Pulsar Physics

Eindhoven, Netherlands

Pulsar Physics

Eindhoven, Netherlands
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Anania M.P.,University of Strathclyde | Anania M.P.,National Institute of Nuclear Physics, Italy | Brunetti E.,University of Strathclyde | Wiggins S.M.,University of Strathclyde | And 15 more authors.
Applied Physics Letters | Year: 2014

Narrow band undulator radiation tuneable over the wavelength range of 150-260 nm has been produced by short electron bunches from a 2 mm long laser plasma wakefield accelerator based on a 20 TW femtosecond laser system. The number of photons measured is up to 9 × 106 per shot for a 100 period undulator, with a mean peak brilliance of 1 × 1018 photons/s/mrad2/mm2/0.1% bandwidth. Simulations estimate that the driving electron bunch r.m.s. duration is as short as 3 fs when the electron beam has energy of 120-130 MeV with the radiation pulse duration in the range of 50-100 fs. © 2014 Author(s).


Poplau G.,University of Rostock | Van Rienen U.,University of Rostock | Van Der Geer S.B.,Pulsar Physics | De Loos M.J.,TU Eindhoven
IPAC 2011 - 2nd International Particle Accelerator Conference | Year: 2011

Efficient and accurate space-charge computations are essential for the design of high-brightness charged particle sources. Recently a new adaptive meshing strategy based on multigrid was implemented in GPT and the capabilities were demonstrated. This new meshing scheme uses the solution of an intermediate step in the multigrid algorithm itself to define optimal mesh line positions. In this paper we discuss further developments of this adaptive meshing strategy. We compare the new algorithm with the meshing scheme of GPT where the mesh line positions are based upon the projected charge density. Copyright © 2011 by IPAC'11/EPS-AG.


Chatelain R.P.,McGill University | Morrison V.,McGill University | Godbout C.,McGill University | van der Geer B.,Pulsar Physics | And 2 more authors.
Ultramicroscopy | Year: 2012

The impact of electron-electron interactions in the post-specimen region of ultrafast electron diffraction and dynamic transmission electron microscopy instruments has been studied. Specifically, space-charge induced distortions of ultrafast electron diffraction patterns from single crystal specimens and their dependence on electron bunch-charge, beam energy, energy spread, focusing conditions and specimen thickness have been investigated using the General Particle Tracer code. We have found that these space-charge interactions lead to significant broadening and displacement of the Bragg spots at currently realizable electron beam illumination conditions. These impacts increase in severity with beam brightness and are reduced with increasing (relativistic) beam energies. The primary mechanism for the distortions has been determined to be space-charge interactions between the scattered beamlets and the main unscattered beam. Overall, these results suggest that creative post-specimen electron optical design, relativistic beam energies and post-processing of diffraction patterns to correct for space-charge distortion should be explored as routes to make good use of any future enhancements to beam brightness in UED and DTEM instruments. © 2012 Elsevier B.V.


Schonhense G.,Johannes Gutenberg University Mainz | Medjanik K.,Johannes Gutenberg University Mainz | Tusche C.,Max Planck Institute of Microstructure Physics | de Loos M.,Pulsar Physics | And 7 more authors.
Ultramicroscopy | Year: 2015

Ultrahigh spectral brightness femtosecond XUV and X-ray sources like free electron lasers (FEL) and table-top high harmonics sources (HHG) offer fascinating experimental possibilities for analysis of transient states and ultrafast electron dynamics. For electron spectroscopy experiments using illumination from such sources, the ultrashort high-charge electron bunches experience strong space-charge interactions. The Coulomb interactions between emitted electrons results in large energy shifts and severe broadening of photoemission signals. We propose a method for a substantial reduction of the effect by exploiting the deterministic nature of space-charge interaction. The interaction of a given electron with the average charge density of all surrounding electrons leads to a rotation of the electron distribution in 6D phase space. Momentum microscopy gives direct access to the three momentum coordinates, opening a path for a correction of an essential part of space-charge interaction. In a first experiment with a time-of-flight momentum microscope using synchrotron radiation at BESSY, the rotation in phase space became directly visible. In a separate experiment conducted at FLASH (DESY), the energy shift and broadening of the photoemission signals were quantified. Finally, simulations of a realistic photoemission experiment including space-charge interaction reveals that a gain of an order of magnitude in resolution is possible using the correction technique presented here. © 2015.


PubMed | Johannes Gutenberg University Mainz, Pulsar Physics, Max Planck Institute of Microstructure Physics and University of Hamburg
Type: | Journal: Ultramicroscopy | Year: 2015

Ultrahigh spectral brightness femtosecond XUV and X-ray sources like free electron lasers (FEL) and table-top high harmonics sources (HHG) offer fascinating experimental possibilities for analysis of transient states and ultrafast electron dynamics. For electron spectroscopy experiments using illumination from such sources, the ultrashort high-charge electron bunches experience strong space-charge interactions. The Coulomb interactions between emitted electrons results in large energy shifts and severe broadening of photoemission signals. We propose a method for a substantial reduction of the effect by exploiting the deterministic nature of space-charge interaction. The interaction of a given electron with the average charge density of all surrounding electrons leads to a rotation of the electron distribution in 6D phase space. Momentum microscopy gives direct access to the three momentum coordinates, opening a path for a correction of an essential part of space-charge interaction. In a first experiment with a time-of-flight momentum microscope using synchrotron radiation at BESSY, the rotation in phase space became directly visible. In a separate experiment conducted at FLASH (DESY), the energy shift and broadening of the photoemission signals were quantified. Finally, simulations of a realistic photoemission experiment including space-charge interaction reveals that a gain of an order of magnitude in resolution is possible using the correction technique presented here.


D'Arcy R.T.P.,University College London | Jolly S.,University College London | Muratori B.D.,Daresbury Laboratory | Jones J.K.,Daresbury Laboratory | Van Der Geer B.,Pulsar Physics
IPAC 2012 - International Particle Accelerator Conference 2012 | Year: 2012

EMMA (Electron Machine with Many Applications) is a prototype non-scaling Fixed-Field Alternating Gradient (ns-FFAG) accelerator whose construction at Daresbury Laboratory, UK, was completed in the autumn of 2010. The energy recovery linac ALICE [1] will serve as an injector for EMMA, within an energy range of 10 to 20 MeV. The injection line consists of a symmetric 30o dogleg to extract the beam from ALICE, a matching section and a tomography section for transverse emittance measurements. This is followed by a transport section to the injection point of the EMMA ring. The ring is composed of 42 cells, each containing one focusing and one defocusing quadrupole. Commissioning of the EMMA ring started in late 2010. A number of different injection energy and bunch charge configurations are planned; for some the effects of spacecharge may be significant. It is therefore necessary to model the electron beam transport in the injection line and ring using a code capable of both calculating the effect of and compensating for space-charge. Therefore the General Particle Tracer (GPT) code [2] has been used. A range of injection beam parameters have been modelled for comparison with experimental results. Copyright © 2012 by IEEE.


Wiggins S.M.,University of Strathclyde | Issac R.C.,University of Strathclyde | Welsh G.H.,University of Strathclyde | Brunetti E.,University of Strathclyde | And 14 more authors.
Plasma Physics and Controlled Fusion | Year: 2010

High quality electron beams have been produced in a laser-plasma accelerator driven by femtosecond laser pulses with a peak power of 26TW. Electrons are produced with an energy up to 150MeV from the 2mm gas jet accelerator and the measured rms relative energy spread is less than 1%. Shot-to-shot stability in the central energy is 3%. Pepper-pot measurements have shown that the normalized transverse emittance is ̃1Φ mmmrad while the beam charge is in the range 2-10 pC. The generation of high quality electron beams is understood from simulations accounting for beam loading of the wakefield accelerating structure. Experiments and self-consistent simulations indicate that the beam peak current is several kiloamperes. Efficient transportation of the beam through an undulator is simulated and progress is being made towards the realization of a compact, high peak brilliance free-electron laser operating in the vacuum ultraviolet and soft x-ray wavelength ranges. © 2010 IOP Publishing Ltd.


Mancini G.F.,Ecole Polytechnique Federale de Lausanne | Mansart B.,Ecole Polytechnique Federale de Lausanne | Pagano S.,Ecole Polytechnique Federale de Lausanne | Van Der Geer B.,Pulsar Physics | And 2 more authors.
Optics InfoBase Conference Papers | Year: 2014

We report the design and implementation of a table-top apparatus for Ultrafast Electron Diffraction capable of experiments in both transmission and reflection geometry with electron packets of 30 keV. The electron pulse properties in terms of charge per pulse, transverse spot-size and temporal duration on the sample can be controlled with the use of radiofrequency technology combined with a set of electron optics. The characterization of the beam is performed via a lightelectrons cross-correlation experiment and we demonstrate an overall temporal resolution around 300 fs for bunches containing up to 105 electrons at 20 kHz repetition rate. © 2014 OSA.


Mancini G.F.,Ecole Polytechnique Federale de Lausanne | Mansart B.,Ecole Polytechnique Federale de Lausanne | Pagano S.,Ecole Polytechnique Federale de Lausanne | Van Der Geer B.,Pulsar Physics | And 2 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2012

Ultrafast Electron Diffraction (UED) has been widely used to investigate the structural dynamics of molecules and materials. Femtosecond (fs) electron bunches are used to obtain diffraction images of a specimen upon photo-excitation by a temporally delayed light pulse. The high cross-section of electrons makes it a very flexible tool for the study of light elements, monolayers and surfaces; at the same time, electrons can travel down to few nanometers (nm) and structural information from the bulk can also be retrieved. In this article, we discuss the design and implementation of a flexible beamline for fs electron diffraction experiments in transmission or reflection geometry. By the use of a radiofrequency (RF) compression cavity synchronized to our laser system, in combination with a set of electron optics, we demonstrate that we can control the beam properties in terms of charge per pulse, transverse spot-size on the sample and temporal duration of the bunches. The characterization of the beam is performed via a light-electrons cross-correlation experiment and we demonstrate an overall temporal resolution around 300 fs for bunches containing up to 10 5 electrons at a repetition rate of 20 kHz. © 2012 Elsevier B.V. All rights reserved.


Anania M.P.,University of Strathclyde | Brunetti E.,University of Strathclyde | Cipiccia S.,University of Strathclyde | Clark D.,University of Strathclyde | And 13 more authors.
IPAC 2010 - 1st International Particle Accelerator Conference | Year: 2010

Recent progress in developing laser-plasma accelerators is raising the possibility of a compact coherent radiation source that could be housed in a medium sized university department. Furthermore, since the duration of electron bunches from laser-plasma wakefield accelerators (LWFAs) is determined by the relativistic plasma wavelength, radiation sources based on these accelerators can produce pulses with femtosecond durations. Beam properties from laser-plasma accelerators have been traditionally thought of as not being of sufficient quality to produce amplification. However, our work shows this not to be the case. Here, we present a study of the beam characteristics of a laser-plasma accelerator and the compact ALPHA-X (Advanced Laser Plasma High-energy Accelerators towards X-rays) FEL. We discuss the implementation of a focussing system consisting of a triplet of permanent magnet quadrupoles and a triplet of electromagnetic quadrupoles [1, 2]. The design of these devices has been carried out using the GPT (General Particle Tracer) code [3, 4], which considers space charge effects and allows a realistic estimate of electron beam properties along the beam line. We will present a study of the influence of beam transport on FEL action in the undulator, paying particular attention to bunch dispersion in the undulator. This is an important step for developing a compact synchrotron source or a SASE free-electron laser [5, 6].

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