Digital Signal Processing for the Canadian Hydrogen Intensity Mapping Experiment

This thesis presents the design, development, operation, and performance of digital signal processing systems for the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and its Pathfinder. CHIME is designed to investigate the behaviour of Dark Energy in order to constrain its physical mechanism; it will do so by examining the geometry of the recent universe using as a `standard ruler' the imprint of the Baryon Acoustic Oscillation (BAO) feature in the 21 cm emission of neutral Hydrogen. In order to construct the complete set of visibilities for CHIME's 2048 inputs and 400\,MHz of bandwidth, the FX correlator's X-Engine must be capable of ingesting 6 Tib/s of data and completing 8.4×1014 complex multiply-and-accumulate operations per second; these requirements make CHIME's X-Engine by far the largest currently in operation. Using mass-produced Graphics Processing Units (GPUs), commercial off-the-shelf computer hardware, and a sealed-loop liquid-cooling system, the CHIME correlator X-Engine achieves high performance and exceptional efficiency. This thesis presents a detailed description of the X-Engine hardware design and a thorough evaluation of its performance, with additional commentary on aspects of the design and deployment which may warrant additional consideration by those planning similar systems. The substantial computational power available in the correlator system provided an opportunity for pre-integration excision of transient Radio-Frequency Interference (RFI). A number of RFI mitigation techniques were examined, including Median Absolute Deviation and Spectral Kurtosis measures; the latter was implemented on CHIME and the Pathfinder, and results from tests of the RFI detection system are presented. The CHIME Pathfinder, in addition to acting as a test-bed for hardware and analysis techniques, produced an archive of visibility data spanning three years; from this, maps were produced covering the entire northern sky for 609 sidereal days. This thesis details the data processing pipeline which was employed to generate these maps as well as analysis of the resulting data products with regards to their overall variability and the properties of known point-like sources.

Department dc:contributor.department

Astronomy and Astrophysics

Year dc:date.issued

2019

Author dc:creator

• Denman, Nolan Thomas

Advisor dc:contributor.advisor

• Vanderlinde, Keith

• CHIME
• Correlators
• Radio Astronomy
• Radio Instrumentation
• RFI Mitigation

Handle dc:identifier.uri

http://hdl.handle.net/1807/95790

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/95790