E.O. Ballard

The Atlas project-a new pulsed power facility for high energy density physics experiments

Atlas is a facility being designed at Los Alamos National Laboratory (LANL) to perform high-energy-density experiments in support of weapon physics and basic research programs. It is designed to be an international user facility, providing experimental opportunities to researchers from national laboratories and academic institutions. For hydrodynamic experiments, it will be capable of achieving a pressure exceeding 30 Mbar in a several cubic centimeter volume. With the development of a suitable opening switch, it will be capable of producing more than 3 MJ of soft X-rays. The capacitor bank design consists of a 36 MJ array of 240 kV Marx modules. The system is designed to deliver a peak current of 45-50 MA with a 4-5-/spl mu/s rise time. The Marx modules are designed to be reconfigured to a 480-kV configuration for opening switch development. The capacitor bank is resistively damped to limit fault currents and capacitor voltage reversal. An experimental program for testing and certifying prototype components is currently under way. The capacitor bank design contains 300 closing switches. These switches are a modified version of a railgap switch originally designed for the DNA-ACE machines. Because of the large number of switches in the system, individual switch prefire rates must be less than 10/sup -4/ to protect the expensive target assemblies. Experiments are under way to determine if the switch-prefire probability can be reduced with rapid capacitor charging.

The atlas power-flow system - A status report

The design requirements, design features, test results and status of the Atlas high-energy pulsed-power facility power flow system are described

Application of Lean Manufacturing Principles to DARHT-II Induction Cell Refurbishment

The induction cells of the Dual Axis Radiographic Hydrotest (DARHT) second axis facility are scheduled to be refurbished with performance and reliability upgrades. The refurbishment process involves extracting each cell from the accelerator hall, performing a complete teardown of the cell, reassembling with new or modified components, fidulizing the magnetic axis, testing and certifying pulse power performance, and reinstalling into the accelerator hall. Each step of the refurbishment process is comprised of many complex steps, necessitating attention to details and following strict assembly protocol to ensure that high quality cell assemblies are attained. All this must be accomplished at an accelerated production rate to meet the commissioning milestones of the DARHT second-axis accelerator. To this end, Los Alamos National Laboratory (LANL) has adopted the principles of lean manufacturing and applied them to the cell refurbishment effort. These principles emphasize streamline thinking and methodologies for manufacturing environments that promote the most effective use of resources. After workshops and application of these methodologies, the cell manufacturing facility at LANL has been transformed to support lean manufacturing. This paper presents and discusses the processes and facility configuration developed to apply lean manufacturing for cell refurbishment.

The Atlas pulsed power facility for high energy density physics experiments

The Atlas facility, now under construction at Los Alamos National Laboratory (LANL), will provide a unique capability for performing high-energy-density experiments in support of weapon-physics and basic-research programs. Here, the authors describe how the primary element of Atlas is a 23-MJ capacitor bank, comprised of 96 separate Marx generators housed in 12 separate oil-filled tanks, surrounding a central target chamber. Each tank will house two, independently-removable maintenance units, with each maintenance unit consisting of four Marx modules. Each Marx module has four capacitors that can each be charged to a maximum of 60 kilovolts. When railgap switches are triggered, the Marx modules erect to a maximum of 240 kV. The parallel discharge of these 96 Marx modules will deliver a 30-MA current pulse with a 4-5-ys risetime to a cylindrical, imploding liner via 24 vertical, tri-plate, oil-insulated transmission lines. An experimental program for testing and certifying all Marx and transmission line components has been completed. A complete maintenance module and its associated transmission line are now under construction and testing.

Atlas chamber, power flow channel, and diagnostic interface design

The Atlas pulsed-power machine, being designed at Los Alamos, will deliver a pulse of /spl sim/45 MA, in 4-5 /spl mu/sec, with energies of up to 6 MJ (from a bank of 36 MJ maximum) to a load assembly, located in vacuum. Design considerations for the vacuum vessel, power flow channel from the vessel inward, are presented. In contrast to Sandias PBFA II-Z, where 20 MA currents and 2-2.5 MJ of energy are delivered to (/spl sim/15 mg) loads in /spl sim/100 nsec, the Atlas structures will have to be designed for longer timescales and higher energies to drive heavy liners (/spl sim/70 g). Design issues for the chamber include materials stresses, formation of (and protection from) debris and molten jets, impulse loading, and survivability and ease of replacement of internal structures. For the power flow channel designs, issues are minimizing inductance, preventing movement of conductors during and after firing, damage mitigation, reducing the cost of materials and installation, and electrical insulation. A key issue for damage mitigation is the radius within which total destruction of material objects occurs. Choices of vessel size, insulator materials, cost and ease of manufacturing, and mechanical stability issues are presently in the conceptual design phase. Typical access requirements for diagnostics (including radial and axial X-ray backlighting, flux loops, spectroscopy, interferometry, bolometry, etc.) are provided for in the design.

An overview of the Atlas pulsed-power systems

Atlas is a facility being designed at Los Alamos National Laboratory (LANL) to perform high energy-density experiments in support of weapon-physics and basic-research programs. It is designed to be an international user facility, providing experimental opportunities to researchers from national laboratories and academic institutions. For hydrodynamic experiments, it will be capable of achieving pressures exceeding 20-Mbar in a several cm/sup 3/ volume. With the development of a suitable opening switch, it will also be capable of producing soft X-rays. The 36 MJ capacitor bank will consist of 240 kV Marx modules arranged around a central target chamber. The Marx modules will be discharged through vertical triplate transmission lines to a parallel plate collector inside the target chamber. The capacitor bank is designed to deliver a peak current of 45 to 50 MA with a 4- to 5-/spl mu/s risetime. The Marx modules are designed to be reconfigured to a 480 kV configuration for opening switch development. Predicted performance with a typical load is presented. Descriptions of the major subsystems are also presented.

Atlas - a new pulsed power tool at Los Alamos

The Atlas pulsed power driver has recently been commissioned at Los Alamos National Laboratory. This paper provides an overview of the ATLAS facility, its initial experimental program and plans for the future. The reader desiring more detailed information is referred to papers in this conference by Keinigs et al. on materials studies, Cochrane et al. on machine performance and Ballard et al. on fabrication and assembly. Atlas is a high current generator capable of driving 30 megamps through a low-inductance load. It has been designed to require minimal maintenance, provide excellent diagnostic access, and rapid turnaround. Its capacitor bank stores 23.5 megajoules in a four-stage Marx configuration which erects to 240 kV at maximum charge. It has a quarter-cycle time of 4.5 microseconds. It will typically drive cylindrical aluminum liners in a Z-pinch configuration to velocities up to 10 mm/usec while maintaining the inner surface in the solid state. Diagnostic access includes 360/spl deg/ of radial view as well as axial views from above and below. The photograph shows the circle of tanks containing capacitor banks, the diagnostic platform and load area. Atlas construction began in 1996 and high-current acceptance tests were completed in December of 2000. Initial shots include liner characterization shots using a target design similar to NTLX experiments (see several papers by Turchi et al., this meeting). These will be followed by experiments studying hydro features, useful for validating hydrodynamic algorithms used in weapons computer codes. DOE plans to relocate the Atlas generator to the Nevada Test Site as early as 2002, where it will continue its experimental program supporting the Stockpile Stewardship program and other users.

The Atlas load protection switch

Atlas is a high-energy pulsed-power facility under development to study materials properties and hydrodynamics experiments under extreme conditions. Atlas will implode heavy liner loads (m/spl sim/45 gm) with a peak current of 27-32 MA delivered in 4 /spl mu/s, and is energized by 96, 240 kV Marx generators storing a total of 23 MJ. A key design requirement for Atlas is obtaining useful data for 95% of all loads installed on the machine. Materials response calculations show current from a prefire can damage the load requiring expensive and time consuming replacement. Therefore, we have incorporated a set of fast-acting mechanical switches in the Atlas design to reduce the probability of a prefire damaging the load. These switches, referred to as the load protection switches, short the load through a very low inductance path during system charge. Once the capacitors have reached full charge, the switches open on a time scale short compared to the bank charge time, allowing current to flow to the load when the trigger pulse is applied. The time window of vulnerability for load damage is thus substantially reduced. The design of the load protection switches and test results are presented.

Atlas-a new pulsed power tool at Los Alamos National Laboratory

The Atlas pulsed power driver has recently been commissioned at Los Alamos National Laboratory. This paper provides an overview of the ATLAS facility, its initial experimental program and plans for the future. The reader desiring more detailed information is referred to papers in this conference by Keinigs et al. on materials studies, Cochrane et al. on machine performance and Ballard et al. on fabrication and assembly. Atlas is a high current generator capable of driving 30 megamps through a low-inductance load. It has been designed to require minimal maintenance, provide excellent diagnostic access, and rapid turnaround. Its capacitor bank stores 23.5 megajoules in a four-stage Marx configuration which erects to 240 kV at maximum charge. It has a quarter-cycle time of 4.5 microseconds. It will typically drive cylindrical aluminum liners in a Z-pinch configuration to velocities up to 10 mm/usec while maintaining the inner surface in the solid state. Diagnostic access includes 360/spl deg/ of radial view as well as axial views from above and below. The photograph shows the circle of tanks containing capacitor banks, the diagnostic platform and load area. Atlas construction began in 1996 and high-current acceptance tests were completed in December of 2000. Initial shots include liner characterization shots using a target design similar to NTLX experiments (see several papers by Turchi et al., this meeting). These will be followed by experiments studying hydro features, useful for validating hydrodynamic algorithms used in weapons computer codes. DOE plans to relocate the Atlas generator to the Nevada Test Site as early as 2002, where it will continue its experimental program supporting the Stockpile Stewardship program and other users.

Atlas facility fabrication and assembly

Atlas is a pulsed-power facility recently completed at Los Alamos National Laboratory to drive hydrodynamic experiments. This new generation pulsed-power machine consists of a radial array of 24, 240-kV Marx modules and transmission lines supplying current to the load region at the machine center. The transmission lines, powered by the Marx modules, consist of cable headers, load protection switches and tri-plates interfacing to the center transition section through detachable current joints. A conical power-flow-channel attaches to the transition section providing an elevated interface to attach the experimental loads for diagnostic access. Fabrication and assembly of all components for the Atlas machine was completed in August 2000. The machine has also progressed through a test phase where the Marx module/transmission line units were fired, individually, into a test load. Progression continued with eight and sixteen lines being fired. Subsequently, an overall machine test was conducted where all 24 transmission lines were fired simultaneously, delivering 28.6 MA into the test load.