Upgraded CLARA delivers first user beam for advanced beam-diagnostics experiment
11 Mar 2026
The newly upgraded Compact Linear Accelerator for Research and Applications (CLARA) at STFC Daresbury Laboratory has successfully delivered beam to its first user. This first run was led by Dr Joseph Wolfenden (QUASAR Group/University of Liverpool/Cockcroft Institute (CI)), marking an important milestone in CLARA’s transition into full user operations following its upgrade.
The beam time supported a demanding experimental programme focused on high-resolution emittance measurements using optical transition radiation (OTR). The work centred on demonstrating an “optical pepper-pot” diagnostic. This is a technique designed to measure beam emittance in a single shot by sampling the beam’s angular distribution using a microlens array and bespoke imaging optics. Alongside the demonstration itself, the experiment aimed to fully quantify the resolution limits of the system, in order to define its operational range and identify where this type of novel device could be deployed most effectively.
Once installed, the team carried out a structured set of beam dynamics scans to probe the diagnostic response across a wide parameter space, including fixed-β and fixed-α scans, as well as additional control studies to isolate the effects that ultimately set measurement resolution.
Dr Wolfenden said: “I had a really positive experience running on CLARA. Support was professional throughout, from preparation through to delivery and follow-up. The beam was stable and tightly controlled. The diagnostic coverage was excellent, and the operators really knew the machine and how to respond to changes in beam behaviour. It’s clear that CLARA has been designed to operate comfortably in complex parameter spaces, with real flexibility in how the machine can be configured and run. The measurement programme we carried out would have been systematically hard, if not impossible, to achieve at most other similar facilities.”
The ability to run these kinds of controlled, repeatable scans is central to turning a novel diagnostic concept into something that is genuinely usable. By quantifying where the optical pepper-pot performs well, and where resolution limits begin to dominate, the experiment provides a practical framework for how and where the technique could be applied at other accelerators, including environments where non-invasive or rapid emittance measurement would bring clear operational benefit.
The success of the first-user run underlines both the readiness of the upgraded CLARA facility and its potential as a national capability for accelerator R&D that can deliver experiments requiring significant flexibility, strong diagnostics, and expert operational support.
