The year 2017 started with Yves Watier joining the ESRF to lead the Sample Environment Unit that is part of the EMD group but serves all ESRF beamlines. We are excited to have Yves on board and, by January 2018, two newly recruited technicians will complete Yves’ team. The ESRF Sample Environment Unit mainly develops and maintains cryostats and furnaces for in situ experiments. With Yves’ arrival the portfolio will be extended to cover other instrumentation such as robotics. The year ended for the EMD group with the departure of Marco Moretti, who joined the ESRF in 2011 and has been in charge of beamline ID20 since 2015. Marco accepted a professorship at the Politecnico di Milano. We thank Marco for his invaluable contributions to the ESRF, wish him a wonderful career at the Politecnico and are looking forward to welcoming him at the ESRF as a scientific collaborator.

Theoretical spectroscopy is the key to understanding the experimental results obtained at the EMD beamlines. The software Crispy is a modern graphical user interface for the simulation of core-level spectra using semi-empirical multiplet theory. The code is hosted at GitHub and is released using a free and open-source license following the ESRF’s policy on software development, which simplifies the integration of contributions from the user community. With the latest release it is possible to easily perform X-ray absorption (including X-ray dichroism) and resonant inelastic X-ray scattering (RIXS) simulations for transition metals and lanthanides for different site symmetries of the absorbing atom. Some support for angular-dependent calculations has also been added. In the case of non-centrosymmetric site symmetries, the inclusion of elaborate p-d mixing terms has been greatly simplified. Special attention was given to provide easy-to-use package installers for Windows and macOS operating systems in order to make the interface more accessible for non-expert users. Future developments concern other spectroscopies, such as XES and NIXS, and the extension of the interface to the analysis of density functional-based calculations.

A 5 micron-thick Si quarter wave plate was installed on ID12 that produces a high degree of circular polarisation at photon energies in the vicinity of 2.8 keV (Brewster angle of double crystal Si [111] monochromator). Users now have the possibility of performing circular dichroism experiments at the L-edges of 4d metals and the K-edge of Cl. The beamline furthermore improved an experimental station dedicated to X-ray magnetic circular dichroism spectroscopy under a magnetic field of up to 17 Tesla and at low temperatures down to 2 K. Use of this unique instrumentation made it possible to elucidate the “non-magnetic” ground state not only in osmium ions in molecular systems (see page 118) but also in Pu atoms in a vortex phase of the PuCoGa5 superconductor (see page 104).

Most of the research activities at ID20 address problems in hard condensed matter, chemistry and material sciences. A growing number of experiments take advantage of the small X-ray spot size to explore samples under extreme pressure conditions. Developments are under way to provide, in the near future, not only the ability to manipulate precisely the polarisation of the incident X-ray beam but also the possibility to analyse the polarisation of the inelastically scattered beam. The beamline is also working toward providing a high-resolution spectrometer for non-resonant inelastic X-ray scattering. As examples for the research on ID20 we chose the unambiguous determination of the symmetry of the 5f ground-state wave function in URu2Si2 using non-resonant inelastic X-ray scattering (see page 98) and a study of the evolution of magnetic order and magnetic excitations in (Sr1-xLax)3Ir2O7 upon electron doping using high-resolution resonant inelastic X-ray scattering (see page 114).

The staff on ID26 was very busy installing a new spectrometer for inelastic X-ray scattering in the tender X-ray regime between 1.5 and 5 keV. Almost 6 tonnes of steel were installed in the first experimental hutch. Eleven Johansson-type crystals select a wavelength and focus the beam onto a multi-wire proportional counter. The instrument operates between 35° and 85° Bragg angle and accepts bending radii of 500 and 1000 mm to optimise either efficiency or energy resolution. The commissioning is ongoing and the characteristics of the instrument will be presented in an upcoming publication. First experiments with users are scheduled for April 2018. This year’s highlights present a study of Hg in human hair down to a few ppm concentration (see page 99), made possible by newly developed high-efficiency analyser crystals, and the revelation of an intermediate spin-state in proteins carrying a heme factor (see page 112).

Beamline ID28 was running in 2017 with full user access to its new side station for diffuse scattering experiments. The success of the tandem operation between inelastic X-ray scattering and diffuse scattering is evident from the increasing demand for the diffraction side station. The benefit to the user community is demonstrated in this section by Wehinger et al. (see page 102). The inelastic X-ray scattering station reported the first observation of the breakdown of the Born-Oppenheimer approximation in the phonon spectra of a three-dimensional solid (see page 105).  An interesting development for sample environment was achieved in collaboration with MPI Stuttgart, MPI Dresden and KIT: well-controlled uniaxial stress can now be applied to tiny single crystals even when the crystals are very fragile.

The past year has been an intense period for the resonant inelastic X-ray scattering branch of ID32. These efforts are beginning to be rewarded by interesting scientific results, as showcased in this chapter. The articles show results from the initial thrust of research on the cuprate high temperature superconductors (see pages 103, 107 and 115) using the new capabilities – for example, very high-energy resolution and continuous momentum selection – presented by ID32. Such work is continuing and there is now an expansion of the application of RIXS to all the 3d transition metal elements, from titanium to copper and, in particular, their oxides, and also to the rare-earths, from cerium to samarium, where crystal field effects can be studied. This broadening of the applications of soft X-ray RIXS is very healthy and it will be very interesting to see what new scientific insights the technique will bring in the coming year.

P. Glatzel