Non-physical numerical noise when using Nm > 5

fbpic / fbpic

Spectral, quasi-3D Particle-In-Cell code, for CPU and GPU

http://fbpic.github.io

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Non-physical numerical noise when using Nm > 5 #649

Closed dattiyah closed 6 months ago

dattiyah commented 1 year ago

Hi,

I am running FBPIC simulations with higher order Laguerre modes (L>3), and have come across a weird bug. I am getting excessive numerical noise in m=5 as shown below. I have also attached the input deck. Any help resolving this issue would be greatly appreciated.

Thanks, Danny Attiyah

Figure 0(1) Figure 0(2) Figure 0(3) Figure 0(4) Figure 0(5) input.txt

MKirchen commented 6 months ago

Dear @dattiyah, sorry for the late reply. You need to increase the number of particles per cell when using more modes (nt = 4*Nm). See als Issue #220 and #554 for additional information. Note that setting Nm > 6 can cause problems with the field solver in some simulations. Hence, we recommend setting Nm < 6. We plan to improve the implementation of the Hankel transform in the future to resolve this issue. For Nm = 5, however, the simulation should be stable.