22 August 2019

Bruno Pontecorvo - nuclear physicist

Defection to Soviet Union sparked unsolved mystery 


Bruno Pontecorvo hailed from a family of talented individuals
Bruno Pontecorvo hailed from a family
of talented individuals
Bruno Pontecorvo, a nuclear physicist whose defection to the Soviet Union in 1950 led to  suspicions of espionage after he had worked on research programmes in the United States, Canada, and the United Kingdom, was born on this day in 1913 in Marina di Pisa.

One of eight children born to Massimo Pontecorvo - a Jewish textile manufacturer who owned three factories - Bruno was from a family rich in intellectual talent. One of his brothers was the film director Gillo Pontecorvo, another the geneticist Guido Pontecorvo.

After high school, he enrolled at the University of Pisa to study engineering, but after two years switched to physics in 1931. He received a doctorate to study at the University of Rome La Sapienza, where Enrico Fermi had gathered together a group of promising young scientists, whom he dubbed “the Via Panisperna boys” after the name of the street where the Institute of Physics  was then situated.

Fermi described the 18-year-old Pontecorvo as one of the brightest young men he had met and invited Pontecorvo to work with him on his experiments bombarding atomic nuclei with slow neutrons.

Everything changed, however, after Benito Mussolini’s Fascist government passed a series of race laws, one of which excluded Jews from participating in higher education.

Enrico Fermi (above) rated Pontecorvo as one of his brightest young scientists
Enrico Fermi (above) rated Pontecorvo
as one of his brightest young scientists
Pontecorvo fled to Paris to work at the laboratory of Frédéric Joliot-Curie. During this period, influenced by his cousin, Emilio Sereni, he became a supporter of the ideals of communism and married Marianne Nordblom, a Swedish woman working in Paris as a nanny.

When Paris was invaded by the Germans in 1940, he became unsettled again.  He could not return to Italy and instead travelled to the United States, where Fermi had also gone. His new wife accompanied him.

In 1943 Pontecorvo joined the Anglo-Canadian nuclear research team at Chalk River, Ontario. There he worked on the design of the world’s first nuclear reactor using heavy water as a neutron moderator.

Despite earlier being seen as “undesirable”, in 1948 he was granted British citizenship. He joined the Atomic Energy Authority research station at Harwell, Berkshire, where classified research was being conducted.

Once Mussolini had been toppled, Pontecorvo had felt comfortable to begin taking holidays in Italy but during on such trip, in 1950, instead of returning to London, he and Marianne and their three children flew to Stockholm in Sweden and then on to Helsinki in Finland, at which point they disappeared.

Pontecorvo worked in France, the United States and the United Kingdom before his defection in 1950
Pontecorvo worked in France, the United States and
the United Kingdom before his defection in 1950
Ten months earlier, one of Pontecorvo’s colleagues at Harwell, Klaus Fuchs, confessed to spying for the Soviet Union - be was blamed by the US for Russia's development of nuclear weapons - and there was speculation that Pontecorvo had followed suit.

Pontecorvo’s relatives, including his sister, Anna, who lived in London, were at a loss to explain his disappearance, insisting he had given no indication that he was planning to fly from Rome to Stockholm.

Nothing was heard of him until 1955, when Pontecorvo appeared at a press conference in Moscow to promote the peaceful use of nuclear power. He denied ever having worked on nuclear weapons research.

Nonetheless, amid speculation that he and Fuchs and others had seriously endangered the West, he was stripped of his British passport. It has never been established why he left so abruptly and there is no concrete evidence that he was ever a spy. An alternative theory is that, because of his links with Fuchs - although they were not close friends - he was under surveillance by agents from America's FBI and feared for his safety if he remained in the West.

He would remain in the Soviet Union for the rest of his life, mainly at the Joint Institute for Nuclear Research (JINR) in Dubna, outside Moscow.

Pontecorvo received numerous awards for his work in Russia, including the Lenin Prize (1963) and the Order of Lenin (1983). After his death,  the JINR founded the annual Bruno Pontecorvo Prize to honour work done in particle physics. 

In accordance with his wishes, half of Pontecorvo's ashes were buried in the Protestant Cemetery in Rome, and another half in Dubna.

The yacht harbour at Marina di Pisa, the town where the Pontecorvo family grew up
The yacht harbour at Marina di Pisa, the town where
the Pontecorvo family grew up
Travel tip:

Pisa used to be one of Italy’s major maritime powers, rivalling Genoa and Venice, until silt deposits from the Arno river gradually changed the landscape and ultimately cut the city off from the sea in the 15th century. Nowadays, almost 15km (9 miles) inland, it is a university city renowned for its art and architectural treasures, notably the Campo dei Miracoli, formerly known as Piazza del Duomo, located at the northwestern end of the city, which contains the cathedral (Duomo), baptistery and famously the tilting campanile known as the Leaning Tower of Pisa.  Marina di Pisa is situated where the Arno now meets the sea.  A popular seaside resort with a mix of sand and pebble beaches, it is home to the modern Port of Pisa yacht harbour.

The Via Panisperna (right) looking towards the Basilica di Santa Maria Maggiore from the junction with Via Cesare Balbo
The Via Panisperna (right) looking towards the Basilica di Santa
Maria Maggiore from the junction with Via Cesare Balbo
Travel tip:

The Via Panisperna is a Roman street that runs from Largo Angelicum, close to Trajan’s Forum and the Villa Aldobrandini in the direction of the Basilica di Santa Maria Maggiore. It forms part of the Rione Monti Roma district. It follows a straight, undulating path and crosses three of Rome’s seven hills - the Quirinale, the Viminale and the Esquilino.  The street is thought to take it name from the practice of the nearby convent of the Order of the Poor Clares for distributing “pane e perna” - bread and ham - among the local poor. The Church of San Lorenzo in Panisperna can reputedly trace its history to the reign of Emperor Constantine I in the early fourth century, only 100 years after the martyrdom of St Lawrence.

More reading:

Enrico Fermi - the Roman scientist who produced the world's first nuclear reactor

The first woman to head up Europe's major nuclear research body

Why Gillo Pontecorvo's most famous film was banned in France

Also on this day:

1599: The death of influential composer Luca Marenzio

1849: Austria launches world's first 'air raid' against Venice

1914: The death of Bishop Giacomo Radini-Tedeschi


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