source: trunk/MagicSoft/TDAS-Extractor/Introduction.tex@ 5995

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1\section{Introduction}
2
3\begin{itemize}
4\item{Short description of the MAGIC read-out system}
5\end{itemize}
6
7Figure~\ref{fig:MAGIC_read-out_scheme} shows a sketch of the MAGIC read-out scheme, including the PMT camera,
8the analog-optical link, the majority trigger logic and
9FADCs. The used PMTs provide a very fast
10response to the input light signal. The response of the PMTs to sub-ns input light pulses shows a FWHM of
111.0 - 1.2 ns and rise and fall times of 600 and 700 ps correspondingly \cite{Magic-PMT}. By modulating VCSEL
12type laser diodes in amplitude, the fast analogue signals from the PMTs are transferred via 162\,m long,
1350/125\,$\mu$m diameter optical fibers to the counting house \cite{MAGIC-analog-link-2}. After transforming the
14light back to an electrical signal, the original PMT pulse has a FWHM of about 2.2 ns and rise and fall
15times of about 1\,ns. % was 2.2 ns
16
17%an analog optical link \ci
18%te{MAGIC-analog-link-2} to the counting house.
19
20
21\begin{figure}[h!]
22\begin{center}
23\includegraphics[width=\textwidth]{Magic_readout_scheme1.eps}
24\end{center}
25\caption[Current MAGIC read-out scheme.]{Current MAGIC read-out scheme: the analog PMT signals are
26transferred via an analog optical link to the counting house where after the trigger decision the signals
27are digitized by using a 300 MHz FADCs system and written to the hard disk of a DAQ PC.}
28\label{fig:MAGIC_read-out_scheme}
29\end{figure}
30
31
32
33%After modulating VCSEL type laser diodes, after traveling through 162m of multi-mode graded index fiber of 50/125 $\mu$m diameter and.
34
35
36In order to sample this pulse shape with the used 300 MSamples/s FADC system, the pulse is shaped to a
37FWHM greater than 6\,ns
38(the original pulse is folded with a stretching function of 6ns). Because the MAGIC FADCs have a
39resolution of 8 bit only, the signals are split into two branches with gains differing by a factor 10.
40One branch is delayed by 55\,ns and then both branches are multiplexed and consecutively read-out by one FADC.
41Figure~\ref{fig:pulpo_shape_high} shows a typical average of identical input signals.
42% The maximum sustained trigger rate could be 1 kHz. The FADCs feature a FIFO memory which allows a significantly higher short-time rate.
43% Obviously by doing this, more LONS is integrated and thus the performance of the telescope on the analysis level is degraded.
44
45\par
46
47\ldots {\textit{STILL MISSING:} \ldots
48\begin{itemize}
49\item DAQ jumps
50\item clock noise
51\item inner and outer pixels
52\end{itemize}
53
54} \ldots
55
56
57%%% Local Variables:
58%%% mode: latex
59%%% TeX-master: "MAGIC_signal_reco"
60%%% End:
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