  We present 12mm Mopra observations of dense molecular gas towards the W28
supernova remnant (SNR) field. The focus is on the dense molecular gas towards
the TeV gamma-ray sources detected by the H.E.S.S. telescopes, which likely
trace the cosmic-rays from W28 and possibly other sources in the region. Using
the NH3 inversion transitions we reveal several dense cores inside the
molecular clouds, the majority of which coincide with high-mass star formation
and HII regions, including the energetic ultra-compact HII region G5.89-0.39. A
key exception to this is the cloud north east of W28, which is well-known to be
disrupted as evidenced by clusters of 1720MHz OH masers and broad CO line
emission. Here we detect broad NH3, up to the (9,9) transition, with linewidths
up to 16 km/s. This broad NH3 emission spatially matches well with the TeV
source HESS J1801-233 and CO emission, and its velocity dispersion distribution
suggests external disruption from the W28 SNR direction. Other lines are
detected, such as HC3N and HC5N, H2O masers, and many radio recombination
lines, all of which are primarily found towards the southern high-mass star
formation regions. These observations provide a new view onto the internal
structures and dynamics of the dense molecular gas towards the W28 SNR field,
and in tandem with future higher resolution TeV gamma-ray observations will
offer the chance to probe the transport of cosmic-rays into molecular clouds.
