USPTO provisional patent application # 63/769,475 titled "Production of Spin-Polarized Molecular Beams via Microwave or Infrared Rotational Excitation"
Creators: name: Rakitzis, T. Peter
name: Diallo, Ahmed
name: Parisi, Jason
name: Kannis, Chrysovalantis
Publisher: name: USPTO
Year: 2025

description: As detailed in the Appendix, disclosed herein is production of spin-polarized molecular beams via microwave or infrared rotational excitation, including a process for nuclear spin polarizing molecules necessary for spin polarized fusion. By way of background, nuclear spin-polarized tritium deuteride (DT) molecules can enhance the cross section of the D-T fusion reaction, and make a fusion reactor more efficient. The disclosed approach can produce highly spin-polarized tritium deuteride (DT) molecules in large quantities, needed for a fusion reactor.

In addition, the disclosed approach can spin polarize other molecules, which may be used to enhance nuclear magnetic resonance signals of these molecules. There may be applications for this in chemistry, biochemistry, and medicine. There are currently no methods that can produce spin-polarized DT in sufficient quantities for a nuclear reactor. Current methods fall short by several orders of magnitude, such as the atomic beam source (ABS), which produces about 1017 spin-polarized H/D/T atoms per second, short of at least 10^21 s^-1 needed for a nuclear reactor. For methods of polarization of small molecules, there are no methods that can produce pure spin-polarized small molecules in macroscopic quantities. Dynamics Nuclear Polarization (DNP) uses the microwave excitation of radicals at low temperatures to polarize small molecules. However, for medical applications, the radicals need to be removed, which is a difficult and costly process.

An important feature of the disclosed approach is that it polarizes small molecules by the IR or microwave excitation of molecular beams, which can be trapped at cold surfaces. Advantages of the disclosed approach include: (1) It can work for non-symmetric hydrogenmolecule isotopes with a weak electric dipole moment (specifically HD, DT, and HT), for which disclosed herein are IR excitation schemes that can highly polarize the nuclear spins; (2) It can spin polarize small molecules directly in a molecular beam via IR or microwave excitation schemes, without the need of radicals (such as needed for DNP).

An exemplary process is as follows:

(1) Production of a molecular beam expansion, with a production rate of up to ~10^23 s^-1, which cools the rotational population to predominantly the lowest molecular rotational state (J = 0).

(2) Circularly polarized microwave or IR beams, transfer ideally 100% of the molecules from the ground state to specific rovibrational states |v J M⟩, from which subsequently the rotational polarization is transferred to the nuclear spin. In some cases, more than one excitation and polarization-transfer step are needed.

(3) After the nuclear spins are polarized, the hyperfine beating can be stopped, when the molecular beam enters a region with a sufficiently large magnetic field.

(4) The polarized molecular beam is finally collected and stored at a cold surface.

The production rate of spin-polarized DT is limited by the photon production rate of the IR laser. Currently commercially available, narrow-band, tunable, IR lasers produce up to about 1020 photons/s (which is a few W). A nuclear reactor will require at least 10-100 times more, and so some laser engineering will be needed to scale up the IR lasers to the 100-1000 W range.

The disclosed approach, being a means of producing improved fusion fuel, will potentially be of interest to any company that is interested in fusion involving H isotopes.

Further description of the disclosed approach is included in the Appendix which is part of the application and is incorporated by reference in its entirety as if fully set forth herein. The Appendix comprises a paper entitled “Production of Spin-Polarized Molecular Beams via Microwave or Infrared Rotational Excitation”. In addition, the references listed in the appended material are also part of the application and are incorporated by reference in their entirety as if fully set forth herein.