Analysis of Nb₃Sn Accelerator Magnet Training

Abstract

Nb3S n accelerator magnet technology has made s i gnificant progress during the past decades. For the first time, it is planned to be used in a real accelerator. A relatively small number of Nb3S n quadrupoles and dipoles will be installed in th e LHC to increase machine luminosity. Although it will prove the possibil ity of using Nb3S n magnets in real machines, many questions of s caling this technology up remain. One of them is related to slow training of Nb3S n magnets compared to the traditional Nb-Ti accele rator magnets. S ince the goal is to operate thousands of Nb3S n magnets in a future post-LHC accelerator, the slow training will affe ct both the practical design margin and the nominal operation fi eld. Consequently, the cost of the project to reach the design field le ve l is also increased. To improve our understanding of slow magnet training the existing Fermilab data from Nb3S n magnet tests we re re-analyzed. A summary of coil training features and correlation s with fabrication parameters observed is presented in this paper.

Improved training in paraffin-wax impregnated Nb3Sn Rutherford cables demonstrated in BOX samples

“…Avoiding extensive training and/or performance degradation has proven to be a difficult challenge for epoxy-resinimpregnated high-field Nb 3 Sn accelerator magnets wound from Rutherford cable [1][2][3][4][5][6]. Several recent magnets with designs ranging from canted-cosine-theta (CCT) [7][8][9][10] to classical cosine-theta [1,11], exhibited severe training that complicates their application on a large scale in future * Author to whom any correspondence should be addressed.…”

MDPCT1 Quench Data and Performance Analysis

“…MDPCT1 training data were previously presented [5] but better understanding of features requires a more complete representation [9]. Short Sample Limits (SSL) for inner coils were extracted earlier and determined to be 10.8 kA / 12.2 kA at 4.5 K / 1.9 K. For outer coils those were 12.0 kA / 13.5 kA at 4.5 K / 1.9 K. Values for each coil pair agreed to within kA.…”

“…Inner coils 82/90 % of their SSL at 1.9/4.5 K with little quenching which is extraordinary for Nb3Sn coils. Earlier Nb3Sn coils showed semi-independent training in magnets [9].…”

Heat Diffusion in High-Cp Nb3Sn Composite Superconducting Wires

“…This includes both high field accelerator magnets developed and tested in the U.S. and abroad [2,3], and superconducting undulator magnets under development for installation in the advanced photon source (APS) storage ring at Argonne National Lab [4,5]. In short models of Nb 3 Sn accelerator magnets, the first quench (i.e., transition from superconducting to normal phase) generally occurs at 60-70% of the short sample limits and more than 20 quenches are required to reach the magnet nominal field [6]. Training duration is expected to further increase for full-scale magnets, since the number of quenches grows with magnet length, as observed for NbTi and Nb 3 Sn accelerators magnets, and in superconducting undulators.…”

“…In short models of Nb3Sn accelerator magnets, the first quench (i.e. transition from superconducting to normal phase) generally occurs at 60-70% of the short sample limits and more than 20 quenches are required to reach the magnet nominal field [6]. In many cases, the number of quenches is proportional to magnet length, and training duration is expected to further increase for full-scale magnets.…”