Paper  Title  Page 

FRB01  TimeDomain Analysis of Attosecond Pulse Generation in an XRay FreeElectron Laser  1 


The method of enhanced selfamplified spontaneous emission (eSASE) is one of the strongest candidates for the generation of subfemtosecond Xray pulses in a freeelectron laser. The optimization of an eSASE experiment involves many independent parameters, which makes the exploration of the parameter space with 3D simulations computationally intensive. Therefore, a robust theoretical analysis of this problem is extremely desirable. We provide a selfconsistent, analytical treatment of such a configuration using a onedimensional, timedependent FEL model that includes the key effects of linear ebeam chirp and linear undulator taper. Verified via comparison with numerical simulation, our formalism is also utilized in parameter studies that seek to determine the optimum setup of the FEL.  
FRB02 
Theory and Simulation of FELs with Planar, Helical, and Elliptical Undulators  


Freeelectron lasers (FELs) that produce different polarizations of the output radiation ranging from linear through elliptic to circular polarization are currently under study. In particular, elliptic polarizations are undergoing increased interest. In this paper, we develop an analytic model of the resonant wavelength and JJfactor for an elliptic undulator as well as both one and threedimensional, timedependent formulations that are capable of simulating elliptic undulators using the PUFFIN and MINERVA simulation codes.*,** We present an analytic model of an APPLEII undulator that is capable of modeling arbitrary elliptic polarizations, and discuss examples of simulation results.
* J. Henderson, L. Campbell, H. Freund, and B. McNeil, New J. Phys. 18, 062003 (2016). ** H. Freund, P. van der Slot, D. Grimminck, I. Setya, and P. Falgari, New J. Phys. 19, 023020 (2017). 

FRB03  Dynamics of Superradiant Emission by a Prebunched EBeam and its Spontaneous Emission SelfInteraction  1 


Funding: Partial support by USIsrael Binational Science Foundation (BSF) and by DeutscheIsraelische Projektkooperation (DIP). In the context of radiation emission from an electron beam, Dicke's superradiance (SR) is the enhanced coherent spontaneous radiation emission from a prebunched beam, and StimulatedSuperradiance (STSR) is the further enhanced emission of the bunched beam in the presence of a phasematched radiation wave.* These processes are analyzed for undulator radiation in the framework of radiation field modeexcitation theory. In the nonlinear saturation regime the synchronicity of the bunched beam and an injected radiation wave may be sustained by wiggler tapering: TaperingEnhanced Superradiance (TES) and TaperingEnhanced Stimulated Superradiance Amplification (TESSA).** Identifying these processes is useful for understanding the enhancement of radiative emission in the tapered wiggler section of seeded FELs.***,**** The nonlinear formulation of the energy transfer dynamics between the radiation wave and the bunched beam fully conserves energy. This includes conservation of energy without radiation reaction terms in the interesting case of spontaneous selfinteraction (no input radiation). * A. Gover, Phys. Rev. STAB 8, 030701 (2005). ** J. Duris et al., New J.Phys. 17 063036 (2015). *** E. A. Schneidmiller et al., PRSTAB 18, 03070 (2015). **** C. Emma et al., this conference. 

Slides FRB03 [2.656 MB]  
FRB04  Canonical Formulation of 1D FEL Theory Revisited, Quantized and Applied to Electron Evolution  1 


An original FEL theory relied on quantum analysis of photon generation by relativistic electrons in alternating magnetic field.* In most cases, however, the system of pendulum equations for noncanonical variables and the theory of classical electromagnetism proved to be adequate. As XFELs advance to higher energy photons, quantum effects of electron recoil and shot noise has to be considered. This work presents quantization procedure based on the Hamiltonian formulation of an XFEL interaction in 1D case. The procedure relates the conventional variables to canonical coordinates and momenta and does not require the transformation to the BambiniRenieri frame.** The relation of a field operator to a photon annihilation operator reveals the meaning of the quantum FEL parameter, introduced by Bonifacio, as a number of photons emitted by a single electron before the saturation takes place.*** The quantum description is then applied to study how quantum nature of electrons affects the startup of XFEL and how quantum electrons become indistinguishable from a classical ensemble of electrons due to their interaction with a ponderomotive potential of an XFEL.
* Madey JMJ 1971 J. Appl. Phys. 42 1906 13. ** Bambini A and Renieri A 1978 Lett. Nuovo Cimento 21 399404. *** Bonifacio R, Piovella N, Robb G R M and Schiavi A 2006 PRSTAB 9 090701. 

FRB05  Wide Bandwidth, Frequency Modulated Free Electron Laser  1 


The resonant frequency of a free electron laser may be modulated via the undulator or electron beam parameters. This modulation may generate sidebands which can subsequently undergo amplification, analogous to frequency modulation in a conventional cavity laser. However, due to the relative slippage of the light through the relativistic electron beam, the FMFEL system has a more complex behavior than its conventional laser counterpart. The system may be described in the linear regime by a summation over exponential gain modes, allowing the amplification of multiple light frequencies simultaneously. It is found that, with only small, few percent variations of the FEL parameters, one may generate and amplify multiple modes within a frequency bandwidth which greatly exceeds that of normal FEL operation.  