Direct-to-digital holography and holovision

DOEpatents

Thomas, Clarence E.; Baylor, Larry R.; Hanson, Gregory R.; Rasmussen, David A.; Voelkl, Edgar; Castracane, James; Simkulet, Michelle; Clow, Lawrence

2000-01-01

Systems and methods for direct-to-digital holography are described. An apparatus includes a laser; a beamsplitter optically coupled to the laser; a reference beam mirror optically coupled to the beamsplitter; an object optically coupled to the beamsplitter, a focusing lens optically coupled to both the reference beam mirror and the object; and a digital recorder optically coupled to the focusing lens. A reference beam is incident upon the reference beam mirror at a non-normal angle, and the reference beam and an object beam are focused by the focusing lens at a focal plane of the digital recorder to form an image. The systems and methods provide advantages in that computer assisted holographic measurements can be made.

Metamaterial Designs for Photovoltaic and IR Focal-Plane-Imaging Array Applications

DTIC Science & Technology

2013-03-01

incident angles above 17 degrees. There also seems to be no Brewster angle (i.e. the angle at which reflection = 0) for the reflection from the MTM...half- space, while glass has as Brewster angle at 56 degrees incident for TM polarized light. 0 5 10 15 20 25 30 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9...and incident spot beams from an objective lens . The spot beams hitting the detectors are absorbed, but the power of the spot beams falling in between

PRECISE ANGLE MONITOR BASED ON THE CONCEPT OF PENCIL-BEAM INTERFEROMETRY

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

QIAN,S.; TAKACS,P.

2000-07-30

The precise angle monitoring is a very important metrology task for research, development and industrial applications. Autocollimator is one of the most powerful and widely applied instruments for small angle monitoring, which is based on the principle of geometric optics. In this paper the authors introduce a new precise angle monitoring system, Pencil-beam Angle Monitor (PAM), base on pencil beam interferometry. Its principle of operation is a combination of physical and geometrical optics. The angle calculation method is similar to the autocollimator. However, the autocollimator creates a cross image but the precise pencil-beam angle monitoring system produces an interference fringemore » on the focal plane. The advantages of the PAM are: high angular sensitivity, long-term stability character making angle monitoring over long time periods possible, high measurement accuracy in the order of sub-microradian, simultaneous measurement ability in two perpendicular directions or on two different objects, dynamic measurement possibility, insensitive to the vibration and air turbulence, automatic display, storage and analysis by use of the computer, small beam diameter making the alignment extremely easy and longer test distance. Some test examples are presented.« less

Eliminating Unwanted Far-Field Excitation in Objective-Type TIRF. Part II. Combined Evanescent-Wave Excitation and Supercritical-Angle Fluorescence Detection Improves Optical Sectioning

PubMed Central

Brunstein, Maia; Hérault, Karine; Oheim, Martin

2014-01-01

Azimuthal beam scanning makes evanescent-wave (EW) excitation isotropic, thereby producing total internal reflection fluorescence (TIRF) images that are evenly lit. However, beam spinning does not fundamentally address the problem of propagating excitation light that is contaminating objective-type TIRF. Far-field excitation depends more on the specific objective than on cell scattering. As a consequence, the excitation impurities in objective-type TIRF are only weakly affected by changes of azimuthal or polar beam angle. These are the main results of the first part of this study (Eliminating unwanted far-field excitation in objective-type TIRF. Pt.1. Identifying sources of nonevanescent excitation light). This second part focuses on exactly where up beam in the illumination system stray light is generated that gives rise to nonevanescent components in TIRF. Using dark-field imaging of scattered excitation light we pinpoint the objective, intermediate lenses and, particularly, the beam scanner as the major sources of stray excitation. We study how adhesion-molecule coating and astrocytes or BON cells grown on the coverslip surface modify the dark-field signal. On flat and weakly scattering cells, most background comes from stray reflections produced far from the sample plane, in the beam scanner and the objective lens. On thick, optically dense cells roughly half of the scatter is generated by the sample itself. We finally show that combining objective-type EW excitation with supercritical-angle fluorescence (SAF) detection efficiently rejects the fluorescence originating from deeper sample regions. We demonstrate that SAF improves the surface selectivity of TIRF, even at shallow penetration depths. The coplanar microscopy scheme presented here merges the benefits of beam spinning EW excitation and SAF detection and provides the conditions for quantitative wide-field imaging of fluorophore dynamics at or near the plasma membrane. PMID:24606929

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.

An electron beam linear scanning mode for industrial limited-angle nano-computed tomography.

PubMed

Wang, Chengxiang; Zeng, Li; Yu, Wei; Zhang, Lingli; Guo, Yumeng; Gong, Changcheng

2018-01-01

Nano-computed tomography (nano-CT), which utilizes X-rays to research the inner structure of some small objects and has been widely utilized in biomedical research, electronic technology, geology, material sciences, etc., is a high spatial resolution and non-destructive research technique. A traditional nano-CT scanning model with a very high mechanical precision and stability of object manipulator, which is difficult to reach when the scanned object is continuously rotated, is required for high resolution imaging. To reduce the scanning time and attain a stable and high resolution imaging in industrial non-destructive testing, we study an electron beam linear scanning mode of nano-CT system that can avoid mechanical vibration and object movement caused by the continuously rotated object. Furthermore, to further save the scanning time and study how small the scanning range could be considered with acceptable spatial resolution, an alternating iterative algorithm based on ℓ 0 minimization is utilized to limited-angle nano-CT reconstruction problem with the electron beam linear scanning mode. The experimental results confirm the feasibility of the electron beam linear scanning mode of nano-CT system.

An electron beam linear scanning mode for industrial limited-angle nano-computed tomography

NASA Astrophysics Data System (ADS)

Wang, Chengxiang; Zeng, Li; Yu, Wei; Zhang, Lingli; Guo, Yumeng; Gong, Changcheng

2018-01-01

Nano-computed tomography (nano-CT), which utilizes X-rays to research the inner structure of some small objects and has been widely utilized in biomedical research, electronic technology, geology, material sciences, etc., is a high spatial resolution and non-destructive research technique. A traditional nano-CT scanning model with a very high mechanical precision and stability of object manipulator, which is difficult to reach when the scanned object is continuously rotated, is required for high resolution imaging. To reduce the scanning time and attain a stable and high resolution imaging in industrial non-destructive testing, we study an electron beam linear scanning mode of nano-CT system that can avoid mechanical vibration and object movement caused by the continuously rotated object. Furthermore, to further save the scanning time and study how small the scanning range could be considered with acceptable spatial resolution, an alternating iterative algorithm based on ℓ0 minimization is utilized to limited-angle nano-CT reconstruction problem with the electron beam linear scanning mode. The experimental results confirm the feasibility of the electron beam linear scanning mode of nano-CT system.

SU-F-T-352: Development of a Knowledge Based Automatic Lung IMRT Planning Algorithm with Non-Coplanar Beams

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

Zhu, W; Wu, Q; Yuan, L

Purpose: To improve the robustness of a knowledge based automatic lung IMRT planning method and to further validate the reliability of this algorithm by utilizing for the planning of clinical cases with non-coplanar beams. Methods: A lung IMRT planning method which automatically determines both plan optimization objectives and beam configurations with non-coplanar beams has been reported previously. A beam efficiency index map is constructed to guide beam angle selection in this algorithm. This index takes into account both the dose contributions from individual beams and the combined effect of multiple beams which is represented by a beam separation score. Wemore » studied the effect of this beam separation score on plan quality and determined the optimal weight for this score.14 clinical plans were re-planned with the knowledge-based algorithm. Significant dosimetric metrics for the PTV and OARs in the automatic plans are compared with those in the clinical plans by the two-sample t-test. In addition, a composite dosimetric quality index was defined to obtain the relationship between the plan quality and the beam separation score. Results: On average, we observed more than 15% reduction on conformity index and homogeneity index for PTV and V{sub 40}, V{sub 60} for heart while an 8% and 3% increase on V{sub 5}, V{sub 20} for lungs, respectively. The variation curve of the composite index as a function of angle spread score shows that 0.6 is the best value for the weight of the beam separation score. Conclusion: Optimal value for beam angle spread score in automatic lung IMRT planning is obtained. With this value, model can result in statistically the “best” achievable plans. This method can potentially improve the quality and planning efficiency for IMRT plans with no-coplanar angles.« less

Dynamic Analysis of Irradiation of High Intensity Focused Ultrasound (HIFU) to Achieve a Living Tissue Perforation

NASA Astrophysics Data System (ADS)

Mochizuki, Takashi; Kitazumi, Gontaro; Katsuike, Yasumasa; Hotta, Sayo; Maruyama, Hirotaka; Chiba, Toshio

2010-03-01

It is well known that tissue perforation is performed by the shock waves generated by the collapse of micro bubbles due to HIFU irradiation. However, the angle-dependency between the HIFU irradiation beam and the tissue membrane has not been studied in detail so far. The objective of this study was to investigate the HIFU parameters which were the most effective in perforating the tissues with the heart beating, especially the angle dependency of the beam with the observation using high speed video camera. The result shows that the ultrasound beam should be at right angle to the membrane to perforate the tissue membrane effectively.

Methods and Devices for Space Optical Communications Using Laser Beams

NASA Technical Reports Server (NTRS)

Goorjian, Peter M. (Inventor)

2018-01-01

Light is used to communicate between objects separated by a large distance. Light beams are received in a telescopic lens assembly positioned in front of a cat's-eye lens. The light can thereby be received at various angles to be output by the cat's-eye lens to a focal plane of the cat's-eye lens, the position of the light beams upon the focal plane corresponding to the angle of the beam received. Lasers and photodetectors are distributed along this focal plane. A processor receives signals from the photodetectors, and selectively signal lasers positioned proximate the photodetectors detecting light, in order to transmit light encoding data through the cat's-eye lens and also through a telescopic lens back in the direction of the received light beams, which direction corresponds to a location upon the focal plane of the transmitting lasers.

Particle beam injector system and method

DOEpatents

Guethlein, Gary

2013-06-18

Methods and devices enable coupling of a charged particle beam to a radio frequency quadrupole accelerator. Coupling of the charged particle beam is accomplished, at least in-part, by relying on of sensitivity of the input phase space acceptance of the radio frequency quadrupole to the angle of the input charged particle beam. A first electric field across a beam deflector deflects the particle beam at an angle that is beyond the acceptance angle of the radio frequency quadrupole. By momentarily reversing or reducing the established electric field, a narrow portion of the charged particle beam is deflected at an angle within the acceptance angle of the radio frequency quadrupole. In another configuration, beam is directed at an angle within the acceptance angle of the radio frequency quadrupole by the first electric field and is deflected beyond the acceptance angle of the radio frequency quadrupole due to the second electric field.

SU-E-T-577: Obliquity Factor and Surface Dose in Proton Beam Therapy

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

Das, I; Andersen, A; Coutinho, L

2015-06-15

Purpose: The advantage of lower skin dose in proton beam may be diminished creating radiation related sequalae usually seen with photon and electron beams. This study evaluates the surface dose as a complex function of beam parameters but more importantly the effect of beam angle. Methods: Surface dose in proton beam depends on the beam energy, source to surface distance, the air gap between snout and surface, field size, material thickness in front of surface, atomic number of the medium, beam angle and type of nozzle (ie double scattering, (DS), uniform scanning (US) or pencil beam scanning (PBS). Obliquity factormore » (OF) is defined as ratio of surface dose in 0° to beam angle Θ. Measurements were made in water phantom at various beam angles using very small microdiamond that has shown favorable beam characteristics for high, medium and low proton energy. Depth dose measurements were performed in the central axis of the beam in each respective gantry angle. Results: It is observed that surface dose is energy dependent but more predominantly on the SOBP. It is found that as SSD increases, surface dose decreases. In general, SSD, and air gap has limited impact in clinical proton range. High energy has higher surface dose and so the beam angle. The OF rises with beam angle. Compared to OF of 1.0 at 0° beam angle, the value is 1.5, 1.6, 1,7 for small, medium and large range respectively for 60 degree angle. Conclusion: It is advised that just like range and SOBP, surface dose should be clearly understood and a method to reduce the surface dose should be employed. Obliquity factor is a critical parameter that should be accounted in proton beam therapy and a perpendicular beam should be used to reduce surface dose.« less

Spatial-heterodyne interferometry for transmission (SHIFT) measurements

DOEpatents

Bingham, Philip R.; Hanson, Gregory R.; Tobin, Ken W.

2006-10-10

Systems and methods are described for spatial-heterodyne interferometry for transmission (SHIFT) measurements. A method includes digitally recording a spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis using a reference beam, and an object beam that is transmitted through an object that is at least partially translucent; Fourier analyzing the digitally recorded spatially-heterodyned hologram, by shifting an original origin of the digitally recorded spatially-heterodyned hologram to sit on top of a spatial-heterodyne carrier frequency defined by an angle between the reference beam and the object beam, to define an analyzed image; digitally filtering the analyzed image to cut off signals around the original origin to define a result; and performing an inverse Fourier transform on the result.

Optimizing highly noncoplanar VMAT trajectories: the NoVo method.

PubMed

Langhans, Marco; Unkelbach, Jan; Bortfeld, Thomas; Craft, David

2018-01-16

We introduce a new method called NoVo (Noncoplanar VMAT Optimization) to produce volumetric modulated arc therapy (VMAT) treatment plans with noncoplanar trajectories. While the use of noncoplanar beam arrangements for intensity modulated radiation therapy (IMRT), and in particular high fraction stereotactic radiosurgery (SRS), is common, noncoplanar beam trajectories for VMAT are less common as the availability of treatment machines handling these is limited. For both IMRT and VMAT, the beam angle selection problem is highly nonconvex in nature, which is why automated beam angle selection procedures have not entered mainstream clinical usage. NoVo determines a noncoplanar VMAT solution (i.e. the simultaneous trajectories of the gantry and the couch) by first computing a [Formula: see text] solution (beams from every possible direction, suitably discretized) and then eliminating beams by examing fluence contributions. Also all beam angles are scored via geometrical considerations only to find out the usefulness of the whole beam space in a very short time. A custom path finding algorithm is applied to find an optimized, continuous trajectory through the most promising beam angles using the calculated score of the beam space. Finally, using this trajectory a VMAT plan is optimized. For three clinical cases, a lung, brain, and liver case, we compare NoVo to the ideal [Formula: see text] solution, nine beam noncoplanar IMRT, coplanar VMAT, and a recently published noncoplanar VMAT algorithm. NoVo comes closest to the [Formula: see text] solution considering the lung case (brain and liver case: second), as well as improving the solution time by using geometrical considerations, followed by a time effective iterative process reducing the [Formula: see text] solution. Compared to a recently published noncoplanar VMAT algorithm, using NoVo the computation time is reduced by a factor of 2-3 (depending on the case). Compared to coplanar VMAT, NoVo reduces the objective function value by 24%, 49% and 6% for the lung, brain and liver cases, respectively.

Optimizing highly noncoplanar VMAT trajectories: the NoVo method

NASA Astrophysics Data System (ADS)

Langhans, Marco; Unkelbach, Jan; Bortfeld, Thomas; Craft, David

2018-01-01

We introduce a new method called NoVo (Noncoplanar VMAT Optimization) to produce volumetric modulated arc therapy (VMAT) treatment plans with noncoplanar trajectories. While the use of noncoplanar beam arrangements for intensity modulated radiation therapy (IMRT), and in particular high fraction stereotactic radiosurgery (SRS), is common, noncoplanar beam trajectories for VMAT are less common as the availability of treatment machines handling these is limited. For both IMRT and VMAT, the beam angle selection problem is highly nonconvex in nature, which is why automated beam angle selection procedures have not entered mainstream clinical usage. NoVo determines a noncoplanar VMAT solution (i.e. the simultaneous trajectories of the gantry and the couch) by first computing a 4π solution (beams from every possible direction, suitably discretized) and then eliminating beams by examing fluence contributions. Also all beam angles are scored via geometrical considerations only to find out the usefulness of the whole beam space in a very short time. A custom path finding algorithm is applied to find an optimized, continuous trajectory through the most promising beam angles using the calculated score of the beam space. Finally, using this trajectory a VMAT plan is optimized. For three clinical cases, a lung, brain, and liver case, we compare NoVo to the ideal 4π solution, nine beam noncoplanar IMRT, coplanar VMAT, and a recently published noncoplanar VMAT algorithm. NoVo comes closest to the 4π solution considering the lung case (brain and liver case: second), as well as improving the solution time by using geometrical considerations, followed by a time effective iterative process reducing the 4π solution. Compared to a recently published noncoplanar VMAT algorithm, using NoVo the computation time is reduced by a factor of 2-3 (depending on the case). Compared to coplanar VMAT, NoVo reduces the objective function value by 24%, 49% and 6% for the lung, brain and liver cases, respectively.

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

Ohmi, K.

In recent high luminosity colliders, the finite crossing angle scheme becomes popular to gain the multiplicity of luminosity with multi-bunch or long bunch operation. Success of KEKB showed that the finite crossing angle scheme was no problem to achieve the beam-beam parameter up to 0.05. The authors have studied the beam-beam interactions with/without crossing angle toward higher luminosity. They discuss how the crossing angle affects the beam-beam parameter and luminosity in the present KEK B factory (KEKB) using computer simulations.

Sequential, progressive, equal-power, reflective beam-splitter arrays

NASA Astrophysics Data System (ADS)

Manhart, Paul K.

2017-11-01

The equations to calculate equal-power reflectivity of a sequential series of beam splitters is presented. Non-sequential optical design examples are offered for uniform illumination using diode lasers. Objects created using Boolean operators and Swept Surfaces can create objects capable of reflecting light into predefined elevation and azimuth angles. Analysis of the illumination patterns for the array are also presented.

The Discovery of Low-Luminosity BL Lacs

NASA Astrophysics Data System (ADS)

Rector, Travis A.; Stocke, John T.

1995-12-01

Many of the properties of BL Lacs have become explicable in terms of the ``relativistic beaming'' hypothesis whereby BL Lacs are ``highly beamed'' FR-I radio galaxies (i.e. our line of sight to these objects is nearly along the jet axis). Further, radio-selected BL Lacs (RBLs) are believed to be seen nearly ``on-axis'' (the line-of-sight angle theta ~ 8deg ) while X-ray selected BL Lacs (XBLs) are seen at larger angles (theta ~ 30deg ; the X-ray emitting jet is believed to be less collimated). However, a major problem with this model was that a transition population between beamed BL Lacs and unbeamed FR-Is had not been detected. Low-luminosity BL Lacs may be such a transition population, and were predicted to exist by Browne and Marcha (1993). We present ROSAT HRI images, VLA radio maps and optical spectra which confirm the existence of low-luminosity BL Lacs, objects which were previously mis-identified in the EMSS catalog as clusters of galaxies. Thus our results strengthen the relativistic beaming hypothesis.

Comparative analysis of Pareto surfaces in multi-criteria IMRT planning

NASA Astrophysics Data System (ADS)

Teichert, K.; Süss, P.; Serna, J. I.; Monz, M.; Küfer, K. H.; Thieke, C.

2011-06-01

In the multi-criteria optimization approach to IMRT planning, a given dose distribution is evaluated by a number of convex objective functions that measure tumor coverage and sparing of the different organs at risk. Within this context optimizing the intensity profiles for any fixed set of beams yields a convex Pareto set in the objective space. However, if the number of beam directions and irradiation angles are included as free parameters in the formulation of the optimization problem, the resulting Pareto set becomes more intricate. In this work, a method is presented that allows for the comparison of two convex Pareto sets emerging from two distinct beam configuration choices. For the two competing beam settings, the non-dominated and the dominated points of the corresponding Pareto sets are identified and the distance between the two sets in the objective space is calculated and subsequently plotted. The obtained information enables the planner to decide if, for a given compromise, the current beam setup is optimal. He may then re-adjust his choice accordingly during navigation. The method is applied to an artificial case and two clinical head neck cases. In all cases no configuration is dominating its competitor over the whole Pareto set. For example, in one of the head neck cases a seven-beam configuration turns out to be superior to a nine-beam configuration if the highest priority is the sparing of the spinal cord. The presented method of comparing Pareto sets is not restricted to comparing different beam angle configurations, but will allow for more comprehensive comparisons of competing treatment techniques (e.g. photons versus protons) than with the classical method of comparing single treatment plans.

Method and Apparatus for Measuring Near-Angle Scattering of Mirror Coatings

NASA Technical Reports Server (NTRS)

Chipman, Russell A. (Inventor); Daugherty, Brian J. (Inventor); McClain, Stephen C. (Inventor); Macenka, Steven A. (Inventor)

2013-01-01

Disclosed herein is a method of determining the near angle scattering of a sample reflective surface comprising the steps of: a) splitting a beam of light having a coherence length of greater than or equal to about 2 meters into a sample beam and a reference beam; b) frequency shifting both the sample beam and the reference beam to produce a fixed beat frequency between the sample beam and the reference beam; c) directing the sample beam through a focusing lens and onto the sample reflective surface, d) reflecting the sample beam from the sample reflective surface through a detection restriction disposed on a movable stage; e) recombining the sample beam with the reference beam to form a recombined beam, followed by f) directing the recombined beam to a detector and performing heterodyne analysis on the recombined beam to measure the near-angle scattering of the sample reflective surface, wherein the position of the detection restriction relative to the sample beam is varied to occlude at least a portion of the sample beam to measure the near-angle scattering of the sample reflective surface. An apparatus according to the above method is also disclosed.

Sensitivity of Beam Parameters to a Station C Solenoid Scan on Axis II

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

Schulze, Martin E.

Magnet scans are a standard technique for determining beam parameters in accelerators. Beam parameters are inferred from spot size measurements using a model of the beam optics. The sensitivity of the measured beam spot size to the beam parameters is investigated for typical DARHT Axis II beam energies and currents. In a typical S4 solenoid scan, the downstream transport is tuned to achieve a round beam at Station C with an envelope radius of about 1.5 cm with a very small divergence with S4 off. The typical beam energy and current are 16.0 MeV and 1.625 kA. Figures 1-3 showmore » the sensitivity of the bean size at Station C to the emittance, initial radius and initial angle respectively. To better understand the relative sensitivity of the beam size to the emittance, initial radius and initial angle, linear regressions were performed for each parameter as a function of the S4 setting. The results are shown in Figure 4. The measured slope was scaled to have a maximum value of 1 in order to present the relative sensitivities in a single plot. Figure 4 clearly shows the beam size at the minimum of the S4 scan is most sensitive to emittance and relatively insensitive to initial radius and angle as expected. The beam emittance is also very sensitive to the beam size of the converging beam and becomes insensitive to the beam size of the diverging beam. Measurements of the beam size of the diverging beam provide the greatest sensitivity to the initial beam radius and to a lesser extent the initial beam angle. The converging beam size is initially very sensitive to the emittance and initial angle at low S4 currents. As the S4 current is increased the sensitivity to the emittance remains strong while the sensitivity to the initial angle diminishes.« less

Investigating multi-objective fluence and beam orientation IMRT optimization

NASA Astrophysics Data System (ADS)

Potrebko, Peter S.; Fiege, Jason; Biagioli, Matthew; Poleszczuk, Jan

2017-07-01

Radiation Oncology treatment planning requires compromises to be made between clinical objectives that are invariably in conflict. It would be beneficial to have a ‘bird’s-eye-view’ perspective of the full spectrum of treatment plans that represent the possible trade-offs between delivering the intended dose to the planning target volume (PTV) while optimally sparing the organs-at-risk (OARs). In this work, the authors demonstrate Pareto-aware radiotherapy evolutionary treatment optimization (PARETO), a multi-objective tool featuring such bird’s-eye-view functionality, which optimizes fluence patterns and beam angles for intensity-modulated radiation therapy (IMRT) treatment planning. The problem of IMRT treatment plan optimization is managed as a combined monolithic problem, where all beam fluence and angle parameters are treated equally during the optimization. To achieve this, PARETO is built around a powerful multi-objective evolutionary algorithm, called Ferret, which simultaneously optimizes multiple fitness functions that encode the attributes of the desired dose distribution for the PTV and OARs. The graphical interfaces within PARETO provide useful information such as: the convergence behavior during optimization, trade-off plots between the competing objectives, and a graphical representation of the optimal solution database allowing for the rapid exploration of treatment plan quality through the evaluation of dose-volume histograms and isodose distributions. PARETO was evaluated for two relatively complex clinical cases, a paranasal sinus and a pancreas case. The end result of each PARETO run was a database of optimal (non-dominated) treatment plans that demonstrated trade-offs between the OAR and PTV fitness functions, which were all equally good in the Pareto-optimal sense (where no one objective can be improved without worsening at least one other). Ferret was able to produce high quality solutions even though a large number of parameters, such as beam fluence and beam angles, were included in the optimization.

Beam angle selection incorporation of anatomical heterogeneities for pencil beam scanning charged-particle therapy

NASA Astrophysics Data System (ADS)

Toramatsu, Chie; Inaniwa, Taku

2016-12-01

In charged particle therapy with pencil beam scanning (PBS), localization of the dose in the Bragg peak makes dose distributions sensitive to lateral tissue heterogeneities. The sensitivity of a PBS plan to lateral tissue heterogeneities can be reduced by selecting appropriate beam angles. The purpose of this study is to develop a fast and accurate method of beam angle selection for PBS. The lateral tissue heterogeneity surrounding the path of the pencil beams at a given angle was quantified with the heterogeneity number representing the variation of the Bragg peak depth across the cross section of the beams using the stopping power ratio of body tissues with respect to water. To shorten the computation time, one-dimensional dose optimization was conducted along the central axis of the pencil beams as they were directed by the scanning magnets. The heterogeneity numbers were derived for all possible beam angles for treatment. The angles leading to the minimum mean heterogeneity number were selected as the optimal beam angle. Three clinical cases of head and neck cancer were used to evaluate the developed method. Dose distributions and their robustness to setup and range errors were evaluated for all tested angles, and their relation to the heterogeneity numbers was investigated. The mean heterogeneity number varied from 1.2 mm-10.6 mm in the evaluated cases. By selecting a field with a low mean heterogeneity number, target dose coverage and robustness against setup and range errors were improved. The developed method is simple, fast, accurate and applicable for beam angle selection in charged particle therapy with PBS.

Radio frequency source of a weakly expanding wedge-shaped xenon ion beam for contactless removal of large-sized space debris objects.

PubMed

Balashov, Victor; Cherkasova, Maria; Kruglov, Kirill; Kudriavtsev, Arseny; Masherov, Pavel; Mogulkin, Andrey; Obukhov, Vladimir; Riaby, Valentin; Svotina, Victoria

2017-08-01

A theoretical-experimental research has been carried out to determine the characteristics of a radio frequency (RF) ion source for the generation of a weakly expanding wedge-shaped xenon ion beam. Such ion beam geometry is of interest as a prototype of an on-board ion injector for contactless "ion shepherding" by service spacecraft to remove large space debris objects from geostationary orbits. The wedge shape of the ion beam increases its range. The device described herein comprises an inductive gas discharge chamber and a slit-type three-electrode ion extraction grid (IEG) unit. Calculations of accelerating cell geometries and ion trajectories determined the dependence of beam expansion half-angle on normalized perveance based on the measurements of the spatial distributions of the xenon plasma parameters at the IEG entrance for a xenon flow rate q ≈ 0.2 mg/s and an incident RF power P in ≤ 250 W at a driving frequency f = 2 MHz. Experimental studies showed that the ion beam, circular at the IEG exit, accepted the elliptical form at the distance of 580 mm with half-angle of beam expansion across IEG slits about 2°-3° and close to 0° along them. Thus, the obtained result proved the possibility of creating a new-generation on-board ion injector that could be used in spacecrafts for removal of debris.

High-speed reference-beam-angle control technique for holographic memory drive

NASA Astrophysics Data System (ADS)

Yamada, Ken-ichiro; Ogata, Takeshi; Hosaka, Makoto; Fujita, Koji; Okuyama, Atsushi

2016-09-01

We developed a holographic memory drive for next-generation optical memory. In this study, we present the key technology for achieving a high-speed transfer rate for reproduction, that is, a high-speed control technique for the reference beam angle. In reproduction in a holographic memory drive, there is the issue that the optimum reference beam angle during reproduction varies owing to distortion of the medium. The distortion is caused by, for example, temperature variation, beam irradiation, and moisture absorption. Therefore, a reference-beam-angle control technique to position the reference beam at the optimum angle is crucial. We developed a new optical system that generates an angle-error-signal to detect the optimum reference beam angle. To achieve the high-speed control technique using the new optical system, we developed a new control technique called adaptive final-state control (AFSC) that adds a second control input to the first one derived from conventional final-state control (FSC) at the time of angle-error-signal detection. We established an actual experimental system employing AFSC to achieve moving control between each page (Page Seek) within 300 µs. In sequential multiple Page Seeks, we were able to realize positioning to the optimum angles of the reference beam that maximize the diffracted beam intensity. We expect that applying the new control technique to the holographic memory drive will enable a giga-bit/s-class transfer rate.

Transverse tails and higher order moments

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

Spence, W.L.; Decker, F.J.; Woodley, M.D.

1993-05-01

The tails that may be engendered in a beam`s transverse phase space distribution by, e.g., intrabunch wakefields and nonlinear magnetic fields, are all important diagnostic and object of tuning in linear colliders. Wire scanners or phosphorescent screen monitors yield one dimensional projected spatial profiles of such beams that are generically asymmetric around their centroids, and therefore require characterization by the third moment {l_angle}x{sup 3}{r_angle} in addition to the conventional mean-square or second moment. A set of measurements spread over sufficient phase advance then allows the complete set {l_angle}x{sup 3}{r_angle}, {l_angle}xx{prime}{sup 2}{r_angle}, {l_angle}x{prime}{sup 3}{r_angle}, and {l_angle}x{sup 2}x{prime}{r_angle} to be deduced --more » the natural extension of the well-known ``emittance measurement`` treatment of second moments. The four third moments may be usefully decomposed into parts rotating in phase space at the {beta}-tron frequency and at its third harmonic, each specified by a phase-advance-invariant amplitude and a phase. They provide a framework for the analysis and tuning of transverse wakefield tails.« less

Fast wavelength tuning techniques for external cavity lasers

DOEpatents

Wysocki, Gerard [Princeton, NJ; Tittel, Frank K [Houston, TX

2011-01-11

An apparatus comprising a laser source configured to emit a light beam along a first path, an optical beam steering component configured to steer the light beam from the first path to a second path at an angle to the first path, and a diffraction grating configured to reflect back at least a portion of the light beam along the second path, wherein the angle determines an external cavity length. Included is an apparatus comprising a laser source configured to emit a light beam along a first path, a beam steering component configured to redirect the light beam to a second path at an angle to the first path, wherein the optical beam steering component is configured to change the angle at a rate of at least about one Kilohertz, and a diffraction grating configured to reflect back at least a portion of the light beam along the second path.

3D algebraic iterative reconstruction for cone-beam x-ray differential phase-contrast computed tomography.

PubMed

Fu, Jian; Hu, Xinhua; Velroyen, Astrid; Bech, Martin; Jiang, Ming; Pfeiffer, Franz

2015-01-01

Due to the potential of compact imaging systems with magnified spatial resolution and contrast, cone-beam x-ray differential phase-contrast computed tomography (DPC-CT) has attracted significant interest. The current proposed FDK reconstruction algorithm with the Hilbert imaginary filter will induce severe cone-beam artifacts when the cone-beam angle becomes large. In this paper, we propose an algebraic iterative reconstruction (AIR) method for cone-beam DPC-CT and report its experiment results. This approach considers the reconstruction process as the optimization of a discrete representation of the object function to satisfy a system of equations that describes the cone-beam DPC-CT imaging modality. Unlike the conventional iterative algorithms for absorption-based CT, it involves the derivative operation to the forward projections of the reconstructed intermediate image to take into account the differential nature of the DPC projections. This method is based on the algebraic reconstruction technique, reconstructs the image ray by ray, and is expected to provide better derivative estimates in iterations. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a mini-focus x-ray tube source. It is shown that the proposed method can reduce the cone-beam artifacts and performs better than FDK under large cone-beam angles. This algorithm is of interest for future cone-beam DPC-CT applications.

Process and apparatus for measuring degree of polarization and angle of major axis of polarized beam of light

DOEpatents

Decker, Derek E.; Toeppen, John S.

1994-01-01

Apparatus and process are disclosed for calibrating measurements of the phase of the polarization of a polarized beam and the angle of the polarized optical beam's major axis of polarization at a diagnostic point with measurements of the same parameters at a point of interest along the polarized beam path prior to the diagnostic point. The process is carried out by measuring the phase angle of the polarization of the beam and angle of the major axis at the point of interest, using a rotatable polarizer and a detector, and then measuring these parameters again at a diagnostic point where a compensation apparatus, including a partial polarizer, which may comprise a stack of glass plates, is disposed normal to the beam path between a rotatable polarizer and a detector. The partial polarizer is then rotated both normal to the beam path and around the axis of the beam path until the detected phase of the beam polarization equals the phase measured at the point of interest. The rotatable polarizer at the diagnostic point may then be rotated manually to determine the angle of the major axis of the beam and this is compared with the measured angle of the major axis of the beam at the point of interest during calibration. Thereafter, changes in the polarization phase, and in the angle of the major axis, at the point of interest can be monitored by measuring the changes in these same parameters at the diagnostic point.

A multiphoton objective design with incorporated beam splitter for enhanced fluorescence collection

PubMed Central

McMullen, Jesse D.; Zipfel, Warren R.

2010-01-01

We present a de novo design of an objective for use in multi-photon (MPM) and second harmonic generation (SHG) microscopy. This objective was designed to have a large field of view (FOV), while maintaining a moderate numerical aperture (NA) and relative straight forward construction. A dichroic beam splitter was incorporated within the objective itself allowing for an increase in the front aperture of the objective and corresponding enhancement of the solid angle of collected emission by an order of magnitude over existing designs. PMID:20389554

A multiphoton objective design with incorporated beam splitter for enhanced fluorescence collection.

PubMed

McMullen, Jesse D; Zipfel, Warren R

2010-03-15

We present a de novo design of an objective for use in multi-photon (MPM) and second harmonic generation (SHG) microscopy. This objective was designed to have a large field of view (FOV), while maintaining a moderate numerical aperture (NA) and relative straight forward construction. A dichroic beam splitter was incorporated within the objective itself allowing for an increase in the front aperture of the objective and corresponding enhancement of the solid angle of collected emission by an order of magnitude over existing designs.

Impacts of gantry angle dependent scanning beam properties on proton PBS treatment

NASA Astrophysics Data System (ADS)

Lin, Yuting; Clasie, Benjamin; Lu, Hsiao-Ming; Flanz, Jacob; Shen, Tim; Jee, Kyung-Wook

2017-01-01

While proton beam models in treatment planning systems are generally assumed invariant with respect to the beam deliveries at different gantry angles. Physical properties of scanning pencil beams can change. The gantry angle dependent properties include the delivered charge to the monitor unit chamber, the spot position and the spot shape. The aim of this study is to investigate the extent of the changes and their dosimetric impacts using historical pencil beam scanning (PBS) treatment data. Online beam delivery records at the time of the patient-specific qualify assurance were retrospectively collected for a total of 34 PBS fields from 28 patients treated at our institution. For each field, proton beam properties at two different gantry angles (the planned and zero gantry angles) were extracted by a newly-developed machine log analysis method and used to reconstruct the delivered dose distributions in the cubic water phantom geometry. The reconstructed doses at the two different angles and a planar dose measurement by a 2D ion-chamber array were compared and the dosimetric impacts of the gantry angle dependency were accessed by a 3D γ-index analysis. In addition, the pencil beam spot size was independently characterized as a function of the gantry angle and the beam energy. The dosimetric effects of the perturbed beam shape were also investigated. Comparisons of spot-by-spot beam positions between both gantry angles show a mean deviation of 0.4 and 0.7 mm and a standard deviation of 0.3 and 0.6 mm for x and y directions, respectively. The delivered giga-protons per spot show a percent mean difference and a standard deviation of 0.01% and 0.3%, respectively, from each planned spot weight. These small deviations lead to an excellent agreement in dose comparisons with an average γ passing rate of 99.1%. When each calculation for both planned and zero gantry angles was compared to the measurement, a high correlation in γ values was also observed, also indicating the dosimetric differences are small when a field is delivered at different gantry angles. Utilizing the online beam delivery records, the gantry angle dependencies of the PBS beam delivery were assessed and quantified. The study confirms the variations of the physical properties to be sufficiently small within the clinical tolerances without taking into account the gantry angle variation.

Radiation from long pulse train electron beams in space plasmas

NASA Technical Reports Server (NTRS)

Harker, K. J.; Banks, P. M.

1985-01-01

A previous study of electromagnetic radiation from a finite train of electron pulses is extended to an infinite train of such pulses. The electrons are assumed to follow an idealized helical path through a space plasma in such a manner as to retain their respective position within the beam. This leads to radiation by coherent spontaneous emission. The waves of interest in this region are the whistler slow (compressional) and fast (torsional) Alfven waves. Although a general theory is developed, analysis is then restricted to two approximations, the short and long electron beam. Formulas for the radiation per unit solid angle from the short beam are presented as a function of both propagation and ray angles, electron beam pulse width and separation and beam current, voltage, and pitch angle. Similar formulas for the total power radiated from the long beam are derived as a function of frequency, propagation angle, and ray angle. Predictions of the power radiated are presented for representative examples as determined by the long beam theory.

Analytical beam-width characteristics of distorted cat-eye reflected beam

NASA Astrophysics Data System (ADS)

Zhao, Yanzhong; Shan, Congmiao; Zheng, Yonghui; Zhang, Laixian; Sun, Huayan

2015-02-01

The analytical expression of beam-width of distorted cat-eye reflected beam under far-field condition is deduced using the approximate three-dimensional analytical formula for oblique detection laser beam passing through cat-eye optical lens with center shelter, and using the definition of second order moment, Gamma function and integral functions. The laws the variation of divergence angle and astigmatism degree of the reflected light with incident angle, focal shift, aperture size, and center shelter ratio are established by numerical calculation, and physical analysis. The study revealed that the cat-eye reflected beam is like a beam transmitted and collimated by the target optical lens, and has the same characteristics as that of Gaussian beam. A proper choice of positive focal shift would result in a divergence angle smaller than that of no focal shift. The astigmatism is mainly caused by incidence angle.

The variance of angle-of-arrival fluctuation of partially coherent Gaussian-Schell Model beam propagations in slant atmospheric turbulence

NASA Astrophysics Data System (ADS)

Tan, Zhenkun; Ke, Xizheng

2017-10-01

The variance of angle-of-arrival fluctuation of the partially coherent Gaussian-Schell Model (GSM) beam propagations in the slant path, based on the extended Huygens-Fresnel principle and the model of atmospheric refraction index structural constant proposed by the international telecommunication union-radio (ITU-R), has been investigated under the modified Hill turbulence model. The expression of that has been obtained. Firstly, the effects of optical wavelength, the inner-and-outer scale of the turbulence and turbulence intensity on the variance of angle-of-arrival fluctuation have been analyzed by comparing with the partially coherent GSM beam and the completely coherent Gaussian beam. Secondly, the variance of angle-of-arrival fluctuation has been compared with the von Karman spectrum and the modified Hill spectrum under the partially coherent GSM beam. Finally, the effects of beam waist radius and partial coherence length on the variance of angle-of-arrival of the collimated (focused) beam have been analyzed under the modified Hill turbulence model. The results show that the influence of the variance of angle-of-arrival fluctuation for the inner scale effect is larger than that of the outer scale effect. The variance of angle-of-arrival fluctuation under the modified Hill spectrum is larger than that of the von Karman spectrum. The influence of the waist radius on the variance of angle-of-arrival for the collimated beam is less than focused the beam. This study will provide a necessary theoretical basis for the experiments of partially coherent GSM beam propagation through atmosphere turbulence.

SU-E-T-618: Dosimetric Comparison of Manual and Beam Angle Optimization of Gantry Angles in IMRT for Cervical Cancer

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

Lin, X; Sun, T; Liu, T

2014-06-01

Purpose: To evaluate the dosimetric characteristics of intensity-modulated radiotherapy (IMRT) treatment plan with beam angle optimization. Methods: Ten post-operation patients with cervical cancer were included in this analysis. Two IMRT plans using seven beams were designed in each patient. A standard coplanar equi-space beam angles were used in the first plan (plan 1), whereas the selection of beam angle was optimized by beam angle optimization algorithm in Varian Eclipse treatment planning system for the same number of beams in the second plan (plan 2). Two plans were designed for each patient with the same dose-volume constraints and prescription dose. Allmore » plans were normalized to the mean dose to PTV. The dose distribution in the target, the dose to the organs at risk and total MU were compared. Results: For conformity and homogeneity in PTV, no statistically differences were observed in the two plans. For the mean dose in bladder, plan 2 were significantly lower than plan 1(p<0.05). No statistically significant differences were observed between two plans for the mean doses in rectum, left and right femur heads. Compared with plan1, the average monitor units reduced 16% in plan 2. Conclusion: The IMRT plan based on beam angle optimization for cervical cancer could reduce the dose delivered to bladder and also reduce MU. Therefore there were some dosimetric advantages in the IMRT plan with beam angle optimization for cervical cancer.« less

Poster - 23: Dosimetric Characterization and Transferability of an Accessory Mounted Mini-Beam Collimator

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

Davis, William; Crewson, Cody; Alexander, Andrew

Objective: The dosimetric characterization of an accessory-mounted mini-beam collimator across three beam matched linear accelerators. Materials and Methods: Percent depth dose and profiles were measured for the open and mini-beam collimated fields. The average beam quality and peak-to-valley dose ratio (PVDR), the ratio of average peak dose to average valley dose, were obtained from these measurements. The open field relative output and the mini-beam collimator factor, the ratio of the mini-beam dose to open field dose at the beam center, were measured for square fields of side 2, 3, 4, and 5 cm. Mini-beam output as a function of collimatormore » inclination angle relative to the central axis was also investigated. Results and Discussion: Beam quality for both the open and mini-beam collimated fields agreed across all linacs to within ±1.0%. The PVDR was found to vary by up to ±6.6% from the mean. For the 2, 3, and 4 cm fields the average open field relative output with respect to the 5 cm field was 0.874±0.4%, 0.921±0.3%, and 0.962±0.1%. The average collimator factors were 0.450±3.9%, 0.443±3.9%, 0.438±3.9%, and 0.434±3.9%. A decrease in collimator factor greater than 7% was found for an inclination angle change of 0.09°. Conclusion: The mini-beam collimator has revealed a difference between the three linacs not apparent in the open field data, yet transferability can still be attained through thorough dosimetric characterization.« less

Spatial phase-shift dual-beam speckle interferometry.

PubMed

Gao, Xinya; Yang, Lianxiang; Wang, Yonghong; Zhang, Boyang; Dan, Xizuo; Li, Junrui; Wu, Sijin

2018-01-20

The spatial phase-shift technique has been successfully applied to an out-of-plane speckle interferometry system. Its application to a pure in-plane sensitive system has not been reported yet. This paper presents a novel optical configuration that enables the application of the spatial phase-shift technique to pure in-plane sensitive dual-beam speckle interferometry. The new spatial phase-shift dual-beam speckle interferometry (SPS-DBSP) uses a dual-beam in-plane electronic speckle pattern interferometry configuration with individual aperture shears, avoiding the interference in the object plane by the use of a low-coherence source, and different optical paths. The measured object is illuminated by two incoherent beams that are generated by a delay line, which is larger than the coherence length of the laser. The two beams reflected from the object surface interfere with each other at the CCD plane because of different optical paths. A spatial phase shift is introduced by the angle between the two apertures when they are mapped to the same optical axis. The phase of the in-plane deformation can directly be extracted from the speckle patterns by the Fourier transform method. The capability of SPS-DBSI is demonstrated by theoretical discussion as well as experiments.

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

Apparatus for direct-to-digital spatially-heterodyned holography

DOEpatents

Thomas, Clarence E.; Hanson, Gregory R.

2006-12-12

An apparatus operable to record a spatially low-frequency heterodyne hologram including spatially heterodyne fringes for Fourier analysis includes: a laser; a beamsplitter optically coupled to the laser; an object optically coupled to the beamsplitter; a focusing lens optically coupled to both the beamsplitter and the object; a digital recorder optically coupled to the focusing lens; and a computer that performs a Fourier transform, applies a digital filter, and performs an inverse Fourier transform. A reference beam and an object beam are focused by the focusing lens at a focal plane of the digital recorder to form a spatially low-frequency heterodyne hologram including spatially heterodyne fringes for Fourier analysis which is recorded by the digital recorder, and the computer transforms the recorded spatially low-frequency heterodyne hologram including spatially heterodyne fringes and shifts axes in Fourier space to sit on top of a heterodyne carrier frequency defined by an angle between the reference beam and the object beam and cuts off signals around an original origin before performing the inverse Fourier transform.

Influence of laser beam incidence angle on laser lap welding quality of galvanized steels

NASA Astrophysics Data System (ADS)

Mei, Lifang; Yan, Dongbing; Chen, Genyu; Wang, Zhenhui; Chen, Shuixuan

2017-11-01

Based on the characteristics of laser welded structural parts of auto bodies, the influence of variation in laser beam incidence angle on the lap welding performance of galvanized auto-body sheets was studied. Lap welding tests were carried out on the galvanized sheets for auto-body application at different laser beam incidence angles by using the optimal welding parameters obtained through orthogonal experiment. The effects of incidence angle variation on seam appearance, cross-sectional shape, joint mechanical properties and microstructure of weldments were analyzed. In addition, the main factors influencing the value of incidence angle were investigated. According to the results, the weld seams had a good appearance as well as a fine, and uniform microstructure when the laser beam incidence angle was smaller than the critical incidence angle, and thus they could withstand great tensile and shear loads. Moreover, all tensile-shear specimens were fractured in the base material zone. When the laser beam incidence angle was larger than the critical incidence angle, defects like shrinkage and collapse tended to emerge, thereby resulting in the deteriorated weldability of specimens. Meanwhile, factors like the type and thickness of sheet, weld width as well as inter-sheet gap all had a certain effect on the value of laser beam incidence angle. When the sheet thickness was small and the weld width was narrow, the laser beam incidence angle could be increased appropriately. At the same time, small changes in the inter-sheet gap could greatly impact the value of incidence angle. When the inter-sheet gap was small, the laser beam incidence angle should not be too large.

A reconstruction algorithm for helical CT imaging on PI-planes.

PubMed

Liang, Hongzhu; Zhang, Cishen; Yan, Ming

2006-01-01

In this paper, a Feldkamp type approximate reconstruction algorithm is presented for helical cone-beam Computed Tomography. To effectively suppress artifacts due to large cone angle scanning, it is proposed to reconstruct the object point-wisely on unique customized tilted PI-planes which are close to the data collecting helices of the corresponding points. Such a reconstruction scheme can considerably suppress the artifacts in the cone-angle scanning. Computer simulations show that the proposed algorithm can provide improved imaging performance compared with the existing approximate cone-beam reconstruction algorithms.

Measurement and interpretation of electron angle at mabe beam stop

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

Sanford, T.W.L.; Coleman, P.D.; Poukey, J.W.

1985-10-01

This analysis shows that radiation measurements combined with a sophisticated simulation provides a simple but powerful tool for estimating beam temperature in intense pulsed annular electron-beam accelerators. Specifically, the mean angle of incidence of a 60 kA, 7 MeV annular electron-beam at the beam stop of the MABE accelerator and the transverse beam temperature are determined. The angle is extracted by comparing dose profiles measured downstream of the stop with that expected from a simulation of the electron/photon transport in the stop. By calculating and removing the effect on the trajectories due to the change in electric field near themore » stop, the beam temperature is determined. Such measurements help give insight to beam generation and propagation within the accelerator.« less

Ion-beam nanopatterning: experimental results with chemically-assisted beam

NASA Astrophysics Data System (ADS)

Pochon, Sebastien C. R.

2018-03-01

The need for forming gratings (for example used in VR headsets) in materials such as SiO2 has seen a recent surge in the use of Ion beam etching techniques. However, when using an argon-only beam, the selectivity is limited as it is a physical process. Typically, gases such as CHF3, SF6, O2 and Cl2 can be added to argon in order to increase selectivity; depending on where the gas is injected, the process is known as Reactive Ion Beam Etching (RIBE) or Chemically Assisted Ion Beam Etching (CAIBE). The substrate holder can rotate in order to provide an axisymmetric etch rate profile. It can also be tilted over a range of angles to the beam direction. This enables control over the sidewall profile as well as radial uniformity optimisation. Ion beam directionality in conjunction with variable incident beam angle via platen angle setting enables profile control and feature shaping during nanopatterning. These hardware features unique to the Ion Beam etching methods can be used to create angled etch features. The CAIBE technique is also well suited to laser diode facet etch (for optoelectronic devices); these typically use III-V materials like InP. Here, we report on materials such as SiO2 etched without rotation and at a fixed platen angle allowing the formation of gratings and InP etched at a fixed angle with rotation allowing the formation of nanopillars and laser facets.

A simple three dimensional wide-angle beam propagation method

NASA Astrophysics Data System (ADS)

Ma, Changbao; van Keuren, Edward

2006-05-01

The development of three dimensional (3-D) waveguide structures for chip scale planar lightwave circuits (PLCs) is hampered by the lack of effective 3-D wide-angle (WA) beam propagation methods (BPMs). We present a simple 3-D wide-angle beam propagation method (WA-BPM) using Hoekstra’s scheme along with a new 3-D wave equation splitting method. The applicability, accuracy and effectiveness of our method are demonstrated by applying it to simulations of wide-angle beam propagation and comparing them with analytical solutions.

A simple three dimensional wide-angle beam propagation method.

PubMed

Ma, Changbao; Van Keuren, Edward

2006-05-29

The development of three dimensional (3-D) waveguide structures for chip scale planar lightwave circuits (PLCs) is hampered by the lack of effective 3-D wide-angle (WA) beam propagation methods (BPMs). We present a simple 3-D wide-angle beam propagation method (WA-BPM) using Hoekstra's scheme along with a new 3-D wave equation splitting method. The applicability, accuracy and effectiveness of our method are demonstrated by applying it to simulations of wide-angle beam propagation and comparing them with analytical solutions.

Angular distributions of reflected and refracted relativistic electron beams crossing a thin planar target at a small angle to its surface

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

Serov, A. V., E-mail: serov@x4u.lebedev.ru; Mamonov, I. A.; Kol’tsov, A. V., E-mail: koltsov@x4u.lebedev.ru

2015-10-15

The scattering of electrons by aluminum, copper, and lead foils, as well as by bimetallic aluminum-lead and aluminum-copper foils, has been studied experimentally. A microtron with an energy of particles of 7.4 MeV has been used as a source of electrons. The beam of particles incident on a target at small angles is split into particles reflected from the foil, which constitute a reflected beam, and particles crossing the foil, which constitute a refracted beam. The effect of the material and thickness of the foil, as well as the angle between the initial trajectory of the beam and the planemore » of the target, on the direction of motion and the angular divergence of the beam crossing the foil and the beam reflected from the foil has been analyzed. Furthermore, the effect of the sequence of metal layers in bimetallic films on the angles of refraction and reflection of the beam has been examined.« less

Angle Performance on Optima XE

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

David, Jonathan; Satoh, Shu

2011-01-07

Angle control on high energy implanters is important due to shrinking device dimensions, and sensitivity to channeling at high beam energies. On Optima XE, beam-to-wafer angles are controlled in both the horizontal and vertical directions. In the horizontal direction, the beam angle is measured through a series of narrow slits, and any angle adjustment is made by steering the beam with the corrector magnet. In the vertical direction, the beam angle is measured through a high aspect ratio mask, and any angle adjustment is made by slightly tilting the wafer platen during implant.Using a sensitive channeling condition, we were ablemore » to quantify the angle repeatability of Optima XE. By quantifying the sheet resistance sensitivity to both horizontal and vertical angle variation, the total angle variation was calculated as 0.04 deg. (1{sigma}). Implants were run over a five week period, with all of the wafers selected from a single boule, in order to control for any crystal cut variation.« less

Probe for measurement of velocity and density of vapor in vapor plume

DOEpatents

Berzins, L.V.; Bratton, B.A.; Fuhrman, P.W.

1997-03-11

A probe is disclosed which directs a light beam through a vapor plume in a first direction at a first angle ranging from greater than 0{degree} to less than 90{degree}, reflecting the light beam back through the vapor plume at a 90{degree} angle, and then reflecting the light beam through the vapor plume a third time at a second angle equal to the first angle, using a series of mirrors to deflect the light beam while protecting the mirrors from the vapor plume with shields. The velocity, density, temperature and flow direction of the vapor plume may be determined by a comparison of the energy from a reference portion of the beam with the energy of the beam after it has passed through the vapor plume. 10 figs.

Probe for measurement of velocity and density of vapor in vapor plume

DOEpatents

Berzins, Leon V.; Bratton, Bradford A.; Fuhrman, Paul W.

1997-01-01

A probe which directs a light beam through a vapor plume in a first direction at a first angle ranging from greater than 0.degree. to less than 90.degree., reflecting the light beam back through the vapor plume at a 90.degree. angle, and then reflecting the light beam through the vapor plume a third time at a second angle equal to the first angle, using a series of mirrors to deflect the light beam while protecting the mirrors from the vapor plume with shields. The velocity, density, temperature and flow direction of the vapor plume may be determined by a comparison of the energy from a reference portion of the beam with the energy of the beam after it has passed through the vapor plume.

Measurement and interpretation of electron angle at MABE beam stop

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

Sanford, T.W.L.; Coleman, P.D.; Poukey, J.W.

1985-01-01

This analysis shows that radiation measurements combined with a sophisticated simulation provides a simple but powerful tool for estimating beam temperature in intense pulsed annular electron-beam accelerators. Specifically, the mean angle of incidence of a 60 kA, 7 MeV annular electron-beam at the beam stop of the MABE accelerator and the transverse beam temperature are determined. The angle is extracted by comparing dose profiles measured downstream of the stop with that expected from a simulation of the electron/photon transport in the stop. By calculating and removing the effect on the trajectories due to the change in electric field near themore » stop, the beam temperature is determined. Such measurements help give insight to beam generation and propagation within the accelerator. 9 refs., 6 figs., 1 tab.« less

Energy exchange between a laser beam and charged particles using inverse transition radiation and method for its use

DOEpatents

Kimura, Wayne D.; Romea, Richard D.; Steinhauer, Loren C.

1998-01-01

A method and apparatus for exchanging energy between relativistic charged particles and laser radiation using inverse diffraction radiation or inverse transition radiation. The beam of laser light is directed onto a particle beam by means of two optical elements which have apertures or foils through which the particle beam passes. The two apertures or foils are spaced by a predetermined distance of separation and the angle of interaction between the laser beam and the particle beam is set at a specific angle. The separation and angle are a function of the wavelength of the laser light and the relativistic energy of the particle beam. In a diffraction embodiment, the interaction between the laser and particle beams is determined by the diffraction effect due to the apertures in the optical elements. In a transition embodiment, the interaction between the laser and particle beams is determined by the transition effect due to pieces of foil placed in the particle beam path.

Video sensor with range measurement capability

NASA Technical Reports Server (NTRS)

Howard, Richard T. (Inventor); Briscoe, Jeri M. (Inventor); Corder, Eric L. (Inventor); Broderick, David J. (Inventor)

2008-01-01

A video sensor device is provided which incorporates a rangefinder function. The device includes a single video camera and a fixed laser spaced a predetermined distance from the camera for, when activated, producing a laser beam. A diffractive optic element divides the beam so that multiple light spots are produced on a target object. A processor calculates the range to the object based on the known spacing and angles determined from the light spots on the video images produced by the camera.

Measurement of Rayleigh Wave Beams Using Angle Beam Wedge Transducers as the Transmitter and Receiver with Consideration of Beam Spreading

PubMed Central

Zhang, Shuzeng; Li, Xiongbing; Jeong, Hyunjo

2017-01-01

A theoretical model, along with experimental verification, is developed to describe the generation, propagation and reception of a Rayleigh wave using angle beam wedge transducers. The Rayleigh wave generation process using an angle beam wedge transducer is analyzed, and the actual Rayleigh wave sound source distributions are evaluated numerically. Based on the reciprocity theorem and considering the actual sound source, the Rayleigh wave beams are modeled using an area integral method. The leaky Rayleigh wave theory is introduced to investigate the reception of the Rayleigh wave using the angle beam wedge transducers, and the effects of the wave spreading in the wedge and transducer size are considered in the reception process. The effects of attenuations of the Rayleigh wave and leaky Rayleigh wave are discussed, and the received wave results with different sizes of receivers are compared. The experiments are conducted using two angle beam wedge transducers to measure the Rayleigh wave, and the measurement results are compared with the predictions using different theoretical models. It is shown that the proposed model which considers the wave spreading in both the sample and wedges can be used to interpret the measurements reasonably. PMID:28632183

Measurement of Rayleigh Wave Beams Using Angle Beam Wedge Transducers as the Transmitter and Receiver with Consideration of Beam Spreading.

PubMed

Zhang, Shuzeng; Li, Xiongbing; Jeong, Hyunjo

2017-06-20

A theoretical model, along with experimental verification, is developed to describe the generation, propagation and reception of a Rayleigh wave using angle beam wedge transducers. The Rayleigh wave generation process using an angle beam wedge transducer is analyzed, and the actual Rayleigh wave sound source distributions are evaluated numerically. Based on the reciprocity theorem and considering the actual sound source, the Rayleigh wave beams are modeled using an area integral method. The leaky Rayleigh wave theory is introduced to investigate the reception of the Rayleigh wave using the angle beam wedge transducers, and the effects of the wave spreading in the wedge and transducer size are considered in the reception process. The effects of attenuations of the Rayleigh wave and leaky Rayleigh wave are discussed, and the received wave results with different sizes of receivers are compared. The experiments are conducted using two angle beam wedge transducers to measure the Rayleigh wave, and the measurement results are compared with the predictions using different theoretical models. It is shown that the proposed model which considers the wave spreading in both the sample and wedges can be used to interpret the measurements reasonably.

A BPF-FBP tandem algorithm for image reconstruction in reverse helical cone-beam CT

PubMed Central

Cho, Seungryong; Xia, Dan; Pellizzari, Charles A.; Pan, Xiaochuan

2010-01-01

Purpose: Reverse helical cone-beam computed tomography (CBCT) is a scanning configuration for potential applications in image-guided radiation therapy in which an accurate anatomic image of the patient is needed for image-guidance procedures. The authors previously developed an algorithm for image reconstruction from nontruncated data of an object that is completely within the reverse helix. The purpose of this work is to develop an image reconstruction approach for reverse helical CBCT of a long object that extends out of the reverse helix and therefore constitutes data truncation. Methods: The proposed approach comprises of two reconstruction steps. In the first step, a chord-based backprojection-filtration (BPF) algorithm reconstructs a volumetric image of an object from the original cone-beam data. Because there exists a chordless region in the middle of the reverse helix, the image obtained in the first step contains an unreconstructed central-gap region. In the second step, the gap region is reconstructed by use of a Pack–Noo-formula-based filteredbackprojection (FBP) algorithm from the modified cone-beam data obtained by subtracting from the original cone-beam data the reprojection of the image reconstructed in the first step. Results: The authors have performed numerical studies to validate the proposed approach in image reconstruction from reverse helical cone-beam data. The results confirm that the proposed approach can reconstruct accurate images of a long object without suffering from data-truncation artifacts or cone-angle artifacts. Conclusions: They developed and validated a BPF-FBP tandem algorithm to reconstruct images of a long object from reverse helical cone-beam data. The chord-based BPF algorithm was utilized for converting the long-object problem into a short-object problem. The proposed approach is applicable to other scanning configurations such as reduced circular sinusoidal trajectories. PMID:20175463

A BPF-FBP tandem algorithm for image reconstruction in reverse helical cone-beam CT.

PubMed

Cho, Seungryong; Xia, Dan; Pellizzari, Charles A; Pan, Xiaochuan

2010-01-01

Reverse helical cone-beam computed tomography (CBCT) is a scanning configuration for potential applications in image-guided radiation therapy in which an accurate anatomic image of the patient is needed for image-guidance procedures. The authors previously developed an algorithm for image reconstruction from nontruncated data of an object that is completely within the reverse helix. The purpose of this work is to develop an image reconstruction approach for reverse helical CBCT of a long object that extends out of the reverse helix and therefore constitutes data truncation. The proposed approach comprises of two reconstruction steps. In the first step, a chord-based backprojection-filtration (BPF) algorithm reconstructs a volumetric image of an object from the original cone-beam data. Because there exists a chordless region in the middle of the reverse helix, the image obtained in the first step contains an unreconstructed central-gap region. In the second step, the gap region is reconstructed by use of a Pack-Noo-formula-based filteredback-projection (FBP) algorithm from the modified cone-beam data obtained by subtracting from the original cone-beam data the reprojection of the image reconstructed in the first step. The authors have performed numerical studies to validate the proposed approach in image reconstruction from reverse helical cone-beam data. The results confirm that the proposed approach can reconstruct accurate images of a long object without suffering from data-truncation artifacts or cone-angle artifacts. They developed and validated a BPF-FBP tandem algorithm to reconstruct images of a long object from reverse helical cone-beam data. The chord-based BPF algorithm was utilized for converting the long-object problem into a short-object problem. The proposed approach is applicable to other scanning configurations such as reduced circular sinusoidal trajectories.

The Influence of Inspection Angle, Wave Type and Beam Shape on Signal-to-Noise Ratios in Ultrasonic Pitch-Catch Inspections

NASA Astrophysics Data System (ADS)

Margetan, F. J.; Li, Anxiang; Thompson, R. B.

2007-03-01

Grain noise, which arises from the scattering of sound waves by microstructure, can limit the detection of small internal defects in metal components. Signal-to-noise (S/N) ratios for ultrasonic pitch/catch inspections are primarily determined by three factors: the scattering ability of the defect; the inherent noisiness of the microstructure (per unit volume); and finite-beam effects. An approximate single-scattering model has been formulated which contains terms representing each of these factors. In this paper the model is applied to a representative pitch/catch inspection problem, namely, the detection of a circular crack in a nickel cylinder. The object is to estimate S/N ratios for various choices of the inspection angle and sonic wave types, and to demonstrate how S/N is determined by the interplay of the defect, microstructure, and finite-beam factors. We also explore how S/N is influenced by the sizes, shapes, and orientations of the transmitter and receiver sound beams.

Ultra-fast fluence optimization for beam angle selection algorithms

NASA Astrophysics Data System (ADS)

Bangert, M.; Ziegenhein, P.; Oelfke, U.

2014-03-01

Beam angle selection (BAS) including fluence optimization (FO) is among the most extensive computational tasks in radiotherapy. Precomputed dose influence data (DID) of all considered beam orientations (up to 100 GB for complex cases) has to be handled in the main memory and repeated FOs are required for different beam ensembles. In this paper, the authors describe concepts accelerating FO for BAS algorithms using off-the-shelf multiprocessor workstations. The FO runtime is not dominated by the arithmetic load of the CPUs but by the transportation of DID from the RAM to the CPUs. On multiprocessor workstations, however, the speed of data transportation from the main memory to the CPUs is non-uniform across the RAM; every CPU has a dedicated memory location (node) with minimum access time. We apply a thread node binding strategy to ensure that CPUs only access DID from their preferred node. Ideal load balancing for arbitrary beam ensembles is guaranteed by distributing the DID of every candidate beam equally to all nodes. Furthermore we use a custom sorting scheme of the DID to minimize the overall data transportation. The framework is implemented on an AMD Opteron workstation. One FO iteration comprising dose, objective function, and gradient calculation takes between 0.010 s (9 beams, skull, 0.23 GB DID) and 0.070 s (9 beams, abdomen, 1.50 GB DID). Our overall FO time is < 1 s for small cases, larger cases take ~ 4 s. BAS runs including FOs for 1000 different beam ensembles take ~ 15-70 min, depending on the treatment site. This enables an efficient clinical evaluation of different BAS algorithms.

Velocity measurement by vibro-acoustic Doppler.

PubMed

Nabavizadeh, Alireza; Urban, Matthew W; Kinnick, Randall R; Fatemi, Mostafa

2012-04-01

We describe the theoretical principles of a new Doppler method, which uses the acoustic response of a moving object to a highly localized dynamic radiation force of the ultrasound field to calculate the velocity of the moving object according to Doppler frequency shift. This method, named vibro-acoustic Doppler (VAD), employs two ultrasound beams separated by a slight frequency difference, Δf, transmitting in an X-focal configuration. Both ultrasound beams experience a frequency shift because of the moving objects and their interaction at the joint focal zone produces an acoustic frequency shift occurring around the low-frequency (Δf) acoustic emission signal. The acoustic emission field resulting from the vibration of the moving object is detected and used to calculate its velocity. We report the formula that describes the relation between Doppler frequency shift of the emitted acoustic field and the velocity of the moving object. To verify the theory, we used a string phantom. We also tested our method by measuring fluid velocity in a tube. The results show that the error calculated for both string and fluid velocities is less than 9.1%. Our theory shows that in the worst case, the error is 0.54% for a 25° angle variation for the VAD method compared with an error of -82.6% for a 25° angle variation for a conventional continuous wave Doppler method. An advantage of this method is that, unlike conventional Doppler, it is not sensitive to angles between the ultrasound beams and direction of motion.

Effect of geometrical features various objects on the data quality obtained with measured by TLS

NASA Astrophysics Data System (ADS)

Pawłowicz, J. A.

2017-08-01

Collecting data on different building structures using Terrestrial Laser Scanning (TLS) has become in recent years a very popular due to minimize the time required to complete the task as compared to traditional methods. Technical parameters of 3D scanning devices (digitizers) are increasingly being improved, and the accuracy of the data collected allows you to play not only the geometry of an existing object in a digital image, but also enables the assessment of his condition. This is possible thanks to the digitalization of existing objects e.g., a 3D laser scanner, with which is obtained a digital data base is presented in the form of a cloud of points and by using reverse engineering. Measurements using laser scanners depends to a large extent, on the quality of the returning beam reflected from the target surface, towards the receiver. High impact on the strength and quality of the beam returning to the geometric features of the object. These properties may contribute to the emergence of some, sometimes even serious errors during scanning of various shapes. The study defined the effect of the laser beam distortion during the measurement objects with the same material but with different geometrical features on their three-dimensional imaging obtained from measurements made using TLS. We present the problem of data quality, dependent on the deflection of the beam intensity and shape of the object selected examples. The knowledge of these problems allows to obtain valuable data necessary for the implementation of digitization and the visualization of virtually any building structure made of any materials. The studies has been proven that the increase in the density of scanning does not affect the values of mean square error. The increase in the angle of incidence of the beam onto a flat surface, however, causes a decrease in the intensity of scattered radiation that reaches the receiver. The article presents an analysis of the laser beam reflected from broken at different angles surface. Scan quality was assessed using check the density of the number of points on the test object’s surface.

Propagation of rotational Risley-prism-array-based Gaussian beams in turbulent atmosphere

NASA Astrophysics Data System (ADS)

Chen, Feng; Ma, Haotong; Dong, Li; Ren, Ge; Qi, Bo; Tan, Yufeng

2018-03-01

Limited by the size and weight of prism and optical assembling, Rotational Risley-prism-array system is a simple but effective way to realize high power and superior beam quality of deflecting laser output. In this paper, the propagation of the rotational Risley-prism-array-based Gaussian beam array in atmospheric turbulence is studied in detail. An analytical expression for the average intensity distribution at the receiving plane is derived based on nonparaxial ray tracing method and extended Huygens-Fresnel principle. Power in the diffraction-limited bucket is chosen to evaluate beam quality. The effect of deviation angle, propagation distance and intensity of turbulence on beam quality is studied in detail by quantitative simulation. It reveals that with the propagation distance increasing, the intensity distribution gradually evolves from multiple-petal-like shape into the pattern that contains one main-lobe in the center with multiple side-lobes in weak turbulence. The beam quality of rotational Risley-prism-array-based Gaussian beam array with lower deviation angle is better than its counterpart with higher deviation angle when propagating in weak and medium turbulent (i.e. Cn2 < 10-13m-2/3), the beam quality of higher deviation angle arrays degrades faster as the intensity of turbulence gets stronger. In the case of propagating in strong turbulence, the long propagation distance (i.e. z > 10km ) and deviation angle have no influence on beam quality.

Pyramid beam splitter

DOEpatents

McKeown, Mark H.; Beason, Steven C.; Fairer, George

1992-01-01

The apparatus of the present invention provides means for obtaining accurate, dependable, measurement of bearings and directions for geologic mapping in subterranean shafts, such as, for example, nuclear waste storage investigations. In operation, a laser beam is projected along a reference bearing. A pyramid is mounted such that the laser beam is parallel to the pyramid axis and can impinge on the apex of the pyramid thus splitting the beam several ways into several beams at right angles to each other and at right angles to the reference beam. The pyramid is also translatable and rotatable in a plane perpendicular to the reference beam.

SU-E-T-230: Creating a Large Number of Focused Beams with Variable Patient Head Tilt to Improve Dose Fall-Off for Brain Radiosurgery

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

Chiu, J; Ma, L

2015-06-15

Purpose: To develop a treatment delivery and planning strategy by increasing the number of beams to minimize dose to brain tissue surrounding a target, while maximizing dose coverage to the target. Methods: We analyzed 14 different treatment plans via Leksell PFX and 4C. For standardization, single tumor cases were chosen. Original treatment plans were compared with two optimized plans. The number of beams was increased in treatment plans by varying tilt angles of the patient head, while maintaining original isocenter and the beam positions in the x-, y- and z-axes, collimator size, and beam blocking. PFX optimized plans increased beammore » numbers with three pre-set tilt angles, 70, 90, 110, and 4C optimized plans increased beam numbers with tilt angles increasing arbitrarily from range of 30 to 150 degrees. Optimized treatment plans were compared dosimetrically with original treatment plans. Results: Comparing total normal tissue isodose volumes between original and optimized plans, the low-level percentage isodose volumes decreased in all plans. Despite the addition of multiple beams up to a factor of 25, beam-on times for 1 tilt angle versus 3 or more tilt angles were comparable (<1 min.). In 64% (9/14) of the studied cases, the volume percentage decrease by >5%, with the highest value reaching 19%. The addition of more tilt angles correlates to a greater decrease in normal brain irradiated volume. Selectivity and coverage for original and optimized plans remained comparable. Conclusion: Adding large number of additional focused beams with variable patient head tilt shows improvement for dose fall-off for brain radiosurgery. The study demonstrates technical feasibility of adding beams to decrease target volume.« less

A surrogate-based metaheuristic global search method for beam angle selection in radiation treatment planning.

PubMed

Zhang, H H; Gao, S; Chen, W; Shi, L; D'Souza, W D; Meyer, R R

2013-03-21

An important element of radiation treatment planning for cancer therapy is the selection of beam angles (out of all possible coplanar and non-coplanar angles in relation to the patient) in order to maximize the delivery of radiation to the tumor site and minimize radiation damage to nearby organs-at-risk. This category of combinatorial optimization problem is particularly difficult because direct evaluation of the quality of treatment corresponding to any proposed selection of beams requires the solution of a large-scale dose optimization problem involving many thousands of variables that represent doses delivered to volume elements (voxels) in the patient. However, if the quality of angle sets can be accurately estimated without expensive computation, a large number of angle sets can be considered, increasing the likelihood of identifying a very high quality set. Using a computationally efficient surrogate beam set evaluation procedure based on single-beam data extracted from plans employing equallyspaced beams (eplans), we have developed a global search metaheuristic process based on the nested partitions framework for this combinatorial optimization problem. The surrogate scoring mechanism allows us to assess thousands of beam set samples within a clinically acceptable time frame. Tests on difficult clinical cases demonstrate that the beam sets obtained via our method are of superior quality.

A surrogate-based metaheuristic global search method for beam angle selection in radiation treatment planning

PubMed Central

Zhang, H H; Gao, S; Chen, W; Shi, L; D’Souza, W D; Meyer, R R

2013-01-01

An important element of radiation treatment planning for cancer therapy is the selection of beam angles (out of all possible coplanar and non-coplanar angles in relation to the patient) in order to maximize the delivery of radiation to the tumor site and minimize radiation damage to nearby organs-at-risk. This category of combinatorial optimization problem is particularly difficult because direct evaluation of the quality of treatment corresponding to any proposed selection of beams requires the solution of a large-scale dose optimization problem involving many thousands of variables that represent doses delivered to volume elements (voxels) in the patient. However, if the quality of angle sets can be accurately estimated without expensive computation, a large number of angle sets can be considered, increasing the likelihood of identifying a very high quality set. Using a computationally efficient surrogate beam set evaluation procedure based on single-beam data extracted from plans employing equally-spaced beams (eplans), we have developed a global search metaheuristic process based on the Nested Partitions framework for this combinatorial optimization problem. The surrogate scoring mechanism allows us to assess thousands of beam set samples within a clinically acceptable time frame. Tests on difficult clinical cases demonstrate that the beam sets obtained via our method are superior quality. PMID:23459411

Variable laser attenuator

DOEpatents

Foltyn, Stephen R.

1988-01-01

The disclosure relates to low loss, high power variable attenuators comprng one or more transmissive and/or reflective multilayer dielectric filters. The attenuator is particularly suitable to use with unpolarized lasers such as excimer lasers. Beam attenuation is a function of beam polarization and the angle of incidence between the beam and the filter and is controlled by adjusting the angle of incidence the beam makes to the filter or filters. Filters are selected in accordance with beam wavelength.

Continuous angle steering of an optically- controlled phased array antenna based on differential true time delay constituted by micro-optical components.

PubMed

Wang, Jian; Hou, Peipei; Cai, Haiwen; Sun, Jianfeng; Wang, Shunan; Wang, Lijuan; Yang, Fei

2015-04-06

We propose an optically controlled phased array antenna (PAA) based on differential true time delay constructed optical beamforming network (OBFN). Differential true time delay is realized by stack integrated micro-optical components. Optically-controlled angle steering of radio frequency (RF) beams are realized and demonstrated by this configuration. Experimental results demonstrate that OBFN based PAA can accomplish RF-independent broadband beam steering without beam squint effect and can achieve continuous angle steering. In addition, multi-beams for different steering angles are acquired synchronously.

Large incidence angle and defocus influence cat's eye retro-reflector

NASA Astrophysics Data System (ADS)

Zhang, Lai-xian; Sun, Hua-yan; Zhao, Yan-zhong; Yang, Ji-guang; Zheng, Yong-hui

2014-11-01

Cat's eye lens make the laser beam retro-reflected exactly to the opposite direction of the incidence beam, called cat's eye effect, which makes rapid acquiring, tracking and pointing of free space optical communication possible. Study the influence of cat's eye effect to cat's eye retro-reflector at large incidence angle is useful. This paper analyzed the process of how the incidence angle and focal shit affect effective receiving area, retro-reflected beam divergence angle, central deviation of cat's eye retro-reflector at large incidence angle and cat's eye effect factor using geometrical optics method, and presented the analytic expressions. Finally, numerical simulation was done to prove the correction of the study. The result shows that the efficiency receiving area of cat's eye retro-reflector is mainly affected by incidence angle when the focal shift is positive, and it decreases rapidly when the incidence angle increases; the retro-reflected beam divergence and central deviation is mainly affected by focal shift, and within the effective receiving area, the central deviation is smaller than beam divergence in most time, which means the incidence beam can be received and retro-reflected to the other terminal in most time. The cat's eye effect factor gain is affected by both incidence angle and focal shift.

Remote steering of laser beams by radar- and laser-induced refractive-index gradients in the atmosphere Remote steering of laser beams

NASA Astrophysics Data System (ADS)

Zheltikov, A. M.; Shneider, M. N.; Voronin, A. A.; Sokolov, A. V.; Scully, M. O.

2012-01-01

Refractive-index gradients induced in the atmospheric air by properly tailored laser and microwave fields are shown to enable a remote steering of laser beams. Heating-assisted modulation of the refractive index of the air by microwave radiation is shown to support small-angle laser-beam bending with bending angles on the order of 10-2. Ionization of the atmospheric air by dyads of femto- and nanosecond laser pulses, on the other hand, can provide beam deflection angles in excess of π/5, offering an attractive strategy for radiation transfer, free-space communications, and laser-based standoff detection.

Analyzation of photopolymer materials shrunken influence for thick hologram gratings

NASA Astrophysics Data System (ADS)

Li, Zhenzhen; Xiao, Xue; Chen, Wei; Kang, Guoguo; Huang, Yong; Tan, Xiaodi

2016-09-01

The photopolymer materials are good media to record thick hologram gratings, because photopolymer materials have high resolution, low cost, simple process technology and so on. According to coupled wave theory for thick hologram gratings, we know that the same object beam can be reconstructed if the same reference beam is used to retrieve a thick hologram grating. However, the shrinkage always occurs in the photopolymer materials because of environment temperature, humidity, vibration etc. For instance, the same object beam cannot be reconstructed even the same reference beam to be used. In this paper, we will analysis the shrinkage influence of photopolymer materials for thick hologram gratings. We divide the photopolymer materials into several geometry layers, and analysis the reconstructed characteristics separately basing on coupled wave theory of Kogelnik. Through gradually continuous changing the angle between gratings and the border (we call it slant angle), we can build the geometry model of gratings bending caused by shrinkage of materials. We calculate wave complex amplitude diffracted from every layer, and superpose them to compute the total diffraction efficiency. We simulate above methods to obtain the curve of diffraction efficiency with reconstruction wavelength by using Matlab software. Comparing the simulated results with the experiments results, we can deduce the probable situation of thick hologram gratings bending after photopolymer materials shrink.

In-situ determination of energy species yields of intense particle beams

DOEpatents

Kugel, H.W.; Kaita, R.

1983-09-26

Objects of the present invention are provided for a particle beam having a full energy component at least as great as 25 keV, which is directed onto a beamstop target, such that Rutherford backscattering, preferably near-surface backscattering occurs. The geometry, material composition and impurity concentration of the beam stop are predetermined, using any suitable conventional technique. The energy-yield characteristic response of backscattered particles is measured over a range of angles using a fast ion electrostatic analyzer having a microchannel plate array at its focal plane. The knee of the resulting yield curve, on a plot of yield versus energy, is analyzed to determine the energy species components of various beam particles having the same mass.

Variable laser attenuator

DOEpatents

Foltyn, S.R.

1987-05-29

The disclosure relates to low loss, high power variable attenuators comprising one or more transmissive and/or reflective multilayer dielectric filters. The attenuator is particularly suitable to use with unpolarized lasers such as excimer lasers. Beam attenuation is a function of beam polarization and the angle of incidence between the beam and the filter and is controlled by adjusting the angle of incidence the beam makes to the filter or filters. Filters are selected in accordance with beam wavelength. 9 figs.

Three types of planar structure microspring electro-thermal actuators with insulating beam constraints

NASA Astrophysics Data System (ADS)

Luo, J. K.; Flewitt, A. J.; Spearing, S. M.; Fleck, N. A.; Milne, W. I.

2005-08-01

A new concept of using an electrically insulating beam as a constraint is proposed to construct planar spring-like electro-thermal actuators with large displacements. On the basis of this concept, three types of microspring actuators with multi-chevron structures and constraint beams are introduced. The constraint beams in one type (the spring) of these devices are horizontally positioned to restrict the expansion of the active arms in the x-direction, and to produce a displacement in the y-direction only. In the other two types of actuators (the deflector and the contractor), the constraint beams are positioned parallel to the active arms. When the constraint beams are on the inner side of the active arms, the actuator produces an outward deflection in the y-direction. When they are on the outside of the active arms, the actuator produces an inward contraction. Finite-element analysis was used to model the performances. The simulation shows that the displacements of these microspring actuators are all proportional to the number of the chevron sections in series, thus achieving superior displacements to alternative actuators. The displacement of a spring actuator strongly depends on the beam angle, and decreases with increasing the beam angle, the deflector is insensitive to the beam angle, while the displacement of a contractor actuator increases with the beam angle.

Deformation analysis of tilted primary mirror for an off-axis beam compressor

NASA Astrophysics Data System (ADS)

Clark, James H., III; Penado, F. Ernesto; Dugdale, Joel

2011-09-01

The Navy Prototype Optical Interferometer (NPOI), located near Flagstaff, Arizona, is a ground-based interferometer that collects and transports stellar radiation from six primary flat collectors, known as siderostats, through a common vacuum relay system to a beam combiner where the beams are combined, fringes are obtained and modulated, and data are recorded for further analysis. The current number of observable stellar objects can increase from 6,000 to approximately 47,000 with the addition of down-tilting beam compressors in the optical train. The increase in photon collection area from the beam compressors opens the sky to many additional and fainter stars. The siderostats are capable of redirecting 35 cm stellar beams into the vacuum relay system. Sans beam compressors, any portion of the beam greater than the capacity of the vacuum transport system, 12.5 cm, is wasted. Engineering analysis of previously procured as-built beam compressor optics show the maximum allowable primary mirror surface sag, resulting in λ/10 peak-to-valley wavefront aberration, occurs at 2.8° down-tilt angle. At the NPOI operational down-tilt angle of 20° the wavefront aberration reduces to an unacceptable λ/4. A design modification concept that reduces tilt-induced sag was investigated. Four outwardly applied 4-lb forces on the rear surface of the mirror reduce the sag from 155 nm to 32 nm at 20° down-tilt and reduce peak-to-valley wavefront deviation to λ/8.6. This preliminary effort indicates that this solution path is a viable and economic way to repair an expensive set of optical components. However, it requires further work to optimize the locations, magnitudes, and quantity of the forces within this system and their influence on the mirror surface.

Measurement and interpretation of electron angle at MABE beam stop

NASA Astrophysics Data System (ADS)

Sanford, T. W. L.; Coleman, P. D.; Poukey, J. W.

1985-02-01

The mean angle of incidence at the beam stop of a 60 kA, 7 MV annular electron beam, in the 20 kG guide field of the MABE accelerator, was determined. Radiation dose measured in TLD arrays mounted downstream of the stop is compared with the radiation dose expected using a CYLTRAN Monte Carlo simulation of the electron/photon transport in the stop as a function of incident angles and energies. All radiation profiles measured are well fit, if the electrons are assumed to be incident with a polar angle theta of 15(0) + or - 2(0). A comparison of theta with that expected from the Adler-Miller model, and a MAGIC code simulation of beam behavior at the stop enables the mean transverse beam velocity to be estimated.

Measurement of electron angle at MABE beam stop

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

Sanford, T.W.L.; Coleman, P.D.; Poukey, J.W.

1984-01-01

The mean angle of incidence at the beam stop of a 60 KA, 7 MV annular electron beam, in the 20 kg guide field of the MABE accelerator, is determined. Radiation measured in TLD arrays mounted downstream of the stop is compared with the radiation expected using a CYLTRAN Monte Carlo simulation of the electron/photon transport in the stop as a function of incident angles and energies. All radiation profiles measured are well fit, if the electrons are assumed to be incident with a polar angle theta of 15/sup 0/ +- 2/sup 0/. Comparing theta with that expected from themore » Adler-Miller model, and a MAGIC code simulation of beam behavior at the stop enables the mean transverse beam velocity to be estimated.« less

An orthogonal return method for linearly polarized beam based on the Faraday effect and its application in interferometer

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

Chen, Benyong, E-mail: chenby@zstu.edu.cn; Zhang, Enzheng; Yan, Liping

2014-10-15

Correct return of the measuring beam is essential for laser interferometers to carry out measurement. In the actual situation, because the measured object inevitably rotates or laterally moves, not only the measurement accuracy will decrease, or even the measurement will be impossibly performed. To solve this problem, a novel orthogonal return method for linearly polarized beam based on the Faraday effect is presented. The orthogonal return of incident linearly polarized beam is realized by using a Faraday rotator with the rotational angle of 45°. The optical configuration of the method is designed and analyzed in detail. To verify its practicabilitymore » in polarization interferometry, a laser heterodyne interferometer based on this method was constructed and precision displacement measurement experiments were performed. These results show that the advantage of the method is that the correct return of the incident measuring beam is ensured when large lateral displacement or angular rotation of the measured object occurs and then the implementation of interferometric measurement can be ensured.« less

Laser scanning confocal microscope with programmable amplitude, phase, and polarization of the illumination beam.

PubMed

Boruah, B R; Neil, M A A

2009-01-01

We describe the design and construction of a laser scanning confocal microscope with programmable beam forming optics. The amplitude, phase, and polarization of the laser beam used in the microscope can be controlled in real time with the help of a liquid crystal spatial light modulator, acting as a computer generated hologram, in conjunction with a polarizing beam splitter and two right angled prisms assembly. Two scan mirrors, comprising an on-axis fast moving scan mirror for line scanning and an off-axis slow moving scan mirror for frame scanning, configured in a way to minimize the movement of the scanned beam over the pupil plane of the microscope objective, form the XY scan unit. The confocal system, that incorporates the programmable beam forming unit and the scan unit, has been implemented to image in both reflected and fluorescence light from the specimen. Efficiency of the system to programmably generate custom defined vector beams has been demonstrated by generating a bottle structured focal volume, which in fact is the overlap of two cross polarized beams, that can simultaneously improve both the lateral and axial resolutions if used as the de-excitation beam in a stimulated emission depletion confocal microscope.

Two-beam pumped cascaded four-wave-mixing process for producing multiple-beam quantum correlation

NASA Astrophysics Data System (ADS)

Liu, Shengshuai; Wang, Hailong; Jing, Jietai

2018-04-01

We propose a two-beam pumped cascaded four-wave-mixing (CFWM) scheme with a double-Λ energy-level configuration in 85Rb vapor cell and experimentally observe the emission of up to 10 quantum correlated beams from such CFWM scheme. During this process, the seed beam is amplified; four new signal beams and five idler beams are generated. The 10 beams show strong quantum correlation which is characterized by the intensity-difference squeezing of about -6.7 ±0.3 dB. Then, by altering the angle between the two pump beams, we observe the notable transition of the number of the output beams from 10 to eight, and even to six. We find that both the number of the output quantum correlated beams and their degree of quantum correlation from such two-beam pumped CFWM scheme increase with the decrease of the angle between the two pump beams. Such system may find potential applications in quantum information and quantum metrology.

Depth-encoded dual beam phase-resolved Doppler OCT for Doppler-angle-independent flow velocity measurement

NASA Astrophysics Data System (ADS)

Qian, Jie; Cheng, Wei; Cao, Zhaoyuan; Chen, Xinjian; Mo, Jianhua

2017-02-01

Phase-resolved Doppler optical coherence tomography (PR-D-OCT) is a functional OCT imaging technique that can provide high-speed and high-resolution depth-resolved measurement on flow in biological materials. However, a common problem with conventional PR-D-OCT is that this technique often measures the flow motion projected onto the OCT beam path. In other words, it needs the projection angle to extract the absolute velocity from PR-D-OCT measurement. In this paper, we proposed a novel dual-beam PR-D-OCT method to measure absolute flow velocity without separate measurement on the projection angle. Two parallel light beams are created in sample arm and focused into the sample at two different incident angles. The images produced by these two beams are encoded to different depths in single B-scan. Then the Doppler signals picked up by the two beams together with the incident angle difference can be used to calculate the absolute velocity. We validated our approach in vitro on an artificial flow phantom with our home-built 1060 nm swept source OCT. Experimental results demonstrated that our method can provide an accurate measurement of absolute flow velocity with independency on the projection angle.

Noncoplanar Beam Angle Class Solutions to Replace Time-Consuming Patient-Specific Beam Angle Optimization in Robotic Prostate Stereotactic Body Radiation Therapy

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

Rossi, Linda, E-mail: l.rossi@erasmusmc.nl; Breedveld, Sebastiaan; Aluwini, Shafak

Purpose: To investigate development of a recipe for the creation of a beam angle class solution (CS) for noncoplanar prostate stereotactic body radiation therapy to replace time-consuming individualized beam angle selection (iBAS) without significant loss in plan quality, using the in-house “Erasmus-iCycle” optimizer for fully automated beam profile optimization and iBAS. Methods and Materials: For 30 patients, Erasmus-iCycle was first used to generate 15-, 20-, and 25-beam iBAS plans for a CyberKnife equipped with a multileaf collimator. With these plans, 6 recipes for creation of beam angle CSs were investigated. Plans of 10 patients were used to create CSs based on themore » recipes, and the other 20 to independently test them. For these tests, Erasmus-iCycle was also used to generate intensity modulated radiation therapy plans for the fixed CS beam setups. Results: Of the tested recipes for CS creation, only 1 resulted in 15-, 20-, and 25-beam noncoplanar CSs without plan deterioration compared with iBAS. For the patient group, mean differences in rectum D{sub 1cc}, V{sub 60GyEq}, V{sub 40GyEq}, and D{sub mean} between 25-beam CS plans and 25-beam plans generated with iBAS were 0.2 ± 0.4 Gy, 0.1% ± 0.2%, 0.2% ± 0.3%, and 0.1 ± 0.2 Gy, respectively. Differences between 15- and 20-beam CS and iBAS plans were also negligible. Plan quality for CS plans relative to iBAS plans was also preserved when narrower planning target volume margins were arranged and when planning target volume dose inhomogeneity was decreased. Using a CS instead of iBAS reduced the computation time by a factor of 14 to 25, mainly depending on beam number, without loss in plan quality. Conclusions: A recipe for creation of robust beam angle CSs for robotic prostate stereotactic body radiation therapy has been developed. Compared with iBAS, computation times decreased by a factor 14 to 25. The use of a CS may avoid long planning times without losses in plan quality.« less

Optical activity via Kerr nonlinearity in a spinning chiral medium

NASA Astrophysics Data System (ADS)

Khan, Anwar Ali; Bacha, Bakht Amin; Khan, Rahmat Ali

2016-11-01

Optical activity is investigated in a chiral medium by employing the four level cascade atomic model, in which the optical responses of the atomic medium are studied with Kerr nonlinearity. Light entering into a chiral medium splits into circular birefringent beams. The angle of divergence between the circular birefringent beams and the polarization states of the two light beams is manipulated with Kerr nonlinearity. In the stationary chiral medium the angle of divergence between the circular birefringent beams is calculated to be 1.3 radian. Furthermore, circular birefringence is optically controlled in a spinning chiral medium, where the maximum rotary photon drag angle for left (right) circularly polarized beam is ±1.1 (±1.5) microradian. The change in the angle of divergence between circular birefringent beams by rotary photon drag is calculated to be 0.4 microradian. The numerical results may help to understand image designing, image coding, discovery of photonic crystals and optical sensing technology.

Measurement and interpretation of electron angle at MABE beam stop

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

Sanford, T.W.L.; Coleman, P.D.; Poukey, J.W.

1985-02-01

The mean angle of incidence at the beam stop of a 60 kA, 7 MV annular electron beam, in the 20 kG guide field of the MABE accelerator, is determined. Radiation dose measured in TLD arrays mounted downstream of the stop is compared with the radiation dose expected using a CYLTRAN Monte Carlo simulation of the electron/photon transport in the stop as a function of incident angles and energies. All radiation profiles measured are well fit, if the electrons are assumed to be incident with a polar angle theta of 15/sup 0/ +- 2/sup 0/. Comparing this theta with thatmore » expected from the Adler-Miller model, and a MAGIC code simulation of beam behavior at the stop enables the mean transverse beam velocity to be estimated.« less

Aerodynamic Characteristics of a Flying-Boat Hull Having a Length-Beam Ratio of 15, TED No. NACA 2206

NASA Technical Reports Server (NTRS)

Riebe, John M.; Naeseth, Rodger L.

1951-01-01

An investigation was made in the Langley 300 MPH 7- by 10-foot tunnel to determine the aerodynamic characteristics of a flying-boat hull of a length-beam ratio of 15 in the presence of a wing. The investigation was an extension of previous tests made on hulls of length-beam ratios of 6, 9, and 12; these hulls were designed to have approximately the same hydrodynamic performance with respect to spray and resistance characteristics. Comparison with the previous investigation at lower length-beam ratios indicated a reduction in minimum drag coefficients of 0.0006 (10 peroent)with fixed transition when the length-beam ratio was extended from 12 to 15. As with the hulls of lower length-beam ratio, the drag reduction with a length-beam ratio of 15 occurred throughout the range of angle of attack tested and the angle of attack for minimum drag was in the range from 2deg to 3deg. Increasing the length-beam ratio from 12 to 15 reduced the hull longitudinal instability by an mount corresponding to an aerodynamic-center shift of about 1/2 percent of the mean aerodynamic chord of the hypothetical flying boat. At an angle of attack of 2deg, the value of the variation of yawing-moment coefficient with angle of yaw for a length-beam ratio of 15 was 0.00144, which was 0.00007 larger than the value for a length-beam ratio of 12.

Ultra-high resolution computed tomography imaging

DOEpatents

Paulus, Michael J.; Sari-Sarraf, Hamed; Tobin, Jr., Kenneth William; Gleason, Shaun S.; Thomas, Jr., Clarence E.

2002-01-01

A method for ultra-high resolution computed tomography imaging, comprising the steps of: focusing a high energy particle beam, for example x-rays or gamma-rays, onto a target object; acquiring a 2-dimensional projection data set representative of the target object; generating a corrected projection data set by applying a deconvolution algorithm, having an experimentally determined a transfer function, to the 2-dimensional data set; storing the corrected projection data set; incrementally rotating the target object through an angle of approximately 180.degree., and after each the incremental rotation, repeating the radiating, acquiring, generating and storing steps; and, after the rotating step, applying a cone-beam algorithm, for example a modified tomographic reconstruction algorithm, to the corrected projection data sets to generate a 3-dimensional image. The size of the spot focus of the beam is reduced to not greater than approximately 1 micron, and even to not greater than approximately 0.5 microns.

Neutral particle beam sensing and steering

DOEpatents

Maier, II, William B.; Cobb, Donald D.; Robiscoe, Richard T.

1991-01-01

The direction of a neutral particle beam (NPB) is determined by detecting Ly.alpha. radiation emitted during motional quenching of excited H(2S) atoms in the beam during movement of the atoms through a magnetic field. At least one detector is placed adjacent the beam exit to define an optical axis that intercepts the beam at a viewing angle to include a volume generating a selected number of photons for detection. The detection system includes a lens having an area that is small relative to the NPB area and a pixel array located in the focal plane of the lens. The lens viewing angle and area pixel array are selected to optimize the beam tilt sensitivity. In one embodiment, two detectors are placed coplanar with the beam axis to generate a difference signal that is insensitive to beam variations other than beam tilt.

A BPF-FBP tandem algorithm for image reconstruction in reverse helical cone-beam CT

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

Cho, Seungryong; Xia, Dan; Pellizzari, Charles A.

2010-01-15

Purpose: Reverse helical cone-beam computed tomography (CBCT) is a scanning configuration for potential applications in image-guided radiation therapy in which an accurate anatomic image of the patient is needed for image-guidance procedures. The authors previously developed an algorithm for image reconstruction from nontruncated data of an object that is completely within the reverse helix. The purpose of this work is to develop an image reconstruction approach for reverse helical CBCT of a long object that extends out of the reverse helix and therefore constitutes data truncation. Methods: The proposed approach comprises of two reconstruction steps. In the first step, amore » chord-based backprojection-filtration (BPF) algorithm reconstructs a volumetric image of an object from the original cone-beam data. Because there exists a chordless region in the middle of the reverse helix, the image obtained in the first step contains an unreconstructed central-gap region. In the second step, the gap region is reconstructed by use of a Pack-Noo-formula-based filteredbackprojection (FBP) algorithm from the modified cone-beam data obtained by subtracting from the original cone-beam data the reprojection of the image reconstructed in the first step. Results: The authors have performed numerical studies to validate the proposed approach in image reconstruction from reverse helical cone-beam data. The results confirm that the proposed approach can reconstruct accurate images of a long object without suffering from data-truncation artifacts or cone-angle artifacts. Conclusions: They developed and validated a BPF-FBP tandem algorithm to reconstruct images of a long object from reverse helical cone-beam data. The chord-based BPF algorithm was utilized for converting the long-object problem into a short-object problem. The proposed approach is applicable to other scanning configurations such as reduced circular sinusoidal trajectories.« less

SU-F-T-177: Impacts of Gantry Angle Dependent Scanning Beam Properties for Proton Treatment

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

Lin, Y; Clasie, B; Lu, H

Purpose: In pencil beam scanning (PBS), the delivered spot MU, position and size are slightly different at different gantry angles. We investigated the level of delivery uncertainty at different gantry angles through a log file analysis. Methods: 34 PBS fields covering full 360 degrees gantry angle spread were collected retrospectively from 28 patients treated at our institution. All fields were delivered at zero gantry angle and the prescribed gantry angle, and measured at isocenter with the MatriXX 2D array detector at the prescribed gantry angle. The machine log files were analyzed to extract the delivered MU per spot and themore » beam position from the strip ionization chambers in the treatment nozzle. The beam size was separately measured as a function of gantry angle and beam energy. Using this information, the dose was calculated in a water phantom at both gantry angles and compared to the measurement using the 3D γ-index at 2mm/2%. Results: The spot-by-spot difference between the beam position in the log files from the delivery at the two gantry angles has a mean of 0.3 and 0.4 mm and a standard deviation of 0.6 and 0.7 mm for × and y directions, respectively. Similarly, the spot-by-spot difference between the MU in the log files from the delivery at the two gantry angles has a mean 0.01% and a standard deviation of 0.7%. These small deviations lead to an excellent agreement in dose calculations with an average γ pass rate for all fields being approximately 99.7%. When each calculation is compared to the measurement, a high correlation in γ was also found. Conclusion: Using machine logs files, we verified that PBS beam delivery at different gantry angles are sufficiently small and the planned spot position and MU. This study brings us one step closer to simplifying our patient-specific QA.« less

Beam position reconstruction for the g2p experiment in Hall A at Jefferson lab

NASA Astrophysics Data System (ADS)

Zhu, Pengjia; Allada, Kalyan; Allison, Trent; Badman, Toby; Camsonne, Alexandre; Chen, Jian-ping; Cummings, Melissa; Gu, Chao; Huang, Min; Liu, Jie; Musson, John; Slifer, Karl; Sulkosky, Vincent; Ye, Yunxiu; Zhang, Jixie; Zielinski, Ryan

2016-02-01

Beam-line equipment was upgraded for experiment E08-027 (g2p) in Hall A at Jefferson Lab. Two beam position monitors (BPMs) were necessary to measure the beam position and angle at the target. A new BPM receiver was designed and built to handle the low beam currents (50-100 nA) used for this experiment. Two new super-harps were installed for calibrating the BPMs. In addition to the existing fast raster system, a slow raster system was installed. Before and during the experiment, these new devices were tested and debugged, and their performance was also evaluated. In order to achieve the required accuracy (1-2 mm in position and 1-2 mrad in angle at the target location), the data of the BPMs and harps were carefully analyzed, as well as reconstructing the beam position and angle event by event at the target location. The calculated beam position will be used in the data analysis to accurately determine the kinematics for each event.

Large angle nonmechanical laser beam steering at 4.6 μm using a digital micromirror device

NASA Astrophysics Data System (ADS)

Lindle, James Ryan; Watnik, Abbie T.

2018-02-01

Large angle, nonmechanical beam steering is demonstrated at 4.62 μm using the digital light processing technology. A 42-deg steering range is demonstrated, limited by the field-of-view of the recollimating lens. The measured diffraction efficiency is 8.1% on-axis and falls-off with a sin2 dependence with the steering angle. However, within the 42-deg steering range, the power varied less than 25%. The profile of the steered laser beam is Gaussian with a divergence of 5.2 mrad. Multibeam, randomly addressable beam steering, is also demonstrated.

Agile wide-angle beam steering with electrowetting microprisms

NASA Astrophysics Data System (ADS)

Smith, Neil R.; Abeysinghe, Don C.; Haus, Joseph W.; Heikenfeld, Jason

2006-07-01

A novel basis for beam steering with electrowetting microprisms (EMPs) is reported. EMPs utilize electrowetting modulation of liquid contact angle in order to mimic the refractive behavior for various classical prism geometries. Continuous beam steering through an angle of 14° (±7°) has been demonstrated with a liquid index of n=1.359. Experimental results are well-matched to theoretical behavior up to the point of electrowetting contact-angle saturation. Projections show that use of higher index liquids (n~1.6) will result in steering through ~30° (±15°). Fundamental factors defining achievable deflection range, and issues for Ladar use, are reviewed. This approach is capable of good switching speed (~ms), polarization independent operation, modulation of beam field-of-view (lensing), and high steering efficiency that is independent of deflection angle.

Behavior of Double-Web Angles Beam to column connections

NASA Astrophysics Data System (ADS)

Fakih, K. Al; Chin, S. C.; Doh, S. I.

2018-04-01

This paper contains the study performed on the behavior of double-web angles by using finite element analysis computer package known as “Abaqus”. The aim of this present study was simulating the behavior of double-web angles (DWA) steel connections. The purpose of this article is to provide the basis for the fastest and most economical design and analysis and to ensure the required steel connection strength. This study, started used review method of behavior of steel beam-to-column bolted connections. Two models of different cross-section were examined under the effect of concentrated load and different boundary conditions. In all the studied case, material nonlinearity was accounted. A sample study on DWA connections was carried out using both material and geometric nonlinearities. This object will be of great value to anyone who wants to better understand the behavior of the steel beam to column connection. The results of the study have a field of reference for future research for members of the development of the steel connection approach with simulation model design.

SU-G-JeP3-06: Lower KV Image Dose Are Expected From a Limited-Angle Intra-Fractional Verification (LIVE) System for SBRT Treatments

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

Ding, G; Yin, F; Ren, L

Purpose: In order to track the tumor movement for patient positioning verification during arc treatment delivery or in between 3D/IMRT beams for stereotactic body radiation therapy (SBRT), the limited-angle kV projections acquisition simultaneously during arc treatment delivery or in-between static treatment beams as the gantry moves to the next beam angle was proposed. The purpose of this study is to estimate additional imaging dose resulting from multiple tomosynthesis acquisitions in-between static treatment beams and to compare with that of a conventional kV-CBCT acquisition. Methods: kV imaging system integrated into Varian TrueBeam accelerators was modeled using EGSnrc Monte Carlo user code,more » BEAMnrc and DOSXYZnrc code was used in dose calculations. The simulated realistic kV beams from the Varian TrueBeam OBI 1.5 system were used to calculate dose to patient based on CT images. Organ doses were analyzed using DVHs. The imaging dose to patient resulting from realistic multiple tomosynthesis acquisitions with each 25–30 degree kV source rotation between 6 treatment beam gantry angles was studied. Results: For a typical lung SBRT treatment delivery much lower (20–50%) kV imaging doses from the sum of realistic six tomosynthesis acquisitions with each 25–30 degree x-ray source rotation between six treatment beam gantry angles were observed compared to that from a single CBCT image acquisition. Conclusion: This work indicates that the kV imaging in this proposed Limited-angle Intra-fractional Verification (LIVE) System for SBRT Treatments has a negligible imaging dose increase. It is worth to note that the MV imaging dose caused by MV projection acquisition in-between static beams in LIVE can be minimized by restricting the imaging to the target region and reducing the number of projections acquired. For arc treatments, MV imaging acquisition in LIVE does not add additional imaging dose as the MV images are acquired from treatment beams directly during the treatment.« less

Theoretical Study of Large-Angle Bending Transport of Microparticles by 2D Acoustic Half-Bessel Beams.

PubMed

Li, Yixiang; Qiu, Chunyin; Xu, Shengjun; Ke, Manzhu; Liu, Zhengyou

2015-08-17

Conventional microparticle transports by light or sound are realized along a straight line. Recently, this limit has been overcome in optics as the growing up of the self-accelerating Airy beams, which are featured by many peculiar properties, e.g., bending propagation, diffraction-free and self-healing. However, the bending angles of Airy beams are rather small since they are only paraxial solutions of the two-dimensional (2D) Helmholtz equation. Here we propose a novel micromanipulation by using acoustic Half-Bessel beams, which are strict solutions of the 2D Helmholtz equation. Compared with that achieved by Airy beams, the bending angle of the particle trajectory attained here is much steeper (exceeding 90(o)). The large-angle bending transport of microparticles, which is robust to complex scattering environment, enables a wide range of applications from the colloidal to biological sciences.

Phase singularities of the transverse field component of high numerical aperture dark-hollow Gaussian beams in the focal region

NASA Astrophysics Data System (ADS)

Liu, Pusheng; Lü, Baida

2007-04-01

By using the vectorial Debye diffraction theory, phase singularities of high numerical aperture (NA) dark-hollow Gaussian beams in the focal region are studied. The dependence of phase singularities on the truncation parameter δ and semi-aperture angle α (or equally, NA) is illustrated numerically. A comparison of phase singularities of high NA dark-hollow Gaussian beams with those of scalar paraxial Gaussian beams and high NA Gaussian beams is made. For high NA dark-hollow Gaussian beams the beam order n additionally affects the spatial distribution of phase singularities, and there exist phase singularities outside the focal plane, which may be created or annihilated by variation of the semi-aperture angle in a certain region.

SU-E-T-446: Group-Sparsity Based Angle Generation Method for Beam Angle Optimization

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

Gao, H

2015-06-15

Purpose: This work is to develop the effective algorithm for beam angle optimization (BAO), with the emphasis on enabling further improvement from existing treatment-dependent templates based on clinical knowledge and experience. Methods: The proposed BAO algorithm utilizes a priori beam angle templates as the initial guess, and iteratively generates angular updates for this initial set, namely angle generation method, with improved dose conformality that is quantitatively measured by the objective function. That is, during each iteration, we select “the test angle” in the initial set, and use group-sparsity based fluence map optimization to identify “the candidate angle” for updating “themore » test angle”, for which all the angles in the initial set except “the test angle”, namely “the fixed set”, are set free, i.e., with no group-sparsity penalty, and the rest of angles including “the test angle” during this iteration are in “the working set”. And then “the candidate angle” is selected with the smallest objective function value from the angles in “the working set” with locally maximal group sparsity, and replaces “the test angle” if “the fixed set” with “the candidate angle” has a smaller objective function value by solving the standard fluence map optimization (with no group-sparsity regularization). Similarly other angles in the initial set are in turn selected as “the test angle” for angular updates and this chain of updates is iterated until no further new angular update is identified for a full loop. Results: The tests using the MGH public prostate dataset demonstrated the effectiveness of the proposed BAO algorithm. For example, the optimized angular set from the proposed BAO algorithm was better the MGH template. Conclusion: A new BAO algorithm is proposed based on the angle generation method via group sparsity, with improved dose conformality from the given template. Hao Gao was partially supported by the NSFC (#11405105), the 973 Program (#2015CB856000) and the Shanghai Pujiang Talent Program (#14PJ1404500)« less

Double wedge prism based beam deflector for precise laser beam steering

NASA Astrophysics Data System (ADS)

Tyszka, Krzysztof; Dobosz, Marek; Bilaszewski, Tomasz

2018-02-01

Aiming to increase laser beam pointing stability required in interferometric measurements, we designed a laser beam deflector intended for active laser beam stabilization systems. The design is based on two wedge-prisms: the deflecting wedge driven by a tilting piezo-platform and the fixed wedge to compensate initial beam deflection. Our design allows linear beam steering, independently in the horizontal or vertical direction, with resolution of less than 1 μrad in a range of more than 100 μrad, and no initial deflection of the beam. Moreover, the ratio of the output beam deflection angle and the wedge tilt angle is less than 0.1; therefore, the noise influence is significantly reduced in comparison to standard mirror-based deflectors. The theoretical analyses support the designing process and can serve as a guide to wedge-prism selection. The experimental results are in agreement with theory and confirm the advantages of the presented double wedge system.

A Cadaveric Analysis of the Optimal Radiographic Angle for Evaluating Trochlear Depth.

PubMed

Weinberg, Douglas Stanley; Gilmore, Allison; Guraya, Sahejmeet S; Wang, David M; Liu, Raymond W

2017-02-01

Disorders of the patellofemoral joint are common. Diagnosis and management often involves the use tangential imaging of the patella and trochlear grove, with the sunrise projection being the most common. However, imaging protocols vary between institutions, and limited data exist to determine which radiographic projections provide optimal visualization of the trochlear groove at its deepest point. Plain radiographs of 48 cadaveric femora were taken at various beam-femur angles and the maximum trochlear depth was measured; a tilt-board apparatus was used to elevate the femur in 5-degree increments between 40 and 75 degrees. A corollary experiment was undertaken to investigate beam-femur angles osteologically: digital representations of each bone were created with a MicroScribe digitizer, and trochlear depth was measured on all specimens at beam-femur angles from 0 to 75 degrees. The results of the radiographic and digitizer experiments showed that the maximum trochlear grove depth occurred at a beam-femur angle of 50 degrees. These results suggest that the optimal beam-femur angle for visualizing maximum trochlear depth is 50 degrees. This is significantly lower than the beam-femur angle of 90 degrees typically used in the sunrise projection. Clinicians evaluating trochlear depth on sunrise projections may be underestimating maximal depth and evaluating a nonarticulating portion of the femur. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

The effect of contact stresses in four-point bend testing of graphite/epoxy and graphite/PMR-15 composite beams

NASA Technical Reports Server (NTRS)

Binienda, Wieslaw K.; Roberts, Gary D.; Papadopoulos, Demetrios S.

1992-01-01

The results of in-plane four-point bend experiments on unidirectionally reinforced composite beams are presented for graphite/epoxy (T300/934) and graphite/polyimide (G30-500/PMR-15) composites. The maximum load and the location of cracks formed during failure were measured for testpieces with fibers oriented at various angles to the beam axis. Since most of the beams failed near one or more of the load points, the strength of the beams was evaluated in terms of a proposed model, for the local stress distribution. In this model, an exact solution to the problem of a localized contact force acting on a unidirectionally reinforced half plane is used to describe the local stress field. The stress singularity at the load points is treated in a manner similar to the stress singularity at a crack tip in fracture mechanisms problems. Using this approach, the effect of fiber angle and elastic material properties on the strength of the beam is described in terms of a load intensity factor. For fiber angles less than 45 deg from the beam axis, a single crack is initiated near one of the load points at a critical value of the load intensity factor. The critical load intensity factor decreases with the increasing fiber angle. For larger fiber angles, multiple cracks occur at locations both near and away from the load points, and the load intensity factor at failure increases sharply with increasing fiber angle.

Effect of contact stresses in four-point bend testing of graphite/epoxy and graphite/PMR-15 composite beams

NASA Technical Reports Server (NTRS)

Binienda, W. K.; Roberts, G. D.; Papadopoulos, D. S.

1992-01-01

The results of in-plane four-point bend experiments on unidirectionally reinforced composite beams are presented for graphite/epoxy (T300/934) and graphite/polyimide (G30-500/PMR-15) composites. The maximum load and the location of cracks formed during failure were measured for testpieces with fibers oriented at various angles to the beam axis. Since most of the beams failed near one or more of the load points, the strength of the beams was evaluated in terms of a proposed model for the local stress distribution. In this model, an exact solution to the problem of a localized contact force acting on a unidirectionally reinforced half plane is used to describe the local stress field. The stress singularity at the load points is treated in a manner similar to the stress singularity at a crack tip in fracture mechanisms problems. Using this approach, the effect of fiber angle and elastic material properties on the strength of the beam is described in terms of a load intensity factor. For fiber angles less than 45 deg from the beam axis, a single crack is initiated near one of the load points at a critical value of the load intensity factor. The critical load intensity factor decreases with increasing fiber angle. For larger fiber angles, multiple cracks occur at locations both near and away from the load points, and the load intensity factor at failure increases sharply with increasing fiber angle.

Large deflection angle, high-power adaptive fiber optics collimator with preserved near-diffraction-limited beam quality.

PubMed

Zhi, Dong; Ma, Yanxing; Chen, Zilun; Wang, Xiaolin; Zhou, Pu; Si, Lei

2016-05-15

We report on the development of a monolithic adaptive fiber optics collimator, with a large deflection angle and preserved near-diffraction-limited beam quality, that has been tested at a maximal output power at the 300 W level. Additionally, a new measurement method of beam quality (M² factor) is developed. Experimental results show that the deflection angle of the collimated beam is in the range of 0-0.27 mrad in the X direction and 0-0.19 mrad in the Y direction. The effective working frequency of the device is about 710 Hz. By employing the new measurement method of the M² factor, we calculate that the beam quality is Mx2=1.35 and My2=1.24, which is in agreement with the result from the beam propagation analyzer and is preserved well with the increasing output power.

Fan-beam intensity modulated proton therapy.

PubMed

Hill, Patrick; Westerly, David; Mackie, Thomas

2013-11-01

This paper presents a concept for a proton therapy system capable of delivering intensity modulated proton therapy using a fan beam of protons. This system would allow present and future gantry-based facilities to deliver state-of-the-art proton therapy with the greater normal tissue sparing made possible by intensity modulation techniques. A method for producing a divergent fan beam of protons using a pair of electromagnetic quadrupoles is described and particle transport through the quadrupole doublet is simulated using a commercially available software package. To manipulate the fan beam of protons, a modulation device is developed. This modulator inserts or retracts acrylic leaves of varying thickness from subsections of the fan beam. Each subsection, or beam channel, creates what effectively becomes a beam spot within the fan area. Each channel is able to provide 0-255 mm of range shift for its associated beam spot, or stop the beam and act as an intensity modulator. Results of particle transport simulations through the quadrupole system are incorporated into the MCNPX Monte Carlo transport code along with a model of the range and intensity modulation device. Several design parameters were investigated and optimized, culminating in the ability to create topotherapy treatment plans using distal-edge tracking on both phantom and patient datasets. Beam transport calculations show that a pair of electromagnetic quadrupoles can be used to create a divergent fan beam of 200 MeV protons over a distance of 2.1 m. The quadrupole lengths were 30 and 48 cm, respectively, with transverse field gradients less than 20 T/m, which is within the range of water-cooled magnets for the quadrupole radii used. MCNPX simulations of topotherapy treatment plans suggest that, when using the distal edge tracking delivery method, many delivery angles are more important than insisting on narrow beam channel widths in order to obtain conformal target coverage. Overall, the sharp distal falloff of a proton depth-dose distribution was found to provide sufficient control over the dose distribution to meet objectives, even with coarse lateral resolution and channel widths as large as 2 cm. Treatment plans on both phantom and patient data show that dose conformity suffers when treatments are delivered from less than approximately ten angles. Treatment time for a sample prostate delivery is estimated to be on the order of 10 min, and neutron production is estimated to be comparable to that found for existing collimated systems. Fan beam proton therapy is a method of delivering intensity modulated proton therapy which may be employed as an alternative to magnetic scanning systems. A fan beam of protons can be created by a set of quadrupole magnets and modified by a dual-purpose range and intensity modulator. This can be used to deliver inversely planned treatments, with spot intensities optimized to meet user defined dose objectives. Additionally, the ability of a fan beam delivery system to effectively treat multiple beam spots simultaneously may provide advantages as compared to spot scanning deliveries.

Dependence of reflection and transmission of soliton on angle of incidence at an interface between chalcogenide fibre and gallium nanoparticle film by phase plane trajectories

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

Naruka, Preeti, E-mail: preety-naruka@Yyahoo.co.in; Bissa, Shivangi; Nagar, A. K.

In the present paper, we study propagation of a soliton at an interface formed between special type of chalcogenide fibre and gallium in three different phases with the help of equivalent particle theory. Critical angle of incidence and critical power required for transmission and reflection of soliton beam have investigated. Here it is found that if the incident angle of the beam or initial velocity of the equivalent particle is insufficient to overcome the maximum increase in potential energy then the particle (light beam) is reflected by the interface and if this incident angle is greater than a critical anglemore » then light beam will be transmitted by the interface. From an equation these critical angles for α-gallium, one of a metastable phase and liquid gallium are calculated and concluded that at large incident angles, the soliton is transmitted through the boundary, whereas at small incidence angles the soliton get reflected on keeping the power of incident beam constant. These results are explained by phase plane trajectories of the effective potential which are experimentally as well as theoretically proved.« less

High resolution quantitative phase imaging of live cells with constrained optimization approach

NASA Astrophysics Data System (ADS)

Pandiyan, Vimal Prabhu; Khare, Kedar; John, Renu

2016-03-01

Quantitative phase imaging (QPI) aims at studying weakly scattering and absorbing biological specimens with subwavelength accuracy without any external staining mechanisms. Use of a reference beam at an angle is one of the necessary criteria for recording of high resolution holograms in most of the interferometric methods used for quantitative phase imaging. The spatial separation of the dc and twin images is decided by the reference beam angle and Fourier-filtered reconstructed image will have a very poor resolution if hologram is recorded below a minimum reference angle condition. However, it is always inconvenient to have a large reference beam angle while performing high resolution microscopy of live cells and biological specimens with nanometric features. In this paper, we treat reconstruction of digital holographic microscopy images as a constrained optimization problem with smoothness constraint in order to recover only complex object field in hologram plane even with overlapping dc and twin image terms. We solve this optimization problem by gradient descent approach iteratively and the smoothness constraint is implemented by spatial averaging with appropriate size. This approach will give excellent high resolution image recovery compared to Fourier filtering while keeping a very small reference angle. We demonstrate this approach on digital holographic microscopy of live cells by recovering the quantitative phase of live cells from a hologram recorded with nearly zero reference angle.

Surface dose measurements for highly oblique electron beams.

PubMed

Ostwald, P M; Kron, T

1996-08-01

Clinical applications of electrons may involve oblique incidence of beams, and although dose variations for angles up to 60 degrees from normal incidence are well documented, no results are available for highly oblique beams. Surface dose measurements in highly oblique beams were made using parallel-plate ion chambers and both standard LiF:Mg, Ti and carbon-loaded LiF Thermoluminescent Dosimeters (TLD). Obliquity factors (OBF) or surface dose at an oblique angle divided by the surface dose at perpendicular incidence, were obtained for electron energies between 4 and 20 MeV. Measurements were performed on a flat solid water phantom without a collimator at 100 cm SSD. Comparisons were also made to collimated beams. The OBFs of surface doses plotted against the angle of incidence increased to a maximum dose followed by a rapid dropoff in dose. The increase in OBF was more rapid for higher energies. The maximum OBF occurred at larger angles for higher-energy beams and ranged from 73 degrees for 4 MeV to 84 degrees for 20 MeV. At the dose maximum, OBFs were between 130% and 160% of direct beam doses, yielding surface doses of up to 150% of Dmax for the 20 MeV beam. At 2 mm depth the dose ratio was found to increase initially with angle and then decrease as Dmax moved closer to the surface. A higher maximum dose was measured at 2 mm depth than at the surface. A comparison of ion chamber types showed that a chamber with a small electrode spacing and large guard ring is required for oblique dose measurement. A semiempirical equation was used to model the dose increase at the surface with different energy electron beams.

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

Optical levitation of a non-spherical particle in a loosely focused Gaussian beam.

PubMed

Chang, Cheong Bong; Huang, Wei-Xi; Lee, Kyung Heon; Sung, Hyung Jin

2012-10-08

The optical force on a non-spherical particle subjected to a loosely focused laser beam was calculated using the dynamic ray tracing method. Ellipsoidal particles with different aspect ratios, inclination angles, and positions were modeled, and the effects of these parameters on the optical force were examined. The vertical component of the optical force parallel to the laser beam axis decreased as the aspect ratio decreased, whereas the ellipsoid with a small aspect ratio and a large inclination angle experienced a large vertical optical force. The ellipsoids were pulled toward or repelled away from the laser beam axis, depending on the inclination angle, and they experienced a torque near the focal point. The behavior of the ellipsoids in a viscous fluid was examined by analyzing a dynamic simulation based on the penalty immersed boundary method. As the ellipsoids levitated along the direction of the laser beam propagation, they moved horizontally with rotation. Except for the ellipsoid with a small aspect ratio and a zero inclination angle near the focal point, the ellipsoids rotated until the major axis aligned with the laser beam axis.

Coherent Beam-Beam Instability in Collisions with a Large Crossing Angle

NASA Astrophysics Data System (ADS)

Ohmi, K.; Kuroo, N.; Oide, K.; Zhou, D.; Zimmermann, F.

2017-09-01

In recent years the "crab-waist collision" scheme [P. Raimondi, Proceedings of 2nd SuperB Workshop, Frascati, 2006.; M. Zobov et al., Phys. Rev. Lett. 104, 174801 (2010), 10.1103/PhysRevLett.104.174801] has become popular for circular e+ e- colliders. The designs of several future colliders are based on this scheme. So far the beam-beam effects for collisions under a large crossing angle with or without crab waist were mostly studied using weak-strong simulations. We present here strong-strong simulations showing a novel strong coherent head-tail instability, which can limit the performance of proposed future colliders. We explain the underlying instability mechanism starting from the "cross-wake force" induced by the beam-beam interaction. Using this beam-beam wake, the beam-beam head tail modes are studied by an eigenmode analysis. The instability may affect all collider designs based on the crab-waist scheme. We suggest an experimental verification at SuperKEKB during its commissioning phase II.

Angle performance on optima MDxt

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

David, Jonathan; Kamenitsa, Dennis

2012-11-06

Angle control on medium current implanters is important due to the high angle-sensitivity of typical medium current implants, such as halo implants. On the Optima MDxt, beam-to-wafer angles are controlled in both the horizontal and vertical directions. In the horizontal direction, the beam angle is measured through six narrow slits, and any angle adjustment is made by electrostatically steering the beam, while cross-wafer beam parallelism is adjusted by changing the focus of the electrostatic parallelizing lens (P-lens). In the vertical direction, the beam angle is measured through a high aspect ratio mask, and any angle adjustment is made by slightlymore » tilting the wafer platen prior to implant. A variety of tests were run to measure the accuracy and repeatability of Optima MDxt's angle control. SIMS profiles of a high energy, channeling sensitive condition show both the cross-wafer angle uniformity, along with the small-angle resolution of the system. Angle repeatability was quantified by running a channeling sensitive implant as a regular monitor over a seven month period and measuring the sheet resistance-to-angle sensitivity. Even though crystal cut error was not controlled for in this case, when attributing all Rs variation to angle changes, the overall angle repeatability was measured as 0.16 Degree-Sign (1{sigma}). A separate angle repeatability test involved running a series of V-curves tests over a four month period using low crystal cut wafers selected from the same boule. The results of this test showed the angle repeatability to be <0.1 Degree-Sign (1{sigma}).« less

Fully Mechanically Controlled Automated Electron Microscopic Tomography

DOE PAGES

Liu, Jinxin; Li, Hongchang; Zhang, Lei; ...

2016-07-11

Knowledge of three-dimensional (3D) structures of each individual particles of asymmetric and flexible proteins is essential in understanding those proteins' functions; but their structures are difficult to determine. Electron tomography (ET) provides a tool for imaging a single and unique biological object from a series of tilted angles, but it is challenging to image a single protein for three-dimensional (3D) reconstruction due to the imperfect mechanical control capability of the specimen goniometer under both a medium to high magnification (approximately 50,000-160,000×) and an optimized beam coherence condition. Here, we report a fully mechanical control method for automating ET data acquisitionmore » without using beam tilt/shift processes. This method could reduce the accumulation of beam tilt/shift that used to compensate the error from the mechanical control, but downgraded the beam coherence. Our method was developed by minimizing the error of the target object center during the tilting process through a closed-loop proportional-integral (PI) control algorithm. The validations by both negative staining (NS) and cryo-electron microscopy (cryo-EM) suggest that this method has a comparable capability to other ET methods in tracking target proteins while maintaining optimized beam coherence conditions for imaging.« less

Ambient neutron dose equivalent during proton therapy using wobbling scanning system: Measurements and calculations

NASA Astrophysics Data System (ADS)

Lin, Yung-Chieh; Lee, Chung-Chi; Chao, Tsi-Chian; Tsai, Hui-Yu

2017-11-01

Neutron production is a concern in proton therapy, particularly in scattering proton beam delivery systems. Despite this fact, little is known about the effects of secondary neutron exposure around wobbling scattered proton treatment nozzles. The objective of this study was to estimate the neutron dose level resulting from the use of a wobbling scattered proton treatment unit. We applied the Monte Carlo method for predict the ambient neutron dose equivalent, H*(10), per absorbed dose at the treatment isocenter, D, in the proton therapy center of Chang Gung Memorial Hospital, Linkou, Taiwan. For a 190-MeV proton beam, H* (10) / D values typically decreased with the distance from the isocenter, being 1.106 mSv/Gy at the isocenter versus 0.112 mSv/Gy at a distance of 150 cm from the isocenter. The H* (10) / D values generally decreased as the neutron receptors moved away from the isocenter, and increased when the angle from the initial beam axis increased. The ambient neutron dose equivalents were observed to be slightly lower in the direction of multileaf collimator movement. For radiation protection, the central axis of a proton-treated patient is suggested to be at the 0° angle of the beam. If the beam direction at the 90° angle is necessary, the patient axis is suggested to be along with the direction of MLC movement. Our study provides the neutron dose level and neutron energy fluence for the first wobbling proton system at the proton therapy center of Chang Gung Memorial Hospital.

Controllable Airy-like beams induced by tunable phase patterns

NASA Astrophysics Data System (ADS)

Li, D.; Qian, Y.

2016-01-01

We propose and experimentally observe a novel family of Airy-like beams. First, we theoretically investigate the physical generation of our proposed controllable Airy-like beams by introducing a rotation angle factor into the phase function, which can regulate and flexibly control the beam wavefront. Meanwhile we can also readily control the main lobes of these beams to follow appointed parabolic trajectories using the rotation angle factor. We also demonstrate that the controllable Airy-like beams lack the properties of being diffraction-free and self-healing. The experiments are performed and the results are in accord with the theoretical simulations. We believe that the intriguing characteristics of our proposed Airy-like beams could provide more degrees of freedom, and are likely to give rise to new applications and lend versatility to the emerging field.

Phase-space analysis of charged and optical beam transport: Wigner rotation angle

NASA Technical Reports Server (NTRS)

Dattoli, G.; Torre, Amalia

1994-01-01

The possibility of using the phase space formalism to establish a correspondence between the dynamical behavior of squeezed states and optical or charged beams, propagating through linear systems, has received a great deal of attention during the last years. In this connection, it has been indicated how optical experiments may be conceived to measure the Wigner rotation angle. In this paper we address the topic within the context of the paraxial propagation of optical or charged beams and suggest a possible experiment for measuring the Wigner angle using an electron beam passing through quadrupoles and drift sections. The analogous optical system is also discussed.

Vortex gas lens

NASA Technical Reports Server (NTRS)

Bogdanoff, David W.; Berschauer, Andrew; Parker, Timothy W.; Vickers, Jesse E.

1989-01-01

A vortex gas lens concept is presented. Such a lens has a potential power density capability of 10 to the 9th - 10 to the 10th w/sq cm. An experimental prototype was constructed, and the divergence half angle of the exiting beam was measured as a function of the lens operating parameters. Reasonably good agreement is found between the experimental results and theoretical calculations. The expanded beam was observed to be steady, and no strong, potentially beam-degrading jets were found to issue from the ends of the lens. Estimates of random beam deflection angles to be expected due to boundary layer noise are presented; these angles are very small.

Beam commissioning of a superconducting rotating-gantry for carbon-ion radiotherapy

NASA Astrophysics Data System (ADS)

Iwata, Y.; Fujimoto, T.; Matsuba, S.; Fujita, T.; Sato, S.; Furukawa, T.; Hara, Y.; Mizushima, K.; Saraya, Y.; Tansho, R.; Saotome, N.; Shirai, T.; Noda, K.

2016-10-01

A superconducting rotating-gantry for carbon-ion radiotherapy was developed. This isocentric gantry can transport carbon ions having kinetic energies of between E=430 and 48 MeV/u to an isocenter over an angle of ±180°, and is further capable of performing three-dimensional raster-scanning irradiation. Construction of the entire rotating-gantry system was completed by the end of September 2015. Prior to beam commissioning, phase-space distributions of extracted carbon beams from the synchrotron were deduced by using an empirical method. In this method, phase-space distributions at the extraction channel of the synchrotron were modeled with 8 parameters, and the best parameters were determined so as to minimize a difference between the calculated and measured beam profiles by using a simplex method. Based on the phase-space distributions, beam optics through the beam-transport lines as well as the rotating gantry were designed. Since horizontal and vertical beam emittances, as extracted slowly from the synchrotron, generally differ with each other, a horizontal-vertical beam coupling would occur when the gantry rotates. Thus, the size and shape of beam spots at the isocenter should vary depending on the gantry angle. To compensate for the difference in the emittances, we employed a method to utilize multiple Coulomb scattering of the beam particles by a thin scatterer. Having compensated for the emittances and designed beam optics through the rotating gantry, beam commissioning over various combinations of gantry angles and beam energies was performed. By finely tuning the superconducting quadrupoles of the rotating gantry, we could successfully obtain the designed beam quality, which satisfies the requirements of scanning irradiation.

Simulations of x-ray speckle-based dark-field and phase-contrast imaging with a polychromatic beam

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

Zdora, Marie-Christine, E-mail: marie-christine.zdora@diamond.ac.uk; Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE; Department of Physics & Astronomy, University College London, London WC1E 6BT

2015-09-21

Following the first experimental demonstration of x-ray speckle-based multimodal imaging using a polychromatic beam [I. Zanette et al., Phys. Rev. Lett. 112(25), 253903 (2014)], we present a simulation study on the effects of a polychromatic x-ray spectrum on the performance of this technique. We observe that the contrast of the near-field speckles is only mildly influenced by the bandwidth of the energy spectrum. Moreover, using a homogeneous object with simple geometry, we characterize the beam hardening artifacts in the reconstructed transmission and refraction angle images, and we describe how the beam hardening also affects the dark-field signal provided by specklemore » tracking. This study is particularly important for further implementations and developments of coherent speckle-based techniques at laboratory x-ray sources.« less

Effect of beam steering on the visibility of echogenic and non-echogenic needles: a laboratory study.

PubMed

Uppal, Vishal; Sondekoppam, Rakesh V; Ganapathy, Sugantha

2014-10-01

During peripheral nerve block procedures, needle visibility decreases as the angle of needle insertion relative to skin increases due to loss of reflective signals. The primary aim of our study was to compare the effect of beam steering on the visibility of echogenic and non-echogenic block needles. PAJUNK non-echogenic and echogenic needles were inserted into pork meat at 20°, 40°, 60°, and 70° angles, and electronic beam steering was applied at three different angles (shallow, medium, and steep) to obtain the best possible needle images. Eleven anesthesiologists blinded to the type of needle or use of beam steering scored the images obtained (0 = needle not visible; 10 = excellent needle shaft and tip visibility). Mean scores were used to classify the needles as poor visibility (mean score 0-3.3), intermediate visibility (mean score 3.4-6.6), or good visibility (mean score 6.7-10). At 20°, the visibility scores were intermediate to good in all groups. At 40°, the mean (SD) visibility score for the non-echogenic needle improved significantly from 3.1 (1.4) to 7.9 (1.8) with application of beam steering (difference = 4.8; 95% confidence interval [CI]: 3.1 to 6.6; P < 0.001). At 60°, the mean (SD) visibility score for the non-echogenic needle was poor 0.6 (0.7) and remained poor 2.4 (1.1) with beam steering. One the other hand, the echogenic needle without beam steering 6.5 (1.8) scored significantly better than the non-echogenic needle with beam steering 2.4 (1.1) (difference = 4.2; 95% CI: 2.7 to 5.6; P < 0.001). At 70°, the mean needle visibility score was poor for the non-echogenic needle with or without beam steering. In contrast, the echogenic needle attained an intermediate visibility score with or without beam steering. Beam steering did not significantly change the visibility scores of either the echogenic or the non-echogenic needle (P = 0.088 and 0.056, respectively) at a 70° angle. The PAJUNK echogenic needle, with or without beam steering, was more visible when compared with the non-echogenic needle at 60° and 70° angles of insertion. In contrast, at a 40° angle of needle insertion, the non-echogenic needle with beam steering was more visible compared with the echogenic needle.

Electron radiography

DOEpatents

Merrill, Frank E.; Morris, Christopher

2005-05-17

A system capable of performing radiography using a beam of electrons. Diffuser means receive a beam of electrons and diffuse the electrons before they enter first matching quadrupoles where the diffused electrons are focused prior to the diffused electrons entering an object. First imaging quadrupoles receive the focused diffused electrons after the focused diffused electrons have been scattered by the object for focusing the scattered electrons. Collimator means receive the scattered electrons and remove scattered electrons that have scattered to large angles. Second imaging quadrupoles receive the collimated scattered electrons and refocus the collimated scattered electrons and map the focused collimated scattered electrons to transverse locations on an image plane representative of the electrons' positions in the object.

The development of W-PBPM at diagnostic beamline

NASA Astrophysics Data System (ADS)

Kim, Seungnam; Kim, Myeongjin; Kim, Seonghan; Shin, Hocheol; Kim, Jiwha; Lee, Chaesun

2017-12-01

The photon beam position monitor (PBPM) plays a critically important role in the accurate monitoring of the beam position. W (Wire)-PBPMs are installed at the front end and photon transfer line (PTL) of the diagnostic beamline and detect the change of position and angle of the beam orbit applied to the beamline. It provides beam stability and position data in real time, which can be used in feedback system with BPM in storage-ring. Also it provides beam profile, which makes it possible to figure out the specifications of beam. With two W-PBPMs, the angle information of beam could be acquired and the results coupled with beam profile are used with orbit correction. The W-PBPM has been designed and installed in the diagnostic beamline at Pohang Light Source. Herein the details of the design, analysis and performance for the W-PBPM will be reported.

Method for the production of wideband THz radiation

DOEpatents

Krafft, Geoffrey A [Newport News, VA

2008-01-01

A method for the production of extremely wide bandwidth THz radiation comprising: delivering an electron beam from a source to an undulator that does not deflect the angle or transversely move the electron beam; and optimizing the undulator to yield peak emission in the middle of the THz band (1 THz). These objectives are accomplished by magnetically bending the orbit of the incoming electron beam in the undulator according to the function x(z)=x.sub.o exp(-z.sup.2/2.sigma..sup.2) and controlling the transverse magnetic field to be B(z)=B.sub.0(1-z.sup.2/.sigma..sup.2)exp(-z.sup.2/2.sigma..sup.2).

Compensation of the long-range beam-beam interactions as a path towards new configurations for the high luminosity LHC

DOE PAGES

Fartoukh, Stéphane; Valishev, Alexander; Papaphilippou, Yannis; ...

2015-12-01

Colliding bunch trains in a circular collider demands a certain crossing angle in order to separate the two beams transversely after the collision. The magnitude of this crossing angle is a complicated function of the bunch charge, the number of long-range beam-beam interactions, of β* and type of optics (flat or round), and possible compensation or additive effects between several low-β insertions in the ring depending on the orientation of the crossing plane at each interaction point. About 15 years ago, the use of current bearing wires was proposed at CERN in order to mitigate the long-range beam-beam effects [J.P. Koutchouk,more » CERN Report No. LHC-Project-Note 223, 2000], therefore offering the possibility to minimize the crossing angle with all the beneficial effects this might have: on the luminosity performance by reducing the need for crab-cavities or lowering their voltage, on the required aperture of the final focus magnets, on the strength of the orbit corrector involved in the crossing bumps, and finally on the heat load and radiation dose deposited in the final focus quadrupoles. In this paper, a semianalytical approach is developed for the compensation of the long-range beam-beam interactions with current wires. This reveals the possibility of achieving optimal correction through a careful adjustment of the aspect ratio of the β functions at the wire position. We consider the baseline luminosity upgrade plan of the Large Hadron Collider (HL-LHC project), and compare it to alternative scenarios, or so-called ''configurations,'' where modifications are applied to optics, crossing angle, or orientation of the crossing plane in the two low-β insertions of the ring. Furthermore, for all these configurations, the beneficial impact of beam-beam compensation devices is then demonstrated on the tune footprint, the dynamical aperture, and/or the frequency map analysis of the nonlinear beam dynamics as the main figures of merit.« less

Multibeam collimator uses prism stack

NASA Technical Reports Server (NTRS)

Minott, P. O.

1981-01-01

Optical instrument creates many divergent light beams for surveying and machine element alignment applications. Angles and refractive indices of stack of prisms are selected to divert incoming laser beam by small increments, different for each prism. Angles of emerging beams thus differ by small, precisely-controlled amounts. Instrument is nearly immune to vibration, changes in gravitational force, temperature variations, and mechanical distortion.

Beam position reconstruction for the g2p experiment in Hall A at Jefferson Lab

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

Zhu, Pengjia; Allada, Kalyan; Allison, Trent

2015-11-03

Beam-line equipment was upgraded for experiment E08-027 (g2p) in Hall A at Jefferson Lab. Two beam position monitors (BPMs) were necessary to measure the beam position and angle at the target. A new BPM receiver was designed and built to handle the low beam currents (50-100 nA) used for this experiment. Two new super-harps were installed for calibrating the BPMs. In addition to the existing fast raster system, a slow raster system was installed. We found that before and during the experiment, these new devices were tested and debugged, and their performance was also evaluated. In order to achieve themore » required accuracy (1-2 mm in position and 1-2 mrad in angle at the target location), the data of the BPMs and harps were carefully analyzed, as well as reconstructing the beam position and angle event by event at the target location. Finally, the calculated beam position will be used in the data analysis to accurately determine the kinematics for each event.« less

TH-EF-BRB-05: 4pi Non-Coplanar IMRT Beam Angle Selection by Convex Optimization with Group Sparsity Penalty

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

O’Connor, D; Nguyen, D; Voronenko, Y

Purpose: Integrated beam orientation and fluence map optimization is expected to be the foundation of robust automated planning but existing heuristic methods do not promise global optimality. We aim to develop a new method for beam angle selection in 4π non-coplanar IMRT systems based on solving (globally) a single convex optimization problem, and to demonstrate the effectiveness of the method by comparison with a state of the art column generation method for 4π beam angle selection. Methods: The beam angle selection problem is formulated as a large scale convex fluence map optimization problem with an additional group sparsity term thatmore » encourages most candidate beams to be inactive. The optimization problem is solved using an accelerated first-order method, the Fast Iterative Shrinkage-Thresholding Algorithm (FISTA). The beam angle selection and fluence map optimization algorithm is used to create non-coplanar 4π treatment plans for several cases (including head and neck, lung, and prostate cases) and the resulting treatment plans are compared with 4π treatment plans created using the column generation algorithm. Results: In our experiments the treatment plans created using the group sparsity method meet or exceed the dosimetric quality of plans created using the column generation algorithm, which was shown superior to clinical plans. Moreover, the group sparsity approach converges in about 3 minutes in these cases, as compared with runtimes of a few hours for the column generation method. Conclusion: This work demonstrates the first non-greedy approach to non-coplanar beam angle selection, based on convex optimization, for 4π IMRT systems. The method given here improves both treatment plan quality and runtime as compared with a state of the art column generation algorithm. When the group sparsity term is set to zero, we obtain an excellent method for fluence map optimization, useful when beam angles have already been selected. NIH R43CA183390, NIH R01CA188300, Varian Medical Systems; Part of this research took place while D. O’Connor was a summer intern at RefleXion Medical.« less

Propagation characteristics of partially coherent anomalous elliptical hollow Gaussian beam propagating through atmospheric turbulence along a slant path

NASA Astrophysics Data System (ADS)

Tian, Huanhuan; Xu, Yonggen; Yang, Ting; Ma, Zairu; Wang, Shijian; Dan, Youquan

2017-02-01

Based on the extended Huygens-Fresnel principal and the Wigner distribution function, the root mean square (rms) angular width and propagation factor (M2-factor) of partially coherent anomalous elliptical hollow Gaussian (PCAEHG) beam propagating through atmospheric turbulence along a slant path are studied in detail. Analytical formulae of the rms angular width and M2-factor of PCAEHG beam are derived. Our results show that the rms angular width increases with increasing of wavelength and zenith angle and with decreasing of transverse coherence length, beam waist sizes and inner scale. The M2-factor increases with increasing of zenith angle and with decreasing of wavelength, transverse coherence length, beam waist sizes and inner scale. The saturation propagation distances (SPDs) increase as zenith angle increases. The numerical calculations also indicate that the SPDs of rms angular width and M2-factor for uplink slant paths with zenith angle of π/12 are about 0.2 and 20 km, respectively.

Sidelooking laser altimeter for a flight simulator

NASA Technical Reports Server (NTRS)

Webster, L. D. (Inventor)

1983-01-01

An improved laser altimeter for a flight simulator which allows measurement of the height of the simulator probe above the terrain directly below the probe tip is described. A laser beam is directed from the probe at an angle theta to the horizontal to produce a beam spot on the terrain. The angle theta that the laser beam makes with the horizontal is varied so as to bring the beam spot into coincidence with a plumb line coaxial with the longitudinal axis of the probe. A television altimeter camera observes the beam spot and has a raster line aligned with the plumb line. Spot detector circuit coupled to the output of the TV camera monitors the position of the beam spot relative to the plumb line.

Low-loss VIS/IR-XUV beam splitter for high-power applications.

PubMed

Pupeza, Ioachim; Fill, Ernst E; Krausz, Ferenc

2011-06-20

We present a low-loss VIS/IR-XUV beam splitter, suitable for high-power operation. The spatial separation of the VIS/IR and XUV components of a beam is achieved by the wedged top layer of a dielectric multilayer structure, onto which the beam is impinging under Brewster's angle (for VIS/IR). With a fused silica wedge with an angle of 0.5° we achieve a separation angle of 2.2° and an IR reflectivity of 0.9995. Typical XUV reflectivities amount to 0.1-0.2. The novel element is mechanically robust, exhibiting two major advantages over free-standing Brewster plates: (i) a significant improvement of heat conduction and (ii) easier handling, in particular for high-optical-quality fabrication. The beam splitter could be used as an output coupler for intracavity-generated XUV radiation, promising a boost of the power regime of current MHz-HHG experiments. It is also suited for single-pass experiments and as a beam combiner for pump-probe experiments.

Single-laser, one beam, tetrahedral magneto-optical trap.

PubMed

Vangeleyn, Matthieu; Griffin, Paul F; Riis, Erling; Arnold, Aidan S

2009-08-03

We have realized a 4-beam pyramidal magneto-optical trap ideally suited for future microfabrication. Three mirrors split and steer a single incoming beam into a tripod of reflected beams, allowing trapping in the four-beam overlap volume. We discuss the influence of mirror angle on cooling and trapping, finding optimum efficiency in a tetrahedral configuration. We demonstrate the technique using an ex-vacuo mirror system to illustrate the previously inaccessible supra-plane pyramid MOT configuration. Unlike standard pyramidal MOTs both the pyramid apex and its mirror angle are non-critical and our MOT offers improved molasses free from atomic shadows in the laser beams. The MOT scheme naturally extends to a 2-beam refractive version with high optical access. For quantum gas experiments, the mirror system could also be used for a stable 3D tetrahedral optical lattice.

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.

Beam splitter used in dual filming technique

NASA Technical Reports Server (NTRS)

Zeldin, S.

1966-01-01

Tubular tee is intersected at its junction by a reflecting/transmitting mirror angled to provide two images of an object for simultaneous photographing from two positions. This method is used when space and focal conditions are limited.

Dual energy approach for cone beam artifacts correction

NASA Astrophysics Data System (ADS)

Han, Chulhee; Choi, Shinkook; Lee, Changwoo; Baek, Jongduk

2017-03-01

Cone beam computed tomography systems generate 3D volumetric images, which provide further morphological information compared to radiography and tomosynthesis systems. However, reconstructed images by FDK algorithm contain cone beam artifacts when a cone angle is large. To reduce the cone beam artifacts, two-pass algorithm has been proposed. The two-pass algorithm considers the cone beam artifacts are mainly caused by high density materials, and proposes an effective method to estimate error images (i.e., cone beam artifacts images) by the high density materials. While this approach is simple and effective with a small cone angle (i.e., 5 - 7 degree), the correction performance is degraded as the cone angle increases. In this work, we propose a new method to reduce the cone beam artifacts using a dual energy technique. The basic idea of the proposed method is to estimate the error images generated by the high density materials more reliably. To do this, projection data of the high density materials are extracted from dual energy CT projection data using a material decomposition technique, and then reconstructed by iterative reconstruction using total-variation regularization. The reconstructed high density materials are used to estimate the error images from the original FDK images. The performance of the proposed method is compared with the two-pass algorithm using root mean square errors. The results show that the proposed method reduces the cone beam artifacts more effectively, especially with a large cone angle.

A three-dimensional laser vibration measurement technology realized on five laser beam and its calibration

NASA Astrophysics Data System (ADS)

Li, Lu-Ke; Zhang, Shen-Feng

2018-03-01

Put forward a kind of three-dimensional vibration information technology of vibrating object by the mean of five laser beam of He-Ne laser, and with the help of three-way sensor, measure the three-dimensional laser vibration developed by above mentioned technology. The technology based on the Doppler principle of interference and signal demodulation technology, get the vibration information of the object, through the algorithm processing, extract the three-dimensional vibration information of space objects, and can achieve the function of angle calibration of five beam in the space, which avoid the effects of the mechanical installation error, greatly improve the accuracy of measurement. With the help of a & B K4527 contact three axis sensor, measure and calibrate three-dimensional laser vibrometer, which ensure the accuracy of the measurement data. Summarize the advantages and disadvantages of contact and non-contact sensor, and analysis the future development trends of the sensor industry.

Long-range active retroreflector to measure the rotational orientation in conjunction with a laser tracker

NASA Astrophysics Data System (ADS)

Hofherr, O.; Wachten, Christian; Müller, C.; Reinecke, H.

2014-11-01

High precision optical non-contact position measurement is a key technology in modern engineering. Laser trackers (LT) accurately determine x-y-z coordinates of passive retroreflectors. Next-generation systems answer the need to measure an object`s rotational orientation (pitch, yaw, roll). So far, these devices are based either on photogrammetry or on enhanced retroreflectors. Here we present a new method to measure all six degrees of freedom in conjunction with a LT. The basic principle is to analyze the orientation to the LT's beam path by coupling-out laser radiation. The optical design is inspired by a cat's eye retroreflector equipped with an integrated beam splitter layer. The optical spherical aberration is compensated, which reduces the divergence angle for the reflected beam by one order of magnitude compared to an uncompensated standard system of the same size. The wave front distortion is reduced to less than 0.1 λ @ 633 nm for beam diameters up to 8 mm. Our active retroreflector is suitable for long-range measurements for a distance > 10 m.

Performance analysis of a CsI-based flat panel detector in a cone beam variable resolution x-ray system

NASA Astrophysics Data System (ADS)

Dahi, Bahram; Keyes, Gary S.; Rendon, David A.; DiBianca, Frank A.

2007-03-01

A new Cone-Beam CT (CBCT) system is introduced that uses the concept of Variable Resolution X-ray (VRX) detection, which has previously been demonstrated to significantly increase spatial resolution for small objects. An amorphous silicon Flat Panel Detector (FPD) with a CsI scintillator (PaxScan 2020, Varian, Salt Lake City, UT) is coupled with a micro-focus x-ray tube (35 - 80 kVp, 10 - 250 μA) to form a CBCT. The FPD is installed on a rotating arm that can be adjusted to any angle θ, called the VRX angle, between 90° and 0° with respect to the x-ray direction. A VRX angle of 90° for the detector corresponds to a conventional CBCT whereas a VRX angle of 30° means that the detector is tilted 90° - 30° = 60° from its perpendicular position. Tilting the FPD in this manner reduces both the line-spread function width and the sampling distance by a factor of sin(θ), thereby increasing detector spatial resolution proportionately. An in-house phantom is used to measure the MTF of the reconstructed CT images using different VRX angles. An increase by a factor of 1.67 +/- 0.007 is observed in the MTF cutoff frequency at 30° compared to 90° in images acquired at 75 kVp. Expected theoretical value for this case is 2.0. The new Cone-Beam Variable Resolution X-ray (CB-VRX) CT system is expected to significantly improve the images acquired from small objects - such as small animals - while exploiting the opportunities offered by a conventional CBCT.

Compact laser transmitter delivering a long-range infrared beam aligned with a monitoring visible beam.

PubMed

Lee, Hong-Shik; Kim, Haeng-In; Lee, Sang-Shin

2012-06-10

A compact laser transmitter, which takes advantage of an optical subassembly module, was proposed and demonstrated, providing precisely aligned collinear IR and visible beams. The collimated IR beam acts as a long-range projectile for simulated combat, carrying an optical pulsed signal, whereas the visible beam plays the role of tracking the IR beam. The proposed laser transmitter utilizes IR (λ(1)=905 nm) and visible (λ(2)=660 nm) light sources, a fiber-optic collimator, and a beam combiner, which includes a wavelength division multiplexing (WDM) filter in conjunction with optical fiber. The device was built via the laser welding technique and then evaluated by investigating the characteristics of the generated light beams. The IR collimated beam produced had a Gaussian profile and a divergence angle of ~1.3 mrad, and the visible monitoring beam was appropriately collimated to be readily discernible in the vicinity of the transmitter. The two beams were highly aligned within an angle of 0.004 deg as anticipated. Finally, we performed a practical outdoor field test to assess the IR beam with the help of a receiver. An effective trajectory was observed ranging up to 660 m with an overall detectable beam width of ~60 cm.

Eliminating Unwanted Far-Field Excitation in Objective-Type TIRF. Part I. Identifying Sources of Nonevanescent Excitation Light

PubMed Central

Brunstein, Maia; Teremetz, Maxime; Hérault, Karine; Tourain, Christophe; Oheim, Martin

2014-01-01

Total internal reflection fluorescence microscopy (TIRFM) achieves subdiffraction axial sectioning by confining fluorophore excitation to a thin layer close to the cell/substrate boundary. However, it is often unknown how thin this light sheet actually is. Particularly in objective-type TIRFM, large deviations from the exponential intensity decay expected for pure evanescence have been reported. Nonevanescent excitation light diminishes the optical sectioning effect, reduces contrast, and renders TIRFM-image quantification uncertain. To identify the sources of this unwanted fluorescence excitation in deeper sample layers, we here combine azimuthal and polar beam scanning (spinning TIRF), atomic force microscopy, and wavefront analysis of beams passing through the objective periphery. Using a variety of intracellular fluorescent labels as well as negative staining experiments to measure cell-induced scattering, we find that azimuthal beam spinning produces TIRFM images that more accurately portray the real fluorophore distribution, but these images are still hampered by far-field excitation. Furthermore, although clearly measureable, cell-induced scattering is not the dominant source of far-field excitation light in objective-type TIRF, at least for most types of weakly scattering cells. It is the microscope illumination optical path that produces a large cell- and beam-angle invariant stray excitation that is insensitive to beam scanning. This instrument-induced glare is produced far from the sample plane, inside the microscope illumination optical path. We identify stray reflections and high-numerical aperture aberrations of the TIRF objective as one important source. This work is accompanied by a companion paper (Pt.2/2). PMID:24606927

Faster processing of multiple spatially-heterodyned direct to digital holograms

DOEpatents

Hanson, Gregory R.; Bingham, Philip R.

2006-10-03

Systems and methods are described for faster processing of multiple spatially-heterodyned direct to digital holograms. A method includes of obtaining multiple spatially-heterodyned holograms, includes: digitally recording a first spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; digitally recording a second spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; Fourier analyzing the recorded first spatially-heterodyned hologram by shifting a first original origin of the recorded first spatially-heterodyned hologram including spatial heterodyne fringes in Fourier space to sit on top of a spatial-heterodyne carrier frequency defined as a first angle between a first reference beam and a first, object beam; applying a first digital filter to cut off signals around the first original origin and performing an inverse Fourier transform on the result; Fourier analyzing the recorded second spatially-heterodyned hologram by shifting a second original origin of the recorded second spatially-heterodyned hologram including spatial heterodyne fringes in Fourier space to sit on top of a spatial-heterodyne carrier frequency defined as a second angle between a second reference beam and a second object beam; and applying a second digital filter to cut off signals around the second original origin and performing an inverse Fourier transform on the result, wherein digitally recording the first spatially-heterodyned hologram is completed before digitally recording the second spatially-heterodyned hologram and a single digital image includes both the first spatially-heterodyned hologram and the second spatially-heterodyned hologram.

Faster processing of multiple spatially-heterodyned direct to digital holograms

DOEpatents

Hanson, Gregory R [Clinton, TN; Bingham, Philip R [Knoxville, TN

2008-09-09

Systems and methods are described for faster processing of multiple spatially-heterodyned direct to digital holograms. A method includes of obtaining multiple spatially-heterodyned holograms, includes: digitally recording a first spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; digitally recording a second spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; Fourier analyzing the recorded first spatially-heterodyned hologram by shifting a first original origin of the recorded first spatially-heterodyned hologram including spatial heterodyne fringes in Fourier space to sit on top of a spatial-heterodyne carrier frequency defined as a first angle between a first reference beam and a first object beam; applying a first digital filter to cut off signals around the first original origin and performing an inverse Fourier transform on the result; Fourier analyzing the recorded second spatially-heterodyned hologram by shifting a second original origin of the recorded second spatially-heterodyned hologram including spatial heterodyne fringes in Fourier space to sit on top of a spatial-heterodyne carrier frequency defined as a second angle between a second reference beam and a second object beam; and applying a second digital filter to cut off signals around the second original origin and performing an inverse Fourier transform on the result, wherein digitally recording the first spatially-heterodyned hologram is completed before digitally recording the second spatially-heterodyned hologram and a single digital image includes both the first spatially-heterodyned hologram and the second spatially-heterodyned hologram.

SU-F-BRD-08: Guaranteed Epsilon-Optimal Treatment Plans with Minimum Number of Beams for SBRT Using RayStation

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

Yarmand, H; Winey, B; Craft, D

2014-06-15

Purpose: To efficiently find quality-guaranteed treatment plans with the minimum number of beams for stereotactic body radiation therapy using RayStation. Methods: For a pre-specified pool of candidate beams we use RayStation (a treatment planning software for clinical use) to identify the deliverable plan which uses all the beams with the minimum dose to organs at risk (OARs) and dose to the tumor and other structures in specified ranges. Then use the dose matrix information for the generated apertures from RayStation to solve a linear program to find the ideal plan with the same objective and constraints allowing use of allmore » beams. Finally we solve a mixed integer programming formulation of the beam angle optimization problem (BAO) with the objective of minimizing the number of beams while remaining in a predetermined epsilon-optimality of the ideal plan with respect to the dose to OARs. Since the treatment plan optimization is a multicriteria optimization problem, the planner can exploit the multicriteria optimization capability of RayStation to navigate the ideal dose distribution Pareto surface and select a plan of desired target coverage versus OARs sparing, and then use the proposed technique to reduce the number of beams while guaranteeing quality. For the numerical experiments two liver cases and one lung case with 33 non-coplanar beams are considered. Results: The ideal plan uses an impractically large number of beams. The proposed technique reduces the number of beams to the range of practical application (5 to 9 beams) while remaining in the epsilon-optimal range of 1% to 5% optimality gap. Conclusion: The proposed method can be integrated into a general algorithm for fast navigation of the ideal dose distribution Pareto surface and finding the treatment plan with the minimum number of beams, which corresponds to the delivery time, in epsilon-optimality range of the desired ideal plan. The project was supported by the Federal Share of program income earned by Massachusetts General Hospital on C06 CA059267, Proton Therapy Research and Treatment Center and partially by RaySearch Laboratories.« less

Electro-optic high voltage sensor

DOEpatents

Davidson, James R.; Seifert, Gary D.

2002-01-01

A small sized electro-optic voltage sensor capable of accurate measurement of high levels of voltages without contact with a conductor or voltage source is provided. When placed in the presence of an electric field, the sensor receives an input beam of electromagnetic radiation into the sensor. A polarization beam displacer serves as a filter to separate the input beam into two beams with orthogonal linear polarizations. The beam displacer is oriented in such a way as to rotate the linearly polarized beams such that they enter a Pockels crystal having at a preferred angle of 45 degrees. The beam displacer is therefore capable of causing a linearly polarized beam to impinge a crystal at a desired angle independent of temperature. The Pockels electro-optic effect induces a differential phase shift on the major and minor axes of the input beam as it travels through the Pockels crystal, which causes the input beam to be elliptically polarized. A reflecting prism redirects the beam back through the crystal and the beam displacer. On the return path, the polarization beam displacer separates the elliptically polarized beam into two output beams of orthogonal linear polarization representing the major and minor axes. The system may include a detector for converting the output beams into electrical signals, and a signal processor for determining the voltage based on an analysis of the output beams. The output beams are amplitude modulated by the frequency of the electric field and the amplitude of the output beams is proportional to the magnitude of the electric field, which is related to the voltage being measured.

Airborne Laser Polar Nephelometer

NASA Technical Reports Server (NTRS)

Grams, Gerald W.

1973-01-01

A polar nephelometer has been developed at NCAR to measure the angular variation of the intensity of light scattered by air molecules and particles. The system has been designed for airborne measurements using outside air ducted through a 5-cm diameter airflow tube; the sample volume is that which is common to the intersection of a collimated source beam and the detector field of view within the airflow tube. The source is a linearly polarized helium-neon laser beam. The optical system defines a collimated field-of-view (0.5deg half-angle) through a series of diaphragms located behind a I72-mm focal length objective lens. A photomultiplier tube is located immediately behind an aperture in the focal plane of the objective lens. The laser beam is mechanically chopped (on-off) at a rate of 5 Hz; a two-channel pulse counter, synchronized to the laser output, measures the photomultiplier pulse rate with the light beam both on and off. The difference in these measured pulse rates is directly proportional to the intensity of the scattered light from the volume common to the intersection of the laser beam and the detector field-of-view. Measurements can be made at scattering angles from 15deg to 165deg with reference to the direction of propagation of the light beam. Intermediate angles are obtained by selecting the angular increments desired between these extreme angles (any multiple of 0.1deg can be selected for the angular increment; 5deg is used in normal operation). Pulses provided by digital circuits control a stepping motor which sequentially rotates the detector by pre-selected angular increments. The synchronous photon-counting system automatically begins measurement of the scattered-light intensity immediately after the rotation to a new angle has been completed. The instrument has been flown on the NASA Convair 990 airborne laboratory to obtain data on the complex index of refraction of atmospheric aerosols. A particle impaction device is operated simultaneously to collect particles from the same airflow tube used to make the scattered-light measurements. A size distribution function is obtained by analysis of the particles collected by the impaction device. Calculated values of the angular variation of the scattered-light intensity are obtained by applying Mie scattering theory to the observed size distribution function and assuming different values of the complex index of refraction of the particles. The calculated values are then compared with data on the actual variation of the scattered-light intensity obtained with the polar nephelometer. The most probable value of the complex refractive index is that which provides the best fit between the experimental light scattering data and the parameters calculated from the observed size distribution function.

Ion beam sputtering of Ag - Angular and energetic distributions of sputtered and scattered particles

NASA Astrophysics Data System (ADS)

Feder, René; Bundesmann, Carsten; Neumann, Horst; Rauschenbach, Bernd

2013-12-01

Ion beam sputter deposition (IBD) provides intrinsic features which influence the properties of the growing film, because ion properties and geometrical process conditions generate different energy and spatial distribution of the sputtered and scattered particles. A vacuum deposition chamber is set up to measure the energy and spatial distribution of secondary particles produced by ion beam sputtering of different target materials under variation of geometrical parameters (incidence angle of primary ions and emission angle of secondary particles) and of primary ion beam parameters (ion species and energies).

Antenna Beam Pattern Characteristics of HAPS User Terminal

NASA Astrophysics Data System (ADS)

Ku, Bon-Jun; Oh, Dae Sub; Kim, Nam; Ahn, Do-Seob

High Altitude Platform Stations (HAPS) are recently considered as a green infrastructure to provide high speed multimedia services. The critical issue of HAPS is frequency sharing with satellite systems. Regulating antenna beam pattern using adaptive antenna schemes is one of means to facilitate the sharing with a space receiver for fixed satellite services on the uplink of a HAPS system operating in U bands. In this letter, we investigate antenna beam pattern characteristics of HAPS user terminals with various values of scan angles of main beam, null position angles, and null width.

Achieving highly efficient and broad-angle polarization beam filtering using epsilon-near-zero metamaterials mimicked by metal-dielectric multilayers

NASA Astrophysics Data System (ADS)

Wu, Feng

2018-03-01

We report a highly efficient and broad-angle polarization beam filter at visible wavelengths using an anisotropic epsilon-near-zero metamaterial mimicked by a multilayer composed of alternative subwavelength magnesium fluoride and silver layers. The underlying physics can be explained by the dramatic difference between two orthogonal polarizations' iso-frequency curves of anisotropic epsilon-near-zero metamaterials. Transmittance for two orthogonal polarization waves and the polarization extinction ratio are calculated via the transfer matrix method to assess the comprehensive performance of the proposed polarization beam filter. From the simulation results, the proposed polarization beam filter is highly efficient (the polarization extinction ratio is far larger than two orders of magnitude) and has a broad operating angle range (ranging from 30° to 75°). Finally, we show that the proper tailoring of the periodic number enables us to obtain high comprehensive performance of the proposed polarization beam filter.

A study of nondiffracting Lommel beams propagating in a medium containing spherical scatterers

NASA Astrophysics Data System (ADS)

Belafhal, A.; Ez-zariy, L.; Hricha, Z.

2016-11-01

By means of the expansion of the nondiffracting beams on plane waves with help of the Whittaker integral, an exact analytical expression of the far-field form function of the scattering of the acoustic and optical nondiffracting Lommel beams propagating in a medium containing spherical particles, considered as rigid and single spheres, is investigated in this work. The form function of the scattering of the high order Bessel beam by a rigid and isolated sphere is deduced, from our finding, as a special case. The effects of the wave number-sphere radius product (ka) , the polar angle (φ) , the propagation half-cone angle (β) and the scattering angle (θ) on the far-field form function of the scattered wave have been analyzed and discussed numerically. The numerical results show that the illumination of a rigid sphere by Lommel beams produces asymmetrical scattering.

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.

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.

Undersampled digital holographic interferometry

NASA Astrophysics Data System (ADS)

Halaq, H.; Demoli, N.; Sović, I.; Šariri, K.; Torzynski, M.; Vukičević, D.

2008-04-01

In digital holography, primary holographic fringes are recorded using a matricial CCD sensor. Because of the low spatial resolution of currently available CCD arrays, the angle between the reference and object beams must be limited to a few degrees. Namely, due to the digitization involved, the Shannon's criterion imposes that the Nyquist sampling frequency be at least twice the highest signal frequency. This means that, in the case of the recording of an interference fringe pattern by a CCD sensor, the inter-fringe distance must be larger than twice the pixel period. This in turn limits the angle between the object and the reference beams. If this angle, in a practical holographic interferometry measuring setup, cannot be limited to the required value, aliasing will occur in the reconstructed image. In this work, we demonstrate that the low spatial frequency metrology data could nevertheless be efficiently extracted by careful choice of twofold, and even threefold, undersampling of the object field. By combining the time-averaged recording with subtraction digital holography method, we present results for a loudspeaker membrane interferometric study obtained under strong aliasing conditions. High-contrast fringes, as a consequence of the vibration modes of the membrane, are obtained.

Reflective Optics Design for an LED High Beam Headlamp of Motorbikes

PubMed Central

Ge, Peng; Wang, Xiang; Li, Yang; Wang, Hong

2015-01-01

We propose a reflective optics design for an LED motorbike high beam lamp. We set the measuring screen as an elliptical zone and divide it into many small lattices and divide the spatial angle of the LED source into many parts and make relationships between them. According to the conservation law of energy and the Snell's law, the reflector is generated by freeform optics design method. Then the optical system is simulated by Monte Carlo method using ASAP software. Light pattern of simulation could meet the standard. The high beam headlamp is finally fabricated and assembled into a physical object. Experiment results can fully comply with United Nations Economic Commission for Europe (ECE) vehicle regulations R113 revision 2 (Class C). PMID:25961073

Phase-stepping fiber-optic projected fringe system for surface topography measurements

NASA Technical Reports Server (NTRS)

Mercer, Carolyn R. (Inventor); Beheim, Glenn (Inventor)

1992-01-01

A projected fringe interferometer for measuring the topography of an object is presented. The interferometer periodically steps the phase angle between a pair of light beams emanating from a common source. The steps are pi/2 radians (90 deg) apart, and at each step a video image of the fringes is recorded and stored. Photodetectors measure either the phase and theta of the beams or 2(theta). Either of the measures can be used to control one of the light beams so that the 90 deg theta is accurately maintained. A camera, a computer, a phase controller, and a phase modulator established closed-loop control of theta. Measuring the phase map of a flat surface establishes a calibration reference.

Reflective optics design for an LED high beam headlamp of motorbikes.

PubMed

Ge, Peng; Wang, Xiang; Li, Yang; Wang, Hong

2015-01-01

We propose a reflective optics design for an LED motorbike high beam lamp. We set the measuring screen as an elliptical zone and divide it into many small lattices and divide the spatial angle of the LED source into many parts and make relationships between them. According to the conservation law of energy and the Snell's law, the reflector is generated by freeform optics design method. Then the optical system is simulated by Monte Carlo method using ASAP software. Light pattern of simulation could meet the standard. The high beam headlamp is finally fabricated and assembled into a physical object. Experiment results can fully comply with United Nations Economic Commission for Europe (ECE) vehicle regulations R113 revision 2 (Class C).

Focusing of concentric piecewise vector Bessel-Gaussian beam

NASA Astrophysics Data System (ADS)

Li, Jinsong; Fang, Ying; Zhou, Shenghua; Ye, Youxiang

2010-12-01

The focusing properties of a concentric piecewise vector Bessel-Gaussian beam are investigated in this paper. The beam consists of three portions: the center circular portion and outer annular portion are radially polarized, while the inner annular portion is generalized polarized with tunable polarized angle. Numerical simulations show that the evolution of focal pattern is altered considerably with different Bessel parameters in the Bessel term of the vector Bessel-Gaussian beam. The polarized angle also affects the focal pattern remarkably. Some interesting focal patterns may appear, such as two-peak, dark hollow focus; ring focus; spherical shell focus; cylindrical shell focus; and multi-ring-peak focus, and transverse focal switch occurs with increasing polarized angle of the inner annular portion, which may be used in optical manipulation.

Voltage sensing systems and methods for passive compensation of temperature related intrinsic phase shift

DOEpatents

Davidson, James R.; Lassahn, Gordon D.

2001-01-01

A small sized electro-optic voltage sensor capable of accurate measurement of high levels of voltages without contact with a conductor or voltage source is provided. When placed in the presence of an electric field, the sensor receives an input beam of electromagnetic radiation into the sensor. A polarization beam displacer serves as a filter to separate the input beam into two beams with orthogonal linear polarizations. The beam displacer is oriented in such a way as to rotate the linearly polarized beams such that they enter a Pockels crystal at a preferred angle of 45 degrees. The beam displacer is therefore capable of causing a linearly polarized beam to impinge a crystal at a desired angle independent of temperature. The Pockels electro-optic effect induces a differential phase shift on the major and minor axes of the input beam as it travels through the Pockels crystal, which causes the input beam to be elliptically polarized. A reflecting prism redirects the beam back through the crystal and the beam displacer. On the return path, the polarization beam displacer separates the elliptically polarized beam into two output beams of orthogonal linear polarization representing the major and minor axes. In crystals that introduce a phase differential attributable to temperature, a compensating crystal is provided to cancel the effect of temperature on the phase differential of the input beam. The system may include a detector for converting the output beams into electrical signals, and a signal processor for determining the voltage based on an analysis of the output beams. The output beams are amplitude modulated by the frequency of the electric field and the amplitude of the output beams is proportional to the magnitude of the electric field, which is related to the voltage being measured.

On the maximum off-axis gain of symmetrical pencil-beam antennas

NASA Technical Reports Server (NTRS)

Sawitz, P. H.

1977-01-01

For a general class of symmetrical pencil-beam antennas, the gain at a given off-axis angle can be maximized by choosing the proper antenna size. The maximum gain at the given angle relative to the on-axis gain is independent of the given angle and dependent only on the main-beam pattern. It is computed here for four commonly used gain functions. Its value, in all cases, is close to 4 dB. This result is important in the definition of service areas for communication and broadcast satellites.

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.

Coherent Detector for Near-Angle Scattering and Polarization Characterization of Telescope Mirror Coatings

NASA Technical Reports Server (NTRS)

Macenka, Steven A.; Chipman, Russell A.; Daugherty, Brian J.; McClain, Stephen C.

2012-01-01

A report discusses the difficulty of measuring scattering properties of coated mirrors extremely close to the specular reflection peak. A prototype Optical Hetero dyne Near-angle Scatterometer (OHNS) was developed. Light from a long-coherence-length (>150 m) 532-nm laser is split into two arms. Acousto-optic modulators frequency shift the sample and reference beams, establishing a fixed beat frequency between the beams. The sample beam is directed at very high f/# onto a mirror sample, and the point spread function (PSF) formed after the mirror sample is scanned with a pinhole. This light is recombined by a non-polarizing beam splitter and measured through heterodyne detection with a spectrum analyzer. Polarizers control the illuminated and analyzed polarization states, allowing the polarization dependent scatter to be measured. The bidirectional reflective or scattering distribution function is normally measured through use of a scattering goniometer instrument. The instrumental beam width (collection angle span) over which the scatterometer responds is typically many degrees. The OHNS enables measurement at angles as small as the first Airy disk diameter.

Solid state laser

NASA Technical Reports Server (NTRS)

Rines, Glen A. (Inventor); Moulton, Peter F. (Inventor); Harrison, James (Inventor)

1993-01-01

A wavelength-tunable, injection-seeded, dispersion-compensated, dispersively-pumped solid state laser includes a lasing medium; a highly reflective mirror; an output coupler; at least one isosceles Brewster prism oriented to the minimum deviation angle between the medium and the mirror for directing light of different wavelengths along different paths; means for varying the angle of the highly reflective mirror relative to the light from at least one Brewster angle for selecting a predetermined laser operating wavelength; a dispersion compensation apparatus associated with the lasing medium; a laser injection seeding port disposed between the dispersion compensation apparatus and one of the mirror and coupler and including a reflective surface at an acute non-Brewster angle to the laser beam for introducing a seed input; a dispersion compensation apparatus associated with the laser medium including opposite chirality optical elements; the lasing medium including a pump surface disposed at an acute angle to the laser beam to define a discrete path for the pumping laser beam separate from the pumped laser beam.

Tandem-Mirror Ion Source

NASA Technical Reports Server (NTRS)

Biddle, A.; Stone, N.; Reasoner, D.; Chisholm, W.; Reynolds, J.

1986-01-01

Improved ion source produces beam of ions at any kinetic energy from 1 to 1,000 eV, with little spread in energy or angle. Such ion beams useful in studies of surface properties of materials, surface etching, deposition, and development of plasma-diagnostic instrumentation. Tandemmirror ion source uses electrostatic and magnetic fields to keep electrons in ionization chamber and assure uniform output ion beam having low divergence in energy and angle.

Echolocation call intensity and directionality in flying short-tailed fruit bats, Carollia perspicillata (Phyllostomidae).

PubMed

Brinkløv, Signe; Jakobsen, Lasse; Ratcliffe, John M; Kalko, Elisabeth K V; Surlykke, Annemarie

2011-01-01

The directionality of bat echolocation calls defines the width of bats' sonar "view," while call intensity directly influences detection range since adequate sound energy must impinge upon objects to return audible echoes. Both are thus crucial parameters for understanding biosonar signal design. Phyllostomid bats have been classified as low intensity or "whispering bats," but recent data indicate that this designation may be inaccurate. Echolocation beam directionality in phyllostomids has only been measured through electrode brain-stimulation of restrained bats, presumably excluding active beam control via the noseleaf. Here, a 12-microphone array was used to measure echolocation call intensity and beam directionality in the frugivorous phyllostomid, Carollia perspicillata, echolocating in flight. The results showed a considerably narrower beam shape (half-amplitude beam angles of approximately 16° horizontally and 14° vertically) and louder echolocation calls [source levels averaging 99 dB sound pressure level (SPL) root mean square] for C. perspicillata than was found for this species when stationary. This suggests that naturally behaving phyllostomids shape their sound beam to achieve a longer and narrower sonar range than previously thought. C. perspicillata orient and forage in the forest interior and the narrow beam might be adaptive in clutter, by reducing the number and intensity of off-axis echoes.

A modular approach to intensity-modulated arc therapy optimization with noncoplanar trajectories

NASA Astrophysics Data System (ADS)

Papp, Dávid; Bortfeld, Thomas; Unkelbach, Jan

2015-07-01

Utilizing noncoplanar beam angles in volumetric modulated arc therapy (VMAT) has the potential to combine the benefits of arc therapy, such as short treatment times, with the benefits of noncoplanar intensity modulated radiotherapy (IMRT) plans, such as improved organ sparing. Recently, vendors introduced treatment machines that allow for simultaneous couch and gantry motion during beam delivery to make noncoplanar VMAT treatments possible. Our aim is to provide a reliable optimization method for noncoplanar isocentric arc therapy plan optimization. The proposed solution is modular in the sense that it can incorporate different existing beam angle selection and coplanar arc therapy optimization methods. Treatment planning is performed in three steps. First, a number of promising noncoplanar beam directions are selected using an iterative beam selection heuristic; these beams serve as anchor points of the arc therapy trajectory. In the second step, continuous gantry/couch angle trajectories are optimized using a simple combinatorial optimization model to define a beam trajectory that efficiently visits each of the anchor points. Treatment time is controlled by limiting the time the beam needs to trace the prescribed trajectory. In the third and final step, an optimal arc therapy plan is found along the prescribed beam trajectory. In principle any existing arc therapy optimization method could be incorporated into this step; for this work we use a sliding window VMAT algorithm. The approach is demonstrated using two particularly challenging cases. The first one is a lung SBRT patient whose planning goals could not be satisfied with fewer than nine noncoplanar IMRT fields when the patient was treated in the clinic. The second one is a brain tumor patient, where the target volume overlaps with the optic nerves and the chiasm and it is directly adjacent to the brainstem. Both cases illustrate that the large number of angles utilized by isocentric noncoplanar VMAT plans can help improve dose conformity, homogeneity, and organ sparing simultaneously using the same beam trajectory length and delivery time as a coplanar VMAT plan.

Proton Therapy Facility Planning From a Clinical and Operational Model.

PubMed

Das, Indra J; Moskvin, Vadim P; Zhao, Qingya; Cheng, Chee-Wai; Johnstone, Peter A

2015-10-01

This paper provides a model for planning a new proton therapy center based on clinical data, referral pattern, beam utilization and technical considerations. The patient-specific data for the depth of targets from skin in each beam angle were reviewed at our center providing megavoltage photon external beam and proton beam therapy respectively. Further, data on insurance providers, disease sites, treatment depths, snout size and the beam angle utilization from the patients treated at our proton facility were collected and analyzed for their utilization and their impact on the facility cost. The most common disease sites treated at our center are head and neck, brain, sarcoma and pediatric malignancies. From this analysis, it is shown that the tumor depth from skin surface has a bimodal distribution (peak at 12 and 26 cm) that has significant impact on the maximum proton energy, requiring the energy in the range of 130-230 MeV. The choice of beam angles also showed a distinct pattern: mainly at 90° and 270°; this indicates that the number of gantries may be minimized. Snout usage data showed that 70% of the patients are treated with 10 cm snouts. The cost of proton beam therapy depends largely on the type of machine, maximum beam energy and the choice of gantry versus fixed beam line. Our study indicates that for a 4-room center, only two gantry rooms could be needed at the present pattern of the patient cohorts, thus significantly reducing the initial capital cost. In the USA, 95% and 100% of patients can be treated with 200 and 230 MeV proton beam respectively. Use of multi-leaf collimators and pencil beam scanning may further reduce the operational cost of the facility. © The Author(s) 2014.

Wide steering angle microscanner based on curved surface

NASA Astrophysics Data System (ADS)

Sabry, Yasser; Khalil, Diaa; Saadany, Bassam; Bourouina, Tarik

2013-03-01

Intensive industrial and academic research is oriented towards the design and fabrication of optical beam steering systems based on MEMS technology. In most of these systems, the scanning is achieved by rotating a flat micromirror around a central axis in which the main challenge is achieving a wide mirror rotation angle. In this work, a novel method of optical beam scanning based on reflection from a curved surface is presented. The scanning occurs when the optical axis of the curved surface is displaced with respect to the optical axis of the incident beam. To overcome the possible deformation of the spot with the scanning angle, the curved surface is designed with a specific aspherical profile. Moreover, the scanning exhibits a more linearized scanning angle-displacement relation than the conventional spherical profile. The presented scanner is fabricated using DRIE technology on an SOI wafer. The curved surface (reflector) is metalized and attached to a comb-drive actuator fabricated in the same lithography step. A single-mode fiber, behaving as a Gaussian beam source, is positioned on the substrate facing the mirror. The reflected optical beam angle and spotsize in the far field is recorded versus the relative shift between the fiber and the curved mirror. The spot size is plotted versus the scanning angle and a scanning spot size uniformity of about +/-10% is obtained for optical deflection angles up to 100 degrees. As the optical beam is propagating parallel to the wafer substrate, a completely integrated laser scanner can be achieved with filters and actuators self-aligned on the same chip that allows low cost and mass production of this important product.

A high brightness proton injector for the Tandetron accelerator at Jožef Stefan Institute

NASA Astrophysics Data System (ADS)

Pelicon, Primož; Podaru, Nicolae C.; Vavpetič, Primož; Jeromel, Luka; Ogrinc Potocnik, Nina; Ondračka, Simon; Gottdang, Andreas; Mous, Dirk J. M.

2014-08-01

Jožef Stefan Institute recently commissioned a high brightness H- ion beam injection system for its existing tandem accelerator facility. Custom developed by High Voltage Engineering Europa, the multicusp ion source has been tuned to deliver at the entrance of the Tandetron™ accelerator H- ion beams with a measured brightness of 17.1 A m-2 rad-2 eV-1 at 170 μA, equivalent to an energy normalized beam emittance of 0.767 π mm mrad MeV1/2. Upgrading the accelerator facility with the new injection system provides two main advantages. First, the high brightness of the new ion source enables the reduction of object slit aperture and the reduction of acceptance angle at the nuclear microprobe, resulting in a reduced beam size at selected beam intensity, which significantly improves the probe resolution for micro-PIXE applications. Secondly, the upgrade strongly enhances the accelerator up-time since H and He beams are produced by independent ion sources, introducing a constant availability of 3He beam for fusion-related research with NRA. The ion beam particle losses and ion beam emittance growth imply that the aforementioned beam brightness is reduced by transport through the ion optical system. To obtain quantitative information on the available brightness at the high-energy side of the accelerator, the proton beam brightness is determined in the nuclear microprobe beamline. Based on the experience obtained during the first months of operation for micro-PIXE applications, further necessary steps are indicated to obtain optimal coupling of the new ion source with the accelerator to increase the normalized high-energy proton beam brightness at the JSI microprobe, currently at 14 A m-2 rad-2 eV-1, with the output current at 18% of its available maximum.

Two-screen single-shot electron spectrometer for laser wakefield accelerated electron beams.

PubMed

Soloviev, A A; Starodubtsev, M V; Burdonov, K F; Kostyukov, I Yu; Nerush, E N; Shaykin, A A; Khazanov, E A

2011-04-01

The laser wakefield acceleration electron beams can essentially deviate from the axis of the system, which distinguishes them greatly from beams of conventional accelerators. In case of energy measurements by means of a permanent-magnet electron spectrometer, the deviation angle can affect accuracy, especially for high energies. A two-screen single-shot electron spectrometer that correctly allows for variations of the angle of entry is considered. The spectrometer design enables enhancing accuracy of measuring narrow electron beams significantly as compared to a one-screen spectrometer with analogous magnetic field, size, and angular acceptance. © 2011 American Institute of Physics

Active control of acoustic field-of-view in a biosonar system.

PubMed

Yovel, Yossi; Falk, Ben; Moss, Cynthia F; Ulanovsky, Nachum

2011-09-01

Active-sensing systems abound in nature, but little is known about systematic strategies that are used by these systems to scan the environment. Here, we addressed this question by studying echolocating bats, animals that have the ability to point their biosonar beam to a confined region of space. We trained Egyptian fruit bats to land on a target, under conditions of varying levels of environmental complexity, and measured their echolocation and flight behavior. The bats modulated the intensity of their biosonar emissions, and the spatial region they sampled, in a task-dependant manner. We report here that Egyptian fruit bats selectively change the emission intensity and the angle between the beam axes of sequentially emitted clicks, according to the distance to the target, and depending on the level of environmental complexity. In so doing, they effectively adjusted the spatial sector sampled by a pair of clicks-the "field-of-view." We suggest that the exact point within the beam that is directed towards an object (e.g., the beam's peak, maximal slope, etc.) is influenced by three competing task demands: detection, localization, and angular scanning-where the third factor is modulated by field-of-view. Our results suggest that lingual echolocation (based on tongue clicks) is in fact much more sophisticated than previously believed. They also reveal a new parameter under active control in animal sonar-the angle between consecutive beams. Our findings suggest that acoustic scanning of space by mammals is highly flexible and modulated much more selectively than previously recognized.

Performance characteristics of mobile MOSFET dosimeter for kilovoltage X-rays used in image guided radiotherapy.

PubMed

Kumar, A Sathish; Singh, I Rabi Raja; Sharma, S D; Ravindran, B Paul

2015-01-01

The main objective of this study was to investigate the characteristics of metal oxide semiconductor field effect transistor (MOSFET) dosimeter for kilovoltage (kV) X-ray beams in order to perform the in vivo dosimetry during image guidance in radiotherapy. The performance characteristics of high sensitivity MOSFET dosimeters were investigated for 80, 90, 100, 110, 120, and 125 kV X-ray beams used for imaging in radiotherapy. This study was performed using Clinac 2100 C/D medical electron linear accelerator with on-board imaging and kV cone beam computed tomography system. The characteristics studied in this work include energy dependence, angular dependence, and linearity. The X-ray beam outputs were measured as per American Association of Physicists in Medicine (AAPM) TG 61 recommendations using PTW parallel plate (PP) ionization chamber, which was calibrated in terms of air kerma (Nk) by the National Standard Laboratory. The MOSFET dosimeters were calibrated against the PP ionization chamber for all the kV X-ray beams and the calibration coefficient was found to be 0.11 cGy/mV with a standard deviation of about ±1%. The response of MOSFET was found to be energy independent for the kV X-ray energies used in this study. The response of the MOSFET dosimeter was also found independent of angle of incidence for the gantry angles in the range of 0° to 360° in-air as well as at 3 cm depth in tissue equivalent phantom.

Acquisition and replay systems for direct-to-digital holography and holovision

DOEpatents

Thomas, Clarence E.; Hanson, Gregory R.

2003-02-25

Improvements to the acquisition and replay systems for direct-to-digital holography and holovision are described. A method of recording an off-axis hologram includes: splitting a laser beam into an object beam and a reference beam; reflecting the reference beam from a reference beam mirror; reflecting the object beam from an illumination beamsplitter; passing the object beam through an objective lens; reflecting the object beam from an object; focusing the reference beam and the object beam at a focal plane of a digital recorder to form an off-axis hologram; digitally recording the off-axis hologram; and transforming the off-axis hologram in accordance with a Fourier transform to obtain a set of results. A method of writing an off-axis hologram includes: passing a laser beam through a spatial light modulator; and focusing the laser beam at a focal plane of a photorefractive crystal to impose a holographic diffraction grating pattern on the photorefractive crystal. A method of replaying an off-axis hologram includes: illuminating a photorefractive crystal having a holographic diffraction grating with a replay beam.

Angularly symmetric splitting of a light beam upon reflection and refraction at an air-dielectric plane boundary.

PubMed

Azzam, R M A

2015-12-01

Conditions for achieving equal and opposite angular deflections of a light beam by reflection and refraction at an air-dielectric boundary are determined. Such angularly symmetric beam splitting (ASBS) is possible only if the angle of incidence is >60° by exactly one third of the angle of refraction. This simple law, plus Snell's law, leads to several analytical results that clarify all aspects of this phenomenon. In particular, it is shown that the intensities of the two symmetrically deflected beams can be equalized by proper choice of the prism refractive index and the azimuth of incident linearly polarized light. ASBS enables a geometrically attractive layout of optical systems that employ multiple prism beam splitters.

Calibration of the radiation monitors from DESY and SPring-8 at the quasi-mono-energetic neutron beams using 100 and 300 MeV 7Li(p,n) reaction at RCNP in Osaka Japan in November 2014

NASA Astrophysics Data System (ADS)

Leuschner, Albrecht; Asano, Yoshihiro; Klett, Alfred

2017-09-01

At the ring cyclotron facility of the Research Center for Nuclear Physics (RCNP) Osaka University, Osaka, Japan a series of measurement campaigns had been continued with quasi mono-energetic neutron beams in November 2014. A 7Li target was bombarded with 100 and 300 MeV protons and the generated neutron beams were directed into a long time-of-flight tunnel at 0 and 25 degrees deflection angle with respect to the proton beam. At a distance of 41 m the cross section of the neutron beam was large enough for the illumination of square meter sized objects like extended range rem-counters. The research institutes SPring-8/RIKEN, Japan, and DESY, Germany, participated in this campaign for the calibration of 4 different types of active ambient dose rate monitors: LB 6411, LB 6411-Pb, LB 6419 and LB 6420. The measurements of their responses are reported and compared with the calculated values.

Combination Light

NASA Astrophysics Data System (ADS)

1990-01-01

The Rayovac TANDEM is an advanced technology combination work light and general purpose flashlight that incorporates several NASA technologies. The TANDEM functions as two lights in one. It features a long range spotlight and wide angle floodlight; simple one-hand electrical switching changes the beam from spot to flood. TANDEM developers made particular use of NASA's extensive research in ergonomics in the TANDEM's angled handle, convenient shape and different orientations. The shatterproof, water resistant plastic casing also draws on NASA technology, as does the shape and beam distance of the square diffused flood. TANDEM's heavy duty magnet that permits the light to be affixed to any metal object borrows from NASA research on rare earth magnets that combine strong magnetic capability with low cost. Developers used a NASA-developed ultrasonic welding technique in the light's interior.

SU-E-T-171: Evaluation of the Analytical Anisotropic Algorithm in a Small Finger Joint Phantom Using Monte Carlo Simulation

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

Chow, J; Owrangi, A; Jiang, R

2014-06-01

Purpose: This study investigated the performance of the anisotropic analytical algorithm (AAA) in dose calculation in radiotherapy concerning a small finger joint. Monte Carlo simulation (EGSnrc code) was used in this dosimetric evaluation. Methods: Heterogeneous finger joint phantom containing a vertical water layer (bone joint or cartilage) sandwiched by two bones with dimension 2 × 2 × 2 cm{sup 3} was irradiated by the 6 MV photon beams (field size = 4 × 4 cm{sup 2}). The central beam axis was along the length of the bone joint and the isocenter was set to the center of the joint. Themore » joint width and beam angle were varied from 0.5–2 mm and 0°–15°, respectively. Depth doses were calculated using the AAA and DOSXYZnrc. For dosimetric comparison and normalization, dose calculations were repeated in water phantom using the same beam geometry. Results: Our AAA and Monte Carlo results showed that the AAA underestimated the joint doses by 10%–20%, and could not predict joint dose variation with changes of joint width and beam angle. The calculated bone dose enhancement for the AAA was lower than Monte Carlo and the depth of maximum dose for the phantom was smaller than that for the water phantom. From Monte Carlo results, there was a decrease of joint dose as its width increased. This reflected the smaller the joint width, the more the bone scatter contributed to the depth dose. Moreover, the joint dose was found slightly decreased with an increase of beam angle. Conclusion: The AAA could not handle variations of joint dose well with changes of joint width and beam angle based on our finger joint phantom. Monte Carlo results showed that the joint dose decreased with increase of joint width and beam angle. This dosimetry comparison should be useful to radiation staff in radiotherapy related to small bone joint.« less

Digital electron diffraction – seeing the whole picture

PubMed Central

Beanland, Richard; Thomas, Paul J.; Woodward, David I.; Thomas, Pamela A.; Roemer, Rudolf A.

2013-01-01

The advantages of convergent-beam electron diffraction for symmetry determination at the scale of a few nm are well known. In practice, the approach is often limited due to the restriction on the angular range of the electron beam imposed by the small Bragg angle for high-energy electron diffraction, i.e. a large convergence angle of the incident beam results in overlapping information in the diffraction pattern. Techniques have been generally available since the 1980s which overcome this restriction for individual diffracted beams, by making a compromise between illuminated area and beam convergence. Here a simple technique is described which overcomes all of these problems using computer control, giving electron diffraction data over a large angular range for many diffracted beams from the volume given by a focused electron beam (typically a few nm or less). The increase in the amount of information significantly improves the ease of interpretation and widens the applicability of the technique, particularly for thin materials or those with larger lattice parameters. PMID:23778099

Vectorial diffraction properties of THz vortex Bessel beams.

PubMed

Wu, Zhen; Wang, Xinke; Sun, Wenfeng; Feng, Shengfei; Han, Peng; Ye, Jiasheng; Yu, Yue; Zhang, Yan

2018-01-22

A vortex Bessel beam combines the merits of an optical vortex and a Bessel beam, including a spiral wave front and a non-diffractive feature, which has immense application potentials in optical trapping, optical fabrication, optical communications, and so on. Here, linearly and circularly polarized vortex Bessel beams in the terahertz (THz) frequency range are generated by utilizing a THz quarter wave plate, a spiral phase plate, and Teflon axicons with different opening angles. Taking advantage of a THz focal-plane imaging system, vectorial diffraction properties of the THz vortex Bessel beams are comprehensively characterized and discussed, including the transverse (Ex, Ey) and longitudinal (Ez) polarization components. The experimental phenomena are accurately simulated by adopting the vectorial Rayleigh diffraction integral. By varying the opening angle of the axicon, the characteristic parameters of these THz vortex Bessel beams are exhibited and compared, including the light spot size, the diffraction-free range, and the phase evolution process. This work provides the precise experimental and theoretical bases for the comprehension and application of a THz vortex Bessel beam.

Fast Ion Mesurements in LAPD

NASA Astrophysics Data System (ADS)

Zhao, L.; Boehmer, H.; Edrich, D.; Heidbrink, W.; McWilliams, R.; Zimmerman, D.; Leneman, D.

2003-10-01

To study fast-ion transport, a 3-cm diameter, 17 MHZ, ˜80W, ˜3 mA argon source launches ˜500 eV ions in the LArge Plasma Device (LAPD). The beam is diagnosed with a gridded analyzer and, on a test stand at Irvine, laser-induced fluorescence (LIF). Neutral scattering is important near the source. The measured beam energy can be more than 100 eV larger than the accelerating voltage applied to the extraction grids. In LAPD the profile of the pulsed ion beam is measured at various axial locations between z=0.3-6.0 m from the source. When the beam velocity is parallel to the solenoidal field (0^o) evidence of peristaltic focusing, beam attenuation, and radial scattering is observed. At an angle of 22^o with respect to the field the beam follows the expected helical trajectory. Three meters axially from the source strong attenuation and elongation of the beam in the direction of the gyro-angle are observed. The data are compared with classical Coulomb and neutral scattering theory.

Angle Control on the Optima HE/XE Ion Implanter

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

Bell, Edward; Satoh, Shu

2008-11-03

The Optima HE/XE is the latest generation of high energy ion implanter from Axcelis, combining proven RF linear accelerator technology with new single wafer processing. The architecture of the implanter is designed to provide a parallel beam at the wafer plane over the full range of implant energies and beam currents. One of the advantages of this system is the ability to control both the horizontal and vertical implant angles for each implant. Included in the design is the ability to perform in situ measurements of the horizontal and vertical angles of the beam in real time. The method ofmore » the horizontal and vertical angle measurements is described in this paper.« less

Operational characteristics of a translation screen grid beam deflection system for a 5-cm Kaufman thruster

NASA Technical Reports Server (NTRS)

Lathem, W. C.; Hudson, W. R.

1972-01-01

Measurements of beam deflection angle with respect to spring positioning power and accelerator impingement current as a function of deflection angle were made on a 5-cm diameter system. Response time measurements on the translational grid beam deflection system showed that the time for the maximum deflection angle analyzed (+16.4 deg to -16.4 deg) could be reduced by a factor of nine by increasing the heating power applied to the positioning spring from 4 to 16 watts. At 14 watts the response time for maximum deflection was about 1 minute.

Application of dot-matrix illumination of liquid crystal phase space light modulator in 3D imaging of APD array

NASA Astrophysics Data System (ADS)

Wang, Shuai; Sun, Huayan; Guo, Huichao

2018-01-01

Aiming at the problem of beam scanning in low-resolution APD array in three-dimensional imaging, a method of beam scanning with liquid crystal phase-space optical modulator is proposed to realize high-resolution imaging by low-resolution APD array. First, a liquid crystal phase spatial light modulator is used to generate a beam array and then a beam array is scanned. Since the sub-beam divergence angle in the beam array is smaller than the field angle of a single pixel in the APD array, the APD's pixels respond only to the three-dimensional information of the beam illumination position. Through the scanning of the beam array, a single pixel is used to collect the target three-dimensional information multiple times, thereby improving the resolution of the APD detector. Finally, MATLAB is used to simulate the algorithm in this paper by using two-dimensional scalar diffraction theory, which realizes the splitting and scanning with a resolution of 5 x 5. The feasibility is verified theoretically.

Scanning laser reflection tool for alignment and period measurement of critical-angle transmission gratings

NASA Astrophysics Data System (ADS)

Song, Jungki; Heilmann, Ralf K.; Bruccoleri, Alexander R.; Hertz, Edward; Schatternburg, Mark L.

2017-08-01

We report progress toward developing a scanning laser reflection (LR) tool for alignment and period measurement of critical-angle transmission (CAT) gratings. It operates on a similar measurement principle as a tool built in 1994 which characterized period variations of grating facets for the Chandra X-ray Observatory. A specularly reflected beam and a first-order diffracted beam were used to record local period variations, surface slope variations, and grating line orientation. In this work, a normal-incidence beam was added to measure slope variations (instead of the angled-incidence beam). Since normal incidence reflection is not coupled with surface height change, it enables measurement of slope variations more accurately and, along with the angled-incidence beam, helps to reconstruct the surface figure (or tilt) map. The measurement capability of in-grating period variations was demonstrated by measuring test reflection grating (RG) samples that show only intrinsic period variations of the interference lithography process. Experimental demonstration for angular alignment of CAT gratings is also presented along with a custom-designed grating alignment assembly (GAA) testbed. All three angles were aligned to satisfy requirements for the proposed Arcus mission. The final measurement of roll misalignment agrees with the roll measurements performed at the PANTER x-ray test facility.

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

Koh, S.K.; Song, S.K.; Choi, W.K.

A Kaufman-type 5 cm convex gridded ion-beam source is characterized in terms of angle-resolved ion-beam current density and beam uniformity at various discharge currents, electromagnet currents, and acceleration potentials. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Superiorized algorithm for reconstruction of CT images from sparse-view and limited-angle polyenergetic data

NASA Astrophysics Data System (ADS)

Humphries, T.; Winn, J.; Faridani, A.

2017-08-01

Recent work in CT image reconstruction has seen increasing interest in the use of total variation (TV) and related penalties to regularize problems involving reconstruction from undersampled or incomplete data. Superiorization is a recently proposed heuristic which provides an automatic procedure to ‘superiorize’ an iterative image reconstruction algorithm with respect to a chosen objective function, such as TV. Under certain conditions, the superiorized algorithm is guaranteed to find a solution that is as satisfactory as any found by the original algorithm with respect to satisfying the constraints of the problem; this solution is also expected to be superior with respect to the chosen objective. Most work on superiorization has used reconstruction algorithms which assume a linear measurement model, which in the case of CT corresponds to data generated from a monoenergetic x-ray beam. Many CT systems generate x-rays from a polyenergetic spectrum, however, in which the measured data represent an integral of object attenuation over all energies in the spectrum. This inconsistency with the linear model produces the well-known beam hardening artifacts, which impair analysis of CT images. In this work we superiorize an iterative algorithm for reconstruction from polyenergetic data, using both TV and an anisotropic TV (ATV) penalty. We apply the superiorized algorithm in numerical phantom experiments modeling both sparse-view and limited-angle scenarios. In our experiments, the superiorized algorithm successfully finds solutions which are as constraints-compatible as those found by the original algorithm, with significantly reduced TV and ATV values. The superiorized algorithm thus produces images with greatly reduced sparse-view and limited angle artifacts, which are also largely free of the beam hardening artifacts that would be present if a superiorized version of a monoenergetic algorithm were used.

An optimal beam alignment method for large-scale distributed space surveillance radar system

NASA Astrophysics Data System (ADS)

Huang, Jian; Wang, Dongya; Xia, Shuangzhi

2018-06-01

Large-scale distributed space surveillance radar is a very important ground-based equipment to maintain a complete catalogue for Low Earth Orbit (LEO) space debris. However, due to the thousands of kilometers distance between each sites of the distributed radar system, how to optimally implement the Transmitting/Receiving (T/R) beams alignment in a great space using the narrow beam, which proposed a special and considerable technical challenge in the space surveillance area. According to the common coordinate transformation model and the radar beam space model, we presented a two dimensional projection algorithm for T/R beam using the direction angles, which could visually describe and assess the beam alignment performance. Subsequently, the optimal mathematical models for the orientation angle of the antenna array, the site location and the T/R beam coverage are constructed, and also the beam alignment parameters are precisely solved. At last, we conducted the optimal beam alignment experiments base on the site parameters of Air Force Space Surveillance System (AFSSS). The simulation results demonstrate the correctness and effectiveness of our novel method, which can significantly stimulate the construction for the LEO space debris surveillance equipment.

High-resolution study of dynamical diffraction phenomena accompanying the Renninger (222/113) case of three-beam diffraction in silicon

PubMed Central

Kazimirov, A.; Kohn, V. G.

2010-01-01

X-ray optical schemes capable of producing a highly monochromatic beam with high angular collimation in both the vertical and horizontal planes have been evaluated and utilized to study high-resolution diffraction phenomena in the Renninger (222/113) case of three-beam diffraction in silicon. The effect of the total reflection of the incident beam into the nearly forbidden reflected beam was observed for the first time with the maximum 222 reflectivity at the 70% level. We have demonstrated that the width of the 222 reflection can be varied many times by tuning the azimuthal angle by only a few µrad in the vicinity of the three-beam diffraction region. This effect, predicted theoretically more than 20 years ago, is explained by the enhancement of the 222 scattering amplitude due to the virtual two-stage 000 113 222 process which depends on the azimuthal angle. PMID:20555185

Optical superimposed vortex beams generated by integrated holographic plates with blazed grating

NASA Astrophysics Data System (ADS)

Zhang, Xue-Dong; Su, Ya-Hui; Ni, Jin-Cheng; Wang, Zhong-Yu; Wang, Yu-Long; Wang, Chao-Wei; Ren, Fei-Fei; Zhang, Zhen; Fan, Hua; Zhang, Wei-Jie; Li, Guo-Qiang; Hu, Yan-Lei; Li, Jia-Wen; Wu, Dong; Chu, Jia-Ru

2017-08-01

In this paper, we demonstrate that the superposition of two vortex beams with controlled topological charges can be realized by integrating two holographic plates with blazed grating. First, the holographic plate with blazed grating was designed and fabricated by laser direct writing for generating well-separated vortex beam. Then, the relationship between the periods of blazed grating and the discrete angles of vortex beams was systemically investigated. Finally, through setting the discrete angle and different revolving direction of the holographic plates, the composite fork-shaped field was realized by the superposition of two vortex beams in a particular position. The topological charges of composite fork-shaped field (l = 1, 0, 3, and 4) depend on the topological charges of compositional vortex beams, which are well agreed with the theoretical simulation. The method opens up a wide range of opportunities and possibilities for applying in optical communication, optical manipulations, and photonic integrated circuits.

An instrument for 3D x-ray nano-imaging

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

Holler, M.; Raabe, J.; Diaz, A.

We present an instrument dedicated to 3D scanning x-ray microscopy, allowing a sample to be precisely scanned through a beam while the angle of x-ray incidence can be changed. The position of the sample is controlled with respect to the beam-defining optics by laser interferometry. The instrument achieves a position stability better than 10 nm standard deviation. The instrument performance is assessed using scanning x-ray diffraction microscopy and we demonstrate a resolution of 18 nm in 2D imaging of a lithographic test pattern while the beam was defined by a pinhole of 3 {mu}m in diameter. In 3D on amore » test object of copper interconnects of a microprocessor, a resolution of 53 nm is achieved.« less

Active retroreflector with in situ beam analysis to measure the rotational orientation in conjunction with a laser tracker

NASA Astrophysics Data System (ADS)

Hofherr, O.; Wachten, C.; Müller, C.; Reinecke, H.

2013-04-01

High precision optical non-contact position measurement is a key technology in modern engineering. Laser trackers (LT) can determine accurately x-y-z coordinates of passive retroreflectors. Next-generation systems answer the additional need to measure an object`s rotational orientation (pitch, yaw, roll). These devices are based either on photogrammetry or on enhanced retroreflectors. However, photogrammetry relies on costly camera systems and time-consuming image processing. Enhanced retroreflectors analyze the LT`s beam but are restricted in roll angle measurements. In the past we have presented a new method [1][2] to measure all six degrees of freedom in conjunction with a LT. Now we dramatically optimized the method and designed a new prototype, e.g. taking into consideration optical alignment, reduced power loss, highly optimized measuring signals and higher resolution. A method is described that allows compensating the influence of the LT's beam offset during tracking the active retroreflector. We prove the functionality of the active retroreflector with the LT and, furthermore, demonstrate the capability of the system to characterize the tracking behavior of a LT. The measurement range for the incident laser beam is +/-12° with a resolution of 0.6".

Partially coherent polarized atmospheric transmission characteristics and application technology research

NASA Astrophysics Data System (ADS)

Fu, Qiang; Gao, Duorui; Liu, Zhi; Chen, Chunyi; Lou, Yan; Jiang, Huilin

2014-11-01

Based on partially coherent polarized light transmission characteristics of the atmosphere, an intensity expression of completely coherent flashing light is derived from Andrews scale modulation method. According to the generalized Huygens-Fresnel principle and Rytov theory, the phase fluctuation structure function is obtained on condition that the refractive index profile in the atmosphere meet Von Karman spectrum, then get the arrival Angle fluctuation variance. Through the RMS beam width of gaussian beams in turbulent atmosphere, deviation angle formula of fully coherent gaussian beams in turbulence atmosphere is attained, then get the RMS beam width of partially coherent and derivation angle expression of GSM beam in turbulent atmosphere. Combined with transmission properties of radial polarized laser beam, cross spectral density matrix of partially coherent radially polarized light can be gained by using generalized huygens-fresnel principle. And light intensity and polarization after transmission can be known according to the unity of coherence and polarization theory. On the basis of the analysis model and numerical simulation, the simulation results show that: the light spot caused by atmospheric turbulence of partially coherent polarization will be superior to completely polarized light.Taking advantage of this feature, designed a new wireless suppression technology of atmospheric turbulence, that is the optimization criterion of initial degree of coherent light beam. The optimal initial degree of coherent light beam will change along with the change of atmospheric turbulence conditions,make control the beam's initial degree of coherence to realize the initial degree of coherence of light beam in real time and dynamic control. A spatial phase screen before emission aperture of fully coherent light is to generate the partially coherent light, liquid crystal spatial light modulator is is a preferable way to realize the dynamic random phase. Finally look future of the application research of partially coherent light.

Process Performance of Optima XEx Single Wafer High Energy Implanter

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

Kim, J. H.; Yoon, Jongyoon; Kondratenko, S.

2011-01-07

To meet the process requirements for well formation in future CMOS memory production, high energy implanters require more robust angle, dose, and energy control while maintaining high productivity. The Optima XEx high energy implanter meets these requirements by integrating a traditional LINAC beamline with a robust single wafer handling system. To achieve beam angle control, Optima XEx can control both the horizontal and vertical beam angles to within 0.1 degrees using advanced beam angle measurement and correction. Accurate energy calibration and energy trim functions accelerate process matching by eliminating energy calibration errors. The large volume process chamber and UDC (upstreammore » dose control) using faraday cups outside of the process chamber precisely control implant dose regardless of any chamber pressure increase due to PR (photoresist) outgassing. An optimized RF LINAC accelerator improves reliability and enables singly charged phosphorus and boron energies up to 1200 keV and 1500 keV respectively with higher beam currents. A new single wafer endstation combined with increased beam performance leads to overall increased productivity. We report on the advanced performance of Optima XEx observed during tool installation and volume production at an advanced memory fab.« less

Method and apparatus for optimizing the efficiency and quality of laser material processing

DOEpatents

Susemihl, Ingo

1990-01-01

The efficiency of laser welding and other laser material processing is optimized according to this invention by rotating the plane of polarization of a linearly polarized laser beam in relation to a work piece of the material being processed simultaneously and in synchronization with steering the laser beam over the work piece so as to keep the plane of polarization parallel to either the plane of incidence or the direction of travel of the beam in relation to the work piece. Also, depending to some extent on the particular processing being accomplished, such as welding or fusing, the angle of incidence of the laser beam on the work piece is kept at or near the polarizing or Brewster's angle. The combination of maintaining the plane of polarization parallel to plane of incidence while also maintaining the angle of incidence at or near the polarizing or Brewster's angle results in only minimal, if any, reflection losses during laser welding. Also, coordinating rotation of the plane of polarization with the translation or steering of a work piece under a laser cutting beam maximizes efficiency and kerf geometry, regardless of the direction of cut.

Method and apparatus for optimizing the efficiency and quality of laser material processing

DOEpatents

Susemihl, I.

1990-03-13

The efficiency of laser welding and other laser material processing is optimized according to this invention by rotating the plane of polarization of a linearly polarized laser beam in relation to a work piece of the material being processed simultaneously and in synchronization with steering the laser beam over the work piece so as to keep the plane of polarization parallel to either the plane of incidence or the direction of travel of the beam in relation to the work piece. Also, depending to some extent on the particular processing being accomplished, such as welding or fusing, the angle of incidence of the laser beam on the work piece is kept at or near the polarizing or Brewster's angle. The combination of maintaining the plane of polarization parallel to plane of incidence while also maintaining the angle of incidence at or near the polarizing or Brewster's angle results in only minimal, if any, reflection losses during laser welding. Also, coordinating rotation of the plane of polarization with the translation or steering of a work piece under a laser cutting beam maximizes efficiency and kerf geometry, regardless of the direction of cut. 7 figs.

A Waveguide Antenna with an Extended Angular Range for Remote Steering of Wave-Beam Direction

NASA Astrophysics Data System (ADS)

Sobolev, D. I.; Denisov, G. G.

2018-03-01

A new method for increasing the angular range of a waveguide antenna for remote steering of the wave-beam direction in thermonuclear-fusion experimental setups with plasma magnetic confinement is proposed. Characteristics for large beam inclination angles can be improved using the synthesized nonuniform waveguide profile. For small angles, the characteristics remain invariable, the waveguide profile differs only slightly from the regular shape, and can be fit to limited waveguide-channel sizes.

Scatter measurement and correction method for cone-beam CT based on single grating scan

NASA Astrophysics Data System (ADS)

Huang, Kuidong; Shi, Wenlong; Wang, Xinyu; Dong, Yin; Chang, Taoqi; Zhang, Hua; Zhang, Dinghua

2017-06-01

In cone-beam computed tomography (CBCT) systems based on flat-panel detector imaging, the presence of scatter significantly reduces the quality of slices. Based on the concept of collimation, this paper presents a scatter measurement and correction method based on single grating scan. First, according to the characteristics of CBCT imaging, the scan method using single grating and the design requirements of the grating are analyzed and figured out. Second, by analyzing the composition of object projection images and object-and-grating projection images, the processing method for the scatter image at single projection angle is proposed. In addition, to avoid additional scan, this paper proposes an angle interpolation method of scatter images to reduce scan cost. Finally, the experimental results show that the scatter images obtained by this method are accurate and reliable, and the effect of scatter correction is obvious. When the additional object-and-grating projection images are collected and interpolated at intervals of 30 deg, the scatter correction error of slices can still be controlled within 3%.

Fraction-variant beam orientation optimization for non-coplanar IMRT

NASA Astrophysics Data System (ADS)

O'Connor, Daniel; Yu, Victoria; Nguyen, Dan; Ruan, Dan; Sheng, Ke

2018-02-01

Conventional beam orientation optimization (BOO) algorithms for IMRT assume that the same set of beam angles is used for all treatment fractions. In this paper we present a BOO formulation based on group sparsity that simultaneously optimizes non-coplanar beam angles for all fractions, yielding a fraction-variant (FV) treatment plan. Beam angles are selected by solving a multi-fraction fluence map optimization problem involving 500-700 candidate beams per fraction, with an additional group sparsity term that encourages most candidate beams to be inactive. The optimization problem is solved using the fast iterative shrinkage-thresholding algorithm. Our FV BOO algorithm is used to create five-fraction treatment plans for digital phantom, prostate, and lung cases as well as a 30-fraction plan for a head and neck case. A homogeneous PTV dose coverage is maintained in all fractions. The treatment plans are compared with fraction-invariant plans that use a fixed set of beam angles for all fractions. The FV plans reduced OAR mean dose and D 2 values on average by 3.3% and 3.8% of the prescription dose, respectively. Notably, mean OAR dose was reduced by 14.3% of prescription dose (rectum), 11.6% (penile bulb), 10.7% (seminal vesicle), 5.5% (right femur), 3.5% (bladder), 4.0% (normal left lung), 15.5% (cochleas), and 5.2% (chiasm). D 2 was reduced by 14.9% of prescription dose (right femur), 8.2% (penile bulb), 12.7% (proximal bronchus), 4.1% (normal left lung), 15.2% (cochleas), 10.1% (orbits), 9.1% (chiasm), 8.7% (brainstem), and 7.1% (parotids). Meanwhile, PTV homogeneity defined as D 95/D 5 improved from .92 to .95 (digital phantom), from .95 to .98 (prostate case), and from .94 to .97 (lung case), and remained constant for the head and neck case. Moreover, the FV plans are dosimetrically similar to conventional plans that use twice as many beams per fraction. Thus, FV BOO offers the potential to reduce delivery time for non-coplanar IMRT.

Integrated phased array for wide-angle beam steering.

PubMed

Yaacobi, Ami; Sun, Jie; Moresco, Michele; Leake, Gerald; Coolbaugh, Douglas; Watts, Michael R

2014-08-01

We demonstrate an on-chip optical phased array fabricated in a CMOS compatible process with continuous, fast (100 kHz), wide-angle (51°) beam-steering suitable for applications such as low-cost LIDAR systems. The device demonstrates the largest (51°) beam-steering and beam-spacing to date while providing the ability to steer continuously over the entire range. Continuous steering is enabled by a cascaded phase shifting architecture utilizing, low power and small footprint, thermo-optic phase shifters. We demonstrate these results in the telecom C-band, but the same design can easily be adjusted for any wavelength between 1.2 and 3.5 μm.

Laser velocimeter for near-surface measurements

NASA Technical Reports Server (NTRS)

Johnson, Dennis A. (Inventor)

1992-01-01

The present invention relates to a laser Doppler velocimeter for near-wall measurements which includes at least one beam-turning device. The beam-turning device receives laser light, reflects and redirects the light at various angles in order to obtain measurements for all three velocity components at grazing incident angles. The beam-turning device includes a mirror or prism at one end which reflects the received light in a particular direction. A collector lens receives the particle scattered light from which the relevant velocity components are determined. The beam-turning device can also be a miniature fiber optic head which outputs laser light and can be turned in any direction.

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

Beam Normal Single Spin Asymmetry in Forward Angle Inelastic Electron-Proton Scattering using the Q-Weak Apparatus

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

., Nuruzzaman

2014-12-01

The Q-weak experiment in Hall-C at the Thomas Jefferson National Accelerator Facility has made the first direct measurement of the weak charge of the proton through the precision measurement of the parity-violating asymmetry in elastic electron-proton scattering at low momentum transfer. There is also a parity conserving Beam Normal Single Spin Asymmetry or transverse asymmetry (B_n) on H_2 with a sin(phi)-like dependence due to two-photon exchange. If the size of elastic B_n is a few ppm, then a few percent residual transverse polarization in the beam, combined with small broken azimuthal symmetries in the detector, would require a few ppbmore » correction to the Q-weak data. As part of a program of B_n background studies, we made the first measurement of B_n in the N-to-Delta(1232) transition using the Q-weak apparatus. The final transverse asymmetry, corrected for backgrounds and beam polarization, was found to be B_n = 42.82 ± 2.45 (stat) ± 16.07 (sys) ppm at beam energy E_beam = 1.155 GeV, scattering angle theta = 8.3 deg, and missing mass W = 1.2 GeV. B_n from electron-nucleon scattering is a unique tool to study the gamma^* Delta Delta form factors, and this measurement will help to improve the theoretical models on beam normal single spin asymmetry and thereby our understanding of the doubly virtual Compton scattering process. To help correct false asymmetries from beam noise, a beam modulation system was implemented to induce small position, angle, and energy changes at the target to characterize detector response to the beam jitter. Two air-core dipoles separated by ~10 m were pulsed at a time to produce position and angle changes at the target, for virtually any tune of the beamline. The beam energy was modulated using an SRF cavity. The hardware and associated control instrumentation will be described in this dissertation. Preliminary detector sensitivities were extracted which helped to reduce the width of the measured asymmetry. The beam modulation system has also proven valuable for tracking changes in the beamline optics, such as dispersion at the target.« less

Sensitivity improvement of one-shot Fourier spectroscopic imager for realization of noninvasive blood glucose sensors in smartphones

NASA Astrophysics Data System (ADS)

Kawashima, Natsumi; Nogo, Kosuke; Hosono, Satsuki; Nishiyama, Akira; Wada, Kenji; Ishimaru, Ichiro

2016-11-01

The use of the wide-field-stop and beam-expansion method for sensitivity enhancement of one-shot Fourier spectroscopy is proposed to realize health care sensors installed in smartphones for daily monitoring. When measuring the spectral components of human bodies noninvasively, diffuse reflected light from biological membranes is too weak for detection using conventional hyperspectral cameras. One-shot Fourier spectroscopy is a spatial phase-shift-type interferometer that can determine the one-dimensional spectral characteristics from a single frame. However, this method has low sensitivity, so that only the spectral characteristics of light sources with direct illumination can be obtained, because a single slit is used as a field stop. The sensitivity of the proposed spectroscopic method is improved by using the wide-field-stop and beam-expansion method. The use of a wider field stop slit width increases the detected light intensity; however, this simultaneously narrows the diffraction angle. The narrower collimated objective beam diameter degrades the visibility of interferograms. Therefore, a plane-concave cylindrical lens between the objective plane and the single slit is introduced to expand the beam diameter. The resulting sensitivity improvement achieved when using the wide-field-stop and beam-expansion method allows the spectral characteristics of hemoglobin to be obtained noninvasively from a human palm using a midget lamp.

Bar coded retroreflective target

DOEpatents

Vann, Charles S.

2000-01-01

This small, inexpensive, non-contact laser sensor can detect the location of a retroreflective target in a relatively large volume and up to six degrees of position. The tracker's laser beam is formed into a plane of light which is swept across the space of interest. When the beam illuminates the retroreflector, some of the light returns to the tracker. The intensity, angle, and time of the return beam is measured to calculate the three dimensional location of the target. With three retroreflectors on the target, the locations of three points on the target are measured, enabling the calculation of all six degrees of target position. Until now, devices for three-dimensional tracking of objects in a large volume have been heavy, large, and very expensive. Because of the simplicity and unique characteristics of this tracker, it is capable of three-dimensional tracking of one to several objects in a large volume, yet it is compact, light-weight, and relatively inexpensive. Alternatively, a tracker produces a diverging laser beam which is directed towards a fixed position, and senses when a retroreflective target enters the fixed field of view. An optically bar coded target can be read by the tracker to provide information about the target. The target can be formed of a ball lens with a bar code on one end. As the target moves through the field, the ball lens causes the laser beam to scan across the bar code.

Miniature Laser Tracker

DOEpatents

Vann, Charles S.

2003-09-09

This small, inexpensive, non-contact laser sensor can detect the location of a retroreflective target in a relatively large volume and up to six degrees of position. The tracker's laser beam is formed into a plane of light which is swept across the space of interest. When the beam illuminates the retroreflector, some of the light returns to the tracker. The intensity, angle, and time of the return beam is measured to calculate the three dimensional location of the target. With three retroreflectors on the target, the locations of three points on the target are measured, enabling the calculation of all six degrees of target position. Until now, devices for three-dimensional tracking of objects in a large volume have been heavy, large, and very expensive. Because of the simplicity and unique characteristics of this tracker, it is capable of three-dimensional tracking of one to several objects in a large volume, yet it is compact, light-weight, and relatively inexpensive. Alternatively, a tracker produces a diverging laser beam which is directed towards a fixed position, and senses when a retroreflective target enters the fixed field of view. An optically bar coded target can be read by the tracker to provide information about the target. The target can be formed of a ball lens with a bar code on one end. As the target moves through the field, the ball lens causes the laser beam to scan across the bar code.

Experimental teaching and training system based on volume holographic storage

NASA Astrophysics Data System (ADS)

Jiang, Zhuqing; Wang, Zhe; Sun, Chan; Cui, Yutong; Wan, Yuhong; Zou, Rufei

2017-08-01

The experiment of volume holographic storage for teaching and training the practical ability of senior students in Applied Physics is introduced. The students can learn to use advanced optoelectronic devices and the automatic control means via this experiment, and further understand the theoretical knowledge of optical information processing and photonics disciplines that have been studied in some courses. In the experiment, multiplexing holographic recording and readout is based on Bragg selectivity of volume holographic grating, in which Bragg diffraction angle is dependent on grating-recording angel. By using different interference angle between reference and object beams, the holograms can be recorded into photorefractive crystal, and then the object images can be read out from these holograms via angular addressing by using the original reference beam. In this system, the experimental data acquisition and the control of the optoelectronic devices, such as the shutter on-off, image loaded in SLM and image acquisition of a CCD sensor, are automatically realized by using LabVIEW programming.

The AKARI IRC asteroid flux catalogue: updated diameters and albedos

NASA Astrophysics Data System (ADS)

Alí-Lagoa, V.; Müller, T. G.; Usui, F.; Hasegawa, S.

2018-05-01

The AKARI IRC all-sky survey provided more than twenty thousand thermal infrared observations of over five thousand asteroids. Diameters and albedos were obtained by fitting an empirically calibrated version of the standard thermal model to these data. After the publication of the flux catalogue in October 2016, our aim here is to present the AKARI IRC all-sky survey data and discuss valuable scientific applications in the field of small body physical properties studies. As an example, we update the catalogue of asteroid diameters and albedos based on AKARI using the near-Earth asteroid thermal model (NEATM). We fit the NEATM to derive asteroid diameters and, whenever possible, infrared beaming parameters. We fit groups of observations taken for the same object at different epochs of the survey separately, so we compute more than one diameter for approximately half of the catalogue. We obtained a total of 8097 diameters and albedos for 5170 asteroids, and we fitted the beaming parameter for almost two thousand of them. When it was not possible to fit the beaming parameter, we used a straight line fit to our sample's beaming parameter-versus-phase angle plot to set the default value for each fit individually instead of using a single average value. Our diameters agree with stellar-occultation-based diameters well within the accuracy expected for the model. They also match the previous AKARI-based catalogue at phase angles lower than 50°, but we find a systematic deviation at higher phase angles, at which near-Earth and Mars-crossing asteroids were observed. The AKARI IRC All-sky survey is an essential source of information about asteroids, especially the large ones, since, it provides observations at different observation geometries, rotational coverages and aspect angles. For example, by comparing in more detail a few asteroids for which dimensions were derived from occultations, we discuss how the multiple observations per object may already provide three-dimensional information about elongated objects even based on an idealised model like the NEATM. Finally, we enumerate additional expected applications for more complex models, especially in combination with other catalogues. Full Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A85

Pitch Angle Scattering of Upgoing Electron Beams in Jupiter's Polar Regions by Whistler Mode Waves

NASA Astrophysics Data System (ADS)

Elliott, S. S.; Gurnett, D. A.; Kurth, W. S.; Clark, G.; Mauk, B. H.; Bolton, S. J.; Connerney, J. E. P.; Levin, S. M.

2018-02-01

The Juno spacecraft's Jupiter Energetic-particle Detector Instrument has observed field-aligned, unidirectional (upgoing) electron beams throughout most of Jupiter's entire polar cap region. The Waves instrument detected intense broadband whistler mode emissions occurring in the same region. In this paper, we investigate the pitch angle scattering of the upgoing electron beams due to interactions with the whistler mode waves. Profiles of intensity versus pitch angle for electron beams ranging from 2.53 to 7.22 Jovian radii show inconsistencies with the expected adiabatic invariant motion of the electrons. It is believed that the observed whistler mode waves perturb the electron motion and scatter them away from the magnetic field line. The diffusion equation has been solved by using diffusion coefficients which depend on the magnetic intensity of the whistler mode waves.

Optical vibration detection spectral analysis assembly and method for detecting vibration in an object of interest

DOEpatents

Hale, Thomas C.; Telschow, Kenneth L.

1998-01-01

A vibration detection assembly is described which includes an emitter of light which has object and reference beams, the object beam reflected off of a vibrating object of interest; and a photorefractive substance having a given response time and which passes the reflected object beam and the reference beam, the reference beam and the object beam interfering within the photorefractive substance to create a space charge field which develops within the response time of the photorefractive substance.

Optical vibration detection spectral analysis assembly and method for detecting vibration in an object of interest

DOEpatents

Hale, T.C.; Telschow, K.L.

1998-10-27

A vibration detection assembly is described which includes an emitter of light which has object and reference beams, the object beam reflected off of a vibrating object of interest; and a photorefractive substance having a given response time and which passes the reflected object beam and the reference beam, the reference beam and the object beam interfering within the photorefractive substance to create a space charge field which develops within the response time of the photorefractive substance. 6 figs.

In Vitro Validation of an Artefact Suppression Algorithm in X-Ray Phase-Contrast Computed Tomography.

PubMed

Sunaguchi, Naoki; Yuasa, Tetsuya; Hirano, Shin-Ichi; Gupta, Rajiv; Ando, Masami

2015-01-01

X-ray phase-contrast tomography can significantly increase the contrast-resolution of conventional attenuation-contrast imaging, especially for soft-tissue structures that have very similar attenuation. Just as in attenuation-based tomography, phase contrast tomography requires a linear dependence of aggregate beam direction on the incremental direction alteration caused by individual voxels along the path of the X-ray beam. Dense objects such as calcifications in biological specimens violate this condition. There are extensive beam deflection artefacts in the vicinity of such structures because they result in large distortion of wave front due to the large difference of refractive index; for such large changes in beam direction, the transmittance of the silicon analyzer crystal saturates and is no longer linearly dependent on the angle of refraction. This paper describes a method by which these effects can be overcome and excellent soft-tissue contrast of phase tomography can be preserved in the vicinity of such artefact-producing structures.

Study on laser welding of austenitic stainless steel by varying incident angle of pulsed laser beam

NASA Astrophysics Data System (ADS)

Kumar, Nikhil; Mukherjee, Manidipto; Bandyopadhyay, Asish

2017-09-01

In the present work, AISI 304 stainless steel sheets are laser welded in butt joint configuration using a robotic control 600 W pulsed Nd:YAG laser system. The objective of the work is of twofold. Firstly, the study aims to find out the effect of incident angle on the weld pool geometry, microstructure and tensile property of the welded joints. Secondly, a set of experiments are conducted, according to response surface design, to investigate the effects of process parameters, namely, incident angle of laser beam, laser power and welding speed, on ultimate tensile strength by developing a second order polynomial equation. Study with three different incident angle of laser beam 89.7 deg, 85.5 deg and 83 deg has been presented in this work. It is observed that the weld pool geometry has been significantly altered with the deviation in incident angle. The weld pool shape at the top surface has been altered from semispherical or nearly spherical shape to tear drop shape with decrease in incident angle. Simultaneously, planer, fine columnar dendritic and coarse columnar dendritic structures have been observed at 89.7 deg, 85.5 deg and 83 deg incident angle respectively. Weld metals with 85.5 deg incident angle has higher fraction of carbide and δ-ferrite precipitation in the austenitic matrix compared to other weld conditions. Hence, weld metal of 85.5 deg incident angle achieved higher micro-hardness of ∼280 HV and tensile strength of 579.26 MPa followed by 89.7 deg and 83 deg incident angle welds. Furthermore, the predicted maximum value of ultimate tensile strength of 580.50 MPa has been achieved for 85.95 deg incident angle using the developed equation where other two optimum parameter settings have been obtained as laser power of 455.52 W and welding speed of 4.95 mm/s. This observation has been satisfactorily validated by three confirmatory tests.

Beam impingement angle effects on secondary electron emission characteristics of textured pyrolytic graphite

NASA Technical Reports Server (NTRS)

Curren, A. N.; Jensen, K. A.

1984-01-01

Experimentally determined values of true secondary electron emission and relative values of reflected primary electron yield for untreated and ion-textured pyrolytic graphite over a range of primary electron energy levels and electron beam impingement angles are presented. Information required to develop high efficiency multistage depressed collectors (MDC's) for microwave amplifier traveling-wave tubes for space communication and aircraft applications is provided. To attain the highest possible MDC efficiencies, the electrode surfaces must have low secondary electron emission characteristics. Pyrolytic graphite, a chemically vapor-deposited material, is a particularly promising candidate for this application. The pyrolytic graphite surfaces studied were tested over a range of primary electron beam energies and beam impingement angles from 200 to 2000 eV and direct (0 deg) to near-grazing angles (85 deg), respectively. Surfaces both parallel to and normal to the planes of material deposition were examined. The true secondary electron emission and reflected primary electron yield characteristics of the pyrolytic graphite surfaces are compared to those of sooted control surfaces.

Estimating Elevation Angles From SAR Crosstalk

NASA Technical Reports Server (NTRS)

Freeman, Anthony

1994-01-01

Scheme for processing polarimetric synthetic-aperture-radar (SAR) image data yields estimates of elevation angles along radar beam to target resolution cells. By use of estimated elevation angles, measured distances along radar beam to targets (slant ranges), and measured altitude of aircraft carrying SAR equipment, one can estimate height of target terrain in each resolution cell. Monopulselike scheme yields low-resolution topographical data.

Multiple scattering theory for total skin electron beam design.

PubMed

Antolak, J A; Hogstrom, K R

1998-06-01

The purpose of this manuscript is to describe a method for designing a broad beam of electrons suitable for total skin electron irradiation (TSEI). A theoretical model of a TSEI beam from a linear accelerator with a dual scattering system has been developed. The model uses Fermi-Eyges theory to predict the planar fluence of the electron beam after it has passed through various materials between the source and the treatment plane, which includes scattering foils, monitor chamber, air, and a plastic diffusing plate. Unique to this model is its accounting for removal of the tails of the electron beam profile as it passes through the primary x-ray jaws. A method for calculating the planar fluence profile for an obliquely incident beam is also described. Off-axis beam profiles and percentage depth doses are measured with ion chambers, film, and thermoluminescent dosimeters (TLD). The measured data show that the theoretical model can accurately predict beam energy and planar fluence of the electron beam at normal and oblique incidence. The agreement at oblique angles is not quite as good but is sufficiently accurate to be of predictive value when deciding on the optimal angles for the clinical TSEI beams. The advantage of our calculational approach for designing a TSEI beam is that many different beam configurations can be tested without having to perform time-consuming measurements. Suboptimal configurations can be quickly dismissed, and the predicted optimal solution should be very close to satisfying the clinical specifications.

Beam pointing direction changes in a misaligned Porro prism resonator

NASA Astrophysics Data System (ADS)

Lee, Jyh-Fa; Leung, Chung-Yee

1988-07-01

The relative change of the beam pointing direction for a misaligned Porro prism resonator has been analyzed, using an oscillation axis concept for the Porro prism resonator to find the beam direction. Expressions for the beam tilting angles are presented which show that the angular misalignment in the horizontal direction will result in beam tilting in both the horizontal and vertical directions. Good agreement between experimental and theoretical results is found.

Some observations on the behavior of the Langley model rotor blade

NASA Technical Reports Server (NTRS)

Rehfield, L. W.; Atilgan, A. R.

1986-01-01

The design of the model rotor and the comparative study of coupled beam theory and the finite element analysis performed earlier at the Aerostructures Directorate by Robert Hodges and Mark Nixon is examined. Attention is focused upon two matters: (1) an examination of the small discrepancies between twist angle predictions under pure torque and radial loading, and (2) an assessment of nonclassical effects in bending behavior. The primary objective is understanding, particularly with regard to cause and effect relationships. Understanding, together with the simple, affordable nature of the coupled beam analysis, provides a sound basis for design.

Off-axis targets maximize bearing Fisher Information in broadband active sonar.

PubMed

Kloepper, Laura N; Buck, John R; Liu, Yang; Nachtigall, Paul E

2018-01-01

Broadband active sonar systems estimate range from time delay and velocity from Doppler shift. Relatively little attention has been paid to how the received echo spectrum encodes information about the bearing of an object. This letter derives the bearing Fisher Information encoded in the frequency dependent transmitter beampattern. This leads to a counter-intuitive result: directing the sonar beam so that a target of interest is slightly off-axis maximizes the bearing information about the target. Beam aim data from a dolphin biosonar experiment agree closely with the angle predicted to maximize bearing information.

Optical ground station optimization for future optical geostationary satellite feeder uplinks

NASA Astrophysics Data System (ADS)

Camboulives, A.-R.; Velluet, M.-T.; Poulenard, S.; Saint-Antonin, L.; Michau, V.

2017-02-01

An optical link based on a multiplex of wavelengths at 1:55 μm is foreseen to be a valuable alternative to the conventional radio-frequencies for the feeder link of the next-generation of high throughput geostationary satellite. Considering the limited power of lasers envisioned for feeder links, the beam divergence has to be dramatically reduced. Consequently, the beam pointing becomes a key issue. During its propagation between the ground station and a geostationary satellite, the optical beam is deflected (beam wandering), and possibly distorted (beam spreading), by atmospheric turbulence. It induces strong fluctuations of the detected telecom signal, thus increasing the bit error rate (BER). A steering mirror using a measurement from a beam coming from the satellite is used to pre-compensate the deflection. Because of the point-ahead angle between the downlink and the uplink, the turbulence effects experienced by both beams are slightly different, inducing an error in the correction. This error is characterized as a function of the turbulence characteristics as well as of the terminal characteristics, such as the servo-loop bandwidth or the beam diameter, and is included in the link budget. From this result, it is possible to predict intensity fluctuations detected by the satellite statistically (mean intensity, scintillation index, probability of fade, etc.)). The final objective is to optimize the different parameters of an optical ground station capable of mitigating the impact of atmospheric turbulence on the uplink in order to be compliant with the targeted capacity (1Terabit/s by 2025).

Three-beam interferogram analysis method for surface flatness testing of glass plates and wedges

NASA Astrophysics Data System (ADS)

Sunderland, Zofia; Patorski, Krzysztof

2015-09-01

When testing transparent plates with high quality flat surfaces and a small angle between them the three-beam interference phenomenon is observed. Since the reference beam and the object beams reflected from both the front and back surface of a sample are detected, the recorded intensity distribution may be regarded as a sum of three fringe patterns. Images of that type cannot be succesfully analyzed with standard interferogram analysis methods. They contain, however, useful information on the tested plate surface flatness and its optical thickness variations. Several methods were elaborated to decode the plate parameters. Our technique represents a competitive solution which allows for retrieval of phase components of the three-beam interferogram. It requires recording two images: a three-beam interferogram and the two-beam one with the reference beam blocked. Mutually subtracting these images leads to the intensity distribution which, under some assumptions, provides access to the two component fringe sets which encode surfaces flatness. At various stages of processing we take advantage of nonlinear operations as well as single-frame interferogram analysis methods. Two-dimensional continuous wavelet transform (2D CWT) is used to separate a particular fringe family from the overall interferogram intensity distribution as well as to estimate the phase distribution from a pattern. We distinguish two processing paths depending on the relative density of fringe sets which is connected with geometry of a sample and optical setup. The proposed method is tested on simulated data.

Experimental and raytrace results for throat-to-throat compound parabolic concentrators

NASA Technical Reports Server (NTRS)

Leviton, D. B.; Leitch, J. W.

1986-01-01

Compound parabolic concentrators are nonimaging cone-shaped optics with useful angular transmission characteristics. Two cones used throat-to-throat accept radiant flux within one well-defined acceptance angle and redistribute it into another. If the entrance cone is fed with Lambertian flux, the exit cone produces a beam whose half-angle is the exit cone's acceptance angle and whose cross section shows uniform irradiance from near the exit mouth to infinity. (The pair is a beam angle transformer). The design of one pair of cones is discussed, also an experiment to map the irradiance of the emergent beam, and a raytracing program which models the cones fed by Lambertian flux. Experimental results compare favorably with raytrace results.

Fiber optic diffraction grating maker

DOEpatents

Deason, V.A.; Ward, M.B.

1991-05-21

A compact and portable diffraction grating maker is comprised of a laser beam, optical and fiber optics devices coupling the beam to one or more evanescent beam splitters, and collimating lenses or mirrors directing the split beam at an appropriate photosensitive material. The collimating optics, the output ends of the fiber optic coupler and the photosensitive plate holder are all mounted on an articulated framework so that the angle of intersection of the beams can be altered at will without disturbing the spatial filter, collimation or beam quality, and assuring that the beams will always intersect at the position of the plate. 4 figures.

Fiber optic diffraction grating maker

DOEpatents

Deason, Vance A.; Ward, Michael B.

1991-01-01

A compact and portable diffraction grating maker comprised of a laser beam, optical and fiber optics devices coupling the beam to one or more evanescent beam splitters, and collimating lenses or mirrors directing the split beam at an appropriate photosensitive material. The collimating optics, the output ends of the fiber optic coupler and the photosensitive plate holder are all mounted on an articulated framework so that the angle of intersection of the beams can be altered at will without disturbing the spatial filter, collimation or beam quality, and assuring that the beams will always intersect at the position of the plate.

Exciting surface plasmon polaritons in the Kretschmann configuration by a light beam

NASA Astrophysics Data System (ADS)

Vinogradov, A. P.; Dorofeenko, A. V.; Pukhov, A. A.; Lisyansky, A. A.

2018-06-01

We consider exciting surface plasmon polaritons in the Kretschmann configuration. Contrary to common belief, we show that a plane-wave incident at an angle greater than the angle of total internal reflection does not excite surface plasmon polaritons. These excitations do arise, however, if the incident light forms a narrow beam composed of an infinite number of plane waves. The surface plasmon polariton is formed at the geometrical edge of the beam as a result of interference of reflected plane waves.

A novel collinear optical system with annulus mirrors for holographic disc driver

NASA Astrophysics Data System (ADS)

Wang, Ye

2008-12-01

This paper focus on a novel collinear lens system with annulus mirrors for holographic disc driver, both information beam and reference beam are use same laser beam. The expanded and parallel laser beam, center part of it as the information beam then through Fourier transform lens, the beam around center part as a reference beam. On this axis, the ring reference beam reflected by two annulus shaped mirrors, then became a convergent beam, together with the information beam which through the first Fourier transform lens then produce holographic pattern to be write into the holographic disc behind of them, this lens system with two mirrors made the angle between information beam and reference beam more wide, can improved the multiplex level of holographic storage. Pair of Fourier transform lens with advance performance is designed in this paper.

Walk-off reduction, using an external optical plate and Bessel-Gaussian interaction

NASA Astrophysics Data System (ADS)

Masoume, Mansouri; Mohsen, Askarbioki; Saeed Ghavami, Sabouri; Alireza, Khorsandi

2015-02-01

To reduce the walk-off angle of the extraordinary third-harmonic ultraviolet wave at 355 nm generated by type II KTiOPO4 and type I β-BaB2O4 optical crystals, and the Gaussian output beam of a Q-switched Nd:YAG laser, a simple theoretical model was developed based on a rotatable BK7 plate of variable thickness. By rotating the plate up to 35° along the beam direction, we reduced the walk-off angle up to ˜ 13%. The same phenomenon is predicted by the model, confirming the performance of the model. It is found that, due to the walk-off effect, the intensity profile of the third-harmonic generation beam is slightly degraded. To compensate for the observed phenomena and further reduce the walk-off, we used a combination of a convex lens and an axicon to transform the beam profile of the interacting fundamental and second-harmonic generation waves to the zero-order Bessel-Gaussian form. As a result, the walk-off is decreased to ˜48.81 mrad, providing ˜30% relative reduction. By using the same BK7 plate rotated up to 35° along the third-harmonic beam direction, the walk-off angle is further reduced to 38.9 mrad. Moreover, it is observed that the beam profile of the emerged Bessel-Gaussian third-harmonic generation beam remains unchanged with no degradation.

CHICO2, a two-dimensional pixelated parallel-plate avalanche counter

DOE PAGES

Wu, C. Y.; Cline, D.; Hayes, A.; ...

2016-01-27

CHICO 2 (Compact Heavy Ion COunter), is a large solid-angle, charged-particle detector array developed to provide both θ and Φ angle resolutions matching those of GRETINA (Gamma-Ray Energy Tracking In-beam Nuclear Array). CHICO 2 was successfully tested at the Argonne National Laboratory where it was fielded as an auxiliary detector with GRETINA for γ-ray spectroscopic studies of nuclei using a 252Cf spontaneous fission source, stable beams, and radioactive beams from CARIBU. In field tests of the 72,76Ge beams on a 0.5 mg/cm 2208Pb target at the sub-barrier energy, CHICO 2 provided charged-particle angle resolutions (FWHM) of 1.55° in θ andmore » 2.47° in Φ. This achieves the design goal for both coordinates assuming a beam-spot size (>3 mm) and the target thickness (>0.5 mg/cm 2). The combined angular resolution of GRETINA/CHICO 2 resulted in a Doppler-shift corrected energy resolution of 0.60% for 1 MeV coincident de-excitation γ-rays. This is nearly a factor of two improvements in resolution and sensitivity compared to Gammasphere/CHICO. Kinematically-coincident detection of scattered ions by CHICO 2 still maintains the mass resolution (ΔM/M) of ~5% that enhanced isolation of scattered weak beams of interest from scattered contaminant beams.« less

Planck 2013 results. VII. HFI time response and beams

NASA Astrophysics Data System (ADS)

Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bowyer, J. W.; Bridges, M.; Bucher, M.; Burigana, C.; Cardoso, J.-F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chary, R.-R.; Chiang, H. C.; Chiang, L.-Y.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dunkley, J.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Haissinski, J.; Hansen, F. K.; Hanson, D.; Harrison, D.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hou, Z.; Hovest, W.; Huffenberger, K. M.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leonardi, R.; Leroy, C.; Lesgourgues, J.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; MacTavish, C. J.; Maffei, B.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matsumura, T.; Matthai, F.; Mazzotta, P.; McGehee, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Osborne, S.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polegre, A. M.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rusholme, B.; Sandri, M.; Santos, D.; Sauvé, A.; Savini, G.; Scott, D.; Shellard, E. P. S.; Spencer, L. D.; Starck, J.-L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Yvon, D.; Zacchei, A.; Zonca, A.

2014-11-01

This paper characterizes the effective beams, the effective beam window functions and the associated errors for the Planck High Frequency Instrument (HFI) detectors. The effective beam is theangular response including the effect of the optics, detectors, data processing and the scan strategy. The window function is the representation of this beam in the harmonic domain which is required to recover an unbiased measurement of the cosmic microwave background angular power spectrum. The HFI is a scanning instrument and its effective beams are the convolution of: a) the optical response of the telescope and feeds; b) the processing of the time-ordered data and deconvolution of the bolometric and electronic transfer function; and c) the merging of several surveys to produce maps. The time response transfer functions are measured using observations of Jupiter and Saturn and by minimizing survey difference residuals. The scanning beam is the post-deconvolution angular response of the instrument, and is characterized with observations of Mars. The main beam solid angles are determined to better than 0.5% at each HFI frequency band. Observations of Jupiter and Saturn limit near sidelobes (within 5°) to about 0.1% of the total solid angle. Time response residuals remain as long tails in the scanning beams, but contribute less than 0.1% of the total solid angle. The bias and uncertainty in the beam products are estimated using ensembles of simulated planet observations that include the impact of instrumental noise and known systematic effects. The correlation structure of these ensembles is well-described by five error eigenmodes that are sub-dominant to sample variance and instrumental noise in the harmonic domain. A suite of consistency tests provide confidence that the error model represents a sufficient description of the data. The total error in the effective beam window functions is below 1% at 100 GHz up to multipole ℓ ~ 1500, and below 0.5% at 143 and 217 GHz up to ℓ ~ 2000.

Beam-Beam Interaction Simulations with Guinea Pig (LCC-0125)

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

Sramek, C

2003-11-20

At the interaction point of a particle accelerator, various phenomena occur which are known as beam-beam effects. Incident bunches of electrons (or positrons) experience strong electromagnetic fields from the opposing bunches, which leads to electron deflection, beamstrahlung and the creation of electron/positron pairs and hadrons due to two-photon exchange. In addition, the beams experience a ''pinch effect'' which focuses each beam and results in either a reduction or expansion of their vertical size. Finally, if a beam's disruption parameter is too large, the beam can develop a sinusoidal distortion, or two-stream (kink) instability. This project simulated and studied these effectsmore » as they relate to luminosity, deflection angles and energy loss in order to optimize beam parameters for the Next Linear Collider (NLC). Using the simulation program Guinea Pig, luminosity, deflection angle and beam energy data was acquired for different levels of beam offset and distortion. Standard deflection curves and luminosity plots agreed with theoretical models but also made clear the difficulties of e-e- feedback. Simulations emphasizing kink instability in modulated and straight beam collisions followed qualitative behavioral predictions and roughly fit recent analytic calculations. A study of e-e- collisions under design constraints for the NLC provided new estimates of how luminosity, beamstrahlung energy loss, upsilon parameter and deflection curve width scale with beam cross-sections ({sigma}{sub x}, {sigma}{sub y}, {sigma}{sub z}) and number of particles per bunch (N). Finally, this same study revealed luminosity maxima at large N and small {sigma}{sub y} which may merit further investigation.« less

Design of angle-resolved illumination optics using nonimaging bi-telecentricity for 193 nm scatterfield microscopy.

PubMed

Sohn, Martin Y; Barnes, Bryan M; Silver, Richard M

2018-03-01

Accurate optics-based dimensional measurements of features sized well-below the diffraction limit require a thorough understanding of the illumination within the optical column and of the three-dimensional scattered fields that contain the information required for quantitative metrology. Scatterfield microscopy can pair simulations with angle-resolved tool characterization to improve agreement between the experiment and calculated libraries, yielding sub-nanometer parametric uncertainties. Optimized angle-resolved illumination requires bi-telecentric optics in which a telecentric sample plane defined by a Köhler illumination configuration and a telecentric conjugate back focal plane (CBFP) of the objective lens; scanning an aperture or an aperture source at the CBFP allows control of the illumination beam angle at the sample plane with minimal distortion. A bi-telecentric illumination optics have been designed enabling angle-resolved illumination for both aperture and source scanning modes while yielding low distortion and chief ray parallelism. The optimized design features a maximum chief ray angle at the CBFP of 0.002° and maximum wavefront deviations of less than 0.06 λ for angle-resolved illumination beams at the sample plane, holding promise for high quality angle-resolved illumination for improved measurements of deep-subwavelength structures using deep-ultraviolet light.

Active Control of Acoustic Field-of-View in a Biosonar System

PubMed Central

Yovel, Yossi; Falk, Ben; Moss, Cynthia F.; Ulanovsky, Nachum

2011-01-01

Active-sensing systems abound in nature, but little is known about systematic strategies that are used by these systems to scan the environment. Here, we addressed this question by studying echolocating bats, animals that have the ability to point their biosonar beam to a confined region of space. We trained Egyptian fruit bats to land on a target, under conditions of varying levels of environmental complexity, and measured their echolocation and flight behavior. The bats modulated the intensity of their biosonar emissions, and the spatial region they sampled, in a task-dependant manner. We report here that Egyptian fruit bats selectively change the emission intensity and the angle between the beam axes of sequentially emitted clicks, according to the distance to the target, and depending on the level of environmental complexity. In so doing, they effectively adjusted the spatial sector sampled by a pair of clicks—the “field-of-view.” We suggest that the exact point within the beam that is directed towards an object (e.g., the beam's peak, maximal slope, etc.) is influenced by three competing task demands: detection, localization, and angular scanning—where the third factor is modulated by field-of-view. Our results suggest that lingual echolocation (based on tongue clicks) is in fact much more sophisticated than previously believed. They also reveal a new parameter under active control in animal sonar—the angle between consecutive beams. Our findings suggest that acoustic scanning of space by mammals is highly flexible and modulated much more selectively than previously recognized. PMID:21931535

Performance characteristics of mobile MOSFET dosimeter for kilovoltage X-rays used in image guided radiotherapy

PubMed Central

Kumar, A. Sathish; Singh, I. Rabi Raja; Sharma, S. D.; Ravindran, B. Paul

2015-01-01

The main objective of this study was to investigate the characteristics of metal oxide semiconductor field effect transistor (MOSFET) dosimeter for kilovoltage (kV) X-ray beams in order to perform the in vivo dosimetry during image guidance in radiotherapy. The performance characteristics of high sensitivity MOSFET dosimeters were investigated for 80, 90, 100, 110, 120, and 125 kV X-ray beams used for imaging in radiotherapy. This study was performed using Clinac 2100 C/D medical electron linear accelerator with on-board imaging and kV cone beam computed tomography system. The characteristics studied in this work include energy dependence, angular dependence, and linearity. The X-ray beam outputs were measured as per American Association of Physicists in Medicine (AAPM) TG 61 recommendations using PTW parallel plate (PP) ionization chamber, which was calibrated in terms of air kerma (Nk) by the National Standard Laboratory. The MOSFET dosimeters were calibrated against the PP ionization chamber for all the kV X-ray beams and the calibration coefficient was found to be 0.11 cGy/mV with a standard deviation of about ±1%. The response of MOSFET was found to be energy independent for the kV X-ray energies used in this study. The response of the MOSFET dosimeter was also found independent of angle of incidence for the gantry angles in the range of 0° to 360° in-air as well as at 3 cm depth in tissue equivalent phantom. PMID:26500397

Magnetically operated beam dump for dumping high power beams in a neutral beamline

DOEpatents

Dagenhart, W.K.

1984-01-27

It is an object of this invention to provide a beam dump system for a neutral beam generator which lowers the time-averaged power density of the beam dump impingement surface. Another object of this invention is to provide a beam dump system for a neutral particle beam based on reionization and subsequent magnetic beam position modulation of the beam onto a beam dump surface to lower the time-averaged power density of the beam dump ion impingement surface.

Electro-optic high voltage sensor

DOEpatents

Davidson, James R.; Seifert, Gary D.

2003-09-16

A small sized electro-optic voltage sensor capable of accurate measurement of high voltages without contact with a conductor or voltage source is provided. When placed in the presence of an electric field, the sensor receives an input beam of electromagnetic radiation. A polarization beam displacer separates the input beam into two beams with orthogonal linear polarizations and causes one linearly polarized beam to impinge a crystal at a desired angle independent of temperature. The Pockels effect elliptically polarizes the beam as it travels through the crystal. A reflector redirects the beam back through the crystal and the beam displacer. On the return path, the polarization beam displacer separates the elliptically polarized beam into two output beams of orthogonal linear polarization. The system may include a detector for converting the output beams into electrical signals and a signal processor for determining the voltage based on an analysis of the output beams.

Online geometric calibration of cone-beam computed tomography for arbitrary imaging objects.

PubMed

Meng, Yuanzheng; Gong, Hui; Yang, Xiaoquan

2013-02-01

A novel online method based on the symmetry property of the sum of projections (SOP) is proposed to obtain the geometric parameters in cone-beam computed tomography (CBCT). This method requires no calibration phantom and can be used in circular trajectory CBCT with arbitrary cone angles. An objective function is deduced to illustrate the dependence of the symmetry of SOP on geometric parameters, which will converge to its minimum when the geometric parameters achieve their true values. Thus, by minimizing the objective function, we can obtain the geometric parameters for image reconstruction. To validate this method, numerical phantom studies with different noise levels are simulated. The results show that our method is insensitive to the noise and can determine the skew (in-plane rotation angle of the detector), the roll (rotation angle around the projection of the rotation axis on the detector), and the rotation axis with high accuracy, while the mid-plane and source-to-detector distance will be obtained with slightly lower accuracy. However, our simulation studies validate that the errors of the latter two parameters brought by our method will hardly degrade the quality of reconstructed images. The small animal studies show that our method is able to deal with arbitrary imaging objects. In addition, the results of the reconstructed images in different slices demonstrate that we have achieved comparable image quality in the reconstructions as some offline methods.

Propagation optical quarks after an uniaxial crystal: the experiment

NASA Astrophysics Data System (ADS)

Egorov, Yu. A.; Konovalenko, V. L.; Zinovev, A. O.; Anischenko, P. M.; Glumova, M. V.

2013-12-01

There is a lots of different papers reporting about the propagation of the different types of an optical beams in a uniaxial crystals are known by that time. This beams are: Lager-Gaussian and Bessel- Gaussian beams. It is common for all this types of beams, that if propagation axis and crystal axis coincides, and accident beam had a circular polarization, are can get type spiral type degenerated umbilici, which corresponds to the charge 2 optical vortex in the orthogonal polarized beam component, generated by crystal [1] (Fig 1). This generation accurse due to total angular momentum conservation law symmetry axis of the crystal. One to the changing of the spin momentum which is associated with the beam polarization, this leads to the orbital momentum changes that associated with topological charge of formed orthogonal circular component. Double charged optical vortex could be easily perturbed by tilting beam axis with respect to the crystal axis. If the tilt angles are small (<0.1°) central umbilici splits on two lemons and the surrounding ring umbilici splits on two pairs of monster-star. The further increasing of the tilt angle leads to the topological charge of circular components becomes, equal, and additional orbital moment correspond to the beam mass center displacement.

Five-Year Wilkinson Microwave Anisotropy Probe (WMAP)Observations: Beam Maps and Window Functions

NASA Technical Reports Server (NTRS)

Hill, R.S.; Weiland, J.L.; Odegard, N.; Wollack, E.; Hinshaw, G.; Larson, D.; Bennett, C.L.; Halpern, M.; Kogut, A.; Page, L.;

EXTRACTOR FOR HIGH ENERGY CHARGED PARTICLES

DOEpatents

Lambertson, G.R.

1964-04-01

A particle-extracting apparatus for use with a beam of high-energy charged particles such as travel in an evacuated chamber along a circular equilibrium axis is described. A magnetized target is impacted relatively against the beam whereby the beam particles are deflected from the beam by the magnetic induction in the target. To this end the target may be moved into the beam or the beam may coast into the target and achieve high angular particle deflection and slow extraction. A deflecting septum magnet may additionally be used for deflection at even sharper angles. (AEC)

Induced strain actuation of composite beams and rotor blades with embedded piezoceramic elements

NASA Astrophysics Data System (ADS)

Chen, Peter C.; Chopra, Inderjit

1994-05-01

The objective of this research is to develop a dynamically scaled (Froude scale) helicopter rotor blade with embedded piezoceramic elements as sensors and actuators to control blade vibrations. A 6-ft-diameter two-bladed bearingless rotor model was built, where each blade is embedded with banks of piezoelectric actuators at +/- 45-degree angles with respect to the beam axis on the top and bottom surfaces. A twist distribution along the blade span is achieved through in-phase excitation of the top and bottom actuators at equal potentials, while a bending distribution is achieved through out-of-phase excitation. In order to fix design variables and to optimize blade performance, a uniform strain beam theory is formulated to analytically predict the static bending and torsional response of composite rectangular beams with embedded piezoelectric actuators. Parameters such as bond thicknesses, actuator skew angle, and actuator spacing are investigated by experiments and then validated by theory. The static bending and torsional response of the rotor blades is experimentally measured and correlated with theory. Dynamic torsional and bending responses are experimentally determined for frequencies from 2-120 HZ to assess the viability of a vibration reduction system based on piezoactuation of blade twist. Although the magnitudes of blade twist attained in this experiment were small, it is expected that future models can be built with improved performance.

Digital Beam Steering Device Based on Decoupled Birefringent Prism Deflector and Polarization Rotator

NASA Technical Reports Server (NTRS)

Pishnyak, Oleg; Kreminska, Lyubov; Laventovich, Oleg D.; Pouch, John J.; Miranda, Felix A.; Winker, Bruce K.

2004-01-01

We describe digital beam deflectors (DBDs) based on liquid crystals. Each stage of the device comprises a polarization rotator and a birefringent prism deflector. The birefringent prism deflects the beam by an angle that depends on polarization of the incident beam. The prism can be made of the uniaxial smectic A (SmA) liquid crystal (LC) or a solid crystal such as yttrium orthovanadate (YVO4). SmA prisms have high birefringence and can be constructed in a variety of shapes, including single prisms and prismatic blazed gratings of different angles and profiles. We address the challenges of uniform alignment of SmA, such as elimination of focal conic domains. Rotation of linear polarization is achieved by an electrically switched twisted nematic (TN) cell. A DBD composed of N rotator-deflector pairs steers the beam into 2(sup N) directions. As an example, we describe a four-stage DBD deflecting normally incident laser beam within the range of +/- 56 mrad with 8 mrad steps. Redirection of the beam is achieved by switching the TN cells.

Low-Profile, Dual-Wavelength, Dual-Polarized Antenna

NASA Technical Reports Server (NTRS)

Carswell, James R.

2010-01-01

A single-aperture, low-profile antenna design has been developed that supports dual-polarization and simultaneous operation at two wavelengths. It realizes multiple beams in the elevation plane, and supports radiometric, radar, and conical scanning applications. This antenna consists of multiple azimuth sticks, with each stick being a multilayer, hybrid design. Each stick forms the h-plane pattern of the C and Ku-band vertically and horizontally polarized antenna beams. By combining several azimuth sticks together, the elevation beam is formed. With a separate transceiver for each stick, the transmit phase and amplitude of each stick can be controlled to synthesize a beam at a specific incidence angle and to realize a particular side-lobe pattern. By changing the transmit phase distribution through the transceivers, the transmit antenna beam can be steered to different incidence angles. By controlling the amplitude distribution, different side lobe patterns and efficiencies can be realized. The receive beams are formed using digital beam synthesis techniques, resulting in very little loss in the receive path, thus enabling a very-low loss receive antenna to support passive measurements.

Development of a beam ion velocity detector for the heavy ion beam probe

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

Fimognari, P. J., E-mail: PJFimognari@XanthoTechnologies.com; Crowley, T. P.; Demers, D. R.

2016-11-15

In an axisymmetric plasma, the conservation of canonical angular momentum constrains heavy ion beam probe (HIBP) trajectories such that measurement of the toroidal velocity component of secondary ions provides a localized determination of the poloidal flux at the volume where they originated. We have developed a prototype detector which is designed to determine the beam angle in one dimension through the detection of ion current landing on two parallel planes of detecting elements. A set of apertures creates a pattern of ion current on wires in the first plane and solid metal plates behind them; the relative amounts detected bymore » the wires and plates determine the angle which beam ions enter the detector, which is used to infer the toroidal velocity component. The design evolved from a series of simulations within which we modeled ion beam velocity changes due to equilibrium and fluctuating magnetic fields, along with the ion beam profile and velocity dispersion, and studied how these and characteristics such as the size, cross section, and spacing of the detector elements affect performance.« less

Main types of optical beams giving predominant contributions to the light backscatter for the irregular hexagonal columns

NASA Astrophysics Data System (ADS)

Shishko, Victor A.; Konoshonkin, Alexander V.; Kustova, Natalia V.; Borovoi, Anatoli G.

2017-11-01

This work presents the estimation of contribution of the main types of optical beams to the light backscatter for randomly oriented hexagonal ice column, the right dihedral angle of which was distorted within the range of 0° (regular particle) to 10°. Calculations were obtained within the physical optics approximation. The wavelength was 532 nm and the refractive index was 1.3116. The results showed that the total contribution of the main types of optical beams to the total backscattering cross section reach the value of 85% at small distortion angle of the hexagonal column and at substantial distortion angle the total contribution of the main types of optical beams decrease up to 55% of the total backscattering cross section. The obtained conclusions can significantly reduce the calculation time in the case when there is no need for high accuracy of the calculation.

Creation of 3D microsculptures in PMMA by multiple angle proton irradiation

NASA Astrophysics Data System (ADS)

Andrea, T.; Rothermel, M.; Reinert, T.; Koal, T.; Butz, T.

2011-10-01

In recent years the technique of proton beam writing has established itself as a versatile method for the creation of microstructures in resist materials. While these structures can be almost arbitrary in two dimensions, the creation of genuine 3D structures remains a challenge. At the LIPSION accelerator facility a new approach has been developed which combines aspects of ion beam tomography, so far solely an analysis method, with proton beam writing. Key element is the targeted irradiation from multiple angles in order to obtain a much broader range of 3D microstructures than has hitherto been possible. PMMA columns with a diameter of ∼90 μm were used as raw material and placed in an upright position on top of a rotational axis. Using 2.25 MeV protons patterns corresponding to the silhouettes of the desired structures were written from two or more directions. In a subsequent step of chemical etching irradiated portions were dissolved, leaving behind the finished 3D sculpture. Various objects have been created. For the demonstration of the method a 70 μm high model of the Eiffel tower has been sculpted by irradiation from two angles. Using irradiation from three angles a 40 μm wide screw with right-handed thread could be crafted which might find applications in micromachining. Also, a cage structure with a pore size of ca. 20 μm was written with the intention to use it as a scaffold for the growth of biological cells.

SU-E-T-796: Variation of Surface Photon Energy Spectra On Bone Heterogeneity and Beam Obliquity Between Flattened and Unflattened Beam

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

Chow, J; Owrangi, A; Grigorov, G

Purpose: This study investigates the spectra of surface photon energy and energy fluence in the bone heterogeneity and beam obliquity using flattened and unflattened photon beams. The spectra were calculated in a bone and water phantom using Monte Carlo simulation (the EGSnrc code). Methods: Spectra of energy, energy fluence and mean energy of the 6 MV flattened and unflattened photon beams (field size = 10 × 10 cm{sup 2}) produced by a Varian TrueBEAM linear accelerator were calculated at the surfaces of a bone and water phantom using Monte Carlo simulations. The spectral calculations were repeated with the beam anglesmore » turned from 0° to 15°, 30° and 45° in the phantoms. Results: It is found that the unflattened photon beams contained more photons in the low-energy range of 0 – 2 MeV than the flattened beams with a flattening filter. Compared to the water phantom, both the flattened and unflattened beams had slightly less photons in the energy range < 0.4 MeV when a bone layer of 1 cm is present under the phantom surface. This shows that the presence of the bone decreased the low-energy photons backscattered to the phantom surface. When the photon beams were rotated from 0° to 45°, the number of photon and mean photon energy increased with the beam angle. This is because both the flattened and unflattened beams became more hardened when the beam angle increased. With the bone heterogeneity, the mean energies of both photon beams increased correspondingly. This is due to the absorption of low-energy photons by the bone, resulting in more significant beam hardening. Conclusion: The photon spectral information is important in studies on the patient’s surface dose enhancement when using unflattened photon beams in radiotherapy.« less

Ultra-low-frequency vertical vibration isolator based on a two-stage beam structure for absolute gravimetry.

PubMed

Wang, G; Wu, K; Hu, H; Li, G; Wang, L J

2016-10-01

To reduce seismic and environmental vibration noise, ultra-low-frequency vertical vibration isolation systems play an important role in absolute gravimetry. For this purpose, an isolator based on a two-stage beam structure is proposed and demonstrated. The isolator has a simpler and more robust structure than the present ultra-low-frequency vertical active vibration isolators. In the system, two beams are connected to a frame using flexural pivots. The upper beam is suspended from the frame with a normal hex spring and the lower beam is suspended from the upper one using a zero-length spring. The pivot of the upper beam is not vertically above the pivot of the lower beam. With this special design, the attachment points of the zero-length spring to the beams can be moved to adjust the effective stiffness. A photoelectric detector is used to detect the angle between the two beams, and a voice coil actuator attached to the upper beam is controlled by a feedback circuit to keep the angle at a fixed value. The system can achieve a natural period of 100 s by carefully moving the attachment points of the zero-length spring to the beams and tuning the feedback parameters. The system has been used as an inertial reference in the T-1 absolute gravimeter. The experiment results demonstrate that the system has significant vibration isolation performance that holds promise in applications such as absolute gravimeters.

Ultra-low-frequency vertical vibration isolator based on a two-stage beam structure for absolute gravimetry

NASA Astrophysics Data System (ADS)

Wang, G.; Wu, K.; Hu, H.; Li, G.; Wang, L. J.

2016-10-01

To reduce seismic and environmental vibration noise, ultra-low-frequency vertical vibration isolation systems play an important role in absolute gravimetry. For this purpose, an isolator based on a two-stage beam structure is proposed and demonstrated. The isolator has a simpler and more robust structure than the present ultra-low-frequency vertical active vibration isolators. In the system, two beams are connected to a frame using flexural pivots. The upper beam is suspended from the frame with a normal hex spring and the lower beam is suspended from the upper one using a zero-length spring. The pivot of the upper beam is not vertically above the pivot of the lower beam. With this special design, the attachment points of the zero-length spring to the beams can be moved to adjust the effective stiffness. A photoelectric detector is used to detect the angle between the two beams, and a voice coil actuator attached to the upper beam is controlled by a feedback circuit to keep the angle at a fixed value. The system can achieve a natural period of 100 s by carefully moving the attachment points of the zero-length spring to the beams and tuning the feedback parameters. The system has been used as an inertial reference in the T-1 absolute gravimeter. The experiment results demonstrate that the system has significant vibration isolation performance that holds promise in applications such as absolute gravimeters.

RELATIVISTIC DOPPLER BEAMING AND MISALIGNMENTS IN AGN JETS

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

Singal, Ashok K., E-mail: asingal@prl.res.in

Radio maps of active galactic nuclei often show linear features, called jets, on both parsec and kiloparsec scales. These jets supposedly possess relativistic motion and are oriented close to the line of sight of the observer, and accordingly the relativistic Doppler beaming makes them look much brighter than they really are in their respective rest frames. The flux boosting due to the relativistic beaming is a very sensitive function of the jet orientation angle, as seen by the observer. Sometimes, large bends are seen in these jets, with misalignments being 90° or more, which might imply a change in themore » orientation angle that should cause a large change in the relativistic beaming factor. Hence, if relativistic beaming does play an important role in these jets such large bends should usually show high contrast in the brightness of the jets before and after the bend. It needs to be kept in mind that sometimes a small intrinsic change in the jet angle might appear as a much larger misalignment due to the effects of geometrical projection, especially when seen close to the line of sight. What really matters are the initial and final orientation angles of the jet with respect to the observer’s line of sight. Taking the geometrical projection effects properly into account, we calculate the consequences of the presumed relativistic beaming and demonstrate that there ought to be large brightness ratios in jets before and after the observed misalignments.« less

Relativistic Doppler Beaming and Misalignments in AGN Jets

NASA Astrophysics Data System (ADS)

Singal, Ashok K.

2016-08-01

Radio maps of active galactic nuclei often show linear features, called jets, on both parsec and kiloparsec scales. These jets supposedly possess relativistic motion and are oriented close to the line of sight of the observer, and accordingly the relativistic Doppler beaming makes them look much brighter than they really are in their respective rest frames. The flux boosting due to the relativistic beaming is a very sensitive function of the jet orientation angle, as seen by the observer. Sometimes, large bends are seen in these jets, with misalignments being 90° or more, which might imply a change in the orientation angle that should cause a large change in the relativistic beaming factor. Hence, if relativistic beaming does play an important role in these jets such large bends should usually show high contrast in the brightness of the jets before and after the bend. It needs to be kept in mind that sometimes a small intrinsic change in the jet angle might appear as a much larger misalignment due to the effects of geometrical projection, especially when seen close to the line of sight. What really matters are the initial and final orientation angles of the jet with respect to the observer’s line of sight. Taking the geometrical projection effects properly into account, we calculate the consequences of the presumed relativistic beaming and demonstrate that there ought to be large brightness ratios in jets before and after the observed misalignments.

Beam splitter and method for generating equal optical path length beams

DOEpatents

Qian, Shinan; Takacs, Peter

2003-08-26

The present invention is a beam splitter for splitting an incident beam into first and second beams so that the first and second beams have a fixed separation and are parallel upon exiting. The beam splitter includes a first prism, a second prism, and a film located between the prisms. The first prism is defined by a first thickness and a first perimeter which has a first major base. The second prism is defined by a second thickness and a second perimeter which has a second major base. The film is located between the first major base and the second major base for splitting the incident beam into the first and second beams. The first and second perimeters are right angle trapezoidal shaped. The beam splitter is configured for generating equal optical path length beams.

X-ray radiography for container inspection

DOEpatents

Katz, Jonathan I [Clayton, MO; Morris, Christopher L [Los Alamos, NM

2011-06-07

Arrangements of X-ray inspection systems are described for inspecting high-z materials in voluminous objects such as containers. Inspection methods may involve generating a radiographic image based on detected attenuation corresponding to a pulsed beams of radiation transmitted through a voluminous object. The pulsed beams of radiation are generated by a high-energy source and transmitted substantially downward along an incident angle, of approximately 1.degree. to 30.degree., to a vertical axis extending through the voluminous object. The generated radiographic image may be analyzed to detect on localized high attenuation representative of high-z materials and to discriminate high-z materials from lower and intermediate-z materials on the basis of the high density and greater attenuation of high-z material for higher energy (3-10 MeV) X-rays, and the compact nature of threatening masses of fissionable materials.

Highly sensitive beam steering with plasmonic antenna

PubMed Central

Rui, Guanghao; Zhan, Qiwen

2014-01-01

In this work, we design and study a highly sensitive beam steering device that integrates a spiral plasmonic antenna with a subwavelength metallic waveguide. The short effective wavelength of the surface plasmon polaritons (SPPs) mode supported by the metallic waveguide is exploited to dramatically miniaturize the device and improve the sensitivity of the beam steering. Through introducing a tiny displacement of feed point with respect to the geometrical center of the spiral plasmonic antenna, the direction of the radiation can be steered at considerably high angles. Simulation results show that steering angles of 8°, 17° and 34° are obtainable for a displacement of 50 nm, 100 nm and 200 nm, respectively. Benefiting from the reduced device size and the shorter SPP wavelength, the beam steering sensitivity of the beam steering is improved by 10-fold compared with the case reported previously. This miniature plasmonic beam steering device may find many potential applications in quantum optical information processing and integrated photonic circuits. PMID:25091405

Emittance matching of a slow extracted beam for a rotating gantry

NASA Astrophysics Data System (ADS)

Fujimoto, T.; Iwata, Y.; Matsuba, S.; Fujita, T.; Sato, S.; Shirai, T.; Noda, K.

2017-09-01

The introduction of a heavy-ion rotating gantry is in progress at the Heavy Ion Medical Accelerator in Chiba (HIMAC) for realizing high-precision cancer therapy using heavy ions. A scanning irradiation method will be applied to this gantry course with 48-430 MeV/u beam energy. In the rotating gantry, the horizontal and vertical beam parameters are coupled by its rotation. To maintain a circular spot shape at the isocenter irrespective of the gantry angle, achieving symmetric phase space distribution of the horizontal and vertical beam at the entrance of the rotating gantry is necessary. Therefore, compensating the horizontal and vertical emittance is necessary. We consider using a thin scatterer method to compensate the emittance. After considering the optical design for emittance matching, the scatterer device is located in the high-energy beam transport line. In the beam commissioning, we confirm that the symmetrical spot shape is obtained at the isocenter without depending on the gantry angle.

Low-energy beam transport studies supporting the spallation neutron source 1-MW beam operation.

PubMed

Han, B X; Kalvas, T; Tarvainen, O; Welton, R F; Murray, S N; Pennisi, T R; Santana, M; Stockli, M P

2012-02-01

The H(-) injector consisting of a cesium enhanced RF-driven ion source and a 2-lens electrostatic low-energy beam transport (LEBT) system supports the spallation neutron source 1 MW beam operation with ∼38 mA beam current in the linac at 60 Hz with a pulse length of up to ∼1.0 ms. In this work, two important issues associated with the low-energy beam transport are discussed: (1) inconsistent dependence of the post-radio frequency quadrupole accelerator beam current on the ion source tilt angle and (2) high power beam losses on the LEBT electrodes under some off-nominal conditions compromising their reliability.

AGARD Flight Test Techniques Series. Volume 7. Air-to-Air Radar Flight Testing

DTIC Science & Technology

1988-06-01

enters the beam ), a different tilt angle should be used. The emphasis on setting the tilt angle may require a non - standard high accuracy tilt angle...is: the time from pilot designation on a non -maneuvering target to the time that the system achieves target range, range rate and angle tracking...minimal attenuation, distortion, or boresight Shift effects on the radar beam . Thus, radome design for airborne application io largely a process of

Methods and apparatus for laser beam scanners with different actuating mechanisms

NASA Astrophysics Data System (ADS)

Chen, Si-hai; Xiang, Si-hua; Wu, Xin; Dong, Shan; Xiao, Ding; Zheng, Xia-wei

2009-07-01

In this paper, 3 types of laser beam scanner are introduced. One is transmissive beam scanner, which is composed of convex and concave microlens arrays (MLAs). By moving the concave lens in the plane vertical to the optical axis, the incident beam can be deflected in two dimensions. Those two kinds of MLAs are fabricated by thermal reflow and replication process. A set of mechanical scanner frame is fabricated with the two MLAs assembling in it. The testing result shown that the beam deflection angles are 9.5° and 9.6°, in the 2 dimension(2D) with the scanning frequency of 2 HZ and 8 HZ, respectively. The second type of laser beam scanner is actuated by voice coil actuators (VCAs). Based on ANSOFT MAXWELL software, we have designed VCAs with small size and large force which have optimized properties. The model of VCAs is built using AutoCAD and is analyzed by Ansoft maxwell. According to the simulation results, high performance VCAs are fabricated and tested. The result is that the force of the VCAs is 6.39N/A, and the displacement is +/-2.5mm. A set up of beam scanner is fabricated and actuated by the designed VCAs. The testing result shown that the two dimensional scanning angle is 15° and 10° respectively at the frequency of 60HZ. The two dimensional scanning angle is 8.3° and 6° respectively at the frequency of 100HZ. The third type of scanner is actuated by amplified piezoelectric actuators (APAs). The scanning mirror is actuated by the piezoelectric (PZ) actuators with the scanning frequency of 700HZ, 250HZ and 87HZ respectively. The optical scanning angle is +/-0.5° at the three frequencies.

Development of a robotic patient positioning system with a wide beam-angle range for fixed-beam particle therapy

NASA Astrophysics Data System (ADS)

Choi, Hongseok; Park, Jong-Oh; Ko, Seong Young; Park, Sukho; Cho, Sungho; Jung, Won-Gyun; Park, Yong Kyun; Kang, Jung Suk

2016-10-01

This paper describes a robotic patient positioning system (PPS) for a fixed-beam heavy-ion therapy system. In order to extend the limited irradiation angle range of the fixed beam, we developed a 6-degree-of-freedom (6-DOF) serial-link robotic arm and used it as the robotic PPS for the fixed-beam heavy-ion therapy system. This research aims to develop a robotic PPS for use in the Korea Heavy Ion Medical Accelerator (KHIMA) system, which is under development at the Korea Institute of Radiological & Medical Sciences (KIRAMS). In particular, we select constraints and criteria that will be used for designing and evaluating the robotic PPS through full consultation with KIRAMS. In accordance with the constraints and criteria, we develop a 6-DOF serial-link robotic arm that consists of six revolute joints for the robotic PPS, where the robotic arm covers the upper body of a patient as a treatment area and achieves a 15 ° roll and pitch angle in the treatment area without any collision. Various preliminary experiments confirm that the robotic PPS can meet all criteria for extension of the limited irradiation angle range in the treatment area and has a positioning repeatability of 0.275 mm.

SU-E-J-17: A Study of Accelerator-Induced Cerenkov Radiation as a Beam Diagnostic and Dosimetry Tool

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

Bateman, F; Tosh, R

2014-06-01

Purpose: To investigate accelerator-induced Cerenkov radiation imaging as a possible beam diagnostic and medical dosimetry tool. Methods: Cerenkov emission produced by clinical accelerator beams in a water phantom was imaged using a camera system comprised of a high-sensitivity thermoelectrically-cooled CCD camera coupled to a large aperture (f/0.75) objective lens with 16:1 magnification. This large format lens allows a significant amount of the available Cerenkov light to be collected and focused onto the CCD camera to form the image. Preliminary images, obtained with 6 MV photon beams, used an unshielded camera mounted horizontally with the beam normal to the water surface,more » and confirmed the detection of Cerenkov radiation. Several improvements were subsequently made including the addition of radiation shielding around the camera, and altering of the beam and camera angles to give a more favorable geometry for Cerenkov light collection. A detailed study was then undertaken over a range of electron and photon beam energies and dose rates to investigate the possibility of using this technique for beam diagnostics and dosimetry. Results: A series of images were obtained at a fixed dose rate over a range of electron energies from 6 to 20 MeV. The location of maximum intensity was found to vary linearly with the energy of the beam. A linear relationship was also found between the light observed from a fixed point on the central axis and the dose rate for both photon and electron beams. Conclusion: We have found that the analysis of images of beam-induced Cerenkov light in a water phantom has potential for use as a beam diagnostic and medical dosimetry tool. Our future goals include the calibration of the light output in terms of radiation dose and development of a tomographic system for 3D Cerenkov imaging in water phantoms and other media.« less

Scattering calculation and image reconstruction using elevation-focused beams

PubMed Central

Duncan, David P.; Astheimer, Jeffrey P.; Waag, Robert C.

2009-01-01

Pressure scattered by cylindrical and spherical objects with elevation-focused illumination and reception has been analytically calculated, and corresponding cross sections have been reconstructed with a two-dimensional algorithm. Elevation focusing was used to elucidate constraints on quantitative imaging of three-dimensional objects with two-dimensional algorithms. Focused illumination and reception are represented by angular spectra of plane waves that were efficiently computed using a Fourier interpolation method to maintain the same angles for all temporal frequencies. Reconstructions were formed using an eigenfunction method with multiple frequencies, phase compensation, and iteration. The results show that the scattered pressure reduces to a two-dimensional expression, and two-dimensional algorithms are applicable when the region of a three-dimensional object within an elevation-focused beam is approximately constant in elevation. The results also show that energy scattered out of the reception aperture by objects contained within the focused beam can result in the reconstructed values of attenuation slope being greater than true values at the boundary of the object. Reconstructed sound speed images, however, appear to be relatively unaffected by the loss in scattered energy. The broad conclusion that can be drawn from these results is that two-dimensional reconstructions require compensation to account for uncaptured three-dimensional scattering. PMID:19425653

Scattering calculation and image reconstruction using elevation-focused beams.

PubMed

Duncan, David P; Astheimer, Jeffrey P; Waag, Robert C

2009-05-01

Pressure scattered by cylindrical and spherical objects with elevation-focused illumination and reception has been analytically calculated, and corresponding cross sections have been reconstructed with a two-dimensional algorithm. Elevation focusing was used to elucidate constraints on quantitative imaging of three-dimensional objects with two-dimensional algorithms. Focused illumination and reception are represented by angular spectra of plane waves that were efficiently computed using a Fourier interpolation method to maintain the same angles for all temporal frequencies. Reconstructions were formed using an eigenfunction method with multiple frequencies, phase compensation, and iteration. The results show that the scattered pressure reduces to a two-dimensional expression, and two-dimensional algorithms are applicable when the region of a three-dimensional object within an elevation-focused beam is approximately constant in elevation. The results also show that energy scattered out of the reception aperture by objects contained within the focused beam can result in the reconstructed values of attenuation slope being greater than true values at the boundary of the object. Reconstructed sound speed images, however, appear to be relatively unaffected by the loss in scattered energy. The broad conclusion that can be drawn from these results is that two-dimensional reconstructions require compensation to account for uncaptured three-dimensional scattering.

Extreme ultraviolet reflector

DOEpatents

Newnam, Brian E.

1990-01-01

A multi-faceted mirror forms a retroreflector for a resonator loop in a free electron laser (FEL) operating in the XUV (.lambda.=10-100 nm). The number of facets is determined by the angle-of-incidence needed to obtain total external reflectance (TER) from the facet surface and the angle through which the FEL beam is to be turned. Angles-of-incidence greater than the angle for TER may be used to increase the area of the beam incident on the surface and reduce energy absorption density. Suitable surface films having TER in the 10-100 nm range may be formed from a variety of materials, including Al, single-crystal Si, Ag, and Rh. One of the facets is formed as an off-axis conic section to collimate the output beam with minimum astigmatism.

Real-time optical multiple object recognition and tracking system and method

NASA Technical Reports Server (NTRS)

Chao, Tien-Hsin (Inventor); Liu, Hua-Kuang (Inventor)

1990-01-01

System for optically recognizing and tracking a plurality of objects within a field of vision. Laser (46) produces a coherent beam (48). Beam splitter (24) splits the beam into object (26) and reference (28) beams. Beam expanders (50) and collimators (52) transform the beams (26, 28) into coherent collimated light beams (26', 28'). A two-dimensional SLM (54), disposed in the object beam (26'), modulates the object beam with optical information as a function of signals from a first camera (16) which develops X and Y signals reflecting the contents of its field of vision. A hololens (38), positioned in the object beam (26') subsequent to the modulator (54), focuses the object beam at a plurality of focal points (42). A planar transparency-forming film (32), disposed with the focal points on an exposable surface, forms a multiple position interference filter (62) upon exposure of the surface and development processing of the film (32). A reflector (53) directing the reference beam (28') onto the film (32), exposes the surface, with images focused by the hololens (38), to form interference patterns on the surface. There is apparatus (16', 64) for sensing and indicating light passage through respective ones of the positions of the filter (62), whereby recognition of objects corresponding to respective ones of the positions of the filter (62) is affected. For tracking, apparatus (64) focuses light passing through the filter (62) onto a matrix of CCD's in a second camera (16') to form a two-dimensional display of the recognized objects.

Large area ion beam sputtered YBa2Cu3O(7-delta) films for novel device structures

NASA Astrophysics Data System (ADS)

Gauzzi, A.; Lucia, M. L.; Kellett, B. J.; James, J. H.; Pavuna, D.

1992-03-01

A simple single-target ion-beam system is employed to manufacture large areas of uniformly superconducting YBa2Cu3O(7-delta) films which can be reproduced. The required '123' stoichiometry is transferred from the target to the substrate when ion-beam power, target/ion-beam angle, and target temperature are adequately controlled. Ion-beam sputtering is experimentally demonstrated to be an effective technique for producing homogeneous YBa2Cu3O(7-delta) films.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Polarisation splitting of laser beams by large angles with minimal reflection losses

NASA Astrophysics Data System (ADS)

Davydov, B. L.

2006-05-01

New crystal anisotropic prisms for splitting orthogonally polarised components of laser radiation by large angles with minimal reflection losses caused by the Brewster refraction and total internal reflection of polarised waves from the crystal—air interface are considered and the method for their calculation is described. It is shown that, by assembling glue-free combinations of two or three prisms, thermally stable beamsplitters can be fabricated, which are free from the beam astigmatism and the wave dispersion of the output angles of the beams. The parameters and properties of new beamsplitters are presented in a convenient form in figures and tables.

Study on THz wave generation from air plasma induced by quasi-square Airy beam

NASA Astrophysics Data System (ADS)

Zhang, Shijing; Zhang, Liangliang; Jiang, Guangtong; Zhang, Cunlin; Zhao, Yuejin

2018-01-01

Terahertz (THz) wave has attracted considerable attention in recent years because of its potential applications. The intense THz waves generated from air plasma induced by two-color femtosecond laser are widely used due to its high generation efficiency and broad frequency bandwidth. The parameters of the laser change the distribution of the air plasma, and then affect the generation of THz wave. In this research, we investigate the THz wave generation from air plasma induced by quasi-square Airy beam. Unlike the common Gauss beam, the quasi-square Airy beam has ability to autofocus and to increase the maximum intensity at the focus. By using the spatial light modulator (SLM), we can change the parameters of phase map to control the shape of the Airy beam. We obtain the two-color laser field by a 100-um-thick BBO crystal, then use a Golay detector to record THz wave energy. By comparing terahertz generation at different modulation depths, we find that terahertz energy produced by quasi-square Airy beam is up to 3.1 times stronger than that of Gauss beam with identical laser energy. In order to understand the influence of quasi-square Airy beam on the BBO crystal, we record THz wave energy by changing the azimuthal angle of BBO crystal with Gauss beam and Airy beam at different modulation depths. We find that the trend of terahertz energy with respect to the azimuthal angle of the BBO crystal keeps the same for different laser beams. We believe that the quasi-square Airy beam or other auto focusing beam can significantly improve the efficiency of terahertz wave generation and pave the way for its applications.

Fundamentals of angled-beam ultrasonic NDE for potential characterization of hidden regions of impact damage in composites

NASA Astrophysics Data System (ADS)

Aldrin, John C.; Wertz, John N.; Welter, John T.; Wallentine, Sarah; Lindgren, Eric A.; Kramb, Victoria; Zainey, David

2018-04-01

In this study, the use of angled-beam ultrasonic NDE was explored for the potential characterization of the hidden regions of impact damage in composites. Simulated studies using CIVA FIDEL 2D were used to explore this inspection problem. Quasi-shear (qS) modes can be generated over a wide range of angles and used to reflect off the backwall and interrogate under the top delaminations of impact damage. Secondary probe signals that do propagate normal to the surface were found to be significant under certain probe conditions, and can potentially interfere with weakly scattered signals from within the composite panel. Simulations were used to evaluate the source of the multiple paths of reflections from the edge of a delamination; time-of-flight and amplitude will depend on the depth of the delamination and location of neighboring delaminations. For angled-beam inspections, noise from both the top surface roughness and internal features was found to potentially mask the detection of signals from the edge of delaminations. Lastly, the study explored the potential of generating "guided" waves along the backwall using an angled-beam source and subsequently measuring scattered signals from a far surface crack hidden under a delamination.

RF wave observations in beam-plasma discharge

NASA Technical Reports Server (NTRS)

Bernstein, W.

1986-01-01

The Beam Plasma Discharge (BPD) was produced in the large vacuum chamber at Johnson Space Center (20 x 30 m) using an energetic electron beam of moderately high perveance. A more complete expression of the threshold current I sub c taking into account the pitch angle injection dependence is given. Ambient plasma density inferred from wave measurements under various beam conditions are reported. Maximum frequency of the excited RF band behaves differently than the frequency of the peak amplitude. The latter shows signs of parabolic saturation consistent with the light data. Beam plasma state (pre-BPD or BPD) does not affect the pitch angle dependence. Unexpected strong modulation of the RF spectrum at half odd integer of the electron cyclotron frequency (n + 1/2)f sub ce is reported (5 n 10). Another new feature, the presence of wave emission around 3/2 f sub ce for I sub b is approximate I sub c is reported.

Experimental demonstration of in-plane negative-angle refraction with an array of silicon nanoposts.

PubMed

Wu, Aimin; Li, Hao; Du, Junjie; Ni, Xingjie; Ye, Ziliang; Wang, Yuan; Sheng, Zhen; Zou, Shichang; Gan, Fuwan; Zhang, Xiang; Wang, Xi

2015-03-11

Controlling an optical beam is fundamental in optics. Recently, unique manipulation of optical wavefronts has been successfully demonstrated by metasurfaces. However, these artificially engineered nanostructures have thus far been limited to operate on light beams propagating out-of-plane. The in-plane operation is critical for on-chip photonic applications. Here, we demonstrate an anomalous negative-angle refraction of a light beam propagating along the plane, by designing a thin dielectric array of silicon nanoposts. The circularly polarized dipoles induced by the high-permittivity nanoposts at the scattering resonance significantly shape the wavefront of the light beam and bend it anomalously. The unique capability of a thin line of the nanoposts for manipulating in-plane wavefronts makes the device extremely compact. The low loss all-dielectric structure is compatible with complementary metal-oxide semiconductor technologies, offering an effective solution for in-plane beam steering and routing for on-chip photonics.

Second harmonic generation of off axial vortex beam in the case of walk-off effect

NASA Astrophysics Data System (ADS)

Chen, Shunyi; Ding, Panfeng; Pu, Jixiong

2016-07-01

Process of off axial vortex beam propagating in negative uniaxial crystal is investigated in this work. Firstly, we get the formulae of the normalized electric field and calculate the location of vortices for second harmonic beam in two type of phase matching. Then, numerical analysis verifies that the intensity distribution and location of vortices of the first order original vortex beam depend on the walk-off angle and off axial magnitude. It is shown that, in type I phase matching, the distribution of vortices is symmetrical about the horizontal axis, the separation distance increases as the off axial magnitude increases or the off axial magnitude deceases. However, in type II phase matching, the vortices are symmetrical along with some vertical axis, and increase of the walk-off angle or off axial magnitude leads to larger separation distance. Finally, the case of high order original off axial vortex beam is also investigated.

Ultrasound beam characteristics of a symmetric nodal origami based array

NASA Astrophysics Data System (ADS)

Bilgunde, Prathamesh N.; Bond, Leonard J.

2018-04-01

Origami-the ancient art of paper folding-is being explored in acoustics for effective focusing of sound. In this short communication, we present a numerical investigation of beam characteristics for an origami based ultrasound array. A spatial re-configuration of array elements is performed based upon the symmetric nodal origami. The effect of fold angle on the ultrasound beam is evaluated using frequency domain and transient finite element analysis. It was found that increase in the fold angle reduces near field length by 58% and also doubles the beam intensity as compared to the linear array. Transient analysis also indicated 80% reduction in the -6dB beam width, which can improve the lateral resolution of phased array. Such a spatially re-configurable array could potentially be used in the future to reduce the cost of electronics in the phased array instrumentation.

A method of measuring micro-impulse with torsion pendulum based on multi-beam laser heterodyne

NASA Astrophysics Data System (ADS)

Li, Yan-Chao; Wang, Chun-Hui

2012-02-01

In this paper, we propose a novel method of multi-beam laser heterodyne measurement for micro-impulse. The measurement of the micro-impulse, which is converted into the measurement of the small tuning angle of the torsion pendulum, is realized by considering the interaction between pulse laser and working medium. Based on Doppler effect and heterodyne technology, the information regarding the small tuning angle is loaded to the frequency difference of the multi-beam laser heterodyne signal by the frequency modulation of the oscillating mirror, thereby obtaining many values of the small tuning angle after the multi-beam laser heterodyne signal demodulation simultaneously. Processing these values by weighted-average, the small tuning angle can be obtained accurately and the value of the micro-impulse can eventually be calculated. Using Polyvinylchlorid+2%C as a working medium, this novel method is used to simulate the value of the micro-impulse by MATLAB which is generated by considering the interaction between the pulse laser and the working medium, the obtained result shows that the relative error of this method is just 0.5%.

Rotation of a 1-GeV particle beam by a fan system of thin crystals

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

Britvich, G. I.; Maisheev, V. A.; Chesnokov, Yu. A., E-mail: Yury.Chesnokov@ihep.ru

2016-10-15

The deflection of a 1-GeV charged particle beam by a system formed by fan-oriented thin silicon wafers has been studied theoretically and experimentally. Software has been developed for numerical simulation of a particle beam transmission through a fan crystal system. In the U-70 experiment on a proton beam, the particles were deflected by such a system through an angle exceeding 1 mrad. Thus, a new method has been demonstrated for rotating a particle beam, which can be used for creating accelerator beams for medical purposes.

Gyrator transform of Gaussian beams with phase difference and generation of hollow beam

NASA Astrophysics Data System (ADS)

Xiao, Zhiyu; Xia, Hui; Yu, Tao; Xie, Ding; Xie, Wenke

2018-03-01

The optical expression of Gaussian beams with phase difference, which is caused by gyrator transform (GT), has been obtained. The intensity and phase distribution of transform Gaussian beams are analyzed. It is found that the circular hollow vortex beam can be obtained by overlapping two GT Gaussian beams with π phase difference. The effect of parameters on the intensity and phase distributions of the hollow vortex beam are discussed. The results show that the shape of intensity distribution is significantly influenced by GT angle α and propagation distance z. The size of the hollow vortex beam can be adjusted by waist width ω 0. Compared with previously reported results, the work shows that the hollow vortex beam can be obtained without any model conversion of the light source.

Gyrator transform of Gaussian beams with phase difference and generation of hollow beam

NASA Astrophysics Data System (ADS)

Xiao, Zhiyu; Xia, Hui; Yu, Tao; Xie, Ding; Xie, Wenke

2018-06-01

The optical expression of Gaussian beams with phase difference, which is caused by gyrator transform (GT), has been obtained. The intensity and phase distribution of transform Gaussian beams are analyzed. It is found that the circular hollow vortex beam can be obtained by overlapping two GT Gaussian beams with π phase difference. The effect of parameters on the intensity and phase distributions of the hollow vortex beam are discussed. The results show that the shape of intensity distribution is significantly influenced by GT angle α and propagation distance z. The size of the hollow vortex beam can be adjusted by waist width ω 0. Compared with previously reported results, the work shows that the hollow vortex beam can be obtained without any model conversion of the light source.

Magnetic field amplitude and pitch angle measurements using Spectral MSE on EAST

NASA Astrophysics Data System (ADS)

Liao, Ken; Rowan, William; Fu, Jia; Li, Ying-Ying; Lyu, Bo; Marchuk, Oleksandr; Ralchenko, Yuri

2017-10-01

We have developed the Spectral Motional Stark Effect technique for measuring magnetic field amplitude and pitch angle on EAST. The experiments were conducted using the tangential co-injection heating beam at A port and Beam Emission Spectroscopy array at D port. A spatial calibration of the observation channels was conducted before the campaign. As a first check, the measured magnetic field amplitude was compared to prediction. Since the toroidal field is dominant, we recovered the expected 1/R shape over the spatial range 1.75

Self-Pinched Transport Theory for the SABRE Ion Diode

NASA Astrophysics Data System (ADS)

Welch, Dale R.; Olson, Craig L.; Hanson, David L.

1997-05-01

In anticipation of a 90 kA 4 MV SABRE ion diode experiment, we have been examining self-pinch transport of ions for application to ion-driven inertial confinement fusion. The Li^+3 beam will exit the diode with a 30-40 mradian divergence and a shallow focusing angle of 75 mradians. The beam is annular with an 4.6-cm inner radius and a 6.8-cm outer radius. Self-pinch theory and simulation predict that large residual currents are possible in 2-20 mtorr argon gas. The simulations suggest that ≈ 50 kA of Li particle current is necessary to contain the beam's transverse momentum. Some non-ideal effects include large beam divergence, large focusing angle and beam annularity. To address these problems, we have been studying the benefits of beam conditioning in the focus region between the diode and the self pinch region after the beam has reached a small radius. We have found some benefit from including a passive conical structure and a low-pressure gas. A significant lens effect can be attained using only the beam fields in vacuum or a low pressure gas. In this configuration, a large focusing force, that keeps the ions off an inner cone and outer wall as the beam converges, has been calculated using the numerical simulation code uc(iprop.) Results from integrated simulation of the condition cell and self-pinch region look encouraging.

Dark matter beams at LBNF

DOE PAGES

Coloma, Pilar; Dobrescu, Bogdan A.; Frugiuele, Claudia; ...

2016-04-08

High-intensity neutrino beam facilities may produce a beam of light dark matter when protons strike the target. Searches for such a dark matter beam using its scattering in a nearby detector must overcome the large neutrino background. We characterize the spatial and energy distributions of the dark matter and neutrino beams, focusing on their differences to enhance the sensitivity to dark matter. We find that a dark matter beam produced by a Zmore » $$^{'}$$ boson in the GeV mass range is both broader and more energetic than the neutrino beam. The reach for dark matter is maximized for a detector sensitive to hard neutral-current scatterings, placed at a sizable angle off the neutrino beam axis. In the case of the Long-Baseline Neutrino Facility (LBNF), a detector placed at roughly 6 degrees off axis and at a distance of about 200 m from the target would be sensitive to Z$$^{'}$$ couplings as low as 0.05. This search can proceed symbiotically with neutrino measurements. We also show that the MiniBooNE and MicroBooNE detectors, which are on Fermilab’s Booster beamline, happen to be at an optimal angle from the NuMI beam and could perform searches with existing data. As a result, this illustrates potential synergies between LBNF and the short-baseline neutrino program if the detectors are positioned appropriately.« less

High-precision laser microcutting and laser microdrilling using diffractive beam-splitting and high-precision flexible beam alignment

NASA Astrophysics Data System (ADS)

Zibner, F.; Fornaroli, C.; Holtkamp, J.; Shachaf, Lior; Kaplan, Natan; Gillner, A.

2017-08-01

High-precision laser micro machining gains more importance in industrial applications every month. Optical systems like the helical optics offer highest quality together with controllable and adjustable drilling geometry, thus as taper angle, aspect ratio and heat effected zone. The helical optics is based on a rotating Dove-prism which is mounted in a hollow shaft engine together with other optical elements like wedge prisms and plane plates. Although the achieved quality can be interpreted as extremely high the low process efficiency is a main reason that this manufacturing technology has only limited demand within the industrial market. The objective of the research studies presented in this paper is to dramatically increase process efficiency as well as process flexibility. During the last years, the average power of commercial ultra-short pulsed laser sources has increased significantly. The efficient utilization of the high average laser power in the field of material processing requires an effective distribution of the laser power onto the work piece. One approach to increase the efficiency is the application of beam splitting devices to enable parallel processing. Multi beam processing is used to parallelize the fabrication of periodic structures as most application only require a partial amount of the emitted ultra-short pulsed laser power. In order to achieve highest flexibility while using multi beam processing the single beams are diverted and re-guided in a way that enables the opportunity to process with each partial beam on locally apart probes or semimanufactures.

Beam-specific planning volumes for scattered-proton lung radiotherapy

NASA Astrophysics Data System (ADS)

Flampouri, S.; Hoppe, B. S.; Slopsema, R. L.; Li, Z.

2014-08-01

This work describes the clinical implementation of a beam-specific planning treatment volume (bsPTV) calculation for lung cancer proton therapy and its integration into the treatment planning process. Uncertainties incorporated in the calculation of the bsPTV included setup errors, machine delivery variability, breathing effects, inherent proton range uncertainties and combinations of the above. Margins were added for translational and rotational setup errors and breathing motion variability during the course of treatment as well as for their effect on proton range of each treatment field. The effect of breathing motion and deformation on the proton range was calculated from 4D computed tomography data. Range uncertainties were considered taking into account the individual voxel HU uncertainty along each proton beamlet. Beam-specific treatment volumes generated for 12 patients were used: a) as planning targets, b) for routine plan evaluation, c) to aid beam angle selection and d) to create beam-specific margins for organs at risk to insure sparing. The alternative planning technique based on the bsPTVs produced similar target coverage as the conventional proton plans while better sparing the surrounding tissues. Conventional proton plans were evaluated by comparing the dose distributions per beam with the corresponding bsPTV. The bsPTV volume as a function of beam angle revealed some unexpected sources of uncertainty and could help the planner choose more robust beams. Beam-specific planning volume for the spinal cord was used for dose distribution shaping to ensure organ sparing laterally and distally to the beam.

Built-in hyperspectral camera for smartphone in visible, near-infrared and middle-infrared lights region (second report): sensitivity improvement of Fourier-spectroscopic imaging to detect diffuse reflection lights from internal human tissues for healthcare sensors

NASA Astrophysics Data System (ADS)

Kawashima, Natsumi; Hosono, Satsuki; Ishimaru, Ichiro

2016-05-01

We proposed the snapshot-type Fourier spectroscopic imaging for smartphone that was mentioned in 1st. report in this conference. For spectroscopic components analysis, such as non-invasive blood glucose sensors, the diffuse reflection lights from internal human skins are very weak for conventional hyperspectral cameras, such as AOTF (Acousto-Optic Tunable Filter) type. Furthermore, it is well known that the spectral absorption of mid-infrared lights or Raman spectroscopy especially in long wavelength region is effective to distinguish specific biomedical components quantitatively, such as glucose concentration. But the main issue was that photon energies of middle infrared lights and light intensities of Raman scattering are extremely weak. For improving sensitivity of our spectroscopic imager, the wide-field-stop & beam-expansion method was proposed. Our line spectroscopic imager introduced a single slit for field stop on the conjugate objective plane. Obviously to increase detected light intensities, the wider slit width of the field stop makes light intensities higher, regardless of deterioration of spatial resolutions. Because our method is based on wavefront-division interferometry, it becomes problems that the wider width of single slit makes the diffraction angle narrower. This means that the narrower diameter of collimated objective beams deteriorates visibilities of interferograms. By installing the relative inclined phaseshifter onto optical Fourier transform plane of infinity corrected optical systems, the collimated half flux of objective beams derived from single-bright points on objective surface penetrate through the wedge prism and the cuboid glass respectively. These two beams interfere each other and form the infererogram as spatial fringe patterns. Thus, we installed concave-cylindrical lens between the wider slit and objective lens as a beam expander. We successfully obtained the spectroscopic characters of hemoglobin from reflected lights from human fingers.

Survey of discomfort glare from the headlamps of cars widely used in Iran.

PubMed

Mehri, Ahmad; Farhang Dehghan, Somayeh; Hajizadeh, Roohalah; Zakerian, Seyed Abolfazl; Mohammadi, Hamzeh; Abbasi, Milad

2017-10-03

On 2-lane roads, discomfort glare can cause annoyance, discomfort, inconvenience, stress, and fatigue to drivers, posing a risk of accidents. The aim of this study is to evaluate discomfort glare from the headlamps of cars widely used in Iran. The discomfort glare of new vehicles including Pride Saba model GTX, Pride Model 131SL, Samand Soren, Peugeot 405, Megane, and Peugeot Pars was examined at distances of 5 to 100 m at a background luminance of 50 cd/m 2 (late twilight/early dawn lighting) and 1 cd/m 2 (nighttime) using Schmidt-Clausen and Bindels model and de Boer's subjective scale. According to the de Boer scale, at a background luminance of 50 cd/m 2 , the discomfort glare for all studied vehicles was between 1.98 and 4.05 in high-beam mode and between 3.5 and 5.4 in low-beam mode. At a background luminance of 1 cd/m 2 , discomfort glare was between 0.41 and 2.48 in high-beam mode and between 1.93 and 3.84 in low-beam mode. In high-beam mode, the average levels of discomfort glare of these vehicles gradually increased when the distance between cars was reduced by up to about 20 m. In low-beam mode, there was no discomfort glare up to a vehicle distance of 40 m. In addition, at an angle of 1.15°-5.73° between the line of sight and light of vehicles in high-beam mode, the level of discomfort glare was increased, but at an angle of 5.73°-22.9° the level of discomfort glare was reduced. In low-beam mode at an angle of 2.86°-22.9°, the level of discomfort glare was almost identical. The results show that in high-beam mode and with a 100-m distance between vehicles as well as in low-beam mode at intervals of less than 40 m between cars, discomfort glare is created. It can be concluded that by providing solutions such as installing road lighting system, an increase in luminance of roads, separating or widening road lanes, increasing the lateral distance between vehicles, and increasing the angle between lighted vehicles and drivers can noticeably reduce discomfort glare.

Theoretical predictions of the changes in the irradiance and color of light beams traveling in sugared water caused by optical rotation phenomena, and their possible applications for educational purposes

NASA Astrophysics Data System (ADS)

Tokumitsu, S.; Hasegawa, M.

2018-05-01

The coloring phenomena caused by optical rotation of polarized light beams in sugared water can be an appropriate subject for use as an educational tool. In this paper, such coloring phenomena are studied in terms of theory, and the results are compared with experimental results. First, polarized laser beams in red, blue, or green were allowed to travel in sugared water of certain concentrations, and changes in the irradiance of the beams were measured while changing the distance between a pair of polarizing plates arranged in the sugared water. The angle of rotation was then determined for each color. An equation was established for predicting a theoretical value of the angle of rotation for laser beams of specific colors (wavelengths) traveling in sugared water of specific concentrations. The predicted results from the equation exhibited satisfactory agreement with the experimental values obtained from the measurements. In addition, changes in the irradiance of traveling laser beams, as well as the changes in colors observable for white light beams, were also predicted, resulting in good agreement with the observed results.

Performance Test of the Next Generation X-Ray Beam Position Monitor System for The APS Upgrade

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

Yang, B.; Lee, S.; Westferro, F.

The Advanced Photon Source is developing its next major upgrade (APS-U) based on the multi-bend achromat lattice. Improved beam stability is critical for the upgrade and will require keeping short-time beam angle change below 0.25 µrad and long-term angle drift below 0.6 µrad. A reliable white x-ray beam diagnostic system in the front end will be a key part of the planned beam stabilization system. This system includes an x-ray beam position monitor (XBPM) based on x-ray fluorescence (XRF) from two specially designed GlidCop A-15 absorbers, a second XBPM using XRF photons from the Exit Mask, and two white beammore » intensity monitors using XRF from the photon shutter and Compton-scattered photons from the front end beryllium window or a retractable diamond film in windowless front ends. We present orbit stability data for the first XBPM used in the feedback control during user operations, as well as test data from the second XBPM and the intensity monitors. They demonstrate that the XBPM system meets APS-U beam stability requirements.« less

Parallel transmit beamforming using orthogonal frequency division multiplexing applied to harmonic imaging--a feasibility study.

PubMed

Demi, Libertario; Verweij, Martin D; Van Dongen, Koen W A

2012-11-01

Real-time 2-D or 3-D ultrasound imaging systems are currently used for medical diagnosis. To achieve the required data acquisition rate, these systems rely on parallel beamforming, i.e., a single wide-angled beam is used for transmission and several narrow parallel beams are used for reception. When applied to harmonic imaging, the demand for high-amplitude pressure wave fields, necessary to generate the harmonic components, conflicts with the use of a wide-angled beam in transmission because this results in a large spatial decay of the acoustic pressure. To enhance the amplitude of the harmonics, it is preferable to do the reverse: transmit several narrow parallel beams and use a wide-angled beam in reception. Here, this concept is investigated to determine whether it can be used for harmonic imaging. The method proposed in this paper relies on orthogonal frequency division multiplexing (OFDM), which is used to create distinctive parallel beams in transmission. To test the proposed method, a numerical study has been performed, in which the transmit, receive, and combined beam profiles generated by a linear array have been simulated for the second-harmonic component. Compared with standard parallel beamforming, application of the proposed technique results in a gain of 12 dB for the main beam and in a reduction of the side lobes. Experimental verification in water has also been performed. Measurements obtained with a single-element emitting transducer and a hydrophone receiver confirm the possibility of exciting a practical ultrasound transducer with multiple Gaussian modulated pulses, each having a different center frequency, and the capability to generate distinguishable second-harmonic components.

Nondestructive Evaluation of Aircraft Composites Using Terahertz Time Domain Spectroscopy

DTIC Science & Technology

2008-12-10

substrate lenses : collimating and aplanatic. In a collimating lens , the rays emitted near the optic axis emerge as a collimated beam, while the rays...emitted at larger angles emerge at substantial angles or are internally reflected and lost. The aplanatic hyperhemispherical lens design, which...propagates out of the lens before it spreads. Many of the hemispherical designs result in the spreading of the THz beam at a given angle , which can then be

Gigatron microwave amplifier

DOEpatents

McIntyre, P.M.

1993-07-13

An electron tube for achieving high power at high frequency with high efficiency is described, including an input coupler, a ribbon-shaped electron beam and a traveling wave output coupler. The input coupler is a lumped constant resonant circuit that modulates a field emitter array cathode at microwave frequency. A bunched ribbon electron beam is emitted from the cathode in periodic bursts at the desired frequency. The beam has a ribbon configuration to eliminate limitations inherent in round beam devices. The traveling wave coupler efficiently extracts energy from the electron beam, and includes a waveguide with a slot there through for receiving the electron beam. The ribbon beam is tilted at an angle with respect to the traveling wave coupler so that the electron beam couples in-phase with the traveling wave in the waveguide. The traveling wave coupler thus extracts energy from the electron beam over the entire width of the beam.

Gigatron microwave amplifier

DOEpatents

McIntyre, Peter M.

1993-01-01

An electron tube for achieving high power at high frequency with high efficiency, including an input coupler, a ribbon-shaped electron beam and a traveling wave output coupler. The input coupler is a lumped constant resonant circuit that modulates a field emitter array cathode at microwave frequency. A bunched ribbon electron beam is emitted from the cathode in periodic bursts at the desired frequency. The beam has a ribbon configuration to eliminate limitations inherent in round beam devices. The traveling wave coupler efficiently extracts energy from the electron beam, and includes a waveguide with a slot therethrough for receiving the electron beam. The ribbon beam is tilted at an angle with respect to the traveling wave coupler so that the electron beam couples in-phase with the traveling wave in the waveguide. The traveling wave coupler thus extracts energy from the electron beam over the entire width of the beam.

Wide-Field Retroreflectors

NASA Technical Reports Server (NTRS)

Page, Norman A.; Tubbs, Eldred F.

1994-01-01

Retroreflectors made of concentric spherical optical elements developed for use in interferometric metrological systems. Used to provide reference point on structure to be aligned precisely in two or three dimensions by use of intersecting laser beams. Acceptance angle much larger than that of cat's-eye or corner-cube retroreflector: Simultaneously reflects laser beams separated by angles as large as 180 degrees.

Biaxial thin-film coated-plate polarizing beam splitters.

PubMed

Hodgkinson, Ian; Wu, Qi Hong; Arnold, Matthew; De Silva, Lakshman; Beydaghyan, Gisia; Kaminska, Kate; Robbie, Kevin

2006-03-01

We present a design for a biaxial thin-film coated-plate polarizing beam splitter that transmits the p-polarized component of a beam of light without change of direction and reflects the s-polarized component. The beam splitter has a periodic structure and is planned for fabrication by serial bideposition in mutually orthogonal planes. Recent experimental data for form-birefringent silicon is used to establish the feasibility of the design for a beam splitter to be used at 1310 nm and at an angle of 45 degrees in air.

Ultra-compact laser beam steering device using holographically formed two dimensional photonic crystal.

PubMed

Dou, Xinyuan; Chen, Xiaonan; Chen, Maggie Yihong; Wang, Alan Xiaolong; Jiang, Wei; Chen, Ray T

2010-03-01

In this paper, we report the theoretical study of polymer-based photonic crystals for laser beam steering which is based on the superprism effect as well as the experiment fabrication of the two dimensional photonic crystals for the laser beam steering. Superprism effect, the principle for beam steering, was separately studied in details through EFC (Equifrequency Contour) analysis. Polymer based photonic crystals were fabricated through double exposure holographic interference method using SU8-2007. The experiment results showed a beam steering angle of 10 degree for 30 nm wavelength variation.

Experimental investigation of material nonlinearity using the Rayleigh surface waves excited and detected by angle beam wedge transducers.

PubMed

Zhang, Shuzeng; Li, Xiongbing; Jeong, Hyunjo; Hu, Hongwei

2018-05-12

Angle beam wedge transducers are widely used in nonlinear Rayleigh wave experiments as they can generate Rayleigh wave easily and produce high intensity nonlinear waves for detection. When such a transducer is used, the spurious harmonics (source nonlinearity) and wave diffraction may occur and will affect the measurement results, so it is essential to fully understand its acoustic nature. This paper experimentally investigates the nonlinear Rayleigh wave beam fields generated and received by angle beam wedge transducers, in which the theoretical predictions are based on the acoustic model developed previously for angle beam wedge transducers [S. Zhang, et al., Wave Motion, 67, 141-159, (2016)]. The source of the spurious harmonics is fully characterized by scrutinizing the nonlinear Rayleigh wave behavior in various materials with different driving voltages. Furthermore, it is shown that the attenuation coefficients for both fundamental and second harmonic Rayleigh waves can be extracted by comparing the measurements with the predictions when the experiments are conducted at many locations along the propagation path. A technique is developed to evaluate the material nonlinearity by making appropriate corrections for source nonlinearity, diffraction and attenuation. The nonlinear parameters of three aluminum alloy specimens - Al 2024, Al 6061 and Al 7075 - are measured, and the results indicate that the measurement results can be significantly improved using the proposed method. Copyright © 2018. Published by Elsevier B.V.

Scanning optical microscope with long working distance objective

DOEpatents

Cloutier, Sylvain G.

2010-10-19

A scanning optical microscope, including: a light source to generate a beam of probe light; collimation optics to substantially collimate the probe beam; a probe-result beamsplitter; a long working-distance, infinity-corrected objective; scanning means to scan a beam spot of the focused probe beam on or within a sample; relay optics; and a detector. The collimation optics are disposed in the probe beam. The probe-result beamsplitter is arranged in the optical paths of the probe beam and the resultant light from the sample. The beamsplitter reflects the probe beam into the objective and transmits resultant light. The long working-distance, infinity-corrected objective is also arranged in the optical paths of the probe beam and the resultant light. It focuses the reflected probe beam onto the sample, and collects and substantially collimates the resultant light. The relay optics are arranged to relay the transmitted resultant light from the beamsplitter to the detector.

Generation of magneto-immersed electron beams

NASA Astrophysics Data System (ADS)

Pikin, A.; Raparia, D.

2018-05-01

There are many applications of electron beams in accelerator facilities: for electron coolers, electron lenses, and electron beam ion sources (EBIS) to mention a few. Most of these applications require magnetic compression of the electron beam to reduce the beam radius with the goal of either matching the circulating ion beam (electron lenses and electron coolers) or increasing the ionization capability for the production of highly charged ions (EBIS). The magnetic compression of the electron beam comes at a cost of increasing share of the transverse component of energy and therefore increased angles of the electron trajectories to the longitudinal axis. Considering the effect of the magnetic mirror, it is highly desirable to produce a laminar electron beam in the electron gun. The analysis of electron guns with different configurations is given in this paper with emphasis on generating laminar electron beams.

CO.sub.2 optically pumped distributed feedback diode laser

DOEpatents

Rockwood, Stephen D.

1980-01-01

A diode laser optically pumped by a CO.sub.2 coherent source. Interference fringes generated by feeding the optical pumping beam against a second beam, periodically alter the reflectivity of the diode medium allowing frequency variation of the output signal by varying the impingent angle of the CO.sub.2 laser beams.

Homogeneous alignment of nematic liquid crystals by ion beam etched surfaces

NASA Technical Reports Server (NTRS)

Wintucky, E. G.; Mahmood, R.; Johnson, D. L.

1979-01-01

A wide range of ion beam etch parameters capable of producing uniform homogeneous alignment of nematic liquid crystals on SiO2 films are discussed. The alignment surfaces were generated by obliquely incident (angles of 5 to 25 deg) argon ions with energies in the range of 0.5 to 2.0 KeV, ion current densities of 0.1 to 0.6 mA sq cm and etch times of 1 to 9 min. A smaller range of ion beam parameters (2.0 KeV, 0.2 mA sq cm, 5 to 10 deg and 1 to 5 min.) were also investigated with ZrO2 films and found suitable for homogeneous alignment. Extinction ratios were very high (1000), twist angles were small ( or = 3 deg) and tilt-bias angles very small ( or = 1 deg). Preliminary scanning electron microscopy results indicate a parallel oriented surface structure on the ion beam etched surfaces which may determine alignment.

High-performance axicon lenses based on high-contrast, multilayer gratings

NASA Astrophysics Data System (ADS)

Doshay, Sage; Sell, David; Yang, Jianji; Yang, Rui; Fan, Jonathan A.

2018-01-01

Axicon lenses are versatile optical elements that can convert Gaussian beams to Bessel-like beams. In this letter, we demonstrate that axicons operating with high efficiencies and at large angles can be produced using high-contrast, multilayer gratings made from silicon. Efficient beam deflection of incident monochromatic light is enabled by higher-order optical modes in the silicon structure. Compared to diffractive devices made from low-contrast materials such as silicon dioxide, our multilayer devices have a relatively low spatial profile, reducing shadowing effects and enabling high efficiencies at large deflection angles. In addition, the feature sizes of these structures are relatively large, making the fabrication of near-infrared devices accessible with conventional optical lithography. Experimental lenses with deflection angles as large as 40° display field profiles that agree well with theory. Our concept can be used to design optical elements that produce higher-order Bessel-like beams, and the combination of high-contrast materials with multilayer architectures will more generally enable new classes of diffractive photonic structures.

Sonographic investigation of anatomical specimens of infant hip joints.

PubMed

Falliner, Axel; Hahne, Hans-Jürgen; Hassenpflug, Joachim

2002-07-01

The anatomical foundations of infant hip sonography techniques are ill-defined. We investigated anatomical specimens of infant hip joints in a water bath, with Graf's and Terjesen's methods. Acetabular position was varied in defined increments, with respect to the ultrasound beam. The alpha angles and the femoral head coverage were measured. Plastic acetabular casts were sawn along the sonographic section planes, and the cut sections compared with the sonographic sections. For images to be obtained, which were analysable by the two methods, the ultrasound beam had to intersect with the acetabular inlet plane at defined angles. The acetabular notch had to be anteriorly rotated from the ultrasound beam plane by at least 20 degrees. Beam entry within a 50 degrees sector posterior to the perpendicular on the inlet plane gave analysable images. The alpha angles and femoral head coverage were much affected by coronal-plane transducer tilt. Caudad tilts were associated with lesser values, a fact that should be borne in mind in clinical ultrasound investigations.

Compact reflection holographic recording system with high angle multiplexing

NASA Astrophysics Data System (ADS)

Kanayasu, Mayumi; Yamada, Takehumi; Takekawa, Shunsuke; Akieda, Kensuke; Goto, Akiyo; Yamamoto, Manabu

2011-02-01

Holographic memory systems have been widely researched since 1963. However, the size of the drives required and the deterioration of reconstructed data resulting from shrinkage of the medium have made practical use of a hologram memory difficult. In light of this, we propose a novel holographic recording/reconstructing system: a dual-reference beam reflection system that is smaller than conventional systems such as the off-axis or co-axis types, and which is expected to increase the number of multiplexing in angle multiplexed recording. In this multiplex recording system, two laser beams are used as reference beams, and the recorded data are reconstructed stably, even if there is shrinkage of the recording medium. In this paper, a reflection holographic memory system is explained in detail. In addition, the change in angle selectivity resulting from shrinkage of the medium is analyzed using the laminated film three-dimensional simulation method. As a result, we demonstrate that a dual-reference beam multiplex recording system is effective in reducing the influence of medium shrinkage.

Angular Spacing Control for Segmented Data Pages in Angle-Multiplexed Holographic Memory

NASA Astrophysics Data System (ADS)

Kinoshita, Nobuhiro; Muroi, Tetsuhiko; Ishii, Norihiko; Kamijo, Koji; Kikuchi, Hiroshi; Shimidzu, Naoki; Ando, Toshio; Masaki, Kazuyoshi; Shimizu, Takehiro

2011-09-01

To improve the recording density of angle-multiplexed holographic memory, it is effective to increase the numerical aperture of the lens and to shorten the wavelength of the laser source as well as to increase the multiplexing number. The angular selectivity of a hologram, which determines the multiplexing number, is dependent on the incident angle of not only the reference beam but also the signal beam to the holographic recording medium. The actual signal beam, which is a convergent or divergent beam, is regarded as the sum of plane waves that have different propagation directions, angular selectivities, and optimal angular spacings. In this paper, focusing on the differences in the optimal angular spacing, we proposed a method to control the angular spacing for each segmented data page. We investigated the angular selectivity of a hologram and crosstalk for segmented data pages using numerical simulation. The experimental results showed a practical bit-error rate on the order of 10-3.

Optical Interference Coatings Design Contest 2013: angle-independent color mirror and shortwave infrared/midwave infrared dichroic beam splitter.

PubMed

Hendrix, Karen; Kruschwitz, Jennifer D T; Keck, Jason

2014-02-01

An angle-independent color mirror and an infrared dichroic beam splitter were the subjects of a design contest held in conjunction with the 2013 Optical Interference Coatings topical meeting of the Optical Society of America. A total of 17 designers submitted 63 designs, 22 for Problem A and 41 for Problem B. The submissions were created through a wide spectrum of design approaches and optimization strategies. Michael Trubetskov and Weidong Shen won the first contest by submitting color mirror designs with a zero color difference (ΔE00) between normal incidence and all other incidence angles up to 60° as well as the thinnest design. Michael Trubetskov also won the second contest by submitting beam-splitter designs that met the required transmission while having the lowest mechanical coating stress and thinnest design. Fabien Lemarchand received the second-place finish for the beam-splitter design. The submitted designs are described and evaluated.

Beam splitting of low-contrast binary gratings under second Bragg angle incidence.

PubMed

Zheng, Jiangjun; Zhou, Changhe; Wang, Bo; Feng, Jijun

2008-05-01

Beam splitting of low-contrast rectangular gratings under second Bragg angle incidence is studied. The grating period is between lambda and 2lambda. The diffraction behaviors of the three transmitted propagating orders are illustrated by analyzing the first three propagating grating modes. From a simplified modal approach, the design conditions of gratings as a high-efficiency element with most of its energy concentrated in the -2nd transmitted order (~90%) and of gratings as a 1 x 2 beam splitter with a total efficiency over 90% are derived. The grating parameters for achieving exactly the splitting pattern by use of rigorous coupled-wave analysis verified the design method. A 1 x 3 beam splitter is also demonstrated. Moreover, the polarization-dependent diffraction behaviors are investigated, which suggest the possibility of designing polarization-selective elements under such a configuration. The proposed concept of using the second Bragg angle should be helpful for developing new grating-based devices.

Correlation of process parameters and properties of TiO2 films grown by ion beam sputter deposition from a ceramic target

NASA Astrophysics Data System (ADS)

Bundesmann, Carsten; Lautenschläge, Thomas; Spemann, Daniel; Finzel, Annemarie; Mensing, Michael; Frost, Frank

2017-10-01

The correlation between process parameters and properties of TiO2 films grown by ion beam sputter deposition from a ceramic target was investigated. TiO2 films were grown under systematic variation of ion beam parameters (ion species, ion energy) and geometrical parameters (ion incidence angle, polar emission angle) and characterized with respect to film thickness, growth rate, structural properties, surface topography, composition, optical properties, and mass density. Systematic variations of film properties with the scattering geometry, namely the scattering angle, have been revealed. There are also considerable differences in film properties when changing the process gas from Ar to Xe. Similar systematics were reported for TiO2 films grown by reactive ion beam sputter deposition from a metal target [C. Bundesmann et al., Appl. Surf. Sci. 421, 331 (2017)]. However, there are some deviations from the previously reported data, for instance, in growth rate, mass density and optical properties.

Dual beam optical system for pulsed laser ablation film deposition

DOEpatents

Mashburn, D.N.

1996-09-24

A laser ablation apparatus having a laser source outputting a laser ablation beam includes an ablation chamber having a sidewall, a beam divider for dividing the laser ablation beam into two substantially equal halves, and a pair of mirrors for converging the two halves on a surface of the target from complementary angles relative to the target surface normal, thereby generating a plume of ablated material emanating from the target. 3 figs.

Dual beam optical system for pulsed laser ablation film deposition

DOEpatents

Mashburn, Douglas N.

1996-01-01

A laser ablation apparatus having a laser source outputting a laser ablation beam includes an ablation chamber having a sidewall, a beam divider for dividing the laser ablation beam into two substantially equal halves, and a pair of mirrors for converging the two halves on a surface of the target from complementary angles relative to the target surface normal, thereby generating a plume of ablated material emanating from the target.

Two-beam-excited conical emission.

PubMed

Kauranen, M; Maki, J J; Gaeta, A L; Boyd, R W

1991-06-15

We describe a conical emission process that occurs when two beams of near-resonant light intersect as they pass through sodium vapor. The light is emitted on the surface of a circular cone that is centered on the bisector of the two applied beams and has an angular extent equal to the crossing angle of the two applied beams. We ascribe the origin of this effect to a perfectly phase-matched four-wave mixing process.

Two and Three Beam Pumped Optical Parametric Amplifier of Chirped Pulses

NASA Astrophysics Data System (ADS)

Ališauskas, S.; Butkus, R.; Pyragaitė, V.; Smilgevičius, V.; Stabinis, A.; Piskarskas, A.

2010-04-01

We present two and three beam pumped optical parametric amplifier of broadband chirped pulses. The seed pulses from Ti:sapphire oscillator were stretched and amplified in a non-collinear geometry pumping with up to three beams derived from independent laser amplifiers. The signal with ˜90 nm bandwidth was amplified up to 0.72 mJ. The conversion efficiency dependence on intersection angles of pump beams is also revealed.

The Effects of Optical Feedback on Polarization of Vertical Cavity Surface Emitting Lasers

DTIC Science & Technology

1993-12-01

Beam Mode TEMN Dichroic Beam Splitters (2) Manufacturer CVI Maximum Reflectance 375 mrn, 950 un Maximum Transmission 830 rnm, 910 mn Design Angle 5... beam splitter (DBS). The DBS reflects the majority of the light at the VCSEL wavelength (and passes most of the pump wavelength). A normal beamsplitter...degrees Beam Splitters Manufacturer Melles Griot Reflectancetrransnittance -50/50 Filters (2) Manufacturer Ealing Center Wavelength 880 urn, 940 mun

Remotely readable fiber optic compass

DOEpatents

Migliori, Albert; Swift, Gregory W.; Garrett, Steven L.

1986-01-01

A remotely readable fiber optic compass. A sheet polarizer is affixed to a magnet rotatably mounted in a compass body, such that the polarizer rotates with the magnet. The optical axis of the sheet polarizer is preferably aligned with the north-south axis of the magnet. A single excitation light beam is divided into four identical beams, two of which are passed through the sheet polarizer and through two fixed polarizing sheets which have their optical axes at right angles to one another. The angle of the compass magnet with respect to a fixed axis of the compass body can be determined by measuring the ratio of the intensities of the two light beams. The remaining ambiguity as to which of the four possible quadrants the magnet is pointing to is resolved by the second pair of light beams, which are passed through the sheet polarizer at positions which are transected by two semicircular opaque strips formed on the sheet polarizer. The incoming excitation beam and the four return beams are communicated by means of optical fibers, giving a remotely readable compass which has no electrical parts.

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.

Remotely readable fiber optic compass

DOEpatents

Migliori, A.; Swift, G.W.; Garrett, S.L.

1985-04-30

A remotely readable fiber optic compass. A sheet polarizer is affixed to a magnet rotatably mounted in a compass body, such that the polarizer rotates with the magnet. The optical axis of the sheet polarizer is preferably aligned with the north-south axis of the magnet. A single excitation light beam is divided into four identical beams, two of which are passed through the sheet polarizer and through two fixed polarizing sheets which have their optical axes at right angles to one another. The angle of the compass magnet with respect to a fixed axis of the compass body can be determined by measuring the ratio of the intensities of the two light beams. The remaining ambiguity as to which of the four possible quadrants the magnet is pointing to is resolved by the second pair of light beams, which are passed through the sheet polarizer at positions which are transected by two semicircular opaque strips formed on the sheet polarizer. The incoming excitation beam and the four return beams are communicated by means of optical fibers, giving a remotely readable compass which has no electrical parts.

X-ray beam transfer between hollow fibers for long-distance transport

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

Tanaka, Yoshihito, E-mail: tanaka@sci.u-hyogo.ac.jp; Matsushita, Ryuki; Shiraishi, Ryutaro

2016-07-27

Fiber optics for controlling the x-ray beam trajectory has been examined at the synchrotron facility of SPring-8. Up to now, we have achieved beam deflection by several tens of milli-radian and axis shift of around 75 mm with a 1.5 m-long flexible hollow glass capillary. The achievable beam deflecting angle, axis shift, and timing delay are, in principle, proportional to the length, the square of length and the cube of length, respectively. Thus, for further applications, requiring larger beam shift and pulse delay, longer fibers are indispensable. In order to achieve long-distance transport using the fiber, we thus examined themore » connection transferring x-rays between fibers in an experimental hutch. The acceptance angle at the input end and the throughput efficiency of the second fiber is consistent with the consideration of the output beam divergence of the first fiber. The enhancement of the transfer efficiency is also discussed for the cases of a closer joint and the use of a refractive lens as a coupler.« less

CT cardiac imaging: evolution from 2D to 3D backprojection

NASA Astrophysics Data System (ADS)

Tang, Xiangyang; Pan, Tinsu; Sasaki, Kosuke

2004-04-01

The state-of-the-art multiple detector-row CT, which usually employs fan beam reconstruction algorithms by approximating a cone beam geometry into a fan beam geometry, has been well recognized as an important modality for cardiac imaging. At present, the multiple detector-row CT is evolving into volumetric CT, in which cone beam reconstruction algorithms are needed to combat cone beam artifacts caused by large cone angle. An ECG-gated cardiac cone beam reconstruction algorithm based upon the so-called semi-CB geometry is implemented in this study. To get the highest temporal resolution, only the projection data corresponding to 180° plus the cone angle are row-wise rebinned into the semi-CB geometry for three-dimensional reconstruction. Data extrapolation is utilized to extend the z-coverage of the ECG-gated cardiac cone beam reconstruction algorithm approaching the edge of a CT detector. A helical body phantom is used to evaluate the ECG-gated cone beam reconstruction algorithm"s z-coverage and capability of suppressing cone beam artifacts. Furthermore, two sets of cardiac data scanned by a multiple detector-row CT scanner at 16 x 1.25 (mm) and normalized pitch 0.275 and 0.3 respectively are used to evaluate the ECG-gated CB reconstruction algorithm"s imaging performance. As a reference, the images reconstructed by a fan beam reconstruction algorithm for multiple detector-row CT are also presented. The qualitative evaluation shows that, the ECG-gated cone beam reconstruction algorithm outperforms its fan beam counterpart from the perspective of cone beam artifact suppression and z-coverage while the temporal resolution is well maintained. Consequently, the scan speed can be increased to reduce the contrast agent amount and injection time, improve the patient comfort and x-ray dose efficiency. Based up on the comparison, it is believed that, with the transition of multiple detector-row CT into volumetric CT, ECG-gated cone beam reconstruction algorithms will provide better image quality for CT cardiac applications.

Epithermal neutron beams from the 7 Li(p,n) reaction near the threshold for neutron capture therapy

NASA Astrophysics Data System (ADS)

Porras, I.; Praena, J.; Arias de Saavedra, F.; Pedrosa, M.; Esquinas, P.; L. Jiménez-Bonilla, P.

2016-11-01

Two applications for neutron capture therapy of epithermal neutron beams calculated from the 7Li ( p , n reaction are discussed. In particular, i) for a proton beam of 1920 keV of a 30 mA, a neutron beam of adequate features for BNCT is found at an angle of 80° from the forward direction; and ii) for a proton beam of 1910 keV, a neutron beam is obtained at the forward direction suitable for performing radiobiology experiments for the determination of the biological weighting factors of the fast dose component in neutron capture therapy.

Radiation beam collimation system and method

DOEpatents

Schmidt, Oliver A.; Ramanathan, Mohan

2015-08-18

The invention provides a method for collimating a radiation beam, the method comprising subjecting the beam to a collimator that yaws and pitches, either separately or simultaneously relative to the incident angle of the beam. Also provided is a system for collimating radiation beams, the system comprising a collimator body, and a stage for pitching and yawing the body. A feature of the invention is that a single, compact mask body defines one or a plurality of collimators having no moving surfaces relative to each other, whereby the entire mask body is moved about a point in space to provide various collimator opening dimensions to oncoming radiation beams.

Laser-driven deflection arrangements and methods involving charged particle beams

DOEpatents

Plettner, Tomas [San Ramon, CA; Byer, Robert L [Stanford, CA

2011-08-09

Systems, methods, devices and apparatus are implemented for producing controllable charged particle beams. In one implementation, an apparatus provides a deflection force to a charged particle beam. A source produces an electromagnetic wave. A structure, that is substantially transparent to the electromagnetic wave, includes a physical structure having a repeating pattern with a period L and a tilted angle .alpha., relative to a direction of travel of the charged particle beam, the pattern affects the force of the electromagnetic wave upon the charged particle beam. A direction device introduces the electromagnetic wave to the structure to provide a phase-synchronous deflection force to the charged particle beam.

Incident-beam effects in electron-stimulated Auger-electron diffraction

NASA Astrophysics Data System (ADS)

Gao, Y.; Cao, Jianming

1991-04-01

We have examined incident-beam effects in electron-stimulated Auger-electron diffraction (AED) on a cleaved GaAs(110) surface. The results indicate that incident-beam diffraction is significant in an AED experiment, and that the dissipative nature of the incident beam in contributing to the Auger process must be accounted for. We have developed a qualitative model that describes the trend of the polar-angle dependence of the Auger intensity for both the incident and exit beams. In calculating the diffraction features, we used a zeroth-order approximation to simulate the dissipation of the incident beam, which is found to adequately describe the experimental data.

Two-dimensional ultrahigh-density X-ray optical memory.

PubMed

Bezirganyan, Hakob P; Bezirganyan, Siranush E; Bezirganyan, Hayk H; Bezirganyan, Petros H

2007-01-01

Most important aspect of nanotechnology applications in the information ultrahigh storage is the miniaturization of data carrier elements of the storage media with emphasis on the long-term stability. Proposed two-dimensional ultrahigh-density X-ray optical memory, named X-ROM, with long-term stability is an information carrier basically destined for digital data archiving. X-ROM is a semiconductor wafer, in which the high-reflectivity nanosized X-ray mirrors are embedded. Data are encoded due to certain positions of the mirrors. Ultrahigh-density data recording procedure can e.g., be performed via mask-less zone-plate-array lithography (ZPAL), spatial-phase-locked electron-beam lithography (SPLEBL), or focused ion-beam lithography (FIB). X-ROM manufactured by nanolithography technique is a write-once memory useful for terabit-scale memory applications, if the surface area of the smallest recording pits is less than 100 nm2. In this case the X-ROM surface-storage capacity of a square centimetre becomes by two orders of magnitude higher than the volumetric data density really achieved for three-dimensional optical data storage medium. Digital data read-out procedure from proposed X-ROM can e.g., be performed via glancing-angle incident X-ray micro beam (GIX) using the well-developed X-ray reflectometry technique. In presented theoretical paper the crystal-analyser operating like an image magnifier is added to the set-up of X-ROM data handling system for the purpose analogous to case of application the higher numerical aperture objective in optical data read-out system. We also propose the set-up of the X-ROM readout system based on more the one incident X-ray micro beam. Presented scheme of two-beam data handling system, which operates on two mutually perpendicular well-collimated monochromatic incident X-ray micro beams, essentially increases the reliability of the digital information read-out procedure. According the graphs of characteristic functions presented in paper, one may choose optimally the incident radiation wavelength, as well as the angle of incidence of X-ray micro beams, appropriate for proposed digital data read-out procedure.

High-current, relativistic electron-beam transport in metals and the role of magnetic collimation.

PubMed

Storm, M; Solodov, A A; Myatt, J F; Meyerhofer, D D; Stoeckl, C; Mileham, C; Betti, R; Nilson, P M; Sangster, T C; Theobald, W; Guo, Chunlei

2009-06-12

High-resolution coherent transition radiation (CTR) imaging diagnoses electrons accelerated in laser-solid interactions with intensities of approximately 10;{19} W/cm;{2}. The CTR images indicate electron-beam filamentation and annular propagation. The beam temperature and half-angle divergence are inferred to be approximately 1.4 MeV and approximately 16 degrees , respectively. Three-dimensional hybrid-particle-in-cell code simulations reproduce the details of the CTR images assuming an initial half-angle divergence of approximately 56 degrees . Self-generated resistive magnetic fields are responsible for the difference between the initial and measured divergence.

Recording polarization gratings with a standing spiral wave

NASA Astrophysics Data System (ADS)

Vernon, Jonathan P.; Serak, Svetlana V.; Hakobyan, Rafik S.; Aleksanyan, Artur K.; Tondiglia, Vincent P.; White, Timothy J.; Bunning, Timothy J.; Tabiryan, Nelson V.

2013-11-01

A scalable and robust methodology for writing cycloidal modulation patterns of optical axis orientation in photosensitive surface alignment layers is demonstrated. Counterpropagating circularly polarized beams, generated by reflection of the input beam from a cholesteric liquid crystal, direct local surface orientation in a photosensitive surface. Purposely introducing a slight angle between the input beam and the photosensitive surface normal introduces a grating period/orientation that is readily controlled and templated. The resulting cycloidal diffractive waveplates offer utility in technologies requiring diffraction over a broad range of angles/wavelengths. This simple methodology of forming polarization gratings offers advantages over conventional fabrication techniques.

EFFECTS OF X-RAY BEAM ANGLE AND GEOMETRIC DISTORTION ON WIDTH OF EQUINE THORACOLUMBAR INTERSPINOUS SPACES USING RADIOGRAPHY AND COMPUTED TOMOGRAPHY-A CADAVERIC STUDY.

PubMed

Djernaes, Julie D; Nielsen, Jon V; Berg, Lise C

2017-03-01

The widths of spaces between the thoracolumbar processi spinosi (interspinous spaces) are frequently assessed using radiography in sports horses; however effects of varying X-ray beam angles and geometric distortion have not been previously described. The aim of this prospective, observational study was to determine whether X-ray beam angle has an effect on apparent widths of interspinous spaces. Thoracolumbar spine specimens were collected from six equine cadavers and left-right lateral radiographs and sagittal and dorsal reconstructed computed tomographic (CT) images were acquired. Sequential radiographs were acquired with each interspinous space in focus. Measurements were performed for each interspinous space in the focus position and up to eight angled positions as the interspinous space moved away from focus (±). Focus position measurements were compared to matching sagittal CT measurements. Effect of geometric distortion was evaluated by comparing the interspinous space in radiographs with sagittal and dorsal reconstructed CT images. A total of 49 interspinous spaces were sampled, yielding 274 measurements. X-ray beam angle significantly affected measured width of interspinous spaces in position +3 (P = 0.038). Changes in width did not follow a consistent pattern. Interspinous space widths in focus position were significantly smaller in radiographs compared to matching reconstructed CT images for backs diagnosed with kissing spine syndrome (P < 0.001). Geometric distortion markedly affected appearance of interspinous space width between planes. In conclusion, X-ray beam angle and geometric distortion influence radiographically measured widths of interspinous spaces in the equine thoracolumbar spine, and this should be taken into consideration when evaluating sport horses. © 2016 American College of Veterinary Radiology.

Comprehensive evaluation of broad-beam transmission of patient supports from three fluoroscopy-guided interventional systems.

PubMed

DeLorenzo, Matthew C; Yang, Kai; Li, Xinhua; Liu, Bob

2018-04-01

The purpose of the study was to measure, evaluate, and model the broad-beam x-ray transmission of the patient supports from representative modern fluoroscopy-guided interventional systems, for patient skin dose calculation. Broad-beam transmission was evaluated by varying incident angle, kVp, added copper (Cu) filter, and x-ray field size for three fluoroscopy systems: General Electric (GE) Innova 4100 with Omega V table and pad, Siemens Axiom Artis with Siemens tabletop "narrow" (CARD) table and pad, and Siemens Zeego with Trumpf TruSystem 7500 table and pad. Field size was measured on the table using a lead ruler for all setups in this study. Exposure rates were measured in service mode using a calibrated Radcal 10 × 6-60 ion chamber above the patient support at the assumed skin location. Broad-beam transmission factors were calculated by the ratio of air kerma rates measured with and without a patient support in the beam path. First, angle dependency was investigated on the GE system, with the chamber at isocenter, for angles of 0°, 15°, 30°, and 40°, for a variety of kVp, added Cu filters, and for two field sizes (small and large). Second, the broad-beam transmission factor at normal incidence was evaluated for all three fluoroscopes by varying kVp, added Cu filter, and field size (small, medium, and large). An analytical equation was created to fit the data as to maximize R 2 and minimize maximum percentage difference across all measurements for each system. For all patient supports, broad-beam transmission factor increased with field size, kVp, and added Cu filtration and decreased with incident angle. Oblique incidence measurements show that the transmission decreased by about 1%, 3%, and 6% for incident angles of 15°, 30°, and 40°, respectively. The broad-beam transmission factors at 0° for the table and table plus pad ranged from 0.73 to 0.96 and from 0.59 to 0.89, respectively. The GE and Siemens transmission factors were comparable, while the Trumpf transmission factors were the lowest. The data were successfully fitted to a function of angle, field size, kVp, and added Cu filtration using nine parameters, with an average R 2 value of 0.977 and maximum percentage difference of 4.08%. This study evaluated the broad-beam transmission for three representative fluoroscopy systems and their dependency on angle, kVp, added Cu filter, and field size. The comprehensive data provided for patient support transmission will facilitate accurate calculation of peak skin dose (PSD) and may potentially be integrated into real-time and retrospective dose monitoring with access to Radiation Dose Structured Reports (RDSR) and radiation event data. © 2018 American Association of Physicists in Medicine.

Flatness metrology based on small-angle deflectometric procedures with electronic tiltmeters

NASA Astrophysics Data System (ADS)

Ehret, G.; Laubach, S.; Schulz, M.

2017-06-01

The measurement of optical flats, e. g. synchrotron or XFEL mirrors, with single nanometer topography uncertainty is still challenging. At PTB, we apply for this task small-angle deflectometry in which the angle between the direction of the beam sent to the surface and the beam detected is small. Conventional deflectometric systems measure the surface angle with autocollimators whose light beam also represents the straightness reference. An advanced flatness metrology system was recently implemented at PTB that separates the straightness reference task from the angle detection task. We call it `Exact Autocollimation Deflectometric Scanning' because the specimen is slightly tilted in such a way that at every scanning position the specimen is `exactly' perpendicular to the reference light beam directed by a pentaprism to the surface under test. The tilt angle of the surface is then measured with an additional autocollimator. The advantage of the EADS method is that the two tasks (straightness reference and measurement of surface slope) are separated and each of these can be optimized independently. The idea presented in this paper is to replace this additional autocollimator by one or more electro-mechanical tiltmeters, which are typically faster and have a higher resolution than highly accurate commercially available autocollimators. We investigate the point stability and the linearity of a highly accurate electronic tiltmeter. The pros and cons of using tiltmeters in flatness metrology are discussed.

Demonstration of a novel technique to measure two-photon exchange effects in elastic e±p scattering

DOE PAGES

Moteabbed, Maryam; Niroula, Megh; Raue, Brian A.; ...

2013-08-30

The discrepancy between proton electromagnetic form factors extracted using unpolarized and polarized scattering data is believed to be a consequence of two-photon exchange (TPE) effects. However, the calculations of TPE corrections have significant model dependence, and there is limited direct experimental evidence for such corrections. The TPE contributions depend on the sign of the lepton charge in e±p scattering, but the luminosities of secondary positron beams limited past measurement at large scattering angles, where the TPE effects are believe to be most significant. We present the results of a new experimental technique for making direct e±p comparisons, which has themore » potential to make precise measurements over a broad range in Q 2 and scattering angles. We use the Jefferson Laboratory electron beam and the Hall B photon tagger to generate a clean but untagged photon beam. The photon beam impinges on a converter foil to generate a mixed beam of electrons, positrons, and photons. A chicane is used to separate and recombine the electron and positron beams while the photon beam is stopped by a photon blocker. This provides a combined electron and positron beam, with energies from 0.5 to 3.2 GeV, which impinges on a liquid hydrogen target. The large acceptance CLAS detector is used to identify and reconstruct elastic scattering events, determining both the initial lepton energy and the sign of the scattered lepton. The data were collected in two days with a primary electron beam energy of only 3.3 GeV, limiting the data from this run to smaller values of Q 2 and scattering angle. Nonetheless, this measurement yields a data sample for e±p with statistics comparable to those of the best previous measurements. We have shown that we can cleanly identify elastic scattering events and correct for the difference in acceptance for electron and positron scattering. Because we ran with only one polarity for the chicane, we are unable to study the difference between the incoming electron and positron beams. This systematic effect leads to the largest uncertainty in the final ratio of positron to electron scattering: R=1.027±0.005±0.05 for < Q 2 >=0.206 GeV 2 and 0.830 ≤ ε ≤ 0.943. We have demonstrated that the tertiary e ± beam generated using this technique provides the opportunity for dramatically improved comparisons of e±p scattering, covering a significant range in both Q 2 and scattering angle. Combining data with different chicane polarities will allow for detailed studies of the difference between the incoming e + and e - beams.« less

Demonstration of a novel technique to measure two-photon exchange effects in elastic e±p scattering

NASA Astrophysics Data System (ADS)

Moteabbed, M.; Niroula, M.; Raue, B. A.; Weinstein, L. B.; Adikaram, D.; Arrington, J.; Brooks, W. K.; Lachniet, J.; Rimal, Dipak; Ungaro, M.; Afanasev, A.; Adhikari, K. P.; Aghasyan, M.; Amaryan, M. J.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Bennett, R. P.; Biselli, A. S.; Bono, J.; Boiarinov, S.; Briscoe, W. J.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Chandavar, S.; Cole, P. L.; Collins, P.; Contalbrigo, M.; Cortes, O.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Doughty, D.; Dupre, R.; Egiyan, H.; Fassi, L. El; Eugenio, P.; Fedotov, G.; Fegan, S.; Fersch, R.; Fleming, J. A.; Gevorgyan, N.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guler, N.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Heddle, D.; Hicks, K.; Ho, D.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Kim, A.; Klein, F. J.; Koirala, S.; Kubarovsky, A.; Kubarovsky, V.; Kuhn, S. E.; Kuleshov, S. V.; Lewis, S.; Lu, H. Y.; MacCormick, M.; MacGregor, I. J. D.; Martinez, D.; Mayer, M.; McKinnon, B.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Moriya, K.; Moutarde, H.; Munevar, E.; Munoz Camacho, C.; Nadel-Turonski, P.; Nasseripour, R.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Park, S.; Phelps, E.; Phillips, J. J.; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Protopopescu, D.; Puckett, A. J. R.; Ripani, M.; Rosner, G.; Rossi, P.; Sabatié, F.; Saini, M. S.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Seraydaryan, H.; Sharabian, Y. G.; Smith, E. S.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Stepanyan, S.; Strauch, S.; Tang, W.; Taylor, C. E.; Tian, Ye; Tkachenko, S.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.

2013-08-01

Background: The discrepancy between proton electromagnetic form factors extracted using unpolarized and polarized scattering data is believed to be a consequence of two-photon exchange (TPE) effects. However, the calculations of TPE corrections have significant model dependence, and there is limited direct experimental evidence for such corrections.Purpose: The TPE contributions depend on the sign of the lepton charge in e±p scattering, but the luminosities of secondary positron beams limited past measurement at large scattering angles, where the TPE effects are believe to be most significant. We present the results of a new experimental technique for making direct e±p comparisons, which has the potential to make precise measurements over a broad range in Q2 and scattering angles.Methods: We use the Jefferson Laboratory electron beam and the Hall B photon tagger to generate a clean but untagged photon beam. The photon beam impinges on a converter foil to generate a mixed beam of electrons, positrons, and photons. A chicane is used to separate and recombine the electron and positron beams while the photon beam is stopped by a photon blocker. This provides a combined electron and positron beam, with energies from 0.5 to 3.2 GeV, which impinges on a liquid hydrogen target. The large acceptance CLAS detector is used to identify and reconstruct elastic scattering events, determining both the initial lepton energy and the sign of the scattered lepton.Results: The data were collected in two days with a primary electron beam energy of only 3.3 GeV, limiting the data from this run to smaller values of Q2 and scattering angle. Nonetheless, this measurement yields a data sample for e±p with statistics comparable to those of the best previous measurements. We have shown that we can cleanly identify elastic scattering events and correct for the difference in acceptance for electron and positron scattering. Because we ran with only one polarity for the chicane, we are unable to study the difference between the incoming electron and positron beams. This systematic effect leads to the largest uncertainty in the final ratio of positron to electron scattering: R=1.027±0.005±0.05 for =0.206 GeV2 and 0.830⩽ɛ⩽0.943.Conclusions: We have demonstrated that the tertiary e± beam generated using this technique provides the opportunity for dramatically improved comparisons of e±p scattering, covering a significant range in both Q2 and scattering angle. Combining data with different chicane polarities will allow for detailed studies of the difference between the incoming e+ and e- beams.

Transverse field focused system

DOEpatents

Anderson, O.A.

1983-06-01

It is an object of the invention to provide a transport apparatus for a high current negative-ion beam which will bend the beam around corners through a baffled path in a differential pump or a neutron trap. It is another object of the invention to provide a transport apparatus for a high current negative-ion beam which will allow gas molecules in the beam to exit outwardly from the transport apparatus. A further object of the invention is to provide a multi-stage accelerator for a high current negative-ion beam which will enable acceleration of the beam to very high energy levels with a minimum loss of current carrying capacity. A still further object of the invention is to provide an apparatus for transport or accelertion of a sheet beam of negative ions which is shaped to confine the beam against divergence or expansion.

Theory of using magnetic deflections to combine charged particle beams

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

Steckbeck, Mackenzie K.; Doyle, Barney Lee

2014-09-01

Several radiation effects projects in the Ion Beam Lab (IBL) have recently required two disparate charged particle beams to simultaneously strike a single sample through a single port of the target chamber. Because these beams have vastly different mass–energy products (MEP), the low-MEP beam requires a large angle of deflection toward the sample by a bending electromagnet. A second electromagnet located further upstream provides a means to compensate for the small angle deflection experienced by the high-MEP beam during its path through the bending magnet. This paper derives the equations used to select the magnetic fields required by these twomore » magnets to achieve uniting both beams at the target sample. A simple result was obtained when the separation of the two magnets was equivalent to the distance from the bending magnet to the sample, and the equation is given by: B s= 1/2(r c/r s) B c, where B s and B c are the magnetic fields in the steering and bending magnet and r c/r s is the ratio of the radii of the bending magnet to that of the steering magnet. This result is not dependent upon the parameters of the high MEP beam, i.e. energy, mass, charge state. Therefore, once the field of the bending magnet is set for the low-MEP beam, and the field in the steering magnet is set as indicted in the equation, the trajectory path of any high-MEP beam will be directed into the sample.« less

Optoelectronic Tool Adds Scale Marks to Photographic Images

NASA Technical Reports Server (NTRS)

Stevenson, Charlie; Rivera, Jorge; Youngquist, Robert; Cox, Robert; Haskell, William

2003-01-01

A simple, easy-to-use optoelectronic tool projects scale marks that become incorporated into photographic images (including film and electronic images). The sizes of objects depicted in the images can readily be measured by reference to the scale marks. The role played by the scale marks projected by this tool is the same as that of the scale marks on a ruler placed in a scene for the purpose of establishing a length scale. However, this tool offers the advantage that it can put scale marks quickly and safely in any visible location, including a location in which placement of a ruler would be difficult, unsafe, or time-consuming. The tool (see Figure 1) includes an aluminum housing, within which are mounted four laser diodes that operate at a wavelength of 670 nm. The laser diodes are spaced 1 in. (2.54 cm) apart along a baseline. The laser diodes are mounted with setscrews, which are used to adjust their beams to make them all parallel to each other and perpendicular to the baseline. During the adjustment process, the effect of the adjustments is observed by measuring the positions of the laser-beam spots on a target 80 ft (approx.24 m) away. Once the adjustments have been completed, the laser beams define three 1-in. (2.54-cm) intervals and the location of each beam is defined to within 1/16 in. (approx.1.6 mm) at any target distance out to about 80 ft (approx.24 m). The distance between the laser-beam spots as seen in an image is strictly defined only along an axis parallel to the baseline and perpendicular to the laser beam (also perpendicular to the line of sight of the camera, assuming that the camera-to-target distance is much greater than the distance between the tool and the camera lens). If a flat target surface illuminated by the laser beams is tilted with respect to the aforesaid axis, then the distance along the target surface between scale marks is proportional to the secant of the tilt angle. If one knows the tilt angle, one can correct for it. Even if one does not know the tilt angle precisely, it may not matter: For example, at a tilt of 10 , the secant is approximately 1.0154, so that the tilt error is only about 1.54 percent, which is negligibly small for a typical application in which only approximate measurements are needed.

Five-Year Wilkinson Microwave Anisotropy Probe Observations: Beam Maps and Window Functions

NASA Astrophysics Data System (ADS)

Hill, R. S.; Weiland, J. L.; Odegard, N.; Wollack, E.; Hinshaw, G.; Larson, D.; Bennett, C. L.; Halpern, M.; Page, L.; Dunkley, J.; Gold, B.; Jarosik, N.; Kogut, A.; Limon, M.; Nolta, M. R.; Spergel, D. N.; Tucker, G. S.; Wright, E. L.

2009-02-01

Cosmology and other scientific results from the Wilkinson Microwave Anisotropy Probe (WMAP) mission require an accurate knowledge of the beam patterns in flight. While the degree of beam knowledge for the WMAP one-year and three-year results was unprecedented for a CMB experiment, we have significantly improved the beam determination as part of the five-year data release. Physical optics fits are done on both the A and the B sides for the first time. The cutoff scale of the fitted distortions on the primary mirror is reduced by a factor of ~2 from previous analyses. These changes enable an improvement in the hybridization of Jupiter data with beam models, which is optimized with respect to error in the main beam solid angle. An increase in main-beam solid angle of ~1% is found for the V2 and W1-W4 differencing assemblies. Although the five-year results are statistically consistent with previous ones, the errors in the five-year beam transfer functions are reduced by a factor of ~2 as compared to the three-year analysis. We present radiometry of the planet Jupiter as a test of the beam consistency and as a calibration standard; for an individual differencing assembly, errors in the measured disk temperature are ~0.5%. WMAP is the result of a partnership between Princeton University and NASA's Goddard Space Flight Center. Scientific guidance is provided by the WMAP Science Team.

Magnetic plasma confinement for laser ion source.

PubMed

Okamura, M; Adeyemi, A; Kanesue, T; Tamura, J; Kondo, K; Dabrowski, R

2010-02-01

A laser ion source (LIS) can easily provide a high current beam. However, it has been difficult to obtain a longer beam pulse while keeping a high current. On occasion, longer beam pulses are required by certain applications. For example, more than 10 micros of beam pulse is required for injecting highly charged beams to a large sized synchrotron. To extend beam pulse width, a solenoid field was applied at the drift space of the LIS at Brookhaven National Laboratory. The solenoid field suppressed the diverging angle of the expanding plasma and the beam pulse was widened. Also, it was observed that the plasma state was conserved after passing through a few hundred gauss of the 480 mm length solenoid field.

Design and fabrication of a high-precision cylinder beam expander

NASA Astrophysics Data System (ADS)

Zhang, Yong-hong; Yan, Hong; Xie, Bing; Li, Jian-ming; Luo, Zhong-xiang

2018-03-01

In order to compress the beam divergence angle and reduce the energy density, beam expansion system is widely used to expand the beam in laser system. Cylinder beam expander belongs to one-dimension expander, which expands the laser beam in only one direction (X direction or Y direction), a refraction cylinder expander whose beam diameter is 180mm×120mm and magnitude ratio is 12 is designed in this paper, the working wavelength is 1058nm. To solve the problem of inequality of the working wavelength and the testing wavelength, compensation method of using parallel plate to test the system aberration is proposed. By rough grinding (precision grinding) polish and the system grinding, the final system aberration is 0.24λ(peak-valley value)

Rhomboid prism pair for rotating the plane of parallel light beams

NASA Technical Reports Server (NTRS)

Orloff, K. L. (Inventor); Yanagita, H.

1982-01-01

An optical system is described for rotating the plane defined by a pair of parallel light beams. In one embodiment a single pair of rhomboid prisms have their respective input faces disposed to receive the respective input beams. Each prism is rotated about an axis of revolution coaxial with each of the respective input beams by means of a suitable motor and gear arrangement to cause the plane of the parallel output beams to be rotated relative to the plane of the input beams. In a second embodiment, two pairs of rhomboid prisms are provided. In a first angular orientation of the output beams, the prisms merely decrease the lateral displacement of the output beams in order to keep in the same plane as the input beams. In a second angular orientation of the prisms, the input faces of the second pair of prisms are brought into coincidence with the input beams for rotating the plane of the output beams by a substantial angle such as 90 deg.

Angle-domain common-image gathers from anisotropic Gaussian beam migration and its application to anisotropy-induced imaging errors analysis

NASA Astrophysics Data System (ADS)

Han, Jianguang; Wang, Yun; Yu, Changqing; Chen, Peng

2017-02-01

An approach for extracting angle-domain common-image gathers (ADCIGs) from anisotropic Gaussian beam prestack depth migration (GB-PSDM) is presented in this paper. The propagation angle is calculated in the process of migration using the real-value traveltime information of Gaussian beam. Based on the above, we further investigate the effects of anisotropy on GB-PSDM, where the corresponding ADCIGs are extracted to assess the quality of migration images. The test results of the VTI syncline model and the TTI thrust sheet model show that anisotropic parameters ɛ, δ, and tilt angle 𝜃, have a great influence on the accuracy of the migrated image in anisotropic media, and ignoring any one of them will cause obvious imaging errors. The anisotropic GB-PSDM with the true anisotropic parameters can obtain more accurate seismic images of subsurface structures in anisotropic media.

Gyrator transform of generalized sine-Gaussian beams and conversion an edge-dislocation into a vortex

NASA Astrophysics Data System (ADS)

Zhu, Kaicheng; Tang, Huiqin; Tang, Ying; Xia, Hui

2014-12-01

We proposed a scheme that converts a sine-Gaussian beam with an edge dislocation into a dark hollow beam with a vortex. Based on the gyrator transform (GT) relation, the closed-form field distribution of generalized sine-Gaussian beams passing through a GT system is derived; the intensity distribution and the corresponding phase distribution associated with the transforming generalized sine-Gaussian beams are analyzed. According to the numerical method, the distributions are graphically demonstrated and found that, for appropriate beam parameters and the GT angle, dark hollow vortex beams with topological charge 1 can be achieved using sine-Gaussian beams carrying an edge dislocation. Moreover, the orbital angular momentum content of a GT sine-Gaussian beam is analyzed. It is proved that the GT retains the odd- or even-order spiral harmonics structures of generalized sine-Gaussian beams in the transform process. In particular, it is wholly possible to convert an edge dislocation embedded in sine-Gaussian beams into a vortex with GT. The study also reveals that to obtain a dark hollow beam making use of GT of cos-Gaussian beams is impossible.

SU-F-J-192: A Quick and Effective Method to Validate Patient’s Daily Setup and Geometry Changes Prior to Proton Treatment Delivery Based On Water Equivalent Thickness Projection Imaging (WETPI) for Head Neck Cancer (HNC) Patient

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

Liu, G; Qin, A; Zhang, J

Purpose: With the implementation of Cone-beam Computed-Tomography (CBCT) in proton treatment, we introduces a quick and effective tool to verify the patient’s daily setup and geometry changes based on the Water-Equivalent-Thickness Projection-Image(WETPI) from individual beam angle. Methods: A bilateral head neck cancer(HNC) patient previously treated via VMAT was used in this study. The patient received 35 daily CBCT during the whole treatment and there is no significant weight change. The CT numbers of daily CBCTs were corrected by mapping the CT numbers from simulation CT via Deformable Image Registration(DIR). IMPT plan was generated using 4-field IMPT robust optimization (3.5% rangemore » and 3mm setup uncertainties) with beam angle 60, 135, 300, 225 degree. WETPI within CTV through all beam directions were calculated. 3%/3mm gamma index(GI) were used to provide a quantitative comparison between initial sim-CT and mapped daily CBCT. To simulate an extreme case where human error is involved, a couch bar was manually inserted in front of beam angle 225 degree of one CBCT. WETPI was compared in this scenario. Results: The average of GI passing rate of this patient from different beam angles throughout the treatment course is 91.5 ± 8.6. In the cases with low passing rate, it was found that the difference between shoulder and neck angle as well as the head rest often causes major deviation. This indicates that the most challenge in treating HNC is the setup around neck area. In the extreme case where a couch bar is accidently inserted in the beam line, GI passing rate drops to 52 from 95. Conclusion: WETPI and quantitative gamma analysis give clinicians, therapists and physicists a quick feedback of the patient’s setup accuracy or geometry changes. The tool could effectively avoid some human errors. Furthermore, this tool could be used potentially as an initial signal to trigger plan adaptation.« less

Achromatic and uncoupled medical gantry

DOEpatents

Tsoupas, Nicholaos [Center Moriches, NY; Kayran, Dmitry [Rocky Point, NY; Litvinenko, Vladimir [Mt. Sinai, NY; MacKay, William W [Wading River, NY

2011-11-22

A medical gantry that focus the beam from the beginning of the gantry to the exit of the gantry independent of the rotation angle of the gantry by keeping the beam achromatic and uncoupled, thus, avoiding the use of collimators or rotators, or additional equipment to control the beam divergence, which may cause beam intensity loss or additional time in irradiation of the patient, or disadvantageously increase the overall gantry size inapplicable for the use in the medical treatment facility.

Phasing surface emitting diode laser outputs into a coherent laser beam

DOEpatents

Holzrichter, John F [Berkeley, CA

2006-10-10

A system for generating a powerful laser beam includes a first laser element and at least one additional laser element having a rear laser mirror, an output mirror that is 100% reflective at normal incidence and <5% reflective at an input beam angle, and laser material between the rear laser mirror and the output mirror. The system includes an injector, a reference laser beam source, an amplifier and phase conjugater, and a combiner.

Apparatus Translates Crossed-Laser-Beam Probe Volume

NASA Technical Reports Server (NTRS)

Herring, Gregory C.; South, Bruce W.; Exton, Reginald J.

1994-01-01

Optomechanical apparatus translates probe volume of crossed-beam laser velocimeter or similar instrument while maintaining optical alignment of beams. Measures velocity, pressure, and temperature of flowing gas at several locations. Repeated tedious realignments no longer necessary. Designed to accommodate stimulated-Raman-gain spectrometer for noninvasive measurement of local conditions in flowing gas in supersonic wind tunnel. Applicable to other techniques like coherent anti-Stokes Raman spectroscopy involving use of laser beams crossed at small angles (10 degrees or less).

Generation of virtual monochromatic CBCT from dual kV/MV beam projections

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

Li, Hao; Liu, Bo; Yin, Fang-Fang, E-mail: fangfang.yin@duke.edu

Purpose: To develop a novel on-board imaging technique which allows generation of virtual monochromatic (VM) cone-beam CT (CBCT) with a selected energy from combined kilovoltage (kV)/megavoltage (MV) beam projections. Methods: With the current orthogonal kV/MV imaging hardware equipped in modern linear accelerators, both MV projections (from gantry angle of 0°–100°) and kV projections (90°–200°) were acquired as gantry rotated a total of 110°. A selected range of overlap projections between 90° to 100° were then decomposed into two material projections using experimentally determined parameters from orthogonally stacked aluminum and acrylic step-wedges. Given attenuation coefficients of aluminum and acrylic at amore » predetermined energy, one set of VM projections could be synthesized from two corresponding sets of decomposed projections. Two linear functions were generated using projection information at overlap angles to convert kV and MV projections at nonoverlap angles to approximate VM projections for CBCT reconstruction. The contrast-to-noise ratios (CNRs) were calculated for different inserts in VM CBCTs of a CatPhan phantom with various selected energies and compared with those in kV and MV CBCTs. The effect of overlap projection number on CNR was evaluated. Additionally, the effect of beam orientation was studied by scanning the CatPhan sandwiched with two 5 cm solid-water phantoms on both lateral sides and an electronic density phantom with two metal bolt inserts. Results: Proper selection of VM energy [30 and 40 keV for low-density polyethylene (LDPE), polymethylpentene, 2 MeV for Delrin] provided comparable or even better CNR results as compared with kV or MV CBCT. An increased number of overlap kV and MV projection demonstrated only marginal improvements of CNR for different inserts (with the exception of LDPE) and therefore one projection overlap was found to be sufficient for the CatPhan study. It was also evident that the optimal CBCT image quality was achieved when MV beams penetrated through the heavy attenuation direction of the object. Conclusions: A novel technique was developed to generate VM CBCTs from kV/MV projections. This technique has the potential to improve CNR at selected VM energies and to suppress artifacts at appropriate beam orientations.« less

Generation of virtual monochromatic CBCT from dual kV/MV beam projections

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

Li, Hao; Liu, Bo; Yin, Fang-Fang, E-mail: fangfang.yin@duke.edu

2013-12-15

Purpose: To develop a novel on-board imaging technique which allows generation of virtual monochromatic (VM) cone-beam CT (CBCT) with a selected energy from combined kilovoltage (kV)/megavoltage (MV) beam projections. Methods: With the current orthogonal kV/MV imaging hardware equipped in modern linear accelerators, both MV projections (from gantry angle of 0°–100°) and kV projections (90°–200°) were acquired as gantry rotated a total of 110°. A selected range of overlap projections between 90° to 100° were then decomposed into two material projections using experimentally determined parameters from orthogonally stacked aluminum and acrylic step-wedges. Given attenuation coefficients of aluminum and acrylic at amore » predetermined energy, one set of VM projections could be synthesized from two corresponding sets of decomposed projections. Two linear functions were generated using projection information at overlap angles to convert kV and MV projections at nonoverlap angles to approximate VM projections for CBCT reconstruction. The contrast-to-noise ratios (CNRs) were calculated for different inserts in VM CBCTs of a CatPhan phantom with various selected energies and compared with those in kV and MV CBCTs. The effect of overlap projection number on CNR was evaluated. Additionally, the effect of beam orientation was studied by scanning the CatPhan sandwiched with two 5 cm solid-water phantoms on both lateral sides and an electronic density phantom with two metal bolt inserts. Results: Proper selection of VM energy [30 and 40 keV for low-density polyethylene (LDPE), polymethylpentene, 2 MeV for Delrin] provided comparable or even better CNR results as compared with kV or MV CBCT. An increased number of overlap kV and MV projection demonstrated only marginal improvements of CNR for different inserts (with the exception of LDPE) and therefore one projection overlap was found to be sufficient for the CatPhan study. It was also evident that the optimal CBCT image quality was achieved when MV beams penetrated through the heavy attenuation direction of the object. Conclusions: A novel technique was developed to generate VM CBCTs from kV/MV projections. This technique has the potential to improve CNR at selected VM energies and to suppress artifacts at appropriate beam orientations.« less

Comparable ultrasound measurements of ten anatomical specimens of infant hip joints by the methods of Graf and Terjesen.

PubMed

Falliner, A; Hahne, H J; Hedderich, J; Brossmann, J; Hassenpflug, J

2004-04-01

To define which sonographic section planes relative to the acetabular inlet plane will produce analyzable images with the methods of Graf and Terjesen. Anatomical specimens of infant hip joints were investigated in a water bath using the methods of Graf and Terjesen. Acetabular position was varied in defined increments with respect to the ultrasound beam. The alpha angles and the femoral head coverage (FHC) were measured. To obtain images analyzable by the two methods, the ultrasound beam had to intersect with the acetabular inlet plane at defined angles. The acetabular notch had to be anteriorly rotated from the ultrasound beam plane by at least 20 degrees. Beam entry within a 50 degrees sector posterior to the perpendicular on the inlet plane resulted in analyzable images. The stepwise multiple linear regression analysis showed that alpha angles and FHC were much affected by the coronal-plane transducer tilt. The fact that caudal tilts of the transducer are associated with reduced alpha angles and FHC values should be kept in mind in clinical ultrasound investigations. It is recommended that the transducer should be put on the greater trochanter perpendicular to the transverse axis of the body.

Model benchmarking and reference signals for angled-beam shear wave ultrasonic nondestructive evaluation (NDE) inspections

NASA Astrophysics Data System (ADS)

Aldrin, John C.; Hopkins, Deborah; Datuin, Marvin; Warchol, Mark; Warchol, Lyudmila; Forsyth, David S.; Buynak, Charlie; Lindgren, Eric A.

2017-02-01

For model benchmark studies, the accuracy of the model is typically evaluated based on the change in response relative to a selected reference signal. The use of a side drilled hole (SDH) in a plate was investigated as a reference signal for angled beam shear wave inspection for aircraft structure inspections of fastener sites. Systematic studies were performed with varying SDH depth and size, and varying the ultrasonic probe frequency, focal depth, and probe height. Increased error was observed with the simulation of angled shear wave beams in the near-field. Even more significant, asymmetry in real probes and the inherent sensitivity of signals in the near-field to subtle test conditions were found to provide a greater challenge with achieving model agreement. To achieve quality model benchmark results for this problem, it is critical to carefully align the probe with the part geometry, to verify symmetry in probe response, and ideally avoid using reference signals from the near-field response. Suggested reference signals for angled beam shear wave inspections include using the `through hole' corner specular reflection signal and the full skip' signal off of the far wall from the side drilled hole.

SU-E-T-191: Commissioning and Dosimetric Characteristics of Elekta Agility for Total Skin Electron Beam (TSEB) Therapy

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

Sayler, E; Charpentier, P; Micaily, B

2015-06-15

Purpose The purpose of this work is to publish beam data from Elekta Synergy(R) linear accelerators with Agility(TM) MLC for total skin electron beam (TSEB) therapy using the HDRE1 (High Dose Rate Electron 6MeV) energy. Method & Materials The optimal gantry angles for TSEB were determined using ion chamber measurements along a vertical profile at 450cm SSD. After gantry angles were chosen, field uniformity was measured over the entire treatment area. Uniformity was measured with and without the patient support device, allowing the dosimetric effect of the support device to be determined. Beam output and PDD were measured at themore » calibration point (450cm SSD) for a dual beam using a parallel plate chamber in solid water. These measurements were repeated with the chamber and phantom rotated about the patient isocenter at various angles, in order to measure the contribution from oblique beams. This technique provides a precise measurement of the treatment skin dose (TSD). Lastly, ion chamber measurements were verified by film and diodes. Results The optimal gantry angle for 450 cm SSD was determined to be 90±16°. This achieved uniformity better than 96% on the vertical axis, and 92% along the horizontal axis. HDRE1 was calibrated to deliver 10 cGy/MU at standard geometry (100 cm SSD, 1.2 cm depth). Thus at TSEB geometry (450 cm SSD, 0.1 cm depth) the output of the AP dual field was measured to be 0.35 cGy/MU. The TSD of a 20 cm radius cylinder for six (equally, 60° spaced) dual fields was measured to be 1.19 cGy/MU. Percent Depth Dose data for the AP dual field and TSD are shown in Figure 2. Conclusion This paper provides a modern procedure for commissioning TSEB therapy on a linear accelerator, and clinical beam data for the Elekta Synergy(R) with Agility(TM) MLC.« less

Radial Distribution of Absorption in a Cesium Heat Pipe with Axial Laser Heating

DTIC Science & Technology

2011-03-01

The spring is used to maintain a clear circular path through the heat pipe and secure the mesh. Two copper crush gaskets attach the Brewster angled ...necessary. The pump beam is assumed to be a Gaussian beam and has been focused through a convex lens to position the beam waist at the center of

Terahertz radiation generation by beating of two laser beams in a collisional plasma with oblique magnetic field

NASA Astrophysics Data System (ADS)

Hematizadeh, Ayoob; Jazayeri, Seyed Masud; Ghafary, Bijan

2018-02-01

A scheme for excitation of terahertz (THz) radiation is presented by photo mixing of two super-Gaussian laser beams in a rippled density collisional magnetized plasma. Lasers having different frequencies and wave numbers but the same electric fields create a ponderomotive force on the electrons of plasma in the beating frequency. Super-Gaussian laser beam has the exclusive features such as steep gradient in laser intensity distribution, wider cross-section in comparison with Gaussian profiles, which make stronger ponderomotive force and higher THz radiation. The magnetic field is considered oblique to laser beams propagation direction; in this case, depending on the phase matching conditions different mode waves can propagate in plasma. It is found that amplitude and efficiency of the emitted THz radiation not only are sensitive to the beating frequency, collision frequency, and magnetic field strength but to the angle between laser beams and static magnetic field. The efficiency of THz radiation can be optimized in a certain angle.

A study for the installation of the TEXT heavy-ion beam probe on DIII-D

NASA Astrophysics Data System (ADS)

Edmonds, P. H.; Solano, E. R.; Bravenec, R. V.; Wootton, A. J.; Schoch, P. M.; Crowley, T. P.; Hickok, R. L.; West, W. P.; Leuer, J.; Anderson, P.

1997-01-01

An assessment of the feasibility of installing the TEXT 2 MeV heavy-ion beam probe on the DIII-D tokamak has been completed. Detailed drawings of the machine cross section were imported into the CAD application AutoCAD. A set of programs written in AutoLisp were used to generate trajectories. Displays of the accessible cross section of the plasma, scan lines for the entire range of primary beam energy and injection angle ranges, and sample-volume dimensions can be rapidly generated. Because of the large deflection between the primary input beam and the emergent secondary beam, either the analyzer needs to be tracked over a ±20° angle or secondary poloidal deflector plates need to be installed at the exit port. Toroidal deflector plates will be installed at both the injection and exit ports to compensate for toroidal displacements and deflections. The sample volumes generated by this procedure are within a few centimeters of the locations derived from a full three-dimensional calculation.

Extreme-UV lithography condenser

DOEpatents

Sweatt, William C.; Sweeney, Donald W.; Shafer, David; McGuire, James

2001-01-01

Condenser system for use with a ringfield camera in projection lithography where the condenser includes a series of segments of a parent aspheric mirror having one foci at a quasi-point source of radiation and the other foci at the radius of a ringfield have all but one or all of their beams translated and rotated by sets of mirrors such that all of the beams pass through the real entrance pupil of a ringfield camera about one of the beams and fall onto the ringfield radius as a coincident image as an arc of the ringfield. The condenser has a set of correcting mirrors with one of the correcting mirrors of each set, or a mirror that is common to said sets of mirrors, from which the radiation emanates, is a concave mirror that is positioned to shape a beam segment having a chord angle of about 25 to 85 degrees into a second beam segment having a chord angle of about 0 to 60 degrees.

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.

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

Jones, A. Kyle, E-mail: kyle.jones@mdanderson.org

Purpose: To evaluate the sensitivity of the diagnostic radiological index of protection (DRIP), used to quantify the protective value of radioprotective garments, to procedural factors in fluoroscopy in an effort to determine an appropriate set of scatter-mimicking primary beams to be used in measuring the DRIP. Methods: Monte Carlo simulations were performed to determine the shape of the scattered x-ray spectra incident on the operator in different clinical fluoroscopy scenarios, including interventional radiology and interventional cardiology (IC). Two clinical simulations studied the sensitivity of the scattered spectrum to gantry angle and patient size, while technical factors were varied according tomore » measured automatic dose rate control (ADRC) data. Factorial simulations studied the sensitivity of the scattered spectrum to gantry angle, field of view, patient size, and beam quality for constant technical factors. Average energy (E{sub avg}) was the figure of merit used to condense fluence in each energy bin to a single numerical index. Results: Beam quality had the strongest influence on the scattered spectrum in fluoroscopy. Many procedural factors affect the scattered spectrum indirectly through their effect on primary beam quality through ADRC, e.g., gantry angle and patient size. Lateral C-arm rotation, common in IC, increased the energy of the scattered spectrum, regardless of the direction of rotation. The effect of patient size on scattered radiation depended on ADRC characteristics, patient size, and procedure type. Conclusions: The scattered spectrum striking the operator in fluoroscopy is most strongly influenced by primary beam quality, particularly kV. Use cases for protective garments should be classified by typical procedural primary beam qualities, which are governed by the ADRC according to the impacts of patient size, anatomical location, and gantry angle.« less

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

Jones, A; Pasciak, A; Wagner, L

Purpose: To evaluate the sensitivity of the Diagnostic Radiological Index of Protection (DRIP) to procedural factors in fluoroscopy in an effort to determine an appropriate set of scatter-mimicking primary beams (SMPB) to be used in measuring the DRIP. Methods: A series of clinical and factorial Monte Carlo simulations were conducted to determine the shape of the scattered X-ray spectra incident on the operator in different clinical fluoroscopy scenarios. Two clinical evaluations studied the sensitivity of the scattered spectrum to gantry angle and patient size while technical factors were varied according to measured automatic dose rate control (ADRC) data. Factorial evaluationsmore » studied the sensitivity of the scattered spectrum to gantry angle, field of view, patient size and beam quality for constant technical factors. Average energy was the figure of merit used to condense fluence in each energy bin to a single numerical index. Results: Beam quality had the strongest influence on the scattered spectrum in fluoroscopy. Many procedural factors affected the scattered spectrum indirectly through their effects on primary beam quality through ADRC, e.g., gantry angle and patient size. Lateral C-arm rotation, common in interventional cardiology, increased the energy of the scattered spectrum, regardless of the direction of rotation. The effect of patient size on scattered radiation depended on ADRC characteristics, patient size, and procedure type. Conclusion: The scattered spectrum striking the operator in fluoroscopy, and therefore the DRIP, is most strongly influenced by primary beam quality, particularly kV. Use cases for protective garments should be classified by typical procedural primary beam qualities, which are governed by the ADRC according to the impacts of patient size, anatomical location, and gantry angle. These results will help determine an appropriate set of SMPB to be used for measuring the DRIP.« less

Sensitivity of the diagnostic radiological index of protection to procedural factors in fluoroscopy.

PubMed

Jones, A Kyle; Pasciak, Alexander S; Wagner, Louis K

2016-07-01

To evaluate the sensitivity of the diagnostic radiological index of protection (DRIP), used to quantify the protective value of radioprotective garments, to procedural factors in fluoroscopy in an effort to determine an appropriate set of scatter-mimicking primary beams to be used in measuring the DRIP. Monte Carlo simulations were performed to determine the shape of the scattered x-ray spectra incident on the operator in different clinical fluoroscopy scenarios, including interventional radiology and interventional cardiology (IC). Two clinical simulations studied the sensitivity of the scattered spectrum to gantry angle and patient size, while technical factors were varied according to measured automatic dose rate control (ADRC) data. Factorial simulations studied the sensitivity of the scattered spectrum to gantry angle, field of view, patient size, and beam quality for constant technical factors. Average energy (Eavg) was the figure of merit used to condense fluence in each energy bin to a single numerical index. Beam quality had the strongest influence on the scattered spectrum in fluoroscopy. Many procedural factors affect the scattered spectrum indirectly through their effect on primary beam quality through ADRC, e.g., gantry angle and patient size. Lateral C-arm rotation, common in IC, increased the energy of the scattered spectrum, regardless of the direction of rotation. The effect of patient size on scattered radiation depended on ADRC characteristics, patient size, and procedure type. The scattered spectrum striking the operator in fluoroscopy is most strongly influenced by primary beam quality, particularly kV. Use cases for protective garments should be classified by typical procedural primary beam qualities, which are governed by the ADRC according to the impacts of patient size, anatomical location, and gantry angle.

Numerical simulations of novel high-power high-brightness diode laser structures

NASA Astrophysics Data System (ADS)

Boucke, Konstantin; Rogg, Joseph; Kelemen, Marc T.; Poprawe, Reinhart; Weimann, Guenter

2001-07-01

One of the key topics in today's semiconductor laser development activities is to increase the brightness of high-power diode lasers. Although structures showing an increased brightness have been developed specific draw-backs of these structures lead to a still strong demand for investigation of alternative concepts. Especially for the investigation of basically novel structures easy-to-use and fast simulation tools are essential to avoid unnecessary, cost and time consuming experiments. A diode laser simulation tool based on finite difference representations of the Helmholtz equation in 'wide-angle' approximation and the carrier diffusion equation has been developed. An optimized numerical algorithm leads to short execution times of a few seconds per resonator round-trip on a standard PC. After each round-trip characteristics like optical output power, beam profile and beam parameters are calculated. A graphical user interface allows online monitoring of the simulation results. The simulation tool is used to investigate a novel high-power, high-brightness diode laser structure, the so-called 'Z-Structure'. In this structure an increased brightness is achieved by reducing the divergency angle of the beam by angular filtering: The round trip path of the beam is two times folded using internal total reflection at surfaces defined by a small index step in the semiconductor material, forming a stretched 'Z'. The sharp decrease of the reflectivity for angles of incidence above the angle of total reflection leads to a narrowing of the angular spectrum of the beam. The simulations of the 'Z-Structure' indicate an increase of the beam quality by a factor of five to ten compared to standard broad-area lasers.

First light for GRAVITY: Phase referencing optical interferometry for the Very Large Telescope Interferometer

NASA Astrophysics Data System (ADS)

Gravity Collaboration; Abuter, R.; Accardo, M.; Amorim, A.; Anugu, N.; Ávila, G.; Azouaoui, N.; Benisty, M.; Berger, J. P.; Blind, N.; Bonnet, H.; Bourget, P.; Brandner, W.; Brast, R.; Buron, A.; Burtscher, L.; Cassaing, F.; Chapron, F.; Choquet, É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; de Wit, W.; de Zeeuw, P. T.; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; Dexter, J.; Duvert, G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Fédou, P.; Finger, G.; Garcia, P.; Garcia Dabo, C. E.; Garcia Lopez, R.; Gendron, E.; Genzel, R.; Gillessen, S.; Gonte, F.; Gordo, P.; Grould, M.; Grözinger, U.; Guieu, S.; Haguenauer, P.; Hans, O.; Haubois, X.; Haug, M.; Haussmann, F.; Henning, Th.; Hippler, S.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.; Jakob, G.; Janssen, A.; Jochum, L.; Jocou, L.; Kaufer, A.; Kellner, S.; Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Klein, R.; Kok, Y.; Kolb, J.; Kulas, M.; Lacour, S.; Lapeyrère, V.; Lazareff, B.; Le Bouquin, J.-B.; Lèna, P.; Lenzen, R.; Lévêque, S.; Lippa, M.; Magnard, Y.; Mehrgan, L.; Mellein, M.; Mérand, A.; Moreno-Ventas, J.; Moulin, T.; Müller, E.; Müller, F.; Neumann, U.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.; Pflüger, A.; Pfuhl, O.; Phan Duc, T.; Plewa, P. M.; Popovic, D.; Rabien, S.; Ramírez, A.; Ramos, J.; Rau, C.; Riquelme, M.; Rohloff, R.-R.; Rousset, G.; Sanchez-Bermudez, J.; Scheithauer, S.; Schöller, M.; Schuhler, N.; Spyromilio, J.; Straubmeier, C.; Sturm, E.; Suarez, M.; Tristram, K. R. W.; Ventura, N.; Vincent, F.; Waisberg, I.; Wank, I.; Weber, J.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yazici, S.; Ziegler, D.; Zins, G.

2017-06-01

GRAVITY is a new instrument to coherently combine the light of the European Southern Observatory Very Large Telescope Interferometer to form a telescope with an equivalent 130 m diameter angular resolution and a collecting area of 200 m2. The instrument comprises fiber fed integrated optics beam combination, high resolution spectroscopy, built-in beam analysis and control, near-infrared wavefront sensing, phase-tracking, dual-beam operation, and laser metrology. GRAVITY opens up to optical/infrared interferometry the techniques of phase referenced imaging and narrow angle astrometry, in many aspects following the concepts of radio interferometry. This article gives an overview of GRAVITY and reports on the performance and the first astronomical observations during commissioning in 2015/16. We demonstrate phase-tracking on stars as faint as mK ≈ 10 mag, phase-referenced interferometry of objects fainter than mK ≈ 15 mag with a limiting magnitude of mK ≈ 17 mag, minute long coherent integrations, a visibility accuracy of better than 0.25%, and spectro-differential phase and closure phase accuracy better than 0.5°, corresponding to a differential astrometric precision of better than ten microarcseconds (μas). The dual-beam astrometry, measuring the phase difference of two objects with laser metrology, is still under commissioning. First observations show residuals as low as 50 μas when following objects over several months. We illustrate the instrument performance with the observations of archetypical objects for the different instrument modes. Examples include the Galactic center supermassive black hole and its fast orbiting star S2 for phase referenced dual-beam observations and infrared wavefront sensing, the high mass X-ray binary BP Cru and the active galactic nucleus of PDS 456 for a few μas spectro-differential astrometry, the T Tauri star S CrA for a spectro-differential visibility analysis, ξ Tel and 24 Cap for high accuracy visibility observations, and η Car for interferometric imaging with GRAVITY.

SU-F-T-207: Does the Greater Flexibility of Pencil Beam Scanning Reduce the Need for a Proton Gantry?

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

Yan, S; Depauw, N; Flanz, J

2016-06-15

Purpose: Gantry-less proton treatment facility could lower the capital cost of proton therapy. This study investigates the dosimetric feasibility of using only coplanar pencil beam scanning (PBS) beams for those patients who had beam angles that would not have been deliverable without the gantry. Those coplanar beams are implemented on gantry-less horizontal beam-line with patients in sitting or standing positions. Methods: We have selected ten patients (seven head-and-neck, one thoracic, one abdominal and one pelvic case) with clinically delivered double scattering (DS) or PBS treatment plans with beam angles that were challenging to achieve without a gantry. After removing thesemore » beams angles, PBS plans were optimized for gantry-less intensity modulated proton therapy (IMPT) or single field optimization (SFO) with multi-criteria optimization (MCO). For head-and-neck patients who were treated by DS, we generated PBS plans with non-coplanar beams for comparison. Dose-volume-histograms (DVHs), target homogeneity index (HI), mean dose, D-2 and D-98 were reported. Robustness analysis was performed with ±2.5 mm setup errors and ±3.5% range uncertainties for three head-and-neck patients. Results: PBS-gantry-less plans provided more homogenous target coverage and significant improvements on organs-at-risk (OARs) sparing, compared to passive scattering treatments with a gantry. The PBS gantry-less treatments reduced the HI for target coverage by 1.3% to 47.2%, except for a suprasellar patient and a liver patient. The PBS-gantry-less plans reduced the D-mean of OARs by 3.6% to 67.4%. The PBS-gantry plans had similar target coverage and only marginal improvements on OAR sparing as compared to the PBS-gantry-less plans. These two PBS plans also had similar robustness relative to range uncertainties and setup errors. Conclusion: The gantry-less plans have with less mean dose to OARs and more homogeneous target coverage. Although the PBS-gantry plans have slightly improved target coverage and OARs sparing, the overall benefit of having a gantry to provide non-coplanar beams is debatable.« less

Beam and tissue factors affecting Cherenkov image intensity for quantitative entrance and exit dosimetry on human tissue

PubMed Central

Zhang, Rongxiao; Glaser, Adam K.; Andreozzi, Jacqueline; Jiang, Shudong; Jarvis, Lesley A.; Gladstone, David J.; Pogue, Brian W.

2017-01-01

This study’s goal was to determine how Cherenkov radiation emission observed in radiotherapy is affected by predictable factors expected in patient imaging. Factors such as tissue optical properties, radiation beam properties, thickness of tissues, entrance/exit geometry, curved surface effects, curvature and imaging angles were investigated through Monte Carlo simulations. The largest physical cause of variation of the correlation factor between of Cherenkov emission and dose was the entrance/exit geometry (~50%). The largest human tissue effect was from different optical properties (~45%). Beyond these, clinical beam energy varies the correlation factor significantly (~20% for x-ray beams), followed by curved surfaces (~15% for x-ray beams and ~8% for electron beams), and finally, the effect of field size (~5% for x-ray beams). Other investigated factors which caused variations less than 5% were tissue thicknesses and source to surface distance. The effect of non-Lambertian emission was negligible for imaging angles smaller than 60 degrees. The spectrum of Cherenkov emission tends to blue-shift along the curved surface. A simple normalization approach based on the reflectance image was experimentally validated by imaging a range of tissue phantoms, as a first order correction for different tissue optical properties. PMID:27507213

SEPTUM MAGNET DESIGN FOR THE APS-U

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

Abliz, M.; Jaski, M.; Xiao, A.

2017-06-25

The Advanced Photon Source is in the process of upgrading its storage ring from a double-bend to a multi-bend lattice as part of the APS Upgrade Project (APS-U). A swap-out injection scheme is planned for the APS-U to keep a constant beam current and to enable a small dynamic aperture. A septum magnet with a minimum thickness of 2 mm and an injection field of 1.06 T has been designed, delivering the required total deflecting angle is 89 mrad with a ring energy of 6 GeV. The stored beam chamber has an 8 mm x 6 mm super-ellipsoidal aperture. Themore » magnet is straight; however, it is tilted in yaw, roll, and pitch from the stored beam chamber to meet the on axis swap out injection requirements for the APS-U lattice. In order to minimize the leakage field inside the stored beam chamber, four different techniques were utilized in the design. As a result, the horizontal deflecting angle of the stored beam was held to only 5 µrad, and the integrated skew quadrupole inside the stored beam chamber was held to 0.09 T. The detailed techniques that were applied to the design, field multipoles, and resulting trajectories of the injected and stored beams are reported.« less

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

Accelerated x-ray scatter projection imaging using multiple continuously moving pencil beams

NASA Astrophysics Data System (ADS)

Dydula, Christopher; Belev, George; Johns, Paul C.

2017-03-01

Coherent x-ray scatter varies with angle and photon energy in a manner dependent on the chemical composition of the scattering material, even for amorphous materials. Therefore, images generated from scattered photons can have much higher contrast than conventional projection radiographs. We are developing a scatter projection imaging prototype at the BioMedical Imaging and Therapy (BMIT) facility of the Canadian Light Source (CLS) synchrotron in Saskatoon, Canada. The best images are obtained using step-and-shoot scanning with a single pencil beam and area detector to capture sequentially the scatter pattern for each primary beam location on the sample. Primary x-ray transmission is recorded simultaneously using photodiodes. The technological challenge is to acquire the scatter data in a reasonable time. Using multiple pencil beams producing partially-overlapping scatter patterns reduces acquisition time but increases complexity due to the need for a disentangling algorithm to extract the data. Continuous sample motion, rather than step-and-shoot, also reduces acquisition time at the expense of introducing motion blur. With a five-beam (33.2 keV, 3.5 mm2 beam area) continuous sample motion configuration, a rectangular array of 12 x 100 pixels with 1 mm sampling width has been acquired in 0.4 minutes (3000 pixels per minute). The acquisition speed is 38 times the speed for single beam step-and-shoot. A system model has been developed to calculate detected scatter patterns given the material composition of the object to be imaged. Our prototype development, image acquisition of a plastic phantom and modelling are described.

Free-space transmission with passive 2D beam steering for multi-gigabit-per-second per-beam indoor optical wireless networks.

PubMed

Oh, Chin Wan; Cao, Zizheng; Tangdiongga, Eduward; Koonen, Ton

2016-08-22

In order to circumvent radio spectrum congestion, we propose an innovative system which can provide multiple infrared optical wireless beams simultaneously where each beam supports multi-gigabit-per-second communication. Scalable two-dimensional beam steering by means of wavelength tuning is proposed. A passive beam-steering module constructed with cascaded reflection gratings is designed for simultaneous multi-user coverage. We experimentally characterized the beam-steered system and thoroughly evaluated the performance of steered channels using the spectrally efficient and robust discrete multitone modulation in a bandwidth-limited system deploying 10 GHz telecom transceivers. This study reports the achievement of at least 37 Gbps free-space transmission per beam over a distance of up to 2 m over 5.61° × 12.66° scanning angles.

Design and characteristic analysis of shaping optics for optical trepanning

NASA Astrophysics Data System (ADS)

Zeng, D.; Latham, W. P.; Kar, A.

2005-08-01

Optical trepanning is a new laser drilling method using an annular beam. The annular beams allow numerous irradiance profiles to supply laser energy to the workpiece and thus provide more flexibility in affecting the hole quality than a traditional circular laser beam. The refractive axicon system has been designed to generating a collimated annular beam. In this article, calculations of intensity distributions produced by this refractive system are made by evaluating the Kirchhoff-Fresnel diffraction. It is shown that the refractive system is able to transform a Gaussian beam into a full Gaussian annular beam. The base angle of the axicon lens, input laser beam diameter and intensity profiles are found to be important factors for the axcion refractive system. Their effects on the annular beam profiles are analyzed based on the numerical solutions of the diffraction patterns.

Laser-phased-array beam steering based on crystal fiber

NASA Astrophysics Data System (ADS)

Yang, Deng-cai; Zhao, Si-si; Wang, Da-yong; Wang, Zhi-yong; Zhang, Xiao-fei

2011-06-01

Laser-phased-array system provides an elegant means for achieving the inertial-free, high-resolution, rapid and random beam steering. In laser-phased-array system, phase controlling is the most important factor that impacts the system performance. A novel scheme is provided in this paper, the beam steering is accomplished by using crystal fiber array, the difference length between adjacent fiber is fixed. The phase difference between adjacent fiber decides the direction of the output beam. When the wavelength of the input fiber laser is tuned, the phase difference between the adjacent elements has changed. Therefore, the laser beam direction has changed and the beam steering has been accomplished. In this article, based on the proposed scheme, the steering angle of the laser beam is calculated and analyzed theoretically. Moreover, the far-field steering beam quality is discussed.

Design of a Paraxial Inverse Compton Scattering Diagnostic for an Intense Relativistic Electron Beam

DTIC Science & Technology

2013-06-01

with a 50 cm focal length plano-convex lens (Fig. 4). Prior to entering the vacuum the laser light passes through a Brewster angled window, which...1/γ ~ 25 mrad. Brewster angled windows Beam dump Spectra Physics 5J Nd:YAG Focusing lens Insertable power meter z x y 37.8 cm Figure 4...visible green light is upscattered into the soft X-ray range and diverges from the interception point downstream at an angle θs = 1/γ ~ 25 mrad

Post-Newtonian equations of motion for LEO debris objects and space-based acquisition, pointing and tracking laser systems

NASA Astrophysics Data System (ADS)

Gambi, J. M.; García del Pino, M. L.; Gschwindl, J.; Weinmüller, E. B.

2017-12-01

This paper deals with the problem of throwing middle-sized low Earth orbit debris objects into the atmosphere via laser ablation. The post-Newtonian equations here provided allow (hypothetical) space-based acquisition, pointing and tracking systems endowed with very narrow laser beams to reach the pointing accuracy presently prescribed. In fact, whatever the orbital elements of these objects may be, these equations will allow the operators to account for the corrections needed to balance the deviations of the line of sight directions due to the curvature of the paths the laser beams are to travel along. To minimize the respective corrections, the systems will have to perform initial positioning manoeuvres, and the shooting point-ahead angles will have to be adapted in real time. The enclosed numerical experiments suggest that neglecting these measures will cause fatal errors, due to differences in the actual locations of the objects comparable to their size.

Differential correction system of laser beam directional dithering based on symmetrical beamsplitter

NASA Astrophysics Data System (ADS)

Hongwei, Yang; Wei, Tao; Xiaoqia, Yin; Hui, Zhao

2018-02-01

This paper proposes a differential correction system with a differential optical path and a symmetrical beamsplitter for correcting the directional dithering of the laser beams. This system can split a collimated laser beam into two laser beams with equal and opposite movements. Thus, the positional averages of the two split laser beams remain constant irrespective of the dithering angle. The symmetrical beamsplitter designed based on transfer matrix principle is to balance the optical paths and irradiances of the two laser beams. Experimental results show that the directional dithering is reduced to less than one-pixel value. Finally, two examples show that this system can be widely used in one-dimensional measurement.

Even illumination in total internal reflection fluorescence microscopy using laser light.

PubMed

Fiolka, R; Belyaev, Y; Ewers, H; Stemmer, A

2008-01-01

In modern fluorescence microscopy, lasers are a widely used source of light, both for imaging in total internal reflection and epi-illumination modes. In wide-field imaging, scattering of highly coherent laser light due to imperfections in the light path typically leads to nonuniform illumination of the specimen, compromising image analysis. We report the design and construction of an objective-launch total internal reflection fluorescence microscopy system with excellent evenness of specimen illumination achieved by azimuthal rotation of the incoming illuminating laser beam. The system allows quick and precise changes of the incidence angle of the laser beam and thus can also be used in an epifluorescence mode. 2007 Wiley-Liss, Inc

Variable Distance Angular Symbology Reader

NASA Technical Reports Server (NTRS)

Schramm, Harry F., Jr. (Inventor); Corder, Eric L. (Inventor)

2006-01-01

A variable distance angular symbology, reader utilizes at least one light source to direct light through a beam splitter and onto a target. A target may be angled relative to the impinging light beam up to and maybe even greater than 45deg. A reflected beam from the target passes through the beam splitter and is preferably directed 90deg relative to the light source through a telecentric lens to a scanner which records an image of the target such as a direct part marking code.

Satellite Laser Ranging Photon-Budget Calculations for a Single Satellite Cornercube Retroreflector: Attitude Control Tolerance

DTIC Science & Technology

2015-11-01

beam splitter , and an arrangement of polarising prisms and waveplates to measure the diffraction pattern resulting from uni- form laser beams in...cornercube retroreflectors identified in the current satellite design are found to allow for a significant variation in the reflected beam width. The...Surface quality 60-40 Housing tolerance OD:† +0/− 0.5 mm H: ±0.25 mm Beam -angle tolerance 3 arcsec Substrate N-BK7 Coating Internal silver Figure 2: Design

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

A novel imaging technique for measuring kinematics of light-weight flexible structures.

PubMed

Zakaria, Mohamed Y; Eliethy, Ahmed S; Canfield, Robert A; Hajj, Muhammad R

2016-07-01

A new imaging algorithm is proposed to capture the kinematics of flexible, thin, light structures including frequencies and motion amplitudes for real time analysis. The studied case is a thin flexible beam that is preset at different angles of attack in a wind tunnel. As the angle of attack is increased beyond a critical value, the beam was observed to undergo a static deflection that is ensued by limit cycle oscillations. Imaging analysis of the beam vibrations shows that the motion consists of a superposition of the bending and torsion modes. The proposed algorithm was able to capture the oscillation amplitudes as well as the frequencies of both bending and torsion modes. The analysis results are validated through comparison with measurements from a piezoelectric sensor that is attached to the beam at its root.

Design of laser afocal zoom expander system

NASA Astrophysics Data System (ADS)

Jiang, Lian; Zeng, Chun-Mei; Hu, Tian-Tian

2018-01-01

Laser afocal zoom expander system due to the beam diameter variable, can be used in the light sheet illumination microscope to observe the samples of different sizes. Based on the principle of afocal zoom system, the laser collimation and beam expander system with a total length of less than 110mm, 6 pieces of spherical lens and a beam expander ratio of 10 is designed by using Zemax software. The system is focused on laser with a wavelength of 532nm, divergence angle of less than 4mrad and incident diameter of 4mm. With the combination of 6 spherical lens, the beam divergence angle is 0.4mrad at the maximum magnification ratio, and the RMS values at different rates are less than λ/4. This design is simple in structure and easy to process and adjust. It has certain practical value.

A novel imaging technique for measuring kinematics of light-weight flexible structures

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

Zakaria, Mohamed Y., E-mail: zakaria@vt.edu; Eliethy, Ahmed S.; Canfield, Robert A.

2016-07-15

A new imaging algorithm is proposed to capture the kinematics of flexible, thin, light structures including frequencies and motion amplitudes for real time analysis. The studied case is a thin flexible beam that is preset at different angles of attack in a wind tunnel. As the angle of attack is increased beyond a critical value, the beam was observed to undergo a static deflection that is ensued by limit cycle oscillations. Imaging analysis of the beam vibrations shows that the motion consists of a superposition of the bending and torsion modes. The proposed algorithm was able to capture the oscillationmore » amplitudes as well as the frequencies of both bending and torsion modes. The analysis results are validated through comparison with measurements from a piezoelectric sensor that is attached to the beam at its root.« less

Development of acousto-optic spatial light modulator unit for effective control of light beam intensity and diffraction angle in 3D holographic display applications

NASA Astrophysics Data System (ADS)

Kondalkar, Vijay V.; Ryu, Geonhee; Lee, Yongbeom; Lee, Keekeun

2018-07-01

An acousto-optic (AO) based holographic display unit was developed using surface acoustic wave (SAW) with different wavelength to modulate the diffraction angles, intensities, and phases of light. The new configurations were employed to control two beams simultaneously by using a single chirp inter-digital transducer (IDT), and a micro-lens array was integrated at the end of the waveguide layer to focus the diffracted light on to the screen. Two incident light beams were simultaneously modulated by using different refractive grating periods generated from chirp IDT. A diffraction angle of about 5° was obtained by using a SAW with a frequency of 430 MHz. The increase in the SAW input power enhances the diffraction efficiency of the light beam at the exit. The obtained maximum diffraction efficiency is ~70% at a frequency of 430 MHz. The sloped shape of the waveguide entrance and a tall rounded Ni poles help in coupling the incident light to the waveguide layer. The diffracted beam was collected through the lens, which increased the intensity of light in the viewing plane. COMSOL multi-physics and coupling of mode (COM) modeling were performed to predict the device performance and compared with the experimental results.

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.

High-speed volume measurement system

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

Lane, Michael H.; Doyle, Jr., James L.; Brinkman, Michael J.

2018-01-30

Disclosed is a volume sensor having a first axis, a second axis, and a third axis, each axis including a laser source configured to emit a beam; a parallel beam generating assembly configured to receive the beam and split the beam into a first parallel beam and a second parallel beam, a beam-collimating assembly configured to receive the first parallel beam and the second parallel beam and output a first beam sheet and a second beam sheet, the first beam sheet and the second beam sheet being configured to traverse the object aperture; a first collecting lens and a secondmore » collecting lens; and a first photodetector and a second photodetector, the first photodetector and the second photodetector configured to output an electrical signal proportional to the object; wherein the first axis, the second axis, and the third axis are arranged at an angular offset with respect to each other.« less

Alternative irradiation schemes for NIF and LMJ hohlraums

NASA Astrophysics Data System (ADS)

Bourgade, Jean-Luc; Bowen, Christopher; Gauthier, Pascal; Landen, Otto

2018-02-01

We explore two alternative irradiation schemes for the large (‘outer’) and small (‘inner’) angle beams that currently illuminate National Ignition Facility (NIF) and Laser Mégajoule cavities. In the first, while the outer laser beams enter through the usual end laser entrance holes (LEH), the inner beams enter through slots along the cavity axis wall, illuminating the back wall of the cavity. This avoids the current interaction of the inner laser beams with the gold wall bubbles generated by the outer beams, which leads to large time-dependent changes in drive symmetry. Another scheme potentially useful for NIF uses only the outer beams. The radiative losses through the slots or from the use of outer beams only are compensated by using a smaller cavity and LEH.

Alternative irradiation schemes for NIF and LMJ hohlraums

DOE PAGES

Bourgade, Jean-Luc; Bowen, Christopher; Gauthier, Pascal; ...

2017-12-13

Here, we explore two alternative irradiation schemes for the large ('outer') and small ('inner') angle beams that currently illuminate National Ignition Facility (NIF) and Laser Mégajoule cavities. In the first, while the outer laser beams enter through the usual end laser entrance holes (LEH), the inner beams enter through slots along the cavity axis wall, illuminating the back wall of the cavity. This avoids the current interaction of the inner laser beams with the gold wall bubbles generated by the outer beams, which leads to large time-dependent changes in drive symmetry. Another scheme potentially useful for NIF uses only themore » outer beams. The radiative losses through the slots or from the use of outer beams only are compensated by using a smaller cavity and LEH.« less

Alternative irradiation schemes for NIF and LMJ hohlraums

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

Bourgade, Jean-Luc; Bowen, Christopher; Gauthier, Pascal

Here, we explore two alternative irradiation schemes for the large ('outer') and small ('inner') angle beams that currently illuminate National Ignition Facility (NIF) and Laser Mégajoule cavities. In the first, while the outer laser beams enter through the usual end laser entrance holes (LEH), the inner beams enter through slots along the cavity axis wall, illuminating the back wall of the cavity. This avoids the current interaction of the inner laser beams with the gold wall bubbles generated by the outer beams, which leads to large time-dependent changes in drive symmetry. Another scheme potentially useful for NIF uses only themore » outer beams. The radiative losses through the slots or from the use of outer beams only are compensated by using a smaller cavity and LEH.« less

Phase and birefringence aberration correction

DOEpatents

Bowers, Mark; Hankla, Allen

1996-01-01

A Brillouin enhanced four wave mixing phase conjugate mirror corrects phase aberrations of a coherent electromagnetic beam and birefringence induced upon that beam. The stimulated Brillouin scattering (SBS) phase conjugation technique is augmented to include Brillouin enhanced four wave mixing (BEFWM). A seed beam is generated by a main oscillator which arrives at the phase conjugate cell before the signal beams in order to initiate the Brillouin effect. The signal beam which is being amplified through the amplifier chain is split into two perpendicularly polarized beams. One of the two beams is chosen to be the same polarization as some component of the seed beam, the other orthogonal to the first. The polarization of the orthogonal beam is then rotated 90.degree. such that it is parallel to the other signal beam. The three beams are then focused into cell containing a medium capable of Brillouin excitation. The two signal beams are focused such that they cross the seed beam path before their respective beam waists in order to achieve BEFWM or the two signal beams are focused to a point or points contained within the focused cone angle of the seed beam to achieve seeded SBS, and thus negate the effects of all birefringent and material aberrations in the system.

Phase and birefringence aberration correction

DOEpatents

Bowers, M.; Hankla, A.

1996-07-09

A Brillouin enhanced four wave mixing phase conjugate mirror corrects phase aberrations of a coherent electromagnetic beam and birefringence induced upon that beam. The stimulated Brillouin scattering (SBS) phase conjugation technique is augmented to include Brillouin enhanced four wave mixing (BEFWM). A seed beam is generated by a main oscillator which arrives at the phase conjugate cell before the signal beams in order to initiate the Brillouin effect. The signal beam which is being amplified through the amplifier chain is split into two perpendicularly polarized beams. One of the two beams is chosen to be the same polarization as some component of the seed beam, the other orthogonal to the first. The polarization of the orthogonal beam is then rotated 90{degree} such that it is parallel to the other signal beam. The three beams are then focused into cell containing a medium capable of Brillouin excitation. The two signal beams are focused such that they cross the seed beam path before their respective beam waists in order to achieve BEFWM or the two signal beams are focused to a point or points contained within the focused cone angle of the seed beam to achieve seeded SBS, and thus negate the effects of all birefringent and material aberrations in the system. 5 figs.

An automatic alignment system for measuring optical path of transmissometer based on light beam scanning

NASA Astrophysics Data System (ADS)

Zhou, Shudao; Ma, Zhongliang; Wang, Min; Peng, Shuling

2018-05-01

This paper proposes a novel alignment system based on the measurement of optical path using a light beam scanning mode in a transmissometer. The system controls both the probe beam and the receiving field of view while scanning in two vertical directions. The system then calculates the azimuth angle of the transmitter and the receiver to determine the precise alignment of the optical path. Experiments show that this method can determine the alignment angles in less than 10 min with errors smaller than 66 μrad in the azimuth. This system also features high collimation precision, process automation and simple installation.

The role of service areas in the optimization of FSS orbital and frequency assignments

NASA Technical Reports Server (NTRS)

Levis, C. A.; Wang, C. W.; Yamamura, Y.; Reilly, C. H.; Gonsalvez, D. J.

1985-01-01

A relationship is derived, on a single-entry interference basis, for the minimum allowable spacing between two satellites as a function of electrical parameters and service-area geometries. For circular beams, universal curves relate the topocentric satellite spacing angle to the service-area separation angle measured at the satellite. The corresponding geocentric spacing depends only weakly on the mean longitude of the two satellites, and this is true also for alliptical antenna beams. As a consequence, if frequency channels are preassigned, the orbital assignment synthesis of a satellite system can be formulated as a mixed-integer programming (MIP) problem or approximated by a linear programming (LP) problem, with the interference protection requirements enforced by constraints while some linear function is optimized. Possible objective-function choices are discussed and explicit formulations are presented for the choice of the sum of the absolute deviations of the orbital locations from some prescribed ideal location set. A test problem is posed consisting of six service areas, each served by one satellite, all using elliptical antenna beams and the same frequency channels. Numerical results are given for the three ideal location prescriptions for both the MIP and LP formulations. The resulting scenarios also satisfy reasonable aggregate interference protection requirements.

Scanning electron microscopy of the trabecular meshwork: understanding the pathogenesis of primary angle closure glaucoma.

PubMed

Sihota, Ramanjit; Goyal, Amita; Kaur, Jasbir; Gupta, Viney; Nag, Tapas C

2012-01-01

To study ultrastructural changes of the trabecular meshwork in acute and chronic primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG) eyes by scanning electron microscopy. Twenty-one trabecular meshwork surgical specimens from consecutive glaucomatous eyes after a trabeculectomy and five postmortem corneoscleral specimens were fixed immediately in Karnovsky solution. The tissues were washed in 0.1 M phosphate buffer saline, post-fixed in 1% osmium tetraoxide, dehydrated in acetone series (30-100%), dried and mounted. Normal trabecular tissue showed well-defined, thin, cylindrical uveal trabecular beams with many large spaces, overlying flatter corneoscleral beams and numerous smaller spaces. In acute PACG eyes, the trabecular meshwork showed grossly swollen, irregular trabecular endothelial cells with intercellular and occasional basal separation with few spaces. Numerous activated macrophages, leucocytes and amorphous debris were present. Chronic PACG eyes had a few, thickened posterior uveal trabecular beams visible. A homogenous deposit covered the anterior uveal trabeculae and spaces. Converging, fan-shaped trabecular beam configuration corresponded to gonioscopic areas of peripheral anterior synechiae. In POAG eyes, anterior uveal trabecular beams were thin and strap-like, while those posteriorly were wide, with a homogenous deposit covering and bridging intertrabecular spaces, especially posteriorly. Underlying corneoscleral trabecular layers and spaces were visualized in some areas. In acute PACG a marked edema of the endothelium probably contributes for the acute and marked intraocular pressure (IOP) elevation. Chronically raised IOP in chronic PACG and POAG probably results, at least in part, from decreased aqueous outflow secondary to widening and fusion of adjacent trabecular beams, together with the homogenous deposit enmeshing trabecular beams and spaces.

Undersea Laser Communication with Narrow Beams

DTIC Science & Technology

2015-09-29

Abstract Laser sources enable highly efficient optical communications links due to their ability to be focused into very directive beam profiles...Recent atmospheric and space optical links have demonstrated robust laser communications links at high rate with techniques that are applicable to the...undersea environment. These techniques contrast to the broad-angle beams utilized in most reported demonstrations of undersea optical communications

Creating aperiodic photonic structures by synthesized Mathieu-Gauss beams

NASA Astrophysics Data System (ADS)

Vasiljević, Jadranka M.; Zannotti, Alessandro; Timotijević, Dejan V.; Denz, Cornelia; Savić, Dragana M. Jović

2017-08-01

We demonstrate a kind of aperiodic photonic structure realized using the interference of multiple Mathieu-Gauss beams. Depending on the beam configurations, their mutual distances, angles of rotation, or phase relations we are able to observe different classes of such aperiodic optically induced refractive index structures. Our experimental approach is based on the optical induction in a single parallel writing process.

Spin-exchange relaxation-free magnetometer with nearly parallel pump and probe beams

DOE PAGES

Karaulanov, Todor; Savukov, Igor; Kim, Young Jin

2016-03-22

We constructed a spin-exchange relaxation-free (SERF) magnetometer with a small angle between the pump and probe beams facilitating a multi-channel design with a flat pancake cell. This configuration provides almost complete overlap of the beams in the cell, and prevents the pump beam from entering the probe detection channel. By coupling the lasers in multi-mode fibers, without an optical isolator or field modulation, we demonstrate a sensitivity of 10 fTmore » $$/\\sqrt{\\text{Hz}}$$ for frequencies between 10 Hz and 100 Hz. In addition to the experimental study of sensitivity, we present a theoretical analysis of SERF magnetometer response to magnetic fields for small-angle and parallel-beam configurations, and show that at optimal DC offset fields the magnetometer response is comparable to that in the orthogonal-beam configuration. Based on the analysis, we also derive fundamental and probe-limited sensitivities for the arbitrary non-orthogonal geometry. The expected practical and fundamental sensitivities are of the same order as those in the orthogonal geometry. As a result, we anticipate that our design will be useful for magnetoencephalography (MEG) and magnetocardiography (MCG) applications.« less

High contrast laser beam collimation testing using two proximately placed holographic optical elements

NASA Astrophysics Data System (ADS)

Rajkumar; Dubey, Rajiv; Debnath, Sanjit K.; Chhachhia, D. P.

2018-05-01

Accuracy in laser beam collimation is very important in systems used for precision measurements. The present work reports a technique for collimation testing of laser beams using two proximately placed holographic optical elements (HOEs). The required HOEs are designed and fabricated such that upon illumination with the test beam, they release two laterally sheared wavefronts, at desired angles from the directly transmitted beam, that superimpose each other to generate straight interference fringes. Deviation from the collimation of the test beam results in orientation of these otherwise horizontal fringes. The novelty of this setup comes from the fact that HOEs are lightweight, as well as easy to fabricate as compared to conventional wedge plates used for collimation testing, and generate high contrast fringes compared to other interferometry, holography, Talbot and Moiré based techniques in a compact manner. The proposed technique is experimentally validated by measuring the orientation of fringes by an angle of 16.4° when a collimating lens of focal length 200 mm is defocused by 600 μm. The accuracy in the setting of this collimation position is obtained to be 10 μm.

Optical tractor Bessel polarized beams

NASA Astrophysics Data System (ADS)

Mitri, F. G.; Li, R. X.; Guo, L. X.; Ding, C. Y.

2017-01-01

Axial and transverse radiation force cross-sections of optical tractor Bessel polarized beams are theoretically investigated for a dielectric sphere with particular emphasis on the beam topological charge (or order), half-cone angle and polarization. The angular spectrum decomposition method (ASDM) is used to derive the non-paraxial electromagnetic (EM) field components of the Bessel beams. The multipole expansion method using vector spherical harmonics is utilized and appropriate beam-shape coefficients are derived in order to compute the radiation force cross-sections. The analysis has no limitation to a particular range of frequencies such that the Rayleigh, Mie or geometrical optics regimes can all be considered effectively using the present rigorous formalism. The focus of this investigation is to identify some of the tractor beam conditions so as to achieve retrograde motion of a dielectric sphere located arbitrarily in space. Numerical computations for the axial and transverse radiation force cross-sections are presented for linear, right-circular, radial, azimuthal and mixed polarizations of the individual plane waves forming the Bessel beams of zeroth- and first-order (with positive or negative helicity), respectively. As the sphere shifts off the beam's axis, the axial pulling (tractor) force is weakened. Moreover, the transverse radiation force cross-section field changes with the sphere's size factor ka (where k is the wavenumber and a is the sphere radius). Both stable and unstable equilibrium regions around the beam's axis are found, depending on the choice of ka and the half-cone angle α0. These results are particularly important in the development of emergent technologies for the photophoretic assembly of optically-engineered (meta)materials with designed properties using optical tractor (vortex) beams, particle manipulation, levitation and positioning, and other applications.

Control of Angular Intervals for Angle-Multiplexed Holographic Memory

NASA Astrophysics Data System (ADS)

Kinoshita, Nobuhiro; Muroi, Tetsuhiko; Ishii, Norihiko; Kamijo, Koji; Shimidzu, Naoki

2009-03-01

In angle-multiplexed holographic memory, the full width at half maximum of the Bragg selectivity curves is dependent on the angle formed between the medium and incident laser beams. This indicates the possibility of high density and high multiplexing number by varying the angular intervals between adjacent holograms. We propose an angular interval scheduling for closely stacking holograms into medium even when the angle range is limited. We obtained bit error rates of the order of 10-4 under the following conditions: medium thickness of 1 mm, laser beam wavelength of 532 nm, and angular multiplexing number of 300.

Optimization of pencil beam f-theta lens for high-accuracy metrology

NASA Astrophysics Data System (ADS)

Peng, Chuanqian; He, Yumei; Wang, Jie

2018-01-01

Pencil beam deflectometric profilers are common instruments for high-accuracy surface slope metrology of x-ray mirrors in synchrotron facilities. An f-theta optical system is a key optical component of the deflectometric profilers and is used to perform the linear angle-to-position conversion. Traditional optimization procedures of the f-theta systems are not directly related to the angle-to-position conversion relation and are performed with stops of large size and a fixed working distance, which means they may not be suitable for the design of f-theta systems working with a small-sized pencil beam within a working distance range for ultra-high-accuracy metrology. If an f-theta system is not well-designed, aberrations of the f-theta system will introduce many systematic errors into the measurement. A least-squares' fitting procedure was used to optimize the configuration parameters of an f-theta system. Simulations using ZEMAX software showed that the optimized f-theta system significantly suppressed the angle-to-position conversion errors caused by aberrations. Any pencil-beam f-theta optical system can be optimized with the help of this optimization method.

Electron Lenses for the Large Hadron Collider

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

Stancari, Giulio; Valishev, Alexander; Bruce, Roderik

Electron lenses are pulsed, magnetically confined electron beams whose current-density profile is shaped to obtain the desired effect on the circulating beam. Electron lenses were used in the Fermilab Tevatron collider for bunch-by-bunch compensation of long-range beam-beam tune shifts, for removal of uncaptured particles in the abort gap, for preliminary experiments on head-on beam-beam compensation, and for the demonstration of halo scraping with hollow electron beams. Electron lenses for beam-beam compensation are being commissioned in RHIC at BNL. Within the US LHC Accelerator Research Program and the European HiLumi LHC Design Study, hollow electron beam collimation was studied as anmore » option to complement the collimation system for the LHC upgrades. This project is moving towards a technical design in 2014, with the goal to build the devices in 2015-2017, after resuming LHC operations and re-assessing needs and requirements at 6.5 TeV. Because of their electric charge and the absence of materials close to the proton beam, electron lenses may also provide an alternative to wires for long-range beam-beam compensation in LHC luminosity upgrade scenarios with small crossing angles.« less

The X-beam as a deployable boom for the space station

NASA Technical Reports Server (NTRS)

Adams, Louis R.

1988-01-01

Extension of antennas and thrust modules from the primary structure of the space station will require deployable beams of high stiffness and strength, as well as low mass and package volume. A square boom cross section is desirable for interface reasons. These requirements and others are satisfied by the X-beam. The X-beam folds by simple geometry, using single-degree-of-freedom hinges at simple angles, with no strain during deployment. Strut members are of large diameter with unidirectional graphite fibers for maximum beam performance. Fittings are aluminum with phosphor bronze bushings so that compliance is low and joint lifetime is high. The several beam types required for different applications on the space station will use the same basic design, with changes in strut cross section where necessary. Deployment is by a BI-STEM which pushes the beam out; retraction is by cables which cause initial folding and pull the beam in.

Structural attachments for large space structures

NASA Technical Reports Server (NTRS)

Pruett, E. C.; Loughead, T. E.; Robertson, K. B., III

1980-01-01

The feasibility of fabricating beams in space and using them as components of a large, crew assembled structure, was investigated. Two projects were undertaken: (1) design and development of a ground version of an automated beam builder capable of producing triangular cross section aluminum beams; and (2) design and fabrication of lap joints to connect the beams orthogonally and centroidal end caps to connect beams end to end at any desired angle. The first project produced a beam building machine which fabricates aluminum beams suitable for neutral buoyancy evaluation. The second project produced concepts for the lap joint and end cap. However, neither of these joint concepts was suitable for use by a pressure suited crew member in a zero gravity environment. It is concluded that before the beams can be evaluated the joint designs need to be completed and sufficient joints produced to allow assembly of a complex structure.

Studies of beam injection with a compensated bump and uncompensated bump in a synchrotron

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

Akbar Fakhri, Ali; Prajapati, S. K.; Ghodke, A. D.

2013-08-15

Synchrotron radiation sources Indus-1 and Indus-2 have a synchrotron as the common injector. A three kicker compensated bump injection scheme was employed for beam injection into this synchrotron. The stored beam current in the synchrotron is higher, when all the three kickers are operated at the same current than when kickers are operated at currents required to generate compensated bump. Beam dynamics studies have been done to understand why this happens. Theoretical studies indicate that higher stored current in the later case is attributed to smaller residual oscillations of injected beam. These studies also reveal that if the angle ofmore » the injected beam during beam injection is kept varying, the performance could be further improved. This is experimentally confirmed by injecting the beam on rising part of the injection septum magnet current pulse.« less

The influence of physical wedges on penumbra and in-field dose uniformity in ocular proton beams.

PubMed

Baker, Colin; Kacperek, Andrzej

2016-04-01

A physical wedge may be partially introduced into a proton beam when treating ocular tumours in order to improve dose conformity to the distal border of the tumour and spare the optic nerve. Two unwanted effects of this are observed: a predictable broadening of the beam penumbra on the wedged side of the field and, less predictably, an increase in dose within the field along a relatively narrow volume beneath the edge (toe) of the wedge, as a result of small-angle proton scatter. Monte Carlo simulations using MCNPX and direct measurements with radiochromic (GAFCHROMIC(®) EBT2) film were performed to quantify these effects for aluminium wedges in a 60 MeV proton beam as a function of wedge angle and position of the wedge relative to the patient. For extreme wedge angles (60° in eye tissue) and large wedge-to-patient distances (70 mm in this context), the 90-10% beam penumbra increased from 1.9 mm to 9.1 mm. In-field dose increases from small-angle proton scatter were found to contribute up to 21% additional dose, persisting along almost the full depth of the spread-out-Bragg peak. Profile broadening and in-field dose enhancement are both minimised by placing the wedge as close as possible to the patient. Use of lower atomic number wedge materials such as PMMA reduce the magnitude of both effects as a result of a reduced mean scattering angle per unit energy loss; however, their larger physical size and greater variation in density are undesirable. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Sonar beam dynamics in leaf-nosed bats

PubMed Central

Linnenschmidt, Meike; Wiegrebe, Lutz

2016-01-01

Ultrasonic emissions of bats are directional and delimit the echo-acoustic space. Directionality is quantified by the aperture of the sonar beam. Recent work has shown that bats often widen their sonar beam when approaching movable prey or sharpen their sonar beam when navigating through cluttered habitats. Here we report how nose-emitting bats, Phyllostomus discolor, adjust their sonar beam to object distance. First, we show that the height and width of the bats sonar beam, as imprinted on a parabolic 45 channel microphone array, varies even within each animal and this variation is unrelated to changes in call level or spectral content. Second, we show that these animals are able to systematically decrease height and width of their sonar beam while focusing on the approaching object. Thus it appears that sonar beam sharpening is a further, facultative means of reducing search volume, likely to be employed by stationary animals when the object position is close and unambiguous. As only half of our individuals sharpened their beam onto the approaching object we suggest that this strategy is facultative, under voluntary control, and that beam formation is likely mediated by muscular control of the acoustic aperture of the bats’ nose leaf. PMID:27384865

Sonar beam dynamics in leaf-nosed bats.

PubMed

Linnenschmidt, Meike; Wiegrebe, Lutz

2016-07-07

Ultrasonic emissions of bats are directional and delimit the echo-acoustic space. Directionality is quantified by the aperture of the sonar beam. Recent work has shown that bats often widen their sonar beam when approaching movable prey or sharpen their sonar beam when navigating through cluttered habitats. Here we report how nose-emitting bats, Phyllostomus discolor, adjust their sonar beam to object distance. First, we show that the height and width of the bats sonar beam, as imprinted on a parabolic 45 channel microphone array, varies even within each animal and this variation is unrelated to changes in call level or spectral content. Second, we show that these animals are able to systematically decrease height and width of their sonar beam while focusing on the approaching object. Thus it appears that sonar beam sharpening is a further, facultative means of reducing search volume, likely to be employed by stationary animals when the object position is close and unambiguous. As only half of our individuals sharpened their beam onto the approaching object we suggest that this strategy is facultative, under voluntary control, and that beam formation is likely mediated by muscular control of the acoustic aperture of the bats' nose leaf.

SU-E-T-504: Intensity-Modulated Radiosurgery Treatments Derived by Optimizing Delivery of Sphere Packing Treatment Plans

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

Hermansen, M; Bova, F; John, T St.

2015-06-15

Purpose To minimize the number of monitor units required to deliver a sphere packing stereotactic radiosurgery (SRS) plan by eliminating overlaps of individual beam projections. Methods An algorithm was written in C{sup ++} to calculate SRS treatment doses using sphere packing. Three fixed beams were used to approximate each arc in a typical SRS treatment plan. For cases involving multiple isocenters, at each gantry and table angle position beams directed to individual spheres overlap to produce regions of high dose, resulting in intensity modulated beams. These high dose regions were dampened by post-processing of the combined beam profile. The post-processmore » dampening involves removing the excess overlapping fluence from all but the highest contributing beam. The dampened beam profiles at each table and gantry angle position were then summed to produce the new total dose distribution. Results Delivery times for even the most complex multiple sphere plans can be reduced to consistent times of about 20 to 30 minutes. The total MUs required to deliver the plan can also be reduced by as much as 85% of the original plan’s MUs. Conclusion Regions of high dose are removed. Dampening overlapping radiation fluence can produce the new beam profiles that have more uniform dose distributions using less MUs. This results in a treatment that requires significantly fewer intensity values than traditional IMRT or VAMT planning.« less

Automated generation of IMRT treatment plans for prostate cancer patients with metal hip prostheses: Comparison of different planning strategies

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

Voet, Peter W. J.; Dirkx, Maarten L. P.; Breedveld, Sebastiaan

2013-07-15

Purpose: To compare IMRT planning strategies for prostate cancer patients with metal hip prostheses.Methods: All plans were generated fully automatically (i.e., no human trial-and-error interactions) using iCycle, the authors' in-house developed algorithm for multicriterial selection of beam angles and optimization of fluence profiles, allowing objective comparison of planning strategies. For 18 prostate cancer patients (eight with bilateral hip prostheses, ten with a right-sided unilateral prosthesis), two planning strategies were evaluated: (i) full exclusion of beams containing beamlets that would deliver dose to the target after passing a prosthesis (IMRT{sub remove}) and (ii) exclusion of those beamlets only (IMRT{sub cut}). Plansmore » with optimized coplanar and noncoplanar beam arrangements were generated. Differences in PTV coverage and sparing of organs at risk (OARs) were quantified. The impact of beam number on plan quality was evaluated.Results: Especially for patients with bilateral hip prostheses, IMRT{sub cut} significantly improved rectum and bladder sparing compared to IMRT{sub remove}. For 9-beam coplanar plans, rectum V{sub 60Gy} reduced by 17.5%{+-} 15.0% (maximum 37.4%, p= 0.036) and rectum D{sub mean} by 9.4%{+-} 7.8% (maximum 19.8%, p= 0.036). Further improvements in OAR sparing were achievable by using noncoplanar beam setups, reducing rectum V{sub 60Gy} by another 4.6%{+-} 4.9% (p= 0.012) for noncoplanar 9-beam IMRT{sub cut} plans. Large reductions in rectum dose delivery were also observed when increasing the number of beam directions in the plans. For bilateral implants, the rectum V{sub 60Gy} was 37.3%{+-} 12.1% for coplanar 7-beam plans and reduced on average by 13.5% (maximum 30.1%, p= 0.012) for 15 directions.Conclusions: iCycle was able to automatically generate high quality plans for prostate cancer patients with prostheses. Excluding only beamlets that passed through the prostheses (IMRT{sub cut} strategy) significantly improved OAR sparing. Noncoplanar beam arrangements and, to a larger extent, increasing the number of treatment beams further improved plan quality.« less

Optical extensometer

DOEpatents

Walker, Ray A.; Reich, Fred R.; Russell, James T.

1978-01-01

An optical extensometer is described using sequentially pulsed light beams for measuring the dimensions of objects by detecting two opposite edges of the object without contacting the object. The light beams may be of different distinguishable light characteristics, such as polarization or wave length, and are time modulated in an alternating manner at a reference frequency. The light characteristics are of substantially the same total light energy and are distributed symmetrically. In the preferred embodiment two light beam segments of one characteristic are on opposite sides of a middle segment of another characteristic. As a result, when the beam segments are scanned sequentially across two opposite edges of the object, they produce a readout signal at the output of a photoelectric detector that is compared with the reference signal by a phase comparator to produce a measurement signal with a binary level transition when the light beams cross an edge. The light beams may be of different cross sectional geometries, including two superimposed and concentric circular beam cross sections of different diameter, or two rectangular cross sections which intersect with each other substantially perpendicular so only their central portions are superimposed. Alternately, a row of three light beams can be used including two outer beams on opposite sides and separate from a middle beam. The three beams may all be of the same light characteristic. However it is preferable that the middle beam be of a different characteristic but of the same total energy as the two outer beams.

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

Pirlepesov, F.; Shin, J.; Moskvin, V. P.

Purpose: Dose weighted Linear Energy Transfer (LETd) analysis of critical structures may be useful in understanding the side effects of the proton therapy. The objective is to analyze the differences between LETd and dose distributions in brain tumor patients receiving double scattering proton therapy, to quantify LETd variation in critical organs, and to identify beam arrangements contributing to high LETd in critical organs. Methods: Monte Carlo simulations of 9 pediatric brain tumor patients were performed. The treatment plans were reconstructed with the TOPAS Monte Carlo code to calculate LETd and dose. The beam data were reconstructed proximal to the aperturemore » of the double scattering nozzle. The dose and LETd to target and critical organs including brain stem, optic chiasm, lens, optic nerve, pituitary gland, and hypothalamus were computed for each beam. Results: Greater variability in LETd compared to dose was observed in the brainstem for patients with a variety of tumor types including 5 patients with tumors located in the posterior fossa. Approximately 20%–44% brainstem volume received LETd of 5kev/µm or greater from beams within gantry angles 180°±30° for 5 patients treated with a 3 beam arrangement. Critical organs received higher LETd when located in the vicinity of the beam distal edge. Conclusion: This study presents a novel strategy in the evaluation of the proton treatment impact on critical organs. While the dose to critical organs is confined below the required limits, the LETd may have significant variation. Critical organs in the vicinity of beam distal edge receive higher LETd and depended on beam arrangement, e.g. in posterior fossa tumor treatment, brainstem receive higher LETd from posterior-anterior beams. This study shows importance of the LETd analysis of the radiation impact on the critical organs in proton therapy and may be used to explain clinical imaging observations after therapy.« less

Electromagnetic ion/ion cyclotron instability - Theory and simulations

NASA Technical Reports Server (NTRS)

Winske, D.; Omidi, N.

1992-01-01

Linear theory and 1D and 2D hybrid simulations are employed to study electromagnetic ion/ion cyclotron (EMIIC) instability driven by the relative streaming of two field-aligned ion beams. The characteristics of the instability are studied as a function of beam density, propagation angle, electron-ion temperature ratios, and ion beta. When the propagation angle is near 90 deg the EMIIC instability has the characteristics of an electrostatic instability, while at smaller angles electromagnetic effects play a significant role as does strong beam coupling. The 2D simulations point to a narrowing of the wave spectrum and accompanying coherent effects during the linear growth stage of development. The EMIIC instability is an important effect where ion beta is low such as in the plasma-sheet boundary layer and upstream of slow shocks in the magnetotail.

Induced strain actuation of composite beams and rotor blades with embedded piezoceramic elements

NASA Astrophysics Data System (ADS)

Chen, Peter C.; Chopra, Inderjit

1996-02-01

The objective of this research is to develop a dynamically-scaled (Froude scale) helicopter rotor blade with embedded piezoceramic elements as sensors and actuators to control blade vibrations. A 6 ft diameter 2-bladed bearingless rotor model was built where each blade is embedded with banks of piezoelectric actuators at 0964-1726/5/1/005/img1 degree angles with respect to the beam axis on the top and bottom surfaces. A twist distribution along the blade span is achieved through in-phase excitation of the top and bottom actuators at equal potentials, while a bending distribution is achieved through out-of-phase excitation. In order to fix design variables and to optimize blade performance, a uniform strain beam theory is formulated to analytically predict the static bending and torsional response of composite rectangular beams with embedded piezoelectric actuators. Parameters such as bond thicknesses, actuator skew angle and actuator spacing are investigated by experiments and then validated by theory. The static bending and torsional response of the rotor blades is experimentally measured and correlated with theory. Dynamic torsional and bending responses are experimentally determined for frequencies from 2 - 120 Hz to assess the viability of a vibration reduction system based on piezo-actuation of blade twist. To assess the performance of the piezo-actuators in rotation, hover tests were conducted where accelerometers embedded in the blades were used to resolve the tip twist amplitudes. Although the magnitudes of blade twist attained in this experiment were small, it is expected that future models can be built with improved performance.

Applications of electron lenses: scraping of high-power beams, beam-beam compensation, and nonlinear optics

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

Stancari, Giulio

Electron lenses are pulsed, magnetically confined electron beams whose current-density profile is shaped to obtain the desired effect on the circulating beam. Electron lenses were used in the Fermilab Tevatron collider for bunch-by-bunch compensation of long-range beam-beam tune shifts, for removal of uncaptured particles in the abort gap, for preliminary experiments on head-on beam-beam compensation, and for the demonstration of halo scraping with hollow electron beams. Electron lenses for beam-beam compensation are being commissioned in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). Hollow electron beam collimation and halo control were studied as an option to complementmore » the collimation system for the upgrades of the Large Hadron Collider (LHC) at CERN; a conceptual design was recently completed. Because of their electric charge and the absence of materials close to the proton beam, electron lenses may also provide an alternative to wires for long-range beam-beam compensation in LHC luminosity upgrade scenarios with small crossing angles. At Fermilab, we are planning to install an electron lens in the Integrable Optics Test Accelerator (IOTA, a 40-m ring for 150-MeV electrons) as one of the proof-of-principle implementations of nonlinear integrable optics to achieve large tune spreads and more stable beams without loss of dynamic aperture.« less

Tracking rare-isotope beams with microchannel plates

DOE PAGES

Rogers, A. M.; Sanetullaev, A.; Lynch, W. G.; ...

2015-06-06

A system of two microchannel-plate detectors has been successfully implemented for tracking projectile-fragmentation beams. The detectors provide interaction positions, angles, and arrival Limes of ions at the reaction target. Furthermore, the current design is an adaptation of an assembly used for low-energy beams (~1.4 MeV/nucleon). In order to improve resolution in tracking high-energy heavy-ion beams, the magnetic field strength between the secondary-electron accelerating foil and the microchannel plate had to be increased substantially. Results from an experiment using a 37-MeV/nucleon 56Ni beam show that the tracking system can achieve sub-nanosecond timing resolution and a position resolution of ~1 mm formore » beam intensities up to 5 x 10 5 pps.« less

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).

Tracking rare-isotope beams with microchannel plates

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

Rogers, A. M.; Sanetullaev, A.; Lynch, W. G.

A system of two microchannel-plate detectors has been successfully implemented for tracking projectile-fragmentation beams. The detectors provide interaction positions, angles, and arrival Limes of ions at the reaction target. Furthermore, the current design is an adaptation of an assembly used for low-energy beams (~1.4 MeV/nucleon). In order to improve resolution in tracking high-energy heavy-ion beams, the magnetic field strength between the secondary-electron accelerating foil and the microchannel plate had to be increased substantially. Results from an experiment using a 37-MeV/nucleon 56Ni beam show that the tracking system can achieve sub-nanosecond timing resolution and a position resolution of ~1 mm formore » beam intensities up to 5 x 10 5 pps.« less

X-ray Interferometry with Transmissive Beam Combiners for Ultra-High Angular Resolution Astronomy

NASA Technical Reports Server (NTRS)

Skinner, G. K.; Krismanic, John F.

2009-01-01

Abstract Interferometry provides one of the possible routes to ultra-high angular resolution for X-ray and gamma-ray astronomy. Sub-micro-arc-second angular resolution, necessary to achieve objectives such as imaging the regions around the event horizon of a super-massive black hole at the center of an active galaxy, can be achieved if beams from parts of the incoming wavefront separated by 100s of meters can be stably and accurately brought together at small angles. One way of achieving this is by using grazing incidence mirrors. We here investigate an alternative approach in which the beams are recombined by optical elements working in transmission. It is shown that the use of diffractive elements is a particularly attractive option. We report experimental results from a simple 2-beam interferometer using a low-cost commercially available profiled film as the diffractive elements. A rotationally symmetric filled (or mostly filled) aperture variant of such an interferometer, equivalent to an X-ray axicon, is shown to offer a much wider bandpass than either a Phase Fresnel Lens (PFL) or a PFL with a refractive lens in an achromatic pair. Simulations of an example system are presented.

Universal modal radiation laws for all thermal emitters

PubMed Central

Zhu, Linxiao; Fan, Shanhui

2017-01-01

We derive four laws relating the absorptivity and emissivity of thermal emitters. Unlike the original Kirchhoff radiation law derivations, these derivations include diffraction, and so are valid also for small objects, and can also cover nonreciprocal objects. The proofs exploit two recent approaches. First, we express all fields in terms of the mode-converter basis sets of beams; these sets, which can be uniquely established for any linear optical object, give orthogonal input beams that are coupled one-by-one to orthogonal output beams. Second, we consider thought experiments using universal linear optical machines, which allow us to couple appropriate beams and black bodies. Two of these laws can be regarded as rigorous extensions of previously known laws: One gives a modal version of a radiation law for reciprocal objects—the absorptivity of any input beam equals the emissivity into the “backward” (i.e., phase-conjugated) version of that beam; another gives the overall equality of the sums of the emissivities and the absorptivities for any object, including nonreciprocal ones. The other two laws, valid for reciprocal and nonreciprocal objects, are quite different from previous relations. One shows universal equivalence of the absorptivity of each mode-converter input beam and the emissivity into its corresponding scattered output beam. The other gives unexpected equivalences of absorptivity and emissivity for broad classes of beams. Additionally, we prove these orthogonal mode-converter sets of input and output beams are the ones that maximize absorptivities and emissivities, respectively, giving these beams surprising additional physical meaning. PMID:28396436

Measurement of M²-Curve for Asymmetric Beams by Self-Referencing Interferometer Wavefront Sensor.

PubMed

Du, Yongzhao

2016-11-29

For asymmetric laser beams, the values of beam quality factor M x 2 and M y 2 are inconsistent if one selects a different coordinate system or measures beam quality with different experimental conditionals, even when analyzing the same beam. To overcome this non-uniqueness, a new beam quality characterization method named as M²-curve is developed. The M²-curve not only contains the beam quality factor M x 2 and M y 2 in the x -direction and y -direction, respectively; but also introduces a curve of M x α 2 versus rotation angle α of coordinate axis. Moreover, we also present a real-time measurement method to demonstrate beam propagation factor M²-curve with a modified self-referencing Mach-Zehnder interferometer based-wavefront sensor (henceforth SRI-WFS). The feasibility of the proposed method is demonstrated with the theoretical analysis and experiment in multimode beams. The experimental results showed that the proposed measurement method is simple, fast, and a single-shot measurement procedure without movable parts.

Measurement of M2-Curve for Asymmetric Beams by Self-Referencing Interferometer Wavefront Sensor

PubMed Central

Du, Yongzhao

2016-01-01

For asymmetric laser beams, the values of beam quality factor Mx2 and My2 are inconsistent if one selects a different coordinate system or measures beam quality with different experimental conditionals, even when analyzing the same beam. To overcome this non-uniqueness, a new beam quality characterization method named as M2-curve is developed. The M2-curve not only contains the beam quality factor Mx2 and My2 in the x-direction and y-direction, respectively; but also introduces a curve of Mxα2 versus rotation angle α of coordinate axis. Moreover, we also present a real-time measurement method to demonstrate beam propagation factor M2-curve with a modified self-referencing Mach-Zehnder interferometer based-wavefront sensor (henceforth SRI-WFS). The feasibility of the proposed method is demonstrated with the theoretical analysis and experiment in multimode beams. The experimental results showed that the proposed measurement method is simple, fast, and a single-shot measurement procedure without movable parts. PMID:27916845

Excitation of multipolar surface plasmon resonance in plasmonic nanoparticles by complex accelerating beams

NASA Astrophysics Data System (ADS)

Yang, Yang; Li, Jiafang; Li, Zhi-Yuan; Chen, Yue-Gang

2015-07-01

In this paper, through a vector-spherical harmonics approach, we investigate the optical spectra of plasmonic Au nanoparticles excited by two special accelerating beams: a non-paraxial Airy beam and a Bessel beam. We systematically analyze the impacts of the beam profile, phase, and helical wave front of the electromagnetic fields on the optical spectrum and the excitation of the surface plasmon resonance (SPR). We find that the high-order phase in the Airy beam would result in strong plasmonic oscillations in the optical spectra, while the cone angle and orbital angular momentum carried by the Bessel beam could be employed to engineer the plasmon modes excited in Au nanoparticles. Furthermore, the optical spectrum excited by a combined Airy-Bessel-Gauss beam is discussed. The study could help to deeply explore new ways to manipulate SPR in metal nanoparticles via the wave front engineering of optical beams for enhancing light-matter interaction and optical sensing performance.

Spin-orbit beams for optical chirality measurement

NASA Astrophysics Data System (ADS)

Samlan, C. T.; Suna, Rashmi Ranjan; Naik, Dinesh N.; Viswanathan, Nirmal K.

2018-01-01

Accurate measurement of chirality is essential for the advancement of natural and pharmaceutical sciences. We report here a method to measure chirality using non-separable states of light with geometric phase-gradient in the circular polarization basis, which we refer to as spin-orbit beams. A modified polarization Sagnac interferometer is used to generate spin-orbit beams wherein the spin and orbital angular momentum of the input Gaussian beam are coupled. The out-of-phase interference between counter-propagating Gaussian beams with orthogonal spin states and lateral-shear or/and linear-phase difference between them results in spin-orbit beams with linear and azimuthal phase gradient. The spin-orbit beams interact efficiently with the chiral medium, inducing a measurable change in the center-of-mass of the beam, using the polarization rotation angle and hence the chirality of the medium are accurately calculated. Tunable dynamic range of measurement and flexibility to introduce large values of orbital angular momentum for the spin-orbit beam, to improve the measurement sensitivity, highlight the techniques' versatility.

Integrated Micro-Optics for Microfluidic Detection.

PubMed

Kazama, Yuto; Hibara, Akihide

2016-01-01

A method of embedding micro-optics into a microfluidic device was proposed and demonstrated. First, the usefulness of embedded right-angle prisms was demonstrated in microscope observation. Lateral-view microscopic observation of an aqueous dye flow in a 100-μm-sized microchannel was demonstrated. Then, the embedded right-angle prisms were utilized for multi-beam laser spectroscopy. Here, crossed-beam thermal lens detection of a liquid sample was applied to glucose detection.

Spatial-Heterodyne Interferometry For Reflection And Transm Ission (Shirt) Measurements

DOEpatents

Hanson, Gregory R [Clinton, TN; Bingham, Philip R [Knoxville, TN; Tobin, Ken W [Harriman, TN

2006-02-14

Systems and methods are described for spatial-heterodyne interferometry for reflection and transmission (SHIRT) measurements. A method includes digitally recording a first spatially-heterodyned hologram using a first reference beam and a first object beam; digitally recording a second spatially-heterodyned hologram using a second reference beam and a second object beam; Fourier analyzing the digitally recorded first spatially-heterodyned hologram to define a first analyzed image; Fourier analyzing the digitally recorded second spatially-heterodyned hologram to define a second analyzed image; digitally filtering the first analyzed image to define a first result; and digitally filtering the second analyzed image to define a second result; performing a first inverse Fourier transform on the first result, and performing a second inverse Fourier transform on the second result. The first object beam is transmitted through an object that is at least partially translucent, and the second object beam is reflected from the object.

SU-F-T-382: Volumetric Modulated Arc Therapy (VMAT) Beam Angle Optimization in Pulsed Partial Brain Irradiation (PPBI) for Newly Diagnosed Glioblastoma

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

Zhou, J; Wang, Y; Ding, X

Purpose: To optimize VMAT beam parameters in PPBI to minimize treatment time. We investigate the coverage and organs at risk (OR) avoidance capability of shorter arcs with shorter treatment times. Methods: We evaluated the treatment plans for eleven previously treated PPBI patients. Each patient received 46Gy (2Gy×23) to the initial target and an additional 14Gy (2Gy×7) as a sequential boost. Each daily 2-Gy fraction was delivered as ten 0.2-Gy pulses separated by 3-minute intervals using VMAT. Each pulse was delivered using the same arc and covered at least 95% of the PTV with at least 95% of the prescription dose.more » To optimize the VMAT beam angle, an initial 360° full-arc VMAT plan was implemented. Beam control points and their corresponding dose rates were exported. A curve of the product of control point and dose rate was plotted against treatment beam angle. The optimum angle range was determined from this relationship. We chose the minimum continuous angle range that covered 85% of the area under the curve. Planning parameters, including treatment time for each pulse (T-pulse), PTV coverage, maximum dose (Dmax), homogeneity index (HI=D5/D95), R50 (50%IDL/PTV), and Dmax to ORs, were compared. Results: Mean PTV volume was 364.1±181.5cc. Mean T-pulse of partial-arc beams was 34.3±10.6s, vs. 63.0±1.7s (p<0.001) for that of full-arc beams. No significant differences were found for PTV V95, Dmax and R50, 99.4%±1.2% vs. 99.7%±0.5% (p=0.066), 108.0%±1.2% vs. 107.5%±1.1% (p=0.107), 2.95±0.38 vs. 2.87±0.35 (p=0.165), for the plans with partial-arc and full-arc beams, respectively. However, plans using full-arc do provide better PTV V100 and HI, 96.0%±3.0% vs. 97.2%±2.0% (p=0.025) and 1.06±0.03 vs. 1.04±0.01 (p=0.009). No significant difference was found on Dmax to ORs. Conclusion: PPBI with optimized partial-arc plans are clinically comparable to full-arc plans, while treatment time be significantly reduced, average saving of 287s for a 10-pulse treatment.« less

Determination of the beam-spin asymmetry of deuteron photodisintegration in the energy region Eγ=1.1 -2.3 GeV

NASA Astrophysics Data System (ADS)

Zachariou, N.; Ilieva, Y.; Berman, B. L.; Ivanov, N. Ya.; Sargsian, M. M.; Avakian, R.; Feldman, G.; Nadel-Turonski, P.; Adhikari, K. P.; Adikaram, D.; Anderson, M. D.; Pereira, S. Anefalos; Avakian, H.; Badui, R. A.; Baltzell, N. A.; Battaglieri, M.; Baturin, V.; Bedlinskiy, I.; Biselli, A. S.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Cao, T.; Carman, D. S.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P. L.; Compton, N.; Contalbrigo, M.; Cortes, O.; Crede, V.; D'Angelo, A.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dupre, R.; Egiyan, H.; Alaoui, A. El; Fassi, L. El; Elouadrhiri, L.; Fedotov, G.; Fegan, S.; Filippi, A.; Fleming, J. A.; Forest, T. A.; Fradi, A.; Gevorgyan, N.; Ghandilyan, Y.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Glazier, D. I.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Hafidi, K.; Hanretty, C.; Harrison, N.; Hattawy, M.; Hicks, K.; Ho, D.; Holtrop, M.; Hughes, S. M.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jiang, H.; Jo, H. S.; Joo, K.; Keller, D.; Khachatryan, G.; Khandaker, M.; Kim, A.; Kim, W.; Klein, F. J.; Kubarovsky, V.; Lenisa, P.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mattione, P. T.; McKinnon, B.; Mineeva, T.; Mirazita, M.; Mokeeev, V. I.; Montgomery, R. A.; Moutarde, H.; Camacho, C. Munoz; Net, L. A.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Park, K.; Pasyuk, E.; Phelps, W.; Phillips, J. J.; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Prok, Y.; Protopopescu, D.; Puckett, A. J. R.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Roy, P.; Sabatié, F.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Senderovich, I.; Sharabian, Y. G.; Skorodumina, Iu.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Sparveris, N.; Stepanyan, S.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tian, Ye; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D.; Wei, X.; Wood, M. H.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.; CLAS Collaboration

2015-05-01

The beam-spin asymmetry, Σ , for the reaction γ d →p n has been measured using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility (JLab) for six photon-energy bins, between 1.1 and 2.3 GeV, and proton angles in the center-of-mass frame, θc .m ., between 25∘ and 160∘. These are the first measurements of beam-spin asymmetries at θc .m .=90∘ for photon-beam energies above 1.6 GeV, and the first measurements for angles other than θc .m .=90∘ . The angular and energy dependence of Σ is expected to aid in the development of QCD-based models to understand the mechanisms of deuteron photodisintegration in the transition region between hadronic and partonic degrees of freedom, where both effective field theories and perturbative QCD cannot make reliable predictions.

Freeform Deposition Method for Coolant Channel Closeout

NASA Technical Reports Server (NTRS)

Gradl, Paul R. (Inventor); Reynolds, David Christopher (Inventor); Walker, Bryant H. (Inventor)

2017-01-01

A method is provided for fabricating a coolant channel closeout jacket on a structure having coolant channels formed in an outer surface thereof. A line of tangency relative to the outer surface is defined for each point on the outer surface. Linear rows of a metal feedstock are directed towards and deposited on the outer surface of the structure as a beam of weld energy is directed to the metal feedstock so-deposited. A first angle between the metal feedstock so-directed and the line of tangency is maintained in a range of 20-90.degree.. The beam is directed towards a portion of the linear rows such that less than 30% of the cross-sectional area of the beam impinges on a currently-deposited one of the linear rows. A second angle between the beam and the line of tangency is maintained in a range of 5-65 degrees.

Control of quasi-monoenergetic electron beams from laser-plasma accelerators with adjustable shock density profile

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

Tsai, Hai-En; Swanson, Kelly K.; Barber, Sam K.

The injection physics in a shock-induced density down-ramp injector was characterized, demonstrating precise control of a laser-plasma accelerator (LPA). Using a jet-blade assembly, experiments systematically v aried the shock injector profile, including shock angle, shock position, up-ramp width, and acceleration length. Our work demonstrates that beam energy, energy spread, and pointing can be controlled by adjusting these parameters. As a result, an electron beam that was highly tunable from 25 to 300 MeV with 8% energy spread (ΔE FWHM/E), 1.5 mrad divergence, and 0.35 mrad pointing fluctuation was produced. Particle-in-cell simulation characterized how variation in the shock angle and up-rampmore » width impacted the injection process. This highly controllable LPA represents a suitable, compact electron beam source for LPA applications such as Thomson sources and free-electron lasers.« less

Adaptive beam tracking and steering via electrowetting-controlled liquid prism

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

Cheng, JT; Chen, CL

2011-11-07

We report an electrowetting-controlled optofluidic system for adaptive beam tracking and agile steering. With two immiscible fluids in a transparent cell, we can actively control the contact angle along the fluid-fluid-solid tri-junction line and hence the orientation of the fluid-fluid interface via electrowetting. The naturally formed meniscus between the two liquids can function as an optical prism. We have fabricated a liquid prism module with an aperture size of 10 mm -10mm. With 1 wt.% KCl and 1 wt.% Sodium Dodecyl Sulfate added into deionized water, the orientation of the water-silicone oil interface has been modulated between -26 degrees andmore » 26 degrees that can deflect and steer beam within the incidence angle of 0 degrees-15 degrees. The wide-range beam tracking and steering enables the liquid prism work as an electrowetting solar cell. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3660578]« less

Adaptive beam tracking and steering via electrowetting-controlled liquid prism

NASA Astrophysics Data System (ADS)

Cheng, Jiangtao; Chen, Chung-Lung

2011-11-01

We report an electrowetting-controlled optofluidic system for adaptive beam tracking and agile steering. With two immiscible fluids in a transparent cell, we can actively control the contact angle along the fluid-fluid-solid tri-junction line and hence the orientation of the fluid-fluid interface via electrowetting. The naturally formed meniscus between the two liquids can function as an optical prism. We have fabricated a liquid prism module with an aperture size of 10 mm × 10mm. With 1 wt. % KCl and 1 wt. % Sodium Dodecyl Sulfate added into deionized water, the orientation of the water-silicone oil interface has been modulated between -26° and 26° that can deflect and steer beam within the incidence angle of 0°-15°. The wide-range beam tracking and steering enables the liquid prism work as an electrowetting solar cell.

Demonstration of temperature imaging by H₂O absorption spectroscopy using compressed sensing tomography.

PubMed

An, Xinliang; Brittelle, Mack S; Lauzier, Pascal T; Gord, James R; Roy, Sukesh; Chen, Guang-Hong; Sanders, Scott T

2015-11-01

This paper introduces temperature imaging by total-variation-based compressed sensing (CS) tomography of H2O vapor absorption spectroscopy. A controlled laboratory setup is used to generate a constant two-dimensional temperature distribution in air (a roughly Gaussian temperature profile with a central temperature of 677 K). A wavelength-tunable laser beam is directed through the known distribution; the beam is translated and rotated using motorized stages to acquire complete absorption spectra in the 1330-1365 nm range at each of 64 beam locations and 60 view angles. Temperature reconstructions are compared to independent thermocouple measurements. Although the distribution studied is approximately axisymmetric, axisymmetry is not assumed and simulations show similar performance for arbitrary temperature distributions. We study the measurement error as a function of number of beams and view angles used in reconstruction to gauge the potential for application of CS in practical test articles where optical access is limited.

Control of quasi-monoenergetic electron beams from laser-plasma accelerators with adjustable shock density profile

DOE PAGES

Tsai, Hai-En; Swanson, Kelly K.; Barber, Sam K.; ...

2018-04-13

The injection physics in a shock-induced density down-ramp injector was characterized, demonstrating precise control of a laser-plasma accelerator (LPA). Using a jet-blade assembly, experiments systematically v aried the shock injector profile, including shock angle, shock position, up-ramp width, and acceleration length. Our work demonstrates that beam energy, energy spread, and pointing can be controlled by adjusting these parameters. As a result, an electron beam that was highly tunable from 25 to 300 MeV with 8% energy spread (ΔE FWHM/E), 1.5 mrad divergence, and 0.35 mrad pointing fluctuation was produced. Particle-in-cell simulation characterized how variation in the shock angle and up-rampmore » width impacted the injection process. This highly controllable LPA represents a suitable, compact electron beam source for LPA applications such as Thomson sources and free-electron lasers.« less

Compact, flexible, frequency agile parametric wavelength converter

DOEpatents

Velsko, Stephan P.; Yang, Steven T.

2002-01-01

This improved Frequency Agile Optical Parametric Oscillator provides near on-axis pumping of a single QPMC with a tilted periodically poled grating to overcome the necessity to find a particular crystal that will permit collinear birefringence in order to obtain a desired tuning range. A tilted grating design and the elongation of the transverse profile of the pump beam in the angle tuning plane of the FA-OPO reduces the rate of change of the overlap between the pumped volume in the crystal and the resonated and non-resonated wave mode volumes as the pump beam angle is changed. A folded mirror set relays the pivot point for beam steering from a beam deflector to the center of the FA-OPO crystal. This reduces the footprint of the device by as much as a factor of two over that obtained when using the refractive telescope design.

Control of quasi-monoenergetic electron beams from laser-plasma accelerators with adjustable shock density profile

NASA Astrophysics Data System (ADS)

Tsai, Hai-En; Swanson, Kelly K.; Barber, Sam K.; Lehe, Remi; Mao, Hann-Shin; Mittelberger, Daniel E.; Steinke, Sven; Nakamura, Kei; van Tilborg, Jeroen; Schroeder, Carl; Esarey, Eric; Geddes, Cameron G. R.; Leemans, Wim

2018-04-01

The injection physics in a shock-induced density down-ramp injector was characterized, demonstrating precise control of a laser-plasma accelerator (LPA). Using a jet-blade assembly, experiments systematically varied the shock injector profile, including shock angle, shock position, up-ramp width, and acceleration length. Our work demonstrates that beam energy, energy spread, and pointing can be controlled by adjusting these parameters. As a result, an electron beam that was highly tunable from 25 to 300 MeV with 8% energy spread (ΔEFWHM/E), 1.5 mrad divergence, and 0.35 mrad pointing fluctuation was produced. Particle-in-cell simulation characterized how variation in the shock angle and up-ramp width impacted the injection process. This highly controllable LPA represents a suitable, compact electron beam source for LPA applications such as Thomson sources and free-electron lasers.

Integrated Electro-optical Laser-Beam Scanners

NASA Technical Reports Server (NTRS)

Boord, Warren T.

1990-01-01

Scanners using solid-state devices compact, consume little power, and have no moving parts. Integrated electro-optical laser scanner, in conjunction with external lens, points outgoing beam of light in any number of different directions, depending on number of upper electrodes. Offers beam-deflection angles larger than those of acousto-optic scanners. Proposed for such diverse applications as nonimpact laser printing, color imaging, ranging, barcode reading, and robotic vision.

Multibeam Phased Array Antennas

NASA Technical Reports Server (NTRS)

Popovic, Zoya; Romisch, Stefania; Rondineau, Sebastien

2004-01-01

In this study, a new architecture for Ka-band multi-beam arrays was developed and demonstrated experimentally. The goal of the investigation was to demonstrate a new architecture that has the potential of reducing the cost as compared to standard expensive phased array technology. The goals of this specific part of the project, as stated in the yearly statement of work in the original proposal are: 1. Investigate bounds on performance of multi-beam lens arrays in terms of beamwidths, volume (size), isolation between beams, number of simultaneous beams, etc. 2. Design a small-scale array to demonstrate the principle. The array will be designed for operation around 3OGHz (Ka-band), with two 10-degree beamwidth beams. 3. Investigate most appropriate way to accomplish fine-tuning of the beam pointing within 5 degrees around the main beam pointing angle.

Beam collimation and energy spectrum compression of laser-accelerated proton beams using solenoid field and RF cavity

NASA Astrophysics Data System (ADS)

Teng, J.; Gu, Y. Q.; Zhu, B.; Hong, W.; Zhao, Z. Q.; Zhou, W. M.; Cao, L. F.

2013-11-01

This paper presents a new method of laser produced proton beam collimation and spectrum compression using a combination of a solenoid field and a RF cavity. The solenoid collects laser-driven protons efficiently within an angle that is smaller than 12 degrees because it is mounted few millimeters from the target, and collimates protons with energies around 2.3 MeV. The collimated proton beam then passes through a RF cavity to allow compression of the spectrum. Particle-in-cell (PIC) simulations demonstrate the proton beam transport in the solenoid and RF electric fields. Excellent energy compression and collection efficiency of protons are presented. This method for proton beam optimization is suitable for high repetition-rate laser acceleration proton beams, which could be used as an injector for a conventional proton accelerator.

Simulation of therapeutic electron beam tracking through a non-uniform magnetic field using finite element method

PubMed Central

Tahmasebibirgani, Mohammad Javad; Maskani, Reza; Behrooz, Mohammad Ali; Zabihzadeh, Mansour; Shahbazian, Hojatollah; Fatahiasl, Jafar; Chegeni, Nahid

2017-01-01

Introduction In radiotherapy, megaelectron volt (MeV) electrons are employed for treatment of superficial cancers. Magnetic fields can be used for deflection and deformation of the electron flow. A magnetic field is composed of non-uniform permanent magnets. The primary electrons are not mono-energetic and completely parallel. Calculation of electron beam deflection requires using complex mathematical methods. In this study, a device was made to apply a magnetic field to an electron beam and the path of electrons was simulated in the magnetic field using finite element method. Methods A mini-applicator equipped with two neodymium permanent magnets was designed that enables tuning the distance between magnets. This device was placed in a standard applicator of Varian 2100 CD linear accelerator. The mini-applicator was simulated in CST Studio finite element software. Deflection angle and displacement of the electron beam was calculated after passing through the magnetic field. By determining a 2 to 5cm distance between two poles, various intensities of transverse magnetic field was created. The accelerator head was turned so that the deflected electrons became vertical to the water surface. To measure the displacement of the electron beam, EBT2 GafChromic films were employed. After being exposed, the films were scanned using HP G3010 reflection scanner and their optical density was extracted using programming in MATLAB environment. Displacement of the electron beam was compared with results of simulation after applying the magnetic field. Results Simulation results of the magnetic field showed good agreement with measured values. Maximum deflection angle for a 12 MeV beam was 32.9° and minimum deflection for 15 MeV was 12.1°. Measurement with the film showed precision of simulation in predicting the amount of displacement in the electron beam. Conclusion A magnetic mini-applicator was made and simulated using finite element method. Deflection angle and displacement of electron beam were calculated. With the method used in this study, a good prediction of the path of high-energy electrons was made before they entered the body. PMID:28607652

Nonlinear dynamics of 3D beams of fast magnetosonic waves propagating in the ionospheric and magnetospheric plasma

NASA Astrophysics Data System (ADS)

Belashov, V. Yu.; Belashova, E. S.

2016-11-01

On the basis of the model of the three-dimensional (3D) generalized Kadomtsev-Petviashvili equation for magnetic field h = B / B the formation, stability, and dynamics of 3D soliton-like structures, such as the beams of fast magnetosonic (FMS) waves generated in ionospheric and magnetospheric plasma at a low-frequency branch of oscillations when β = 4 πnT/ B 2 ≪ 1 and β > 1, are studied. The study takes into account the highest dispersion correction determined by values of the plasma parameters and the angle θ = ( B, k), which plays a key role in the FMS beam propagation at those angles to the magnetic field that are close to π/2. The stability of multidimensional solutions is studied by an investigation of the Hamiltonian boundness under its deformations on the basis of solving of the corresponding variational problem. The evolution and dynamics of the 3D FMS wave beam are studied by the numerical integration of equations with the use of specially developed methods. The results can be interpreted in terms of the self-focusing phenomenon, as the formation of a stationary beam and the scattering and self-focusing of the solitary beam of FMS waves. These cases were studied with a detailed investigation of all evolutionary stages of the 3D FMS wave beams in the ionospheric and magnetospheric plasma.

Beam dynamic simulations of the CLIC crab cavity and implications on the BDS

NASA Astrophysics Data System (ADS)

Shinton, I. R. R.; Burt, G.; Glasman, C. J.; Jones, R. M.; Wolski, A.

2011-11-01

The Compact Linear Collider (CLIC) is a proposed electron positron linear collider design aiming to achieve a centre of mass energy of up to 3 TeV. The main accelerating structures in CLIC operate at an X-band frequency of 11.994 GHz with an accelerating gradient of 100 MV/m. The present design requires the beams to collide at a small crossing angle of 10 mrad per line giving a resultant overall crossing angle of 20 mrad. Transverse deflecting cavities, referred to as "Crab cavities", are installed in the beam delivery system (BDS) of linear collider designs in order to ensure the final luminosity at the interaction point (IP) is comparable to that in a head on collision. We utilise the beam tracking code PLACET combined with the beam-beam code GUINEA-PIG to calculate the resulting luminosity at the IP. We follow a similar tuning procedure to that used for the design of the ILC crab cavities and anitcrab cavities. However an unexpected loss in luminosity of 10% was observed for the 20 mrad design was observed. It was discovered that the action of the crab cavities can affect the geometric aberrations resulting from the sextupoles used to correct chromatic effects in the beam delivery system. This has direct consequences regarding the design of the present CLIC BDS.

Miniaturized CARS microendoscope probe design for label-free intraoperative imaging

NASA Astrophysics Data System (ADS)

Chen, Xu; Wang, Xi; Xu, Xiaoyun; Cheng, Jie; Liu, Zhengfan; Weng, Sheng; Thrall, Michael J.; Goh, Alvin C.; McCormick, Daniel T.; Wong, Kelvin; Wong, Stephen T. C.

2014-03-01

A Coherent Anti-Stokes Raman Scattering (CARS) microendoscope probe for early stage label-free prostate cancer diagnosis at single cell resolution is presented. The handheld CARS microendoscope probe includes a customized micro-electromechanical systems (MEMS) scanning mirror as well as miniature optical and mechanical components. In our design, the excitation laser (pump and stokes beams) from the fiber is collimated, reflected by the reflecting mirror, and transmitted via a 2D MEMS scanning mirror and a micro-objective system onto the sample; emission in the epi-direction is returned through the micro-objective lens, MEMS and reflecting mirror, and collimation system, and finally the emission signal is collected by a photomultiplier tube (PMT). The exit pupil diameter of the collimator system is designed to match the diameter of the MEMS mirror and the entrance pupil diameter of the micro-objective system. The back aperture diameter of the micro-objective system is designed according to the largest MEMS scanning angle and the distance between the MEMS mirror and the back aperture. To increase the numerical aperture (NA) of the micro-objective system in order to enhance the signal collection efficiency, the back aperture diameter of the micro-objective system is enlarged with an upfront achromatic wide angle Keplerian telescope beam expander. The integration of a miniaturized micro-optics probe with optical fiber CARS microscopy opens up the possibility of in vivo molecular imaging for cancer diagnosis and surgical intervention.

Realization of an Ultra-thin Metasurface to Facilitate Wide Bandwidth, Wide Angle Beam Scanning.

PubMed

Bah, Alpha O; Qin, Pei-Yuan; Ziolkowski, Richard W; Cheng, Qiang; Guo, Y Jay

2018-03-19

A wide bandwidth, ultra-thin, metasurface is reported that facilitates wide angle beam scanning. Each unit cell of the metasurface contains a multi-resonant, strongly-coupled unequal arm Jerusalem cross element. This element consists of two bent-arm, orthogonal, capacitively loaded strips. The wide bandwidth of the metasurface is achieved by taking advantage of the strong coupling within and between its multi-resonant elements. A prototype of the proposed metasurface has been fabricated and measured. The design concept has been validated by the measured results. The proposed metasurface is able to alleviate the well-known problem of impedance mismatch caused by mutual coupling when the main beam of an array is scanned. In order to validate the wideband and wide scanning ability of the proposed metasurface, it is integrated with a wideband antenna array as a wide angle impedance matching element. The metasurface-array combination facilitates wide angle scanning over a 6:1 impedance bandwidth without the need for bulky dielectrics or multi-layered structures.

High-energy coherent terahertz radiation emitted by wide-angle electron beams from a laser-wakefield accelerator

NASA Astrophysics Data System (ADS)

Yang, Xue; Brunetti, Enrico; Jaroszynski, Dino A.

2018-04-01

High-charge electron beams produced by laser-wakefield accelerators are potentially novel, scalable sources of high-power terahertz radiation suitable for applications requiring high-intensity fields. When an intense laser pulse propagates in underdense plasma, it can generate femtosecond duration, self-injected picocoulomb electron bunches that accelerate on-axis to energies from 10s of MeV to several GeV, depending on laser intensity and plasma density. The process leading to the formation of the accelerating structure also generates non-injected, sub-picosecond duration, 1–2 MeV nanocoulomb electron beams emitted obliquely into a hollow cone around the laser propagation axis. These wide-angle beams are stable and depend weakly on laser and plasma parameters. Here we perform simulations to characterise the coherent transition radiation emitted by these beams if passed through a thin metal foil, or directly at the plasma–vacuum interface, showing that coherent terahertz radiation with 10s μJ to mJ-level energy can be produced with an optical to terahertz conversion efficiency up to 10‑4–10‑3.

A study for the installation of the TEXT heavy-ion beam probe on DIII-D

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

Edmonds, P.H.; Solano, E.R.; Bravenec, R.V.

1997-01-01

An assessment of the feasibility of installing the TEXT 2 MeV heavy-ion beam probe on the DIII-D tokamak has been completed. Detailed drawings of the machine cross section were imported into the CAD application AutoCAD. A set of programs written in AutoLisp were used to generate trajectories. Displays of the accessible cross section of the plasma, scan lines for the entire range of primary beam energy and injection angle ranges, and sample{endash}volume dimensions can be rapidly generated. Because of the large deflection between the primary input beam and the emergent secondary beam, either the analyzer needs to be tracked overmore » a {plus_minus}20{degree} angle or secondary poloidal deflector plates need to be installed at the exit port. Toroidal deflector plates will be installed at both the injection and exit ports to compensate for toroidal displacements and deflections. The sample volumes generated by this procedure are within a few centimeters of the locations derived from a full three-dimensional calculation.{copyright} {ital 1997 American Institute of Physics.}« less

First-and Second-Order Displacement Transfer Functions for Structural Shape Calculations Using Analytically Predicted Surface Strains

NASA Technical Reports Server (NTRS)

Ko, William L.; Fleischer, Van Tran

2012-01-01

New first- and second-order displacement transfer functions have been developed for deformed shape calculations of nonuniform cross-sectional beam structures such as aircraft wings. The displacement transfer functions are expressed explicitly in terms of beam geometrical parameters and surface strains (uniaxial bending strains) obtained at equally spaced strain stations along the surface of the beam structure. By inputting the measured or analytically calculated surface strains into the displacement transfer functions, one could calculate local slopes, deflections, and cross-sectional twist angles of the nonuniform beam structure for mapping the overall structural deformed shapes for visual display. The accuracy of deformed shape calculations by the first- and second-order displacement transfer functions are determined by comparing these values to the analytically predicted values obtained from finite element analyses. This comparison shows that the new displacement transfer functions could quite accurately calculate the deformed shapes of tapered cantilever tubular beams with different tapered angles. The accuracy of the present displacement transfer functions also are compared to those of the previously developed displacement transfer functions.

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

Karaulanov, Todor; Savukov, Igor; Kim, Young Jin

We constructed a spin-exchange relaxation-free (SERF) magnetometer with a small angle between the pump and probe beams facilitating a multi-channel design with a flat pancake cell. This configuration provides almost complete overlap of the beams in the cell, and prevents the pump beam from entering the probe detection channel. By coupling the lasers in multi-mode fibers, without an optical isolator or field modulation, we demonstrate a sensitivity of 10 fTmore » $$/\\sqrt{\\text{Hz}}$$ for frequencies between 10 Hz and 100 Hz. In addition to the experimental study of sensitivity, we present a theoretical analysis of SERF magnetometer response to magnetic fields for small-angle and parallel-beam configurations, and show that at optimal DC offset fields the magnetometer response is comparable to that in the orthogonal-beam configuration. Based on the analysis, we also derive fundamental and probe-limited sensitivities for the arbitrary non-orthogonal geometry. The expected practical and fundamental sensitivities are of the same order as those in the orthogonal geometry. As a result, we anticipate that our design will be useful for magnetoencephalography (MEG) and magnetocardiography (MCG) applications.« less

Free torsional vibrations of tapered cantilever I-beams

NASA Astrophysics Data System (ADS)

Rao, C. Kameswara; Mirza, S.

1988-08-01

Torsional vibration characteristics of linearly tapered cantilever I-beams have been studied by using the Galerkin finite element method. A third degree polynomial is assumed for the angle of twist. The analysis presented is valid for long beams and includes the effect of warping. The individual as well as combined effects of linear tapers in the width of the flanges and the depth of the web on the torsional vibration of cantilever I-beams are investigated. Numerical results generated for various values of taper ratios are presented in graphical form.

Monte Carlo simulation of a cesium atom beam in a magnetic field

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

Chen, Jiang, E-mail: chernjiang@aliyun.com; Zhu, Hongwei; Ma, Yinguang

2015-03-07

We present Monte Carlo simulations of the deflection of a beam of {sup 133}Cs atoms in a two wire magnetic field. Our results reveal the relationship between transmission rate of the atoms and incident parameters. Incident angle and position of the beam with maximum transmission are obtained from the simulations. The effect of the deflection field on the spatial distribution (beam profile) of {sup 133}Cs is derived. The method will help with the design of magnetic deflection experiments and to extract the magnetic properties from such experiments.

Beam wavefront and farfield control for ICF laser driver

NASA Astrophysics Data System (ADS)

Dai, Wanjun; Deng, Wu; Zhang, Xin; Jiang, Xuejun; Zhang, Kun; Zhou, Wei; Zhao, Junpu; Hu, Dongxia

2010-10-01

Five main problems of beam wavefront and farfield control in ICF laser driver are synthetically discussed, including control requirements, beam propagation principle, distortions source control, system design and adjustment optimization, active wavefront correction technology. We demonstrate that beam can be propagated well and the divergence angle of the TIL pulses can be improved to less than 60μrad with solving these problems, which meets the requirements of TIL. The results can provide theoretical and experimental support for wavefront and farfield control designing requirements of the next large scale ICF driver.

Trapped-Ion Quantum Simulation of an Ising Model with Transverse and Longitudinal Fields

DTIC Science & Technology

2013-03-29

resonant λ = 355 nm laser beams which drive stimulated Raman transitions [33, 34]. The beams intersect at right angles so that their wavevector difference...ated by a pair of Raman laser beams with a beatnote frequency of ωS , with the field amplitude determined by the beam intensities. The field directions...cool- ing, followed by optical pumping to the state |↓↓↓ ..〉z and 100 µs of Raman sideband cooling that prepares the motion of all modes along ∆~k in

SU-F-T-322: A Comparison of Two Si Detectors for in Vivo Dosimetry

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

Talarico, O; Krylova, T; Lebedenko, I

Purpose: To compare two types of semiconductor detectors for in vivo dosimetry by their dependence from various parameters in different conditions. Methods: QED yellow (Sun Nuclear) and EDP (Scanditronix) Si detectors were radiated by a Varian Clinac 2300 ix with 6 and 18 MV energies. 10 cm thickness water equivalent phantom consisted of 30×30 cm{sup 2} squared plates was used for experiments. Dose dependencies for different beam angles (0 – 180°), field size (3–40 cm), dose (50 – 300 MU), and dose rates (50 – 300 MU/min) were obtained and calibrated with Standard Farmer chamber (PTW). Results: Reproducibility, linearity, dosemore » rate, angular dependence, and field size dependence were obtained for QED and EDP. They show no dose-rate dependence in available clinical dose rate range (100–600 MU/min). Both diodes have linear dependence with increasing the dose. Therefore even in case of high radiation therapy (including total body irradiation) it is not necessary to apply an additional correction during in vivo dosimetry. The diodes have different behavior for angular and field size dependencies. QED diode showed that dose value is stable for beam angles from 0 to 60°, for 60–180° correction factor has to be applied for each beam angle during in vivo measurements. For EDP diode dose value is sensitive to beam angle in whole range of angles. Conclusion: The study shows that QED diode is more suitable for in vivo dosimetry due to dose value independence from incident beam angle in the range 0–60°. There is no need in correction factors for increasing of dose and dose rate for both diodes. The next step will be to carry out measurements in non-standard conditions of total body irradiation. After this modeling of these experiments with Monte Carlo simulation for comparison calculated and obtained data is planned.« less

Explaining negative refraction without negative refractive indices.

PubMed

Talalai, Gregory A; Garner, Timothy J; Weiss, Steven J

2018-03-01

Negative refraction through a triangular prism may be explained without assigning a negative refractive index to the prism by using array theory. For the case of a beam incident upon the wedge, the array theory accurately predicts the beam transmission angle through the prism and provides an estimate of the frequency interval at which negative refraction occurs. The hypotenuse of the prism has a staircase shape because it is built of cubic unit cells. The large phase delay imparted by each unit cell, combined with the staircase shape of the hypotenuse, creates the necessary conditions for negative refraction. Full-wave simulations using the finite-difference time-domain method show that array theory accurately predicts the beam transmission angle.

Providing solid angle formalism for skyshine calculations.

PubMed

Gossman, Michael S; Pahikkala, A Jussi; Rising, Mary B; McGinley, Patton H

2010-08-17

We detail, derive and correct the technical use of the solid angle variable identified in formal guidance that relates skyshine calculations to dose-equivalent rate. We further recommend it for use with all National Council on Radiation Protection and Measurements (NCRP), Institute of Physics and Engineering in Medicine (IPEM) and similar reports documented. In general, for beams of identical width which have different resulting areas, within ± 1.0 % maximum deviation the analytical pyramidal solution is 1.27 times greater than a misapplied analytical conical solution through all field sizes up to 40 × 40 cm². Therefore, we recommend determining the exact results with the analytical pyramidal solution for square beams and the analytical conical solution for circular beams.

Acoustic scattering of a Bessel vortex beam by a rigid fixed spheroid

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2015-12-01

Partial-wave series representation of the acoustic scattering field of high-order Bessel vortex beams by rigid oblate and prolate spheroids using the modal matching method is developed. The method, which is applicable to slightly elongated objects at low-to-moderate frequencies, requires solving a system of linear equations which depends on the partial-wave index n and the order of the Bessel vortex beam m using truncated partial-wave series expansions (PWSEs), and satisfying the Neumann boundary condition for a rigid immovable surface in the least-squares sense. This original semi-analytical approach developed for Bessel vortex beams is demonstrated for finite oblate and prolate spheroids, where the mathematical functions describing the spheroidal geometry are written in a form involving single angular (polar) integrals that are numerically computed. The transverse (θ = π / 2) and 3D scattering directivity patterns are evaluated in the far-field for both prolate and oblate spheroids, with particular emphasis on the aspect ratio (i.e., the ratio of the major axis over the minor axis of the spheroid) not exceeding 3:1, the half-cone angle β and order m of the Bessel vortex beam, as well as the dimensionless size parameter kr0. Periodic oscillations in the magnitude plots of the far-field scattering form function are observed, which result from the interference of the reflected waves with the circumferential (Franz') waves circumnavigating the surface of the spheroid in the surrounding fluid. Moreover, the 3D directivity patterns illustrate the far-field scattering from the spheroid, that vanishes in the forward (θ = 0) and backward (θ = π) directions. Particular applications in underwater acoustics and scattering, acoustic levitation and the detection of submerged elongated objects using Bessel vortex waves to name a few, would benefit from the results of the present investigation.

The effect of a finite focal spot size on location dependent detectability in a fan beam CT system

NASA Astrophysics Data System (ADS)

Kim, Byeongjoon; Baek, Jongduk

2017-03-01

A finite focal spot size is one of the sources to degrade the resolution performance in a fan beam CT system. In this work, we investigated the effect of the finite focal spot size on signal detectability. For the evaluation, five spherical objects with diameters of 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm were used. The optical focal spot size viewed at the iso-center was a 1 mm (height) × 1 mm (width) with a target angle of 7 degrees, corresponding to an 8.21 mm (i.e., 1 mm / sin (7°)) focal spot length. Simulated projection data were acquired using 8 × 8 source lets, and reconstructed by Hanning weighted filtered backprojection. For each spherical object, the detectability was calculated at (0 mm, 0 mm) and (0 mm, 200 mm) using two image quality metrics: pixel signal to noise ratio (SNR) and detection SNR. For all signal sizes, the pixel SNR is higher at the iso-center since the noise variance at the off-center is much higher than that at the iso-center due to the backprojection weightings used in direct fan beam reconstruction. In contrast, detection SNR shows similar values for different spherical objects except 1 mm and 2 mm diameter spherical objects. Overall, the results indicate the resolution loss caused by the finite focal spot size degrades the detection performance, especially for small objects with less than 2 mm diameter.

Behaviour of steel-concrete composite beams using bolts as shear connectors

NASA Astrophysics Data System (ADS)

Tran, Minh-Tung; Nguyen Van Do, Vuong; Nguyen, Tuan-Anh

2018-04-01

The paper presents an experimental program on the application of bolts as shear connectors for steel-composite beams. Four steel- concrete composite beams and a reference steel beam were made and tested. The aim of the testing program is to examine which forms of the steel bolts can be used effectively for steel-composite beams. The four types of the bolts include: Type 1 the bolt with the nut at the end; Type 2 the bolt bending at 900 hook; Type 3 the bolt without the nut at the end and Type 4 the bolt with the nut at the end but connected with the steel beam by hand welding in other to be connected with the steel beam by bolt connection as in the first three types. The test results showed that beside the traditional shear connectors like shear studs, angle type, channel type, bolts can be used effectively as the shear connectors in steel-composite beams and the application of bolts in Types 1 and 2 in the composite beams gave the better performance for the tested beam.

A prototype of a beam steering assistant tool for accelerator operations

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

M. Bickley; P. Chevtsov

2006-10-24

The CEBAF accelerator provides nuclear physics experiments at Jefferson Lab with high quality electron beams. Three experimental end stations can simultaneously receive the beams with different energies and intensities. For each operational mode, the accelerator setup procedures are complicated and require very careful checking of beam spot sizes and positions on multiple beam viewers. To simplify these procedures and make them reproducible, a beam steering assistant GUI tool has been created. The tool is implemented as a multi-window control screen. The screen has an interactive graphical object window, which is an overlay on top of a digitized live video imagemore » from a beam viewer. It allows a user to easily create and edit any graphical objects consisting of text, ellipses, and lines, right above the live beam viewer image and then save them in a file that is called a beam steering template. The template can show, for example, the area within which the beam must always be on the viewer. Later, this template can be loaded in the interactive graphical object window to help accelerator operators steer the beam to the specified area on the viewer.« less

Research notes : keeping steel bars anchored in cracked girders.

DOT National Transportation Integrated Search

2011-01-01

Researchers at Oregon State University fabricated large-size reinforced concrete beams each with an intentional crack made by positioning a plastic sheet in the formwork when the beams were cast. By maintaining control over crack location, crack angl...

Optima MDxt: A high throughput 335 keV mid-dose implanter

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

Eisner, Edward; David, Jonathan; Justesen, Perry

2012-11-06

The continuing demand for both energy purity and implant angle control along with high wafer throughput drove the development of the Axcelis Optima MDxt mid-dose ion implanter. The system utilizes electrostatic scanning, an electrostatic parallelizing lens and an electrostatic energy filter to produce energetically pure beams with high angular integrity. Based on field proven components, the Optima MDxt beamline architecture offers the high beam currents possible with singly charged species including arsenic at energies up to 335 keV as well as large currents from multiply charged species at energies extending over 1 MeV. Conversely, the excellent energy filtering capability allowsmore » high currents at low beam energies, since it is safe to utilize large deceleration ratios. This beamline is coupled with the >500 WPH capable endstation technology used on the Axcelis Optima XEx high energy ion implanter. The endstation includes in-situ angle measurements of the beam in order to maintain excellent beam-to-wafer implant angle control in both the horizontal and vertical directions. The Optima platform control system provides new generation dose control system that assures excellent dosimetry and charge control. This paper will describe the features and technologies that allow the Optima MDxt to provide superior process performance at the highest wafer throughput, and will provide examples of the process performance achievable.« less

FusionArc optimization: a hybrid volumetric modulated arc therapy (VMAT) and intensity modulated radiation therapy (IMRT) planning strategy.

PubMed

Matuszak, Martha M; Steers, Jennifer M; Long, Troy; McShan, Daniel L; Fraass, Benedick A; Romeijn, H Edwin; Ten Haken, Randall K

2013-07-01

To introduce a hybrid volumetric modulated arc therapy/intensity modulated radiation therapy (VMAT/IMRT) optimization strategy called FusionArc that combines the delivery efficiency of single-arc VMAT with the potentially desirable intensity modulation possible with IMRT. A beamlet-based inverse planning system was enhanced to combine the advantages of VMAT and IMRT into one comprehensive technique. In the hybrid strategy, baseline single-arc VMAT plans are optimized and then the current cost function gradients with respect to the beamlets are used to define a metric for predicting which beam angles would benefit from further intensity modulation. Beams with the highest metric values (called the gradient factor) are converted from VMAT apertures to IMRT fluence, and the optimization proceeds with the mixed variable set until convergence or until additional beams are selected for conversion. One phantom and two clinical cases were used to validate the gradient factor and characterize the FusionArc strategy. Comparisons were made between standard IMRT, single-arc VMAT, and FusionArc plans with one to five IMRT∕hybrid beams. The gradient factor was found to be highly predictive of the VMAT angles that would benefit plan quality the most from beam modulation. Over the three cases studied, a FusionArc plan with three converted beams achieved superior dosimetric quality with reductions in final cost ranging from 26.4% to 48.1% compared to single-arc VMAT. Additionally, the three beam FusionArc plans required 22.4%-43.7% fewer MU∕Gy than a seven beam IMRT plan. While the FusionArc plans with five converted beams offer larger reductions in final cost--32.9%-55.2% compared to single-arc VMAT--the decrease in MU∕Gy compared to IMRT was noticeably smaller at 12.2%-18.5%, when compared to IMRT. A hybrid VMAT∕IMRT strategy was implemented to find a high quality compromise between gantry-angle and intensity-based degrees of freedom. This optimization method will allow patients to be simultaneously planned for dosimetric quality and delivery efficiency without switching between delivery techniques. Example phantom and clinical cases suggest that the conversion of only three VMAT segments to modulated beams may result in a good combination of quality and efficiency.

Influence of thermal deformation in cavity mirrors on beam propagation characteristics of high-power slab lasers

NASA Astrophysics Data System (ADS)

Wang, Zhen; Xiao, Longsheng; Wang, Wei; Wu, Chao; Tang, Xiahui

2018-01-01

Owing to their good diffusion cooling and low sensitivity to misalignment, slab-shape negative-branch unstable-waveguide resonators are widely used for high-power lasers in industry. As the output beam of the resonator is astigmatic, an external beam shaping system is required. However, the transverse dimension of the cavity mirrors in the resonator is large. For a long-time operation, the heating of cavity mirrors can be non-uniform. This results in micro-deformation and a change in the radius of curvature of the cavity mirrors, and leads to an output beam of an offset optical axis of the resonator. It was found that a change in the radius of curvature of 0.1% (1 mm) caused by thermal deformation generates a transverse displacement of 1.65 mm at the spatial filter of the external beam shaping system, and an output power loss of more than 80%. This can potentially burn out the spatial filter. In order to analyze the effect of the offset optical axis of the beam on the external optical path, we analyzed the transverse displacement and rotational misalignments of the spatial filter. For instance, if the transverse displacement was 0.3 mm, the loss in the output power was 9.6% and a sidelobe appeared in the unstable direction. If the angle of rotation was 5°, the loss in the output power was 2%, and the poles were in the direction of the waveguide. Based on these results, by adjusting the bending mirror, the deviation angle of the output beam of the resonator cavity was corrected, in order to obtain maximum output power and optimal beam quality. Finally, the propagation characteristics of the corrected output beam were analyzed.

Diffraction-Based Optical Switch

NASA Technical Reports Server (NTRS)

Sperno, Stevan M. (Inventor); Fuhr, Peter L. (Inventor); Schipper, John F. (Inventor)

2005-01-01

Method and system for controllably redirecting a light beam, having a central wavelength lambda, from a first light-receiving site to a second light-receiving site. A diffraction grating is attached to or part of a piezoelectric substrate, which is connected to one or two controllable voltage difference sources. When a substrate voltage difference is changed and the diffraction grating length in each of one or two directions is thereby changed, at least one of the diffraction angle, the diffraction order and the central wavelength is controllably changed. A diffracted light beam component, having a given wavelength, diffraction angle and diffraction order, that is initially received at a first light receiving site (e.g., a detector or optical fiber) is thereby controllably shifted or altered and can be received at a second light receiving site. A polynomially stepped, chirped grating is used in one embodiment. In another embodiment, an incident light beam, having at least one of first and second wavelengths, lambda1 and lambda2, is received and diffracted at a first diffraction grating to provide a first diffracted beam. The first diffracted beam is received and diffracted at a second diffraction grating to produce a second diffracted beam. The second diffracted beam is received at a light-sensitive transducer, having at least first and second spaced apart light detector elements that are positioned so that, when the incident light beam has wavelength lambda1 or lambda2 (lambda1 not equal to lambda2), the second diffracted beam is received at the first element or at the second element, respectively; change in a selected physical parameter at the second grating can also be sensed or measured. A sequence of spaced apart light detector elements can be positioned along a linear or curvilinear segment with equal or unequal spacing.

Extraction of the photon beam asymmetry Sigma in pi 0 photoproduction off the proton using the CBELSA/TAPS experiment

NASA Astrophysics Data System (ADS)

Sparks, Nathan Andrew

The CBELSA/TAPS experiment at the electron accelerator ELSA, in Bonn, Germany, was used in order to study the photoproduction of neutral pions off the proton with a linearly polarized photon beam; Neutral pions were reconstructed through their dominant decay mode into two photons. The photons were detected in a barrel/forward electromagnetic calorimeter system which covered 99% of the 4pi solid angle. The Crystal Barrel CsI(Tl) calorimeter detected photons at polar angles from 30° to 168°, while TAPS, a BaF2 spectrometer, covered forward polar angles from 5.8° to 30° and served as a fast trigger; Both calorimeters had complete azimuthal angular coverage. Coherent bremsstrahlung of electrons in a diamond radiator was used to produce a linearly polarized beam of photons with a coherent peak at 1305 or 1610 MeV. The analysis of these two datasets allowed for the measurement of the photon beam asymmetry in the beam photon energy range of 920 to 1680 MeV. For the first time, these results cover the very forward polar angles of the neutral pion. The measurements are compared to the SAID, MAID, and BnGa models and to previous measurements. These new measurements of the photon beam asymmetry contribute to the ongoing experimentally-driven exploration of the N and Delta resonances. The study of strange baryons provides a link between the strong interaction physics of the excited nucleons and the heavy flavor baryons. The upcoming GlueX experiment at Jefferson Lab is expected to provide an opportunity to examine strange baryons in much greater detail than ever before. GEANT-based Monte Carlo simulations of Cascade baryons at the GlueX experiment were conducted in order to better understand the capabilities of this experiment. A proposal, "An initial study of mesons and baryons containing strange quarks with GlueX", was submitted to the 40th Jefferson Lab Program Advisory Committee (PAC), in part, supported by these Cascade baryon simulations. 200 days of additional beam time were approved, with the proposal receiving an A scientific rating.

Achievement of Runaway Electron Energy Dissipation by High-Z Gas Injection in DIII-D

NASA Astrophysics Data System (ADS)

Hollmann, E. M.

2014-10-01

Disruption runaway electron (RE) formation followed by RE beam-wall strikes is a concern for future tokamaks, motivating the study of mitigation techniques to reduce the RE beam energy in a controlled manner. A promising approach for doing this is the injection of high-Z gas into the RE beam. Massive (100 torr-l) injection of high-Z gas into RE beams in DIII-D is shown to significantly dissipate both RE magnetic and kinetic energy. For example, injection of argon into a typical 300 kA current RE beam is observed to cause a drop in kinetic energy from 50 kJ to 10 kJ in 10 ms, thus rapidly reducing the damage-causing capability of the RE beam. Both the RE kinetic energy and pitch angle are important for determining the resulting wall damage, with high energy, high pitch angle electrons typically considered most dangerous. The RE energy distribution is found to be more skewed toward low energies than predicted by avalanche theory. The pitch angle is not found to be constant, as is frequently assumed, but is shown to drop from sin(θ) ~ 1 for energies less than 1 MeV to sin(θ) ~ 0 . 2 for energies greater than 10 MeV. Injection of high-Z impurities does not appear to change the overall shape of the energy or pitch angle distributions dramatically. The enhanced RE energy dissipation appears to be caused primarily via collisions with the cold plasma leading to line radiation. Synchrotron power loss only becomes significant in the absence of high-Z impurities, while radial transport loss of REs is seen to become dominant if the RE beam moves sufficiently close to the vessel walls. The experiments demonstrate that avalanche theory somewhat underestimates collisional dissipation of REs in the presence of high-Z atoms, even in the absence of radial transport losses, meaning that reducing RE wall damage in large tokamaks should be easier than previously expected. Supported by the US Department of Energy under DE-FG02-07ER54917 and DE-FC02-04ER54698.

Simulator scene display evaluation device

NASA Technical Reports Server (NTRS)

Haines, R. F. (Inventor)

1986-01-01

An apparatus for aligning and calibrating scene displays in an aircraft simulator has a base on which all of the instruments for the aligning and calibrating are mounted. Laser directs beam at double right prism which is attached to pivoting support on base. The pivot point of the prism is located at the design eye point (DEP) of simulator during the aligning and calibrating. The objective lens in the base is movable on a track to follow the laser beam at different angles within the field of vision at the DEP. An eyepiece and a precision diopter are movable into a position behind the prism during the scene evaluation. A photometer or illuminometer is pivotable about the pivot into and out of position behind the eyepiece.

Omni-Directional Viewing-Angle Switching through Control of the Beam Divergence Angle in a Liquid Crystal Panel

NASA Astrophysics Data System (ADS)

Baek, Jong-In; Kim, Ki-Han; Kim, Jae Chang; Yoon, Tae-Hoon

2010-01-01

This paper proposes a method of omni-directional viewing-angle switching by controlling the beam diverging angle (BDA) in a liquid crystal (LC) panel. The LCs aligned randomly by in-cell polymer structures diffuse the collimated backlight for the bright state of the wide viewing-angle mode. We align the LCs homogeneously by applying an in-plane field for the narrow viewing-angle mode. By doing this the scattering is significantly reduced so that the small BDA is maintained as it passes through the LC layer. The dark state can be obtained by aligning the LCs homeotropically with a vertical electric field. We demonstrated experimentally the omni-directional switching of the viewing-angle, without an additional panel or backlighting system.

Optical transition radiation used in the diagnostic of low energy and low current electron beams in particle accelerators.

PubMed

Silva, T F; Bonini, A L; Lima, R R; Maidana, N L; Malafronte, A A; Pascholati, P R; Vanin, V R; Martins, M N

2012-09-01

Optical transition radiation (OTR) plays an important role in beam diagnostics for high energy particle accelerators. Its linear intensity with beam current is a great advantage as compared to fluorescent screens, which are subject to saturation. Moreover, the measurement of the angular distribution of the emitted radiation enables the determination of many beam parameters in a single observation point. However, few works deals with the application of OTR to monitor low energy beams. In this work we describe the design of an OTR based beam monitor used to measure the transverse beam charge distribution of the 1.9-MeV electron beam of the linac injector of the IFUSP microtron using a standard vision machine camera. The average beam current in pulsed operation mode is of the order of tens of nano-Amps. Low energy and low beam current make OTR observation difficult. To improve sensitivity, the beam incidence angle on the target was chosen to maximize the photon flux in the camera field-of-view. Measurements that assess OTR observation (linearity with beam current, polarization, and spectrum shape) are presented, as well as a typical 1.9-MeV electron beam charge distribution obtained from OTR. Some aspects of emittance measurement using this device are also discussed.

Non-periodic high-index contrast gratings reflector with large-angle beam forming ability

NASA Astrophysics Data System (ADS)

Fang, Wenjing; Huang, Yongqing; Duan, Xiaofeng; Fei, Jiarui; Ren, Xiaomin; Mao, Min

2016-05-01

A non-periodic high-index contrast gratings (HCGs) reflector on SOI wafer with large-angle beam forming ability has been proposed and fabricated. The proposed reflector was designed using rigorous coupled-wave analysis (RCWA) and finite-element-method (FEM). A deflection angle of 17.35° and high reflectivity of 92.31% are achieved under transverse magnetic (TM) polarized light in numerical simulation. Experimental results show that the reflected power peaked at 17.2° under a 1550 nm incident light, which is in good accordance with the simulation results. Moreover, the reflected power spectrum was also measured. Under different incident wavelengths around 1550 nm, reflected powers all peaked at 17.2°. The results show that the proposed non-periodic HCGs reflector has a good reflection and beam forming ability in a wavelength range as wide as 40 nm around 1550 nm.

Grating angle magnification enhanced angular sensor and scanner

NASA Technical Reports Server (NTRS)

Sun, Ke-Xun (Inventor); Byer, Robert L. (Inventor)

2009-01-01

An angular magnification effect of diffraction is exploited to provide improved sensing and scanning. This effect is most pronounced for a normal or near-normal incidence angle in combination with a grazing diffraction angle, so such configurations are preferred. Angular sensitivity can be further enhanced because the width of the diffracted beam can be substantially less than the width of the incident beam. Normal incidence configurations with two symmetric diffracted beams are preferred, since rotation and vertical displacement can be readily distinguished. Increased sensitivity to vertical displacement can be provided by incorporating an interferometer into the measurement system. Quad cell detectors can be employed to provide sensitivity to rotation about the grating surface normal. A 2-D grating can be employed to provide sensitivity to angular displacements in two different planes (e.g., pitch and yaw). Combined systems can provide sensitivity to vertical displacement and to all three angular degrees of freedom.

Instrument Design Optimization With Computational Methods

NASA Astrophysics Data System (ADS)

Moore, Michael H.

Using Finite Element Analysis to approximate the solution of differential equations, two different instruments in experimental Hall C at the Thomas Jefferson National Accelerator Facility are analyzed. The time dependence of density fluctuations from the liquid hydrogen (LH2) target used in the Qweak experiment (2011-2012) are studied with Computational Fluid Dynamics (CFD) and the simulation results compared to data from the experiment. The 2.5 kW liquid hydrogen target was the highest power LH2 target in the world and the first to be designed with CFD at Jefferson Lab. The first complete magnetic field simulation of the Super High Momentum Spectrometer (SHMS) is presented with a focus on primary electron beam deflection downstream of the target. The SHMS consists of a superconducting horizontal bending magnet (HB) and three superconducting quadrupole magnets. The HB allows particles scattered at an angle of 5.5° to the beam line to be steered into the quadrupole magnets which make up the optics of the spectrometer. Without mitigation, remnant fields from the SHMS may steer the unscattered beam outside of the acceptable envelope on the beam dump and limit beam operations at small scattering angles. A solution is proposed using optimal placement of a minimal amount of shielding iron around the beam line.

Ultrasound beam steering of oxygen nanobubbles for enhanced bladder cancer therapy.

PubMed

Bhandari, Pushpak; Novikova, Gloriia; Goergen, Craig J; Irudayaraj, Joseph

2018-02-15

New intravesical treatment approaches for bladder cancer are needed as currently approved treatments show several side effects and high tumor recurrence rate. Our study used MB49 murine urothelial carcinoma model to evaluate oxygen encapsulated cellulosic nanobubbles as a novel agent for imaging and ultrasound guided drug delivery. In this study, we show that oxygen nanobubbles (ONB) can be propelled (up to 40 mm/s) and precisely guided in vivo to the tumor by an ultrasound beam. Nanobubble velocity can be controlled by altering the power of the ultrasound Doppler beam, while nanobubble direction can be adjusted to different desired angles by altering the angle of the beam. Precise ultrasound beam steering of oxygen nanobubbles was shown to enhance the efficacy of mitomycin-C, resulting in significantly lower tumor progression rates while using a 50% lower concentration of chemotherapeutic drug. Further, dark field imaging was utilized to visualize and quantify the ONB ex vivo. ONBs were found to localize up to 500 µm inside the tumor using beam steering. These results demonstrate the potential of an oxygen nanobubble drug encapsulated system to become a promising strategy for targeted drug delivery because of its multimodal (imaging and oxygen delivery) and multifunctional (targeting and hypoxia programming) properties.

Instrument design optimization with computational methods

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

Moore, Michael H.

Using Finite Element Analysis to approximate the solution of differential equations, two different instruments in experimental Hall C at the Thomas Jefferson National Accelerator Facility are analyzed. The time dependence of density uctuations from the liquid hydrogen (LH2) target used in the Q weak experiment (2011-2012) are studied with Computational Fluid Dynamics (CFD) and the simulation results compared to data from the experiment. The 2.5 kW liquid hydrogen target was the highest power LH2 target in the world and the first to be designed with CFD at Jefferson Lab. The first complete magnetic field simulation of the Super High Momentummore » Spectrometer (SHMS) is presented with a focus on primary electron beam deflection downstream of the target. The SHMS consists of a superconducting horizontal bending magnet (HB) and three superconducting quadrupole magnets. The HB allows particles scattered at an angle of 5:5 deg to the beam line to be steered into the quadrupole magnets which make up the optics of the spectrometer. Without mitigation, remnant fields from the SHMS may steer the unscattered beam outside of the acceptable envelope on the beam dump and limit beam operations at small scattering angles. A solution is proposed using optimal placement of a minimal amount of shielding iron around the beam line.« less

Laser Induced Breakdown Spectroscopy Based on Single Beam Splitting and Geometric Configuration for Effective Signal Enhancement

PubMed Central

Yang, Guang; Lin, Qingyu; Ding, Yu; Tian, Di; Duan, Yixiang

2015-01-01

A new laser induced breakdown spectroscopy (LIBS) based on single-beam-splitting (SBS) and proper optical geometric configuration has been initially explored in this work for effective signal enhancement. In order to improve the interaction efficiency of laser energy with the ablated material, a laser beam operated in pulse mode was divided into two streams to ablate/excite the target sample in different directions instead of the conventional one beam excitation in single pulse LIBS (SP-LIBS). In spatial configuration, the laser beam geometry plays an important role in the emission signal enhancement. Thus, an adjustable geometric configuration with variable incident angle between the two splitted laser beams was constructed for achieving maximum signal enhancement. With the optimized angles of 60° and 70° for Al and Cu atomic emission lines at 396.15 nm and 324.75 nm respectively, about 5.6- and 4.8-folds signal enhancements were achieved for aluminum alloy and copper alloy samples compared to SP-LIBS. Furthermore, the temporal analysis, in which the intensity of atomic lines in SP-LIBS decayed at least ten times faster than the SBS-LIBS, proved that the energy coupling efficiency of SBS-LIBS was significantly higher than that of SP-LIBS. PMID:25557721

Light scattering of a Bessel beam by a nucleated biological cell: An eccentric sphere model

NASA Astrophysics Data System (ADS)

Wang, Jia Jie; Han, Yi Ping; Chang, Jiao Yong; Chen, Zhu Yang

2018-02-01

Within the framework of generalized Lorenz-Mie theory (GLMT), an eccentrically stratified dielectric sphere model illuminated by an arbitrarily incident Bessel beam is applied to investigate the scattering characteristics of a single nucleated biological cell. The Bessel beam propagating in an arbitrary direction is expanded in terms of vector spherical wave functions (VSWFs), where the beam shape coefficients (BSCs) are calculated rigorously in a closed analytical form. The effects of the half-cone angle of Bessel beam, the location of the particle in the beam, the size ratio of nucleus to cell, and the location of the nucleus inside the cell on the scattering properties of a nucleated cell are analyzed. The results provide useful references for optical diagnostic and imaging of particle having nucleated structure.

Characterizing the propagation evolution of wave patterns and vortex structures in astigmatic transformations of Hermite-Gaussian beams

NASA Astrophysics Data System (ADS)

Chen, Y. F.; Chang, C. C.; Lee, C. Y.; Tung, J. C.; Liang, H. C.; Huang, K. F.

2018-01-01

Theoretical wave functions are analytically derived to characterize the propagation evolution of the Hermite-Gaussian (HG) beams transformed by a single-lens astigmatic mode converter with arbitrary angle. The derived wave functions are related to the combination of the rotation transform and the antisymmetric fractional Fourier transform. The derived formula is systematically validated by using an off-axis diode-pumped solid-state laser to generate various high-order HG beams for mode conversions. In addition to validation, the creation and evolution of vortex structures in the transformed HG beams are numerically manifested. The present theoretical analyses can be used not only to characterize the evolution of the transformed beams but to design the optical vortex beams with various forms.

Direction-dependent waist-shift-difference of Gaussian beam in a multiple-pass zigzag slab amplifier and geometrical optics compensation method.

PubMed

Li, Zhaoyang; Kurita, Takashi; Miyanaga, Noriaki

2017-10-20

Zigzag and non-zigzag beam waist shifts in a multiple-pass zigzag slab amplifier are investigated based on the propagation of a Gaussian beam. Different incident angles in the zigzag and non-zigzag planes would introduce a direction-dependent waist-shift-difference, which distorts the beam quality in both the near- and far-fields. The theoretical model and analytical expressions of this phenomenon are presented, and intensity distributions in the two orthogonal planes are simulated and compared. A geometrical optics compensation method by a beam with 90° rotation is proposed, which not only could correct the direction-dependent waist-shift-difference but also possibly average the traditional thermally induced wavefront-distortion-difference between the horizontal and vertical beam directions.

Interferometer. [high resolution

NASA Technical Reports Server (NTRS)

Breckinridge, J. B.; Norton, R. H.; Schindler, R. A. (Inventor)

1981-01-01

A high resolution interferometer is described. The interferometer is insensitive to slight misalignment of its elements, avoids channeling in the spectrum, generates a maximum equal path fringe contrast, produces an even two sided interferogram without critical matching of the wedge angles of the beamsplitter and compensator wedges, and is optically phase tunable. The interferometer includes a mirror along the path of each beam component produced by the beamsplitter, for reflecting the beam component from the beamsplitter, for reflecting the beam component from the beamsplitter to a corresponding retroreflector and for reflecting the beam returned by the retroreflector back to the beamsplitter. A wedge located along each beam component path, is large enough to cover the retroreflector, so that each beam component passes through the wedge during movement towards the retroreflector and away therefrom.

A simulation of temperature influence on echolocation click beams of the Indo-Pacific humpback dolphin (Sousa chinensis).

PubMed

Song, Zhongchang; Zhang, Yu; Wang, Xianyan; Wei, Chong

2017-10-01

A finite element method was used to investigate the temperature influence on sound beams of the Indo-Pacific humpback dolphin. The numerical models of a dolphin, which originated from previous computed tomography (CT) scanning and physical measurement results, were used to investigate sound beam patterns of the dolphin in temperatures from 21 °C to 39 °C, in increments of 2 °C. The -3 dB beam widths across the temperatures ranged from 9.3° to 12.6°, and main beam angle ranged from 4.7° to 7.2° for these temperatures. The subsequent simulation suggested that the dolphin's sound beam patterns, side lobes in particular, were influenced by temperature.

Design of multiple-ply laminated composite tapered beams

NASA Technical Reports Server (NTRS)

Rodriguez, P.

1993-01-01

A study of a special case of symmetric laminated composite cantilever beams is presented. The approach models beams that are tapered both in depth and width and investigates the effect of the ply layup angle and the ply taper on bending and interlaminar shearing stresses. For the determination of stresses and deflections, the beam stiffness matrices are expressed as linear functions of the beam length. Using classical lamination theory (CLT) the stiffness matrices are determined and assembled at strategic locations along the length of the beam. They are then inverted and necessary stiffness parameters are obtained numerically and extracted for determination of design information at each location chosen. Several ply layup configurations are investigated, and design considerations are presented based on the findings. Finally, recommendations for the design of these beams are presented, and a means for anticipating the location of highest stresses is offered.

Design of multiple-ply laminated composite tapered beams

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

Rodriguez, P.

1993-06-01

A study of a special case of symmetric laminated composite cantilever beams is presented. The approach models beams that are tapered both in depth and width and investigates the effect of the ply layup angle and the ply taper on bending and interlaminar shearing stresses. For the determination of stresses and deflections, the beam stiffness matrices are expressed as linear functions of the beam length. Using classical lamination theory (CLT) the stiffness matrices are determined and assembled at strategic locations along the length of the beam. They are then inverted and necessary stiffness parameters are obtained numerically and extracted formore » determination of design information at each location chosen. Several ply layup configurations are investigated, and design considerations are preSDsented based on the findings. Finally, recommendations for the design of these beams are presented, and a means for anticipating the location of highest stresses is offered.« less

Linear Stability and Instability Patterns in Ion Bombarded Silicon Surfaces

NASA Astrophysics Data System (ADS)

Madi, Charbel Said

2011-12-01

This thesis is a combined experimental and theoretical study of the fundamental physical mechanisms governing nanoscale surface morphology evolution of Ar + ion bombarded silicon surfaces. I experimentally determined the topographical phase diagram resulting from Ar+ ion irradiation of Si surfaces at room temperature in the linear regime of surface dynamics as we vary the control parameters ion beam energy and incidence angle. At all energies, it is characterized by a diverging wavelength bifurcation from a smooth stable surface to parallel mode ripples (wavevector parallel to the projected ion beam on the surface) as the ion beam incidence angle is varied. At sufficiently high angles theta ≈ 85°, I observed perpendicular mode ripples (wavevector perpendicular to the ion beam). Through real-time Grazing-Incidence Small Angle X-ray Scattering, I have definitively established that ion-induced erosion, which is the consensus predominant cause of pattern formation, is not only of the wrong sign to explain the measured curvature coefficients responsible in driving the surface dynamics, but also is so small in magnitude as to be essentially negligible for pattern formation except possibly at the most grazing angles of incidence where both erosion and redistribution effects converge to zero. That the contribution of ion impact induced prompt atomic redistribution effects entirely overwhelms that of erosion in both the stabilizing and destabilizing regimes is of profound significance, as it overturns the erosion-based paradigm that has dominated the pattern formation field for over two decades. In situ wafer curvature measurements using the Multi-beam Optical Stress Sensor system were performed during amorphization of silicon by normal incidence 250 eV ion irradiation. An average compressive saturation stress built up in the amorphous layer was found to be as large as 1.5 GPa. By assuming the ion-induced amorphization layer to be modeled as a viscoelastic film that is anisotropically stressed by ion beam irradiation, we measure the deformation imparted per ion due to anisotropic deformation to be equal to A =1.15x10-16 cm2/ion. Although compressive stress is being injected into a thin viscoelastic ion-stimulated surface layer, the surface is unconditionally stable to topographic perturbations, corroborating the measured experimental phase diagram.

A novel verification method using a plastic scintillator imagining system for assessment of gantry sag in radiotherapy.

PubMed

Tsuneda, Masato; Nishio, Teiji; Saito, Akito; Tanaka, Sodai; Suzuki, Tatsuhiko; Kawahara, Daisuke; Matsushita, Keiichiro; Nishio, Aya; Ozawa, Shuichi; Karasawa, Kumiko; Nagata, Yasushi

2018-06-01

High accuracy of the beam-irradiated position is required for high-precision radiation therapy such as stereotactic body radiation therapy (SBRT), volumetric modulated arc therapy (VMAT), and intensity modulated radiation therapy (IMRT). Users generally perform the verification of the mechanical and radiation isocenters using the star shot test and the Winston Lutz test that allow evaluation of the displacement at the isocenter. However, these methods are unable to evaluate directly and quantitatively the sagging angle that is caused by the weight of the gantry itself along the gantry rotation axis. In addition, the verification of the central axis of the irradiated beam that is not dependent at the isocenter is needed for the mechanical quality assurance of a nonisocentric irradiation technique. In this study, we have developed a prototype system for the verification of three-dimensional (3D) beam alignment and we have verified the system concept for 3D isocentricity. Our system allows detection of the central axis in 3D coordinates and evaluation of the irradiated oblique angle to the gantry rotation axis, i.e., the sagging angle. In order to measure the central axis of the irradiated beam in 3D coordinates, we constructed the prototype verification system consisting of a column-shaped plastic scintillator (CoPS), a truncated cone-shaped mirror (TCsM), and a cooled charged-coupled device (CCD) camera. This verification system was irradiated with 6-MV photon beams and the scintillation light was measured using the CCD camera. The central axis on the axial plane (two-dimensional (2D) central axis) was acquired from the integration of the scintillation light along the major axis of the CoPS, and the central axis in 3D coordinates (3D central axis) was acquired from two curve-shaped profiles which were reflected by the TCsM. We verified the calculation accuracy of the gantry rotation axis, θ z . Additionally, we calculated the 3D central axis and the sagging angle at each gantry angle. We acquired the measurement images composed of the 2D central axis and the two curve-shaped profiles. The relationship between the irradiated and measured angles with respect to the gantry rotation axis had good linearity. The mean and standard deviation of the difference between the irradiated and measured angles were 0.012 and 0.078 degrees, respectively. The size of the 2D and 3D radiation isocenters were 0.470 and 0.652 mm on the axial plane and in 3D coordinates, respectively. The sagging angles were -0.31, 0.39, and 0.38 degrees at the gantry angles of 0, 180, and 180E degrees, respectively. We developed a novel verification system, designated as the "kompeito shot test system," to verify the 3D beam alignment. This system concept works for both verification of the 3D isocentricity and the direct evaluation of the sagging angle. Next, we want to improve the aspects of this system, such as the shape and the type of scintillator, to increase the system accuracy and nonisocentric beam alignment performance. © 2018 American Association of Physicists in Medicine.

Influence of eye size and beam entry angle on dose to non-targeted tissues of the eye during stereotactic x-ray radiosurgery of AMD

NASA Astrophysics Data System (ADS)

Cantley, Justin L.; Hanlon, Justin; Chell, Erik; Lee, Choonsik; Smith, W. Clay; Bolch, Wesley E.

2013-10-01

Age-related macular degeneration is a leading cause of vision loss for the elderly population of industrialized nations. The IRay® Radiotherapy System, developed by Oraya® Therapeutics, Inc., is a stereotactic low-voltage irradiation system designed to treat the wet form of the disease. The IRay System uses three robotically positioned 100 kVp collimated photon beams to deliver an absorbed dose of up to 24 Gy to the macula. The present study uses the Monte Carlo radiation transport code MCNPX to assess absorbed dose to six non-targeted tissues within the eye—total lens, radiosensitive tissues of the lens, optic nerve, distal tip of the central retinal artery, non-targeted portion of the retina, and the ciliary body--all as a function of eye size and beam entry angle. The ocular axial length was ranged from 20 to 28 mm in 2 mm increments, with the polar entry angle of the delivery system varied from 18° to 34° in 2° increments. The resulting data showed insignificant variations in dose for all eye sizes. Slight variations in the dose to the optic nerve and the distal tip of the central retinal artery were noted as the polar beam angle changed. An increase in non-targeted retinal dose was noted as the entry angle increased, while the dose to the lens, sensitive volume of the lens, and ciliary body decreased as the treatment polar angle increased. Polar angles of 26° or greater resulted in no portion of the sensitive volume of the lens receiving an absorbed dose of 0.5 Gy or greater. All doses to non-targeted structures reported in this study were less than accepted thresholds for post-procedure complications.

High-speed volume measurement system and method

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

Lane, Michael H.; Doyle, Jr., James L.; Brinkman, Michael J.

2017-12-12

Disclosed is a volume sensor having first, second, and third laser sources emitting first, second, and third laser beams; first, second, and third beam splitters splitting the first, second, and third laser beams into first, second, and third beam pairs; first, second, and third optical assemblies expanding the first, second, and third beam pairs into first, second, and third pairs of parallel beam sheets; fourth, fifth, and sixth optical assemblies focusing the first, second, and third beam sheet pairs into fourth, fifth, and sixth beam pairs; and first, second, and third detector pairs receiving the fourth, fifth, and sixth beammore » pairs and converting a change in intensity of at least one of the beam pairs resulting from an object passing through at least one of the first, second, and third parallel beam sheets into at least one electrical signal proportional to a three-dimensional representation of the object.« less

Dynamics of a high-current relativistic electron beam

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

Strelkov, P. S., E-mail: strelkov@fpl.gpi.ru; Tarakanov, V. P., E-mail: karat@gmail.ru; Ivanov, I. E., E-mail: iei@fpl.gpi.ru

2015-06-15

The dynamics of a high-current relativistic electron beam is studied experimentally and by numerical simulation. The beam is formed in a magnetically insulated diode with a transverse-blade explosive-emission cathode. It is found experimentally that the radius of a 500-keV beam with a current of 2 kA and duration of 500 ns decreases with time during the beam current pulse. The same effect was observed in numerical simulations. This effect is explained by a change in the shape of the cathode plasma during the current pulse, which, according to calculations, leads to a change in the beam parameters, such as themore » electron pitch angle and the spread over the longitudinal electron momentum. These parameters are hard to measure experimentally; however, the time evolution of the radial profile of the beam current density, which can be measured reliably, coincides with the simulation results. This allows one to expect that the behavior of the other beam parameters also agrees with numerical simulations.« less

Scaling effects in the impact response of graphite-epoxy composite beams

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Fasanella, Edwin L.

1989-01-01

In support of crashworthiness studies on composite airframes and substructure, an experimental and analytical study was conducted to characterize size effects in the large deflection response of scale model graphite-epoxy beams subjected to impact. Scale model beams of 1/2, 2/3, 3/4, 5/6, and full scale were constructed of four different laminate stacking sequences including unidirectional, angle ply, cross ply, and quasi-isotropic. The beam specimens were subjected to eccentric axial impact loads which were scaled to provide homologous beam responses. Comparisons of the load and strain time histories between the scale model beams and the prototype should verify the scale law and demonstrate the use of scale model testing for determining impact behavior of composite structures. The nonlinear structural analysis finite element program DYCAST (DYnamic Crash Analysis of STructures) was used to model the beam response. DYCAST analysis predictions of beam strain response are compared to experimental data and the results are presented.

Raman signal enhancement by multiple beam excitation and its application for the detection of chemicals

NASA Astrophysics Data System (ADS)

Gupta, Sakshi; Ahmad, Azeem; Gambhir, Vijayeta; Reddy, Martha N.; Mehta, Dalip S.

2015-08-01

In a typical Raman based sensor, a single laser beam is used for exciting the sample and the backscattered or forward scattered light is collected using collection optics and is analyzed by a spectrometer. We have investigated that by means of exciting the sample with multiple beams, i.e., by dividing the same input power of the single beam into two or three or more beams and exciting the sample from different angles, the Raman signal enhances significantly. Due to the presence of multiple beams passing through the same volume of the sample, an interference pattern is formed and the volume of interaction of excitation beams with the sample increases. By means of this geometry, the enhancement in the Raman signal is observed and it was found that the signal strength increases linearly with the increase in number of excitation beams. Experimental results of this scheme for excitation of the samples are reported for explosive detection at a standoff distance.

Uniformity analysis for a direct-drive laser fusion reactor

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

Lund, L.D.; Skupsky, S.; Goldman, L.M.

1983-01-01

We show the results of an analysis of the uniformity for a direct-drive reactor using 20, 32, 60, or 96 beams. Several of these options achieve less than the 1% nonuniformity that is required. These options are considered for the cases where the solid angle fraction of the beam ports is 2% and 8%. The analysis is facilitated by separating the contributions due to the geometrical effects related to the number and orientation of the beams from those due to the spatial profile of the individual beams. Emphasis is placed on the wavelength of the nonuniformities, as the shorter wavelengthmore » nonuniformities are more easily smoothed by thermal conduction within the target. The analysis demonstrates that the longer wavelengths can be minimized by suitable choices of geometry and by maintaining beam balance, whereas the shorter wavelength nonuniformities can be reduced by optimizing parameters such as the focal position and the spatial intensity profile of each beam. The tolerances required for beam-to-beam energy balance will be discussed.« less

Electron gun for a multiple beam klystron with magnetic compression of the electron beams

DOEpatents

Ives, R. Lawrence; Tran, Hien T; Bui, Thuc; Attarian, Adam; Tallis, William; David, John; Forstall, Virginia; Andujar, Cynthia; Blach, Noah T; Brown, David B; Gadson, Sean E; Kiley, Erin M; Read, Michael

2013-10-01

A multi-beam electron gun provides a plurality N of cathode assemblies comprising a cathode, anode, and focus electrode, each cathode assembly having a local cathode axis and also a central cathode point defined by the intersection of the local cathode axis with the emitting surface of the cathode. Each cathode is arranged with its central point positioned in a plane orthogonal to a device central axis, with each cathode central point an equal distance from the device axis and with an included angle of 360/N between each cathode central point. The local axis of each cathode has a cathode divergence angle with respect to the central axis which is set such that the diverging magnetic field from a solenoidal coil is less than 5 degrees with respect to the projection of the local cathode axis onto a cathode reference plane formed by the device axis and the central cathode point, and the local axis of each cathode is also set such that the angle formed between the cathode reference plane and the local cathode axis results in minimum spiraling in the path of the electron beams in a homogenous magnetic field region of the solenoidal field generator.

Gradient metasurface for four-direction anomalous reflection in terahertz

NASA Astrophysics Data System (ADS)

Wang, Jiao; Jiang, Yannan

2018-06-01

In this paper, a four-direction anomalous reflection metasurface is proposed. The basic cells comprise of squares and circles, which are designed at various sizes and arranged in a super cell at regular spacing. Then, properly combining super cells molds a square phase gradient metasurface (PGM). It is mounted on an optical thickness gold mirror, which inhibits all light transmission. Markedly different from previously reported metasurfaces, the square PGM is characterized by four-direction reflection beams. It takes into consideration the normal incidence and the oblique incidence. For the normal incidence, that the degrees of the four reflection angles are identical is due to the x, - x, y and - y directional discontinuous phase gradients, and lies on the symmetric structure in the xoy plane, which is then revealed by the surface current distribution. Incident angles varying from -20° to 20°, the reflection angles are demonstrated in the oblique incidence. Moreover, the PGM is polarization-independent. The performance is attributed to the symmetry of structure, which is verified by Radar cross section. Simulated results prove that our method offers a simple and effective strategy for metasurface design in terahertz. The proposed PGM can aid in focused beams, steering beams, and shaped beams.

Formation and characterization of perpendicular mode Si ripples by glancing angle O{sub 2}{sup +} sputtering at room temperature

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

Mollick, S. A.; Ghose, D.

Off-normal low energy ion beam sputtering of solid surfaces often leads to morphological instabilities resulting in the spontaneous formation of ripple structures in nanometer length scales. In the case of Si surfaces at ambient temperature, ripple formation is found to take place normally at lower incident angles with the wave vector parallel to the ion beam direction. The absence of ripple pattern on Si surface at larger angles is due to the dominance of ion beam polishing effect. We have shown that a gentle chemical roughening of the starting surface morphology can initiate ripple pattern under grazing incidence ion beammore » sputtering (theta>64 deg. with respect to the surface normal), where the ripple wave vector is perpendicular to the ion beam direction. The characteristics of the perpendicular mode ripples are studied as a function of pristine surface roughness (2-30 nm) and projectile fluence (5x10{sup 16}-1.5x10{sup 18} O atoms cm{sup -2}). The quality of the morphological structure is assessed from the analysis of ion induced topological defects.« less

Active retroreflector to measure the rotational orientation in conjunction with a laser tracker

NASA Astrophysics Data System (ADS)

Hofherr, O.; Wachten, C.; Müller, C.; Reinecke, H.

2012-10-01

High precision optical non-contact position measurement is a key technology in modern engineering. Laser trackers (LT) can determine accurately x-y-z coordinates of passive retroreflectors. Next-generation systems answer the additional need to measure an object's rotational orientation (pitch, yaw, roll). These devices are based on photogrammetry or on enhanced retroreflectors. However, photogrammetry relies on camera systems and time-consuming image processing. Enhanced retroreflectors analyze the LT's beam but are restricted in roll angle measurements. Here we present an integrated laser based method to evaluate all six degrees of freedom. An active retroreflector directly analyzes its orientation to the LT's beam path by outcoupling laser light on detectors. A proof of concept prototype has been designed with a specified measuring range of 360° for roll angle measurements and +/-15° for pitch and yaw angle respectively. The prototype's optical design is inspired by a cat's eye retroreflector. First results are promising and further improvements are under development. We anticipate our method to facilitate simple and cost-effective six degrees of freedom measurements. Furthermore, for industrial applications wide customizations are possible, e.g. adaptation of measuring range, optimization of accuracy, and further system miniaturization.

Flow-through compression cell for small-angle and ultra-small-angle neutron scattering measurements

NASA Astrophysics Data System (ADS)

Hjelm, Rex P.; Taylor, Mark A.; Frash, Luke P.; Hawley, Marilyn E.; Ding, Mei; Xu, Hongwu; Barker, John; Olds, Daniel; Heath, Jason; Dewers, Thomas

2018-05-01

In situ measurements of geological materials under compression and with hydrostatic fluid pressure are important in understanding their behavior under field conditions, which in turn provides critical information for application-driven research. In particular, understanding the role of nano- to micro-scale porosity in the subsurface liquid and gas flow is critical for the high-fidelity characterization of the transport and more efficient extraction of the associated energy resources. In other applications, where parts are produced by the consolidation of powders by compression, the resulting porosity and crystallite orientation (texture) may affect its in-use characteristics. Small-angle neutron scattering (SANS) and ultra SANS are ideal probes for characterization of these porous structures over the nano to micro length scales. Here we show the design, realization, and performance of a novel neutron scattering sample environment, a specially designed compression cell, which provides compressive stress and hydrostatic pressures with effective stress up to 60 MPa, using the neutron beam to probe the effects of stress vectors parallel to the neutron beam. We demonstrate that the neutron optics is suitable for the experimental objectives and that the system is highly stable to the stress and pressure conditions of the measurements.

Scaling effects in the static and dynamic response of graphite-epoxy beam-columns. Ph.D. Thesis - Virginia Polytechnic Inst. and State Univ.

NASA Technical Reports Server (NTRS)

Jackson, Karen E.

1990-01-01

Scale model technology represents one method of investigating the behavior of advanced, weight-efficient composite structures under a variety of loading conditions. It is necessary, however, to understand the limitations involved in testing scale model structures before the technique can be fully utilized. These limitations, or scaling effects, are characterized. in the large deflection response and failure of composite beams. Scale model beams were loaded with an eccentric axial compressive load designed to produce large bending deflections and global failure. A dimensional analysis was performed on the composite beam-column loading configuration to determine a model law governing the system response. An experimental program was developed to validate the model law under both static and dynamic loading conditions. Laminate stacking sequences including unidirectional, angle ply, cross ply, and quasi-isotropic were tested to examine a diversity of composite response and failure modes. The model beams were loaded under scaled test conditions until catastrophic failure. A large deflection beam solution was developed to compare with the static experimental results and to analyze beam failure. Also, the finite element code DYCAST (DYnamic Crash Analysis of STructure) was used to model both the static and impulsive beam response. Static test results indicate that the unidirectional and cross ply beam responses scale as predicted by the model law, even under severe deformations. In general, failure modes were consistent between scale models within a laminate family; however, a significant scale effect was observed in strength. The scale effect in strength which was evident in the static tests was also observed in the dynamic tests. Scaling of load and strain time histories between the scale model beams and the prototypes was excellent for the unidirectional beams, but inconsistent results were obtained for the angle ply, cross ply, and quasi-isotropic beams. Results show that valuable information can be obtained from testing on scale model composite structures, especially in the linear elastic response region. However, due to scaling effects in the strength behavior of composite laminates, caution must be used in extrapolating data taken from a scale model test when that test involves failure of the structure.

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.