Re: About the Shielding Caculation of Electron Accelerator

 Dear Xu Lijun,

  I gave a look to your input. If I have well understood, you have a 12
MeV electron beam going in the vertical direction toward the floor.
Since you want to calculate the dose equivalent outside the most external
shielding walls of your accelerator complex, it is natural to expect that
you have to cope with a poor statistics. In any case your goal, for sure,
must be to reach a level better then your 20%.

 You could start, in my opinion, with the optimization of few important
things. The main is the point 1.

  1. You use the DEFAULTS card EM-CASCA. This means that you requires a
very detailed transport of electrons/positrons/photons, with the
production and transport thresholds down to the lowest available values.
If you want to use it, you have, in my opinion, to put cuts via the EMFCUT
card at least for the production through the shielding walls. It is
unuseful (if you want to evaluate the transmitted radiation and the doses
beyond the walls) and highly time-consuming to have a such accurate
simulation, down to very low energies, inside the concrete.
You can evaluate an appropriate cut.

  2. Your region AIR, which is external to the region that you call VOID
but that you fill with the AIR material (and that is reasonably the air
box outside your shielding complex) should be, more correctly, to be
filled with VACUUM and not with AIR. Consider that, in your way, you
force FLUKA
to simulate interactions in a sphere of air of 1000 m of diameter, with
your low production/transport cuts...

  A last comment. Since you also asked about FLUKA performances, I would
suggest to give a look to this Lecture:

https://www.fluka.org/free_download/course/demokritos2009/Lectures/EM_0409.pdf

 There you can also learn how to properly address your cuts.

   Best regards,

   Anna

> Dear Fluka experts:
> I am very fortunately to meet the FLUKA&FLAIR, and it's the greatest
> MC tools. But I hesitate to use it in the shielding calculation
of the > low energy EM (12MeV). My project (see the attachment
please) is about > the shielding design of an electron accelerator
using in radiation
> processing. Can you give some advices about:
> 1. According to your experience, how much difference between the
FLUKA > Simulation and the practical situation;
> 2. In my calculation, the error is about 20% even if I increase the >
      particle number to 1e8 (cpu time is 80 hour). I used the BIAS
card > to chang the importance of the region to get better
error value. > Are there any else methods to decrease the error
while using less > time?
> Thank all of you very much in advance!
> Yours faithfully
> Xu Lijun
Received on Sat Sep 19 2009 - 09:30:24 CEST