Electronic magnetic resonance sample heating

Abstract

In a general aspect, an electronic magnetic resonance apparatus includes a resonator in a refrigerated environment in a main magnetic field. A sample holder in the refrigerated environment maintains a spaced apart relationship with the resonator. The sample holder includes a sample container. The sample heating device is positioned such that the sample container is thermally coupled to the sample heating device, and the sample heating device controls the temperature of the sample within a temperature range above the operating temperature of the resonator.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 492,084, filed March 24, 2023, entitled “Electron Paramagnetic Resonance (EPR) Sample Heating,” which is incorporated herein by reference. Background Technology

[0003] The following description pertains to heating a sample in an electron magnetic resonance system.

[0004] Electron magnetic resonance (EMR) systems are used to study a wide variety of samples and phenomena. The resonator manipulates the spin in a sample by generating a magnetic field at or near its spin resonance frequency. In some cases, the resonator detects spin based on the voltage induced by the precessing spin. Attached Figure Description

[0005] Figure 1A This is a schematic diagram of an example electron magnetic resonance system;

[0006] Figure 1B This is a block diagram of an example electron magnetic resonance system with a sample heater;

[0007] Figure 2 This is a top view of an example sample holder used in an electronic magnetic resonance system, illustrating the sample heater and resonator;

[0008] Figure 3 This is a perspective view of the sample holder and an example sample heater with tapered wires, showing their placement on the resonator;

[0009] Figure 4 This is a perspective view of the sample holder and an example sample heater with transverse meandered line filament, showing their placement on the resonator;

[0010] Figure 5 An example of a tapered heating wire and an example of a transversely meandering heating wire are shown;

[0011] Figure 6A This is a plan view of an example of a longitudinally winding thread;

[0012] Figure 6B This is a plan view of an example of a horizontally winding thread;

[0013] Figure 6C This is a plan view of an example sample heater with a tapered filament array;

[0014] Figure 7A This is a cross-sectional view of an example resonator package;

[0015] Figure 7B This is a cross-sectional view of an example resonator package with a separate sample holder cover;

[0016] Figure 8A This is a perspective view of an example spiral sample heater used with a prismatic sample holder;

[0017] Figure 8B This is a perspective view of an example spiral sample heater used with a tubular sample holder;

[0018] Figure 9 This is a perspective view of an example sample holder, illustrating the sample heater and resonator;

[0019] Figure 10 This is a perspective view of an example sample holder, illustrating an example electrical connection of the sample heater;

[0020] Figure 11 This is a graph illustrating the behavior of an example resonator in the presence of an example sample heater;

[0021] Figure 12 This is an electromagnetic simulation of the current density in the heater of the example sample shown in the figure;

[0022] Figure 13 It is a graph showing the temperature profile along a line perpendicular to the sample holder, plotted relative to the current flowing through the sample heater.

[0023] Figure 14 This is a graph showing the temperature rise of the sample relative to the current flowing through the sample heater, with respect to the lateral position of the sample heater.

[0024] Figure 15 It is the temperature field superimposed on the bottom surface of the sample holder;

[0025] Figure 16 It is the superposition of temperature fields in the sample container; and

[0026] Figure 17 This is a flowchart of an example process for heating a sample. Detailed Implementation

[0027] In some of the aspects described, the electron magnetic resonance system includes a sample heater that can be used to raise the temperature of the electron magnetic resonance sample above the operating temperature of the resonator. In some cases, the sample and resonator are configured to interact with each other in a cooled operating environment, with the sample thermally isolated from the resonator, such that the sample and resonator are maintained at different temperatures during operation. The resonator may be 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), while 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).

[0028] The sample heater may include a heating wire electrically connected to a feed line (e.g., a first feed line and a second feed line). The heating wire and feed line may be formed on a heating substrate. In other embodiments, the heating wire and feed line may be spaced apart from the sample holder. The heating substrate may be arranged on the sample holder together with the heating wire and feed line. In some cases, the heating substrate also serves to seal the sample container of the sample holder. In embodiments where the sample holder includes one or more capillaries, the heating substrate may be omitted. The sample heater may include additional components that operate to heat the electron magnetic resonance sample to a temperature above the resonator operating temperature. For example, the sample heating system may include a temperature control device, a temperature sensor, or a combination of these and other components. In some cases, the sample heater is arranged in a controlled environment near the resonator in the main magnetic field of the electron magnetic resonance system.

[0029] In some implementations, the resonator operates at a cooling temperature, and the sample heater can raise the temperature of the electron magnetic resonance sample above the resonator's temperature. For example, in some electron paramagnetic resonance (EPR) systems, the resonator can be a microwave resonator operating below the critical temperature of the superconducting material, and the sample can be held above the critical temperature during operation. 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 a cooling system with a pressure of, for example, about 500 mTorr or less. In some cases, a solid or fluid thermal insulation material can be arranged between the sample holder and the resonator. In some cases, the insulation material is a low thermal conductivity material, such as aerogel, Teflon, glass fiber, or any other insulation material. In systems operating at cooling temperatures, the temperature of the resonator can be controlled to a desired operating temperature, while the sample heater can be used to raise the temperature of the electron magnetic resonance sample to a desired sample temperature above the resonator's operating temperature. This can improve the performance of the electron magnetic resonance system, among other advantages.

[0030] The system and technical aspects described herein are applicable to 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 other types of EMR systems. As another example, all or part of the heater device can be deployed on a probe used in an EMR system, or the sample heater can be deployed 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 (e.g., blood samples, urine samples, saliva samples, etc.), or other types of samples to be measured or otherwise analyzed by the EMR system. As another example, the sample heater can be deployed with a resonator that operates in a cooled environment (e.g., at 77 K, 4 K, 300 mKelvin, 10 mKelvin, or other cooled temperatures below 273 K). In various embodiments, the sample holder and resonator are arranged in a partially vacuum environment, such as an environment with a pressure of approximately 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 used in electronic magnetic resonance systems. Additionally, the resonator can be, for example, a rectangular cavity resonator, a cylindrical cavity resonator, a dielectric resonator, an annular gap resonator, or any lumped element resonator.

[0031] In some cases, the systems and techniques described herein can be deployed in conjunction with various cooling systems, including, for example, compact closed-loop systems, open-loop systems, liquid-cooled systems, etc. In other cases, the systems and techniques described herein can be deployed in conjunction with various probes, including compact probe designs that allow low-noise cooled receiver amplifiers to be used in various configurations without interfering with sample change methods. In still other cases, the techniques and systems described herein can be deployed in conjunction with continuous-wave (CW) magnetic resonance (e.g., using CW spectroscopy), pulsed magnetic resonance (e.g., using pulsed spectroscopy), or combinations of these and other MR schemes.

[0032] In some implementations, the systems and techniques described herein offer technical advantages and improvements over existing technologies. Operating an electron magnetic resonance (EMR) system at cryogenic temperatures provides several benefits for enhancing the quality of EMR measurements. First, in some cases, cryogenic temperatures reduce the thermal noise contribution from electrical and microwave components maintained at refrigerated temperatures, leading to an increase in the signal-to-noise ratio and sensitivity of the EMR system. Second, in some cases, cryogenic environments enable the use of superconducting resonators to excite the spin ensemble of a sample and measure the electromagnetic signal generated by its response to excitation. The ultra-low dissipation of superconducting resonators is reflected in their high mass factor (Q), which has a significant impact on spin-cavity interactions, useful for a variety of applications. Finally, the polarization of the spin system (the relative difference between spin groups at energy levels) increases significantly at refrigerated temperatures, resulting in a stronger EMR signal. However, it is important to note that EMR samples are typically solid at cryogenic temperatures, making it impossible to test liquid samples or examine samples with free spins. Liquid samples often freeze and typically crystallize at refrigerated temperatures, which does not accurately reflect their normal conditions.

[0033] On the other hand, some parameters of the electron magnetic resonance sample, such as relaxation times T1 and T2 (or collectively referred to as phase memory decay time T), m Instead of T2, T1 is temperature-dependent, and this can negatively impact electron magnetic resonance measurements at low temperatures. Specifically, the spin lattice relaxation process, denoted as T1, is susceptible to lattice motion and phonon dynamics, and therefore, for most electron magnetic resonance samples, it is more temperature-dependent than T2. ​​Typically, T1 is longer at low temperatures, which reduces the saturation factor in continuous-wave (CW) magnetic resonance. When s is less than 1, the amplitude of the CW magnetic resonance signal decreases, and signal broadening can be observed. This makes CW measurements more difficult to perform.

[0034] In pulsed magnetic resonance spectroscopy, T1 characterizes the return of spin magnetization to its initial thermal equilibrium. The time scale. This process is... Given, where M z (0 + The longitudinal magnetization immediately following the RF pulse is called the T1 pulse. Therefore, the slow recovery of materials at low temperatures with long T1 values ​​requires an extended repetition time for signals averaging more than 5 T1 signals.

[0035] Therefore, in some cases, improvements can be achieved by maintaining the resonator at a low temperature to obtain optimal sensitivity and noise suppression, while keeping the temperature of the electron magnetic resonance sample significantly higher. This configuration results in a shorter T1 time, reduced thermal noise, and enables the use of low-noise cooled electronics. It also leads to an enhancement of the continuous-wave (CW) spin signal and allows for rapid signal averaging, making the overall electron magnetic resonance measurement more efficient.

[0036] The systems and techniques described herein are adaptable to a wide range 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 can be used in clinical applications, such as diagnostics, treatment, drug discovery / development, and understanding the structure and function of membrane proteins, among other applications.

[0037] Figure 1A This is a schematic diagram of an example electron magnetic resonance system 100. In various embodiments, the electron magnetic resonance system 100 can be used for applications such as 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 that holds a sample thermally coupled to a sample heater 104. In various embodiments, the sample holder 102 is constructed of a material having advantageous dielectric properties (e.g., low tangent loss) and suitable for cooling temperatures. In various embodiments, the sample holder 102 may be constructed of, for example, quartz, sapphire, borosilicate glass, polystyrene, or other similar materials. Figure 1A In the example shown, the sample holder 102 is attached to the first end of the sample transfer device 106 via an attachment 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 embodiments, the resonator 110 may be encapsulated in a resonator housing or other type of resonator package.

[0038] exist Figure 1AIn the example shown, sample heater 104 is electrically connected to temperature controller 105. In various embodiments, temperature controller 105 can be an open-loop controller (no feedback) or a closed-loop (feedback) controller. In embodiments where temperature controller 105 is an open-loop controller, temperature controller 105 can supply current to sample heater 104 in relation to a desired temperature of sample heater 104. In embodiments where temperature controller 105 is a closed-loop controller, 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 combinations thereof. In various embodiments employing closed-loop temperature control, other devices such as temperature sensors can be used in conjunction with temperature controller 105. In various embodiments, the current supplied by temperature controller 105 to sample heater 104 can be direct current (DC), alternating current (AC), current pulse sequences, periodic waveforms (such as square, sawtooth, triangular), or other types of current.

[0039] exist Figure 1A In the example shown, the second end of the sample transfer device 106 is coupled to the actuator 112. In operation, the actuator 112 drives the movement of the sample transfer device 106 and, in various embodiments, can be, for example, a single-degree-of-freedom linear actuator that translates 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 and coiled 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 the operation of the actuator. In various embodiments, the position control system 115 can be, for example, an automatic 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 can include or 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 element, such as, for example, a caliper, a micrometer, or a manual crank. This can be further enhanced by combining it with a laser pointer.

[0040] exist Figure 1AIn the example shown, the resonator 110 and sample holder 102 are arranged in a controlled environment cooled by the cooling system 114, while the second end of the sample transfer device 106 is arranged outside the controlled environment. The sample transfer device 106 is introduced into the cooling system 114 via an insertion point 113. In various embodiments, the insertion point 113 may be or may include a valve, a load locking system, or other types of components providing 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 within the cooling system 114 and the room temperature environment. In various embodiments, the vacuum pressure environment may be a millitor pressure. In various embodiments, the cooling system 114 maintains a refrigerated thermal environment for the resonator 110 and sample holder 102. In some cases, the cooling system 114 may maintain a refrigerated temperature for the resonator 110 and sample holder 102. Figure 1A In the example shown, the cooling system 114 is in thermal contact with the resonator 110 and the sample holder 102. In some cases, the cooling system 114 is cooled to liquid helium temperature (e.g., approximately 4 Kelvin), liquid nitrogen temperature (e.g., approximately 77 Kelvin), or other refrigeration temperatures. In some cases, the cooling system 114 includes a cryostat without refrigeration (“dry”). In some cases, the cooling system 114 may be implemented, with or without a liquid refrigerant, as, for example, a continuous-flow helium or nitrogen cryostat (e.g., 4 Kelvin to 300 Kelvin), a variable-temperature pulse tube cryostat (e.g., 3.5 Kelvin to 300 Kelvin), a pumped helium cryostat (e.g., 1 Kelvin to 10 Kelvin), a helium-3 cryostat (e.g., 250 mKelvin to 400 mKelvin), a dilution cryostat (e.g., 5 mKelvin to 100 mKelvin), or other types of systems or combinations thereof. Both the resonator 110 and the sample holder 102 are maintained at refrigeration temperatures. In some cases, the resonator 110 and the sample holder 102 are immersed in a cooling liquid or cooling gas and can be maintained in a vacuum or partial vacuum environment during operation. In various embodiments, the sample holder 102 and the resonator 110 are arranged in a partial vacuum environment, for example, about 500 mTorr or less. In some cases, the sample holder 102, the resonator 110, or both are maintained at a higher temperature (e.g., room temperature, etc.).

[0041] exist Figure 1A In the example shown, the main magnet system 116 generates a main magnetic field, which the resonator 110 and sample holder 102 are exposed to during operation. In various embodiments, the main magnet system 116 may be located within or outside the cooling system 114. The main magnet system 116 generates a magnetic field in a controlled environment for the resonator 110 and sample holder 102. Figure 1AThe illustrated master magnet system 116 can be implemented as a superconducting solenoid, an electromagnet, a permanent magnet, or another type of magnet that generates the master magnetic field. In various embodiments, the magnetic field is uniform over the volume of the sample region defined by the resonator 110. In various embodiments, the sample region is a region that gives a desired fill factor for a particular application. In some cases, the gradient system generates one or more gradient fields that vary spatially over the sample volume. In some cases, the gradient system includes multiple independent gradient coils that can generate gradient fields that vary along different spatial dimensions of the sample region.

[0042] exist Figure 1A In the example shown, the spin sets in the sample region of resonator 110 interact with resonator 110. A master magnetic field generated by master magnet system 116 quantizes the spin states and sets the Larmor frequency of the spin sets. Control of spin magnetization can be achieved, for example, by a radio frequency or microwave magnetic field generated by resonator 110. Figure 1A In the example shown, the spin set can be any collection of particles with non-zero spin that magnetically interact with the applied field of the electron magnetic resonance system 100. For example, the spin set can include electron spin or a combination of nuclear spin and electron spin. Examples of nuclear spin include the hydrogen nucleus (…). 1 H), carbon-13 nucleus ( 13 C) etc. In some implementations (e.g., electron paramagnetic resonance (EPR) systems), the spin set is a collection of identical spin 1 / 2 free electron spins attached to a macromolecular assembly.

[0043] exist Figure 1A In the example shown, resonator 110 is electromagnetically coupled to spectrometer system 118. In various embodiments, spectrometer system 118 acquires electron magnetic resonance data based on electron magnetic resonance signals generated by the interaction between resonator 110 and an electron magnetic resonance sample contained in sample holder 102. Typically, resonator 110 has one or more resonant frequencies and possibly other resonant frequencies or modes.

[0044] Example spectrometer system 118 can control resonator 110 and Figure 1A Other possible components or subsystems in the electron magnetic resonance system 100 shown. A spectrometer system 118 (e.g., via a coaxial cable, waveguide, etc.) is electromagnetically coupled to the resonator 110. For example, the spectrometer system 118 may be adapted to provide a voltage or current signal to drive the resonator 110; the spectrometer system 118 may also acquire a voltage or current signal from the resonator 110.

[0045] In some cases, the spectrometer system 118 includes or is connected to a controller, waveform generator, amplifier, transmitter / receiver switch, receiver, signal processor, and possibly other components. The spectrometer system 118 may include additional or different features (e.g., gradient waveform generators and gradient electronics). Figure 1A In the example shown, the spectrometer system 118 is electromagnetically connected to one or more external sources (e.g., a computer system or other sources) and can operate based on inputs provided by one or more external sources.

[0046] In some aspects of operation, a control signal is generated by the spectrometer system 118 and transmitted to the resonator 110. In some cases, the control signal may be filtered, amplified, or processed before being transmitted 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 may receive the control signal and generate a radio frequency or microwave frequency control field (e.g., a drive field) in response to the received magnetic resonance control signal. The drive frequency of the control field may be tuned to the resonant frequency of the spin, which is determined by the strength of the main magnetic field and the gyromagnetic ratio of the spin. In some aspects of operation, an electron magnetic resonance signal (e.g., an 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.

[0047] In some cases, the spectrometer system 118 can operate in multiple operating modes. In one operating mode, the spectrometer system 118 generates a control signal (e.g., a radio frequency signal, a microwave signal, etc.) which is transmitted to the resonator 110 to control the spin system in 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., digitized) and provided to a computer system for analysis, display, storage, or other actions. The computer system may include one or more digital electronic controllers, microprocessors, or other types of data processing devices. The computer system may include memory and a processor, and may operate as a general-purpose computer or as a special-purpose device.

[0048] Figure 1B This is a block diagram of an example electron magnetic resonance system 150 with a sample heater 152. The sample heater 152 is thermally coupled to the sample 154. This thermal coupling occurs in... Figure 1B The image is illustrated by arrow 156. In various embodiments, the sample heater 152 can be, for example... Figure 1A The figure shows a sample heater 104. Sample 154 may be included in a sample holder, for example... Figure 1AThe sample holder 102 is illustrated. In various embodiments, the sample holder may have a prismatic geometry. In such embodiments, the sample holder may include a cap that closes the sample holder. In some embodiments, a sample heater 152 may be coupled to the cap. In other embodiments, the sample heater 152 may be spaced apart from the sample holder. In still other embodiments, the sample holder may include, for example, one or more capillaries or other means suitable for receiving the sample 154. During use, the sample 154 is arranged in the sample region of the resonator 160. In various embodiments, the sample region is the region that gives a desired fill factor for a particular application. The resonator 160 may be, for example... Figure 1A The illustrated resonator 110 may be another type of resonator. Resonator 160 interacts with sample 154 via an electromagnetic connection. This electromagnetic connection is schematically illustrated by arrow 162. A thermal insulator 158 is disposed between sample 154 and resonator 160. In various embodiments, thermal insulator 158 may be, for example, a partial vacuum with a pressure of approximately 500 mTorr or less. In other embodiments, thermal insulator 158 may be, for example, aerogel, glass fiber, or other types of solid or fluid thermal insulation material. During operation, sample 154 and resonator 160 are disposed in a cooled environment. Sample heater 152 is used to raise the temperature of sample 154 to a desired temperature above the temperature of resonator 160. Thermal insulator 158 limits the thermal interaction between resonator 160 and sample heater 152 and prevents the introduction of thermal noise and other performance degradation of resonator 160 due to undesirable temperature rise.

[0049] Figure 2 This is a top view of an example sample holder 200 used in an electron magnetic resonance system. Figure 2 The illustration shows an example sample heater 206 and resonator 204. In various embodiments, Figure 1A The sample holder 102 can be implemented as Figure 2 The sample holder 200 is shown. Similarly, Figure 2 The sample heater 206 and resonator 204 in the sample heater 206 and resonator 204 can be, for example, about Figure 1AThe sample heater 104 and resonator 110 are discussed. In various embodiments, a sample container 202 is formed in the sample holder 200. In various embodiments, the sample container 202 may be, for example, a void formed in the sample holder 200. In other embodiments, the sample container 202 may include a plurality of microcapillaries or other structures that can hold the sample. In still other embodiments, the sample container 202 may be an array of sample containers spaced apart along the length of the sample holder 200. During use, the sample container 202 is positioned in the sample region of the resonator 204. By way of example, the resonator 204 is illustrated as a planar microstripline resonator; however, in other embodiments, other types of resonators may be utilized, such as three-dimensional cavities, coils, coplanar waveguides (CPWs), or other types of resonators used in electron magnetic resonance systems.

[0050] The sample heater 206 is positioned above the sample holder 200, such that the sample container 202 is thermally connected to the sample heater 206. The sample heater includes a first feed line 208, a second feed line 210, and a heating wire 212 electrically connected to the first feed line 208 and the second feed line 210. During operation, the first feed line 208 and the second feed line 210 are electrically connected to a temperature controller 105 and supply current to the heating wire 212.

[0051] Heating wire 212 converts electrical energy into heat energy. In various embodiments, any type of current (such as DC, AC, pulse sequences, periodic waveforms (such as square, triangular, sawtooth, etc.)) passes through heating wire 212 via first feed line 208 and second feed line 210, generating heat due to the resistance of heating wire 212. In various embodiments, heating wire 212 may be made of a high-resistivity metal or ceramic, such as tungsten, molybdenum, nickel-chromium alloy, kanthal, etc. Current is supplied to heating wire 212 by temperature controller 105 and transmitted to heating wire 212 via first feed line 208 and second feed line 210. To reduce overall circuit losses, first feed line 208 and second feed line 210 may be made of highly conductive materials such as copper, gold, etc.

[0052] Figure 3 This is a perspective view of an example sample holder 200 and an example sample heater 206 with tapered wire, showing their placement on a resonator 204. In various embodiments, the heating wire 302 can be designed as a straight line, a tapered line, a meandering line, or other patterns, such as... Figures 3 to 6B As illustrated, and can be a single unit or as shown in the diagram. Figure 6C The illustration shows an array of filament unit cells. This is presented as an example. Figure 3 The illustration shows a heating wire 302 with a conical geometry. Figure 4 Another example heating wire 402 is illustrated with a pattern of horizontally meandering lines. Figure 5 Details of heating wire 302, which is located alongside heating wire 402, are provided for comparison. Figure 3 The heating wire 302 shown includes an end portion 304 electrically connected to a first feed line 208 and a second feed line 210. A central portion 306 has a narrower width than the end portion 304, thereby increasing resistance and generating heat in the region of the central portion 306. Figure 4 The heating wire 402 shown includes parallel segments 404 that are joined sequentially at opposite ends by vertical connecting segments 406, giving the heating wire 402 a meandering shape. This shape increases the total length of the heating wire 402, which increases resistance and the heat generated.

[0053] In one example, if the length, width, and thickness of heating wire 212 are 0.8 mm, 0.05 mm, and 0.001 mm, respectively, and heating wire 212 is made of molybdenum with a conductivity of σ = 1.76 × 10⁷ S / m, then the resistance of heating wire 212 will be R = 0.9091 Ω. Additionally, a meandering heating wire with a total length of 10 mm will have a resistance of R = 11.3636 Ω. These example calculations demonstrate the dependence of the wire's resistance on its size, shape, and material. For comparison, a copper feeder with a conductivity of σ = 5.8 × 10⁷ S / m, a width of 0.5 mm, a thickness of 0.001 mm, and a length of 13.82 mm will have a resistance of R = 0.4766 Ω. Since the source of heat flow in the structure is determined by the relationship P = RI... 2 Depending on the electrical power dissipated in the resistance wire, the amount of electrical loss and heat transfer can be controlled by adjusting the current source of the drive wire circuit (e.g., temperature controller 10). Figures 4 to 6C The paper introduces alternative design schemes for heating wires.

[0054] Figures 6A to 6C The illustration shows a side-by-side comparison of various implementation schemes with heating wires of various geometries. Figure 6A An embodiment of a heating wire 602 having a longitudinally meandering geometry is illustrated. The heating wire 602 includes parallel segments 604 connected sequentially at opposite ends via connecting segments 606. The parallel segments 604 are configured perpendicular to the longitudinal axis of the sample holder 608. Figure 6B An embodiment of a heating wire 612 with a transversely meandering geometry is illustrated. The heating wire 612 is structurally similar to the one described above. Figure 4 The heating wire 402 is described. The heating wire 612 includes parallel segments 614, which are joined at opposite ends by vertical connecting segments 616, thereby giving the heating wire 402 a meandering shape. The parallel segments 614 are arranged parallel to the longitudinal axis of the sample holder 615. Figure 6C An embodiment of a sample heater 620 having an array of heating wires 618 is illustrated. Figure 6C In the example shown, the heating wire 618 has a tapered geometry; however, in other embodiments, the heating wire 618 may have... Figures 2 to 6B The types of straight geometry, longitudinal meandering geometry, or transverse meandering geometry, or other geometries are illustrated in the diagram. During operation, the array of heating wires 618 increases the surface area of ​​the sample holder 626 thermally connected to the sample heater 620. In other embodiments, the array of heating wires 618 may also heat an array of sample containers. In various embodiments, heating wires 602, 612, and sample heater 620 may be integrated with an electromagnetic resonance system (such as those described above). Figure 1A The described electronic magnetic resonance system 100 is used in conjunction with it.

[0055] Figure 7A This is a cross-sectional view of an example resonator package. The heating wire 702 can be, for example, as described above. Figures 2 to 6C The heating wires described are 212, 302, 402, 602, 612, or 618. In various embodiments, the heating wire 702 has a planar geometry and may be fabricated on a heater substrate 704 made of a dielectric material. In some embodiments, the heating wire 702 and the heater substrate 704 are positioned on top of a sample holder 706 and form a cover for the sample holder. The sample holder 706 is a dielectric plate having one or more sample containers 708 serving as a carrier and container for an electron magnetic resonance sample. In various embodiments, the sample heater 701, together with the heater substrate 704, acts as a cover for the sample holder 706 to seal the electron magnetic resonance sample. As will be discussed below, in other embodiments, the sample heater may be spaced apart from the sample holder. In still other embodiments, the sample holder may include at least one microcapillary that does not require a cover. In some embodiments, the heater substrate 704 of the sample heater 701 may be the same dielectric material as the sample holder 706 and may be selected from any of the following: borosilicate glass, fused silica glass, fused silica, sapphire, silicon, or any other dielectric material suitable for electronic magnetic resonance applications.

[0056] Furthermore, the heater substrate 704 and the sample holder 706 serve as a medium to conduct heat from the heating wire 702 located on the heater substrate 704 to the electron magnetic resonance sample in the sample holder 706, such as Figure 7A As shown. To maintain the highest possible quality factor for the resonator 712, the heating wire 702 is positioned at a distance D from the electron magnetic resonance sample located directly above the resonator 712 (e.g., ...). Figure 2(as shown). Therefore, the thermal conductivity of the heater substrate 704 should be high enough to transfer heat to the electron magnetic resonance sample, but not so high that it cannot 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 plate of the sample container 708 can be determined based on the spatial magnetic field distribution of the resonator 712.

[0057] While transferring heat to the electron magnetic resonance sample to increase its temperature, significant temperature changes in the resonator 712 should be avoided, as such an increase could lead to a decrease in the quality factor of the resonator 712 or otherwise degrade its performance and introduce thermal noise. To suppress heat transfer to the resonator 712, a thermal insulation layer 714 is used between the sample holder 706 and the resonator 712. Figure 7A In the illustrated example, the thermal insulation layer 714 can be a partial vacuum implemented to enhance thermal insulation. In various embodiments, the partial vacuum is provided by the internal environment of the cryostat system. In various embodiments, the thermal insulation layer 714 can be a region having a pressure of approximately 500 mTorr or less. In other embodiments, other forms of thermal insulation can be utilized. In some cases, a low thermal conductivity material, such as aerogel, Teflon, glass fiber, or any other insulating material, can be disposed within the thermal insulation layer 714.

[0058] exist Figure 7B In the illustrated example, a sample heater 751 with a heating wire 752 is arranged on a heater substrate 754. A cover 753 is placed on top of a sample holder 706, and the heater substrate 754 is placed on top of the cover 753. Therefore, in various embodiments, the sample heater 751 and the heater substrate 754 do not need to be integral with the cover 753.

[0059] Figure 8A This is a perspective view of an example sample heater 802 contained within a resonator package 804. A resonator 806 is housed within the resonator package 804, which is constructed of a thermally and electrically conductive material (e.g., copper). In various embodiments, the resonator package 804 can be used in electronic magnetic resonance systems, such as those described above relative to... Figure 1A The illustrated electronic magnetic resonance system 100. Resonator 806 can be any of the types described above. During use, resonator 806 is arranged within a resonator package. For clarity, Figure 8A The upper portion of the resonator package 804 is not shown. The sample heater 802 extends from the upper portion of the resonator package 804 and is positioned such that when the sample container 808 is positioned in the sample region of the resonator 806, the sample container 808 of the sample holder 810 is thermally coupled to the sample heater 802. The sample heater 802 is located in... Figure 8AThe example is illustrated as having a spiral heating wire; however, in other embodiments, the sample heater 802 may comprise any type of heating wire, such as a straight wire, a tapered wire, a longitudinally meandering wire, a transversely meandering wire, or other types of wire. Therefore, the heating wire can be arranged in a manner similar to that described above. Figures 2 to 6C The heating wires 212, 302, 402, 602, 612, or 618 are constructed as described.

[0060] Figure 8B This is a perspective view of an example spiral sample heater used with a tubular sample holder 860 and included in a resonator package 854. The sample holder 860 is a tubular member, such as a capillary or microcapillary. In various embodiments, the sample holder 860 does not use a cap. Similar to Figure 8A The sample heater 802 extends from the upper part of the resonator package 804 and is positioned such that when the sample container 858 is positioned in the sample region of the resonator 806, the sample container 858 of the sample holder 860 is thermally coupled to the sample heater 802. Figure 8B The sample heater 802 is illustrated by way of example as having a spiral heating wire; however, in other embodiments, the sample heater 802 may include any type of heating wire, such as a straight wire, a tapered wire, a longitudinally wavy wire, a transversely wavy wire, or other types of wire.

[0061] Figure 9 This is a perspective view of an example sample holder, illustrating the sample heater 206 and resonator 204. (As mentioned above regarding...) Figure 2 The sample heater 206 includes a first feed line 208 and a second feed line 210 electrically connected to the heating wire 912. By way of example, the heating wire 912... Figure 9 The heating wire 912 is illustrated as a tapered heating wire; however, in other embodiments, the heating wire may comprise any type of heating wire, such as a straight wire, a tapered wire, a longitudinally meandering wire, or a transversely meandering wire. Therefore, the heating wire 912 may be arranged in a manner similar to that described above. Figures 2 to 6C The heating wires 212, 302, 402, 602, 612, or 618 are constructed as described. A first feed line 208 and a second feed line 210 supply current to the heating wire 912. In various embodiments, the widths of the first feed line 208 and the second feed line 210 are greater than the width of the heating wire 912 to reduce the resistance through the first feed line 208 and the second feed line 210.

[0062] Figure 10This is a perspective view of an example sample holder 102, illustrating an example electrical connection of the sample heater 206. When the sample container 202 is inserted into a resonator package (not shown for clarity), a first feed 208 and a second feed 210 contact a pair of electrical conductors 1002 extending from the upper part of the resonator package, such as resonator package 804. In various embodiments, the pair of electrical conductors 1002 are, for example, spring-loaded pins. In this embodiment, the pair of electrical conductors 1002 are spring-loaded against the first feed 208 and the second feed 210 to maintain electrical connection with the first feed 208 and the second feed 210. Figure 10 In the illustrated example, a pair of electrical conductors 1002 include a bent spring section 1004; however, in other embodiments, the electrical conductors 1002 may utilize, for example, a linear telescopic spring or any other configuration to maintain electrical contact with the first feed 208 and the second feed 210.

[0063] The following paragraphs discuss the simulation of the example sample heater and its impact on the performance of the example resonator. While the simulations discussed below illustrate specific characteristics by way of example, those skilled in the art will recognize that the principles described below can be applied to any of the examples illustrated herein.

[0064] Figure 11 The illustration shows the simulated S-parameters of an example planar microstrip superconducting microwave resonator in the presence of a heating wire. Regarding... Figures 11 to 16 The components described may be those mentioned above regarding Figures 1 to 12. Figure 10 Any component described. Specifically, regarding... Figures 11 to 16 The heating wire being discussed can be Figures 2 to 6C Any heating wire described herein. Data indicates that by positioning the heating wire at a lateral distance D away from the resonator (e.g., ... Figure 2 At the location shown, the quality factor and insertion loss of the device can be effectively maintained with minimal influence from the heating wire. Superconducting resonators are a general-purpose technique that can be implemented in various ways, including but not limited to microstrip lines, coplanar waveguides (CPWs), and lumped-element planar resonators. Furthermore, resonators can be configured as arrays. Figure 11 In the example shown, the gap between individual microstrip resonators is 450 μm, the substrates of the housing and heating circuit are both 0.5 mm thick, and they are made of borosilicate with a dielectric constant of 4.0472 and a loss tangent of 0.0022.

[0065] Table 1 presents the calculated quality factor and insertion loss for various lateral positions of the heating wire. The data show that both the Q-factor and insertion loss deteriorate as the heating wire is placed closer to the resonator. This leads to a significant decrease in resonator performance, highlighting the importance of proper placement of the heating wire relative to the resonator. Furthermore, a comparison of simulation results for bare resonators with and without a dielectric sample holder and heating substrate shows that a significant amount of dielectric loss is introduced through the borosilicate material. The data indicate that resonator performance improves as the distance (D) between the heating wire and the resonator increases. Specifically, when the distance D = 12 mm, the performance is comparable to the case where the heating wire is removed. When the distance D = -1 mm, the heating circuit passes through the resonator, causing the heating wire to shift closer to the microwave connector.

[0066] structure Q IL(dB) Resonator only (no borosilicate) 17249 -0.4788 A resonator with borosilicate material (without heating wire) 10796 -4.2305 D = 12mm (very far from the heating wire) 10774 -4.2361 D = 3mm (behind the resonator) 9972 -5.2494 D = 2mm (behind the resonator) 9238 -5.6727 D = 1 mm (behind the resonator) 7218 -7.5769 D = -1mm (in front of the resonator) 6984 -7.2025 D = 0mm (on the resonator) 5848 -8.7675

[0067] The electron magnetic resonance sample is heated by converting electrical energy into heat energy through resistive elements. Figure 12 A superimposed graph of the current density through the heating circuit is shown. This graph illustrates that when a current of 250 mA is applied to the circuit, it results in a current density of 5 × 10⁻⁶ in the heating wire. 9 A / m 2 This results in a power dissipation of 0.0568 W in the wire and 0.0302 W in each feeder. The temperature of the electron magnetic resonance sample can be controlled by adjusting the input current and thus the power dissipation. However, to ensure effective operation of the cooling system at its operating temperature (ambient temperature), a temperature controller 105 should be used to regulate the power input to the heating circuit to keep it within the limits set by the cooling system's rated power.

[0068] During operation, a resonator with a sample heater is placed within a cooling system, which can take the form of a continuous-flow cryostat or a vacuum cryostat, such as a closed-loop cooling system or a He... 3 Cryostats, dilution freezers, or other types of refrigeration systems. To protect the resonator (resonator in various embodiments) from the temperature rise caused by the sample heater, a thermal insulation layer acts as a thermal barrier between the resonator and the sample holder. In vacuum cryostats, this layer is effectively provided by a partial vacuum generated within the cryostat's internal environment, eliminating the need for additional materials. In various embodiments, the partial vacuum has a pressure of approximately 500 mTorr or less. However, continuous-flow cryostats can also be used for resonators with sample heaters. The cryostat environment is maintained at the system's base temperature, such as 4 K (-269 °C), which is maintained at ambient temperature T. ∞ And the temperature of external radiation used for resonators, sample heaters, and microwave packages.

[0069] In cryogenic systems with a partial vacuum, the primary modes of heat transfer are conduction or radiation, as no fluid is present. However, in continuous-flow cryogenic systems, all three modes of heat transfer (conduction, convection, and radiation) are present and can contribute to the overall heat transfer process.

[0070] The thermal properties of the sample heater were simulated. Since vacuum materials are unacceptable for thermal analysis, a "near-vacuum" medium was used for the simulation. The material was modeled using the ideal gas equation PV = nRT, where n is the number of moles of gas, R = 8.31 J / K·mole is the universal gas constant, and P, V, and T are the state variables of gas pressure, volume, and temperature, respectively. Mass density can be calculated using the equation... To determine this, we need to find M, where M is the molar mass of the gas. For example, using this equation and the following data for refrigeration systems and dry air materials: M = 18.97 g / mole, P = 2 × 10⁻⁶. -6 With Bar = 0.2 Pa and T = 4 K, we find that ρ = 1.1414 × 10⁻⁶. -4 Kg / m 3 The mass density of normal air at atmospheric pressure is ρ = 1.1614 kg / m³. 3 .

[0071] There are two main types of specific heat, also known as heat capacity—limited to fluids: one that, under constant volume (isochoric), is generated by C v This indicates that another type of C, under constant pressure (isobaric), p It is indicated that, by utilizing Maxwell's thermodynamic equations, the following equation can be used to calculate C at a constant temperature. p (and C) v The partial derivatives of ) with respect to pressure (and volume).

[0072]

[0073] By substituting the ideal gas equation with state PV = nRT into the previous equation, we obtain... and Therefore, for an ideal gas, the heat capacity does not depend on pressure (or volume) and is only a function of temperature, as shown in equation [equation missing]. and As shown. Therefore, "near-vacuum" materials can be used with normal air (i.e., C). p =1000J / Kg.K, and C V =720J / Kg.K) has the same heat capacity.

[0074] The thermal conductivity of absolute vacuum is zero because there are no atomic vibrations to transfer heat. The relationship between the thermal conductivity of air and pressure was plotted, and a low value of κ = 0.000261 W / mK was chosen.

[0075] The governing equations for heat transfer are

[0076]

[0077] In the above equation, T is the temperature, and q”’ is the volumetric heat source density (W / m³). 3 ), C is the thermal conductivity tensor of isotropic or heterogeneous materials. p ρ is the specific heat capacity, and ρ is the mass density. This equation combines Fourier's law of heat conduction. The results, among which It is the heat flux per unit area (W / m²) 2 Law of Conservation of Energy It is the first law of thermodynamics (for the source free region) and the definition of specific heat capacity ΔQ = mC p ΔT, where Q is the thermal energy. For an isotropic medium without a heat source, this equation can be simplified to... The normal heat diffusion equation in the form of [formula missing], where the right side represents the heat of diffusion (or heat of conduction), and the left side represents the heat of accumulation (or heat of storage). Parameters It is called thermal diffusivity and is a measure of the ratio of diffuse heat to stored heat. Furthermore, for the case of transient conduction, the time constant of the temperature change is estimated as... Where Δx is the length of the thermal conduction. This is for steady-state conditions on materials with uniaxial thermal conductivity. Heat transfer, represented by the partial differential equation for heat equilibrium, is as follows:

[0078]

[0079] When an electrothermal generator with a flowing current I and a resistance R is present, the quick 1D approximation used to estimate the temperature rise is:

[0080]

[0081] Where κ is the thermal conductivity of the medium, A is the cross-sectional area for heat transfer, and Δx (represented as L in the following sentences) is the length scale of the heat conduction. For example, if borosilicate glass with a thermal conductivity of κ = 1.14891 W / mK, a length scale of Δx = 2 mm, a cross-sectional area of ​​A = 0.8 mm × 1.8 mm, I = 150 mA, and R = 0.9 Ω is used, the estimated temperature will be ΔT ~ 24.47 K, which is close to Figure 13 The chart in the image.

[0082] In this case, the equation τ=L can be used. 2 / α=ρC p L 2 / κ is used to calculate the time constant. If the specific heat capacity of the borosilicate used is C... p =799.744 J / (Kg·K), and the mass density is ρ = 2124.85 Kg / m³ 3 We found that τ ~ 5.9s.

[0083] Another contribution to heat transfer in our devices and platforms is thermal radiation. Radiation is a highly nonlinear mode of heat transfer. A simplified form of the equations describing radiation from one surface to another (surface to surface) is...

[0084]

[0085] Where A i It is the surface area, ∈ i The emissivity of the surface determines the amount of emitted thermal radiation, σ = 5.67 × 10⁻⁶. -8 W / m 2 K 4 It is the Stefan-Boltzmann constant, and F ij It is the perspective factor between surfaces, which is defined at temperature T i The fraction of the total radiant energy leaving surface i at [K], which at temperature T j [K] directly reaches surface j, and has the following relationship:

[0086]

[0087] In Equation 7, s represents the infinitesimal area dA on surface i. i With the infinitesimal area dA on surface j j The distance between them. Angle θ i (or θ) j ) is at position dA i (or dA j The normal on surface i (or surface j) at point ) intersects with the line connecting dA. i to dA j The angle between the lines.

[0088] Surface-to-surface equations are a cost-effective method for considering thermal radiation in geometrically simple surfaces. However, they are limited by several assumptions, including that the surface is gray (emissivity equals absorptivity and is wavelength-independent), opaque to thermal radiation (transmittance is neglected), inherently diffuse (reflectivity is independent of the incident direction), and does not consider medium-dependent absorption, re-emission, and scattering. More advanced methods employ ray-tracing radiation models, where simple surfaces are replaced by clusters of cell surfaces.

[0089] The general equations for radiative heat transfer in absorbing, emitting, and anisotropically scattering media can be expressed by the following global differential radiative transfer equation:

[0090]

[0091] Where I and I b These are the radiation intensity and the blackbody intensity, respectively, and σ s κ and β are the scattering, absorption, and extinction coefficients. The scattering phase function Φ is expressed as [Sr -1 The unit is ]. This model is effective for complex geometries with many participating surfaces and is considered a more conservative approach. The first term on the right-hand side represents emission, the second absorption, and the third scattering in the medium, which is represented by integration over solid angles. Due to the complexity of the equations and their associated boundary conditions, a "discrete coordinate" method or S... n This method approximates the problem. The model is used in simulations to illustrate radiative heat transfer.

[0092] In heat transfer via convection, fluid motion is involved to transfer heat. Convection models are generally the most efficient way to transfer heat in liquids and gases. This involves heat conduction through surfaces and heat transport to / from surfaces via fluid advection. The velocity field has a significant impact on the rate of heat transfer, therefore accurate prediction of fluid flow is crucial for accurate prediction of heat transfer. The simple equation for heat transfer in convection is given by Newton's law of cooling, where the heat transfer coefficient is h:

[0093] q ″ =h(TT) ∞ (Equation 9)

[0094] In more complex cases, convection models are described by a combination of the continuity equation (mass conservation), the momentum equation (Navier-Stokes equations), and the energy equation (temperature distribution):

[0095]

[0096] Where V,p, τ, and g are the velocity vector, pressure, stress tensor, and gravity vector, respectively. A convection model is not used in the simulation because the example apparatus is housed in a vacuum cryostat.

[0097] Figure 13 This is a graph illustrating the temperature distribution along a line perpendicular to the sample holder, plotted relative to a changing current flowing through the heating wire. The line begins at the resonator and passes through all the borosilicate material. The heating wire is 2 mm laterally away from the resonator and the sample. Figure 13 In the diagram, the leftmost segment of the temperature distribution is due to thermal radiation. Figure 14 These sections are magnified and displayed for closer inspection. In all simulations, it is assumed that the emissivity of all surfaces is ∈ = 0.8.

[0098] Figure 14 The figure shows the temperature rise curves relative to the current when the heating wire is positioned laterally 1 mm and 2 mm away from the center of the sample. Additionally, the temperature rise directly above the resonator is shown, and it is found to be significantly lower than the temperature rise within the sample.

[0099] Figure 15 The figure illustrates the superposition of temperature fields (shown in degrees Celsius) on the bottom surface of the sample holder when a current of 150 mA flows through a heating element 2 mm away from the sample.

[0100] Figure 16 The figure illustrates the superposition of the temperature field (shown in degrees Celsius) across the sample volume when a current of 150 mA flows through a heating element 2 mm away from the sample. The temperature change across the sample volume is less than 0.5 K.

[0101] Figure 17 This is a flowchart illustrating a process 1700 for heating a sample in an electron magnetic resonance system. In various embodiments, the electron magnetic resonance system is as described above. Figure 1A The example electron magnetic resonance system 100 discussed, or other types of electron magnetic resonance systems, may be used. Example process 1700 may include additional or different operations, and these operations may be performed in the order shown or in a different order. In some cases, one or more operations may be repeated, omitted, or performed in a different manner.

[0102] At position 1702, the sample holder is received in the sample region of the resonator. The sample holder can be, for example... Figure 1A The example sample holder 102 shown above and Figures 2 to 10 Any example sample holder shown, or other types of sample holders. The resonator operates in the main magnetic field of the main magnet system. The resonator package can be arranged in a refrigerated thermal environment controlled by a cooling system. The sample holder is thermally coupled to the sample heater. The sample heater can be, for example... Figure 1AThe sample heater 104 shown Figures 2 to 10 The sample heater shown may be any example sample heater or other type of sample heater. In various embodiments, the sample heater includes a heating wire arranged between two feed lines. The feed lines are connected to a power source via, for example, a pair of spring-loaded pins or other configuration.

[0103] At 1704, the sample holder and sample heater are thermally insulated from the resonator. In various embodiments, the thermal insulation may be a partial vacuum layer having a pressure of approximately 500 mTorr or less, generated, for example, by a refrigeration system. In some embodiments, the partial vacuum layer may be thermal insulation layer 714. In other embodiments, the thermal insulation may be a fluid or solid layer. In some cases, the thermal insulation is a low thermal conductivity material, such as aerogel, Teflon, glass fiber, or any other insulating material.

[0104] At 1706, the temperature of the resonator is controlled. In various embodiments, a cooling system is used to control the temperature of the resonator. In embodiments where the resonator is a superconducting resonator, the temperature is controlled to a level below the critical temperature of the resonator.

[0105] At 1708, a sample heater is used to control the sample temperature. In various embodiments, the sample temperature is controlled by supplying current to the feed line and heating wire of the sample heater. In various embodiments, the sample temperature is controlled by applying current to the sample heater. The sample heater can be as shown in Figure 1 to... Figure 11 This can be any sample heater or other type of sample heater described herein. In various embodiments, a temperature controller, such as temperature controller 105, is used to control the temperature. In various embodiments, the temperature control of the sample can be open-loop or closed-loop. In embodiments employing open-loop control, a current corresponding to the desired temperature is applied to the sample heater. In embodiments utilizing closed-loop control, feedback information, such as sample temperature or relaxation times (T1 and T2), can be utilized. In various embodiments, measurements of temperature-dependent spin dynamics, such as spin signal amplitude, relaxation time (T1 and T2) measurements, or any other temperature-dependent spin signal, can be measured as a representation of the sample temperature, thereby allowing closed-loop control of the sample heater while eliminating the need for a temperature sensor near the electron magnetic resonance sample.

[0106] In a first example, this disclosure relates to an electron magnetic resonance apparatus. The electron magnetic resonance apparatus includes a microwave resonator disposed in a cooled environment. A sample holder is disposed together with the microwave resonator in the cooled environment. The sample holder includes a sample container that is thermally insulated from the microwave resonator and holds the 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 above the temperature of the resonator.

[0107] In various embodiments of the first example, the device may include a heater substrate in thermal contact with the sample holder. In various embodiments of the first example, the sample heating device may be in mechanical contact with the sample holder. In other embodiments, the sample heating device may be spaced apart from the sample holder.

[0108] In various embodiments of the first example, the sample heating device may include a heating wire electrically connected to a pair of electrical feeders. A temperature controller may be connected to the pair of electrical feeders via a pair of spring-loaded pins. In various embodiments, the heating wire may be a resistance heating wire and may be one of a straight wire, a tapered heating wire, a longitudinally meandering wire, or a transversely meandering wire.

[0109] In various embodiments of the first example, the device may include a temperature controller configured to control the temperature of the sample heating device based on the temperature of the sample. In this embodiment, the sample holder may include a temperature sensor configured to measure the temperature of the sample.

[0110] In various embodiments of the first example, the microwave resonator may include a superconducting material and be configured to operate below the critical temperature of the superconducting material.

[0111] In various embodiments of the first example, the sample heating device may include an array of heating wires.

[0112] In various embodiments of the first example, the sample container may be thermally insulated from the resonator by a thermal insulating material disposed between the resonator and the sample holder. In other embodiments, the sample container may be thermally insulated from the resonator by a partial vacuum region disposed between the resonator and the sample holder.

[0113] In various embodiments of the first example, the sample holder and the sample heating device may be arranged in a cooling system that includes a temperature control system for setting the temperature of the resonator to a first cooling temperature.

[0114] In various embodiments of the first example, the sample holder can be configured to operate in the main magnetic field of a probeless magnetic resonance system. In other embodiments, the sample holder can be configured to operate on a probe in the main magnetic field of the magnetic resonance system.

[0115] In a second example, aspects of this disclosure relate to an electron magnetic resonance system. The electron magnetic resonance system includes a main magnet system configured to generate a main magnetic field and a cooling system. A microwave resonator is arranged in the cooling system. The microwave resonator is configured to operate in the main magnetic field and interact with a sample in a 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 above the temperature of the microwave resonator.

[0116] The various implementation schemes of the second example include the features and variations described above with respect to the first example.

[0117] In a third example, this disclosure relates to an electron magnetic resonance method. The method includes positioning a sample in a sample region of a resonator arranged in the main magnetic field of an electron magnetic resonance system. The sample is thermally isolated from the resonator. The temperature of the resonator is controlled within a cooling temperature range by operating a cooling system. The temperature of the sample is controlled within a temperature range above the resonator temperature by operating a sample heating system. A control field is applied to the sample in the sample region by operating the resonator.

[0118] In various embodiments of the third example, the sample holder includes a sample container for holding the sample, and the method includes positioning a sample heating system in thermal contact with the sample holder.

[0119] In various embodiments of the third example, the sample heating system includes a heating wire electrically connected to a pair of electrical feeders, and controlling the temperature of the sample includes transferring current to the heating wire.

[0120] In various embodiments of the third example, the method may include measuring the temperature of the sample and controlling the temperature of the sample based on the measured temperature. In various embodiments, the temperature of the sample may be measured by the operation of a temperature sensor.

[0121] In various implementations of the third example, the method may include obtaining a spin signal from the sample through operation of a resonator and measuring the temperature of the sample based on the temperature-dependent characteristics of the spin signal.

[0122] In various embodiments of the third example, the sample holder may include a sample container for holding the sample, and the method may include thermally isolating the sample container from the resonator by means of a thermal insulating material disposed between the resonator and the sample holder. In other embodiments, the method may include thermally isolating the sample container from the resonator by means of a partial vacuum region disposed between the resonator and the sample holder.

[0123] In a fourth example, this 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 wire is electrically connected to the first and second feed lines. A temperature control unit is electrically connected to the heating wire via the first and second feed lines. A sample holder includes a sample container thermally connected to the heating wire. The sample container is thermally insulated from the microwave resonator operating in a cooled environment.

[0124] The various implementation schemes of the fourth example include the features and variations described above with respect to the first example.

[0125] While this specification contains numerous details, these should not be construed as limiting the scope of the claims, but rather as descriptions of features specific to particular examples. Certain features described in this specification or illustrated in the drawings may also be combined in the context of individual embodiments. Conversely, various features described or illustrated in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments.

[0126] Similarly, although the operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring these operations to be performed in the specific order shown or in a sequential order, or to perform all the illustrated operations to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of the various system components in the above embodiments should not be construed as requiring such separation in all embodiments, and it should be understood that the illustrated program components and systems can generally be integrated together in a single product or packaged into multiple products.

[0127] Several implementations have been described. Nevertheless, it should be understood that various modifications can be made. For example, in various embodiments, a guiding system can be used to facilitate the insertion and placement of the sample holder within the resonator package and to prevent breakage of the sample holder. Such a guiding system may include, for example, tracks that support opposite edges of the sample holder during placement. Therefore, other implementations are within the scope of the appended claims.

Claims

1. An electron magnetic resonance imaging (MRI) device, comprising: A microwave resonator, wherein the microwave resonator is arranged in a cooled environment; A sample holder, disposed together with the microwave resonator in the cooling environment, wherein the sample holder includes a sample container that is thermally insulated from the microwave resonator and holds the sample in the sample region of the microwave resonator; and A sample heating device thermally connected to the sample container and configured to control the temperature of the sample above the temperature of the resonator.

2. The device according to claim 1, wherein the sample heating device includes a heater substrate in thermal contact with the sample holder.

3. The apparatus according to any one of claims 1 to 2, wherein the sample heating device is in mechanical contact with the sample holder.

4. The apparatus according to any one of claims 1 to 2, wherein the sample heating device is spaced apart from the sample holder.

5. The apparatus of claim 1, wherein the sample heating device comprises a heating wire electrically connected to a pair of electrical feeders.

6. The device of claim 5, further comprising a temperature controller connected to the pair of electrical feeders via a pair of spring-loaded pins.

7. The device according to claim 5, wherein the heating wire comprises a resistance heating element.

8. The device according to claim 7, wherein the heating wire is one of a straight wire, a tapered heating wire, a longitudinally serrated wire, and a transversely serrated wire.

9. The apparatus according to any one of claims 1 to 2, comprising a temperature controller configured to control the temperature of the sample heating device based on the temperature of the sample.

10. The apparatus of claim 9, wherein the sample holder includes a temperature sensor configured to measure the temperature of the sample.

11. The device according to any one of claims 1 to 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 apparatus according to any one of claims 1 to 2, wherein the sample heating device comprises an array of heating wires.

13. The apparatus according to any one of claims 1 to 2, wherein the sample container is thermally insulated from the resonator by a thermal insulation material disposed between the resonator and the sample holder.

14. The apparatus according to any one of claims 1 to 2, wherein the sample container is thermally insulated from the resonator by a partial vacuum region disposed between the resonator and the sample holder.

15. The apparatus according to any one of claims 1 to 2, wherein the sample holder and the sample heating device are arranged in a cooling system, the cooling system comprising a temperature control system that sets the temperature of the resonator to a first cooling temperature.

16. The apparatus according to any one of claims 1 to 2, wherein the sample holder is configured to operate in the main magnetic field of a probeless magnetic resonance system.

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

18. An electron magnetic resonance system, comprising: A main magnet system, which is configured to generate a main magnetic field; Refrigeration system; A microwave resonator is arranged in the cooling system, wherein the microwave resonator is configured to operate in the 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 in the sample region; and A sample heating device thermally connected to the sample container and configured to control the temperature of the sample above the temperature of the microwave resonator.

19. The system of claim 18, wherein the sample heating device comprises a heater substrate in thermal contact with the sample holder.

20. The system according to any one of claims 18 to 19, wherein the sample heating device is in mechanical contact with the sample holder.

21. The system according to any one of claims 18 to 19, wherein the sample heating device is spaced apart from the sample holder.

22. The system of claim 18, wherein the sample heating device comprises a heating wire electrically connected to a pair of electrical feeders.

23. The system of claim 22, further comprising a temperature controller connected to the pair of electrical feeders via a pair of spring-loaded pins.

24. The system of claim 22, wherein the heating wire comprises a resistance heating element.

25. The system of claim 24, wherein the heating wire is one of a straight wire, a tapered heating wire, a longitudinally serrated wire, and a transversely serrated wire.

26. The system according to any one of claims 18 to 19, comprising a temperature controller configured to control the temperature of the sample heating device based on the temperature of the sample.

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

28. The system according to any one of claims 18 to 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 any one of claims 18 to 19, wherein the sample heating device comprises an array of heating wires.

30. The system according to any one of claims 18 to 19, wherein the sample container is thermally insulated from the resonator by a thermal insulation material disposed between the resonator and the sample holder.

31. The system according to any one of claims 18 to 19, wherein the sample container is thermally insulated from the resonator by a partial vacuum region disposed between the resonator and the sample holder.

32. The system according to any one of claims 18 to 19, wherein: The sample holder and the sample heating device are arranged in the refrigeration system; and The cooling system includes a temperature control system, which sets the temperature of the resonator to a first cooling temperature.

33. An electron magnetic resonance method, comprising: Position the sample in the sample region of the resonator arranged in the main magnetic field of the electron magnetic resonance system; This thermally isolates the sample from the resonator. The temperature of the resonator is controlled within the cooling temperature range by operating the cooling system; By operating the sample heating system, the temperature of the sample is controlled within a temperature range above the temperature of the resonator; as well as By operating the resonator, a control field is applied to the sample in the sample region.

34. The method of claim 33, wherein the sample holder includes a sample container for holding the sample, and the method includes 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 wire electrically connected to a pair of electrical feeders, and controlling the temperature of the sample comprises transmitting current to the heating wire.

36. The method according to any one of claims 33 to 35, comprising: Measure the temperature of the sample; as well as The temperature of the sample is controlled based on the measured temperature of the sample.

37. The method of claim 36, further comprising measuring the temperature of the sample by operating a temperature sensor.

38. The method of claim 36, comprising: Spin signals are obtained from the sample by operating the resonator; as well as The temperature of the sample is measured based on the temperature correlation characteristics of the spin signal.

39. 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 thermally isolating the sample container from the resonator by means of a thermal insulating material disposed between the resonator and the sample holder.

40. The method of any one of claims 33 to 35, wherein the sample holder comprises a sample container for holding the sample, and the method comprises thermally isolating the sample container from the resonator by means of a partial vacuum region disposed between the resonator and the sample holder.

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