Re: [fluka-discuss]: Contribution of different particles to the detector signal !

From: Vittorio Boccone <dr.vittorio.boccone_at_ieee.org>
Date: Fri, 25 Nov 2016 20:28:04 +0100

Dear Yang
> 1. <<The "fiction" you do in the simulation is to account all the energy lost by delta rays to the original particle interaction.<<
> Reply: OK, indeed, the outside electrons cannot enter in the detector. However, if we assume that the radiation field only has gamma ray, it's reasonable to attribute the energy deposition causing by gamma incident (despite of the detail process inside the detector) to the gamma contribution to the eventual detector signal.
>
No it depends on the energy of the photon and where the photon covert. The MC code takes care of tracking all the secondaries for each event and to evaluate all the energy deposition as the particle history evolves.
> Obviously, gamma has 100% contribution to the detector signal since it assumes that the radiation field only has gamma.
>
No, the gamma might only leave a fraction of the energy in the detector and the rest outside.
> Using USRBIN+AUXSCORE card inside the detector sensitive volume, then we respectively score energy depositon by selecting option "ALL-PART", "PHOTON" and "ELECTRON", thus, the total energy deposition (value:A), deposition by gamma(B) and by electron(C) are obtained. Simulation always shows that A≈C>>B.
>

This only means that you have an almost pure EM problem w/o nuclear reactions. A>C anyway. This evaluation will anyway be completely useless because everything depends on the particle spectrum.
> There is no problem that electrons inside the sensitive volume are also generated by the gamma, and A also corresponds to the detector signal. But if there is a method to suppress the gamma-generated electrons or other particles generated electrons in the sensitive volume, I don't know if I will obtain that B equals to A for electrons cannot be created by doing this, if it is true, we can simplify the contribution of different particles in the mixed radiation field to the detector signal.
>
I still don’t get what you want to achieve with this. Yes you can suppress the secondary transport but this might give you artefact in the simulation. Energy will almost never correspond to the signal intensity of the detector. The signal of the detector is ofter simulated by the convolution of the particle fluencies (as function of the energy) with the detector response to the specific particle interaction (for a specific energy). Evaluating the signal of the detector in terms on energy deposition is typically only an acceptable approximation only in some calorimetry related studies. Please be more specific for your case or the discussion risks to be too general.

> 2.<< Your detector will see only the effects of the particles crossing it. Each particle has a history, a "father" process/interaction which generated it, and "children" particles which were generated by the interaction. therefore the AUXSCORE card uses this information to understand how much energy deposition was caused by a gamma, neutron or whatever else effect.<<
>
> Reply: as replied above, when I add an AUXSCORE card for PHOTON, the result seems to show that energy deposition of gamma only generates the 1st-generation electrons, and the 1st generation electrons also generate the 2nd-generation electrons and so on, FLUKA seems to attribute the energy deposition after the 1st generation electrons by gamma interaction to ELECTRON's contribution, thus, we get a maximum deposition value from electrons and we cannot evaluate the contribution to the detector signal from particles in the outside mixed field. Perhaps the problem should be simply solved, but I don't know the specific method.

An AUXSCORE selecting PHOTON for an energy USRBIN will allow you to sum up the contribution of the delta rays (electrons) generated by the PHOTON.
You keep saying "we cannot evaluate the contribution to the detector signal from particles in the outside mixed field”. The situation is simple: when any of the secondaries/primary looses energy in the detector you will score it. If the particle does not reach the detector what do you want to score???? I really don’t know what to answer you as I don’t know what you want to achieve. All the particle are transported and tracked until their energies fall below their transport thresholds. Why do you care about the effects of n-th generation particles not entering in the detector???

> 3.<< If you need the full particle tree history following the primary interaction you can always use the USERDUMP card, but this can generate a lot of data.I would first try to have under control the simulation of the detector response for specific primaries. In real life you would do the same by calibrating your detector response with specific particles and specific energy relevant to your problem.Second you need to get familiar with the particle fluences and spectra at the detector using a few USRTRACK and USRYIELD cards.Only then you can introduce the mixed radiation field. This can be achieved by changing the source term.<<
>
> Reply: This suggestion may be the "fold method" but it is too complex and hard for me. Nevertheless, I get the detector response function of different primaries, but the response function only corresponds to some simplified situations that the primary beam direction with respect to the detector longitudinal direction is respectively 0, 90, 180, 270 degree. In the real mixed field, the direction of coming particles has all the possible values, but it's impossible to calculate response functions of all orientations. So how to use the obtained response function or could you send me some detailed references?
I think you have a bit of confusion about the theory of the particle interaction with matter. You keep being very general. You don’t specify anything about your problem and you insist asking very wide question which prevents me to give you a valid suggestion for your specific problem. Fluence convolution is actually not as difficult as it might look like.

Best
 Vittorio





__________________________________________________________________________
You can manage unsubscription from this mailing list at https://www.fluka.org/fluka.php?id=acc_info
Received on Fri Nov 25 2016 - 22:04:17 CET

This archive was generated by hypermail 2.3.0 : Fri Nov 25 2016 - 22:04:29 CET