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 -beams ?

5. Conclusion

CYCLONE 44

CYCLONE 30

ARES

OFF-LIGNEECR SOURCE

CYCLONE 110 ON-LINEECR SOURCE PRODUCTION

TARGET

Layout of the RIB facility.

PUBLIC CAO HALL 222

Pj19_01,s01 rv cyclo-1

634 1

1 25 7

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.

1. Magnet yoke

2. Main coil

3. Accelerating electrode

4. RF amplifier

5. Hill sector (spiraled)

6. Injected beam

7. Extracted beam

Element T1/2 q Intensity

(pps)*Energy range

(MeV)

6Helium1992

0.8 s 1+2+

9 106

3 105

5.3-1830-73

7Beryllium 53 days 1+2+

2 107

4 106

5.3-12.925-62

10Carbon 19.3 s 1+2+

2 105

1 104

5.6-1124-44

11Carbon 20 min 1+ 1 107 6.2-10

13Nitrogen1st beam :1989

10 min 1+2+3+

4 108

3 108

1 108

7.3-8.511-3445-70

15Oxygen 2 min 2+ 6 107

1 108

10-296-10.5†

18Fluorine 110 min 2+ 5 106 11-24

18Neon1992

1.7 s 2+3+

6 106

4 106

11-2424-33,45-55

19Neon 17 s 2+2+3+4+

2 109

5 109

1.5 109

8 108

11-234-9.5†

23-35,45-5060-93

35Argon 1.8 s 3+5+

2 106

1 105

20-2850-79

* Beam intensities measured in the main beam line after the cyclotron

† With CYCLONE44

Table of RIB’s produced at CRC

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 (MeV/u)

1.7 - 25

CIME characteristics

On-line ISOL

ACCULINNA SPIRAL DRIBs

6He, t1/2 = 808 ms 1.5 106 pps,

25 MeV/n

9 107 pps,

7 MeV/n

9 109 pps,

8 13 MeV/n

Primary beam 7Li, 5 pA,

32 MeV/n

13C, 3 pA,

75 MeV/n

7Li, 10 pA,

32 MeV/n

Target Be Be, C Be

8He, t1/2 = 119 ms 2 104 pps,

28 MeV/n

3 105 pps,

5 15 MeV/n

1.5 107 pps,

6 8 MeV/n

Primary beam 11B, 5 pA,

34 MeV/n

13C, 3 pA,

75 MeV/n

11B, 10 pA,

34 MeV/n

Target Be Be, C 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

vmBvq

2...

R.F. frequency

Bm

qf partpart 2

Harmonic mode acceleration

.partRF fHf

Size of the magnet

22

2extrMAX

MAX

rB

m

qT

In « cyclotron » units:

BMAX KM

QT

2

Examples :

Protons to 50 MeV KB = 50

6He1+ to 300 MeV KB = 1.800

18Ne1+ to 900 MeV KB = 16.200

Forget it !!

r e xtr

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+ at H = 6

FRF = 15 MHz

The Isochronous Cyclotron

• fRF = constant !

but : 2/1

2

2

0

1

cv

mm

Field index : 0/

/ n

rdr

BdBn

Axial defocusing : nZ 2Sector focusing Hills & valleys

Increased by spiralling of the sectors

Flutter function :2

2fF with Bhill = Bavg (1 + f)

Bvalley = Bavg (1 – f)

New « betatron » frequencies :

...12 nr

...tan211

2

2

22

spiralz FN

Nn

determines A

TK MAX

F (MeV/AMU)

Example : 50 MeV protons or 50 MeV/A 6He1+

= peanuts !!!

PSI’s cyclotron : KF = 590 MeV/A !

rwithrB )(

with : N = number of sectors

spiral = sector spiral angle

Element T1/2 Mass (AMU)

Charge state

M/Q (M/Q)

12C 12.00000 2+ 6.000 0

6He* 0,8 s 6.01889 1+ 6.01889 + 31.5 10-4

18O 17.99916 3+ 5.99972 - 0,47 10-4

18F* 110 min

18.00094 3+ 6.00031 + 0,52 10-4

18Ne* 18 s 18.00571 3+ 6.001903

+ 3.2 10-4

18O3+ 18F3+ *

12C2+

-0.47 0 +0.52

18Ne3+ *

6He 1+ *

+3.2 +31.5 (M/Q) 10-4

Isobaric contamination – mass separation

The issue of mass separation : the « mass resolution » R of a cyclotron in 1st approximation

m

qBHfHf partRF 22

+ suppose a frequency error f phase slip

f

fNH

02sin

When reaches –90° or +90°, acceleration stops !

2sinsin MAXstopstart

0

1

NHf

f

mq

mq

B

B

f

f

/

/

0/

/NH

mq

mqR

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 !

where N0 = number of turns when f = 0

(1)

(2)

(3)

(4)

(5)

Substitute (3) in (2)

From (1) we have :

Substitute (5) in (4)

3. Bottlenecks

a : Schematic layout of CYCLONE110’s axial injection system

b. Schematic layout of CYCLONE110’s extraction system

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)

R ext (m ) 1 .5B (T) 1.56We ig ht (to n) 500

6.4m5 .1 m

R ext (m ) 0 .9 3B (T) 1 .6We ig ht (to n) 200

K 11 0 -M e V C Y C L O N E K 2 6 5 -M e V S P IR A L

K 1 2 0 0 -M e V C S C - M S U

4 .4 m

R ext (m ) 1B (T) 5We ig ht (to n) 280

K 5 4 0 -M e V R R C K 2 5 0 0 -M e V S R CK 9 3 0 -M e V IR C

R in j (m ) 3 .5 6R ext (m ) 5 .36B (T ) 4 .4Weig h t (ton ) 4 ,3 00

R in j 2 .7 7R ext (m ) 4 .1 5B (T ) 1 .9Weig h t (ton ) 2 ,40 0

R in j (m ) 0 .8 9R ext (m ) 3 .5 6B (T ) 1 .7Weig h t (ton ) 2 ,1 0 0

1 9 m1 4 m1 3 m

C o m p a riso n o f d iffe re n t c y c lo tro n s

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 s 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 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.