Refs #11736 Add extra length option for gravity

Code/Mantid/Framework/API/inc/MantidAPI/MatrixWorkspace.h

@@ -90,8 +90,7 @@ class MANTID_API_DLL MatrixWorkspace : public IMDWorkspace,
   Geometry::IDetector_const_sptr getDetector(const size_t workspaceIndex) const;
   double detectorTwoTheta(Geometry::IDetector_const_sptr det) const;
   double detectorSignedTwoTheta(Geometry::IDetector_const_sptr det) const;
-  double gravitationalDrop(Geometry::IDetector_const_sptr det,
-                           const double waveLength) const;
+
   //@}
 
   virtual void populateInstrumentParameters();

Code/Mantid/Framework/API/src/MatrixWorkspace.cpp

@@ -813,33 +813,7 @@ MatrixWorkspace::detectorTwoTheta(Geometry::IDetector_const_sptr det) const {
   return det->getTwoTheta(samplePos, beamLine);
 }
 
-/**Calculates the distance a neutron coming from the sample will have deviated
-* from a
-*  straight tragetory before hitting a detector. If calling this function many
-* times
-*  for the same detector you can call this function once, with waveLength=1, and
-* use
-*  the fact drop is proportional to wave length squared .This function has no
-* knowledge
-*  of which axis is vertical for a given instrument
-*  @param det :: the detector that the neutron entered
-*  @param waveLength :: the neutrons wave length in meters
-*  @return the deviation in meters
-*/
-double MatrixWorkspace::gravitationalDrop(Geometry::IDetector_const_sptr det,
-                                          const double waveLength) const {
-  using namespace PhysicalConstants;
-  /// Pre-factor in gravity calculation: gm^2/2h^2
-  static const double gm2_OVER_2h2 =
-      g * NeutronMass * NeutronMass / (2.0 * h * h);
-
-  const V3D samplePos = getInstrument()->getSample()->getPos();
-  const double pathLength = det->getPos().distance(samplePos);
-  // Want L2 (sample-pixel distance) squared, times the prefactor g^2/h^2
-  const double L2 = gm2_OVER_2h2 * std::pow(pathLength, 2);
 
-  return waveLength * waveLength * L2;
-}
 
 //---------------------------------------------------------------------------------------
 /** Add parameters to the instrument parameter map that are defined in

Code/Mantid/Framework/Algorithms/inc/MantidAlgorithms/GravitySANSHelper.h

@@ -36,7 +36,8 @@ class GravitySANSHelper {
   GravitySANSHelper()
       : m_beamLineNorm(-1), m_dropPerAngstrom2(-1), m_cachedDrop(-1) {}
   GravitySANSHelper(API::MatrixWorkspace_const_sptr ws,
-                    Geometry::IDetector_const_sptr det);
+                    Geometry::IDetector_const_sptr det,
+                    const double extraLength = 0.0);
   double calcSinTheta(const double wavAngstroms) const;
   double calcComponents(const double wavAngstroms, double &xFrac,
                         double &yFrac) const;
@@ -71,6 +72,11 @@ class GravitySANSHelper {
   double gravitationalDrop(const double wav) const {
     return m_dropPerAngstrom2 * wav * wav;
   }
+
+ double gravitationalDrop(API::MatrixWorkspace_const_sptr ws,
+                          Geometry::IDetector_const_sptr det,
+                          const double waveLength,
+                          const double extraLength) const;
   double calcSinTheta() const;
 };
 }

Code/Mantid/Framework/Algorithms/inc/MantidAlgorithms/Q1D2.h

@@ -87,7 +87,8 @@ class DLLExport Q1D2 : public API::Algorithm {
                   const MantidVec::iterator theNorms,
                   const MantidVec::iterator errorSquared) const;
   void convertWavetoQ(const size_t specInd, const bool doGravity,
-                      const size_t offset, MantidVec::iterator Qs) const;
+                      const size_t offset, MantidVec::iterator Qs,
+                      const double extraLength) const;
   void getQBinPlus1(const MantidVec &OutQs, const double QToFind,
                     MantidVec::const_iterator &loc) const;
   void normalize(const MantidVec &normSum, const MantidVec &normError2,

Code/Mantid/Framework/Algorithms/src/GravitySANSHelper.cpp

@@ -12,7 +12,8 @@ using Kernel::V3D;
 *  @param det :: the detector for which the calculations will be for
 */
 GravitySANSHelper::GravitySANSHelper(API::MatrixWorkspace_const_sptr ws,
-                                     Geometry::IDetector_const_sptr det)
+                                     Geometry::IDetector_const_sptr det,
+                                     const double extraLength)
     : m_beamLineNorm(-1), m_det(det), m_dropPerAngstrom2(-1), m_cachedDrop(0) {
   m_samplePos = ws->getInstrument()->getSample()->getPos();
   const V3D sourcePos = ws->getInstrument()->getSource()->getPos();
@@ -25,7 +26,7 @@ GravitySANSHelper::GravitySANSHelper(API::MatrixWorkspace_const_sptr ws,
   m_cachedLineOfSight = m_det->getPos() - m_samplePos;
   // the drop is proportional to the wave length squared and using this to do
   // the full calculation only once increases the speed a lot
-  m_dropPerAngstrom2 = ws->gravitationalDrop(m_det, 1e-10);
+  m_dropPerAngstrom2 = gravitationalDrop(ws, m_det, 1e-10, extraLength);
 }
 /** Caclulates the sin of the that the neutron left the sample at, before the
 * effect of gravity
@@ -79,5 +80,37 @@ double GravitySANSHelper::calcSinTheta() const {
   // This is sin(theta)
   return sqrt(0.5 - halfcosTheta);
 }
-}
+
+
+/**Calculates the distance a neutron coming from the sample will have deviated
+* from a
+*  straight tragetory before hitting a detector. If calling this function many
+* times
+*  for the same detector you can call this function once, with waveLength=1, and
+* use
+*  the fact drop is proportional to wave length squared .This function has no
+* knowledge
+*  of which axis is vertical for a given instrument
+*  @param ws :: workspace
+*  @param det :: the detector that the neutron entered
+*  @param waveLength :: the neutrons wave length in meters
+*  @param extraLength :: additional length
+*  @return the deviation in meters
+*/
+double GravitySANSHelper::gravitationalDrop(API::MatrixWorkspace_const_sptr ws,
+                                            Geometry::IDetector_const_sptr det,
+                                           const double waveLength,
+                                           const double extraLength) const {
+  using namespace PhysicalConstants;
+  /// Pre-factor in gravity calculation: gm^2/2h^2
+  static const double gm2_OVER_2h2 =
+      g * NeutronMass * NeutronMass / (2.0 * h * h);
+
+  const V3D samplePos = ws->getInstrument()->getSample()->getPos();
+  const double pathLength = det->getPos().distance(samplePos) + extraLength;
+  // Want L2 (sample-pixel distance) squared, times the prefactor g^2/h^2
+  const double L2 = gm2_OVER_2h2 * std::pow(pathLength, 2);
+
+  return waveLength * waveLength * L2;
+}}
 }

Code/Mantid/Framework/Algorithms/src/Q1D2.cpp

@@ -81,6 +81,9 @@ void Q1D2::init() {
                   "_sumOfCounts and _sumOfNormFactors equals the workspace"
                   " returned by the property OutputWorkspace "
                   "(default is false).");
+  declareProperty(
+      "ExtraLength", 0.0, mustBePositive,
+      "Additional length for gravity correction.");
 }
 /**
   @ throw invalid_argument if the workspaces are not mututially compatible
@@ -173,7 +176,7 @@ void Q1D2::exec() {
                            binNormEs, norms, normETo2s);
 
     // now read the data from the input workspace, calculate Q for each bin
-    convertWavetoQ(i, doGravity, wavStart, QIn);
+    convertWavetoQ(i, doGravity, wavStart, QIn, getProperty("ExtraLength"));
 
     // Pointers to the counts data and it's error
     MantidVec::const_iterator YIn = m_dataWS->readY(i).begin() + wavStart;
@@ -483,13 +486,15 @@ void Q1D2::normToMask(const size_t offSet, const size_t specIndex,
 *  @param[in] specInd the spectrum to calculate
 *  @param[in] doGravity if to include gravity in the calculation of Q
 *  @param[in] offset index number of the first input bin to use
+*  @param[in] extraLength for gravitational correction
 *  @param[out] Qs points to a preallocated array that is large enough to contain
 * all the calculated Q values
 *  @throw NotFoundError if the detector associated with the spectrum is not
 * found in the instrument definition
 */
 void Q1D2::convertWavetoQ(const size_t specInd, const bool doGravity,
-                          const size_t offset, MantidVec::iterator Qs) const {
+                          const size_t offset, MantidVec::iterator Qs,
+                          const double extraLength) const {
   static const double FOUR_PI = 4.0 * M_PI;
 
   IDetector_const_sptr det = m_dataWS->getDetector(specInd);
@@ -499,7 +504,7 @@ void Q1D2::convertWavetoQ(const size_t specInd, const bool doGravity,
   // going from bin boundaries to bin centered x-values the size goes down one
   const MantidVec::const_iterator end = m_dataWS->readX(specInd).end() - 1;
   if (doGravity) {
-    GravitySANSHelper grav(m_dataWS, det);
+    GravitySANSHelper grav(m_dataWS, det, extraLength);
     for (; waves != end; ++Qs, ++waves) {
       // the HistogramValidator at the start should ensure that we have one more
       // bin on the input wavelengths

Code/Mantid/Framework/Algorithms/src/Qxy.cpp

@@ -78,6 +78,8 @@ void Qxy::init() {
                   "OutputWorkspace_sumOfNormFactors. The division of "
                   "_sumOfCounts and _sumOfNormFactors equals the workspace "
                   "returned by the property OutputWorkspace");
+  declareProperty("ExtraLength", 0.0, mustBePositive,
+                  "Additional length for gravity correction.");
 }
 
 void Qxy::exec() {
@@ -187,7 +189,7 @@ void Qxy::exec() {
     // constructed once per spectrum
     GravitySANSHelper grav;
     if (doGravity) {
-      grav = GravitySANSHelper(inputWorkspace, det);
+      grav = GravitySANSHelper(inputWorkspace, det, getProperty("ExtraLength"));
     }
 
     for (int j = static_cast<int>(numBins) - 1; j >= static_cast<int>(wavStart);

Code/Mantid/Framework/Algorithms/test/Q1D2Test.h

@@ -255,7 +255,7 @@ class Q1D2Test : public CxxTest::TestSuite
 
     Mantid::API::AnalysisDataService::Instance().remove(outputWS);
   }
-  
+
   void testCuts()
   {
     Mantid::Algorithms::Q1D2 Q1D;

Code/Mantid/MantidQt/CustomInterfaces/inc/MantidQtCustomInterfaces/SANSRunWindow.ui

@@ -93,7 +93,7 @@
        <string notr="true"/>
       </property>
       <property name="currentIndex">
-       <number>5</number>
+       <number>1</number>
       </property>
       <property name="elideMode">
        <enum>Qt::ElideNone</enum>
@@ -868,6 +868,42 @@
             </property>
            </widget>
           </item>
+          <item>
+           <spacer name="horizontalSpacer_23">
+            <property name="orientation">
+             <enum>Qt::Horizontal</enum>
+            </property>
+            <property name="sizeHint" stdset="0">
+             <size>
+              <width>40</width>
+              <height>20</height>
+             </size>
+            </property>
+           </spacer>
+          </item>
+          <item>
+           <widget class="QLabel" name="label_15">
+            <property name="text">
+             <string>Extra Length</string>
+            </property>
+           </widget>
+          </item>
+          <item>
+           <widget class="QLineEdit" name="gravity_extra_length_line_edit">
+            <property name="sizePolicy">
+             <sizepolicy hsizetype="Preferred" vsizetype="Maximum">
+              <horstretch>0</horstretch>
+              <verstretch>0</verstretch>
+             </sizepolicy>
+            </property>
+            <property name="maximumSize">
+             <size>
+              <width>70</width>
+              <height>16777215</height>
+             </size>
+            </property>
+           </widget>
+          </item>
           <item>
            <spacer name="horizontalSpacer">
             <property name="orientation">

Code/Mantid/MantidQt/CustomInterfaces/src/SANSRunWindow.cpp

@@ -951,7 +951,12 @@ bool SANSRunWindow::loadUserFile()
   {
     m_uiForm.gravity_check->setChecked(false);
   }
-
+
+  // Read the extra length for the gravity correction
+  const double extraLengthParam =  runReduceScriptFunction(
+    "print i.ReductionSingleton().to_Q.get_extra_length()").toDouble();
+  m_uiForm.gravity_extra_length_line_edit->setText(QString::number(extraLengthParam));
+
   ////Detector bank: support REAR, FRONT, HAB, BOTH, MERGED, MERGE options
   QString detName = runReduceScriptFunction(
     "print i.ReductionSingleton().instrument.det_selection").trimmed();
@@ -2268,7 +2273,9 @@ QString SANSRunWindow::readUserFileGUIChanges(const States type)
   {
     exec_reduce += "False";
   }
-  exec_reduce += ")\n";
+  // Take into acount of the additional length
+  exec_reduce += ", extra_length=" + m_uiForm.gravity_extra_length_line_edit->text().trimmed() + ")\n";
+
   //Sample offset
   exec_reduce += "i.SetSampleOffset('"+
                  m_uiForm.smpl_offset->text()+"')\n";

Code/Mantid/scripts/SANS/ISISCommandInterface.py

@@ -171,9 +171,10 @@ def SetTransSpectrum(specNum, interp=False):
 def SetSampleOffset(value):
     ReductionSingleton().instrument.set_sample_offset(value)
 
-def Gravity(flag):
-    _printMessage('Gravity(' + str(flag) + ')')
+def Gravity(flag, extra_length = 0.0):
+    _printMessage('Gravity(' + str(flag) + ', '+ str(extra_length) + ')')
     ReductionSingleton().to_Q.set_gravity(flag)
+    ReductionSingleton().to_Q.set_extra_length(extra_length)
 
 def SetFrontDetRescaleShift(scale=1.0, shift=0.0, fitScale=False, fitShift=False, qMin=None, qMax=None):
     """

Code/Mantid/scripts/SANS/isis_reduction_steps.py

@@ -1672,6 +1672,7 @@ class ConvertToQISIS(ReductionStep):
                      '2D' : 'Qxy'}
     # defines if Q1D should correct for gravity by default
     _DEFAULT_GRAV = False
+    _DEFAULT_EXTRA_LENGTH = 0.0
     def __init__(self, normalizations):
         """
             @param normalizations: CalculateNormISIS object contains the workspace, ReductionSteps or files require for the optional normalization arguments
@@ -1689,6 +1690,8 @@ def __init__(self, normalizations):
         self._use_gravity = self._DEFAULT_GRAV
         #used to implement a default setting for gravity that can be over written but doesn't over write
         self._grav_set = False
+        #can be used to add an additional length to the neutron path during the correction for gravity in the Q calcuation
+        self._grav_extra_length = self._DEFAULT_EXTRA_LENGTH
         #this should contain the rebin parameters
         self.binning = None
 
@@ -1733,6 +1736,16 @@ def set_gravity(self, flag, override=True):
             print msg
             sanslog.warning(msg)
 
+    def get_extra_length(self):
+        return self._grav_extra_length
+
+    def set_extra_length(self, extra_length):
+        """
+            Add extra length when correcting for gravity when calculating Q
+            @param extra_length : additional length for the gravity correction during the calculation of Q
+        """
+        self._grav_extra_length = extra_length
+
     def execute(self, reducer, workspace):
         """
         Calculate the normalization workspaces and then call the chosen Q conversion algorithm.
@@ -1754,9 +1767,9 @@ def execute(self, reducer, workspace):
 
         try:
             if self._Q_alg == 'Q1D':
-                Q1D(DetBankWorkspace=workspace,OutputWorkspace= workspace, OutputBinning=self.binning, WavelengthAdj=wave_adj, PixelAdj=pixel_adj, AccountForGravity=self._use_gravity, RadiusCut=self.r_cut*1000.0, WaveCut=self.w_cut, OutputParts=self.outputParts, WavePixelAdj = wavepixeladj)
+                Q1D(DetBankWorkspace=workspace,OutputWorkspace= workspace, OutputBinning=self.binning, WavelengthAdj=wave_adj, PixelAdj=pixel_adj, AccountForGravity=self._use_gravity, RadiusCut=self.r_cut*1000.0, WaveCut=self.w_cut, OutputParts=self.outputParts, WavePixelAdj = wavepixeladj, ExtraLength=self._grav_extra_length)
             elif self._Q_alg == 'Qxy':
-                Qxy(InputWorkspace=workspace,OutputWorkspace= workspace,MaxQxy= reducer.QXY2,DeltaQ= reducer.DQXY, WavelengthAdj=wave_adj, PixelAdj=pixel_adj, AccountForGravity=self._use_gravity, RadiusCut=self.r_cut*1000.0, WaveCut=self.w_cut, OutputParts=self.outputParts)
+                Qxy(InputWorkspace=workspace,OutputWorkspace= workspace,MaxQxy= reducer.QXY2,DeltaQ= reducer.DQXY, WavelengthAdj=wave_adj, PixelAdj=pixel_adj, AccountForGravity=self._use_gravity, RadiusCut=self.r_cut*1000.0, WaveCut=self.w_cut, OutputParts=self.outputParts, ExtraLength=self._grav_extra_length)
                 ReplaceSpecialValues(InputWorkspace=workspace,OutputWorkspace= workspace, NaNValue="0", InfinityValue="0")
             else:
                 raise NotImplementedError('The type of Q reduction has not been set, e.g. 1D or 2D')
@@ -2068,15 +2081,21 @@ def read_line(self, line, reducer):
                 # for /DET/FRONT and /DET/REAR commands
                 reducer.instrument.setDetector(det_specif)
 
+        # There are two entries for Gravity: 1. ON/OFF (TRUE/FALSE)
+        #                                    2. LEXTRA=xx.xx
         elif upper_line.startswith('GRAVITY'):
-            flag = upper_line[8:].strip()
-            if flag == 'ON' or flag == 'TRUE':
+            grav = upper_line[8:].strip()
+            if grav == 'ON' or grav == 'TRUE':
                 reducer.to_Q.set_gravity(True, override=False)
-            elif flag == 'OFF' or flag == 'FALSE':
+            elif grav == 'OFF' or grav == 'FALSE':
                 reducer.to_Q.set_gravity(False, override=False)
+            elif grav.startswith('LEXTRA'):
+                extra_length = grav[6:].strip()
+                reducer.to_Q.set_extra_length(float(extra_length))
             else:
                 _issueWarning("Gravity flag incorrectly specified, disabling gravity correction")
                 reducer.to_Q.set_gravity(False, override=False)
+                reducer.to_Q.set_extra_length(0.0)
 
         elif upper_line.startswith('FIT/TRANS/'):
             #check if the selector is passed: