Simulation of the γγ coincidence detection efficiency in activation measurment for neutron yield

In order to evaluate the influence resulted from the difference between the situation in which fusion neutrons are measured by Cu activation method and the situation in which the calibration factor is obtained by accelerator neutron Cu activation method, the author, by further developing the MCNP code, calculated the angular correlated γγ coincidence detection efficiency. The correction of calculation is demonstrated by comparing the calculation with the experimental result and the difference of less than 3% between the two situations is concluded.