CN118818585A - Multifunctional beam monitoring device and method for heavy ion irradiation terminal - Google Patents

Abstract

The invention relates to beam monitoring of low-energy heavy ions, in particular to a multifunctional beam monitoring device and a method for a heavy ion irradiation terminal, which aim to solve the defects that the position resolution capability is low, the fluence rate and the uniformity in a small-size sample cannot be reflected and the requirement on the stability of the low-energy heavy ion beam is high in the prior art; the secondary electron emission film is arranged on the incident path of the beam and forms an included angle with the incident direction of the beam; the signal reading module comprises a beam intensity measuring unit and a beam profile distribution measuring unit, and is used for measuring and converting the electric signals of the MCP module, and the multi-functional beam monitoring method is used for calculating the fluence rate and uniformity by utilizing the corresponding electric signals measured by the device.

Description

Multifunctional beam monitoring device and method for heavy ion irradiation terminal

Technical Field

The invention relates to low-energy heavy ion beam monitoring, and in particular to a multifunctional beam monitoring device and method for a heavy ion irradiation terminal.

Background Art

The single-particle effect of aerospace components is one of the main threats faced by spacecraft. Heavy ion accelerators are usually used to carry out single-particle effect research and assessment on the ground. Heavy ion accelerator irradiation tests of aerospace components are generally carried out in a vacuum environment. The commonly used heavy ions are low-energy heavy ions, whose maximum ion energy is only a few MeV/u. Such low-energy heavy ions have a range of less than 1mm in silicon.

During the test, the parameters that users are most concerned about are the fluence rate and its uniformity at the irradiation terminal. Therefore, it is very necessary to measure these key parameters in real time and directly during the irradiation process. However, online monitoring of low-energy heavy ion beams is quite difficult, and commonly used flat-panel ionization chambers, semiconductors, scintillators and other detectors are no longer suitable as transmission-type monitoring devices. At present, there are indirect measurement devices that use a combination of several counting detectors for calibration, but they are limited by the position resolution of conventional counting detectors (generally greater than 1mm). When the irradiation terminal is a small-sized sample, it is impossible to reflect the fluence rate and its uniformity in the small-sized sample. In addition, this indirect measurement device and method have high requirements on the stability of the low-energy heavy ion beam and cannot fully meet the monitoring needs during the irradiation test.

Summary of the invention

The purpose of the present invention is to solve the shortcomings of the prior art, such as low position resolution, inability to reflect the injection rate and its uniformity in small-sized samples, and high requirements for the stability of low-energy heavy ion beams, and to provide a multifunctional beam monitoring device and method for heavy ion irradiation terminals.

To achieve the above objectives, the technical solutions provided by the present invention are as follows:

A multifunctional beam monitoring device for a heavy ion irradiation terminal, which is special in that it includes a secondary electron emission film, an MCP module, a secondary electron confinement module, and a signal readout module; the secondary electron emission film is arranged on the incident path of the beam and has an angle with the incident direction of the beam, the secondary electron emission film is used to emit secondary electrons, and its size is larger than the beam spot size formed by the beam on the secondary electron emission film, and the secondary electron emission film is a conductive material; the MCP module includes a first microchannel plate and a second microchannel plate on both sides of the axial direction of the parallel secondary electron emission film, both of which are used to collect and multiply secondary electrons; the secondary electron confinement module includes a magnetic field confinement unit and an electric field confinement unit; the magnetic field confinement unit The unit includes two permanent magnets which are parallel to the axis of the secondary electron emission film and are respectively arranged on both sides of the secondary electron emission film and the MCP module, the two permanent magnets are arranged opposite to each other, and the polarization direction of the permanent magnets is arranged along the axial direction of the secondary electron emission film; the electric field confinement unit includes a high voltage source connected to the secondary electron emission film, which is used to load an adjustable negative high voltage to the secondary electron emission film; the signal readout module includes a beam intensity measurement unit and a beam profile distribution measurement unit, the beam intensity measurement unit is connected to the first microchannel plate, which is used to measure the electrical signal of the exit surface of the first microchannel plate; the beam profile distribution measurement unit is arranged corresponding to the second microchannel plate, which is used to obtain the electrical signal of the exit surface of the second microchannel plate and convert it into an optical signal.

Furthermore, the thickness of the secondary electron emission film is less than or equal to 1 μm.

Furthermore, the sizes of the first microchannel plate and the second microchannel plate are adapted to the secondary electron emission film; the angle between the secondary electron emission film and the incident direction of the beam is 45°;

The distances between the first microchannel plate, the second microchannel plate and the secondary electron emission film respectively satisfy the following formula:

Wherein, r is the radius of the secondary electron emission film, x is the diameter of the beam spot, d is the distance between the secondary electron emission film and the first microchannel plate or the second microchannel plate, and θ is the angle between the central axis of the beam and the secondary electron emission film.

Furthermore, the secondary electron emission film is made of conductive carbon or aluminum.

Further, the second microchannel plate and the first microchannel plate are sequentially arranged along the emission direction of the beam;

The beam intensity measurement unit includes a single anode arranged on the exit surface of the first microchannel plate and an electronics unit connected to the single anode;

The beam profile distribution measuring unit comprises a fluorescent screen arranged on the exit surface of the second microchannel plate and a camera matched with the fluorescent screen.

Furthermore, the magnetic field of the two permanent magnets between the first microchannel plate and the second microchannel plate is a uniform magnetic field.

At the same time, the present invention also provides a multifunctional beam current monitoring method for a heavy ion irradiation terminal, which adopts the multifunctional beam current monitoring device for a heavy ion irradiation terminal, and its special feature is that it includes the following steps:

Step 1, emitting a beam, controlling the beam to pass through the secondary electron emission film; adjusting the spatial resolution to be higher than 1 mm;

Step 2, acquiring the electrical signal of the first microchannel plate exit surface and the optical signal corresponding to the second microchannel plate exit surface, thereby obtaining the beam intensity and beam profile distribution;

Step 3: Calculate the fluence rate and uniformity at different positions based on the beam intensity and beam profile distribution.

Furthermore, step 1 also includes calibrating the beam intensity;

In step 1, the angle between the plane where the secondary electron emission film is located and the central axis of the beam is 45°;

The second microchannel plate and the first microchannel plate are arranged in sequence along the emission direction of the beam.

Furthermore, in step 1, the calibrating the beam intensity specifically comprises: counting and calibrating the corresponding relationship between the beam intensity and the current magnitude obtained by the electronic unit through a scintillator or a semiconductor detector;

The adjusting the spatial resolution to be higher than 1 mm specifically comprises: using a micro-hole collimator to filter the beam spot, observing the distribution of the beam spot light signal, and adjusting the high voltage loaded on the secondary electron emission film to make the spatial resolution higher than 1 mm.

Beneficial effects of the present invention:

1. Based on the principle of secondary electron emission, the present invention provides a multifunctional beam monitoring device, which can particularly simultaneously utilize the secondary electrons on the front and rear surfaces of the secondary electron emission film to measure the beam intensity and profile distribution, respectively, and obtain the injection rate and uniformity information. The key parameter measurements can be quickly completed using one monitoring device.

2. In the monitoring device of the present invention, a secondary electron emission film is provided, which belongs to a transmission-type monitoring device. During the monitoring process, the beam is controlled to penetrate the secondary electron emission film. The monitored beam energy can be as low as a few MeV/u, and the beam intensity can reach 1 to 10 ⁹ particles/s. The applicable beam energy and beam intensity range far exceeds that of conventional monitoring devices, providing strong support for the measurement of radiation field parameters during irradiation tests.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a multifunctional beam monitoring device according to an embodiment of the present invention;

FIG2 is a schematic diagram of the three-dimensional structure of a multifunctional beam monitoring device according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of the distance between the secondary electron emission film and the MCP module in an embodiment of the present invention.

Description of reference numerals:

1-secondary electron emission film, 2-beam, 3-MCP module, 31-first microchannel plate, 32-second microchannel plate, 41-beam intensity measurement unit, 411-single anode, 412-electronics unit, 42-beam profile distribution measurement unit, 421-fluorescent screen, 422-camera, 5-permanent magnet, 6-high voltage source, 7-fixed component.

DETAILED DESCRIPTION

The invention discloses a multifunctional beam monitoring device for a heavy ion irradiation terminal. The beam monitoring device mainly consists of a secondary electron emission film 1, a secondary electron confinement module, a microchannel plate (MCP) module, and a signal readout module.

Preferably, the normal of the plane where the secondary electron emission film 1 is located is placed in a direction with an angle of 45° with the central axis of the beam 2, and its size needs to cover the beam spot size formed by the beam 2 on the secondary electron emission film 1. The secondary electron emission film 1 is made of conductive material, and the thickness needs to be much smaller than the range of ions in the secondary electron emission film 1 material. The thickness selection needs to be as thin as possible on the basis of satisfying the self-supporting flatness and production process level, so as to minimize the impact on the beam 2, and the thickness is preferably less than or equal to 1μm. For example, a 1μm thick, circular conductive carbon film or aluminum film can be selected. Under the condition that the process level and technical conditions allow, a 0.1μm secondary electron emission film 1 can be selected, and the energy of the beam 2 applicable to it will also be reduced accordingly.

The MCP module 3 includes a first microchannel plate 31 and a second microchannel plate 32. The first microchannel plate 31 and the second microchannel plate 32 are respectively arranged on both sides of the secondary electron emission film 1 in the axial direction, and the planes where they are located are parallel to the plane where the secondary electron emission film 1 is located. Both are used for secondary electron collection and multiplication. The first microchannel plate 31 and the second microchannel plate 32 are respectively spaced the same from the secondary electron emission film 1. To prevent the MCP module 3 from affecting the beam 2, as shown in FIG. 3 , the spacing d satisfies the following formula:

Wherein, r is the radius of the secondary electron emission film 1 , x is the diameter of the beam spot, d is the distance between the secondary electron emission film 1 and the first microchannel plate 31 or the second microchannel plate 32 , and θ is the angle between the central axis of the beam 2 and the secondary electron emission film 1 .

The secondary electron confinement module includes a magnetic field confinement unit and an electric field confinement unit. The magnetic field confinement unit includes two rectangular permanent magnets 5 parallel to the axis of the secondary electron emission film 1 and placed on both sides of the secondary electron emission film 1 and the MCP module 3, respectively. The two rectangular permanent magnets 5 are arranged opposite to each other, and the polarization direction of the permanent magnets 5 is consistent with the axial direction of the secondary electron emission film 1. The electric field confinement unit includes a high voltage source 6 connected to the secondary electron emission film 1. The high voltage source 6 is used to load an adjustable negative high voltage to the secondary electron emission film 1, so that an electric field is formed between the secondary electron emission film 1 and the incident surface of the first microchannel plate 31 and the incident surface of the second microchannel plate 32, respectively. The incident surfaces of the first microchannel plate 31 and the second microchannel plate 32 are both at ground potential. The electric field and the magnetic field work together to confine the lateral diffusion of secondary electrons and improve the spatial resolution of the monitoring device.

Preferably, the axial dimension of the rectangular permanent magnet 5 along the secondary electron emission film 1 needs to be greater than the distance between the first microchannel plate 31 and the second microchannel plate 32, and the radial dimension of the secondary electron emission film 1 needs to be greater than the diameter of the secondary electron emission film 1. The center of the rectangular permanent magnet 5 along the length direction is located in the same plane as the secondary electron emission film 1, and an approximately uniform magnetic field is formed between the secondary electron emission film 1 and the MCP module 3 as much as possible to avoid secondary electron overflow.

The signal readout module is composed of a beam intensity measurement unit 41 and a beam profile distribution measurement unit 42, which are matched with the first microchannel plate 31 and the second microchannel plate 32 respectively. The beam intensity measurement unit 41 obtains the electrical signal of the exit surface of the first microchannel plate 31 through a single anode 411 and an electronic unit 412 connected thereto. The single anode 411 is arranged on the exit surface of the first microchannel plate 31. The second microchannel plate 32 and the first microchannel plate 31 are arranged in sequence along the emission direction of the beam 2. The first microchannel plate 31 is far away from the emission end of the beam 2, and the electrical signal generated on this side is greater than that on the other side. Therefore, it is more suitable for beam intensity measurement. It is necessary to use a scintillator or a semiconductor detector to count and calibrate the corresponding relationship between the number of electrons in the beam 2 and the current size obtained by the electronic unit 412 to achieve absolute measurement of the beam intensity. The beam profile distribution measurement unit 42 includes a fluorescent screen 421 and a camera 422 matched therewith. The fluorescent screen 421 is used to convert the electrical signal of the exit surface of the second microchannel plate 32 into an optical signal. The camera 422 is used to receive the converted optical signal. The fluorescent screen 421 is arranged on the exit surface of the second microchannel plate 32. Further, the fluence rate and uniformity at different positions are calculated according to the following formula based on the beam intensity and beam profile distribution.

Wherein, _fij is the fluence rate, I is the beam intensity, i and j are the position grid indexes on the beam spot, the number of rows and columns of the grid is the same, both are N, i,j = 1, 2, ... N, _sij is the optical signal intensity in the grid of the i-th row and j-th column on the beam spot, a is the grid area, and u is the uniformity.

The first microchannel plate 31 and the second microchannel plate 32 are connected to the secondary electron emission film 1 through a fixing assembly 7, and the fixing assembly 7 includes three annular parts with the same outer diameter and a connecting rod; the three annular parts are arranged in parallel and fixedly connected by the connecting rod; the secondary electron emission film 1, the first microchannel plate 31, and the second microchannel plate 32 are respectively fixedly arranged on the three annular parts, the single anode 411 is arranged on the annular part where the first microchannel plate 31 is located, and the fluorescent screen 421 is arranged on the annular part where the second microchannel plate 32 is located, and the inner diameters of the three annular parts meet the effective diameters of the secondary electron emission film 1, the first microchannel plate 31, and the second microchannel plate 32 respectively.

The uniformity calculation formula listed above is only one way to calculate uniformity. Different application scenarios have different formulas.

The working principle of the present invention is: when the beam 2 passes through the secondary electron emission film 1, the front and rear surfaces of the secondary electron emission film 1 will emit secondary electrons. These secondary electrons are constrained by the electric field and the magnetic field, move to the MCP incident surfaces on both sides, are collected and multiplied, and the measurement signal is obtained through the corresponding signal readout module.

In this embodiment, the beam spot area of the beam 2 to be measured does not exceed 3cm×3cm, the energy is several MeV/u, the secondary electron emission film 1 is a circular carbon film with a thickness of 1μm and an effective diameter greater than 80mm, the effective diameter of the first microchannel plate 31 and the second microchannel plate 32 is 82mm, the outer diameter of the ring is 106mm, and the incident surfaces of the first microchannel plate 31 and the second microchannel plate 32 are 84mm away from the secondary electron emission film 1, as shown in Figure 2. The strength of the permanent magnet 5 is 1T, the area is 130mm×270mm, and the distance between the two permanent magnets 5 is 140mm.

During measurement, a micro-hole collimator is used to filter the beam spot, and the distribution of the beam spot light signal is observed. The spatial resolution is higher than 1 mm by adjusting the high voltage loaded on the secondary electron emission film 1. In order to achieve absolute measurement of the beam intensity, a scintillator or semiconductor detector is first used to count and calibrate the corresponding relationship between the number of electrons in the beam 2 and the current size obtained by the electronics unit 412.

During the measurement, the electrical signal of the exit surface of the first microchannel plate 31 and the optical signal corresponding to the exit surface of the second microchannel plate 32 are obtained simultaneously, and the beam intensity and beam profile distribution are obtained respectively. Then, based on the beam intensity and beam profile distribution obtained above, the fluence rate and uniformity at different positions can be calculated.

The multifunctional beam monitoring device for the heavy ion irradiation terminal of the present invention can simultaneously realize the online monitoring of beam intensity, profile distribution, injection rate and uniformity, and is a means of directly carrying out beam monitoring in irradiation tests.

Claims (9)

1. A multifunctional beam monitoring device for a heavy ion irradiation terminal, characterized in that: It comprises a secondary electron emission film (1), an MCP module (3), a secondary electron confinement module, and a signal readout module; The secondary electron emission film (1) is arranged on the incident path of the beam (2) and has an angle with the incident direction of the beam (2). The secondary electron emission film (1) is used to emit secondary electrons. The size of the secondary electron emission film (1) is larger than the size of the beam spot formed by the beam (2) on the secondary electron emission film (1). The secondary electron emission film (1) is a conductive material. The MCP module (3) comprises a first microchannel plate (31) and a second microchannel plate (32) with parallel secondary electron emission films (1) arranged on both sides of the axial direction thereof, both of which are used to collect and multiply secondary electrons; The secondary electron confinement module comprises a magnetic field confinement unit and an electric field confinement unit; the magnetic field confinement unit comprises two permanent magnets (5) which are parallel to the axis of the secondary electron emission film (1) and are respectively arranged on both sides of the secondary electron emission film (1) and the MCP module (3); the two permanent magnets (5) are arranged opposite to each other, and the polarization direction of the permanent magnets (5) is arranged along the axial direction of the secondary electron emission film (1); the electric field confinement unit comprises a high voltage source (6) connected to the secondary electron emission film (1) and used for loading an adjustable negative high voltage onto the secondary electron emission film (1); The signal readout module comprises a beam intensity measurement unit (41) and a beam profile distribution measurement unit (42); the beam intensity measurement unit (41) is connected to the first microchannel plate (31) and is used to measure the electrical signal of the exit surface of the first microchannel plate (31); the beam profile distribution measurement unit (42) is arranged corresponding to the second microchannel plate (32) and is used to obtain the electrical signal of the exit surface of the second microchannel plate (32) and convert it into an optical signal. 2. The multifunctional beam monitoring device for heavy ion irradiation terminal according to claim 1, characterized in that: The thickness of the secondary electron emission film (1) is less than or equal to 1 μm. 3. The multifunctional beam monitoring device for heavy ion irradiation terminal according to claim 2, characterized in that: The sizes of the first microchannel plate (31) and the second microchannel plate (32) are adapted to the secondary electron emission film (1); the angle between the secondary electron emission film (1) and the incident direction of the beam (2) is 45°; The distances between the first microchannel plate (31) and the second microchannel plate (32) and the secondary electron emission film (1) respectively satisfy the following formula: Wherein, r is the radius of the secondary electron emission film (1), x is the diameter of the beam spot, d is the distance between the secondary electron emission film (1) and the first microchannel plate (31) or the second microchannel plate (32), and θ is the angle between the central axis of the beam (2) and the secondary electron emission film (1). 4. The multifunctional beam monitoring device for a heavy ion irradiation terminal according to any one of claims 1 to 3, characterized in that: The secondary electron emission film (1) is made of conductive carbon or aluminum. 5. The multifunctional beam monitoring device for heavy ion irradiation terminal according to claim 4, characterized in that: The second microchannel plate (32) and the first microchannel plate (31) are arranged in sequence along the emission direction of the beam (2); The beam intensity measurement unit (41) comprises a single anode (411) arranged on the exit surface of the first microchannel plate (31) and an electronics unit (412) connected to the single anode (411); The beam profile distribution measurement unit (42) comprises a fluorescent screen (421) arranged on the exit surface of the second microchannel plate (32) and a camera (422) matched with the fluorescent screen (421). 6. The multifunctional beam monitoring device for heavy ion irradiation terminal according to claim 5, characterized in that: The magnetic field of the two permanent magnets (5) between the first microchannel plate (31) and the second microchannel plate (32) is a uniform magnetic field. 7. A multifunctional beam current monitoring method for a heavy ion irradiation terminal, using the multifunctional beam current monitoring device for a heavy ion irradiation terminal according to any one of claims 1 to 6, characterized in that it comprises the following steps: Step 1, emitting a beam (2), controlling the beam (2) to pass through a secondary electron emission film (1); adjusting the spatial resolution to be higher than 1 mm; Step 2, acquiring an electrical signal from an exit surface of the first microchannel plate (31) and an optical signal corresponding to an exit surface of the second microchannel plate (32), thereby obtaining beam intensity and beam profile distribution; Step 3: Calculate the fluence rate and uniformity at different positions based on the beam intensity and beam profile distribution. 8. The multifunctional beam monitoring method for a heavy ion irradiation terminal according to claim 7, characterized in that: Step 1 also includes calibrating the beam intensity; In step 1, the angle between the plane where the secondary electron emission film (1) is located and the central axis of the beam (2) is 45°; The second microchannel plate (32) and the first microchannel plate (31) are arranged in sequence along the emission direction of the beam (2). 9. The multifunctional beam monitoring method for a heavy ion irradiation terminal according to claim 8, characterized in that: In step 1, the calibrating the beam intensity specifically comprises: counting and calibrating the corresponding relationship between the beam intensity and the current magnitude obtained by the electronic unit (412) through a scintillator or a semiconductor detector; The method of adjusting the spatial resolution to be higher than 1 mm specifically comprises: using a micro-hole collimator to filter the beam spot, observing the distribution of the beam spot light signal, and adjusting the high voltage loaded on the secondary electron emission film (1) to make the spatial resolution higher than 1 mm.