Lionel Cohenfermilabís Neutron Therapy Facility has the highest energy and the deepest penetration of any fast neutron beam in the United States. Fast-moving neutrons are effective against large tumors. Chicago-area radiation oncologists Lionel Cohen and Frank Hendrickson worked with Fermilab Director Robert R. Wilson to build the Neutron Therapy Facility. Cohen served as the first NTF director, and the first patients were treated on September 7, 1976. More than 3,100 patients have been treated in 25 years.