Hi @Nora ,
I’m glad to hear that I could help solving the issue, but the cause is indeed a bit puzzling. I will think about it, but it will be hard to follow this issue without access to the configurations, fields and geometries you are using. Would it be possible for you to provide me with these?
Thanks and cheers
Paul
Dear @pschutze ,
Thank you for your reply, maybe I misunderstood the meanings of some parameters in allpix2. Can I confirm these with you first?
About the gain: In my view, they are calculate step by step, using the average electric field of each step to get the parameter alpha, and then accumulate all the influence of the steps from the position where the incident particle depositing the charge to where they reach the readout pad. But how does it deal with the influence of both electrons and holes propagated from an electron at the same time moving to opposite electrodes? Just as I say before, I think the number of the electrons is equal to that of the holes
About the parameter in the GenericPropagarion module [propagate_electrons &propagate_holes]: I think the holes produced in the process of primary ionization will not propagate because they move to the cathode and the propagation process only happen in the layer under the anode. So the main part of the gain is from the contribution of the electron in the primary ionization, instead of the holes. If I set propagate_electrons = false, which part of electron in the whole process I really ignore? What about propagate_holes = false?
Is there any way I can get the motion trails of the propagation process directly？If I can check the movement of the charges, it will help a lot.
Thank you again for your kind help.
Best regards,
Nora
Hi all,
late to the game, but in LGADs the e-field is usually tuned such that one charge carrier type (electrons) undergo impact ionization while the other one (holes) do not - otherwise we’d be in Geiger mode.
Might that play a role in finally having a difference in the distribution?
Also, @Nora have you considered presenting your work at our next user workshop? 
Best,
Simon
Dear @simonspa ,
Thank you for your reply! But I do not really get your idea, can you explain it detailedly?
Now I try three different set-ups and got different results of the simulation.
Use GenericPropagation module:
Consider both electrons and holes
Consider only holes
Consider only electrons
The distribution of the first and second setup are similar, showing that the electrons contribute a small part to the gain. As my expectation, the holes contribute more to the pulse. But I wonder why the holes also contribute more to the propagation process. As I mentioned before, I think their number should be the same and the difference of their contribution to the pulse is mainly due to the time they use to arrive at the electrodes instead of the gain they cause. So could you explain more about the gain calculation process to me?
Finally, thank you very much for your invitation. But I’m only a new user for allpix2 and do not make much process on my work, I’m afraid I cannot really share something useful for you 
.
Best regards
Nora
there is something (admittedly, it’s several things, but let me start with this one …) I do not understand here: in case 2 (“Consider only holes”), the graph “Gain per electron group …” should not be populated at all, as electron groups should never be propagated.
Again, @Nora , we are eager to understand the issue to help you, but I repeat:
it will be hard to follow this issue without access to the configurations, fields and geometries you are using. Would it be possible for you to provide me with these?
If you are allowed to share any information, please do so, otherwise we are poking around in the dark. If configurations and fields should be confidential, please let us know and we will find a way to discuss this issue in private.
Thank you very much
Paul
Dear @pschutze ,
Thank you so much!
I really agree with you, so it also confused me. That’s also why I ask you about meanings of the parameters
Besides, because I do not get the permission from my supervisor and co-worker to share all the detailed configurations to the public. Could I send them to your email?
Best regards,
Nora
Dear @Nora ,
I’m glad that we could resolve the issue.
For future reference: the issue was most likely an incorrect definition of a radioactive source setup, making it more coherent with the corresponding example configuration seems to solve the issue.
Thanks for reporting this, @Nora !
Cheers
Paul
