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LA-UR-17-25642 (Accepted Manuscript) Exploring lower cost pathways to economical fusion power Hsu, Scott C. Provided by the author(s) and the Los Alamos National Laboratory (2017-10-25). To be published in: Open Access Government DOI to publisher's version: Permalink to record: http://permalink.lanl.gov/object/view?what=info:lanl-repo/lareport/LA-UR-17-25642 Disclaimer: Approved for public release. Los Alamos National Laboratory, an affirmative action/equal opportunity employer, is operated by the Los Alamos National Security, LLC for the National Nuclear Security Administration of the U.S. Department of Energy under contract DE-AC52-06NA25396. Los Alamos National Laboratory strongly supports academic freedom and a researcher's right to publish; as an institution, however, the Laboratory does not endorse the viewpoint of a publication or guarantee its technical correctness. W hen I entered graduate school in 1993 to study plasma physics and fusion, the United States already had designs to build a “burning-plasma” fusion experiment in which the power pro- duced by fusion would, for a short duration, exceed the heating power required to sustain those reactions 1 , i.e., “scientific breakeven.” Had we proceeded then to build such an experiment, we might have achieved that milestone a decade ago. The experiment was never built, and, instead, the multi-national collabora- tion ITER 2 is now aiming to fulfill this mission. ITER’s final cost is projected to exceed US$20bn 3 , and it will take nearly another 20 years from today before ITER might demonstrate scien- tific breakeven. Fusion science and technology have advanced significantly since 1993, but we have frustratingly regressed with respect to the timeline for realising commercial fusion power. Why? The two biggest, interrelated reasons that progress toward fusion power has slowed to a crawl, in this author’s opinion, are (a) the significant cost (>US$10bn) of constructing a burning- plasma experiment based on the most scientifically mature approach (the tokamak), and (b) the absence of consensus that fusion energy is urgently needed. Such consensus, if it can be established, would increase the available public funding and therefore the rate of progress. At the present rate of progress, commercial fusion power will not be realised in time to impact midcen- tury carbon-emission tar- gets. All projected energy solutions (e.g., renewables with storage, fossil fuels with carbon sequestration, and advanced nuclear fis sion) have daunting challenges of their own to overcome in order to achieve the scales needed to meet midcentury energy demands. More timely development of fusion energy would greatly increase our chances of achieving an adequate carbon-free energy mix. But how do we increase the rate of progress toward realising economical fusion power, given the socio-political realities? Lowering costs There are many proposed pathways to fusion energy that are potentially “faster and cheaper” compared to the development path based on ITER. In the remainder of this and a series of subsequent articles, we draw from the story of our own fusion research to explore and advance a lower-cost development pathway toward eco- nomical fusion power, benefitting from and complementing mainstream fusion research that is centred around ITER. We assert that lowering fusion- development costs is essential to accelerate fusion development, such that fusion might penetrate power- generation markets by 2050. Our jour- ney over the past decade benefitted from desirable aspects of a public-pri- vate partnership to develop fusion, but our path occurred against great odds, whereas such paths should be enabled systematically throughout the worldwide fusion-development enterprise to improve its chances of timely success. Our research is focused on developing a reactor-friendly embodiment of magneto-inertial fusion (MIF), aka magnetised target fusion (MTF). MIF is a class of approaches involving the compression of a magnetised target plasma (consisting of the fusion fuel) The cost of fusion energy development is a significant reason why progress remains challenging. Scott C. Hsu of the Los Alamos National Laboratory explains Exploring lower cost pathways to economical fusion power 274 PROFILE Figure 1. Photo of the outer (top) and inner (bottom) electrodes of a (disassembled) coaxial plasma gun used to launch supersonic plasma jets in our fusion research. Photo courtesy of Hyper V Technologies Corp. to fusion conditions by an imploding pusher, called a “liner.” For example, the Canadian company General Fusion is developing MTF via acoustically driven liquid lead-lithium as their liner. MIF is inherently lower cost than other fusion approaches because MIF aims to achieve a compressed fuel density that optimises the combina- tion of plasma heating power and stored energy required to achieve fusion conditions 4 , thereby minimising the capital cost of the required facility. On the other hand, for historical and myriad other reasons, the mainstream, most scientifically mature approaches of magnetic-confinement fusion (MCF, such as ITER) and inertial-confinement fusion (ICF) operate at the lowest and highest extremes of fuel density, respectively. As a result, due to basic laws of plasma physics, MCF requires very large size and stored energy, and ICF requires very high power to com- press the fuel, which both drive costs into the multi-billion ($US) range for breakeven-scale facilities. In contrast, a breakeven-class MIF facility is expected to cost as little as a few hundred million dollars ($US). Our project, the Plasma Liner Experi- ment–ALPHA (PLX-α) 5 ,is one of nine projects supported by the ALPHA Program 6 of the Advanced Research Projects Agency–Energy (ARPA-E) of the U.S. Department of Energy (DOE). We use innovative, low-cost coaxial plasma guns (Fig. 1), developed and built by partner Hyper V Technologies Corp. 7 , to launch a spherically con- verging array of supersonic plasma jets toward the middle of a large, spherical vacuum chamber (Fig. 2). A key near-term goal of PLX-αis to merge up to 60 plasma jets to form a spherically imploding plasma liner, as a low-cost, high-shot-rate driver for compressing magnetised target plasmas to fusion conditions. This approach is known as plasma-jet-driven MIF (or PJMIF) 8 . A new startup company Hyper Jet Fusion Corporation (which recently received seed funding from Strong Atomics, LLC, a new fusion ven- ture fund) aims to develop PJMIF under continued public and private sponsorship. In an ensuing article, we will describe the key elements that led to joint public/private sponsorship of this research, in hopes of motivating public policymakers and private-sector investors to make such sponsorships more commonplace throughout the fusion-development enterprise. 1 For example, Burning Plasma Experiment Special, Fusion Tech- nology 21, 1045-1308 (1992); http://fire.pppl.gov/fusion_li - brary.htm(accessed July 9, 2017) 2 www.iter.org 3 http://www.firefusionpower.org/EU_US_ITER_Cost%20Estimate - s _2017.pdf ( accessed July 9, 2017) 4 I. R. Lindemuth and R. E. Siemon, Amer. J. Phys. 77, 407 (2009) 5 https://arpa-e.energy.gov/?q=slick-sheet-project/plasma-liners- fusion(accessed July 9, 2017) 6 https://arpa-e.energy.gov/?q=arpa-e-programs/alpha (accessed July 9, 2017) 7 www.hyperv.com 8 Y. C. F. Thio et al., “Magnetized Target Fusion in a Spheroidal Geometry with Standoff Drivers,” in Current Trends in International Fusion Research – Proc. 2nd International Symp. (NRC Canada, Ottawa, 1999), p. 113; S. C. Hsu et al., IEEE Trans. Plasma Sci. 40, 1287 (2012). Scott C Hsu Los Alamos National Laboratory Tel: +1 505 667 3386 [email protected] www.lanl.gov/ 275 PROFILE Figure 2. The objective of our research: to form a spherically imploding plasma liner (by merging 60 plasma jets) that will be used to compress a magnetized target plasma to fusion conditions. The cutaway spherical vacuum chamber is 2.7 m in diameter. Figure courtesy of Hyper V Technologies Corp.