PANDA Website

In high energy particle experiments one is interested in observables that require a transverse target polarization. The particle physics experiment PANDA consists of a detector at the particle accelerator FAIR currently under construction at GSI Helmholtz Centre for Heavy Ion Research, Darmstadt (GSI). The detector requires a high magnetic field in longitudinal direction with respect to the antiproton beam to provide high momentum resolution of the electrically charged particles. For the feasibility of a transverse polarized target in PANDA, it is essential to shield the longitudinal magnetic field. The ability to shield an intense magnetic flux with a high temperature superconductor BSCCO in form of a shielding tube was investigated experimentally. A shielding factor was extracted. A measurement of the stability of the shielding in time and a measurement of the residual magnetic flux density along the axis of the tube was performed. A numerical simulation of the induced current in the shielding tube and the residual magnetic flux density along its axis was developed. The experimental results were compared to the predictions based on the numerical simulation. For the measurements a dedicated apparatus consisting of a cryostat, filled with liquid helium, at a temperature of 4.2 K was developed and constructed at the Helmholtz-Institut Mainz (HIM). The shielding tube was equipped with a movable Hall probe, with a Zero-eld Magnet on top. The external magnetic eld was generated by a purpose-built superconducting solenoid, which can be mounted on top of the shielding tube. An external magnetic flux density of 1 T was applied and shielded with a shielding factor of at least 3:2
105 with a 95 % confidence level. In a measurement over four days a penetration of it into the shielding tube could not be observed. The measurement of the residual magnetic flux density along the axis of the tube showed a shielding of the the central region of 80 mm (from total 150 mm shielding tube) up to 1 T. BSCCO is a good shielding material and can be used to shield the high magnetic field within the PANDA spectrometer.