Re: [fluka-discuss]: Energy loss of relativistic nuclei in a crystal

From: Paola Sala <>
Date: Mon, 1 Jul 2019 15:21:44 +0200

Sorry, but I still do not reproduce your problem.
I attach a simple input file, that has the same physics/transport cards
as yours, runs on monochromatic ions, and uses the THRESHOLD card to
inhibit interactions. Results are collected with a DETECT card. Running at
300 GeV/nucleon and 30 TeV/nucleon gives comparable results, as in the two
plots attached (energy deposition in 2 cm PWO, no normalization).
Maybe you could try to run your case adding the THRESHOL card, to be sure
that there is no contamination by inelastic interactions? Although I do
not understand why this should change with energy..
Your source.f seems correct, but maybe try a monoenergetic run?
I'll keep thinking..

> Hello Paola,
> I set the BEAM card at -30000, i.e. 30 TeV/nucleon, if I correctly
> understood the card instructions.
> Oxygen kinetic energy is extracted from a E^-1 distribution up to 200 TeV
> of particle energy, then it should be fine.
> I noticed the same behaviour also using carbon nuclei; the dE/dx
> €œanomalous" rise starts around 10-15 TeV of particle energy.
> I send you annexed my input and geometry cards for physics and the
> source.f file I have modified for spectrum generation.
> Thank you for your help
> Paolo
>> On 24 Jun 2019, at 11:47, Paola Sala <
>> <>> wrote:
>> Hello
>> From a fist check, with oxygen ions at fixed energies, I cannot
>> reproduce
>> your results. The dE/dx stays fairly constant, as expected.
>> One doubt: did you set the energy in the BEAM card to a sufficiently
>> high
>> value to cover all the source ions? If not, de/dx tabulations will not
>> be
>> correctly initialized. If yes.. could you please send me your input, or
>> at
>> least the card you use for physics and transport settings?
>> Thanks
>> Paola
>>> Hello fluka developers,
>>> I am doing simulations of the energy deposit of oxygen nuclei at high
>>> energy in a bar of PWO crystal (density 8.28 g/cm^3, 2 cm thick).
>>> Oxygen nuclei have generated according to KE^-1 spectrum, where KE is
>>> the
>>> kinetic energy per particle spanning from 178 GeV to 316 TeV.
>>> I made plots (see attached figure to this email) of the energy loss
>>> (dE/dx) distributions (computed from the energy deposited in the bar,
>>> and
>>> dividing by
>>> the square of the particle charge) for different energy intervals of
>>> KE.
>>> In these plots, nuclei undergoing hadronic inelastic interaction
>>> (somewhere in the crystal) are not included.
>>> As you can see, dE/dx has a nearly constant value (around 2 MeV
>>> cm^2/g,
>>> as expected) up to KE ~ 10 TeV, then it increases dramatically for
>>> higher
>>> KE.
>>> I wonder which might be the physical reason for this increase of dE/dx.
>>> I would have expected an almost constant value for relativistic charged
>>> particles (in the Fermi plateau).
>>> Are there any radiative effects turned-on for ultra-relativistic
>>> charged
>>> particles?
>>> Thanks for your help.
>>> Paolo Maestro
>> Paola Sala
>> INFN Milano
>> tel. Milano +39-0250317374
>> tel. CERN +41-227679148

Paola Sala
INFN Milano
tel. Milano +39-0250317374
tel. CERN +41-227679148

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Received on Mon Jul 01 2019 - 17:10:02 CEST

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