Kapitsa, Piotr Leonidovitch

[ka pit sa] (1894–1984) Russian physicist: experimenter on high magnetic fields and low temperatures.

Son of one general (an engineer) and grandson of another, Kapitsa studied electrical engineering at the Petrograd Polytechnic (St Petersburg), graduated in 1918, and continued there as a lecturer for 3 years. In 1919 his first wife and two children died in the famine following the revolution, and in 1921 the unhappy young man visited England and secured a place in Cambridge laboratory. Both were energetic, outspoken and talented experimentalists, who formed a high regard for each other. Kapitsa became a popular figure, adventurous, ingenious and with wide-ranging interests.

After completing his PhD he began to work independently, on the problem of obtaining very high magnetic fields. For this he designed and built circuits which passed currents of 10 000 A or more through a small coil for 0.01 s or less, a time shorter than it would take the coil to burn out. By 1924 he could in this way obtain field strengths of up to 50 T, which he used in studies on the properties of materials in high fields. The electrical resistance of metals increases in high fields, and this effect increases at low temperatures, so Kapitsa turned his ingenuity to the design of an improved liquefier for helium. His work went so well that a new laboratory building (the Mond) was built for his work and opened in 1933. (He had the sculptor Eric Gill carve a crocodile over its entrance; it was not until 1966, revisiting his laboratory, that he admitted that this represented Rutherford.) By 1934 his new method for making liquid helium allowed him to study its strange properties; he discovered that it conducts heat better than copper, and it shows superfluidity, ie apparent complete loss of viscosity, below 2.2 K. (Later, his friend was able to explain these properties of helium II.)

Also in 1934 he returned to the USSR to visit his mother and he was not allowed to leave, despite protests from the West. Soon, he learned (from reading Pravda ) that he had been made head of a new and luxurious Institute for Physical Problems near Moscow. His equipment was sent to him from Cambridge, and his wife (he had remarried) was allowed to return to the UK for their children. One of his colleagues was Landau, who was arrested in the 1930s and accused of being ‘an enemy of the state’. Kapitsa protested forcefully and successfully: Landau, unusually, survived.

From 1939 Kapitsa worked on liquid air and oxygen, which aided Soviet steel production. He did not work on atomic weapons, and wrote to Stalin in 1946 criticizing the competence of the notorious Beria, head of the NKVD (secret police) as director of the programme. For this he was exiled to house arrest in the country, where he worked on high temperature physics and on ball lightning (a type of plasma) aided by his sons; after 8 years Stalin was dead and Beria executed, and Kapitsa was restored to his post and worked on plasmas. Soon he was permitted visitors, and in his 70s was allowed to travel. In 1929 he had been elected a Fellow of the Royal Society (the first foreigner for 200 years) and in 1978 he shared a Nobel Prize for his work in low temperature physics.