In a two-cavity klystron amplifier, the input cavity is commonly referred to as which component?

Introduction / Context:
In klystron amplifiers, electron beam velocity modulation is converted to density modulation (bunching) to extract RF power efficiently. The two primary resonant cavities are specialized for distinct roles in this process.

Given Data / Assumptions:

• Standard two-cavity klystron configuration.
• First cavity near the electron gun; second downstream toward the collector.
• Beam passes through both cavities sequentially.

Concept / Approach:

The first (input) cavity imposes velocity modulation onto the electron beam by RF fields. Space-charge effects then cause faster electrons to catch up with slower ones, forming bunches. The second (output) cavity extracts RF power as the bunched beam induces strong RF currents in it.

Step-by-Step Solution:

Verification / Alternative check:

Standard texts consistently use this naming convention: buncher (input), catcher (output).

Why Other Options Are Wrong:

• 'catcher': that is the output cavity.
• 'Pierce gun': the electron gun structure, not a cavity.
• 'collector': collects spent electrons after interaction.
• 'slow-wave helix': element of a TWT, not a klystron.

Common Pitfalls:

Confusing klystron (cavity interaction) with TWT (slow-wave structure); swapping the roles of buncher and catcher.

Final Answer:

buncher