  We report experimental test-beam results on dielectric-loaded waveguide
detectors that utilize microwave Cherenkov signals to time and characterize
high energy particle showers. These results are used to validate models and
produce high-fidelity simulations of timing plane systems which yield
picosecond time tags and millimeter spatial coordinates for the shower
centroid. These timing planes, based on the Askaryan effect in solid
dielectrics, are most effective at the high center-of-momentum energies planned
for the Future Circular Collider (FCC-hh), and are of particular interest in
the forward region due to their high radiation immunity. We use our beam test
results and GEANT4 simulations to validate a hybrid microwave detector model,
which is used to simulate a reference timing plane design for the FCC forward
calorimeters. Our results indicate that 0.5-3 ps particle timing is possible
for a wide range of collision products in the reference FCC hadron collider
detector, even with current technology.
