Investigation of thermal acoustic effects on SRF cavities within CM1 at Fermilab

TL;DR

This paper investigates how thermal acoustic effects, including helium boiling and pressure fluctuations, impact the microphonics in SRF cavities at Fermilab, aiming to improve RF power stability.

Contribution

It provides new insights into the thermal acoustic phenomena affecting SRF cavities, with detailed measurements of helium boiling and pressure effects during cryogenic operation.

Findings

Identification of helium boiling as a source of microphonics

Correlation between pressure spikes and cavity noise

Characterization of thermal acoustic effects across frequencies

Abstract

Radio Frequency (RF) power studies are in progress following the cryogenic commissioning of Cryomodule #1 (CM1) at Fermilab's Superconducting Radio Frequency (SRF) Accelerator Test Facility. These studies are complemented by the characterization of thermal acoustic effects on cavity microphonics manifested by apparent noisy boiling of helium involving vapor bubble and liquid vibration. The thermal acoustic measurements also consider pressure and temperature spikes which drive the phenomenon at low and high frequencies.