Changeset 838 for sans/Dev/trunk/NCNR_User_Procedures/Reduction/SANS/NCNR_Utils.ipf

Timestamp:

Feb 28, 2012 4:51:26 PM (10 years ago)

Author:

srkline

Message:

adding two new help files for real space modeling and description of the 2D resolution function

cleaning up the FFT routines for addition as a beta operation

File:

• sans/Dev/trunk/NCNR_User_Procedures/Reduction/SANS/NCNR_Utils.ipf (modified) (3 diffs)

sans/Dev/trunk/NCNR_User_Procedures/Reduction/SANS/NCNR_Utils.ipf

@@ -190 +190 @@
 // but written in terms of Parallel and perpendicular to the Q vector at each point
 //
-// -- it must be written this way since the 2D function is an ellipse with its major
+// -- it is more naturally written this way since the 2D function is an ellipse with its major
 // axis pointing in the direction of Q_parallel. Hence there is no way to properly define the 
 // elliptical gaussian in terms of sigmaX and sigmaY
 //
-// based on notes from David Mildner, 2008
+// For a full description of the gravity effect on the resolution, see:
+//
+//      "The effect of gravity on the resolution of small-angle neutron diffraction peaks"
+//      D.F.R Mildner, J.G. Barker & S.R. Kline J. Appl. Cryst. (2011). 44, 1127-1129.
+//      [ doi:10.1107/S0021889811033322 ]
+//
+//              2/17/12 SRK
+//              NOTE: the first 2/3 of this code is the 1D code, copied here just to have the beam stop
+//                              calculation here, if I decide to implement it. The real calculation is all at the 
+//                              bottom and is quite compact
+//
+//
 //
 //
@@ -324 +335 @@
 //      ////// this is all new, inclusion of gravity effect into the parallel component
 //       perpendicular component is purely geometric, no gravity component
+//
+// the shadow factor is calculated as above -so keep the above calculations, even though
+// most of them are redundant.
+//
+        
 ////    //
         Variable yg_d,acc,sdd,ssd,lambda0,DL_L,sig_l
         Variable var_qlx,var_qly,var_ql,qx,qy,sig_perp,sig_para, sig_para_new
+        
         G = 981.  //!   ACCELERATION OF GRAVITY, CM/SEC^2
         acc = vz_1              //      3.956E5 //!     CONVERT WAVELENGTH TO VELOCITY CM/SEC
@@ -336 +353 @@
         YG_d = -0.5*G*SDD*(SSD+SDD)*(LAMBDA0/acc)^2
 /////   Print "DISTANCE BEAM FALLS DUE TO GRAVITY (CM) = ",YG
+//              Print "Gravity q* = ",-2*pi/lambda0*2*yg_d/sdd
         
         sig_perp = kap*kap/12 * (3*(S1/L1)^2 + 3*(S2/LP)^2 + (proj_DDet/L2)^2)