beam charge calculation in boosted frame

[spadova-a]

Hello,

I'm working on a simulation of LWFA with boosted frame and rigid injected beam. I set the "beam.q_tot = -1.e-11" (i.e. 10 pC) but then when I look at the beam charge after the simulation is complete I get the beam charge -1e-5. I used the LPA diagnostic .get_charge() from the openPMD as well as direct calculation: "charge = w.sum()*e". I also tried running the example script from your webpage, but the charge is again very different (the value in the input file is beam.q_tot =-1e-14" but the diagnostic says -1e-8). I noticed both values are incorrect by a factor of 1e6. Do you have any idea what can cause this?
Also and more importantly, is it possible that the charge in the simulation is correct and that the problem is only in the diagnostics part? The simulation seems to be working just fine. electrons get accelerated and there is no strange behavior of the beam or the plasma wave. I suppose the electron beam with charge of -1e-5 C would create some problems in the simulation... I'm saving the data in .h5 files. I went through the file structure and I cannot find where the information about the weight is stored so I don't know how to determine whether the weights are correct or not.

Also, I have another question. I would like to later use injection from external file. Assuming I have an openpmd file from another WarpX simulation with particles I want to inject, how do I know which timestep will the code choose? Will it be the last one? I don't see a parameter which I could use to specify this.

Thanks for your help.