The STFC Rutherford Appleton Laboratory site in Oxfordshire is home to ISIS, the world’s leading pulsed spallation neutron source (www.scitech.ac.uk). This impressive facility provides high-energy beams of neutrons and muon particles for a huge variety of experiments, ranging from the detailed study of complex molecules to the authentication of archaeological artefacts. Some 1,600 researchers from over 30 countries visit this site annually to conduct academic- and industry-led experiments into materials technology, engineering components and microbiological processes.
The facility is designed to accelerate a beam of protons within a toroidal shaped chamber and thence along a proton beam line towards a tungsten target. Here, upon impact, it releases neutrons by the process of spallation that are subsequently directed towards experimental stations, placed radially with respect to the target.
In total, there are 18 beam channels and each has a shutter mechanism, which is opened when neutrons are required by a particular experiment. The shutters are made from steel and weight 30 tonnes each; they move vertically, independently one from another.
Providing the linear actuation for each shutter is a Power Jacks 300kN E-Series metric machine screw jack type E1829, driven by a 7.5kW geared motor. The screw jack has an inverted translating screw configuration with 500mm of stroke and 16mm of lead, driven by a 32:1 worm gear set. For this application, the standard design was customised to meet the customer’s installation and operational requirements.
Special features of this installation range from large components, such as a special lead screw, to nuclear grade grease for screw and gear set lubrication. The screw jack is connected to the geared motor via a pin-type, lubricant-free flexible coupling. The combination of the screw jacks gear type, screw type, gear ratio, screw lead and the additional gear set in the geared motor ensures that each screw jack is self-locking to prevent the possibility of back-driving.
These screw jacks were originally installed some twenty years ago. Over this time the Power Jacks Group has provided a continuous after sales support service, including maintaining spares availability.