\section{\label{sec:ring} Storage Ring}
\textcolor{orange}{Renee}
\medskip

The \gmtwo~storage ring is a weak focusing machine with a single adjustable parameter, namely the quadrupole voltage, that determines horizontal and vertical tunes, as well as the $\beta$ and dispersion ($\eta$) functions. Figure~\ref{fig:schematic} shows the layout of the ring. The quads~\cite{Crnkovic:IPAC2018-WEPAF015} are vertically focusing and horizontally defocusing. In the limit where $V_{\textnormal{quad}}\rightarrow0$, the horizontal tune is unity and vertical is zero. With increasing voltage the vertical tune increases and horizontal decreases.

\begin{figure}[]
	\centering
	\begin{subfigure}{\columnwidth}
		\begin{tikzpicture}
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			\draw (0, 0) node[rotate=45,opacity=0.4]{{\fontsize{45}{54}\selectfont\textcolor{red}{\textbf{Preliminary}}}}; % rule of thumb: \fontsize{size}{1.2*size}
		\end{tikzpicture}
		%\includegraphics[width=0.95\columnwidth]{fig02a.jpeg}
		\caption{Annotated storage ring picture \textcolor{red}{\textit{[still need to annotate the picture]}}.}\label{fig:picture}
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		\caption{Storage ring diagram.}\label{fig:diagram}
	\end{subfigure}
	\caption{\textcolor{orange}{Jason} Injected beam enters the \gmtwo~ring through a hole in the back leg iron. It emerges from the back leg and enters the inflector which cancels the field of the storage ring magnet. Beam exits the inflector, and enters the ring through the kicker gap. The circumference of the ring is \SI{44.69}{\meter} (revolution period \SI{149}{\nano\second}). The \SI{1.45}{\tesla} bending field is continuous around the ring.}\label{fig:schematic}
\end{figure}

Three distinct detector systems inform the muon distribution. Twenty-four calorimeters~\cite{Grange:2015fou}, distributed uniformly around the inner circumference of the ring, measure energy, position and time of decay positrons. There are two tracking stations~\cite{Grange:2015fou}, located \SI{180}{\degree} and \SI{270}{\degree} from the injection point, comprised of straw wire chambers, that measure the trajectory of the decay positron. The reconstructed track is then traced back to reveal the position of the parent muon. The fiber harp system provides the most direct measure of the circulating muons. Each of the four harps consists of seven \SI{0.5}{\milli\meter} diameter parallel scintillating fibers with \SI{13}{\milli\meter} spacing. There are two horizontal and two vertically oriented harps at \SI{180}{\degree} and \SI{270}{\degree} respectively. The fiber harps~\cite{Grange:2015fou} are rotated into the beam to measure time dependence of beam centroid and profile, and are retracted during production running.

The fiber harps and the tracking detectors provide complimentary measurements of motion of the centroid (Figs.~\ref{fig:fibercentroid} and~\ref{fig:trackercentroid}) and modulation of the width, Fig.~\ref{fig:fiberwidth}. 

\begin{figure}[]
	\centering
	\begin{tikzpicture}
		\draw (0, 0) node[inner sep=0]{\includegraphics[width=0.95\columnwidth]{fig03.pdf}};
		\draw (0, 0) node[rotate=45,opacity=0.4]{{\fontsize{45}{54}\selectfont\textcolor{red}{\textbf{Preliminary}}}}; % rule of thumb: \fontsize{size}{1.2*size}
	\end{tikzpicture}
	%\includegraphics[width=0.95\columnwidth]{fig03.pdf}
	\caption{\textcolor{orange}{David R.} Horizontal position of centroid measured with the \SI{180}{\degree} fiber harp (blue) and \SI{270}{\degree} harp (red) for the first \SI{30}{\micro\second} of the fill. A discrete Fourier transform yields the horizontal tune.}\label{fig:fibercentroid}
\end{figure}

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	\centering
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		\draw (0, 0) node[inner sep=0]{\includegraphics[width=0.95\columnwidth]{fig04.pdf}};
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	\caption{\textcolor{orange}{David R.} Radial centroid as measured with the \SI{180}{\degree} tracker over the first \SI{220}{\micro\second} of the fill. Red curve is a fitted damped sinusoid. Measurement is increasingly noisy at longer times as statistics are limited.}\label{fig:trackercentroid}
\end{figure}

\begin{figure}[]
	\centering
	\begin{tikzpicture}
		\draw (0, 0) node[inner sep=0]{\includegraphics[width=0.95\columnwidth]{fig05.pdf}};
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	\end{tikzpicture}
	%\includegraphics[width=0.95\columnwidth]{fig05.pdf}
	\caption{\textcolor{orange}{David R.} Horizontal width at \SI{180}{\degree} harp (blue) and \SI{270}{\degree} harp (red) over the first \SI{30}{\micro\second} of the fill. The deep modulation is a combination of $\beta$ and $\eta$ mismatch.}\label{fig:fiberwidth}
\end{figure}

