In general 2 event samples are needed for calibration procedure:
(1) One track events without interaction in target. (Don't forget to do OTR=="NO")
(2) Multitrack events with interaction in target.
Both samples have to be collected
without magnetic field.
Straight lines needed for calibration are reconstructed by
selecting hits in 2 base planes and extrapolation between them.
These base planes, corresponding accuracies and detectors are
listed in BEC$PROC_DB file.
Procedure itself consists of the following steps:
SLT1
Filling of histograms for drift curve determination. This
curve is common for all wires in the chamber so chambers should
be exposed as widely as possible. (Typically sample (2)
or even data events are used)
Processor list file - BEC$PROC1.DAT
Processor used -- SLT1.
SLT2
Primary determination of drift constants for drift chambers
based on the Dalitz-point existence in closed X,Y,V planes(sample
(2) is used for the same reason).
Processor list file - BEC$PROC2.DAT
Processor used -- SLT2.
SLTI
Drift constants determination for INOX chambers based on the
correlated list close
pair of chambers (also sample (2))
Processor list file - BEC$PROCI.DAT
Processor used -- SLTI.
SLTB
Primary chamber position determination along the straight
line for all detectors (evidently only sample (1)
must b used). Practically beam profile is narrow and only few
wires in big chambers are working in these events, so calibration
results are slightly shifted. Final positions for PC, INOX, DRFT
are obtained later on SLT3
stage, but only SLTB
gives positions of beam chambers BHPC, so one should be careful
in order to obtain correct relative position of
BHPC and PC, INOX, DRTF part of setup. In practice this means an
iteration of SLTB -SLT3
stages.
Processor list file - BEC$PROCB.DAT
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SLT3
Main step for final position determination of PC , INOX ,
DRFT in X and Y planes. Only sample (2) should
be used . X,Y plane selection is doing by changing
( LINX, VRX2 ) <->(LINY,VRY2) in processor list file. This program
has 6 different options. They are controlled by 4th parameter in
data line for VRX2, VRY2 in the processor description file. Two
of them are obligatory - 2)- x -chamber position determination
and 5)- drift constants tuning. Both must be repeated a few times
and preferably 5) should be the last at this calibration step.
Also useful are the following options:
3) x position calibration for base planes
1) z position calibration (generally this shouldn't be done, because it's fixed by trigonometric measurement)
6)Determination of drift curves with tracks (t.i. without noise)
Processor list file - BEC$PROCB.DAT
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SLTV
Last stage of the calibration - position determination for
rotated chambers PC15, PC16, POL1, POL2. Also sample (2)
should be used.
Processor list file - BEC$PROC_PRPV.DAT
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Tel. 007-0967-71-36-14
Comments to: IKostyuhina@ mx.ihep.su