Requirements during Installation

Hard stops have been installed in the Front (2 vertical and 4 horizontal) and the Rear (5 'vertical' and 2 horizontal). The switch  is a miniature switch Farnell B3S-1002 (normally off). The contacts are accessible from the beampipe side. The cable used is not part of the set of MVD Combo cables.

Requirements:

• During installation the horizontal movement of the beampipe of 30 cm should remain possible.
• LEDs connected to every stop individually should indicate a contact. The LEDs should represent the physical position of the switches. The device should be usable during installation before the cables to the vetowall area are put into position.
• In case a switch gets stuck, it should be possible to exclude it.
• An audible alarm: the volume of it should be adjustable.

 Interface to GO/GG magnet movement control system.

The Machine Group has 6 possible inputs in total for end switches (MVD and Magnet switches) on  forward and rear side. The MVD group can use 2 end switches, the others are used to monitor when the GO magnet or rear beam pipe hits one of the hard stops located at about z=+2.1 and z=-1.4m .

Available inputs from MVD to Machine Group:

• 1 signal for MVD  'top': OR of FRONT 1, 2, 3 and REAR 1, 2 and 3
• 1 signal for MVD  'bottom' : OR of FRONT 4, 5, 6 and REAR 4, 5, 6 and 7

The switches open to veto movement of the magnets. The signals are potential free.  

When to be used :

• It might be necessary to adjust the HERA bridges or the superconducting magnets during a data taking period.
• Adjusting a bridge was done twice since 1992 . Both times one of the bridge had to be moved by about 1mm. In case this has to be done, the new beam pipe may also change its position.

Conclusions:

• the  selected Farnell switch operates contrary to what is specified above;  the output switch will open when there is contact.
• defect Farnell switches can be  masked out
• interface (position and connector) to the machine group system : 2 pair cable to SEDAC crate of the machine group
• the 'machine 'signals should also be made available for ZEUS SC; ZEUS BBL3 readout of signals on regular basis; (maskable) alarm when touching.
• the cables from the hardstop switches are STP-cables within the MVD volume and are led via the 'miscellaneous' zipper tube to the Patch Box. During installation the LED-box is connected directly to this cable, later via a cable to the vetowall area.

Please mail suggestions/corrections/updates to Leo Wiggers (wiggers.nikhef.nl)