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

2021 ◽  
Vol 28 (6) ◽  
Author(s):  
G. Schönhense ◽  
K. Medjanik ◽  
O. Fedchenko ◽  
A. Zymaková ◽  
S. Chernov ◽  
...  

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.

2016 ◽  
Vol 24 (16) ◽  
pp. 18133 ◽  
Author(s):  
Jan Rothhardt ◽  
Steffen Hädrich ◽  
Yariv Shamir ◽  
Maxim Tschnernajew ◽  
Robert Klas ◽  
...  

2016 ◽  
Vol 49 (17) ◽  
pp. 172002 ◽  
Author(s):  
Steffen Hädrich ◽  
Jan Rothhardt ◽  
Manuel Krebs ◽  
Stefan Demmler ◽  
Arno Klenke ◽  
...  

Author(s):  
Maxim Tschernajew ◽  
Steffen Hädrich ◽  
Robert Klas ◽  
Martin Gebhardt ◽  
Roland Horsten ◽  
...  

2016 ◽  
Vol 18 (31) ◽  
pp. 21921-21929 ◽  
Author(s):  
Ute B. Cappel ◽  
Stefan Plogmaker ◽  
Joachim A. Terschlüsen ◽  
Torsten Leitner ◽  
Erik M. J. Johansson ◽  
...  

The excited electronic structure of PCPDTBT was measured by combining a high harmonic generation source and a time-of-flight spectrometer.


Author(s):  
Maxim Tschernajew ◽  
Steffen Hadrich ◽  
Robert Klas ◽  
Martin Gebhardt ◽  
Roland Horsten ◽  
...  

2004 ◽  
Vol 840 ◽  
Author(s):  
A. J. Nelson ◽  
J. Dunn ◽  
T. van Buuren ◽  
J. Hunter

ABSTRACTWe demonstrate single-shot x-ray laser induced time-of-flight photoelectron spectroscopy on semiconductor and metal surfaces with picosecond time resolution. The LLNL COMET compact tabletop x-ray laser source provides the necessary high photon flux (>1012/pulse), monochromaticity, picosecond pulse duration, and coherence for probing ultrafast changes in the chemical and electronic structure of these materials. Static valence band and shallow core-level photoemission spectra are presented for ambient temperature Ge(100) and polycrystalline Cu foils. Surface contamination was removed by UV ozone cleaning prior to analysis. In addition, the ultrafast nature of this technique lends itself to true single-state measurements of shocked and heated materials. Time-resolved electron time-of-flight photoemission results for ultra-thin Cu will be presented.


2017 ◽  
Vol 3 (2) ◽  
pp. 711-715
Author(s):  
Michael de Wild ◽  
Simon Zimmermann ◽  
Marcel Obrecht ◽  
Michel Dard

AbstractThin mechanically stable Ti-cages have been developed for the in-vivo application as X-ray and histology markers for the optimized evaluation of pre-clinical performance of bone graft materials. A metallic frame defines the region of interest during histological investigations and supports the identification of the defect site. This standardization of the procedure enhances the quality of pre-clinical experiments. Different models of thin metallic frameworks were designed and produced out of titanium by additive manufacturing (Selective Laser Melting). The productibility, the mechanical stability, the handling and suitability of several frame geometries were tested during surgery in artificial and in ex-vivo bone before a series of cages was preclinically investigated in the female Göttingen minipigs model. With our novel approach, a flexible process was established that can be adapted to the requirements of any specific animal model and bone graft testing.


2021 ◽  
Vol 11 (13) ◽  
pp. 6058
Author(s):  
Georgia Paraskaki ◽  
Sven Ackermann ◽  
Bart Faatz ◽  
Gianluca Geloni ◽  
Tino Lang ◽  
...  

Current FEL development efforts aim at improving the control of coherence at high repetition rate while keeping the wavelength tunability. Seeding schemes, like HGHG and EEHG, allow for the generation of fully coherent FEL pulses, but the powerful external seed laser required limits the repetition rate that can be achieved. In turn, this impacts the average brightness and the amount of statistics that experiments can do. In order to solve this issue, here we take a unique approach and discuss the use of one or more optical cavities to seed the electron bunches accelerated in a superconducting linac to modulate their energy. Like standard seeding schemes, the cavity is followed by a dispersive section, which manipulates the longitudinal phase space of the electron bunches, inducing longitudinal density modulations with high harmonic content that undergo the FEL process in an amplifier placed downstream. We will discuss technical requirements for implementing these setups and their operation range based on numerical simulations.


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