Re: Understanding EMF-CUT and residual dose rate

From: Alberto Fasso' <fasso_at_SLAC.Stanford.EDU>
Date: Thu, 29 Mar 2012 06:52:26 -0700 (PDT)

Dear Mina,

to complete the information that Francesco has already sent to you,
I would like to add the following.

* To some people (including myself) it is more natural to input electron
    threshold kinetic energies rather than total energies. It is possible to do
    so by giving the threshold values with a minus sign in the WHAT(1) of command

* There are two different electron and photon thresholds:
    - transport threshold, given _per region_ (command EMFCUT with SDUM blank)
    - production threshold, given _per material_ (command EMFCUT with
    It is recommended to define explicitely both, because the defaults are not
    always reliable (read Note 1 to EMFCUT).
    Except in special cases, it is safe to set both thresholds at the same
    value (read Note 2 to EMFCUT).

* Command DELTARAY, also mentioned in your message, concerns only charged
    particles heavier than electrons (protons, pions, muons, heavy ions etc.)
    In the case of electron and positron transport, "delta rays" are called
    Moller and Bhabha electrons, and their production threshold is defined by
    EMFCUT with SDUM=PROD-CUT as explained above.

* In case of doubt, it is useful to check on output which values have been set.
    Production thresholds are called Ae (for electrons) and Ap (for photons),
    and are found in a Table with title "Quantities/Biasing associated with each
    Transport thresholds are called Ecut (for electrons) and Pcut (for photons),
    and are found in a Table with title "Correspondence of regions and EMF-FLUKA
    material numbers and names:"
    Ecut and Ae are always output as _total_ energy.
    When examining the output with Flair, you find Ae and Ap in the section
    called "Media parameters", and Ecut, Pcut in the following section, "EMF".


On Thu, 29 Mar 2012, Francesco Cerutti wrote:

> Dear Mina,
> all your tries are affected by the meaningless value you requested for the
> e-/e+ threshold. As you write, the latter (being input with the positive
> sign) is intended as total energy, which means kinetic plus rest mass (as
> reminded in the manual). So your 20keV make no sense, since the e-/e+ mass
> amounts to 511keV (and their transport limit in FLUKA is 1keV, implying a
> minimum value of 512keV). Facing this wrong request, the code takes the
> default in case of failing transport threshold setting (1MeV for NEW-DEFA)
> and instead the above minimum value of 1keV in case of failing production
> threshold setting (then assumed also for transport).
> Concerning the default EM thresholds, note that they have got nothing to
> do with the hadronic threshold indicated in the DEFAULTS description
> (10MeV for NEW-DEFA and 100keV for PRECISIO). As echoed in the output
> (where once more Ecut is - always - intended as total energy), they are
> 1MeV for e-/e+ and 333keV for photons in case of NEW-DEFA (and 10 times
> lower in case of PRECISIO).
> Finally, your first try assumes the default region range, which is limited
> to the region #2 - as written in the manual, EMFCUT card - (and makes
> your threshold setting ineffective also for photons if the corresponding
> material is VACUUM or BLCKHOLE).
> Ciao
> Francesco
> **************************************************
> Francesco Cerutti
> CH-1211 Geneva 23
> Switzerland
> tel. ++41 22 7678962
> fax ++41 22 7668854
> On Wed, 28 Mar 2012, wrote:
>> Dear Stefan,
>> Thank you for this information which has helped me investigate this puzzle
>> but I am still having difficulty understanding what is exactly going on
>> with the EMFCUT for gammas and e+/e- and I would appreciate if someone
>> could help clarify this.
>> I have run three sets of runs for a given setup (only varying EMFCUT). I
>> had run two before your message and I ran one after your message and
>> reading the EMFCUT and DEFAULTS part of the manual few times, trying to
>> understand.
>> Please note in all of these tries I used NEW-DEFAults.
>> The relevant EMF default cuts here are:
>> - Particle transport threshold set at 10 MeV
>> - Delta ray production on with threshold 1 MeV
>> 1st try:
>> ========
>> EMFCUT card:
>> EMFCUT 2.0000E-05 2.0000E-05 0.000 0.000 0.000 0.000
>> Here I am only setting the transport energy cut-off for gammas and e+/e-
>> (total energy) here but since I did not defined any region, no cut should
>> have been applied. I had assumed the default behaviour for no region
>> selected would be (from 1st to last region but I was wrong). But even the
>> default behaviour in flair for starting and ending regions does not work.
>> Looking at the output and searching for the Ecut and Pcut for the 11
>> regions defined, I see:
>> Ecut = 1.5110E+00 MeV, Pcut = 3.3333E-01 MeV, BIAS = T, Ray. = F,
>> S(q,Z) = T, Pz(q,Z) = F
>> ===> For all regions, with the exception of BLKHOLE and VACUUM, Ecut is
>> set to 1.511 MeV (Total E) and 0.33333 MeV for gammas.
>> Where is the 1 MeV cut for e+/e- and 333.33 keV for gammas coming from???
>> 2nd try:
>> ========
>> EMFCUT card:
>> EMFCUT 2.0000E-05 2.0000E-05 0.000 3.000 11.00 0.000
>> Here I am again only setting the transport energy cut-off for gammas and
>> e+/e- (total energy) for the regions of interest. So the EMFCUT of 20 keV
>> should have been applied to e+/e- and gammas. But did it?
>> Ecut = 1.5110E+00 MeV, Pcut = 2.0000E-02 MeV, BIAS = T, Ray. = F,
>> S(q,Z) = T, Pz(q,Z) = F
>> ===> Aside from the VACUUM regions, I see that a 20 keV cut is applied to
>> gammas but no cut is applied to e+/e-.
>> After re-reading the manual under the EMFCUT, under NOTE 2, I see:
>> "When instead the transport cutoffs are lower than the production ones,
>> they are increased to be equal to them."
>> So I thought, the default production threshold for e+/e- must be set to
>> higher (1 MeV) and that is why I am seeing this behaviour. Is this from
>> the DETLA-RAY production threshold from NEW-DEFAults? Then why is the
>> gamma production threshold not set to 10 MeV?
>> 3rd try:
>> ========
>> EMFCUT cards:
>> EMFCUT 2.0000E-05 2.0000E-05 0.000 3.000 710.0 0.000 PROD-CUT
>> EMFCUT 2.0000E-05 2.0000E-05 0.000 3.000 11.00 0.000
>> Here I am setting both the transport and production thresholds for gammas
>> and e+/e- (total energy). So in principle the EMFCUT of 20 keV should now
>> be definitely be applied to e+/e- and gammas. Did it?
>> Ecut = 5.1200E-01 MeV, Pcut = 2.0000E-02 MeV, BIAS = T, Ray. = F,
>> S(q,Z) = T, Pz(q,Z) = F
>> Now, I see a total energy cut of 0.512 MeV for e+/e- and 20 keV for
>> photons which sounds about right.
>> In summary: Ecut (MeV) Pcut (MeV)
>> 1st try 1.5110E+00 3.3333E-01 No
>> EMFCUT (effectively)
>> 2nd try
>> EMFCUT (20 keV transport for e+/e-& g) 1.5110E+00 2.0000E-02
>> 3rd try
>> EMFCUT (20 keV tran.& prod. for e+/e-& g) 5.1200E-01 2.0000E-02
>> It is clear that setting the production cut for both e+/e- is essential if
>> the transport cuts are lower than the production cuts. But this is not
>> the case for gammas.
>> It is not clear to me where the default production cut for gammas
>> (3.3333e-1 MeV) comes. In NEW-DEFAults, the default transport cut is set
>> to 10 MeV. As I understand it, this cut applies to all particles, unless
>> changed via EMFCUT card for e+/e-, and gammas and via LOW-NEUT card for
>> neutrons.
>> At the end of the day, the difference between the 3rd and 1st try in terms
>> of dose rates 5 years after EOB is about 9% increase for the 3rd try
>> (which is not much).
>> Thank you and best wishes,
>> Mina
>>> Dear Mina
>>> 1) Please see the manual under EMFCUT Notes 1) and 2) which give some hint
>>> on the default settings. As Note 2) explains the actual settings can be found in the output file (search for 'Ecut' and 'Pcut').
>>> 2) Yes any modification factors defined with RADDECAY/WHAT(5) apply to the
>>> EMFCUT settings.
>>> Cheers
>>> Stefan
>>> Re: Understanding EMF-CUT and residual dose rate
>>> * This message: [ Message body ] [ More options ]
>>> * Related messages: [ Next message ] [ Previous message ] [ In reply to
>> ]
>>> From: Mina Nozar<>
>>> Date: Tue, 13 Mar 2012 11:58:12 -0700
>>> I just realized I attached the wrong file with this message. Here is the correct plot showing residual dose rates for
>>> six targets (separate runs and fluka setups) as a function of time in a cylindrical detector a meter away from the beam
>>> line. When comparing does rates for a given target at a given cooling time
>>> (1.2 years after EOB), we are seeing a
>>> factor of 2 less in dose rates from FLUKA than those measured at the same
>>> time. I am still trying to figure out why
>>> this is.
>>> I have tested few other runs where I don't include an EMFCUT card. The results are the same as the time when I did not
>>> specify a region for the 20 keV transport card. Confirming this by looking
>>> at the echoed input in the output files,
>>> this means the default behaviour as stated in the manual is not correct:
>>> WHAT(4) = lower bound (or corresponding name) of the region indices with
>>> electron cutoff equal to |WHAT(1)|
>>> and/or photon cutoff equal
>>> to WHAT(2) and/or leading particle biasing
>>> ("From region WHAT(4)...") Default: = 2.0.
>>> i.e. not defining any lower and upper bound regions for transport energy cut-offs in the EMFCUT card, does not set the
>>> lower and upper bound regions to the 2nd region in the drop down menu (on
>>> the list of Regions) and the EMFCUT is simply
>>> not applied.
>>> What I still do not understand are:
>>> 1) How are the default decay and prompt transport energy cut-offs determined if one does not use an EMFCUT card. My
>>> results show that the default energy cut-off does not come from PART-THRES
>>> (10 MeV) in NEW-DEFA.
>>> and
>>> 2) Do the decay and prompt cuts in RADDECAY card use the transport cut as
>>> defined in the EMFCUT card?
>>> I would appreciate if one of the FLUKA gurus could shed some light on this.
>>> Thanks again,
>>> Mina

Alberto Fasso`
SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
Phone: (1 650) 926 4762   Fax: (1 650) 926 3569
Received on Fri Mar 30 2012 - 13:40:45 CEST

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