  We present Atacama Large Millimeter/submillimeter Array (ALMA) Band 6
observations of dust continuum emission of the disk around WW Cha. The dust
continuum image shows a smooth disk structure with a faint (low-contrast) dust
ring, extending from $\sim 40$ au to $\sim 70$ au, not accompanied by any gap.
We constructed the simple model to fit the visibility of the observed data by
using MCMC method and found that the bump (we call the ring without the gap the
bump) has two peaks at $40$ au and $70$ au. The residual map between the model
and observation indicates asymmetric structures at the center and the outer
region of the disk. These asymmetric structures are also confirmed by
model-independent analysis of the imaginary part of the visibility. The
asymmetric structure at the outer region is consistent with a spiral observed
by SPHERE. To constrain physical quantities of the disk (dust density and
temperature), we carried out radiative transfer simulations. We found that the
midplane temperature around the outer peak is close to the freezeout
temperature of CO on water ice ($\sim 30$ K). The temperature around the inner
peak is about $50$ K, which is close to the freezeout temperature of H$_2$S and
also close to the sintering temperature of several species. We also discuss the
size distribution of the dust grains using the spectral index map obtained
within the Band 6 data.
