Field-reversed configurations (FRCs) are often the plasma target of choice for magnetized target fusion efforts of multi-microsecond timescale, which require closed-field lines. While Z is fast enough to operate in a hybrid inertial MTF regime (MagLIF), compression of an HED FRC within a MagLIF-like liner may offer many advantages.
Analytic estimates and LASNEX simulations by Slutz et al.1 suggest very interesting fusion gains (QDTsci~1) with FRC compression on Z. In an advantage over FRC liner compression efforts utilizing translation2, it is proposed these FRCs be formed in situ using an AutoMag-type liner.3
To investigate this novel formation method, a high-field FRC formation platform was developed on the MAIZE LTD at UM. Fast-framing images and magnetic probe data reveal interesting dynamics to the plasma annuli formed within deuterium-filled quartz discharge tubes, perhaps suggesting successful FRC production under the proper conditions. Effects of pre-ionization, bias field, and D2 fill pressure are explored.
2-D simulations of FRCs initialized with parameters relevant for MTF on Z predict anomalous lifetimes consistent with empirical scaling laws.4 In fact, resistive lifetimes appear to be ample for compression; formation robustness and stability to tilt and rotational modes remain the primary concern at high-density. The effects of field gradients are explored. Synthetic images are generated for comparison with experimental images.
In summary, prospects for HED FRC compression on Z are bright — but a great deal of work remains. Optimization of energy coupling to a liner on Z with pulse-shaping remains an open question which may influence the desired FRC parameters. Once such parameters have been identified, the proper formation hardware should be designed and tested on the Mykonos LTD. If a proper FRC starting target can be produced and diagnosed on Mykonos, the path to the first HED FRC shot on Z should become clear.
References:
1S. A. Slutz & M. R. Gomez, Phys. of Plasmas 28, 042707 (2021); https://doi.org/10.1063/5.0044919
2J. H. Degnan et al., Nucl. Fusion 53 093003 (2013); https://doi.org/10.1088/0029-5515/53/9/093003
3S. A. Slutz et al., Physics of Plasmas 24.1 (2017); https://doi.org/10.1063/1.4973551
4Alan L. Hoffman et al., Fusion Technology 23:2 (1993); https://doi.org/10.13182/FST93-A30147
This work was supported in part by the NNSA Laboratory Residency Graduate Fellowship program under DOE Contract No. DE-NA0003960 and by the NNSA Stewardship Sciences Academic Programs under DOE Cooperative Agreement DE-NA0003764. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
Authors: B.J. Sporer1, A.P. Shah1, G.V. Dowhan1, J.M. Chen1, T.J. Smith1,2, N.M. Jordan1, G.A. Shipley2, S.A. Slutz2, T.E. Weber3, C.A. Jennings2, A.J. Crilly4, R.D. McBride1
1University of Michigan, USA
2Sandia National Laboratories, USA
3Los Alamos National Laboratories, USA
4Imperial College London, United Kingdom