Ion-Optical System of an Ion Source with Energy Focusing in the Formed Beam

Technical Physics - Ways to reduce ion beam intensity losses in a mass spectrometric ion source, which are caused by chromatic aberration of its immersion ion-optical system, are considered. These...     

Receiver Calorimeter of Fast Atom Beam Injector in Megawatt Range

Physics of Atomic Nuclei - The receiver calorimeter (RC) is one of the main elements of the beam path of an atomic beam injector with ballistic focusing. A water-cooled RC developed for an injector...     

Focusing of an Atomic Beam for the Efficient Loading of an Atom Chip

JETP Letters - A method has been proposed to increase the rate of loading of atoms in a U-magneto-optical trap near an atom chip. The method is based on the focusing of a slow atomic beam into the...     

Concept of Plasma Heating and Current Drive Neutral Beam System for Fusion Neutron Source DEMO-FNS

Steady-state operation of a fusion neutron source (FNS) requires plasma heating and current drive by means of additional power delivered by neutral beams. Six neutral beam injectors (NBI) will provide the DEMO-FNS machine with additional heating power up to 30 MW, with neutral particle energy of 500 keV. NBI systems developed for ITER can serve as the prototype for DEMO-FNS, as both systems have similar ion source current, with accelerated beam power in ITER NBI (1MeV) being twice as large as in DEMOFNS. The paper describes the NBI system with account of its integration into DEMO-FNS tokamak complex.     

Atom Lithography with a Chromium Atomic Beam

Direct write atom lithography is a new technique in which resonant light is used to pattern an atomic beam and the nanostructures are formed when the atoms deposit on the substrate. We design an experiment setup to fabricate chromium nanolines by depositing an atomic beam of ^52Cr through an off-resonant laser standing wave with the wavelength of 425.55 nm onto a silicon substrate. The resulting nanolines exhibit a period of 215±3 nm with height of I nm.     

亚稳态氦原子束在激光驻波场中聚焦的衍射像差研究

用量子力学方法研究了一维激光驻波场对亚稳态氮原子束聚焦的衍射像差。建立了半经典模型，该模型在一定条件下和已有模型一致，提出了直接计算时间演化算符的数值方法，这种计算方法速度较快，收敛性较好，数值模拟结果表明在一定的激光强度和光束半径等参量下，亚稳态氮原子束被聚焦，焦点的半峰全宽为54nm，对比度16：1，焦长、焦深与入射原子束的速度有关，从而与动能有关，焦点的有限宽度主要是来自衍射效应的影响。     

Diffractive Focusing of a Gaussian Beam

The problem of diffraction of a spherical wave with Gaussian amplitude distribution on two infinitesimally thin and ideally reflecting screens with apertures on an optical axis is solved within the framework of the quasi-optical approximation. It is shown theoretically and experimentally that when a Gaussian beam illuminates such a type of bicomponent diffraction system with small Fresnel numbers in a near zone of the second screen, the effect of diffractive multifocal focusing of radiation is observed. In this case, the diffraction picture from the second screen in the focal planes represents the circular nonlocal bands of the Fresnel zones with a bright narrow peak at the center, whose intensity can exceed by six times the value of the incident wave intensity. The energy efficiency of diffractive focusing of Gaussian beams by the bicomponent diffraction system can be as high as 70%. The diffractive method proposed allows the focusing of wide-aperture beams without using classical refraction elements such as lenses and prisms, and it is applicable to both low-intensity and high-power radiation.     

Numerical Modeling of Ion-Optical Systems for Extraction of a Beam of Negative Hydrogen Ions and Its Acceleration and Matching with a Radio-Frequency Quadrupole Accelerator

A source of negative hydrogen ions is constructed at the Institute for High Energy Physics in order to raise the intensity of the U-70 accelerator complex using multiturn charge-exchange injection. The 3D ion-optical IBSimu simulation package was used to model and optimize the system for extraction of an ion beam from plasma, its acceleration to 100 keV, and matching with a radio-frequency quadrupole (RFQ) accelerator. The system of extraction of an ion beam with a current of 50 mA and electron-flow suppression was modeled. The magnetic transport channels with two solenoids and six quadrupole lenses were compared. The end goals of analysis of the matching channel were to obtain the needed Twiss parameters and to minimize the emittance growth at the RFQ input.     

The PLM Plasma Device for Tests of Tungsten with Powerful Stationary Heat Plasma Loads

The PLM plasma device for plasma testing of refractory metals and materials of a fusion reactor (like the fusion neutron source and DEMO) within the framework of the domestic fusion program and the ITER project was constructed at the National Research University Moscow Power Engineering Institute in 2017. The device is a linear trap with a multicusp magnetic confinement of plasma. At the facility, tests of tungsten and experiments are being carried out aimed at creating a technology for producing a highly porous surface structure of refractory metals such as tungsten and molybdenum, including those with a fuzzy surface structure with the size of elements of the structure up to 50 nm.     

Interaction of a Relativistic Electron Beam with a Plasma

The dispersion relation for the interaction of a relativistic electron beam in a thermal plasma, in the absence of an external magnetic field, is studied. It is shown that there are two distinct beam-plasma branches present, and that one of them couples to the electromagnetic eigenmode of the beam-plasma system with a magnetic field and a Poynting flux associated with it. It is also shown that these branches can couple together.     

IH型漂移管直线加速器的束流动力学研究（英文）

为了提高兰州重离子加速器冷却储存环（HIRFL-CSR）的运行效率、改善加速器输出束流品质,并实现几个加速装置分时供束,提高整个重离子加速装置的利用率,特为（HIRFL-CSR）增建一台新的注入器--CSRLINAC。在108.48 MHz的RFQ之后的CSR-LINAC主加速段,主要由一台108.48 MHz和两台216.96 MHz的IH型漂移管直线加速器组成,用于加速荷质比为1/8.5~1/3之间的重离子,其最大的束流流强为3 mA,并将粒子从0.3 MeV/u加速到3.71 MeV/u。运用KONUS动力学原理,在满足设计指标的情况下,首先利用TraceWin程序进行中能束线MEBT设计,后针对高频腔体设计和束流匹配的基本参数的系列讨论,特别是对CSR-LINAC的中能束流匹配线、参数选择和IH型KONUS结构的漂移管直线加速器进行设计模拟优化。最终得出,在保证腔体设计指标和95.3%的传输效率的情况下,该紧凑型直线加速结构经过三个腔体的加速后,束流的纵向归一化均方根发射度增长仅有25%;同时发现,当流强达到3 mA时,存在空间电荷效应,导致其纵向相宽增长约25%,最大横向包络也存在16.5%的涨落。In order to improve the operation efficiency of the Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou (HIRFL-CSR), a heavy ion linac (linear accelerator) was proposed and designed as a new injector for HIRFL-CSR. Following the 108.48 MHz Radio-Frequency Quadrupole (RFQ), three tanks in total with Interdigital H-mode drift tube linac (IH-DTL) structure are installed to boost the beam energy from 0.3 to 3.71 MeV/u, and the beam current of ions with charge-to-mass ratio from 1/8.5 to 1/3 can reach to 3 mA. The first tank operatesat the same frequency as the RFQ, and the rest two operate at 216.96 MHz. The “Combined Zero-Degree Synchronous Particle Structure” (KONUS) beam dynamics was used in the beam dynamics design. The overview of the physics design on the main accelerating components, including RF design and beam dynamics design are introduced in this paper. The optimized structure design, fabrication status and simulation results are presented in this contribution. It shows that under the condition of assurance of 95.3% transmission efficiency, the normalized rms emittance is about 25%. When the beam current is up to 3 mA, owing to the space charge effect, the increase of longitudinal phase spread and transverse envelope are about 25% and 16.3%, respectively.     

Particle-in-Cell Simulation of the Focusing Properties of High Energy Electron Beam in Plasma Ion Channel

The focusing properties of high energy electron beam in ion channel is investigated in the paper. The collisions of electrons with the neutral gas and the ionization resulted are considered to study the formation of ion channels with PIC method. The effects of various parameters on the beam focusing are analyzed.     

Interaction of a Plasma Beam with a Transverse Magnetic Barrier

The interaction of an energetic He plasma beam with a quasi step-like transverse magnetic barrier is reported. When the rate of flow of momentum in the incident beam is less than the pressure of the magnetic field, a collisionless electrostatic shock is observed to form in front of the barrier as a result of the drastic compression of the plasma. The initially cold plasma is substantially thermalized by the shock and the electron density is increased by a factor of four. In the opposite limit the plasma penetrates the barrier in a flute-like manner.     

用于冷原子制备的激光扩束准直器的研制

针对现有的冷原子实验用的多数保偏光纤输入型扩束准直器不能对输入激光束的偏振进行精确调节的缺陷,提出了一种全长度为135mm,输出圆形光斑有效直径为20mm的紧凑型偏振可调激光扩束准直器.该扩束准直器中的偏振棱镜和波片偏振轴均可独立调节,能对单模保偏光纤输入光束的偏振态进行精确调节和保持.所研制的激光扩束准直器在三维磁光阱冷原子实验中制备出了满足冷原子干涉实验要求的冷原子团,冷原子团原子数为5×108,温度约为10μK,并获得了最大上抛高度为1.156m的原子喷泉飞行时间信号.     

Transport Models for Plasma Heating with Second Harmonic of Electron-Cyclotron Frequency

Physics of Atomic Nuclei - The optical thickness of plasma is often insufficient to absorb completely electromagnetic waves when heated at the second harmonic of the electron-cyclotron frequency....     

金刚石探测器用于C-ADS注入器Ⅱ束损探测的模拟研究

加速器驱动次临界系统C-ADS 注入器Ⅱ采用强流超导质子直线加速器,设计流强达到10 mA。强流质子束产生的束流损失有可能损伤超导腔,需要专用的束流损失监测系统进行监测,束流损失探测器(BLM) 需要在高能量沉积导致超导腔失超之前提供警报。通过MCNPX 模拟计算10 MeV 质子在半波谐振腔(HWR)不同位置损失产生的辐射场,比较选取超导腔管道进出口处4 个位置为推荐束损探测器放置的位置,结合HWR腔结构和束损探测器选择的影响因素,计算了次级辐射在金刚石探测器中的能量沉积以及1° ~ 5°不同质子入射角度对探测的影响。结果表明,根据不同位置处探测器的能量沉积关系可以推断出束损点;不同入射角度不会影响生成粒子的能量分布,只轻微影响生成粒子的数目。The Chinese Accelerator Driven Subcritical System (C-ADS) injector II consists of super-conduction accelerating section which is half wave resonator (HWR), the designed beam intensity is 10 mA. To avoid the damage to the resonator due to proton beam loss, special Beam Loss Monitor (BLM) system is essential. BLM system could provide alarm signal when high energy deposition occurs which may cause the resonator quenching. Radiation field of 10 MeV proton lost at different point of the HWR are simulated with MCNPX, BLM could be set at proper positions based on the simulation. Considering the structure of HWR and the BLM detector selecting influence factor, radiation energy deposition in the diamond detector are simulated with MCNPX when the proton incidence angle change from 1°  5°, Possible beam loss point can be deduced from the relationship of energy deposition in detectors at different locations. The results indicate that energy spectra of secondary particles are independent with incidence angle; the number of secondary particles may be influenced slightly.     

Estimation of the Parameters of a Fusion Neutron Source Based on Deuterium Plasma

Physics of Atomic Nuclei - Sources of fusion neutrons with an energy of about 10 MeV can be a driver in hybrid fusion–fission reactor. They can be used for the disposal of radioactive wastes...     

Low Frequency Rf Heating with a Helical Coupler in a Hot Electron Plasma

A magnetic mirror (mirror ratio 2.38:1) containing ECRH generated hydrogen plasma, with a density of 5 x 1010 cm-3 with cold electron temperature of 11 eV, was used to study propagation of an artificially launched wave varying as ej(?t + m? - kz) at approximately the ion cyclotron frequency. The wave was transmitted between two similar internally placed helically wound antennas separated by 11 wavelengths. The coupling between them was enhanced by as much as 50 times in the presence of plasma. The m = 1 left-handed component was cut off when ? > ?ci. Electron temperatures could be increased by more than 2 times with the m = 1 mode, presumably due to ion heating. Little pump-out was observed.