Monsanto Chemical Company, Unit 3 abstracts of progress reports, August 16--31, 1945: Summary of work to date on volatile neutron source

It was proposed to prepare a volatile polonium compound which could be used alone or with another gaseous compound as a neutron source. The objective was to obtain a neutron source which would give off few neutrons in the expanded state, but when condensed would act substantially as a thick target and emit perhaps ten times as many neutrons. Originally, polonium hexafluoride was suggested; with such compound the fluorine atoms would constitute the target. the predicted boiling point of polonium hexafluoride is about -40 {degrees}C. There was reason to believe, however, that lower relatively non-volatile fluorides would be formed rather than the hexafluoride. Polonium alkyls were therefore proposed as alternatives. The predicted boiling point of Po(CH{sub 3}){sub 2} is about 110 {degrees}C. This compound in itself would probably not be suitable as a target material but it could be mixed with other gases such as carbon tetrafluoride, boron trifluoride, etc., as targets. As a longer range possibility, Po(CF{sub 3}){sub 2} was also suggested. This compound would act as its own target and would moreover have the same F/Po ratio as PoF{sub 6}; its boiling point could be expected to be 30{degrees} - 60 {degrees} lower than that of polonium dimethyl. Calculations were made with showed that the desired effect could be obtained either with Po F{sub 6} or with a mixture of Po(CH{sub 3}){sub 2} with a suitable target gas. Investigation of the preparation of these two compounds was therefore undertaken, and later some preliminary attempts to prepare polonium carbonyl were made