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Measuring E and B fields in Laser-produced Plasmas with Monoenergetic Proton Radiography

FSC. 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. 2006. FSC. Collaborators. R. P. J. Town P. A. Amendt S. P. Hatchett O. L. Landen

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Measuring E and B fields in Laser-produced Plasmas with Monoenergetic Proton Radiography

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  1. FSC Measuring E and B fields in Laser-produced Plasmas with Monoenergetic Proton Radiography 9th International Fast Ignition Workshop C. K. Li MIT Cambridge, MA 3-5 Nov. 2006

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

  3. Summary 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 • A monoenergetic backlighter proton spectrum simplifies experiment design and interpretation. • High-resolution, time gated radiography images of a plastic foil driven by a 1014 W/cm2 laser implied B fields of ~ 0.5 MG and E fields of ~ 1.5108 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. MIT MIT

  4. The generation of E and B fields by laser-plasma interactions is a process of fundamental interest in high-energy density (HED) physics 5 mm CH 1 ns square spot diameter  800 mm I ~ 1014 W/cm2 Laser Te ne E B

  5. Proton radiographs already made of B fields generated by laser-plasma interactions demonstrate feasibility for Fast Ignition studies ~ 0.6 ns after laser D3He- implosion backlighter Laser beam Before laser Mesh and foil Grid real images Mesh cartoonimage Implosion

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

  7. 2 mm SiO2 Monoenergetic protons can be generated in nuclear fusion reactions through ICF implosions DD proton D3He proton D + 3He   + p (14.7 MeV) D + D  T + p (3.0 MeV) RSI 2006

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

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

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

  11. 0.05 0.35 0.65 0.95 MG 0.06 0.03 0 -0.03 -0.06 Laser R (cm) 0.08 0.04 0 0.08 0.04 0 Z (cm) LASNEX simulations indicate that the toroidal B fields are concentrated on a hemispherical shell surrounding the ablative plasma bubble 0.30 ns 0.63 ns 0.3 ns 0.6 ns

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

  13. 0 ns 0.41 ns 0.77ns SG4 2.3 mm 0 ns 0.41 ns 0.71ns SG2 The smaller diameter of the SG2 beam resulted in an intensity 2.6 times higher than SG4, causing greatly increased image distortion.

  14. 2.3 mm With phase plates Without phase plates Experiments demonstrate that laser phase plates substantially reduce medium-scale chaotic field structure

  15. Lineout Simulation lineout  2.3 mm Data  A CH foil driven by a 1014 W/cm2 laser beam results in E field of ~ 1.5108 V/m E   Ep Te/Te

  16. Summary 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 • A monoenergetic backlighter proton spectrum simplifies experiment design and interpretation. • High-resolution, time gated radiography images of a plastic foil driven by a 1014 W/cm2 laser implied B fields of ~ 0.5 MG and E fields of ~ 1.5108 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. MIT MIT

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