Developing a Next Generation Readout System for Microwave Kinetic Inductance Detectors

Abstract

Microwave Kinetic Inductance Detectors (MKIDs) are photon detectors based on superconducting resonators, capable of detecting single photons with inherent energy resolution and μs time resolution, while also allowing arrays of tens of thousands of MKIDs to be read out on a single feedline using frequency domain multiplexing (FDM). MKIDs are a promising technology for a range of applications, including astronomy, particle physics, and THz imaging. We are developing MKIDs for optical to near infrared astronomy. This thesis covers work done at Trinity College Dublin and the Dublin Institute for Advanced Studies developing MKIDs optical to near infrared astronomy, as well as the readout electronics needed to perform this FDM.

This thesis gives an outline of the background information needed to understand MKIDs, and also gives an outline of their applications. It details the work done developing a laboratory setup for measuring MKIDs, and also developing code for performing frequency sweep measurements. Code is presented for fitting the data generated to equations from the literature, to obtain the quality factors and resonant frequencies of the MKIDs. The results of this are shown. Following this the work done developing a single pixel readout system based on a Re-configurable Open Access Computer Hardware (ROACH) board is detailed. This setup was used to measure and analyse photon pulses in the MKIDs' phase and I/Q data. The results gathered by this setup are presented. An analysis was performed into some potential future systems for reading out large arrays of MKIDs, ultimately selecting the Xilinx ZCU111 and 2x2 Radio Frequency System on Chips (RFSoCs). This analysis, as well as the work done developing firmware and software for this purpose is also outlined.

MKIDs were designed and fabricated for this project which were measured, using the setups described above, to internal quality factors of the order of 100,000. Moreover, they also displayed energy resolutions ranging from 3.14 for 400 nm light, to 2.50 for 900 nm light.

Finally, a next generation MKID readout system based on a Xilinx 2x2 Radio Frequency System-on-Chip (RFSoC) is proposed, with a potential cost-per-pixel of ~ 1.