Two-dimensional neutron scintillation detector with optimal gamma discrimination

The gamma sensitivity of a two-dimensional scintillation neutron detector based on position sensitive photomultipliers (Hamamatsu R2387) is minimized by a digital differential discrimination unit. Since the photomultiplier gain is position-dependent by ±25%, a discrimination unit is developed where digital upper and lower discrimination levels are set due to the position-dependent photomultiplier gain obtained from calibration measurements. By this method, narrow discriminator windows can be used to reduce the gamma background drastically without affecting the neutron sensitivity of the detector. The new discrimination method and its performance as tested by neutron measurements are described. Experimental results concerning spatial resolution and γ-sensitivity are presented