CBS

Charge breeding system

Charge breeding system | REXTRAP | REXEBIS | Mass separator


Figure 1.	A schematic layout of the charge breeding components

In the EBIS the 1⁺ to n⁺ ion conversion takes place by electron bombardment by a high-energetic electron beam. However, the ISOLDE beam can not be injected into the EBIS with high efficiency without beam preparation. By introducing a Penning trap in front of the EBIS, which accumulates, bunches and phase space cools the semi-continuous beam, a considerably higher injection and trapping efficiency into the EBIS is obtained compared with continuous injection, and ISOL emittances up to >30 p•mm•mrad (at 60 kV) can be accepted.


Figure 2.	Photo showing the complete charge breeding system of REX-ISOLDE

Moreover, the mass selectivity of the side-band cooling technique in the Penning trap could in principle be employed for a further purification of the incoming beam. At extraction of the n⁺ ions from the EBIS the radioactive ions are separated from stable ion peaks originating from the residual gas ionisation in an achromatic mass separator. The total cycle time for ions inside the mass separator ranges from 5 ms for light elements to a few 100 ms for heavier elements (A~150).

The efficiency for trapping, beam transport, charge breeding and mass selection is normally between 5 and15%. Sub-pA beams can be handled and the upper throughput limit is a few 10⁹ ions per second.

Cooling time < 20 ms

Breeding time = 3-200 ms

Trap efficiency > 40%

EBIS efficiency
(in one charge state) < 30%

Beam intensity < 10⁹ions/s

References

1. O. Kester and Dieter Habs, 8th Int. Symposium EBIS/T 2000, Upton NY, 5-8 Nov.,
AIP conf. proc v572 (2001) 217-223.

2. F. Ames et al. , Int. Workshop on JHF Science: JHF-98-2 v2 400-403.

3. F. Wenander, Nucl Phys. A701 (2002) 528-536c.

4. F. Wenander, P. Delahaye, R. Scrivens, R. Savreux, ‘The REX-ISOLDE charge breeder as an operational machine’
Rev. Sci. Instrum., vol.77 (2006) 03B104-1-5.

5. F. Wenander, ‘Charge breeding of radioactive ions with EBIS and EBIT’, Journal of Instrumentation, vol5 (2010) C10004