Development of a single-shot CCD-based data acquisition system for time-resolved X-ray photoelectron spectroscopy at an X-ray free-electron laser facility (original) (raw)
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Journal of Electron Spectroscopy and Related Phenomena, 2015
The advent of Free Electron Lasers (FELs), able to provide short (2-100 fs) and intense (10 33 photons/s/mm 2 /mrad 2 /0.1%bandwidth) pulses of light also in the hard X-ray regime (ω> 2000 eV), opens new possibilities to study the ultrafast dynamics of processes, exploiting the capability of Hard X-ray Photoelectron Spectroscopy (HAXPES) to measure core-level spectra of elements with bulk sensitivity. In order to detect the intense bursts of high kinetic energy electrons generated by the X-ray pulses with an energy resolution comparable to the existing category of electron analyzers, a new class of spectrometers must be designed. We present a characterization of two different TOF spectrometers, namely one based on a retarding cylindrical lens and another one based on the spherical reflector geometry. SIMION® software has been used in order to evaluate electron trajectories of high kinetic energy electrons (5000-10,000 eV) and extract transmission properties, angular acceptance and energy resolution. It resulted that while the linear system is able to accept a larger solid angle (∼50 msr), the spherical mirror offers a better resolving power (around 71,000). Both analyzers are capable of a transmission above 90% within range of kinetic energies wide enough to measure the full line-shape of a core photoionization peak. Furthermore, we proved that both instruments are able to discriminate between two consecutive electron bunches having a temporal separation inferior than 220 ns, which is the distance between two consecutive photon pulses at the European X-ray Free Electron Laser (EXFEL), which is currently under construction in Hamburg.
Electron Dynamics Probed by Time-Resolved Hard X-ray Photoelectron Spectroscopy
Transactions of the Materials Research Society of Japan, 2014
We have realized element-specific pump-probe time-resolved hard X-ray photoelectron spectroscopy (TR-HAXPES) for the study of ultrafast electron dynamics in condensed matter. TR-HAXPES has been applied for the first time to determine the temporal evolution of space-charge effects on Ti 1s core-level photoelectron spectra of SrTiO 3 at the SACLA X-ray free electron laser facility. We found that the temporal evolution of Ti 1s kinetic energy shifts can be well explained by a mean-field model for the electron propagation in the vacuum. We also report preliminary results of a real-time laserassisted valence-transition in YbInCu 4 , observed by measuring Yb 3d 5/2 core-level HAXPES spectra at BL19LXU of SPring-8, under ON/OFF conditions of an optical pump-laser. We observed drastic changes in intensities of the Yb 2+ and Yb 3+ spectral components induced by pump-laser irradiation.
Spectral monitoring at SwissFEL using a high-resolution on-line hard X-ray single-shot spectrometer
Journal of Synchrotron Radiation, 2021
The performance and parameters of the online photon single-shot spectrometer (PSSS) at the Aramis beamline of the SwissFEL free-electron laser are presented. The device operates between the photon energies 4 and 13 keV and uses diamond transmission gratings and bent Si crystals for spectral measurements on the first diffraction order of the beam. The device has an energy window of 0.7% of the median photon energy of the free-electron laser pulses and a spectral resolution (full width at half-maximum) ΔE/E on the order of 10−5. The device was characterized by comparing its performance with reference data from synchrotron sources, and a parametric study investigated other effects that could affect the reliability of the spectral information.
Photon shot-noise limited transient absorption soft X-ray spectroscopy at the European XFEL
Cornell University - arXiv, 2022
Femtosecond transient soft X-ray Absorption Spectroscopy (XAS) is a very promising technique that can be employed at X-ray Free Electron Lasers (FELs) to investigate out-of-equilibrium dynamics for material and energy research. Here we present a dedicated setup for soft X-rays available at the Spectroscopy & Coherent Scattering (SCS) instrument at the European X-ray Free Electron Laser (EuXFEL). It consists of a beam-splitting off-axis zone plate (BOZ) used in transmission to create three copies of the incoming beam, which are used to measure the transmitted intensity through the excited and unexcited sample, as well as to monitor the incoming intensity. Since these three intensity signals are detected shot-by-shot and simultaneously, this setup allows normalized shot-by-shot analysis of the transmission. For photon detection, the DSSC imaging detector, which is capable of recording up to 800 images at 4.5 MHz frame rate during the FEL burst, is employed and allows approaching the photon shot-noise limit. We review the setup and its capabilities, as well as the online and offline analysis tools provided to users.
Few-femtosecond time-resolved measurements of X-ray free-electron lasers
Nature Communications, 2014
X-ray free-electron lasers, with pulse durations ranging from a few to several hundred femtoseconds, are uniquely suited for studying atomic, molecular, chemical and biological systems. Characterizing the temporal profiles of these femtosecond X-ray pulses that vary from shot to shot is not only challenging but also important for data interpretation. Here we report the time-resolved measurements of X-ray free-electron lasers by using an X-band radiofrequency transverse deflector at the Linac Coherent Light Source. We demonstrate this method to be a simple, non-invasive technique with a large dynamic range for single-shot electron and X-ray temporal characterization. A resolution of less than 1 fs root mean square has been achieved for soft X-ray pulses. The lasing evolution along the undulator has been studied with the electron trapping being observed as the X-ray peak power approaches 100 GW.
The Review of scientific instruments, 2014
An apparatus for sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy studies with pulsed and constant wave X-ray light sources is presented. A differentially pumped hemispherical electron analyzer is equipped with a delay-line detector that simultaneously records the position and arrival time of every single electron at the exit aperture of the hemisphere with ~0.1 mm spatial resolution and ~150 ps temporal accuracy. The kinetic energies of the photoelectrons are encoded in the hit positions along the dispersive axis of the two-dimensional detector. Pump-probe time-delays are provided by the electron arrival times relative to the pump pulse timing. An average time-resolution of (780 ± 20) ps (FWHM) is demonstrated for a hemisphere pass energy E(p) = 150 eV and an electron kinetic energy range KE = 503-508 eV. The time-resolution of the setup is limited by the electron time-of-flight (TOF) spread related to the electron trajectory distribution within the an...
Design and operation of a hard x-ray transmissive single-shot spectrometer at LCLS
Journal of Physics: Conference Series, 2013
We describe the design and operation of a transmissive single-shot spectrometer for the measurement of hard x-ray free electron laser (FEL) source spectrum at the Linac Coherent Light Source (LCLS). The spectrometer was built around a 10 µm thick near-perfect silicon single crystal that was cylindrically bent. Its energy range covered the full FEL bandwidth while its resolution was sufficient for resolving single spectral spikes characteristics of the FELs. Its application will not only greatly facilitate the understanding and optimization of the x-ray FEL sources, but can also serve as an invaluable inline diagnostic tool for experiments where the spectral content of the source plays an important role in data interpretation.