Local Ganging in the Central Calorimeter and Major Portions of the Endcap Calorimeters

摘要

This is the minority report on the decision to use local ganging in the central calorimeter and major portions of the end cap calorimeters. The method not chosen for the readout is distant ganging. This method requires that the signal from each pad be carried to the outer radial edge of the board. There the signals from successive boards are connected together in parallel(ganged). From there the signal is carried to the cryostat port. All of the procedures needed to effect this design are known at this time. The line connecting each pad to the outer edge of its board can be produced by routing the line onto the readout board when the pads are routed. The lines are designed to be .007 inches wide with .008 inch spacings between lines. Lines of these dimension have been produced at Fermi Lab with very little difficulty. Three lines each 50 feet long were cut with out a break or short on the first attempt using the Fermi Gerber router. The connection from the lead to ganging cable is made with lands at the outer edge of the board. The ganging cable is created by layering copper and mylar. The first surface is copper with spaces etched on it to create leads with the same spacing as the lands on the boards. the second layer is mylar. The third layer is a solid copper sheath. The fourth layer is mylar. This cable is held in contact with the lands by spring clips. This system was used to connect over 300 lines in series. The test piece was cold shocked in LN(sub 2) ten times without a failure in any connection. The ganging cable is then connected to a twisted pair cable. Several connectors are commercially available for this transition. All are extremely reliable.