Cowan cones

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 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 *partial graduate support from FSC

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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 Leopard laser commissioning in progress

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

Inside sub-micron tip apex: conical, with vestige of Si etch planes. Closer to sharp-tip, Sentoku simulation: 

Inside sub-micron tip apex: conical, with vestige of Si etch planes. Closer to sharp-tip, Sentoku simulation

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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 andamp; 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 Experiment summary of x-ray production and proton beam generation

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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) Range of neck and top parameters explored

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

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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 ! H+ unheated pizza-top Enhanced acceleration efficiency, despite no surface treatment….more to come? Titan: 200 J/500 fs (10 mm Au, flat)

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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 andamp; spectroscopy Concerns about plasma pre-fill on reproducibility  2w vs. 1w comparison at LULI-100 TW

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Transverse Cu Ka imaging: 1w (#119) 2w (#96) High contrast improves laser penetration to cone neck… - 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)

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

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Rear-side (end-on) Cu Ka imaging: Rear surface imaging consistent with transverse… - Smaller transverse size of emission zone at 2w (further into neck)

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1w 2w 1w 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 Defocused 50um Defocused 30um up

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X-ray spectroscopy: increased emission from 'hot' ionized-Cu for high contrast (5th order)

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

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

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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 'Cold' Ka yield (Ne-like to neutral)

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'Hot' Cu x-ray yield (Li-like to F-like)

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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 andamp; pointing) complex geometries possible 2006 progress in sharp-tip cone target physics: