RE: energy deposition in thin beam windows

From: <>
Date: Tue, 20 Apr 2010 14:43:45 +0100

Dear Alberto,

Thanks for your message.

I have seen a paper where for a thin target the energy deposition is not
just defined by dE/dx. They claim that quite a lot of the energy
deposited in the thin target leaves in the form of electrons with their
own kinetic energy. The energy carried by the electrons which leave the
target reduces the heating of the target with respect to the dE/dx
calculation. Is FLUKA accounting for these electrons that are able to
leave a thin target?

Kind Regards


-----Original Message-----
[] On Behalf Of Alberto Fasso'
Sent: 03 April 2010 13:54
To:; Davenne, Tristan (STFC,RAL,EID)
Subject: RE: energy deposition in thin beam windows

Dear Tristan,

energy deposition in a thin target is mainly governed by the
stopping power (dE/dx) of the incident particles and cannot be
improved much by biasing.

Mean free path biasing can be applied, however, to improve statistics of
particle production. The commands are LAM-BIAS (SDUM blank,
WHAT(2)-WHAT(6)) to enhance statistics of nuclear interactions for hadrons
and photons, and


to enhance statistics of bremsstrahlung production by electrons
and positrons.

Apart from that, in your input the START command is placed at the very
beginning, just after the title. This is incorrect: when the code
reads START, it starts doing calculations and ignores everything
which comes later. START should be the last command, or second last
just before STOP.


On Thu, 1 Apr 2010, wrote:

> Dear Andrea,

> Here is my input file attached. I am trying to calculate energy

> deposition in a proton beam window. The window is a 1mm thick, 25mm

> radius beryllium cylinder. It has a proton beam incident on the centre

> of the window. I am looking to find the peak and integrated energy

> deposition in the window. My question is do I need any different

> settings when looking at energy deposition in a thin layer (such as a

> beam window) as compared to a relatively long target.

> Kind Regards

> Tristan

> -----Original Message-----

> From:

> [] On Behalf Of


> Sent: 01 April 2010 13:30

> To:

> Subject: Re: energy deposition in thin beam windows


> Dear Tristan,

> can you provide us your input file or at least some more details on

> what

> your are going to simulate?

> Thanks

> Andrea

>> Dear Fluka experts,

>> I have been successfully modelling energy deposition in long cylindrical
>> targets. I am now interested in energy deposition in thin beam windows
>> of less than 1mm in thickness. Do I need to make any modifications to my
>> inputs to get accurate results?

>> For example I note the following comment in the FLUKA manual which
>> mentions using the EMF-BIAS option for a thin target.

>> "The EMF-BIAS =

>> option
>> can be tuned per region below user-defined energy thresholds and is used
>> very often in shielding calculations for high-energy electron
>> accelerators. The same command can be used also to bias the electron and
>> photon mean free path for various types of interaction, for instance to
>> enhance the probability of interaction in a thin or low-density target."

>> Many Thanks

>> Tristan

Alberto Fasso`

Department Associate
SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
Received on Tue Apr 20 2010 - 23:49:23 CEST

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