[mcstas-users] Question please

Mahmoud Yaseen Suaifan mahma7 at gmail.com
Fri Mar 16 07:41:40 CET 2018

Dear Dr. peter,
Thank you so much for the nice detailed reply.

Kindly find my corresponding Q's & comments:

1) Here i'm following the preference of sharing questions on this open
forum for the sake of benefit for all. I'm still newcomer. Thanks for
telling me this new info.

2) Regarding source defining:
Please allow me to elaborate a little:
Assume i choose combination 1
( dist & rectangle focus) :
If tube nose (immersed in pool reflector tank) has:
Area of A1 and thermal calc. flux at nose (by MCNP)  = X in units of [
Let's pay attention to units please.
Focused to some neck @ dist=R and area A2.

So i enter in McStas value of I1= X as it is? Since i'm defining also
source radius (A1) & dist & A2 ( internally by default McSras controls
solid angle)??!!. Or shall i do some pre-calculations? Like divide by some
solid angle (omega subtended by focus rect.) or 2pi. (One side of emiting
disk source ) Or 4pi or so?

Back to units: McStas output by monitor or detector (counts/sec) am i right?
So if i want to check my source functionality putting a monitor exactly at
z=0 (0.0001 more realstic). What will be the expected result keeping in
mind value of X & its units? How to compare initial & losses ( I understand
these are statistics) & ( i understand that  for comparison research
purposes, the initial input is not important that much) but i'm looking for
some logical explanations for values to feel satisfied more & have a close
view on the mechanism it works.

3) Sorry i didn't attached any (file.instr) since it is still scratches.
But thank you for the examples ( honestly, still haven't got the chance to
check them, but i'll do ASAP). Appreciated.

4) Regarding the suggested workshop:
It's a great idea and i'm really interested but i'm thinking how can i
afford the costs ( flight, accomodation, ..etc). To me, I guess it's
difficult to find financial support at least at this stage. Hope the best
for all.

Sorry for the lengthy email.
Thanks in advance for any body for any helpful efforts to reply.

Best regards for all.
March 16th, 2018

On Wed, Mar 14, 2018, 18:23 Peter Kjær Willendrup <pkwi at fysik.dtu.dk> wrote:

> Hello Mahmoud,
> Find my comments and answers below.
> On 14 Mar 2018, at 06:16 , Mahmoud Yaseen Suaifan <mahma7 at gmail.com>
> wrote:
> Sorry i'm just forwarding the below email as a gentle reminder and since
> my first email (to mcstas-support) was not sent due to (delivery failure
> issues).
> Thanks for reminding me, I have silently removed the
> mcstas-support at mcstas.org address, I much prefer to have users ask their
> questions here in the open forum. :-)
> Actually, i'm a Jordanian graduate student in South Korea trying to make a
> conceptual design for a neutron imaging facility using McStas simulations.
> So i got some questions please like the one attached in the photo regarding
> the source component. Please your help & explanations are highly
> appreciated.
> The numbers in the photo are exact. Neck dimensions ( assume 10 cm × 10
> cm). How can i decide where is target & focus & dist. I understand ray
> trace. I understand solid angle & divergance. I understand Flux,
> intensities units. I got lost because i couldn't find explanation for
> results.
> The logic is that you specify the illuminated solid angle (~divergence out
> of the source) *either* by
> 1) dist in combination with focus_xw, focus_yh (A small rectangle of size
> focus_xw x focus_yh will be placed at (0, 0, dist) wrt the source)
> 2) target_index=N in combination with focus_xw, focus_yh (A small
> rectangle of size focus_xw x focus_yh will be placed at (tx, ty, tz) wrt
> the source, where tx,ty,tz is coordinates of a component N positions
> "further down the instrument"
> ( Attached also part of simple McStas script (source & detector only)
> please check it.
> I found no .instr example attached to your email, but there are many too
> look at within the examples/ folder of your McStas installation.
> Now, to get properly started on McStas, I propose you to e.g.
> 0) Try the simple SANS oriented tutorial available here:
> https://github.com/McStasMcXtrace/McCode/wiki/McStas-tutorial%3A-simplified-SANS-instrument
> <https://github.com/McStasMcXtrace/McCode/wiki/McStas-tutorial:-simplified-SANS-instrument>
> 1) Read chapter 3 of the McStas user manual, available here:
> http://mcstas.org/documentation/manual/mcstas-2.4.1-manual.pdf and by
> running mcdoc.pl -m on your own system
> 2) There are a couple of older sets of “school” material available on the
> web, e.g.
> http://nobugs2016.mcstas.org and http://april2017.mcstas.org that you can
> try following
> Also, there was an email from Georg Ehlers (SNS) <ehlersg at ornl.gov>
> requesting people to indicate if they would be interested in a McStas
> school later this year in Oak Ridge - see
> https://mailman2.mcstas.org//pipermail/mcstas-users/2018q1/001234.html
> Best regards,
> Peter
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