Joel Barr (January 1, 1916 – August 1, 1998), also Iozef Veniaminovich Berg and Joseph Berg, was part of the Soviet Atomic Spy Ring.
Born Joyel Barr in New York City, to immigrant parents of Ukrainian Jewish origin. He attended City College of New York with Julius Rosenberg and later worked with Rosenberg and Alfred Sarant at the United States Army Signal Corps laboratories at Fort Monmouth, New Jersey during World War II.
The Army Signal Corps Engineering Laboratories at Fort Monmouth, New Jersey, hired Barr as an electrical engineer in July 1940. Julius Rosenberg signed on with the corps as a junior engineer two months later. In 1941 they were recruited as Soviet spies by Jacob Golos. Barr's code name was Meter. They in turn persuaded Alfred Sarant to join the network.
According to Alexander Feklissov: "Joel and Alfred were good friends and spent a lot of time together. I must admit that Sarant had the makings of an undercover agent; he was a cautious young man, yet full of resolve, with progressive ideas. Before we recruited him though, he had to pass a test. Barr asked Sarant to borrow some secret documents to which he had access because he, Barr, needed them for his personal use. Alfred did not hesitate in helping his friend and in the meantime the Center approved a bona fide approach." However, he was at first reluctant to become a spy but was eventually convinced to join the network by Barr.
Barr was recruited into espionage by Rosenberg. In turn, he recruited Sarant and the two shared an apartment and were allowed to function as a team by their KGB Case Officer, Alexander Feklisov. Feklisov regarded the pair as the most productive members of the group.
Both Barr and Sarant were trained and employed as electrical engineers and worked on military radar. Barr was discovered by counterintelligence to be a Communist and was fired. He and Sarant then found employment with Western Electric and worked on a highly secret radar bombsight. Barr and Sarant gave the USSR over 9,000 pages of documents detailing over 100 weapons systems.