[b1_ana] draft proposal

[J. P. Chen]

Hi, Oscar,

Good that the field stays the same. This eliminate one of
my worries.

Thanks.

Jian-ping


On 5/3/2013 3:56 PM, O. A. Rondon wrote:
> Hi JP,
>
> The field will always be ON. The polarization will be removed by turning
> off the microwaves and if needed, dumping the LHe in the nose. Of
> course, the nose will be refilled before taking the unpolarized data.
> There is no acceptance change from pol to unpol.
>
> If we do need to turn the field off, it can be reproduced to better than
> 10E-4, per NMR.
>
> Cheers,
>
> Oscar
>
> J. P. Chen wrote:
>> Hi, Oscar and Karl,
>>
>> I just saw Alexandre and asked him to take a look at our data
>> (Pengjia probably would be better, but he is in China and time
>> zone makes it difficult to get him now).
>>
>> One more systematics: The acceptance will change slightly with
>> the target magnet field. Since the scatter electron path will be
>> not along the target field (longitudinal) direction, the spectrometer
>> will be the regular (S)HMS+ target field. The effect is small for
>> small angle (but probably not negligible) and increases for large
>> angle. This should be looked into.
>>
>> Cheers.
>>
>> Jian-ping
>>
>>
>> On 5/3/2013 2:49 PM, O. A. Rondon wrote:
>>> Hi JP,
>>>
>>> That is good news. I think we should put some kind of reference or quote
>>> some numbers in the proposal, so the TAC and PAC know about it, although
>>> the TAC may know already.
>>>
>>> Cheers,
>>>
>>> Oscar
>>>
>>> J. P. Chen wrote:
>>>> Oscar,
>>>>
>>>> The BCM/BPM for low current readout was re-designed for g2p
>>>> (and also used for QWeak, so it is available in Hall C).
>>>> The signal (with noise ratio suppression) was designed to reach
>>>> 1% in significantly less than 1s (we wanted to each helicity at 1KHz).
>>>> If you want, I can ask our student, Pengjia Zhu and/or Hall A staff
>>>> Alexandre Camsonne to give you results.
>>>> The absolute calibration is done with the Tungsten calorimeter, which
>>>> was designed for 1% precision. We achieved probably slightly worse,
>>>> at 1-2% level.
>>>>
>>>> Cheers.
>>>>
>>>> Jian-ping
>>>>
>>>>
>>>> On 5/3/2013 1:54 PM, O. A. Rondon wrote:
>>>>> Hi JP,
>>>>>
>>>>> J. P. Chen wrote:
>>>>>> 2) For charge determination, it is confusing. Should not say 5%.
>>>>>> With the
>>>>>> calibration of Tungsten calorimeter, the BCM will have an absolute
>>>>>> uncertainty
>>>>>> at the level of 1-2%, and relative uncertainty (from one target
>>>>>> polarization period
>>>>>> to next period) should be better than 1%, depending on the
>>>>>> linearity of the
>>>>>> BCM response.
>>>>>>
>>>>> We need to be careful here. Since this is a Hall C proposal, Dave Mack
>>>>> will tell you that he cannot calibrate the low current BCM's to better
>>>>> than 5% (5 nA at 100 nA). See this hclog entry
>>>>> https://hallcweb.jlab.org/hclog/0902_archive/090211140308.html
>>>>>
>>>>> I think the 1% estimate is reasonable, but it involves integrating over
>>>>> time. I believe the charge monitors read every 2s in Hall C. So we'll
>>>>> have to accumulate about 25 readings, or one minute, for a 1% delta
>>>>> Q/Q.
>>>>>
>>>>> I'm sure the Hall A calorimeter will help, but how long does it need to
>>>>> integrate at 100 nA for a 1% error?
>>>>>
>>>>> In any case, we need to be precise about this for the TAC.
>>>>>
>>>>> Cheers,
>>>>>
>>>>> Oscar
>>>>>
>>>>>
>>>>>
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>>