© 2019 Energy confinementSTfield in high M Gryaznevich,M Buxton, P J Wood, Dnestrovskij,A A Nicolai,A experimentalstudies of Salmi , J Olsen, HTanabeandLtd TE team Theoreticaland EPTC 2019, Ghent, Belgium 7 - 10 October 2019 10 October © 2019 Tokamak Energy © 2019 Tokamak Energy TokamakEnergy Technology Roadmap to FasterFusion 2 © 2019 Tokamak Energy • • • • Together we can make Fusion Faster! Our principles: • DEMO), DEMO), with some specifics of anST. Our approach has Strong focus on validate modelling and progress at a Use of Collaboration compact high innovations (i.e. HTS) and the modular approach forpower plant based on we have a So,we rely on the multiplecompact devices andtest beds faster way in development of Fusion Science and Technologies industrial‘deliverability’ - field ST low common groundwith same physicssame to get to acommercially viable device due to use of - powermodules behind the magnetic fusion concept … but faster pace mainstream Tokamak Fusion (e.g. and . cost to advance technologies, and of the commercial device lower financialrisk ITER , 3 © 2019 Tokamak Energy magnets with HTS from compact First patent application filed on tokamak quickly Wecan build a small spherical current drive) (extended to > Plasma pulse Toroidal Field: Poloidal Field: Field: ST25 1.0 of a few milliseconds 2012 2012 20s with micro Copper Copper Low Achievements &Progress to date - wave wave low power spherical tokamak Patent filed on fusion power from magnets Wecan useHTS in tokamak Stable operations Industrial HTS coils,PF Toroidal Field: Poloidal Field: Field: 2013 2013 ST25 1.1 Copper Low HTS applications on HTS magnets First patent grant, have to be hugeto achieve Fusion. Papers published showing do not micro Long pulses feasible with HTS and RF (or 29 Plasma pulse of>100s in 2014 World First Toroidal Field: Poloidal Field: Field: - hour plasma - wave) wave) current drive 2014 2015 2016 2015 2014 Tokamak with ST25 1.2 in 2015 f our new patent Low HTS HTS all HTS all HTS magnets HTS magnets Three further patent applications on 1 financial viability of Compact Fusion and Papers on physics, engineering and is the key to compact fusion energy A high magnetic field in a small tokamak m/c formation achieved, kA 400 plasma current from completed, sub completed, 1st operation campaign highest Sphericalfield Tokamak Construction of Toroidal Field: Poloidal Field: Toroidal Field: st results of publishedST40 ST40 1.0 - ST40 keV ion temperatures - 18 (the world’s Copper Copper 1 T 1 ) in HTS magnets development at main Fusionconferences. Progress Results are published and presented increased TF improvement in performance with Results from first experiments indicate temperatures 2x10 First plasmas: 200 upgrades ofPSUs, coils, diagnostics. isST40 operating with significant Toroidal Field: Poloidal Field: Toroidal Field: 20 m - 3 , , keV 2019 ST40 1.1 - range electron and ion ms Copper Copper , , 400 kA, 1.5 1.5 T 4 © 2019 Tokamak Energy       Well equipped with diagnostics power (200 Pulse flattop length 1s at full ECRH) >4MW of heatingauxiliary (NBI / merging Solenoid R (0.4 MAachieved), B t 0 =3T (1.5T achieved), I =0.4 - 0.6m, - - compression free start ms R/a=1.6 now) - ST40 up using - 1.8 p =2MA – κ =2.5 High field ST © 2019 Tokamak Energy High safetyHigh factor, H 1996 Plasma inCulham,START, better stability - mode, improved confinement Spherical Tokamaks, why? High High beta ( MG19/04/9915:50:25  T ,% 10 20 30 40 50 0 • • 0 normalisedI plasma current, DIII-D, #80108 (achievedthroughHeating) NB RECORD tokamak conventional 1998 1997 1996 Field Field already increased to 1.5T, and will be 3Tnext year already demonstrated in first experiments Improvements in performance with increased field 2 β 4

 ), P ON START ON 6

 N = 6 FUS (Troyon limit) 8  N

p = 3.5 /aB ~ 10 T  2 B FUSION POWER”,FUSION TECHNOLOGYVOL. 33 JAN. 1998 Ron determine its size”. great that the physics of this device will not “Apparently the high beta potential of the ST is so t 4 V, Stambaugh so volume(reactorsize) canbe reduced! , “THE SPHERICALTOKAMAK PATH“THE , TO on ST40 6 © 2019 Tokamak Energy • • • • Reconnectionstudies(merging Fast CD,heating, particles, confinementalpha Edgedivertor and studies Confinementstudies,validation of • • • Not covered in talk:this Li divertorstudies with Oxford University and University of Illinois Materialsstudieswith Imperial College HTSstudies Main areas oftheoretical studies - engineering - compressionformation) scalings for STs 7 © 2019 Tokamak Energy Confinement studies 8 © 2019 Tokamak Energy • • • • • ST40 and beyond. Limitations achievable with as low as 1MW of absorbedpower. In an auxiliary heating regime, we finda evenwhen plasma is only We show that high confinement regimes with path to Fusion. model ST40 parameters and to support thephysics basis compactof the high fieldST Transport simulations with ASTRA, NUBEAM and TSC codes have performed been to operations be extended to ST40 conditions, up to However, we show that iftheperformance achieved onother spherical tokamaks can . of applicability Confinement studies ohmically of confinement heated. 1 of MW Fusion power hot ion mode scalings neoclassical for prediction of performance of with transport can beexpected T i in the 10keV range to be can be expected in DT 9 © 2019 Tokamak Energy • • • in OH regime t E Can Can hot ion mode beachieved in a highfieldST? Can ST40 can check vs line vs line density averaged Q Confinement studies, ASTRA fus ~ 1 be achieved ina high field compact ST? applicability ofneoclassical theory absorbedpower density averaged with 1MW DTneutron line yield vs - NUBEAM simulations in a highfieldST density density absorbedpower with 1MW Central Central T i , T e vs line line vs averaged 10 © 2019 Tokamak Energy • •

Ti flat-top, keV 0.0 0.2 0.4 0.6 0.8 confinement at higher toroidal field. However, at and also with At the flat 0.0 T T i i mid of flat-top of mid flat-top end of - Confinement studies, experiment top, measured 0.5 B t Artsimovich ~ 1T we observe sharp increasein B t , T

1.0 T formula. i and and W 1.5 therm

increasewith - - - - Artsimovich START ST40 GLOBUS improvementTF athigher confirm confinement Most recent results T - i M and B for ST40 for t , in agreement, withSTART and Globus W therm which may suggest transition to better

W , kJ EFIT 10 12 0 2 4 6 8 0.6 W W W W EFIT EFIT EFIT EFIT September 2019 spring 2019 midof flat-top end of flat-top 0.8 B t 1.0 , T - M data 1.2 1.4

11 © 2019 Tokamak Energy • • 100 200 300 400 500 T • • • red crosses #4669: ASTRA modelling, Ions neoclassical,electrons fit to get differentHoh= i blue , eV , 0 Confinementabove Closestyellow, fit: n higher higher than In latest 0.758 0.759 0.76 0.761 0.762 t, sec t, 0.762 0.761 0.76 0.759 0.758 – n e Confinement studies, comparison with = 4 x 10 2 – 00kA T i NeoAlcator from Doppler; 19 200 Hoh=3 e NeoAlcator = 7 x 10 7 = ms shots confinement was estimated~ 45 ; scaling prediction yellow 19 ; ohmic scaling? ohmic – n e = 7 = 7 x 10 19 Hoh=2 ; green – - 50ms, which is about 7 n e = 7 x 10 scalings 19 TauE Hoh=1.4 / TauE_NeoAlcator . red line - 10 times – EFIT, 12 © 2019 Tokamak Energy t • • • E NA W , W , kJ

=0.07 =0.07 dia EFIT W Comparison of W Similar increaseSimilarin T Experiment shows similartrends asin 0 1 2 3 4 5 0 e dia increasesat lower density, in agreement with ASTRA predictions W W W with with EFIT EFIT dia × Confinement studies, comparison with 1 , mid of flat-top of mid , flat-top end of ,  0.5 neoAlcator n W 2 e aR NA , a.u. ,

2 q 3 95 EFIT T scaling and W 4 e NA with TF but withTF but at higher threshold TFthan for ions ~ a R ~ a 5

2 n e q 95 T , keV e 0 2 4 6 0 NeoAlcator OH regime density averaged in T e 2 and W and n 4 e , 10 EFIT 19 scaling, but scaling, much better confinement at higher TF m 6 -3 vs vs line 8 10 0 2 4 6

W , kJ EFIT scalings

T , keV e 0.0 0.5 1.0 1.5 2.0 2.5 1.0 spectrometer TF vs T e measured with SXR 1.1 B t , T 1.2 1.3 1.4

13 © 2019 Tokamak Energy • in GT2simulations reduction in transport at higher toroidal field inanST: Observedsharp increase in Improvement in confinement at higher Toroidal Field T i and W therm at B - - - t ~ 1T may be connected with the predicted one one Threshold toroidal quitefield is low,toclose no betadependenceor shape at highfield electrostatic diffusivitydominated then being by aretearingthese modes; diffusivity isdominatedby At low observed in observedST40, ~1 magnetic field the mixing lengthmagneticfield the twistingmodes. - stabilised athigher 1.5 T 1.5 electromagnetic B 14 t , © 2019 Tokamak Energy Edge simulations 15 © 2019 Tokamak Energy Edge simulations 16 © 2019 Tokamak Energy Edge simulations, Power Profiles 17 © 2019 Tokamak Energy Fast particles studies 18 © 2019 Tokamak Energy • • • • usefulinformation for evenat the highest available fields. However, experiments on ST40 will provide scenario illustrating that the alpha confinement in a small device isvery difficult The orbit following (which is necessary becausethe of large particle alpha gyro radius). The DifferentNBI energies and launch geometries have beenstudied and optimized. Monte Carlo code NFREYA andthe Fokker deposition and Studies of first orbit losses confinement of thermal alphas fast ions andalpha particle momentum Fast particles studies are seento be almost verification transport have performed been usingASCOT, NUBEAM, of such simulations. in ST40 3T/2MA scenario is studied with full transport, heating and current drive, - 60% Planck Planck code NFIFPC. evenin the high - performance torque 19 © 2019 Tokamak Energy • simulationsforST reactor Importancefull of Monte(M Carlo the leftstagnationaway from point. pointand the counter tomovetoward the right stagnation orbits.The co a - particledownslowingby banana - orbit – legs of the bananastry of legs - C) codeC) Fast particles studies, - legs move legs NFREYA . orbit losses. orbit ASCOT Tritonsthe of 50% are Roughly thermalisation). or hit (wall final position the reach to took it time indicates the colour in losses MarkerST40. Tritiumand wall thermalisation a - particles . first neutrons 14MeV producing channel main 1.1x10 1.2T/2MA, for Deuterium thermal Tritium slowing down against MeV1.01 between reaction a DT Fast - thermal TD reaction rate fromrate reaction TD thermal 19 m . ASCOT - 3 ,1MW NBI. This the This is NBI. ,1MW . 20 © 2019 Tokamak Energy Reconnection studies 21 • • •

© 2019 Tokamak Energy This This canachieved beusing magneticreconnectionsmergingduring to 90%), thus usingmagneticfield It is possibleto transfer vessel,applied bythemagnetic externallyfield. Magneticconfinementcontainmentis basedon of hotplasma and insolationfrom ofit theof the wall vacuum • • • Better use of Magnetic Field: reconnection heating >2keV. these predictionsandshow temperatures First from resultsST40 alreadyconfirm with temperatures~10 keV shouldshow andJapanese devices,plasmain experimentaldata fromSTART, MAST dueto reconnection~ B Accordingto theory that predicts heating in astrophysics60 in Reconnectionhastheory beendeveloped ignitionparameters( magnetic energy - 70th 2 , and not not only for the containment nT ST40 t ) directlytheinto plasma Predictions , but also thermal energy - compression formationof theplasmacompression tokamak for the plasma First results: confirmed! scaling with a veryhighwithefficiency (up heating . 22 • • •

© 2019 Tokamak Energy keVisobtained in roughagreement MAST with ST40& results 3 timeof aheating and D(r)reconnectionAssuming the deposition withMWpowerheating of 20 in coAlfven areenergyand poloidalmainly running NFREYA Tomerging model reconnection producedby Orbits of ions the Reconnection heating – MonteCarlosimulations arethe assumption onthations based theformed the reconnectionduring reachthe - compression processcodes NFREYA, Torusand TSC II haveused. been

reconnected ions D(r) Deposition profile of –

injection injection of fast ions - reconnection heating, TSC Time evolution of direction T i due to MASTand of Time evolution of ms , temperatureof T i on ST40 on T e,i on T i ~1 23 can start from from Compactcan ST start with R aslow as 0.4m •

© 2019 Tokamak Energy • high • needed to support the ST path to Fusion • The ST path to commercial application of Fusion Innovations Fusioncan make sooner andcheaper Demonstration ofburning plasma in a compact More theoretical theoretical More and experimental studiesare - field field ST is the currentchallenge for Fusion • ST40 is the first high field Spherical Tokamak CONCLUSIONS 24