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Re: Minutes posted, calib goals requested
Hi Christine,
For the FCAL the Cherenkov distribution is falling like 1 / lambda^2,
so light peaked at the blue end of the spectrum is most realistic. We
will need to come up with a method of quantifying light output and
then we should be able to a produce a measure of what we expect.
I'm not certain that we need individual block scans with a radioactive
source or some other absolute mechanism. I think the most important
things for us are that the calibration source is uniform and time
stable. In addition, it is important that the calibration light
traverse the block to be able to test for radiation damage. I imagine
using online calibration for monitoring relative gains of channels
then doing the absolute energy scaling on physics offline. (We need
to be sure this is a feasible approach.)
Our "default" plan has been to go with what was used in E852. This is
injecting light into a plexiglass sheet that is in front of the
array. If the injection is done in many points around the perimeter,
this produces a relatively uniform source of light for the full
array. A plan like this sounds like it would fit nicely into your
scheme. Of course we will need to better examine/simulate/prototype
this to be sure it does what we want.
Cheers,
Matt
On Apr 22, 2008, at 7:55 AM, Christina Kourkoumeli wrote:
> Dear all,
> that is basically what we are trying to do.Use uniform light to
> illuminate
> many detectors at the same time (or not).The existence of a
> attenuator for
> linerity checking has also to be taken into account.We are
> experimenting
> with the distributor,sources etc
> The real questions though are:wavelength of the output of the
> calorimeter
> (fibers,pb-glass) ,approximate light output expected-so to calibrate
> with
> a comperable source.We would like also to know if the FCAL wants to
> check
> the crystals themseleves ,which would mean a radiactive source scan.
> Cheers,Christine
>> Hi All,
>>
>> This sounds very similar to what PrimEx used to monitor the gains
>> for our calorimeter. Only we used a large LED bundle with an
>> integrating
>> sphere. Same rotating wheel idea though.
>>
>> Regards,
>> -David
>>
>> Alexander Somov wrote:
>>> Dear all,
>>>
>>> I recall at FOPI, GSI, we had a LED trigger to monitor
>>> TOF pmt's performance. The light from LED (as far as I remember
>>> it was led) was sent to a rotating wheel which had different
>>> attenuation steps and was subsequently splitted and distributed to
>>> TOF
>>> plastic paddles.
>>>
>>> The trigger ran quite often (mainly in the beginning of data
>>> taking, as
>>> far as I remember), to monitor linearity/stability.
>>>
>>> Cheers,
>>> Sascha
>>>
>>> P.S. I will check what we had to monitor ECAL pmt's at Hera-B
>>> (there was a monitoring system as well).
>>>
>>>
>>>
>>> On Mon, 21 Apr 2008, Elke-Caroline Aschenauer wrote:
>>>
>>>
>>>> On Mon, 21 Apr 2008, Elton Smith wrote:
>>>>
>>>> Dear all,
>>>>
>>>> just to give a suggestion it would be very important to vary the
>>>> light
>>>> intensity to test and monitor the linearity of the system.
>>>> In hermes we had a system stepping through 5 different light
>>>> intensities.
>>>>
>>>> cheers elke
>>>>
>>>>
>>>>
>>>>> Date: Mon, 21 Apr 2008 12:14:54 -0400 (EDT)
>>>>> From: Elton Smith <elton@jlab.org>
>>>>> To: halld-cal@jlab.org
>>>>> Subject: Minutes posted, calib goals requested
>>>>>
>>>>>
>>>>> HI all,
>>>>>
>>>>> Zisis posted the minutes of today's meeting on the wiki. Thanks!
>>>>> I did
>>>>> add
>>>>> some comments at the end on questions of calibration.
>>>>>
>>>>> We need to clearly identify the goals of the calibration system,
>>>>> so
>>>>> that
>>>>> we build what we need. At the moment, the calibration system is
>>>>> geared
>>>>> toward gain monitoring of pmts. For the next meeting, we would
>>>>> like
>>>>> the
>>>>> Fcal and Bcal and other pmt-based systems to specify what needs
>>>>> to be
>>>>> monitored at to what accuracy. Pavlos suggested that it would
>>>>> also be
>>>>> useful to give an estimate of the signal size (e.g. number of
>>>>> photoelectrons) as well as wavelength response of the detector.
>>>>>
>>>>> Cheers, Elton.
>>>>>
>>>>>
>>>>>
>>>>> Elton Smith
>>>>> Jefferson Lab MS 12H5
>>>>> 12000 Jefferson Ave
>>>>> Suite # 16
>>>>> Newport News, VA 23606
>>>>> elton@jlab.org
>>>>> (757) 269-7625
>>>>> (757) 269-6331 fax
>>>>>
>>>>>
>>>> ( `,_' )+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=
>>>> ) `\ -
>>>> / '. | +
>>>> | `, Elke-Caroline Aschenauer =
>>>> \,_ `-/ -
>>>> ,&&&&&V Jefferson Lab +
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>>>> | | ;--' | Mail: elke@jlab.org Mobil:
>>>> 001-757-256-5224 -
>>>> '--' `-.--.
>>>> | +
>>>> \_ | |---' Tel.:
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>>>> `-._\__/ Fax.: 001-757-269-6331
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>>>>
>>
>> --
>>
>> ------------------------------------------------------------------------
>> David Lawrence Ph.D.
>> Staff Scientist Office: (757)269-5567 [[[ [ [ [
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