[Rich] DREAM tests

[Marco Mirazita]

Dear Sergey,
thanks for your comments, I'll try to answer but first of all let me point 
out why we made these tests.
We knew that the coupling of DREAM with a PMT is not optimal, in fact 
for example we had to design an attenuator board to fit the charge in
the DREAM dynamical range. However, the DREAM presents for us some 
advantage because, being used in CLAS12 for the MicroMega readout, it 
would require minimal work to be integrated in the CLAS12 DAQ. So then, 
Irakli and Pascal have been so nice to let us use their setup and we
decided it was worth to make some test.


On Fri, 24 Jan 2014, Serguei Kuleshov wrote:

>               Dear All,
> I am very surprised with the terminology and an exotic method for the timing measurement in this report.

I'm sorry if the terminology is not the right one and if could lead to 
misunderstandings, I'm not an expert of tests of electronics. Please let 
me know if something in the document should be rephrased or made more 
clear.

> I think that statements "we estimate an intrinsic DREAM time resolution of the order of 1.2ns" and then "This is not sufficient for the RICH application, that requires resolutions below 1ns" are a little bit strange.

I don't understand why it is strange. For the RICH we want time resolution 
definitely below 1ns, we measured with DREAM ~1.2ns with some indication 
that values close to 1ns could be reached. This latter is just a 
speculation, I might be too optimistic or too pessimistic, but we don't 
have measurements to be more quantitative.

> There is very simple and standard method to measure "intrinsic time resolution" with the charge injection. And I would recommend to use this method.
> Ideally the time resolution or the jitter of a chip depends from the noise of the chip, and the noise depends from input capacitance on the chip. I think that somebody has done such measurements for DREAM chip.
> And the question is about a combination of MAPMT and the chip. If a realistic composition of the PMT anode with a connection to the chip provides too large input capacitance for DREAM chip it could be a reason for rejection of this chip from the consideration.

The goal of the tests was to measure the time resolution in conditions as 
close as possible to the experimental ones, which means with a PMT 
attached to DREAM, in the single photoelectron regime and with an 
external trigger. I know that measurements can be done with the charge
injector, but this is not what we will have in out RICH.

Best regards,
Marco

>
>
> Sergey Kuleshov
>
> ________________________________________
> From: rich-bounces at jlab.org [rich-bounces at jlab.org] on behalf of Marco Mirazita [Marco.Mirazita at lnf.infn.it]
> Sent: 21 January 2014 12:24
> To: rich at jlab.org
> Subject: [Rich] DREAM tests
>
> Hi all,
> based on the results I showed at the RICH meeting of a couple of weeks
> ago, I wrote a report on our tests of the DREAM, you can find it in the
> RICH wiki page:
> https://clasweb.jlab.org/wiki/index.php/RICH_Technical_Notes
> Comments are welcome.
> Marco
>
> _______________________________________________
> Rich mailing list
> Rich at jlab.org
> https://mailman.jlab.org/mailman/listinfo/rich
>
>