[Halld-cal] We are proceeding with the SiPM contract award

[Curtis A. Meyer]

  Thanks for all the hard work that people put into this. It was an 
extremely important
decision.

   curtis
On 10/15/10 7:50 PM, Elton Smith wrote:
> Dear collaborators,
>
> At our calorimeter working group meeting yesterday we made the final
> decision to use the SiPMs for the readout of the Hall D barrel
> calorimeter. A brief summary of the evaluation is given in Eugene's note
> below. We have instructed the procurement department to prepare the
> necessary paperwork to make the award.
>
> Cheers, Elton.
>
> ---------- Forwarded message ----------
> Date: Thu, 14 Oct 2010 20:52:33 -0400 (EDT)
> From: Eugene Chudakov<gen at jlab.org>
> To: Glenn Young<gyoung at jlab.org>
> Cc: Elton Smith<elton at jlab.org>
> Subject: Hall D SiPM procurements
>
> Dear Glenn,
>
> after deliberation we confirm our commitment to SiPMs for the BCAL
> readout.
>
> Extensive radiation tests performed allow us to evaluate the lifetime
> of the sensors to be at least 9 years, under certain conditions:
>
> 1) Detectors are kept at about 0C while running, but heated to
>       room temperature or higher for some period every year to anneal them;
>
> 2) The experiment is running at high luminosity: 100 MHz of 8.4-9GeV
>       photons on 30cm long LH2 target, effectively for 1/3 of the calendar
>       period;
>
> 3) The neutron flux is 30 Hz/cm^2 (GEANT prediction). [Note that FLUKA
>      simulations predict lower fluxes by approximately 30%].
>
> In 9 calendar years of running the noise from the downstream SiPMs
> is expected to increase by a factor of less than 5, and be still tolerable
> for GlueX. The damage of the upstream sensors is expected to be about 4 times
> lower.
>
> It was agreed that the radiation hardness of SiPMs was acceptable for GlueX.
> Two other issues were brought up:
> a) after-pulsing and its temperature dependence;
> b) the summing scheme.
>
> The issue a) has been investigated. An upper limit for "slow"
> afterpulsing (decay time of about 200ns) was found to be about
> 10%. "Fast" afterpulsing which can be confused with cross-talk is also
> about 10%.  No temperature dependence of this effects have been
> observed. Such level of afterpulsing is acceptable for the experiment.
>
> We plan to address b) in parallel to moving forward with the SiPM
> procurement, as it is an optimization of their use in our detector.
>
> Regards,
> Eugene
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>


-- 
Prof. Curtis A. Meyer		Department of Physics
Phone:	(412) 268-2745		Carnegie Mellon University
Fax:	(412) 681-0648		Pittsburgh PA 15213-3890
cmeyer at ernest.phys.cmu.edu	http://www.curtismeyer.com/