Measuring the X-ray Background in the Reionization Era with First
  Generation 21 cm Experiments
  The X-ray background during the epoch of reionization is currently poorly
constrained. We demonstrate that it is possible to use first generation 21 cm
experiments to calibrate it. Using the semi-numerical simulation, 21cmFAST, we
calculate the dependence of the 21 cm power spectrum on the X-ray background
flux. Comparing the signal to the sensitivity of the Murchison Widefield Array
(MWA) we find that in the redshift interval z=8-14 the 21 cm signal is
detectable based on the upper limit set by the present-day unresolved soft
X-ray background. We show that there is no degeneracy between the X-ray
production efficiency and the Lyman-Alpha production efficiency and that the
degeneracy with the ionization fraction of the intergalactic medium can be
broken.
