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-%% GSI Scientific Report 2013
+%% GSI Scientific Report 2013
%% \setlength{\titleblockheight}{27mm} KG
\setlength{\titleblockheight}{35mm}
\author[]{M. Deveaux}
\author[]{M. Koziel}
\author[]{C. M{\"u}ntz}
-\author[]{J. Stroth for the CBM-MVD Collaboration}
+\author[]{J. Stroth \\for the CBM-MVD Collaboration}
\affil[]{Institut f{\"u}r Kernphysik, Goethe-Universit{\"a}t, Frankfurt}
\maketitle
-The Micro Vertex Detector (MVD) of the CBM experiment will be equipped with CMOS Monolithic Active Pixel Sensors developed at the IPHC, Strasbourg. This sensor technology will meet the constraints formulated by the physics cases. The latest sensor prototypes, \cite{1}, provide the sensor architecture to be used for the sensors being integrated into the MVD, allowed for defining the sensor arrangement within the acceptance of the MVD.\\
+The Micro Vertex Detector (MVD) of the CBM experiment will be equipped with CMOS Monolithic Active Pixel Sensors developed at IPHC, Strasbourg. This sensor technology will meet the constraints formulated by the physics cases. The latest sensor prototypes~\cite{1} provide the sensor architecture to be used for the sensors being integrated into the MVD and allow for defining the sensor arrangement within the acceptance of the MVD.\\
-The MVD will consist of up to four detector stations at $50 /100 /150 /200$ mm downstream the target. The assumed sensor dimensions of $30 \cdot 13$ mm$^{2}$ feature an in-active area of $3 \cdot 10$ mm$^{2}$ for the on-chip read-out electronics. This in-active area requires a double-sided positioning of the sensors on the MVD stations to achieve the optimum acceptance coverage. A $500 \; \mu$m overlay of the active sensor areas optimizes this coverage for inclined tracks. The thickness of the sensors will be $50\; \mu$m which requires dedicated customized sensor positioning tools.\\
+The MVD will consist of up to four planar detector stations positioned between 50 and 200~mm downstream the target. The assumed sensor dimensions of $30\cdot13$ mm$^{2}$ feature an in-active area of $3\cdot10$ mm$^{2}$ for the on-chip read-out electronics and bonding pads along one side of the chip. This in-active area requires a double-sided positioning of the sensors on the MVD stations to achieve the optimum acceptance coverage. A $500 \; \mu$m overlap of the active sensor areas optimizes this coverage for inclined tracks. The thickness of the sensors will be $50\; \mu$m which requires dedicated sensor positioning tools.\\
\begin{table}[!htbp]
\centering
\begin{tabular}{@{}lllc@{}}
\multicolumn{2}{c}{Station} & Number of & Carrier \\
- number & position [mm] & sensors & type \\
+ Number & Position [mm] & sensors & material \\
\hline
- $0$ & $50$ & $8$ & CVD \\
- $1$ & $100$ & $40$ & CVD \\
+ $0$ & $50$ & $8$ & CVD diamond \\
+ $1$ & $100$ & $40$ & CVD diamond \\
$2$ & $150$ & $84$ & CF-TPG-CF \\
$3$ & $200$ & $160$ & CF-TPG-CF \\
\hline
\label{tab:sensornumber}
\end{table}
-The operation of the MVD in the vacuum to minimize multiple scattering of the produced particles requires an efficient cooling of the sensors. At the same time, the material budget of the MVD stations has to be limited due to its significant impact on the tracking and reconstruction efficiency. High performance carbon-based materials - offering the best combination of an excellent heat conductivity and a low contribution to the material budget of the MVD station - will be used as cooling support in the detector acceptance. For the stations positioned at $50$ mm and $100$ mm, $150\; \mu$m thin polycrystalline CVD diamond (CVD) carriers, \cite{2}, will be used as cooling support, while for the third and fourth MVD station $500\; \mu$m thick carbon fibre-encapsulated Thermal Pyrolithic Grafite (TPG), \cite{3}, is proposed, employing $60\; \mu$m carbon fibre sheets. Outside of the active area, the constraints due to minimizing the material budget and the resulting multiple scattering are less stringent which allows for positioning actively cooled aluminum heat sinks. These are held by dedicated half station support structures levelling the different heat sink dimension of the stations, as shown in figure \ref{fig:overview}. The MVD half stations are positonend on common base plates to allow the movement of the MVD apart the beam line while beam tuning and beam focusing.
-
+Vacuum operation of the MVD requires efficient sensor cooling. At the same time, the material budget of the MVD stations has to be limited due to its significant impact on the tracking and vertexing precision. High performance carbon-based materials - offering the best combination of an excellent heat conductivity and a low contribution to the material budget of the MVD station - will be used as cooling support in the detector acceptance. For the stations positioned at $50$~mm and $100$~mm, $150\; \mu$m thin poly-crystalline CVD diamond carriers~\cite{2} are employed serving as mechanical cooling support, while for the third and fourth MVD station $500\; \mu$m thick sheets of carbon fibre-encapsulated Thermal Pyrolytic Graphite (TPG)~\cite{3} are proposed. Outside of the active area actively cooled aluminum heat sinks are positioned, suspended by dedicated half station support structures leveling the different heat sink dimension of the stations, as shown in figure \ref{fig:overview}. The MVD half stations are positioned on common base plates to allow the movement of the MVD away from the beam line while beam optimization.
+
\begin{figure}[htb]
\centering
\includegraphics*[width=87.5mm]{MVD_overview.pdf}
-\caption{The overview of the MVD is depicted. For one of the two MVD half station groups is set to transparent to ease the visualization. The beam is coming from the left.}
+\caption{The CAD drawing of the MVD is depicted. For one of the two MVD half station groups is set to transparent for visualization. The beam is coming from lower left. The inlay shows the sensor arrangement on the front side of the third station module. Empty and in-active areas are covered by sensors on the back side. }
\label{fig:overview}
\end{figure}
-The material budget limit for the first MVD station of $x/X_{0} \approx 0.3 \%$ will not be exceed with the current sensor arrangement. For the other MVD stations, the material budget limit of $x/X_{0} \approx 0.5 \%$ will be met using advanced technologies for the construction of the Flex Print Cables required to transport the data send by the sensors to the first stage of front-end electronics positioned on the half station support structures.
-
+The material budget benchmark of the first MVD station of $x/X_{0}\approx0.3\%$, crucial for the precision of secondary vertexing, will be met with the current station design and a conservative flex print layout. To meet the benchmark of $x/X_{0}\approx 0.5\%$ also for larger polar angles of the other MVD stations, an advanced read-out flex cable design, based on aluminum traces, is mandatory.
\begin{thebibliography}{9} % Use for 1-9 references
%\begin{thebibliography}{99} % Use for 10-99 references
-
\bibitem{1}
F. Morel et al. ``MISTRAL and ASTRAL: two CMOS Pixel Sensor architectures suited to the Inner Tracking System of the ALICE experiment'', 2014 JINST 9 C01026.
\bibitem{2}
-CVD diamond, Diamond Materials, http://www.diamond-materials.com.
+Diamond Materials, http://www.diamond-materials.com.
\bibitem{3}
-K. Arndt, Talk at the ``Forum on Tracking Detector Mechanics"', June 2013, Oxford, UK.
+K. Arndt, ``Forum on Tracking Detector Mechanics"', June 2013, Oxford, UK.
\end{thebibliography}
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