Re: Number of p.e. and SiPM requirements

[George Lolos <George.Lolos@uregina.ca>]

Hi Elton:

I will go over your numbers carefully and discuss them in detail with 
Zisis and Andrei who has done so much work on the subject.  While we 
have extracted the number of P.E.'s from a combination of blue and green 
SciFi's read out by blue PMT's, now we're extracting the numbers with 
green SciFi's and green sensitive PMT's on loan from the UofA.  So, 
within a week or so we will have further info and I will report them 
during the meeting next week and we can meet separately and review the 
subject.  However, the number that will really count in the end is what 
we'll get with green SciFi's and the SiPM-arrays that will give us more 
reliable results because we have a well mapped PDE curve for the SiPM's.

More later,

Cheers,

George

Elton Smith wrote:

>Hi George,
>
>I have been reviewing the SensL proposal for further development of the
>SiPM and realize that we need to come to grips with the observed number of
>photoelectrons. This is not a new concern, it is a reflection of the fact
>that the measured number of p.e. for cosmic-rays is lower than what we had
>originally expected. However, the specifications for the SiPMs are based
>on the earlier numbers (GlueX-doc-795), and these are directing future
>effort.
>
>Let me summarize the status as I see it. Please set me straight if I am
>missing anything:
>
>1. Measured number of p.e. for a minimum ionizing particle is 22-25 per
>4 cm of readout, or ~ 6p.e./cm. For normal incident muon (radially in the
>detector), this corresponds to 6p.e./cm x 22.5 cm = 135 p.e.
>See http://www.jlab.org/ccc/mail_archives/HALLD/halld-cal/msg00288.html
>
>2. The number used in GlueX-doc-795 is 863 p.e. (See Table 2, row 6 col
>4). This corresponds to 5082 p.e./GeV x 0.17 GeV/muon = 863 p.e. The basis
>for the 42,279/GeVx0.12 comes from GlueX-doc-808, p. 5.
>
>-> The measured number is lower than the original expectation by 863/135 =
>6.4. If we use the measured number, then this is equivalent to using PDE
>valueswhich are 6.4 times SMALLER than those assumed in GlueX-doc-795.
>This has substantial impact on the resolution as well as implications for
>specifications on the readout.
>
>Am I missing anything?
>
>Thanks, Elton.
>
>
>Elton Smith
>Jefferson Lab MS 12H5
>12000 Jefferson Ave
>Suite # 16
>Newport News, VA 23606
>elton@jlab.org
>(757) 269-7625
>
>  
>