\setlength{\titleblockheight}{35mm}
\begin{document}
-\title{Ultra-low material budget Cu-based flexible cable for the CBM-MVD
+\title{An ultra-low material budget Cu-based flexible cable for the CBM-MVD
\thanks{Work supported by BMBF (05P12RFFC7), HIC for FAIR and GSI}}
\author[1]{P. Klaus}
\author[1]{M. Koziel}
\author[1]{T. Tischler}
\author[1]{S. Schreiber}
-\author[1]{C. Müntz}
+\author[1]{C. M\"untz}
\author[1,2]{J. Stroth}
\author[ ]{the CBM-MVD collaboration}
-\affil[1]{Goethe-Universität Frankfurt}
+\affil[1]{Goethe-Universit\"at Frankfurt}
\affil[2]{GSI, Darmstadt, Germany}
\maketitle
-%\section{Brainstorming}
-%
-%\begin{itemize}
-% \item Why a new cable?
-% \item design choices
-% \item features for integration
-% \item Tables of material budget
-% \item Comparison old / new cable
-% \item Setup and toolset for s-curve measurements created
-%\end{itemize}
-
-%\section{The Material Budget}
The CBM Micro-Vertex-Detector (MVD) relies on employing a material budget $x/X_0$ per detector station of 0.3\% (first station) to 0.5\% (following stations) to allow for a secondary vertex resolution of better than $70~\mathrm{\mu m}$ with typical pixel pitches of about $20~\mathrm{\mu m}$.
To reach this ambitious goal, all components in the acceptance of the detector have to be challenged w.r.t.\ their impact on the material budget, while at the same time maintaining their cutting edge performance regarding mechanical and electrical properties as well as radiation hardness.
In addtion, the sensor readout has to be robust with low noise occupancy, which puts strong constraints on the electrical properties of the rather long cables connecting the sensors with the front-end electronics (FEE) being outside the acceptance of the detector.
Those cables are flexible printed circuits (FPC) and provide power to the CMOS Pixel Sensors (CPS), allow to control them, and to read out the hits.
%The connections to the MAPS sensors will be made with wire-bonding while the FEE-facing side is plugged into a ZIF-connector.
The previous generation cable was not specifically optimized for ultra-low material budget being a two-layer copper-based cable with a layer thickness of about $25 \mathrm{\mu m}$.
-% CHECK the value of 25 \mu m
-It was successfully tested in a beamtime with the CBM-MVD prototype\cite{cern2012}.
+It was successfully tested in a beamtime with the CBM-MVD prototype [1].
Reducing the dominant factor of the material budget meant reducing the thickness of the copper layer, see Tab.~\ref{tab:material-budget}.
The cable was redesigned with a readout to the side (see Fig.~\ref{fig:cable-layout}), a smaller feature size ($80 \mathrm{\mu m}$) and thus a reduced total cable width, and copper traces with a thickness of only $12 \mathrm{\mu m}$.
-The cables were manufactured using a commercial technology offered by ILFA\cite{ILFA}
-% The big contribution of the copper layers to the material budget of the cable can be seen in the table \ref{tab:material-budget}.
-%Tab.\ \ref{tab:material-budget} shows the material budget for the new single-layer cable.
+The cables were manufactured using a commercial technology offered by ILFA [2]
\begin{table}[b]
\centering
\begin{tabular}{lrrr}
Polyimide & 25 & 0.009 \% & 8.2 \\ \hline
\textbf{Sum} & 63 & 0.051 \% & 48.1 \\ \hline
\end{tabular}
-\caption{Material budget of the new cable
-%, with an average fill factor of the copper layer of 40 \%
+\caption{Material budget of the new cable.
}
\label{tab:material-budget}
\end{table}
-%\begin{figure}[ht]
-%\centering
-%\includegraphics*[width=70mm]{fpc-layers.eps}
-%\caption{The layers of the new FPC in the cross section}
-%\label{fig:fpc-layers}
-%\end{figure}
+
\begin{figure}[htb]
%\centering
\includegraphics*[width=72mm]{assembly-with-marks-thick-power-cut-out.eps}
-\includegraphics*[width=75mm]{004-material-budget.mb.dir.eps}
+\includegraphics*[width=75mm]{004-material-budget.eps}
\caption{CAD layout of the new ultra-thin FPC showing the bonding zone and the part of the cable situated in the acceptance of the detector (top); an analysis of its material budget in \% of $x/X_0$ (bottom).}
\label{fig:cable-layout}
\end{figure}
%See table \ref{tab:material-properties} for those properties.
The downside of this non-standard Aluminium-based technology is the lower production reliablity, and thus higher cost and production times.
-%\begin{table}[htb]
-%\centering
-%\begin{tabular}{llll}
-% \hline
-% \ & Copper & Aluminium \\ \hline
-% $\sigma$ & $5.96 \cdot 10^7 \ \mathrm{S/m}$ & $3.50 \cdot 10^7 \ \mathrm{S/m}$ \\
-% $X_0$ & $14.36 \ \mathrm{mm}$ & $88.97 \ \mathrm{mm}$ \\
-% \hline
-%\end{tabular}
-%\caption{Material properties of Copper and Aluminium. $\sigma$ denotes conductivity and $X_0$ denotes the radiation length.}
-%\label{tab:material-properties}
-%\end{table}
-
-% Table with tabularx (currently not needed):
-%\begin{tabularx}{0.35\textwidth}{llll}
-% \toprule
-% \ & Copper & Aluminium \\
-% \midrule
-% $\sigma$ & $5.96 \cdot 10^7 \ \mathrm{S/m}$ & $3.50 \cdot 10^7 \ \mathrm{S/m}$ \\
-% $X_0$ & $14.36 \ \mathrm{mm}$ & $88.97 \ \mathrm{mm}$ \\
-% \bottomrule
-%\end{tabularx}
-
-%\section{Next steps and Outlook}
-%
-% In the near future, we will test the properties of the new cables.
-% Experimenting with leaving out the coverlay? Spray-on instead?
-
-%\section{Summary}
To summarize, a new ultra-thin design of the FPC for the CBM Micro-Vertex-Detector was created and the cables produced.
Its suitability will be analyzed including its electrical performance and integration stability.
Further technologies to reduce the material budget even more are being evaluated.
\begin{thebibliography}{9}
-\bibitem{cern2012}
-%M.~Koziel et al., The prototype of the Micro Vertex Detector of the CBM Experiment, Nucl.Instrum.Meth. A732 (2013) 515
-M.~Koziel et al., The prototype of the Micro Vertex Detector of the CBM Exp., Nucl.Instrum.Meth. A732 (2013) 515
-\bibitem{ILFA} ILFA Industrieelektronik und Leiterplattenfertigung aller Art GmbH, Hannover, Germany
+\bibitem{} M.~Koziel et al., The prototype of the Micro Vertex Detector of the CBM Exp., Nucl.Instrum.Meth. A732 (2013) 515
+\bibitem{} ILFA Industrieelektronik und Leiterplattenfertigung aller Art GmbH, Hannover, Germany
\end{thebibliography}
\end{document}
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