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Re: Minutes posted, calib goals requested
Matt,
let me add a couple of comments.
We used your monitoring method with a lucite sheet in front of a 700-block
lead glass calorimeter (RCS experiment in Hall A) and it worked
quite well. The same is now used with a larger calorimeter of Gep-3
in Hall C.
On the other hand, the radiation damage could not be corrected
with the help of this system. Both in Hall A and C the damage was
mostly frontal, absorbing more monitoring light than the shower
light. In Hall D it might be different, but I would better rely
on a frequent re-calibration of FCAL with physics signals, as with the pi0 mass.
Still, monitoring is very useful for various other reasons.
For BCAL, the damage is probably not an issue, and one can indeed
monitor the gains.
Eugene
------------------------------------------------------
Eugene Chudakov
http://www.jlab.org/~gen
phone (757) 269 6959 fax (757) 269 5703
Thomas Jefferson National Accelerator Facility
12000 Jefferson Ave, Newport News, VA 23606 USA
On Thu, 24 Apr 2008, Matthew Shepherd wrote:
>
> 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 +
> >>>> ,&&&&&&&&: HALL-D 12C / F381 121-A Atlantic Avenue =
> >>>> ,&&&&&&&&&&; Suite 8 Hampton, VA 23664 -
> >>>> | |&&&&&&&;\ 12000 Jefferson Ave +
> >>>> | | :_) _ Newport News, VA 23606 Tel.:
> >>>> 001-757-224-1216 =
> >>>> | | ;--' | Mail: elke@jlab.org Mobil:
> >>>> 001-757-256-5224 -
> >>>> '--' `-.--.
> >>>> | +
> >>>> \_ | |---' Tel.:
> >>>> 001-757-269-5352 =
> >>>> `-._\__/ Fax.: 001-757-269-6331
> >>>> -
> >>>> +=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-
> >>>> +=-+=-+
> >>>>
> >>>>
> >>
> >> --
> >>
> >> ------------------------------------------------------------------------
> >> David Lawrence Ph.D.
> >> Staff Scientist Office: (757)269-5567 [[[ [ [ [
> >> Jefferson Lab Pager: (757)584-5567 [ [ [ [ [ [
> >> http://www.jlab.org/~davidl davidl@jlab.org
> >> [[[ [[ [[ [[[
> >> ------------------------------------------------------------------------
> >>
> >>
> >>
> >
> >
>
>