sPHENIX discussion of electronics

[eric mannel <mannel AT bnl.gov>]

To follow up on last weeks discussion, I asked our Hamamatsu rep Ardavan some questions.  I tried to summarize my understandingof both the e-mails and phone discussions in an earlier e-mai, but here are his written comments for the record.

The document that he refers to is the one that I put in DocDB and pointed you to in the last e-mail.

It seems Hamamatsu Japan has simplified S12572-015P-02’s Vop definition to Vbr + 4V. Perhaps, we at Hamamatsu forgot to inform you of this change in Vop’s definition; if so, my apologies on behalf of Hamamatsu for that! Based on this simplified definition, using the Vop data from the delivery sheets accompanying S12572-015P-02 shipments to investigate correlation with gain could potentially result in inconsistent gain vs. Vbias patterns to be observed.

As for how Hamamatsu Japan measures Vbr as part of outgoing inspection testing during mass production, please see section 4-2 on pages 38-40 of Hamamatsu’s MPPC technical note by following this link: https://www.hamamatsu.com/resources/pdf/ssd/mppc_kapd9005e.pdf

If you analyze the population distribution data with the new understanding of the above Vop definition and Vbr measurement method, would any significant lot-to-lot gain variations persist?

I should make an important clarification to my last email: as you, Craig, Sean, and I had discussed many times before, S12572-015P-02’s typical gain at Vop (OV = 4V) is indeed 2.3E5; that is still considered the gain that a typical device would attain when biased at “Vop” or OV = 4V.

So, in that sense, there’s been no change whatsoever…

However, with Vop defined as OV = 4V, its value should be obtained by measuring Vbr rather than gain (though, Vbr and the gain vs. voltage relationship are closely related).  

My question to you is: Do the inconsistencies that you’re reporting get resolved when Vop is assessed in terms of OV = 4V rather than Gain = 2.3E5?

To measure MPPC gain, Hamamatsu Japan uses the method described in Section 4-1 (see pages 36-38) of the MPPC technical note: https://www.hamamatsu.com/resources/pdf/ssd/mppc_kapd9005e.pdf

That same method is also used to measure Vbr on a small scale, but in mass production, Vbr is measured using the method explained in Section 4-2 (pages 38-40).

-- 
Eric Mannel, Ph.D.
PHENIX Group 
Dept of Physics
Brookhaven National Lab.
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