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Re: [Collab] Continuation of Systematics Teleconf later today: 9:30pm; 3:30 pm; 2:30 pm
Jim,
The MPV plotted modulo fill period plot is the way we always talked
about checking gain once WFDs were onboard. The team is making that plot
now. There are recent posts of gain vs average rate that certainly
indicate thta this might be a problem, but we don't yet know the
relevant short-term time scale of gain stability until this plot is
obtained. We do not need LEDs here (nor would they be appropriate or as
good as the data itself, since here we have a MIP to grab).
On timing, we planned to do this kind of thing AFTER the muon data
in a controlled manner. It would have been nice to do it with beam, but
I don't think we can get that to fly just now ... we might let the local
group chew on it though and perhaps it isn't too hard. Here we do want
the LEDs to fire over times in the fill period and we then plot
difference to reference times versus time in period. This shold work
quite well and in g-2 it obtained very good timing stability (there we
used the laser of course, but it's the same idea).
Summary. MPV vs fill is happening (it's not a test, it's just
analysis).
LED mixed in should be discussed.
Thanks,
Dave
James Miller wrote:
>
> Dear All,
> I have a couple of suggestions on sytematic studies which I don't think
> have been mentioned.
> -Jim
>
>
> 1) Gain stability tests across the measurement time interval.
> If the PMT gains shift, this will cause a shift in transit time
> in the PMT and will lead to a timing error. Also, a gain shift will
> shift the
> threshold a bit, and may affect efficiency if the threshold is
> not low enough. How might this be monitored? Some suggestions:
>
> a) Fire the LED at a constant rate, at a fixed early time relative
> to injection.
> Cancel the preceding muon injection every other time that the LED fires.
> Compare pulse height AND timing when there was a muon injection
> immediately
> preceding to when there was not. Repeat this for a range of times,
> middle and late times, and also during the injection period.
> The calibration will obviously work best if the jitter in the pulse
> height and timing of the LEDs is small.
>
> b) Try to use the MIP peak to monitor the gain.
> A potential difficulty is that if the ratio of: events with two particles
> passing through the tiles to the number with one particle- changes for
> some reason early to late-
> This will change the shape of the MIP peak and perhaps make it difficult
> to use for gain studies. Of course, one may well ask why this ratio
> would change- if it does this may be a sign of some background problem.
>
> c) Fire the LEDs at early and late times and compare. One possibility is
> to run the LEDs at a constant rate, synchronized with the injection.
> The first pulse appears at the beginning of the spectrum, the next
> in the center, and the last at the end, then keep rotating. This would
> require
> some careful timing work.
> Another option is to let the LED pulses map out the measurement time in
> random fashion. This would probably require more LED pulses to get a good
> calibration, however. Whatever the scheme, the LED must be triggered
> at an
> even rate so that there is no correlation between the LED pulse height
> and
> the time of firing relative to muon injection.
>
>
> 2) Timing stability tests across the measurement time interval.
> Suggestions on how this might be done:
>
> a) Do 1a).
>
> b) Fire a single LED at the center of the ball. Would it be out of the
> question
> to cut a small hole in the light-tight tape on each tile so that they
> can see the LED? If this does not work for the outer tile, then the
> stability of the outer
> tile timing can be done relative to the inner tile using regular events.
> The time pattern for firing the LED could be as in 1c) above.
>
> 3) Do some runs with data taking enabled during injection. Do timing
> and gain tests as in 1) and 2) above. This will give us information
> about the
> time structure of injection and also the behavior of the gains at the
> higher rates during injection.
>
>
>
> On Fri, 14 Oct 2005, David W Hertzog wrote:
>
>> Folks,
>> We all know we got knocked off the Gizmo. I talked to the PSI
>> group and they are hungry. They would like to CONTINUE the systematics
>> discussion at 9:30 their time.
>>
>> PSI: 930 PM
>> East: 3:30 pm
>> Central: 2:30 pm
>> West: even earlier.
>>
>> Please join in if you can to complete the list. Otherwise, it's
>> Saturday and I fear far fewer people will be available then (or on
>> Sunday).
>>
>> To recap:
>> 1) pileup discussion completed
>> rate variation is only real knob; detector gains are
>> appropriately set
>> 2) flat background ... early and late in fill
>> Ron's calc plus PW et al measurements indicate "no" problem from
>> extinction
>> Introduce Fill Skipper circuit later at 1/20 to check our own
>> electronics effects (hopefully, none)
>> 3) uSR.
>> a) Okay for 99.9% of stops in AK3 (we believe). Discussion to
>> be held is whether and how much dc running to do (at relatively high
>> rate) in order to get the shape of the precession as we have done
>> before. Not much enthusiasm on this side for rotating AK3 Up/Down.
>> b) stops in EMC. Put in thin plastic and run for 3 - 5 x as
>> many mu stops as predicted by integral of our run x 0.001 expected
>> stopping fraction. (probably 1 - 3 hours)
>> c) stops in intermediate "helium" region. Investigate argon
>> substitute so that all stops occur in the gas region and the same
>> essential fraction of muonium is formed (i.e., most of the stops). Same
>> calculation as in b) for amount of time 0.001 x our good stops.
>>
>> 4) Other discussion not had by all:
>> a) lower momentum...thought to be less controllable and
>> therefore not sure what we learn ... don't do this
>> b) silver / sulfur TBD
>>
>> 5) A.0. ideas ?
>>
>> Talk to you later.
>> Daave
>>
>>
>>
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>>
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