Cold test facility for 1.8 m superconducting model magnets at the SSCL

A new facility has been constructed to measure the characteristic features of superconducting model magnets and cable at cryogenic temperatures--a function which supports the design and development process for building full-scale accelerator magnets. There are multiple systems operating in concert to test the model magnets, namely, cryogenic, magnet power, data acquisition and system control. A typical model magnet test includes the following items: warm measurements of magnet coils, strain gauges and voltage taps; hipot testing of insulation integrity; cooling with liquid nitrogen and then liquid helium; measuring quench current and magnetic field; (5) magnet warm-up. While the magnet is being cooled to 4.22 K, the mechanical stress is monitored through strain gauges. Current is then ramped into the magnet until it reaches some maximum value and the magnet transitions from the superconducting state to the normal state. Normal-zone propagation is monitored using voltage taps on the magnet coils during this process, thus indicating where the transition began. The current ramp is usually repeated until a plateau current is reached, where the magnet has mechanically settled. Many variations on the current ramping sequence are used to study different phenomena associated with magnet performance, e.g. magnetization hysteresis, eddy current losses, cryogenic stability, etc. A warm bore cryostat with a rotating coil is inserted in the magnet to measure field strength and homogeneity. These types of measurements yield multipole and current versus field data