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Relativistic Plasmas in Astrophysics and in the Laboratory Edison Liang Rice University

Relativistic Plasmas in Astrophysics and in the Laboratory Edison Liang Rice University Collaborators: H. Chen, S.Wilks, B. Remington (LLNL); W. Liu, H. Li, M. Hegelich, LANL; T. Ditmire, (UT Austin); A. Henderson, P. Yepes, E. Dahlstrom (Rice) LANL Talk , July 28 2010.

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Relativistic Plasmas in Astrophysics and in the Laboratory Edison Liang Rice University

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  1. Relativistic Plasmas in Astrophysics and in the Laboratory Edison Liang Rice University Collaborators: H. Chen, S.Wilks, B. Remington (LLNL); W. Liu, H. Li, M. Hegelich, LANL; T. Ditmire, (UT Austin); A. Henderson, P. Yepes, E. Dahlstrom (Rice) LANL Talk , July 28 2010

  2. made possible by recent advances in High Energy Density Physics Shocks and

  3. New Revolution: Ultra-intense Short Pulse Lasers bring about creation of Relativistic Plasmas in the Lab Matching high energy astrophysical conditions LLNL Titan laser RAL Vulcan Laser

  4. Many new >100J-class PW lasers are coming on line in the US, Europe and Asia Omega laser facility, Univ. of Rochester FIREX Gekko Omega laser Omega-EP ILE Osaka The National Ignition Facility LLNL TPW ARC

  5. Phase space of laser plasmas overlap some relevant high energy astrophysics regimes PulsarWind LWFA GRB 4 3 2 1 0 GRB Afterglow Blazar log<g> 2x1022Wcm-2 LASER PLASMAS 2x1020 solid density Microquasars Stellar Black Holes coronal density 2x1018 100 10 1 0.1 0.01 (magnetization) We/wpe

  6. Topics in Relativistic Plasmas • Pair Plasmas • Poynting Flux Dissipation • Current Sheets and Reconnection • Collisionless Shocks and Weibel Instability 5. Shear Layers 6. Laser cooling of relativistic plasmas Most relativistic plasmas are “collisonless” so MHD fails. Need to use kinetic simulations such as Particle-in-Cell (PIC) codes.

  7. relativistic e+e- plasmas are ubiquitous in the universe NonthermalTeV pairs Thermal MeV pairs Laser-produced pair plasmas can be used to study astrophysics

  8. Gamma-Ray Bursts: High G favors an e+e- plasma outflow? Woosley & MacFadyen, A&A. Suppl. 138, 499 (1999) e+e- e+e- Internal shocks: Hydrodynamic What is primary energy source? How are the e+e- accelerated? How do they radiate? Poynting flux: Electro- magnetic

  9. Ultra-intense Lasers is the most efficient tool to make e+e- pairs In the laboratory Bethe- Heitler e+e- MeV e- e Trident

  10. =100 J /100 fs In reality, the max. achievable pair density is probably around 1019 - 10 20 cm -3

  11. 1019W/cm2 Liang et al 1998 1020W/cm2 Nakashima & Takabe 2002 Pair Creation Rate Rises Rapidly with Laser Intensity to ~1020Wcm-2 but levels off after 1021Wcm-2(Liang et al PRL 1998).

  12. Early laser experiments by Cowan et al (1999) first demonstrated e+e- production with Au foils. But the flux was low due to off-axis measurements and inefficient spectrometer. e+e- Cowan et al 1999 2.1020W.cm-2 0.42 p s 125mm Au

  13. ? quadratic linear I=1020Wcm-2 (Nakashima & Takabe 2002) Trident process dominates for thin targets. Bethe-Heitler dominates for thick targets. How high can the e+ yield go if we use very thick targets?

  14. Au 1 2 Set up of Titan Laser Experiments

  15. Sample Titan data 1 1 2 Monte Carlo simulations MeV

  16. Emergent positrons are attenuated by cold absorption inside target due to ionization losses but also accelerated by sheath fields. incident hot electron spectrum T =17.4mc2= 8.7 MeV 0 mm f(g) 0.25mm 0.5mm sheath electric field modifies emergent e+ spectra 0.75mm 1mm cold attenuation cuts off low energy positrons g

  17. GEANT4 simulations suggest that e+ yield /incident hot electron peaks at around 3 mm and increases with hot electron temperature at least up to ~15 MeV

  18. Adding extra Compton electrons give good match to Titan data . . . . . .

  19. Omega-EP

  20. Assuming that the conversion of laser energy to hot electrons Is ~ 30 %, and the hot electron temperature is ~ 5 -10MeV, the above results suggest that the maximum positron yield is ~ 1012 e+ per kJ of laser energy when the Au target ~ 5 mm The in-situ e+ density should reach > 1018/cm3 The peak e+ current should reach 1024 /sec This would be 1010 higher than conventional schemes using accumulators and electrostatic traps.

  21. Two-sided irradiation may create more pairs, due to hotter electrons and longer confinement time 1021 1021 Ponderomotive forces can lead to a pair cascade by reaccelerating the primary pairs in the foil

  22. blue=2-sided irradiation, red=1-sided irradiation 2 mm foil 20 mm foil 2-sided irradiation of a thin foil seems to produce much hotter electrons for pair production

  23. Myatt et al (2007) proposed to use MG field generated by a second laser to confine pairs for longer time in Omega-EP experiments

  24. The Cygnus X-1 “MeV-flares” may be related to Pair Annihilation. This “bump” has been confirmed by several experiments over many epochs

  25. 2D model of a pair-cloud surrounded by a thin accretion disk to explain the MeV-bump

  26. The Black Hole gamma-ray-bump can be interpreted as emissions from a pair-dominated MeV plasma with n+ ~ 1017cm-3 logL(erg/s) Pair-dominated kT limit T/mc2 Can laser-produced pair plasmas probe the pair-dominated temperature limit?

  27. Double-sided irradiation plus sheath focusing may provide astrophysically relevant pair “fireball” in the center of a thick target cavity: ideal lab for GRB & BH g-flares diagnostics high density “pure” e+e- due to coulomb repulsion of extra e-’s PW laser PW laser 3-5mm 3-5mm diagnostics Thermal equilibrium pair plasma and BKZS limit may be replicated if we have multiple ARC beams staged in time sequence.

  28. Schematic diagram (from Melatos & Skjaeraasen 2008) for an obliquely spinning pulsar wind from Crab (Chandra image left). The field at the equator forms an azimuthally alternating stripe pattern resembling a plasma-loaded linearly-polarized EM wave with folded current sheet. At r>>rLC dE/dt dominates. Bout Bin

  29. i=9o i=60o Inner Wind: Magnetically Striped Force Free Simulation of i=60o Rotator (Spitkovsky) Current Sheet Separating Stripes (Bogovalov) 30

  30. Stripe Wind Dissipation How does high-s flow near light cylinder turns into low-s wind near termination shock? Top View 31

  31. The equatorial stripe wind (ESW) locally resembles a linearly-polarized ultra-intense EM wave loaded with over-dense plasma: so = magnetic/kinetic energy >> 1 ao = eB/mcwo >>1 (wo=wave-frequency) wpe/wo > 1 (wpe=electron plasma frequency) Gwave >> kTo/mc2 (Gwave=group velocity Lorentz factor of EM wave) Above conditions similar to those of linearly polarized laser pulses loaded with cool overdense plasma. Study of such laser propagation may shed light on the propagation and internal dissipation of ESW. We have performed a large number of such PIC simulations for laser applications. They show that self-induced drift current instabilities can be highly efficient in dissipating the EM field and convert EM energy into particle energy. These current instabilities operate efficiently only in the highly nonlinear, relativistic regime.

  32. Electrons can be efficiently accelerated by comoving ponderomotive force of intense EM wave (ao>>1), when E x B drift stays ~ in-phase with wave group velocity (<c due to plasma loading).

  33. Sample 2.5D Run: aomax=30, n=9ncr, so=100, mi=me, plane wave *********************************** Particles are trapped and accelerated by comoving Poynting flux. EM energy is continuously transferred to particle energy. Field decay in pulse tailisdue to self-induced drift currents. By/100 n/ncr pmax ~ 3500 pmax ~ 200

  34. Momentum distribution approaches ~ -1 power-law. maximum particle energy increases with time ~ t0.8 two=4800 g f(g) 0.8 f(g) -1 Xwo/c g

  35. Maximum EM energy conversion to particles typically exceeds 45%, resulting in asymptotic s ~ 1 Elaser Ee two

  36. Asymptotic electron spectra are similar in e+e- and e-ion cases e+e- e-ion fe(g) -1 -1 g g However, for e-ion plasmas, most energy is eventually transferred to ions via charge separation.

  37. 2D and 3D simulations gave similar results. Since our 2D set-up suppresses the tearing mode, the dissipation cannot be caused by x-type reconnection. Instead, the field is dissipated by self-induced polarization-drift currents, and particles are accelerated by comoving ponderomotive forces.

  38. Reconnection in relativistic pair plasmas shows nonlinear interplay between relativistic tearing and drift kink modes. W. Liu et al 2010

  39. 2.5 D PIC 1024x1024 doubly periodic grid, ~108 particles, mi=100me Bx,y=Bosink(y,x) Bz in Jx Ti=0.25mec2 Te=0.25mec2 or 1.5mec2 ywe/c Bz out Jx Bz in xwe/c

  40. Magnetic energy is efficiently converted to hot electrons due to enhanced reconnection Eem EBz Eparticle Ee Ei EE twe EBxy twe

  41. Single mode kL=4p Te=1.5mec2 Bz=10BoWe=5wpe current sheet thickens and bents due to wave perturbations Bz twe=0 1000 4000

  42. Jz twe = 1000 4000

  43. Jx twe=1000 4000

  44. No CS CS fe(g) fe(g) Te=0.25mec2 g g fe(g) CS No CS fe(g) Te=1.5mec2 g g

  45. Magnetic energy density visualization of relativistic Weibel shocks (Spitkovsky 2010)

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