Busbar studies for the LHC interaction region quadrupoles

Fermilab (FNAL) and the Japanese high energy physics lab (KEK) are developi ng the superconducting quadrupole magnets for the interaction regions (IR) of the Large Hadron Collider (LHC). These magnets have a nominal field grad ient of 215T/m in a 70mm bore and operate in superfluid helium at 1.9K. The IR magnets are electrically interconnected with superconducting busbars, w hich need to be protected in the event of a quench. Experiments to determin e the most suitable busbar design for the LHC IR magnets and the analysis o f the data are presented. The main purpose of the study was to find a desig n that allows the inclusion of the superconducting busbars in the magnet qu ench protection scheme, thus avoiding additional quench protection circuitr y. A proposed busbar design that was tested in these experiments consists o f a superconducting cable, which is normally used for the inner layer of th e Fermilab IR quadrupoles, soldered to similar Rutherford type cables as a stabilizer. A series of prototypes with varying numbers and types of stabil izers (one or two stabilizers, pure copper or Cu/NbTi composite) were teste d. These samples were characterized with respect to their quench temperatur e profile and their quench propagation velocity during normal zone growth. From these tests, a suitable design has been determined.