A code that integrates the Lorentz force equation has been developed to trace a single charged particle's trajectory under the influence of toroidally symmetric magnetic fields found in tokamaks. This code is used primarily to design and estimate the efficiency of charged fusion product probes, which detect escaping energetic ions such as the 1 MeV tritons, 3 MeV protons, 15 MeV protons, and 3.5 MeV alphas created in TFTR. This interactive code has also been used as a teaching tool to illustrate classes of orbits such as trapped and passing, as well as subtle orbital motions, e.g., precession of banana orbits in tokamaks, or orbits in dipole magnetic field configuration. This paper describes the code as well as recent modifications which (1) include Shafranov shifts of the magnetic surfaces, (2) use more realistic current density profiles, and (3) allow modeling of the detector and limiters.
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