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					                                                                              ER. 13.02.2004

                                    ALICE 3rd Cone


                  Minutes of the meeting held at CERN on 12.02.2004

Present: J.-J. Gaardohje, N. Golubev, E. Rosso, G. Schneider


Subject discussed:
   Design of the Vacuum Pipe (VP) support by the ALICE 3rd Cone on RB26 side.



                                          -o-o-o-



Reminder of the main technical requirements:

   From the VP team:

     ▪   the VP must be supported by four cables adjustable in length by mean of four
         tension mechanisms mounted on the 3rd Cone.

     ▪   each of the cables must stand a tension 10 DaN ≤ T ≤ 40 DaN.

     ▪   the support must be designed such that the Eigenfrequency is >60 Hz

     ▪   behind the tension mechanisms a free space of 50 mm is needed for an easy
         operation of the system

     ▪   on RB26, along the z-axis, the distance between the Interaction Point (IP) and the
         four tension cables must be of 460 ± 2 mm

   From the FMD team:

     ▪   the 3rd Cone must present the highest transparency to the particles. By
         consequence:

         -   the tension mechanisms should be installed at the maximum possible distance
             with respect to the beam axis

         -   in the realization of the elements installed on the “nose” of the 3rd Cone, one
             should possibly avoid dense materials like metals.
Outcome of the discussion:

▪   general consensus was given to a possible tension mechanism, presented by Gerhard,
    in which the tension of the wire would be provided by non-magnetic calibrated springs

▪   with respect to fig.1, the tension mechanism will be installed in a higher position at a
    minimal distance of 50 mm from the 3rd Cone fixation arm

▪   the tension mechanism will be based on the use of rollers to guide and smoothly tighten
    the four tension cables

▪   the tension cables will consist of classic stainless steel multi wire cables ( = 1.5 mm
    max. 2.0 mm)

▪   in order to reduce the amount of material along the particle trajectories two solutions
    for the system roller-rotation axis will be carefully studied:
    -   the axis of C-fibre composite material coated with a ceramic layer and the roller of
        ceramic
    -   the axis of C-fibre composite material and the roller of polyamide
                                                      Action: Nikolai

    due to the delicacy of the beam pipe positioning and the very serious consequences of a
    possible breakdown of a system roller-rotation axis, all non-metallic solutions must be
    carefully studied and tested in laboratory. It was therefore decided that:

    -   a design of each of the two systems will be realized according to the sketch in fig. 2
                                                      Action: Nikolai

    -   a prototype of each of the two systems will be realized at NBI
                                                      Action: Jens

    -   the small amount of polyamide material needed for the test will be provides by the
        VP team
                                                      Action: Gerhard

    -   the test will be performed at CERN by the two teams VP and FMD
                                                      Action: Ettore, Gerhard and Jens

▪   in the proposal presented by Nikolai, the “nose” of the 3rd Cone is foreseen of massive
    C-fibre composite material. A study will be made to minimize this material (sandwich
    honeycomb-C-Fibre?)
                                                      Action: Nikolai
                Beam Pipe Support
                Adjustments

                                                             Fixation arm




                 First Beam Pipe Support

Fig. 1: Interface between ALICE and VAC: The adjustable beam pipe support.
                                               1.5 mm




                               2.0 mm
     Roller

                                                                         Tension cable


                     5.0 mm                                    16.0 mm




                   Axis
                                               2.0 mm




                                             5.0 mm


Fig. 2: Sketch of the system roller-rotation axis for test

				
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