[d2n-analysis-talk] TDC Thresholds

[Brad Sawatzky]

Looks good.  Thanks.

Now, can you find out how many TDC hits per event there are per PMT for
this run/dataset?

Are the data-sets the same for both of your plots?  ADC:TDC seems to
have 2.7M events, but the TDC only plots have 0.47M events.  Does that
make sense?

Based on these plots it would seem that imposing an ADC_cer cut > 300
(ie. > 1.5 p.e.) should make the TDC cut largely redundant(?)

Also, maybe I'm imagining it, but there seems to be hints of a band
around TDC channel 200--300 in the 2D spectra.  That would be ~600ns
after the prompt peak.  After-pulsing maybe?  If so, then it looks like
the THaCerenkov class is reporting the hit closest to the TDC stop.  The
1877s use a LIFO (last-in first-out) model to store hits in the buffer,
so that would be consistent with the code in THaCherenkov.C that uses
hit[0] only...

Apply the attached patch and see if the TDC spectra cleans up much.

-- Brad

On Wed, 20 Jan 2010, David Flay wrote:

> Here are the TDC thresholds you were interested in seeing.
> 
> This is done for p = 1.13 GeV, 5-pass.
> 
> Attached are the TDC plots, and ADC vs. TDC plots.  I've drawn lines in
> the latter plot so you can see where I got the threshold value from.
> 
> Also attached is a table of the results of the thresholds.
> 
> Dave

-- 
Brad Sawatzky, PhD <brads at jlab.org>  -<>-  Jefferson Lab / Hall C / C111
  Ph: 757-269-5947 -<>- Pager: 757-584-5947 -<>- Fax: 757-269-7848
The most exciting phrase to hear in science, the one that heralds new
  discoveries, is not "Eureka!" but "That's funny..."   -- Isaac Asimov
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