  We analyse the energy cost of building or demolishing a wall for a massless
Dirac field in (1+1)-dimensional Minkowski spacetime and the response of an
Unruh-DeWitt particle detector to the generated radiation. For any
smoothly-evolving wall, both the field's energy density and the detector's
response are finite. In the limit of rapid wall creation or demolition, the
energy density displays a delta function squared divergence. By contrast, the
response of an Unruh-DeWitt detector, evaluated within first-order perturbation
theory, diverges only logarithmically in the duration of the wall evolution.
The results add to the evidence that a localised matter system may not be as
sensitive to the rapid wall creation as the local expectation values of field
observables. This disparity has potential interest for quantum information
preservation scenarios.
