An unbiased Faraday cup device for use in an atmospheric environment and an installation method thereof

Abstract

The present invention belongs to the technical field of charged particle beam detection, and relates to an unbiased Faraday cup device and an installation method for use in an atmospheric environment, including: a thin film electrode, a grounded fastening ring, a signal collection electrode, a triaxial connector, and a grounding electrode. The thin film electrode is fixed on the signal collection electrode through the grounded fastening ring and is in close contact with the signal collection electrode. The beam incident surface and the beam exit surface of the thin film electrode are insulated from each other. The signal output end of the signal collection electrode is connected to the signal end of the triaxial connector, and the grounded fastening ring is connected to the ground end of the triaxial connector through the grounding electrode. It can be directly used in an atmospheric environment without the need for vacuum and bias voltage equipment, has low cost, small volume, and the beam current is not easily leaked, and the detection result is more accurate.

Description

Technical Field

[0001] The present invention relates to a non-biased Faraday cup device and an installation method for use in an atmospheric environment, and belongs to the technical field of charged particle beam detection. Background Art

[0002] A Faraday cup is a basic device for measuring the current intensity of a charged particle beam. Its purpose is to intercept the charged ion beam and collect its charge, thereby realizing the measurement of the beam current intensity.

[0003] Existing Faraday cups are all used in a high-vacuum environment, and at the same time, a bias device needs to be set up to suppress the escape of secondary electrons. The Faraday cups in the prior art generally include: a sealing flange, a vacuum conduction device, a bias ring, and a bias power supply. Due to the need for a high-vacuum environment, the existing Faraday cup devices usually have a complex structure, a large volume, and a high manufacturing cost. At the same time, the introduction of the bias power supply will cause the bias current to leak into the beam current intensity, resulting in inaccurate measurement values. Especially for low-energy high-current beams, the sputtering effect is serious, so that the insulating ceramic between the bias ring and the signal electrode is contaminated, and the leakage current is greater. Summary of the Invention

[0004] Aiming at the above problems, the purpose of the present invention is to provide a non-biased Faraday cup device and an installation method for use in an atmospheric environment, which can be directly used in an atmospheric environment, without the need for vacuum and bias equipment, with low cost, small volume, and the beam is not easy to leak, and the detection result is more accurate.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: A non-biased Faraday cup device for use in an atmospheric environment includes: a thin-film electrode, a grounded fastening ring, a signal collection electrode, a triaxial connector, and a grounding electrode. The thin-film electrode is fixed on the signal collection electrode through the grounded fastening ring and is in close contact with the signal collection electrode. The beam incident surface and the beam exit surface of the thin-film electrode are insulated from each other. The signal output end of the signal collection electrode is connected to the signal end of the triaxial connector, and the grounded fastening ring is connected to the grounding end of the triaxial connector through the grounding electrode.

[0006] Further, a conductive material is plated on the beam incident surface of the thin-film electrode, and the beam exit surface is made of an insulating material.

[0007] Further, a conductive material is also plated on the beam exit surface, but the conductive material on the beam exit surface is not electrically connected to the conductive material on the beam incident surface.

[0008] Further, the grounding electrode is coaxially arranged with the signal collection electrode, the grounding electrode is arranged outside the signal collection electrode and is spaced from the signal collection electrode.

[0009] Further, a protection electrode is provided between the grounding electrode and the signal collection electrode. The protection electrode is coaxially arranged with the signal collection electrode, and its output end is connected to the protective ground terminal of the triaxial connector.

[0010] Further, the protection electrode and the signal collection electrode have equal electric potentials.

[0011] Further, coaxial insulating rings are provided between the grounding electrode, the signal collection electrode and the protection electrode to ensure mutual insulation between the three electrodes.

[0012] Further, the chamfer at the end of the signal collection electrode in contact with the thin film is a rounded corner, and the side of the grounding fastening ring in contact with the thin film electrode is set to an arc shape matching the radian of the rounded corner to ensure the thin film electrode fits with the signal collection electrode.

[0013] The present invention also discloses an installation method of a bias-free Faraday cup device used in an atmospheric environment for installing any one of the bias-free Faraday cup devices used in an atmospheric environment, including the following steps: S1 Insert the first polyethylene ring into the bottom of the grounding electrode, then insert the protection electrode into the first polyethylene ring, insert the second polyethylene ring into the protection electrode, and fasten the second polyethylene ring to the grounding electrode; S2 Insert the signal collection electrode into the second polyethylene ring, lay the thin film electrode flat on the signal collection electrode, then cover the grounding fastening ring and fix the grounding fastening ring on the top of the grounding electrode; S3 Weld the lead-out signal wire of the signal collection electrode to the signal terminal of the triaxial connector, weld the lead-out wire of the protection electrode to the protective ground terminal of the triaxial connector, and weld the lead-out wire of the grounding electrode to the grounding terminal of the triaxial connector to obtain a bias-free Faraday cup device used in an atmospheric environment.

[0014] The present invention also discloses a particle beam cancer treatment system adopting any one of the bias-free Faraday cup devices used in an atmospheric environment.

[0015] Due to the above technical solutions adopted by the present invention, it has the following advantages:

[0016] 1. The device in the present invention can be used to measure the intensity of charged particle beams in an atmospheric environment and can be moved conveniently, so it can be placed on any path where the beam passes, without being installed only on a fixed flange as in the case of a vacuum Faraday cup.

[0017] 2. The device in the present invention does not require an additional bias ring design and bias equipment, which can significantly reduce the economic cost of the Faraday cup.

[0018] 3. The device in the present invention can measure charged particle beams with an energy less than 400 MeV / u and a particle number per second in the range of 1E6 - 1E8.

[0019] 4. The device of the present invention can be applied in the field of particle beam cancer treatment for dose verification before the start of treatment. Its low cost, easy operation, and easy maintenance enable this Faraday cup device to be used as a fast and accurate dose verification means. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 FIG. is a schematic structural diagram of an unbiased Faraday cup device used in an atmospheric environment according to an embodiment of the present invention;

[0021] Figure 2 FIG. is a schematic structural diagram of a triaxial connector according to an embodiment of the present invention.

[0022] REFERENCE SIGNS:

[0023] 1 - thin film electrode; 2 - grounding fastening ring; 3 - signal collection electrode; 4 - triaxial connector; 41 - signal terminal; 42 - grounding terminal; 43 - protective grounding terminal; 5 - grounding electrode; 6 - protective electrode; 7 - first polyethylene ring; 8 - second polyethylene ring. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] In order to enable those skilled in the art to better understand the technical direction of the present invention, the present invention is described in detail through specific embodiments. However, it should be understood that the provision of specific embodiments is only for better understanding of the present invention, and they should not be construed as limitations to the present invention. In the description of the present invention, it should be understood that the terms used are only for the purpose of description and cannot be construed as indicating or implying relative importance.

[0025] Embodiment 1

[0026] This embodiment discloses an unbiased Faraday cup device used in an atmospheric environment, as shown in FIGS. Figure 1 、 2 , which includes: a thin film electrode 1, a grounding fastening ring 2, a signal collection electrode 3, a triaxial connector 4, and a grounding electrode 5. The thin film electrode 1 is fixed on the signal collection electrode 3 through the grounding fastening ring 2 and is in close contact with the signal collection electrode 3. The beam incident surface and the beam exit surface of the thin film electrode 1 are insulated from each other. The signal output end of the signal collection electrode 3 is connected to the signal terminal 41 of the triaxial connector 4, and the grounding fastening ring 2 is connected to the grounding terminal 42 of the triaxial connector 4 through the grounding electrode 5. The triaxial connector 4 is used to lead out the signal. The thin film electrode 1 can isolate the secondary charged particles contained in the ionized atmosphere by the charged particles, ensuring the accuracy of the beam current measurement. At the same time, the thin film electrode 1 can suppress the secondary electrons generated by the signal collection electrode 3, having the same biasing effect as the Faraday cup used in a high vacuum environment.

[0027] The incident surface of the beam of the thin-film electrode 1 is coated with a conductive material, and the exit surface of the beam is an insulating material. It is also possible to coat the exit surface of the beam with a conductive material as well, but the conductive material on the exit surface of the beam is not electrically connected to the conductive material on the incident surface of the beam. The thin-film electrode 1 used in this embodiment is a Cape Town film with aluminum plating on one side, the film thickness is 50 μm, the aluminum layer thickness is 1 μm, and the diameter is 85 mm.

[0028] The grounding fastening ring 2 is supported by oxygen-free copper. The diameter of the incident aperture of the particle beam is 62.5 mm, the outer diameter is 100 mm, and there are four M4 threaded holes at the top. These threaded holes are used to fix the grounding electrode 5 to the grounding fastening ring 2 with screws. The side of the grounding fastening ring 2 in contact with the thin-film electrode 1 is set as an arc that closely fits the rounded corner radian, so as to ensure that the thin-film electrode 1 fits with the signal collection electrode 3 and plays a role in tensioning the thin-film electrode 1. Among them, the radius of the arc is 5 mm.

[0029] The signal collection electrode 3 is used to block the charged particle beam, so its thickness needs to be greater than the range of the particle beam in the material. For 400 MeV / u carbon ions (12C6+), the thickness of this electrode is 120 mm and the diameter is 75 mm. The electrode material is oxygen-free copper. The chamfer on the side covering the thin-film electrode 1 is a rounded corner, and the radius of this rounded corner is 5 mm. This rounded corner design is used to cooperate with the grounding fastening ring 2, and the two are tightly fitted by pressing to tension and flatten the thin-film electrode 1. There is an M4 threaded hole at the bottom of the signal collection electrode 3 for leading out the signal wire, and the led-out signal wire is welded to the signal terminal 41 of the triaxial joint 4.

[0030] The grounding electrode 5 is coaxially arranged with the signal collection electrode 3. The grounding electrode 5 is arranged outside the signal collection electrode 3 and is spaced from the signal collection electrode 3. A protection electrode 6 is provided between the grounding electrode 5 and the signal collection electrode 3. The protection electrode 6 is coaxially arranged with the signal collection electrode 3, and its output end is connected to the protective ground terminal 43 of the triaxial joint 4. The protection electrode 6 and the signal collection electrode 3 are at the same electric potential to ensure the accuracy of this technology for weak current and high-precision measurement. The material of the protection electrode 6 is stainless steel, the inner diameter is 38.25 mm, the outer diameter is 39.25 mm, and the height is 125 mm. The gap with the signal collection electrode 3 is 3 mm. Coaxial insulating rings are provided between the grounding electrode 5, the signal collection electrode 3 and the protection electrode 6 to ensure mutual insulation between the three electrodes. The insulating ring is preferably a polyethylene ring.

[0031] The material of the grounding electrode 5 is aluminum, the inner diameter is 45 mm, the outer diameter is 48 mm, and the height is 153 mm. The gap with the protection electrode 6 is 4.75 mm. The grounding electrode 5 and the protection electrode 6 are fastened with M4 screws.

[0032] The working principle of the Faraday cup device in the present invention is as follows: When charged particles enter the atmosphere, they will ionize the atmosphere and generate electron-ion pairs, that is, secondary particles. If these secondary particles are not excluded, it will affect the accuracy of the Faraday cup in measuring the beam intensity. The Faraday cup used in a vacuum environment minimizes the generation of secondary particles through a high-vacuum environment. In an atmospheric environment, the thin-film electrode in the present invention blocks secondary particles from entering the Faraday cup collecting electrode. Since the thin-film electrode is a conductive material on the beam incident surface and is connected to the grounded electrode, these charged secondary particles will not flow into the collecting electrode, ensuring that the atmospheric environment does not affect the measurement. At the same time, the thin-film electrode can also suppress the secondary electrons generated by the signal collecting electrode. The thin-film electrode is in close contact with the signal collecting electrode, and the contact surface is either an insulator or a conductor. In the case of an insulator, the secondary electrons generated when the beam hits the signal collecting electrode drift to the insulating layer with very low energy and accumulate on the surface of the insulating layer in a short time, and then are quickly conducted away by the signal collecting electrode, thus playing a role in suppressing secondary electrons. A certain amount of secondary electrons will also be generated on the surface of the insulating layer and drift to the signal collecting electrode. However, due to the non-conductivity of the insulator, the escape of secondary electrons will inevitably cause the insulator itself to become positively charged. At this time, the electrons of the signal collecting electrode will transfer to the insulating layer and make the insulating layer regain electrical neutrality. The amount of charge transferred in both directions is equal, indicating that the secondary electrons generated on the surface of the insulating layer will not affect the measurement. In the case where the thin-film electrode is a conductor, it can be regarded as the conductor and the signal collecting electrode being integrated. Therefore, this case can also be regarded as a special case where the thin-film electrode has an insulating contact surface, and there is no difference in principle between the two. When in use, the Faraday cup device is placed in the area where the beam passes through, such as the particle beam cancer treatment terminal, and the beam center is aligned with the axis of the Faraday cup as much as possible. Then, the triaxial interface on the Faraday cup is connected to the triaxial interface of the measuring instrument through a triaxial cable. The user can monitor the beam line current intensity in real time through the measuring instrument.

[0033] In this embodiment, all components can be directly used in an atmospheric environment. This Faraday cup device can be used for particle beam cancer treatment without the need for vacuum pumping, thereby reducing the usage cost of the Faraday cup device. And since there is no need for a bias voltage device, there will be no problem of current leakage, and the detection accuracy is improved.

[0034] Embodiment 2

[0035] Based on the same inventive concept, this embodiment discloses an installation method for a bias-free Faraday cup device used in an atmospheric environment, which is used to install the bias-free Faraday cup device used in the above-mentioned Embodiment 1 in an atmospheric environment, and includes the following steps:

[0036] S1 Insert the first polyethylene ring 7 into the bottom of the grounding electrode 5. Then insert the protection electrode 6 into the first polyethylene ring 7, insert the second polyethylene ring 8 into the protection electrode 6, and fasten the second polyethylene ring 8 to the grounding electrode 5. In this embodiment, it is preferably to fasten the second polyethylene ring 8 to the grounding electrode 5 by M4 screws;

[0037] S2 Insert the signal collection electrode 3 into the second polyethylene ring 8, lay the thin film electrode 1 flat on the signal collection electrode 3. Then cover the grounding fastening ring 2 and fix the grounding fastening ring 2 on the top of the grounding electrode 5. The circumference of the grounding fastening ring 2 is provided with a plurality of threaded holes, and the grounding fastening ring 2 is fixed on the top of the grounding electrode 5 by M4 screws;

[0038] S3 Weld the lead-out signal wire of the signal collection electrode 3 to the signal terminal 41 of the triaxial joint 4, weld the lead-out wire of the protection electrode 6 to the protective ground terminal 43 of the triaxial joint 4, and weld the lead-out wire of the grounding electrode 5 to the grounding terminal 42 of the triaxial joint 4 to obtain a bias-free Faraday cup device for use in an atmospheric environment.

[0039] Embodiment III

[0040] Based on the same inventive concept, this embodiment discloses a particle beam cancer treatment system, which adopts any one of the bias-free Faraday cup devices for use in an atmospheric environment described above.

[0041] 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 them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the specific implementation manners of the present invention can still be modified or equivalently replaced. Any modification or equivalent replacement without departing from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention. The above content is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, and all should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An unbiased Faraday cup device used in an atmospheric environment, characterized in that, Comprising: a thin film electrode, a grounding fastening ring, a signal collection electrode, a triaxial joint, and a grounding electrode; the thin film electrode is fixed on the signal collection electrode through the grounding fastening ring and is in close contact with the signal collection electrode. The beam incident surface and the beam exit surface of the thin film electrode are insulated from each other. The signal output end of the signal collection electrode is connected to the signal end of the triaxial joint, and the grounding fastening ring is connected to the grounding end of the triaxial joint through the grounding electrode; a conductive material is plated on the beam incident surface of the thin film electrode, and the beam exit surface is made of an insulating material; a conductive material is also plated on the beam exit surface, but the conductive material on the beam exit surface is not electrically connected to the conductive material on the beam incident surface; a protection electrode is provided between the grounding electrode and the signal collection electrode. The protection electrode is coaxially arranged with the signal collection electrode, and its output end is connected to the protection ground end of the triaxial joint.

2. The unbiased Faraday cup device used in an atmospheric environment as claimed in claim 1, wherein the grounding electrode is coaxially arranged with the signal collection electrode. The grounding electrode is arranged outside the signal collection electrode and is spaced from the signal collection electrode.

3. The unbiased Faraday cup device used in an atmospheric environment according to claim 2, characterized in that, the protection electrode and the signal collection electrode have equal electric potentials.

4. The unbiased Faraday cup device used in an atmospheric environment according to claim 3, wherein coaxial insulating rings are provided between the grounding electrode, the signal collection electrode, and the protection electrode to ensure mutual insulation between the three electrodes.

5. The unbiased Faraday cup device used in an atmospheric environment as claimed in claim 1, wherein the chamfer at the end of the signal collection electrode in contact with the thin film is rounded, and the side of the grounding fastening ring in contact with the thin film electrode is set to be an arc shape matching the radian of the rounded corner to ensure the close contact between the thin film electrode and the signal collection electrode.

6. A method for installing a bias-free Faraday cup device used in an atmospheric environment, for installing the bias-free Faraday cup device used in an atmospheric environment according to any one of claims 1-5, characterized in that, Comprising the following steps: S1 Insert the first polyethylene ring into the bottom of the grounding electrode, then insert the protection electrode into the first polyethylene ring, insert the second polyethylene ring into the protection electrode, and fasten the second polyethylene ring to the grounding electrode; S2 Insert the signal collection electrode into the second polyethylene ring, lay the thin film electrode flat on the signal collection electrode, then cover the grounding fastening ring and fix the grounding fastening ring on the top of the grounding electrode; S3 Weld the lead-out signal wire of the signal collection electrode to the signal end of the triaxial joint, weld the lead-out wire of the protection electrode to the protection ground end of the triaxial joint, and weld the lead-out wire of the grounding electrode to the grounding end of the triaxial joint to obtain a bias-free Faraday cup device for use in an atmospheric environment.

7. A particle beam cancer treatment system, characterized in that, Adopt the bias-free Faraday cup device for use in an atmospheric environment according to any one of claims 1-5.

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