TY - JOUR

T1 - Three dimensional simulation of high harmonic transverse optical klystron

AU - Dutt, S. K.

AU - Friedman, A.

AU - Gover, A.

AU - Pellegrini, C.

N1 - Funding Information:
FEL3D is a three dimensional simulation code for the transverse optical klystron (TOK) experiment presently underway at the National Synchrotron Light Source . The program is capable of simulating the coherent super-radiant harmonic frequency emission from electrons interacting with an external laser beam while propagating in an undulator. The code is based on a semi-analytic concept: instead of a full numerical solution of the coupled Maxwell-Lorentz equations, electron trajectories within the undulator are approximated by analytic solutions, and the radiation fields are expanded in terms of free space eigenmodes (Hermite-Gauss modes, or plane waves) . This approach is well justified in the optical regime [1,2], and has the advantage of shortening computation time . * * FEL3D incorporates the important three dimensional features of -the electron beam : spread in the transverse coordinates and velocities, as well as in the beam energy, can be specified according to a given probability distribution function ; -the modulating laser beam : this is achieved by using * Research carried out under the auspices of the U .S De-partment of Energy Work supported m part by ONR contract No . N00014-87-C-0362 ** Scalar implementations of FEL3D on the BNL IBM 3090 yield an average CPU time of < 0.1 seconds per electron The vectorized code is expected to run significantly faster

PY - 1988/10

Y1 - 1988/10

N2 - We present the results of a three dimensional simulation code, which calculates the parameters of coherent super-radiant harmonic frequency emission by electrons which are being bunched by an external laser beam while propagating in a planar undulator. This code was written in order to simulate the TOK experiment, which is presently underway at BNL. Instead of a full numerical simulation of Maxwell's equations and the electron force equations, a semi-analytical approach is adopted. Electron trajectories are computed analytically, and the radiation fields are expanded in terms of free space eigenmodes. Phase space and energy profiles of the electron beam are incorporated by a variable space sampling according to a given distribution function, rather than via Monte Carlo simulation. Computation time of about 0.1 s/electron was achieved with the present version of the code on the IBM 3090. We present the expected radiometric parameters as a function of the electron beam parameters (emittance and energy spread), and the modulating laser beam parameters (Rayleigh length, waist position and power). Statistical averaging is carried out by weighted averaging of the initial electron moments and energy phase space distribution. This approach results in the best prediction of the expected experimental measurement of the optical parameters which can be achieved with a finite number of sampling electrons (much smaller than in the experiment), without introducing artificial noise as in the Monte Carlo approach.

AB - We present the results of a three dimensional simulation code, which calculates the parameters of coherent super-radiant harmonic frequency emission by electrons which are being bunched by an external laser beam while propagating in a planar undulator. This code was written in order to simulate the TOK experiment, which is presently underway at BNL. Instead of a full numerical simulation of Maxwell's equations and the electron force equations, a semi-analytical approach is adopted. Electron trajectories are computed analytically, and the radiation fields are expanded in terms of free space eigenmodes. Phase space and energy profiles of the electron beam are incorporated by a variable space sampling according to a given distribution function, rather than via Monte Carlo simulation. Computation time of about 0.1 s/electron was achieved with the present version of the code on the IBM 3090. We present the expected radiometric parameters as a function of the electron beam parameters (emittance and energy spread), and the modulating laser beam parameters (Rayleigh length, waist position and power). Statistical averaging is carried out by weighted averaging of the initial electron moments and energy phase space distribution. This approach results in the best prediction of the expected experimental measurement of the optical parameters which can be achieved with a finite number of sampling electrons (much smaller than in the experiment), without introducing artificial noise as in the Monte Carlo approach.

UR - http://www.scopus.com/inward/record.url?scp=0024087898&partnerID=8YFLogxK

U2 - 10.1016/0168-9002(88)90284-7

DO - 10.1016/0168-9002(88)90284-7

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AN - SCOPUS:0024087898

SN - 0168-9002

VL - 272

SP - 564

EP - 573

JO - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

JF - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

IS - 1-2

ER -