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Reinforcing BOL modules. F. Grancagnolo, R. Perrino INFN Lecce. ATLAS-RPC Meeting / Roma, Nov. 5 th , 2002. History of the BOL sagitta problem.

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Reinforcing bol modules

Reinforcing BOL modules

F. Grancagnolo, R. Perrino

INFN Lecce

ATLAS-RPC Meeting / Roma, Nov. 5th, 2002.

History of the bol sagitta problem
History of the BOL sagitta problem

  • Since the very first muon spectrometer layouts, the asymmetric BOL MDT/RPC package, due to its weight and length, has been considered safer if reinforced by a bridge structure fixed on the RPC to the aim of relieving the mechanical stress due to the torque of MDT weight with respect to the supporting rails.

  • As a first step, the rotation axis of the common support has been placed on a line which contains the center of mass of the package, so reducing to zero the torque. This is actually only approximately true, since the position of the rails has been frozen when the weights of MDTs and RPCs were not known precisely.

Current status of bol common support
Current status of BOL common support

  • The current design of the BOL common support, has been developed after some interaction between NIKHEF and INFN-Lecce, with the involvement of INFN-LNF, since the design was inspired by the BML one.

  • The concept is similar, but the BOL support has asymmetric branches.

  • The connection to RPCs is ensured by a connector bar made of Al extruded profile.

Current status of bol common support1
Current status of BOL common support

  • Detail of the connection between the common support and RPC end-plate.

  • The connection bar is complex and heavy, requires special extrusion head and a lot of machining.

Connection bar is charged on infn lecce
Connection bar is charged on INFN-Lecce

  • Profile as in the designer’s view may be expensive.

  • Different option enviewed?

Reinforcement of rpc panel 3 i
Reinforcement of RPC Panel #3 - I

  • A study has been done (thanks to Salver) to investigate the option of increasing the stiffness of the RPC modules by acting on the Support Panel #3

  • The first option is a change from paper to Al honeycomb, then a transition to a smaller cell honeycomb

  • The sagitta [mm] has been evaluated as a function of the shear for the initial situation, and for the two other options

  • Conclusion:

    The reduction of sagitta is obtained with an unaffordable cost increase (according to density)

    In addition: the uncertainty on the sagitta is high

Reinforcement of rpc panel 3 ii
Reinforcement of RPC Panel #3 - II

  • Second option:

    Changing the support panel skin from Aluminium to Steel, while leaving the same thickness

  • Conclusion:

    The same reduction of sagitta can be obtained by using either material (better Al <=> worst steel)

    It is only matter of cost

Reinforcement of rpc panel 3 iii
Reinforcement of RPC Panel #3 - III

  • Choice of the Aluminium skin thickness

    Thickness of 1.2 mm instead of the current 0.3 mm would drop the expected sagitta from 10 to 3 mm

  • Conclusion:

    The choice of increasing the Al skin thickess seems convincing and easily applicable

    A prototype should be planned asap and Protvino collaborators should be made aware of this change of production of panel #3

Bml d mdt rpc integration test @ lnf sketched tools procedure
BML-D MDT/RPC INTEGRATION TEST @ LNFSketched tools + procedure