Method and device for improving beam duty cycle using colored noise

Abstract

The present invention provides a method and device for increasing the beam duty cycle by using colored noise, and relates to the field of particle accelerators and signal processing technology. The method comprises: generating a digital noise signal through a finite impulse response filter; converting the digital noise signal into two branch signals of equal magnitude and opposite sign through a phase shifter; and loading the two branch signals onto a transverse electrode plate after each of the two branch signals passes through an attenuator, an amplitude modulator, an impedance converter, and an all-pass network in sequence, thereby obtaining an extracted beam subjected to transverse excitation. The present invention can effectively improve the impact of the current traditional RF-KO sweep mode on beam extraction, making the time structure of the slow extraction beam more uniform, promoting the widespread application of precise point scanning, and improving treatment efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of particle accelerators and signal processing, and in particular to a method and device for improving beam duty cycle by utilizing colored noise. Background Art

[0002] Medical devices based on particle accelerators have been widely developed because the proton beam or heavy ion beam (mainly carbon ions) they produce has an inverted Bragg peak in dose deposition distribution when penetrating biological tissue cells. This can effectively kill tumor cells at the end of the range while causing less harm to normal tissue cells in the path.

[0003] Particle accelerators typically consist of an ion source, a cyclotron / linear accelerator, an injection line, a synchronization ring, and a high-energy transmission line. To ensure uniform terminal dose distribution and size, accelerators often employ a third-order resonant slow extraction method to slowly extract the beam over a few seconds. This requires the coordinated action of a sextupole magnet within the ring, transverse excitation, an extraction bump, electrostatic deflection plates (ES), and a cutting magnet (MS). The overall process is as follows: with the extraction platform accelerator's horizontal operating point near the 1 / 3 resonance line, the beam, under the influence of the resonant sextupole within the ring, forms a triangle in the transverse phase space. Particles within the triangle are stable, while those near the edges are in an unstable region. They gradually move along the three boundary tracks of the triangle, experiencing a sharp increase in transverse amplitude until they enter the electrostatic deflection plates and are extracted.

[0004] Currently, the preferred extraction scheme for accelerator medical devices is the resonant extraction scheme based on transverse excitation, proposed by Japan's NIRS. In this scheme, the transverse excitation is primarily composed of two electrode plates, forming a high-voltage electric field between them. This creates a horizontal kick angle on the passing beam, causing particles in the stable region of phase space to gradually increase their transverse oscillation amplitude under the excitation, moving them to the unstable region and being extracted. The basic working principle is shown in Figures 1(a) and 1(b). Its advantages include maintaining the synchronization ring optics, shortening the beam shutoff time, maintaining a constant position and angle of the extracted beam, making the temporal structure easily adjustable, and controlling the flux intensity.

[0005] After ensuring particle extraction, research focuses on improving extraction efficiency, achieving a more uniform extracted beam temporal structure, and increasing beam duty cycle and flatness. As described above, throughout the slow extraction process, particles are primarily affected by transverse excitation, and its operating mode directly determines the beam extraction temporal structure. Currently, the excitation plate voltage primarily operates in swept frequency and amplitude modes, including single-frequency, dual-frequency, and swept amplitude modes. The corresponding waveforms are shown in Figures 2(a), 2(b), and 2(c).

[0006] As can be seen, the current excitation sweep frequency curve is a sawtooth wave, with the frequency varying regularly from small to large. Therefore, when the excitation frequency resonates with particles at the edge of the phase-stable region, the beam is extracted. However, when the excitation frequency increases, it resonates with particles within the phase-stable region and does not directly extract the beam. Therefore, within a given repetition frequency, gaps appear in the beam's temporal structure, resulting in a decrease in the duty cycle. Summary of the Invention

[0007] In order to solve the limitations of the current slow extraction transverse excitation working mode in improving the beam extraction uniformity and duty cycle, the present invention provides a method and device for improving the beam duty cycle by using colored noise.

[0008] A first aspect of the present invention provides a method for improving the beam duty cycle by using colored noise, comprising: generating a digital noise signal through a finite impulse response filter; converting the digital noise signal into two branch signals of equal magnitude and opposite sign through a phase shifter; and loading the two branch signals onto a transverse plate after each of the two branch signals passes through an attenuator, an amplitude modulator, an impedance converter, and an all-pass network in sequence, thereby obtaining an extracted beam after transverse excitation.

[0009] A second aspect of the present invention provides a device for increasing the beam duty cycle using colored noise, comprising: a finite impulse response filter for generating a digital noise signal; a phase shifter for converting the digital noise signal into two branch signals of equal magnitude and opposite sign; an attenuator, an amplitude modulator, an impedance converter, and an all-pass network, wherein the two branch signals each pass through the attenuator, amplitude modulator, impedance converter, and all-pass network in sequence, and are then loaded onto a transverse plate to obtain an extracted beam subjected to transverse excitation.

[0010] Compared with the prior art, the method and device for improving beam duty cycle by using colored noise provided by the present invention have at least the following beneficial effects:

[0011] (1) It can effectively improve the impact of the current traditional RF-KO sweep mode on beam extraction, making the time structure of the slow extraction beam more uniform, which will promote the widespread application of precise point scanning and improve treatment efficiency;

[0012] (2) Since digital noise signals are relatively easy to generate and the entire device is easy to build, the present invention has good promotion and practicality.

[0013] (3) The present invention is used to generate a more uniform, high-duty-cycle extraction beam, thereby improving the beam utilization rate and treatment efficiency of accelerator medical devices and promoting the development of its own industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0015] FIG1( a ) and FIG1( b ) schematically illustrate the principle diagrams of existing resonance extraction schemes based on lateral excitation;

[0016] Figures 2(a), 2(b), and 2(c) schematically illustrate the excitation single-frequency curve, the excitation dual-frequency curve, and the excitation sweep curve in the existing resonance extraction scheme based on transverse excitation, respectively;

[0017] Figure 3 A flowchart of a method for improving beam duty cycle by using colored noise according to an embodiment of the present invention is schematically shown;

[0018] Figure 4 The flowchart schematically shows a process of generating a digital noise signal according to an embodiment of the present invention;

[0019] 5( a ) and 5 ( b ) schematically illustrate a flow chart of a process for generating a digital noise signal according to an embodiment of the present invention;

[0020] Figure 6 Schematically shows a structural block diagram of a device for improving beam duty cycle by using colored noise according to an embodiment of the present invention;

[0021] Figure 7 Schematically shows a structural block diagram of a finite impulse response filter according to an embodiment of the present invention;

[0022] Figure 8 The figure schematically shows a circuit diagram of an impedance converter and an all-pass network according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments and the accompanying drawings. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0024] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the presence of the features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0025] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0026] During the process of implementing the present invention, the inventors discovered at least the following issues with the prior art: To ensure resonance with every particle during beam deflection, the operating frequency of the transverse excitation must have a certain bandwidth, resulting in a sawtooth-like curve. This results in the excitation sweep mode modulating the beam extraction temporal structure, reducing the duty cycle. Under these circumstances, the traditional slow extraction mode exhibits its limitations.

[0027] Based on the limitations of the current slow extraction lateral excitation operating mode in improving beam extraction uniformity and duty cycle, the present invention provides a method and device for improving beam duty cycle using colored noise. By changing the swept frequency operating mode of the lateral excitation itself, the limitations of frequency modulation on the extracted beam duty cycle and uniformity are fundamentally resolved, thereby achieving better extracted beam quality.

[0028] Figure 3 The flowchart of the method for improving the beam duty cycle by using colored noise according to an embodiment of the present invention is schematically shown.

[0029] like Figure 3 As shown, the method for improving the beam duty cycle by using colored noise according to this embodiment may include operations S310 to S330.

[0030] In operation S310 , a digital noise signal is generated through a finite impulse response filter.

[0031] In operation S320 , the digital noise signal is converted into two branch signals of equal magnitude and opposite signs through a phase shifter.

[0032] In operation S330 , the two branch signals are sequentially passed through an attenuator, an amplitude modulator, an impedance converter, and an all-pass network, and then loaded onto a transverse plate to obtain an extracted beam after transverse excitation.

[0033] Noise signals can be categorized as white noise and colored noise. White noise, for example, has a power spectral density that is constant across the entire frequency domain and is the simplest random process composed of a series of uncorrelated random variables. Colored noise, on the other hand, is characterized by a non-constant power spectral density function. A filtered, bandwidth-consistent colored noise signal can overcome the low duty cycle of beam extraction associated with traditional sawtooth-like sweeps, eliminating the modulation of the beam's temporal structure.

[0034] Through the above embodiments, the present invention uses digital noise as a signal source, which is converted into two sets of signals of equal magnitude and opposite signs through a phase shifter. Then, after passing through an attenuator, an amplitude modulator, an impedance converter and an all-pass network, the output voltage signal is loaded onto the two lateral plates of the excitation.

[0035] Figure 4 The flowchart schematically shows a process of generating a digital noise signal according to an embodiment of the present invention.

[0036] like Figure 4 As shown, in the embodiment of the present invention, the digital noise signal in the above operation S310 is generated by a finite impulse response filter, and can be specifically generated according to the following operations S3101 to S3103.

[0037] In operation S3101, a plurality of random noise signals x with amplitudes between -1 and 1 are generated. k , forming the initial signal sequence {x k}.

[0038] In operation S3102, a finite impulse response filter is used to filter the initial signal sequence {x k} is filtered to obtain the digital signal sequence {y k}.

[0039] In the embodiment of the present invention, the digital signal sequence is obtained according to the following formula:

[0040]

[0041] Among them, y k is a digital signal sequence; k is the sequence number; N h is the order of the finite impulse response filter; h n is the filter coefficient; x k-n is a random noise signal; n is the number of turns.

[0042] Furthermore, the filter coefficient h n It is derived according to the following formula:

[0043]

[0044] h0=4f b T,m=0

[0045] Among them, the value range of m is ±N h / 2; f0=(f H +f L ) / 2,f b =(f H -f L ) / 2,f H and fL are the upper and lower cut-off frequencies, respectively, and the digital signal sequence y k The frequency bandwidth is f L and f H T is the sampling period.

[0046] In operation S3103, the digital signal sequence {yk} is limited using a preset amplitude coefficient to obtain a digital noise signal δ k .

[0047] In the embodiment of the present invention, the digital noise signal is obtained according to the following formula:

[0048] δ k =Cy k

[0049] Where C is the amplitude coefficient; δ k is the digital noise signal, that is, the excitation kick angle per circle.

[0050] It is understandable that the larger the bandwidth, the better the uniformity of the extracted beam. H and f L and the particle cyclotron frequency f rev It is closely related to the lateral emittance (i.e. the particle working point drift). Usually, the upper and lower cutoff frequencies f H and f L The following relationship is satisfied:

[0051] f L <f rev

[0052] f H >f rev

[0053] Among them, f rev is the particle cyclotron frequency.

[0054] It can be seen that the present invention fundamentally solves the limitations of frequency modulation on the duty cycle and uniformity of the extracted beam by changing the sweep frequency working mode of the transverse excitation itself, thereby obtaining better extracted beam quality.

[0055] FIG5(a) and FIG5(b) schematically illustrate a flow chart of a process for generating a digital noise signal according to an embodiment of the present invention.

[0056] As shown in Figures 5(a) and 5(b), the present invention eliminates the periodic modulation of single or dual frequencies in traditional excitation signals because the frequency variation is a random signal. While maintaining the scanning bandwidth, it can more effectively extract beam particles, improving uniformity and duty cycle.

[0057] The embodiments of the present invention can effectively improve the impact of the current traditional RF-KO sweep mode on beam extraction, making the time structure of the slow extraction beam more uniform, which will promote the widespread application of precise point scanning and improve treatment efficiency.

[0058] Furthermore, the present invention is used to generate a more uniform, high-duty-cycle extracted beam, thereby improving the beam utilization and treatment efficiency of accelerator medical devices and promoting the development of the industry itself. Furthermore, since digital noise signals are relatively easy to generate and the entire device is simple to set up, the present invention has excellent scalability and practicality.

[0059] Based on the above disclosed method, the present invention also provides a device for improving the beam duty cycle by using colored noise. Figure 6 The device is described in detail.

[0060] Figure 6 The structure block diagram of the device for improving the beam duty cycle by using colored noise according to an embodiment of the present invention is schematically shown.

[0061] like Figure 6 As shown, the apparatus 600 for improving beam duty cycle by using colored noise according to this embodiment includes a finite impulse response filter FIR, a phase shifter YX, an attenuator ATT, an amplitude modulator AMP, an impedance transformer IT, and an all-pass network APN.

[0062] Finite impulse response filter FIR is used to generate digital noise signals.

[0063] The phase shifter YX is used to convert the digital noise signal into two branch signals of equal magnitude and opposite signs.

[0064] Attenuator ATT, amplitude modulator AMP, impedance converter IT and all-pass network APN, wherein the two branch signals respectively pass through the attenuator ATT, amplitude modulator AMP, impedance converter IT and all-pass network APN in sequence, and are then loaded onto the transverse plate RF-KO to obtain the extracted beam after transverse excitation.

[0065] Through the above-described embodiment, the present invention utilizes digital noise as a signal source, which is converted into two signals of equal magnitude and opposite sign by a phase shifter YX. After passing through an attenuator ATT, an amplitude modulator AMP, an impedance converter IT, and an all-pass network APN, the output voltage signal is applied to the two excitation transverse plates RF-KO. The digital noise signal can be generated using a finite impulse response filter (FIR).

[0066] Figure 7 The structure block diagram of the finite impulse response filter according to an embodiment of the present invention is schematically shown.

[0067] like Figure 7 As shown, in the embodiment of the present invention, the finite impulse response filter FIR specifically includes a random noise generating unit 710 , a filtering unit 720 and a limiting unit 730 .

[0068] The random noise generating unit 710 is configured to generate a plurality of random noise signals with amplitudes between -1 and 1 to form an initial signal sequence.

[0069] The filtering unit 720 is configured to filter the initial signal sequence using a finite impulse response filter to obtain a digital signal sequence.

[0070] The limiting unit 730 is configured to limit the digital signal sequence using a preset amplitude coefficient to obtain a digital noise signal.

[0071] Figure 8 The figure schematically shows a circuit diagram of an impedance converter and an all-pass network according to an embodiment of the present invention.

[0072] like Figure 8 As shown, in the embodiment of the present invention, the impedance converter IT includes a first inductor L1, a second inductor L2, a third inductor L3 and a fourth inductor L4, and the first inductor L1, the second inductor L2, the third inductor L3 and the fourth inductor L4 are all common-mode inductors including a primary coil and a secondary coil.

[0073] Among them, the first end of the primary coil of the first inductor L1 is respectively connected to the first end of the primary coil of the second inductor L2, the first end of the primary coil of the third inductor L3, the first end of the primary coil of the fourth inductor L4 and the second end of the secondary coil of the fourth inductor L4 and serves as the signal input end of the impedance converter IT, and the second end of the primary coil of the first inductor L1 serves as the signal output end of the impedance converter IT.

[0074] The first end of the secondary coil of the first inductor L1, the first end of the secondary coil of the second inductor L2, the first end of the secondary coil of the third inductor L3 and the first end of the secondary coil of the fourth inductor L4 are respectively grounded, the second end of the secondary coil of the first inductor L1 is connected to the second end of the primary coil of the second inductor L2, the second end of the secondary coil of the second inductor L2 is connected to the second end of the primary coil of the third inductor L3, and the second end of the secondary coil of the third inductor L3 is connected to the second end of the primary coil of the fourth inductor L4.

[0075] Please continue reading Figure 8 In the embodiment of the present invention, the all-pass network APN includes a fifth inductor L5, a sixth inductor L6, a capacitor C and a resistor R.

[0076] The first end of the fifth inductor L5 is connected to the first end of the capacitor C and both are connected to the second end of the primary coil of the first inductor L1 .

[0077] The second end of the capacitor C is connected to the first end of the resistor R and the first end of the sixth inductor L6 respectively. The second end of the fifth inductor L5 is connected to the second end of the sixth inductor L6 and is commonly connected to the first end of the transverse plate. The second end of the resistor R and the second end of the transverse plate are commonly grounded.

[0078] Through the above embodiments, since the digital noise signal is relatively easy to generate and the entire device is convenient to build, the present invention has good promotion and practicality.

[0079] It should be noted that the embodiment of the device part is similar to the embodiment of the method part, and the technical effects achieved are also similar. For specific details, please refer to the above-mentioned method embodiment part, which will not be repeated here.

[0080] The accompanying drawings show some block diagrams and / or flow charts. It should be understood that some blocks in the block diagrams and / or flow charts, or combinations thereof, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when these instructions are executed by the processor, they can create a device for implementing the functions / operations described in the block diagrams and / or flow charts.

[0081] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly specifying the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined. Furthermore, the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0082] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for improving beam duty cycle by using colored noise, characterized in that: include: Generate a digital noise signal through a finite impulse response filter; Converting the digital noise signal into two branch signals of equal magnitude and opposite signs through a phase shifter; The two branch signals are sequentially passed through an attenuator, an amplitude modulator, an impedance converter and an all-pass network, and then loaded onto a transverse plate to obtain an extracted beam after transverse excitation.

2. The method for improving beam duty cycle by using colored noise according to claim 1, characterized in that: The digital noise signal is generated according to the following method: Generate multiple random noise signals with amplitudes between -1 and 1 to form an initial signal sequence; Filtering the initial signal sequence using the finite impulse response filter to obtain a digital signal sequence; The digital signal sequence is amplitude limited using a preset amplitude coefficient to obtain the digital noise signal.

3. The method for improving beam duty cycle by using colored noise according to claim 2, characterized in that: The digital signal sequence is obtained according to the following formula: in, is the digital signal sequence; k is the sequence number; is the order of the finite impulse response filter; is the filter coefficient; is a random noise signal; n is the number of turns.

4. The method for improving beam duty cycle by using colored noise according to claim 3, characterized in that: The filter coefficient It is derived according to the following formula: Among them, the value range of m is ± between; , , and They are the upper and lower cut-off frequencies, the digital signal sequence The frequency bandwidth is and T is the sampling period.

5. The method for improving beam duty cycle by using colored noise according to claim 4, characterized in that: The upper and lower cut-off frequencies and The following relationship is satisfied: in, is the particle cyclotron frequency.

6. The method for improving beam duty cycle by using colored noise according to claim 3, characterized in that: The digital noise signal is obtained according to the following formula: Wherein, C is the amplitude coefficient; is the digital noise signal.

7. A device for increasing beam duty cycle using colored noise, characterized in that: include: Finite impulse response filters for generating digital noise signals; a phase shifter, configured to convert the digital noise signal into two branch signals of equal magnitude and opposite signs; Attenuator, amplitude modulator, impedance converter and all-pass network, wherein the two branch signals are respectively loaded on the transverse plate after passing through the attenuator, amplitude modulator, impedance converter and all-pass network in sequence to obtain the extracted beam after transverse excitation.

8. The device for increasing beam duty cycle using colored noise according to claim 7, characterized in that: The finite impulse response filter specifically includes: A random noise generating unit, configured to generate a plurality of random noise signals with amplitudes between -1 and 1 to form an initial signal sequence; a filtering unit, configured to filter the initial signal sequence using the finite impulse response filter to obtain a digital signal sequence; The limiting unit is used to limit the digital signal sequence using a preset amplitude coefficient to obtain the digital noise signal.

9. The device for increasing beam duty cycle using colored noise according to claim 7, characterized in that: The impedance converter comprises a first inductor (L1), a second inductor (L2), a third inductor (L3) and a fourth inductor (L4), wherein the first inductor (L1), the second inductor (L2), the third inductor (L3) and the fourth inductor (L4) are all common-mode inductors comprising a primary coil and a secondary coil, wherein: The first end of the primary coil of the first inductor (L1) is respectively connected to the first end of the primary coil of the second inductor (L2), the first end of the primary coil of the third inductor (L3), the first end of the primary coil of the fourth inductor (L4), and the second end of the secondary coil of the fourth inductor (L4) and serves as a signal input end of the impedance converter, and the second end of the primary coil of the first inductor (L1) serves as a signal output end of the impedance converter; The first end of the secondary coil of the first inductor (L1), the first end of the secondary coil of the second inductor (L2), the first end of the secondary coil of the third inductor (L3) and the first end of the secondary coil of the fourth inductor (L4) are each grounded, the second end of the secondary coil of the first inductor (L1) is connected to the second end of the primary coil of the second inductor (L2), the second end of the secondary coil of the second inductor (L2) is connected to the second end of the primary coil of the third inductor (L3), and the second end of the secondary coil of the third inductor (L3) is connected to the second end of the primary coil of the fourth inductor (L4).

10. The device for increasing beam duty cycle by using colored noise according to claim 9, characterized in that: The all-pass network includes a fifth inductor (L5), a sixth inductor (L6), a capacitor (C) and a resistor (R), wherein: The first end of the fifth inductor (L5) is connected to the first end of the capacitor (C) and is commonly connected to the second end of the primary coil of the first inductor (L1); The second end of the capacitor (C) is connected to the first end of the resistor (R) and the first end of the sixth inductor (L6) respectively, the second end of the fifth inductor (L5) is connected to the second end of the sixth inductor (L6) and is commonly connected to the first end of the transverse plate, and the second end of the resistor (R) and the second end of the transverse plate are commonly grounded.

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