  The excess broadening of high-temperature spectral lines, long observed near
the tops of flare arcades, is widely considered to result from
magnetohydrodynamic (MHD) turbulence. According to different theories, plasma
turbulence is also believed to be a candidate mechanism for particle
acceleration during solar flares. However, the degree to which this broadening
is connected to the acceleration of non-thermal electrons remains largely
unexplored outside of recent work, and many observations have been limited by
limited spatial resolution and cadence. Using the Interface Region Imaging
Spectrometer (IRIS), we present spatially resolved observations of loop-top
broadenings using hot (11MK) Fe XXI 1354.1 \r{A} line emission at ~9s cadence
during the 2022 March 30 X1.3 flare. We find non-thermal velocities upwards of
65km/s that decay linearly with time, indicating the presence and subsequent
dissipation of plasma turbulence. Moreover, the initial Fe XXI signal was found
to be co-spatial and co-temporal with microwave emission measured by the
Expanded Owens Valley Solar Array (EOVSA), placing a population of non-thermal
electrons in the same region as the loop-top turbulence. Evidence of electron
acceleration at this time is further supported by hard X-ray measurements from
the Spectrometer/Telescope for Imaging X-rays (STIX) aboard Solar Orbiter.
Using the decay of non-thermal broadenings as a proxy for turbulent
dissipation, we found the rate of energy dissipation to be consistent with the
power of non-thermal electrons deposited into the chromosphere, suggesting a
possible connection between turbulence and electron acceleration.
