Mark S. Brown edited centroid discussion.tex  about 10 years ago

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\subsubsection{Other 30mm Results}   Beyond CTR, other \subsubsection{Additional timing and energy results for 30mm}   In the coincidence apparatus measurements additional  properties are  recorded; namely the delay peak centroid, the light output and the  energy resolution can be explored. resolution.  In figure \ref{fig:centroidposition} the shift in the delay peak position with increasing DOI is plotted. It can be seen that a plateau is reached for both configurations at 20mm. In \cite{Moses_Derenzo_1999} this plateau is attributed to the travel time between photons travelling 'towards' and 'away' from the photodetector approaching equality. As the electronic trigger from the discriminator is tuned as close to the beginning of the signal as possible this cannot come before generated light has physically travelled from it's emission position to the photodetector. This is supported by the total shift seen of 150ps to 370ps corresponding to an approximate physical distance of 30mm.