Method and apparatus for treating the surface of an accelerating cavity by ion implantation

Abstract

The present invention relates to a technique for treating the surfaces of one or more accelerator cavities (C) of an accelerator module (M). The technique relies on at least partially scanning the inner surface (S) of one or more accelerator cavities using a particle beam. Such a technique provides a more suitable treatment solution for the accelerator cavities and better control of implantation parameters.

Description

Technical Field

[0001] The present invention is in the field of surface treatment. More particularly, the present invention relates to a technique for treating the inner surface of a cavity, generally called an accelerating cavity or a resonant cavity, such as used in a particle accelerator.

Background Art

[0002] The following description is particularly relevant to the problems existing in the field of superconducting particle accelerators faced by the inventors of the present application. Of course, the present invention is not limited to this specific field of application and is important for any surface treatment technology that has to address closely related problems or similar problems.

[0003] A particle accelerator is a device aimed at accelerating elementary particles to high energies. Among various existing devices, some are equipped with one or more accelerator modules in the form of a series of (RF) radio frequency accelerating cavities, and in each of the accelerating cavities, the particles are accelerated by the electromagnetic field applied thereto. The shape and dimensions of the accelerating cavity vary from accelerator to accelerator and depend on various factors. These RF accelerating cavities can be formed from various metallic materials or alloys, and the most commonly used ones are copper and niobium (chemical symbol Nb). Niobium is a superconducting material that exhibits excellent performance at very low temperatures (generally below 2°K). In such a cavity, superconductivity makes it possible to reduce the surface resistance of its inner wall. Therefore, this phenomenon is localized at the level of the first nanometer layer of niobium.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to improve the resonance performance of accelerating cavities, and in particular to increase the quality factor of these cavities, it has been demonstrated that surface treatment by nitrogen doping of niobium walls is possible. Nevertheless, such treatment remains a delicate operation to carry out, particularly due to the shape and dimensions of the accelerating cavities, as well as the difficult access to these specific internal regions.

[0005] Known treatment methods are based on the technique of doping niobium cavities by nitrogen implantation. This process includes a high-temperature heat treatment (usually 600 - 1000 °C) of the niobium cavities in a treatment chamber saturated with nitrogen gas. By such a method, it becomes possible to change the physico-chemical properties of the surface and internal structure of the cavity to improve the quality factor. However, this is a process that consumes a large amount of time and energy. Furthermore, in this type of process, it remains difficult to control not only the depth of nitrogen implanted into the cavity walls, but also the nitrogen concentration. And depending on the dimensions and specific shape of the accelerating cavity, it is necessary to use a relatively large-sized treatment chamber. Also, in this process, it is necessary to perform an electrochemical polishing step in the cavity to remove the niobium nitride layer formed on the surface over a thickness of several microns (about 5 - 10 μm). In fact, the high-temperature treatment results in the formation of a niobium nitride layer that has the effect of degrading the superconducting properties and significantly increasing the surface resistance of the cavity. Also, this electrochemical polishing treatment makes it possible to find an acceptable roughness to obtain the desired properties.

[0006] Therefore, it is particularly interesting to have a surface treatment technology that is technically more suitable for accelerating cavities and that can more appropriately control the doping parameters, especially to increase the treatment efficiency.

Means for Solving the Problem

[0007] In certain embodiments of the present invention, a method for treating the surface of at least one accelerating cavity of an accelerator module is proposed, the method comprising using a particle beam to treat the inner surface of said at least one cavity by injection of particles.

[0008] "Inner surface" means all or part of the inner surface of said at least one cavity. In other words, the use of the particle beam according to the present invention is carried out to treat at least partially the inner surface of said at least one cavity.

[0009] Accordingly, the present invention proposes an alternative to prior art techniques, which involves exposing the inner surface of one or more accelerating cavities to a particle beam in order to perform surface treatment by injection of particles. This new approach offers the possibility of performing surface treatment of accelerating cavities at low temperature (i.e., around ambient temperature), and such treatment can be carried out selectively or not at all. Also, this new approach allows for better control of the injection parameters, in particular better control of the depth and concentration of the injection, unlike the methods of the aforementioned prior art (implant doping).

[0010] According to certain aspects of the present invention, the use step includes a step of scanning the inner surface by moving a particle beam relative to the inner surface or by moving the inner surface relative to the particle beam. Thereby, an effective and high-quality surface treatment can be performed. By performing the scanning of the particle beam, in particular, easier access to specific inner portions of cavities that are difficult to access becomes possible. Thus, unlike the prior art, the present invention provides a method that more easily adapts to the dimensions and shapes of the accelerating cavities to be processed. Furthermore, by using a particle beam, it becomes possible to reduce the amount of particles used compared to the case of doping by implantation according to the prior art. Furthermore, due to the advantages of low-temperature treatment, it becomes possible to avoid or at least reduce the formation of a surface of a compound that is harmful to the characteristics of the cavity. Thereby, it becomes possible to omit an electrochemical polishing step as in the case of the prior art method. In fact, the present invention provides a processing solution that is simple and inexpensive to implement.

[0011] According to certain characteristics, the scanning step is preceded by the following steps, namely, - introducing a scanning head for the inner surface by at least one of electricity and magnetism through an orifice of an accelerator module into the at least one cavity; - generating a particle beam in the direction of the scanning head introduced into the at least one cavity in a vacuum; and is The scanning step is carried out by driving the scanning head.

[0012] Thus, the present invention provides the possibility of performing an electrical, magnetic or electromagnetic scan of the inner surface by simply driving a scanning head pre-introduced into the cavity. The scan is performed around a first scan axis.

[0013] According to an additional aspect of the present invention, the scanning step includes rotating the at least one cavity relative to the scanning head, or rotating the scanning head relative to the at least one cavity. The rotational drive is performed around a second scanning axis. Thus, the present invention provides the possibility of further performing mechanical scanning of the inner surface by simply rotating the cavity relative to the scanning head, or the scanning head relative to the cavity.

[0014] Alternatively, or in addition thereto, the scanning step includes translating the scanning head relative to the at least one cavity, or translating the at least one cavity relative to the scanning head. The translational drive is performed along the aforementioned second scanning axis. Thus, the present invention provides another way to mechanically sweep the inner surface of the cavity. The rotation step and the translational drive step can be performed continuously or simultaneously depending on the desired scanning pattern.

[0015] According to a particular aspect of the present invention, the particles of the beam are particles selected from species belonging to a group including species based on atomic species, molecular species, ionic species, molecular and ionic species, at least one elementary particle. Thus, the method according to the present invention is adapted to different types of particles to be implanted, and the selection depends on the material of the inner wall of the cavity to be treated and the nature of the desired surface treatment.

[0016] According to a particular aspect of the present invention, the particles of the beam are ions selected from elements belonging to a group including nitrogen (N), helium (He), titanium (Ti), argon (Ar), oxygen (O), iron (Fe), aluminum (Al), neon (Ne), krypton (Kr), xenon (Xe), boron (B), carbon (C), fluorine (F), silicon (Si), phosphorus (P), sulfur (S). Thus, the process according to the present invention is adapted to ions of different natures. This list of items does not necessarily cover all of them. The selection depends on the material of the cavity to be treated and the nature of the desired surface treatment.

[0017] According to a particularly advantageous feature, the inner surface of the at least one cavity is formed from niobium (Nb), and the particle beam used is a beam of nitrogen ions with a single charge or multiple charges. The use of such a beam makes it possible to improve the resonance quality factor of the niobium cavity thus treated.

[0018] The present invention also relates to products directly obtained from this process and, in particular, to the subsequent use of the products in particle accelerators. Thus, according to other specific embodiments, an accelerating cavity of an accelerator module obtained by the aforementioned treatment method in any one of the various embodiments is proposed. In this regard, it should be noted that such a treatment process is usually carried out in a more comprehensive process of manufacturing accelerating cavities for particle accelerators. Such an accelerating cavity is obtained by a surface treatment carried out by the aforementioned method, characterized by a step of scanning the inner surface of the cavity by moving a particle beam relative to the inner surface or the inner surface relative to the particle beam. After treatment, the accelerating cavity has a quality factor of 1×10 11 ~1×10 14 In another embodiment of the present invention, a computer program product is provided, which includes program code instructions for implementing the aforementioned method (in any one of its various embodiments) when the program is executed on a computer.

[0019] In another embodiment of the present invention, a computer-readable persistent storage medium is provided that stores a computer program including a set of computer-executable instructions for executing the aforementioned method (in any one of its various embodiments).

[0020] In another embodiment of the present invention, a surface treatment device for at least one accelerating cavity of an accelerator module is proposed, the device comprising means for scanning the inner surface of the at least one cavity with a particle beam.

[0021] In another embodiment of the present invention, a surface treatment device for at least one accelerating cavity of an accelerator module is proposed, the device comprising means for scanning the inner surface of the at least one cavity with a particle beam.

[0022] Accordingly, the present invention proposes a more efficient and easier-to-implement alternative to the prior art surface treatment apparatus. The general principle of the present invention in this embodiment is to expose the inner surface of one or more acceleration cavities to particle beam scanning and perform surface treatment by particle implantation within the acceleration cavities. This new approach enables low-temperature treatment, which can be either selective (e.g., by scanning part of the inner surface of the cavity) or non-selective (e.g., by scanning the entire inner surface). And, compared with the aforementioned prior art, the use of particle beams provides better control of the implantation parameters, particularly the depth and concentration of the implanted particles.

[0023] Supplementary, the apparatus further - means for introducing a scanning head for the inner surface by at least one of electricity and magnetism into the at least one cavity, the means for introducing and the scanning head being configured to be insertable into the at least one cavity; - means for generating a particle beam under vacuum in the direction of the scanning head; and the scanning means comprises a scanning head.

[0024] More specifically, the scanning head comprises a beam deflector capable of deflecting the generated beam towards the inner surface, and a beam exit aperture arranged relative to the beam deflector so as to allow the deflected beam to pass in the direction of the inner surface. In this way, by applying at least one of simple electric and magnetic forces, the particle beam is deflected from its trajectory within the cavity itself for the purpose of surface treatment. The present invention actually gives the possibility of performing purely electrical, magnetic, or electromagnetic scanning around a first scanning axis in order to treat the inner surface of the cavity.

[0025] Supplementary, the scanning means comprises means for rotationally driving the at least one cavity relative to the scanning head, or the scanning head relative to the at least one cavity. Thus, in a clever way, a hybrid scan of purely mechanical or electromechanical or magnetomechanical type can be performed to process the inner surface of the cavity.

[0026] Supplementary or alternative, the scanning means comprises means for translationally driving the scanning head relative to the at least one cavity, or the at least one cavity relative to the scanning head. Thus, the present invention also gives the possibility of performing the scan alone or in combination with the aforementioned rotational driving means.

[0027] According to a particular form, the accelerator module comprises a plurality of successive acceleration cavities, and the translational driving means is configured to continuously introduce the scanning head in order to scan the inner surface of each of the plurality of cavities. Thus, it is possible to continuously process the inner surfaces of several cavities over time with a single scanning head.

[0028] According to a variant embodiment, the accelerator module comprises a plurality of successive acceleration cavities, the introducing means comprises a plurality of separate scanning heads arranged continuously along the introducing means, and each scanning head is configured to operate so as to scan the inner surface of a different cavity from the others. This variant is particularly interesting because it can perform the processing of several cavities without the need to perform the translation of the scanning head during the multi-cavity processing. Thus, such a form is easier to implement and can shorten the processing time. Furthermore, compared with the aforementioned particular form, it is possible to rely on introducing means that shorten the length by half for an accelerator module of the same length. Note the dual function of the translational driving means according to the present invention, namely, the positioning of the scanning head within at least one acceleration cavity and, if necessary, the involvement in the scanning of the inner surface of the acceleration cavity related to the first scanning axis.

[0029] According to certain features, the device is configured to form a housing, which can be placed under vacuum, together with the accelerator module. In this way, the device and the accelerator module form a system comprising a processing housing that can be placed under a controlled atmosphere. Thus, unlike the aforementioned prior art in which the accelerator module is arranged in a dedicated processing housing, the device according to the present invention makes good use of the accelerator module (regardless of the number of cavities) to form a processing housing, and thus provides a device with reduced dimensions. In this case, the processing housing is formed by the at least one acceleration cavity, a connection and vacuum guide connecting means for generating a particle beam under vacuum to a first orifice of the at least one cavity, and an absorption closure member coupled to a second port of the at least one cavity. Placing the storage container under vacuum facilitates the use of the particle beam generated by the generating means.

[0030] More generally, the processing device according to the present invention comprises means for carrying out the steps to be executed by the aforementioned processing method in any of its various embodiments. Further features and advantages of the present invention will become apparent from the following description, given by way of illustrative and non-limiting example, and from the accompanying drawings.

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 6A

Figure 6B

Figure 7

Mode for Carrying Out the Invention

[0032] In the drawings attached to this specification, the same elements are denoted by the same reference numerals. The general principle of the present invention is based on processing the inner surface of one or more accelerating cavities of an accelerator module using a particle beam. Such an approach enables effective surface treatment and is particularly suitable for this type of cavity.

[0033] In the remainder of this document, particular attention is paid to the description of the present invention in the case of a linear superconducting acceleration structure. Of course, this is a specific application example that can be easily adapted to many other uses without departing from the scope of the present invention.

[0034] 〔Single Cavity Processing〕 FIG. 1 schematically shows the operating principle of a processing apparatus D1 according to a specific embodiment of the present invention.

[0035] In this specific embodiment, the apparatus D1 is configured to process the inner surface S of the accelerating cavity C by ion implantation. This surface treatment aims to enhance the resonance performance of the accelerating cavity.

[0036] As an example, the accelerator module M shown in this figure has only one accelerating cavity. The inner surface S of the accelerating cavity C is formed of niobium (symbol Nb), a superconducting material frequently used in the manufacture of accelerator modules. The particle beam used here is a nitrogen-based ion beam. The apparatus D1 and the accelerator module M form a processing system according to the present invention, which is represented here by a coordinate system X, Y, Z.

[0037] The cavity C has rotational symmetry about the vertical axis X. This axis is shown by the dotted line X in the figure. Orthogonal to this vertical axis X, the cavity C extends radially in the YZ plane, but extends progressively along the vertical axis X, defining a substantially annular overall shape. The cavity C comprises an inlet orifice O1 and an outlet orifice O2 with circular cross-sections, both of these orifices being centered on the vertical axis X.

[0038] Particularly with regard to energy, in order to make the surface treatment more efficient and less costly, the device according to the invention has scanning means configured to perform a controlled scan of the inner surface S of the cavity C by means of an ion beam. The scan is performed either by the movement of the ion beam relative to the inner surface S or, conversely, by the displacement of the inner surface S relative to the ion beam. The scanning means presented below are of different types. These can be operated individually or in combination, sequentially or simultaneously, depending on the desired scan pattern. The principle of use of the ion beam will be explained in detail later in connection with Figure 2.

[0039] In this particular embodiment, the device D1 comprises - means 10 for generating a beam of ions, such as an electron cyclotron resonance source (or ECR source) configured to generate a beam of monovalent nitrogen ions (symbol N+), - a magnetic scanning head 30 capable of scanning the inner surface S by deflecting the ion beam towards the inner surface S by means of a magnetic force applied to this beam, - means 20 for introducing the scanning head 30 into the cavity C, - a connection and vacuum guide 40, - an absorption closure member 50 arranged at the cavity outlet, - a control unit 80 configured to control the above-mentioned means 10, 20, 30 and 40, and comprises.

[0040] In the example shown here, the scanning means is magnetically ensured by the scanning head 30 included in the introducing means 20. Such a scanning head is composed of, for example, a beam exit opening and a magnetic dipole arranged in the vicinity of this opening, as shown in FIGS. 5A and 5B.

[0041] The introducing means 20 exists here in the form of a long rod centered on the vertical axis X and extending along the vertical axis X. The rod 20 is designed to have sufficient rigidity to be able to carry the scanning head 30 to the center of the cavity C without undergoing mechanical deformation. Further, the rod 20 is dimensioned such that the rod 20 and the scanning head 30 can be inserted into the cavity C through the orifices O1 - O2. According to a particular embodiment, the rod 20 must be shaped so as not to interfere with the incident ion beam Fi emitted by the ion source 10. For example, a tubular rod centered on the vertical axis X and extending along the vertical axis X is suitable for the ion beam to pass through its center along the vertical axis X. Further details regarding the implementation of the magnetic scanning head 30 will be described later in relation to FIGS. 5A and 5B.

[0042] The connection guide 40 is a tubular element centered on the vertical axis X and extending along the vertical axis X. The connection guide is hermetically connected on the one hand to the ion source 10 and on the other hand to the inlet orifice O1 of the cavity C by the annular connection flange R1. Also, the guide 40 is provided with a support member T fixedly attached to the inner wall of the guide and arranged to align and support the insertion rod 20 along the vertical axis X. Additionally, the support member T provided in the guide 40 can serve to translate the introduction rod 20 along the vertical axis X. And in order to place the system in a controlled atmosphere, a vacuum pump (not shown) is connected to the guide 40 by a sealing member (also not shown).

[0043] The absorption and closure member 50 is in the form of a tube with one end closed by the absorption bottom, and the other end is hermetically connected to the O2 outlet orifice by the annular connection flange R2. The absorption bottom comprises at least one layer of a material selected for its absorption properties of ionizing radiation (in other words, in this case, a material selected for its stopping power for nitrogen ions) for the purpose of blocking residual or unused ions during processing. Thus, the member 50 performs the ion absorption function but also seals the O2 outlet orifice.

[0044] According to a particularly advantageous form, the elements referred to by 10, 40, O1, C, O2 and 50 are module elements configured to form a sealed processing housing that can be placed under vacuum. In fact, in order to improve the performance of ion implantation, it is preferable to have the processing chamber under controlled vacuum. This vacuum prevents the blocking of the ion beam by residual gases and makes it possible to avoid the contamination of the inner surface of the object to be processed by these same gases during the implantation process. The ion beam thus generated is more stable, thereby improving the implantation accuracy. The housing is evacuated in the conventional manner by a vacuum pump connected to the guide 40. Thus, unlike the prior art, there is no longer a need to provide a full-sized processing housing of the size that houses the accelerator module. This is because the device according to the invention enables the accelerator module M itself to be used well to form a housing with a controlled atmosphere. Thus, thanks to the present invention, it is possible to have a processing device of reduced size.

[0045] As can be seen from the above, in the example shown in FIG. 1, the scanning means is ensured by the magnetic scanning head 30 (hereinafter referred to as "the first scanning means").

[0046] Supplementally, the scanning means according to the present invention is also ensured by means of rotationally driving the cavity C around the vertical axis X with respect to the magnetic scanning head 30. These driving means are essentially mechanical and are hereinafter referred to as "second scanning means". The rotational driving means are here represented by the rotating annular flanges R1 and R2 respectively arranged at the outlets of the inlet orifice O1 and the outlet orifice O2. These flanges are designed, in more detail, to be able to rotate the cavity C with respect to the connection guide 40 (given by the rotating flange R1) on the one hand and with respect to the closing member 50 (given by the rotating flange R2) on the other hand. The axis of rotation of the cavity C coincides with the vertical axis X. Each of the rotating flanges R1 to R2 is provided, for example, with a part of an annular seal, which can ensure a vacuum-tight connection with each element to which it is connected.

[0047] Here, in relation to FIG. 2, the main steps of the method according to a particular embodiment of the present invention are presented. This method is partially implemented by a control unit, the principle of which will be described in detail later in relation to FIG. 7. This control unit is configured to control the ion source 10, the first scanning means (30) and the second scanning means (R1, R2), as well as a vacuum pump. The control of these various elements by the control unit is executed by control commands.

[0048] First, the device D1 is fixed by assembling the following modular elements, that is, by assembling the connection guide 40 to the ion source 10, assembling the connection guide 40 to the inlet orifice O1 via the flange R1, and assembling the closing absorption member 50 to the outlet port via the flange R2. The insertion rod 20 supporting the magnetic head 30 is introduced into the cavity C through the orifice O1 so that the magnetic head is arranged at the center of the cavity C as shown in FIG. 1. This insertion step is labeled 100 in FIG. 2 and is manually executed during the assembly of the various modular elements. At least one modular element support structure can be used to make the modular elements movable and facilitate the assembly of the modular elements.

[0049] Supplementally or alternatively, the magnetic head 30 can be automatically introduced into the cavity C with the aid of a programmable automaton or by using means for driving the rod 20 in translational motion along the vertical axis X. In this example, this function is performed by the translator T. In this case, the control unit must be configured to also control the translator T. Of course, alternatively, it is also possible to proceed with the introduction of the rod and thus the scanning head via the outlet orifice, and the above principle is applied in the same manner.

[0050] Next, in step 200, the processing housing is placed under vacuum by operating a vacuum pump connected to the connection guide 40. When the pressure in the processing housing reaches about 10 -5 ~10 -8 mbar, it is considered that the inside of the housing has reached a vacuum, and the next step is executed.

[0051] Although it is preferable to place the processing housing under vacuum in order to improve the ion implantation conditions according to the present invention, embodiments with a "low degree of vacuum" in which the processing housing is out of vacuum (i.e., at atmospheric pressure) can be fully considered.

[0052] In step 300, the ion source 10 is activated so as to generate a beam of monovalent or polyvalent nitrogen-based ions in the direction of the guide head 30 via the connection guide 40 under vacuum. The ion beam usually has a circular cross-section and generally has a predetermined diameter of 0.5 mm to 200 mm. The diameter of the beam is selected in particular according to the size of the cavity to be treated and the desired scanning speed. The ion beam is irradiated with an acceleration voltage of 1 kV to 500 MV. The flow rate of the ion beam is adapted to form a layer of implanted ions of a predetermined thickness. Regarding the surface concentration of the implanted ions, it mainly depends on the scanning speed of the beam at the cavity surface. The longer the beam irradiation time, the more ions are implanted per square centimeter. According to a specific implementation, the control unit ensures that the quality factor finally imparted to the processed cavity is at least 3.10 10 exceeds, the fluence (number of ions / cm2 It is possible to consider (represented by). More specifically, regarding the niobium cavity processed according to the treatment with a nitrogen ion beam, a quality factor of 1×10 11 ~1×10 14 can be obtained.

[0053] To obtain these parameters related to the ion beam, the control unit loads from the memory a scanning pattern previously defined for performing a scan of the inner surface of cavity C. This scanning pattern generally includes a series of instructions that can define the parameters of the emitted beam and the relative movement parameters of the ion beam with respect to the inner surface of the object to be treated or the inner surface of the object to be treated with respect to the ion beam. Therefore, this series of instructions, which are to be executed by the unit control, includes a large amount of data related to the scanning procedure executed by the unit control. For example, mention can also be made of the acceleration voltage of the ion beam, the intensity of the ion beam, the diameter of the beam, the nature of the ions emitted, the scanning sequence by the operating scanning means, the scanning speed, the scanning steps, etc., but this list is not exhaustive.

[0054] Step 400 is based on performing a scan of the inner surface of cavity C using the ion beam generated by ion source 10 for the purpose of improving its characteristics. The scan adjusted by the control unit varies depending on the scanning pattern being executed.

[0055] According to a particular embodiment, the control unit performs a magneto-mechanical hybrid scan of the inner surface S. The control unit then sends a series of commands that enable it to operate the first and second scanning means in response to the instructions included in the scanning pattern.

[0056] Thus, when the magnetic head 30 is activated (first scanning means), in order to sweep the inner surface S around the first scanning axis (the rotation axis coinciding with the axis Y of the cavity), the ion beam moves relative to the cavity C around the first scanning axis. This step is embodied by arrow A in Fig. 1 and box 400a in Fig. 2.

[0057] When a pair of rotating flanges R1, R2 are activated (second scanning means), in order to scan the inner surface S around the second scanning axis (the rotation axis coinciding with the X axis of the cavity), the cavity C moves relative to the ion beam around the second scanning axis. This step is embodied by arrow B in Fig. 1 and box 400b in Fig. 2.

[0058] Note that the first scanning means and the second scanning means can be activated sequentially or simultaneously during step 400 of the method.

[0059] Alternatively or in addition, a translator T that ensures the translation of the insertion rod 20 with respect to the module M can also be activated as a third scanning means to participate in the scanning of the inner surface of the cavity C. In this case, the ion beam is moved relative to the cavity C along the third scanning axis (the translation axis coinciding with the vertical axis X). This optional step is embodied by arrow D in Fig. 1 and box 400c in Fig. 2. These third scanning means can be implemented sequentially or simultaneously with at least one of the first scanning means and the second scanning means that scan during step 400 of the method.

[0060] The scanning method described here includes a scanning cycle that is adapted to process the entire inner surface of the cavity C by ion implantation (described later for comprehensive processing). Of course, this is a specific embodiment, and many other scanning methods can be considered according to the needs defined by the user.

[0061] To ensure the uniformity of the treatment, for example, a scanning method involving several scanning cycles can be envisioned.

[0062] To perform local processing of the cavity, scanning cycles can also be envisaged that follow the above principle but target only part of the inner surface or a plurality of separate parts (selective processing will be described later).

[0063] And the use of the ion beam according to the invention provides the possibility of ion implantation at a depth and concentration that can be constant or variable at any point on the processing surface as required. In fact, it has been demonstrated that these two implantation parameters depend on the implantation energy of the ion beam. However, the implantation energy itself depends in particular on two factors. That is, on the one hand, it depends on the travel distance of the ion beam from the ion source to the collision point on the inner surface, and on the other hand, it depends on the angle of incidence of the ion beam on the inner surface at the collision point of the beam on the inner surface. Since these two factors can change during processing, the aforementioned implantation parameters can be affected. To compensate for this drawback, in order to change the amount of ions implanted at the level of the inner surface S, taking into account at least one of the aforementioned two factors, the relative speed of movement of these two elements during processing can be adjusted, whether it is the module M or the beam that is about to move.

[0064] Thus, according to a particular implementation, the scanning pattern defines a constant scanning speed. Alternatively, the scanning method defines a variable scanning speed in order to take into account the shape of the cavity to be processed. This has the effect of homogenizing the ion implantation over the entire inner surface of the object to be processed.

[0065] According to another alternative, the scanning method defines a scanning speed that is a function of a predetermined concentration or implantation depth profile for a given cavity. This implementation is particularly advantageous in that it makes it possible to obtain an accurate ion implantation profile that was difficult to obtain with prior art doping techniques.

[0066] At the end of step 400, the vacuum pump is stopped in order to return the housing to atmospheric pressure. In this way, an acceleration cavity with an improved quality factor is obtained.

[0067] It should be noted that, depending on the assumed use, particularly the shape and dimensions of the acceleration cavity of the object to be processed, the shape and dimensions of the components of the device according to the present invention are not limited to the above embodiments. For example, elements such as the introduction rod, connection guide, annular flange, and absorber can take different shapes and can have dimensions adapted to the accelerator module of the object to be processed.

[0068] Here, the ion beam is emitted by an electron cyclotron resonance source. This type of ion source is generally used to generate monovalent or polyvalent ions, that is, atoms of a specific chemical species from which one or more electrons have been removed, but is not limited to this example. Although not exhaustive, other types of ion sources that can generate high-energy particle beams, such as, for example, discharge, ionization, thermal ionization sources, or plasmas, can be used within the scope of the present invention. In order to ensure the formation of a particle beam of the desired shape, it is also preferable to equip the ion source to be exposed to high vacuum or even ultra-high vacuum (except for plasma ion sources).

[0069] It should also be noted that it is possible to use the original ion source of a particle accelerator that is adapted to process the cavity, rather than an ion source dedicated to surface treatment as shown in the above example. Since this original ion source is originally configured to generate particles with high energy along the longitudinal axis of the acceleration module, it may be advantageous to use this original ion source as a means for generating the beam according to the present invention to process the inner surface of the cavity of this module.

[0070] Note that the accelerator module M shown above has only one acceleration cavity. The number of acceleration cavities shown above is initially spontaneously limited for purely educational explanations. Of course, as shown below in connection with FIGS. 3 and 4, it is possible to perform the surface treatment according to the present invention using a larger number of acceleration cavities.

[0071] 〔Multi-cavity processing〕 The operating principle of the multi-cavity processing apparatus will be described below in connection with FIG. 3 according to a specific embodiment of the present invention. Different from FIG. 1, the accelerator module M' consists of a set of 10 consecutive accelerating cavities labeled C 1 ~C 10 Each of these cavities is mainly made of niobium, similar to the above-mentioned cavity C. The accelerator module M' is provided with an inlet orifice O1' and an outlet orifice O2' centered on the X-axis. Regarding the processing apparatus, it includes an introduction rod 20' and a connection guide 40' sized to fit the dimensions of the multi-cavity module M'. Each of these two elements must have an appropriate length so that, in fact, the scanning head 30 can be introduced into each cavity of the module M' along the longitudinal axis X of the introduction rod 20' from cavity C 1 to cavity C 10 up to cavity C

[0072] In this specific form, the support member T fixed to the connection guide 40' functions as a translator for the insertion rod 20' along the longitudinal axis X, thereby making the insertion rod 20' translatable with respect to the accelerator module M'. Therefore, in order to scan the inner surfaces of the cavities C 1 ~C 10 of the module M' using an ion beam according to the present invention, the support member T is configured to continuously introduce the scanning head 30 into each of the cavities C 1 ~C 10 of the module M'. The translational movement of the rod 20' and thus the scanning head 30 along the longitudinal axis X is embodied by the arrow D in the figure.

[0073] Taking the example of the cavities C 1 ~C 10 that are processed continuously in numerical order of these cavities 1 to 10. The control unit first controls the cavity C of the module M' 1To process it, steps 100 to 400 described above are moved to execution (in accordance with the above-described principle applied to cavity C). Accordingly, the control unit introduces the scanning head 30 into the center of cavity C 1 and then scans the inner surface of this cavity C1 with a beam of nitrogen ions emitted by the ion source 10. Then, when the scanning stage for cavity C 1 ends, the control unit repeats steps 100 to 400 described above to process the cavity C 2 of module M'. Accordingly, the control unit introduces the scanning head 30 into the center of cavity C 2 and then scans the inner surface of this cavity C 2 with a beam of nitrogen ions emitted by the ion source 10. Similarly, the process is carried out up to the cavity C 10 of module M'. In FIG. 3, cavity C 10 is being processed.

[0074] Thanks to this particular form, it is possible to process the inner surfaces of several cavities successively over time with a single scanning head. This form can be particularly advantageous when the number of cavities to be processed is limited.

[0075] FIG. 4 shows a modification of the processing apparatus shown in FIG. 3 according to the present invention. Different from FIG. 3, the apparatus has a 20-inch multi-scanning head introduction rod. More precisely, this introduction rod 20'' comprises a set of 10 scanning heads, referenced 30 1 to 30 10 , which are arranged continuously along the scanning rod such that when the rod 20'' is introduced into module M', each scanning head is positioned at the center of a different cavity of module M' and the inner surface of this cavity is processed with an ion beam emitted by the ion source 10. Accordingly, scanning heads 30 1 to 30 10 are each dedicated to the respective processing of cavities C 1 to C 10 of module M'.

[0076] Furthermore, unlike in FIG. 3, the second scanning means is no longer ensured by a pair of rotary flanges R1 and R2 that ensure the rotational drive of the module M' around the vertical axis X with respect to the introduction rod, but is ensured by a stepping positioning motor P that cooperates with the introduction rod 20'' so as to rotationally drive the introduction rod 20'' around the vertical axis X with respect to the module M'. This alternative is particularly advantageous for implementation when the parts to be processed that make up the accelerator module are bulky, thereby avoiding the need for heavy, bulky and expensive means for rotationally driving the module.

[0077] FIGS. 5A and 5B show the operating principle of the magnetic scanning head according to the present invention. These two figures represent an enlarged detailed view of a part of the introduction rod 20.

[0078] The scanning head 30 includes a magnetic beam deflector 30a and a beam passage opening 30b. The deflector shown here is a magnetic dipole formed from windings (commonly also referred to as “coils”) of a pair of electrical wirings 30a1, 30a2 that can receive a predetermined current. This pair of coils 30a1, 30a2 is disposed on the outer surface of the rod 20. The first winding of the wiring 30a1 constitutes the N pole of the magnetic dipole, and the second winding of the wiring 30a2 constitutes the S pole of the magnetic dipole. The opening 30b is a through opening formed in the introduction rod 200 perpendicular to the through axis of the pair of windings 30a1 to 30a2 so that the ion beam deflected by the deflector 30a can pass toward the inner surface of the cavity to be processed. The magnetic deflector 30a and the passage opening 30b are configured such that, according to the current flowing through the magnetic deflector 30a, the incident beam Fi coming from the ion source 10 is deflected from its initial trajectory (deflected beam Fd) and directed toward the inner surface of the cavity according to the deflection angle α through the opening 30b. This deflection angle is defined by the axis of the incident beam Fi (the axis that coincides with the vertical axis X) and the axis of the deflected beam Fd and depends on the magnetic force applied to the ion beam by the deflector 30a. The greater the intensity of the current passing through the deflector, the greater the deflection of the ion beam from its initial trajectory. The intensity of the current passing through the pair of windings is controlled by the control unit according to the scanning pattern executed by the control unit.

[0079] To ensure effective and reliable control of the operation of the scanning head 30, it is preferable that the occupied area of each of the coils 30a1 to 30a2 is larger than the occupied area of the opening 30b.

[0080] The magnetic deflector shown here is an example for purely illustrative purposes, and other types of magnetic deflectors can be considered without departing from the scope of the present invention. For example, deflectors based on one or more permanent magnets or electromagnets, or even more complex magnetic circuits that can perform the aforementioned functions, can be highly suitable.

[0081] Figures 6A and 6B illustrate the operating principle of the electric scanning head according to the present invention. Figure 6B is a cross-sectional view taken along axis A-A shown in Figure 6A. Figure 6A is an enlarged view of a part of the introduction rod 300 according to the present invention.

[0082] Unlike the aforementioned Figures 5A and 5B, the scanning head 30' shown here is essentially electrical. The scanning head 30' includes an electron beam deflector 30a' and a beam passage opening 30b'. The electric deflector 30a' consists of a conductive plate that extends along the vertical axis X and can deflect the ion beam when the ion beam is exposed to a predetermined voltage. This plate is mounted and fixed to the inner surface of the rod 30 via at least one electrical insulation support means. The opening 30b' is a non-penetrating opening formed in the introduction rod 300 disposed facing the plate so as to allow the ion beam deflected by the deflector 30b' to pass in the direction of the inner surface of the cavity to be processed. The electric plate 30a' and the passage opening 30b' are configured such that, depending on the voltage applied to the plate 30a', the incident beam Fi coming from the ion source 10 is deflected from its initial trajectory (deflected beam Fd) and directed towards the inner surface of the cavity according to the deflection angle β through the opening 30b’. Thus, unlike the previous form, due to the presence of the electric field in the incident beam, the beam can be deflected in the direction of the inner surface of the injection target. The principle of the variability of the deflection angle β is the same as the principle described above for the deflection angle α (related to Figures 5A and 5B), except for matters related to the electric field. The level of the voltage applied to the conductive plate is controlled by the control unit according to the scanning pattern being executed.

[0083] As described above, in order to ensure effective and reliable control of the operation of the scanning head 30', it is preferable that the surface occupied by the electric plate is larger than the surface occupied by the opening.

[0084] The electric deflector shown here is purely an illustrative example, and deflectors having other types of electrical properties can be envisioned without departing from the scope of the present invention. For example, a simple pair of metal electrodes, an electrostatic element, or even a more complex electrical circuit capable of performing the aforementioned functions can be quite suitable.

[0085] Therefore, considering the above description, various elements having the function of deflecting or causing to deflect an ion beam (and more generally a charged particle beam) from its initial trajectory can be envisioned.

[0086] The above description has attempted to explain the present invention based on the use of a beam of monovalent nitrogen ions. However, this example is not limiting, and the present invention can be applied in all cases where a particle beam enabling the injection of particles onto the inner surface of the cavity can be used.

[0087] More generally, the particles of the beam can be particles selected from atomic species, molecular species, ionic species (as described above), molecular and ionic species, species based on at least one elementary particle, or combinations of at least two of these species. Therefore, the present invention is adaptable to different types of particles to be injected. The choice of particles used depends on the material to be treated on the inner surface of the cavity and the nature of the desired treatment.

[0088] Finally, according to a particular aspect of the present invention, the particles of the beam are ions selected from the following elements, namely nitrogen (with the symbol N as described above), helium (He), titanium (Ti), argon (Ar), oxygen (O), iron (Fe), aluminum (Al), neon (Ne), krypton (Kr), xenon (Xe), boron (B), carbon (C), fluorine (F), silicon (Si), phosphorus (P), sulfur (S), or a combination of at least two of these elements. The selection from among these elements depends on the material to be treated on the inner surface of the cavity and the nature of the surface treatment to be determined. If the ion source of the apparatus is a plurality of ion sources, an extraction filter (for example, capable of extracting at least one specific type of ion from among several types from the above list) can be coupled to or within the ion source 10 to generate the desired type of ion. In this case, the control unit must be configured to pre-select, by means of the extraction filter, the nature of the ions to be used according to the instructions included in the scanning pattern.

[0089] Figure 7 shows a simplified structure of a control unit 70 for implementing a processing method according to the present invention (for example, the specific embodiment described above in relation to FIGS. 1 and 2). This apparatus includes a random access memory 73 (for example, a RAM memory), and a processing unit 71 that includes, for example, a processor and is controlled by a computer program stored in a read only memory 72 (for example, a ROM memory or a hard disk). At initialization, the code instructions of the computer program are loaded into the RAM 73, for example, before being executed by the processor of the processing unit 71. The processing unit 71 receives the scanning pattern 70E as an input. The processor of the processing unit 71 processes the scanning pattern 70E and generates drive commands (represented by the arrow 70S) to be output according to the instructions of the program stored in the memory 72. Accordingly, the processing unit 71 sends out, as an output, the control commands necessary to control the scanning means of the inner surface of the acceleration cavity or the cavity to be treated (as described above in any of the various embodiments).

[0090] It should be noted that this Figure 7 shows only one specific way out of several possible ways of executing the algorithm detailed above in relation to Figure 1. In fact, the technology of the present invention, without distinction, - by a reprogrammable computer (PC computer, DSP processor, or microcontroller) that executes a program including a series of instructions, or, - by a dedicated computer (for example, a series of logic gates such as an FPGA or ASIC, or other hardware modules), is executed.

[0091] When the present invention is implemented by a reprogrammable computer, regardless of whether the corresponding program (i.e., a sequence of instructions) can be stored on a removable storage medium (such as a floppy disk, CD-ROM, or DVD), this storage medium is partially or fully readable by the computer or processor.

Claims

1. A method for treating the surface of at least one elementary particle acceleration cavity (C) of an accelerator module (M), including a scanning step (400) of scanning the inner surface (S) by moving a particle beam relative to the inner surface (S) of the at least one elementary particle acceleration cavity or by moving the inner surface (S) relative to the particle beam, The scanning step (400) includes: A step (100) of introducing a scanning head (30) capable of deflecting the particle beam toward the inner surface by at least one of electricity and magnetism into the at least one elementary particle acceleration cavity through an orifice of the accelerator module; A step (200, 300) of generating a vacuum for the particle beam directed toward the scanning head (30) introduced into the at least one elementary particle acceleration cavity; preceded by The scanning step (400) is implemented by operating the scanning head (30) (400a). A method.

2. The method according to claim 1, wherein the scanning step includes a step (400b) of rotating the at least one elementary particle acceleration cavity (C) relative to the scanning head (30) or the scanning head (30) relative to the at least one elementary particle acceleration cavity (C).

3. The method according to claim 1 or 2, wherein the scanning step includes a step (400c) of translating the scanning head (30) relative to the at least one elementary particle acceleration cavity (C) or the at least one elementary particle acceleration cavity relative to the scanning head (30).

4. The method according to any one of claims 1 to 3, wherein the inner surface of the at least one elementary particle acceleration cavity is formed of niobium (Nb), and the particle beam generation step includes a step of selecting a beam of nitrogen ions having a single or multiple charges.

5. A computer program product downloadable from a communication network, a computer program product storable by a computer-readable medium, and at least one computer program product executable by a microprocessor, the computer program product including program code instructions for executing the processing method according to any one of claims 1 to 4 when executed by a computer.

6. A computer-readable persistent storage means for storing the computer program product according to claim 5.

7. An apparatus for processing the surface of at least one elementary particle acceleration cavity (C) of an accelerator module (M), the apparatus including scanning means for scanning the inner surface by moving a particle beam relative to the inner surface of the at least one elementary particle acceleration cavity or by moving the inner surface relative to the particle beam, means (20) for introducing into the at least one elementary particle acceleration cavity a scanning head (30) capable of deflecting the particle beam toward the inner surface by at least one of electricity and magnetism, the means for introducing and the scanning head being configured to be insertable into the at least one elementary particle acceleration cavity through an orifice of the accelerator module, means (10) for generating in a vacuum a particle beam directed toward the scanning head (30), and the apparatus comprising the above.

8. The apparatus according to claim 7, wherein the scanning head (30) includes a beam deflector (30a) capable of deflecting the generated beam toward the inner surface and a beam exit opening (30b) arranged with respect to the beam deflector so as to direct the deflected beam toward the inner surface.

9. The apparatus according to claim 7 or claim 8, wherein the scanning means includes means (R1, R2) for rotating the at least one elementary particle acceleration cavity (C) relative to the scanning head (30) or the scanning head (30) relative to the at least one elementary particle acceleration cavity (C).

10. The scanning means comprises means (T) for translating the at least one elementary particle acceleration cavity (C) relative to the scanning head (30) or for translating the scanning head (30) relative to the at least one elementary particle acceleration cavity (C). The apparatus according to any one of claims 7 to 9.

11. wherein the accelerator module includes a plurality of consecutive elementary particle acceleration cavities (C １ to C １０ ), and the means for causing the translational movement is configured to continuously introduce the scanning head (30) for scanning the inner surfaces of respective ones of the plurality of elementary particle acceleration cavities, the apparatus according to claim 10.

12. The accelerator module includes a plurality of successive elementary particle acceleration cavities (C １ to C １０ ), and the means for introducing includes a plurality of scanning heads (30 １ to 30 １０ ) arranged continuously along the means for introducing, each scanning head being configured to perform scanning of the inner surfaces of different ones of the plurality of elementary particle acceleration cavities. The device according to any one of claims 7 to 11

13. The at least one elementary particle acceleration cavity, the elementary particle acceleration cavity having a first flange and a second flange, A connection / vacuum guide connecting means (10) for generating in the vacuum to the first flange, An absorption closure member coupled to the second flange, Comprising The at least one elementary particle acceleration cavity, the connection / vacuum guide, means (10) for generating in the vacuum, and the absorption closure member form a processing housing of the at least one elementary particle acceleration cavity that can be depressurized to a vacuum. The apparatus according to any one of claims 7 to 12.

14. A method of manufacturing at least one elementary particle acceleration cavity of an accelerator module, A preparation step of preparing at least one elementary particle acceleration cavity, Scanning the inner surface (S) of the at least one elementary particle acceleration cavity by moving the particle beam relative to the inner surface or by moving the inner surface relative to the particle beam, wherein the flow rate and the scanning speed of the particle beam are controlled to produce the at least one elementary particle acceleration cavity having a quality factor included from 1×10 １１ to 1×10 １４ ; and a scanning step Including The scanning step is Introducing a scanning head (30) capable of deflecting the particle beam towards the inner surface by at least one of electricity and magnetism into the at least one elementary particle acceleration cavity through an orifice of the accelerator module (step 100), Generating a vacuum for the particle beam directed towards the scanning head (30) introduced into the at least one elementary particle acceleration cavity (steps 200, 300), Preceded by The scanning step (400) is implemented by operating the scanning head (30) (400a). A method.

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