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.     

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。     

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。     

Stability of equilibrium orbits in isochronous ultrarelativistic cyclotron II

The paper investigates the stability of equilibrium orbits of charged particles in one variant of the ultrarelativistic cyclotron. The Bogoljubov-Krylov method of averaging is used to show that one of the pairs of principal equilibrium orbits, which were found in the first part of the paper, is stable while the second is unstable. The stability limit is identical with the limit of the existence of equilibrium orbits. The dependence of the frequencies of betatron oscillations on the field parameters is shown in the stability diagrams. Brief mention is made of the magnet of the variant of an ultrarelativistic cyclotron with axially scalloped equilibrium orbit.     

Stability of equilibrium orbits in isochronous ultrarelativistic cyclotron I

The paper deals with an investigation into the equilibrium orbits of charged particles in one variant of the isochronous ultrarelativistic cyclotron, i.e. accelerator with time independent, axially increasing magnetic field and strong focusing for accelerating charged particles at constant orbital time. The author finds phenomena well known from the theory of oscillations of non-linear mechanical systems (in a certain region of the parameters of a magnetic field there exist substantially two equilibrium orbits, while in another region none exist), which have no analogy in other accelerators. A variant of the ultrarelativistic cyclotron with axially scalloped equilibrium orbit is proposed.     

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.     

Optimization of spin-valve parameters for magnetic bead trapping and manipulation

Magneto-optic Kerr effect (MOKE) and magnetoresistance (MR) measurements were used to measure the switching characteristics of spin-valve (SV) arrays currently being developed to trap and release superparamagnetic beads within a fluid medium. The effect of SV size on switching observed by MOKE showed that a 1 μm×8 μm SV element was found to have optimal switching characteristics. MR measurements on a single 1 μm×8 μm SV switched with either an external applied magnetic field or a local magnetic field generated by an integrated write wire (current density ranging from 10⁶ to 10⁷ A/cm²) confirmed the MOKE findings. The 1 μm×8 μm SV low field switching was observed to be +8 and −2 mT with two stable states at zero field; the high field switching was observed to be −18 mT. The low switching fields and the large magnetic moment of the SV trap along with our observation of minimal magnetostatic effects for dense arrays are necessary design characteristics for high-force, “switchable-magnet,” microfluidic bead trap applications.     

Designing magnetic systems for advanced compact isochronous cyclotrons by means of mathematical simulation

Specific features in designing magnetic systems for compact isochronous cyclotrons using the methods of mathematical simulation are described. A method based on the mathematical synthesis of cyclotron electromagnets is suggested that has made it possible to design, fabricate, adjust, and put in production a number of accelerators with common design patterns. Developed systems of movable shims allow magnetic field reconfiguration to provide acceleration of different sorts of ions.     

Time-of-flight system for the multipurpose detector (MPD)

A conceptual design for a multipurpose detector (MPD) [1] is proposed for the study of hot and dense barony matter in collisions of heavy ions over the atomic mass range A = 1–197 at center-of-mass energies of up to 11 GeV (for Au⁷⁹⁺). The MPD experiment is scheduled to be performed at a future JINR accelerator complex facility for heavy ions, the Nuclotron-based Ion Collider Facility (NICA), which is designed to reach the required parameters with an average luminosity of L = 10²⁹ cm⁻² s⁻¹. Identification of charged hadrons (PIDs) at intermediate momenta (0.1–2 GeV/c) is achieved via time-of-flight (TOF) measurements. As a base element of the TOF detector, we consider a 10 gap MRPC with a strip or pad readout. Results from an MRCP prototype test are presented.     

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%.     

Optimization of the reflecting system parameters in the mass-reflectron

The optimal selection of mass-reflectron parameters is discussed on the basis of solutions of the equations of motion of the ions. The influence of the grid misalignment and the potential instability upon the reflectron mass-resolution is considered. The mesh parameters of the reflectron grids were found to impose the main limitation on the value of the ultimate mass-resolution. The defocusing of the ion packets at small deflection angles is shown to be negligible.     

Optimization of the magnetic field in the analyzing magnet of the axial injection beam line of the cyclotron DC-280

The optimization of the field distribution of the analyzing magnet installed in the axial injection beam line of the cyclotron DC-280 is carried out. This optimization is done on the basis of a three-dimensional calculation of the magnet field. The optimum value of the basic geometrical characteristics of the magnet influencing the form of the field distribution is found.     

HIMM回旋加速器控制系统中连锁保护功能设计与实现

在HIMM医用重离子加速器（Heavy Ion Medical Machine）中,回旋加速器的连锁保护功能针对离子源、高频、真空、电源、冷却水等子系统的连锁要求,设计实现了设备+PLC+软件三层结构的连锁系统,并保证连锁功能在系统断电、线缆连接故障、数据传输异常等情况下的正常工作。连锁系统可实现硬连锁毫秒级、软连锁次秒级别的反应速度。整体功能在回旋调试过程中得到验证,保障了整个加速器的顺利供束。     

Flat-top system of the DC-280 cyclotron

The flat-top cavity of the radio-frequency accelerating system designed at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, for the DC-280 cyclotron is described. The cyclotron is intended for increasing the capabilities and efficiency of experiments on the synthesis of super-heavy elements and an investigation of their nuclear physical and chemical properties. The DC-280 isochronous heavy-ion cyclotron will produce accelerated beam of ions in the range from neon to uranium. The parameters, design, and results of the experimental and 3D computer modeling of the flat-top cavity of the RF accelerating system of the DC-280 cyclotron are reported.     

Optimization of the parameters of a virtual-cathode oscillator with an inhomogeneous magnetic field

A two-dimensional numerical model is used to study the generation of powerful microwave radiation in a vircator with an inhomogeneous magnetic field applied to focus a beam. The characteristics of the external inhomogeneous magnetic field are found to strongly affect the vircator generation characteristics. Mathematical optimization is used to search for the optimum parameters of the magnetic periodic focusing system of the oscillator in order to achieve the maximum power of the output microwave radiation. The dependences of the output vircator power on the characteristics of the external inhomogeneous magnetic field are studied near the optimum control parameters. The physical processes that occur in optimized virtual cathode oscillators are investigated.     

Mathematical modelling of the ion motion in the isochronous magnetic and radio frequency electric fields

The results of mathematical modelling of the ion motion show the possibility of the phase focusation of the ions with utilization of the radial force. This force is realized with a radial component of electric field. The beam monochromatization is analyzed simultaneously.     

Design of a magnetic system for an MCC 30/15 cyclotron and field formation with movable shims

To accelerate ions with different charge-to-mass ratios, isochronous dependences of the magnetic field that differ both in the mean value of the field and in its spatial distribution are needed. An approach to configuring such a field in isochronous cyclotrons using magnetic shims is suggested. Field maps obtained experimentally and via computer simulation to accelerate negative hydrogen and deuteron ions in an MCC 30/15 cyclotron intended for medical purposes are presented. The cyclotron was designed and fabricated in 2007–2009 in NIIEFA (St. Petersburg, Russia) and delivered to the University of Jyväskylä (Finland).     

Proposed design of axial injection system for the DC-280 cyclotron

The design of the high-voltage axial injection system for the DC-280 cyclotron that is being constructed at the Flerov Laboratory of Nuclear Reactions (FLNR) at the Joint Institute for Nuclear Research (JINR) is presented. The injection system will make it possible to efficiently inject ions of elements ranging from helium to uranium with the ratios of their atomic mass to the charge varying from 4 to 7.5.     

光谱位相干涉仪参数的优化选取

模拟研究了光谱位相相干直接电场重构法的三个主要参数：时间延迟τ、频率剪切量Ω和展宽器色散φ之间的相互关系.研究结果表明：不同的待测脉冲，具有不同的最佳时间延迟τ；而τ的改变所引起的Ω的改变又限制了τ的选取范围；在此情况下只有适当调整φ才能在τ的较宽的范围内保证测量精度. 关键词： 光谱位相相干直接电场重构法 飞秒脉冲测量 光谱相干