Re: Secondary Alpha and Recoil Nuclei

From: Fawaz Ali <>
Date: Thu, 17 May 2012 16:04:59 -0400 (EDT)

Hi Mary,

Thanks for your response. I am doing microdosimetry simulations in FLUKA (simulating the response of a Tissue Equivalent
Proportional Counter to low energy neutron irradiation) and generally, the following is observed in the pulse height spectrum:

- Protons produced by neutron elastic scatter with H-1 and by 14N(n,p) deposit roughly between 13 - 133 keV of kinetic energy

- Alphas produced by fast neutron capture with C-12, O-16, and N-14 deposit between 133 - 667 keV of kinetic energy

- Carbon, Oxygen, and Nitrogen recoil nuclei deposit 667 - 1333 keV of kinetic energy

In the pulse height spectrum I obtained from the DETECT card, I only see the proton region populated (i.e. counts are present
between the 13 - 133 keV span). However, no counts have been registered in the energy spans pertaining to alpha and heavy recoil
nuclei energy deposition. I will certainly have a look at USRBIN and RESNUCLEi to see if I can score the kinetic energy deposited
by these particles in the sensitive volume of the counter.


On 5/17/12 3:03 PM, Mary Chin wrote:
> Hello Fawaz,
> > Is this because FLUKA does not transport these particles?
> *I assume you mean heavy ions. FLUKA does transport them if the user:
> - requests so via the IONTRANS card; or
> - asks for an ion beam.
> > Is this because ...
> *No. Even without ion transport activated, ions are ranged out and the
> energy IS always deposited.
> > I am applying the DETECT card
> > I am seeing the protons but I am not seeing the alpha and C, O, N
> *How do you "see protons but not alphas, C, O, N" in the DETECT output?
> Residual nuclei are typically scored using the RESNUCLEi card.
> Energy deposition can be scored not only using DETECT but also USRBIN.
> DETECT is for (anti-)coincidence, trigger and/or pulse-height spectrum
> (i.e. multiple energy depositions resulting from the same primary are
> summed as one count). USRBIN is generally more versatile.
> If you really need to see each recoil in action, then mgdraw would be the
> user routine to go for.
> :) mary
> On Thu, 17 May 2012, Fawaz Ali wrote:
> > Hello Everyone,
> >
> > I am performing a simulation whereby low energy neutrons (with kinetic
> > energy on the order of keV) are irradiating a target. I am applying the
> > DETECT card to the sensitive volume of the target and I am expecting to
> > see the following secondary particles which will contribute to the
> > counts vs. energy deposited spectrum: protons, alpha, and recoil Carbon,
> > Oxygen, and Nitrogen nuclei (note that I have set their respective
> > transport thresholds down to 1 keV). I am seeing the protons but I am
> > not seeing the alpha and C, O, N recoil nuclei. Is this because FLUKA
> > does not transport these particles? Would I have to go into the
> > USERDUMP tape to find the kinetic energy they deposit in the sensitive
> > volume?
> >
> > I appreciate any help that can be provided.
> >
> > Thanks,
> > Fawaz
> >
> >
Received on Fri May 18 2012 - 12:06:43 CEST

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