SLAC, Menlo Park, California
UCLA, Los Angeles, California
Duke University, Durham, North Carolina
USC, Los Angeles, California
Funding: Work supported in part by the U.S. Department of Energy under contract number DE-AC02-76SF00515.
Recent progress in generating gradients in the 10's of GV/m range with beam driven plasmas has renewed interest in developing a linear collider based on this technology. This talk will explore possible configurations of such a machine, discuss the key demonstrations and the facilities needed to advance this effort and highlight possible alternative uses of this technology.
SLAC, Menlo Park, California
UCLA, Los Angeles, California
Duke University, Durham, North Carolina
USC, Los Angeles, California
Funding: Work supported in part by the U.S. Department of Energy under contract number DE-AC02-76SF00515.
An electron beam driven Plasma Wake-Field Accelerator (PWFA) has recently sustained accelerating gradients above 50GeV/m for almost a meter. Future experiments will transition from using a single bunch to both drive and sample the wakefield, to a two bunch configuration that will accelerate a discrete bunch of particles with a narrow energy spread and preserved emittance. The plasma works as an energy transformer to transform high-current, low-energy bunches into relatively lower-current higher-energy bunches. This method is expected to provide high energy transfer efficiency (from 30% up to 95%) from the drive bunch to the accelerated witness bunch. The PWFA has a wide variety of applications and also has the potential to greatly lower the cost of future accelerators. We discuss various possible uses of this technique such as: linac based light sources, injector systems for ring based synchrotron light sources, and for generation of electron beams for high energy electron-hadron colliders.
UCLA, Los Angeles, California
Duke University, Durham, North Carolina
Plasma Wake Field Accelerator (PWFA) has a very attractive accelerating gradient which can be three orders of magnitude higher than that of the traditional accelerator. In this paper the positron acceleration in a particle beam driven PWFA is studied both in the linear and weakly nonlinear region by using Particle In Cell (PIC) simulation. A preliminary parameters design is obtained for such acceleration scheme.
UCLA, Los Angeles, California
SLAC, Menlo Park, California
Duke University, Durham, North Carolina
USC, Los Angeles, California
Funding: Work supported by DOE under contracts DE-FG03-92ER40727, DE-FG52-06NA26195, DE-FC02-07ER41500, DE-FG02-03ER54721.
Recent Plasma Wake-Field Acceleration (PWFA) experiments at Stanford Linear Accelerator Center has demonstrated electron acceleration from 42GeV to 84GeV in less than one meter long plasma section. The accelerating gradient is above 50GeV/m, which is three orders of magnitude higher than those in current state-of-art RF linac. Further experiments are also planned with the goal of achieving acceleration of a witness bunch with high efficiency and good quality. Such PWFA sections with 25 GeV energy gain will be the building blocks for a staged TeV electron-positron linear collider concept based on PWFA (PWFA-LC). We conduct Particle-In-Cell simulations of these PWFA sections at both the initial and final witness beam energies. Different design options, such as Gaussian and shaped bunch profiles, self-ionized and pre-ionized plasmas, optimal bunch separation and plasma density are explored. Theoretical analysis of the beam-loading* in the blow-out regime of PWFA and simulation results show that highly efficient PWFA stages are possible. The simulation needs, code developments and preliminary simulation results for future collider parameters will be discussed.
*M. Tzoufras et al, Phys. Rev. Lett. {10}1, 145002 (2008).
UCLA, Los Angeles, California
SLAC, Menlo Park, California
Funding: Work supported by DOE grant numbers: DE-FG03-92ER40727, DE-FG52-06NA26195, DE-FC02-07ER41500, DE-FG02-03ER54721
The fourth generation of light sources (such as LCLS and the XFEL) require high energy electron drivers (16-20GeV) of very high quality. We are exploring the possibility of using a high transformer ratio PWFA to meet these challenging requirements. This may have the potential to reduce the size of the electron drivers by a factor of 5 or more, therefore making these light source much smaller and more affordable. In our design, a high charge (5-10nC) low energy driver (1-3GeV) with an elongated current profile is used to drive a plasma wake in the blowout regime with a high transformer ratio (5 or more). A second ultra-short beam that has high quality and low charge beam (1nC) can be loaded into the wake at a proper phase and be accelerated to high energy (5-15GeV) in very short distances (10s of cms). The parameters can be optimized, such that high quality (0.1% energy spread and 1mm mrad normalized emittance) and high efficiency (60-80%) can be simultaneously achieved. The major obstacle for achieving the above goals is the electron hosing instabilities in the blowout regime. In this poster, we will use both theoretical analysis and PIC simulations to study this concept.
UCLA, Los Angeles, California
Funding: This work was supported by The Department of Energy Grant No.DEFG02-92ER40727.
The self-guiding of relativistically intense but ultra-short laser pulses has been experimentally investigated as a function of laser power, plasma density and plasma length in the so-called "blowout" regime. Although etching of the short laser pulse due to diffraction and local pump depletion erodes the the head of the laser pulse, an intense portion of the pulse is guided over tens of Rayleigh lengths, as observed by imaging the exit of the plasma. Spectrally-resolved images of the laser pulse at the exit of the plasma show evidence for photon acceleration as well as deceleration (pump depletion)in a well defined narrow guided region. This is indicative of the self-guided pulse residing in the wake excited in the plasma. Energy outside the guided region was found to be minimized when the initial conditions at the plasma entrance were closest to the theoretical matching conditions for guiding in the blowout regime. The maximum extent of the guided length is shown to be consistent with the nonlinear pump depletion length predicted by theory.
Instituto Superior Tecnico, Lisbon
UCLA, Los Angeles, California
Funding: F.C.Gulbenkian, F.C.T. [SFRH/BD/35749/2007, PTDC/FIS/66823/2006 (Portugal)], and European Community - New and Emerging Science and Technology Activity, FP6 program (project EuroLeap, contract #028514)
We address full particle-in-cell simulations of the next generation of Laser Wakefield Accelerators with energy gains > 10 GeV. The distances involved in these numerical experiments are very demanding in terms of computational resources and are not yet possible to (easily) accomplish. Following the work on simulations of particle beam-plasma interaction scenarios in optimized Lorentz frames by J.-L. Vay*, the Lorentz transformation for a boosted frame was implemented in OSIRIS**, leading to a dramatic change in the computational resources required to model LWFA. The critical implementation details will be presented, and the main difficulties discussed. Quantitative comparisons between lab/boost frame results with OSIRIS, QuickPIC***, and experiment will be given. Finally, the results of a three-dimensional PIC simulation of a > 10 GeV accelerator stage will be presented, including a discussion on radiation emission.
* J.-L. Vay, PRL 98, 130405 (2007)
** R.A. Fonseca et al., LNCS 2329, III-342 (Springer-Verlag, 2002)
*** C. Huang, et al., JCP 217, Issue 2, 20 (2006)
SLAC, Menlo Park, California
UCLA, Los Angeles, California
USC, Los Angeles, California
High gradient acceleration of electrons has recently been achieved in meter scale plasmas at SLAC. Results from these experiments show that the wakefield is sensitive to parameters in the electron beam which drives it. In the experiment the bunch lengths were varied systematically at constant charge. Here we investigate the correlation of peak beam current to the wake amplitude. The effect of beam head erosion will be discussed and an experimental limit on the transformer ratio set. The results are compared to simulation.