RU2608365C1 - Induction synchrotron accelerator with constant magnetic field - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to acceleration engineering and can be used in physics of high-energy particles, industry, medicine and scientific research. Accelerator includes: a pulse induction system with beam time of flight sensors for synchronisation of accelerating pulses with beam current pulses; system for forming closed orbits of accelerated particles, consisting of beam-reflecting magnetic dipoles and correcting devices for compensation of defocusing action of dipoles in vertical plane; system for rigid focusing on straight sections; beam input and output system; vacuum system. Correcting devices are arranged at inlet and outlet of each beam deflecting section and are a short lens. Magnetic dipoles of orbit forming system, by reflecting beam particles, create closed orbits. Angle of incidence of beam on dipole is equal to angle of reflection. Since this equality does not depend on nature of distribution of field across longitudinal axis of dipole, equality of angles of incidence and reflection is preserved in edge fields of dipoles as well. This fact removes restrictions on lower injection energy threshold.

EFFECT: acceleration in a constant magnetic field with almost constant radius of orbit in entire range of acceleration, significant reduction of lower injection threshold, increased range of accelerated energies and particle Z/A ratio (where Ζ is charge, A is atomic number), absence of pre-accelerators, reduced cost of creation and operation of accelerator.

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Description

The field of technology.

The invention relates to accelerator technology and can be used in the field of high-energy particle physics, industry, medicine and scientific research.

The level of technology.

Accelerators are known: 1) including a dipole with a constant magnetic field, and a high-frequency accelerating system in which charged particles, accelerating, move in a spiral orbit from the center of a magnetic dipole, gradually increasing the radius of the orbit with increasing energy: cyclotrons, synchrocyclotrons or phasotrons (for example , J. Livingood, Principles of Operation of Classical Accelerators. - M.: Publishing House of Foreign Literature, 1963, p. 19-23), 2) accelerators, including dipoles with increasing magnetic field and high-frequency resonators with tunable frequency, in which the particles in the process of acceleration keep the radius of the orbit constant: synchrophasotron (for example, J. Livingood. Principles of operation of classical accelerators. - M .: Publishing house of foreign literature, 1963, pp. 23-25, 199-234), 3) induction synchrotrons including dipoles with a constant magnetic field in time and an accelerating system consisting of induction sections connected with beam transit time sensors and used to start these sections (for example, G.V. Dolbilov, “Cyclic accelerator of charged particles”, JINR Patent No. 2477936, 2014; [one]. GV Dolbilov "The Induction Synchrotron with a Constant Magnetic Field" // Proc. Of the XXIV Russian article Conference, RuPAC 2014, Obninsk, Russia, http://accelconf.web.cern.ch/AccelConf/rupac2014/papers/wepsb29 ) [2]

The main disadvantage of accelerators with a constant magnetic field of a dipole is the limitation of the maximum energy of accelerated particles due to the large weight of the dipole (hundreds of thousands of tons), which is proportional to approximately a cube of the diameter of the pole of the dipole, i.e. maximum momentum of accelerated particles.

The disadvantage of accelerators with a constant radius in the acceleration process is the need to have current pulse generators in the accelerator to power magnetic dipoles, the pulse shape of which depends on the energy of the accelerated particles and the mode of operation of the accelerator. In addition, high-frequency accelerating resonators must change their resonant frequency in accordance with the change in the cyclic frequency of the particles during acceleration. A wide range of changes in cyclic frequency requires the use of pre-accelerators (boosters) to accelerate particles to high energies.

As a prototype, we choose the induction synchrotron, which is described in the works: G.V. Dolbilov, “Cyclic accelerator of charged particles”, JINR Patent No. 2477936, 2014 [1]. GV Dolbilov "The Induction Synchrotron with a Constant Magnetic Field" // Proc. Of the XXIV Russian article Conference, RuPAC 2014, Obninsk, Russia, http://accelconf.web.cern.ch/AccelConf/rupac2014/papers/wepsb29 ) [2].

This charged particle accelerator includes a pulsed induction accelerating system with beam transit time sensors for synchronizing the launch of induction sections, a system for generating magnetic dipoles by the fields of closed particle orbits that are close to the accelerator’s equilibrium orbit during the acceleration process, and a beam focusing system in the form of quadrupole lenses beam input and output systems and a vacuum system.

The disadvantages of such an accelerator is that particles with very low energy may not reach the region of a homogeneous dipole field and will be rejected by the edge fields of the dipole and lost. This circumstance reduces the range of accelerated energies and requires higher energies of injected particles, which complicates the design and makes the creation and operation of the accelerator more expensive.

Disclosure from gaining.

The invention solves the problem of increasing the range of accelerated energies and the Z / A ratio of accelerated particles during cyclic acceleration of particles in a constant magnetic field by reducing the lower threshold of accelerated energies (Z-charge, Α-atomic number). In addition, it allows to reduce the requirements for the parameters of the injected beam, simplify and reduce the cost of the injector design, abandon the pre-accelerator, and reduce the cost of creating and operating the accelerator.

This goal is achieved by the fact that the cyclic accelerator of charged particles includes a pulsed induction accelerating system with beam transit time sensors, which are designed to synchronize the start of induction sections with pulsed circulating beam currents, and a system for generating magnetic dipoles by fields of closed particle orbits that are close to the equilibrium orbit of the accelerator, the system of rigid focusing of the beam in the form of quadrupole lenses that are located on the straight sections of the orbit, the system we have a beam input system, a beam output system and a vacuum system. Moreover, the system of formation of closed orbits during beam acceleration close to the equilibrium orbit consists of a set of deflecting sections with corrective devices at the input and output of the section. Each section deflecting the beam at an angle θ contains two reflecting particles of the dipole beam with a magnetic field that is constant in time and uniform along the longitudinal axis of the dipole and with an arbitrary field distribution across this axis. The longitudinal axes of the dipoles are located at an angle π-θ / 2 to each other and an angle θ / 4 to the axes of the straight sections at the input and output of each deflecting section. Corrective devices compensate for the vertical defocusing of the beam in reflecting dipoles. The corrective device contains two short lenses, quadrupole and symmetrical, which are located in close proximity to each other and represent one corrective lens.

A distinctive feature of the invention is the following: a system for generating closed orbits during beam acceleration, which are close to an equilibrium orbit, consists of a set of deflecting sections with corrective devices at the input and output of the section. Each section deflecting the beam at an angle θ contains two reflecting particles of the dipole beam with a magnetic field that is constant in time and uniform along the longitudinal axis of the dipole and with an arbitrary field distribution across this axis. The longitudinal axes of the dipoles are located at an angle π-θ / 2 to each other and an angle θ / 4 to the axes of the straight sections at the input and output of each deflecting section. Corrective devices compensate for the vertical defocusing of the beam in reflecting dipoles. The corrective device contains two short lenses, quadrupole and symmetrical, which are located in close proximity to each other and are one assembled short corrective lens.

The combination of the above features can significantly reduce the lower threshold of accelerated energies, reduce the energy of injected particles and abandon expensive particle accelerators when accelerating particles to high energies.

With the indicated arrangement of dipoles and the distribution of magnetic fields in them, the beam deflection angle in each deflecting section will be equal to θ in the entire range of accelerated particle energies. Since in the region where the magnetic field is uniform along the longitudinal axis, the angle of reflection of the beam from the dipole will be equal to the angle of incidence of the beam on the dipole and does not depend on the nature of the field distribution across the axis. Therefore, the beam will be deflected by the section through the angle θ in the edge fields of the dipoles at very low particle energies. This circumstance makes it possible to substantially reduce the energy of the particles injected into the accelerator and to reduce the cost of the creation and operation of the accelerator. Since the magnetic fields of the reflecting dipole focus the beam in the radial direction and defocus in the vertical direction, correcting devices are installed at the input and output of each deflecting section, which compensate for the vertical defocusing of the beam using symmetric and quadrupole magnetic lenses.

Pulse induction sections and beam transit time sensors, used to synchronize the launch time of accelerating sections with the beam transit time around the orbit, allow particles to be accelerated over a wide range of velocities (energies) and particle charge to mass ratios, Ζ / A.

List of drawings

FIG. 1 -_ Fragment of the trajectories of a beam of charged particles during acceleration with an induction synchrotron with a constant magnetic field;

FIG. 2 - Scheme of a magnetic dipole reflecting charged particles;

FIG. 3 - Diagram of the deflecting magnetic section;

FIG. 4 - Diagram of a variant of an induction synchrotron with six deflecting sections with a constant magnetic field.

In FIG. 1 shows a fragment of the trajectories of a beam of charged particles in an induction synchrotron with a constant magnetic field,

where 1 is the trajectory of the accelerated beam; 2 - beam path with injection energy, which is much less than the maximum energy.

A diagram of a magnetic dipole reflecting charged particles is shown in FIG. 2

where 3 is the reflecting magnetic dipole, 4 is the trajectory of the “falling” particles, 5 is the trajectory of the reflected particles (see 9, Fig. 3, Appendix 1), the energy and trajectory of which changes during acceleration, (α) are the angles of incidence and particle reflections.

FIG. 3 (Appendix 1) shows a diagram of the deflecting magnetic section, where 6 are the reflecting magnetic dipoles, 7 are the trajectories of the incoming particles, 8 are the trajectories of the outgoing particles, 9 are the trajectories of the particles in the deflecting section during acceleration. (θ) is the beam deflection angle in the section.

In FIG. Figure 4 shows a diagram of a variant of an induction synchrotron with six sections deflecting the beam with a constant magnetic field (six pairs of reflecting dipoles). Each pair of dipoles deflects the beam by 60 °. Here 10 are reflective magnetic dipoles; 11 - straight sections where an induction accelerating system with beam transit time sensors, quadrupole lenses of a hard focusing system, a beam input system, a vacuum system are installed; 12 - chamber of the deflecting section for transporting particles reflected from the dipole (see (9), Fig. 3); 13 - corrective devices, which are a combined lens, consisting of two magnetic lenses, quadrupole and symmetric, which compensate for the vertical defocusing of the beam when the particles are reflected from dipoles.

The implementation of the invention

The device operates as follows.

A beam of charged particles is injected into the accelerator in one of the straight sections of the orbit and accelerated by a pulsed induction system. During acceleration, the frequency of accelerating pulses increases in accordance with an increase in the particle revolution frequency. Pulse and beam synchronization is carried out using beam transit time sensors. Acceleration of current pulses of a particle beam by induction pulses with a controlled repetition rate allows synchronous acceleration to be realized over a wide range of particle velocities and their energies.

Closed orbits of accelerated particles are formed using magnetic sections deflecting the beam, which contain two magnetic dipoles reflecting the beam. If the longitudinal axes of the reflecting dipoles are π-θ / 2 to each other, and the input path of the beam is θ / 4 with the axis of the input reflecting dipole, then the output path and the axis of the output reflecting dipole will be the same angle θ / 4, and the angle between the input and output trajectories of the beam will be equal to θ. Under these conditions, the angle θ will not depend on the energy of the accelerated particles. The ability of the deflecting sections to work in the marginal fields of the dipoles allows us to further expand the acceleration range, reduce the injection energy, and refuse to use pre-accelerators.

Since in the deflecting section the beam is focused in the horizontal plane and defocused in the vertical, the correcting devices installed at the input and output compensate for the defocusing of the beam.

For input and output of the beam from the accelerator, traditional schemes are used.

An example of a specific implementation. The dipole magnets for reflecting the beam are either electromagnets with a magnetic induction of about 2 Tesla, or NdFeB or SmCo permanent magnets with an induction of ~ 1 Tesla. The use of permanent magnets does not require the creation of sources of a magnetic system, but due to the smaller magnitude of magnetic induction increases the size of the equilibrium orbit.

Pulse induction sections are based on traditional ferromagnetic materials (for example, permalloy, ferrite, etc.). Induction sections are a set of ferromagnetic core-inductors, each of which is supplied with a pulse voltage of the order of 1 kV, which allows the use of transistor pulse generators and increase the reliability of the system.

Correction devices of the beam deflection system and quadrupole lenses of straight sections use standard and widely used magnetic lenses.

Claims (2)

1. A cyclic accelerator of charged particles, including a pulsed induction accelerating system, equipped with particle-beam transit time sensors designed to synchronize the start of induction sections, a system for generating closed particle orbits through magnetic dipole fields, whose orbits during acceleration are close to the equilibrium orbit of the accelerator, a rigid system focusing the beam in the form of quadrupole lenses that are located on the straight sections of the orbit, the input system, the output system of the beam and the vacuum system The system is characterized in that the system for generating closed orbits during beam acceleration consists of a set of deflecting sections with corrective devices located at the input and output of each section, and each section deflecting the beam contains two reflecting dipole beams, while the longitudinal axes of the reflecting dipoles form an angle π- θ / 2 to each other and the angle θ / 4 to the axes of the straight sections at the input and output of each deflecting section, where θ is the specified beam deflection angle in each deflecting section, and π is 180 °. 2. The accelerator according to claim 1, characterized in that the corrective device is an assembled lens containing two short lenses, quadrupole and symmetrical, which are located in close proximity to each other in an arbitrary order.

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