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\begin{document}
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\begin{frontmatter}
\title{McStas ESS source}
% \title{This is a specimen title\tnoteref{t1,t2}}
%%%%\noindent \qquad \\[-6pt] \qquad  Version 1.1\\\qquad 
%\newline
%\today 
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\author{Peter Willendrup$^{1,2}$, Esben Klinkby$^{3,4}$}
\address{1) DTU Physics, Technical University of Denmark, DTU Lyngby Campus, Anker Engelunds Vej 1, DK-2800 Kgs. Lyngby, Denmark}
\address{2) ESS design update programme - Denmark}
\address{3) European Spallation Source ESS AB, Box 176, S-221 00 Lund, Sweden}
\address{4) DTU Nutech, Technical University of Denmark, DTU Ris\o~Campus,\\ Frederiksborgvej 399, DK-4000 Roskilde, Denmark}
\end{frontmatter}
\section{Abstract}
short description




\emph{Keywords}: Neutron, ESS, spallation, MCNPX, McStas, simulation, source, spectrum

\section{Introduction}
In this document the development of the ESS source description in McStas\cite{lefm:1999,will:2013,man,comp} is outlined by comparing brilliance curves of the various versions.

\section{Comparison between ESS source in McStas versions 1.12c, 2.0,
  2.0$+$ and 2.1}
\label{sec:val}

\begin{figure}[h!]
\begin{minipage}{\linewidth}
\centering
\epsfig{figure=figs/Mezei-cold-mean.eps,width=0.48\linewidth}
\epsfig{figure=figs/Mezei-cold-peak.eps,width=0.48\linewidth}
\epsfig{figure=figs/Mezei-thermal-mean.eps,width=0.48\linewidth}
\epsfig{figure=figs/Mezei-thermal-peak.eps,width=0.48\linewidth}
\caption{Mezei moderators. Above left: Mean cold brightness, above right: peak cold. Below left: Mean thermal brightness,. Below right: Peak thermal brightness.}
\label{fig:2001}
\end{minipage}\hfill
\end{figure}

\begin{figure}[h!]
\begin{minipage}{\linewidth}
\centering
\epsfig{figure=figs/1.12c_cold_16.67Hz/Mean_brill.sim.ps,width=0.35\linewidth,angle=-90}
\epsfig{figure=figs/1.12c_cold_16.67Hz/Peak_brill.sim.ps,width=0.35\linewidth,angle=-90}
\epsfig{figure=figs/1.12c_cold_14Hz/Mean_brill.sim.ps,width=0.35\linewidth,angle=-90}
\epsfig{figure=figs/1.12c_cold_14Hz/Peak_brill.sim.ps,width=0.35\linewidth,angle=-90}
\caption{Average(left) and peak(right) cold brilliance curves obtained from running McStas 1.12c using frequenzy 16.67~Hz 3ms (above) and 14~Hz, 2.86~ms below}
\label{fig:2001}
\end{minipage}\hfill
\end{figure}


\begin{figure}[h!]
\begin{minipage}{\linewidth}
\centering
\epsfig{figure=figs/1.12c_therm_16.67Hz/Mean_brill.sim.ps,width=0.35\linewidth,angle=-90}
\epsfig{figure=figs/1.12c_therm_16.67Hz/Peak_brill.sim.ps,width=0.35\linewidth,angle=-90}
\epsfig{figure=figs/1.12c_therm_14Hz/Mean_brill.sim.ps,width=0.35\linewidth,angle=-90}
\epsfig{figure=figs/1.12c_therm_14Hz/Peak_brill.sim.ps,width=0.35\linewidth,angle=-90}
\caption{Average(left) and peak(right) thermal brilliance curves obtained from running McStas 1.12c using frequenzy 16.67~Hz 3ms (above) and 14~Hz, 2.86~ms below}
\label{fig:2001_t}
\end{minipage}\hfill
\end{figure}


Figures~\ref{fig:2001} and \ref{fig:2001_t} show the cold and thermal average and peak brightness respectively.

Figure~\ref{fig:2012vs2001} shows the average(left) and peak(right) brilliance curves obtained from running McStas 2.0 using 2012(upper) and 2001(lower) source descriptions respectively.

\begin{figure}[h!]
\begin{minipage}{\linewidth}
\centering
\epsfig{figure=figs/2.0_cold_14Hz/Mean_brill.sim.ps,width=0.35\linewidth,angle=-90}
\epsfig{figure=figs/2.0_cold_14Hz/Peak_brill.sim.ps,width=0.35\linewidth,angle=-90}
\epsfig{figure=figs/2.0_cold_14Hz_TDR_corr/Mean_brill.sim.ps,width=0.35\linewidth,angle=-90}
\epsfig{figure=figs/2.0_cold_14Hz_TDR_corr/Peak_brill.sim.ps,width=0.35\linewidth,angle=-90}
\caption{Average(left) and peak(right) thermal brilliance curves
  obtained from running McStas 2.0, 14Hz without (above) and with (below)
  $\lambda$-dependent correction from TDR }
\label{fig:2.0_cold}
\end{minipage}\hfill
\end{figure}


\begin{figure}[h!]
\begin{minipage}{\linewidth}
\centering
\epsfig{figure=figs/2.0_therm_14Hz/Mean_brill.sim.ps,width=0.35\linewidth,angle=-90}
\epsfig{figure=figs/2.0_therm_14Hz/Peak_brill.sim.ps,width=0.35\linewidth,angle=-90}
\caption{Average(left) and peak(right) thermal brilliance curves
  obtained from running McStas 2.0, 14Hz. Note: Brilliance is still
  2001 Mezei for this moderator }
\label{fig:2.0_thermal}
\end{minipage}\hfill
\end{figure}

FIXME: Describe how use of cold\_frac gives systematic error in
2.0a. Check influence of doubled thermal source area.
\begin{figure}[h!]
\begin{minipage}{\linewidth}
\centering
\epsfig{figure=figs/2.0a_cold_14Hz/Mean_brill.sim.ps,width=0.35\linewidth,angle=-90}
\epsfig{figure=figs/2.0a_cold_14Hz/Peak_brill.sim.ps,width=0.35\linewidth,angle=-90}
\caption{Average(left) and peak(right) thermal brilliance curves
  obtained from running McStas 2.0 with the updated source from march 2013, 14Hz without (above) and with (below)
  $\lambda$-dependent correction from TDR }
\label{fig:2.0_cold}
\end{minipage}\hfill
\end{figure}


\begin{figure}[h!]
\begin{minipage}{\linewidth}
\centering
\epsfig{figure=figs/2.0a_therm_14Hz/Mean_brill.sim.ps,width=0.35\linewidth,angle=-90}
\epsfig{figure=figs/2.0a_therm_14Hz/Peak_brill.sim.ps,width=0.35\linewidth,angle=-90}
\caption{Average(left) and peak(right) thermal brilliance curves
  obtained from running McStas 2.0 with the updated source from march 2013, 14Hz Note: Brilliance is still
  2001 Mezei for this moderator  }
\label{fig:2.0_thermal}
\end{minipage}\hfill
\end{figure}



%measure flux / heat load /(spectra). Monitor flux/spectra in the beam extraction windows





%\section{References}

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%\newpage
%\section{Appendix}
%\begin{figure}[h!]
%\begin{minipage}{\linewidth}
%\centering
%\epsfig{figure=figs/ucn_impact_vs_flux_cold.eps,width=0.90\linewidth} %flux_vs_impact.eps
%\caption{Relation between cold flux (0-5~meV) available the lower cold/thermal beam-lines versus the flux available for UCN, central% in the through-going tube.}
%\label{fig:impact_vs_flux_cold}
%\end{minipage}\hfill
%\end{figure}
%\begin{figure}[h!]
%\begin{minipage}{\linewidth}
%\centering
%\epsfig{figure=figs/ucn_impact_vs_flux_interm.eps,width=0.90\linewidth} %flux_vs_impact.eps
%\caption{Relation between intermediate flux (5-20~meV) available the lower cold/thermal beam-lines versus the flux available for UCN%, central in the through-going tube.}
%\label{fig:impact_vs_flux_interm}
%\end{minipage}\hfill
%\end{figure}
%\begin{figure}
%\begin{minipage}{\linewidth}
%\centering
%\epsfig{figure=figs/ucn_impact_vs_flux_thermal.eps,width=0.90\linewidth} %flux_vs_impact.eps
%\caption{Relation between cold flux (20-100~meV) available the lower cold/thermal beam-lines versus the flux available for UCN, cent%ral in the through-going tube.}
%\label{fig:impact_vs_flux_thermal}
%\end{minipage}\hfill
%\end{figure}

\end{document}
