An overview of the center frame (see drawing TVM 03) is given in Figure 1.
The figure shows that the center frame will be mounted on the Y-translation frame on top of the stand.
The four spindles of the Y-translation frame allow adjustments of the center frame in the y direction by + and -5mm
in order to accommodate the beam in this plane.
The position in the x z plane is determined both by a rod on the center frame and a linear bearing on the y frame.
The rotation in the same plane is fixed both by a rail on the center frame and cam followers on the Y-translation frame.
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Figure 1: Center frame of the LHCb vertex locator.
Also shown is the thin-walled container for the silicon detectors.
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The center frame holds the left and right detector support frames.
On the detector support frames there are three 25 mm diameter spheres, which are fitted in sphere holders.
The upstream holder (closest to the interaction point) is a hole to determine the xyz position, downstream it is a slot.
The top slots determine they x y positions.
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| Figure 2: Pivot support for the detector housing.
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The pivot support for the detectors is shown in some detail in Fig. 2.
The three holders on each side are mounted on linear bearings and are driven by a stepper motor via a teeth
belt with a 40:1 gearbox and a ball screw. This allows the detectors to move in the x direction by +/- 15 mm.
The radiation resistance of the belt the motors and the encoder is 108 rad.
The expected radiation level at the position is 20 krad /year
An encoder on the motor checks the actual motion of the motor,
while linear pot meters on these holders measure the movement of the holders.
Precision switches and hard stops determine the outer positions and reset of the tables.
Precision switches sense the inner positions, while hard stops are mounted on strips on the holders.
This allows the detector halves to move over the centerline without hitting each other.
All rotating and moving parts will be protected by a cover in the final assembly.
On the corners of the center frame there are holes provided for alignment spheres,
and in the x y plane of the interaction point a mirror face for auto collimation
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