# US 11,079,457 B2 · Microwave resonator for an EPR probehead providing Q-, M- and D-variation using a variable fluid volume > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,079,457 B2 - Document ID: US11079457B2 - Status: Granted - Kind: B2 - Application number: 16/933,222 - Filed: 2020-07-20 - Published: 2021-01-21 - Granted: 2021-08-03 - Earliest claimed: 2019-07-19 - Applicants: Bruker BioSpin GmbH - Inventors: Ion Prisecaru; Peter Höfer - Web page: https://patentgrep.com/patent/US11079457B2 ## CPC - G01R 33/345: of waveguide type (G01R33/343 takes precedence) - G01R 33/60: using electron paramagnetic resonance (G01R33/24, G01R33/62 take precedence) - G01N 24/10: by using electron paramagnetic resonance (G01N24/12 takes precedence) - H01P 7/06: Cavity resonators - 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) - H01P: WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE (operating at optical frequencies G02B) ## Abstract A microwave resonator for an electron paramagnetic resonance probehead comprises a cavity body supporting an electromagnetic microwave resonance mode, at least one sample opening for inserting a sample in a sample container, at least one microwave opening for transmitting microwave radiation into the resonator, and at least one access opening for inserting and removing a modifier in a modifier vessel into or out of the cavity body. The modifier vessel is fixed in the at least one access opening, the modifier is a fluid comprising attenuator fluid and/or marker fluid and/or adaptor fluid, and the modifier vessel has an insert opening for filling and discharging the modifier gradually into or out of the cavity body. This improves performance greatly, enabling a gradual modification of specific experimental conditions without moving any mechanical parts in the cavity body, and without changing other experimental conditions for Q- and/or M- and/or D-variation. ## Claims ### Claim 1 A microwave resonator for an electron paramagnetic resonance (“EPR”) probehead comprising: a cavity body supporting an electromagnetic microwave resonance mode, and comprising at least one sample opening for inserting a sample in a sample container, at least one microwave opening for transmitting microwave radiation into the resonator, and at least one access opening; a modifier vessel fixed in the at least one access opening for containing a modifier fluid comprising at least one of an attenuator fluid that varies a Q-factor of the resonator, a marker fluid for calibrating an EPR signal of the resonator and an adaptor fluid that varies a dielectric loading of the resonator, the modifier vessel being configured for filling and discharging the modifier fluid gradually into or out of the cavity body; and a modifier reservoir outside the cavity body that is connected to the modifier vessel via a first pump. ### Claim 2 (depends on 1) A resonator according to claim 1, wherein the cavity body has two access openings for accommodating an inlet and an outlet of the modifier vessel. ### Claim 3 (depends on 2) A resonator according to claim 2, wherein the two access openings are located symmetrically with respect to a microwave B-field symmetry plane in the cavity body. ### Claim 4 (depends on 1) A resonator according to claim 1, wherein a part of the modifier vessel extending inside the cavity body is spatially fixed to a support fixed to the cavity body. ### Claim 5 (depends on 1) A resonator according to claim 1, wherein the cavity body is a cylindrical TE011 mode cavity and the modifier vessel inside the cavity body is arranged to a minimum extent of 50% of its length along a cylindrical surface centered around an axis of the cylindrical TE011 mode cavity. ### Claim 6 (depends on 1) A resonator according to claim 1 wherein the cavity body is a rectangular TE102 mode cavity or a cylindrical TM110 mode cavity and the modifier vessel traverses the walls of the cavity body and runs partially outside the cavity body. ### Claim 7 (depends on 1) A resonator according to claim 1 wherein the modifier vessel inside the cavity body is arranged to a minimum extent of 50% of its length along isolines of constant electric field E for Q-variation and D-variation or along isolines of constant magnetic field B for M-variation. ### Claim 8 (depends on 1) A resonator according to claim 1 wherein the modifier vessel inside the cavity body is arranged to a minimum extent of 80% of its length along isolines of constant electric field E for Q-variation and D-variation or along isolines of constant magnetic field B for M-variation. ### Claim 9 (depends on 1) A resonator according to claim 1, wherein the modifier vessel is branched to the modifier reservoir via a first valve and to a neutral fluid reservoir via a second valve and a second pump, thereby allowing replacement of the modifier fluid in the cavity body with the neutral fluid, the neutral fluid having no dominant effect on Q-variation and/or M-variation and/or D-variation. ### Claim 10 (depends on 1) A resonator according to claim 1, wherein the resonator comprises at least two modifier vessels, each modifier vessel containing a different type of modifier fluid. ### Claim 11 (depends on 10) A resonator according to claim 10, wherein each modifier vessel is connected to a separate modifier reservoir via a pump allowing for independently filling and discharging each modifier fluid into or out of the cavity body. ### Claim 12 (depends on 1) A resonator according to claim 1, wherein the modifier fluid contains at least two different types of modifier materials. ### Claim 13 (depends on 1) A resonator according to claim 1, wherein the modifier vessel in the cavity body is arranged to a minimum extent of 50% of its length at the maximum of the electric field energy of the microwave mode for Q-variation, at the minimum of the z-component of the magnetic field strength of the microwave mode for D-variation, in a region where the z-component of the magnetic field strength of the microwave mode is not zero for M-variation, whereas the z-axis is defined by the center of the sample opening and the center of the cavity. ### Claim 14 (depends on 1) A resonator according to claim 1 wherein the modifier vessel comprises a dielectric capillary. ### Claim 15 (depends on 1) An EPR spectrometer with a probehead comprising a microwave resonator according to claim 1.