Velmozhna O. Development methods for producing Gd-loaded plastic scintillator

The thesis is devoted to creating gadolinium-loaded plastic scintillator (PS). The aim of thesis was to produce the PS with the maximum of gadolinium concentration as possible with the saving its scintillating efficiency. Three methods of loading polymer matrix PS by gadolinium compounds were proposed. It was experimentally established that only gadolinium salt of aliphatic-aromatic acids is possible to enter in a polymer base of PS with desirable level. It was developed method of synthesis gadolinium carboxylates under anhydrous conditions. These conditions allowed to exclude a hydrolysis of carboxylates to increase it solubility. It was found that a most effective neutral ligand is triphenylphosphine oxide (TPPO) for obtaining stable gadolinium complexes. Thermographic properties of gadolinium compounds were investigated. It was demonstrated that the crosslinking agent (DPDMA) allow to reduce the temperature and time of polymerization in during to 48 houses. It was established the limit of the DPDMA concentration in combination with initiator AIBN for low-temperature polymerization. It is established the optimal conditions for the polymerization process of gadolinium loaded PS with different polymer basis. Polystyrene scintillator containing Gd(PhB)3·2ТРРО and Gd(PhV)3·2ТРРО complexes were produced. Light yield for these PS with 3.0 wt.% of Gd are 75 % relative to the unloaded plastic scintillator. Method of a chemical binding of the Gd - complex with the polymer backbone has allowed to reach the loaded level of PS with the maximum concentration 1.5 wt.% of Gd. The entering of Gd(PhB)2(MA)·2TPPO in polystyrene and copolymer bases has allowed to produce PS containing 1.5 wt.% of gadolinium, that have light yield 78 % for copolymer base, and 75 % for polystyrene base to response to the unloaded plastic scintillator. The using of Gd-containing oligomer for loading polystyrene matrix was permit to produce 1.0 wt.% Gd-loaded PS with its light yield as high as 70 % with respect to the unloaded one.