Study of Factors Which Affect Training in ISABELLE R&d Magnets

Five R&D dipole magnets have been assembled with different levels of tangential prestress applied to the windings. Four magnets have trained beyond the ISABELLE 5T operating field. Three have trained to the short sample limit of the superconducting braid. The two magnets with the highest level of tangential prestress required the fewest training quenches to reach 5T. The training history of these R&D magnets is better than that of the eleven industrial magnets. Two of the industrial magnets were trained beyond 4.5T; the others reached fields in the range 3.8T to 4.2T. The industrial magnets had generally lower levels of prestress than the R&D magnets and differed in other important respects as well. These changes were designed to reduce the heat generated by conductor motion due to Lorentz forces. Construction of magnets with the present design has eliminated the largest part of the training quenches seen in the industrial series of magnets.