Transverse field focused system

DOEpatents

Anderson, Oscar A.

1986-01-01

A transverse field focused (TFF) system for transport or acceleration of an intense sheet beam of negative ions in which a serial arrangement of a plurality of pairs of concentric cylindrical-arc electrodes is provided. Acceleration of the sheet beam can be achieved by progressively increasing the mean electrode voltage of successive electrode pairs. Because the beam is curved by the electrodes, the system can be designed to transport the beam through a maze passage which is baffled to prevent line of sight therethrough. Edge containment of the beam can be achieved by shaping the side edges of the electrodes to produce an electric force vector directed inwardly from the electrode edges.

Accurate expansion of cylindrical paraxial waves for its straightforward implementation in electromagnetic scattering

NASA Astrophysics Data System (ADS)

Naserpour, Mahin; Zapata-Rodríguez, Carlos J.

2018-01-01

The evaluation of vector wave fields can be accurately performed by means of diffraction integrals, differential equations and also series expansions. In this paper, a Bessel series expansion which basis relies on the exact solution of the Helmholtz equation in cylindrical coordinates is theoretically developed for the straightforward yet accurate description of low-numerical-aperture focal waves. The validity of this approach is confirmed by explicit application to Gaussian beams and apertured focused fields in the paraxial regime. Finally we discuss how our procedure can be favorably implemented in scattering problems.

Direction-of-arrival estimation for a uniform circular acoustic vector-sensor array mounted around a cylindrical baffle

NASA Astrophysics Data System (ADS)

Yang, DeSen; Zhu, ZhongRui

2012-12-01

This work investigates the direction-of-arrival (DOA) estimation for a uniform circular acoustic Vector-Sensor Array (UCAVSA) mounted around a cylindrical baffle. The total pressure field and the total particle velocity field near the surface of the cylindrical baffle are analyzed theoretically by applying the method of spatial Fourier transform. Then the so-called modal vector-sensor array signal processing algorithm, which is based on the decomposed wavefield representations, for the UCAVSA mounted around the cylindrical baffle is proposed. Simulation and experimental results show that the UCAVSA mounted around the cylindrical baffle has distinct advantages over the same manifold of traditional uniform circular pressure-sensor array (UCPSA). It is pointed out that the acoustic Vector-Sensor (AVS) could be used under the condition of the cylindrical baffle and that the UCAVSA mounted around the cylindrical baffle could also combine the anti-noise performance of the AVS with spatial resolution performance of array system by means of modal vector-sensor array signal processing algorithms.

Displacement Vector Measurement Using 2D Modulation by Virtual Hyperbolic Beam Forming

NASA Astrophysics Data System (ADS)

Kondo, Kengo; Yamakawa, Makoto; Shiina, Tsuyoshi

For the purpose of diagnosing ischemic heart disease by detection of malfunction area and cancer tumor by detection of hard area, 3-D tissue motion must be correctly evaluated. So far various methods of measuring multidimensional displacement have been developed. Most of present techniques are restricted to one-dimensional measurement of tissue displacement such as myocardial stain-rate imaging. Although lateral modulation method enables us to attain high-accuracy measurement of lateral displacement as well as axial direction by generating lateral oscillating RF signals, the method causes distorted RF far from center of aperture. As a result, the method is not suited to sector scan which is used for myocardial examination. We propose a method to solve the problem by using 2-D modulation with the virtual hyperbolic beam forming and detection of 2-D displacement vector. The feasibilities of the proposed method were evaluated by numerically simulating the left ventricle short-axis imaging of cylindrical myocardial model. The volume strain image obtained by the proposed method clearly depicted the hard infarction area where conventional multi-beam Doppler imaging could not.

Review on structured optical field generated from array beams

NASA Astrophysics Data System (ADS)

Hou, Tianyue; Zhou, Pu; Ma, Yanxing; Zhi, Dong

2018-03-01

Structured optical field (SOF), which includes vortex beams, non-diffraction beams, cylindrical vector beams and so on, has been under intensive investigation theoretically and experimentally in recent years. Generally, current research focus on the extraordinary properties (non-diffraction propagation, helical wavefront, rotation of electrical field, et al), which can be widely applied in micro-particle manipulation, super-resolution imaging, free-space communication and so on. There are mainly two technical routes, that is, inner-cavity and outer-cavity (spatial light modulators, diffractive phase holograms, q-plates). To date, most of the SOFs generated from both technical routes involves with single monolithic beam. As a novel technical route, SOF based on array beams has the advantage in more flexible freedom degree and power scaling potential. In this paper, research achievements in SOF generation based on array beams are arranged and discussed in detail. Moreover, experiment of generating exotic beam by array beams is introduced, which illustrates that SOF generated from array beams is theoretically valid and experimentally feasible. SOF generated from array beams is also beneficial for capacity increasing and data receiving for free-space optical communication systems at long distance.

Azimuthally and radially excited charge transfer plasmon and Fano lineshapes in conductive sublayer-mediated nanoassemblies.

PubMed

Ahmadivand, Arash; Gerislioglu, Burak; Pala, Nezih

2017-11-01

Here, the plasmon responses of both symmetric and antisymmetric oligomers on a conductive substrate under linear, azimuthal, and radial polarization excitations are analyzed numerically. By observing charge transfer plasmons under cylindrical vector beam (CVB) illumination for what we believe is the first time, we show that our studies open new horizons to induce significant charge transfer plasmons and antisymmetric Fano resonance lineshapes in metallic substrate-mediated plasmonic nanoclusters under both azimuthal and radial excitation as CVBs.

All-fiber radially/azimuthally polarized lasers based on mode coupling of tapered fibers.

PubMed

Mao, Dong; He, Zhiwen; Lu, Hua; Li, Mingkun; Zhang, Wending; Cui, Xiaoqi; Jiang, Biqiang; Zhao, Jianlin

2018-04-01

We demonstrate a mode converter with an insertion loss of 0.36 dB based on mode coupling of tapered single-mode and two-mode fibers, and realize all-fiber flexible cylindrical vector lasers at 1550 nm. Attributing to the continuous distribution of a tangential electric field at taper boundaries, the laser is switchable between the radially and azimuthally polarized states by adjusting the input polarization. In the temporal domain, the operation is controllable among continuous-wave, Q-switched, and mode-locked statuses by changing the saturable absorber or pump strength. The duration of Q-switched radially/azimuthally polarized laser spans from 10.4/10.8 to 6/6.4 μs at the pump range of 38 to 58 mW, while that of the mode-locked pulse varies from 39.2/31.9 to 5.6/5.2 ps by controlling the laser bandwidth. The proposed laser combines the features of a cylindrical vector beam, a fiber laser, and an ultrafast pulse, providing a special and cost-effective source for practical applications.

Conversion of the high-mode solitons in strongly nonlocal nonlinear media

NASA Astrophysics Data System (ADS)

Zhang, Xiaping

2017-01-01

The conversion of high-mode solitons propagating in Strongly Nonlocal Nonlinear Media (SNNM) in three coordinate systems, namely, the elliptic coordinate system, the rectangular coordinate system and the cylindrical coordinate system, based on the Snyder-Mitchell Model that describes the paraxial beam propagating in SNNM, is discussed. Through constituting the trial solution with modulating the Gaussian beam by Ince polynomials, the closed-solution of Gaussian beams in elliptic coordinate is accessed. The Ince-Gaussian (IG) beams constitute the exact and continuous transition modes between Hermite-Gaussian beams and Laguerre-Gaussian (LG) beams, which is controlled by the elliptic parameter. The conditions of conversion in the three types of solitons are given in relation to the Gouy phase invariability in stable propagation. The profiles of the IG breather at a different propagating distance are numerically obtained, and the conversions of a few IG solitons are illustrated. The difference between the IG soliton and the corresponding LG soliton is remarkable from the Poynting vector and phase plots at their profiles along the propagating axis.

Achromatic vector vortex beams from a glass cone

PubMed Central

Radwell, N.; Hawley, R. D.; Götte, J. B.; Franke-Arnold, S.

2016-01-01

The reflection of light is governed by the laws first described by Augustin-Jean Fresnel: on internal reflection, light acquires a phase shift, which depends on its polarization direction with respect to the plane of incidence. For a conical reflector, the cylindrical symmetry is echoed in an angular variation of this phase shift, allowing us to create light modes with phase and polarization singularities. Here we observe the phase and polarization profiles of light that is back reflected from a solid glass cone and, in the case of circular input light, discover that not only does the beam contain orbital angular momentum but can trivially be converted to a radially polarized beam. Importantly, the Fresnel coefficients are reasonably stable across the visible spectrum, which we demonstrate by measuring white light polarization profiles. This discovery provides a highly cost-effective technique for the generation of broadband orbital angular momentum and radially polarized beams. PMID:26861191

Achromatic vector vortex beams from a glass cone

NASA Astrophysics Data System (ADS)

Radwell, N.; Hawley, R. D.; Götte, J. B.; Franke-Arnold, S.

2016-02-01

The reflection of light is governed by the laws first described by Augustin-Jean Fresnel: on internal reflection, light acquires a phase shift, which depends on its polarization direction with respect to the plane of incidence. For a conical reflector, the cylindrical symmetry is echoed in an angular variation of this phase shift, allowing us to create light modes with phase and polarization singularities. Here we observe the phase and polarization profiles of light that is back reflected from a solid glass cone and, in the case of circular input light, discover that not only does the beam contain orbital angular momentum but can trivially be converted to a radially polarized beam. Importantly, the Fresnel coefficients are reasonably stable across the visible spectrum, which we demonstrate by measuring white light polarization profiles. This discovery provides a highly cost-effective technique for the generation of broadband orbital angular momentum and radially polarized beams.

Control of polarization rotation in nonlinear propagation of fully structured light

NASA Astrophysics Data System (ADS)

Gibson, Christopher J.; Bevington, Patrick; Oppo, Gian-Luca; Yao, Alison M.

2018-03-01

Knowing and controlling the spatial polarization distribution of a beam is of importance in applications such as optical tweezing, imaging, material processing, and communications. Here we show how the polarization distribution is affected by both linear and nonlinear (self-focusing) propagation. We derive an analytical expression for the polarization rotation of fully structured light (FSL) beams during linear propagation and show that the observed rotation is due entirely to the difference in Gouy phase between the two eigenmodes comprising the FSL beams, in excellent agreement with numerical simulations. We also explore the effect of cross-phase modulation due to a self-focusing (Kerr) nonlinearity and show that polarization rotation can be controlled by changing the eigenmodes of the superposition, and physical parameters such as the beam size, the amount of Kerr nonlinearity, and the input power. Finally, we show that by biasing cylindrical vector beams to have elliptical polarization, we can vary the polarization state from radial through spiral to azimuthal using nonlinear propagation.

Elliptic-symmetry vector optical fields.

PubMed

Pan, Yue; Li, Yongnan; Li, Si-Min; Ren, Zhi-Cheng; Kong, Ling-Jun; Tu, Chenghou; Wang, Hui-Tian

2014-08-11

We present in principle and demonstrate experimentally a new kind of vector fields: elliptic-symmetry vector optical fields. This is a significant development in vector fields, as this breaks the cylindrical symmetry and enriches the family of vector fields. Due to the presence of an additional degrees of freedom, which is the interval between the foci in the elliptic coordinate system, the elliptic-symmetry vector fields are more flexible than the cylindrical vector fields for controlling the spatial structure of polarization and for engineering the focusing fields. The elliptic-symmetry vector fields can find many specific applications from optical trapping to optical machining and so on.

Generation of a cylindrically symmetric, polarized laser beam with narrow linewidth and fine tunability

NASA Astrophysics Data System (ADS)

Hirayama, Toru; Kozawa, Yuichi; Nakamura, Takahiro; Sato, Shunichi

2006-12-01

We demonstrated a generation of cylindrically symmetric, polarized laser beams with narrow linewidth and fine tunability. Since an LP11 mode beam in an optical fiber is a superposition of an HE21 (hybrid) mode beam and a TE01 or TM01 mode beam, firstly, a higher order transverse (TEM01 or TEM10) mode laser beam with narrow linewidth and fine tunability was generated from an external cavity diode laser (ECDL) in conjunction with a phase adjustment plate. Then the beam generated was passed in a two mode optical fiber. A doughnut shaped laser beam with the cylindrically symmetric polarization (a radially or azimuthally polarized beam) was obtained by properly adding stress-induced birefringence in the optical fiber.

Enhanced optical limiting effects in a double-decker bis(phthalocyaninato) rare earth complex using radially polarized beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Jia-Lu; Gu, Bing, E-mail: gubing@seu.edu.cn; Liu, Dahui

2014-10-27

Optical limiting (OL) effects can be enhanced by exploiting various limiting mechanisms and by designing nonlinear optical materials. In this work, we present the large enhancement of OL effects by manipulating the polarization distribution of the light field. Theoretically, we develop the Z-scan and nonlinear transmission theories on a two-photon absorber under the excitation of cylindrical vector beams. It is shown that both the sensitivity of Z-scan technique and the OL effect using radially polarized beams have the large enhancement compared with that using linearly polarized beams (LPBs). Experimentally, we investigate the nonlinear absorption properties of a double-decker Pr[Pc(OC{sub 8}H{submore » 17}){sub 8}]{sub 2} rare earth complex by performing Z-scan measurements with femtosecond-pulsed radially polarized beams at 800 nm wavelength. The observed two-photon absorption process, which originates from strong intramolecular π–π interaction, is exploited for OL application. The results demonstrate the large enhancement of OL effects using radially polarized beams instead of LPBs.« less

Generation of dark hollow beam by focusing a sine-Gaussian beam using a cylindrical lens and a focusing lens

NASA Astrophysics Data System (ADS)

Tang, Huiqin; Zhu, Kaicheng

2013-12-01

Based on the generalized Huygens-Fresnel diffraction integral, a closed-form propagation equation related to sine-Gaussian beams through a cylindrical lens and a focusing lens is derived and illustrated with numerical methods. It is found that a sine-Gaussian beam through such a system may be converted into a dark hollow beam (DHB) with topological charge index one and its bright enclosure is approximately an elongated ellipse with very high ellipticity. Moreover, the parameter values at which the DHBs have perfect intensity patterns are designed. The optimal relative orientation between the dislocation line of the input sine-Gaussian beam and the axial orientation of the cylindrical lens is specified. And the ellipticity of the elliptical DHBs is mainly defined by the focal length of the cylindrical lens and the Fresnel number of the optical system.

SU-E-T-598: The Effects of Arm Speed for Quality Assurance and Commissioning Measurements in Rectangular and Cylindrical Scanners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bakhtiari, M; Schmitt, J

2014-06-01

Purpose: Cylindrical and rectangular scanning water tanks are examined with different scanning speeds to investigate the TG-106 criteria and the errors induced in the measurements. Methods: Beam profiles were measured in a depth of R50 for a low-energy electron beam (6 MeV) using rectangular and cylindrical tanks. The speeds of the measurements (arm movement) were varied in different profile measurements. Each profile was measured with a certain speed to obtain the average and standard deviation as a parameter for investigating the reproducibility and errors. Results: At arm speeds of ∼0.8 mm/s the errors were as large as 2% and 1%more » with rectangular and cylindrical tanks, respectively. The errors for electron beams and for photon beams in other depths were within the TG-106 criteria of 1% for both tank shapes. Conclusion: The measurements of low-energy electron beams in a depth of R50, as an extreme case scenario, are sensitive to the speed of the measurement arms for both rectangular and cylindrical tanks. The measurements in other depths, for electron beams and photon beams, with arm speeds of less than 1 cm/s are within the TG-106 criteria. An arm speed of 5 mm/s appeared to be optimal for fast and accurate measurements for both cylindrical and rectangular tanks.« less

Visualization of the energy flow for guided forward and backward waves in and around a fluid-loaded elastic cylindrical shell via the Poynting vector field

NASA Astrophysics Data System (ADS)

Dean, Cleon E.; Braselton, James P.

2004-05-01

Color-coded and vector-arrow grid representations of the Poynting vector field are used to show the energy flow in and around a fluid-loaded elastic cylindrical shell for both forward- and backward-propagating waves. The present work uses a method adapted from a simpler technique due to Kaduchak and Marston [G. Kaduchak and P. L. Marston, ``Traveling-wave decomposition of surface displacements associated with scattering by a cylindrical shell: Numerical evaluation displaying guided forward and backward wave properties,'' J. Acoust. Soc. Am. 98, 3501-3507 (1995)] to isolate unidirectional energy flows.

[Determination of absorbed dose to water for high energy photon and electron beams--comparison of different dosimetry protocols].

PubMed

Zakaria, Golam Abu; Schütte, Wilhelm

2003-01-01

The determination of absorbed dose to water for high-energy photon and electron beams is performed in Germany according to the dosimetry protocol DIN 6800-2 (1997). At an international level, the main protocols used are the AAPM dosimetry protocol TG-51 (1999) and the IAEA Code of Practice TRS-398 (2000). The present paper systematically compares these three dosimetry protocols, and identifies similarities and differences. The investigations were performed using 4 and 10 MV photon beams, as well as 6, 8, 9, 10, 12 and 14 MeV electron beams. Two cylindrical and two plane-parallel type chambers were used for measurements. In general, the discrepancies among the three protocols were 1.0% for photon beams and 1.6% for electron beams. Comparative measurements in the context of measurement technical control (MTK) with TLD showed a deviation of less than 1.3% between the measurements obtained according to protocols DIN 6800-2 and MTK (exceptions: 4 MV photons with 2.9% and 6 MeV electrons with 2.4%). While only cylindrical chambers were used for photon beams, measurements of electron beams were performed using both cylindrical and plane-parallel chambers (the latter used after a cross-calibration to a cylindrical chamber, as required by the respective dosimetry protocols). Notably, unlike recommended in the corresponding protocols, we found out that cylindrical chambers can be used also for energies from 6 to 10 MeV.

Sci-Fri PM: Planning-10: The replacement correction factors for cylindrical chambers in megavoltage beams.

PubMed

Wang, L; Rogers, Dwo

2008-07-01

The replacement correction factor (P repl ) in ion chamber dosimetry accounts for the effects of the medium being replaced by the air cavity of the chamber. In TG-21, P repl was conceptually separated into two components: fluence correction, P fl , and gradient correction, P gr . In TG-51, for electron beams, the calibration is at d ref where P gr is required for cylindrical chambers and P fl is unknown and assumed to be the same as that for a beam having the same mean electron energy at d max . For cylindrical chambers in high-energy photon beams, P repl also represents a major uncertainty in current dosimetry protocols. In this study, P repl is calculated with high precision (<0.1%) by the Monte Carlo method as the ratio of the dose in a phantom to the dose scored in water-walled cylindrical cavities of various radii (with the center of the cavity being the point of measurement) in both high energy photon and electron beams. It is found that, for electron beams, the mean electron energy at depth is a good beam quality specifier for P fl ; and TG-51's adoption of P fl at d max with the same mean electron energy for use at d ref is proven to be accurate. For Farmer chambers in photon beams, there is essentially no beam quality dependence for P repl values. In a Co photon beam, the calculated P repl is about 0.4-0.6% higher than the TG-21 value, indicating TG-21 (and TG-51) used incorrect values of P repl for cylindrical chambers. © 2008 American Association of Physicists in Medicine.

Probe compensation in cylindrical near-field scanning: A novel simulation methodology

NASA Technical Reports Server (NTRS)

Hussein, Ziad A.; Rahmat-Samii, Yahya

1993-01-01

Probe pattern compensation is essential in near-field scanning geometry, where there is a great need to accurately know far-field patterns at wide angular range. This paper focuses on a novel formulation and computer simulation to determine the precise need for and effect of probe compensation in cylindrical near-field scanning. The methodology is applied to a linear test array antenna and the NASA scatterometer radar antenna. The formulation is based on representing the probe by its equivalent tangential magnetic currents. The interaction between the probe equivalent aperture currents and the test antenna fields is obtained with the application of a reciprocity theorem. This allows us to obtain the probe vector output pickup integral which is proportional to the amplitude and phase of the electric field induced in the probe aperture with respect to its position to the test antenna. The integral is evaluated for each probe position on the required sampling point on a cylindrical near-field surface enclosing the antenna. The use of a hypothetical circular-aperture probe with a different radius permits us to derive closed-form expressions for its far-field radiation patterns. These results, together with the probe vector output pickup, allow us to perform computer simulated synthetic measurements. The far-field patterns of the test antenna are formulated based on cylindrical wave expansions of both the probe and test antenna fields. In the limit as the probe radius becomes very small, the probe vector output is the direct response of the near-field at a point, and no probe compensation is needed. Useful results are generated to compare the far-field pattern of the test antenna constructed from the knowledge of the simulated near-field with and without probe pattern compensation and the exact results. These results are important since they clearly illustrate the angular range over which probe compensation is needed. It has been found that a probe with an aperture radius of 0.25(lambda), 0.5(lambda), and 1(lambda) needs a little probe compensation, if any, near the test antenna main beam. In addition, a probe with low directivity may provide a better signal-to-noise ratio than a highly directive one. This is evident in test antenna patterns without probe compensation at wide angles.

Propagation properties of cylindrical sinc Gaussian beam

NASA Astrophysics Data System (ADS)

Eyyuboğlu, Halil T.; Bayraktar, Mert

2016-09-01

We investigate the propagation properties of cylindrical sinc Gaussian beam in turbulent atmosphere. Since an analytic solution is hardly derivable, the study is carried out with the aid of random phase screens. Evolutions of the beam intensity profile, beam size and kurtosis parameter are analysed. It is found that on the source plane, cylindrical sinc Gaussian beam has a dark hollow appearance, where the side lobes also start to emerge with increase in width parameter and Gaussian source size. During propagation, beams with small width and Gaussian source size exhibit off-axis behaviour, losing the dark hollow shape, accumulating the intensity asymmetrically on one side, whereas those with large width and Gaussian source size retain dark hollow appearance even at long propagation distances. It is seen that the beams with large widths expand more in beam size than the ones with small widths. The structure constant values chosen do not seem to alter this situation. The kurtosis parameters of the beams having small widths are seen to be larger than the ones with the small widths. Again the choice of the structure constant does not change this trend.

Two-Lens, Anamorphic, Brewster-Angle, Fourier-Transform Relay

NASA Astrophysics Data System (ADS)

Berggren, Ralph R.

1987-06-01

A two-lens system provides a simple and versatile means to relay a laser beam. The pair of lenses can provide true volume imaging, reproducing both amplitude and phase of the input beam. By using cylindrical lenses it is possible to change the aspect ratio of the beam. By adjusting the cylindrical curvatures, it is possible to minimize reflections by tilting the lenses at the Brewster angle.

Non-coaxial superposition of vector vortex beams.

PubMed

Aadhi, A; Vaity, Pravin; Chithrabhanu, P; Reddy, Salla Gangi; Prabakar, Shashi; Singh, R P

2016-02-10

Vector vortex beams are classified into four types depending upon spatial variation in their polarization vector. We have generated all four of these types of vector vortex beams by using a modified polarization Sagnac interferometer with a vortex lens. Further, we have studied the non-coaxial superposition of two vector vortex beams. It is observed that the superposition of two vector vortex beams with same polarization singularity leads to a beam with another kind of polarization singularity in their interaction region. The results may be of importance in ultrahigh security of the polarization-encrypted data that utilizes vector vortex beams and multiple optical trapping with non-coaxial superposition of vector vortex beams. We verified our experimental results with theory.

Experimental determination of the effective point of measurement of cylindrical ionization chambers for high-energy photon and electron beams.

PubMed

Huang, Yanxiao; Willomitzer, Christian; Zakaria, Golam Abu; Hartmann, Guenther H

2010-01-01

Measurements of depth-dose curves in water phantom using a cylindrical ionization chamber require that its effective point of measurement is located at the measuring depth. Recommendations for the position of the effective point of measurement with respect to the central axis valid for high-energy electron and photon beams are given in dosimetry protocols. According to these protocols, the use of a constant shift P(eff) is currently recommended. However, this is still based on a very limited set of experimental results. It is therefore expected that an improved knowledge of the exact position of the effective point of measurement will further improve the accuracy of dosimetry. Recent publications have revealed that the position of the effective point of measurement is indeed varying with beam energy, field size and also with chamber geometry. The aim of this study is to investigate whether the shift of P(eff) can be taken to be constant and independent from the beam energy. An experimental determination of the effective point of measurement is presented based on a comparison between cylindrical chambers and a plane-parallel chamber using conventional dosimetry equipment. For electron beams, the determination is based on the comparison of halfvalue depth R(50) between the cylindrical chamber of interest and a well guarded plane-parallel Roos chamber. For photon beams, the depth of dose maximum, d(max), the depth of 80% dose, d(80), and the dose parameter PDD(10) were used. It was again found that the effective point of measurement for both, electron and photon beams Dosimetry, depends on the beam energy. The deviation from a constant value remains very small for photons, whereas significant deviations were found for electrons. It is therefore concluded that use of a single upstream shift value from the centre of the cylindrical chamber as recommended in current dosimetry protocols is adequate for photons, however inadequate for accurate electron beam dosimetry.

Imaging chemical reactions - 3D velocity mapping

NASA Astrophysics Data System (ADS)

Chichinin, A. I.; Gericke, K.-H.; Kauczok, S.; Maul, C.

Visualising a collision between an atom or a molecule or a photodissociation (half-collision) of a molecule on a single particle and single quantum level is like watching the collision of billiard balls on a pool table: Molecular beams or monoenergetic photodissociation products provide the colliding reactants at controlled velocity before the reaction products velocity is imaged directly with an elaborate camera system, where one should keep in mind that velocity is, in general, a three-dimensional (3D) vectorial property which combines scattering angles and speed. If the processes under study have no cylindrical symmetry, then only this 3D product velocity vector contains the full information of the elementary process under study.

Deflection-Compensating Beam for use inside a Cylinder

NASA Technical Reports Server (NTRS)

Goodman, Dwight; Myers, Neill; Herren, Kenneth

2008-01-01

A design concept for a beam for a specific application permits variations and options for satisfying competing requirements to minimize certain deflections under load and to minimize the weight of the beam. In the specific application, the beam is required to serve as a motion-controlled structure for supporting a mirror for optical testing in the lower third portion of a horizontal, cylindrical vacuum chamber. The cylindrical shape of the chamber is fortuitous in that it can be (and is) utilized as an essential element of the deflection-minimizing design concept. The beam is, more precisely, a table-like structure comprising a nominally flat, horizontal portion with vertical legs at its ends. The weights of the beam and whatever components it supports are reacted by the contact forces between the lower ends of the legs and the inner cylindrical chamber wall. Whereas the bending moments arising from the weights contribute to a beam deflection that is concave with its lowest point at midlength, the bending moments generated by the contact forces acting on the legs contribute to a beam deflection that is convex with its highest point at midlength. In addition, the bending of the legs in response to the weights causes the lower ends of the legs to slide downward on the cylindrical wall. By taking the standard beam-deflection equations, combining them with the geometric relationships among the legs and the horizontal portion of the beam, and treating the sliding as a component of deflection, it is possible to write an equation for the net vertical deflection as a function of the load and of position along the beam. A summary of major conclusions drawn from the equation characterization is included.

Method of and apparatus for collecting solar radiation utilizing variable curvature cylindrical reflectors

DOEpatents

Treytl, William J.; Slemmons, Arthur J.; Andeen, Gerry B.

1979-01-01

A heliostat apparatus includes a frame which is rotatable about an axis which is parallel to the aperture plane of an elongate receiver. A plurality of flat flexible mirror elements are mounted to the frame between several parallel, uniformly spaced resilient beams which are pivotally connected at their ends to the frame. Channels are mounted to the sides of the beams for supporting the edges of the mirror elements. Each of the beams has a longitudinally varying configuration designed to bow into predetermined, generally circular curvatures of varying radii when the center of the beam is deflected relative to the pivotally connected ends of the beams. All of the parallel resilient beams are simultaneously deflected by a cam shaft assembly extending through openings in the centers of the beams, whereby the mirror elements together form an upwardly concave, cylindrical reflecting surface. The heliostat is rotated about its axis to track the apparent diurnal movement of the sun, while the reflecting surface is substantially simultaneously bowed into a cylindrical trough having a radius adapted to focus incident light at the plane of the receiver aperture.

Structured light generation by magnetic metamaterial half-wave plates at visible wavelength

NASA Astrophysics Data System (ADS)

Zeng, Jinwei; Luk, Ting S.; Gao, Jie; Yang, Xiaodong

2017-12-01

Metamaterial or metasurface unit cells functioning as half-wave plates play an essential role for realizing ideal Pancharatnam-Berry phase optical elements capable of tailoring light phase and polarization as desired. Complex light beam manipulation through these metamaterials or metasurfaces unveils new dimensions of light-matter interactions for many advances in diffraction engineering, beam shaping, structuring light, and holography. However, the realization of metamaterial or metasurface half-wave plates in visible spectrum range is still challenging mainly due to its specific requirements of strong phase anisotropy with amplitude isotropy in subwavelength scale. Here, we propose magnetic metamaterial structures which can simultaneously exploit the electric field and magnetic field of light for achieving the nanoscale half-wave plates at visible wavelength. We design and demonstrate the magnetic metamaterial half-wave plates in linear grating patterns with high polarization conversion purity in a deep subwavelength thickness. Then, we characterize the equivalent magnetic metamaterial half-wave plates in cylindrical coordinate as concentric-ring grating patterns, which act like an azimuthal half-wave plate and accordingly exhibit spatially inhomogeneous polarization and phase manipulations including spin-to-orbital angular momentum conversion and vector beam generation. Our results show potentials for realizing on-chip beam converters, compact holograms, and many other metamaterial devices for structured light beam generation, polarization control, and wavefront manipulation.

Efficient excitations of radially and azimuthally polarized Nd3+:YAG ceramic microchip laser by use of subwavelength multilayer concentric gratings composed of Nb2O5/SiO2.

PubMed

Li, Jian-Lang; Ueda, Ken-ichi; Zhong, Lan-xiang; Musha, Mitsuru; Shirakawa, Akira; Sato, Takashi

2008-07-07

Cylindrical vector beams were produced from laser diode end-pumped Nd:YAG ceramic microchip laser by use of two types of subwavelength multilayer gratings as the axisymmetric-polarization output couplers respectively. The grating mirrors are composed of high- and low-refractive- index (Nb(2)O(5)/SiO(2)) layers alternately while each layer is shaped into triangle and concentric corrugations. For radially polarized laser output, the beam power reached 610mW with a polarization extinction ratio (PER) of 61:1 and a slope efficiency of 68.2%; for azimuthally polarized laser output, the beam power reached 626mW with a PER of 58:1 and a slope efficiency of 47.6%. In both cases, the laser beams had near-diffraction limited quality. Small differences of beam power, PER and slope efficiency between radially and azimuthally polarized laser outputs were not critical, and could be minimized by further optimized adjustment to laser cavity and the reflectances of respective grating mirrors. The results manifested, by use of the photonic crystal gratings mirrors and end-pumped microchip laser configuration, CVBs can be generated efficiently with high modal symmetry and polarization purity.

Method for laser welding a fin and a tube

DOEpatents

Fuerschbach, Phillip W.; Mahoney, A. Roderick; Milewski, John O

2001-01-01

A method of laser welding a planar metal surface to a cylindrical metal surface is provided, first placing a planar metal surface into approximate contact with a cylindrical metal surface to form a juncture area to be welded, the planar metal surface and cylindrical metal surface thereby forming an acute angle of contact. A laser beam, produced, for example, by a Nd:YAG pulsed laser, is focused through the acute angle of contact at the juncture area to be welded, with the laser beam heating the juncture area to a welding temperature to cause welding to occur between the planar metal surface and the cylindrical metal surface. Both the planar metal surface and cylindrical metal surface are made from a reflective metal, including copper, copper alloys, stainless steel alloys, aluminum, and aluminum alloys.

Versatile generation of optical vector fields and vector beams using a non-interferometric approach.

PubMed

Tripathi, Santosh; Toussaint, Kimani C

2012-05-07

We present a versatile, non-interferometric method for generating vector fields and vector beams which can produce all the states of polarization represented on a higher-order Poincaré sphere. The versatility and non-interferometric nature of this method is expected to enable exploration of various exotic properties of vector fields and vector beams. To illustrate this, we study the propagation properties of some vector fields and find that, in general, propagation alters both their intensity and polarization distribution, and more interestingly, converts some vector fields into vector beams. In the article, we also suggest a modified Jones vector formalism to represent vector fields and vector beams.

Variable-focus side-firing endoscopic device

NASA Astrophysics Data System (ADS)

Lemberg, Vladimir G.; Black, Michael

1996-05-01

Conventional side-firing fiber technology exhibits performance limitations and utilizes expensive single-use only devices which often require multiple fibers for laser prostatectomy. Another limitation of existing side-firing fiber technology is its inability to focus the beam to create incisions for urologic applications such as laser TURP (transurethral resectional prostatectomy), tumor necrosis, lithotripsy, genital warts, and photodynamic therapy. Newly introduced variable-focus side-firing endoscopic device utilizes either one or two lenses and a mirror, onto a single cylinder of molded glass. The laser beam exits the optical fiber, passes through the lens, strikes the cylindrical mirror, and traverses the cylindrical surface. Depending on the design, the laser beam is reflected at the angles ranging from 30 degrees to 120 degrees out of the cylindrical lens. A second lens can be formed onto the side of the cylindrical surface at the beam's exit point. Another advantage of the innovative side-firing device is its capability to provide versatile matching to multiple laser wavelengths from 360 nm to 2.5 microns, and achieve power densities great enough to perform vaporization, incision and coagulation of tissue. Precise focusing of the laser beam results in reduced tissue necrosis of surrounding the treatment area as well as in decreased laser radiation back-scattering. Surgeons can very the focus by adjusting the distance from the tip to the target area. The variable focus side-firing device provides a focused beam at the range of 1.0 to 1.5 mm, for incision. Outside this range, it produces a defocused beam for coagulation.

NOTE: Calibration of low-energy electron beams from a mobile linear accelerator with plane-parallel chambers using both TG-51 and TG-21 protocols

NASA Astrophysics Data System (ADS)

Beddar, A. S.; Tailor, R. C.

2004-04-01

A new approach to intraoperative radiation therapy led to the development of mobile linear electron accelerators that provide lower electron energy beams than the usual conventional accelerators commonly encountered in radiotherapy. Such mobile electron accelerators produce electron beams that have nominal energies of 4, 6, 9 and 12 MeV. This work compares the absorbed dose output calibrations using both the AAPM TG-51 and TG-21 dose calibration protocols for two types of ion chambers: a plane-parallel (PP) ionization chamber and a cylindrical ionization chamber. Our results indicate that the use of a 'Markus' PP chamber causes 2 3% overestimation in dose output determination if accredited dosimetry-calibration laboratory based chamber factors \\big(N_{{\\rm D},{\\rm w}}^{{}^{60}{\\rm Co}}, N_x\\big) are used. However, if the ionization chamber factors are derived using a cross-comparison at a high-energy electron beam, then a good agreement is obtained (within 1%) with a calibrated cylindrical chamber over the entire energy range down to 4 MeV. Furthermore, even though the TG-51 does not recommend using cylindrical chambers at the low energies, our results show that the cylindrical chamber has a good agreement with the PP chamber not only at 6 MeV but also down to 4 MeV electron beams.

SU-D-19A-01: Can Farmer-Type Ionization Chambers Be Used to Improve the Accuracy of Low-Energy Electron Beam Reference Dosimetry?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muir, B R; McEwen, M R

2014-06-01

Purpose: To investigate the use of cylindrical Farmer-type ionization chambers to improve the accuracy of low-energy electron beam calibration. Historically, these chamber types have not been used in beams with incident energies less than 10 MeV (R{sub 5} {sub 0} < 4.3 cm) because early investigations suggested large (up to 5 %) fluence perturbation factors in these beams, implying that a significant component of uncertainty would be introduced if used for calibration. More recently, the assumptions used to determine perturbation corrections for cylindrical chambers have been questioned. Methods: Measurements are made with cylindrical chambers in Elekta Precise 4, 8 andmore » 18 MeV electron beams. Several chamber types are investigated that employ graphite walls and aluminum electrodes with very similar specifications (NE2571, NE2505/3, FC65-G). Depth-ionization scans are measured in water in the 8 and 18 MeV beams. To reduce uncertainty from chamber positioning, measurements in the 4 MeV beam are made at the reference depth in Virtual Water™. The variability of perturbation factors is quantified by comparing normalized response of various chambers. Results: Normalized ion chamber response varies by less than 0.7 % for similar chambers at average electron energies corresponding to that at the reference depth from 4 or 6 MeV beams. Similarly, normalized measurements made with similar chambers at the reference depth in the 4 MeV beam vary by less than 0.4 %. Absorbed dose calibration coefficients derived from these results are stable within 0.1 % on average over a period of 6 years. Conclusion: These results indicate that the uncertainty associated with differences in fluence perturbations for cylindrical chambers with similar specifications is only 0.2 %. The excellent long-term stability of these chambers in both photon and electron beams suggests that these chambers might offer the best performance for all reference dosimetry applications.« less

Demonstration of a terahertz pure vector beam by tailoring geometric phase.

PubMed

Wakayama, Toshitaka; Higashiguchi, Takeshi; Sakaue, Kazuyuki; Washio, Masakazu; Otani, Yukitoshi

2018-06-06

We demonstrate the creation of a vector beam by tailoring geometric phase of left- and right- circularly polarized beams. Such a vector beam with a uniform phase has not been demonstrated before because a vortex phase remains in the beam. We focus on vortex phase cancellation to generate vector beams in terahertz regions, and measure the geometric phase of the beam and its spatial distribution of polarization. We conduct proof-of-principle experiments for producing a vector beam with radial polarization and uniform phase at 0.36 THz. We determine the vortex phase of the vector beam to be below 4%, thus highlighting the extendibility and availability of the proposed concept to the super broadband spectral region from ultraviolet to terahertz. The extended range of our proposed techniques could lead to breakthroughs in the fields of microscopy, chiral nano-materials, and quantum information science.

Propagation of partially coherent vector anomalous vortex beam in turbulent atmosphere

NASA Astrophysics Data System (ADS)

Zhang, Xu; Wang, Haiyan; Tang, Lei

2018-01-01

A theoretical model is proposed to describe a partially coherent vector anomalous vortex(AV) beam. Based on the extended Huygens-Fresnel principle, analytical propagation formula for the proposed beams in turbulent atmosphere is derived. The spectral properties of the partially coherent vector AV beam are explored by using the unified theory of coherence and polarization in detail. It is interesting to find that the turbulence of atmosphere and the source parameter of the partially coherent vector AV beam( order, topological charge, coherence length, beam waist size etc) have significantly impacted the propagation properties of the partially coherent vector AV beam in turbulent atmosphere.

Study of the effective point of measurement for ion chambers in electron beams by Monte Carlo simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, L. L. W.; Rogers, D. W. O.

In current dosimetry protocols for electron beams, for plane-parallel chambers, the effective point of measurement is at the front face of the cavity, and, for cylindrical chambers, it is at a point shifted 0.5r upstream from the cavity center. In this study, Monte Carlo simulations are employed to study the issue of effective point of measurement for both plane-parallel chambers and cylindrical thimble chambers in electron beams. It is found that there are two ways of determining the position of the effective point of measurement: One is to match the calculated depth-ionization curve obtained from a modeled chamber to amore » calculated depth-dose curve; the other is to match the electron fluence spectrum in the chamber cavity to that in the phantom. For plane-parallel chambers, the effective point of measurement determined by the first method is generally not at the front face of the chamber cavity, which is obtained by the second method, but shifted downstream toward the cavity center by an amount that could be larger than one-half a millimeter. This should not be ignored when measuring depth-dose curves in electron beams. For cylindrical chambers, these two methods also give different positions of the effective point of measurement: The first gives a shift of 0.5r, which is in agreement with measurements for high-energy beams and is the same as the value currently used in major dosimetry protocols; the latter gives a shift of 0.8r, which is closer to the value predicted by a theoretical calculation assuming no-scatter conditions. The results also show that the shift of 0.8r is more appropriate if the cylindrical chamber is to be considered as a Spencer-Attix cavity. In electron beams, since the water/air stopping-power ratio changes with depth in a water phantom, the difference of the two shifts (0.3r) will lead to an incorrect evaluation of the water/air stopping-power ratio at the point of measurement, thus resulting in a systematic error in determining the absorbed dose by cylindrical chambers. It is suggested that a shift of 0.8r be used for electron beam calibrations with cylindrical chambers and a shift of 0.4r-0.5r be used for depth-dose measurements.« less

Study of the effective point of measurement for ion chambers in electron beams by Monte Carlo simulation.

PubMed

Wang, L L W; Rogers, D W O

2009-06-01

In current dosimetry protocols for electron beams, for plane-parallel chambers, the effective point of measurement is at the front face of the cavity, and, for cylindrical chambers, it is at a point shifted 0.5r upstream from the cavity center. In this study, Monte Carlo simulations are employed to study the issue of effective point of measurement for both plane-parallel chambers and cylindrical thimble chambers in electron beams. It is found that there are two ways of determining the position of the effective point of measurement: One is to match the calculated depth-ionization curve obtained from a modeled chamber to a calculated depth-dose curve; the other is to match the electron fluence spectrum in the chamber cavity to that in the phantom. For plane-parallel chambers, the effective point of measurement determined by the first method is generally not at the front face of the chamber cavity, which is obtained by the second method, but shifted downstream toward the cavity center by an amount that could be larger than one-half a millimeter. This should not be ignored when measuring depth-dose curves in electron beams. For cylindrical chambers, these two methods also give different positions of the effective point of measurement: The first gives a shift of 0.5r, which is in agreement with measurements for high-energy beams and is the same as the value currently used in major dosimetry protocols; the latter gives a shift of 0.8r, which is closer to the value predicted by a theoretical calculation assuming no-scatter conditions. The results also show that the shift of 0.8r is more appropriate if the cylindrical chamber is to be considered as a Spencer-Attix cavity. In electron beams, since the water/air stopping-power ratio changes with depth in a water phantom, the difference of the two shifts (0.3r) will lead to an incorrect evaluation of the water/air stopping-power ratio at the point of measurement, thus resulting in a systematic error in determining the absorbed dose by cylindrical chambers. It is suggested that a shift of 0.8r be used for electron beam calibrations with cylindrical chambers and a shift of 0.4r-0.5r be used for depth-dose measurements.

Image reconstruction in cone-beam CT with a spherical detector using the BPF algorithm

NASA Astrophysics Data System (ADS)

Zuo, Nianming; Zou, Yu; Jiang, Tianzi; Pan, Xiaochuan

2006-03-01

Both flat-panel detectors and cylindrical detectors have been used in CT systems for data acquisition. The cylindrical detector generally offers a sampling of a transverse image plane more uniformly than does a flat-panel detector. However, in the longitudinal dimension, the cylindrical and flat-panel detectors offer similar sampling of the image space. In this work, we investigate a detector of spherical shape, which can yield uniform sampling of the 3D image space because the solid angle subtended by each individual detector bin remains unchanged. We have extended the backprojection-filtration (BPF) algorithm, which we have developed previously for cone-beam CT, to reconstruct images in cone-beam CT with a spherical detector. We also conduct computer-simulation studies to validate the extended BPF algorithm. Quantitative results in these numerical studies indicate that accurate images can be obtained from data acquired with a spherical detector by use of our extended BPF cone-beam algorithms.

A physics-based solver to optimize the illumination of cylindrical targets in spherically distributed high power laser systems.

PubMed

Gourdain, P-A

2017-05-01

In recent years, our understanding of high energy density plasmas has played an important role in improving inertial fusion confinement and in emerging new fields of physics, such as laboratory astrophysics. Every new idea required developing innovative experimental platforms at high power laser facilities, such as OMEGA or NIF. These facilities, designed to focus all their beams onto spherical targets or hohlraum windows, are now required to shine them on more complex targets. While the pointing on planar geometries is relatively straightforward, it becomes problematic for cylindrical targets or target with more complex geometries. This publication describes how the distribution of laser beams on a cylindrical target can be done simply by using a set of physical laws as a pointing procedure. The advantage of the method is threefold. First, it is straightforward, requiring no mathematical enterprise besides solving ordinary differential equations. Second, it will converge if a local optimum exists. Finally, it is computationally inexpensive. Experimental results show that this approach produces a geometrical beam distribution that yields cylindrically symmetric implosions.

A physics-based solver to optimize the illumination of cylindrical targets in spherically distributed high power laser systems

NASA Astrophysics Data System (ADS)

Gourdain, P.-A.

2017-05-01

In recent years, our understanding of high energy density plasmas has played an important role in improving inertial fusion confinement and in emerging new fields of physics, such as laboratory astrophysics. Every new idea required developing innovative experimental platforms at high power laser facilities, such as OMEGA or NIF. These facilities, designed to focus all their beams onto spherical targets or hohlraum windows, are now required to shine them on more complex targets. While the pointing on planar geometries is relatively straightforward, it becomes problematic for cylindrical targets or target with more complex geometries. This publication describes how the distribution of laser beams on a cylindrical target can be done simply by using a set of physical laws as a pointing procedure. The advantage of the method is threefold. First, it is straightforward, requiring no mathematical enterprise besides solving ordinary differential equations. Second, it will converge if a local optimum exists. Finally, it is computationally inexpensive. Experimental results show that this approach produces a geometrical beam distribution that yields cylindrically symmetric implosions.

Investigation of propagation dynamics of truncated vector vortex beams.

PubMed

Srinivas, P; Perumangatt, C; Lal, Nijil; Singh, R P; Srinivasan, B

2018-06-01

In this Letter, we experimentally investigate the propagation dynamics of truncated vector vortex beams generated using a Sagnac interferometer. Upon focusing, the truncated vector vortex beam is found to regain its original intensity structure within the Rayleigh range. In order to explain such behavior, the propagation dynamics of a truncated vector vortex beam is simulated by decomposing it into the sum of integral charge beams with associated complex weights. We also show that the polarization of the truncated composite vector vortex beam is preserved all along the propagation axis. The experimental observations are consistent with theoretical predictions based on previous literature and are in good agreement with our simulation results. The results hold importance as vector vortex modes are eigenmodes of the optical fiber.

Behavior of reinforcement SCC beams under elevated temperatures

NASA Astrophysics Data System (ADS)

Fathi, Hamoon; Farhang, Kianoosh

2015-09-01

This experimental study focuses on the behavior of heated reinforced concrete beams. Four types of concrete mixtures were used for the tested self-compacting concrete beams. A total of 72 reinforced concrete beams and 72 standard cylindrical specimens were tested. The compressive strength under uniaxial loading at 23 °C ranged from 30 to 45 MPa. The specimens were exposed to different temperatures. The test parameters of interest were the compressive strength and the temperature of the specimens. The effect of changes in the parameters was examined so as to control the behavior of the tested concrete and that of the reinforced concrete beam. The results indicated that flexibility and compressive strength of the reinforced concrete beams decreased at higher temperatures. Furthermore, heating beyond 400 °C produced greater variations in the structural behavior of the materials in both the cylindrical samples and the reinforced concrete beams.

Cylindrical surface profile and diameter measuring tool and method

NASA Technical Reports Server (NTRS)

Currie, James R. (Inventor); Kissel, Ralph R. (Inventor); Smith, Earnest C. (Inventor); Oliver, Charles E. (Inventor); Redmon, John W., Sr. (Inventor); Wallace, Charles C. (Inventor); Swanson, Charles P. (Inventor)

1987-01-01

A tool is shown having a cross beam assembly made of beams joined by a center box structure. The assembly is adapted to be mounted by brackets to the outer end of a cylindrical case. The center box structure has a vertical shaft rotatably mounted therein and extending beneath the assembly. Secured to the vertical shaft is a radius arm which is adapted to rotate with the shaft. On the longer end of the radius arm is a measuring tip which contacts the cylindrical surface to be measured and which provides an electric signal representing the radius of the cylindrical surface from the center of rotation of the radius arm. An electric servomotor rotates the vertical shaft and an electronic resolver provides an electric signal representing the angle of rotation of the shaft. The electric signals are provided to a computer station which has software for its computer to calculate and print out the continuous circumference profile of the cylindrical surface, and give its true diameter and the deviations from the ideal circle.

Acoustic scattering of a cylindrical quasi-Gaussian beam with arbitrary incidence focused on a rigid elliptical cylinder

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitri, F. G., E-mail: F.G.Mitri@ieee.org

2015-11-14

Using the partial-wave series expansion method in cylindrical coordinates, a formal analytical solution for the acoustical scattering of a 2D cylindrical quasi-Gaussian beam with an arbitrary angle of incidence θ{sub i}, focused on a rigid elliptical cylinder in a non-viscous fluid, is developed. The cylindrical focused beam expression is an exact solution of the Helmholtz equation. The scattering coefficients for the elliptical cylinder are determined by forcing the expression of the total (incident + scattered) field to satisfy the Neumann boundary condition for a rigid immovable surface, and performing the product of matrices involving an inversion procedure. Computations for the matrices elementsmore » require a single numerical integration procedure for each partial-wave mode. Numerical results are performed with particular emphasis on the focusing properties of the incident beam and its angle of incidence with respect to the major axis a of the ellipse as well as the aspect ratio a/b where b is the minor axis (assuming a > b). The method is validated and verified against previous results obtained via the T-matrix for plane waves. The present analysis is the first to consider an acoustical beam on an elliptic cylinder of variable cross-section as opposed to plane waves of infinite extent. Other 2D non-spherical and Chebyshev surfaces are mentioned that may be examined throughout this analytical formalism assuming a small deformation parameter ε.« less

Magnetic field configurations on thruster performance in accordance with ion beam characteristics in cylindrical Hall thruster plasmas

NASA Astrophysics Data System (ADS)

Kim, Holak; Choe, Wonho; Lim, Youbong; Lee, Seunghun; Park, Sanghoo

2017-03-01

Magnetic field configuration is critical in Hall thrusters for achieving high performance, particularly in thrust, specific impulse, efficiency, etc. Ion beam features are also significantly influenced by magnetic field configurations. In two typical magnetic field configurations (i.e., co-current and counter-current configurations) of a cylindrical Hall thruster, ion beam characteristics are compared in relation to multiply charged ions. Our study shows that the co-current configuration brings about high ion current (or low electron current), high ionization rate, and small plume angle that lead to high thruster performance.

Research of beam conditioning technologies on SG-III laser facility

NASA Astrophysics Data System (ADS)

Zhang, Rui; Su, Jingqin; Yuan, Haoyu; Li, Ping; Tian, Xiaocheng; Wang, Jianjun; Dong, Jun; Zhang, Ying; Yuan, Qiang; Wang, Yuancheng; Zhou, Wei; Peng, Zhitao; Wang, Fang; Hu, Dongxia; Zhu, Qihua; Zheng, Wanguo; Zhang, Xiaomin

2014-12-01

Multi-FM SSD and CPP was experimentally studied in high fluence and will be equipped on all the beams of SG-III laser facility. The output spectrum of the cascade phase modulators are stable and the residual amplitude modulation is small. FM-to-AM effect caused by free-space propagation after using smoothing by spectral dispersion is theoretically analyzed. Results indicate inserting a dispersion grating in places with larger beam aperture could alleviate the FM-to- AM effect, suggesting minimizing free-space propagation and adopting image relay. Experiments taken on SG-III laser facility indicate when the number of color cycles (Nc) adopts 1, imposing of SSD with 3.3 times diffraction limit (TDL) did not lead to pinhole closure in the spatial filters of the preamplifier and main amplifier with 30-TDL pinhole size. The nonuniformity of the focal spot using Multi-FM SSD and CPP drops to 0.26, comparing to 0.84 only using CPP. The experiments solve some key technical problems using SSD and CPP on SG-III laser facility, and provide a flexible platform for laser-plasma interaction experiments. Combined beam smoothing and polarization smoothing are also analyzed. Simulation results indicate through adjusting dispersion directions of one-dimensional SSD beams in a quad, two-dimensional SSD could be obtained. The near field and far field properties of beams using polarization smoothing were also studied, including birefringent wedge and polarization control plate (PCP). By using PCP, cylindrical vector beams could be obtained. New solutions will be provided to solve the LPI problem encountered in indirect drive laser fusion.

Cylindrical particle manipulation and negative spinning using a nonparaxial Hermite-Gaussian light-sheet beam

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2016-10-01

Based on the angular spectrum decomposition method (ASDM), a nonparaxial solution for the Hermite-Gaussian (HG m ) light-sheet beam of any order m is derived. The beam-shape coefficients (BSCs) are expressed in a compact form and computed using the standard Simpson’s rule for numerical integration. Subsequently, the analysis is extended to evaluate the longitudinal and transverse radiation forces as well as the spin torque on an absorptive dielectric cylindrical particle in 2D without any restriction to a specific range of frequencies. The dynamics of the cylindrical particle are also examined based on Newton’s second law of motion. The numerical results show that a Rayleigh or Mie cylindrical particle can be trapped, pulled or propelled in the optical field depending on its initial position in the cross-sectional plane of the HG m light-sheet. Moreover, negative or positive axial spin torques can arise depending on the choice of the non-dimensional size parameter ka (where k is the wavenumber and a is the radius of the cylinder) and the location of the absorptive cylinder in the beam. This means that the HG m light-sheet beam can induce clockwise or anti-clockwise rotations depending on its shift from the center of the cylinder. In addition, individual vortex behavior can arise in the cross-sectional plane of wave propagation. The present analysis presents an analytical model to predict the optical radiation forces and torque induced by a HG m light-sheet beam on an absorptive cylinder for applications in optical light-sheet tweezers, optical micro-machines, particle manipulation and opto-fluidics to name a few areas of research.

Effect of laser beam on temperature distribution on artificial cylindrical shaped hard tissue bones

NASA Astrophysics Data System (ADS)

Al-Akhras, M.-Ali H.; Qaseer, Mohammad-Khair; Albiss, B. A.; Gezawa, Umar S.

2018-02-01

Samples from fresh lamb chest bones were made in cylindrical shapes to study the time variation of temperature T as functions of the cylindrical radius and depth when its front surface exposed to a laser beam of 110Mw power and 642nm wavelength. The laser beam was directed at the center of the front surface of the horizontal cylinder. The measurements were done in vacuum and at atmospheric pressure. Our data reveal the linear variation of T with time, followed by a gradual increase before it reaches a plateau value at higher time. This sort of behavior independent of the radius or the depth where the temperature was measured. Moreover, the maximum variation occurs on the front surface where the laser beam was hitting and diminishes gradually with depth deep inside the cylinder. Data at atmospheric pressure showed less changes in temperature. The temperature distribution in bone due to laser irradiation is very important for a rational use of laser therapy as well as in the surgery to minimizes the thermal tissue damage.

Slipping and tangential discontinuity instabilities in quasi-one-dimensional planar and cylindrical flows

NASA Astrophysics Data System (ADS)

Kuzelev, M. V.

2017-09-01

An analytical linear theory of instability of an electron beam with a nonuniform directional velocity (slipping instability) against perturbations with wavelengths exceeding the transverse beam size is offered. An analogy with hydrodynamic instabilities of tangential discontinuity of an incompressible liquid flow is drawn. The instability growth rates are calculated for particular cases and in a general form in planar and cylindrical geometries. The stabilizing effect of the external magnetic field is analyzed.

Fast readout algorithm for cylindrical beam position monitors providing good accuracy for particle bunches with large offsets

NASA Astrophysics Data System (ADS)

Thieberger, P.; Gassner, D.; Hulsart, R.; Michnoff, R.; Miller, T.; Minty, M.; Sorrell, Z.; Bartnik, A.

2018-04-01

A simple, analytically correct algorithm is developed for calculating "pencil" relativistic beam coordinates using the signals from an ideal cylindrical particle beam position monitor (BPM) with four pickup electrodes (PUEs) of infinitesimal widths. The algorithm is then applied to simulations of realistic BPMs with finite width PUEs. Surprisingly small deviations are found. Simple empirically determined correction terms reduce the deviations even further. The algorithm is then tested with simulations for non-relativistic beams. As an example of the data acquisition speed advantage, a Field Programmable Gate Array-based BPM readout implementation of the new algorithm has been developed and characterized. Finally, the algorithm is tested with BPM data from the Cornell Preinjector.

Fast readout algorithm for cylindrical beam position monitors providing good accuracy for particle bunches with large offsets

DOE PAGES

Thieberger, Peter; Gassner, D.; Hulsart, R.; ...

2018-04-25

Here, a simple, analytically correct algorithm is developed for calculating “pencil” relativistic beam coordinates using the signals from an ideal cylindrical particle beam position monitor (BPM) with four pickup electrodes (PUEs) of infinitesimal widths. The algorithm is then applied to simulations of realistic BPMs with finite width PUEs. Surprisingly small deviations are found. Simple empirically determined correction terms reduce the deviations even further. The algorithm is then tested with simulations for non-relativistic beams. As an example of the data acquisition speed advantage, a FPGA-based BPM readout implementation of the new algorithm has been developed and characterized. Lastly, the algorithm ismore » tested with BPM data from the Cornell Preinjector.« less

Fast readout algorithm for cylindrical beam position monitors providing good accuracy for particle bunches with large offsets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thieberger, Peter; Gassner, D.; Hulsart, R.

Here, a simple, analytically correct algorithm is developed for calculating “pencil” relativistic beam coordinates using the signals from an ideal cylindrical particle beam position monitor (BPM) with four pickup electrodes (PUEs) of infinitesimal widths. The algorithm is then applied to simulations of realistic BPMs with finite width PUEs. Surprisingly small deviations are found. Simple empirically determined correction terms reduce the deviations even further. The algorithm is then tested with simulations for non-relativistic beams. As an example of the data acquisition speed advantage, a FPGA-based BPM readout implementation of the new algorithm has been developed and characterized. Lastly, the algorithm ismore » tested with BPM data from the Cornell Preinjector.« less

Fast readout algorithm for cylindrical beam position monitors providing good accuracy for particle bunches with large offsets.

PubMed

Thieberger, P; Gassner, D; Hulsart, R; Michnoff, R; Miller, T; Minty, M; Sorrell, Z; Bartnik, A

2018-04-01

A simple, analytically correct algorithm is developed for calculating "pencil" relativistic beam coordinates using the signals from an ideal cylindrical particle beam position monitor (BPM) with four pickup electrodes (PUEs) of infinitesimal widths. The algorithm is then applied to simulations of realistic BPMs with finite width PUEs. Surprisingly small deviations are found. Simple empirically determined correction terms reduce the deviations even further. The algorithm is then tested with simulations for non-relativistic beams. As an example of the data acquisition speed advantage, a Field Programmable Gate Array-based BPM readout implementation of the new algorithm has been developed and characterized. Finally, the algorithm is tested with BPM data from the Cornell Preinjector.

Magnetic compound refractive lens for focusing and polarizing cold neutron beams.

PubMed

Littrell, K C; te Velthuis, S G E; Felcher, G P; Park, S; Kirby, B J; Fitzsimmons, M R

2007-03-01

Biconcave cylindrical lenses are used to focus beams of x rays or neutrons using the refractive properties of matter. In the case of neutrons, the refractive properties of magnetic induction can similarly focus and simultaneously polarize the neutron beam without the concomitant attenuation of matter. This concept of a magnetic refractive lens was tested using a compound lens consisting of 99 pairs of cylindrical permanent magnets. The assembly successfully focused the intensity of a white beam of cold neutrons of one spin state at the detector, while defocusing the other. This experiment confirmed that a lens of this nature may boost the intensity locally by almost an order of magnitude and create a polarized beam. An estimate of the performance of a more practically dimensioned device suitable for incorporation in reflectometers and slit-geometry small angle scattering instruments is given.

Higher-order vector beams produced by photonic-crystal lasers.

PubMed

Iwahashi, Seita; Kurosaka, Yoshitaka; Sakai, Kyosuke; Kitamura, Kyoko; Takayama, Naoki; Noda, Susumu

2011-06-20

We have successfully generated vector beams with higher-order polarization states using photonic-crystal lasers. We have analyzed and designed lattice structures that provide cavity modes with different symmetries. Fabricated devices based on these lattice structures produced doughnut-shaped vector beams, with symmetries corresponding to the cavity modes. Our study enables the systematic analysis of vector beams, which we expect will lead to applications such as high-resolution microscopy, laser processing, and optical trapping.

Vector-beam solutions of Maxwell's wave equation.

PubMed

Hall, D G

1996-01-01

The Hermite-Gauss and Laguerre-Gauss modes are well-known beam solutions of the scalar Helmholtz equation in the paraxial limit. As such, they describe linearly polarized fields or single Cartesian components of vector fields. The vector wave equation admits, in the paraxial limit, of a family of localized Bessel-Gauss beam solutions that can describe the entire transverse electric field. Two recently reported solutions are members of this family of vector Bessel-Gauss beam modes.

Robotic radiosurgery system patient-specific QA for extracranial treatments using the planar ion chamber array and the cylindrical diode array.

PubMed

Lin, Mu-Han; Veltchev, Iavor; Koren, Sion; Ma, Charlie; Li, Jinsgeng

2015-07-08

Robotic radiosurgery system has been increasingly employed for extracranial treatments. This work is aimed to study the feasibility of a cylindrical diode array and a planar ion chamber array for patient-specific QA with this robotic radiosurgery system and compare their performance. Fiducial markers were implanted in both systems to enable image-based setup. An in-house program was developed to postprocess the movie file of the measurements and apply the beam-by-beam angular corrections for both systems. The impact of noncoplanar delivery was then assessed by evaluating the angles created by the incident beams with respect to the two detector arrangements and cross-comparing the planned dose distribution to the measured ones with/without the angular corrections. The sensitivity of detecting the translational (1-3 mm) and the rotational (1°-3°) delivery errors were also evaluated for both systems. Six extracranial patient plans (PTV 7-137 cm³) were measured with these two systems and compared with the calculated doses. The plan dose distributions were calculated with ray-tracing and the Monte Carlo (MC) method, respectively. With 0.8 by 0.8 mm² diodes, the output factors measured with the cylindrical diode array agree better with the commissioning data. The maximum angular correction for a given beam is 8.2% for the planar ion chamber array and 2.4% for the cylindrical diode array. The two systems demonstrate a comparable sensitivity of detecting the translational targeting errors, while the cylindrical diode array is more sensitive to the rotational targeting error. The MC method is necessary for dose calculations in the cylindrical diode array phantom because the ray-tracing algorithm fails to handle the high-Z diodes and the acrylic phantom. For all the patient plans, the cylindrical diode array/ planar ion chamber array demonstrate 100% / > 92% (3%/3 mm) and > 96% / ~ 80% (2%/2 mm) passing rates. The feasibility of using both systems for robotic radiosurgery system patient-specific QA has been demonstrated. For gamma evaluation, 2%/2 mm criteria for cylindrical diode array and 3%/3 mm criteria for planar ion chamber array are suggested. The customized angular correction is necessary as proven by the improved passing rate, especially with the planar ion chamber array system.

Gyrotron whispering gallery mode coupler with a mode conversion reflector for exciting a circular symmetric uniform phase RF beam in a corrugated waveguide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neilson, Jeffrey M.

A cylindrical waveguide with a mode converter transforms a whispering gallery mode from a gyrotron cylindrical waveguide with a helical cut launch edge to a quasi-Gaussian beam suitable for conveyance through a corrugated waveguide. This quasi-Gaussian beam is radiated away from the waveguide using a spiral cut launch edge, which is in close proximity to a first mode converting reflector. The first mode converting reflector is coupled to a second mode converting reflector which provides an output free-space HE11 mode wave suitable for direct coupling into a corrugated waveguide. The radiated beam produced at the output of the second modemore » converting reflector is substantially circular.« less

Formation of a quasi-hollow beam of high-energy heavy ions using a multicell resonance RF deflector

NASA Astrophysics Data System (ADS)

Minaev, S. A.; Sitnikov, A. L.; Golubev, A. A.; Kulevoy, T. V.

2012-09-01

The generation of matter in an extreme state with precisely measurable parameters is of great interest for contemporary physics. One way of obtaining such a state is to irradiate the end of a hollow cylindrical shell at the center of which a test material is kept at a temperature of several Kelvin by an annular beam of high-energy heavy ions. Under the action of the beam, the shell starts explosively expanding both outwards and inwards, compressing the material to an extremely high pressure without subjecting it to direct heating. A method of producing a hollow cylindrical beam of high-energy heavy ions using a resonance rf deflector is described. The deflection of the beam in two transverse directions by means of an rf electric field allows it to rotate about the longitudinal axis and irradiate an annular domain on the end face of the target.

Theory and simulation of electron beam dynamics in the AWE superswarf magnetically immersed diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oliver, B.V.; Welch, D.R.; Olson, C.L.

1999-07-01

Results from numerical simulation and analytic theory of magnetically immersed diode behavior on the United Kingdom's Atomic Weapons Establishment (AWE) Superswarf accelerator are presented. The immersed diode consists of a cylindrical needle point cathode immersed in a strong {approximately}10--20 T solenoidal magnetic field. The anode-cathode (A-K) accelerating gap is held at vacuum and is {approximately}5--10 cm in length, with the anode/target located at the mid-plane of the solenoid. Typical accelerator parameters are 5--6 MeV and 40 kA. Ions emitted from the anode target stream toward the cathode and interact strongly with the electron beam. Collective oscillations between the beam electronsmore » and counter-streaming ions are driven unstable and results in a corkscrew rotation of the beam, yielding a time-integrated spot size substantially larger than that expected from single particle motion. This magnetized ion-hose instability is three dimensional. On the other hand, beam transverse temperature variations, although slightly enhanced in 3D, are primarily due to changes in the effective potential at the cathode (a combination of both the electrostatic and vector potential) and are manifest in 2D. Simulation studies examining spot and dose variation with varying cathode diameter and A-K gap distance are presented and confirm the above mentioned trends. Conclusions are that the diode current is determined by standard di-polar space-charge limited emissions, the minimum beam spot-size is limited by the ion-hose instability saturation amplitude, and the beam transverse temperature at the target is a function of the initial conditions on the cathode. Comparison to existing data will also be presented.« less

Comparison of large-angle production of charged pions with incident protons on cylindrical long and short targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apollonio, M.; Chimenti, P.; Giannini, G.

2009-12-15

The HARP Collaboration has presented measurements of the double-differential {pi}{sup {+-}} production cross section in the range of momentum 100 MeV/c{<=}p{<=}800 MeV/c and angle 0.35 rad{<=}{theta}{<=}2.15 rad with proton beams hitting thin nuclear targets. In many applications the extrapolation to long targets is necessary. In this article the analysis of data taken with long (one interaction length) solid cylindrical targets made of carbon, tantalum, and lead is presented. The data were taken with the large-acceptance HARP detector in the T9 beam line of the CERN proton synchrotron. The secondary pions were produced by beams of protons with momenta of 5,more » 8, and 12GeV/c. The tracking and identification of the produced particles were performed using a small-radius cylindrical time projection chamber placed inside a solenoidal magnet. Incident protons were identified by an elaborate system of beam detectors. Results are obtained for the double-differential yields per target nucleon d{sup 2}{sigma}/dpd{theta}. The measurements are compared with predictions of the MARS and GEANT4 Monte Carlo simulations.« less

Coupler for coupling gyrotron whispering gallery mode RF into HE11 waveguide

DOEpatents

Neilson, Jeffrey M

2015-02-24

A cylindrical waveguide with a mode converter transforms a whispering gallery mode from a gyrotron cylindrical waveguide with a helical cut launch edge to a quasi-Gaussian beam suitable for conveyance through a corrugated waveguide. This quasi-Gaussian beam is radiated away from the waveguide using a spiral cut launch edge, which is in close proximity to a first mode converting reflector. The first mode converting reflector is coupled to a second mode converting reflector which provides an output free-space HE11 mode wave suitable for direct coupling into a corrugated waveguide. The radiated beam produced at the output of the second mode converting reflector is substantially circular.

Problems in nonlinear acoustics: Pulsed finite amplitude sound beams, nonlinear acoustic wave propagation in a liquid layer, nonlinear effects in asymmetric cylindrical sound beams, effects of absorption on the interaction of sound beams, and parametric receiving arrays

NASA Astrophysics Data System (ADS)

Hamilton, Mark F.

1990-12-01

This report discusses five projects all of which involve basic theoretical research in nonlinear acoustics: (1) pulsed finite amplitude sound beams are studied with a recently developed time domain computer algorithm that solves the KZK nonlinear parabolic wave equation; (2) nonlinear acoustic wave propagation in a liquid layer is a study of harmonic generation and acoustic soliton information in a liquid between a rigid and a free surface; (3) nonlinear effects in asymmetric cylindrical sound beams is a study of source asymmetries and scattering of sound by sound at high intensity; (4) effects of absorption on the interaction of sound beams is a completed study of the role of absorption in second harmonic generation and scattering of sound by sound; and (5) parametric receiving arrays is a completed study of parametric reception in a reverberant environment.

Topological features of vector vortex beams perturbed with uniformly polarized light

PubMed Central

D’Errico, Alessio; Maffei, Maria; Piccirillo, Bruno; de Lisio, Corrado; Cardano, Filippo; Marrucci, Lorenzo

2017-01-01

Optical singularities manifesting at the center of vector vortex beams are unstable, since their topological charge is higher than the lowest value permitted by Maxwell’s equations. Inspired by conceptually similar phenomena occurring in the polarization pattern characterizing the skylight, we show how perturbations that break the symmetry of radially symmetric vector beams lead to the formation of a pair of fundamental and stable singularities, i.e. points of circular polarization. We prepare a superposition of a radial (or azimuthal) vector beam and a uniformly linearly polarized Gaussian beam; by varying the amplitudes of the two fields, we control the formation of pairs of these singular points and their spatial separation. We complete this study by applying the same analysis to vector vortex beams with higher topological charges, and by investigating the features that arise when increasing the intensity of the Gaussian term. Our results can find application in the context of singularimetry, where weak fields are measured by considering them as perturbations of unstable optical beams. PMID:28079134

Topological features of vector vortex beams perturbed with uniformly polarized light

NASA Astrophysics Data System (ADS)

D'Errico, Alessio; Maffei, Maria; Piccirillo, Bruno; de Lisio, Corrado; Cardano, Filippo; Marrucci, Lorenzo

2017-01-01

Optical singularities manifesting at the center of vector vortex beams are unstable, since their topological charge is higher than the lowest value permitted by Maxwell’s equations. Inspired by conceptually similar phenomena occurring in the polarization pattern characterizing the skylight, we show how perturbations that break the symmetry of radially symmetric vector beams lead to the formation of a pair of fundamental and stable singularities, i.e. points of circular polarization. We prepare a superposition of a radial (or azimuthal) vector beam and a uniformly linearly polarized Gaussian beam; by varying the amplitudes of the two fields, we control the formation of pairs of these singular points and their spatial separation. We complete this study by applying the same analysis to vector vortex beams with higher topological charges, and by investigating the features that arise when increasing the intensity of the Gaussian term. Our results can find application in the context of singularimetry, where weak fields are measured by considering them as perturbations of unstable optical beams.

Topological features of vector vortex beams perturbed with uniformly polarized light.

PubMed

D'Errico, Alessio; Maffei, Maria; Piccirillo, Bruno; de Lisio, Corrado; Cardano, Filippo; Marrucci, Lorenzo

2017-01-12

Optical singularities manifesting at the center of vector vortex beams are unstable, since their topological charge is higher than the lowest value permitted by Maxwell's equations. Inspired by conceptually similar phenomena occurring in the polarization pattern characterizing the skylight, we show how perturbations that break the symmetry of radially symmetric vector beams lead to the formation of a pair of fundamental and stable singularities, i.e. points of circular polarization. We prepare a superposition of a radial (or azimuthal) vector beam and a uniformly linearly polarized Gaussian beam; by varying the amplitudes of the two fields, we control the formation of pairs of these singular points and their spatial separation. We complete this study by applying the same analysis to vector vortex beams with higher topological charges, and by investigating the features that arise when increasing the intensity of the Gaussian term. Our results can find application in the context of singularimetry, where weak fields are measured by considering them as perturbations of unstable optical beams.

Design and initial results from a kilojoule level Dense Plasma Focus with hollow anode and cylindrically symmetric gas puff.

PubMed

Ellsworth, J L; Falabella, S; Tang, V; Schmidt, A; Guethlein, G; Hawkins, S; Rusnak, B

2014-01-01

We have designed and built a Dense Plasma Focus (DPF) Z-pinch device using a kJ-level capacitor bank and a hollow anode, and fueled by a cylindrically symmetric gas puff. Using this device, we have measured peak deuteron beam energies of up to 400 keV at 0.8 kJ capacitor bank energy and pinch lengths of ∼6 mm, indicating accelerating fields greater than 50 MV/m. Neutron yields of on the order of 10(7) per shot were measured during deuterium operation. The cylindrical gas puff system permitted simultaneous operation of DPF with a radiofrequency quadrupole accelerator for beam-into-plasma experiments. This paper describes the machine design, the diagnostic systems, and our first results.

Generation of vector beams using a double-wedge depolarizer: Non-quantum entanglement

NASA Astrophysics Data System (ADS)

Samlan, C. T.; Viswanathan, Nirmal K.

2016-07-01

Propagation of horizontally polarized Gaussian beam through a double-wedge depolarizer generates vector beams with spatially varying state of polarization. Jones calculus is used to show that such beams are maximally nonseparable on the basis of even (Gaussian)-odd (Hermite-Gaussian) mode parity and horizontal-vertical polarization state. The maximum nonseparability in the two degrees of freedom of the vector beam at the double wedge depolarizer output is verified experimentally using a modified Sagnac interferometer and linear analyser projected interferograms to measure the concurrence 0.94±0.002 and violation of Clauser-Horne-Shimony-Holt form of Bell-like inequality 2.704±0.024. The investigation is carried out in the context of the use of vector beams for metrological applications.

Simulation and Testing of a Linear Array of Modified Four-Square Feed Antennas for the Tianlai Cylindrical Radio Telescope

NASA Astrophysics Data System (ADS)

Cianciara, Aleksander J.; Anderson, Christopher J.; Chen, Xuelei; Chen, Zhiping; Geng, Jingchao; Li, Jixia; Liu, Chao; Liu, Tao; Lu, Wing; Peterson, Jeffrey B.; Shi, Huli; Steffel, Catherine N.; Stebbins, Albert; Stucky, Thomas; Sun, Shijie; Timbie, Peter T.; Wang, Yougang; Wu, Fengquan; Zhang, Juyong

A wide bandwidth, dual polarized, modified four-square antenna is presented as a feed antenna for radio astronomical measurements. A linear array of these antennas is used as a line-feed for cylindrical reflectors for Tianlai, a radio interferometer designed for 21cm intensity mapping. Simulations of the feed antenna beam patterns and scattering parameters are compared to experimental results at multiple frequencies across the 650-1420MHz range. Simulations of the beam patterns of the combined feed array/reflector are presented as well.

Goos-Hänchen effect on Si thin films with spherical and cylindrical pores

NASA Astrophysics Data System (ADS)

Olaya, Cherrie May; Garcia, Wilson O.; Hermosa, Nathaniel

2018-02-01

We examine the effects on the spatial and angular Goos-Hanchen (GH) beam shifts of spherical and cylindrical pores in a thin film. In our calculations, a p-polarized light is incident on a 1-μm thick porous silicon (Si) thin film on a Si substrate. The beam shifts are within the measurement range of usual optical detectors. Our results show that a technique based on GH shift can be used to determine the porosity and pore structure of thin films at a given thickness.

Determination of the effects of wind-induced vibration on cylindrical beams

NASA Technical Reports Server (NTRS)

Artusa, E. A.

1991-01-01

The objective of the analysis was to determine the critical length to diameter ratio (L/Do) of a hollow, cylindrical beam subjected to wind-induced vibration. The sizes of beams ranged from 4 to 24 inches and were composed of ASTM grade A and grade B and American Petroleum Institute grade X42 steels. Calculations used maximum steady-state wind speeds of 130 mph associated with hurricane conditions possible at the Kennedy Space Center. The study examined the effect that different end support and load conditions have on the natural frequencies of the beams. Finally, methods of changing the frequency of the wind-induced vibration were examined. The conclusions drawn were that the greatest possible L/Do is achieved using welded supports and limiting the maximum applied axial and bending loads to less than 50 percent.

Cylindrical surface profile and diameter measuring tool and method

NASA Technical Reports Server (NTRS)

Currie, James R. (Inventor); Kissel, Ralph R. (Inventor); Oliver, Charles E. (Inventor); Smith, Earnest C. (Inventor); Redmon, John W. (Inventor); Wallace, Charles C. (Inventor); Swanson, Charles P. (Inventor)

1989-01-01

A tool is shown having a cross beam assembly (15) made of beams (18, 19, 20, 21) joined by a center box structure (23). The assembly (15) is adapted to be mounted by brackets (16) to the outer end of a cylindrical case (11). The center box structure (23) has a vertical shaft (25) rotatably mounted therein and extending beneath the assembly (15). Secured to the vertical shaft (25) is a radius arm (28) which is adapted to rotate with shaft (25). On the longer end of the radius arm (28) is a measuring tip (30) which contacts the cylindrical surface to be measured and which provides an electric signal representing the radius of the cylindrical surface from the center of rotation of the radius arm (28). An electric servomotor (49) rotates the vertical shaft (25) and an electronic resolver (61) provides an electric signal representing the angle of rotation of the shaft (25). The electric signals are provided to a computer station (73) which has software for its computer to calculate and print out the continuous circumference profile of the cylindrical surface, and give its true diameter and the deviations from the ideal circle.

Vector optical fields with bipolar symmetry of linear polarization.

PubMed

Pan, Yue; Li, Yongnan; Li, Si-Min; Ren, Zhi-Cheng; Si, Yu; Tu, Chenghou; Wang, Hui-Tian

2013-09-15

We focus on a new kind of vector optical field with bipolar symmetry of linear polarization instead of cylindrical and elliptical symmetries, enriching members of family of vector optical fields. We design theoretically and generate experimentally the demanded vector optical fields and then explore some novel tightly focusing properties. The geometric configurations of states of polarization provide additional degrees of freedom assisting in engineering the field distribution at the focus to the specific applications such as lithography, optical trapping, and material processing.

Transverse spin in the scattering of focused radially and azimuthally polarized vector beams

NASA Astrophysics Data System (ADS)

Singh, Ankit Kumar; Saha, Sudipta; Gupta, Subhasish Dutta; Ghosh, Nirmalya

2018-04-01

We study the effect of focusing of the radially and azimuthally polarized vector beams on the spin angular momentum (SAM) density and Poynting vector of scattered waves from a Mie particle. Remarkably, the study reveals that the SAM density of the scattered field is solely transverse in nature for radially and azimuthally polarized incident vector beams; however, the Poynting vector shows the usual longitudinal character. We also demonstrate that the transverse SAM density can further be tuned with wavelength and focusing of the incident beam by exploiting the interference of different scattering modes. These results may stimulate further experimental techniques to detect the transverse spin and Belinfante's spin-momentum densities.

Structuring Stokes correlation functions using vector-vortex beam

NASA Astrophysics Data System (ADS)

Kumar, Vijay; Anwar, Ali; Singh, R. P.

2018-01-01

Higher order statistical correlations of the optical vector speckle field, formed due to scattering of a vector-vortex beam, are explored. Here, we report on the experimental construction of the Stokes parameters covariance matrix, consisting of all possible spatial Stokes parameters correlation functions. We also propose and experimentally realize a new Stokes correlation functions called Stokes field auto correlation functions. It is observed that the Stokes correlation functions of the vector-vortex beam will be reflected in the respective Stokes correlation functions of the corresponding vector speckle field. The major advantage of proposing Stokes correlation functions is that the Stokes correlation function can be easily tuned by manipulating the polarization of vector-vortex beam used to generate vector speckle field and to get the phase information directly from the intensity measurements. Moreover, this approach leads to a complete experimental Stokes characterization of a broad range of random fields.

Experimental investigation of the effect of air cavity size in cylindrical ionization chambers on the measurements in 60Co radiotherapy beams

NASA Astrophysics Data System (ADS)

Swanpalmer, John; Johansson, Karl-Axel

2011-11-01

In the late 1970s, Johansson et al (1978 Int. Symp. National and International Standardization of Radiation Dosimetry (Atlanta 1977) vol 2 (Vienna: IAEA) pp 243-70) reported experimentally determined displacement correction factors (pdis) for cylindrical ionization chamber dosimetry in 60Co and high-energy photon beams. These pdis factors have been implemented and are currently in use in a number of dosimetry protocols. However, the accuracy of these factors has recently been questioned by Wang and Rogers (2009a Phys. Med. Biol. 54 1609-20), who performed Monte Carlo simulations of the experiments performed by Johansson et al. They reported that the inaccuracy of the pdis factors originated from the normalization procedure used by Johansson et al. In their experiments, Johansson et al normalized the measured depth-ionization curves at the depth of maximum ionization for each of the different ionization chambers. In this study, we experimentally investigated the effect of air cavity size of cylindrical ionization chambers in a PMMA phantom and 60Co γ-beam. Two different pairs of air-filled cylindrical ionization chambers were used. The chambers in each pair had identical construction and materials but different air cavity volume (diameter). A 20 MeV electron beam was utilized to determine the ratio of the mass of air in the cavity of the two chambers in each pair. This ratio of the mass of air in each pair was then used to compare the ratios of the ionizations obtained at different depths in the PMMA phantom and 60Co γ-beam using the two pairs of chambers. The diameter of the air cavity of cylindrical ionization chambers influences both the depth at which the maximum ionization is observed and the ionization per unit mass of air at this depth. The correction determined at depths of 50 mm and 100 mm is smaller than the correction currently used in many dosimetry protocols. The results presented here agree with the findings of Wang and Rogers' Monte Carlo simulations and show that the normalization procedure employed by Johansson et al is not correct.

Design, Assembly, Integration, and Testing of a Power Processing Unit for a Cylindrical Hall Thruster, the NORSAT-2 Flatsat, and the Vector Gravimeter for Asteroids Instrument Computer

NASA Astrophysics Data System (ADS)

Svatos, Adam Ladislav

This thesis describes the author's contributions to three separate projects. The bus of the NORSAT-2 satellite was developed by the Space Flight Laboratory (SFL) for the Norwegian Space Centre (NSC) and Space Norway. The author's contributions to the mission were performing unit tests for the components of all the spacecraft subsystems as well as designing and assembling the flatsat from flight spares. Gedex's Vector Gravimeter for Asteroids (VEGA) is an accelerometer for spacecraft. The author's contributions to this payload were modifying the instrument computer board schematic, designing the printed circuit board, developing and applying test software, and performing thermal acceptance testing of two instrument computer boards. The SFL's cylindrical Hall effect thruster combines the cylindrical configuration for a Hall thruster and uses permanent magnets to achieve miniaturization and low power consumption, respectively. The author's contributions were to design, build, and test an engineering model power processing unit.

Beam heated linear theta-pinch device for producing hot plasmas

DOEpatents

Bohachevsky, Ihor O.

1981-01-01

A device for producing hot plasmas comprising a single turn theta-pinch coil, a fast discharge capacitor bank connected to the coil, a fuel element disposed along the center axis of the coil, a predetermined gas disposed within the theta-pinch coil, and a high power photon, electron or ion beam generator concentrically aligned to the theta-pinch coil. Discharge of the capacitor bank generates a cylindrical plasma sheath within the theta-pinch coil which heats the outer layer of the fuel element to form a fuel element plasma layer. The beam deposits energy in either the cylindrical plasma sheath or the fuel element plasma layer to assist the implosion of the fuel element to produce a hot plasma.

TU-D-201-03: Results of a Survey On the Implementation of the TG-51 Protocol and Associated Addendum On Reference Dosimetry of External Beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, G; Muir, B; Culberson, W

Purpose: The working group on the review and extension of the TG-51 protocol (WGTG51) collected data from American Association of Physicists in Medicine (AAPM) members with respect to their current TG-51 and associated addendum usage in the interest of considering future protocol addenda and guidance on reference dosimetry best practices. This study reports an overview of this survey on dosimetry of external beams. Methods: Fourteen survey questions were developed by WGTG51 and released in November 2015. The questions collected information on reference dosimetry, beam quality specification, and ancillary calibration equipment. Results: Of the 190 submissions completed worldwide (U.S. 70%), 83%more » were AAPM members. Of the respondents, 33.5% implemented the TG-51 addendum, with the maximum calibration difference for any photon beam, with respect to the original TG-51 protocol, being <1% for 97.4% of responses. One major finding is that 81.8% of respondents used the same cylindrical ionization chamber for photon and electron dosimetry, implying that many clinics are foregoing the use of parallel-plate chambers. Other evidence suggests equivalent dosimetric results can be obtained with both cylindrical and parallel-plate chambers in electron beams. This, combined with users comfort with cylindrical chambers for electrons will likely impact recommendations put forward in an upcoming electron beam addendum to the TG-51 protocol. Data collected on ancillary equipment showed 58.2% (45.0%) of the thermometers (barometers) in use for beam calibration had NIST traceable calibration certificates, but 48.4% (42.7%) were never recalibrated. Conclusion: This survey provides a snapshot of TG-51 external beam reference dosimetry practice in radiotherapy centers. Findings demonstrate the rapid take-up of the TG-51 photon beam addendum and raise issues for the WGTG51 to focus on going forward, including guidelines on ancillary equipment and the choice of chamber for electron beam dosimetry.« less

Design and verification of a novel hollow vibrating module for laser machining.

PubMed

Wang, Zhaozhao; Jang, Seungbong; Kim, EunHee; Jeon, Yongho; Lee, Soo-Hun; Lee, Moon G

2015-04-01

If a vibration module is added on laser machining system, the quality of surface finish and aspect ratio on metals can be significantly enhanced. In this study, a single mobility model of vibrating laser along the path of laser beam was put forward. In order to realize the desired unidirectional motion, a resonance type vibration module with optical lens was designed and manufactured. This cylindrical module was composed of curved-beam flexure elements. The cylindrical coordinate system was established to describe the relationship of a curved-beam flexure element's motion and deformation. In addition, the stiffness matrix of the curved-beam element was obtained. Finite element method and dynamical modeling were provided to analyze the resonance frequency and the displacement of the motion. The feasibility of the design was demonstrated with the help of experiments on frequency response. Experimental results show good agreement with theoretical analysis and simulation predictions.

Spatially sculpted laser scissors for study of DNA damage and repair

NASA Astrophysics Data System (ADS)

Stephens, Jared; Mohanty, Samarendra K.; Genc, Suzanne; Kong, Xiangduo; Yokomori, Kyoko; Berns, Michael W.

2009-09-01

We present a simple and efficient method for controlled linear induction of DNA damage in live cells. By passing a pulsed laser beam through a cylindrical lens prior to expansion, an elongated elliptical beam profile is created with the ability to expose controlled linear patterns while keeping the beam and the sample stationary. The length and orientation of the beam at the sample plane were reliably controlled by an adjustable aperture and rotation of the cylindrical lens, respectively. Localized immunostaining by the DNA double strand break (DSB) markers phosphorylated H2AX (γH2AX) and Nbs1 in the nuclei of HeLa cells exposed to the ``line scissors'' was shown via confocal imaging. The line scissors method proved more efficient than the scanning mirror and scanning stage methods at induction of DNA DSB damage with the added benefit of having a greater potential for high throughput applications.

Thrust vectoring of broad ion beams for spacecraft attitude control

NASA Technical Reports Server (NTRS)

Collett, C. R.; King, H. J.

1973-01-01

Thrust vectoring is shown to increase the attractiveness of ion thrusters for satellite control applications. Incorporating beam deflection into ion thrusters makes it possible to achieve attitude control without adding any thrusters. Two beam vectoring systems are described that can provide up to 10-deg beam deflection in any azimuth. Both systems have been subjected to extended life tests on a 5-cm thruster which resulted in projected life times of from 7500 to 20,000 hours.

Monte Carlo calculations of electron beam quality conversion factors for several ion chamber types.

PubMed

Muir, B R; Rogers, D W O

2014-11-01

To provide a comprehensive investigation of electron beam reference dosimetry using Monte Carlo simulations of the response of 10 plane-parallel and 18 cylindrical ion chamber types. Specific emphasis is placed on the determination of the optimal shift of the chambers' effective point of measurement (EPOM) and beam quality conversion factors. The EGSnrc system is used for calculations of the absorbed dose to gas in ion chamber models and the absorbed dose to water as a function of depth in a water phantom on which cobalt-60 and several electron beam source models are incident. The optimal EPOM shifts of the ion chambers are determined by comparing calculations of R50 converted from I50 (calculated using ion chamber simulations in phantom) to R50 calculated using simulations of the absorbed dose to water vs depth in water. Beam quality conversion factors are determined as the calculated ratio of the absorbed dose to water to the absorbed dose to air in the ion chamber at the reference depth in a cobalt-60 beam to that in electron beams. For most plane-parallel chambers, the optimal EPOM shift is inside of the active cavity but different from the shift determined with water-equivalent scaling of the front window of the chamber. These optimal shifts for plane-parallel chambers also reduce the scatter of beam quality conversion factors, kQ, as a function of R50. The optimal shift of cylindrical chambers is found to be less than the 0.5 rcav recommended by current dosimetry protocols. In most cases, the values of the optimal shift are close to 0.3 rcav. Values of kecal are calculated and compared to those from the TG-51 protocol and differences are explained using accurate individual correction factors for a subset of ion chambers investigated. High-precision fits to beam quality conversion factors normalized to unity in a beam with R50 = 7.5 cm (kQ (')) are provided. These factors avoid the use of gradient correction factors as used in the TG-51 protocol although a chamber dependent optimal shift in the EPOM is required when using plane-parallel chambers while no shift is needed with cylindrical chambers. The sensitivity of these results to parameters used to model the ion chambers is discussed and the uncertainty related to the practical use of these results is evaluated. These results will prove useful as electron beam reference dosimetry protocols are being updated. The analysis of this work indicates that cylindrical ion chambers may be appropriate for use in low-energy electron beams but measurements are required to characterize their use in these beams.

Determination of absorbed dose to water for high-energy photon and electron beams-comparison of the standards DIN 6800-2 (1997), IAEA TRS 398 (2000) and DIN 6800-2 (2006)

PubMed Central

Zakaria, Golam Abu; Schuette, Wilhelm

2007-01-01

For the determination of the absorbed dose to water for high-energy photon and electron beams the IAEA code of practice TRS-398 (2000) is applied internationally. In Germany, the German dosimetry protocol DIN 6800-2 (1997) is used. Recently, the DIN standard has been revised and published as Draft National Standard DIN 6800-2 (2006). It has adopted widely the methodology and dosimetric data of the code of practice. This paper compares these three dosimetry protocols systematically and identifies similarities as well as differences. The investigation was done with 6 and 18 MV photon as well as 5 to 21 MeV electron beams. While only cylindrical chambers were used for photon beams, measurements of electron beams were performed using cylindrical as well as plane-parallel chambers. The discrepancies in the determination of absorbed dose to water between the three protocols were 0.4% for photon beams and 1.5% for electron beams. Comparative measurements showed a deviation of less than 0.5% between our measurements following protocol DIN 6800-2 (2006) and TLD inter-comparison procedure in an external audit. PMID:21217912

Determination of absorbed dose to water for high-energy photon and electron beams-comparison of the standards DIN 6800-2 (1997), IAEA TRS 398 (2000) and DIN 6800-2 (2006).

PubMed

Zakaria, Golam Abu; Schuette, Wilhelm

2007-01-01

For the determination of the absorbed dose to water for high-energy photon and electron beams the IAEA code of practice TRS-398 (2000) is applied internationally. In Germany, the German dosimetry protocol DIN 6800-2 (1997) is used. Recently, the DIN standard has been revised and published as Draft National Standard DIN 6800-2 (2006). It has adopted widely the methodology and dosimetric data of the code of practice. This paper compares these three dosimetry protocols systematically and identifies similarities as well as differences. The investigation was done with 6 and 18 MV photon as well as 5 to 21 MeV electron beams. While only cylindrical chambers were used for photon beams, measurements of electron beams were performed using cylindrical as well as plane-parallel chambers. The discrepancies in the determination of absorbed dose to water between the three protocols were 0.4% for photon beams and 1.5% for electron beams. Comparative measurements showed a deviation of less than 0.5% between our measurements following protocol DIN 6800-2 (2006) and TLD inter-comparison procedure in an external audit.

Purity of Vector Vortex Beams through a Birefringent Amplifier

NASA Astrophysics Data System (ADS)

Sroor, Hend; Lisa, Nyameko; Naidoo, Darryl; Litvin, Igor; Forbes, Andrew

2018-04-01

Creating high-quality vector vortex (VV) beams is possible with a myriad of techniques at low power, and while a few studies have produced such beams at high power, none have considered the impact of amplification on the vector purity. Here we employ tools to study the amplification of VV beams and, in particular, the purity of such modes. We outline a versatile toolbox for such investigations and demonstrate its use in the general case of VV beams through a birefringent gain medium. Intriguingly, we show that it is possible to enhance the purity of such beams during amplification, paving the way for high-brightness VV beams, a requirement for their use in high-power applications such as optical communication and laser-enabled manufacturing.

Monte Carlo calculation model for heat radiation of inclined cylindrical flames and its application

NASA Astrophysics Data System (ADS)

Chang, Zhangyu; Ji, Jingwei; Huang, Yuankai; Wang, Zhiyi; Li, Qingjie

2017-07-01

Based on Monte Carlo method, a calculation model and its C++ calculating program for radiant heat transfer from an inclined cylindrical flame are proposed. In this model, the total radiation energy of the inclined cylindrical flame is distributed equally among a certain number of energy beams, which are emitted randomly from the flame surface. The incident heat flux on a surface is calculated by counting the number of energy beams which could reach the surface. The paper mainly studies the geometrical evaluation criterion for validity of energy beams emitted by inclined cylindrical flames and received by other surfaces. Compared to Mudan's formula results for a straight cylinder or a cylinder with 30° tilt angle, the calculated view factors range from 0.0043 to 0.2742 and the predicted view factors agree well with Mudan's results. The changing trend and values of incident heat fluxes computed by the model is consistent with experimental data measured by Rangwala et al. As a case study, incident heat fluxes on a gasoline tank, both the side and the top surface are calculated by the model. The heat radiation is from an inclined cylindrical flame generated by another 1000 m3 gasoline tank 4.6 m away from it. The cone angle of the flame to the adjacent oil tank is 45° and the polar angle is 0°. The top surface and the side surface of the tank are divided into 960 and 5760 grids during the calculation, respectively. The maximum incident heat flux on the side surface is 39.64 and 51.31 kW/m2 on the top surface. Distributions of the incident heat flux on the surface of the oil tank and on the ground around the fire tank are obtained, too.

Propagation and scattering of vector light beam in turbid scattering medium

NASA Astrophysics Data System (ADS)

Doronin, Alexander; Milione, Giovanni; Meglinski, Igor; Alfano, Robert R.

2014-03-01

Due to its high sensitivity to subtle alterations in medium morphology the vector light beams have recently gained much attention in the area of photonics. This leads to development of a new non-invasive optical technique for tissue diagnostics. Conceptual design of the particular experimental systems requires careful selection of various technical parameters, including beam structure, polarization, coherence, wavelength of incident optical radiation, as well as an estimation of how the spatial and temporal structural alterations in biological tissues can be distinguished by variations of these parameters. Therefore, an accurate realistic description of vector light beams propagation within tissue-like media is required. To simulate and mimic the propagation of vector light beams within the turbid scattering media the stochastic Monte Carlo (MC) technique has been used. In current report we present the developed MC model and the results of simulation of different vector light beams propagation in turbid tissue-like scattering media. The developed MC model takes into account the coherent properties of light, the influence of reflection and refraction at the medium boundary, helicity flip of vortexes and their mutual interference. Finally, similar to the concept of higher order Poincaŕe sphere (HOPS), to link the spatial distribution of the intensity of the backscattered vector light beam and its state of polarization on the medium surface we introduced the color-coded HOPS.

An Efficient Crankshaft Dynamic Analysis Using Substructuring with Ritz Vectors

NASA Astrophysics Data System (ADS)

MOURELATOS, Z. P.

2000-11-01

A structural analysis using dynamic substructuring with Ritz vectors is presented for predicting the dynamic response of an engine crankshaft, based on the finite-element method. A two-level dynamic substructuring is performed using a set of load-dependent Ritz vectors. The rotating crankshaft is properly coupled with the non-rotating, compliant engine block. The block compliance is represented by a distributed linear elastic foundation at each main bearing location. The stiffness of the elastic foundation can be different in the vertical and horizontal planes, thereby considering the anisotropy of the engine block compliance with respect to the crankshaft rotation. The analysis accounts for the kinematic non-linearity resulting from the crankangle-dependent circumferential contact location between each journal and the corresponding bore of the engine block. Crankshaft “bent” and block “misboring” effects due to manufacturing imperfections are considered in the analysis. The superior accuracy and reduced computational effort of the present method as compared with the equivalent superelement analysis in MSC/NASTRAN, are demonstrated using the free and forced vibrations of a slender cylindrical beam and free vibrations of a four-cylinder engine crankshaft. Subsequently, the accuracy of the present method in calculating the dynamic response of engine crankshafts is shown through comparisons between the analytical predictions and experimental results for the torsional vibrations of an in-line five cylinder engine and the bending vibrations of the crankshaft-flywheel assembly of a V6 engine.

Cantilever Beam Design for Projectile Internal Moving Mass Systems

DTIC Science & Technology

2010-09-01

instabilities. Soper (1) considered the stability of a projectile with a cylindrical mass fitted loosely within a cavity. Using a similar...oscillating beam configuration shows promise as a viable, cost-effective, reliable projectile control mechanism. 25 5. References 1. Soper , W

Radiation and scattering from printed antennas on cylindrically conformal platforms

NASA Technical Reports Server (NTRS)

Kempel, Leo C.; Volakis, John L.; Bindiganavale, Sunil

1994-01-01

The goal was to develop suitable methods and software for the analysis of antennas on cylindrical coated and uncoated platforms. Specifically, the finite element boundary integral and finite element ABC methods were employed successfully and associated software were developed for the analysis and design of wraparound and discrete cavity-backed arrays situated on cylindrical platforms. This work led to the successful implementation of analysis software for such antennas. Developments which played a role in this respect are the efficient implementation of the 3D Green's function for a metallic cylinder, the incorporation of the fast Fourier transform in computing the matrix-vector products executed in the solver of the finite element-boundary integral system, and the development of a new absorbing boundary condition for terminating the finite element mesh on cylindrical surfaces.

Stochastic Evolution of Augmented Born-Infeld Equations

NASA Astrophysics Data System (ADS)

Holm, Darryl D.

2018-06-01

This paper compares the results of applying a recently developed method of stochastic uncertainty quantification designed for fluid dynamics to the Born-Infeld model of nonlinear electromagnetism. The similarities in the results are striking. Namely, the introduction of Stratonovich cylindrical noise into each of their Hamiltonian formulations introduces stochastic Lie transport into their dynamics in the same form for both theories. Moreover, the resulting stochastic partial differential equations retain their unperturbed form, except for an additional term representing induced Lie transport by the set of divergence-free vector fields associated with the spatial correlations of the cylindrical noise. The explanation for this remarkable similarity lies in the method of construction of the Hamiltonian for the Stratonovich stochastic contribution to the motion in both cases, which is done via pairing spatial correlation eigenvectors for cylindrical noise with the momentum map for the deterministic motion. This momentum map is responsible for the well-known analogy between hydrodynamics and electromagnetism. The momentum map for the Maxwell and Born-Infeld theories of electromagnetism treated here is the 1-form density known as the Poynting vector. Two appendices treat the Hamiltonian structures underlying these results.

Optical cage generated by azimuthal- and radial-variant vector beams.

PubMed

Man, Zhongsheng; Bai, Zhidong; Li, Jinjian; Zhang, Shuoshuo; Li, Xiaoyu; Zhang, Yuquan; Ge, Xiaolu; Fu, Shenggui

2018-05-01

We propose a method to generate an optical cage using azimuthal- and radial-variant vector beams in a high numerical aperture optical system. A new kind of vector beam that has azimuthal- and radial-variant polarization states is proposed and demonstrated theoretically. Then, an integrated analytical model to calculate the electromagnetic field and Poynting vector distributions of the input azimuthal- and radial-variant vector beams is derived and built based on the vector diffraction theory of Richards and Wolf. From calculations, a full polarization-controlled optical cage is obtained by simply tailoring the radial index of the polarization, the uniformity U of which is up to 0.7748, and the cleanness C is zero. Additionally, a perfect optical cage can be achieved with U=1, and C=0 by introducing an amplitude modulation; its magnetic field and energy flow are also demonstrated in detail. Such optical cages may be helpful in applications such as optical trapping and high-resolution imaging.

Method and apparatus for second-rank tensor generation

NASA Technical Reports Server (NTRS)

Liu, Hua-Kuang (Inventor)

1991-01-01

A method and apparatus are disclosed for generation of second-rank tensors using a photorefractive crystal to perform the outer-product between two vectors via four-wave mixing, thereby taking 2n input data to a control n squared output data points. Two orthogonal amplitude modulated coherent vector beams x and y are expanded and then parallel sides of the photorefractive crystal in exact opposition. A beamsplitter is used to direct a coherent pumping beam onto the crystal at an appropriate angle so as to produce a conjugate beam that is the matrix product of the vector beam that propagates in the exact opposite direction from the pumping beam. The conjugate beam thus separated is the tensor output xy (sup T).

Pump-probe imaging of the fs-ps-ns dynamics during femtosecond laser Bessel beam drilling in PMMA.

PubMed

Yu, Yanwu; Jiang, Lan; Cao, Qiang; Xia, Bo; Wang, Qingsong; Lu, Yongfeng

2015-12-14

A pump-probe shadowgraph imaging technique was used to reveal the femtosecond-picosecond-nanosecond multitimescale fundamentals of high-quality, high-aspect-ratio (up to 287:1) microhole drilling in poly-methyl-meth-acrylate (PMMA) by a single-shot femtosecond laser Bessel beam. The propagation of Bessel beam in PMMA (at 1.98 × 10⁸ m/s) and it induced cylindrical pressure wave expansion (at 3000-3950 m/s in radius) were observed during drilling processes. Also, it was unexpectedly found that the expansion of the cylindrical pressure wave in PMMA showed a linear relation with time and was insensitive to the laser energy fluctuation, quite different from the case in air. It was assumed that the energy insensitivity was due to the anisotropy of wave expansion in PMMA and the ambient air.

Implosion of multilayered cylindrical targets driven by intense heavy ion beams.

PubMed

Piriz, A R; Portugues, R F; Tahir, N A; Hoffmann, D H H

2002-11-01

An analytical model for the implosion of a multilayered cylindrical target driven by an intense heavy ion beam has been developed. The target is composed of a cylinder of frozen hydrogen or deuterium, which is enclosed in a thick shell of solid lead. This target has been designed for future high-energy-density matter experiments to be carried out at the Gesellschaft für Schwerionenforschung, Darmstadt. The model describes the implosion dynamics including the motion of the incident shock and the first reflected shock and allows for calculation of the physical conditions of the hydrogen at stagnation. The model predicts that the conditions of the compressed hydrogen are not sensitive to significant variations in target and beam parameters. These predictions are confirmed by one-dimensional numerical simulations and thus allow for a robust target design.

Managing focal fields of vector beams with multiple polarization singularities.

PubMed

Han, Lei; Liu, Sheng; Li, Peng; Zhang, Yi; Cheng, Huachao; Gan, Xuetao; Zhao, Jianlin

2016-11-10

We explore the tight focusing behavior of vector beams with multiple polarization singularities, and analyze the influences of the number, position, and topological charge of the singularities on the focal fields. It is found that the ellipticity of the local polarization states at the focal plane could be determined by the spatial distribution of the polarization singularities of the vector beam. When the spatial location and topological charge of singularities have even-fold rotation symmetry, the transverse fields at the focal plane are locally linearly polarized. Otherwise, the polarization state becomes a locally hybrid one. By appropriately arranging the distribution of the polarization singularities in the vector beam, the polarization distributions of the focal fields could be altered while the intensity maintains unchanged.

Investigation on partially coherent vector beams and their propagation and focusing properties.

PubMed

Hu, Kelei; Chen, Ziyang; Pu, Jixiong

2012-11-01

The propagation and focusing properties of partially coherent vector beams including radially polarized and azimuthally polarized (AP) beams are theoretically and experimentally investigated. The beam profile of a partially coherent radially or AP beam can be shaped by adjusting the initial spatial coherence length. The dark hollow, flat-topped, and Gaussian beam spots can be obtained, which will be useful in trapping particles. The experimental observations are consistent with the theoretical results.

Comment on "Effects of Magnetic Field Gradient on Ion Beam Current in Cylindrical Hall Ion Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raitses, Y.; Smirnov A.; Fisch, N.J.

It is argued that the key difference of the cylindrical Hall thruster (CHT) as compared to the end-Hall ion source cannot be exclusively attributed to the magnetic field topology [Tang et al. J. Appl. Phys., 102, 123305 (2007)]. With a similar mirror-type topology, the CHT configuration provides the electric field with nearly equipotential magnetic field surfaces and a better suppression of the electron cross-field transport, as compared to both the end-Hall ion source and the cylindrical Hall ion source of Tang et al.

Process for sensing defects on a smooth cylindrical interior surface in tubing

DOEpatents

Dutton, G. Wayne

1987-11-17

The cylindrical interior surface of small diameter metal tubing is optically inspected to determine surface roughness by passing a slightly divergent light beam to illuminate the entire interior surface of the tubing. Impingement of the input light beam components on any rough spots on the interior surface generates forward and backward scattered radiation components. The forward scattered components can be measured by blocking direct and specular radiation components exiting the tubing while allowing the forward scattered radiation to travel past the blocking location. Collecting optics are employed to converge the forward scattered radiation onto a photodetector generating a signal indicative of surface roughness. In the back scattered mode, back scattered radiation exiting the tubing through the entrance opening is reflected 90.degree. by a beam splitter towards collecting optics and a photodetector. Alternatively, back scattered radiation can be transmitted through a fiber optic bundle towards the collecting optics. The input light beam can be supplied through a white light fiber optic bundle mounted coaxial with the first bundle.

Process for sensing defects on a smooth cylindrical interior surface in tubing

DOEpatents

Dutton, G.W.

1987-11-17

The cylindrical interior surface of small diameter metal tubing is optically inspected to determine surface roughness by passing a slightly divergent light beam to illuminate the entire interior surface of the tubing. Impingement of the input light beam components on any rough spots on the interior surface generates forward and backward scattered radiation components. The forward scattered components can be measured by blocking direct and specular radiation components exiting the tubing while allowing the forward scattered radiation to travel past the blocking location. Collecting optics are employed to converge the forward scattered radiation onto a photodetector generating a signal indicative of surface roughness. In the back scattered mode, back scattered radiation exiting the tubing through the entrance opening is reflected 90[degree] by a beam splitter towards collecting optics and a photodetector. Alternatively, back scattered radiation can be transmitted through a fiber optic bundle towards the collecting optics. The input light beam can be supplied through a white light fiber optic bundle mounted coaxial with the first bundle. 6 figs.

Process and apparatus for sensing defects on a smooth cylindrical surface in tubing

DOEpatents

Dutton, G.W.

1985-08-05

The cylindrical interior surface of small diameter metal tubing is optically inspected to determine surface roughness by passing a slightly divergent light beam to illuminate the entire interior surface of the tubing. Impingement of the input light beam components on any rough spots on the interior surface generates forward and backward scattered radiation components. The forward scattered components can be measured by blocking direct and specular radiation components exiting the tubing while allowing the forward scattered radiation to travel past the blocking location. Collecting optics are employed to converge the forward scattered radiation onto a photodetector generating a signal indicative of surface roughness. In the back scattered mode, back scattered radiation exiting the tubing through the entrance opening is reflected 90/sup 0/ by a beam splitter towards collecting optics and a photodetector. Alternatively, back scattered radiation can be transmitted through a fiber optic bundle towards the collecting optics. The input light beam can be supplied through a white light fiber optic bundle mounted coaxial with the first bundle.

Segmented beryllium target for a 2 MW super beam facility

DOE PAGES

Davenne, T.; Caretta, O.; Densham, C.; ...

2015-09-14

The Long Baseline Neutrino Facility (LBNF, formerly the Long Baseline Neutrino Experiment) is under design as a next generation neutrino oscillation experiment, with primary objectives to search for CP violation in the leptonic sector, to determine the neutrino mass hierarchy and to provide a precise measurement of θ 23. The facility will generate a neutrino beam at Fermilab by the interaction of a proton beam with a target material. At the ultimate anticipated proton beam power of 2.3 MW the target material must dissipate a heat load of between 10 and 25 kW depending on the target size. This paper presents amore » target concept based on an array of spheres and compares it to a cylindrical monolithic target such as that which currently operates at the T2K facility. Thus simulation results show that the proposed technology offers efficient cooling and lower stresses whilst delivering a neutrino production comparable with that of a conventional solid cylindrical target.« less

Space Charge Effect in the Sheet and Solid Electron Beam

NASA Astrophysics Data System (ADS)

Song, Ho Young; Kim, Hyoung Suk; Ahn, Saeyoung

1998-11-01

We analyze the space charge effect of two different types of electron beam ; sheet and solid electron beam. Electron gun simulations are carried out using shadow and control grids for high and low perveance. Rectangular and cylindrical geometries are used for sheet and solid electron beam in planar and disk type cathode. The E-gun code is used to study the limiting current and space charge loading in each geometries.

Laser-Plasma Interactions in Drive Campaign targets on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Hinkel, D. E.; Callahan, D. A.; Moody, J. D.; Amendt, P. A.; Lasinski, B. F.; MacGowan, B. J.; Meeker, D.; Michel, P. A.; Ralph, J.; Rosen, M. D.; Ross, J. S.; Schneider, M. B.; Storm, E.; Strozzi, D. J.; Williams, E. A.

2016-03-01

The Drive campaign [D A Callahan et al., this conference] on the National Ignition Facility (NIF) laser [E. I. Moses, R. N. Boyd, B. A. Remington, C. J. Keane, R. Al-Ayat, Phys. Plasmas 16, 041006 (2009)] has the focused goal of understanding and optimizing the hohlraum for ignition. Both the temperature and symmetry of the radiation drive depend on laser and hohlraum characteristics. The drive temperature depends on the coupling of laser energy to the hohlraum, and the symmetry of the drive depends on beam-to-beam interactions that result in energy transfer [P. A. Michel, S. H. Glenzer, L. Divol, et al, Phys. Plasmas 17, 056305 (2010).] within the hohlraum. To this end, hohlraums are being fielded where shape (rugby vs. cylindrical hohlraums), gas fill composition (neopentane at room temperature vs. cryogenic helium), and gas fill density (increase of ∼ 150%) are independently changed. Cylindrical hohlraums with higher gas fill density show improved inner beam propagation, as should rugby hohlraums, because of the larger radius over the capsule (7 mm vs. 5.75 mm in a cylindrical hohlraum). Energy coupling improves in room temperature neopentane targets, as well as in hohlraums at higher gas fill density. In addition cross-beam energy transfer is being addressed directly by using targets that mock up one end of a hohlraum, but allow observation of the laser beam uniformity after energy transfer. Ideas such as splitting quads into “doublets” by re-pointing the right and left half of quads are also being pursued. LPI results of the Drive campaign will be summarized, and analyses of future directions presented.

Helicons in uniform fields. I. Wave diagnostics with hodograms

NASA Astrophysics Data System (ADS)

Urrutia, J. M.; Stenzel, R. L.

2018-03-01

The wave equation for whistler waves is well known and has been solved in Cartesian and cylindrical coordinates, yielding plane waves and cylindrical waves. In space plasmas, waves are usually assumed to be plane waves; in small laboratory plasmas, they are often assumed to be cylindrical "helicon" eigenmodes. Experimental observations fall in between both models. Real waves are usually bounded and may rotate like helicons. Such helicons are studied experimentally in a large laboratory plasma which is essentially a uniform, unbounded plasma. The waves are excited by loop antennas whose properties determine the field rotation and transverse dimensions. Both m = 0 and m = 1 helicon modes are produced and analyzed by measuring the wave magnetic field in three dimensional space and time. From Ampère's law and Ohm's law, the current density and electric field vectors are obtained. Hodograms for these vectors are produced. The sign ambiguity of the hodogram normal with respect to the direction of wave propagation is demonstrated. In general, electric and magnetic hodograms differ but both together yield the wave vector direction unambiguously. Vector fields of the hodogram normal yield the phase flow including phase rotation for helicons. Some helicons can have locally a linear polarization which is identified by the hodogram ellipticity. Alternatively the amplitude oscillation in time yields a measure for the wave polarization. It is shown that wave interference produces linear polarization. These observations emphasize that single point hodogram measurements are inadequate to determine the wave topology unless assuming plane waves. Observations of linear polarization indicate wave packets but not plane waves. A simple qualitative diagnostics for the wave polarization is the measurement of the magnetic field magnitude in time. Circular polarization has a constant amplitude; linear polarization results in amplitude modulations.

Optimal condition for employing an axicon-generated Bessel beam to fabricate cylindrical microlens arrays

NASA Astrophysics Data System (ADS)

Luo, Zhi; Yin, Kai; Dong, Xinran; Duan, Ji’an

2018-05-01

A numerical algorithm, modelling the transformation from a Gaussian beam to a Bessel beam, is presented for the purpose to study the optimal condition for employing an axicon-generated Bessel beam to fabricate cylindrical microlens arrays (CMLAs). By applying the numerical algorithm to simulate the spatial intensity distribution behind the axicon under different defects of a rotund-apex and different diameter ratios of an incident beam to the axicon, we find that the diffraction effects formed by the axicon edge can be almost eliminated when the diameter ratio is less than 1:2, but the spatial intensity distribution is disturbed dramatically even a few tens of microns deviation of the apex, especially for the front part of the axicon-generated Bessel beam. Fortunately, the lateral intensity profile in the rear part still maintains a desirable Bessel curve. Therefore, the rear part of the Bessel area and the less than 1:2 diameter ratio are the optimal choice for employing an axicon-generated Bessel beam to implement surface microstructures fabrication. Furthermore, by applying the optimal conditions to direct writing microstructures on fused silica with a femtosecond (fs) laser, a large area close-packed CMLA is fabricated. The CMLA presents high quality and uniformity and its optical performance is also demonstrated.

Microdosimetric investigation at the therapeutic proton beam facility of CATANA.

PubMed

De Nardo, L; Moro, D; Colautti, P; Conte, V; Tornielli, G; Cuttone, G

2004-01-01

Proton beams (62 Mev) are used by the Laboratori Nazionali del Sud of the Italian Institute of Nuclear Physics to treat eye melanoma tumours at the therapeutic facility called CATANA. A cylindrical slim tissue-equivalent proportional counter (TEPC) of 2.7 mm external diameter has been used to compare the radiation quality of two spread-out Bragg peaks (SOBP) at the CATANA proton beam.

Optical inspection system for cylindrical objects

DOEpatents

Brenden, Byron B.; Peters, Timothy J.

1989-01-01

In the inspection of cylindrical objects, particularly O-rings, the object is translated through a field of view and a linear light trace is projected on its surface. An image of the light trace is projected on a mask, which has a size and shape corresponding to the size and shape which the image would have if the surface of the object were perfect. If there is a defect, light will pass the mask and be sensed by a detector positioned behind the mask. Preferably, two masks and associated detectors are used, one mask being convex to pass light when the light trace falls on a projection from the surface and the other concave, to pass light when the light trace falls on a depression in the surface. The light trace may be either dynamic, formed by a scanned laser beam, or static, formed by such a beam focussed by a cylindrical lens. Means are provided to automatically keep the illuminating receiving systems properly aligned.

A cylindrical tripleGEM detector for the BESIII experiment: Measurement of the performance in a magnetic field and project status

NASA Astrophysics Data System (ADS)

Farinelli, R.; BESIII CGEM Group

2017-01-01

A new cylindrical GEM detector is under development to upgrade the tracking system of the BESIII experiment at the IHEP in Beijing. The new detector will replace the current inner drift chamber of the experiment in order to increase significantly the spatial resolution along the beam direction (σ_z ˜ 300 μ m) and to grant the performance of momentum resolution (σ_{p_t}/p_t ˜ 0.5% at 1GeV) and spatial resolution (σ_{xy} ˜ 130 μ m). A cylindrical prototype with the final detector dimensions has been built and the assembly procedure has been successfully validated. Moreover the performance of a 10 × 10 cm ^2 planar GEM has been studied inside a magnetic field by means of a beam test at CERN. The data have been analyzed using two different readout mode: the charge centroid (CC) and the micro time projection chamber ( μ TPC) method.

Understanding Beam Alignment in a Coherent Lidar System

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Roychoudhari, Chandrasekhar

2015-01-01

Optical beam alignment in a coherent lidar (or ladar) receiver system plays a critical role in optimizing its performance. Optical alignment in a coherent lidar system dictates the wavefront curvature (phase front) and Poynting vector) matching of the local oscillator beam with the incoming receiver beam on a detector. However, this alignment is often not easy to achieve and is rarely perfect. Furthermore, optical fibers are being increasingly used in coherent lidar system receivers for transporting radiation to achieve architectural elegance. Single mode fibers also require stringent mode matching for efficient light coupling. The detector response characteristics vary with the misalignment of the two pointing vectors. Misalignment can lead to increase in DC current. Also, a lens in front of the detector may exasperate phase front and Poynting vector mismatch. Non-Interaction of Waves, or the NIW property indicates the light beams do not interfere by themselves in the absence of detecting dipoles. In this paper, we will analyze the extent of misalignment on the detector specifications using pointing vectors of mixing beams in light of the NIW property.

Optical theorem for two-dimensional (2D) scalar monochromatic acoustical beams in cylindrical coordinates.

PubMed

Mitri, F G

2015-09-01

The optical theorem for plane waves is recognized as one of the fundamental theorems in optical, acoustical and quantum wave scattering theory as it relates the extinction cross-section to the forward scattering complex amplitude function. Here, the optical theorem is extended and generalized in a cylindrical coordinates system for the case of 2D beams of arbitrary character as opposed to plane waves of infinite extent. The case of scalar monochromatic acoustical wavefronts is considered, and generalized analytical expressions for the extinction, absorption and scattering cross-sections are derived and extended in the framework of the scalar resonance scattering theory. The analysis reveals the presence of an interference scattering cross-section term describing the interaction between the diffracted Franz waves with the resonance elastic waves. The extended optical theorem in cylindrical coordinates is applicable to any object of arbitrary geometry in 2D located arbitrarily in the beam's path. Related investigations in optics, acoustics and quantum mechanics will benefit from this analysis in the context of wave scattering theory and other phenomena closely connected to it, such as the multiple scattering by a cloud of particles, as well as the resulting radiation force and torque. Copyright © 2015 Elsevier B.V. All rights reserved.

Video-rate terahertz electric-field vector imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takai, Mayuko; Takeda, Masatoshi; Sasaki, Manabu

We present an experimental setup to dramatically reduce a measurement time for obtaining spatial distributions of terahertz electric-field (E-field) vectors. The method utilizes the electro-optic sampling, and we use a charge-coupled device to detect a spatial distribution of the probe beam polarization rotation by the E-field-induced Pockels effect in a 〈110〉-oriented ZnTe crystal. A quick rotation of the ZnTe crystal allows analyzing the terahertz E-field direction at each image position, and the terahertz E-field vector mapping at a fixed position of an optical delay line is achieved within 21 ms. Video-rate mapping of terahertz E-field vectors is likely to bemore » useful for achieving real-time sensing of terahertz vector beams, vector vortices, and surface topography. The method is also useful for a fast polarization analysis of terahertz beams.« less

Surface Tension Driven Convection Experiment (STDCE)

NASA Technical Reports Server (NTRS)

Ostrach, S.; Kamotani, Y.

1996-01-01

This document reports the results obtained from the Surface Tension Driven Convection Experiment (STDCE) conducted aboard the USML-1 Spacelab in 1992. The experiments used 10 cSt silicone oil placed in an open circular container that was 10 cm wide and 5 cm deep. Thermocapillary flow was induced by using either a cylindrical heater placed along the container centerline or by a CO2 laser. The tests were conducted under various power settings, laser beam diameters, and free surface shapes. Thermistors located at various positions in the test section recorded the temperature of the fluid, heater, walls, and air. An infrared imager was used to measure the free surface temperature. The flow field was studied by flow visualization and the data was analyzed by a PTV technique. The results from the flow visualization and the temperature measurements are compared with the numerical analysis that was conducted in conjunction with the experiment. The compared results include the experimental and numerical velocity vector plots, the streamline plots, the fluid temperature, and the surface temperature distribution.

Comparison of Astigmatic Correction after Femtosecond Lenticule Extraction and Small-Incision Lenticule Extraction for Myopic Astigmatism

PubMed Central

Kobashi, Hidenaga; Kamiya, Kazutaka; Ali, Mohamed A.; Igarashi, Akihito; Elewa, Mohamed Ehab M.; Shimizu, Kimiya

2015-01-01

Purpose To compare postoperative astigmatic correction between femtosecond lenticule extraction (FLEx) and small-incision lenticule extraction (SMILE) in eyes with myopic astigmatism. Methods We examined 26 eyes of 26 patients undergoing FLEx and 26 eyes of 26 patients undergoing SMILE to correct myopic astigmatism (manifest astigmatism of 1 diopter (D) or more). Visual acuity, cylindrical refraction, the predictability of the astigmatic correction, and the astigmatic vector components using Alpin’s method, were compared between the two groups 3 months postoperatively. Results We found no statistically significant difference in manifest cylindrical refraction (p=0.74) or in the percentage of eyes within ± 0.50 D of their refraction (p=0.47) after the two surgical procedures. Moreover, no statistically significant difference was detected between the groups in astigmatic vector components, namely, surgically induced astigmatism (0.80), target induced astigmatism (p=0.87), astigmatic correction index (p=0.77), angle of error (p=0.24), difference vector (p=0.76), index of success (p=0.91), flattening effect (p=0.79), and flattening index (p=0.84). Conclusions Both FLEx and SMILE procedures are essentially equivalent in correcting myopic astigmatism using vector analysis, suggesting that the lifting or non-lifting of the flap does not significantly affect astigmatic outcomes after these surgical procedures. PMID:25849381

Generation of spirally polarized propagation-invariant beam using fiber microaxicon.

PubMed

Philip, Geo M; Viswanathan, Nirmal K

2011-10-01

We present here a fiber microaxicon (MA)based method to generate spirally polarized propagation-invariant optical beam. MA chemically etched in the tip of a two-mode fiber efficiently converts the generic cylindrically polarized vortex fiber mode into a spirally polarized propagation-invariant (Bessel-type) beam via radial dependence of polarization rotation angle. The combined roles of helico-conical phase and nonparaxial propagation in the generation and characteristics of the output beam from the fiber MA are discussed. © 2011 Optical Society of America

Coherent Structures and Chaos Control in High-Power Microwave Devices

DTIC Science & Technology

2006-06-29

Theory of Multiresonator Cylindrical Magnetrons 2. High - Power Klystron Research 9 2.1. Determination of the Current Limit on the Confinement of Finite...Size Bunched Pencil Beams in High - Power Relativistic Klystrons 2.2. Exploration of the Possibility of Magnetic Cusp Formation in Highly Bunched...Annular Beams in High - Power Relativistic Klystrons 3. Development of Ellipse-Shaped Ribbon-Beam Theory for HPM Device Applications 12 3.1. Theory of

The effect of electric field geometry on the performance of electromembrane extraction systems: footprints of a third driving force along with migration and diffusion.

PubMed

Moazami, Hamid Reza; Hosseiny Davarani, Saied Saeed; Mohammadi, Jamil; Nojavan, Saeed; Abrari, Masoud

2015-09-03

The distribution of electric field vectors was first calculated for electromembrane extraction (EME) systems in classical and cylindrical electrode geometries. The results showed that supported liquid membrane (SLM) has a general field amplifying effect due to its lower dielectric constant in comparison with aqueous donor/acceptor solutions. The calculated norms of the electric field vector showed that a DC voltage of 50 V can create huge electric field strengths up to 64 kV m(-1) and 111 kV m(-1) in classical and cylindrical geometries respectively. In both cases, the electric field strength reached its peak value on the inner wall of the SLM. In the case of classical geometry, the field strength was a function of the polar position of the SLM whereas the field strength in cylindrical geometry was angularly uniform. In order to investigate the effect of the electrode geometry on the performance of real EME systems, the analysis was carried out in three different geometries including classical, helical and cylindrical arrangements using naproxen and sodium diclofenac as the model analytes. Despite higher field strength and extended cross sectional area, the helical and cylindrical geometries gave lower recoveries with respect to the classical EME. The observed decline of the signal was proved to be against the relations governing migration and diffusion processes, which means that a third driving force is involved in EME. The third driving force is the interaction between the radially inhomogeneous electric field and the analyte in its neutral form. Copyright © 2015 Elsevier B.V. All rights reserved.

A novel three-axis cylindrical hohlraum designed for inertial confinement fusion ignition

NASA Astrophysics Data System (ADS)

Kuang, Longyu; Li, Hang; Jing, Longfei; Lin, Zhiwei; Zhang, Lu; Li, Liling; Ding, Yongkun; Jiang, Shaoen; Liu, Jie; Zheng, Jian

2016-10-01

A novel ignition hohlraum for indirect-drive inertial confinement fusion is proposed, which is named three-axis cylindrical hohlraum (TACH). TACH is a kind of 6 laser entrance holes (LEHs) hohlraum, which is orthogonally jointed of three cylindrical hohlraums. Laser beams are injected through every entrance hole with the same incident angle of 55°. A view-factor simulation result shows that the time-varying drive asymmetry of TACH is less than 1.0% in the whole drive pulse period without any supplementary technology. Coupling efficiency of TACH is close to that of 6 LEHs spherical hohlraum with corresponding size. Its plasma-filling time is close to that of typical cylindrical ignition hohlraum. Its laser plasma interaction has as low backscattering as the outer cone of the cylindrical ignition hohlraum. Therefore, TACH combines most advantages of various hohlraums and has little predictable risk, providing an important competitive candidate for ignition hohlraum.

A novel three-axis cylindrical hohlraum designed for inertial confinement fusion ignition

PubMed Central

Kuang, Longyu; Li, Hang; Jing, Longfei; Lin, Zhiwei; Zhang, Lu; Li, Liling; Ding, Yongkun; Jiang, Shaoen; Liu, Jie; Zheng, Jian

2016-01-01

A novel ignition hohlraum for indirect-drive inertial confinement fusion is proposed, which is named three-axis cylindrical hohlraum (TACH). TACH is a kind of 6 laser entrance holes (LEHs) hohlraum, which is orthogonally jointed of three cylindrical hohlraums. Laser beams are injected through every entrance hole with the same incident angle of 55°. A view-factor simulation result shows that the time-varying drive asymmetry of TACH is less than 1.0% in the whole drive pulse period without any supplementary technology. Coupling efficiency of TACH is close to that of 6 LEHs spherical hohlraum with corresponding size. Its plasma-filling time is close to that of typical cylindrical ignition hohlraum. Its laser plasma interaction has as low backscattering as the outer cone of the cylindrical ignition hohlraum. Therefore, TACH combines most advantages of various hohlraums and has little predictable risk, providing an important competitive candidate for ignition hohlraum. PMID:27703250

A novel three-axis cylindrical hohlraum designed for inertial confinement fusion ignition.

PubMed

Kuang, Longyu; Li, Hang; Jing, Longfei; Lin, Zhiwei; Zhang, Lu; Li, Liling; Ding, Yongkun; Jiang, Shaoen; Liu, Jie; Zheng, Jian

2016-10-05

A novel ignition hohlraum for indirect-drive inertial confinement fusion is proposed, which is named three-axis cylindrical hohlraum (TACH). TACH is a kind of 6 laser entrance holes (LEHs) hohlraum, which is orthogonally jointed of three cylindrical hohlraums. Laser beams are injected through every entrance hole with the same incident angle of 55°. A view-factor simulation result shows that the time-varying drive asymmetry of TACH is less than 1.0% in the whole drive pulse period without any supplementary technology. Coupling efficiency of TACH is close to that of 6 LEHs spherical hohlraum with corresponding size. Its plasma-filling time is close to that of typical cylindrical ignition hohlraum. Its laser plasma interaction has as low backscattering as the outer cone of the cylindrical ignition hohlraum. Therefore, TACH combines most advantages of various hohlraums and has little predictable risk, providing an important competitive candidate for ignition hohlraum.

Sum-Frequency Generation from a Thin Cylindrical Layer

NASA Astrophysics Data System (ADS)

Shamyna, A. A.; Kapshai, V. N.

2018-01-01

In the Rayleigh-Gans-Debye approximation, we have solved the problem of the sum-frequency generation by two plane elliptically polarized electromagnetic waves from the surface of a dielectric particle of a cylindrical shape that is coated by a thin layer possessing nonlinear optical properties. The formulas that describe the sum-frequency field have been presented in the tensor and vector forms for the second-order nonlinear dielectric susceptibility tensor, which was chosen in the general form, containing chiral components. Expressions describing the sum-frequency field from the cylindrical particle ends have been obtained for the case of a nonlinear layer possessing chiral properties. Three-dimensional directivity patterns of the sum-frequency radiation have been analyzed for different combinations of parameters (angles of incidence, degrees of ellipticity, orientations of polarization ellipses, cylindrical particle dimensions). The mathematical properties of the spatial distribution functions of the sum-frequency field, which characterize the symmetry of directivity patterns, have been revealed.

Space charge effect in the spiral inflector

NASA Astrophysics Data System (ADS)

Toprek, Dragan

2000-10-01

This paper presents the analytical and numerical theory of the space charge effects in the beam in the spiral inflector. It considers a simplified model of a "straight" cylindrical beam by using a uniform particle distribution. Numerical results represented in this paper are obtained by using a modified version of the program CASINO.

Relativistic electron motion in cylindrical waveguide with strong guiding magnetic field and high power microwave

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Ping; Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an 710024; Sun, Jun

2015-06-15

In O-type high power microwave (HPM) devices, the annular relativistic electron beam is constrained by a strong guiding magnetic field and propagates through an interaction region to generate HPM. Some papers believe that the E × B drift of electrons may lead to beam breakup. This paper simplifies the interaction region with a smooth cylindrical waveguide to research the radial motion of electrons under conditions of strong guiding magnetic field and TM{sub 01} mode HPM. The single-particle trajectory shows that the radial electron motion presents the characteristic of radial guiding-center drift carrying cyclotron motion. The radial guiding-center drift is spatiallymore » periodic and is dominated by the polarization drift, not the E × B drift. Furthermore, the self fields of the beam space charge can provide a radial force which may pull electrons outward to some extent but will not affect the radial polarization drift. Despite the radial drift, the strong guiding magnetic field limits the drift amplitude to a small value and prevents beam breakup from happening due to this cause.« less

Transient fields produced by a cylindrical electron beam flowing through a plasma

NASA Astrophysics Data System (ADS)

Firpo, Marie-Christine

2012-10-01

Fast ignition schemes (FIS) for inertial confinement fusion should involve in their final stage the interaction of an ignition beam composed of MeV electrons laser generated at the critical density surface with a dense plasma target. In this study, the out-of-equilibrium situation in which an initially sharp-edged cylindrical electron beam, that could e.g. model electrons flowing within a wire [1], is injected into a plasma is considered. A detailed computation of the subsequently produced magnetic field is presented [2]. The control parameter of the problem is shown to be the ratio of the beam radius to the electron skin depth. Two alternative ways to address analytically the problem are considered: one uses the usual Laplace transform approach, the other one involves Riemann's method in which causality conditions manifest through some integrals of triple products of Bessel functions.[4pt] [1] J.S. Green et al., Surface heating of wire plasmas using laser-irradiated cone geometries, Nature Physics 3, 853--856 (2007).[0pt] [2] M.-C. Firpo, http://hal.archives-ouvertes.fr/hal-00695629, to be published (2012).

TU-CD-207-10: Dedicated Cone-Beam Breast CT: Design of a 3-D Beam-Shaping Filter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vedantham, S; Shi, L; Karellas, A

2015-06-15

Purpose: To design a 3 -D beam-shaping filter for cone-beam breast CT for equalizing x-ray photon fluence incident on the detector along both fan and cone angle directions. Methods: The 3-D beam-shaping filter was designed as the sum of two filters: a bow-tie filter assuming cylindrical breast and a 3D difference filter equivalent to the difference in projected thickness between the cylinder and the real breast. Both filters were designed with breast-equivalent material and converted to Al for the targeted x-ray spectrum. The bow-tie was designed for the largest diameter cylindrical breast by determining the fan-angle dependent path-length and themore » filter thickness needed to equalize the fluence. A total of 23,760 projections (180 projections of 132 binary breast CT volumes) were averaged, scaled for the largest breast, and subtracted from the projection of the largest diameter cylindrical breast to provide the 3D difference filter. The 3 -D beam shaping filter was obtained by summing the two filters. Numerical simulations with semi-ellipsoidal breasts of 10–18 cm diameter (chest-wall to nipple length=0.75 x diameter) were conducted to evaluate beam equalization. Results: The proposed 3-D beam-shaping filter showed a 140% -300% improvement in equalizing the photon fluence along the chest-wall to nipple (cone-angle) direction compared to a bow-tie filter. The improvement over bow-tie filter was larger for breasts with longer chest-wall to nipple length. Along the radial (fan-angle) direction, the performance of the 3-D beam shaping filter was marginally better than the bow-tie filter, with 4%-10% improvement in equalizing the photon fluence. For a ray traversing the chest-wall diameter of the breast, the filter transmission ratio was >0.95. Conclusion: The 3-D beam shaping filter provided substantial advantage over bow-tie filter in equalizing the photon fluence along the cone-angle direction. In conjunction with a 2-axis positioner, the filter can accommodate breasts of varying dimensions and chest-wall inclusion. Supported in part by NIH R01 CA128906 and R21 CA134128. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or NCI.« less

Design and measurement of a TE{sub 13} input converter for high order mode gyrotron travelling wave amplifiers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yan; Liu, Guo, E-mail: liuguo@uestc.edu.cn; Shu, Guoxiang

2016-03-15

A technique to launch a circular TE{sub 13} mode to interact with the helical electron beam of a gyrotron travelling wave amplifier is proposed and verified by simulation and cold test in this paper. The high order (HOM) TE{sub 13} mode is excited by a broadband Y-type power divider with the aid of a cylindrical waveguide system. Using grooves and convex strips loaded at the lateral planes of the output cylindrical waveguide, the electric fields of the potential competing TE{sub 32} and TE{sub 71} modes are suppressed to allow the transmission of the dominant TE{sub 13} mode. The converter performancemore » for different structural dimensions of grooves and convex strips is studied in detail and excellent results have been achieved. Simulation predicts that the average transmission is ∼−1.8 dB with a 3 dB bandwidth of 7.2 GHz (91.5–98.7 GHz) and port reflection is less than −15 dB. The conversion efficiency to the TE{sub 32} and TE{sub 71} modes are, respectively, under −15 dB and −24 dB in the operating frequency band. Such an HOM converter operating at W-band has been fabricated and cold tested with the radiation boundary. Measurement from the vector network analyzer cold test and microwave simulations show a good reflection performance for the converter.« less

Apparatus for and method of correcting for astigmatism in a light beam reflected off of a light reflecting surface

DOEpatents

Sawicki, R.H.; Sweatt, W.

1985-11-21

A technique for adjustably correcting for astigmatism in a light beam is disclosed herein. This technique defines a flat, rectangular light reflecting surface having opposite reinforced side edges and which is resiliently bendable, to a limited extent, into different concave and/or convex cylindrical curvatures about a particular axis and provides for adjustably bending the light reflecting surface into one of different curvatures depending upon the astigmatism to be corrected and for fixedly maintaining the curvature selected. In the embodiment disclosed, the light reflecting surface is adjustably bendable into the selected cylindrical curvature by application of a particular bending moment to the reinforced side edges of the light reflecting surface.

Apparatus for and method of correcting for astigmatism in a light beam reflected off of a light reflecting surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sawicki, R.H.; Sweatt, W.

1985-11-21

A technique for adjustably correcting for astigmatism in a light beam is disclosed herein. This technique defines a flat, rectangular light reflecting surface having opposite reinforced side edges and which is resiliently bendable, to a limited extent, into different concave and/or convex cylindrical curvatures about a particular axis and provides for adjustably bending the light reflecting surface into one of different curvatures depending upon the astigmatism to be corrected and for fixedly maintaining the curvature selected. In the embodiment disclosed, the light reflecting surface is adjustably bendable into the selected cylindrical curvature by application of a particular bending moment tomore » the reinforced side edges of the light reflecting surface.« less

Recommended coordinate systems for thin spherocylindrical lenses.

PubMed

Deal, F C; Toop, J

1993-05-01

Because the set of thin spherocylindrical lenses forms a vector space, any such lens can be expressed in terms of its cartesian coordinates with respect to whatever set of basis lenses we may choose. Two types of cartesian coordinate systems have become prominent, those having coordinates associated with the lens power matrix and those having coordinates associated with the Humphrey Vision Analyzer. This paper emphasizes the value of a particular cartesian coordinate system of the latter type, and the cylindrical coordinate system related to it, by showing how it can simplify the trigonometry of adding lenses and how it preserves symmetry in depicting the sets of all spherical lenses, all Jackson crossed-cylinders, and all cylindrical lenses. It also discusses appropriate coordinates for keeping statistics on lenses and shows that an easy extension of the lens vector space to include general optical systems is not possible.

Comparison of the IAEA TRS-398 and AAPM TG-51 absorbed dose to water protocols in the dosimetry of high-energy photon and electron beams

NASA Astrophysics Data System (ADS)

Saiful Huq, M.; Andreo, Pedro; Song, Haijun

2001-11-01

The International Atomic Energy Agency (IAEA TRS-398) and the American Association of Physicists in Medicine (AAPM TG-51) have published new protocols for the calibration of radiotherapy beams. These protocols are based on the use of an ionization chamber calibrated in terms of absorbed dose to water in a standards laboratory's reference quality beam. This paper compares the recommendations of the two protocols in two ways: (i) by analysing in detail the differences in the basic data included in the two protocols for photon and electron beam dosimetry and (ii) by performing measurements in clinical photon and electron beams and determining the absorbed dose to water following the recommendations of the two protocols. Measurements were made with two Farmer-type ionization chambers and three plane-parallel ionization chamber types in 6, 18 and 25 MV photon beams and 6, 8, 10, 12, 15 and 18 MeV electron beams. The Farmer-type chambers used were NE 2571 and PTW 30001, and the plane-parallel chambers were a Scanditronix-Wellhöfer NACP and Roos, and a PTW Markus chamber. For photon beams, the measured ratios TG-51/TRS-398 of absorbed dose to water Dw ranged between 0.997 and 1.001, with a mean value of 0.999. The ratios for the beam quality correction factors kQ were found to agree to within about +/-0.2% despite significant differences in the method of beam quality specification for photon beams and in the basic data entering into kQ. For electron beams, dose measurements were made using direct ND,w calibrations of cylindrical and plane-parallel chambers in a 60Co gamma-ray beam, as well as cross-calibrations of plane-parallel chambers in a high-energy electron beam. For the direct ND,w calibrations the ratios TG-51/TRS-398 of absorbed dose to water Dw were found to lie between 0.994 and 1.018 depending upon the chamber and electron beam energy used, with mean values of 0.996, 1.006, and 1.017, respectively, for the cylindrical, well-guarded and not well-guarded plane-parallel chambers. The Dw ratios measured for the cross-calibration procedures varied between 0.993 and 0.997. The largest discrepancies for electron beams between the two protocols arise from the use of different data for the perturbation correction factors pwall and pdis of cylindrical and plane-parallel chambers, all in 60Co. A detailed analysis of the reasons for the discrepancies is made which includes comparing the formalisms, correction factors and the quantities in the two protocols.

Optical Bench Interferometer - From LISA Pathfinder to NGO/eLISA

NASA Astrophysics Data System (ADS)

Taylor, A.; d'Arcio, L.; Bogenstahl, J.; Danzmann, K.; Diekmann, C.; Fitzsimons, E. D.; Gerberding, O.; Heinzel, G.; Hennig, J.-S.; Hogenhuis, H.; Killow, C. J.; Lieser, M.; Lucarelli, S.; Nikolov, S.; Perreur-Lloyd, M.; Pijnenburg, J.; Robertson, D. I.; Sohmer, A.; Tröbs, M.; Ward, H.; Weise, D.

2013-01-01

We present a short summary of some optical bench construction and alignment developments that build on experience gained during the LISA Pathfinder optical bench assembly. These include evolved fibre injectors, a new beam vector measurement system, and thermally stable mounting hardware. The beam vector measurement techniques allow the alignment of beams to targets with absolute accuracy of a few microns and 20 microradians. We also describe a newly designed ultra-low-return beam dump that is expected to be a crucial element in the control of ghost beams on the optical benches.

Comment on 'Effects of magnetic field gradient on ion beam current in cylindrical Hall ion source' [J. Appl. Phys. 102, 123305 (2007)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raitses, Y.; Smirnov, A.; Fisch, N. J.

It is argued that the key difference in the cylindrical Hall thruster (CHT) as compared to the end-Hall ion source cannot be exclusively attributed to the magnetic field topology [Tang et al., J. Appl. Phys. 102, 123305 (2007)]. With a similar mirror-type topology, the CHT configuration provides the electric field with nearly equipotential magnetic field surfaces and a better suppression of the electron cross-field transport, as compared to both the end-Hall ion source and the cylindrical Hall ion source of [Tang et al., J. Appl. Phys. 102, 123305 (2007)].

Scattering of Airy elastic sheets by a cylindrical cavity in a solid.

PubMed

Mitri, F G

2017-11-01

The prediction of the elastic scattering by voids (and cracks) in materials is an important process in structural health monitoring, phononic crystals, metamaterials and non-destructive evaluation/imaging to name a few examples. Earlier analytical theories and numerical computations considered the elastic scattering by voids in plane waves of infinite extent. However, current research suggesting the use of (limited-diffracting, accelerating and self-healing) Airy acoustical-sheet beams for non-destructive evaluation or imaging applications in elastic solids requires the development of an improved analytical formalism to predict the scattering efficiency used as a priori information in quantitative material characterization. Based on the definition of the time-averaged scattered power flow density, an analytical expression for the scattering efficiency of a cylindrical empty cavity (i.e., void) encased in an elastic medium is derived for compressional and normally-polarized shear-wave Airy beams. The multipole expansion method using cylindrical wave functions is utilized. Numerical computations for the scattering energy efficiency factors for compressional and shear waves illustrate the analysis with particular emphasis on the Airy beam parameters and the non-dimensional frequency, for various elastic materials surrounding the cavity. The ratio of the compressional to the shear wave speed stimulates the generation of elastic resonances, which are manifested as a series of peaks in the scattering efficiency plots. The present analysis provides an improved method for the computations of the scattering energy efficiency factors using compressional and shear-wave Airy beams in elastic materials as opposed to plane waves of infinite extent. Copyright © 2017 Elsevier B.V. All rights reserved.

Modulation transfer function assessment in parallel beam and fan beam collimators with square and cylindrical holes.

PubMed

Khorshidi, Abdollah; Ashoor, Mansour

2014-05-01

This study investigates modulation transfer function (MTF) in parallel beam (PB) and fan beam (FB) collimators using the Monte Carlo method with full width at half maximum (FWHM), square and circular-shaped holes, and scatter and penetration (S + P) components. A regulation similar to the lead-to-air ratio was used for both collimators to estimate output data. The hole pattern was designed to compare FB by PB parameters. The radioactive source in air and in a water phantom placed in front of the collimators was simulated using MCNP5 code. The test results indicated that the square holes in PB (PBs) had better FWHM than did the cylindrical (PBc) holes. In contrast, the cylindrical holes in the FB (FBc) had better FWHM than the square holes. In general, the resolution of FBc was better than that of the PBc in air and scatter mediums. The S + P decreased for all collimators as the distance from the source to the collimator surface (z) increased. The FBc had a lower S + P than FBs, but PBc had a higher S + P than PBs. Of the FB and PB collimators with the identical hole shapes, PBs had a smaller S + P than FBs, and FBc had a smaller S + P than PBc. The MTF value for the FB was greater than for the PB and had increased spatial frequency; the FBc had higher MTF than the FBs and PB collimators. Estimating the FB using PB parameters and diverse hole shapes may be useful in collimator design to improve the resolution and efficiency of SPECT images.

Vector calculus in non-integer dimensional space and its applications to fractal media

NASA Astrophysics Data System (ADS)

Tarasov, Vasily E.

2015-02-01

We suggest a generalization of vector calculus for the case of non-integer dimensional space. The first and second orders operations such as gradient, divergence, the scalar and vector Laplace operators for non-integer dimensional space are defined. For simplification we consider scalar and vector fields that are independent of angles. We formulate a generalization of vector calculus for rotationally covariant scalar and vector functions. This generalization allows us to describe fractal media and materials in the framework of continuum models with non-integer dimensional space. As examples of application of the suggested calculus, we consider elasticity of fractal materials (fractal hollow ball and fractal cylindrical pipe with pressure inside and outside), steady distribution of heat in fractal media, electric field of fractal charged cylinder. We solve the correspondent equations for non-integer dimensional space models.

Cylindrical angular spectrum using Fourier coefficients of point light source and its application to fast hologram calculation.

PubMed

Oh, Seungtaik; Jeong, Il Kwon

2015-11-16

We will introduce a new simple analytic formula of the Fourier coefficient of the 3D field distribution of a point light source to generate a cylindrical angular spectrum which captures the object wave in 360° in the 3D Fourier space. Conceptually, the cylindrical angular spectrum can be understood as a cylindrical version of the omnidirectional spectral approach of Sando et al. Our Fourier coefficient formula is based on an intuitive observation that a point light radiates uniformly in all directions. Our formula is defined over all frequency vectors lying on the entire sphere in the 3D Fourier space and is more natural and computationally more efficient for all around recording of the object wave than that of the previous omnidirectional spectral method. A generalized frequency-based occlusion culling method for an arbitrary complex object is also proposed to enhance the 3D quality of a hologram. As a practical application of the cylindrical angular spectrum, an interactive hologram example is presented together with implementation details.

Elasticity of fractal materials using the continuum model with non-integer dimensional space

NASA Astrophysics Data System (ADS)

Tarasov, Vasily E.

2015-01-01

Using a generalization of vector calculus for space with non-integer dimension, we consider elastic properties of fractal materials. Fractal materials are described by continuum models with non-integer dimensional space. A generalization of elasticity equations for non-integer dimensional space, and its solutions for the equilibrium case of fractal materials are suggested. Elasticity problems for fractal hollow ball and cylindrical fractal elastic pipe with inside and outside pressures, for rotating cylindrical fractal pipe, for gradient elasticity and thermoelasticity of fractal materials are solved.

Apparatus for and method of correcting for astigmatism in a light beam reflected off of a light reflecting surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sawicki, R.H.; Sweatt, W.

1987-03-03

An apparatus is described for correcting for astigmatism in a light beam reflected off of a light reflecting surface, comprising: (a) a first means defining a flat, rectangular light reflecting surface which is resiliently bendable, to a limited extent, into different concave and/or convex cylindrical curvatures about a particular axis. The first means is configured so that the light reflecting surface can be adjustably bent into the selected cylindrical curvature by applying a particular bending moment to the first means with respect to the surface, depending upon the curvature desired. The first means includes an integrally formed body member havingmore » a main plate-like segment including a front fact defining the light reflecting surface and a pair of spaced-apart flange segments extending rearwardly of the main segment; and (b) second means acting on the first means for adjustably bending the light reflecting surface into a particular selected one of the different cylindrical curvatures, depending upon the astigmatism to be corrected for.« less

Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Obst, Lieselotte; Gode, Sebastian; Rehwald, Martin

We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (Ø 5 μm) and planar (20 μm × 2 μm). In bothmore » cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. As a result, this is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions.« less

Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets

DOE PAGES

Obst, Lieselotte; Gode, Sebastian; Rehwald, Martin; ...

2017-08-31

We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (Ø 5 μm) and planar (20 μm × 2 μm). In bothmore » cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. As a result, this is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions.« less

Sonar Imaging of Elastic Fluid-Filled Cylindrical Shells.

NASA Astrophysics Data System (ADS)

Dodd, Stirling Scott

1995-01-01

Previously a method of describing spherical acoustic waves in cylindrical coordinates was applied to the problem of point source scattering by an elastic infinite fluid -filled cylindrical shell (S. Dodd and C. Loeffler, J. Acoust. Soc. Am. 97, 3284(A) (1995)). This method is applied to numerically model monostatic oblique incidence scattering from a truncated cylinder by a narrow-beam high-frequency imaging sonar. The narrow beam solution results from integrating the point source solution over the spatial extent of a line source and line receiver. The cylinder truncation is treated by the method of images, and assumes that the reflection coefficient at the truncation is unity. The scattering form functions, calculated using this method, are applied as filters to a narrow bandwidth, high ka pulse to find the time domain scattering response. The time domain pulses are further processed and displayed in the form of a sonar image. These images compare favorably to experimentally obtained images (G. Kaduchak and C. Loeffler, J. Acoust. Soc. Am. 97, 3289(A) (1995)). The impact of the s_{ rm o} and a_{rm o} Lamb waves is vividly apparent in the images.

Design and fabrication of optical homogenizer with micro structure by injection molding process

NASA Astrophysics Data System (ADS)

Chen, C.-C. A.; Chang, S.-W.; Weng, C.-J.

2008-08-01

This paper is to design and fabricate an optical homogenizer with hybrid design of collimator, toroidal lens array, and projection lens for beam shaping of Gaussian beam into uniform cylindrical beam. TracePro software was used to design the geometry of homogenizer and simulation of injection molding was preceded by Moldflow MPI to evaluate the mold design for injection molding process. The optical homogenizer is a cylindrical part with thickness 8.03 mm and diameter 5 mm. The micro structure of toroidal array has groove height designed from 12 μm to 99 μm. An electrical injection molding machine and PMMA (n= 1.4747) were selected to perform the experiment. Experimental results show that the optics homogenizer has achieved the transfer ratio of grooves (TRG) as 88.98% and also the optical uniformity as 68% with optical efficiency as 91.88%. Future study focuses on development of an optical homogenizer for LED light source.

Single lens laser beam shaper

DOEpatents

Liu, Chuyu [Newport News, VA; Zhang, Shukui [Yorktown, VA

2011-10-04

A single lens bullet-shaped laser beam shaper capable of redistributing an arbitrary beam profile into any desired output profile comprising a unitary lens comprising: a convex front input surface defining a focal point and a flat output portion at the focal point; and b) a cylindrical core portion having a flat input surface coincident with the flat output portion of the first input portion at the focal point and a convex rear output surface remote from the convex front input surface.

Electron beam extraction on plasma cathode electron sources system

NASA Astrophysics Data System (ADS)

Purwadi, Agus; Taufik, M., Lely Susita R.; Suprapto, Saefurrochman, H., Anjar A.; Wibowo, Kurnia; Aziz, Ihwanul; Siswanto, Bambang

2017-03-01

ELECTRON BEAM EXTRACTION ON PLASMA CATHODE ELECTRON SOURCES SYSTEM. The electron beam extraction through window of Plasma Generator Chamber (PGC) for Pulsed Electron Irradiator (PEI) device and simulation of plasma potential has been studied. Plasma electron beam is extracted to acceleration region for enlarging their power by the external accelerating high voltage (Vext) and then it is passed foil window of the PEI for being irradiated to any target (atmospheric pressure). Electron beam extraction from plasma surface must be able to overcome potential barrier at the extraction window region which is shown by estimate simulation (Opera program) based on data of plasma surface potential of 150 V with Ueks values are varied by 150 kV, 175 kV and 200 kV respectively. PGC is made of 304 stainless steel with cylindrical shape in 30 cm of diameter, 90 cm length, electrons extraction window as many as 975 holes on the area of (15 × 65) cm2 with extraction hole cell in 0.3 mm of radius each other, an cylindrical shape IEP chamber is made of 304 stainless steel in 70 cm diameter and 30 cm length. The research result shown that the acquisition of electron beam extraction current depends on plasma parameters (electron density ne, temperature Te), accelerating high voltage Vext, the value of discharge parameter G, anode area Sa, electron extraction window area Se and extraction efficiency value α.

Monte Carlo simulation for scanning technique with scattering foil free electron beam: A proof of concept study

PubMed Central

Sung, Wonmo; Park, Jong In; Kim, Jung-in; Carlson, Joel; Ye, Sung-Joon

2017-01-01

This study investigated the potential of a newly proposed scattering foil free (SFF) electron beam scanning technique for the treatment of skin cancer on the irregular patient surfaces using Monte Carlo (MC) simulation. After benchmarking of the MC simulations, we removed the scattering foil to generate SFF electron beams. Cylindrical and spherical phantoms with 1 cm boluses were generated and the target volume was defined from the surface to 5 mm depth. The SFF scanning technique with 6 MeV electrons was simulated using those phantoms. For comparison, volumetric modulated arc therapy (VMAT) plans were also generated with two full arcs and 6 MV photon beams. When the scanning resolution resulted in a larger separation between beams than the field size, the plan qualities were worsened. In the cylindrical phantom with a radius of 10 cm, the conformity indices, homogeneity indices and body mean doses of the SFF plans (scanning resolution = 1°) vs. VMAT plans were 1.04 vs. 1.54, 1.10 vs. 1.12 and 5 Gy vs. 14 Gy, respectively. Those of the spherical phantom were 1.04 vs. 1.83, 1.08 vs. 1.09 and 7 Gy vs. 26 Gy, respectively. The proposed SFF plans showed superior dose distributions compared to the VMAT plans. PMID:28493940

Monte Carlo simulation for scanning technique with scattering foil free electron beam: A proof of concept study.

PubMed

Sung, Wonmo; Park, Jong In; Kim, Jung-In; Carlson, Joel; Ye, Sung-Joon; Park, Jong Min

2017-01-01

This study investigated the potential of a newly proposed scattering foil free (SFF) electron beam scanning technique for the treatment of skin cancer on the irregular patient surfaces using Monte Carlo (MC) simulation. After benchmarking of the MC simulations, we removed the scattering foil to generate SFF electron beams. Cylindrical and spherical phantoms with 1 cm boluses were generated and the target volume was defined from the surface to 5 mm depth. The SFF scanning technique with 6 MeV electrons was simulated using those phantoms. For comparison, volumetric modulated arc therapy (VMAT) plans were also generated with two full arcs and 6 MV photon beams. When the scanning resolution resulted in a larger separation between beams than the field size, the plan qualities were worsened. In the cylindrical phantom with a radius of 10 cm, the conformity indices, homogeneity indices and body mean doses of the SFF plans (scanning resolution = 1°) vs. VMAT plans were 1.04 vs. 1.54, 1.10 vs. 1.12 and 5 Gy vs. 14 Gy, respectively. Those of the spherical phantom were 1.04 vs. 1.83, 1.08 vs. 1.09 and 7 Gy vs. 26 Gy, respectively. The proposed SFF plans showed superior dose distributions compared to the VMAT plans.

Vector spherical quasi-Gaussian vortex beams

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2014-02-01

Model equations for describing and efficiently computing the radiation profiles of tightly spherically focused higher-order electromagnetic beams of vortex nature are derived stemming from a vectorial analysis with the complex-source-point method. This solution, termed as a high-order quasi-Gaussian (qG) vortex beam, exactly satisfies the vector Helmholtz and Maxwell's equations. It is characterized by a nonzero integer degree and order (n,m), respectively, an arbitrary waist w0, a diffraction convergence length known as the Rayleigh range zR, and an azimuthal phase dependency in the form of a complex exponential corresponding to a vortex beam. An attractive feature of the high-order solution is the rigorous description of strongly focused (or strongly divergent) vortex wave fields without the need of either the higher-order corrections or the numerically intensive methods. Closed-form expressions and computational results illustrate the analysis and some properties of the high-order qG vortex beams based on the axial and transverse polarization schemes of the vector potentials with emphasis on the beam waist.

Spatial Combining of Laser-Diode Beams for Pumping an NPRO

NASA Technical Reports Server (NTRS)

Gelsinger, Paul; Liu, Duncan; Mulder, Jerry; Aguayo, Francisco

2008-01-01

A free-space optical beam combiner now undergoing development makes it possible to use the outputs of multiple multimode laser diodes to pump a neodymium-doped yttrium aluminum garnet (Nd:YAG) non-planar ring oscillator (NPRO) laser while ensuring that the laser operates at only a single desired frequency. Heretofore, a Nd:YAG NPRO like the present one has been pumped by a single multimode laser-diode beam delivered via an optical fiber. It would be desirable to use multiple pump laser diodes to increase reliability beyond that obtainable from a single pump laser diode. However, as explained in this article, simplistically coupling multiple multimode laser-diode beams through a fiber-optic combiner would entail a significant reduction in coupling efficiency, and lasing would occur at one or more other frequencies in addition to the single desired frequency. To minimize coupling loss, one must ensure that the NA (approximately equal to 0.3) of the combined laser-diode beams is less than the NA of the fiber. The A(Omega) of the laser-diode beam in the slow-axis plane is 1/1.3 as large as that of the fiber. This A(Omega) is small enough to enable efficient coupling of light into the optical fiber, but too large for combining of beams in the slow-axis plane. Therefore, a pair of cylindrical lenses is used to cancel the slow-axis plane magnification introduced by the on-cylindrical lenses used to effect magnification in the fast-axis plane.

Vector Beam Polarization State Spectrum Analyzer.

PubMed

Moreno, Ignacio; Davis, Jeffrey A; Badham, Katherine; Sánchez-López, María M; Holland, Joseph E; Cottrell, Don M

2017-05-22

We present a proof of concept for a vector beam polarization state spectrum analyzer based on the combination of a polarization diffraction grating (PDG) and an encoded harmonic q-plate grating (QPG). As a result, a two-dimensional polarization diffraction grating is formed that generates six different q-plate channels with topological charges from -3 to +3 in the horizontal direction, and each is split in the vertical direction into the six polarization channels at the cardinal points of the corresponding higher-order Poincaré sphere. Consequently, 36 different channels are generated in parallel. This special polarization diffractive element is experimentally demonstrated using a single phase-only spatial light modulator in a reflective optical architecture. Finally, we show that this system can be used as a vector beam polarization state spectrum analyzer, where both the topological charge and the state of polarization of an input vector beam can be simultaneously determined in a single experiment. We expect that these results would be useful for applications in optical communications.

Design of magnets inside cylindrical superconducting shields

NASA Technical Reports Server (NTRS)

Rigby, K. W.

1988-01-01

The design of magnets inside closed, cylindrical, superconducting shields is discussed. The Green function is given for the magnetic vector potential for cylindrically symmetric currents inside such a shield. The magnetic field everywhere inside the shield can be obtained from this function, which includes the effects of the induced shield currents exactly. The field is given for a thin solenoid as an example and the convergence of the series solution for this case is discussed. The shield can significantly reduce the strength and improve the homogeneity of a magnet. The improvement in homogeneity is of particular importance in the design of correction coils. These effects, and the maximum field on the shield, are examined for a typical solenoid. The results given are also useful, although not exact, for long shields with one or two open ends.

Feasibility of Using Lateral Mode Coupling Method for a Large Scale Ultrasound Phased Array for Noninvasive Transcranial Therapy

PubMed Central

Song, Junho; Hynynen, Kullervo

2009-01-01

A hemispherical-focused, ultrasound phased array was designed and fabricated using 1372 cylindrical piezoelectric transducers that utilize lateral coupling for noninvasive transcranial therapy. The cylindrical transducers allowed the electrical impedance to be reduced by at least an order of magnitude, such that effective operation could be achieved without electronic matching circuits. In addition, the transducer elements generated the maximum acoustic average surface intensity of 27 W/cm2. The array, driven at the low (306 kHz) or high frequency (840 kHz), achieved excellent focusing through an ex vivo human skull and an adequate beam steering range for clinical brain treatments. It could electronically steer the ultrasound beam over cylindrical volumes of 100 mm in diameter and 60 mm in height at 306 kHz, and 30-mm in diameter and 30-mm in height at 840 kHz. A scanning laser vibrometer was used to investigate the radial and length mode vibrations of the element. The maximum pressure amplitudes through the skull at the geometric focus were predicted to be 5.5 MPa at 306 kHz and 3.7 MPa at 840 kHz for RF power of 1 W on each element. This is the first study demonstrating the feasibility of using cylindrical transducer elements and lateral coupling in construction of ultrasound phased arrays. PMID:19695987

Optical image security using Stokes polarimetry of spatially variant polarized beam

NASA Astrophysics Data System (ADS)

Fatima, Areeba; Nishchal, Naveen K.

2018-06-01

We propose a novel security scheme that uses vector beam characterized by the spatially variant polarization distribution. A vector beam is so generated that its helical components carry tailored phases corresponding to the image/images that is/are to be encrypted. The tailoring of phase has been done by employing the modified Gerchberg-Saxton algorithm for phase retrieval. Stokes parameters for the final vector beam is evaluated and is used to construct the ciphertext and one of the keys. The advantage of the proposed scheme is that it generates real ciphertext and keys which are easier to transmit and store than complex quantities. Moreover, the known plaintext attack is not applicable to this system. As a proof-of-concept, simulation results have been presented for securing single and double gray-scale images.

Structuring Light to Manipulate Multipolar Resonances for Metamaterial Applications

NASA Astrophysics Data System (ADS)

Das, Tanya

Multipolar electromagnetic phenomena in sub-wavelength resonators are at the heart of metamaterial science and technology. Typically, researchers engineer multipolar light-matter interactions by modifying the size, shape, and composition of the resonators. Here, we instead engineer multipolar interactions by modifying properties of the incident radiation. In this dissertation, we propose a new framework for determining the scattering response of resonators based on properties of the local excitation field. First, we derive an analytical theory to determine the scattering response of spherical nanoparticles under any type of illumination. Using this theory, we demonstrate the ability to drastically manipulate the scattering properties of a spherical nanoparticle by varying the illumination and demonstrate excitation of a longitudinal quadrupole mode that cannot be accessed with conventional illumination. Next, we investigate the response of dielectric dimer structures illuminated by cylindrical vector beams. Using finite-difference time-domain simulations, we demonstrate significant modification of the scattering spectra of dimer antennas and reveal how the illumination condition gives rise to these spectra through manipulation of electric and magnetic mode hybridization. Finally, we present a simple and efficient numerical simulation based on local field principles for extracting the multipolar response of any resonator under illumination by structured light. This dissertation enhances the understanding of fundamental light-matter interactions in metamaterials and lays the foundation for researchers to identify, quantify, and manipulate multipolar light-matter interactions through optical beam engineering.

System analysis of wavelength beam combining of high-power diode lasers for photoacoustic endoscopy

NASA Astrophysics Data System (ADS)

Leggio, Luca; Gallego, Daniel C.; Gawali, Sandeep B.; Sánchez, Miguel; Rodriguez, Sergio; Osiński, Marek; Sacher, Joachim; Carpintero, Guillermo; Lamela, Horacio

2016-04-01

This paper, originally published on 27 April 2016, was replaced with a corrected/revised version on 8 June 2016. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance. The purpose of wavelength-beam combining (WBC) is to improve the output power of a multi-wavelength laser system while maintaining the quality of the combined beam. This technique has been primarily proposed for industrial applications, such as metal cutting and soldering, which require optical peak power between kilowatts and megawatts. In order to replace the bulkier solid-state lasers, we propose to use the WBC technique for photoacoustic (PA) applications, where a multi-wavelength focused beam with optical peak power between hundreds of watts up to several kilowatts is necessary to penetrate deeply into biological tissues. In this work we present an analytical study about the coupling of light beams emitted by diode laser bars at 808 nm, 880 nm, 910 nm, 940 nm, and 980 nm into a < 600-μm core-diameter optical fiber for PA endoscopy. In order to achieve an efficient coupling it is necessary to collimate the beams in both fast and slow axes by means of cylindrical lenses and to use partial reflection mirrors at 45° tilt. We show an example of beam collimation using cylindrical lenses in both fast and slow axes. In a real PA scenario, the resulting beam should have a sufficient peak power to generate significant PA signals from a turbid tissue>.

Vector vortex beam generation with dolphin-shaped cell meta-surface.

PubMed

Yang, Zhuo; Kuang, Deng-Feng; Cheng, Fang

2017-09-18

We present a dolphin-shaped cell meta-surface, which is a combination of dolphin-shaped metallic cells and dielectric substrate, for vector vortex beam generation with the illumination of linearly polarized light. Surface plasmon polaritons are excited at the boundary of the metallic cells, then guided by the metallic structures, and finally squeezed to the tips to form highly localized strong electromagnetic fields, which generate the intensity of vector vortex beams at z component. Synchronously, the abrupt phase change produced by the meta-surface is utilized to explain the vortex phase generated by elements. The new kind of structure can be utilized for communication, bioscience, and materiality.

Knudsen torque on heated micro beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Qi; Liang, Tengfei; Ye, Wenjing

Thermally induced mechanical loading has been shown to have significant effects on micro/nano objects immersed in a gas with a non-uniform temperature field. While the majority of existing studies and related applications focus on forces, we investigate the torque, and thus the rotational motion, produced by such a mechanism. Using the asymptotic analysis in the near continuum regime, the Knudsen torque acting on an asymmetrically located uniformly heated microbeam in a cold enclosure is investigated. The existence of a non-zero net torque is demonstrated. In addition, it has been found that by manipulating the system configuration, the rotational direction ofmore » the torque can be changed. Two types of rotational motion of the microbeam have been identified: the pendulum motion of a rectangular beam, and the unidirectional rotation of a cylindrical beam. A rotational frequency of 4 rpm can be achieved for the cylindrical beam with a diameter of 3μm at Kn = 0.005. Illustrated by the simulations using the direct simulation of Monte Carlo, the Knudsen torque can be much increased in the transition regime, demonstrating the potential of Knudsen torque serving as a rotation engine for micro/nano objects.« less

Research on soundproof properties of cylindrical shells of generalized phononic crystals

NASA Astrophysics Data System (ADS)

Liu, Ru; Shu, Haisheng; Wang, Xingguo

2017-04-01

Based on the previous studies, the concept of generalized phononic crystals (GPCs) is further introduced into the cylindrical shell structures in this paper. And a type of cylindrical shells of generalized phononic crystals (CS-GPCs) is constructed, the structural field and acoustic-structural coupled field of the composite cylindrical shells are examined respectively. For the structural field, the transfer matrix method of mechanical state vector is adopted to build the transfer matrix of radial waves propagating from inside to outside. For the acoustic-structural coupled field, the expressions of the acoustic transmission/reflection coefficients and the sound insulation of acoustic waves with the excitation of center line sound source are set up. And the acoustic transmission coefficient and the frequency response of sound insulation in this mode were numerical calculated. Furthermore, the theoretical analysis results are verified by using the method of combining the numerical calculation and finite element simulation. Finally, the effects of inner and outer fluid parameters on the transmission/reflection coefficients of CS-GPCs are analyzed in detail.

Two mechanisms of resonance overlapping in excitation of azimuthal surface waves by rotating relativistic electron beams

NASA Astrophysics Data System (ADS)

Girka, Igor O.; Pavlenko, Ivan V.; Thumm, Manfred

2018-05-01

Azimuthal surface waves are electromagnetic eigenwaves of cylindrical plasma-filled metallic waveguides with a stationary axial magnetic field. These waves with extraordinary polarization can effectively interact with relativistic electron beams rotating along large Larmor orbits in the gap, which separates the plasma column from the waveguide wall. Both widening the layer and increasing the beam particle density are demonstrated to cause resonance overlapping seen from the perspective of the growth rate dependence on the effective wave number.

Nonparaxial and paraxial focusing of azimuthal-variant vector beams.

PubMed

Gu, Bing; Cui, Yiping

2012-07-30

Based on the vectorial Rayleigh-Sommerfeld formulas under the weak nonparaxial approximation, we investigate the propagation behavior of a lowest-order Laguerre-Gaussian beam with azimuthal-variant states of polarization. We present the analytical expressions for the radial, azimuthal, and longitudinal components of the electric field with an arbitrary integer topological charge m focused by a nonaperturing thin lens. We illustrate the three-dimensional optical intensities, energy flux distributions, beam waists, and focal shifts of the focused azimuthal-variant vector beams under the nonparaxial and paraxial approximations.

Determining beam parameters in a storage ring with a cylindrical hodoscope using elastic proton proton scattering

NASA Astrophysics Data System (ADS)

Rohdjeß, H.; Albers, D.; Bisplinghoff, J.; Bollmann, R.; Büßer, K.; Diehl, O.; Dohrmann, F.; Engelhardt, H.-P.; Eversheim, P. D.; Gasthuber, M.; Greiff, J.; Groß, A.; Groß-Hardt, R.; Hinterberger, F.; Igelbrink, M.; Langkau, R.; Maier, R.; Mosel, F.; Müller, M.; Münstermann, M.; Prasuhn, D.; von Rossen, P.; Scheid, H.; Schirm, N.; Schwandt, F.; Scobel, W.; Trelle, H. J.; Wellinghausen, A.; Wiedmann, W.; Woller, K.; Ziegler, R.

2006-01-01

The EDDA-detector at the cooler-synchrotron COSY/Jülich has been operated with an internal CH2 fiber target to measure proton-proton elastic scattering differential cross-sections. For data analysis knowledge of beam parameters, like position, width and angle, are indispensable. We have developed a method to obtain these values with high precision from the azimuthal and polar angles of the ejectiles only, by exploiting the coplanarity of the two final-state protons with the beam and the kinematic correlation. The formalism is described and results for beam parameters obtained during beam acceleration are given.

Experimental validation of beam quality correction factors for proton beams

NASA Astrophysics Data System (ADS)

Gomà, Carles; Hofstetter-Boillat, Bénédicte; Safai, Sairos; Vörös, Sándor

2015-04-01

This paper presents a method to experimentally validate the beam quality correction factors (kQ) tabulated in IAEA TRS-398 for proton beams and to determine the kQ of non-tabulated ionization chambers (based on the already tabulated values). The method is based exclusively on ionometry and it consists in comparing the reading of two ionization chambers under the same reference conditions in a proton beam quality Q and a reference beam quality 60Co. This allows one to experimentally determine the ratio between the kQ of the two ionization chambers. In this work, 7 different ionization chamber models were irradiated under the IAEA TRS-398 reference conditions for 60Co beams and proton beams. For the latter, the reference conditions for both modulated beams (spread-out Bragg peak field) and monoenergetic beams (pseudo-monoenergetic field) were studied. For monoenergetic beams, it was found that the experimental kQ values obtained for plane-parallel chambers are consistent with the values tabulated in IAEA TRS-398; whereas the kQ values obtained for cylindrical chambers are not consistent—being higher than the tabulated values. These results support the suggestion (of previous publications) that the IAEA TRS-398 reference conditions for monoenergetic proton beams should be revised so that the effective point of measurement of cylindrical ionization chambers is taken into account when positioning the reference point of the chamber at the reference depth. For modulated proton beams, the tabulated kQ values of all the ionization chambers studied in this work were found to be consistent with each other—except for the IBA FC65-G, whose experimental kQ value was found to be 0.6% lower than the tabulated one. The kQ of the PTW Advanced Markus chamber, which is not tabulated in IAEA TRS-398, was found to be 0.997 ± 0.042 (k = 2), based on the tabulated value of the PTW Markus chamber.

Direct determination of k Q factors for cylindrical and plane-parallel ionization chambers in high-energy electron beams from 6 MeV to 20 MeV.

PubMed

Krauss, A; Kapsch, R-P

2018-02-06

For the ionometric determination of the absorbed dose to water, D w , in high-energy electron beams from a clinical accelerator, beam quality dependent correction factors, k Q , are required. By using a water calorimeter, these factors can be determined experimentally and potentially with lower standard uncertainties than those of the calculated k Q factors, which are tabulated in various dosimetry protocols. However, one of the challenges of water calorimetry in electron beams is the small measurement depths in water, together with the steep dose gradients present especially at lower energies. In this investigation, water calorimetry was implemented in electron beams to determine k Q factors for different types of cylindrical and plane-parallel ionization chambers (NE2561, NE2571, FC65-G, TM34001) in 10 cm  ×  10 cm electron beams from 6 MeV to 20 MeV (corresponding beam quality index R 50 ranging from 1.9 cm to 7.5 cm). The measurements were carried out using the linear accelerator facility of the Physikalisch-Technische Bundesanstalt. Relative standard uncertainties for the k Q factors between 0.50% for the 20 MeV beam and 0.75% for the 6 MeV beam were achieved. For electron energies above 8 MeV, general agreement was found between the relative electron energy dependencies of the k Q factors measured and those derived from the AAPM TG-51 protocol and recent Monte Carlo-based studies, as well as those from other experimental investigations. However, towards lower energies, discrepancies of up to 2.0% occurred for the k Q factors of the TM34001 and the NE2571 chamber.

Direct determination of k Q factors for cylindrical and plane-parallel ionization chambers in high-energy electron beams from 6 MeV to 20 MeV

NASA Astrophysics Data System (ADS)

Krauss, A.; Kapsch, R.-P.

2018-02-01

For the ionometric determination of the absorbed dose to water, D w, in high-energy electron beams from a clinical accelerator, beam quality dependent correction factors, k Q, are required. By using a water calorimeter, these factors can be determined experimentally and potentially with lower standard uncertainties than those of the calculated k Q factors, which are tabulated in various dosimetry protocols. However, one of the challenges of water calorimetry in electron beams is the small measurement depths in water, together with the steep dose gradients present especially at lower energies. In this investigation, water calorimetry was implemented in electron beams to determine k Q factors for different types of cylindrical and plane-parallel ionization chambers (NE2561, NE2571, FC65-G, TM34001) in 10 cm  ×  10 cm electron beams from 6 MeV to 20 MeV (corresponding beam quality index R 50 ranging from 1.9 cm to 7.5 cm). The measurements were carried out using the linear accelerator facility of the Physikalisch-Technische Bundesanstalt. Relative standard uncertainties for the k Q factors between 0.50% for the 20 MeV beam and 0.75% for the 6 MeV beam were achieved. For electron energies above 8 MeV, general agreement was found between the relative electron energy dependencies of the k Q factors measured and those derived from the AAPM TG-51 protocol and recent Monte Carlo-based studies, as well as those from other experimental investigations. However, towards lower energies, discrepancies of up to 2.0% occurred for the k Q factors of the TM34001 and the NE2571 chamber.

Focused beams of fast neutral atoms in glow discharge plasma

NASA Astrophysics Data System (ADS)

Grigoriev, S. N.; Melnik, Yu. A.; Metel, A. S.; Volosova, M. A.

2017-06-01

Glow discharge with electrostatic confinement of electrons in a vacuum chamber allows plasma processing of conductive products in a wide pressure range of p = 0.01 - 5 Pa. To assist processing of a small dielectric product with a concentrated on its surface beam of fast neutral atoms, which do not cause charge effects, ions from the discharge plasma are accelerated towards the product and transformed into fast atoms. The beam is produced using a negatively biased cylindrical or a spherical grid immersed in the plasma. Ions accelerated by the grid turn into fast neutral atoms at p > 0.1 Pa due to charge exchange collisions with gas atoms in the space charge sheaths adjoining the grid. The atoms form a diverging neutral beam and a converging beam propagating from the grid in opposite directions. The beam propagating from the concave surface of a 0.24-m-wide cylindrical grid is focused on a target within a 10-mm-wide stripe, and the beam from the 0.24-m-diameter spherical grid is focused within a 10-mm-diameter circle. At the bias voltage U = 5 kV and p ˜ 0.1 Pa, the energy of fast argon atoms is distributed continuously from zero to eU ˜ 5 keV. The pressure increase to 1 Pa results in the tenfold growth of their equivalent current and a decrease in the mean energy by an order of magnitude, which substantially raises the efficiency of material etching. Sharpening by the beam of ceramic knife-blades proved that the new method for the generation of concentrated fast atom beams can be effectively used for the processing of dielectric materials in vacuum.

The perturbation correction factors for cylindrical ionization chambers in high-energy photon beams.

PubMed

Yoshiyama, Fumiaki; Araki, Fujio; Ono, Takeshi

2010-07-01

In this study, we calculated perturbation correction factors for cylindrical ionization chambers in high-energy photon beams by using Monte Carlo simulations. We modeled four Farmer-type cylindrical chambers with the EGSnrc/Cavity code and calculated the cavity or electron fluence correction factor, P (cav), the displacement correction factor, P (dis), the wall correction factor, P (wall), the stem correction factor, P (stem), the central electrode correction factor, P (cel), and the overall perturbation correction factor, P (Q). The calculated P (dis) values for PTW30010/30013 chambers were 0.9967 +/- 0.0017, 0.9983 +/- 0.0019, and 0.9980 +/- 0.0019, respectively, for (60)Co, 4 MV, and 10 MV photon beams. The value for a (60)Co beam was about 1.0% higher than the 0.988 value recommended by the IAEA TRS-398 protocol. The P (dis) values had a substantial discrepancy compared to those of IAEA TRS-398 and AAPM TG-51 at all photon energies. The P (wall) values were from 0.9994 +/- 0.0020 to 1.0031 +/- 0.0020 for PTW30010 and from 0.9961 +/- 0.0018 to 0.9991 +/- 0.0017 for PTW30011/30012, in the range of (60)Co-10 MV. The P (wall) values for PTW30011/30012 were around 0.3% lower than those of the IAEA TRS-398. Also, the chamber response with and without a 1 mm PMMA water-proofing sleeve agreed within their combined uncertainty. The calculated P (stem) values ranged from 0.9945 +/- 0.0014 to 0.9965 +/- 0.0014, but they are not considered in current dosimetry protocols. The values were no significant difference on beam qualities. P (cel) for a 1 mm aluminum electrode agreed within 0.3% with that of IAEA TRS-398. The overall perturbation factors agreed within 0.4% with those for IAEA TRS-398.

Direct generation of vector vortex beams with switchable radial and azimuthal polarizations in a monolithic Nd:YAG microchip laser

NASA Astrophysics Data System (ADS)

He, Hong-Sen; Chen, Zhen; Dong, Jun

2017-05-01

A hollow focus lens (HFL) has been designed to effectively produce a focused annular beam for high-intensity pumping. By applying the central-dark pump beam, a monolithic Nd:YAG microchip laser without any extra optical elements is demonstrated to generate vector vortex beams with switchable radially polarized (RP) and azimuthally polarized (AP) states by easily controlling the pump power. The order and handedness of the output vortex beam remain stable during the switching of the RP and AP states. The monolithic Nd:YAG microchip laser provides a new laser source for applications such as material processing and optical manipulation.

Electrostatic plasma lens for focusing negatively charged particle beams.

PubMed

Goncharov, A A; Dobrovolskiy, A M; Dunets, S M; Litovko, I V; Gushenets, V I; Oks, E M

2012-02-01

We describe the current status of ongoing research and development of the electrostatic plasma lens for focusing and manipulating intense negatively charged particle beams, electrons, and negative ions. The physical principle of this kind of plasma lens is based on magnetic isolation electrons providing creation of a dynamical positive space charge cloud in shortly restricted volume propagating beam. Here, the new results of experimental investigations and computer simulations of wide-aperture, intense electron beam focusing by plasma lens with positive space charge cloud produced due to the cylindrical anode layer accelerator creating a positive ion stream towards an axis system is presented.

Effect of transverse nonuniformity of the rf field on the efficiency of microwave sources driven by linear electron beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nusinovich, G.S.; Sinitsyn, O.V.

This paper contains a simple analytical theory that allows one to evaluate the effect of transverse nonuniformity of the rf field on the interaction efficiency in various microwave sources driven by linear electron beams. The theory is, first, applied to the systems where the beams of cylindrical symmetry interact with rf fields of microwave circuits having Cartesian geometry. Also, various kinds of microwave devices driven by sheet electron beams (orotrons, clinotrons) are considered. The theory can be used for evaluating the efficiency of novel sources of coherent terahertz radiation.

Large-aperture interferometer using local reference beam

NASA Technical Reports Server (NTRS)

Howes, W. L.

1982-01-01

A large-aperture interferometer was devised by adding a local-reference-beam-generating optical system to a schlieren system. Two versions of the interferometer are demonstrated, one employing 12.7 cm (5 in.) diameter schlieren optics, the other employing 30.48 cm (12 in.) diameter parabolic mirrors in an off-axis system. In the latter configuration a cylindrical lens is introduced near the light source to correct for astigmatism. A zone plate is a satisfactory decollimating element in the reference-beam arm of the interferometer. Attempts to increase the flux and uniformity of irradiance in the reference beam by using a diffuser are discussed.

Radiation of sound from unflanged cylindrical ducts

NASA Technical Reports Server (NTRS)

Hartharan, S. L.; Bayliss, A.

1983-01-01

Calculations of sound radiated from unflanged cylindrical ducts are presented. The numerical simulation models the problem of an aero-engine inlet. The time dependent linearized Euler equations are solved from a state of rest until a harmonic solution is attained. A fourth order accurate finite difference scheme is used and solutions are obtained from a fully vectorized Cyber-203 computer program. Cases of both plane waves and spin modes are treated. Spin modes model the sound generated by a turbofan engine. Boundary conditions for both plane waves and spin modes are treated. Solutions obtained are compared with experiments conducted at NASA Langley Research Center.

Spatially varying geometric phase in classically entangled vector beams of light

NASA Astrophysics Data System (ADS)

King-Smith, Andrew; Leary, Cody

We present theoretical results describing a spatially varying geometric (Pancharatnam) phase present in vector modes of light, in which the polarization and transverse spatial mode degrees of freedom exhibit classical entanglement. We propose an experimental setup capable of characterizing this effect, in which a vector mode propagates through a Mach-Zehnder interferometer with a birefringent phase retarder present in one arm. Since the polarization state of a classically entangled light beam exhibits spatial variation across the transverse mode profile, the phase retarder gives rise to a spatially varying geometric phase in the beam propagating through it. When recombined with the reference beam from the other interferometer arm, the presence of the geometric phase is exhibited in the resulting interference pattern. We acknowledge funding from the Research Corporation for Science Advancement by means of a Cottrell College Science Award.

A method for generating double-ring-shaped vector beams

NASA Astrophysics Data System (ADS)

Huan, Chen; Xiao-Hui, Ling; Zhi-Hong, Chen; Qian-Guang, Li; Hao, Lv; Hua-Qing, Yu; Xu-Nong, Yi

2016-07-01

We propose a method for generating double-ring-shaped vector beams. A step phase introduced by a spatial light modulator (SLM) first makes the incident laser beam have a nodal cycle. This phase is dynamic in nature because it depends on the optical length. Then a Pancharatnam-Berry phase (PBP) optical element is used to manipulate the local polarization of the optical field by modulating the geometric phase. The experimental results show that this scheme can effectively create double-ring-shaped vector beams. It provides much greater flexibility to manipulate the phase and polarization by simultaneously modulating the dynamic and the geometric phases. Project supported by the National Natural Science Foundation of China (Grant No. 11547017), the Hubei Engineering University Research Foundation, China (Grant No. z2014001), and the Natural Science Foundation of Hubei Province, China (Grant No. 2014CFB578).

Apparatus for and method of correcting for astigmatism in a light beam reflected off of a light reflecting surface

DOEpatents

Sawicki, Richard H.; Sweatt, William

1987-01-01

A technique for adjustably correcting for astigmatism in a light beam is disclosed herein. This technique utilizes first means which defines a flat, rectangular light reflecting surface having opposite reinforced side edges and which is resiliently bendable, to a limited extent, into different concave and/or convex cylindrical curvatures about a particular axis and second means acting on the first means for adjustably bending the light reflecting surface into a particular selected one of the different curvatures depending upon the astigmatism to be corrected for and for fixedly maintaining the curvature selected. In the embodiment disclosed, the light reflecting surface is adjustably bendable into the selected cylindrical curvature by application of a particular bending moment to the reinforced side edges of the light reflecting surface.

Algorithms for Computing the Magnetic Field, Vector Potential, and Field Derivatives for Circular Current Loops in Cylindrical Coordinates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walstrom, Peter Lowell

A numerical algorithm for computing the field components B r and B z and their r and z derivatives with open boundaries in cylindrical coordinates for circular current loops is described. An algorithm for computing the vector potential is also described. For the convenience of the reader, derivations of the final expressions from their defining integrals are given in detail, since their derivations (especially for the field derivatives) are not all easily found in textbooks. Numerical calculations are based on evaluation of complete elliptic integrals using the Bulirsch algorithm cel. Since cel can evaluate complete elliptic integrals of a fairlymore » general type, in some cases the elliptic integrals can be evaluated without first reducing them to forms containing standard Legendre forms. The algorithms avoid the numerical difficulties that many of the textbook solutions have for points near the axis because of explicit factors of 1=r or 1=r 2 in the some of the expressions.« less

Shallow-trap-induced positive absorptive two-beam coupling 'gain' and light-induced transparency in nominally undoped barium titanate

NASA Technical Reports Server (NTRS)

Garrett, M. H.; Tayebati, P.; Chang, J. Y.; Jenssen, H. P.; Warde, C.

1992-01-01

The asymmetry of beam coupling with respect to the orientation of the polar axis in a nominally undoped barium titanate crystal is used to determine the electro-optic and absorptive 'gain' in the usual beam-coupling geometry. For small grating wave vectors, the electrooptic coupling vanishes but the absorptive coupling remains finite and positive. Positive absorptive coupling at small grating wave vectors is correlated with the light-induced transparency of the crystal described herein. The intensity and grating wave vector dependence of the electrooptic and absorptive coupling, and the light-induced transparency are consistent with a model incorporating deep and shallow levels.

Proof of concept demonstration for coherent beam pattern measurements of KID detectors

NASA Astrophysics Data System (ADS)

Davis, Kristina K.; Baryshev, Andrey M.; Jellema, Willem; Yates, Stephen J. C.; Ferrari, Lorenza; Baselmans, Jochem J. A.

2016-07-01

Here we summarize the initial results from a complex field radiation pattern measurement of a kinetic inductance detector instrument. These detectors are phase insensitive and have thus been limited to scalar, or amplitude-only, beam measurements. Vector beam scans, of both amplitude and phase, double the information received in comparison to scalar beam scans. Scalar beam measurements require multiple scans at varying distances along the optical path of the receiver to fully constrain the divergence angle of the optical system and locate the primary focus. Vector scans provide this information with a single scan, reducing the total measurement time required for new systems and also limiting the influence of system instabilities. The vector scan can be taken at any point along the optical axis of the system including the near-field, which makes beam measurements possible for large systems at high frequencies where these measurements may be inconceivable to be tested in-situ. Therefore, the methodology presented here should enable common heterodyne analysis for direct detector instruments. In principle, this coherent measurement strategy allows phase dependent analysis to be performed on any direct-detect receiver instrument.

Parameterized Finite Element Modeling and Buckling Analysis of Six Typical Composite Grid Cylindrical Shells

NASA Astrophysics Data System (ADS)

Lai, Changliang; Wang, Junbiao; Liu, Chuang

2014-10-01

Six typical composite grid cylindrical shells are constructed by superimposing three basic types of ribs. Then buckling behavior and structural efficiency of these shells are analyzed under axial compression, pure bending, torsion and transverse bending by finite element (FE) models. The FE models are created by a parametrical FE modeling approach that defines FE models with original natural twisted geometry and orients cross-sections of beam elements exactly. And the approach is parameterized and coded by Patran Command Language (PCL). The demonstrations of FE modeling indicate the program enables efficient generation of FE models and facilitates parametric studies and design of grid shells. Using the program, the effects of helical angles on the buckling behavior of six typical grid cylindrical shells are determined. The results of these studies indicate that the triangle grid and rotated triangle grid cylindrical shell are more efficient than others under axial compression and pure bending, whereas under torsion and transverse bending, the hexagon grid cylindrical shell is most efficient. Additionally, buckling mode shapes are compared and provide an understanding of composite grid cylindrical shells that is useful in preliminary design of such structures.

Novel spherical hohlraum with cylindrical laser entrance holes and shields

NASA Astrophysics Data System (ADS)

Lan, Ke; Zheng, Wudi

2014-09-01

Our recent works [K. Lan et al., Phys. Plasmas 21, 010704 (2014); K. Lan et al., Phys. Plasmas 21, 052704 (2014)] have shown that the octahedral spherical hohlraums are superior to the cylindrical hohlraums in both higher symmetry during the capsule implosion and lower backscatter without supplementary technology. However, both the coupling efficiency from the drive laser energy to the capsule and the capsule symmetry decrease remarkably when larger laser entrance holes (LEHs) are used. In addition, the laser beams injected at angles > 45° transport close to the hohlraum wall, thus the wall blowoff causes the LEH to close faster and results in strong laser plasma interactions inside the spherical hohlraums. In this letter, we propose a novel octahedral hohlraum with LEH shields and cylindrical LEHs to alleviate these problems. From our theoretical study, with the LEH shields, the laser coupling efficiency is significantly increased and the capsule symmetry is remarkably improved in the spherical hohlraums. The cylindrical LEHs take advantage of the cylindrical hohlraum near the LEH and mitigate the influence of the blowoff on laser transport inside a spherical hohlraum. The cylindrical LEHs can also be applied to the rugby and elliptical hohlraums.

Measurement of Systematic Error Effects for a Sensitive Storage Ring EDM Polarimeter

NASA Astrophysics Data System (ADS)

Imig, Astrid; Stephenson, Edward

2009-10-01

The Storage Ring EDM Collaboration was using the Cooler Synchrotron (COSY) and the EDDA detector at the Forschungszentrum J"ulich to explore systematic errors in very sensitive storage-ring polarization measurements. Polarized deuterons of 235 MeV were used. The analyzer target was a block of 17 mm thick carbon placed close to the beam so that white noise applied to upstream electrostatic plates increases the vertical phase space of the beam, allowing deuterons to strike the front face of the block. For a detector acceptance that covers laboratory angles larger than 9 ^o, the efficiency for particles to scatter into the polarimeter detectors was about 0.1% (all directions) and the vector analyzing power was about 0.2. Measurements were made of the sensitivity of the polarization measurement to beam position and angle. Both vector and tensor asymmetries were measured using beams with both vector and tensor polarization. Effects were seen that depend upon both the beam geometry and the data rate in the detectors.

Simple method for the characterization of intense Laguerre-Gauss vector vortex beams

NASA Astrophysics Data System (ADS)

Allahyari, E.; JJ Nivas, J.; Cardano, F.; Bruzzese, R.; Fittipaldi, R.; Marrucci, L.; Paparo, D.; Rubano, A.; Vecchione, A.; Amoruso, S.

2018-05-01

We report on a method for the characterization of intense, structured optical fields through the analysis of the size and surface structures formed inside the annular ablation crater created on the target surface. In particular, we apply the technique to laser ablation of crystalline silicon induced by femtosecond vector vortex beams. We show that a rapid direct estimate of the beam waist parameter is obtained through a measure of the crater radii. The variation of the internal and external radii of the annular crater as a function of the laser pulse energy, at fixed number of pulses, provides another way to evaluate the beam spot size through numerical fitting of the obtained experimental data points. A reliable estimate of the spot size is of paramount importance to investigate pulsed laser-induced effects on the target material. Our experimental findings offer a facile way to characterize focused, high intensity complex optical vector beams which are more and more applied in laser-matter interaction experiments.

Method and apparatus for reading lased bar codes on shiny-finished fuel rod cladding tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goldenfield, M.P.; Lambert, D.V.

1990-10-02

This patent describes, in a nuclear fuel rod identification system, a method of reading a bar code etched directly on a surface of a nuclear fuel rod. It comprises: defining a pair of light diffuser surfaces adjacent one another but in oppositely inclined relation to a beam of light emitted from a light reader; positioning a fuel rod, having a cylindrical surface portion with a bar code etched directly thereon, relative to the light diffuser surfaces such that the surfaces are disposed adjacent to and in oppositely inclined relation along opposite sides of the fuel rod surface portion and themore » fuel rod surface portion is aligned with the beam of light emitted from the light reader; directing the beam of light on the bar code on fuel rod cylindrical surface portion such that the light is reflected therefrom onto one of the light diffuser surfaces; and receiving and reading the reflected light from the bar code via the one of the light diffuser surfaces to the light reader.« less

A description on plasma background effect in growth rate of THz waves in a metallic cylindrical waveguide, including a dielectric tube and two current sources

NASA Astrophysics Data System (ADS)

Hajijamali-Arani, Z.; Jazi, B.

2018-04-01

The propagation of slow waves in a dielectric tube surrounded by a long cylindrical metallic waveguide is investigated. The dielectric tube located in a background region of plasma under two different states A and B. In the A-state the dielectric tube hollow filled with the plasma and in the B-state the outer surface of dielectric tube has been covered by the plasma layer. There are two relativistic electron beams with opposite velocities injected in the waveguide as the energy sources. Using the fluid theory for the plasmas, the Cherenkov instability in the mentioned waveguide will be analyzed. The dispersion relations of E-mode waves for the states A, B have been obtained. The time growth rate of surface waves are compared with each other for two cases A and B. The effect of plasma region on time growth rate of the waves, will be investigated. In all cases it will be shown, while an electron beam is responsible for instability, another electron beam plays a stabilizing role.

Langmuir instability in partially spin polarized bounded degenerate plasma

NASA Astrophysics Data System (ADS)

Iqbal, Z.; Jamil, M.; Murtaza, G.

2018-04-01

Some new features of waves inside the cylindrical waveguide on employing the separated spin evolution quantum hydrodynamic model are evoked. Primarily, the instability of Langmuir wave due to the electron beam in a partially spin polarized degenerate plasma considering a nano-cylindrical geometry is discussed. Besides, the evolution of a new spin-dependent wave (spin electron acoustic wave) due to electron spin polarization effects in the real wave spectrum is elaborated. Analyzing the growth rate, it is found that in the absence of Bohm potential, the electron spin effects or exchange interaction reduce the growth rate as well as k-domain but the inclusion of Bohm potential increases both the growth rate and k-domain. Further, we investigate the geometry effects expressed by R and pon and find that they have opposite effects on the growth rate and k-domain of the instability. Additionally, how the other parameters like electron beam density or streaming speed of beam electrons influence the growth rate is also investigated. This study may find its applications for the signal analysis in solid state devices at nanoscales.

An improved exact inversion formula for solenoidal fields in cone beam vector tomography

NASA Astrophysics Data System (ADS)

Katsevich, Alexander; Rothermel, Dimitri; Schuster, Thomas

2017-06-01

In this paper we present an improved inversion formula for the 3D cone beam transform of vector fields supported in the unit ball which is exact for solenoidal fields. It is well known that only the solenoidal part of a vector field can be determined from the longitudinal ray transform of a vector field in cone beam geometry. The inversion formula, as it was developed in Katsevich and Schuster (2013 An exact inversion formula for cone beam vector tomography Inverse Problems 29 065013), consists of two parts. The first part is of the filtered backprojection type, whereas the second part is a costly 4D integration and very inefficient. In this article we tackle this second term and obtain an improved formula, which is easy to implement and saves one order of integration. We also show that the first part contains all information about the curl of the field, whereas the second part has information about the boundary values. More precisely, the second part vanishes if the solenoidal part of the original field is tangential at the boundary. A number of numerical tests presented in the paper confirm the theoretical results and the exactness of the formula. Also, we obtain an inversion algorithm that works for general convex domains.

Focusing corner cube

DOEpatents

Monjes, J.A.

1985-09-12

This invention retortreflects and focuses a beam of light. The invention comprises a modified corner cube reflector wherein one reflective surface is planar, a second reflective surface is spherical, and the third reflective surface may be planar or convex cylindrical.

Three dimensional reconstruction of therapeutic carbon ion beams in phantoms using single secondary ion tracks

NASA Astrophysics Data System (ADS)

Reinhart, Anna Merle; Spindeldreier, Claudia Katharina; Jakubek, Jan; Martišíková, Mária

2017-06-01

Carbon ion beam radiotherapy enables a very localised dose deposition. However, even small changes in the patient geometry or positioning errors can significantly distort the dose distribution. A live, non-invasive monitoring system of the beam delivery within the patient is therefore highly desirable, and could improve patient treatment. We present a novel three-dimensional method for imaging the beam in the irradiated object, exploiting the measured tracks of single secondary ions emerging under irradiation. The secondary particle tracks are detected with a TimePix stack—a set of parallel pixelated semiconductor detectors. We developed a three-dimensional reconstruction algorithm based on maximum likelihood expectation maximization. We demonstrate the applicability of the new method in the irradiation of a cylindrical PMMA phantom of human head size with a carbon ion pencil beam of {226} MeV u-1. The beam image in the phantom is reconstructed from a set of nine discrete detector positions between {-80}^\\circ and {50}^\\circ from the beam axis. Furthermore, we demonstrate the potential to visualize inhomogeneities by irradiating a PMMA phantom with an air gap as well as bone and adipose tissue surrogate inserts. We successfully reconstructed a three-dimensional image of the treatment beam in the phantom from single secondary ion tracks. The beam image corresponds well to the beam direction and energy. In addition, cylindrical inhomogeneities with a diameter of {2.85} cm and density differences down to {0.3} g cm-3 to the surrounding material are clearly visualized. This novel three-dimensional method to image a therapeutic carbon ion beam in the irradiated object does not interfere with the treatment and requires knowledge only of single secondary ion tracks. Even with detectors with only a small angular coverage, the three-dimensional reconstruction of the fragmentation points presented in this work was found to be feasible.

Three dimensional reconstruction of therapeutic carbon ion beams in phantoms using single secondary ion tracks.

PubMed

Reinhart, Anna Merle; Spindeldreier, Claudia Katharina; Jakubek, Jan; Martišíková, Mária

2017-06-21

Carbon ion beam radiotherapy enables a very localised dose deposition. However, even small changes in the patient geometry or positioning errors can significantly distort the dose distribution. A live, non-invasive monitoring system of the beam delivery within the patient is therefore highly desirable, and could improve patient treatment. We present a novel three-dimensional method for imaging the beam in the irradiated object, exploiting the measured tracks of single secondary ions emerging under irradiation. The secondary particle tracks are detected with a TimePix stack-a set of parallel pixelated semiconductor detectors. We developed a three-dimensional reconstruction algorithm based on maximum likelihood expectation maximization. We demonstrate the applicability of the new method in the irradiation of a cylindrical PMMA phantom of human head size with a carbon ion pencil beam of [Formula: see text] MeV u -1 . The beam image in the phantom is reconstructed from a set of nine discrete detector positions between [Formula: see text] and [Formula: see text] from the beam axis. Furthermore, we demonstrate the potential to visualize inhomogeneities by irradiating a PMMA phantom with an air gap as well as bone and adipose tissue surrogate inserts. We successfully reconstructed a three-dimensional image of the treatment beam in the phantom from single secondary ion tracks. The beam image corresponds well to the beam direction and energy. In addition, cylindrical inhomogeneities with a diameter of [Formula: see text] cm and density differences down to [Formula: see text] g cm -3 to the surrounding material are clearly visualized. This novel three-dimensional method to image a therapeutic carbon ion beam in the irradiated object does not interfere with the treatment and requires knowledge only of single secondary ion tracks. Even with detectors with only a small angular coverage, the three-dimensional reconstruction of the fragmentation points presented in this work was found to be feasible.

Evolution of beams in a plasma channel due to beam break up

NASA Astrophysics Data System (ADS)

Penn, Gregory; Lehe, Remi; Vay, Jean-Luc; Schroeder, Carl; Esarey, Eric

2016-10-01

We study the dynamics of beam break-up (BBU) of an accelerated electron beam in a plasma channel. Particle-in-cell simulations using the codes WARP and FBPIC are presented and interpreted in terms of theoretical calculations for the plasma-induced fields and the evolution of the instability. We focus on cylindrical channels for simplicity, and other geometries are considered to better understand the impact of BBU on electron beams undergoing laser-plasma wake field acceleration. We compare our findings with other published results. This work was supported by the Director, Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Laser extensometer

NASA Technical Reports Server (NTRS)

Stocker, P. J.; Marcus, H. L. (Inventor)

1977-01-01

A drift compensated and intensity averaged extensometer for measuring the diameter or other properties of a substantially cylindrical sample based upon the shadow of the sample is described. A beam of laser light is shaped to provide a beam with a uniform intensity along an axis normal to the sample. After passing the sample, the portion of the beam not striking said sample is divided by a beam splitter into a reference signal and a measurement signal. Both of these beams are then chopped by a light chopper to fall upon two photodiode detectors. The resulting ac currents are rectified and then divided into one another, with the final output being proportional to the size of the sample shadow.

Thrust generation experiments on microwave rocket with a beam concentrator for long distance wireless power feeding

NASA Astrophysics Data System (ADS)

Fukunari, Masafumi; Yamaguchi, Toshikazu; Nakamura, Yusuke; Komurasaki, Kimiya; Oda, Yasuhisa; Kajiwara, Ken; Takahashi, Koji; Sakamoto, Keishi

2018-04-01

Experiments using a 1 MW-class gyrotron were conducted to examine a beamed energy propulsion rocket, a microwave rocket with a beam concentrator for long-distance wireless power feeding. The incident beam is transmitted from a beam transmission mirror system. The beam transmission mirror system expands the incident beam diameter to 240 mm to extend the Rayleigh length. The beam concentrator receives the beam and guides it into a 56-mm-diameter cylindrical thruster tube. Plasma ignition and ionization front propagation in the thruster were observed through an acrylic window using a fast-framing camera. Atmospheric air was used as a propellant. Thrust generation was achieved with the beam concentrator. The maximum thrust impulse was estimated as 71 mN s/pulse from a pressure history at the thrust wall at the input energy of 638 J/pulse. The corresponding momentum coupling coefficient, Cm was inferred as 204 N/MW.

Guided Radiation Beams in Free Electron Lasers.

DTIC Science & Technology

1988-05-19

the electron beam in an FEL that the radiation beam will remain guided. 0 20 II. Refractive Index Associated with FELs In our model, the vector ...eIAw/ymOc(exp(ikwz) + c.c.) ex/2 , is the wiggle velocity, y is the Lorentz factor, Aw is the vector potential amplitude of the planar wiggler...Balboa Avenue Palo Alto, CA 94303 San Diego, CA 92123 38 Dr. S. Krinsky Nat. Synchrotron Light Source Dr. Michael Lavan Brookhaven National Laboratory U.S

Vector mode conversion based on tilted fiber Bragg grating in ring-core fibers

NASA Astrophysics Data System (ADS)

Mi, Yuean; Ren, Guobin; Gao, Yixiao; Li, Haisu; Zhu, Bofeng; Liu, Yu

2018-03-01

We propose a vector mode conversion approach based on tilted fiber Bragg grating (TFBG) written in ring-core fiber with effective separation of eigenmodes. The mode coupling properties of TFBG are numerically investigated. It is shown that under the constraint of phase matching, the conversion of high-order vector modes could be achieved at specific wavelengths. Moreover, the polarization of incident light and tilt angle of TFBG play critical roles in mode coupling process. The proposed TFBG provides an efficient method to realize high-order vector mode conversion, and it shows great potential for fibers based OAM beam generation and fiber lasers with vortex beams output.

Vector fields in a tight laser focus: comparison of models.

PubMed

Peatross, Justin; Berrondo, Manuel; Smith, Dallas; Ware, Michael

2017-06-26

We assess several widely used vector models of a Gaussian laser beam in the context of more accurate vector diffraction integration. For the analysis, we present a streamlined derivation of the vector fields of a uniformly polarized beam reflected from an ideal parabolic mirror, both inside and outside of the resulting focus. This exact solution to Maxwell's equations, first developed in 1920 by V. S. Ignatovsky, is highly relevant to high-intensity laser experiments since the boundary conditions at a focusing optic dictate the form of the focus in a manner analogous to a physical experiment. In contrast, many models simply assume a field profile near the focus and develop the surrounding vector fields consistent with Maxwell's equations. In comparing the Ignatovsky result with popular closed-form analytic vector models of a Gaussian beam, we find that the relatively simple model developed by Erikson and Singh in 1994 provides good agreement in the paraxial limit. Models involving a Lax expansion introduce a divergences outside of the focus while providing little if any improvement in the focal region. Extremely tight focusing produces a somewhat complicated structure in the focus, and requires the Ignatovsky model for accurate representation.

Electron beam collector for a microwave power tube

DOEpatents

Dandl, Raphael A.

1980-01-01

This invention relates to a cylindrical, electron beam collector that efficiently couples the microwave energy out of a high power microwave source while stopping the attendant electron beam. The interior end walls of the collector are a pair of facing parabolic mirrors and the microwave energy from an input horn is radiated between the two mirrors and reassembled at the entrance to the output waveguide where the transmitted mode is reconstructed. The mode transmission through the collector of the present invention has an efficiency of at least 94%.

First Experiments with the Polarized Internal Gas Target (PIT) at ANKE/COSY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Engels, R.; Lorentz, B.; Prasuhn, D.

2008-02-06

For future few-nucleon interaction studies with polarized beams and targets at COSY-Juelich, a polarized internal storage-cell gas target was implemented at the magnet spectrometer ANKE in summer 2005. First commissioning of the polarized Atomic Beam Source (ABS) at ANKE was carried out and some improvements of the system have been done. Storage-cell tests to determine the COSY beam dimensions have been performed. Electron cooling combined with stacking and stochastic cooling have been studied. Experiments with N{sub 2} gas in the storage cell to simulate the background produced by beam interaction with the aluminum cell walls were performed to investigate themore » beam heating by the target gas. The analysis of the d-vector p-vector {yields}dp and d-vector p-vector{yields}(dp{sub sp}){pi}{sup 0} reactions showed that events from the extended target can be clearly identified in the ANKE detector system.The polarization of the atomic beam of the ABS, positioned close to the strong dipole magnet D2 of ANKE, was tuned with a Lamb-shift polarimeter (LSP) beneath the target chamber. With use of the known analyzing powers of the quasi-free np{yields}d{pi}{sup 0} reaction, the polarization in the storage cell was measured to be Q{sub y} = 0.79{+-}0.07 in the vertical stray field of the D2 magnet acting as a holding field. The achieved target thickness was 2x10{sup 13} atoms/cm{sup 2} for one hyperfine state populated in the ABS beam only. With a COSY beam intensity of 6x10{sup 9} stored polarized deuterons in the ring, the luminosity for double polarized experiments was 1x10{sup 29} cm{sup -2} s{sup -1}.« less

Comparison between broadband Bessel beam launchers based on either Bessel or Hankel aperture distribution for millimeter wave short pulse generation.

PubMed

Pavone, Santi C; Mazzinghi, Agnese; Freni, Angelo; Albani, Matteo

2017-08-07

In this paper, a comparison is presented between Bessel beam launchers at millimeter waves based on either a cylindrical standing wave (CSW) or a cylindrical inward traveling wave (CITW) aperture distribution. It is theoretically shown that CITW launchers are better suited for the generation of electromagnetic short pulses because they maintain their performances over a larger bandwidth than those realizing a CSW aperture distribution. Moreover, the wavenumber dispersion of both the launchers is evaluated both theoretically and numerically. To this end, two planar Bessel beam launchers, one enforcing a CSW and the other enforcing a CITW aperture distribution, are designed at millimeter waves with a center operating frequency of f¯=60GHz and analyzed in the bandwidth 50 - 70 GHz by using an in-house developed numerical code to solve Maxwell's equations based on the method of moments. It is shown that a monochromatic Bessel beam can be efficiently generated by both the launchers over a wide fractional bandwidth. Finally, we investigate the generation of limited-diffractive electromagnetic pulses at millimeter waves, up to a certain non-diffractive range. Namely, it is shown that by feeding the launcher with a Gaussian short pulse, a spatially confined electromagnetic pulse can be efficiently generated in front of the launcher.

Advanced Precipitation Radar Antenna to Measure Rainfall From Space

NASA Technical Reports Server (NTRS)

Rahmat-Samii, Yahya; Lin, John; Huang, John; Im, Eastwood; Lou, Michael; Lopez, Bernardo; Durden, Stephen

2008-01-01

To support NASA s planned 20-year mission to provide sustained global precipitation measurement (EOS-9 Global Precipitation Measurement (GPM)), a deployable antenna has been explored with an inflatable thin-membrane structure. This design uses a 5.3 5.3-m inflatable parabolic reflector with the electronically scanned, dual-frequency phased array feeds to provide improved rainfall measurements at 2.0-km horizontal resolution over a cross-track scan range of up to 37 , necessary for resolving intense, isolated storm cells and for reducing the beam-filling and spatial sampling errors. The two matched radar beams at the two frequencies (Ku and Ka bands) will allow unambiguous retrieval of the parameters in raindrop size distribution. The antenna is inflatable, using rigidizable booms, deployable chain-link supports with prescribed curvatures, a smooth, thin-membrane reflecting surface, and an offset feed technique to achieve the precision surface tolerance (0.2 mm RMS) for meeting the low-sidelobe requirement. The cylindrical parabolic offset-feed reflector augmented with two linear phased array feeds achieves dual-frequency shared-aperture with wide-angle beam scanning and very low sidelobe level of -30 dB. Very long Ku and Ka band microstrip feed arrays incorporating a combination of parallel and series power divider lines with cosine-over-pedestal distribution also augment the sidelobe level and beam scan. This design reduces antenna mass and launch vehicle stowage volume. The Ku and Ka band feed arrays are needed to achieve the required cross-track beam scanning. To demonstrate the inflatable cylindrical reflector with two linear polarizations (V and H), and two beam directions (0deg and 30deg), each frequency band has four individual microstrip array designs. The Ku-band array has a total of 166x2 elements and the Ka-band has 166x4 elements with both bands having element spacing about 0.65 lambda(sub 0). The cylindrical reflector with offset linear array feeds reduces the complexity from "NxN" transmit/receive (T/R) modules of a conventional planar-phased array to just "N" T/R modules. The antenna uses T/R modules with electronic phase-shifters for beam steering. The offset reflector does not provide poor cross-polarization like a double- curved offset reflector would, and it allows the wide scan angle in one plane required by the mission. Also, the cylindrical reflector with two linear array feeds provides dual-frequency performance with a single, shared aperture. The aperture comprises a reflective surface with a focal length of 1.89 m and is made from aluminized Kapton film. The reflective surface is of uniform thickness in the range of a few thousandths of an inch and is attached to the chain-link support structure via an adjustable suspension system. The film aperture rolls up, together with the chain-link structure, for launch and can be deployed in space by the deployment of the chain-link structure.

Generalized M-factor of hollow Gaussian beams through a hard-edge circular aperture

NASA Astrophysics Data System (ADS)

Deng, Dongmei

2005-06-01

Based on the generalized truncated second-order moments, the generalized M-factor (MG2-factor) of three-dimensional hollow Gaussian beams (HGBs) through a hard-edge circular aperture is studied in cylindrical coordinate system analytically and numerically. The closed-form expression for the MG2-factor of the truncated HGBs, which is dependent on the truncation parameter β and the beam order n, can be simplified to that of the truncated, the untruncated Gaussian beams and the untruncated HGBs. Also, the power fraction is demonstrated analytically and numerically, which shows that the area of the dark region across the HGBs increases as n increasing.

RF Behavior of Cylindrical Cavity Based 240 GHz, 1 MW Gyrotron for Future Tokamak System

NASA Astrophysics Data System (ADS)

Kumar, Nitin; Singh, Udaybir; Bera, Anirban; Sinha, A. K.

2017-11-01

In this paper, we present the RF behavior of conventional cylindrical interaction cavity for 240 GHz, 1 MW gyrotron for futuristic plasma fusion reactors. Very high-order TE mode is searched for this gyrotron to minimize the Ohmic wall loading at the interaction cavity. The mode selection process is carried out rigorously to analyze the mode competition and design feasibility. The cold cavity analysis and beam-wave interaction computation are carried out to finalize the cavity design. The detail parametric analyses for interaction cavity are performed in terms of mode stability, interaction efficiency and frequency. In addition, the design of triode type magnetron injection gun is also discussed. The electron beam parameters such as velocity ratio and velocity spread are optimized as per the requirement at interaction cavity. The design studies presented here confirm the realization of CW, 1 MW power at 240 GHz frequency at TE46,17 mode.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, C; Liu, H; Indiana University Bloomington, Bloomington, IN

Purpose: A rapid cycling proton beam has several distinct characteristics superior to a slow extraction synchrotron: The beam energy and energy spread, beam intensity and spot size can be varied spot by spot. The feasibility of using a spot scanning beam from a rapidc-ycling-medical-synchrotron (RCMS) at 10 Hz repetition frequency is investigated in this study for its application in proton therapy. Methods: The versatility of the beam is illustrated by two examples in water phantoms: (1) a cylindrical PTV irradiated by a single field and (2) a spherical PTV irradiated by two parallel opposed fields. A uniform dose distribution ismore » to be delivered to the volumes. Geant4 Monte Carlo code is used to validate the dose distributions in each example. Results: Transverse algorithms are developed to produce uniform distributions in each transverseplane in the two examples with a cylindrical and a spherical PTV respectively. Longitudinally, different proton energies are used in successive transverse planes toproduce the SOBP required to cover the PTVs. In general, uniformity of dosedistribution within 3% is obtained for the cylinder and 3.5% for the sphere. The transversealgorithms requires only few hundred beam spots for each plane The algorithms may beapplied to larger volumes by increasing the intensity spot by spot for the same deliverytime of the same dose. The treatment time can be shorter than 1 minute for any fieldconfiguration and tumor shape. Conclusion: The unique beam characteristics of a spot scanning beam from a RCMS at 10 Hz repetitionfrequency are used to design transverse and longitudinal algorithms to produce uniformdistribution for any arbitrary shape and size of targets. The proposed spot scanning beam ismore versatile than existing spot scanning beams in proton therapy with better beamcontrol and lower neutron dose. This work is supported in part by grants from the US Department of Energy under contract; DE-FG02-12ER41800 and the National Science Foundation NSF PHY-1205431.« less

Focusing of white synchrotron radiation using large-acceptance cylindrical refractive lenses made of single – crystal diamond

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polikarpov, M., E-mail: polikarpov.maxim@mail.ru; Snigireva, I.; Snigirev, A.

2016-07-27

Large-aperture cylindrical refractive lenses were manufactured by laser cutting of single-crystal diamond. Five linear single lenses with apertures of 1 mm and the depth of the structure of 1.2 mm were fabricated and tested at the ESRF ID06 beamline performing the focusing of white-beam synchrotron radiation. Uniform linear focus was stable during hours of exposure, representing such lenses as pre-focusing and collimating devices suitable for the front-end sections of today synchrotron radiation sources.

Visual enhancements in pick-and-place tasks: Human operators controlling a simulated cylindrical manipulator

NASA Technical Reports Server (NTRS)

Kim, Won S.; Tendick, Frank; Stark, Lawrence

1989-01-01

A teleoperation simulator was constructed with vector display system, joysticks, and a simulated cylindrical manipulator, in order to quantitatively evaluate various display conditions. The first of two experiments conducted investigated the effects of perspective parameter variations on human operators' pick-and-place performance, using a monoscopic perspective display. The second experiment involved visual enhancements of the monoscopic perspective display, by adding a grid and reference lines, by comparison with visual enhancements of a stereoscopic display; results indicate that stereoscopy generally permits superior pick-and-place performance, but that monoscopy nevertheless allows equivalent performance when defined with appropriate perspective parameter values and adequate visual enhancements.

General description of circularly symmetric Bessel beams of arbitrary order

NASA Astrophysics Data System (ADS)

Wang, Jia Jie; Wriedt, Thomas; Lock, James A.; Mädler, Lutz

2016-11-01

A general description of circularly symmetric Bessel beams of arbitrary order is derived in this paper. This is achieved by analyzing the relationship between different descriptions of polarized Bessel beams obtained using different approaches. It is shown that a class of circularly symmetric Davis Bessel beams derived using the Hertz vector potentials possesses the same general functional dependence as the aplanatic Bessel beams generated using the angular spectrum representation (ASR). This result bridges the gap between different descriptions of Bessel beams and leads to a general description of circularly symmetric Bessel beams, such that the Davis Bessel beams and the aplanatic Bessel beams are merely the two simplest cases of an infinite number of possible circularly symmetric Bessel beams. Additionally, magnitude profiles of the electric and magnetic fields, the energy density and the Poynting vector are displayed for Bessel beams in both paraxial and nonparaxial cases. The results presented in this paper provide a fresh perspective on the description of Bessel beams and cast some insights into the light scattering and light-matter interactions problems in practice.

Photorefractive Tungsten Bronze Crystals for Optical Limiters and Filters.

DTIC Science & Technology

1996-01-01

vector , X is the laser light wavelength, 0 is the half- angle between the two crossing laser beams, and k0 is the Debye screening wave vector given by...between the grating and the dielectric constant E’ = 950) such that the grating’ vector is interference pattern, the intensities of the output beams from...substituting Io, I, and Id into expression 0 ple d 2o0o 25i00 (8), we can calculate the phase shift between the grating and Applied Electric Feild in V

Spin Resonances for Stored Deuteron Beams in COSY. Vector Polarization. Tracking with Spink

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luccio,A.; Lehrach, A.

2008-04-01

Results of measurements of vector and tensor polarization of a deuteron beam in the storage ring COSY have been published by the SPIN{at}COSY collaboration. In this experiment a RF Dipole was used that produced spin flip. The strength of the RFD-induced depolarizing resonance was calculated from the amount of spin flipping and the results shown in the figures of the cited paper. In this note we present the simulation of the experimental data (vector polarization) with the spin tracking code Spink.

Finite Element Analysis of Geodesically Stiffened Cylindrical Composite Shells Using a Layerwise Theory

NASA Technical Reports Server (NTRS)

Gerhard, Craig Steven; Gurdal, Zafer; Kapania, Rakesh K.

1996-01-01

Layerwise finite element analyses of geodesically stiffened cylindrical shells are presented. The layerwise laminate theory of Reddy (LWTR) is developed and adapted to circular cylindrical shells. The Ritz variational method is used to develop an analytical approach for studying the buckling of simply supported geodesically stiffened shells with discrete stiffeners. This method utilizes a Lagrange multiplier technique to attach the stiffeners to the shell. The development of the layerwise shells couples a one-dimensional finite element through the thickness with a Navier solution that satisfies the boundary conditions. The buckling results from the Ritz discrete analytical method are compared with smeared buckling results and with NASA Testbed finite element results. The development of layerwise shell and beam finite elements is presented and these elements are used to perform the displacement field, stress, and first-ply failure analyses. The layerwise shell elements are used to model the shell skin and the layerwise beam elements are used to model the stiffeners. This arrangement allows the beam stiffeners to be assembled directly into the global stiffness matrix. A series of analytical studies are made to compare the response of geodesically stiffened shells as a function of loading, shell geometry, shell radii, shell laminate thickness, stiffener height, and geometric nonlinearity. Comparisons of the structural response of geodesically stiffened shells, axial and ring stiffened shells, and unstiffened shells are provided. In addition, interlaminar stress results near the stiffener intersection are presented. First-ply failure analyses for geodesically stiffened shells utilizing the Tsai-Wu failure criterion are presented for a few selected cases.

Prevalence and associations of anisometropia with spherical ametropia, cylindrical power, age, and sex in refractive surgery candidates.

PubMed

Linke, Stephan J; Richard, Gisbert; Katz, Toam

2011-09-29

To analyze the prevalence and associations of anisometropia with spherical ametropia, astigmatism, age, and sex in a refractive surgery population. Medical records of 27,070 eyes of 13,535 refractive surgery candidates were reviewed. Anisometropia, defined as the absolute difference in mean spherical equivalent powers between right and left eyes, was analyzed for subjective (A(subj)) and cycloplegic refraction (A(cycl)). Correlations between anisometropia (>1 diopter) and spherical ametropia, cylindrical power, age, and sex, were analyzed using χ² and nonparametric Kruskal-Wallis or Mann-Whitney tests and binomial logistic regression analyses. Power vector analysis was applied for further analysis of cylindrical power. Prevalence of A(subj) was 18.5% and of A(cycl) was 19.3%. In hyperopes, logistic regression analysis revealed that only spherical refractive error (odds ratio [OR], 0.72) and age (OR, 0.97) were independently associated with anisometropia. A(subj) decreased with increasing spherical ametropia and advancing age. Cylindrical power and sex did not significantly affect A(subj). In myopes all explanatory variables (spherical power OR, 0.93; cylindrical power OR, 0.75; age OR, 1.02; sex OR, 0.8) were independently associated with anisometropia. Cylindrical power was most strongly associated with anisometropia. Advancing age and increasing spherical/cylindrical power correlated positively with increasing anisometropia in myopic subjects. Female sex was more closely associated with anisometropia. This large-scale retrospective analysis confirmed an independent association between anisometropia and both spherical ametropia and age in refractive surgery candidates. Notably, an inverse relationship between these parameters in hyperopes was observed. Cylindrical power and female sex were independently associated with anisometropia in myopes.

Rapid electron beam accelerator (REBA-tron)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kapetanakos, C.A.; Sprangle, P.A.; Dialetis, D.

1986-03-05

This invention comprises a particle accelerator with a toroidal vacuum chamber, an injector for injecting a charged-paticle beam into the chamber and an exit port to extract the accelerated particle beam. A toroidal magnetic field to confine the beam in the chamber is generated by a set of coils with their axis along the minor axis of the chamber and by two twisted wires that carry current in the same direction wrapped around the chamber. The two twisted wires also generate a torsatron magnetic field that controls the minor radius of the beam. A time-varying magnetic field is generated bymore » two concentric cylindrical plates surrounding the chamber. A convoluted transmission line generates a localized electric field in the chamber to accelerate the beam.« less

Generation of low-emittance electron beams in electrostatic accelerators for FEL applications

NASA Astrophysics Data System (ADS)

Chen, Teng; Elias, Luis R.

1995-02-01

This paper reports results of transverse emittance studies and beam propagation in electrostatic accelerators for free electron laser applications. In particular, we discuss emittance growth analysis of a low current electron beam system consisting of a miniature thermoionic electron gun and a National Electrostatics Accelerator (NEC) tube. The emittance growth phenomenon is discussed in terms of thermal effects in the electron gun cathode and aberrations produced by field gradient changes occurring inside the electron gun and throughout the accelerator tube. A method of reducing aberrations using a magnetic solenoidal field is described. Analysis of electron beam emittance was done with the EGUN code. Beam propagation along the accelerator tube was studied using a cylindrically symmetric beam envelope equation that included beam self-fields and the external accelerator fields which were derived from POISSON simulations.

High power microwave generator

DOEpatents

Ekdahl, Carl A.

1986-01-01

A microwave generator efficiently converts the energy of an intense relativistic electron beam (REB) into a high-power microwave emission using the Smith-Purcell effect which is related to Cerenkov radiation. Feedback for efficient beam bunching and high gain is obtained by placing a cylindrical Smith-Purcell transmission grating on the axis of a toroidal resonator. High efficiency results from the use of a thin cold annular highly-magnetized REB that is closely coupled to the resonant structure.

Dealing with Beam Structure in PIXIE

NASA Technical Reports Server (NTRS)

Fixsen, D. J.; Kogut, Alan; Hill, Robert S.; Nagler, Peter C.; Seals, Lenward T., III; Howard, Joseph M.

2016-01-01

Measuring the B-mode polarization of the CMB radiation requires a detailed understanding of the projection of the detector onto the sky. We show how the combination of scan strategy and processing generates a cylindrical beam for the spectrum measurement. Both the instrumental design and the scan strategy reduce the cross coupling between the temperature variations and the B-modes. As with other polarization measurements some post processing may be required to eliminate residual errors.

Dispersion Characteristics of a Beam-Driven Cylindrical Waveguide with Dielectric Liner.

DTIC Science & Technology

1982-04-01

applications of near-millimeter waves. The experiment initiated at HDL represents one approach to designing such a radiation source. The foundation for this...experiment has been laid by Felch et al at Dartmouth College.1 𔃼 Very simply, that experiment consists of passing an intense, relativistic electron beam...accelerated to relativistic speeds through the dielectric-lined resonator, where the actual produc- tion of radiation takes place. As a result of the

High power microwave generator

DOEpatents

Ekdahl, C.A.

1983-12-29

A microwave generator efficiently converts the energy of an intense relativistic electron beam (REB) into a high-power microwave emission using the Smith-Purcell effect which is related to Cerenkov radiation. Feedback for efficient beam bunching and high gain is obtained by placing a cylindrical Smith-Purcell transmission grating on the axis of a toroidal resonator. High efficiency results from the use of a thin cold annular highly-magnetized REB that is closely coupled to the resonant structure.

Simulation of the development and interaction of instabilities in a relativistic electron beam under variation of the beam wall thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Badarin, A. A.; Kurkin, S. A.; Koronovskii, A. A.

The development and interaction of Bursian and diocotron instabilities in an annular relativistic electron beam propagating in a cylindrical drift chamber are investigated analytically and numerically as functions of the beam wall thickness and the magnitude of the external uniform magnetic field. It is found that the interaction of instabilities results in the formation of a virtual cathode with a complicated rotating helical structure and several reflection regions (electron bunches) in the azimuthal direction. It is shown that the number of electron bunches in the azimuthal direction increases with decreasing beam wall thickness and depends in a complicated manner onmore » the magnitude of the external magnetic field.« less

Measuring the self-healing of the spatially inhomogeneous states of polarization of vector Bessel beams

NASA Astrophysics Data System (ADS)

Milione, Giovanni; Dudley, Angela; Nguyen, Thien An; Chakraborty, Ougni; Karimi, Ebrahim; Forbes, Andrew; Alfano, Robert R.

2015-03-01

We experimentally measured the self-healing of the spatially inhomogeneous states of polarization of vector Bessel beams. Radially and azimuthally polarized vector Bessel beams were experimentally generated via a digital version of Durnin's method, using a spatial light modulator in concert with a liquid crystal q-plate. As a proof of principle, their intensities and spatially inhomogeneous states of polarization were experimentally measured using Stokes polarimetry as they propagated through two disparate obstructions. It was found, similar to their intensities, that their spatially inhomogeneous states of polarization self-healed. The self-healing can be understood via geometric optics, i.e., the interference of the unobstructed conical rays in the shadow region of the obstruction, and may have applications in, for example, optical trapping.

Airy acoustical-sheet spinner tweezers

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2016-09-01

The Airy acoustical beam exhibits parabolic propagation and spatial acceleration, meaning that the propagation bending angle continuously increases before the beam trajectory reaches a critical angle where it decays after a propagation distance, without applying any external bending force. As such, it is of particular importance to investigate its properties from the standpoint of acoustical radiation force, spin torque, and particle dynamics theories, in the development of novel particle sorting techniques and acoustically mediated clearing systems. This work investigates these effects on a two-dimensional (2D) circular absorptive structure placed in the field of a nonparaxial Airy "acoustical-sheet" (i.e., finite beam in 2D), for potential applications in surface acoustic waves and acousto-fluidics. Based on the characteristics of the acoustic field, the beam is capable of manipulating the circular cylindrical fluid cross-section and guides it along a transverse or parabolic trajectory. This feature of Airy acoustical beams could lead to a unique characteristic in single-beam acoustical tweezers related to acoustical sieving, filtering, and removal of particles and cells from a section of a small channel. The analysis developed here is based on the description of the nonparaxial Airy beam using the angular spectrum decomposition of plane waves in close association with the partial-wave series expansion method in cylindrical coordinates. The numerical results demonstrate the ability of the nonparaxial Airy acoustical-sheet beam to pull, propel, or accelerate a particle along a parabolic trajectory, in addition to particle confinement in the transverse direction of wave propagation. Negative or positive radiation force and spin torque causing rotation in the clockwise or the anticlockwise direction can occur depending on the nondimensional parameter ka (where k is the wavenumber and a is the radius) and the location of the cylinder in the beam. Applications in acoustic levitation, long-distance particle transport and manipulation, as well as acousto-fluidics directly benefit from the results of this analysis.

Multiple pinhole collimator based X-ray luminescence computed tomography

PubMed Central

Zhang, Wei; Zhu, Dianwen; Lun, Michael; Li, Changqing

2016-01-01

X-ray luminescence computed tomography (XLCT) is an emerging hybrid imaging modality, which is able to improve the spatial resolution of optical imaging to hundreds of micrometers for deep targets by using superfine X-ray pencil beams. However, due to the low X-ray photon utilization efficiency in a single pinhole collimator based XLCT, it takes a long time to acquire measurement data. Herein, we propose a multiple pinhole collimator based XLCT, in which multiple X-ray beams are generated to scan a sample at multiple positions simultaneously. Compared with the single pinhole based XLCT, the multiple X-ray beam scanning method requires much less measurement time. Numerical simulations and phantom experiments have been performed to demonstrate the feasibility of the multiple X-ray beam scanning method. In one numerical simulation, we used four X-ray beams to scan a cylindrical object with 6 deeply embedded targets. With measurements from 6 angular projections, all 6 targets have been reconstructed successfully. In the phantom experiment, we generated two X-ray pencil beams with a collimator manufactured in-house. Two capillary targets with 0.6 mm edge-to-edge distance embedded in a cylindrical phantom have been reconstructed successfully. With the two beam scanning, we reduced the data acquisition time by 50%. From the reconstructed XLCT images, we found that the Dice similarity of targets is 85.11% and the distance error between two targets is less than 3%. We have measured the radiation dose during XLCT scan and found that the radiation dose, 1.475 mSv, is in the range of a typical CT scan. We have measured the changes of the collimated X-ray beam size and intensity at different distances from the collimator. We have also studied the effects of beam size and intensity in the reconstruction of XLCT. PMID:27446686

Comparison of astigmatic correction after femtosecond lenticule extraction and wavefront-guided LASIK for myopic astigmatism.

PubMed

Ali, Mohamed A; Kobashi, Hidenaga; Kamiya, Kazutaka; Igarashi, Akihito; Miyake, Toshiyuki; Elewa, Mohamed Ehab M; Komatsu, Mari; Shimizu, Kimiya

2014-12-01

To compare postoperative astigmatic correction between femtosecond lenticule extraction (FLEx) and wavefront-guided LASIK in eyes with myopic astigmatism. Fifty-eight eyes of 41 patients undergoing FLEx and 49 eyes of 29 patients undergoing wavefront-guided LASIK to correct myopic astigmatism were examined. Visual acuity, cylindrical refraction, predictability of the astigmatic correction, and astigmatic vector components were compared between groups 6 months after surgery. There was no statistically significant difference in manifest cylindrical refraction (P = .08) or percentage of eyes within ± 0.50 diopter (D) of its refraction (P = .11) between the surgical procedures. The index of success in FLEx was statistically significantly better than that of wavefront-guided LASIK (P = .02), although there was no significant difference between the groups in other indices (eg, surgically induced astigmatism, target-induced astigmatism, astigmatic correction index, angle of error, difference vector, and flattening index). Subgroup analysis showed that FLEx had a better index of success (P = .02) and difference vector (P = .04) than wavefront-guided LASIK in the low cylinder subgroup; the angle of error in FLEx was significantly smaller than that of wavefront-guided LASIK in the moderate cylinder subgroup (P = .03). Both FLEx and wavefront-guided LASIK worked well for the correction of myopic astigmatism by the 6-month follow-up visit. Although FLEx had a better index of success than wavefront-guided LASIK when using vector analysis, it appears equivalent to wavefront-guided LASIK in terms of visual acuity and the correction of astigmatism. Copyright 2014, SLACK Incorporated.

LASIK versus photorefractive keratectomy for high myopic (> 3 diopter) astigmatism.

PubMed

Katz, Toam; Wagenfeld, Lars; Galambos, Peter; Darrelmann, Benedikt Große; Richard, Gisbert; Linke, Stephan Johannes

2013-12-01

To compare the efficacy, safety, predictability, and vector analysis indices of LASIK and photorefractive keratectomy (PRK) for correction of high cylinder of greater than 3 diopters (D) in myopic eyes. The efficacy, safety, and predictability of LASIK or PRK performed in 114 consecutive randomly selected myopic eyes with an astigmatism of greater than 3 D were retrospectively analyzed at the 2- to 6-month follow-up visits. Vector analysis of the cylindrical correction was compared between the treatment groups. A total of 57 eyes receiving PRK and 57 eyes receiving LASIK of 114 refractive surgery candidates were enrolled in the study. No statistically significant difference in efficacy [efficacy index = 0.76 (±0.32) for PRK vs 0.74 (±0.19) for LASIK (P = .82)], safety [safety index = 1.10 (±0.26) for PRK vs 1.01 (±0.17) for LASIK (P = .121)], or predictability [achieved astigmatism < 1 D in 39% of PRK- and 54% of LASIK-treated eyes, and < 2 D in 88% of PRK- and 89% of LASIK-treated eyes (P = .218)] was demonstrated. Using Alpins vector analysis, the surgically induced astigmatism and difference vector were not significantly different between the surgery methods, whereas the correction index showed a slight and significant advantage of LASIK over PRK (1.25 for PRK and 1.06 for LASIK, P < .001). LASIK and PRK are comparably safe, effective, and predictable procedures for excimer laser correction of high astigmatism of greater than 3 D in myopic eyes. Predictability of the correction of the cylindrical component is lower than that of the spherical equivalent. Copyright 2013, SLACK Incorporated.

A systematic Monte Carlo study of secondary electron fluence perturbation in clinical proton beams (70-250 MeV) for cylindrical and spherical ion chambers.

PubMed

Verhaegen, F; Palmans, H

2001-10-01

Current dosimetry protocols for clinical protons do not take into account any secondary electron fluence perturbation in ion chambers. In this work, we performed a systematic study of secondary electron fluence perturbation factors for spherical and cylindrical ion chambers in proton beams (70-250 MeV). The electron fluence perturbation factor, pe, was calculated using Monte Carlo transport of protons and secondary electrons. The influence of proton energy, cavity wall material (graphite, water, A150, PMMA, polystyrene), cavity radius, cavity wall thickness and positioning depth in water is studied. The influence of inelastic nuclear proton interactions is briefly discussed. It was found that pe depends on wall material; the largest values for pe were obtained for ion chambers with A150 walls (pe=1.009), the smallest values for graphite walls. The perturbation factor was found to be largely independent of proton energy. A slight decrease of pe with cavity radius was obtained, especially for low energy protons. The wall thickness was found to have no effect on pe in the range studied (0.025-0.1 cm). The depth of the cavity in a water phantom was also found to have an insignificant effect on pe. Based on the results in the paper for spherical and cylindrical ion chambers, a method to calculate pe for a thimble ion chamber is presented. The results presented in this paper for cylindrical and spherical ion chambers are in contradiction to the calculated electron fluence perturbation factors for planar ion chambers in the paper by Casnati et al.

Analytic Solutions of the Vector Burgers Equation

NASA Technical Reports Server (NTRS)

Nerney, Steven; Schmahl, Edward J.; Musielak, Z. E.

1996-01-01

The well-known analytical solution of Burgers' equation is extended to curvilinear coordinate systems in three dimensions by a method that is much simpler and more suitable to practical applications than that previously used. The results obtained are applied to incompressible flow with cylindrical symmetry, and also to the decay of an initially linearly increasing wind.

Experiments on Ion Beam Deflection Using Ion Optics with Slit Apertures

NASA Astrophysics Data System (ADS)

Okawa, Yasushi; Hayakawa, Yukio; Kitamura, Shoji

2004-03-01

An experimental investigation on ion beam deflection by grid translation was performed. The ion beam deflection in ion optics is a desired technology for ion thrusters because thrust vector control utilizing this technique can eliminate the need for conventional gimbaling devices and thus reduce propulsion system mass. A grid translation mechanism consisting of a piezoelectric motor, a ceramic lever, and carbon-based grids with slit apertures was fabricated and high repeatability in beam deflection characteristics was obtained using this mechanism. Results showed that the beam deflection angle was proportional to the grid translation distance and independent of slit width and grid voltage. A numerical simulation successfully reproduced the beam deflection characteristics in a qualitative and quantitative sense. A maximum beam deflection angle of approximately plus or minus 6 degrees, which was comparable to that of the ordinary gimbaling devices used in space, was obtained without a severe drain current. Therefore, the beam deflection by grid translation is promising as a thrust vectoring method in ion thrusters.

Investigation of proposed AASHTO rut test procedure using the Asphalt Pavement Analyzer.

DOT National Transportation Integrated Search

2006-01-01

The Virginia Department of Transportation uses the Asphalt Pavement Analyzer with beam specimens to test and approve asphalt mixtures for rut resistance. Some agencies use cylindrical specimens that impart distinct testing advantages such as the ease...

[The application of vector analysis for evaluation of astigmatism correction in the corneal refractive surgery].

PubMed

Zhang, Jiamei; Wang, Yan

2016-01-01

Since sixty percent of ametropes obtain astigmatism, which has influence on the visual quality, correcting the astigmatism is always the focus of concerns during visual correction procedures especially for the corneal refractive surgery. The postoperative spherical equivalent or residual cylindrical dioptors was used as quantitative index to evaluate the correction of astigmatism previously; however, such results neglect the effect of astigmatic axis shift on the treatment. Taking astigmatism as a vector parameter could describe the magnitude and direction of astigmatism accurately, thus it was increasingly applied in the evaluation of astigmatism correction. This paper reviews the present vector analysis methods, evaluation indexes and its application for the correction of astigmatism in the corneal refractive surgery.

All-fiber 3D vector displacement (bending) sensor based on an eccentric FBG.

PubMed

Bao, Weijia; Rong, Qiangzhou; Chen, Fengyi; Qiao, Xueguang

2018-04-02

We demonstrate a fiber-optic 3D vector displacement sensor based on the monitoring of Bragg reflection from an eccentric grating inscribed in a depressed-cladding fiber using the femtosecond laser side-illumination and phase-mask technique. The compact sensing probe consists of a short section of depressed cladding fiber (DCF) containing eccentrically positioned fiber Bragg gratings. The eccentric grating breaks the cylindrical symmetry of the fiber cross-section and further has bending orientation-dependence. The generated fundamental resonance is strongly sensitive to bending of the fiber, and the direction of the bending plane can be determined from its responses. When integrated with axis strain monitoring, the sensor achieves a 3D vector displacement measurement via simple geometric analysis.

Wavefront Engineering with Phase Discontinuities: Designer Interfaces for High Performance Planar Optical Components

DTIC Science & Technology

2015-08-27

ABSTRACT The PI and his group opened up new directions of research: the generation of vector beams with metasurfaces that control amplitude, phase...and polarization of wavefronts, the detection of wavefronts using metasurfaces , new metasurfaces for controlling surface plasmon wavefronts and high...performance device applications of metasurfaces on graphene. In the vector beam area they generated radially polarized light with a single

Double lens device for tunable harmonic generation of laser beams in KBBF/RBBF crystals or other non-linear optic materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaminski, Adam

A method and apparatus to generate harmonically related laser wavelengths includes a pair of lenses at opposing faces of a non-linear optical material. The lenses are configured to promote incoming and outgoing beams to be normal to each outer lens surface over a range of acceptance angles of the incoming laser beam. This reduces reflection loss for higher efficiency operation. Additionally, the lenses allow a wider range of wavelengths for lasers for more universal application. Examples of the lenses include plano-cylindrical and plano-spherical form factors.

Diffraction of Nondiverging Bessel Beams by Fork-Shaped and Rectilinear Grating

NASA Astrophysics Data System (ADS)

Janicijevic, Ljiljana; Topuzoski, Suzana

2007-04-01

We present an investigation about Fresnel diffraction of Bessel beams, propagating as nondiverging within a distance Ln, with or without phase singularities, by rectilinear and fork-shaped gratings. The common general transmission function of these gratings is defined and specialized for three different cases: binary amplitude gratings, amplitude holograms and their phase versions. Solving the Fresnel diffraction integral in cylindrical coordinates, we obtain analytical expressions for the diffracted wave amplitude for all types of proposed gratings, and make conclusions about the existence of phase singularities and corresponding topological charges in the created by the gratings beams of different diffraction orders.

Shock effects in particle beam fusion targets

NASA Astrophysics Data System (ADS)

Sweeney, M. A.; Perry, F. C.; Asay, J. R.; Widner, M. M.

1982-04-01

At Sandia National Laboratorics we are assessing the response of fusion target materials to shock loading with the particle beam accelerators HYDRA and PROTO I and the gas gun facility. Nonlinear shock-accelerated unstable growth of fabriction irregularities has been demonstrated, and jetting is found to occur in imploding targets because of asymmetric beam deposition. Cylindrical ion targets display an instability due either to beam or target nonuniformity. However, the data suggest targets with aspect ratios of 30 may implode stably. The first time- and space-resolved measurements of shock-induced vaporization have been made. A homogeneous mixed phase EOS model cannot adequately explain the results because of the kinetic effects of vapor formation and expansion.

Propagation of Bessel-Gaussian beams through a double-apertured fractional Fourier transform optical system.

PubMed

Tang, Bin; Jiang, Chun; Zhu, Haibin

2012-08-01

Based on the scalar diffraction theory and the fact that a hard-edged aperture function can be expanded into a finite sum of complex Gaussian functions, an approximate analytical solution for Bessel-Gaussian (BG) beams propagating through a double-apertured fractional Fourier transform (FrFT) system is derived in the cylindrical coordinate. By using the approximate analytical formulas, the propagation properties of BG beams passing through a double-apertured FrFT optical system have been studied in detail by some typical numerical examples. The results indicate that the double-apertured FrFT optical system provides a convenient way for controlling the properties of the BG beams by properly choosing the optical parameters.

Hidden symmetry and nonlinear paraxial atom optics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Impens, Francois

2009-12-15

A hidden symmetry of the nonlinear wave equation is exploited to analyze the propagation of paraxial and uniform atom-laser beams in time-independent and quadratic transverse potentials with cylindrical symmetry. The quality factor and the paraxial ABCD formalism are generalized to account exactly for mean-field interaction effects in such beams. Using an approach based on moments, these theoretical tools provide a simple yet exact picture of the interacting beam profile evolution. Guided atom laser experiments are discussed. This treatment addresses simultaneously optical and atomic beams in a unified manner, exploiting the formal analogy between nonlinear optics, nonlinear paraxial atom optics, andmore » the physics of two-dimensional Bose-Einstein condensates.« less

Electron beam transport with current above the Alfven--Lawson limit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al'terkop, B.A.; Sokulin, A.Y.; Tarakanov, V.P.

1989-08-01

The quasisteady state of a magnetized electron beam with a current above the Alfven-Lawson limit in a cylindrical waveguide of finite length is analyzed. The distribution of the electrostatic field, the limiting current, and the critical length of the waveguide are found in a two-dimensional system. The basic characteristics of the beam for the injection of a current above the limit---the position of the virtual cathode, the beam thickness, and the current which can be transported---are determined. The current which can be transported may exceed the theoretical limit. The accuracy of the analytic results is confirmed by comparison with themore » results of experiments and numerical simulations.« less

Characterization of cylindrically imploded magnetized plasma by spectroscopy and proton probing

NASA Astrophysics Data System (ADS)

Dozieres, M.; Forestier-Colleoni, P.; Wei, M. S.; Gourdain, P.-A.; Davies, J. R.; Fujioka, S.; Peebles, J.; Campbell, M.; Santos, J. J.; Batani, D.; McGuffey, C.; Beg, F. N.

2017-10-01

Understanding the role of magnetic field in relativistic electron beam transport and energy deposition is important for several applications including fast ignition inertial confinement fusion. We report the development of a cylindrically compressed target platform with externally applied magnetic fields on OMEGA. As a first step, we performed an experiment to characterize the imploded plasma and compressed field condition. The implosion of the target was performed using 36 UV beams (400 J per beam, 1.5 ns square pulse), and the magnetic field was measured by proton deflection using mono-energetic protons produced from D3He capsule implosion. The target was a CH foam cylinder doped with 1% chlorine in order to detect the time-resolved 1s-2p Cl absorption structures, using a gold foil as a broad band backlighter source. A Cu foil at the beginning of the foam cylinder and a Zn foil at the end, allowed us to measure the K α and the 1s-2p transitions of He-like and Li-like ions for both elements. The emission and absorption spectroscopic data are compared to atomic physics codes to determine the plasma temperature and density under the influence of the magnetic field. FOA-0001568.

The study of hard x-ray emission and electron beam generation in wire array Z-pinch and X-pinch plasmas at university-scale generators

NASA Astrophysics Data System (ADS)

Shrestha, Ishor Kumar

The studies of hard x-ray (HXR) emission and electron beam generation in Z-pinch plasmas are very important for Inertial Confinement Fusion (ICF) research and HXR emission application for sources of K-shell and L-shell radiation. Energetic electron beams from Z-pinch plasmas are potentially a problem in the development of ICF. The electron beams and the accompanying HXR emission can preheat the fuel of a thermonuclear target, thereby preventing the fuel compression from reaching densities required for the ignition of a fusion reaction. The photons above 3-4 keV radiated from a Z pinch can provide detailed information about the high energy density plasmas produced at stagnation. Hence, the investigation of characteristics of hard x-rays and electron beams produced during implosions of wire array loads on university scale-generators may provide important data for future ICF, sources of K-shell and L-shell radiations and basic plasma research. This dissertation presents the results of experimental studies of HXR and electron beam generation in wire-array and X-pinch on the 1.7 MA, 100-ns current rise time Zebra generator at University of Nevada, Reno and 1-MA 100-ns current rise-time Cornell Beam Research Accelerator (COBRA) at Cornell University. The experimental study of characteristics of HXR produced by multi-planar wire arrays, compact cylindrical wire array (CCWA) and nested cylindrical wire array (NCWA) made from Al, Cu, Mo, Ag, W and Au were analyzed. The dependence of the HXR yield and power on geometry of the load, the wire material, and load mass was observed. The presence of aluminum wires in the load with the main material such as stainless steel, Cu, Mo, Ag, W or Au in combined wire array decreases HXR yield. The comparison of emission characteristics of HXR and generation of electron beams in CCWA and NCWA on both the high impedance Zebra generator and low impedance COBRA generator were investigated. Some of the "cold" K- shell spectral lines (0.7-2.3Á) and cold L-shell spectral lines (1-1.54Á) in the HXR region were observed only during the interaction of electron beam with load material and anode surface. These observations suggest that the mechanism of HXR emission should be associated with non-thermal mechanisms such as the interaction of the electron beam with the load material. In order to estimate the characteristics of the high-energetic electron beam in Z-pinch plasmas, a hard x-ray polarimeter (HXP) has been developed and used in experiments on the Zebra generator. The electron beams (energy more than 30keV) have been investigated with measurements of the polarization state of the emitted bremsstrahlung radiation from plasma. We also analyzed characteristics of energetic electron beams produced by implosions of multi-planar wire arrays, compact cylindrical and nested wire arrays as well as X-pinches. Direct indications of electron beams (electron cutoff energy EB from 42-250 keV) were obtained by using the measured current of a Faraday cup placed above the anode or mechanical damage observed in the anode surface. A comparison of total electron beam energy and the spatial and spectral analysis of the parameters of plasmas were investigated for different wire materials. The dependences of the total electron beam energy (E b) on the wire material and the geometry of the wire array load were studied.

Design and simulation of MEMS vector hydrophone with reduced cross section based meander beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Manoj; Dutta, S.; Pal, Ramjay

MEMS based vector hydrophone is being one of the key device in the underwater communications. In this paper, we presented a bio-inspired MEMS vector hydrophone. The hydrophone structure consists of a proof mass suspended by four meander type beams with reduced cross-section. Modal patterns of the structure were studied. First three modal frequencies of the hydrophone structure were found to be 420 Hz, 420 Hz and 1646 Hz respectively. The deflection and stress of the hydrophone is found have linear behavior in the 1 µPa – 1Pa pressure range.

Traveling-wave laser-produced-plasma energy source for photoionization laser pumping and lasers incorporating said

DOEpatents

Sher, Mark H.; Macklin, John J.; Harris, Stephen E.

1989-09-26

A traveling-wave, laser-produced-plasma, energy source used to obtain single-pass gain saturation of a photoionization pumped laser. A cylindrical lens is used to focus a pump laser beam to a long line on a target. Grooves are cut in the target to present a surface near normal to the incident beam and to reduce the area, and hence increase the intensity and efficiency, of plasma formation.

Relativistic-electron-beam/target interaction in plasma channels

NASA Astrophysics Data System (ADS)

Halbleib, J. A., Sr.; Wright, T. P.

1980-08-01

A model describing the transport of relativistic electron beams in plasma channels and their subsequent interaction with solid targets is developed and applied to single-beam and multiple-beam configurations. For single beams the targets consist of planar tantalum foils and, in some cases, cusp fields on the transmission side of the foils are employed to improve beam/target coupling efficiency. In the multi-beam configurations, several beams are arranged in wagon-wheel fashion so as to converge upon cylindrical targets, consisting of either hollow tantalum or solid graphite cylinders, located at the hub. For 0.3-cm beam radii that are less than or equal to the channel radii, mean specific power depositions up to about 17 TW/g per MA of injected beam current are obtained for single beams; 12-beam results are typically an order-of-magnitude less. The corresponding enhancements are up to five times the collisional stopping power for either single or multiple beams. Substantial improvement is predicted for the multi-beam interaction should future channel technology permit transport at higher current densities in smaller channels.

Sound radiation from randomly vibrating beams of finite circular cross section

NASA Technical Reports Server (NTRS)

Sutterlin, M. W.; Pierce, A. D.

1976-01-01

The radiation of sound from vibrating cylindrical beams is analyzed based on the frequency of the beam vibrations and the physical characteristics of the beam and its surroundings. A statistical analysis of random beam vibrations allows this result to be independent of the boundary conditions at the ends of the beam. The acoustic power radiated by the beam can be determined from a knowledge of the frequency band vibration data without a knowledge of the individual modal vibration amplitudes. A practical example of the usefulness of this technique is provided by the application of the theoretical calculations to the prediction of the octave band acoustic power output of the picking sticks of an automatic textile loom. Calculations are made of the expected octave band sound pressure levels based on measured acceleration data. These theoretical levels are subsequently compared with actual sound pressure level measurements of loom noise.

Spontaneous generation of vortex and coherent vector beams from a thin-slice c-cut Nd:GdVO4 laser with wide-aperture laser-diode end pumping: application to highly sensitive rotational and translational Doppler velocimetry

NASA Astrophysics Data System (ADS)

Otsuka, Kenju; Chu, Shu-Chun

2017-07-01

Selective excitation of Laguerre-Gauss modes (optical vortices: helical LG0,2 and LG0,1), reflecting their weak transverse cross-saturation of population inversions against a preceding higher-order Ince-Gauss (IG0,2) or Hermite-Gauss (HG2,1) mode, was observed in a thin-slice c-cut Nd:GdVO4 laser with wide-aperture laser-diode end pumping. Single-frequency coherent vector beams were generated through the transverse mode locking of a pair of orthogonally polarized IG2,0 and LG0,2 or HG2,1 and LG0,1 modes. Highly sensitive self-mixing rotational and translational Doppler velocimetry is demonstrated by using vortex and coherent vector beams.

Omnidirectional, circularly polarized, cylindrical microstrip antenna

NASA Technical Reports Server (NTRS)

Stanton, Philip H. (Inventor)

1985-01-01

A microstrip cylindrical antenna comprised of two concentric subelements on a ground cylinder, a vertically polarized (E-field parallel to the axis of the antenna cylinder) subelement on the inside and a horizontally polarized (E-field perpendicular to the axis) subelement on the outside. The vertical subelement is a wraparound microstrip radiator. A Y-shaped microstrip patch configuration is used for the horizontally polarized radiator that is wrapped 1.5 times to provide radiating edges on opposite sides of the cylindrical antenna for improved azimuthal pattern uniformity. When these subelements are so fed that their far fields are equal in amplitude and phased 90.degree. from each other, a circularly polarized EM wave results. By stacking a plurality of like antenna elements on the ground cylinder, a linear phased array antenna is provided that can be beam steered to the desired elevation angle.

A Guided Tour of Mathematical Methods

NASA Astrophysics Data System (ADS)

Snieder, Roel

2009-04-01

1. Introduction; 2. Dimensional analysis; 3. Power series; 4. Spherical and cylindrical co-ordinates; 5. The gradient; 6. The divergence of a vector field; 7. The curl of a vector field; 8. The theorem of Gauss; 9. The theorem of Stokes; 10. The Laplacian; 11. Conservation laws; 12. Scale analysis; 13. Linear algebra; 14. The Dirac delta function; 15. Fourier analysis; 16. Analytic functions; 17. Complex integration; 18. Green's functions: principles; 19. Green's functions: examples; 20. Normal modes; 21. Potential theory; 22. Cartesian tensors; 23. Perturbation theory; 24. Asymptotic evaluation of integrals; 25. Variational calculus; 26. Epilogue, on power and knowledge; References.

Electric fields and vector potentials of thin cylindrical antennas

NASA Astrophysics Data System (ADS)

King, Ronold W. P.

1990-09-01

The vector potential and electric field generated by the current in a center-driven or parasitic dipole antenna that extends from z = -h to z = h are investigated for each of the several components of the current. These include sin k(h - absolute value of z), sin k (absolute value of z) - sin kh, cos kz - cos kh, and cos kz/2 - cos kh/2. Of special interest are the interactions among the variously spaced elements in parallel nonstaggered arrays. These depend on the mutual vector potentials. It is shown that at a radial distance rho approximately = h and in the range z = -h to h, the vector potentials due to all four components become alike and have an approximately plane-wave form. Simple approximate formulas for the electric fields and vector potentials generated by each of the four distributions are derived and compared with the exact results. The application of the new formulas to large arrays is discussed.

Generation of tunable chain of three-dimensional optical bottle beams via focused multi-ring hollow Gaussian beam.

PubMed

Philip, Geo M; Viswanathan, Nirmal K

2010-11-01

We report here the generation of a chain of three-dimensional (3-D) optical bottle beams by focusing a π-phase shifted multi-ring hollow Gaussian beam (HGB) using a lens with spherical aberration. The rings of the HGB of suitable radial (k(r)) and axial (k(z)) wave vectors are generated using a double-negative axicon chemically etched in the optical fiber tips. Moving the lens position with respect to the fiber tip results in variation of the semi-angle of the cones of wave vectors of the HGBs and their diameter, using which we demonstrate tunability in the size and the periodicity of the 3-D optical bottle beams over a wide range, from micrometers to millimeters. The propagation characteristics of the beams resulting from focusing of single- and multi-ring HGBs and resulting in a quasi-non-diffracting beam and a chain of 3-D optical bottle beams, respectively, are simulated using only the input beam parameters and are found to agree well with experimental results.

Development of a vector-tensor system to measure the absolute magnetic flux density and its gradient in magnetically shielded rooms.

PubMed

Voigt, J; Knappe-Grüneberg, S; Gutkelch, D; Haueisen, J; Neuber, S; Schnabel, A; Burghoff, M

2015-05-01

Several experiments in fundamental physics demand an environment of very low, homogeneous, and stable magnetic fields. For the magnetic characterization of such environments, we present a portable SQUID system that measures the absolute magnetic flux density vector and the gradient tensor. This vector-tensor system contains 13 integrated low-critical temperature (LTc) superconducting quantum interference devices (SQUIDs) inside a small cylindrical liquid helium Dewar with a height of 31 cm and 37 cm in diameter. The achievable resolution depends on the flux density of the field under investigation and its temporal drift. Inside a seven-layer mu-metal shield, an accuracy better than ±23 pT for the components of the static magnetic field vector and ±2 pT/cm for each of the nine components of the gradient tensor is reached by using the shifting method.

Development of a vector-tensor system to measure the absolute magnetic flux density and its gradient in magnetically shielded rooms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voigt, J.; Knappe-Grüneberg, S.; Gutkelch, D.

2015-05-15

Several experiments in fundamental physics demand an environment of very low, homogeneous, and stable magnetic fields. For the magnetic characterization of such environments, we present a portable SQUID system that measures the absolute magnetic flux density vector and the gradient tensor. This vector-tensor system contains 13 integrated low-critical temperature (LTc) superconducting quantum interference devices (SQUIDs) inside a small cylindrical liquid helium Dewar with a height of 31 cm and 37 cm in diameter. The achievable resolution depends on the flux density of the field under investigation and its temporal drift. Inside a seven-layer mu-metal shield, an accuracy better than ±23more » pT for the components of the static magnetic field vector and ±2 pT/cm for each of the nine components of the gradient tensor is reached by using the shifting method.« less

Photonic Crystal-Based High-Power Backward Wave Oscillator

DOE PAGES

Poole, Brian R.; Harris, John R.

2017-12-01

An electron beam traversing a slow wave structure can be used to either generate or amplify electromagnetic radiation through the interaction of the slow space charge wave on the beam with the slow wave structure modes. Here, a cylindrical waveguide with a periodic array of conducting loops is used for the slow wave structure. This paper considers operation as a backward wave oscillator. The dispersion properties of the structure are determined using a frequency-domain eigenmode solver. The interaction of the electron beam with the structure modes is investigated using a 2-D particle-in-cell (PIC) code. In conclusion, the operating frequency andmore » growth rate dependence on beam energy and beam current are investigated using the PIC code and compared with analytic and scaling estimates where possible.« less

Photonic Crystal-Based High-Power Backward Wave Oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poole, Brian R.; Harris, John R.

An electron beam traversing a slow wave structure can be used to either generate or amplify electromagnetic radiation through the interaction of the slow space charge wave on the beam with the slow wave structure modes. Here, a cylindrical waveguide with a periodic array of conducting loops is used for the slow wave structure. This paper considers operation as a backward wave oscillator. The dispersion properties of the structure are determined using a frequency-domain eigenmode solver. The interaction of the electron beam with the structure modes is investigated using a 2-D particle-in-cell (PIC) code. In conclusion, the operating frequency andmore » growth rate dependence on beam energy and beam current are investigated using the PIC code and compared with analytic and scaling estimates where possible.« less

Flow velocity vector fields by ultrasound particle imaging velocimetry: in vitro comparison with optical flow velocimetry.

PubMed

Westerdale, John; Belohlavek, Marek; McMahon, Eileen M; Jiamsripong, Panupong; Heys, Jeffrey J; Milano, Michele

2011-02-01

We performed an in vitro study to assess the precision and accuracy of particle imaging velocimetry (PIV) data acquired using a clinically available portable ultrasound system via comparison with stereo optical PIV. The performance of ultrasound PIV was compared with optical PIV on a benchmark problem involving vortical flow with a substantial out-of-plane velocity component. Optical PIV is capable of stereo image acquisition, thus measuring out-of-plane velocity components. This allowed us to quantify the accuracy of ultrasound PIV, which is limited to in-plane acquisition. The system performance was assessed by considering the instantaneous velocity fields without extracting velocity profiles by spatial averaging. Within the 2-dimensional correlation window, using 7 time-averaged frames, the vector fields were found to have correlations of 0.867 in the direction along the ultrasound beam and 0.738 in the perpendicular direction. Out-of-plane motion of greater than 20% of the in-plane vector magnitude was found to increase the SD by 11% for the vectors parallel to the ultrasound beam direction and 8.6% for the vectors perpendicular to the beam. The results show a close correlation and agreement of individual velocity vectors generated by ultrasound PIV compared with optical PIV. Most of the measurement distortions were caused by out-of-plane velocity components.

Analysis of the far-field characteristics of hybridly polarized vector beams from the vectorial structure

NASA Astrophysics Data System (ADS)

Li, Jia; Wu, Pinghui; Chang, Liping

2016-01-01

Based on the angular spectrum representation of electromagnetic beams, analytical expressions are derived for the TE term, TM term and the whole energy fluxes of a hybridly polarized vector (HPV) beam propagating in the far field. It is shown that both the TE and TM terms of the energy fluxes are strongly dependent of the truncation radius of the circular aperture. By choosing the truncation radius as a certain value, it is found that the far-zone distributions of TE and TM terms exhibit four-petal patterns with surrounding side-lobes displaying oscillating intensities. Interestingly, such phenomenon becomes extremely obvious particularly when the truncation radius is comparable with the wavelength of the propagating beam.

Development of a small single-ring OpenPET prototype with a novel transformable architecture.

PubMed

Tashima, Hideaki; Yoshida, Eiji; Inadama, Naoko; Nishikido, Fumihiko; Nakajima, Yasunori; Wakizaka, Hidekatsu; Shinaji, Tetsuya; Nitta, Munetaka; Kinouchi, Shoko; Suga, Mikio; Haneishi, Hideaki; Inaniwa, Taku; Yamaya, Taiga

2016-02-21

The single-ring OpenPET (SROP), for which the detector arrangement has a cylinder shape cut by two parallel planes at a slant angle to form an open space, is our original proposal for in-beam PET. In this study, we developed a small prototype of an axial-shift type SROP (AS-SROP) with a novel transformable architecture for a proof-of-concept. In the AS-SROP, detectors originally forming a cylindrical PET are axially shifted little by little. We designed the small AS-SROP prototype for 4-layer depth-of-interaction detectors arranged in a ring diameter of 250 mm. The prototype had two modes: open and closed. The open mode formed the SROP with the open space of 139 mm and the closed mode formed a conventional cylindrical PET. The detectors were simultaneously moved by a rotation handle allowing them to be transformed between the two modes. We evaluated the basic performance of the developed prototype and carried out in-beam imaging tests in the HIMAC using (11)C radioactive beam irradiation. As a result, we found the open mode enabled in-beam PET imaging at a slight cost of imaging performance; the spatial resolution and sensitivity were 2.6 mm and 5.1% for the open mode and 2.1 mm and 7.3% for the closed mode. We concluded that the AS-SROP can minimize the decrease of resolution and sensitivity, for example, by transforming into the closed mode immediately after the irradiation while maintaining the open space only for the in-beam PET measurement.

Circular dichroism in photoelectron images from aligned nitric oxide molecules

DOE PAGES

Sen, Ananya; Pratt, S. T.; Reid, K. L.

2017-05-03

We have used velocity map photoelectron imaging to study circular dichroism of the photoelectron angular distributions (PADs) of nitric oxide following two-color resonanceenhanced two-photon ionization via selected rotational levels of the A 2Σ +, v' = 0 state. By using a circularly polarized pump beam and a counter-propagating, circularly polarized probe beam, cylindrical symmetry is preserved in the ionization process, and the images can be reconstructed using standard algorithms. The VMI set up enables individual ion rotational states to be resolved with excellent collection efficiency, rendering the measurements considerably simpler to perform than previous measurements conducted with a conventional photoelectronmore » spectrometer. The results demonstrate that circular dichroism is observed even when cylindrical symmetry is maintained, and serve as a reminder that dichroism is a general feature of the multiphoton ionization of atoms and molecules. Furthermore, the observed PADs are in good agreement with calculations based on parameters extracted from previous experimental results obtained by using a time-offlight electron spectrometer.« less

Circular dichroism in photoelectron images from aligned nitric oxide molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sen, Ananya; Pratt, S. T.; Reid, K. L.

We have used velocity map photoelectron imaging to study circular dichroism of the photoelectron angular distributions (PADs) of nitric oxide following two-color resonanceenhanced two-photon ionization via selected rotational levels of the A 2Σ +, v' = 0 state. By using a circularly polarized pump beam and a counter-propagating, circularly polarized probe beam, cylindrical symmetry is preserved in the ionization process, and the images can be reconstructed using standard algorithms. The VMI set up enables individual ion rotational states to be resolved with excellent collection efficiency, rendering the measurements considerably simpler to perform than previous measurements conducted with a conventional photoelectronmore » spectrometer. The results demonstrate that circular dichroism is observed even when cylindrical symmetry is maintained, and serve as a reminder that dichroism is a general feature of the multiphoton ionization of atoms and molecules. Furthermore, the observed PADs are in good agreement with calculations based on parameters extracted from previous experimental results obtained by using a time-offlight electron spectrometer.« less

Measuring implosion velocities in experiments and simulations of laser-driven cylindrical implosions on the OMEGA laser

NASA Astrophysics Data System (ADS)

Hansen, E. C.; Barnak, D. H.; Betti, R.; Campbell, E. M.; Chang, P.-Y.; Davies, J. R.; Glebov, V. Yu; Knauer, J. P.; Peebles, J.; Regan, S. P.; Sefkow, A. B.

2018-05-01

Laser-driven magnetized liner inertial fusion (MagLIF) on OMEGA involves cylindrical implosions, a preheat beam, and an applied magnetic field. Initial experiments excluded the preheat beam and magnetic field to better characterize the implosion. X-ray self-emission as measured by framing cameras was used to determine the shell trajectory. The 1D code LILAC was used to model the central region of the implosion, and results were compared to 2D simulations from the HYDRA code. Post-processing of simulation output with SPECT3D and Yorick produced synthetic x-ray images that were used to compare the simulation results with the x-ray framing camera data. Quantitative analysis shows that higher measured neutron yields correlate with higher implosion velocities. The future goal is to further analyze the x-ray images to characterize the uniformity of the implosions and apply these analysis techniques to integrated laser-driven MagLIF shots to better understand the effects of preheat and the magnetic field.

Acoustic Levitator With Furnace And Laser Heating

NASA Technical Reports Server (NTRS)

Barmatz, Martin B.; Stoneburner, James D.

1991-01-01

Acoustic-levitation apparatus incorporates electrical-resistance furnace for uniform heating up to temperature of about 1,000 degrees C. Additional local heating by pair of laser beams raise temperature of sample to more than 1,500 degrees C. High temperature single-mode acoustic levitator generates cylindrical-mode accoustic resonance levitating sample. Levitation chamber enclosed in electrical-resistance furnace. Infrared beams from Nd:YAG laser provide additional local heating of sample. Designed for use in containerless processing of materials in microgravity or in normal Earth gravity.

Inertial confinement fusion method producing line source radiation fluence

DOEpatents

Rose, Ronald P.

1984-01-01

An inertial confinement fusion method in which target pellets are imploded in sequence by laser light beams or other energy beams at an implosion site which is variable between pellet implosions along a line. The effect of the variability in position of the implosion site along a line is to distribute the radiation fluence in surrounding reactor components as a line source of radiation would do, thereby permitting the utilization of cylindrical geometry in the design of the reactor and internal components.

An advanced negative hydrogen ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goncharov, Alexey A., E-mail: gonchar@iop.kiev.ua; Dobrovolsky, Andrey N.; Goretskii, Victor P.

2016-02-15

The results of investigation of emission productivity of negative particles source with cesiated combined discharge are presented. A cylindrical beam of negative hydrogen ions with density about 2 A/cm{sup 2} in low noise mode on source emission aperture is obtained. The total beam current values are up to 200 mA for negative hydrogen ions and up to 1.5 A for all negative particles with high divergence after source. The source has simple design and can produce stable discharge with low level of oscillation.

High speed cylindrical roller bearing analysis. SKF computer program CYBEAN. Volume 2: User's manual

NASA Technical Reports Server (NTRS)

Dyba, G. J.; Kleckner, R. J.

1981-01-01

CYBEAN (CYlindrical BEaring ANalysis) was created to detail radially loaded, aligned and misaligned cylindrical roller bearing performance under a variety of operating conditions. Emphasis was placed on detailing the effects of high speed, preload and system thermal coupling. Roller tilt, skew, radial, circumferential and axial displacement as well as flange contact were considered. Variable housing and flexible out-of-round outer ring geometries, and both steady state and time transient temperature calculations were enabled. The complete range of elastohydrodynamic contact considerations, employing full and partial film conditions were treated in the computation of raceway and flange contacts. The practical and correct implementation of CYBEAN is discussed. The capability to execute the program at four different levels of complexity was included. In addition, the program was updated to properly direct roller-to-raceway contact load vectors automatically in those cases where roller or ring profiles have small radii of curvature. Input and output architectures containing guidelines for use and two sample executions are detailed.

Electromagnetic scattering by a uniaxial anisotropic sphere located in an off-axis Bessel beam.

PubMed

Qu, Tan; Wu, Zhen-Sen; Shang, Qing-Chao; Li, Zheng-Jun; Bai, Lu

2013-08-01

Electromagnetic scattering of a zero-order Bessel beam by an anisotropic spherical particle in the off-axis configuration is investigated. Based on the spherical vector wave functions, the expansion expression of the zero-order Bessel beam is derived, and its convergence is numerically discussed in detail. Utilizing the tangential continuity of the electromagnetic fields, the expressions of scattering coefficients are given. The effects of the conical angle of the wave vector components of the zero-order Bessel beam, the ratio of the radius of the sphere to the central spot radius of the zero-order Bessel beam, the shift of the beam waist center position along both the x and y axes, the permittivity and permeability tensor elements, and the loss of the sphere on the radar cross section (RCS) are numerically analyzed. It is revealed that the maximum RCS appears in the conical direction or neighboring direction when the sphere is illuminated by a zero-order Bessel beam. Furthermore, the RCS will decrease and the symmetry is broken with the shift of the beam waist center.

Profiles of ion beams and plasma parameters on a multi-frequencies microwaves large bore electron cyclotron resonance ion source with permanent magnets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kato, Yushi; Sakamoto, Naoki; Kiriyama, Ryutaro

2012-02-15

In order to contribute to various applications of plasma and beams based on an electron cyclotron resonance, a new concept on magnetic field with all magnets on plasma production and confinement has been proposed with enhanced efficiency for broad and dense ion beam. The magnetic field configuration consists of a pair of comb-shaped magnet surrounding plasma chamber cylindrically. Resonance zones corresponding for 2.45 GHz and 11-13 GHz frequencies are positioned at spatially different positions. We launch simultaneously multiplex frequencies microwaves operated individually, try to control profiles of the plasma parameters and the extracted ion beams, and to measure them inmore » detail.« less

View Factor and Radiation-Hydrodynamic Simulations of Gas-Filled Outer-Quad-Only Hohlraums at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Young, Christopher; Meezan, Nathan; Landen, Otto

2017-10-01

A cylindrical National Ignition Facility hohlraum irradiated exclusively by NOVA-like outer quads (44 .5° and 50° beams) is proposed to minimize laser plasma interaction (LPI) losses and avoid problems with propagating the inner (23 .5° and 30°) beams. Symmetry and drive are controlled by shortening the hohlraum, using a smaller laser entrance hole (LEH), beam phasing the 44 .5° and 50° beams, and correcting the remaining P4 asymmetry with a capsule shim. Ensembles of time-resolved view factor simulations help narrow the design space of the new configuration, with fine tuning provided by the radiation-hydrodynamic code HYDRA. Prepared by LLNL under Contract DE-AC52-07NA27344.

A {3,2}-Order Bending Theory for Laminated Composite and Sandwich Beams

NASA Technical Reports Server (NTRS)

Cook, Geoffrey M.; Tessler, Alexander

1998-01-01

A higher-order bending theory is derived for laminated composite and sandwich beams thus extending the recent {1,2}-order theory to include third-order axial effect without introducing additional kinematic variables. The present theory is of order {3,2} and includes both transverse shear and transverse normal deformations. A closed-form solution to the cylindrical bending problem is derived and compared with the corresponding exact elasticity solution. The numerical comparisons are focused on the most challenging material systems and beam aspect ratios which include moderate-to-thick unsymmetric composite and sandwich laminates. Advantages and limitations of the theory are discussed.

Amplitude and phase beam shaping for highest sensitivity in sidewall angle detection.

PubMed

Cisotto, Luca; Paul Urbach, H

2017-01-01

In integrated circuits manufacturing, specific structures are used as tools to evaluate the quality of the lithographic process, and the shape of these structures is often described by a few parameters, of which in particular the sidewall angle suffers from considerable inaccuracies. Using scalar diffraction theory, we investigate whether a properly shaped cylindrically focused probing beam could increase the ability to detect tiny changes in this angle in the case of a cliff-like structure, modeled as a phase object. This paper describes the theoretical formulation used to calculate the optimized beam and compares its performance with the case of a focused plane wave.

High-order optical vortex position detection using a Shack-Hartmann wavefront sensor.

PubMed

Luo, Jia; Huang, Hongxin; Matsui, Yoshinori; Toyoda, Haruyoshi; Inoue, Takashi; Bai, Jian

2015-04-06

Optical vortex (OV) beams have null-intensity singular points, and the intensities in the region surrounding the singular point are quite low. This low intensity region influences the position detection accuracy of phase singular point, especially for high-order OV beam. In this paper, we propose a new method for solving this problem, called the phase-slope-combining correlation matching method. A Shack-Hartmann wavefront sensor (SH-WFS) is used to measure phase slope vectors at lenslet positions of the SH-WFS. Several phase slope vectors are combined into one to reduce the influence of low-intensity regions around the singular point, and the combined phase slope vectors are used to determine the OV position with the aid of correlation matching with a pre-calculated database. Experimental results showed that the proposed method works with high accuracy, even when detecting an OV beam with a topological charge larger than six. The estimated precision was about 0.15 in units of lenslet size when detecting an OV beam with a topological charge of up to 20.

The Use of an Electron Microchannel as a Self-Extracting and Focusing Plasma Cathode Electron Gun

NASA Astrophysics Data System (ADS)

Cornish, S.; Khachan, J.

2016-02-01

A new and simple type of electron gun is presented. Unlike conventional electron guns, which require a heated filament or extractor, accelerator and focusing electrodes, this gun uses the collimated electron microchannels of an inertial electrostatic confinement (IEC) discharge to achieve the same outcome. A cylindrical cathode is placed coaxially within a cylindrical anode to create the discharge. Collimated beams of electrons and fast neutrals emerge along the axis of the cylindrical cathode. This geometry isolates one of the microchannels that emerge in a negatively biased IEC grid. The internal operating pressure range of the gun is 35-190 mTorr. A small aperture separates the gun from the main vacuum chamber in order to achieve a pressure differential. The chamber was operated at pressures of 4-12 mTorr. The measured current produced by the gun was 0.1-3 mA (0.2-14 mA corrected measurement) for discharge currents of 1-45 mA and discharge voltages of 0.5-12 kV. The collimated electron beam emerges from the aperture into the vacuum chamber. The performance of the gun is unaffected by the pressure differential between the vacuum chamber and the gun. This allows the aperture to be removed and the chamber pressure to be equal to the gun pressure if required.

Fabrication of parabolic cylindrical microlens array by shaped femtosecond laser

NASA Astrophysics Data System (ADS)

Luo, Zhi; Yin, Kai; Dong, Xinran; Duan, Ji'an

2018-04-01

A simple and efficient technique for fabricating parabolic cylindrical microlens arrays (CMLAs) on the surface of fused silica by shaped femtosecond (fs) laser direct-writing is demonstrated. By means of spatially shaping of a Gaussian fs laser beam to a Bessel distribution, an inversed cylindrical shape laser intensity profile is formed in a specific cross-sectional plane among the shaped optical field. Applying it to experiments, large area close-packed parabolic CMLAs with line-width of 37.5 μm and array size of about 5 × 5 mm are produced. The cross-sectional outline of obtained lenslets has a satisfied parabolic profile and the numerical aperture (NA) of lenslets is more than 0.35. Furthermore, the focusing performance of the fabricated CMLA is also tested in this work and it has been demonstrated that the focusing power of the CMLA with a parabolic profile is better than that with a semi-circular one.

A Survey of Permanently-Manned Lunar Base Concepts

DTIC Science & Technology

1989-06-01

of warmth and illumination. Heliostat mirr -s direct the solar beam into a periscope-like tunnel. The shape and configuration of the reflector...the tower is continuously oriented toward the sun. Installed on the tower are heliostat mirrors for a solar furnace, a cylindrical collector for lower

Proof-of-principle experiment of measurement-device-independent quantum key distribution with vector vortex beams

NASA Astrophysics Data System (ADS)

Dong, Chen; Zhao, Shang-Hong; Li, Wei; Yang, Jian

2018-03-01

In this paper, by combining measurement-device-independent quantum key distribution (MDI-QKD) scheme with entangled photon sources, we present a modified MDI-QKD scheme with pairs of vector vortex(VV) beams, which shows a structure of hybrid entangled entanglement corresponding to intrasystem entanglement and intersystem entanglement. The former entanglement, which is entangled between polarization and orbit angular momentum within each VV beam, is adopted to overcome the polarization misalignment associated with random rotations in quantum key distribution. The latter entanglement, which is entangled between the two VV beams, is used to perform entangled-based MDI-QKD protocol with pair of VV beams to inherit the merit of long distance. The numerical simulations show that our modified scheme can tolerate 97dB with practical detectors. Furthermore, our modified protocol only needs to insert q-plates in practical experiment.

Ellipsoidal terrain correction based on multi-cylindrical equal-area map projection of the reference ellipsoid

NASA Astrophysics Data System (ADS)

Ardalan, A. A.; Safari, A.

2004-09-01

An operational algorithm for computation of terrain correction (or local gravity field modeling) based on application of closed-form solution of the Newton integral in terms of Cartesian coordinates in multi-cylindrical equal-area map projection of the reference ellipsoid is presented. Multi-cylindrical equal-area map projection of the reference ellipsoid has been derived and is described in detail for the first time. Ellipsoidal mass elements with various sizes on the surface of the reference ellipsoid are selected and the gravitational potential and vector of gravitational intensity (i.e. gravitational acceleration) of the mass elements are computed via numerical solution of the Newton integral in terms of geodetic coordinates {λ,ϕ,h}. Four base- edge points of the ellipsoidal mass elements are transformed into a multi-cylindrical equal-area map projection surface to build Cartesian mass elements by associating the height of the corresponding ellipsoidal mass elements to the transformed area elements. Using the closed-form solution of the Newton integral in terms of Cartesian coordinates, the gravitational potential and vector of gravitational intensity of the transformed Cartesian mass elements are computed and compared with those of the numerical solution of the Newton integral for the ellipsoidal mass elements in terms of geodetic coordinates. Numerical tests indicate that the difference between the two computations, i.e. numerical solution of the Newton integral for ellipsoidal mass elements in terms of geodetic coordinates and closed-form solution of the Newton integral in terms of Cartesian coordinates, in a multi-cylindrical equal-area map projection, is less than 1.6×10-8 m2/s2 for a mass element with a cross section area of 10×10 m and a height of 10,000 m. For a mass element with a cross section area of 1×1 km and a height of 10,000 m the difference is less than 1.5×10-4m2/s2. Since 1.5× 10-4 m2/s2 is equivalent to 1.5×10-5m in the vertical direction, it can be concluded that a method for terrain correction (or local gravity field modeling) based on closed-form solution of the Newton integral in terms of Cartesian coordinates of a multi-cylindrical equal-area map projection of the reference ellipsoid has been developed which has the accuracy of terrain correction (or local gravity field modeling) based on the Newton integral in terms of ellipsoidal coordinates.

RF cavity design and qualification for proton accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teotia, Vikas; Malhotra, Sanjay; Ukarde, Priti

Alvarez type Drift Tube Linac (DTL) is used for acceleration of proton beam in low energy section of beta ranging from 0.04 to 0.40. DTL is cylindrical RF cavity resonating in TM010 mode at 352.21 MHz frequency. It consists of array of drift tubes arranged ensuring that DTL centre and Drift Tube centre are concentric. The Drift Tubes also houses Permanent Magnet Quadrupole for transverse focusing of proton beam. A twelve cell prototype of DTL section is designed, developed and fabricated at Bhabha Atomic Research Centre, Trombay. Complete DTL accelerator consists of eight such DTL sections. High frequency microwave simulationsmore » are carried out in SOPRANO, vector fields and COMSOL simulation software. This prototype DTL is 1640.56 mm long cavity with 520 mm ID, 600 mm OD and consists of eleven Drift Tubes, two RF end flanges, three slug tuners, six post couplers, three RF field monitors, one RF waveguide coupler, two DN100 vacuum flanges and DTL tank platform with alignment features. Girder based Drift tube mounting arrangement utilizing uncompressing energy of disc springs for optimum combo RF-vacuum seal compression is worked out and implemented. This paper discusses design of this RF vacuum cavity operating at high accelerating field gradient in ultra-high vacuum. Detailed vacuum design and results of RF and vacuum qualifications are discussed. Results on mechanical accuracy achieved on scaled pre-prototype are also presented. Paper summarizes the engineering developments carried out for this RF cavity and brings out the future activities proposed in indigenous development of high gradient RF cavities for ion accelerators. (author)« less

Crosstalk Cancellation for a Simultaneous Phase Shifting Interferometer

NASA Technical Reports Server (NTRS)

Olczak, Eugene (Inventor)

2014-01-01

A method of minimizing fringe print-through in a phase-shifting interferometer, includes the steps of: (a) determining multiple transfer functions of pixels in the phase-shifting interferometer; (b) computing a crosstalk term for each transfer function; and (c) displaying, to a user, a phase-difference map using the crosstalk terms computed in step (b). Determining a transfer function in step (a) includes measuring intensities of a reference beam and a test beam at the pixels, and measuring an optical path difference between the reference beam and the test beam at the pixels. Computing crosstalk terms in step (b) includes computing an N-dimensional vector, where N corresponds to the number of transfer functions, and the N-dimensional vector is obtained by minimizing a variance of a modulation function in phase shifted images.

Reference Dosimetry according to the New German Protocol DIN 6800-2 and Comparison with IAEA TRS 398 and AAPM TG 51*

PubMed Central

Zakaria, A; Schuette, W; Younan, C

2011-01-01

The preceding DIN 6800-2 (1997) protocol has been revised by a German task group and its latest version was published in March 2008 as the national standard dosimetry protocol DIN 6800-2 (2008 March). Since then, in Germany the determination of absorbed dose to water for high-energy photon and electron beams has to be performed according to this new German dosimetry protocol. The IAEA Code of Practice TRS 398 (2000) and the AAPM TG-51 are the two main protocols applied internationally. The new German version has widely adapted the methodology and dosimetric data of TRS-398. This paper investigates systematically the DIN 6800-2 protocol and compares it with the procedures and results obtained by using the international protocols. The investigation was performed with 6 MV and 18 MV photon beams as well as with electron beams from 5 MeV to 21 MeV. While only cylindrical chambers were used for photon beams, the measurements of electron beams were performed by using cylindrical and plane-parallel chambers. It was found that the discrepancies in the determination of absorbed dose to water among the three protocols were 0.23% for photon beams and 1.2% for electron beams. The determination of water absorbed dose was also checked by a national audit procedure using TLDs. The comparison between the measurements following the DIN 6800-2 protocol and the TLD audit-procedure confirmed a difference of less than 2%. The advantage of the new German protocol DIN 6800-2 lies in the renouncement on the cross calibration procedure as well as its clear presentation of formulas and parameters. In the past, the different protocols evoluted differently from time to time. Fortunately today, a good convergence has been obtained in concepts and methods. PMID:22287987

Reference Dosimetry according to the New German Protocol DIN 6800-2 and Comparison with IAEA TRS 398 and AAPM TG 51.

PubMed

Zakaria, A; Schuette, W; Younan, C

2011-04-01

The preceding DIN 6800-2 (1997) protocol has been revised by a German task group and its latest version was published in March 2008 as the national standard dosimetry protocol DIN 6800-2 (2008 March). Since then, in Germany the determination of absorbed dose to water for high-energy photon and electron beams has to be performed according to this new German dosimetry protocol. The IAEA Code of Practice TRS 398 (2000) and the AAPM TG-51 are the two main protocols applied internationally. The new German version has widely adapted the methodology and dosimetric data of TRS-398. This paper investigates systematically the DIN 6800-2 protocol and compares it with the procedures and results obtained by using the international protocols. The investigation was performed with 6 MV and 18 MV photon beams as well as with electron beams from 5 MeV to 21 MeV. While only cylindrical chambers were used for photon beams, the measurements of electron beams were performed by using cylindrical and plane-parallel chambers. It was found that the discrepancies in the determination of absorbed dose to water among the three protocols were 0.23% for photon beams and 1.2% for electron beams. The determination of water absorbed dose was also checked by a national audit procedure using TLDs. The comparison between the measurements following the DIN 6800-2 protocol and the TLD audit-procedure confirmed a difference of less than 2%. The advantage of the new German protocol DIN 6800-2 lies in the renouncement on the cross calibration procedure as well as its clear presentation of formulas and parameters. In the past, the different protocols evoluted differently from time to time. Fortunately today, a good convergence has been obtained in concepts and methods.

Impedance of curved rectangular spiral coils around a conductive cylinder

NASA Astrophysics Data System (ADS)

Burke, S. K.; Ditchburn, R. J.; Theodoulidis, T. P.

2008-07-01

Eddy-current induction due to a thin conformable coil wrapped around a long conductive cylinder is examined using a second-order vector potential formalism. Compact closed-form expressions are derived for the self- and mutual impedances of curved rectangular spiral coils (i) in free space and (ii) when wrapped around the surface of the cylindrical rod. The validity of these expressions was tested against the results of a systematic series of experiments using a cylindrical Al-alloy rod and conformable coils manufactured using flexible printed-circuit-board technology. The theoretical expressions were in very good agreement with the experimental measurements. The significance of the results for eddy-current nondestructive inspection using flexible coils and flexible coil arrays is discussed.

Model of depositing layer on cylindrical surface produced by induction-assisted laser cladding process

NASA Astrophysics Data System (ADS)

Kotlan, Václav; Hamar, Roman; Pánek, David; Doležel, Ivo

2017-12-01

A model of hybrid cladding on a cylindrical surface is built and numerically solved. Heating of both substrate and the powder material to be deposited on its surface is realized by laser beam and preheating inductor. The task represents a hard-coupled electromagnetic-thermal problem with time-varying geometry. Two specific algorithms are developed to incorporate this effect into the model, driven by local distribution of temperature and its gradients. The algorithms are implemented into the COMSOL Multiphysics 5.2 code that is used for numerical computations of the task. The methodology is illustrated with a typical example whose results are discussed.

Effect of multiply charged ions on the performance and beam characteristics in annular and cylindrical type Hall thruster plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Holak; Lim, Youbong; Choe, Wonho, E-mail: wchoe@kaist.ac.kr

2014-10-06

Plasma plume and thruster performance characteristics associated with multiply charged ions in a cylindrical type Hall thruster (CHT) and an annular type Hall thruster are compared under identical conditions such as channel diameter, channel depth, propellant mass flow rate. A high propellant utilization in a CHT is caused by a high ionization rate, which brings about large multiply charged ions. Ion currents and utilizations are much different due to the presence of multiply charged ions. A high multiply charged ion fraction and a high ionization rate in the CHT result in a higher specific impulse, thrust, and discharge current.

Surface Structuring with Polarization-Singular Femtosecond Laser Beams Generated by a q-plate

PubMed Central

Nivas, Jijil JJ; Cardano, Filippo; Song, Zhenming; Rubano, Andrea; Fittipaldi, Rosalba; Vecchione, Antonio; Paparo, Domenico; Marrucci, Lorenzo; Bruzzese, Riccardo; Amoruso, Salvatore

2017-01-01

In the last few years femtosecond optical vortex beams with different spatial distributions of the state of polarization (e.g. azimuthal, radial, spiral, etc.) have been used to generate complex, regular surface patterns on different materials. Here we present an experimental investigation on direct femtosecond laser surface structuring based on a larger class of vector beams generated by means of a q-plate with topological charge q = +1/2. In fact, voltage tuning of q-plate optical retardation allows generating a family of ultrashort laser beams with a continuous spatial evolution of polarization and fluence distribution in the focal plane. These beams can be thought of as a controlled coherent superposition of a Gaussian beam with uniform polarization and a vortex beam with a radial or azimuthal state of polarization. The use of this family of ultrashort laser beams in surface structuring leads to a further extension of the achievable surface patterns. The comparison of theoretical predictions of the vector beam characteristics at the focal plane and the generated surface patterns is used to rationalize the dependence of the surface structures on the local state of the laser beam, thus offering an effective way to either design unconventional surface structures or diagnose complex ultrashort laser beams. PMID:28169342

Surface Structuring with Polarization-Singular Femtosecond Laser Beams Generated by a q-plate.

PubMed

Nivas, Jijil Jj; Cardano, Filippo; Song, Zhenming; Rubano, Andrea; Fittipaldi, Rosalba; Vecchione, Antonio; Paparo, Domenico; Marrucci, Lorenzo; Bruzzese, Riccardo; Amoruso, Salvatore

2017-02-07

In the last few years femtosecond optical vortex beams with different spatial distributions of the state of polarization (e.g. azimuthal, radial, spiral, etc.) have been used to generate complex, regular surface patterns on different materials. Here we present an experimental investigation on direct femtosecond laser surface structuring based on a larger class of vector beams generated by means of a q-plate with topological charge q = +1/2. In fact, voltage tuning of q-plate optical retardation allows generating a family of ultrashort laser beams with a continuous spatial evolution of polarization and fluence distribution in the focal plane. These beams can be thought of as a controlled coherent superposition of a Gaussian beam with uniform polarization and a vortex beam with a radial or azimuthal state of polarization. The use of this family of ultrashort laser beams in surface structuring leads to a further extension of the achievable surface patterns. The comparison of theoretical predictions of the vector beam characteristics at the focal plane and the generated surface patterns is used to rationalize the dependence of the surface structures on the local state of the laser beam, thus offering an effective way to either design unconventional surface structures or diagnose complex ultrashort laser beams.

Surface Structuring with Polarization-Singular Femtosecond Laser Beams Generated by a q-plate

NASA Astrophysics Data System (ADS)

Nivas, Jijil Jj; Cardano, Filippo; Song, Zhenming; Rubano, Andrea; Fittipaldi, Rosalba; Vecchione, Antonio; Paparo, Domenico; Marrucci, Lorenzo; Bruzzese, Riccardo; Amoruso, Salvatore

2017-02-01

In the last few years femtosecond optical vortex beams with different spatial distributions of the state of polarization (e.g. azimuthal, radial, spiral, etc.) have been used to generate complex, regular surface patterns on different materials. Here we present an experimental investigation on direct femtosecond laser surface structuring based on a larger class of vector beams generated by means of a q-plate with topological charge q = +1/2. In fact, voltage tuning of q-plate optical retardation allows generating a family of ultrashort laser beams with a continuous spatial evolution of polarization and fluence distribution in the focal plane. These beams can be thought of as a controlled coherent superposition of a Gaussian beam with uniform polarization and a vortex beam with a radial or azimuthal state of polarization. The use of this family of ultrashort laser beams in surface structuring leads to a further extension of the achievable surface patterns. The comparison of theoretical predictions of the vector beam characteristics at the focal plane and the generated surface patterns is used to rationalize the dependence of the surface structures on the local state of the laser beam, thus offering an effective way to either design unconventional surface structures or diagnose complex ultrashort laser beams.

Real-time direct measurement of liquid (water) evaporation by simple disturbance inhibited interfometry technique

NASA Astrophysics Data System (ADS)

Kim, Yong Gi

2017-11-01

A real-time in-situ interferometry method was proposed to measure water (liquid) evaporation directly over the liquid surface inside the reservoir. The direct evaporation measurement relied on the counting the number of sinusoidal fringes. As the water inside reservoir evaporated, the depth of the water decreases a little thus the optical path length changes. Evaporation signals have been determined as a function of the focusing beam position of the signal beam over the liquid surface. In interferometry technique, the most limiting factors are surface disturbances and vibrations over the liquid surface. This limiting factor was simply inhibited by placing a long cylindrical aluminum tube around the signal beam of the interferometer over the liquid surface. A small diameter cylindrical Al tube diminished vibrations and wind induced surface ripples more effectively than that of the larger one. Water evaporation was successfully measured in real-time with a warm water and cold water even under windy condition with an electric fan. The experimental results demonstrated that the interferometry technique allows determining of liquid evaporation in real-time. Interferometric technique opens up a new possibility of methodology for liquid evaporation measurement even in several environmental disturbances, such as, vibration, surface disturbance, temperature change and windy environments.

Variability of surface and center position radiation dose in MDCT: Monte Carlo simulations using CTDI and anthropomorphic phantoms

PubMed Central

Zhang, Di; Savandi, Ali S.; Demarco, John J.; Cagnon, Chris H.; Angel, Erin; Turner, Adam C.; Cody, Dianna D.; Stevens, Donna M.; Primak, Andrew N.; McCollough, Cynthia H.; McNitt-Gray, Michael F.

2009-01-01

The larger coverage afforded by wider z-axis beams in multidetector CT (MDCT) creates larger cone angles and greater beam divergence, which results in substantial surface dose variation for helical and contiguous axial scans. This study evaluates the variation of absorbed radiation dose in both cylindrical and anthropomorphic phantoms when performing helical or contiguous axial scans. The approach used here was to perform Monte Carlo simulations of a 64 slice MDCT. Simulations were performed with different radiation profiles (simulated beam widths) for a given collimation setting (nominal beam width) and for different pitch values and tube start angles. The magnitude of variation at the surface was evaluated under four different conditions: (a) a homogeneous CTDI phantom with different combinations of pitch and simulated beam widths, (b) a heterogeneous anthropomorphic phantom with one measured beam collimation and various pitch values, (c) a homogeneous CTDI phantom with fixed beam collimation and pitch, but with different tube start angles, and (d) pitch values that should minimize variations of surface dose—evaluated for both homogeneous and heterogeneous phantoms. For the CTDI phantom simulations, peripheral dose patterns showed variation with percent ripple as high as 65% when pitch is 1.5 and simulated beam width is equal to the nominal collimation. For the anterior surface dose on an anthropomorphic phantom, the percent ripple was as high as 40% when the pitch is 1.5 and simulated beam width is equal to the measured beam width. Low pitch values were shown to cause beam overlaps which created new peaks. Different x-ray tube start angles create shifts of the peripheral dose profiles. The start angle simulations showed that for a given table position, the surface dose could vary dramatically with minimum values that were 40% of the peak when all conditions are held constant except for the start angle. The last group of simulations showed that an “ideal” pitch value can be determined which reduces surface dose variations, but this pitch value must take into account the measured beam width. These results reveal the complexity of estimating surface dose and demonstrate a range of dose variability at surface positions for both homogeneous cylindrical and heterogeneous anthropomorphic phantoms. These findings have potential implications for small-sized dosimeter measurements in phantoms, such as with TLDs or small Farmer chambers. PMID:19378763

Propagation and wavefront ambiguity of linear nondiffracting beams

NASA Astrophysics Data System (ADS)

Grunwald, R.; Bock, M.

2014-02-01

Ultrashort-pulsed Bessel and Airy beams in free space are often interpreted as "linear light bullets". Usually, interconnected intensity profiles are considered a "propagation" along arbitrary pathways which can even follow curved trajectories. A more detailed analysis, however, shows that this picture gives an adequate description only in situations which do not require to consider the transport of optical signals or causality. To also cover these special cases, a generalization of the terms "beam" and "propagation" is necessary. The problem becomes clearer by representing the angular spectra of the propagating wave fields by rays or Poynting vectors. It is known that quasi-nondiffracting beams can be described as caustics of ray bundles. Their decomposition into Poynting vectors by Shack-Hartmann sensors indicates that, in the frame of their classical definition, the corresponding local wavefronts are ambiguous and concepts based on energy density are not appropriate to describe the propagation completely. For this reason, quantitative parameters like the beam propagation factor have to be treated with caution as well. For applications like communication or optical computing, alternative descriptions are required. A heuristic approach based on vector field based information transport and Fourier analysis is proposed here. Continuity and discontinuity of far field distributions in space and time are discussed. Quantum aspects of propagation are briefly addressed.

Eight cm technology thruster development. [structurally integrated ion thruster for attitude control and stationkeeping of synchronous satellites

NASA Technical Reports Server (NTRS)

Hyman, J., Jr.

1974-01-01

A structural integrated ion thruster with 8-cm beam diameter (SIT-8) was developed for attitude control and stationkeeping of synchronous satellites. As optimized, the system demonstrates a thrust T=1.14 mlb (not corrected for beam V sub B = 1200 V (I sub sp = 2200 sec) total propellant utilization efficiency nu sub u = 59.8% (is approximately 72% without auxiliary pulse-igniter electrode), and electrical efficiency n sub E 61.9%. The thruster incorporates a wire-mesh anode and tantalum cover surfaces to control discharge chamber flake formation and employs an auxiliary pulse-igniter electrode for hollow-cathode ignition. When the SIT-8 is integrated with the compatible SIT-5 propellant tankage, the system envelope is 35 cm long by 13 cm flange bolt circle with a mass of 9.8 kg including 6.8 kg of mercury propellant. Two thrust vectoring systems which generate beam deflections in two orthogonal directions were also developed under the program and tested with the 8-cm thruster. One system vectors the beam over + or - 10 degrees by gimbaling of the entire thruster (not including tankage), while the other system vectors the beam over + or - 7 degrees by translating the accel electrode relative to the screen electrode.

A proposed physical analog for a quantum probability amplitude

NASA Astrophysics Data System (ADS)

Boyd, Jeffrey

What is the physical analog of a probability amplitude? All quantum mathematics, including quantum information, is built on amplitudes. Every other science uses probabilities; QM alone uses their square root. Why? This question has been asked for a century, but no one previously has proposed an answer. We will present cylindrical helices moving toward a particle source, which particles follow backwards. Consider Feynman's book QED. He speaks of amplitudes moving through space like the hand of a spinning clock. His hand is a complex vector. It traces a cylindrical helix in Cartesian space. The Theory of Elementary Waves changes direction so Feynman's clock faces move toward the particle source. Particles follow amplitudes (quantum waves) backwards. This contradicts wave particle duality. We will present empirical evidence that wave particle duality is wrong about the direction of particles versus waves. This involves a paradigm shift; which are always controversial. We believe that our model is the ONLY proposal ever made for the physical foundations of probability amplitudes. We will show that our ``probability amplitudes'' in physical nature form a Hilbert vector space with adjoints, an inner product and support both linear algebra and Dirac notation.

DC corona discharge ozone production enhanced by magnetic field

NASA Astrophysics Data System (ADS)

Pekárek, S.

2010-01-01

We have studied the effect of a stationary magnetic field on the production of ozone from air at atmospheric pressure by a negative corona discharge in a cylindrical electrode configuration. We used a stainless steel hollow needle placed at the axis of the cylindrical discharge chamber as a cathode. The outer wall of the cylinder was used as an anode. The vector of magnetic induction was perpendicular to the vector of current density. We found that: (a) the magnetic field extends the current voltage range of the discharge; (b) for the discharge in the Trichel pulses regime and in the pulseless glow regime, the magnetic field has no substantial effect on the discharge voltage or on the concentration of ozone that is produced; (c) for the discharge in the filamentary streamer regime for a particular current, the magnetic field increases the discharge voltage and consequently an approximately 30% higher ozone concentration can be obtained; (d) the magnetic field does not substantially increase the maximum ozone production yield. A major advantage of using a magnetic field is that the increase in ozone concentration produced by the discharge can be obtained without additional energy requirements.

Expanded Equations for Torque and Force on a Cylindrical Permanent Magnet Core in a Large-Gap Magnetic Suspension System

NASA Technical Reports Server (NTRS)

Groom, Nelson J.

1997-01-01

The expanded equations for torque and force on a cylindrical permanent magnet core in a large-gap magnetic suspension system are presented. The core is assumed to be uniformly magnetized, and equations are developed for two orientations of the magnetization vector. One orientation is parallel to the axis of symmetry, and the other is perpendicular to this axis. Fields and gradients produced by suspension system electromagnets are assumed to be calculated at a point in inertial space which coincides with the origin of the core axis system in its initial alignment. Fields at a given point in the core are defined by expanding the fields produced at the origin as a Taylor series. The assumption is made that the fields can be adequately defined by expansion up to second-order terms. Examination of the expanded equations for the case where the magnetization vector is perpendicular to the axis of symmetry reveals that some of the second-order gradient terms provide a method of generating torque about the axis of magnetization and therefore provide the ability to produce six-degree-of-freedom control.

A Guided Tour of Mathematical Methods for the Physical Sciences

NASA Astrophysics Data System (ADS)

Snieder, Roel; van Wijk, Kasper

2015-05-01

1. Introduction; 2. Dimensional analysis; 3. Power series; 4. Spherical and cylindrical coordinates; 5. Gradient; 6. Divergence of a vector field; 7. Curl of a vector field; 8. Theorem of Gauss; 9. Theorem of Stokes; 10. The Laplacian; 11. Scale analysis; 12. Linear algebra; 13. Dirac delta function; 14. Fourier analysis; 15. Analytic functions; 16. Complex integration; 17. Green's functions: principles; 18. Green's functions: examples; 19. Normal modes; 20. Potential-field theory; 21. Probability and statistics; 22. Inverse problems; 23. Perturbation theory; 24. Asymptotic evaluation of integrals; 25. Conservation laws; 26. Cartesian tensors; 27. Variational calculus; 28. Epilogue on power and knowledge.

Laser-scanning techniques for rapid ballistics identification

NASA Technical Reports Server (NTRS)

Woodburgy, R. C.; Nakich, R. B.

1974-01-01

Two different laser-scanning methods may be utilized. In each case scanned cylindrical bullet surface is displayed ""unwrapped'' on oscilloscope screen. Bullets are compared by photographing each display and superimposing negatives of two images. With some modifications bullets can be scanned and compared by superimposing images on screen of dual-beam oscilloscope.

Creation of vector beams from a polarization diffraction grating using a programmable liquid crystal spatial light modulator and a q-plate

NASA Astrophysics Data System (ADS)

Badham, Katherine Emily

This thesis presents the ability of complete polarization control of light to create a polarization diffraction grating (PDG). This system has the ability to create diffracted light with each order having a separate high-order polarization state in one location on the optical axis. First, an external Excel program is used to create a grating phase profile from userspecified target diffraction orders. High-order vector beams in this PDG are created using a combination of two devices---a liquid crystal spatial light modulator (LC-SLM) manufactured by Seiko Epson, and a tunable q -plate from Citizen Holdings Co. The transmissive SLM is positioned in an optical setup with a reflective architecture allowing control over both the horizontal and vertical components of the laser beam. The SLM has its LC director oriented vertically only affecting the vertically polarized state, however, the optical setup allows modulation of both vertical and horizontal components by the use of a quarter-wave plate (QWP) and a mirror to rotate the polarizations 90 degrees. Each half of the SLM is encoded with an anisotropic phase-only diffraction grating which are superimposed to create a select number of orders with the desired polarization states and equally distributed intensity. The technique of polarimetry is used to confirm the polarization state of each diffraction order. The q-plate is an inhomogeneous birefringent waveplate which has the ability to convert zero-order vector beams into first-order vector beams. The physical placement of this device into the system converts the orders with zero-order polarization states to first-order polarization states. The light vector patterns of each diffraction order confirm which first-order polarization state of is produced. A specially made PDG sextuplicator is encoded onto the SLM to generate six diffraction orders with separate states of polarization.

Beam characterization at BATMAN for variation of the Cs evaporation asymmetry and comparing two driver geometries

NASA Astrophysics Data System (ADS)

Aza, E.; Schiesko, L.; Wimmer, C.; Wünderlich, D.; Fantz, U.

2017-08-01

The properties of the negative hydrogen ion beam produced by the scaled prototype ITER NBI source at the BATMAN testbed were investigated by means of two beam diagnostics: Beam Emission Spectroscopy (BES) and a calorimeter. Two modifications to the prototype were applied. The first was the installation of a second Cs oven at the bottom part of the backplate in addition to the standard one at the upper part of the backplate varying the Cs evaporation asymmetry inside the source. The second consisted in the replacement of the cylindrical driver with a larger racetrack-shaped RF driver and placing a single Cs oven in a central position at the backplate of the driver. The resulting beam characteristics are discussed and compared with those obtained with the previous source design. The position of the Cs oven and the different driver size and geometry appear not to influence the beam profile and the beam deflection for a well-conditioned source.

Generation of arbitrary vector beams with liquid crystal polarization converters and vector-photoaligned q-plates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Peng; Ji, Wei; Wei, Bing-Yan

Arbitrary vector beams (VBs) are realized by the designed polarization converters and corresponding vector-photoaligned q-plates. The polarization converter is a specific twisted nematic cell with one substrate homogeneously aligned and the other space-variantly aligned. By combining a polarization-sensitive alignment agent with a dynamic micro-lithography system, various categories of liquid crystal polarization converters are demonstrated. Besides, traditional radially/azimuthally polarized light, high-order and multi-ringed VBs, and a VB array with different orders are generated. The obtained converters are further utilized as polarization masks to implement vector-photoaligning. The technique facilitates both the volume duplication of these converters and the generation of another promisingmore » optical element, the q-plate, which is suitable for the generation of VBs for coherent lasers. The combination of proposed polarization converters and correspondingly fabricated q-plates would drastically enhance the capability of polarization control and may bring more possibilities for the design of photonic devices.« less

SU-G-IeP4-04: DD-Neutron Source Collimation for Neutron Stimulated Emission Computed Tomography: A Monte Carlo Simulation Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fong, G; Kapadia, A

Purpose: To optimize collimation and shielding for a deuterium-deuterium (DD) neutron generator for an inexpensive and compact clinical neutron imaging system. The envisioned application is cancer diagnosis through Neutron Stimulated Emission Computed Tomography (NSECT). Methods: Collimator designs were tested with an isotropic 2.5 MeV neutron source through GEANT4 simulations. The collimator is a 52×52×52 cm{sup 3} polyethylene block coupled with a 1 cm lead sheet in sequence. Composite opening was modeled into the collimator to permit passage of neutrons. The opening varied in shape (cylindrical vs. tapered), size (1–5 cm source-side and target-side openings) and aperture placements (13–39 cm frommore » source-side). Spatial and energy distribution of neutrons and gammas were tracked from each collimator design. Parameters analyzed were primary beam width (FWHM), divergence, and efficiency (percent transmission) for different configurations of the collimator. Select resultant outputs were then used for simulated NSECT imaging of a virtual breast phantom containing a 2.5 cm diameter tumor to assess the effect of the collimator on spatial resolution, noise, and scan time. Finally, composite shielding enclosure made of polyethylene and lead was designed and evaluated to block 99.99% of neutron and gamma radiation generated in the system. Results: Analysis of primary beam indicated the beam-width is linear to the aperture size. Increasing source-side opening allowed at least 20% more neutron throughput for all designs relative to the cylindrical openings. Maximum throughput for all designs was 364% relative to cylindrical openings. Conclusion: The work indicates potential for collimating and shielding a DD neutron generator for use in a clinical NSECT system. The proposed collimator designs produced a well-defined collimated neutron beam that can be used to image samples of interest with millimeter resolution. Balance in output efficiency, noise reduction, and scan time should be considered to determine the optimal design for specific NSECT applications.« less

Tight focusing of spatially variant vector optical fields with elliptical symmetry of linear polarization.

PubMed

Lerman, Gilad M; Levy, Uriel

2007-08-01

We study the tight-focusing properties of spatially variant vector optical fields with elliptical symmetry of linear polarization. We found the eccentricity of the incident polarized light to be an important parameter providing an additional degree of freedom assisting in controlling the field properties at the focus and allowing matching of the field distribution at the focus to the specific application. Applications of these space-variant polarized beams vary from lithography and optical storage to particle beam trapping and material processing.

The feasibility of polychromatic cone-beam x-ray fluorescence computed tomography (XFCT) imaging of gold nanoparticle-loaded objects: a Monte Carlo study.

PubMed

Jones, Bernard L; Cho, Sang Hyun

2011-06-21

A recent study investigated the feasibility to develop a bench-top x-ray fluorescence computed tomography (XFCT) system capable of determining the spatial distribution and concentration of gold nanoparticles (GNPs) in vivo using a diagnostic energy range polychromatic (i.e. 110 kVp) pencil-beam source. In this follow-up study, we examined the feasibility of a polychromatic cone-beam implementation of XFCT by Monte Carlo (MC) simulations using the MCNP5 code. In the current MC model, cylindrical columns with various sizes (5-10 mm in diameter) containing water loaded with GNPs (0.1-2% gold by weight) were inserted into a 5 cm diameter cylindrical polymethyl methacrylate phantom. The phantom was then irradiated by a lead-filtered 110 kVp x-ray source, and the resulting gold fluorescence and Compton-scattered photons were collected by a series of energy-sensitive tallies after passing through lead parallel-hole collimators. A maximum-likelihood iterative reconstruction algorithm was implemented to reconstruct the image of GNP-loaded objects within the phantom. The effects of attenuation of both the primary beam through the phantom and the gold fluorescence photons en route to the detector were corrected during the image reconstruction. Accurate images of the GNP-containing phantom were successfully reconstructed for three different phantom configurations, with both spatial distribution and relative concentration of GNPs well identified. The pixel intensity of regions containing GNPs was linearly proportional to the gold concentration. The current MC study strongly suggests the possibility of developing a bench-top, polychromatic, cone-beam XFCT system for in vivo imaging.

Balancing Beams--For a Few Moments

ERIC Educational Resources Information Center

Kibble, Bob

2008-01-01

A 2 m long wooden beam provides an ideal demonstration tool for exploring moments. A class set is cheap and can be used at introductory and advanced levels. This article explores how such beams can be used to support learning about moments, equilibrium, vectors, and simultaneous equations. (Contains 7 figures.)

Interaction of upgoing auroral H(+) and O(+) beams

NASA Technical Reports Server (NTRS)

Kaufmann, R. L.; Ludlow, G. R.; Collin, H. L.; Peterson, W. K.; Burch, J. L.

1986-01-01

Data from the S3-3 and DE 1 satellites are analyzed to study the interaction between H(+) and O(+) ions in upgoing auroral beams. Every data set analyzed showed some evidence of an interaction. The measured plasma was found to be unstable to a low-frequency electrostatic wave that propagates at an oblique angle to vector-B(0). A second wave, which can propagate parallel to vector-B(0), is weakly damped in the plasma studied in most detail. It is likely that the upgoing ion beams generate this parallel wave at lower altitudes. The resulting wave-particle interactions qualitatively can explain most of the features observed in ion distribution functions.

Laser cutting nozzle

DOEpatents

Ramos, T.J.

1982-09-30

A laser cutting nozzle for use with a laser cutting apparatus directing a focused beam to a spot on a work piece. The nozzle has a cylindrical body with a conical tip which together have a conically shaped hollow interior with the apex at a small aperture through the tip. The conical hollow interior is shaped to match the profile of the laser beam, at full beamwidth, which passes through the nozzle to the work piece. A plurality of gas inlet holes extend through the body to the hollow interior and are oriented to produce a swirling flow of gas coaxially through the nozzle and out the aperture, aligned with the laser beam, to the work piece.

Laser cutting nozzle

DOEpatents

Ramos, Terry J.

1984-01-01

A laser cutting nozzle for use with a laser cutting apparatus directing a focused beam to a spot on a work piece. The nozzle has a cylindrical body with a conical tip which together have a conically shaped hollow interior with the apex at a small aperture through the tip. The conical hollow interior is shaped to match the profile of the laser beam, at full beamwidth, which passes through the nozzle to the work piece. A plurality of gas inlet holes extend through the body to the hollow interior and are oriented to produce a swirling flow of gas coaxially through the nozzle and out the aperture, aligned with the laser beam, to the work piece. BACKGROUND OF THE INVENTION

Exact nonparaxial beams of the scalar Helmholtz equation.

PubMed

Rodríguez-Morales, Gustavo; Chávez-Cerda, Sabino

2004-03-01

It is shown that three-dimensional nonparaxial beams are described by the oblate spheroidal exact solutions of the Helmholtz equation. For what is believed to be the first time, their beam behavior is investigated and their corresponding parameters are defined. Using the fact that the beam width of the family of paraxial Gaussian beams is described by a hyperbola, we formally establish the connection between the physical parameters of nonparaxial spheroidal beam solutions and those of paraxial beams. These results are also helpful for investigating exact vector nonparaxial beams.

Measuring Flow With Laser-Speckle Velocimetry

NASA Technical Reports Server (NTRS)

Smith, C. A.; Lourenco, L. M. M.; Krothapalli, A.

1988-01-01

Spatial resolution sufficient for calculation of vorticity.In laser-speckle velocimetry, pulsed or chopped laser beam expanded in one dimension by cylindrical lens to illuminate thin, fan-shaped region of flow measured. Flow seeded by small particles. Lens with optical axis perpendicular to illuminating beam forms image of illuminated particles on photographic plate. Speckle pattern of laser-illuminiated, seeded flow recorded in multiple-exposure photographs and processed to extract data on velocity field. Technique suited for study of vortical flows like those about helicopter rotor blades or airplane wings at high angles of attack.

Experimental investigation of electron guns for THz microwave vacuum amplifiers

NASA Astrophysics Data System (ADS)

Burtsev, A. A.; Grigor'ev, Yu. A.; Navrotsky, I. A.; Rogovin, V. I.; Sakhadzhi, G. V.; Shumikhin, K. V.

2016-05-01

Single-sheet and multiple beam electron emitters based on thermionic minicathodes for terahertz traveling-wave tubes have been studied. Data are presented for impregnated blade thermionic cathode with dimensions 0.1 × 0.7 mm and a maximum current density of 114 A/cm2 in a pulsed mode. A variant of the five-beam electron gun with 0.25-mm-diameter cylindrical minicathodes in cells of a control grid is proposed that provides a current density of 85.5 A/cm2 at a grid potential of 900-1000 V.

Beam deviation method as a diagnostic tool for the plasma focus.

PubMed

Schmidt, H; Rückle, B

1978-04-15

The application of an optical method for density measurements in cylindrical plasmas is described. The angular deviation of a probing light beam sent through a plasma is proportional to the maximum of the density in the plasma column. The deviation does not depend on the plasma dimensions; however, it is influenced to a certain degree by the density profile. The method is successfully applied to the investigation of a dense plasma focus with a time resolution of 2 nsec and a spatial resolution (in axial direction) of 2 mm.

Design and experimental verification for optical module of optical vector-matrix multiplier.

PubMed

Zhu, Weiwei; Zhang, Lei; Lu, Yangyang; Zhou, Ping; Yang, Lin

2013-06-20

Optical computing is a new method to implement signal processing functions. The multiplication between a vector and a matrix is an important arithmetic algorithm in the signal processing domain. The optical vector-matrix multiplier (OVMM) is an optoelectronic system to carry out this operation, which consists of an electronic module and an optical module. In this paper, we propose an optical module for OVMM. To eliminate the cross talk and make full use of the optical elements, an elaborately designed structure that involves spherical lenses and cylindrical lenses is utilized in this optical system. The optical design software package ZEMAX is used to optimize the parameters and simulate the whole system. Finally, experimental data is obtained through experiments to evaluate the overall performance of the system. The results of both simulation and experiment indicate that the system constructed can implement the multiplication between a matrix with dimensions of 16 by 16 and a vector with a dimension of 16 successfully.

Superposition of nonparaxial vectorial complex-source spherically focused beams: Axial Poynting singularity and reverse propagation

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2016-08-01

In this work, counterintuitive effects such as the generation of an axial (i.e., long the direction of wave motion) zero-energy flux density (i.e., axial Poynting singularity) and reverse (i.e., negative) propagation of nonparaxial quasi-Gaussian electromagnetic (EM) beams are examined. Generalized analytical expressions for the EM field's components of a coherent superposition of two high-order quasi-Gaussian vortex beams of opposite handedness and different amplitudes are derived based on the complex-source-point method, stemming from Maxwell's vector equations and the Lorenz gauge condition. The general solutions exhibiting unusual effects satisfy the Helmholtz and Maxwell's equations. The EM beam components are characterized by nonzero integer degree and order (n ,m ) , respectively, an arbitrary waist w0, a diffraction convergence length known as the Rayleigh range zR, and a weighting (real) factor 0 ≤α ≤1 that describes the transition of the beam from a purely vortex (α =0 ) to a nonvortex (α =1 ) type. An attractive feature for this superposition is the description of strongly focused (or strongly divergent) wave fields. Computations of the EM power density as well as the linear and angular momentum density fluxes illustrate the analysis with particular emphasis on the polarization states of the vector potentials forming the beams and the weight of the coherent beam superposition causing the transition from the vortex to the nonvortex type. Should some conditions determined by the polarization state of the vector potentials and the beam parameters be met, an axial zero-energy flux density is predicted in addition to a negative retrograde propagation effect. Moreover, rotation reversal of the angular momentum flux density with respect to the beam handedness is anticipated, suggesting the possible generation of negative (left-handed) torques. The results are particularly useful in applications involving the design of strongly focused optical laser tweezers, tractor beams, optical spanners, arbitrary scattering, radiation force, angular momentum, and torque in particle manipulation, and other related topics.

Impact of high energy high intensity proton beams on targets: Case studies for Super Proton Synchrotron and Large Hadron Collider

NASA Astrophysics Data System (ADS)

Tahir, N. A.; Sancho, J. Blanco; Shutov, A.; Schmidt, R.; Piriz, A. R.

2012-05-01

The Large Hadron Collider (LHC) is designed to collide two proton beams with unprecedented particle energy of 7 TeV. Each beam comprises 2808 bunches and the separation between two neighboring bunches is 25 ns. The energy stored in each beam is 362 MJ, sufficient to melt 500 kg copper. Safety of operation is very important when working with such powerful beams. An accidental release of even a very small fraction of the beam energy can result in severe damage to the equipment. The machine protection system is essential to handle all types of possible accidental hazards; however, it is important to know about possible consequences of failures. One of the critical failure scenarios is when the entire beam is lost at a single point. In this paper we present detailed numerical simulations of the full impact of one LHC beam on a cylindrical solid carbon target. First, the energy deposition by the protons is calculated with the FLUKA code and this energy deposition is used in the BIG2 code to study the corresponding thermodynamic and the hydrodynamic response of the target that leads to a reduction in the density. The modified density distribution is used in FLUKA to calculate new energy loss distribution and the two codes are thus run iteratively. A suitable iteration step is considered to be the time interval during which the target density along the axis decreases by 15%-20%. Our simulations suggest that the full LHC proton beam penetrates up to 25 m in solid carbon whereas the range of the shower from a single proton in solid carbon is just about 3 m (hydrodynamic tunneling effect). It is planned to perform experiments at the experimental facility HiRadMat (High Radiation Materials) at CERN using the proton beam from the Super Proton Synchrotron (SPS), to compare experimental results with the theoretical predictions. Therefore simulations of the response of a solid copper cylindrical target hit by the SPS beam were performed. The particle energy in the SPS beam is 440 GeV while it has the same bunch structure as the LHC beam, except that it has only up to 288 bunches. Beam focal spot sizes of σ=0.1, 0.2, and 0.5 mm have been considered. The phenomenon of significant hydrodynamic tunneling due to the hydrodynamic effects is also expected for the experiments.

Surface profiling interferometer

DOEpatents

Takacs, Peter Z.; Qian, Shi-Nan

1989-01-01

The design of a long-trace surface profiler for the non-contact measurement of surface profile, slope error and curvature on cylindrical synchrotron radiation (SR) mirrors. The optical system is based upon the concept of a pencil-beam interferometer with an inherent large depth-of-field. The key feature of the optical system is the zero-path-difference beam splitter, which separates the laser beam into two colinear, variable-separation probe beams. A linear array detector is used to record the interference fringe in the image, and analysis of the fringe location as a function of scan position allows one to reconstruct the surface profile. The optical head is mounted on an air bearing slide with the capability to measure long aspheric optics, typical of those encountered in SR applications. A novel feature of the optical system is the use of a transverse "outrigger" beam which provides information on the relative alignment of the scan axis to the cylinder optic symmetry axis.

Creation of diffraction-limited non-Airy multifocal arrays using a spatially shifted vortex beam

NASA Astrophysics Data System (ADS)

Lin, Han; Gu, Min

2013-02-01

Diffraction-limited non-Airy multifocal arrays are created by focusing a phase-modulated vortex beam through a high numerical-aperture objective. The modulated phase at the back aperture of the objective resulting from the superposition of two concentric phase-modulated vortex beams allows for the generation of a multifocal array of cylindrically polarized non-Airy patterns. Furthermore, we shift the spatial positions of the phase vortices to manipulate the intensity distribution at each focal spot, leading to the creation of a multifocal array of split-ring patterns. Our method is experimentally validated by generating the predicted phase modulation through a spatial light modulator. Consequently, the spatially shifted circularly polarized vortex beam adopted in a dynamic laser direct writing system facilitates the fabrication of a split-ring microstructure array in a polymer material by a single exposure of a femtosecond laser beam.

Electrostatic dispersion lenses and ion beam dispersion methods

DOEpatents

Dahl, David A [Idaho Falls, ID; Appelhans, Anthony D [Idaho Falls, ID

2010-12-28

An EDL includes a case surface and at least one electrode surface. The EDL is configured to receive through the EDL a plurality of ion beams, to generate an electrostatic field between the one electrode surface and either the case surface or another electrode surface, and to increase the separation between the beams using the field. Other than an optional mid-plane intended to contain trajectories of the beams, the electrode surface or surfaces do not exhibit a plane of symmetry through which any beam received through the EDL must pass. In addition or in the alternative, the one electrode surface and either the case surface or the other electrode surface have geometries configured to shape the field to exhibit a less abrupt entrance and/or exit field transition in comparison to another electrostatic field shaped by two nested, one-quarter section, right cylindrical electrode surfaces with a constant gap width.

Paul Trap Simulator Experiment (PTSX) to simulate intense beam propagation through a periodic focusing quadrupole field

NASA Astrophysics Data System (ADS)

Davidson, Ronald C.; Efthimion, Philip C.; Gilson, Erik; Majeski, Richard; Qin, Hong

2002-01-01

The Paul Trap Simulator Experiment (PTSX) is under construction at the Princeton Plasma Physics Laboratory to simulate intense beam propagation through a periodic quadrupole magnetic field. In the Paul trap configuration, a long nonneutral plasma column is confined axially by dc voltages on end cylinders at z=+L and z=-L, and transverse confinement is provided by segmented cylindrical electrodes with applied oscillatory voltages ±V0(t) over 90° segments. Because the transverse focusing force is similar in waveform to that produced by a discrete set of periodic quadrupole magnets in a frame moving with the beam, the Paul trap configuration offers the possibility of simulating intense beam propagation in a compact laboratory facility. The experimental layout is described, together with the planned experiments to study beam mismatch, envelope instabilities, halo particle production, and collective wave excitations.

Dual-wavelength vortex beam with high stability in a diode-pumped Yb:CaGdAlO4 laser

NASA Astrophysics Data System (ADS)

Shen, Yijie; Meng, Yuan; Fu, Xing; Gong, Mali

2018-05-01

We present a stable dual-wavelength vortex beam carrying orbital angular momentum (OAM) with two spectral peaks separated by a few terahertz in a diode-pumped Yb:CaGdAlO4 (CALGO) laser. The dual-wavelength spectrum is controlled by the pump power and off-axis loss in a laser resonator, arising from the broad emission bandwidth of Yb:CALGO. The OAM beam is obtained by a pair of cylindrical lenses serving as a π/2 convertor for high-order Hermite–Gaussian modes. The stability is verified by the fact that a 1\\hbar OAM beam with two spectral peaks at 1046.1 nm and 1057.2 nm (3.01 THz interval) can steadily operate for more than 3 h. It has great potential for scaling the application of OAM beams in terahertz spectroscopy, high-resolution interferometry, and so on.

Electrostatic lens to focus an ion beam to uniform density

DOEpatents

Johnson, Cleland H.

1977-01-11

A focusing lens for an ion beam having a gaussian or similar density profile is provided. The lens is constructed to provide an inner zero electrostatic field, and an outer electrostatic field such that ions entering this outer field are deflected by an amount that is a function of their distance from the edge of the inner field. The result is a beam that focuses to a uniform density in a manner analogous to that of an optical ring lens. In one embodiment, a conically-shaped network of fine wires is enclosed within a cylindrical anode. The wire net together with the anode produces a voltage field that re-directs the outer particles of the beam while the axial particles pass undeflected through a zero field inside the wire net. The result is a focused beam having a uniform intensity over a given target area and at a given distance from the lens.

Excitation of high density surface plasmon polariton vortex array

NASA Astrophysics Data System (ADS)

Kuo, Chun-Fu; Chu, Shu-Chun

2018-06-01

This study proposes a method to excite surface plasmon polariton (SPP) vortex array of high spatial density on metal/air interface. A doughnut vector beam was incident at four rectangularly arranged slits to excite SPP vortex array. The doughnut vector beam used in this study has the same field intensity distribution as the regular doughnut laser mode, TEM01* mode, but a different polarization distribution. The SPP vortex array is achieved through the matching of both polarization state and phase state of the incident doughnut vector beam with the four slits. The SPP field distribution excited in this study contains stable array-distributed time-varying optical vortices. Theoretical derivation, analytical calculation and numerical simulation were used to discuss the characteristics of the induced SPP vortex array. The period of the SPP vortex array induced by the proposed method had only half SPPs wavelength. In addition, the vortex number in an excited SPP vortex array can be increased by enlarging the structure.

Measuring implosion velocities in experiments and simulations of laser-driven cylindrical implosions on the OMEGA laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, E. C.; Barnak, D. H.; Betti, R.

Laser-driven magnetized liner inertial fusion (MagLIF) on OMEGA involves cylindrical implosions, a preheat beam, and an applied magnetic field. Initial experiments excluded the preheat beam and magnetic field to better characterize the implosion. X-ray self-emission as measured by framing cameras was used to determine the shell trajectory. The 1-D code LILAC was used to model the central region of the implosion, and results were compared to 2-D simulations from the HYDRA code. Post-processing of simulation output with SPECT3D and Yorick produced synthetic x-ray images that were used to compare the simulation results with the x-ray framing camera data. Quantitative analysismore » shows that higher measured neutron yields correlate with higher implosion velocities. The future goal is to further analyze the x-ray images to characterize the uniformity of the implosions and apply these analysis techniques to integrated laser-driven MagLIF shots to better understand the effects of preheat and the magnetic field.« less

Acoustic streaming, fluid mixing, and particle transport by a Gaussian ultrasound beam in a cylindrical container

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marshall, Jeffrey S., E-mail: jeffm@cems.uvm.edu; Wu, Junru

A computational study is reported of the acoustic streaming flow field generated by a Gaussian ultrasound beam propagating normally toward the end wall of a cylindrical container. Particular focus is given to examining the effectiveness of the acoustic streaming flow for fluid mixing within the container, for deposition of particles in suspension onto the bottom surface, and for particle suspension from the bottom surface back into the flow field. The flow field is assumed to be axisymmetric with the ultrasound transducer oriented parallel to the cylinder axis and normal to the bottom surface of the container, which we refer tomore » as the impingement surface. Reflection of the sound from the impingement surface and sound absorption within the material at the container bottom are both accounted for in the computation. The computation also accounts for thermal buoyancy force due to ultrasonic heating of the impingement surface, but over the time period considered in the current simulations, the flow is found to be dominated by the acoustic streaming force, with only moderate effect of buoyancy force.« less

Measuring implosion velocities in experiments and simulations of laser-driven cylindrical implosions on the OMEGA laser

DOE PAGES

Hansen, E. C.; Barnak, D. H.; Betti, R.; ...

2018-04-04

Laser-driven magnetized liner inertial fusion (MagLIF) on OMEGA involves cylindrical implosions, a preheat beam, and an applied magnetic field. Initial experiments excluded the preheat beam and magnetic field to better characterize the implosion. X-ray self-emission as measured by framing cameras was used to determine the shell trajectory. The 1-D code LILAC was used to model the central region of the implosion, and results were compared to 2-D simulations from the HYDRA code. Post-processing of simulation output with SPECT3D and Yorick produced synthetic x-ray images that were used to compare the simulation results with the x-ray framing camera data. Quantitative analysismore » shows that higher measured neutron yields correlate with higher implosion velocities. The future goal is to further analyze the x-ray images to characterize the uniformity of the implosions and apply these analysis techniques to integrated laser-driven MagLIF shots to better understand the effects of preheat and the magnetic field.« less

Effect of anode position on the performance characteristics of a low-power cylindrical Hall thruster

NASA Astrophysics Data System (ADS)

Gao, Yuanyuan; Liu, Hui; Hu, Peng; Huang, Hongyan; Yu, Daren

2017-06-01

In this paper, the design of a new cylindrical Hall thruster (CHT) is presented. Its anode is separated from the gas distributor, which is made of ceramic. The effect of the anode position on the performance characteristics of the CHT was investigated by mounting a series of anodes with different radii inside the CHT. It is found that progressively positioning the anode away from the axis along the radial direction increases the ion current and reduces the electron current. Meanwhile, the peak energy in the ion energy distribution function increases, and the shape of the ion energy distribution function noticeably narrows; the ion beam in the plume converges. It is suggested that moving the anode away from the axis may strengthen the electron confinement, thus optimizing the ionization efficiency. Additionally, the electric field near the anode appears to deflect toward the axis, which may promote the collimation of the ion beam in the plume. As a result, the overall performance of the CHT is significantly enhanced in our proposed design.

Acoustic streaming, fluid mixing, and particle transport by a Gaussian ultrasound beam in a cylindrical container

NASA Astrophysics Data System (ADS)

Marshall, Jeffrey S.; Wu, Junru

2015-10-01

A computational study is reported of the acoustic streaming flow field generated by a Gaussian ultrasound beam propagating normally toward the end wall of a cylindrical container. Particular focus is given to examining the effectiveness of the acoustic streaming flow for fluid mixing within the container, for deposition of particles in suspension onto the bottom surface, and for particle suspension from the bottom surface back into the flow field. The flow field is assumed to be axisymmetric with the ultrasound transducer oriented parallel to the cylinder axis and normal to the bottom surface of the container, which we refer to as the impingement surface. Reflection of the sound from the impingement surface and sound absorption within the material at the container bottom are both accounted for in the computation. The computation also accounts for thermal buoyancy force due to ultrasonic heating of the impingement surface, but over the time period considered in the current simulations, the flow is found to be dominated by the acoustic streaming force, with only moderate effect of buoyancy force.

Comparative evaluation of the accuracy of linear measurements between cone beam computed tomography and 3D microtomography.

PubMed

Mangione, Francesca; Meleo, Deborah; Talocco, Marco; Pecci, Raffaella; Pacifici, Luciano; Bedini, Rossella

2013-01-01

The aim of this study was to evaluate the influence of artifacts on the accuracy of linear measurements estimated with a common cone beam computed tomography (CBCT) system used in dental clinical practice, by comparing it with microCT system as standard reference. Ten bovine bone cylindrical samples containing one implant each, able to provide both points of reference and image quality degradation, have been scanned by CBCT and microCT systems. Thanks to the software of the two systems, for each cylindrical sample, two diameters taken at different levels, by using implants different points as references, have been measured. Results have been analyzed by ANOVA and a significant statistically difference has been found. Due to the obtained results, in this work it is possible to say that the measurements made with the two different instruments are still not statistically comparable, although in some samples were obtained similar performances and therefore not statistically significant. With the improvement of the hardware and software of CBCT systems, in the near future the two instruments will be able to provide similar performances.

I-cored Coil Probe Located Above a Conductive Plate with a Surface Hole

NASA Astrophysics Data System (ADS)

Tytko, Grzegorz; Dziczkowski, Leszek

2018-02-01

This work presents an axially symmetric mathematical model of an I-cored coil placed over a two-layered conductive material with a cylindrical surface hole. The problem was divided into regions for which the magnetic vector potential of a filamentary coil was established applying the truncated region eigenfunction expansion method. Then the final formula was developed to calculate impedance changes for a cylindrical coil with reference to both the air and to a material with no hole. The influence of a surface flaw in the conductive material on the components of coil impedance was examined. Calculations were made in Matlab for a hole with various radii and the results thereof were verified with the finite element method in COMSOL Multiphysics package. Very good consistency was achieved in all cases.

Broadband notch filter design for millimeter-wave plasma diagnostics.

PubMed

Furtula, V; Michelsen, P K; Leipold, F; Salewski, M; Korsholm, S B; Meo, F; Nielsen, S K; Stejner, M; Moseev, D; Johansen, T

2010-10-01

Notch filters are integrated in plasma diagnostic systems to protect millimeter-wave receivers from intensive stray radiation. Here we present a design of a notch filter with a center frequency of 140 GHz, a rejection bandwidth of ∼900 MHz, and a typical insertion loss below 2 dB in the passband of ±9 GHz. The design is based on a fundamental rectangular waveguide with eight cylindrical cavities coupled by T-junction apertures formed as thin slits. Parameters that affect the notch performance such as physical lengths and conductor materials are discussed. The excited resonance mode in the cylindrical cavities is the fundamental TE(11). The performance of the constructed filter is measured using a vector network analyzer monitoring a total bandwidth of 30 GHz. We compare the measurements with numerical simulations.

Scattering from a cylindrical reflector: modified theory of physical optics solution.

PubMed

Yalçin, Ugur

2007-02-01

The problem of scattering from a perfectly conducting cylindrical reflector is examined with the method of the modified theory of physical optics. In this technique the physical optics currents are modified by using a variable unit vector on the scatterer's surface. These current components are obtained for the reflector, which is fed by an offset electric line source. The scattering integral is expressed by using these currents and evaluated asymptotically with the stationary phase method. The results are compared numerically by using physical optics theory, geometrical optics diffraction theory, and the exact solution of the Helmholtz equation. It is found that the modified theory of physical optics scattering field equations agrees with the geometrical optics diffraction theory and the exact solution of the Helmholtz equation.

Minimum Variance Distortionless Response Beamformer with Enhanced Nulling Level Control via Dynamic Mutated Artificial Immune System

PubMed Central

Kiong, Tiong Sieh; Salem, S. Balasem; Paw, Johnny Koh Siaw; Sankar, K. Prajindra

2014-01-01

In smart antenna applications, the adaptive beamforming technique is used to cancel interfering signals (placing nulls) and produce or steer a strong beam toward the target signal according to the calculated weight vectors. Minimum variance distortionless response (MVDR) beamforming is capable of determining the weight vectors for beam steering; however, its nulling level on the interference sources remains unsatisfactory. Beamforming can be considered as an optimization problem, such that optimal weight vector should be obtained through computation. Hence, in this paper, a new dynamic mutated artificial immune system (DM-AIS) is proposed to enhance MVDR beamforming for controlling the null steering of interference and increase the signal to interference noise ratio (SINR) for wanted signals. PMID:25003136

Minimum variance distortionless response beamformer with enhanced nulling level control via dynamic mutated artificial immune system.

PubMed

Kiong, Tiong Sieh; Salem, S Balasem; Paw, Johnny Koh Siaw; Sankar, K Prajindra; Darzi, Soodabeh

2014-01-01

In smart antenna applications, the adaptive beamforming technique is used to cancel interfering signals (placing nulls) and produce or steer a strong beam toward the target signal according to the calculated weight vectors. Minimum variance distortionless response (MVDR) beamforming is capable of determining the weight vectors for beam steering; however, its nulling level on the interference sources remains unsatisfactory. Beamforming can be considered as an optimization problem, such that optimal weight vector should be obtained through computation. Hence, in this paper, a new dynamic mutated artificial immune system (DM-AIS) is proposed to enhance MVDR beamforming for controlling the null steering of interference and increase the signal to interference noise ratio (SINR) for wanted signals.

Wide-angle full-vector beam propagation method based on an alternating direction implicit preconditioner

NASA Astrophysics Data System (ADS)

Chui, Siu Lit; Lu, Ya Yan

2004-03-01

Wide-angle full-vector beam propagation methods (BPMs) for three-dimensional wave-guiding structures can be derived on the basis of rational approximants of a square root operator or its exponential (i.e., the one-way propagator). While the less accurate BPM based on the slowly varying envelope approximation can be efficiently solved by the alternating direction implicit (ADI) method, the wide-angle variants involve linear systems that are more difficult to handle. We present an efficient solver for these linear systems that is based on a Krylov subspace method with an ADI preconditioner. The resulting wide-angle full-vector BPM is used to simulate the propagation of wave fields in a Y branch and a taper.

Wide-angle full-vector beam propagation method based on an alternating direction implicit preconditioner.

PubMed

Chui, Siu Lit; Lu, Ya Yan

2004-03-01

Wide-angle full-vector beam propagation methods (BPMs) for three-dimensional wave-guiding structures can be derived on the basis of rational approximants of a square root operator or its exponential (i.e., the one-way propagator). While the less accurate BPM based on the slowly varying envelope approximation can be efficiently solved by the alternating direction implicit (ADI) method, the wide-angle variants involve linear systems that are more difficult to handle. We present an efficient solver for these linear systems that is based on a Krylov subspace method with an ADI preconditioner. The resulting wide-angle full-vector BPM is used to simulate the propagation of wave fields in a Y branch and a taper.

Molten core retention assembly

DOEpatents

Lampe, Robert F.

1976-06-22

Molten fuel produced in a core overheating accident is caught by a molten core retention assembly consisting of a horizontal baffle plate having a plurality of openings therein, heat exchange tubes having flow holes near the top thereof mounted in the openings, and a cylindrical, imperforate baffle attached to the plate and surrounding the tubes. The baffle assembly is supported from the core support plate of the reactor by a plurality of hanger rods which are welded to radial beams passing under the baffle plate and intermittently welded thereto. Preferably the upper end of the cylindrical baffle terminates in an outwardly facing lip to which are welded a plurality of bearings having slots therein adapted to accept the hanger rods.

Sector magnets or transverse electromagnetic fields in cylindrical coordinates

DOE PAGES

Zolkin, T.

2017-04-10

Laplace’s equation is considered for scalar and vector potentials describing electric or magnetic fields in cylindrical coordinates, with invariance along the azimuthal coordinate. In a series, we found special functions which, when expanded to lowest order in power series in radial and vertical coordinates, replicate harmonic polynomials in two variables. These functions are based on radial harmonics found by Edwin M. McMillan forty years ago. In addition to McMillan’s harmonics, a second family of radial harmonics is introduced to provide a symmetric description between electric and magnetic fields and to describe fields and potentials in terms of the same functions.more » Formulas are provided which relate any transverse fields specified by the coefficients in the power series expansion in radial or vertical planes in cylindrical coordinates with the set of new functions. Our result is important for potential theory and for theoretical study, design and proper modeling of sector dipoles, combined function dipoles and any general sector element for accelerator physics. All results are presented in connection with these problems.« less

Sector magnets or transverse electromagnetic fields in cylindrical coordinates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zolkin, T.

Laplace’s equation is considered for scalar and vector potentials describing electric or magnetic fields in cylindrical coordinates, with invariance along the azimuthal coordinate. In a series, we found special functions which, when expanded to lowest order in power series in radial and vertical coordinates, replicate harmonic polynomials in two variables. These functions are based on radial harmonics found by Edwin M. McMillan forty years ago. In addition to McMillan’s harmonics, a second family of radial harmonics is introduced to provide a symmetric description between electric and magnetic fields and to describe fields and potentials in terms of the same functions.more » Formulas are provided which relate any transverse fields specified by the coefficients in the power series expansion in radial or vertical planes in cylindrical coordinates with the set of new functions. Our result is important for potential theory and for theoretical study, design and proper modeling of sector dipoles, combined function dipoles and any general sector element for accelerator physics. All results are presented in connection with these problems.« less

Comparison between TG-51 and TG-21: Calibration of photon and electron beams in water using cylindrical chambers.

PubMed

Cho, S H; Lowenstein, J R; Balter, P A; Wells, N H; Hanson, W F

2000-01-01

A new calibration protocol, developed by the AAPM Task Group 51 (TG-51) to replace the TG-21 protocol, is based on an absorbed-dose to water standard and calibration factor (N(D,w)), while the TG-21 protocol is based on an exposure (or air-kerma) standard and calibration factor (N(x)). Because of differences between these standards and the two protocols, the results of clinical reference dosimetry based on TG-51 may be somewhat different from those based on TG-21. The Radiological Physics Center has conducted a systematic comparison between the two protocols, in which photon and electron beam outputs following both protocols were compared under identical conditions. Cylindrical chambers used in this study were selected from the list given in the TG-51 report, covering the majority of current manufacturers. Measured ratios between absorbed-dose and air-kerma calibration factors, derived from the standards traceable to the NIST, were compared with calculated values using the TG-21 protocol. The comparison suggests that there is roughly a 1% discrepancy between measured and calculated ratios. This discrepancy may provide a reasonable measure of possible changes between the absorbed-dose to water determined by TG-51 and that determined by TG-21 for photon beam calibrations. The typical change in a 6 MV photon beam calibration following the implementation of the TG-51 protocol was about 1%, regardless of the chamber used, and the change was somewhat smaller for an 18 MV photon beam. On the other hand, the results for 9 and 16 MeV electron beams show larger changes up to 2%, perhaps because of the updated electron stopping power data used for the TG-51 protocol, in addition to the inherent 1% discrepancy presented in the calibration factors. The results also indicate that the changes may be dependent on the electron energy.

Harmonics generation of a terahertz wakefield free-electron laser from a dielectric loaded waveguide excited by a direct current electron beam.

PubMed

Li, Weiwei; Lu, Yalin; He, Zhigang; Jia, Qika; Wang, Lin

2016-06-01

We propose to generate high-power terahertz (THz) radiation from a cylindrical dielectric loaded waveguide (DLW) excited by a direct-current electron beam with the harmonics generation method. The DLW supports a discrete set of modes that can be excited by an electron beam passing through the structure. The interaction of these modes with the co-propagating electron beam results in micro-bunching and the coherent enhancement of the wakefield radiation, which is dominated by the fundamental mode. By properly choosing the parameters of DLW and beam energy, the high order modes can be the harmonics of the fundamental one; thus, high frequency radiation corresponding to the high order modes will benefit from the dominating bunching process at the fundamental eigenfrequency and can also be coherently excited. With the proposed method, high power THz radiation can be obtained with an easily achievable electron beam and a large DLW structure.

Ion beams extraction and measurements of plasma parameters on a multi-frequencies microwaves large bore ECRIS with permanent magnets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nozaki, Dai; Kiriyama, Ryutaro; Takenaka, Tomoya

2012-11-06

We have developed an all-permanent magnet large bore electron cyclotron resonance ion source (ECRIS) for broad ion beam processing. The cylindrically comb-shaped magnetic field configuration is adopted for efficient plasma production and good magnetic confinement. To compensate for disadvantages of fixed magnetic configuration, a traveling wave tube amplifier (TWTA) is used. In the comb-shaped ECRIS, it is difficult to achieve controlling ion beam profiles in the whole inside the chamber by using even single frequency-controllable TWTA (11-13GHz), because of large bore size with all-magnets. We have tried controlling profiles of plasma parameters and then those of extracted ion beams bymore » launching two largely different frequencies simultaneously, i.e., multi-frequencies microwaves. Here we report ion beam profiles and corresponding plasma parameters under various experimental conditions, dependence of ion beams against extraction voltages, and influence of different electrode positions on the electron density profile.« less

Measurement of ultrasonic fields in transparent media using a scanning differential interferometer

NASA Technical Reports Server (NTRS)

Dockery, G. D.; Claus, R. O.

1983-01-01

An experimental system for the detection of three dimensional acoustic fields in optically transparent media using a dual beam differential interferometer is described. In this system, two coherent, parallel, focused laser beams are passed through the specimen and the interference fringe pattern which results when these beams are combined shifts linearly by an amount which is related to the optical pathlength difference between the two beams. It is shown that for small signals, the detector output is directly proportional to the amplitude of the acoustic field integrated along the optical beam path through the specimen. A water tank and motorized optical platform were constructed to allow these dual beams to be scanned through an ultrasonic field generated by a piezoelectric transducer at various distances from the transducer. Scan data for the near, Fresnel, and far zones of a uniform, circular transducer are presented and an algorithm for constructing the radial field profile from this integrated optical data, assuming cylindrical symmetry, is described.

Adjustable vector Airy light-sheet single optical tweezers: negative radiation forces on a subwavelength spheroid and spin torque reversal

NASA Astrophysics Data System (ADS)

Mitri, Farid G.

2018-01-01

Generalized solutions of vector Airy light-sheets, adjustable per their derivative order m, are introduced stemming from the Lorenz gauge condition and Maxwell's equations using the angular spectrum decomposition method. The Cartesian components of the incident radiated electric, magnetic and time-averaged Poynting vector fields in free space (excluding evanescent waves) are determined and computed with particular emphasis on the derivative order of the Airy light-sheet and the polarization on the magnetic vector potential forming the beam. Negative transverse time-averaged Poynting vector components can arise, while the longitudinal counterparts are always positive. Moreover, the analysis is extended to compute the optical radiation force and spin torque vector components on a lossless dielectric prolate subwavelength spheroid in the framework of the electric dipole approximation. The results show that negative forces and spin torques sign reversal arise depending on the derivative order of the beam, the polarization of the magnetic vector potential, and the orientation of the subwavelength prolate spheroid in space. The spin torque sign reversal suggests that counter-clockwise or clockwise rotations around the center of mass of the subwavelength spheroid can occur. The results find useful applications in single Airy light-sheet tweezers, particle manipulation, handling, and rotation applications to name a few examples.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, C.T.

Linear and nonlinear photochemistries of 1,4-diazabicyclo(2.2.2)octane (DABCO) are investigated at room temperature by using ArF (193 nm) and KrF (248 nm) lasers. With an unfocused beam geometry, DABCO vapor displays a strong fluorescence when excited at 248 nm, but it shows no detectable emission with 193-nm excitation. The linear photochemistry quantum yield for DABCO is determined as phi/sub p/(248nm) approx. 0.1 and phi/sub p/(193 nm) approx. 0.3. The main stable photochemical products are analyzed as C/sub 2/H/sub 4/ and C/sub 2/H/sub 2/ for 248- and 193-nm excitation, respectively. When focused beam excitation is used, both ArF and KrF lasers dissociatemore » DABCO molecules and give three strong radical emissions of CN*(B vector /sup 2/..sigma.. ..-->.. X vector /sup 2/ ..sigma../sup +/), CH*(A vector /sup 2/..delta.. ..-->.. X vector /sup 2/II), and C/sub 2/*(D vector /sup 3/II/sub g/ ..-->.. a vector /sup 3/II/sub u/). The time behavior, the laser power dependence, and the sample pressure dependence of these emissive radicals are examined. The possible mechanisms for the Rydberg state photochemistry of DABCO are discussed.« less

Progress on CBET Platform at the Nike Laser

NASA Astrophysics Data System (ADS)

Weaver, J. L.; McKenty, P.; Oh, J.; Kehne, D.; Schmitt, A. J.; Obenschain, S.; Serlin, V.; Lehmberg, R.; Tsung, F.

2015-11-01

Cross-beam energy transport (CBET) studies are underway at the Nike krypton-fluoride (KrF) laser at NRL. This facility has unique characteristics that provide an excellent platform for CBET work - including short wavelength (248 nm), large bandwidth (1-3 THz), beam smoothing by induced spatial incoherence (ISI), and full aperture focal spot zooming. Nike's two beam arrays are widely separated (135° in azimuth) which facilitates CBET studies in a nearly opposing geometry, relevant to Polar Direct Drive implosions. Various target types are planned: planar slabs, cylindrical and spherical shells, and low-density targets. The solid targets will be used to examine gradient geometries and the latter will access larger volume, more uniform plasmas. The initial campaign is exploring changes observed by scattered light diagnostics for both beam arrays as the probe laser spectrum is modified. Work supported by DoE/NNSA.

High intensity multi beam design of SANS instrument for Dhruva reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abbas, Sohrab, E-mail: abbas@barc.gov.in; Aswal, V. K.; Désert, S.

A new and versatile design of Small Angle Neutron Scattering (SANS) instrument based on utilization of multi-beam is presented. The multi-pinholes and multi-slits as SANS collimator for medium flux Dhruva rearctor have been proposed and their designs have been validated using McStas simulations. Various instrument configurations to achieve different minimum wave vector transfers in scattering experiments are envisioned. These options enable smooth access to minimum wave vector transfers as low as ~ 6×10{sup −4} Å{sup −1} with a significant improvement in neutron intensity, allowing faster measurements. Such angularly well defined and intense neutron beam will allow faster SANS studies ofmore » agglomerates larger than few tens of nm.« less

Coherence and dimensionality of intense spatiospectral twin beams

NASA Astrophysics Data System (ADS)

Peřina, Jan

2015-07-01

Spatiospectral properties of twin beams at their transition from low to high intensities are analyzed in parametric and paraxial approximations using decomposition into paired spatial and spectral modes. Intensity auto- and cross-correlation functions are determined and compared in the spectral and temporal domains as well as the transverse wave-vector and crystal output planes. Whereas the spectral, temporal, and transverse wave-vector coherence increases with the increasing pump intensity, coherence in the crystal output plane is almost independent of the pump intensity owing to the mode structure in this plane. The corresponding auto- and cross-correlation functions approach each other for larger pump intensities. The entanglement dimensionality of a twin beam is determined with a comparison of several approaches.

Generation of elliptical and circular vector hollow beams with different polarizations by a Mach-Zehnder-type optical path

NASA Astrophysics Data System (ADS)

Wang, Zhizhang; Pei, Chunying; Xia, Meng; Yin, Yaling; Xia, Yong; Yin, Jianping

2018-01-01

We present an experimental approach to convert linearly polarized Gaussian beams into elliptical and circular vector hollow beams (VHBs) with different polarization states. The scheme employed is based on a Mach-Zehnder-type optical path combined with a reflective spatial light modulator (SLM) in each path. The resulting VHBs have radial, azimuthal, and other polarization states. Our studies also show that the size of the generated VHBs remains constant during the propagation in free space over a certain distance, and can be controlled by the axial ratio of the SLM’s binary phase plate. These studies deliver great optical parameters and hold promising applications in the fields of optical trapping and manipulation of particles.

Transverse Beam Dynamics in the Modified Betatron.

DTIC Science & Technology

1982-03-01

charge, m is the electron rest mass, and c is the speed of light . Self field effects will modify Eq. (1) however. A nonneutral current ring produces both a...magnetic flux or stream func- tion *P(p.) rA, where A, is the usual vector potential. The equations for 4 and 1 are 17 CHERNJN AND SPRANGLE p-[ l 2 - ( o...8217- 4). (A-21) m m 2 Using Eq. (A-21) in Eq. (A-20) the resulting integrals are elementary. The result, for the vector potential inside the beam is Ask

Scale model test results of several STOVL ventral nozzle concepts

NASA Technical Reports Server (NTRS)

Meyer, B. E.; Re, R. J.; Yetter, J. A.

1991-01-01

Short take-off and vertical landing (STOVL) ventral nozzle concepts are investigated by means of a static cold flow scale model at a NASA facility. The internal aerodynamic performance characteristics of the cruise, transition, and vertical lift modes are considered for four ventral nozzle types. The nozzle configurations examined include those with: butterfly-type inner doors and vectoring exit vanes; circumferential inner doors and thrust vectoring vanes; a three-port segmented version with circumferential inner doors; and a two-port segmented version with cylindrical nozzle exit shells. During the testing, internal and external pressure is measured, and the thrust and flow coefficients and resultant vector angles are obtained. The inner door used for ventral nozzle flow control is found to affect performance negatively during the initial phase of transition. The best thrust performance is demonstrated by the two-port segmented ventral nozzle due to the elimination of the inner door.

E-beam deposited Ag-nanoparticles plasmonic organic solar cell and its absorption enhancement analysis using FDTD-based cylindrical nano-particle optical model.

PubMed

Kim, Richard S; Zhu, Jinfeng; Park, Jeung Hun; Li, Lu; Yu, Zhibin; Shen, Huajun; Xue, Mei; Wang, Kang L; Park, Gyechoon; Anderson, Timothy J; Pei, Qibing

2012-06-04

We report the plasmon-assisted photocurrent enhancement in Ag-nanoparticles (Ag-NPs) embedded PEDOT:PSS/P3HT:PCBM organic solar cells, and systematically investigate the causes of the improved optical absorption based on a cylindrical Ag-NPs optical model which is simulated with a 3-Dimensional finite difference time domain (FDTD) method. The proposed cylindrical Ag-NPs optical model is able to explain the optical absorption enhancement by the localized surface plasmon resonance (LSPR) modes, and to provide a further understanding of Ag-NPs shape parameters which play an important role to determine the broadband absorption phenomena in plasmonic organic solar cells. A significant increase in the power conversion efficiency (PCE) of the plasmonic solar cell was experimentally observed and compared with that of the solar cells without Ag-NPs. Finally, our conclusion was made after briefly discussing the electrical effects of the fabricated plasmonic organic solar cells.

Spin manipulating vector & tensor polarized deuterons stored in COSY

NASA Astrophysics Data System (ADS)

Morozov, V. S.; Krisch, A. D.; Leonova, M. A.; Raymond, R. S.; Sivers, D. W.; Wong, V. K.; Yonehara, K.; Gebel, R.; Lehrach, A.; Lorentz, B.; Maier, R.; Prasuhn, D.; Schnase, A.; Stockhorst, H.; Eversheim, D.; Hinterberger, F.; Rohdjess, H.; Ulbrich, K.

2006-04-01

We recently studied the spin manipulation of a simultaneously vector and tensor polarized deuteron beam stored at 1.85 GeV/c in the COSY Cooler Synchrotron. Using the EDDA detector, we first calibrated the vector and tensor analyzing powers, which were earlier unmeasured at 1.85 GeV/c; this allowed us to measure the absolute values of both the vector and tensor polarizations. Then we manipulated the deuteron's polarization by sweeping the frequency of a ferrite rf dipole through an rf-induced spin resonance. We first experimentally determined the resonance's frequency and then varied the rf dipole's frequency sweep range δf and frequency ramp time δt to maximize the spin-flip efficiency. We then obtained a measured vector spin-flip efficiency of 98.5 ± 0.3% [1]. We also studied, in detail, the behavior of the tensor polarization during spin manipulation; these new data may allow a better understanding of the interesting quantum behavior of spin-1 bosons. This research was supported by the German BMBF Science Ministry. [1] V.S. Morozov et al., Phys. Rev. ST Accel. Beams 8, 061001 (2005).

Simultaneous full-field 3-D vibrometry of the human eardrum using spatial-bandwidth multiplexed holography

NASA Astrophysics Data System (ADS)

Khaleghi, Morteza; Guignard, Jérémie; Furlong, Cosme; Rosowski, John J.

2015-11-01

Holographic interferometric methods typically require the use of three sensitivity vectors in order to obtain three-dimensional (3-D) information. Methods based on multiple directions of illumination have limited applications when studying biological tissues that have temporally varying responses such as the tympanic membrane (TM). Therefore, to measure 3-D displacements in such applications, the measurements along all the sensitivity vectors have to be done simultaneously. We propose a multiple-illumination directions approach to measure 3-D displacements from a single-shot hologram that contains displacement information from three sensitivity vectors. The hologram of an object of interest is simultaneously recorded with three incoherently superimposed pairs of reference and object beams. The incident off-axis angles of the reference beams are adjusted such that the frequency components of the multiplexed hologram are completely separate. Because of the differences in the directions and wavelengths of the reference beams, the positions of each reconstructed image corresponding to each sensitivity vector are different. We implemented a registration algorithm to accurately translate individual components of the hologram into a single global coordinate system to calculate 3-D displacements. The results include magnitudes and phases of 3-D sound-induced motions of a human cadaveric TM at several excitation frequencies showing modal and traveling wave motions on its surface.

Burgers Vector Analysis of Vertical Dislocations in Ge Crystals by Large-Angle Convergent Beam Electron Diffraction.

PubMed

Groiss, Heiko; Glaser, Martin; Marzegalli, Anna; Isa, Fabio; Isella, Giovanni; Miglio, Leo; Schäffler, Friedrich

2015-06-01

By transmission electron microscopy with extended Burgers vector analyses, we demonstrate the edge and screw character of vertical dislocations (VDs) in novel SiGe heterostructures. The investigated pillar-shaped Ge epilayers on prepatterned Si(001) substrates are an attempt to avoid the high defect densities of lattice mismatched heteroepitaxy. The Ge pillars are almost completely strain-relaxed and essentially defect-free, except for the rather unexpected VDs. We investigated both pillar-shaped and unstructured Ge epilayers grown either by molecular beam epitaxy or by chemical vapor deposition to derive a general picture of the underlying dislocation mechanisms. For the Burgers vector analysis we used a combination of dark field imaging and large-angle convergent beam electron diffraction (LACBED). With LACBED simulations we identify ideally suited zeroth and second order Laue zone Bragg lines for an unambiguous determination of the three-dimensional Burgers vectors. By analyzing dislocation reactions we confirm the origin of the observed types of VDs, which can be efficiently distinguished by LACBED. The screw type VDs are formed by a reaction of perfect 60° dislocations, whereas the edge types are sessile dislocations that can be formed by cross-slips and climbing processes. The understanding of these origins allows us to suggest strategies to avoid VDs.

Theoretical and experimental study on multimode optical fiber grating

NASA Astrophysics Data System (ADS)

Yunming, Wang; Jingcao, Dai; Mingde, Zhang; Xiaohan, Sun

2005-06-01

The characteristics of multimode optical fiber Bragg grating (MMFBG) are studied theoretically and experimentally. For the first time the analysis of MMFBG based on a novel quasi-three-dimensional (Q-3D) finite-difference time-domain beam propagation method (Q-FDTD-BPM) is described through separating the angle component of vector field solution from the cylindrical coordinate so that several discrete two-dimensional (2D) equations are obtained, which simplify the 3D equations. And then these equations are developed using an alternating-direction implicit method and generalized Douglas scheme, which achieves higher accuracy than the regular FD scheme. All of the 2D solutions for the field intensities are also added with different power coefficients for different angle mode order numbers to obtain 3D field distributions in MMFBG. The presented method has been demonstrated as suitable simulation tool for analyzing MMFBG. In addition, based on the hydrogen-loaded and phase mask techniques, a series of Bragg grating have been written into the silicon multimode optical fiber loaded hydrogen for a month, and the spectrums for that have been measured, which obtain good results approximate to the results in the experiment. Group delay/differentiate group delay spectrums are obtained using Agilent 81910A Photonic All-Parameter Analyzer.

SU-F-P-47: Estimation of Skin Dose by Performing the Measurements On Cylindrical Phantom

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bosma, S; Sanders, M; Aryal, P

Purpose: To evaluate the skin dose by performing the measurements on cylindrical phantom with 6X beam. Methods: A cylindrical phantom was used to best model a patient surface. The source to surface distance (SSD) was 100 cm at phantom surface along central axis (CAX). The EBT2 films were cut into 2×2 cm2 pieces. Each piece of film was placed at CAX on phantom surface for each measurement at 0°, 15°, 30°, 45°, 60°, 75°, and 90° gantry angles for field sizes of 5×5, 10×10, 15×15, and 20×20 cm{sup 2} respectively. One hundred monitor units (MU) with 6X beam were deliveredmore » for each set up. Similarly, the measurements were repeated using lithium fluoride (LiF) thermoluminescent dosimeter (TLD) chips (1X1X1 mm{sup 3}). Two TLD chips were placed for each gantry angle and field size. The calibration curves were produced for both film and TLD. The computed tomography (CT) was also performed on the same cylindrical phantom and dose was evaluated at the phantom surface using Eclipse treatment planning system ( AAA algorithm) for skin dose comparison. Results: Data showed small differences at smaller angles among EBT2, TLD and Eclipse treatment planning system. But Eclipse treatment planning system under estimated the skin dose between 20% and 50% at larger gantry angles (between 40° and 80°) at all field sizes before dose differences began to converge. Conclusion: Given this data, we can conclude that Eclipse treatment planning system under estimated the dose especially between 40 and 80 degrees of obliquity compared to the measurements results. Ideally, this study can be applied largely to head and neck patients where contours differ drastically and where skin dose is paramount.« less

Design and simulation of a ~390 GHz seventh harmonic gyrotron using a large orbit electron beam

NASA Astrophysics Data System (ADS)

Li, Fengping; He, Wenlong; Cross, Adrian W.; Donaldson, Craig R.; Zhang, Liang; Phelps, Alan D. R.; Ronald, Kevin

2010-04-01

A ~390 GHz harmonic gyrotron based on a cusp electron gun has been designed and numerically modelled. The gyrotron operates at the seventh harmonic of the electron cyclotron frequency with the beam interacting with a TE71 waveguide mode. Theoretical as well as numerical simulation results using the 3D particle-in-cell code MAGIC are presented. The cusp gun generated an axis-encircling, annular shaped electron beam of energy 40 keV, current 1.5 A with a velocity ratio α of 3. Smooth cylindrical waveguides have been studied as the interaction cavities and their cavity Q optimized for 390 GHz operation. In the simulations ~600 W of output power at the design frequency has been demonstrated.

Comparison of the effects of cylindrical correction with and without iris recognition technology in wavefront laser-assisted in situ keratomileusis.

PubMed

Wang, Tsung-Jen; Lin, Yu-Huang; Chang, David C-K; Chou, Hsiu-Chu; Wang, I-Jong

2012-04-01

  To analyse the magnitude of cylindrical corrections over which cyclotorsion compensation with iris recognition (IR) technology is beneficial during wavefront laser-assisted in situ keratomileusis.   A retrospectively comparative case series.   Fifty-four eyes that underwent wavefront laser-assisted in situ keratomileusis without IR (non-IR group) and 53 eyes that underwent wavefront laser-assisted in situ keratomileusis with IR (IR group) were recruited.   Subgroup analysis based on baseline astigmatism were: a low degree of astigmatism (≥1.00 D to <2.00 D), a moderate degree of astigmatism (≥2.00 D to <3.00 D) and a high degree of astigmatism (≥3.00 D).   Vector and non-vector analyses were used for comparison.   The mean cylinder was -1.89 ± 0.76 D in the non-IR group and -2.00 ± 0.77 D in the IR group. Postoperatively, 38 eyes (74.50%) in the IR group and 31 eyes (57.50%) in the non-IR group were within ± 0.50 D of the target induced astigmatism vector (P = 0.063). The difference vector was 0.49 ± 0.28 in the IR group and 0.63 ± 0.40 in the non-IR group (P = 0.031). In the analysis of subgroups, the magnitude of error was significantly lower in the moderate IR subgroup than that of the moderate non-IR subgroup (P = 0.034). Furthermore, the moderate IR subgroup had a lower mean difference vector (P = 0.0078) and a greater surgically induced astigmatism (P = 0.036) than those of the moderate non-IR group.   Wavefront laser-assisted in situ keratomileusis for the treatment of astigmatism using IR technology was effective and accurate for the treatment of myopic astigmatism. © 2011 The Authors. Clinical and Experimental Ophthalmology © 2011 Royal Australian and New Zealand College of Ophthalmologists.

Lasing action from photonic bound states in continuum

NASA Astrophysics Data System (ADS)

Kodigala, Ashok; Lepetit, Thomas; Gu, Qing; Bahari, Babak; Fainman, Yeshaiahu; Kanté, Boubacar

2017-01-01

In 1929, only three years after the advent of quantum mechanics, von Neumann and Wigner showed that Schrödinger’s equation can have bound states above the continuum threshold. These peculiar states, called bound states in the continuum (BICs), manifest themselves as resonances that do not decay. For several decades afterwards the idea lay dormant, regarded primarily as a mathematical curiosity. In 1977, Herrick and Stillinger revived interest in BICs when they suggested that BICs could be observed in semiconductor superlattices. BICs arise naturally from Feshbach’s quantum mechanical theory of resonances, as explained by Friedrich and Wintgen, and are thus more physical than initially realized. Recently, it was realized that BICs are intrinsically a wave phenomenon and are thus not restricted to the realm of quantum mechanics. They have since been shown to occur in many different fields of wave physics including acoustics, microwaves and nanophotonics. However, experimental observations of BICs have been limited to passive systems and the realization of BIC lasers has remained elusive. Here we report, at room temperature, lasing action from an optically pumped BIC cavity. Our results show that the lasing wavelength of the fabricated BIC cavities, each made of an array of cylindrical nanoresonators suspended in air, scales with the radii of the nanoresonators according to the theoretical prediction for the BIC mode. Moreover, lasing action from the designed BIC cavity persists even after scaling down the array to as few as 8-by-8 nanoresonators. BIC lasers open up new avenues in the study of light-matter interaction because they are intrinsically connected to topological charges and represent natural vector beam sources (that is, there are several possible beam shapes), which are highly sought after in the fields of optical trapping, biological sensing and quantum information.

Propagation of hollow Gaussian beam through a misaligned first-order optical system and its propagation properties

NASA Astrophysics Data System (ADS)

Zhao, Cheng Liang; Lu, Xuan Hui

2007-06-01

Propagation properties of hollow Gaussian beam through a misaligned first-order ABCD system is studied using the generalized Huygens-Fresnel diffraction integral, augmented matrix. It is shown that, as a hollow Gaussian beam passes through the misaligned first-order ABCD system, the beam shape is not preserved, the out-put beams have differences when passing different misaligned optical systems. We can adjust the size of dark region through adjusting the misaligned transverse vector E.

Superficial dosimetry imaging based on Čerenkov emission for external beam radiotherapy with megavoltage x-ray beam

PubMed Central

Zhang, Rongxiao; Glaser, Adam K.; Gladstone, David J.; Fox, Colleen J.; Pogue, Brian W.

2013-01-01

Purpose: Čerenkov radiation emission occurs in all tissue, when charged particles (either primary or secondary) travel at velocity above the threshold for the Čerenkov effect (about 220 KeV in tissue for electrons). This study presents the first examination of optical Čerenkov emission as a surrogate for the absorbed superficial dose for MV x-ray beams. Methods: In this study, Monte Carlo simulations of flat and curved surfaces were studied to analyze the energy spectra of charged particles produced in different regions near the surfaces when irradiated by MV x-ray beams. Čerenkov emission intensity and radiation dose were directly simulated in voxelized flat and cylindrical phantoms. The sampling region of superficial dosimetry based on Čerenkov radiation was simulated in layered skin models. Angular distributions of optical emission from the surfaces were investigated. Tissue mimicking phantoms with flat and curved surfaces were imaged with a time domain gating system. The beam field sizes (50 × 50–200 × 200 mm2), incident angles (0°–70°) and imaging regions were all varied. Results: The entrance or exit region of the tissue has nearly homogeneous energy spectra across the beam, such that their Čerenkov emission is proportional to dose. Directly simulated local intensity of Čerenkov and radiation dose in voxelized flat and cylindrical phantoms further validate that this signal is proportional to radiation dose with absolute average discrepancy within 2%, and the largest within 5% typically at the beam edges. The effective sampling depth could be tuned from near 0 up to 6 mm by spectral filtering. The angular profiles near the theoretical Lambertian emission distribution for a perfect diffusive medium, suggesting that angular correction of Čerenkov images may not be required even for curved surface. The acquisition speed and signal to noise ratio of the time domain gating system were investigated for different acquisition procedures, and the results show there is good potential for real-time superficial dose monitoring. Dose imaging under normal ambient room lighting was validated, using gated detection and a breast phantom. Conclusions: This study indicates that Čerenkov emission imaging might provide a valuable way to superficial dosimetry imaging in real time for external beam radiotherapy with megavoltage x-ray beams. PMID:24089916

Development of a composite geodetic structure for space construction, phase 2

NASA Technical Reports Server (NTRS)

1981-01-01

Primary physical and mechanical properties were defined for pultruded hybrid HMS/E-glass P1700 rod material used for the fabrication of geodetic beams. Key properties established were used in the analysis, design, fabrication, instrumentation, and testing of a geodetic parameter cylinder and a lattice cone closeout joined to a short cylindrical geodetic beam segment. Requirements of structural techniques were accomplished. Analytical procedures were refined and extended to include the effect of rod dimensions for the helical and longitudinal members on local buckling, and the effect of different flexural and extensional moduli on general instability buckling.

Single-Sided Noinvasive Inspection of Multielement Sample Using Fan-Beam Multiplexed Compton Scatter Tomography

DTIC Science & Technology

2000-05-01

a vector , ρ "# represents the set of voxel densities sorted into a vector , and ( )A ρ $# "# represents a 8 mapping of the voxel densities to...density vector in equation (4) suggests that solving for ρ "# by direct inversion is not possible, calling for an iterative technique beginning with...the vector of measured spectra, and D is the diagonal matrix of the inverse of the variances. The diagonal matrix provides weighting terms, which

CFD evaluation of an advanced thrust vector control concept

NASA Technical Reports Server (NTRS)

Tiarn, Weihnurng; Cavalleri, Robert

1990-01-01

A potential concept that can offer an alternate method for thrust vector control of the Space Shuttle Solid Rocket Booster is the use of a cylindrical probe that is inserted (on demand) through the wall of the rocket nozzle. This Probe Thrust Vector Control (PTVC) concept is an alternate to that of a gimbaled nozzle or a Liquid Injection Thrust Vector (LITVC) system. The viability of the PTVC concept can be assessed either experimentally and/or with the use of CFD. A purely experimental assessment can be time consuming and expensive, whereas a CFD assessment can be very time- and cost-effective. Two key requirements of the proposed concept are PTVC vectoring performance and the active cooling requirements for the probe to maintain its thermal and structural integrity. An active thermal cooling method is the injection of coolant around the pheriphery of the probe. How much coolant is required and how this coolant distributes itself in the flow field is of major concern. The objective of the work reported here is the use of CFD to answer these question and in the design of test hardware to substantiate the results of the CFD predictions.

Quantum Space Charge Waves in a Waveguide Filled with Fermi-Dirac Plasmas Including Relativistic Wake Field and Quantum Statistical Pressure Effects

NASA Astrophysics Data System (ADS)

Hong, Woo-Pyo; Jung, Young-Dae

2018-03-01

The effects of quantum statistical degeneracy pressure on the propagation of the quantum space charge wave are investigated in a cylindrically bounded plasma waveguide filled with relativistically degenerate quantum Fermi-Dirac plasmas and the relativistic ion wake field. The results show that the domain of the degenerate parameter for the resonant beam instability significantly increases with an increase of the scaled beam velocity. It is found that the instability domain of the wave number increases with an increase of the degenerate parameter. It is also found that the growth rate for the resonant beam instability decreases with an increase of the degenerate parameter. In addition, it is shown that the lowest harmonic mode provides the maximum value of the growth rates. Moreover, it is shown that the instability domain of the wave number decreases with an increase of the beam velocity.

A Higher-Order Bending Theory for Laminated Composite and Sandwich Beams

NASA Technical Reports Server (NTRS)

Cook, Geoffrey M.

1997-01-01

A higher-order bending theory is derived for laminated composite and sandwich beams. This is accomplished by assuming a special form for the axial and transverse displacement expansions. An independent expansion is also assumed for the transverse normal stress. Appropriate shear correction factors based on energy considerations are used to adjust the shear stiffness. A set of transverse normal correction factors is introduced, leading to significant improvements in the transverse normal strain and stress for laminated composite and sandwich beams. A closed-form solution to the cylindrical elasticity solutions for a wide range of beam aspect ratios and commonly used material systems. Accurate shear stresses for a wide range of laminates, including the challenging unsymmetric composite and sandwich laminates, are obtained using an original corrected integration scheme. For application of the theory to a wider range of problems, guidelines for finite element approximations are presented.

Continuously variable focal length lens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adams, Bernhard W; Chollet, Matthieu C

2013-12-17

A material preferably in crystal form having a low atomic number such as beryllium (Z=4) provides for the focusing of x-rays in a continuously variable manner. The material is provided with plural spaced curvilinear, optically matched slots and/or recesses through which an x-ray beam is directed. The focal length of the material may be decreased or increased by increasing or decreasing, respectively, the number of slots (or recesses) through which the x-ray beam is directed, while fine tuning of the focal length is accomplished by rotation of the material so as to change the path length of the x-ray beammore » through the aligned cylindrical slows. X-ray analysis of a fixed point in a solid material may be performed by scanning the energy of the x-ray beam while rotating the material to maintain the beam's focal point at a fixed point in the specimen undergoing analysis.« less

Equilibrium, confinement and stability of runaway electrons in tokamaks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spong, D A

1976-03-01

Some of the ramifications of the runaway population in tokamak experiments are investigated. Consideration is given both to the normal operating regime of tokamaks where only a small fraction of high energy runaways are present and to the strong runaway regime where runaways are thought to carry a significant portion of the toroidal current. In particular, the areas to be examined are the modeling of strong runaway discharges, single particle orbit characteristics of runaways, macroscopic beam-plasma equilibria, and stability against kink modes. A simple one-dimensional, time-dependent model has been constructed in relation to strong runaway discharges. Single particle orbits aremore » analyzed in relation to both the strong runaway regime and the weak regime. The effects of vector E x vector B drifts are first considered in strong runaway discharges and are found to lead to a slow inward shrinkage of the beam. Macroscopic beam-plasma equilibria are treated assuming a pressureless relativistic beam with inertia and using an ideal MHD approximation for the plasma. The stability of a toroidal relativistic beam against kink perturbations is examined using several models. (MOW)« less

Wavefront reconstruction using computer-generated holograms

NASA Astrophysics Data System (ADS)

Schulze, Christian; Flamm, Daniel; Schmidt, Oliver A.; Duparré, Michael

2012-02-01

We propose a new method to determine the wavefront of a laser beam, based on modal decomposition using computer-generated holograms (CGHs). Thereby the beam under test illuminates the CGH with a specific, inscribed transmission function that enables the measurement of modal amplitudes and phases by evaluating the first diffraction order of the hologram. Since we use an angular multiplexing technique, our method is innately capable of real-time measurements of amplitude and phase, yielding the complete information about the optical field. A measurement of the Stokes parameters, respectively of the polarization state, provides the possibility to calculate the Poynting vector. Two wavefront reconstruction possibilities are outlined: reconstruction from the phase for scalar beams and reconstruction from the Poynting vector for inhomogeneously polarized beams. To quantify single aberrations, the reconstructed wavefront is decomposed into Zernike polynomials. Our technique is applied to beams emerging from different kinds of multimode optical fibers, such as step-index, photonic crystal and multicore fibers, whereas in this work results are exemplarily shown for a step-index fiber and compared to a Shack-Hartmann measurement that serves as a reference.

Beam profile measurement on HITU transducers using a thermal intensity sensor technique

NASA Astrophysics Data System (ADS)

Wilkens, V.; Sonntag, S.; Jenderka, K.-V.

2011-02-01

Thermal intensity sensors based on the transformation of the incident ultrasonic energy into heat inside a small cylindrical absorber have been developed at PTB in the past, in particular to determine the acoustic output of medical diagnostic ultrasound equipment. Currently, this sensor technique is being expanded to match the measurement challenges of high intensity therapeutic ultrasound (HITU) fields. At the high acoustic power levels as utilized in the clinical application of HITU transducers, beam characterization using hydrophones is critical due to the possible damage of the sensitive and expensive measurement devices. Therefore, the low-cost and robust thermal sensors developed offer a promising alternative for the determination of high intensity output beam profiles. A sensor prototype with a spatial resolution of 0.5 mm was applied to the beam characterization of an HITU transducer operated at several driving amplitude levels. Axial beam plots and lateral profiles at focus were acquired. The absolute continuous wave output power was, in addition, determined using a radiation force balance.

Secondary Electron Emission Yields

NASA Technical Reports Server (NTRS)

Krainsky, I.; Lundin, W.; Gordon, W. L.; Hoffman, R. W.

1981-01-01

The secondary electron emission (SEE) characteristics for a variety of spacecraft materials were determined under UHV conditions using a commercial double pass CMA which permits sequential Auger electron electron spectroscopic analysis of the surface. The transparent conductive coating indium tin oxide (ITO) was examined on Kapton and borosilicate glass and indium oxide on FED Teflon. The total SEE coefficient ranges from 2.5 to 2.6 on as-received surfaces and from 1.5 to 1.6 on Ar(+) sputtered surfaces with 5 nm removed. A cylindrical sample carousel provides normal incidence of the primary beam as well as a multiple Faraday cup measurement of the approximately nA beam currents. Total and true secondary yields are obtained from target current measurements with biasing of the carousel. A primary beam pulsed mode to reduce electron beam dosage and minimize charging of insulating coatings was applied to Mg/F2 coated solar cell covers. Electron beam effects on ITO were found quite important at the current densities necessary to do Auger studies.

Beam current sensor

DOEpatents

Kuchnir, M.; Mills, F.E.

1984-09-28

A current sensor for measuring the dc component of a beam of charged particles employs a superconducting pick-up loop probe, with twisted superconducting leads in combination with a Superconducting Quantum Interference Device (SQUID) detector. The pick-up probe is in the form of a single-turn loop, or a cylindrical toroid, through which the beam is directed and within which a first magnetic flux is excluded by the Meisner effect. The SQUID detector acts as a flux-to-voltage converter in providing a current to the pick-up loop so as to establish a second magnetic flux within the electrode which nulls out the first magnetic flux. A feedback voltage within the SQUID detector represents the beam current of the particles which transit the pick-up loop. Meisner effect currents prevent changes in the magnetic field within the toroidal pick-up loop and produce a current signal independent of the beam's cross-section and its position within the toroid, while the combination of superconducting elements provides current measurement sensitivities in the nano-ampere range.

Beam current sensor

DOEpatents

Kuchnir, Moyses; Mills, Frederick E.

1987-01-01

A current sensor for measuring the DC component of a beam of charged particles employs a superconducting pick-up loop probe, with twisted superconducting leads in combination with a Superconducting Quantum Interference Device (SQUID) detector. The pick-up probe is in the form of a single-turn loop, or a cylindrical toroid, through which the beam is directed and within which a first magnetic flux is excluded by the Meisner effect. The SQUID detector acts as a flux-to-voltage converter in providing a current to the pick-up loop so as to establish a second magnetic flux within the electrode which nulls out the first magnetic flux. A feedback voltage within the SQUID detector represents the beam current of the particles which transit the pick-up loop. Meisner effect currents prevent changes in the magnetic field within the toroidal pick-up loop and produce a current signal independent of the beam's cross-section and its position within the toroid, while the combination of superconducting elements provides current measurement sensitivites in the nano-ampere range.

Novel cryogenic sources for liquid droplet and solid filament beams

NASA Astrophysics Data System (ADS)

Grams, Michael P.

Two novel atomic and molecular beam sources have been created and tested consisting first of a superfluid helium liquid jet, and secondly a solid filament of argon. The superfluid helium apparatus is the second of its kind in the world and uses a modified liquid helium cryostat to inject a cylindrical stream of superfluid helium into vacuum through glass capillary nozzles with diameters on the order of one micron created on-site at Arizona State University. The superfluid beam is an entirely new way to study superfluid behavior, and has many new applications such as superfluid beam-surface scattering, beam-beam scattering, and boundary-free study of superfluidity. The solid beam of argon is another novel beam source created by flowing argon gas through a capillary 50 microns in diameter which is clamped by a small copper plate to a copper block kept at liquid nitrogen temperature. The gas subsequently cools and solidifies plugging the capillary. Upon heating, the solid plug melts and liquid argon exits the capillary and immediately freezes by evaporative cooling. The solid filaments may find application as wall-less cryogenic matrices, or targets for laser plasma sources of extreme UV and soft x-ray sources.

Computation of transonic potential flow about 3 dimensional inlets, ducts, and bodies

NASA Technical Reports Server (NTRS)

Reyhner, T. A.

1982-01-01

An analysis was developed and a computer code, P465 Version A, written for the prediction of transonic potential flow about three dimensional objects including inlet, duct, and body geometries. Finite differences and line relaxation are used to solve the complete potential flow equation. The coordinate system used for the calculations is independent of body geometry. Cylindrical coordinates are used for the computer code. The analysis is programmed in extended FORTRAN 4 for the CYBER 203 vector computer. The programming of the analysis is oriented toward taking advantage of the vector processing capabilities of this computer. Comparisons of computed results with experimental measurements are presented to verify the analysis. Descriptions of program input and output formats are also presented.

Understanding the power reflection and transmission coefficients of a plane wave at a planar interface

NASA Astrophysics Data System (ADS)

Ye, Qian; Jiang, Yikun; Lin, Haoze

2017-03-01

In most textbooks, after discussing the partial transmission and reflection of a plane wave at a planar interface, the power (energy) reflection and transmission coefficients are introduced by calculating the normal-to-interface components of the Poynting vectors for the incident, reflected and transmitted waves, separately. Ambiguity arises among students since, for the Poynting vector to be interpreted as the energy flux density, on the incident (reflected) side, the electric and magnetic fields involved must be the total fields, namely, the sum of incident and reflected fields, instead of the partial fields which are just the incident (reflected) fields. The interpretation of the cross product of partial fields as energy flux has not been obviously justified in most textbooks. Besides, the plane wave is actually an idealisation that is only ever found in textbooks, then what do the reflection and transmission coefficients evaluated for a plane wave really mean for a real beam of limited extent? To provide a clearer physical picture, we exemplify a light beam of finite transverse extent by a fundamental Gaussian beam and simulate its reflection and transmission at a planar interface. Due to its finite transverse extent, we can then insert the incident fields or reflected fields as total fields into the expression of the Poynting vector to evaluate the energy flux and then power reflection and transmission coefficients. We demonstrate that the power reflection and transmission coefficients of a beam of finite extent turn out to be the weighted sum of the corresponding coefficients for all constituent plane wave components that form the beam. The power reflection and transmission coefficients of a single plane wave serve, in turn, as the asymptotes for the corresponding coefficients of a light beam as its width expands infinitely.

Trigger drift chamber for the upgraded mark II detector at PEP

NASA Astrophysics Data System (ADS)

Ford, W. T.; Smith, J. G.; Wagner, S. R.; Weber, P.; White, S. L.; Alvarez, M.; Calviño, F.; Fernandez, E.

1987-04-01

A small cylindrical track detector was built as an array of single-wire drift cells with aluminized mylar cathode tubes. Point measurement resolution of ˜ 90 μm was achieved with a drift gas of 50% argon-50% ethane at atmospheric pressure. The chamber construction, electronics, and calibration are discussed. Performance results from PEP colliding-beam data are presented.

Fluorometer with a quartz-rod waveguide-integrating sphere configuration to measure evanescent-field luminescence

USDA-ARS?s Scientific Manuscript database

A fluorometer was designed to measure evanescent-field luminescence. A quartz-rod waveguide (d = 2 mm) was installed coaxally inside a cylindrical flow-through cell (id = 2.3 mm, od = 6.3 mm, l = 116 mm). An excitation beam from a UV LED or a miniature xenon flashlamp was focused by a ball lens and ...

Laminar and Turbulent Flow in Water

ERIC Educational Resources Information Center

Riveros, H. G.; Riveros-Rosas, D.

2010-01-01

There are many ways to visualize flow, either for laminar or turbulent flows. A very convincing way to show laminar and turbulent flows is by the perturbations on the surface of a beam of water coming out of a cylindrical tube. Photographs, taken with a flash, show the nature of the flow of water in pipes. They clearly show the difference between…

Formation of 2D bright spatial solitons in lithium niobate with photovoltaic response and incoherent background

NASA Astrophysics Data System (ADS)

Pustozerov, A.; Shandarov, V.

2017-12-01

The influence of incoherent background illumination produced by light-emitting diodes (LED's) of different average wavelengths and laser diode emitting in blue region of visible on diffraction characteristics of narrow coherent light beams of He-Ne laser due to refractive index changes of Fe-doped lithium niobate sample are studied. It has been experimentally demonstrated that nonlinear diffraction of red beams with wavelength 633 nm and diameters on full width of half maximum (FWHM) near to 15 μm may be totally compensated using background light with average wavelengths 450 - 465 nm. To provide the necessary intensity of incoherent background, the combinations of spherical and cylindrical concave lenses with blue LED and laser diode module without focusing its beam have been used.

Preliminary research on flow rate and free surface of the accelerator driven subcritical system gravity-driven dense granular-flow target

PubMed Central

Li, Xiaodong; Wan, Jiangfeng; Zhang, Sheng; Lin, Ping; Zhang, Yanshi; Yang, Guanghui; Wang, Mengke; Duan, Wenshan; Sun, Jian’an

2017-01-01

A spallation target is one of the three core parts of the accelerator driven subcritical system (ADS), which has already been investigated for decades. Recently, a gravity-driven Dense Granular-flow Target (DGT) is proposed, which consists of a cylindrical hopper and an internal coaxial cylindrical beam pipe. The research on the flow rate and free surface are important for the design of the target whether in Heavy Liquid Metal (HLM) targets or the DGT. In this paper, the relations of flow rate and the geometry of the DGT are investigated. Simulations based on the discrete element method (DEM) implementing on Graphics Processing Units (GPUs) and experiments are both performed. It is found that the existence of an internal pipe doesn’t influence the flow rate when the distance from the bottom of the pipe to orifice is large enough even in a larger system. Meanwhile, snapshots of the free surface formed just below the beam pipe are given. It is observed that the free surface is stable over time. The entire research is meaningful for the design of DGT. PMID:29095910

Preliminary research on flow rate and free surface of the accelerator driven subcritical system gravity-driven dense granular-flow target.

PubMed

Li, Xiaodong; Wan, Jiangfeng; Zhang, Sheng; Lin, Ping; Zhang, Yanshi; Yang, Guanghui; Wang, Mengke; Duan, Wenshan; Sun, Jian'an; Yang, Lei

2017-01-01

A spallation target is one of the three core parts of the accelerator driven subcritical system (ADS), which has already been investigated for decades. Recently, a gravity-driven Dense Granular-flow Target (DGT) is proposed, which consists of a cylindrical hopper and an internal coaxial cylindrical beam pipe. The research on the flow rate and free surface are important for the design of the target whether in Heavy Liquid Metal (HLM) targets or the DGT. In this paper, the relations of flow rate and the geometry of the DGT are investigated. Simulations based on the discrete element method (DEM) implementing on Graphics Processing Units (GPUs) and experiments are both performed. It is found that the existence of an internal pipe doesn't influence the flow rate when the distance from the bottom of the pipe to orifice is large enough even in a larger system. Meanwhile, snapshots of the free surface formed just below the beam pipe are given. It is observed that the free surface is stable over time. The entire research is meaningful for the design of DGT.

Simultaneous full-field 3-D vibrometry of the human eardrum using spatial-bandwidth multiplexed holography

PubMed Central

Khaleghi, Morteza; Guignard, Jérémie; Furlong, Cosme; Rosowski, John J.

2015-01-01

Abstract. Holographic interferometric methods typically require the use of three sensitivity vectors in order to obtain three-dimensional (3-D) information. Methods based on multiple directions of illumination have limited applications when studying biological tissues that have temporally varying responses such as the tympanic membrane (TM). Therefore, to measure 3-D displacements in such applications, the measurements along all the sensitivity vectors have to be done simultaneously. We propose a multiple-illumination directions approach to measure 3-D displacements from a single-shot hologram that contains displacement information from three sensitivity vectors. The hologram of an object of interest is simultaneously recorded with three incoherently superimposed pairs of reference and object beams. The incident off-axis angles of the reference beams are adjusted such that the frequency components of the multiplexed hologram are completely separate. Because of the differences in the directions and wavelengths of the reference beams, the positions of each reconstructed image corresponding to each sensitivity vector are different. We implemented a registration algorithm to accurately translate individual components of the hologram into a single global coordinate system to calculate 3-D displacements. The results include magnitudes and phases of 3-D sound-induced motions of a human cadaveric TM at several excitation frequencies showing modal and traveling wave motions on its surface. PMID:25984986

Design and Near-Field Measurement Performance Evaluation of the Sea Winds Dual- Beam Reflector Antenna

NASA Technical Reports Server (NTRS)

Hussein, Z.; Rahmat-Samii, Y.; Kellogg, K.

1997-01-01

This paper presents the design and performance evaluation of a lightweight, composite material, elliptical-aperture, parabolic-reflector antenna. The performance characterization is obtained using the cylindrical near-field measurement facility at JPL as shown. The reflector has been designed and calibrated for the SeaWinds spaceborne scatterometer instrument. The instrument operates at Ku-band and is designed to accurately measure wind speed and direction over Earth's ocean surface. The SeaWinds antenna design requires two linearly polarized independent beams pointed at 40 deg.and 46 deg. from nadir as shown. The inner beam, pointed at 40 deg. from nadir, is horizontally polarized with 1.6 in x 1.8 in required beamwidths in the elevation and azimuth planes, respectively. The outer beam, pointed at 46 deg. from nadir, is vertically polarized with 1.4 in x 1.7 in required beamwidths. Noteworthy, the reflector boresight axis is pointed at 43 deg. from nadir. Both beams are required to have the first sidelobe level below -15 dB relative to the peak of the beam.

Design of collimating and rearrangement systems of laser diode array beam

NASA Astrophysics Data System (ADS)

Gao, Runmei; Fang, Tao; Fu, Rulian; Yao, Jianquan

2015-10-01

To improve the laser diode output beam quality, micro-cylindrical lens and the step-type lens combination are designed. The former is used to collimate beam in fast-axis direction, while the latter plays a role in the slow-axis of splitting and the rearrangement. The micro-column semi-elliptical lens is made with the drops of spherical zoom lensin electric field and with the help of the material properties of light-cured production, which can reduce the reflection of the front surface and total reflection loss of the after. The divergence angle in the fast axis is compressed to roughly the same as that in the slow-axis direction; Stepped lens splits compressed long strip beam in the slow axis, with parallelogram style of level equidistant and rearrange in the fast axis direction. The spot in the slow axis gets smaller and the spot becomes larger in the fast axis. At last divergence angle and the beam spot achieve balanced in the fast axis and slow axis, optical parameters BPP integrates approximate the same, and beam quality can be improved.

A dosimetry study comparing NCS report-5, IAEA TRS-381, AAPM TG-51 and IAEA TRS-398 in three clinical electron beam energies

NASA Astrophysics Data System (ADS)

Palmans, Hugo; Nafaa, Laila; de Patoul, Nathalie; Denis, Jean-Marc; Tomsej, Milan; Vynckier, Stefaan

2003-05-01

New codes of practice for reference dosimetry in clinical high-energy photon and electron beams have been published recently, to replace the air kerma based codes of practice that have determined the dosimetry of these beams for the past twenty years. In the present work, we compared dosimetry based on the two most widespread absorbed dose based recommendations (AAPM TG-51 and IAEA TRS-398) with two air kerma based recommendations (NCS report-5 and IAEA TRS-381). Measurements were performed in three clinical electron beam energies using two NE2571-type cylindrical chambers, two Markus-type plane-parallel chambers and two NACP-02-type plane-parallel chambers. Dosimetry based on direct calibrations of all chambers in 60Co was investigated, as well as dosimetry based on cross-calibrations of plane-parallel chambers against a cylindrical chamber in a high-energy electron beam. Furthermore, 60Co perturbation factors for plane-parallel chambers were derived. It is shown that the use of 60Co calibration factors could result in deviations of more than 2% for plane-parallel chambers between the old and new codes of practice, whereas the use of cross-calibration factors, which is the first recommendation in the new codes, reduces the differences to less than 0.8% for all situations investigated here. The results thus show that neither the chamber-to-chamber variations, nor the obtained absolute dose values are significantly altered by changing from air kerma based dosimetry to absorbed dose based dosimetry when using calibration factors obtained from the Laboratory for Standard Dosimetry, Ghent, Belgium. The values of the 60Co perturbation factor for plane-parallel chambers (katt . km for the air kerma based and pwall for the absorbed dose based codes of practice) that are obtained from comparing the results based on 60Co calibrations and cross-calibrations are within the experimental uncertainties in agreement with the results from other investigators.

FDTD simulation of trapping nanowires with linearly polarized and radially polarized optical tweezers.

PubMed

Li, Jing; Wu, Xiaoping

2011-10-10

In this paper a model of the trapping force on nanowires is built by three dimensional finite-difference time-domain (FDTD) and Maxwell stress tensor methods, and the tightly focused laser beam is expressed by spherical vector wave functions (VSWFs). The trapping capacities on nanoscale-diameter nanowires are discussed in terms of a strongly focused linearly polarized beam and radially polarized beam. Simulation results demonstrate that the radially polarized beam has higher trapping efficiency on nanowires with higher refractive indices than linearly polarized beam.

FDTD simulation of trapping nanowires with linearly polarized and radially polarized optical tweezers

PubMed Central

Li, Jing; Wu, Xiaoping

2011-01-01

In this paper a model of the trapping force on nanowires is built by three dimensional finite-difference time-domain (FDTD) and Maxwell stress tensor methods, and the tightly focused laser beam is expressed by spherical vector wave functions (VSWFs). The trapping capacities on nanoscale-diameter nanowires are discussed in terms of a strongly focused linearly polarized beam and radially polarized beam. Simulation results demonstrate that the radially polarized beam has higher trapping efficiency on nanowires with higher refractive indices than linearly polarized beam. PMID:21997083

Scattering of a high-order Bessel beam by a spheroidal particle

NASA Astrophysics Data System (ADS)

Han, Lu

2018-05-01

Within the framework of generalized Lorenz-Mie theory (GLMT), scattering from a homogeneous spheroidal particle illuminated by a high-order Bessel beam is formulated analytically. The high-order Bessel beam is expanded in terms of spheroidal vector wave functions, where the spheroidal beam shape coefficients (BSCs) are computed conveniently using an intrinsic method. Numerical results concerning scattered field in the far zone are displayed for various parameters of the incident Bessel beam and of the scatter. These results are expected to provide useful insights into the scattering of a Bessel beam by nonspherical particles and particle manipulation applications using Bessel beams.

The magnetic field of a permanent hollow cylindrical magnet

NASA Astrophysics Data System (ADS)

Reich, Felix A.; Stahn, Oliver; Müller, Wolfgang H.

2016-09-01

Based on the rational version of M AXWELL's equations according to T RUESDELL and T OUPIN or KOVETZ, cf. (Kovetz in Electromagnetic theory, Oxford University Press, Oxford, 2000; Truesdell and Toupin in Handbuch der Physik, Bd. III/1, Springer, Berlin, pp 226-793; appendix, pp 794-858, 2000), we present, for stationary processes, a closed-form solution for the magnetic flux density of a hollow cylindrical magnet. Its magnetization is constant in axial direction. We consider M AXWELL's equations in regular and singular points that are obtained by rational electrodynamics, adapted to stationary processes. The magnetic flux density is calculated analytically by means of a vector potential. We obtain a solution in terms of complete elliptic integrals. Therefore, numerical evaluation can be performed in a computationally efficient manner. The solution is written in dimensionless form and can easily be applied to cylinders of arbitrary shape. The relation between the magnetic flux density and the magnetic field is linear, and an explicit relation for the field is presented. With a slight modification the result can be used to obtain the field of a solid cylindrical magnet. The mathematical structure of the solution and, in particular, singularities are discussed.

Synchrotron X-ray measurement techniques for thermal barrier coated cylindrical samples under thermal gradients.

PubMed

Siddiqui, Sanna F; Knipe, Kevin; Manero, Albert; Meid, Carla; Wischek, Janine; Okasinski, John; Almer, Jonathan; Karlsson, Anette M; Bartsch, Marion; Raghavan, Seetha

2013-08-01

Measurement techniques to obtain accurate in situ synchrotron strain measurements of thermal barrier coating systems (TBCs) applied to hollow cylindrical specimens are presented in this work. The Electron Beam Physical Vapor Deposition coated specimens with internal cooling were designed to achieve realistic temperature gradients over the TBC coated material such as that occurring in the turbine blades of aeroengines. Effects of the circular cross section on the x-ray diffraction (XRD) measurements in the various layers, including the thermally grown oxide, are investigated using high-energy synchrotron x-rays. Multiple approaches for beam penetration including collection, tangential, and normal to the layers, along with variations in collection parameters are compared for their ability to attain high-resolution XRD data from the internal layers. This study displays the ability to monitor in situ, the response of the internal layers within the TBC, while implementing a thermal gradient across the thickness of the coated sample. The thermal setup maintained coating surface temperatures in the range of operating conditions, while monitoring the substrate cooling, for a controlled thermal gradient. Through variation in measurement location and beam parameters, sufficient intensities are obtained from the internal layers which can be used for depth resolved strain measurements. Results are used to establish the various techniques for obtaining XRD measurements through multi-layered coating systems and their outcomes will pave the way towards goals in achieving realistic in situ testing of these coatings.

Synchrotron X-ray measurement techniques for thermal barrier coated cylindrical samples under thermal gradients

NASA Astrophysics Data System (ADS)

Siddiqui, Sanna F.; Knipe, Kevin; Manero, Albert; Meid, Carla; Wischek, Janine; Okasinski, John; Almer, Jonathan; Karlsson, Anette M.; Bartsch, Marion; Raghavan, Seetha

2013-08-01

Measurement techniques to obtain accurate in situ synchrotron strain measurements of thermal barrier coating systems (TBCs) applied to hollow cylindrical specimens are presented in this work. The Electron Beam Physical Vapor Deposition coated specimens with internal cooling were designed to achieve realistic temperature gradients over the TBC coated material such as that occurring in the turbine blades of aeroengines. Effects of the circular cross section on the x-ray diffraction (XRD) measurements in the various layers, including the thermally grown oxide, are investigated using high-energy synchrotron x-rays. Multiple approaches for beam penetration including collection, tangential, and normal to the layers, along with variations in collection parameters are compared for their ability to attain high-resolution XRD data from the internal layers. This study displays the ability to monitor in situ, the response of the internal layers within the TBC, while implementing a thermal gradient across the thickness of the coated sample. The thermal setup maintained coating surface temperatures in the range of operating conditions, while monitoring the substrate cooling, for a controlled thermal gradient. Through variation in measurement location and beam parameters, sufficient intensities are obtained from the internal layers which can be used for depth resolved strain measurements. Results are used to establish the various techniques for obtaining XRD measurements through multi-layered coating systems and their outcomes will pave the way towards goals in achieving realistic in situ testing of these coatings.

The biomechanics of zygomatic arch shape

PubMed Central

Smith, Amanda L.; Grosse, Ian R.

2017-01-01

Mammalian zygomatic arch shape is remarkably variable, ranging from nearly cylindrical to blade-like in cross section. Based on geometry, the arch can be hypothesized to be a sub-structural beam whose ability to resist deformation is related to cross sectional shape. We expect zygomatic arches with different cross sectional shapes to vary in the degree to which they resist local bending and torsion due to the contraction of the masseter muscle. A stiffer arch may lead to an increase in the relative proportion of applied muscle load being transmitted through the arch to other cranial regions, resulting in elevated cranial stress (and thus, strain). Here, we examine the mechanics of the zygomatic arch using a series of finite element modeling experiments in which the cross section of the arch of Pan troglodytes has been modified to conform to idealized shapes (cylindrical, elliptical, blade-like). We find that the shape of the zygomatic arch has local effects on stain that do not conform to beam theory. One exception is that possessing a blade-like arch leads to elevated strains at the postorbital zygomatic junction and just below the orbits. Furthermore, although modeling the arch as solid cortical bone did not have the effect of elevating strains in other parts of the face, as had been expected, it does have a small effect on stress associated with masseter contraction. These results are counterintuitive. Even though the arch has simple beam-like geometry, we fail to find a simple mechanical explanation for the diversity of arch shape. PMID:27870343

Primary aberrations in focused radially polarized vortex beams

NASA Astrophysics Data System (ADS)

Biss, David P.; Brown, T. G.

2004-02-01

We study the effect of primary aberrations on the 3-D polarization of the electric field in a focused lowest order radially polarized beam. A full vector diffraction treatment of the focused beams is used. Attention is given to the effects of primary spherical, astigmatic, and comatic aberrations on the local polarization, Strehl ratio, and aberration induced degradation of the longitudinal field at focus

Electron Beam Propagation Through a Magnetic Wiggler with Random Field Errors

DTIC Science & Technology

1989-08-21

Another quantity of interest is the vector potential 6.A,.(:) associated with the field error 6B,,,(:). Defining the normalized vector potentials ba = ebA...then follows that the correlation of the normalized vector potential errors is given by 1 . 12 (-a.(zj)a.,(z2)) = a,k,, dz’ , dz" (bBE(z’)bB , (z")) a2...Throughout the following, terms of order O(z:/z) will be neglected. Similarly, for the y-component of the normalized vector potential errors, one

Simulation and Assessment of a Ku-Band Full-Polarized Radar Scatterometer for Ocean Surface Vector Wind Measurement

NASA Astrophysics Data System (ADS)

Dong, X.; Lin, W.; Zhu, D.; Song, Z.

2011-12-01

Spaceborne radar scatterometry is the most important tool for global ocean surface wind vector (OSVW) measurement. Performances under condition of high-wind speed and accuracy of wind direction retrievals are two very important concerns for the development of OSVW measurement techniques by radar scatterometry. Co-polarized sigma 0 measurements are employed, for all the spaceborne radar scatterometers developed in past, and future planned missions. The main disadvantages of co-polarized only radar scatterometers for OSVW measurement are: firstly, wind vector retrieval performances varies with the position of the wind vector cells (WVC) within the swath, where WVCs with small incident angels with weaker modulation effect between sigma0 and azimuth incident angle, and the WVCs located in the outer part of the swath with lower signal-to-noise ratio and lower radiometric accuracies, have worse retrieval performances; secondly, for co-polarization measurements, Sigma 0 is the even function of the azimuth incident angle with respect to the real wind direction, which can results in directional ambiguity, and more additional information is need for the ambiguity removal. Theoretical and experimental results show that the cross-polarization measurement can provide complementary directional information to the co-polarization measurements, which can provide useful improvement to the wind vector retrieval performances. In this paper, the simulation and performance assessment of a full-polarized Ku-band radar scatterometer are provided. Some important conclusions are obtained: (1) Compared with available dual co-polarized radar scatterometer, the introduction of cross-polarization information can significantly improve the OSVW retrieval accuracies, where a relatively identical performance can be obtained within the whole swath. Simulation show that without significantly power increase, system design based on rotating-pencil beam design has much better performances than rotation fan-beam system due to its higher antenna gain and signal-to-noise ratio; (2) The performances of the full-polarized measurement, where all the 9 element covariant coefficient elements will be measurement, only have a little improvement compared with the "dual-co-polarization+HVVV" design, which is because of the almost identical characteristics of HVVV and VHHH measurement due to reciprocity; (3) The propagation error of rotation pencil-beam system is obviously much smaller than that of the rotation fan-beam system, which is due to the significant difference of antenna gains and signal-to-noise ratios; (4) Introduction of cross-polarized HVVV measurement can lead to almost identical wind direction retrieval performance for both the rotation pencil-beam and rotation fan-beam systems, which show that the cross-polarization information can significantly improve the wind direction retrieval performances by increasing the number of look angles, compared with the available fixed-fan-beam systems.

Absolute surface reconstruction by slope metrology and photogrammetry

NASA Astrophysics Data System (ADS)

Dong, Yue

Developing the manufacture of aspheric and freeform optical elements requires an advanced metrology method which is capable of inspecting these elements with arbitrary freeform surfaces. In this dissertation, a new surface measurement scheme is investigated for such a purpose, which is to measure the absolute surface shape of an object under test through its surface slope information obtained by photogrammetric measurement. A laser beam propagating toward the object reflects on its surface while the vectors of the incident and reflected beams are evaluated from the four spots they leave on the two parallel transparent windows in front of the object. The spots' spatial coordinates are determined by photogrammetry. With the knowledge of the incident and reflected beam vectors, the local slope information of the object surface is obtained through vector calculus and finally yields the absolute object surface profile by a reconstruction algorithm. An experimental setup is designed and the proposed measuring principle is experimentally demonstrated by measuring the absolute surface shape of a spherical mirror. The measurement uncertainty is analyzed, and efforts for improvement are made accordingly. In particular, structured windows are designed and fabricated to generate uniform scattering spots left by the transmitted laser beams. Calibration of the fringe reflection instrument, another typical surface slope measurement method, is also reported in the dissertation. Finally, a method for uncertainty analysis of a photogrammetry measurement system by optical simulation is investigated.

Experimental investigation of the effect of the laser beam polarization state on the quality of steel sheet cutting

NASA Astrophysics Data System (ADS)

Golyshev, A. A.; Orishich, A. M.; Shulyatyev, V. B.

2017-10-01

The paper presents the results of experimental investigation of the effect of the beam polarization on the quality of the oxygen-assisted laser cutting of steel by a CO2-laser. Under consideration is the effect of the laser cutting parameters by the beam with the linear polarization on the cut surface roughness. It is founded that the minimal roughness is reached when the electric field vector is perpendicular to the cutting speed vector. It is concluded that the absorbed power distribution imposes the essential influence on the surface quality, and that the radiation heating of side walls is important to have lower roughness. Obtained results enabled to present probable reasons of the worse surface quality of the metals cut by a fiber laser than the ones cut by a CO2-laser.

Millimeter Wave Generation by Relativistic Electron Beams.

DTIC Science & Technology

1984-12-01

frequency and wave vector matching relations for influence of various nonlinear effects on this instability is this four-wave interaction require...following coupled mode equations _ 6 = 6 _ (14)-- v vx (14) ." .’ for the lower hybrid sidebands: v - V 2 - The x component of the resultant vector equation...involves a purely growing modte, a four-wave interaction plitoces is analysed, including a u ap ti wave- vector up-shifted and ilown-shiftes upper

The 80 kV electrostatic wire septum for AmPS

NASA Astrophysics Data System (ADS)

Vanderlinden, A.; Bijleveld, J. H. M.; Rookhuizen, H. Boer; Bruinsma, P. J. T.; Heine, E.; Lassing, P.; Prins, E.

The characteristics of the wire septum for the Amsterdam Pulse Stretcher (AmPS) are summarized. In the extraction process of the AmPS the extracted beam is intercepted from the circulating beam by the 1 m long electrostatic wire septum. For a bending angle of 4.4 mrad, the maximum anode voltage is 80 kV. The system developed consists of a wire spacing of 0.65 mm between tungsten wires of 50 micrometers diameter. Stainless steel spring wires, bent in a half cylindrical carrier, stretch the septum wires two by two. Prototype tests were successful up to an anode voltage of 120 kV.

Design study of 10 kW direct fission target for RISP project

NASA Astrophysics Data System (ADS)

Tshoo, K.; Jang, D. Y.; Woo, H. J.; Kang, B. H.; Kim, G. D.; Hwang, W.; Kim, Y. K.

2014-03-01

We are developing Isotope Separation On-Line (ISOL) target system, which consists of 1.3 mm-thick uranium-carbide multi-disks and cylindrical tantalum heater, to be installed in new facility for Rare Isotope Science Project in Korea. The intense neutron-rich nuclei are produced via the fission process using the uranium carbide targets with a 70 MeV proton beam. The fission rate was estimated to be ˜1.5 × 1013/sec for 10 kW proton beam. The target system has been designed to be operated at a temperature of ˜2000 °C so as to improve the release effciency.

An inverted cylindrical sputter magnetron as metal vapor supply for electron cyclotron resonance ion sources.

PubMed

Weichsel, T; Hartung, U; Kopte, T; Zschornack, G; Kreller, M; Silze, A

2014-05-01

An inverted cylindrical sputter magnetron device has been developed. The magnetron is acting as a metal vapor supply for an electron cyclotron resonance (ECR) ion source. FEM simulation of magnetic flux density was used to ensure that there is no critical interaction between both magnetic fields of magnetron and ECR ion source. Spatially resolved double Langmuir probe and optical emission spectroscopy measurements show an increase in electron density by one order of magnitude from 1 × 10(10) cm(-3) to 1 × 10(11) cm(-3), when the magnetron plasma is exposed to the magnetic mirror field of the ECR ion source. Electron density enhancement is also indicated by magnetron plasma emission photography with a CCD camera. Furthermore, photographs visualize the formation of a localized loss-cone - area, when the magnetron is operated at magnetic mirror field conditions. The inverted cylindrical magnetron supplies a metal atom load rate of R > 1 × 10(18) atoms/s for aluminum, which meets the demand for the production of a milliampere Al(+) ion beam.

Analysis of Precursor Properties of mixed Al/Alumel Cylindrical Wire Arrays*

NASA Astrophysics Data System (ADS)

Stafford, A.; Safronova, A. S.; Kantsyrev, V. L.; Esaulov, A. A.; Weller, M. E.; Shrestha, I.; Osborne, G. C.; Shlyaptseva, V. V.; Keim, S. F.; Coverdale, C. A.; Chuvatin, A. S.

2012-10-01

Previous studies of mid-Z (Cu and Ni) cylindrical wire arrays (CWAs) on Zebra have found precursors with high electron temperatures of >300 eV. However, past experiments with Al CWAs did not find the same high temperature precursors. New precursor experiments using mixed Al/Alumel (Ni 95%, Si 2%, and Al 2%) cylindrical wire arrays have been performed to understand how the properties of L-shell Ni precursor will change and whether Al precursor will be observed. Time gated spectra and pinholes are used to determine precursor plasma conditions for comparison with previous Alumel precursor experiments. A full diagnostic set which included more than ten different beam-lines was implemented. Future work in this direction is discussed. [4pt] *This work was supported by NNSA under DOE Cooperative Agreements DE-FC52-06NA27588, and in part by DE-FC52-06NA27586, and DE-FC52-06NA27616. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.

Low distortion laser welding of cylindrical components

NASA Astrophysics Data System (ADS)

Kittel, Sonja

2011-02-01

Automotive components are for the most part cylindrical and thus the weld seams are of radial shape. Radial weld seams are usually produced by starting at a point on the component's surface rotating the component resulting in an overlap zone at the start/end of the weld. In this research, it is shown that the component's distortion strongly depends on the overlap of weld start and end. A correlation between overlap zone and distortion is verified by an experimental study. In order to reduce distortion generated by the overlap zone a special optics is used which allows shaping the laser beam into a ring shape which is then focused on the cylindrical surface and produces a radial ring weld seam simultaneously by one laser pulse. In doing this, the overlap zone is eliminated and distortion can be reduced. Radial weld seams are applied on precision samples and distortion is measured after welding. The distortion of the precision samples is measured by a tactile measuring method and a comparison of the results of welding with the ring optics to reference welds is done.

The Rocket Electric Field Sounding (REFS) program: Prototype design and successful first launch

NASA Astrophysics Data System (ADS)

Willett, J. C.; Curtis, D. C.; Driesman, A. R.; Longstreth, R. K.; Rison, W.; Winn, W. P.; Jones, J. J.

1992-01-01

The motivation, design, and successful first flight of a sounding rocket to measure profiles of vector electrostatic field in the lower troposphere are described. The design employs eight shutter field mills amd a corona-charging system in a manner similar to aircraft previously instrumented for the measurement of electric fields. A rocket offers significant advantages over an aircraft in simplicity and calibration. A single cylindrical rotor covering most of the payload acts as the shutter for all eight mills in this design. The cylindrical symmetry and circular cross sections of the vehicle facilitate straightforward calibration. Also included in the payload are a pressure sensor, a longitudinal accelerometer, a transverse magnometer, and a novel cloud-penetration detector. A fair-weather test flight at the NASA Wallops Flight Facility demonstrated the workability of the basic design and identified a few necessary modifications.

Static axisymmetric Einstein equations in vacuum: Symmetry, new solutions, and Ricci solitons

NASA Astrophysics Data System (ADS)

Akbar, M. M.; MacCallum, M. A. H.

2015-09-01

An explicit one-parameter Lie point symmetry of the four-dimensional vacuum Einstein equations with two commuting hypersurface-orthogonal Killing vector fields is presented. The parameter takes values over all of the real line and the action of the group can be effected algebraically on any solution of the system. This enables one to construct particular one-parameter extended families of axisymmetric static solutions and cylindrical gravitational wave solutions from old ones, in a simpler way than most solution-generation techniques, including the prescription given by Ernst for this system. As examples, we obtain the families that generalize the Schwarzschild solution and the C -metric. These in effect superpose a Levi-Civita cylindrical solution on the seeds. Exploiting a correspondence between static solutions of Einstein's equations and Ricci solitons (self-similar solutions of the Ricci flow), this also enables us to construct new steady Ricci solitons.

High-flux source of low-energy neutral beams using reflection of ions from metals

NASA Technical Reports Server (NTRS)

Cuthbertson, John W.; Motley, Robert W.; Langer, William D.

1992-01-01

Reflection of low-energy ions from surfaces can be applied as a method of producing high-flux beams of low-energy neutral particles, and is an important effect in several areas of plasma technology, such as in the edge region of fusion devices. We have developed a beam source based on acceleration and reflection of ions from a magnetically confined coaxial RF plasma source. The beam provides a large enough flux to allow the energy distribution of the reflected neutrals to be measured despite the inefficiency of detection, by means of an electrostatic cylindrical mirror analyzer coupled with a quadrupole mass spectrometer. Energy distributions have been measured for oxygen, nitrogen, and inert gas ions incident with from 15 to 70 eV reflected from amorphous metal surfaces of several compositions. For ions of lighter atomic mass than the reflecting metal, reflected beams have peaked energy distributions; beams with the peak at 4-32 eV have been measured. The energy and mass dependences of the energy distributions as well as measurements of absolute flux, and angular distribution and divergence are reported. Applications of the neutral beams produced are described.

Passively Damped Laminated Piezoelectric Shell Structures with Integrated Electric Networks

NASA Technical Reports Server (NTRS)

Saravanos, Dimitris A.

1999-01-01

Multi-field mechanics are presented for curvilinear piezoelectric laminates interfaced with distributed passive electric components. The equations of motion for laminated piezoelectric shell structures with embedded passive electric networks are directly formulated and solved using a finite element methodology. The modal damping and frequencies of the piezoelectric shell are calculated from the poles of the system. Experimental and numerical results are presented for the modal damping and frequency of composite beams with a resistively shunted piezoceramic patch. The modal damping and frequency of plates, cylindrical shells and cylindrical composite blades with piezoelectric-resistor layers are predicted. Both analytical and experimental studies illustrate a unique dependence of modal damping and frequencies on the shunting resistance and show the effect of structural shape and curvature on piezoelectric damping.

Observation of a high-energy tail in ion energy distribution in the cylindrical Hall thruster plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Youbong; Kim, Holak; Choe, Wonho, E-mail: wchoe@kaist.ac.kr

2014-10-15

A novel method is presented to determine populations and ion energy distribution functions (IEDFs) of individual ion species having different charge states in an ion beam from the measured spectrum of an E × B probe. The inversion of the problem is performed by adopting the iterative Tikhonov regularization method with the characteristic matrices obtained from the calculated ion trajectories. In a cylindrical Hall thruster plasma, an excellent agreement is observed between the IEDFs by an E × B probe and those by a retarding potential analyzer. The existence of a high-energy tail in the IEDF is found to be mainly due to singlymore » charged Xe ions, and is interpreted in terms of non-linear ion acceleration.« less

Complete data listings for CSEM soundings on Kilauea Volcano, Hawaii

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kauahikaua, J.; Jackson, D.B.; Zablocki, C.J.

1983-01-01

This document contains complete data from a controlled-source electromagnetic (CSEM) sounding/mapping project at Kilauea volcano, Hawaii. The data were obtained at 46 locations about a fixed-location, horizontal, polygonal loop source in the summit area of the volcano. The data consist of magnetic field amplitudes and phases at excitation frequencies between 0.04 and 8 Hz. The vector components were measured in a cylindrical coordinate system centered on the loop source. 5 references.

A three-dimensional nonlinear Timoshenko beam based on the core-congruential formulation

NASA Technical Reports Server (NTRS)

Crivelli, Luis A.; Felippa, Carlos A.

1992-01-01

A three-dimensional, geometrically nonlinear two-node Timoshenkoo beam element based on the total Larangrian description is derived. The element behavior is assumed to be linear elastic, but no restrictions are placed on magnitude of finite rotations. The resulting element has twelve degrees of freedom: six translational components and six rotational-vector components. The formulation uses the Green-Lagrange strains and second Piola-Kirchhoff stresses as energy-conjugate variables and accounts for the bending-stretching and bending-torsional coupling effects without special provisions. The core-congruential formulation (CCF) is used to derived the discrete equations in a staged manner. Core equations involving the internal force vector and tangent stiffness matrix are developed at the particle level. A sequence of matrix transformations carries these equations to beam cross-sections and finally to the element nodal degrees of freedom. The choice of finite rotation measure is made in the next-to-last transformation stage, and the choice of over-the-element interpolation in the last one. The tangent stiffness matrix is found to retain symmetry if the rotational vector is chosen to measure finite rotations. An extensive set of numerical examples is presented to test and validate the present element.

Precise on-machine extraction of the surface normal vector using an eddy current sensor array

NASA Astrophysics Data System (ADS)

Wang, Yongqing; Lian, Meng; Liu, Haibo; Ying, Yangwei; Sheng, Xianjun

2016-11-01

To satisfy the requirements of on-machine measurement of the surface normal during complex surface manufacturing, a highly robust normal vector extraction method using an Eddy current (EC) displacement sensor array is developed, the output of which is almost unaffected by surface brightness, machining coolant and environmental noise. A precise normal vector extraction model based on a triangular-distributed EC sensor array is first established. Calibration of the effects of object surface inclination and coupling interference on measurement results, and the relative position of EC sensors, is involved. A novel apparatus employing three EC sensors and a force transducer was designed, which can be easily integrated into the computer numerical control (CNC) machine tool spindle and/or robot terminal execution. Finally, to test the validity and practicability of the proposed method, typical experiments were conducted with specified testing pieces using the developed approach and system, such as an inclined plane and cylindrical and spherical surfaces.

Numerical analysis for the stick-slip vibration of a transversely moving beam in contact with a frictional wall

NASA Astrophysics Data System (ADS)

Won, Hong-In; Chung, Jintai

2018-04-01

This paper presents a numerical analysis for the stick-slip vibration of a transversely moving beam, considering both stick-slip transition and friction force discontinuity. The dynamic state of the beam was separated into the stick state and the slip state, and boundary conditions were defined for both. By applying the finite element method, two matrix-vector equations were derived: one for stick state and the other for slip state. However, the equations have different degrees of freedom depending on whether the end of a beam sticks or slips, so we encountered difficulties in time integration. To overcome the difficulties, we proposed a new numerical technique to alternatively use the matrix-vector equations with different matrix sizes. In addition, to eliminate spurious high-frequency responses, we applied the generalized-α time integration method with appropriate value of high-frequency numerical dissipation. Finally, the dynamic responses of stick-slip vibration were analyzed in time and frequency domains: the dynamic behavior of the beam was explained to facilitate understanding of the stick-slip motion, and frequency characteristics of the stick-slip vibration were investigated in relation to the natural frequencies of the beam. The effects of the axial load and the moving speed upon the dynamic response were also examined.

Bessel beams with spatial oscillating polarization

PubMed Central

Fu, Shiyao; Zhang, Shikun; Gao, Chunqing

2016-01-01

Bessel beams are widely used in optical metrology mainly because of their large Rayleigh range (focal length). Radial/azimuthal polarization of such beams is of interest in the fields of material processing, plasma absorption or communication. In this paper an experimental set-up is presented, which generates a Bessel-type vector beam with a spatial polarization, oscillating along the optical axis, when propagating in free space. A first holographic axicon (HA) HA1 produces a normal, linearly polarized Bessel beam, which by a second HA2 is converted into the spatial oscillating polarized beam. The theory is briefly discussed, the set-up and the experimental results are presented in detail. PMID:27488174

Development of Grazing Incidence Optics for Neutron Imaging and Scattering

NASA Technical Reports Server (NTRS)

Gubarev, M. V.; Khaykovich, B.; Liu, D.; Ramsey, B. D.; Zavlin, V. E.; Kilaru, K.; Romaine, S.; Rosati, R. E.; Bruni, R.; Moncton, D. E.

2012-01-01

Because of their wave nature, thermal and cold neutrons can be reflected from smooth surfaces at grazing incidence angles, be reflected by multilayer coatings or be refracted at boundaries of different materials. The optical properties of materials are characterized by their refractive indices which are slightly less than unity for most elements and their isotopes in the case of cold and thermal neutrons as well as for x-rays. The motivation for the optics use for neutrons as well as for x-rays is to increase the signal rate and, by virtue of the optic's angular resolution, to improve the signal-to-noise level by reducing the background so the efficiency of the existing neutron sources use can be significantly enhanced. Both refractive and reflective optical techniques developed for x-ray applications can be applied to focus neutron beams. Typically neutron sources have lower brilliance compared to conventional x-ray sources so in order to increase the beam throughput the neutron optics has to be capable of capturing large solid angles. Because of this, the replicated optics techniques developed for x-ray astronomy applications would be a perfect match for neutron applications, so the electroformed nickel optics under development at the Marshall Space Flight Center (MSFC) can be applied to focus neutron beams. In this technique, nickel mirror shells are electroformed onto a figured and superpolished nickel-plated aluminum cylindrical mandrel from which they are later released by differential thermal contraction. Cylindrical mirrors with different diameters, but the same focal length, can be nested together to increase the system throughput. The throughput can be increased further with the use of the multilayer coatings deposited on the reflectivr surface of the mirror shells. While the electroformed nickel replication technique needs to be adopted for neutron focusing, the technology to coat the inside of cylindrical mirrors with neutron multilayers has to be developed. The availability of these technologies would bring new capabilities to neutron instrumentation and, hence, lead to new scientific breakthroughs. We have established a program to adopt the electroformed nickel replication optics technique for neutron applications and to develop the neutron multilayer replication technology.

Dark Matter Search in a Proton Beam Dump with MiniBooNE

NASA Astrophysics Data System (ADS)

Aguilar-Arevalo, A. A.; Backfish, M.; Bashyal, A.; Batell, B.; Brown, B. C.; Carr, R.; Chatterjee, A.; Cooper, R. L.; deNiverville, P.; Dharmapalan, R.; Djurcic, Z.; Ford, R.; Garcia, F. G.; Garvey, G. T.; Grange, J.; Green, J. A.; Huelsnitz, W.; de Icaza Astiz, I. L.; Karagiorgi, G.; Katori, T.; Ketchum, W.; Kobilarcik, T.; Liu, Q.; Louis, W. C.; Marsh, W.; Moore, C. D.; Mills, G. B.; Mirabal, J.; Nienaber, P.; Pavlovic, Z.; Perevalov, D.; Ray, H.; Roe, B. P.; Shaevitz, M. H.; Shahsavarani, S.; Stancu, I.; Tayloe, R.; Taylor, C.; Thornton, R. T.; Van de Water, R.; Wester, W.; White, D. H.; Yu, J.; MiniBooNE-DM Collaboration

2017-06-01

The MiniBooNE-DM Collaboration searched for vector-boson mediated production of dark matter using the Fermilab 8-GeV Booster proton beam in a dedicated run with 1.86 ×1 020 protons delivered to a steel beam dump. The MiniBooNE detector, 490 m downstream, is sensitive to dark matter via elastic scattering with nucleons in the detector mineral oil. Analysis methods developed for previous MiniBooNE scattering results were employed, and several constraining data sets were simultaneously analyzed to minimize systematic errors from neutrino flux and interaction rates. No excess of events over background was observed, leading to a 90% confidence limit on the dark matter cross section parameter, Y =ɛ2αD(mχ/mV)4≲10-8 , for αD=0.5 and for dark matter masses of 0.01

Dark Matter Search in a Proton Beam Dump with MiniBooNE.

PubMed

Aguilar-Arevalo, A A; Backfish, M; Bashyal, A; Batell, B; Brown, B C; Carr, R; Chatterjee, A; Cooper, R L; deNiverville, P; Dharmapalan, R; Djurcic, Z; Ford, R; Garcia, F G; Garvey, G T; Grange, J; Green, J A; Huelsnitz, W; de Icaza Astiz, I L; Karagiorgi, G; Katori, T; Ketchum, W; Kobilarcik, T; Liu, Q; Louis, W C; Marsh, W; Moore, C D; Mills, G B; Mirabal, J; Nienaber, P; Pavlovic, Z; Perevalov, D; Ray, H; Roe, B P; Shaevitz, M H; Shahsavarani, S; Stancu, I; Tayloe, R; Taylor, C; Thornton, R T; Van de Water, R; Wester, W; White, D H; Yu, J

2017-06-02

The MiniBooNE-DM Collaboration searched for vector-boson mediated production of dark matter using the Fermilab 8-GeV Booster proton beam in a dedicated run with 1.86×10^{20} protons delivered to a steel beam dump. The MiniBooNE detector, 490 m downstream, is sensitive to dark matter via elastic scattering with nucleons in the detector mineral oil. Analysis methods developed for previous MiniBooNE scattering results were employed, and several constraining data sets were simultaneously analyzed to minimize systematic errors from neutrino flux and interaction rates. No excess of events over background was observed, leading to a 90% confidence limit on the dark matter cross section parameter, Y=ε^{2}α_{D}(m_{χ}/m_{V})^{4}≲10^{-8}, for α_{D}=0.5 and for dark matter masses of 0.01

Microstructures and magnetic properties of Co-Al-O granular thin films

NASA Astrophysics Data System (ADS)

Ohnuma, M.; Hono, K.; Onodera, H.; Ohnuma, S.; Fujimori, H.; Pedersen, J. S.

2000-01-01

The microstructures of Co-Al-O thin films of wide varieties of compositions are studied by transmission electron microscopy and small angle x-ray scattering (SAXS). In the superparamagnetic specimens, high resolution electron microscope images reveal that isolated spherical Co particles are surrounded by an amorphous aluminum oxide matrix. However, in the soft ferromagnetic films, the shape of the Co particles is prolate ellipsoidal. SAXS intensities from the soft magnetic specimens decrease inversely with the wave vector, q, in a low wave-vector region, while an interparticle interference peak is observed for the superparamagnetic specimens. The scattering profiles of the soft magnetic films imply that the Co particles have a cylindrical shape and are randomly oriented. The correlation between the magnetic properties and the microstructures is discussed.

Method and apparatus for two-dimensional spectroscopy

DOEpatents

DeCamp, Matthew F.; Tokmakoff, Andrei

2010-10-12

Preferred embodiments of the invention provide for methods and systems of 2D spectroscopy using ultrafast, first light and second light beams and a CCD array detector. A cylindrically-focused second light beam interrogates a target that is optically interactive with a frequency-dispersed excitation (first light) pulse, whereupon the second light beam is frequency-dispersed at right angle orientation to its line of focus, so that the horizontal dimension encodes the spatial location of the second light pulse and the first light frequency, while the vertical dimension encodes the second light frequency. Differential spectra of the first and second light pulses result in a 2D frequency-frequency surface equivalent to double-resonance spectroscopy. Because the first light frequency is spatially encoded in the sample, an entire surface can be acquired in a single interaction of the first and second light pulses.

Bias of cylinder diameter estimation from ground-based laser scanners with different beam widths: A simulation study

NASA Astrophysics Data System (ADS)

Forsman, Mona; Börlin, Niclas; Olofsson, Kenneth; Reese, Heather; Holmgren, Johan

2018-01-01

In this study we have investigated why diameters of tree stems, which are approximately cylindrical, are often overestimated by mobile laser scanning. This paper analyzes the physical processes when using ground-based laser scanning that may contribute to a bias when estimating cylinder diameters using circle-fit methods. A laser scanner simulator was implemented and used to evaluate various properties, such as distance, cylinder diameter, and beam width of a laser scanner-cylinder system to find critical conditions. The simulation results suggest that a positive bias of the diameter estimation is expected. Furthermore, the bias follows a quadratic function of one parameter - the relative footprint, i.e., the fraction of the cylinder width illuminated by the laser beam. The quadratic signature opens up a possibility to construct a compensation model for the bias.

Linear theory of plasma Čerenkov masers

NASA Astrophysics Data System (ADS)

Birau, M.

1996-11-01

A different theoretical model of Čerenkov instability in the linear amplification regime of plasma Čerenkov masers is developed. The model assumes a cold relativistic annular electron beam propagating through a column of cold dense plasma, the two bodies being immersed in an infinite magnetic guiding field inside a perfect cylindrical waveguide. In order to simplify the calculations, a radial rectangular distribution of plasma and beam density is assumed and only azimuthal symmetric modes are under investigation. The model's difference consists of taking into account the whole plasma and beam electromagnetic structures in the interpretation of the Čerenkov instability. This model leads to alternative results such as the possibility of emission at several frequencies. In addition, the electric field is calculated taking into account its radial phase dependence, so that a map of the field in the interaction region can be presented.

[Liposome-mediated glial growth factor 2 gene therapy in brain injury: an experimental study with rats].

PubMed

Xue, Ya-jun; Dong, Yan; Han, Xi; Wei, Mei-yang; Ge, Jun-hui; Cai, Ru-jue; Hu, Guo-han; Luo, Chun; Zhu, Cheng; Lu, Yi-cheng

2006-09-05

To explore the protective effect of glial growth factor-2 (GGF2) on brain injury. Thirty-four SD rats underwent lateral fluid percussion to establish brain injury models and then were randomly divided into 4 groups: treatment group (n = 10, the plasmid pEGFP-N1-GGF2 mixed with liposome was injected into the brain tissue directly), vector control group (n = 10, the vector pEGFP-N1 mixed with liposome was injected into the brain tissue directly), liposome control group (n = 10, liposome was injected), and sham operation group (n = 4). Three assessment tasks were performed for neurobehavioral evaluation: Clivas Test, Beam Balance Test and Beam Walking Test. 10 days after brain injury, the rats were sacrificed and their brains were embedded in paraffin for HE staining, Nissle staining and immunohistochemical examination of MBP, NSE, and GFAP. The Clivas test score of the treatment group was 66.25 +/- 3.54, significantly higher than those of the vector control group and. liposome control group (58.31 +/- 3.72 and 57.21 +/- 3.93 respectively, both P < 0.05). The beam test score of the treatment group was 2.59 +/- 0.21, significantly lower than those the vector control group and liposome control group (3.41 +/- 0.25 and 3.24 +/- 0.22 respectively, both P < 0.05). The walking test score of the treatment group was 20.15 +/- 2.59, significantly lower than those of control group and liposome control group (27.00 +/- 3.47 and 27.80 +/- 3.00 respectively, both P < 0.05). The improvement in beam walking test was the greatest. The neuron number in the external granular layer and external pyramidal layer in cortex of the treatment group was 98 +/- 10, significantly more than those of the vector control group and liposome group (75 +/- 7 and 67 +/- 8, both P < 0.05). The neuron number in the internal pyramidal layer in cortex of the treatment group was 37 +/- 4, significantly more than those of the vector control group and liposome group (19 +/- 3 and 23 +/- 4 respectively, both P < 0.05). The neuron number in the CA1 region in hippocampus of the treatment group was 102 +/- 11, significantly more than those of the vector control group and liposome group (67 +/- 8 and 58 +/- 9 respectively, both P < 0.01). Higher level of immunoreactivity with MBP was also detected in the cortex in the rats of the treatment group. Cationic liposome-mediated GGF2 gene therapy effectively promotes the recovery of brain injury.

Diffraction-based optical correlator

NASA Technical Reports Server (NTRS)

Spremo, Stevan M. (Inventor); Fuhr, Peter L. (Inventor); Schipper, John F. (Inventor)

2005-01-01

Method and system for wavelength-based processing of a light beam. A light beam, produced at a chemical or physical reaction site and having at least first and second wavelengths, ?1 and ?2, is received and diffracted at a first diffraction grating to provide first and second diffracted beams, which are received and analyzed in terms of wavelength and/or time at two spaced apart light detectors. In a second embodiment, light from first and second sources is diffracted and compared in terms of wavelength and/or time to determine if the two beams arise from the same source. In a third embodiment, a light beam is split and diffracted and passed through first and second environments to study differential effects. In a fourth embodiment, diffracted light beam components, having first and second wavelengths, are received sequentially at a reaction site to determine whether a specified reaction is promoted, based on order of receipt of the beams. In a fifth embodiment, a cylindrically shaped diffraction grating (uniform or chirped) is rotated and translated to provide a sequence of diffracted beams with different wavelengths. In a sixth embodiment, incident light, representing one or more symbols, is successively diffracted from first and second diffraction gratings and is received at different light detectors, depending upon the wavelengths present in the incident light.

A feasibility study of the use of bounded beams resembling the shape of evanescent and inhomogeneous waves.

PubMed

Declercq, Nico F; Leroy, Oswald

2011-08-01

Plane waves are solutions of the visco-elastic wave equation. Their wave vector can be real for homogeneous plane waves or complex for inhomogeneous and evanescent plane waves. Although interesting from a theoretical point of view, complex wave vectors normally only emerge naturally when propagation or scattering is studied of sound under the appearance of damping effects. Because of the particular behavior of inhomogeneous and evanescent waves and their estimated efficiency for surface wave generation, bounded beams, experimentally mimicking their infinite counterparts similar to (wide) Gaussian beams imitating infinite harmonic plane waves, are of special interest in this report. The study describes the behavior of bounded inhomogeneous and bounded evanescent waves in terms of amplitude and phase distribution as well as energy flow direction. The outcome is of importance to the applicability of bounded inhomogeneous ultrasonic waves for nondestructive testing. Copyright © 2011. Published by Elsevier B.V.

Correcting systematic errors in high-sensitivity deuteron polarization measurements

NASA Astrophysics Data System (ADS)

Brantjes, N. P. M.; Dzordzhadze, V.; Gebel, R.; Gonnella, F.; Gray, F. E.; van der Hoek, D. J.; Imig, A.; Kruithof, W. L.; Lazarus, D. M.; Lehrach, A.; Lorentz, B.; Messi, R.; Moricciani, D.; Morse, W. M.; Noid, G. A.; Onderwater, C. J. G.; Özben, C. S.; Prasuhn, D.; Levi Sandri, P.; Semertzidis, Y. K.; da Silva e Silva, M.; Stephenson, E. J.; Stockhorst, H.; Venanzoni, G.; Versolato, O. O.

2012-02-01

This paper reports deuteron vector and tensor beam polarization measurements taken to investigate the systematic variations due to geometric beam misalignments and high data rates. The experiments used the In-Beam Polarimeter at the KVI-Groningen and the EDDA detector at the Cooler Synchrotron COSY at Jülich. By measuring with very high statistical precision, the contributions that are second-order in the systematic errors become apparent. By calibrating the sensitivity of the polarimeter to such errors, it becomes possible to obtain information from the raw count rate values on the size of the errors and to use this information to correct the polarization measurements. During the experiment, it was possible to demonstrate that corrections were satisfactory at the level of 10 -5 for deliberately large errors. This may facilitate the real time observation of vector polarization changes smaller than 10 -6 in a search for an electric dipole moment using a storage ring.

A 24-GHz portable FMCW radar with continuous beam steering phased array (Conference Presentation)

NASA Astrophysics Data System (ADS)

Peng, Zhengyu; Li, Changzhi

2017-05-01

A portable 24-GHz frequency-modulated continuous-wave (FMCW) radar with continuous beam steering phased array is presented. This board-level integrated radar system consists of a phased array antenna, a radar transceiver and a baseband. The phased array used by the receiver is a 4-element linear array. The beam of the phased array can be continuously steered with a range of ±30° on the H-plane through an array of vector controllers. The vector controller is based on the concept of vector sum with binary-phase-shift attenuators. Each vector controller is capable of independently controlling the phase and the amplitude of each element of the linear array. The radar transceiver is based on the six-port technique. A free-running voltage controlled oscillator (VCO) is controlled by an analog "sawtooth" voltage generator to produce frequency-modulated chirp signal. This chirp signal is used as the transmitter signal, as well as the local oscillator (LO) signal to drive the six-port circuit. The transmitter antenna is a single patch antenna. In the baseband, the beat signal of the FMCW radar is detected by the six-port circuit and then processed by a laptop in real time. Experiments have been performed to reveal the capabilities of the proposed radar system for applications including indoor inverse synthetic aperture radar (ISAR) imaging, vital sign detection, and short-range navigation, etc. (This abstract is for the profiles session.)

Quantitative comparison of self-healing ability between Bessel–Gaussian beam and Airy beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wen, Wei; Chu, Xiuxiang, E-mail: xiuxiangchu@yahoo.com

The self-healing ability during propagation process is one of the most important properties of non-diffracting beams. This ability has crucial advantages to light sheet-based microscopy to reduce scattering artefacts, increase the quality of the image and enhance the resolution of microscopy. Based on similarity between two infinite-dimensional complex vectors in Hilbert space, the ability to a Bessel–Gaussian beam and an Airy beam have been studied and compared. Comparing the evolution of the similarity of Bessel–Gaussian beam with Airy beam under the same conditions, we find that Bessel–Gaussian beam has stronger self-healing ability and is more stable than that of Airymore » beam. To confirm this result, the intensity profiles of Bessel–Gaussian beam and Airy beam with different similarities are numerically calculated and compared.« less

The Electrostatic Instability for Realistic Pair Distributions in Blazar/EBL Cascades

NASA Astrophysics Data System (ADS)

Vafin, S.; Rafighi, I.; Pohl, M.; Niemiec, J.

2018-04-01

This work revisits the electrostatic instability for blazar-induced pair beams propagating through the intergalactic medium (IGM) using linear analysis and PIC simulations. We study the impact of the realistic distribution function of pairs resulting from the interaction of high-energy gamma-rays with the extragalactic background light. We present analytical and numerical calculations of the linear growth rate of the instability for the arbitrary orientation of wave vectors. Our results explicitly demonstrate that the finite angular spread of the beam dramatically affects the growth rate of the waves, leading to the fastest growth for wave vectors quasi-parallel to the beam direction and a growth rate at oblique directions that is only a factor of 2–4 smaller compared to the maximum. To study the nonlinear beam relaxation, we performed PIC simulations that take into account a realistic wide-energy distribution of beam particles. The parameters of the simulated beam-plasma system provide an adequate physical picture that can be extrapolated to realistic blazar-induced pairs. In our simulations, the beam looses only 1% of its energy, and we analytically estimate that the beam would lose its total energy over about 100 simulation times. An analytical scaling is then used to extrapolate the parameters of realistic blazar-induced pair beams. We find that they can dissipate their energy slightly faster by the electrostatic instability than through inverse-Compton scattering. The uncertainties arising from, e.g., details of the primary gamma-ray spectrum are too large to make firm statements for individual blazars, and an analysis based on their specific properties is required.

Laser beam propagation through bulk nonlinear media: Numerical simulation and experiment

NASA Astrophysics Data System (ADS)

Kovsh, Dmitriy I.

This dissertation describes our efforts in modeling the propagation of high intensity laser pulses through optical systems consisting of one or multiple nonlinear elements. These nonlinear elements can be up to 103 times thicker than the depth of focus of the laser beam, so that the beam size changes drastically within the medium. The set of computer codes developed are organized in a software package (NLO_BPM). The ultrafast nonlinearities of the bound-electronic n2 and two-photon absorption as well as time dependent excited-state, free-carrier and thermal nonlinearities are included in the codes for modeling propagation of picosecond to nanosecond pulses and pulse trains. Various cylindrically symmetric spatial distributions of the input beam are modeled. We use the cylindrical symmetry typical of laser outputs to reduce the CPU and memory requirements making modeling a real- time task on PC's. The hydrodynamic equations describing the rarefaction of the medium due to heating and electrostriction are solved in the transient regime to determine refractive index changes on a nanosecond time scale. This effect can be simplified in some cases by an approximation that assumes an instantaneous expansion. We also find that the index change obtained from the photo-acoustic equation overshoots its steady-state value once the ratio between the pulse width and the acoustic transit time is greater than unity. We numerically study the sensitivity of the closed- aperture Z-scan experiment to nonlinear refraction for various input beam profiles. If the beam has a ring structure with a minimum (or zero) on axis in the far field, the sensitivity of Z-scan measurements can be increased by up to one order of magnitude. The linear propagation module integrated with the nonlinear beam propagation codes allows the simulation of typical experiments such as Z-scan and optical limiting experiments. We have used these codes to model the performance of optical limiters. We study two of the most promising limiter designs: the monolithic self-protective semiconductor limiter (MONOPOL) and a multi-cell tandem limiter based on a liquid solution of reverse saturable absorbing organic dye. The numerical outputs show good agreement with experimental results up to input energies where nonlinear scattering becomes significant.

Trirotron: triode rotating beam radio frequency amplifier

DOEpatents

Lebacqz, Jean V.

1980-01-01

High efficiency amplification of radio frequencies to very high power levels including: establishing a cylindrical cloud of electrons; establishing an electrical field surrounding and coaxial with the electron cloud to bias the electrons to remain in the cloud; establishing a rotating electrical field that surrounds and is coaxial with the steady field, the circular path of the rotating field being one wavelength long, whereby the peak of one phase of the rotating field is used to accelerate electrons in a beam through the bias field in synchronism with the peak of the rotating field so that there is a beam of electrons continuously extracted from the cloud and rotating with the peak; establishing a steady electrical field that surrounds and is coaxial with the rotating field for high-energy radial acceleration of the rotating beam of electrons; and resonating the rotating beam of electrons within a space surrounding the second field, the space being selected to have a phase velocity equal to that of the rotating field to thereby produce a high-power output at the frequency of the rotating field.

Parametric study of beam refraction problems across laser anemometer windows

NASA Technical Reports Server (NTRS)

Owen, A. K.

1986-01-01

The experimenter is often required to view flows through a window with a different index of refraction than either the medium being observed or the medium that the laser anemometer is immersed in. The refraction that occurs at the window surfaces may lead to undesirable changes in probe volume position or beam crossing angle and can lead to partial or complete beam uncrossing. This report describes the results of a parametric study of this problem using a ray tracing technique to predict these changes. The windows studied were a flat plate and a simple cyclinder. For the flat-plate study: (1) surface thickness, (2) beam crossing angle, (3) bisecting line - surface normal angle, and (4) incoming beam plane surface orientation were varied. For the cylindrical window additional parameters were also varied: (1) probe volume immersion, (2) probe volume off-radial position, and (3) probe volume position out of the R-theta plane of the lens. A number of empirical correlations were deduced to aid the interested reader in determining the movement, uncrossing, and change in crossing angle for a particular situation.

A parametric study of the beam refraction problems across laser anemometer windows

NASA Technical Reports Server (NTRS)

Owen, Albert K.

1986-01-01

The experimenter is often required to view flows through a window with a different index of refraction than either the medium being observed or the medium that the laser anemometer is immersed in. The refraction that occurs at the window surfaces may lead to undesirable changes in probe volume position or beam crossing angle and can lead to partial or complete beam uncrossing. This report describes the results of a parametric study of this problem using a ray tracing technique to predict these changes. The windows studied were a flat plate and a simple cylinder. For the flat-plate study: (1) surface thickness, (2) beam crossing angle, (3) bisecting line - surface normal angle, and (4) incoming beam plane surface orientation were varied. For the cylindrical window additional parameters were also varied: (1) probe volume immersion, (2) probe volume off-radial position, and (3) probe volume position out of the r-theta plane of the lens. A number of empirical correlations were deduced to aid the reader in determining the movement, uncrossing, and change in crossing angle for a particular situations.

EPICS Controlled Collimator for Controlling Beam Sizes in HIPPO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Napolitano, Arthur Soriano; Vogel, Sven C.

2017-08-03

Controlling the beam spot size and shape in a diffraction experiment determines the probed sample volume. The HIPPO - High-Pressure-Preferred Orientation– neutron time-offlight diffractometer is located at the Lujan Neutron Scattering Center in Los Alamos National Laboratories. HIPPO characterizes microstructural parameters, such as phase composition, strains, grain size, or texture, of bulk (cm-sized) samples. In the current setup, the beam spot has a 10 mm diameter. Using a collimator, consisting of two pairs of neutron absorbing boron-nitride slabs, horizontal and vertical dimensions of a rectangular beam spot can be defined. Using the HIPPO robotic sample changer for sample motion, themore » collimator would enable scanning of e.g. cylindrical samples along the cylinder axis by probing slices of such samples. The project presented here describes implementation of such a collimator, in particular the motion control software. We utilized the EPICS (Experimental Physics Interface and Control System) software interface to integrate the collimator control into the HIPPO instrument control system. Using EPICS, commands are sent to commercial stepper motors that move the beam windows.« less

New Materials, Techniques and Device Concepts for Organic NLO Chromophore-based Electrooptic Devices. Part 1

DTIC Science & Technology

2006-08-23

polarization the electric field vector is parallel to the substrate, for TM polarization the magnetic field vector is parallel to the substrate. Figure...section can be obtained for the case of the two electromagnetic field polarization vectors λ and µ describing the two photons being absorbed (of the same or... polarization effects on two-photon absorption as investigated by the technique of thermal lensing detected absorption of a mode- locked laser beam. This

Optical apparatus for conversion of whispering-gallery modes into a free space gaussian like beam

DOEpatents

Stallard, Barry W.; Makowski, Michael A.; Byers, Jack A.

1992-01-01

An optical converter for efficient conversion of millimeter wavelength whispering-gallery gyrotron output into a linearly polarized, free-space Gaussian-like beam. The converter uses a mode-converting taper and three mirror optics. The first mirror has an azimuthal tilt to eliminate the k.sub..phi. component of the propagation vector of the gyrotron output beam. The second mirror has a twist reflector to linearly polarize the beam. The third mirror has a constant phase surface so the converter output is in phase.

A 5000-hour test of a grid-translation beam-deflection system for a 5-cm diameter Kaufman thruster

NASA Technical Reports Server (NTRS)

Lathem, W. C.

1973-01-01

A grid-translation type beam deflection system was tested on a 5-cm diameter mercury ion thruster for 5000 hours at a thrust level of about 0.36 mlb. During the first 2000 hours the beam was vectored 10 degrees in one direction. No erosion damage attributable to beam deflection was detected. Results indicate a possible lifetime of 15,000 to 20,000 hours. An optimized neutralizer position was used which eliminated the sputter erosion groove observed on the SERT 2 thrusters.

Thin film absorption characterization by focus error thermal lensing

NASA Astrophysics Data System (ADS)

Domené, Esteban A.; Schiltz, Drew; Patel, Dinesh; Day, Travis; Jankowska, E.; Martínez, Oscar E.; Rocca, Jorge J.; Menoni, Carmen S.

2017-12-01

A simple, highly sensitive technique for measuring absorbed power in thin film dielectrics based on thermal lensing is demonstrated. Absorption of an amplitude modulated or pulsed incident pump beam by a thin film acts as a heat source that induces thermal lensing in the substrate. A second continuous wave collimated probe beam defocuses after passing through the sample. Determination of absorption is achieved by quantifying the change of the probe beam profile at the focal plane using a four-quadrant detector and cylindrical lenses to generate a focus error signal. This signal is inherently insensitive to deflection, which removes noise contribution from point beam stability. A linear dependence of the focus error signal on the absorbed power is shown for a dynamic range of over 105. This technique was used to measure absorption loss in dielectric thin films deposited on fused silica substrates. In pulsed configuration, a single shot sensitivity of about 20 ppm is demonstrated, providing a unique technique for the characterization of moving targets as found in thin film growth instrumentation.

EBQ code: Transport of space-charge beams in axially symmetric devices

NASA Astrophysics Data System (ADS)

Paul, A. C.

1982-11-01

Such general-purpose space charge codes as EGUN, BATES, WODF, and TRANSPORT do not gracefully accommodate the simulation of relativistic space-charged beams propagating a long distance in axially symmetric devices where a high degree of cancellation has occurred between the self-magnetic and self-electric forces of the beam. The EBQ code was written specifically to follow high current beam particles where space charge is important in long distance flight in axially symmetric machines possessing external electric and magnetic field. EBQ simultaneously tracks all trajectories so as to allow procedures for charge deposition based on inter-ray separations. The orbits are treated in Cartesian geometry (position and momentum) with z as the independent variable. Poisson's equation is solved in cylindrical geometry on an orthogonal rectangular mesh. EBQ can also handle problems involving multiple ion species where the space charge from each must be included. Such problems arise in the design of ion sources where different charge and mass states are present.

Measurement of microdosimetric spectra with a wall-less tissue-equivalent proportional counter for a 290 MeV/u 12C beam.

PubMed

Tsuda, Shuichi; Sato, Tatsuhiko; Takahashi, Fumiaki; Satoh, Daiki; Endo, Akira; Sasaki, Shinichi; Namito, Yoshihito; Iwase, Hiroshi; Ban, Shuichi; Takada, Masashi

2010-09-07

The frequency distribution of the lineal energy, y, of a 290 MeV/u carbon beam was measured to obtain the dose-weighted mean of y and compare it with the linear energy transfer (LET). In the experiment, a wall-less tissue-equivalent proportional counter (TEPC) in a cylindrical volume with a simulated diameter of 0.72 microm was used. The measured frequency distribution of y as well as its dose-mean value agrees within 10% uncertainty with the corresponding data from microdosimetric calculations using the PHITS code. The ratio of the measured dose-mean lineal energy to the LET of the 290 MeV/u carbon beam is 0.73, which is much smaller than the corresponding data obtained by a wall TEPC. This result demonstrates that a wall-less TEPC is necessary to precisely measure the dose-mean of y for energetic heavy ion beams.

Multi-Frequency Microwaves Plasma Production for Active Profile Control of Ion Beams on a Large Bore ECR Ion Source with Permanent Magnets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakamoto, Naoki; Kato, Yushi; Kiriyama, Ryutaro

2011-01-07

A new concept on magnetic field of plasma production and confinement by using permanent magnets, i.e. cylindrically comb-shaped magnets, has been proposed to enhance efficiency of an electron cyclotron resonance (ECR) plasma for broad and dense ion beam source under the low pressure and also the low microwave power. The resonance zones corresponding to the fundamental ECR for 2.45 GHz and 11-13 GHz frequency are constructed at different positions. The profiles of the plasma parameters in the ECR ion source are different from each frequency of microwave. Large bore extractor is set at the opposite side against the microwave feeds.more » It is found that differences of their profiles also appear at those of ion beam profiles. We conducted to launch simultaneously multiplex frequency microwaves controlled individually, and tried to control the profiles of the plasma parameters and then those of extracted ion beam.« less

Passive OCT probe head for 3D duct inspection

NASA Astrophysics Data System (ADS)

Ford, Helen D.; Tatam, Ralph P.

2013-09-01

A passive, endoscopic optical coherence tomography (OCT) probe has been demonstrated, incorporating an imaging fibre bundle and 45° conical mirror, and with no electromechanical components at the probe tip. Circular scanning, of the beam projected onto the proximal face of the imaging bundle, produces a corresponding circular scan at the distal end of the bundle. The beam is turned through 90° by the conical mirror and converted into a radially-scanned sample beam, permitting circumferential OCT scanning in quasi-cylindrical ducts. OCT images, displayed as polar plots and as 3D reconstructions, are presented, showing the internal profile of a metallic test sample containing a 660 µm step in the internal wall. Results have been acquired using two methods: one that makes use of multiple beam-circle diameters, and a mechanical ‘pull-back’ technique. The effects of the convex surface of the conical mirror on spatial resolution are discussed, with suggested working distances given for different application regimes.

Thermoelectric phonon-glass electron-crystal via ion beam patterning of silicon

NASA Astrophysics Data System (ADS)

Zhu, Taishan; Swaminathan-Gopalan, Krishnan; Stephani, Kelly; Ertekin, Elif

2018-05-01

Ion beam irradiation has recently emerged as a versatile approach to functional materials design. We show in this work that patterned defective regions generated by ion beam irradiation of silicon can create a phonon-glass electron-crystal (PGEC), a long-standing goal of thermoelectrics. By controlling the effective diameter of and spacing between the defective regions, molecular dynamics simulations suggest a reduction of the thermal conductivity by a factor of ˜20 is achievable. Boltzmann theory shows that the thermoelectric power factor remains largely intact in the damaged material. To facilitate the Boltzmann theory, we derive an analytical model for electron scattering with cylindrical defective regions based on partial-wave analysis. Together we predict a figure of merit of Z T ≈0.5 or more at room temperature for optimally patterned geometries of these silicon metamaterials. These findings indicate that nanostructuring of patterned defective regions in crystalline materials is a viable approach to realize a PGEC, and ion beam irradiation could be a promising fabrication strategy.

Superenergy flux of Einstein-Rosen waves

NASA Astrophysics Data System (ADS)

Domínguez, P. J.; Gallegos, A.; Macías-Díaz, J. E.; Vargas-Rodríguez, H.

In this work, we consider the propagation speed of the superenergy flux associated to the Einstein-Rosen cylindrical waves propagating in vacuum and over the background of the gravitational field of an infinitely long mass line distribution. The velocity of the flux is determined considering the reference frame in which the super-Poynting vector vanishes. This reference frame is then considered as comoving with the flux. The explicit expressions for the velocities are given with respect to a reference frame at rest with the symmetry axis.

Exactly solvable relativistic model with the anomalous interaction

NASA Astrophysics Data System (ADS)

Ferraro, Elena; Messina, Antonino; Nikitin, A. G.

2010-04-01

A special class of Dirac-Pauli equations with time-like vector potentials of an external field is investigated. An exactly solvable relativistic model describing the anomalous interaction of a neutral Dirac fermion with a cylindrically symmetric external electromagnetic field is presented. The related external field is a superposition of the electric field generated by a charged infinite filament and the magnetic field generated by a straight line current. In the nonrelativistic approximation the considered model is reduced to the integrable Pron’ko-Stroganov model.

Reflection holograms using peristrophic multiplexing

NASA Astrophysics Data System (ADS)

Sayeh, Mohammed R.; Jeong, Y.

2000-07-01

In this paper, we consider a peristrophic multiplexing for reflection holograms. This type of multiplexing the rotation of either the material or the reference beam causes the grating vector to be off the plane of the reference and image beams. In the case of reflection hologram, we developed a relationship for the angular selectivity which is verified experimentally.

Vectorial structures of linear-polarized Butterfly-Gauss vortex beams in the far zone

NASA Astrophysics Data System (ADS)

Cheng, Ke; Zhou, Yan; Lu, Gang; Yao, Na; Zhong, Xianqiong

2018-05-01

By introducing the Butterfly catastrophe to optics, the far-zone vectorial structures of Butterfly-Gauss beam with vortex and non-vortex are studied using the angular spectrum representation and stationary phase method. The influence of topological charge, linear-polarized angle, off-axis distance and scaling length on the far-zone vectorial structures, especially in the Poynting vector and angular momentum density of the corresponding beam is emphasized. The results show that the embedded optical vortex at source plane lead to special dark zones in the far zone, where the number of dark zone equals the absolute value of topological charge of optical vortex. Furthermore, the symmetry and direction of the special dark zones can be controlled by off-axis distance and scaling length, respectively. The linear-polarized angle adjusts only the Poynting vectors of TE and TM terms, but it does not affect those of whole beam. Finally, the vectorial expressions also indicate that the total angular momentum density is certainly zero owing to the far-zone stable structures rather than rotation behaviors.

The Biomechanics of Zygomatic Arch Shape.

PubMed

Smith, Amanda L; Grosse, Ian R

2016-12-01

Mammalian zygomatic arch shape is remarkably variable, ranging from nearly cylindrical to blade-like in cross section. Based on geometry, the arch can be hypothesized to be a sub-structural beam whose ability to resist deformation is related to cross sectional shape. We expect zygomatic arches with different cross sectional shapes to vary in the degree to which they resist local bending and torsion due to the contraction of the masseter muscle. A stiffer arch may lead to an increase in the relative proportion of applied muscle load being transmitted through the arch to other cranial regions, resulting in elevated cranial stress (and thus, strain). Here, we examine the mechanics of the zygomatic arch using a series of finite element modeling experiments in which the cross section of the arch of Pan troglodytes has been modified to conform to idealized shapes (cylindrical, elliptical, blade-like). We find that the shape of the zygomatic arch has local effects on stain that do not conform to beam theory. One exception is that possessing a blade-like arch leads to elevated strains at the postorbital zygomatic junction and just below the orbits. Furthermore, although modeling the arch as solid cortical bone did not have the effect of elevating strains in other parts of the face, as had been expected, it does have a small effect on stress associated with masseter contraction. These results are counterintuitive. Even though the arch has simple beam-like geometry, we fail to find a simple mechanical explanation for the diversity of arch shape. Anat Rec, 299:1734-1752, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Radial Internal Material Handling System (RIMS) for Circular Habitat Volumes

NASA Technical Reports Server (NTRS)

Howe, Alan S.; Haselschwardt, Sally; Bogatko, Alex; Humphrey, Brian; Patel, Amit

2013-01-01

On planetary surfaces, pressurized human habitable volumes will require a means to carry equipment around within the volume of the habitat, regardless of the partial gravity (Earth, Moon, Mars, etc.). On the NASA Habitat Demonstration Unit (HDU), a vertical cylindrical volume, it was determined that a variety of heavy items would need to be carried back and forth from deployed locations to the General Maintenance Work Station (GMWS) when in need of repair, and other equipment may need to be carried inside for repairs, such as rover parts and other external equipment. The vertical cylindrical volume of the HDU lent itself to a circular overhead track and hoist system that allows lifting of heavy objects from anywhere in the habitat to any other point in the habitat interior. In addition, the system is able to hand-off lifted items to other material handling systems through the side hatches, such as through an airlock. The overhead system consists of two concentric circle tracks that have a movable beam between them. The beam has a hoist carriage that can move back and forth on the beam. Therefore, the entire system acts like a bridge crane curved around to meet itself in a circle. The novelty of the system is in its configuration, and how it interfaces with the volume of the HDU habitat. Similar to how a bridge crane allows coverage for an entire rectangular volume, the RIMS system covers a circular volume. The RIMS system is the first generation of what may be applied to future planetary surface vertical cylinder habitats on the Moon or on Mars.

Selectable light-sheet uniformity using tuned axial scanning

PubMed Central

Duocastella, Martí; Arnold, Craig B.; Puchalla, Jason

2016-01-01

Light-sheet fluorescence microscopy (LSFM) is an optical sectioning technique capable of rapid three-dimensional (3D) imaging of a wide range of specimens with reduced phototoxicity and superior background rejection. However, traditional light-sheet generation approaches based on elliptical or circular Gaussian beams suffer an inherent trade-off between light-sheet thickness and area over which this thickness is preserved. Recently, an increase in light-sheet uniformity was demonstrated using rapid biaxial Gaussian beam scanning along the lateral and beam propagation directions. Here we apply a similar scanning concept to an elliptical beam generated by a cylindrical lens. In this case, only z-scanning of the elliptical beam is required and hence experimental implementation of the setup can be simplified. We introduce a simple dimensionless uniformity statistic to better characterize scanned light-sheets and experimentally demonstrate custom tailored uniformities up to a factor of 5 higher than those of un-scanned elliptical beams. This technique offers a straightforward way to generate and characterize a custom illumination profile that provides enhanced utilization of the detector dynamic range and field of view, opening the door to faster and more efficient 2D and 3D imaging. PMID:28132409

Ion Temperature Measurements in an electron beam ion trap (EBIT)

NASA Astrophysics Data System (ADS)

Beiersdorfer, P.; Decaux, V.; Widmann, K.

1997-11-01

An electron beam ion trap consists of a Penning-type cylindrical trap traversed by a high-energy (<= 200 keV), high-density (Ne <= 10^13 cm-3) electron beam. Ions are trapped by the space charge potential of the electron beam, a static potential on the end electrodes, and a 3-T axial magnetic field [1]. The ions are heated by the electron beam and leave the trap once their kinetic energy suffices to overcome the potential barriers. Using high-resolution x-ray spectroscopy, we have made systematic measurements of the temperature of Ti^20+ and Cs^45+ ions in the trap [2]. The dependence of the ion temperature on operating parameters, such as trapping potential, beam current, and neutral gas pressure, will be presented. Temperatures as low as 15.4 ± 4.4 eV and as high as 2 keV were observed. *Work performed under the auspices of the U.S.D.o.E. by Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48. [1] M. Levine et al., Phys. Scripta T22, 157 (1989). [2]P. Beiersdorfer et al., PRL 77, 5356 (1996); P. Beiersdorfer, in AIP Conf. Proc. No. 389, p. 121 (1997).

Dynamic tailoring of surface plasmon polaritons through incident angle modulation.

PubMed

Qiu, Peizhen; Zhang, Dawei; Jing, Ming; Lu, Taiguo; Yu, Binbin; Zhan, Qiwen; Zhuang, Songlin

2018-04-16

Dynamic tailoring of the propagating surface plasmon polaritons (SPPs) through incident angle modulation is proposed and numerically demonstrated. The generation and tailoring mechanism of the SPPs are discussed. The relationship formula between the incident angle and the generated SPP wave vector direction is theoretically derived. The correctness of the formula is verified with three different approaches using finite difference time domain method. Using this formula, the generated SPP wave vector direction can be precisely modulated by changing the incident angle. The precise modulation results of two dimensional Bessel-like SPP beam and SPP bottle beam array are given. The results can deepen the understanding of the generation and modulation mechanism of the SPPs.

Beam-smiling in bent-Laue monochromators

NASA Astrophysics Data System (ADS)

Ren, B.; Dilmanian, F. A.; Chapman, L. D.; Wu, X. Y.; Zhong, Z.; Ivanov, I.; Thomlinson, W. C.; Huang, X.

1997-07-01

When a wide fan-shaped x-ray beam is diffracted by a bent crystal in the Laue geometry, the profile of the diffracted beam generally does not appear as a straight line, but as a line with its ends curved up or curved down. This effect, referred to as "beam-smiling", has been a major obstacle in developing bent-Laue crystal monochromators for medical applications of synchrotron x-ray. We modeled a cylindrically bent crystal using the Finite Element Analysis (FEA) method, and we carried out experiments at the National Synchrotron Light Source and Cornell High Energy Synchrotron Source. Our studies show that, while beam-smiling exists in most of the crystal's area because of anticlastic bending effects, there is a region parallel to the bending axis of the crystal where the diffracted beam is "smile-free". By applying asymmetrical bending, this smile-free region can be shifted vertically away from the geometric center of the crystal, as desired. This leads to a novel method of compensating for beam-smiling. We will discuss the method of "differential bending" for smile removal, beam-smiling in the Cauchios and the polychromatic geometry, and the implications of the method on developing single- and double-bent Laue monochromators. The experimental results will be discussed, concentrating on specific beam-smiling observation and removal as applied to the new monochromator of the Multiple Energy Computed Tomography [MECT] project of the Medical Department, Brookhaven National Laboratory.

Generation of tunable radially polarized array beams by controllable coherence

NASA Astrophysics Data System (ADS)

Wang, Jing; Zhang, Jipeng; Zhu, Shijun; Li, Zhenhua

2017-05-01

In this paper, a new method for converting a single radial polarization beam into an arbitrary radially polarized array (RPA) beam such as a radial or rectangular symmetry array in the focal plane by modulating a periodic correlation structure is introduced. The realizability conditions for such source and the beam condition for radiation generated by such source are derived. It is illustrated that both the amplitude and the polarization are controllable by means of initial correlation structure and coherence parameter. Furthermore, by designing the source correlation structure, a tunable NUST-shaped RPA beam is demonstrated, which can find widespread applications in micro-nano engineering. Such a method for generation of arbitrary vector array beams is useful in beam shaping and optical tweezers.

Acoustic radiation force induced by two Airy-Gaussian beams on a cylindrical particle

NASA Astrophysics Data System (ADS)

Gao, Sha; Mao, Yiwei; Liu, Jiehui; Liu, Xiaozhou

2018-01-01

Not Available Project supported by the National Key R & D Program, China (Grant No. 2016YFF0203000), the National Natural Science Foundation of China (Grant Nos. 11774167 and 61571222), Fundamental Research Funds for the Central Universities, China (Grant No. 020414380001), State Key Laboratory of Acoustics, Chinese Academy of Sciences (Grant No. SKLA201609), and AQSIQ Technology R & D Program, China (Grant No. 2017QK125).

Gyrotron Gun Study Report,

DTIC Science & Technology

1981-09-18

of bern current to space-charge limited Langmuir current - Cathode surface current density S 2 a Cylindrical diode geometry function (tabulated in...design factor . t -13- " r =J... .. ::!, qm ! . ... ... - . , m- d nc- Cd (3) lsically, this equation arises from the recognition that the gap...S. Beam Current as a Fraction of the Limiting Langmuir Current (o/IL) Equation 5 in Table I is basically intended to provide a measure of the C

Feasibility study of a synthesis procedure for array feeds to improve radiation performance of large distorted reflector antennas

NASA Technical Reports Server (NTRS)

Stutzman, W. L.; Takamizawa, K.; Werntz, P.; Lapean, J.; Barts, R.

1991-01-01

The following subject areas are covered: General Reflector Antenna Systems Program version 7(GRASP7); Multiple Reflector Analysis Program for Cylindrical Antennas (MRAPCA); Tri-Reflector 2D Synthesis Code (TRTDS); a geometrical optics and a physical optics synthesis techniques; beam scanning reflector, the type 2 and 6 reflectors, spherical reflector, and multiple reflector imaging systems; and radiometric array design.

MCNP simulation of a Theratron 780 radiotherapy unit.

PubMed

Miró, R; Soler, J; Gallardo, S; Campayo, J M; Díez, S; Verdú, G

2005-01-01

A Theratron 780 (MDS Nordion) 60Co radiotherapy unit has been simulated with the Monte Carlo code MCNP. The unit has been realistically modelled: the cylindrical source capsule and its housing, the rectangular collimator system, both the primary and secondary jaws and the air gaps between the components. Different collimator openings, ranging from 5 x 5 cm2 to 20 x 20 cm2 (narrow and broad beams) at a source-surface distance equal to 80 cm have been used during the study. In the present work, we have calculated spectra as a function of field size. A study of the variation of the electron contamination of the 60Co beam has also been performed.

Structural similitude and scaling laws for laminated beam-plates

NASA Technical Reports Server (NTRS)

Simitses, George J.; Rezaeepazhand, Jalil

1992-01-01

The establishment of similarity conditions between two structural systems is discussed. Similarity conditions provide the relationship between a scale model and its prototype and can be used to predict the behavior of the prototype by extrapolating the experimental data of the corresponding small-scale model. Since satisfying all the similarity conditions simultaneously is difficult or even impossible, distorted models with partial similarity (with at least one similarity condition relaxed) are more practical. Establishing similarity conditions based on both dimensional analysis and direct use of governing equations is discussed, and the possibility of designing distorted models is investigated. The method is demonstrated through analysis of the cylindrical bending of orthotropic laminated beam-plates subjected to transverse line loads.

Chalcogenide molded freeform optics for mid-infrared lasers

NASA Astrophysics Data System (ADS)

Chenard, Francois; Alvarez, Oseas; Yi, Allen

2017-05-01

High-precision chalcogenide molded micro-lenses were produced to collimate mid-infrared Quantum Cascade Lasers (QCLs). Molded cylindrical micro-lens prototypes with aspheric contour (acylindrical), high numerical aperture (NA 0.8) and small focal length (f<2 mm) were fabricated to collimate the QCL fast-axis beam. Another innovative freeform micro-lens has an input acylindrical surface to collimate the fast axis and an orthogonal output acylindrical surface to collimate the slow axis. The thickness of the freeform lens is such that the output fast- and slow-axis beams are circular. This paper presents results on the chalcogenide molded freeform micro-lens designed to collimate and circularize QCL at 4.6 microns.

ION PULSE GENERATION

DOEpatents

King, R.F.; Moak, C.D.; Parker, V.E.

1960-10-11

A device for generating ions in an ion source, forming the ions into a stream, deflecting the stream rapidly away from and back to its normal path along the axis of a cylindrical housing, and continually focusing the stream by suitable means into a sharp, intermittent beam along the axis is described. The beam exists through an axial aperture into a lens which focuses it into an accelerator tube. The ions in each burst are there accelerated to very high energies and are directed against a target placed in the high-energy end of the tube. Radiations from the target can then be analyzed in the interval between incidence of the bursts of ions on the target.

Polarization Shaping for Control of Nonlinear Propagation.

PubMed

Bouchard, Frédéric; Larocque, Hugo; Yao, Alison M; Travis, Christopher; De Leon, Israel; Rubano, Andrea; Karimi, Ebrahim; Oppo, Gian-Luca; Boyd, Robert W

2016-12-02

We study the nonlinear optical propagation of two different classes of light beams with space-varying polarization-radially symmetric vector beams and Poincaré beams with lemon and star topologies-in a rubidium vapor cell. Unlike Laguerre-Gauss and other types of beams that quickly experience instabilities, we observe that their propagation is not marked by beam breakup while still exhibiting traits such as nonlinear confinement and self-focusing. Our results suggest that, by tailoring the spatial structure of the polarization, the effects of nonlinear propagation can be effectively controlled. These findings provide a novel approach to transport high-power light beams in nonlinear media with controllable distortions to their spatial structure and polarization properties.

Validation of a Hartmann-Moiré wavefront sensor with large dynamic range.

PubMed

Wei, Xin; Van Heugten, Tony; Thibos, Larry

2009-08-03

Our goal was to validate the accuracy, repeatability, sensitivity, and dynamic range of a Hartmann-Moiré (HM) wavefront sensor (PixelOptics, Inc.) designed for ophthalmic applications. Testing apparatus injected a 4 mm diameter monochromatic (532 nm) beam of light into the wavefront sensor for measurement. Controlled amounts of defocus and astigmatism were introduced into the beam with calibrated spherical (-20D to + 18D) and cylindrical (-8D to + 8D) lenses. Repeatability was assessed with three repeated measurements within a 2-minute period. Correlation coefficients between mean wavefront measurements (n = 3) and expected wavefront vergence for both sphere and cylinder lenses were >0.999. For spherical lenses, the sensor was accurate to within 0.1D over the range from -20D to + 18D. For cylindrical lenses, the sensor was accurate to within 0.1D over the range from -8D to + 8D. The primary limitation to demonstrating an even larger dynamic range was the increasingly critical requirements for optical alignment. Sensitivity to small changes of vergence was constant over the instrument's full dynamic range. Repeatability of measurements for fixed condition was within 0.01D. The Hartmann-Moiré wavefront sensor measures defocus and astigmatism accurately and repeatedly with good sensitivity over a large dynamic range required for ophthalmic applications.

Ultrasonic transient bounded-beam propagation in a solid cylinder waveguide embedded in a solid medium.

PubMed

Laguerre, Laurent; Grimault, Anne; Deschamps, Marc

2007-04-01

A semianalytical solution alternative and complementary to modal technique is presented to predict and interpret the ultrasonic pulsed-bounded-beam propagation in a solid cylinder embedded in a solid matrix. The spectral response to an inside axisymmetric velocity source of longitudinal and transversal cylindrical waves is derived from Debye series expansion of the embedded cylinder generalized cylindrical reflection/transmission coefficients. So, the transient guided wave response, synthesized by inverse double Fourier-Bessel transform, is expressed as a combination of the infinite medium contribution, longitudinal, transversal, and coupled longitudinal and transversal waveguide sidewall interactions. Simulated (f, 1/lambdaz) diagrams show the influence of the number of waveguide sidewall interactions to progressively recover dispersion curves. Besides, they show the embedding material filters specific signal portions by concentrating the propagating signal in regions where phase velocity is closer to phase velocity in steel. Then, simulated time waveforms using broadband high-frequency excitation show that signal leading portions exhibit a similar periodical pattern, for both free and embedded waveguides. Debye series-based interpretation shows that double longitudinal/transversal and transversal/longitudinal conversions govern the time waveform leading portion as well as the radiation attenuation in the surrounding cement grout. Finally, a methodology is deduced to minimize the radiation attenuation for the long-range inspection of embedded cylinders.

Transformations of Gaussian Light Beams Caused by Reflection in FEL (free Electron Lasers) Resonators

DTIC Science & Technology

1988-10-27

il FILE COPy Naval Research Laboratory Washingon, DC 20375-500 NRL Memorandum Report 6347 ,qJ. o Transformations of Gaussian Light Beams N Caused by...Transformations of 7aussian Light Beams Caused by Reflection in FEL Resonators 12 PERSONAL AUTHOR(S) Riyopoulos,* S., Tang, C.M. and Sprangle, P...34 𔃾-6603 -"I, -,’ SECURITY CLASSIFICATION OF THIS PAGE 19. ABSTRACTS (Continued) cross-coupling among vector components of the radiation field, caused

Large-angle production of charged pions with incident pion beams on nuclear targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apollonio, M.; Chimenti, P.; Giannini, G.

2009-12-15

Measurements of the double-differential {pi}{sup {+-}} production cross section in the range of momentum 100{<=}p{<=}800 MeV/c and angle 0.35{<=}{theta}{<=}2.15 rad using {pi}{sup {+-}} beams incident on beryllium, aluminum, carbon, copper, tin, tantalum, and lead targets are presented. The data were taken with the large-acceptance hadron production (HARP) detector in the T9 beam line of the CERN Proton Synchrotron. The secondary pions were produced by beams in a momentum range from 3 to 12.9GeV/c hitting a solid target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was performed using a small-radiusmore » cylindrical time projection chamber placed inside a solenoidal magnet. Incident particles were identified by an elaborate system of beam detectors. Results are obtained for the double-differential cross sections d{sup 2}{sigma}/dp d{theta} at six incident-beam momenta. Data at 3,5,8, and 12GeV/c are available for all targets, while additional data at 8.9 and 12.9GeV/c were taken in positive particle beams on Be and Al targets, respectively. The measurements are compared with several generators of GEANT4 and the MARS Monte Carlo simulation.« less

Kerr-lens mode-locked Ti:Sapphire laser pumped by a single laser diode

NASA Astrophysics Data System (ADS)

Kopylov, D. A.; Esaulkov, M. N.; Kuritsyn, I. I.; Mavritskiy, A. O.; Perminov, B. E.; Konyashchenko, A. V.; Murzina, T. V.; Maydykovskiy, A. I.

2018-04-01

The performance of a Ti:sapphire laser pumped by a single 461 nm laser diode is presented for both the continuous-wave and the mode-locked regimes of operation. We introduce a simple astigmatism correction scheme for the laser diode beam consisting of two cylindrical lenses affecting the pump beam along the fast axis of the laser diode, which provides the mode-matching between the nearly square-shaped pump beam and the cavity mode. The resulting efficiency of the suggested Ti:Sapphire oscillator pumped by such a laser diode is analyzed for the Ti:sapphire crystals of 3 mm, 5 mm and 10 mm in length. We demonstrate that such a system provides the generation of ultrashort pulses up to 15 fs in duration with the repetition rate of 87 MHz, the average power being 170 mW.

Cusped magnetic field mercury ion thruster. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Beattie, J. R.

1976-01-01

The importance of a uniform current density profile in the exhaust beam of an electrostatic ion thruster is discussed in terms of thrust level and accelerator system lifetime. A residence time approach is used to explain the nonuniform beam current density profile of the divergent magnetic field thruster. Mathematical expressions are derived which relate the thruster discharge power loss, propellant utilization, and double to single ion density ratio to the geometry and plasma properties of the discharge chamber. These relationships are applied to a cylindrical discharge chamber model of the thruster. Experimental results are presented for a wide range of the discharge chamber length. The thruster designed for this investigation was operated with a cusped magnetic field as well as a divergent field geometry, and the cusped field geometry is shown to be superior from the standpoint of beam profile uniformity, performance, and double ion population.

Method of increasing power within an optical cavity with long path lengths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leen, John Brian; Bramall, Nathan E.

A cavity-enhanced absorption spectroscopy instrument has an optical cavity with two or more cavity mirrors, one mirror of which having a hole or other aperture for injecting a light beam, and the same or another mirror of which being partially transmissive to allow exit of light to a detector. A spherical-spherical configuration with at least one astigmatic mirror or a spherical-cylindrical configuration where the spherical mirror could also be astigmatic prevents a reentrant condition wherein the injected beam would prematurely exit the cavity through the aperture. This combination substantially increases the number of passes of the injected beam through amore » sample volume for sensitive detection of chemical species even in less than ideal conditions including low power laser or LED sources, poor mirror reflectivity or detector noise at the wavelengths of interest, or cavity alignment issues such as vibration or temperature and pressure changes.« less

Simulation of transvertron high power microwave sources

NASA Astrophysics Data System (ADS)

Sullivan, Donald J.; Walsh, John E.; Arman, M. Joseph; Godfrey, Brendan B.

1989-07-01

The transvertron oscillator or amplifier is a new and efficient type of intense relativistic electron-beam-driven microwave radiation source. In the m = 0 axisymmetric version, it consists of single or multiple cylindrical cavities driven at one of the TM(0np) resonances by a high-voltage, low-impedance electron beam. There is no applied magnetic field, and the oscillatory transverse motion acquired by the axially-injected electron beam is an essential part of the drive mechanism. The transvertron theory was systematically tested for a wide range of parameters and two possible applications. The simulations were designed to verify the theoretical predictions, assess the transvertron as a possible source of intense microwave radiation, and study its potential as a microwave amplifier. Numerical results agree well in all regards with the analytical theory. Simulations were carried out in two dimensions using CCUBE, with the exception of radial loading cases, where the three-dimensional code SOS was required.

Optical Magnetometry using Multipass Cells with overlapping beams

NASA Astrophysics Data System (ADS)

McDonough, Nathaniel David; Lucivero, Vito Giovanni; Dural, Nezih; Romalis, Michael

2017-04-01

In recent years, multipass cells with cylindrical mirrors have proven to be a successful way of making highly sensitive atomic magnetometers. In such cells a small laser beam makes 40 to 100 passes within the cell without significant overlap with itself. Here we describe a new multi-pass geometry which uses spherical mirrors to reflect the probe beam multiple times over the same cell region. Such geometry reduces the effects of atomic diffusion while preserving the advantages of multi-pass cells over standing-wave cavities, namely a deterministic number of passes and absence of interference. We have fabricated several cells with this geometry and obtained good agreement between the measured and calculated levels of quantum spin noise. We will report on our effort to characterize the diffusion spin-correlation function in these cells and operation of the cell as a magnetometer. This work is supported by DARPA.

OSIRIS - an object-oriented parallel 3D PIC code for modeling laser and particle beam-plasma interaction

NASA Astrophysics Data System (ADS)

Hemker, Roy

1999-11-01

The advances in computational speed make it now possible to do full 3D PIC simulations of laser plasma and beam plasma interactions, but at the same time the increased complexity of these problems makes it necessary to apply modern approaches like object oriented programming to the development of simulation codes. We report here on our progress in developing an object oriented parallel 3D PIC code using Fortran 90. In its current state the code contains algorithms for 1D, 2D, and 3D simulations in cartesian coordinates and for 2D cylindrically-symmetric geometry. For all of these algorithms the code allows for a moving simulation window and arbitrary domain decomposition for any number of dimensions. Recent 3D simulation results on the propagation of intense laser and electron beams through plasmas will be presented.

MULTIPLE ELECTRON BEAM ION PUMP AND SOURCE

DOEpatents

Ellis, R.E.

1962-02-27

A vacuum pump is designed which operates by ionizing incoming air and by withdrawing the ions from the system by means of electrical fields. The apparatus comprises a cylindrical housing communicable with the vessel to be evacuated and having a thin wall section in one end. Suitable coils provide a longitudinal magnetic field within the cylinder. A broad cathode and an anode structure is provided to establish a plurality of adjacent electron beams which are parallel to the cylinder axis. Electron reflector means are provided so that each of the beams constitutes a PIG or reflex discharge. Such structure provides a large region in which incoming gas molecules may be ionized by electron bombardment. A charged electrode assembly accelerates the ions through the thin window, thereby removing the gas from the system. The invention may also be utilized as a highly efficient ion source. (AEC)

Velocity Vector Field Visualization of Flow in Liquid Acquisition Device Channel

NASA Technical Reports Server (NTRS)

McQuillen, John B.; Chao, David F.; Hall, Nancy R.; Zhang, Nengli

2012-01-01

A capillary flow liquid acquisition device (LAD) for cryogenic propellants has been developed and tested in NASA Glenn Research Center to meet the requirements of transferring cryogenic liquid propellants from storage tanks to an engine in reduced gravity environments. The prototypical mesh screen channel LAD was fabricated with a mesh screen, covering a rectangular flow channel with a cylindrical outlet tube, and was tested with liquid oxygen (LOX). In order to better understand the performance in various gravity environments and orientations at different liquid submersion depths of the screen channel LAD, a series of computational fluid dynamics (CFD) simulations of LOX flow through the LAD screen channel was undertaken. The resulting velocity vector field visualization for the flow in the channel has been used to reveal the gravity effects on the flow in the screen channel.

Vector meson photoproduction with a linearly polarized beam

NASA Astrophysics Data System (ADS)

Mathieu, V.; Nys, J.; Fernández-Ramírez, C.; Jackura, A.; Pilloni, A.; Sherrill, N.; Szczepaniak, A. P.; Fox, G.; Joint Physics Analysis Center

2018-05-01

We propose a model based on Regge theory to describe photoproduction of light vector mesons. We fit the SLAC data and make predictions for the energy and momentum-transfer dependence of the spin-density matrix elements in photoproduction of ω , ρ0 and ϕ mesons at Eγ˜8.5 GeV , which are soon to be measured at Jefferson Lab.

Blazed vector gratings fabricated using photosensitive polymer liquid crystals and control of polarization diffraction

NASA Astrophysics Data System (ADS)

Ono, Hiroshi; Kuzuwata, Mitsuru; Sasaki, Tomoyuki; Noda, Kohei; Kawatsuki, Nobuhiro

2014-03-01

The blazed vector grating possessing antisymmetric distributions of the birefringence were fabricated by exposing the line-focused linearly polarized ultraviolet light on the photosensitive polymer liquid crystals. The polarization states of the diffraction beams can be highly and widely controlled by designing the blazed structures, and the diffraction properties were well-explained by Jones calculus.

An inverted cylindrical sputter magnetron as metal vapor supply for electron cyclotron resonance ion sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weichsel, T., E-mail: tim.weichsel@fep.fraunhofer.de; Hartung, U.; Kopte, T.

2014-05-15

An inverted cylindrical sputter magnetron device has been developed. The magnetron is acting as a metal vapor supply for an electron cyclotron resonance (ECR) ion source. FEM simulation of magnetic flux density was used to ensure that there is no critical interaction between both magnetic fields of magnetron and ECR ion source. Spatially resolved double Langmuir probe and optical emission spectroscopy measurements show an increase in electron density by one order of magnitude from 1 × 10{sup 10} cm{sup −3} to 1 × 10{sup 11} cm{sup −3}, when the magnetron plasma is exposed to the magnetic mirror field of themore » ECR ion source. Electron density enhancement is also indicated by magnetron plasma emission photography with a CCD camera. Furthermore, photographs visualize the formation of a localized loss-cone - area, when the magnetron is operated at magnetic mirror field conditions. The inverted cylindrical magnetron supplies a metal atom load rate of R > 1 × 10{sup 18} atoms/s for aluminum, which meets the demand for the production of a milliampere Al{sup +} ion beam.« less

Laser microbeam CT scanning of dosimetry gels

NASA Astrophysics Data System (ADS)

Maryanski, Marek J.; Ranade, Manisha K.

2001-06-01

A novel design of an optical tomographic scanner is described that can be used for 3D mapping of optical attenuation coefficient within translucent cylindrical objects with spatial resolution on the order of 100 microns. Our scanner design utilizes the cylindrical geometry of the imaged object to obtain the desired paths of the scanning light rays. A rotating mirror and a photodetector are placed at two opposite foci of the translucent cylinder that acts as a cylindrical lens. A He-Ne laser beam passes first through a focusing lens and then is reflected by the rotating mirror, so as to scan the interior of the cylinder with focused and parallel paraxial rays that are subsequently collected by the photodetector to produce the projection data, as the cylinder rotates in small angle increments between projections. Filtered backprojection is then used to reconstruct planar distributions of optical attenuation coefficient in the cylinder. Multiplanar scans are used to obtain a complete 3D tomographic reconstruction. Among other applications, the scanner can be used in radiation therapy dosimetry and quality assurance for mapping 3D radiation dose distributions in various types of tissue-equivalent gel phantoms that change their optical attenuation coefficients in proportion to the absorbed radiation dose.

Dark Matter Search in a Proton Beam Dump with MiniBooNE

DOE PAGES

Aguilar-Arevalo, A. A.; Backfish, M.; Bashyal, A.; ...

2017-05-31

The MiniBooNE-DM Collaboration searched for vector-boson mediated production of dark matter using the Fermilab 8-GeV Booster proton beam in a dedicated run with 1.86 × 10 20 protons delivered to a steel beam dump. The MiniBooNE detector, 490 m downstream, is sensitive to dark matter via elastic scattering with nucleons in the detector mineral oil. Analysis methods developed for previous MiniBooNE scattering results were employed, and several constraining data sets were simultaneously analyzed to minimize systematic errors from neutrino flux and interaction rates. No excess of events over background was observed, leading to a 90% confidence limit on the darkmore » matter cross section parameter, Y = ε 2α D(m χ/m V) 4≲10 –8, for α D = 0.5 and for dark matter masses of 0.01 < m χ < 0.3 GeV in a vector portal model of dark matter. This is the best limit from a dedicated proton beam dump search in this mass and coupling range and extends below the mass range of direct dark matter searches. Here, these results demonstrate a novel and powerful approach to dark matter searches with beam dump experiments.« less

Analytical description of lateral binding force exerted on bi-sphere induced by high-order Bessel beams

NASA Astrophysics Data System (ADS)

Bai, J.; Wu, Z. S.; Ge, C. X.; Li, Z. J.; Qu, T.; Shang, Q. C.

2018-07-01

Based on the generalized multi-particle Mie equation (GMM) and Electromagnetic Momentum (EM) theory, the lateral binding force (BF) exerted on bi-sphere induced by an arbitrary polarized high-order Bessel beam (HOBB) is investigated with particular emphasis on the half-conical angle of the wave number components and the order (or topological charge) of the beam. The illuminating HOBB with arbitrary polarization angle is described in terms of beam shape coefficients (BSCs) within the framework of generalized Lorenz-Mie theories (GLMT). Utilizing the vector addition theorem of the spherical vector wave functions (SVWFs), the interactive scattering coefficients are derived through the continuous boundary conditions on which the interaction of the bi-sphere is considered. Numerical effects of various parameters such as beam polarization angles, incident wavelengths, particle sizes, material losses and the refractive index, including the cases of weak, moderate, and strong than the surrounding medium are numerically analyzed in detail. The observed dependence of the separation of optically bound particles on the incidence of HOBB is in agreement with earlier theoretical prediction. Accurate investigation of BF induced by HOBB could provide an effective test for further research on BF between more complex particles, which plays an important role in using optical manipulation on particle self-assembly.

Dark Matter Search in a Proton Beam Dump with MiniBooNE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aguilar-Arevalo, A. A.; Backfish, M.; Bashyal, A.

The MiniBooNE-DM Collaboration searched for vector-boson mediated production of dark matter using the Fermilab 8-GeV Booster proton beam in a dedicated run with 1.86 × 10 20 protons delivered to a steel beam dump. The MiniBooNE detector, 490 m downstream, is sensitive to dark matter via elastic scattering with nucleons in the detector mineral oil. Analysis methods developed for previous MiniBooNE scattering results were employed, and several constraining data sets were simultaneously analyzed to minimize systematic errors from neutrino flux and interaction rates. No excess of events over background was observed, leading to a 90% confidence limit on the darkmore » matter cross section parameter, Y = ε 2α D(m χ/m V) 4≲10 –8, for α D = 0.5 and for dark matter masses of 0.01 < m χ < 0.3 GeV in a vector portal model of dark matter. This is the best limit from a dedicated proton beam dump search in this mass and coupling range and extends below the mass range of direct dark matter searches. Here, these results demonstrate a novel and powerful approach to dark matter searches with beam dump experiments.« less

SU-F-T-649: Dosimetric Evaluation of Non-Coplanar Arc Therapy Using a Novel Rotating Gamma Ray System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eldib, A; Chibani, O; Jin, L

2016-06-15

Purpose: Stereotactic intra and extra-cranial body radiation therapy has evolved with advances in treatment accuracy, effective radiation dose, and parameters necessary to maximize machine capabilities. Novel gamma systems with a ring type gantry were developed having the ability to perform oblique arcs. The aim of this study is to explore the dosimetric advantages of this new system. Methods: The rotating Gamma system is named CybeRay (Cyber Medical Corp., Xian, China). It has a treatment head of 16 cobalt-60 sources focused to the isocenter, which can rotate 360° on the ring gantry and swing 35° in the superior direction. Treatment plansmore » were generated utilizing our in-house Monte Carlo treatment planning system. A cylindrical phantom was modeled with 2mm voxel size. Dose inside the cylindrical phantom was calculated for coplanar and non-coplanar arcs. Dosimetric differences between CybeRay cobalt beams and CyberKnife 6MV beams were compared in a lung phantom and for previously treated SBRT patients. Results: The full width at half maxima of cross profiles in the S-I direction for the coplanar setup matched the cone sizes, while for the non-coplanar setup, FWHM was larger by 2mm for a 10mm cone and about 5mm for larger cones. In the coronal and sagittal view, coplanar beams showed elliptical shaped isodose lines, while non-coplanar beams showed circular isodose lines. Thus proper selection of the oblique angle and cone size can aid optimal dose matching to the target volume. Comparing a single 5mm cone from CybeRay to that from CyberKnife showed similar penumbra in a lung phantom but CybeRay had significant lower doses beyond lung tissues. Comparable treatment plans were obtained with CybeRay as that from CyberKnife.ConclusionThe noncoplanar multiple source arrangement of CybeRay will be of great clinical benefits for stereotactic intra and extra-cranial radiation therapy.« less

Beam Position and Phase Monitor - Wire Mapping System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watkins, Heath A; Shurter, Robert B.; Gilpatrick, John D.

2012-04-10

The Los Alamos Neutron Science Center (LANSCE) deploys many cylindrical beam position and phase monitors (BPPM) throughout the linac to measure the beam central position, phase and bunched-beam current. Each monitor is calibrated and qualified prior to installation to insure it meets LANSCE requirements. The BPPM wire mapping system is used to map the BPPM electrode offset, sensitivity and higher order coefficients. This system uses a three-axis motion table to position the wire antenna structure within the cavity, simulating the beam excitation of a BPPM at a fundamental frequency of 201.25 MHz. RF signal strength is measured and recorded formore » the four electrodes as the antenna position is updated. An effort is underway to extend the systems service to the LANSCE facility by replacing obsolete electronic hardware and taking advantage of software enhancements. This paper describes the upgraded wire positioning system's new hardware and software capabilities including its revised antenna structure, motion control interface, RF measurement equipment and Labview software upgrades. The main purpose of the wire mapping system at LANSCE is to characterize the amplitude response versus beam central position of BPPMs before they are installed in the beam line. The wire mapping system is able to simulate a beam using a thin wire and measure the signal response as the wire position is varied within the BPPM aperture.« less

Design optimization of a smooth headlamp reflector to SAE/DOT beam-shape requirements

NASA Astrophysics Data System (ADS)

Shatz, Narkis E.; Bortz, John C.; Dassanayake, Mahendra S.

1999-10-01

The optical design of Ford Motor Company's 1992 Mercury Grand Marquis headlamp utilized a Sylvania 9007 filament source, a paraboloidal reflector and an array of cylindrical lenses (flutes). It has been of interest to Ford to determine the practicality of closely reproducing the on- road beam pattern performance of this headlamp, with an alternate optical arrangement whereby the control of the beam would be achieved solely by means of the geometry of the surface of the reflector, subject to a requirement of smooth-surface continuity; replacing the outer lens with a clear plastic cover having no beam-forming function. To this end the far-field intensity distribution produced by the 9007 bulb was measured at the low-beam setting. These measurements were then used to develop a light-source model for use in ray tracing simulations of candidate reflector geometries. An objective function was developed to compare candidate beam patterns with the desired beam pattern. Functional forms for the 3D reflector geometry were developed with free parameters to be subsequently optimized. A solution was sought meeting the detailed US SAE/DOT constraints for minimum and maximum permissible levels of illumination in the different portions of the beam pattern. Simulated road scenes were generated by Ford Motor Company to compare the illumination properties of the new design with those of the original Grand Marquis headlamp.

Dependences of mucosal dose on photon beams in head-and-neck intensity-modulated radiation therapy: a Monte Carlo study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chow, James C.L., E-mail: james.chow@rmp.uhn.on.ca; Department of Radiation Oncology, University of Toronto, Toronto, Ontario; Department of Physics, Ryerson University, Toronto, Ontario

2012-07-01

Dependences of mucosal dose in the oral or nasal cavity on the beam energy, beam angle, multibeam configuration, and mucosal thickness were studied for small photon fields using Monte Carlo simulations (EGSnrc-based code), which were validated by measurements. Cylindrical mucosa phantoms (mucosal thickness = 1, 2, and 3 mm) with and without the bone and air inhomogeneities were irradiated by the 6- and 18-MV photon beams (field size = 1 Multiplication-Sign 1 cm{sup 2}) with gantry angles equal to 0 Degree-Sign , 90 Degree-Sign , and 180 Degree-Sign , and multibeam configurations using 2, 4, and 8 photon beams inmore » different orientations around the phantom. Doses along the central beam axis in the mucosal tissue were calculated. The mucosal surface doses were found to decrease slightly (1% for the 6-MV photon beam and 3% for the 18-MV beam) with an increase of mucosal thickness from 1-3 mm, when the beam angle is 0 Degree-Sign . The variation of mucosal surface dose with its thickness became insignificant when the beam angle was changed to 180 Degree-Sign , but the dose at the bone-mucosa interface was found to increase (28% for the 6-MV photon beam and 20% for the 18-MV beam) with the mucosal thickness. For different multibeam configurations, the dependence of mucosal dose on its thickness became insignificant when the number of photon beams around the mucosal tissue was increased. The mucosal dose with bone was varied with the beam energy, beam angle, multibeam configuration and mucosal thickness for a small segmental photon field. These dosimetric variations are important to consider improving the treatment strategy, so the mucosal complications in head-and-neck intensity-modulated radiation therapy can be minimized.« less

Polarimetry of uncoupled light on the NIF.

PubMed

Turnbull, D; Moody, J D; Michel, P; Ralph, J E; Divol, L

2014-11-01

Polarimetry has been added to the full aperture backscatter diagnostic on the NIF. Wollaston prisms are used to sample a small region of a beam's backscatter, effectively separating it into two linear polarizations, one of which is parallel to the incident beam. A time-averaged measurement of each polarization is obtained by imaging the separated spots off of a scatter plate. Results have improved understanding of crossed beam energy transfer, glint, and sidescatter, and motivated plans to upgrade to a time-resolved polarimeter measuring the full Stokes vector.

Probe beam deflection technique as acoustic emission directionality sensor with photoacoustic emission source.

PubMed

Barnes, Ronald A; Maswadi, Saher; Glickman, Randolph; Shadaram, Mehdi

2014-01-20

The goal of this paper is to demonstrate the unique capability of measuring the vector or angular information of propagating acoustic waves using an optical sensor. Acoustic waves were generated using photoacoustic interaction and detected by the probe beam deflection technique. Experiments and simulations were performed to study the interaction of acoustic emissions with an optical sensor in a coupling medium. The simulated results predict the probe beam and wavefront interaction and produced simulated signals that are verified by experiment.

Theory of free electron vortices

PubMed Central

Schattschneider, P.; Verbeeck, J.

2011-01-01

The recent creation of electron vortex beams and their first practical application motivates a better understanding of their properties. Here, we develop the theory of free electron vortices with quantized angular momentum, based on solutions of the Schrödinger equation for cylindrical boundary conditions. The principle of transformation of a plane wave into vortices with quantized angular momentum, their paraxial propagation through round magnetic lenses, and the effect of partial coherence are discussed. PMID:21930017

Flow noise of an underwater vector sensor embedded in a flexible towed array.

PubMed

Korenbaum, Vladimir I; Tagiltsev, Alexander A

2012-05-01

The objective of this work is to simulate the flow noise of a vector sensor embedded in a flexible towed array. The mathematical model developed, based on long-wavelength analysis of the inner space of a cylindrical multipole source, predicts the reduction of the flow noise of a vector sensor embedded in an underwater flexible towed array by means of intensimetric processing (cross-spectral density calculation of oscillatory velocity and sound-pressure-sensor responses). It is found experimentally that intensimetric processing results in flow noise reduction by 12-25 dB at mean levels and by 10-30 dB in fluctuations compared to a squared oscillatory velocity channel. The effect of flow noise suppression in the intensimetry channel relative to a squared sound pressure channel is observed, but only for frequencies above the threshold. These suppression values are 10-15 dB at mean noise levels and 3-6 dB in fluctuations. At towing velocities of 1.5-3 ms(-1) and an accumulation time of 98.3 s, the threshold frequency in fluctuations is between 30 and 45 Hz.

A conservative scheme of drift kinetic electrons for gyrokinetic simulation of kinetic-MHD processes in toroidal plasmas

NASA Astrophysics Data System (ADS)

Bao, J.; Liu, D.; Lin, Z.

2017-10-01

A conservative scheme of drift kinetic electrons for gyrokinetic simulations of kinetic-magnetohydrodynamic processes in toroidal plasmas has been formulated and verified. Both vector potential and electron perturbed distribution function are decomposed into adiabatic part with analytic solution and non-adiabatic part solved numerically. The adiabatic parallel electric field is solved directly from the electron adiabatic response, resulting in a high degree of accuracy. The consistency between electrostatic potential and parallel vector potential is enforced by using the electron continuity equation. Since particles are only used to calculate the non-adiabatic response, which is used to calculate the non-adiabatic vector potential through Ohm's law, the conservative scheme minimizes the electron particle noise and mitigates the cancellation problem. Linear dispersion relations of the kinetic Alfvén wave and the collisionless tearing mode in cylindrical geometry have been verified in gyrokinetic toroidal code simulations, which show that the perpendicular grid size can be larger than the electron collisionless skin depth when the mode wavelength is longer than the electron skin depth.