System-generated electromagnetic pulse (SGEMP) arises from electromagnetic fields produced by photoelectrons emitted from spacecraft surfaces under intense X-ray or γ -ray irradiation. Cavity SGEMP, a critical subset of SGEMP, involves complex interactions within enclosed structures. While scaling laws have been established for external SGEMP, their applicability to cavity SGEMP remains debated due to photon spectrum distortion caused by variations in cavity wall thickness and other factors.

This study aims to validate the applicability of SGEMP scaling laws to cavity SGEMP by proposing a canonical transformation method that maintains constant wall thickness. The goal is to provide a theoretical basis for analyzing cavity SGEMP mechanisms and designing laboratory-scale experiments.

A cylindrical cavity model with an aluminum wall was irradiated by a laser-produced plasma X-ray source. Numerical simulations were performed using a 3D particle-in-cell (PIC) code under two conditions: an original model and a 10×scaled-up model. Key parameters, including grid size and time steps, were scaled according to the derived laws. The wall thickness was kept constant to avoid photon spectrum distortion. Simulations compared electric fields, magnetic fields, charge densities, and current distributions between the two models.

The original and scaled-up models exhibited identical spatial distributions of electromagnetic fields and charge densities. Specific validation results include: Peak electric fields decreased from 2.0 MV/m (original) to 200 kV/m (scaled-up); peak magnetic fields reduced from 0.8×10⁻³ T (original) to 0.8×10⁻⁴ T (scaled-up); and charge densities maxima dropped from 6.0×10⁻³ /m³ to 6.0×10⁻⁵ /m³. Waveform shapes for currents and fields remained unchanged across models. These results all adhere to the scaling laws.

The scaling laws for SGEMP are validated for cavity SGEMP when wall thickness remains unchanged. This work provides a universal theoretical tool for cavity SGEMP studies and reliable scaling criteria for laboratory experiments.