The Dual-Axis Radiographic Hydrodynamic Test Facility (DARHT) at Los Alamos National Laboratory consists of two linear induction accelerators at right angles to each other. The First Axis produces a nominal 20-MeV, 2 kA single pulse with 60 ns width. In contrast, the DARHT Second Axis produces up to four pulses in a variable pulse format by slicing micro-pulses out of a longer pulse (~1.6 microseconds flattop) of nominal beam energy and current of 17 MeV and 1.65 kA respectively. Bremsstrahlung x-rays are produced by focusing the electron beam-pulses onto a high-Z target. This paper focuses on the second axis accelerator and maintenance of its components. The injector Marx delivers 2.1 MV to a 6.25 inch diameter thermionic cathode producing a 1.65 kA beam. The beam is accelerated in a Linear Induction Accelerator (LIA) consisting of 74 cells operating at a total of 14.8 MV, delivering a beam of ~17 MeV and ~1.6 μs flattop at the accelerator exit. Each cell is driven by an individual Pulse Forming Network Marx (PFN Marx) tuned to provide voltage regulation of +1%. The Axis II LIA uses solenoids for focusing the beam and dipole pairs for steering. Each cell incorporates a solenoid and a pair of dipoles. Including all magnets in between blocks of cells, in the diode anode region and elsewhere, there are 91 solenoids and 80 pairs of dipoles. The ideal energizing currents in the focusing and steering magnets to optimize the electron-beam transport is very dependent on cell gap locations and potential in those gaps. Excessive PFN Marx jitter or a prefire would seriously compromise beam transport and the bremsstrahlung radiographic spot sizes. Low erection time jitter and exceptionally low prefire rates of the 74 PFN Marxes is required to ensure proper transport of the electron beam. The design and maintenance of the four-stage unipolar PFN Marxes are described here for the first time.

The Dual-Axis Radiographic Hydrodynamics Test (DARHT) facility will employ two perpendicular electron Linear Induction Accelerators to produce intense, bremsstrahlung x-ray pulses for flash radiography. The second axis, DARHT II [1], features a 2.5-MeV injector and a 15.5-MeV, 2-kA, 1.6-microsecond accelerator consisting of 74 induction cells and drivers. Major induction cell components include high flux swing magnetic material (Metglas 2605SC) and a Mycalex™ insulator. The cell drivers are pulse forming networks (PFNs). The DARHT II accelerator cells have undergone a series of test and modeling efforts to fully understand their operational parameters. These R&D efforts identified problems in the original cell design and means to upgrade the design, performance and reliability of the linear induction cells [2]. Physical changes in the cell oil region, the cell vacuum region, and the cell drivers, together with different operational and maintenance procedures, have been implemented in the refurbished units resulting in greatly enhanced cell performance and reliability. All 74 cells have now been refurbished and tested for acceptance. This paper gives the results of those tests and the performance of the 26 refurbished cells in the Scaled Accelerator.

Megagauss Magnetic Field Generation, Its Application to Science and Ultra-High Pulsed-Power Technology, pp. 671-675 (2004) No AccessTHE ATLAS PULSED POWER SYSTEM: A DRIVER FOR PRODUCING MULTI-MEGAGAUSS FIELDSJ. C. COCHRANE, JR., R. R. BARTSCH, G. A. BENNETT, D. W. BOWMAN, H. A. DAVIS, C. A. EKDAHL, R. F. GRIBBLE, H. J. KIMERLY, K. E. NIELSEN, W. M. PARSONS, J. D. PAUL, D. W. SCUDDER, R. J. TRAINOR, M. C. THOMPSON, and R. G. WATTJ. C. COCHRANE, JR.Los Alamos National Laboratory, Los Alamos, NM, USA, R. R. BARTSCHLos Alamos National Laboratory, Los Alamos, NM, USA, G. A. BENNETTLos Alamos National Laboratory, Los Alamos, NM, USA, D. W. BOWMANLos Alamos National Laboratory, Los Alamos, NM, USA, H. A. DAVISLos Alamos National Laboratory, Los Alamos, NM, USA, C. A. EKDAHLLos Alamos National Laboratory, Los Alamos, NM, USA, R. F. GRIBBLELos Alamos National Laboratory, Los Alamos, NM, USA, H. J. KIMERLYLos Alamos National Laboratory, Los Alamos, NM, USA, K. E. NIELSENLos Alamos National Laboratory, Los Alamos, NM, USA, W. M. PARSONSLos Alamos National Laboratory, Los Alamos, NM, USA, J. D. PAULLos Alamos National Laboratory, Los Alamos, NM, USA, D. W. SCUDDERLos Alamos National Laboratory, Los Alamos, NM, USA, R. J. TRAINORLos Alamos National Laboratory, Los Alamos, NM, USA, M. C. THOMPSONLos Alamos National Laboratory, Los Alamos, NM, USA, and R. G. WATTLos Alamos National Laboratory, Los Alamos, NM, USAhttps://doi.org/10.1142/9789812702517_0141Cited by:1 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: Atlas is a pulsed power machine designed for hydrodynamic experiments for the Los Alamos High Energy Density Physics Experimental program. It is presently under construction and should be operational in late 2000. Atlas will store 23 MJ at an erected voltage of 240 kV. This will produce a current of 30 MA into a static load and as much as 32 MA into a dynamic load. The current pulse will have a rise time of ~5 μs and will produce a magnetic field driving the impactor liner of several hundred Tesla at the target radius of one to two centimeters. The collision can produce shock pressures of ~15 megabars. Design of the pulsed power system will be presented along with data obtained from the Atlas prototype Marx module. FiguresReferencesRelatedDetailsCited By 1Test results of the Atlas Marxed pulsed power systemJ.C. Cochrane, G. Bennett, W. Hinckley, K. Hosack and K. Nielsen et al. Megagauss Magnetic Field Generation, Its Application to Science and Ultra-High Pulsed-Power TechnologyMetrics History PDF download

The Dual-Axis Radiographic Hydrodynamics Test (DARHT) facility will employ two perpendicular electron Linear Induction Accelerators to produce intense, bremsstrahlung x-ray pulses for flash radiography. We intend to produce measurements containing three-dimensional information with sub-millimeter spatial resolution of the interior features of very dense, explosively-driven objects. The facility will be completed in two phases with the first phase having become operational in July 1999 utilizing a single-pulse, 20-MeV, 2-kA, 60-ns accelerator, a high-resolution electro-optical x-ray imaging system, and other hydrodynamics testing systems. We will briefly describe this machine. The first electron beams will be generated in the second phase of DARHT this year. The second DARHT accelerator consists of a 18.4-MeV, 2-kA, 2-microsecond pulse-width accelerator. Four short electron micropulses of variable pulse-width and spacing will be chopped out of the original, long accelerator pulse for producing time-resolved x-ray images. The second phase also features an extended, high-resolution electro-optical x-ray system with a framing speed of about 2-MHz. We will discuss this accelerator by summarizing the overall design of the long-pulse injector and accelerator. We will also discuss the fast kicker used to separate the long-pulse beam into short bursts suitable for radiography.

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.

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

Atlas is a pulsed-power facility under development at Los Alamos National Laboratory to drive high-energy density experiments. Atlas will be operational in the summer of 2000 and is optimized for the study of dynamic material properties, hydrodynamics, and dense plasmas under extreme conditions. Atlas is designed to implode heavy-liner loads in a z-pinch configuration. The peak current of 30 MA is delivered in 4 µs. A typical Atlas liner is a 47-gram-aluminum cylinder with ∼4-cm radius and 4-cm length. Three to five MJ of kinetic energy will be delivered to the load. Using composite layers and a variety of interior target designs, a wide variety of experiments in ∼cm 3 volumes will be performed. Atlas applications, machine design, and the status of the project are reviewed.

The Atlas facility will use 24 radially converging, vertically oriented and tapered, oil insulated, triplate transmission lines between the Marx generators and the central load region. Among the requirements of the transmission lines are low inductance and high reliability. The inter-conductor gap is nominally 2 cm and the lines taper from a height of 1.75 m at the Marx end to 0.32 m at the output end. The aluminum conductors, held together by 20 insulating spacers, are assembled and inserted as a unit into radial oil-filled steel tanks. The negative, high-voltage, center conductor is 2.54-cm thick and the outer ground conductors are 1.59-cm thick. All 24 triplate transmission lines connect to a transition section at near 1 m radius that couples the transmission lines to a disk/conical solid-dielectric-insulated power flow channel transmission line terminating at the load. Peak operating voltage on the lines can be as high as 240 kV with an effective stress time of 0.8 /spl mu/s. Testing of small sections of the total area have been completed and the test results are analyzed to show that the probability of failure at these voltage levels is less than 1 in 1000 system shots.