Re: Understanding PDE information

[Elke-Caroline Aschenauer <elke@jlab.org>]

On Wed, 18 Apr 2007, Richard Jones wrote:

Dear Richard,

I think we have to be careful again comparing numbers.
the PDE depends on the breakdown voltage (carls talk page 11 not counting
overlays), which you have taken care of in your comparision, but it also
depends on the fill factor (zisis talk page 5 and 7)

PDE = Q_E*alpha*F

so what is the fill factor for your Photonique SiPMTs and than you have
2mm x 2mm active area and the ones from carl a 1mm x 1mm, I think we
should also account for this, like Carl does in his eq on page 9.

Maybe I'm wrong.

Cheers elke





> Date: Wed, 18 Apr 2007 15:41:10 -0400
> From: Richard Jones <richard.t.jones@uconn.edu>
> To: Elton Smith <elton@jlab.org>
> Cc: halld-cal@jlab.org
> Subject: Re: Understanding PDE information
>
> Elton and all,
>
> I have created a page on the wiki (under main page, link "Silicon
> Photomultiplier Performance") to record this conversation, because I think
> things are starting to become clearer.  Please look at my new section added at
> the end, in particular my final paragraph quoted below.
>
>       If one wants to compare the Sensl and Photonique devices, it is
>       only fair to compare them under the same operating conditions: 1.5V
>       over threshold. From Carl's measurements, the actual efficiency of
>       the Sensl C20 device is about 5% [he measured 4.4% at 1.2V
>       overbias, so I round up to 5% at 1.5V] compared with 24% for the
>       2 mm Photonique device under the same conditions. The factor of 5
>       in PDE between the Sensl and Photonique devices can only be
>       explained by the supposition that Sensl never intended their C20
>       device to be considered for scintillator readout.  Nor should 12% @
>       500 nm be considered acceptable, given that commercial devices from
>       Photonique exist with a factor 2 larger PDE.  We have heard that
>       CPTA technology is primitive, and that may be so, but then it
>       should not be difficult to reproduce their performance in these new
>       devices from Sensl.
>
> Richard Jones
>
>
> Elton Smith wrote:
>
>  Understanding PDE information
> -----------------------------
>
> Elke, Carl and I went over the information we have on the SiPM photon detection efficiency. We believe now that we understand the various pieces of information and they are consistent. Let me start with the first two rows of Zisis talk at the collaboration meeting (p 5, 1x1 mm2 SiPM parameters)
>
> Design  # Pixels DR @ 4V  Fill Factor  Dark Current   Peak PDE
>                   (MHz)      (%)         (muA)         @4V (%)
> C20        620     2.9       17           -2            8.5
> A20L       920     5.9       34           -3           17.0
>
> >From Carl's talk (p 37, QE and PDE), you can determine the ratio of the PDE@4V to PDE@1.2V, which was the chosen operating point for Carl's measurements. The ratio is approximately 2. Therefore, the expected PDE@1.2V for the C20 is about 8.5/2=4.2. Carl measured it to be 4.4+/-0.5.
>
> -> Conclusion: At the operating point of about 1.2 V above breakdown, the PDE for the C20 (1mm2, 17% fill factor) SiPM is about 4.5%.
>
> So far, our experience tells us that the practical operating point for these devices is about 1V over voltage. As the voltage above the breakdown increases further signal to noise decreases and even pulse shape become distorted.
>
> If we use the A20L instead of the C20, the PDE will double, but so will the dark rate. We believe that the estimated 110MHz rate for the 4x4 array is for the 1V over voltage, thereby consistent with a PDE of 4.5%.
>
> Comments are welcome. In particular, it would be useful for Richard to remind us the conditions that were used for his measurements of the PDE for the 1x1 and 2x2 mm2 SiPMs.
>
> Cheers, Elton.
>
> Elton Smith
> Jefferson Lab MS 12H5
> 12000 Jefferson Ave
> Suite # 16
> Newport News, VA 23606
> elton@jlab.org
> (757) 269-7625
>
>
>
>
>
>

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