On 16th June, in beautiful Bristol sunshine, experts from across the world arrived for the Forum on Tracking Detector Mechanics, co-hosted by Bristol Particle Physics and Bristol Composites Institute. Particle Physics and Composites might not seem like the most obvious combination- so why spend a week talking about it?

Particle physics experiments such as those in the Large Hadron Collider seek to detect subatomic particles created in high energy collisions. These experiments involve many layers of detectors around the collision point. In order to detect and measure the particles as precisely as possible, physicists do not want the support structures, cooling pipes or similar to scatter or absorb them. This is quantified by the material property radiation length – the average distance of travel by an electron through the material in which the electron energy reduces by a set factor (1/e). The structures need to have a low material budget (measured as the fraction of a radiation length) while supporting significant load – our composites are perfect for this, particularly carbon fibre reinforced polymer structures.

The collaboration between BCI and CERN began some years ago with a request to help with a challenge. The detector electronics produce significant heat, so need cooling. At the moment this is done by pumping coolant through pipes attached to the composite plates the detectors sit on. In addition to being extra material which might scatter or absorb the particles, these pipes have a different coefficient of thermal expansion to the composite, so when the temperature changes – such as by heating from the detector electronics – pipe and panel expand different amounts, which causes damage and makes the cooling less efficient. CERN is interested in changing this, instead making integral channels within the composite plate – like the veins of a leaf. This can be done by including a filament between layers of carbon fibre, which is vaporised off to leave a channel through the composite – but their channels were bursting at far below the target pressure.
My work on the NextCOMP programme provided a possible solution – ‘fuzzy carbon’ micro braids had been used to reinforce pultruded rods for nature-inspired novel composites. Braiding over the filament before it is integrated into the composite and vaporised results in a reinforced channel – and holds approximately 10 times the pressure. This collaborative work was funded by the University of Bristol Career Development Fellowship and International Strategic Fund, and led to a discussion regarding a wider collaboration. A workshop followed – funded by Bristol International Research Collaboration Activities – then we were honoured by a request by the particle physics community to host the Forum on Tracking Detector Mechanics in Bristol, to build better links with our composites community.
We took the opportunity to show off some of the best Bristol has to offer. The city gave our visitors a glorious welcome with sunshine and balloons during the Welcome drinks at the Sky Lounge atop the Life Sciences building. On the technical side, tours of NCC, Bristol Digital Futures Institute, Bristol Composites Institute and Bristol Particle Physics were well received and led to some fascinating discussions regarding possible future work together. Could a digital representation of the experimental hardware be helpful in design, maintenance, upgrades? Will lightweight trusses or tailored fibre placement form the structures of the next generation of particle physics experiments?

Olivia Stodieck of iCOMAT impressed us with a fascinating keynote address about Rapid Tow Shearing and its applications – particle physics experiments may soon be added to the list. iCOMAT is a spin-out from Bristol Composites Institute commercialising research led by Eric Kim, not only amazing in its own right but also a great example of how our research can get out into the world and change it.
The technical programme included a range of fantastic talks and posters on topics including cryogenics, precision manufacturing, design of lightweight structures, cooling systems and repair when something has gone wrong! Congratulations to Massimo Angeletti of CERN for the award for best presentation; Cristiano Turrioni of INFN Perrugia and BCI’s David Brearley for the poster prizes.

Our conference dinner at the SS Great Britain was a particular highlight, with a fascinating technical talk regarding Brunel’s famous ship, her many configurations and the conservation process from conservation engineer Nicola Grahamslaw. Attendees took the chance to explore the ship, observe the balloons flying over and sample some of Bristol’s best pubs afterwards. Many delighted in the opportunity to find as many Banksys as possible during their time in Bristol, visited the Clifton Suspension bridge and spent time in museums, and we heard plans to come back both for work and pleasure.
Running an international conference is no small feat, so huge thanks to Joel Goldstein, Emma Woodland, Megan Worrall and Robert Oxford Pope, plus everyone who volunteered their time for the tours. Robert, a CoSEM CDT student, is further developing the work on microvascular channels for detector cooling and is co-supervised by BCI and CERN.

This event demonstrates how a small collaboration can grow and has the potential to become much more. Bristol Composites Institute and Bristol Particle Physics are both now signed up to a larger international collaboration, coordinated by CERN, to develop the next generation of detector mechanics and we are actively working with partners in the UK and beyond. The challenges of building tracking detectors are relevant to many other industries – extreme lightweighting, integrated cooling, precision manufacturing, vibration control, materials for extremes of temperature and radiation to name but a few. We are putting together our plans for the collaboration now – this is the time to get involved.
If this is of interest to you, contact Laura.Pickard@Bristol.ac.uk