Contact: Evgeniy Pyata
The provision of a magnetic field of 2T over a length of about 4m and a diameter of 1.9m whilst simultaneously keeping this region free for detectors is far from trivial. The technological challenge is complicated by additional requirements concerning, e.g. field homogeneity (see table below), the intersection of a warm target feed pipe and detector access, to name only a few.
We have designed the PANDA solenoid magnet using a superconducting split coil with Rutherford type cable and indirect cooling. Though the detector layout requires an asymmetric arrangement of the cryostat and flux return yoke, the stringent requirements for the field, its homogeneity and the magnetic forces are satisfied by this design. The cryostat will surround all detectors and serve as their mounting structure. The flux-return yoke will serve as an active muon range system by incorporating mini-drift tubes between 13 layers of iron. Both ends of the return yoke will be fabricated as opening doors, whilst in parts simultaneously serving as the muon range system. In addition, the whole set up of more than 300t will be retractable to a parking position well outside the beam, where it can be operated for commissioning and maintenance.
The main parameters are summarised in the table below.
| Central field | 2.0 T |
|---|---|
| Field homogeneity | ≤2% |
| Norm. radial field integral | ≤2 mm |
| Inner bore | 1.9 m |
| Cold mass parameters | |
| Length | 2.7 m |
| Energy | 20 MJ |
| Current | 5000 A |
| Weight | 4.5 t |
| Cable cross section | 3.4 × 2 mm |
| Current density | 59 A/mm |
| Yoke parameters | |
| Length | 4.9 m |
| Outer radius | 2.30 m |
| Iron layers | 13 |
| Total weight | 300 t |