Dear TOPAS users/developers,
Did you notice the descriptions about LP factor in TOPAS Technical Reference/Tutorial/User Manual v4.2 are inconsistent?
Technical Reference DOC-M88-EXX066 V4.2 – 01.2009, p37:
The LP_Factor macro is applied by the "LP factor" correction in GUI mode. The following polarisation values apply:
Synchrotron use : 90
Neutron use : 90
No monochromator use : 0
Monochromator use (most common monochromators, Cu radiation):
Ge : 27.3
Graphite : 26.4
Quartz : 26.6
Technical Reference DOC-M88-EXX066 V4.2 – 01.2009, p116:
For unpolarized radiation v is 90 (e.g. X-ray diffractometers without any monochromator), for fully polarized radiation v is 0 (e.g. synchrotron radiation). Values for most common monochromators (Cu radiation) are:
Ge : 27.3
Graphite : 26.4
Quartz : 26.6
There is no polarization factor for neutron data and thus the angle for Lorentz Polarization should be set to 90; this gives the Lorentz only part. Alternatively the Lorentz_Factor macro can be used for fixed wavelength neutron data.
User Manual DOC-M88-EXX065 V4.2 – 01.2009, p36:
The Lorentz-Polarisation factor for unpolarized radiation is 90 (e.g. X-ray diffractometers without any monochromator) and 0 for fully polarized radiation (e.g. synchrotron radiation). Values for most common monochromators (Cu radiation) are:
Ge : 27.3
Graphite : 26.4
Quartz : 26.6
There is no polarization factor for neutron data and thus the angle for Lorentz Polarization should be set to 90; this gives the Lorentz only part.
What's New DOC-M88-EXX067 V4.2 – 01.2009 p14:
The default value for Lorentz-Polarisation has been changed to 90, that is no monochromator present
TECHNICAL REFERENCE TOPAS ACADEMIC Version 4.1, p89:
LP_Factor(c, v) Lorentz and Lorentz-Polarisation factor. [c, v]: Monochromator angle in [°2] For unpolarized radiation v is 90 (e.g. X-ray diffractometers without any monochromator), for fully polarized radiation v is 0 (e.g. synchrotron radiation). Values for most common monochromators (Cu radiation) are:
Ge : 27.3
Graphite : 26.4
Quartz : 26.6
The first quotation is different from the rest quotations. May I ask which one is correct?
Thank you very much.