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6.5.2011 Kamil Sedlak

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1) Adding/improving the simulation of light signals and APD
2) Many small changes and improvements
3) Adding manual to musrSimAna to the svn repository
4) Adding some example files for musrSim
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doc/musrSim.tex
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@ -23,7 +23,7 @@
%\title{GEANT Simulation Program for the
%$\mathbf{\mu}$SR Instruments}
\author{Kamil Sedl\'ak$^1$, Toni Shiroka$^1$, Zaher Salman$^1$, Tom Lancaster$^2$, Thomas Prokscha$^1$, Taofiq Paraiso$^1$}
\author{Kamil Sedl\'ak$^1$, Toni Shiroka$^1$, Zaher Salman$^1$, Jose Rodriguez$^1$, Tom Lancaster$^2$, Thomas Prokscha$^1$, Taofiq Paraiso$^1$}
\address{{$^1$ Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland}\\
$^2$ Clarendon Laboratory, Department of Physics, Oxford University, Parks Road, Oxford OX1 3PU, UK}
@ -1292,6 +1292,176 @@ scintillator tiles.}
illustrates a simple geometry made of an electron source and two blocks
of scintilator tiles with the dimensions of $3 \times 3 \times 2\,$mm,
which is defined in the macro file ``101.mac''.
The primary particles are electrons with the energy of 2.15\,MeV shooted
into the first scintillator. There the electron can be scattered, and therefore
it may or may not hit the second scintillator. We have used the command\\[2ex]
{\tt /musr/command storeOnlyEventsWithHitInDetID 11}\\[2ex]
and therefore only the events, in which there was some energy deposited
in the second collimator, will be saved into the output Root file.
To run this example, do the following:
\begin{enumerate}
\item Change to the directory {\tt musrSim/run/}
\item If the subdirectory {\tt data} does not exist, create it.
\item Run your Geant4 initialisation script (typically something like \\
{\tt source /home/install/geant4.9.4/env.sh}\\
where the path to the {\tt env.sh} script depends on the directory where Geant4
is installed on your computer.
\item Execute the command {\tt musrSim 101.mac}
\item The example file {\tt 101.mac} will try to visualise the events using the
Dawn graphics program. To simulate some data (without the visualisation),
uncomment the line {\tt /vis/disable}, comment the line
{\tt /control/execute visDawn101.mac} and change number of generated events
to e.g.\ 1000 (by command {\tt /run/beamOn 1000}).
\item Look at the output using Root, e.g.\ by commands \\
{\tt \$ root} \\
{\tt root [0] TFile* f2=new TFile("data/musr\_101.root") } \\
{\tt root [1] .ls } \\
{\tt root [2] t1->Print() } \\
{\tt root [3] t1->Draw("det\_edep","det\_ID==10") } \emph{\small //energy deposited in the first scintillator}\\
{\tt root [4] t1->Draw("det\_edep","det\_ID==11") } \emph{\small //energy deposited in the second scintillator}\\
{\tt root [5] t1->Draw("det\_time\_start[0]-det\_time\_start[1]")} \emph{\small //T.O.F. between the two scint.} \\
{\tt root [6] .q}\\
Note that the hits in one event are ordered according to the deposited energy, and therefore the
first hit sometimes corresponds to the hit in scintillator counter 10, sometimes to the hit in counter 11.
Therefore the histogram created by the command {\tt t1->Draw("det\_time\_start[0]-det\_time\_start[1]")}
has two peaks -- at a positive and at a negative time.
\end{enumerate}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Example 2 -- Sr decay electrons passing through two scintillator tiles (102.mac)}
This example is very similar to the previous one. The only difference is that initial
particles are decay electrons from a $^{90}$Sr source. Because $^{90}$Sr decays to $^{90}$Y,
which in turn also decays emitting an electron, we have in fact two decay electrons per event
(two emission spectra from the strontium source).
The data for the strontium and yttrium decay are taken
from the Geant4 data files, namely\\
{\tt /home/install/data\_geant4.9.4/RadioactiveDecay3.3/z38.a90}~~~~ and\\
{\tt /home/install/data\_geant4.9.4/RadioactiveDecay3.3/z39.a90}. \\
There is, however, one problem in musrSim -- it has to handle times with picoseond precission,
and the \emph{double} precision used in the c{\tt ++} program is then not enough to deal with
the $^{90}$Sr decay time of 29 years.
For this reason, one has to modify the decay times in the two data files, i.e.\
in the file {\tt z38.a90}, one should replace the line\\
\hspace*{1cm}{\tt P~~~~~~~0.0000~~~9.0820e+08}\\
by the line\\
\hspace*{1cm}{\tt P~~~~~~~0.0000~~~9.0820e-08}\\[2ex]
and in the file {\tt z39.a90}, one should replace the lines\\
\hspace*{1cm}{\tt P~~~~~~~0.0000~~~2.3080e+05}\\
\hspace*{1cm}{\tt P~~~~~682.0300~~~1.1480e+04}\\
by the lines\\
\hspace*{1cm}{\tt P~~~~~~~0.0000~~~2.3080e-05}\\
\hspace*{1cm}{\tt P~~~~~682.0300~~~1.1480e-04}\\
This way, the decay times are reasonably short, and musrSim can handle them.
Another complication comes from the fact, that the decay electrons are emitted
isotropically from the Sr source. In principle, it is possible to restrict the
emission angles in the GPS (General Particle Source), but we have not done this
intentionally, because we did not want to exclude events in which the decay electron
enters a counter after scattering in the air. In the end only a very small fraction
of events hits the second counter, and is written out to the output file.
(In any case -- the events in which electron does not enter any counter are simulated in a much
shorter time than the ``interesting'' events.)
The example {\tt 102.mac} is based on the results published in~\cite{kkkkk}.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Example 3 -- Simulation of the light transport (103.mac)}
This example is similar to example~1, and extended by the simulation of light (``optical
photons''). The light simulation slows down the execution of musrSim dramatically.
The simulation of light is a new feature in musrSim, and it is being tested. Once
this is finished, we will improve this example. However, it seems to be running fine
in its current implementation, so you can start using it. A lot of usefull information
about the optical photons is given in chapter ``Optical Photon Processes'' in
the Geant4 User Manual~\cite{geantUserManual}.\\
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Example 4 -- GPD instrument (201.mac)}
%
The General Purpose Decay-Channel Spectrometer (GPD)
instrument~\cite{GPD} at PSI, more or less as implemented in reality in the year 2010, is exemplified in
run {\tt 201.mac}. GPD instrument is optimised for the measurements of pressuarised samples
in a special pressure cells.
The detector system is relatively simple -- it consist of a rectangular muon counter (10x10x2\,mm),
two backward positron counters, three forward positron counters, cylidrical sample in a cylindrical
sample holder, two lead collimators, one copper collimator, GPD magnet, and some additional ``dead'' material.
The GPD geometry is illustrated in Fig.~\ref{fig:vis_201_1}-\ref{fig:vis_201_4},
where some of the elements present in the simulation (beampipe, magnet, aluminium profiles) are not displayed
for simplicity.
The most important parameters of the simulation are summarised in table~\ref{dimensions}.
%
\begin{figure}[tbp]\centering
\epsfig{file=pict/vis_201_1.eps,width=0.5\linewidth,%
bbllx=70pt,bblly=270pt,bburx=455pt,bbury=640pt,clip=}
\caption{3D view at the GPD detector system (run 201). Blue colour indicates the positron counters,
magenta stands for collimators, red is the muon counter. GPD magnet, some Aluminium U-profiles and beampipe
are not shown in the plot, however they are included in the simulation.}
\label{fig:vis_201_1}
\end{figure}
%
%
\begin{figure}[tbp]\centering
\epsfig{file=pict/vis_201_2.eps,width=0.8\linewidth,%
bbllx=90pt,bblly=310pt,bburx=450pt,bbury=525pt,clip=}
\caption{Side view of the GPD detector.}
\label{fig:vis_201_2}
\end{figure}
%
%
\begin{figure}[tbp]\centering
\epsfig{file=pict/vis_201_3.eps,width=0.4\linewidth,%
bbllx=210pt,bblly=320pt,bburx=380pt,bbury=525pt,clip=}
\caption{Front view of the GPD detector.}
\label{fig:vis_201_3}
\end{figure}
%
%
\begin{figure}[tbp]\centering
\epsfig{file=pict/vis_201_4.eps,width=0.9\linewidth,%
bbllx=70pt,bblly=309pt,bburx=485pt,bbury=513pt,clip=}
\caption{Top view of the GPD detector.}
\label{fig:vis_201_4}
\end{figure}
%
\begin{table}[htbp]\centering
\renewcommand{\arraystretch}{1.05}
\begin{tabular}{|l|c|c|}
\hline
\lower 1mm \hbox{\textbf{Component}} & \lower 1mm \hbox{\textbf{Dimension}} & \lower 1mm \hbox{\textbf{Material}} \\[5pt]
\hline
positron counter scintillator & $26 \times 90 \times 5$\,mm & plastic vinyltoluene \\
middle forw. positron counter scint. & $14 \times 90 \times 5$\,mm & plastic vinyltoluene \\
muon counter & $10 \times 10 \times 2$\,mm & plastic vinyltoluene \\
sample & R=3.5\,mm, L=14\,mm & Cu \\
sample cell & R=12\,mm, L=100\,mm & Cu \\
Cu collimator & $80 \times 120 \times (\sim 20 - 30)$\,mm & Cu \\
Cu collimator opening & $5 \times 12$\,mm & \\
Pb collimator & $140 \times 140 \times 30$ & Pb \\
Pb collimator opening & $4 \times 10$\,mm & \\
Collimator 1 & R=100\,mm, L=30\,mm & Pb \\
Collimator 1 opening & R$_{opening}$=8\,mm & \\
distance sample -- Pb collimator & 90\,mm (centre -- centre) & \\
distance sample -- collimator1 & 250\,mm (centre -- centre) & \\
distance sample -- beampipe window & 600\,mm & \\ \hline
muon initial momentum & $100 \pm 3$\,MeV/c & \\
muon initial $z$-coordinate & -1.0\,m with respect to sample & \\
muon initial $x$ and $y$ coordinate & Gaussian smearing, $\sigma_x=\sigma_y=25$\,mm & \\
magnetic field & 300 gauss & \\
\hline
\end{tabular}
\caption{Main parameters of the simulation.}
\label{dimensions}
\end{table}
%
A non-standard feature of this simulation is the muon momentum, which is $~sim$100\,MeV/c.
The copper collimator used in GPD has a bit complicate shape, which required to use subtraction
of logical volumes in Geant\,4. This operation can not be specified through the macro file,
and therefore a special kind of volume called {\tt GPDcollimator} has been hard-coded into
the source code (namely in the routine {\tt musrDetectorConstruction.cc}), and it is
then activated in the macro file using the command \\[2ex]
{\tt /musr/command construct GPDcollimator \ldots}\\[2ex]
%
The results of this GPD simulation are described in the \emph{musrSimAna} manual~\cite{musrSimAna}.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@ -1332,7 +1502,7 @@ in~\cite{Aktas:2004px}.
\bibitem{AlexeyTestAPD} A.~Stoykov {\it et al.}, ``First experience with G-APDs in $\mu$SR instrumentation'',
NDIP08, to be published in Nucl. Instrum. Meth. A.
\bibitem{geant} S.~Agostinelli, et al., Nucl. Instr. and Meth. A 506 (2003) 250.\\ %-303. \\
\bibitem{geant} S.~Agostinelli {\it et al.}, Nucl. Instr. and Meth. A 506 (2003) 250.\\ %-303. \\
J.~Allison, et al., IEEE Trans. Nucl.\ Sci.\ 53 (2006) 270. %-278.
\bibitem{root} R.~Brun, F.~Rademakers ``ROOT - An Object Oriented Data Analysis Framework'',
%Proceedings AIHENP'96 Workshop, Lausanne, Sep. 1996,
@ -1357,9 +1527,12 @@ A.~Aktas {\it et al.} [H1 Collaboration],
Submitted to Eur.\,Phys.\,J.\,{\bf C}, [hep-ex/0401010].
%%CITATION = HEP-EX 0401010;%%
\bibitem{GPD}
http://lmu.web.psi.ch/facilities/gpd/gpd.html
\bibitem{musrSimAna}
K.Sedlak, ``Manual of musrSimAna''.
\end{thebibliography}
\end{document}
\end{document}