Letters Sent to Dr. F.B. Flinn [Dr. Frederick B. Flinn], February 23, 1940

February 23, 1940. Homorandum to: Doctor F. B. Flinn Subject: Radio-active Film Mr. Gordon and I have discussed the status of the above problem, and he suggests that I outline the progress for you. We have at the present time an experimental film which provides con- siderable alpha radiation and appears to possess the properties you require. Altho we have not subjected it to hard usage, the active deposit seems to be firmly attached, a factor we determined by a sories of garma ray measurements which indicate also that the omanation is not being roleased, but decays in the film and would theroforo be effective for your work. The quantitative alpha ray measurements have not been completed, and will probably require several weeks more. Our measuring equipment requires some modification, and until it functions satisfactorily we will not be able to deternine the success of our work. Rough preliminary work indicates that we are obtaining perhaps 20% to 25% efficiency, but this figure is subject to op nsiderable modification. Because of the naturo of this film, we would not care to rolease it for use until we are more cortain that it is fool-proof. A film such as wo originally discussed can be prepared. However, even such a film should be measured care- fully before released to forestall the possibility of its failure to work success- fully being attributed to the wrong factors. Here again, we must wait for the completion of our measurement equipment, unless you would oare to do your pre- liminary work and malce the activity determinations later. If you prefer to take this course, we will prepare the film immediately and give you the results of our experinental work later.