Hi Tamer,
Yes, I think that you are misunderstanding the number of trials = primaries, with the number of particles in your beam, source or whatever it is.
(Suggested reading: Monte Carlo Methods, Second Edition. Author(s):. Malvin H. Kalos · Paula A. Whitlock. First published:17 September 2008. Print ISBN:9783527407606)
I will give it a last try with this example.
Imagine that you want to guess how many blond students there are in a school with 2000 students, but you cannot go there and count.
Instead, you are allowed to go to other schools in the area, let us say 5 other schools (assume that the population is fairly homogeneous), each with 1000 students.
Each school is a cycle. Each student is a primary.
The counts from each school are, e.g. 120, 110, 135, 100, 140 blond students, i.e. 12%, 11%, 13.5%, 10%, 14%. (Total count = 605)
The FLUKA result would be 0.121 (I’ll let you compute the sigma), i.e. 12.1% blond students
If you count in another five schools (=five more cycles), the total count the total count will increase approximately in another ~605, but the percentage will NOT double, i.e. it is supposed to stay close to 12%.
So finally, your best guess for the unknown school of 2000 students (2000 = your integrated current), will be 2000*0.121=242 (plus minus sigma).
(By the way, comscw.f does not play any role in determining the energy deposition. It was required in the past to compute the DOSE, but now you have a built-in estimator)
Thanks,
Mario
On Mar 23, 2020, at 9:23 AM, Tamer Tolba <t.tolba_at_fz-juelich.de<mailto:t.tolba_at_fz-juelich.de>> wrote:
Hi Mario and Paola,
Thanks for your detailed description.
I do agree with your calculations, Mario. However I am still confused with the integrated deposited energy/power in the volume from multi-cycles!
Here is how I understand it by myself:
>The relation between Edep and P (deposited energy from fluka and incident beam power):
Power[W] = No.of.Particles * Edep [eV]/time[s] or
Power[W]*time[s] = No.of.Protons * Edep[eV]
* Remembr 1 [eV] = 1.602x10^-19 [W*s]
> then, the conversion factor:
EtoP (Edep[GeV] to Pdep[MW]) = Power_beam/Energy_beam
* multiply by 10^3. to have the power in [kW]
> This, above, covers the blue part of your equation P*V*E*dT/Ee. (your E is my Edep, so they are the same)
> Now, since the Edep (or E in your case) is normalized per primary and per volume, so I agree with your equation that multiplying E/Edep by the volume V (assuming P*dT/Ee is constant and can be used as a conversion factor in comscw file) will give the integrated E/Edep in the volume "normalized to the number of incident particles, right?"
> So to my understanding is that to get the total/integrated deposited E in the volume, I still need to multiply the integrated E (exported by usbrea) for the specific cycle by the number primaries generated in that cycle.
> Then, for each independent cycle (not gathered yet by flair) the integrated E will be the same for all!
> But after applying, in flair: run->Data->Process on the number of cycles (i.e. to gather the results from the cycles) and then exporting this value by usbrea code, I expect that the Edep values from the different cycles (still the normalized "by volume and primary" values) will be added (in whatever way). But, this integrated value from the different cycles must be different if I gather only 2 cycles or 10 cycles. So when I multiply, the integrated value of E, by the volume and the number of incident particles (from the cycles) it gives me the total deposited energy, which I think must be different if you hit a volume by 2000 particles (from 2 cycles each of 1000 generated particle) or 1000000 particles (from 1000 cycles each of 1000 generated particle).
Or do I misunderstand the role of "run->Data->Process"? Or I misunderstand a fundamental in fluka calculations!
Regards,
Tamer
On 3/23/2020 12:38 AM, Santana, Mario wrote:
Hi Tamer,
You increase the number of primaries to reduce the statistical uncertainty of the 'observable' that you are trying to measure, not the observable itself.
For example, if you run 5 cycles with N particles and the volumetric energy deposition is E [GeV/cm^3/primary] with er=10% statistical error, you will have to another 15 cycles so that the statistical error is down to about half, i.e. 5%, but the expected energy deposition will still be E (+/- 0.5*er*E).
So going to your question, Fluka will (generally) give you magnitudes per primary (actually per normalized primary statistical weight...), so you need to normalize results to your actual intensity.
For example, if you have an electron beam of power P[kW], with electrons of energy Ee[GeV/e-], with a result from Fluka of E [GeV/(cm^3 e-)], then this means that the fraction of energy deposition per each electron in the beam is E*V/Ee, with V the volume of the scoring.
Thus, the power [kW] deposited in the volume for your beam conditions will be:
P*V*E/Ee
And the energy deposited in a given time interval dT:
P*V*E*dT/Ee
-M
________________________________
From: owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it> <owner-fluka-discuss_at_mi.infn.it><mailto:owner-fluka-discuss_at_mi.infn.it> on behalf of Tamer Tolba <t.tolba_at_fz-juelich.de><mailto:t.tolba_at_fz-juelich.de>
Sent: Sunday, March 22, 2020 7:22 AM
To: paola.sala_at_mi.infn.it<mailto:paola.sala_at_mi.infn.it> <paola.sala_at_mi.infn.it><mailto:paola.sala_at_mi.infn.it>
Cc: fluka-discuss <fluka-discuss_at_fluka.org><mailto:fluka-discuss_at_fluka.org>
Subject: Re: [fluka-discuss]: E deposition dependence on incident intensity
Dear Paola,
Thanks so much for your fast reply.
Then, what should I do to export/get the total energy deposited in a volume?
Regards,
Tamer
On 3/22/2020 2:22 PM, Paola Sala wrote:
> Dear Tamer,
>
> Almost all FLUKA estimators (usrbin, usrbdx etc) give results
> normalized per primary particle.
> Thus, they do NOT depend on the number of cycles, nor on the number of
> primaries in the START card.
> Regards
> Paola
>
>> Dear fluka experts,
>>
>> In my "usual" fluka simplified model, usbrea.inp, I am scoring the
>> energy in a specified region, which was hit by a proton beam. Then I am
>> using usbrea code to export the integrated energy deposited in this
>> region for different beam intensities.
>>
>> The problem: I realized that, for a fixed beam energy, increasing the
>> number of runs, hence the number of primaries/beam intensity, does NOT
>> change the value of the integrated energy deposited in the target volume?!
>>
>> Attached, you will find:
>>
>> - usbrea_3Runs_98.bnn file: integrated binary file using flair, for 3
>> Runs (each of 1000 primaries, i.e. 3000 pot).
>>
>> - usbrea_10Runs_98.bnn file: integrated binary file using flair, for 10
>> Runs (each of 1000 primaries, i.e. 10000 pot).
>>
>> - Edep_3Runs.txt file: formatted file for the integrated deposited
>> energy in the specified region, generated by applying usbrea code on
>> usbrea_3Runs_98.bnn.
>>
>> - Edep_10Runs.txt file: formatted file for the integrated deposited
>> energy in the specified region, generated by applying usbrea code on
>> usbrea_10Runs_98.bnn.
>>
>> As you can see, whether integrate over 3 runs or 10 runs, the total
>> deposited energy, in the two txt file, is same in the target volume! Is
>> the integrated deposited energy in a volume is independent of the
>> intensity of the incident radiation? Or I misunderstand some physics?
>>
>> Regards,
>>
>> Tamer
>>
>> --
>> Dr. Tamer Tolba
>> Forschungszentrum Jülich
>> Institut für Kernphysik (IKP)
>> 52425 Jülich, Germany
>> Tel.: +49 2461 61 6860
>> Fax.: +49 2461 61 96415
>>
>>
>>
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>
> Paola Sala
> INFN Milano
> tel. Milano +39-0250317374
> tel. CERN +41-227679148
>
--
Dr. Tamer Tolba
Forschungszentrum Jülich
Institut für Kernphysik (IKP)
52425 Jülich, Germany
Tel.: +49 2461 61 6860
Fax.: +49 2461 61 96415
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--
Dr. Tamer Tolba
Forschungszentrum Jülich
Institut für Kernphysik (IKP)
52425 Jülich, Germany
Tel.: +49 2461 61 6860
Fax.: +49 2461 61 96415
__________________________________________________________________________
You can manage unsubscription from this mailing list at
https://www.fluka.org/fluka.php?id=acc_info
Received on Mon Mar 23 2020 - 19:32:19 CET