Quasi-PML for waves in cylindrical coordinates

We prove that the straightforward extension of Berenger's original perfectly matched layer (PML) is not reflectionless at a cylindrical interface in the continuum limit. A quasi-PLM is developed as an absorbing boundary condition (ABC) for the finite-difference time-domain method in cylindrical coordinates. For three-dimensional problems, this quasi-PML requires only ten equations, instead of 12 equations in the best true PML formulations. With a satisfactory absorption level, it is simpler, and requires about 20% less computer memory than the true PML ABC.