supplement Number1

Additional information supporting the results presented in the main text is provided in the supplementary material. This includes detailed fabrication procedures for the metal-powder epoxy composite used in the filters, covering mixing ratios, temperature treatment, and degassing steps to ensure uniform performance. Comparative data on different epoxy variants are included in Fig. S1, showing their impact on frequency-dependent attenuation and parasitic capacitance. The role of epoxy coating on the internal surfaces of the filter chassis and its effect on suppressing parasitic resonances is also demonstrated in Fig. S2. Furthermore, variations in attenuation characteristics among multiple handmade filters are demonstrated in Fig S3, to highlight reproducibility. Finally, a comparison with other cryogenic low-pass filters is presented to contextualize the performance advantages of the developed powder filter design.