a better situation in his imprisonment, he agreed to go to Hamburg and start building a German Betatron. During this period, already in 1943, he introduced the theoretical concept of colliding particles head-on to increase interaction energy and a storage ring device. Several sources claims that his Norwegian citizenship was ultimately revoked for working with the Nazi government, but this is not correct. His Norwegian passport was confiscated for some time and he accepted a penalty notice of NOK 5000, loss of civil liberties and to forfeit NOK 120000 of the amount he was paid in licence fees for use of his patent rights during the betatron development. In the end, early in 1946, he received an intermediate passport and emigrated to Switzerland. Later years In 1946 he filed a patent in Norway for an accelerator based on synchronous acceleration. He would go on to publish over 180 papers in scientific and engineering journals, and filed over 200 patent applications over his lifetime. In his later life he devoted much time to medicinal technology, focusing on cancer treatment, including developing megavolt radiation therapy technologies. He would collaborate with CERN beginning in 1952 doing the preliminary studies for the Proton Synchrotron, lectured at ETH Zurich in 1953, and collaborated at DESY in 1959 in Hamburg. Rolf Widerøe died on 11 October 1996 in Obersiggenthal, Switzerland. Since 2011 the European Physical Society awards every third year a prize to individuals in recognition of outstanding work in the field of accelerator physics in memory of Rolf Widerøe. Honors Doctorate Honoris Causa-RWTH Aachen (1962) Honorary Medical Doctorate-Zurich University (1964) Röntgen Medal (1969) Röntgen prize (1972) JRC gold medal (1973) Robert R. Wilson Prize (1992) Memberships Norwegian Academy of Science American Physical Society American Radium Society British Institute of Radiology Deutsche Röntgengesellschaft European Society for Radiation Therapy ESTRO European Physical Society Naturforschende Gesellschaft Norwegian Society of Radiology Norwegian Society of Physics Schweizerische Physikalische Gesellschaft Schweizerische Gesellschaft für Radiobiologie Scandinavian Society for Medical Physics Society of Nuclear Medicine References External links Images of Rolf Widerøe at Emilio Segrè Visual Archives 1902 births 1996 deaths Norwegian physicists Experimental physicists Accelerator physicists Academic staff of ETH Zurich People associated with CERN Norwegian expatriates in Germany RWTH Aachen University alumni