Imploding cone-in-shell capsule 2.7 mm 15-MeV proton backlighter Imaging detector Protons per unit area on detector protons Proton Radiography of Electromagnetic Fields in Laser-Produced High-Energy-Density Plasmas HEDLP Workshop Washington DC August 08 C. K. Li MIT

MIT Summary Time-gated, monoenergetic proton radiography provides unique measurements of E+B fields in laser-produced HED plasmas Radiography of laser-foil interactions:  Observation generations of ~10 6 gauss B field and 10 9 V/m E field  Observation of decay dynamics and instabilities of MG B field  Observation of field topology change due to magnetic reconnection Radiography of direct-drive cone-in-shell/spherical implosions:  Observation of radial, filamentary structures with complex striations and bifurcations, of B field magnitude 0.6×10 6 gauss  Observation of radial E field of order 10 9 V/m and its direction reversal Radiography of laser-irradiated gold hohlraums:  Observation of ~10 6 gauss B field and its evolution  Observation of ~10 9 V/m E field and its evolution

LLE-UR R. Betti J. Delettrez V. Goncharov J. Knauer F. Marshall D. Meyerhofer V. Smalyuk Collaborators MIT F. Séguin J. Frenje R. Petrasso M. Manuel (G) D. Casey (G) N. Sinenian (G) LLNL P. Amendt O. Landen J. Rygg R. Town GA C. Back J. Kilkenny A. Nikroo

The proton source is a laser-driven glass capsule filled with D 2 and 3 He gas × (MeV) protons MeV source spectrum 3% FWHM 3× (ns) protons s source emission 130 ps FWHM 14.7 MeV protons D + 3 He → 4 He + p (14.7 MeV) Heating of the gas during implosion leads to nuclear fusion production: Source Emission of 14.7 MeV D 3 He protons is pulsed, monoenergetic, and isotropic PRL 2006

Radiographs of laser-generated plasma bubbles on opposite sides of a foil prove that deflecting fields are B rather than E OMEGA shot a A Petrasso et al APS 2007

Data and LASNEX simulations are similar with the laser on, but diverge afterwards Interaction laser on for 1 ns 5mm Outer bubble Burn-through hole 0.3 ns ns Mean bubble radius (µm) (a) (b) RMS bubble asymmetry (µm) (c)   B  d ℓ  (MG-µm) 2D code LASNEX produces credible simulations of the hydrodynamics and field growth as long as the laser was on, failing only when 3D instabilities appeared. LASNEX+LSP by R. Town PRL 2007a

Magnetic reconnection has been observed and quantified 5 mm   B  d ℓ  (MG-µm) 0.31 ns 0.51 ns 0.69 ns 0.97 ns 1.24 ns 1.72 ns 2.35 ns 5mm 0.04 ns 0.67 ns 1.42 ns   B  d ℓ  (MG-µm) > 95% field strength was reduced in the region where bubbles overlap PRL 2007b

Face-on 15-MeV radiographs show the evolution from “corrugated” to cellular structures Drive laser ~0.6 MG fields in these cellular structures with cell size ~ 120 μm Position (µm) P-P amp. ~ 18% Position (µm) P-P amp. ~ 5% Diameter = 2.5 mm Thickness = 20±1  m Modulation ~ 120  m P-V modulation ~ 0.5  m “ linear” (2D) Petrasso et al APS 2007

Radiography of a cone-in-shell capsule implosion reveals field topology and capsule compression Fluence Energy 14 kJ laser drive filamentary field structures radial focusing E-field capsule compressed by a factor of two cone shadow Rygg et al Science 2008

Time-gated proton radiography of direct-drive ICF spherical implosions provides the spatial structure and time evolution of E+B fields Drive laser 3 mm Fluence Seguin et al APS 2007

The reversal of proton fluence focusing indicates the direction change of a self-generated radial E field 0.8 ns 1.2 ns 1.4 ns 1.6 ns 1.9 ns 2.1ns E (V/m) Data Simulation PRL 2008

2mm 7mm Radiograph E+B fields generated inside Au hohlraums with protons (DD and D 3 He) and with alphas (D 3 He) B B before reconnection after reconnection OMEGA-Scale beams (1ns-square,SG4+SSD) from Cone 3 drive the hohlraum 21 beams drive the backlighter Fields are very important for : understanding ignition experiments at the National Ignition Facility. laboratory astrophysics of plasmas with lower β (~1)

Protons μm mm t = 0.52 ns Observation of ~10 6 gauss B field and ~10 9 V/m E field and their temporal evolution have been made LASNEX+LSP simulation by R. Town

MIT Summary Time-gated, monoenergetic proton radiography provides unique measurements of E+B fields in laser-produced HED plasmas Radiography of laser-foil interactions:  Observation generations of ~10 6 gauss B field and 10 9 V/m E field  Observation of decay dynamics and instabilities of MG B field  Observation of field topology change due to magnetic reconnection Radiography of direct-drive cone-in-shell/spherical implosions:  Observation of radial, filamentary structures with complex striations and bifurcations, of B field magnitude 0.6×10 6 gauss  Observation of radial E field of order 10 9 V/m and its direction reversal Radiography of laser-irradiated gold hohlraums:  Observation of ~10 6 gauss B field and its evolution  Observation of ~10 9 V/m E field and its evolution