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debye-scherrer_specimen_displacement [2012/01/03 00:10] (current)
rowlesmr created
Line 1: Line 1:
 +This is a macro to correct for capillary specimen displacement in Debye-Scherrer geometry
 +
 +
 +<code topas>
 +/*
 +Debye-Scherrer correction for a non-concentric capillary placement.
 +
 +This follows the maths of K&A and describes the offset in polar coordinates.
 +The normal "​vertical"​ (or "​perpendicular"​) displacement is when sigma == 90
 +The normal "​horizontal"​ (or "​parallel"​) displacement is when sigma == 0
 +*/
 +macro Debye-Scherrer_Specimen_Displacement { DSSD }
 +macro DSSD(u, u_v) { DSSD(u, u_v,,90) } ''​standard displacement perpendicular to the beam
 +macro DSSD(u, u_v, s, s_v)
 +{
 +   #​m_argu u ''​offset of the sample from the centre of the gonio
 +   #​m_argu s ''​angle subtended from the "​sample"​ position to the actual centre of the gonio (in deg)
 +
 +   ​If_Prm_Eqn_Rpt(u,​ u_v, min =-Rs/10; max =Rs/10;) ''​max offset of a tenth of a radius
 +   ​If_Prm_Eqn_Rpt(s,​ s_v, min =0; max =180;) ''​full rotation is provided by a negative u length.
 +
 +   ''​ You need "​Rad"​ at the beginning, as th2_offset takes a value in degrees, and this formula is in radians
 +   ''​This is the small angle implementation,​ the full one should have Arcsin() around everything after the Rad
 +   ​th2_offset = Rad (CeV(u, u_v) / Rs) Sin(2 Th - CeV(s, s_v) Deg); 
 +}</​code>​
  

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