Author: Fallahi, A.
Paper Title Page
MOPRI026 Complete Simulation of Laser Induced Field Emission from Nanostructures Using a DGTD, PIC and FEM Code 645
 
  • A. Fallahi, F.X. Kärtner
    CFEL, Hamburg, Germany
  • K.K. Berggren, R. Hobbs, F.X. Kärtner, P.D. Keathley, M.E. Swanwick, L.F. Velasquez-Garcia, Y. Yang
    MIT, Cambridge, Massachusetts, USA
 
  Funding: DARPA contract number N66001-11-1-4192 and the Center for Free-Electron Laser Science, DESY Hamburg.
We present a general and efficient numerical algorithm for studying laser induced field emission from nanostructures. The method combines the Discontinuous Galerkin Time Domain (DGTD) method for solving the optical field profile, the Particle-In-Cell (PIC) method for capturing the electron dynamics and the Finite Element Method (FEM) for solving the static field distribution. The charge distribution is introduced to the time-domain method based on a modified Fowler-Nordheim field emission model, which accounts for the band-bending of the charge carriers at the emitter surface. This algorithm is capable of considering various effects in the emission process such as space-charge, Coulomb blockade and image charge. Simulation results are compared with experimental findings for optically driven electron emission from nanosharp Si-tips.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI026  
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WEOAB03 Linear Electron Acceleration in THz Waveguides 1896
 
  • E.A. Nanni, W.S. Graves, K.-H. Hong, W.R. Huang, F.X. Kärtner, KR. Ravi, L.J. Wong
    MIT, Cambridge, Massachusetts, USA
  • A. Fallahi, F.X. Kärtner
    CFEL, Hamburg, Germany
  • R.J.D. Miller
    DESY, Hamburg, Germany
  • G. Moriena
    University of Toronto, Toronto, Ontario, Canada
 
  Funding: Supported by DARPA N66001-11-1-4192, CFEL DESY, DOE DEFG02-10ER46745, DOE DE-FG02-08ER41532, ERC Synergy Grant 609920 and NSF DMR-1042342.
We report the first experimental demonstration of linear electron acceleration using an optically generated single cycle THz pulse centered at 0.45 THz. 7 keV of acceleration is achieved using 10 microJ THz pulses in a 3 mm interaction length. The THz pulse is produced via optical rectification of a 1.2 mJ, 1 micron laser pulse with a 1 kHz repetition rate. The THz pulse is coupled into a dielectric-loaded circular waveguide with 10 MeV/m on-axis accelerating gradient. A 25 fC input electron bunch is produced with a 60 keV DC photo-emitting cathode. The achievable accelerating gradient in the THz structures being investigated will scale rapidly by increasing the IR pulse energy (100 mJ - 1 J) and correspondingly the THz pulse energy. Additionally, with recent advances in the generation of THz pulses via optical rectification, in particular improvements to efficiency and generation of multi-cycle pulses, GeV/m accelerating gradients could be achieved. An ultra-compact high-gradient THz accelerator would be of interest for a wide variety of applications.
 
slides icon Slides WEOAB03 [7.185 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEOAB03  
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