Built-in radio frequency antenna for radio frequency negative hydrogen ion source and manufacturing process

Abstract

The application discloses a built-in radio frequency antenna for a radio frequency negative hydrogen ion source and a manufacturing process, the radio frequency antenna has 2.5-3.5 turns, and the average loop diameter is 58mm; the coating of the built-in radio frequency antenna is an enamel structure, when the enamel structure simultaneously satisfies the conditions that the coating thickness is 0.6-0.7mm, the relative dielectric constant is less than 30, and the coating resistivity is greater than 45000Ω.cm, the warping voltage is close to 0; the process method comprises the following steps: manufacturing a sheet-shaped porcelain enamel; covering layer dipping; drying the copper antenna with the covering layer; firing the finished product; putting the dried copper antenna with the glaze into a melting furnace for firing and heat preservation; taking out the finished product and cooling to normal temperature. The steps (2) to (4) are repeated until the thickness of the glaze layer reaches about 0.6-0.7mm. The application effectively solves the problem of plasma back-bombing antenna, and the enamel coating is adopted, so that the cost is low, the manufacturing is simple, the material is solid, and the adhesion, impact resistance and thermal shock resistance are excellent.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency antenna technology, and particularly relates to a built-in radio frequency antenna for a radio frequency negative hydrogen ion source and its manufacturing process. Background Technology

[0002] In cyclotrons, ion source technology is a key technology. An ion source is a device that ionizes neutral atoms or molecules and extracts an ion beam from them. The ion source is the source of the beam, determines the beam quality, and directly affects the performance of the cyclotron.

[0003] High-current negative hydrogen radio frequency ion sources are a type of high-yield, high-current ion source that has been widely in demand in recent years, with extraction current exceeding 100 mA. Compared with existing low-yield, low-current ion sources, the difficulty in achieving high-yield, high-current ion sources lies in:

[0004] The contradiction lies in the high yield of plasma extraction and the relatively short lifespan of the built-in antenna. High yield extraction first requires high feed power efficiency of the ion source RF antenna (the ion source RF antenna is used to generate a vortex electric field, where residual electrons in the vacuum collide with hydrogen molecules or hydrogen atoms under the acceleration of the ion source RF antenna electric field to generate negative hydrogen ions). To solve the problem of low power utilization efficiency and weak extraction current of traditional external antenna RF ion sources, those skilled in the art have attempted to use built-in antenna RF ion sources to replace external antenna RF ion sources. This is because the built-in antenna is in direct contact with the plasma, resulting in high power feed efficiency and strong extraction current. However, the built-in antenna, being in direct contact with the plasma, will generate a plasma sheath: any object that directly contacts the plasma, especially if the object is charged, will generate a sheath. The sheath is a dynamic process of particle inflow and outflow, and the continuous inflow and outflow of particles will constantly hit the antenna, shortening its lifespan. Existing technologies, using external coils, do not come into contact with the plasma and therefore do not generate a sheath. Summary of the Invention

[0005] The purpose of this invention is to provide a built-in radio frequency antenna and manufacturing process for a radio frequency negative hydrogen ion source, which addresses the problems existing in the prior art. Under the premise of ensuring the normal operation of the radio frequency ion source, it effectively solves the problem of plasma back-boosting antenna and increases the service life of radio frequency antenna.

[0006] To solve its technical problem, the present invention adopts the following technical solution:

[0007] An embedded radio frequency antenna with an enamel coating for use in a radio frequency negative hydrogen ion source, wherein the embedded radio frequency antenna (2) is used in a pulse-mode multi-peak field embedded antenna type radio frequency high-current negative hydrogen ion source, which is capable of generating a high-current pulsed negative hydrogen ion beam, and is characterized by:

[0008] The built-in radio frequency antenna coil (2) has 2.5-3.5 turns, with an average winding diameter of 58mm, a leg spacing of 25mm between the straight sections at both ends, and a height of 40mm-50mm for the spiral winding section of the coil.

[0009] The coating of the built-in radio frequency antenna (2) is an enamel structure. When the enamel structure simultaneously meets the conditions of a coating thickness of 0.6-0.7 mm, a relative permittivity of less than 30, and a coating resistivity of greater than 45000 Ω·cm, the sheath voltage approaches 0.

[0010] The enamel glaze of this enamel structure comprises the following substances in parts by weight:

[0011] The composition consists of 95-105 parts base glaze, 4-8 parts clay, 1-5 parts quartz, 0.1-0.8 parts urea, 0.1-0.5 parts nitrite, and 45-55 parts water.

[0012] Furthermore, the enamel structure is an enamel structure that removes the metal oxides used for coloring, in order to reduce the relative permittivity of the coating.

[0013] Furthermore, the dielectric breakdown strength of this enamel structure exceeds 3kV / mm.

[0014] A fabrication process for an embedded radio frequency antenna capable of achieving a plasma sheath with no potential is characterized by the following steps:

[0015] Step 1: Making sheet-like porcelain glaze;

[0016] a. Mixing raw materials: The raw materials of the glaze are mixed evenly to obtain a mixture of glaze materials;

[0017] b. Melting: The mixture of glazes is placed in a crucible and melted;

[0018] c. Pressing: The molten glaze mixture is pressed into sheet-like porcelain glaze using a pressing machine;

[0019] Step 2: Enameling the coating layer;

[0020] The partial sheet-like porcelain glaze obtained in step one is ball-milled to obtain glaze powder for impregnating copper-bodied enamel antennas; the glaze powder is evenly impregnated onto the copper-bodied antenna to form a copper-bodied enamel antenna with a covering layer;

[0021] Step 3: Dry the copper-fiber antenna with the covering layer;

[0022] Step 4: Firing the finished product; Place the dried copper antenna covered with glaze into a furnace for firing and keep it warm; Remove the finished product and cool it to room temperature.

[0023] Step 5: Repeat steps (2) to (4) until the thickness of the glaze layer reaches about 0.6-0.7 mm.

[0024] Furthermore, in step one, the temperature for melting the glaze mixture is 1200-1250℃, and the melting time is 1-3 hours.

[0025] Furthermore, the glaze powder after ball milling in step two is sieved to a mesh size of 60-80; the bulk density of the glaze powder is 1.6-1.7 g / ml.

[0026] Furthermore, the thickness of the covering layer in step two is 100-250 μm.

[0027] Furthermore, the drying process conditions in step three are: temperature 70-120℃, time 5-30min.

[0028] Furthermore, the firing process conditions in step four are: a temperature of 760-860℃ and a firing time of 4-10 minutes; the heat preservation process conditions in step four are: a temperature of 400-600℃ and a heat preservation time of 1-5 minutes.

[0029] Advantages and effects of the present invention

[0030] 1. This invention provides an embedded radio frequency antenna with an enamel coating for use in radio frequency negative hydrogen ion sources. Based on the working principle of radio frequency ion sources, it effectively solves the problem of plasma back-boosting antennas and increases the service life of radio frequency antennas, addressing the technical requirements of isolating the potential difference between the embedded radio frequency antenna and the plasma, insulating between the coils and between the antenna and the inner cavity to prevent breakdown, and extending the working life.

[0031] 2. This invention achieves a plasma sheath without potential by simultaneously satisfying the conditions for coating thickness, relative permittivity, coating resistivity, and the mass composition ratio of the enamel glaze through the design of both the antenna structure and the enamel structure, fundamentally solving the problem of plasma back-boom antennas. Currently, the very few antenna coatings that meet the above requirements are mostly ceramic structures, which are expensive, complex to manufacture, brittle, and have poor adhesion to metals. The coating used in this invention is a commonly used enamel coating, which is low in cost, simple to manufacture, and robust, with excellent adhesion, impact resistance, and resistance to thermal shock. Furthermore, the enamel structure used in this invention was originally used in water heater inner tanks. While meeting the above coating requirements, it also has strong water resistance, i.e., low material porosity, which perfectly matches the requirements of antenna coatings and is highly conducive to the formation of a vacuum environment within the ion source.

[0032] 3. This invention achieves a significant cost reduction by setting the antenna coil number to 2.5-3.5 turns, the average coil diameter to 58mm, and the enamel structure simultaneously satisfying the following requirements: coating thickness of 0.6-0.7mm, relative permittivity less than 30, coating resistivity greater than 45000Ω·cm, and the enamel structure glaze comprising, by weight, 95-105 parts base glaze, 4-8 parts clay, 1-5 parts quartz, 0.1-0.8 parts urea, 0.1-0.5 parts nitrite, and 45-55 parts water. This allows the use of enamel coating instead of ceramic coating. For example, manufacturing a built-in RF antenna of the same specifications would cost tens of thousands of yuan using a ceramic coating, while using enamel coating would only cost several hundred yuan, a difference of 100 times, reducing the cost to one percent of the original. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the negative hydrogen ion source device of the present invention;

[0034] Figure 2 This is a schematic diagram of the built-in radio frequency antenna of the ion source of the present invention;

[0035] Figure 2a This is a schematic diagram showing that when the thickness, dielectric constant, and resistivity of the built-in antenna coating of the present invention meet certain conditions, the plasma sheath approaches zero potential.

[0036] Figure 2b This is a schematic diagram illustrating the realization of a plasma sheath without potential in this invention;

[0037] In the figure: 1: Negative hydrogen ion source; 1-1: Top cover of the ion source built-in radio frequency antenna; 1-2: Inner cavity of the ion source; 1-3: Outer cavity of the ion source; 2: Built-in radio frequency antenna of the ion source; 3: Permanent magnet array; 4: Ion source extraction structure; 3-1: Filter magnet array. Detailed Implementation

[0038] Design principle of the invention

[0039] Design of a high-yield, high-current negative hydrogen built-in radio frequency antenna:

[0040] ① The Relationship Between Coil Structure Design and Coil Coating Design: When an alternating current is applied to the coil to generate a vortex electric field for accelerating electrons, the antenna itself will generate a self-induced voltage. Research shows that the antenna's self-induced voltage must be maintained by the coating and the plasma sheath; that is, the voltages of the antenna coating and the plasma sheath must jointly limit the self-induced voltage. Simultaneously, a relatively low plasma sheath potential difference can reduce the sputtering of ions from the plasma onto the antenna coating, increasing the lifespan of the RF antenna. Therefore, it is desirable for the plasma sheath to have no potential difference, thus confining the potential within the coating and preventing breakdown between the antenna and the internal cavity. In this case, the design of an internal RF antenna requires the structure and coating of the internal coil. The structural design of the internal coil determines the magnitude of the self-induced voltage; only by predicting the magnitude of the self-induced voltage can breakdown be avoided. The design of the internal coil coating determines how to ensure that the plasma sheath has no potential.

[0041] like Figure 2b As shown, from left to right, there are four regions: antenna, antenna coating, plasma sheath, and plasma. There are two lines running vertically. When the upper line confines the potential within the antenna coating, there is almost no potential difference in the plasma layer; this is called "no potential in the sheath." Confining the potential within the antenna coating means that the highest voltage point is located within the antenna coating. When the highest voltage point is in the plasma sheath, the plasma sheath "has" a potential. Because the sheath is a dynamic environment with particles flowing in and out, the continuous inflow and outflow of particles will constantly bombard the antenna, shortening its lifespan.

[0042] ② Design of the Built-in RF Antenna: The design of the built-in antenna in this invention includes two aspects. First, the design of the coil structure: Research shows that in an inductively coupled (ICP) RF ion source, the RF current flowing through the RF antenna induces a RF vortex electric field coaxial with the coil. Residual electrons within the cavity undergo reciprocating swirling motion under the influence of the vortex electric field, colliding with gas molecules and ionizing them, ultimately generating plasma. When the RF frequency is selected, the magnitude of the vortex electric field is only related to the coil diameter and number of turns. Therefore, the main parameters for antenna design are the loop diameter and the number of turns. Specifically: The ion source's built-in radio frequency antenna has 2.5-3.5 turns, with an average coil diameter of 58mm, a leg spacing of 25mm at both ends, and a coil spiral height of 40mm-50mm. Secondly, the coil coating design: Research indicates that the impedance distribution of the plasma sheath and insulating coating is a parallel combination of capacitance and resistance. Referring to the numerical calculation model of fusion plasma and replacing the parameters with typical ion source parameters, numerical calculations were performed. The final calculation shows that to achieve zero voltage distribution in the plasma sheath, the following conditions must be met simultaneously: coating thickness greater than 0.4mm, relative permittivity less than 30, coating resistivity greater than 45000Ω·cm, and dielectric breakdown strength exceeding 3kV / mm. For most enamels, the ideal resistivity is approximately 10. 14 The dielectric constant is approximately 10 kV / mm, with an average dielectric breakdown strength of Ω·cm and a relative permittivity of approximately 20 after removing the metal oxides used for coloring. Furthermore, since the thermal effect of the radio frequency field on the antenna is almost uniform across the thickness, and the antenna is directly water-cooled, the influence of the thermal effect on the coating can be ignored. Therefore, enamel material can meet the requirements for radio frequency antenna coatings, but a certain porosity is necessary.

[0043] Based on the above principles, this invention designs a built-in radio frequency antenna with an enamel coating for use as a radio frequency negative hydrogen ion source.

[0044] An embedded radio frequency antenna with an enamel coating for use in a radio frequency negative hydrogen ion source, wherein the embedded radio frequency antenna 2 is used in a pulse-mode multi-peak field embedded antenna type radio frequency high-current negative hydrogen ion source, the ion source being capable of generating a high-current pulsed negative hydrogen ion beam, characterized in that:

[0045] The built-in radio frequency antenna coil has 2.5-3.5 turns, with an average winding diameter of 58mm. The distance between the legs of the straight sections at both ends is 25mm, and the height of the spiral winding section of the coil is 40mm-50mm.

[0046] like Figure 2aAs shown, the coating of the built-in radio frequency antenna 2 is an enamel structure. When the enamel structure simultaneously meets the conditions of a coating thickness of 0.6-0.7 mm, a relative permittivity of less than 30, and a coating resistivity of greater than 45000 Ω·cm, the sheath voltage approaches 0.

[0047] The enamel glaze of this enamel structure comprises the following substances in parts by weight:

[0048] The composition consists of 95-105 parts base glaze, 4-8 parts clay, 1-5 parts quartz, 0.1-0.8 parts urea, 0.1-0.5 parts nitrite, and 45-55 parts water.

[0049] Supplementary Note 1:

[0050] The pulse-mode multi-peak field built-in antenna type radio frequency high-current negative hydrogen ion source 1, as shown in the example Figure 1 As shown, from top to bottom and from outside to inside, it includes: an ion source built-in radio frequency antenna 2, an ion source built-in radio frequency antenna cover plate 1-1, an ion source inner cavity 1-2, an ion source outer cavity 1-3, a permanent magnet array 3 located between the ion source inner cavity 1-2 and the ion source outer cavity 1-3, an ion source extraction structure 4, and an ion source composite structure filter field located at the bottom layer of the permanent magnet array and the ion source extraction structure. The ion source composite structure filter field is composed of a filter magnet array 3-1 and a magnet 4-3 attracting magnet of the ion source extraction structure. The ion source built-in radio frequency antenna 2 is externally connected to a dual-frequency drive system. The dual-frequency drive system is connected to the built-in radio frequency antenna 2 located on the cover plate via an impedance matching and isolation system, and its radio frequency power is coupled to the ion source through the built-in radio frequency antenna 2. The ion source cavity 1-2 is composed of an ion source built-in radio frequency antenna 2, which generates a vortex electric field, causing residual free electrons in the air to collide with hydrogen gas introduced into the ion source under the action of the electric field to generate negative hydrogen ions; the permanent magnet array 3 is used to provide a confinement magnetic field for the ion source cavity 1-2; the ion source composite structure filter field is used to form a transverse magnetic field to filter fast electrons and slow electrons respectively; the ion source built-in radio frequency antenna 2 is a built-in radio frequency antenna with an enamel coating that can achieve no potential in the plasma sheath; the composite structure filter field is a composite structure filter field in which a magnetic field is superimposed at the highest point of the filter field to filter fast electrons; the ion source extraction structure 4 is an ion source extraction structure that extracts a negative hydrogen current intensity of more than 100mA under a high voltage of 60kV.

[0051] Supplementary Note 2:

[0052] like Figure 2bAs shown, the ultimate goal of this invention is to cancel out the self-induced voltage in the built-in coil by the voltage of the antenna coating and the voltage of the plasma sheath. Since it is desirable that the voltage of the plasma sheath is essentially zero potential, the highest point of the voltage must be cut off within the antenna coating. As shown in the figure, the highest point of the upper line is essentially within the antenna coating.

[0053] Figure 2a As shown, in order to make the voltage of the plasma sheath essentially zero, the antenna coating must simultaneously meet three conditions: a coating thickness of 0.6-0.7 mm, a relative permittivity of less than 30, and a coating resistivity greater than 45000 Ω·cm.

[0054] Most commonly used antenna coatings only consider insulation and breakdown protection, failing to meet the aforementioned requirements and thus not fundamentally solving the problem of plasma return bombardment antennas. The very few currently used coatings that meet these requirements are mostly ceramic structures, which are expensive, complex to manufacture, brittle, and have poor adhesion to metals. The coating used in this invention is a commonly used enamel coating, which is lower in cost, simple to manufacture, and robust, exhibiting excellent adhesion, impact resistance, and resistance to thermal shock. Furthermore, the enamel structure used in this invention was originally used in water heater inner tanks; while meeting the aforementioned coating requirements, it also possesses strong waterproof properties, indicating low material porosity, which perfectly matches the requirements of antenna coatings and is highly conducive to the formation of a vacuum environment within the ion source.

[0055] Furthermore, the enamel structure is an enamel structure that removes the metal oxides used for coloring, in order to reduce the relative permittivity of the coating.

[0056] The dielectric breakdown strength of the enamel structure exceeds 3kV / mm.

[0057] A fabrication process for an embedded radio frequency antenna capable of achieving a plasma sheath with no potential is characterized by the following steps:

[0058] Step 1: Making sheet-like porcelain glaze;

[0059] a. Mixing raw materials: The raw materials of the glaze are mixed evenly to obtain a mixture of glaze materials;

[0060] b. Melting: The mixture of glazes is placed in a crucible and melted;

[0061] c. Pressing: The molten glaze mixture is pressed into sheet-like porcelain glaze using a pressing machine;

[0062] Step 2: Enameling the coating layer;

[0063] The partial sheet-like porcelain glaze obtained in step one is ball-milled to obtain glaze powder for impregnating copper-bodied enamel antennas; the glaze powder is evenly impregnated onto the copper-bodied antenna to form a copper-bodied enamel antenna with a covering layer;

[0064] Step 3: Dry the copper-fiber antenna with the covering layer;

[0065] Step 4: Firing the finished product; Place the dried copper antenna covered with glaze into a furnace for firing and keep it warm; Remove the finished product and cool it to room temperature.

[0066] Step 5: Repeat steps (2) to (4) until the thickness of the glaze layer reaches about 0.6-0.7 mm.

[0067] Furthermore, in step one, the temperature for melting the glaze mixture is 1200-1250℃, and the melting time is 1-3 hours.

[0068] Furthermore, the glaze powder after ball milling in step two is sieved to a mesh size of 60-80; the bulk density of the glaze powder is 1.6-1.7 g / ml.

[0069] Furthermore, the thickness of the covering layer in step two is 100-250 μm.

[0070] Furthermore, the drying process conditions in step three are: temperature 70-120℃, time 5-30min.

[0071] Furthermore, the firing process conditions in step four are: a temperature of 760-860℃ and a firing time of 4-10 minutes; the heat preservation process conditions in step four are: a temperature of 400-600℃ and a heat preservation time of 1-5 minutes.

[0072] It should be emphasized that the above specific embodiments are merely explanations of the present invention and are not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to the above embodiments without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A built-in radio frequency antenna with an enamel coating for use in a radio frequency negative hydrogen ion source, wherein the built-in radio frequency antenna (2) is used in a pulse-mode multi-peak field built-in antenna type radio frequency high-current negative hydrogen ion source, the ion source being capable of generating a high-current pulsed negative hydrogen ion beam, characterized in that: The built-in radio frequency antenna (2) has 2.5-3.5 turns of coil, with an average winding diameter of 58mm, a leg spacing of 25mm between the straight sections at both ends, and a height of 40mm-50mm for the spiral winding section of the coil. The coating of the built-in radio frequency antenna (2) is an enamel structure. When the enamel structure simultaneously meets the conditions of a coating thickness of 0.6-0.7 mm, a relative permittivity of less than 30, and a coating resistivity of greater than 45000 Ω·cm, the warp voltage approaches 0. The enamel glaze of this enamel structure comprises the following substances in parts by weight: Base glaze 95-105 parts, clay 4-8 parts, quartz 1-5 parts, urea 0.1-0.8 parts, nitrite 0.1-0.5 parts, water 45-55 parts; The enamel structure is an enamel structure that removes the metal oxides used for coloring, in order to reduce the relative permittivity of the coating; The dielectric breakdown strength of the enamel structure exceeds 3kV / mm.

2. A process for the production of an internal radio frequency antenna for a radio frequency negative hydrogen ion source with a sputtered coating for the potential free plasma sheath of claim 1, characterized in that Includes the following steps: Step 1: Making sheet-like porcelain glaze; a. Mixing raw materials: The raw materials of the glaze are mixed evenly to obtain a mixture of glaze materials; b. Melting: The mixture of glazes is placed in a crucible and melted; c. Pressing: The molten glaze mixture is pressed into sheet-like porcelain glaze using a pressing machine; Step 2: Enameling the coating layer; The partial sheet-like porcelain glaze obtained in step one is ball-milled to obtain glaze powder for impregnating copper-bodied enamel antennas; the glaze powder is evenly impregnated onto the copper-bodied antenna to form a copper-bodied enamel antenna with a covering layer; Step 3: Dry the copper-fiber antenna with the covering layer; Step 4: Firing the finished product; Place the dried copper antenna covered with glaze into a furnace for firing and keep it warm; Remove the finished product and cool it to room temperature; Step 5: Repeat steps (2) to (4) until the thickness of the glaze layer reaches about 0.6-0.7 mm.

3. The process for making a built-in radio frequency antenna capable of realizing a plasma sheath potential-free according to claim 2, wherein: The temperature for melting the glaze mixture in step one is 1200-1250℃, and the melting time is 1-3 hours.

4. The process for making a built-in RF antenna capable of realizing a plasma sheath potential-free according to claim 2, wherein: In step two, the ball-milled glaze powder is sieved to a mesh size of 60-80; the bulk density of the glaze powder is 1.6-1.7 g / ml.

5. The process for making a built-in radio frequency antenna capable of realizing a plasma sheath potential-free according to claim 2, wherein: The thickness of the cover layer in step two is 100-250 μm.

6. The process for making a built-in radio frequency antenna capable of realizing a plasma sheath potential-free according to claim 2, wherein: The drying process conditions in step three are: temperature 70-120℃, time 5-30min.

7. The process for making a built-in radio frequency antenna capable of realizing a plasma sheath potential-free according to claim 2, wherein: The firing conditions in step four are: a temperature of 760-860℃ and a firing time of 4-10 minutes; the heat preservation conditions in step four are: a temperature of 400-600℃ and a heat preservation time of 1-5 minutes.

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