XXXVIII th Rencontres de Moriond

1. XXXVIIIth Rencontres de Moriond MORIOND WORKSHOP ON Radioactive beams for nuclear physics and neutrino physics Acceleration of RIB using cyclotrons Guido Ryckewaert Cyclotron Research Centre Louvain-la-Neuve, Belgium Overview • A few examples of cyclotrons as postaccelerators for RIB :CRC - LLN, SPIRAL - GANIL, DRIBS – Dubna • Why cyclotrons ? The issue of Mass Separation • The bottlenecks : injection and extraction • Which cyclotron(s) for the b-beams ? • Conclusion

3. Artist’s view of CRC’s CYCLONE110 It is used in stand alone mode for the acceleration of protons (up to 80 MeV) and heavy ions and as RIB postaccelerator. • Magnet yoke • Main coil • Accelerating electrode • RF amplifier • Hill sector (spiraled) • Injected beam • Extracted beam

4. Table of RIB’s produced at CRC • * Beam intensities measured in the main beam line after the cyclotron • † With CYCLONE44

5. Layout of the GANIL – SPIRAL facility Beams with SPIRAL - See : http://www.ganil.fr/operation/available_beams/radioactive_beams.html

6. Magnet structure of CIME CIME characteristics

9. 2. Why use cyclotrons ? 3 good reasons : • Local expertise. • Cyclotrons are compact, versatile and efficient low and medium energy accelerators. • Cyclotrons can provide very high mass separation : the clue to success of our project in Louvain-la-Neuve from 1989 on.

10. THE CYCLOTRON AS SEEN BY THE INVENTOR (The non-relativistic case …..) R.F. frequency Size of the magnet Harmonic mode acceleration In « cyclotron » units: Where Q = ion’s charge state M = mass in AMU KB = Cyclotron Bending constant in MeV • Examples : • B = 1 T • * Protons at H=1 •  • f = 15 MHz • * 6He1+ atH = 6 •  • FRF = 15 MHz Examples : Protons to 50 MeV  KB = 50 6He1+ to 300 MeV  KB = 1.800 18Ne1+ to 900 MeV  KB = 16.200 Forget it !!

11. The Isochronous Cyclotron • fRF = constant ! but : Field index : Axial defocusing : Sector focusing  Hills & valleys  Increased by spiralling of the sectors Flutter function : with Bhill = Bavg (1 + f) Bvalley = Bavg (1 – f) New « betatron » frequencies : with : N = number of sectors qspiral = sector spiral angle determines (MeV/AMU) Example : 50 MeV protons or 50 MeV/A 6He1+ = peanuts !!! PSI’s cyclotron : KF = 590 MeV/A !

12. Isobaric contamination – mass separation 12C2+ 6He 1+* 18O3+ 18F3+* 18Ne3+* D (M/Q) 10-4 -0.47 0 +0.52 +3.2 +31.5

13. The issue of mass separation : the « mass resolution » R of a cyclotron in 1st approximation (1) + suppose a frequency error Df  phase slip j (2) where N0 = number of turns when Df = 0 When j reaches –90° or +90°, acceleration stops ! (3) Substitute (3) in (2) (4) From (1) we have : (5) Substitute (5) in (4) Example : To separate 18F (T(1/2) = 110 min) from 18O (see previous table) we require R = 104 A cyclotron working in H = 3 should have N0 1000 turns !

14. 3. Bottlenecks a : Schematic layout of CYCLONE110’s axial injection system b. Schematic layout of CYCLONE110’s extraction system

15. 4. Which cyclotron(s) for the Beta-beams ? • Acceleration of 3He1+ and 18Ne3+ to 50 MeV/A require a cyclotron with KB = 1800 MeV • Examples of the larger cyclotrons (used for in-flight RIB production) : • the National Superconducting Cyclotron Laboratory coupled cyclotron upgrade •  Compact Superconducting Cyclotron • the RIKEN project. •  (Superconducting) Separated Sector cyclotron • (requires an injector accelerator : linac or compact cyclotron)

19. 5. CONCLUSION • Cyclotrons have proven to be very effective in the post- acceleration of RIB’s and in particular in producing high purity weak beams in the presence of large stable isobaric contaminants. • Beta-beams could be well served by either a superconducting compact cylotron or by a separated sector cyclotron–injector combination. An energy range from 30-50 MeV/A for 3He1+ and 18Ne3+ are ideal. The required intensities are several orders of magnitude below space-charge limits in the DC-mode. • Special attention should be given to : • * efficient ionisation of 18Ne to the 3+ charge state ; • * space charge limits at low energy after the source in case of pulsed operation (e.g. a train of ns beam bunches during 100 ms every 20 ms out of the cyclotron).

20. Some references • http://www.cyc.ucl.ac.be • http://www.ganil.fr • http://www.jinr.ru • Cyclotrons as Mass Spectrometers, David J. Clark,¨Proceedings Tenth International Conference on Cyclotrons and their Applications (1984 , East Lansing), Editor : F. Marti, IEEE Cat. No 84CH1996-3, p. 354. • Radioactive Ion Beam Production using the Louvain-la-Neuve Cyclotrons - present status and future developments, G. Ryckewaert, M. Loiselet and N. Postiau, Proceedings of the 13th International Conference on Cyclotrons and their Applications (1992), World Scientific, p. 737. • Cyclic Particle Accelerators by John J. Livingood, D. Van Nostrand Company, Inc. • The NSCL Coupled Cyclotron Project – Overview and Status, R.C. York et al., Proceedings 15th International Conference on Cyclotrons and their Applications (Caen, 1998), Institute of Physics Publishing, London, p. 687. • RI Beam factory Project at RIKEN, Proceedings 16th International Conference on Cyclotrons and their Applications 2001 (East Lansing) – AIP Conference Proceedings #600, p. 161.