Re: Bremsstrahlung Variance Reduction

From: Alberto Fasso' <>
Date: Thu, 30 May 2013 01:26:21 -0700 (PDT)

Hi Mario,

what you have suggested is indeed a variance reduction option for
bremsstrahlung radiation, as requested by Ehsan, but it is not the same
as that provided by the bnum option in MCNP (and by the option "bremsstrahlung
splitting" in EGS and in Geant). In FLUKA we don't have bremsstrahlung
splitting, and I don't think that I would like to have it. Indeed, in EGS
and in Geant, at a bremsstrahlung interaction several photons are emitted,
but the energy of the electron is decreased by the energy of one single photon,
creating a problem of energy conservation.
In FLUKA, one can obtain a similar effect in a more "clean" way by surrounding
the target with a boundary, and playing ordinary splitting with the normal
BIASING option (limiting the biasing to photons only, as it can be done with
WHAT(1)<0: see Note 3 to BIASING option in the manual).
The EMF-BIAS/LABBREM option you suggested is also clean, and can be used
without any problem


On Wed, 29 May 2013, Santana, Mario wrote:

> Ehsan,
> This feature is available in FLUKA. Use the EMF-BIAS card with
> SDUM='LAMBBREM'. You need to specify biasing factor and materials in which
> biasing is activated.
> (
> Mario
> On 5/29/13 1:05 AM, "Ehsan Salimi" <> wrote:
>> Dear FLUKA users
>> In my problem, I want to multiply the number of bremsstrahlung photons
>> produced by primary electrons by a specific number so that
>> each time an electron generates bremsstrahlung radiation; it produces
>> more than one photon but with reduced weight. For instance, 8
>> bremsstrahlung photons with 1/8 weight, just like the bnum option in
>> electron physics in mcnpx. I want to evaluate my mcnp results
>> with FLUKA and therefor, I need to use the same variance reduction method
>> in both simulations. Anyway, if this variance reduction
>> method is not available in FLUKA, I would like to know what other
>> variance reduction options I have for bremsstralung radiation.
>> Thanks in advance
>> Ehsan Salimi
Received on Thu May 30 2013 - 13:30:51 CEST

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