Understanding PDE information

[Elton Smith <elton@jlab.org>]

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