Speaker
Description
Neutron Guide Systems serve a central purpose in the functioning of an instrument. While the guides are high-tech assemblies purpose built for each beamline, their supporting systems are less cutting edge and more structural engineering.
This presentation aims to demonstrate the importance of supposedly overbuilding the guide support assemblies to facilitate smoother installation and operation of an instrument.
Neutron guides are passive components that are for the most part not under mechanical loads during normal operation. The main loads the guide system needs to contend with are vacuum forces, as the guides are operated in a vacuum. While neutron science does not require a high vacuum class, the vacuum still causes pressure differentials of around 10N/cm², which can result in large, unbalanced forces where a housing is capped by a window at one end or has different sizes of flanges at the ends.
Gravity and forces applied during guide alignment are also factors the system needs to handle. While these forces are either constant or very small, they can contribute to throwing the system out of tolerance, typically ±0.02mm, if the support system is inadequate.
To mitigate negative impacts from these forces the support system should adhere to design guidelines described in the presentation to minimise the described negative effects. A preliminary example list of possible strategies is found below.
Institute level:
- Avoid excessive beam height above the floor
Instrument level:
- Reduce the number of windows and asymmetrical housings (merging or splitting of beams, non-matching flanges, conical guides and housings)
Design level:
- Use steel instead of Aluminium wherever possible
- Use more material to resist deformations
- Place fixed bearings over the support base to avoid deflections
- Avoid seesaw- and other cross talking arrangements (one housing influencing its neighbours when it is removed/replaced etc.)
