Application of Plasma Waveguides to Advanced High Energy Accelerators H.M. Milchberg +* and T.M. Antonsen, Jr. #* * Institute for Physical Science and Technology # Institute for Research in Electronics and Applied Physics * Departments of Electrical Engineering and Physics University of Maryland, College Park, MD *Supported by USDOE DEFG0297ER41039

Scientific Goal To develop the basic science and technology of intense laser pulse propagation in plasma waveguides for laser- plasma based accelerators Experiment: plasma channel formation, laser pulse propagation and coupling, novel plasma media (cluster gases), advanced diagnostics Theory: nonlinear pulse propagation, advanced computational models and algorithms, laser - cluster interactions Success: stable propagation of intense(I ~ W/cm 2 ) guided laser pulses for 10s of cm.

Major Accomplishments Conceived and developed hydrodynamically formed plasma channels; characterized channels and pulse propagation Developed Single Shot Supercontinuum Spectral Interferometry (SSSI) Discovered and characterized self-focusing in cluster gases Delineated competition between self-focusing and Raman scattering for intense laser pulses Developed quasistatic particle modeling of plasma wakes

University of Maryland Channel Formation Scheme Generation of a plasma waveguide in an elongated, high repetition rate gas jet J. Fan, T.R. Clark, and H.M. Milchberg, Appl. Phys. Lett. 73, 3064 (1998)

Use of Axicon to Generate Plasma Channel axicon (conical lens) plasma channel moderate intensity fibre generating pulse: mJ, um 100 ps hole for guided pulse r z J 0 (kr)

Channel Measurement Time-and space-resolved density evolution of the plasma waveguide T.R. Clark and H.M. Milchberg, Phys. Rev. Lett. 78, 2373 (1997). General layout of experimental set-up 200 torr N 2 O at delays of 70ps, and 1, 6, and 10 ns Radial density profiles extracted using Abel Inversion of phase data for 150 torr Kr Density inversion required for guiding

cutoff condition parabolic waveguide r NeNe rmrm TR Clark et al, PRE 61, 1954 (2000) ring: p=0, m<6 central spot: numerous p>0, m=0 skewed coupling selects azimuthal modes Plasma waveguide mode structure p = radial index m = azimuthal index p=0 m=0 m=0 m=3 multimode  Probed with weak diverging beam

Frequency shifts are given by = where L : Interaction length : Laser wavelength n : Refractive index N c : Number of clusters per cm 3 and : Ensemble averaged cluster polarizability  Spectral redshifts (  < 0) are expected when the real part of cluster polarizability increases with time at the early stage of interaction. † Polarizability : Gas jet nozzle t (ps) × cm 3 r (  m) (+)  n (  )  n Laser pulse I(r)I(r) r Clusters † K. Y. Kim et al., Phys. Rev. Lett. 90, (2003). * I. Alexeev et al., Phys. Rev. Lett. 90, (2003). Self-focusing and frequency shifts In cluster gases Self-focusing *

single shot supercontinuum spectral interferometry transient guiding profile (n r -1) x10 -4 n i x10 -4 Advanced Diagnostics PRL(2003)

Self-focusing of intense laser pulses in clustered gases 1.4 ps 600 fs 150 fs 350 fs VFVF SF 600  m 80 fs 2.8 mm VFVF 80 fs beam I. Alexeev, T.M. Antonsen K.Y. Kim and H.M. Milchberg PHYS REV LETT 90 (10): Art. No MAR Focusing varies with pulse length due to time dependence of polarizability Side imaging End Imaging

Guiding of Intense Laser Pulses in Plasma Waveguides Produced from Efficient, Femtosecond End-Pumped Heating of Clustered Gases (PRL2005) Experimental layout Extracted electron density profile Imaged guided mode

Plasma waveguides efficiently generated by long- pulse Bessel beams in elongated cluster gas jets PRE (2005)

PIC simulations of cluster heating (PRL 2004) y=0 Energy absorbed vs Intensity Phase space (x - v x ) for electrons y=0

Modeling Propagation of Ultra-Intense Laser Pulses Accomplishments Developed first quasi-static laser- plasma particle code (WAKE-2D PoP 1997) -raman instability -self-focusing -wakefield generation -test particle acceleration -ionization Extended to 3D with UCLA group (QuickPIC, JCP 2006) -beam driver -wake loading Planned: plasma pick-up Simulation of Ionization Scattering Instability Laser Pulse

Funding Current: DoE-HEP $245k NSF-DoE Plasma $250k Cumulative: DoE-HEP : $2.0M NSF-DoE :$2.2M Staff FY05: 2 faculty, 1 postdoc (left 6/05), 7 Ph.D. students Ph.D.s: (9) Z. Bian, J Wu, J. Cooley, T.R. Clark, S. P. Nikitin, I. Alexeev, J. Fan, E. Parra, K.Y. Kim

Highlights Honors and Awards 1999 American Physical Society Doctoral Dissertation Award in Plasma Physics (Tom Clark) 2004 American Physical Society Doctoral Dissertation Award in Plasma Physics (Kiyong Kim) 2003 IEEE Plasma Science Applications Award (Antonsen) 2004 A. James Clark Outstanding Faculty Research Award (Antonsen) 2005 University of Maryland Distinguished Scholar-Teacher Award (Milchberg) 2005 APS Award for Excellence in Plasma Physics Research (Milchberg) New laser facility (IREAP) 20 Terawatt Ti:Sapphire laser (10 Hz, 600 mJ, 30 femtosecond pulse), capable of >10 20 W/cm 2 Funding: DoE supplemental budget request for $300k UMD commitment $503k We are seeking to add a new faculty position

Program Review/Community Feedback Starting (5/06) 4th 3-year grant Current renewal proposal is under review Previous 3 proposals reviewed by ~3 anonymous reviewers, comments forwarded to us for consideration/action 3 site visits by DoE-HEP personnel Advanced Accelerator Concepts Workshops Computation working group Guiding working group

Experimental verification of resonance absorption of Bessel beams in plasma waveguide formation pump axicon beam splitter energy meter plasma channel for side-coupled mode imaging 350 mJ, 100ps 1064 nm Experimental Set-Up