Relativistic Plasmas and Strong B-Fields: New Synergism Between HEA and HEDP Edison Liang

1. Relativistic Plasmas and Strong B-Fields: New Synergism Between HEA and HEDP Edison Liang Rice University Collaborators: H. Chen, S.Wilks, B. Remington (LLNL); T. Ditmire, (UTX); W. Liu, H. Li, M. Hegelich, (LANL); A. Henderson, P. Yepes, E. Dahlstrom (Rice) Santa Fe, NM, August 4, 2010

2. New Revolution: Ultra-intense Short Pulse Lasers bring about the creation of Relativistic Plasmas in the Lab Matching high energy astrophysical conditions LLNL Titan laser TPW Trident

3. Many kJ-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 ARC RAL Vulcan Laser

4. 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

5. Relativistic Plasmas and Strong B-Fields • Pair Plasma Creation Experiments. • Strong-B Creation Experiments. • Applications of Pair Plasmas + Strong B Most relativistic plasmas are “collisionless”. Need to use kinetic, e.g. Particle-in-Cell (PIC), simulations to capture essential physics.

6. e+e- pair plasmas are ubiquitous in the universe NonthermalTeV pairs Thermal MeV pairs it is highly desirable to create pair plasmas in the laboratory

7. 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

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

9. Early laser experiments by Cowan et al (1999) first demonstrated e+e- production with Au foils. But e+/e- was low (~10-4) due to off-axis measurements and thin target. e+e- Cowan et al 1999 2.1020W.cm-2 0.42 p s 125mm Au

10. ? quadratic linear I=1020Wcm-2 Liang et al 1998 (Nakashima & Takabe 2002) Trident process dominates for thin targets. Bethe-Heitler dominates for thick targets. Can the e+ yield keep increasing if we use very thick targets?

11. Au 1 2 Set up of Titan Laser Experiments

12. Sample Titan data 1 1 2 e+/e- ~ few % Monte Carlo simulations MeV

13. Absolute e+ yield (per incident hot electron or laser energy) peaks around 3 mm and increases with hot electron temperature

14. Only emergent e+/e- ratio can be measured, but discrepancy between theory and data for thick targets remains to be resolved

15. Omega-EP

16. 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 ~ 3-5 mm The in-situ e+ density should exceed 1018/cm3 The peak e+ current should exceed 1024 /sec This would be 1010 higher than conventional sources using accumulators and electrostatic traps.

17. 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.

19. How are relativistic jets confined and dissipate?

20. Laser-driven Helmohltz coil can generate MG axial fields (Daido et al 1986). Myatt et al (2007) proposed Omega-EP experiments to confine pair jets. We proposed similar experiments for TPW. TPW short pulse to make pairs or proton beam TPW long pulse to drive B (courtsey J. Myatt 2007)

21. Helmholtz coil B-field Scaling Estimates Energy Scaling: EB ~ 10% of absorbed laser energy For cylindrical volume of 0.1mm radius x 1 mm length we find Bmax ~ 15 MG per kJ of incident laser energy assuming 30% absorption into hot electrons. Current Scaling: I scales linearly with foil gap d. For d ~ 1 mm, Imax ~ 1.2x105 A. Hence we estimate Bmax ~ 10 MG per kJ of incident laser energy Capacitance Scaling: Assuming 5 x1013 hot electrons per kJ of laser energy with 50% into capacitor, and d ~1 mm, we find maximum voltage V ~ 2 x106 V. Using L (inductance) ~14 nH for copper circuit, we find Bmax ~ 10 MG per kJ of incident laser energy.

22. A Novel Application of Relativistic Pairs + Strong B: Laser Cooling of “Landau Atom” to make dense Ps Key advantages of laser produced positrons are short pulse (~ps), high density (>1017/cc) and high yield efficiency (~10-3). To convert these >> MeV positrons to slow positrons using conventional techniques, such as moderation with solid noble gas, loses the above inherent advantages. We are exploring intense laser cooling, using photons as “optical molasses” similar to atomic laser cooling, to rapidly slow/cool MeV pairs down to keV or eV energies. g 4g2no e+/e- no

23. In a strong B field, resonant scattering cross-section can become much larger than Thomson cross-section, allowing for efficient laser cooling: analogy to atomic laser cooling f>103sT • To Compton cool an unmagnetized >>MeV electron, needs laser fluence F~mc2/sT ~ 1011J.cm-2 = 8MJ for ____~ 100mm diameter laser But resonant scattering cross section peaks at fsT, f>103, F is reduced to 8MJ/f < kJ. As in atomic laser cooling, we need to “tune” the laser frequency as the electron cools to stay in ________resonance. How?_________ . For B=108G, hwcyc=1eV • cyc=1mm sT

24. Idea: we can tune the effective laser frequency as seen by the e+/e- beams by changing the laser incident angle to match the resonant frequency as the positron slows. t3 t2 t1 g e+/e- to B~100MG lcyc = llaserg(1-vcosq)

25. Idea: change the incident angle by using a mirror and multiple beams phased in time to t1 t2 g e+/e- t3 B~100MG lcyc = llaserg(1-vcosq) We are developing a Monte Carlo code to model this in full 3-D. Initial results seem promising (Liang et al 2010 in preparation)

26. High density slow positron source can be used To make BEC of Ps at cryogenic temperatures (from Liang and Dermer 1988).

27. Ground state of ortho-Ps has long live, but it can be spin-flipped into para-Ps using 204 GHz microwaves. Since para-Ps annihilates into 2-’s, there is no recoil shift. The 511 keV line has only natural broadening if the Ps is in the condensed phase.

28. A Ps column density of 1021 cm-2 could in principle achieve a gain-length of 10 for gamma-ray amplification via stimulated annihilation radiation (GRASAR). (from Liang and Dermer 1988). Such a column would require ~1013 Ps for a cross-section of (1 micron)2. 1014 e+ is achievable with 10kJ ARC beams of NIF. Ps annihilation cross-section with only natural broadening

29. Porous silica matrix at 10oK sweep with 204 GHz microwave pulse 1021cm-2 Ps column density 10 ps pulse of 1014 e+ 1 micron diameter cavity Artist conception of a GRASAR (gL=10) experimental set-up

30. Short pulse laser plasma interactions naturally generate superstrong B in laser plasmas Solid target laser ionization B-field high energy B-field protons absorption ablation energy fast particle transport generation B-field & trajectories radiation (Courtesy of Tony Bell)

31. X-Wave cutoffs (courtesy of Krushelnick et al) gnc Region of harmonic generation nc wo=1µm 2wo 3wo 4wo 5wo 6wo 7wo 8wo 9wo

32. Experimental results are in agreement with “ponderomotive” source for fields

33. can create reconnection layer

34. shows thin current sheet

35. Summary: New Synergism between HEA and HEDP 1. Titan laser experiments and numerical simulations point towards copious production of e+e- pairs using lasers with I > 1020 Wcm-2. Maximum e+ yield can exceed 1012 per kJ of laser energy (emergent e+/hot e- ~ few %). The in-situ e+ density can exceed 1018 cm-3. Laser-driven Helmholtz coil can create B > 107G 4. Dense pair plasmas and jets, coupled with > 107G magnetic fields, can simulate many astrophysics phenomena, from black hole flares, pulsar winds, blazar jets to g-ray bursts. Collisionless shocks, reconnection, and shear layers may also be studied in the laboratory with HEA applications.