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<div class="moz-cite-prefix">Dear all,<br>
<br>
just a remark to getting the Q-resolution out of a
McStas-Simulation:<br>
You can do it with the Incoherent ("Vanadium") or any other
sample, as you have access to all variables in contrast to a real
instrument:<br>
Calculate the 'real' Q for each neutron ray, and monitor the
correlation with theta on the detector. Have a look at the
attached demo instrument file and the output plot, you can see
which Q-range is detected in each detector angle bin.<br>
<br>
There is a specialized sample/detector component which can do this
'behind the scenes' without the code extensions, like the
Res_Sample component, but I don't have an example for that right
now.<br>
<br>
Cheers<br>
Markus<br>
<br>
On 12/12/17 09:56, Andrew Wildes wrote:<br>
</div>
<blockquote type="cite"
cite="mid:807D1F8E-6F9A-40A8-9663-2257592E902C@ill.fr">
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Hi new user,
<div class=""><br class="">
</div>
<div class="">I won’t comment on your request for the ‘.instr’
files. I don't, however, understand how you plan to get
Q-resolution from a vanadium sample?</div>
<div class=""><br class="">
</div>
<div class="">Vanadium scatters isotropically. The scattering
cross-section is pretty much purely incoherent and elastic.
It’s a good choice to get the energy resolution of a
spectrometer, but not the Q-resolution for a diffractometer.</div>
<div class=""><br class="">
</div>
<div class="">Normally, I’d recommend using the Bragg peaks from a
powdered crystalline sample to get the Q-resolution. The sample
component should give resolution-limited peaks. Once you’ve
simulated the scattering, you can then plot the widths of the
peaks as a function of Q to get the resolution. You can even
fit the widths with an appropriate analytical function to get
the resolution for all Q.</div>
<div class=""><br class="">
</div>
<div class="">If you’re planning an instrument for liquids, you
don’t need brilliant Q-resolution. You should probably simulate
for only one peak at a time, or with only a few peaks, to avoid
problems with peaks merging at high Q. I think a component like
‘Powder1’ will suffice, although it will take a longer time to
simulate because you will need to run it for a number of peaks
over the usable range of Q on your instrument. Alternatively,
you can choose something like ‘PowderN’ with, say beryllium as a
sample, but edit the input file to only have ~10 peaks over the
usable range of Q for your instrument.</div>
<div class=""><br class="">
</div>
<div class="">I’m guessing that your instrument will be a TOF
diffractometer. The resolution should probably be pretty flat.
You can get more information on TOF resolution functions at:</div>
<div class=""><a
href="http://wwwisis2.isis.rl.ac.uk/Disordered/Manuals/ATLAS%20manual%20and%20SSG.pdf"
class="" moz-do-not-send="true"><span class="Apple-tab-span" style="white-space:pre"> </span></a><a
href="http://wwwisis2.isis.rl.ac.uk/Disordered/Manuals/ATLAS%20manual%20and%20SSG.pdf"
class="" moz-do-not-send="true">http://wwwisis2.isis.rl.ac.uk/Disordered/Manuals/ATLAS%20manual%20and%20SSG.pdf</a></div>
<div class=""><br class="">
</div>
<div class="">
<div class="">I’m also not sure what a "Q detector" is.
Personally, I would use a straight-forward monitor that
measured the position and energy (possibly as a
time-of-flight) of the neutron and then calculate Q myself
from there. I see that there is one component
(TOF2Q_cylPSD_monitor) that will also convert to Q, but I’ve
never used it so I can’t vouch for it.</div>
<div class=""><br class="">
</div>
</div>
<div class="">Sorry I can’t be more help.</div>
<div class=""><br class="">
</div>
<div class="">Cheers,</div>
<div class=""><br class="">
</div>
<div class="">Andrew</div>
<div class=""><br class="">
</div>
<div class="">
<div><br class="">
<blockquote type="cite" class="">
<div class="">On 12 Dec 2017, at 01:14, 韩泽华 <<a
href="mailto:hanzh@ihep.ac.cn" class=""
moz-do-not-send="true">hanzh@ihep.ac.cn</a>> wrote:</div>
<br class="Apple-interchange-newline">
<div class="">Dear all
<p class=""> I'm a new hand on McStas.I hope for some
help from you.
</p>
<p class=""> Recently I've been trying to make a
series of simulations of a Total Scattering
Diffractometer, which is almost like NIMROD. Now I'm
facing two problems.
</p>
<p class=""> First, I want to make a simulation with a
D2O sample and then detect Q. I've got "D2O-coh.sqw" and
"D2O-inc.sqw", but I couldn't get a correct result.
Could you offer me some "*.instr" files or codes
containing a D2O sample or H2O sample together with a Q
detector?
</p>
<p class=""> Second, I want to get a result of the
Q-resolution of the Diffratometer with a Vanadium
sample. Can I use a Detector Component to get the
Q-resolution directly, even though at a certain angle?
If it can be, please offer me some "*.instr" files or
codes as well. If it can't be, then what should I do to
get enough data to calculate the Q-resolution
afterwards?
</p>
<p class=""> Finally I'd like to remind that all my
simulations are based on a Total Scattering
Diffractometer.
</p>
<p class=""> I'd appreciate all your help and
suggestions.
</p>
<div class="">
<br class="webkit-block-placeholder">
</div>
<p class=""> PS: I may have sent it yesterday, but
with no reply, I think I need to send it once again. May
you forgive my disturbance.
</p>
<p class=""> <br class="">
</p>
<p class=""> <br class="">
</p>
<p class=""> <br class="">
</p>
<p class=""> A new user
</p>
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class="">
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</blockquote>
</div>
<br class="">
</div>
<br>
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