A space time-of-flight mass spectrometer based on diamond detectors

Abstract

The present invention provides a space time-of-flight mass spectrometer based on a diamond detector, which includes a secondary electron emission thin film, an electrode system, a microchannel plate detector, and electronics; the secondary electron emission thin film is used to generate secondary electrons when ions pass through; the electrode system is used to apply a voltage to the secondary electrons and guide them to the microchannel detector; the microchannel detector receives the secondary electrons and outputs signals to the electronics; the diamond detector is used to receive ions, convert the total ion energy into charge pulses, and output them to the electronics; the electronics is used to process the output signals of the microchannel detector and the charge pulses output by the diamond detector, and analyze to obtain information about the incident ions. The present invention applies the diamond detector to the SEE TOF×E mass spectrometer, which can improve the detection efficiency, long-term performance stability, and adaptability to harsh space radiation environments of the SEE TOF×E mass spectrometer.

Description

Technical Field

[0001] The present invention belongs to the technical fields of diamond detector applications, time-of-flight mass spectrometry technology, and space charged particle detection technology, and particularly relates to a space time-of-flight mass spectrometer based on a diamond detector. Background Art

[0002] Time-of-flight mass spectrometers have very important application values in the field of space charged particle detection. The SEE TOF×E mass spectrometer based on the secondary electron time-of-flight measurement technology and a solid state detector (SSD) is commonly used to measure the medium-energy ion components, energy spectra, and angular distribution information in the range of dozens of keV to several MeV in the space environment. The SEE TOF×E mass spectrometer usually consists of a secondary electron emission film, an electrode system, a micro channel plate detector (MCP detector), and a silicon detector (array), but this traditional solution has some inevitable disadvantages.

[0003] The silicon detector commonly used in the SEE TOF×E mass spectrometer is sensitive to visible light. There is often a large amount of visible light in the space environment that may interfere with the SEE TOF×E mass spectrometer. The common light shielding means is to add a certain thickness of light shielding material, such as polyimide, Ni, Al, Pd, etc., on the secondary electron emission film. In order to obtain sufficient light shielding ability, the total thickness of the film cannot be too thin, generally not less than dozens of nm. This will cause relatively serious energy loss, energy straggling, and scattering of incident ions with lower energy and larger mass numbers after passing through the film, thus affecting the energy resolution, mass resolution, and detection efficiency of the mass spectrometer for heavy ions at the low-energy end. If a thinner and lighter secondary electron emission film is used, the anti-photon interference ability of the detector will be reduced, and it can only be applied to a space environment with weak light interference. The detection performance and anti-interference ability restrict each other and are difficult to decouple.

[0004] The traditional SEE TOF×E mass spectrometer completely relies on secondary electrons to trigger the start and stop timing signals to measure the ion flight time. To ensure mechanical strength, the secondary electron emission film needs to be supported by a grid, and the transmittance is generally not higher than 90%. If two layers of films are used, the transmittance is not higher than 80%. In addition, the response efficiency of the MCP to secondary electrons is at most no more than 85%. Coupled with the fact that the collection efficiency of the electrode system for secondary electrons cannot be guaranteed to be 100%, for ions with a lower secondary electron emission efficiency (heavy ions with lower mass and higher energy), the efficiency of measuring the flight time through secondary electrons will be significantly reduced. Considering both factors, the traditional SEE TOF×E mass spectrometer's scheme of simply relying on secondary electrons to measure the flight time is not conducive to improving the detection efficiency.

[0005] During the space mission cycle, the performance of silicon detectors degrades after being irradiated by high-energy particles in space at high doses. The main mechanism is the displacement damage caused by the collision of incident particles with the silicon nuclei in the sensitive area of the silicon detector. The accumulation of a large amount of displacement damage will thicken the dead layer of the silicon detector, increase the noise, and reduce the carrier collection efficiency, thereby causing an increase in the lower limit of energy measurement, attenuation of the output pulse amplitude, and reduction of energy resolution. Therefore, it is difficult for traditional SEE TOF×E mass spectrometers based on silicon detectors to ensure long-term stable performance in space missions with long mission cycles and harsh irradiation environments. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defect that traditional SEE TOF×E mass spectrometers based on silicon detectors are difficult to ensure long-term stable performance in space missions with long mission cycles and harsh irradiation environments.

[0007] To achieve the above purpose, the present invention proposes a space time-of-flight mass spectrometer based on a diamond detector, including a secondary electron emission thin film, an electrode system, a microchannel plate detector, and electronics;

[0008] The secondary electron emission thin film is used to generate secondary electrons when ions pass through;

[0009] The electrode system is used to apply a voltage to the secondary electrons and guide them to the microchannel detector;

[0010] The microchannel detector receives the secondary electrons and outputs signals to the electronics;

[0011] The mass spectrometer further includes a diamond detector;

[0012] The diamond detector is used to receive ions, convert the total ion energy into charge pulses, and output them to the electronics;

[0013] The electronics is used to process the output signals of the microchannel detector and the charge pulses output by the diamond detector, and analyze to obtain information about the incident ions, including species and ion energy spectra.

[0014] As an improvement of the above system, the electrode system includes an acceleration electrode and a deflection electrode;

[0015] The structure of the mass spectrometer is arranged in sequence along the ion entry direction as a secondary electron emission thin film, an acceleration electrode, a deflection electrode, and a diamond detector;

[0016] A microchannel plate detector is arranged below the deflection electrode.

[0017] As an improvement of the above system, the electronics includes:

[0018] A delay module, which is used to receive the charge pulses sent by the diamond detector, divide the charge pulses into two paths, delay one path first and then output it to the fast preamplifier module, and output the other path to the preamplifier module;

[0019] A fast preamplifier module, which is used to receive the signals sent by the microchannel detector or the delay module, amplify the signals, and then output them to the constant fraction timing discriminator;

[0020] A preamplifier module, which is used to pre-amplify the received signals and then output them to the main amplifier;

[0021] A main amplifier, which is used to amplify and shape the received signals and then output them to the peak hold circuit;

[0022] A peak hold circuit, which is used to pick up the pulse amplitude of the received signals and then send the processed signals to the analog-to-digital converter;

[0023] An analog-to-digital converter, which is used to convert the received signals into analyzable digital quantities ESSD and output them to the programmable array logic;

[0024] A constant fraction timing discriminator, which is used to pick up the timing of the signals and then send them to the time-to-digital converter;

[0025] A time-to-digital converter, which is used to process the signals whose sources are the diamond detector and the microchannel detector respectively, convert the time difference of the signals into analyzable digital quantity τ, and output it to the programmable array logic;

[0026] A programmable array logic, which is used to perform coincidence measurement and analysis processing on τ and ESSD to obtain information about the incident ions, and the information includes the type and ion energy spectrum.

[0027] As an improvement of the above system, the delay is 2 ns.

[0028] As an improvement of the above system, the mass spectrometer includes 1 secondary electron emission film, 1 electrode system, 1 microchannel detector and 1 diamond detector.

[0029] As an improvement of the above system, the mass spectrometer includes 1 secondary electron emission film, 1 electrode system, 1 microchannel detector and n diamond detectors; n > 1.

[0030] As an improvement of the above system, the mass spectrometer includes n secondary electron emission films, n electrode systems, n microchannel detectors; n > 1;

[0031] The electronics device further includes a position resolution signal processing module, which is used to receive the position resolution signals, process and analyze them to obtain the incident position information of the ions, and then send them to the programmable array logic;

[0032] After the microchannel detector receives the secondary electrons, it outputs a signal for position resolution and a timing signal; the signal for position resolution is output to the position resolution signal processing module; the timing signal is output to the fast preamplifier module.

[0033] As an improvement to the above system, the diamond detector included in the mass spectrometer is one or more.

[0034] As an improvement to the above system, the programmable array logic performs coincidence measurement and analysis processing on the position information, τ, and ESSD to obtain information about the incident ions, and the information includes species, ion energy spectrum, and angular distribution information.

[0035] Compared with the prior art, the advantages of the present invention are as follows:

[0036] 1. The diamond detector is insensitive to visible light, reducing the requirement for visible light shielding in the SEE TOF×E mass spectrometer. There is no need to add light shielding material on the secondary electron film, and the thickness can also be reduced, thereby reducing the energy loss, energy straggling, and scattering of incident ions, and improving the measurement efficiency of ions with lower energy and larger mass.

[0037] 2. When using the diamond detector for time-of-flight measurement, a secondary electron emission film can be omitted, avoiding the influence of the support grid on the ion transmission rate, and also avoiding the reduction of measurement efficiency caused by factors such as secondary electron emission yield, collection efficiency, and MCP response efficiency.

[0038] 3. The diamond detector has strong anti-interference ability and better performance stability in space missions with harsh space radiation environments and long mission cycles. Description of the Drawings

[0039] Figure 1 The figure shows a schematic diagram of a SEE TOF×E mass spectrometer based on a diamond detector;

[0040] Figure 2 The figure shows a schematic diagram of a unidirectional implementation scheme;

[0041] Figure 3 The figure shows a schematic diagram of a multi-channel SEE start, single diamond scheme;

[0042] Figure 4 The figure shows a schematic diagram of a single-channel SEE start, multi-diamond scheme;

[0043] Figure 5 The figure shows a schematic diagram of a multi-channel SEE start, multi-diamond scheme;

[0044] Figure 6The figure shows the electronic block diagram of the unidirectional implementation scheme;

[0045] Figure 7 The figure shows the electronic block diagram of the single SEE start and multi-diamond scheme;

[0046] Figure 8 The figure shows the electronic block diagram of the multi-channel SEE start and single-channel diamond detector scheme. Detailed implementation mode

[0047] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0048] The probe of the present invention is composed as Figure 1 shown in the figure. The silicon detector in the traditional scheme of the SEE TOF×E mass spectrometer is replaced with a single-crystal diamond detector. A secondary electron emission film is used to provide secondary electrons and deflect them to the MCP through electrodes to trigger the start signal. Then, the pulse generated by the ions depositing energy in the diamond detector and output is used as both the stop signal and the energy signal ESSD at the same time. The ion flight distance L is determined by the distance between the secondary electron emission film and the diamond detector. The larger L is, the higher the mass resolution is.

[0049] The secondary electron emission film is located at the incident end of the ion optical path, and its main function is to provide the secondary electrons required for time-of-flight measurement.

[0050] The electrode system generally includes two parts: an acceleration electrode and a deflection electrode. The acceleration electrode is set 1-2 mm away from the secondary electron emission surface. By applying a voltage difference between the film and the acceleration electrode, an electric potential difference is generated to accelerate the secondary electrons and guide them to the deflection electrode. The deflection electrode is located between the acceleration electrode and the diamond detector. By applying different voltages to the deflection electrode and the MCP surface, an electric potential difference is generated to deflect the secondary electrons and guide them to the MCP surface.

[0051] The SEE TOF×E mass spectrometer based on the diamond detector can adopt unidirectional and multi-directional implementation schemes.

[0052] The unidirectional implementation scheme is as Figure 2 shown in the figure. One-channel SEE start timing measurement is used, and one diamond detector provides the stop and ESSD signals.

[0053] There are three ways for the multi-directional implementation scheme:

[0054] 1. Multi-channel SEE start measurement, and single-channel diamond detector measures stop and ESSD;

[0055] 2. Single-channel SEE start measurement, and multi-channel diamond detector measures stop and ESSD;

[0056] 3. Multi-channel SEE start measurement, multi-channel diamond detector measurement of stop and ESSD.

[0057] As Figure 2 and Figure 6 shown, Embodiment 1 of the present invention proposes a space time-of-flight mass spectrometer based on a diamond detector:

[0058] The probe consists of a collimator, a set of SEE time measurement systems, and a diamond detector. The SEE time measurement system includes a secondary electron emission film, an electrode system, and an MCP detector. By applying appropriate voltages to the electrode system and the MCP detector to construct an internal electric field, the secondary electrons emitted when ions pass through are deflected onto the MCP to trigger the start timing signal. The ions deposit energy in the diamond detector and are converted into charge pulses for output. The start signal is amplified by a fast preamplifier, and the constant fraction discriminator (CFD) is used for timing pickup and then input into the time-to-digital converter (TDC). The charge pulses output by the diamond detector are preamplified by a charge-sensitive preamplifier, and the output pulses are divided into two paths. One path first undergoes a delay of approximately 2 ns, then enters the CFD for timing pickup, and is then input into the TDC as the stop signal. The TDC converts the time difference between the start signal and the stop signal into an analyzable digital quantity τ. The other path of the charge pulses output by the diamond detector enters the charge-sensitive preamplifier for preamplification, then is amplified and shaped by the main amplifier, and then the pulse amplitude is picked up by the peak hold circuit, and then is converted into an analyzable digital quantity ESSD output through the analog-to-digital converter (AD). By performing coincidence measurement and logical analysis on τ and ESSD through the field programmable gate array (FPGA), information such as the type and energy of the incident ions can be obtained.

[0059] As Figure 4 and Figure 7 shown, Embodiment 2 of the present invention proposes a space time-of-flight mass spectrometer based on a diamond detector:

[0060] The electronics block diagram of the multi-direction implementation scheme of single-channel SEE start combined with multi-channel diamond detectors is as Figure 7As shown, the electronics of the single-channel SEE start is consistent with the unidirectional scheme. The electronics of the multi-channel diamond detector is similar to the unidirectional scheme. The signal output from each channel of the diamond is split into two. One is processed as the stop signal, and the other is processed as the ESSD signal. Each incident ion can trigger a set of start, stop, and ESSD. The stop and ESSD are output from the same channel of the diamond detector. By performing coincidence measurement and logical analysis on the signals through the FPGA, information such as the type, energy spectrum, and angular distribution of the incident ions can be obtained.

[0061] As Figure 3 and Figure 8 shown, Embodiment 3 of the present invention proposes a time-of-flight mass spectrometer in space based on a diamond detector:

[0062] The electronics block diagram of the multi-direction implementation scheme of the multi-channel SEE start combined with a single-channel diamond detector is as Figure 8 shown. The multi-channel SEE start needs to use a position-sensitive anode for position identification. When the MCP receives the secondary electrons emitted by the thin film, it will trigger the position-sensitive anode to output several signals for position resolution (depending on the type of the position-sensitive anode) and a timing signal start. The electronics of the diamond detector is similar to the unidirectional scheme. The signal output from each channel of the diamond is split into two. One is processed as the stop signal, and the other is processed as the ESSD signal. Each incident ion can trigger a set of anode positions, start, stop, and ESSD. By performing coincidence measurement and logical analysis on these signals through the FPGA, information such as the type, energy spectrum, and angular distribution of the incident ions can be obtained.

[0063] As Figure 5 shown, Embodiment 4 of the present invention proposes a time-of-flight mass spectrometer in space based on a diamond detector:

[0064] The electronics block diagram of the multi-channel SEE start combined with the multi-channel diamond detector can combine the forms of (3) and (4). The multi-channel SEE start is output by the position-sensitive anode combined with the corresponding electronics, and the ion incident position information and the start timing signal can be obtained. As Figure 8 . The electronics of the multi-channel diamond detector is in the form of Figure 7 , and multiple stop signals and ESSD signals can be output. When an ion is incident, a set of anode positions, start, stop, and ESSD will be obtained. The stop and ESSD are output from the same channel of the diamond detector. By performing coincidence measurement and logical analysis on this information through the FPGA, information such as the type, energy spectrum, and angular distribution of the incident ions can be obtained.

[0065] The present invention applies a diamond detector to a SEE TOF×E mass spectrometer, which is used for both time-of-flight measurement and energy measurement. By taking advantage of the advantages of the diamond detector, such as insensitivity to visible light, fast time response, and strong anti-radiation ability, the detection efficiency, long-term performance stability, and adaptability to harsh space radiation environments of the SEE TOF×E mass spectrometer can be improved.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A space time-of-flight mass spectrometer based on a diamond detector, comprising a secondary electron emission thin film, an electrode system, a microchannel plate detector, and electronics; The secondary electron emission thin film is used to generate secondary electrons when ions pass through; The electrode system is used to apply a voltage to the secondary electrons and guide them to the microchannel detector; The microchannel detector is used to receive the secondary electrons and output signals to the electronics; It is characterized in that The mass spectrometer further includes a diamond detector; The diamond detector is used to receive ions, convert the total ion energy into a charge pulse, and output it to the electronics; the charge pulse output by the diamond detector serves as both a stop signal and an energy signal ESSD; The electronics is used to process the output signals of the microchannel detector and the charge pulses output by the diamond detector, and analyze to obtain information about the incident ions, including species and ion energy spectra; The electrode system includes an acceleration electrode and a deflection electrode; The structure of the mass spectrometer is arranged in sequence along the ion entry direction with a secondary electron emission thin film, an acceleration electrode, a deflection electrode, and a diamond detector; A microchannel plate detector is arranged below the deflection electrode.

2. The space time-of-flight mass spectrometer based on a diamond detector according to claim 1, wherein, The electronics includes: A delay module, used to receive the charge pulses sent by the diamond detector, divide the charge pulses into two paths, delay one path first and then output it to the fast preamplifier module, and output the other path to the preamplifier module; A fast preamplifier module, used to receive the signals sent by the microchannel detector or the delay module, amplify the signals, and then output them to the constant fraction timing discriminator; A preamplifier module, used to pre-amplify the received signals and then output them to the main amplifier; A main amplifier, used to amplify and shape the received signals and then output them to the peak hold circuit; A peak hold circuit, used to pick up the pulse amplitude of the received signals and then send the processed signals to the analog-to-digital converter; An analog-to-digital converter, used to convert the received signals into analyzable digital quantities ESSD and output them to the programmable array logic; A constant fraction timing discriminator, used to pick up the timing of the signals and then send them to the time-to-digital converter; A time-to-digital converter, used to process the signals whose sources are the diamond detector and the microchannel detector respectively, convert the time difference of the signals into analyzable digital quantities τ, and output them to the programmable array logic; A programmable array logic, used to perform coincidence measurement and analysis processing on τ and ESSD to obtain information about the incident ions, and the information includes species and ion energy spectra.

3. The space time-of-flight mass spectrometer based on a diamond detector according to claim 2, wherein, The mass spectrometer includes 1 secondary electron emission thin film, 1 electrode system, 1 microchannel detector, and 1 diamond detector.

4. The space time-of-flight mass spectrometer based on a diamond detector according to claim 2, wherein, The mass spectrometer includes 1 secondary electron emission thin film, 1 electrode system, 1 microchannel detector, and n diamond detectors; n > 1.

5. The time-of-flight mass spectrometer in space based on a diamond detector according to claim 2, characterized in that the mass spectrometer includes n secondary electron emission films, n electrode systems, and n microchannel detectors; n > 1; the electronics device further includes a position resolution signal processing module, configured to receive the position resolution signal, process and analyze it to obtain the incident position information of the ions, and then send it to the programmable array logic; after receiving the secondary electrons, the microchannel detector outputs a signal for position resolution and a timing signal; the signal for position resolution is output to the position resolution signal processing module; the timing signal is output to the fast preamplifier module.

6. The time-of-flight mass spectrometer in space based on a diamond detector according to claim 5, characterized in that the diamond detector included in the mass spectrometer is one or more.

7. The time-of-flight mass spectrometer in space based on a diamond detector according to any one of claims 4 to 6, characterized in that the programmable array logic performs coincidence measurement and analysis processing on the position information, τ, and ESSD to obtain information on the incident ions, and the information includes species, ion energy spectrum, and angular distribution information.

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