Study of Cross-talk on the MAPMT-to-Hybrid cable

1
Study of Cross-talk on the MAPMT-to-Hybrid cable

2
Overview

• As HV is increased beyond 600V, we start to see
  capacitive coupling between channels.
• Initial studies indicated it was due (mostly) to
  the flat cable connecting the baseboard to
  hybrid.

3
Possible Short-Term Solutions

• Use the same cable (3) but with spacing between
  the wires.
• Use a very short cable of 0.5 (approximated a
  direct connection from baseboard to hybrid)
• Study each alternative cable as a function of HV
  and Threshold.

4
Schematics

• 
  MAPMT

Optical fiber
LED
5
Plots

• Old cable (3) at 600V and threshold 117
  New cable (3) at 600V and threshold 117
• Old cable (3) at 700V and threshold 117
  New cable (3) at 700V and threshold 117
• Old cable (3) at 700V and threshold 105
  New cable (3) at 700V and threshold 105

6
Plots

• Old cable (3) at 750V and threshold 105
  New cable (3) at 750V and threshold 105
• Old cable (3) at 750V and threshold 90
  New cable (3) at 750V and threshold
  90
• 
  
  
  
  
  
  
  
  
  
• Old cable (3) at 800V and threshold 90
  New cable (3) at 800V and threshold
  90

7
Plots

• Old cable (3) at 700V and threshold 105
  Old cable (3) at 800V and threshold 90
• New cable (3) at 700V and threshold 105
  New cable (3) at 800V and threshold 90
• Short cable (0.5) at 700V and threshold 105
  Short cable (0.5) at 800V and threshold 90

8
Summary

• Both the split cable and short cable reduce the
  interwire coupling, but neither eliminates it.
• Possible other sources/tests.
• Make a cable with 2 wires only at positions 1
  32and check if coupling still persists.
• Connectors?
• Traces on hybrid, baseboard?
• Possibly try injecting charge directly into the
  pre-amp through a 10 pF cap (nominally, 62Ke-/mV)