Installation and Operation Safety 2
400/54 Premium Shielded NMR Magnet System Product Overview 13
Nature of the Magnetic Field
The greatest hazard presented by a superconducting magnet
is the fringe magnetic field. Once the magnet is energized,
the magnetic field is always present, even when all power to
the system is turned off. This magnetic field extends above,
below and to the sides of the magnet. It extends through
doors, walls ceilings, and floors.
The strength of the magnetic field increases as the magnet is
approached. Objects and people at risk from the magnetic
field are considered safe outside the 5 gauss line.
Occasionally, fault conditions cause magnets to lose their
superconducting properties, which in turn causes their
magnetic fields to collapse. For a magnet that is actively
shielded, before the magnetic field collapses it can
momentarily “bloom” slightly beyond its normal dimensions.
For further details on this subject for any specific magnet,
consult Agilent Technologies.
A magnet that has been de-energized but remains at liquid helium
temperatures still exhibits a small residual magnetic field. Make
measurements of this field, and restrict public access as per national and
state requirements. (See “Magnetic Field Safety Requirements” on
page 15.)
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