We present high-dynamic-range images of circumstellar dust around HR 4796A that were obtained with MIRLIN at the Keck II telescope at \lambda  = 7.9 , 10.3 , 12.5 and 24.5 \mu m. We also present a new continuum measurement at 350 \mu m obtained at the Caltech Submillimeter Observatory .
Emission is resolved in Keck images at 12.5 and 24.5 \mu m with PSF FWHM ’ s of 0.37 ^ { \prime \prime } and 0.55 ^ { \prime \prime } , respectively , and confirms the presence of an outer ring centered at 70 AU .
Unresolved excess infrared emission is also detected at the stellar position and must originate well within 13 AU of the star .
A model of dust emission fit to flux densities at 12.5 , 20.8 , and 24.5 \mu m indicates dust grains are located 4 ^ { +3 } _ { -2 }  AU from the star with effective size , 28 \pm 6 \mu m , and an associated temperature of 260 \pm 40 K .

We simulate all extant data with a simple model of exozodiacal dust and an outer exo-Kuiper ring .
A two-component outer ring is necessary to fit both Keck thermal infrared and HST scattered-light images .
Bayesian parameter estimates yield a total cross-sectional area of 0.055Â AU ^ { 2 } for grains roughly 4Â AU from the star and an outer-dust disk composed of a narrow large-grain ring embedded within a wider ring of smaller grains .
The narrow ring is 14 \pm 1Â AU wide with inner radius 66 \pm 1Â AU and total cross-sectional area 245Â AU ^ { 2 } .
The outer ring is 80 \pm 15Â AU wide with inner radius 45 \pm 5Â AU and total cross-sectional area 90Â AU ^ { 2 } .
Dust grains in the narrow ring are about 10 times larger and have lower albedos than those in the wider ring .
These properties are consistent with a picture in which radiation pressure dominates the dispersal of an exo-Kuiper belt .