Large area neutron detector based on 6Li ionization chamber with integrated body-moderator of high density polyethylene

We describe the development of a large area neutron detector based on a pulse-mode ionization chamber lined with ⁶Li foil in a low-cost housing of HDPE (high density polyethylene) that serves as the moderator. The use of inexpensive materials, technology for mass production and simple construction, which integrates the basic components of the sensor together, results in a substantial cost reduction. For a given sensor size, detection efficiency, or counting time, the proposed detector is expected to provide an order-of magnitude cost reduction compared to current neutron detection technology. This paper describes the detection concept including the optimization of the design using neutron transport calculations. It also gives experimental results on some prototype units using neutron and gamma sources. The properties affecting long term counting stability are discussed. An approach to reduce the effect of outgassing from the HDPE body is suggested.