Hi
Answering your ulterior questions…
- EMF-OFF will certainly safe CPU time because EM showers will be produced
and all the products (e-,e+,gamma) tracked up to low energies. This has a
CPU penalty.
- No, the result will not be altered in your case because:
1) you were only scoring protons, not electrons, positrons or photons
2) protons could not be produced from the EM cascades because a) you don't
have photo nuclear reactions activated and b) photomuon reactions have
much higher threshold than your proton primary energy. Thus proton fields
are not altered in your case by not tracking EM showers.
Mario
On 12/13/13 8:49 PM, "yyc2011_at_mail.ustc.edu.cn" <yyc2011_at_mail.ustc.edu.cn>
wrote:
>Dear Santana,
>
> Thanks for your suggestions.In your reply,you said "In particular, for
>your proton case you could save a lot of CPU with EMF-OFF." Why using
>EMF-OFF will save a lot of CPU for protons? On the other hand,will the
>result be changed when use EMF-OFF comparing with not using EMF-OFF?
>
>Best Regards
>Chen Yuan
>
>
>> -----Original E-mail-----
>> From: "Santana, Mario" <msantana_at_slac.stanford.edu>
>> Sent Time: 2013-12-14 3:28:40
>> To: "fluka-discuss_at_fluka.org" <fluka-discuss_at_fluka.org>
>> Cc:
>> Subject: Re: [fluka-discuss]: How to optimize input files?
>>
>> Chen,
>>
>> I believe the purpose of this list is to provide guidance of specific
>> FLUKA questions. With that spirit, I will give you some tips and
>> recommendations, but I cannot go in-depth and perform your work.
>>
>> The first thing to say, is that speed of computation is not an absolute
>> number to quantify the efficiency of your input file. It is all relative
>> to the statistical uncertainty of the observables that you are scoring
>>for
>> that amount of CPU. For example, the CPU/history may be high when you
>>have
>> intense region biasing, but this does not necessarily mean you are
>>wasting
>> CPU, on the contrary, if region biasing is well tuned, you may be
>> following many split trajectories towards your region of interest for a
>> single history.
>>
>> Now, the question is whether you are wasting CPU time in processes that
>> you don't need. In that regard I have recommend the following:
>> 1) Reduce the number of particles per cycle and run several cycles.
>> Analyze your results and evaluate how many particles you need in total
>>to
>> converge to the desired result
>>
>> 2) You use PRECISIO as your DEFAULT. This cards includes many options
>>and
>> precise settings which you may not need. I copy them at the end of the
>> email. You should decide whether this is the DEFAULT that you want
>>(maybe
>> you could survive with NEW-DEFA?), or switch off those cards that are
>>not
>> needed for your problem. In particular, for your proton case you could
>> save a lot of CPU with EMF-OFF. For your ELECTRON case you could play
>>with
>> the cut-off energies (the lower the energy the longer the simulation).
>> 3) You are using MULSOPT. This may impact your processing speed.
>> 4) Your USRBIN has a 2000x2000 grid. The more you write to files the
>> slower the simulation can get. Try having a coarser grid if CPU is a
>> concern to you. Also, the smaller the bin, the more individual
>>statistical
>> error you will get for a given CPU time.
>>
>> I hope this helps
>>
>>
>> DEFAULTS=PRECISIO
>>
>>
>> * EMF <http://www.fluka.org/fluka.php?id=man_onl&sub=25> on
>>
>> * Rayleigh scattering and inelastic form factor corrections to Compton
>> scattering and Compton profiles activated
>>
>> * Detailed photoelectric edge treatment and fluorescence photons
>>activated
>>
>> * Low energy neutron transport on down to thermal energies included,
>>(high
>> energy neutron threshold at 20 MeV)
>>
>> * Fully analogue absorption for low-energy neutrons
>>
>> * Particle transport threshold set at 100 keV, except neutrons (1E-5
>>eV),
>> and (anti)neutrinos (0, but they are discarded by default anyway)
>>
>> * Multiple scattering threshold at minimum allowed energy, for both
>> primary and secondary charged particles
>>
>> * Delta ray production on with threshold 100 keV (see option DELTARAY
>> <http://www.fluka.org/fluka.php?id=man_onl&sub=21>)
>>
>> * Restricted ionisation fluctuations on, for both hadrons/muons and EM
>> particles (see option IONFLUCT
>> <http://www.fluka.org/fluka.php?id=man_onl&sub=42>)
>>
>> * Tabulation ratio for hadron/muon dp/dx set at 1.04, fraction of the
>> kinetic energy to be lost in a step set at 0.05, number of dp/dx
>> tabulation points set at 80 (see options DELTARAY
>> <http://www.fluka.org/fluka.php?id=man_onl&sub=21>, EMFFIX
>> <http://www.fluka.org/fluka.php?id=man_onl&sub=28>, FLUKAFIX
>> <http://www.fluka.org/fluka.php?id=man_onl&sub=35>)
>>
>> * Heavy particle e+/e- pair production activated with full explicit
>> production (with the minimum threshold = 2m_e)
>>
>> * Heavy particle bremsstrahlung activated with explicit photon
>>production
>> above 300 keV
>>
>> * Muon photonuclear interactions activated with explicit generation of
>> secondaries
>>
>> * Heavy fragment transport activated
>>
>>
>>
>>
>>
>> On 12/13/13 3:38 AM, "yyc2011_at_mail.ustc.edu.cn"
>><yyc2011_at_mail.ustc.edu.cn>
>> wrote:
>>
>> >Dear all,
>> >
>> > The attachmens are my input files.The first one is the input file for
>> >protons.since I have run it for eleven days,but my computer have not
>> >finished the first cycle.The calculation is too slow.So,I wish you
>>could
>> >see my input file,and optimize the input file so as to improve the
>> >calculation speed.The second input file is about electrons.Likewise,I
>> >wish you could see my input file and find whether there are something
>> >wrong in my input file.I am not sure about this.So I wish you could
>>help
>> >me.
>> > Thanks for any suggestion.Thanks for your help.
>> >
>> >Best Regards
>> >Chen Yuan
>> >
>> >
>> >> -----Original E-mail-----
>> >> From: "Giuseppe Battistoni" <giuseppe.battistoni_at_mi.infn.it>
>> >> Sent Time: 2013-11-25 22:56:18
>> >> To: yyc2011_at_mail.ustc.edu.cn
>> >> Cc: fluka-discuss_at_fluka.org
>> >> Subject: Re: [fluka-discuss]: some questions about charged particle
>> >>transport
>> >>
>> >> Dear Chen Yuan
>> >> you are asking something very difficult to be summarized by e-mail:
>> >> you have to refer to text books on the argument.
>> >> From your questions it seems that you have to
>> >> improve your background knowledge in the studies of
>> >> interaction of radiation with matter: this is essential for
>> >> any user of general purpose Monte Carlo codes as FLUKA.
>> >>
>> >> If I may give and advice, I strongly suggest to use always multiple
>> >>scattering
>> >> for all standard problems of realistic detectors and situation. Avoid
>> >>single scattering
>> >> which is to be considered only something exceptional for very very
>>thin
>> >>layers.
>> >> (by the way, it's very CPU time consuming).
>> >>
>> >> For your study on Molière's Theory of Multiple Scattering
>> >> let me also advice a historical paper by H. Bethe in Phys. Rev. 89,
>> >>12561266 (1953)
>> >>
>> >> Best regards
>> >> Giuseppe Battistoni
>> >>
>> >> On 11/25/2013 11:54 AM, yyc2011_at_mail.ustc.edu.cn wrote:
>> >> > Dear Giuseppe,
>> >> >
>> >> > First,Thanks for your reply.But,I still have some questions.
>> >> > (1)I wil study the paper so as to solve the problem.
>> >> > (2)In the Fluka course,you refer to the validity conditions of
>> >>Moliere theory more than once. But, what are the validity conditions
>>of
>> >>Moliere theory? Could you tell me in detail?
>> >> >
>> >> > Any multiple scattering therory applies when in a given step you
>>have
>> >>several coulomb scattering.Several is a qualitative word. In practice,
>> >>as a rule of thumb, you may be safe if you expect many tens of
>> >>scatterings.
>> >> >
>> >> > So,According to your view,when refer to scattering,I can only
>> >>estimate scattering numbers to determine whether it is appropriate to
>> >>use the mutiple scattering.And in general,how could you estimate
>> >>scattering numbers?
>> >> > (3)We advice single scattering only when you have thickness of
>> >>materials so small that the above conditions risks to be not
>>respected.A
>> >>couple of practical examples:
>> >> > - layers of nuclear photographic emulsions.where you aim to measure
>> >>charged tracks with few micron accuracy
>> >> > - very thin layers of silicon trackers (order of 100 micron or
>>less)
>> >> >
>> >> > According to your idea,There are no specific conditions to tell me
>> >>when should I use single scattering.I must judge whether I should use
>> >>single sattering as specific questions change.
>> >> >
>> >> > I don't know whether my understanding are right.Wish to receive
>> >>from you.
>> >> >
>> >> > Best regards
>> >> > Chen Yuan
>> >> >
>> >> >
>> >> >
>> >> >> -----Original E-mail-----
>> >> >> From: "Giuseppe Battistoni" <giuseppe.battistoni_at_mi.infn.it>
>> >> >> Sent Time: 2013-11-25 16:59:43
>> >> >> To: yyc2011_at_mail.ustc.edu.cn, fluka-discuss_at_fluka.org
>> >> >> Cc:
>> >> >> Subject: Re: [fluka-discuss]: some questions about charged
>>particle
>> >>transport
>> >> >>
>> >> >> Dear Chen Yuan
>> >> >>>
>> >> >>> When I learn charged particle transport,There are a few
>> >>problems I cannot understand.The questions are as followings.
>> >> >>> (1)The Fluka course said "Accurate PLC (not the average value
>> >>but sampled from a distribution), giving a complete independence from
>> >>step size",I cannot understand this sentence at all. What kind of the
>> >>distribution is? Could you give me a simple interpretations?
>> >> >>
>> >> >> I advice to study the paper (quoted in FLUKA references):
>> >> >> A. Ferrari et al., Nucl. Instr. Meth. in Phys. Res. B71, 412-426
>> >>(1992)
>> >> >> and references therein
>> >> >>
>> >> >>> (2)In the Fluka course,you refer to the validity conditions
>>of
>> >>Moliere theory more
>> >> >> than once. But, what are the validity conditions of Moliere
>> >>theory? Could you tell me in detail?
>> >> >>
>> >> >> Any multiple scattering therory applies when in a given step you
>> >>have several coulomb scattering.
>> >> >> Several is a qualitative word. In practice, as a rule of thumb,
>>you
>> >>may be safe
>> >> >> if you expect many tens of scatterings.
>> >> >>
>> >> >>> (3)In the Fluka course,you mentioned "full single scattering
>> >>are used to handle very low energy electron problems and very thin
>> >>layers problems. But,how much low is the electron energy? How much
>>thin
>> >>are the layers?
>> >> >>> In a word,I want to know when I should use mutiple scattering
>> >>and when I should use the full single scattering.
>> >> >>> I'm looking forward to receive from you.Thanks for your
>> >>time.Thanks for your reply.
>> >> >>
>> >> >> We advice single scattering only when you have thickness of
>> >>materials so small that the above
>> >> >> conditions risks to be not respected.
>> >> >> A couple of practical examples:
>> >> >> - layers of nuclear photographic emulsions.
>> >> >> where you aim to measure charged tracks with few micron accuracy
>> >> >> - very thin layers of silicon trackers (order of 100 micron or
>>less)
>> >> >>
>> >> >> Best regards
>> >> >> Giuseppe Battistoni
>> >> >>
>> >> >> --
>> >> >> INFN Milano
>> >> >> via Celoria 16, 20133 Milano, Italy
>> >> >> tel: +39 02 50317307
>> >> >> fax: +39 02 50317617
>> >> >>
>> >>
>>
>
Received on Sat Dec 14 2013 - 09:58:44 CET