In 1928, von Ardenne had come into his inheritance with full control as to how it could be spent, and he established his private research laboratory the "Forschungslaboratoriums für Elektronenphysik", in Berlin-Lichterfelde, to conduct his own research on radio and television technology and electron microscopy. He financed the laboratory with income he received from his inventions and from contracts with other concerns. For example, his research on nuclear physics and high-frequency technology was financed by the "Reichspostministerium" (RPM, Reich Postal Ministry), headed by Wilhelm Ohnesorge. Von Ardenne attracted top-notch personnel to work in his facility, such as the nuclear physicist Fritz Houtermans, in 1940. Von Ardenne had also conducted research on isotope separation. Taking Ewald's suggestion he began building a prototype for the RPM. The work was hampered by war shortages and ultimately ended by the war.