DE1591867C - Magnetometer with nuclear magnetic resonance for measuring the field strength of a weak magnetic field - Google Patents

Description

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The invention relates to a magnetometer with magnetization at the nuclear magnetic resonance frequency of the atomic nucleus nuclear magnetic resonance, which effects an oscillator with spin, while the ^ saturation of the other line causes the has coupling, rf. H. an oscillator with two stimulated energy emission at the nuclear resonance Blochschen Coils connected to the input and generated at the frequency, devices being provided Output of a linear amplifier connected 5, which in each. Sample an electromagnetic ' are and form a loop in which the oscillation field with the frequency of an electronic resonance frequency at the nuclear magnetic resonance frequency generated line to produce the two in the two samples which is to saturate electronic resonance lines to the strength of the magnetic field, is proportional to that measured by the magnetometer. For simplicity, the following

shall be. io description uses the following expressions:

The subject of patent 1516 924 is a magnetometer with the following components: The term "sample" to designate one of a pair of containers, each of which contains a sample ( ^{contained in a} container) solvent of a substance with gyromagnetic !! Properties ^{mass with} atomic nuclei with a magnetic contains · ¹⁵ moment and a kinetic moment, which a practically linear amplifier; are different from zero (i.e. with exactly two coils, of which the first gyromagnetic ^ ratio defined at the input), where • and the second is connected to the output of the amplifier the solvent in solution is a paramagnetic one; The two coils contain a substance (e.g. an ion or a free radical and the same. Pair practically identical to- ^{20 mi} * unpaired electrons) with at least one mutually and with parallel axes, -but against- electronic resonance line, which makes sense wrapped around a different container " ^{through an} electromagnetic field with one, so that at the input of the amplifier the in the given high frequency with any type of the two coils connected to its input, weak magnetic field in which the sample is induced by the nuclear magnetic resonance ²⁵ electromotive forces are added together while ^and the term "head" to designate de / the electromotive forces that ^h in this ^dur ^ the coils and their associated two coils both formed by any outer probe assembly, electromagnetic fields as; is brought is saturable also by any _. ■ _,. · «..,. · movements of the magnetometer in the to ³⁰ The ■ invention relates particularly, when measured magnetic field can be induced, ^"I., Exclusively, a magnetometer which as opposed to each other and cancel each other out, oscillator formed with spin coupling and and ο ο ο accurate measurement of weak magnetic fields also beeinem to the output of the amplifier ^ ¹ "" ¹ * «* · ^z · ^B - ^the earth's magnetic field, its connected frequency meter. ³⁵ Value of the order of 0.5 Oe, i.e. 50,000 yarn

ma, amounts, or to determine changes

In the main patent there are two classes of very low amplitude out such fields, e.g. B. in the management forms are described in which the order of magnitude of a tenth of a gamma, two coils surrounding one and the same sample, there are already different magnetometers with

one of which is known to the input and the other 40 oscillators with spin coupling. Most connected to the output of the amplifier, contain only one sample and two mutually sink either mutually perpendicular axes (first class) right coils and have various disadvantages, or axes parallel to each other (second class) in particular the presence of two prohibited ones to have. Measuring axes (i.e. along which no measurement is

The invention relates in particular to a continuation (45 can be taken), this term Formation of the second class of embodiments means that any measurement is impossible if the of the main patent, namely the one in which lines of force of the magnetic field parallel to the axis the two wound on the same container one of the two arranged perpendicular to each other Coils have parallel axes, the coupling coils being, and excessive sensitivity to coefficients for the two samples oppositely 50 electromagnetic interference fields and for fast being, which on the one hand a solvent with atomic movements of the measuring head.

cores with a magnetic moment and one that was double excessive sensitivity

kinetic moment, which is already practically different from zero by the main patent with two are, and thus have been suppressed with a precisely defined gyro sample and two pairs of coils, magnetic relationship, and on the other hand in this 55 also possesses when the two one and the same Solvent dissolved a paramagnetic substance sample associated with coils according to the second contain, in particular an ion or a free radical, class of embodiments of the main patent with an unpaired electron, at least one of which are parallel to each other, the magnetometer of the electronic resonance line, which has the additional advantage of a main patent, the number of to reduce the electromagnetic field with a measuring axis forbidden by zero to one, different frequency itself in a stray towards zero In most cases forms the presence

benden magnetic field is saturable, whereby the one forbidden axis by a single forbidden axis is not essential two identical or different samples (which disadvantage. In certain applications, in particular but then the same atomic nuclei in the solution on board airplanes and in particular from medium included) formed arrangement two electro- 65 rockets and satellites, however, it can happen Niche resonance lines with different frequencies that the measuring head assumes such a position that or with the same frequency, the saturation its forbidden axis with the direction of the force of one These lines coincide with an increase in the energy absorption lines.

3 4

The invention aims to produce a sion frequency of the nuclear spins with the axis of the coil magnetometer, which is measured better than the previous reference axis, and that, if magnetometer meets the requirements of practice, this axis corresponds to a certain angular speed, in particular because it no forbidden speed moved around the magnetic field, this speed axis no longer has, but 'the power 5 speed added to the precession speed or' the. previous embodiments retained and withdraws from this. In the case of the invention, they can even be improved. ^; - ~ '' arrangement arises, 'when the gyromagnetic

The subject of the invention is a further development of the effect on one of the coil pairs greatest and on a magnetometer of the type mentioned (according to which the other is zero, the amplifier on a frequency second class of embodiments of the main io, which is practically the mean value between the patents), which consists in dividing each sample into two real ones (of those of the gyromagnetic effect Samples and each coil detected in two zero-exposed coils connected in series) precession coils to split up, the first of which has its original frequency and that of the other coils Maintains position while the second frequency is lowered. This can practically the right to the first one, so that the magnitude of the gyromagnetic effect is of the order of magnitude gnetometer The following parts contains moderately reduced by half.

• four arrangements, which according to two iden- fjf. Invention is hereinafter referred to

tables, pairs offset from one another by 90 ° ^aü L ^{explained in the} drawing by way of example
'are arranged, where each arrangement is represented by ^F 1} f ^l '? ^{in a} block diagram of an inventive

a magnetometer connected to the input of a linear amplifier ²⁰ , which has two types of connected coil and one connected to the output ^Pro £ ^en *? ^e " ^{uses which} different paramagnetic coil connected to this amplifier is formed ^bt ° ^tt . ^e ;..

is, the two coils of one and the same ^F ψ ^{2 ze} f- ^ ^ mutual arrangement of the arrange order parallel to a different in their Community components of the head of the magnetoresistance _r common axis arranged sample with coupling ^{me 25} * ^{e. rsder} \ ¹ S-. ^1; . . _. ,. ,

coefficients are wound, which at the two ^ ^F ' \ ^{3 zei} ? ¹ '"," 5? ^F' 8 ¹ corresponding arrangements entgegen- a same pair *? ArsteHung an embodiment, which are idengesetzt four, wherein the four input coils used in diagram samples.

^The F while schematically illustrated magnesium m 1 g 1 and 2 are connected in series and to each other,

the four output coils in series of two different ³ ° »° ™ ^ ^Γ contains ^εΐη / η in the field to be measured

- Coils belonging to different pairs in parallel ßndhchen measuring head Λ, a loop amplifier B are connected to * generating a signal with the devices through the head, 'which an electromagnetic given nuclear magnetic resonance frequency F an oscillator C field with the electronic resonance frequency ^m * ^eme . ^In each pair of arrangements ³⁵ electronic resonance lines of the samples of the head, a line of one sample, which shows the increase ^{and e} "l ^Ge " ^r , ^{at D.} ™ ^Me ? ^sun S ^de ü ^Fre quenz ^ _{A A of} the energy absorption at the resonance frequency ^The ^ ^eßk ° P ^f j ^ ^{eht a} " ^s causes four identical arrangements of the atomic nuclei, and a line of ™ ⁿ &? ^4a > ^4b > ⁴ % ^4d > ^ ^{he 2} T ^{1 by} 9 ° &&? - other samples, which form an energy emission with mutually offset pairs, each of which causes two to saturate in the nuclear magnetic resonance frequency; ⁴ ° ^{a r FIu} f ¹¹ Jf ^ ⁿ de arrangements contain each an _{un (} j order 4fl, 46,4c, 4rf consists of two coils 6a, 6b,

Equipment for .Measuring the frequency in the ■ ^6c . ^{or 6d} . ^{and 8} . ^a ' ⁸ *' ^8c ° J ^er * ί> ™? ^ ϊ ° ^ηζ Λ ^η ; the coil and the amplifier containing a sample bottle 10 a, Wb, 10 c or 10a containing a sample 12 ", i: Ib, lic or lld loop.

45 are wound. To clarify the drawing

In a preferred but not exclusive one, the coils pertaining to each sample are shown in FIG. 1 embodiment of the invention contain the four shown side by side and next to this sample.
Samples in an identical volume of the same. The input coils 6a and 6d are in the same

Solvent two paramagnetic substances, wound at sense, which is opposite to that of the input coils 6b which the same frequency of the electromagnetic 5 ° and 6 c of the same pair. The field of two opposing electronic lines both of the same pair belonging to excitement, ie one of which is an increase in the output coils are directed in the same direction.
Energy absorption and the other the stimulated Since the input coils are coaxial to the

Energy emissions are at the nuclear magnetic resonance frequency of the speaking output coils, they are from these Solvent causes. 55 not decoupled by their location. For excretion

- In a second embodiment, the four of the signals generated in the coils by sources of interference (external electro-samples, and the magnetometer has two magnetic fields, movements of the magnetometer, very high frequency generators for generation in the field to be measured, etc.) are generated of the electromagnetic field, the frequencies of which the coefficient of coupling by mutual are chosen so that two opposite electro- ⁶ ° induction between the coils 6a and 8a (or 6d niche lines of the same in the two samples A and Sd) have a value, which the coupling coefficient. and the same pair of paramagnetic ducks contained between the coils 6b and Sb (or 6c and 8c) of matter are excited. of the same pair is equal and opposite.

It should be noted that in both embodiments, after establishing equality, the coupling

shape the invention offers an additional advantage, 65 coefficients through regulation and opposition

which in the reduction of the gyromagnetic by the above-mentioned arrangement allows one

Effect exists. This term denotes a suitable arrangement of the

Measurement error, which arises from the fact that the precision coils have the effect of the

5. 6th

adorned electromotive forces on the Ver- defined solution from TANO and on the other hand a

more to compensate. - · · Millinormal solution of »tanoxime six«

Each sample 12a, 126, 12c, lld contains the following be ■ NO [C (CH ₃ ) CH] ₂ C = NOH

components: ..- ■■■ · _v 3222

-. "5 in water to which a third of the glycol has been added

A solvent, which atomic nuclei with a (resonance frequency 69 MHz), use,

magnetic moment and a kinetic The excitation of the electronic resonance lines

Moment contains which non-zero of the samples takes place from a (the arrangement C

are. These moments create the gyromagnetic forming) single oscillator with a very high frequency:

Ratio γ of the cores fixed, and the resonance 10 sequence 14 from via coaxial cables 16a, 16b, 16c and

frequency F of these nuclei in a magnetic field with " 16jd, which (in Fig. 1 not shown) cavity-

the strength H is given by the formula: resonators act on the samples 12a,

12b, 12c and 12d included, which are in annular

_ γ f. _m bottles 10a, IQb, 10c and IQd are located. Against-

t - j ' "5 ^se ITIG ^e position of each coaxial cable and corresponds

^π- speaking sample can be the one shown in FIG. 4 and 5 of the

. '. . Main patent shown correspond.

The atomic nuclei are generally protons, the input or excitation coils 6a, 6b, 6c, 6d

However, other cores can also be used in series at the input of a linear low-

- be, especially fluorine cores. In the former 20 frequency amplifier 18 (for 2000 to 2100 Hz, if

Case the solvent is generally H = 0.5 Oersted and the nuclei are protons)

by a mixture of water and one only when closed. One connected in parallel with the input

low temperature freezing, water adjustable tuning capacitor 20 of some

miscible hydrogenated liquid is formed. a thousand pF forms with the series connection group

A paramagnetic substance in a stable solution 25 of the four coils 6a, 6b, 6c, 6d form a resonance circuit

(Ion or free radical with an unpaired low figure of merit to avoid dcf

Electron interacting with an atom frequency entrainment.

core of the substance). The four output or take-off coils 8, Sb,

8c, 8d are connected to the output of amplifier 18

In the embodiment shown in Fig. 1 30 tied. and assigned to one another in such a way that the

contain the two forming a pair in a Ftocht 'add useful signals of all arrangements while

lying arrangements (e.g. Aa and Ab) two "convert the interfering signals as a result of the opposition of the in two

separate samples 12 'and 12b with preferably and the same pair belonging coils on- ^

same volume. The two paramagnetic emerging interference signals are eliminated (in Fig. 1

Substances of these samples are chosen so that they are at 35 the input and the output of some coils with

practically the same excitation frequency two opposite - E and S respectively).

have set electronic resonance lines. For this purpose, the two coils Sa and Sd, which are a sample (e.g. 12 "), the paramagnetic substance are both assigned to a first type of sample and are selected in such a way that the saturation of an electronic input coils 6a and 6b are the same and equal. Resonance line through the electromagnetic field which has 40 meaningful coupling coefficients, in series with a frequency / with a sound close to /. The two coils Sb and 8c are also connected in series with an increase in energy absorption at the frequency. The two branches thus formed, given by the formula (1), are generated on the one hand at 21 with the body and on the other hand (nuclear resonance frequency) with the nuclei. For the other sample with the ends of an adjustable potentiometer 22, the substance is selected so that the same 45 to 23 is connected, the center point 24 of which is connected to the frequency / an electronic resonance line, output of the amplifier 18. The more potent saturation of a stimulated energy emission at tiometer 22 to 23 enables the complete abder of the resonance equation given by the formula (1) for the circuit with small differences in the frequency (nuclear magnetic resonance frequency) of the nuclei. Induction coefficients.

You can z. B. as the first sample a solution with 50. The frequency meter 26 allows the measurement of the

the concentration M 800 of DTBN (ditertiobutyl nuclear magnetic resonance frequency F in the loop of the

nitroxyd) in a mixture of 50 percent by volume, which exactly corresponds to the strength of the magnetic field

Water and 50 percent by volume acetone and second is proportional. if there is no frequency port

Sample a solution Λ / 1600 of TANO (triacetone occurs, which is practically due to the low quality factor

amine nitroxide) in a mixture of 70 ° _{/ 0} water 55 of the input circuit is excluded.

and 30 °; _O use ethylene glycol, pie application of a The work of the magnetometer is clear from the

electromagnetic field with a frequency / in the above statements and the information of the main

the order of magnitude of 68.5 MHz saturates the lower patent, so that it is only briefly described.

electronic resonance line of the TANO, which is a die generated by the oscillator 14 in the four samples of the energy absorption through these at the 60 excited electronic resonance lines generate (at

Nuclear magnetic resonance frequency (2000 to 2100 Hz for the pro-existence of a "magnetic field") the occurrence

tones in the earth's magnetic field), and that of a macroscopic component, which is a

upper electronic resonance line at 69.4 MHz of the given sense in samples 12a and 12a "and

DTBN, indicating stimulated energy emission by the opposite sense in samples 126 and 12c has this at the core frequency of 2000 to 2100 Hz for 65. This has the consequence that the macroscopic

which gives protons in the earth's magnetic field. Resultant of the magnetic moments of the

Of course, other pairs of samples, including the atomic nuclei of Prohcn 12a and 12b

to be used. For example, on the one hand the above on the one hand and 12c and 12a '' on the other hand can be in the opposite phase

are, because the winding direction of the two coils 6a and 6d. • that of the two coils 6b and 6c is opposite and the couplings between the coils of the arrangements have fixed values. The electromotive forces induced by the nuclear resonance in the coils 6a, 6b, 6c and 6d therefore add up.

The measuring head shown schematically in FIG. 2, which is arranged in a housing (not shown) made of a non-magnetic material, is formed by four arrangements which are combined by the conductors connecting the coils, indicated by dots. Assemblies Aa and Ad contain an annular bottle containing a few cubic centimeters of a solution of DTBN with a concentration of M / 800 in 50 percent by volume water and 50 percent by volume acetone. The Ab and Ac arrangements contain an equal amount of a solution of A // 1600 from TANO in a mixture of water and ethylene glycol.

The saturation of the electronic resonance lines of the four samples takes place through four branches 16a, 166, 16c and 16de \ n and the same, fed by a coaxial cable, not shown, of 68.5 MHz. Each branch 16a, 166, 16c or 16d acts on a cavity resonator, which is delimited by silver foils, which are arranged next to one another on the outer wall of the bottle and form a screen that is impermeable to the electromagnetic field of 68.5 MHz, but which is impervious to the nuclear resonance frequency (in the size disorder from 2000 to 2100 Hz in the earth's magnetic field) is permeable.

For example, an input coil 6a and an output coil 8a are arranged concentrically around the bottle 10a. The coil 6a connected in series with the coils 6b, 6c and 6d picks up a voltage at the nuclear magnetic resonance frequency. The output coils which cause the signal to be fed back, e.g. B. the coil 8 a, are connected in parallel between the body and the output of the amplifier 18 in pairs

Each input coil can e.g. B. 2128 turns of enamelled wire (diameter ⁸ % oo mm) and each output coil 114 turns of enamelled wire (diameter also ⁸ % oo ^mi "). The resistors 23 (Fig. 1) can each be 4700 ohms, and the potentiometer 22 can have a total value of 100 ohms.

It should be noted that the symmetrical structure of this head offers numerous advantages. A first ■ Alignment can be achieved by simply changing the mechanical attachment of the four arrangements be made towards the center of the head. The excitement of the four samples from the Coaxial cables are the same for all samples. This last point constitutes an advantage over the with reference to Fig.4 and 5 of the main patent described arrangement in which the 'Input of the coaxial cable may have to be adjusted for a sample.

Furthermore, the central space between the four arrays provides a sheltered place for accommodation the connections between the coils of the assemblies.

F i g. 3 shows schematically the head and the high frequency oscillators a magnetometer forming another embodiment of the invention with identical samples. In Fig. 3 wear the parts of the F i g. Parts corresponding to 1 have the same reference number as in Fig. 1. The four samples are, for example, by a solution of DTBN is formed in a solvent, which is a mixture of 50 percent by volume Water and 50 percent by volume of acetone are made up of; The DTBN 'has two opposite electronic components Resonance lines of 69.4 and 72 MHz in a - magnetic field of the order of magnitude of 50000 gamma (which is the mean value of the earth's field.

ίο corresponds). The oscillator 30 exciting the samples of the arrangements Aa and Ad is set to a frequency of 69.4 MHz by a quartz, while the oscillator 32 exciting the samples of the arrangements Ab and Ac is set to 72 mHz by a quartz. The operation is then the same as that of the previous embodiment.

While this design modification is functional, it has certain difficulties. Because the samples are very close to one another, there are interference effects between the two oscillators difficult to avoid. Tuning the cavity resonators becomes considerably more difficult than

■ in the previous case in which they were through the symmetrical structure is facilitated. The presence of two oscillators instead of a single one results in increased energy consumption.

Claims (5)

Patent claims: 1. Magnetometer with nuclear magnetic resonance for measuring the field strength of a weak magnetic field with the following components: a) a pair of containers, each of which contains a sample of a substance containing gyromagnetic Contains properties; b) a practically linear amplifier; c) two coils, the first of which to the input and the second to the output of the amplifier is connected, the two coils of one and the same pair 'practically identical to each other and with parallel axes, but are wrapped around a different container in opposite directions, so that at the entrance of the amplifier in the two coils connected to its input through the Nuclear magnetic resonance induced electromotive forces add up while the electromotive forces generated in these two coils both by any external electromagnetic fields as well as any movements of the magnetometer can be induced in the magnetic field to be measured, opposite to each other are and cancel, and d) a frequency meter also connected to the output of the amplifier, where the two reels wound on the same container have parallel axes, where the coupling coefficients are opposite for the two samples, which on the one hand a solvent with atomic nuclei with a magnetic moment and a kinetic moment, which are different from zero, and therefore with an exact defined, gyromagnetic ratio, and 009 687/292 - 'On the other hand, dissolved in this solvent. contain a paramagnetic substance, ".- in particular an ion or a free radical • with an unpaired electron, which at least one electronic resonance line, soft by an electromagnetic field with a - · ■ frequency different from zero even in a magnetic field tending to zero is saturable, whereby the samples produced by the two identical or different samples (which but then contain the same atomic nuclei in the solvent) formed arrangement two electronic resonance lines with different frequencies or with the same Frequency possesses, with the saturation of one - of these lines. an increase in energy absorption at the nuclear magnetic resonance frequency of the atomic nuclei, while the saturation of the other line causes the stimulated emission of energy at? the nuclear magnetic resonance frequency generated, with devices being provided, soft an electromagnetic field with the frequency of an electronic one in each sample Generate a resonance line to create the two electronic resonance lines in the two samples to satiate according to patent 1516924, characterized in that each sample (12) is formed in two samples and each coil (6, 8) in two series ³⁰ . The first coils are stacked, of which the first ° 'retains its original position, while the': second is placed perpendicular to the first, so that the magnetometer contains the following parts: J ' four arrangements (4a, Ab, 4c, 4Od), which are arranged according to two identical pairs (4a to 4b; 4c to Ad) offset by 90 °, each arrangement being connected by one to the input of a linear amplifier (18) Coil (6a, 6b, 6c, 6d) and a coil (8a, 8b, 8c, 8d) connected to the output of this amplifier is formed, the two coils of one and the same arrangement parallel around a sample with coupling coefficients arranged in their common axis are wrapped,. which in the two arrangements are one and the same pair opposite, the four input coils (6a to 6d) being connected in series and in opposite directions, while the four output coils (8a to 8d) are connected in parallel in series of two different pairs of coils belonging to it; Bodies, soak; generate an electromagnetic field with the electronic resonance frequency in order to create a line of the one sample in each pair of arrangements, which _v .-. - the addition of the, causes energy absorption at the resonance frequency of the atomic nuclei, and a line of the other sample, soft an energy emission at the ^. Nuclear magnetic resonance frequency causes saturation} ¹ '*''' ·· "■ · -." ·, 'And means for measuring the frequency in the loop containing the coil and the amplifier. ~ -. ■. . 2. Magnetometer according to claim 1, characterized in that the two samples of each pair (4a to Ab; Ac to 40) contain two paramagnetic substances in an identical volume of the same solvent / soft at the same frequency of the electromagnetic field two opposite electronic lines excited, ie one of which causes an increase in energy absorption and the other causes the stimulated energy emission at the nuclear resonance frequency of the solvent, a single generator (14) being provided to excite these two opposite electronic lines of the two paramagnetic substances. ' 3. Magnetometer - according to claim 2, characterized in that 'the four arrangements (4a to Ad) are arranged offset from one another by 90 ° on a non-magnetic housing and are excited by four coaxial cables (16a to 16d) which are fed from a single coaxial cable which is arranged in the center of symmetry of the four arrangements and is fed by the generator (14). 4. Magnetometer according to claim 1, characterized in that all samples (12a to Ud) are identical, and that two generators (30, 32 in F i g. 3) are provided with a very high frequency for exciting the electromagnetic field, the Frequencies of these two generators are chosen so that they excite two opposite electronic lines (i.e. one of which generates an increase in energy absorption and the other generates stimulated energy emission at the nuclear resonance frequency) of the paramagnetic substance contained in the same samples of one and the same pair. 5. Magnetometer according to one of claims 1 to 4, characterized in that each of the four arrangements (4a to Ad) is attached to a non-magnetic housing by means which allow a slight change in the position of one arrangement with respect to the other. 1 sheet of drawings