Executive Summary:  All dark currents look good prior to the start of the run.  Some useful code is attached.

We have taken 3 IV scans so far this year, so we have the characteristics of the SiPMs prior to the start of beam.

The first scan was taken Feb 9th, with the plots at:

One channel per page: drupal.star.bnl.gov/STAR/system/files/ivout_ivhist_run_02_09_03_12.pdf
EW/PP/TT: drupal.star.bnl.gov/STAR/system/files/ivout_ewpptt_ivhist_run_02_09_03_12.pdf
Tuff: drupal.star.bnl.gov/STAR/system/files/ivout_tuff_ivhist_run_02_09_03_12.pdf

The second scan was taken Feb 20th, with the plots at:

One channel per page: drupal.star.bnl.gov/STAR/system/files/ivout_ivhist_run_02_21_03_07.pdf
EW/PP/TT: drupal.star.bnl.gov/STAR/system/files/ivout_ewpptt_ivhist_run_02_21_03_07.pdf
Tuff: drupal.star.bnl.gov/STAR/system/files/ivout_tuff_ivhist_run_02_21_03_07.pdf

In both of these runs, there was one weird channel (same channel both times):

Figure 1: Dark current from sipms associated with tiles 16 - 31 in ew = 0, pp = 10.  "Bad" tile is TT 22.

This also could be seen in the GUI when the voltage was turned up to 64 V:

Figure 2: Flaky channel in the EPD.  Note: Mapping in the GUI agrees with mapping in Tonko's IVscan script.

In addition to showing high current, this particular tile would jump around with time, so it was unstable.  Prashanth and Joey replaced the bad SiPM card (#28) with one from the cabinet (#32), afterwards all currents looked normal in the physics mode.  We then took a third IV scan.  It should be noted that Tonko changed the step size from 0.2 V to 0.4 V in the mean time.

The second scan was taken Feb 21st, with the plots at:
One channel per page: drupal.star.bnl.gov/STAR/system/files/ivout_ivhist_run_02_22_01_02.pdf
EW/PP/TT: drupal.star.bnl.gov/STAR/system/files/ivout_ewpptt_ivhist_run_02_22_01_02.pdf
Tuff: drupal.star.bnl.gov/STAR/system/files/ivout_tuff_ivhist_run_02_22_01_02.pdf

Everything looks good!

The code used to make these files can be found at:

ivscanconvert: drupal.star.bnl.gov/STAR/system/files/ivscanconvert_0.txt

This runs over the ascii file created by Tonko's IV scan script and creates a root file of histograms.  Each histogram keeps track of the ew/pp/tt and tuff parameters from the script output.

DrawIVhistos: drupal.star.bnl.gov/STAR/system/files/DrawIVhistos_0.txt
This takes the root files from ivsacnconvert and creates 3 PDFs.  One pdf (ivout_ivhist) simply shows the histograms one by one.  iveout_ewpptt groups the histograms based on what physical tiles they are attached to.  ivout_tuff groups the histograms based on what tuff channels, etc they have.