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--- /dev/null
+
+
+\documentclass[a4paper,11pt]{article}
+\usepackage{lineno}
+\setpagewiselinenumbers
+% \linenumbers
+
+\pdfoutput=1 % if your are submitting a pdflatex (i.e. if you have
+ % images in pdf, png or jpg format)
+
+\usepackage{jinstpub} % for details on the use of the package, please
+ % see the JINST-author-manual
+
+\title{ Electronics for the RICH Detectors of the HADES and CBM Experiments}
+
+
+%% %simple case: 2 authors, same institution
+%% \author{A. Uthor}
+%% \author{and A. Nother Author}
+%% \affiliation{Institution,\\Address, Country}
+
+% more complex case: 4 authors, 3 institutions, 2 footnotes
+\author[a]{J. Michel,}
+\author[c]{M. Faul,}
+\author[d]{J. Friese,}
+\author[b]{K.-H. Kampert,}
+\author[b]{V. Patel,}
+\author[b]{C. Pauly,}
+\author[b]{D. Pfeifer,}
+\author[c]{P. Skott,}
+\author[c]{M. Traxler}
+\author[c]{and C. Ugur}
+
+% The "\note" macro will give a warning: "Ignoring empty anchor..."
+% you can safely ignore it.
+
+\affiliation[a]{Goethe University Frankfurt, Institute for Nuclear Physics\newline
+Max-von-Laue-Str. 1, Frankfurt, Germany}
+\affiliation[b]{Bergische Universit\"at Wuppertal, Germany}
+\affiliation[c]{GSI Helmholtz Center for Heavy Ion Research GmbH, Planckstr. 1, Darmstadt, Germany}
+\affiliation[d]{Technical University Munich, Arcisstr. 21, M\"unchen, Germany}
+
+% e-mail addresses: only for the forresponding author
+\emailAdd{michel@physik.uni-frankfurt.de}
+
+
+
+
+\abstract{The RICH detectors of the existing HADES spectrometer and the CBM experiment (to be built at FAIR) will use 64 channel Multi-Anode PMTs.
+We designed a complete set of digitizing electronics, consisting of analog and digital frontend modules, power supply and data concentrator cards plugged into a backplane carrying 3x2 MAPMTs on the front side, and all readout modules on the backside.
+These contain all necessary supply electronics, preamplifiers and FPGA-based TDC as well as the digital data and trigger handling logic and an optical transceiver. We are going to present the electronics along with performance test results.}
+
+
+
+\keywords{Analogue electronic circuits, Front-end electronics for detector readout}
+
+
+% \arxivnumber{1234.56789} % only if you have one
+
+
+
+\collaboration[c]{on behalf of the HADES and CBM collaborations}
+
+
+% if you write for a special issue this may be useful
+\proceeding{TWEPP 2016 - Topical Workshop on Electronics for Particle Physics\\
+ 26-30 September 2016\\
+ Karlsruhe }
+
+
+
+\begin{document}
+\maketitle
+\flushbottom
+
+\section{Introduction}
+The two heavy ion spectrometers (HADES and CBM) at the GSI Helmholtz Center for Heavy Ion Research (Darmstadt, Germany) and the FAIR accelerator contain a Ring Imaging Cherenkov (RICH)
+detector for particle identification. The existing RICH at the HADES experiment is in operation since the year 2000. Originally, it was built using a CsI photo cathode plane for photon detection. At the moment it is being upgraded with a new MAPMT readout plane consisting of 428 64-channel PMTs (Hamamatsu H12700). Here, the sensitive area of about $1.3~\rm{m}^2$ will be covered with 28,000 inidividual PMT cells.
+
+The RICH detector for the CBM experiment will follow the same design, albeit with a larger read-out plane of about twice the size and an even larger sensitive volume. This detector is going to use identical electronics to the HADES setup, with modifications to the read-out system.
+As a third project, the PANDA experiment, to be built at FAIR during the next years, comprises a DIRC as one of its central parts that is planned to use very similar electronics as well.
+
+\section{The Components}
+ \begin{figure}[htbp]
+ \centering % \begin{center}/\end{center} takes some additional vertical space
+ \includegraphics[width=.5\textwidth]{../figures/dirich/dirich_system.jpg}
+ \caption{\label{fig:module} The full module, partially equipped. Connecting 6 MA-PMTs and all related electronics on a 10 cm by 15 cm backplane.}
+ \end{figure}
+The read-out plane of both RICH detectors is segmented into small modules, consisting of an array of two by three photo multipliers. Such a module measures 10 by 15 cm and houses 384 individual photon detection channels. Scalability dictates that all electronics necessary for this detector are to be integrated on the same footprint. Hence, a modular concept with individual plug-in cards has been developed. The main component is a backplane that connects all cards and is used to route all analog and digital connections as well as power lines.
+
+
+\subsection{The DiRich Board}
+ \begin{figure}[htbp]
+ \centering % \begin{center}/\end{center} takes some additional vertical space
+ \includegraphics[width=.7\textwidth]{../figures/dirich/dirich1_07_170816.jpg}
+ \caption{\label{fig:dirich} The DiRich board. From left to right: Backplane connector, Amplifiers, TDC-FPGA with threshold filters, auxillary electronics, voltage regulators}
+ \end{figure}
+
+The DiRich board houses all electronics necessary for PMT read-out, from the analog pre-amplifiers to the digital read-out data stream. It is completely based on off-the-shelf components to be independent of hard to acquire ASICs. Each board has 32 input channels, serving one half of a MA-PMT. Both boards have to fit to the back of a single photo multiplier to allow for seamless scaling of the system. The size of each board is $47 \times 100 \times 10~\rm{mm}^3$. To keep the cooling requirements on moderate levels, a low power consumption was one of the key design aspects.
+
+The central part of the system is formed by an FPGA. The FPGA does not only do time-to-digital conversion (described below), but also contains the signal discriminator, threshold generation and the complete DAQ network stack.
+
+Discrimination of input signals is realized in the devices LVDS receivers: One input is connected to the amplified signal, the other is supplied with an adjustable threshold voltage. The thresholds are generated by the FPGA using a 16 Bit delta-sigma DAC for each channel. Time measurement is accomplished by a tapped delay line TDC, capable of an accuracy of down to 10~ps (see below).
+
+In the triggered read-out architecture of HADES, data is stored in internal buffers until a read-out request is received. A trigger window can be applied to recorded data before it is sent out over a 2 GBit/s link over the backplane. For data communication, the TrbNet\cite{trbnet} protocol is employed. This protocol has been developed for the full data acquisition system of the HADES experiment and is able to transport trigger information, read-out data and slow-control simultaneously over the same serial link.
+
+\subsubsection{Analog Stage}
+ \begin{figure}[htbp]
+ \centering % \begin{center}/\end{center} takes some additional vertical space
+ \includegraphics[width=.7\textwidth]{figures/analog.png}
+ \caption{\label{fig:analog} The schematics of one channel of the analog stage of the DiRich board.}
+ \end{figure}
+ \begin{figure}[htbp]
+ \centering % \begin{center}/\end{center} takes some additional vertical space
+ \includegraphics[width=.5\textwidth]{figures/pulses.png}
+ \caption{\label{fig:pulses} Examples of input (top) and output (bottom) signals.}
+ \end{figure}
+
+The typical input signals from the PMTs has a length of about 2~ns and an amplitude between 5 and 40~mV. Before this signal can be fed into a fast discriminator, it has to be amplified by a factor of 20. The discrete amplification stage is built around a wideband transistor (BFU760F) as a common emitter amplifier. The typical resistor at the collector has been replaced by an inductor in this circuit for various reasons. First, it allows to use a low operating voltage of only 1.1~V while keeping the static current in the transistor low. Additionally it helps in shaping the output signal as a high-pass filter. The rise time is preserved, but an undershoot is added at the end of the signal to help in returning to the baseline. In the current configuration, the amplifier takes only 50~ns to return to the baseline, avoiding pile-up and wrong time-over-threshold measurements for close signals. Lastly, the undershoots generates a fast crossing of the threshold resulting in a better timing measurement. The amplification stage has been measured to consume 12mW per channel.
+
+The amplified signal with a very fast rise time is then fed into an input of an LVDS-receiver of the FPGA (LFE5UM-85F-8BG381C). The individual threshold
+voltage for the discriminator is produced by a delta-sigma DAC output of the FPGA with a simple, two-stage low pass filter connected to the output pin. This DAC reaches a resolution of 38uV and shows no measureable ripple. The switiching of the 32 channels is timed such that no two channels switch at the same time and the switiching of each channel is limited to few MHz to keep the generated noise level as low as possible.
+
+\subsubsection{Time Measurement}
+
+\subsection{Supplementary Boards}
+ \begin{figure}[htbp]
+ \centering % \begin{center}/\end{center} takes some additional vertical space
+ \includegraphics[width=.4\textwidth]{../figures/dirich/dirich_power.jpg}
+ \qquad
+ \includegraphics[width=.4\textwidth]{../figures/dirich/dirich_concentrator.jpg}
+ \caption{\label{fig:aux} The two auxillary boards: Power supplies (left) and data concentrator (right)}
+ \end{figure}
+The front-end module is complemented by two auxillary boards. The power board houses switiching and linear voltage regulators to provide all necessary supply voltages. Additionally, trigger (reference time) and clock signals are distributed to all front-ends from this board. Two ADC allow for detailed monitoring of all voltages and currents. The board currently forsees two possible powering schemes: A 24~V input and DC-DC converters provide the most simple external supply. A second option is the direct input of externally regulated low voltages (1.1~V - 3.3~V). In this case, only linear regulators are active and the electromagnetic noise in the system is reduced. Which of the two options will be used in the final system is currently under investigation.
+
+The second board is the data concentrator. Built around a Lattice ECP3 FPGA, it serves as hub to connect all front-end modules to the central DAQ system. In the HADES configuration, this board runs a total of 13 links at 2 GBit/s using the TrbNet protocol. The reference time for all TDC is supplied by an additional LVDS signal generated by the central trigger system (CTS). In the CBM experiment, data acquisition will not be triggered, but free-streaming. This can be achieved by altering the data processing scheme inside the network and endpoints while keeping the underlying network protocol the same. In this setup, also the clock distribution and fixed-latency synchronization messages will be embedded into the optical data stream to reduce the number of electrical connections inside the detector.
+
+The 2 GBit/s link of the concentrator board is able to transport the data of up to 40 Mhits/s from each module. As the CBM and PANDA detectors expect hit rates of up to 200 kHz per channel and 60 MHits/s per module in the central parts of the detector, this bandwidth is not sufficient. Here, an upgraded version of the concentrator, using a 4.8 GBit/s optical link will be employed.
+
+
+\section{Summary}
+
+
+\acknowledgments
+
+This work has been supported by BMBF grant 05P15PXFCA. All photographs where kindly provided by G. Otto, GSI.
+
+
+
+
+
+% We suggest to always provide author, title and journal data:
+% in short all the informations that clearly identify a document.
+
+\begin{thebibliography}{99}
+
+% \bibitem{a}
+% Author, \emph{Title}, \emph{J. Abbrev.} {\bf vol} (year) pg.
+%
+% \bibitem{b}
+% Author, \emph{Title},
+% arxiv:1234.5678.
+%
+% \bibitem{c}
+% Author, \emph{Title},
+% Publisher (year).
+
+\bibitem{cbmrich}
+C. H\"ohne (Ed) et al.,
+\emph{Technical Design Report for the CBM Ring Imaging Cherenkov (RICH) Detector},
+GSI-2014-00528, http://repository.gsi.de/record/65526
+
+\bibitem{trb-web}
+The TRB3 website, \href{http://trb.gsi.de}{http://trb.gsi.de}.
+
+\bibitem{cbm-web}
+The CBM website,
+\href{http://www.fair-center.eu/for-users/experiments/cbm.html}{http://www.fair-center.eu/for-users/experiments/cbm.html}.
+
+\bibitem{trbnet}
+J. Michel et al.,
+\emph{The HADES DAQ system: Trigger and readout board network}, IEEE Trans.Nucl.Sci. 58 (2011) 1745-1750
+
+% Please avoid comments such as "For a review'', "For some examples",
+% "and references therein" or move them in the text. In general,
+% please leave only references in the bibliography and move all
+% accessory text in footnotes.
+
+% Also, please have only one work for each \bibitem.
+
+
+\end{thebibliography}
+\end{document}
jspc29 / publication.git / commitdiff
