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new unit for speed of light

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nam
2017-01-27 12:23:12 -05:00
parent 2d693b3a41
commit daee5ed40d
7 changed files with 34 additions and 32 deletions
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32
thesis/chapters/chap3_comet.tex
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@@ -90,8 +90,8 @@ to reduce the radiative pion capture and other prompt backgrounds. Cosmic
backgrounds are
rejected using a combination of
passive shielding, veto counters and reconstruction cuts. The momenta of beam
muons used in the experiment were \SI{52}{\MeV\per\cc} and
\SI{53}{\MeV\per\cc}, and the momentum spread was 2\%.
muons used in the experiment were \SI{52}{\MeV\per\hepclight} and
\SI{53}{\MeV\per\hepclight}, and the momentum spread was 2\%.
\begin{figure}[htbp] \centering
\includegraphics[width=0.85\textwidth]{figs/sindrumII_setup}
\caption{SINDRUM-II experimental set up, reprinted from
@@ -409,9 +409,9 @@ transport section.
The \ang{180} bending electron transport solenoids help remove line-of-sight
between the target and the detector system. It works similarly to the muon
transportation section, but is tuned differently to accept electrons of about
\SI{105}{\MeV\per\cc}. A compensation field of \SI{0.17}{\tesla} along the
\SI{105}{\MeV\per\hepclight}. A compensation field of \SI{0.17}{\tesla} along the
vertical direction will be applied. Electrons with momentum less than
\SI{80}{\MeV\per\cc} are blocked at the exit of this section by
\SI{80}{\MeV\per\hepclight} are blocked at the exit of this section by
a collimator to reduce DIO electrons rate. The net acceptance of signals of
\mueconv is about 0.32, and the detector hit rate will be in the order of
\SI{1}{\kHz} for a muon stopping rate of \SI{E11}{\Hz}.
@@ -429,12 +429,12 @@ active shielding against cosmic rays is considered.
The tracking detector has to provide a momentum resolution less than
%%TODO 350 or 150?
350~\si{\kilo\electronvolt\per\cc} in order to achieve a sensitivity of
350~\si{\kilo\electronvolt\per\hepclight} in order to achieve a sensitivity of
\sn{3}{-17}. There are five stations of straw-tube gas chambers, each provides
two dimensional information. Each straw tube is 5~\si{\milli\meter} in diameter
and has a 25-\si{\micro\meter}-thick wall. According to a GEANT4 Monte Carlo
simulation, a position resolution of 250~\si{\micro\meter} can be obtained,
which is enough for 350~\si{\kilo\electronvolt\per\cc} momentum resolution. The
which is enough for 350~\si{\kilo\electronvolt\per\hepclight} momentum resolution. The
DIO background of 0.15 events is expected.
The electromagnetic calorimeter serves three purposes: a) to measure electrons
@@ -450,11 +450,11 @@ hit positions. Two candidate crystals, GSO and LYSO, are under consideration.
The requirements for \mueconv signals are:
\begin{itemize}
\item from the 350~\si{\kilo\electronvolt\per\cc}~momentum resolution, the signal
region is determined to be 103.5~\si{\mega\electronvolt\per\cc}~to
105.2~\si{\mega\electronvolt\per\cc};
\item from the 350~\si{\kilo\electronvolt\per\hepclight}~momentum resolution, the signal
region is determined to be 103.5~\si{\mega\electronvolt\per\hepclight}~to
105.2~\si{\mega\electronvolt\per\hepclight};
\item transversal momentum of signal electrons is required to be greater than
52~\si{\mega\electronvolt\per\cc} to remove backgrounds from beam electrons and
52~\si{\mega\electronvolt\per\hepclight} to remove backgrounds from beam electrons and
muons decay in flight;
\item timing wise, conversion electrons should arrive in the time window of
detection which is about 700~\si{\nano\second}~after each proton pulses
@@ -675,7 +675,7 @@ avalanche gain of
approximately \sn{4}{4}. A gas mixture of helium:isobutane(90:10) is preferred
since the CDC momentum resolution is dominated by multiple scattering. With
these configurations, an intrinsic momentum resolution of
197~\si{\kilo\electronvolt\per\cc} is achievable according to our tracking study.
197~\si{\kilo\electronvolt\per\hepclight} is achievable according to our tracking study.
\begin{table}[htb]
\begin{center}
@@ -712,7 +712,7 @@ these configurations, an intrinsic momentum resolution of
\label{ssub:hit_rate_on_the_cdc}
The maximal usable muon beam intensity will be limited by the detector hit
occupancy. Charge particles with transversal momentum greater than 70
\si{\mega\electronvolt\per\cc} are expected to reach the CDC. Those include:
\si{\mega\electronvolt\per\hepclight} are expected to reach the CDC. Those include:
protons emitted from nuclear muon capture, and electrons from muon decay in
orbit (DIO). It is calculated that the hit rate due to proton emission dominates,
where the highest rate is \SI{11}{\kHz\per}cell compares to
@@ -733,9 +733,9 @@ $^{28}$Si~\cite{SobottkaWills.1968}. The baseline design for the proton
absorber is 0.5~\si{\milli\meter}-thick CFRP, making the total thickness
of material before the sensitive region is \SI{1.0}{\mm} in CFRP. In this
configuration, the inner wall and the proton absorber contribute a spread of
\SI{167}{\keV\per\cc} to the momentum of a \mueconv signal electron. This
\SI{167}{\keV\per\hepclight} to the momentum of a \mueconv signal electron. This
figure is a little below the spread cause by multiple scatterings on the
chamber gas at \SI{197}{\keV\per\cc}.
chamber gas at \SI{197}{\keV\per\hepclight}.
The impact of the proton absorber on the CDC's hit rate and momentum
resolution is summarised in \cref{tab:comet_absorber_impact}.
\begin{table}[htb]
@@ -745,7 +745,7 @@ resolution is summarised in \cref{tab:comet_absorber_impact}.
\textbf{Absorber }& \textbf{Total CFRP }&\textbf{Proton }&
\textbf{$\Delta p$}\\
\textbf{thickness }& \textbf{thickness }&\textbf{hit rate }& \\
(\si{\mm}) &(\si{\mm}) & (\si{\kHz}) & (\si{\keV\per\cc}) \\
(\si{\mm}) &(\si{\mm}) & (\si{\kHz}) & (\si{\keV\per\hepclight}) \\
\midrule
0 & 0.5 & 130 & 131 \\
0.5 & 1.0 & 34 & 167 \\
@@ -756,7 +756,7 @@ resolution is summarised in \cref{tab:comet_absorber_impact}.
\end{center}
\caption{Hit rates and contributions to momentum spread of the proton
absorber and inner wall of the CDC. The resolutions are calculated for
mono-energetic electrons of \SI{104.96}{\MeV\per\cc}.}
mono-energetic electrons of \SI{104.96}{\MeV\per\hepclight}.}
\label{tab:comet_absorber_impact}
\end{table}