% CORRETTO BABBO
The test-beam experimental setup was conceived so to make use of the RD51-GDD\footnote{Abbreviations stand for the CERN \textit{Research and Development} group no. \textit{51}, and the \textit{Gas Detector Development} group.} tracker. The tracker is made of:
\begin{itemize}
	\item $3$ scintillators, used as a trigger;
	\item $3$ $10 \cdot 10 cm^2$ GEM detectors, used as a track detecting system;
	\item a metallic frame to support the tracker together with the detector prototypes that were to be tested.
\end{itemize}

The GEM chambers of the tracker feature a strip-based readout plane, made of two layers (one for $x$ and one for $y$ direction). The strip \textit{pitch} is $391 \mu m$, which represents the distance between the axes of two adjacent strips. The distribution of gaps between the hit channels of different tracker chambers is Gaussian; its sigma defines the spacial resolution of the tracker:
$$
\Delta x = \dfrac{\sigma_{\left(G1-G2\right)}}{\sqrt{2}} = 0.0915mm
$$
where $G1$ and $G2$ stand for the position of hit clusters in the first and in the second GEM chamber, respectively.\\

Our measurements gave a resolution of~$0.0915mm$, compatible within the error with that expected by such strip pitch ($ \dfrac{pitch
}{\sqrt{12}} = 0.113mm $).\\

All the cables, the dividers and the cards were also fixed to the metallic frame, which was aligned so that the detectors were perpendicular to the beam line. \figurename~\vref{tbsetup} shows the final setup. The signals from the scintillators were sent to three comparators connected to an \texttt{AND} port, the output signal of which was used as \textbf{trigger}. % ADD DETAILS?
The trigger signal was sent to the \textit{turbo\subscript{0}} card, which acted as master and forwarded that signal to itself (into another input pin) and to the slave card \textit{turbo\subscript{1}}. The two \textit{turbo} cards controlled and received inputs from the \textit{VFAT2} chips (both those on the tracking GEM detectors and those on the LG prototype).\\

\begin{figure}[!htbp]
	\centering
	\subfigure[Tracker system setup]
	{\includegraphics[width=6.6cm]{Images/tb_trk}\label{tbtrk}}		% WIDTH=6.7cm TO HAVE THEM ON THE SAME LINE
	\hspace{2mm}
	\subfigure[Large GEM prototype setup]
	{\includegraphics[width=6.6cm]{Images/tb_LG}\label{tblg}}
	\vspace{2mm}
	\subfigure[View of the telescope]
	{\includegraphics[width=10cm]{Images/tb_telescope}\label{tbtlscp}}
	\caption{The test-beam experimental setup: a telescope made of scintillators and of small GEM tracking chambers, and the Large GEM prototype}
	\label{tbsetup}
\end{figure}