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Sandia National Laboratories is pursuing a variation of Magneto-Inertial Fusion called Magnetized Liner Inertial Fusion, or MagLIF. The MagLIF approach requires magnetization of the deuterium fuel, which is accomplished by an initial external B-Field and laser-driven pre-heat. While magnetization is crucial to the concept, it is challenging to couple sufficient energy to the fuel, since laser-plasma instabilities exist, and a compromise between laser spot size, laser entrance window thickness, and fuel density must be found. Nonlinear processes in laser plasma interaction, or laser-plasma instabilities (LPI), complicate the deposition of laser energy by enhanced absorption, backscatter, filamentation and beam-spray. Key LPI processes are determined, and mitigation methods are discussed. Results with and without improvement measures are presented.

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TYPE Journal Article YEAR 2016

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Measuring mix in Magnetized Liner Inertial Fusion (MagLIF) Experiments

Hansen, Stephanie B.; Gomez, Matthew R.; Knapp, Patrick K.; Harding, Eric H.

Abstract not provided.

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TYPE Conference Poster YEAR 2015

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X-ray Imaging and Spectroscopy of MagLIF Experiments Using Spherically-Bent Crystals

Harding, Eric H.; Gomez, Matthew R.; Knapp, Patrick K.; Hansen, Stephanie B.; Jennings, Christopher A.; Slutz, Stephen A.; Sefkow, Adam B.; Awe, Thomas J.; Peterson, Kyle J.; Hahn, Kelly D.; McBride, Ryan D.; Rochau, G.A.; Sinars, Daniel S.; Golovkin, Igor G.

Abstract not provided.

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TYPE Conference Poster YEAR 2015

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The Physics of Stagnation in magnetically driven implosions at z

Knapp, Patrick K.

Abstract not provided.

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TYPE Presentation YEAR 2015

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Laser Pre-Heat Studies for magLIF with Z-Beamlet

Geissel, Matthias G.; Harvey-Thompson, Adam J.; Awe, Thomas J.; Campbell, Edward M.; Gomez, Matthew R.; Harding, Eric H.; Hansen, Stephanie B.; Jennings, Christopher A.; Kimmel, Mark W.; Knapp, Patrick K.; Lewis, Sean M.; McBride, Ryan D.; Peterson, Kyle J.; Schollmeier, Marius; Sefkow, Adam B.; Shores, Jonathon S.; Sinars, Daniel S.; Slutz, Stephen A.; Smith, Ian C.; Speas, Christopher S.; Vesey, Roger A.; Porter, John L.

Abstract not provided.

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TYPE Conference Poster YEAR 2015

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Implementing and diagnosing magnetic flux compression on the Z pulsed power accelerator

McBride, Ryan D.; Bliss, David E.; Gomez, Matthew R.; Hansen, Stephanie B.; Martin, Matthew; Jennings, Christopher A.; Slutz, Stephen A.; Rovang, Dean C.; Knapp, Patrick K.; Schmit, Paul S.; Awe, Thomas J.; Hess, Mark H.; Lemke, Raymond W.; Dolan, Daniel H.; Lamppa, Derek C.; Jobe, Marc R.; Fang, Lu F.; Hahn, Kelly D.; Chandler, Gordon A.; Cooper, Gary W.; Ruiz, Carlos L.; Robertson, Grafton K.; Cuneo, M.E.; Sinars, Daniel S.; Tomlinson, Kurt T.; Smith, Gary S.; Paguio, Reny P.; Intrator, Tom P.; Weber, Thomas E.; Greenly, John B.

We report on the progress made to date for a Laboratory Directed Research and Development (LDRD) project aimed at diagnosing magnetic flux compression on the Z pulsed-power accelerator (0-20 MA in 100 ns). Each experiment consisted of an initially solid Be or Al liner (cylindrical tube), which was imploded using the Z accelerator's drive current (0-20 MA in 100 ns). The imploding liner compresses a 10-T axial seed field, B z ( 0 ) , supplied by an independently driven Helmholtz coil pair. Assuming perfect flux conservation, the axial field amplification should be well described by B z ( t ) = B z ( 0 ) x [ R ( 0 ) / R ( t )] 2 , where R is the liner's inner surface radius. With perfect flux conservation, B z ( t ) and dB z / dt values exceeding 10 4 T and 10 12 T/s, respectively, are expected. These large values, the diminishing liner volume, and the harsh environment on Z, make it particularly challenging to measure these fields. We report on our latest efforts to do so using three primary techniques: (1) micro B-dot probes to measure the fringe fields associated with flux compression, (2) streaked visible Zeeman absorption spectroscopy, and (3) fiber-based Faraday rotation. We also mention two new techniques that make use of the neutron diagnostics suite on Z. These techniques were not developed under this LDRD, but they could influence how we prioritize our efforts to diagnose magnetic flux compression on Z in the future. The first technique is based on the yield ratio of secondary DT to primary DD reactions. The second technique makes use of the secondary DT neutron time-of-flight energy spectra. Both of these techniques have been used successfully to infer the degree of magnetization at stagnation in fully integrated Magnetized Liner Inertial Fusion (MagLIF) experiments on Z [P. F. Schmit et al. , Phys. Rev. Lett. 113 , 155004 (2014); P. F. Knapp et al. , Phys. Plasmas, 22 , 056312 (2015)]. Finally, we present some recent developments for designing and fabricating novel micro B-dot probes to measure B z ( t ) inside of an imploding liner. In one approach, the micro B-dot loops were fabricated on a printed circuit board (PCB). The PCB was then soldered to off-the-shelf 0.020- inch-diameter semi-rigid coaxial cables, which were terminated with standard SMA connectors. These probes were recently tested using the COBRA pulsed power generator (0-1 MA in 100 ns) at Cornell University. In another approach, we are planning to use new multi-material 3D printing capabilities to fabricate novel micro B-dot packages. In the near future, we plan to 3D print these probes and then test them on the COBRA generator. With successful operation demonstrated at 1-MA, we will then make plans to use these probes on a 20-MA Z experiment.

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TYPE SAND Report YEAR 2015

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