Re: Temperature test FCAL plastic

[Matthew Shepherd <mashephe@indiana.edu>]

Hi Elke,

Were your HERMES bases conventional resistor bases?  The current  
through the FEU bases when live might be a little less due to lower  
gain.  Besides this, the CW bases generate a factor of 10 less heat  
than the equivalent resistor base.  The bases were engineered by Paul  
Smith precisely for this tight packing application.  Beni should be  
able to answer these other questions -- I believe the setup he was  
using had an active current meter.

-Matt


On Jan 29, 2008, at 6:41 PM, 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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