Establishment of a precision long counter as a secondary standard for fast neutron flux density measurement

A precision long counter based on the design by De Pangher and Nichols has been set up as a standard for fast neutron flux density measurements. Results of measurements carried out in this laboratory to determine the characteristics of this detector, using a wide range of neutron standards such as Sb/Bw (γ,n); 252Cf; Ra/Be (γ,n); Ra/Be (α,n); Am/Be (α,n) and Pu/Be (α,n) are given. The efficiency of the detector is found to be constant within +- 5% in the energy range of 21 KeV to 4.5 MeV. A comparison is made with the results obtained by earlier workers. (author)