Probably you refer to the thread “PDD comparison”. In that case I guess you privately sent your input to the person on shift last week.
In this reply I will refer to the last input you sent me.
Respect to the previous setup, you now shot a 12.9 MeV electron on a water phantom.
As you can see from the attached snapshot from your input, the USRBIN is defined after about 10 cm of water: more than enough to stop the electrons and preventing them to reach the scoring region.
Moreover, the importance biasing implemented (the colors in the snapshot indicate the importance of each region) mainly affects the regions that are downstream the phantom, where of course it plays no role
Best, luigi
P.S. Please keep the mail exchange on the list.
[cid:C1DE8081-BCA3-4516-9ACF-58FF5A7A2FEC_at_cern.ch]
On 22 Aug 2019, at 12:23, TYRRELL, JASON <J.TYRRELL3_at_nuigalway.ie<mailto:J.TYRRELL3_at_nuigalway.ie>> wrote:
The input I sent you yesterday had the wrong input file attached. I actually already read the bias lecture you sent me, but I'm not completely sure I understand it.
The input file I have sent in my last email is the correct one.
Kind regards,
Jason.
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________________________________
From: TYRRELL, JASON <J.TYRRELL3_at_nuigalway.ie<mailto:J.TYRRELL3_at_nuigalway.ie>>
Sent: Thursday, August 22, 2019 9:58:44 AM
To: Luigi Salvatore Esposito <luigi.salvatore.esposito_at_cern.ch<mailto:luigi.salvatore.esposito_at_cern.ch>>
Subject: Re: [fluka-discuss]: Importance Biasing
Hi Luigi,
I have attached a new input with new biasing.
I have started with a bias card from the vacuum to the target with a bias of 1(default). I have set target to copper with an importance of 3 (greater than 1 so splitting occurs). Therefore, the ratio is 1/3 and every particle is split into 3 with weight 1/3?
I have increased the importance in small amounts to make sure the ratio is less than 5. since the phantom is the region I am scoring, I set the ratio (from aircone to phantom) at 4 to increase statistics.
Do you think this is correct and will work?
Thanks for your help,
Jason.
________________________________
From: Luigi Salvatore Esposito <luigi.salvatore.esposito_at_cern.ch<mailto:luigi.salvatore.esposito_at_cern.ch>>
Sent: 22 August 2019 10:33:11
To: TYRRELL, JASON <J.TYRRELL3_at_nuigalway.ie<mailto:J.TYRRELL3_at_nuigalway.ie>>
Cc: fluka-discuss <fluka-discuss_at_fluka.org<mailto:fluka-discuss_at_fluka.org>>
Subject: Re: [fluka-discuss]: Importance Biasing
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 - 14:11:33 CEST