221 research outputs found
Acceleration-induced self-interactions within a relativistic electron bunch : an analytical study
VIII+146hlm.;24c
Automatic tuning of Free Electron Lasers
Existing FEL facilities often suffer from stability issues: so electron
orbit, transverse electron optics, electron bunch compression and other
parameters have to be readjusted often to account for drifts in performance of
various components. The tuning procedures typically employed in operation are
often manual and lengthy. We have been developing a combination of model-free
and model-based automatic tuning methods to meet the needs of present and
upcoming XFEL facilities. Our approach has been implemented at FLASH
\cite{flash} to achieve automatic SASE tuning using empirical control of orbit,
electron optics and bunch compression. In this paper we describe our approach
to empirical tuning, the software which implements it, and the results of using
it at FLASH. We also discuss the potential of using machine learning and
model-based techniques in tuning methods
A Method for Ultrashort Electron Pulse Shape-Measurement Using Coherent Synchrotron Radiation
In this paper we discuss a method for nondestructive measurements of the
longitudinal profile of sub-picosecond electron bunches for X-Ray Free Electron
Lasers (XFELs). The method is based on the detection of the Coherent
Synchrotron Radiation (CSR) spectrum produced by a bunch passing a dipole
magnet system. This work also contains a systematic treatment of synchrotron
radiation theory which lies at the basis of CSR. Standard theory of synchrotron
radiation uses several approximations whose applicability limits are often
forgotten: here we present a systematic discussion about these assumptions.
Properties of coherent synchrotron radiation from an electron moving along an
arc of a circle are then derived and discussed. We describe also an effective
and practical diagnostic technique based on the utilization of an
electromagnetic undulator to record the energy of the coherent radiation pulse
into the central cone. This measurement must be repeated many times with
different undulator resonant frequencies in order to reconstruct the modulus of
the bunch form-factor. The retrieval of the bunch profile function from these
data is performed by means of deconvolution techniques: for the present work we
take advantage of a constrained deconvolution method. We illustrate with
numerical examples the potential of the proposed method for electron beam
diagnostics at the TESLA Test Facility (TTF) accelerator. Here we choose, for
emphasis, experiments aimed at the measure of the strongly non-Gaussian
electron bunch profile in the TTF femtosecond-mode operation. We demonstrate
that a tandem combination of a picosecond streak camera and a CSR spectrometer
can be used to extract shape information from electron bunches with a narrow
leading peak and a long tail.Comment: 60 pages, 39 figure
Development of a hard X-ray split-and-delay line and performance simulations for two-color pump-probe experiments at the European XFEL
This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Review of Scientific Instruments 89, 063121 (2018) and may be found at https://doi.org/10.1063/1.5027071.A hard X-ray Split-and-Delay Line (SDL) under construction for the Materials Imaging and Dynamics station at the European X-Ray Free-Electron Laser (XFEL) is presented. This device aims at providing pairs of X-ray pulses with a variable time delay ranging from −10 ps to 800 ps in a photon energy range from 5 to 10 keV for photon correlation and X-ray pump-probe experiments. A custom designed mechanical motion system including active feedback control ensures that the high demands for stability and accuracy can be met and the design goals achieved. Using special radiation configurations of the European XFEL’s SASE-2 undulator (SASE: Self-Amplified Spontaneous Emission), two-color hard x-ray pump-probe schemes with varying photon energy separations have been proposed. Simulations indicate that more than 109 photons on the sample per pulse-pair and up to about 10% photon energy separation can be achieved in the hard X-ray region using the SDL.BMBF, 05K13KT4, Verbundprojekt FSP 302 - Freie-Elektronen-Laser: Nanoskopische Systeme. Teilprojekt 1: Split-and-Delay Instrument für die European XFEL Beamline Materials Imaging and DynamicsBMBF, 05K16BC1, Split-and-Delay Instrument für die European XFEL Beamline Materials Imaging and Dynamic
Design and throughput simulations of a hard x-ray split and delay line for the MID station at the European XFEL
This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in AIP Conference Proceedings 1741, 030010 (2016) and may be found at https://doi.org/10.1063/1.4952833.A hard X-ray Split and Delay Line (SDL) under development for the Materials Imaging and Dynamics (MID) station at the European X-Ray Free-Electron Laser (XFEL.EU) is presented. This device will provide pairs of X-ray pulses with a variable time delay ranging from −10 ps to 800 ps in a photon energy range from 5 to 10 keV. Throughput simulations in the SASE case indicate a total transmission of 1.1% or 3.5% depending on the operation mode. In the self-seeded case of XFEL.EU operation simulations indicate that the transmission can be improved to more than 11%.BMBF, 05K13KT4, Verbundprojekt FSP 302 - Freie-Elektronen-Laser: Nanoskopische Systeme. Teilprojekt 1: Split-and-Delay Instrument für die European XFEL Beamline Materials Imaging and Dynamic
Small-angle approximation in the description of radiative collective effects within an ultrarelativistic electron bunch
The problem of the evaluation of radiative collective effects accompanying accelerated motion of a short ultrarelativistic electron bunch in vacuum is considered within the framework of the small-angle approximation; second order expansion in the transverse velocity of electrons is performed in order to obtain an analytical expression for energy spread within the bunch. Comparison with earlier results by other authors shows good agreement
On the feasibility of a nuclear exciton laser
Nuclear excitons known from M\"ossbauer spectroscopy describe coherent
excitations of a large number of nuclei -- analogous to Dicke states (or Dicke
super-radiance) in quantum optics. In this paper, we study the possibility of
constructing a laser based on these coherent excitations. In contrast to the
free electron laser (in its usual design), such a device would be based on
stimulated emission and thus might offer certain advantages, e.g., regarding
energy-momentum accuracy. Unfortunately, inserting realistic parameters, the
window of operability is probably not open (yet) to present-day technology --
but our design should be feasible in the UV regime, for example.Comment: 7 pages RevTeX, 4 figure
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