbluth, M. N; Walls, W. A; Weldon, W. F; Woodson, H. H.
Fusion Ignition Experiment (IGNITEX)
(1987-10) Carrera, R.; Driga, M. D; Gully, J. H; Hsieh, K. T; Montalvo, E; Ordonez, C; Walls, W. A; Weldon, W. F; Woodson, H. H; Wu, A. Y; Rosenbluth, M; Van Dam, J.
Fusion Testing Device
(1988-04) Carrera, R.; Driga, M. D; Gully, J. H; Hsieh, K. T; Montalvo, E; Ordonez, C; Rosenbluth, M; Walls, W. A; Weldon, W. F; Woodson, H. H.
A recently proposed fusion testing device called IGNITEX is described in this paper. The original idea was recently proposed by M.N. Rosenbluth, W.A. Weldon, and H.H. Woodson. The bases for the concept are B. Coppi's ideas for a compact thermonuclear experiment and technological progress in high-current pulsed-power systems. The concept utilizes a single-turn-coil tokamak to produce a 20 Tesla magnetic field and induce plasma currents in excess of 12 Megamperes which beat the plasma ohmically to thermonuclear temperatures. The IGNITEX experiment can produce a self-sustained fusion reaction and a stable ignited phase of the plasma discharge. Low-cost unconventional fusion technologies based on single-turn coils and homopolar generators will be employed. Low-voltage operation will minimize problems of insulation degradation and increase the strength of the magnet system. The neutron wall load during ignition will be high enough to be relevant to the design of future fusion systems. Machine activation problems will be addressed with a close shielding of the device. Diagnostic equipment will be located outside of the primary shielding, in a large experimental hall. A simple tritium system will provide the fuel to the device. Remote maintenance and repair of in-vessel components will be utilized. The compactness, the simplicity of design and the unconventional magnet and power supply technologies of IGNITEX make the basic cost or construction of the experiment relatively low.
High Current Transmission and Switching System for a Prototype, 20 Tesla, Toroidal Magnet
(1991-09) Sledge, R.L.; Hsieh, K.T; Weldon, W.F; Werst, M.D.
The Ignition Technology Demonstration (ITD) is a 0.06 scale prototype toroidal field magnet of the proposed full-scale IGNITEX (Ignition Experiment) tokamak. The goal of ITD is to achieve an on-axis magnetic confinement field of 20 T while demonstrating the magnet's ability to withstand high magnetic and thermal stresses [1,2]. To accomplish this task, a peak current of 9 MA must be transferred from six balanced homopolar generator (HPG)/busbar circuits to the liquid nitrogen (LN2) cooled magnet. HPGs are well suited for operation of single-turn coils because they are inherently high current, low voltage machines which can inertially store the energy required for a pulsed discharge. To date the system has delivered pulses of up to 8.14 MA to the toroidal magnet, producing an onaxis field of 18.1 T. In order to properly synchronize current transfer, an explosive closing switch is employed for each of the six independent HPG/busbar circuits. The switches operate by explosively driving a scalloped copper ring into a tapered annular gap made up of two copper alloy rings. With a jitter time of 10 μs, parallel circuit synchronization is better than 0.03% relative to the current rise time. The excellent performance of the switches during discharges of up to 8.14 MA is attributed to several design features which assure proper current distribution. Busbar design considerations have included electromagnetic loading, thermal gradients and magnet preloading effects. The switches and busbars have successfully operated at 82% of their rated action of 1.24 x 1011A2s per switch. Description of the ITD busbar/switching system, design improvements, and operational experience are presented.
Homopolar Generator Powered High Field Magnet Experiment for the Ignitex Fusion Device
(IEEE, 1989-06) Werst, M. D.; Brunson, G. W; Driga, M. D; Hsieh, K. T; Sledge, R. L; Weldon, W. F; Woodson, H. H.
The design of a scaled down prototype of the IGNITEX (Texas Ignition Experiment) toroidal field (TF) magnet is discussed. The IGNITEX concept is a single-tum tokamak designed to produce and control an ignited plasma with ohmic heating alone [l,2]. The objective of the IGNITEX Technology Demonstrator (ITD) is to design, fabricate and test the operation of a single turn, 20 tesla, toroidal field coil powered by a homopolar generator (HPG) power supply. An existing 60 MJ, 9MA homopolar power supply located at the Center for Electromechanics at The University of Texas at Austin (CEM-UT) will be used to drive the experiment [3]. Test results from the ITD program will validate the technology required to generate a 20 tesla, toroidal magnetic field in the necessary geometry to produce fusion by ohmic heating alone.
Magnetic System for the Ignitex Fusion Ignition Experiment
(1987-10) Driga, M.D.; Weldon, W.F; Woodson, H.H; Walls, W.A; Hsieh, K.T.
Controlled D-T fusion in a tokamak device by ohmic heating alone can be realized with toroidal confinement fields between 15 and 20 T and plasma currents in the 12- to 15-MA range. These conditions are achieved in the IGNITEX concept [1,2) by using a single turn toroidal field coil designed for 20-T operation and a set of five, single turn poloidal field coil pairs located within the plasma bore of the 1.5 m major radius machine (0.5 m minor radius). Total pulse length for the experiment is 10 s, including a 5 s flat-top period. A single-turn configuration for the toroidal field coil was adopted to maximize load-carrying ability and virtually eliminate insulation problems. Peak current for 20-T operation is 150 MA which results in an average inner leg current density of 57 MA/m2, a relatively low value for the field produced. Support of the toroidal field coil includes axial preloading of the inner leg to a 469 MPa compressive stress with an externa 1 hydraulic press structure, a 234 MPa radial compressive preload applied at the top and bottom of the coil by two thermally fitted steel rings, and a 0.8 m diameter compression bar located in the coil central bore. The coil itself is housed in a cryostat for precooling to liquid nitrogen temperature to extend the usable temperature excursion. Time dependent finite element analysis of the single-turn coil indicates that a maximum von Mises stress of 531 MPa will occur in the inner leg region. The analysis also includes time evolution of temperature and current distribution within the coil as well as calculation of energy requirements. Peak temperature after the 10-s pulse will be less than 100°c. A dispersion strengthened copper alloy has been selected as the toroidal coil material for its excel lent combination of yield strength and conductivity, which are 582 MPa and 92% IACS, respectively. The material exhibits a high fatigue limit of 207 MPa. To demonstrate the operation of the single-turn coil at the 20-T level, a 1/6th scaled prototype is proposed using an existing 60 MJ, 9 MA six module hompolar generator (HPG) power supply located at the Center for Electromechanics at The University of Texas at Austin (CEM-UT).
Monolithic Coil Tokamak Ignition Experiment (IGNITEX)
(1986-04) Carrera, R.; Montalvo, E; Weldon, W.F; Woodson, H.H; Gully, J.H; Walls, W.A; Driga, M.D; Wu, A.Y; Hsieh, K.T.
Optimization Studies in IGNITEX
(1993-10) Ingram, S.K.
In the existing budgetary environment, low-cost, high-payoff fusion experiments are increasingly attractive. IGNITEX, a homopolar generator powered single-turn tokamak, has the potential to achieve ignition at relatively low cost. A 60 MJ homopolar generator facility (with an easy upgrade path to 90 MJ) is in place at CEM-UT. Using this facility, CEM-UT researchers have produced a 20 T on-axis magnetic field in a 1/16 scale IGNITEX prototype. This paper presents the results of optimization studies conducted to determine the lowest-cost homopolar generator facility which can power an IGNITEX prototype of any chosen scale operating at 20 T on-axis.