A Bitter electromagnet or Bitter solenoid is a type of electromagnet used in scientific research to create extremely strong magnetic fields. Bitter electromagnets have been used to produce some of the strongest continuous manmade magnetic fields on earth (up to 35 teslas [1] as of 2008).
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Bitter magnets are constructed of circular metal plates and insulating spacers stacked in a helical configuration, rather than coils of wire. This design was invented in 1933 by American physicist Francis Bitter. In his honor the plates are known as Bitter plates. The purpose of the stacked plate design is to withstand the enormous outward mechanical pressure produced by Lorentz forces, which increase with the square of the magnetic field strength. Additionally, water circulates through holes in the plates as a coolant, to carry away the enormous heat created in the plates due to resistive heating by the large currents flowing through them. The heat dissipation also increases with the square of the magnetic field strength.
Despite the drawback of resistive heating, Bitter electromagnets are used where extremely strong fields are required because superconducting electromagnets cannot operate above the field strength at which the magnet materials cease to be superconducting (typically on the order of 10 to 20 teslas, due to flux creep, though theoretical limits are higher).
The strongest continuous manmade magnetic field, 45 T, was produced by a device consisting of a Bitter magnet inside a superconducting magnet.[1]
As of 2011 the National High Magnetic Field Laboratory in Tallahassee, Florida, USA, houses the current world's largest resistive magnet. This system has a maximum output of 36.2 teslas and consists of hundreds of separate Bitter plates. The system consumes 19.6 megawatts of electric power and requires about 139 litres of water pumped through it per second for cooling.[2]. This magnet is mainly used for material science experimentation. For similarly designed examples of bitter coils see the external links below.