  We examine the radiation emitted by high energy positrons channeled into
silicon crystal samples. The positrons are modeled as semiclassical vector
currents coupled to an Unruh-DeWitt detector to incorporate any local change in
the energy of the positron. In the subsequent accelerated QED analysis, we
discover a Larmor formula and power spectrum that are both thermalized by the
acceleration. Thus, these systems explicitly exhibit thermalization of the
detector energy gap at the celebrated Fulling-Davies-Unruh (FDU) temperature.
Our derived power spectrum, with a nonzero energy gap, is then shown to have an
excellent statistical agreement with high energy channeling experiments and
also provides a method to directly measure the FDU temperature. We also
investigate the Rindler horizon dynamics and confirm that the
Bekenstein-Hawking area-entropy law is satisfied in these experiments. As such,
we present the evidence for the first observation of acceleration-induced
thermality in a non-analogue system.
