Comparison investigation on the low temperature Specific Heat Capacity of nine different commercial REBCO tapes

In this paper, the specific heat in the temperature range from 5K to 200K of commercial REBCO tapes from nine different manufacturers was systematically investigated. Although all nine REBCO tapes have a similar coated conductor structure, the specific heat can differ by over 120% at low temperatures, far beyond what many superconducting magnet designers previously believed. It shows that the specific heat of the REBCO tape must be measured during design rather than relying on data from the literature, which can lead to significant errors in the superconducting magnet design. After careful measurement of the different layers of the REBCO tape, it is confirmed that the difference in the specific heat primarily comes from the Cu stabilizer. Moreover, we demonstrated that the measurement error could exceed ±200% when the background data were misused. This paper could serve as a handbook for the superconducting magnet designer on how to obtain accurate low-temperature specific heat data.