## 5 Angular Measurements  
Further insight is now provided into the measurements carried out with the angular sample holder. Considering the possibility of measuring tapes at fixed angles, without the complexity introduced by an in situ angular movement system [5], different sample holder concepts could have been developed, such as variations in the flat concept at different fixed angles, as introduced by [PERSON] et al. [3]. This design, however, either relies on pressure contacts or needs to take into account the high-temperature de-soldering, removal, and movement of the sample into a new position, or the use of a different sample for every angular measurement. Instead, we designed our clamping design to be able to carry out different measurements in the whole angular range on the same soldered sample without further thermal treatments other than the first one, as previously reported for measurements carried out in liquid nitrogen [10]. This does not come without a price, however: the adoption of the round clamping system brings about uncertainty in the measured angle, which we estimated as \(\pm 5^{\circ}\), and requires repeated heating and cooling runs for different angles. The issues introduced by several cooling and heating cycles are mitigated by the limited helium consumption achieved with the new current probe, and these drawbacks were considered as minor issues when facing the robustness of the set-up; we are sure that differences in the measurement were only due to the angular contribution. In Figure 11, we show the results of the critical current measurements for a SuNAM tape at different angles and fields. It can be observed how the critical current was raised sensibly when approaching the condition with the field parallel to the ab planes, with the effect being much more pronounced at higher fields, where a \(\sim\)7-fold increase is shown between the perpendicular and parallel condition. The N-index, the exponent of the fit of the superconducting transition following the well-known \(\left(\frac{I}{L}\right)^{N}\) formula, was evaluated in the 0.1-1 \(\upmu\)V/cm range, showing similar values for angles in the 0-70\({}^{\circ}\) range and increasing instead at 90\({}^{\circ}\). Figure 12 instead depicts the results of the angular measurements for a Shanghai Technology tape. It is clear how the introduction of APC mitigates the loss of critical current with the field perpendicular to the tape surface with respect to the parallel scenario. Furthermore, the measurement highlights a similar angular behavior to that observed for similar tapes at higher temperatures and lower fields [11], suggesting that the pinning landscape exhibited at high temperatures and low fields is also effective at lower temperatures and higher fields. \(n\)-index values seem to exhibit a decreasing trend when moving from the field perpendicular to the surface to parallel to the ab planes. Figure 10: Field–current curves for a Shanghai Technologies tape at different magnetic fields measured with a flat sample holder. The comparison of the two tapes shown here confirms the consideration we put forth in the first section about the choice of SuNAM tapes for the application of current leads in a liquid helium environment. Despite the low critical current value (around 100 A at maximum fields) with fields perpendicular to the tape, the critical current when the field was parallel to the tape was, in fact, significantly enhanced in the SuNAM sample due to its intrinsic pinning landscape. The current leads, in our design, work with the field always parallel to the surface, granting us a significant theoretical current margin in operating conditions. Qualitatively analyzing this aspect, in fact, if we were to consider the performance of the probe to be limited only by the high-field performance of the eight tapes, we would be limited to an astonishingly high value of 7 kA, well above the acceptable load of the resistive part.