Minimum quench energies of Rutherford cables and single wires

The stability of magnet conductors may be characterized by their minimum quench energy (MQE), i.e. the minimum energy pulse (of small extent and short duration) needed to trigger a quench, Using small graphite paste and epoxy heaters, we have measured the MQE on a broad range of single wires and Rutherford cables as a function of current, field, temperature and pulse duration. Surface heat transfer to the helium plays an important role. For the cables, we find that specially processed 'porous-metal' cables have by far the highest degree of stability. Measurements are compared with theory.