Publications

Douglass, Jonathan D.; Hutsel, Brian T.; Leckbee, Joshua J.; Stoltzfus, Brian S.; Savage, Mark E.; Cuneo, M.E.; Kiefer, Mark L.

Abstract not provided.

IEEE International Pulsed Power Conference

Douglass, Jonathan D.; Cuneo, M.E.; Jaramillo, Deanna M.; Johns, Owen J.; Jones, M.C.; Lucero, Diego J.; Moore, James M.; Sceiford, Matthew S.; Kiefer, Mark L.; Mulville, Thomas D.; Sullivan, Michael A.; Hutsel, Brian T.; Hohlfelder, Robert J.; Leckbee, J.J.; Stoltzfus, B.S.; Wisher, M.L.; Savage, Mark E.; Stygar, W.A.; Breden, E.W.; Calhoun, Jacob D.

Herein we describe the design, simulation and performance of a 118-GW linear transformer driver (LTD) cavity at Sandia National Laboratories. The cavity consists of 20 to 24 'Bricks'. Each brick is comprised of two 80 nF, 100 kV capacitors connected electrically in series with a custom, 200 kV, three-electrode, field-distortion gas switch. The brick capacitors are bi-polar charged to a total of 200 kV. Typical brick circuit parameters are 40 nF (two 80 nF capacitors in series) and 160 nH inductance. Over the course of over 10,000 shots the cavity generated a peak electrical current and power of 1.19 MA and 118 GW.

Physics of Plasmas

Shipley, Gabriel A.; Awe, T.J.; Hutsel, Brian T.; Greenly, J.B.; Jennings, C.A.; Slutz, S.A.

In the first auto-magnetizing liner implosion experiments on the Z Facility, precompressed internal axial fields near 150 T were measured and 7.2-keV radiography indicated a high level of cylindrical uniformity of the imploding liner's inner surface. An auto-magnetizing (AutoMag) liner is made of discrete metallic helical conductors encapsulated in insulating material. The liner generates internal axial magnetic field as a 1-2 MA, 100-200 ns current prepulse flows through the helical conductors. After the prepulse, the fast-rising main current pulse causes the insulating material between the metallic helices to break down ceasing axial field production. After breakdown, the helical liner, nonuniform in both density and electrical conductivity, implodes in 100 ns. In-flight radiography data demonstrate that while the inner wall maintains cylindrical uniformity, multiple new helically oriented structures are self-generated within the outer liner material layers during the implosion; this was not predicted by simulations. Furthermore, liner stagnation was delayed compared to simulation predictions. An analytical implosion model is compared with experimental data and preshot simulations to explore how changes in the premagnetization field strength and drive current affect the liner implosion trajectory. Both the measurement of >100 T internal axial field production and the demonstration of cylindrical uniformity of the imploding liner's inner wall are encouraging for promoting the use of AutoMag liners in future MagLIF experiments.

Gomez, Matthew R.; Jennings, Christopher A.; Lamppa, Derek C.; Hutsel, Brian T.; Slutz, Stephen A.; Laity, George R.

Abstract not provided.

Physical Review Accelerators and Beams

Douglass, Jonathan D.; Hutsel, Brian T.; Leckbee, Joshua L.; Mulville, Thomas D.; Stoltzfus, Brian S.; Savage, Mark E.; Breden, E.W.; Calhoun, Jacob D.; Cuneo, M.E.; De Smet, Dennis J.; Hohlfelder, Robert J.; Jaramillo, Deanna M.; Johns, Owen J.; Lombrozo, Aaron C.; Lucero, Diego J.; Moore, James M.; Porter, John L.; Radovich, S.; Sceiford, Matthew S.; Sullivan, Michael A.; Walker, Charles A.; Yazzie, Nicole T.

Here we present details of the design, simulation, and performance of a 100-GW linear transformer driver (LTD) cavity at Sandia National Laboratories. The cavity consists of 20 “bricks.” Each brick is comprised of two 80 nF, 100 kV capacitors connected electrically in series with a custom, 200 kV, three-electrode, field-distortion gas switch. The brick capacitors are bipolar charged to ±100 kV for a total switch voltage of 200 kV. Typical brick circuit parameters are 40 nF capacitance (two 80 nF capacitors in series) and 160 nH inductance. The switch electrodes are fabricated from a WCu alloy and are operated with breathable air. Over the course of 6,556 shots the cavity generated a peak electrical current and power of 1.03 MA (±1.8%) and 106 GW (±3.1%). Experimental results are consistent (to within uncertainties) with circuit simulations for normal operation, and expected failure modes including prefire and late-fire events. New features of this development that are reported here in detail include: (1) 100 ns, 1 MA, 100-GW output from a 2.2 m diameter LTD into a 0.1 Ω load, (2) high-impedance solid charging resistors that are optimized for this application, and (3) evaluation of maintenance-free trigger circuits using capacitive coupling and inductive isolation.

Physics of Plasmas

Slutz, S.A.; Gomez, Matthew R.; Hansen, Stephanie B.; Harding, Eric H.; Hutsel, Brian T.; Knapp, P.F.; Lamppa, Derek C.; Awe, T.J.; Ampleford, David A.; Bliss, David E.; Chandler, Gordon A.; Cuneo, M.E.; Geissel, Matthias G.; Glinsky, Michael E.; Harvey-Thompson, Adam J.; Hess, Mark H.; Jennings, C.A.; Jones, Brent M.; Laity, G.R.; Martin, M.R.; Peterson, Kyle J.; Porter, John L.; Rambo, Patrick K.; Rochau, G.A.; Ruiz, Carlos L.; Savage, Mark E.; Schwarz, Jens S.; Schmit, Paul S.; Shipley, Gabriel A.; Sinars, Daniel S.; Smith, Ian C.; Vesey, Roger A.; Weis, M.R.

The Magnetized Liner Inertial Fusion concept (MagLIF) [Slutz et al., Phys. Plasmas 17, 056303 (2010)] is being studied on the Z facility at Sandia National Laboratories. Neutron yields greater than 1012 have been achieved with a drive current in the range of 17-18 MA and pure deuterium fuel [Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)]. We show that 2D simulated yields are about twice the best yields obtained on Z and that a likely cause of this difference is the mix of material into the fuel. Mitigation strategies are presented. Previous numerical studies indicate that much larger yields (10-1000 MJ) should be possible with pulsed power machines producing larger drive currents (45-60 MA) than can be produced by the Z machine [Slutz et al., Phys. Plasmas 23, 022702 (2016)]. To test the accuracy of these 2D simulations, we present modifications to MagLIF experiments using the existing Z facility, for which 2D simulations predict a 100-fold enhancement of MagLIF fusion yields and considerable increases in burn temperatures. Experimental verification of these predictions would increase the credibility of predictions at higher drive currents.

Hess, Mark H.; Laity, George R.; Peterson, Kyle J.; Hutsel, Brian T.; Jennings, Christopher A.; VanDevender, Pace V.; Gomez, Matthew R.; Ampleford, David A.; Knapp, Patrick K.; Porwitzky, Andrew J.; Dolan, Daniel H.; Lamppa, Derek C.; Robertson, Grafton K.; Aragon, Carlos A.; Tomlinson, Kurt T.; Payne, Sheri L.; Martin, Matthew; Stygar, William S.; Sinars, Daniel S.

Abstract not provided.

Laity, George R.; Aragon, Carlos A.; Bennett, Nichelle L.; Bliss, David E.; Dolan, Daniel H.; Fierro, Andrew S.; Gomez, Matthew R.; Hess, Mark H.; Hutsel, Brian T.; Jennings, Christopher A.; Johnston, Mark D.; Kossow, Michael R.; Lamppa, Derek C.; Martin, Matthew; Patel, Sonal P.; Porwitzky, Andrew J.; Robinson, Allen C.; Rose, David V.; VanDevender, Pace V.; Waisman, Eduardo M.; Webb, Timothy J.; Welch, Dale R.; Rochau, G.A.; Savage, Mark E.; Stygar, William S.; White, William M.; Sinars, Daniel S.; Cuneo, M.E.

Abstract not provided.

Hutsel, Brian T.; Gansz, Jacy N.; Jaramillo, Deanna M.; Lucero, Diego J.; Moore, James M.; Rose, David V.; Stygar, William S.

Current loss in magnetically insulated transmission lines (MITLs) was investigated using data from experiments conducted on Z and Mykonos. Data from experiments conducted on Z were used to optimize an ion diode current loss model that has been implemented into the transmission line circuit model of Z. Details on the current loss model and comparisons to data from Z experiments have been previously published in a peer-reviewed journal [Hutsel, et al., Phys. Rev. Accel. Beams 21, 030401]. Dedicated power flow experiments conducted on Mykonos investigated current loss in a millimeter-scale anode-cathode gap MITL operated at lineal current densities greater than 410 kA/cm and with electric field stresses in excess of 240 kV/cm where it is expected that both anode and cathode plasmas are formed. The experiment MITLs were exposed to varying vacuum conditions; including vacuum pressure at shot time, time under vacuum, and vacuum storage protocols. The results indicate that the vacuum conditions have an effect on current loss in high lineal current density MITLs.

Shipley, Gabriel A.; Awe, Thomas J.; Hutsel, Brian T.; Slutz, Stephen A.; Greenly, John B.; Jennings, Christopher A.; Lamppa, Derek C.; Hutchinson, T.M.

Abstract not provided.

Shipley, Gabriel A.; Awe, Thomas J.; Hutsel, Brian T.; Slutz, Stephen A.; Greenly, John B.; Jennings, Christopher A.; Lamppa, Derek C.; Hutchinson, T.M.

Abstract not provided.

Shipley, Gabriel A.; Awe, Thomas J.; Hutsel, Brian T.; Slutz, Stephen A.; Greenly, John B.; Jennings, Christopher A.; Lamppa, Derek C.; Hutchinson, T.M.

Abstract not provided.

Physics of Plasmas

Shipley, Gabriel A.; Awe, T.J.; Hutsel, Brian T.; Slutz, S.A.; Lamppa, Derek C.; Greenly, J.B.; Hutchinson, T.M.

Auto-magnetizing (AutoMag) liners [Slutz et al., Phys. Plasmas 24, 012704 (2017)] are designed to generate up to 100 T of axial magnetic field in the fuel for Magnetized Liner Inertial Fusion [Slutz et al., Phys. Plasmas 17, 056303 (2010)] without the need for external field coils. AutoMag liners (cylindrical tubes) are composed of discrete metallic helical conduction paths separated by electrically insulating material. Initially, helical current in the AutoMag liner produces internal axial magnetic field during a long (100 to 300 ns) current prepulse with an average current rise rate d I / d t = 5 k A / n s. After the cold fuel is magnetized, a rapidly rising current (200 k A / n s) generates a calculated electric field of 64 M V / m between the helices. Such field is sufficient to force dielectric breakdown of the insulating material after which liner current is reoriented from helical to predominantly axial which ceases the AutoMag axial magnetic field production mechanism and the z-pinch liner implodes. Proof of concept experiments have been executed on the Mykonos linear transformer driver to measure the axial field produced by a variety of AutoMag liners and to evaluate what physical processes drive dielectric breakdown. A range of field strengths have been generated in various cm-scale liners in agreement with magnetic transient simulations including a measured field above 90 T at I = 350 kA. By varying the helical pitch angle, insulator material, and insulator geometry, favorable liner designs have been identified for which breakdown occurs under predictable and reproducible field conditions.

Hess, Mark H.; Laity, George R.; Peterson, Kyle J.; Hutsel, Brian T.; Jennings, Christopher A.; Dolan, Daniel H.; Aragon, Carlos A.; Tomlinson, Kurt T.

Abstract not provided.

Fierro, Andrew S.; Laity, George R.; Jennings, Christopher A.; Bennett, Nichelle L.; Hess, Mark H.; Hutsel, Brian T.; Hopkins, Matthew M.; Robinson, Allen C.; Pointon, Timothy D.; Vandevender, J.P.; Cartwright, Keith C.

Abstract not provided.

Physics of Plasmas

Hess, Mark H.; Peterson, Kyle J.; Ampleford, David A.; Hutsel, Brian T.; Jennings, C.A.; Gomez, Matthew R.; Dolan, Daniel H.; Robertson, Grafton K.; Payne, S.L.; Stygar, William A.; Martin, M.R.; Sinars, Daniel S.

A critical component of the magnetically driven implosion experiments at Sandia National Laboratories is the delivery of high-current, 10s of MA, from the Z pulsed power facility to a target. In order to assess the performance of the experiment, it is necessary to measure the current delivered to the target. Recent Magnetized Liner Inertial Fusion (MagLIF) experiments have included velocimetry diagnostics, such as PDV (Photonic Doppler Velocimetry) or Velocity Interferometer System for Any Reflector, in the final power feed section in order to infer the load current as a function of time. However, due to the nonlinear volumetrically distributed magnetic force within a velocimetry flyer, a complete time-dependent load current unfold is typically a time-intensive process and the uncertainties in the unfold can be difficult to assess. In this paper, we discuss how a PDV diagnostic can be simplified to obtain a peak current by sufficiently increasing the thickness of the flyer. This effectively keeps the magnetic force localized to the flyer surface, resulting in fast and highly accurate measurements of the peak load current. In addition, we show the results of experimental peak load current measurements from the PDV diagnostic in recent MagLIF experiments.

Physical Review Accelerators and Beams

Hutsel, Brian T.; Corcoran, Patrick A.; Cuneo, M.E.; Gomez, Matthew R.; Hess, Mark H.; Hinshelwood, D.D.; Jennings, C.A.; Laity, G.R.; Lamppa, Derek C.; McBride, Ryan D.; Moore, James M.; Myers, A.; Rose, D.V.; Slutz, S.A.; Stygar, William A.; Waisman, Eduardo M.; Welch, Dale R.; Whitney, B.A.

We have developed a physics-based transmission-line-circuit model of the Z pulsed-power accelerator. The 33-m-diameter Z machine generates a peak electrical power as high as 85 TW, and delivers as much as 25 MA to a physics load. The circuit model is used to design and analyze experiments conducted on Z. The model consists of 36 networks of transmission-line-circuit elements and resistors that represent each of Zs 36 modules. The model of each module includes a Marx generator, intermediate-energy-storage capacitor, laser-triggered gas switch, pulse-forming line, self-break water switches, and tri-plate transmission lines. The circuit model also includes elements that represent Zs water convolute, vacuum insulator stack, four parallel outer magnetically insulated vacuum transmission lines (MITLs), double-post-hole vacuum convolute, inner vacuum MITL, and physics load. Within the vacuum-transmission-line system the model conducts analytic calculations of current loss. To calculate the loss, the model simulates the following processes: (i) electron emission from MITL cathode surfaces wherever an electric-field threshold has been exceeded; (ii) electron loss in the MITLs before magnetic insulation has been established; (iii) flow of electrons emitted by the outer-MITL cathodes after insulation has been established; (iv) closure of MITL anode-cathode (AK) gaps due to expansion of cathode plasma; (v) energy loss to MITL conductors operated at high lineal current densities; (vi) heating of MITL-anode surfaces due to conduction current and deposition of electron kinetic energy; (vii) negative-space-charge-enhanced ion emission from MITL anode surfaces wherever an anode-surface-temperature threshold has been exceeded; and (viii) closure of MITL AK gaps due to expansion of anode plasma. The circuit model is expected to be most accurate when the fractional current loss is small. We have performed circuit simulations of 52 Z experiments conducted with a variety of accelerator configurations and load-impedance time histories. For these experiments, the apparent fractional current loss varies from 0% to 20%. Results of the circuit simulations agree with data acquired on 52 shots to within 2%.

IEEE International Pulsed Power Conference

Savage, Mark E.; Austin, Kevin N.; Hutsel, Brian T.; Kamm, Ryan J.; Mckee, G.R.; Stygar, William A.; Wakeland, P.; Wemple, Nathan R.; White, W.M.

The Z machine is a 36-module, multi-megavolt, low impedance magnetic pressure driver for high-energy-density physics experiments. In 2007, a major re-build doubled the stored energy and increased the peak current capability of Z. The upgraded system routinely drives 27 MA through low inductance dynamic loads with 110 nanosecond time to peak current. The Z pulsed power system is expected to be prepared for a full-energy experiment every day, with a small (<2%) chance of pulsed power system failure, and ±2 ns timing precision. To maintain that schedule with 20 MJ stored, it becomes essential to minimize failures that can damage hardware. We will show the results of several improvements made to the system that reduce spurious breakdowns and improve precision. In most cases, controlling electric fields is key, both to reliable insulation and to precision switching. The upgraded Z pulsed power system was originally intended to operate with 5 MV peak voltage in the pulse-forming section. Recent operation has been above 6 MV. Critical items in the pulsed power system are the DC-charged Marx generators, oil-water barriers, laser-triggered gas switches, and the vacuum insulator. We will show major improvements to the laser-triggered gas switches, and the water-insulated pulse forming lines, as well as delivered current reproducibility results from user experiments on the machine.

Hess, Mark H.; Peterson, Kyle J.; Ampleford, David A.; Hutsel, Brian T.; Jennings, Christopher A.; Dolan, Daniel H.; Gomez, Matthew R.; Robertson, Grafton K.; Payne, Sherri P.; Sinars, Daniel S.

Abstract not provided.

Hess, Mark H.; Peterson, Kyle J.; Ampleford, David A.; Hutsel, Brian T.; Jennings, Christopher A.; Dolan, Daniel H.; Stygar, William A.; Gomez, Matthew R.; Martin, Matthew; Robertson, Grafton K.; Sinars, Daniel S.

Abstract not provided.

Gomez, Matthew R.; Slutz, Stephen A.; Jennings, Christopher A.; Harvey-Thompson, Adam J.; Weis, Matthew R.; Lamppa, Derek C.; Hutsel, Brian T.; Ampleford, David A.; Awe, Thomas J.; Bliss, David E.; Chandler, Gordon A.; Geissel, Matthias G.; Hahn, Kelly D.; Hansen, Stephanie B.; Harding, Eric H.; Hess, Mark H.; Knapp, Patrick K.; Laity, George R.; Martin, Matthew; Nagayama, Taisuke N.; Rovang, Dean C.; Ruiz, Carlos L.; Savage, Mark E.; Schmit, Paul S.; Schwarz, Jens S.; Smith, Ian C.; Vesey, Roger A.; Yu, Edmund Y.; Cuneo, M.E.; Jones, Brent M.; Peterson, Kyle J.; Porter, John L.; Rochau, G.A.; Sinars, Daniel S.; Stygar, William A.

Abstract not provided.

Lamppa, Derek C.; Vandevender, J.P.; Hutsel, Brian T.; Jobe, Marc R.; Aragon, Carlos A.; Robertson, Grafton K.; Laity, George R.; Gomez, Matthew R.; Ampleford, David A.; Cuneo, M.E.

Abstract not provided.

Savage, Mark E.; Austin, Kevin N.; Hutsel, Brian T.; Kamm, Ryan J.; McKee, George R.; Stygar, William A.; Wakeland, P.; White, William M.

Abstract not provided.

Hutsel, Brian T.; Corcoran, Patrick A.; Cuneo, M.E.; Gomez, Matthew R.; Hinshelwood, Dave H.; Jennings, Christopher A.; Jones, Michael J.; Laity, George R.; Lamppa, Derek C.; Moore, James M.; Myers, Allanah M.; Rose, David V.; Stygar, William A.; Waisman, Eduardo M.; Welch, Dale R.; Whitney, Brandon W.

Abstract not provided.

Lamppa, Derek C.; Vandevender, J.P.; Jobe, Marc R.; Hutsel, Brian T.; Laity, George R.; Gomez, Matthew R.; Ampleford, David A.; Cuneo, M.E.

Abstract not provided.