MiniBooNE PMT Testing

1 PE width writeup

Collaboration meeting 8/31/00 Report

• Diagnostic Report. Two different methods of calculating number of photoelectrons now basically agree. Tubes off "main sequence" are indications of problems. For example:
  • Events in lower right are tubes with large light leaks from light flasher.
  • Tube at (-1,-1) had voltage scale mis-set.
  • Two tubes in upper portion of plot had such a high light level that thre were less than ten basline sweeps each.
  • Two tubes at (0,0) had no pulses for entire run.
• Width of 1 PE peak. We can calculate the width of the one PE peak assuming a Poisson distribution for the photoelectron. When this is divided by the 1 PE gain, you get the intrinsic pulse height resolution for the tube.
• Width of timing distributions for tubes. This distribution gives the PMT's intrinsic time resolution. These distributions are for time crossing threshold of 2.5 mV. (Red are LSND tubes; Blue are new Hamamatsu tubes.)
• Comparison of PMT gains for "b" settings for LSND tubes on ZIP11 (black) to "d" settings for new tubes (red hashed). Since average gain of "d" setting of the new tubes is about the same as the "b" settings of the old tubes, we presume that this setting is above our operating point.
• Typical integrated charge distribution for an LSND tube. Tube DC46, voltage setting "a". 1 PE = .9 pC. Number of PE = .7 +/- .3. 1 PE sigma / 1 PE PH = 1.3. Black is for all sweeps; red is for sweeps with recoignizable in-time pulse. Questions for LSND members:
  • What are we going to use the 1 PE width for?
  • Do we need to know a tube by tube 1 PE distribution or is just the width good enough?
  • The events about 6 pC (red hashed region) in the above plot are highly non-statistical. I presume that they come from the light pulser just sometimes giving off a hugh pulse. These are going to skew our measurement of the 1 PE width somewhat, though they will probably affect each tube in the same manner. Is this going to be a problem?
• Typical integrated charge distribution for a new tube. Tube = SA2574; voltage setting "c". 1 PE = .95 pC. Number of PE = 1.15 +/- .05. 1 PE sigma / 1 PE PH = .42. Black is for all sweeps; red is for sweeps with recoignizable in-time pulse. Same questions apply.

Layabout's meeting 7/27/00 Report

• SA2303 PMT integrated charge for three different voltage settings. Black histogram is all sweeps. Red histogram is events with pulse as isolated by integration algorithm. This tube saw approximately .5 pe/pulse.
• SA2362 PMT integrated charge. This tube saw approximately 2 pe/pulse.
• Two examples of afterpulsing in tube SA2303. Found by scanning first 100 events in low voltage file.
• Small pulse examples that do not pass traditional threshold cut. (SA2303 low voltage file.) Upper left pulse is consistent with noise. Others are probably pulses.