Re: Biasing advice needed...

From: Alberto Fasso' (fasso@SLAC.Stanford.EDU)
Date: Tue Jul 24 2007 - 10:37:20 CEST

  • Next message: Feracci Vincent: "Low energy Neutrons"

    Hi Frances,

    the recommendations of the FLUKA manual are right in principle,
    but a long experience with electron accelerator shielding has
    shown that you can get very good results with EMF-BIAS alone.
    Apply it EVERYWHERE, and with WHAT(1) = 1022.
    You will not need anything else.


    On Mon, 23 Jul 2007, Burge, F (Frances) wrote:

    > Hello Fluka users,
    > I'm looking for some advice on using the biasing options in fluka. My
    > input file consists of a 3 GeV electron beam striking a target within a
    > shielded enclosure, and I need to score dose rates outside the
    > shielding, from photons and neutrons. Without biasing, the run is very
    > slow.
    > I guess that for the photons, EMF-BIAS is the appropriate option,
    > activated for all processes and with SDUM = LPBEMF. I intended to apply
    > this in the target region and also the vacuum surrounding it. However
    > the fluka manual recommends avoiding biasing in the scoring region and
    > adjacent regions, so should I not apply biasing within the shield wall
    > regions ? If I wanted to also score dose rates within the shielding,
    > would this mean that I should not use EMF-BIAS in this region either ?
    > Also, the manual recommends using the weight window biasing to avoid
    > large fluctuations in the dose scoring due to heavily weighted low
    > energy particles. So it looks like I also need the WW-THRESh and
    > WW-FACTOr cards. Can anyone give me any advice on how to choose the
    > upper and lower weight limits of the weight window, or is this only
    > possible by carrying out repeated runs on a trial-and-error basis ?
    > Finally, would it be safer to use neither of the above options and use
    > just the BIASING card instead ? In this case, am I correct in thinking
    > that the method would be to divide the target and/or shield wall into
    > layers (as different regions) and assign each layer an importance which
    > increases with distance through the shield ? Presumably I could also use
    > this biasing for neutrons.
    > All advice gratefully received.
    > Frances
    > Frances Burge
    > Health Physicist
    > 01235 778269
    > Diamond Light Source Ltd.
    > Rutherford Appleton Laboratory
    > Chilton
    > Didcot
    > OX11 0DE
    > <DIV><FONT size="1" color="gray">This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail.
    > Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd.
    > Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message.
    > Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom
    > </FONT></DIV>

    Alberto FassÚ
    SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
    Phone: (1 650) 926 4762   Fax: (1 650) 926 3569

  • Next message: Feracci Vincent: "Low energy Neutrons"

    This archive was generated by hypermail 2.1.6 : Tue Jul 24 2007 - 14:35:35 CEST