Non Double-Layer Regime: a new laser driven ion acceleration mechanism toward TeV 1

outline  significance 、 implications 、 goals for high energetic ion beams  one-stage acceleration ： target normal sheath acceleration (TNSA) 、 phase-stable acceleration or radiation pressure acceleration(RPA)  multi-stage acceleration for TeV proton beam ： non double layer regime  Tens TeV or even higher energetic heavy ion beam 2

1.Motivation and current situation of laser-plasma ion acceleration The produced high energetic ion by target normal sheath acceleration( TNSA ） experimentally ： energy gain ： 67 MeV for proton and 500MeV for Carbon ion. acceleration field strength: 100 GV/m GV/m energy spread: 20% good repetitiveness applications ： ion cancer therapy 、 fast ignition of thermonuclear fusion 、 high energy physics and astrophysics goals ： mono-energetic 、 collimated 、 higher energy 、 higher transfer efficiency 3

2.1(a) TNSA Laser TNSA Thick solid target Typical values: 4 2.One stage acceleration

2.2 circularly polarized laser-thin target interaction for ion acceleration phase stable acceleration or radiation pressure acceleration Thin solid target v From an immobile sheath to a moving sheath/double layer 5

2.One stage acceleration 2.2 circularly polarized laser-thin target interaction for ion acceleration phase stable acceleration or radiation pressure acceleration (a) The light pressure balances the electrostatic pressure to form double layer (electron and ion layer) structure, green ： proton blue ： electron 6 matching condition:

2.One stage acceleration b.The ion dynamical motion obeys ： scaling law : p>>1 ， dp/dt ∝ (1/p 2 ), p ∝ t 1/3, x 1/3 7 （ T. Esirkepov et al., PRL92, (2004) ）

2. One stage acceleration B A B A Phase space (x~p x ) X. Yan et al., PRL 100, (2008) ; Bin.Qiao et al,PRL 102,145002(2009); X. Yan et al., PRL 103, (2009); M. Chen et al., PRL 103, (2009); 8

Linearly polarized laser pulse + thick solid target (2002) 9 Circularly polarized laser pulse + thin solid target (2008) Circularly polarized laser pulse + combination target TNSA regime length: l d energy: 67MeV Phase stable regime: length: tens mm energy: GeV Non-double-layer regime length: cm energy: TeV ?????

3.multi-stage acceleration for proton beam: non double layer regime 10 matching condition: The light pressure exerted on the electron layer is larger than the electrostatic pressure. The electron layer is pushed out by the ponderomotive force before double-layer is formed.

Wakefield structure 、 electron and proton density 11 Simulation parameters ： laser pusle: a 0 =250 ； foil : 20n c ， D=0.5mm ； gas length:12000mm ， 0.01n c double layer:Non-double layer :

Wakefield structure, phase space and energy distribution of proton beam 12 Maximum relativistic factor Gamma=580 ， W max >0.5TeV, 8 times higher than that in the double-layer regime t=5000T l t=12000T l

Dynamical process in the non-double layer regime versus background gas density Maximum energy scaling ： 13 Minimum gas density ： distance between the electron and proton layer maximum electrostatic field Dephasing length maximum energy

4.Heavy ion toward tens TeV Assuming the same acceleration length for both proton and heavy ion Defining the dephasing length ratio between heavy ion and proton ： dynamical equation in describing the acceleration process of heavy ion the maximum energy of heavy ion reads:

Simulation results for carbon ion beams: the same laser and plasma parameters as given for proton beam 15 t= 0.5T l t= 0.6T l In the non-double layer regime: the electron layer runs faster than the carbon ion layer. The double-layer structure can’t be formed in the laser-foil stage.

16 Wakefield structure, electron density, carbon ion density, laser pulse t=5000T l t=15000T l The inset in Fig.(d) indicating: the energy transfer efficiency converted to carbon ion is greater than 30% The acceleration process is terminated at t=15000T l,meanwhile the laser pulse is completely absorbed, suggesting that the dephasing length is equal to pump depletion length.

17 Heavy ion information The longitudinal phase space and energy spectrum of the trapped carbon ion at t=15000T l Maximum energy of carbon ion versus time in unit of laser cycles (a); maximum energy for different ion with charge number Z (b). C 6+ : 3.2TeV Cu 29+ : 16TeV Au 50+ : 25TeV

THANK YOU! 18