# Differences

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 — debye-scherrer_specimen_displacement [2012/01/03 00:10] (current)rowlesmr created 2012/01/03 00:10 rowlesmr created 2012/01/03 00:10 rowlesmr created Line 1: Line 1: + This is a macro to correct for capillary specimen displacement in Debye-Scherrer geometry + + + + /* + 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); + }

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