Search

Nowadays, electrochemistry has a considerable technological impact, involving fuel cells, super capacitors and batteries. These devices are based on complex architectures, which complicates monitoring their evolution in situ under operating conditions to reveal the reasons for reduced lifetime and performances. Here, we present a design of a multipurpose electrochemical cell for grazing incidence small and wide angle X-ray scattering (GISAXS and GIWAXS) where the environment for operating conditions can be recreated. We focus on proton exchange membrane fuel cells (PEMFCs) which operational conditions are simulated by means of potentiodynamic-based accelerated stress tests, applied to a thin film of Pt nanoparticles representing a model system of a benchmark catalyst. Two different upper potentials are used to mimic fuel cell operating conditions: at 1.0 V RHE the catalyst film preserves its initial morphology, while at 1.5 V RHE (simulating fuel cell start-up/shut-down cycles) significant coarsening has been observed. The initial dimension of the Pt particles of 4.0 nm increases to 8.7 nm due to the predominant process of coalescence and final Ostwald ripening. In parallel, the distance between the particles increases, the catalyst film (9 nm thick) becomes thinner at first and exhibit a higher roughness at the end.

This paper reports a simplified and compact mechanical scheme designed for providing alternatively high flux or high spectral resolution from a monochromator for the 2 - 14 keV X-ray range in a stationary spot at a sample. The example case treats a bending magnet source at the Elettra storage ring. The properties of the continuously tunable monochromatic beam are adapted for a variety of experimental techniques, which include also the need to operate the sample in the total reflection regime, i.e. at angles of grazing incidence smaller than the critical angle of the sample material. The positional stability of the monochromatised beam during tuning was the major concern in the design of the monochromator.

ELETTRA is an intermediate energy Synchrotron Light Source located in the outskirts of Trieste, Italy, open to researchers of basic and applied fields such as material and life sciences, physics, chemistry and geology. The synchrotron is operated 24 hours/day, 7 days/week with few periods of shutdown, mostly dedicated to maintenance. During one of these periods, in August 2001, ENEA Fusion Technology Division (Italy), in collaboration with ELETTRA Accelerator Sector and Paul Scherrer Institut (PSI, Switzerland), carried out the 3D dimensional survey of the storage ring using its own optical metrology system (Leica laser tracker LTD500). The aim of the survey was re-alignment of the storage ring magnets of the synchrotron. Within a two-weeks time shutdown, more than 2300 single measurements were taken on the 24 bending magnets, 108 quadrupoles and 72 sextupoles placed in the 259.2 m circumference storage ring. The overall root mean square error of the oriented network were less than 0.1 mm , thus making possible a subsequent and successful one-week alignment of one fourth of the storage ring (October 2001). This performance completely fulfilled the very demanding survey specifications in terms of accuracy, time required, and usability of the measurements. This paper illustrates the survey, the method and the instrumentation adopted and the results obtained. Moreover, it gives guidelines to be taken into account when planning the alignment of accelerators or large and heavy components.

A precise measuring method for detecting the in situ distortion profile of a high-heat-load mirror for synchrotron radiation by use of a pentaprism long trace profiler (LTP) is presented. A maximum distortion of 0.47 microm across a length of 180 mm was measured for an internally water-cooled mirror on an undulator beam line at ELETTRA while exposed to a total emitted power of 600 W. This first successfully tested in situ distortion profile points out the importance and need for this method. Two configurations for performing in situ LTP tests are discussed. For this measurement the configuration with all the equipment external to the vacuum chamber was used. The experiment has an accuracy and a repeatability of 0.04 microm. Suggestions for improving the accuracy and stability are presented.