1：Experimental Design and Method Selection:

The study uses a one-dimensional large signal analysis model (SUNRAY-1D) for stability analysis of helix slow wave structures (SWS). It involves analyzing both tapered and untapered helix SWS cases, with a focus on backward wave amplifier (BWA) gain as a function of taper parameter (D) and frequency parameter (B). Theoretical models and equations from two-wave theory are employed to calculate efficiency and start oscillation current.

2：Sample Selection and Data Sources:

The analysis is based on design parameters of a Ku-band space helix TWT, as specified in Table 1 of the paper. No external datasets are mentioned; the data is derived from simulations or theoretical calculations using the in-house model.

3：List of Experimental Equipment and Materials:

The paper does not specify physical equipment; it relies on computational models. Materials implied include helix slow wave structures with support rods (e.g., APBN support rods), but no specific models or brands are detailed.

4：Experimental Procedures and Operational Workflow:

The procedure involves using the SUNRAY-1D model to simulate and analyze the effects of tapering on BWO. Parameters such as helix pitch, beam current, and voltage are varied. The workflow includes calculating BWA gain, start oscillation current, and optimizing taper parameters through mathematical analysis.

5：Data Analysis Methods:

Data analysis is performed using derived equations for BWA gain, start oscillation current, and interaction parameters. Statistical techniques are not mentioned; the analysis is primarily theoretical and based on the provided formulas.