When there is no magnetic field in the simulation, emittances given by the postprocessing and my own code are same. But when there is magnetc field in the simulation, no matter how small of the field, emittances parallel to magnetic induction are different.
The simulation software is CST Studio Suite 2020 Particle Tracking Solver. For the same structure of RF negative hydrogen ion source, the H- beam is extracted from plasma electrode and accelerated by the extracted electrode and accelerated electrode. There are two pairs of rod filter magnet in this structure.
The simulation file and datafiles is given below. The RMS emittance of x and y direction given by postprocessing are 0.00994 and 0.0101 mm rad repectively. The RMS emittance of x and y direction given by my code are 0.00994 and 0.00992 mm rad repectively. The direction of the magnetic induction line is parallel to the y-axis. As the magnetic field strength increases, the difference in the emittance calculated in the y direction is even greate.
Christian Baumgarten I understand what you're saying is that the presence of a magnetic field can cause an increase in the emittance, and that is normal.
Finally, I found the issue. It was caused by an error in the emittance calculation method in CST. Nonetheless, I appreciate your help, and I will contact the technical support team at CST to further investigate and confirm the cause of the problem. Thank you.
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