A Ukrainian laboratory has come through challenging conditions caused by Russia’s full-scale invasion to successfully complete a three-year EU-funded project to develop scintillators for innovative electromagnetic calorimeters for use in high energy physics and other industrial applications. 

From January 2023 to December 2025, the Institute for Scintillation Materials (ISMA) in Kharkiv led the project, TWISMA, alongside partners CERN and the Institute of Light and Matter (ILM) at the University of Lyon.  

The project was funded under the Twinning instrument of the EU’s R&D framework programme, Horizon Europe. As well as funding a scientific component, Twinning projects connect leading scientific laboratories to ones located in countries that are lagging in R&D performance to support networking, knowledge sharing, and training. It marked the continuation of CERN’s collaboration with ISMA, with the institutions previously working together on an EU Horizon 2020 Rise project INTELUM, as well as a more than 30-year participation in the Crystal Clear collaboration. 

“The project wouldn’t have been possible without the huge help from our partners,” said Oleg Sidletskiy, head of the crystal growth technology department at ISMA and coordinator of TWISMA.

In fact, it nearly didn’t happen at all. 

The project team was notified of the grant success in May 2022, shortly after Russia’s full-scale invasion of the country. There was a lot of doubt whether it would be possible to accept, with Kharkiv under heavy shelling. 

“Fortunately, we had a few months to think, and it became clear that we could try and adapt the project to move certain elements online. It was not an easy decision to accept this project, but in the end it was the right one,” Sidletskiy said. 

Still, challenges remained. A big problem was power cuts caused by Russian attacks. The role of ISMA in the project was to grow specially adapted crystals, which take weeks to produce. “We could spend a week or two growing a crystal and then have a few seconds’ electrical cut and we’d need to start again, Sidletskiy said. “It wasn’t easy.”

But the team were able to work through the issues and have now produced prototypes that are currently being tested at CERN, with one type being explored for use in an upgrade to CERN’s LHCb experiment. 

Novel scintillation materials

A calorimeter based on scintillation is a detector that measures the energy of particles by capturing the flashes of light they produce. When a high-energy particle passes through a scintillating crystal inside the detector, it causes the crystal to emit a brief burst of light in a process called scintillation. By measuring that light, scientists can determine how much energy the particle carried.

The TWISMA project investigated two types of scintillators for novel electromagnetic calorimeters. 

The first uses crystals from the garnet family grown in the shape of thin fibres. Ce-doped garnets are already used in some detection applications, but the TWISMA team enhanced them by adding small amounts of additional elements to the crystal structure to speed up the light pulse in such crystals.

The goal was to have materials that would emit very bright light, very fast. This is important because in CERN's Large Hadron Collider, bunches of particles collide every 25ns, so a detector must be able to capture one collision and reset before the next one arrives. The project team managed to improve the scintillation decay time of these Ce-doped garnets from around 60ns to 18ns, still a little short of their desired target of under 10-15ns, but a significant improvement all the same.

The second scintillating crystal looked at by the project was made of bismuth silicate oxides (BSO) which can produce two distinct types of light signal simultaneously: scintillation light, and Cherenkov emission. 

The main technical challenge was producing BSO in large, highly transparent crystal form, particularly in the ultraviolet range of light. Growing crystals at this size is something only a handful of institutions worldwide can do. The team has so far produced prototypes of 5cm in length and hopes to scale up to the target of 20–25cm if further funding is secured. 

These crystals are being tested and characterised at CERN and could potentially be used in detectors at future collider experiments. Aside from high-energy physics, these scintillation materials may be used in other fields, such as medical imaging for positron emission tomography, PET scans, or security scanning devices, for example. 

The results of the CERN tests are expected later this year. 

With the TWISMA coming to a close at the end of last year, the team is now working on applying for new funding under the European Innovation Council’s Pathfinder grant, which funds teams to increase the technological readiness of their research. 

“I hope we can scale up our production and switch to the more industrial phase of development,” Sidletskiy said. 

The TWISMA project was led by Oleg Sidletskiy and his team from ISMA, Etiennette Auffray and her team from CERN’s Experimental Physics Department, and Kheirreddine Lebbou and his team from the University of Lyon.