Showing posts with label Enrico Fermi. Show all posts
Showing posts with label Enrico Fermi. Show all posts

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


29 September 2017

Enrico Fermi – nuclear physicist

Scientist from Rome who created world’s first nuclear reactor

Enrico Fermi discovered how splitting uranium atoms could generate vast amounts of energy
Enrico Fermi discovered how splitting uranium
atoms could generate vast amounts of energy
Enrico Fermi, who has been called the architect of the nuclear age and even the father of the atomic bomb, was born on this day in 1901 in Rome.

Fermi, who won a Nobel Prize in 1938, created the world’s first nuclear reactor, the so-called Chicago Pile-1, after he had settled in the United States, and also worked on the Manhattan Project, which was the code name for the secret US research project aimed at developing nuclear weapons in the Second World War.

The third child of Alberto Fermi, an official in Italy’s Ministry of Railways, and Ida de Gattis, a school teacher, Fermi took an interest in science from an early age, inspired by a book about physics he had discovered in the local market in Campo de’ Fiori in Rome, written in Latin by a Jesuit priest in about 1840.

He read avidly as he was growing up, conducting many experiments. After high school, he was granted a place at the prestigious Scuola Normale Superiore, part of the University of Pisa, where it became clear the depth of knowledge he had already acquired was greater than that of many of his professors. It was not long before they began asking him to organise seminars in quantum physics. He graduated with honours in 1922.

After spending several months in Germany and Holland on scholarships, working alongside renowned professors such as  Max Born and Paul Ehrenfest, he returned to Italy to take up a lectureship at the University of Florence. In 1927 he was appointed Professor of Theoretical Physics at the University of Rome.

Fermi (centre), with his fellow scientists at the University of Pisa, Franco Rasetti and Emilio Segrè
Fermi (centre), with his fellow scientists at the University of
Pisa, Franco Rasetti and Emilio Segrè
In the same year, he married Laura Capon, who came from a respected Jewish family in Rome.  They would soon have two children, Giulio and Nella.

In 1934, Fermi began working with the atom, the area of physics that would define his life. He discovered that nuclear transformation could occur in nearly every element.

One of the elements whose atoms he split was uranium. This led to discovery of slow neutrons, which in turn led to nuclear fission and the production of new elements.

When, in 1938, Fermi was awarded the Nobel Prize in Physics "for his work with artificial radioactivity produced by neutrons, and for nuclear reactions brought about by slow neutrons”, it could not have come at a more timely moment.

Benito Mussolini, whose Fascist party Fermi had joined when he was made a member of the Royal Academy of Italy in 1929, had introduced tough new race laws in his support for the German leader Adolf Hitler. The anti-Jewish element of these laws threatened Fermi’s family and he became desperate to leave Italy.

The eerie mushroom cloud formed by the  first test explosion of an atomic bomb
The eerie mushroom cloud formed by the
first test explosion of an atomic bomb
Strict travel restrictions were being implemented, too, but Mussolini wanted Fermi to receive his Nobel award in person at the ceremony in Sweden and allowed him to travel with his family. Once in Stockholm, they made arrangements to escape to America.

Thus Fermi, his wife and their children disembarked a passenger liner in New York in January 1939.  He quickly settled into an academic career in American universities.

Fermi was appointed professor of physics at New York's Columbia University, where he discovered that if uranium neutrons were emitted into fissioning uranium, they could split other uranium atoms, setting off a chain reaction that would release enormous amounts of energy. His experiments led to the first controlled nuclear chain reaction, which he prosaically christened Chicago Pile-1, on December 2, 1942, under Chicago University's athletic stadium.

During the Second World War, Fermi was invited to join the Manhattan Project, which focused on the development of the atomic bomb. Worried that scientists in Germany were close to developing their own bomb, Fermi and other scientists encouraged the US Government to invest in the project without delay.

He witnessed the first test detonation of a nuclear weapon, codenamed Trinity, in a remote area of desert in New Mexico on July 16, 1945.  He advised the US Government on target selection, recommending the bomb be used without warning against an industrial area.

General Leslie R Groves presents Fermi with his Medal of Merit for wartime service to the US
General Leslie R Groves presents Fermi with his
Medal of Merit for wartime service to the US 
After the war, Enrico Fermi was appointed to the General Advisory Committee for the Atomic Energy Commission. In October 1949, the commission met to discuss the development of the hydrogen bomb, a weapon 500 times more powerful than the atomic bombs dropped on Hiroshima and Nagasaki in Japan, which themselves killed 129,000 people.

Fermi was appalled at the prospect, however, opposing it on both technical and moral grounds.

In 1944, Fermi and his wife had become American citizens, and at the end of the war he accepted a professorship at the University of Chicago's Institute for Nuclear Studies, a position which he held until his death. There he turned his attention to high-energy physics, and led investigations into the pion-nucleon interaction.

He died in 1954 at the age of only 53 from stomach cancer. It is thought likely now that he developed the disease as a result of his exposure to radiation, possibly when he witnessed the Trinity explosion, when he reported feeling the heat from the blast, or from his work creating the Chicago reactor.

He confessed to friends during his life that he was aware that he might be at risk but considered scientific advancement more important than his own long-term health.

As well as his Nobel prize, Fermi won many other awards for his research, while others granted to modern scientists bear his name.  Among other things named after him are the Fermilab particle accelerator and physics lab in Batavia, Illinois and the Fermi Gamma-ray Space Telescope.  Three nuclear reactor installations have been named after him: the Fermi 1 and Fermi 2 nuclear power plants in Newport, Michigan, the Enrico Fermi Nuclear Power Plant at Trino Vercellese in Italy, and the RA-1 Enrico Fermi research reactor in Argentina.

A synthetic element isolated from the debris of the 1952 Ivy Mike nuclear test was named fermium, in honour of Fermi's contributions to the scientific community.

The Basilica of Santa Croce in Florence, known as the Temple of Italian Glories for its many graves of artists, scientists and prominent figures in Italian history, has a plaque commemorating Fermi.

Fermi's birthplace in Via Gaeta in Rome
Fermi's birthplace in Via Gaeta in Rome
Travel tip:

Fermi’s birthplace in Rome was in Via Gaeta, not far from the Termini railway station, and the house is marked with a plaque. The area around Via Gaeta has nothing in particular to recommend it but nearby are the ruins of the Terme di Diocleziano – the Baths of Diocletian – a Roman bathing complex that covered 13 acres and could accommodate up to 3,000 people. The complex today houses one of the four sites of the Museo Nazionale Romana, containing a fascinating collection of objects and artefacts to help visitors build a picture of Roman life in the days of the empire. Also worth visiting at the site is a large and peaceful cloister built from designs by Michelangelo.

The magnificent Basilica of Santa Croce in Florence
The magnificent Basilica of Santa Croce in Florence
Travel tip:

The Basilica of Santa Croce, with its 16 chapels, is the largest Franciscan church in the world, and has been one of Florence’s most impressive buildings since it was completed towards the end of the 14th century. Inside can be found work by many of the great artists of the Renaissance, including Giotto, Cimabue, Donatello, Antonio Canova and Domenico Veneziano. The Basilica is also notable as the burial place of a host of illustrious Italians, such as Michelangelo, Galileo, Machiavelli, the poet Ugo Foscolo, the philosopher Giovanni Gentile and the composer Rossini.