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The requirement here was to provide a mechanical support structure for the
large mass of 7500 detector crystals, yet allow them to be extremely
precisely positioned.
This was achieved with 'D' shaped backplates which are cantilevered from
the main body of CMS by a specially cast large aluminium support ring. The
back plates have hundreds of precisely machined holes to locate the
detectors. The design also allows the services to be routed back through
the backplate and support ring.
Technical Specification
- Support ~30 tonnes of exotic (and expensive) crystals of lead tungstate
- ~60,000 channels of HV electronic readout
- Temperature control to ~0.1 degrees
- 90 kGray radiation environment
- Minimum-mass support structure
- Tight constraints on space and shape of detector volume
- Crystal location precise to <1mm in volume of ~4m dimensions
Technical Achievements
- Novel local support structure in carbon fibre.
- Very tight control of services requirements to minimise required space.
- Main support structures machined from single piece aluminium bar 200mm
by 300mm by 5m long sections rolled to a 1.7m radius then machined to high
precision.
- Complex database for tracking of tens of thousands of parts.
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