Secondary Particles Hit to Radiator

So We are doing a high school project and we wanted to use geant4 to simulate it
We want to make a proton beam to hit a Aluminium target to create secondary particles which i have coded and send those particles to a radiator to create chernekov radiation

Now the problem is that not all of the particles hit the radiator because of them being created randomly.

Here set the worldMat as aluminium and as you can see not all particles reach it
Is there a way to get all these secondary particles to hit the radiator