FEL2017 - Table of Session: FRB (FEL Theory)

Paper	Title	Page
FRB01	Time-Domain Analysis of Attosecond Pulse Generation in an X-Ray Free-Electron Laser	569
	P. Baxevanis, Z. Huang, A. Marinelli SLAC, Menlo Park, California, USA
	The method of enhanced self-amplified spontaneous emission (eSASE) is one of the strongest candidates for the generation of sub-femtosecond X-ray pulses in a free-electron laser. The optimization of an eSASE experiment involves many independent parameters, which makes the exploration of the parameter space with 3-D simulations computationally intensive. Therefore, a robust theoretical analysis of this problem is extremely desirable. We provide a self-consistent, analytical treatment of such a configuration using a one-dimensional, time-dependent FEL model that includes the key effects of linear e-beam 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB01
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FRB02	Theory and Simulation of FELs with Planar, Helical, and Elliptical Undulators
	H. Freund CSU, Fort Collins, Colorado, USA L.T. Campbell STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom P. Falgari Lime BV, Eindhoven, The Netherlands D.L.A. Grimminck, I. Setya ASML, Veldhoven, The Netherlands J. Henderson, B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom P.J.M. van der Slot Mesa+, Enschede, The Netherlands
	Free-electron 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 JJ-factor for an elliptic undulator as well as both one- and three-dimensional, time-dependent formulations that are capable of simulating elliptic undulators using the PUFFIN and MINERVA simulation codes.,* We present an analytic model of an APPLE-II 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).
	Slides FRB02 [0.574 MB]
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FRB03	Dynamics of Superradiant Emission by a Prebunched E-Beam and its Spontaneous Emission Self-Interaction	572
	R. Ianconescu, A. Gover University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel C. Emma, P. Musumeci UCLA, Los Angeles, USA A. Friedman Ariel University, Ariel, Israel
	Funding: Partial support by US-Israel Binational Science Foundation (BSF) and by Deutsche-Israelische 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 Stimulated-Superradiance (ST-SR) is the further enhanced emission of the bunched beam in the presence of a phase-matched radiation wave.* These processes are analyzed for undulator radiation in the framework of radiation field mode-excitation theory. In the nonlinear saturation regime the synchronicity of the bunched beam and an injected radiation wave may be sustained by wiggler tapering: Tapering-Enhanced Superradiance (TES) and Tapering-Enhanced 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 self-interaction (no input radiation). * A. Gover, Phys. Rev. ST-AB 8, 030701 (2005). J. Duris et al., New J.Phys. 17 063036 (2015). * E. A. Schneidmiller et al., PRST-AB 18, 03070 (2015). **** C. Emma et al., this conference.
	Slides FRB03 [1.437 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB03
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FRB04	Canonical Formulation of 1D FEL Theory Revisited, Quantized and Applied to Electron Evolution	576
	P.M. Anisimov LANL, Los Alamos, New Mexico, USA
	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 non-canonical 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 Bambini-Renieri 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 21 399-404. * Bonifacio R, Piovella N, Robb G R M and Schiavi A 2006 PRSTAB 9 090701.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB04
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FRB05	Wide Bandwidth, Frequency Modulated Free Electron Laser	581
	L.T. Campbell, B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom
	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 FM-FEL 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB05
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Paper

Title

Page

Time-Domain Analysis of Attosecond Pulse Generation in an X-Ray Free-Electron Laser

569

P. Baxevanis, Z. Huang, A. Marinelli
SLAC, Menlo Park, California, USA

The method of enhanced self-amplified spontaneous emission (eSASE) is one of the strongest candidates for the generation of sub-femtosecond X-ray pulses in a free-electron laser. The optimization of an eSASE experiment involves many independent parameters, which makes the exploration of the parameter space with 3-D simulations computationally intensive. Therefore, a robust theoretical analysis of this problem is extremely desirable. We provide a self-consistent, analytical treatment of such a configuration using a one-dimensional, time-dependent FEL model that includes the key effects of linear e-beam 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.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB01

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FRB02

Theory and Simulation of FELs with Planar, Helical, and Elliptical Undulators

H. Freund
CSU, Fort Collins, Colorado, USA
L.T. Campbell
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
P. Falgari
Lime BV, Eindhoven, The Netherlands
D.L.A. Grimminck, I. Setya
ASML, Veldhoven, The Netherlands
J. Henderson, B.W.J. MᶜNeil
USTRAT/SUPA, Glasgow, United Kingdom
P.J.M. van der Slot
Mesa+, Enschede, The Netherlands

Free-electron 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 JJ-factor for an elliptic undulator as well as both one- and three-dimensional, time-dependent formulations that are capable of simulating elliptic undulators using the PUFFIN and MINERVA simulation codes.*,** We present an analytic model of an APPLE-II 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).

Slides FRB02 [0.574 MB]

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FRB03

Dynamics of Superradiant Emission by a Prebunched E-Beam and its Spontaneous Emission Self-Interaction

572

R. Ianconescu, A. Gover
University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
C. Emma, P. Musumeci
UCLA, Los Angeles, USA
A. Friedman
Ariel University, Ariel, Israel

Funding: Partial support by US-Israel Binational Science Foundation (BSF) and by Deutsche-Israelische 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 Stimulated-Superradiance (ST-SR) is the further enhanced emission of the bunched beam in the presence of a phase-matched radiation wave.* These processes are analyzed for undulator radiation in the framework of radiation field mode-excitation theory. In the nonlinear saturation regime the synchronicity of the bunched beam and an injected radiation wave may be sustained by wiggler tapering: Tapering-Enhanced Superradiance (TES) and Tapering-Enhanced 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 self-interaction (no input radiation).
* A. Gover, Phys. Rev. ST-AB 8, 030701 (2005).
** J. Duris et al., New J.Phys. 17 063036 (2015).
*** E. A. Schneidmiller et al., PRST-AB 18, 03070 (2015).
**** C. Emma et al., this conference.

Slides FRB03 [1.437 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB03

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FRB04

Canonical Formulation of 1D FEL Theory Revisited, Quantized and Applied to Electron Evolution

576

P.M. Anisimov
LANL, Los Alamos, New Mexico, USA

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 non-canonical 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 Bambini-Renieri 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 21 399-404.
*** Bonifacio R, Piovella N, Robb G R M and Schiavi A 2006 PRSTAB 9 090701.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB04

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FRB05

Wide Bandwidth, Frequency Modulated Free Electron Laser

581

L.T. Campbell, B.W.J. MᶜNeil
USTRAT/SUPA, Glasgow, United Kingdom

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 FM-FEL 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.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB05

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)