  Energetic particle transport in the interplanetary medium is known to be
affected by magnetic structures. It has been demonstrated for solar energetic
particles in near-Earth orbit studies, and also for the more energetic cosmic
rays. In this paper, we show observational evidence that intensity variations
of solar energetic particles can be correlated with the occurrence of helical
magnetic flux tubes and their boundaries. The analysis is carried out using
data from Parker Solar Probe orbit 5, in the period 2020 May 24 to June 2. We
use FIELDS magnetic field data and energetic particle measurements from the
Integrated Science Investigation of the Sun (\isois) suite on the Parker Solar
Probe. We identify magnetic flux ropes by employing a real-space evaluation of
magnetic helicity, and their potential boundaries using the Partial Variance of
Increments method. We find that energetic particles are either confined within
or localized outside of helical flux tubes, suggesting that the latter act as
transport boundaries for particles, consistent with previously developed
viewpoints.
