[Frost] Moeller measurements for g9a

[Eugene Pasyuk]

I don't think anything is wrong with measurements. Our measurements were 
consistent with other halls with given linac energy, Wien angle setting 
and Mott measurements in the injector.
If there are no changes in the accelerator configuration thera no 
reasons for beam polarization to change. There are a few parameters that 
may affect polarization: linac energy, Wien angle and there is some 
correlation with quantum efficiency of the photo cathode.
The first two were kept constant for given accelerator energy. The 
energy also was constant within certain periods when we intentionally 
changed it. We always did Moeller measurements after they did spot move 
on the cathode or any other changes that may affect polarization.


-Eugene

Michael Dugger wrote, On 03/10/11 00:28:
>
> Eugene,
>
> We have three Moeller measurements that do not have a +/- pair. The runs
> lacking the pairwise measurements are: 55608, 56194, and 56202. It looks
> like these Moeller measurements need to be thrown out.
>
> I still think that the Moeller measurement for run 55552 is probably
> garbage. I do not see how that measurement can be trusted.
>
> -Michael
>
>
>
> On Thu, 10 Mar 2011, Eugene Pasyuk wrote:
>
>> There was some incorrect handling of beam charge asymmetry correction in
>> Moeller measurements at the beginning. For that reason we always did two
>> measurement with opposite Moeller target polarization.
>> If you take an average of the two without sign, the it cancels that
>> problem.  Uncertainties shown there are statistical only. Sytematics of
>> our Moeller polarimeter is believed to be between 2 and 3%
>> If you do this average, than you will see that all three pairs of
>> measurements are consistent with each other within their uncertainties.
>> For the first pair it is 81.9%, for the second one it is 83.9 and for
>> the third one it is 84.4%
>>
>> -Eugene
>>
>> Michael Dugger wrote, On 03/09/11 18:23:
>>>
>>> Hi,
>>>
>>> It looks like there are potential problems with some of the Moeller
>>> measurements.
>>>
>>> Run 55544:
>>> We have 4 measurements taken over a 14 minute time period with
>>> P = 85.228 +/- 1.42
>>> P = -78.523 +/- 1.35
>>> P = -79.150 +/- 1.26
>>> P = 88.700 +/- 1.48
>>>
>>> There is a large change between the polarization values (>   10%). The Two
>>> negative measurements are much lower than is typical and I want to take
>>> these out of the average. Is there a reason not to remove these negative
>>> measurements?
>>>
>>> Run 55552:
>>> We have 2 measurements:
>>> P = 84.167 +/- 1.33
>>> P = -84.725 +/- 1.53
>>>
>>> The first measurement had True Rates = 0.00 and Accidental Rates = 0.00,
>>> also the SLM Current = 0.125 (whereas most all other runs had SLM
>>> Current ~ 6). The second measurement had True Rates = 1002.00 and
>>> Accidental Rates = 3.50, with SLM Current = 1.192. (Typically the True
>>> Rate is about 6000). Moreover, 2C21 X = 0.0 (-4.455) and 2C21 Y = 0.0
>>> (1.560) for the first (second) measurement.  I think that the Moeller
>>> measurements for run 55552 are highly suspect and should be thrown out of
>>> the determination of the polarization average.
>>>
>>> Additional question: How important are the 2C21 X and Y values for the
>>> Moeller measurement?
>>>
>>> Take care,
>>> Michael
>>>
>>> _______________________________________________
>>> Frost mailing list
>>> Frost at jlab.org
>>> https://mailman.jlab.org/mailman/listinfo/frost
>> _______________________________________________
>> Frost mailing list
>> Frost at jlab.org
>> https://mailman.jlab.org/mailman/listinfo/frost
>>
> _______________________________________________
> Frost mailing list
> Frost at jlab.org
> https://mailman.jlab.org/mailman/listinfo/frost