How to interpret grey tracks from 60Co decay

Particles, Track, Event, Run and Biasing
1

Hi all,
I’m a newby, working with a student to simulate a 60Co source surrounded by lead. We’re basing our work on the example rdecay02. My question is, what are the grey tracks I’m observing in the visualizer (Qt)? The image is below. The relevant portion of the vis.mac is below that. In the image, red blocks are lead, grey panels are aluminum, and dark green is polyethylene. Ten primary events were simulated.

My understanding is the track colors are green = photons (I see two per primary event) and red = electron (I see one produced in this run, squigling in the middle of the lead tunnel). But what are the grey lines?? I see 1 grey track per primary. Are these primary electrons (there should be one per primary)? If so, why are these tracks grey. If they are primary electrons, then there’s a mistake in my code, since they should be stopped by the lead.

Thanks for your help.

image
image1405×600 10 KB

Here are the important potions of the vis.mac file.

/vis/scene/add/trajectories smooth
/vis/modeling/trajectories/create/drawByCharge
/vis/modeling/trajectories/drawByCharge-0/default/setDrawStepPts false
/vis/modeling/trajectories/drawByCharge-0/default/setStepPtsSize 1

/vis/modeling/trajectories/create/drawByParticleID
/vis/modeling/trajectories/drawByParticleID-0/set e- red
/vis/modeling/trajectories/drawByParticleID-0/set gamma green
/vis/modeling/trajectories/drawByParticleID-0/set neutron yellow
/vis/modeling/trajectories/drawByParticleID-0/set alpha blue
/vis/modeling/trajectories/drawByParticleID-0/set GenericIon blue
#
# To superimpose all of the events from a given run:
/vis/scene/endOfEventAction accumulate

Geant4 Version: 11.2.2
Operating System: Windows 11
Compiler/Version: VS 17.10.2
CMake Version: 3.30.0

2

They are NEUTRINOS!!! I figured this out by adding drawByParticleID… set anti_nu_e blue. This leads to another question. Where are the primary electrons? There should be one per primary decay, right?

Thanks again

3

I see red tracks in your image. Keep in mind the concept of “range” as production cuts which will likely mean you only see part of the track of the fastest (primary) electrons and maybe occasional compton electrons.

4

Thank you jrellin. Your comment has helped me understand better how GEANT4 works.

The primary electrons should have an energy of around 100 keV. I’ll have my student check the verbose output to see what range that corresponds to in air.