Which microwave electron device employs a slow-wave structure to achieve continuous interaction between the RF wave and the electron beam?

Introduction / Context:
Microwave linear beam devices achieve energy transfer from an electron beam to an RF field through velocity or density modulation. A slow-wave structure lowers the phase velocity of the RF wave so the beam can effectively interact over a long distance.

Given Data / Assumptions:

• TWT uses a helix or coupled-cavity slow-wave structure.
• Klystrons use discrete cavities with gaps; interaction is localized.
• Reflex klystron relies on a single cavity and repeller electrode.

Concept / Approach:

The hallmark of a TWT is distributed, broadband interaction along a slow-wave structure, enabling wide bandwidth and gain. Klystrons (two-cavity or multicavity) do not employ a continuous slow-wave helix; they employ resonant cavities for bunching and power extraction.

Step-by-Step Solution:

Verification / Alternative check:

Device datasheets describe TWT helices and coupled-cavity SWS used for high gain and bandwidth; klystron literature references gaps and cavities instead.

Why Other Options Are Wrong:

• Klystrons (two-cavity or multicavity) and reflex klystron: cavity interaction, not SWS.
• Magnetron: different principle (crossed E–B fields), no SWS.

Common Pitfalls:

Generalizing 'linear beam devices' to all—only TWTs use slow-wave structures for distributed gain.

Final Answer:

TWT