The latest SKF rolling bearings and condition monitoring systems are
      playing a vital role in maximising the uptime of specialised precision
      devices used in the ISIS neutron and muon source at the Rutherford
      Appleton Laboratory in Oxfordshire. In particular, the SKF bearings
      provide a unique combination of reliability and precision, on motor driven
      shafts rotating at up to 6,000 rpm and balanced to speeds that are
      controlled to within ±5 microseconds, while the condition monitoring
      systems ensure continuous measurement of critical operating parameters.

      The Rutherford Appleton Laboratory is a world-leading scientific research
      centre, with ISIS being one of a number of facilities on the site. The
      ISIS system generates streams of neutrons, which are then used to bombard
      samples of, for example, engineering materials, enabling scientists to
      learn more about their properties at a subatomic level.

      The production of neutrons begins with an ion source, with a stream of
      negatively charged ions being fed into a sequence of three accelerators.
      The first two accelerators focus and speed up the ions, with the final
      synchrotron being used to strip away unwanted electrons leaving a beam of
      protons separated into two pulses travelling at 84% of the speed of light.
      The proton pulses are subsequently directed down one of two beam lines to
      two separate Target Stations, where they strike solid tungsten rods,
      causing neutrons to be driven off from the nuclei of the tungsten atoms.

      Neutrons are emitted from the target in a series of intense pulses, which
      are directed down multiple beamlines, arranged like spokes of a wheel
      around each Target Station. At the head of each beamline are dedicated
      instruments used for particular scientific experiments.

      Target Station 1 has been in operation for some 20 years, while Target
      Station 2 has recently opened to provide both increased capacity and new
      opportunities for research using low energy neutrons, which are ideal for
      investigating the properties of soft matter, advanced composites and
      materials used in bio-sciences.

      Peter Galsworthy, Senior Design Engineer for the ISIS Engineering Group,
      explains that, "Neutron pulses last just 1/50th of a second and contain a
      sequence of individual neutrons, each of which has a unique energy and
      wavelength. These have to be separated to meet the specific needs of each
      instrument; for example, one experiment might require high energy
      neutrons, while another needs only low energy neutrons".

      Separating each pulse is an extremely challenging operation and is
      achieved using rotating neutron choppers or rotors, spinning at speeds of
      up to 6,000rpm, and synchronised precisely with the frequency of each
      pulse, normally to within ±5µsecs. Each rotor has either boron coated
      blades to adsorb neutrons or machined orifices to allow neutrons to pass
      through.

      Peter Galsworthy adds, "Each rotor shaft is powered by a direct drive
      motor, with an encoder and SKF rolling bearings fitted on either side of
      the rotor, providing almost frictionless and perfectly balanced shaft
      alignment. SKF bearings are used exclusively as they are reliable and
      produce consistent, predictable results over time, even under extreme
      operating conditions. For example, the ball bearing races are under
      considerable load and have to function without slipping, while each roller
      bearing assembly has to accommodate thermal expansion of the rotor shaft
      caused by the heat from windage effects".