Method and apparatus for the detection and/or analysis of compounds simultaneously exhibiting nuclear quadrupolar resonance and nuclear magnetic resonance

A method and sensing element for detecting compounds with nuclear magnetic resonance and quadrupole nuclear resonance

Method and sensor element for the detection of compounds exhibiting both nuclear magnetic and quadrupolar resonances

Full description

Background of the invention

This invention relates to a method, sensing elements and system for identifying and/or analyzing compounds that simultaneously exhibit nuclear quadrupolar resonance (NQR) and nuclear magnetic resonance, or double nuclear quadruple resonance polar resonance. This method concerns the identification and/or analysis of compounds, especially explosives, drugs, etc., placed in various types of containers, especially in luggage, suitcases, postal parcels, etc.

Nuclear quadrupole resonance (NQR) represents the response of a given compound containing any quadrupole nucleus to a high-frequency pulse applied “during resonance.” It is used in particular to identify explosives and other miscellaneous materials hidden inside luggage, travel bags and packages, which are difficult to detect and identify. There are two versions of this device, one of which is used to inspect hand luggage such as travel bags, folders for papers and documents, fuel bags, etc., while the second version is used with bags and luggage that are larger in size, such as shipments that are transported through air transport systems.

The quadrupole resonance technology does not in any way cause harm to the environment, luggage or humans, as it contains rays carried on radio waves with a very long wavelength or with a low frequency measuring some megahertz, at the same time with the application Pulses have a magnetic field of some tens of Gauss, even less than those used in common magnetic resonance imaging (MRI) devices. The application of this technique is characterized by being direct. This application does not require preparing the objects under examination in advance. Through this method, traditional examination operations can be carried out very quickly. Also, checking the presence of explosives in luggage or transported shipments will only take a few seconds without the need to open them or handle them with any mechanical tool and/or examine them by palpating or touching them. No ionizing radiations are used, and thus it is possible to avoid When luggage or personnel are exposed to risks, selection is made once and each device is fully computerized, allowing ease of use at a personal level for those who must make effective decisions.

Nuclear quadrupole resonance (NQR) is a technique for measuring spectra that is widely used during chemical and physical analyzes of non-metallic materials. The response generated by nuclear quadrupole resonance (NQR) is characteristic of the magnetic and electrical properties of the resonant nuclei. The phenomenon of nuclear quadrupole resonance (NQR) occurs with certain atoms that have a significant quadrupole moment, called spin (I > 1/2), and it can be observed when it represents a portion of crystalline or amorphous materials. Therefore, for example, explosives containing chlorine and/or nitrogen can be identified using this technique.

Nitrogen nuclear quadrupole resonance (NQR) signals can be detected in RDX and other explosives (for example, see: VS Grechishkin, “NQR device for detecting plastic explosives Mines and Drugs”, Applied Physics, Vol. A55, pp. 505-507 (1992), in a manner sensitive enough to provide detection information that can be used to examine travel bags, closed packages, personal belongings, etc. The phenomenon of resonance can be observed in nitrogenous materials at the high-frequency level, that is, explosives can be identified through the use of radio waves, and are adapted using special electronic devices. The explosive material consists of a chemical substance that has one or more single resonant frequencies that are useful in distinguishing it. Unlike other compounds found in nature.

The electrical and magnetic properties of atomic nuclei cause the phenomenon of nuclear quadrupole resonance (NQR). Nuclei's with an asymmetric spherical electrical charge are characterized by their four-pole electric moment. Another nuclear property is related to the possession of a magnetic moment, also known as nuclear spin. Nuclear quadrupole resonance arises as a result of the interference between the nuclear electric quadrupolar moment and the electric field resulting from the electric charges connected to the nucleus.

Graphically, the albite compound does not appear to be very strict, and it can be said that experiments with the quadrupole nucleus use the graduated electric field resulting from the atomic medium. This results when different parts of the nucleus are subjected to a torque that forces them to rotate in a direction around the axis of maximum variation (slant) of the field. Electrophoresis at the position of the nucleus is a quadrupole. This advanced movement causes the withdrawal of the nuclear magnetic moment. The sample must be temporarily subjected to a vibrating magnetic field. In line with this progress, the direction of the nuclear magnetic moment can be modified by looking at the direction of the electric field. The vibrating electric field can be obtained by placing the sample or part to be examined next to an antenna connected to a radio frequency generator during an appropriate period of time (microseconds), known under the name “radio frequency pulse.” At the end of the pulse, the magnetization of the sample, in harmony with the frequency Quadrupole resonance produces an identifiable signal known as the “free induction decay signal” and usually called FID.

The advance of the aforementioned frequency depends on two determinants: - First, it is proportional to the four-pole moment P of the nucleus, which is related to the distribution of the electrical charge of the four-pole nucleus. The value of the determinant P represents zero in cases where the distribution of the charge of the nucleus is spherically symmetrical, and it is positive when it is The distribution of charge longitudinally across the major axis, and it is negative when it is flat with respect to the aforementioned axis. The required symmetry properties of the nucleus are important factors for the P value of the nucleus, which is not equal to zero, and in particular the periodic quantum number (or magnetic quantum number) that is more than half: I > 1/2; Second, the frequency is controlled by the main components of the electric fields, q.

For example, in the case of a group characterized by a spin I = 3/2 core, the resonant frequency in the absence of an external magnetic field can be obtained from the equation: V = e2 Qp/4h, where h represents Planck’s constant, and e represents electron charge. In the case of nuclei with spin I spin = 1, it is possible to observe three frequencies, which are called using the equation: V+/- = (3e2 qP/4h) (1+/-h/3)yv0= (e2qP/2h)h Where h represents the determinant of the asymmetry of the electric field slope.

The purpose of these terms is to explain the value of the resonance frequency, which can be measured with a high degree of accuracy during quadrupole nuclear resonance (NQR) experiments. This represents a distinctive effect of the part carrying the resonant nucleus, for example the “fingerprint” and in nature there is Many different quadrupole nuclei. It is commonly found in explosives, i.e. nitrogen, chlorine, sodium, potassium, etc. These nuclei are identified using quadrupole resonance (NQR) spectrometers used in scientific research, and this also happens in the case of detecting explosives. For example, it is possible to check for the presence of different types of explosives by setting the identification device to the frequency(s) with the characteristics of that molecule, which are completely known before.

Many devices have been invented that use pure quadrupole resonance to identify different compounds or materials. According to the user in this context, "pure" means not involving any external magnetic field, also known as the "Zeeman magnetic field".

In general, crystalline salt compounds are characterized by the fact that the free induction of signal decay (FID) and the shape of the nuclear resonance line for a group of nuclei with spin A can be defined by coupling the magnetic moments of another magnetic group whose nuclei have spin B. In these cases, the coupling through the same spin A is worthless, and thus the loss of convergence related to the advance phase of spin A is due to undulations of local magnetic fields generated by spins B, which occupy adjacent positions in the crystal lattice or in the molecule itself. By reference: Herzog and Hahn (B. Herzog and EL Hahn, Phys. Rev. 103, 148 (1956), there was talk about applying a weak magnetic field H0 (few Gauss units) by continuous radiation of protons under the resonance conditions of an oscillating magnetic field H2, and this coupling can be broken. The decay time of the orthogonal convergence of the quadrupole nuclei is beyond limitation due to the occurrence of ripples in the local fields arising from the protons, and the double proton beam brings these fields down to zero, resulting in a noticeable increase in the decay time of the magnetization of the group of spins A nuclei.

This is explained physically by the fact that the latitude of spins A suffers a noticeable narrowing when the externally driven redirection speed of spins B is high enough to cause a reduction to small values of the average value of the resulting local field in the group of nuclei of spins A. This rate is similar to the effect known as “kinetic narrowing” in liquids, with “linear narrowing” resulting from mechanical rotation of fluid samples in an external heterogeneous magnetic field, as well as with “spin” or mechanical rotation of solids, as well as for magnetic resonance (NMR) narrowing. , which is expanded using magnetic fields, and for mechanical rotation to be effective, the speed of rotation must exceed the expansion of the Larmor frequencies occurring as a result of the lack of field uniformity. Likewise, the linear narrowing caused by double resonances in solids requires that the reorientation velocity of the B spins be greater than the minimum amplitude of the Larmor frequencies of the A spins, which exists following the double resonance decrease. During a double resonance experiment, the decay time of the A-spin echo envelope, known as T2, increases or decreases depending on several combined effects: (1) internal coupling between the spins (homonuclear coupling); And (2) pairing between A and B spindles (heteronuclear coupling).

The vibrating magnetic field H2 is of equal intensity, and this also complements the resonance conditions of the spins B in the weak magnetic field H0, and the decay time is extended with reference to the envelope of the T2 echoes until it reaches its theoretical maximum, which is determined by the longitudinal decay extension time T1, or the decay extension time T2. for A spindles, which is usually lower.

General description of the invention

The present invention contributes to solving the problem of identifying, for example, plastic explosives, which are not easy to identify using known detection techniques, such as those in which an X-ray device is used; Or those in which one or more complex methods are used using small quantities of explosive materials that may still “contaminate” the outer surface of the luggage. With reference to the first technique, the invention is entirely subjective and, as such, does not depend on the operator's ability to interpret low-contrast images. With reference to the second technology, the main advantage of the present invention is the speed and security with which luggage is checked.

The present invention is preferred because it identifies compounds that may be present outside the determination volume, for example, as in the case of surface determination devices, and it also identifies substances that are present inside the determination volume, as in the case of devices called “quantitative determinants,” neither of which requires intrusion into the internal space of the luggage. Or the things that are examined. Therefore, the identification devices can be referred to depending on their type as vacuum or surface and the proposed method can be considered as “remote inspection”. Although this definition is not entirely complete, the remote identification method refers to a situation in which luggage or objects placed outside the normal plane occupied by the detector's pointing device are inspected and which can be compared to the dimensions of the detector. With reference to surface detection devices, the identification method may be called the “one-side detection method,” through which the compound or thing to be detected is identified on one side of the baggage containing something similar to it. Although the use of this device implies low sensitivity and therefore the minimum size of the compound that can be detected, its location can be easily identified using the aforementioned device within the luggage space. In the case of volumetric detectors, they can detect the minimum level of the compound to be determined. In any case, these two models are complementary, and it is possible to use a volumetric detector during the first step or during a conventional inspection, and then identify the correct position of explosives using a surface detector. From now on we will refer to volumetric detectors, the use of which can be extended by changing the design of the detector using a surface detection model.

Double resonance, or DOR, is used as follows: Once the quadrupole resonance of the A-spins is observed during spin echoes, for example, the B-spins radiate continuous waves, or pulses, at the MRI frequency, which differs from that of the A-spins and is defined by dH0, where d is A gyromagnetic coupling factor, and the local field undulations are averaged according to the driven reorientation of the B spins, which affects the decay time of the orthogonal convergence of the A spins. In this case, the spin signal A contains a special resonance sensor B. When the coupling between the A and B spindles is strong enough, the DOR can be easily determined. This type of resonance is suggested by references to study this type of coupling (B. Herzog and E.L. Hahn, Phys. Rev, 103, 148 (1956). The double resonance method also allows for finding the resonance frequencies of the spins of the B nuclei group, which are low Noticeably, it is also possible to measure the shape of its lines.

The amplitude of the resonance of the spindles of nuclei A (the nuclear quadrupole resonance for any of 14N, 35Cl, or 37Cl) increases, and the increase is vertical, as the time between the pulses t of both TT/2 and TT decreases; the signal-to-noise ratio, and thus the sensitivity of the identification device, represents an improvement The reality is based on the parameter. The time t decreases in a limited manner, and in practice, as soon as the radio-frequency pulses end, a dead time appears (in fact, it is called the dead time of the spectrum analyzer), which blocks the echo signal. Following the increase in the spin-to-spin decay time T2 of spin A, due to the presence of resonance of spin B, and as a result, the lowest possible value of t (or that allowed by electronics spectrometer) results in a significant increase in the spin echo, and this becomes clear. In spindles of group A nuclei.

The DOR method is used to encode the stereodensity of the nuclei, thus transforming it into solid matter imaging, known as DRI, according to reference: J. Perlo et al. (J. Perlo, F. Casanova, H. Robert and D. J. Pusio, Solid state proton imaging detected by quadrupole resonace), J. Magn. Reson., 150, I (2001) This work explains the details of the method used to transform conditions into an ideal state between the value of the weak static magnetic field H0 and the low-frequency magnetic field H2, and this is applied to a special compound.

It is known that the weak magnetic field H0, when applied to polycrystalline compounds during the period of determining the four-pole signal, greatly expands the resonance line and at the same time the information about the spectrum is lost. This phenomenon has been extensively referred to in reference: E. Rommel, P. Nickel, R. Kimmich and D. Pusiol in “NQR Imaging”, J. Magn., Reson. 91, 630 (1990) cited by reference in this context. It can be said that when applied in practice, a double effect appears: first, double resonance is introduced by inducing a sharp decrease in the dissolution of the interfering magnetization, and it shows a clear improvement with regard to the signal-to-noise ratio of the signal; Second, in cases where B spins are not coupled with quadrupole nuclei to be observed by nuclear magnetic resonance (NMR) (as in the case of protons), line broadening results in a loss in the signal-to-noise ratio itself.

It is noteworthy, and according to what Herzog and Hahns mentioned, that B spin resonance is not limited to the nuclear magnetic resonance of protons, but can extend to the nuclear magnetic resonance (NMR) of fluorine, phosphorous, etc., or the quadrupole resonance of groups of nuclei that have... Small quadrupole coupling constant. In the last case, we will see that DOR occurs between groups of quadrupole nuclei, and this is necessary during the use of the weak static magnetic field H0. This topic will be explained in detail later.

This invention proposes the use of a magnetic field H0 using pulses. The basic and main idea depends on achieving two effects simultaneously:

(1) improving the signal-to-noise ratio by the use of DOR, and (2) allowing the quadrupole signal of the A-spins to be converted into digital form in the case of pure quadrupole nuclear resonance or, in other words, without the use of any external magnetic field.

It can be said that the magnetic field H0 (which is generated in conjunction with a low-frequency field H2 magnetic resonance on spindles B) matches the first high-frequency pulse of the value TT/2 of the field H1. The latter is used in the case of quadrupole resonance on spindles A and is best in echo sequences. - The spindle - (i.e., in DOR conditions), and thus it is possible to close when the echo of the quadrupole resonance signal of the spindle A itself is identified, the intensity of which rises to a maximum at the beginning of the numbering and summing of the identified signals, and during this process it must The low-frequency field H2 remains valid. We will call this sequence PUDOR, from pulsating double resonance. After the end of the numbering and collection of the identified signals, the H0 on/off sequence is repeated until the signal-to-noise ratio for identifying and/or analyzing the compound is obtained. Once this percentage is obtained, a warning signal is emitted upon positive detection, or upon negative detection, the next detection and/or identification of the compound will occur.

It is not possible to obtain an equal signal-to-noise ratio before the effective attenuation of the quadrupole signal of the spindles A, as well as the detection and/or analysis of an additional sequence, consisting of the stored resulting signals; While waiting for the mentioned group of spindles A to relax until it is thermally balanced with the network, then a new H0 on/off sequence begins, and the average is calculated between the resulting signals and those stored before. This additional cascade should be done when more is needed until an equal signal-to-noise ratio is obtained for the identification and/or analysis of the compound.

After the signal-to-noise ratio is obtained, a warning signal will be emitted, at which point the detection must be positive, or the next compound is detected and/or analyzed to produce a negative result.

It has been noted that the definition of the high frequency and low frequency of the consultation associated with the magnetic fields H1 and H2 given through this application describes the A spins of the nuclear group (quadrupole nuclear resonance) and the B spins of the nuclear group (NMR), respectively, which means that The H1 field oscillates at a frequency higher than that of the H2 field. In general, the H1 field is measured in Mhz units, while the H2 field is measured in tens or hundreds of Mhz units. We will explain in detail the situation regarding some compounds that have quadrupole resonance properties and require vibration of the H1 field at a frequency of a few units of Mhz. The A and B spins of the nuclei groups are distributed in such a way that the A spins show the best pure quadrupole nuclear resonance (NQR) signal.

This method is not limited to the combination of PUDOR with the spin-echo sequence, but is extended to include all known pulse sequences, consisting of single pulses and compound pulses. More clearly, the set of pulse sequences mentioned will be designated as “fixed” or “non-fixed” sequences, and the fixed set includes, for example:

(1) Steady-state free advance sequence, or SSFP, which consists of irradiating a sample with successive TT/2 pulses onto spindles A and digitizing the quadrupole signals arising from them during the intervals between the pulses. In this case, the H0 pulse begins, coincides with each TT/2 pulse of the H1 field, and ends at an appropriate time chosen between successive TT/2 pulses (2) A sequence known as strong off resonant comb or SORC pulses (an example of this is what was mentioned in Throughout the reference (eg see VS Grechishkin, Appl. Phys. A58, 63-65 (1994), or G.V. Mozjuokhine, The frequency offset effects of NQR of spin I= 1 for remote detection, Z. Naturforschung, Vo. 57a, pp. 297-303 (2002) and represents a heterogeneous SSFP, where a quadrupole signal is consulted and determined in the off-ring state. This sequence uses compound pulses of different amplitudes and phases, where their amplitudes a and b are equal in time. Again the identification signal is constructed by digitally summing hundreds or thousands of nuclear quadrupole resonance (NQR) signals that follow each composite pulse of the SORC sequence, and at the same time the radiation and pulses of the magnetic field H0 are combined into a quasi-period that includes the special induced pulses At the high frequency of the magnetic field H1, and part of the period of free transformation between the high-frequency pulses, and over time the radiation remains continuous with the low-frequency magnetic field H2.

The set of "non-stationary" sequences contains those that maintain the resonance of the nuclear quadrupole resonance (NQR) signal during a time (called the "T2 effect") that is greater than the T2 decay time of the Carr and Purcell pulse sequences. Those called: Spin :ock Spin Echo" or SLSE, and that of Carr, Purcell, eiboom and Gill or CPMG, and their practical description can be referred to by reference: R. Kimmich, NMR-Tomography, Diffusometry Relaxometry, Springer (1997) The SLSE technique consists of a method through which a high-frequency pulse is used on the compound to be detected, with an amplitude capable of redirecting the nuclear quadrupole magnetization at an angle of 90°C at zero phase. To create a highly reproducible signal. After a period of time t has passed, a second high-frequency pulse is used, thus reorienting the sample by 180°C and in phase by 90°C relative to the first pulse. The spin echo appears at exactly the same time period t due to the end of the second high-frequency pulse. After that, another 180°C pulse with a 90°C phase is used, and the amplitude of the second frequency appears smaller than the first. Then a third high-frequency pulse is used and the third echo appears, whose amplitude is Always a little less than the first one mentioned above, and so on until the echoes are collected (hundreds and thousands of them), and the “detecting pulse” represents a group of echoes of all the echoes that have been numbered and grouped together. In many practical cases, it is possible to replace both the first and second high-frequency pulse with what are called “composite pulses.” For example, reference: (see Agreev et al., “Composite pulses in nuclear quadrupole resonance,” Molecular Physics, vol. 83 , pp. 193-220 (1994) in order to increase the efficiency of identification.

Through this invention, three previous sequences of fixed and non-fixed pulses are discussed, both of which are used under conditions of double resonance DOR and double resonance pulse PUDOR, resulting from the use of a resonance excitation process and determining the resonance closure, which is called TONROF (the transition between resonance flow and non-resonance flow). ) in both fixed and non-fixed succession, which will be determined later.

The basic idea of pulse sequences is to obtain the largest possible number of signals for an average operation, without the need to wait for the necessary time for a set of spindle nuclei A to relax again until thermal equilibrium is achieved in the network, and before repeating the experiment, the necessary period of time required to reach equilibrium. Thermal increases at least 5 times the longitudinal relaxation time T1 of the A spindles. In each case, the TT and TT/2 pulses can be replaced by multiple pulse sequences, the purpose of which is to improve the sensitivity And the conditions through which resonance can be achieved. Regarding this effect, information related to it can be consulted through the reference GV Mozjoukhine, Z. Naturforschung, 57 a, 297-303 (2002) >

Among the subjects of the present invention is providing a method for identifying and/or analyzing compounds that have a nuclear quadrupole resonance at the same time as having a nuclear magnetic resonance, and these compounds contain spins A of a group of nuclei with a quadrupole resonance; And the B spins of the Aniwa group, with nuclear magnetic resonance, as this method includes:

(a) Using a first magnetic field H1 with the spins A of a group of nuclei, where the aforementioned field H1 oscillates at the four-pole resonance frequency of the spins A of a group of nuclei, and at the same time in the spins B of a group of nuclei, as well as a second and third magnetic field, where the field represents The second magnetic field, HO, which corresponds to the first pulse of the aforementioned vibrating magnetic field, H1; While the third mentioned magnetic field, represented by the H2 magnetic field, oscillates with a frequency Magnetic resonance of B spins of a group of nuclei located in the mentioned magnetic field HO;

(b) Stopping the second mentioned magnetic field, HO, when the quadrupole resonance signal coming from the A-spins of a group of nuclei is at its maximum, and thus the signal-to-noise ratio of the quadrupole signal increases, and thus the minimum size of the compound that can be detected and/or analyzed decreases. ,

(c) numbering and summing of the signals that are determined in the HO non-operation state in conjunction with the sequence of advisory pulses of the H1 field;

(d) Turning the HO magnetic field on again once the digitization step is finished;

(e) Repeat steps (b) to (d) until a signal-to-noise ratio equal to that required to identify the compound in question is obtained; And

(f) Emission of a warning signal in the event of a positive detection or progress in identifying and/or analyzing the next compound in the event of a negative signal.

Another purpose of the invention is to identify and/or analyze compounds having double quadrupole resonance.

Another subject matter of the present invention consists of sensing elements that identify and/or analyze compounds with nuclear quadrupole resonance and nuclear magnetic resonance, or double quadrupole nuclear resonance.

Other topics include a system that uses sensing elements and electrical circuits to identify and/or analyze compounds with nuclear quadrupole resonance, nuclear magnetic resonance, or double quadrupole nuclear resonance.

Brief explanation of the drawings

The concept of the invention can be explained by using the following figures:

Figure 1 shows:

(a) Resonance signal via pure quadrupole resonance of the 35Cl atom in paradichlorobenzene or P-C6H4Cl2; and (b) the P-C6H4Cl2 resonance signal in a double resonance, i.e. nuclear quadrupolar resonance (NQR) for the 35Cl atom and nuclear quadrupolar resonance for protons (1H).

Figure 2A depicts a spin echo of part of b of Figure 1, acquired in the presence of the static 20G magnetic field.

Figure 2B depicts an echo of Figure 2A, but with the static 20G magnetic field interrupted at the maximum set point, the limit and so the decay time increases with decreasing minimum volume of the compound to be detected and/or analyzed.

Figure 3 depicts a pulsating magnetic field H0 generated in an electric circuit, connected to a solenoid.

Figure 4A and 4B depict different bird cage-shaped coils from those known in the field.

Figure 4C shows an electrical coupling circuit used with the coil of Figure 4A.

Figure 5A shows a first embodiment of a sensing element of the present invention.

Figure 5B shows a second embodiment of the invention for a sensing element of the present invention.

Figure 5C shows a third embodiment of a sensing element of the present invention.

Figure 6 shows a block diagram of a turning/selecting device containing a sensing element of the invention.

Figure 7 depicts an arrangement containing a sensing element.

Detailed description

Part (a) of Figure (1) depicts the echo signal resulting from the quadrupole resonance of a compound such as paradichlorobenzene or P-C6H4Cl2 in its TT/2-TT pulse sequence to a vacuum pulse where t = 0.8 ms, for the nuclear resonance mode The pure quadrupole of the 35Cl atom.

Part (b) of Figure (1) depicts a resonance signal in the case of double resonance, that is, nuclear quadrupole resonance (NQR) of the 35Cl atom following the influence of the high-frequency magnetic field H1, and NMR of the 1H protons. The NMR state for protons can be achieved with a weak static field (known as the Zeeman field) H0 = 21 Gauss and a vibrating field H2 = 8 Gauss with a vibration frequency of 90 kHz (J. Perlo, Final Paper for the Physics Degree, College of Mathematics, Astronomy and Physics, Iniversidad Nacional de Cordoba, Argentina (2000).

Figure 2A shows in more detail a spin echo signal identical to the quadrupole signal from part (b) of Figure 1, i.e., such as coming from the DOR sequence, which has strong amplification relative to the signal generated by pure quadrupole nuclear resonance (NQR).

Figure 2B depicts the same spin-echo signal as in Figure 2A with the magnetic field H0 not flowing when this particular signal is at its maximum value, i.e., when using the PUDOR sequence. When compared to Figure 2A, it now becomes clear that the echo increases in a relatively short time (by an amount equal to the required increase in Figure 2A), and therefore the result is that when the magnetic field H0 does not flow, once the echo reaches its maximum, the echo decreases very slowly, and in this case the magnetization develops freely Under pure nuclear quadrupole resonance (NQR) conditions. The Fourier transform of the second half has a purer spectrum echo than its DOR counterpart. Thus, it can be said that after the separation of the H0 field, when the echo is at its maximum, the effect of the resonance line expansion during the identification period may decrease. Therefore, the minimum volume of the compound to be identified/analyzed decreases significantly, and at the same time the sensitivity of the detector increases.

The development of the observed oscillation in the echo amplitude shown in Figure 2B is due to the inclusion, following identification, of the process of excitation of the resonator and turning off the identification of the resonator (TONROF). This process consists of irradiating the A-spins of groups of nuclei with the H1 field, tuned to their resonance frequency. Then, the frequency of the direct digital sensor (SDD) is programmed in advance, as the sensor is accompanied by a spectrum analyzer in the state of resonance. "On", therefore, at the beginning of the detection phase, the frequency of the synthesis unit is changed by a command pulse emanating from the pulse programmer. The signal is then converted into a digital image via a digital analog converter, to the external frequency group. For example, when the frequency is between 10 and 100 kHz out of resonance (“off ring”), this is more appropriate.

Two effects can be obtained at the same time by using TONFROF technology.

(a) Due to the fact that the signal-to-noise ratio increases when the signal frequency is converted to digital form, the limits of detection for a small amount of compound are proportional to the seventh of the low signal that can be separated from the noise, and any increase in the signal-to-noise ratio directly causes a decrease in the size of The compound to be detected and/or analysed; And

(b) When the frequency content of the digital signal increases, the base noise and/or interference of the quadrupole signal resulting from turning off the weak magnetic field H0 can be easily filtered out, for example, by a digital filter.

This technique can be applied, as it is, through this invention either in connection with double resonance (DOR) or pulsed double resonance, PUDOR, in combination with the aforementioned sets of fixed and non-fixed sequences.

The interruption time for the H0 field ranges from 10 microseconds to 100 microseconds, and the best is 10 microseconds, and it can be controlled by a MOSFET electrical circuit according to the position in Figure 3, and this will be explained in detail later. To reduce the interruption time mentioned in the H0 field, it is also possible to use a GTO circuit with electronic switches such as those mentioned in reference: CR. Rodriguez, Estudio de la dinamica lenta y la estructua en cristales liquidos liotropicos miscelares mediante la RMN, Doctorate Thesis, College of Mathematics, Astronomy and Physics, Universidad Nacional de Cordoba, Argentina (2000).

The coil generating the weak magnetic field H0 may take any of the general geometric shapes such as Maxwell shape, solenoid, saddle shape, surface shape, etc. The importance of file design is to provide:

(1) a homogeneous magnetic field H0 in the volume occupied by the compound to be detected and/or analysed; and (2) the smallest possible amount of induction, to limit the on and off times of the field H0 to suitably equal values, and in the case of nuclear magnetic resonance (NMR) of the B spins of a group of nuclei, the required magnetic field homogeneity, H0/DH0, can be calculated From the frequency bandwidth DW of the B spindles and the excitation frequency bandwidth DW2, known as H2(t). The width of the spin resonance frequency band B, DW, represents one of the distinguishing features of the compound to be detected. For practical purposes, regardless of the molecular dynamic effects, it is possible for the magnetic field to be expressed through the equation Dω = dDH, where DH mainly refers to The local (local) fields that can be sensed by protons in the molecule of the compound to be detected, d represent the magnetic gyromagnetic coupling factor. This is to reach the maximum effectiveness of the double resonance, and this requires the excitation of all protons present during the resonance in the volume occupied by the compound to be detected. Therefore, it is reasonable that the maximum difference of the field H0 be at the dispersion order of the local field DH or less than that; And the frequency bandwidth Dω2 = gDH2 responds to the maximum excitation state, i.e., Dω, DωO < Dω2.

One of the characteristics of the weak magnetic field H0 is that it is temporarily stable. This stability mentioned must be controlled so that the width of the mentioned frequency band Dω2 = gDH0 (t) remains at the level imposed by DW2 throughout the entire period of use of the field.

In order to fulfill this purpose, it is possible to use Helmholtz coils, which are built from two pairs of N-shaped spins separated by a distance equal to their radius, and in general, depending on the width of the nuclear magnetic resonance (NMR) frequency range of the protons of the compound to be detected. The diameter of each conjugate must be several times larger than the diameter of the volume occupied by the compound to be examined and/or analyzed.

To reduce the size of the coil generated by H0, a variable-width solenoid with circular parts around its axis of symmetry can be used, and this axis is placed along the length of the examination tube. The ratio between the width of the spiral and the pitch was calculated using the method of: E. Rommel, K. Mischker, G. Osswald, KH Schweikert and F. Noack, J. Magn. Reason. 70, 219 (1986) For example, when a 70 cm long solenoid is installed to provide a free diameter of 60 cm for the baggage screening tube over at least one cylindrical shape on top of which a copper spiral bracket rests, the separation between the rounded parts is reduced so that the separation distance between them is less than 0.5 mm, and there are other possible compositions, through which it is possible to improve the cutting time of the magnetic field and/or achieve special uniformity in the size suitable for examination, according to what technicians specialized in this field know.

The coil must be protected by covering it from other coils contained in the sensor. The coil is shielded to protect it from the electromagnetic coupling that occurs between the coils in order to keep the electric field free from the magnetic field in the volume occupied by the compound to be examined and/or analysed. An engineering design is made for the cover to ensure the prevention of the generation of reverse currents, the effect of which reduces the quality factor q of the high- and low-frequency coil(s), which generate the vibrating magnetic fields H1 and H2, respectively. In order to achieve this purpose, geometric cuts must be made on the metal membrane of the cover, for example in the form of bars, circles, etc., or the H0 generating coil must be installed in an engineering manner that allows it to have self-protection, for example by being two-level (see (see D). . Panepucci, Shielded biplanar Gradient Coil Design, Journal of Magnetic Resonance Imaging, 9, 725 (1999). .

In one of the preferred embodiments, which are not limited to the present invention, an illustration of the solenoid (1) is given in Figure 3, which is characterized by a variable width and a rotational step around its axis of symmetry, and is surrounded from the inside by an inner diaphragm 2 made of a cylindrical epoxy layer. A copper film is deposited on it, on which are installed thin copper rods arranged in one line with the axis of the coil (1), and it is electrically connected to the ground from one of its terminals. According to what follows, as in the case of compounds with nuclear quadrupole resonance, the solenoid (1) and the inner diaphragm (2) are not necessary parts.

The structure of the outer diaphragm (3) is similar in structure to the inner diaphragm (2), and it isolates the accompanying sensor from external electromagnetic pollution. A second coil is placed in the area between the inner veil 2 and the tube-free volume through which the luggage passes, and this coil generates an oscillating magnetic field with a high frequency level H1, and a third coil 4 also generates an oscillating magnetic field with a low frequency level H2 and is Applying the definition of high frequency and low frequency to both DOR and PUDOR, which simply means, for example, that the first high frequency is in the megahertz level (nuclear quadrupolar resonance), While the second frequency falls within a level measured in tens or hundreds of kilohertz (nuclear magnetic resonance) in the presence of a weak magnetic field H0, and there is a case in which the signals are within a level that can be determined in megahertz (MHz). A low-pass filter (5) is connected to one end of the first solenoid coil mentioned (1), where it prevents induction of interferences occurring between the high-frequency coil and the low-frequency coil 4 and 4, respectively. The electrical current is delivered from the first current source V1, which is protected from reverse currents, preferably by a diode D1. The second end of the solenoid (1) is connected to the electrical regulation circuit 16, which consists of a suitable control device that controls the current through the MOSFET series 10 (for example, BUZ48). This process is directed by the first direction pulse of field 6, from the circuit Electrocardiogram 44 programmed pulse (see Figure 7). The current intensity is controlled using the control device (7) of H0. The controller (7) senses the current inside the resistor (8) connected in parallel with the aforementioned series of 10 MOSFETs through the integrator (PID), and the commands of the controller (“bus”) include transistor units (9) (for example, BC-546). It connects the appropriate command current to the MOSFET 10 series.

The starting electrical circuit 16 consists of a pair of diodes D3, D2 in series, a capacitor C, a second source of electrical power V2, and a GTO11 tiristor, which provides more electrical energy to deliver current to solenoid 1, in order to reduce the communication time. The energy provided by V2 is stored in capacitor C. Diode D2 and diode D3 perform functions to protect opposite currents generated after turning on and stopping the current generated by the weak magnetic current H0. A second command pulse 12, called a “short pulse” 12, arises from the electrical pulses programming circuit 44 (see Figure 7) and delivers commands to the tyristor 11GTO through another control device 11. Another short pulse 12 arises immediately before the field command pulse 6, and begins by connecting capacitor C with the solenoid circuit (1), thus generating a magnetic field H0, and thus all the energy collected in the aforementioned capacitor C is transferred to solenoid 1. The voltage in V2 is regulated until the desired H0 intensity is reached. It is possible that the regular circuit 16 can be replaced by a switch consisting of a tyristor and its control device, which works simply with an on-off switch system, according to what was previously mentioned through reference: Doctorate Thesis of CR Rodrigues. This electrical circuit is simpler and easier to implement, but it It requires excellent control of the electrical force source v1 to maintain the stability of the H0 field necessary for the experiments. The specific characteristics of a particular application will govern the installation of each circuit.

Figures 4B and 4A show two previous models known in this field, one of which represents a bird-cage-shaped coil (18). The coil 18 shown in Figure 4A consists of metal windings E connected in series by capacitors C1, and this represents a configuration known as “low-pass”. It results in oscillating magnetic fields that are polarized periodically at a low level of frequency. When a time-varying magnetic field has periodic polarization, it can become visible as a circular magnetic field with a constant intensity or constant coefficient.

The coil 18 of Figure 4B also contains metallic turns connected to each other in parallel by capacitors C2. Compared to what was shown in Figure 4A, this coil generates magnetic fields in a high-frequency field. This configuration is called "fast-pass".

In both cases, the coupling between the electrical excitation and detection circuits can be investigated, according to what is known in this field before and as depicted in Figure 4C, which depicts the bird cage coil 18 of Figure 4A coupled by mutual induction with two induction coils 60 61 which responds to the same excitation frequency, placed on the square of the circuit, and couples their electrical circuit 62 to the converter and receiver shown on the right.

The sensing elements that will be mentioned contain a number of coils capable of generating three fields H0, H1 and H2. In particular, in order to reduce the size of said sensing element, a first embodiment of the sensing element will include a coil to generate the magnetic field, said H0, and a bird cage-shaped coil to generate the fields H1 and H2. Through a second embodiment, said sensing element contains Helmholtz coils to generate said field H0 and a solenoid to generate said fields H1 and H2 at the same time.

On the other hand, the spatial position of different coils is known as the “filling factor.” It can be said that the coil responsible for generating the high-frequency H1 field that affects the A spindles of a group of nuclei must be as close as possible to the size of the compound to be detected. /or specify it. This is one of the well-known things in this field and we will not discuss it in this context. Thus, through the first embodiment of the sensing element, the birdcage coil 18 is surrounded by said solenoid (1), and through the second embodiment, said solenoid (1) is surrounded by Helmholtz coils 73.

Figure 5A shows a sensing element containing a solenoid 1 surrounded by a birdcage-shaped coil 18 . The aforementioned construction of the solenoid coil (1) is identical to the accompanying electrical circuits, preferably those mentioned in the explanation of Figure 3. Coil 18, on the other hand, acts at the same time as a low-pass filter for low frequencies and a high-pass filter for high frequencies.

The coil 18, similar to a bird cage, contains a series of windings E connected by capacitors C1 parallel to capacitors C2. In parallel with the capacitors C1, several multi-band coupling circuits, MBC, are connected, consisting of L3C3 circuits that resonate with the capacitors C1. When the frequency of the current passing through the aforementioned coils E is at a low level, the capacitance of the capacitors C2 is like an electrical short circuit at that frequency, and the aforementioned coil 18 operates according to the phase mentioned in Figure 4A. On the contrary, the frequency of the current passing through the coils E is in the high-frequency order, and the capacitors C1, assisted by L3 and C3, are short-circuits, and the aforementioned coil 18 works according to the method of Figure 4B. Both high-frequency current and low-frequency current flow automatically through the aforementioned coil 18. Any specialist in this field can determine the values of C3, C2, C1, and L3 according to the characteristics of what is to be detected and/or analysed. The high-frequency coils 63 64 and the low-frequency coils 65 66, placed on the square of the circuit, are coupled by mutual inductance with the coil 18 mentioned before.

The aforementioned induction coils 63 66 correspond to the resonance of the coil 18 similar to a bird’s cage at the resonance frequencies of the spindles A and B, and adapt to their own impedance related to the electrical filtering and coupling circuit 20, and the high-frequency excitation signals 21 and low-frequency excitation signals 22 reach the coupling circuit The aforementioned electrical filtration 20 is one of the special generators. Thus, the outputs of the electrical coupling and filtering circuits 20 guide the pulse coming from the receiver Rx23, and on the other hand, they guide the high- and low-frequency excitation signals 24 25, out of phase at 90 °C, to the high-frequency and low-frequency coils 63-64 and 65-66 on straight.

What is meant by the 90°C out-of-phase excitation signals is that for each pair of high-frequency and low-frequency induction coils, the signal reaches one of the coil pairs at an angle of 90°C out of phase with respect to the excitation signal that reaches the other. Also, the fact that the coils are on the square of the circle means that for each pair of high-frequency or low-frequency coils, one of the pairs is placed at an angle of 90 degrees according to what is mentioned in Figure 4C.

In cases where the excitation frequency of the A-spins is within a few megahertz levels, as is the case with the quadrupole resonance of 14N nitrogen, the calculation of high-pass coordination capacitors produces commercial values that are difficult to obtain, where it is necessary to choose The low-pass format in the birdcage-shaped coil shown in Figure 4A responds to such conditions.

Figure 5B shows a birdcage-shaped coil 18, also surrounded by a solenoid 1 (not shown) as in Figure 5A, and adapted to match the low-frequency resonance conditions of the A-spins of the aforementioned group of nuclei. In this sense, the capacitors C3 are connected in series with the different coils E and are calculated in relation to the aforementioned coil in order to produce a resonance with H1, located at the resonance frequency of the spindles A of a group of nuclei, which measures some units of megahertz (MHz). In parallel to each capacitor C3 are connected several multi-band electrical coupling circuits, MBC, which in this case contains a high-frequency stabilizing element Lch that acts as a high impedance for the resonant frequency of spindles A and as a short circuit for the resonant frequency of spindles B. On the other hand, the capacitors C4 is calculated inversely, that is, in a way similar to that of a short circuit at the resonance frequency of spins A and with a high impedance at low-frequency resonances of spins B. Thus in the case of signals induced at the resonant frequency of the A spindles, coil 18 operates through a low-pass configuration. In order to excite the B spins of a group of nuclei, a magnetic field H2 is generated in a manner similar to the basis of the rotating field of an electric motor. A microcontroller 69 (or alternatively a digital signal actuator or the like) generates successive current pulses that are transmitted to each of the windings E by a set of control devices 70, Mosfet switches 71 and low-pass filters 71, control devices 70 connected to an output Microcontroller 69, low-pass filters 71 with each of the E-turns of one end of said coil 18, and said MOSFET switches are placed between said controllers 70 and low-pass filters 71. Thus, it can be said that we are presenting an anti-resonance electrical circuit that works as a signal collection device or as a multi-communication device, enabling coil 18, which is in the shape of a bird cage, to operate at the H2 frequency, whose measurement ranges between tens and hundreds of kilohertz. In particular, the assembly formed by said microcontroller-69, controller 70, MOSFET series 71, and low-pass filters 71, functions as a low-frequency coupling and filtering circuit similar to the filtering and coupling circuit 20 mentioned by Fig. 5A, but in In this case, it represents a direct, non-inductive coupling to the aforementioned birdcage coil 18.

It is possible to foresee another high-frequency coupling and filtering circuit 67 of the resonant frequency of the spindles A of a nuclear group, which is connected to a TX bus, an RX receiver, and a pair of coils 65 66 placed on the quadrature of the circuit and coupled by mutual induction with the aforementioned coil 18, and these coils 65 66 can Excited by high-frequency excitation signals out of phase at an angle of 90°C.

One of the features of birdcage-shaped coils 18 is that they generate polarized fields on a periodic basis, which makes it possible, in the case of polarized compounds, to collect signals from polycrystallines with many directions relative to the axis of the coil 18, resulting in a signal-to-noise ratio. better ; Thus, an increase in the sensitivity of the detector. In contrast, the quality factor Q is significantly reduced relative to that which would be obtained from construction solenoids. When compared to solenoids, this effect has a poorer effect on the signal-to-noise ratio (see Y. K. Lee, H. Robert, D. K. Lathrop, Circular Polarization Excitation and Detection in NQR, Journal of Magnetic Resonance, 148, 355 (2001) On the other hand, an increase in the value of Q results in “lost time” or a delay in the start time of the spectrometer, which is clearly the highest, and it cannot be controlled by an electrical circuit of the damper type - Q, and it can develop the signal ratio - to - The noise is of lower quality than that produced by a birdcage-shaped coil by an amount less than Q. This depends on the electronic technology available and the characteristics of the samples drawn to be examined, and it may be more desirable to replace the birdcage coil 18 with a solenoid 72 according to the following. Remind him.

Figure 5C shows a solenoid 72 that generates a double oscillating field, H1, H2, and this aforementioned coil 72 is installed so that it has a variable width and a rotating pitch with the aim of obtaining homogeneous fields (see see AF Privalov, SV Dvinskikh and HM Vieth, Coil Design for Large-Volume High-BI Homogeneity for Solid-State NMR Applications", Journal of Magnetic Resonance, A 123, 157-160 (1996) In this case, the axis of the coil 72 coincides with the axis of the tunnel through which the compound to be examined and/or analyzed rotates . During the plane perpendicular to the longitudinal axis of the aforementioned file 72, a longitudinal axis is placed consisting of a pair of Helmoholtz 73 longitudinal or two-level, non-gradient variable files, such as the designs cited through the reference: E.C. Caparelli, D. Tomasi, and H. Panepucci, “ Shielded biplanar Gradient Coil Design", Journal of Magnetic Resonance, 139, 725 (1999) or those with a similar function. The exciter signal for the spindles A of the group of nuclei is generated at the bus 74, passes through a pair of perpendicular isolating diodes 75 and enters the aforementioned solenoid 72, and after the first pass through a balanced-unbalanced axis or “balum” 76. The electrical coupling and filtering circuit 77 for the resonance frequency of the spindles A resonance occurs, through a general configuration called “balanced,” with the solenoid. The electrical coupling and filtering circuit 77 includes a series of capacitors 78 through 80; One of them can be changed to obtain the aforementioned resonance in a balanced manner. It is not necessary for it to contain another coupling and filtering circuit, such as this sensing organ for example, and the field is linearly polarized.

In particular, this embodiment of the sensor can be applied to such cases where the resonance frequency of the A-spins of a nuclei array is low, i.e., consists of a few megahertz, as in the case illustrated by Fig. 5B.

On the other hand, the nuclear quadrupole resonance (NQR) signal does not enter the digital receiver/converter assembly 81 through the quadrupole (l/4) waveguide 82. The signal stimulus for the B spindles of a group of nuclei arises from a pulse generator, which is synchronized with the pulse generator (see Figure 3) and the frequency, phase and intensity of the H2 field are determined by a controlled computer 30 (see Figure 7). The low-pass filter 84 depicts the pulsating generator 83 of the high-frequency solenoid 72. Finally, the pulsating magnetic field generator 85 generates the field H0 in the pair of Helholtz coils 73, and through this structural scheme, both H1 and H2 are in a plane perpendicular to the direction of H0.

The general rule is that the magnetic fields H1 and H2 must be homogeneous at the volume occupied by the compound to be determined. In addition, the direction of the field H2 must be organized so that it is perpendicular to the direction of H0, in the case of magnetic resonance of B spins belonging to the group cores in order to reach the maximum possible degree of efficiency.

Figure 6 shows a structural diagram of the device without mechanical parts, i.e. assemblies, conveyor belt, etc. As for the signal stimulus for the four-pole cores of vehicles, it is generated from a transmitter and goes to the sensor 33, which may be any of those mentioned above in this context.

The aforementioned sensing element identifies the nuclear quadrupole resonance (NQR) signal and guides its counterparts to the receiver. The signal enters the aforementioned receiver through the receiver protection device 34. This signal is amplified by several high-frequency amplifiers 35 and filtered by filters 36 and 37. Then the early signal enters the phase-sensitive identification device 38 and then passes through a phase-splitter and drawer circuit 39 of the spectrometer determined in the quadrature of the circuit. Finally, the analog signal is converted into a digital signal in the A/D converter 41, after being filtered again with filters 40. The digital signal enters the control computer 30 for analysis and decision-making. The receiving amplifiers are controlled by computer using 42 control devices, in order to suit the size of each compound. Returning to the point about how the excitation signal is generated, we start from the high-frequency pulse that is generated in the Direct Digital Synthesis (DDS) unit 43, which receives its commands from a computer 30, and the digital signals originate from the pulse programmer 44, and also receives its commands from the computer 30. The pulses enter the high-frequency switch 45, and the signal is amplified at the pre-amplifier 46 and the electrical power amplifier 47, thus generating high-frequency force pulses that are responsible for exciting the quadrupole nuclei (spindle nuclei group A), for both 14N and 35Cl). The compound to be examined and/or analyzed with the sensor 33, under the influence of the magnetic field H1. The pulse programmer 44 also directs commands to the circuit for changing the quality factor Q 48. In this way, the wastage time of the spectrometer 29 is essentially reduced (see Figure 7), thus increasing the signal-to-noise ratio and thus reducing the minimum possible volume of the compound to be identified and/or analyzed. This wastage time can be defined as starting immediately after the pulse is turned off. High frequency. Over time, energy remains stored in the coil (birdcage coil 18 or solenoid 72), thus stopping the detection of blocking of the very weak nuclear quadrupole resonance (NQR) signal, and the change in quality factor Q 48 allows for a rapid decrease in the energy stored in the coil ( Birdcage coil 18a and solenoid 72), allowing the signal to be detected as the end of the high-frequency pulse approaches. When the nuclear quadrupole resonance (NQR) signal for some compounds depends on temperature, it is necessary to maintain the self-resonance process of spectrometer 29 (shown in Figure 7) in order to analyze the different resonance frequencies. This depends on the temperature of the compound inside the luggage that is to be examined. When this point is reached, the self-resonance circuit 49 can be introduced. Finally, the control computer 30 sends warning commands and various output information. The silent warning 50, audio outputs 52, visual outputs are displayed through the display unit 53, and graphic output 54. A group of lights 31 (see also Figure 7) is used to give instructions to passengers. Operators in the various positions that must be taken: For example, a green light means that the passenger/luggage must pass, which means that the inspection has been completed successfully, a yellow light means that the inspection process must be repeated, a red light means a visual alert to security personnel, while a white light means exit from service. The quality factor change circuit Q 48 of the PIN type includes a diode that is connected in reverse and receives its commands via the pulse control from the pulse programmer 44. The purpose of using a set of orthogonal diodes is: The reverse zener reduces low-frequency noise produced by PIN diodes. In order to protect the receiver from high-frequency pulses from the high-frequency pulse carrier, a quad-wave line (not shown) is usually used and is there for the purpose of preventing manual manipulation of the coaxial wire, which produces the same effect but at a frequency of a few units. One megahertz, and its length makes it difficult to trade. Finally, the self-arranging device 49 is formed when capacitance is added or subtracted from a syntony capacitor(s) (according to the type of coil used) by one or more relays of the coaxial type. Finally, a low-frequency excitation signal is generated by a magnetic field H2, and is generated at the generator or microcontroller 55, and the computer 30 directs commands, through a low-frequency amplifier 56, before entering the sensor 33. The assembly diagram of this device can be applied to compounds that have double quadrupole resonance. An assembly diagram of the device must be provided for generating H0, as mentioned in Figure 3, as well as in cases where a complex NMR and NMR are detected and/or analyzed.

An applied example is used, as Figure 7 shows a schematic view of a system in which a sensing element is used. It is possible to use an external cover 32 to perform the same function as the detection device, for example, the one used in airports that works with x-rays to detect luggage using X-rays. This cover 32 carries a sensing element inside it. The luggage 27 is entered into a corridor with dimensions Y and X, using a conveyor belt 28. The external dimensions can be represented by the letters C, B, A according to the size of the sensor, which in turn depends on the size of the luggage to be checked. These dimensions fall within the range of dimensions of the devices used for screening at airports. The excitation signals for the magnetic fields, as well as the nuclear quadrupole resonance (NQR) signal, are generated initially in the carrier and finally in the detector receiver, and these two devices are placed in the spectrometer 29. The computer 30 controls the entire detection process so that it turns it into an automatic method, and at the same time collects the nuclear quadrupole resonance signal after converting it to digital form and issues commands and, among other indicators, visual warning means 31.

It is necessary to prove that the low-frequency magnetic field, H2, can be compressed at the same time as it coincides with the H0 pulses, because it is effective only when H# is zero. This possibility has been mentioned in relation to those cases in which it is not possible to isolate the nuclear quadrupole resonance signal. (NQR) generated by spins A due to interferences generated by H2.

Finally, we will discuss the double quadrupole resonance of compounds in which the quadrupole nucleus is mainly coupled to another quadrupole nucleus of another resonance frequency, for example, nitrogen with potassium, sodium, etc. The A spins of a group of nuclei remain directly observable using quadrupole resonance, such as nitrogen or chlorine, and the B spins of a group of nuclei are formed by any of its nuclei, for example, from a small constant of quadrupole coupling, and thus are not directly detected, but are coupled. Strongly with nitrogen, in this case, it will not be necessary to have a static H0 magnetic field. It will only be necessary to have two magnetic fields, H1 and H2, where the first oscillates at the four-pole resonance frequency corresponding to the A-spins of a group of nuclei and the second oscillates at the four-pole resonance frequency corresponding to the B-spins of a group of nuclei. In other words, it will not be necessary to have a solenoid. (1) For Figures 5A and 5B, it will also not be necessary to have Helmholtz coils in Figure 5C, as both of them generate a weak magnetic field H0, and coil 18, which is in the shape of a bird’s cage, will suffice. As shown in Figures 5A and 5B, or a solenoid 72 as shown in Figure 5C, which can generate the two aforementioned magnetic fields H1 and H2, and the four-pole resonance frequencies of both must be high, and thus it can be said that they are at the level of megahertz units, and it represents The sensing elements in Figures 5A and 5C represent those preferred by the preferred application, or the preferred sensing elements represent those similar to those in Figures 5B and/or 5C. According to what was previously mentioned, the higher frequency in the two frequencies can be defined as the high frequency, while the lower frequency in the two frequencies can be defined as the low frequency. Any technical specialist in this field can calculate multi-band coupling circuits (MBCs) as well as electrical coupling and filtering circuits in a way that is compatible with the previous functions. The A and B spins are distributed in order to identify the A spins of a group of nuclei that carry the best pure nuclear quadrupole resonance (NQR) signal.

The resonant frequency of the quadrupole of the B-spins of a group of nuclei has a quadrupole coupling constant, which is generally small, and it depends on the quadrupole of the B-spins of the group of nuclei. The magnetic field H1, to which the A spins of a group of nuclei are subject, is homogeneous and oscillates at a high frequency, while the magnetic field H2, to which the spins B of a group of nuclei are subject, is homogeneous and oscillates at a high or low frequency, according to the quadrupole spectrum of the B nuclei.

The quadrupole resonance signal can be determined by a succession of spin echo signals.

Likewise, something similar can be obtained through steps through which the resonance excitation is determined and the resonance off (TONROF) is determined, which consists of:

The radiation of the A-spins of a group of nuclei is tuned to the first mentioned magnetic field H1 with its resonant frequency;

Programming the frequency of the Direct Digital Synthesizer (DDS) unit accompanying the spectrometer in Resonance;

During the detection phase, the DDS frequency can be changed by a command pulse from the pulse programmer to increase the signal-to-noise ratio; And

Converting the signal into digital form via an analog/digital converter at a fixed frequency ranging between 10 and 100 KHz, in an appropriate manner.

Likewise, the aforementioned TONROF technique can be calculated using a sequence of complex signals or pulses, known to be constant and non-stationary, according to what follows.

The aforementioned TONROF method can be applied to a fixed sequence of single pulses known as steady state free progression (SSFP) and consists of:

Irradiation of a sample with successive pulses of TT/2 on the A spins of the nuclei groups; And

Converting a quadrupole signal into a digital image at intervals between pulses.

The TONROF technique can also be applied to a fixed sequence of signal pulses known as strong stop resonance (SORC), where both the quadrupole signals are excited and the stop resonance condition is detected.

Finally, a non-stationary sequence known as spin-locked spin echo (SLSE) can be applied, which retains the nuclear quadrupole resonance (NQR) echo signal through an effective time T2 higher than the decay time T2 of the pulse sequence, and consists of: - Application to the component of the first high frequency of the aforementioned first magnetic field, H1, which has an amplitude that allows the redirection of the magnetization of the quadrupole nuclei at an angle of 90°C and a phase of 0°C for the aforementioned direct rheosynthesis unit (DDS); - After a period of time t has passed, a new high-frequency pulse is applied, which is then double-permanent or able to reorient the sample at an angle of 180°C with a phase that makes an angle of 90°C with respect to the previous pulse in order, exactly at the same time period. t from the end of the new high-frequency pulse mentioned, and a spin echo appears; - Repeat the previous step until n frequencies are collected and converted into a digital image, all in the same way.

Regarding the sensing elements used to detect and/or analyze compounds that have at the same time double nuclear quadrupole resonance, it must be taken into account that generating a weak magnetic field H0 is unnecessary.

The preferred sensing element contains a first coil 4 that generates a high-frequency oscillating magnetic field first and a second coil that generates a low- or high-frequency oscillating magnetic field - H2 4 , according to the quadrupole spectrum of the B cores. An internal diaphragm 2 is placed between the two aforementioned coils 4, 4 and the free volume of the tube through which the compound to be detected and/or analyzed passes. Therefore, the two coils 4 and 4 are surrounded by an outer diaphragm 3, which, as can be seen in Figure 3, does not include solenoid 1 or the accompanying electrical circuit used to generate and control the field H0.

The first coil 4 and the second coil 4 may resemble, according to the previous examples, the single coil 18 similar to the bird cage shown in Figures 5A and 5B, provided that the first magnetic field H1 oscillates at a high frequency, and the second magnetic field H2 is able to Oscillation at high or low frequency, according to the quadrupole spectrum of the B cores. In particular, the birdcage coil (18) shown in Figure 5A will contain several E windings connected in series with the help of capacitors C1 and in parallel with capacitors C2, connected on Parallel with multi-band coupling circuits (MBC) in parallel with the aforementioned capacitors C1, and inductors 63 64 and 65 66 at high frequencies and low frequencies, respectively, where they are placed in the quadrature of the circuit and excited by signals out of phase by 90 ° C. These coils are connected to the electrical coupling and filtering circuit 20 as shown in Figure 5A.

The multi-band coupling circuit (MBC) consists of an electrical circuit L3C3 that resonates with the aforementioned capacitor C1. High and low frequencies flow through the aforementioned E windings so that the current passing through the mentioned E windings is in the high frequency range. The short circuits of the capacitor C1 operate with the help of the MBC and a cage coil. Bird 18 acts as a high-pass filter, the current passing through the windings E must be in the low-frequency range, and the short circuits of the capacitor C2 and the aforementioned bird-cage coil act as a low-pass filter. The veil is installed at least 2 from a cylindrical sheet made of epoxy with a thin copper deposited in the form of suitable geometric pieces, for example in the form of rods, circles, etc., and above it are installed sticks of copper foil parallel to the longitudinal axis of the baggage inspection tube, and one of them is connected Its ends are electrically grounded.

There is another embodiment of the birdcage coil 18 similar to that shown in Figure 5B, which corresponds to the low-frequency state of the resonance of the A-spins of a nuclei array. Thus, the capacitors C3 connected through a different series of windings E can be calculated so that the winding mentioned by H1 tunes at the frequency of the resonance of the spins A of a group of nuclei, at a level of some megahertz. In parallel with each capacitor C3, multi-band coupling circuits are connected, containing an element with a high-frequency choke Lch, which blocks the resonance frequency of the spindles A, and acts as a short circuit for the low-frequency resonance of the spindles B. On the other hand, the capacitors C4 can be calculated inversely, in such a way that they act as a short circuit at the resonance frequency of the A spindles in the presence of a high impedance at the low-frequency resonance of the B spindles. For this, the induced signals of the resonance frequency of the spindles A and the birdcage coil 18 act as a low-pass filter (Fig. 4A), and the magnetic field H1 arises such that it represents the basis of the rotation field of an electric motor. The microcontroller 69 (or a digital signal actuator or similar device) generates a stream of successive pulses that is transmitted to all windings of E by a set of controllers 70, MOSFET switches 71 and low-pass filters 71, and the controllers 70 are connected to an output Adjuster - precision 69, low-pass filters 71 with each of the E-turns of the bird cage coil 18 and MOSFET switches between the said adjusters 70 and the said low-pass filters 71. Thus, it can be said that we have presented an anti-resonance electrical circuit that acts as a signal collector and thus allows the bird cage coil (18) to operate at a frequency that, with respect to H2, falls in the range between tens and hundreds of kilohertz, and in particular the group that includes the fine-tuning 69 , the controllers 70, the MOSFET series 71 and the low-pass sprinklers 71 operate as an electrical coupling and filtering circuit similar to the electrical coupling and filtering circuit 20 of the previous example, but in this case they are direct and their coupling is not incident to a cage coil. The bird (18) mentioned.

There is another electrical coupling and filtering circuit 67 that can be used with the resonance frequency of the spindles A of a group of nuclei, which are connected to the carrier TX and the receiver RX. The aforementioned electrical coupling and filtering circuit excites the inductance of the coils 65 66 placed in the square of the circuit and is coupled by mutual inductance with the bird cage coil 18 mentioned by Signals out of phase by 90°C.

Finally, a sensing element similar to that mentioned in Figure 5C can be used to consist only of a solenoid 72 that automatically generates a first magnetic field H1 and a second magnetic field H2. File 72 contains turns of variable width and pitch; The transformer 74 generates an excitation signal; A pair of orthogonal diodes 75 are connected to the output of said transformer; The balum transformer 76 is connected to the output of the aforementioned pair of orthogonal diodes 75; An electrical coupling and coupling circuit 77 for high-frequency tuning, connected to the aforementioned transformer output 76, consisting of several capacitors 78 to 80, one of which is variable in order to allow tuning of the electrical coupling and filtering circuit 77 with a solenoid 72. There is no need to incorporate another electrical coupling and filtering circuit, since the example of the sensing element is linearly polarized field law. It also includes a digital receiver/portable assembly 81 whose signal is entered via a quarter-wave conductor (l/4) that connects the pair of diodes. The aforementioned perpendiculars 75 and the balance-and-unbalance transformer 76 mentioned. The signal is played back after converting it into a digital image using a controlled computer 30.

From the assembly diagram of the device, which accompanies the various sensing elements mentioned above, it is not possible to anticipate the control and regulation circuits for the pulsating field H0 of Figure 2. The sensing element represents the birdcage coil (18) which has no solenoid (1) shown by Figures 5a and 5B, or the solenoid 72 which does not have Helmholtz coils shown by Figure 5C.

The arrangement containing the previous sensing elements, used to detect and/or analyze compounds with a double quadrupole nuclear resonance, is similar to that shown in Figure 7.