Upgrading the OVRO-LWA for improved cosmic ray detection capabilities

The Owens Valley Long Wavelength Array has made self-triggered radio detections of cosmic-ray air showers (Monroe et al. 2019 submitted, see Romero-Wolf et al. proceedings PoS(ICRC2019)405) using 256 irregularly-spaced dual-polarization dipole antennas with ~60 MHz bandwidth centered around 55 MHz and maximum antenna separations of 1.5 km. Over the next two years, an upgrade to 352 antennas up to 2.6 km apart and new signal processing infrastructure will expand the capabilities of the array, including its sensitivity to cosmic ray air showers. In addition to the benefit of a larger area, wider antenna separations will improve the sensitivity to inclined events, thus increasing the detection rate of higher-energy cosmic rays. Furthermore, an observing mode with hierarchical beam-forming (grouping subsets of dipoles in-phase) will increase the detection rate of lower-energy cosmic rays. Detecting air showers requires response to ten-nanosecond-timescale signals, coincidenced across the array, and thus requires novel FPGA firmware. This poster will focus on the preliminary design of the new digital signal processing system.