Clarification on Boundary InvokeSD behavior

Physics Processes, Models and Cross Sections
1

Dear experts,

I am simulating a simple Cherenkov detector, which consists of a gas-filled cube (with a defined refractive index), and placed inside, a smaller silicon cube representing the photon sensor (with the same refractive index).

The silicon cube is linked to a sensitive detector that records the optical photon’s kinematics and then kills the optical photon.

Initially, I had BoundaryInvokeSD set to true, but I observed that the photon is killed before entering the silicon volume. To make the simulation work as intended, I had to disable this option.

Questions:

  1. What are the intended use cases for BoundaryInvokeSD = true versus false?
  2. Why was the default value changed from true in Geant4 version 10 to false in version 11?

I would appreciate your time and insights.

Best regards,
Alvaro

2

With BoundaryInvokeSD = false, one gets the usual Geant4 SD behaviour (for any particle).

If instead you want to optical boundary process to detect and kill the optical photon, set the EFFICIENCY material property and BoundaryInvokeSD = true.

3

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