Townhall Report – Frontiers of Measurement

Title: Queen’s University Belfast Hosts UKXFEL for Townhall discussions  

Amidst the backdrop of summer thunderstorms, scientists, engineers and staff from local companies headed to Queen’s University Belfast to take part in our first UK XFEL townhall event to discuss the possibilities which could be opened up by providing the UK direct access to a next generation X-ray Free Electron Laser (XFEL).  

At this event (the first of many around the UK over the next two years), we focused discussions on the ‘Frontiers of Measurements Techniques’ exploring possibilities around nanoscale imaging, ultrafast X-ray scattering, hard x-ray transient grating measurements, coherent control with X-ray radiation and dynamics of matter and fields.  

What are XFELs and why do we need them? 

XFELs enable scientists to observe the intricate workings of matter, on timescales like no other machine. These machines represent a revolutionary leap forward in laser technology, surpassing traditional X-ray sources in terms of intensity, coherence, and time resolution. They do this by passing electrons through an undulating magnetic field, the process of which emits intense bursts of X-ray radiation. The resulting X-ray pulses are incredibly short, measured in femtoseconds and are a billion times brighter than conventional X-ray sources.  

With XFEL technology, researchers can better understand chemical reactions, study the fundamental structures of life, study materials in real time and will revolutionise our understanding of the natural world. Our town hall events are aimed at discussing how to push those boundaries even further by envisioning what work could be done on a next generation XFEL.  

The UK XFEL Townhall in Belfast 

The Belfast event was split over two days, which where top-and-tailed with discussion around a new facility and an update to the 2020 science case. The main sessions consisted of a number of talks from eminent scientists and engineers: Carlo Callegari (FERMI), Nina Rohringer (Hamburg), John Costello (Dublin City University), Rebeca Boll (European XFEL), Christian Svetina (Madrid), Adam Kirrander (Oxford), Mark Dean (BNL, USA), Andrew Brown (QUB), Henry Chapman (Hamburg), David Keen (Oxford) and David Ayuso (Imperial).  

The researchers highlighted the need for collaboration in this cutting-edge field to bring these techniques to future experimental stations. Amongst the outstanding speakers, Henry Chapman shared insights on nanoscale imaging with X-rays with the goal to go beyond traditional cryo-electron microscopy by provide structural information at room temperature and femtosecond time resolution.  

David Keen, one of many to have inputted to the original UKXFEL Science Case, spoke on time-resolved pair distribution functions. Explaining that this technique allows information about local atomic arrangements in solids, liquids, and gases, even detecting defects that break periodicity.  

Rebecca Boll, endured flight delays but made it just in time to give a wonderful talk on the coulomb explosion imaging at XFELs. Where X-ray pulses of ~ 10 femtoseconds are used to ensure instantaneous ionisation at Eu-XFEL. Using this technique, they can track fragment momenta and reconstruct molecular structures.  

John Costello, from Dublin University, who’s work involves the study of photoelectron dynamics with extreme precision on the attosccond scale and can resolve photoelectron-Auger delays as well as core excited wave packets. Stated that for this sort of work ultra-precise X-ray / laser synchronisation is required – a difficult engineering feat something a next generation FEL should strive for. Nina Rohringer, joined us remotely and presented “X-ray non-linear optics,” where she explored the potential of generating stimulated Raman signals with XFEL pulses and using photon-photon covariance techniques for detection. Her techniques require multiple colour SASE pulses – something plenty of other discussed would be required on a next-generation facility. 

John Marangos, Imperial Colledge London, came away from the event filled with positivity:  

 “I was impressed with the compelling scientific material in the talks showcasing the substantial advances being made in the field. Likewise the audience was very engaged and contributed to stimulating discussions”.  

The design team attended to join discussions and ensure that the research currently being undertaken could be incorporated into a new facility design. A number of the scientists pointed out that it’s important to get the fundamentals right, things like focusing on diagnostics, ensuring space constraints for large experiments like RIXs be taken into account and that throughput and available beam time be addressed early on in the design phase.  

Digging deeper though it was stressed that a next generation machine should focus on higher repetition rates, multi=colour X-rays (potentially with more than two X-ray colours with phase coherence), polarisation as standard and nano focused beams along with investigating higher energies than we have yet thought of.  

Overall there was a lot for the design team to reflect on and discuss in the coming months.  

The meeting showcased the exciting advancements in Measurement Technology, offering promising opportunities for scientific discoveries in various fields, and served as a fantastic example for our future Townhall events. Our next event being just around the corner in October and focusing on ‘Materials Chemistry and Biology at extreme conditions, so come and join us to discuss the secrets of the Universe at the University of Strathclyde in Glasgow, tickets available here.