Re: pmt glass radiation

From: Janet Conrad (
Date: Wed Jun 01 2005 - 10:24:42 CDT

Hi Joe,

If I gave you a tube, with base, dipped in the protective enamel, could
you send it to
your low backgorund counting facility and have them measure the rates
and what is coming out?
Because there is more than just the tube -- there is the basis, the
protective coating, etc.
It would be nice to know where we stand with the whole package.


Matthew Worcester wrote:

> Hi Joe,
> Thanks again for the talk. I think the background must scale much
> more like the amount of material. So if you assume equal density of
> the glass, we should scale by volume. Assuming the 5912 is a 5 mm
> thick sphere and that the 2" tube is also 5 mm thick I get about 6
> Bq/pmt for the 8" tube, which is ballpark.
> Cheers,
> Matt
> On Tue, 31 May 2005, Joseph Formaggio wrote:
>> Dear Matt,
>> Forgive me if I have sent you this talk before. It is a talk from
>> Moriyama from LRT2004. If you check out his slide 14, he quotes
>> ~0.025 decays/sec/PMT, though these are much smaller PMTs (2").
>> However, scaling to an 8" tube, that means a rate of ~0.4 Hz/tube
>> (rather than 10). However, the background may not scale simply with
>> area. Hamamatsu does not list the R8778 in their catalog, so it
>> might be what we would expect to see in the future.
>> Hope it helps,
>> Joe

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