Hartmut and Dick,
Here are my comments and action items:
1) Since G chip looks more promising, we
should spend more resources in making G chip work reliably. That is the first priority is to make sure removing
the added(?) threshold stabilizer would not affect other characteristics of the
G chip.
2) TOT has turned out to be quite useful
event it was poorly functioning in
Balloon
Flight Eng. Model:
2a) Mizuno discovered unexpectedly large slewing time in the BFEM
threshold circuit going to trigger.
2b) Eduardo found BFEM TOT gives about a factor of 2 rejection of
Compton background: (Pair conversion gives 2 unresolved tracks
but Compton scattering gives only 1 track.)
3) In BFEM low energy X-rays gave about 1
extra hit per tower per trigger. So the noise occupancy lower than 10**2 per
chip (assuming 1us gate for readin) will be tolerable. What I would like to see is
"stability" of threshold relative to the noise curve. External conditions like temperature, supply
voltage, counting rate, etc.should not change the noise occupancy
significantly.
4) Read in rate of 10MHz will not be
acceptable because this will mean twice longer time to read the coordinates in. We need a realistic filtering time from
JJ. My past experiences tell me untill
you implement and run in a realistic environment, you'd better be very
conservative. No DAQ nor on-line
software worked as well as the design: if it comes within a factor of 2-3, it
should be commended.
Action item 1) As all agreed, cut the two
connections in the G design and prove that the characteristics do not change.
Action item 2) Test that 18MHz will give
ample margin in timing: temperature supply voltage and counting rate need to be
varied.
Action item 3) Test stability of TOT against
counting rate and heavy ion crossing.
Tune Kamae