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Development of a Compact Fusion Device Based on the Flow Z-Pinch

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Development of a Compact Fusion Device Based on the Flow Z-Pinch Development of a Compact Fusion Device based on the Flow Z-Pinch 2016 ARPA-e Annual Review Seattle, WA August 9-11, 2015 Harry S. McLean for the FUZE Team H.S. McLean1, U. Shumlak2, B. A. Nelson2, R. Golingo2, E.L. Claveau2, T.R. Weber2, A. Schmidt1 D.P Higginson, K. Tummel 1Lawrence Livermore National Laboratory 2University of Washington LLNL-PRES-678157 This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC Outline • What are we trying to do? • Scale up an existing 50 kAmp z-pinch device to higher current and performance: [Goal = 300 kAmp of pinch current.] • This requires new electrodes, new capacitor bank, new gas injection/pumping • Understand the plasma physics involved in the scale up to improve and inform projections of performance to reactor conditions • Why is this important? • A stable pinch at 300 kA of pinch current has some exciting applications • If the concept works at >1 MA of current, a power reactor may be possible • Direct adoption of liquid walls solves critical reactor materials issues • Fundamental questions about plasmas in these regimes are unresolved. • Why now? • First attempt at scaling up by large factor. (6x in current) • First look at physics with recently developed kinetic modeling methods • First use of agile power drive and gas input (multiple cap bank modules and multiple gas valves) • Why are the major challenges? • Unknown physics as discharge current is increased • The difficulty in generating and maintaining shear stabilization at higher currents for long (enough) duration is unknown 2 Lawrence Livermore National Laboratory LLNL-PRES-678157 Outline • What are we trying to do? • Scale up an existing 50 kAmp z-pinch device to higher current and performance: [Goal = 300 kAmp of pinch current.] • This requires new electrodes, new capacitor bank, new gas injection/pumping • Understand the plasma physics involved in the scale up to improve and inform projections of performance to reactor conditions • Why is this important? • A stable pinch at 300 kA of pinch current has some exciting applications • If the concept works at >1 MA of current, a power reactor may be possible • Direct adoption of liquid walls solves critical reactor materials issues • Fundamental questions about plasmas in these regimes are unresolved. • Why now? • First attempt at scaling up by large factor. (6x in current) • First look at physics with recently developed kinetic modeling methods • First use of agile power drive and gas input (multiple cap bank modules and multiple gas valves) • Why are the major challenges? • Unknown physics as discharge current is increased • The difficulty in generating and maintaining shear stabilization at higher currents for long (enough) duration is unknown 3 Lawrence Livermore National Laboratory LLNL-PRES-678157 Shear-stabilized pinch concept Gas injection valves Outer cylindrical Electrode 1) 2) 3) Inner cylindrical Electrode Capacitor Bank Neutral gas is injected through Neutral gas expands before a The plasma accelerates down puff valves into the annulus of capacitor bank is discharged the coaxial accelerator due to a coaxial plasma accelerator. across the electrodes. generated currents and magnetic fields. 4) 5) 6)t6 The plasma continues down At the end of the accelerator Inertia and gun currents the accelerator in a snow- the plasma assembles into a Z- maintain the plasma flow and plow manner. pinch configuration. supply until the accelerator plasma empties or the capacitor current vanishes. 4 Lawrence Livermore National Laboratory LLNL-PRES-678157 Existing Device (ZAP) Results: Axial plasma flow with velocity shear in the radial direction has been shown to stabilize a 1 m long x 1 cm diameter 50 kA z-pinch column for 20-40 usec VOLUME 87, NUMBER 20 PHYSICAL REVIEW LETTERS 12NOVEMBER 2001 Evidence of Stabilization in the Z-Pinch U. Shumlak, R. P. Golingo, and B. A. Nelson University of Washington, Aerospace and Energetics Research Program, Seattle, Washington 98195-2250 D. J. Den Hartog* Sterling Scientific, Inc., Madison, Wisconsin (Received 11 June 2001; published 29 October 2001) Theoretical studies have predicted that the Z-pinch can be stabilized with a sufficiently sheared axial flow [U. ShumlakPHYSICS and OF C.W. PLASMAS Hartman, Phys. Rev. Lett. 75, 3285 (1995)]. VOLUME A Z 10,-pinch NUMBER experiment 5 is MAY 2003 designed to generate a plasma which contains a large axial flow. Magnetic fluctuations and velocity … profiles in the plasmaSheared pinch areflow measured. stabilization Experimental results experiments show a stable period inthe which ZaP is overfl 700owZpincha times the expected instability growth time in a static Z-pinch. The experimentally measured axial velocity shear is greater than theU. theoretical Shumlak, thresholdb) B. A. during Nelson, theR. stable P. Golingo, period and S. approximately L. Jackson, zero and afterwards E. A. Crawford when the magnetic modeUniversity fluctuations of Washington, are high. Aerospace and Energetics Research Program, Seattle, Washington 98195–2250 DOI: 10.1103/PhysRevLett.87.205005D. J. Den Hartog PACS numbers: 52.58.Lq, 52.30.–q, 52.35.Py Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 ͑Received 7 November 2002; accepted 9 January 2003͒ Z The -pinch plasma configuration has been studied from the plasma boundaryϭ that it has no effect. Nonlinear since the beginning of the pursuitThe of stabilizing magnetic effect plasma of a shearedresults axial for theflowm on෇ the0 modem 1 are kink presented instability in inFig. Z pinches1. The re- has been confinement fusion [1–3]. The Z-pinchstudied was numerically largely aban- with a linearizedsults are ideal generated magnetohydrodynamic using Mach2 [12,13], model a totime-dependent, reveal that a sheared axial flow stabilizes the kink mode when the shear exceeds a threshold. The sheared flow stabilizing Nucl. Fusion 49 (2009) 075039 U. Shumlak etal doned as a magnetic confinement configuration due to resistive MHD code. An equilibrium is initialized with effect is investigated with the ZaP ͑Z-Pinch͒ Flow Z-pinch experiment at the University of violent magnetohydrodynamic (MHD) instabilities (gross a sheared axial plasma flow and an axially periodic den- Washington. An axially flowing Z pinch is generated with a 1 m coaxial accelerator coupled to a m ෇ 0 “sausage” and m ෇ 1 “kink” modes) demonstrated sity perturbation. The figure shows the pressure contours 1.0 200 pinch assembly chamber.IOP PUBLISHING Thean plasmad INTERNA assemblesTIONAL ATOMIC intoENERGY a pinchAGENCY 50 cm long with a radius of NUCLEAR FUSION 200 both theoretically and experimentally [4]. However, ex- for the case of (a) no flow and (b) yz͞a ෇ 0.2kVA at the 1.0 approximately 1 cm.Nucl. An Fusi azimuthalon 49 (2009) 075039array (9pp)of surface mounted magnetic probes located at the doi:10.1088/0029-5515/49/7/075039 m = 1 periments have generated Z-pinch plasmas with inherent same simulation time. Figure 1(a) shows a well-developedϭ midplane of the pinch measuresm the෇ fl0uctuation levels of the azimuthalZ modes m 1, 2, and 3. After axial plasma flows exhibiting stablethe confinement pinch assembles for times a quiescent periodinstability is found where in a static the mode-pinch activity plasma. is signi Figureficantly 1(b) reduced. m = 2 m ෇ 0 0.8 much longer than the predicted growthOptical imagestimes [5,6]. from a fastA framingshows camera a substantially and a ruby less holographic developed interferometerinstability indicate ina stable, m = 3 Z Z 0.8 150 stable, high-density -pinch configurationdiscrete pinch would plasmaEqu have duringa thisil-pinch time.ibr Multichord plasmaium, with Doppler a sheared flow shift axial measurementssh flow. ear of impurity and lines stability Z I 150 profound implications for magneticshow confinement a large, sheared thermo-flow duringThe the quiescent ZaP ( -pinch) period and experiment low, uniform atfl theow pro Universityfiles during of periods kAmps p nuclear fusion [7–9]. of high mode activity.m Z-pincheasurWashington plasmase havem has been beene producednts usedto thatinth investigate are globallye the stableZ-p effect for overofinch 700 Theoretical studies have demonstrated that the Z-pinch plasma flow on the stability of a Z-pinch. The experiment Edge Probe 0.6 Stable for: times the theoretically predicted growth time for the kink mode of a static Z pinch. The plasma has 0.6 Pulse 40108045 (kA) can be stabilized with a sufficientlya sheared sheared axial axial flowflow [10]. that exceedsis designed the theoretical to generate threshold a Z for-pinch stability plasma during which the quiescent contains period 0 Experimental results presented here show a stable period a large axial flow. The experimental device is depicted in 100 and is lower than theU. threshold Shumlak, during C.S. periods Adams, of high J.M. mode Blak activity.ely, B.-J. © Chan,2003 American R.P. Gol Instituteingo, /B 100 Z (kA) which is over 700 times the expected instability͓ growth Fig. 2.͔ The flow -pinch configuration is generated by m of Physics. DOI: 10.1063/1.1558294S.D. Knecht, B.A. Nelson, R.J. Oberto, M.R. Sybouts and Fluctuations p Z 0.4 I time in a static -pinch. The experimentally measuredG.V. ax- Vogmanusing a coaxial accelerator to initiate the hydrogen plasma B 0.4 ial velocity shear is greater than the theoretical threshold T ~ 40 us during the stable period and approximately zero afterwardsAerospace andEnergetics Research Program, University of Washington, Seattle, WA,USA quiescent I. INTRODUCTION The MHD instabilities of a Z pinch can be stabilized. A B /B when the magnetic mode fluctuations are high. TheE-ma cor-il: [email protected] m 0 B /B 50 close-fitting, conducting wall can be placed around the pinch m 0 50 discharge relation of the experimental stabilitySome of data the withfirst attempts the plasma to achieve controlled thermo- 7 0.2 plasma.
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