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- 2019
- polycrystalline ferrite-garnet
- magnetoplasmonic crystals
- magnetooptical effects
- deposition
- ion-beam methods
- sputtering
- plasmon resonance
- Physics
- Moscow Technological University
- Moscow State University
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The design and implementation of the beam diagnostics control system for HIMM
摘要： The Heavy Ion Medical Machine (HIMM) is a compact synchrotron based facility built by the Institute of Modern Physics (IMP) in China. This facility delivers carbon ion beams with kinetic energies up to 400 MeV/u for clinical applications. The beam diagnostics system for HIMM is based on 18 different types of monitors and is used to measure all relevant beam parameters from the ion source to the irradiation therapy terminals which are critical for the commissioning of the accelerator as well as during the regular operation to ensure high up-time of the machine. The control system for all the monitors is designed, developed and implemented globally based on a 3-tier architecture with the aim to achieve a clear separation between front-end devices and their controllers. This paper presents the architecture, the design principle and the implementation of this control system. The beam parameters measured based on the detectors′ motion control and data acquisition control system are analyzed in detail. Furthermore, this beam diagnostics control system (BDCS) will be transplanted to the next heavy ion medical machine in Lanzhou city on account of the successful application in Wuwei city, the precise beam parameters measurement, and long term operation with high stability and reliability.
关键词： Beam diagnostics,Control system,HIMM,LabVIEW
更新于2025-09-04 15:30:14
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Tunable Goos–H?nchen and Imbert–Fedorov shifts
摘要： The optical beam shift is a spatial displacement of an optical beam in geometrical optics that particularly occurs when a laser beam reflects from an interface. In this paper, the dependence of the Goos–H?nchen (GH) and Imbert–Fedorov (IF) shifts from the interface of quartz and garnet on the external direct current voltage (EDCV) are investigated by a Thorlabs BP209-IR slit beam profiler. The optical properties of the circularly polarized and linearly polarized laser beams are measured using a Thorlabs PAX 5710IR3 polarimeters. The results show that the change trend of the GH and IF shifts are the same, whereas the initial and terminal voltages are different. The maximum value of the GH and IF shifts are 20.9 μm and 33.4 μm when the EDCVs are at about 3.2 V and 2.0 V, respectively.
关键词： Direct current,Optical beam shift,Polarization
更新于2025-09-04 15:30:14
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Effects of anisotropic oceanic turbulence on the propagation of the OAM mode of a partially coherent modified Bessel correlated vortex beam
摘要： We have studied the impacts of anisotropic turbulence on the orbital angular momentum (OAM) mode of a partially coherent modified Bessel correlated vortex beam propagation in an oceanic channel. In the weak turbulence paraxial channel, a new model of the probability density of OAM modes has been established. Effects of specific parameters of the oceanic turbulence on it have been studied, it is shown that there is an optimizing receiving aperture diameter in the specific interval of the ratio of temperature and salinity (cid:2) , which can reduce the effect of (cid:2) on the normalized energy weight of OAM modes and the reception of fluctuation signal. The effect of oceanic turbulence with higher anisotropy on the OAM signal is weaker than the turbulence possessing lower anisotropy. We can choose the mode carrying lower OAM quantum number to transfer information more efficiently, and we can utilize the OAM mode with large energy level difference between modes and so on to reduce mode interference and enhance the information capacity of optical communication links.
关键词： optical communication,partially coherent modified Bessel correlated vortex beam,propagation,OAM mode,anisotropic oceanic turbulence
更新于2025-09-04 15:30:14
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Mg induced compositional change in InGaN alloys
摘要： Tunnel junctions are indispensable elements of multi-junction solar cells. The fabrication of InGaN tunnel junctions requires the growth of degenerately doped n- and p-type layers. While highly doped n-type InGaN films have been demonstrated, the growth of degenerately p-doped InGaN films and the fabrication of high indium fraction InGaN tunnel junctions is still to be demonstrated. We present an investigation of the effect of Mg doping on the InGaN crystal properties over a large range of Mg fluxes and InN mole fractions in the range from 30% to 40%, using multiple characterization techniques. InGaN thin films were grown on GaN/sapphire templates and doped with Mg using plasma assisted molecular beam epitaxy (PAMBE). We have found that the Mg concentration in the film increases linearly with the Mg beam equivalent pressure (BEP) at first, followed by a saturation at ~4x1021 cm-3 similar to the Mg doping behavior reported for GaN. The growth rate of the alloy changes by more than 50% with the changes in the surface availability of Mg. These effects can be explained through the saturation of the atomic sites available for incorporation in the case of Mg concentration saturation and by the passivation of the free nitrogen radicals in the case of the growth rate variation. The incorporation of In and Ga depends on the flux ratio (ΦIn + ΦGa) /(ΦMg) at the growth surface and it is shown that the decrease of this ratio below a threshold of ~2000 causes the almost complete loss of In and the formation of a new quaternary wide band gap semiconductor alloy (InGaMg)N.
关键词： In incorporation,(InGaMg)N alloy,Plasma-assisted molecular beam epitaxy,Tunnel junction,Mg-doped P-type InGaN,InGaN
更新于2025-09-04 15:30:14
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[IEEE 2018 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC) - Xuzhou (2018.7.21-2018.7.24)] 2018 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC) - Study of Propagation of Airy Array Vortex Beams in Turbulent Atmosphere
摘要： A circular phased-locked Airy beam array carrying orbital angular momentum (OAM) propagating through turbulent atmosphere is investigated in detail. The results testify that the OAM modes generated by the array are closely associated with the number of beamlets, requiring the number of beamlets at least twice more than the values of the OAM signal precisely. Furthermore, through multiple-phase-screen simulations, it is shown that the anti-jamming performance of an Airy beam array is significantly enhanced.
关键词： Atmospheric optics,Atmospheric propagation,Airy array vortex beam
更新于2025-09-04 15:30:14
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The Effect of Antenna Mutual Coupling on MIMO Radar System Performance
摘要： Multiple-input multiple-output (MIMO) radar systems use orthogonal signaling to enable combined transmit and receive beamforming through signal processing on the received signals. Because of the combined role of transmit and receive arrays in this processing for monostatic MIMO radar, mutual coupling present in these arrays impacts the beamforming in a unique way. This paper therefore presents a mathematical model of a MIMO radar with coupled antennas and appropriate radio frequency circuitry. Application of the model to evaluate radar detection of a single target demonstrates that coupling can result in target detection angles that are in error by as much as 12? and increase beamformer response side lobe levels by as much as 8 dB. The results also show that a simple matching network can improve detection performance, particularly when array mutual coupling is high.
关键词： Radar antennas,Beam steering,MIMO systems,Mutual coupling
更新于2025-09-04 15:30:14
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A micro-scale plasma spectrometer for space and plasma edge applications (invited)
摘要： A plasma spectrometer design based on advances in lithography and microchip stacking technologies is described. A series of curved plate energy analyzers, with an integrated collimator, is etched into a silicon wafer. Tests of spectrometer elements, the energy analyzer and collimator, were performed with a 5 keV electron beam. The measured collimator transmission and energy selectivity were in good agreement with design targets. A single wafer element could be used as a plasma processing or fusion first wall diagnostic.
关键词： electron beam,microchip stacking,silicon wafer,plasma processing,fusion first wall diagnostic,lithography,plasma spectrometer,collimator,energy analyzer
更新于2025-09-04 15:30:14