Suppression of microbunching instability in the linac coherent light source

Huang, Zhirong; Borland, M.; Emma, P.; Wu, Juhao; Limborg, C.; Stupakov, Gennady; Welch, J.

doi:10.1103/physrevstab.7.074401

Cited by 223 publications

(243 citation statements)

References 12 publications

(25 reference statements)

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“…This amplification process (the gain in microbunching) is accompanied by a growth of energy modulation and a possible growth of emittance if significant energy modulation is induced in a dispersive region such as the chicane. Thus, the instability can be harmful to FEL performance, which depends critically on the high quality of the electron beam [6]. We study the microbunching instability with parameters for the first bunch compressor system of FERMI@Elettra.…”

Section: Simulation Comparison: Tfct Vs Twtmentioning

confidence: 99%

“…This effect was first observed in numerical simulations with the code ELEGANT and led to a serious concern for its impact on FEL performance [2]. Several theoretical studies advanced our understanding of the microbunching instability [3][4][5] leading to the development of various suppression schemes [6], while simple numerical methods have been successful in simulating its basic mechanism [7]. Encouraged by these advancements, the FEL community set out to organize a series of workshops [8] to further our theoretical understanding and numerical modeling of the microbunching instability, as well as improve experimental observations and diagnostic techniques.…”

Section: Introductionmentioning

confidence: 99%

“…Numerical and theoretical investigations of high-brightness electron bunch compression lead to a microbunching instability driven by CSR that can significantly degrade the beam quality [6].…”

Section: Simulation Comparison: Tfct Vs Twtmentioning

confidence: 99%

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New density estimation methods for charged particle beams with applications to microbunching instability

Terzić

Bassi

2011

Phys. Rev. ST Accel. Beams

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In this paper we discuss representations of charge particle densities in particle-in-cell simulations, analyze the sources and profiles of the intrinsic numerical noise, and present efficient methods for their removal. We devise two alternative estimation methods for charged particle distribution which represent significant improvement over the Monte Carlo cosine expansion used in the 2D code of Bassi et al. ], designed to simulate coherent synchrotron radiation (CSR) in charged particle beams. The improvement is achieved by employing an alternative beam density estimation to the Monte Carlo cosine expansion. The representation is first binned onto a finite grid, after which two grid-based methods are employed to approximate particle distributions: (i) truncated fast cosine transform; and (ii) thresholded wavelet transform (TWT). We demonstrate that these alternative methods represent a staggering upgrade over the original Monte Carlo cosine expansion in terms of efficiency, while the TWT approximation also provides an appreciable improvement in accuracy. The improvement in accuracy comes from a judicious removal of the numerical noise enabled by the wavelet formulation. The TWT method is then integrated into the CSR code [G. Bassi, J. A. Ellison, K. Heinemann, and R. Warnock, Phys. Rev. ST Accel. Beams 12, 080704 (2009)], and benchmarked against the original version. We show that the new density estimation method provides a superior performance in terms of efficiency and spatial resolution, thus enabling high-fidelity simulations of CSR effects, including microbunching instability.

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Section: Simulation Comparison: Tfct Vs Twtmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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New density estimation methods for charged particle beams with applications to microbunching instability

Terzić

Bassi

2011

Phys. Rev. ST Accel. Beams

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“…The undulator length L u is considered small compared to the Rayleigh length Z r of the laser, as well as the horizontal and vertical beta functions β x and β y of the electrons. The amplitude of energy modulation for an electron located at the radial position r ≪ σ r is [16]:…”

Section: Energy Modulation In the First Undulatormentioning

confidence: 99%

A Proof-of-Principle Echo-enabled Harmonic Generation Free Electron Laser Experiment at SLAC

Pernet

2010

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With the advent of X-ray Free Electron Lasers (FELs), new methods have been developed to extend capabilities at short wavelengths beyond Self-Amplified Spontaneous Emission (SASE). In particular, seeding of a FEL allows for temporal control of the radiation pulse and increases the peak brightness by orders of magnitude. Most recently, Gennady Stupakov and colleagues at SLAC proposed a new technique: Echo-Enabled Harmonic Generation (EEHG). Here a laser microbunches the beam in an undulator and the beam is sheared in a chicane. This process is repeated with a second laser, undulator and chicane. The interplay between these allows a seeding of the X-ray laser up to the 100th harmonic of the first laser. After introducing the physics of FELs and the EEHG seeding technique, we describe contributions to the experimental effort. We will present detailed studies of the experiment including the choice of parameters and their optimization, the emittance effect, spontaneous emission in the undulators, the second laser phase effect, and measurements of the jitter between RF stations. Finally, the status and preliminary results of the Echo-7 experiment will be outlined.

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“…Such perturbations can lead to instabilities that disrupt the beam under certain circumstances. For example, in electron machines, coherent synchrotron radiation can be generated from a density-modulated beam in a bend, causing the growth of energy spread and emittance [1][2][3], beam instability, and microbunching [4][5][6]. Hence, in order to preserve high beam quality, it is important to understand the longitudinal space-charge beam dynamics in the injector region.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of large-amplitude perturbations in space-charge dominated beams

Tian

Kishek

Haber

et al. 2010

Phys. Rev. ST Accel. Beams

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Detailed experimental measurements are presented concerning the propagation of space-charge waves of varying amplitudes in an intense, charged-particle beam. A short perturbation to the density profile is applied at the electron gun, and both current and mean energy profiles are measured at two locations downstream. The measurements are compared to predictions of a linear 1D cold-fluid model, and selfconsistent particle-in-cell simulations. For sufficiently small perturbation amplitudes, the experiment, simulation, and 1D theory agree. For larger amplitudes, the simulation begins to diverge from theoretical predictions due to nonlinear effects. Experimental observations for large-amplitude perturbations differ markedly from either theory or simulation. With the aid of simulations with mismatched and misaligned beams, this departure of experiments from predictions is demonstrated to be caused by the loss of beam current due to scraping aided by the larger radius of the perturbation.

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Suppression of microbunching instability in the linac coherent light source

Cited by 223 publications

References 12 publications

New density estimation methods for charged particle beams with applications to microbunching instability

New density estimation methods for charged particle beams with applications to microbunching instability

A Proof-of-Principle Echo-enabled Harmonic Generation Free Electron Laser Experiment at SLAC

Experimental study of large-amplitude perturbations in space-charge dominated beams

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