kunyang
Hi all,
There's a question about instrument calibration of time-of-flight neutron diffraction. With the same instrument with the same banks, if only changed slit size, will it affect the calibration of instrument and profile parameters?
For example, we have done two series of measurements by the same instrument with the same banks, but with two different setting of slits sizes. Do I need to do two calibration procedures respectively, due to the slit size difference? Or maybe only need to do once, because the instrument bank files are the same (same t0,t1,t2)?
Thanks a lot~
johnsoevans
This is probably a question for your local contact who will know the instrument well.
In an ideal world you would run a standard in each setting to determine instrument calibration constants and instrumental peak shape for each bank. You'd then fix these for your samples. Any factors that influence peak positions or shapes between the two configurations will potentially change the calibration (e.g. different peak asymmetries, slightly different path lengths due to slightly different effective sample positions, etc).
In general though the most important of the calibrations is t1 which scales between d-spacing and time of flight. If you've got a good value for t1 (e.g. from Si) in one configuration you can probably use this value in the other configuration. t0 and t2 are often refined for each sample.
If you've measured the same sample in the two configurations you can always use those data to calibrate. i.e. use your standard in one configuration to determine calibration constants. With these (particularly t1) fixed, determine the cell parameter of your material. In the second configuration fix the cell parameter of your material and use this to determine t1 in that configuration. Then fix t1 when you analyse other samples. If the two values of t1 you determine are significantly different you probably ought to ask your local contact why.