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.     

DC-60 heavy ion cyclotron complex: The first beams and project parameters

The construction of the DC-60 Heavy Ion Cyclotron for the Interdisciplinary Scientific Research Complex (ISRC) in Astana started in early 2004. The cyclotron was manufactured and tested at the Flerov Laboratory of Nuclear Reactions (FLNR) in Dubna. The main units were delivered to Astana and assembled in the ISRC building in the summer of 2006. The cyclotron was turned on in September, 2006. The first heavy ion beams in the whole A/Z and energy ranges were accelerated and extracted in December, 2006. The complex, based on the DC-60 cyclotron, is intended for applied and fundamental research using accelerated heavy ion beams ranging from Carbon to Xenon with energies in the range of 0.34–1.77 MeV/nucleon, as well as for experiments on the channel of low energy ion beams, where the ion extraction voltage supplied by the ECR source reaches 25 kV. The energy variation of the accelerated ions is accomplished by changing the ion charge. The possibility of smoothly tuning the ion energy by ±30% of its nominal value can be seen by changing the cyclotron magnetic field. Within the framework of commissioning the DC-60 cyclotron, a number of experiments were carried out with accelerating charged particle beams in the main points of the working diagram

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.     

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.     

Magnetic system of a superconducting separated-sector cyclotron for hadron therapy

The development of a cyclotron magnetic system based on superconducting sector magnets is discussed. The cyclotron is conceived as a booster accelerator of a source of ¹²С⁶⁺ ions with energy of 400MeV/nucleon for the purposes of hadron therapy. The results of preliminary investigations aimed at developing such a facility have been reported in our previous papers. In this paper, we consider various configurations of the booster’s magnetic system for various field levels. We also analyze the effects of the positions and shapes of superconducting coils on the magnetic field and select the optimum configuration for the cyclotron’s magnetic system.     

Giant magnetoresistance oscillations induced by microwave radiation and a zero-resistance state in a 2D electron system with a moderate mobility

The effect of a microwave field in the frequency range from 54 to 140 GHz on the magnetotransport in a GaAs quantum well with AlAs/GaAs superlattice barriers and with an electron mobility no higher than 10⁶ cm²/V s is investigated. In the given two-dimensional system under the effect of microwave radiation, giant resistance oscillations are observed with their positions in the magnetic field being determined by the ratio of the radiation frequency to the cyclotron frequency. Earlier, such oscillations had only been observed in GaAs/AlGaAs heterostructures with much higher mobilities. When the samples under study are irradiated with a 140-GHz microwave field, the resistance corresponding to the main oscillation minimum, which occurs near the cyclotron resonance, appears to be close to zero. The results of the study suggest that a mobility value lower than 10⁶ cm²/V s does not prevent the formation of zero-resistance states in a magnetic field in a two-dimensional system under the effect of microwave radiation.     

High frequency acceleration system of the DC-280 cyclotron

The radio-frequency (RF) accelerating system designed at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research (FLNR JINR), for the DC-280 cyclotron is described. The cyclotron is intended to increase the capabilities and efficiency of experiments on the synthesis of superheavy elements and investigate their nuclear-physical and chemical properties. The DC-280 isochronous heavyion cyclotron will produce an accelerated beam of ions in the range from neon to uranium. The results of the preliminary and 3D numerical calculations of the main cavity of this system are reported. The preliminary calculations by the Coaxresonator software have allowed the geometry of the main cavity to be chosen. 3D numerical simulation has completely confirmed the correctness of the preliminary calculations. For example, the difference in frequency between the preliminary and 3D numerical calculations is no larger than 1%. The electric-field component maps obtained from the simulations are used to calculate the beam dynamics in the cyclotron.     

C235-V3 cyclotron for a proton therapy center to be installed in the hospital complex of radiation medicine (Dimitrovgrad)

Proton therapy is an effective method of treating oncologic diseases. In Russia, construction of several centers for proton and ion therapy is slated for the years to come. A proton therapy center in Dimitrovgrad will be the first. The Joint Institute for Nuclear Research (Russia) in collaboration with Ion Beam Application (IBA) (Belgium) has designed an C235-V3 medical proton cyclotron for this center. It outperforms previous versions of commercial IBA cyclotrons, which have already been installed in 11 oncologic hospital centers in different countries. Experimental and calculation data for the beam dynamics in the C235-V3 medical cyclotron are presented. Reasons for beam losses during acceleration are considered, the influence of the magnetic field radial component in the midplane of the accelerator and main resonances is studied, and a beam extraction system is designed. In 2011–2012 in Dubna, the cyclotron was mounted, its magnetic field was properly configured, acceleration conditions were optimized, and beam extraction tests were carried out after which it was supplied to Dimitrovgrad. In the C235-V3 cyclotron, an acceleration efficiency of 72% and an extraction efficiency of 62% have been achieved without diaphragming to form a vertical profile of the beam.     

Development of radiation medicine at DLNP, JINR

The Dzhelepov Laboratory of Nuclear Problems’ activity is aimed at developing three directions in radiation medicine: 3D conformal proton therapy, accelerator techniques for proton and carbon treatment of tumors, and new types of detector systems for spectrometric computed tomography (CT) and positron emission tomography (PET). JINR and IBA have developed and constructed the medical proton cyclotron C235-V3. At present, all basic cyclotron systems have been built. We plan to assemble this cyclotron at JINR in 2011 and perform tests with the extracted proton beam in 2012. A superconducting isochronous cyclotron C400 has been designed by the IBA-JINR collaboration. This cyclotron will be used for radiotherapy with proton, helium and carbon ions. The ¹²C⁶⁺ and ⁴He²⁺ ions will be accelerated to an energy of 400 MeV/amu, the protons will be extracted at the energy 265 MeV. The construction of the C400 cyclotron was started in 2010 within the framework of the Archarde project (France). Development of spectrometric CT tomographs may allow one to determine the chemical composition of a substance together with the density, measured using traditional CT. This may advance modern diagnostic methods significantly. JINR develops fundamentally new pixel detector systems for spectrometric CT. The time-of-flight (TOF) system installed in the positron emission tomograph (PET) permits essential reduction in the detector noise from occasional events of different positron annihilations. The micropixel avalanche photodiodes (MAPDs) developed at JINR allow a factor of 1.5 reduction in the resolution time for the PET TOF system and suppression of the noise level as compared to commercial PET. The development of a combined PET/MRI is of considerable medical interest, but it cannot be made with the existing PET tomographs based on detectors of compact photomultipliers due to strong alternating magnetic field of MRI. Change-over to detectors of micropixel avalanche photodiodes permits making a combined PET/MRI.     

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.     

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%.     

正电子发射成像回旋加速器磁铁设计与测试

中国工程物理研究院流体物理研究所目前正在建造一台医用11 MeV回旋加速器,该加速器磁铁采用小气隙、深谷结构以提供更高的平均磁场和更强的聚焦能力。为实现510-4的测量精度,自行研发了一套磁场点测装置,该装置可实现二维极坐标下的精确测量。经过多次磁场垫补,束流的相位偏移控制在9,一次谐波幅值控制在0.001 T以内,满足了磁铁的设计需求。在束流调试过程中,成功实现了质子束的引出,表明回旋加速器磁铁建造成功。此外,还对磁铁研制过程中出现的磁场缺陷及磁测误差进行了讨论。     

分离扇回旋加速器的接受度及效率

以9.7MeV/u的238U36+,5.62MeV/u的70Zn10+为典型离子,分析并模拟了分离扇回旋加速器(SSC)的注入、加速和引出,得到了SSC在理论等时场下横向和纵向的接受度。为了研究SSC在实际情况下的接受度,在实测场的基础上采用Kr-Kb方法以及Lagrange插值方法建立了与实际比较符合的等时场,计算了该等时场下SSC横向和纵向的接受度,发现了导致SSC实际接受度和传输效率低的主要原因在于注入系统中的MSI3元件和引出系统中的MSE3元件设计存在缺陷。模拟结果显示,通过改变MSI3和MSE3的曲率或者垫铁改变元件内部的场分布可以改善SSC的实际接受度和传输效率。     

Formation of Annihilation-Cyclotron Lines in Strong Magnetic Fields Near Neutron Stars

We study cyclotron and polarization spectral features in magnetized vacuum at frequencies near the one-photon annihilation resonance in a subcritical magnetic field. On the basis of this study, we propose a new method for determination of the neutron-star magnetic field. Using the dipole-field model, we show that detection of the annihilation line in absorption and an additional line in emission at MeV energies is evidence of the existence of a magnetic field (2.8-3.6)· 10¹²G on the surface of a neutron star.     

正电子发射成像回旋加速器磁铁设计与测试

中国工程物理研究院流体物理研究所目前正在建造一台医用11 MeV回旋加速器,该加速器磁铁采用小气隙、深谷结构以提供更高的平均磁场和更强的聚焦能力。为实现510-4的测量精度,自行研发了一套磁场点测装置,该装置可实现二维极坐标下的精确测量。经过多次磁场垫补,束流的相位偏移控制在9,一次谐波幅值控制在0.001 T以内,满足了磁铁的设计需求。在束流调试过程中,成功实现了质子束的引出,表明回旋加速器磁铁建造成功。此外,还对磁铁研制过程中出现的磁场缺陷及磁测误差进行了讨论。     

CyclSyntWin software application for synthesis and optimization of cyclotron magnetic structures and magnets

The Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research in Dubna is developing and creating new cyclotrons. In the initial stage of development, it is necessary to analyze several variants of their magnetic structures in a relatively short time. Examined herein is the Laboratory’s developed CyclSyntWin software application which allows preliminary analysis of several variants and determination of the main physical and geometrical parameters of the cyclotron magnetic structure and magnet itself. The data obtained thereby can subsequently be used in 3D software applications, which substantially accelerates the final synthesis of the cyclotron magnetic structure and magnet. The CyclSyntWin application can be used to synthesize and optimize the magnetic structures of straight and spiral sector cyclotrons, close to azimuthally symmetric. The ratio of their air gaps in the valley and in the region of the sectors shouldn’t exceed 25 and the average magnetic field shouldn’t be more than 2 T.     

Correction of vertical displacement of extracted beam during commissioning tests of the DC-110 cyclotron

The specialized DC-110 heavy ion cyclotron has been developed and created at the Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research for the BETA research and production complex in Dubna (Russia), which allows producing intense accelerated Ar, Kr, and Xe ion beams with a fixed energy of 2.5 MeV/nucleon. Commissioning works on the cyclotron complex, during which the design parameters were obtained, were carried out at the end of 2012. During commissioning of the accelerator, vertical displacement of the beam was found at the final acceleration radii and during its extraction. It is shown that the main cause of this displacement was the occurrence of a radial component of the magnetic field in the median plane of the magnet caused by asymmetry of the magnetic circuit. Vertical beam displacement was corrected by creating asymmetry of the current in the main electromagnet winding of the DC-110 cyclotron.     

Beam dynamics in a C253-V3 cyclotron for proton therapy

In recent years, oncologic diseases have become a severe issue in developed countries. Proton therapy is viewed as one of the most efficient methods of treating oncologic diseases. The results of computing the beam dynamics in a C235 medical cyclotron intended for proton therapy are presented. The cyclotron was modified by teams of researchers at the Joint Institute for Nuclear Research and Ion Beam Application (IBA Group, Belgium). Possible reasons for losses in the beam under acceleration are considered, and the influence of the magnetic field radial component in the median plane of the accelerator is studied. The results of analysis and upgrading of the beam extraction system are presented. Based on analytical data, the design of the commercial C235 cyclotron is considerably modified. A new version of the C235-V3 cyclotron will be placed in commission at the Dimitrovgrad center of radiation medicine.     

Analytical dependences used for preliminary synthesis and optimization of cyclotron magnetic structures

Analytical dependences used for preliminary synthesis and determination of the main physical and geometrical parameters of cyclotron magnetic structures and magnet itself are examined herein. A method of obtaining, describing, and graphically representing these two-dimensional analytical dependences are also examined. Their use allows preliminary synthesis and optimization of near-azimuthically magnetic structures of cyclotrons with straight and spiral sectors. The ratio of their air gaps in the valley and in the region of the sectors shouldn’t exceed 25 and the average magnetic field shouldn’t be more than 2 T. The use of some of these became the basis in developing the CyclSyntWin software application, which has been used already for several years at the Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research in Dubna for preliminary synthesis and optimization of the main parameters of cyclotron magnetic structures and magnets.     

Measuring magnetic fields in plasmas by means of light scattering

The theory of light scattering in plasmas containing a magnetic field yields the special case of modulated scattering spectra. The modulation frequency is governed by the field in the plasma and is equal to the electron cyclotron frequency. In this investigation magnetic fields in a plasma were determined by a laser scattering experiment. The experimental data were: electron densityn _e=10¹⁶cm^?3, electron temperatureT _e=3.2 eV, scattering angle θ=90 °, scattering parameter α=0.6, and a maximum field in the plasma of 125 kG. The spectrum measured at the maximum magnetic field was modulated with 3.6 × 10¹¹ Hz. In scattering experiments with a field reduced by about 20% the observed modulation frequency was 2.8 × 10¹¹ Hz. A thermal spectrum with a smooth profile was found when no field was present in the plasma. Applying the theory of cyclotron modulated spectra one obtains from the scattering experiment magnetic fields of 128, 100, and 0 kG. Within the experimental accuracy these values agree well with the fields determined by means of magnetic probes. Other possible interpretations of the measured deviations from thermal spectra (modulation with the plasma frequency or additional cold electron components in the plasma) are discussed, but they afford no explanation. This experiment has domonstrated that magnetic fields in plasmas can be measured locally and almost without disturbance by means of light scattering.