Fast Calculation of Space Charge in Beam Line Tracking by Multigrid Techniques

Pöplau, Gisela; Rienen, Ursula van; Loos, Marieke de; Geer, Bas van der

doi:10.1007/978-3-642-55872-6_36

Cited by 14 publications

(14 citation statements)

References 5 publications

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“…Simulations using the GPT code [118,119] revealed that under realistic conditions, an order of magnitude gain in resolution can be achieved when the space-charge shift is properly corrected for [116]. The simulation Fig.…”

Section: Momentum Microscopy Towards Higher Energiesmentioning

confidence: 99%

Space-, time- and spin-resolved photoemission

Schoenhense

Medjanik

Elmers

2015

Journal of Electron Spectroscopy and Related Phenomena

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This article reviews photoemission experiments that simultaneously resolve at least two of the following degrees of freedom: space (real and momentum space), time (intrinsic time scale of a fast experiment or time-of-flight) and spin. In the spatiotemporal domain, imaging of fast processes by PEEM gives direct insight into plasmon dynamics or magnetization processes. In the category real space & spin the novel concept of imaging spin filters is discussed. In the time & spin chapter we address time-of-flight spin detectors and ultrafast spin processes that are accessible by pump-and-probe techniques. A main part of the paper is devoted to the resolution of momentum-space & time. This is implemented in form of the time-of-flight momentum microscope, a very recent development of which the first instrument has been in operation since 2014. In an extended outlook chapter, the potential of new developments and of a novel, highly parallelized delay-line type electron detector will be discussed. The combination of all three degrees of freedom k-space, time & spin is emerging through the combination of the ToF momentum microscope with imaging spin filter. Outline

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Section: Momentum Microscopy Towards Higher Energiesmentioning

confidence: 99%

Space-, time- and spin-resolved photoemission

Schoenhense

Medjanik

Elmers

2015

Journal of Electron Spectroscopy and Related Phenomena

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“…Although the initial conditions, the cavity fields, and the solenoids are all cylindrically symmetric, space-charge forces still need to be calculated in 3D to obtain tolerances on misalignment and the effect of nonuniform emission from the cathode. This is challenging for high aspect-ratio bunches, and numerical instabilities are overcome with a tailor made 3D anisotropic multigrid Poisson solver with adaptive meshing based on bunch charge density, as described in detail in [19]. The effect of image charges can be included for a flat cathode, but not in the curved cathode case due to limitations of the multigrid space-charge model.…”

Section: J De Loos Et Almentioning

confidence: 99%

Radial bunch compression: Path-length compensation in an rf photoinjector with a curved cathode

Loos

Geer²,

Saveliev

et al. 2006

Phys. Rev. ST Accel. Beams

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Electron bunch lengthening due to space-charge forces in state-of-the-art rf photoinjectors limits the minimum bunch length attainable to several hundreds of femtoseconds. Although this can be alleviated by increasing the transverse dimension of the electron bunch, a larger initial radius causes path-length differences in both the rf cavity and in downstream focusing elements. In this paper we show that a curved cathode virtually eliminates these undesired effects. Detailed numerical simulations confirm that significantly shorter bunches are produced by an rf photogun with a curved cathode compared to a flat cathode device. The proposed novel method will be used to provide 100 fs duration electron bunches for injection into a laser-driven plasma wakefield accelerator.

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“…The solenoids are modeled by a 4th order off-axis Taylor expansion from the analytical expression for the on-axis field. The effect of space-charge is accounted for by a Particle In Cell (PIC) method based on a 3-dimensional anisotropic multigrid Poisson solver, tailor made for bunches with extreme aspect ratio's [17,18]. Image charges are taken into account by a Dirichlet boundary condition at the cathode.…”

mentioning

confidence: 99%

Electron source concept for single-shot sub-100 fs electron diffraction in the 100 keV range

Oudheusden

Jong

Siwick

et al. 2007

Journal of Applied Physics

220

221

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We present a method for producing sub-100 fs electron bunches that are suitable for single-shot ultrafast electron diffraction experiments in the 100 keV energy range. A combination of analytical results and state-of-the-art numerical simulations show that it is possible to create 100 keV, 0.1 pC, 20 fs electron bunches with a spotsize smaller than 500 µm and a transverse coherence length of 3 nm, using established technologies in a table-top set-up. The system operates in the space-charge dominated regime to produce energy-correlated bunches that are recompressed by established radio-frequency techniques. With this approach we overcome the Coulomb expansion of the bunch, providing an entirely new ultrafast electron diffraction source concept.PACS numbers: 61.14. 87.64Bx, 41.75.Fr, 52.59.Sa The development of a general experimental method for the determination of nonequilibrium structures at the atomic level and femtosecond timescale would provide an extraordinary new window on the microscopic world. Such a method opens up the possibility of making 'molecular movies' which show the sequence of atomic configurations between reactant and product during bondmaking and bond-breaking events. The observation of such transition states structures has been called one of the holy-grails of chemistry, but is equally important for biology and condensed matter physics [1, 2].There are two promising approaches for complete structural characterization on short timescales: Ultrafast X-ray diffraction and ultrafast electron diffraction (UED). These methods use a stroboscopic -but so far multi-shot-approach that can capture the atomic structure of matter at an instant in time. Typically, dynamics are initiated with an ultrashort (pump) light pulse and then -at various delay times-the sample is probed in transmission or reflection with an ultrashort electron [3,4] or X-ray pulse [5]. By recording diffraction patterns as a function of the pump-probe delay it is possible to follow various aspects of the real-space atomic configuration of the sample as it evolves. Time resolution is fundamentally limited by the X-ray/electron pulse duration, while structural sensitivity depends on source properties like the beam brightness and the nature of the samples.Electron diffraction has some unique advantages compared with the X-ray techniques, see e.g. Ref.[6]. However, until recently femtosecond electron diffraction experiments had been considered unlikely. It was thought that the strong Coulombic repulsion (spacecharge) present inside of high-charge-density electron bunches produced through photoemission with femtosecond lasers fundamentally limited this technique to picosecond timescales and longer. Several recent developments, however, have resulted in a change of outlook. Three approaches to circumvent the space-charge problem have been attempted by several groups. The traditional way is to accelerate the bunch to relativistic energies to effectively damp the Coulomb repulsion. Bunches of several hundred femtosecond duration containi...

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Fast Calculation of Space Charge in Beam Line Tracking by Multigrid Techniques

Cited by 14 publications

References 5 publications

Space-, time- and spin-resolved photoemission

Space-, time- and spin-resolved photoemission

Radial bunch compression: Path-length compensation in an rf photoinjector with a curved cathode

Electron source concept for single-shot sub-100 fs electron diffraction in the 100 keV range

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