MPC DATA timing correction measurement
In order to measure the multiphoton correction for data the MPC processor requires two sets of runs be taken. First a norm single photon PCA, second a set of extremely high light output laserball runs. In order for the correction to extend to as high a charge as possible most of the runs should be run at 100% occupancy.
Measuring the multiple photon time shift requires two passes of the MPC
processor, two standard command files are provided for this purpose. The
first command file mpc_select_tubes.cmd, is run on the regular
PCA run. It generates a summary titles file
(mpc_pca_summary.dat) containing information about each of the
tubes in the detector. This summary titles file is used during the
second pass of MPC. It must be loaded explicitly on the second pass
within the second command file, mpc_make_titles.cmd. The second
pass produces the MPCA titles bank which is used by CAL to implement
the correction.
A third pass, run using mpc_measure_rms.cmd, has been deemed obsolete, as the RMS measured by mpc_select_tubes.cmd is in fact a more appropriate measure of the first photon time spread. If you would like to run this obsolete code for some reason, it requires the MPCA banks
and produces a new copy of the same banks, so be sure to use distinct
names for the input and output titles banks!
The zdab(s) to analyze should be input on stream one, and if you do not want to use the default output file names they should be specified on stream two. If MPC is being run on relatively new data you will probably have to load the DQXX and PECA/TECA titles banks explicitly. The most recent GPCA, LRBP, and WPCA titles files must be loaded explicitly.
NOTE: The user MUST measure the mean time of the time residuals for the PCA run using path corrected (21.8cm/ns) PCA times, and input this as word 14 of bank TMPC.
NOTE 2: The most recent PCA titles files will be the ones generated by the PCA run which MPC is being run on. It may be the case that the validity range of those PCA constants do not cover the run itself, so this should be checked before running the code.
MPC MC timing correction measurement
The measurement of the Monte Carlo timing correction requires only a
single pass with the command file mpc_make_mc_titles.cmd. As of SNOMAN verision 5_0082 solid cones of photons are generated with random central directions and with a flat distribution
in the number of photons. In order illuminate a reasonable number of
tubes with hundreds of photons the maximum number of simulated photons
must be enormous. The default settings of a half cone angle of 20
degrees for the generated photons and an analysis angle of 15 degrees
require over 700,000 photons to be simulated in order to measure the
correction to near 200pe. This requires considerable computing time,
and results in store full errors with default SNOMAN. Perl scripts
which spread the job to multiple processors and combine the resulting
titles files will be gladly provided by Christopher Kyba upon request.
The SNOMAN memory allocation can be changed in
define_memory_size.for. The following settings are suggested:
parameter (KSHL_MT_SIZE = 12000000,
+ KSHL_PAWC_SIZE = 4000000,
+ KSHL_Z_SIZE = 30000000)