Gain simulation: add comparison factor to test beam


I’m trying to simulate LGAD sensors and compare their results with test beam data. As I wrote in another thread before, gain in the simulation does not appear to be similar to the one expected in reality (I’m assuming here that the charge deposition simulation instead is matching).
However this might not be a problem in the allpix simulation itself, but could be related to the electric field map I’m using.

I wanted to ask what could be the best way to add a factor to account (let’s say I expect a gain on average two times higher) for that in the code and where I should place this factor. I thought was a trivial task but I see that the gain is calculated locally and based on that secondaries are produced, so I’m not sure if makes sense to multiply the total charge at the end of the multiplication process for example or I should do something different.

Thanks in advance,


Dear Andrea,

this question is a bit hard to answer, to be honest. Of course it is always possible to include tweak factors, at every stage of the simulation. However, we aim to describe the physical processes or the phenomenons as well as possible, based on validated models, hence we don’t inherently plan for tweak factors.

From my point of view, revisiting the electric field would be most appropriate, as it is one of the two inputs. The other input is the impact ionisation model. It is possible to include custom models, see documentation, this could be a good spot to adapt the behaviour.


Dear Paul,
thanks for your answer!
Indeed I also think that the best thing would be to have a correct description of the electric field but that’s what I’m missing to reproduce TB data I think.
That’s why I wanted to artificially change the gain simulation to try to narrow down the problem, however I see your point, maybe I can find a different way of doing it.

Thanks again,