Dear Friends,
Below macro was already developed in 10th TOPAS user meeting @ Adelaide:
TOPAS syntax code for the modified intensity correction and flat specimen
asymmetry peak shape convolution
‘Variable_Divergence_Shape_Correction: v = footprint (EDFL); keh = knife edge
height
macro Variable_Divergence_Shape_with_knife_edge(v, keh)
{one_on_x_conv = If(Th < 2*ArcTan(2keh/v), -v^2 Sin(2 Th) Rad/(4 Rs^2), -2
keh^2 (Cos(Th))^3/Sin(Th) Rad/Rs^2);}
‘Variable_Divergence_Intensity_Correction: v = footprint (EDFL); keh = knife
edge height
macro Variable_Divergence_Intensity_with_knife_edge(v, keh)
{scale_pks = If(Th < 2*ArcTan(2keh/v), Sin(Th), 2 keh/v Cos(Th));}
If you use fix divergence slit:
‘Fix_Divergence_Shape_Correction: divang = divergence angle (EDFA); keh = knife
edge height
macro Fix_Divergence_Shape_with_knife_edge(v, keh)
{prm v = R divang Deg /Sin(Th);
one_on_x_conv = If( Rs Sin(divang/2 Deg) / Sin(Th - divang/2 Deg) Tan( (Th -
divang/2 Deg) > keh, -(Pi/360)/Tan(Th) divang^2, -2 keh^2 (Cos(Th))^3/Sin(Th)
Rad/Rs^2);}
‘Fix_Divergence_Intensity_Correction: v = footprint; keh = knife edge height
macro Fix_Divergence_Intensity_with_knife_edge(v, keh)
{scale_pks = If(Rs Sin(divang/2 Deg) / Sin(Th - divang/2 Deg) Tan( (Th -
divang/2 Deg) > keh, 1, 2 keh/v Cos(Th));}
or something similar...
Cheers!
--
Yours Sincerely,
Dr. Xiaodong(Tony) Wang
XRD Application Scientist
Bruker Singapore Pte. Ltd.
At 2015-07-30 21:29:40, "Matthew Rowles" <rowle...@gmail.com> wrote:
Hi Robert
Exactly! If installed properly, it doesn't affect anything except the
background. I had a nice spreadsheet setup to give me knife heights vs
divergence vs maximum 2T value to make sure that I don't run into forbidden
teritory.
I dispute your assertion that a knife wouldn't be necessary if the optics
worked properly. As far as I know, the only way to get rid of air scatter would
be to evacuate the beam path.
I'm currently doing some experiments with an old knife setup on a D8, and I'm
getting some funny bumps at low angle, but in my experience with a newer know
setup, that is due to a divergence that is too big. I'll see if I can put
something together.
Matthew
On 30 Jul 2015 2:04 pm, "Dr. Robert Möckel" <r.moec...@hzdr.de> wrote:
Hi Matthew,
what you mentioned earlier is not completely correct:
An anti-air scatter (or beam knife) does not only reduce background (mainly at
low angles), but also cuts intensity at higher 2theta values, if not installed
correctly. It does not result in a sample displacement error, it just cuts
intensity as it cuts off the beam like you mentioned.
This is also an relatively easy issue to modell, I even managed to put it into
an excel-file to calculate the max. 2theta angle that can be measured at a
certain knife height and detector length. BGMN "handles" this properly as well.
Nowadays, there are even knifes available that move vertically, depending on
the actual 2theta value.
In general, a beam knife would not be necessary if the optics worked properly,
i.e. the optical path is not disturbed or diffracted or fluorescence would not
be generated somewhere in the beam path. Basing on our experience, the main
source of these unwanted X-rays are within or close to the tube itself, making
it hard to suppress it effectively.
All these things result in some strange background phenomena at low angles
(bumps/edges...). We discussed these issues with Reinhard Kleeberg and others
for a while. It seems to be a serious problem in modern devices, as we
experienced this on our own PANalytical and other (Bruker) devices from
colleagues.
Regards,
Robert
, 30 Jul 2015 11:53:15 +0800 schrieb Matthew Rowles <rowle...@gmail.com>:
Hi Jilin
You could probably add a note to your input file.
Not everything you use in your hardware can be either properly modelled, or
influence the pattern significantly. Do you need to model the anti-scatter
slits? They help reduce background.
One thing that could happen is that if the knife is set up incorrectly, it
will cut off the beam, shifting the centroid of diffraction. That may mimic
a sample displacement type error.
Re your comment about double-digit results. Are you talking about the quant
results given in the GUI? The actual answer is going to be a lot less
precise than that.
Matthew
On 30 July 2015 at 09:19, ji zhang <jilin_zhang_hous...@yahoo.ca> wrote:
Matthew
I was thinking shouldn't we be able to input some parameters to reflect
this hardware configuration in the program?
I forgot that I had asked the same question in2007 in this list. Nobody
seemed to care enough except Dr Bergmann. Then I went to do log analysis,
and this thing is completely forgotten.
Currently we have topaz where I can't find a way to circumvent this yet or
to handle this as I called it. I am thinking we may need a copy of bgmn.
Certainly both give double digit results (albeit not the same) and both
look accurate.
Sent from Yahoo Mail for iPhone <https://yho.com/footer0>
On Jul 29, 2015, 5:56:41 PM, Matthew Rowles wrote:
Hi
What do you mean by "handle it"?
If the knife edge is correctly set up, the only thing that should change
is the background.
Matthew Rowles
On 30 Jul 2015 3:04 am, "ji zhang" <jilin_zhang_hous...@yahoo.ca> wrote:
About ten years ago, I was working on a D4 with lynx eye, had to put an
air scatter blocker 1 or 2 mm above the powder sample. In the beginning, I
had to put simple geometry into the bgmn configuration sav-file until Dr
Bergmann put a parameter airscatter=#.
Now I came back to the business with a D8 with lynx eye; is there anybody
here willing to share the experience of handling it in TOPAZ?
thanks
Jilin zhang
Sent from Yahoo Mail for iPhone <https://yho.com/footer0>
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Diplom-Mineraloge
Helmholtz-Institut Freiberg für Ressourcentechnologie
Tel.: +49 (0) 3731 39 2079
Helmholtz-Zentrum Dresden-Rossendorf
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