1. Measurement of Magnetic field in intense laser-matter interaction via Relativistic electron deflectometry Osaka University *N. Nakanii, H. Habara, K. A. Tanaka University of California San Diego T. Yabuuchi, H. Sawada, B.S. Paradkar, M.S. Wei, F.N. Beg General Atomics R.B. Stephens University of Michigan C. McGuffey, K. Krushelnick * Also at University of California San Diego

2. Outline Motivation Laser-driven relativistic electron deflectometry Measurement of B field in intense laser-solid interaction –Long-pulse (ns) low-intensity (~ 10 14 W/cm 2 ) Proposed experiment Integrated rad-hydro/hybrid PIC modeling –Short-pulse (fs-ps) high-intensity (> 10 18 W/cm 2 ) Experimental plan Summary

3. Outline Motivation Laser-driven relativistic electron deflectometry Measurement of B field in intense laser-solid interaction –Long-pulse (ns) low-intensity (~ 10 14 W/cm 2 ) Proposed experiment Integrated rad-hydro/hybrid PIC modeling –Short-pulse (fs-ps) high-intensity (> 10 18 W/cm 2 ) Experimental plan Summary

4. Motivation Characterization of strong spontaneous magnetic (B) fields in intense laser-matter interaction is an important issue in High Energy Density (HED) sciences. –Fast ignition (Electron energy transport) –Generation of energetic electrons, ions, and x-rays –and so on…

5. Strong spontaneous magnetic fields are generated in laser-matter interactions Long-pulse (ns) low-intense (-10 14 W/cm 2 ) laser – ∇ T x ∇ n in ablated plasma (dominantly) –100 kGauss ~ MGauss Short-pulse (fs~ps) high-intense (>10 18 W/cm 2 ) laser – ∇ T x ∇ n Ponderomotive force Current of fast electrons and etc… –Over 100 Mega-Gauss

6. Outline Motivation Laser-driven relativistic electron deflectometry Measurement of B field in intense laser-solid interaction –Long-pulse (ns) low-intensity (~ 10 14 W/cm 2 ) Proposed experiment Integrated rad-hydro/hybrid PIC modeling –Short-pulse (fs-ps) high-intensity (> 10 18 W/cm 2 ) Experimental plan Summary

7. Intense laser-driven electrons have advantages to diagnose B field with deflectometry method Enough particle number for imaging [Laser-solid] ~ 10 11 with broad energy spread [LWFA] > 10 8 with monoenergetic spectrum Variable energies enable to detect wide-range B field [Laser-solid]up to several ten MeV [LWFA]up to 1 GeV Ultrashort pulse duration can provide high temporal resolution [Laser-solid]a few ps [LWFA]several ten fs Small source size can provide high spatial resolution ~ focal spot size

8. Relativistic electrons have advantages to measure B field in overdense plasmas Relativistic electrons are penetrative in dense matter without significant energy loss in a short time The electrons are susceptive to B field because they have the high velocity ~ c Laser-produced relativistic electrons are very useful for measuring the B field with deflectometry method

9. B field with wide range of strength or scale can be detected by using laser-produced electrons Deflection angle Changing the electron energy, different range of B field can be detected. 360[deg] 180 9090 10 1 0.1 0.01 0.001 1e-4 Trapped electrons Deflection angle map with respect to e - energy and integrated B field along e - path RelativisticNon-relativistic Integrated B field along e - path Kinetic energy

10. Outline Motivation Laser-driven relativistic electron deflectometry Measurement of B field in intense laser-solid interaction –Long-pulse (ns) low-intensity (~ 10 14 W/cm 2 ) Proposed experiment Integrated rad-hydro/hybrid PIC modeling –Short-pulse (fs-ps) high-intensity (> 10 18 W/cm 2 ) Experimental plan Summary

11. Experiment to measure ns-laser-produced B fields with relativistic electron deflectometry is proposed We demonstrated the feasibility of this relativistic electron deflectmetry using hybrid PIC (LSP) and rad-hydro code (h2d) Schematic of proposed experiment Electrons are produced in short pulse laser interaction with solid 10 MeV electrons with narrow- bandwidth (~0.3 MeV) are selected by a pair magnet and used as backlighter Mesh provides initial spatial information of electron beam

12. Integrated rad-hydro/hybrid PIC modeling Rad-hydro code (h2d): B field & Ablated plasma profile Rad-hydro code (h2d): B field & Ablated plasma profile Z R Target Long pulse Ablated plasma & B field

13. 0.1 Mega-Gauss toroidal B field generated around laser spot near the critical dense region Laser (~ Titan long pulse @LLNL) Energy 100J Pulse width 1ns (square) Wavelength 0.5um Spot size 300um Intensity 1.4x10 14 W/cm 2 Target Polystyrene plane Thickness 50um B field map at 1.5 ns after the laser irradiation (2D Cylindrical geometry)

14. Integrated rad-hydro/hybrid PIC modeling Hybrid PIC code (LSP): Deflection of probe e - beam by the B field Hybrid PIC code (LSP): Deflection of probe e - beam by the B field e - source (10MeV) LSP Simulation area Z Target Long pulse Ablated plasma & B field Mesh (30um) 2mm0.7mm Electron bunch path w/o B field Deflected electron path by B field Rad-hydro code (h2d): B field & Ablated plasma profile Rad-hydro code (h2d): B field & Ablated plasma profile

15. Electron bunches were passing through CH plasma and slightly deflected by the B field Solid dense region Corona plasma region Te: 300 eV, Ti: 250 eV, Ave Z: 3.5 0.1334ps 0.5337ps 1.400ps2.200ps Track of electron bunches in LSP simulation

16. Integrated rad-hydro/hybrid PIC modeling Shift Target Long pulse Ablated plasma & B field e - source (10MeV) Detector Shift Z Mesh (30um) 10cm Extra calculations: e - distribution on detector Deflection angle Extra calculations: e - distribution on detector Deflection angle Rad-hydro code (h2d): B field & Ablated plasma profile Rad-hydro code (h2d): B field & Ablated plasma profile Hybrid PIC code (LSP): Deflection of probe e - beam by the B field Hybrid PIC code (LSP): Deflection of probe e - beam by the B field

17. Electron bunches were slightly focused to center by the toroidal B field Deflection angle at the each point was calculated from the spike shift in the distribution on detector. (b) w/o plasma and B field(a) w/ plasma and B field Electron distribution on detector Deflected

18. Integrated rad-hydro/hybrid PIC modeling Shift Target Long pulse Ablated plasma & B field e - source (10MeV) Detector Shift Z Mesh (30um) Extra calculation: e - distribution on detector Deflection angle Extra calculation: e - distribution on detector Deflection angle 10cm Reconstruction of integrated B field profile Rad-hydro code (h2d): B field & Ablated plasma profile Rad-hydro code (h2d): B field & Ablated plasma profile Hybrid PIC code (LSP): Deflection of probe e - beam by the B field Hybrid PIC code (LSP): Deflection of probe e - beam by the B field

19. Distribution of integrated B field reconstructed from deflection angle are comparable to actual one Deflection angles and profile of reconstructed integrated B field and actual one.

20. Outline Motivation Laser-driven relativistic electron deflectometry Measurement of B field in intense laser-solid interaction –Long-pulse (ns) low-intensity (~ 10 14 W/cm 2 ) Proposed experiment Integrated rad-hydro/hybrid PIC modeling –Short-pulse (fs-ps) high-intensity (> 10 18 W/cm 2 ) Experimental plan Summary

21. Experiment to measure fs ultra-intense laser produced B fields with LWFA monoenegetic electrons Monoenergetic relativistic electron beam is created by laser wakefield acceleration with gas-jet. Deflected electrons pass through the hole of 2 nd OAP and are detected Temporal evolution of the B field can be observed by changing the delay of optical delay unit with ultra-short time resolution

22. Summary We proposed a B field deflectometry experiment using laser- produced relativistic electrons We demonstrated the feasibility of electron deflectmetry to measure the B field produced in ns-laser-matter interaction using hybrid PIC (LSP) and rad-hydro code (h2d) Integrated magnetic field along electron path can be reconstructed from the deflected electron distribution on deflection Experiment for measuring B field in interaction of ultra-intense laser with solid will be performed soon

23. Acknowledgements This work supported by –Japan Society for the Promotion of Sciences (JSPS) Research Fellowship DC1 –Global COE Program Center for Electronic Device Innovation (CEDI) –U.S. Department of Energy DE-FG-02-05ER54834 (ACE) –JSPS Core-to-Core Program International Collaboration for High Energy Density Science (ICHEDS)