064ec37e9a
- Refactored site specific stuff into a site module - PSI specific stuff is now in the PSI directory. - The old version has been tagged with pre-ansto
68 lines
2.3 KiB
OpenEdge ABL
68 lines
2.3 KiB
OpenEdge ABL
\subsection{SANS Wavelength Calculation}
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The instrument SANS has a neutron velocity selector. A wavelength is
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selected by varying tilt angle and rotation speed of the velocity selector.
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The relation between tilt angle and rotation speed to wavelength is given by
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a formula: \begin{eqnarray}
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\lambda & = & A + \frac{B}{rot}\\
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\lambda & = & wavelength in nm\\
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rot & = & rotation speed in revolutions per minute.
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\end{eqnarray}
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A and B are coefficients which are calculated from fourth degree polynoms.
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The coefficients of these polynoms have been obtained by fitting them
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against experimental data. This module now provides for this calculation and
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the driving of wavelength. This code does not vary tilt angle.
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This object data structure is simple:
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@d wavedat @{
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typedef struct __SANSwave {
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pObjectDescriptor pDes;
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pIDrivable pDrivInt;
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pVelSel pSelector;
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};
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@}
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The fields are:
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\begin{description}
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\item[pDes] The standard SICS object descriptor.
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\item[pDrivInt] A standard drivable interface.
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\item[pSelector] The velocity selector to act upon.
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\end{description}
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Most functionality of this module is hidden in the functions comprising the
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drivable interface. Thus the external functions of this object are limited
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to:
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@d sanswaveint @{
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typedef struct __SANSwave *pSANSWave;
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/*-----------------------------------------------------------------------*/
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int CalculateLambda(float fRot, float fTilt, float *fLambda);
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int MakeSANSWave(SConnection *pCon, SicsInterp *pSics, void *pData,
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int argc, char *argv[]);
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int SANSWaveAction(SConnection *pCon, SicsInterp *pSics, void *pData,
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int argc, char *argv[]);
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@}
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The coefficients for the calculation of A and B are hidden in the module
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static function CalculateCoefficients.
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@o sanswave.h @{
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/*---------------------------------------------------------------------------
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S A N S W A V E
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Wavelength calculations for a neutron velocity selector. Allows to drive
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the neutron wavelength directly.
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copyright: see copyright.h
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Mark Koennecke, October 1998
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---------------------------------------------------------------------------*/
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#ifndef SANSWAVE
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#define SANSWAVE
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@<sanswaveint@>
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#endif
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@}
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