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| MOPPH001 |
Quantum Electrodynamics Theory of a Multimode Undulator Oscillator
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- G. S. Oganesyan, S. G. Oganesyan
LT CSC, Yerevan
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We have studied the operation of a free electron oscillator (FEO) in a multimode regime. Our device includes a long undulator, two mirrors and a space-uniform e-beam of a Gaussian energy spread. Using the Heisenberg picture and neglecting both the contributions of the electron intrinsic magnetic moment and the positron fields we have derived a set of temporal equations for the operators of the electron and electromagnetic fields. The set correctly describes both the evolution of the modes’ fields from a spontaneous noise and the process of amplification. We have neglected the nonlinear losses and studied a non steady-state lasing regime. Namely, applying a perturbation theory for the electron operators and a technique of slowly varying functions for the electromagnetic field operators we have calculated the operators of the electric fields. Using this result we have estimated the oscillator energy flux in the forward direction. It is shown that within the framework of the chosen model the total flux is a sum of fluxes of unlocked modes. We have estimated the oscillator line width, the number of activated modes and, as a result, the power of the FEO that operates in the exponential regime with unlocked modes.
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| MOPPH002 |
Generation of Short Pulses by an Undulator Oscillator with an Electron Absorber Placed into Cavity
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- G. S. Oganesyan, S. G. Oganesyan
LT CSC, Yerevan
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We have considered the operation of an e electron oscillator, which contains a long undulator, two mirrors, a space-uniform e-beam and an absorber which allows tuning the lifetime of the electrons within the cavity. Our study is based on the quantum electrodynamics approach. Using a Heisenberg picture we have derived two temporal deferential equations for the electromagnetic field operators. The equations describe the electron absorption by the absorber as well as a wide-band spontaneous noise produced by the electron, and the process of the amplification of the activated modes by the electron beam. To maintain a constant value of the system gain we have adopted that there is a pumping mechanism, which compensates the process of the electron absorption and supports the same density of the active medium. We have estimated the oscillator energy flux in the forward direction at a fixed point. It is shown that the device produces a chain of pulses. Since the contribution of losses is omitted the pulse amplitudes exponentially increase in time. The duration of the pulses may be short due to the large number of the locked modes.
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