[Rich] H12700 review

[Marco Contalbrigo]

Dear Andrey,
thank you for this nice and interesting piece of work.
We may discuss it this Friday at the RICH meeting, anyway
I anticipate few comments.

If this report is intended (also) for Hamamatsu I guess
we should pay attention on completeness of information
and motivation of the assumptions (model). This is
important since your conclusions are somewhat in
contradiction with Hamamatsu claim the new dynode
structure is optimized for SPE.

In this sense, I would say the report needs at
minimum:
- page number
- a slide with the fitting formula/procedure
- an explanation/motivation of Pavel's model

but I think it calls also for 
- a reference SPE analysis where only the center of
the pixel is illuminated or a SPE analysis as a
function of the laser spot within the pixel
- a cross-talk analysis

Indeed your conclusions heavily depends on the
funny shape of the H12700 SPE signal. Thus one
immediate question is how much this shape
changes within the pixel and/or if it is
affected by the cross-talk.

I find odd that the H12700 gain is independent of HV
(pag.8). Do you have an explanation for this ?

On page 11, where the SPE signal is shown,
are the dotted vertical lines the 5sigma cut ?
How can be fit a (small, but evident for H8500) SPE
peak under the pedestal ?

Thnaks again, Marco.

On Tue, 19 Aug 2014, Andrey Kim wrote:

> Dear collaborators,
> Please find H12700-H8500 comparison review attached.
> "Short" summary: H12700 is still better than H8500 due to the higher photocathode
> quantum efficiency. The nearly uniform illumination of pixel shows that SPE
> spectrum is not as good as it was anticipated. It has more complicated structure
> than H8500. The structure was described using Pavel Degtiarenko's model, and using
> his model's fit results the collection efficiency was estimated for both MAPMT
> types. The H8500 demonstrated higher collection efficiency than H12700 (unexpected
> and rather saddening behaviour). Fortunately, H12700 has higher photocathode
> quantum efficiency, and it was determinative factor in H12700 superiority.
> Please note that separation of quantum and collection efficiencies is possible
> within model framework only. However, the global efficiency (decisive criteria) is
> model independent as it is the fraction of events with signal over pedestal's 5
> sigma (assuming, of course, that light source is stable and constant).
> Any comments, suggestions or corrections are welcome!
> Thank you!
> 
>