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Assessment of Electrode Contamination Mitigation at 0.5 MA Scale

Lamppa, Derek C.; Simpson, Sean S.; Hutsel, Brian T.; Cuneo, M.E.; Laity, George R.; Rose, David R.

The Z Machine at Sandia National Laboratories uses current pulses with peaks up to 27 MA to drive target implosions and generate high energy density conditions of interest for stockpile stewardship programs pertinent to the NNSA program portfolio . Physical processes in the region near the Z Machine target create electrode plasmas which seed parasitic current loss that reduce the performance and output of a Z experiment. Electrode surface contaminants (hydrogen, water, hydrocarbons) are thought to be the primary constituent of electrode plasmas which contribute to loss mechanisms. The Sandia team explore d in situ heating and plasma discharge techniques by integrating requisite infrastructure into Sandia's Mykonos LTD accelerator, addressing potential impacts to accelerator operation, and reporting on the impact of these techniques on electrode plasma formation and shot performance. The in situ discharge cleaning utilizes the electrodes of the accelerator to excite an argon-oxygen plasma to sputter and chemically react contaminants from electrode surfaces. Insulating breaks are required to isolate the plasma in electrode regions where loss processes are most likely to occur. The shots on Mykonos validate that these breaks do not perturb experiment performance, reducing the uncertainty on the largest unknown about the in situ cleaning system. Preliminary observations with electrical and optical diagnostics suggest that electrode plasma formation is delayed, and overall inventory has been substantively reduced. In situ heating embeds cartridge heaters into accelerator electrodes and employs a thermal bakeout to rapidly desorb contaminants from electrode surfaces. For the first time, additively manufactured (AM) electrode assemblies were used on a low impedance accelerator to integrate cooling channels and manage thermal gradients. Challenges with poor supplier fabrication to specifications, load alignment, thermal expansion and hardware movement and warpage appears to have introduced large variability in observed loss, though, preventing strong assertions of loss reduction via in situ heating. At this time, an in situ discharge cleaning process offers the lowest risk path to reduce electrode contaminant inventories on Z, though we recommend continuing to develop both approaches. Additional engineering and testing are required to improve the implementation of both systems. .

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TYPE SAND Report YEAR 2021
OSTIDOI

Towards Predictive Plasma Science and Engineering through Revolutionary Multi-Scale Algorithms and Models (Final Report)

Laity, George R.; Robinson, Allen C.; Cuneo, M.E.; Alam, Mary K.; Beckwith, Kristian B.; Bennett, Nichelle L.; Bettencourt, Matthew T.; Bond, Stephen D.; Cochrane, Kyle C.; Criscenti, Louise C.; Cyr, Eric C.; De Zetter, Karen J.; Drake, Richard R.; Evstatiev, Evstati G.; Fierro, Andrew S.; Gardiner, Thomas A.; Glines, Forrest W.; Goeke, Ronald S.; Hamlin, Nathaniel D.; Hooper, Russell H.; Koski, Jason K.; Lane, James M.; Larson, Steven R.; Leung, Kevin L.; McGregor, Duncan A.; Miller, Philip R.; Miller, Sean M.; Ossareh, Susan J.; Phillips, Edward G.; Simpson, Sean S.; Sirajuddin, David S.; Smith, Thomas M.; Swan, Matthew S.; Thompson, Aidan P.; Tranchida, Julien G.; Bortz-Johnson, Asa J.; Welch, Dale R.; Russell, Alex M.; Watson, Eric D.; Rose, David V.; McBride, Ryan D.

This report describes the high-level accomplishments from the Plasma Science and Engineering Grand Challenge LDRD at Sandia National Laboratories. The Laboratory has a need to demonstrate predictive capabilities to model plasma phenomena in order to rapidly accelerate engineering development in several mission areas. The purpose of this Grand Challenge LDRD was to advance the fundamental models, methods, and algorithms along with supporting electrode science foundation to enable a revolutionary shift towards predictive plasma engineering design principles. This project integrated the SNL knowledge base in computer science, plasma physics, materials science, applied mathematics, and relevant application engineering to establish new cross-laboratory collaborations on these topics. As an initial exemplar, this project focused efforts on improving multi-scale modeling capabilities that are utilized to predict the electrical power delivery on large-scale pulsed power accelerators. Specifically, this LDRD was structured into three primary research thrusts that, when integrated, enable complex simulations of these devices: (1) the exploration of multi-scale models describing the desorption of contaminants from pulsed power electrodes, (2) the development of improved algorithms and code technologies to treat the multi-physics phenomena required to predict device performance, and (3) the creation of a rigorous verification and validation infrastructure to evaluate the codes and models across a range of challenge problems. These components were integrated into initial demonstrations of the largest simulations of multi-level vacuum power flow completed to-date, executed on the leading HPC computing machines available in the NNSA complex today. These preliminary studies indicate relevant pulsed power engineering design simulations can now be completed in (of order) several days, a significant improvement over pre-LDRD levels of performance.

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TYPE SAND Report YEAR 2021
OSTIDOI

Stagnation performance scaling of Magnetized Liner Inertial Fusion

Gomez, Matthew R.; Yager-Elorriaga, David A.; Myers, Clayton E.; Slutz, Stephen A.; Weis, Matthew R.; Jennings, Christopher A.; Lamppa, Derek C.; Harvey-Thompson, Adam J.; Geissel, Matthias G.; Knapp, Patrick K.; Harding, Eric H.; Hansen, Stephanie B.; Mangan, Michael M.; Ruiz, Carlos L.; Chandler, Gordon A.; Webb, Timothy J.; Moore, Thomas M.; Laity, George R.; Ampleford, David A.; Peterson, Kyle J.; Rochau, G.A.; Sinars, Daniel S.

Abstract not provided.

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TYPE Conference Poster YEAR 2019
OSTI

Stagnation Performance Scaling of Magnetized Liner Inertial Fusion

Gomez, Matthew R.; Yager-Elorriaga, David A.; Myers, Clayton E.; Slutz, Stephen A.; Weis, Matthew R.; Jennings, Christopher A.; Lamppa, Derek C.; Harvey-Thompson, Adam J.; Geissel, Matthias G.; Knapp, Patrick K.; Harding, Eric H.; Hansen, Stephanie B.; Mangan, Michael M.; Ruiz, Carlos L.; Chandler, Gordon A.; Hahn, Kelly D.; Webb, Timothy J.; Moore, Thomas M.; Laity, George R.; Ampleford, David A.; Peterson, Kyle J.; Rochau, G.A.; Sinars, Daniel S.

Abstract not provided.

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TYPE Conference Poster YEAR 2019
OSTI

Recent Diagnostic Platform Accomplishments for Studying Vacuum Power Flow Physics at the Sandia Z Accelerator

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.

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TYPE Conference Poster YEAR 2018
OSTI

A Path to Increased Performance in Magnetized Liner Inertial Fusion

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.

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TYPE Conference Poster YEAR 2017
OSTI

A microwave resonance diagnostic for measuring characteristics of pulsed ion beams

Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014

Laity, George R.; Barnat, Edward V.

This paper describes an experiment to characterize ions generated by a pulsed vacuum arc by using a microwave resonant cavity (MRC) as a transient diagnostic. Specific information is desired on the various species which can drift into the beam during repetitive operations of arc plasma generation. The arc source reference voltage is elevated above ground (∼200V), which results in a separation of ion species in the beam due to the acceleration experienced by the ions. The cylindrical MRC used in this study has a resonant frequency of ∼2.8 GHz when excited by a continuous RF source in the TM01 mode of operation. When the neutralized ion beam propagates through the MRC located downstream from the arc source, the resonant frequency of the MRC is shifted by the local disturbance in electric field inside the cavity due to the presence of the electron space charge in the beam. Coupled with the time-of-flight separation of various ion masses, the MRC resonance shift provides a temporally resolved measurement of beam species and density downstream from the vacuum ion source without the use of a potentially invasive diagnostic such as charge collector plates within the beam cross-section. This diagnostic technique should prove useful in a variety of pulsed ion beam studies and applications in research and industrial environments.

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TYPE Conference Poster YEAR 2015
ScopusOSTIDOI
54 Results
54 Results