Shrink Tube Insulation Apparatus for Rebco Superconducting Tapes for Use in High Field Magnets

An increasing number of applications require the use of high temperature superconductors (HTS) such as (RE=Rare Earth) Ba2Cu3O7-x (REBCO) coated conductors [1]. HTS conductors show particularly great potential for high field magnets applications [1] due to their high upper critical fields [2], But several groups have shown that REBCO coated conductors are prone to delamination failure [3] [4] [5]. Under relatively low transverse stress the HTS film separates from the substrate and the conductor degrades [6]. This is problematic due to high transverse stresses that occur in fully epoxy impregnated solenoids wound with this conductor. Application of thin walled heat shrink tubing introduces a weak plane around the conductor, preventing delamination degradation [7]. However, manual application of the shrink tubing is impractical, requiring three operators limited to insulating 100 m lengths or less of REBCO conductor. The high risk of damage to the conductor, also associated with this process, shows the need for a mechanized process. Strict guidelines for the capabilities of the mechanized process were set: a single operator must have the capability to insulate continuous 200 m lengths of REBCO conductor with a minimum insulation rate of 50 m per work day. This thesis presents the ideation, prototyping, and construction of such a mechanized insulation process. Results of prototyping yielded an insulation rate of 100 m per work day with two operators, and the capacity to insulate 130 m of REBCO conductor [8]. Local critical current test indicated that no damage is caused to the tape from the insulation process [9]. A final mechanized Shrink Tube Insulation Apparatus (STIA) was developed, increasing the conductor length capacity to 450 m and reducing the number of operators to one. Due to unforeseen motor and tape tension issues, modifications to STIA were required, which increased the number of operators to two. Through a collaborative effort between the Applied Superconductivity Center (ASC) and the Kyushu University in Japan, a continuous 200 m length of Fujikora-produced REBCO conductor was provided, to be insulated by STIA. An insulation rate of 100 m per work day was achieved with two operators. In the latter of the paper, current work to rectify the issues causing the need for two operators is presented.