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Title: Frahm - EVM Research Guiding the Future.


Abstract not provided.

Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Resource Relation:
Conference: Proposed for presentation at the EVM World 2017 held May 31 - June 2, 2017 in New Orleans, LA.
Country of Publication:
United States

Citation Formats

Frahm, Vicki L. Frahm - EVM Research Guiding the Future.. United States: N. p., 2017. Web.
Frahm, Vicki L. Frahm - EVM Research Guiding the Future.. United States.
Frahm, Vicki L. Mon . "Frahm - EVM Research Guiding the Future.". United States. doi:.
title = {Frahm - EVM Research Guiding the Future.},
author = {Frahm, Vicki L},
abstractNote = {Abstract not provided.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2017},
month = {Mon May 01 00:00:00 EDT 2017}

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  • The effect on optical guiding of the undulations of an electron beam in an FEL is investigated, and a model for a fully saturated FEL amplifier with no remaining gain is developed. The density of the electron beam in the model fully includes the effects of both transverse and longitudinal undulation of the beam. The longitudinal density modulation is expressed in terms of the Bessel functions of zeta, where zeta = a/sub w//sup 2//2(1 + a/sub w//sup 2/) is the shift of the electron phase in the electron bucket caused by its longitudinal undulation. The transverse density modulation is evaluatedmore » to second order in the ratio of undulation amplitude deltar to beam radial scale length r/sub b/. The radiation field from the modeled beam is calculated in terms of spatial modes proportional to exp(i(k + deltak + lk/sub w/)z - iwt), where l is an arbitrary integer. Here, deltak is the change of the wavenumber of the radiation caused by the electron bunches. Radially radiating modes with intensity on the order of (deltak/k/sub w/)zeta/sup 2/ are found. Optical guiding is found to be modified by the transverse undulations of the beam at second order in deltar/r/sub b/, and by the longitudinal undulations to first order in deltak/k/sub w/. For the usual FEL parameters, the correction is quite small. 15 refs., 5 figs.« less
  • A three-dimensional nonisothermal jet in a room is analyzed numerically by the standard {kappa}-{epsilon} eddy viscosity model (EVM) and two second-moment closure models-the algebraic stress model (ASM) (Hossain and Rodi 1982) and the differential stress model (DSM) (Launder et al. 1975). Numerical results given by these turbulence models are compared with experimental results, and the prediction errors existing in the results are examined, thus clarifying the relative structural differences between the {kappa}-{epsilon} EVM and the second-moment closure models. Since the second moment closure models clearly manifest the turbulence structures of the flow field, they are more accurate than the {kappa}-{epsilon}more » EVM. A small difference between the DSM and the ASM -- one based on an inappropriate approximation of the convection and diffusion terms in the Reynolds stress transport equations in the ASM -- is also observed.« less