1. Paris 8 juin 2013 1 Geneva 17 December2014 ISOLDE at 50 HAPPY BIRTHDAY TO YOU ISOLDE at 50 HAPPY BIRTHDAY TO YOU From pre- ISOLDE to ISOLDE : some background and personal recollections Torleif Ericson A not so likely event

2. Paris 8 juin 2013 2 Geneva 17 December2014 The origin of ISOLDE goes back to Niels Bohr in 1952 1952: Niels Bohr persuades Alexis Pappas from Oslo to do Cern-related radiochemistry at the 180 MeV SC at Uppsala 1957: the 600 MeV SC starts operations at CERN A world class high energy machine though not highest in energy

3. Paris 8 juin 2013 3 Geneva 17 December2014 Nuclear Chemistry at CERN 1957:The SC director Gentner asks Pappas to assemble a Nuclear Chemistry Group 1958: Gösta Rudstam becomes its first leader; Pappas becomes a CERN advisor on nuclear chemistry for a decade Pappas becomes a CERN advisor on nuclear chemistry for a decade Remember: nuclear physics and nuclear chemistry are then closely related fields General mission of the radio chemistry group (Memorandum 1961): measurements of fission and spallation cross sections at 600 MeV and 25 GeV to understand the mechanism of complex processes and for various practical purposes of other experiments.

4. Paris 8 juin 2013 4 Geneva 17 December2014 1958: The SC puts CERN on particle physics map The first important CERN contribution: the confirmation of π - to e - + neutrino suppression by a factor ten thousand Maria and Giuseppe Fidecaro with Alec Merrison and Helmut Paul The Fidecaros 1963

5. Paris 8 juin 2013 5 Geneva 17 December2014 SC’s golden years of particle physics 1958-65 Many leading physicist preferred SC to the PS which started 1960 The SC was the perfect low energy pion and muon machine Key discoveries and tests of weak interactions were ripe fruits Some names on publications G. Charpak, L. Dick, M. Fidecaro, C. Rubbia (very young), V. Soergel, V. Telegdi, A. Zichichi, K. Winter together with some young theorists like N. Cabibbo and A. de Rujula Machine time was vigorously fought for and allocated in hours, not shift BUT TIME WAS OBVIOUSLY RUNNING OUT !

6. Paris 8 juin 2013 6 Geneva 17 December2014 The decisive rôle of Viki Weisskopf Director general 1961-5; shaped the CERN traditions for decades One of Weisskopf’s visions A peril for particle physics: brilliant success and isolation from other science A remedy: reestablished links to nuclear physics

7. Paris 8 juin 2013 7 Geneva 17 December2014 An initiative: The 1963 Conference on High Energy Physics and Nuclear Structure A watershed and the birth of intermediate Energy Physics Topics relevant for the SC Interactions of pions with complex nuclei T. E. O. Ericson Fragmentation induced by high energy particles N. A. Perfilov Muons and nuclear structure J. C Sens Complex nuclei as a tool in elementary particle physics V. Telegdi Viki Weisskopf closed the meeting with a call for proposals in nuclear physics at CERN.

8. Paris 8 juin 2013 8 Geneva 17 December2014 In parallel to ISOLDE a lively program using mainly low energy and stopped muons and pions in nuclear physics developed rapidly at the SC and pions in nuclear physics developed rapidly at the SC as a consequence of Weisskopf’s invitation. as a consequence of Weisskopf’s invitation. In particular, the mesonic X-ray programs developed by Gerhard Backenstoss and Hans Sens skillfully exploited their non-commercial access to big GeLi detectors, gaining 2 orders of magnitude in resolution. They mostly were ahead of the US competition mainly from Mme Wu and James Rainwater at Columbia, but also from the Chicago group. This however, is not real part of the background to ISOLDE.

9. Paris 8 juin 2013 9 Geneva 17 December2014 First trace of the on-line separator project: Internal memorandum by G. Andersson and G. Rudstam November 19 th 1963 After the Conference and Weisskopf’s call for proposals A meeting of Weisskopf, Pappas, Rudstam and TE February 1964 A meeting of Weisskopf, Pappas, Rudstam and TE February 1964 about possibilities mentions radio-isotopes at the SC by special techniques for short half-lives, Q-values and spectroscopy without any details. A huge difference with experimental proposals: it concerns a facility and resources well beyond those of the Nuclear Chemistry Group October 26 th 1964 I recommend as an ‘expert’ the proposal to the Nuclear Physics Experiments Committee which encourages a final version A polished version is approved on December 17 th 1964 A meeting on April 10 th organized by the Nuclear Chemistry discusses enthusiastically Scientific aims and organization.

10. Paris 8 juin 2013 10 Geneva 17 December2014 Peter Preiswerk Nuclear Physics Division Leader 1964 Nuclear Physics Division Leader 1964 Who were the crucial people who made it possible besides the initiators? Most likely Wolfgang Gentner, Peter Preiswerk and Alexis Pappas They had all important nuclear physics links in their career via the Joliot-Curie group in Paris Viki Weisskopf played an important role as a major support strongly positive to the field. Wolfgang Gentner Chairman of the CERN Scientific Policy Committee

11. Paris 8 juin 2013 11 Geneva 17 December2014 The ISOLDE program is no longer fragile and exposed to timely coincidences. It is an integral part of CERN and will presumably last as long as CERN exists. GOOD LUCK ISOLDE FOR MANY FRUITFUL YEARS TO COME! Who would have guessed my wish to-day in 1964!