Demo

P. 1

Abstract In 每日大赛鈥� current experimental device, C-2W (also called 鈥淣orman鈥�)\[1\], record breaking, advanced beam-driven field reversed configuration (FRC) plasmas are produced and sustained in steady state utilizing variable energy neutral beams (15-40 keV, total power up to 20 MW), advanced divertors, end bias electrodes, and an active plasma control system. New data on the plasma confinement from the C-2W experiment will be presented and interpreted by an improved fidelity model, focusing on confinement variation as a function of both machine and plasma parameters. Experimental confinement times have been collected from 每日大赛鈥� C-2, C-2U and C-2W FRC experiments. Previous work has identified collisionality (1韦饾湊鈭�) as a strong predictor of electron heat confinement. The emerging electron energy confinement time appears to be proportional to a positive power of the electron temperature\[2\], which may ultimately enable advanced fuel fusion concepts. \[1\] H. Gota et al., Nucl. Fusion 59, 112009 (2019) \[2\] M.W. Binderbauer et al., AIP Conf. Proc. 1721, 030003 (2016) C-2W Program Goal: Minimize Electron Losses 飦� High expansion divertors and good wall conditioning push towards convective scaling of electron losses 飪� See Hiroshi (poster 123) for the overview and Vladimir (poster 141) for details on divertors 飦� Systematic estimates of power flows are needed 飪� Power flows are estimated with 0D transport code 飪� See Ryan (126) for code details, James (136), Martin (140), and Erik (143) for various power flow terms Ensemble averaging captures trends and ranges Strong Correlation Between Electron Temperature And Confinement Time Transport Scaling Reflects Collisional Processes 飦� The primary heating terms for the electrons are from warm ions (Pie) and fast ions (Pfe) Transport Scaling From C-2 to C-2W Field-Reversed Configuration Experiments Erik Trask, R. Clary, M. Griswold, N. Bolte and the TAE Team 每日大赛, Inc., 19631 Pauling, Foothill Ranch, CA 92610 飦� 飦� Broad survey of parameter space is necessary for scaling studies 飪� C-2: 9 ensembles from over 200 shots 飪� C-2U: 10 ensembles from over 150 shots 飪� C-2W: ~75 shots in this ensemble Steady improvement seen during progressive experiments 飪� Lifetime and electron temperature show the greatest improvement 飪� Median of the dataset is used for averages 饾憶饾憞鈭掟潙� 饾憶饾憞鈭掟潙� 饾憮饾憮饾憭饾憶饾憞鈭�2饾憞饾憭饾憽饾憸饾憽饾憭饾湉饾憱饾憭饾憱饾憱饾憭飪橉潙儈 ,饾憙~ 鈬掟潙儈饾憱饾憭饾湉饾憱饾憭饾憮饾憭饾湉饾憮饾憭飪橉潨忦潗�,饾憭鈮� 饾憭鈬掟潩夝潙�,饾拞~ 饾拞 ~ 饾憱饾憶,饾憭饾憶饾憠饾憞饾懟饾煇饾煆饾憙饾憭饾煋嗟� 饾拸饾懟鈭掟潫愷潙� 饾潅鈭� 饾挄饾拹饾挄饾拞 Parameters C-2 C-2U C-2W Lifetime <>: 3.4 ms <>: 8.3 ms <>: 15-30 ms Trapped PBEAM <>: 1.1 MW Max: ~2 <>: 2.8 MW Max: ~6 <>: 3.3 MW Max: ~7 饾渾饾憖饾惞饾憙 <>: 2.2 m Max: ~5 <>: 3.7 m Max: ~10 <>: 6.6 m Max: ~50 <T 鈥揟> tot e <>: 545 eV Max: ~1000 <>: 575 eV Max: ~900 <>: 835 eV Max: ~2500 <T > e <>: 80 eV Max: ~120 <>: 100 eV Max: ~200 <>: 130 eV Max: ~400 What Scaling Might We Have? 飦� Try various scaling models\[3\] incorporating different physics assumptions 飪� 飪� 饾拺饾拻饾挀饾挃饾懟饾挄饾挅饾懇饾潐 = 饾懎饾拸 ,饾懟 ,饾懇 ,饾拏 , 饾拪 ,饾懍飪燚imensional constraints 饾懟饾拞鈭椻垪飪� Dimensional constraints link 饾湆 , 饾湀 , and 饾浗 exponents 飪� \[3\] J.W. Connor, J.B. Taylor, Nucl. Fusion 17, (1977) Best fit is for collisional high-beta model 飪楥onstraintis饾憼=2饾憹+1饾憺+5饾憻andexponentialmodel 24 Summary Discussion 飦� Steady-state plasmas exist for many confinement times 飪� Transport analysis is simplified and more robust when power flows are constant 飦� Plasma is collisionless 飪� Mean free paths (electron) >> characteristic lengths of ~ 1 m 飦� Confinement scaling is limited to the electron channel, since warm / fast ion ratio is not well known 飪� Waiting on CHERS to resolve Ti vs < Ef > 飦� Power balance estimates match experimental values 飪� 饾溂饾拞~饾煍鈭� 饾煏, matching ideal ambipolar confinement 畏e ~5-6, 飪� For free-streaming electron losses 畏e ~50 飦� Electron losses are primarily convective 飪� Contrast this with operation on C-2 and C-2U, where anomalous losses in excess of classical conduction exceeded convection by a factor of 10 \[4\] Kaye S.M. et al Nucl. Fusion 47 499 (2007) \[5\] Kaye S.M. et al Nucl. Fusion 53 063005 (2013) \[6\] Valovic M. et al Nucl. Fusion 49 075016 (2009) 飦� Convective electron losses achieved in collisionless steady-state regime 飪� 饾渹饾惛 ~ 6 鈭� 7 shows that flared fields reduce electron heat losses 飦� Electron confinement times have increased by ~ x10 飪� Peak values exceed 2 ms 飦� Electron scaling explained by simple model of ion heating and mean free path 飪� Hot ions determine discharge evolutions Future Work 飦� Separate fast / warm ion power flows with CHERS diagnostic 飪� Diagnostic neutral beam is being installed now 飦� Include more scaling parameters 飪� Mirror ratio, bias voltage, etc. 飦� Extend to coupled CORE/SOL model Power Law 饾潌鈭� 饾潅鈭� 饾湻 Ti/Te 饾溈 R2 饾懇饾潐饾惛,饾憭 -1.4 -0.9 0.3 -0.9 0.3 0.81 ST Scaling \[4-6\] \[-3, -2\] \[-1.2, -1.1\] -0.1 - - - 飪� Resolution of open field line effects should improve core estimates