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@@ -382,7 +382,8 @@ the cut on protons is estimated to be small compared to the statistical ones.
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\subsection{Corrections for the number of protons}
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\label{sub:corrections_for_the_number_of_protons}
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The protons spectra observed by the silicon detectors have been modified by
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the energy loss inside the target so correction (or unfolding) is necessary.
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the energy loss inside the target so correction (also called unfolding, or
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reconstruction) is necessary.
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The unfolding, essentially, is finding a response function that relates proton's
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true energy and measured value. This can be done in MC simulation by generating
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protons with a spatial distribution as close as possible to the real
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@@ -413,4 +414,57 @@ method is implemented.
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\label{fig:al100_resp_matrices}
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\end{figure}
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After training the unfolding code is applied on the measured spectra from the
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left and right arms. The unfolded proton spectra
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left and right arms. The unfolded proton spectra in \cref{fig:al100_unfold}
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reasonably reflect the distribution of initial protons which is off-centred to
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the right arm. The path length to the left arm is longer so less protons at
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energy lower than \SI{5}{\MeV} could reach the detectors. The sharp low-energy
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cut off on the right arm is consistent with the Coulomb barrier for protons,
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which is \SI{4.1}{\MeV} for protons emitted from $^{27}$Mg.
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Comparing the reconstructed spectra from \SIrange{5}{8}{\MeV}, the protons
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yields are consistent with each other:
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\begin{align}
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N_{\textrm{p reco. left}} &= (110.9 \pm 2.0)\times 10^3\\
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N_{\textrm{p reco. right}} &= (110.2 \pm 2.3)\times 10^3
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\end{align}
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Therefore, the number of emitted protons is taken as average value:
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\begin{equation}
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N_{\textrm{p reco.}} = (110.6 \pm 2.2) \times 10^3
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\end{equation}
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\begin{figure}[htb]
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\centering
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\includegraphics[width=0.85\textwidth]{figs/al100_unfold}
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\caption{Unfolded proton spectra from the 100-\si{\um} aluminium target.}
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\label{fig:al100_unfold}
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\end{figure}
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\subsection{Number of nuclear captures}
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\label{sub:number_of_nuclear_captures}
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\begin{figure}[htb]
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\centering
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\includegraphics[width=0.85\textwidth]{figs/al100_ge_spec}
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\caption{X-ray spectrum from the aluminium target, the characteristic
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$(2p-1s)$ line shows up at 346.67~keV}
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\label{fig:al100_ge_spec}
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\end{figure}
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The X-ray spectrum on the germanium detector is shown on
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\cref{fig:al100_ge_spec}. Fitting the double peaks on top of a first-order
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polynomial gives the X-ray peak area of $5903.5 \pm 109.2$. With the same
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procedure as in the case of the active target, the number stopped muons and
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the number of nuclear captures are:
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\begin{align}
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N_{\mu \textrm{ stopped}} &= (1.57 \pm 0.05)\times 10^7\\
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N_{\mu \textrm{ nucl. cap.}} &= (9.57\pm 0.31)\times 10^6
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\end{align}
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The proton emission rate in the range from \SIrange{5}{8}{\MeV} is therefore:
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\begin{equation}
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R_{\textrm{p}} = \frac{110.6\times 10^3}{9.57\times 10^6} = 1.16\times
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10^{-2}
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\label{eq:proton_rate_al}
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\end{equation}
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\subsection{Uncertainties of the emission rate}
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\label{sub:uncertainties_of_the_emission_rate}
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