The effect of shot noise on the start up of the fundamental and harmonics in free-electron lasers

Journal Article · Mon Dec 15 04:00:00 EST 2008 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3040689· OSTI ID:21180040

Freund, H P; Miner, Jr, W H ^[1]; Giannessi, L ^[2]

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1. Science Applications International Corp., McLean, Virginia 22102 (United States)
2. ENEA CR Frascati, Via E. Fermi45, 00044 Frascati (Italy)

The problem of radiation start up in free-electron lasers (FELs) is important in the simulation of virtually all FEL configurations including oscillators and amplifiers in both seeded master oscillator power amplifier (MOPA) and self-amplified spontaneous emission (SASE) modes. Both oscillators and SASE FELs start up from spontaneous emission due to shot noise on the electron beam, which arises from the random fluctuations in the phase distribution of the electrons. The injected power in a MOPA is usually large enough to overwhelm the shot noise. However, this noise must be treated correctly in order to model the initial start up of the harmonics. In this paper, we discuss and compare two different shot noise models that are implemented in both one-dimensional wiggler-averaged (PERSEO) and non-wiggler-averaged (MEDUSA1D) simulation codes, and a three-dimensional non-wiggler-averaged (MEDUSA) formulation. These models are compared for examples describing both SASE and MOPA configurations in one dimension, in steady-state, and time-dependent simulations. Remarkable agreement is found between PERSEO and MEDUSA1D for the evolution of the fundamental and harmonics. In addition, three-dimensional correction factors have been included in the MEDUSA1D and PERSEO, which show reasonable agreement with MEDUSA for a sample MOPA in steady-state and time-dependent simulations.

• OSTI ID: 21180040
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 12 Vol. 104; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COMPUTERIZED SIMULATION
ELECTRON BEAMS
FREE ELECTRON LASERS
HARMONICS
M CODES
OSCILLATORS
P CODES
POWER AMPLIFIERS
RANDOMNESS
STEADY-STATE CONDITIONS
SUPERRADIANCE
THREE-DIMENSIONAL CALCULATIONS
TIME DEPENDENCE