RU2524571C1 - Induction cyclic electron accelerator - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: cyclic electron accelerator includes deflecting dipole magnets, an induction accelerating system, beam input and output systems located in rectangular sections. To accelerate electrons in the energy range of 0.3-10 MeV, the accelerator includes a generator for exciting inductor coils of the accelerating system with a rectangular voltage wave. Duration of the accelerating wave pulses is equal not to S, the duration of the orbiting period of the electrons, which is several nanoseconds, but the duration of the full cycle of acceleration from the injection energy go a given final energy of about 10^-4-10^-6 s. To maintain an equilibrium radius of orbit during acceleration and slow ejection of electrons, the accelerator includes a generator for supplying the deflecting dipole magnets, having a property of exciting trapezoidal magnetic induction wave. The accelerator also includes a hard-focusing system in the deflecting dipole magnets and straight sections.

EFFECT: high average power of the accelerated electron beam, reduced size and weight of the accelerator, simple accelerating system and wider range of controlling energy of accelerated electrons.

4 dwg

Description

Technical field

The invention relates to accelerator technology and can be used to create induction cyclic accelerators for industrial use, for example, for the modification and production of new materials, sterilization of medical instruments and food products, disinfection of medical and other wastes, purification of industrial gases from harmful SO _x and NO _x oxides.

State of the art

Known electron accelerators for industrial technologies such as ELV [1]. These are direct action accelerators in which an accelerating electric field is created by the difference of constant potentials between the cathode and the anode electrode. To remove the beam from the accelerator, the anode must be at ground potential, therefore, in direct-acting accelerators, the cathode is at a voltage equal to the energy of accelerated electrons. At an energy of 2.5 MeV, the voltage at the cathode will be 2.5 MB, and the design of the direct-action accelerator should provide electrical insulation of the cathode for a constant voltage equal to the maximum allowable energy. This determines the large size of direct-acting accelerators (height over 4 m).

In high-frequency accelerators (which include ILU-type accelerators), an alternating high-frequency (HF) electric field is used to accelerate electrons, so the question of ensuring electrical insulation is easier to solve. In ILU-type accelerators, electrons are accelerated in the gap of a high-Q resonator. The resonator is excited by an RF generator through a communication loop, and the RF circuit acts as a step-up transformer.

Accelerators of the ILU type [2-4] are single-resonator machines operating in the standing half-wave mode. The operating frequencies of the ILU accelerators are in the meter range of radio waves - 118 MHz (ILU-6 and ILU-10) and 180 MHz (ILU-8). The length of the accelerating gap of the ILU-8 accelerator is 3.6 cm, ILU-6 is 16 cm, ILU-10 is 26 cm. The accelerating gap of these machines is shorter than the wavelength in vacuum, so that in the process of acceleration the electrons acquire an energy almost equal the maximum voltage across the resonator in ILU accelerators uses a triode electron gun (having a control electrode) located immediately in front of the accelerating gap.

Using the control voltage on the electron gun allows you to quickly adjust the beam current and reduces the phase angle of injection, which significantly reduces the spread of electron energy in the beam.

Accelerators of the ILU type have their advantages and disadvantages with respect to the most common type of accelerators, direct-acting accelerators, which include ELV-type accelerators produced by INP. ILU accelerators are impulse machines. Their dimensions are smaller (height 2-2.4 m), and the energy of accelerated electrons is greater (1-5 MeV) than ELV accelerators. They do not need a tank with compressed sulfur hexafluoride SF ₆ gas for insulation of high-voltage parts of the accelerator. In the ILU-10 accelerator, an RF voltage with an adjustable phase shift relative to the accelerating voltage is applied to the triode electron gun, which changes the phase angle of injection and reduces the spread of electron energies in the beam.

The disadvantages of ILU accelerators include: a relatively low coefficient of conversion of electric power consumed from the network into beam power, and the maximum accelerator power (up to 50 kW) is limited by the power of the generated generator lamps.

Unlike linear ELV and ILU accelerators, cyclic accelerators do not have high-voltage accelerating systems with a voltage of the order of 1-5 MB. Electrons acquire the required energy by repeatedly passing the accelerating gap with an average voltage [5, 6]. For radiation technologies used in industry, accelerated electron beams with an energy of 0.5-10 MeV are required. Cyclic accelerators in this energy range are much more compact and cheaper than direct-acting accelerators and microwave accelerators.

Induction cyclic accelerators [5, 6] and the criteria proposed in these works have a small mass of magnetic material and do not have tunable resonant accelerating structures, but they are designed for induction acceleration of light particles - electrons that quickly gain speed at first revolutions, and the main The acceleration process is carried out at a particle velocity close to the speed of light.

In the accelerator [5, 6], the acceleration of electrons is carried out during ½ period of electron revolution (τ), during the second half of the period the magnetization reversal of the cores of the inductors occurs, which brings them to their initial state. A small period of revolution requires the formation of short, nanosecond pulses with fronts <1 ns.

As a prototype, we choose the accelerator [5, 6]. This induction accelerator contains: a deflecting magnetic system with an increasing magnetic field in time and an average value of magnetic induction, much smaller than the magnetic field induction in orbit; (the magnetic field of the deflecting system has an alternating gradient in orbit with a field index much larger than unity) (strong focusing); an induction pulse accelerating system with an accelerating voltage Vacc = R ₀ LdB / dt, where R ₀ is the equilibrium radius of the orbit constant during acceleration, L is the total period of the orbit, dB / dt is the rate of change of magnetic induction, focusing system, electron injection and output systems . The difficulties in the formation of nanosecond accelerating pulses (1 / 2τ) with fronts <10 ^-9 sec prevent a decrease in the total perimeter of the electron orbit (taking into account the rectilinear sections) and a decrease in the duration of the electron revolution, a decrease in the size and cost of the accelerator, and reduce the efficiency and average beam power.

Disclosure of invention

The invention solves the problem of increasing the average power of the accelerated beam, as well as reducing the size and weight of the accelerator by reducing the perimeter of the orbit and shortening the cycle time, simplifying and cheapening the accelerating system, reducing the cost of the accelerator and increasing the range of adjustment of the energy of accelerated electrons.

This goal is achieved by the fact that a cyclic electron accelerator, including a vacuum casing, consisting of arched and rectilinear sections, a system of deflecting magnets located on arched sections connected to power generators of the windings of deflecting magnets, an induction accelerating system consisting of a set of ferromagnetic core-inductors and excitation coils of inductors connected to pulse generators of accelerating pulses, focusing system, cross section of each of inductors of the accelerating system meets the condition

,

,

where ΔB _ind ≤2B _S is the specified change in induction in the accelerating core during acceleration, B _S is the induction of core saturation, T ₀ is the duration of the full acceleration cycle from the injection energy to the final given energy, V _ind is the voltage across the exciting coil of the inductor, while the pulse voltage generator has the property of exciting the turns of inductors by a square wave with an amplitude V _ind equal to:

where ΔР = P _max -P ₀ is the specified increase in the electron momentum during acceleration (P ₀ is the electron momentum of the injection, P _max is the electron momentum at the end of the acceleration process), L = 2πR ₀ + ∑l is the electron orbit perimeter (R ₀ - a given equilibrium radius of the orbit of electrons, ∑l is a given total duration of straight sections), n is the number of inductors in the induction section, e is the electron charge, T ₀ is the duration of the accelerating pulse of a square wave equal to the given duration of the electron acceleration cycle, and the power generator of the deflecting windings magnets gives the property of excitation of a trapezoidal wave of magnetic induction with the parameters:

a) amplitude B _max equal to

,

,

where W _max and β _max are the specified energy and relative speed of electrons at the end of the acceleration process, R ₀ is the specified radius of the equilibrium orbit in the deflecting magnets, e is the electron charge, c is the speed of light;

b) the duration of the linear wave growth T ₀ equal to a given acceleration cycle time;

C) the duration of the flat top of the wave T ₁ equal to the specified time of slow output of electrons.

Distinctive features of the invention is the following: the cross section of each of the inductors of the accelerating system meets the condition:

,

,

where ΔB _ind ≤2B _S is the specified change in the induction in the accelerating core during the acceleration process, B _S is the saturation induction of the core, T ₀ is the duration of the full acceleration cycle from the injection energy to the final given energy, V _ind is the voltage across the exciting coil of the inductor,

wherein the pulse generator has the property of exciting the turns of inductors by a square wave with an amplitude V _ind equal to:

where ΔP = P _max -P ₀ is the specified increase in the electron momentum during acceleration (P ₀ is the electron momentum of the injection, P _max is the electron momentum at the end of the acceleration process), L = 2πR ₀ + ∑l is the perimeter of the electron orbit (R ₀ - a given equilibrium radius of the orbit of electrons, задl is a given total duration of rectilinear sections), n is the number of inductors in the induction section, e is the charge of an electron, T ₀ is the duration of the accelerating pulse of a square wave equal to a given duration of the electron acceleration cycle,

the power generator of the windings of the deflecting magnets has the property of exciting a trapezoidal wave of magnetic induction with the parameters:

amplitude B _max equal to

,

,

where W _max and β _max are the specified energy and relative speed of electrons at the end of the acceleration process, R ₀ is the specified radius of the equilibrium orbit in the deflecting magnets, e is the electron charge, c is the speed of light;

b) the duration of the linear wave growth T ₀ equal to a given acceleration cycle time;

C) the duration of the flat top of the wave T ₁ equal to the specified time of slow output of electrons.

The combination of the above characteristics allows us to reduce the duration of the period of revolution of accelerated electrons in equilibrium orbit by reducing the equilibrium radius of the orbit R ₀ , reducing the length of straight sections, which is accompanied by a decrease in the time of revolution of electrons in equilibrium orbit and will lead to an increase in the average power of the accelerated beam, a decrease in the dimensions and weight of the accelerator . The accelerating system, which forms a square wave with pulses of duration ~ 10 ^-4 -10 ^-6 s, is much simpler and cheaper than the system, which generates and synchronizes a series of nanosecond pulses with the beam, with fronts ≤10 ^-9 s. The energy of accelerated electrons is adjusted by changing the duration of the induction electric field.

List of illustrations

Figure 1. (Appendix 1) Accelerator circuit;

Figure 2. (Appendix 1) Schemes of core deflecting magnets;

Figure 3. (Appendix 2) Scheme of the induction accelerating section;

Figure 4. (Appendix 2) Waveform of induction of a leading magnetic field and accelerating voltage of inductors.

Description of illustrations

A diagram of a cyclic accelerator is shown in FIG. 1 (Appendix 1), where: (1) - a system of deflecting magnets with strong focusing; (2) - induction accelerating system; (3) - electron input and output systems.

Figure 2 (Appendix 1) shows a diagram of the core deflecting magnets with alternating magnetic field gradient (strong focusing).

Figure 3 (Appendix 2) shows a diagram of an induction accelerating section, where (4) are the ferromagnetic cores of the inductors; (5) - coils of excitation of inductors; (6) - field lines of the induction electric field.

Figure 4 (Appendix 2) shows: a) the trapezoidal waveform of the magnetic field induction B _(t) , excited by the power generator of the deflecting magnets, b) the square wave form V _{ind (t)} , excited by the pulse voltage generator on the excitation coils of the inductors (ferromagnetic cores). Here T ₀ is the duration of the linear growth of magnetic field induction in equilibrium orbit, equal to the duration of the accelerating pulse of a square wave, T ₁ is the duration of the flat top of a trapezoidal wave, which is equal to the time of slow electron output.

The case of the accelerator (Figure 1) consists of 2, 4 or n - arcuate sections connected by straight sections. Arcuate sections are located inside the systems of deflecting magnets (1), rectilinear sections are used to accommodate the induction accelerating system (2), electron input and output systems.

The deflecting system consists of a set of deflecting magnets (Figure 2) with an alternating magnetic field gradient (n >> 1 and n << 1), which ensures strong focusing of electrons.

An induction accelerating system consists of a set of ferromagnetic cores (inductors) (4) with excitation coils of inductors (5) that create an accelerating electric field (6) (see Figure 3).

The implementation of the invention

(W₀ и β₀ - энергия и относительная скорость инжектируемых электронов, R₀ - заданный равновесный радиус, е и с - заряд электрона и скорость света).The device operates as follows: electrons are injected into a growing magnetic field at time t ₀ , when the magnitude of the field induction

(W ₀ and β ₀ are the energy and relative velocity of the injected electrons, R ₀ is the given equilibrium radius, e and c are the electron charge and the speed of light).

The electrons are accelerated by the electric field of the inductors (4) (see Figure 3) of the induction system (2), (see Figure 1). The duration of the accelerating pulses of the inductors is equal to the time of acceleration of electrons from the injection energy to a given energy (Fig.4b).

должна соответствовать условию:In the process of acceleration, the magnetic field of the deflecting magnets increases (Figa). For a constant equilibrium radius in deflecting magnets, the rate of rise of magnetic induction

must meet the condition:

,

,

where n is the number of inductors, V _ind is the voltage of the inductor, L is the total perimeter of the orbit, R ₀ is the equilibrium radius of the electrons in the deflecting magnets.

In the process of slow output of accelerated electrons, the magnitude of the magnetic induction remains constant (Fig.4b). The duration of the top of the trapezoidal pulse of magnetic induction is equal to the time of the slow output of electrons.

An example of a specific implementation.

Inductors (4), (Figure 3) are cores of ferromagnetic material designed to operate in a given range of pulse durations. To reduce the scattering fluxes, each inductor has 3 or more turns of excitation (5) (Fig. 3) connected in parallel.

The excitation generator of the inductors connected to the excitation coils is a transistor transformer of direct voltage into a square wave (Fig.4b).

The power generator of the winding deflecting magnets contains capacitor energy storage devices and transistor switches. The waveform of the magnetic induction created by the generator has a trapezoidal shape (Figa).

The transistors in the excitation generators of the inductors and the power of the windings of the deflecting magnets operate in the switching mode, which can significantly reduce power losses during the formation of the given pulse shapes.

If the specified energy of accelerated electrons is 10 MeV, and the magnitude of the magnetic field induction of the deflecting magnets is 0.1 T, then the equilibrium radius of the orbit in such a field is 0.33 m.

With the total voltage of the accelerating section V = n · V _ind = 10 ³ B, for the electrons to reach the energy of 10 ⁷ eV, the electrons must make 10 ⁴ revolutions. If the total perimeter of the trajectory is ≈3 m, then the period of one acceleration cycle will be 10 ^-8 s, and the full acceleration cycle and the duration of the accelerating pulse T ₀ = 10 ^-4 s. If ΔB _ind ≈1T (permalloy), then the cross section of the inductor should be S = 0.1 / n m ² (n is the number of inductors). With a decrease in the given energy of accelerated electrons, the required cross section of the inductors decreases. For example, to accelerate electrons to an energy of 1 MeV (10 ⁶ eV), the required cross section of the inductors will be approximately 10 times smaller.

Literature

1. Salimov R.A., Cherepkov V.G., Golubenko J.I. et al. DC high power electron accelerators of ELV-series: status, development, applications // Radiation Physics and Chemistry. 2000. No57. P.661-665.

2. Auslender V.L. ILU-type electron accelerator for industrial technologies // Nuclear Instruments and Methods in Physical Research. 1994. No. B 89. P. 46-48.

3. Auslander V.L., Bezuglov V.V., Bryazgin A.A. et al. Electron accelerators of the ILU series and their use in radiation-technological processes // Vopr. atomic science and technology. Series: Technical Physics and Automation. 2004. Issue. 58. S.78-85.

4. Auslander V.L., Bryazgin A.A., Voronin L.A. et al. Electron accelerators of the ILU series and their application in industry and medicine // Collection of reports of the Eleventh International Meeting on the Use of Charged Particle Accelerators in Industry and Medicine. SPb., 2005. S.78-81.

5. G. V. Dolbilov, “The Compact Iduction Circular Accelerator for Radiation Technologies”, Proceedings of APAC 2007, Raja Ramanna Center for Advanced Technology (RRCAT), Indore, India, pp. 628-629.

6. G.V.Dolbilov, “Method of induction acceleration of charged particles”, Patent for invention No. 2359434, July 05, 2007

Claims (1)

A cyclic electron accelerator, including a vacuum casing, consisting of arcuate and rectilinear sections, a system of deflecting magnets located on the arcuate sections and connected to the power generators of the windings of the deflecting magnets, an induction accelerating system consisting of a set of ferromagnetic cores-inductors and excitation turns of inductors connected to pulse generators of accelerating pulses, a focusing system, characterized in that the cross section of each of the inductors reproaching the system corresponds to the condition

,
where ΔB _ind ≤2B _S is the specified change in induction in the accelerating core during acceleration, B _S is the induction of core saturation, T ₀ is the duration of the full acceleration cycle from the injection energy to the final given energy, V _ind is the voltage across the exciting coil of the inductor, while the pulse voltage generator has the property of exciting the turns of inductors by a square wave with an amplitude V _ind equal to:

where ΔР = P _max -P ₀ is the specified increase in the electron momentum during acceleration (P ₀ is the electron momentum of the injection, P _max is the electron momentum at the end of the acceleration process), L = 2πR ₀ + ∑l is the electron orbit perimeter (R ₀ - a given equilibrium radius of the orbit of electrons, ∑l is a given total duration of straight sections), n is the number of inductors in the induction section, e is the electron charge, T ₀ is the duration of the accelerating pulse of a square wave equal to the given duration of the electron acceleration cycle, and
the power generator of the windings of the deflecting magnets has the property of exciting a trapezoidal wave of magnetic induction with the parameters:
a) amplitude B _max equal to

,
where W _max and β _max are the specified energy and relative speed of electrons at the end of the acceleration process, R ₀ is the specified radius of the equilibrium orbit in the deflecting magnets, e is the electron charge, c is the speed of light;
b) the duration of the linear wave growth T ₀ equal to a given acceleration cycle time;
C) the duration of the flat top of the wave T ₁ equal to the specified time of slow output of electrons.

Images