Osaka University *N. Nakanii, H. Habara , K. A. Tanaka University of California San Diego

1. Measurement of Magnetic fieldin intense laser-matter interactionvia 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 (~ 1014 W/cm2) • Proposed experiment • Integrated rad-hydro/hybrid PIC modeling • Short-pulse (fs-ps) high-intensity (> 1018 W/cm2) • 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 (~ 1014 W/cm2) • Proposed experiment • Integrated rad-hydro/hybrid PIC modeling • Short-pulse (fs-ps) high-intensity (> 1018 W/cm2) • 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 (-1014W/cm2) laser • ∇T x∇n in ablated plasma (dominantly) • 100 kGauss ~ MGauss • Short-pulse (fs~ps) high-intense (>1018W/cm2) 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 (~ 1014 W/cm2) • Proposed experiment • Integrated rad-hydro/hybrid PIC modeling • Short-pulse (fs-ps) high-intensity (> 1018 W/cm2) • Experimental plan • Summary

7. Intense laser-driven electrons have advantages to diagnose B field with deflectometry method Enough particle number for imaging [Laser-solid] ~ 1011 with broad energy spread [LWFA] > 108 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 providehigh 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. Non-relativistic Relativistic Trapped electrons 90 Integrated B field along e- path 180 360[deg] Kinetic energy 10 1 0.1 0.01 0.001 1e-4 Deflection angle map with respect to e- energy and integrated B field along e- path

10. Outline • Motivation • Laser-driven relativistic electron deflectometry • Measurement of B field in intense laser-solid interaction • Long-pulse (ns) low-intensity (~ 1014 W/cm2) • Proposed experiment • Integrated rad-hydro/hybrid PIC modeling • Short-pulse (fs-ps) high-intensity (> 1018 W/cm2) • Experimental plan • Summary

11. Experiment to measure ns-laser-produced B fields with relativistic electron deflectometry is proposed 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 Schematic of proposed experiment We demonstrated the feasibility of this relativistic electron deflectmetry using hybrid PIC (LSP) and rad-hydro code (h2d)

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

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 1.4x1014 W/cm2 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 Electron bunch path w/o B field Rad-hydro code (h2d): B field& Ablated plasma profile Deflected electron path by B field LSP Simulation area 2mm 0.7mm Hybrid PIC code (LSP): Deflection of probe e- beam by the B field Long pulse e- source (10MeV) Z Mesh (30um) Ablated plasma & B field Target

15. Electron bunches were passing through CH plasma and slightly deflected by the B field Solid dense region 0.1334ps Corona plasma region Te: 300 eV, Ti: 250 eV, Ave Z: 3.5 0.5337ps 1.400ps 2.200ps Track of electron bunches in LSP simulation

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

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. Deflected (a) w/ plasma and B field (b) w/o plasma and B field Electron distribution on detector

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

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 (~ 1014 W/cm2) • Proposed experiment • Integrated rad-hydro/hybrid PIC modeling • Short-pulse (fs-ps) high-intensity (> 1018 W/cm2) • Experimental plan • Summary

21. Experiment to measure fsultra-intense laser produced B fields with LWFA monoenegetic electrons • Monoenergetic relativistic electron beam iscreated by laser wakefield acceleration with gas-jet. • Deflected electrons pass through the hole of 2nd 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 theBfield produced in ns-laser-matter interaction using hybrid PIC (LSP) andrad-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)