COBRA magnet is a superconducting solenoidal magnet designed for the MUEGAMMA experiment at PSI. Design concept is as follows.
- Gradient magnetic field for constant projected bending radius and fast sweeping of the low energy positrons.
- Small magnetic field around the liquid xenon calorimeter.
The magnet consists of the six coils with different radii to realize gradient magnetic field. Two Compensation coils suppress the residual field around the liquid xenon calorimeter.
A thin superconducting cable for the COBRA magnet was newly developed. Aluminum stabilizer in the cable is reinforced by adding small amount of materials into pure aluminum. The cross-sectional view of the cable is shown in Fig.1. The parameters of the cable are listed in Table1
Fig.1 Cross-sectional view of the superconducting cable.
| Conductor Material | NbTi/Cu |
|---|---|
| NbTi/Cu diameter | 0.597mm&phi |
| NbTi/Cu ratio | 0.815 |
| Cable size | 0.81 x 1.108mm2 |
Table1 Parameters of the superconducting cable.
The stray field around the liquid xenon calorimeter has to be minimized because the PMT to be used in the calorimeter doesn't work in the magnetic field above around 100 Gauss.
