[mcstas-users] Question please

Peter Kjær Willendrup pkwi at fysik.dtu.dk
Fri Mar 16 09:42:34 CET 2018

Dear Mahmoud,

On 16 Mar 2018, at 07:41 , Mahmoud Yaseen Suaifan <mahma7 at gmail.com<mailto:mahma7 at gmail.com>> wrote:

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.

No worries, and that is exactly what the mcstas-users list is meant for. :-)

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 [ n/cm^2.sec].
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?

I admit the documentation is perhaps not completely clear - but I believe I1 is meant to be the source emission into 4PI steradian in neutrons. McStas then takes care of the weighting wrt. the chosen solid angle (in your case dist + rectangle focus)

Back to units: McStas output by monitor or detector (counts/sec) am i right?

Yes. And most monitors do not normalise by (their own) measurement area.

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.

If you have experimental data - or benchmark tally data from e.g. MCNP, e.g. at the tube nose, I would put my monitor(s) there.

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.

No worries.

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.

OK, I see. I know that in earlier cases workshop participants have been able to receive support from e.g. the IAEA for these types of events.

All the best and have a nice weekend,

Peter Willendrup

Peter Kjær Willendrup
Forskningsingeniør, Speciakonsulent
Næstformand for DTU Fysik LSU

DTU Physics

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Technical University of Denmark

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Department of Physics

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DK-2800 Kongens Lyngby

Direct +45 2125 4612

Mobil +45 2125 4612
Fax +45 4593 2399

pkwi at fysik.dtu.dk<mailto:pkwi at fysik.dtu.dk>

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