## 2 Materials and Methods
We extended the manufacturing procedure for producing the smaller samples to full size NLTLs by replacing the aluminum mold with the NLTLs outer and inner coaxial electrodes. This eliminated the requirement for mold release since the composite did not need to be removed and the composite could be form fitted to different sized center conductors. An additional outgassing step was added after filling the NLTL to ensure no air bubbles were present in the line. Aluminum caps were used to fix the center and outer conductors in place while the composite cured. The impedance of the manufactured NLTLs was altered for a fixed composite loading by varying the diameter of the center conductor with the inner diameter of the outer conductor fixed at 25.4 mm. The diameters of the center conductor for the 50 \(\Omega\), 25 \(\Omega\), and 10 \(\Omega\) NLTLs were 3.7 mm, 9.5 mm, and 14.7 mm, respectively. Using (1), these parameters give saturation impedances of 13.1 \(\Omega\), 23.5 \(\Omega\), and 46.1 \(\Omega\). Figure 2 shows a photograph and a schematic of the experimental setup. While our previous experiments focused on various compositions of BST and NZF [22; 23], this study used a mixture of 10% BST and 15% NZF inclusions in polydimethylsiloxane (SylgardTM 184, PDMS), which was chosen to match the highest NZF loading in our previous study [22]. The reasoning for selecting this volume fraction is further discussed in the Discussion section but the primary motivation was that NZF exhibits greater nonlinearity relative to BST at the field strengths presented here. Figure 2: **(Top)** Photograph and (**bottom**) schematic of a 10 \(\Omega\) NLTL attached to the 3D printed spark gap switch and load. The load consists of four 40 \(\Omega\) branches of four 10 \(\Omega\) resistors placed in parallel to achieve a 10 \(\Omega\) load. Invasive D-dot probes were used to observe the pulse waveform as a function of line length. We charged the NLTLs with DC voltages ranging from 6 kV to 20 kV using a high voltage supply ([PERSON] model EJ40P15) by attaching the output of the HV supply to the center conductor of the NLTL. The opposing end of the center conductor was connected to a spark gap switch (SGS), which was designed and constructed in-house using a Formlabs3 + 3D printer and Formlabs durable resin. The switch was pressurized using dry nitrogen (Indiana Oxygen, Lafayette, IN USA). The spark gap switch utilized round electrodes which were fabricated out of brass. Gap spacing was fixed at 3 mm while the pressure was adjusted between 10 and 65 psi to achieve the desired standoff voltage. The lines were terminated with the appropriate resistive load, made in-house using HVR RT series non-inductive resistors (HVR Advanced Power Components, Cheektowaga, NY, USA), to match the impedance of the NLTL. Due to power handling concerns, the loads were made by making four branches of four resistors in series. Each branch was then connected in parallel to achieve the appropriate load termination. Figure 2 shows an example of this setup with four 40 \(\Omega\) branches, each consisting of four 10 \(\Omega\) resistors in series, connected in parallel to form the load for the 10 \(\Omega\) NLTL. Additionally, the output waveforms for each line were measured using a voltage divider, which was attached to the output of the spark gap switch. The voltage divider consisted of HVR RT series resistors with a 30 dB attenuator. The output waveform was viewed using a 4 GHz oscilloscope (Tektronix MSO64, Beaverton, OR, USA).