A magnetic analysis system for high-density sample analysis

Abstract

The present invention discloses a magnetic analysis system for high-density sample analysis, including a cesium sputterer, a cesium sputtering target, extraction and focusing electrodes, an accelerating electrode, a magnetic deflection mass analyzer, a free drift region, a microchannel plate and a data acquisition card. The present invention has the characteristics of relatively simple structure, safe and simple operation, and easy repair and maintenance; the beam of the invention has a strong flow intensity, stable beam output, high detection efficiency, and high instrument stability. The present invention is a modular system, which is flexible in use and can even be divided into multiple parts for separate use. It is very convenient to replace and modify modules when the equipment is retired or upgraded. The present invention can be used for trace amounts (parts per million) of 54 Mn, 55 Fe, 60 Co. 63 You, 90 Sr. 152 The Eu radioactive nuclide content can be determined, and the relevant nuclides can be separated with high precision, which can be used to measure the activity and specific activity of the nuclides.

Description

Technical Field

[0001] The invention belongs to the technical field of mass spectrometry equipment, and in particular relates to a magnetic analysis system for high-density sample analysis. Background Art

[0002] As early as 1912, JJ Thomson and others built the world's first mass spectrometer. Subsequently, people improved its design and carried out the determination of element isotope abundance. In the 1930s, scientists completed the measurement of natural isotope abundance. In 1940, AONier and others successfully designed a 60° sector magnetic field mass spectrometer for the first time, which became the basis of modern mass spectrometers. In the early days, mass spectrometry technology was mainly used to explore the measurement of isotopes and atomic weights of elements, and was later applied to isotope fractionation. This technology has played an extremely important role in the artificial separation of isotopes and their enrichment processes, and has made great contributions to the development of atomic energy. Lawrence and others from Oak Ridge National Laboratory and the University of California, Berkeley, studied the electromagnetic separation of uranium based on mass spectrometry technology. The uranium used in the first atomic bomb in the United States was provided by this method. Therefore, the need to separate and purify related nuclides in radioactive waste is imminent.

[0003] The core component of mass spectrometry separation is the magnetic deflection device. Magnetic deflection is divided into two types: permanent magnet and electromagnetic. At present, the magnetic field strength of large-area permanent magnets has reached up to 1.2T, but the magnetic field strength of permanent magnets will decrease with the use time. Electromagnetism is currently a common method for making high-strength magnets. Electromagnets have higher magnetic field strength and there is no demagnetization phenomenon. However, the stability and uniformity of their magnetic field strength are not as good as permanent magnets, and they are larger in size and consume more energy. At present, the ion source technology and deflection magnetic field mass spectrometry analysis technology involved in ion magnetic field separation technology are very mature technologies and have been commercially produced.

[0004] The main ion sources used are: eccentric extraction dual plasma negative ion source, Li charge exchange source and Cs sputtering negative ion source. Cs sputtering negative ion source uses positive ions with a certain energy to bombard the target surface, so that the target atoms are sputtered out. The target atoms form negative ions through interaction with the thin layer of the target surface. Its outstanding feature is its simple structure. Negative ions can be directly emitted from the target surface and enter the extraction system. The size of the negative ion flow is determined by the size of the sputtering yield, electron affinity and surface work function. Almost all the nuclides we are concerned about can be ionized by Cs sputtering. At present, Cs beam sputtering sources can produce negative ions of almost all elements, and the beam intensity can reach dozens of μA, or even mA level, which can meet the needs of separation and purification of related nuclides in radioactive waste.

[0005] Based on the above, the present invention organically combines the two technologies to propose a cesium sputtering source magnetic analysis technology, which can realize the separation and purification of radioactive nuclides in radioactive waste in decommissioned nuclear facilities, and then realize the activity and specific activity measurement of the corresponding nuclides. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a magnetic analysis system for high-density sample analysis, including a cesium sputtering device, a cesium sputtering target, an extraction and focusing electrode, an accelerating electrode, a magnetic deflection mass analyzer, a free drift zone, a microchannel plate detector and a data acquisition card; the free drift zone is connected to the microchannel plate detector, the microchannel plate is connected to the data acquisition card, and the data acquisition card is directly connected to a computer.

[0007] In the cesium sputtering part, cesium vapor is introduced into the target chamber, a part of the cesium vapor is adsorbed on the surface of the cesium sputtering target, and the other part is ionized into Cs + After being focused by the accelerating electrode described in the figure, it bombards the target surface, sputtering out negative ions of the analyte, which are extracted through the anode and accelerated and enter the magnetic deflection area and finally enter the microchannel plate detector to obtain mass-to-charge ratio information. The sample is placed in the sputtering target area, and the extraction acceleration electrode is designed for extracting and accelerating negative ions, so it is closely connected to the cesium sputtering part, the magnetic deflection mass analyzer is connected to the ionization target chamber to realize particle deflection, and the drift zone is set between the magnetic deflection mass analyzer and the microchannel plate detector, and the microchannel plate detector is connected to the data acquisition card, and the data acquisition card is directly connected to the computer.

[0008] Preferably, the magnetic analysis system for high-density sample analysis can detect trace amounts (parts per million) of 54 Mn, 55 Fe, 60 Co. 63 You, 90 Sr. 152 Eu radionuclide content was determined.

[0009] Preferably, the vacuum degree in the vacuum target chamber is less than 10 -8 Pa.

[0010] Preferably, the vacuum degree of the free flight zone is less than 10 -4 Pa, which means that the working vacuum of the microchannel plate detector is required to be less than 10 -4 Pa.

[0011] Preferably, the deflection magnet of the magnetic deflection mass analyzer is a 45° deflection magnet.

[0012] Preferably, the extraction and focusing electrodes are applied with suitable voltages.

[0013] Preferably, the heating cesium pot of the cesium sputtering device reaches 1200°C to ensure the amount of cesium vapor introduced, thereby reducing the work function of the target surface and meeting the cesium sputtering start-up requirements. The magnitude of the tungsten ionizer current has a significant effect on the beam intensity and stability, and the current generally used is 20-23A. Again, the target voltage is another factor affecting the beam intensity and stability. Generally, the target voltage has an optimal value between 3.5-6kV. For different target materials, the optimal target voltage value is also different.

[0014] Preferably, the cesium sputtering target part presses the prepared sample powder into the target groove to form a target block. The target position also affects the intensity and stability of the beam. A difference of 1-2 mm will cause an order of magnitude change in the beam. The best target position is usually found in conjunction with other operating parameters.

[0015] Preferably, in the manufacture of the target block, the target block embedded in the target holder can be just flush with the mouth of the target groove or slightly concave in the middle, and a small hole is punched in the middle to form a self-focusing output state after operation and meet the beam output requirements.

[0016] Preferably, the microchannel plate is a large-array electron multiplication detector with high spatial resolution and very high temporal resolution.

[0017] Preferably, the data acquisition card ADQ412 can provide two sampling rates of 3.6GHz and 1.8GHz, and can collect four signals at the same time. Each signal can store 175M data points at one time, and the minimum amplitude of the analog signal that can be collected is ±350mV, which can be converted into a digital signal that can be read by a computer.

[0018] Compared with the shortcomings and deficiencies of the prior art, the present invention has the following beneficial effects:

[0019] The present invention provides a magnetic analysis system for high-density sample analysis, which is a method for high-precision ion sputtering ionization and magnetic deflection separation of radioactive isotopes in activated samples of research reactors. The equipment constructed by this method has the characteristics of relatively simple structure, safe and simple operation, and easy repair and maintenance; the beam of the invention has strong flow intensity, stable beam output, high detection efficiency, and high instrument stability. Because it is a modular system, it is particularly flexible in use and can even be divided into multiple parts for separate use. At the same time, it is very convenient to replace and modify modules when the equipment is retired or upgraded. The present invention can be used for trace amounts (one part per million) of 54 Mn, 55 Fe, 60 Co. 63 You, 90 Sr. 152The Eu radioactive nuclide content can be determined, and the relevant nuclides can be separated with high precision, which can be used to measure the activity and specific activity of the nuclides. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be described in further detail below in conjunction with the accompanying drawings.

[0021] Figure 1 It is a schematic diagram of the structure of a magnetic analysis system for high-density sample analysis according to an embodiment of the present invention.

[0022] In the figure: 1. Cesium sputtering device; 2. Cesium sputtering target; 3. Extraction and focusing electrodes; 4. Accelerating electrode; 5. Magnetic deflection mass analyzer; 6. Free drift region; 7. Microchannel plate detector. DETAILED DESCRIPTION

[0023] like Figure 1 As shown, the present invention discloses a magnetic analysis system for high-density sample analysis, including a cesium sputterer 1, a cesium sputtering target 2, an extraction and focusing electrode 3, an accelerating electrode 4, a magnetic deflection mass analyzer 5, a free drift region 6, and a microchannel plate detector 7.

[0024] The vacuum degree in the cesium sputtering device 1, the cesium sputtering target 2, the extraction and focusing electrode 3, the accelerating electrode 4, and the magnetic deflection mass analyzer 5 is less than 10 -8 Pa, using a cesium pot to heat alkali metal cesium to form cesium vapor, the cesium vapor enters the reaction chamber, i.e., the cesium sputtering device 1, through the cesium vapor inlet shown in the figure, and a part of the introduced cesium vapor is adsorbed on the surface of the cesium sputtering target 2 to reduce the work function on the surface of the cesium sputtering target 2. Secondly, the electrons coming out of the heating filament collide with the neutral cesium vapor and the auxiliary gas molecules during the movement, ionizing them to form a plasma, i.e., the ionized Cs + In the figure, the accelerating electrode with negative high voltage in the cesium sputtering device 1 is focused and bombarded onto the surface of the cesium sputtering target 2, and the positive ions in the plasma (mostly positive cesium ions) are accelerated to hit the sputtering target, and sputtering produces negative ions corresponding to the target material; the cesium sputtering target 2 is made by pressing the prepared sample powder into the target groove to form a target block. In particular, in the production of the target block, the target block embedded in the target seat can be just flush with the mouth of the target groove or slightly concave in the middle, and a small hole is punched in the middle, which can form a self-focusing output state after working. , a cesium sputtering target 2 is made to meet the beam requirements; the optimal values ​​of the target voltage, target position, and tungsten ionizer current are found in conjunction with other operating parameters; negative ions of the analyte are sputtered on the surface of the cesium sputtering target 2, and the sputtered negative ions are drawn out by the extraction and focusing electrode 3 applied with a suitable voltage and accelerated by the acceleration electrode 4 applied with a suitable voltage, and the sputtered negative ions enter the magnetic deflection mass analyzer 5 made of the 45° deflection magnet; the vacuum degree of the free drift region 6 and the microchannel plate detector 7 is less than 10 -4Pa, the deflected negative ions finally pass through the free drift zone 6 to reach the microchannel plate detector 7 to obtain the mass-to-charge ratio information; the microchannel plate detector 7 is a large-array electron multiplication detector with high spatial resolution and a very high time resolution detector. The microchannel plate detector 7 is connected to the data acquisition card ADQ412, and the data acquisition card ADQ412 can convert the data into computer-readable data and convert it into mass-to-charge ratio information.

[0025] The dependence of the mass number of the emitted ions of the magnetic analysis system for high-density sample analysis on the applied current of the 45° deflection analysis magnet is given. This gives the calibration curve of the mass number of Fe, Ni, Co, Sr, Cs, Eu and other elements on the magnetic field current intensity under the optimal deflection magnetic field current, so as to achieve trace (parts per million) 54 Mn, 55 Fe, 60 Co. 63 You, 90 Sr. 152 Eu radionuclide determination.

[0026] In the present invention, the output strength of the negative ion flow is controlled by changing the target voltage, target position, and tungsten ionizer current of the cesium sputtering device 1 and the cesium sputtering target 2. In addition, a collector can be installed at the front end of the microchannel plate detector for sample collection. The collector includes a polyethylene card slot, a high thermal conductivity graphite sheet for collection, and a transmission system thereof. The graphite sheet is installed in a polyethylene card slot, and the card slot is installed on the transmission system. By adjusting the transmission system, the collection system can be moved in and out of the collection plate to be designed into a card slot structure.

[0027] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A magnetic analysis system for high-density sample analysis, characterized in that: It includes cesium sputterer, cesium sputtering target, extraction and focusing electrodes, accelerating electrodes, magnetic deflection mass analyzer, free drift region, microchannel plate detector and data acquisition card; In the cesium sputtering part, cesium vapor enters the cesium sputtering part through the cesium vapor inlet, and a part of the cesium vapor is adsorbed on the surface of the cesium sputtering target; the other part is ionized into Cs + , after being focused by the accelerating electrode with negative high voltage in the cesium sputtering device, the negative ions are bombarded onto the surface of the cesium sputtering target, the sample is placed in the sputtering target area, and the negative ions of the sample are bombarded and sputtered. The negative ions are extracted through the extraction and focusing electrode (3) and accelerated by the accelerating electrode (4). The magnetic deflection mass analyzer is connected to the cesium sputtering device, and the negative ions enter the magnetic deflection mass analyzer to achieve particle deflection. The deflected negative ions pass through the free drift region to reach the microchannel plate detector. The free drift region is arranged between the magnetic deflection mass analyzer and the microchannel plate detector. The deflected negative ions pass through the free drift region to reach the microchannel plate detector. The microchannel plate detector is connected to a data acquisition card, and the data acquisition card converts the data into computer-readable data and mass-to-charge ratio information. The data acquisition card is connected to a computer; The vacuum degree in the vacuum target chamber is less than 10 -8 Pa; the vacuum degree in the free flight zone is less than 10 -4 Pa, the working vacuum of the microchannel plate detector is less than 10 -4 Pa; The deflection magnet of the magnetic deflection mass analyzer is a 45° deflection magnet; The extraction and focusing electrodes are applied with voltage; The cesium sputtering target part presses the prepared sample powder into the target groove to form a target block; The microchannel plate detector is a large-array electron multiplication detector with high spatial resolution.

2. The magnetic analysis system for high-density sample analysis according to claim 1, characterized in that: The magnetic analysis system for high-density sample analysis can detect trace amounts (parts per million) of 54 Mn, 55 Fe, 60 Co. 63 You, 90 Sr. 152 Eu radionuclide content was determined.

3. The magnetic analysis system for high-density sample analysis according to claim 1, characterized in that: The heating cesium pot of the cesium sputtering device reaches 1200°C to ensure the amount of cesium vapor introduced, thereby reducing the work function of the target surface and meeting the cesium sputtering start-up requirements; the current of the tungsten ionizer is 20-23A, and the target voltage is between 3.5-6kV.

4. The magnetic analysis system for high-density sample analysis according to claim 1, characterized in that: In the production of the target block, the target block embedded in the target seat can be just flush with the mouth of the target groove or slightly concave in the middle, and a small hole is punched in the middle to form a self-focusing output state after work and meet the beam output requirements.

5. The magnetic analysis system for high-density sample analysis according to claim 1, characterized in that: The data acquisition card is an ADQ412 high-speed data acquisition card, which can provide two sampling rates of 3.6GHz and 1.8GHz, and can collect four signals at the same time; each signal can store 175M data points at a time, and the minimum amplitude of the analog signal that can be collected is ±350mV, which can be converted into a digital signal that can be read by a computer.

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