Measuring E and B fields in Laser-produced Plasmas with Monoenergetic Proton Radiography 9 th International Fast Ignition Workshop C. K. Li MIT Cambridge, MA 3-5 Nov FSC

MIT Collaborators F. H. Séguin J. A. Frenje J. R. Rygg R. D. Petrasso MIT R. P. J. Town P. A. Amendt S. P. Hatchett O. L. Landen A. J. Mackinnon P. K. Patel M. Tabak LLNL J. P. Knauer T. C. Sangster V. A. Smalyuk LLE FSC

MIT Summary  A monoenergetic backlighter proton spectrum simplifies experiment design and interpretation.  High-resolution, time gated radiography images of a plastic foil driven by a W/cm 2 laser implied B fields of ~ 0.5 MG and E fields of ~ 1.5  10 8 V/m.  Simulations of these experiments with LASNEX+LSP are in overall agreement with the data both for field strengths and for spatial distributions while the laser is on; this is the first direct experimental test of the B-field generation package in LASNEX.  The experiments also demonstrated that laser phase plates substantially reduce medium-scale chaotic field structure. E and B fields generated by the interaction with plasmas of long-pulse, low-intensity laser beams relevant to ICF are measured with novel monoenergetic proton radiography

The generation of E and B fields by laser-plasma interactions is a process of fundamental interest in high-energy density (HED) physics 5  m CH 1 ns square spot diameter  800  m I ~ W/cm 2  Laser  TeTe nene

Grid D 3 He- implosion backlighter Laser beam Mesh and foil Implosion Before laser ~ 0.6 ns after laser Mesh cartoon image real images Proton radiographs already made of B fields generated by laser-plasma interactions demonstrate feasibility for Fast Ignition studies

The same concept can be applied to investigate B field generated by short-pulse laser-plasma interaction Fast ignition (Short pulse)  e Laser protons   Laser protons

Monoenergetic protons can be generated in nuclear fusion reactions through ICF implosions 2  m SiO2 DD proton D 3 He proton D + 3 He   + p (14.7 MeV) D + D  T + p (3.0 MeV) RSI 2006

Several nuclear and x-ray diagnostics are used to characterize the proton backlighter Proton spectrum Proton emission image x-ray emission image Protons Laser Proton production history

E and B fields can be simultaneously measured using a single proton backlighter mesh “Backlighter” Backlighter drive beams CR-39 Interaction beam CH foil side-on face-on Face-on radiography is sensitive to the B field, while side-on radiography is sensitive to the E field

Experimental data and LASNEX+LSP simulations agree both for field strengths and for spatial distributions Simulation By R. Town Data 2.3 mm 0 ns 0.33 ns 0.64 ns 0 ns 0.30 ns 0.63 ns PRL 2006

0.30 ns 0.63 ns R (cm) Z (cm) MG Laser LASNEX simulations indicate that the toroidal B fields are concentrated on a hemispherical shell surrounding the ablative plasma bubble 0.3 ns 0.6 ns

Experimental data and LASNEX+LSP simulation show that the largest B field occurs near the surface of the plasma bubble protons Simulation Data

The smaller diameter of the SG2 beam resulted in an intensity 2.6 times higher than SG4, causing greatly increased image distortion. SG4 0 ns 0.41 ns 0.71ns 2.3 mm SG2 0 ns 0.41 ns 0.77ns

Experiments demonstrate that laser phase plates substantially reduce medium-scale chaotic field structure 2.3 mm With phase plates Without phase plates

A CH foil driven by a W/cm 2 laser beam results in E field of ~ 1.5  10 8 V/m E   E p  T e /T e lineout  Lineout Simulation  Data 2.3 mm

MIT Summary  A monoenergetic backlighter proton spectrum simplifies experiment design and interpretation.  High-resolution, time gated radiography images of a plastic foil driven by a W/cm 2 laser implied B fields of ~ 0.5 MG and E fields of ~ 1.5  10 8 V/m.  Simulations of these experiments with LASNEX+LSP are in overall agreement with the data both for field strengths and for spatial distributions while the laser is on; this is the first direct experimental test of the B-field generation package in LASNEX.  The experiments also demonstrated that laser phase plates substantially reduce medium-scale chaotic field structure. E and B fields generated by the interaction with plasmas of long-pulse, low-intensity laser beams relevant to ICF are measured with novel monoenergetic proton radiography