Summer shutdown 2026
28 Sep 2026 - Rosie de Laune
What did you do over the summer? Look for new ways to keep cool? The same is true for our linear accelerator and choke. Our engineering and technical teams were busy working on these projects, as well as some instrument upgrades. Find out more about these, and other examples of work that happened at ISIS during the summer shutdown.
Accelerator projects
NINA choke cooling upgrade
The NINA choke, an iconic part of the synchrotron magnet power system, has been operating for over 40 years. This year, the ageing oil-cooling system was upgraded with a modern water-cooled heat exchanger, alongside new environmental safeguards and refurbishment work to reduce oil leaks. The project brought together expertise from ISIS Plant Design, Ancillary Plant, Magnet Power Supplies, Electrical Design and Controls to ensure the continued reliability of this critical infrastructure.
Cryogenic pump trialled on linac tank 3
This summer, the ISIS accelerator group team carried out a trial to use a cryogenic pump on Tank 3 of the linear accelerator. The existing method of pumping down tanks 2 and 3 to put them back under vacuum after maintenance is to use turbo pumps. There are some closed-loop cryogenic refrigeration units installed that could make the process faster, but using these risks contaminating the surface of the RF windows when the tanks warm up.
The cryogenic pump traps gases by condensing and adsorbing them onto extremely cold internal surfaces. The early results from this summer’s trial were successful, as they suggest that pumping down the tank from atmospheric pressure to operational vacuum levels can be achieved in half the time taken using the turbo pumps alone. This would reduce the downtime of the linac if venting is required for maintenance, which is especially important if this happens during a user cycle.
The next step is for the team to look at making the cryogenic pump a permanent installation on the tank and integrating it into the tank vacuum control system.
Injector profile monitors replaced
Injector profile monitors are vital diagnostics tools for optimising the magnet currents in the high-energy drift space at the end of the linac to achieve an efficient transfer and injection into the synchrotron. This summer, a new suite of injector wire scanners was installed to measure the beam’s position and size, replacing the original devices installed when ISIS was built. The new scanners have upgraded motor systems and a grid of sensor wires, which significantly reduces the time for a measurement while improving accuracy and precision.
Replacing the injector profile monitors presented our accelerator engineers with some complex challenges because of where they are and how they can be accessed. Because the crane doesn’t reach them, lifting and moving them was very complicated. This required specialist lifting and handling equipment to be designed and manufactured by a local specialist handling company to facilitate the replacement within the tight, fixed timescale.
During installation, they found that one of the components connecting to a profile monitor had different vacuum connections from what they expected. To avoid delaying the programme, replacement components were rapidly manufactured on ISIS, enabling the installation to be completed within the planned timeframe.
New extract kicker connections installed
During the summer shutdown the Pulsed Power section replaced three high voltage vacuum feedthrough connections (‘heads’) for the fast extract kickers.
Six extract kickers are required to extract the proton beam from the synchrotron once it has been accelerated. Each one has operational voltages and currents of 37.5 kV and 5 kA respectively, supplied via high voltage coaxial cables, each terminated using a connector designed in house. Four of these connect to each ‘head’. Where they connect, there have been breakdowns of the dielectric and conductors, requiring long periods of intervention during user runs, prompting their replacement.
The ‘heads’ also contain several vacuum seals and this upgrade saw three completely refurbished by the Vacuum section and subsequently installed by the Mechanical section. The Pulsed Power section refurbished and rebuilt all twelve of the high voltage connectors. This was a detailed and complex operations for all the sections involved because of the weight of the heads, the fragility of the ceramic feedthrough connectors mounted on the vacuum seals, and the required tolerances on the conductor and dielectric interfaces. The newly refurbished connections, which are critical to ISIS operations, have now been tested and are expected to last for many years to come.
The removed, activated heads will now be modified and refurbished to provide a stock of spares for future kicker maintenance programmes.
Liquid resistors designed, manufactured and installed
To simplify the cooling of the radio frequency (RF) cavities in the synchrotron, two replacement liquid resistors have been designed and manufactured. The new design removes the requirement for copper sulphate cooling, instead using the high-purity water supply already used by other RF systems, reducing complexity and running costs.
After initial trials during the January shutdown, the design was reviewed and modified, with the revised version much improved. This second-iteration prototype is currently undergoing testing and has been largely manufactured and assembled on ISIS through a close collaboration between ISIS design, engineering and RF physicist teams, who worked closely throughout the design and development process.
To provide an extended test under operational conditions, the team have installed both prototype units in the synchrotron for the current user run. The results from the cycle will inform the final design and enable the team to establish a programme to manufacture and replace the remaining units during future shutdowns. This will improve long-term reliability while reducing maintenance requirements and operational running costs.
Targets
A major repair carried out during the summer shutdown has resolved a vacuum leak on the Target Station 1 cold boxes, helping to ensure the continued reliable operation of the moderator systems. The ISIS Target Controls group, working with colleagues from Target Operations, Target Design, Electrical Systems and the Main Control Room, has successfully completed a major upgrade to the Target Station 2 water cooling control system. The new system introduces variable-speed water flow and a new target trip system, which will improve safety, reliability and sustainability.
Instruments
IMAT
The installation of the new diffraction detectors and collimators on IMAT meant that new access requirements and restrictions were needed to keep staff and users safe. After almost a year of working on the electrical design, armed with 150 pages of drawings, Simon Cooper and the motion control team used this shutdown to install a new motion safety and motion control system. This required Mykola Kolchev and the Electrical Services team to do significant amounts of cable rerouting to take over 150 cables from the blockhouse into a new control panel. Simon then did the necessary programming to change the controls over to the new system migrating all 43 axes of motion and making IMAT the first fully Beckhoff motion-controlled instrument at ISIS. There is now a pendant for the instrument scientists to control moving equipment up close when aligning samples.
ChipIr
A new sample table has been installed on ChipIr to enable users to move the position of their sample without having to go into the blockhouse. This is the first sample table to be designed, built, tested and installed wholly by ISIS staff (some of whom are pictured, left), with tables used on other instruments usually manufactured elsewhere, and it’s a lot safer to use.
Installing the sample table was looking like it would be a complicated operation, requiring small mobile engine cranes. However, as the roof of ChipIr needed to be removed during this shutdown to replace the jaw set, the team were able to crane the new sample table into the blockhouse instead. Although easier than navigating the tight turns going through the blockhouse door, putting the shielding panels back on top of the instrument is the equivalent of playing Tetris with 21 tonne blocks (pictured below, left)!
ChipIr has also had new electrical patch panels installed, with more modern and higher-voltage cables. This was the next task for Mykola and the rest of the Electrical Services team (pictured below, right), once they had finished the electrical installation on IMAT.
