  The SWEAP instrument suite on Parker Solar Probe (PSP) has detected numerous
proton beams associated with coherent, circularly polarized, ion-scale waves
observed by PSP's FIELDS instrument suite. Measurements during PSP Encounters
4-8 revealed pronounced complex shapes in the proton velocity distribution
functions (VDFs), in which the tip of the beam undergoes strong perpendicular
diffusion, resulting in VDF level contours that resemble a `hammerhead.' We
refer to these proton beams, with their attendant `hammerhead' features, as the
ion strahl. We present an example of these observations occurring
simultaneously with a 7-hour ion-scale wave storm and show results from a
preliminary attempt at quantifying the occurrence of ion-strahl broadening
through 3-component ion-VDF fitting. We also provide a possible explanation of
the ion perpendicular scattering based on quasilinear theory and the resonant
scattering of beam ions by parallel-propagating, right circularly polarized,
fast-magnetosonic/whistler waves.
