Presentation Speech by Professor Carl Nordling of the Royal Swedish Academy of Sciences

Translation from the Swedish text

Your Majesties, Your Royal Highnesses, Ladies and Gentlemen,

This year the Nobel Prize in Physics has been awarded to Georges Charpak, France, for his invention and development of particle detectors, in particular the multiwire proportional chamber. It is the tenth time in the history of the Nobel Prize that the word “invention” has been used in the citation for the award in physics.

None of us owns the kind of detector for which the prize is being awarded today, but we are all equipped with other forms of detectors. Our eyes are detectors of light, our ears detect sound, our noses detect odors and so on. The signals from these sense organs are sent to a computer – the brain. There they are processed, communicated to our consciousness and used as the basis of our actions and our conception of the world in which we live.

But we are not always content with this. Our curiosity about the world extends beyond our immediate sensory impressions. For this reason inventive people have constructed devices of various kinds which intensify our senses or replace them completely – if this is at all possible in principle. Galileo Galilei constructed telescopes, Zacharias Janssen invented the microscope etc.

Today’s elementary particle physicists look deep inside matter using accelerators as microscopes. In these accelerators particles chosen as suitable projectiles, electrons for instance, are raised to high energies and then made to collide with each other. This produces new particles like the sparks from fireworks. In this invisible deluge of sparks, which can be discharged a hundred million times each second, there is information about the innermost constituents of matter and the forces with which they interact.

In order to acquire this information, enormous installations are built, which contain various kinds of detectors. Professor Charpak has invented the detector which has meant most for the progress in the area of elementary particle physics during the last few decades.

The list of qualities demanded of a detector of elementary particles is a long one. It must react quickly, must be able to cover large surfaces hundreds of square meters – and must send its signals direct to a computer. It must be sensitive to position, i.e. it must not only be able to say if something has happened but also, where, and it must also be capable of following the total length of the trajectory of a particle, often several meters. And it must be able to do all this even when it is placed in a strong magnetic field.

All of these requirements are fulfilled by the multiwire proportional chamber, the detector which Georges Charpak invented in 1968. This detector is used, in some form or other, in more or less every experiment within elementary particle physics today, and Georges Charpak has been at the centre of the development which has taken place since the original invention was made. Many important discoveries have been made using his detectors.

Charpak’s research is an example of an advanced technological development within basic science. Its original purpose was to contribute to the development of nuclear physics and elementary particle physics in order to provide further facets of our conception of the world. This aim has been achieved, but Charpak’s detector has also found applications well outside the field of elementary particle physics, for instance in medicine. In this development too, Charpak plays a central role.

Monsieur Charpak,

Le Prix Nobel de Physique de l’année 1992 vous a été decerné pour votre invention et développement de détecteurs de particules, notarnment de la chambre proportionelle multifits. J’ai l’honneur de vous adresser les félicitations les plus chaleureuses de I’Académie Royale des Sciences de Suede, et je vous invite à recevoir votre Prix des mains de Sa Majesté le Roi.