[b1_ana] Fwd: Re: Luminosity monitoring

[J. P. Chen]

-------- Original Message --------
Subject: 	Re: Luminosity monitoring
Date: 	Tue, 11 Jun 2013 10:43:21 -0400
From: 	Mark Pitt <pitt at vt.edu>
To: 	Mark Dalton <dalton at jlab.org>
CC: 	Jian-Ping Chen <jpchen at jlab.org>



Hi Mark,

I certainly agree that 10^{-4} should be achievable in a counting mode
setup, especially if one runs with a slow lock on beam position and
angle at the target like we did during Qweak.

Mark

On 6/11/2013 9:50 AM, Mark Dalton wrote:
> Hi Mark,
>
> Thanks for the quick response.  This is what I concluded too, it would have to be a counting setup.
>
> It seems to me that the leading systematic would be due to changes in the beam trajectory affecting the total rate due to the non-linear form factor.  However, I am sure that a correction can be made from the measured trajectory and the relative rates of the individual lumis.  The statistics would be no problem.  I can't think of a reason why 10^-4 couldn't be achieved.
>
> Mark
>
>
> On Jun 11, 2013, at 9:18 AM, Mark Pitt <pitt at vt.edu> wrote:
>
>> Hi Mark,
>>
>> My quick response is that achieving a stability in the integration mode yield at the 10^{-4} level over a 12 hour period sounds pretty challenging.  That has never really been a design goal for parity-violating electron scattering type "luminosity" monitors.  I think one would be better off going to large enough angles to allow running in counting mode.
>>
>> If it is important to get more information on this, Wade Duvall can look bin the luminosity monitor yields versus time (https://qweak.jlab.org/elog/Analysis+%26+Simulation/920) into 12 hour periods to get a sense of how close the existing monitor/electronics design might be to the 10^{-4} level you mention.
>>
>> Mark
>>
>> On 6/10/2013 6:12 PM, Mark Dalton wrote:
>>> Hi Mark,
>>>
>>> JP wants to use luminosity monitors in a future experiment to monitor the luminosity in a 100 nA polarized target experiment.  This would be needed to help normalize the luminosity over the 12 hour target polarization reversals.  The required accuracy would be 10^-4 for each 12 hour period.
>>>
>>> A naive scaling of the Qweak dslumi rate suggests that the rate might be ~1 MHz, too high to count (hopefully I've done this correctly.)  Although, I guess the angle could be increased until the rate was manageable.  So, the question is, to what level do you think that drifts can be controlled in a set of lumis in the integrating mode?
>>>
>>> Thanks,
>>> Mark
>>>
>>>
>>> -----------------------------------------------
>>> Mark Dalton
>>> Research Scientist
>>> University of Virginia
>>> dalton at jlab.org
>>> mobile: +1 757 849 2929
>>> -----------------------------------------------
>>>
>>>
>>>
>
>
> -----------------------------------------------
> Mark Dalton
> Research Scientist
> University of Virginia
> dalton at jlab.org
> mobile: +1 757 849 2929
> -----------------------------------------------
>
>
>



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