A large cryogen free iron shielded 6.5 Tesla magnet for nuclear beam experiments

The fusion of energetic beam nuclei with target nuclei produces new unstable nuclei. In order to study such nuclei they must be separated from the main particle beam so that the detectors used to identify the fusion products are not swamped by the high flux of incoming elastically scattered particles. A new particle detector 500 times more efficient than the previous design has been developed by the Nuclear Physics Department of the Australian National University. It requires a 6.5 Tesla 200 mm bore superconducting magnet, known as "SOLITAIRE," which has been built by Cryogenic Ltd. The magnet operates without cryogens and is iron shielded. The coil is designed within 0.05% of the axis of the iron shield. The magnet cryostat can be moved within the iron shield by means of alignment screws and the force between the solenoid and iron is monitored by means of pressure sensors. The high axial magnetic field produced by the superconducting solenoid is used to focus elastically scattered beam particles at a point inside the solenoid. At this point they are collected by a Faraday cup, which does not intercept the fusion products, since their focus is at a different point further down the beam line. The system is computer controlled under the National Instruments LabVIEW system for control of the magnetic field and monitor of the internal temperatures and the pressure sensors.