A scalable packetised radio astronomy imager

Includes bibliographical referencesModern radio astronomy telescopes the world over require digital back-ends. The complexity of these systems depends on many site-specific factors, including the number of antennas, beams and frequency channels and the bandwidth to be processed. With the increasing popularity for ever larger interferometric arrays, the processing requirements for these back-ends have increased significantly. While the techniques for building these back-ends are well understood, every installation typically still takes many years to develop as the instruments use highly specialised, custom hardware in order to cope with the demanding engineering requirements. Modern technology has enabled reprogrammable FPGA-based processing boards, together with packet-based switching techniques, to perform all the digital signal processing requirements of a modern radio telescope array. The various instruments used by radio telescopes are functionally very different, but the component operations remain remarkably similar and many share core functionalities. Generic processing platforms are thus able to share signal processing libraries and can acquire different personalities to perform different functions simply by reprogramming them and rerouting the data appropriately. Furthermore, Ethernet-based packet-switched networks are highly flexible and scalable, enabling the same instrument design to be scaled to larger installations simply by adding additional processing nodes and larger network switches. The ability of a packetised network to transfer data to arbitrary processing nodes, along with these nodes' reconfigurability, allows for unrestrained partitioning of designs and resource allocation. This thesis describes the design and construction of the first working radio astronomy imaging instrument hosted on Ethernet-interconnected re- programmable FPGA hardware. I attempt to establish an optimal packetised architecture for the most popular instruments with particular attention to the core array functions of correlation and beamforming. Emphasis is placed on requirements for South Africa's MeerKAT array. A demonstration system is constructed and deployed on the KAT-7 array, MeerKAT's prototype. This research promises reduced instrument development time, lower costs, improved reliability and closer collaboration between telescope design teams

Passive terahertz imaging with lumped element kinetic inductance detectors

Progress towards large format, background limited detector arrays in and around the terahertz or sub-millimetre region of the electromagnetic spectrum has – until recently – been hampered by the complexities in fabrication and cryogenic electronic readout associated with increasing pixel counts. Kinetic inductance detectors or KIDs are a superconducting pair breaking detector technology designed to overcome these complexities. Traditionally, KID arrays have been developed for imaging in astronomy. However, the high sensitivities, broadband responses, fast time constants and high detector counts that are achievable – along with the simplicity of fabrication and readout compared to other contemporary technologies – make them suitable (and in fact desirable) for a variety of applications. This thesis documents the development of a concept instrument to demonstrate KID technology for general purpose imaging applications. Specifically, I present the design, construction and performance of a near background limited, quasi-video rate, passive imaging system based on arrays of Aluminium lumped-element KIDs. The camera operates in two atmospheric windows at 150 GHz (2 mm) and 350GHz (850 μm) with 60 and 152 pixels, respectively. Array fabrication was achieved with a single photolithographic cycle of thin film deposition, patterning and etching. Full array readout is with a single cryogenic amplifier and room temperature FPGA based frequency domain multiplexing electronics. The camera is the first of its kind in applying KID arrays to imaging systems outside of pure astrophysics research and is the result of efforts from the staff and students of the Astronomy Instrumentation Group (AIG) in the School of Physics and Astronomy with support from QMC Instruments Ltd. The system exemplifies the AIG’s world-leading expertise in the development of far-infrared/sub-mm instrumentation as well as QMCI’s vision to provide the highest quality terahertz optical components and detector systems to the global marketplace