Re: Re: [fluka-discuss]: negative deposit energy from EVENTBIN using Fluka2011.2x.8

From: Paola Sala <paola.sala_at_mi.infn.it>
Date: Thu, 5 Mar 2020 13:48:30 +0100

Dear Mingyang
I confirm that the negative energy deposition you see is indeed physically
sound: It comes from a neutron at ~ thermal energy hitting an Hydrogen
atom and gaining energy from the thermal motion of the target.

This can happen only when pointwise treatment of neutron transport is
activated, as it happens since a while with the DEFAULTS PRECISION (only
for a few materials, see the manual)

For groupwise transport, kerma is averaged and is never negative.

If you do not "like" to see negative energies, (which are tiny quantities
indeed), you can either
- disable pointwise treatment through the LOW-NEUT card . This I do not
advise, the simulations will be less precise
- intercept them with a comscw.f routine. I attach an example that writes
informations whenever a negative energy dep occours. It has to be
activated with a USERWEIG card, what(6)=3.

I am sorry I cannot find the other discrepancy you mention, probably I
missed it: you point to event 56, could you, please, tell me in which
region do you see it?

Be careful: the two MULSOPT cards have wrong SDUMS, they should be GLOBEMF
and GLOBHAD.



> Dear Paola,
>
> The attachment is an example to illustrate the problem.
>
> More details:
> If conducting a run using FLUKA 2011.2x.8,
> 1) You'll find negative deposit in 62nd event in
> negative_demo001_fort.113.
> 2) The relative difference of energy deposit extracted from EVENTDAT and
> EVENTBIN card could be very large, say 90%, for instance in 56th event.
>
> Thanks a lot for your help!
>
> Best regards,
> Mingyang
>
>
>> -----原始邮件-----
>> 发件人: "Paola Sala" <paola.sala_at_mi.infn.it>
>> 发送时间: 2020-02-28 17:15:43 (星期五)
>> 收件人: "\"崔明阳\"" <mycui_at_pmo.ac.cn>
>> 抄送: fluka-discuss_at_fluka.org, "\"李翔\"" <xiangli_at_pmo.ac.cn>,
>> "\"岳川\"" <yuechuan_at_pmo.ac.cn>, "\"袁强\""
>> <yuanq_at_pmo.ac.cn>
>> 主题: Re: [fluka-discuss]: negative deposit energy from EVENTBIN using
>> Fluka2011.2x.8
>>
>> Dear Migyang
>> Could you, please, give some more details about your simulation and the
>> effect you see?
>> ( You can send me your input file if you wish)
>> Please note that very small negative energy depositions are possible
>> when
>> thermal neutrons are transported: being thermal, they can gain energy by
>> reducing the thermal motion of the target.
>> Hope this helps
>> Paola
>> > Dear Fluka experts,
>> >
>> >
>> >
>> >
>> > When we update Fluka from version 2011.2x.7 to 2011.2x.8 recently, a
>> > problem arises.
>> >
>> > Negative energy deposit will occur as we scoring energy using EVENTBIN
>> > card.
>> >
>> > Besides, we have added SDUM=OLDFLAIR in the GLOBAL card as mentioned
>> in
>> > the release note.
>> >
>> >
>> >
>> >
>> > Are there other necessary modifications on input file?
>> >
>> > We appreciate your help with this.
>> >
>> >
>> >
>> >
>> > Best,
>> >
>> > Mingyang
>>
>>
>> Paola Sala
>> INFN Milano
>> tel. Milano +39-0250317374
>> tel. CERN +41-227679148


Paola Sala
INFN Milano
tel. Milano +39-0250317374
tel. CERN +41-227679148



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Received on Thu Mar 05 2020 - 15:34:42 CET