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Heason Supplies Specialised Position Systems for ISIS Facility Instruments

Date: 19 June 2008

Custom engineered positioning system uses ceramic servo motor technology and other specialist components to suit low vacuum, non magnetic environment...

The STFC's ISIS Neutron Source recently awarded a contract to motion control specialist Heason Technology Limited to provide neutron beam modifying Jaw Packages for the WISH and NIMROD instruments on its new Second Target Station which is due to be fully operational by October 2008.

ISIS uses neutron scattering as a powerful non-destructive tool that can penetrate and reveal the molecular structure of materials using beams of neutrons and incredibly sensitive detectors. WISH and NIMROD are two of several instruments in TS2 that use a variety of techniques that allow scientists to understand the atomic structure of materials by measuring the spacing of atoms and the forces between them. Building upon the huge contribution the facility has made to science over several decades, the ISIS Second Target Station will open new opportunities with particular emphasis on soft matter, bio-molecular science and advanced materials.

Both WISH and NIMROD use a technique known as magnetic diffraction but are suited to different types of materials. WISH is aimed at the study of the large crystaline structures of solid materials and NIMROD for liquids and surface studies. For these instruments, the Jaw Packages are essentially motorised blades that modify the face area of the neutron beam perpendicular to the target, to tune its resolution and divergence to the optimal frequency required for the materials under test - which varies considerably between solids and liquids as well as for differing test temperatures and environments. Several sets of large and small Jaw Packages, each with four motorised iron boron/nimonic steel blades are typically used depending upon the characteristics of the material to be tested.

Whilst the objective of these instruments is exceptionally mind-boggling and the environmental restrictions, which include low vacuum, zero tolerance of magnetic materials, and extremes of temperature are somewhat demanding, Heason undertakes such challenges as part of its customised design and engineering service. Working closely with global partners and with its own team of specialist engineers, the Company has developed a specialist service to provide the enabling motion system technologies for a broad base of applications in aerospace & defence, printing and packaging, semiconductor and photonics, simulation and robotics.

The design specification for both applications called for the construction materials to be aluminium, non magnetic stainless steel or plastic. Ceramic servo motors were a natural choice for positioning each of the four blades in the Jaw package assembly. Supplied by NanoMotion, an exclusive distribution partner of Heason's and with a legacy of demanding nanometre-scale positioning applications, the technology is completely non-magnetic and suits vacuum environments perfectly. Each blade was driven with two synchronised ceramic motors, configured with either four or eight elements depending upon the load and force required for the Jaw Package size.

A further benefit of the ceramic motor is its ability to hold and lock position with zero position shift when power is removed.

As part of the Variohm Holdings Group, Heason's designers called upon its sister company, Variohm EuroSensor to provide linear potentiometers for jaw position feedback. Swiss manufacturer Novotechnik was selected for its experience of conductive plastic technology potentiometers used in similar harsh environments. Novotechnik has pioneered the development of this materials technology which has proven to be critical to the development of the modern linear displacement transducer. These transducers employ conductive plastic resistance and collector tracks to provide direct, absolute measurement of displacement or length in control, regulation, measuring, and laboratory applications. With the resistance output providing absolute position measurement, there was no need to include datum switches to home each axis which reduced set-up time and simplified control.

Each blade was supported and retained in a special holder with a quick release mechanism to allow for simple in-field blade replacement. To provide support for each jaw axis, special polymer bearings with a PTFE liner offered a non-magnetic alternative to standard steel bushings.

Dynamic load calculations and compound axis motor sizing was carried out to ensure that the motors and complete assembly were able to meet and exceed the bearing friction and stage loading for the life and duty cycle requirements for the application. This also involved development work carried out at Heason's manufacturing and assembly facility to evaluate materials and designs.

Note about the ISIS Pulsed Neutron and Muon Source:

ISIS is a world-leading centre for research in physical and life sciences operated by the Science and Technology Facilities Council at the Rutherford Appleton Laboratory, Didcot, Oxfordshire, UK.

ISIS supports an international community of over 2000 scientists who use neutrons and muons for research in physics, chemistry, materials science, geology, engineering and biology. It is the most productive research centre of its type in the world.

Neutron scattering is a vital research and analysis technique in exploring the structure and dynamics of materials and molecules. It provides unique and complementary information to that available from synchrotron light sources.

The ISIS Second Target Station Project complements the facilities already operating at ISIS and enables the science programme to expand into the key research areas of soft matter, advanced materials and bio-science.  The experimental programme at the new target station will begin in October 2008.

Note about Science and Technology Facilities Council:

The Science and Technology Facilities Council ensures the UK retains its leading place on the world stage by delivering world class science; accessing and hosting international facilities; developing innovative technologies; and increasing the socio-economic impact of its research through effective knowledge exchange partnerships.

The Council has a broad science portfolio including Astronomy, Particle Physics, Particle Astrophysics, Nuclear Physics, Space Science, Synchrotron Radiation, Neutron Sources and High Power Lasers. In addition the Council manages and operates three internationally renowned laboratories:

• The Rutherford Appleton Laboratory, Oxfordshire

• The Daresbury Laboratory, Cheshire

• The UK Astronomy Technology Centre, Edinburgh
  

The Council gives researchers access to world class facilities and funds the UK membership of international bodies such as the European Laboratory for Particle Physics (CERN), the Institute Laue Langevin (ILL), European Synchrotron Radiation Facility (ESRF), the European organisation for Astronomical Research in the Southern Hemisphere (ESO) and the European Space Agency (ESA). It also contributes money for the UK telescopes overseas on La Palma, Hawaii, Australia and in Chile, and the MERLIN/VLBI National Facility, which includes the Lovell Telescope at Jodrell Bank Observatory.

The Council distributes public money from the Government to support scientific research. Between 2007 and 2008 they will invest £678 million.

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