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-\title{PRESTO: PREcursor of Station TwO of the CBM-MVD\thanks{This work has been supported by BMBF (05P12RFFC7), EU-FP7 HadronPhysics3, HGS-HIRe, GSI and HIC for FAIR.}}
+\title{PRESTO: PREcursor of the Second sTatiOn of the CBM-MVD\thanks{This work has been supported by BMBF (05P12RFFC7), EU-FP7 HadronPhysics3, HGS-HIRe, GSI and HIC for FAIR.}}
\author[]{M. Koziel}
\author[]{T. Tischler}
-\author[]{J. Michel}
-\author[]{M. Wiebusch}
-\author[]{P. Klaus}
\author[]{C. M{\"u}ntz}
\author[]{J. Stroth for the CBM-MVD collaboration}
\maketitle
-This report summarizes the activities undertaken to construct a precursor of the second station of the MVD.\\
+This report summarizes the activities undertaken to construct a precursor of a quadrant of the second MVD-station.\\
%\section{Sensor integration}
-The PREcursor of Station TwO (PRESTO) project of the CBM-MVD addresses the double-sided integration of $15$ MIMOSA-$26$ sensors (dummies and working sensors, $9$ of these on the front in a $3\times3$ and $6$ sensors on the back in a $2 \times 3$ arrangement) onto a $8 \times 8~\text{cm}^{2}$ CVD diamond carrier \cite{CVD} featuring a thickness of $150~\upmu$m. The PRESTO module will employ the new flex cables \cite{FPC} providing all signals needed to operate and read out the sensors, see sketch \ref{fig:presto_sketch}. In total, $10$ FPCs are required to read out these sensors.\\
-To assembly this module, new sensor positioning jigs aiming for a sensor positioning precision with respect to the support and the neighboring sensors of below $100~\upmu$m were manufactured. To evaluate the integration concept, the RAL-$247$ adhesive \cite{glue} and the new jigs, a dummy PRESTO module based on $200~\upmu$m glass plate was selected to server as sensor carrier, employing $50~\upmu$m MIMOSA-$26$ dummies, see fig.~\ref{fig:presto_dummy}.\\
-The number of air bubbles introduced into the glue during its mixing process has been significantly reduced by degassing it in an exicator at about $4\cdot 10^{-1}$~mbar for about $1$ hour. However, this did not prevent the air bubbles to appear after the gluing of the sensors onto the carrier. The introduced air bubbles featured a size of about $100-300~\upmu$m diameter. To verify their impact on the $50~\upmu$m thin sensor dummies, the cured module has been placed inside a small vacuum chamber which has been evacuated for about $48$ hours to a value of $4\cdot 10^{-1}$~mbar. The visual inspection of the sensor dummies using a high precision microscope did not reveal any mechanical damage. Further studies will be addressed with working sensors to check on-fly any possible correlation between sensor performance, pressure and bubble sizes.\\
-The gluing of the dummy sensors onto the glass carrier demonstrated that a glue volume of $3-5~\upmu$l\textemdash a different glue volume has been used for each row of sensors\textemdash is sufficient to dispense a uniform and thin (about $30~\upmu$m) layer underneath the sensors.\\
-The horizontal sensor-to-sensor distances were measured to be below $5~\upmu$m. The vertical shifts between the sensors were measured to be of about $20~\upmu$m. The achieved precision is significantly below the envisioned one. Next steps comprise the establishing of procedures for the integration of the flex cables, the exercise of double-sided bonding and the verification of the vacuum compatibility.
+The PRESTO (PREcursor of the Second sTatiOn) project of the CBM-MVD addresses the double-sided integration of $15$ MIMOSA-$26$ sensors (dummies and working sensors, $9$ of these on the front in a $3\times3$ and $6$ sensors on the back in a $2 \times 3$ arrangement) onto a $8 \times 8~\text{cm}^{2}$ CVD diamond carrier \cite{CVD} featuring a thickness of $150~\upmu$m. The PRESTO module will employ new flex cables (FPC) \cite{FPC} providing all signals needed to operate and read out the sensors\textemdash $10$ FPCs in total\textemdash, see fig. \ref{fig:presto_sketch}.\\
+To assembly this module, new sensor positioning jigs aiming for a sensor positioning precision with respect to the support and the neighboring sensors of below $100~\upmu$m were manufactured. To evaluate the integration concept, the RAL-$247$ adhesive \cite{glue} and the new jigs, a dummy PRESTO module has been assembled employing $50~\upmu$m thin MIMOSA-$26$ dummies and a $200~\upmu$m thin glass plate which serves as sensor carrier, see fig.~\ref{fig:presto_dummy}.\\
+In the process of gluing, the inclusion of air bubbles should be avoided due to the vacuum operation of the MVD and the use of thinned sensors. This triggered a study focusing on optimizing the preparation of the glue, its dispensing and the quality assurance of the results. The number of air bubbles introduced into the glue during its mixing process has been significantly reduced by degassing it in an exicator at about $4\cdot 10^{-1}$~mbar for about $1$ hour. However, this did not prevent the air bubbles to appear after the gluing of the sensors onto the carrier. The introduced air bubbles featured a size of about $100-300~\upmu$m diameter. To verify their impact on the $50~\upmu$m thin sensor dummies, the cured module has been placed inside a small vacuum chamber which has been evacuated for about $48$ hours to a value of $4\cdot 10^{-1}$~mbar. The visual inspection of the sensor dummies using a high precision microscope did not reveal any mechanical damage. Further studies will be addressed with working sensors to check on-the-fly any possible correlation between sensor performance, pressure and bubble sizes.\\
+The gluing of the dummy sensors onto the glass carrier demonstrated that a glue volume of $3-5~\upmu$l\textemdash a different glue volume has been used for each row of sensors\textemdash is sufficient to dispense a uniform and thin (about $10-17~\upmu$m) layer underneath the sensors. The horizontal sensor-to-sensor distances were measured to be below $5~\upmu$m. The vertical variation in the distances between the sensor edges were measured to be of about $20~\upmu$m. The achieved precision is significantly below the envisioned one. Next steps comprise the establishing of procedures for the integration of the FPCs, the exercise of double-sided bonding and the verification of the vacuum compatibility.
\begin{figure}[htb]
\centering
-\includegraphics*[width=60mm]{PRESTO_sketch.png}
-\caption{Sketch of the arrangement of the sensors and the FPCs with respect to the support carrier within the PRESTO module.}
+\includegraphics*[width=55mm]{PRESTO_sketch.png}
+\caption{Sketch of the arrangement of the sensors and the FPCs on the support carrier of the PRESTO module.}
\label{fig:presto_sketch}
\end{figure}
\begin{figure}[htb]
\centering
-\includegraphics*[width=55mm]{integration1.eps}
+\includegraphics*[width=50mm]{integration1.eps}
\caption{Assembled dummy module of PRESTO.}
\label{fig:presto_dummy}
\end{figure}
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\textbf{Development of the heat sinks for the MVD:$\;\;$}
-The operation of the MVD in vacuum requires a continuous cooling of the sensors to limit radiation induced defects as well as noise. To keep the material budget of the individual MVD station as low as possible, the cooling approach of the MVD employs highly thermal conductive sensor support materials (CVD diamond \cite{CVD} and encapsulated graphite) in the acceptance of the MVD and actively cooled aluminum-based heat sinks outside of this area. To evaluate the cooling concept and its vacuum compatibility, half-station heat sinks of the first three MVD stations were manufactured at COOLTEK GmbH. The heat sinks incorporate a buried cooling pipe and have thermally been simulated prior their manufacturing using a worst case scenario for the sensor power dissipation plus an additional safety factor of four. These heat sinks are currently being evaluated under laboratory conditions focusing on their vacuum compatibility \cite{vacuum}. The heat dissipation of the MVD sensors is provided by kapton insulated flexible heaters from OMEGA Engineering, INC.
+The operation of the MVD in vacuum requires a continuous cooling of the sensors to limit radiation induced defects as well as noise. To keep the material budget of the individual MVD station as low as possible, the cooling approach of the MVD employs highly thermal conductive sensor support materials (CVD diamond \cite{CVD} and encapsulated high performance graphite) in the acceptance of the MVD and actively cooled aluminum-based heat sinks outside of this area. To evaluate the cooling concept and its vacuum compatibility, half-station heat sinks of the first three MVD stations were manufactured at COOLTEK GmbH. The heat sinks incorporate a buried cooling pipe and have thermally been simulated prior their manufacturing using a worst case scenario for the sensor power dissipation plus an additional safety factor of four. These heat sinks are currently being evaluated under laboratory conditions focusing on their vacuum compatibility \cite{vacuum}. The heat dissipation of the MVD sensors is provided by kapton insulated flexible heaters from OMEGA Engineering, INC.
\begin{thebibliography}{9}
\bibitem{PRESTO}
-M. Koziel et al., "PRESTO: PREcursor of Station TwO of the CBM-MVD." GSI annual report 2014.
+M. Koziel et al., "PRESTO: PREcursor of the Second sTatiOn of the CBM-MVD." GSI annual report 2014.
\bibitem{FPC}
P. Klaus et al., "Ultra-low material budget Cu flex cable for the CBM-MVD. "GSI annual report 2014.
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