We begin by presenting the analysis of a set of deep B - and V -band images of the central density cusp of the globular cluster M30 ( NGC 7099 ) , taken with the Faint Object Camera aboard the Hubble Space Telescope . These images are the first to resolve lower-mass main-sequence stars in the cluster ’ s central 10 ^ { \prime \prime } . From the positions of individual stars , we measure an improved position for the cluster center ; this new position is 2 \farcs 6 from the previously known position .
We find no evidence of a “ flat ” , constant-surface-density core ; however , the data do not rule out the presence of a core of radius up to 1 \farcs 9 ( 95 % confidence level ) .
We measure a logarithmic cusp slope ( d \log \sigma / d \log r ) of -0.76 \pm 0.07 ( 1-sigma ) for stars with masses between 0.69 and 0.76 M _ { \odot } , and -0.82 \pm 0.11 for stars with masses between 0.57 and 0.69 M _ { \odot } .
We also compare the overall mass function ( MF ) of the cluster cusp with the MF of a field at r = 4 \farcm 6 ( near the cluster half-mass radius ) .
The observed degree of mass segregation is well matched by the predictions of an isotropic , multimass King model .

We then use the Jeans equation to compare the structure of M30 with that of M15 , another cusped cluster , using data from this and a previous paper .
We find that M30 is very close to achieving equipartition of energy between stellar species , at least over the observed range in mass and radius , while M15 is not .
This difference may be a result of the longer relaxation time in the observed field in M15 .
The data also suggest that the degree of mass segregation within the two cluster cusps is smaller than one would expect from the measurements at larger radius .
If so , this phenomenon might be the result of gravothermal oscillations , of centrally-concentrated populations of binaries , or of a \sim 10 ^ { 3 } M _ { \odot } black hole in one or more clusters .