The problem of falsified counting statistics (deviating from Poisson
distribution) sometimes arises even from (wrong) conversion of 0D
detector data (typically when originally cps have been stored and the
counting time got lost in the conversion), and is quite common when 1D
detector data are exported to 3rd party formats and the number of active
channels is not considered correctly in the export routine.
As a tool for a quick coarse check of the correct noise (like Matthew
has suggested below), Nicola Doebelin has integrated a "noise" cursor in
his PROFEX software
https://profex.doebelin.org/
simply showing the +-sqrt(n) bars.
If the noise of a pattern significantly deviates from this interval,
something was going wrong, either in instrumental data
collection/pretreatment or during export or conversion. No big science,
but very helpful to identify bad or manipulated data.
Reinhard
Am 27/09/2019 um 08:15 schrieb Matthew Rowles:
Hi Tony
If you want to have a look at what the uncertainties are doing, then
try scanning over a peak a couple of dozen times (maybe with a few
different mA settings on the tube, maybe with some different step
times) to collect a range of different intensities. The standard
deviation of the "raw" counts (not raw CPS) should approximately the
square root of the number of counts. If it is different, then
something squirrelly is going on.
Matthew
On Fri, 27 Sep 2019 at 13:46, iangie <ian...@126.com
<mailto:ian...@126.com>> wrote:
Dear Rietvelders,
Thanks for your opinions!
The "re-binning" of 1D data was done by my measurement software
automatically, rather than by analysis software.
The CPS is unchanged after its "re-binning". This means, rather
than adding counts of neighboring steps, it is *averaging* my data
(sum counts up then divided by the number of combined bins)!
I have a feeling what my measurement software doing is not correct...
--
*Dr. Xiaodong (Tony) Wang*
*Research Infrastructure Specialist (XRD)*
Central Analytical Research Facility (CARF) | Institute for
Future Environments
Queensland University of Technology
*
*
在 2019-09-27 10:31:45，alancoe...@bigpond.com
<mailto:alancoe...@bigpond.com> 写道：
Hi Tony
>My I ask is this re-bined data from the measurement software considered as
"raw data"
or "treated data"?
I’m not sure what is meant by treated data. Almost all neutron
data and synchrotron data with area detectors are “treated data”.
If the detector has a slit width in the equatorial plane that
is 0.03 degrees 2Th then it makes little sense using a step
size that is less than 0.03/2 degrees 2Th. If rebinning is
done correctly (see rebin_with_dx_of in the Technical
Reference) then rebinning is basically collecting redoing the
experiment with a wider slit.
In the case of your PSD then the resolution of the PSD would
be the smallest slit width. If the data has broad features
relative to the slit width then rebinning (or using a bigger
slit width) should not change the results. You could simulate
all this using TOPAS to see the difference. Correct rebinning
should not affect parameter errors.
This is a question that is not simple to answer and if there’s
concern then:
1. Simulating data with the small step size and performing a fit
2. And then rebinning with various slit widths and then fitting
3. And then comparing parameters errors and parameter values
for all the refinements should shine light on the area.
I don’t know where but I feeling is that there should be
papers on this.
Cheers
Alan
*From:*rietveld_l-requ...@ill.fr
<mailto:rietveld_l-requ...@ill.fr> <rietveld_l-requ...@ill.fr
<mailto:rietveld_l-requ...@ill.fr>> *On Behalf Of *iangie
*Sent:* Thursday, September 26, 2019 1:40 PM
*To:* rietveld_l@ill.fr <mailto:rietveld_l@ill.fr>
*Subject:* Software re-binned PD data
Dear Rietvelder,
I hope you are doing well.
It is generally acknolwdged that Rietveld refinement should be
performed on raw data, without any data processing.
One of our diffractometer/PSD scans data at its minimal step
size (users can see that the step size during scan is much
smaller than what was set), and upon finishing, the
measurement software re-bin the counts to the step size what
users set (so the data also looks smoother, after re-bin).
My I ask is this re-bined data from the measurement software
considered as "raw data" or "treated data"? And can we apply
Rietveld refinement on this data?
Any comments are welcome. :)
--
*Dr. Xiaodong (Tony) Wang*
*Research Infrastructure Specialist (XRD)*
Central Analytical Research Facility (CARF) | Institute for
Future Environments
Queensland University of Technology
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Please do NOT attach files to the whole list
<alan.he...@neutronoptics.com>
Send commands to <lists...@ill.fr <mailto:lists...@ill.fr>> eg:
HELP as the subject with no body text
The Rietveld_L list archive is on
http://www.mail-archive.com/rietveld_l@ill.fr/
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Please do NOT attach files to the whole list <alan.he...@neutronoptics.com>
Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
--
TU Bergakademie Freiberg
Dr. R. Kleeberg
Mineralogisches Labor
Brennhausgasse 14
D-09596 Freiberg
Tel. ++49 (0) 3731-39-3244
Fax. ++49 (0) 3731-39-3129
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Please do NOT attach files to the whole list <alan.he...@neutronoptics.com>
Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
