Science under Extreme Conditions

Transcription

1 Science under Extreme Conditions Presented to: NAS Meeting of the Board on Physics and Astronomy Presented by: Dr. C. Deeney Director, Office of Inertial Confinement Fusion April 24, 2009

2 Outline Science under extreme conditions within NNSA New facilities Ignition as a grand challenge HEDP Science, nuclear science and dynamic materials science recent results NNSA/Office of Science - joint sponsors of HEDLP Conclusions 2

3 Understanding states of matter over a wide range of temperatures and pressures is at the heart of NNSA Omega 3

4 Computational science and experimental science must be integrated from the atomic- to the continuum-level to predict the properties of materials under extreme conditions Computational Materials Sciences e Microscale Atomic Scale Continuum Length scales m µm DAC Gas Gun Pulsed power Lasers nm Experimental platforms Static s s s 1 Strain Rates Pressure 4

5 For its mission, NNSA has built and operates the world s three largest HED facilities: NIF, OMEGA, and Z New 2009 Performance Enhanced 2008 Refurbished % of the energy from a weapon is generated in the high energy density state 5

6 NIF is Operational! 6

7 The Next Really Cool Thing by OP-ED Columnist Thomas L. Friedman March 14, 2009 NY Times Last Monday at 3 a.m., for the first time, all 192 lasers were fired at high energy precisely at once no small feat 1.1 MJ in ultraviolet laser energy (3? ) with a shaped laser pulse on target 7

8 Ignition will be the start of a new scientific era for NNSA and the Nation Ignition on NIF will be a defining moment for inertial confinement fusion energy 8

9 The National Ignition Campaign (NIC) is preparing for the 2010 ignition attempt on the NIF Laser-plasma instabilities can scatter light from capsule Capsules must remain spherically symmetric as they implode FFLEX spectrometer ( kev) X-ray emission thru LEH Backscattered light High-Z ball, or implosion, viewed in emission Four laser shocks used to heat capsule must be timed precisely Layered implosion with dudded fuel (THD) to test cryosystem VISAR and/or SOP Diagnostic holes 9

10 The NIC is on an aggressive schedule NIF Project CD4 96 beams Drive temperature T rad 96 beams Symmetry, shock timing, and ablation rate technique validation 192 beams Symmetry, shock timing, and ablation rate 192 beams Layered THD Layered dudded fuel (THD) implosions, 192 beams NIC runs into FY12 DT Ignition Implosions DT high yield 10

11 On Jan 14-16, 2009 JASONs studied the NIC at the request of NNSA CHARTER: Assess the readiness of the National Ignition Campaign (NIC) to execute credible ignition experiments by end of 2010 including: Target physics, including the specific ignition designs; Target fabrication; Diagnostics; Facilities and associated technologies Specific focus areas: Progress including addressing issues in the 2005 JASON report Will the NIC provide a reasonably optimal chance of success in the first ignition experiments in 2010? Is the plan for diagnostics deployment and preliminary experiments adequate to support the 2010 goal? Will the set of initial diagnostics enable early experiments to guide next steps? Are the risks at an acceptable level and reasonably mitigated? After the first ignition experiment in 2010, how should the risk mitigation efforts change? 11

12 JASON Summary While impressive progress has been made in the intervening period [since the 2005 JASON study] substantial scientific challenges remain. - Extent of challenges will only be fully revealed once NIC experiments are underway. - Diagnostics are planned for success and may not be sufficient to diagnose failures. - JASON is not the appropriate body to review the NIC - NIC is a scientific program [and must be managed differently from a project since it requires flexibility to adjust perhaps radically - as things are learned] NNSA is preparing its response 12

13 A technique to time the four shock waves in the NIF ignition target design has been demonstrated 13

14 An MIT-LLE collaboration has developed a Magnetic Recoil Spectrometer (MRS) to measure fuel areal density The number of neutrons downscattered from the cold fuel in ignition tuning experiments is determined by the fuel areal density. An MRS has been deployed on OMEGA and measured the downscattered neutron spectrum in a cryogenic target implosion. This was used to infer the areal density. 14

15 The new Z provides increased capability. Extracted Ta data to a stress of Mbar to complete first stewardship experiment on new Z in September anode cathode Required very precise shaping of the current pulse, via a predictive capability using MHD and circuit codes, and a load geometry (the stripline load) to provide high uniformity and accuracy. sample locations Capability Before refurbishment After refurbishment peak load current 18 MA 26 MA (dynamic materials load) peak current reproducibility + 5% deviation 24 MA (radiation-producing load) + 1% deviation stripline load geometry pulse shaping flexibility minimal variable pulse length, ns diagnostic lines of sight

16 Inferred stress-density of tantalum from first ZR stewardship experiment LANL model top sample pair LANL provided Ta equation of state and samples. SNL designed, fielded, and analyzed the data. Red, green, and blue heavy (light) lines correspond to inferred isentrope (uncertainty) for top, middle, and bottom sample pairs, respectively. Black line is principal isentrope from LANL model. 16

17 High pressure measurements have been published in Science, and demonstrate greater capability than those published in UGT days Nuclear-driven data point Data from one week of Z shots 17

18 Experiments have begun on the OMEGA Extended Performance (EP) Laser OMEGA EP was completed in April 2008 at the University of Rochester Operation as an NNSA User Facility began in FY09 OMEGA EP significantly extends OMEGA s research capabilities 18

19 The first attempt of 22 kev high energy radiography showed superb spatial resolution at 22 kev (926J, 90 ps, Jan 27, 2009) Au 50 mm thick substrate 30 mm grids 22 kev x-rays Ag micro-flag Intensity (PSL) Line outs along the grid pattern 10 mm grids 80 mm grids 10 mm grids 20 mm grids pxl 19

20 The propagation of a shock wave in Aluminum has been observed with a 17 kev backlighter Radiograph of shock in kev EP shot 4541 (Jan 29, 2009) 150 mm backlighter target 4 mm UV drive: 907J, 4 ns long 10 mm Al Sample TCC 80 ps backlighter Shock front radiography after 4 ns through 800 mm thick Al Radiographic imager 4 ns UV drive 20

21 LANSCE provides important contributions to the nuclear weapons program 8 mo/yr, 24/7, highly flexible beam delivery, simultaneous experiments - ~1200 user visits Lujan Center Materials and nuclear physics Weapons Nuclear Research (WNR) Nuclear Physics Neutron Irradiation Proton Radiography Dynamic Materials science Hydrodynamics Ultra-Cold Neutron (UCN) Fundamental Physics Isotope Production Facility Medical radioisotopes Nuclear cross-sections in support of Boost and Nuclear Forensics (Weapons Nuclear Research WNR) New Time Projection Chamber capability supports Boost Proton Radiographic measurements needed for PCF and Boost Materials research Data supports PCF and Boost All of these require LANSCE for the next ten years LANSCE-R provides needed improvements for reliable LINAC operations 21

22 LANSCE: Proton Radiography is a key capability for developing science-based prediction of weapons performance Shock Physics Melt on release in Sn Dynamic Materials Studies Equation of state measurement with prad and a powder Gun Catch tank Proton Beam 12' barrel 300g Breech HE Science Detonation Failure Studies in PBX /16 Tin experimental chamber 5/16 Tin sabot Flyer velocity 6/16 Tin 7/16 Tin 8/16 Tin Density (g/cm 3 ) Flyer shock 3 Target shock 2.9 Flyer Edge 2.8 LASL Shock Hugoniot Data Emperical fit Radiographic velocity measurements Pin velocity and radiographic density Up (km/s) Position (cm) Burn Front Position Time (microseconds) 22

23 Nuclear measurements on LANSCE are key to boost and forensics Final data analysis of 241 Am(n,γ) (DANCE) > 50 kev some disagreement with ENDF/B-VII found New data evaluation eliminates discrepancy with Jezebel results Time-Projection Chamber for high-precision fission cross section measurements Pu fission neutron spectra and cross-sections are crucial factors for predicting and determining yield QMU and other national weapons initiatives required precise knowledge of these factors LLNL/LANL collaboration will measure LLNL lead: Fission cross-sections to 1% accuracy using a Time- Projection Chamber (TPC) LANL lead: Fission neutron output spectra will be measured using an advanced neutron detector array 23

24 Our NNSA funded universities are doing pioneering work: first dynamic x-ray diffraction at a light source Advanced Photon Source at Argonne National Laboratory LiF(111) elastic Mg doped LiF(100) plastic Ambient Shocked Ambient HPCAT Shocked target chamber detector APS x-ray beam stress LiF(111) ; Mg doped LiF(100) ; Ultra-pure LiF(100) Lattice Compression (percent) Density Change (percent) gun-barrel position mosaic Spread (degrees) stress (kbar) 24

25 DARHT 2 nd Axis has exceeded all the goals and JASON predictions Technical Accomplishments Full Current 2 ka, 1.6 ms Four pulses with more dose and smaller spot size than the project goals!!! Full Energy 17 MeV Cells are all refurbished, installed and commissioned on schedule 25

26 Triangular ( Taylor ) spall is an important area of research to support development of predictive models Metals subjected to HE loading have triangular wave shape Much of the research on shockwave induced damage (spall, ejecta) using shock techniques has been done with flat top waves. Time & Length scales in experiments are important: Phase transitions occur in finite times Loading / unloading rates affect processes such as shock hardening & damage evolution (spallation / ejecta) Gun expts. are of similar timeframe to HE drive Various Techniques can yield a Triangular-Shaped Shockwave Profile msec PBX 9501 Longitudinal stress in PMMA (GPa) GPa 316L SS Gas Launcher A few msec Time (µs) Laser A few nanosec 26

27 Recent Experiments on Bi-crystals Have Shown Dependence on Crystal Orientation 27

28 Improved Explosive Models : Collaborative Isentropic Compression Experiment & Analyses SNL s Z-Machine & mini-pulser: constant entropy compression experiments to probe basic material properties under ramp wave loading High-P shots: unacceptable error in EOS [J. Appl. Phys. 99, (2006) ] Technique is very good at: - distinguishing phase changes, elastic limit behavior - comparing response of multiple materials PBX 9501 Dirty binder HMX 28

29 NNSA mission needs have driven the creation of environments that are ideal to study complex HED plasmas and materials in extreme conditions High Mach Number unstable flows Jets Rayleigh Taylor Instabilities Materials in the Extreme Mass Outflow Shocks and radiation transport MHD, thermo-electric, and anomalous heating 29

30 The broader importance of fundamental HEDP is recognized National Academy/workshop reports 30

31 The NNSA/SC Joint Program in Laboratory High Energy Density Plasmas was created to steward HEDLP within DOE 2004 Davidson report provided the starting point for the HEDP Interagency Task Force Key DOE finding: Stewardship of HEDLP needs to be improved DOE has taken action to improve stewardship: Joint Program in Laboratory HEDP announced February 2007 Oversight of HEDLP now a joint NNSA/SC responsibility Joint Solicitation with Office of Science for FY09 Large number of proposals currently being reviewed The DOE charged the Fusion Energy Science Advisory Committee (FESAC) to: work with the HEDLP community to provide information to develop a scientific roadmap for the joint HEDLP program in the next decade A FESAC subpanel was formed, chaired by R. Betti, Univ. of Rochester 31

32 NNSA and OFES are working on stewarding HED Physics We have establish a joint program on High Energy Density Laboratory Plasmas (HEDLP) We have planned a Research Needs Workshop for later this year We ran a joint program solicitation in 2009 and have received a significant number of proposals (~140) NNSA academic funding has been stabilized 32

33 Conclusions and Path Forward The academic involvement in High Energy Density Laboratory Plasmas (HEDLP) is being stewarded through the Joint Program World-leading HED facilities, nuclear physics facilities, and facilities that support studies dynamic materials studies have been built and funded by NNSA Our program is making great progress towards ignition and other applications in HEDP materials, nuclear physics and dynamic materials science 33