Lithium-containing radiator materials for neutron ionization chambers

The paper presents the results of material testing for the purpose of obtaining radiator material – acomposite coating with neutron conversion material – for ionization chambers (IC) which contain the 6 Li isotope and convert neutron radiation to a flux of high-energy charged particles through the 6 Li(n, α) 3 H nuclear reaction. The proposed method for forming lithium-containing radiator material allows ensuring a high temperature resistance of up to 600 °C and a mechanical strength at the expense of adhesion to the IC electrode material (grade 321 steel). The advantages of a lithium-containing radiator, compared to a boron radiator, are explained by the smaller cross-section of the 6 Li-neutron interaction: the smaller efficiency of the "neutron → charged particle" conversion is made up for by a high power density and a prolonged free path of reaction products in the radiator material, which makes it possible to increase the surface density of 6 Li atoms, while reducing the extent of "burnup" in neutron fields. The IC electrode radiator material consists of a two-layer composite coating comprising an adhesive silicate layer and a functional neutron-sensitive lithium fluoride layer. Measurements at an alpha spectrometric facility have shown that the coating has a high energy output (~ 2.8·10 –3 MeV/neutron), which remains stable after four thermal cycles of up to 600 °C. The coating is resistant to vibration when exposed to frequencies of 35 to 200 Hz. The paper presents the results of testing the IC mockup with a lithium-containing radiator material. When irradiated with a neutron flux of 6·10 3 cm –2 ·s –1 , the IC mockup sensitivity value was about 10 –15 A·s·cm 2 /neutron, which agrees with the calculated value.