Preliminary results of a new boron coated neutron detector

The proliferation of neutron detection application based upon 3He proportional counter has triggered a critical shortage of 3He gas. The annual demand of 3He for US homeland security alone has been evaluated more than the worldwide supply, with the effect of limiting the perspectives of nuclear physics applications that up to now rely strongly upon 3He-based detectors. Nowadays there is an increasing demand for alternative neutron detection technologies that can cover large solid angle, have low sensitivity to gamma background and, last but not least, low cost. We present a low cost neutron detector based upon a long cylindrical metal tube coated on the inside with a thin layer of 10B-enriched boron carbide (10B4C). 10B-rich layer captures neutrons: 10B undergoes to (n,) reaction producing an -particle and a 7Li recoil nucleus that travel off in opposite direction. The movement of both creates ion pairs when crossing the gas inside the cylinder. The best gas for neutron detection efficiency that could be used is boron trifluoride (BF3) also enriched in 10B, but this gas is on the black list of gases associated to the atmospheric ozone depletion. Nitrogen gas it is used as low cost alternative. We present the preliminary performances of the detector 180 cm long and 6 cm diameter with a nitrogen pressure ranging from 1 to 3.5 atm, exposed to 252Cf source. Neutron relative detection efficiency compared to 3He set-up is evaluated and discussed.