  Scattering from large, open cavity structures is of importance in a variety
of electromagnetic applications. In this paper, we propose a new well
conditioned integral equation for scattering from general open cavities
embedded in an infinite, perfectly conducting half-space. The integral
representation permits the stable evaluation of both the electric and magnetic
field, even in the low-frequency regime, using the continuity equation in a
post-processing step. We establish existence and uniqueness results, and
demonstrate the performance of the scheme in the cavity-of-revolution case.
High-order accuracy is obtained using a Nystrom discretization with generalized
Gaussian quadratures.
