Peter's cerenkov

Method for calibrating Peter's gas Cerenkov 08/31/05

After replaying all the runs (my pass0), I calibrated the Cerenkov. I plotted the spe peak position vs run and looked for jumps. Anywhere where there was a jump I determined a new spe peak position. The red line shows what I estimated was a good place to set the spe peak.

Because it was very hard to even see the spe peak for some runs, I also plotted the mean and leading edge of the spe peak. By keeping track of the shape of the entire Cerenkov spectrum, I had a chance to spot jumps in the calibration when the spe peak could not be fit.

You can see what I mean by "mean and leading edge"in the entry below and scroll down to the plot. I fit a gaussian to the top right plot for the x-axis values greater than the spe peak. The mean of this fit is the "mean of all pe peak", and the point at which it is 1/3 of the max is the leading edge. The leading edge seemed to be more reliable because for some runs the max in the fit was off the scale.

Anyway, so you can see why the red line does not dip down and follow the runs near 52350. These runs were just too hard to fit the spe peak.

Pages 15-21 in this presentation may help also.

There is a link to an early version of my scer_peter_cal.kumac in the link in the entry below. The new param file is also included there.

Other kumacs that may help:

This kumac loops over runs and opens the ntuples, just uncomment the kumac you want to execute (scer_peter_cal).
~clasie/work/replay/run_paw_here/calib.kumac

This one fits the spe peak and writes the results to file. It also partially writes a param file for the run.
~clasie/work/replay/kumacs/display/scer_peter_cal.kumac

Fits the leading edge and writes to file.
~clasie/work/replay/kumacs/display/scer_peter_allfit.kumac

A root macro to make the plots with the red line. You can change the values of the red line in the macro. I believe it also partially writes the param files for those runs you change.
~clasie/work/replay/summary_pass0/fscer_peter.C

How to calibrate Peter's gas Cerenkov 01/22/05

Peter's new gas Cerenkov has only one PMT, and the 1st photopeak is hidden in the pedestal peak. This is partly due to noise in the PMT signal. Dave found that by using sceradc1-sceradc2 that this noise is reduced and the photopeak is easier to find. There is only one PMT on the gas cerenkov, and sceradc2 is simply the negative of sceradc1 with some scale factor. The detector signal that makes sceradc2 is from the inverted output of the PMT.

So, there are two signals sig1 and sig2 (sceradc1 and sceradc2 in the sos ntuple). sig2 = alpha * sig1, where alpha is approximately -0.6.

The calibration constant for sig1, call it gamma1 = 1/(spe peak position adc1)
The calibration constant for sig2, call it gamma2 = 1/(spe peak position adc2)
Then if you just use sig1 for calculating the npe, then npe= sig1 * gamma1
Or, if you just use sig2 for calculating the npe, then npe= sig2 * gamma2

If, instead, you use sig1-sig2, then gamma = 1/(spe of peak sig1-sig2)
If you use sig1-sig2 for calculating npe, then npe = (sig1-sig2)*gamma = sig1*gamma - sig2*gamma

The trick is to make replay do this last subtraction. We can do this by:

1) Fitting the spe peak of (sceradc1-sceradc2), call this spe_adc
2) In the scer.param file, set PMT1 calib constant to 1/spe_adc and PMT2 to -1/spe_adc
3) The param file will also need other changes to allow this to work

Here is a copy of one of my param files.
Here is a copy of a kumac that can calibrate the cerenkov that will produce this picture.