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+\setlength{\titleblockheight}{32mm}
\begin{document}
-\title{Analysis of the CBM MVD prototype CERN SPS beam-time\thanks{supported by BMBF (05P12RFFC7), HIC for FAIR and GSI}}
+\title{Results from the CBM MVD prototype CERN SPS beam-time\thanks{supported by BMBF (05P12RFFC7), EU-FP7 HardronPhysics3, HIC for FAIR and GSI}}
-\author[1]{S Amar-Youcef}
-\author[1]{K. ..}
+\author[]{S. Amar-Youcef, M. Deveaux, M. Koziel, Q. Li, J. Michel, B. Milanovic, C. Müntz, B. Neumann, J. Stroth, T. Tischler and M. Wiebusch for the CBM-MVD Collaboration}
-\affil[1]{Goethe-University, Frankfurt, Germany}
+\affil[]{Goethe-University, Frankfurt, Germany}
\maketitle
-\section{Introduction}
-As part of the development the MVD prototype was commissioned and extensively tested at a beam time at CERN SPS.
-In doing so the performance of the sensors along with the customized frond-end and TRB based DAQ system was investigated
-with regard to the synchronization and long-term stability of the continuous multi-channel readout, the positional stability and the sensor performance (efficiency, resolution, fake hit rate).
-As sensors MIMOSA-26 was used, which is a sizable precursor to the final sensor.
+%\section{Introduction}
+The prototype of the CBM Micro Vertex Detector (MVD) was commissioned and extensively tested at a beam time at CERN SPS.
+The performance of the sensors along with the customized frond-end and TRB based DAQ system was investigated
+regarding the synchronization and long-term stability of the continuous multi-channel readout, the positional stability and the sensor performance (efficiency, resolution, fake hit rate).
+As pixel sensors MIMOSA-26 \cite{MW} was used, which represents a sizable precursor to the final sensor.
It comprises the prototype readout concept including on-chip hit discrimination and data sparsification.
-Further, the sensor is based on a high-resistivity epitaxy layer and was thinned down all up to a thickness of 50\ $\mu$m.
+Further, the sensor is based on a high-resistivity epitaxy layer and was thinned down to a thickness of 50\ $\mu$m.
-Here, the results related to the analysis of the detection performance are discussed.
-A discussion related to the DAQ can be found in \cite{BM, BM2} and related to the mechanics in \cite{TT}.
-It should be shared that related to the synchronization and stability of the DAQ no reservation was diagnosed.
-However, at highest occupancies and/or very low thresholds fluctuations in the supply voltage of the sensors were observed, which led to a bad sensor performance.
-%The stability of the DAQ remained unaffected.
-
-\section{Setup}
-Altogether 12 identical sensors were arranged in four single-sided reference and one double-sided DUT station,
-whereas ``one side'' denotes two sensors side by side.
+%\section{Setup}
+12 identical sensors were arranged in four single-sided reference and one double-sided DUT station,
+whereas ``one side'' comprises two sensors side by side.
According to this the beam particles were tracked by up to 6 hit points.
-Further the setup permitted to vary the relative arrangement of the stations and the relative inclination of the DUT,
-which was positioned between two reference stations upstream and two downstream for best arm of lever.
+Further, the setup allowed to vary the relative distance of the stations and the inclination of the DUT relative to the reference system.
+The DUT was sandwiched between two reference stations, respectively.
In addition the temperature of the DUT could be varied independent of the temperature of the reference system.
The material budget amounts to 0.05\%\ $X_{0}$ for each of the reference stations and 0.3\%\ $X_{0}$ for the DUT.
-The DUT station corresponds to one fourth of a first MVD station covering an area of up to $\sim$\ 8\ cm$^{2}$.
+The DUT station corresponds to one fourth of a first MVD station.
+
+The DAQ has worked reliably and has delivered 1.2\ TB of data.
+Its most important analysis results are presented in the following.
+Further information on the MVD can be found in \cite{BM, TT}.
-\section{Results}
+%\section{Results}
A diversity of measurements at different discriminating thresholds, inclination angles and temperatures were carried out.
% to determine the performance of the MVD prototype.
-In total 1.2\ TB significant data was recorded.
-The data was analyzed by an internal custom software, which was developed following the development process of the MVD prototype.
-The software performs data consistency checks, unpacking and the high level analysis including quick overview functions and alignment.
+The data was analyzed by an internal customized software.
+The software performs data consistency checks, unpacking and high level analysis including QA functionalities and a dedicated alignment package, which was established according to its application to simultaneously align up to 6 sensors in the telescope setup.
-In fig. \ref{fig:ShiftSpillTime} and \ref{fig:EffVsFakes} the excellent performance of the MVD prototype should be pointed out.
+Figures \ref{fig:ShiftSpillTime} and \ref{fig:EffVsFakes} demonstrate the excellent performance of the MVD prototype.
Fig. \ref{fig:ShiftSpillTime} shows the temporal course of the alignment of the DUT relative to the reference system.
-A changing of $0.003\ \mu m/s$ could be resolved.
+A change of $0.003\ \mu m/min$ could be resolved.
The single point resolution of the DUT including the resolution of the sensor and the positional stability of the mechanics was found to be about $3.6\ \mu m$.
-This is equivalent to the resolution of the sensor only.
-Fig. \ref{fig:EffVsFakes} shows the efficiency-fake hit properties of the two DUT sensors.
+This is equivalent to the resolution of the sensor only, suggested by the pixel pitch of $20\ \mu m$, no charge decoding and an average cluster size between 1 and 2.
+Fig. \ref{fig:EffVsFakes} shows the efficiency-fake hit relation of the two DUT sensors.
%For the experiment it is necessary to reduce the number of noisy pixels to a minimum at maximum efficiency in order to reduce the data throughput and ambiguities in the tracking.
-In the figure the two approaches masking of noisy pixels and increasing the threshold are confronted.
-The sensors allow to operate at the desired operating point of above $99\%$ efficiency and below $10^{-5}$ hits per pixel and event fake rate.
-For simplicity reasons only the matrix 1 of both sensors is shown.
+The working points are given as a result from varying the on-chip discriminator thresholds.
+For each working point a significant decrease of the fake rate with a slight loss of efficiency only can be obtained by masking noisy pixels.
+This suggests that the majority of fake hits is caused by a subset of hot pixels only.
+%In the figure the two approaches masking of noisy pixels and increasing the threshold are confronted.
+In summary the sensors allow to operate at the desired operating point of above $99\%$ efficiency and below $10^{-5}$ hits per pixel and event fake rate.
\begin{figure}[h]
\centering
\includegraphics[width=0.335\textwidth]{ShiftSpillTime1.pdf}
- \caption{Changing of the translational alignment during one run. Each data point corresponds to one spill.}
+ \caption{Change of the translational relative alignment during one run. Each data point corresponds to one spill.}
\label{fig:ShiftSpillTime}
\end{figure}
\begin{figure}[h]
\centering
\includegraphics[width=0.335\textwidth]{EffVsFakes.pdf}
- \caption{Efficiency as a function of the fake hit rate for two different DUT sensors.
+ \caption{Efficiency as a function of the fake hit rate for two different DUT sensors w/o (solid lines) and w/ (broken lines) masking hot pixels.
%Solid: different threshold settings; dashed: masking of noisy pixels for one threshold setting
}
\label{fig:EffVsFakes}
\begin{thebibliography}{9} % Use for 1-9 references
%\begin{thebibliography}{99} % Use for 10-99 references
-
+\bibitem{MW}
+ J. Baudot, ``First test results of MIMOSA-26, a fast CMOS sensor with integrated zero suppression and digitized output'', IEEE Nucl. Sci. Symp. Conf. Rec.(2009) 1169.
\bibitem{BM}
-B. Milanovic: ``Beamtime Results of the MVD Prototype DAQ Network'', GSI Scientific Report 2012
-\bibitem{BM2}
-B. Milanovic: ``...'', this report
+B. Milanovic, ``Beamtime Results of the MVD Prototype DAQ Network'', GSI Scientific Report 2012
\bibitem{TT}
-T. Tischler: ``...'', this report
+T. Tischler, ``Layout of the Micro Vertex Detector for the CBM experiment'', this report
\end{thebibliography}
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