Björn Fåk (1959-2024)
It is with deep sadness that we announce the tragic and untimely passing of our friend and colleague Björn Fåk, who died in a motorcycle accident on 25 July 2024 at the age of 65. A distinguished physicist, Björn was renowned for his profound knowledge in neutron scattering, which he applied to many different areas of condensed matter physics, in particular studying quantum magnetism and many-body quantum systems.
Björn studied at the Kungliga Tekniska Högskolan (KTH – Royal Institute of Technology) in Stockholm and at the Tekniska Högskolan Linköping, Sweden. He did his PhD with Kurt Sköld and Reinhard Scherm. During that time, he built a time-of-flight spectrometer at the Studsvik research reactor and prepared and performed a series of very challenging experiments on instrument IN6 at the ILL, which had just been completed and designed specifically for that task. He defended his PhD thesis on elementary excitations in liquid 3He and 3He/4He mixtures in early 1990, shortly after starting a five-year contract at the ILL.
In 1989-91, he worked on IN8 (with José-Luis Martinez), IN14 (with Michel Alba and Roland Currat) and IN12 (with Bill Stirling). He also started a long track record of mentoring younger scientists as local supervisor for PhD student Ken Andersen, presently director of the ILL.
In 1991, at the beginning of the five-year ILL shutdown, Björn joined the Laboratory for Statistical Physics, Magnetism and Superconductivity (SPSMS) at the CEA Grenoble, in the group of Jacques Flouquet, where he worked in various functions until 2014. During that period, he returned to the ILL site from 1995 to 2000 as instrument responsible for the then CEA-operated CRG instrument IN12. He did numerous experiments at the LLB as well as in the US, at ISIS, and on the newly-built instruments at FRM-II and HZB. From 2000 to 2003, Björn worked at the UK spallation source ISIS on PRISMA and then on MARI, deepening his skills on time-of-flight techniques and frustrated quantum materials.
Björn returned full-time to the ILL in 2014. He became part of the then IN4C team with Stéphane Rols and Olivier Meulien. He joined the ENDURANCE upgrade project PANTHER, under the technical direction of Giuliana Manzin, and led this project until its successful commissioning phase in 2022. He played an essential role in preparing the polarised neutron option for PANTHER as well as in many fundamental issues concerning the theory of polarised neutron scattering. As instrument scientist on Panther, he was very busy through the 2024 cycles (concluded on 9 July) running the instrument and looking after users and experiments.
Björn’s contributions to instrumentation and science leaves an indelible mark on the field of condensed matter physics. He will be remembered for his scientific achievements but also for his generosity as a mentor and a colleague. We will greatly miss him at the ILL, and our thoughts and condolences go out to all of Björn’s family and friends.
“Björn was a most reliable pillar of the ILL spectroscopy group for years. His expertise and interests were incredibly versatile. He was the person to get an expert opinion from on classical music, quantum critical phenomena or the quality of racing bicycles. His views were often unassailable and their absence will undeniably create a gap in expertise.
But Björn's disappearance leaves his friends and colleagues above all with an emotional gap. His humour and the ironic flicker in his eyes were discreet but always present. His impatience with problems he saw as nonsensical contrasted with his patience and pedagogy in explaining science, particularly to the more than twenty PhD students he supervised throughout his career.”
Martin Böhm, ILL scientist, head of the Spectroscopy Group
“Björn worked tirelessly to hold ILL to the highest standards and leaves a unique legacy of excellence in science, instrumentation and user support. He was a mentor to me when I was a student and for many others subsequently, helping us with both patience and wisdom to make the most of our strengths and improve on our weaknesses.
He was my introduction to the fantastic ILL tradition of speaking the truth, even when it was most inconvenient, invariably with kindness and usually with a wry smile.
As we both grew in our roles and experience since then he was always someone whose judgement mattered and whose good opinion I sought. He was a friend whom I will miss in so many ways.”
Ken Andersen, Director of the ILL