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Re: Temperature test FCAL plastic



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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