Efficiency Calculation and Measurement of Large NE213 Neutron Counter (Commemoration Issue Dedicated to Professor Sakae Shimizu on the Occasion of his Retirement)

A 14 cm diameter and 19 cm depth counter with liquid scintillator (NE213) was constructed for the fast neutron detection. Design, performance and efficiency calibration are described. Calculated efficiency and experimental efficiency are compared at low energy region. They agree within about 20%.