Induction Synchrotron Research Articles

Longitudinal splitting of bunches with variable energies in synchrotron

The ever-enriching beam application has put for-ward more demands on accelerators. If multiple bunches of different energies can be extracted for FLASH point scanning in a short time (< 500 ms), the spatial dose distribution advantage of proton Bragg peak can be combined with the temporal effect ad-vantage of FLASH. This paper provides three methods for generating short bunches in synchrotron. By adjusting the pulse parameters of the barrier voltages in the induction synchrotron, the short bunches can be easily generated. The short bunches can be kicked out of the beam reference orbit by kickers. When the pro-cess is repeated for many times, and the energy-changing process is added to the time interval during which the short bunches are continuously generated, the short bunches of multiple energies can be extracted in one working cycle. By finely controlling the changes of rectangular pulses, the number of particles in the short bunches can be better controlled, making an important contribution to further enriching the application of synchrotron.

Study the closed orbit correction of a compact hadron driver for cancer therapy

A design of a compact hadron driver for future cancer therapies based on the induction synchrotron concept is given. In order to realize a slow extraction technique in a fast cycling synchrotron, which allows the energy sweep beam scanning, the zero momentum-dispersion D(s) region and high flat D(s) region are necessary. The present design meets both requirements. The lattice has the two-fold symmetry with a circumference of 52.8 m, 2 m-long dispersion-free straight section, and 3 m-long large flat dispersion straight section. Assuming a 1.5 T bending magnet, the ring can deliver heavy ions of 200 MeV/au at 10 Hz. Details of the lattice parameters and orbit correction approach and method are discussed.

Fourth generation switching power supply for circular induction accelerators.

A switching power supply (SPS) was applied as the high-frequency bipolar high-voltage pulse source required to accelerate charged particles in the induction synchrotron, which was a novel synchrotron proposed at the High Energy Accelerator Research Organization (KEK) in 2006, and it was also used in other circular induction accelerators proposed thereafter, including the induction sector cyclotron and the induction microtron. As the heart of the circular induction accelerator, the SPS has recently been developed up to a fourth generation system that uses newly developed 3.3kV high-speed SiC metal-oxide-semiconductor field-effect transistors(MOSFETs). The updates involved in this new SPS include the use of two parallel MOSFETs in each arm to shunt heat dissipation at high frequencies, optimization of the bus pattern, with low parasitic capacitance among the arms to improve the drain-source voltage (VDS) balance, and addition of current sampling circuits to provide an economical method to monitor the operating status in large-scale application scenarios. The heat power and temperature characteristics of the MOSFETs were studied specifically in both individual tests and SPS tests. To date, the new SPS has achieved 2.5 kV-17.4A bipolar output at 350kHz in continuous mode operation. The highest junction temperature of the MOSFETs was estimated to be 98 °C.

Lattice Design of a Compact Hadron Driver for Cancer Therapy

A next generation cancer therapy driver by using a fast-cycling induction synchrotron is given. The design of the lattice parameters with zero momentum-dispersion and high-flat momentum-dispersion region as essential parameters must be fulfilled and the optimization process with results are discussed here. Finally, the optimization process and method are developed and the lattice parameters are well defined.

Fast ion bunch compression by barrier pulse control

We report a novel scheme for fast ion bunch compression by barrier pulse control in an induction synchrotron in which an effective acceleration voltage pulse with a pseudo-linear slope is generated by temporal handling of rectangular induction acceleration pulses. With beam handling, a head-to-tail momentum gradient is yielded to the beam in a desired manner and the beam is gradually compressed over 30 turns. In the proof-of-principle experiment, which used a 75 μA He1+ beam at 50 keV per nucleon, the root mean square bunch length was reduced to 0.44 μs by a factor of 3.5 in 30 turns with no appreciable beam loss due to the beam compression scheme. This scheme is useful for various beam applications including ion beam heating.

An analytical approach of the chromaticity correction for compact hadron river

A design of a compact hadron driver for future cancer therapies based on the induction synchrotron concept is given. In order to realize a slow extraction technique in a fast cycling synchrotron, which allows the energy sweep beam scanning, the zero momentum-dispersion D(s) region and high flat D(s) region are necessary. The present design lattice which meets both requirements. In this study, details of the lattice parameters is introduced and an analytical solution for chromaticity correction are described and discussed.

A massive-ion beam driver for high-energy-density physics and future inertial fusion

Several heavy ion drivers for heavy ion inertial fusion have been proposed in the US and Europe, based on linear induction accelerator technology [1] and existing RF technology [2], respectively, although they have not been realized on a large scale. Developing accelerator technology may provide an alternative efficient, robust, and relatively cheap massive-ion beam driver for future particle beam inertial fusion. Here, we propose an accelerator complex for accelerating giant cluster ions, instead of lead or bismuth ions, toward 120 GeV by using induction acceleration over the entire energy region. The proposed two-way multiplex induction synchrotron that is the main accelerator for the giant cluster ion beam would be equivalent to 10 synchrotrons of the same size for a single beam.

ESCORT: Energy sweep compact rapid cycling hadron therapy

The Energy Sweep Compact Rapid Cycling Hadron driver for future cancer therapies based on the induction synchrotron concept is described. This fast cycling synchrotron that allows the energy sweep beam scanning. Assuming a 1.5 T bending magnet, the ring can deliver heavy ions of 430 MeV/u at 10 Hz. A beam fraction is dropped from the barrier bucket at the desired timing and the increasing negative momentum deviation of this beam fraction becomes enough large for the fraction to fall in the electrostatic septum extraction gap, which is placed at the large D(s) region. The programmed energy sweeping extraction makes spot scanning beam irradiation on a cancer area in depth possible.

Evolution of Induction Synchrotron and Its Applications

Evolution of Induction Synchrotron and Its Applications

Beam-core evolution equation and space-charge limit

The nonlinear beam-core evolution equation approach is proposed as a powerful tool to estimate the acceptable beam current in a given circular accelerator. The approach is justified by the macroparticle simulation over a wide beam current parameter region. Space-charge effects on the beam-core evolution are discussed by Poincaré mapping on the beam-core phase space (σ, dσ/ds). The instability seen in the beam-core evolution is rigorously analyzed as an eigenvalue problem in the coupled linear system derived from the linearized beam-core evolution equations. A threshold current resulting in the instability is given by both the nonlinear beam-core evolution equation approach and the coupled linear system approach. As an example, a fast cycling induction synchrotron is evaluated in which the space-charge effects are significant because it is injector-free.

Design of Compact Accelerator Module of the Induction Synchrotron

Induction synchrotron (IS) has become the focus of improving the intensity of high energy ion beams in recent years. But because of the pulse voltage of the induction accelerating cell cannot adjust quickly, causing the mismatch of the magnetic deflection field and accelerate electric field, there is a serious beam loss problem in IS. The simulation of beams longitude dynamics proves that increasing the number of accelerating cells can effectively reduce the loss. In this paper, a novel compact induction accelerator module is introduced. Compared with the existing induction accelerator module of KEK, the new design can increase the number of accelerating cells to more than five times in the same installation space and improves the voltage top drop of the acceleration pulse significantly.

Application of Permanent Magnets for Particle Extraction from Cyclic Accelerators with Constant Orbit Radius

Closed orbits with almost constant radius in an induction synchrotron with a permanent magnetic field are formed using the method of particle reflection by fields of permanent magnets. In this study we consider the application of such permanent magnets for automatic particle extraction from cyclic accelerators with R = const, B = var. The problem of formation of orbits with almost constant radius in a cyclic accelerator with a permanent leading magnetic field was considered in [1]. In this study we consider the application of such permanent magnets for automatic particle extraction from cyclic accelerators with R = const, B = var.

Direct injection of fully stripped carbon ions into a fast-cycling induction synchrotron and their capture by the barrier bucket

Fully stripped carbon ions generated in a laser-ablation ion source are directly injected into a small-scale induction synchrotron. Carbon-ion beams of ${\mathrm{C}}^{6+}$, ${\mathrm{C}}^{5+}$, and ${\mathrm{C}}^{4+}$ are trapped in the barrier bucket. Beam properties, such as the momentum spread and beam lifetime in the low-energy ring, are measured and discussed in relation to the essential characteristics required in a carbon driver for future carbon therapies.

Induction synchrotron with a constant magnetic field

In this paper the possibility of accelerating charged particles in a “nearly constant” orbit in a timeconstant magnetic field is discussed. The closed trajectories of the accelerated particles are formed by azimuthally set short bending magnet sections, each comprised of two particle-deflecting magnetic dipoles in which the incidence and deflection angles do not depend on the particle energy. The sign-alternating focusing of the beam is carried out by the dipole fields and quadrupole lenses placed between the bending sections. The particles are accelerated by pulses of the electric field of the induction sections. The inductive pulses and the beam pulses are synchronized by a beam-transit time transducer. The stability of the longitudinal oscillations is determined by the shape of the top of the accelerating pulse. The nonresonance acceleration method does not require preaccelerators and boosters.

Compact hadron driver for cancer therapies using continuous energy sweep scanning

A design of a compact hadron driver for future cancer therapies based on the induction synchrotron concept is presented. To realize a slow extraction technique in a fast-cycling synchrotron, which allows energy sweep beam scanning, a zero momentum-dispersion $D(s)$ region and a high flat $D(s)$ region are necessary. The proposed design meets both requirements. The lattice has two-fold symmetry with a circumference of 52.8 m, a 2-m dispersion-free straight section, and a 3-m-long large flat dispersion straight section. Assuming a 1.5-T bending magnet, the ring can deliver heavy ions ($200\text{ }\text{ }\mathrm{MeV}/\mathrm{u}$) at 10 Hz. A beam fraction is dropped from the barrier bucket at the desired timing, and the increasing negative momentum deviation of this beam fraction becomes large enough for the fraction to fall in the electrostatic septum extraction gap, which is placed at the large $D(s)$ region. The programmed energy sweep extraction enables scanning beam irradiation on a cancer site in depth without an energy degrader, avoiding the production of secondary particles and the degradation of emittance. Details of the lattice parameters and computer simulations for slow extraction are discussed. An example extraction scenario is presented. Qualities of the spilled beam such as emittance and momentum spread are discussed, as well as necessary functions and parameters required for the extraction system.

Wideband induction acceleration and its intrinsic nature in the KEK digital accelerator

The wideband induction acceleration method makes it possible to accelerate any ion species directly from the low-energy region of several hundred kiloelectron volts in the KEK induction synchrotron. The wideband acceleration method for heavy ions in the KEK digital accelerator (KEK-DA), which is a fast cycling induction synchrotron, is presented and the experimental results are discussed. A macroparticle simulation is described that well reproduces the longitudinal beam motion of the experiment, which is characterized by a non-uniform bunch motion in the longitudinal phase space. This is caused by as an intrinsic characteristic of the current acceleration system of the KEK-DA.

Induction acceleration of heavy ions in the KEK digital accelerator: Demonstration of a fast-cycling induction synchrotron

A fast-cycling induction synchrotron was demonstrated. Ions with extremely low energies and mass-to-charge ratios ($A/Q$) in the range from 2 to 10 were injected, captured by barrier voltages, and accelerated to the end of the acceleration cycle of 50 ms by flat pulse voltages generated by pulse transformers referred to as induction cells. Induction acceleration in a wide dynamic frequency range of 56 kHz to 1 MHz was also demonstrated. This accelerator is expected as the next generation of a heavy ion driver for cancer therapy, where a large scale injector is not required. A wide variety of ions for ion energy implantation experiments needing novel materials will be delivered from this compact circular accelerator.

Development of a Compact Switching Power Supply for an Induction Synchrotron Utilizing a SiC-JFET

Development of a Compact Switching Power Supply for an Induction Synchrotron Utilizing a SiC-JFET

Einzel lens chopper and behavior of the chopped beam in the KEK digital accelerator

The KEK digital accelerator (KEK-DA), which is a small-scale rapid-cycle induction synchrotron (IS), has commenced operation. A permanent magnet $x$-band electron cyclotron resonance ion source serves as the KEK-DA ion source and delivers various ions. A new Einzel lens beam chopper has been developed to provide the necessary pulse width of a few microseconds. The chopper is implemented by applying a rectangular pulse voltage generated by a solid-state Marx generator to the middle electrode of the Einzel lens. Momentum modulation at the bunch head and tail resulting from chopping in longitudinal direction has been observed. This intrinsic property of the chopped pulse has been clearly observed in a long drift (a free run in the circular ring) in KEK-DA.

A Compact Switching Power Supply Utilizing SiC-JFET for an Induction Synchrotron

Utilizing a high power discrete SiC-JFET developed by KEK, a switching power supply (SPS) that had a circuit topology of H-bridge was designed and constructed to drive the induction acceleration system for the KEK digital accelerator. The SPS was operated with a 38 Ω dummy resistance load and bipolar outputs of 800V and 21A were successfully demonstrated at 1 MHz. Also, the combination test with an actual accelerator cell is being conducted.