Re: Re: [fluka-discuss]: Why single scattering is extremely demanding in CPU time?
Dear Paola,
Thanks for your reply.Thanks for your time.
Best Regards
Chen Yuan
> -----Original E-mail-----
> From: "Paola Sala" <paola.sala_at_mi.infn.it>
> Sent Time: 2013-11-29 14:25:00
> To: yyc2011_at_mail.ustc.edu.cn
> Cc: fluka-discuss_at_fluka.org
> Subject: Re: [fluka-discuss]: Why single scattering is extremely demanding in CPU time?
>
> Dear Chen Yuan,
> as the words say:
> -multiple scattering : many scatterings are cosidered all together to
> calculate the deflection over a "step"
> - single scattering: each scattering is considered independently, each one
> needs a "step"
>
> guess what takes more time..
>
>
> Please, we had already lots of discussin on this item that is a basic item
> for all particle transport problems, there is PLENTY of literature on it,
> starting from the Partivcle Data Book to dedicated papers on the multiple
> scattering theory. Please refer to these unless you have a fluka-specific
> problem
> Paola
>
> > Dear Fluka Experts,
> > When I use MULSOPT card, setting WHAT(6)> 1000.0 with SDUM = GLOBAL,
> > GLOBHAD or GLOBEMF, replaces systematically multiple
> > scattering with single scattering everywhere. This choice is generally
> > extremely demanding in CPU time.(1)But why? In other words,what causes the
> > long computing time?(2)But,When I deal with the same problem with mutiple
> > scattering,the computing time is greatly reduced. So,Are there any
> > differences between single scattering and multiple scattering in the
> > codes?And what are the differences?
> > Thanks for any suggestions.Thanks for your time.
> >
> > 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 Moli¨¨re's Theory of Multiple Scattering
> >> let me also advice a historical paper by H. Bethe in Phys. Rev. 89,
> >> 1256¨C1266 (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
> >> >>
> >
> >
>
>
> Paola Sala
> INFN Milano
> tel. Milano +39-0250317374
> tel. CERN +41-227679148
>
Received on Fri Nov 29 2013 - 09:54:43 CET
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