  We analyse the mass distribution in the core of A383 (z=0.188), one of 12
X-ray luminous clusters at z~0.2 selected for a comprehensive and unbiased
study of the mass distribution in massive clusters. Deep HST imaging reveals a
wide variety of gravitationally lensed features in A383, including a giant arc
formed from the strongly-lensed images of 2 background galaxies, 2 radial arcs,
several multiply-imaged arcs and numerous arclets. Based upon the constraints
from the various lensed features, we construct a detailed mass model for the
central regions of the cluster, taking into account both the cluster-scale
potential and perturbations from individual cluster galaxies. Keck spectroscopy
of one component of the giant arc identifies it as a star-forming galaxy at
z=1.01 and provides an accurate measurement of the cluster mass within the
radius of the giant arc (65kpc) of (3.5+/-0.1)*10^13 Mo. Using the weak shear
measured from our HST observations we extend our mass model to determine a mass
of (1.8+/-0.2)*10^14 Mo within a radius of 250kpc. On smaller scales we employ
the radial arcs as probes of the shape of the mass distribution in the cluster
core (r<20kpc), and find that the mass profile is more peaked than a single NFW
profile. The optical and X-ray properties of A383 indicate the presence of a
central cooling flow, for which we derive a mass deposition rate of >200 Mo/yr.
We also use the X-ray emission from A383 to obtain independent estimates of the
total mass within projected radii of 65 and 250kpc: (4.0+/-1.4)*10^13 Mo and
(1.2+/-0.5)*10^14 Mo, which are consistent with the lensing measurements.
[Abridged]
