A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z    

Wurtele, J.S.

Paper Title Page
TPAE054 Ultraintense and Ultrashort Laser Pulses from Raman Amplification in Plasma for Laser-Plasma Accelerators 3274
 
  • M.S. Hur, G.-H. Kim, H. Suk
    KERI, Changwon
  • A.E. Charman, R.R. Lindberg, J.S. Wurtele
    LBNL, Berkeley, California
 
  Funding: Korea Electrotechnology Research Institute, Korea; Creative Research Initiatives, Korea.

We present analysis and simulations of kinetic effects in the Raman pulse amplification in plasma. An ultraintense and ultrashort laser pulse is a very essential part in an advanced acceleration scheme using laser and plasma. To make strong pulses, a noble scheme of using Raman backscatter in plasma was proposed and has been studied intensively.* The Raman amplification in plasma does not have a restriction in material damage threshold. However, for the new amplifier to be a promising alternative of the CPA technique, more extensive studies on various issues are required. One of the fundamental issues is the electron kinetic effect such as particle trapping or wavebreaking. We present a theoretical analysis of the kinetic effect; a new kinetic term is derived to be added to the fluid model and the effect of the new term is verified by averaged-PIC (aPIC)** simulations. Various one dimensional and semi-two dimensional aPIC simulations of pulse amplification are presented. We discuss the future application of the Raman scheme to upgrading the laser pulse of the Center of Advanced Accelerator in KERI, which are currently 2 TW and 700 fs, into a few more TW and less than 100 fs.

*V. M. Malkin, G. Shvets, and N. J. Fisch, Phys. Rev. Lett. vol. 82, 4448 (1999).**M. S. Hur, G. Penn, J. S. Wurtele, and R. Lindberg, Phys. Plasmas vol. 11, 5204 (2004).

 
TPPE064 Space-Charge Effects Near a Cathode 3629
 
  • V. Gorgadze
    UCB, Berkeley, California
  • J.S. Wurtele
    LBNL, Berkeley, California
 
  Funding: This work was supported by the Director, Office of Science of the U.S. DOE under Contract No. DE-AC03-76SF00098.

RF photocathode guns are excellent sources of high brightness electron bunches. In the limit of high-current short bunches the electron are complicated space-charge fields. To mitigate space charge effect downstream of the gun it is often desirable to produce electorn bunches with uniform distribution. Our goal is to understand to what extent the non-uniformity of the laser pulse intensity is responsible for a non-uniform electron distribution and to what extent this is due to the electron beam dynamics near to the cathode. We investigate these effects with particle-in-cell simulations and simple theory. These studies are focused on the regime where the peak current as well as the temporal current profile are influenced by the self-fields of the bunch. The simulation code XOOPIC has been employed. The critical current limitation for virtual cathode formation and current density profile at the exit of the injector have been found.

 
RPAP039 Accelerator and Ion Beam Tradeoffs for Studies of Warm Dense Matter 2568
 
  • J.J. Barnard, D. A. Callahan, A. Friedman, R.W. Lee, M. Tabak
    LLNL, Livermore, California
  • R.J. Briggs
    SAIC, Alamo, California
  • R.C. Davidson, L. Grisham
    PPPL, Princeton, New Jersey
  • E. P. Lee, B. G. Logan, P. Santhanam, A. Sessler, J.W.  Staples, J.S. Wurtele, S. Yu
    LBNL, Berkeley, California
  • C. L. Olson
    Sandia National Laboratories, Albuquerque, New Mexico
  • D. Rose, D.R. Welch
    ATK-MR, Albuquerque, New Mexico
 
  Funding: Work performed under the auspices of the U.S. Department of Energy under University of California contract W-7405-ENG-48 at LLNL, University of California contract DE-AC03-76SF00098 at LBNL, and contract DEFG0295ER40919 at PPPL.

One approach to heat a target to "Warm Dense Matter" conditions (similar, for example, to the interiors of giant planets or certain stages in Inertial Confinement Fusion targets), is to use intense ion beams as the heating source. By consideration of ion beam phase space constraints, both at the injector, and at the final focus, and consideration of simple equations of state, approximate conditions at a target foil may be calculated. Thus target temperature and pressure may be calculated as a function of ion mass, ion energy, pulse duration, velocity tilt, and other accelerator parameters. We examine the variation in target performance as a function of various beam and accelerator parameters, in the context of several different accelerator concepts, recently proposed for WDM studies.

 
TPAE066 Robust Autoresonant Excitation in the Plasma Beat-Wave Accelerator: A Theoretical Study 3688
 
  • A.E. Charman, R.R. Lindberg, J.S. Wurtele
    UCB, Berkeley, California
  • L. Friedland
    The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem
 
  Funding: Division of High Energy Physics, U.S. Department of Energy, DARPA, U.S. Department of Defense.

A modified version of the Plasma Beat-Wave Accelerator scheme is introduced and analyzed, which is based on autoresonant phase-locking of the nonlinear Langmuir wave to the slowly chirped beat frequency of the driving lasers via adiabatic passage through resonance. This new scheme is designed to overcome some of the limitations of previous approaches, namely relativistic detuning and nonlinear modulations in the driven Langmuir wave amplitude, and sensitivity to frequency mismatch from density fluctuations. As in previous schemes, instabilities of the ionic background ultimately limit the useful interaction time, but nevertheless peak electric fields approaching the wave-breaking limit seem readily attainable. Compared to traditional approaches, the autoresonant scheme achieves larger accelerating electric fields for given laser intensity; the plasma wave excitation is more robust to variations in plasma density; it is largely insensitive to the choice of chirp rate, provided that chirping is sufficiently slow; and the quality and uniformity of the resulting plasma wave and its suitability for accelerator applications may be superior.

 
RPPT025 Beam Conditioning and FEL Studies Using MAD and Genesis
 
  • Y. Vinokurov, E. Esarey, G. Penn, A. Sessler, A. Wolski, J.S. Wurtele
    LBNL, Berkeley, California
 
  Funding: This work was supported by the Office of Science, High Energy Physics, U.S. Department of Energy under Contract No. DE-AC03-76SF00098.

Beam conditioning using a variety of lattices is explored using MAD in conjunction with Genesis. In particular, the conditioning effects of a simple FODO lattice are simulated in MAD and the resulting particle distribution is then used as an input to Genesis to examine the effects of a conditioner on FEL performance. Studies of a plasma-based conditioner have been performed. In this scheme conventional RF accelerating cavities are replaced by a plasma accelerator. The wavelength of the plasma wave is typically shorter than the longitudinal bunch length, resulting in regions of conditioned and unconditioned beam. Studies were also performed analyzing the sensitivity of FEL performance to changes in various system parameters.

 
ROAB003 Highly Compressed Ion Beams for High Energy Density Science 339
 
  • A. Friedman, J.J. Barnard, D. A. Callahan, G.J. Caporaso, D.P. Grote, R.W. Lee, S.D. Nelson, M. Tabak
    LLNL, Livermore, California
  • R.J. Briggs
    SAIC, Alamo, California
  • C.M. Celata, A. Faltens, E. Henestroza, E. P. Lee, M. Leitner, B. G. Logan, G. Penn, L. R. Reginato, A. Sessler, J.W.  Staples, W. Waldron, J.S. Wurtele, S. Yu
    LBNL, Berkeley, California
  • R.C. Davidson, L. Grisham, I. Kaganovich
    PPPL, Princeton, New Jersey
  • C. L. Olson, T. Renk
    Sandia National Laboratories, Albuquerque, New Mexico
  • D. Rose, C.H. Thoma, D.R. Welch
    ATK-MR, Albuquerque, New Mexico
 
  Funding: Work performed under auspices of USDOE by U. of CA LLNL & LBNL, PPPL, and SNL, under Contract Nos. W-7405-Eng-48, DE-AC03-76SF00098, DE-AC02-76CH03073, and DE-AC04-94AL85000, and by MRC and SAIC.

The Heavy Ion Fusion Virtual National Laboratory (HIF-VNL) is developing the intense ion beams needed to drive matter to the High Energy Density (HED) regimes required for Inertial Fusion Energy (IFE) and other applications. An interim goal is a facility for Warm Dense Matter (WDM) studies, wherein a target is heated volumetrically without being shocked, so that well-defined states of matter at 1 to 10 eV are generated within a diagnosable region. In the approach we are pursuing, low to medium mass ions with energies just above the Bragg peak are directed onto thin target "foils," which may in fact be foams or "steel wool" with mean densities 1% to 100% of solid. This approach complements that being pursued at GSI, wherein high-energy ion beams deposit a small fraction of their energy in a cylindrical target. We present the requirements for warm dense matter experiments, and describe suitable accelerator concepts, including novel broadband traveling wave pulse-line, drift-tube linac, RF, and single-gap approaches. We show how neutralized drift compression and final focus optics tolerant of large velocity spread can generate the necessarily compact focal spots in space and time.