New Pigtail Design Description

    The idea here is to try to use "standard" cables and "standard" connectors to connect the CPC to the junction card. There are several constraints which we must deal with.
  • We need to keep the total power loss in the cable to ~1 Watt per cable
  • The Fib signal cables should have ~100 Ohm impedence.
  • The cables need to be able to snake around various alignment features, cooling tubes, barrel mounts, etc.
  • Space is a big limitiation. Between CPC's there is a total of 2.66", so that any solution must not stck out more than 1.33" (along the Z-direction) from the CPC. Also, the width must not be more than 2" and the height must not exceed 0.60".
  • There are 23 conductors for the low voltage: 5 Analog pairs, 5 Digital pairs, 5V_DOIM, 2V_DOIM, and DGNDP. For flexibility, we want to be able to use different gauge wire for each of the low voltages.
  • There are 15 lines for the Bias: V+, V- and Vref for 5 layers.
  • There are 11 differential pairs for the FIB control signals
  • We would like to use unshielded cable if possible, and only use shielded cable if necessary.
  • The expected currents, voltage drops and power loss for all the low voltage power can be found here.
    The overall picture is the following. There is a small pigtail, not longer than 1.25" long from the end of the CPC. To this kapton cable mounts 3 surface-mount connectors: 1 for low voltage (LV), 1 for Bias, and one for Fib signals.
    The LV, Bias and Fib signals are carried are terminated on each end with standard connectors. Here are the relevant data sheets for the connectors and cable on the CPC side of the connection.
  • Low Voltage
  • Bias Voltage
  • Fib Signals
    • Open Questions/Issues
      • We probably need two versions of the pigtail so that the cables exit straight out and don't have to loop around.
      • Need a material estimate (radiation lengths)?
      • ISL needs to be made aware of any such changes.
      • Can Jim design such a pigtail, ie., right angle corners.
      • This pigtail wiull have to be strian relieved so that any force on the cables is not imparted to the CPC.
      • Can we get away with unshielded cable for Bias, Sense?
      • Impact on junction card. Do we modify the junction card? Use the same/similar connectors on the junction card side?
      • Must have an adaptor which mates these 3 cables to the test junction card (TJC) so Yuri can do the port card burn-in with the TJC.