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\section{Reference surfaces and coordinate systems}
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\label{Sect:RefSurf&CoordSysts}
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\subsection{Doublet layer}
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\label{SubSect:RefCoordDoublet}
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The doublet-layer reference surface is defined to be the flat plane
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that is tangential to the outer surface of the mylar plane as shown in
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Figure \ref{Fig:DblLyrRef&Coord}a.
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The measured coordinate, $\alpha \in {u, v, w}$, is defined to lie in
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this plane and the $\alpha$ axis is perpendicular to the direction in
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The doublet-layer $z_d$ axis is defined to to be perpendicular to the
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doublet-layer reference surface increasing in the direction indicated
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The direction in which the measured coordinate, $\alpha$ increases is
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indicated in figure \ref{Fig:DblLyrRef&Coord}b.
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The orthogonal coordinate in the doublet-layer reference surface that
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with $\alpha$ and $z_d$ completes a right handed coordinate system is
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referred to as $\beta$.
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The $\beta$ axis is also indicated in figure
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\ref{Fig:DblLyrRef&Coord}b.
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\includegraphics[width=0.7\linewidth]
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{03-Reference-surfaces-and-coordinate-systems/Figures/doublet-layer.eps}
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Reference surfaces and coordinate-system definitions for the
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double layer and station.
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a) The fibres in the doublet layer are shown as the shaded
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circles, the central channel being shaded pink.
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The mylar layer is indicated by the solid black corrugated line.
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The doublet-layer reference surface is indicated by the vertical
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straight line, the arrow labelled $\alpha$ indicates the direction
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in which the coordinate measured by the doublet layer ($u$, $v$ or
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The direction of the $z_d$ axis is indicated.
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b) View of doublet layer looking down on the mylar layer with the
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optical connectors at the bottom of the figure.
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The coordinate measured by the doublet layer ($u$, $v$ or $w$) is
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indicated by the axis labelled $\alpha$.
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The orthogonal axis, i.e. the direction in which the fibres
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run, is labelled $\beta$.
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The origin of the $(\alpha, \beta)$ coordinate system is taken to
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be at the centre of the circular active area.
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\label{Fig:DblLyrRef&Coord}
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\label{SubSect:RefCoordStn}
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The station reference surface is defined to coincide with the
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reference surface of the $v$ doublet layer (see figure
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\ref{Fig:StnRef&Coord}).
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The station coordinate system is defined such that the $y_s$ axis is
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coincident with $v$ axis, the $z_s$ axis is coincident with the $z_d$ axis
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of the $v$ layer and the $x_s$ axis completes a right-handed coordinate
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\includegraphics[width=0.22\linewidth]
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{03-Reference-surfaces-and-coordinate-systems/Figures/station.eps}
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The carbon-fibre station body is indicated by the heavy solid
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The three doublet layers are indicated by the solid grey ($u$),
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green ($w$) and blue ($v$) lines.
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The station reference surface is shown by the solid vertical
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line coincident with the reference surface of the doublet layer
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The direction $y_s$ axis, defined to be coincident with the $v$ axis
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and the $z_s$ axes are shown as the solid, black arrows.
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The $x_s$ axis completes a right-handed coordinate system and
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therefore points into the page.
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\label{Fig:StnRef&Coord}
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\label{SubSect:TrkrCoordStn}
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The tracker reference surface is defined to coincide with the
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reference surface of station 1.
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The tracker coordinate system is defined such that the $z_t$ axis
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coincides with the nominal axis of cylindrical symmetry of the tracker
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as shown in figure \ref{Fig:TrkRef&Coord}.
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The tracker $z_t$ coordinate increases from station 1 to station 5.
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The tracker $y_t$ axis is defined to coincide with the $y_s$ axis of
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station 1 and the tracker $x_t$ axis completes a right-handed coordinate
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\includegraphics[width=0.7\linewidth]
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{03-Reference-surfaces-and-coordinate-systems/Figures/tracker.eps}
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The outline of the components that make up the MICE tracker are
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shown in the line drawing.
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The tracker reference surface coincides with the reference surface
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The tracker coordinate system is indicated by the solid lines.
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The $y_t$ axis is defined to be coincident with the $y_s$ axis in the
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station coordinate system.
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The $z_t$ axis runs along the nominar axis of the tracker.
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The $x_t$ axis completes a right-handed coordinate system.
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\label{Fig:TrkRef&Coord}
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\subsection{Coordinate transformations}
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\label{SubSect:CoordTran}
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\subsubsection{Doublet-layer to station}
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\label{SubSubSect:DblStn}
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The transformation from doublet-layer to station coordinates is
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achieved using the rotation $\underline{\underline{R}}_{SD}$ defined
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\right) = \underline{\underline{R}}_{SD} {\bf m} =
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\cos \theta_D & -\sin \theta_D \\
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\sin \theta_D & -\cos \theta_D
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where $\theta_D$ is the angle which the fibres that make up the
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doublet-layer make to the $x_s$ axis in the station coordinate