Patent ID: 6147844
Filing Date: 2000-11-14
Classification: G01R,H02H,Y02E

Abstract:
A superconducting main magnet coil quench protection for a magnetic resonance imager magnet assembly comprising:a cryogen pressure vessel surrounding a central imaging bore;a plurality of spatially separated superconducting main magnet coil portions connected in series forming a main coil series circuit in said cryogen vessel and surrounding said imaging bore to provide a magnetic field in said imaging bore;a liquid cryogen in said cryogen vessel which produces cryogen gas in cooling said coil portions to superconducting temperatures;a first temperature limiting circuit electrically connected in parallel with each main magnet coil portion to limit the temperature rise of each of said magnet coil portions upon the start of quenching of superconducting operation of any one of said magnet coil portions;each of said first temperature limiting circuits including a quench heater circuit with a plurality of quench heaters connected in parallel for all of the parallel quench heaters to be simultaneously energized upon quenching action of the main magnet coil portion they are in parallel with; anddifferent of said parallel quench heaters of each temperature limiting circuit positioned in thermal contact with different of said separated main magnet coil portions being protected to raise the temperature of all of said separated main magnet coil portions being protected and to simultaneously begin quenching the superconducting operation of all of such different main magnet coil portions upon the quenching action of said one or more main magnet coil portions through the simultaneous heating of all of said main magnet coil portions upon quenching of any of said main magnet coil portions;the number of said quench heaters connected across each of said separated main magnet coil portions being at least equal to the number of said main magnet coil portions being protected;said main coil series circuit distributing the energy and heat within said magnetic field upon said start of quenching of said any one of said main magnet coil portions to avoid the development of a hot spot in said any one of said main magnet coil portions.