A new method of modeling the working mode of the multipurpose isochronous cyclotron

The method of modeling the working mode is based on the selection of currents in concentric trim coils of the multipurpose isochronous cyclotron for the formation of the required magnetic field at a certain level of the main coil current. The traditional method of selecting currents is based on finding the solution for all concentric trim coils simultaneously. As a rule, after setting the calculated working mode, it is necessary to perform control measurement of the magnetic field and repeat the calculation to obtain the desired working mode. The new method of selecting currents is based on finding the solution for each separate concentric trim coil. The concentric trim coils are taken in turn in a specified order. A number of experiments on handling the proton beam in the range of working acceleration radii with an output energy between 45 and 60 MeV, performed using the multipurpose isochronous cyclotron AIC144 at the Institute of Nuclear Physics of the Polish Academy of Sciences in Krakov showed that the new method of obtaining the desired working mode does not require control measurements of magnetic fields, which testifies the high accuracy of the calculation.     

Effect of the magnetic field from the accelerating system on the beam dynamics in the cyclotron

Magnetic components of the HF field in a cyclotron can change the transverse beam size and the phase width of bunches during acceleration. As a consequence, the phase portraits of the beam at the entrance to the electrostatic deflector and thus the efficiency of the extraction system can change. Expressions are obtained for the components of the magnetic field from the HF system in the vicinity of the cyclotron median plane. The effect of this field on the beam parameters during acceleration and at the entrance to the electrostatic deflector is shown by numerical simulation. For the C235 proton cyclotron, the beam parameter variation is as large as 50%.     

Simulation of the required operation modes and analysis of their stability for multipurpose isochronous cyclotrons

A mathematical and computer simulation of the operation modes of multipurpose isochronous cyclotrons is based on a calculation of current values in trim coils correcting the main magnetic field (I _i , i = 1, 2, ..., n) for a certain current level in the main coil (I _mc). This calculation is performed for the given kinetic energy (E _k ) at a certain radius or for the particle orbital frequency (F ₀). The results of this calculation provide a formation with the necessary precision of the required magnetic field in the range from the ion source to the particle extraction system. A number of numerical and physical experiments on calculating the main operation mode of the multipurpose isochronous cyclotron AIC-144 (Institute of Nuclear Physics, Polish Academy of Sciences, Krakow) (p, E _k = 60 MeV, F ₀ = 26.25 MHz) proved the necessity of taking into account the estimate of the stability of the sought solution and the possibility of obtaining accelerated ion beams in the whole range of acceleration radii for small phase losses in the isochronization range of the required magnetic field.     

A Magnetic Transport Middle Eastern Positron Beam

A magnetically guided slow positron beam is being constructed at Qatar University and is currently being optimised for regular operation. This is the first positron beam in the Middle East, as well as being the first Arabic positron beam. Novel features in the design include a purely magnetic in-line deflector, working in the solenoid guiding field, to eliminate un-moderated positrons and block the direct line of sight to the source. The impact of this all-magnetic transport on the Larmor radius and resultant beam characteristics are studied by SIMION simulations for both ideal and real life magnetic field variations. These results are discussed in light of the coupled effect arising from electrostatic beam extraction.     

Numerical simulation of ions acceleration and extraction in cyclotron DC-110

In Flerov’s Laboratory of Nuclear Reactions of JINR in the framework of project “Beta” a cyclotron complex for a wide range of applied research in nanotechnology (track membranes, surface modification, etc.) is created. The complex includes a dedicated heavy-ion cyclotron DC-110, which yields intense beams of accelerated ions Ar, Kr and Xe with a fixed energy of 2.5 MeV/A. The cyclotron is equipped with external injection on the base of ECR ion source, a spiral inflector and the system of ions extraction consisting of an electrostatic deflector and a passive magnetic channel. The results of calculations of the beam dynamics in measured magnetic field from the exit of spiral inflector to correcting magnet located outside the accelerator vacuum chamber are presented. It is shown that the design parameters of ion beams at the entrance of correcting magnet will be obtained using false channel, which is a copy of the passive channel, located on the opposite side of the magnetic system. Extraction efficiency of ions will reach 75%.     

分离扇回旋加速器的等时场在线优化

针对兰州重离子加速器冷却储存环（HIRFL-CSR）的分离扇回旋加速器（SSC）的等时场优化问题,依托HIRFL-CSR的主数据库系统Oracle,设计了系统控制界面,该界面不仅能够读取和给定电源电流值,而且能够实时更新束流相位信息。根据束流相位的实时数据,利用Kb-Kr方法以及Lagrange插值算法建立的等时场,实现了对SSC束流等时场的在线优化。优化后的等时场可以有效控制束流相位的漂移,提高束流品质。     

Positron emission isotope production cyclotron in DLNP JINR (Status Report)

A C10-cyclotron for radioisotope production is under construction at the Dzhelepov Laboratory of Nuclear Problem, Joint Institute for Nuclear Research (DLNP JINR). It is a compact isochronous cyclotron for accelerating H⁻ ions to the energy of about 10 MeV. The magnetic system, vacuum chamber and accelerating system is being built now. Results of the calculation and forming of the cyclotron magnetic field and the study of the beam dynamics from an ion source to an extraction system in calculated magnetic field are presented. The text was submitted by the authors in English.     

RF cavity simulations for superconducting cyclotron C400

Compact superconducting isochronous cyclotron C400 [1] has been designed at IBA (Belgium) in collaboration with the JINR (Dubna). This cyclotron will be the first cyclotron in the world capable of delivering protons, carbon and helium ions for therapeutic use. ¹²C⁶⁺ and ⁴He²⁺ ions will be accelerated to 400 MeV/u energy and extracted by electrostatic deflector, H₂⁺ ions will be accelerated to the energy of 265 MeV/u and extracted by stripping. It is planned to use two normal conducting RF cavities for ion beam acceleration in the cyclotron C400. Computer model of the double gap delta RF cavity with 4 stems was developed in the general-purpose simulation software CST STUDIO SUITE. Necessary resonant frequency and increase of the voltage along the gaps were achieved. Optimization of the RF cavity parameters leads us to the cavity with quality factor about 14000, RF power dissipation is equal to about 50 kW per cavity.     

Nonlinear amplitude osçillations of absolutely unstable electrostatic ion cyclotron waves in an ion beam-plasma system

We have observed experimentally the amplitude oscillations of absolutely unstable electrostatic ion cyclotron waves in an ion beam-plasma system due to nonlinear interaction between the beam ions and electrostatic ion cyclotron waves.     

强流回旋加速器综合试验装置的磁场测量与垫补

强流回旋加速器综合试验装置的主体是一台紧凑型回旋加速器, 加速器主磁铁材料的不均匀性, 磁铁加工和安装的非理想因素将引起中心平面的磁场的非理想分布, 因此有必要对其中心平面的磁场进行测量和垫补. 本文主要讲述该综合试验装置的霍尔感应磁场测量系统的设计和使用;通过磁场测量数据分析进行镶条的再加工, 最终实现对等时性磁场和束流的纵向聚焦的垫补;研究与实践了一种对磁场一次谐波进行垫补的方法, 垫补的结果满足了设计的要求.     

Computer modeling of the acceleration of low-charge krypton ions in the CYTRACK cyclotron

The basic results of numeric simulations of krypton ion motion with decreased charge in the CYTRACK cyclotron are presented. CYTRACK is the world??s first industrial cyclotron dedicated to the production of track membranes. Computer modeling confirms the possibility of Kr ₈₄ ⁺¹¹ ion acceleration in the magnetic field with an increase in the level of the magnetic field by 1.6% on the 6 harmonic of the accelerating system. The beam energy will be sufficient for the exposure of a film with a thickness of 10 ??m.     

Stability of electrostatic ion cyclotron waves in a multi-ion plasma

We have studied the stability of the electrostatic ion cyclotron wave in a plasma consisting of isotropic hydrogen ions (H⁺) and temperature-anisotropic positively (O⁺) and negatively (O⁻) charged oxygen ions, with the electrons drifting parallel to the magnetic field. Analytical expressions have been derived for the frequency and growth/damping rate of ion cyclotron waves around the first harmonic of both hydrogen and oxygen ion gyrofrequencies. We find that the frequencies and growth/damping rates are dependent on the densities and temperatures of all species of ions. A detailed numerical study, for parameters relevant to comet Halley, shows that the growth rate is dependent on the magnitude of the frequency. The ion cyclotron waves are driven by the electron drift parallel to the magnetic field; the temperature anisotropy of the oxygen ions only slightly enhance the growth rates for small values of temperature anisotropies. A simple explanation, in terms of wave exponentiation times, is offered for the absence of electrostatic ion cyclotron waves in the multi-ion plasma of comet Halley.     

Computation of Beam Extraction from TR-24 and dc-140 Cyclotrons

Physics of Particles and Nuclei Letters - Two main cyclotron beam extraction methods using a stripping foil and an electrostatic deflector are considered. Computation results are presented for two...     

The physics design of magnet in 14 MeV cyclotron

The 14 MeV, 400 μA compact cyclotron is under construction at China Institute of Atomic Energy (CIAE). The design of main magnet and the result of beam dynamics in the cyclotron will be described in this paper, including the choice of main parameters of magnet, the method of shimming isochronous field in the compact cyclotron and optimization of the magnetic field in central region. The beam will be accelerated to 14.6 MeV by optimizing the magnet structure.

     

Simulation of beam extraction from C235 cyclotron for proton therapy

The extraction of an accelerated beam from C235 cyclotron (IBA, Belgium) for proton therapy is simulated. The results of optimizing the parameters of the extraction system to increase the beam extraction efficiency are presented. Our theoretical results agree well with the experimental data. A new configuration of electrostatic deflector is proposed based on the numerical results; using this configuration essentially increases the efficiency of the cyclotron extraction system.     

Effect of imperfections of the radial component of a magnetic field on beam dynamics in medical cyclotron C235-V3

This paper presents numerical simulations and experimental results related to the effect of imperfections of the radial component of a magnetic field on the beam dynamics in the medical cyclotron C235-V3 of the Dimitrovgrad Proton Therapy Center. These imperfections in the region of the minimal axial betatron frequency lead to a transformation of coherent motion of the center of gravity of the beam to the incoherent motion of separate particles. The radial component increases the axial size of the beam by a factor of 2 at a radius of 20 cm, which produces additional losses of protons. To reduce undesirable actions of the radial component on the axial motion, the magnetic system in the central region has been optimized using two procedures: the positioning of shim correctors on sectors and selecting a special asymmetric arrangement of the upper and lower central plugs. This led to a twofold reduction in the axial size of the beam and a decrease in proton losses. Eventually, the beam transmission in C235-V3 has been increased to 72% without a limiting aperture diaphragm, which is commonly used in cyclotrons of this type. This makes it possible to reduce the irradiation dose of machine elements and increase the beam current at a deflector entrance of the cyclotron C235-V3 by a factor of 1.5 when compared to a serial C235 cyclotron.     

Numerical Simulation of Autoresonant Ion Acceleration

Computational and analytic studies of the Autoresonant Acceleration proposal for collective ion acceleration are presented. Linear theory is reviewed, the electrostatic well depth is estimated nonlinearly, and an electron beam envelope equation is derived and solved. Two-dimensional numerical simulation results are given. Together, these calcualtions demonstrate unneutralized electron beam equilibrium in a diverging magnetic guide field, the behaviour of large amplitude slow cyclotron waves in the beam, and the acceleration of test ions over short distances in the wave troughs. In addition, the computer simulations point up the need for improved understanding of the linear theory of radially inhomogeneous noneutral beams and for methods of suppressing radial modulation at the diode-waveguide interface.     

A study on the performance of a gyromonotron

A method is presented which allows to calculate the large signal beam efficiency of a gyromonotron working at the s-th harmonic of the cyclotron frequency. The results of this calculation using efficiency optimized parameters are given for different TE_mn distributions and also for a magnetic taper. It is shown that beam efficiencies, which are higher than twice the value at constant electric and magnetic fields are theoretically possible. Also the influence of the beam voltage is considered. For a given beam voltage and a given electric field distribution in the resonator power calculations are performed and it is shown what powerlevels are available for different resonator modes and for different cyclotron harmonics.     

Magnet design and beam dynamics in computed fields for the DC-350 cyclotron

The DC-350 is an isochronous cyclotron designed in the Flerov Laboratory of Nuclear Reaction (FLNR). It is intended for accelerating ions with a mass-to-charge ratio A/Z within an interval of 5–10 and with an energy of 3–12 MeV/u at the extraction radius. These ion beams will be used in nuclear and applied physics experiments. The paper describes the results of a 3D magnet simulation. The cyclotron magnet and IM90 analiziting-bend magnet of the axial injection channel are studied here. The influence of correction coils on the cyclotron magnet is calculated. All magnet fields were calculated by MERMAID 3D code [1]. The text was submitted by the authors in English.     

10 MeV质子等时性回旋加速器的设计研究

给出10MeV质子等时性回旋加速器的等时性磁场设计,中心区的设计以及加速后最终的束流品质,该加速器可作为正电子断层扫描装置的配套设备,用于生产中短寿命放射性同位素等.它沿半径方向只用一套线圈励磁,等时性磁场的建立完全由磁极形状决定.中心区的设计满足了轨道中心化的要求,并给出较大的横向和纵向接受度,以获得足够的束流强度. 经过172圈加速后,最终的束流品质满足要求.