Magnetic resonance transmitter

Abstract

Device with a coil (102) for applying magnetic resonance (MR) pulse sequences to a substance (101), wherein the coil (102) a first coil section (202) and comprising a second coil section (204), wherein the first coil section (202) and the second coil section (204) allow current of opposite polarity to pass through, with a transmitter circuit (110) for generating the MR pulse sequences and supplying the MR pulse sequences to the coil (102), characterized in that the coil (102) comprises the first coil section (202) and the second coil section (204) along a longitudinal axis (203) of the coil (102), wherein the first coil section (202) comprises a first winding length, the second coil section (204) comprises a second winding length, and at least one section of the first winding length and at least one section of the second winding length overlap along the longitudinal axis (203) of the coil (102) and are connected to a first switch (502) coupled to the first coil section (202) and configured to selectively supply the first coil section (202) with current, and to a second switch (504) coupled to the second coil section (204) and configured to selectively supply the first coil section (202) with current. is configuredto selectively supply current to the second coil section (204).

Description

[0001] The application relates to a device with a coil for applying magnetic resonance (MR) pulse frequencies to a substance according to the preamble of claim 1. The application further relates to a method for applying high-frequency pulses to a substance and a magnetic resonance (MR) system. TECHNICAL AREA

[0002] A device with a coil for applying magnetic resonance (MR) pulses to a substance according to the preamble of claim 1 is known from US 5,903,150 A. Magnetic resonance (MR) systems and in particular MR transmitters are also known from US 7,117,752 B2, US 5,047,992 A, US 201110127999 A1, US 2012 / 0001629 A1 and US 2013 / 0234705 A1. GENERAL STATE OF THE ART

[0003] Magnetic resonance (MR) systems can be used to determine the properties of a substance. One example of an MR system is a nuclear magnetic resonance (NMR) system. An NMR system performs an NMR measurement by applying a static magnetic field to the substance. The static magnetic field induces an initial magnetization of atomic nuclei within the substance. The NMR system also includes an NMR transmitter with a coil that applies an oscillating magnetic field at a specific frequency to the substance. The oscillating field consists of a sequence of pulses that move the magnetization of the atomic nuclei away from the initial magnetization. The NMR pulse sequence can be arranged such that the pulses and the static field interact with the nuclei to generate a resonance signal, consisting of "echoes," within at least a portion of the substance.The resonance signal is detected and then used to determine NMR properties such as T1 relaxation time, T2 relaxation time, and signal attenuation due to molecular diffusion. These NMR properties can be used to determine the properties of the substance.

[0004] In some cases, NMR pulse sequences of different frequencies are applied to the substance to study different parts of a substance in an inhomogeneous magnetic field or to examine different atomic nuclei. To switch between frequencies, narrowband NMR transmitters use rows of fixed capacitors and mechanical switches coupled to the coil. The mechanical switches tune the coil to different frequencies between a predetermined number of fixed capacitors. These narrowband transmitters have several disadvantages. First, the switching process is slow (e.g., switching times of 10–100 ms). Second, the switches in the capacitor rows introduce noise into the NMR measurement. Third, a predetermined, separate set of narrowband frequencies can be fixed, since each frequency depends on separate capacitors.Fourth, the frequency switching process introduces dynamics and may not maintain the phase coherence of the pulse sequence waveform. Consequently, narrowband NMR transmitters do not switch between frequencies efficiently and effectively. SUMMARY

[0005] Illustrative embodiments of the present disclosure relate to a transmitter for a magnetic resonance (MR) system, such as a nuclear magnetic resonance (NMR) system. The transmitter includes a coil for applying NMR pulse sequences to a substance. The coil comprises a first coil section and a second coil section. The first coil section and the second coil section allow current of opposite polarity to pass through.

[0006] In some embodiments, the transmitter may include a transmitter circuit for generating and supplying the MR pulse sequences to the coil. The transmitter circuit includes a first switch that selectively energizes the first coil section and a second switch that selectively energizes the second coil section. The operation of the first and second switches generates the MR pulse sequences.

[0007] Several embodiments of the present disclosure also relate to a method for applying MR pulse sequences to a substance. The method involves applying current to a first coil section and applying current to a second coil section. The current flows through the coil sections with opposite polarity. In some embodiments, the current is selectively applied to the first coil section by means of a first switch, and the current is selectively applied to the second coil section by means of a second switch. The operation of the first switch and the second switch generates the MR pulse sequences.

[0008] Further illustrative embodiments of the present disclosure relate to a magnetic resonance (MR) system. The system comprises a coil with a first coil section and a second coil section. The first coil section and the second coil section are wound with opposite polarity. The system also comprises a first transistor coupled to the first coil section and selectively supplying current to the first coil section, and a second transistor coupled to the second coil section and selectively supplying current to the second coil section. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For experts, the advantages of different embodiments will become clearer with reference to the following description of illustrative embodiments, which are discussed with reference to the drawings briefly described below. Fig. 1 shows an NMR system according to an embodiment of the present disclosure; Fig. 2 shows a coil according to an embodiment of the present disclosure; Fig. Figure 3 shows a cable with several strands of wire; Fig. 4 shows a coil according to a further embodiment of the present disclosure; Fig. 5 shows a transmitter circuit according to an embodiment of the present disclosure; Fig. 6 shows switching logic according to an embodiment of the present disclosure; Fig. Figure 7 shows a logging-while-drilling (LWD) system according to an embodiment of the present disclosure; Fig. Figure 8 shows an LWD-NMR survey module according to an embodiment of the present disclosure; and Fig. Figure 9 shows a method for applying high-frequency pulses to a substance according to an embodiment of the present disclosure. DESCRIPTION OF ILLUSTRATORY EXECUTION FORMS

[0010] Illustrative embodiments of the present disclosure relate to a transmitter for a magnetic resonance (MR) system, such as a nuclear magnetic resonance (NMR) system. The transmitter includes a coil for applying NMR pulse sequences to a substance. The coil comprises a first coil section and a second coil section. The first coil section and the second coil section conduct current of opposite polarity. In various embodiments, the transmitter also includes a transmitter circuit for generating the NMR pulse sequences and supplying them to the coil. The transmitter circuit includes a first switch that selectively supplies current to the first coil section and a second switch that selectively supplies current to the second coil section. The operation of the first and second switches generates the NMR pulse sequences.In this way, various embodiments of the coil and transmitter circuit can transmit NMR pulse sequences over a wide frequency range, while also providing a simplified transmitter circuit design. Details of different embodiments are discussed below.

[0011] Fig. Figure 1 shows an NMR system 100 according to an embodiment of the present disclosure. The NMR system 100 includes a coil 102 coupled to the NMR electronics 104, 106, 108. A sample substance 101 is arranged inside and / or outside the coil 102. The coil 102 applies NMR pulse sequences to the substance 101. The NMR electronics include a transmitter 104 and a receiver 106. The transmitter 104 and the receiver 106 are each coupled to the coil 102. In some embodiments, however, the NMR system 100 may include separate transmitter and receiver coils.

[0012] Fig. Figure 2 shows a detailed view of the coil 102. The coil 102 comprises a first coil section 202 and a second coil section 204, each containing a plurality of turns along a longitudinal axis 203 of the coil. In this embodiment, each coil section is wound around a core element 206. Each coil section has a specific turn length L. A and L Balong the longitudinal axis 203 of the coil 102, and the winding segments overlap each other along the longitudinal axis 203. The first coil section 202 includes connections A+ and A- at its ends, while the second coil section 204 includes connections B+ and B- at its ends. The first coil section 202 and the second coil section 204 allow current of opposite polarity to pass through. In one embodiment, for example, the connections A+ and B+ of the coil sections are connected to one terminal of a power source, while the ends A- and B- of the coil sections are connected to another terminal of the power source. In this way, the coil sections allow current to pass through the length of the core element 206 in opposite directions.

[0013] In some embodiments, the individual windings of the coil sections are offset from each other, as in Fig. Figure 2 shows that in other embodiments, the windings of the coil sections overlap. In one embodiment, for example, the coil sections are made from a cable with several insulated strands, such as a stranded cable. Fig. Figure 3 shows an example of a cable 300 with several wire strands that are insulated from each other. Three of the seven wire strands are intended for the first section of the coil 302, and three other wire strands are intended for the section of the coil 304. The remaining wire strand can be intended for the neutral conductor 306.

[0014] The coil and coil sections are not limited to any specific dimensions or configurations. For example, each coil section can have between 2 and 20 turns. Furthermore, the turn length of each coil section can range from 1.3 cm to 13 cm, and the cross-sectional area of ​​the coil can range from 6.5 cm². 2 and 645 cm 2The coil and coil sections are also not based on the configuration. Fig. 2 limited. For example, shows Fig. 4. A coil 400 with a planar configuration. The planar configuration also includes a first coil section 402 and a second coil section 404. In illustrative embodiments, each coil section in this planar configuration can have 1 to 10 loops. The connection points at A+ and A- are spaced apart from the connection points B- and B+ to avoid electrical noise between the connections.

[0015] The NMR transmitter 104 also includes an NMR transmitter circuit 110, which is coupled to the coil 102. The transmitter circuit 110 generates NMR pulse sequences and delivers these sequences to the coil 102. The transmitter circuit 110 is "non-resonant" because its resonant frequency does not necessarily correspond to the Larmor frequency of interest. In contrast, as explained above, narrowband circuits tune their resonant frequencies to match the Larmor frequency of interest by selecting a specific capacitance for the circuit. Although the non-resonant transmitter circuit 110 and coil 102 may use capacitors and have some associated capacitance, this capacitance is not specifically chosen to match a Larmor frequency of interest.

[0016] Fig. Figure 5 shows a transmitter circuit 110 according to the invention. The NMR transmitter circuit 110 includes two switches 502 and 504. The first switch 502 is coupled to the first coil section 202 and configured to selectively supply current to the first coil section. The second switch 504 is coupled to the second coil section 204 and configured to selectively supply current to the second coil section. Each switch and corresponding coil section are arranged in parallel. In a particular embodiment, the switches 502 and 504 are transistors, such as metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), or various other switches based on the high-frequency switching (HFS) family. In various embodiments, the switches can operate in less than 10 ns.

[0017] The transmitter circuit 110 can also include a current source (e.g., a high-power current source) 506, which is selectively coupled to the first coil section 202 via the first switch 502 and selectively coupled to the second coil section 204 via the second switch 504. The current source 506 supplies current at a specific voltage to the first coil section 202 and the second coil section 204. The terminals A+ and B+ of the coil sections 202 and 204 are coupled to a positive terminal of the current source 506, while the terminals A- and B- of the coil sections are coupled to the switches 502 and 504, which are then coupled to ground. Although in Fig. Not shown in Figure 5, coil sections 202 and 204 are arranged with opposite polarity, as shown for example in Figure 5. Fig. 2 shown. The circuit 110 can also include a load resistor (R) 508 or a fuse, which can be used in series with the current source 506 to limit the current applied to the switches 502, 504.

[0018] By selectively coupling coil sections 202 and 204 to the current source 506, switches 502 and 504 control the timing of the current flow in each section of the coil. Switching these switches 502 and 504 on and off according to a specific switching logic generates a current in coil 102 and thus produces radiofrequency radiation. In this way, the operation of switches 502 and 504 generates radiofrequency pulses and the NMR pulse sequences.

[0019] Fig. Figure 6 shows an example of the switching logic 600, which is used to operate the first switch 502 and the second switch 504. In this case, the switching logic includes a set of two non-superimposed digital signals, designated φ1 and φ2. The signals φ1 and φ2 are used to operate the individual switches. The first signal φ1 operates the first switch 502, while the second signal φ2 operates the second switch 504. The switching logic often includes a period with positive current (or negative current), generated by turning on a switch, followed by a period without current, generated by turning off the switch. In various embodiments, the switching logic alternates between supplying current to the individual coil sections 202, 204, as shown in Fig. 5 shown, and thus generates alternating current in coil 102. The total current generated by the coil sections can be determined according to the following relationship: IT=|IA|−|IB|, where I T the total current through the coil, I A the current through the first coil section and I B The current flows through the second coil section. The current in one coil section is subtracted from the other because the coil sections are wound with opposite polarities. Fig. Figure 6 shows the total current 602 in coil 102, generated by the switching logic 600. As shown in the figure, the switching logic generates a sinusoidal waveform in coil 102. Repeating the switching logic at a specific frequency generates radio frequency power and NMR pulse sequences at a specific frequency. In this case, the waveform is shown as a square waveform. Depending on the inductance and resistance of the coil and the transmitter circuit, the waveform can also have other shapes (e.g., triangular).

[0020] Transmitter 104 also includes a driver 112, which is coupled to transmitter circuit 110. In a specific embodiment, the driver 112 can be a computer processor. The driver 112 serves to control the operation of switches 502 and 504 in transmitter circuit 110. As in Fig. As shown in Figure 5, the individual switches 502 and 504 are also coupled to the driver 102, allowing the driver to control the operation of the switches. The driver 112 switches the switches 502 and 504 according to a switching logic (e.g., φ1 and φ2). In various embodiments, the driver 112 also receives NMR pulse sequences from an NMR spectrometer 108. In some embodiments, the NMR pulse sequences are transmitted via a multitude of channels. An adder circuit (not shown) can be used to combine the multitude of channels. Furthermore, in various embodiments, the transmitter 104 includes a comparator 114 for receiving the NMR pulse sequences from the spectrometer 108 and for generating a square waveform, which is provided to the driver 112.The NMR pulse sequences can be translated by the driver 112 into the specific switching logic by selecting waveforms of the NMR pulse sequences and then conditioning the waveforms to a suitable voltage.

[0021] Illustrative embodiments of the NMR transmitter described here can switch between frequencies outside the natural resonant frequency bandwidth of a coil with a regulated circuit. In other words, the NMR transmitter does not rely on a coil being regulated to tune a specific frequency. Unlike narrowband systems that use mechanical switches and arrays of fixed capacitors to tune the coil, various embodiments of the transmitter described here achieve multi-frequency operation without the need for hardware modulation (e.g., switching between fixed capacitors or tuning between variable capacitors). Instead, the frequency can be modulated directly by a spectrometer.The NMR transmitter is frequency-insensitive and allows the pulse sequence frequency to be dynamically varied by the spectrometer while maintaining the phase coherence of an output waveform. In some cases, the transmitter (and coil) can switch between frequencies with a frequency difference of up to 10% of an initially applied frequency. In various other embodiments, the frequency difference can be even greater (e.g., 20%, 30%, or 50%). Furthermore, in some embodiments, the transmitter can switch between frequencies in less than 5 ps. In still other embodiments, the transmitter can switch between frequencies in less than 20 ps or 50 ps. In addition, in some embodiments, the transmitter can operate in a frequency range of 100 kHz to 3.2 MHz.

[0022] As in Fig. As shown in Figure 5, the transmitter circuit uses two switches, both connected to ground. This arrangement reduces the number of components in the transmitter circuit and also results in simplified switching logic and a simplified driver. For example, no high-voltage driver circuit is needed because the two switches are both connected to ground. Furthermore, by configuring the coil sections with opposite polarity, a single power supply can be used to power both coil sections, while the coil itself generates both a "positive" and a "negative" current.

[0023] As in Fig. As shown in Figure 1, the coil 102 is also coupled to an NMR receiver 106, so that NMR resonance signals generated in the substance 101 can be detected, amplified, and analyzed. In a specific embodiment, the receiver 106 is a broadband NMR receiver capable of receiving and processing resonant NMR signals over a wide frequency range. The coil 102 is coupled to the receiver 106 by means of a duplexer 116. The duplexer 116 decouples the receiver 106 from the coil 102 when the coil is operating in a transmit mode (e.g., transmitting an NMR pulse sequence). In a particular embodiment, the duplexer 116 includes switches and a switch driver 118 that opens the switches during a transmit mode and closes them during a receive mode. In this way, the duplexer 116 protects the receiver 106 during a transmit mode.A duplexer does not need to be used if the NMR system includes 100 separate transmitter and receiver coils.

[0024] The NMR system also includes a spectrometer 108, which serves to provide NMR pulse sequences to the NMR transmitter 104 and to analyze the NMR signal received by the NMR receiver 106. In various embodiments, the detected NMR signal is output by the NMR receiver 106 in analog form. In such embodiments, the spectrometer 108 may include a digitizer 120 (e.g., an analog-to-digital converter) for converting the detected NMR signal into digital data. Furthermore, in various embodiments, demodulation of the NMR signal may take place in the spectrometer 108. In other embodiments, however, demodulation of the NMR signal may also take place in the NMR receiver 106. The spectrometer 116 also includes a post-processing unit 122, which is used to interpret the detected digital NMR data and to determine NMR properties from the detected data.This data can be presented to a user via an operator interface with a graphical user interface (GUI). The spectrometer 108 also includes a pulse sequence generator 124, which generates NMR pulse sequences based on parameters selected by an operator at the operator interface. The pulse sequence generator provides the sequences to the NMR transmitter 104. In one particular embodiment, the spectrometer 108 is a KEA™, which can be obtained from Magritek in Aachen, Germany. The spectrometer 108 can be controlled via the operator interface using the PROSPA™ software, which can also be obtained from Magritek.

[0025] Further details of the NMR electronics, NMR transmitters and NMR receivers are described in US Publication No. 2012 / 0001629 published on January 5, 2012, and US Application No. 13 / 774,457 filed on February 22, 2013, both of which are hereby incorporated in their entirety into the present subject matter.

[0026] As in Fig. As shown in Figure 1, the NMR system 100 includes an electromagnetic device 126 for applying a static magnetic field to the substance 101. In some embodiments, the electromagnetic device 126 is a magnet or a magnet array. The magnets can be made of a magnetic samarium-cobalt (SmCo) material.

[0027] The NMR system 100 also includes an operator interface 128 for communicating with the spectrometer 108. The operator interface 128 includes a computer system. The computer system can include a computer processor 130 (e.g., a microprocessor, microcontroller, digital signal processor, or general-purpose computer) for executing any of the procedures and processes described herein. The computer system can further include a memory 132 such as a semiconductor memory device (e.g., RAM, ROM, PROM, EEPROM, or Flash-Programmable RAM), a magnetic storage device (e.g., a floppy disk or hard disk), an optical storage device (e.g., a CD-ROM), a PC card (e.g., a PCMCIA card), or other storage device. The memory 132 can be used to store computer instructions (e.g., computer program code) that are interpreted and executed by the processor 130.

[0028] NMR pulse sequences can be implemented as a series of computer instructions (e.g., software or firmware) that are permanently stored on a non-volatile tangible medium, such as a computer-readable medium (e.g., memory), or that can be transmitted to the computer system via a modem or other interface device, such as a communication adapter connected to a network via a tangible medium (e.g., optical or analog communication lines). The series of computer instructions can represent all or part of the NMR pulse sequences. The processor 130 can be configured to retrieve the sequences from memory 132 and provide instructions to the NMR electronics 104, 106, and 108 to apply the sequences to substance 101. The detected resonance signals can also be transmitted from the NMR electronics 104, 106, 108 to the processor 130 for storage on the memory 132.

[0029] The operator interface 128 also supports the graphical user interface 134 (GUI) (e.g., a monitor, a touchscreen, a mouse, a keyboard, and / or a joystick). The GUI 134 allows an operator to control and communicate with the NMR electronics 104, 106, 108. In various embodiments, the operator interface 128 can be used to perform functions selected from the following non-restrictive list: • Transmitting instructions to the NMR electronics 104, 106, 108 to initiate and / or • Ending NMR measurements; • Transmitting instructions to change parameters of NMR sequences to the NMR electronics (e.g. pulse amplitude of the sequences, pulse lengths, timing between pulses, shape of pulses and / or frequency of pulses); • Transmitting detected NMR signal data from the NMR electronics 104, 106, 108 to the operator interface 128; • Transmitting NMR pulse sequences from the operator interface 128 to the NMR electronics 104, 106, 108; • Performing an analysis of the detected NMR signal data at the operator interface 128 to determine NMR properties of substances; • Displaying various curve diagrams of NMR properties to the operator at the operator interface 128; and • Transmitting NMR pulse sequences from the operator interface 128 to the NMR electronics 104, 106, 108.

[0030] Illustrative embodiments of the present disclosure are not limited to the NMR system 100. Fig. 1. Various modifications can be made to the system. For example, in one specific embodiment, the NMR electronics 104, 106, 108 includes an additional computer system that supports the NMR electronics. In such an embodiment, the NMR electronics 104, 106, 108 and the operator interface 128 can include their own communication modules that enable communication between the NMR electronics and the operator interface. A communication link between the communication modules can be established, for example, using a hard-wired connection, an optical connection, an acoustic connection, and / or a wireless connection. By using the communication modules, the NMR electronics 104, 106, 108 and the operator interface 128 can be physically located at two separate sites.In a borehole application, for example, the NMR electronics 104, 106, 108 can be located underground, while the operator interface 128 is located on the surface.

[0031] Illustrative embodiments of the present disclosure further relate to oil and gas field applications, such as wellbore surveying tools. In particular, it shows Fig. 7 A logging-while-drilling (LWD) system 700 for investigating a substance 702 in situ within an earth formation 704 and determining a property of the substance while a drilling operation is being carried out. The LWD system 700 includes a drill string 708. The drill string 708 is arranged in a borehole 706 that passes through the formation 704. The drill string 708 includes a main shaft 710 with a drill bit 712 located at the lower end of the main shaft. The LWD system 700 includes a surface system with a drill rig assembly and a platform assembly 714 located above the borehole 706. The drilling rig assembly 714 rotates the drill string 708, and as the drill string rotates, the drill bit 712 bores deeper into the borehole 706. An LWD-NMR survey module 716 is arranged in the main shaft 710, so that the module can measure the surrounding earth formation while the drilling operation is carried out.The surveying module 716 communicates with surface equipment 718, which includes an operator interface for communicating with the module. Such an operator interface was already described with reference to... Fig. 1 described. In various embodiments, the NMR survey module 716 and the operator interface can communicate via any of the following: a wired drill pipe connection, an acoustic telemetry link, optical communication and / or electronic communication.

[0032] Fig. Figure 8 shows an LWD-NMR survey module 800 for applying NMR pulse sequences to the formation. The module 800 includes magnetic sections 804 that generate a static magnetic field in a sensitivity zone 806 in the formation 802. The module 800 also includes a heavy rod 808 with an axial slot 810. A coil 812 is arranged in the axial slot 810, and the slot is filled with an insulator such as ceramic, epoxy, or glass fiber. As explained above, the coil 812 includes two coil sections arranged with opposite polarity. The coil sections are wound around the heavy rod 808 in the axial slot 812. The axial slot 812 is closed with a cover 814. In some embodiments, the cover 814 is formed from a non-magnetic and / or non-conductive material. The coil sections are grounded at one end (e.g., to the heavy bar 808).At the other end, the coil sections are coupled to the NMR electronics 816, which includes a transmitter with a transmitter circuit, as in . Fig. 5 described. The NMR electronics 816, for example, are coupled to the coil 812 via pressure medium feedthroughs. The coil 812 applies an oscillating magnetic field (e.g., NMR pulse sequences) to a region of interest 820 in the sensitivity zone 806 of the formation 802. In some embodiments, the oscillating magnetic field is axially symmetric to simplify measurements during rotation of the drill string. Further details of NMR-LWD systems are described in U.S. Patent Nos. 5,629,623, issued May 13, 1997, and U.S. Patent Nos. 6,392,410, issued May 21, 2002. Each of these patents is hereby incorporated in its entirety into the present subject matter. A specific example of an NMR-LWD tool is the VISION™ tool from Schlumberger.

[0033] Fig. Figure 9 shows a method 900 for applying radio frequency pulses (e.g., NMR pulse sequences) to a substance. Before the start of the method, a substance can be placed in or near a coil for evaluation. In step 902, current is applied to a first coil section, and in step 904, current is also applied to a second coil section. The current flows through the coil sections with opposite polarity. As explained above, the current is selectively applied to the first coil section by means of a first switch, and the current is selectively applied to the second coil section by means of a second switch. By alternately supplying current to the individual coil sections, the coil generates an oscillating magnetic field. Steps 902 and 904 are repeated to generate a radio frequency pulse of a specific duration.An NMR pulse sequence comprises a series of such pulses of specific duration with delays between adjacent pulses. NMR pulse sequences can include, for example, a free-induction decay (FID) sequence, a spin-echo sequence, a stimulated echo sequence, an inversion-recovery sequence, a Carr-Purcell-Meiboom-Gill (CPMG) sequence, or combination sequences. In some embodiments, the NMR signal generated in the substance is detected using the coil. The NMR signal is then used to determine a property of the substance, such as the T1 relaxation time, T2 relaxation time, and signal attenuation due to molecular diffusion.

[0034] The NMR emitters and coils described here are not limited to a specific device type or system. They can be implemented in surface environments, such as in a laboratory, or in underground environments. Applications include chemical production, food production, materials testing, and infrastructure investigation (e.g., buildings and bridges).

[0035] With regard to borehole applications, the NMR systems and methods described here are not limited to LWD systems such as the one described in Fig. 7 and Fig.The application of this disclosure is limited to the embodiments shown in Figure 8. Various embodiments of the present disclosure can also be applied to wired systems (e.g., a wired tool) or measuring-while-drilling systems (e.g., MWD tools). In one specific embodiment, a coil with two sections having a planar configuration is used as a block on a wired tool. Illustrative embodiments can also be used with any suitable delivery means, such as a reinforced cable or wound conduit. Furthermore, the NMR emitters and methods described herein can be used to investigate a substance in a soil formation outside the borehole tool (e.g., outside the coil) or to investigate a substance in a flow line or chamber within a borehole tool (e.g., inside the coil).

[0036] The NMR transmitters and coils described here are not limited to implementing NMR techniques and sequences. The systems and devices described here can also be used to implement other magnetic resonance (MR) techniques and sequences, such as nuclear quadrupole resonance (NQR) techniques and sequences.

[0037] Although several embodiments have been described in detail above, those skilled in the art will readily understand that many variations of these embodiments are possible without significantly deviating from the scope of this disclosure. Accordingly, it is intended that all such variations fall within the scope of this disclosure.

Claims

[1] Device with a coil (102) for applying magnetic resonance (MR) pulse sequences to a substance (101), wherein the coil (102) a first coil section (202) and comprising a second coil section (204), wherein the first coil section (202) and the second coil section (204) allow current of opposite polarity to pass through, with a transmitter circuit (110) for generating the MR pulse sequences and providing the MR pulse sequences to the coil (102), characterized by, that the coil (102) comprises the first coil section (202) and the second coil section (204) along a longitudinal axis (203) of the coil (102), wherein the first coil section (202) comprises a first turn length segment, the second coil section (204) comprises a second turn length segment, and at least one segment of the first turn length segment and at least one segment of the second turn length segment overlap along the longitudinal axis (203) of the coil (102) and are connected to a first switch (502) coupled to the first coil section (202) and configured to selectively energize the first coil section (202), and to a second switch (504) coupled to the second coil section (204) and configured to selectively energize the second coil section (204). [2] Device according to claim 1, wherein the first switch (502) and the second switch (504) comprise transistors. [3] Device according to claim 1, wherein the first switch (502) and the second switch (504) are configured to switch in less than 10 ns. [4] Device according to claim 1, further comprising: a driver (112) which is coupled to the transmitter circuit (110) and configured to control the operation of the first switch (502) and the second switch (504). [5] Device according to claim 4, wherein the operation of the first switch (502) and the second switch (504) generates the MR pulse sequences. [6] Device according to claim 5, wherein the driver (112) is further configured to control the operation of the first switch (502) and the second switch (504) according to a switching logic (600). [7] Device according to claim 1, further comprising: a current source (506) which is selectively coupled to the first coil section (202) via the first switch (502) and selectively coupled to the second coil section (204) via the second switch (504). [8] Device according to claim 1, wherein the device is a component of a borehole surveying tool (716). [9] Method for applying high-frequency pulses to a substance, the method comprising: Applying current to a first coil section of a coil; and Applying current to a second coil section of the coil, with current of opposite polarity flowing through the coil sections, characterized by, that the first coil section includes a first turn length segment, the second coil section includes a second turn length segment, and the first turn length segment and the second turn length segment superimpose along a common longitudinal axis of the coil, and wherein the current is selectively applied to the first coil section by means of a first switch and the current is selectively applied to the second coil section by means of a second switch. [10] Method according to claim 9, wherein the operation of the first switch and the second switch generates the high-frequency pulses. [11] Method according to claim 9, wherein the first switch and the second switch are transistors. [12] The method of claim 11, wherein the substance is a formation and the method further comprises: Applying the high-frequency pulses to the formation. [13] Magnetic resonance (MR) system, comprising: a coil, comprising: a first coil section; a second coil section, wherein the first coil section and the second coil section are configured with opposite polarity; a first transistor coupled to the first coil section and configured to selectively supply current to the first coil section; and a second transistor coupled to the second coil section and configured to selectively supply power to the second coil section. [14] System according to claim 13, further comprising: a power source that is selectively coupled to the first coil section via the first switch and selectively coupled to the second coil section via the second switch. [15] System according to claim 13, wherein the operation of the first transistor and the second transistor generates the MR pulse sequences.

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