Method and apparatus to monitor and provide additional safety during quench at MRI-scanner
Original Publication Date: 2005-Jan-25
Included in the Prior Art Database: 2005-Jan-25
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An MRI-scanner (Magnetic Resonance Imaging) uses strong magnetic fields for producing images of the investigated objects. The required intensity of the magnetic field is excited by an arrangement of superconductive electromagnets. Concerning MRI-scanner, a quench is a sudden loss of superconductivity in the wire of the magnet. The stored magnetic energy turns into heat, causing the liquid helium to boil off very rapidly. A huge volume of helium gas can be released in a few minutes, and the vent pipe of the apparatus has to be able to carry this flow safely. Quenching of superconducting magnet coils can be hazardous. This occurs when (for some reason) the current-carrying coil turns from the superconducting to the normal state, thereby suddenly changing its resistance from zero to a finite value. Then the tremendous dissipation energy (~I2R) generated in the coils vaporizes the liquid helium, creating large internal pressures within the magnet Dewar (the section that holds the liquefied helium coolant) and a large helium gas outflow from the magnet's pressure relief valves.