[d2n-analysis-talk] BB cer ped shifts

[MATTHEW R POSIK]

Hi Brad,

   Here are the peds from an LED and a fivepass run with ~8uA current, both
taken on the 1881 ADC.

LED beam line side:
http://jlab.org/~posik/d2n/BB/cer/peds/led/1829.png

LED RHRS side:
http://jlab.org/~posik/d2n/BB/cer/peds/led/1834.png

fivepass beam line side:
http://jlab.org/~posik/d2n/BB/cer/peds/fivepass/1849_beam.png

fivepass rhrs side:
http://jlab.org/~posik/d2n/BB/cer/peds/fivepass/1849_RHRS.png

I will get working looking at the peds over all hardware changes as you
suggested in the previous email. Been a little slow with the APS talk.

-matt

On Mon, Feb 8, 2010 at 11:16 AM, Brad Sawatzky <brads at jlab.org> wrote:

> On Fri, 05 Feb 2010, posik at jlab.org wrote:
>
> > So I looked at the Big bite cerenkov ped location for run 1849, which
> > is a He3 production run at ~8-9 uA.  I did this by plotting the ADC
> > for the first 100,000 events and making a T8 trigger cut (pulser)
> > which is "(DBB.evtypebits&1<<8)==(1<<8)". Using this cut, I then fit a
> > Gaussian to the ped and extract the mean. Then I compared these "beam
> > on" ped positions with those of the LED runs. Here is a list of the
> > mean ped values:
> [ . . . ]
>
> Interesting.  Good work!  Please generate a couple of slides showing the
> LED-run pedestals overlaid on top of the beam pedestals for the 20 PMTs.
> I'd like to see how the characteristics of the pedestal change.
>
> Also, we need to determine if the pedestals change between the LED runs
> and what you show here is due to beam loading or something else.  Look
> for a cosmics/no-beam run in this period and redo your pedestal checks
> (and generate the above plots) for a beam-off run and an adjacent
> beam-on run.
>
> If you can find appropriate runs, here's what would be ideal:
>  A) peds with beam-off (cosmics or rest run)
>  B) peds at low current (1 uA or so)
>  C) peds at full current
> Having A-C for each hardware configuration (v792, 1881, with pre-amp on
> beamline side, without pre-amp on beamline side).  would help
> disentangle configuration from beam-loading effects.
>
> > You can see that there is a significant ped drift with the beam line
> > side pmts (1-10) from the LED peds, and the RHRS side (pmts 11-20) are
> > fairly close to the LED peds. I also calculated the rates for this
> > run, using TDC hits and cutting away beam trips, here are the results:
> [ . . . ]
> Rate for cell 05:    0.9315 MHz
> ------------------------
> Rate for cell 06:    0.4108 MHz
> ------------------------
> Rate for cell 07:    1.0756 MHz
> ------------------------
> Rate for cell 08:    0.7693 MHz
> ------------------------
> Rate for cell 09:    0.9036 MHz
> ------------------------
> Rate for cell 10:    0.7387 MHz
> ------------------------
> Rate for cell 11:    0.1087 MHz
> ------------------------
> Rate for cell 12:    0.0224 MHz
> ------------------------
> Rate for cell 13:    0.0802 MHz
> ------------------------
> Rate for cell 14:    0.0816 MHz
> [ . . . ]
>
> > pmt 6 and 12 seem to be much lower than the rest of the pmts on that
> > side.  This was also seen in run 1848.
>
> There was some Pb shielding installed at the beamline height on the
> beamline side.  The shadow should have been cast over more than PMTs 6,
> 12 though...  I'm not sure what's going on there.
>
> I don't think I beleive the 20kHz number associated with cell 12.
> There's either a bug in the calculation, or the hardware is doing
> something really strange.
>
> > Using these ped values as well as mirror and TDC cuts I plotted the
> > ADC for mirror 3 (1849_mir3_pe.png) and 12 (1849_mir12_pe.png) for run
> > 1849.  Please note that the x-axis is in #p.e. The red histo is the
> > signal and blue histo is an off mirror background. Mirror 3 shows
> > about 4-6 p.e and mirror 12 7-8 p.e. I am thinking about including
> > these two images in my APS talk.
>
> Using PMT 12 as a 'representative' histogram probably isn't a good idea.
> What do 11 and 13 look like?
>
> > So since the ped were stable with beam on/off with the v792 ADC, then
> > that means the 1881 ADC is responsible for the ped shift. I assume
> > then is has to do with the electronic differences between the 792 and
> > 1881. I was wondering what exactly this difference is that results in
> > the ped location shifting with beam on/off?
>
> I did the with/without beam pedestal stability test before Transversity.
> All I can say is that it was stable then.  That was with the v792s and
> with no extra amplification on the beamline side PMTs...
>
> I suspect/hope that the difference you see is due to some other change
> that happened at the same time.  The tests mentioned at the top of the
> email should clarify things.
>
> -- Brad
>
> --
> 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
> _______________________________________________
> d2n-analysis-talk mailing list
> d2n-analysis-talk at jlab.org
> https://mailman.jlab.org/mailman/listinfo/d2n-analysis-talk
>



-- 
Matthew Posik
Email: posik at temple.edu
Temple University Physics Dept.
Office: BA-319
Office #:  215-204-1331
-------------- next part --------------
An HTML attachment was scrubbed...
URL: https://mailman.jlab.org/pipermail/d2n-analysis-talk/attachments/20100210/8ef4888b/attachment.html