Charge sharing recognition in x-ray diffraction

Abstract

An X-ray diffraction apparatus and a method of processing a signal from the X-ray diffraction apparatus are disclosed. By analyzing a time delay between a first pulse and a second pulse generated by respective first and second detector units, and by analyzing an energy of each of the first and second pulses, a charge sharing event and a coincidence photon event can be identified.

Description

[0001] Invention Field This invention relates to methods and apparatus for X-ray diffraction. Background of the Invention X-ray diffraction (XRD) analysis is performed by measuring the X-ray pattern diffracted from a sample, most commonly in one dimension within the diffraction angle range. Solid-state 1D detectors (strip detectors) or 2D detectors allow for simultaneous measurements at several angles, thus speeding up the overall measurement process. Furthermore, the use of solid-state sensor materials and application-specific integrated circuits (ASICs) for sensor readout results in significantly lower noise levels, and in this way, better energy resolution of detected X-ray photons can be achieved (compared to older systems based on gas-filled detectors).

[0003] However, solid-state detectors (such as 1D strip detectors) can suffer from charge-sharing problems, where a single X-ray photon induces a response at two (typically adjacent) detector cells. When this occurs, the photon's energy may be distributed between the two cells, giving the appearance of two lower-energy photons. This results in a reduction in the energy resolution of XRD measurements.

[0004] It is known that this problem is addressed by suppressing signals that occur substantially simultaneously in two adjacent detector units. In other words, when both detector units respond simultaneously, the system infers that charge sharing has occurred, and both responses are ignored / disregarded, meaning that photons are not counted as having arrived at either unit. Invention Overview The known methods described above for suppressing simultaneous detector responses in adjacent detector units introduce another drawback. It is possible that two real photons can arrive at adjacent detector units simultaneously. This possibility increases at higher X-ray intensities (higher total incident rate of photons). Particularly at these higher intensities, the known suppression methods described above will degrade count rate linearity because truly overlapping photons are incorrectly suppressed as charge-sharing events.

[0006] According to one aspect of the present invention, an X-ray diffraction apparatus is provided. The X-ray diffraction apparatus comprises: X-ray source; A sample stage for receiving a sample to be irradiated by X-rays from the X-ray source; A detector is arranged to receive X-rays diffracted from the sample; One or more readout circuits coupled to the detector; and A detection processor is configured to process signals generated by the one or more readout circuits to count the number of photons arriving at the detector. The detector includes at least a first detector unit and a second detector unit, each detector unit being configured to convert incoming X-ray photons into corresponding electrical pulses. The one or more readout circuits are configured to receive electrical pulses from the first detector unit and the second detector unit, and to generate one or more readout signals for the detection processor. The detection processor is configured to analyze a first pulse generated by the first detector unit and a second pulse generated by the second detector unit based on the one or more readout signals, including: --If the time delay between the first pulse and the second pulse is less than a predetermined time threshold, then it is determined that one of the charge-sharing event and the coincident photon event has occurred, and --If the energy of each of the first pulse and the second pulse is higher than a first threshold and lower than a second threshold, then it is determined that a photon coincidence event has occurred; otherwise, it is determined that a charge-sharing event has occurred. The detection processor is also configured to count the overlapping photon events as X-ray photons arriving at each of the first detector unit and the second detector unit, and to ignore the charge-sharing events.

[0007] By examining the energy of each pulse and counting only two pulses that have the correct energy (above V), L And below V H The device is capable of counting coincident photons with the desired type of X-ray radiation, while suppressing charge-shared photons and photons of other energies that are not intended to be counted for X-ray diffraction measurements.

[0008] The inventors have recognized that examining the energy of photons and their temporal relationships can help improve the linearity of the count rate. By distinguishing charge-shared and truly overlapping photons based on energy, the device can reduce the number of truly overlapping photons that are mistakenly ignored.

[0009] The inventors also recognized that by examining the energy of each of the two pulses separately, they could better distinguish between overlapping photons and charge-sharing photons (and other unwanted photons). The inventors have recognized that, for example, examining the aggregate energy detected in both units is insufficient, as this can still be susceptible to charge sharing caused by photons with energies higher than the X-ray photons of interest used for diffraction measurements. Embodiments of the present invention attempt to address this problem. By examining the energy of each pulse individually and setting upper and lower limits for the energy, for example, the device can suppress (undesired) Kβ (K-beta) X-ray photons even when charge sharing occurs and / or even when (desired) Kα (K-alpha) X-ray photons arrive simultaneously in adjacent detector units.

[0010] Examining the energy of individual pulses improves robustness to noise compared to analyzing the total energy, because when examining an aggregate measure (e.g., the sum of two pulse energies), the noise in each signal can be additively combined. It also provides a relatively simple approach, avoiding unnecessary increases in circuit complexity.

[0011] The detector can be a solid-state detector, including semiconductor materials.

[0012] The first and second detector units can be positioned adjacent to each other, meaning that there are no other detector units between them. (In some embodiments, electronic components other than the detector units may be positioned between the detector units; however, it is desirable that the spacing between the detector units be as small as possible.) The detection processor can be provided as a component separate from one or more readout circuits. The one or more readout circuits can be provided as one or more application-specific integrated circuits (ASICs). The detection processor can be provided as a programmable processor, such as a digital signal processor (DSP), or a reconfigurable processor, such as a field-programmable gate array (FPGA).

[0013] Ignoring charge-sharing events may mean that when the detection processor determines that a charge-sharing event has occurred, the detection processor does not count any pulse as an arriving photon.

[0014] The first threshold can be selected as the photon energy corresponding to a Kα emission line smaller than that of the X-ray source. The second threshold can be selected as the photon energy corresponding to a Kα emission line larger than that of the X-ray source. Optionally, the second threshold can be selected as the photon energy corresponding to a Kβ emission line smaller than that of the X-ray source.

[0015] The detection processor and / or one or more readout circuits can also be configured to operate based on a detection threshold (V). D The presence of a first pulse and a second pulse is detected, where a pulse is detected only if its energy exceeds a detection threshold. The timing of each pulse (and therefore the time delay between pulses) can be determined by referencing the detection threshold. For example, to determine the time delay between two pulses, the detection processor can compare the time when the first pulse crosses the detection threshold with the time when the second pulse crosses the detection threshold. (In this context, the rising or falling edge of the respective pulse can be considered.) The inventors have discovered that it is desirable to set a first threshold and a second threshold such that they define a relatively narrow energy “window” with respect to the characteristic X-ray energy of interest (e.g., Kα emission line). This allows unwanted X-ray energy to be suppressed. Simultaneously, it has been found advantageous to set the detection threshold at a relatively low level (close to the noise floor) for both detection and suppression of charge sharing. Using a detection threshold different from each of the first and second thresholds makes it possible to achieve both of these benefits simultaneously.

[0016] The energy of a pulse can be determined by measuring its amplitude. Therefore, in practice, each of the first threshold, the second threshold, and the detection threshold can be implemented as an amplitude threshold.

[0017] One or more readout signals can be digital signals.

[0018] For each detector unit, one or more readout signals can indicate whether the pulse generated at that unit is: (i) higher than the detection threshold (V). D (ii) Higher than the first threshold (V) L (iii) is above the second threshold (V) H ), where the detection threshold is less than the first threshold, and the first threshold is less than the second threshold.

[0019] For example, the readout signal can include two bits per detector unit, encoding the value [0, 1, 2, 3]. Value 0 (binary "00") can represent no detected pulse. Value 1 (binary "01") can represent a pulse that exceeds a detection threshold but does not reach a first threshold. Value 2 (binary "10") can represent a pulse that exceeds the first threshold but does not reach a second threshold; and value 3 (binary "11") can represent a pulse that exceeds the second threshold. Of course, other encodings can also be used.

[0020] One or more readout circuits can periodically sample the output signal of each detector unit to generate one or more readout signals.

[0021] For each detector unit, the time interval between consecutive samples can be less than 600 ns, preferably less than 400 ns, and most preferably less than 200 ns. Frequent sampling is desirable in order to accurately detect photon overlap.

[0022] The time interval between consecutive samples can be at least 10 ns, and optionally at least 20 ns, 50 ns, 100 ns, or 150 ns. Excessively frequent sampling may result in the collection of large amounts of redundant data.

[0023] The detector may include a third detector unit and a fourth detector unit, each detector unit being configured to convert incoming X-ray photons into corresponding electrical pulses, and one or more readout circuits including a first readout circuit and a second readout circuit, each readout circuit being coupled to the detector, wherein the first readout circuit is configured to receive electrical pulses from the first detector unit and the third detector unit and generate a first readout signal for the detection processor, and wherein the second readout circuit is configured to receive electrical pulses from the second detector unit and the fourth detector unit and generate a second readout signal for the detection processor.

[0024] In this way, the detection processor can ignore charge-sharing events occurring between cells that are read out by different readout circuits. This is an advantage of implementing overlap detection processing separately from the readout circuits.

[0025] The detection processor can be configured to analyze a third pulse generated by a third detector unit and a fourth pulse generated by a fourth detector unit based on a first readout signal and a second readout signal, including: If the time delay between the third and fourth pulses is less than a predetermined time threshold, it is determined that either a charge-sharing event or a photon-coinciding event has occurred. The energy of each of the third and fourth pulses is higher than the first threshold (V). L And below the second threshold (V) H In the case of ( ), it is determined that a photon coincidence event has occurred; otherwise, it is determined that a charge sharing event has occurred. The detection processor is also configured to count overlapping photon events as X-ray photons arriving at each of the third and fourth detector units, and to ignore charge-sharing events.

[0026] The third detector unit can be located in the detector adjacent to the fourth detector unit. The second detector unit can be located in the detector between the first and third detector units.

[0027] The detector can be a 1D strip detector.

[0028] A method for processing signals from an X-ray diffraction apparatus is also disclosed. The apparatus includes a detector arranged to receive X-rays diffracted from a sample, the detector comprising at least a first detector unit and a second detector unit, each detector unit being configured to convert incoming X-ray photons into corresponding electrical pulses. The method includes: Obtain one or more readout signals, said one or more readout signals describing a first pulse generated by the first detector unit and a second pulse generated by the second detector unit; and Analyzing the first pulse and the second pulse based on the one or more readout signals includes: --If the time delay between the first pulse and the second pulse is less than a predetermined time threshold, then it is determined that one of the charge-sharing event and the coincident photon event has occurred, and --If the energy of each of the first pulse and the second pulse is higher than a first threshold and lower than a second threshold, then it is determined that a photon coincidence event has occurred; otherwise, it is determined that a charge-sharing event has occurred. The method further includes counting the coincident photon events as X-ray photons arriving at each of the first detector unit and the second detector unit, and ignoring the charge-sharing events.

[0029] A computer program is also provided, comprising computer program code configured to cause the one or more physical computing devices to perform all the steps of the method according to the embodiments when the program is run on one or more physical computing devices.

[0030] Computer programs can be embodied in computer-readable media. Computer-readable media can be non-transitory computer-readable media. Brief description of the attached diagram The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of an X-ray diffraction apparatus based on an example; Figure 2 It is shown Figure 1 A block diagram of the readout circuit and detection processor of the device; Figure 3 This is a schematic diagram of charge sharing and photon coincidence events; Figure 4 It is shown Figure 1 and Figure 2 A block diagram of the readout of a single detector unit in the detector; Figure 5 This demonstrates how these pulses can be distinguished based on the amplitude of the pulses generated by the detector unit; Figure 6 This is a block diagram illustrating the readout circuitry and detection processor according to another example; Figure 7 This is a flowchart illustrating the method based on the example; and Figure 8 This is a flowchart illustrating another method based on the example.

[0032] It should be noted that these figures are illustrative, not drawn to scale. For clarity and convenience, the relative dimensions and proportions of the parts in these figures are exaggerated or reduced in size.

[0033] Detailed description It should be noted that in this paper, the word "sample" is used in two specific and distinct contexts. On the one hand, it is used as a noun to refer to the physical "sample" (or specimen) studied in X-ray diffraction measurements. On the other hand, it is used as a verb to refer to the step of "sampling" an analog signal, such as the step performed during analog-to-digital conversion. It is believed that the meaning of the word will be clear in each case, depending on the context of its usage.

[0034] Figure 1 An X-ray diffraction apparatus 100 according to an example is shown. The apparatus includes an X-ray source 110, which in this example is an X-ray tube. It also includes a sample stage 120 supporting a sample holder 122 that holds a sample 130. The X-ray source 110 emits X-rays in an incident beam 112 that irradiates the sample 130. The sample 130 diffracts the X-rays, producing a diffracted beam 114. A detector 140 is provided, configured to receive and detect the X-rays diffracted from the sample in the diffracted beam 114.

[0035] Figure 2 This is a block diagram of an apparatus configured to process the output of detector 140. A first readout circuit 210a and a second readout circuit 210b are coupled to detector 140. Both readout circuits 210a and 210b communicate with a detection processor 230, which is configured to process the signals generated by the readout circuits. In this example, the detection processor 230 is implemented by a programmable microprocessor. This allows the detection processing to be defined at least partially in software or firmware, which increases flexibility by allowing the processing to be reconfigured for a variety of different applications and measurements.

[0036] Before describing the operation of the device in more detail, we will first refer to... Figure 3 Explain the issues of charge sharing and overlapping photons. Figure 3Five X-ray photons 114a-114e incident on detector 140 are shown. The detector comprises N detector elements 1421 to 142. N Each detector unit 1421 to 142 N Including the corresponding detection elements 1441 to 144 N In this example, detector 140 is a microstrip detector, and each detection element is a strip electrode. The arrival of each photon 114a-114e generates a charge cloud (shown by shaded gray triangles 116a-116e). The charge cloud is sensed by detection element 144, thereby converting the incoming X-ray photon into an electrical pulse.

[0037] For the first photon 114a, there is no problem in principle, because all the converted charges 116a are collected by a single strip of a single detector unit 1422. The generated charge will be transferred to a single preamplifier, and the corresponding signal can be interpreted as the signal of a single photon, and thus represent the energy of that photon (see below, reference). Figure 4 ).

[0038] The charge 116b generated by the second photon 114b is shared between detector units 1424 and 1425 and will be sensed by the corresponding bars (i.e., detection elements) of these units. The charge collected in each bar represents a portion of the energy of the incoming photon. This makes it impossible to infer the energy of the photon when considering a single channel, and thus leads to a deterioration in energy resolution, biased towards lower energies. The same effect occurs for the charge 116c generated by the third photon 114c, which is shared between detector units 1427 and 1428.

[0039] The challenge can be illustrated by considering an example where the X-ray source 110 is a tube using a copper (Cu) anode. This tube would give characteristic energies of 8 keV (Kα) and 8.9 keV (Kβ). If the strip detector has good intrinsic energy resolution (full width at half maximum < 400 eV @ 8 keV), it should be possible, for example, to measure only 8 keV photons by recording only events between 7.6 keV and 8.4 keV. However, when 8.9 keV photons share charge between two channels, the following situation may occur: one channel receives a charge equivalent to an 8 keV signal, while the adjacent channel will receive a charge equivalent to a 0.9 keV signal. If the device can determine that these two events occur simultaneously, it can infer that the photon must have an energy different from the expected 8 keV energy, and we can therefore discard it.

[0040] However, as mentioned earlier, simply checking the incident timing to suppress charge sharing has drawbacks (especially as intensity increases). The probability of two 8keV photons arriving simultaneously on two adjacent bars increases. However, according to the logic described above, these valid events will be discarded because they occur simultaneously. This means that count rate linearity will degrade significantly at high count rates. The example described below will attempt to mitigate this effect. Figure 3 It was also shown that two overlapping photons 114d and 114e arrived at two adjacent detector units 142 essentially simultaneously. N-1 and 142 N Detecting and counting these photons would be desirable, rather than (mistakenly) ignoring them as charge-sharing events.

[0041] Figure 4 This is a schematic diagram of a single channel of one of the readout circuits 210 in the example. In this example, the readout circuit 210 is implemented as an ASIC coupled to the detector 140. The detector unit discussed... i Detection element 144 i Depicted as a diode. Corresponding channel of ASIC readout circuit 210. i This includes a charge-sensitive preamplifier 212 with a certain gain and a shaping filter 214. The preamplifier 212 and shaping filter 214 constitute the analog front end. The shaping filter 214 has a time constant that affects the duration of the pulse output by the analog front end. In some examples, several selectable time constants (or several selectable shaping filters, each with a different time constant) may exist, which can be selected based on the required count rate and energy resolution of the detected photons. Typically, a shorter output pulse required for a higher count rate contains more electronic noise, which degrades the energy resolution. After the analog front end, the energy of the detected photons is evaluated by passing the voltage pulse generated by the photons through three comparators 216, 217, and 218. The comparators detect whether the pulse height has exceeded a threshold level, thereby digitizing the pulse amplitude (which is related to the photon energy). The first comparator 216 compares the pulse amplitude with a first threshold V. L The second comparator 217 compares the pulse amplitude with the second threshold V. H The third comparator 218 compares the pulse amplitude with the third threshold (i.e., the detection threshold V). D Compare them. For example... Figure 5 As shown, the detection threshold V D Less than the first threshold V L And the first threshold V L Less than the second threshold V HEach threshold can be configurable. Alternatively, some or all of them can be fixed, for example, hardwired into the ASIC design. The information digitized by the comparator is transferred from the readout circuitry 210 to the detection processor 230 via the digital section 220.

[0042] Figure 5 It shows the use of Figure 4 The circuit detects different pulse amplitudes. Pulse 1 exceeds the first threshold V. L However, it did not exceed the second threshold V. H This is the energy range of interest (e.g., the energy of a Kα line from an X-ray source). Pulse 2 exceeds the second threshold V. H For example, this is the case with an unwanted Kβ line. Pulse 3 exceeds the detection threshold V. D And accordingly, it is detected as a pulse, but it has a value lower than the first threshold V. L Low energy. In this example, pulse 1 will be counted, but pulses 2 and 3 will be ignored (i.e., ignored and not counted).

[0043] Note that in the example above, the precise connection between the individual detector unit 142 and the two readout circuits 210a and 210b is not described. This is because, in general, the device is not limited to any particular arrangement of connections. The two readout circuits can be used to increase the bandwidth of the data read from the detector 140. This highlights the advantage of implementing detection processing in a detection processor 230 separate from one or more readout circuits 210: the detection processor 230 can access data from all detector units because it is connected to both readout circuits 210. Conversely, each individual readout circuit 210a, 210b processes only a subset of signals from the detector units. Therefore, each readout circuit 210a, 210b can only detect charge sharing between the detector units it is responsible for.

[0044] Figure 6 An example is shown where the detection processor 230 is configured to detect charge sharing between adjacent detector units, whose signals are processed by different readout circuits 210. In this example, a first detector unit 3421 and a third detector unit 3423 are connected to a first readout circuit 210a. A second detector unit 3422 and a fourth detector unit 3424 are connected to a second readout circuit 210b. The second detector unit is adjacent to and positioned between the first and third detector units. The third detector unit is adjacent to and positioned between the second and fourth detector units.

[0045] Now refer to Figure 7The flowchart describes the method performed by the XRD device 100. This example method is applicable to... Figure 6 The readout arrangement shown is applicable, but more generally to any readout arrangement, such as in Figure 2 The readout arrangement is generally shown in the diagram.

[0046] In step 610, the detection processor 230 receives a read signal from the readout circuit 210. In this example, each readout circuit 210a, 210b is implemented as an ASIC; and the detection processor 230 is implemented as a programmable microprocessor. The readout signal is as referenced above. Figure 4 The digital signal is described above. Specifically, for each channel, each readout circuit 210 generates a 2-bit output. These two bits can encode four levels, representing the following discrete cases of pulse amplitude: (i) No pulse, i.e. the amplitude does not rise above the detection threshold; (ii) A pulse exists, the amplitude of which is higher than the detection threshold but lower than the first threshold; (iii) A pulse exists whose amplitude is higher than the first threshold but lower than the second threshold; or (iv) There exists a pulse whose amplitude is higher than the second threshold.

[0047] Each readout circuit has a total of 128 channels. Therefore, the number of detector units is 256 (128 × 2). Each readout circuit 210 provides a 16-bit output at a clock rate of 100 MHz. The channels are multiplexed together in 16 groups of 8, meaning that each 16-bit output consists of 8 × 2 bits of digital value. For each readout circuit 210, 16 groups of channels are output over 16 clock cycles. An additional two clock cycles are used for synchronization / handshake with the detection processor 230, giving a total time period of 18 cycles (180 ns) between consecutive samples from the same detector unit appearing in the readout signal. The high sampling rate is desirable to ensure accuracy in determining whether two pulses from adjacent units are generated substantially simultaneously.

[0048] Let us assume that the first pulse with amplitude V1 is generated by the first detection unit 1427, and the second pulse with amplitude V2 is generated by the second detection unit 1428.

[0049] In step 620, the detection processor 230 evaluates whether the amplitudes V1 and V2 of each of the first pulse and the second pulse are greater than the detection threshold V. DIf both amplitudes are above a detection threshold, the detection processor 210 detects the presence of the first and second pulses (step 630). After determining the presence of two pulses to be considered, the detection processor 230 next (in step 640) evaluates whether the time delay Δt between the two pulses is less than a predetermined time threshold T. If so, the detection processor considers the two pulses to have occurred substantially simultaneously. In this example, if pulses are detected within 640 ns of each other in the readout signal, the pulses are considered to have occurred substantially simultaneously.

[0050] Note that although charge sharing will generate pulses simultaneously in both detector units, digitization in the readout circuit 210 will introduce small timing differences. As described above, the channel group is serially sampled and read out over a time period of 180 ns. Furthermore, when measuring pulses by comparing them to a threshold amplitude, the precise moment when a pulse crosses the threshold is affected by jitter depending on the pulse amplitude. Therefore, in practice, the detection processor 230 needs to account for a finite range of time differences in order to detect substantially simultaneous pulses.

[0051] The optimal time threshold T is related to the pulse duration, which in turn depends on the time constant of the shaping filter integrated after the preamplifier. In this example, the device has four selectable time constants for the filter. The time threshold T should be approximately as long as the maximum possible time difference between two pulses generated by charge-shared photons. Furthermore, jitter due to digital readout should be added. This is why fast digital readout is desirable. When the time constant of the shaping filter changes, the time threshold T should be adjusted accordingly (because the maximum possible time difference between charge-shared pulses is related to the time constant of the shaping filter). In this example, good results were obtained where the pulse shaping filter time threshold T = 640 ns and the time constant is 1.1 µs. This constant is the rise time of the pulse reaching its peak (and the pulse takes approximately the same amount of time to fall back). In practice, the time threshold T is set to be less than this time constant because the detection threshold V... D Not at zero level. If needed, the time threshold T can be easily modified and adjusted according to the level of the detection threshold.

[0052] For completeness, note that in this example, the readout circuit 210 detects the pulse at its falling edge (tail edge) rather than its rising edge (leading edge). That is, comparators 216-218 are triggered after the pulse rises above a corresponding threshold, when the amplitude subsequently falls below that threshold. The time delay between pulses is determined based on when the tail edge of each pulse crosses down back below the detection threshold.

[0053] When it is determined in step 640 that the time delay Δt is less than a threshold time T, the detection processor 230 (in step 650) determines that either a charge sharing event or a photon coincidence event has occurred. To distinguish between these two possibilities, the detection processor 230 evaluates the pulse amplitude relative to a first threshold and a second threshold. Specifically, in step 660, the detection processor 230 evaluates whether the amplitudes of both the first pulse and the second pulse are greater than the first threshold and less than the second threshold. If this is found, the detection processor 230 determines that a photon coincidence event has occurred (step 670). That is, the two photons arrive at adjacent detector units essentially at the same time. On the other hand, if it is determined in step 660 that the amplitudes of the first pulse and the second pulse are not both between the first and second thresholds, the detection processor 230 determines that a charge sharing event has occurred (step 680). That is, the charge generated by at least one photon has been collected by two adjacent detector units.

[0054] When the detection processor 230 determines that a photon coincidence event has occurred, both pulses are counted as photons (step 675). When the detection processor 230 determines that a charge-sharing event has occurred, neither pulse is counted as a photon (step 685).

[0055] A first threshold and a second threshold can be chosen such that only coincident X-ray photons with the desired Kα characteristic transition energy are accepted as coincident photons. This can maximally suppress charge-sharing events and unwanted X-ray energies while minimizing the loss of count rate linearity at high intensities.

[0056] Note that if If t > T, then the pulses are considered to be generated by individual events, whereas if they are within an energy window (greater than V), then the pulses are considered to be generated by individual events. L And less than V H If the time T before the pulse is reached, then the pulses are counted. Overlap checks are performed around each pulse within the time T before and after the pulse. In this example, the check considers events only in adjacent cells.

[0057] Now refer to Figure 6 The apparatus describes a specific example of the method. As described above, in Figure 6 In this process, the first readout circuit 210a reads the first pulse and the third pulse from the first detector unit 3421 and the third detector unit 3423 and provides a first readout signal to the detection processor 230. The second readout circuit 210b reads the second pulse and the fourth pulse from the second detector unit 3422 and the fourth detector unit 3424 and provides a second readout signal to the detection processor 230. The detection processor 230 analyzes the pulses based on the first readout signal and the second readout signal.

[0058] As referenced above Figure 7 The analysis focuses on the first and second pulses. Figure 8 As shown, the third and fourth pulses are analyzed. Steps 620' - 685' are essentially related to them in... Figure 7 The corresponding steps 620-685 are the same, except that the third and fourth pulses are evaluated instead of the first and second pulses. A similar analysis can also be performed to evaluate the second pulse from the second detector unit (compared to the third pulse from the third detector unit).

[0059] The foregoing example demonstrates some benefits of using a detection processor provided separately from one or more readout circuits. This allows for easy programming or reconfiguration of the detection processor 230. Furthermore, it allows the detection processor 230 to evaluate potential charge sharing between all relevant pairs of detector units, regardless of whether the unit is read out by the first readout circuit 210a or the second readout circuit 210b.

[0060] Variations of the above examples are possible without departing from the scope of this disclosure. The following are some non-exhaustive examples of possible variations.

[0061] The timing of a pulse can be determined by its rising or falling edge. In the example above, the readout circuit detects a pulse when the signal amplitude rises to at least above a detection threshold and then falls back below that threshold. In other words, each pulse is detected at its falling / tailing edge. Alternatively, the pulse can be detected at its rising / leading edge.

[0062] The above description focuses on examples of charge sharing between adjacent detector elements; however, the invention is not necessarily limited thereto. It is possible that, depending on the size and arrangement of the detector elements, charge sharing may occur between detector elements that are not directly adjacent to each other.

[0063] In the example above, there are two readout circuits 210a and 210b. However, it will be understood that this is not necessary. In other examples, there may be more than two readout circuits 210, or there may be only a single readout circuit 210.

[0064] In the example above, the detector is a 1D strip detector; however, the same principle can be applied to the detection and suppression of charge sharing measured by XRD using a 2D solid-state detector.

[0065] An X-ray source is not necessarily a copper source. Those skilled in XRD will be familiar with other sources. Similar considerations and analyses apply to these other sources.

[0066] It should be noted that the examples mentioned above illustrate the invention and are not intended to limit it, and those skilled in the art will be able to devise many alternative examples without departing from the scope of the appended claims. Any reference numerals placed between parentheses in the claims should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps different from those listed in the claims. The words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements. Examples can be implemented by hardware comprising several different elements. In device claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The indisputable fact that certain measures are referenced in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously. Furthermore, in the appended claims, a list including "at least one of A; B; and C" should be interpreted as (A and / or B) and / or C.

[0067] Furthermore, in general, various examples can be implemented in hardware or dedicated circuitry, software, logic, or any combination thereof. For example, some aspects may be implemented in hardware, while others may be implemented in firmware or software executable by a controller, microprocessor, or other computing device, although these are not limiting examples. While the various aspects described herein may be shown and described as block diagrams, flowcharts, or other graphical representations, it is well known that the blocks, apparatuses, systems, techniques, or methods described herein can be implemented as non-limiting examples of hardware, software, firmware, dedicated circuitry or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0068] The examples described herein can be implemented by computer software executable by a device's data processor (such as in a detection processor entity), or by hardware, or by a combination of software and hardware. Furthermore, it should be noted that any block in the logical flow as shown in the figures can represent a program step, or interconnected logic circuitry, a block or function, or a combination of program steps and logic circuitry, blocks and functions. Software can be stored on physical media such as memory chips or memory blocks implemented within a processor, magnetic media (such as hard disks or floppy disks), and optical media (such as, for example, CD-ROMs or DVDs).

[0069] The memory can be of any type suitable for the local technical environment and can be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. As a non-limiting example, the data processor can be of any type suitable for the local technical environment and can include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a gate-level circuit, and a processor based on a multi-core processor architecture.

[0070] The examples discussed in this article can be practiced in various components such as integrated circuit modules. The design of integrated circuits is largely a highly automated process. Sophisticated and powerful software tools can be used to transform logic-level designs into semiconductor circuit designs ready for etching and forming on a semiconductor substrate.

Claims

1. An X-ray diffraction apparatus (100), comprising: X-ray source (110); A sample stage (120) for receiving a sample to be irradiated by X-rays from the X-ray source; A detector (140) is arranged to receive X-rays diffracted from the sample; One or more readout circuits (210) coupled to the detector; as well as A detection processor (230) is configured to process signals generated by the one or more readout circuits to count the number of photons arriving at the detector. The detector (140) includes at least a first detector unit (1427; 3421) and a second detector unit (1428; 3422), each detector unit being configured to convert incoming X-ray photons into corresponding electrical pulses. The one or more readout circuits (210) are configured to receive electrical pulses from the first detector unit and the second detector unit, and to generate one or more readout signals for the detection processor. The detection processor (230) is configured to analyze a first pulse generated by the first detector unit and a second pulse generated by the second detector unit based on the one or more readout signals, including: If the time delay between the first pulse and the second pulse is less than a predetermined time threshold, then it is determined that one of the charge-sharing event and the coincident photon event has occurred, and If the energy of each of the first pulse and the second pulse is higher than the first threshold (V L And below the second threshold (V) H If the result is positive, then it is determined that a photon coincidence event has occurred; otherwise, it is determined that a charge sharing event has occurred. The detection processor is also configured to count the overlapping photon events as X-ray photons arriving at each of the first detector unit and the second detector unit, and to ignore the charge-sharing events.

2. The apparatus according to claim 1, wherein, The one or more readout signals are digital signals.

3. The apparatus according to claim 1 or claim 2, wherein, For each detector unit, the one or more readout signals indicate whether the pulse generated at that unit: (i) Above the detection threshold (V) D ); (ii) Higher than the first threshold (V) L );as well as (iii) Higher than the second threshold (V) H ), Wherein, the detection threshold is less than the first threshold, and the first threshold is less than the second threshold.

4. The apparatus according to claim 1 or claim 2, wherein, The one or more readout circuits (210) periodically sample the output signal of each of the detector units (142) to generate the one or more readout signals.

5. The apparatus according to claim 1 or claim 2, wherein, The detector (140) includes a third detector unit (3423) and a fourth detector unit (3424), each of which is configured to convert incoming X-ray photons into corresponding electrical pulses. Furthermore, the one or more readout circuits include a first readout circuit (210a) and a second readout circuit (210b), each of which is coupled to the detector (140). The first readout circuit (210a) is configured to receive electrical pulses from the first detector unit (3421) and the third detector unit (3423) and generate a first readout signal for the detection processor (230). The second readout circuit is configured to receive electrical pulses from the second detector unit (3422) and the fourth detector unit (3424) and generate a second readout signal for the detection processor (230).

6. The apparatus according to claim 5, wherein, The third detector unit (3423) is located in the detector and is adjacent to the fourth detector unit (3424).

7. The apparatus according to claim 1 or claim 2, wherein, The detector (140) is a 1D strip detector.

8. A method for processing signals from an X-ray diffraction apparatus (100), the apparatus comprising a detector (140) arranged to receive X-rays diffracted from a sample, the detector comprising at least a first detector unit (1427; 3421) and a second detector unit (1428; 3422), each detector unit being configured to convert incoming X-ray photons into corresponding electrical pulses, the method comprising: Obtain one or more readout signals, wherein the one or more readout signals describe a first pulse generated by the first detector unit and a second pulse generated by the second detector unit; as well as Analyzing the first pulse and the second pulse based on the one or more readout signals includes: If the time delay between the first pulse and the second pulse is less than a predetermined time threshold, then it is determined that one of the charge-sharing event and the coincident photon event has occurred, and If the energy of each of the first pulse and the second pulse is higher than the first threshold (V L And below the second threshold (V) H If the result is positive, then it is determined that a photon coincidence event has occurred; otherwise, it is determined that a charge sharing event has occurred. The method further includes counting the overlapping photon events as X-ray photons arriving at each of the first detector unit and the second detector unit, and ignoring the charge-sharing events.

9. The method according to claim 8, wherein, The one or more readout signals are digital signals.

10. The method according to claim 8 or claim 9, wherein, For each detector unit, the one or more readout signals indicate whether the pulse generated at that unit: (i) Above the detection threshold (V) D ); (ii) Higher than the first threshold (V) L );as well as (iii) Higher than the second threshold (V) H ), Wherein, the detection threshold is less than the first threshold, and the first threshold is less than the second threshold.

11. A computer program product, the computer program comprising computer program code configured to, when the program is run on one or more physical computing devices, cause the one or more physical computing devices to perform all the steps of any one of claims 8-10.

12. The computer program product according to claim 11, embodied on a computer-readable medium.

Images