Electrical Resistance of the Solder Connections for the Consolidation of the LHC Main Interconnection Splices

Abstract

For the consolidation of the LHC 13 kA main interconnection splices, shunts will be soldered onto each of the 10170 splices. The solder alloy selected for this purpose is Sn60Pb40. In this context the electrical resistance of shunt to busbar lap splices has been measured in the temperature range from RT to 20 K. A cryocooler set-up has been adapted such that a test current of 150 A could be injected for accurate resistance measurements in the low nΩ range. To study the influence of the solder bulk resistivity on the overall splice resistance, connections produced with Sn96Ag4 and Sn77.2In20Ag2.8 have been studied as well. The influence of the Sn60Pb40 solder resistance is negligible when measuring the splice resistance in a longitudinal configuration over a length of 6 cm. In a transverse measurement configuration the splice resistance is significantly influenced by the solder. The connections prepared with Sn77.2In20Ag2.8 show significantly higher resistance values, as expected from the relatively high solder resistivity at cryogenic temperatures. The experimental results are complemented by simulations with Comsol multiphysics, showing the contribution of each splice component on the overall splice resistance. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. 3LPA-09

Electromechanical behaviour of REBCO tape lap splices under transverse compressive loading

“…Contact resistances can be neglected [22]. 14 The resistance of soldered Nb-Ti or Nb 3 Sn splices depends significantly on the electrical resistivity of the solder that is used [23]. The solders used in the present study (Sn60Pb40 and Sn96Ag4) have both a relatively low 4.2 K resistivity, and their influence on the overall splice resistance is also comparatively small.…”

“…The solders used in the present study (Sn60Pb40 and Sn96Ag4) have both a relatively low 4.2 K resistivity, and their influence on the overall splice resistance is also comparatively small. As an example, the 4.2 K electrical resistance of soldered Nb-Ti and Nb 3 Sn wire splices is about 20 nΩ.cm higher than that of welded splices [22].…”

Nondestructive Testing and Quality Control of the LHC Main Interconnection Splices

“…It has been shown that the low-temperature stabilizer resistance can be estimated from the RT resistance results [5], [9], [10] when the residual resistivity ratio (RRR) of the splice Cu profiles [11] is known. In case of a complete transverse gap between the Cu splice profiles and the busbar stabilizer, the RT excess resistance is nearly proportional to the defect size, i.e., the length of the busbar cable that is insulated from the busbar stabilizer [5].…”

The Electrical Resistance of Rutherford-Type Superconducting Cable Splices

“…DISCUSSION AND CONCLUSION 168 In the following discussion it is assumed that the influence 169 of the solder resistance on the overall splice resistance can 170 be neglected. This assumption is based on the resistivity re-171 sults obtained for the solder material [13], and on resistance 172 measurements of splices soldered with different solder alloys 173 [14]. The resistance of Nb-Ti/Cu Rutherford-type cables lap 174 Because of the strong field dependence of the critical current 205 density of Nb-Ti and Nb 3 Sn superconductors, there is always a 206 huge margin in terms of critical current density for splices that 207 are outside the high field region of a magnet.…”