  Characteristics of the hadronic final state of diffractive deep inelastic
scattering events, ep -> eXp, were studied in the kinematic range 4 < M_X < 35
GeV, 4 < Q^2 < 150 GeV^2, 70 < W < 250 GeV and 0.0003 < x_pom < 0.03 with the
ZEUS detector at HERA using an integrated luminosity of 13.8 pb^{-1}. The
events were tagged by identifying the diffractively scattered proton using the
leading proton spectrometer. The properties of the hadronic final state, X,
were studied in its center-of-mass frame using thrust, thrust angle,
sphericity, energy flow, transverse energy flow and ``seagull'' distributions.
As the invariant mass of the system increases, the final state becomes more
collimated, more aligned and more asymmetric in the average transverse momentum
with respect to the direction of the virtual photon. Comparisons of the
properties of the hadronic final state with predictions from various Monte
Carlo model generators suggest that the final state is dominated by qqg states
at the parton level.
