A time-of-flight based energy ion spectrometer in space

Abstract

The application provides a time-of-flight method-based ion spectrometer in space, which comprises a secondary electron emission film, an electrode system, a micro-channel plate detector, a solid-state detector and an electronic device. The secondary electron emission film is used for generating secondary electrons when ions pass through; the electrode system is used for guiding the secondary electrons to the micro-channel plate detector under the action of a voltage; the micro-channel plate detector receives the secondary electrons and outputs start signals and stop signals; the solid-state detector is used for receiving ions and converting total energy of the ions into a charge signal; and the electronic device is used for processing the start signals, the stop signals and the charge signal to obtain information of incident ions. The application fills the gap of the space heavy ion composition and energy spectrum measurement technology in the energy range of tens of keV to several MeV in China, and realizes full-element and full-spectrum covering capability of space charged particles.

Description

Technical Field

[0001] This invention belongs to the field of space charged particle detection technology, specifically relating to a space medium-energy ion spectrometer based on the time-of-flight method. Background Technology

[0002] In the space environment, heavy ions (1≤Z≤26) with energies between tens of keV and several MeV are generally referred to as medium-energy ions. Currently, space charged particle detectors capable of ion composition analysis and energy measurement generally employ two principles: the "electrostatic analyzer + time-of-flight method" and the "ΔE-E telescope method" based on semiconductor detectors.

[0003] The "electrostatic analyzer + time-of-flight" method is limited by the voltage applied by the electrostatic analyzer, achieving a maximum heavy ion resolution of no more than 40 keV / e, making it difficult to cover higher-energy heavy ions. Energy measurement requires gradation using the scanning voltage of the electrostatic analyzer, making it impossible to simultaneously measure incident ions in the continuous energy spectrum, resulting in low detection efficiency. The "ΔE-E telescope method" can simultaneously achieve ion component resolution and energy measurement in the continuous energy spectrum, but this method is limited by the thickness of the first thin semiconductor detector. With current technology, the lower energy limit for ion component resolution using this method is ≥400 keV. The energy gap between 40 and 400 keV is difficult for both detector principles to cover. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing equipment in being unable to perform compositional analysis and energy measurement of ions with energies between 40 and 400 keV.

[0005] To achieve the above objectives, this invention proposes a space-based medium-energy ion spectrometer based on the time-of-flight method, comprising a secondary electron emission thin film, an electrode system, a microchannel plate detector, a solid-state detector, and electronic devices;

[0006] The secondary electron emission film is used to generate secondary electrons when ions pass through it, and includes a start film and a stop film;

[0007] The electrode system is used to guide the applied voltage of the secondary electrons onto the microchannel detector. The electrode system includes an accelerating electrode and a deflecting electrode. The accelerating electrode includes a start accelerating electrode and a stop accelerating electrode.

[0008] The microchannel detector receives the secondary electrons and outputs start and stop signals, including an upper surface, a lower surface, a start anode, and a stop anode;

[0009] The solid-state detector is used to receive ions and convert the total energy of the ions into a charge signal.

[0010] The electronic device is used to process start signals, stop signals, and charge signals to obtain information about the incident ions, including their type and energy spectrum.

[0011] Along the ion entry direction, the start film, start accelerating electrode, deflection electrode, stop accelerating electrode, stop film and solid detector are sequentially arranged;

[0012] A microchannel plate detector is placed below the deflection electrode.

[0013] As an improvement to the above system, the electronic device includes:

[0014] The fast preamplifier is used to receive the start signal sent by the start anode and the stop signal sent by the stop anode, amplify the signals, and then send them to the constant ratio timing discriminator.

[0015] A constant ratio timing discriminator is used to pick up the start and stop signals for timing and send the timing signals to a time-to-digital converter.

[0016] A time-to-digital converter is used to convert the timing signals of the start and stop signals into a digital quantity τ that can be analyzed and output to the programmable array logic.

[0017] A charge-sensitive preamplifier is used to receive the charge signal sent by the solid-state detector, perform large-scale protection, and then send it to the main amplifier;

[0018] The main amplifier is used to amplify and shape the charge signal before sending it to the peak hold circuit.

[0019] The peak hold circuit is used to pick up the pulse amplitude of the charge signal and then send the widened signal to the analog-to-digital converter.

[0020] Analog-to-digital converters are used to convert charge signals into analyzable digital quantities, which are then output to programmable array logic (ESSD).

[0021] Programmable array logic is used to perform coincidence measurement and analysis on τ and ESSD to obtain information about the incident ions, including their species and ion energy spectrum.

[0022] As an improvement to the above system, the accelerating electrode is disposed 1-2 mm above the surface of the secondary electron emission film. A potential difference is generated by applying a voltage difference to the film and the accelerating electrode, which accelerates the secondary electrons and guides them toward the deflection electrode.

[0023] By applying different voltages to the deflection electrode and the surface of the microchannel plate detector, a potential difference is generated, which deflects and guides the secondary electrons to the surface of the microchannel plate detector.

[0024] As an improvement to the above system, the secondary electron thin film, the accelerating electrode, and the deflecting electrode are connected to a negative high voltage; the upper surface of the microchannel plate detector is grounded; and a positive high voltage is applied to the lower surface of the microchannel plate detector, the start anode, and the stop anode.

[0025] As an improvement to the above system, the secondary electron thin film is grounded; the accelerating electrode is connected to a negative high voltage; the upper surface, lower surface, start anode, and stop anode of the microchannel plate detector are all connected to a positive high voltage; and the deflection electrode is connected to a negative high voltage.

[0026] As an improvement to the above system, the secondary electron thin film, the accelerating electrode, the deflecting electrode, the upper surface of the microchannel plate detector, and the lower surface of the microchannel plate detector are all connected to a negative high voltage; the start anode and stop anode of the microchannel plate detector are grounded.

[0027] As an improvement to the above system, the secondary electron emission thin film includes n start films and 1 stop film; the accelerating electrode includes n start accelerating electrodes and 1 stop accelerating electrode; the microchannel detector includes n start anodes and 1 stop anode; n>1;

[0028] The start anode receives secondary electrons and outputs a signal for position resolution and a start signal for timing.

[0029] As an improvement to the above system, the secondary electron emission thin film includes one start thin film and n stop thin films; the accelerating electrode includes one start accelerating electrode and n stop accelerating electrodes; the microchannel detector includes one start anode and n stop anodes; n>1; each stop thin film corresponds to one solid-state detector;

[0030] The stop anode receives secondary electrons and outputs a signal for position resolution and a stop signal for timing.

[0031] As an improvement to the above system, the secondary electron emission thin film includes n start films and n stop films; the accelerating electrode includes n start accelerating electrodes and n stop accelerating electrodes; n>1; each stop film corresponds to a solid-state detector;

[0032] The start anode receives secondary electrons and outputs a signal for position resolution and a start signal for timing.

[0033] The stop anode receives secondary electrons and outputs a signal for position resolution and a stop signal for timing.

[0034] As an improvement to the above system, the electronic device also includes a position resolution signal processing module, which is used to receive the position resolution signal sent by the start anode or stop anode, process and analyze it to obtain the incident position information of the ions, and then send it to the programmable array logic.

[0035] The programmable array logic performs coincidence measurement and analysis on the position information, τ, and ESSD to obtain information about the incident ions, including the type, ion energy spectrum, and angular distribution information.

[0036] Compared with the prior art, the advantages of the present invention are:

[0037] This invention addresses the current gap in China's technology for measuring the composition and energy spectrum of heavy ions in the energy range of tens of keV to several MeV. my country already possesses measurement technologies for low-energy electrons, low-energy ions, medium-energy electrons, medium-energy protons, high-energy electrons, and high-energy ions in space. Combined with the medium-energy heavy ion measurement capabilities provided by this invention, my country will achieve full-element and full-spectrum coverage of charged particles in space. Attached Figure Description

[0038] Figure 1 The diagram shown is a schematic of the TOF×E method.

[0039] Figure 2 The diagram shown is a basic schematic of the probe.

[0040] Figure 3 The diagram shows the electrode system and the MCP detector, illustrating how the internal electric field guides secondary electrons.

[0041] Figure 4 The diagram shown is a schematic of a unidirectional implementation method;

[0042] Figure 5 The diagram shows a multi-start, single-stop, single-SSD implementation scheme.

[0043] Figure 6 The diagram shows a single-start, multi-stop, multi-SSD implementation scheme.

[0044] Figure 7 The diagram shows a multi-start, multi-stop, multi-SSD implementation scheme.

[0045] Figure 8 The diagram shown is an electronic block diagram of a unidirectional implementation scheme.

[0046] Figure 9 The diagram shown is an electronic block diagram of a multi-directional implementation scheme. Detailed Implementation

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

[0048] (1) Principle of TOF×E method

[0049] The energy E, velocity v, and mass m of a medium-energy ion conform to the kinetic energy formula.

[0050]

[0051] The flight time τ between the incident ion and the distance L is measured by two timed detectors, start and stop, which are spaced L apart. The ion's velocity v = L / τ can then be obtained. The residual energy ESSD of the ion is then measured using a solid-state detector (SSD). For different types of ions, due to their different masses, the correspondence between the measured τ and ESSD depends on the ion's mass m. Analysis of τ and ESSD allows for the differentiation of ion types.

[0052] After obtaining ion type information, the incident energy E of the ion can be obtained in two ways. For higher-energy ions, the energy loss ΔE in the time-of-flight detector is smaller, and the measurement accuracy of ESSD is higher. Through correction, the ion incident energy E = ΔE + E can be obtained. SSD For ions with lower energy, the ion energy can be corrected using the methods described above, or the ion's energy ETOF during flight can be calculated using the time-of-flight (τ) and ion mass (m), and then the energy loss ΔE of the ion in the start-time detector can be corrected. start The incident ion energy E = ΔE can then be obtained. start +E TOF .

[0053] (2) Probe Composition

[0054] This invention utilizes the TOF×E method to measure the composition and energy of medium-energy ions. The probe consists of two secondary electron emission thin films (start and stop films), an electrode system (accelerating electrode and deflecting electrode), a microchannel plate detector (MCP detector), and an SSD.

[0055] The basic structure of the probe of this invention is as follows: Figure 2As shown, ions enter the probe through the collimator at the entrance, passing through the start and stop films successively. The resulting secondary electrons are guided to the MCP detector by a voltage applied through the electrode system, and receive gain electrons through the start and stop anodes respectively, generating timing signals start and stop. Finally, the ions enter the SSD sensitive region, depositing all their energy there and converting it into the charge signal ESSD output.

[0056] The ion flight distance L is determined by the distance between the two secondary electron thin films. The longer L is, the higher the quality resolution. It can be adjusted according to the quality resolution requirements.

[0057] (3) Secondary electron emission thin film

[0058] The secondary electron emission thin film is located at the incident end (start) and the end (stop) of the ion optical path. Its main function is to provide secondary electrons required for time-of-flight measurement. Materials with high secondary electron emission yields such as C, Al, and Ni can be used. If necessary, light-absorbing material layers such as polyimide and Pd can be added to the thin film to reduce light pollution.

[0059] Secondary electrons that trigger the stop signal are generally emitted through a stop film, but can also be provided directly using the electrode material on the surface of the silicon semiconductor detector, or by depositing secondary electron emission material on the surface of the silicon semiconductor detector.

[0060] (4) Construction of internal electric field

[0061] It is necessary to apply specific voltages to the start and stop films, the electrode system, and the surface of the MCP detector to create an internal electric field, which will accelerate, deflect, and guide the ion-triggered secondary electrons to a specific position on the MCP surface to trigger a timing signal.

[0062] An electrode system generally consists of two parts: an accelerating electrode and a deflecting electrode. The accelerating electrode is positioned 1-2 mm above the secondary electron emission surface. A potential difference is generated by applying a voltage difference between the thin film and the accelerating electrode, accelerating the secondary electrons and guiding them towards the deflecting electrode. The deflecting electrode is located between the start and stop films. A potential difference is generated by applying different voltages to the deflecting electrode and the MCP surface, deflecting the secondary electrons and guiding them to the MCP surface. By controlling the potential difference between the thin film, the electrode, and the MCP, the following three electrification methods can create the same internal electric field:

[0063] a. The secondary electron thin film, accelerating electrode and deflecting electrode are connected to negative high voltage, the upper surface of the MCP is grounded, and positive high voltage is applied to the lower surface and anode.

[0064] b. The secondary electron thin film is grounded, and the accelerating electrode, the upper and lower surfaces of the MCP and the anode are all connected to positive high voltage, while the deflection electrode is connected to negative high voltage.

[0065] c. The secondary electron thin film, accelerating electrode, deflecting electrode, upper surface of MCP, and lower surface of MCP are all connected to negative high voltage, and the anode is grounded.

[0066] The specific voltage value needs to be set according to the morphological relationship between the thin film, electrodes and MCP and the performance requirements of the detector.

[0067] (5) MCP detector

[0068] In this invention, secondary electrons are received and start and stop signals are output through an MCP detector. This can be achieved by the two anodes of a set of MCP detectors, or by two different sets of MCP detectors.

[0069] (6) SSD

[0070] In principle, SSDs can use detectors such as semiconductor detectors and scintillation detectors that can convert the total ion energy into an analyzable electrical signal, and the choice can be made according to specific performance requirements. The principle for selecting an SSD is that its thickness must be sufficient to completely deposit all remaining ion energy.

[0071] (7) Unidirectional and multidirectional implementation schemes

[0072] This invention can be implemented in unidirectional and multidirectional ways.

[0073] The unidirectional implementation scheme includes one start measurement, one stop measurement, and one SSD ( Figure 4 The start measurement is achieved by the start film in conjunction with the corresponding electrode and MCP anode, and the stop measurement is achieved by the stop film (or SSD surface material) in conjunction with the corresponding electrode and MCP anode.

[0074] Multi-directional implementation schemes can be broadly categorized into three types:

[0075] a. Multi-channel start measurement, single-channel stop measurement, single-channel SSD ( Figure 5 );

[0076] b. Single-channel start measurement, multi-channel stop measurement, multi-channel SSD ( Figure 6 );

[0077] c. Multi-channel start measurement, multi-channel stop measurement, multi-channel SSD ( Figure 7 ).

[0078] Multi-channel start and stop measurements require the use of a position-sensitive anode in an MCP. The diagrams are shown in three directions, but measurements in more directions can be achieved in the same way.

[0079] 1) Unidirectional Implementation Plan

[0080] The probe configuration of the unidirectional embodiment of the present invention is as follows Figure 2 As shown, the structure, arranged according to the ion incident direction, includes a collimator, a start film, a stop film, an electrode system, an MCP detector, and an SSD. A high-voltage power supply is used to power the electrode system, the MCP detector, and the SSD. Figure 8 As shown, ions passing through the start and stop films emit secondary electrons, which are deflected by the constructed internal electric field and guided to the surface of the MCP detector, triggering two timing signals, start and stop. These timing signals are amplified using two fast preamplifiers, then picked up by two constant-fraction discriminators (CFDs), and finally input to a time-to-digital converter (TDC) to convert the time difference between the start and stop signals into an analyzable digital output, τ. After passing through the films, the ions enter the sensitive region of the SSD, depositing all their energy and converting it into a charge signal output. This signal is amplified by a charge-sensitive preamplifier, then amplified and shaped by the main amplifier. A peak-hold circuit is used to pick up the pulse amplitude, and the broadened signal is then converted into an analyzable digital output, ESSD, via an analog-to-digital converter (AD). Finally, a field-programmable gate array (FPGA) is used to perform coincidence measurement and analysis on τ and ESSD to obtain information on the type and energy of the incident ions.

[0081] 2) Multi-directional implementation plan

[0082] Taking a multi-channel start, single-channel stop, and single-channel SSD implementation as an example, the start anode of the MCP detector adopts a one-dimensional position-sensitive design. For example... Figure 9As shown, when ions are incident from a certain direction, the start anode receives secondary electrons emitted from the start film corresponding to that direction and outputs several signals for position resolution (depending on the specific form of the position-sensitive anode) and a start signal for timing. Secondary electrons emitted by ions passing through the stop film are received by a single stop anode, which outputs a stop signal. This signal is then received by the SSD and outputs a charge pulse. Processing and analyzing the position resolution signals yields the ion incident position information. The start and stop signals are amplified by a fast preamplifier and picked up by a CFD before being input to the TDC, converting the time difference into a digital quantity τ. The charge pulse output by the SSD is converted into a digital quantity ESSD after passing through a preamplifier, main amplifier, peak protector, and AD converter. By performing coincidence measurement and logic analysis on the position information, τ, and ESSD using an FPGA, the ion species, ion energy spectrum, and angular distribution information can be obtained.

[0083] The other two multi-directional implementation schemes also adopt a similar approach. The "single start, multiple stop, multiple SSD" scheme requires position analysis of the stop signal, while the "multiple start, multiple stop, multiple SSD" scheme requires position analysis of both the start and stop signals. The SSD electronics are changed from a single group to multiple groups, and the measurement and logic analysis methods will be adjusted accordingly.

[0084] This invention combines a time-of-flight measurement system based on secondary electrons and an MCP detector with an energy measurement system based on SSD, achieving ion species resolution and energy spectrum measurement in the tens of keV to several MeV range using the TOF×E method. This addresses the current gap in domestic technology for measuring the composition and energy spectrum of space heavy ions in the tens of keV to several MeV energy range. my country currently possesses measurement technologies for low-energy electrons, low-energy ions, medium-energy electrons, medium-energy protons, high-energy electrons, and high-energy ions in space. Combined with the medium-energy heavy ion measurement capability provided by this invention, my country will achieve full-element and full-spectrum coverage of charged particles in space.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A space-based medium-energy ion spectrometer based on the time-of-flight method, comprising a secondary electron emission thin film, an electrode system, a microchannel plate detector, a solid-state detector, and electronic devices; The secondary electron emission film is used to generate secondary electrons when ions pass through it, and includes a start film and a stop film; The electrode system is used to guide the applied voltage of the secondary electrons onto the microchannel detector. The electrode system includes an accelerating electrode and a deflecting electrode. The accelerating electrode includes a start accelerating electrode and a stop accelerating electrode. The microchannel detector receives the secondary electrons and outputs start and stop signals, including an upper surface, a lower surface, a start anode, and a stop anode; The solid-state detector is used to receive ions and convert the total energy of the ions into a charge signal. The electronic device is used to process start signals, stop signals, and charge signals to obtain information about the incident ions, including their type and energy spectrum. Along the ion entry direction, the start film, start accelerating electrode, deflection electrode, stop accelerating electrode, stop film and solid detector are sequentially arranged; A microchannel plate detector is placed below the deflection electrode.

2. The space-based medium-energy ion spectrometer based on the time-of-flight method according to claim 1, characterized in that, The electronic device includes: The fast preamplifier is used to receive the start signal sent by the start anode and the stop signal sent by the stop anode, amplify the signals, and then send them to the constant ratio timing discriminator. A constant ratio timing discriminator is used to pick up the start and stop signals for timing and send the timing signals to a time-to-digital converter. A time-to-digital converter is used to convert the timing signals of the start and stop signals into a digital quantity τ that can be analyzed and output to the programmable array logic. A charge-sensitive preamplifier is used to receive the charge signal sent by the solid-state detector, perform large-scale protection, and then send it to the main amplifier; The main amplifier is used to amplify and shape the charge signal before sending it to the peak hold circuit. The peak hold circuit is used to pick up the pulse amplitude of the charge signal and then send the widened signal to the analog-to-digital converter. Analog-to-digital converters are used to convert charge signals into analyzable digital quantities, which are then output to programmable array logic (ESSD). Programmable array logic is used to perform coincidence measurement and analysis on τ and ESSD to obtain information about the incident ions, including their species and ion energy spectrum.

3. The space-based medium-energy ion spectrometer based on the time-of-flight method according to claim 1, characterized in that, The accelerating electrode is disposed 1-2 mm on the surface of the secondary electron emission film. A potential difference is generated by applying a voltage difference to the film and the accelerating electrode, which accelerates the secondary electrons and guides them toward the deflection electrode. By applying different voltages to the deflection electrode and the surface of the microchannel plate detector, a potential difference is generated, which deflects and guides the secondary electrons to the surface of the microchannel plate detector.

4. The space-based medium-energy ion spectrometer based on the time-of-flight method according to claim 3, characterized in that, The secondary electron emission film, the accelerating electrode, and the deflecting electrode are connected to a negative high voltage; the upper surface of the microchannel plate detector is grounded; and a positive high voltage is applied to the lower surface of the microchannel plate detector, the start anode, and the stop anode.

5. The space-based medium-energy ion spectrometer based on the time-of-flight method according to claim 3, characterized in that, The secondary electron emission thin film is grounded; the accelerating electrode is connected to a negative high voltage; the upper and lower surfaces, start anode, and stop anode of the microchannel plate detector are all connected to a positive high voltage; and the deflection electrode is connected to a negative high voltage.

6. The space-based medium-energy ion spectrometer based on the time-of-flight method according to claim 3, characterized in that, The secondary electron emission film, the accelerating electrode, the deflecting electrode, the upper surface of the microchannel plate detector, and the lower surface of the microchannel plate detector are all connected to a negative high voltage; the start anode and stop anode of the microchannel plate detector are grounded.

7. The space-based medium-energy ion spectrometer based on the time-of-flight method according to claim 2, characterized in that, The secondary electron emission thin film includes n start films and 1 stop film; the accelerating electrode includes n start accelerating electrodes and 1 stop accelerating electrode; the microchannel detector includes n start anodes and 1 stop anode; n>1; The start anode receives secondary electrons and outputs a signal for position resolution and a start signal for timing.

8. The space-based medium-energy ion spectrometer based on the time-of-flight method according to claim 2, characterized in that, The secondary electron emission thin film includes one start film and n stop films; the accelerating electrode includes one start accelerating electrode and n stop accelerating electrodes; the microchannel detector includes one start anode and n stop anodes; n>1; each stop film corresponds to one solid-state detector; The stop anode receives secondary electrons and outputs a signal for position resolution and a stop signal for timing.

9. The space-based medium-energy ion spectrometer based on the time-of-flight method according to claim 2, characterized in that, The secondary electron emission thin film includes n start films and n stop films; the accelerating electrode includes n start accelerating electrodes and n stop accelerating electrodes; n>1; each stop film corresponds to a solid-state detector; The start anode receives secondary electrons and outputs a signal for position resolution and a start signal for timing. The stop anode receives secondary electrons and outputs a signal for position resolution and a stop signal for timing.

10. The space-based medium-energy ion spectrometer based on the time-of-flight method according to any one of claims 7-9, characterized in that, The electronic device also includes a position resolution signal processing module, which is used to receive the position resolution signal sent by the start anode or stop anode, process and analyze it to obtain the incident position information of the ions, and then send it to the programmable array logic. The programmable array logic performs coincidence measurement and analysis on the position information, τ, and ESSD to obtain information about the incident ions, including the type, ion energy spectrum, and angular distribution information.

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