The CdH is a conduction type, LHe-cooled current lead. The cold terminal is immerged in a bath of liquid helium, which removes the heat conducted from the warm terminal (QC) and any heat generated from resistive losses in the current lead (QR). This design is used for operating currents ranging from 10-100 A.

The CvH is a convection type, LHe + GHe-cooled current lead. It has, similarly to the CdH, the cold terminal immerged in a bath of liquid helium. In addition, the helium gas generated from the boil-off is funnelled into one or several channels inside the current lead and the gas is used to cool the current lead from the inside. This is a very efficient design compared to the CdH, as it takes advantage of the helium boil-off. This design is used for operating currents ranging from 100-30 kA.

The CvHH is a convection type, LHe + GHe-cooled current lead, which introduces high-temperature superconducting material. Section 1 (see sketch) is similar to the traditional CvH, while section 2 has HTS material as conductor of the current. This design requires that the intersection point is kept at a fixed temperature, above the critical temperature of the chosen HTS. Since the HTS part fortunately is a poor conductor of heat compared to copper and the HTS does not have any resistive losses, the amount of heat that reaches the helium bath is very low. This design can be used for operating currents of 2-70 kA.

The CvHNH is similar to the CvHH, but here liquid nitrogen (LN2) is introduced to cool the resistive part of the current lead (section 1 (see sketch)). When the design specification allows for LN2 to be used as a coolant, the helium consumption can be significantly reduced. This design is used for operating currents of 2-70 kA.

The retrofit current leads are designed to fit into existing set-ups. It can utilize either the CvHH or CvHNH design to upgrade your existing current lead. Mark & Wedell is specialists in implementing new solutions in old cryostats taking spatial constrains into account. Such a retrofit can enable a current increase of up to 50% and/or a significant reduction in the LHe consumption. This in done by utilizing HTS material and LN2 as a coolant. This design is used for operating currents of 2-30 kA.