Thin films for X-ray astronomy

A method is described for casting the commercial plastic known as Formvar directly on the surface of water and building up the desired thickness by a lamination of several layers. The thin, plastic films obtained can be used for the entrance window in the proportional counters normally used as X-ray detector in rocket-borne astrophysical experiments. Attention is given to three films, each of which has been flown several times on Aerobee sounding rockets.