Accelerated Lifetime Test of The SRF Dressed Cavity/Tuner System for LCLS II HE Project

TL;DR

This paper reports on accelerated lifetime testing of the SRF dressed cavity and tuner system for the LCLS II HE project, focusing on durability, performance impacts, and actuator wear under extended operational conditions.

Contribution

It introduces an accelerated testing methodology to evaluate the longevity of the cavity and tuner system, addressing increased tuning range and operational demands.

Findings

Tuner longevity increased by 20 times compared to previous requirements.

Piezo and stepper motor actuators showed acceptable wear levels after testing.

Cavity bellow maintained performance after 2000 cycles at 2 K and 2.6 mm compression.

Abstract

The off-frequency detune method is being considered for application in the LCLS-II-HE superconducting linac to produce multi-energy electron beams for supporting multiple undulator lines simultaneously [1]. Design of the tuner has been changed to deliver roughly 3 times larger frequency tuning range. Working requirements for off-frequency operation (OFO) state that cavities be tuned at least twice a month. This specification requires the in-crease of the tuner longevity by 20 times compared with LCLS-II demands. Accelerated longevity tests of the LCLS-II HE dressed cavity with tuner were conducted at FNAL's HTS. Detail analysis of wearing and impacts on performances of the tuner's piezo and stepper motor actuators will be presented. Additionally, results of longevity testing of the dressed cavity bellow, when cooled down to 2 K and compressed by 2.6 mm for roughly 2000 cycles, will be presented.