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None Shark fin in Compton spectrum 

Forum: Biasing and Scoring
Date: 02 Apr, 2014
From: Kyle Schmitt <Kyle Schmitt>

Hello,

I am having trouble with strange features in energy spectra from a germanium detector. I am using a 60 keV gamma source 30cm from the window of a germanium detector with a thin dead layer (varies from 0 to 1000 um). I see a strange fin-shaped hump at around 1/6 of the primary particle energy. Also, the area between 50 and 60 keV is populated. I do not think these two features are physical. It is likely that I am doing something silly, but I do not know what.

I am recording the energy using the GetTotalEnergyDeposit and GetNonIonizingEnergyDeposit methods in my stepping action and passing that information to my event action, where the histogram is populated. I will attempt to attach spectra. If I remove the dead layer so that the only material in the envelope is G4_Galactic and the active volume (G4_Ge), I get the latter spectrum.

Many thanks, Kyle

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/04/02/13.28-56737-Spectrum58.gif
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/04/02/13.28-90297-Spectrum59.gif

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