Charge breeder

In the EBIS the 1⁺ to n⁺ ion conversion takes place using electron bombardment by a high-energetic electron beam. However, the ISOLDE beam cannot 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 from ISOLDE, a considerably higher injection and trapping efficiency into the EBIS is obtained compared with continuous injection, and ISOLDE emittances up to 30 mm.mrad (at 60 kV) can be accepted.

Moreover, the mass selectivity of the side-band cooling technique in the Penning trap can 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 ions originating from the EBIS residual gas ionisation in an achromatic mass separator. The total cycle time for ions inside the charge breeder ranges from 5 ms for light elements to a few 100 ms for heavier elements (A~200).

The efficiency for trapping, beam transport, charge breeding and mass selection is normally between 5 and 15%. Sub-pA beams can be handled and the upper throughput limit is approximately 10⁹ ions per second.

References

[1] Challenges in C charge breeding Pitters, J (CERN) ; Breitenfeldt, M (ADAM, Geneva) ; Pahl, H (CERN ; Heidelberg U.) ; Pikin, A (CERN ; Manchester U.) ; Wenander, F (CERN)

[2] Charge breeding of CO+ beams at REX-ISOLDE Pitters, J (CERN) ; Breitenfeldt, M (CERN) ; Wenander, F (CERN)

[3] Slow Extraction of Charged Ion Pulses from the REXEBIS N. Bidault (CERN), J. A. Rodriguez (CERN), M. Lozano (CERN) and S. Sadovich (CERN)