A medium-energy x-ray absorption spectroscopy system and method

Abstract

The application discloses a kind of in-situ X-ray absorption spectroscopy testing system and testing method of energy.This system includes vacuum cavity, which is equipped with double flat crystal monochromator, front ionization chamber, sample cavity and detector;Among them, sample cavity is used to place sample to be measured;Computer unit is used to send instruction to QXAFS electronics control double flat crystal monochromator continuous rotation, and the synchrotron radiation light incident on double flat crystal monochromator is continuously output to sample cavity, and sample is excited to generate fluorescent signal and Auger electron;Front ionization chamber is used to collect X-ray and send to current amplifier;Current amplifier is amplified to incident light intensity signal I0 after input to low-pass filter;Fluorescent signal is collected by detector and sent to weak current meter;Weak current meter is collected Auger electron and obtains the total electron yield signal I of sample t , fluorescent yield signal I f Send to low-pass filter;Low-pass filter is filtered to input signal after high-frequency noise and input to electronics to form the X-ray absorption spectrum of sample.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of spectroscopy, and relates to an in-situ X-ray absorption spectroscopy testing system and a testing method. BACKGROUND

[0002] With the rapid growth of global energy consumption, how to efficiently use renewable resources has become a global hot issue. High-performance and low-cost rechargeable batteries are one of the important ways to solve this problem. Government departments of several countries have formulated a research plan to increase the energy density of rechargeable battery (or secondary battery) cells to 350-500 W·h / kg. However, filling more active energy storage materials in a limited battery space and further reducing the proportion of non-active materials has reached a bottleneck from a technical point of view. In order to achieve this goal, it is necessary to rely on the development of a new generation of battery systems with high energy density. Among many battery systems, lithium-sulfur batteries are one of the key technical routes to achieve an energy density of 500 W·h / kg, which uses elemental sulfur (1675 mA·h / g) and metal lithium (3860 mA·h / g) as positive and negative electrode materials, respectively. These two electrode materials are the highest capacity per unit mass of positive and negative electrode materials, respectively, and are the key to achieving high-energy-density batteries.

[0003] During discharge of lithium-sulfur batteries, the elemental sulfur (S8) of the positive electrode is gradually reduced to form lithium polysulfides (Li2S n , 4≤n≤8), lithium sulfide (Li2S); during the charging process, lithium sulfide needs to be completely oxidized to elemental sulfur to complete one electrochemical cycle. Each S8 molecule can transfer 16 electrons when it is reduced to lithium sulfide, which is a multi-electron redox reaction and is the core of lithium-sulfur batteries to achieve high energy density. However, many factors hinder the electrochemical reaction of sulfur, resulting in the overall performance of lithium-sulfur batteries far from expectations. Among them, the difficulty of electrochemical conversion between sulfur and lithium sulfide and lithium polysulfide is the key to limiting the energy density, power density, and cycle stability / lifetime of the battery, and the electrocatalytic conversion mechanism between them is still unclear and controversial.

[0004] In-situ X-ray absorption spectroscopy (XAS) measurement is a dynamic test of the sample by changing the sample environment with external equipment, so as to reveal the dynamic structural evolution of the sample and then correlate the sample performance, which puts a certain requirement on the time resolution of the XAS acquisition method, i.e. it needs to correspond to the change time of the sample. In the conventional XAS measurement, the double-crystal monochromator (DCM) is rotated by one angle, then the electronic signal is collected, and then the next angle is continued to be rotated and completed. The single spectrum acquisition time generally needs about twelve minutes. In this time scale, this measurement method cannot capture the continuous change of the sample in a short time during the in-situ process, and due to the change of the sample properties, the measured XAS spectrum will be inaccurate.

[0005] In-situ measurement technology with element and time resolution is a necessary means to overcome the above difficulties and reveal the electrocatalytic reaction process of sulfur. At present, the time-resolved XAS method has been widely used in the hard X-ray energy region, but for the medium energy region where sulfur elements are located, there are few related test methods at present, so it is very important to develop corresponding time-resolved XAS, such as fast scanning X-ray absorption spectrum (QXAFS) to characterize the lithium-sulfur battery system and other systems. SUMMARY

[0006] In view of the problems in the prior art, the purpose of the present application is to provide a medium energy in-situ X-ray absorption spectroscopy test system and test method.

[0007] In in-situ XAS testing, because medium energy X-rays are easily affected by air scattering, the sample to be tested needs to be placed in a vacuum chamber, and the test is selected in a vacuum environment or a pure helium environment. Then, through the wires connected between the inside and outside of the vacuum chamber, the external equipment is connected with the sample, so as to monitor and apply in-situ conditions. Because the system is independent of the sample environment in the vacuum chamber, this method is not limited to in-situ testing related to lithium-sulfur batteries, and can be extended to various in-situ characterization of elements in the medium energy region.

[0008] The technical scheme of the present application is:

[0009] A medium energy in-situ X-ray absorption spectroscopy test system, characterized in that it comprises a computer unit, QXAFS electronics, a driver, a current amplifier, a low-pass filter, a weak current meter and a vacuum cavity, wherein a double flat crystal monochromator, a pre-ionization chamber, a sample cavity and a detector are arranged in the vacuum cavity.

[0010] The sample cavity is used for placing the medium energy region sample to be tested.

[0011] The computer unit is used for sending instructions to the QXAFS electronics to control the driver to drive the double flat crystal monochromator to rotate continuously, so that the synchrotron radiation light incident on the double flat crystal monochromator is continuously output into the sample cavity to excite the sample to generate fluorescent signals and Auger electrons.

[0012] The pre-ionization chamber is used for collecting the X-rays output by the double flat crystal monochromator and sending them to the current amplifier.

[0013] The current amplifier is used for amplifying the incident light intensity signal I0 of the X-rays incident on the sample cavity and inputting it to the low-pass filter.

[0014] The detector is used for collecting the fluorescent signals and converting them into electrical signals before sending them to the weak current meter.

[0015] The weak current meter is connected with the sample chamber to collect the Auger electrons and obtain the total electron yield signal I of the sample t The detector is connected with the low-pass filter to obtain the fluorescence yield signal I of the sample f and sends to the low-pass filter;

[0016] The low-pass filter is used to filter the high-frequency noise of the input signal and input to the QXAFS electronics;

[0017] The QXAFS electronics processes the input signal to generate the XAFS under the total electron yield or the XAFS under the fluorescence yield of the sample and input to the computer unit to form the X-ray absorption spectrum of the sample.

[0018] Further, the computer unit is connected with the double-crystal monochromator through an encoder to monitor the position of the double-crystal monochromator.

[0019] Further, the sample chamber is a metal frame, and the weak current meter is connected with the metal frame through a wire to collect the Auger electrons and obtain the total electron yield signal I of the sample t .

[0020] Further, the detector is a silicon diode.

[0021] Further, the low-pass filter is an SR640 dual-channel low-pass filter, which inputs I0, I t and I f in the form of I0 / I t or I0 / I f two by two to the SR640 dual-channel low-pass filter for high-frequency noise filtering.

[0022] A method for in-situ medium-energy X-ray absorption spectroscopy, comprising the steps of:

[0023] 1) placing a sample to be tested in a medium-energy region into a sample chamber;

[0024] 2) the computer unit sends instructions to the QXAFS electronics control driver to drive the double-crystal monochromator to continuously rotate, continuously output the synchrotron radiation light incident on the double-crystal monochromator into the sample chamber, and excite the sample to generate fluorescence signals and Auger electrons;

[0025] 3) using a pre-ionization chamber to collect the X-rays output by the double-crystal monochromator and sending to a current amplifier;

[0026] 4) the current amplifier amplifies the incident light intensity signal I0 of the X-rays incident on the sample chamber and inputs to the low-pass filter;

[0027] 5) When total electron yield test is performed, the total electron yield signal I of the sample is obtained by connecting the weak galvanometer with the sample chamber to collect the Auger electrons; t and sending to the low pass filter; when fluorescence yield test is performed, the fluorescence yield signal I of the sample is obtained by connecting the weak galvanometer with the detector to collect the fluorescence signal and convert it into an electric signal and then send it to the weak galvanometer; f and sending to the low pass filter;

[0028] 6) The input signal is filtered by the low pass filter to remove high frequency noise and then input to the QXAFS electronics;

[0029] 7) The input signal is processed by the QXAFS electronics to generate XAFS under total electron yield or XAFS under fluorescence yield of the sample and then input to the computer unit to form the X-ray absorption spectrum of the sample;

[0030] Wherein, the double flat crystal monochromator, the front ionization chamber, the sample chamber and the detector are located in a vacuum environment.

[0031] A medium energy in-situ X-ray absorption spectroscopy test system, characterized in that it comprises a computer unit, QXAFS electronics, a driver, a current amplifier, a low pass filter, a weak galvanometer, an in-situ test system and a vacuum chamber, wherein the vacuum chamber is provided with a double flat crystal monochromator, a front ionization chamber, a sample chamber and a detector.

[0032] The sample chamber is used to place the medium energy region sample to be tested; the sample chamber is filled with helium to expel air to keep the air pressure in the sample chamber constant;

[0033] The computer unit is used to send instructions to the QXAFS electronics to control the driver to drive the double flat crystal monochromator to rotate continuously, so that the synchrotron radiation light incident on the double flat crystal monochromator is continuously output to the sample chamber to excite the sample to generate a fluorescence signal and Auger electrons;

[0034] The front ionization chamber is used to collect the X-ray output by the double flat crystal monochromator and send it to the current amplifier;

[0035] The current amplifier is used to amplify the incident light intensity signal I0 of the X-ray incident on the sample chamber and then input it to the low pass filter;

[0036] The detector is used to collect the fluorescence signal and convert it into an electric signal and then send it to the weak galvanometer;

[0037] The weak galvanometer is used to connect with the sample chamber to collect the Auger electrons and obtain the total electron yield signal I of the sample.t and sent to the low-pass filter, and the fluorescence yield signal I of the sample is obtained by connecting the weak current meter with the sample chamber f and sent to the low-pass filter;

[0038] The low-pass filter is used to filter high-frequency noise of the input signal and input the signal to the QXAFS electronics.

[0039] The QXAFS electronics processes the input signal to generate XAFS under full electron yield or XAFS under fluorescence yield of the sample and input the signal to the computer unit to form the X-ray absorption spectrum of the sample.

[0040] The in-situ testing system is connected with the sample in the sample chamber and used to perform in-situ testing on the sample.

[0041] A method for performing in-situ X-ray absorption spectroscopy testing on a medium-energy region sample, comprising the following steps:

[0042] 1) placing the medium-energy region sample to be tested into a sample chamber; the sample chamber is filled with helium to expel air and keep the air pressure in the sample chamber constant;

[0043] 2) the computer unit sends instructions to the QXAFS electronics control driver to drive the double-crystal monochromator to continuously rotate, continuously output the synchrotron radiation light incident on the double-crystal monochromator into the sample chamber, and excite the sample to generate fluorescence signals and Auger electrons;

[0044] 3) the in-situ testing system is connected with the sample in the sample chamber and used to perform in-situ testing on the sample;

[0045] 4) the pre-ionization chamber is used to collect the X-rays output by the double-crystal monochromator and send the X-rays to the current amplifier;

[0046] 5) the current amplifier amplifies the incident light intensity signal I0 of the X-rays incident on the sample chamber and inputs the signal to the low-pass filter;

[0047] 6) when performing full electron yield testing, the weak current meter is connected with the sample chamber to collect the Auger electrons and obtain the full electron yield signal I of the sample t and sent to the low-pass filter; when performing fluorescence yield testing, the weak current meter is connected with the detector, the fluorescence signals are collected by the detector and converted into electrical signals, and then the signals are sent to the weak current meter to obtain the fluorescence yield signal I of the sample f and sent to the low-pass filter;

[0048] 7) the low-pass filter filters high-frequency noise of the input signal and inputs the signal to the QXAFS electronics.

[0049] 8) the QXAFS electronics processes the input signal to generate XAFS at full electron yield or XAFS at fluorescence yield for the sample and inputs the computer unit to form the X-ray absorption spectrum of the sample;

[0050] Wherein, the double flat crystal monochromator, the front ionization chamber, the sample cavity and the detector are located in a vacuum environment.

[0051] The advantages of the present application are as follows:

[0052] 1. A fast scanning mode, i.e. QXAFS, which can be used with the conventional step scanning mode collected by the experimental station XAFS in BSRF-4B7A, is established, the single spectrum collection time can be increased by two orders of magnitude while ensuring the accuracy of XAFS, thereby providing conditions for carrying out in-situ experiments in the medium energy X-ray energy region;

[0053] 2. The signal current obtained by the two detection methods of full electron yield and fluorescence yield is weak, which leads to a long response time of the weak current meter when the range is appropriate, and if the response time is to be improved, the range position needs to be increased, which will introduce additional noise, therefore, the method of combining the high range position of the ammeter with the double channel low pass filter of SR640 is adopted, the response speed of the system is improved while the high frequency noise is filtered out, thereby significantly improving the XAFS quality.

[0054] The different gears of the current amplifier have two effects: one is the measurement accuracy of the ammeter, for example, the actual signal amount is 50pA, which can be accurately measured in the 200pA range, but may have errors in the high range, i.e. 2nA or 20nA. The present application uses the 2nA range in the test process, which can completely cover the fluorescence or Auger electron signal amount excited by X-rays, and it is found through tests that good accuracy can also be maintained at a lower signal amount. The other effect is the response speed of the ammeter, which is determined by the basic amplification circuit. Measuring smaller signals requires a longer time to stabilize the measured current. For example, the response speed of the ammeter will decrease significantly in the 200pA range, resulting in distortion of the measured XAS spectrum, while the response speed of the ammeter in the 2nA range is sufficient to capture the current change. Therefore, in the present application, even if the sample signal amount is below 200pA, we do not choose the 200pA range, because the response speed of this range is not sufficient to capture the sample signal change. The speed of the monochromator does not affect the size of the sample signal current, so only the response speed of the ammeter needs to be considered. The faster the monochromator speed, the faster the response speed of the ammeter is required. Therefore, in terms of the ammeter range or the amplification factor of the current amplifier, the ammeter can respond to the monochromator speed in a timely manner while ensuring the accuracy of the reading. In the present application, the 2nA range of the 6517B ammeter can accurately measure the signal size and respond to the speed change of the monochromator, and the selection of this range in the test is determined by these two points.

[0055] When determining the cutoff frequency of the low-pass filter, only two factors need to be considered, i.e. the monochromator speed and the absorption edge energy of the measured element. A lower monochromator speed and a lower absorption edge can set the filter cutoff frequency slightly lower. For example, in the present application, the cutoff frequency of 5Hz for the sulfur element (K edge is 2472eV) can obtain very good filtering effect at various monochromator speeds. Of course, this frequency is not absolute, as long as the effect is good enough. In addition, for elements with higher energy, such as potassium (K edge is 3608eV), we found that 15Hz can achieve good filtering effect at various speeds. Taking potassium as an example, if the cutoff frequency is set too high, the noise cannot be filtered well, and if the cutoff frequency is too small, the XAS signal may also be filtered out. Therefore, the setting of the cutoff frequency of the SR640 low-pass filter needs to be tested in advance for a certain element.

[0056] 3. The two detection methods in the QXAFS, i.e. the total electron yield method and the fluorescence yield method, can select the appropriate detection method according to the content of the sample. The total electron yield method is generally used for samples with high content of the element to be measured, and the fluorescence yield method is used for samples with low content or samples that are not suitable for current measurement. The two methods only differ in the detector, and the time resolution is completely the same. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 is a test system diagram of the present application.

[0058] Figure 2 is a test effect diagram of the present application;

[0059] (a) comparison diagram of fast scan XAS and step XAS at different rotating speeds of DCM in full electron yield mode,

[0060] (b) comparison diagram of fast scan XAS and step XAS at different rotating speeds of DCM in fluorescence yield mode,

[0061] (c) two-dimensional diagram and projection diagram of lithium-sulfur battery change within one hour of discharge. DETAILED DESCRIPTION

[0062] The present application will be further described in detail below with reference to the accompanying drawings, and the examples are only used to explain the present application, and are not used to limit the scope of the present application.

[0063] In order to capture the X-ray absorption spectrum change of elements in situ process, a new method of fast scan X-ray absorption spectrum for medium energy X-ray energy region is developed, and the test system is as shown in Figure 1 The present application realizes continuous rotation of DCM by changing the motion mode of double flat crystal monochromator, so that the collection speed of XAS is greatly improved, and the time scale of single spectrum can be shortened from dozens of minutes in the original step scan mode to seconds, so that the in-situ process in a short time can be captured. The SR640 low-pass filter can filter the high-frequency noise generated by the weak current meter in the large range during the collection process, so as to improve the XAS quality. The method can be used for different sample conditions, and the full electron yield and fluorescence yield modes are collected, and at the same time, the method is compatible with the original experimental mode of the experimental station, and can be easily switched between the two.

[0064] The present application is a QXAFS method developed for X-rays in the medium energy region, so it will be limited by this energy region. First, the quantum yield of low-Z elements is low, so that the sample signal excited by X-rays is weak, and the detection of weak signal will inevitably be affected by the response speed of the amplifier circuit. Secondly, the weak signal is more seriously interfered by noise, and in addition, due to the short integration time of the single energy point in the fast scan mode itself, the signal-to-noise ratio of the XAS signal is inevitably poor. Therefore, the present application proposes a solution, that is, selecting appropriate current amplifier gear or current meter range to ensure that the signal can be accurately measured under the premise of sufficient speed to respond to the signal obtained during high-speed rotation of the monochromator, and combining the SR640 double-channel low-pass filter to filter high-frequency noise to obtain XAS spectrum with good signal-to-noise ratio.

[0065] In this invention, we use an SR570 current amplifier and a 6517B weak current meter, both of which are selected within appropriate magnification and range. The SR570 current amplifier measures the intensity of incident light I0, resulting in high signal strength, a low current magnification, and a sufficiently fast response time. The specific magnification range is limited by the experimental station and the absorption edge energy of the element being measured. The signals excited by X-rays entering the sample, including fluorescence and Auger electron signals, are weak, typically only a few hundred pA. The 6517B weak current meter used in this experimental station has insufficient response speed to measure such signals within its appropriate range. After testing, we fixed it to the 2nA range, which ensures sufficient response speed while accurately measuring fluorescence or Auger electron signals. At the same time, the 2nA range introduces high-frequency noise generated by the circuit when measuring weak signals far below the upper range limit (e.g., 100pA). In this case, the SR640 low-pass filter can be used to remove this high-frequency noise, allowing for a good XAS spectrum. The choice of the low-pass filter cutoff frequency depends on the absorption edge energy of the element being measured and the monochromator speed. In tests near sulfur, we found that a cutoff frequency of 5Hz provides good filtering results. This cutoff frequency increases with increasing monochromator speed and absorption edge energy. The following is a description of the acquisition process using this method.

[0066] Synchrotron radiation is extracted from the storage ring bent iron, and then the X-rays are monochromated and optimized by optical elements such as the double-crystal monochromator. After the double-crystal monochromator sends instructions from the computer to the QXAFS electronics, the QXAFS electronics controls the rotation of the driver and monitors the position of the double-crystal monochromator through an encoder. The X-rays first pass through the pre-ionization chamber, and the SR570 current amplifier obtains and records the incident light intensity signal I0, which is then irradiated on the sample to generate fluorescence or current signals. Among them, the current signal I t It can be directly detected by 6517B weak current meter. The ratio of this signal to the front ionization chamber signal is I t / I0 is the absorption coefficient of the total electron yield. The XAFS under the total electron yield can be obtained by plotting the X-ray energy as the horizontal axis. The fluorescence signal needs to be converted from the light signal excited by the sample by X-rays into an electrical signal by a silicon diode and then detected by a 6517B weak current meter. The fluorescence signal I f The ratio of the signal from the front ionization chamber to the f / I0 is the absorption coefficient of fluorescence yield. Plotting with X-ray energy as the horizontal axis can obtain the XAFS under fluorescence yield.

[0067] The current signals I0 and I t and I f The high-frequency noise is filtered out by the SR640 low-pass filter to improve the signal quality before entering the QXAFS electronics system, which is responsible for controlling the continuous rotation of the monochromator and inputting the processed signal into the computer to form the final XAFS spectrum.

[0068] Because medium-energy X-rays are significantly affected by air scattering, the entire beam path must be protected by a vacuum. The monochromator, pre-ionization chamber, sample, and silicon diode are located in the beam path and are therefore kept in a vacuum environment. The sample can be placed in a vacuum or pure helium atmosphere depending on the experimental requirements. The remaining hardware, not located in the beam path, can be kept in normal atmospheric conditions.

[0069] The testing method of the present invention comprises the following steps:

[0070] (1) Tests for ex situ experiments:

[0071] ① Here we choose FeS2 standard sample as an example. The powder is evenly coated on the conductive carbon glue and placed on the metal sample holder in the sample cavity for testing. Since the sample is not affected by vacuum, it is tested in a vacuum environment.

[0072] ② X-ray white light is drawn out by the storage ring bent iron, monochromated by the monochromator and optimized by other optical elements on the beam line before being transmitted backward. The signal is collected by the front ionization chamber and amplified by the SR570 current amplifier. The X-ray intensity before entering the sample cavity is recorded as the incident light intensity signal I0.

[0073] ③ After passing through the front ionization chamber, X-rays enter the sample cavity and irradiate the FeS2 sample to generate Auger electrons and fluorescence generated by the transition of outer-shell electrons to inner-shell electrons. The Auger electron signal is led out of the sample cavity by a wire connected to the metal sample holder to the 6517B weak current meter for recording, and the full electron yield signal I is obtained. t The fluorescence signal is first converted into an electrical signal by the silicon diode in the sample chamber and then transmitted to the 6517B weak current meter by a wire to obtain the fluorescence yield signal I f .

[0074] ④ The three signals I0, I t and I f Take I0 / I t or I0 / I f The two combinations are input into the SR640 dual-channel low-pass filter to filter high-frequency noise. The cutoff frequency of the filter can be selected according to the type of element. In this test, a cutoff frequency of 5Hz is selected. For the two XAS measurement methods, only one of the fluorescence yield and the full electronic yield can be measured at the same time. The fluorescence yield measurement requires I0 / I f The data of electron yield is I0 / I t The SR640 has only two channels for low-pass filtering of current. Taking the fluorescence output as an example, when using it, I0 and I fThe two channels are input respectively, and after the filtering circuit in SR640 works, the filtered I0 and I f Two current signals, and then the current continues to transmit to the QXAFS system, and the two independent signals are analyzed by the QXAFS system to generate the final XAS spectrum.

[0075] ⑤The signal filtered by the filter enters the QXAFS electronics system, which processes the signal into XAFS under full electron yield or XAFS under fluorescence yield, and then inputs the computer to form the final XAFS spectrum, Figure 2 (a) and (b) are the XAS of DCM at 1000pps (pulses per second), 2000pps, 3000pps, 4000pps and 4500pps under two modes of full electron yield and fluorescence yield, which are consistent with the XAS obtained by the conventional step mode.

[0076] (2) Test for in-situ experiment:

[0077] ①Select an in-situ lithium-sulfur battery system as an example, the negative electrode of which is metal lithium, and the positive electrode is Li2S6 cathode liquid, and a hole is opened at the positive electrode shell and covered by a polyimide film to ensure that the X-ray can pass through without liquid flowing out.

[0078] ②The transmission process of X-ray is consistent with (1), and the difference is that the environment in the sample chamber is filled with helium to maintain the constant gas pressure in the chamber because the change of gas pressure will affect the performance of the battery.

[0079] ③During the test, the blue sky battery test system is used for testing, and the wires on the sample chamber can conveniently connect the battery test system outside the chamber with the sample in the chamber. The initial voltage of the battery is 2.8V, and the cycle test is carried out at a charge and discharge current of 5mA. During this process, the QXAFS electronics will work to obtain the XAFS spectrum, Figure 2 (c) is the result in the first hour of the cycle test.

[0080] Figure 2 (a) and Figure 2 (b) shows the working performance of the QXAFS system under two modes of full electron yield and fluorescence yield. It can be seen that the XAFS spectrum obtained by fast scanning is basically consistent with the XAFS spectrum obtained by ordinary step scanning in energy resolution, but the time resolution is greatly improved, which proves the reliability of the method. In addition, as the speed of DCM increases, the overall absorption spectrum moves to high energy, so the step XAFS spectrum needs to be collected first during each test, and the fast XAFS spectrum can be corrected by the step XAFS spectrum during subsequent processing. Figure 2(c) The XAFS variation of sulfur element of a lithium-sulfur battery one hour before discharging is shown, and because the battery reaction is slow, the test is carried out at a speed of 900 pps, and 73 spectra are obtained in one hour, and the variation of the sulfur element during discharging can be clearly seen.

[0081] From the above analysis, it can be seen that the method has good performance and reliability in the middle-energy absorption spectrum test, and can timely reflect the valence state and structural change of the element in the in-situ environment.

[0082] Although specific embodiments of the present application are disclosed herein for illustrative purposes, and are intended to aid in the understanding of the application, it will be readily understood by those skilled in the art that various substitutions, modifications and changes can be made without departing from the spirit and scope of the present application and the appended claims. Therefore, the present application should not be limited to the disclosed best mode. The scope of the present application is defined by the scope of the claims.

Claims

1. A medium energy in situ X-ray absorption spectroscopy testing system, characterized in that: It includes a computer unit, QXAFS electronic equipment, a driver, a current amplifier, a low-pass filter, a weak current meter and a vacuum chamber, wherein the vacuum chamber is provided with a double flat crystal monochromator, a front ionization chamber, a sample chamber and a detector; wherein, The sample cavity is used to place the medium energy zone sample to be tested; The computer unit is used to send instructions to the QXAFS electronic device to control the driver to drive the double-crystal monochromator to continuously rotate, continuously output the synchrotron radiation incident on the double-crystal monochromator into the sample cavity, and excite the sample to generate fluorescence signals and Auger electrons; The front ionization chamber is used to collect the X-rays output by the double-flat crystal monochromator and send them to the current amplifier; The current amplifier is used to obtain an incident light intensity signal I0 of the X-ray incident on the sample cavity according to the input X-ray, and to amplify the incident light intensity signal I0 and then input it into the low-pass filter; The detector is used to collect the fluorescence signal and convert it into an electrical signal and then send it to the weak current meter; The weak current meter is used to connect to the sample chamber to collect the Auger electrons and obtain the total electron yield signal I of the sample. t And sent to the low-pass filter, connected to the detector to obtain the fluorescence yield signal I of the sample f and sent to the low-pass filter; The low-pass filter is used to filter the high-frequency noise of the input signal before inputting it into the QXAFS electronic device; The QXAFS electronic device processes the input signal to generate XAFS under full electron yield or XAFS under fluorescence yield of the sample and inputs the signal into the computer unit to form an X-ray absorption spectrum of the sample.

2. The system according to claim 1, wherein: The computer unit is connected to the double-flat-crystal monochromator via an encoder for monitoring the position of the double-flat-crystal monochromator.

3. The system according to claim 1, wherein: The sample chamber is a metal frame. The weak current meter is connected to the metal frame through a wire to collect the Auger electrons to obtain the total electron yield signal I of the sample. t .

4. The system according to claim 1, 2 or 3, characterized in that: The detector is a silicon diode.

5. The system according to claim 1, 2 or 3, characterized in that: The low-pass filter is a SR640 dual-channel low-pass filter, which converts I0, I t and I f Take I0 / I t or I0 / I f The two-way combination is input into the SR640 dual-channel low-pass filter to filter high-frequency noise.

6. A medium-energy in-situ X-ray absorption spectroscopy testing method, comprising the following steps: 1) Place the medium energy zone sample to be tested into the sample chamber; 2) The computer unit sends instructions to the QXAFS electronic equipment to control the driver to drive the double-crystal monochromator to continuously rotate, continuously outputting the synchrotron radiation incident on the double-crystal monochromator into the sample cavity, and exciting the sample to generate fluorescence signals and Auger electrons; 3) using a front ionization chamber to collect the X-rays output by the double-flat crystal monochromator and sending them to a current amplifier; 4) The current amplifier amplifies the incident light intensity signal I0 of the X-ray incident on the sample cavity and then inputs the amplified signal into the low-pass filter; 5) When performing full electron yield testing, a weak current meter is connected to the sample chamber to collect the Auger electrons to obtain the full electron yield signal I of the sample. t When the fluorescence yield test is performed, the weak current meter is connected to the detector, the fluorescence signal is collected by the detector and converted into an electrical signal and sent to the weak current meter to obtain the fluorescence yield signal I of the sample. f and sent to the low-pass filter; 6) Using a low-pass filter to filter the high-frequency noise of the input signal and then input it into the QXAFS electronic device; 7) The QXAFS electronic device processes the input signal to generate the XAFS under the full electronic yield or the XAFS under the fluorescence yield of the sample and inputs the signal into the computer unit to form the X-ray absorption spectrum of the sample; The double-flat crystal monochromator, the front ionization chamber, the sample cavity and the detector are located in a vacuum environment.

7. The method according to claim 6, characterized in that The computer unit is connected to the double-flat-crystal monochromator via an encoder for monitoring the position of the double-flat-crystal monochromator.

8. A medium energy in situ X-ray absorption spectroscopy testing system, characterized in that: It includes a computer unit, QXAFS electronic equipment, a driver, a current amplifier, a low-pass filter, a weak current meter, an in-situ test system and a vacuum chamber, wherein the vacuum chamber is provided with a double flat crystal monochromator, a front ionization chamber, a sample chamber and a detector; wherein, The sample chamber is used to place the medium energy zone sample to be tested; the sample chamber is filled with helium and the air is expelled to maintain a constant pressure in the sample chamber; The computer unit is used to send instructions to the QXAFS electronic device to control the driver to drive the double-crystal monochromator to continuously rotate, continuously output the synchrotron radiation incident on the double-crystal monochromator into the sample cavity, and excite the sample to generate fluorescence signals and Auger electrons; The front ionization chamber is used to collect the X-rays output by the double-flat crystal monochromator and send them to the current amplifier; The current amplifier is used to amplify the incident light intensity signal I0 of the X-ray incident on the sample cavity and then input it into the low-pass filter; The detector is used to collect the fluorescence signal and convert it into an electrical signal and then send it to the weak current meter; The weak current meter is used to connect to the sample chamber to collect the Auger electrons and obtain the total electron yield signal I of the sample. t And sent to the low-pass filter, connected to the detector to obtain the fluorescence yield signal I of the sample f and sent to the low-pass filter; The low-pass filter is used to filter the high-frequency noise of the input signal before inputting it into the QXAFS electronic device; The QXAFS electronic device processes the input signal to generate XAFS under full electron yield or XAFS under fluorescence yield of the sample and inputs the signal into the computer unit to form an X-ray absorption spectrum of the sample; The in-situ testing system is connected to the sample in the sample chamber and is used to perform in-situ testing on the sample.

9. A medium energy in situ X-ray absorption spectroscopy testing method comprising the following steps: 1) Place the medium energy zone sample to be tested into the sample chamber; The sample chamber is filled with helium and the air is expelled to maintain a constant pressure in the sample chamber; 2) The computer unit sends instructions to the QXAFS electronic equipment to control the driver to drive the double-crystal monochromator to continuously rotate, continuously outputting the synchrotron radiation incident on the double-crystal monochromator into the sample cavity, and exciting the sample to generate fluorescence signals and Auger electrons; 3) connecting an in-situ testing system to the sample in the sample chamber to perform in-situ testing on the sample; 4) using a front ionization chamber to collect the X-rays output by the double-flat crystal monochromator and sending them to a current amplifier; 5) The current amplifier amplifies the incident light intensity signal I0 of the X-ray incident on the sample cavity and then inputs the amplified signal into the low-pass filter; 6) When performing full electron yield testing, a weak current meter is connected to the sample chamber to collect the Auger electrons to obtain the full electron yield signal I of the sample. t When the fluorescence yield test is performed, the weak current meter is connected to the detector, the fluorescence signal is collected by the detector and converted into an electrical signal and sent to the weak current meter to obtain the fluorescence yield signal I of the sample. f and sent to the low-pass filter; 7) Using a low-pass filter to filter the input signal for high-frequency noise and then input it into the QXAFS electronic device; 8) The QXAFS electronic device processes the input signal to generate the XAFS under the full electronic yield or the XAFS under the fluorescence yield of the sample and inputs the signal into the computer unit to form the X-ray absorption spectrum of the sample; The double-flat crystal monochromator, the front ionization chamber, the sample cavity and the detector are located in a vacuum environment.

10. The method according to claim 9, characterized in that The computer unit is connected to the double-flat-crystal monochromator via an encoder for monitoring the position of the double-flat-crystal monochromator.

Images