Georges Charpak, a French physicist and 1992 Nobel Prize winner, died yesterday.

Of Polish origin, Charpak gave crucial contributions to experimental physics, in particular for his invention of the multiwire proportional chamber in 1968.

Back then, the signal of passage of charged particles was recorded by bubble chamber images and images triggered by spark chambers - where the charge deposition would create a discharge in a very high electric field.

There were problems with such technologies, because the processing of photographic images limited the data acquisition severely. Spark chambers would also bring in large dead times during which the system would be insensitive to additional interactions.

Charpak found a different way to record the information: imaging through the recording of small charge deposition signals by fast electronics. He studied and developed gaseous detectors where the avalanches would be located only in the immediate surroundings of the high-potential wires, and the signal due to ion drift could be recorded very neatly in nearby wires. Designs with planes of wires orthogonal to each other would allow the precise location of the passage of the ionizing radiation.

The Nobel lecture he gave in 1992, where he explains in detail his work on multiwire chambers, is here.

Charpak's work was seminal to the design of tracking chambers that are still in use in modern-day particle detectors, such as the COT (right), which is installed in the core of CDF, the experiment operating at the Tevatron proton-antiproton collider.

[This article is also available in Greek here]