thyratron
High-voltage switching vacuum tube in the linac's pulse-forming network (PFN). Drives the modulated high-voltage pulse that feeds the klystron or magnetron. Modern solid-state pulse-forming networks (on newer linac chassis) replace thyratrons with semiconductor switches; many Clinac iX and predecessor-class platforms still run thyratrons.
Why it matters to buyers: Scheduled consumable on thyratron-based platforms. Replace on interval, don't wait for hard failure — pulse-timing jitter before failure can cause subtle dose-delivery anomalies that flag in monthly QA before the unit fails outright.
Why it matters to engineers: Thyratron degradation causes pulse-timing jitter, output drift, and eventually arcing. Solid-state modulators on newer chassis eliminate this maintenance line item but introduce different service-tree branches.