Phone Meeting: HRS-R Carbon runs problems (02/13/2009)
Problem:
Aditional peaks appear in the C-single runs, while there is no additional
peaks in the Optics 7-foil target runs.
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I have performed various narrow cuts on scattering angles tg.th and tg.ph, but these cuts did not
remove these additional peaks, only the number of good events got smaller.
Same additional peaks appear in both Tantalum and Carbon (single) target.
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Question: Why do I see additional peaks in single foil cabon target, while these peaks do not appear in the 7-foil optics target?
Hypothesis: I suspect that these additional peaks in the middle of the momentum spectrum are caused by those electrons that scatter off the aluminium framework and an aluminium "ring" that holds target in the place and is attached to the framework from behind.
Images of a target ladder:
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If these two additional peaks are really Al peaks from the frame, than the first peak corresponds to the electrons that scatter off an aluminium plate with thickness d_1 approx. 0.375 cm ,
while the second peak corresponds to electrons that scatter off a thicker aluminium plate with thickness d_2 approx. 1cm
If we assume that electrons that scatter off a framework also travel though the Al ring, behind the target, since the scattering angle is small (approx. 24 deg), than this means, that target frame is approximately 0.6cm thick while the Al plate behind the target, that holds target in place is 0.4cm wide.
Subtracting "Al" peaks from the Carbon spectra:
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