Preparing the MAX IV storage rings for timing-based experiments

Stråhlman, Christian; Olsson, Teresia; Leemann, Simon; Sankari, R.; Sörensen, Stacey Ristinmaa

doi:10.1063/1.4952822

Cited by 8 publications

(5 citation statements)

References 13 publications

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“…We could thereby run both TOF spectrometers with approximately twice the extraction potentials, increasing the collection efficiency of, in particular, the positive-ion TOF spectrometer. The cutoff kinetic energy for full detection was increased to 5.5 eV in the positive-ion TOF spectrometer (previously 2 eV) [19]. This, in effect, allows for more efficient detection of fast H + ions.…”

Section: Methodsmentioning

confidence: 99%

Negative- and positive-ion fragmentation of core-excited formic-acid molecules studied with three- and four-ion coincidence spectroscopy

et al. 2017

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The negative-ion fragmentation of formic acid (HCOOH) is studied with negative-and positive-ion coincidence spectroscopy. We report four-body ionic fragmentation where up to three positive ions are collected in coincidence with one negative ion. We report yields for 21 three-body channels and five four-body channels. More than 80% of all negative-ion fragmentation involves production of O − , and it is dominated by complete dissociation of all molecular bonds. Negative-ion creation is most abundant at high-Rydberg resonances and just above the molecule's core-ionization potentials. The existence of four-body fragmentation channels evidences a strong charge redistribution in the molecule.

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Section: Methodsmentioning

confidence: 99%

Negative- and positive-ion fragmentation of core-excited formic-acid molecules studied with three- and four-ion coincidence spectroscopy

et al. 2017

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“…The relatively large time gap on both sides of the solitaire pulse relaxes the requirement for the slope of the leading and trailing edges of the blanking signal. Electrostatic gating of the camshaft pulse at BESSY II has previously been shown using a blanker electrode in a PEEM [45] and gating of the MCP-detector was applied in an angle-resolved ToF spectrometer [46]. In the present experiment we used a rectangular blanking signal U(t) of 700ns length.…”

Section: Selection Of the 'Camshaft' Pulse With 125 Mhz At Bessy II (...mentioning

confidence: 99%

Time-of-flight photoelectron momentum microscopy with 80–500 MHz photon sources: electron-optical pulse picker or bandpass pre-filter

Schönhense¹,

Medjanik²,

Fedchenko³

et al. 2021

J Synchrotron Radiat

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The small time gaps of synchrotron radiation in conventional multi-bunch mode (100–500 MHz) or laser-based sources with high pulse rate (∼80 MHz) are prohibitive for time-of-flight (ToF) based photoelectron spectroscopy. Detectors with time resolution in the 100 ps range yield only 20–100 resolved time slices within the small time gap. Here we present two techniques of implementing efficient ToF recording at sources with high repetition rate. A fast electron-optical beam blanking unit with GHz bandwidth, integrated in a photoelectron momentum microscope, allows electron-optical `pulse-picking' with any desired repetition period. Aberration-free momentum distributions have been recorded at reduced pulse periods of 5 MHz (at MAX II) and 1.25 MHz (at BESSY II). The approach is compared with two alternative solutions: a bandpass pre-filter (here a hemispherical analyzer) or a parasitic four-bunch island-orbit pulse train, coexisting with the multi-bunch pattern on the main orbit. Chopping in the time domain or bandpass pre-selection in the energy domain can both enable efficient ToF spectroscopy and photoelectron momentum microscopy at 100–500 MHz synchrotrons, highly repetitive lasers or cavity-enhanced high-harmonic sources. The high photon flux of a UV-laser (80 MHz, <1 meV bandwidth) facilitates momentum microscopy with an energy resolution of 4.2 meV and an analyzed region-of-interest (ROI) down to <800 nm. In this novel approach to `sub-µm-ARPES' the ROI is defined by a small field aperture in an intermediate Gaussian image, regardless of the size of the photon spot.

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“…Such an injection scheme would be compatible with very limited dynamic aperture while at the same time exploiting a key MAX IV advantage: the 100 MHz RF system renders a 10 ns intra-bunch spacing and hence, an on-axis dipole kicker with a rise and fall time of several ns allows for user operation with transparent single-bunch top-off injection 5 without the need for any gaps in the fill pattern or swap-out of bunch trains. Such a fast kicker incidentally also opens up several interesting possibilities for timing experiments at the storage ring [25][26][27] without requiring a single-bunch or hybrid fill pattern (e.g. pseudo-single bunch [28]).…”

Section: Analysis and Outlookmentioning

confidence: 99%

Pushing the MAX IV 3 GeV storage ring brightness and coherence towards the limit of its magnetic lattice

Leemann

Wurtz

2018

Nuclear Instruments and Methods in Physics Research Section A:

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The MAX IV 3 GeV storage ring is presently being commissioned and crucial parameters such as machine functions, emittance, and stored current have either already been reached or are approaching their design specifications. Once the baseline performance has been achieved, a campaign will be launched to further improve the brightness and coherence of this storage ring for typical X-ray users. During recent years, several such improvements have been designed. Common to these approaches is that they attempt to improve the storage ring performance using existing hardware provided for the baseline design. Such improvements therefore present more short-term upgrades. In this paper, however, we investigate medium-term improvements assuming power supplies can be exchanged in an attempt to push the brightness and coherence of the storage ring to the limit of what can be achieved without exchanging the magnetic lattice itself. We outline optics requirements, the optics optimization process, and summarize achievable parameters and expected performance. Published by Elsevier B.V. 1 This is an important restriction in the MAX IV 3 GeV storage ring because most magnets in the achromat are connected in series to a common power supply for the entire family. 2 The transverse focusing gradients are provided by the shape of the dipole iron poles, however, the pole-face strips (PFSs) installed in each dipole allow a ±4% variation of this gradient, sufficient to move about ±0.5 in tune space.

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Preparing the MAX IV storage rings for timing-based experiments

Cited by 8 publications

References 13 publications

Negative- and positive-ion fragmentation of core-excited formic-acid molecules studied with three- and four-ion coincidence spectroscopy

Negative- and positive-ion fragmentation of core-excited formic-acid molecules studied with three- and four-ion coincidence spectroscopy

Time-of-flight photoelectron momentum microscopy with 80–500 MHz photon sources: electron-optical pulse picker or bandpass pre-filter

Pushing the MAX IV 3 GeV storage ring brightness and coherence towards the limit of its magnetic lattice

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