First Season MWA Phase II EoR Power Spectrum Results at Redshift 7
  The compact configuration of Phase II of the Murchison Widefield Array (MWA)
consists of both a redundant subarray and pseudo-random baselines, offering
unique opportunities to perform sky-model and redundant interferometric
calibration. The highly redundant hexagonal cores give improved power spectrum
sensitivity. In this paper, we present the analysis of nearly 40 hours of data
targeting one of the MWA's EoR fields observed in 2016. We use both improved
analysis techniques presented in Barry et al. (2019) as well as several
additional techniques developed for this work, including data quality control
methods and interferometric calibration approaches. We show the EoR power
spectrum limits at redshift 6.5, 6.8 and 7.1 based on our deep analysis on this
40-hour data set. These limits span a range in $k$ space of $0.18$ $h$
$\mathrm{Mpc^{-1}}$ $<k<1.6$ $h$ $\mathrm{Mpc^{-1}}$, with a lowest measurement
of $\Delta^2\leqslant2.39\times 10^3$ $\mathrm{mK}^2$ at $k=0.59$ $h$
$\mathrm{Mpc^{-1}}$ and $z=6.5$.
