Figure 1: Support stand for the LHCb VELO. Also shown are the y-translation frame and the flexible support for the vacuum vessel.

The stand (drawing TVM 21) describes the support for the VErtex LOcator (VELO) of the LHCb experiment. The total weight of the detector, including the stand, is approximately 2,600 kg. The top of the stand features machined surfaces, four M16 studs, and four holes. Mounted onto the machined surfaces are the vessel support tables (drawing TVM 22). The stand also features holes, which accommodate the mounting of the y-translation frame (drawing TVM 04). The four M16 studs are there to allow mounting of the secondary vacuum pump-out pipe.

The feet of the frame host four M30 bolts, which are spherically shaped at the bottom end and are fitted into disks. These disks are able to slide over the sliding tables (drawing TVM 17 and TVM 18). The M30 bolts allow the adjustment of the detector in the y-direction and the eight bolts enable adjustments in x and z direction with an accuracy of 0.2 mm. The frame of this stand (drawing TVM 23) is made out of AISI 304 stainless steel. On the top corners there are lifting points with allow us to lift the complete detector into position.

The vessel support (drawing TVM 22) is split in an upstream and a downstream support. Each of these supports has a sliding table for adjusting the vessel in x and z-direction and three M16 studs. The latter allow adjustments in the y-direction. The vessel is fixed on both sides with three M16 bolts to the vessel supports (note that the weight of the vessel is approximately 1,000 kg). The upstream vessel support is fitted with two bending hinges. These bending hinges accommodate movements due to thermal expansion, for example during bake out of the vessel.

The y translation frame (drawing TVM 04) is equipped with four bolts for adjusting and fixing the frame in the y-direction. Adjustments in the x and z-direction are done by using the eight M8 bolds mounted in the corner stands on top of the top plate of the stand. The purpose of the y-translation frame is to allow movement of the two detector halves mounted in a center frame in the y-direction. Consequently, the center frame is mounted onto the four spindles on the y-frame. These spindles are coupled via rods, flexible couplings, and gearboxes and are driven by a single stepper motor. The current of this motor is limited in order to avoid possible damage to the mechanics. Using four linear potentiometers checks the actual movement and coupling. The position of the center frame in the x and z-direction is fixed in a linear bearing upstream and the two cam followers (i.e. bearings) against rotation downstream. Sliding tables (drawing TVM 17 and TVM 18) are bolted and glued to the concrete of the floor of the tunnel and made out of steel.

On the top corners of the stand are 4 removable lifting points (drawing TVL 07)which allow us to lift the complete detector into position.