“…Examples of work in the physics literature are the papers of Bernstein and Friedland, 22 Friedland, 23 Friedland and Kaufman, 24 Littlejohn and co-workers, 25 Tracy and Kaufman, 5 Tracy, Kaufman, and Liang, 26 Krasniak and Tracy,27,28 and NassiriMofakham and Sabzevari. 29 In the mathematics literature, of particular note is the work of Braam and Duistermaat, 30,31 Colin de Verdière, 32,33 Kammerer and Gérard, 34 and Emmrich and Weinstein. 35,36 One practical application we aim to develop is a modular ray-based algorithm to obtain the linear wave field E͑x , t͒ associated with rf heating and current drive in tokamaks.…”