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GlueX electronics
In the spirit of Elton's email about the Start Counter, I'd like to
summarize my recollections regarding electronics discussions at last
week's collaboration meeting. Some of these are taken from my notes on
talks, and some are from personal discussions. As the newly appointed
"Electronics Coordinator" let me say I have no desire or intention to
micromanage GlueX electronics R&D; my goal is make sure all relevant
information is easily available to everyone working on this part of
GlueX so that electronics built at different institutions will all work
together.
Please be sure to let me know if you disagree with anything below, or
if something should be added.
------------------
Central Tracking
3250 channels
amplifiers need gain of about 10**2 or 10**3
FADCs need 10 - 12 bits at 125 MSPS
-----------------
Forward Tracking
2856 anode channels - F1 TDC in 120 pS mode.
5712 cathode channels - FADC; speed and resolution to be determined
-----------------
Forward Time of Flight
Current design has 140 channels; going to 2.5 meter length will
increase this slightly.
PMTs are XP2020
Discriminators are probably "Constant Fraction" type; this will be
settled soon.
May want hardware "Mean Timers".
May want HPTDCs instead of F1 TDCs. JLab has some CAEN HPTDC modules
being evaluated.
------------------
PID
Gas Cherenkov in CDR may be replace by DIRC; this is a large
perturbation on total channel count; Stefan estimates 2340 PMTs.
------------------
Tagger
128 "fixed" counters, 64 "movable" counters; peak rate in a single
counter is 10**6.
------------------
DAQ
Ed Jastrzembski will develop a next generation Trigger Supervisor which
supports "blocked" event readout as well as an experiment-wide clock
distribution system. The distributed clock will be 62.5 MHz; crates
will generate local clocks phase-locked to this distributed clock.
Ed, could you produce a short description of your thoughts on this
clock distribution system? Is it fiber optics? I assume a global
"reset" will be distributed as well? The FADCs need this to
synchronize all channels. How about special triggers for calibration,
etc? Are the F1 TDCs capable of using this clock as a reference?
The current and near future work by the DAQ group assume a VME64X
"form-factor", but other "form-factors" such as VXS, VXI, ATCA, cPCI,
PXI, etc are not being ruled out for GlueX.
------------------
Trigger
We want the ability to use the Start Counter in the level 1 trigger.
Other detectors such as the backward veto may also be part of the level
1 trigger. Dave Doughty will make the CNU student's thesis on trigger
simulations available. Dave is requesting NSF money to continue the
level 1 energy sum prototype work, especially the high speed serial
links.
---------------------
Start Counter
In level 1 trigger.
About 40 channels.
High field PMTs or SiPMs
Constant fraction discriminators.
Hardware "mean-timer"?
---------------------
From my summary talk:
Fernando Barbosa will be working on a prototype FADC which could be
used in the existing JLab experiments and would be suitable for the
GlueX central and forward drift chambers. Paul Smith will be working
on a prototype FADC for the GlueX calorimeters which will include the
energy sum needed for the level 1 trigger. Paul and Fernando will
communicate and try to keep the FADCs as similar as possible. If it is
possible to converge on one design for all GlueX FADCs (for example by
stuffing different front end components) this will be done.
Here is my table of institutions responsible various electronics
subsystems with names added. Please let me know of any mistakes
and/or additions:
Vertex tracking deleted
Calorimeter FADCs IU Paul Smith
Tracking FADCs JLab Fernando Barbosa
TDCs JLab Fernando Barbosa
CF discriminators Alberta Jim Pinfold
Drift chamber amps Alberta Jim Pinfold
Level 1 Trigger CNU Dave Doughty
Clock distribution JLab Ed Jastrzembski
Power & grounding JLab Chris Cuevas
Tagger CUA Dan Sober
Goniometer Glasgow Jim Kellie
Active Collimator UConn Richard Jones
Track count ????
Calibration ????
Pipeline issues ????
Alex will continue to communicate with ORNL regarding their involvement
in GlueX electronics.
I've asked Zisis to add an electronics forum to the GlueX portal. My
hope is that this will be the starting place for links to documents on
GlueX electronics designs. I will put this email there when the forum
is available. I encourage people to place minutes of any meetings
where GlueX electronics are discussed there as well. If this forum
doesn't work out, we could consider a listserv for electronics
discussions.
We should consider occasional electronics oriented conference calls.
Sometime after the detector review we should consider a GlueX
electronics workshop.
Paul