Note that, while enlarging the transistor size reduces the RTS, cooling seems not to show a positive impact. This stands in contrast to our observations on RTS-noise originating from the pixel \mbox{diodes \cite{RTS}}.
\subsection{Impact of the transistor layout on the sensor performance}
-The relation between the charge collection efficiency (CCE), the gain and the median noise of the pixels was measured with MIMOSA-34. All pixels were derived from pixel D and the diode size was varied. Figure \ref{fig:Diodesurface} shows the noise and the gain of the different pixels. Moreover, the CCE representing the most probable fraction of charge collected by the seed pixel of a pixel cluster is shown. For the CCE, only the matrices with the same pitch of $XX\mum$ are comparable. The CCE was measured by means of a $^{55}$Fe-source.
+The relation between the charge collection efficiency (CCE), the gain and the median noise of the pixels was measured with MIMOSA-34. All pixels were derived from pixel D and the diode size was varied. Figure \ref{fig:Diodesurface} shows the noise and the gain of the different pixels. Moreover, the CCE representing the most probable fraction of charge collected by the seed pixel of a pixel cluster is shown. For the CCE, only the matrices with the same pitch of $22\mum\times 33\mum$ are comparable. The CCE was measured by means of a $^{55}$Fe-source.
One observes that the gain is strongly reduced with increasing diode size and the capacitive noise of the pixels raises accordingly. However, this effect comes with an increase in terms of charge collection efficiency, which raises the signal. This is shown in figure \ref{fig:StoNDiodeSize}, which shows the noise, the most probable signal and the S/N as recorded once the sensor was illuminated by $\upbeta$-rays from a $^{90}$Sr-source. One observes that the S/N, which is defined as the most probable signal in the seed pixel divided by the median of the noise distribution, is in the order of 50. Once propagating the ``99\%-noise'' to the S/N, one finds that 99\% of all pixels exceeds 22 and no significant impact of the diode pitch is observed. Note that this S/N is sufficient for reliable MIP-detection and remains fairly above the average S/N of our early successful prototypes like MIMOSA-2.
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