Dear Jason,
from your input I see that you shoot a 12.9 MeV electron beam on a
~0.1 cm W target + ~1 cm Cu frame + several cm stainless steel filter.
Then you want to score dose in a water phantom about 1 m behind.
If this is the setup you intent to simulate, I’m not surprised that you need to accumulate a large statistics.
Just consider that the range of 12.9 MeV electron in copper is 0.8 cm…
Besides that, there is an error in the definition of the BIASING card, where you set WHAT(4) = aircone and WHAT(5) = Phantom.
Since these regions appear in reversed order in the geometry definition, you are not setting any important biasing to any region.
You could have verified it in the output file or — before running the simulation — by defining a Flair geometry layer that shows the region importance.
Finally, there is probably also a conceptual misunderstanding: what matters is not the absolute importance of a region, rather its importance relatively to the importance of adjacent regions.
I recommend you to give a look at the slides about the biasing techniques
https://indico.cern.ch/event/694979/contributions/2927118/
Best, luigi
On 21 Aug 2019, at 22:34, TYRRELL, JASON <J.TYRRELL3_at_nuigalway.ie<mailto:J.TYRRELL3_at_nuigalway.ie>> wrote:
Hi Luigi,
I have attached my input file.
Thanks a lot,
Jason
________________________________
From: Luigi Salvatore Esposito <luigi.salvatore.esposito_at_cern.ch<mailto:luigi.salvatore.esposito_at_cern.ch>>
Sent: 21 August 2019 23:18:00
To: TYRRELL, JASON <J.TYRRELL3_at_nuigalway.ie<mailto:J.TYRRELL3_at_nuigalway.ie>>
Cc: fluka-discuss_at_fluka.org<mailto:fluka-discuss_at_fluka.org> <fluka-discuss_at_fluka.org<mailto:fluka-discuss_at_fluka.org>>
Subject: Re: [fluka-discuss]: Importance Biasing
Dear Jason,
could you send your input?
Thanks, luigi
On 21 Aug 2019, at 17:52, TYRRELL, JASON <J.TYRRELL3_at_nuigalway.ie<mailto:J.TYRRELL3_at_nuigalway.ie>> wrote:
Hello Fluka Experts,
I am trying to score absorbed dose using USRBIN. However, it requires a lot of histories to get the results that I want. I tried to use importance biasing but it doesnt seem to make a difference to the statistics or the time it takes to run a simulation.
I have set the importance from the blackhole to _at_LASTREG to 0.0001. I created an RPP filled with air adjacent to the water phantom.I added a second bias card and selected the regions RPP to the phantom and set the importance equal to 10. I was under the impression that the first bias card sets the importance of everything to 0.0001 and the second bias card over rights this for regions I am interested in? But, no improvement. I read in the manual that it is not the importance itself but the ratio of the importance that is understood by FLUKA. Is this the ratio of the importance of the first and second bias card for adjacent regions?
I am coming to the end of my project soon so any help would be greatly appreciated.
Thanks a lot,
Jason.
<PDD3.inp>
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Received on Thu Aug 22 2019 - 11:35:53 CEST