Measuring the Refractive Index of a Laser-Plasma System

Transcription

1 Measuring the Refractive Index of a Laser-Plasma System 1 dh ( 10 4 ) 0 1 J (dh) R (dh) D. Turnbull University of Rochester Laboratory for Laser Energetics Dm (Å) 58th Annual Meeting of the American Physical Society Division of Plasma Physics San Jose, CA 31 October 4 November

2 Summary Recent experiments have validated the linear cross-beam energy transfer (CBET) theory and used it to demonstrate plasma photonic devices Linear coupled-wave theory is used to calculate CBET in direct- and indirect-drive inertial confinement fusion (ICF), but historically has not agreed with experimental data The theory was revisited recently with the proposal for laser-plasma photonic devices (wave plates and polarizers)* A recent experiment has found good agreement with the linear CBET theory and demonstrated an ultrafast, high-power, tunable laser-plasma polarizer** E25587 *P. Michel et al., Phys. Rev. Lett. 113, (2014). **D. Turnbull et al., Phys. Rev. Lett. 116, (2016). 2

3 Collaborators P. Michel, C. Goyon, B. B. Pollock, G. E. Kemp, T. Chapman, D. Mariscal, L. Divol, J. S. Ross, S. Patankar, and J. D. Moody Lawrence Livermore National Laboratory National Ignition Facility 3

4 CBET affects energy coupling and implosion symmetry in direct-drive and indirect-drive ICF Indirect drive Direct drive CBET Target Validating CBET models is an important component of simulating ICF implosions. E

5 CBET theory* can be formulated as a laser-plasma system with a complex refractive-index perturbation operating on a probe beam El 1,9 = E 1,9 Interaction is anisotropic Optical system = [plasma (n e, T e, T i, v f, Z) + pump laser (I 0, a cr ) " dh] E 0 El 1,z = E 1,z e ik 0 dhl/h 0 Im (dh) " energy transfer Re (dh) " phase delay I = E + E m = r k -k beat B E 1 Beat wave E 1,9 E 1,z h = _ 1 / -ne nci 12 Refractiveindex modulation Such a system can modify the amplitude and/or polarization of the probe beam. E25589 P. Michel et al., Phys. Rev. Lett. 113, (2014). 5

6 A pump-probe experiment with wavelength tuning was carried out to measure dh as a function of Dm U 135 Thomson scattering (n e, T e at TCC*) Polarimetry Probe U 45 Wollaston prism U 0 U 90 E 0, m 0 E25589c E 1,9 E 1, m 1 E 1,z Interferometry [n e (z)] Polarization is generally elliptical because of induced phase delay 0 D{ r r 4 r 2 3r 4 D { = cos -1 Amplification G ln_ U U I = 0c 90c Phasedelay 6U - 6U + U f 2 U U U + U 45c 135c 45c 135c 0c 90c 0c 90c *TCC: target chamber center p 6

7 dh is in good agreement with linear theory using inputs from measurements and HYDRA dh ( 10 4 ) G = -2k J^dhhL h D { = k R^dhhL h I J (dh) R (dh) Parameter Theory input Measured value HYDRA simulation n e /n c !0.001 ~0.009 T e (ev) !24 ~231 T i /T e ~0.090 v flow (m/s) ~ ~ I 0 ~ ~ * ~ Dm (Å) Z 3 2 This is the first time that the gain curve is resolved this accurately, and found to be in good agreement with linear theory; the first measurement of R (dh) versus Dm. E25590 *Measurement did not include transport optic losses, IB absorption, or the possibility of nonideal pump spot. 7

8 The system can act as a plasma polarizer with 85% to 87% extinction for these laser and plasma parameters Vertical (preshot) Counts 8000 m1 > m0: laser-plasma polarizer E0 E1 E1,z dh ( 10 4) E1, G I = -2k 0 J ^dhh L h 0 Vertical (shot) Horizontal (shot) E25591 Horizontal (preshot) J (dh) 0 1 Dm (Å) 2 3 ~85% to 87% extinction P. Michel et al., Phys. Rev. Lett. 113, (2014); D. Turnbull et al., Phys. Rev. Lett. 116, (2016). D. Turnbull et al., Measuring the Refractive Index of a Laser-Plasma Optical System, submitted to Physical Review Letters. 8

9 Summary/Conclusions Recent experiments have validated the linear cross-beam energy transfer (CBET) theory and used it to demonstrate plasma photonic devices Linear coupled-wave theory is used to calculate CBET in direct- and indirect-drive inertial confinement fusion (ICF), but historically has not agreed with experimental data The theory was revisited recently with the proposal for laser-plasma photonic devices (wave plates and polarizers)* A recent experiment has found good agreement with the linear CBET theory and demonstrated an ultrafast, high-power, tunable laser-plasma polarizer** E25587 *P. Michel et al., Phys. Rev. Lett. 113, (2014). **D. Turnbull et al., Phys. Rev. Lett. 116, (2016). 9

10 The elliptical probe was converted to a nearly ideal circularly polarized beam by inducing a 52 phase delay in plasma Phase delay Dz 0 = 38.1 U 135 /U 45 c 0.11 Dz = 90.2 U 135 /U 45 c 1.01 Dz c 180 U 135 /U 45 c 54.3 Probe U 135 U 45 Pump U 45 U 135 U 45 Wollaston prism Laser-plasma wave plate Quartz m/4 wave plate This is the first demonstration of a near-ideal tunable laser-plasma wave plate. E25594 P. Michel et al., Phys. Rev. Lett. 113, (2014). D. Turnbull et al., Phys. Rev. Lett. 116, (2016). 10