shock wave particle acceleration in laser-plasma interaction

SCT-2012, Novosibirsk, June 8, 2012

SHOCK WAVE PARTICLE ACCELERATION in LASER-PLASMA INTERACTION

G.I.Dudnikova, T.V.LeseykinaICT SBRAS

NOVA Laser(1999, LLNL, petawatt)

HERCULES (CUOS),Table Top Petawatt

The progress in laser technology has led to light sources delivering pulses of femtosecond duration and focused intensities up to 1022 W/cm2

Introduction & Motivation

Experiments carried out in recent years on the laser-plasma interaction show the possibility of ions acceleration to high energy (tens of MeV)

Compact and affordable ion accelerator based on laser produced plasmas have potential applications in many fields of science and medicine (radiography, isotopes generation, cancer therapy, inertial fusion).

Two more studied mechanism of ion acceleration are TNSA (60MeV, energy spread 20%), RPA ( 30 Mev, 50%, ).

The light pressure, P=2I/c, from Gigabar to Terabar may compress plasma and generate shock waves that lead to acceleration of ions due to reflection by shock front (monoenergetic component in ion spectra are produced )

Introduction & Motivation

TNSA accelerating ions by ultra-intense laser pulses

4 λ< R < 10 λ5 λ< L < 400 λ 5 λ< X1< 10 λ2 λ< X2 < 5λ2 λ< X1 < 10 λ

Set -up

Foil size: 3-20 λ

Foil density: 2-100 n*, Laser pulse: circular polarized

Amplitude a: 2-50

a=sqrt(I/1.35 1018 Wcm -2 (λ/µm) 2)

Foil: full ionized H plasma

HERCULES (MI), ATF BNL (NY), Sokol-P (Snezhinsk, Russia)

n*= 1.1 10^21 cm^-3, λ=0.8 µm

a=eE/ mcɷ

Numerical Model

Numerical modelling is carried out on the basis of code UMKA2D3V*, allowing to carry out calculations of interaction of laser radiation with plasma of any complex structure and to choose type of boundary conditions for an electromagnetic field (reflection, absorption, periodic conditions). The effective algorithm of parallel calculations is created, and its realization on multiprocessing complexes MBC-15000 (Moscow) is carried out. At the decision it was used 100-150 processors of complex MBC-15000, calculation up to the moment of time to the equal 400 laser periods has occupied approximately 5000 hours of processor time.

* Vshivkov V.A., Dudnikova G.I. Comput. Technol., 2001.

Plasma formations observed in experiment (ATF BNL) and simulated (bottom row) shadowgram and a simulated plasma profile for case filamentation and solitons for ne<n*, postsolitons for ne<n*; ne=2n*; ne=2.5 n*

*I. V. Pogorelsky, et.al, Proceedings of IPAC’10, Kyoto, Japan, 2010.

Channel & caviton formation

Hole-boring and shock formation

Vhb= sqrt((1+k) I / ƍc)

Cs=sqrt(kTe /mi) M=1.3

Te=mc2sqrt(1+a2/2)

V=0.06 c

Palmer Charlotte A. J.; Dover N. P.; Dudnikova G. I., et. al Phys. Rev. Lett. 106, 014801 (2011)

Ion phase space

Ion trajectories

Distribution function

T.C.Liu, G. Dudnikova, et.al, Phys.Plasma, 18, 2011

Ion density

Proton energy spectra

Ion energy phase space

Flat pulse

R-T instability

a=32

Plasma density temporal evolution. a=32, n=169 n*, d=0.25 λI=1.4 10 21W/cm2, n=1.9 10 23 cm-3, d=0.25 µm

Energy spectrum

• Laser acceleration is potentially an affordable alternative to traditional cyclotron acceleration. Intense, high quality ion beams driven by relativistic laser plasma - the next generation ion accelerators.

• Shock-like acceleration due to the ion reflection at the front of the compressed layer in the plasma lets to obtain the quasi-monoenergetic ion bunch.

• In realistic geometries there are two independent obstacles to sustain quasi-mono-energetic regime of acceleration: Rayleigh-Taylor instability of plasma sheet lateral expansion of plasma

Summary