NMR polarization monitoring coils, hyperpolarizers with same, and methods for determining the polarization level of accumulated hyperpolarized noble gases during production

A hyperpolarizer for producing polarized noble gases, comprising:

• an optical pumping cell having a primary body having a non-polarized gas inlet port and a longitudinally extending polarized gas outlet port with an outer surface;
• and
• an NMR rf coil having first and second opposing ends and defining a center aperture therethrough, said NMR rf coil positioned on said outlet port such that a portion of said outlet port extends through said NMR rf coil aperture, said NMR rf coil first end being positioned adjacent said primary body of said optical pumping cell,
• wherein said NMR rf coil is configured such that during operation of said hyperpolarizer said NMR rf coil is able to excite a quantity of polarized gas positioned proximate to said optical cell outlet port.

A hyperpolarizer for producing optically pumped polarized noble gases, comprising:

• an optical pumping cell having a primary body with an unpolarized gas inlet port and a polarized gas outlet port;
• a cryogenic accumulator in fluid communication with said optical pumping cell outlet port, comprising;
• an elongated closed end tube defining a polarized gas collection chamber for holding a quantity of collected polarized gas therein, said gas collection chamber being operably associated with first and second sealable valves, said first valve positioned upstream of said collection chamber to control the flow of gas therein and said second valve positioned downstream of said collection chamber to control the flow of gas thereout;
• a cryogenic bath, wherein said collection chamber is immersed into said cryogenic bath;
• a magnetic field source arranged to provide a magnetic field with a region of homogeneity adjacent said collection chamber in said cryogenic bath;
• a first NMR rf coil positioned in said cryogenic bath adjacent said closed end of said tube in said magnetic field region of homogeneity, wherein said NMR rf coil is configured to have an inductance of about 0.24 mH or less;
• a polarized gas-dispensing outlet in fluid communication with said cryogenic accumulator;
• and
• a polarized gas exit flow path extending from said cryogenic accumulator to a polarized gas dispensing outlet,
• wherein said first NMR rf coil is configured such that during operation of said hyperpolarizer, said first NMR rf coil monitors the level of polarization associated with the collected polarized gas held proximate to the closed end of said elongated tube.

A method of monitoring the polarization level of hyperpolarized noble gas during production thereof, comprising the steps of:

• polarizing a quantity of noble gas in an optical pumping chamber configured to hyperpolarize noble gas via spin-exchange with optically pumped alkali metal vapor;
• directing the polarized noble gas in the optical pumping chamber to a gas flow path;
• providing a magnetic field having a region of homogeneity, the region of homogeneity including at least a volume of space associated with a portion of the optical pumping chamber and the gas collection path proximate to the optical pumping chamber;
• positioning a first NMR rf coil adjacent the gas flow path in the magnetic field region of homogeneity;
• exciting the polarized gas by transmitting an excitation signal to the first NMR rf coil;
• measuring the level of polarization associated with the hyperpolarized gas adjacent the NMR rf coil via NMR polarimetry using the NMR coil to thereby monitor the level of polarization associated with the polarized gas in a region of the polarizer adjacent the polarized gas flow path;
• cryogenically accumulating the polarized gas in a cryogenic accumulator, wherein a portion of said polarized gas is frozen;
• and
• subsequently thawing said frozen polarized gas prior to said dispensing step and after said thawing step;
• wherein during or after said thawing step, a minor portion of the quantity of thawed polarized gas is directed away from a major portion of the hyperpolarized gas into the gas flow path proximate to the NMR coil.