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nam
2016-05-02 13:08:13 +09:00
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commit 1dd6fe6878
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93
thesis/chapters/chap5_alcap_setup.tex
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@@ -18,7 +18,7 @@ provide veto signals for the silicon and germanium detectors. Two liquid
scintillators for neutron measurements were also tested in this run.
\begin{figure}[btp]
\centering
\includegraphics[width=0.65\textwidth]{figs/alcap_setup_detailed}
\includegraphics[width=0.95\textwidth]{figs/alcap_setup_detailed}
\caption{AlCap detectors: two silicon packages inside the vacuum vessel,
muon beam detectors including plastic scintillators and a wire chamber,
germanium detector and veto plastic scintillators.}
@@ -30,9 +30,11 @@ Muons in the $\pi$E1 beam line are decay products of pions created
as a \SI{590}{\mega\electronvolt} proton beam hits a thick carbon target. The
beam line was designed to deliver muons with momenta ranging from
\SIrange{10}{500}{\mega\electronvolt\per\cc} and momentum spread from
\SIrange{0.26}{8.0}{\percent}~\cite{Foroughli.1997}. These parameters can be
selected by changing various magnets and slits shown in
\cref{fig:psi_piE1_elements}.
\SIrange{0.26}{8.0}{\percent}~\cite{Foroughli.1997}. The beam parameters can
be tuned by adjusting magnets and slits along the beam line.
%These parameters can be
%selected by changing various magnets and slits
%\cref{fig:psi_piE1_elements}.
%(E-target in \cref{fig:psi_exp_hall_all}).
%\begin{figure}[p]
@@ -44,40 +46,46 @@ selected by changing various magnets and slits shown in
%\label{fig:psi_exp_hall_all}
%\end{figure}
\begin{figure}[btp]
\centering
\includegraphics[width=0.7\textwidth]{figs/psi_piE1_elements}
\caption{The $\pi$E1 beam line}
\label{fig:psi_piE1_elements}
\end{figure}
%\begin{figure}[btp]
%\centering
%\includegraphics[width=0.7\textwidth]{figs/psi_piE1_elements}
%\caption{The $\pi$E1 beam line}
%\label{fig:psi_piE1_elements}
%\end{figure}
One of the main requirements of the AlCap experiment was a low energy muon beam
with narrow momentum bite in order to achieve a high fraction of stopping muons
in the very thin targets. In this Run 2013, muons from
\SIrange{28}{45}{\mega\electronvolt\per\cc} and momentum spread of 1\% and
3\%, respectively, were used.
\SIrange{28}{45}{\MeV\per\cc} and momentum spread of 1\% and
3\% were used.
For part of the experiment the target was replaced with one of the silicon
detector packages allowed an accurate momentum and range calibration
%(via range-energy relations)
of the beam at the target. \Cref{fig:Rates} shows the measured muon rates
as a function of momentum for two different momentum bites.
\Cref{fig:Beam} shows an example of the resulting energy spectra.
\Cref{fig:Beam} shows an example of the resulting energy spectra recorded by
our silicon detector.
\begin{figure}[btp]
\centering
\includegraphics[width=0.6\textwidth]{figs/Rates.png}
\caption{Measured muon rate (kHz) at low momenta. Momentum bite of 3 and 1 \%
FWHM, respectively.}
\includegraphics[width=0.65\textwidth]{figs/Rates.png}
\caption{Measured muon rates at low momenta during the Run 2013. Beam rates
at 1 \% FWHM momentum bite were about 3 times smaller than the rates at
3 \% FWHM.}
\label{fig:Rates}
\end{figure}
\begin{figure}[btp]
\centering
\includegraphics[width=0.9\textwidth]{figs/beam.pdf}
\includegraphics[width=1.00\textwidth]{figs/beam.pdf}
\caption{Energy deposition at \SI{36.4}{/c} incident muon beam in an
\SI{1500}{\micro\meter}-thick active target. The peak at low energy is due
to beam electrons, the peaks at higher energies are due to muons. Momentum
bite of 1 and 3\% FWHM on left and right hand side, respectively.}
bite of 1 and 3\% FWHM on left and right hand side, respectively. The
electron peak are the same in both plots as beam electrons are minimum
ionisation particles and passed though the detector easily. The muon peak
at the 3 \% FWHM momentum bite is notably broader than that at 1 \% FWHM
setting.}
\label{fig:Beam}
\end{figure}
@@ -254,19 +262,25 @@ The germanium detector is
a GMX20P4-70-RB-B-PL, n-type, coaxial high purity germanium detector produced
by ORTEC. The detector was optimised for low energy gamma and X-rays
measurement with an ultra-thin entrance window of 0.5-mm-thick beryllium and
a 0.3-\si{\micro\meter}-thick ion implanted contact (\cref{fig:ge_det_dimensions}).
This detector is equipped with a transistor reset preamplifier which,
according to the producer, enables it to work in an ultra-high rate environment
a 0.3-\si{\micro\meter}-thick ion implanted contact. The germanium crystal is
\SI{52.5}{\mm} in diameter, and \SI{55.3}{\mm} in length. The axial well has
a diameter of \SI{9.9}{\mm} and \SI{47.8}{\mm} deep.
%(\cref{fig:ge_det_dimensions}).
ORTEC quoted the energy resolution of the detector is \SI{1.90}{\keV} at the
\SI{1.73}{\MeV} gamma line. The detector is equipped with a transistor reset
preamplifier which, according to the producer, enables it to work in an
ultra-high rate environment
up to $10^6$ counts\si{\per\second} at \SI{1}{\mega\electronvolt}.
\begin{figure}[btp]
\centering
\includegraphics[width=0.9\textwidth]{figs/ge_det_dimensions}
\caption{Dimensions of the germanium detector}
\label{fig:ge_det_dimensions}
\end{figure}
%\begin{figure}[btp]
%\centering
%\includegraphics[width=0.9\textwidth]{figs/ge_det_dimensions}
%\caption{Dimensions of the germanium detector}
%\label{fig:ge_det_dimensions}
%\end{figure}
The detector was installed outside of the vacuum chamber at 32 cm from the
target, seeing the target through a 10-mm-thick aluminium window, behind
target, viewing the target through a 10-mm-thick aluminium window, behind
a plastic scintillator counter used to veto electrons. Liquid nitrogen
necessary for the operation of the detector had to be refilled every 8 hours.
A timer was set up in the data acquisition system to remind this.
@@ -837,12 +851,12 @@ algorithm that takes the pulse parameters from the peak of the waveform. In
parallel, a pulse finding and template fitting code is being developed because
it would provide more accurate pulse information. The first iteration of this
code has been completed and is being tested.
\begin{figure}[btp]
\centering
\includegraphics[width=0.85\textwidth]{figs/analysis_scheme}
\caption{Concept of the analysis framework in \rootana{}}
\label{fig:rootana_scheme}
\end{figure}
%\begin{figure}[btp]
%\centering
%\includegraphics[width=0.85\textwidth]{figs/analysis_scheme}
%\caption{Concept of the analysis framework in \rootana{}}
%\label{fig:rootana_scheme}
%\end{figure}
After obtaining pulse parameters for individual channel, the pairing up of
fast and slow pulses from the same physical detector needs to be done. This
@@ -1030,10 +1044,15 @@ shown in \cref{fig:lldq}.
\includegraphics[width=0.47\textwidth]{figs/lldq_noise}
\includegraphics[width=0.47\textwidth]{figs/lldq_tdiff}
\caption{Example trend plots used in the low level data quality checking:
noise level in FWHM (left) and time correlation with muon hits (right). The
noise level in FWHM (left) and time correlation with muon hits (right).
The horizontal axis is run number, the vertical axis is the channel name
(left), or the time difference between hit in the germanium
detector and a hit in upstream counter (right). Colors in both plots
indicate the number of events. In the left plot, the
noise level was basically stable in in this data set, except for one
channel. On the right hand side, this sanity check helped find out the
sampling frequency was wrongly applied in the first tranche of the data
channel where there was a sudden jump in a range of runs. On the right hand
side, this sanity check helped find out the sampling frequency was wrongly
applied in the first tranche of the data
set.}
\label{fig:lldq}
\end{figure}