Ulsan National Institute of Science and Technology

1. 2011. 7.5 Y.K KIM Toward a World-Leading University Ulsan National Institute of Science and Technology

2. on the table on the village

3. Hegelich_Nature (2001) S.C.Wilks_POP(2001) LEE.K_POP(2009) 10nm 100nm 1μm LEE.H.J_POP(2004) T.Okada_PRE(2006) T.P.Yu_POP(2009) W.P.Wang_POP(2011) T.Esirkepov_PRL(2004) Target thickness F.Wang_POP(2009) Bulanov_PRE(2008) B.Qiao_PRL(2009) M.Chen_PRL(2009) L.Yin_POP(2007) C.K.Huang_PRST(2011) Henig_PRL(2009) Laser intensity etc 2D Simulation only TNSA RPA DCE

4. TNSA Target Normal Sheath Acceleration(TNSA) Target -> Someone say that target is target. Someone say that target is a contaminant layer Someone say that target is a layer on the backside of the substrate Normal -> Hot electrons are emitted to the normal direction of the target Sheath -> Electrons form a electron cloud like as ‘sheath’ at the backside of the target and this make ‘sheath field’

5. TNSA reflection Target Target Cold e- Pre-plasma Return current Pre-plasma e- Pre-pulse CH & H2O CH & H2O e- Main pulse Main pulse reflection Target Return current Sheath field p+ e- Sheath Target expansion Ref:

6. Front side Hot electrons

7. Electron sheath acceleration Intense Laser Sheath Field Electron sheath Target Normal Sheath Acceleration(TNSA) is achieved when the intense laser pulse irradiates on the thin target. The front side electrons are heated and accelerated. These hot electrons penetrate the target and form electron sheath. These sheath make intense sheath field which is enough to accelerate protons. Ion velocity vs position

8. Electron sheath (Middle) (Front) (Back) <Density of the front, middle and backside electrons> Electrons at the front side of the target play an important role in TNSA. They are more energetic and participated in a sheath field. <Energy of the front, middle and backside electrons>

9. • Target parameters → thickness d - beam characteristics are improved by thin d → q/m - beam characteristics are improved by high q/m • Beam parameters → Intensity - Maximum energy and efficiency are improved → Duration - There are no effects on TNSA

10. Target • In TNSA, the ions with the highest charge-to-mass ratio (q/m) dominate the acceleration, gaining the most energy. e+ Pb Pb q/m=0.2 C5+(10Å) C5+ q/m=0.42 Ionization and acceleration Substrate expansion Sheath field ionizes rear surface e+ Pb Pb q/m=0.2 C5+(>10Å) C5+ C4+ C3+ Pb overlaps with C Substrate expansion q/m=0.42, 0.33,0.25… Ref: Hegelichet al. Nature. 439/26 (2006)

11. Target • In TNSA, the ions with the highest charge-to-mass ratio (q/m) dominate the acceleration, gaining the most energy. • black: C5+ ions (highest q/m) • blue: highest substrate charge state Pd22+ • green: C5+ ions (simul)(highest q/m) • red: Pd22+ (simul) • gray: C4+ ions • magenta: C5+ ions from a cold Pd target C4+(~80Å) C5+(~10Å) • the measured C5+ spectrum (black curve) with the lowest ratio dE/E of ~ 17% • C5+ is accelerated alone and thickness is very thin (~10Å) → equal force → monoenergetic • C4+ is accelerated alone but thickness is thin (~80Å) → varied force → maxwellian Ref: Hegelichet al. Nature. 439/26 (2006)

12. Pulse • Maximum proton energy is related with laser intensity. Experiment and simulation data are well agree with each other. • Maximum proton energy is not related with laser duration. Experiment and simulation data show that results. Ref: Robson et al. Nphys. 476 (2006)

13. Pulse • Conversion efficiency is related with laser intensity. • Conversion efficiency is not related with laser duration. Ref: Robson et al. Nphys. 476 (2006)

14. Application • Proton can also be emitted to the normal direction to the target • Target shaping is able to concentrate proton beam at some point Ref: Okada et al. PRE. 74, 026401 (2006), Wilkset al. POP. 8, 2 (2001)

15. Summary • TNSA is due to sheath field • Hot electrons comes from the front side of the target and compose electron sheath • Thickness, q/m, intensity are important parameters • In TNSA, the ions with the highest charge-to-mass ratio dominate the acceleration, gaining the most energy. • Target shaping, contaminant control, target meterial, double foil or some idea are needed for TNSA

16. END

17. • Laser-driven acceleration of monoenergetic (energy spread 17%, mean energy 3MeV) ion beams using specifically designed and treated targets (catalytic processes) • They suggest proper carbon thickness as 10Å • Lower carbon ionization states appear with increasing layer thickness, and the ion energies eventually approach a maxwellian distribution. • In TNSA, the ions with the highest charge-to-mass ratio dominate the acceleration, gaining the most energy. • Owing to the extremely small spatial extent of the carbon layer and its localization at the rear surface, all of the carbon ions are accelerated at once at the peak of the accelerating field, leading to the monoenergetic ion pulse.

18. • Having the highest charge-to-mass ratio of 0.42, the C5+ is dominantly accelerated • extremely small spatial extent of the carbon layer and its localization at the rear surface, all of the carbon ions are accelerated at once at the peak of the accelerating field, leading to the monoenergetic ion pulse • After all carbon ions are accelerated, the field is still very strong and only moderately screened by the carbon, therefore the next highest charge-to-mass ratio ion- that is, Pd22+ with a charge-to-mass ratio of 0.2-is now dominantly accelerated and gains a large fraction of the energy before the field decays and lower Pd charge states are created and accelerated.