Coincidence scoring in ΔE–E detector shifts Residual-E peaks

[Carlos.Vitor (Carlos Eduardo Vítor)]

Dear FLUKA team and community,

I am simulating a ΔE–E detector with an alpha source (three energy peaks). The setup includes:

• A thin Delta-E (ΔE) detector in front.
• A thicker Residual-E detector behind it.

I score:

1. Energy deposition in ΔE.
2. Energy deposition in Residual-E.
3. Coincidence: energy in ΔE only when the same particle also hits Residual-E.

Without coincidence, the Residual-E peaks for the alfa show the expected energy loss.
With coincidence active:

• Residual-E peaks shift back to the original source energies — as if no energy was lost in ΔE.
  
  

I believe this should not happen. Any advice would be very appreciated.

Thank you.

[ceruttif (Francesco Cerutti)]

It looks like there is a syntax error in your last two DETECT cards: in order to distinguish between detector and trigger region, you need to input the latter with the minus sign.