A device for experimental calibration of scintillator-based fast ion loss probe

Abstract

The present invention discloses a device for experimental calibration of a scintillator-based fast ion loss probe, comprising a two-dimensional electric rotating table, wherein a magnetic ring is installed at the output end of the two-dimensional electric rotating table, and a probe is arranged at the geometric center of the magnetic ring; an image acquisition component is arranged on one side of the magnetic ring, and a carbon stripping film, a protective sleeve, a neutralization chamber, an electric lens, and an ion source extractor are arranged in sequence from near to far. The present invention adopts a permanent magnet ring structure to solve the problem of difficulty in generating a uniform magnetic field of the order of 1T; adopts a "neutralization first and then charge stripping" solution to solve the problem that high-energy ions cannot pass through a non-uniform magnetic field area; an electric lens structure is arranged at the ion source outlet to ensure the collimation of a high-energy particle beam for long-distance transmission; a protective sleeve structure is adopted to protect the magnetic ring from being damaged by high-energy ions; and a high-precision two-dimensional rotating table is adopted to adjust the posture of the magnetic ring and the probe to facilitate the probe to receive high-energy ions of different energies and throw angles.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic confinement fusion plasma diagnosis, and in particular to a device for experimentally calibrating a scintillator-based fast ion loss probe. Background Art

[0002] The scintillator-based fast ion loss probe is a probe used in magnetic confinement fusion plasma experimental devices to detect high-energy ions lost from plasma. Its probe mainly includes a collimator and a scintillator sheet. When high-energy ions that have lost confinement escape to the edge of the plasma, they are first screened by the collimator. The ions that pass through the collimator perform Larmor cyclotron motion under the strong magnetic field of the magnetic confinement device and finally collide with a certain position on the scintillator sheet to emit fluorescence. Since ions with different energies and pitch angles collide at different positions, the experimenters can read the energy and pitch angle of the lost ions based on the position of the fluorescence emitted on the scintillator sheet, and then invert the motion trajectory of the lost ions, which helps to study the loss mechanism of high-energy ions.

[0003] However, the correspondence between the energy and pitch angle of the lost ions and their positions on the scintillator sheet is not easy to obtain. The energy and pitch angle corresponding to different positions on the scintillator sheet are calculated using a numerical program, which is called "program calibration". High-energy ions are generated by an energy-controllable ion source outside the magnetic confinement device, and the probe is calibrated by applying a uniform external magnetic field to simulate the magnetic field of the magnetic confinement device, which is called "experimental calibration". At present, the scintillator fast ion loss probes on major international magnetic confinement fusion devices mainly use program calibration, and the more convincing "experimental calibration" has not yet been completed by anyone in the world.

[0004] The difficulties of “experimental calibration” are:

[0005] 1. The magnetic field in the magnetic confinement fusion device is too strong, reaching the 1T level. It is difficult to generate a uniform magnetic field of the 1T level in a space area the size of the probe in the laboratory. The electromagnet that can complete this task is expensive, about RMB 1 million, which is even more expensive than the probe itself, and the economic efficiency is extremely low.

[0006] 2. Even if a uniform magnetic field of 1T can be generated in an area the size of the probe, due to the characteristics of the magnetic field itself, there will inevitably be a non-uniform magnetic field area outside the uniform magnetic field area. The full ion trajectory simulation shows that the high-energy ions generated by the ion source cannot pass through the outer non-uniform magnetic field area to enter the internal uniform magnetic field area, let alone enter the probe. Summary of the invention

[0007] The purpose of the present invention is to solve the shortcomings existing in the prior art and to propose a device for experimentally calibrating a scintillator-based fast ion loss probe.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A device for experimental calibration of a scintillator-based fast ion loss probe comprises a two-dimensional electric rotating table, a magnetic ring is installed at the output end of the two-dimensional electric rotating table, and a probe is arranged at the geometric center of the magnetic ring;

[0010] An image acquisition component is provided on one side of the magnetic ring, and a carbon stripping film, a protective sleeve, a neutralization chamber, an electric lens and an ion source exporter are provided on the other side in sequence from near to far, and the central axes of the ion source exporter, the electric lens, the neutralization chamber, the protective sleeve and the carbon stripping film coincide.

[0011] Preferably, the image acquisition component comprises an image transmission optical path and a high-speed camera, and the image transmission optical path connects the high-speed camera and the probe.

[0012] Preferably, the image transmission optical path is one of a flexible optical path and a rigid optical path.

[0013] Preferably, the magnetic ring is a neodymium magnet in the shape of a circular ring, which is divided into sixteen units along the radial direction. The magnetic ring is broken in the axial direction into two parts, and the upper and lower parts are spaced apart.

[0014] The magnetization directions of the sixteen magnet units are specially designed to strengthen the magnetic field in the gaps in the core of the magnetic ring while ensuring the uniformity of the magnetic field. By adjusting the size of the magnet units, the magnetic ring can generate a uniform magnetic field of the order of 1T in an area the size of the probe.

[0015] In order to improve the uniformity of the magnetic field in the gap of the magnetic ring core in the height direction of the magnetic ring, the magnetic ring is cut in half in the height direction, so that the upper and lower parts are separated by a certain distance, thereby lengthening the size of the magnetic field uniformity area and reducing the processing difficulty of the magnet unit. Finite element analysis of professional multi-physics field simulation software shows that the magnetic ring designed in this way can fully generate a magnetic field with strength and uniformity that meets the requirements in the probe size area, and the manufacturing cost is only 20,000 to 30,000 yuan, which is highly economical.

[0016] Preferably, a collimator is installed on the probe.

[0017] Preferably, a plurality of ventilation holes are formed on the side wall of the protective sleeve, and the central axes of the ventilation holes are arranged horizontally.

[0018] Preferably, the carbon stripping film is closely attached to the end of the protective sleeve and is arranged close to the probe.

[0019] Preferably, the two-dimensional electric rotating stage has two rotating axes, the two rotating axes are vertically arranged, and one of the rotating axes is arranged based on the other rotating axis.

[0020] Preferably, a graphite shell is installed outside the probe.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention adopts a permanent magnet ring structure to solve the problem of difficulty in generating a 1T-level uniform magnetic field;

[0023] 2. The present invention adopts the solution of "neutralization first and then charge stripping" to solve the problem that high-energy ions cannot pass through the non-uniform magnetic field area;

[0024] 3. The present invention sets an electric lens structure at the ion source outlet to ensure the collimation of the high-energy particle beam during long-distance transmission;

[0025] 4. The present invention adopts a protective sleeve structure to protect the magnetic ring from being damaged by high-energy ions;

[0026] 5. The present invention adopts a high-precision two-dimensional rotating table to adjust the posture of the magnetic ring and the probe to facilitate the probe to receive high-energy ions with different energies and throwing angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more specifically and intuitively illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0028] Figure 1 A stereoscopic view of a device for experimentally calibrating a scintillator-based fast ion loss probe according to the present invention;

[0029] Figure 2 A cross-sectional view of a device for experimentally calibrating a scintillator-based fast ion loss probe according to the present invention;

[0030] Figure 3 It is an oblique view of a magnetic ring of a device for experimentally calibrating a scintillator-based fast ion loss probe according to the present invention;

[0031] Figure 4 A schematic diagram of the magnetization direction of a magnetic ring unit of a device for experimentally calibrating a scintillator-based fast ion loss probe according to the present invention;

[0032] Figure 5 A schematic diagram of the magnetic field strength of a magnetic ring on a cross section perpendicular to the z-axis of a device for experimentally calibrating a scintillator-based fast ion loss probe according to the present invention;

[0033] Figure 6 The fluctuation range of magnetic field intensity of a magnetic ring on several cross sections perpendicular to the z-axis in a device for experimentally calibrating a scintillator-based fast ion loss probe in a special application example of the present invention;

[0034] Figure 7 The invention discloses a magnetic field intensity fluctuation range of a magnetic ring of a device for experimentally calibrating a scintillator-based fast ion loss probe at several cross sections perpendicular to the z-axis.

[0035] In the figure: ion source exporter 1, electric lens 2, neutralization chamber 3, protective sleeve 4, vent 401, carbon stripping film 5, magnetic ring 6, probe 7, image transmission optical path 8, high-speed camera 9, two-dimensional electric rotating stage 10. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0037] Reference Figure 1-7 , a device for experimental calibration of a scintillator-based fast ion loss probe, comprising a two-dimensional electric rotating stage 10, a magnetic ring 6 is installed at the output end of the two-dimensional electric rotating stage 10, and a probe 7 is set at the geometric center of the magnetic ring 6;

[0038] An image acquisition component is provided on one side of the magnetic ring 6, and a carbon stripping film 5, a protective sleeve 4, a neutralization chamber 3, an electric lens 2 and an ion source exporter 1 are provided on the other side in sequence from near to far, and the central axes of the ion source exporter 1, the electric lens 2, the neutralization chamber 3, the protective sleeve 4 and the carbon stripping film 5 coincide.

[0039] In this embodiment, the image acquisition component includes an image transmission optical path 8 and a high-speed camera 9. The image transmission optical path 8 connects the high-speed camera 9 and the probe 7. The image transmission optical path 8 is one of a flexible optical path and a rigid optical path.

[0040] In this embodiment, the magnetic ring 6 is a neodymium magnet in the shape of a circular ring, which is divided into sixteen units along the radial direction. The magnetic ring 6 is broken in the axial direction into two parts, and the upper and lower parts are spaced apart.

[0041] In order to solve the problem that it is difficult to generate a uniform magnetic field of 1T level, the present invention adopts a permanent magnet ring structure. The magnetic ring is made of neodymium magnets and is in the shape of a ring. It is divided into 16 units along the radial direction. The magnetization directions of the 16 magnet units are specially designed to strengthen the magnetic field in the gap of the core of the magnetic ring while ensuring the uniformity of the magnetic field. Adjusting the size of the magnet unit can make the magnetic ring generate a uniform magnetic field of 1T level in an area of ​​the probe size.

[0042] In order to improve the uniformity of the magnetic field in the gap of the magnetic ring core in the height direction of the magnetic ring, the magnetic ring is cut in half in the height direction, so that the upper and lower parts are separated by a certain distance, thereby lengthening the size of the magnetic field uniformity area and reducing the processing difficulty of the magnet unit. Finite element analysis of professional multi-physics field simulation software shows that the magnetic ring designed in this way can fully generate a magnetic field with strength and uniformity that meets the requirements in the probe size area, and the manufacturing cost is only 20,000 to 30,000 yuan, which is highly economical.

[0043] In this embodiment, a plurality of ventilation holes 401 are opened on the side wall of the protective sleeve 4, and the central axis of the ventilation holes 401 is set horizontally. In order to prevent the airflow from damaging the carbon stripping film 5 when the entire calibration experimental device is evacuated, a plurality of ventilation holes 401 are opened on the left and right sides of the protective sleeve 4 for ventilation.

[0044] In this embodiment, the carbon stripping film 5 is closely attached to the end of the protective sleeve 4 and is disposed close to the probe 7 .

[0045] In this embodiment, the two-dimensional electric rotating stage 10 has two rotating axes, the two rotating axes are vertically arranged, and one of the rotating axes is arranged based on the other rotating axis.

[0046] In order to facilitate the probe to receive high-energy ions with different energies and pitch angles, the present invention uses a high-precision two-dimensional rotating stage 10 to adjust the posture of the magnetic ring 6 and the probe 7. The magnetic ring 6 and the probe 7 are fixed to ensure that the magnetic field in the probe remains stable. When calibrating ions with specific energy and pitch angle, the pitch and yaw postures of the magnetic ring 6 and the probe 7 can be adjusted by the two-dimensional rotating stage 10 with the collimator receiving hole as the rotation center, so as to complete the reception of such ions. A graphite shell is installed outside the probe 7.

[0047] When high-energy ions are extracted by the ion source extractor 1, they are immediately collimated by the electric lens 2, thereby obtaining an ion beam with better collimation.

[0048] In order to ensure the collimation of high-energy particle beams during long-distance transmission, the present invention sets an electric lens 2 at the ion source outlet to collimate the ion beam when high-energy ions are emitted to prevent weak experimental signals caused by ion beam divergence.

[0049] Next, the ion beam enters the neutralization chamber 3, into which the unionized neutral gas in the ion source has been injected in advance to form a gas target. The high-energy ion beam collides with the gas target in the neutralization chamber 3 and exchanges charges, capturing electrons to become high-energy neutral particles.

[0050] A high-energy particle beam (mostly high-energy neutral particles) is emitted from the neutralization chamber 3 and enters the protective sleeve 4. The protective sleeve 4 is located in the non-uniform magnetic field area outside the magnetic ring 6. The high-energy neutral particles can move in a straight line in the protective sleeve 4 without being affected by the magnetic field. A small number of charged ions that have not been completely neutralized are deflected in the non-uniform magnetic field and collide with the inner wall of the protective sleeve 4. Due to the direction of the external magnetic field, the ions mainly hit the upper and lower inner walls of the protective sleeve 4. The side vents 401 of the protective sleeve 4 will not affect the protective effect, and prevent high-energy ions from damaging the magnetic ring 6.

[0051] In order to solve the problem that high-energy ions cannot pass through the non-uniform magnetic field area, the present invention adopts the solution of "neutralization first and then charge stripping". A gas neutralization chamber 3 is set at the outlet of the ion source, and the unionized neutralized gas in the ion source is injected into the neutralization chamber 3 to form a gas target. After entering the neutralization chamber 3, the high-energy ions collide and exchange charges in the gas target, and capture electrons to become high-energy neutral particles. The neutralization efficiency can be controlled by supplementing the gas supply to the neutralization chamber 3 and adjusting the thickness of the gas target.

[0052] After the high-energy ions are converted into uncharged high-energy neutral particles, they will no longer be affected by the non-uniform magnetic field region and can maintain straight-line motion through the non-uniform magnetic field region to reach the uniform magnetic field region.

[0053] At the same time, in order to protect the magnetic ring 6 from being damaged by high-energy ions, the present invention adopts a protective sleeve 4 structure. Since the neutralization efficiency of the neutralization chamber 3 cannot reach 100%, the high-energy particles emitted from the neutralization chamber 3 may contain charged ions, and these charged ions may be deflected under the influence of the non-uniform magnetic field area of ​​the magnetic ring 6 and collide with the magnetic ring 6 to cause damage to the magnetic ring 6. The protective sleeve 4 is a long cylindrical structure, the front end of which is arranged behind the neutralization chamber 3, and the rear end extends to the collimator receiving hole of the probe 7 as a forward movement channel for high-energy particles. The charged particles deflected in the non-uniform magnetic field area will collide with the inner wall of the protective sleeve 4 without damaging the magnetic ring.

[0054] The high-energy neutral particles that move to the end of the protective sleeve 4 will be stripped of electrons and converted back into high-energy ions after passing through the carbon stripping film 5. At this time, the high-energy ions come to the collimator receiving hole of the probe 7 located in the core uniform magnetic field area of ​​the magnetic ring 6. Next, the high-energy ions perform Larmor cyclotron motion under the influence of the uniform magnetic field and enter the probe 7 and collide with the scintillator sheet to emit fluorescence. The fluorescence pattern on the scintillator sheet is transmitted to the high-speed camera 9 at the rear via the image transmission optical path 8. The high-speed camera 9 records the changes of the fluorescence pattern over time for subsequent data analysis.

[0055] In addition, based on the working principle of the fast ion loss probe of the scintillator, high-energy ions of different energies and pitch angles need to enter the collimator at different angles to pass the screening of the collimator. When calibrating high-energy ions of different energies and pitch angles, the two-dimensional electric rotating stage 10 can conveniently adjust the posture of the magnetic ring 6 and the probe 7, so that the device can complete the calibration of ions of any energy and pitch angle within the detection range of the probe.

[0056] The magnetic field strength of the magnetic ring 5 in its central air gap tends to be uniform. The calculation results of the large-scale multi-physics finite element simulation software are as follows: Figure 5 As shown, the uniformity of the magnetic field can be qualitatively observed. By reasonably designing the size parameters of the magnetic ring 6, the strength of the uniform magnetic field at the center of the magnetic ring 6 can reach more than 1T, which is equivalent to the magnetic field strength in the magnetic confinement fusion device, such as Figure 7 As shown, the strength of the uniform magnetic field at the center of the magnetic ring 6 can be adjusted according to the size of the magnetic ring 6.

[0057] The following is an application example. Since the 1T magnetic field is too strong, there is a certain risk in the experiment. For the personal safety of the experimenters, the magnetic ring 6 can change its size parameters to make the magnetic field strength in the central uniform area about 0.35T. The magnetic field strength fluctuation range of the magnetic ring 6 on several cross sections perpendicular to the z-axis is as follows: Figure 6 As shown, it can be seen that in the cylindrical air gap of the magnetic ring 6, the uniformity of the magnetic field is best in the space with a length of about 30 mm in the center (the shaded area in the figure), the mean magnetic field along the negative direction of the x-axis is basically stable at 0.35 T, and the magnetic field intensity fluctuation on each cross section is very small; the mean magnetic field along the y-axis and z-axis are both near 0, and the fluctuation is also very small, which is the best area for placing the probe.

[0058] We use the equation of motion of ions performing Larmor cyclotron motion in a magnetic field:

[0059]

[0060]

[0061] v ⊥ =v*sin(a)

[0062] You can get:

[0063]

[0064] Among them, q represents the amount of charge carried by the ion; r represents the cyclotron radius of the ion's motion in the magnetic field; represents the component of the ion's velocity in the direction perpendicular to the magnetic field; B represents the magnetic field strength; m represents the ion's mass; E represents the ion's kinetic energy; and v represent the ion's velocity vector and the modulus of the velocity vector, respectively; a represents the angle between the ion's velocity and the magnetic field direction, also known as the "throw angle".

[0065] Taking this into consideration, the present invention mainly detects high-energy D+ ions of about 40 keV in the magnetic confinement fusion device. H+ ions can be used instead in the calibration device experiment. The mass m of H+ ions is 0.5 times that of D+, and the charge q is equal to that of D+. According to the expression of the cyclotron radius r derived above, the trajectory of 5 keV H+ ions under a 0.35T magnetic field is the same as the trajectory of 40 keV D+ ions under 1.4T. Therefore, it is entirely possible to use low-energy H ions to replace high-energy D ions for calibration experiments under the current magnetic ring 0.35T magnetic field. The weaker magnetic field and lower ion energy reduce the danger of the experiment and ensure the personal safety of the experimenters.

[0066] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A device for experimentally calibrating a scintillator-based fast ion loss probe, comprising a two-dimensional electric rotating stage (10), characterized in that: The output end of the two-dimensional electric rotating platform (10) is provided with a magnetic ring (6), and a probe (7) is arranged at the geometric center of the magnetic ring (6); An image acquisition component is provided on one side of the magnetic ring (6), and a carbon stripping film (5), a protective sleeve (4), a neutralization chamber (3), an electric lens (2), and an ion source exporter (1) are provided on the other side in sequence from near to far, and the central axes of the ion source exporter (1), the electric lens (2), the neutralization chamber (3), the protective sleeve (4), and the carbon stripping film (5) are overlapped.

2. The device for experimentally calibrating a scintillator-based fast ion loss probe according to claim 1, characterized in that: The image acquisition component comprises an image transmission optical path (8) and a high-speed camera (9), and the image transmission optical path (8) connects the high-speed camera (9) and the probe (7).

3. The device for experimentally calibrating a scintillator-based fast ion loss probe according to claim 2, characterized in that: The image transmission optical path (8) is one of a flexible optical path and a rigid optical path.

4. The device for experimentally calibrating a scintillator-based fast ion loss probe according to claim 3, characterized in that: The magnetic ring (6) is a neodymium magnet in the shape of a circular ring, which is divided into sixteen units along the radial direction. The magnetic ring (6) is broken in the axial direction into two parts, and the upper and lower parts are spaced apart.

5. The device for experimentally calibrating a scintillator-based fast ion loss probe according to claim 4, characterized in that: A collimator is installed on the probe (7).

6. The device for experimentally calibrating a scintillator-based fast ion loss probe according to claim 5, characterized in that: The side wall of the protective sleeve (4) is provided with a plurality of ventilation holes (401), and the central axis of the ventilation holes (401) is arranged horizontally.

7. The device for experimentally calibrating a scintillator-based fast ion loss probe according to claim 6, characterized in that: The carbon stripping film (5) is closely attached to the end of the protective sleeve (4) and is arranged close to the probe (7).

8. The device for experimentally calibrating a scintillator-based fast ion loss probe according to claim 7, characterized in that: The two-dimensional electric rotating table (10) has two rotating axes, which are arranged vertically, and one of the rotating axes is arranged based on the other rotating axis.

9. The device for experimentally calibrating a scintillator-based fast ion loss probe according to claim 8, characterized in that: The probe (7) is provided with a graphite shell outside.

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