Test Beam 2003 Trigger Plans

(revised 21 May 2003)

Phase I: Debugging and synchronizing the trigger and its readout

Cosmic rays can be used as they are used at the FAST sites for setup before beam is available. However, it would be good if during this time the scintillators could be brought close together and perhaps arranged in a more vertical arrangement. Can the chambers be turned horizontal? Can the phi and theta angles of the chambers be changed easily? Do we need a plumb bob and a protractor, or what?

The operations below can be done first with cosmic rays, and then repeated when structured beam becomes available.

Trigger debugging with individual chamber operations:

Timing-in procedure is well-defined and debugged. Among the procedures:

CFEB-TMB data transmission: run PHOS4 delay curves to make sure comparator bits are latched at exactly the right phase (optimizing 6-hit halfstrip track fraction).
ALCT-TMB data timing.
Rough timing for the TMB matching window of ALCT vs. CLCT

Use TMB logic analyzer and histogramming to debug arrival of signals.
Check the DMB readout: do we always have ALCT, CLCT, and CFEB readout?
Do we have the same BX numbers for ALCT, CLCT, and CFEB readout? If not, then adjust BX offsets.

Trigger debugging with two chambers:

Make sure we get the same BX numbers for both chambers.
What is the fraction of events for which we have really full information (both ALCT, CLCT, and CFEB readouts)? It should be nearly 100% for a good scintillator trigger.
Does the MPC receive the muon at the same time from both chambers? Do they have the same BX tag?

Phase II: Trigger test plan when fully functional, with structured beam

The minimal set of key goals for this test beam are:

Measure the efficiency for ALCT and CLCT on straight-through tracks.
Study, check and measure the ALCT-CLCT matching efficiency
Measure ALCT BX identification efficiency and learn how to adjust BXN clock with respect to ALCT timing to maximize this efficiency. This is crucial

Verify that trigger primitives sent correctly to the MPC.

A more comprehensive list is:

Single-chamber test goals:

Measure the scintillator trigger purity - how?
Measure the efficiency for ALCT on straight-through tracks.
Measure the efficiency for CLCT on straight-through tracks.
Study the ALCT BX identification efficiency: we wish to get the correct BX on 99% or more of the events. Measure the ALCT delay settings needed on different ends of the chamber. Study the time distribution of the ALCT BX versus the scintillator trigger BX.
Understand what the width of the CLCT time window needs to be in order to match ALCT, is it +-1 BX or does it need to be wider?
Measure the overall chamber trigger efficiency, i.e. requiring ALCT*CLCT*(correct BX).
Vary the pretrigger threshold (currently 2 for ALCT, 4 for CLCT) and measure the resulting ALCT-scintillator and ALCT-CLCT relative timing, i.e. make histograms of delta(BX). The ALCT delay chip settings will have to be changed slightly if the ALCT pretrigger threshold is changed.
Measure the efficiency for CLCT versus phi angle. Study how the patterns vary with angle. (Is this well described by the Monte Carlo simulation?)
Measure the efficiency for ALCT versus theta angle to map out the envelope for high efficiency. (Is this well described by the Monte Carlo simulation?)
The efficiency for CLCT should not vary much with theta angle, verify that this is true. Likewise, the efficiency for ALCT should not vary much with phi angle, verify this.
Measure efficiencies versus chamber HV.
Measure timing versus chamber HV.
Measure the rate dependence of efficiencies (and timing?).

Two-chamber test goals:

Check the relative ALCT timing between the two chambers. Is it consistent with the rate of BX misidentification for the chambers individually?
Measure the 2-chamber "global" ALCT*CLCT trigger efficiency.
Check the BX numbers match in the readout at all stages (ALCT, TMB, DMB, DDU).
Measure position and angular resolution.
Make sure that the readout of 2 chambers do not interfere with each other (all data present and valid).

Procedures:

Look with a scope at CCB input from scintillators with respect to the 40 MHz clock. Is it centered? If not, add a cable delay to the scintillator trigger so that it is. Do the muons vary with respect to the clock (they shouldn't vary more than 1-2ns)? What is the "jitter" of muon arrival time? Can some actual data be taken on this in order to accumulate a histogram? (GPIB scope readout?)
Event displays should look "perfect" when the system is really ready. Both chambers should show the same muon on the event display.
TMB logic analyzer events and histograms should also look "perfect" when the system is ready to go.
Data dumps should be thoroughly studied before the system is declared to be working properly.
Run delay curves of ALCT delay chips with beam in at least 5 places on the chamber: center, and near each of 4 corners. Set all of the ALCT delays to the proper values.
Take data and look at timing: the BX of the ALCT should be plotted versus the BX of the scintillator trigger. One convenient place to look is using the logic analyzer display of the TMB.
One way to measure efficiencies: use the scintillator trigger to define "events", simply look at the DDU data which has one record for every Level 1 Accept as the denominator.
Another way to measure efficiencies: use one chamber as "trigger", use ALCT*CLCT or any other configuration, and look at how often the particular type of data is seen in the other chamber. This should be fairly symmetric between the two chambers if they are operating pretty much the same.