Kategorie: Articles

Current Leads

Current leads are a cryo-electrical component of the circuit of a superconducting magnet, a pair for each electrical circuit. One end, the warm terminal, has ambient temperature, about 300 K (Kelvin). The other end, the cold terminal, has the temperature of liquid helium, approximately 4 K.

If the cross-section of the conductor is too large, a lot of heat comes from the warm to the cold terminal. On the other hand, if the cross-section is too small, the electrical current will cause a significant heating and the current leads may burn through. The designer has to find a compromise.

There are current leads which are only cooled at the cold terminal. This is the conduction cooled type. The vapour cooled current leads guide the helium vapour all along the whole length from the cold to the warm terminal. Sometimes the temperature is fixed in between with liquid nitrogen (77 K) by the employment of a thermal anchor.

Computational Fluid Dynamics

In CFD a computer solves the discretized equations on a numerical grid which should be fine enough in order not to neglect important features of the flow in between. Beside of the real experiment and pure theory it has established itself as the third column of fluid dynamics. In contrast to the real experiment, the numerical experiment offers much more data. Pure theory has the disadvantage that it can only provide solutions of few simple problems. It shall not be concealed that by far not all situations of interest can be simulated accurately. For example, in most cases turbulent flows have to be modelled which involves simplifications.

A mocking interpretation of CFD is Colors For Dollars, since the visualisation is very colourful and the software in most cases expensive. Alas, this is only the opinion of the mockers! 🙂