Re: [fluka-discuss]: The use of EMFCUT

From: paola sala <paola.sala_at_cern.ch>
Date: Thu, 2 Jan 2014 10:33:26 +0100

...
please look at the unit on the z axis, as I wrote in my e-mail I used a
LONGER target. In the first part the flux increases, after that it
decreases.

On 01/02/2014 08:51 AM, yyc2011_at_mail.ustc.edu.cn wrote:
> Dear Paola,
>
> First,Thanks for your reply in detail.Thanks for your time.I am very grateful for you.
> Second,You said "the higher electron flux on the target side is due to the production of secondary electrons".About this,I agree with you.But,I am a little confused about the plot you gave. From the plot,I can only see elctron flux decrease on the target side.Just like you said,"you can clearly see the initial buildup followed by decrease".But this seems contrary to the higher electron flux on the target side. So,Could you explain to me?
>
> Best Regards
> Chen Yuan
>
>
>> -----Original E-mail-----
>> From: "Paola Sala" <paola.sala_at_mi.infn.it>
>> Sent Time: 2014-1-1 23:11:48
>> To: yyc2011_at_mail.ustc.edu.cn
>> Cc: fluka-discuss_at_fluka.org
>> Subject: Re: [fluka-discuss]: The use of EMFCUT
>>
>> Dear Chen Yuan,
>>
>> Indeed, I would expect an higher electron flux on the target side, that is
>> what you have. The target (10 microns carbon) is not thick enough to stop
>> the 60 KeV electrons. On the contrary, it is thick enough to allow for the
>> production of secondary electrons that increase the total electron flux
>> (buildup). This is a very well known behaviour in radiation transport.
>> You can see it in the attached plot, where I took your input and extended
>> the target in the z direction. The plot shows the electron flux as a
>> function of z and x, you can clearly see the initial buildup followed by
>> decrease. (I had small statistics, small color variations are due to
>> statistics).
>>
>> About the two spikes in your plot, at the left and right of the target
>> boundary, I'm not completely sure but they might be due to the fact that
>> scattered and secondary electrons can only go from the target to the
>> vacuum, not vice-versa, thus creating a depletion zone on the target side
>> and an overpopulation on the vacuum side.
>>
>> You also sent me another mail, about the what(60 in MULSOPT. Above 1000 it
>> has no influence, therefore it cannot influence the CPU time.
>>
>> Regards
>> Paola
>>
>>> Dear everyone,
>>>
>>> The attachment is my input file and the figure of flux density.In the
>>> input file,the primary energy of electron is 0.06MeV.The thickness of
>>> carbon target is 10um.The electron transport cutoff energy I set is
>>> 1KeV.
>>> However,the figure of flux density I got is odd. The flux density on the
>>> left side of the border is larger than the flux density on the right
>>> side of the border.You know,the 10um carbon target is located on the
>>> left side.In theory,the flux density on the left side of the border
>>> should be less than the flux density on the right side of the border.
>>> So,I doubt the EMFCUT card I set is wrong.Could you have a look at my
>>> input file?Is there any wrong about the EMFCUT card I set?
>>>
>>> Best Regards
>>> Chen Yuan
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>> Paola Sala
>> INFN Milano
>> tel. Milano +39-0250317374
>> tel. CERN +41-227679148
Received on Thu Jan 02 2014 - 11:25:22 CET