Two-dimensional neutron scintillation detector with optimal gamma discrimination

For a two-dimensional scintillation neutron detector based on position-sensitive photomultipliers a digital differential discrimination unit has been developed which minimizes the gamma sensitivity of the detector and was necessary because of position- dependent PM gain. The digital upper and lower discrimination levels are set position-dependent due to the position-dependent photomultiplier gain which is obtained from calibration measurements. Narrow discriminator windows can be used to reduce the gamma background drastically without affecting the homogeneous neutron sensitivity of the detector. The new discrimination method is described and its function is tested with neutrons.