Paul Ulrich Villard | |
|---|---|
 Villard, c. 1908 | |
| Born | (1860-09-28)28 September 1860 Saint-Germain-au-Mont-d'Or, France |
| Died | 13 January 1934(1934-01-13) (aged 73) Bayonne, France |
| Alma mater | École normale supérieure |
| Known for | Discovery ofgamma rays Villard circuit |
| Scientific career | |
| Fields | Physics |
| Institutions | École normale supérieure |
Paul Ulrich Villard (28 September 1860 – 13 January 1934) was a Frenchchemist andphysicist. He discoveredgamma rays in 1900 while studying the radiation emanating fromradium.
Villard was born inSaint-Germain-au-Mont-d'Or,Rhône. He graduated from theÉcole Normale Supérieure in 1881 and taught in several Lycées, ending with a Lycée in Montpellier. He would maintain a laboratory position at the Ecole Normale Supérieure until his retirement. At the time when he discovered what we now call gamma rays, Villard was working in the chemistry department of the École Normale Supérieure rue d'Ulm,Paris.
Villard is also credited with the discovery of argon hydrate. He spent the early part of his career (1888–1896) focusing on similar compounds at high pressure.
Villard investigated the radiation emitted byradium salts via a narrow aperture in a shielded container onto a photographic plate, through a thin layer oflead that was known to stopalpha rays. He was able to show that the remaining radiation consisted of a second and third type of rays. One of those was deflected by a magnetic field (as were the familiar "canal rays") and could be identified withRutherford'sbeta rays. The last type was a very penetrating kind of radiation which had not been identified before.
Villard was a modest man and he did not suggest a specific name for the type of radiation he had discovered. In 1903, it wasErnest Rutherford who proposed to call Villard's raysgamma rays because they were far more penetrating than thealpha rays andbeta rays which he himself had already differentiated and named (in 1899) on the basis of their respective penetrating powers. The name stuck.
Villard spent much time perfecting safer and more accurate methods of radiationdosimetry, which had been done very crudely up until then (typically by evaluating the quality of the image of the experimenter's hand produced on a photographic plate). In 1908, Villard pioneered the use of anionization chamber for the dosimetry of ionizing radiation. He defined a unit ofkinetic energy released per unit mass which was later renamed theroentgen.[1]
When Villard retired, he left Paris. He died inBayonne, France, on January 13, 1934.
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