Search

The advent of free electron lasers (FELs) in the soft and hard X-ray spectral region has opened the possibility to probe electronic, magnetic and structural dynamics, in both diluted and condensed matter samples, with femtosecond time resolution. In particular, FELs strongly enhanced the capabilities of several analytical techniques, which took advantage of the high degree of transverse coherence provided. FELs based on the harmonic up-conversion of an external seed laser are characterised also by a high degree of longitudinal coherence, since electrons inherit the coherence properties of the seed. At the present state of the art, the shortest wavelength delivered to user experiments by an externally seeded FEL light source is about 4 nm. We show here that pulses with a high longitudinal degree of coherence (first and second order) covering the water window and with photon energy extending up to 790 eV can be generated by exploiting the so-called nonlinear harmonic regime, which allows generation of radiation at harmonics of the resonant FEL wavelength. Moreover, we report the results of two proof-of-principle experiments: one measuring the oxygen K-edge absorption in water ($\sim$ 530 eV), the other analysing the spin dynamics of Fe and Co through magnetic small angle x-ray scattering at their L-edges (707 eV and 780 eV)

supplementary document .tex file plus figures

The intrinsic stability of the 5 V LiCoPO4-LiCo2P3O10 thin-film (carbon-free) cathode material coated with MoO3 thin layer is studied using a comprehensive synchrotron electron spectroscopy in situ approach combined with firstprinciple calculations. The atomic-molecular level study demonstrates fully reversible electronic properties of the cathode after the first electrochemical cycle. The polyanionic oxide is not involved in chemical reactions with the tluoroethylene-containing liquid electrolyte even when charged to 5.1 V vs Li+/Li. The high stability of the cathode is explained on the basis of the developed energy level model. In contrast, the chemical composition of the cathode-electrolyte interface evolves continuously by involving MoO3 in the decomposition reaction with consequent leaching of oxide from the surface. The proposed mechanisms of chemical reactions are attributed to external electrolyte oxidation via charge transfer from the relevant electron level to the MoO3 valence band state and internal electrolyte oxidation via proton transfer to the solvents. This study provides a deeper insight into the development of both a doping strategy to enhance the electronic conductivity of high-voltage cathode materials and an efficient surface coating against unfavorable interfacial chemical reactions.

The dynamic response of gas sensors based on poly(3-hexylthiophene) (P3HT) nanofibers (NFs) to gaseous acetone was assessed using a setup based on flow-injection analysis, aimed at emulating actual breath exhalation. The setup was validated by using a commercially available sensor. The P3HT NFs sensors tested in dynamic flow conditions showed satisfactory reproducibility down to about 3.5 ppm acetone concentration, a linear response over a clinically relevant concentration range (3.5-35 ppm), excellent baseline recovery and reversibility upon repeated exposures to the analyte, short pulse rise and fall times (less than 1 s and about 2 s, respectively) and low power consumption (few nW), with no relevant response to water. Comparable responses’ decay times under either nitrogen or dry air suggest that the mechanisms at work is mainly attributable to specific analyte-semiconducting polymer interactions. These results open the way to the use of P3HT NFs-based sensing elements for the realization of portable, real-time electronic noses for on-the-fly exhaled breath analysis.

Wire-scanners with micrometer resolution are in operation at SwissFEL and FERMI for measurements of the beam emittance and for beam profile monitoring (*,**). In addition, both laboratories are developing and testing innovative nano-fabricated wire-scanners capable of providing sub-micrometer resolution and being quasi non-destructive to the beam. Nano-fabricated wire-scanners with a free-standing design (***) and a sub-micrometer resolution (****) has been already successfully tested. In the present work, innovative nano-fabricated wire-scanners joining both features of a free-standing design and sub-micrometer resolution are presented. Experimental tests carried out at SwissFEL demonstrated the capability of such innovative wire-scanner solutions to resolve transverse profiles of the electron beams with a size of 400-500 nm without incurring in any resolution limit constraint and with a minimal beam perturbation. An overview on current status and results along with future developments of these nano-fabricated wire-scanners are here presented., Proceedings of the 8th International Beam Instrumentation Conference, IBIC2019, Malmö, Sweden

Monitors of the beam transverse profile with ever more demanding spatial resolution and minimal invasivity are required by the FEL community. In order to improve the spatial resolution towards the sub-micrometer limit as well as to decrease the impact on the lasing process, nano-fabricated wire-scanners have been manufactured independently at PSI and FERMI by means of a lithographic technique [1,2]. Experimental tests carried out at SwissFEL at a low emittance demonstrated the capability of such innovative wire-scanner solutions to resolve beam transverse profiles with a size of 400-500 nm without being affected by any resolution limit. Status and outlook of nano-fabricated wire-scanners will be presented., Proceedings of the 39th Free Electron Laser Conference, FEL2019, Hamburg, Germany

6th International Beam Instrumentation Conference, IBIC17, Grand Rapids, Michigan, USA, 20 Aug 2017 - 24 Aug 2017; JACoW, 4 pp. (2017)., Measuring the transverse size of electron beams is of crucial importance in modern accelerators, from large colliders to free electron lasers to storage rings. For this reason severalkind of diagnostics have been developed such as: optical transition radiation screens, scintillating screens, laser scanners and wirescanners. The last ones although providingonly a multishot profile in one plane have proven capable of very high resolution. Wirescanners employ thin wires with typical thickness of the order of tens of microns that are scanner across the beam, whilst ionizing radiation generated from the impact of the electrons with the wires is detected. In this paper we describe a new approach to wirescanners design based on nanofabrication technologies. This approach opens up new possibilities in term of wires shape, size, material and thickness with potential for even higher resolution and increase flexibility for instrumentation designers. We describe the device, the fabrication process and report measurement performed on the FERMI FEL electronbeam., Published by JACoW