ABSTRACT: This message outlines a proposal to plug the Bari trigger
into one of the calibration "fake box" fanout channels. This will
give the ERP GC monitor software information about ST hits which will
decrease background for the ERP GC monitor. This change will have
some effects on the ERP data, and will require some changes to
existing software. The exact "Bari box" configuration must still be
decided -- I ask for feedback from ERP calibration software people. I
would like to set this up by July 14 if possible.
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Hello all,
Anyone involved in scintillator data analysis (especially ERP) and
calibrations should pay careful attention to this message.
A few weeks back I posted a message to the macro-general mailing list
in which I outlined an idea of Ed Kearns', which was to plug the Bari
trigger into one of the ERP "fake box" inputs, currently being used
for laser and LED calibration event triggers for the ERP. This "Bari
box" will allow many muons to be cut easily from the GC data sample
seen by the ERP GC monitor, and will substantially reduce background
for the GC monitor (see my previous message, and messages posted to
the macro-erpgc mailing list, for more details about this).
The feedback I got from people about this was in general quite positive.
So, I'd like to make a serious proposal for setting up an ERP Bari box
(please refer to my previous message as well).
Here is the basic plan:
I will get two copies of the Bari trigger for each microvax and send
one to each supermodule of that microvax. For each supermodule, one
of these copies will get plugged into the back of one of the fanout
channels which are currently being used for calibration fake boxes
(exactly which fake box channel is not yet clear -- see below). This
signal would be set up to produce only an Elow trigger in the ERP
(either by adjusting the pulse size, or by tuning the LUT for that
channel -- see below).
So, every Bari trigger would get recorded in the GC buffer (available
to allow vetoes of muons in the ERP GC monitor software), and would
also get read out as a hit with every ERP muon event which is
accompanied by a Bari trigger.
Here are some of the issues, and comments about them:
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QUESTION:
Will the new signal going into the fanout cause problems for any
other circuit which takes signals from the fanout?
ANSWER:
I don't think so. Here are all the cases:
WFD: uses channel-specific lemo connectors on the fanout, and nothing
is plugged into the fake box channels
SMT: same as above
CSPAM/FMT: uses AMP ribbon cable connectors, but I've been told that
traces have been cut for the fake box channels (can anyone
confirm this?)
Phrase: has AMP connector but fake box channels are unused
(calibration signals come directly from
calibration hardware).
So... putting extra Bari signals into the fanout should be no problem
(although I need to make sure about the CSPAM).
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QUESTION: Will this change cause software to break?
ANSWER: Well, yes. ERP calibration software in particular will
need to get rewritten to take the change into account. However,
Jim Musser and Bob Nolty have told me that the necessary changes
probably won't be so terrible and they are willing to go ahead with
it.
Other software might possibly also break. For instance, any analysis
software which counts up the number of boxes in muon events may have
to take the change into account. See below for comments on runs
getting flagged as calibration runs.
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QUESTION: Which calibration fake box channel should become the Bari box?
ANSWER: Very good question. There are several possibilities.
There are 3 fake boxes per SM: one for LED, one for the lower
laser, and one for the attico laser.
1. The Bari trigger could get ORed in with one of the current fake box
signals. The obvious problem with this is that it would be confusing
to tell whether a fake box hit was due to a Bari trigger or due to a
calibration event. This problem isn't insurmountable however: I could
set up the Bari trigger signal going into the fanout such that it
would have much less charge than a calibration signal (by attenuating
it and/or making it narrow), so that when the ERP digitizes it, the
ADC value for a Bari trigger hit would be smaller than for a
calibration event hit. Of course software would have to be written to
deal with this.
2. One of the calibration fake boxes could be made into a dedicated
Bari box, and two of the three fake box signals could be ORed into the
same channel. In principle this should work fine because LED, lower
laser and attico laser calibration runs are done separately. Here are
the basic possibilities for the configuration:
2a. Bari trigger gets the current LED fake box channel,
LED signal gets ORed into one of the laser fake box
channels.
2b. Bari trigger gets one of the laser fake box channels,
LED gets its own fake box channel, both laser signals
go into the same fake box channel.
These configurations make it trivial to distinguish Bari from
calibration events, and also make it easy to set up the ERP triggering
for the Bari signal (I don't need to worry about pulse size, and can
just set the LUTs for the Bari channel such that a Bari channel will
always make an Elow and never make an Ehigh. Calibration fake box
LUTs can stay as they are).
Personally I am in favor of either of the #2 configurations. I would
like to put this question to the ERP calibration software folks in
particular-- which of these configurations would make life easier for
you? Please let me know your preferences.
--------------------------------------------------------------
QUESTION:
Will runs get mistakenly flagged as calibration runs due to the
presence of Bari triggers in one of the former calibration fake boxes?
ANSWER:
No. The acquisition flags runs as calibration runs based on a bit set
in one of the scintillator pattern unit words, and this module gets
the information directly from the calibration hardware.
However, any software which *does* flag calibration runs on the basis
of the presence of ERP fake box hits would have to take the Bari box
change into account.
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QUESTION:
It will be impossible to use one of the current fake boxes for the
Bari box because... <insert hypothetical fatal flaw here>. Are there any
alternatives?
ANSWER:
Nat has suggested a possible alternative way of implementing a Bari
box for the ERP: we could conceivably set up some actual extra ERP
channels. There is space for one extra S/H card in the ERP VME crate,
and interERP TDC's could be moved such that there would be space for
another trigger processor module in each ERP Camac crate.
This scheme has the advantage of having no impact on current
calibration setup software (might possibly affect other ERP decoding
software?)and the changes would be essentially transparent to all
others. However there would certainly be various hardware-related
hurdles to overcome (some easy, some hard): e.g. spare ERP modules
would have to be brought here from the US, trimpots on new cards would
have to be twiddled, trigger bus cables would need an extra connector,
interERP cables would need to be relaid, etc. This could not be set
up right away, and I think it would end up being a good deal more work
than the fake-box-substitution. We should keep this in mind
though.
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I would like to implement this before I leave the Gran Sasso on July
14. If I do not hear objections within several days, I will go
ahead and do it.
All comments welcome.
Kate.