CN102879316A - Device and method for testing feedback ions of low-light-level image intensifier component - Google Patents

Abstract

A low-light image intensifier component feedback ion test device and method belong to the field of photoelectric imaging devices, including a focused ultraviolet light source, a vacuum chamber, a cathode-less low-light image intensifier component, an ion guide, an ion detector, and a shielding box; the method is: focusing The ultraviolet light source is incident on the surface of the microchannel plate through the ultraviolet window, and the excited electrons make the low-light image intensifier component work, and the feedback ions generated in the low-light image intensifier component are accelerated and enter the ion detection through the ion guide and the isolation grid. The output signal is amplified by the charge amplifier and then input to the multi-channel pulse amplitude analyzer. The ion pulse signal and the noise signal are separated through the pulse amplitude analysis, and the feedback ion pulse signal amplitude value is obtained, and then the signal amplitude is input as the threshold value to the In a single-channel spectrometer, ion pulse counting is realized. The device can realize the detection of extremely weak ion current in a complex electromagnetic environment, and is used for the measurement of the ion barrier characteristics of the anti-ion feedback membrane in the low-light image intensifier.

Description

Low-light image intensifier component feedback ion test device and method

technical field

The invention relates to a low-light image intensifier component feedback ion testing device and a method thereof, which is a device capable of realizing extremely weak ion current detection in a complex electromagnetic environment, and can be used for anti-ion feedback membrane ion resistance in low-light devices. Permeability measurement.

Background technique

When working like a tube, the residual gas molecules in the tube are ionized by the high-density electron cloud at the output end of the microchannel plate to form gas ions, and feed back to the input end of the microchannel plate along the microchannel. The photocathode makes the photocathode emit electrons, which reduces the signal-to-noise ratio and forms ion spots on the fluorescent screen; the bombardment of high-speed ions will also damage the Cs-O layer on the surface of the GaAs photocathode, and the sensitivity will drop sharply, which will greatly shorten the life of the cathode. . In order to solve this problem, a layer of dielectric film is covered on the input surface of the microchannel plate to prevent gas ions from ejecting from the channel and achieve the purpose of protecting the photocathode. This film is called anti-ion feedback film. According to reports, after MCP covers the ion feedback film, the working life of the image tube can reach more than 10,000 hours.

For a high-performance anti-ion feedback film, it is necessary to have a high electron transmission rate and ion barrier rate. The performance of the film layer is related to factors such as the production process of the film layer and the film composition. Therefore, a method that can directly measure the anti-ion feedback film is required. The device for ion feedback membrane ion barrier properties can quantitatively detect the performance of the membrane layer and provide a basis for the preparation of high-quality membrane layers. The thickness of the anti-ion feedback film is only a few nanometers, and there must be a substrate when it is fabricated, so the film layer cannot be isolated to measure the ion barrier characteristics; from the results obtained from theoretical analysis and software simulation, it can be known that the low-light image tube Feedback ion current is less than 10 ^-15 A, the ion source with such a low ion current cannot be obtained under the current technical conditions, and it is not feasible to use ion source for measurement. At present, there are no reports and products of relevant testing equipment at home and abroad.

Invention content:

The technical problem to be solved by the present invention is to provide a low-light image intensifier component feedback ion test device and its method, which can simulate the working state of the real image tube and realize the measurement of ion barrier characteristics of the anti-ion feedback membrane.

The technical solution of the present invention is to design a low-light image intensifier assembly feedback ion test device, including a focused ultraviolet light source, a vacuum chamber, a cathode-free low-light image intensifier assembly, an ion guide, an ion detector, and a shielding box; The vacuum chamber is provided with an ultraviolet window, and the cathode-free low-light image intensifier assembly inside the vacuum chamber is aligned with the ion guide obliquely; the shielding box is equipped with an electric field isolation grid, a diaphragm and an ion detector. It is connected with a charge amplifier; the charge amplifier is respectively connected with a multi-channel pulse amplitude analyzer and a single-channel spectrometer; an ion guide, an electric field isolation net and an aperture are arranged between the cathode-free micro-light image intensifier assembly and the ion detector. The spot size of the focused ultraviolet light source is adjustable; the ion guide is seamlessly connected with the shielding box; the projection of the ion guide outlet along the axial direction completely covers the diaphragm.

Invented a low-light image intensifier component feedback ion test method, the focused ultraviolet light, that is, the focused ultraviolet light source is incident on the surface of the microchannel plate in the cathode-free low-light image intensifier component through the ultraviolet window, and the excited electrons make The non-cathode low-light image intensifier component works, and the feedback ions generated in the non-cathode low-light image intensifier component are accelerated, then enter the ion detector through the ion guide and the electric field isolation grid, and the output signal is amplified by the charge amplifier and then input to the multiple The channel pulse amplitude analyzer separates the ion pulse signal from the noise signal through pulse amplitude analysis to obtain the feedback ion pulse signal amplitude value interval, and then inputs the lower limit of the signal amplitude as a threshold value into the single channel spectrometer to realize ion pulse counting; Wherein, the excitation light source adopts a focused ultraviolet light source with adjustable spot size.

The ion guide has an inclination angle of 30-40 degrees to the measured surface. The setup is used to detect feedback ion currents in low-light image intensifier assemblies.

The working principle and beneficial effects of the present invention are as follows: the non-cathode low-light image intensifier assembly and the ion detection assembly of the present invention are installed in a vacuum chamber, and an ultraviolet incident window is set on the top of the vacuum chamber; an ultraviolet light source is used to directly excite the low-light image intensifier Secondary electrons are emitted from the surface of the microchannel plate in the detector assembly to form the input current of the microchannel plate, which replaces the photocathode and provides a running channel for the feedback ions to be incident on the ion detector.

The ion detector is installed in a shielding box, which is made of metal materials, which can not only realize electromagnetic shielding, but also effectively shield ultraviolet light, avoiding direct incident ultraviolet light and multiple reflections of ultraviolet light in the vacuum chamber incident on the ion detector; The lower end of the shielding box is connected to the ion guide, and the entrance of the ion guide is aligned with the upper surface of the non-cathode low-light image intensifier component at an inclination angle of 30 degrees to 40 degrees and ensures that the upper surface is not covered to avoid blocking the ultraviolet beam. The ion guide adopts a medium that absorbs ultraviolet rays Made of materials, it can reduce the intensity of ultraviolet light reflected by the surface of the low-light image intensifier, and at the same time provide a running channel for ions; an electric field isolation net is set between the ion guide and the ion detector to eliminate the impact of the ion acceleration electric field on the ion detector The impact of normal working conditions; a diaphragm is set between the electric field isolation net and the ion detector to further reduce the intensity of ultraviolet light incident through the ion guide, thereby minimizing the photocurrent generated by the ion detector excited by ultraviolet light.

The measurement method is that ions are incident on the ion detector to generate a current pulse, and sent to the charge amplifier for amplification; there are multiple sets of high-voltage power supplies in the measurement device, and the turbomolecular pump also keeps working during the test, and the residual ultraviolet light will excite the ion detector. The secondary electrons are generated by the ion detector, and the ion detector itself has an inherent dark count rate. The above-mentioned various interference factors will affect the detection of the extremely weak ion current. Therefore, a multi-channel pulse amplitude analyzer is connected to the rear end of the charge amplifier to Analyze the pulse amplitude of the output signal of the charge amplifier to find the critical point of the ion signal pulse and the noise pulse, so as to determine the amplitude characteristics of the ion signal pulse; Due to the influence of the working speed of the channel pulse amplitude analyzer, signal loss occurs, which affects the measurement accuracy of the ion signal pulse. A single channel spectrometer is connected to the back end of the charge amplifier at the same time, and the threshold voltage of the ion pulse is obtained according to the pulse amplitude analysis results. , so that the non-missing counting measurement of ion signal pulses is realized on a single-channel spectrometer, and the measurement accuracy is greatly improved.

The test device and method provided by the invention can realize the measurement of the feedback ion flow of the microchannel plate with and without the membrane, so as to realize the measurement of the ion barrier property of the anti-ion feedback membrane.

Description of drawings

Below in conjunction with accompanying drawing and specific embodiment the present invention will be further described

Fig. 1 is the sketch map of feedback ion testing device of micro-light image intensifier assembly of the present invention

Fig. 2 is the signal pulse amplitude analysis result of the present invention

Figure 3 shows the analysis results of the signal pulse amplitude enlarged along the y-axis

In the figure 1-focused ultraviolet light source, 2-ultraviolet window, 3-vacuum chamber, 4-non-cathode low-light image intensifier assembly, 5-electric field isolation grid, 6-diaphragm, 7-ion guide, 8-ion detection Device, 9-shielding box, 10-charge amplifier, 11-multi-channel pulse amplitude analyzer, 12-single-channel spectrometer.

Detailed ways

Fig. 1 is a schematic diagram of the low-light image intensifier component feedback ion test device of the present invention, and the device of the present invention will be further described below.

The device of the present invention includes a focused ultraviolet light source 1, a vacuum chamber 3 with an ultraviolet window 2 arranged at the top, a cathode-less low-light image intensifier assembly 4, an ion guide 7 seamlessly connected with the ion entrance, and a built-in electric field isolation grid 5, The shield box 9 of the diaphragm 6 and the ion detector 8, the charge amplifier 10, the multi-channel pulse amplitude analyzer 11, and the single-channel spectrometer 12; The upper surface of the optical image intensifier assembly is guaranteed not to cover the upper surface; the ion detector is connected to the charge amplifier; the single-channel spectrometer and the multi-channel pulse amplitude analyzer are respectively connected to the charge amplifier; the low-light image intensifier assembly and the ion detection assembly are both Placed in a vacuum chamber where the projection of the exit of the ion guide along the axial direction completely covers the diaphragm.

During measurement, the ultraviolet light spot is focused on the upper surface of the non-cathode low-light image intensifier component, and the ultraviolet light excites the micro-channel plate to generate secondary electrons as the incident electrons of the micro-channel plate. After the low-light image intensifier component is close to the space, a high-density electron cloud is formed, and the residual gas molecules in the component are bombarded to form ions. After the ions are accelerated by the working voltage of the micro-channel plate, they are fed back to the input end of the micro-channel plate to form feedback ions. Under the action of the ion accelerating electric field, it is incident to the ion detector, thereby forming a current pulse formed by ion excitation, and the extremely weak ion current can be measured by counting the current pulse.

However, there are high-voltage power supply, turbomolecular pump, residual ultraviolet light excitation ion detector, ion detector dark count rate and other influencing factors in the measuring device, which generate a large number of interference pulses and affect the detection of extremely weak ion current. After analysis It can be seen that the amplitude of the interference pulse signal is generally low. Figure 2 shows the result of the pulse amplitude analysis of the output signal of the charge amplifier. There are a large number of interference pulse signals in the low amplitude range.

In the case of a large number of pulse signal inputs, a relatively small number of ion signal pulses will cause signal loss due to the influence of the working speed of the multi-channel pulse amplitude analyzer, thereby affecting the measurement accuracy of ion signal pulses. In order to solve the problem of ion signal pulse loss, a multi-channel pulse amplitude analyzer is connected to the back end of the charge amplifier to analyze the pulse amplitude of the output signal of the charge amplifier, find the critical point of the ion signal pulse and the noise pulse, and determine the ion signal pulse Fig. 3 is the y-axis enlarged result of the pulse amplitude analysis result in Fig. 2. It can be seen from Fig. 3 that in this embodiment, the interference pulse and the ion signal pulse have an obvious critical point in track 65. A single-channel spectrometer is connected to the back end of the charge amplifier at the same time, and the number of channels that generate the critical point is converted into a voltage value as the threshold voltage of the single-channel spectrometer, which filters out the counting of interference pulses, thereby realizing the lossless counting of ion signal pulses measurement, which greatly improves the measurement accuracy, thereby realizing the purpose of the low-light image intensifier component feedback ion test, so that the ion barrier characteristics of the anti-ion feedback film in the low-light device can be measured quantitatively with high precision, and its performance can be objectively evaluated .

It should be pointed out that, on the basis of not departing from the technical idea of the present invention, the testing device and method formed by any form of equivalent substitution all belong to the protection scope of the present invention.

Claims (7)

1. A low-light image intensifier assembly feedback ion test device, characterized by: including a focused ultraviolet light source (1), a vacuum chamber (3), a cathode-less low-light image intensifier assembly (4), and an ion guide (7) , an ion detector (8), and a shielding box (9); the vacuum chamber (3) is provided with an ultraviolet window (2), and the cathode-free low-light image intensifier assembly (4) inside the vacuum chamber is aligned obliquely above the ions Conduit (7); said shielding box (9) is built with electric field isolation grid (5), diaphragm (6) and ion detector (8), said ion detector (8) and charge amplifier (10) connection; the charge amplifier is respectively connected to the multi-channel pulse amplitude analyzer (11) and the single-channel spectrometer (12); the cathode-free low-light image intensifier assembly (4) and the ion detector (8) are arranged in the middle Ion guide (7), electric field isolation net (5) and aperture (6). 2. The low-light image intensifier component feedback ion test device according to claim 1, characterized in that: the spot size of the focused ultraviolet light source is adjustable. 3. The low-light image intensifier component feedback ion test device according to claim 1, characterized in that: said ion guide is seamlessly connected with the shielding box. 4. The low-light image intensifier assembly feedback ion test device according to claim 2, characterized in that the projection of the ion guide outlet along the axial direction completely covers the diaphragm. 5. A method for testing feedback ions of a low-light image intensifier component, which is characterized in that: the focused ultraviolet light, that is, the focused ultraviolet light source (1) enters the cathode-less low-light image intensifier component ( 4) On the surface of the microchannel plate, the electrons excited make the non-cathode low-light image intensifier component work, and the feedback ions generated in the non-cathode low-light image intensifier component are accelerated and separated by the ion guide (7) and electric field The grid (5) enters the ion detector (8), and the output signal is amplified by the charge amplifier (10) and then input to the multi-channel pulse amplitude analyzer (11). The ion pulse signal and the noise signal are separated by pulse amplitude analysis, and the obtained Feedback the ion pulse signal amplitude range, and input the lower limit of the signal amplitude as a threshold into the single-channel spectrometer (12) to realize ion pulse counting; wherein, the excitation light source adopts a focused ultraviolet light source with adjustable spot size. 6. The method for testing ion feedback of low-light image intensifier assembly according to claim 5, characterized in that said ion guide has an inclination angle of 30-40 degrees to the measured surface. 7. The low-light image intensifier assembly feedback ion test device according to claim 1, characterized in that: the device is used to detect the feedback ion flow in the low-light image intensifier assembly.

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