Interaction of plasmas with intense laser pulses carrying orbital - PowerPoint PPT Presentation

Interaction of plasmas with intense laser pulses carrying orbital angular momentum Zsolt Lecz, Alexander Andreev, Andrei Seryi, Ivan Konoplev John Adams Institute for Accelerator Science Lecture Series 14.04.2016

Content ➔ Introduction, motivation ➔ Circularly polarized (CP) intense pulse interacting with solid density targets ➔ Laser induced Coherent Synchrotron Emission (CSE) ➔ Attopulse and attospiral generation ➔ Screw-shaped pulses interacting with underdense plasmas ➔ Generation of GigaGauss axial magnetic fields ➔ Possible applications in LWFA 04/14/16 Zsolt Lecz 2

Orbital Angular Momentum (OAM) EM Waves Particles S =(⃗ E ×⃗ B ) r = √ y 2 + z 2 ⃗ ⃗ p ⃗ μ 0 S ⃗ r z ⃗ r y 04/14/16 Zsolt Lecz 3

Synchrotron radiation I (ω)∼| ∫ dt ⃗ 2 2 ϵ×[⃗ ϵ× J (⃗ r ,t )] exp [ i ω( t −⃗ ϵ⋅⃗ r / c )]| I (ω)∼| J ⊥ ( x ,t ) exp [ i ω( t − x ( t )/ c )]| v ⊥ ≪ c ⃗ v ⃗ ⃗ r Observer v x ≈ c ⃗ ϵ ⃗ ⃗ J ⊥ 04/14/16 Zsolt Lecz 4

Synchrotron radiation I (ω)∼| ∫ dt ⃗ 2 2 ϵ×[⃗ ϵ× J (⃗ r ,t )] exp [ i ω( t −⃗ ϵ⋅⃗ r / c )]| I (ω)∼| J ⊥ ( x ,t ) exp [ i ω( t − x ( t )/ c )]| x ( t )= r ( t )= ? v ⊥ ≪ c ⃗ 2 / c 2 ) − 1 / 2 γ=( 1 −˙ x ( t ) v ⃗ ⃗ r Observer v x ≈ c ⃗ ϵ ⃗ 2 n + 1 2 n − 1 ⇒ω r ∼γ n x ( t )∼ t ¨ ⃗ J ⊥ − 2 n + 2 2 n + 1 I (ω)∼ω D. an der Brügge and A. Pukhov, arxiv:1111.4133 (2011) 04/14/16 Zsolt Lecz 5

Twisted pulses (using electron beams) Erik Hemsing et al., Nature Physics 9 , 549 (2013) Electron gamma: 100-1000 Undulator length: ~cm-m Gy. Toth et al., Optics Letters 40 , 4317 (2015) 04/14/16 Zsolt Lecz 6

Simulation setup: Solid density target, CP pulse Codes : Collissionless, relativistic particle-in-cell plasma ✔ Vsim (VORPAL), Tech-X simulations. Corp. ✔ EPOCH Normalized laser amplitude a 0 = √ 2 ]λ L 2 [μ m ] I [ W / cm 18 1.4 × 10 04/14/16 Zsolt Lecz 7

CP pulse vs. flat foil Zs. Lécz et al., LPB 34, p. 31-42 (2016) Simulation parameters: 20 W / cm 2 I L = 10 h = 0.2 μ m n 0 = 28 n cr t L = 20 fs solid hydrogenfoil w L = 2 μ m z y x 04/14/16 Zsolt Lecz 8

Attopulse generation Relativistic electrons near the plasma surface emit coherent radiation. v ∥ ≈ c v ⊥ ≈ 0 Electron a ⊥ ≈ eA 0 nanobunches m e ω 0 z y x 04/14/16 Zsolt Lecz 9

Rotation symmetric interaction: CP pulse vs. cone-like targets Cone target Cylinder target Focusing of attospiral near Energetic electrons move on the exit hole a spiral path 04/14/16 Zsolt Lecz 10

Movie 04/14/16 Zsolt Lecz 11

OAM in attopulse Transversal poynting vector Incident pulse Attospiral 25 W Max :1.4 × 10 2 m 24 W Max :10 2 m 1 μ m 0.4 μ m 04/14/16 Zsolt Lecz 12

Coherent Synchrotron Emission 2 E y 2 E z E y < 0 Electrons 04/14/16 Zsolt Lecz 13

Coherent Synchrotron Emission 2 E y 2 E z a y ( t ' ) E y ( t )=− N e 2 R 2 ( 1 − v x ( t ' )/ c ) c 4 4 γ =− C a y ( t ' ) E y < 0 2 t ' 2 n ) 2 ( 1 +α 1 γ x' = x − c ( t − t ' ) t ' ( t ) 2 n ) v x ( t ' )= v 0 ( 1 −α 1 t ' Electrons J.M. Mikhailova et al., PRL 109 , 245005 (2012) 04/14/16 Zsolt Lecz 14

Harmonic spectrum Zs. Lécz and A. Andreev, PRE 93, 013207 (2015) 2 N dr =ω dr /ω L ≈( 3 / 2 ) a 0 2 I ω 0 I ω 0 = ? − 1 t L , I atto =( N dr / 2 ) t atto = 0.21 N dr 04/14/16 Zsolt Lecz 15

Screw-shaped laser pulse http://arxiv.org/abs/1604.01259 Front View: λ sp / 2 The ponderomotive force has an azimuthal component as well! The laser pulse is represented 2 ∼( I L /λ sp )λ L 2 F p ∼∇ I L λ L by the envelope function of the intensity distribution. 04/14/16 Zsolt Lecz 16

Envelope model EM wave Inensity F p F p Mesh resolution If the electron plasma period v ×⃗ B ∼⃗ E ×⃗ F p = e ⃗ B is much larger than the laser period: 2 ⋅[ 1 + cos ( 2 k x )] ∼ E ∂ E /∂ x ∼∇ E env F p ∼∇ I L 04/14/16 Zsolt Lecz 17

Electron dynamics In the moving frame of the laser pulse! In the back of the bubble. 04/14/16 Zsolt Lecz 18

Bubble solenoid × 10 27 m − 3 n e / n 0 B x ( kT ) The plasma has to be underdense, otherwise the pulse depletion becomes significant. 04/14/16 Zsolt Lecz 19

Scaling of peak magnetic field 1 / 2 B ∼(γ n 0 ) 14 m − 2 1.12 ⋅ 10 − 1 n 0 < 0.1 n cr =λ L γ∼ I L λ L For larger B-field small wavelength and high intensity is required!! 28 m − 3 , λ L = 20 nm , I L = 8 × 10 23 W / cm 2 B = 1 MT ⇒ n 0 = 7 ⋅ 10 28 m − 3 , λ L = 800 nm,I L = 2 × 10 22 W / cm 2 B = 50 kT ⇒ n 0 = 7 ⋅ 10 04/14/16 Zsolt Lecz 20

Parameter map λ L = 800 nm λ L = 100 nm k = n 0 / n cr λ p = 2 π c /ω p = plasma wavelength 04/14/16 Zsolt Lecz 21

Electron collimation: Low emittance via synchrotron cooling? 04/14/16 Zsolt Lecz 22

Steady solenoid The plasma wavelength is smaller than the laser pulse length (or spiral step). In this regime bubble can not be formed, but rotational current is generated behind the pulse. The length and lifetime of the uniform axial field depends on the depletion time and diffusion time respectively. 100 micrometers long for 100 fs 04/14/16 Zsolt Lecz 23

Future plans Project 1 Project 2 ● Electron cooling via ● Generalize the driver synchrotron emission beam: does it work with e-beam as well? ● Near the laser axis higher grid resolution ● is needed ● ● Improved beam emittance? New short wavelength source ? 04/14/16 Zsolt Lecz 24

Multi-scale problem Record the absorbed EM wave ⃗ B x e- Speed of light 04/14/16 Zsolt Lecz 25

Thank you for your attention! 04/14/16 Zsolt Lecz 26

Twisted pulses (using plasmas) Yin Shi et al., Physical Review Letters 112 , 235001 (2014) OAM conversion of Laguerre- The wavefront of the incoming Gaussian pulses pulse is distorted by the tailored Attosecond UV vortex spiral-shaped surface. In gas target : Carlos Hernandez-Garcıa et al., Physical Review Letters 111 , 083602 (2013) 04/14/16 Zsolt Lecz 27

Collimated electron and ion beams Electron trajectories Z. Najmudin etal., Phys Rev Lett S. V. Bulanov et al., JETP Letters, Vol. 87 , 215004 (2001) 71 , No. 10, 2000, pp. 407–411 Inertial Confinement Fusion : Axial magneic field : T. AKAYUKI , A. & K EISHIRO , N. (1987). N. Naseri et al., PHYSICS OF PLASMAS 17, Laser Part. Beams 5, 481–486 083109 (2010) 04/14/16 Zsolt Lecz 28