From the November 1972 issue

Applied research at CERN

In the words of its Convention, CERN exists “for nuclear research of a pure scientific and fundamental character and in research essentially related thereto”.

The applied research undertaken at CERN has thus been directed to problems related to its physics programme. These often generate extreme needs in both scientific and technical skills, thus “frontier” research tends to promote advances in a variety of surrounding disciplines.

All knowledge emerging from the work of CERN is freely available for application elsewhere: by the direct use of a device or technique, by other uses of the knowledge unearthed, or from the increased expertise of industry working with CERN.

Perhaps we do not do enough to make known our applied-research activities.

• Compiled from texts on p359.

Multiwire and multipurpose

The multiwire proportional chamber (MWPC), in its present form, was born in 1968. The [single wire] proportional counter was around in the 1930s and its operation in the “proportional mode” was studied. Various types of multiwire chambers had been tried but a lack of understanding of the mechanisms at play limited their applications. In 1967 we constructed a small multiwire chamber using the knowledge we had from proportional counters, and the following were among the properties having the most consequences [on price, practicality and performance].

1. Considerable expenditure is needed on electronics, to collect and amplify a signal from each wire. A variety of gas mixtures were studied and a “magic gas” was found that gives a signal a hundred times higher than “classical” gases, easing the burden on the electronics. Techniques for grouping the circuits of several wires on the same wafer and specifying an integrated circuit for large-scale production should considerably reduce costs.

2. For some uses there were constructional difficulties in building large chambers. For example, a strong metal frame able to withstand the tension of hundreds of stretched wires would fill a significant proportion of the valuable aperture of the Split Field Magnet (SFM) at the Intersecting Storage Rings, so special honeycomb sandwiches of plastic foam are to be used. They have great strength and introduce much less matter.

3. Large MWPCs have been in action in the CERN–Heidelberg neutral kaon experiments for over a year, and the new technique allows several thousand events to be collected per Proton Synchrotron pulse [several orders of magnitude faster than spark chambers]. Another type of multiwire detector, the drift chamber, correlates the arrival time of a pulse at the wires with the position of the originating track. This correlation is so good that track coordinates can be measured with a precision of the order of 0.1 mm. Groups at Saclay and Heidelberg have put a lot of applied research into drift chambers, with a great role to play in the future.

A technique used to detect the coordinate parallel to the sensitive wire is not very interesting for high-energy physics, but gives the MWPC certain properties that the medical people consider essential to measure the distribution of radiation, X-rays or gamma rays, emitted by isotopes which have been fed into a human being. Active research on further uses is now being carried out in several hospitals.

Thus important applications for MWPCs have been found elsewhere. Serious difficulties have had to be overcome and perhaps are yet to be overcome. But, with the understanding which we have acquired of the phenomena underlying the behaviour of these chambers, we should be able to surmount them.

• Compiled from texts on pp362–364.

Compiler’s Note

The 1972 article was written by the MWPC Nobel laureate himself, the late Georges Charpak: It is an exemplary account of how frontier research is done and how it generates spin-off.

Is it widely known that particle detectors and accelerators used in nuclear medicine were developed for high-energy physics? And what about some familiar widgets? In 1973, Danish engineer Bent Stumpe was asked to replace the buttons, switches, etc, in CERN’s Super Proton Synchrotron (SPS) control room by something simple (CERN Courier April 2010 p13). Within a matter of days, Bent had produced proposals for a touchscreen, a tracker ball and a programmable knob. Instantly deployed in the Lab, these were slower to catch on in industry, but nowadays no self(ie)-respecting geek would be seen without a touchscreen, Stumpe tracker-ball principles drive our mice, and programmable knobs are everywhere, such as a “Security programmable keyless-entry electronic digital door-lock knob”, to quote the advertising blurb!

Perhaps CERN didn’t do enough to make known some of its applied researchers.

About the author

Compiled by Peggie Rimmer.