The four neutral beam injectors built for Doublet III will be modified to reoptimize beam transmi... more The four neutral beam injectors built for Doublet III will be modified to reoptimize beam transmission into the Big Dee vessel. All beamline components will be remounted 90° to their original position in the cylindrical vacuum vessel. This will permit optimum alignment with the available port opening. While these modifications are being incorporated into the disassembled injectors, it is planned that improvements and upgrading features will be added at the least possible cost. The calorimeter will be replaced by two independently driven calorimeters, thus decoupling the operation of the two ion sources. The beam path is being opened up to accommodate a long pulse (cw) source and all beam absorbing surfaces are being increased in size to withstand up to 5 s of operation with heat fluxes up to 700 W/cm². By opening up the apertures along the beam trajectory, an increase in power transmission into the plasma of 33% is realized compared with the present Doublet III performance.
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Oct 1, 1981
In the Doublet III (D-III) neutral beam injectors, cast, rigid-epoxy insulators are joined to the... more In the Doublet III (D-III) neutral beam injectors, cast, rigid-epoxy insulators are joined to the AISI 304 stainless steel corona rings with semi-rigid epoxy adhesive. Selected mechanical properties of these materials were measured between 11/sup 0/C and 65/sup 0/C, well below the material temperature limits, to identify the trends and to confirm adequate mechanical strength for the insulators. Significant creep deformation was measured at 22/sup 0/C. Empirical relationships were developed to predict long term strain over a range of stress and temperature of design interest. Delayed failure was observed in bonded specimens at stress levels well below the ultimate strength. In order to protect the D-III neutral beam ion source epoxy from elevated temperature effects, a chill was installed in the cooling water circuit. Outgassing measurements of the insulator epoxy were made and found to be low and primarily H/sub 2/O.
IEEE Transactions on Applied Superconductivity, Jun 1, 2009
It is known that MgB 2-based strands may be used in fault current limiters as a low-cost alternat... more It is known that MgB 2-based strands may be used in fault current limiters as a low-cost alternative to high-temperature YBCO coated conductors. Numerical modeling of the ac limiting properties of MgB 2 strands with Kapton insulation and conduction cooling have been performed using a finite element method. Two 2D ac Poisson equations, one for calculating the electric field and one for determining the heat transfer were solved simultaneously with input parameters taken from experimental results. As boundary conditions, we took the full non-linear curve of the heat flux into a cryocooler cold head as well as heat radiation from the free surfaces of the wire. The influence of different values and durations of fault electric fields were studied and the maximum temperatures, limiting currents and recovery times were calculated. Obtained results may be useful for understanding the behavior of different kinds of MgB 2 multifilamentary wires under conditions encountered in fault current limiter devices.
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Aug 1, 1978
The Doublet III noncircular tokamak recently began operating at General Atomic Company. In order ... more The Doublet III noncircular tokamak recently began operating at General Atomic Company. In order to fully exploit its capabilities and to study new and exciting plasma physics regimes, a Neutral Beam Injector System is being constructed. Initially, a two beamline system will supply 7 MW of heat to the plasma. Ultimately the system will be expanded to inject approximately 20 MW of power. Each beamline will be equipped with two LBL-type rectangular ion sources with 10 cm x 40 cm extraction grids. These will accelerate hydrogen ions to 80 keV, and extracted beam currents in excess of 80 A per source are expected. This high energy beam is needed, together with near perpendicular injection into the torus, to penetrate the high density hydrogen plasmas (n(0) greater than 3 x 10/sup 14/ cm/sup -3/) expected in Doublet III.
7th Symposium on Engineering Problems of Fusion Research, Sep 1, 1977
A conceptual design has been developed for an upgradable ignition test reactor (UITR) as part of ... more A conceptual design has been developed for an upgradable ignition test reactor (UITR) as part of the ERDA-sponsored TNS program to identify the next major tokamak device beyond Doublet III and TFTR. This reactor, which is based on the doublet plasma concept, has a major radius of 4.2 m, a minor radius of 1.2 m, and a plasma height-to-width ratio of 2.7. The plasma is contained in a water-cooled vacuum vessel fabricated of Inconel 625. A 25 cm thick helium-cooled blanket made of 316 stainless steel is installed outboard of the plasma chamber. The field-shaping coil system, shielding system, toroidal field coils, and induction coil system are installed outside the blanket. In its ITR mode, the reactor operates in moderate length pulses (30 sec) with a duty factor of 0.1 (5 min cycles). For net power experimental power reactor (EPR) operating mode, the machine operates with 90 sec pulses and a duty factor of 0.78. While the UITR initially costs about 30% more than an ITR without upgrade capability, and additional costs are incurred when implementing the upgrade, the total program costs far less than the sum of separate ITR and EPR facilities.
MAGLEV'2006: The 19th International Conference on Magnetically Levitated Systems and Linear DrivesTransrapid International GmbH und Company KGMax Bogl Bauunternehmung GmbH und Company KGDeutsche Bahn AGIABG mbHNexans Deutschland GmbHDornier Consulting GmbH, Sep 1, 2006
Abstract Coefficient of friction and wear rate were determined under conditions of reciprocative ... more Abstract Coefficient of friction and wear rate were determined under conditions of reciprocative sliding in vacuum for a number of state-of-the-art hard coatings, including oxides, nitrides and carbides. These materials were tested in contact with one another and against the alloys Inconel 718 and Nitronic 60. For some selected conditions, similar tests were conducted in air to enable environmental influence to be assessed. The program also investigated cyclic compression loading of coated surfaces against uncoated Inconel 718. The results are reported and were used to select and qualify coating materials for limiter component applications that operate both in vacuum and in low pressure hydrogen at elevated temperature in the tokamak fusion test reactor.
Abstract Two kinds of plasma-related damage, spotty damage and wide area damage, have been photog... more Abstract Two kinds of plasma-related damage, spotty damage and wide area damage, have been photographically recognized on the TiC-coated surface of the new graphite primary limiter in Doublet III. TV and infrared-camera observations revealed the relationship of these damages to the plasma operations. The spotty damage was generated by a single runaway discharge. The runaway electron energy was deposited not only on the surface but also penetrated into the bulk graphite. Thermal analysis showed that runaway electron of 5–6 MeV penetrates into the limiter to approximately 1.5–2.0 cm. Wide area damage was caused by one or more successive discharges which exhibited rapid termination of the plasma current. In this case, the electron energy was deposited only on the limiter surface.
Replacement of the Doublet III vacuum vessel by a large dee-shaped vessel is now in progress. Mul... more Replacement of the Doublet III vacuum vessel by a large dee-shaped vessel is now in progress. Multisecond auxiliary heating will be needed to reach peak plasma parameters. Plans for modifying the existing neutral beam injection system to a 5 s capability and for a new, high power, long pulse ion cyclotron heating system are described.
Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366), 1999
An ogive shaped carbon-carbon composite (CCC) beamstop has been designed to replace the original ... more An ogive shaped carbon-carbon composite (CCC) beamstop has been designed to replace the original nickel ogive beam stop for the Low Energy Development Accelerator (LEDA) of the APT (Accelerator Production of Tritium) project. The nickel beamstop has been used for initial testing of the 6.7 MeV, 100 mA cw proton beam from the APT RFQ (Radio Frequency Quadrupole). Because of activation concerns, another beam stop is needed for future tests on the first module of the Coupled-Cavity Drift-Tube Linac (CCDTL), which will increase proton beam energy to 10.4 MeV. The CCC ogive has been integrated into the nickel structure as a direct replacement. The design and fabrication of the CCC ogive beamstop is presented with a review of the original nickel ogive design.
8th Symposium on Engineering Problems of Fusion Research, Mar 1, 1980
A simple condensing cryopanel has been designed for the Doublet III neutral beam test tank with a... more A simple condensing cryopanel has been designed for the Doublet III neutral beam test tank with a 320,000 liters per second pumping capacity for hydrogen. This maintains a vacuum in the test tank which simulates the Doublet III vessel, 1.3 x 10â»Â³ Pa (approx.10â»âµ torr). The hydrogen gas load comes from the beam striking the test tank calorimeter and amounts to about 7.2 torr liters per second. The cryopanel is cylindrical shaped with a liquid helium (LHe) surface that pumps through liquid nitrogen (LN) cooled aluminum chevrons located in squirrel-cage fashion around the inside surface of the cylinder. The LHe cooled surface is a smooth cylinder 2.09m in diameter by .69m long with LHe flowing in a approx. 1mm annular space between concentric cylinders. The chevrons which are not blackened are cooled from each end with LN flowing in ring manifolds that serve as the primary cryopanel structure. The LHe is force fed at 55.2 kPa remaining in the liquid phase through the panel. External heat exchanger capability permits use of helium at 3.8 to 4.2°K. Normal operating flow rate is 1.4 g/sec for a heat load expected to be 12.2 W total.
Long pulse physics questions have been raised for auxiliary heated plasma discharges in Tokamaks.... more Long pulse physics questions have been raised for auxiliary heated plasma discharges in Tokamaks. A one-second pulse encloses present experiments and is adequate for studying quasi-steady-state operation, whereas, a 5 to 10 second pulse may be required to examine impurity effects of plasma-wall interaction and current profile relaxation. In order to sustain heating in the multi-second pulse range, neutral beam devices must be capable of the same pulse durations. By upgrading the beam collimators and ion source components, the Doublet III neutral beam injectors can be made to operate with pulses up to 5 seconds in duration with the interpulse period extended to maintain approximately the same duty factor. The scope of the upgrading includes: (1) exchanging the accelerator section of the ion source with one having actively cooled tubular grids, and (2) removing or replacing collimators where necessary to stay below 600/sup 0/C peak temperature. An actively cooled ion dump is necessary for pulses substantially longer than 5 seconds. Effects of drift duct choking and induced eddy currents in the cryopanels were examined and found to have a negligible effect on operating the neutral beam injectors up to 5 second pulse duration.
The Doublet III neutral beam injectors consist of three separable spools two meters in diameter b... more The Doublet III neutral beam injectors consist of three separable spools two meters in diameter by four meters long overall when assembled. Contained within these spools are the neutralizers, ion dumps, deflecting magnet, calorimeter dumps, cryogenic panels and beam scraping collimators 3,7. To date three beamlines are in operation on Doublet III, and the beams have accumulated operating time of approximately 32 months, with the oldest having been in operation for 18 months. During this time operation of DIII with the neutral beam sources has demonstrated the following: 7.8 MW injected neutrals from three beamlines (6 sources), high ..beta.. (4.5%), and non-circular plasma shape. The sources have also exhibited a very reliable injected shot history 4, 5, 6, 8. Material failures encountered during the operation of DIII N.B. injectors and the solutions to these failures are described. Failures include cracking of the neutralizer exit collimator due to heating cycles, failure of cyropanel support rods due to cooling cycles, failure of the sliding drive of the moveable calorimeter due to friction.
tank has been designed f o r t e s t i n g the Doublet u t r a l Beam Injector which simulates th... more tank has been designed f o r t e s t i n g the Doublet u t r a l Beam Injector which simulates the entrance m r e conditions of the Doublet I11 vacuum vese cylindrical shape vacuum vessel ie the Sam? the neutral beam i n j e c t o r vessel. Contained a r e a cylindrical cryopanel, a ''Vee" shaped caler, and a retractable sample-holding device t o be r proof testing. The cryopanel has surface f o r pumping the hydrogen load created impingement on the calorimeter. A tank prw-.3 x 10-'-1. 3 x lom6 Pa
A new set of movable limiter blades has been designed for TFTR that will meet both the requiremen... more A new set of movable limiter blades has been designed for TFTR that will meet both the requirements of the 4 MW ohmic heated and the 33 MW neutral beam heated plasmas. This is accomplished with three limiter blades each having and elliptical shape along the toroidal direction. Heat flux levels are acceptable for both ohmic heated and pre-strong compression plasmas. The construction consists of graphite tiles attached to cooled backing plates. The tiles have an average thickness of approx. 4.7 cm and are drawn against the backing plate with spring loaded fasteners that are keyed into the graphite. The cooled backing plate provides the structure for resisting disruption and fault induced loads. A set of rollers attached to the top and bottom blades allow them to be expanded and closed in order to vary the plasma surface for scaling experiments. Water cooling lines penetrate only the mid-plane port cover/support plate in such a way as to avoid bolted water connections inside the vacuum boundary and at the same time allow blade movement. Both the upper and lower blades are attached to the mid-plane limiter blade through pivots. Pivot connections are protected against arcing with an alumina coating and a shunt bar strap. Remote handling is considered throughout the design.
Coatings applied to copper and graphite have been thermal. shock tested up to 7.5 kW/cm' for puls... more Coatings applied to copper and graphite have been thermal. shock tested up to 7.5 kW/cm' for pulses up to 1 set in length, using 10 keV electrons. Plated nickel, iron, gold, and a carbon coating applied with a glow discharge process on copper survived up to approximately the melting point of the copper without debonding. Plasma sprayed tungsten behaves abqut the same as plated coatings. Both ion vapor deposited carbon and plasma spray deposited boron carbide failed from brittle fracture at comparatively low power densities (4.5 kW/cm2 at 0.25 set and 0.1 set respectively). The results show that for thin coatings (At < 0.2 mm), failure occurs when the surface temperature exceeds either the melting point of the coating or the substrate. Only a laminated thermal insulating coating can stand off a significant temperature difference (> 500°C) but is subject to brittle failure at much lower heating rates than for uncoated material. Fatigue tests on the glow discharge deposited carbon and plasma sprayed tungsten showed no serious failures for 1000 cycles at > 3.7 kW/cm2 for 0.5 set pulses on the carbon coating and incipient failure on the tungsten coating.
A unique nuclear shield design for a high beta ignited tokamak has been completed. Maximum advant... more A unique nuclear shield design for a high beta ignited tokamak has been completed. Maximum advantage is taken of the shielding properties of the vacuum vessel and coil structures with the remaining space being filled with bulk shielding. The basic unit is an aluminum-bronze casting with integrally cast stainless steel coolant tubes. Each module is fitted for the particular zone around the vessel. The modules are sized to minimize the decay time of induced eddy currents and, for this reason, are insulated from one another. Lifting holes are castin as are offsets and alignment pins. Using vertical lifts, this permits easy removal for access to components buried in the shielded zones.
The four neutral beam injectors built for Doublet III will be modified to reoptimize beam transmi... more The four neutral beam injectors built for Doublet III will be modified to reoptimize beam transmission into the Big Dee vessel. All beamline components will be remounted 90° to their original position in the cylindrical vacuum vessel. This will permit optimum alignment with the available port opening. While these modifications are being incorporated into the disassembled injectors, it is planned that improvements and upgrading features will be added at the least possible cost. The calorimeter will be replaced by two independently driven calorimeters, thus decoupling the operation of the two ion sources. The beam path is being opened up to accommodate a long pulse (cw) source and all beam absorbing surfaces are being increased in size to withstand up to 5 s of operation with heat fluxes up to 700 W/cm². By opening up the apertures along the beam trajectory, an increase in power transmission into the plasma of 33% is realized compared with the present Doublet III performance.
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Oct 1, 1981
In the Doublet III (D-III) neutral beam injectors, cast, rigid-epoxy insulators are joined to the... more In the Doublet III (D-III) neutral beam injectors, cast, rigid-epoxy insulators are joined to the AISI 304 stainless steel corona rings with semi-rigid epoxy adhesive. Selected mechanical properties of these materials were measured between 11/sup 0/C and 65/sup 0/C, well below the material temperature limits, to identify the trends and to confirm adequate mechanical strength for the insulators. Significant creep deformation was measured at 22/sup 0/C. Empirical relationships were developed to predict long term strain over a range of stress and temperature of design interest. Delayed failure was observed in bonded specimens at stress levels well below the ultimate strength. In order to protect the D-III neutral beam ion source epoxy from elevated temperature effects, a chill was installed in the cooling water circuit. Outgassing measurements of the insulator epoxy were made and found to be low and primarily H/sub 2/O.
IEEE Transactions on Applied Superconductivity, Jun 1, 2009
It is known that MgB 2-based strands may be used in fault current limiters as a low-cost alternat... more It is known that MgB 2-based strands may be used in fault current limiters as a low-cost alternative to high-temperature YBCO coated conductors. Numerical modeling of the ac limiting properties of MgB 2 strands with Kapton insulation and conduction cooling have been performed using a finite element method. Two 2D ac Poisson equations, one for calculating the electric field and one for determining the heat transfer were solved simultaneously with input parameters taken from experimental results. As boundary conditions, we took the full non-linear curve of the heat flux into a cryocooler cold head as well as heat radiation from the free surfaces of the wire. The influence of different values and durations of fault electric fields were studied and the maximum temperatures, limiting currents and recovery times were calculated. Obtained results may be useful for understanding the behavior of different kinds of MgB 2 multifilamentary wires under conditions encountered in fault current limiter devices.
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Aug 1, 1978
The Doublet III noncircular tokamak recently began operating at General Atomic Company. In order ... more The Doublet III noncircular tokamak recently began operating at General Atomic Company. In order to fully exploit its capabilities and to study new and exciting plasma physics regimes, a Neutral Beam Injector System is being constructed. Initially, a two beamline system will supply 7 MW of heat to the plasma. Ultimately the system will be expanded to inject approximately 20 MW of power. Each beamline will be equipped with two LBL-type rectangular ion sources with 10 cm x 40 cm extraction grids. These will accelerate hydrogen ions to 80 keV, and extracted beam currents in excess of 80 A per source are expected. This high energy beam is needed, together with near perpendicular injection into the torus, to penetrate the high density hydrogen plasmas (n(0) greater than 3 x 10/sup 14/ cm/sup -3/) expected in Doublet III.
7th Symposium on Engineering Problems of Fusion Research, Sep 1, 1977
A conceptual design has been developed for an upgradable ignition test reactor (UITR) as part of ... more A conceptual design has been developed for an upgradable ignition test reactor (UITR) as part of the ERDA-sponsored TNS program to identify the next major tokamak device beyond Doublet III and TFTR. This reactor, which is based on the doublet plasma concept, has a major radius of 4.2 m, a minor radius of 1.2 m, and a plasma height-to-width ratio of 2.7. The plasma is contained in a water-cooled vacuum vessel fabricated of Inconel 625. A 25 cm thick helium-cooled blanket made of 316 stainless steel is installed outboard of the plasma chamber. The field-shaping coil system, shielding system, toroidal field coils, and induction coil system are installed outside the blanket. In its ITR mode, the reactor operates in moderate length pulses (30 sec) with a duty factor of 0.1 (5 min cycles). For net power experimental power reactor (EPR) operating mode, the machine operates with 90 sec pulses and a duty factor of 0.78. While the UITR initially costs about 30% more than an ITR without upgrade capability, and additional costs are incurred when implementing the upgrade, the total program costs far less than the sum of separate ITR and EPR facilities.
MAGLEV'2006: The 19th International Conference on Magnetically Levitated Systems and Linear DrivesTransrapid International GmbH und Company KGMax Bogl Bauunternehmung GmbH und Company KGDeutsche Bahn AGIABG mbHNexans Deutschland GmbHDornier Consulting GmbH, Sep 1, 2006
Abstract Coefficient of friction and wear rate were determined under conditions of reciprocative ... more Abstract Coefficient of friction and wear rate were determined under conditions of reciprocative sliding in vacuum for a number of state-of-the-art hard coatings, including oxides, nitrides and carbides. These materials were tested in contact with one another and against the alloys Inconel 718 and Nitronic 60. For some selected conditions, similar tests were conducted in air to enable environmental influence to be assessed. The program also investigated cyclic compression loading of coated surfaces against uncoated Inconel 718. The results are reported and were used to select and qualify coating materials for limiter component applications that operate both in vacuum and in low pressure hydrogen at elevated temperature in the tokamak fusion test reactor.
Abstract Two kinds of plasma-related damage, spotty damage and wide area damage, have been photog... more Abstract Two kinds of plasma-related damage, spotty damage and wide area damage, have been photographically recognized on the TiC-coated surface of the new graphite primary limiter in Doublet III. TV and infrared-camera observations revealed the relationship of these damages to the plasma operations. The spotty damage was generated by a single runaway discharge. The runaway electron energy was deposited not only on the surface but also penetrated into the bulk graphite. Thermal analysis showed that runaway electron of 5–6 MeV penetrates into the limiter to approximately 1.5–2.0 cm. Wide area damage was caused by one or more successive discharges which exhibited rapid termination of the plasma current. In this case, the electron energy was deposited only on the limiter surface.
Replacement of the Doublet III vacuum vessel by a large dee-shaped vessel is now in progress. Mul... more Replacement of the Doublet III vacuum vessel by a large dee-shaped vessel is now in progress. Multisecond auxiliary heating will be needed to reach peak plasma parameters. Plans for modifying the existing neutral beam injection system to a 5 s capability and for a new, high power, long pulse ion cyclotron heating system are described.
Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366), 1999
An ogive shaped carbon-carbon composite (CCC) beamstop has been designed to replace the original ... more An ogive shaped carbon-carbon composite (CCC) beamstop has been designed to replace the original nickel ogive beam stop for the Low Energy Development Accelerator (LEDA) of the APT (Accelerator Production of Tritium) project. The nickel beamstop has been used for initial testing of the 6.7 MeV, 100 mA cw proton beam from the APT RFQ (Radio Frequency Quadrupole). Because of activation concerns, another beam stop is needed for future tests on the first module of the Coupled-Cavity Drift-Tube Linac (CCDTL), which will increase proton beam energy to 10.4 MeV. The CCC ogive has been integrated into the nickel structure as a direct replacement. The design and fabrication of the CCC ogive beamstop is presented with a review of the original nickel ogive design.
8th Symposium on Engineering Problems of Fusion Research, Mar 1, 1980
A simple condensing cryopanel has been designed for the Doublet III neutral beam test tank with a... more A simple condensing cryopanel has been designed for the Doublet III neutral beam test tank with a 320,000 liters per second pumping capacity for hydrogen. This maintains a vacuum in the test tank which simulates the Doublet III vessel, 1.3 x 10â»Â³ Pa (approx.10â»âµ torr). The hydrogen gas load comes from the beam striking the test tank calorimeter and amounts to about 7.2 torr liters per second. The cryopanel is cylindrical shaped with a liquid helium (LHe) surface that pumps through liquid nitrogen (LN) cooled aluminum chevrons located in squirrel-cage fashion around the inside surface of the cylinder. The LHe cooled surface is a smooth cylinder 2.09m in diameter by .69m long with LHe flowing in a approx. 1mm annular space between concentric cylinders. The chevrons which are not blackened are cooled from each end with LN flowing in ring manifolds that serve as the primary cryopanel structure. The LHe is force fed at 55.2 kPa remaining in the liquid phase through the panel. External heat exchanger capability permits use of helium at 3.8 to 4.2°K. Normal operating flow rate is 1.4 g/sec for a heat load expected to be 12.2 W total.
Long pulse physics questions have been raised for auxiliary heated plasma discharges in Tokamaks.... more Long pulse physics questions have been raised for auxiliary heated plasma discharges in Tokamaks. A one-second pulse encloses present experiments and is adequate for studying quasi-steady-state operation, whereas, a 5 to 10 second pulse may be required to examine impurity effects of plasma-wall interaction and current profile relaxation. In order to sustain heating in the multi-second pulse range, neutral beam devices must be capable of the same pulse durations. By upgrading the beam collimators and ion source components, the Doublet III neutral beam injectors can be made to operate with pulses up to 5 seconds in duration with the interpulse period extended to maintain approximately the same duty factor. The scope of the upgrading includes: (1) exchanging the accelerator section of the ion source with one having actively cooled tubular grids, and (2) removing or replacing collimators where necessary to stay below 600/sup 0/C peak temperature. An actively cooled ion dump is necessary for pulses substantially longer than 5 seconds. Effects of drift duct choking and induced eddy currents in the cryopanels were examined and found to have a negligible effect on operating the neutral beam injectors up to 5 second pulse duration.
The Doublet III neutral beam injectors consist of three separable spools two meters in diameter b... more The Doublet III neutral beam injectors consist of three separable spools two meters in diameter by four meters long overall when assembled. Contained within these spools are the neutralizers, ion dumps, deflecting magnet, calorimeter dumps, cryogenic panels and beam scraping collimators 3,7. To date three beamlines are in operation on Doublet III, and the beams have accumulated operating time of approximately 32 months, with the oldest having been in operation for 18 months. During this time operation of DIII with the neutral beam sources has demonstrated the following: 7.8 MW injected neutrals from three beamlines (6 sources), high ..beta.. (4.5%), and non-circular plasma shape. The sources have also exhibited a very reliable injected shot history 4, 5, 6, 8. Material failures encountered during the operation of DIII N.B. injectors and the solutions to these failures are described. Failures include cracking of the neutralizer exit collimator due to heating cycles, failure of cyropanel support rods due to cooling cycles, failure of the sliding drive of the moveable calorimeter due to friction.
tank has been designed f o r t e s t i n g the Doublet u t r a l Beam Injector which simulates th... more tank has been designed f o r t e s t i n g the Doublet u t r a l Beam Injector which simulates the entrance m r e conditions of the Doublet I11 vacuum vese cylindrical shape vacuum vessel ie the Sam? the neutral beam i n j e c t o r vessel. Contained a r e a cylindrical cryopanel, a ''Vee" shaped caler, and a retractable sample-holding device t o be r proof testing. The cryopanel has surface f o r pumping the hydrogen load created impingement on the calorimeter. A tank prw-.3 x 10-'-1. 3 x lom6 Pa
A new set of movable limiter blades has been designed for TFTR that will meet both the requiremen... more A new set of movable limiter blades has been designed for TFTR that will meet both the requirements of the 4 MW ohmic heated and the 33 MW neutral beam heated plasmas. This is accomplished with three limiter blades each having and elliptical shape along the toroidal direction. Heat flux levels are acceptable for both ohmic heated and pre-strong compression plasmas. The construction consists of graphite tiles attached to cooled backing plates. The tiles have an average thickness of approx. 4.7 cm and are drawn against the backing plate with spring loaded fasteners that are keyed into the graphite. The cooled backing plate provides the structure for resisting disruption and fault induced loads. A set of rollers attached to the top and bottom blades allow them to be expanded and closed in order to vary the plasma surface for scaling experiments. Water cooling lines penetrate only the mid-plane port cover/support plate in such a way as to avoid bolted water connections inside the vacuum boundary and at the same time allow blade movement. Both the upper and lower blades are attached to the mid-plane limiter blade through pivots. Pivot connections are protected against arcing with an alumina coating and a shunt bar strap. Remote handling is considered throughout the design.
Coatings applied to copper and graphite have been thermal. shock tested up to 7.5 kW/cm' for puls... more Coatings applied to copper and graphite have been thermal. shock tested up to 7.5 kW/cm' for pulses up to 1 set in length, using 10 keV electrons. Plated nickel, iron, gold, and a carbon coating applied with a glow discharge process on copper survived up to approximately the melting point of the copper without debonding. Plasma sprayed tungsten behaves abqut the same as plated coatings. Both ion vapor deposited carbon and plasma spray deposited boron carbide failed from brittle fracture at comparatively low power densities (4.5 kW/cm2 at 0.25 set and 0.1 set respectively). The results show that for thin coatings (At < 0.2 mm), failure occurs when the surface temperature exceeds either the melting point of the coating or the substrate. Only a laminated thermal insulating coating can stand off a significant temperature difference (> 500°C) but is subject to brittle failure at much lower heating rates than for uncoated material. Fatigue tests on the glow discharge deposited carbon and plasma sprayed tungsten showed no serious failures for 1000 cycles at > 3.7 kW/cm2 for 0.5 set pulses on the carbon coating and incipient failure on the tungsten coating.
A unique nuclear shield design for a high beta ignited tokamak has been completed. Maximum advant... more A unique nuclear shield design for a high beta ignited tokamak has been completed. Maximum advantage is taken of the shielding properties of the vacuum vessel and coil structures with the remaining space being filled with bulk shielding. The basic unit is an aluminum-bronze casting with integrally cast stainless steel coolant tubes. Each module is fitted for the particular zone around the vessel. The modules are sized to minimize the decay time of induced eddy currents and, for this reason, are insulated from one another. Lifting holes are castin as are offsets and alignment pins. Using vertical lifts, this permits easy removal for access to components buried in the shielded zones.
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