Beam Sweep Research Articles

Beam-Aware Dormant and Scheduling Mechanism for 5G Millimeter Wave Cellular Systems

In this paper, an analytical model for millimeter wave (mmWave) cellular systems that characterizes user equipment (UE) power-saving constraint is studied. On the basis of the realistic radio propagation, we model the channel quality by curve fitting and create a Markov chain based channel model. The reference signal for channel measurement in conventional cellular systems can be transmitted to the whole cell at a time, but the beam sweeping is needed in mmWave systems in order to overcome the high path loss of high-frequency electromagnetic wave. This constraint further affects the timing of channel measurement, channel quality feedback, and power consumption. A novel beam-aware dormant mechanism for power saving in mmWave systems is proposed. UEs may enter the dormant mode for power-saving when the base station (BS) is not transmitting on their beams. Therefore, the BS is suggested to consider the time gap between channel measurement and data transmission when scheduling UEs. Beam-aware scheduling framework is proposed and integrated with the beam-aware dormant mechanism. It is shown that the policy to schedule a UE after its channel measurement outperforms the one to schedule every time slot. The simulation results and mathematical expression both demonstrate that the beam-aware media access control (MAC) framework improves throughput under power constraint.

A Dual-Plane Beam-Sweeping Millimeter-Wave Antenna Using Reconfigurable Frequency Selective Surfaces

In this letter, a dual-plane beam-sweeping dielectric resonator antenna (DRA) using cantilever enabled frequency selective surfaces (FSSs) is presented. The proposed antenna consists of a conventional cylindrical DRA and a hexagonally arranged active FSS operating at 30 GHz frequency band. Initially, the reconfigurable FSS using cantilever beams is designed and analyzed. Furthermore, a prototype of the proposed antenna with FSS is designed, fabricated, and measured. The beam sweeping is obtained in both azimuth and elevation planes of the antenna. The whole azimuth plane is covered by the switched beams in six steps of an angle of 60 $^\circ$ . In the elevation plane, two steps of angles are obtained at 90 $^\circ$ and 30 $^\circ$ . The measured antenna gain of 8.1 dB is obtained.

Magnetic Sweep of a Relativistic Electron Beam into a Rectangular Raster

The design of a magnetic sweep unit that provides a combination of two linear (with respect to time) sweeps of the relativistic electron beam and the radiation field of the accelerated electron beam swept into a rectangular raster and scattered by an air layer when approaching the target have been considered. Expressions for the distribution of absorbed dose over the whole exposed surface have been obtained taking into account the real distribution of beam current density. The considered expressions for the distribution function of absorbed dose can be used as a foundation for the calculations of magnetic sweep units for radiochemical equipment with high-current industrial electron accelerators, in particular, with escape of a focused beam of accelerated electrons into the atmosphere.

Statistical MIMO beam codebook design for mmWave transmissions

We propose a novel method for constructing beam codebooks, i.e., a set of beamforming weights, to be used for beam sweeping and data transmission in mmWave massive MIMO channels. The proposed beam codebooks are designed according to the statistical distribution of the channel’s angles of departure in order to efficiently sectorize the angular space covered by the beams. In particular, the cumulative distribution function of these angles is used to sectorize the angular beam space in order to design the beams. We first present a general closed-form construction of beam codebooks for an arbitrary distribution and then tailor the results to the Laplace distribution. We consider both narrow and broad beams. The resulting beams are a priori better adapted to the channel statistics and thus enhance the spectral efficiency of the transmission as compared to the state-of-the-art beam designs. Finally, we investigate the performance of the design and also present some analytical bounds quantifying the inherent loss of a directional beamforming compared to the optimal beamforming with perfect channel state information at the transmitter.

Narrow-aperture electron beam in the forevacuum pressure range as a tool for dimensional processing of silica glass

The paper gives overview of the results of using narrow-aperture electron beam generated by a forevacuum plasma electron source as a tool for treatment of electrically non-conductive materials, such as technical glass. Effectiveness of electron beam treatment of non-conductive materials is caused by almost complete neutralization of target charge on the treated surface. Charge neutralization occurs due to ion flow from beam plasma generated while transporting the beam through forevacuum pressure area. The study demonstrates the possibility to control depth and form of milling by changing modes of electron beam treatment. Combined use of electron beam and automated system for beam deflection and sweep makes possible to perform dimensional processing, particularly cutting and milling with complex trajectory. Milling rates were experimentally found depending on treatment time and mode. The suggested method of silica glass treatment represents an alternative for traditional treatment methods.

Angular Sampling, Test Signal, and Near-Field Aspects for Over-The-Air Total Radiated Power Assessment in Anechoic Chambers

5th-generation mobile network systems operating in millimeter-wave bands will employ base stations with integrated active antenna systems. Such systems are capable of beam-tracking using narrow beams obtained from antenna arrays. Regulatory limits for unwanted radio frequency and Over-The-Air methods for TRP of unwanted emissions are needed. The method investigated here uses power density measurements on a spherical surface in an anechoic chamber. Two major challenges with such a method are: need for a large number of angular points and search for a worst case antenna configuration per frequency for electrically large devices at high frequencies. These challenges are addressed by investigating sparse sampling and use of beam sweeping. Finally, it is investigated how and in which spatial regions near-field tangential electric field measurements can be used to assess TRP.

March

March Rebecca Pelky (bio) When feathers frosted cinder blocks and boathouse glass,we leaned on cracking ice and watched our breath becomeAurora, exhaled our ancestors into constellations. We spoke of wispy things—how earth and ox and air becameour words, how we lost ki and káhsh and wapunak, how evensilence dims the dark in storms, but more, a distant moan, a boat to open sea, the long eye of a red beam sweeping,telling us it's time to quit the rim, time to turn in, it's timefor roads laid out like spokes to lead us home. [End Page 82] Rebecca Pelky Rebecca Pelky is Ridgel Fellow in the PhD program at the University of Missouri. She also holds an MFA from Northern Michigan University. She is an enrolled member of the Brothertown Indian Nation of Wisconsin. Her work has appeared in The Chattahoochee Review, Booth, and River Styx, among other journals. Copyright © 2018 University of Wisconsin Board of Regents

Laser line scan underwater imaging by complementary metal–oxide–semiconductor camera

This work employs the complementary metal–oxide–semiconductor (CMOS) camera to acquire images in a scanning manner for laser line scan (LLS) underwater imaging to alleviate backscatter impact of seawater. Two operating features of the CMOS camera, namely the region of interest (ROI) and rolling shutter, can be utilized to perform image scan without the difficulty of translating the receiver above the target as the traditional LLS imaging systems have. By the dynamically reconfigurable ROI of an industrial CMOS camera, we evenly divided the image into five subareas along the pixel rows and then scanned them by changing the ROI region automatically under the synchronous illumination by the fun beams of the lasers. Another scanning method was explored by the rolling shutter operation of the CMOS camera. The fun beam lasers were turned on/off to illuminate the narrow zones on the target in a good correspondence to the exposure lines during the rolling procedure of the camera’s electronic shutter. The frame synchronization between the image scan and the laser beam sweep may be achieved by either the strobe lighting output pulse or the external triggering pulse of the industrial camera. Comparison between the scanning and nonscanning images shows that contrast of the underwater image can be improved by our LLS imaging techniques, with higher stability and feasibility than the mechanically controlled scanning method.

Codebook-Based Hybrid Precoding for Millimeter Wave Multiuser Systems

In millimeter wave (mmWave) systems, antenna architecture limitations make it difficult to apply conventional fully digital precoding techniques but call for low cost analog radio-frequency (RF) and digital baseband hybrid precoding methods. This paper investigates joint RF-baseband hybrid precoding for the downlink of multiuser multi-antenna mmWave systems with a limited number of RF chains. Two performance measures, maximizing the spectral efficiency and the energy efficiency of the system, are considered. We propose a codebook based RF precoding design and obtain the channel state information via a beam sweep procedure. Via the codebook based design, the original system is transformed into a virtual multiuser downlink system with the RF chain constraint. Consequently, we are able to simplify the complicated hybrid precoding optimization problems to joint codeword selection and precoder design (JWSPD) problems. Then, we propose efficient methods to address the JWSPD problems and jointly optimize the RF and baseband precoders under the two performance measures. Finally, extensive numerical results are provided to validate the effectiveness of the proposed hybrid precoders.

SRF cavity alignment detection method using beam-induced HOM with curved beam orbit

We have developed a method to obtain mechanical centers of nine cell superconducting radio frequency (SRF) cavities from localized dipole modes, that is one of the higher order modes (HOM) induced by low-energy beams. It is to be noted that low-energy beams, which are used as alignment probes, are easy to bend in fringe fields of accelerator cavities. The estimation of the beam passing orbit is important because only information about the beam positions measured by beam position monitors outside the cavities is available. In this case, the alignment information about the cavities can be obtained by optimizing the parameters of the acceleration components over the beam orbit simulation to consistently represent the position of the beam position monitors measured at every beam sweep. We discuss details of the orbit estimation method, and estimate the mechanical center of the localized modes through experiments performed at the STF accelerator. The mechanical center is determined as x,y=(0.44±0.56mm,−1.95±0.40mm). We also discuss the error and the applicable range of this method.

Beam Sweeping for Long-Pulse Operation of an Ion Source in Neutral Beam Injectors

Long-pulse operation has been initially and successfully demonstrated during a 100-s stable beam extraction in the neutral beam test stand (NBTS) system of the Korea Atomic Energy Research Institute (KAERI) for the positive ion source (IS) of the JT-60SA neutral beam injector. The NBTS system was constructed at KAERI to develop 300-s deuterium beam extractions of 100 kV/50 A as an auxiliary heating system of the Korea Superconducting Tokamak Advanced Research (KSTAR). The IS of the JT-60SA neutral beam injector is composed of a plasma generator and a set of tetrode accelerators. The beamline components include an optical multichannel analyzer duct, a neutralizer, a bending magnet (BM), a calorimeter, and a vacuum pump system. The beam power deposition of the IS and the beamline components along the NBTS have been measured by water flow calorimetry (WFC), and a total of 99.7% of the extracted beam power (Vacc∙Iacc) was counted for a hydrogen beam of 82 kV/25 A (2.05 MW) during 100-s beam extraction. To reduce the localized heat load on the calorimeter plate, a method of small-angle deflection for the ion beam particles was applied using a small alternate current of 8 A, 0.5 Hz for the BM coil.

Initial Beam Association in Millimeter Wave Cellular Systems: Analysis and Design Insights

Enabling the high data rates of millimeter wave (mmWave) cellular systems requires deploying large antenna arrays at both the basestations and mobile users. Prior work on coverage and rate of mmWave cellular networks focused on the case when basestations and mobile beamforming vectors are predesigned for maximum beamforming gains. Designing beamforming/combining vectors, though, requires training, which may impact both the SINR coverage and rate of mmWave systems. This paper evaluates mmWave cellular network performance while accounting for the beam training/association overhead. First, a model for the initial beam association is developed based on beam sweeping and downlink control pilot reuse. To incorporate the impact of beam training, a new metric, called the effective reliable rate, is defined and adopted. Using stochastic geometry, the effective rate of mmWave cellular networks is derived for two special cases: near-orthogonal pilots and full pilot reuse. Analytical and simulation results provide insights into the answers of two important questions. First, what is the impact of beam association on mmWave network performance? Then, should orthogonal or reused pilots be employed? The results show that unless the employed beams are very wide, initial beam training with full pilot reuse is nearly as good as perfect beam alignment.

Hydrogen diffusion in steels under electron bombardment

We report on the results of measurement of the coefficients of hydrogen diffusion through metal membranes in the course of their simultaneous hydrogen saturation and bombardment with electrons (energy 30 keV, current density from 3 to 30 µA/cm2) both in a broad and in a narrow beam. It is found that the time of hydrogen discharge from the membrane is determined by the parameters of the electron beam, its periodicity and duration, and also depends on the structure of the phase state of the metal membrane. It is shown that the diffusion coefficient increases when a narrow electron beam in the scanning regime is used. Analysis of the hydrogen yield as a function of time is carried out on a mass spectrometer connected to a vacuum chamber containing an electron gun, a beam sweep oscillator, and an electrolytic cell. The hydrogen diffusion coefficients under the action of a scanning electron beam are 15 times larger than under the same conditions without irradiation.

Compact hadron driver for cancer therapies using continuous energy sweep scanning

A design of a compact hadron driver for future cancer therapies based on the induction synchrotron concept is presented. To realize a slow extraction technique in a fast-cycling synchrotron, which allows energy sweep beam scanning, a zero momentum-dispersion $D(s)$ region and a high flat $D(s)$ region are necessary. The proposed design meets both requirements. The lattice has two-fold symmetry with a circumference of 52.8 m, a 2-m dispersion-free straight section, and a 3-m-long large flat dispersion straight section. Assuming a 1.5-T bending magnet, the ring can deliver heavy ions ($200\text{ }\text{ }\mathrm{MeV}/\mathrm{u}$) at 10 Hz. A beam fraction is dropped from the barrier bucket at the desired timing, and the increasing negative momentum deviation of this beam fraction becomes large enough for the fraction to fall in the electrostatic septum extraction gap, which is placed at the large $D(s)$ region. The programmed energy sweep extraction enables scanning beam irradiation on a cancer site in depth without an energy degrader, avoiding the production of secondary particles and the degradation of emittance. Details of the lattice parameters and computer simulations for slow extraction are discussed. An example extraction scenario is presented. Qualities of the spilled beam such as emittance and momentum spread are discussed, as well as necessary functions and parameters required for the extraction system.

Quantitative assessment of damage during MCET: a parametric study in a rodent model.

BackgroundMyocardial cavitation-enabled therapy (MCET) has been proposed as a means to achieve minimally invasive myocardial reduction using ultrasound to produce scattered microlesions by cavitating contrast agent microbubbles.MethodsRats were treated using burst mode focused ultrasound at 1.5 MHz center frequency and varying envelope and pressure amplitudes. Evans blue staining indicated lethal cardiomyocytic injury. A previously developed quantitative scheme, evaluating the histologic treatment results, provides an insightful analysis for MCET treatment parameters. Such include ultrasound exposure amplitude and pulse modulation, contrast agent dose, and infusion rate.ResultsThe quantitative method overcomes the limitation of visual scoring and works for a large dynamic range of treatment impact. Macrolesions are generated as an accumulation of probability driven microlesion formations. Macrolesions grow radially with radii from 0.1 to 1.6 mm as the ultrasound exposure amplitude (peak negative) increases from 2 to 4 MPa. To shorten treatment time, a swept beam was investigated and found to generate an acceptable macrolesion volume of about 40 μL for a single beam position.ConclusionsUltrasound parameters and administration of microbubbles directly influence lesion characteristics such as microlesion density and macrolesion dimension. For lesion generation planning, control of MCET is crucial, especially when targeting larger pre-clinical models.

Periodic shedding of vortex dipoles from a moving penetrable obstacle in a Bose-Einstein condensate

We investigate vortex shedding from a moving penetrable obstacle in a highly oblate Bose-Einstein condensate. The penetrable obstacle is formed by a repulsive Gaussian laser beam that has the potential barrier height lower than the chemical potential of the condensate. The moving obstacle periodically generates vortex dipoles and the vortex shedding frequency ${f}_{v}$ linearly increases with the obstacle velocity $v$ as ${f}_{v}=a(v\ensuremath{-}{v}_{c})$, where ${v}_{c}$ is a critical velocity. Based on the periodic shedding behavior, we demonstrate deterministic generation of a single vortex dipole by applying a short linear sweep of a laser beam. This method will allow further controlled vortex experiments such as dipole-dipole collisions.

Transversally-flat dose field formation and primary radiobiological exercises with the carbon beam extracted from the U-70 synchrotron

We describe a technique for attaining extended transversally-flat paraxial dose fields with the intermediateenergy carbon beam slowly extracted at the magnetic-field flat-bottom from the IHEP U-70 synchrotron. To this end, a fixed-radius circular beam sweep with the aid of a compact electromechanical wobbler with rotating permanent dipole magnets is applied. A technique for tuning the beam transfer line and the irradiation facility proper at the interim radiobiological workbench with an external fixed target is substantiated. A brief description of its engineering implementation is presented. Results of the successful experimental verification of the technique in question with a carbon nuclear beam from the U-70 machine are reported, in particular, results of the primary radiobiological exercises accomplished in cooperation with the scientists at the MRRC of the Russian Ministry of Healthcare.

Superluminal Spot Pair Events in Astronomical Settings: Sweeping Beams

AbstractSweeping beams of light can cast spots moving with superluminal speeds across scattering surfaces. Such faster-than-light speeds are well-known phenomena that do not violate special relativity. It is shown here that under certain circumstances, superluminal spot pair creation and annihilation events can occur that provide unique information to observers. These spot pair events are not particle pair events—they are the sudden creation or annihilation of a pair of relatively illuminated spots on a scattering surface. Real spot pair illumination events occur unambiguously on the scattering surface when spot speeds diverge, while virtual spot pair events are observer dependent and perceived only when real spot radial speeds cross the speed of light. Specifically, a virtual spot pair creation event will be observed when a real spot’s speed toward the observer drops below c, while a virtual spot pair annihilation event will be observed when a real spot’s radial speed away from the observer rises above c. Superluminal spot pair events might be found angularly, photometrically, or polarimetrically, and might carry useful geometry or distance information. Two example scenarios are briefly considered. The first is a beam swept across a scattering spherical object, exemplified by spots of light moving across Earth’s Moon and pulsar companions. The second is a beam swept across a scattering planar wall or linear filament, exemplified by spots of light moving across variable nebulae including Hubble’s Variable Nebula. In local cases where the sweeping beam can be controlled and repeated, a three-dimensional map of a target object can be constructed. Used tomographically, this imaging technique is fundamentally different from lens photography, radar, and conventional lidar.

TH‐A‐18C‐06: A Scatter Elimination Scheme for Cone Beam CT Using An Oscillating Narrow Beam

Purpose:While cone beam CT (CBCT) has been widely used in image guided radiation therapy, its low image quality, primarily caused by scattered x‐rays, hinders advanced clinical applications, e.g., CBCT based on‐line adaptive re‐planning. We propose in this abstract a new scheme called oscillating narrow beam CBCT (ONB‐CBCT) to eliminate scatter signals.Methods:ONB‐CBCT consists of two major components. 1) Oscillating narrow beam (ONB) scan and 2) partitioned flat panel containing multiple individual detector strips and their own readouts. Both the beam oscillation and detector partition are along the superior‐inferior (SI) direction. During data acquisition, at a given projection, the narrow beam sweep through the detector region, and different portions of the detector acquires projection data in synchrony with the narrow beam. ONB can be generated by a rotating slit collimator design with conventional tube with single focal spot, or by directly using a new source with multiple focal spots. A proof‐of‐principle study via Monte Carlo simulation is conducted to demonstrate the feasibility of ONB‐CBCT.Results:As the beam becomes narrower, more and more scatter signals are eliminated. For the case with a bowtie filter and using 15 ONBs, the maximum and the average intensity error due to scatter are below 20 and 10 HU, respectively.Conclusion:ONB yields a narrowed exposure field at each snapshot and hence an inherently negligible scatter effect. Meanwhile, the individualized detector units guarantee high frame rate detection and hence a same large volume coverage as that in conventional CBCT. In summary, ONB‐CBCT is a promising design to achieve high‐quality CBCT imaging.This study is supported in part by NIH (1R01CA154747‐01).

First tests of the ion irradiation and implantation beamline at the CMAM

The implantation and irradiation beamline of the Tandem ion accelerator of the Centro de Micro Análisis de Materiales (CMAM), in Madrid, has been recently completed with a beam sweep and monitoring system, and a cryostat/furnace. These new implementations convert the beamline into a versatile tool to implant ions, between H and Au2, in different materials with precise control of the sample temperature, which may be varied between −180°C and 600°C. The size of the swept area on target may be as large as 10 ×10cm2. The implantation chamber also allows carrying out in situ or/and on line analyses during the irradiations by means of advanced optical measurements, as well as ion beam analyses (IBA). These advancements can be employed in novel applications such as the fabrication of optical waveguides and irradiation tests of structural and functional materials for future fusion reactors. The results of beam tests and first experiments are shown.