Comments on TRD rail system CERN-AIS 1/14/2019

Two flat bars, two 80 degree L shaped bars Basic Idea Two flat bars, two 80 degree L shaped bars Adjustabe in radial direction 1/14/2019

‘Waving’ of TRD rails in ‘phi’ direction of possibly up to10mm ‘Waving’ of TRD rails in ‘phi’ direction of possibly up to10mm. Can the TRD cope with this ? If not, is there a realistic ‘shimming’ procedure ? 1/14/2019

There should be a way to get the rails flat to mm precision. Because of the ‘waving’ of TRD rails the TRD box will be bent and will touch only in 2-3 points along the rails. In case the TRD box is bending around the waving rails the alignment procedure will probably be extremely difficult. There should be a way to get the rails flat to mm precision. Shimming is definitely an extremely difficult and time consuming procedure. Could there be a scenario with adjustment screws ? In short: What is the procedure to guarantee a well defined position of the TRD in phi direction ? 1/14/2019

TRD rails are currently 3 TRD rails are currently 3.5mm INOX sticking 80mm into the cavity (in phi direction) on both sides – is the O.K. for TOF ? Can the rails be made of Aluminum ? 1/14/2019

In case the rails are mounted such that the TRD should touch 3 of them, the system is not statically defined since in reality the TRD box will touch only two. We expect cavity deformations of up to 5mRad for the optimum loading sequences and 10mRad for less optimal loading sequences (presented in Sept 2003 Forum). In case the TRD is touching 3 rails this will cause forces on the TRD box. The rails should be mounted such that the TRD is always touching only two rails with sufficient clearance to the other rails. 10mRad*750mm = 7.5mm worst case. 1/14/2019

Touching Points ? To be tested with the first module in the rotator. ? ? ? ? ? 1/14/2019

What about the rails in the baby spaceframe What about the rails in the baby spaceframe ? When and how will the rails be installed ? 1/14/2019

What about the rails in the baby spaceframe ? Summary of questions Because of ‘waving’ of TRD rails in ‘phi’ direction of possibly up to10mm the TRD will be bent which doesn’t seem desirable. Is there a realistic procedure to adjust the rails in phi direction ? What is the overall procedure to define the rail position in the sectors ? TRD rails are currently 3.5mm INOX sticking 80mm into the cavity (in phi direction) on both sides – are they entering the sensitive TOF region ? Is it a problem ? Can the rails be made of Aluminum ? We expect cavity deformations of up to 5mRad for the optimum loading sequences and 10mRad for less optimal loading sequences. In case the TRD is touching 3 rails this will cause forces on the TRD box. The rails should be mounted such that the TRD is always touching only two rails with sufficient clearance to the other rails. 10mRad*750mm = 7.5mm worst case. What about the rails in the baby spaceframe ? 1/14/2019

Optimum Installation Sequence 1/14/2019

Optimum Installation Sequence, cavity deformations Distortion of cavities up to ±5mRad. In asymmetric loading conditions the deformation can reach up to ±10mRad – these numbers were presented in the Sept2003 Forum. 1/14/2019

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Full+TPC+HMPID 1/14/2019