The radioactive ions produced by the Light Ion Guide (LIG) facility must have the proper charge-state for acceleration. The boosting of a singly charged ion to higher charge-states is termed “charge breeding”. The ECR3 ion source (CB-ECRIS) will be devoted mainly to charge breeding the radioactive ions produced by the LIG. However, the CB-ECRIS can be used as a regular ECR source and provide highly charge states ions (gases only) for the regular operation of the K500 cyclotron. It was designed and built by Scientific Solutions of San Diego, California with a Phase I and a Phase II Small Business Innovative Research grant from the U.S. Department of Energy.
The efficiency of capture and charge breeding is provided for by high magnetic containment fields and the plasma-chamber cooling protection that allows high microwave power input. Two large coils supply the axial mirror magnetic field, and a surrounding Halbach type hexapole, assembled with Nd-Fe-B permanent magnets, provides the radial mirror field. The plasma chamber is formed by a water-cooled aluminum liner. The source is of medium volume and will operate at 14.5 GHz with the possibility of adding a lower second frequency later.
The efficiency of the CB-ECRIS has been tested extensively in the past years. Various injection schemes for single charged ions were verified and a final solution has been chosen: a RF-only sextupole feeding directly low energy ions into the plasma chamber. In the picture below is an example of rubidium single charged ions injected into the CB-ECRIS and the charge states spectrum. The efficiency of the charge breeding was measured to be between 20% to 40%.
The charge breeding of radioactive ions it is more complicated due to the presence of the residual helium gas “leaking” from the LIG device. Evidently the measurements are more complex, in this case counting stations are set up to count the decay of the radioactive products.
Up to this date, the table below shows the current radioactive beams selection developed using proton beams.
|
Target |
Product (half-life, charge state) |
Proton beam energy [MeV] |
Yield [ions/µA] |
|
114Cd (isotopic target) |
114In (t1/2 =72 s, Q=19) |
10 |
685 |
|
114Cd (isotopic target) |
112In (t1/2 =20.5 m/15 m, Q=21) |
28 |
975 |
|
106Cd (isotopic target) |
106In (t1/2 =5.3 m/6.2 m, Q=20) |
14 |
410 |
|
106Cd (isotopic target) |
105Cd (t1/2 =55 m, Q=20) |
24 |
620 |
|
90Zr (isotopic target) |
90Nb (t1/2 =18.8 s, Q=17) |
13 |
300 |
|
90Zr (isotopic target) |
89Zr (t1/2 =4.16 m/78.4 h, Q=17) |
22 |
200 |
|
64Zn (isotopic target) |
64Ga (t1/2 =2.6 m , Q=14) |
14 |
210 |
|
64Zn (isotopic target) |
63Zn (t1/2 =38.5 m , Q=14) |
24 |
250 |
