Modelling of plasma gamma ray sources in large tokamaks

Understanding the physics of fast ions in a fusion plasma is widely considered as one of the crucial tasks for the reliable operation of fusion tokamak reactors. Measurements on tokamaks have shown that gamma rays are produced when fast ions react with either plasma fuel ions or with the plasma impurities such as beryllium, carbon and oxygen. The spectroscopy of these gamma rays can be used for measurement of fusion rates in plasma or behaviour and confinement of fusion reaction products, such as the alpha particles. To computationally support experiments a methodology has been developed for creation of a realistic plasma gamma ray source for Monte Carlo simulations. The methodology presented in this paper consists of several steps. First the generation of realistic plasma parameters with the code TRANSP on the basis of experimental measurements. Second the generation of sampling distribution functions from the calculated plasma parameters such as the calculation of the source position distribution function based on the rate densities for the gamma ray emitting reaction. Third the creation of realistic plasma gamma ray source for the code MCNP gamma ray transport simulation. The developed methodology was analysed on a MCNP tokamak model to demonstrate that the methodology generates a realistic plasma gamma ray source for Monte Carlo simulations.