A superconducting magnet includes a liquid helium reservoir (14), superconducting magnet windings (12) disposed in the liquid helium reservoir, and a vacuum jacket (20) surrounding the liquid helium reservoir. A cold head (30) passes through the vacuum jacket. The cold head has a warm end (32) welded to an outer wall (22) of the vacuum jacket and a cold station (46) disposed in the liquid helium reservoir. A heat exchanger (60) is disposed inside the vacuum jacket and secured to or integral with the cold head. The heat exchanger includes a fluid passage (62) having an inlet (64) in fluid communication with the liquid helium reservoir and having an outlet (66) in fluid communication with ambient air. While the cold head is turned off, gas helium flows from the liquid helium reservoir to ambient air via the heat exchanger, thereby cooling the non-operating cold head.

Apparatus for imaging during surgical procedures includes an operating room for the surgical procedure and an MRI for obtaining images periodically through the surgical procedure by moving the magnet up to the table. The magnet wire is formed of a superconducting material such as magnesium di-boride or Niobium-Titanium which is cooled by a vacuum cryocooling system to superconductivity without use of liquid helium. The magnet weighs less than 1 to 2 tonne and has a floor area in the range 15 to 35 sq feet so that it can be carried on the floor by a support system having an air cushion covering the base area of the magnet having side skirts so as to spread the weight over the entire base area. The magnet remains in the room during surgery and is powered off to turn off the magnetic field when in the second position remote from the table.

A system (100) for controlling temperature of a persistent current switch (120) operating in a background magnetic field includes a heat exchanger (138), a loop tube (135), a ball valve (245) and multiple electromagnets (251, 252). The heat exchanger disperses heat to a cryocooler (106). The loop tube enables flow of coolant to convectively transfer thermal energy generated by the persistent current switch to the heat exchanger. The ball valve is integrated with the loop tube between the persistent current switch and the heat exchanger, and contains a ferromagnetic ball (250). The electromagnets are positioned outside the loop tube adjacent to the ball valve, where energizing a first electromagnet of the multiple electromagnets magnetically moves the ferromagnetic ball to a first position opening the loop tube and enabling the flow of the coolant, and energizing a second electromagnets magnetically moves the ferromagnetic ball to a second position closing the loop tube and blocking the flow of the coolant.

A temperature-control system for an NMR magnet system. A permanent magnet arrangement (1) with a central air gap (2) generates a homogeneous static magnetic field inside the air gap. A probehead (3) transmits RF pulses and receives RF signals from a test sample (0). An H0 coil changes the amplitude of the static magnetic field. A shim system (4) in the air gap further homogenizes the magnetic field. A first insulation chamber (5) surrounds and thermally shields the permanent magnet arrangement and includes an arrangement (6) controlling a temperature Ti of the first insulation chamber. The shim system, the H0 coil and the NMR probehead are arranged outside the first insulation chamber in the air gap. A heat-conducting body (7) is arranged between the shim system and the H0 coil on one side and the permanent magnet arrangement on the other, thereby enhancing field stability and suppressing drift.

A magnetic resonance system may include a magnetic resonance magnet and a storage container configured to accommodate the magnetic resonance magnet. The storage container may also contain an endothermic liquid. The magnetic resonance system may further include a ramping-down device configured to trigger releasing electric energy by the magnetic resonance magnet. The first ramping-down device may include an electric energy consumption device configured to consume at least a portion of the released electric energy by the magnetic resonance magnet.

In a magnet system: —a superconducting main field magnet (7) generates a magnetic field in a first sample volume (16), —a superconducting additional field magnet (22) generates another field in a second sample volume (24), —a cryostat (2) has a cooled main coil container (6), an evacuated RT (room temperature) covering (4), and an RT bore (14) which extends through the main and the additional field magnets, and —a cooled additional coil container (21) in a vacuum. The RT covering has a flange connection (17) with an opening (19) through which the RT bore extends, a front end of the additional coil container protrudes through the opening into the RT covering such that the additional field magnet also protrudes through the opening into the RT covering, and a closure structure (20) seals the RT covering between the flange connection and the RT bore.

A cryocooler includes a second-stage cooling stage, a second cylinder which includes the second-stage cooling stage on a terminal of the second-stage cylinder, a second-stage displacer which includes a magnetic regenerator material and is accommodated in the second-stage cylinder so as to be able to reciprocate in the second-stage cylinder, and a tubular magnetic shield which is installed on the second-stage cooling stage and extends along the second-stage cylinder outside the second-stage cylinder. The magnetic shield is formed of a normal conductor and a product of an electrical conductivity in a temperature range of 10 K (Kelvin) or less and a thickness of the tubular magnetic shield is 60 MS (Mega-Siemens) to 1980 MS.

Techniques are provided for controlling a ramping process of a superconducting magnet of a magnetic resonance imaging device comprising the steps of: acquiring an information indicating a status of a cryocooler configured for cooling of the superconducting magnet via an interface, acquiring an information on a parameter of the superconducting magnet via an interface, determining an operational status of the magnetic resonance imaging device in dependence of the information indicating the status of the cryocooler and/or the information on the parameter of the superconducting magnet via a processing unit and providing a control signal via a control unit, wherein the control signal is configured to control the ramping process of the superconducting magnet. The disclosure also relates to a magnetic resonance imaging system comprising a control unit configured to provide a control signal for controlling the ramping process of the superconducting magnet.

A magnetic resonance (MR) apparatus comprises magnet means for generating a main magnetic field in a sample region, encoding means for generating encoding magnetic fields superimposed to the main magnetic field, RF transmitter means for generating MR radiofrequency fields, driver means for operating said encoding means and RF transmitter means to generate superimposed time dependent encoding fields and radiofrequency fields according to an MR sequence for forming images or spectra; and acquisition means for acquiring an MR signal from said object. The magnet means comprise a primary magnetic field source providing a static magnetic field B.sub.0 and at least one secondary magnetic field source providing an adjustable magnetic field B′. To provide improved shimming, the secondary magnetic field source comprises at least two spatially distinct portions of a first magnetic material and of a second magnetic material, respectively, said first magnetic material having a first magnetic moment density m1 and said second magnetic material having a second magnetic moment density m2, and means for independently adjusting said second magnetic moment density m2 by variation of an external control parameter.

According to one embodiment, a magnetic resonance imaging apparatus includes processing circuitry. The processing circuitry calculates a limit imaging condition based on one or more imaging parameters for determining an imaging condition, the limit imaging condition being an allowable limit relating to heat input to a superconducting magnet. The processing circuitry limits an input range of an imaging parameter input by an operator based on the limit imaging condition.