Design of a Fast Reactive Tuner for 1.3 GHz TESLA cavities at MESA

TL;DR

This paper introduces a novel Ferroelectric Fast Reactive Tuner (FE-FRT) for 1.3 GHz TESLA cavities, enabling rapid reactive power modulation and reducing RF power requirements, validated through analytical and simulation methods.

Contribution

The paper presents the design and validation of a new ferroelectric tuner capable of microsecond response times for TESLA cavities, addressing microphonics-induced detuning more effectively than existing piezoelectric solutions.

Findings

FE-FRT can handle substantial reactive power.

Offers a tuning range of 50 Hz.

Reduces peak RF power by about ten times.

Abstract

This work presents a state-of-the-art design of a Ferroelectric Fast Reactive Tuner (FE-FRT), capable of modulating high reactive power in TESLA type cavities on a microsecond time scale. The Mainz Energy-Recovering Superconducting Accelerator employs superconducting radio frequency cavities operating at 1.3 GHz, achieving quality factors on the order of $10^{10}$. However, detuning of $\pm$25 Hz induced by microphonics have led to the use of strong coupling for the fundamental power coupler, requiring high-power amplifiers, orders of magnitude above the intrinsic dissipation. Current solutions to mitigate microphonics rely on piezoelectric tuners, which are not fast enough for the spectral range of the microphonics. A novel alternative is the FE-FRT, a technology made possible by the development of low-loss ferroelectric materials, which offer sub-microsecond response times. Analytical results are provided along with their validation through finite-element simulations. The FE-FRT is expected to handle substantial reactive power while offering a tuning range of 50 Hz in these type of cavities, resulting in a reduction in peak forward RF power by about an order of magnitude.