\section{Wiggle fit residuals}
\label{app:fitres}

Figure~\ref{fig:res_fit} shows the wiggle fit residuals for different time windows with the common
lower value being the start time of the fit of 30 $\mu s$. The residuals, as expected, are nott
randomly distributed according to the statistical uncertainty. The residuals exhibit clear features. 
These features are due to missing ingredients in the fit: vertial waist modulation, muon loss, gain correction, pile-up etc.

Figure~\ref{fig:res_fit2} shows the wiggle fit residuals for the time window 4-31 $\mu s$. 
The residuals exhibit features with larger amplitude. The main one is due to the CBO modulation. The CBO frequency changes over the course
of the first 30 $\mu s$ due to scraping and thus is not properly modeled for a fit start time of
30 $\mu s$ with a fitted constant CBO frequency.

\begin{figure}[bt]
\centering
\subfigure[]{\includegraphics[width=0.42\textwidth]{fig/Residuals_30us_31us}}
\subfigure[]{\includegraphics[width=0.42\textwidth]{fig/Residuals_30us_40us}}
\subfigure[]{\includegraphics[width=0.42\textwidth]{fig/Residuals_30us_80us}}
\subfigure[]{\includegraphics[width=0.42\textwidth]{fig/Residuals_30us_130us}}
\subfigure[]{\includegraphics[width=0.42\textwidth]{fig/Residuals_30us_230us}}
\subfigure[]{\includegraphics[width=0.42\textwidth]{fig/Residuals_30us_300us}}
\caption{Residuals of the 9-parameter wiggle fit for six different time window: (a) 30-31, (b) 30-40, (c) 30-80, (d) 30-130, (e) 30-230 and (f) 30-300 $\mu s$.
The start time of the fit is \mbox{30 $\mu s$}.}
\label{fig:res_fit}
\end{figure}

\begin{figure}[bt]
\centering
\includegraphics[width=0.6\textwidth]{fig/Residuals_4us_31us}
\caption{Residuals of the 9-parameter wiggle fit for the time window 4-31 $\mu s$. The start time of the fit is 30 $\mu s$.}
\label{fig:res_fit2}
\end{figure}

