The gain calibration code collects up charge histograms for every tube in the detector. On termination the histograms are fitted and the positions of the threshold, peak and high half point are written out to titles banks. The high half point is the point where the number of entries in a bin falls to half that of the peak.
User control is via the TPCA 2 bank in the file pca_data.dat. These
settings should not normally be modified. An example of a command file which
runs the gain fitter is pca_gain.cmd.
The validity ranges should be adjusted to the desired values.
Clearly the gain fitter requires ECA calibrated data so if the ECA constants
are not in the database then they must be loaded through titles (CAL does not
need to be called in the processor list).
Similarly if the DQXX banks are not in the database they should also be loaded
through titles.
The gpca titles banks are written to the file on stream PCA 1 which must be
defined. The file name can be automatically generated by putting AUTO in place
of the file name. If a file name is supplied on stream PCA 2 then the fit
ntuple will be written there. Similarly if a file name is given on stream
PCA 3 the charge histograms will be written out to files with the same name
but ending in .qhs , .qhl or .qlx. Which charge histogram
files will be created can be changed by editing pca_data.dat.
The gain calibration produces the GPCA titles banks, an optional ntuple and
optional histogram files as output. The histograms have 
.
The ntuple, id 100, contains the following statistics:
lcn Logical Channel Number
crate Crate Number
card Card Number
chan Channel Number
online 0=Offline 1=Online
type 1=Normal PMT (see ccc_type.inc)
stat 0=Fine 1=Offline 2=Zero occ 3=Low occ 4=Low ECA
mask 0=OK +1=QHS Bad +2=QHL Bad +3=QLX Bad
ntotal Total Number of Hits
hs_ncal Number of QHS calibrated hits
hl_ncal Number of QHL calibrated hits
ntypical Typical number of hits a PMT received
blown 0=OK 1=Blown 75 Ohm resistor
vthr DAQ Threshold
hs_th Fitted QHS threshold
hs_pk Fitted QHS peak
hs_hi Fitted QHL high half point
hs_rlo Low edge of range containing bulk of data
hs_rhi High edge of range containing bulk of data
hs_pave The height of the peak
hs_lave The height of the lower average
hs_rout Fraction of hits outside the range thresh to hhp
hs_rdble Ratio of entries in 2nd most numerous peak range to peak range
etc. Followed by the same statistics for QHL and QLX