XXXVIIIth Rencontres de Moriond MORIOND WORKSHOP ON Radioactive

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 1. A few examples of cyclotrons as postaccelerators for RIB : CRC - LLN, SPIRAL - GANIL, DRIBS – Dubna 2. Why cyclotrons ? The issue of Mass Separation 3. The bottlenecks : injection and extraction 4. Which cyclotron(s) for the b-beams ? 5. Conclusion

Artist’s view of CRC’s CYCLONE 110 It is used in stand alone mode for the acceleration of protons (up to 80 Me. V) and heavy ions and as RIB postaccelerator. 1. Magnet yoke 2. Main coil 3. Accelerating electrode 4. RF amplifier 5. Hill sector (spiraled) 6. Injected beam 7. Extracted beam

Table of RIB’s produced at CRC Element T 1/2 q Intensity (pps)* 6 Helium Energy range (Me. V) 0. 8 s 1+ 2+ 9 106 3 105 5. 3 -18 30 -73 53 days 1+ 2+ 2 107 4 106 5. 3 -12. 9 25 -62 10 Carbon 19. 3 s 1+ 2+ 2 105 1 104 5. 6 -11 24 -44 11 Carbon 20 min 1+ 1 107 6. 2 -10 13 Nitrogen 10 min 1+ 2+ 3+ 4 108 3 108 1 108 7. 3 -8. 5 11 -34 45 -70 15 Oxygen 2 min 2+ 6 107 1 108 10 -29 6 -10. 5† 18 Fluorine 110 min 2+ 5 106 11 -24 1. 7 s 2+ 3+ 6 106 4 106 11 -24 24 -33, 45 -55 19 Neon 17 s 2+ 2+ 3+ 4+ 2 109 5 109 1. 5 109 8 108 11 -23 4 -9. 5† 23 -35, 45 -50 60 -93 35 Argon 1. 8 s 3+ 5+ 2 106 1 105 20 -28 50 -79 1992 7 Beryllium 1 st beam : 1989 18 Neon 1992 * Beam intensities measured in the main beam line after the cyclotron † With CYCLONE 44

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

Magnet structure of CIME Energy constant K 265 Average magnetic field (T) 0. 75 – 1. 56 Ejection radius (m) 1. 5 Frequency range (MHz) 9. 6 – 14. 5 Nominal energy range (Me. V/u) 1. 7 - 25 CIME characteristics

On-line 6 He, t 1/2 = 808 ms Primary beam ACCULINNA SPIRAL DRIBs 1. 5 106 pps, 25 Me. V/n 9 107 pps, 7 Me. V/n 9 109 pps, 8 13 Me. V/n 7 Li, 5 pm. A, 32 Me. V/n Target 8 He, t 1/2 = 119 ms Primary beam Target ISOL 13 C, 3 pm. A, 75 Me. V/n 7 Li, 10 pm. A, 32 Me. V/n Be Be, C Be 2 104 pps, 28 Me. V/n 3 105 pps, 5 15 Me. V/n 1. 5 107 pps, 6 8 Me. V/n 11 B, 5 pm. A, 34 Me. V/n Be 13 C, 3 pm. A, 75 Me. V/n Be, C 11 B, 10 pm. A, 34 Me. V/n Be

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.

THE CYCLOTRON AS SEEN BY THE INVENTOR (The non-relativistic case …. . ) R. F. frequency Harmonic mode acceleration Size of the magnet In « cyclotron » units: Where Q = ion’s charge state Examples : B=1 T M = mass in AMU KB = Cyclotron Bending constant in Me. V * Protons at H=1 f = 15 MHz * 6 He 1+ at H = 6 FRF = 15 MHz Examples : Protons to 50 Me. V KB = 50 6 He 1+ to 300 Me. V KB = 1. 800 18 Ne 1+ to 900 Me. V KB = 16. 200 Forget it !!

The Isochronous Cyclotron • f. RF = 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 (Me. V/AMU) Example : 50 Me. V protons or 50 Me. V/A 6 He 1+ = peanuts !!! PSI’s cyclotron : KF = 590 Me. V/A !

Isobaric contamination – mass separation Element T 1/2 12 C 6 He* 0, 8 s 18 O Mass (AMU) Charge state M/Q D (M/Q) 12. 00000 2+ 6. 000 0 6. 01889 1+ 6. 01889 + 31. 5 10 -4 17. 99916 3+ 5. 99972 - 0, 47 10 -4 18 F* 110 min 18. 00094 3+ 6. 00031 + 0, 52 10 -4 18 Ne* 18 s 18. 00571 3+ 6. 001903 + 3. 2 10 -4 12 C 2+ 18 O 3+ D (M/Q) 10 -4 -0. 47 18 F 3+ 0 * +0. 52 18 Ne 3+ * +3. 2 6 He 1+ * +31. 5

The issue of mass separation : the « mass resolution » R of a cyclotron in 1 st approximation (1) + suppose a frequency error Df phase slip j (2) where N 0 = 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 18 F (T(1/2) = 110 min) from 18 O (see previous table) we require R = 104 A cyclotron working in H = 3 should have N 0 1000 turns !

3. Bottlenecks a : Schematic layout of CYCLONE 110’s axial injection system b. Schematic layout of CYCLONE 110’s extraction system

4. Which cyclotron(s) for the Beta-beams ? Acceleration of 3 He 1+ and 18 Ne 3+ to 50 Me. V/A require a cyclotron with KB = 1800 Me. V 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)

5. CONCLUSION - Cyclotrons have proven to be very effective in the postacceleration 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 Me. V/A for 3 He 1+ and 18 Ne 3+ 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 18 Ne 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).

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 84 CH 1996 -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 13 th 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 15 th International Conference on Cyclotrons and their Applications (Caen, 1998), Institute of Physics Publishing, London, p. 687. • RI Beam factory Project at RIKEN, Proceedings 16 th International Conference on Cyclotrons and their Applications 2001 (East Lansing) – AIP Conference Proceedings #600, p. 161.