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update r15a_gamma report according to Jim's comments

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Nam Tran
2017-05-09 11:59:57 -05:00
parent d793c98663
commit c15636f660
3 changed files with 217 additions and 58 deletions
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52
r15a_1809_rate/r15a_gamma.tex
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@@ -119,7 +119,9 @@ pulses from HPGe and \ce{LaBr3} detectors are shown in
\includegraphics[width=1.0\textwidth]{figs/typical_pulses}
\caption{Typical output pulses of HPGe and \ce{LaBr3} detectors: energy
output HPGe high gain (top left), energy output HPGe low gain (top
right), timing output HPGe (bottom left), and \ce{LaBr3} (bottom right).}
right), timing output HPGe (bottom left), and \ce{LaBr3} (bottom right).
Each clock tick corresponds to \SI{10}{\ns} and \SI{2}{\ns} for top and
bottom plots, respectively.}
\label{fig:typical_pulses}
\end{figure}
\end{center}
@@ -127,8 +129,9 @@ pulses from HPGe and \ce{LaBr3} detectors are shown in
The timing pulses from the HPGe detector were not used in this analysis because
they are too long and noisy (see bottom left \cref{fig:typical_pulses}).
Energy of the HPGe detector is taken as amplitude of spectroscopy amplifier
outputs, its timing is determined by the clock tick where the trace passing
\SI{30}{\percent} of the amplitude.
outputs, its timing is determined by the clock tick where the trace passes
\SI{30}{\percent} of the amplitude. The timing resolution is \SI{235}{\ns}
using this method.
\ce{LaBr3} pulses were passed through a moving average window filter (60
samples wide), then integrated to obtain energy resolution.
@@ -141,14 +144,16 @@ position. There was a separate run for background radiation.
\cref{fig:uncalibrated_labr3_spectra} shows \ce{LaBr3}
spectra with calibration sources \ce{^{88}Y}, \ce{^{60}Co}, and background
radiation. It can be seen that the self activation from \ce{Ac} dominates the
spectra. The \SI{1173}{\kilo\eV} peak barely shows up in \ce{^{60}Co}
spectrum, while the \SI{1332}{\keV} peak is buried under the
\SI{1436}{\kilo\eV} peak from \ce{^{138}La}. The \SI{1836}{\kilo\eV}
peak of \ce{^{88}Y} and the annihilation peak \SI{511}{\kilo\eV} can be
distinguished, but the \SI{898}{\kilo\eV} has been distorted by the electrons
and \SI{789}{\kilo\eV} gammas from the beta decay of \ce{^{138}La}. The energy
resolution (FWHM) at the \SI{1836}{\kilo\eV} peak was \SI{5.9}{\percent}.
radiation. It can be seen that below \SI{1.5}{\MeV} region the self activation
from \ce{^{138}La} shows up clearly, and above that products from the chain
decay of \ce{^{227}Ac} dominate the spectrum. The \SI{1173}{\kilo\eV} peak
barely shows up in \ce{^{60}Co} spectrum, while the \SI{1332}{\keV} peak is
buried under the \SI{1436}{\kilo\eV} peak from \ce{^{138}La}. The
\SI{1836}{\kilo\eV} peak of \ce{^{88}Y} and the annihilation peak
\SI{511}{\kilo\eV} can be distinguished, but the \SI{898}{\kilo\eV} has been
distorted by the electrons and \SI{789}{\kilo\eV} gammas from the beta decay of
\ce{^{138}La}. The energy resolution (FWHM) at the \SI{1836}{\kilo\eV} peak was
\SI{5.9}{\percent}.
\begin{center}
\begin{figure}[htbp]
@@ -162,6 +167,7 @@ resolution (FWHM) at the \SI{1836}{\kilo\eV} peak was \SI{5.9}{\percent}.
\end{center}
The HPGe spectra are much cleaner as shown in Figure~\ref{fig:hpge_ecal}.
Energy resolutions are better than \SI{3.2}{\keV} for all calibrated peaks.
\begin{center}
\begin{figure}[htbp]
\centering
@@ -215,12 +221,20 @@ $2p-1s$ & 346.8 & \num{7.26e-4} &\num{4.73e-5} \\
\label{sub:labr3_spectra}
The \ce{LaBr3} energy spectra for the Al dataset are presented in
\cref{fig:labr3_all_al_runs}. The muonic $2p-1s$ peak shows up clearly in
the prompt spectrum as expected. The \SI{1809}{\kilo\eV} peak can be
recognized, it has better
signal-to-background ratio in the prompt spectrum than in the delay spectrum
(0.88 to 0.33). The background under the \SI{1809}{\kilo\eV} is dominated by
the $\alpha$ decay of progenies from \ce{^{227}Ac}. I think that this
\ce{LaBr3} in the current set up is not suitable to use as a STM detector.
the prompt spectrum as expected, the signal-to-background ratio is
\num{3.13(2)}. The \SI{1809}{\kilo\eV} peak can be
recognized, it has better signal-to-background ratio in the prompt spectrum
than in the delay spectrum (0.88 to 0.33). The background under the
\SI{1809}{\kilo\eV} is dominated by
the $\alpha$ decay of progenies from \ce{^{227}Ac}.
It is clear that this
\ce{LaBr3} detector in the current set up is not good enough to measure the
\SI{1809}{\keV} line. The situation of the $2p-1s$ line is a little better, but
more studies is needed to understand the background and possible interferences
around the peak. On another note, there have been steady progress in
manufacturing \ce{LaBr3} detectors, and better performance has been observed.
\begin{center}
\begin{figure}[htbp]
\centering
@@ -288,7 +302,7 @@ Therefore the emission rate per nuclear capture is:
R_{1808.7} = \frac{N_{1808.7}}{A_{1808.7} \times N_{\mu} \times 0.609} = 0.51 \pm 0.05,
\end{equation}
, where the factor 0.609 comes from the fact that only \SI{60.9}{\percent} of
stopped muons are captured. This result is consistent with the rate reported
by Measday et al.
stopped muons are captured. This result is consistent with the rate
\num{0.51(5)} reported by Measday et al.
\end{document}