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We present X-ray dust scattering halo results based on our 76 ks {\itChandra} ACIS-S/HETGS observation of the LMXB dipping source 4U 1624-490.Through analysis of the halo light curves with 2-6 keV spectra over thepersistent and dipping periods, we estimate a geometric distance of $\sim$15kpc to 4U 1624-490. We also fit halo radial profiles with different ISM dustgrain models to assess the location, uniformity, and density of the halo. Ouranalysis shows that the dust spatial distribution is not uniform along theline-of-sight; rather, it is consistent with the spiral arm structure mapped in{\sc Hii}. The large difference between the absorption Hydrogen column ($N_{\rmH}^{abs} \sim 8 \times10^{22} \rm cm^{-2}$; probes all gas along theline-of-sight) derived from broadband spectral fitting, and the scatteringHydrogen column ($N_{\rm H}^{sca} \sim 4 \times10^{22} \rm cm^{-2}$; probesonly Galactic gas) derived from our studies of the 4U 1624-490 X-ray halosuggests that a large fraction of the column is local to the X-ray binary. Wealso present (and apply) a new method for assessing the {\it Chandra} pointspread function at large ($> 50''$) angles, through use of the time delays fromthe observed dips.Comment: 24 pages including 9 figures, accepted for publication in the  Astrophysical Journa

Using the X‐Ray Dust Scattering Halo of 4U 1624−490 to Determine Distance and Dust Distributions