Dr. David H. Crandall Dr. Crandall is Advisor on National Security and Inertial Fusion to the Under Secretary for Science at the Department of Energy. His experience includes 16 years of physics research, 28 years of science program management, and 3 years as Chief Scientist for the National Nuclear Security Administration (NNSA). He has led significant scientific programs in plasma physics and Fusion Energy and in nuclear weapon Stockpile Stewardship prior to his current role. He entered the Senior Executive Service in 1987. Substituting for Dr. Robert McCrory and the Polar Drive team. Opening comment: This paper is about using direct drive and seeking a good set of parameters for compression of ICF capsules at low enough adiabat, high enough velocity and low enough Rayleigh-Taylor to reach ignition. The paper will illustrate these general comments. NIF is a highly capable facility and the ICF endeavor now has the opportunity to match that physical facility with research basis created by thinkers/doers. ICF has many avenues to be explored and we in the US have facilities (NIF, Omega, Z) to match with the avenues and the people. The exploration paths are flexible (we can change targets rapidly). Our high energy density science community is growing, vigorous and youthful.- that gives me confidence. The associated weapons and science programs do not require ignition to get value from these facilities; the IFE concept does. Fortunately ignition will also be valuable to the weapon scientists at our labs; we will continue to pursue it both for that reason and for the IFE concept. The DOE requires a proven ignition basis for any substantial IFE program. For scientists this is a wonderful time to match capability to challenge in ICF.
Progress Toward Polar-Drive Ignition for the NIF 10 ITFx NIF equivalent Neutron yield ( × 10 13 ) 1.0 P x ~ 3 atm-s Si-doped CD ablator 2012 0.5 Pure CD ablator 1 2010 IAEA FEC 0.2 0.1 0.05 0.02 0.01 0.1 P x ~ 1.7 atm-s 0 50 100 150 200 250 300 350 2010 t R ( mg / cm 2 ) R. L. McCrory Professor of Physics and Astronomy Professor of Mechanical Engineering 24th IAEA Fusion Energy Director, Vice Provost, and Vice President Conference University of Rochester San Diego, CA Laboratory for Laser Energetics 8 – 13 October 2012
• Performance continues to improve: – Multi-FM beam smoothing has been demonstrated on OMEGA EP on OMEGA • Progress in developing polar drive is ongoing • OMEGA direct-drive cryogenic target implosions are defjning the NIF Summary Direct-drive inertial confjnement fusion ( ICF ) research has made signifjcant progress since the 2010 IAEA meeting • Polar drive ( PD ) will allow for direct-drive–ignition experiments at the National Ignition Facility ( NIF ) in the x-ray-drive beam confjguration PD design space – neutron yields exceeding 10 13 ( up to ~ 20% of clean 1-D simulations ) - ion temperature increased from 2.2 to 3.0 keV – P x increased from 1.7 to 3.0 atm-s • A NIF-scaled experimental ignition threshold factor has increased from 0.05 to 0.15 – new phase plates will allow polar-drive cryogenic implosions Initial polar-drive experiments have been carried out on the NIF. TC10125
Collaborators D.D. Meyerhofer, 1 *, R. Betti 1 *, T.R. Boehly 1 , D.T. Casey 2, T.J.B. Collins 1 , R.S. Craxton 1 , J.A. Delettrez 1 , D.H. Edgell 1 , R. Epstein, J.A. Frenje 2 , D.H. Froula 1 , M. Gatu-Johnson 2 , Y.Yu. Glebov 1 , V.N. Goncharov 1 , D.R. Harding 1 , M. Hohenberger 1 , S.X. Hu 1 , I.V. Igumenshchev 1 , T.J. Kessler 1 , J.P. Knauer 1 , C.K. Li 2 , J.A. Marozas 1 , F.J. Marshall 1 , P.W. McKenty 1 , D.T. Michel 1 , J.F. Myatt 1 , P.M. Nilson 1 , S.J. Padalino 3 , R.D. Petrasso 2 , P.B. Radha 1 , S.P. Regan 1 , T.C. Sangster 1 , F.H. Séguin 2 , W. Seka 1 , R.W. Short 1 , A. Shvydky 1 , S. Skupsky 1 , J.M. Soures 1 , C. Stoeckl 1 , W. Theobald 1 , B. Yaakobi 1 , and J.D. Zuegel 1 1 Laboratory for Laser Energetics, University of Rochester 2 Plasma Science Fusion Center, Massachusetts Institute of Technology 3 State University of New York at Geneseo *also Depts. of Mechanical Engineering and Physics and Astronomy, University of Rochester
• LLE is developing polar drive • Cryogenic target implosions Direct-drive ICF is a viable ignition alternative for the NIF Three-picket NIF design • Direct-drive is predicted 37 n m CH 3 to couple 7 to 9 times more Power / beam ( TW ) Gain 1-D 160 n m DT energy to the compressed = 48 2 core than indirect drive 1700 n m DT gas • 2-D simulations predict 1 gains of ~ 50 on the NIF with symmetric irradiation 0 0 2 4 6 8 10 12 are studied on OMEGA at ~ 1 / 4 Time ( ns ) of the NIF target scale 23.5 ° 30 ° Repointing for polar drive* – R ~ ( E L ) 1 / 3 50 ° 23.5 ° to allow direct-drive–ignition 40 ° experiments while the NIF 75 ° is confjgured for x-ray drive 2-D simulations predict polar-drive ignition on the NIF when appropriate beam smoothing has been added. E18400l
The in-fmight aspect ratio and adiabat determine the target stability and areal density • In-fmight aspect ratio ( IFAR ) : Ratio of the implosion radius to the shell thickness at 2 / 3 of the in-fmight radius IFAR 2 / 3 = R 2 / 3 / D 2 / 3 – IFAR determines of the amplitude of the Rayleigh–Taylor ( RT ) modulations that disrupt the implosion – the 1-D minimum energy for ignition, E min ~ 1 /( IFAR ) 3 • Adiabat : Mass-averaged adiabat contributing to the stagnation pressure ^ h pressure Mbar P ^ h adiabat = = P 5 3 3 2 2 . g cm / f t – the adiabat determines the target compressibility and the RT growth rate TC10126
• The implosion velocity is varied • The target adiabat is changed with • The IFAR is varied through the OMEGA direct-drive cryogenic target implosions are defjning the NIF PD design space Target design – picket-pulse spacing b l a t o A r and heights T i c 0.3 D e – step on main pulse rise 430 n m D 2 / DT Power ( TW ) gas 0.2 – ablator thickness – ice thickness 0.1 through the 0.0 – target mass 0 1 2 3 4 – laser intensity Time ( ns ) ^ h Cryogenic target implosions are validating 0 6 . 0 34 . Y P ~ R x t meas the physics models used in simulations. TC10127
Cryogenic target performance is parameterized by the ratio of the neutron yield to that predicted by 1-D simulations [ yield over clean ( YOC )] Symmetric point design Map of Y exp / Y 1-D ( YOC ) 25 24 20 YOC ( % ) IFAR < 22 22 > 22.5 YOC ( % ) 20.0 to 22.5 15 20 IFAR 17 .5 to 20.0 15.0 to 17 .5 18 10 12.5 to 15.0 10.0 to 12.5 16 7 .5 to 10.0 5 < 7 .5 14 IFAR $ 22 Measured YOC 0 0 1 2 3 4 1.5 2.0 2.5 3.0 3.5 Adiabat Adiabat The 1-D simulations include all of the known physics with no adjustable “knobs.” TC10123
The areal density is degraded for lower adiabats 1.0 0.8 t R / t R ( 1-D ) 0.6 0.4 Offset < 20 n m 0.2 0.0 1 2 3 4 Adiabat TC10128
Growth factor • Fusion reactions occur Use simple clean volume analysis: Hydro-equivalency Hydrodynamic scaling suggests less yield degradation due to nonuniformities on NIF Shell 3 f p 3 D - R Y n 3 D - YOC = in the clean volume ( red ) . 1 D - R Y Hot spot Cold 1 D - n R 3-D G v o H ≈ 0 R 1-D • The required YOC on OMEGA is difficult to estimate. X NIF D R D R 3 = R – R ~ G G G v . - D 1 - D RT RT 0 RT RT RT RT spike amplitude Initial seed R V 3 1 3 / S W NIF f X p ^ h b l E v 1 3 / 0 L NIF S X W YOC 1 – 1 – YOC . S W X NIF S W E v L 0 T X YOC’s are expected to be higher on the NIF because of a signifjcantly larger clean volume fraction. TC8660a
on measurable quantities Implosion performance can be parameterized by an ignition threshold factor and the Lawson criterion • Betti et al .* derived an ICF Lawson criterion for ICF implosions based R V 0 34 . 0 8 16 . > H 0 24 . Y _ i S W ^ h 4 7 exp . 0 61 . ^ h 2 S W ^ h P atm - s ~ 27 R g cm / x t M g n S W S W T keV DT n T X † • LLNL derived an Experimental Ignition Threshold Factor ( ITFx ) – ITFx ( ID ) = ( Y / 3.2 × 10 15 ) × ( DSR/0.07 ) 2.3 , where t R ( g / cm 2 ) = 21 × DSR ( % ) – ITFx = 1 corresponds to a 50% likelihood of ignition – ITFx ~ ( P x ) 3 • This formula can be scaled to OMEGA ( X ) energies* – ITFx ( NIF equivalent ) = ITFx ( ID X ) × ( E NIF / E X ) 1.28 × ( M fuel NIF / M fuel X ) × YOC NIF / YOC X – E NIF = 1.8 MJ, E X = 25 kJ, M fuel NIF = 0.17 g, M fuel X = 0.02 g † S. W. Haan et al. , Phys. Plasmas 18, 051001 ( 2011 ) . * C.D. Zhou and R. Betti, Phys. Plasmas 15, 102707 ( 2008 ) ; R. Betti et al ., Bull. Am. Phys. Soc. 54, 219 ( 2009 ) ; R. Betti et al ., this conference. TC10131
OMEGA ITFx scaled to NIF has increased to ~ 0.15 10 ITFx NIF equivalent Neutron yield ( × 10 13 ) 1.0 P x ~ 3 atm-s Si-doped CD ablator 2012 0.5 Pure CD ablator 1 2010 IAEA FEC 0.2 0.1 0.05 0.02 0.01 0.1 P x ~ 1.7 atm-s 0 50 100 150 200 250 300 350 2010 t R ( mg / cm 2 ) TC10124a
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