Plasma as an amplifying medium a new paradigm

Transcription

1 Dino Jaroszynski University of Strathclyde Plasma as an amplifying medium a new paradigm

2 Outline of talk Scottish Universities Plasma medium Raman amplification Chirped pulse Raman amplification Broad-bandwidth amplification Strathclyde experiments High gain measurements at RAL New facility: SCAPA

3 Plasma media: capillary, gas jet & plasma cells Gas Cell 10 J, 50 fs = 850 MeV (at RAL) 2 mm Gas jet 1 J, 40 fs = 300 MeV 200 consecutive Images (Strathclyde) 4 cm Plasma capillary 10 J, 50 fs ~ 1 GeV (at RAL)

4 4 cm long preformed plasma waveguide Strathclyde Plasma waveguide medium n = cm -3 Originally developed by Simon Hooker s group Strathclyde laser micromachining

5 Raman & Compton amplification using colliding pulses ω p ω pump ω seed Shvets, Fisch, Pukhov, Meyer-ter-Vehn, PRL 1998 Malkin, Shvets, Fisch PRL 1999

6 Dynamic chirped grating compressor p b 2 0 1aa 0 1 Compton regime Energy and momentum is conserved pump seed p k k k pump seed p

7 Chirped pulse broadband Raman gain probe intensity e gain coefficient a g Chirp rate: DT/D 50 GHz/ps Single frequency gain G = e g(d)t CPA interaction time t ~ g 0 DT/D Broadband gain Distributed gain 2 0 DT D G e g G. Vieux New J. Phys g ( d) g d g 0 g (d) g d -g /2 g /2 Beat wave phase velocity a 0 0 v 0 2 p pc/20

8 Chirped pulse Raman amplification Linear RBS Exponential growth g a / 2 exp[ g t] p 0 Narrow bandwidth limited to 2g 0 Temporal broadening Not suitable for short pulse amplification Chirped Pulse RBS Constant gain exp[ g / 2 ] 2 0 Seed frequencies amplified at different longitudinal positions No temporal broadening Superradiant scaling

9 Superradiance: Pump Depletion & Compton regimes 1 / pd 50% c p 0 I z pd 2 1 z Simulations using analytical and fluid model Superradiant scaling in the linear regime for chirped pulses! Same for pump depletion. Dicke superradiance? Burnham Chao Ringing? c 1 z Ersfeld & Jaroszynski PRL 2005

10 Thermal Effects Thermal effects: Bohm-Gross shift of resonance: 2 3kBT /( mev ), v ( 0 1)/( k0 k1) pc /(20 ) Landau damping: plasma wave transfers energy to electrons with velocity close to phase velocity; 1/ 2 3/ 2 rate: ( /8) (3/ ) exp( 3[1/ 1]/ 2), L p Lower threshold for wave breaking (electrons 1/ 4 1/ 2 overtake wave): ee wb /( m ) v (1 8 /3 2 /3) Trapping of electrons reduces backscattering. Time-dependent shift if plasma heated rapidly (e.g. collisions in initially cold plasma) chirped resonance p res (1 ) p 1/ 2,

11 Experiment setup Pump: ps 100 mj 1 J Probe: fs mj Beam waist: mm pump Plasma: 4 cm cm -3

12 Stokes and anti-stokes satellites Stokes anti-stokes Stokes Measurement of Raman gain: Broadband amplification

13 Spectral measurements Seed no pump Seed with pump 200 ps, 350 mj pump amplifies a 200 fs, 200 μj seed Energy gains of 400% over full spectral bandwidth Peak energy transfer efficiency is 1 2 %.

14 RAL experiment Pump J 1.06 mm 10 ps Frequency-shifted seed - Raman crystal frequency shift from mm to mm plasma density to match frequency difference: n = cm -3

15 Maximum gain at 70 J Amplified Seed: Pump J g a / 2 exp[ g t] p 0 gain coefficient ( ) a I E 0 pump 170 mj measured with 70 J pump (100 mj in seed only) Saturation above 70 J Spontaneous Raman scattering Maximum energy density 10 Jcm -2.

16 Efficiency Efficiency Maximum η 0.25% energy transfer for maximum energy. η 0.15% energy transfer for seed only. Efficiency η 1% for central spot (which contains 25 30% of total energy).

17 Scottish Centre for the Application of Plasma Based Accelerators SCAPA 1200 m 2 laboratory space: TW laser and 7+ beam lines - particles and coherent and incoherent radiation sources for applications: nuclear physics, health sciences, plasma physics etc. Also part of Strathclyde Technology and Innovation Centre (TIC) New appointments: Strathclyde: 2 Chairs, 2 PDRAs, Technicians Glasgow: 1 Reader USW: 2 Readers/Lectures Edinburgh SUPA Fellow infrastructure + staff + beam lines

18 Shielded area: 7 beam lines HEALTH IONS ELECTRONS & RADIATION: FEL, BETATRON etc.

19 Expansion of ALPHA-X laser-plasma accelerator facilities at Strathclyde with new laboratories. In-depth programme of Applications. Accelerator and source Research & Development. Knowledge Exchange & Commercialisation Engagement in European and other large projects. Training: Centre for Doctoral Training in the Application of Next Generation Accelerations Scottish Centre for the Application of Plasma-based Accelerators (SCAPA) SCAPA unique facility 3 shielded areas with 7 accelerator beam lines. High-intensity femtosecond laser systems: a) TW (with provision for 5 Hz, b) Hz, c) 1 khz. High-energy proton, ion and electron bunches. High-brightness fs duration X-ray & gamma-ray pulses. 40 mm Compact GeV electron accelerator and gamma-ray source APPLICATIONS Radiobiology Ultrafast Probing High-Resolution Imaging Radioisotope Production Detector Development Radiation Damage Testing

20 Strathclyde (students and staff): ALPHA-X project Team: Dino Jaroszynski (Director), Salima Abu-Azoum, Maria-Pia Anania, Constantin Aniculaesei, Rodolfo Bonifacio, Enrico Brunetti, Sijia Chen, Silvia Cipiccia, David Clark, Bernhard Ersfeld, Paul Farrell, John Farmer, David Grant, Peter Grant, Ranaul Islam, Yevgen Kravets, Panos Lepipas, Tom McCanny, Grace Manahan, Martin Mitchell, Adam Noble, Guarav Raj, David Reboredo Gil, Anna Subiel, Xue Yang, Gregory Vieux, Gregor Welsh and Mark Wiggins Collaborators: Marie Boyd, Annette Sorensen, Gordon Rob, Brian McNeil, Ken Ledingham and Paul McKenna ALPHA-X: Current and past collaborators: Lancaster U., Cockcroft Institute / STFC - ASTeC, STFC RAL CLF, U. St. Andrews, U. Dundee, U. Abertay-Dundee, U. Glasgow, Imperial College, IST Lisbon, U. Paris- Sud - LPGP, Pulsar Physics, UTA, CAS Beijing, U. Tsinghua, Shanghai Jiao Tong U., Beijing, Capital Normal U. Beijing, APRI, GIST Korea, UNIST Korea, LBNL, FSU Jena, U. Stellenbosch, U. Oxford, LAL, PSI, U. Twente, TUE, U. Bochum, IU Simon Cancer Center, Indianapolis, MGS Research, Inc., Madison, Royal Marsden,... Support: University of Strathclyde, EPSRC, CSO, EU Laserlab, STFC consortium

21 FIN Thank you