Kai Siegbahn Prize 2015 awarded to long-standing ESRF user

Giacomo Ghiringhelli from the Politecnico di Milano, Italy, was selected by an international committee of top researchers in the field of synchrotron radiation for the Kai Siegbahn Prize 2015. The prize recognises his outstanding, innovative work in the experimental development and scientific exploitation of Resonant Inelastic X-ray Scattering (RIXS) in the soft X-ray regime as a new and key tool to understanding magnetic and electronic excitations in highly correlated transition metal compounds. Over the years he has devoted great efforts to the development of advanced instrumentation. The main scientific focus has been on the physics of high Tc superconducting (HTS) cuprates, which he studied with spin resolved photoemission, X-ray absorption spectroscopy and high resolution resonant inelastic X-ray scattering.

The award ceremony was held at the University of Uppsala in September, in the presence of eminent physicists including Josef Nordgren, Swedish physicist and former Chairman of the Nobel Prize Committee for Physics. Giacomo Ghiringhelli was delighted to have been awarded the prize and in such significant surroundings. Indeed, resonant X-ray emission spectroscopy making use of synchrotron radiation, which is the ancestor of RIXS, originated in Uppsala in the 1980s. The field was largely developed in the 1980s and 1990s by Josef Nordgren and co-workers.

Ghiringhelli has a long-standing relationship with the ESRF. In 1994, he first came to work on the ESRF's former ID12B beamline as an undergraduate. He extended the stay as a PhD student from 1997-2000 and since 2001 has been a very active and regular user. In the early days at the ESRF Ghiringhelli took charge, with Lucio Braicovich, also from the Politecnico di Milano, of running and updating an instrument for RIXS, named AXES, and pushed its performance every year until the ID08 beamline was shutdown. In 2005, Ghiringhelli and Braicovich started working on a project to build a similar RIXS instrument for the Swiss Light Source (SLS), based on the results and technical achievements obtained on ID08. Ghiringhelli worked on the conceptual, optical and mechanical design and construction of the instrument, called SAXES as Super AXES, property of the Paul Scherrer Institute and open to users at the ADRESS beamline since 2007. It proved to be a great success, opening new fields of research and attracting a lot of interest from different research groups and other facilities.

When the ESRF announced the first phase of its upgrade programme, Ghiringhelli, together with Nick Brookes, scientist in charge of beamline ID08, came up with the conceptual and optical design proposal for a new instrument that would surpass the one installed at the SLS I terms of energy resolution. The project, which included several additional features and polarisation analysis, was received with much enthusiasm. This instrument, called ERIXS for European RIXS facility, is the 10-metre long spectrometer that stands proud today on the ESRF's ID32 beamline.

For Harald Reichert, ESRF Director of Research, “The ESRF is fortunate to have scientists like Giacomo among its users. Giacomo and the team from the Politecnico di Milano have been instrumental to reach the leadership position the ESRF has today in one of the most advanced spectroscopy techniques. The Kai Siegbahn Prize is a well-deserved recognition for the service Giacomo’s relentless efforts have provided to the entire community.” 

Unequivocally, after the conception, close follow-up and commissioning of the instrument, Ghiringhelli was present as first user on ID32 when it opened in July of this year.

Today, he is back at the ESRF for a second experiment on ID32 to measure magnetic excitation of high Tc superconductors with very high resolution. "The performance of ID32 is 3-4 times better than what can be found elsewhere in the world in terms of energy resolution. It's amazing the distance that has been covered in this area recently. Seven years ago dispersing spin excitations could only be observed with neutron scattering whereas today RIXS has become the method of choice for several classes of materials, in particular high Tc superconductors. And the exceptional sensitivity and resolution of RIXS make it applicable to many other problems and materials."

Ghiringhelli is not one to rest on his laurels and he has already been discussing possible developments of the instrument. "The technology is improving all the time so it's absolutely certain we'll be able to push performances further in the future. Other facilities have projects in the pipeline however the incredible investment of resources carried by the ESRF has given such an outstanding result that's it's going to be very hard to match!"

About the Kai Siegbahn Prize

Professor Kai Siegbahn was a Swedish physicist and joint winner of the Nobel Prize in Physics in 1981. He was the founder, and for many years the editor, of the journal Nuclear Instruments and Methods in Physics Research and when he passed away in 2007 the journal instituted the Kai Siegbahn Prize. It is conferred every third year and aims to recognize and encourage outstanding experimental achievements in synchrotron radiation research with a significant component of instrument development. Particular preference is given to the development of synchrotron radiation spectroscopies and the winner should have made significant contributions to instrument development in science.

Text by Kirstin Colvin

Top image: Giacomo Ghiringhelli in front of the spectrometer that he helped to build on ESRF's ID32 beamline. Credit: ESRF/C. Argoud