Re: Temperature test FCAL plastic

[beni zihlmann <bzihlman@indiana.edu>]

Hi Elke,
to test the air convection cooling I covered the whole assembly with
a garbage bin so that almost no air exchange can happen.
The PMTs are wrapped in black plastic but there is enough light leakage
that I see signals at the base output. the bases use about 0.1 Watt but 
I have
not measurement of the actual current drawn by the bases.
I can repeat the test trying to make the light leak bigger.

cheers,
Beni


Elke-Caroline Aschenauer wrote:
> On Tue, 29 Jan 2008, beni zihlmann wrote:
>
> Dear Beni,
>
> thanks for the results. But honestly is that what you would naively
> expect. I can believe that you don't see a worrying increase but to see no
> difference is from my expectation impossible. Beni remember the 2000 tubes
> of the rich caused the soft steel matrix to increase by 2-3 degree over some time
> like a day or so. In your case the bases are in air, so there is some
> convection cooling going on.
>
> What is the current this bases draw, I guess the measurement was done with
> the cockroft walton ones, correct. Have you actually done this
> measurements also under rate. so with a source in front of the PMTs or a
> light source or ....
>
> Cheers elke
>
>
>
>
>   
>> Date: Tue, 29 Jan 2008 09:31:39 -0500
>> From: beni zihlmann <bzihlman@indiana.edu>
>> To: Tim Whitlatch <whitey@jlab.org>, Matthew Shepherd <mashephe@indiana.edu>,
>>      Elke-Caroline Aschenauer <elke@jlab.org>, Elton Smith <elton@jlab.org>
>> Subject: Temperature test FCAL plastic
>>
>> Hi Tim,
>> The temperature test I did came out negative. Meaning I did not
>> sea any measurable temperature increase while running 4 PMTs
>> at 1800 Volts.
>>
>> 4 holes are drilled into the high density plastic. the plastic is about
>> 16cm thick. The bases stick out in the back of the plastic by 5 cm
>> the PMTs stick out in the front of the plastic by about 6 cm.
>> The BASES are powered up to 1800 Volts and signals are seen on the
>> PMTs. (The PMTs are covered with black plastic to shield light.)
>> A temperature is inserted into the hole and located next to a PMT
>> such that it is separated by the thin wall of plastic from the neighbouring
>> PMT. At some point a cover was put over the whole assembly to prevent
>> air exchange (cooling). In all cases over a time period of 1 week I did not
>> see any temperature change withing the accuracy of the measurement.
>>
>> I think the conclusion is that high density plastic is a viable option.
>>
>> cheers,
>> Beni
>>
>>     
>
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