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Laser ion acceleration and applications A bouquet of flowers Munib Amin Institute for Laser and Plasma Physics Heinrich Heine University Düsseldorf Introduction ● You need Thin foil target Short pulse High intensity High contrast Munib Amin – ILPP Düsseldorf ● You get Up to 1013 protons up to about 60 MeV high laminarity beam Small virtual source size 2 Overview ● Acceleration ● Beam Properties and Control ● Applications ● Conclusion Munib Amin – ILPP Düsseldorf 3 How to accelerate protons? TNSA! (Target Normal Sheath Acceleration) Munib Amin – ILPP Düsseldorf 4 How to accelerate protons (I) + + ++ + ++ + + + + ++ + ++ + + Munib Amin – ILPP Düsseldorf 5 How to accelerate protons (II) Munib Amin – ILPP Düsseldorf 6 Properties (I): Laminarity ● Longitudinal laminarity ● Transversal laminarity Proton generation foil Slow protons Fast protons Virtual source Munib Amin – ILPP Düsseldorf Borghesi et al. (2004) Cowan et al. (2004) 7 Properties (II): Ion species ● Heating Ions/MeV 1011 F7+ heated ● Ablation 1010 109 108 F7+ unheated 107 0.0 20.0 40.0 60.0 80.0 100.0 120.0 Energy [MeV] Munib Amin – ILPP Düsseldorf Hegelich et al (2002) 8 Properties (III): Divergence/spectrum ● Focus Laser pulse 2 ● Collimate ● Select energy Protons Metal foil cylinder Munib Amin – ILPP Düsseldorf Toncian et al (2006) 9 Properties (IV): Energy ● Energy increase: Laser piston regime? Munib Amin – ILPP Düsseldorf Esirkepov et al (2004) 10 Applications ● Diagnostics for dense plasmas ● Isochoric heating Already done ● Ion source for conventional particle accelerators ● Fast ignition ● Medical applications Munib Amin – ILPP Düsseldorf Maybe one day 11 Probing (I): Principle Object moving downwards ● Time variation can mapped. Munib Amin – ILPP Düsseldorf Borghesi et al (2001) 12 Probing (II): Electric field Higher density Displacement ++ + ● Measure: Density distribution/displacement of protons having the same energy Lower density Proton trajectories Higher density ● Find out: Temporal evolution of the electric field Munib Amin – ILPP Düsseldorf 13 Probing (III): Deflectometry Munib Amin – ILPP Düsseldorf 14 Probing (IV): Deflectometry ● Identify grid nodes ● Measure their displacement Munib Amin – ILPP Düsseldorf 15 Isochoric heating: Creating WDM ● Hemispherical target Al-foil 320 µm Al Munib Amin – ILPP Düsseldorf Patel et al (2003) 16 Fast ignition Petawatt beams (5ps 6kJ) Proton beams Conical shaped target Primary driver Fuel Munib Amin – ILPP Düsseldorf Roth et al (2001) 17 Medical applications (I): Radioisotopes Munib Amin – ILPP Düsseldorf Ledingham et al (2004) 18 Medical applications (II): Cancer therapy X-rays Munib Amin – ILPP Düsseldorf Protons 19 Conclusion ● Attractive applications are waiting for laser accelerated ion beams ● …if we are able to control their properties. Munib Amin – ILPP Düsseldorf 20 Thank you Munib Amin – ILPP Düsseldorf 21 Detection – radiochromic film stack RCF stack ● The density distribution of the proton beam is recorded by a stack of radiochromic films. ● Since protons deposit most of their energy in the Bragg peak, one film shows the distribution corresponding to only one specific energy. Munib Amin – ILPP Düsseldorf 22 Overview (2) ● Quasi monoenergetic particles can be generated by A special treatment of the foil target (thin layer or dots containing the particles to be accelerated on the rear surface) A second target that selects one velocity class of protons: a laser irradiated hollow metal foil cylinder ● The proton beam can be focused by using A hemispherical proton generation foil A second target that focuses the divergent proton beam: a laser irradiated hollow metal foil cylinder Munib Amin – ILPP Düsseldorf B. M. Hegelich, et al., Nature, 439, 441-444 (2006). H. Schwoerer, et al., Nature, 439, 445-448 (2006). P. K. Patel, et al., Phys. Rev. Lett. 91, 125004 (2003). T. Toncian, et al., Science 312, 410-413 (2006). 23 Temporal and spatial field evolution on the target surface Laser pulse 2 RCF stack (detector) Laser pulse 1 Proton beam Metal foil cylinder Proton generation foil ● A proton beam is used to probe the electric field on the surface of a laser irradiated metal foil cylinder. ● The density distribution of the electron beam is recorded by a stack of radiochromic films. Munib Amin – ILPP Düsseldorf 24 Reconstruction of the electric field – an iterative method Experiment 1: Streaking Experiment 2: Imaging Modelling Imaging Streaking Experimental result Experimental result Parameter fit Simulation Munib Amin – ILPP Düsseldorf Parameter transfer Parameter fit Simulation 25 Modelling ● Setting up a one dimensional field configuration from simulations or previously published models or experimental results ● Setting reasonable starting parameters for the analysis of the experimental results ● Generalizing to three dimensions according to the experimental geometry Munib Amin – ILPP Düsseldorf 26 The electric field configuration ● The fraction of laser energy absorbed by hot electrons and the hot electron temperature are estimated depending on laser intensity and wave length according to Fuchs[2006]. ● The electric field is supposed to build up in a plasma expanding into vacuum as described by Mora[2003]. ● Spatial dependence in one dimension and temporal evolution are given by PIC and MHD-simulations conducted by Romagnani[2005]. Munib Amin – ILPP Düsseldorf J. Fuchs, et al., Nature Physics 2, 48-54 (2006). P. Mora, Phys. Rev. Lett. 90, 185002 (2003). L. Romagnani, et al., Phys. Rev. Lett. 95, 195001 (2005). 27 One dimensional electric field Field strength / (V/m) Position / m Time / s The field distribution according to Mora[2003] and Romagnani[2006] is modelled in one dimension. Munib Amin – ILPP Düsseldorf 28 Generalizing to more dimensions Front E E x x y Weaker and retarded The field distribution can be generalized to two or three dimensions by assuming the expansion to start later and the electron density to be lower at larger distances from the centre of the interaction. Munib Amin – ILPP Düsseldorf 29 The target geometry The one dimensional field distribution is applied along the dashed lines x t3 t2 t1 y Plain target Munib Amin – ILPP Düsseldorf Curved or cylindrical target 30