3D cavity Superconducting Parametric Amplifiers for high frequency radio astronomy

Abstract

Superconducting parametric amplifiers have recently seen a great deal of interest due to their promising gain (often above 20 dB) and sub-quantum noise performance of the amplifying element. Most of these amplifiers are 2D structures exploiting the non-linear inductance of Josephson junctions or the kinetic inductance of a superconducting material for parametric gain. However, 3D cavities can be a valuable alternative to push these types of amplifiers to frequencies well above 30 GHz, as long as a reliable way to couple a non-linear component to these devices is found. This work is centred on two 3D cavity superconducting parametric amplifiers: the niobium pillbox cavity and the Disc Stack Resonator. A maximum signal gain of 5 dB has been measured from the pillbox cavity at 1 K for a signal power in input of -60 dBm and a frequency spacing between the pump and the signal tones of 10 kHz. The measured signal gain map agreed with the one obtained using the Josephson resonator amplifier model in the four-wave mixing regime and the non-linear behaviour of the cavity has been successfully simulated in ADS using a parallel RLC circuit for the resonator and a Josephson junction component to account for the non-linearity of the superconducting contacts, expected to be formed by the surface pair between the irises and the bulk niobium. These results gave confidence to the development of the Disc Stack Resonator, made of 75 niobium discs stacked in series to form a more non-linear Ka band 3D cavity. This device has been simulated in ADS obtaining a maximum signal gain of 28 dB for a signal power in input of -110 dBm and a frequency spacing between the two input tones of 10 kHz. Preliminary measurements performed with different irises showed reasonably strong mixing effects at 1 K but the quality factor of the resonance of interest (TM110 mode) was too low compared to the one measured from the pillbox cavity, which would lead to a worse gain performance. These results motivate the idea of testing this cavity at lower temperatures to increase the quality factor and possibly development a new 3D cavity superconducting parametric amplifiers based on the same technology.

Date of Award	31 Dec 2023
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Lucio Piccirillo (Supervisor) & Keith Grainge (Supervisor)