Re: Npe/MeV from 2-m-long single fiber and 3x3 mm^2 A20H

[Elton Smith <elton@jlab.org>]

HI Andrei,

It would be very useful for you to writeup these results. We will need to
review them in light of other measurements and discuss how to use them
regarding our fiber specs. We should probably plan a meeting to go over
all this once we have background information collected. Next week is a
possibility, but it might be worth waiting till you down at the beginning
of August.

By the way did you make any attenuation length measurements for these
fibers?

Thanks, 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

On Tue, 22 Jul 2008, Andrei Semenov wrote:

>
> Elton and Elke:
>
> Kathryn just finished measurements of number of photoelectrons for 3x3
> mm^2 A20H SiPM (3.0 V overbias) attached to 2-m-long BCF-20 green fiber
> and Sr90 collimated source (located in about 2 m from SiPM).
>
> For the latest shipment of fibers, we got:
>
>  2.68 phe (with Sr90) - 0.88 phe (pedestal contribution) = 1.8 phe
>
> Taking into account that FLUKA simulation gives about 0.183 MeV energy
> deposition from Sr90+Y90 electrons in the fiber, we can conclude that we
> have
>
>  1.8 phe / 0.183 MeV = 9.8 phe/MeV
>
> For the "old" fiber (the shipment that was used to build the Module-2
> prototype), we got:
>
>  (2.36 phe - 0.88 phe) / 0.183 MeV = 8.1 phe/MeV
>
> Again, these numbers are after attenuation in 2-m fiber (that is about
> factor of 2).
>
> Previously (I believe, it was in May 2008), we made a measurement with
> short BCF-20 fiber and 1x1 mm^2 A20H SiPM, and after subtraction of
> pedestal contribution, we had about 2 phe for about 0.17 MeV energy
> deposition (the Sr90 source was not collimated). So the value of interest
> FOR SHORT FIBER was about 2 / 0.17 = 11.6 phe/MeV
> If we assume attenuation in 2-m fiber, that value will be  about factor 2
> smaller (viz., about 5.5 - 5.8 phe/MeV).
>
> The difference between the results for 1-mm A20H SiPM (5.5-5.8 phe/MeV
> after attenuation in 2-m long fiber) and for 3-mm A20H SiPM (8.1 phe/MeV)
> reflects the light loss in between 1-mm-diameter fiber and 1-mm SiPM
> window.
>
> Sincerely,
> Andrei
>
>