DC field

A magnetic field that does not vary in time, as opposed to an AC field.

Decay

For superconducting magnets, decay refers to the infinitesimally small and slow loss of current and corresponding decrease in magnetic field. The decay rate is more rapid right after a magnet – especially a new magnet – is first ramped up.

Dipole magnet

A magnet with two poles, a north and a south, separated by a gap. As opposed to a multipole or solenoid magnet.

Drift

The gradual loss of an instrument's accuracy. NMR teslameters drift because their time base drifts; this can be easily checked and limited to very low values. Fluxmeters drift during a single measurement because they integrate a constant offset voltage; this is often called baseline drift. Hall magnetometers can drift for many reasons; short-term drift is often caused by temperature fluctuations, and long-term drift by aging of the semiconductor.