Study of Transient Heat Transport Mechanisms in Superfluid Helium Cooled Rutherford-Cables

The Large Hadron Collider leverages superconducting magnets to focus the particle beam or keep it in its circular track. These superconducting magnets are composed of NbTi-cables with a special insulation that allows superfluid helium to enter and cool the superconducting cable. Loss mechanisms, e.g. continuous random loss of particles escaping the collimation system heating up the magnets. Hence, a local temperature increase can occur and lead to a quench of the magnets when the superconductor warms up above the critical temperature. A detailed knowledge about the temperature increases in the superconducting cable (Rutherford type) ensures a secure operation of the LHC. A sample of the Rutherford cable has been instrumented with temperature sensors. Experiments with this sample have been performed within this study to investigate the cooling performance of the helium in the cable due to heat deposition. The experiment uses a superconducting coil, placed in a cryostat, to couple with the magnetic field loss mechanisms in the sample (interstrand resistance) and deposit heat. The results of this experiment show a turbulent behavior below a heating power of 1.8 mW/cm³. A laminar performance could not be observed. However, at the higher heating powers a linear relationship of the temperature increase and the deposited heat was found up to a certain point, till some of the helium channels get deactivated. Depending on the dynamics of the heating curve, these channels play a major role and are dominant for the cooling performance. Further experiments with higher heating powers are needed to investigate this relationship. The results of the performed experiments have been compared with further outcomes of research groups after an intense literature research within this thesis. The experiments showed the most effective cooling at a bath temperature of 2.0 K.