Medical Proton Accelerator and Radiotherapy System

Abstract

The present invention discloses a medical proton accelerator and a radiotherapy system, which relate to the technical field of radiotherapy. The medical proton accelerator includes an ion source, a terahertz source, a dielectric acceleration structure, a proton injection section, and a proton extraction section. The ion source is used to generate a proton beam; the terahertz source is used to generate high-power terahertz waves; the terahertz waves are transmitted in the dielectric acceleration structure and generate a high-gradient accelerating electric field for accelerating the proton beam to a preset energy value; the proton injection section is arranged between the ion source and the dielectric acceleration structure and is used to introduce the proton beam from the ion source into the dielectric acceleration structure; the proton extraction section is used to extract the proton beam accelerated to the preset energy value to an external treatment device. The radiotherapy system includes the medical proton accelerator, a power supply, and a treatment head, and the treatment head is used to direct the proton beam to a target treatment position. Compared with the prior art, the medical proton accelerator and the radiotherapy system proposed by the present invention have the advantages of small volume scale and adjustable proton beam energy.

Description

Technical Field

[0001] The present invention relates to the field of radiotherapy technology, and particularly to a medical proton accelerator and a radiotherapy system. Background Art

[0002] The incidence of cancer has been on the rise in recent years, posing a severe health threat. At present, the treatment of cancer includes drug treatment and radiotherapy methods. Traditional radiotherapy uses X-rays and gamma rays, both of which can kill normal tissues, so the patient's postoperative recovery is slow. Compared with traditional radiotherapy, proton therapy has the advantages of precise irradiation, reducing the risk of secondary tumors, and improving the survival rate, and is more suitable for children and elderly patients. When performing proton therapy, the energy of protons needs to be adjusted within a large range, generally 70 - 250 MeV, depending on the location of the tumor.

[0003] Currently, proton accelerators mainly include proton synchrotrons, proton cyclotrons, and proton linear accelerators. Synchrotrons are a common structure for proton acceleration in modern medical applications, but due to their large volume and high manufacturing cost, they limit the layout and promotion of the equipment in hospitals, and the complex structure also keeps the maintenance and operation costs high. Although proton cyclotrons can be designed to be very compact and provide a stable and continuous proton beam, due to the fixed and non-adjustable energy, there are difficulties in actual use. Proton cyclotrons can also regulate the proton beam energy through an additional energy regulator, but the precise control is difficult and it is hard to adapt to different treatment requirements. Proton linear accelerators can provide a stable proton beam, and the injection and extraction of the beam are simple and there is no energy loss during transmission, so they are attracting more and more attention. However, the acceleration gradient of traditional proton linear accelerators is low, and it is difficult to accelerate electrons to a very high energy within a short distance. Therefore, traditional proton linear accelerators are large in size and difficult to meet medical use. There is an urgent need for a more efficient, precise, and small-scale solution for medical proton accelerators. Summary of the Invention

[0004] The main object of the present invention is to provide a medical proton accelerator and a radiotherapy system, aiming to solve the problems of large volume and non-adjustable energy of existing medical proton accelerators.

[0005] To achieve the above object, the medical proton accelerator proposed by the present invention includes:

[0006] An ion source for generating a proton beam;

[0007] A terahertz source for generating terahertz waves with a preset power value;

[0008] A dielectric acceleration structure for transmitting the terahertz waves to generate an accelerating electric field, and the accelerating electric field is used to accelerate the proton beam to a preset energy value;

[0009] A proton injection section, provided between the ion source and the dielectric acceleration structure, for introducing the proton beam from the ion source into the dielectric acceleration structure;

[0010] A proton extraction section, for extracting the proton beam accelerated to a preset energy value to an external treatment device.

[0011] In one embodiment, the ion source includes:

[0012] A laser, for generating laser light;

[0013] A zinc telluride crystal, for generating terahertz waves under the action of the laser light.

[0014] In one embodiment, the dielectric acceleration structure includes a low-energy acceleration section and a medium-energy acceleration section, and the low-energy acceleration section and the medium-energy acceleration section are arranged in sequence along the propagation direction of the proton beam.

[0015] In one embodiment, the low-energy acceleration section includes a first cylindrical structure provided with an inner cavity.

[0016] In one embodiment, the first cylindrical structure is provided with a first tapered section, and the inner diameter of the first tapered section is set to gradually increase along the propagation direction of the proton beam.

[0017] In one embodiment, the first tapered section is superimposed with a perturbation structure with a variable period.

[0018] In one embodiment, the medium-energy acceleration section includes a second cylindrical structure provided with an inner cavity.

[0019] In one embodiment, the second cylindrical structure is provided with a second tapered section, and the inner diameter of the second tapered section is set to gradually increase along the propagation direction of the proton beam.

[0020] In one embodiment, the medium-energy acceleration section includes a plurality of cascaded acceleration sections cascaded in sequence.

[0021] In one embodiment, the medium-energy acceleration section further includes:

[0022] At least one drift tube, provided after each of the cascaded acceleration sections, for matching the acceleration phase of the proton beam with the cascaded acceleration section.

[0023] In one embodiment, the medical proton accelerator further includes a beam splitting system, and the beam splitting system is used for splitting the laser light into multiple optical paths.

[0024] In one embodiment, the material of the dielectric acceleration structure includes at least one of fused quartz, quartz, and diamond.

[0025] In one embodiment, the ion source includes:

[0026] A discharge chamber filled with a working gas;

[0027] A microwave source for providing a microwave field to the discharge chamber;

[0028] A magnetic field assembly for providing a magnetic field to the discharge chamber; and,

[0029] An accelerating electrode;

[0030] The working gas is ionized under the combined action of the microwave field and the magnetic field to generate protons, and the protons are extracted through the accelerating electrode to form a proton beam.

[0031] In one embodiment, the proton injection section includes:

[0032] Pole shoes;

[0033] At least one set of solenoid lenses for focusing the proton beam; and,

[0034] A current-limiting cone for reducing the beam emittance of the proton beam.

[0035] The present invention also provides a radiotherapy system, including the medical proton accelerator described above, and:

[0036] A power supply for supplying power to the medical proton accelerator;

[0037] A treatment head connected to the proton extraction section for guiding the proton beam to a target treatment position.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] 1. By the action of terahertz waves on the dielectric acceleration structure, an accelerating electric field with a high acceleration gradient is generated for accelerating the proton beam. Compared with the acceleration structure of a traditional linear accelerator, the acceleration gradient of the terahertz acceleration structure is large. Therefore, the required scale of the acceleration structure is smaller, and a small and compact proton accelerator can be constructed, solving the problem that the occupied space of a traditional proton linear accelerator is too large;

[0040] 2. By changing the power of the terahertz wave, the intensity of the accelerating electric field can be changed, so that the energy of the proton beam is adjustable, meeting the clinical treatment needs of cancer. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0042] Figure 1 Structural block diagram of an embodiment of the medical proton accelerator of the present invention;

[0043] Figure 2 Schematic structural diagram of an embodiment of the terahertz source and the dielectric acceleration structure of the present invention;

[0044] Figure 3 Schematic structural diagram of an embodiment of the first tapered section of the present invention;

[0045] Figure 4 Structural block diagram of an embodiment of the cascade acceleration section of the present invention;

[0046] Figure 5 Schematic structural diagram of an embodiment of the ion source of the present invention;

[0047] Figure 6 Schematic structural diagram of an embodiment of the proton injection section of the present invention.

[0048] Explanation of the reference numerals in the drawings:

[0049] 1. Ion source; 2. Terahertz source; 3. Proton injection section; 4. Low-energy acceleration section; 5. Medium-energy acceleration section; 6. Proton extraction section.

[0050] The realization, functional features and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. Specific embodiments

[0051] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0052] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0053] In addition, if there are descriptions such as "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second" may explicitly or implicitly include at least one such feature. In addition, if "and / or" or "and / or" appears throughout the text, its meaning includes three parallel scenarios. Taking "A and / or B" as an example, it includes scenario A, or scenario B, or the scenario where both A and B are satisfied simultaneously. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0054] In the clinical treatment of cancer, compared with traditional radiotherapy, proton therapy has the advantages of precise irradiation, reducing the risk of secondary tumors, and improving the survival rate. The proton synchrotron is limited in its layout and promotion in hospitals due to its large volume and high manufacturing cost. The proton cyclotron has difficulties in actual use because its energy is fixed and non-adjustable. The linear accelerator can provide a stable proton beam, and the injection and extraction of the beam are simple and there is no energy loss during transmission. However, the acceleration gradient of the traditional proton linear accelerator is low. Especially because the mass of the proton is much larger than that of the electron, to accelerate the proton to a very high energy, the corresponding linear accelerator will be very long. Therefore, the volume scale of the traditional linear accelerator used to accelerate protons is large, mainly used for scientific research, and it is difficult to meet medical use.

[0055] To solve the above problems, the present invention proposes a medical proton accelerator.

[0056] Referring to Figure 1 and Figure 2 , in an embodiment of the present invention, the medical proton accelerator includes:

[0057] Ion source 1, used to generate a proton beam;

[0058] Terahertz source 2, used to generate terahertz waves with a preset power value;

[0059] Dielectric acceleration structure (including Figure 1 4 and 5 in

[0060] ), used to transmit the terahertz waves to generate an accelerating electric field, and the accelerating electric field is used to accelerate the proton beam to a preset energy value;

[0061] The proton extraction section 6 is used to extract the proton beam accelerated to a preset energy value to an external treatment device.

[0062] In this embodiment, terahertz waves (abbreviated as THz waves) are electromagnetic waves with a frequency range between microwaves and infrared light, with a frequency of approximately between 0.1 and 10 THz, corresponding to a wavelength of approximately 30 μm to 3 mm. In recent years, terahertz acceleration technology has been verified in principle and realized in the application of electron beam acceleration. Feeding terahertz waves into a cylindrical dielectric acceleration structure can excite a TM01-like mode with a longitudinal accelerating electric field. Among them, the TM01 mode is a transmission mode in microwave technology. In this mode, the magnetic field of the electromagnetic wave is distributed transversely and the electric field is distributed longitudinally. In microwave technology, the TM01 mode is the lowest-order mode of the TM type wave in a cylindrical waveguide, and its field structure is centrosymmetric; the TM01-like mode here means that the mode of terahertz waves in the dielectric acceleration structure is a transverse magnetic field distribution and a longitudinal electric field distribution, and the electromagnetic field polarization situation is similar to the TM01 mode in microwave technology.

[0063] In this embodiment, compared with electromagnetic waves in the radio frequency band, the electric field change rate in the terahertz band is faster, and a higher peak electric field can be provided within a shorter time interval; compared with traditional acceleration structures operating in the radio frequency band, the breakdown threshold of acceleration structures operating in the terahertz band can be increased by two orders of magnitude, and a larger input power can be loaded; therefore, terahertz acceleration has a higher acceleration gradient, thereby shortening the scale of the acceleration section. In addition, the wavelength of terahertz waves is in the millimeter and sub-millimeter range, and the size of its acceleration structure is also in the same range, so its dielectric acceleration structure can be processed by traditional processing methods.

[0064] The proton beam can be generated by ionizing gas (usually hydrogen) through an electron cyclotron resonance ion source (ECRIS) or a DC ion source.

[0065] In an alternative embodiment, the ion source is an electron cyclotron resonance ion source, which can efficiently generate a proton beam using the electron cyclotron resonance phenomenon, and because there is no filament cathode, it can work continuously for a long time to meet medical needs.

[0066] Terahertz waves can be generated by irradiating an ultrashort laser pulse into a nonlinear crystal, such as semiconductor crystals such as gallium phosphide (GaP) and zinc telluride (ZnTe), or organic crystals and ferroelectric crystals with a large effective nonlinear coefficient.

[0067] In an alternative embodiment, the terahertz source includes: a laser for generating laser light; a zinc telluride crystal for generating high-power terahertz waves under the action of the laser light.

[0068] In an alternative embodiment, such as Figure 2As shown, the terahertz wave generated by laser irradiating a zinc telluride crystal is reflected and focused by a reflector, and then longitudinally fed into the dielectric acceleration structure, moving coaxially with the accelerated proton beam. By designing reasonable dimensions of the dielectric acceleration structure, phase synchronization between the terahertz wave and the accelerated proton beam can be achieved.

[0069] Specifically, the steps of accelerating the proton beam by this embodiment and using it for treatment are as follows:

[0070] The proton beam generated by the ion source 1 enters the acceleration cavity of the dielectric acceleration structure (4 and 5 in sequence) after being focused by the proton injection section 3 and reducing the beam emittance.

[0071] Meanwhile, the terahertz wave is coupled into the dielectric acceleration structure, is constrained to propagate in the dielectric acceleration structure, and excites a TM01-like mode in the dielectric acceleration structure to generate an accelerating electric field in the axial direction. Under appropriate timing control, the proton beam located in the dielectric acceleration structure is in the acceleration phase, so as to convert the energy in the terahertz field into the kinetic energy of the proton beam and achieve the acceleration of the proton beam. By adjusting the laser power of the terahertz source, the power of the terahertz wave can be correspondingly changed, and then the intensity of the accelerating electric field in the dielectric acceleration structure can be changed to obtain proton beams with different energy values. The proton beam accelerated by the dielectric acceleration structure is led out to an external treatment device through the proton extraction section. The external treatment device generally includes a treatment head and related auxiliary systems to accurately irradiate the tumor site of the patient to achieve the treatment effect of removing cancer cells.

[0072] Therefore, in the embodiment of the present invention, the terahertz wave propagates in the dielectric acceleration structure and excites a TM01-like mode to generate a longitudinal accelerating electric field with a high acceleration gradient in the inner cavity of the dielectric acceleration structure to accelerate the proton beam longitudinally transmitted in the inner cavity. Compared with the acceleration structure of a traditional linear accelerator, the acceleration gradient of the terahertz acceleration structure is large, so the required scale of the acceleration structure is smaller, and a small and compact proton accelerator can be constructed to solve the problem that the occupied space of a traditional proton linear accelerator is too large. At the same time, by changing the power of the terahertz wave, the intensity of the accelerating electric field can be changed, so that the energy of the proton beam is adjustable to meet the clinical treatment requirements for cancer.

[0073] In one embodiment, referring to Figure 1 , the dielectric acceleration structure includes a low-energy acceleration section 4 and a medium-energy acceleration section 5, and the low-energy acceleration section 4 and the medium-energy acceleration section 5 are arranged in sequence along the propagation direction of the proton beam.

[0074] In this embodiment, the design of the low-energy acceleration section 4 and the medium-energy acceleration section 5 is to gradually increase the energy of the proton beam and ensure that the beam maintains high brightness and stability throughout the acceleration process. Among them, in the low-energy acceleration section 4, the terahertz wave and the corresponding dielectric acceleration structure need to match the speed change during the proton acceleration process. The longer the acceleration structure is, the more protons in the mismatched phase will be. Therefore, the low-energy acceleration section 4 needs to be designed with a high acceleration gradient and a short acceleration distance, and usually the proton beam needs to be accelerated to 3-5 MeV. The medium-energy acceleration section 5 is used to further accelerate the proton beam accelerated by the low-energy acceleration section 4 to the energy required for clinical treatment, and usually the proton beam needs to be accelerated to 70-250 MeV.

[0075] Referring to Figure 2 and Figure 3 , in one embodiment, the low-energy acceleration section 4 includes a first cylindrical structure with an inner cavity, and the first cylindrical structure is axially symmetrically designed.

[0076] Among them, the first cylindrical structure is provided with a first tapered section, and the inner diameter of the first tapered section is set to gradually increase along the propagation direction of the proton beam.

[0077] Referring to Figure 3 , the first tapered section is superimposed with a periodically perturbed structure.

[0078] In this embodiment, terahertz acceleration mainly uses short-pulse high-power terahertz waves. The spectrum of the terahertz wave itself is very wide, and there is also dispersion in the acceleration structure. Therefore, a main difficulty in terahertz acceleration is to solve the problem of phase drift, which is more obvious in the low-energy section. In addition, the mass of the proton is much larger than that of the electron (the mass of the proton is more than 1800 times higher than that of the electron). Compared with terahertz-accelerated electrons, it is more difficult to accelerate protons, and the problem of phase drift will be more obvious, resulting in a reduction in the acceleration efficiency of terahertz acceleration.

[0079] Among them, phase drift refers to the deviation of the phase of the proton beam from the ideal synchronous phase due to various factors (such as small energy dispersion in the beam, small changes in the electric field, spontaneous radiation loss of the beam, etc.) during the long-term acceleration process. Phase drift will cause the protons to no longer be accurately synchronized with the accelerating electric field, and thus may not be effectively accelerated or even decelerated.

[0080] Therefore, in this embodiment, the low-energy section is designed with a first tapered section whose inner diameter gradually increases along the propagation direction of the proton beam, so that the phase velocity of the terahertz wave transmitted in the dielectric structure of the first tapered section also changes gradually. In order to more accurately modulate the phase velocity, the first tapered section is also superimposed with a periodically perturbed structure, such as Figure 3The wavy surface shown in [figure]. The specific inner diameter numerical design of the first tapered section and the perturbation structure it contains is designed to achieve the matching of the phase velocity of the terahertz wave and the velocity of the proton beam in the low-energy acceleration section.

[0081] Among them, the phase velocity of the terahertz wave refers to the distance that the phase of the terahertz wave propagates per unit time; in the TM01-like mode, the phase velocity of the terahertz wave is closely related to factors such as the specific geometric shape and boundary conditions of the dielectric acceleration structure.

[0082] In this embodiment, the cross-sectional area of the dielectric acceleration structure of the first tapered section is a tapered design. The effective refractive index of the dielectric acceleration structure is usually greater than the refractive index of free space, that is, the phase velocity of the terahertz wave in the dielectric acceleration structure will be lower than the phase velocity in vacuum; and as the height of the dielectric structure increases, the cut-off frequency of the TM01 mode becomes smaller, and the phase velocity of the terahertz wave at the same frequency becomes smaller.

[0083] Therefore, in the first tapered section, as the inner diameter gradually increases, the phase velocity of the terahertz wave gradually increases. Correspondingly, the proton beam needs to be precisely matched with the peak electric field of the terahertz wave in a longer acceleration structure. The proton beam propagates in the direction where the inner diameter of the first tapered section gradually increases, and its speed becomes higher and higher. It can pass through a longer acceleration structure per unit time. Therefore, the first tapered section proposed in this embodiment can achieve the matching of the phase velocity of the terahertz wave and the velocity of the proton beam.

[0084] In the embodiment of the present invention, by designing a first tapered section with a gradually changing inner diameter in the low-energy acceleration section 4, the first tapered section is superimposed with a perturbation structure to accurately modulate the phase velocity of the terahertz in the low-energy section to match the velocity of the proton beam during the acceleration process in the low-energy acceleration section 4, ensuring that the protons meet the peak electric field of the terahertz wave at the right time and at the right distance, thereby efficiently accelerating the protons and achieving the maximum acceleration efficiency and the longest-distance synchronous phase acceleration of the proton beam in the low-energy acceleration section 4.

[0085] Refer to Figure 2 , in an embodiment, the medium-energy acceleration section 5 includes a second cylindrical structure with an inner cavity, and the second cylindrical structure is an axisymmetric design.

[0086] Among them, the second cylindrical structure is provided with a second tapered section, and the inner diameter of the second tapered section is set to gradually increase along the propagation direction of the proton beam.

[0087] In this embodiment, the purpose of setting the second tapered section is the same as that of the first tapered section provided in the low-energy acceleration section 4. The medium-energy acceleration section 5 is provided with a second tapered section with a gradually increasing inner diameter, so that the phase velocity of the terahertz wave transmitted in the medium-energy acceleration section 5 also changes gradually. The specific inner diameter value of the second tapered section is designed so that the phase velocity of the terahertz wave matches the velocity of the proton beam, ensuring that the proton beam is always in the accelerating phase. Since in the medium-energy acceleration section 5, the relativistic mass of the proton increases, and the velocity change obtained by acceleration at the same terahertz energy is relatively smaller than that in the low-energy acceleration section 4, the second tapered section can adopt a relatively simplified design without a variable-period perturbation structure.

[0088] In an embodiment of the present invention, by adjusting the inner wall shape of the dielectric acceleration structure, the phase velocity of the terahertz wave transmitted therein is changed to match the velocity of the proton beam, so that the proton beam is always in the accelerating phase in the dielectric acceleration structure, achieving the maximum acceleration efficiency and the longest-distance synchronous phase acceleration of the proton beam in the dielectric acceleration structure.

[0089] Refer to Figure 4 , in an embodiment, the medium-energy acceleration section 5 includes a plurality of cascaded acceleration sections cascaded in sequence.

[0090] Among them, the medium-energy acceleration section 5 further includes:

[0091] At least one drift tube, provided after each of the cascaded acceleration sections, for matching the acceleration phase of the proton beam with that of the cascaded acceleration section.

[0092] In this embodiment, since the interaction length between the terahertz wave and the proton beam in a single dielectric acceleration structure is currently limited, the energy gain of the proton beam in a single-stage dielectric acceleration structure is not high. Therefore, in order to obtain a proton beam with a higher energy, the medium-energy acceleration section 5 of the present invention is designed as a plurality of cascaded acceleration sections cascaded in sequence.

[0093] In this embodiment, each cascaded acceleration section adopts a traveling-wave acceleration structure. However, due to the dispersion of the acceleration structure, the proton can no longer be synchronized with the terahertz wave after accelerating for a certain distance. Therefore, a drift tube is added between each of the cascaded acceleration sections, so that the proton beam can be rematched with the terahertz wave of the next cascaded acceleration section after passing through the drift tube and obtain effective acceleration.

[0094] In an embodiment of the present invention, by designing the medium - energy acceleration section 5 as a plurality of cascaded acceleration sections cascaded in sequence, the acceleration distance of the proton beam is increased to obtain a higher proton - beam energy gain than that of a single - section dielectric acceleration structure, solving the problem of the limited interaction length between the terahertz wave and the proton beam in the single - section dielectric acceleration structure. At the same time, the number of cascaded acceleration sections can be selected according to the actual requirements for the proton - beam energy, which is convenient for manufacturing in stages and segments and for later energy upgrading. In addition, a drift tube is arranged after each cascaded acceleration section to solve the phase - drift problem that occurs to the proton beam after passing through the cascaded acceleration section, ensuring that the acceleration process of the proton beam in the medium - energy acceleration section always matches the phase velocity of the terahertz wave therein.

[0095] Referring to Figure 1 , in one embodiment, the medical proton accelerator further includes a beam - splitting system, and the beam - splitting system is used to split the laser into multiple optical paths.

[0096] In this embodiment, the terahertz source of the present invention uses a single high - power laser to accurately drive the dielectric acceleration structure in the correct time sequence. The beam - splitting system proposed by the present invention has the functions of optical - path splitting and time - delay optical path. The high - power laser is split into multiple laser beams through optical - path splitting and time - delay optical path, and respectively interacts with the corresponding zinc - telluride crystals to generate terahertz waves, so as to drive the corresponding dielectric acceleration structures respectively. The dielectric acceleration structure includes a low - energy acceleration section and a plurality of cascaded acceleration sections included in the medium - energy acceleration section.

[0097] In addition, the beam - splitting system is also a power - distribution network, which is used to adjust the terahertz - wave driving power on each dielectric acceleration structure to provide a suitable acceleration electric field.

[0098] In an embodiment of the present invention, by splitting the single high - power laser through the beam - splitting system, the one - by - one driving of each dielectric acceleration structure is realized. Since the multiple laser beams after splitting are of the same origin, the terahertz waves used to drive each dielectric acceleration structure have accurate time - synchronization characteristics and can accurately drive each dielectric acceleration structure in the correct time sequence. At the same time, the beam - splitting system can realize the power distribution of the high - power laser, provide a suitable acceleration electric field for each dielectric acceleration section, and ensure the continuity of proton - beam acceleration.

[0099] In one embodiment, the material of the dielectric acceleration structure includes at least one of fused quartz, quartz, and diamond.

[0100] In this embodiment, the dielectric acceleration structure can be processed from fused - quartz material, and the fused quartz can be processed by photolithography or ion etching. As an alternative, diamond or quartz can also be used. They have better electromagnetic properties and higher damage thresholds, but the processing difficulty is greater and the cost is higher.

[0101] Referring toFigure 5 , in one embodiment, the ion source 1 includes:

[0102] A discharge chamber filled with a working gas;

[0103] A microwave source for providing a microwave field to the discharge chamber;

[0104] A magnetic field assembly for providing a magnetic field to the discharge chamber; and,

[0105] An accelerating electrode;

[0106] The working gas is ionized under the combined action of the microwave field and the magnetic field to generate protons, and the protons are extracted through the accelerating electrode to form a proton beam.

[0107] In this embodiment, the ion source is an electron cyclotron resonance type ion source. Since the electron cyclotron resonance type ion source has no filament cathode, it can work continuously for a long time and is suitable for medical applications.

[0108] In this embodiment, the steps of generating a proton beam through the ion source are generally as follows: In the discharge chamber, an easily ionizable light gas such as hydrogen or other hydrogen-containing substances is injected; a constant magnetic field is provided to the discharge chamber through the magnetic field assembly, and electrons perform cyclotron motion in the constant magnetic field; the microwave source feeds a microwave field with appropriate power into the discharge chamber through a microwave window; when the microwave frequency is the same as the cyclotron frequency of electrons at this magnetic field intensity, the electron cyclotron resonance phenomenon will occur, and electrons will continuously absorb microwave energy and accelerate; the accelerated high-energy electrons collide inelastically with the injected gas atoms or molecules, thereby ionizing the gas atoms to form protons and electrons; the magnetic field is also used to confine and stabilize the formed ion and electron plasma, so that protons accumulate in the magnetic field region and may further obtain a higher charge state; once the protons are effectively ionized and accumulated, they can be extracted through the accelerating electrode and further accelerated and then transmitted to the proton injection section.

[0109] In an alternative embodiment, the microwave source includes a magnetron and a tuning section. Electrons are cycled in the magnetic field and accelerated back and forth between the anode and the cathode to generate microwave energy. The tuning section is used to modulate the microwave generated by the magnetron to a specific frequency and pulse width; the discharge chamber is a quartz discharge chamber, and the microwave power is fed into the quartz discharge chamber through a microwave window; the microwave window is a ceramic window; the magnetic field assembly consists of an excitation coil, magnetic poles, and soft iron (the excitation coil and magnetic poles are not shown in the figure), which is used to generate an axially symmetric circular beam and can be adjusted to obtain a specific magnetic field structure to maximize the extraction current intensity.

[0110] In an alternative embodiment, the proton beam generated by the ion source has an energy of 50 kV, a beam current greater than 20 mA, and a normalized root mean square emittance less than 0.6 mm·mrad, so as to match the requirements of the dielectric acceleration structure. In addition, the microwave field generated by the microwave source in the ion source has a frequency of 2.45 GHz.

[0111] In an embodiment of the present invention, by selecting a suitable electron cyclotron resonance type ion source, an incident proton beam that meets the requirements of the dielectric acceleration structure can be generated, and it can work for a long time and can be adapted to medical needs.

[0112] Refer to Figure 6 , in an embodiment, the proton injection section 3 includes:

[0113] Pole shoes;

[0114] At least one set of solenoid lenses for focusing the proton beam; and,

[0115] A current limiting cone for reducing the beam emittance of the proton beam.

[0116] In this embodiment, the proton injection section is used to match the beam parameters between the ion source and the low-energy acceleration section, further focus the proton beam and reduce the beam emittance. The solenoid lens provides the magnetic field strength required for focusing the proton beam to focus the proton beam; the current limiting cone is used to reduce the beam emittance of the proton beam. When protons with a large emittance pass through the current limiting cone, they will hit its tube wall and be lost, and the remaining protons have a small emittance and good directivity; the pole shoes are mainly used to form and / or adjust the magnetic field distribution, work together with the solenoid lens and the current limiting cone, and guide and focus the proton beam through the generated magnetic field to ensure that the protons accelerate accurately and efficiently along the designed path. The design and arrangement of the pole shoes can optimize the magnetic field distribution, prevent excessive beam divergence, and maintain the stability of the beam.

[0117] In an alternative embodiment, refer to Figure 6 , the proton injection section is designed with two sets of solenoid lenses, the current limiting cone is arranged between the two sets of solenoid lenses, and a set of pole shoes is arranged between each set of solenoid lenses and the current limiting cone. The proton beam emitted by the ion source is focused by the first set of solenoid lenses, the beam emittance is reduced by the current limiting cone, and then further focused by the second set of solenoid lenses. By adjusting the current of the solenoid and the position of the pole shoes, the aberration brought by the focusing element can be compensated.

[0118] In an embodiment of the present invention, by designing a reasonable proton injection section, the proton injection section includes pole shoes, solenoid lenses and a current limiting cone to focus the proton beam emitted by the ion source and reduce its beam emittance, ensuring that the proton beam has a suitable size and shape and can maintain good beam quality at different stages of the accelerator.

[0119] In an optional embodiment, the energy of the proton beam emitted by the ion source is 50 keV; the proton beam is focused and its beam emittance is reduced through the proton injection section and then injected into the low-energy acceleration section, and is accelerated by the low-energy acceleration section to 3 - 5 MeV; then the proton beam is further accelerated in multiple cascaded acceleration sections of the medium-energy acceleration section, and the output energy is adjustable from 70 to 250 MeV, and the specific energy value depends on the treatment requirements (usually related to the tumor location); the accelerated proton beam is led out through the proton extraction section to an external treatment device for patient treatment. Among them, the proton extraction section mainly includes a magnetic focusing system for beam guidance to ensure that the proton beam has an accurate trajectory and a suitable beam spot size when leaving the accelerator.

[0120] In summary, the technical solution of the medical proton accelerator of the present invention generates an accelerating electric field through the action of terahertz waves on the dielectric acceleration structure, and applies the high accelerating gradient advantage of terahertz acceleration to the acceleration of medical proton beams. Compared with the acceleration structure of traditional linear accelerators, the acceleration structure of terahertz acceleration requires a smaller scale, and a small and compact proton accelerator can be constructed to solve the problem that the traditional proton linear accelerator occupies too much space. At the same time, to solve the problem of phase drift of the terahertz-accelerated proton beam, both the low-energy acceleration section and the medium-energy acceleration section are provided with tapered sections, so that the phase velocity of the terahertz wave in the dielectric acceleration structure matches the velocity of the proton beam, and the proton beam is always in the accelerating phase in the dielectric acceleration structure. The first tapered section located in the low-energy acceleration section is also superimposed with a periodically perturbed structure to further modulate the phase velocity of the terahertz wave in the low-energy acceleration section. Since the accelerating electric field strength in the dielectric acceleration structure can be adjusted by adjusting the terahertz wave power, the energy of the proton beam emitted by this medical proton accelerator is adjustable to meet the needs of tumor clinical treatment. This medical proton accelerator is also designed with a reasonable ion source, proton injection section, proton extraction section, terahertz source and beam splitting system to provide proton beams with good beam quality and stable terahertz waves to achieve the above beneficial effects.

[0121] The present invention also proposes a radiotherapy system, which includes the above-mentioned medical proton accelerator, and:

[0122] A power supply for supplying power to the medical proton accelerator;

[0123] A treatment head connected to the proton extraction section for guiding the proton beam to the target treatment position.

[0124] Specifically, the treatment head is a conformal irradiation device to ensure that the accelerated proton beam can accurately project to the tumor position of the patient.

[0125] In an alternative embodiment, the treatment head includes a scanning system, a collimation system, an image guidance system, and a monitoring system. The scanning system is used to adjust the lateral position of the proton beam; the collimation system is used to define the shape of the proton beam to match the irradiation requirements of tumors with different contours; the image guidance system is used to accurately locate the target area through images during the treatment process to ensure the precise irradiation of the proton beam; the monitoring system is used to monitor the actual dose to ensure that the treatment process is safely implemented as planned.

[0126] The radiotherapy system of the present invention adopts all the technical solutions of all the embodiments of the above-mentioned medical proton accelerator, and thus at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated herein one by one.

[0127] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the description and drawings of the present invention under the inventive concept of the present invention, or directly or indirectly applied to other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A medical proton accelerator, characterized in that, The medical proton accelerator includes: An ion source for generating a proton beam; A terahertz source for generating terahertz waves with a preset power value; A dielectric acceleration structure for transmitting the terahertz waves to generate an accelerating electric field, which is used to accelerate the proton beam to a preset energy value; the dielectric acceleration structure includes a low-energy acceleration section and a medium-energy acceleration section, and the low-energy acceleration section and the medium-energy acceleration section are arranged in sequence along the propagation direction of the proton beam; the low-energy acceleration section includes a first cylindrical structure with an inner cavity; the first cylindrical structure is provided with a first tapered section, and the inner diameter of the first tapered section is set to gradually increase along the propagation direction of the proton beam; the first tapered section is superimposed with a perturbation structure with a variable period; A proton injection section arranged between the ion source and the dielectric acceleration structure for introducing the proton beam from the ion source into the dielectric acceleration structure; A proton extraction section for extracting the proton beam accelerated to a preset energy value to an external treatment device.

2. The medical proton accelerator according to claim 1, characterized in that, The medium-energy acceleration section includes a second cylindrical structure with an inner cavity.

3. The medical proton accelerator according to claim 2, wherein, The second cylindrical structure is provided with a second tapered section, and the inner diameter of the second tapered section is set to gradually increase along the propagation direction of the proton beam.

4. The medical proton accelerator according to claim 3, wherein The medium-energy acceleration section includes a plurality of cascaded acceleration sections cascaded in sequence.

5. The medical proton accelerator according to claim 4, wherein, The medium-energy acceleration section further includes: At least one drift tube arranged after each of the cascaded acceleration sections for matching the acceleration phase of the proton beam and the cascaded acceleration section.

6. The medical proton accelerator according to claim 1, wherein, The ion source includes: A discharge cavity filled with a working gas; A microwave source for providing a microwave field for the discharge cavity; A magnetic field assembly for providing a magnetic field for the discharge cavity; and, An accelerating electrode; The working gas is ionized under the combined action of the microwave field and the magnetic field to generate protons, and the protons are extracted through the accelerating electrode to form a proton beam.

7. The medical proton accelerator according to claim 1, characterized in that, The proton injection section includes: A pole shoe; At least one set of solenoid lenses for focusing the proton beam; and, A current-limiting cone for reducing the beam emittance of the proton beam.

8. A radiotherapy system, characterized in that, The radiotherapy system includes the medical proton accelerator according to any one of claims 1 to 7, and: A power supply for supplying power to the medical proton accelerator; A treatment head connected to the proton extraction section for guiding the proton beam to a target treatment position.

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