Image Number 7 for United States Patent #4187445.
A solenoidal electric field lamp comprises a plurality of toroidal ferrite cores connected to a radio frequency energy source and disposed in an ionizable gas. The cores are so connected and oriented that circulating discharge currents passing through each core produce magnetic dipole fields which tend to cancel one another. Near and far field electromagnetic interference is thus reduced even when the lamp is operated at higher, more efficient frequencies. The cores are disposed in a variety of configurations.