MR> Because alphas can be blocked only by a sheet of paper, I must have a
MR> close access directly to the diode. I've seen the OSRAM BPX 61 (a 
MR> silicon PIN photodiode) seems to be quite similar (from the package) to 
MR> the photodiodes in the article.

MR> I have to order it by mail so has anyone worked with this diode and can 
MR> tell me whether it has a glass lense that I can cut away or is the whole 
MR> space covered with a plastic substance (epoxy). An alternative diode for 
MR> me seems to be the BPW 21 (lense or plastic?). The osram datasheet says 
MR> nothing to this aspect (but who wants to cut a diode in pieces?)

MR> Regards
MR> Markus

"thorium alphas" will travel about 3-8cm in air, according to their
energies
3.954MeV   (Th232)
5.34031MeV (Th228)
5.68542MeV (Ra224)
6.28813MeV (Rn220)
7.800MeV   (At216)
10.554MeV  (Po212)
6.05/6.08MeV (Bi212)
If you don't detect any signal with your diode and do not have any
other ability to test your Gl�strumpf, the error is not neccessarily
in the circuit: there are modern cerium based incandescent mantles
around which will not give you any significant amount of alpha
radiation.

BPW21 and BPX61 will both do the job. There is no epoxy filling inside
the can, but the distance between the lens/window and the chip appears
to be shorter than in the old ones from the article - it might be more
difficult to remove the lens without damaging the thin front side
bonding wire.

Uwe.



-- 
Mit freundlichen Gr�ssen
Uwe Zimmermann
mailto:[EMAIL PROTECTED]

-- 
Author: Uwe Zimmermann
  INET: [EMAIL PROTECTED]

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