Changeset 57 for sans/SASCalc

Timestamp:

Mar 19, 2007 12:16:40 PM (16 years ago)

Author:

srkline

Message:

incorporated beamstop diameter projection to the qMin and shadow
factor calculations. very important at short SDD, negligible at long SDD.

File:

• sans/SASCalc/trunk/SASCALC.ipf (modified) (6 diffs)

sans/SASCalc/trunk/SASCALC.ipf

@@ -8 +8 @@
 // 09 MAR 2007 SRK - now appends text of each frozen configuration for printing
 //                                        - colorized frozen traces so that they aren't all red (unfrozen is black)
+// 19 MAR 2007 SRK - corrections added for projected BS diameter at anode plane
 //
 // calculate what q-values you get based on the instruments settings
@@ -26 +27 @@
 // - resolution smeared models
 // - "simulation" of data and error bars given a model and a total number of detector counts
-// - sequence of colors for frozen plots
 // - streamline code (globals needed in panel vs. wave needed for calculation)
 //
@@ -685 +685 @@
 
 ///////////////////////////////////////////////////////////
+// 19MAR07 uses correction for beamstop diameter projection to get shadow factor correct
+//
 Function S_CircularAverageTo1D(type)
         String type
@@ -927 +929 @@
 
         Variable L2 = reals[18]
-        Variable BS = reals[21]
+//      Variable BS = reals[21]         //this the diameter is stored in mm
+        Variable BS = beamstopDiamProjection() * 10             //calculated projection in cm *10 = mm
         Variable S1 = reals[23]
         Variable S2 = reals[24]
@@ -1356 +1359 @@
         
         SDD = detDist + s12*(2-tableposition())
-        rw[18] = SDD/100                // convert to meters
+        rw[18] = SDD/100                // convert to meters for header
         return(SDD)
 End
@@ -1418 +1421 @@
 End
 
-
+//returns the projected diameter of the beamstop at the anode plane.
+// most noticeable at short SDD
+Function beamstopDiamProjection()
+
+        NVAR L2diff = root:SAS:L2diff
+        Variable a2 = sampleApertureDiam()
+        Variable bs = beamstopDiam()
+        Variable l2, LB, BS_P
+    
+        l2 = sampleToDetectorDist() + L2diff
+        LB = 20.1 + 1.61*BS                     //distance in cm from beamstop to anode plane (empirical)
+        BS_P = bs + (bs+a2)*lb/(l2-lb)          //diameter of shadow from parallax
+
+        return (bs_p)           //return projected diameter in cm
+End
+
+// 19MAR07 - using correction from John for an estimate of the shadow of the beamstop
+// at the detection plane. This is a noticeable effect at short SDD, where the projected
+// diameter of the beamstop is much larger than the physical diameter.
 Function qMin()
 
-    Variable l2s = sampleToDetectorDist()       //distance from sample to detector
-    Variable bs = beamstopDiam()                //beamstop diameter
+    Variable l2s = sampleToDetectorDist()       //distance from sample to detector in cm
+//    Variable bs = beamstopDiam()              //beamstop diameter in cm
+    Variable bs_p = beamstopDiamProjection()            //projected beamstop diameter in cm
     NVAR lambda = root:SAS:gLambda
-    NVAR d_det = root:SAS:d_det
-    NVAR a_pixel = root:SAS:a_pixel
-    
-    return( (pi/lambda)*(bs + d_det + a_pixel)/l2s )
+    NVAR d_det = root:SAS:d_det         //cm
+    NVAR a_pixel = root:SAS:a_pixel     //cm
+
+    return( (pi/lambda)*(bs_p + d_det + a_pixel)/l2s )          //use bs_p rather than bs
+   // return( (pi/lambda)*(bs + d_det + a_pixel)/l2s )          //use bs (incorrect)
 End