Method and apparatus for X-ray fluorescence spectroscopy

Claim 2

An X-ray fluorescence method for assaying the concentration of a chemical element in an object using a source of particles or electromagnetic radiation having sufficient energy to produce X-ray fluorescence of said element and a detector capable of detecting a spectrum of X-ray fluorescence from said element, said method comprising the steps of: calibrating the source and detector by: irradiating with said source a group of samples of known concentration of the element to be assayed, said source and samples being arranged in a first geometrical relationship; measuring with said detector the X-ray radiation received at the detector from said samples having energies in a first range which encompasses at least one X-ray fluorescence spectral line associated with said element; fitting a first equation to said measurements, said equation using at least a first correction factor which relates the concentration of the samples of known concentration to said measurements; and storing said correction factor; irradiating an object having an unknown concentration of said chemical element with said source of particles or electromagnetic radiation, said source and object having a different geometrical relationship from that used in said calibrating step; measuring with said detector the X-ray radiation received from said object having energies in the same range as that in which said X-ray fluorescence spectral line was measured in said calibrating step; and I calculating from said measured values and said stored correction factor the concentration of said chemical element in said object.

Claim 3

The method of Claim 1 wherein the equation that is fitted to said measurements has the form: percent concentration = A + B · S where S is a function of the X-ray radiation received at the detector from said samples having energies in said first range, and A and B are correction factors.

Claim 4

The method of Claim 1 wherein the equation that is fitted to said measurements has the general form: percent concentration = A + B - S/C where S is a function of the X-ray radiation received at the detector from said samples having energies in said first range, C is a function of the X-ray radiation received at the detector having energies in a second range where the Compton peak is observed, and A and B are correction factors.

Claim 5

The method of claim 2 or claim 3 wherein A and B are functions of the ratio of the X-ray radiation received at the detector which has energies in a third range adjacent that in which the Compton peak is observed to the X-ray radiation received at the detector having energies in said second range.

Claim 6

The method of claim 2 or claim 3 wherein A and B are functions of the ratio of the X-ray radiation received at the detector which has energies in a range within which a known radiation peak is observed to the X -ray radiation received at the detector which has energies in a range adjacent to that within which said known radiation peak is observed.

Claim 7

The method of claim 1 wherein the equation that is fitted to said measurements is: where S is a function of the X-ray radiation received at the detector from said samples having energies in said first range, C is a function of the radiation received at the detector having energies in a second range where a radiation peak is observed, E is a function of the radiation received at the detector having energies in a third range which is adjacent to that in which the radiation peak is observed, B is a function of the radiation received at the detector having energies in a fourth range where background radiation is observed, K I and K 2 are constants which are used to compensate for the effect of leakage between the source of radiation and the detector and K 3 through K 6 are constants which are used to relate the known concentration of said samples to said measurement of the X-ray radiation received from said samples.

Claim 8

The method of claim 6 wherein S is the number of photons detected by said detector having energies in said first range, C is the number of photons detected having energies in said second range, E is the number of photons detected having energies in said third range and B is the number of photons detected having energies in said fourth range.

Claim 9

The method of claim 1 wherein said calibrating step further comprises the steps of: measuring the X-ray radiation received at the detector having energies in a second range where the Compton peak is observed, said first equation being fitted to said measurements as well; measuring the X-ray radiation received at the detector having energies in a third range adjacent to that in which the Compton peak is observed; measuring the X-ray radiation received from said samples having energies in a fifth range corresponding to the first range but displaced therefrom, the X-ray radiation received having energies in a sixth range corresponding to the second range but displaced therefrom, and the X-ray radiation received having energies in a seventh range corresponding to the third range but displaced therefrom; fitting a second equation to the measurements of X-ray radiation, said second equation having the same form as that to which the measurements made over the first and second ranges were fitted, said second equation using at least a second correction factor which relates the concentration of the samples of known concentration to said measurements of X-ray radiation in said fifth and sixth ranges; fitting a third equation to said first and second correction factors which relates the magnitude of said correction factors to at least one of the measurements made in said first, second and third ranges and the corresponding measurement(s) made in said fifth, sixth and seventh ranges; and storing said third equation as said correction factor.

Claim 10

The method of claim 9 wherein said first and second equations have the form where S is the X-ray radiation measured in the first or fifth ranges, C is the X-ray radiation measured in the second or sixth, ranges and A and B are correction factors which relate the concentration of the samples of known concentration to said measurements in the first and second, or fifth and sixth, ranges, A and B being functions of the ratio of the X-ray radiation received at the detector which has energies in a range within which a known radiation peak is observed to the X-ray radiation received at the detector which has energies in a range adjacent to that within which said known radiation peak is observed.

Claim 11

The method of claim 10 wherein the third equation has the form where E is the X-ray radiation measured in the third or seventh ranges, C is the X-ray radiation measured in the second or sixth ranges and m and b are the slope and intercept of a straight line which relates the magnitude of the correction factor to the ratio E/C.

Claim 12

The method of claim 1 wherein said steps of irradiating an object having an unknown concentration and measuring the radiation received from said object comprise the steps of: drilling a borehole through a matrix of material; inserting into,said borehole a probe containing said source of particles or electromagnetic radiation and said detector; and irradiating said object and measuring the radiation therefrom when said probe is nearby said object.

Claim 13

The method of claim 1 wherein said steps of irradiating an object having an unknown concentration and measuring the radiation received from said object comprise the steps of: irradiating a mineface with said source of particles or electromagnetic radiation; and measuring the radiation from said mineface as a result of said irradiating step.

Claim 16

The method of claim 14 further comprising the step of calibrating the source and detector by: irradiating with said source a group of samples of known concentration of the element to be assayed; measuring with said detector the X-ray radiation received at the detector from said samples having energies in a first range which encompasses at least one X-ray fluorescence spectral line associated with said element; fitting a first equation to said measurements, said equation using at least a first correction factor which relates the concentration of the samples of known concentration to said measurements; and storing said correction factor(s), said correction factor(s) being used in developing said quantitative estimate of the concentration of at least one said element present in said matrix.

Claim 17

In an apparatus for assaying the concentration of a chemical element in an object using a source of particles or electromagnetic radiation having sufficient energy to produce X-ray fluorescence of said element and a detector capable of detecting a spectrum of X -ray fluorescence from said element, a probe comprising: a cylindrical casing, less than 1-1/2 inches (38mm) in diameter. a source of particles or electromagnetic radiation having sufficient energy to produce X-ray fluorescence of said element, said source being mounted in said casing, a detector mounted in said casing capable of detecting a spectrum of X-ray fluorescence from said element, shielding mounted in said casing between said source and said detector, and electronic means mounted within said casing comprising means for amplifying a signal from said detector and means for transmitting said signal to a remotely located station.

Claim 18

In an apparatus for assaying the concentration of a chemical element in an object using a source of particles or electromagnetic radiation having sufficient energy to produce X-ray fluorescence of said element and a detector capable of detecting a spectrum of X -ray fluorescence from said element, a probe comprising: a cylindrical casing, less than 1-1/2 inches (38mm) in diameter. a source of particles or electromagnetic radiation having sufficient energy to produce X-ray fluorescence of said element, said source being mounted in said casing, a detector mounted in said casing capable of detecting a spectrum of X-ray fluorescence from said element, shielding mounted in said casing between said source and said detector, and electronic means mounted within said casing comprising means for amplifying a signal from said detector and means for transmitting said signal to a remotely located station.

Claim 19

The probe of claim 16 wherein said detector is made of cadmium telluride.

Claim 20

The probe of claim 16 wherein said shielding is shaped so as to define a substantially circular radiation pattern emanating from said cylinder in a direction transverse to the longitudinal axis of said cylinder.

Claim 21

The probe of claim 16 wherein said electronic means mounted within said casing further comprises means for shaping the output of said amplifying means, a sample and hold circuit connected to the output of the shaping means and an analog-to-digital converter for digitizing a signal stored by said sample and hold circuit, the output of said converter being transmitted by said transmitting means.

Claim 22

Apparatus for assaying the concentration of a chemical element of an object by means of X-ray fluorescence, said apparatus comprising: a probe comprising: a cylindrical casing, less than 1-1/2 inches (38mm) in diameter, a source of particles or electromagnetic radiation having sufficient energy to produce X-ray fluorescence of said element, said source being mounted in said casing, a detector mounted in said casing capable of detecting a spectrum of X-ray fluorescence from said element, shielding mounted in said casing between said source and said detector, and electronic means mounted in said casing for amplifying a signal from said detector and for transmitting said signal to a remotely located station; means for lowering said probe into a borehole and for removing it therefrom; and means at said remotely located station for calculating from signals transmitted by said probe a quantitative estimate of at least one element present in a matrix of material surrounding said borehole.

Claim 23

Apparatus for assaying the concentration of a chemical element of an object by means of X-ray fluorescence, said apparatus comprising: a probe comprising: a cylindrical casing, less than 1-1/2 inches (38mm) in diameter, a source of particles or electromagnetic radiation having sufficient energy to produce X-ray fluorescence of said element, said source being mounted in said casing, a detector mounted in said casing capable of detecting a spectrum of X-ray fluorescence from said element, shielding mounted in said casing between said source and said detector, and electronic means mounted in said casing for amplifying a signal from said detector and for transmitting said signal to a remotely located station; means for lowering said probe into a borehole and for removing it therefrom; and means at said remotely located station for calculating from signals transmitted by said probe a quantitative estimate of at least one element present in a matrix of material surrounding said borehole.

Claim 24

In an X-ray fluorescence method for assaying the concentration of a chemical element in an object using a source of particles or electromagnetic radiation having sufficient energy to produce X-ray fluorescence of said element, a detector capable of detecting a spectrum of X-ray fluorescence from said element and electronic means for generating signals having magnitudes that are a function of the energy of the X-ray fluorescence detected, a method of compensating for changes in the gain of said electronic means that alter the magnitude of the signal generated by said electronic means, said method comprising the steps of: (a) irradiating with said source a group of samples of known concentration of the element to be assayed; (b) measuring with said detector the X-ray radiation received at the detector from said samples having energies in a first range which encompasses at least one X-ray fluorescence spectral line associated with said element, the radiation received at the detector having energies in a second range within which a known radiation peak is observed, and the X-ray radiation received at the detector having energies in a third range which is adjacent to said second range; (c) fitting a first equation to said measurements, said first equation using at least a first correction factor which relates the concentration of the samples of known concentration to said measurements; (d) measuring the X-ray radiation received by said detector having energies in a fourth range corresponding to the first range but displaced therefrom, the X-ray radiation received having energies in a fifth range corresponding to the second range but displaced therefrom, and the X-ray radiation received having energies in a sixth range corresponding to the third range but displaced therefrom; (e) fitting a second equation to said measurements of X-ray radiation so determined in said fourth, fifth, and sixth ranges, said second equation having the same form as that of said first equation and using at least a second correction factor to relate the concentration of the samples of known concentration to said measurements; (f) fitting a third equation to at least said first and second correction factors which relates the magnitude of said correction factors to at least one of the measurements made in step (b) and the corresponding measurement(s) made in step (d); (g) storing said third equation; (h) irradiating an object having an unknown concentration of said chemical element with said source of particles or electromagnetic radiation; (i) measuring with said detector the X-ray radiation received from said unknown material having energies in a seventh range corresponding to the first range, an eighth range corresponding to the second range, and a ninth range corresponding to the third range; (j) using said third equation to determine the magnitude of a third correction factor using the measurement(s) made in step (i) that correspond to those used in fitting said third equation; and (k) calculating from said measured values and said third correction factor the concentration of said chemical element in said object.

Claim 25

In an X-ray fluorescence method for assaying the concentration of a chemical element in an object using a source of particles or electromagnetic radiation having sufficient energy to produce X-ray fluorescence of said element, a detector capable of detecting a spectrum of X-ray fluorescence from said element and electronic means for generating signals having magnitudes that are a function of the energy of the X-ray fluorescence detected, a method of compensating for changes in the gain of said electronic means that alter the magnitude of the signal generated by said electronic means, said method comprising the steps of: (a) irradiating with said source a group of samples of known concentration of the element to be assayed; (b) measuring with said detector the X-ray radiation received at the detector from said samples having energies in a first range which encompasses at least one X-ray fluorescence spectral line associated with said element, the radiation received at the detector having energies in a second range within which a known radiation peak is observed, and the X-ray radiation received at the detector having energies in a third range which is adjacent to said second range; (c) fitting a first equation to said measurements, said first equation using at least a first correction factor which relates the concentration of the samples of known concentration to said measurements; (d) measuring the X-ray radiation received by said detector having energies in a fourth range corresponding to the first range but displaced therefrom, the X-ray radiation received having energies in a fifth range corresponding to the second range but displaced therefrom, and the X-ray radiation received having energies in a sixth range corresponding to the third range but displaced therefrom; (e) fitting a second equation to said measurements of X-ray radiation so determined in said fourth, fifth, and sixth ranges, said second equation having the same form as that of said first equation and using at least a second correction factor to relate the concentration of the samples of known concentration to said measurements; (f) fitting a third equation to at least said first and second correction factors which relates the magnitude of said correction factors to at least one of the measurements made in step (b) and the corresponding measurement(s) made in step (d); (g) storing said third equation; (h) irradiating an object having an unknown concentration of said chemical element with said source of particles or electromagnetic radiation; (i) measuring with said detector the X-ray radiation received from said unknown material having energies in a seventh range corresponding to the first range, an eighth range corresponding to the second range, and a ninth range corresponding to the third range; (j) using said third equation to determine the magnitude of a third correction factor using the measurement(s) made in step (i) that correspond to those used in fitting said third equation; and (k) calculating from said measured values and said third correction factor the concentration of said chemical element in said object.

Claim 26

The method of claim 21 wherein said first and second equations have the general form: percent concentration = A + B . S/C where S is the X-ray radiation measured in said first or fourth ranges, C is the X-ray radiation measured in said second or fifth ranges and A and B are correction factors which relate the concentration of the samples of known concentration to said measurements.

Claim 27

The method of claim 22 wherein A and B are functions of the ratio of the X-ray radiation received at the detector which has energies in a range adjacent to that where a known radiation peak is observed to the X-ray radiation received at the detector having energies in a range where a known radiation peak is observed.

Claim 28

The method of claim 22 wherein: A is function having the form: where E is the X-ray radiation measured in a range adjacent to that where a known radiation peak is observed, C is the X-ray radiation measured in a range where a known radiatign peak is observed and K 3 and K 4 are constants which adjust said correction factor for changes in the gain of the apparatus which performs said measuring steps; and B is a function having the form where E and C are as defined above and K 5 and K 6 are constants which adjust said correction factor for changes in the gain of the apparatus which performs said measuring steps.

Claim 29

Apparatus for assaying in the field the concentration of a chemical element in an object using X-ray fluorescence, said apparatus comprising: means for storing at least a first correction factor determined by irradiating a group of samples of known concentration of the element to be assayed with a source of particles or electromagnetic radiation having sufficient energy to produce X-ray fluorescence of said element; measuring with a detector capable of detecting X-ray fluorescence from said element the X-ray radiation received at the detector from said samples having energies in a first range which encompasses at least one X-ray fluorescence spectral line associated with said element; and fitting a first equation to said measurements, said equation using at least a first correction factor which relates the #concentration of the samples of known concentration to said measurements; means for irradiating an object having an unknown concentration of said chemical element with said source of particles or electromagnetic radiation; means for measuring the X-ray radiation received from said object having energies in the same range as that in which said X-ray fluorescence spectral line was measured in determining said correction factor; and means for calculating from said measured radiation and said stored correction factor(s) tne concentration of said chemical element in said object.

Claim 30

Apparatus for assaying in the field the concentration of a chemical element in an object using X-ray fluorescence, said apparatus comprising: means for storing at least a first correction factor determined by irradiating a group of samples of known concentration of the element to be assayed with a source of particles or electromagnetic radiation having sufficient energy to produce X-ray fluorescence of said element; measuring with a detector capable of detecting X-ray fluorescence from said element the X-ray radiation received at the detector from said samples having energies in a first range which encompasses at least one X-ray fluorescence spectral line associated with said element; and fitting a first equation to said measurements, said equation using at least a first correction factor which relates the #concentration of the samples of known concentration to said measurements; means for irradiating an object having an unknown concentration of said chemical element with said source of particles or electromagnetic radiation; means for measuring the X-ray radiation received from said object having energies in the same range as that in which said X-ray fluorescence spectral line was measured in determining said correction factor; and means for calculating from said measured radiation and said stored correction factor(s) tne concentration of said chemical element in said object.

Claim 31

An X-ray fluorescence method for assaying the concentration of a chemical element in an object using a source of particles or electromagnetic radiation having sufficient energy to produce X-ray fluorescence of said element and a detector capable of detecting a spectrum of X-ray fluorescence from said element, said method comprising the steps of: calibrating the source and detector by: irradiating with said source a group of samples of known concentration of the element to be assayed; measuring with said detector the X-ray radiation received at the detector from said samples having energies in a first range which encompasses at least one X-ray fluorescence spectral line associated with said element; fitting a first equation to said measurements, said equation using at least a first correction factor which relates the concentration of the samples of known concentration to said measurements; and storing said correction factor; irradiating an object having a unknown concentration of said chemical element with said source of particles or electromagnetic radiation without prior preparation of said object for irradiation or control of the geometrical relation between said object and the source and detector; measuring with said detector the X-ray radiation received from said object having energies in the same range as that in which said X-ray fluorescence spectral line was measured in said calibrating step; and calculating from said measured values and said stored correction factor the concentration of said chemical element in said object.

Claim 32

An X-ray fluorescence method for assaying the concentration of a chemical element in an object using a source of particles or electromagnetic radiation having sufficient energy to produce X-ray fluorescence of said element and a detector capable of detecting a spectrum of X-ray fluorescence from said element, said method comprising the steps of: calibrating the source and detector by: irradiating with said source a group of samples of known concentration of the element to be assayed; measuring with said detector the X-ray radiation received at the detector from said samples having energies in a first range which encompasses at least one X-ray fluorescence spectral line associated with said element; fitting a first equation to said measurements, said equation using at least a first correction factor which relates the concentration of the samples of known concentration to said measurements; and storing said correction factor; irradiating an object having a unknown concentration of said chemical element with said source of particles or electromagnetic radiation without prior preparation of said object for irradiation or control of the geometrical relation between said object and the source and detector; measuring with said detector the X-ray radiation received from said object having energies in the same range as that in which said X-ray fluorescence spectral line was measured in said calibrating step; and calculating from said measured values and said stored correction factor the concentration of said chemical element in said object.