# US 10,120,044 B2 · Microwave coupler for optimizing a NMR probe head for MAS-DNP > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,120,044 B2 - Document ID: US10120044B2 - Status: Granted - Kind: B2 - Application number: 14/910,706 - Filed: 2014-07-23 - Published: 2016-07-07 - Granted: 2018-11-06 - Earliest claimed: 2013-08-09 - Assignees: Bruker BioSpin GmbH - Applicants: Bruker Biospin GmbH - Inventors: Armin Purea; Frank Engelke; Alexander Krahn - Web page: https://patentgrep.com/patent/US10120044B2 ## CPC - G01R 33/345: of waveguide type (G01R33/343 takes precedence) - G01N 24/08: by using nuclear magnetic resonance (G01N24/12 takes precedence) - G01R 33/282: {Means specially adapted for hyperpolarisation or for hyperpolarised contrast agents, e.g. for the generation of hyperpolarised gases using optical pumping cells, for storing hyperpolarised contrast agents or for the determination of the polarisation of a hyperpolarised contrast agent} - G01R 33/307: {specially adapted for moving the sample relative to the MR system, e.g. spinning mechanisms, flow cells or means for positioning the sample inside a spectrometer} - G01R 33/62: using double resonance (G01R33/24 takes precedence) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract An NMR DNP-MAS probe head (10) has an MAS stator (2) for receiving an MAS rotor (3) having a sample substance in a sample volume (4), and a hollow microwave waveguide (5)′ for feeding microwave radiation through an opening (5a) of the microwave waveguide into the sample volume, an axially expanded rod-shaped microwave coupler (6) located in the opening made of dielectric material, characterized in that the microwave waveguide has a conically tapered hollow transition piece for coupling in an HE 11 mode, into which the microwave coupler projects at an all-round radial distance to the opening of the microwave waveguide. It is thus possible, in a surprisingly simple manner and by means of readily available technical means, to irradiate a considerably higher microwave energy in the HE 11 mode into the NMR measuring sample than by means of the known arrangements. ## Claims ### Claim 1 An NMR (=nuclear magnetic resonance) DNP (=dynamic nuclear polarization)-MAS (=magic angle spinning) probe head for examination of a sample substance in a sample volume, the probe head comprising: an MAS rotor structured for holding the sample substance; an MAS stator structured for receiving said MAS rotor; a hollow microwave waveguide having a conically tapered hollow transition piece structured for coupling in an HE 11 mode of microwave radiation and for passing said microwave radiation through an opening in said microwave waveguide into the sample volume; and an axially extended rod-shaped microwave coupler made of dielectric material and disposed in said opening of said microwave waveguide, wherein said microwave coupler projects into said conically tapered, hollow transition piece and is disposed at an all-round radial distance to said opening of said microwave waveguide. ### Claim 2 (depends on 1) The probe head of claim 1, wherein dimensions of said microwave coupler perpendicular to a rod axis thereof are at least half a wavelength of irradiated microwave radiation in said microwave coupler. ### Claim 3 (depends on 1) The probe head of claim 1, wherein said microwave coupler is structured for a microwave frequency in a range of 100-1000 GHz, with a minimum extent in a rod-shaped region of said microwave coupler being 0.15 mm/√εr-1.5 mm/√εr, wherein εr is a relative permittivity of a material from which said microwave coupler is made. ### Claim 4 (depends on 1) The probe head of claim 1, wherein said microwave coupler has at least one stepped, conical and/or funnel-shaped end section. ### Claim 5 (depends on 1) The probe head of claim 1, wherein said microwave coupler has a cross-sectional profile, which is constant in an axially central region. ### Claim 6 (depends on 1) The probe head of claim 1, wherein microwave coupler has a cross-sectional profile, which is constant in an axially central region said on a radially outer surface thereof in said axially central region. ### Claim 7 (depends on 1) The probe head of claim 1, wherein said microwave waveguide is hollow and has periodic ribbing in an interior thereof. ### Claim 8 (depends on 1) The probe head of claim 1, wherein an axis of said microwave coupler is disposed transversely or perpendicularly to an axis of rotation of said MAS rotor. ### Claim 9 (depends on 1) The probe head of claim 1, wherein an axis of said microwave coupler is disposed essentially parallel with an axis of rotation of said MAS rotor. ### Claim 10 (depends on 9) The probe head of claim 9, wherein an axial end of said microwave coupler facing the sample volume is constituted as a base bearing of said MAS stator and is permanently connected thereto. ### Claim 11 (depends on 10) The probe head of claim 10, wherein dimensions of said microwave coupler perpendicular to a rod axis thereof are at least half a wavelength of irradiated microwave radiation in said microwave coupler except at conical and/or funnel-shaped segments at a beginning and an end of said microwave coupler. ### Claim 12 (depends on 1) The probe head of claim 1, further comprising a mirror structured for reflecting microwave radiation exiting said microwave coupler and penetrating through the sample volume, wherein said mirror is disposed on a side of said MAS stator that is opposite to said microwave coupler. ### Claim 13 (depends on 1) The probe head of claim 1, further comprising at least one spacer made of dielectric material and disposed between said microwave coupler and said microwave waveguide to bridge a distance of at least one quarter of a wavelength of microwave radiation being coupled. ### Claim 14 (depends on 13) The probe head of claim 13, wherein at least one spacer is constituted as a spacer ring or as a multiplicity of spacer rings. ### Claim 15 (depends on 13) The probe head of claim 13, wherein at least one spacer is constituted as a cap plugged onto said microwave waveguide and into which said microwave coupler is integrated. ### Claim 16 (depends on 1) The probe head of claim 1, wherein said microwave coupler is made of non-magnetic dielectric materials with a small loss angle (tan δ<10−3), is made of PTFE or is made of sapphire.