External injection of electron bunches into plasma wakefields

Transcription

1 External injection of electron bunches into plasma wakefields Studies on emittance growth and bunch compression p x x Timon Mehrling, Julia Grebenyuk and Jens Osterhoff FLA, Plasma Acceleration Group ( Student Seminar on particle physics November, 10th 2011

2 Contents >Motivation and introduction into laser-wakefield >Basics of Particle-In-Cell simulations >Emittance growth in Laser-wakefield >Bunch compression of external injected electron bunches Longitudinal dynamics of a single electron in a linear plasma wave Collective dynamics of an electron bunch Comparison between theory and simulations >Summary >Outlook Timon Mehrling Student Seminar on particle physics slide 2

3 >Gradient of conventional RF accelerators is limited < 100 MV/m 17 GeV 3.4 km Timon Mehrling Student Seminar on particle physics slide 3

4 >Plasma accelerators allow gradients > 100 GV/m ~3 cm c V W. P. Leemans and E. Esarey, Physics Today (March 2009) an be guided by a preformed narrow channel of se primary purpose is to excite a large-amplitude for producing a plasma channel was initially developed m gas in the capillary and drives a heating current ard the capillary s boundary to form a suitable lowharge apparatus recently developed by our group at gh a sapphire Leemans block, is et illuminated al., Nature by Physics a glowing 2, hydro- (2006) ~1 GeV Timon Mehrling Student Seminar on particle physics slide 4

5 >Principle of laser-plasma Highly intense laser pulse Gas target MeV-GeV electron bunch Timon Mehrling Student Seminar on particle physics slide 5

6 >Particle-In-Cell simulation by GoLP of laser-wakefield (LWFA) with highly nonlinear plasma waves and self injection Timon Mehrling Student Seminar on particle physics slide 6

7 >External injection of electron bunches into plasma wakefields laser pulse well defined electron bunch MeV-GeV well defined electron bunch Timon Mehrling Student Seminar on particle physics slide 7

8 >Charge density of a linear plasma wave Normalized values of: Vector potential of laser pulse Plasma electron density - 1 Longitudinal electric field y [c / ω p ] Charge Density [e ω p 3 / c 3 ] z [c / ω p ] Timon Mehrling Student Seminar on particle physics slide 8

9 y [c / ω p ] >Longitudinal electric field of a plasma wave z [c / ω p ] E z E y [c / ω p ] >Transverse electric field of a plasma wave E z [m e c ω p e -1 ] z [c z /[c ω/ ω p ] p ] E y E 0 Figure 1.4: y-z slice plane of E z field component of a 3D PIC-simulation with a 0 = Figure 1.5: y-z slice plane of E z field component of a 3D PIC-simulation with a 0 = Timon Mehrling Student Seminar on particle physics slide ] 9

10 >PIC simulation of external injection of a gaussian electron bunch into a plasma wakefield laser pulse electron bunch Timon Mehrling Student Seminar on particle physics slide 10

11 >What is emittance? x 0 = p x p z x 0 " " x x >Vacuum drift >Focussing force Timon Mehrling Student Seminar on particle physics slide 11

12 >Low emittance: essential for any application e.g. colliders or FELs Ṅ = L L 1 p "1 " 2 collision rate Ṅ cross section luminosity L emittance " >Bunch compression: high current, short pulse X-ray production in FELs or pump-probe experiments for few fs-short atomic processes I l b 1 current I bunch length l b Timon Mehrling Student Seminar on particle physics slide 12

13 Basics of Particle-in-cell simulations >Full electrodynamic and kinetic approach >Macroparticles with continuous positions and momenta >PIC code used: OSIRIS by GoLP, Lissbon Maxwell solver Solving Maxwell equations for current on the lattice Current scatter Current of particles is deposited onto the lattice Field gather Interpolation of fields from the lattice to the particles position Particle pusher Solving equation of motion Timon Mehrling Student Seminar on particle physics slide 13

14 Emittance growth in Laser-wakefield >Transverse dynamics of an electron bunch, injected into a plasma wakefield Timon Mehrling Student Seminar on particle physics slide 14

15 Bunch compression of external injected electron bunches >Bunch compression in a 2D PIC simulation Relative delay [fs] Charge [pc/fs] z position [mm] 0 Timon Mehrling Student Seminar on particle physics slide 15

16 Bunch compression of external injected electron bunches >Thank you for your attention! Timon Mehrling Student Seminar on particle physics slide 16