Delta electrons and their effect on energy deposition vs loss

Physics, Transport and Magnetic Fields
1

Hello FLUKA Team,

I am currently conducting simulations involving a muon- beam interacting with a Si target, aiming to investigate the effect of varying target thicknesses on the ratio of energy deposition to energy loss.

In my simulations, I have observed an unexpected phenomenon: contrary to my initial hypothesis, the ratio of energy deposition to energy loss seems to decrease as the target thickness increases. This result is puzzling to me, as I had anticipated that thicker targets would lead to a higher ratio due to the potential for delta-electrons to escape the target in the case of thin targets.

I use EVENTBIN to score energy deposition within the target using a region binning.
To score the energy loss after the target, I use 2 EVENTBIN cards to score the fluence and the weighted fluence (fluscw) and divide the two.
I then calculate the ratio of deposition / loss, average the ratio for all events and get the attached result.

In the FLUKA input I use:

  • IONFLUCT to turn off fluctuations
  • EMFCUT (for transport)
  • DELTARAY

I would greatly appreciate any insights or suggestions you may have to help resolve this issue.
Thank you for your attention to this matter.

Kind regards,
Michael

DeltaE.inp (1.5 KB)
results.pdf (14.0 KB)
fluscw.f (5.1 KB)

3

Hi @mibauer
when increasing the target thickness, what makes the difference here is not the decreasing escaping probability of a secondary particle, namely a delta electron (or a bremsstrahlung photon), rather its increasing generation probability, which increases the number of events with lower ratio.
In fact, your expectation holds for the ratio of the average energy deposition to the average energy loss, which is not the average ratio of energy deposition to energy loss!