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+%The first run of the AlCap experiment was performed at the $\pi$E1 beam line
+%area, PSI from November 26 to December 23, 2013. The goal of the run was to
+%measure protons rate and their spectrum following muon capture on aluminium.
+
+The low energy muons from the $\pi$E1 beam line were stopped in thin aluminium
+and silicon targets, and charged particles emitted were measured by two pairs
+of silicon detectors inside of a vacuum vessel
+(\cref{fig:alcap_setup_detailed}).  A stopped muon event is defined by
+a group of upstream detectors and a muon veto plastic scintillator. 
+The number of stopped muons is monitored by a germanium detector placed outside
+of the vacuum chamber. In addition, several plastic scintillators were used to
+provide veto signals for the silicon and germanium detectors.
+\begin{figure}[btp] 
+	\centering
+	\includegraphics[width=0.55\textwidth]{figs/alcap_setup_detailed} 
+	\caption{AlCap detectors: two silicon packages inside the vacuum vessel, 
+    muon beam detectors including plastic scintillators and a wire chamber, 
+    germanium detector and veto plastic scintillators.}
+	\label{fig:alcap_setup_detailed} 
+\end{figure} 
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+\subsubsection{Muon beam}
+\label{ssub:muon_beam}
+%\Cref{fig:alcap_setup_detailed} shows the experimental setup. The muon
+%beam enters from the right of the image and hits the target, which is
+%placed at the center of the vacuum chamber and orientated at 45
+%degrees to the beam axis.
+
+  %In order to define
+%stopped muon events, four muon counters are used: a 500~\rmmu m thick
+%scintillator muon trigger counter (\rmmu SC); a muon anti-coincidence
+%counter (\rmmu SCA) surrounding the trigger counter with a hole of 35
+%mm diameter to define the beam radius; and a multiwire proportional
+%chamber (\rmmu PC) that uses 24 X wires and 24 Y wires with at 2 mm
+%intervals. This detector system belongs to the MuSun experiment and
+%was well tuned in advance.  A muon veto counter (\rmmu Ve) is placed
+%at the downstream end of the chamber and is used to reject muons that
+%pass through the stopping target.
+One of the main requirements of the AlCap experiment was a muon beam
+with narrow momentum bite in order to achieve a high fraction of
+stopping muons in the very thin targets. The actual set up used in the Run
+2013 was: muon momentum from \SIrange{28}{45}{\MeV\cc} and momentum spread of
+3\% FWHM.