Zero Magnetic Field From a Superconducting Balloon

William Fairbank, William Hamilton and their collaborators at Stanford University are building an apparatus to produce a truly zero magnetic field. Since magnetic flux trapped in the hole in a superconducting cylinder is quantized, the Fairbank group expects to produce zero field inside a hollow superconducting shield by cooling the shield through its transition temperature in a field so small that the total flux passing through the shield is less than half a flux unit (less than $2×10−7 gauss cm2$⁠). With the apparatus they plan to look for an electric dipole moment in $He3$ to see if time‐reversal invariance is violated.