Fukuoka, Japan. 23 August National Ignition Facility (NIF) Laboratory for Laser Energetics (OPERA)

Transcription

1 Fukuoka, Japan 23 August 2012 National Ignition Facility (NIF) LLNL-PRES This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA Lawrence Livermore National Security, LLC Laboratory for Laser Energetics (OPERA)

2 Capsule diameter ~1 mm National Ignition Facility NIF is a three football stadium-sized laser, which delivers ~1.8 MJ to a cm-scaled hohlraum Hohlraum 2

3 The opportunities for fundamental science experiments at NIF are expected to increase gradually over the next few decades.

4 Advantages Plasma environment is like a star Negligible electron screening corrections New phenomena Neutron flux is very bright Smaller targets Experiment is short (1 ps 1 ns) No radioactive backgrounds Flux (n/s/cm 2 ) { { 10 0 WNR Reactor SNS ~1 cm Capsule NIF

5 Disadvantages Plasma environment is complex Spatial and temporal profiles Currently not well modeled Laser environment is complex Difficult to cover large solid angle n D, n T [cm!3 ] 10 x 1020 OMEGA ns ns LSP, fully ns n D, n T Experiment is short (1 ps 1 ns) No coincidence events x [µm]! ei We are performing our measurements at the OMEGA laser, U. of Rochester. This 60-beam, 30-kJ facility is ideal for developing these new techniques.

6 MIT LLNL LLE/UR GA LANL D. Casey J. Frenje M. Gatu Johnson R. Petrasso C. Li M. Manuel H. Rinderknecht M. Rosenberg F. Séguin N. Sinenian H. Sio C. Waugh A. Zylstra D. McNabb J. Caggiano P. Navrátil** S. Quaglioni J. Pino I. Thomson C. Cerjan J. Edwards S. Hatchett O. Jones O. Landen A. Mackinnon R. Rygg R. Betti J. Delettrez, V. Glebov D. Meyerhofer P. Radha T. Sangster Indiana A. Bacher J. Kilkenny A. Nikroo H. Herrmann Y. Kim G. Hale ** Now at TRIUMF 6

7 The easy: n-t elastic scattering at E n = 14 MeV The hard: Prospects for 3 He( 3 He, 2p) In-between: Some surprising results for T(T,2n) Conclude

8 3.5 µm SiO2 Laser Power: 30 kj 1-ns square pulse 20 atm DT ~900 µm t n' DT n n SiO 2 glass shell ablated entirely at bang time d Spectrometer Y n = <T ion > n = 9 kev ρr ~ 20 mg/cm 2 n' E n = 14 MeV Plasma serves as both the source and the target.

9 F.H. Séguin et al., RSI 74, 975 (2003) Target OMEGA chamber 50keV (p) 2cm 30 MeV (p) 15 MeV (d) 10 MeV (t) 3 MeV (p) Electronic detectors are too slow CR-39 film is used to record ions tracks DD-p spectrum for reference CR-39: d : MeV t : MeV

10 Shot Shot Shot Counts / bin t' d' Counts / bin t' d' Counts / bin t' d' MeV The differential cross sections were obtained by deconvolving the Doppler broadening and spectrometer-response function

11 J. Frenje et al., PRL 107, (2011) n-d n-t 1. E. Epelbaum et al., Phys. Rev. C 66, (2002). Angle 2. P. Navrátil et al., LLNL-TR (2010). 3. G.A. Hale et al., Phys. Rev. C 42, 438 (1990). Nuclear diagnostics enabled an HED-based nuclear physics experiment that is better than previous accelerator experiments

12 3 He( 3 He,2p) 4 He S-factor for 3 He+ 3 He at LUNA accelerator Proton spectrum from LUNA at E cm = 30 kev Since there is weak screening in ICF implosions, NIF could be a place to test electron screening corrections observed with the LUNA underground facility.

13 ( 10 6 ) Shot ( 10 6 ) Shot p+ 5 Li resonance 1.0 p+ 5 Li resonance Yield / MeV p+p+ 4 He D- 3 He p Yield / MeV 0.5 p+p+ 4 He D- 3 He p Proton energy [MeV] Proton energy [MeV] Yields near solar temperatures will be very low (better at NIF) Need to develop techniques to measure protons <4 MeV

14 4 µm SiO 2 10 atm DT 10 µm CD 15 µm CH 12 atm DT 17 atm DT OMEGA Possible reaction channels: T + T 4 He + 2n (0-9.5 MeV) T + T 5 He + n (8.7 MeV) T + T 5 He* + n 20 µm CH ~135 µm CH ~70 µm THD ice 17 atm DT Understanding the T(T,2n) 4 He reaction at low CM energies has important implications for: 1. Stellar nucleosynthesis [ 3 He( 3 He,2p) 4 He] 2. HEDP/ICF 3. Nuclear physics THD gas 0.3 mg/cc NIF

15 3.0 dn / de [au] This work Neutron energy [MeV] Wong (1965) Allen (1951) Casey (2012) ECM = 250 kev ECM = 110 kev EG = 23 kev Data obtained at 90 Data obtained at all angles Improved experiment scheduled in November Better resolution Lower background Alphas Larger energy range D.T. Casey et al., PRL accepted (2012). K. W. Allen et al., PR 82, 262 (1951). C. Wong et al., NP 71, 106 (1965).

16 R-matrix resonance model fit (G. Hale) Resonance analysis of the Wong spectrum Cross section data are consistent with R-matrix parameters independent of energy. Experiments suggest that the reaction mechanism is changing at lower energies. S. Quaglioni, P. Navratil et al. are working to extend ab initio methods.

17 8 ( 10-3 ) 8 ( 10-3 ) 6 TT 6 DD Y TT / Y DT 4 2 Expected Y DD / Y DT Temperature [kev] D.T. Casey et al., PRL 108, (2012). P. Amendt et al., PRL 105, (2010). 4 Expected Temperature [kev] D T Hot core These results suggest that the implosion core becomes tritium rich. What particle transport mechanisms are responsible for this effect? 17

18 The T+T reaction mechanism is changing as the reaction energy is lowered 3He+3He is probably similar This is not understood in the context of R-matrix methods Three bodies in the final state make this complicated Better data are expected shortly from both OMEGA and NIF Nuclear physics is helping to shed light on complex behavior occurring in these dynamic experiments Central region of the plasma is tritium-rich as fusion occurs Is there something else? There are many other astrophysical reactions which can be studied at these laser-driven plasma facilities relevant to pp-chain, CNO cycle and BBN

19 Hot/Dense Plasma kbt 1-20 kev ρ ~ g/cm3 High Neutron Brightness Φ ~ in few ps 10% nuclei react Stellar and Big Bang Nucleosynthesis in Plasmas Nuclear Probes of Hydro and Transport Formation of the Heavy Elements and the Role of Excited Nuclear States

20