Sample heating by electron magnetic resonance

Abstract

In its overall form, the electron magnetic resonance spectrometer includes a resonator located in a cryogenic environment within a main magnetic field. A sample holder in the cryogenic environment is held at a distance from the resonator. The sample holder includes a sample container. A sample heating device is positioned so that the sample container is thermally coupled to the sample heating device, and the sample heating device controls the temperature of the sample to a temperature range higher than the operating temperature of the resonator.

Description

[Technical Field]

[0001] (Related applications) This application claims priority to U.S. Provisional Patent Application No. 63 / 492,084, “Electron Paramagnetic Resonance (EPR) Sample Heating,” filed on 24 March 2023, which incorporates its disclosures by reference. [Background technology]

[0002] The following explanation concerns sample heating in an electron magnetic resonance system.

[0003] Electron magnetic resonance (EMR) systems are used to study various types of samples and phenomena. The resonator manipulates spins in a sample by generating a magnetic field at or near the spin resonance frequency. In some cases, the resonator detects spins based on the voltage induced by the precessing spins. [Brief explanation of the drawing]

[0004] [Figure 1A] This is a schematic diagram illustrating an exemplary electron magnetic resonance system. [Figure 1B] This is a block diagram showing an example of an electron magnetic resonance system with a sample heater. [Figure 2] This is a top view showing an exemplary sample holder used in an electron magnetic resonance system, and it shows the sample heater and resonator. [Figure 3] This is a perspective view showing an exemplary sample heater equipped with a sample holder and tapered filaments, indicating its placement on a resonator. [Figure 4] This is a perspective view showing an exemplary sample heater having a sample holder and a lateral meandering filament, and it is shown to be placed on a resonator. [Figure 5] Exemplary tapered heating filaments and exemplary lateral meandering heating filaments are shown. [Figure 6A]This is a plan view showing an example of a longitudinally meandering filament railway track. [Figure 6B] This is a plan view showing an example of a lateral meandering filament railway track. [Figure 6C] This is a plan view of an exemplary sample heater having an array of tapered filaments. [Figure 7A] This is a cross-sectional view of an exemplary resonator package. [Figure 7B] This is a cross-sectional view of an exemplary resonator package with an independent sample holder cover. [Figure 8A] This is a perspective view of an exemplary spiral sample heater used with a prismatic sample holder. [Figure 8B] This is a perspective view of an exemplary spiral sample heater used with a tubular sample holder. [Figure 9] This is a perspective view of an exemplary sample holder showing a sample heater and a resonator. [Figure 10] This is a perspective view of an exemplary sample holder showing exemplary electrical connections of a sample heater. [Figure 11] This is a plot of an electromagnetic simulation showing the behavior of an exemplary resonator in the presence of an exemplary sample heater. [Figure 12] This is an electromagnetic simulation showing the current density inside an exemplary sample heater. [Figure 13] This is a plot of the temperature profile along a line perpendicular to the sample holder, plotted against the current flowing through an exemplary sample heater. [Figure 14] This plot shows the relationship between the rise in sample temperature and the current flowing through a sample heater when the lateral position of the sample heater is changed. [Figure 15] This is a temperature field overlay on the bottom surface of the sample holder. [Figure 16] This is an example of a temperature field overlay in a sample container. [Figure 17] This is a flowchart illustrating an exemplary process for heating a sample. [Modes for carrying out the invention]

[0005] In some of the described aspects, the electron magnetic resonance system includes a sample heater that can be used to raise the temperature of an electron magnetic resonance sample above the operating temperature of the resonator. In some cases, the sample and the resonator are configured to interact with each other in a cryogenic operating environment with the sample thermally insulated from the resonator, so that during operation, the sample and the resonator are maintained at different temperatures. The resonator is maintained at a lower temperature (e.g., to reduce or suppress thermal noise, to maintain the superconducting state of the resonator, or for other purposes), and the sample is maintained at a higher temperature (e.g., to reduce the thermal relaxation rate of the sample, to maintain the liquid state of the sample, or for other purposes).

[0006] The sample heater can include a heating filament electrically connected to a power supply line (e.g., a first power supply line and a second power supply line). The heating filament and the power supply line can be formed on a heating substrate. In other configurations, the heating filament and the power supply line can be spaced apart from the sample holder. The heating substrate can be disposed on the sample holder together with the heating filament and the power supply line. In some cases, the heating substrate also functions to seal the sample container of the sample holder. In an embodiment where the sample holder includes one or more capillary tubes, the heating substrate can be omitted. The sample heater can include additional components that operate to heat an electron magnetic resonance sample to a temperature higher than the operating temperature of the resonator. For example, the sample heating system can include a temperature controller, a temperature sensor, or a combination of these and other components. In some cases, the sample heater is disposed within a control environment near the resonator within the main magnetic field of the electron magnetic resonance system.

[0007] In some implementations, the resonator operates at cryogenic temperatures, and a sample heater can raise the temperature of the electron magnetic resonance sample above the resonator temperature. For example, in certain electron paramagnetic resonance (EPR) systems, the resonator is a microwave resonator operating below the critical temperature of the superconducting material, and during operation, the sample can be held above the critical temperature. The sample holder and sample heater can be thermally insulated from the resonator. In some cases, thermal insulation is provided by a vacuum or partial vacuum environment of the cryogenic system, for example, with a pressure of about 500 mTorr or less. In some cases, a solid or fluid insulating material can be placed between the sample holder and the resonator. In some cases, the insulating material can be a material with low thermal conductivity, such as aerogel, Teflon, glass fiber, or other insulating material. In systems operating at cryogenic temperatures, the resonator temperature can be controlled to a predetermined operating temperature, but the temperature of the electron magnetic resonance sample can be raised to a predetermined sample temperature higher than the resonator operating temperature using a sample heater. This can improve the performance of the electron magnetic resonance system, along with other advantages.

[0008] Embodiments of systems and techniques described herein can be implemented in various types of electron magnetic resonance (EMR) systems. For example, a sample heater can be implemented in an electron spin resonance (ESR) or electron paramagnetic resonance (EPR) system, or in any other EMR system. As another example, all or part of the heater device can be placed in a probe of the EMR system, or the sample heater can be placed in a probeless EMR system. In some cases, the sample heater can be adapted to heat liquid samples, solid samples, liquid crystal samples, spin-labeled protein samples, other biological samples (such as blood samples, urine samples, saliva samples, etc.), or other types of samples measured or analyzed in the EMR system. As yet another example, the sample heater can be placed with a resonator operating in a cryogenic environment (e.g., 77K, 4K, 300 millikelvin, 10 millikelvin, or other cryogenic temperatures below 273K). In various embodiments, the sample holder and resonator are placed in a partial vacuum environment with a pressure of, for example, about 500 mTorr or less. The resonator can be, for example, a planar microstrip, a three-dimensional cavity, a coil, a coplanar waveguide, or other types of resonators for an electron magnetic resonance system. In addition, the resonator can be, for example, a rectangular cavity resonator, a cylindrical cavity resonator, a dielectric resonator, a loop-gap resonator, or some kind of lumped-element element resonator.

[0009] In some cases, the systems and techniques presented herein can be implemented in combination with various cryogenic systems, including, for example, small closed-cycle systems, open-cycle systems, and liquid cryogenic systems. In some cases, the systems and techniques presented herein can be implemented in combination with various probes, including, for example, small probe designs, which enable the use of low-noise cryogenic receiving amplifiers in various configurations without interfering with sample exchange methods. In some cases, the systems and techniques presented herein can be implemented in connection with continuous-wave (CW) magnetic resonance (e.g., using CW spectroscopy), pulsed magnetic resonance (e.g., using pulsed spectroscopy), or combinations thereof with other MR modes.

[0010] In some implementations, the systems and techniques described herein can offer technical advantages and improvements over existing techniques. Operating electron magnetic resonance (EMR) systems in low-temperature environments offers several advantages in improving the quality of EMR measurements. Firstly, in some cases, low temperatures reduce the thermal noise contribution from electrical and microwave components, keeping them at cryogenic temperatures and enabling high signal-to-noise ratios and sensitivities in the EMR system. Secondly, in some cases, low-temperature environments allow for the excitation of a sample's spin ensemble using a superconducting resonator and measurement of the electromagnetic signal generated by the response to the excitation. The ultra-low losses of the superconducting resonator are reflected in a high quality factor (Q-factor), which significantly impacts the interaction between spin and the resonator, and is useful in several applications. Finally, at cryogenic temperatures, the polarization of the spin system (the relative difference in spin distribution at energy levels) increases significantly, enhancing the EMR signal. However, it is important to note that EMR samples are typically solid at low temperatures, and testing liquid samples or analyzing samples with free spins is not possible. Generally, liquid samples often freeze and crystallize at extremely low temperatures, and therefore do not accurately reflect their normal state.

[0011] On the other hand, the relaxation times T1 and T2 (or the phase memory decay time T instead of T2) of the electron magnetic resonance sample m Some parameters, such as ), are temperature-dependent, which can negatively impact electron magnetic resonance measurements at low temperatures. More specifically, the spin-lattice relaxation process represented by T1 is more temperature-dependent than T2 in most electron magnetic resonance samples because it is susceptible to the influence of lattice motion and phonon dynamics. Generally, T1 lengthens at low temperatures, and the saturation factor in continuous-wave (CW) magnetic resonance is affected. Decreases JPEG2026511187000002.jpg10170. If s is less than 1, the amplitude of the CW magnetic resonance signal decreases, and the signal spread is reduced. It can be observed as JPEG2026511187000003.jpg9156, making CW measurements more difficult.

[0012] In pulsed magnetic resonance spectroscopy, T1 is the initial thermal equilibrium state of spin magnetization. Characterizing the time scale back to JPEG2026511187000004.jpg6170. This process, Given as JPEG2026511187000005.jpg11170, here JPEG2026511187000006.jpg6170 shows the longitudinal magnetization immediately after the RF pulse. Therefore, nuclides with long T1 values ​​at low temperatures recover slowly, and long repetition times are required to average signals exceeding 5T1.

[0013] Therefore, in some cases, improvements can be achieved by keeping the resonator at a low temperature to obtain optimal sensitivity and noise suppression, while significantly increasing the temperature of the electron magnetic resonance sample. This configuration shortens the T1 time, reduces thermal noise, and enables the use of low-noise cryogenic electronic equipment. It also leads to enhancement of the continuous-wave (CW) spin signal, improving the overall efficiency of the electron magnetic resonance measurement and enabling rapid signal averaging.

[0014] The systems and techniques described herein can be adapted to various types of applications. For example, the systems and techniques described herein can be used for structural biology measurements, such as measuring the structural properties of proteins or protein complexes in biological samples (e.g., blood samples, urine samples, or other types of biological samples). Such measurements are useful in clinical applications (diagnosis, therapy, drug discovery / development, and elucidation of the structure and function of membrane proteins, etc.) or other applications.

[0015] Figure 1A is a schematic diagram showing an exemplary electron magnetic resonance system 100. In various embodiments, the electron magnetic resonance system 100 can be used, for example, for electron spin resonance (ESR) or electron paramagnetic resonance (EPR) spectroscopy, electron magnetic resonance imaging (EMRI), or other applications. The electron magnetic resonance system 100 includes a sample holder 102, which holds a sample that is thermally coupled to a sample heater 104 that heats the sample. In various embodiments, the sample holder 102 is made of a material that has good dielectric properties (e.g., low loss tangent) and is suitable for cryogenic temperatures. In various embodiments, the sample holder 102 can be made of, for example, quartz, sapphire, borosilicate glass, polystyrene, or other similar materials. In the embodiment shown in Figure 1A, the sample holder 102 is coupled to the first end of a sample transfer device 106 via a mounting mechanism 108. The sample transfer device 106 can move the sample holder 102 and position it relative to the resonator 110 in the main magnetic field of the electron magnetic resonance system 100. In various implementations, the resonator 110 can be housed in a resonator housing or other types of resonator packages.

[0016] In the embodiment shown in Figure 1A, the sample heater 104 is electrically connected to the temperature controller 105. In various embodiments, the temperature controller 105 can be an open-loop (non-feedback) controller or a closed-loop (feedback) controller. In embodiments where the temperature controller 105 is an open-loop controller, the temperature controller 105 can supply a current to the sample heater 104 that is associated with a desired temperature of the sample heater 104. In embodiments where the temperature controller 105 is a closed-loop controller, the temperature controller 105 can receive feedback information indicating, for example, the temperature of the sample heater, the relaxation times (T1 and T2) of the electron magnetic resonance sample, other parameters, or a combination thereof. In various embodiments, in embodiments employing closed-loop temperature control, other devices such as temperature sensors can be used in combination with the temperature controller 105. In various embodiments, the current supplied by the temperature controller 105 to the sample heater 104 can be direct current (DC), alternating current (AC), a sequence of current pulses, a periodic waveform such as a square wave, sawtooth wave, or triangular wave, or other types of current.

[0017] In the embodiment shown in Figure 1A, the second end of the sample transfer device 106 is coupled to an actuator 112. When operating, the actuator 112 can cause the sample transfer device 106 to move, and in various embodiments, it can be, for example, a single-degree-of-freedom linear actuator that moves the sample transfer device 106 linearly along its axis. Examples of single-degree-of-freedom linear actuators include, for example, mechanical linear actuators, electromechanical linear actuators, linear motors, piezoelectric actuators, twisted-coil polymer (TCP) actuators, hydraulic actuators, pneumatic actuators, or other types of linear actuators. The actuator 112 is coupled to a position control system 115 that controls its operation. In various embodiments, the position control system 115 can be, for example, an automated control system such as a CNC control system, a PID control system, or other types of controllers. In some cases, the position control system 115 includes, or can be implemented as, software or firmware running on a computer system (e.g., a microprocessor or other type of data processing device). In some cases, the control mechanism can be a manual control, such as a caliper, micrometer, or hand crank. This can be further enhanced by incorporating a laser indicator.

[0018] In the embodiment shown in Figure 1A, the resonator 110 and sample holder 102 are located within a controlled environment cooled by a cooling system 114, while the second end of the sample transfer device 106 is located outside the controlled environment. The sample transfer device 106 is introduced into the cooling system 114 through an insertion point 113. In various embodiments, the insertion point 113 may be or include a valve, a load lock system, or other type of component that provides environmental isolation. For example, in various embodiments, the insertion point 113 may provide a vacuum pressure environment or a low-pressure gas seal between the controlled environment in the cooling system 114 and the room temperature environment. In various embodiments, the vacuum pressure environment may be millitoll pressure. In various embodiments, the cooling system 114 maintains a cryogenic thermal environment for the resonator 110 and sample holder 102. In some cases, the cooling system 114 may maintain the cryogenic temperatures of the resonator 110 and sample holder 102. In the embodiment shown in Figure 1A, the cooling system 114 is in thermal contact with the resonator 110 and the sample holder 102. In some cases, the cooling system 114 cools to liquid helium temperature (e.g., about 4 Kelvin), liquid nitrogen temperature (e.g., about 77 Kelvin), or other cryogenic temperatures. In some cases, the cooling system 114 includes a cryostat that does not use cryogenic agents ("dry"). In some cases, the cooling system 114 can be implemented with or without liquid cryogenic agents, for example, as a continuous-flow helium or nitrogen cryostat (e.g., 4–300 Kelvin), a variable-temperature pulsed-tube refrigerator (e.g., 3.5–300 Kelvin), a pump-type helium cryostat (e.g., 1–10 Kelvin), a helium-3 refrigerator (e.g., 250–400 millikelvin), a dilution refrigerator (e.g., 5–100 millikelvin), or as another type of system or combination of systems. Both the resonator 110 and the sample holder 102 are maintained at cryogenic temperatures. In some cases, the resonator 110 and the sample holder 102 can be immersed in a cryogenic liquid or cryogenic gas and maintained in a vacuum or partial vacuum environment during operation. In various implementations, the sample holder 102 and the resonator 110 are placed in a partial vacuum environment, for example, below about 500 mTorr.In some cases, the sample holder 102, the resonator 110, or both are maintained at a higher temperature (e.g., room temperature).

[0019] In the embodiment shown in Figure 1A, the main magnet system 116 generates the main magnetic field, and when operating, the resonator 110 and sample holder 102 are exposed to this main magnetic field. In various embodiments, the main magnet system 116 may be located inside or outside the cooling system 114. The main magnet system 116 generates the magnetic field within the controlled environment of the resonator 110 and sample holder 102. The exemplary main magnet system 116 shown in Figure 1A can be implemented as a superconducting solenoid, electromagnet, permanent magnet, or other type of magnet that generates the main magnetic field. In various embodiments, the magnetic field is uniform across the entire volume of the sample area defined by the resonator 110. In various embodiments, the sample area is the area that provides a desired filling factor for a particular application. In some cases, a gradient system generates one or more spatially varying gradient magnetic fields over the sample volume. In some cases, the gradient system includes a number of independent gradient coils that can generate gradient magnetic fields that vary along various spatial dimensions of the sample area.

[0020] In the embodiment shown in Figure 1A, a spin ensemble within the sample region of the resonator 110 interacts with the resonator 110. The principal magnetic field generated by the principal magnet system 116 quantizes the spin states and sets the Larmor frequency of the spin ensemble. Control of spin magnetization can be achieved, for example, by a high-frequency or microwave magnetic field generated by the resonator 110. In the embodiment shown in Figure 1A, the spin ensemble can be any collection of particles with non-zero spin that magnetically interact with the applied magnetic field of the electron magnetic resonance system 100. For example, the spin ensemble can include electron spins, or a combination of nuclear spins and electron spins. Examples of nuclear spins include hydrogen nuclei (1H) and carbon-13 nuclei (13C). In some implementations (e.g., electron paramagnetic resonance (EPR) systems), the spin ensemble is an identical spin 1 / 2 free electron spin ensemble added to an ensemble of macromolecules.

[0021] In the embodiment shown in Figure 1A, the resonator 110 is electromagnetically coupled to the spectrometer system 118. In various embodiments, the spectrometer system 118 acquires electron magnetic resonance data based on the electron magnetic resonance signal generated by the interaction between the resonator 110 and the electron magnetic resonance sample housed in the sample holder 102. Typically, the resonator 110 has one or more resonance frequencies, and may have other resonance frequencies or modes.

[0022] An exemplary spectrometer system 118 can control the resonator 110 and other components or subsystems of the electron magnetic resonance system 100 shown in Figure 1A. The spectrometer system 118 is electromagnetically coupled to the resonator 110 (e.g., by a coaxial cable, waveguide, etc.). For example, the spectrometer system 118 can be configured to supply a voltage or current signal to drive the resonator 110, and the spectrometer system 118 can also acquire a voltage or current signal from the resonator 110.

[0023] In some cases, the spectrometer system 118 includes or is connected to a controller, waveform generator, amplifier, transmit / receive switch, receiver, signal processing device, and possibly other components. The spectrometer system 118 may include additional or different features (e.g., a gradient waveform generator, gradient electronics, etc.). In the embodiment shown in Figure 1A, the spectrometer system 118 can be electromagnetically coupled to one or more external sources (e.g., a computer system or other sources) and operate based on inputs supplied by those sources.

[0024] In some operating modes, a control signal is generated by the spectrometer system 118 and sent to the resonator 110. In some cases, the control signal can be filtered, amplified, or processed before being sent to the resonator 110. In some cases, the control signal causes the resonator 110 to generate one or more control fields in the sample region of the resonator 110. For example, the resonator 110 receives the control signal and generates a high-frequency or microwave-frequency control field (e.g., a driving field) in response to the received magnetic resonance control signal. The driving frequency of the control field can be adjusted to the resonance frequency of the spin, which is determined by the strength of the main field and the gyromagnetic ratio of the spin. In some operating modes, the electron magnetic resonance signal (e.g., electron spin signal) is received from the resonator 110 and processed by the spectrometer 118 (e.g., amplified, filtered, down-converted, etc.). In some cases, the electron magnetic resonance signal is processed, for example, to analyze the properties of the sample.

[0025] In some cases, the spectrometer system 118 can operate in multiple operating modes. In one operating mode, the spectrometer system 118 generates control signals (e.g., high-frequency signals, microwave signals, etc.), which are supplied to the resonator 110 to control the spin system of the sample. In another operating mode, the spectrometer system 118 acquires an electron magnetic resonance signal from the resonator 110. The electron magnetic resonance signal can be processed (e.g., digitally converted) and supplied to a computer system for analysis, display, storage, or other actions. The computer system may include one or more digital electronic control units, microprocessors, or other types of data processing devices. The computer system may include memory, a processor, and may operate as a general-purpose computer, or it may operate as an application-specific device.

[0026] Figure 1B is a block diagram showing an electron magnetic resonance system 150 having an exemplary sample heater 152. The sample heater 152 is thermally coupled to a sample 154. This thermal coupling is indicated by arrow 156 in Figure 1B. In various embodiments, the sample heater 152 may be, for example, the sample heater 104 shown in Figure 1A. The sample 154 may be housed in a sample holder, such as the sample holder 102 shown in Figure 1A. In various embodiments, the sample holder may have a prismatic shape. In such embodiments, the sample holder may include a cover that closes the sample holder. In some embodiments, the sample heater 152 may be coupled to the cover. In other embodiments, the sample heater 152 may be positioned at a distance from the sample holder. In yet another embodiment, the sample holder may include, for example, one or more capillary tubes, or other devices suitable for housing the sample 154. When in use, the sample 154 is placed in the sample area of ​​the resonator 160. In various embodiments, the sample region is a region that provides a desired packing density for a particular application. The resonator 160 can be, for example, the resonator 110 shown in Figure 1A or another type of resonator. The resonator 160 interacts with the sample 154 by electromagnetic coupling. Such electromagnetic coupling is schematically indicated by arrow 162. An insulating material 158 is placed between the sample 154 and the resonator 160. In various embodiments, the insulating material 158 can be, for example, a partial vacuum with a pressure of about 500 mTorr or less. In other embodiments, the insulating material 158 can be, for example, aerogel, fiberglass, or other solid or fluid insulating material. During operation, the sample 154 and the resonator 160 are placed in an cryogenic environment. The sample heater 152 functions to raise the temperature of the sample 154 to a desired temperature higher than the temperature of the resonator 160. The thermal insulation material 158 limits the thermal interaction between the resonator 160 and the sample heater 152, preventing the intrusion of thermal noise into the resonator 160 or other performance degradation caused by undesirable temperature rises.

[0027] Figure 2 is a top view showing an exemplary sample holder 200 used in an electron magnetic resonance system. Figure 2 shows an exemplary sample heater 206 and resonator 204. In various embodiments, the sample holder 102 in Figure 1A can be implemented as the sample holder 200 shown in Figure 2. Similarly, the sample heater 206 and resonator 204 in Figure 2 can be, for example, the sample heater 104 and resonator 110 described with respect to Figure 1A. In various embodiments, the sample holder 200 has a sample container 202 formed therein. In various embodiments, the sample container 202 can be, for example, a void formed within the sample holder 200. In other embodiments, the sample container 202 can include a plurality of microcapillaries or other structures capable of holding a sample. In yet another embodiment, the sample container 202 can be an array of sample containers spaced apart along the length of the sample holder 200. When in use, the sample container 202 is placed in the sample area of ​​the resonator 204. Exemplarily, the resonator 204 is shown as a planar microstrip line resonator, but in other embodiments, other types of resonators may be used, such as a three-dimensional cavity, a coil, a coplanar waveguide (CPW), or other types of resonators for electromagnetic resonance systems.

[0028] The sample heater 206 is positioned above the sample holder 200, and the sample container 202 is thermally coupled to the sample heater 206. The sample heater includes a first feed line 208, a second feed line 210, and a heating filament 212 electrically connected to the first feed line 208 and the second feed line 210. When in operation, the first feed line 208 and the second feed line 210 are electrically connected to a temperature controller 105, which supplies current to the heating filament 212.

[0029] The heating filament 212 converts electrical energy into thermal energy. In various embodiments, some type of current, such as DC, AC, pulse train, square wave, triangular wave, sawtooth wave, or other periodic waveform, flows through the heating filament 212 via the first feed line 208 and the second feed line 210, generating heat due to the electrical resistance of the heating filament 212. In various embodiments, the heating filament 212 can be made of a high-resistance metal or ceramic, such as tungsten, molybdenum, nichrome, or Kanthal. The current is supplied to the heating filament 212 by the temperature controller 105 and transmitted to the heating filament 212 through the first feed line 208 and the second feed line 210. To reduce overall circuit losses, the first feed line 208 and the second feed line 210 can be made of a highly conductive material, such as copper or gold.

[0030] Figure 3 is a perspective view showing an exemplary sample holder 200 and an exemplary sample heater 206 with tapered filaments, the sample heater 206 being positioned on a resonator 204. In various embodiments, the heating filaments 302 can be designed in straight lines, tapered lines, meandering lines, and other patterns, as shown in Figure 3-6B, and can be a single unit or an array of filament unit cells, as shown in Figure 6C. Exemplarily, Figure 3 shows a heating filament 302 having a tapered geometry. Figure 4 shows another exemplary heating filament 402 arranged in a transverse meandering line pattern. Figure 5 shows details of heating filaments 302 and 402 side by side for comparison. The heating filament 302 shown in Figure 3 includes ends 304 electrically coupled to a first feed line 208 and a second feed line 210. The central portion 306 has a narrower width than the ends 304, thereby increasing the electrical resistance and heat generated in the region of the central portion 306. The heating filament 402 shown in Figure 4 includes parallel segments 404, which are sequentially joined at opposite ends by orthogonal connecting segments 406, thereby giving the heating filament 402 a meandering shape. Such a shape increases the overall length of the heating filament 402, increasing its electrical resistance and heat generation.

[0031] In one embodiment, if the heating filament 212 has a length, width, and thickness of 0.8 mm, 0.05 mm, and 0.001 mm, respectively, and is made of molybdenum with conductivity σ = 1.76 × 10⁷ S / m, the resistance of the heating filament 212 is R = 0.9091 Ω. In addition, the resistance of a serpentine heating filament with a total length of 10 mm is R = 11.3636 Ω. These calculation examples demonstrate that the resistance of a filament depends on its dimensions, shape, and material. For comparison, the resistance of a copper feed wire with conductivity σ = 5.8 × 10⁷ S / m, width 0.5 mm, thickness 0.001 mm, and length 13.82 mm is R = 0.4766 Ω. The source of heat flow within the structure is the power P = RI consumed by the resistive filament. 2 Because it depends on the current source driving the filament circuit, such as the temperature controller 105, the amount of power loss and the amount of heat transferred can be controlled by adjusting the current source. Figure 4-6C shows an alternative design for the heated filament.

[0032] Figures 6A-6C show a side-by-side comparison of various implementations of heating filaments having various geometric shapes. Figure 6A shows an implementation of a heating filament 602 having a longitudinal meandering track shape. The heating filament 602 includes parallel segments 604, whose opposite ends are sequentially joined by connecting segments 606. The parallel segments 604 are arranged perpendicular to the longitudinal axis of the sample holder 608. Figure 6B shows an implementation of a heating filament 612 having a transverse meandering track shape. The heating filament 612 has a similar structure to the heating filament 402 described with respect to Figure 4. The heating filament 612 includes parallel segments 614, which are sequentially joined at their opposite ends by orthogonal connecting segments 616, thereby giving the heating filament 612 a meandering shape. The parallel segments 614 are arranged parallel to the longitudinal axis of the sample holder 615. Figure 6C shows an implementation of a sample heater 620 having an array of heating filaments 618. In the embodiment shown in Figure 6C, the heating filament 618 has a tapered geometry, but in other embodiments, the heating filament 618 may have a straight path geometry of the type shown in Figure 2-6B, a longitudinal meandering path geometry, a transverse meandering path geometry, or other geometry. When in operation, the array of heating filaments 618 increases the surface area of ​​the sample holder 626, which is thermally coupled to the sample heater 620. In other embodiments, the array of heating filaments 618 may also heat an array of sample containers. In various embodiments, the heating filaments 602, heating filament 612, and sample heater 620 can be used in conjunction with an electron magnetic resonance system, such as the electron magnetic resonance system 100 described above in relation to Figure 1A.

[0033] Figure 7A is a cross-sectional view of an exemplary resonator package. The heating filament 702 can be, for example, the heating filaments 212, 302, 402, 602, 612, or 618 described above in relation to Figure 2-6C. In various embodiments, the heating filament 702 has a planar geometry and can be fabricated on a heater substrate 704 made of dielectric material. In some embodiments, the heating filament 702 and the heater substrate 704 are positioned on top of the sample holder 706 and constitute a cover for the sample holder. The sample holder 706 is a dielectric slab with one or more sample containers 708 that function as carriers and containers for the electron magnetic resonance sample. In various embodiments, the sample heater 701, together with the heater substrate 704, serves as a cover for the sample holder 706 for sealing the electron magnetic resonance sample. As will be discussed later, in other embodiments, the sample heater may be positioned at a distance from the sample holder. In yet another embodiment, the sample holder may include at least one microcapillary that does not require a cover. In some implementations, the heater substrate 704 of the sample heater 701 can be the same dielectric material as that of the sample holder 706, and can be selected from any of the following: borosilicate glass, fused silica glass, fused silica, sapphire, silicon, or any other dielectric material suitable for electron magnetic resonance applications.

[0034] In addition, as can be seen from Figure 7A, the heater substrate 704 and the sample holder 706 function as a medium for conducting heat from the heating filament 702 located on the heater substrate 704 to the electron magnetic resonance sample in the sample holder 706. In order to maintain the quality factor of the resonator 712 as high as possible, the heating filament 702 is positioned at a distance D (see Figure 2) from the electron magnetic resonance sample located directly above the resonator 712. Therefore, the thermal conductivity of the heater substrate 704 needs to be high enough to transfer heat to the electron magnetic resonance sample, but it should not be high enough to dissipate energy without heating the sample. The thickness of the heater substrate 704, the thickness of the sample holder 706, the size of the sample container 708, and the height of the bottom surface of the sample container 708 can be determined based on the spatial magnetic field distribution of the resonator 712.

[0035] When transferring heat to an electron magnetic resonance (EMR) sample to raise its temperature, significant temperature changes in the resonator 712 must be avoided because such temperature increases can cause a decrease in the EMR quality coefficient of the resonator 712, or worsen its performance and generate thermal noise. To suppress heat transfer to the resonator 712, an insulating layer 714 is used between the sample holder 706 and the resonator 712. In the embodiment shown in Figure 7A, the insulating layer 714 can be a partial vacuum implemented to enhance insulation. In various embodiments, the partial vacuum is provided by the internal environment of the cryostat system. In various embodiments, the insulating layer 714 can be in a region where the pressure is approximately 500 mTorr or less. In other embodiments, other forms of insulating material may be used. In some cases, materials with low thermal conductivity, such as aerogel, Teflon, fiberglass, or some other insulating material, can be placed in the insulating layer 714.

[0036] In the embodiment shown in Figure 7B, a sample heater 751 having a heating filament 752 is positioned on a heater substrate 754. A cover 753 is positioned on top of the sample holder 706, and the heater substrate 754 is positioned on top of the cover 753. Therefore, in various embodiments, the sample heater 751 and the heater substrate 754 do not need to be integrated with the cover 753.

[0037] Figure 8A is a perspective view showing an exemplary sample heater 802 housed within a resonator package 804. The resonator 806 is housed within the resonator package 804, which is constructed of a thermally conductive and conductive material such as copper. In various embodiments, the resonator package 804 can be used in an electron magnetic resonance system, such as the electron magnetic resonance system 100 described above in relation to Figure 1A. The resonator 806 can be any of the above-described types of resonators. When in use, the resonator 806 is located within the resonator package. For clarity, the top of the resonator package 804 is not shown in Figure 8A. The sample heater 802 extends from the top surface of the resonator package 804 and is positioned so that the sample container 808 of the sample holder 810 is thermally coupled to the sample heater 802 when the sample container 808 is placed in the sample area of ​​the resonator 806. Although the sample heater 802 is shown exemplary in Figure 8A as having a helical heating filament, in other embodiments, the sample heater 802 may include any type of heating filament, such as a linear filament, a tapered filament, a longitudinally meandering filament, a transversely meandering filament, or other types of filaments. Thus, the heating filament can be configured similarly to any of the heating filaments 212, 302, 402, 602, 612, or 618 described above in relation to Figure 2-6C.

[0038] Figure 8B is a perspective view of an exemplary helical sample heater used with a tubular sample holder 860 and housed within a resonator package 854. The sample holder 860 is a tubular member such as a capillary tube or microcapillary tube. In various embodiments, the sample holder 860 does not use a cover. Similar to Figure 8A, the sample heater 802 extends from the top surface of the resonator package 804 and is positioned so that the sample container 858 of the sample holder 860 is thermally coupled to the sample heater 802 when the sample container 858 is placed in the sample area of ​​the resonator 806. Although the sample heater 802 is shown exemplary in Figure 8B as having a helical heating filament, in other embodiments, the sample heater 802 may include any type of heating filament, such as a linear filament, a tapered filament, a longitudinally meandering filament, a transversely meandering filament, or other types of filaments.

[0039] Figure 9 is a perspective view of an exemplary sample holder showing a sample heater 206 and a resonator 204. As described above with respect to Figure 2, the sample heater 206 includes a first feed line 208 and a second feed line 210 electrically coupled to a heating filament 912. Exemplarily, the heating filament 912 is shown as a tapered heating filament 912 in Figure 9, but in other embodiments, the heating filament may include any type of heating filament, such as a straight filament, a tapered filament, a longitudinally meandering filament, or a transversely meandering filament. Thus, the heating filament 912 can be configured similarly to any of the heating filaments 212, 302, 402, 602, 612, or 618 described above in relation to Figures 2-6C. The first feed line 208 and the second feed line 210 supply current to the heating filament 912. In various implementations, the first feed line 208 and the second feed line 210 are wider than the heating filament 912, reducing the electrical resistance passing through the first feed line 208 and the second feed line 210.

[0040] Figure 10 is a perspective view of an exemplary sample holder 102 showing exemplary electrical connections of an exemplary sample heater 206. When the sample container 202 is inserted into the resonator package (not shown for clarity), the first feed line 208 and the second feed line 210 contact a pair of conductors 1002 extending from the top surface of the resonator package, for example, the resonator package 804. In various embodiments, the pair of conductors 1002 are, for example, spring-biased pins. In such embodiments, the pair of conductors 1002 are spring-biased to the first feed line 208 and the second feed line 210 to maintain electrical connections with the first feed line 208 and the second feed line 210. In the embodiment shown in Figure 10, the pair of conductors 1002 include a curved spring portion 1004, but in other embodiments, the conductors 1002 may utilize, for example, a linear extension spring or other configuration to maintain electrical contact with the first power supply line 208 and the second power supply line 210.

[0041] The following paragraphs discuss simulations of an exemplary sample heater and their influence on the performance of an exemplary resonator. While the simulations described below illustrate specific characteristics in an illustrative manner, those skilled in the art will recognize that the principles described below can be applied to any embodiment described herein.

[0042] Figure 11 shows the simulated s-parameters of an exemplary planar microstrip line superconducting microwave resonator in the presence of a heating filament. The components described in relation to Figure 11-16 can be any of the components described above in relation to Figure 1-10. More specifically, the heating filament described in relation to Figure 11-16 can be any of the heating filaments described in Figure 2-6C. The data shows that by positioning the heating filament at a lateral distance D (see Figure 2) from the resonator, the influence of the heating filament can be minimized while effectively maintaining the device quality factor and insertion loss. Superconducting resonators are a versatile technology and can be implemented in various ways, including, but not limited to, microstrip lines, coplanar waveguides (CPWs), and lumped-parameter planar resonators. In addition, resonators can be arranged in arrays. In the embodiment shown in Figure 11, the gap of the single microstrip line resonator is 450 μm, and the thickness of both the cartridge and heating circuit board is 0.5 mm. These are made of borosilicate glass with a dielectric constant of 4.0472 and a loss tangent of 0.0022.

[0043] Table 1 shows the calculated quality factor (Q) and insertion loss at various lateral positions of the heating filament. The data shows that both the Q and insertion loss worsen as the heating filament approaches the resonator. This significantly reduces resonator performance, highlighting the importance of proper placement of the heating filament relative to the resonator. In addition, a comparison of simulation results for a bare resonator with and without a dielectric sample holder and heating substrate reveals that borosilicate glass material causes significant dielectric loss. The data shows that resonator performance improves as the distance (D) between the heating filament and the resonator increases. Specifically, at a distance D = 12 mm, performance is comparable to that without the heating filament. At a distance D = -1 mm, the heating circuit penetrates the resonator, and the heating filament approaches the microwave connector. [Table 1]

[0044] The electron magnetic resonance (EMR) sample is heated by converting electrical energy into thermal energy through a resistive element. Figure 12 shows a plot of the current density overlay through the heating circuit. This plot shows that when a current of 250 mA is applied to the circuit, 5 × 10⁻¹⁰ mA is generated within the heating filament. 9 A / m 2 This indicates that a current density of 0.0568W is generated in the filament and 0.0302W in each feed line. The temperature of the electron magnetic resonance sample can be controlled by adjusting the input current, which changes the power consumption. However, in order to ensure effective function at the operating temperature (ambient temperature) of the cryogenic system, the power input to the heating circuit must be adjusted, for example using a temperature controller 105, so that it remains within the range set by the cooling capacity of the cryogenic system.

[0045] During operation, the resonator equipped with a sample heater is located within the cryogenic system, which is a closed-loop cryogenic system, He 3 Cryostats can take the form of continuous-flow cryostats or vacuum cryostats, such as cryostats, dilution refrigerators, or other types of cryogenic systems. In various implementations, the resonator, which is a resonator, is protected from the temperature rise caused by the sample heater, and an insulating layer is used as a thermal barrier between the resonator and the sample holder. In vacuum cryostats, this layer is effectively provided by the partial vacuum created in the internal environment of the cryostat, so no additional material is required. In various implementations, the pressure of the partial vacuum is approximately 500 mTorr or less. However, it is also possible to use a continuous-flow cryostat for a resonator equipped with a sample heater. The cryostat environment is maintained at the system's reference temperature (e.g., 4 K (-269 °C)), which is the ambient temperature T for the resonator, sample heater, and microwave package. ∞ And it is maintained as the external radiation temperature.

[0046] In a cryostat with a partial vacuum space, since there is no fluid, the main modes of heat transfer are heat conduction or thermal radiation. However, in a continuous flow cryostat, all three heat transfer modes of conduction, convection, and radiation exist and can contribute to the overall heat transfer process.

[0047] The thermal performance of the sample heater was simulated. Since vacuum materials cannot be used in thermal analysis, a "quasi-vacuum" medium was defined for the simulation. This material is modeled by the ideal gas equation of state PV = nRT, where n is the number of moles of the gas, R = 8.31 J / K.mole is the universal gas constant, and P, V, and T are the state variables of the gas (pressure, volume, temperature), respectively. The mass density can be determined by the equation ρ = MP / RT, where M is the molar mass of the gas. For example, using this equation and the data of the cryogenic system and dry air material M = 18.97 g / mole, P = 2×10 -6 Bar = 0.2 Pa, T = 4 K, we get ρ = 1.1414×10 -4 Kg / m 3 while the mass density of normal air at atmospheric pressure is ρ = 1.1614 Kg / m 3 .

[0048] For fluids, two main specific heats, also called heat capacities, are defined. One is the specific heat at constant volume Cv, and the other is the specific heat at constant pressure Cp. By using Maxwell's thermodynamic equations, the partial differential coefficients of Cp (and Cv) with respect to pressure (and volume) at a constant temperature can be calculated using the following equations. JPEG2026511187000008.jpg12170 Equation 1 JPEG2026511187000009.jpg12170 Equation 2

[0049] Substituting the ideal gas equation of state PV = nRT into the above equations, JPEG2026511187000010.jpg8156 and JPEG2026511187000011.jpg8156 are obtained. Therefore, for an ideal gas, the specific heat does not depend on pressure (or volume), JPEG2026511187000012.jpg8156 and As can be seen from JPEG2026511187000013.jpg7156, it is a function of temperature only. Therefore, the heat capacity of a "quasi-vacuum" material can be the same as that of ordinary air, namely Cp = 1000 J / Kg·K and Cv = 720 J / Kg·K.

[0050] The thermal conductivity of absolute vacuum is zero because there are no atomic vibrations to transfer thermal energy. The relationship between the thermal conductivity of air and pressure was plotted, and a low value of κ = 0.000261 W / m·K was selected.

[0051] The governing equations for heat transfer by conduction are: JPEG2026511187000014.jpg9170 formula 3 In the above equation, T is the temperature and q''' is the volumetric heat source density (W / m³). 3 ), JPEG2026511187000015.jpg5156 is the thermal conductivity tensor of an anisotropic or heterogeneous material, where Cp is the specific heat capacity and ρ is the mass density. This equation is Fourier's law of heat conduction. JPEG2026511187000016.jpg7170 (here JPEG2026511187000017.jpg7156 shows the heat flux coefficient per unit area (W / m²). 2 ) and the law of conservation of energy JPEG2026511187000018.jpg11170 (This is the first law of thermodynamics (in a region without a heat source)) and the definition of specific heat capacity ΔQ=mCpΔT (where Q is thermal energy) are combined. In an isotropic medium without a heat source, this equation is, The equation can be simplified to the usual thermal diffusion equation of the form JPEG2026511187000019.jpg9170, where the right-hand side represents the heat of diffusion (or conduction) and the left-hand side represents the heat of storage (or storage). Parameters JPEG2026511187000020.jpg7156 is called thermal diffusivity, and it is a measure of the ratio of heat of diffusion to heat of storage. In addition, in the case of transient conduction, the time constant of temperature change is It is estimated as JPEG2026511187000021.jpg10170, where Δx is the length of heat conduction. In steady-state (∂T / ∂t=0) heat transfer in a material with uniaxial thermal conductivity, the partial differential equation representing thermal equilibrium is: JPEG2026511187000022.jpg10170 formula 4 That is the case.

[0052] Given the presence of an electrically heated element with current I and resistance R, a simple 1D approximation formula for estimating the temperature rise is: JPEG2026511187000023.jpg10170 formula 5 Here, κ is the thermal conductivity of the medium, A is the cross-sectional area for heat transfer, and Δx (hereinafter denoted as L) is the length scale at which heat conduction occurs. For example, when using borosilicate glass with thermal conductivity κ = 1.14891 W / mK, length scale Δx = 2 mm, cross-sectional area A = 0.8 mm × 1.8 mm, I = 150 mA, and R = 0.9 Ω, the estimated temperature is ΔT ~ 24.47 K, which is close to the plot in Figure 13.

[0053] In this case, the time constant is given by the equation τ = L 2 / α=ρCpL 2 It can be calculated using / κ. The specific heat of borosilicate glass is Cp = 799.744 J / (Kg·K), and its mass density is ρ = 2124.85 Kg / m³. 3 Using this, τ ~ 5.9s.

[0054] Another factor contributing to heat transfer in this device and platform is thermal radiation. Radiation is a highly nonlinear mode of heat transfer. A simplified form of the equation describing surface-to-surface radiation from one surface to another is: JPEG2026511187000024.jpg16170 formula 6 And here, A i ε is the surface area. i σ = 5.67 × 10⁻¹⁰, which is the surface emissivity that determines the amount of thermal radiation.-8 W / m 2 K 4 is the Stefan-Boltzmann constant, F ij This is the view factor between surfaces, and the view factor is determined by the temperature T i Of the total radiation energy emitted from surface i at temperature T, j [K] is defined as the fraction that directly reaches surface j. JPEG2026511187000025.jpg12170 formula 7 It can be expressed by the following relationship.

[0055] In Equation 7, s represents the distance between a small area dAi on surface i and a small area dAj on surface j. The angle θi (or θj) is the angle between the normal to surface i (or surface j) at position dAi and the line connecting position dAi and position dAj.

[0056] The surface-to-surface formulation is a cost-effective method for considering thermal radiation on geometrically simple surfaces. However, it is limited by several assumptions, such as the surface being gray with respect to thermal radiation (emissivity equal to absorptivity and independent of wavelength) and opaque (transmittance is ignored), being inherently diffusive (reflectivity is independent of the direction of incidence), and not considering medium-related absorption, re-emission, and scattering. A more advanced method is the "ray-tracing" radiation model, where the simple surface is replaced by an aggregate of cell surfaces.

[0057] The general equation for radiative heat transfer in a medium that absorbs, emits, and scatters anisotropically can be described as an integral-differential radiative transfer equation. JPEG2026511187000026.jpg16156 formula 8 Here, I and Ib are the radiant intensity and blackbody intensity, respectively, and σs, κ, and β are the scattering coefficient, absorption coefficient, and extinction coefficient. The scattering phase function Φ is [Sr -1It is expressed in units of ]. This model is effective for complex shapes with many joining surfaces and is considered a more conservative method. The first term on the right-hand side represents radiation, the second term represents absorption, and the third term represents scattering in the medium, expressed as an integral over the solid angle. Due to the complexity of the equation and associated boundary conditions, the "discrete coordinate method" or Sn method is used to approximately solve the problem. In the simulation, this model was used to consider radiative heat transfer.

[0058] In convection-mediated heat transfer, fluid motion is involved in the transfer of heat. Convection models are generally considered the most efficient methods of heat transfer in liquids and gases. This includes both heat conduction through the surface and heat transport to and from the surface via fluid advection. Since the velocity field significantly affects the heat transfer coefficient, precise prediction of fluid flow is crucial for accurate heat transfer predictions. The linear equation for heat transfer in convection is described by Newton's law of cooling, and with respect to the heat transfer coefficient h, JPEG2026511187000027.jpg10156 formula 9 That is the case.

[0059] In more complex situations, convection models are described by a combination of the continuity equation (mass conservation law), the momentum equation (Navier-Stokes equation), and the energy equation (temperature distribution). That is, JPEG2026511187000028.jpg10156 formula 10 JPEG2026511187000029.jpg15156 formula 11 JPEG2026511187000030.jpg15156 formula 12 Here, V, p, τ, and g are the velocity vector, pressure, stress tensor, and gravity vector, respectively. In the simulation, a convection model was not used because the exemplary device is inside a vacuum cryostat.

[0060] Figure 13 is a plot showing the temperature profile along a line perpendicular to the sample holder for various currents flowing through the heating filament. This line starts from the resonator and passes through the entire borosilicate glass material. The heating filament is 2 mm laterally away from both the resonator and the sample. In Figure 13, the leftmost section of the temperature profile is due to thermal radiation. These sections are shown enlarged in Figure 14 for a more detailed examination. In all simulations, the emissivity of all surfaces was assumed to be ε = 0.8.

[0061] Figure 14 shows the temperature rise profiles plotted against current when the heating filament is located 1 mm and 2 mm laterally from the center of the sample. In addition, the temperature rise directly above the resonator is shown, and it can be seen that it is significantly lower than the temperature rise inside the sample.

[0062] Figure 15 shows an overlay of the temperature distribution (in Celsius) at the bottom surface of the sample holder when a current of 150 mA flows through a heating element located 2 mm away from the sample.

[0063] Figure 16 shows an overlay of the temperature distribution (in Celsius) across the sample volume when a current of 150 mA flows through a heating element located 2 mm away from the sample. The temperature change across the sample volume is less than 0.5 K.

[0064] Figure 17 is a flowchart of process 1700 relating to sample heating in an electron magnetic resonance system. In various implementations, the electron magnetic resonance system is the exemplary electron magnetic resonance system 100 described above with respect to Figure 1A, or other types of electron magnetic resonance systems. The exemplary process 1700 may include additional or different operations, which may be performed in the order shown or in different orders. In some cases, one or more operations may be repeated, omitted, or performed in different ways.

[0065] In 1702, the sample holder is housed in the sample area of ​​the resonator. The sample holder can be, for example, sample holder 102 shown in Figure 1A, one of the sample holders shown in Figure 2-10 and described above, or another type of sample holder. The resonator operates in the main magnetic field of the main magnet system. The resonator package can be placed in a cryogenic environment controlled by a cooling system. The sample holder is thermally coupled to a sample heater. The sample heater can be, for example, sample heater 104 shown in Figure 1A, one of the exemplary sample heaters shown in Figure 2-10, or another type of sample heater. In various embodiments, the sample heater includes a heating filament positioned between two feed lines. The feed lines are connected to a power source, for example, via a pair of spring-loaded pins or other configurations.

[0066] In 1704, the sample holder and sample heater are thermally insulated from the resonator. In various embodiments, the insulation can be a partial vacuum layer with a pressure of, for example, about 500 mTorr or less, which is generated by a cryogenic system. In some embodiments, the partial vacuum layer can be an insulating layer 714. In other embodiments, the insulation can be a fluid layer or a solid layer. In some cases, the insulation is a material with low thermal conductivity, such as aerogel, Teflon, glass fiber, or other insulating material.

[0067] In 1706, the resonator temperature is controlled. In various implementations, the resonator temperature is controlled using a cryosystem. In implementations where the resonator is a superconducting resonator, the temperature is controlled below the resonator's critical temperature.

[0068] In 1708, the sample temperature is controlled using a sample heater. In various implementations, the sample temperature is controlled by supplying current to the power supply line and the heating filament of the sample heater. In various implementations, the sample temperature is controlled by applying current to the sample heater. The sample heater can be any of the sample heaters shown in Figure 1-11 or other types of sample heaters. In various implementations, the temperature is controlled using, for example, a temperature controller 105. In various implementations, the sample temperature control can be open-loop control or closed-loop control. In implementations using open-loop control, a current corresponding to the desired temperature is applied to the sample heater. In implementations using closed-loop control, feedback information such as, for example, the sample temperature or relaxation times (T1 and T2) can be used. In various implementations, measurements of temperature-dependent spin dynamics such as spin signal amplitude, relaxation time (T1 and T2) measurements, or other temperature-dependent spin signals can be measured instead of the sample temperature, thereby enabling closed-loop control of the sample heater while eliminating the need to install a temperature sensor near the electron magnetic resonance sample.

[0069] In a first embodiment, the disclosure relates to an electron magnetic resonance apparatus. The electron magnetic resonance apparatus includes a microwave resonator placed in a cryogenic environment. A sample holder is placed in the cryogenic environment together with the microwave resonator. The sample holder includes a sample container thermally insulated from the microwave resonator and holds a sample in the sample region of the microwave resonator. A sample heating device is thermally coupled to the sample container and configured to control the temperature of the sample at a temperature higher than the temperature of the resonator.

[0070] In various embodiments of the first embodiment, the apparatus may include a heating substrate that is in thermal contact with the sample holder. In various embodiments of the first embodiment, the sample heating device may be in mechanical contact with the sample holder. In other embodiments, the sample heating device may be positioned at a distance from the sample holder.

[0071] In various embodiments of the first embodiment, the sample heating device may include a heating filament electrically connected to a pair of power lines. A temperature controller may be connected to the pair of power lines via a pair of spring-biased pins. In various embodiments, the heating filament is a resistance heating filament and may be one of a straight filament, a tapered heating filament, a longitudinal meandering line, or a transverse meandering line.

[0072] In various embodiments of the first embodiment, the apparatus may include a temperature controller configured to control the temperature of the sample heating device based on the temperature of the sample. In such embodiments, the sample holder may include a temperature sensor configured to measure the temperature of the sample.

[0073] In various embodiments of the first embodiment, the microwave resonator may include a superconducting material and be configured to operate below the critical temperature of the superconducting material.

[0074] In various embodiments of the first embodiment, the sample heating device may include an array of heating filaments.

[0075] In various embodiments of the first embodiment, the sample container can be thermally insulated from the resonator by an insulating material placed between the resonator and the sample holder. In other embodiments, the sample container can be thermally insulated from the resonator by a partial vacuum region placed between the resonator and the sample holder.

[0076] In various embodiments of the first embodiment, the sample holder and sample heating device are located within a cryogenic system that includes a temperature control system that sets the temperature of the resonator to a first cryogenic temperature.

[0077] In various embodiments of the first embodiment, the sample holder is configured to operate within the main magnetic field of the probeless magnetic resonance system. In other embodiments, the sample holder may be configured to operate on the probe within the main magnetic field of the magnetic resonance system.

[0078] In a second embodiment, aspects of the present disclosure relate to an electron magnetic resonance system. The electron magnetic resonance system includes a main magnet system and a cryogenic system configured to generate a main magnetic field. A microwave resonator is located within the cryogenic system. The microwave resonator is configured to operate within the main magnetic field and interact with a sample in the sample region. A sample holder includes a sample container that is thermally insulated from the resonator and holds the sample in the sample region. A sample heating device is thermally coupled to the sample container and configured to control the temperature of the sample at a temperature higher than the temperature of the microwave resonator.

[0079] Various embodiments of the second embodiment include the features and modifications described above with respect to the first embodiment.

[0080] In a third embodiment, the disclosure relates to an electron magnetic resonance (EMR) method. The method includes the step of placing a sample in a sample region of a resonator located within the main magnetic field of an EMR system. The sample is thermally insulated from the resonator. By operating a cryogenic system, the temperature of the resonator is controlled to a cryogenic range. By operating a sample heating system, the temperature of the sample is controlled to a temperature range higher than the temperature of the resonator. By operating the resonator, a control magnetic field is applied to the sample in the sample region.

[0081] In various embodiments of the third embodiment, the sample holder includes a sample container for holding the sample, and the method includes the step of positioning the sample heating system in thermal contact with the sample holder.

[0082] In various embodiments of the third embodiment, the sample heating system includes a heating filament electrically connected to a pair of power lines, and the step of controlling the temperature of the sample includes supplying current to the heating filament.

[0083] In various embodiments of the third embodiment, the method may include the steps of measuring the temperature of a sample and controlling the temperature of the sample based on the measured temperature of the sample. In various embodiments, the temperature of the sample can be measured by the operation of a temperature sensor.

[0084] In various embodiments of the third embodiment, the method may include the steps of acquiring a spin signal from a sample by operating a resonator and measuring the temperature of the sample based on the temperature-dependent characteristics of the spin signal.

[0085] In various embodiments of the third embodiment, the sample holder includes a sample container for holding the sample, and the method may include the step of thermally insulating the sample container from the resonator by an insulating material placed between the resonator and the sample holder. In other embodiments, the method may include the step of thermally insulating the sample container from the resonator by a partial vacuum region placed between the resonator and the sample holder.

[0086] In a fourth embodiment, the disclosure relates to a sample heating device for an electron magnetic resonance system. The sample heating device includes a substrate, a first feed line disposed on the substrate, and a second feed line disposed on the substrate. A heating filament is electrically connected to the first and second feed lines. A temperature control unit is electrically connected to the heating filament via the first and second feed lines. A sample holder includes a sample container thermally coupled to the heating filament. The sample container is thermally insulated from a microwave resonator operating in a cryogenic environment.

[0087] Various embodiments of the fourth embodiment include the features and modifications described above with respect to the first embodiment.

[0088] This specification contains many details, which should not be construed as limiting the scope of the claims, but rather understood as descriptions of features specific to particular embodiments. Certain features described herein or shown in the drawings in the context of separate embodiments can be combined. Conversely, various features described or shown in the context of a single embodiment can be implemented individually or in some appropriate partial combination in multiple embodiments.

[0089] Similarly, while the diagrams show operations in a specific order, this should not be interpreted as requiring that the operations be performed in the specific order or sequence shown, or that all illustrated operations be performed, in order to obtain the desired result. In certain situations, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system components in the implementation configurations described above should not be interpreted as requiring such separation in all implementations, and it should be understood that the described principles concerning program components and systems may generally be integrated into a single product or packaged into multiple products.

[0090] Numerous embodiments have been described. However, it should be understood that various modifications are possible. For example, in various embodiments, a guide system can be used to facilitate the insertion and placement of the sample holder into the resonator package and to prevent damage to the sample holder. Such a guide system may include, for example, rails that support both ends of the sample holder during placement. Therefore, other embodiments are also included in the scope of the following claims. [Explanation of symbols]

[0091] 152 Heater 156 Thermal bonding 154 samples 162 Electromagnetic coupling 158 Insulation 160 Resonator

Claims

1. A microwave resonator placed in an extremely low-temperature environment, A sample holder disposed in the cryogenic environment together with the microwave resonator, wherein the sample holder is thermally insulated from the microwave resonator and comprises a sample container that holds a sample within the sample region of the microwave resonator. A sample heating device is thermally coupled to the sample container and configured to control the temperature of the sample at a temperature higher than the temperature of the resonator. An electron magnetic resonance apparatus equipped with [the necessary components].

2. The apparatus according to claim 1, wherein the sample heating apparatus comprises a heating substrate that is in thermal contact with the sample holder.

3. The apparatus according to claim 1 or 2, wherein the sample heating device is in mechanical contact with the sample holder.

4. The apparatus according to claim 1 or 2, wherein the sample heating device is arranged at a distance from the sample holder.

5. The sample heating device according to claim 1, comprising a heating filament electrically connected to a pair of power supply lines.

6. The apparatus according to claim 5, further comprising a temperature controller connected to the pair of power supply lines via a pair of spring biasing pins.

7. The apparatus according to claim 5, wherein the heating filament comprises a resistance heating element.

8. The apparatus according to claim 7, wherein the heating filament is one of a straight filament, a tapered heating filament, a longitudinally meandering track, and a transversely meandering track.

9. The apparatus according to claim 1 or 2, further comprising a temperature controller configured to control the temperature of the sample heating device based on the temperature of the sample.

10. The apparatus according to claim 9, wherein the sample holder is equipped with a temperature sensor configured to measure the temperature of the sample.

11. The apparatus according to claim 1 or 2, wherein the microwave resonator comprises a superconducting material, and the microwave resonator is configured to operate below the critical temperature of the superconducting material.

12. The sample heating device according to claim 1 or 2, comprising an array of heating filaments.

13. The apparatus according to claim 1 or 2, wherein the sample container is thermally insulated from the resonator by an insulating material placed between the resonator and the sample holder.

14. The sample container is thermally insulated from the resonator by a partial vacuum region positioned between the resonator and the sample holder. The apparatus according to claim 1 or 2.

15. The apparatus according to claim 1 or 2, wherein the sample holder and the sample heating device are located within a cryogenic system that includes a temperature control system for setting the temperature of the resonator to a first extremely low temperature.

16. The apparatus according to claim 1 or 2, wherein the sample holder is configured to operate within the main magnetic field of the probeless magnetic resonance system.

17. The apparatus according to claim 1 or 2, wherein the sample holder is configured to operate on a probe in the main magnetic field of a magnetic resonance system.

18. A main magnet system configured to generate the main magnetic field, Cryogenic systems and A microwave resonator located within the cryogenic system, wherein the microwave resonator is configured to operate within a main magnetic field and interact with a sample in the sample region, A sample holder comprising a sample container that is thermally insulated from the resonator and holds the sample within the sample region, A sample heating device is thermally coupled to the sample container and configured to control the temperature of the sample at a temperature higher than the temperature of the microwave resonator. An electron magnetic resonance system equipped with this system.

19. The system according to claim 18, wherein the sample heating device comprises a heating substrate that is in thermal contact with the sample holder.

20. The system according to claim 18 or 19, wherein the sample heating device is in mechanical contact with the sample holder.

21. The system according to claim 18 or 19, wherein the sample heating device is positioned at a distance from the sample holder.

22. The system according to claim 18, wherein the sample heating device comprises a heating filament electrically connected to a pair of power supply lines.

23. The system according to claim 22, further comprising a temperature controller connected to the pair of power supply lines via a pair of spring-biased pins.

24. The system according to claim 22, wherein the heating filament comprises a resistance heating element.

25. The system according to claim 24, wherein the heating filament is one of a straight filament, a tapered heating filament, a longitudinally meandering track, or a transversely meandering track.

26. The system according to claim 18 or 19, further comprising a temperature controller configured to control the temperature of the sample heating device based on the temperature of the sample.

27. The system according to claim 26, wherein the sample holder comprises a temperature sensor configured to measure the temperature of the sample.

28. The system according to claim 18 or 19, wherein the microwave resonator comprises a superconducting material, and the microwave resonator is configured to operate below the critical temperature of the superconducting material.

29. The system according to claim 18 or 19, wherein the sample heating device comprises an array of heating filaments.

30. The system according to claim 18 or 19, wherein the sample container is thermally insulated from the resonator by an insulating material placed between the resonator and the sample holder.

31. The system according to claim 18 or 19, wherein the sample container is thermally insulated from the resonator by a partial vacuum region positioned between the resonator and the sample holder.

32. The sample holder and the sample heating device are located within the extreme temperature system. The cryogenic system further comprises a temperature control system for setting the temperature of the resonator to a first extremely low temperature, according to claim 18 or 19.

33. An electron magnetic resonance method, The steps include: placing the sample in the sample region of the resonator located within the main magnetic field of the electron magnetic resonance system; The steps include: thermally insulating the sample from the resonator; The steps include controlling the temperature of the resonator within the cryogenic temperature range by operating the cryogenic system, The steps include controlling the temperature of the sample to a temperature range higher than the temperature of the resonator by operating the sample heating system, The steps include applying a control magnetic field to the sample within the sample region by operating the resonator, A method that includes this.

34. The method according to claim 33, wherein the sample holder includes a sample container for holding the sample, and the method includes the step of positioning the sample heating system in thermal contact with the sample holder.

35. The method of claim 33, wherein the sample heating system comprises a heating filament electrically connected to a pair of power lines, and the step of controlling the temperature of the sample includes supplying an electric current to the heating filament.

36. The steps include measuring the temperature of the sample, A step of controlling the temperature of the sample based on the measured temperature of the sample, The method according to any one of claims 33 to 35, including the method described in any one of claims 33 to 35.

37. The method according to claim 36, further comprising the step of measuring the temperature of the sample by the operation of a temperature sensor.

38. The steps include: obtaining a spin signal from the sample by operating the resonator; The steps include: measuring the temperature of the sample based on the temperature-dependent characteristics of the spin signal; The method according to claim 36, including the method described in claim 36.

39. The method according to any one of claims 33 to 35, wherein the sample holder comprises a sample container for holding the sample, and the method includes the step of thermally insulating the sample container from the resonator by an insulating material placed between the resonator and the sample holder.

40. The method according to any one of claims 33 to 35, wherein the sample holder includes a sample container for holding the sample, and the method includes the step of thermally insulating the sample container from the resonator by a partial vacuum region positioned between the resonator and the sample holder.

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