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T.E. Cowan, Y. Sentoku, M. Bakeman, B. Chrisman*, E. d’Humieres, S. Gaillard, J. Rassuchine*

Fusion Science Center of Excellence for Fast Ignition and Extreme States of Matter NTF Status, Cone Target Physics Chicago O’Hare Hilton 28 February 2007. T.E. Cowan, Y. Sentoku, M. Bakeman, B. Chrisman*, E. d’Humieres, S. Gaillard, J. Rassuchine* Department of Physics

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T.E. Cowan, Y. Sentoku, M. Bakeman, B. Chrisman*, E. d’Humieres, S. Gaillard, J. Rassuchine*

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  1. Fusion Science Center of Excellence for Fast Ignition and Extreme States of MatterNTF Status, Cone Target PhysicsChicago O’Hare Hilton 28 February 2007 T.E. Cowan, Y. Sentoku, M. Bakeman, B. Chrisman*, E. d’Humieres, S. Gaillard, J. Rassuchine* Department of Physics University of Nevada, Reno *partial graduate support from FSC

  2. Leopard laser commissioning in progress • Schedule shift due to budget continuing resolution (CR) • Commissioning and laser characterization planned through FY07 • Insufficient support for outside “users” while under CR • Minimal “start up” test experiments might be possible within limited UNR program (i.e., collaboration, not as user) • Point of Contact: T.C., or Jeff Thompson, Acting Director

  3. On the brighter side…. Good progress with nanofabricated cone-shaped laser targets…. Free Standing Au (10 mm wall) x-ray proton Free Standing Cu (10mm wall) x-ray HED Smoother (!) than prior cones

  4. 16.7 um 37.3 um 3.33 um 500 nm 1.0 um Inside sub-micron tip apex: conical, with vestige of Si etch planes. Closer to sharp-tip, Sentoku simulation

  5. Experiment summary of x-ray production and proton beam generation March 2006 LANL-Trident, enhanced proton beam, Au “pizza” tops ~2.5% conversion efficiency to protons, 1.5x max energy (M. Hegelich, K. Flippo) June 2006 LLNL-Titan, proton acceleration (P. Patel, J. Rassuchine, S. Gaillard) July 2006 LULI-100 TW, Au “pizza” tops, reduced mass, pre-pulse! (S. Gaillard, J. Rassuchine, M. Bakeman, J. Fuchs, M. Borghesi, O. Willi) August 2006 LANL-Trident, systematics of Au “pizza” tops, alignment! (K. Flippo, S. Gaillard, J. Rassuchine, M. Bakeman, M. Hegelich) December 2006 LULI-100 TW, 1w, 2w comparison with Cu cones & funnels x-ray emission from hot Cu – similar to 50 mm reduced mass (S. Baton, M. Koenig, J. Rassuchine, R. Kodama) summer/fall 2007 LBNL-L’OASIS (3 J, 30 fs); LULI; LANL; Leopard

  6. Range of neck and top parameters explored 25 / 5 / 80 mm 50 / 30 / 90 mm Typical Reduced-Mass “Pizza” Target Parameters: Neck OD / Neck ID / Top Diameter Enhanced laser-coupling efficiency, and some increase in proton energy observed at Trident (LANL, UNR, GSI)

  7. Alignment is crucial… a postieri determination of laser coupling to cone (central or offset) from proton pattern Central: acceleration from pizza top; 1.5x higher peak proton energy, better collimation, conversion eff. compared to flat foil PIC simulation of longitudinal E-field (E. d’Humieres) Offset: acceleration from cone sides, lower peak proton energy

  8. Enhanced acceleration efficiency, despite no surface treatment….more to come? Titan: 200 J/500 fs (10 mm Au, flat) H+ unheated pizza-top dN/dE = 1.5e11 [p/MeV] * exp(-E / 4.5 MeV) N ~ 6.1011 protons, 0.49 J, Elaser = 19 J, h ~ 2.5% several-fold increase in laser-proton acceleration efficiency !

  9. Concerns about plasma pre-fill on reproducibility  2w vs. 1w comparison at LULI-100 TW Nov-Dec 2006 S. Baton, M. Koenig, D. Batani, R. Kodama, J. Fuchs J. Rassuchine, Y. Sentoku, T.E. Cowan, E. d’Humieres (UNR) Cu cones – sharp, blunt, “funnel”, with Cu Ka imaging & spectroscopy

  10. Defocused 50um with New PHA Defocused 50um High contrast improves laser penetration to cone neck… Transverse Cu Ka imaging: 1w (#119)2w (#96) • - Smaller transverse size of emission zone at 2w (further into neck) • Laser absorption occurs approx. further 50 mm upstream, for 1w • (ASE/prepulse contrast ~ 10-7:1)

  11. 1w: Shot #121: Cone #31 1w: Shot #119: Cone #49 1w: Shot #120: Cone #50 New PHA Defocused 50um with New PHA Defocused 50um with New PHA Dcrystal= 8mm ∆lambda = [1.5407:1.54] = 0.0007 A Dcrystal= 8mm ∆lambda = [1.5407:1.54] = 0.0007 A 2w,PH: Shot #97: Cone #48 2w,PH: Shot #98: Cone #43 2w,PH: Shot #96: Cone #47 Defocused 50um Dcrystal= 8mm ∆lambda = [1.5408:1.5402] = 0.0006 A

  12. 1w,Shot #119: Cone #49 2w,Shot #96: Cone #47 Defocused 50um Defocused 50um with New PHA Rear surface imaging consistent with transverse… Rear-side (end-on) Cu Ka imaging: • - Smaller transverse size of emission zone at 2w (further into neck)

  13. 1w 2w 1w Defocused 50um Defocused 30um up 1w Blunt Cone is 22-37% smaller than Sharp Cone 1w Funnel Cone is 32% and 8% smaller than Sharp and Blunt cone respectively 2w Funnel Cone is 11% and 19% smaller than Sharp and Blunt cone respectively Funnel Cone is 87% smaller than 300um Disk at 1w and 90% at 2w

  14. X-ray spectroscopy: increased emission from “hot” ionized-Cu for high contrast (5th order) Spectrometer Data Definition Kα1 and Kα2 Lower energy continuum Total hot spectrum Hot Spectrum Continuum background

  15. Hot Cu (Ka pk-to-valley) observed for cones vs. flat at 1w

  16. 2w: ionization above F-like. Comparable yield/heating to 50 mm dia. reduced mass, despite huge mass

  17. 1w 2w 1w “Cold” Ka yield (Ne-like to neutral) 1w: Total Cold Cu Ka for cones ~ 1.5x higher yield than Multilayer 2w: Total Cold Cu Ka for cone~ 2-4x higher yield than Multilayer and Reduced Mass

  18. 1w 2w 1w “Hot” Cu x-ray yield (Li-like to F-like)

  19. 2006 progress in sharp-tip cone target physics: • Nanofabrication techniques are promising.…. • Preplasma filling (laser contrast) appears to be very important…. • Enhanced proton acceleration observed (confined hot electron sheath) • X-ray emisison from hot matter observed (similar to reduced mass foils) • Interesting alternative/complement to reduced mass targets: • hot electron concentration • maintains sheath quality for acceleration • more mass for x-ray production • mass produced on wafer • relaxed handling (at cost of more stringent contrast & pointing) • complex geometries possible

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