Nuclear Astrophysics with NIF: Studying Stars in the Laboratory This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 LLNL-PRES Richard N. Boyd Workshop on Statistical Nuclear Physics and Applications in Astrophysics and Technology July 11, 2008

NIF pptR. Boyd 04/18/072 NIF has 3 Missions National Ignition Facility Peer-reviewed Basic Science is a fundamental part of NIF’s plan Stockpile Stewardship Basic Science Fusion Energy

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NIF pptR. Boyd 04/18/075 We have already fielded ~ half of all the types of diagnostic systems needed for NIF science Full Aperture Backscatter Diagnostic Instrument Manipulator (DIM) X-ray imager Streaked x-ray detector VISAR Velocity Measurements Static x-ray imager FFLEX Hard x-ray spectrometer Near Backscatter Imager DANTE Soft x-ray temperature Diagnostic Alignment System Cross Timing System We have 30 types of diagnostic systems planned for NIC

NIF pptR. Boyd 04/18/076 NIF’s Unprecedented Scientific Environments: T >10 8 K matter temperature  >10 3 g/cc density Those are both 7x what the Sun does! Helium burning, stage 2 in stellar evolution, occurs at 2x10 8 K!  n = neutrons/cc Core-collapse Supernovae, colliding neutron stars, operate at ~10 22 ! Electron Degenerate conditions, Rayleigh-Taylor instabilities for (continued) laboratory study. These apply to Type Ia Supernovae! Pressure > bar Only need ~Mbar in shocked hydrogen to study the EOS in Jupiter & Saturn These certainly qualify as “unprecedented.” And Extreme!

NIF pptR. Boyd 04/18/077 Reaction Studies for Nuclear Astrophysics

NIF pptR. Boyd 04/18/078 Thermonuclear Reaction Rates between charged particles are of the form: Rate ~ = (8/  ) 1/2 (k B T) -3/2  0  E  (E) exp[-E/k B T] dE. Define  (E) = [S(E)/E] exp[- bE -1/2 ], where penetrability = exp[- 2  z 1 Z 1 e 2 /  v] = exp[- bE -1/2 ] S factors are extrapolated to the relevant stellar energies, in the Gamow window, from higher energy experimental data Screening Laboratory atomic electron screening effects are significant Stellar electron screening effects are also significant, but quite different NIF screening is due to degenerate electrons; that’s different still Stellar Astrophysics at NIF: Measurements of Basic Thermonuclear Reactions

NIF pptR. Boyd 04/18/079 NIF and Neutrino Mixing The Sun emits electron-neutrinos e, but some of them change to some other “flavor” of neutrino x by the time they get to Earth: Oscillation probability = sin 2 2  sin 2 (  m 2 L/4E), where  = the mixing angle,  m 2 = m 2 2 – m 1 2, where the m’s are the masses of the two neutrino species, and L = the distance they have travel from Sun to Earth. The KamLAND neutrino oscillation result, showing the ratio of detected neutrinos from reactors to the no-oscillation result (for which the data points would be at 1.0), versus L/E. From Abe et al Two types of neutrino oscillations have been observed, solar and atmospheric: their solutions are indicated. The lower mass solution is the result from solar neutrino oscillations. From Bahcall et al.

NIF pptR. Boyd 04/18/0710 Nuclear Reactions and Solar Neutrinos 1H1H 1H1H 1H1H 8B8B e-e-3 He 1H1H 7 Li 7 Be 4 He 3 He 2 H; LE- ’s 1H1H 4 He+ 1 H+ 1 H 4 He+ 4 He 8 Be*; HE- ’s 4 He+ 4 He pp-I pp-IIpp-III The pp-chains describe how 4 1 H → 4 He + energy in the Sun. Blue indicates where neutrinos are emitted. pp-III emits the highest energy, and therefore most detectable, neutrinos, but that branch is very weak. The pp-chains of H-burning 3 He+ 4 He→ 7 Be+  is crucial for predicting the neutrino spectrum. But it has proved to be a difficult reaction for which to measure the cross section.

NIF pptR. Boyd 04/18/0711 Comparison of 3 He( 4 He,  ) 7 Be Measured at an Accelerator Lab and Using NIF NIF-Based Experiments Gamow window Resonance Accelerator-Based Experiments Mono-energetic Low event rate (few events/month) Inconsistency between two techniques High Count rate (~10 5 atoms per shot) Integral experiment Should resolve inconsistency Detect 7 Be with RadChem diagnostic system Be Ablator 3 He( 4 He,  ) 7 Be X X He + 4 He atoms √ √ √ √ √ NIF Point? 3 He( 4 He,  ) provides important definition of neutrino parameters! Gyurky et al.

NIF pptR. Boyd 04/18/0712 Measuring The Age of the Universe Globular clusters are clusters of ~1 million stars that formed at about the same time, early in the history of our Universe. Stars on the main sequence (MS; red curve) of the H-R diagram burn H until it is gone; then they leave the main sequence. Knowing the age of the stars that have just turned off the MS gives a lower limit on the age of the Universe. Globular cluster NGC 104. From South African Large Telescope H-R diagram for the globular cluster M3. Note the characteristic "knee" in the curve at magnitude 19 where stars begin entering the giant stage of their evolutionary path. From Wikipedia M3 MS

NIF pptR. Boyd 04/18/0713 NIF’s Contribution: 14 N(p,  ) Reaction Rate Astrophysical S-factor for 14 N(p,  ) from the LUNA (underground) facility (filled squares). The new reaction rate is 60% of the older rate at stellar temperatures. From Lemut et al., The 14 N(p,  ) 15 O reaction is the slowest one in the primary CNO cycle; thus it determines (with a stellar evolution code) how long stars exist in their H- burning, or main sequence, phase. 12 C 13 N 13 C 14 N 15 O 15 N (p,  ) (p,  )  -decay This reaction is so crucial to determining the ages of the globular clusters that it needs to be studied again, preferably with a different technique. NIF will provide that. Primary CNO-cycle This is a difficult reaction to study with an accelerator beam; it’s less complicated (!) with NIF.

NIF pptR. Boyd 04/18/ He( 3 He,2p)  ~ reactions at 10 8 K in 50 ps (10 18 initial nuclei) 4 He( 3 He,  ) 7 Be ~ 4 x 10 4 reactions at 10 8 K 12 C(p,  13 N ~ 3 x 10 5 reactions at 10 8 K 14 N(p,  ) 15 O ~ 6 x 10 6 reactions at 10 8 K Some Estimated Thermonuclear Reaction Yields at NIF (Greife): Detect protons— could be difficult, won’t be monoenergetic Detect 7 Be using RadChem or AMS; T 1/2 = 53 days Detect 13 N using RadChem; T 1/2 = 10 minutes Detect 15 O using RadChem; T 1/2 = 2 minutes Some other potential reactions:  17 O(p,  ) 18 F (interesting case for CNO cycles, strong resonances)  21 Ne(p,  ) 22 Na (strong yield from unmeasured resonance at 94 keV)  22 Na(p,  ) 23 Mg (difficult, since a radioactive target)  24 Mg(p,  ) 25 Al and 25 Mg(p,  ) 26 Al (might allow study through 26 Al m ).

NIF pptR. Boyd 04/18/0715 Measuring s-process rates in a hot plasma Er Tm Yb Lu Hf d d d1.9y64h h d h 1.9h The s-process occurs at kT ~ 8 keV or ~25 keV; NIF will achieve kT ~ 10 keV. 171 Tm has an excited state at 12 keV; that will be populated in the s-process environment, and in the NIF capsule. An excited state will affect both the effective  -decay rate and the effective cross section, possibly by large factors. NIF will be able to measure that effect for the neutron captures.

NIF pptR. Boyd 04/18/0716 How to do an s-process experiment on NIF? N 172 =  collection ∫∫∫  n (r,t,E n ) N 171  (n,  ) 171 (E n ) (4  r 2 ) -1 dr dt dE n ↓ N 172 /N 170 → ∫N 171  (n,  ) 171 dE n / ∫N 169  (n,  ) 169 dE n Co-loading isotopes for which the cross section is known with that on which it is to be measured minimizes systematic uncertainties  n determined from NTOF Ablator T Ice T Gas Compress pellet by a (radial) factor of 20; get neutrons up to a few MeV from T+T→ 4 He+2n Insert ~ Tm Tm

NIF pptR. Boyd 04/18/0717 A unique NIF opportunity: Study of a Three-Body Reaction in the r-Process Abundance after  decay Mass Number (A) Currently believed to take place in supernovae, but we don’t know for sure r-process abundances depend on: —Weak decay rates far from stability —Nuclear Masses far from stability The cross section for the  +  +n  9 Be reaction

NIF pptR. Boyd 04/18/0718   8 Be During its s half- life, a 8 Be can capture a neutron to make 9 Be, in the r-process environment, and even in the NIF target n 9 Be If this reaction is strong, 9 Be becomes abundant,  + 9 Be  12 C+n is frequent, and the light nuclei will all have all been captured into the seeds by the time the r-process seeds get to ~Fe If it’s weak, less 12 C is made, and the seeds go up to mass 100 u or so; this seems to be what a successful r-process (at the supernova site) requires The NIF target would be a mixture of 2 H and 3 H, to make the neutrons (not at the right energy—but it might be modified), with some 4 He (and more 4 He will be made during ignition). This type of experiment can’t be done with any other facility that has ever existed  +n  9 Be is the “Gatekeeper” for the r-Process

NIF pptR. Boyd 04/18/0719 How to detect the reaction products from NIF?

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NIF pptR. Boyd 04/18/0721 Core-collapse supernova explosion mechanisms remain uncertain 6 x 10 9 cm SN observations suggest rapid core penetration to the “surface” This observed turbulent core inversion is not yet fully understood Standard (spherical shock) model [Kifonidis et al., AA. 408, 621 (2003)] Density t = 1800 sec Jet model [Khokhlov et al., Ap.J.Lett. 524, L107 (1999)] Pre-supernova structure is multilayered Supernova explodes by a strong shock Turbulent hydrodynamic mixing results Core ejection depends on this turbulent hydro. Accurate 3D modeling is required, but difficult Scaled 3D testbed experiments are possible cm 9 x 10 9 cm

NIF pptR. Boyd 04/18/0722 Core-collapse supernova explosion mechanisms remain uncertain A new model of Supernova explosions: from Adam Burrows et al. A cutaway view shows the inner regions of a star 25 times more massive than the sun during the last split second before exploding as a SN, as visualized in a computer simulation. Purple represents the star’s inner core; Green (Brown) represents high (low) heat content From In the Burrows model, after about half a second, the collapsing inner core begins to vibrate in “g-mode” oscillations. These grow, and after about 700 ms, create sound waves with frequencies of 200 to 400 hertz. This acoustic power couples to the outer regions of the star with high efficiency, causing the SN to explode Burrows’ solution hasn’t been accepted by everyone; it’s very different from any previously proposed. But others (Blondin/Mezzacappa) are also looking at instabilities as the source of the explosion mechanism

NIF pptR. Boyd 04/18/0723 HEDP provides crucial experiments to interpreting astrophysical observations We envision that NIF will play a key role in these measurements Eleven science questions for the new century: 2. What is the nature of dark energy? — Type 1A SNe (burn, hydro, rad flow, opacities, EOS, age of universe) 6. How do cosmic accelerators work and what are they accelerating? — Cosmic rays (strong field physics, nonlinear plasma waves) 4. Did Einstein have the last word on gravity? — Accreting black holes (photoionized plasmas, spectroscopy) 8. Are there new states of matter at exceedingly high density and temperature? — Neutron star interior (photoionized plasmas, spectroscopy, EOS) 10. How were the elements from iron to uranium made and ejected? — Core-collapse SNe (reactions of stellar burning, turbulent hydro, rad flow, neutrinos) NATIONAL RESEARCH COUNCIL OF THE NATIONAL ACADEMIES The NRC committee on the Physics of the Universe highlighted the new frontier of HED Science

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