RE: pmt glass radiation

From: Horton-Smith, Glenn (
Date: Thu Jun 02 2005 - 09:11:04 CDT

Hi all,
   Indeed, the approach followed at KamLAND and Palo Verde was to sacrifice a tube: specifically, smash it into little bits and pack the pieces of glass into a bottle. Besides the practicalities of fitting the thing into the shielded counting chamber, one generally wants a MC simulation to get the detector efficiency for a given sample geometry and to correct for Compton scattering in the sample itself, with the MC validated using a known activity sample in each standard sample shape (e.g., a 250 mL bottle). That's another reason it is convenient to reshape the sample into a standard shape.
   I once shipped a large piece of quite solid, fractureless granite from the KamLAND site to Caltech for counting, back in late 1998 or early 1999. It was an odd shape and much too big to fit in the counter, and the person who manually reduced it to gravel before counting (Andreas Piepke) explained these facts of life to me later. :-)

Joseph Formaggio wrote:

            I am not absolutely sure, but I believe it is difficult to take background counts of a large object such as a phototube. Parts of it are ok (base, pieces of glass, etc). But the whole thing assembled I think is difficult. It depends on how big the chamber where they do the counting is, and how big their Ge crystals are.

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