text: It is not possible to produce gamma sources that emit all the energies needed to calculate accurately the response of a TAS detector. For this reason, it is better to perform a Montecarlo simulation of the response. For this simulation to be reliable, the interactions of all the particles emitted in the decay (γ, e−/e+, Auger e, x rays, etc.) have to be modeled accurately, and the geometry and materials in the way of these particles have to be well reproduced. Also, the light production of the scintillator has to be included. The way to perform this simulation is explained in detail in paper by D. Cano-Ott et al. GEANT3 and GEANT4 are well suited for these kind of simulations.
  If the scintillator material of the TAS detector suffers from a non proportionality in the light production, the peaks produced by a cascade will be displaced further for every increment in the multiplicity and the width of these peaks will be different from the width of single peaks with the same energy. This effect can be introduced in the simulation by means of a hyperbolic scintillation efficiency.
  The simulation of the light production will widen the peaks of the TAS spectrum; however, this still does not reproduce the real width of the experimental peaks. During the measurement there are additional statistical processes that affect the energy collection and are not included in the Montecarlo. The effect of this is an extra widening of the TAS experimental peaks. Since the peaks reproduced with the Montecarlo do not have the correct width, a convolution with an empirical instrumental resolution distribution has to be applied to the simulated response.
  Finally, if the data to be analyzed comes from electron capture events, a simulated gamma response matrix must be built using the simulated responses to individual monoenergetic γ rays of several energies. This matrix contains the information related to the dependence of the response function on the detector. To include also the dependence on the level scheme that is being measured, the above-mentioned matrix should be convoluted with the branching ratio matrix calculated previously. In this way, the final global response R is obtained.