WEYBA1
CERN, Geneva, Switzerland
WEYBA2
LBNL, Berkeley, California, USA
Laser plasma accelerators are able to generate large acceleration gradients, tens to hundreds of GV/m, several orders of magnitude larger than conventional radio frequency technology. To achieve high beam energies, preformed plasma waveguides can be used to mitigate laser diffraction of focused laser pulses, increasing the acceleration length and the energy gain for a given laser power. Here we report on guiding of relativistically intense laser pulses with PW peak power over 20 diffraction lengths by increasing the focusing strength of a capillary discharge waveguide using laser inverse Bremsstrahlung heating. This allowed production of electron beams with quasi-monoenergetic peaks in energy up to 7.8 GeV,* almost double what was previously demonstrated.**
* A. J. Gonsalves, et al., Phys. Rev. Lett. Phys. Rev. Lett. 122, 084801 (2018).
** W. P. Leemans, A. J. Gonsalves, et al., Phys. Rev. Lett. 113, 245002 (2014).
SLAC, Menlo Park, California, USA
Work supported by the Department of Energy under Contract Number: DE-AC02-76SF00515.
WEYBA4
Stony Brook University, Stony Brook, USA
Particle-driven Plasma Wakefield Accelerators (PWFAs) are promising candidates for future free electron laser and collider applications. In PWFAs, energy is transferred from a relativistic drive beam to a trailing bunch in a plasma wake. One of the challenges of PWFAs is reducing energy spread of the beam from typically few percent to the required 0.1% range. This can be accomplished by generating a trailing bunch with a trapezoidal density profile, which will allow the PWFA to operate in the beam-loading regime, therefore circumventing the energy-spread growth of the trailing beam during acceleration. In this work we show how the Beam Induced Ionization Injection (BIII) technique can produce a trailing bunch of electrons with a trapezoidal shape suitable for beam-loading. In BIII, the trailing beam is created by ionization injection of an impurity due to the increased field of the beam during betatron oscillations. By tailoring the longitudinal profile of the impurity, we can shape the injected trailing electron bunch to reach the beam-loading regime. We will present results of numerical simulations done to model BIII shaped beams with the Particle In Cell code OSIRIS*.
* R. A. Fonseca et al., Lect. Notes Comput. Sci. 2331, 342 (2002).
LANL, Los Alamos, New Mexico, USA
Euclid Beamlabs LLC, Bolingbrook, USA
IIT, Chicago, Illinois, USA
ANL, Lemont, Illinois, USA
Diamond Field Emitter Array (DFEA) cathodes are arbitrarily shaped arrays of sharp (~50 nm tip size) nano-diamond pyramids with bases on the order of 3 to 25 microns and pitches 5 microns and greater. These cathodes have demonstrated very high bunch charge in tests at the L-band RF gun at the Argonne National Laboratory (ANL) Advanced Cathode Test Stand (ACTS). Intrinsically shaped electron beams have a variety of applications, but primarily to achieve high transformer ratios for Dielectric Wakefield Accelerators (DWA) when used in conjunction with Emittance Exchange (EEX) systems. Here we will present results from a number of recent cathode tests including bunch charge and YAG images. We have demonstrated shaped beam transport down the 2.54-meter beamline. In addition we will present emission simulations that demonstrate shielding effects for this geometry.
Northern Illinois University, DeKalb, Illinois, USA
The high-intensity, high-brightness and precision frontiers for charged particle beams are an increasingly important focus for study. Ultimately for electron beam applications, including FELs and microscopy, the quality of the source is the limiting factor in the final quality of the beam. It is imperative to understand and develop a new generation of sub-Kelvin electron sources, and the current state of PIC codes are not precise enough to adequately treat this ultracold regime. Our novel computational framework is capable of modelling electron field emission from nanoscale structures on a substrate, with the precision to handle the ultracold regime. This is accomplished by integrating a newly developed Poisson integral solver capable of treating highly curved surfaces and an innovative collisional N-body integrator to propagate the emitted electron with prescribed accuracy. The electrons are generated from a distribution that accounts for quantum confinement and material properties and propagated to the cathode surface. We will discuss the novel techniques that we have developed and implemented, and show emission characteristics for several cathode designs.
