  Low-disorder two-dimensional electron systems in the presence of a strong,
perpendicular magnetic field terminate at very small Landau level filling
factors in a Wigner crystal (WC), where the electrons form an ordered array to
minimize the Coulomb repulsion. The nature of this exotic, many-body, quantum
phase is yet to be fully understood and experimentally revealed. Here we probe
one of WC's most fundamental parameters, namely the energy gap that determines
its low-temperature conductivity, in record-mobility, ultra-high-purity,
two-dimensional electrons confined to GaAs quantum wells. The WC domains in
these samples contain $\simeq$ 1000 electrons. The measured gaps are a factor
of three larger than previously reported for lower quality samples, and agree
remarkably well with values predicted for the lowest-energy, intrinsic,
hyper-corelated bubble defects in a WC made of flux-electron composite
fermions, rather than bare electrons. The agreement is particularly noteworthy,
given that the calculations are done for disorder-free composite fermion WCs,
and there are no adjustable parameters. The results reflect the exceptionally
high quality of the samples, and suggest that composite fermion WCs are indeed
more stable compared to their electron counterparts.
