Joint inversion of potential filed data using cross-gradient constraint

Hello, I am currently working on the cross-gradient joint inversion method for gravity and magnetic data in the context of iron deposits. My question is about the joint inversion Jupyter notebook in the SimPEG documentation: Does this notebook primarily demonstrate L2-norm joint inversion or L1-norm joint inversion? Additionally, I encountered an issue during forward modeling where I was unable to achieve a more favorable geometry for simple shapes by reducing the coupling factor to 1e6. I would greatly appreciate any insights or guidance on this matter. Thank you in advance for your response.