Kjell Johnsen 1921-2007

Kjell Johnsen (right) with Mervyn Hine in the PS control room in 1960. Both of them have been major contributors to the development of this accelerator, the first ambitious and innovative big project of the young laboratory. (Photo : Bengt Sagnell)

On 27 January 1971, Kjell Johnsen, who led the project of the Intersecting Storage Rings, announced that the first ever interactions from colliding proton beams had been recorded.

Kjell Johnsen passed away at his home in La Rippe (VD) on Wednesday 18 July following a long battle with cancer.

Kjell was born in Norway in June 1921 and studied Electrical Engineering at the Technical University of Trondheim. He was selected by Professor Odd Dahl of Bergen, one of the founding fathers of CERN, to take part in the early studies for the accelerators of the future European physics centre.

Kjell joined CERN in 1952 and took part in the design of the most ambitious project of the newly born laboratory (the alternating gradient Proton Synchrotron, now called the PS). He rapidly developed into one of the few real accelerator experts in the world at the time.

Kjell dedicated his enormous energy and vision for several years to obtain approval for the construction of the world’s first proton-proton collider. This project (the Intersecting Storage Rings, ISR) was approved under Kjell’s leadership and construction was launched in 1966 with completion in 1971. At the time, the ISR was an incredibly ambitious and controversial project. Many eminent scientists openly stated that the beams would not survive long enough to produce physics data. It is now history that the ISR is one of the great accelerator success stories. It has opened up a new energy domain for high energy physics and has paved the way for approval and construction of many larger projects (SPPbarS, Tevatron and the LHC). Under Kjell’s leadership the ISR project was an inspiring example of well-directed teamwork. For all of us who had the privilege to work on this machine under Kjell’s leadership, we can honestly say that this was a very rewarding and unique major scientific experience and adventure.

Kjell was nominated Professor at the Technical University of Trondheim and for several years dedicated an important part of his time to the teaching at doctoral level and the training of young people.

Kjell was also the creator and inaugural Director of the CERN Accelerator School (CAS). CAS has become a very successful enterprise, attracting many talented and gifted young students from all over the world, and thereby promoting scientific collaboration at a European and world-wide level.

Kjell’s many friends around the world have always valued his kindness, competence, intellectual honesty, seriousness, scientific vision, courage and dedication. It was to Kjell that people went for clarifications, advice and guidance, and we will dearly miss him.

We should, however, be comforted by the thought that he has been a great example and role model to many of us; that he has been respected, appreciated and has left a permanent mark in his professionally chosen field of accelerator research.

We offer our sincere condolences and deepest sympathy to his wife and family.