Robert Oppenheimer's brother Frank from the Radiation Laboratory, damaging his relationship with Robert. An acrimonious loyalty oath campaign at the University of California also drove away faculty members. When hearings were held to revoke Robert Oppenheimer's security clearance, Lawrence declined to attend on account of illness, but a transcript in which he was critical of Oppenheimer was presented in his absence. Lawrence's success in building a creative, collaborative laboratory was undermined by the ill-feeling and distrust resulting from political tensions. Thermonuclear weapons Lawrence was alarmed by the Soviet Union's first nuclear test in August 1949. The proper response, he concluded, was an all-out effort to build a bigger nuclear weapon: the hydrogen bomb. He proposed to use accelerators instead of nuclear reactors to produce the neutrons needed to create the tritium the bomb required, as well as plutonium, which was more difficult, as much higher energies would be required. He first proposed the construction of Mark I, a prototype $7 million, 25 MeV linear accelerator, codenamed Materials Test Accelerator (MTA). He was soon talking about a new, even larger MTA known as the Mark II, which could produce tritium or plutonium from depleted uranium-238. Serber and Segrè attempted in vain to explain the technical problems that made it impractical, but Lawrence felt that they were being unpatriotic. Lawrence strongly backed Edward Teller's campaign for a second nuclear weapons laboratory, which Lawrence proposed to locate with the MTA Mark I at Livermore, California. Lawrence and Teller had to argue their case not only with the Atomic Energy Commission, which did not want it, and the Los Alamos National Laboratory, which was implacably opposed but with proponents who felt that Chicago was the more obvious site for it. The new laboratory at Livermore was finally approved on July 17, 1952, but the Mark II MTA was canceled. By this time, the Atomic Energy Commission had spent $45 million on the Mark I, which had commenced operation, but was mainly used to produce polonium for the nuclear weapons program. Meanwhile, the Brookhaven National Laboratory's Cosmotron had generated a 1 GeV beam. Death and legacy In addition to the Nobel Prize, Lawrence received the Elliott Cresson Medal and the Hughes Medal in 1937, the Comstock Prize in Physics in 1938, the Duddell Medal and Prize in 1940, the Holley Medal in 1942, the Medal for Merit in 1946, the William Procter Prize in 1951,