Open Microwave Cavity for use in a Purcell Enhancement Cooling Scheme

TL;DR

This paper presents an open microwave cavity design that enhances plasma cooling via the Purcell Effect, enabling efficient lepton plasma cooling for antihydrogen synthesis without moving parts.

Contribution

It introduces a novel open geometry microwave cavity with adjustable quality factors for improved plasma cooling applications.

Findings

Cavity design achieves high quality factors with open ends

Surface treatments allow tuning of cavity quality

Design is applicable to various open-geometry plasma systems

Abstract

A microwave cavity is described which can be used to cool lepton plasmas for potential use in synthesis of antihydrogen. The cooling scheme is an incarnation of the Purcell Effect: when plasmas are coupled to a microwave cavity, the plasma cooling rate is resonantly enhanced through increased spontaneous emission of cyclotron radiation. The cavity forms a three electrode section of a Penning-Malmberg trap and has a bulged cylindrical geometry with open ends aligned with the magnetic trapping axis. This allows plasmas to be injected and removed from the cavity without the need for moving parts while maintaining high quality factors for resonant modes. The cavity includes unique surface preparations for adjusting the cavity quality factor and achieving anti-static shielding using thin layers of nichrome and colloidal graphite respectively. Geometric design considerations for a cavity with strong cooling power and low equilibrium plasma temperatures are discussed. Cavities of this weak-bulge design will be applicable to many situations where an open geometry is required.