[Gate-users] Scandium-44 ion source - angular correlation?

[Satyajit Ghosh]

Dear Gaters,


           I am working with Scandium-44 ion point source placed at the
centre of a scanner system with four silicon strip detectors in a square
array. We know that scandium-44 is a nonpure beta emitter and acts as a
triple gamma source - two 511 keV annihilation gammas and a
quasi-simultaneous 1157 keV gamma.


           I am detecting two annihilation gamma on opposite end strip
detectors which are expected as they emit in different directions. *But
interestingly I am getting 1157 keV gamma "always" in rest of the detectors
and not in same strip detectors where 511 keVs are already detected*. I
thought there should be *no angular correlation *between 1157 keV and 511
keVs as those are independent nuclear processes. In essence, 511's are
emitted from electron-positron annihilation outside the nucleus and 1157 is
from the nucleus itself. I have double-checked the simulation.


          It is worth to notice that this particular paper (attached) had
considered trigger logic where 1157 keV indeed is considered to be detected
in different detector other than where 511 keVs are already detected. [See
figure 1 and highlighted line on page 7]


Regards

Satyajit Ghosh

-- 
*Satyajit Ghosh*
*PhD Student*

*Nuclear Spectroscopy and Molecular Imaging Lab,*
*Physics Department, IIT Bombay,*
*Mumbai-400076, INDIA*
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