A Monte Carlo study of the energy spectra and transmission characteristics of scattered radiation from x-ray computed tomography.

PubMed

Platten, David John

2014-06-01

Existing data used to calculate the barrier transmission of scattered radiation from computed tomography (CT) are based on primary beam CT energy spectra. This study uses the EGSnrc Monte Carlo system and Epp user code to determine the energy spectra of CT scatter from four different primary CT beams passing through an ICRP 110 male reference phantom. Each scatter spectrum was used as a broad-beam x-ray source in transmission simulations through seventeen thicknesses of lead (0.00-3.50 mm). A fit of transmission data to lead thickness was performed to obtain α, β and γ parameters for each spectrum. The mean energy of the scatter spectra were up to 12.3 keV lower than that of the primary spectrum. For 120 kVp scatter beams the transmission through lead was at least 50% less than predicted by existing data for thicknesses of 1.5 mm and greater; at least 30% less transmission was seen for 140 kVp scatter beams. This work has shown that the mean energy and half-value layer of CT scatter spectra are lower than those of the corresponding primary beam. The transmission of CT scatter radiation through lead is lower than that calculated with currently available data. Using the data from this work will result in less lead shielding being required for CT scanner installations.

Design and development of the 6-18 MeV electron beam system for medical and other applications

NASA Astrophysics Data System (ADS)

Shahzad, A.; Phatangare, A. B.; Bharud, V. D.; Bhadane, M. S.; Tahakik, C. D.; Patil, B. J.; Dahiwale, S. S.; Chavan, S. T.; Pethe, S. N.; Dhole, S. D.; Bhoraskar, V. N.

2017-12-01

A system for the electron and photon therapy has been designed and developed at SAMEER, IITB, Mumbai. All the components of the system such as the 270° beam bending electromagnet, trim coils, magnet chamber, electron scattering foil, slits, applicators, etc., were designed and fabricated indigenously. The electrons of 6, 8, 9, 12, 15 and 18 MeV energies were provided by a linear accelerator, indigenously designed and made at SAMEER, IITB campus, Mumbai. The electron beam from the LINAC enters the magnet chamber horizontally, and after deflection and focusing in the 270° bending magnet, comes out of the exit port, and travels a straight path vertically down. After passing through the beryllium and tantalum scattering foils, the electron beam gets scattered and turns into a solid cone shape such that the diameter increases with the travel distance. The simulation results indicate that at the exit port of the 270° beam bending magnet, the electron beam has a divergence angle of ≤ 3 mrad and diameter ∼2-3 mm, and remains constant over 6-18 MeV. Normally, 6-18 MeV electrons are used for the electron therapy of skin and malignant cancer near the skin surface. On a plane at a distance of 100 cm from the scattering foils, the size of the electron beam could be varied from 10 cm × 10 cm to 25 cm × 25 cm using suitable applicators and slits. Different types of applicators were therefore designed and fabricated to provide required beam profile and dose of electrons to a patient. The 6 MeV cyclic electron accelerator called Race-Track Microtron of S. P. Pune University, Pune, was extensively used for studying the performances of the scattering foils, electron beam uniformity and radiation dose measurement. Different types of thermoluminescent dosimetry dosimeters were developed to measure dose in the range of 1-10kGy.

Effects of rain and fog on the Shuttle Ku-band microwave scanning beam landing system range and accuracy performance

NASA Technical Reports Server (NTRS)

Butler, D.

1981-01-01

The microwave Scanning Beam Landing System's (MSBLS) performance in fog and rain was studied. The fog and rain effects on the Shuttle Ku-band system were determined. Specifically, microwave attenuation, beam distortion, and coordinate errors resulting from operation of the MSBLS in poor weather conditions were evaluated. The main physical processes giving rise to microwave attenuation were found to be absorption and scattering by water droplets. The general theory of scattering and absorption used is discussed and a listing of applicable computer programs is provided.

Prior image constrained scatter correction in cone-beam computed tomography image-guided radiation therapy.

PubMed

Brunner, Stephen; Nett, Brian E; Tolakanahalli, Ranjini; Chen, Guang-Hong

2011-02-21

X-ray scatter is a significant problem in cone-beam computed tomography when thicker objects and larger cone angles are used, as scattered radiation can lead to reduced contrast and CT number inaccuracy. Advances have been made in x-ray computed tomography (CT) by incorporating a high quality prior image into the image reconstruction process. In this paper, we extend this idea to correct scatter-induced shading artifacts in cone-beam CT image-guided radiation therapy. Specifically, this paper presents a new scatter correction algorithm which uses a prior image with low scatter artifacts to reduce shading artifacts in cone-beam CT images acquired under conditions of high scatter. The proposed correction algorithm begins with an empirical hypothesis that the target image can be written as a weighted summation of a series of basis images that are generated by raising the raw cone-beam projection data to different powers, and then, reconstructing using the standard filtered backprojection algorithm. The weight for each basis image is calculated by minimizing the difference between the target image and the prior image. The performance of the scatter correction algorithm is qualitatively and quantitatively evaluated through phantom studies using a Varian 2100 EX System with an on-board imager. Results show that the proposed scatter correction algorithm using a prior image with low scatter artifacts can substantially mitigate scatter-induced shading artifacts in both full-fan and half-fan modes.

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.

Variable ratio beam splitter for laser applications

NASA Technical Reports Server (NTRS)

Brown, R. M.

1971-01-01

Beam splitter employing birefringent optics provides either widely different or precisely equal beam ratios, it can be used with laser light source systems for interferometry of lossy media, holography, scattering measurements, and precise beam ratio applications.

Synchrotron-based coherent scatter x-ray projection imaging using an array of monoenergetic pencil beams.

PubMed

Landheer, Karl; Johns, Paul C

2012-09-01

Traditional projection x-ray imaging utilizes only the information from the primary photons. Low-angle coherent scatter images can be acquired simultaneous to the primary images and provide additional information. In medical applications scatter imaging can improve x-ray contrast or reduce dose using information that is currently discarded in radiological images to augment the transmitted radiation information. Other applications include non-destructive testing and security. A system at the Canadian Light Source synchrotron was configured which utilizes multiple pencil beams (up to five) to create both primary and coherent scatter projection images, simultaneously. The sample was scanned through the beams using an automated step-and-shoot setup. Pixels were acquired in a hexagonal lattice to maximize packing efficiency. The typical pitch was between 1.0 and 1.6 mm. A Maximum Likelihood-Expectation Maximization-based iterative method was used to disentangle the overlapping information from the flat panel digital x-ray detector. The pixel value of the coherent scatter image was generated by integrating the radial profile (scatter intensity versus scattering angle) over an angular range. Different angular ranges maximize the contrast between different materials of interest. A five-beam primary and scatter image set (which had a pixel beam time of 990 ms and total scan time of 56 min) of a porcine phantom is included. For comparison a single-beam coherent scatter image of the same phantom is included. The muscle-fat contrast was 0.10 ± 0.01 and 1.16 ± 0.03 for the five-beam primary and scatter images, respectively. The air kerma was measured free in air using aluminum oxide optically stimulated luminescent dosimeters. The total area-averaged air kerma for the scan was measured to be 7.2 ± 0.4 cGy although due to difficulties in small-beam dosimetry this number could be inaccurate.

A picosecond beam-timing system for the OMEGA laser

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

Donaldson, W. R.; Katz, J.; Huff, R.

Here, a timing system is demonstrated for the OMEGA Laser System that guarantees all 60 beams will arrive on target simultaneously with a root mean square variability of 4 ps. The system relies on placing a scattering sphere at the target position to couple the UV light from each beam into a single photodetector.

A picosecond beam-timing system for the OMEGA laser

DOE PAGES

Donaldson, W. R.; Katz, J.; Huff, R.; ...

2016-05-27

Here, a timing system is demonstrated for the OMEGA Laser System that guarantees all 60 beams will arrive on target simultaneously with a root mean square variability of 4 ps. The system relies on placing a scattering sphere at the target position to couple the UV light from each beam into a single photodetector.

A picosecond beam-timing system for the OMEGA laser

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

Donaldson, W. R.; Katz, J.; Huff, R.

A timing system is demonstrated for the OMEGA Laser System that guarantees all 60 beams will arrive on target simultaneously with a root mean square variability of 4 ps. The system relies on placing a scattering sphere at the target position to couple the ultraviolet light from each beam into a single photodetector.

Design of a collective scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research

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

Lee, W., E-mail: woochanglee@unist.ac.kr; Lee, D. J.; Park, H. K.

The design characteristics of a multi-channel collective (or coherent) scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research (KSTAR), which is planned to be installed in 2017, are given in this paper. A few critical issues are discussed in depth such as the Faraday and Cotton-Mouton effects on the beam polarization, radial spatial resolution, probe beam frequency, polarization, and power. A proper and feasible optics with the 300 GHz probe beam, which was designed based on these issues, provides a simultaneous measurement of electron density fluctuations at four discrete poloidal wavenumbers up to 24 cm{sup −1}.more » The upper limit corresponds to the normalized wavenumber k{sub θ}ρ{sub e} of ∼0.15 in nominal KSTAR plasmas. To detect the scattered beam power and extract phase information, a quadrature detection system consisting of four-channel antenna/detector array and electronics will be employed.« less

The effect of residual gas scattering on Ga ion beam patterning of graphene

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

Thissen, Nick F. W., E-mail: n.f.w.thissen@tue.nl, E-mail: a.a.bol@tue.nl; Vervuurt, R. H. J.; Weber, J. W.

2015-11-23

The patterning of graphene by a 30 kV Ga{sup +} focused ion beam (FIB) is studied by in-situ and ex-situ Raman spectroscopy. It is found that the graphene surrounding the patterned target area can be damaged at remarkably large distances of more than 10 μm. We show that scattering of the Ga ions in the residual gas of the vacuum system is the main cause of the large range of lateral damage, as the size and shape of the tail of the ion beam were strongly dependent on the system background pressure. The range of the damage was therefore greatly reduced bymore » working at low pressures and limiting the total amount of ions used. This makes FIB patterning a feasible alternative to electron beam lithography as long as residual gas scattering is taken into account.« less

The time resolved SBS and SRS research in heavy water and its application in CARS

NASA Astrophysics Data System (ADS)

Liu, Jinbo; Gai, Baodong; Yuan, Hong; Sun, Jianfeng; Zhou, Xin; Liu, Di; Xia, Xusheng; Wang, Pengyuan; Hu, Shu; Chen, Ying; Guo, Jingwei; Jin, Yuqi; Sang, Fengting

2018-05-01

We present the time-resolved character of stimulated Brillouin scattering (SBS) and backward stimulated Raman scattering (BSRS) in heavy water and its application in Coherent Anti-Stokes Raman Scattering (CARS) technique. A nanosecond laser from a frequency-doubled Nd: YAG laser is introduced into a heavy water cell, to generate SBS and BSRS beams. The SBS and BSRS beams are collinear, and their time resolved characters are studied by a streak camera, experiment show that they are ideal source for an alignment-free CARS system, and the time resolved property of SBS and BSRS beams could affect the CARS efficiency significantly. By inserting a Dye cuvette to the collinear beams, the time-overlapping of SBS and BSRS could be improved, and finally the CARS efficiency is increased, even though the SBS energy is decreased. Possible methods to improve the efficiency of this CARS system are discussed too.

Two-dimensional simulations of stimulated Brillouin scattering in laser produced plasmas

NASA Astrophysics Data System (ADS)

Amin, M. R.; Capjack, C. E.; Frycz, P.; Rozmus, W.; Tikhonchuk, V. T.

1993-07-01

A system of electromagnetic and ion acoustic wave equations coupled via the ponderomotive force are solved numerically in a two-dimensional planar geometry. The competition between forward, side, and backward Brillouin scattering of the finite size laser beam is studied for the first time without the standard paraxial optics approximation. Simulations reveal a strong dependence of the scattered light characteristics on the geometry of the interaction region, the shape of the pump beam, and the ion acoustic wave damping. The main effects include side and forward scattering enhancement and a stimulation of collimated backward scattered radiation.

Quantum optics of lossy asymmetric beam splitters.

PubMed

Uppu, Ravitej; Wolterink, Tom A W; Tentrup, Tristan B H; Pinkse, Pepijn W H

2016-07-25

We theoretically investigate quantum interference of two single photons at a lossy asymmetric beam splitter, the most general passive 2×2 optical circuit. The losses in the circuit result in a non-unitary scattering matrix with a non-trivial set of constraints on the elements of the scattering matrix. Our analysis using the noise operator formalism shows that the loss allows tunability of quantum interference to an extent not possible with a lossless beam splitter. Our theoretical studies support the experimental demonstrations of programmable quantum interference in highly multimodal systems such as opaque scattering media and multimode fibers.

Correction of scatter in megavoltage cone-beam CT

NASA Astrophysics Data System (ADS)

Spies, L.; Ebert, M.; Groh, B. A.; Hesse, B. M.; Bortfeld, T.

2001-03-01

The role of scatter in a cone-beam computed tomography system using the therapeutic beam of a medical linear accelerator and a commercial electronic portal imaging device (EPID) is investigated. A scatter correction method is presented which is based on a superposition of Monte Carlo generated scatter kernels. The kernels are adapted to both the spectral response of the EPID and the dimensions of the phantom being scanned. The method is part of a calibration procedure which converts the measured transmission data acquired for each projection angle into water-equivalent thicknesses. Tomographic reconstruction of the projections then yields an estimate of the electron density distribution of the phantom. It is found that scatter produces cupping artefacts in the reconstructed tomograms. Furthermore, reconstructed electron densities deviate greatly (by about 30%) from their expected values. The scatter correction method removes the cupping artefacts and decreases the deviations from 30% down to about 8%.

WE-AB-207A-08: BEST IN PHYSICS (IMAGING): Advanced Scatter Correction and Iterative Reconstruction for Improved Cone-Beam CT Imaging On the TrueBeam Radiotherapy Machine

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

Wang, A; Paysan, P; Brehm, M

2016-06-15

Purpose: To improve CBCT image quality for image-guided radiotherapy by applying advanced reconstruction algorithms to overcome scatter, noise, and artifact limitations Methods: CBCT is used extensively for patient setup in radiotherapy. However, image quality generally falls short of diagnostic CT, limiting soft-tissue based positioning and potential applications such as adaptive radiotherapy. The conventional TrueBeam CBCT reconstructor uses a basic scatter correction and FDK reconstruction, resulting in residual scatter artifacts, suboptimal image noise characteristics, and other artifacts like cone-beam artifacts. We have developed an advanced scatter correction that uses a finite-element solver (AcurosCTS) to model the behavior of photons as theymore » pass (and scatter) through the object. Furthermore, iterative reconstruction is applied to the scatter-corrected projections, enforcing data consistency with statistical weighting and applying an edge-preserving image regularizer to reduce image noise. The combined algorithms have been implemented on a GPU. CBCT projections from clinically operating TrueBeam systems have been used to compare image quality between the conventional and improved reconstruction methods. Planning CT images of the same patients have also been compared. Results: The advanced scatter correction removes shading and inhomogeneity artifacts, reducing the scatter artifact from 99.5 HU to 13.7 HU in a typical pelvis case. Iterative reconstruction provides further benefit by reducing image noise and eliminating streak artifacts, thereby improving soft-tissue visualization. In a clinical head and pelvis CBCT, the noise was reduced by 43% and 48%, respectively, with no change in spatial resolution (assessed visually). Additional benefits include reduction of cone-beam artifacts and reduction of metal artifacts due to intrinsic downweighting of corrupted rays. Conclusion: The combination of an advanced scatter correction with iterative reconstruction substantially improves CBCT image quality. It is anticipated that clinically acceptable reconstruction times will result from a multi-GPU implementation (the algorithms are under active development and not yet commercially available). All authors are employees of and (may) own stock of Varian Medical Systems.« less

Development of Thomson scattering system on Shenguang-III prototype laser facility

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

Gong, Tao; Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, Sichuan 621900; Li, Zhichao

2015-02-15

A Thomson scattering diagnostic system, using a 263 nm laser as the probe beam, is designed and implemented on Shenguang-III prototype laser facility. The probe beam is provided by an additional beam line completed recently. The diagnostic system allows simultaneous measurements of both ion feature and red-shifted electron feature from plasmas in a high-temperature (≥2 keV) and high-density (≥10{sup 21} cm{sup −3}) regime. Delicate design is made to satisfy the requirements for successful detection of the electron feature. High-quality ion feature spectra have already been diagnosed via this system in recent experiments with gas-filled hohlraums.

Direct observation of the two-plasmon-decay common plasma wave using ultraviolet Thomson scattering.

PubMed

Follett, R K; Edgell, D H; Henchen, R J; Hu, S X; Katz, J; Michel, D T; Myatt, J F; Shaw, J; Froula, D H

2015-03-01

A 263-nm Thomson-scattering beam was used to directly probe two-plasmon-decay (TPD) excited electron plasma waves (EPWs) driven by between two and five 351-nm beams on the OMEGA Laser System. The amplitude of these waves was nearly independent of the number of drive beams at constant overlapped intensity, showing that the observed EPWs are common to the multiple beams. In an experimental configuration where the Thomson-scattering diagnostic was not wave matched to the common TPD EPWs, a broad spectrum of TPD-driven EPWs was observed, indicative of nonlinear effects associated with TPD saturation. Electron plasma waves corresponding to Langmuir decay of TPD EPWs were observed in both Thomson-scattering spectra, suggesting the Langmuir decay instability as a TPD saturation mechanism. Simulated Thomson-scattering spectra from three-dimensional numerical solutions of the extended Zakharov equations of TPD are in excellent agreement with the experimental spectra and verify the presence of the Langmuir decay instability.

Direct observation of the two-plasmon-decay common plasma wave using ultraviolet Thomson scattering

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

Follett, R. K.; Edgell, D. H.; Henchen, R. J.

2015-03-26

A 263-nm Thomson-scattering beam was used to directly probe two-plasmon-decay (TPD) excited electron plasma waves (EPWs) driven by between two and five 351-nm beams on the OMEGA Laser System. The amplitude of these waves was nearly independent of the number of drive beams at constant overlapped intensity, showing that the observed EPWs are common to the multiple beams. In an experimental configuration where the Thomson-scattering diagnostic was not wave matched to the common TPD EPWs, a broad spectrum of TPD-driven EPWs was observed, indicative of nonlinear effects associated with TPD saturation. Electron plasma waves corresponding to Langmuir decay of TPDmore » EPWs were observed in both Thomson-scattering spectra, suggesting the Langmuir decay instability as a TPD saturation mechanism. Simulated Thomson-scattering spectra from three-dimensional numerical solutions of the extended Zakharov equations of TPD are in excellent agreement with the experimental spectra and verify the presence of the Langmuir decay instability.« less

WE-DE-207B-09: Scatter Radiation Measurement From a Digital Breast Tomosynthesis System and Its Impact On Shielding Consideration

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

Yang, K; Li, X; Liu, B

2016-06-15

Purpose: To accurately measure the scatter radiation from a Hologic digital breast tomosynthesis (DBT) system and to provide updated scatter distribution to guide radiation shielding calculation for DBT rooms. Methods: A high sensitivity GOS-based linear detector was used to measure the angular distribution of scatter radiation from a Hologic Selenia Dimensions DBT system. The linear detector was calibrated for its energy response of typical DBT spectra. Following the NCRP147 approach, the measured scatter intensity was normalized by the primary beam area and primary air kerma at 1m from the scatter phantom center and presented as the scatter fraction. Direct comparisonmore » was made against Simpkin’s initial measurement. Key parameters including the phantom size, primary beam area, and kV/anode/target combination were also studied. Results: The measured scatter-to-primary-ratio and scatter fraction data closely matched with previous data from Simpkin. The measured data demonstrated the unique nonisotropic distribution of the scattered radiation around a Hologic DBT system, with two strong peaks around 25° and 160°. The majority scatter radiation (>70%) originated from the imaging detector assembly, instead of the phantom. With a workload from a previous local survey, the scatter air kerma at 1m from the phantom center for wall/door is 0.018mGy/patient, for floor is 0.164mGy/patient, and for ceiling is 0.037mGy/patient. Conclusion: Comparing to Simpkin’s previous data, the scatter air kerma from Holgoic DBT is at least two times higher. The main reasons include the harder primary beam with higher workload, added tomosynthesis acquisition, and strong small angle forward scattering. Due to the highly conservative initial assumptions, the shielding recommendation from NCRP147 is still sufficient for the Hologic DBT system given the workload from a previous local survey. With the data provided from this study, accurate shielding calculation can be performed for Hologic DBT systems with specific workload and barrier distance.« less

Beam Measurement of 11.424 GHz X-Band Linac for Compton Scattering X-ray Source

NASA Astrophysics Data System (ADS)

Natsui, Takuya; Mori, Azusa; Masuda, Hirotoshi; Uesaka, Mitsuru; Sakamoto, Fumito

2010-11-01

An inverse Compton scattering X-ray source for medical applications, consisting of an X-band (11.424 GHz) linac and Q-switched Nd:YAG laser, is currently being developed at the University of Tokyo. This system uses an X-band 3.5-cell thermionic cathode RF gun for electron beam generation. We can obtain a multi-bunch electron beam with this gun. The beam is accelerated to 30 MeV by a traveling-wave accelerating tube. So far, we have verified stable beam generation (around 2.3 MeV) by using the newly designed RF gun and we have succeeded in beam transportation to a beam dump.

The Los ALamos Neutron Science Center Hydrogen Moderator System

NASA Astrophysics Data System (ADS)

Jarmer, J. J.; Knudson, J. N.

2006-04-01

At the Los Alamos Neutron Science Center (LANSCE), spallation neutrons are produced by an 800-MeV proton beam interacting with tungsten targets. Gun-barrel-type penetrations through the heavy concrete and steel shielding that surround the targets collimate neutrons to form neutron beams used for scattering experiments. Two liquid hydrogen moderators of one-liter volume each are positioned adjacent to the neutron-production targets. Some of the neutrons that pass through a moderator interact with or scatter from protons in the hydrogen. The neutron-proton interaction reduces the energy or moderates neutrons to lower energies. Lower energy "moderated" neutrons are the most useful for some neutron scattering experiments. We provide a description of the LANSCE hydrogen-moderator system and its cryogenic performance with proton beams of up to 125 micro-amp average current.

An advanced molecule-surface scattering instrument for study of vibrational energy transfer in gas-solid collisions.

PubMed

Ran, Qin; Matsiev, Daniel; Wodtke, Alec M; Auerbach, Daniel J

2007-10-01

We describe an advanced and highly sensitive instrument for quantum state-resolved molecule-surface energy transfer studies under ultrahigh vacuum (UHV) conditions. The apparatus includes a beam source chamber, two differential pumping chambers, and a UHV chamber for surface preparation, surface characterization, and molecular beam scattering. Pulsed and collimated supersonic molecular beams are generated by expanding target molecule mixtures through a home-built pulsed nozzle, and excited quantum state-selected molecules were prepared via tunable, narrow-band laser overtone pumping. Detection systems have been designed to measure specific vibrational-rotational state, time-of-flight, angular and velocity distributions of molecular beams coming to and scattered off the surface. Facilities are provided to clean and characterize the surface under UHV conditions. Initial experiments on the scattering of HCl(v = 0) from Au(111) show many advantages of this new instrument for fundamental studies of the energy transfer at the gas-surface interface.

Intra-beam scattering and its application to ERL

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

Fedotov A. V.

Treatment of Coulomb collisions within the beam requires consideration of both large and small angle scattering. Such collisions lead to the Touschek effect and Intrabeam Scattering (IBS). The Touschek effect refers to particle loss as a result of a single collision, where only transfer from the transverse direction into longitudinal plays a role. It is important to consider this effect for ERL design to have an appropriate choice of collimation system. The IBS is a diffusion process which leads to changes of beam distribution but does not necessarily result in a beam loss. Evaluation of IBS in ERLs, where beammore » distribution is non-Gaussian, requires special treatment. Here we describe the IBS and Touschek effects with application to ERLs.« less

Scatter of X-rays on polished surfaces

NASA Technical Reports Server (NTRS)

Hasinger, G.

1981-01-01

In investigating the dispersion properties of telescope mirrors used in X-ray astronomy, the slight scattering characteristics of X-ray radiation by statistically rough surfaces were examined. The mathematics and geometry of scattering theory are described. The measurement test assembly is described and results of measurements on samples of plane mirrors are given. Measurement results are evaluated. The direct beam, the convolution of the direct beam and the scattering halo, curve fitting by the method of least squares, various autocorrelation functions, results of the fitting procedure for small scattering, and deviations in the kernel of the scattering distribution are presented. A procedure for quality testing of mirror systems through diagnosis of rough surfaces is described.

SU-E-T-25: Real Time Simulator for Designing Electron Dual Scattering Foil Systems.

PubMed

Carver, R; Hogstrom, K; Price, M; Leblanc, J; Harris, G

2012-06-01

To create a user friendly, accurate, real time computer simulator to facilitate the design of dual foil scattering systems for electron beams on radiotherapy accelerators. The simulator should allow for a relatively quick, initial design that can be refined and verified with subsequent Monte Carlo (MC) calculations and measurements. The simulator consists of an analytical algorithm for calculating electron fluence and a graphical user interface (GUI) C++ program. The algorithm predicts electron fluence using Fermi-Eyges multiple Coulomb scattering theory with a refined Moliere formalism for scattering powers. The simulator also estimates central-axis x-ray dose contamination from the dual foil system. Once the geometry of the beamline is specified, the simulator allows the user to continuously vary primary scattering foil material and thickness, secondary scattering foil material and Gaussian shape (thickness and sigma), and beam energy. The beam profile and x-ray contamination are displayed in real time. The simulator was tuned by comparison of off-axis electron fluence profiles with those calculated using EGSnrc MC. Over the energy range 7-20 MeV and using present foils on the Elekta radiotherapy accelerator, the simulator profiles agreed to within 2% of MC profiles from within 20 cm of the central axis. The x-ray contamination predictions matched measured data to within 0.6%. The calculation time was approximately 100 ms using a single processor, which allows for real-time variation of foil parameters using sliding bars. A real time dual scattering foil system simulator has been developed. The tool has been useful in a project to redesign an electron dual scattering foil system for one of our radiotherapy accelerators. The simulator has also been useful as an instructional tool for our medical physics graduate students. © 2012 American Association of Physicists in Medicine.

Focal-Plane Imaging of Crossed Beams in Nonlinear Optics Experiments

NASA Technical Reports Server (NTRS)

Bivolaru, Daniel; Herring, G. C.

2007-01-01

An application of focal-plane imaging that can be used as a real time diagnostic of beam crossing in various optical techniques is reported. We discuss two specific versions and demonstrate the capability of maximizing system performance with an example in a combined dual-pump coherent anti-Stokes Raman scattering interferometric Rayleigh scattering experiment (CARS-IRS). We find that this imaging diagnostic significantly reduces beam alignment time and loss of CARS-IRS signals due to inadvertent misalignments.

Optical radiation hazards of laser welding processes. Part II: CO2 laser.

PubMed

Rockwell, R J; Moss, C E

1989-08-01

There has been an extensive growth within the last five years in the use of high-powered lasers in various metalworking processes. The two types of lasers used most frequently for laser welding/cutting processes are the Neodymium-yttrium-aluminum-garnet (Nd:YAG) and the carbon dioxide (CO2) systems. When such lasers are operated in an open beam configuration, they are designated as a Class IV laser system. Class IV lasers are high-powered lasers that may present an eye and skin hazard under most common exposure conditions, either directly or when the beam has been diffusely scattered. Significant control measures are required for unenclosed (open beam), Class IV laser systems since workers may be exposed to scattered or reflected beams during the operation, maintenance, and service of these lasers. In addition to ocular and/or skin exposure hazards, such lasers also may present a multitude of nonlaser beam occupational concerns. Radiant energy measurements are reported for both the scattered laser radiation and the plasma-related plume radiations released during typical high-powered CO2 laser-target interactions. In addition, the application of the nominal hazard zone (NHZ) and other control measures also are discussed with special emphasis on Class IV industrial CO2 laser systems.

An empirical model for calculation of the collimator contamination dose in therapeutic proton beams

NASA Astrophysics Data System (ADS)

Vidal, M.; De Marzi, L.; Szymanowski, H.; Guinement, L.; Nauraye, C.; Hierso, E.; Freud, N.; Ferrand, R.; François, P.; Sarrut, D.

2016-02-01

Collimators are used as lateral beam shaping devices in proton therapy with passive scattering beam lines. The dose contamination due to collimator scattering can be as high as 10% of the maximum dose and influences calculation of the output factor or monitor units (MU). To date, commercial treatment planning systems generally use a zero-thickness collimator approximation ignoring edge scattering in the aperture collimator and few analytical models have been proposed to take scattering effects into account, mainly limited to the inner collimator face component. The aim of this study was to characterize and model aperture contamination by means of a fast and accurate analytical model. The entrance face collimator scatter distribution was modeled as a 3D secondary dose source. Predicted dose contaminations were compared to measurements and Monte Carlo simulations. Measurements were performed on two different proton beam lines (a fixed horizontal beam line and a gantry beam line) with divergent apertures and for several field sizes and energies. Discrepancies between analytical algorithm dose prediction and measurements were decreased from 10% to 2% using the proposed model. Gamma-index (2%/1 mm) was respected for more than 90% of pixels. The proposed analytical algorithm increases the accuracy of analytical dose calculations with reasonable computation times.

An Accurate Scatter Measurement and Correction Technique for Cone Beam Breast CT Imaging Using Scanning Sampled Measurement (SSM) Technique.

PubMed

Liu, Xinming; Shaw, Chris C; Wang, Tianpeng; Chen, Lingyun; Altunbas, Mustafa C; Kappadath, S Cheenu

2006-02-28

We developed and investigated a scanning sampled measurement (SSM) technique for scatter measurement and correction in cone beam breast CT imaging. A cylindrical polypropylene phantom (water equivalent) was mounted on a rotating table in a stationary gantry experimental cone beam breast CT imaging system. A 2-D array of lead beads, with the beads set apart about ~1 cm from each other and slightly tilted vertically, was placed between the object and x-ray source. A series of projection images were acquired as the phantom is rotated 1 degree per projection view and the lead beads array shifted vertically from one projection view to the next. A series of lead bars were also placed at the phantom edge to produce better scatter estimation across the phantom edges. Image signals in the lead beads/bars shadow were used to obtain sampled scatter measurements which were then interpolated to form an estimated scatter distribution across the projection images. The image data behind the lead bead/bar shadows were restored by interpolating image data from two adjacent projection views to form beam-block free projection images. The estimated scatter distribution was then subtracted from the corresponding restored projection image to obtain the scatter removed projection images.Our preliminary experiment has demonstrated that it is feasible to implement SSM technique for scatter estimation and correction for cone beam breast CT imaging. Scatter correction was successfully performed on all projection images using scatter distribution interpolated from SSM and restored projection image data. The resultant scatter corrected projection image data resulted in elevated CT number and largely reduced the cupping effects.

Design of a new Nd:YAG Thomson scattering system for MAST

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

Scannell, R.; Walsh, M. J.; Carolan, P. G.

2008-10-15

A new infrared Thomson scattering system has been designed for the MAST tokamak. The system will measure at 120 spatial points with {approx_equal}10 mm resolution across the plasma. Eight 30 Hz 1.6 J Nd:YAG lasers will be combined to produce a sampling rate of 240 Hz. The lasers will follow separate parallel beam paths to the MAST vessel. Scattered light will be collected at approximately f/6 over scattering angles ranging from 80 deg. to 120 deg. The laser energy and lens size, relative to an existing 1.2 J f/12 system, greatly increases the number of scattered photons collected per unitmore » length of laser beam. This is the third generation of this polychromator to be built and a number of modifications have been made to facilitate mass production and to improve performance. Detected scattered signals will be digitized at a rate of 1 GS/s by 8 bit analog to digital converters (ADCs.) Data may be read out from the ADCs between laser pulses to allow for real-time analysis.« less

Development of KSTAR Thomson scattering system.

PubMed

Lee, J H; Oh, S T; Wi, H M

2010-10-01

To measure the electron temperature (T(e)) and electron density (n(e)) profiles in the Korean Superconducting Tokamak Advanced Research (KSTAR) device for the KSTAR third campaign (September 2010), we designed and installed a Thomson scattering system. The KSTAR Thomson scattering system is designed as a tangential Thomson scattering system and utilizes the N-, L-, and B-ports. The N-port is designed for the collection optics with a cassette system, the L-port is the laser input port, and the B-port is the location of the beam dump. In this paper, we will describe the final design of the KSTAR Thomson scattering system.

Improvements, upgrades, and plans for Thomson scattering on DIII-D

NASA Astrophysics Data System (ADS)

Carlstrom, T. N.; Du, D.; Glass, F.; Liu, C.; Watkins, M.; McLean, A. G.

2016-10-01

The Thomson scattering diagnostic on DIII-D consists of 3 beam lines that probe vertically, horizontally, and in the divertor region of the tokamak, with 54 spatial locations, edge spatial resolution down to 5 mm, and 10 Nd:YAG lasers. In its 25-year history, the collection lens optics and interference filters degraded and have been replaced, restoring previous performance. In addition, improved calibrations and detector temperature control (+/- 0.1 C) have reduced systematic errors. Cross calibration with the CO2 interferometer and ECE cut-off have improved the density calibration. Improvements to the beam line and lasers have increased the laser energy delivered to the scattering volume in the plasma. Future plans include moving the divertor system to measure regions of high triangularity using in-vessel mirrors to redirect the laser beam; adding a wide angle lens to the horizontal system to view the entire plasma radius near the plasma mid plane; and reversing the direction of the laser beam on the horizontal system to reduce the scattering angle and compressing the spectrum in wavelength space so that higher central Te measurements (<5 KeV) can be made with improved accuracy. Work supported by the US DOE under DE-FC02-04ER54698 and by LLNL under DE-AC52-07NA27344.

Airborne Laser Systems Testing and Analysis (essals et analyse des systemes laser embarques)

DTIC Science & Technology

2010-04-01

of Surface/ Paints Reflection Properties (PILASTER targets); • PILASTER Sensors Testing and Calibration; • LOAS Laser System Testing; and • Test...PILASTER targets candidate paints and materials), a Laser Scatter-meter (LSM) was built. To briefly summarise the fundamental concepts involved...Green Painted Target. 7.6.3 Laser Beam Misalignment with Respect to the Beam-Expander Support For measuring the beam misalignment, the beam expander

Coherent beam combination using self-phase locked stimulated Brillouin scattering phase conjugate mirrors with a rotating wedge for high power laser generation.

PubMed

Park, Sangwoo; Cha, Seongwoo; Oh, Jungsuk; Lee, Hwihyeong; Ahn, Heekyung; Churn, Kil Sung; Kong, Hong Jin

2016-04-18

The self-phase locking of a stimulated Brillouin scattering-phase conjugate mirror (SBS-PCM) allows a simple and scalable coherent beam combination of existing lasers. We propose a simple optical system composed of a rotating wedge and a concave mirror to overcome the power limit of the SBS-PCM. Its phase locking ability and the usefulness on the beam-combination laser are demonstrated experimentally. A four-beam combination is demonstrated using this SBS-PCM scheme. The relative phases between the beams were measured to be less than λ/24.7.

MO-F-CAMPUS-I-04: Characterization of Fan Beam Coded Aperture Coherent Scatter Spectral Imaging Methods for Differentiation of Normal and Neoplastic Breast Structures

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

Morris, R; Albanese, K; Lakshmanan, M

Purpose: This study intends to characterize the spectral and spatial resolution limits of various fan beam geometries for differentiation of normal and neoplastic breast structures via coded aperture coherent scatter spectral imaging techniques. In previous studies, pencil beam raster scanning methods using coherent scatter computed tomography and selected volume tomography have yielded excellent results for tumor discrimination. However, these methods don’t readily conform to clinical constraints; primarily prolonged scan times and excessive dose to the patient. Here, we refine a fan beam coded aperture coherent scatter imaging system to characterize the tradeoffs between dose, scan time and image quality formore » breast tumor discrimination. Methods: An X-ray tube (125kVp, 400mAs) illuminated the sample with collimated fan beams of varying widths (3mm to 25mm). Scatter data was collected via two linear-array energy-sensitive detectors oriented parallel and perpendicular to the beam plane. An iterative reconstruction algorithm yields images of the sample’s spatial distribution and respective spectral data for each location. To model in-vivo tumor analysis, surgically resected breast tumor samples were used in conjunction with lard, which has a form factor comparable to adipose (fat). Results: Quantitative analysis with current setup geometry indicated optimal performance for beams up to 10mm wide, with wider beams producing poorer spatial resolution. Scan time for a fixed volume was reduced by a factor of 6 when scanned with a 10mm fan beam compared to a 1.5mm pencil beam. Conclusion: The study demonstrates the utility of fan beam coherent scatter spectral imaging for differentiation of normal and neoplastic breast tissues has successfully reduced dose and scan times whilst sufficiently preserving spectral and spatial resolution. Future work to alter the coded aperture and detector geometries could potentially allow the use of even wider fans, thereby making coded aperture coherent scatter imaging a clinically viable method for breast cancer detection. United States Department of Homeland Security; Duke University Medical Center - Department of Radiology; Carl E Ravin Advanced Imaging Laboratories; Duke University Medical Physics Graduate Program.« less

A technique for simultaneous detection of individual vortex states of Laguerre-Gaussian beams transmitted through an aqueous suspension of microparticles

NASA Astrophysics Data System (ADS)

Khonina, S. N.; Karpeev, S. V.; Paranin, V. D.

2018-06-01

A technique for simultaneous detection of individual vortex states of the beams propagating in a randomly inhomogeneous medium is proposed. The developed optical system relies on the correlation method that is invariant to the beam wandering. The intensity distribution formed at the optical system output does not require digital processing. The proposed technique based on a multi-order phase diffractive optical element (DOE) is studied numerically and experimentally. The developed detection technique is used for the analysis of Laguerre-Gaussian vortex beams propagating under conditions of intense absorption, reflection, and scattering in transparent and opaque microparticles in aqueous suspensions. The performed experimental studies confirm the relevance of the vortex phase dependence of a laser beam under conditions of significant absorption, reflection, and scattering of the light.

Golden beam data for proton pencil-beam scanning.

PubMed

Clasie, Benjamin; Depauw, Nicolas; Fransen, Maurice; Gomà, Carles; Panahandeh, Hamid Reza; Seco, Joao; Flanz, Jacob B; Kooy, Hanne M

2012-03-07

Proton, as well as other ion, beams applied by electro-magnetic deflection in pencil-beam scanning (PBS) are minimally perturbed and thus can be quantified a priori by their fundamental interactions in a medium. This a priori quantification permits an optimal reduction of characterizing measurements on a particular PBS delivery system. The combination of a priori quantification and measurements will then suffice to fully describe the physical interactions necessary for treatment planning purposes. We consider, for proton beams, these interactions and derive a 'Golden' beam data set. The Golden beam data set quantifies the pristine Bragg peak depth-dose distribution in terms of primary, multiple Coulomb scatter, and secondary, nuclear scatter, components. The set reduces the required measurements on a PBS delivery system to the measurement of energy spread and initial phase space as a function of energy. The depth doses are described in absolute units of Gy(RBE) mm² Gp⁻¹, where Gp equals 10⁹ (giga) protons, thus providing a direct mapping from treatment planning parameters to integrated beam current. We used these Golden beam data on our PBS delivery systems and demonstrated that they yield absolute dosimetry well within clinical tolerance.

Progress on Thomson scattering in the Pegasus Toroidal Experiment

NASA Astrophysics Data System (ADS)

Schlossberg, D. J.; Bongard, M. W.; Fonck, R. J.; Schoenbeck, N. L.; Winz, G. R.

2013-11-01

A novel Thomson scattering system has been implemented on the Pegasus Toroidal Experiment where typical densities of 1019 m-3 and electron temperatures of 10 to 500 eV are expected. The system leverages technological advances in high-energy pulsed lasers, volume phase holographic (VPH) diffraction gratings, and gated image intensified (ICCD) cameras to provide a relatively low-maintenance, economical, robust diagnostic system. Scattering is induced by a frequency-doubled, Q-switched Nd:YAG laser (2 J at 532 nm, 7 ns FWHM pulse) directed to the plasma over a 7.7 m long beam path, and focused to < 3 mm throughout the collection region. Inter-shot beam alignment is adjustable with less than a 0.01 mm spatial resolution in the collection region. A custom lens system collects scattered photons at radii 15 cm to 85 cm from the machine's center, at ~ F/6 with 14 mm radial resolution. The initial configuration provides scattering measurements at 12 spatial locations and 12 simultaneous background measurements at adjacent locations. If plasma background subtraction proves to be insignificant, these background channels will be used as viewing channels. Each spectrometer supports 8 spatial channels and can provide 8 or more spectral bins each. The spectrometers use high-efficiency VPH transmission gratings (eff. > 80%) and fast-gated ICCDs (gate > 2 ns, Gen III intensifier) with high-throughput (F/1.8), achromatic lensing. A stray light mitigation facility has been implemented, consisting of a multi-aperture optical baffle system and a simple beam dump. Successful stray light reduction has enabled detection of scattered signal, and Rayleigh scattering has been used to provide a relative calibration. Initial temperature measurements have been made and data analysis algorithms are under development.

Method and apparatus for determining the physical properties of materials using dynamic light scattering techniques

NASA Technical Reports Server (NTRS)

Dhadwal, Harbans S. (Inventor)

1992-01-01

A system for determining the physical properties of materials through the use of dynamic light scattering is disclosed. The system includes a probe, a laser source for directing a laser beam into the probe, and a photodetector for converting scattered light detected by the probe into electrical signals. The probe includes at least one optical fiber connected to the laser source and a second optical fiber connected to the photodetector. Each of the fibers may adjoin a gradient index microlens which is capable of providing a collimated laser beam into a scattering medium. The position of the second optical fiber with respect to the optical axis of the probe determines whether homodyne or self-beating detection is provided. Self-beating detection may be provided without a gradient index microlens. This allows a very small probe to be constructed which is insertable through a hypodermic needle or the like into a droplet extending from such a needle. A method of detecting scattered light through the use of a collimated, Gaussian laser beam is also provided. A method for controlling the waist and divergence of the optical field emanating from the free end of an optical fiber is also provided.

Raman microspectroscopy of optically trapped micro- and nanoobjects

NASA Astrophysics Data System (ADS)

Jonáš, Alexandr; Ježek, Jan; Šerý, Mojmír; Zemánek, Pavel

2008-12-01

We describe and characterize an experimental system for Raman microspectroscopy of micro- and nanoobjects optically trapped in aqueous suspensions with the use of a single-beam gradient optical trap (Raman tweezers). This system features two separate lasers providing light for the optical trapping and excitation of the Raman scattering spectra from the trapped specimen, respectively. Using independent laser beams for trapping and spectroscopy enables optimizing the parameters of both beams for their respective purposes. Moreover, it is possible to modulate the position of the trapped object relative to the Raman beam focus for maximizing the detected Raman signal and obtaining spatially resolved images of the trapped specimen. Using this experimental system, we have obtained Raman scattering spectra of individual optically confined micron and sub-micron sized polystyrene beads and baker's yeast cells. Sufficiently high signal-to-noise ratio of the spectra could be achieved using a few tens of milliwatts of the Raman beam power and detector integration times on the order of seconds.

A symmetrical laser Doppler velocity meter and its application to turbulence characterization

NASA Technical Reports Server (NTRS)

Mazumder, M. K.

1972-01-01

A symmetrical method of optical heterodyning of the Doppler shifted scattered laser radiation developed for velocity measurements with a minimal instrumental spectral broadening and a high signal-to-noise ratio. The method employs two laser beams incident on the moving scatterer and does not use any reference beam for heterodyning. The Doppler signal frequency is independent of the scattering angle and the signal possesses no receiving aperture broadening. Optical alignment is simple. Typical values of the instrumental spectral broadening were approximately 0.8 percent of the center frequency of the Doppler signal, and the signal-to-noise ratio was approximately 25 dB, obtained from an air flow system using submicron dioctylphthalate scattering aerosol. Experimental and theoretical studies were made on the characteristics of the Doppler signal and the effect of system parameters in turbulent flow measurement. The optimization process involved in the beam optics and in the use of a spatial filter is described. For localized flow measurement in any direction of the three-dimensional orthogonal coordinates, the system, using uncorrected optical components, had a sensing volume which can be described by a sensitive length of 600 microns and a diameter of 100 microns.

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

Scattering of a high-order Bessel beam by a spheroidal particle

NASA Astrophysics Data System (ADS)

Han, Lu

2018-05-01

Within the framework of generalized Lorenz-Mie theory (GLMT), scattering from a homogeneous spheroidal particle illuminated by a high-order Bessel beam is formulated analytically. The high-order Bessel beam is expanded in terms of spheroidal vector wave functions, where the spheroidal beam shape coefficients (BSCs) are computed conveniently using an intrinsic method. Numerical results concerning scattered field in the far zone are displayed for various parameters of the incident Bessel beam and of the scatter. These results are expected to provide useful insights into the scattering of a Bessel beam by nonspherical particles and particle manipulation applications using Bessel beams.

Intra-beam scattering and its application to ERL

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

Fedotov, A.

Treatment of Coulomb collisions within the beam requires consideration of both large and small angle scattering. Such collisions lead to the Touschek effect and Intrabeam Scattering (IBS). The Touschek effect refers to particle loss as a result of a single collision, where only transfer from the transverse direction into longitudinal plays a role. It is important to consider this effect for ERL design to have an appropriate choice of collimation system. The IBS is a diffusion process which leads to changes of beam distribution but does not necessarily result in a beam loss. Evaluation of IBS in ERLs, where beammore » distribution is non-Gaussian, requires special treatment. Here we describe the IBS and Touschek effects with application to ERLs. In circular accelerators both the Touschek effect and IBS were found important. The generalized formulas for Touschek calculations are available and are already being used in advanced tracking simulations of several ERL-based projects. The IBS (which is diffusion due to multiple Coulomb scattering) is not expected to cause any significant effect on beam distribution in ERLs, unless one considers very long transport of high-brightness beams at low energies. Both large and small-angle Coulomb scattering can contribute to halo formation in future ERLs with high-brightness beams, as follows from simple order-of-magnitude estimates. In this report, a test comparison between 'local' and 'sliced' IBS models within the BET ACOOL code was presented for an illustrative ERL distribution. We also presented accumulated current loss distribution due to Touschek scattering for design parameters of ERL proposed for the eRHIC project, as well as scaling for multi-pass ERLs.« less

Investigation on Beam-Blocker-Based Scatter Correction Method for Improving CT Number Accuracy

NASA Astrophysics Data System (ADS)

Lee, Hoyeon; Min, Jonghwan; Lee, Taewon; Pua, Rizza; Sabir, Sohail; Yoon, Kown-Ha; Kim, Hokyung; Cho, Seungryong

2017-03-01

Cone-beam computed tomography (CBCT) is gaining widespread use in various medical and industrial applications but suffers from substantially larger amount of scatter than that in the conventional diagnostic CT resulting in relatively poor image quality. Various methods that can reduce and/or correct for the scatter in the CBCT have therefore been developed. Scatter correction method that uses a beam-blocker has been considered a direct measurement-based approach providing accurate scatter estimation from the data in the shadows of the beam-blocker. To the best of our knowledge, there has been no record reporting the significance of the scatter from the beam-blocker itself in such correction methods. In this paper, we identified the scatter from the beam-blocker that is detected in the object-free projection data investigated its influence on the image accuracy of CBCT reconstructed images, and developed a scatter correction scheme that takes care of this scatter as well as the scatter from the scanned object.

Plasma formed ion beam projection lithography system

DOEpatents

Leung, Ka-Ngo; Lee, Yung-Hee Yvette; Ngo, Vinh; Zahir, Nastaran

2002-01-01

A plasma-formed ion-beam projection lithography (IPL) system eliminates the acceleration stage between the ion source and stencil mask of a conventional IPL system. Instead a much thicker mask is used as a beam forming or extraction electrode, positioned next to the plasma in the ion source. Thus the entire beam forming electrode or mask is illuminated uniformly with the source plasma. The extracted beam passes through an acceleration and reduction stage onto the resist coated wafer. Low energy ions, about 30 eV, pass through the mask, minimizing heating, scattering, and sputtering.

NONLINEAR AND FIBER OPTICS: Transient stimulated thermal scattering in a field of quasiplanar counterpropagating pump beams

NASA Astrophysics Data System (ADS)

Arutyunov, Yu A.; Bagan, A. A.; Gerasimov, V. B.; Golyanov, A. V.; Ogluzdin, Valerii E.; Sugrobov, V. A.; Khizhnyak, A. I.

1990-04-01

Theoretical analyses and experimental studies are made of transient stimulated thermal scattering in a thermal nonlinear medium subjected to a field of counterpropagating quasiplane waves. The equations for the counterpropagating four-beam interaction are solved analytically for pairwise counterpropagating scattered waves using the constant pump wave intensity approximation. The conditions for the occurrence of an absolute instability of the scattered waves are determined and the angular dependence of their increment is obtained; these results are in good agreement with experimental data. An investigation is reported of the dynamics of spiky lasing in a laser with resonators coupled by a dynamic hologram in which stimulated thermal scattering is a source of radiation initiating lasing in the system as a whole.

SU-F-J-211: Scatter Correction for Clinical Cone-Beam CT System Using An Optimized Stationary Beam Blocker with a Single Scan

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

Liang, X; Zhang, Z; Xie, Y

Purpose: X-ray scatter photons result in significant image quality degradation of cone-beam CT (CBCT). Measurement based algorithms using beam blocker directly acquire the scatter samples and achieve significant improvement on the quality of CBCT image. Within existing algorithms, single-scan and stationary beam blocker proposed previously is promising due to its simplicity and practicability. Although demonstrated effectively on tabletop system, the blocker fails to estimate the scatter distribution on clinical CBCT system mainly due to the gantry wobble. In addition, the uniform distributed blocker strips in our previous design results in primary data loss in the CBCT system and leads tomore » the image artifacts due to data insufficiency. Methods: We investigate the motion behavior of the beam blocker in each projection and design an optimized non-uniform blocker strip distribution which accounts for the data insufficiency issue. An accurate scatter estimation is then achieved from the wobble modeling. Blocker wobble curve is estimated using threshold-based segmentation algorithms in each projection. In the blocker design optimization, the quality of final image is quantified using the number of the primary data loss voxels and the mesh adaptive direct search algorithm is applied to minimize the objective function. Scatter-corrected CT images are obtained using the optimized blocker. Results: The proposed method is evaluated using Catphan@504 phantom and a head patient. On the Catphan©504, our approach reduces the average CT number error from 115 Hounsfield unit (HU) to 11 HU in the selected regions of interest, and improves the image contrast by a factor of 1.45 in the high-contrast regions. On the head patient, the CT number error is reduced from 97 HU to 6 HU in the soft tissue region and image spatial non-uniformity is decreased from 27% to 5% after correction. Conclusion: The proposed optimized blocker design is practical and attractive for CBCT guided radiation therapy. This work is supported by grants from Guangdong Innovative Research Team Program of China (Grant No. 2011S013), National 863 Programs of China (Grant Nos. 2012AA02A604 and 2015AA043203), the National High-tech R&D Program for Young Scientists by the Ministry of Science and Technology of China (Grant No. 2015AA020917)« less

Extending the range of turbidity measurement using polarimetry

DOEpatents

Baba, Justin S.

2017-11-21

Turbidity measurements are obtained by directing a polarized optical beam to a scattering sample. Scattered portions of the beam are measured in orthogonal polarization states to determine a scattering minimum and a scattering maximum. These values are used to determine a degree of polarization of the scattered portions of the beam, and concentrations of scattering materials or turbidity can be estimated using the degree of polarization. Typically, linear polarizations are used, and scattering is measured along an axis that orthogonal to the direction of propagation of the polarized optical beam.

Improved Gaussian Beam-Scattering Algorithm

NASA Technical Reports Server (NTRS)

Lock, James A.

1995-01-01

The localized model of the beam-shape coefficients for Gaussian beam-scattering theory by a spherical particle provides a great simplification in the numerical implementation of the theory. We derive an alternative form for the localized coefficients that is more convenient for computer computations and that provides physical insight into the details of the scattering process. We construct a FORTRAN program for Gaussian beam scattering with the localized model and compare its computer run time on a personal computer with that of a traditional Mie scattering program and with three other published methods for computing Gaussian beam scattering. We show that the analytical form of the beam-shape coefficients makes evident the fact that the excitation rate of morphology-dependent resonances is greatly enhanced for far off-axis incidence of the Gaussian beam.

Nuclear structure research at the Triangle Universities Nuclear Laboratory

NASA Astrophysics Data System (ADS)

Mitchell, G. E.

1992-10-01

Studies of fundamental symmetries by the TRIPLE collaboration using the unique capabilities at LAMTF have found unexpected systematics in the parity-violating amplitudes for epithermal-neutron scattering. Tests to lower the present limits on time-reversal-invariance violation in the strong interaction are being made at in experiments on the scattering of polarized fast neutrons from aligned holmium targets. Studies of few-nucleon systems have received increasing emphasis over the past year, involving a broad program for testing the low- to medium-energy internucleon interactions, from the tensor component in n-p scattering and the n-n scattering lengths, through three-nucleon systems and the alpha particle, on up to Be-8. Of particular interest are three-nucleon systems, both in elastic scattering and in three-body breakup. Beam requirements range from production of intense and highly-polarized neutron beams to tensor-polarized beams for measurements at both very low energies (25-80 keV) and at tandem energies for definitive measurements of D-state components of the triton, He-3, and He-4 obtained from transfer reactions. The program in nuclear astrophysics expanded during 1991-1992. Several facets of the nuclear many-body problem and of excitation mechanisms of the nucleus are being elucidated, including measurements and analyses to elucidate the neutron-nucleus elastic-scattering interaction over a wide range of nuclei and energies. Several projects involved developments in electronuclear physics, instrumentation, RF-transition units, and low-temperature bolometric particle detectors.

Precision Electron Beam Polarimetry in Hall C at Jefferson Lab

NASA Astrophysics Data System (ADS)

Gaskell, David

2013-10-01

The electron beam polarization in experimental Hall C at Jefferson Lab is measured using two devices. The Hall-C/Basel Møller polarimeter measures the beam polarization via electron-electron scattering and utilizes a novel target system in which a pure iron foil is driven to magnetic saturation (out of plane) using a superconducting solenoid. A Compton polarimeter measures the polarization via electron-photon scattering, where the photons are provided by a high-power, CW laser coupled to a low gain Fabry-Perot cavity. In this case, both the Compton-scattered electrons and backscattered photons provide measurements of the beam polarization. Results from both polarimeters, acquired during the Q-Weak experiment in Hall C, will be presented. In particular, the results of a test in which the Møller and Compton polarimeters made interleaving measurements at identical beam currents will be shown. In addition, plans for operation of both devices after completion of the Jefferson Lab 12 GeV Upgrade will also be discussed.

Advances in the FTU collective Thomson scattering system

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

Bin, W., E-mail: wbin@ifp.cnr.it; Bruschi, A.; Grosso, G.

The new collective Thomson scattering diagnostic installed on the Frascati Tokamak Upgrade device started its first operations in 2014. The ongoing experiments investigate the presence of signals synchronous with rotating tearing mode islands, possibly due to parametric decay processes, and phenomena affecting electron cyclotron beam absorption or scattering measurements. The radiometric system, diagnostic layout, and data acquisition system were improved accordingly. The present status and near-term developments of the diagnostic are presented.

Application of a scattered-light radiometric power meter.

PubMed

Caron, James N; DiComo, Gregory P; Ting, Antonio C; Fischer, Richard P

2011-04-01

The power measurement of high-power continuous-wave laser beams typically calls for the use of water-cooled thermopile power meters. Large thermopile meters have slow response times that can prove insufficient to conduct certain tests, such as determining the influence of atmospheric turbulence on transmitted beam power. To achieve faster response times, we calibrated a digital camera to measure the power level as the optical beam is projected onto a white surface. This scattered-light radiometric power meter saves the expense of purchasing a large area power meter and the required water cooling. In addition, the system can report the power distribution, changes in the position, and the spot size of the beam. This paper presents the theory of the scattered-light radiometric power meter and demonstrates its use during a field test at a 2.2 km optical range. © 2011 American Institute of Physics

Analysis of laser light-scattering interferometric devices for in-line diagnostics of moving particles

NASA Astrophysics Data System (ADS)

Naqwi, Amir A.; Durst, Franz

1993-07-01

Dual-beam laser measuring techniques are now being used, not only for velocimetry, but also for simultaneous measurements of particle size and velocity in particulate two-phase flows. However, certain details of these optical techniques, such as the effect of Gaussian beam profiles on the accuracy of the measurements, need to be further explored. To implement innovative improvements, a general analytic framework is needed in which performances of various dual-beam instruments could be quantitatively studied and compared. For this purpose, the analysis of light scattering in a generalized dual-wave system is presented in this paper. The present simulation model provides a basis for studying effects of nonplanar beam structures of incident waves, taking into account arbitrary modes of polarization. A polarizer is included in the receiving optics as well. The peculiar aspects of numerical integration of scattered light over circular, rectangular, and truncated circular apertures are also considered.

Propagation and scattering of vector light beam in turbid scattering medium

NASA Astrophysics Data System (ADS)

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

2014-03-01

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

Thomson scattering diagnostic on the Compact Toroidal Hybrid Experiment

NASA Astrophysics Data System (ADS)

Traverso, Peter; Maurer, D. A.; Ennis, D. A.; Hartwell, G. J.

2016-10-01

A Thomson scattering system is being commissioned for the non-axisymmetric plasmas of the Compact Toroidal Hybrid (CTH), a five-field period current-carrying torsatron. The system takes a single point measurement at the magnetic axis to both calibrate the two- color soft x-ray Te system and serve as an additional diagnostic for the V3FIT 3D equilibrium reconstruction code. A single point measurement will reduce the uncertainty in the reconstructed peak pressure by an order of magnitude for both current-carrying plasmas and future gyrotron-heated stellarator plasmas. The beam, generated by a frequency doubled Continuum 2 J, Nd:YaG laser, is passed vertically through an entrance Brewster window and a two-aperture optical baffle system to minimize stray light. The beam line propagates 8 m to the CTH device mid-plane with the beam diameter < 3 mm inside the plasma volume. Thomson scattered light is collected by two adjacent f/2 plano-convex condenser lenses and focused onto a custom fiber bundle. The fiber is then re-bundled and routed to a Holospec f/1.8 spectrograph to collect the red-shifted scattered light from 535-565 nm. The system has been designed to measure plasmas with core Te of 100 to 200 eV and densities of 5 ×1018 to 5 ×1019 m-3. Work supported by USDOE Grant DE-FG02-00ER54610.

SU-F-T-142: An Analytical Model to Correct the Aperture Scattered Dose in Clinical Proton Beams

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

Sun, B; Liu, S; Zhang, T

2016-06-15

Purpose: Apertures or collimators are used to laterally shape proton beams in double scattering (DS) delivery and to sharpen the penumbra in pencil beam (PB) delivery. However, aperture-scattered dose is not included in the current dose calculations of treatment planning system (TPS). The purpose of this study is to provide a method to correct the aperture-scattered dose based on an analytical model. Methods: A DS beam with a non-divergent aperture was delivered using a single-room proton machine. Dose profiles were measured with an ion-chamber scanning in water and a 2-D ion chamber matrix with solid-water buildup at various depths. Themore » measured doses were considered as the sum of the non-contaminated dose and the aperture-scattered dose. The non-contaminated dose was calculated by TPS and subtracted from the measured dose. Aperture scattered-dose was modeled as a 1D Gaussian distribution. For 2-D fields, to calculate the scatter-dose from all the edges of aperture, a sum of weighted distance was used in the model based on the distance from calculation point to aperture edge. The gamma index was calculated between the measured and calculated dose with and without scatter correction. Results: For a beam with range of 23 cm and aperture size of 20 cm, the contribution of the scatter horn was ∼8% of the total dose at 4 cm depth and diminished to 0 at 15 cm depth. The amplitude of scatter-dose decreased linearly with the depth increase. The 1D gamma index (2%/2 mm) between the calculated and measured profiles increased from 63% to 98% for 4 cm depth and from 83% to 98% at 13 cm depth. The 2D gamma index (2%/2 mm) at 4 cm depth has improved from 78% to 94%. Conclusion: Using the simple analytical method the discrepancy between the measured and calculated dose has significantly improved.« less

Scattering of aerosol particles by a Hermite-Gaussian beam in marine atmosphere.

PubMed

Huang, Qingqing; Cheng, Mingjian; Guo, Lixin; Li, Jiangting; Yan, Xu; Liu, Songhua

2017-07-01

Based on the complex-source-point method and the generalized Lorenz-Mie theory, the scattering properties and polarization of aerosol particles by a Hermite-Gaussian (HG) beam in marine atmosphere is investigated. The influences of beam mode, beam width, and humidity on the scattered field are analyzed numerically. Results indicate that when the number of HG beam modes u (v) increase, the radar cross section of aerosol particles alternating appears at maximum and minimum values in the forward and backward scattering, respectively, because of the special petal-shaped distribution of the HG beam. The forward and backward scattering of aerosol particles decreases with the increase in beam waist. When beam waist is less than the radius of the aerosol particle, a minimum value is observed in the forward direction. The scattering properties of aerosol particles by the HG beam are more sensitive to the change in relative humidity compared with those by the plane wave and the Gaussian beam (GB). The HG beam shows superiority over the plane wave and the GB in detecting changes in the relative humidity of marine atmosphere aerosol. The effects of relative humidity on the polarization of the HG beam have been numerically analyzed in detail.

Helium Atom Scattering from C2H6, F2HCCH3, F3CCH2F and C2F6 in Crossed Molecular Beams

NASA Astrophysics Data System (ADS)

Hammer, Markus; Seidel, Wolfhart

1997-10-01

Rotationally unresolved differential cross sections were measured in crossed molecular beam experiments by scattering Helium atoms from Ethane, 1,1-Difluoroethane, 1,1,1,2-Tetrafluoroethane and Hexafluoroethane. The damping of observed diffraction oscillations was used to extract anisotropic interaction potentials for these scattering systems applying the infinite order sudden approximation (IOSA). Binary macroscopic parameters such as second heterogeneous virial coefficients and the coefficients of diffusion and viscosity were computed from these potentials and compared to results from macroscopic experiments.

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.

Propagation and transmission of optical vortex beams through turbid scattering wall with orbital angular momentums

NASA Astrophysics Data System (ADS)

Wang, W. B.; Gozali, Richard; Nguyen, Thien An; Alfano, R. R.

2015-03-01

Light scattering and transmission of optical Laguerre Gaussian (LG) vortex beams with different orbital angular momentum (OAM) states in turbid scattering media were investigated in comparison with Gaussian (G) beam. The scattering media used in the experiments consist of various sizes and concentrations of latex beads in water solutions. The LG beams were generated using a spatial light modulator in reflection mode. The ballistic transmissions of LG and G beams were measured with different ratios of thickness of samples (z) to scattering mean free path (ls) of the turbid media, z/ls. The results show that in the ballistic region where z/ls is small, the LG and G beams show no significant difference, while in the diffusive region where z/ls is large, LG beams show higher transmission than Gaussian beam. In the diffusive region, the LG beams with higher orbital angular momentum L values show higher transmission than the beams with lower L values. The transition points from ballistic to diffusive regions for different scattering media were studied and determined.

X-ray diffraction-based electronic structure calculations and experimental x-ray analysis for medical and materials applications

NASA Astrophysics Data System (ADS)

Mahato, Dip Narayan

This thesis includes x-ray experiments for medical and materials applications and the use of x-ray diffraction data in a first-principles study of electronic structures and hyperfine properties of chemical and biological systems. Polycapillary focusing lenses were used to collect divergent x rays emitted from conventional x-ray tubes and redirect them to form an intense focused beam. These lenses are routinely used in microbeam x-ray fluorescence analysis. In this thesis, their potential application to powder diffraction and focused beam orthovoltage cancer therapy has been investigated. In conventional x-ray therapy, very high energy (˜ MeV) beams are used, partly to reduce the skin dose. For any divergent beam, the dose is necessarily highest at the entry point, and decays exponentially into the tissue. To reduce the skin dose, high energy beams, which have long absorption lengths, are employed, and rotated about the patient to enter from different angles. This necessitates large expensive specialized equipment. A focused beam could concentrate the dose within the patient. Since this is inherently skin dose sparing, lower energy photons could be employed. A primary concern in applying focused beams to therapy is whether the focus would be maintained despite Compton scattering within the tissue. To investigate this, transmission and focal spot sizes as a function of photon energy of two polycapillary focusing lenses were measured. The effects of tissue-equivalent phantoms of different thicknesses on the focal spot size were studied. Scatter fraction and depth dose were calculated. For powder diffraction, the polycapillary optics provide clean Gaussian peaks, which result in angular resolution that is much smaller than the peak width due to the beam convergence. Powder diffraction (also called coherent scatter) without optics can also be used to distinguish between tissue types that, because they have different nanoscale structures, scatter at different angles. Measurements were performed on the development of coherent scatter imaging to provide tissue type information in mammography. Atomic coordinates from x-ray diffraction data were used to study the nuclear quadrupole interactions and nature of molecular binding in DNA/RNA nucleobases and molecular solid BF3 systems.

Profiling of back-scattered electrons in opposed magnetic field of a Twin Electron Beam Gun

NASA Astrophysics Data System (ADS)

Sethi, S.; Gupta, Anchal; Dileep Kumar, V.; Mukherjee, Jaya; Gantayet, L. M.

2012-11-01

Electron gun is extensively used in material processing, physical vapour deposition and atomic vapour based laser processes. In these processes where the electron beam is incident on the substrate, a significant fraction of electron beam gets back-scattered from the target surface. The trajectory of this back scattered electron beam depends on the magnetic field in the vicinity. The fraction of back-scattered depends on the atomic number of the target metal and can be as high as ~40% of the incident beam current. These back-scattered electrons can cause undesired hot spots and also affect the overall process. Hence, the study of the trajectory of these back-scattered electrons is important. This paper provides the details of experimentally mapped back-scattered electrons of a 2×20kW Twin Electron Beam Gun (TEBG) in opposed magnetic field i.e. with these guns placed at 180° to each other.

Method for using polarization gating to measure a scattering sample

DOEpatents

Baba, Justin S.

2015-08-04

Described herein are systems, devices, and methods facilitating optical characterization of scattering samples. A polarized optical beam can be directed to pass through a sample to be tested. The optical beam exiting the sample can then be analyzed to determine its degree of polarization, from which other properties of the sample can be determined. In some cases, an apparatus can include a source of an optical beam, an input polarizer, a sample, an output polarizer, and a photodetector. In some cases, a signal from a photodetector can be processed through attenuation, variable offset, and variable gain.

Setting up a Rayleigh Scattering Based Flow Measuring System in a Large Nozzle Testing Facility

NASA Technical Reports Server (NTRS)

Panda, Jayanta; Gomez, Carlos R.

2002-01-01

A molecular Rayleigh scattering based air density measurement system has been built in a large nozzle testing facility at NASA Glenn Research Center. The technique depends on the light scattering by gas molecules present in air; no artificial seeding is required. Light from a single mode, continuous wave laser was transmitted to the nozzle facility by optical fiber, and light scattered by gas molecules, at various points along the laser beam, is collected and measured by photon-counting electronics. By placing the laser beam and collection optics on synchronized traversing units, the point measurement technique is made effective for surveying density variation over a cross-section of the nozzle plume. Various difficulties associated with dust particles, stray light, high noise level and vibration are discussed. Finally, a limited amount of data from an underexpanded jet are presented and compared with expected variations to validate the technique.

Method and apparatus for aerosol particle absorption spectroscopy

DOEpatents

Campillo, Anthony J.; Lin, Horn-Bond

1983-11-15

A method and apparatus for determining the absorption spectra, and other properties, of aerosol particles. A heating beam source provides a beam of electromagnetic energy which is scanned through the region of the spectrum which is of interest. Particles exposed to the heating beam which have absorption bands within the band width of the heating beam absorb energy from the beam. The particles are also illuminated by light of a wave length such that the light is scattered by the particles. The absorption spectra of the particles can thus be determined from an analysis of the scattered light since the absorption of energy by the particles will affect the way the light is scattered. Preferably the heating beam is modulated to simplify the analysis of the scattered light. In one embodiment the heating beam is intensity modulated so that the scattered light will also be intensity modulated when the particles absorb energy. In another embodiment the heating beam passes through an interferometer and the scattered light reflects the Fourier Transform of the absorption spectra.

SU-E-I-55: The Contribution to Skin Dose Due to Scatter From the Patient Table and the Head Holder During Fluoroscopy

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

Islam, N; Xiong, Z; Vijayan, S

2015-06-15

Purpose: To determine contributions to skin dose due to scatter from the table and head holder used during fluoroscopy, and also to explore alternative design material to reduce the scatter dose. Methods: Measurements were made of the primary and scatter components of the xray beam exiting the patient table and a cylindrical head holder used on a Toshiba Infinix c-arm unit as a function of kVp for the various beam filters on the machine and for various field sizes. The primary component of the beam was measured in air with the object placed close to the x-ray tube with anmore » air gap between it and a 6 cc parallel-plate ionization chamber and with the beam collimated to a size just larger than the chamber. The primary plus scatter radiation components were measured with the object moved to a position in the beam next to the chamber for larger field sizes. Both sets of measurements were preformed while keeping the source-to-chamber distance fixed. The scatter fraction was estimated by taking the ratio of the difference between the two measurements and the reading that included both primary and scatter. Similar measurements were also made for a 2.3 cm thick Styrofoam block which could substitute for the patient support. Results: The measured scatter fractions indicate that the patient table as well as the head holder contributes an additional 10–16% to the patient entrance dose depending on field size. Forward scatter was reduced with the Styrofoam block so that the scatter fraction was about 4–5%. Conclusion: The results of this investigation demonstrated that scatter from the table and head holder used in clinical fluoroscopy contribute substantially to the skin dose. The lower contribution of scatter from Styrofoam suggests that there is an opportunity to redesign patient support accessories to reduce the skin dose. Partial support from NIH grant R01EB002873 and Toshiba Medical Systems Corporation Equipment Grant.« less

Photoluminescence-based quality control for thin film absorber layers of photovoltaic devices

DOEpatents

Repins, Ingrid L.; Kuciauskas, Darius

2015-07-07

A time-resolved photoluminescence-based system providing quality control during manufacture of thin film absorber layers for photovoltaic devices. The system includes a laser generating excitation beams and an optical fiber with an end used both for directing each excitation beam onto a thin film absorber layer and for collecting photoluminescence from the absorber layer. The system includes a processor determining a quality control parameter such as minority carrier lifetime of the thin film absorber layer based on the collected photoluminescence. In some implementations, the laser is a low power, pulsed diode laser having photon energy at least great enough to excite electron hole pairs in the thin film absorber layer. The scattered light may be filterable from the collected photoluminescence, and the system may include a dichroic beam splitter and a filter that transmit the photoluminescence and remove scattered laser light prior to delivery to a photodetector and a digital oscilloscope.

Recent results on reactions with radioactive beams at RIBRAS (Radioactive Ion Beams in Brazil)

NASA Astrophysics Data System (ADS)

Lépine-Szily, A.; Lichtenthäler, R.; Guimarães, V.; Arazi, A.; Barioni, A.; Benjamim, E. A.; de Faria, P. N.; Descouvemont, P.; Gasques, L. R.; E; Leistenschneider; Mendes, D. R., Jr.; Morais, M. C.; Morcelle, V.; Moro, A. M.; Pampa Condori, R.; Pires, K. C. C.; Rodriguez-Gallardo, M.; Scarduelli, V.; Shorto, J. M. B.; Zamora, J. C.

2015-04-01

We present a quick description of RIBRAS (Radioactive Ion beams in Brazil), which is a superconducting double solenoid system, installed at the Pelletron Laboratory of the University of São Paulo and extends the capabilities of the original Pelletron Tandem Accelerator of 8MV terminal voltage (8UD) by producing secondary beams of unstable nuclei. The experimental program of the RIBRAS covers the study of elastic and inelastic scattering with the objective to study the interaction potential and the reaction mechanisms between weakly bound (RIB) and halo (6He and 8B) projectiles on light, medium and heavy mass targets. With highly purified beams, the study of resonant elastic scattering and resonant transfer reactions, using inverse kinematics and thick targets, have also been included in our recent experimental program.

Field-size dependence of doses of therapeutic carbon beams.

PubMed

Kusano, Yohsuke; Kanai, Tatsuaki; Yonai, Shunsuke; Komori, Masataka; Ikeda, Noritoshi; Tachikawa, Yuji; Ito, Atsushi; Uchida, Hirohisa

2007-10-01

To estimate the physical dose at the center of spread-out Bragg peaks (SOBP) for various conditions of the irradiation system, a semiempirical approach was applied. The dose at the center of the SOBP depends on the field size because of large-angle scattering particles in the water phantom. For a small field of 5 x 5 cm2, the dose was reduced to 99.2%, 97.5%, and 96.5% of the dose used for the open field in the case of 290, 350, and 400 MeV/n carbon beams, respectively. Based on the three-Gaussian form of the lateral dose distributions of the carbon pencil beam, which has previously been shown to be effective for describing scattered carbon beams, we reconstructed the dose distributions of the SOBP beam. The reconstructed lateral dose distribution reproduced the measured lateral dose distributions very well. The field-size dependencies calculated using the reconstructed lateral dose distribution of the therapeutic carbon beam agreed with the measured dose dependency very well. The reconstructed beam was also used for irregularly shaped fields. The resultant dose distribution agreed with the measured dose distribution. The reconstructed beams were found to be applicable to the treatment-planning system.

Characteristics of an axisymmetric sudden expansion flow

NASA Technical Reports Server (NTRS)

Stevenson, W. H.; Thompson, H. D.

1985-01-01

A two-color, two component Laser Doppler Velocimeter (LDV) system operating in forward scatter has been developed in order to make simultaneous measurements of the axial and radial velocity components in an axisymmetric sudden expansion flow with and without combustion. The LDV system includes Bragg cell modulators in the four beam paths to allow a net frequency shift of 5MHz in both the green and blue beams. This permits an unambiguous measurement of negative velocities and also eliminates incomplete signal bias. The green beam probe volume has a waist diameter of 0.200 mm and is approximately 2mm long. The blue beam has a probe volume waist of 0.250 mm and is approximately 1 mm long. The scattered light from the probe volume is separated so that approximately 80% of each color passes to its respective photomultiplier tube by using a dichroic filter. Narrow bandpass filters are used to further filter unwanted signals before they are detected. A schematic diagram of the LDV system is shown.

Development of a hybrid molecular beam epitaxy deposition system for in situ surface x-ray studies

NASA Astrophysics Data System (ADS)

Andersen, Tassie K.; Cook, Seyoung; Benda, Erika; Hong, Hawoong; Marks, Laurence D.; Fong, Dillon D.

2018-03-01

A portable metalorganic gas delivery system designed and constructed to interface with an existing molecular beam epitaxy chamber at beamline 33-ID-E of the Advanced Photon Source is described. This system offers the ability to perform in situ X-ray measurements of complex oxide growth via hybrid molecular beam epitaxy. The performance of the hybrid molecular beam epitaxy system while delivering metalorganic source materials is described. The high-energy X-ray scattering capabilities of the hybrid molecular beam epitaxy system are demonstrated both on oxide films grown solely from the metalorganic source and ABO3 oxide perovskites containing elements from both the metalorganic source and a traditional effusion cell.

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.

Optical vortex beam transmission with different OAM in scattering beads and brain tissue media

NASA Astrophysics Data System (ADS)

Wang, W. B.; Shi, Lingyan; Lindwasser, Lukas; Marque, Paulo; Lavery, M. P. J.; Alfano, R. R.

2016-03-01

Light transmission of Laguerre Gaussian (LG) vortex beams with different orbital angular momentum (OAM) values (L) in scattering beads and mouse brain tissue media were experimentally investigated for the first time in comparison with Gaussian (G) beams. The LG beams with different OAM were generated using a spatial light modulator (SLM) in reflection mode. The scattering beads media consist of various sizes and concentrations of latex beads in water solutions. The transmissions of LG and G beams through scattering beads and brain tissue media were measured with different ratios of sample thicknesses (z) to scattering mean free path (ls) of the turbid media, z/ls. The results indicate that within the ballistic region where z/ls is small, the LG and G beams show no significant difference, while in the diffusive region where z/ls is higher, the vortex beams show higher transmission than G beams. In the diffusive region, the LG beams with higher L values show higher transmission than the beams with lower L values due to the eigen channels in the media. The transition points from the ballistic to diffusive regions for different scattering beads and brain tissue media were studied.

Depth Dose Measurement using a Scintillating Fiber Optic Dosimeter for Proton Therapy Beam of the Passive-Scattering Mode Having Range Modulator Wheel

NASA Astrophysics Data System (ADS)

Hwang, Ui-Jung; Shin, Dongho; Lee, Se Byeong; Lim, Young Kyung; Jeong, Jong Hwi; Kim, Hak Soo; Kim, Ki Hwan

2018-05-01

To apply a scintillating fiber dosimetry system to measure the range of a proton therapy beam, a new method was proposed to correct for the quenching effect on measuring an spread out Bragg peak (SOBP) proton beam whose range is modulated by a range modulator wheel. The scintillating fiber dosimetry system was composed of a plastic scintillating fiber (BCF-12), optical fiber (SH 2001), photo multiplier tube (H7546), and data acquisition system (PXI6221 and SCC68). The proton beam was generated by a cyclotron (Proteus-235) in the National Cancer Center in Korea. It operated in the double-scattering mode and the spread out of the Bragg peak was achieved by a spinning range modulation wheel. Bragg peak beams and SOBP beams of various ranges were measured, corrected, and compared to the ion chamber data. For the Bragg peak beam, quenching equation was used to correct the quenching effect. On the proposed process of correcting SOBP beams, the measured data using a scintillating fiber were separated by the Bragg peaks that the SOBP beam contained, and then recomposed again to reconstruct an SOBP after correcting for each Bragg peak. The measured depth-dose curve for the single Bragg peak beam was well corrected by using a simple quenching equation. Correction for SOBP beam was conducted with a newly proposed method. The corrected SOBP signal was in accordance with the results measured with an ion chamber. We propose a new method to correct for the SOBP beam from the quenching effect in a scintillating fiber dosimetry system. This method can be applied to other scintillator dosimetry for radiation beams in which the quenching effect is shown in the scintillator.

SU-E-T-90: Concrete Forward-Scatter Fractions for Radiotherapy Shielding Applications

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

Tanny, S; Parsai, E

2014-06-01

Purpose: There is little instruction within the primary shielding guidance document NCRP 151 for vault designs where the primary beam intercepts the maze. We have conducted a Monte-Carlo study to characterize forward-scattered radiation from concrete barriers with the intent of quantifying what amount of additional shielding outside the primary beam is needed in this situation. Methods: We reproduced our vault in MCNP 5 and simulated spectra obtained from the literature and from our treatment planning system for 10 and 18 MV beams. Neutron and gamma-capture contributions were not simulated. Energy deposited was scored at isocenter in a water phantom, withinmore » various cells that comprised the maze, and within cells that comprised the vault door. Tracks were flagged that scattered from within the maze to the door and their contributions were tallied separately. Three different concrete mixtures found in the literature were simulated. An empirically derived analytic equation was used for comparison, utilizing patient scatter fractions to approximate the scatter from concrete. Results: Our simulated data confirms that maze-scattered radiation is a significant contribution to total photon dose at the door. It contributes between 20-35% of the photon shielding workload. Forward-scatter fractions for concrete were somewhat dependent on concrete composition and the relative abundance of higher-Z elements. Scatter fractions were relatively insensitive to changes in the primary photon spectrum. Analytic results were of the same magnitude as simulated results. Conclusions: Forward-scattered radiation from the maze barrier needs to be included in the photon workload for shielding calculations in non-standard vault designs. Scatter fractions will vary with concrete composition, but should be insensitive to spectral changes between machine manufacturers. Further plans for investigation include refined scatter fractions for various concrete compositions, scatter fraction measurement, and simulation of photo-nuclear interaction within the maze barrier for high-energy beams.« less

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

PubMed

Mitri, F G

2015-09-01

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

Scattering of a longitudinal Bessel beam by a sphere embedded in an isotropic elastic solid.

PubMed

Leão-Neto, J P; Lopes, J H; Silva, G T

2017-11-01

The scattering of a longitudinal Bessel beam of arbitrary order by a sphere embedded in an isotropic solid matrix is theoretically analyzed. The spherical inclusion can be made of a viscoelastic, elastic, or fluid-filled isotropic material. In the analysis, the absorbing, scattering, and extinction efficiency factors are obtained, e.g., the corresponding power per characteristic beam intensity per sphere's cross-section area. Furthermore, the extended optical theorem, which expresses the extinction efficiency in terms of an integral of the longitudinal scattering function is derived. Several features of zeroth- and first-order Bessel beams scattering in solids are illustrated considering a polymer adhesive (cured) sphere embedded in a stainless steel matrix. For instance, omnidirectional scattering can be achieved by choosing specific values of the half-cone angle of the Bessel beam, which is the beam's geometrical parameter. Additionally, it is demonstrated that mode suppression leads to lower absorption inside the inclusion when compared to plane wave scattering results.

The Radioactive Ion Beams in Brazil (RIBRAS) facility. Description, program, main results, future plans

NASA Astrophysics Data System (ADS)

Lépine-Szily, A.; Lichtenthäler, R.; Guimarães, V.

2014-08-01

RIBRAS (Radioactive Ion Beams in Brazil) is a facility installed at the Institute of Physics of the University of São Paulo (IFUSP), Brazil. The RIBRAS system consists of two superconducting solenoids and uses the "in-flight method" to produce radioactive ion beams using the primary beam provided by the 8UD Pelletron Tandem of IFUSP. The ion beams produced so far by RIBRAS are 6He, 8Li, 7Be, 10Be, 8B, 12B with intensities that can vary from 104 to 106 pps. Initially the experimental program covered the study of elastic and inelastic scattering with the objective to study the interaction potential and the reaction mechanisms between weakly bound (RIB) and halo (6He and 8B projectiles on light, medium and heavy mass targets. With highly purified beams, the study of resonant elastic scattering and resonant transfer reactions, using inverse kinematics and thick targets, has also been included in our experimental program. Also, transfer reactions of astrophysical interest and fusion reactions induced by halo nuclei are part of the near-future research program. Our recent results on elastic scattering, alpha-particle production and total reaction cross sections, as well as the resonant elastic and transfer reactions, are presented. Our plans for the near future are related to the installation of a new beam line and a cave for gamma-ray detection. We intend to place in operation a large area neutron detector available in our laboratory. The long-range plans could be the move of the RIBRAS system to the more energetic beam line of the LINAC post-accelerator (10MeV/nucleon primary beams) still in construction in our laboratory.

Scattering of a Tightly Focused Beam by an Optically Trapped Particle

NASA Technical Reports Server (NTRS)

Lock, James A.; Wrbanek, Susan Y.; Weiland, Kenneth E.

2006-01-01

Near-forward scattering of an optically trapped 5 m radius polystyrene latex sphere by the trapping beam was examined both theoretically and experimentally. Since the trapping beam is tightly focused, the beam fields superpose and interfere with the scattered fields in the forward hemisphere. The observed light intensity consists of a series of concentric bright and dark fringes centered about the forward scattering direction. Both the number of fringes and their contrast depend on the position of the trapping beam focal waist with respect to the sphere. The fringes are caused by diffraction due to the truncation of the tail of the trapping beam as the beam is transmitted through the sphere.

Two-photon absorption induced stimulated Rayleigh-Bragg scattering

NASA Astrophysics Data System (ADS)

He, Guang S.; Prasad, Paras N.

2005-01-01

A frequency-unshifted and backward stimulated scattering can be efficiently generated in one-photon-absorption free but two-photon absorbing materials. Using a number of novel two-photon absorbing dye solutions as the scattering media and nanosecond pulsed laser as the pump beams, a highly directional backward stimulated scattering at the exact pump wavelength can be readily observed once the pump intensity is higher than a certain threshold level. The spectral and spatial structures as well as the temporal behavior and optical phase-conjugation property of this new type of backward stimulated scattering have been experimentally studied. This stimulated scattering phenomenon can be explained by using a model of two-photon-excitation enhanced standing-wave Bragg grating initially formed by the strong forward pump beam and much weaker backward Rayleigh scattering beam; the partial reflection of the pump beam from this grating provides an positive feedback to the initial backward Rayleigh scattering beam without suffering linear attenuation influence. Comparing to other known stimulated (Raman, Brillouin, Rayleigh-wing, and Kerr) scattering effects, the stimulated Rayleigh-Bragg scattering exhibits the advantages of no frequency-shift, low pump threshold, and low spectral linewidth requirement.

Coherent Multiple Light Scattering in Ultracold Atomic Rb

NASA Astrophysics Data System (ADS)

Kulatunga, Pasad; Sukenik, C. I.; Balik, Salim; Havey, M. D.; Kupriyanov, D. V.; Sokolov, I. M.

2003-05-01

Wave transport in mesoscopic systems can be strongly influenced by coherent multiple scattering,which can lead to novel magneto-optic, transmission, and backscattering effects of light in atomic vapors. Although related to traditional studies of radiation trapping, in ultracold vapors negligible frequency or phase redistribution takes place in the scattering, and high-order coherent light scattering occurs. Among other things, this leads to enhancement of the influence of otherwise small non-resonant terms in the scattering amplitudes. We report investigation of multiple coherent light scattering from ultracold Rb atoms confined in a magneto-optic trap (MOT). In experimental studies, measurements are made of the angular, spectral, and polarization-dependent coherent backscattering profile of a low-intensity probe beam tuned near the F = 3 - F' = 4 hyperfine transition. The influence of higher probe beam intensity is also studied. In a theoretical study of angular intensity enhancement of backscattered light, we consider scattering orders up to 10 and a realistic and asymmetric Gaussian atom distribution in the MOT. Supported by NSF, NATO, and RFBR.

SU-E-I-09: The Impact of X-Ray Scattering On Image Noise for Dedicated Breast CT

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

Yang, K; Gazi, P; Boone, J

2015-06-15

Purpose: To quantify the impact of detected x-ray scatter on image noise in flat panel based dedicated breast CT systems and to determine the optimal scanning geometry given practical trade-offs between radiation dose and scatter reduction. Methods: Four different uniform polyethylene cylinders (104, 131, 156, and 184 mm in diameter) were scanned as the phantoms on a dedicated breast CT scanner developed in our laboratory. Both stationary projection imaging and rotational cone-beam CT imaging was performed. For each acquisition type, three different x-ray beam collimations were used (12, 24, and 109 mm measured at isocenter). The aim was to quantifymore » image noise properties (pixel variance, SNR, and image NPS) under different levels of x-ray scatter, in order to optimize the scanning geometry. For both projection images and reconstructed CT images, individual pixel variance and NPS were determined and compared. Noise measurement from the CT images were also performed with different detector binning modes and reconstruction matrix sizes. Noise propagation was also tracked throughout the intermediate steps of cone-beam CT reconstruction, including the inverse-logarithmic process, Fourier-filtering before backprojection. Results: Image noise was lower in the presence of higher scatter levels. For the 184 mm polyethylene phantom, the image noise (measured in pixel variance) was ∼30% lower with full cone-beam acquisition compared to a narrow (12 mm) fan-beam acquisition. This trend is consistent across all phantom sizes and throughout all steps of CT image reconstruction. Conclusion: From purely a noise perspective, the cone-beam geometry (i.e. the full cone-angle acquisition) produces lower image noise compared to the lower-scatter fan-beam acquisition for breast CT. While these results are relevant in homogeneous phantoms, the full impact of scatter on noise in bCT should involve contrast-to-noise-ratio measurements in heterogeneous phantoms if the goal is to optimize the scanning geometry for dedicated breast CT. This work was supported by a grant from the National Institute for Biomedical Imaging and Bioengineering (R01 EB002138)« less

Elastic scattering and total reaction cross section of {sup 6}He+{sup 120}Sn

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

Faria, P. N. de; Lichtenthaeler, R.; Pires, K. C. C.

The elastic scattering of {sup 6}He on {sup 120}Sn has been measured at four energies above the Coulomb barrier using the {sup 6}He beam produced at the RIBRAS (Radioactive Ion Beams in Brasil) facility. The elastic angular distributions have been analyzed with the optical model and three- and four-body continuum-discretized coupled-channels calculations. The total reaction cross sections have been derived and compared with other systems of similar masses.

Dynamic Airblast Simulator (DABS) Instrumentation Development. Phase 1

DTIC Science & Technology

1978-08-01

the laser system employing two beams . This theory will be expanded to provide insight to the design of a suitable velocity measure- ment system for...Laser Beam Crossover Region 91 B3 Cross Section of Ellipsoidal Interference Region 95 B4 Doppler Difference Measurement Geometry 96 B5 Scattering...Volume Assumptions 116 B6 Microwave Veloclmeter, Tunnel Floor Installation Layout, Typical for 120° Beam Intersection at 10.525 GHz 119 B7 Ku-Band

Development of a hybrid molecular beam epitaxy deposition system for in situ surface x-ray studies

DOE PAGES

Andersen, Tassie K.; Cook, Seyoung; Benda, Erika; ...

2018-03-08

A portable metalorganic gas delivery system designed and constructed to interface with an existing molecular beam epitaxy chamber at beamline 33-ID-E of the Advanced Photon Source is described. This system offers the ability to perform in situ X-ray measurements of complex oxide growth via hybrid molecular beam epitaxy. The performance of the hybrid molecular beam epitaxy system while delivering metalorganic source materials is described. In conclusion, the high-energy X-ray scattering capabilities of the hybrid molecular beam epitaxy system are demonstrated both on oxide films grown solely from the metalorganic source and ABO 3 oxide perovskites containing elements from both themore » metalorganic source and a traditional effusion cell.« less

Development of a hybrid molecular beam epitaxy deposition system for in situ surface x-ray studies

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

Andersen, Tassie K.; Cook, Seyoung; Benda, Erika

A portable metalorganic gas delivery system designed and constructed to interface with an existing molecular beam epitaxy chamber at beamline 33-ID-E of the Advanced Photon Source is described. This system offers the ability to perform in situ X-ray measurements of complex oxide growth via hybrid molecular beam epitaxy. The performance of the hybrid molecular beam epitaxy system while delivering metalorganic source materials is described. In conclusion, the high-energy X-ray scattering capabilities of the hybrid molecular beam epitaxy system are demonstrated both on oxide films grown solely from the metalorganic source and ABO 3 oxide perovskites containing elements from both themore » metalorganic source and a traditional effusion cell.« less

Quality assurance of proton beams using a multilayer ionization chamber system

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

Dhanesar, Sandeep; Sahoo, Narayan; Kerr, Matthew

2013-09-15

Purpose: The measurement of percentage depth-dose (PDD) distributions for the quality assurance of clinical proton beams is most commonly performed with a computerized water tank dosimetry system with ionization chamber, commonly referred to as water tank. Although the accuracy and reproducibility of this method is well established, it can be time-consuming if a large number of measurements are required. In this work the authors evaluate the linearity, reproducibility, sensitivity to field size, accuracy, and time-savings of another system: the Zebra, a multilayer ionization chamber system.Methods: The Zebra, consisting of 180 parallel-plate ionization chambers with 2 mm resolution, was used tomore » measure depth-dose distributions. The measurements were performed for scattered and scanned proton pencil beams of multiple energies delivered by the Hitachi PROBEAT synchrotron-based delivery system. For scattered beams, the Zebra-measured depth-dose distributions were compared with those measured with the water tank. The principal descriptors extracted for comparisons were: range, the depth of the distal 90% dose; spread-out Bragg peak (SOBP) length, the region between the proximal 95% and distal 90% dose; and distal-dose fall off (DDF), the region between the distal 80% and 20% dose. For scanned beams, the Zebra-measured ranges were compared with those acquired using a Bragg peak chamber during commissioning.Results: The Zebra demonstrated better than 1% reproducibility and monitor unit linearity. The response of the Zebra was found to be sensitive to radiation field sizes greater than 12.5 × 12.5 cm; hence, the measurements used to determine accuracy were performed using a field size of 10 × 10 cm. For the scattered proton beams, PDD distributions showed 1.5% agreement within the SOBP, and 3.8% outside. Range values agreed within −0.1 ± 0.4 mm, with a maximum deviation of 1.2 mm. SOBP length values agreed within 0 ± 2 mm, with a maximum deviation of 6 mm. DDF values agreed within 0.3 ± 0.1 mm, with a maximum deviation of 0.6 mm. For the scanned proton pencil beams, Zebra and Bragg peak chamber range values demonstrated agreement of 0.0 ± 0.3 mm with a maximum deviation of 1.3 mm. The setup and measurement time for all Zebra measurements was 3 and 20 times less, respectively, compared to the water tank measurements.Conclusions: Our investigation shows that the Zebra can be useful not only for fast but also for accurate measurements of the depth-dose distributions of both scattered and scanned proton beams. The analysis of a large set of measurements shows that the commonly assessed beam quality parameters obtained with the Zebra are within the acceptable variations specified by the manufacturer for our delivery system.« less

Passive beam forming and spatial diversity in meteor scatter communication systems

NASA Astrophysics Data System (ADS)

Akram, Ammad; Cannon, Paul S.

1996-03-01

The method of passive beam formation using a four-element Butler matrix to improve the signal availability of meteor scatter communication systems is investigated. Signal availability, defined as the integrated time that the signal-to-noise ratio (snr) exceeds some snr threshold, serves as an important indicator of system performance. Butler matrix signal availability is compared with the performance of a single four-element Yagi reference system using ˜6.5 hours of data from a 720 km north-south temperate latitude link. The signal availability improvement factor of the Butler matrix is found to range between 1.6-1.8 over the snr threshold range of 20-30 dB in a 300-Hz bandwidth. Experimental values of the Butler matrix signal availability improvement factor are compared with analytical predictions. The experimental values show an expected snr threshold dependency with a dramatic increase at high snr. A theoretical analysis is developed to describe this increase. The signal availability can be further improved by ˜10-20% in a system employing two four-element Butler matrices with squinted beams so as to illuminate the sky with eight high-gain beams. Space diversity is found to increase the signal availability of a single antenna system by ˜10-15%, but the technique has very little advantage in a system already employing passive beam formation.

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.

A Thomson scattering diagnostic on the Pegasus Toroidal experiment.

PubMed

Schlossberg, D J; Schoenbeck, N L; Dowd, A S; Fonck, R J; Moritz, J I; Thome, K E; Winz, G R

2012-10-01

By exploiting advances in high-energy pulsed lasers, volume phase holographic diffraction gratings, and image intensified CCD cameras, a new Thomson scattering system has been designed to operate from 532 - 592 nm on the Pegasus Toroidal Experiment. The system uses a frequency-doubled, Q-switched Nd:YAG laser operating with an energy of 2 J at 532 nm and a pulse duration of 7 ns FWHM. The beam path is < 7m, the beam diameter remains ≤ 3 mm throughout the plasma, and the beam dump and optical baffling is located in vacuum but can be removed for maintenance by closing a gate valve. A custom lens system collects scattered photons from 15 cm < R(maj) < 85 cm at ~F∕6 with 14 mm radial resolution. Initial measurements will be made at 12 spatial locations with 12 simultaneous background measurements at corresponding locations. The estimated signal at the machine-side collection optics is ~3.5 × 10(4) photons for plasma densities of 10(19) m(-3). Typical plasmas measured will range from densities of mid-10(18) to mid-10(19) m(-3) with electron temperatures from 10 to 1000 eV.

Design and implementation of a robust and cost-effective double-scattering system at a horizontal proton beamline

NASA Astrophysics Data System (ADS)

Helmbrecht, S.; Baumann, M.; Enghardt, W.; Fiedler, F.; Krause, M.; Lühr, A.

2016-11-01

Purpose: particle therapy has the potential to improve radiooncology. With more and more facilities coming into operation, also the interest for research at proton beams increases. Though many centers provide beam at an experimental room, some of them do not feature a device for radiation field shaping, a so called nozzle. Therefore, a robust and cost-effective double-scattering system for horizontal proton beamlines has been designed and implemented. Materials and methods: the nozzle is based on the double scattering technique. Two lead scatterers, an aluminum ridge-filter and two brass collimators were optimized in a simulation study to form a laterally homogeneous 10 cm × 10 cm field with a spread-out Bragg-peak (SOBP). The parts were mainly manufactured using 3D printing techniques and the system was set up at OncoRay's experimental beamline. Measurement of the radiation field were carried out using a water phantom. Results: high levels of dose homogeneity were found in lateral (dose variation ΔD/D < ±2%) as well as in beam direction (ΔD/D < ± 3% in the SOBP). The system has already been used for radiobiology and physical experiments. Conclusion: the presented setup allows for creating clinically realistic extended radiation fields at fixed horizontal proton beamlines and is ready to use for internal and external users. The excellent performance combined with the simplistic design let it appear as a valuable option for proton therapy centers intending to foster their experimental portfolio.

Low-energy ion beamline scattering apparatus for surface science investigations

NASA Astrophysics Data System (ADS)

Gordon, M. J.; Giapis, K. P.

2005-08-01

We report on the design, construction, and performance of a high current (monolayers/s), mass-filtered ion beamline system for surface scattering studies using inert and reactive species at collision energies below 1500 eV. The system combines a high-density inductively coupled plasma ion source, high-voltage floating beam transport line with magnet mass-filter and neutral stripping, decelerator, and broad based detection capabilities (ions and neutrals in both mass and energy) for products leaving the target surface. The entire system was designed from the ground up to be a robust platform to study ion-surface interactions from a more global perspective, i.e., high fluxes (>100μA/cm2) of a single ion species at low, tunable energy (50-1400±5eV full width half maximum) can be delivered to a grounded target under ultrahigh vacuum conditions. The high current at low energy problem is solved using an accel-decel transport scheme where ions are created at the desired collision energy in the plasma source, extracted and accelerated to high transport energy (20 keV to fight space charge repulsion), and then decelerated back down to their original creation potential right before impacting the grounded target. Scattered species and those originating from the surface are directly analyzed in energy and mass using a triply pumped, hybrid detector composed of an electron impact ionizer, hemispherical electrostatic sector, and rf/dc quadrupole in series. With such a system, the collision kinematics, charge exchange, and chemistry occurring on the target surface can be separated by fully analyzing the scattered product flux. Key design aspects of the plasma source, beamline, and detection system are emphasized here to highlight how to work around physical limitations associated with high beam flux at low energy, pumping requirements, beam focusing, and scattered product analysis. Operational details of the beamline are discussed from the perspective of available beam current, mass resolution, projectile energy spread, and energy tunability. As well, performance of the overall system is demonstrated through three proof-of-concept examples: (1) elastic binary collisions at low energy, (2) core-level charge exchange reactions involving Ne+20 with Mg /Al/Si/P targets, and (3) reactive scattering of CF2+/CF3+ off Si. These studies clearly demonstrate why low, tunable incident energy, as well as mass and energy filtering of products leaving the target surface is advantageous and often essential for studies of inelastic energy losses, hard-collision charge exchange, and chemical reactions that occur during ion-surface scattering.

Chevron beam dump for ITER edge Thomson scattering system.

PubMed

Yatsuka, E; Hatae, T; Vayakis, G; Bassan, M; Itami, K

2013-10-01

This paper contains the design of the beam dump for the ITER edge Thomson scattering system and mainly concerns its lifetime under the harsh thermal and electromagnetic loads as well as tight space allocation. The lifetime was estimated from the multi-pulse laser-induced damage threshold. In order to extend its lifetime, the structure of the beam dump was optimized. A number of bent sheets aligned parallel in the beam dump form a shape called a chevron which enables it to avoid the concentration of the incident laser pulse energy. The chevron beam dump is expected to withstand thermal loads due to nuclear heating, radiation from the plasma, and numerous incident laser pulses throughout the entire ITER project with a reasonable margin for the peak factor of the beam profile. Structural analysis was also carried out in case of electromagnetic loads during a disruption. Moreover, detailed issues for more accurate assessments of the beam dump's lifetime are clarified. Variation of the bi-directional reflection distribution function (BRDF) due to erosion by or contamination of neutral particles derived from the plasma is one of the most critical issues that needs to be resolved. In this paper, the BRDF was assumed, and the total amount of stray light and the absorbed laser energy profile on the beam dump were evaluated.

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%.

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

Islam, M; Ahmad, S; Jin, H

Purpose: The out-of-beam dose is important for understanding the peripheral dose in radiation therapy. In proton radiotherapy, the study of out-of-beam dose is scarce and the treatment planning system (TPS) based on pencil beam algorithm cannot accurately predict the out-of-beam dose. This study investigates the out-of-beam dose for the single-room Mevion S250 double scattering proton therapy system using experimentally measured and treatment planning software generated data. The results are compared with those reported for conventional photon beam therapy. However, this study does not incorporate the neutron contribution in the scattered dose. Methods: A total of seven proton treatment plans weremore » generated using Varian Eclipse TPS for three different sites (brain, lung, and pelvis) in an anthropomorphic phantom. Three field sizes of 5×5, 10×10, and 20×20 cm{sup 2} (lung only) with typical clinical range (13.3–22.8 g/cm{sup 2}) and modulation widths (5.3–14.0 g/cm{sup 2}) were used. A single beam was employed in each treatment plan to deliver a dose of 181.8 cGy (200.0 cGy (RBE)) to the selected target. The out-of-beam dose was measured at 2.0, 5.0, 10.0, and 15.0 cm from the beam edge in the phantom using a thimble chamber (PTW TN31010). Results: The out-of-beam dose generally increased with field size, range, and volume irradiated. For all the plans, the scattered dose sharply fell off with distance. At 2.0 cm, the out-of-beam dose ranged from 0.35% to 2.16% of the delivered dose; however, the dose was clinically negligible (<0.3%) at a distance of 5.0 cm and greater. In photon therapy, the slightly greater out-of-beam dose was reported (TG36; 4%, 2%, and 1% for 2.0, 5.0, and 10.0 cm, respectively, using 6 MV beam). Conclusion: The measured out-of-beam dose in proton therapy excluding neutron contribution was observed higher than the TPS calculated dose and comparable to that of photon beam therapy.« less

Phoenix's Laser Beam in Action on Mars

NASA Technical Reports Server (NTRS)

2008-01-01

[figure removed for brevity, see original site] Click on image to view the animation

The Surface Stereo Imager camera aboard NASA's Phoenix Mars Lander acquired a series of images of the laser beam in the Martian night sky. Bright spots in the beam are reflections from ice crystals in the low level ice-fog. The brighter area at the top of the beam is due to enhanced scattering of the laser light in a cloud. The Canadian-built lidar instrument emits pulses of laser light and records what is scattered back.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

Heating and scattering of ring-beam distributions by turbulence

NASA Technical Reports Server (NTRS)

Gray, P. C.; Pontius, D. H., Jr.; Matthaeus, W. H.

1995-01-01

Pickup ions in the solar wind are initially are born in ring-beam distributions, i.e. f(v) varies as delta(v(sub perpendicular) - V(sub sw)sin(Theta)) delta(v(sub parallel) - V(sub sw)cos(Theta)), where Theta is the angle between the solar wind velocity and the IMF(Interplanetary Magnetic Field), and V(sub sw) is the solar wind speed. Often the distribution has been presumed to relax to a distribution that is isotropic in Theta and essentially mono-energetic, a shell or a 'bi-spherical distribution.' However solar wind turbulence is capable of heating the ring distribution on the timescale of a few tens of gyroperiods, a timescale not greatly distinct from that required for pitch angle scattering to a shell. To describe this effect, we have performed test-particle studies of the heating/scattering of the ring beam distribution by MHD turbulence, adopting various models for the MHD fluctuations, including slab and fully dynamic 2D and 3D incompressible turbulence. Furthermore, a system composed of a cold ion ring and a background plasma is unstable to several kinetic plasma instabilities. We carried out kinetic simulations of the ring beam distribution, showing that plasma instabilities also rapidly energize and scatter particles. Results will be presented comparing relaxation and heating rates of the ring-beam distribution by the various mechanisms.

High-power laser radiation in atmospheric aerosols: Nonlinear optics of aerodispersed media

NASA Astrophysics Data System (ADS)

Zuev, V. E.; Zemlianov, A. A.; Kopytin, Iu. D.; Kuzikovskii, A. V.

The bulk of this book contains the results of investigations carried out at the Institute of Atmospheric Optics, Siberian Branch, USSR Academy of Science with the participation of the authors. The microphysical and optical characteristics of atmospheric aerosols are considered, taking into account light scattering by a single aerosol particle, light scattering by a system of particles, the scattering phase matrix, light scattering by clouds and fogs, light scattering by hazes, and scattering phase functions of polydispersed aerosols. Other topics studies are related to low-energy (subexplosive) effects of radiation on individual particles, the formation of clear zones in clouds and fogs due to the vaporization of droplets under regular regimes, self-action of a wave beam in a water aerosol under conditions of regular droplet vaporization, laser beam propagation through an explosively evaporating water-droplet aerosol, the propagation of high-power laser radiation through hazes, the ionization and optical breakdown in aerosol media, and laser monitoring of a turbid atmosphere using nonlinear effects.

Neutron production from beam-modifying devices in a modern double scattering proton therapy beam delivery system.

PubMed

Pérez-Andújar, Angélica; Newhauser, Wayne D; Deluca, Paul M

2009-02-21

In this work the neutron production in a passive beam delivery system was investigated. Secondary particles including neutrons are created as the proton beam interacts with beam shaping devices in the treatment head. Stray neutron exposure to the whole body may increase the risk that the patient develops a radiogenic cancer years or decades after radiotherapy. We simulated a passive proton beam delivery system with double scattering technology to determine the neutron production and energy distribution at 200 MeV proton energy. Specifically, we studied the neutron absorbed dose per therapeutic absorbed dose, the neutron absorbed dose per source particle and the neutron energy spectrum at various locations around the nozzle. We also investigated the neutron production along the nozzle's central axis. The absorbed doses and neutron spectra were simulated with the MCNPX Monte Carlo code. The simulations revealed that the range modulation wheel (RMW) is the most intense neutron source of any of the beam spreading devices within the nozzle. This finding suggests that it may be helpful to refine the design of the RMW assembly, e.g., by adding local shielding, to suppress neutron-induced damage to components in the nozzle and to reduce the shielding thickness of the treatment vault. The simulations also revealed that the neutron dose to the patient is predominated by neutrons produced in the field defining collimator assembly, located just upstream of the patient.

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.

Method and apparatus for inspecting reflection masks for defects

DOEpatents

Bokor, Jeffrey; Lin, Yun

2003-04-29

An at-wavelength system for extreme ultraviolet lithography mask blank defect detection is provided. When a focused beam of wavelength 13 nm is incident on a defective region of a mask blank, three possible phenomena can occur. The defect will induce an intensity reduction in the specularly reflected beam, scatter incoming photons into an off-specular direction, and change the amplitude and phase of the electric field at the surface which can be monitored through the change in the photoemission current. The magnitude of these changes will depend on the incident beam size, and the nature, extent and size of the defect. Inspection of the mask blank is performed by scanning the mask blank with 13 nm light focused to a spot a few .mu.m in diameter, while measuring the reflected beam intensity (bright field detection), the scattered beam intensity (dark-field detection) and/or the change in the photoemission current.

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.

Measurements of refractive index and size of a spherical drop from Gaussian beam scattering in the primary rainbow region

NASA Astrophysics Data System (ADS)

Yu, Haitao; Sun, Hui; Shen, Jianqi; Tropea, Cameron

2018-03-01

The primary rainbow observed when light is scattered by a spherical drop has been exploited in the past to measure drop size and relative refractive index. However, if higher spatial resolution is required in denser drop ensembles/sprays, and to avoid then multiple drops simultaneously appearing in the measurement volume, a highly focused beam is desirable, inevitably with a Gaussian intensity profile. The present study examines the primary rainbow pattern resulting when a Gaussian beam is scattered by a spherical drop and estimates the attainable accuracy when extracting size and refractive index. The scattering is computed using generalized Lorenz-Mie theory (GLMT) and Debye series decomposition of the Gaussian beam scattering. The results of these simulations show that the measurement accuracy is dependent on both the beam waist radius and the position of the drop in the beam waist.

A breast-specific, negligible-dose scatter correction technique for dedicated cone-beam breast CT: a physics-based approach to improve Hounsfield Unit accuracy

NASA Astrophysics Data System (ADS)

Yang, Kai; Burkett, George, Jr.; Boone, John M.

2014-11-01

The purpose of this research was to develop a method to correct the cupping artifact caused from x-ray scattering and to achieve consistent Hounsfield Unit (HU) values of breast tissues for a dedicated breast CT (bCT) system. The use of a beam passing array (BPA) composed of parallel-holes has been previously proposed for scatter correction in various imaging applications. In this study, we first verified the efficacy and accuracy using BPA to measure the scatter signal on a cone-beam bCT system. A systematic scatter correction approach was then developed by modeling the scatter-to-primary ratio (SPR) in projection images acquired with and without BPA. To quantitatively evaluate the improved accuracy of HU values, different breast tissue-equivalent phantoms were scanned and radially averaged HU profiles through reconstructed planes were evaluated. The dependency of the correction method on object size and number of projections was studied. A simplified application of the proposed method on five clinical patient scans was performed to demonstrate efficacy. For the typical 10-18 cm breast diameters seen in the bCT application, the proposed method can effectively correct for the cupping artifact and reduce the variation of HU values of breast equivalent material from 150 to 40 HU. The measured HU values of 100% glandular tissue, 50/50 glandular/adipose tissue, and 100% adipose tissue were approximately 46, -35, and -94, respectively. It was found that only six BPA projections were necessary to accurately implement this method, and the additional dose requirement is less than 1% of the exam dose. The proposed method can effectively correct for the cupping artifact caused from x-ray scattering and retain consistent HU values of breast tissues.

Analytic image reconstruction from partial data for a single-scan cone-beam CT with scatter correction

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

Min, Jonghwan; Pua, Rizza; Cho, Seungryong, E-mail: scho@kaist.ac.kr

Purpose: A beam-blocker composed of multiple strips is a useful gadget for scatter correction and/or for dose reduction in cone-beam CT (CBCT). However, the use of such a beam-blocker would yield cone-beam data that can be challenging for accurate image reconstruction from a single scan in the filtered-backprojection framework. The focus of the work was to develop an analytic image reconstruction method for CBCT that can be directly applied to partially blocked cone-beam data in conjunction with the scatter correction. Methods: The authors developed a rebinned backprojection-filteration (BPF) algorithm for reconstructing images from the partially blocked cone-beam data in amore » circular scan. The authors also proposed a beam-blocking geometry considering data redundancy such that an efficient scatter estimate can be acquired and sufficient data for BPF image reconstruction can be secured at the same time from a single scan without using any blocker motion. Additionally, scatter correction method and noise reduction scheme have been developed. The authors have performed both simulation and experimental studies to validate the rebinned BPF algorithm for image reconstruction from partially blocked cone-beam data. Quantitative evaluations of the reconstructed image quality were performed in the experimental studies. Results: The simulation study revealed that the developed reconstruction algorithm successfully reconstructs the images from the partial cone-beam data. In the experimental study, the proposed method effectively corrected for the scatter in each projection and reconstructed scatter-corrected images from a single scan. Reduction of cupping artifacts and an enhancement of the image contrast have been demonstrated. The image contrast has increased by a factor of about 2, and the image accuracy in terms of root-mean-square-error with respect to the fan-beam CT image has increased by more than 30%. Conclusions: The authors have successfully demonstrated that the proposed scanning method and image reconstruction algorithm can effectively estimate the scatter in cone-beam projections and produce tomographic images of nearly scatter-free quality. The authors believe that the proposed method would provide a fast and efficient CBCT scanning option to various applications particularly including head-and-neck scan.« less

Magnetically confined electron beam system for high resolution electron transmission-beam experiments

NASA Astrophysics Data System (ADS)

Lozano, A. I.; Oller, J. C.; Krupa, K.; Ferreira da Silva, F.; Limão-Vieira, P.; Blanco, F.; Muñoz, A.; Colmenares, R.; García, G.

2018-06-01

A novel experimental setup has been implemented to provide accurate electron scattering cross sections from molecules at low and intermediate impact energies (1-300 eV) by measuring the attenuation of a magnetically confined linear electron beam from a molecular target. High-resolution electron energy is achieved through confinement in a magnetic gas trap where electrons are cooled by successive collisions with N2. Additionally, we developed and present a method to correct systematic errors arising from energy and angular resolution limitations. The accuracy of the entire measurement procedure is validated by comparing the N2 total scattering cross section in the considered energy range with benchmark values available in the literature.

Apparatus for measuring particle properties

DOEpatents

Rader, Daniel J.; Castaneda, Jaime N.; Grasser, Thomas W.; Brockmann, John E.

1998-01-01

An apparatus for determining particle properties from detected light scattered by the particles. The apparatus uses a light beam with novel intensity characteristics to discriminate between particles that pass through the beam and those that pass through an edge of the beam. The apparatus can also discriminate between light scattered by one particle and light scattered by multiple particles. The particle's size can be determined from the intensity of the light scattered. The particle's velocity can be determined from the elapsed time between various intensities of the light scattered.

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.

Progress on the development of the next generation x-ray beam position monitors at the advanced photon source

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

Lee, S. H., E-mail: shlee@aps.anl.gov; Yang, B. X., E-mail: bxyang@aps.anl.gov; Decker, G., E-mail: decker@aps.anl.gov

Accurate and stable x-ray beam position monitors (XBPMs) are key elements in obtaining the desired user beam stability in the Advanced Photon Source (APS). The next generation XBPMs for high heat load front ends (HHL FEs) have been designed to meet these requirements by utilizing Cu K-edge x-ray fluorescence (XRF) from a pair of copper absorbers and have been installed at the front ends (FEs) of the APS. Commissioning data showed a significant performance improvement over the existing photoemission-based XBPMs. While a similar design concept can be applied for the canted undulator front ends, where two undulator beams are separatedmore » by 1.0-mrad, the lower beam power (< 10 kW) per undulator allows us to explore lower-cost solutions based on Compton scattering from the diamond blades placed edge-on to the x-ray beam. A prototype of the Compton scattering XBPM system was installed at 24-ID-A in May 2015. In this report, the design and test results for XRF-based XBPM and Compton scattering based XBPM are presented. Ongoing research related to the development of the next generation XBPMs on thermal contact resistance of a joint between two solid bodies is also discussed.« less

Compact FEL-driven inverse compton scattering gamma-ray source

DOE PAGES

Placidi, M.; Di Mitri, Simone; Pellegrini, C.; ...

2017-02-28

Many research and applications areas require photon sources capable of producing gamma-ray beams in the multi-MeV energy range with reasonably high fluxes and compact footprints. Besides industrial, nuclear physics and security applications, a considerable interest comes from the possibility to assess the state of conservation of cultural assets like statues, columns etc., via visualization and analysis techniques using high energy photon beams. Computed Tomography scans, widely adopted in medicine at lower photon energies, presently provide high quality three-dimensional imaging in industry and museums. We explore the feasibility of a compact source of quasi-monochromatic, multi-MeV gamma-rays based on Inverse Compton Scatteringmore » (ICS) from a high intensity ultra-violet (UV) beam generated in a free-electron laser by the electron beam itself. This scheme introduces a stronger relationship between the energy of the scattered photons and that of the electron beam, resulting in a device much more compact than a classic ICS for a given scattered energy. As a result, the same electron beam is used to produce gamma-rays in the 10–20 MeV range and UV radiation in the 10–15 eV range, in a ~4 × 22 m 2 footprint system.« less

Compact FEL-driven inverse compton scattering gamma-ray source

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

Placidi, M.; Di Mitri, Simone; Pellegrini, C.

Many research and applications areas require photon sources capable of producing gamma-ray beams in the multi-MeV energy range with reasonably high fluxes and compact footprints. Besides industrial, nuclear physics and security applications, a considerable interest comes from the possibility to assess the state of conservation of cultural assets like statues, columns etc., via visualization and analysis techniques using high energy photon beams. Computed Tomography scans, widely adopted in medicine at lower photon energies, presently provide high quality three-dimensional imaging in industry and museums. We explore the feasibility of a compact source of quasi-monochromatic, multi-MeV gamma-rays based on Inverse Compton Scatteringmore » (ICS) from a high intensity ultra-violet (UV) beam generated in a free-electron laser by the electron beam itself. This scheme introduces a stronger relationship between the energy of the scattered photons and that of the electron beam, resulting in a device much more compact than a classic ICS for a given scattered energy. As a result, the same electron beam is used to produce gamma-rays in the 10–20 MeV range and UV radiation in the 10–15 eV range, in a ~4 × 22 m 2 footprint system.« less

Wavelength-detuning cross-beam energy transfer mitigation scheme for direct drive: Modeling and evidence from National Ignition Facility implosions

NASA Astrophysics Data System (ADS)

Marozas, J. A.; Hohenberger, M.; Rosenberg, M. J.; Turnbull, D.; Collins, T. J. B.; Radha, P. B.; McKenty, P. W.; Zuegel, J. D.; Marshall, F. J.; Regan, S. P.; Sangster, T. C.; Seka, W.; Campbell, E. M.; Goncharov, V. N.; Bowers, M. W.; Di Nicola, J.-M. G.; Erbert, G.; MacGowan, B. J.; Pelz, L. J.; Moody, J.; Yang, S. T.

2018-05-01

Cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces laser-energy absorption for direct-drive inertial confinement fusion. Consequently, ablation pressure and implosion velocity suffer from the decreased absorption, reducing target performance in both symmetric and polar direct drive. Additionally, CBET alters the time-resolved scattered-light spectra and redistributes absorbed and scattered-light-changing shell morphology and low-mode drive symmetry. Mitigating CBET is demonstrated in inertial confinement implosions at the National Ignition Facility by detuning the laser-source wavelengths (±2.3 Å UV) of the interacting beams. In polar direct drive, wavelength detuning was shown to increase the equatorial region velocity experimentally by 16% and to alter the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation-hydrodynamic simulations that indicate a 10% increase in the average ablation pressure. These results indicate that wavelength detuning successfully mitigates CBET. Simulations predict that optimized phase plates and wavelength-detuning CBET mitigation utilizing the three-legged beam layout of the OMEGA Laser System significantly increase absorption and achieve >100-Gbar hot-spot pressures in symmetric direct drive.

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.

Optical detection of tracer species in strongly scattering media.

PubMed

Brauser, Eric M; Rose, Peter E; McLennan, John D; Bartl, Michael H

2015-03-01

A combination of optical absorption and scattering is used to detect tracer species in a strongly scattering medium. An optical setup was developed, consisting of a dual-beam scattering detection scheme in which sample scattering beam overlaps with the characteristic absorption feature of quantum dot tracer species, while the reference scattering beam is outside any absorption features of the tracer. This scheme was successfully tested in engineered breakthrough tests typical of wastewater and subsurface fluid analysis, as well as in batch analysis of oil and gas reservoir fluids and biological samples. Tracers were detected even under highly scattering conditions, conditions in which conventional absorption or fluorescence methods failed.

Multi-beam effects on backscatter and its saturation in experiments with conditions relevant to ignition

DOE PAGES

Kirkwood, R. K.; Michel, P.; London, R.; ...

2011-05-26

To optimize the coupling to indirect drive targets in the National Ignition Campaign (NIC) at the National Ignition Facility, a model of stimulated scattering produced by multiple laser beams is used. The model has shown that scatter of the 351 nm beams can be significantly enhanced over single beam predictions in ignition relevant targets by the interaction of the multiple crossing beams with a millimeter scale length, 2.5 keV, 0.02 - 0.05 x critical density, plasma. The model uses a suite of simulation capabilities and its key aspects are benchmarked with experiments at smaller laser facilities. The model has alsomore » influenced the design of the initial targets used for NIC by showing that both the stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) can be reduced by the reduction of the plasma density in the beam intersection volume that is caused by an increase in the diameter of the laser entrance hole (LEH). In this model, a linear wave response leads to a small gain exponent produced by each crossing quad of beams (<~1 per quad) which amplifies the scattering that originates in the target interior where the individual beams are separated and crosses many or all other beams near the LEH as it exits the target. As a result all 23 crossing quads of beams produce a total gain exponent of several or greater for seeds of light with wavelengths in the range that is expected for scattering from the interior (480 to 580 nm for SRS). This means that in the absence of wave saturation, the overall multi-beam scatter will be significantly larger than the expectations for single beams. The potential for non-linear saturation of the Langmuir waves amplifying SRS light is also analyzed with a two dimensional, vectorized, particle in cell code (2D VPIC) that is benchmarked by amplification experiments in a plasma with normalized parameters similar to ignition targets. The physics of cumulative scattering by multiple crossing beams that simultaneously amplify the same SBS light wave is further demonstrated in experiments that benchmark the linear models for the ion waves amplifying SBS. Here, the expectation from this model and its experimental benchmarks is shown to be consistent with observations of stimulated Raman scatter in the first series of energetic experiments with ignition targets, confirming the importance of the multi-beam scattering model for optimizing coupling.« less

Spin angular momentum transfer from TEM00 focused Gaussian beams to negative refractive index spherical particles

PubMed Central

Ambrosio, Leonardo A.; Hernández-Figueroa, Hugo E.

2011-01-01

We investigate optical torques over absorbent negative refractive index spherical scatterers under the influence of linear and circularly polarized TEM00 focused Gaussian beams, in the framework of the generalized Lorenz-Mie theory with the integral localized approximation. The fundamental differences between optical torques due to spin angular momentum transfer in positive and negative refractive index optical trapping are outlined, revealing the effect of the Mie scattering coefficients in one of the most fundamental properties in optical trapping systems. PMID:21833372

3-dimensional beam scanning system for particle radiation therapy

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

Leemann, C.; Alonso, J.; Grunder, H.

1977-03-01

In radiation therapy treatment volumes up to several liters have to be irradiated. Today's charged particle programs use ridge filters, scattering foils, occluding rings collimators and boluses to shape the dose distribution. An alternative approach, scanning of a small diameter beam, is analyzed and tentative systems specifications are derived. Critical components are scheduled for fabrication and testing at LBL.

Resonance scattering of a dielectric sphere illuminated by electromagnetic Bessel non-diffracting (vortex) beams with arbitrary incidence and selective polarizations

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

Mitri, F.G., E-mail: F.G.Mitri@ieee.org; Li, R.X., E-mail: rxli@mail.xidian.edu.cn; Collaborative Innovation Center of Information Sensing and Understanding, Xidian University, Xi’an 710071

A complete description of vector Bessel (vortex) beams in the context of the generalized Lorenz–Mie theory (GLMT) for the electromagnetic (EM) resonance scattering by a dielectric sphere is presented, using the method of separation of variables and the subtraction of a non-resonant background (corresponding to a perfectly conducting sphere of the same size) from the standard Mie scattering coefficients. Unlike the conventional results of standard optical radiation, the resonance scattering of a dielectric sphere in air in the field of EM Bessel beams is examined and demonstrated with particular emphasis on the EM field’s polarization and beam order (or topologicalmore » charge). Linear, circular, radial, azimuthal polarizations as well as unpolarized Bessel vortex beams are considered. The conditions required for the resonance scattering are analyzed, stemming from the vectorial description of the EM field using the angular spectrum decomposition, the derivation of the beam-shape coefficients (BSCs) using the integral localized approximation (ILA) and Neumann–Graf’s addition theorem, and the determination of the scattering coefficients of the sphere using Debye series. In contrast with the standard scattering theory, the resonance method presented here allows the quantitative description of the scattering using Debye series by separating diffraction effects from the external and internal reflections from the sphere. Furthermore, the analysis is extended to include rainbow formation in Bessel beams and the derivation of a generalized formula for the deviation angle of high-order rainbows. Potential applications for this analysis include Bessel beam-based laser imaging spectroscopy, atom cooling and quantum optics, electromagnetic instrumentation and profilometry, optical tweezers and tractor beams, to name a few emerging areas of research.« less

Poster — Thur Eve — 43: Monte Carlo Modeling of Flattening Filter Free Beams and Studies of Relative Output Factors

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

Zhan, Lixin; Jiang, Runqing; Osei, Ernest K.

2014-08-15

Flattening filter free (FFF) beams have been adopted by many clinics and used for patient treatment. However, compared to the traditional flattened beams, we have limited knowledge of FFF beams. In this study, we successfully modeled the 6 MV FFF beam for Varian TrueBeam accelerator with the Monte Carlo (MC) method. Both the percentage depth dose and profiles match well to the Golden Beam Data (GBD) from Varian. MC simulations were then performed to predict the relative output factors. The in-water output ratio, Scp, was simulated in water phantom and data obtained agrees well with GBD. The in-air output ratio,more » Sc, was obtained by analyzing the phase space placed at isocenter, in air, and computing the ratio of water Kerma rates for different field sizes. The phantom scattering factor, Sp, can then be obtained from the traditional way of taking the ratio of Scp and Sc. We also simulated Sp using a recently proposed method based on only the primary beam dose delivery in water phantom. Because there is no concern of lateral electronic disequilibrium, this method is more suitable for small fields. The results from both methods agree well with each other. The flattened 6 MV beam was simulated and compared to 6 MV FFF. The comparison confirms that 6 MV FFF has less scattering from the Linac head and less phantom scattering contribution to the central axis dose, which will be helpful for improving accuracy in beam modeling and dose calculation in treatment planning systems.« less

A small-angle x-ray scattering system with a vertical layout.

PubMed

Wang, Zhen; Chen, Xiaowei; Meng, Lingpu; Cui, Kunpeng; Wu, Lihui; Li, Liangbin

2014-12-01

A small-angle x-ray scattering (SAXS) system with a vertical layout (V-SAXS) has been designed and constructed for in situ detection on nanostructures, which is well suitable for in situ study on self-assembly of nanoparticles at liquid interface and polymer processing. A steel-tower frame on a reinforced basement is built as the supporting skeleton for scattering beam path and detector platform, ensuring the system a high working stability and a high operating accuracy. A micro-focus x-ray source combining parabolic three-dimensional multi-layer mirror and scatteringless collimation system provides a highly parallel beam, which allows us to detect the very small angle range. With a sample-to-detector distance of 7 m, the largest measurable length scale is 420 nm in real space. With a large sample zone, it is possible to install different experimental setups such as film stretching machine, which makes the system perfect to follow the microstructures evolution of materials during processing. The capability of the V-SAXS on in situ study is tested with a drying experiment of a free latex droplet, which confirms our initial design.

Spectrum bandwidth narrowing of Thomson scattering X-rays with energy chirped electron beams from laser wakefield acceleration

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

Xu, Tong; Chen, Min, E-mail: minchen@sjtu.edu.cn; Li, Fei-Yu

2014-01-06

We study incoherent Thomson scattering between an ultrashort laser pulse and an electron beam accelerated from a laser wakefield. The energy chirp effects of the accelerated electron beam on the final radiation spectrum bandwidth are investigated. It is found that the scattered X-ray radiation has the minimum spectrum width and highest intensity as electrons are accelerated up to around the dephasing point. Furthermore, it is proposed that the electron acceleration process inside the wakefield can be studied by use of 90° Thomson scattering. The dephasing position and beam energy chirp can be deduced from the intensity and bandwidth of themore » scattered radiation.« less

A comparison of phantom scatter from flattened and flattening filter free high-energy photon beams.

PubMed

Richmond, Neil; Allen, Vince; Daniel, Jim; Dacey, Rob; Walker, Chris

2015-01-01

Flattening filter free (FFF) photon beams have different dosimetric properties from those of flattened beams. The aim of this work was to characterize the collimator scatter (Sc) and total scatter (Scp) from 3 FFF beams of differing quality indices and use the resulting mathematical fits to generate phantom scatter (Sp) data. The similarities and differences between Sp of flattened and FFF beams are described. Sc and Scp data were measured for 3 flattened and 3 FFF high-energy photon beams (Varian 6 and 10MV and Elekta 6MV). These data were fitted to logarithmic power law functions with 4 numerical coefficients. The agreement between our experimentally determined flattened beam Sp and published data was within ± 1.2% for all 3 beams investigated and all field sizes from 4 × 4 to 40 × 40cm(2). For the FFF beams, Sp was only within 1% of the same flattened beam published data for field sizes between 6 × 6 and 14 × 14cm(2). Outside this range, the differences were much greater, reaching - 3.2%, - 4.5%, and - 4.3% for the fields of 40 × 40cm(2) for the Varian 6-MV, Varian 10-MV, and Elekta 6-MV FFF beams, respectively. The FFF beam Sp increased more slowly with increasing field size than that of the published and measured flattened beam of a similar reference field size quality index, i.e., there is less Phantom Scatter than that found with flattened beams for a given field size. This difference can be explained when the fluence profiles of the flattened and FFF beams are considered. The FFF beam has greatly reduced fluence off axis, especially as field size increases, compared with the flattened beam profile; hence, less scatter is generated in the phantom reaching the central axis. Copyright © 2015 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.

Near-field spectral shift of a zero-order Bessel beam scattered from a spherical particle

NASA Astrophysics Data System (ADS)

Chen, Feinan; Li, Jia; Belafhal, Abdelmajid; Chafiq, Abdelghani; Sun, Xiaobing

2018-06-01

Within the accuracy of the first-order Born approximation, expressions are derived for the near-zone spectrum of a zero-order Bessel beam scattered from a spherical particle whose correlation function satisfies a Gaussian distribution. The dependence of the spectral shift and spectral switch of the scattered field on the effective size of the scattering potential (ESSP) are determined by numerical simulations. It is shown that the spectral shift of the scattered field does not occur along the longitudinal propagation direction. Furthermore, when the medium’s ESSP is comparable with the central wavelength of the beam, the spectrum of the scattered field loses the Gaussian distribution and exhibits a blue shift as the reference point sufficiently far away from central origin. These results may have prospective applications in guiding tiny particles when the near-zone spectrums of scattered beams are captured and analyzed.

[Laser speckle suppression due to dynamic multiple scattering scheme introduced by oblique incidence].

PubMed

Xu, Mei-fang; Gao, Wen-hong; Shi, Yun-bo; Wang, Hao-quan; Du, Bin-bin

2014-06-01

Speckle suppression has been the research focus in laser display technology. In the present paper, the relation between multiple scattering and the size of speckle grains is established by analyzing the properties of speckle generated by the laser beam through SiO2 suspension. Combined with dynamic light scattering theory, laser speckle suppression due to dynamic multiple scattering scheme introduced by oblique incidence is proposed. A speckle suppression element consists of a static diffuser and a light pipe containing the water suspension of SiO2 microspheres with a diameter of 300 nm and a molar concentration of 3.0 x 10(-4) μm3, which is integrated with the laser display system. The laser beam with different incident angles into the SiO2 suspension affecting the contrast of the speckle images is analyzed by the experiments. The results demonstrate that the contrast of the speckle image can be reduced to 0.067 from 0.43 when the beam with the incident angle of approximately 8 degrees illuminates into the SiO2 suspension. The spatial average of speckle granules and the temporal average of speckle images were achieved by the proposed method, which improved the effect of speckle suppression. The proposed element for speckle suppression improved the reliability and reduced the cost of laser projection system, since no mechanical vibration is needed and it is convenient to integrate the element with the existing projection system.

Development of a golden beam data set for the commissioning of a proton double-scattering system in a pencil-beam dose calculation algorithm

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

Slopsema, R. L., E-mail: rslopsema@floridaproton.org; Flampouri, S.; Yeung, D.

2014-09-15

Purpose: The purpose of this investigation is to determine if a single set of beam data, described by a minimal set of equations and fitting variables, can be used to commission different installations of a proton double-scattering system in a commercial pencil-beam dose calculation algorithm. Methods: The beam model parameters required to commission the pencil-beam dose calculation algorithm (virtual and effective SAD, effective source size, and pristine-peak energy spread) are determined for a commercial double-scattering system. These parameters are measured in a first room and parameterized as function of proton energy and nozzle settings by fitting four analytical equations tomore » the measured data. The combination of these equations and fitting values constitutes the golden beam data (GBD). To determine the variation in dose delivery between installations, the same dosimetric properties are measured in two additional rooms at the same facility, as well as in a single room at another facility. The difference between the room-specific measurements and the GBD is evaluated against tolerances that guarantee the 3D dose distribution in each of the rooms matches the GBD-based dose distribution within clinically reasonable limits. The pencil-beam treatment-planning algorithm is commissioned with the GBD. The three-dimensional dose distribution in water is evaluated in the four treatment rooms and compared to the treatment-planning calculated dose distribution. Results: The virtual and effective SAD measurements fall between 226 and 257 cm. The effective source size varies between 2.4 and 6.2 cm for the large-field options, and 1.0 and 2.0 cm for the small-field options. The pristine-peak energy spread decreases from 1.05% at the lowest range to 0.6% at the highest. The virtual SAD as well as the effective source size can be accurately described by a linear relationship as function of the inverse of the residual energy. An additional linear correction term as function of RM-step thickness is required for accurate parameterization of the effective SAD. The GBD energy spread is given by a linear function of the exponential of the beam energy. Except for a few outliers, the measured parameters match the GBD within the specified tolerances in all of the four rooms investigated. For a SOBP field with a range of 15 g/cm{sup 2} and an air gap of 25 cm, the maximum difference in the 80%–20% lateral penumbra between the GBD-commissioned treatment-planning system and measurements in any of the four rooms is 0.5 mm. Conclusions: The beam model parameters of the double-scattering system can be parameterized with a limited set of equations and parameters. This GBD closely matches the measured dosimetric properties in four different rooms.« less

WE-EF-207-06: Dedicated Cone-Beam Breast CT with Laterally-Shifted Detector: Monte Carlo Evaluation of X-Ray Scatter Distribution and Scatter-To-Primary Ratio

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

Shi, L; Vedantham, S; Karellas, A

2015-06-15

Purpose: To determine the spatial distribution of x-ray scatter and scatter-to-primary ratio (SPR) in projections during cone-beam breast CT (CBBCT) with laterally-shifted detector that results in coronal (fan-angle) truncation. Methods: We hypothesized that CBBCT with coronal truncation would lower SPR due to reduction in irradiated breast volume, and that the location of maximum x-ray scatter fluence (scatter-peak) in the detector plane can be determined from the ratio of irradiated-to-total breast volume, breast dimensions and system geometry. Monte Carlo simulations (GEANT4) reflecting a prototype CBBCT system were used to record the position-dependent primary and scatter x-ray photon fluence incident on themore » detector without coronal truncation (full fan-angle, 2f=24-degrees) and with coronal truncation (fan-angle, f+ f=12+2.7-degrees). Semi-ellipsoidal breasts (10/14/18-cm diameter, chest-wall to nipple length: 0.75xdiameter, 2%/14%/100% fibroglandular content) aligned with the axis-of-rotation (AOR) were modeled. Mono-energy photons were simulated and weighted for 2 spectra (49kVp, 1.4-mm Al HVL; 60kVp, 3.76-mm Al HVL). In addition to SPR, the scatter maps were analyzed to identify the location of the scatter-peak. Results: For CBBCT without fan-angle truncation, the scatter-peaks were aligned with the projection of the AOR onto the detector for all breasts. With truncated fan-beam, the scatter-peaks were laterally-shifted from the projection of the AOR along the fan-angle direction by 14/38/70-pixels for 10/14/18-cm diameter breasts. The corresponding theoretical shifts were 14.8/39.7/68-pixels (p=0.47, 2-tailed paired-ratio t-test). Along the cone-angle, the shift in scatter-peaks between truncated and full-fan angle CBBCT were 2/2/4 -pixels for 10/14/18-cm diameter breasts. CBBCT with fan-angle truncation reduced SPR by 14/22/28% for 10/14/18-cm diameter breasts. 60kVp reduced SPR by 21–25% compared to 49kVp. Peak SPR for CBBCT with fan-angle truncation (60kVp) were 0.09/0.25/0.73 for 10/14/18-cm diameter breasts. Conclusion: CBBCT with laterally-shifted detector geometry and with appropriate kVp/beam quality reduces SPR. If residual scatter needs correction, the location corresponding to scatter-peak can be analytically computed. This work was supported in part by NIH R01 CA128906. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or NCI.« less

Apparatus for measuring particle properties

DOEpatents

Rader, D.J.; Castaneda, J.N.; Grasser, T.W.; Brockmann, J.E.

1998-08-11

An apparatus is described for determining particle properties from detected light scattered by the particles. The apparatus uses a light beam with novel intensity characteristics to discriminate between particles that pass through the beam and those that pass through an edge of the beam. The apparatus can also discriminate between light scattered by one particle and light scattered by multiple particles. The particle`s size can be determined from the intensity of the light scattered. The particle`s velocity can be determined from the elapsed time between various intensities of the light scattered. 11 figs.

Chevron beam dump for ITER edge Thomson scattering system

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

Yatsuka, E.; Hatae, T.; Bassan, M.

This paper contains the design of the beam dump for the ITER edge Thomson scattering system and mainly concerns its lifetime under the harsh thermal and electromagnetic loads as well as tight space allocation. The lifetime was estimated from the multi-pulse laser-induced damage threshold. In order to extend its lifetime, the structure of the beam dump was optimized. A number of bent sheets aligned parallel in the beam dump form a shape called a chevron which enables it to avoid the concentration of the incident laser pulse energy. The chevron beam dump is expected to withstand thermal loads due tomore » nuclear heating, radiation from the plasma, and numerous incident laser pulses throughout the entire ITER project with a reasonable margin for the peak factor of the beam profile. Structural analysis was also carried out in case of electromagnetic loads during a disruption. Moreover, detailed issues for more accurate assessments of the beam dump's lifetime are clarified. Variation of the bi-directional reflection distribution function (BRDF) due to erosion by or contamination of neutral particles derived from the plasma is one of the most critical issues that needs to be resolved. In this paper, the BRDF was assumed, and the total amount of stray light and the absorbed laser energy profile on the beam dump were evaluated.« less

SU-F-J-198: A Cross-Platform Adaptation of An a Priori Scatter Correction Algorithm for Cone-Beam Projections to Enable Image- and Dose-Guided Proton Therapy

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

Andersen, A; Casares-Magaz, O; Elstroem, U

Purpose: Cone-beam CT (CBCT) imaging may enable image- and dose-guided proton therapy, but is challenged by image artefacts. The aim of this study was to demonstrate the general applicability of a previously developed a priori scatter correction algorithm to allow CBCT-based proton dose calculations. Methods: The a priori scatter correction algorithm used a plan CT (pCT) and raw cone-beam projections acquired with the Varian On-Board Imager. The projections were initially corrected for bow-tie filtering and beam hardening and subsequently reconstructed using the Feldkamp-Davis-Kress algorithm (rawCBCT). The rawCBCTs were intensity normalised before a rigid and deformable registration were applied on themore » pCTs to the rawCBCTs. The resulting images were forward projected onto the same angles as the raw CB projections. The two projections were subtracted from each other, Gaussian and median filtered, and then subtracted from the raw projections and finally reconstructed to the scatter-corrected CBCTs. For evaluation, water equivalent path length (WEPL) maps (from anterior to posterior) were calculated on different reconstructions of three data sets (CB projections and pCT) of three parts of an Alderson phantom. Finally, single beam spot scanning proton plans (0–360 deg gantry angle in steps of 5 deg; using PyTRiP) treating a 5 cm central spherical target in the pCT were re-calculated on scatter-corrected CBCTs with identical targets. Results: The scatter-corrected CBCTs resulted in sub-mm mean WEPL differences relative to the rigid registration of the pCT for all three data sets. These differences were considerably smaller than what was achieved with the regular Varian CBCT reconstruction algorithm (1–9 mm mean WEPL differences). Target coverage in the re-calculated plans was generally improved using the scatter-corrected CBCTs compared to the Varian CBCT reconstruction. Conclusion: We have demonstrated the general applicability of a priori CBCT scatter correction, potentially opening for CBCT-based image/dose-guided proton therapy, including adaptive strategies. Research agreement with Varian Medical Systems, not connected to the present project.« less

Laser scattering method applied to determine the concentration of alfa 1-antitrypsin

NASA Astrophysics Data System (ADS)

Riquelme, Bibiana D.; Foresto, Patricia; Valverde, Juana R.; Rasia, Rodolfo J.

2000-04-01

An optical method has been developed to find (alpha) 1- antitrypsin unknown concentrations in human serum samples. This method applies light scattering properties exhibited by initially formed enzyme-inhibitor complexes and uses the curves of aggregation kinetics. It is independent of molecular hydrodynamics. Theoretical approaches showed that scattering properties of transient complexes obey the Rayleigh-Debie conditions. Experiments were performed on the Trypsin/(alpha) 1-antitrypsin system. Measurements were performed in newborn, adult and pregnant sera containing (alpha) 1-antitrypsin in the Trypsin excess region. The solution was excite by a He-Ne laser beam. SO, the particles formed during the reaction are scattering centers for the interacting light. The intensity of the scattered light at 90 degrees from incident beam depends on the nature of those scattering centers. Th rate of increase in scattered intensity depends on the variation in size and shape of the scatterers, being independent of its original size. Peak values of the first derivative linearly correlate with the concentration of (alpha) 1-antitrypsin originally present in the sample. Results are displayed 5 minutes after the initiation of the experimental process. Such speed is of great importance in the immuno-biochemistry determinations.

SU-E-T-660: Quantitative Fault Testing for Commissioning of Proton Therapy Machines

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

Reilly, M; Rankine, L; Grantham, K

2015-06-15

Purpose: To ensure proper fault testing for the first single room proton therapy machine by establishing a common set of acceptance testing and commissioning parameters with the manufacturer. The following work details the parameters tested and associated results. Methods: Dose rates in service mode were varied to ensure that when the threshold for maximum or minimum MU/min was met, the beam promptly shut off. The flatness parameter was tested by purposely assigning an incorrect secondary scatter, to ensure the beam shut off when detecting a heterogeneous profile. The beam symmetry parameter was tested by altering the steering coil up tomore » 3.0A, thereby forcing the beam to be asymmetric and shut off. Lastly, the quench system was tested by ramping down the magnet to 5% capacity, whereby the quench button was engaged to bring down the magnet current to a safe level. Results: A dose rate increase or decrease in excess of 10% shut the beam off within 5 seconds as observed by the current on a Matrixx ionization chamber array (IBA Dosimetry, Bartlett, TN) A 3.0A change in the beam steering coil introduced a 2% change in the flatness and symmetry profiles with respect to baseline measurements resulting in the beam shutting off within 5 seconds. An incorrect 2nd scatterer introduced a flatness of 4.1% and symmetry of 6.4% which immediately triggered a beam shut off. Finally, the quench system worked as expected during the ramp down procedure. Conclusion: A fault testing plan to check dosimetric faults and the quench system was performed for the first single room proton therapy system. All dosimetric parameters and machine conditions were met to our satisfaction. We propose that the same type of fault testing should be applied to any proton system during commissioning, including scanning beam systems.« less

Raman scattering in a whispering mode optical waveguide

DOEpatents

Kurnit, Norman A.

1982-01-01

A device and method for Raman scattering in a whispering mode optical waveguide. Both a helical ribbon and cylinder are disclosed which incorporate an additional curvature .rho. p for confining the beam to increase intensity. A Raman scattering medium is disposed in the optical path of the beam as it propagates along the waveguide. Raman scattering is enhanced by the high intensities of the beam and long interaction path lengths which are achieved in a small volume.

Light scattering apparatus and method for determining radiation exposure to plastic detectors

DOEpatents

Hermes, Robert E.

2002-01-01

An improved system and method of analyzing cumulative radiation exposure registered as pits on track etch foils of radiation dosimeters. The light scattering apparatus and method of the present invention increases the speed of analysis while it also provides the ability to analyze exposure levels beyond that which may be properly measured with conventional techniques. Dosimeters often contain small plastic sheets that register accumulated damage when exposed to a radiation source. When the plastic sheet from the dosimeter is chemically etched, a track etch foil is produced wherein pits or holes are created in the plastic. The number of these pits, or holes, per unit of area (pit density) correspond to the amount of cumulative radiation exposure which is being optically measured by the apparatus. To measure the cumulative radiation exposure of a track etch foil a high intensity collimated beam is passed through foil such that the pits and holes within the track etch foil cause a portion of the impinging light beam to become scattered upon exit. The scattered light is focused with a lens, while the primary collimated light beam (unscattered light) is blocked. The scattered light is focused by the lens onto an optical detector capable of registering the optical power of the scattered light which corresponds to the cumulative radiation to which the track etch foil has been exposed.

Dual-domain point diffraction interferometer

DOEpatents

Naulleau, Patrick P.; Goldberg, Kenneth Alan

2000-01-01

A hybrid spatial/temporal-domain point diffraction interferometer (referred to as the dual-domain PS/PDI) that is capable of suppressing the scattered-reference-light noise that hinders the conventional PS/PDI is provided. The dual-domain PS/PDI combines the separate noise-suppression capabilities of the widely-used phase-shifting and Fourier-transform fringe pattern analysis methods. The dual-domain PS/PDI relies on both a more restrictive implementation of the image plane PS/PDI mask and a new analysis method to be applied to the interferograms generated and recorded by the modified PS/PDI. The more restrictive PS/PDI mask guarantees the elimination of spatial-frequency crosstalk between the signal and the scattered-light noise arising from scattered-reference-light interfering with the test beam. The new dual-domain analysis method is then used to eliminate scattered-light noise arising from both the scattered-reference-light interfering with the test beam and the scattered-reference-light interfering with the "true" pinhole-diffracted reference light. The dual-domain analysis method has also been demonstrated to provide performance enhancement when using the non-optimized standard PS/PDI design. The dual-domain PS/PDI is essentially a three-tiered filtering system composed of lowpass spatial-filtering the test-beam electric field using the more restrictive PS/PDI mask, bandpass spatial-filtering the individual interferogram irradiance frames making up the phase-shifting series, and bandpass temporal-filtering the phase-shifting series as a whole.

SU-D-12A-07: Optimization of a Moving Blocker System for Cone-Beam Computed Tomography Scatter Correction

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

Ouyang, L; Yan, H; Jia, X

2014-06-01

Purpose: A moving blocker based strategy has shown promising results for scatter correction in cone-beam computed tomography (CBCT). Different parameters of the system design affect its performance in scatter estimation and image reconstruction accuracy. The goal of this work is to optimize the geometric design of the moving block system. Methods: In the moving blocker system, a blocker consisting of lead strips is inserted between the x-ray source and imaging object and moving back and forth along rotation axis during CBCT acquisition. CT image of an anthropomorphic pelvic phantom was used in the simulation study. Scatter signal was simulated bymore » Monte Carlo calculation with various combinations of the lead strip width and the gap between neighboring lead strips, ranging from 4 mm to 80 mm (projected at the detector plane). Scatter signal in the unblocked region was estimated by cubic B-spline interpolation from the blocked region. Scatter estimation accuracy was quantified as relative root mean squared error by comparing the interpolated scatter to the Monte Carlo simulated scatter. CBCT was reconstructed by total variation minimization from the unblocked region, under various combinations of the lead strip width and gap. Reconstruction accuracy in each condition is quantified by CT number error as comparing to a CBCT reconstructed from unblocked full projection data. Results: Scatter estimation error varied from 0.5% to 2.6% as the lead strip width and the gap varied from 4mm to 80mm. CT number error in the reconstructed CBCT images varied from 12 to 44. Highest reconstruction accuracy is achieved when the blocker lead strip width is 8 mm and the gap is 48 mm. Conclusions: Accurate scatter estimation can be achieved in large range of combinations of lead strip width and gap. However, image reconstruction accuracy is greatly affected by the geometry design of the blocker.« less

WE-AB-207A-10: Transmission Characteristics of a Two Dimensional Antiscatter Grid Prototype for CBCT

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

Altunbas, C; Kavanagh, B; Miften, M

2016-06-15

Purpose: Scattered radiation remains to be a major contributor to image quality degradation in CBCT. To address the scatter problem, a focused, 2D antiscatter grid (2DASG) prototype was designed, and fabricated using additive manufacturing processes. Its scatter and primary transmission properties were characterized using a linac mounted CBCT system. Methods: The prototype 2DASG was composed of rectangular grid holes separated by tungsten septa, and has a grid pitch of 2.91 mm, grid ratio of 8, and a septal thickness of 0.1 mm. Each grid hole was aligned or focused towards the x-ray source in half-fan (i.e. offset detector) geometry ofmore » the Varian TrueBeam CBCT system. Scatter and primary transmission experiments were performed by using acrylic blocks and the beam-stop method. Transmission properties of a radiographic ASG (1DASG) (grid ratio of 10) was also performed by using the identical setup. Results: At 30 cm phantom thickness, scatter to primary ratio (SPR) was 4.51 without any ASG device. SPR was reduced to 1.28 with 1DASG, and it was further reduced to 0.28 with 2DASG. Scatter transmission fraction (Ts) of 1DASG was 21%, and Ts was reduced to 5.8% with 2DASG. The average primary transmission fraction (Tp) of 1DASG was 70.6%, whereas Tp increased to 85.1% with 2DASG. Variation of Tp across 40 cm length (the long axis of flat panel detector) was 2.6%. Conclusion: When compared to conventional ASGs, the focused 2DASG can vastly improve scatter suppression and primary transmission performance. Due to precise alignment of 2DASG’s grid holes with respect to beam divergence, high degree of primary transmission through the 2DASG was maintained across the full length of the prototype. We strongly believe that robust scatter rejection and primary transmission characteristics of our 2DASG can translate into both improved quantitative accuracy and soft tissue resolution in linac mounted CBCT systems.« less

Neutron production from beam-modifying devices in a modern double scattering proton therapy beam delivery system

PubMed Central

Pérez-Andújar, Angélica; Newhauser, Wayne D; DeLuca, Paul M

2014-01-01

In this work the neutron production in a passive beam delivery system was investigated. Secondary particles including neutrons are created as the proton beam interacts with beam shaping devices in the treatment head. Stray neutron exposure to the whole body may increase the risk that the patient develops a radiogenic cancer years or decades after radiotherapy. We simulated a passive proton beam delivery system with double scattering technology to determine the neutron production and energy distribution at 200 MeV proton energy. Specifically, we studied the neutron absorbed dose per therapeutic absorbed dose, the neutron absorbed dose per source particle and the neutron energy spectrum at various locations around the nozzle. We also investigated the neutron production along the nozzle's central axis. The absorbed doses and neutron spectra were simulated with the MCNPX Monte Carlo code. The simulations revealed that the range modulation wheel (RMW) is the most intense neutron source of any of the beam spreading devices within the nozzle. This finding suggests that it may be helpful to refine the design of the RMW assembly, e.g., by adding local shielding, to suppress neutron-induced damage to components in the nozzle and to reduce the shielding thickness of the treatment vault. The simulations also revealed that the neutron dose to the patient is predominated by neutrons produced in the field defining collimator assembly, located just upstream of the patient. PMID:19147903

Space-Wave Routing via Surface Waves Using a Metasurface System.

PubMed

Achouri, Karim; Caloz, Christophe

2018-05-15

We introduce the concept of a metasurface system able to route space waves via surface waves. This concept may be used to laterally shift or modulate the beam width of scattered waves. The system is synthesized based on a momentum transfer approach using phase-gradient metasurfaces. The concept is experimentally verified in an "electromagnetic periscope". Additionally, we propose two other potential applications namely a beam expander and a multi-wave refractor.

Spin-Hall effect in the scattering of structured light from plasmonic nanowire.

PubMed

Sharma, Deepak K; Kumar, Vijay; Vasista, Adarsh B; Chaubey, Shailendra K; Kumar, G V Pavan

2018-06-01

Spin-orbit interactions are subwavelength phenomena that can potentially lead to numerous device-related applications in nanophotonics. Here, we report the spin-Hall effect in the forward scattering of Hermite-Gaussian (HG) and Gaussian beams from a plasmonic nanowire. Asymmetric scattered radiation distribution was observed for circularly polarized beams. Asymmetry in the scattered radiation distribution changes the sign when the polarization handedness inverts. We found a significant enhancement in the spin-Hall effect for a HG beam compared to a Gaussian beam for constant input power. The difference between scattered powers perpendicular to the long axis of the plasmonic nanowire was used to quantify the enhancement. In addition, the nodal line of the HG beam acts as the marker for the spin-Hall shift. Numerical calculations corroborate experimental observations and suggest that the spin flow component of the Poynting vector associated with the circular polarization is responsible for the spin-Hall effect and its enhancement.

Spin-Hall effect in the scattering of structured light from plasmonic nanowire

NASA Astrophysics Data System (ADS)

Sharma, Deepak K.; Kumar, Vijay; Vasista, Adarsh B.; Chaubey, Shailendra K.; Kumar, G. V. Pavan

2018-06-01

Spin-orbit interactions are subwavelength phenomena which can potentially lead to numerous device related applications in nanophotonics. Here, we report Spin-Hall effect in the forward scattering of Hermite-Gaussian and Gaussian beams from a plasmonic nanowire. Asymmetric scattered radiation distribution was observed for circularly polarized beams. Asymmetry in the scattered radiation distribution changes the sign when the polarization handedness inverts. We found a significant enhancement in the Spin-Hall effect for Hermite-Gaussian beam as compared to Gaussian beam for constant input power. The difference between scattered powers perpendicular to the long axis of the plasmonic nanowire was used to quantify the enhancement. In addition to it, nodal line of HG beam acts as the marker for the Spin-Hall shift. Numerical calculations corroborate experimental observations and suggest that the Spin flow component of Poynting vector associated with the circular polarization is responsible for the Spin-Hall effect and its enhancement.

SU-F-SPS-06: Implementation of a Back-Projection Algorithm for 2D in Vivo Dosimetry with An EPID System

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

Hernandez Reyes, B; Rodriguez Perez, E; Sosa Aquino, M

Purpose: To implement a back-projection algorithm for 2D dose reconstructions for in vivo dosimetry in radiation therapy using an Electronic Portal Imaging Device (EPID) based on amorphous silicon. Methods: An EPID system was used to calculate dose-response function, pixel sensitivity map, exponential scatter kernels and beam hardenig correction for the back-projection algorithm. All measurements were done with a 6 MV beam. A 2D dose reconstruction for an irradiated water phantom (30×30×30 cm{sup 3}) was done to verify the algorithm implementation. Gamma index evaluation between the 2D reconstructed dose and the calculated with a treatment planning system (TPS) was done. Results:more » A linear fit was found for the dose-response function. The pixel sensitivity map has a radial symmetry and was calculated with a profile of the pixel sensitivity variation. The parameters for the scatter kernels were determined only for a 6 MV beam. The primary dose was estimated applying the scatter kernel within EPID and scatter kernel within the patient. The beam hardening coefficient is σBH= 3.788×10{sup −4} cm{sup 2} and the effective linear attenuation coefficient is µAC= 0.06084 cm{sup −1}. The 95% of points evaluated had γ values not longer than the unity, with gamma criteria of ΔD = 3% and Δd = 3 mm, and within the 50% isodose surface. Conclusion: The use of EPID systems proved to be a fast tool for in vivo dosimetry, but the implementation is more complex that the elaborated for pre-treatment dose verification, therefore, a simplest method must be investigated. The accuracy of this method should be improved modifying the algorithm in order to compare lower isodose curves.« less

Simulating the influence of scatter and beam hardening in dimensional computed tomography

NASA Astrophysics Data System (ADS)

Lifton, J. J.; Carmignato, S.

2017-10-01

Cone-beam x-ray computed tomography (XCT) is a radiographic scanning technique that allows the non-destructive dimensional measurement of an object’s internal and external features. XCT measurements are influenced by a number of different factors that are poorly understood. This work investigates how non-linear x-ray attenuation caused by beam hardening and scatter influences XCT-based dimensional measurements through the use of simulated data. For the measurement task considered, both scatter and beam hardening are found to influence dimensional measurements when evaluated using the ISO50 surface determination method. On the other hand, only beam hardening is found to influence dimensional measurements when evaluated using an advanced surface determination method. Based on the results presented, recommendations on the use of beam hardening and scatter correction for dimensional XCT are given.

Thomson scattering diagnostic system design for the Compact Toroidal Hybrid experiment

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

Traverso, P. J., E-mail: pjt0002@auburn.edu; Maurer, D. A.; Ennis, D. A.

2014-11-15

A new Thomson scattering system using standard commercially available components has been designed for the non-axisymmetric plasmas of the Compact Toroidal Hybrid (CTH). The beam, generated by a frequency doubled Continuum PL DLS 2 J Nd:YAG laser, is passed vertically through an entrance Brewster window and an aperturing baffle system to minimize the stray laser light that could enter the collection optics. The beam line has been designed with an 8 m propagation distance to the mid-plane of the CTH device with the beam diameter kept less than 3 mm inside the plasma volume. The beam exits the vacuum systemmore » through another Brewster window and enters a beam dump, again to minimize the stray light in the vacuum chamber. Light collection, spectral processing, and signal detection are accomplished with an f/#∼ 1 aspheric lens, a commercially available Holospec f/1.8 spectrometer, and an Andor iStar DH740-18U-C3 image intensified camera. Spectral rejection of stray laser light, if needed, can be performed with the use of an optional interference filter at the spectrometer input. The system has been developed for initial single point measurements of plasmas with core electron temperatures of approximately 20–300 eV and densities of 5 × 10{sup 18} to 5 × 10{sup 19} m{sup −3} dependent upon operational scenario.« less

Axisymmetric scattering of an acoustical Bessel beam by a rigid fixed spheroid.

PubMed

Mitri, Farid G

2015-10-01

Based on the partial-wave series expansion (PWSE) method in spherical coordinates, a formal analytical solution for the acoustic scattering of a zeroth-order Bessel acoustic beam centered on a rigid fixed (oblate or prolate) spheroid is provided. The unknown scattering coefficients of the spheroid are determined by solving a system of linear equations derived for the Neumann boundary condition. Numerical results for the modulus of the backscattered pressure (θ = π) in the near field and the backscattering form function in the far field for both prolate and oblate spheroids are presented and discussed, with particular emphasis on the aspect ratio (i.e., the ratio of the major axis over the minor axis of the spheroid), the half-cone angle of the Bessel beam, and the dimensionless frequency. The plots display periodic oscillations (versus the dimensionless frequency) because of the interference of specularly reflected waves in the backscattering direction with circumferential Franz' waves circumnavigating the surface of the spheroid in the surrounding fluid. Moreover, the 3-D directivity patterns illustrate the near- and far-field axisymmetric scattering. Investigations in underwater acoustics, particle levitation, scattering, and the detection of submerged elongated objects and other related applications utilizing Bessel waves would benefit from the results of the present study.

STATUS OF VARIOUS SNS DIAGNOSTIC SYSTEMS

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

Blokland, Willem; Purcell, J David; Patton, Jeff

2007-01-01

The Spallation Neutron Source (SNS) accelerator systems are ramping up to deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. Enhancements or additions have been made to several instrument systems to support the ramp up in intensity, improve reliability, and/or add functionality. The Beam Current Monitors now support increased rep rates, the Harp system now includes charge density calculations for the target, and a new system has been created to collect data for the beam accounting and present the data over the web and to the operator consoles. The majority of themore » SNS beam instruments are PC-based and their configuration files are now managed through the Oracle relational database. A new version for the wire scanner software was developed to add features to correlate the scan with beam loss, parking in the beam, and measuring the longitudinal beam current. This software is currently being tested. This paper also includes data from the selected instruments.« less

Real-time simulator for designing electron dual scattering foil systems.

PubMed

Carver, Robert L; Hogstrom, Kenneth R; Price, Michael J; LeBlanc, Justin D; Pitcher, Garrett M

2014-11-08

The purpose of this work was to develop a user friendly, accurate, real-time com- puter simulator to facilitate the design of dual foil scattering systems for electron beams on radiotherapy accelerators. The simulator allows for a relatively quick, initial design that can be refined and verified with subsequent Monte Carlo (MC) calculations and measurements. The simulator also is a powerful educational tool. The simulator consists of an analytical algorithm for calculating electron fluence and X-ray dose and a graphical user interface (GUI) C++ program. The algorithm predicts electron fluence using Fermi-Eyges multiple Coulomb scattering theory with the reduced Gaussian formalism for scattering powers. The simulator also estimates central-axis and off-axis X-ray dose arising from the dual foil system. Once the geometry of the accelerator is specified, the simulator allows the user to continuously vary primary scattering foil material and thickness, secondary scat- tering foil material and Gaussian shape (thickness and sigma), and beam energy. The off-axis electron relative fluence or total dose profile and central-axis X-ray dose contamination are computed and displayed in real time. The simulator was validated by comparison of off-axis electron relative fluence and X-ray percent dose profiles with those calculated using EGSnrc MC. Over the energy range 7-20 MeV, using present foils on an Elekta radiotherapy accelerator, the simulator was able to reproduce MC profiles to within 2% out to 20 cm from the central axis. The central-axis X-ray percent dose predictions matched measured data to within 0.5%. The calculation time was approximately 100 ms using a single Intel 2.93 GHz processor, which allows for real-time variation of foil geometrical parameters using slider bars. This work demonstrates how the user-friendly GUI and real-time nature of the simulator make it an effective educational tool for gaining a better understanding of the effects that various system parameters have on a relative dose profile. This work also demonstrates a method for using the simulator as a design tool for creating custom dual scattering foil systems in the clinical range of beam energies (6-20 MeV). 

Scattering effects in passive foil focusing of ion beams

DOE PAGES

Yuen, Albert; Lund, Steven M.; Barnard, John J.; ...

2015-09-11

A stack of thin, closely spaced conducting foils has been investigated by Lund et al. [ Phys. Rev. ST Accel. Beams 16, 044202 (2013)] as a passive focusing lens for intense ion beams. The foils mitigate space-charge defocusing forces to enable the beam self-magnetic field to focus. In this study, we analyze possible degradation of focusing due to scattering of beam ions resulting from finite foil thickness using an envelope model and numerical simulations with the particle-in-cell code WARP. Ranges of kinetic energy where scattering effects are sufficient to destroy passive focusing are quantified. The scheme may be utilized tomore » focus protons produced in intense laser-solid accelerator schemes. The spot size of an initially collimated 30 MeV proton beam with initial rms radius 200 μm, perveance Q=1.8×10 -2, and initial transverse emittance ϵ x,rms=0.87 mm mrad propagating through a stack of 6.4 μm thick foils, spaced 100 μm apart, gives a 127.5 μm spot with scattering and a 81.0 μm spot without scattering, illustrating the importance of including scattering effects.« less

Beam halo collimation in heavy ion synchrotrons

NASA Astrophysics Data System (ADS)

Strašík, I.; Prokhorov, I.; Boine-Frankenheim, O.

2015-08-01

This paper presents a systematic study of the halo collimation of ion beams from proton up to uranium in synchrotrons. The projected Facility for Antiproton and Ion Research synchrotron SIS100 is used as a reference case. The concepts are separated into fully stripped (e.g., 238U92+ ) and partially stripped (e.g., 238U28+ ) ion collimation. An application of the two-stage betatron collimation system, well established for proton accelerators, is intended also for fully stripped ions. The two-stage system consists of a primary collimator (a scattering foil) and secondary collimators (bulky absorbers). Interaction of the particles with the primary collimator (scattering, momentum losses, and nuclear interactions) was simulated by using fluka. Particle-tracking simulations were performed by using mad-x. Finally, the dependence of the collimation efficiency on the primary ion species was determined. The influence of the collimation system adjustment, lattice imperfections, and beam parameters was estimated. The concept for the collimation of partially stripped ions employs a thin stripping foil in order to change their charge state. These ions are subsequently deflected towards a dump location using a beam optical element. The charge state distribution after the stripping foil was obtained from global. The ions were tracked by using mad-x.

Scattering matrix elements of biological particles measured in a flow through system: theory and practice.

PubMed

Sloot, P M; Hoekstra, A G; van der Liet, H; Figdor, C G

1989-05-15

Light scattering techniques (including depolarization experiments) applied to biological cells provide a fast nondestructive probe that is very sensitive to small morphological differences. Until now quantitative measurement of these scatter phenomena were only described for particles in suspension. In this paper we discuss the symmetry conditions applicable to the scattering matrices of monodisperse biological cells in a flow cytometer and provide evidence that quantitative measurement of the elements of these scattering matrices is possible in flow through systems. Two fundamental extensions to the theoretical description of conventional scattering experiments are introduced: large cone integration of scattering signals and simultaneous implementation of the localization principle to account for scattering by a sharply focused laser beam. In addition, a specific calibration technique is proposed to account for depolarization effects of the highly specialized optics applied in flow through equipment.

Catadioptric Optics for laser Doppler velocimeter applications

NASA Technical Reports Server (NTRS)

Dunagan, Stephen E.

1989-01-01

In the design of a laser velocimeter system, attention must be given to the performance of the optical elements in their two principal tasks: focusing laser radiation into the probe volume, and collecting the scattered light. For large aperture applications, custom lens design and fabrication costs, long optical path requirements, and chromatic aberration (for two color operation) can be problematic. The adaptation of low cost Schmidt-Cassegrain astronomical telescopes to perform these laser beam manipulation and scattered light collection tasks is examined. A generic telescope design is analyzed using ray tracing and Gaussian beam propagation theory, and a simple modification procedure for converting from infinite to near unity conjugate ratio operation with image quality near the diffraction limit was identified. Modification requirements and performance are predicted for a range of geometries. Finally, a 200-mm-aperture telescope was modified for f/10 operation; performance data for this modified optic for both laser beam focusing and scattered light collection tasks agree well with predictions.

Topical Meeting on Lasers in Material Diagnostics Held in Albuquerque, New Mexico on 11-12 February 1987. Technical Digest Series. Volume 7

DTIC Science & Technology

1987-10-31

measurement. A cube beam splitter divided incident laser light, I, into two beams , IR and I0, of approximately equal intensity. The reference laser...scattered molecules were found to be strongly dependent on beam kinetic energy. These distributions are markedly non -Boltzmann and indicate that the...satisfy these requirements has been developed. The system, named OBIR for optical beam induced reflectance, is non -destructive and operates at 20C in

Optical-beam wavefront control based on the atmospheric backscatter signal

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

Banakh, V A; Razenkov, I A; Rostov, A P

2015-02-28

The feasibility of compensating for aberrations of the optical-beam initial wavefront by aperture sounding, based on the atmospheric backscatter signal from an additional laser source with a different wavelength, is experimentally studied. It is shown that the adaptive system based on this principle makes it possible to compensate for distortions of the initial beam wavefront on a surface path in atmosphere. Specifically, the beam divergence decreases, while the level of the detected mean backscatter power from the additional laser source increases. (light scattering)

Wavelength-detuning cross-beam energy transfer mitigation scheme for direct drive: Modeling and evidence from National Ignition Facility implosions

DOE PAGES

Marozas, J. A.; Hohenberger, M.; Rosenberg, M. J.; ...

2018-05-25

Here, cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces laser-energy absorption for direct-drive inertial confinement fusion. Consequently, ablation pressure and implosion velocity suffer from the decreased absorption, reducing target performance in both symmetric and polar direct drive. Additionally, CBET alters the time-resolved scattered-light spectra and redistributes absorbed and scattered-light–changing shell morphology and low-mode drive symmetry. Mitigating CBET is demonstrated in inertial confinement implosions at the National Ignition Facility by detuning the laser-source wavelengths (±2.3 Å UV) of the interacting beams. In polar direct drive, wavelength detuning was shown to increase themore » equatorial region velocity experimentally by 16% and to alter the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation–hydrodynamic simulations that indicate a 10% increase in the average ablation pressure. These results indicate that wavelength detuning successfully mitigates CBET. Simulations predict that optimized phase plates and wavelength-detuning CBET mitigation utilizing the three-legged beam layout of the OMEGA Laser System significantly increase absorption and achieve >100-Gbar hot-spot pressures in symmetric direct drive.« less

Wavelength-detuning cross-beam energy transfer mitigation scheme for direct drive: Modeling and evidence from National Ignition Facility implosions

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

Marozas, J. A.; Hohenberger, M.; Rosenberg, M. J.

Here, cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces laser-energy absorption for direct-drive inertial confinement fusion. Consequently, ablation pressure and implosion velocity suffer from the decreased absorption, reducing target performance in both symmetric and polar direct drive. Additionally, CBET alters the time-resolved scattered-light spectra and redistributes absorbed and scattered-light–changing shell morphology and low-mode drive symmetry. Mitigating CBET is demonstrated in inertial confinement implosions at the National Ignition Facility by detuning the laser-source wavelengths (±2.3 Å UV) of the interacting beams. In polar direct drive, wavelength detuning was shown to increase themore » equatorial region velocity experimentally by 16% and to alter the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation–hydrodynamic simulations that indicate a 10% increase in the average ablation pressure. These results indicate that wavelength detuning successfully mitigates CBET. Simulations predict that optimized phase plates and wavelength-detuning CBET mitigation utilizing the three-legged beam layout of the OMEGA Laser System significantly increase absorption and achieve >100-Gbar hot-spot pressures in symmetric direct drive.« less

Inverse atmospheric radiative transfer problems - A nonlinear minimization search method of solution. [aerosol pollution monitoring

NASA Technical Reports Server (NTRS)

Fymat, A. L.

1976-01-01

The paper studies the inversion of the radiative transfer equation describing the interaction of electromagnetic radiation with atmospheric aerosols. The interaction can be considered as the propagation in the aerosol medium of two light beams: the direct beam in the line-of-sight attenuated by absorption and scattering, and the diffuse beam arising from scattering into the viewing direction, which propagates more or less in random fashion. The latter beam has single scattering and multiple scattering contributions. In the former case and for single scattering, the problem is reducible to first-kind Fredholm equations, while for multiple scattering it is necessary to invert partial integrodifferential equations. A nonlinear minimization search method, applicable to the solution of both types of problems has been developed, and is applied here to the problem of monitoring aerosol pollution, namely the complex refractive index and size distribution of aerosol particles.

Laser intensity scaling through stimulated scattering in optical fibers

NASA Astrophysics Data System (ADS)

Russell, Timothy H.

The influence of stimulated scattering on laser intensity in fiber optic waveguides is examined. Stimulated Brillouin scattering (SBS) in long, multimode optical waveguides is found to generate a Stokes beam that propagates in the fiber LP01 mode. This characteristic of the Stokes beam was first applied to beam cleanup, where an aberrated pump generated a Gaussian-like Stokes beam. Additionally, the same process is found to combine multiple laser beams into a single spatially coherent source. The mean square difference between the two beams was used to measure the degree of spatial overlap, demonstrating spatial coherence between the Stokes beams even when the pump beams are not spatially correlated. This result is obtained regardless of whether the pump beams are at the same or different frequencies; producing two temporally coherent or incoherent Stokes beams respectively. Limitations in beam cleanup and combining are also examined to identify ways to overcome them. Output couplers are designed that could be used to spatially filter the Stokes beam from the pump, thus increasing the number of beams that could be combined. The combined power restriction induced by second order Stokes threshold is examined experimentally and theoretically and is not found to be a significant limitation. Finally, stimulated Raman scattering (SRS) beam cleanup is examined to overcome the stringent spectral requirements on the pump beams required by SBS. The last portion of the dissertation theoretically examines suppression of stimulated Raman scattering in fibers to eliminate the restriction this imposes on the power of a fiber laser or amplifier. The suppression was modeled using both a holmium dopant and adding a long period grating to the fiber. Both methods were shown to have a significant effect on the SRS threshold.

Design and performance of the spin asymmetries of the nucleon experiment

NASA Astrophysics Data System (ADS)

Maxwell, J. D.; Armstrong, W. R.; Choi, S.; Jones, M. K.; Kang, H.; Liyanage, A.; Meziani, Z.-E.; Mulholland, J.; Ndukum, L.; Rondón, O. A.; Ahmidouch, A.; Albayrak, I.; Asaturyan, A.; Ates, O.; Baghdasaryan, H.; Boeglin, W.; Bosted, P.; Brash, E.; Brock, J.; Butuceanu, C.; Bychkov, M.; Carlin, C.; Carter, P.; Chen, C.; Chen, J.-P.; Christy, M. E.; Covrig, S.; Crabb, D.; Danagoulian, S.; Daniel, A.; Davidenko, A. M.; Davis, B.; Day, D.; Deconinck, W.; Deur, A.; Dunne, J.; Dutta, D.; El Fassi, L.; Elaasar, M.; Ellis, C.; Ent, R.; Flay, D.; Frlez, E.; Gaskell, D.; Geagla, O.; German, J.; Gilman, R.; Gogami, T.; Gomez, J.; Goncharenko, Y. M.; Hashimoto, O.; Higinbotham, D. W.; Horn, T.; Huber, G. M.; Jones, M.; Kalantarians, N.; Kang, H. K.; Kawama, D.; Keith, C.; Keppel, C.; Khandaker, M.; Kim, Y.; King, P. M.; Kohl, M.; Kovacs, K.; Kubarovsky, V.; Li, Y.; Liyanage, N.; Luo, W.; Mamyan, V.; Markowitz, P.; Maruta, T.; Meekins, D.; Melnik, Y. M.; Mkrtchyan, A.; Mkrtchyan, H.; Mochalov, V. V.; Monaghan, P.; Narayan, A.; Nakamura, S. N.; Nuruzzaman; Pentchev, L.; Pocanic, D.; Posik, M.; Puckett, A.; Qiu, X.; Reinhold, J.; Riordan, S.; Roche, J.; Sawatzky, B.; Shabestari, M.; Slifer, K.; Smith, G.; Soloviev, L.; Solvignon, P.; Tadevosyan, V.; Tang, L.; Vasiliev, A. N.; Veilleux, M.; Walton, T.; Wesselmann, F.; Wood, S. A.; Yao, H.; Ye, Z.; Zhu, L.

2018-03-01

The Spin Asymmetries of the Nucleon Experiment (SANE) performed inclusive, double-polarized electron scattering measurements of the proton at the Continuous Electron Beam Accelerator Facility at Jefferson Lab. A novel detector array observed scattered electrons of four-momentum transfer 2 . 5

Performance evaluation of PEP

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

Zisman, M.S.

An investigation of collective effects has been undertaken to assess the possibilities for using the low emittance operating mode of the PEP storage ring as a dedicated source of synchrotron radiation. Beam current limitations associated with longitudinal and transverse instabilities, and the expected emittance growth due to intrabeam scattering have been studied as a function of beam energy. Calculations of the beam lifetime due to Touschek and gas scattering are presented, and the growth times of coupled-bunch instabilities are estimated. In general, the results are encouraging, and no fundamental problems have been uncovered. It appears that beam currents up tomore » about 10 mA per bunch should be achievable, and that the emittance growth is not a severe problem at an energy of about 8 GeV. A feedback system to deal with coupled-bunch instabilities is likely to be required. 7 refs., 13 figs.« less

Multiple-Point Mass Flux Measurement System Using Rayleigh Scattering

NASA Technical Reports Server (NTRS)

Mielke, Amy F.; Elam, Kristie A.; Clem, Michelle M.

2009-01-01

A multiple-point Rayleigh scattering diagnostic is being developed to provide mass flux measurements in gas flows. Spectroscopic Rayleigh scattering is an established flow diagnostic that has the ability to provide simultaneous density, temperature, and velocity measurements. Rayleigh scattered light from a focused 18 Watt continuous-wave laser beam is directly imaged through a solid Fabry-Perot etalon onto a CCD detector which permits spectral analysis of the light. The spatial resolution of the measurements is governed by the locations of interference fringes, which can be changed by altering the etalon characteristics. A prototype system has been used to acquire data in a Mach 0.56 flow to demonstrate feasibility of using this system to provide mass flux measurements. Estimates of measurement uncertainty and recommendations for system improvements are presented

Time-resolved diode dosimetry calibration through Monte Carlo modeling for in vivo passive scattered proton therapy range verification.

PubMed

Toltz, Allison; Hoesl, Michaela; Schuemann, Jan; Seuntjens, Jan; Lu, Hsiao-Ming; Paganetti, Harald

2017-11-01

Our group previously introduced an in vivo proton range verification methodology in which a silicon diode array system is used to correlate the dose rate profile per range modulation wheel cycle of the detector signal to the water-equivalent path length (WEPL) for passively scattered proton beam delivery. The implementation of this system requires a set of calibration data to establish a beam-specific response to WEPL fit for the selected 'scout' beam (a 1 cm overshoot of the predicted detector depth with a dose of 4 cGy) in water-equivalent plastic. This necessitates a separate set of measurements for every 'scout' beam that may be appropriate to the clinical case. The current study demonstrates the use of Monte Carlo simulations for calibration of the time-resolved diode dosimetry technique. Measurements for three 'scout' beams were compared against simulated detector response with Monte Carlo methods using the Tool for Particle Simulation (TOPAS). The 'scout' beams were then applied in the simulation environment to simulated water-equivalent plastic, a CT of water-equivalent plastic, and a patient CT data set to assess uncertainty. Simulated detector response in water-equivalent plastic was validated against measurements for 'scout' spread out Bragg peaks of range 10 cm, 15 cm, and 21 cm (168 MeV, 177 MeV, and 210 MeV) to within 3.4 mm for all beams, and to within 1 mm in the region where the detector is expected to lie. Feasibility has been shown for performing the calibration of the detector response for three 'scout' beams through simulation for the time-resolved diode dosimetry technique in passive scattered proton delivery. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

A 3% Measurement of the Beam Normal Single Spin Asymmetry in Forward Angle Elastic Electron-Proton Scattering using the Qweak Setup

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

Waidyawansa, Dinayadura Buddhini

2013-08-01

The beam normal single spin asymmetry generated in the scattering of transversely polarized electrons from unpolarized nucleons is an observable of the imaginary part of the two-photon exchange process. Moreover, it is a potential source of false asymmetry in parity violating electron scattering experiments. The Q{sub weak} experiment uses parity violating electron scattering to make a direct measurement of the weak charge of the proton. The targeted 4% measurement of the weak charge of the proton probes for parity violating new physics beyond the Standard Model. The beam normal single spin asymmetry at Q{sub weak} kinematics is at least threemore » orders of magnitude larger than 5 ppb precision of the parity violating asymmetry. To better understand this parity conserving background, the Q{sub weak} Collaboration has performed elastic scattering measurements with fully transversely polarized electron beam on the proton and aluminum. This dissertation presents the analysis of the 3% measurement (1.3% statistical and 2.6% systematic) of beam normal single spin asymmetry in electronproton scattering at a Q2 of 0.025 (GeV/c)2. It is the most precise existing measurement of beam normal single spin asymmetry available at the time. A measurement of this precision helps to improve the theoretical models on beam normal single spin asymmetry and thereby our understanding of the doubly virtual Compton scattering process.« less

Scatter correction in cone-beam CT via a half beam blocker technique allowing simultaneous acquisition of scatter and image information

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

Lee, Ho; Xing Lei; Lee, Rena

2012-05-15

Purpose: X-ray scatter incurred to detectors degrades the quality of cone-beam computed tomography (CBCT) and represents a problem in volumetric image guided and adaptive radiation therapy. Several methods using a beam blocker for the estimation and subtraction of scatter have been proposed. However, due to missing information resulting from the obstruction of the blocker, such methods require dual scanning or dynamically moving blocker to obtain a complete volumetric image. Here, we propose a half beam blocker-based approach, in conjunction with a total variation (TV) regularized Feldkamp-Davis-Kress (FDK) algorithm, to correct scatter-induced artifacts by simultaneously acquiring image and scatter information frommore » a single-rotation CBCT scan. Methods: A half beam blocker, comprising lead strips, is used to simultaneously acquire image data on one side of the projection data and scatter data on the other half side. One-dimensional cubic B-Spline interpolation/extrapolation is applied to derive patient specific scatter information by using the scatter distributions on strips. The estimated scatter is subtracted from the projection image acquired at the opposite view. With scatter-corrected projections where this subtraction is completed, the FDK algorithm based on a cosine weighting function is performed to reconstruct CBCT volume. To suppress the noise in the reconstructed CBCT images produced by geometric errors between two opposed projections and interpolated scatter information, total variation regularization is applied by a minimization using a steepest gradient descent optimization method. The experimental studies using Catphan504 and anthropomorphic phantoms were carried out to evaluate the performance of the proposed scheme. Results: The scatter-induced shading artifacts were markedly suppressed in CBCT using the proposed scheme. Compared with CBCT without a blocker, the nonuniformity value was reduced from 39.3% to 3.1%. The root mean square error relative to values inside the regions of interest selected from a benchmark scatter free image was reduced from 50 to 11.3. The TV regularization also led to a better contrast-to-noise ratio. Conclusions: An asymmetric half beam blocker-based FDK acquisition and reconstruction technique has been established. The proposed scheme enables simultaneous detection of patient specific scatter and complete volumetric CBCT reconstruction without additional requirements such as prior images, dual scans, or moving strips.« less

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

DOEpatents

Dutton, G. Wayne

1987-11-17

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

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

DOEpatents

Dutton, G.W.

1987-11-17

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

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

DOEpatents

Dutton, G.W.

1985-08-05

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

Time-of-flight scattering and recoiling spectrometer (TOF-SARS) for surface analysis

NASA Astrophysics Data System (ADS)

Grizzi, O.; Shi, M.; Bu, H.; Rabalais, J. W.

1990-02-01

A UHV spectrometer system has been designed and constructed for time-of-flight scattering and recoiling spectrometry (TOF-SARS). The technique uses a pulsed primary ion beam and TOF methods for analysis of both scattered and recoiled neutrals (N) and ions (I) simultaneously with continuous scattering angle variation over a flight path of ≊1 m. The pulsed ion beam line uses an electron impact ionization source with acceleration up to 5 keV; pulse widths down to 20 ns with average current densities of 0.05-5.0 nA/mm2 have been obtained. Typical current densities used herein are ≊0.1 nA/mm2 and TOF spectra can be collected with a total ion dose of <10-3 ions/surface atom. A channel electron multiplier detector, which is sensitive to both ions and fast neutrals, is mounted on a long tube connected to a precision rotary motion feedthru, allowing continuous rotation over a scattering angular range 0°<θ<165°. The sample is mounted on a precision manipulator, allowing azimuthal δ and incident α angle rotation, as well as translation along three orthogonal axes. The system also accommodates standard surface analysis instrumentation for LEED, AES, XPS, and UPS. The capabilities of the system are demonstrated by the following examples: (A) TOF spectra versus scattering angle θ; (B) comparison to LEED and AES; (C) surface and adsorbate structure determinations; (D) monitoring surface roughness; (E) surface semichanneling measurements; (F) measurements of scattered ion fractions; and (G) ion induced Auger electron emission.

Evaluation of beam halo from beam-gas scattering at the KEK Accelerator Test Facility

NASA Astrophysics Data System (ADS)

Yang, R.; Naito, T.; Bai, S.; Aryshev, A.; Kubo, K.; Okugi, T.; Terunuma, N.; Zhou, D.; Faus-Golfe, A.; Kubytskyi, V.; Liu, S.; Wallon, S.; Bambade, P.

2018-05-01

In circular colliders, as well as in damping rings and synchrotron radiation light sources, beam halo is one of the critical issues limiting the performance as well as potentially causing component damage and activation. It is imperative to clearly understand the mechanisms that lead to halo formation and to test the available theoretical models. Elastic beam-gas scattering can drive particles to large oscillation amplitudes and be a potential source of beam halo. In this paper, numerical estimation and Monte Carlo simulations of this process at the ATF of KEK are presented. Experimental measurements of beam halo in the ATF2 beam line using a diamond sensor detector are also described, which clearly demonstrate the influence of the beam-gas scattering process on the transverse halo distribution.

A comparison of phantom scatter from flattened and flattening filter free high-energy photon beams

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

Richmond, Neil, E-mail: neil.richmond@stees.nhs.uk; Allen, Vince; Daniel, Jim

2015-04-01

Flattening filter free (FFF) photon beams have different dosimetric properties from those of flattened beams. The aim of this work was to characterize the collimator scatter (S{sub c}) and total scatter (S{sub cp}) from 3 FFF beams of differing quality indices and use the resulting mathematical fits to generate phantom scatter (S{sub p}) data. The similarities and differences between S{sub p} of flattened and FFF beams are described. S{sub c} and S{sub cp} data were measured for 3 flattened and 3 FFF high-energy photon beams (Varian 6 and 10 MV and Elekta 6 MV). These data were fitted to logarithmicmore » power law functions with 4 numerical coefficients. The agreement between our experimentally determined flattened beam S{sub p} and published data was within ± 1.2% for all 3 beams investigated and all field sizes from 4 × 4 to 40 × 40 cm{sup 2}. For the FFF beams, S{sub p} was only within 1% of the same flattened beam published data for field sizes between 6 × 6 and 14 × 14 cm{sup 2}. Outside this range, the differences were much greater, reaching − 3.2%, − 4.5%, and − 4.3% for the fields of 40 × 40 cm{sup 2} for the Varian 6-MV, Varian 10-MV, and Elekta 6-MV FFF beams, respectively. The FFF beam S{sub p} increased more slowly with increasing field size than that of the published and measured flattened beam of a similar reference field size quality index, i.e., there is less Phantom Scatter than that found with flattened beams for a given field size. This difference can be explained when the fluence profiles of the flattened and FFF beams are considered. The FFF beam has greatly reduced fluence off axis, especially as field size increases, compared with the flattened beam profile; hence, less scatter is generated in the phantom reaching the central axis.« less

Beam tracking phase tomography with laboratory sources

NASA Astrophysics Data System (ADS)

Vittoria, F. A.; Endrizzi, M.; Kallon, G. K. N.; Hagen, C. K.; Diemoz, P. C.; Zamir, A.; Olivo, A.

2018-04-01

An X-ray phase-contrast laboratory system is presented, based on the beam-tracking method. Beam-tracking relies on creating micro-beamlets of radiation by placing a structured mask before the sample, and analysing them by using a detector with sufficient resolution. The system is used in tomographic configuration to measure the three dimensional distribution of the linear attenuation coefficient, difference from unity of the real part of the refractive index, and of the local scattering power of specimens. The complementarity of the three signals is investigated, together with their potential use for material discrimination.

Elastic scattering and total reaction cross section for the 6He +58Ni system

NASA Astrophysics Data System (ADS)

Morcelle, V.; Lichtenthäler, R.; Lépine-Szily, A.; Guimarães, V.; Mendes, D. R., Jr.; Pires, K. C. C.; de Faria, P. N.; Barioni, A.; Gasques, L.; Morais, M. C.; Shorto, J. M. B.; Zamora, J. C.; Scarduelli, V.; Condori, R. Pampa; Leistenschneider, E.

2014-11-01

Elastic scattering measurements of 6He + 58Ni system have been performed at the laboratory energy of 21.7 MeV. The 6He secondary beam was produced by a transfer reaction 9Be (7Li , 6He ) and impinged on 58Ni and 197Au targets, using the Radioactive Ion Beam (RIB) facility, RIBRAS, installed in the Pelletron Laboratory of the Institute of Physics of the University of São Paulo, Brazil. The elastic angular distribution was obtained in the angular range from 15° to 80° in the center of mass frame. Optical model calculations have been performed using a hybrid potential to fit the experimental data. The total reaction cross section was derived.

Single-scan patient-specific scatter correction in computed tomography using peripheral detection of scatter and compressed sensing scatter retrieval

PubMed Central

Meng, Bowen; Lee, Ho; Xing, Lei; Fahimian, Benjamin P.

2013-01-01

Purpose: X-ray scatter results in a significant degradation of image quality in computed tomography (CT), representing a major limitation in cone-beam CT (CBCT) and large field-of-view diagnostic scanners. In this work, a novel scatter estimation and correction technique is proposed that utilizes peripheral detection of scatter during the patient scan to simultaneously acquire image and patient-specific scatter information in a single scan, and in conjunction with a proposed compressed sensing scatter recovery technique to reconstruct and correct for the patient-specific scatter in the projection space. Methods: The method consists of the detection of patient scatter at the edges of the field of view (FOV) followed by measurement based compressed sensing recovery of the scatter through-out the projection space. In the prototype implementation, the kV x-ray source of the Varian TrueBeam OBI system was blocked at the edges of the projection FOV, and the image detector in the corresponding blocked region was used for scatter detection. The design enables image data acquisition of the projection data on the unblocked central region of and scatter data at the blocked boundary regions. For the initial scatter estimation on the central FOV, a prior consisting of a hybrid scatter model that combines the scatter interpolation method and scatter convolution model is estimated using the acquired scatter distribution on boundary region. With the hybrid scatter estimation model, compressed sensing optimization is performed to generate the scatter map by penalizing the L1 norm of the discrete cosine transform of scatter signal. The estimated scatter is subtracted from the projection data by soft-tuning, and the scatter-corrected CBCT volume is obtained by the conventional Feldkamp-Davis-Kress algorithm. Experimental studies using image quality and anthropomorphic phantoms on a Varian TrueBeam system were carried out to evaluate the performance of the proposed scheme. Results: The scatter shading artifacts were markedly suppressed in the reconstructed images using the proposed method. On the Catphan©504 phantom, the proposed method reduced the error of CT number to 13 Hounsfield units, 10% of that without scatter correction, and increased the image contrast by a factor of 2 in high-contrast regions. On the anthropomorphic phantom, the spatial nonuniformity decreased from 10.8% to 6.8% after correction. Conclusions: A novel scatter correction method, enabling unobstructed acquisition of the high frequency image data and concurrent detection of the patient-specific low frequency scatter data at the edges of the FOV, is proposed and validated in this work. Relative to blocker based techniques, rather than obstructing the central portion of the FOV which degrades and limits the image reconstruction, compressed sensing is used to solve for the scatter from detection of scatter at the periphery of the FOV, enabling for the highest quality reconstruction in the central region and robust patient-specific scatter correction. PMID:23298098

Detector-specific correction factors in radiosurgery beams and their impact on dose distribution calculations.

PubMed

García-Garduño, Olivia A; Rodríguez-Ávila, Manuel A; Lárraga-Gutiérrez, José M

2018-01-01

Silicon-diode-based detectors are commonly used for the dosimetry of small radiotherapy beams due to their relatively small volumes and high sensitivity to ionizing radiation. Nevertheless, silicon-diode-based detectors tend to over-respond in small fields because of their high density relative to water. For that reason, detector-specific beam correction factors ([Formula: see text]) have been recommended not only to correct the total scatter factors but also to correct the tissue maximum and off-axis ratios. However, the application of [Formula: see text] to in-depth and off-axis locations has not been studied. The goal of this work is to address the impact of the correction factors on the calculated dose distribution in static non-conventional photon beams (specifically, in stereotactic radiosurgery with circular collimators). To achieve this goal, the total scatter factors, tissue maximum, and off-axis ratios were measured with a stereotactic field diode for 4.0-, 10.0-, and 20.0-mm circular collimators. The irradiation was performed with a Novalis® linear accelerator using a 6-MV photon beam. The detector-specific correction factors were calculated and applied to the experimental dosimetry data for in-depth and off-axis locations. The corrected and uncorrected dosimetry data were used to commission a treatment planning system for radiosurgery planning. Various plans were calculated with simulated lesions using the uncorrected and corrected dosimetry. The resulting dose calculations were compared using the gamma index test with several criteria. The results of this work presented important conclusions for the use of detector-specific beam correction factors ([Formula: see text] in a treatment planning system. The use of [Formula: see text] for total scatter factors has an important impact on monitor unit calculation. On the contrary, the use of [Formula: see text] for tissue-maximum and off-axis ratios has not an important impact on the dose distribution calculation by the treatment planning system. This conclusion is only valid for the combination of treatment planning system, detector, and correction factors used in this work; however, this technique can be applied to other treatment planning systems, detectors, and correction factors.

Scattering volume in the collective Thomson scattering measurement using high power gyrotron in the LHD

NASA Astrophysics Data System (ADS)

Kubo, S.; Nishiura, M.; Tanaka, K.; Moseev, D.; Ogasawara, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Takahashi, H.; Tsujimura, T. I.; Makino, R.

2016-06-01

High-power gyrotrons prepared for the electron cyclotron heating at 77 GHz has been used for a collective Thomson scattering (CTS) study in LHD. Due to the difficulty in removing fundamental and/or second harmonic resonance in the viewing line of sight, the subtraction of the background ECE from measured signal was performed by modulating the probe beam power from a gyrotron. The separation of the scattering component from the background has been performed successfully taking into account the response time difference between both high-energy and bulk components. The other separation was attempted by fast scanning the viewing beam across the probing beam. It is found that the intensity of the scattered spectrum corresponding to the bulk and high energy components were almost proportional to the calculated scattering volume in the relatively low density region, while appreciable background scattered component remains even in the off volume in some high density cases. The ray-trace code TRAVIS is used to estimate the change in the scattering volume due to probing and receiving beam deflection effect.

Selective suppression of CARS signal with three-beam competing stimulated Raman scattering processes.

PubMed

Choi, Dae Sik; Rao, B Jayachander; Kim, Doyeon; Shim, Sang-Hee; Rhee, Hanju; Cho, Minhaeng

2018-06-14

Coherent Raman scattering spectroscopy and microscopy are useful methods for studying the chemical and biological structures of molecules with Raman-active modes. In particular, coherent anti-Stokes Raman scattering (CARS) microscopy, which is a label-free method capable of imaging structures by displaying the vibrational contrast of the molecules, has been widely used. However, the lack of a technique for switching-off the CARS signal has prevented the development of the super-resolution Raman imaging method. Here, we demonstrate that a selective suppression of the CARS signal is possible by using a three-beam double stimulated Raman scattering (SRS) scheme; the three beams are the pump, Stokes, and depletion lights in order of frequency. Both pump-Stokes and pump-depletion beam pairs can generate SRS processes by tuning their beat frequencies to match two different vibrational modes, then two CARS signals induced by pump-Stokes-pump and pump-depletion-pump interactions can be generated, where the two CARS signals are coupled with each other because they both involve interactions with the common pump beam. Herein, we show that as the intensity of the depletion beam is increased, one can selectively suppress the pump-Stokes-pump CARS signal because the pump-depletion SRS depletes the pump photons. A detailed theoretical description of the coupled differential equations for the three incident fields and the generated CARS signal fields is presented. Taking benzene as a molecular system, we obtained a maximum CARS suppression efficiency of about 97% with our experimental scheme, where the ring breathing mode of the benzene is associated with pump-Stokes-pump CARS, while the C-H stretching mode is associated with the competing pump-depletion SRS process. We anticipate that this selective switching-off scheme will be of use in developing super-resolution label-free CARS microscopy.

Dose comparison between conventional and quasi-monochromatic systems for diagnostic radiology

NASA Astrophysics Data System (ADS)

Baldelli, P.; Taibi, A.; Tuffanelli, A.; Gambaccini, M.

2004-09-01

Several techniques have been introduced in the last year to reduce the dose to the patient by minimizing the risk of tumour induced by radiation. In this work the radiological potential of dose reduction in quasi-monochromatic spectra produced via mosaic crystal Bragg diffraction has been evaluated, and a comparison with conventional spectra has been performed for four standard examinations: head, chest, abdomen and lumbar sacral spine. We have simulated quasi-monochromatic x-rays with the Shadow code, and conventional spectra with the Spectrum Processor. By means of the PCXMC software, we have simulated four examinations according to parameters established by the European Guidelines, and calculated absorbed dose for principal organs and the effective dose. Simulations of quasi-monochromatic laminar beams have been performed without anti-scatter grid, because of their inherent scatter geometry, and compared with simulations with conventional beams with anti-scatter grids. Results have shown that the dose reduction due to the introduction of quasi-monochromatic x-rays depends on different parameters related to the quality of the beam, the organ composition and the anti-scatter grid. With parameters chosen in this study a significant dose reduction can be achieved for two out of four kinds of examination.

Survey of background scattering from materials found in small-angle neutron scattering.

PubMed

Barker, J G; Mildner, D F R

2015-08-01

Measurements and calculations of beam attenuation and background scattering for common materials placed in a neutron beam are presented over the temperature range of 300-700 K. Time-of-flight (TOF) measurements have also been made, to determine the fraction of the background that is either inelastic or quasi-elastic scattering as measured with a 3 He detector. Other background sources considered include double Bragg diffraction from windows or samples, scattering from gases, and phonon scattering from solids. Background from the residual air in detector vacuum vessels and scattering from the 3 He detector dome are presented. The thickness dependence of the multiple scattering correction for forward scattering from water is calculated. Inelastic phonon background scattering at small angles for crystalline solids is both modeled and compared with measurements. Methods of maximizing the signal-to-noise ratio by material selection, choice of sample thickness and wavelength, removal of inelastic background by TOF or Be filters, and removal of spin-flip scattering with polarized beam analysis are discussed.

Survey of background scattering from materials found in small-angle neutron scattering

PubMed Central

Barker, J. G.; Mildner, D. F. R.

2015-01-01

Measurements and calculations of beam attenuation and background scattering for common materials placed in a neutron beam are presented over the temperature range of 300–700 K. Time-of-flight (TOF) measurements have also been made, to determine the fraction of the background that is either inelastic or quasi-elastic scattering as measured with a 3He detector. Other background sources considered include double Bragg diffraction from windows or samples, scattering from gases, and phonon scattering from solids. Background from the residual air in detector vacuum vessels and scattering from the 3He detector dome are presented. The thickness dependence of the multiple scattering correction for forward scattering from water is calculated. Inelastic phonon background scattering at small angles for crystalline solids is both modeled and compared with measurements. Methods of maximizing the signal-to-noise ratio by material selection, choice of sample thickness and wavelength, removal of inelastic background by TOF or Be filters, and removal of spin-flip scattering with polarized beam analysis are discussed. PMID:26306088

Commissioning of full energy scanning irradiation with carbon-ion beams ranging from 55.6 to 430 MeV/u at the NIRS-HIMAC

NASA Astrophysics Data System (ADS)

Hara, Y.; Furukawa, T.; Mizushima, K.; Inaniwa, T.; Saotome, N.; Tansho, R.; Saraya, Y.; Shirai, T.; Noda, K.

2017-09-01

Since 2011, a three-dimensional (3D) scanning irradiation system has been utilized for treatments at the National Institute of Radiological Sciences-Heavy Ion Medical Accelerator in Chiba (NIRS-HIMAC). In 2012, a hybrid depth scanning method was introduced for the depth direction, in which 11 discrete beam energies are used in conjunction with the range shifter. To suppress beam spread due to multiple scattering and nuclear reactions, we then developed a full energy scanning method. Accelerator tuning and beam commissioning tests prior to a treatment with this method are time-consuming, however. We therefore devised a new approach to obtain the pencil beam dataset, including consideration of the contribution of large-angle scattered (LAS) particles, which reduces the time spent on beam data preparation. The accuracy of 3D dose delivery using this new approach was verified by measuring the dose distributions for different target volumes. Results confirmed that the measured dose distributions agreed well with calculated doses. Following this evaluation, treatments using the full energy scanning method were commenced in September 2015.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Laser Doppler visualisation of the velocity field by excluding the influence of multiparticle scattering

NASA Astrophysics Data System (ADS)

Dubnishchev, Yu N.; Chugui, Yu V.; Kompenhans, J.

2009-10-01

The method of laser Doppler visualisation and measurement of the velocity field in gas and liquid flows by suppressing the influence of multiparticle scattering is discussed. The cross section of the flow under study is illuminated by a laser beam transformed by an anamorphic optical system into a laser sheet. The effect of multiparticle scattering is eliminated by obtaining differential combinations of frequency-demodulated images of the laser sheet in different regions of the angular spectrum of scattered light.

A small-angle x-ray scattering system with a vertical layout

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

Wang, Zhen; Chen, Xiaowei; Meng, Lingpu

A small-angle x-ray scattering (SAXS) system with a vertical layout (V-SAXS) has been designed and constructed for in situ detection on nanostructures, which is well suitable for in situ study on self-assembly of nanoparticles at liquid interface and polymer processing. A steel-tower frame on a reinforced basement is built as the supporting skeleton for scattering beam path and detector platform, ensuring the system a high working stability and a high operating accuracy. A micro-focus x-ray source combining parabolic three-dimensional multi-layer mirror and scatteringless collimation system provides a highly parallel beam, which allows us to detect the very small angle range.more » With a sample-to-detector distance of 7 m, the largest measurable length scale is 420 nm in real space. With a large sample zone, it is possible to install different experimental setups such as film stretching machine, which makes the system perfect to follow the microstructures evolution of materials during processing. The capability of the V-SAXS on in situ study is tested with a drying experiment of a free latex droplet, which confirms our initial design.« less

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

NASA Astrophysics Data System (ADS)

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

2018-04-01

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

Effect of collisions on amplification of laser beams by Brillouin scattering in plasmas

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

Humphrey, K. A.; Speirs, D. C.; Trines, R. M. G. M.

2013-10-15

We report on particle in cell simulations of energy transfer between a laser pump beam and a counter-propagating seed beam using the Brillouin scattering process in uniform plasma including collisions. The results presented show that the ion acoustic waves excited through naturally occurring Brillouin scattering of the pump field are preferentially damped without affecting the driven Brillouin scattering process resulting from the beating of the pump and seed fields together. We find that collisions, including the effects of Landau damping, allow for a more efficient transfer of energy between the laser beams, and a significant reduction in the amount ofmore » seed pre-pulse produced.« less

Review of the inverse scattering problem at fixed energy in quantum mechanics

NASA Technical Reports Server (NTRS)

Sabatier, P. C.

1972-01-01

Methods of solution of the inverse scattering problem at fixed energy in quantum mechanics are presented. Scattering experiments of a beam of particles at a nonrelativisitic energy by a target made up of particles are analyzed. The Schroedinger equation is used to develop the quantum mechanical description of the system and one of several functions depending on the relative distance of the particles. The inverse problem is the construction of the potentials from experimental measurements.

Characterization of single particle aerosols by elastic light scattering at multiple wavelengths

NASA Astrophysics Data System (ADS)

Lane, P. A.; Hart, M. B.; Jain, V.; Tucker, J. E.; Eversole, J. D.

2018-03-01

We describe a system to characterize individual aerosol particles using stable and repeatable measurement of elastic light scattering. The method employs a linear electrodynamic quadrupole (LEQ) particle trap. Charged particles, continuously injected by electrospray into this system, are confined to move vertically along the stability line in the center of the LEQ past a point where they are optically interrogated. Light scattered in the near forward direction was measured at three different wavelengths using time-division multiplexed collinear laser beams. We validated our method by comparing measured silica microsphere data for four selected diameters (0.7, 1.0, 1.5 and 2.0 μm) to a model of collected scattered light intensities based upon Lorenz-Mie scattering theory. Scattered light measurements at the different wavelengths are correlated, allowing us to distinguish and classify inhomogeneous particles.

Light scattering in optical CT scanning of Presage dosimeters

NASA Astrophysics Data System (ADS)

Xu, Y.; Adamovics, J.; Cheeseborough, J. C.; Chao, K. S.; Wuu, C. S.

2010-11-01

The intensity of the scattered light from the Presage dosimeters was measured using a Thorlabs PM100D optical power meter (Thorlabs Inc, Newton, NJ) with an optical sensor of 1 mm diameter sensitive area. Five Presage dosimeters were made as cylinders of 15.2 cm, 10 cm, 4 cm diameters and irradiated with 6 MV photons using a Varian Clinac 2100EX. Each dosimeter was put into the scanning tank of an OCTOPUS" optical CT scanner (MGS Research Inc, Madison, CT) filled with a refractive index matching liquid. A laser diode was positioned at one side of the water tank to generate a stationary laser beam of 0.8 mm width. On the other side of the tank, an in-house manufactured positioning system was used to move the optical sensor in the direction perpendicular to the outgoing laser beam from the dosimeters at an increment of 1 mm. The amount of scattered photons was found to be more than 1% of the primary light signal within 2 mm from the laser beam but decreases sharply with increasing off-axis distance. The intensity of the scattered light increases with increasing light attenuations and/or absorptions in the dosimeters. The scattered light at the same off-axis distance was weaker for dosimeters of larger diameters and for larger detector-to-dosimeter distances. Methods for minimizing the effect of the light scattering in different types of optical CT scanners are discussed.

Development of a Hydrogen Møller Polarimeter for Precision Parity-Violating Electron Scattering

NASA Astrophysics Data System (ADS)

Gray, Valerie M.

2013-10-01

Parity-violating electron scattering experiments allow for testing the Standard Model at low energy accelerators. Future parity-violating electron scattering experiments, like the P2 experiment at the Johannes Gutenberg University, Mainz, Germany, and the MOLLER and SoLID experiments at Jefferson Lab will measure observables predicted by the Standard Model to high precision. In order to make these measurements, we will need to determine the polarization of the electron beam to sub-percent precision. The present way of measuring the polarization, with Møller scattering in iron foils or using Compton laser backscattering, will not easily be able to reach this precision. The novel Hydrogen Møller Polarimeter presents a non-invasive way to measure the electron polarization by scattering the electron beam off of atomic hydrogen gas polarized in a 7 Tesla solenoidal magnetic trap. This apparatus is expected to be operational by 2016 in Mainz. Currently, simulations of the polarimeter are used to develop the detection system at College of William & Mary, while the hydrogen trap and superconducting solenoid magnet are being developed at the Johannes Gutenberg University, Mainz. I will discuss the progress of the design and development of this novel polarimeter system. This material is based upon work supported by the National Science Foundation under Grant No. PHY-1206053.

A new dump system design for stray light reduction of Thomson scattering diagnostic system on EAST.

PubMed

Xiao, Shumei; Zang, Qing; Han, Xiaofeng; Wang, Tengfei; Yu, Jin; Zhao, Junyu

2016-07-01

Thomson scattering (TS) diagnostic is an important diagnostic for measuring electron temperature and density during plasma discharge. However, the measurement of Thomson scattering signal is disturbed by the stray light easily. The stray light sources in the Experimental Advanced Superconducting Tokamak (EAST) TS diagnostic system were analyzed by a simulation model of the diagnostic system, and simulation results show that the dump system is the primary stray light source. Based on the optics theory and the simulation analysis, a novel dump system including an improved beam trap was proposed and installed. The measurement results indicate that the new dump system can reduce more than 60% of the stray light for the diagnostic system, and the influence of stray light on the error of measured density decreases.

800-MeV magnetic-focused flash proton radiography for high-contrast imaging of low-density biologically-relevant targets using an inverse-scatter collimator

NASA Astrophysics Data System (ADS)

Freeman, Matthew S.; Allison, Jason; Espinoza, Camilo; Goett, John Jerome; Hogan, Gary; Hollander, Brian; Kwiatkowski, Kris; Lopez, Julian; Mariam, Fesseha; Martinez, Michael; Medina, Jason; Medina, Patrick; Merrill, Frank E.; Morley, Deborah; Morris, Chris; Murray, Matthew; Nedrow, Paul; Saunders, Alexander; Schurman, Tamsen; Sisneros, Thomas; Tainter, Amy; Trouw, Frans; Tupa, Dale; Tybo, Josh; Wilde, Carl

2016-03-01

Proton radiography shows great promise as a tool to guide proton beam therapy (PBT) in real time. Here, we demonstrate two ways in which the technology may progress towards that goal. Firstly, with a proton beam that is 800 MeV in energy, target tissue receives a dose of radiation with very tight lateral constraint. This could present a benefit over the traditional treatment energies of ~200 MeV, where up to 1 cm of lateral tissue receives scattered radiation at the target. At 800 MeV, the beam travels completely through the object with minimal deflection, thus constraining lateral dose to a smaller area. The second novelty of this system is the utilization of magnetic quadrupole refocusing lenses that mitigate the blur caused by multiple Coulomb scattering within an object, enabling high resolution imaging of thick objects, such as the human body. This system is demonstrated on ex vivo salamander and zebrafish specimens, as well as on a realistic hand phantom. The resulting images provide contrast sufficient to visualize thin tissue, as well as fine detail within the target volumes, and the ability to measure small changes in density. Such a system, combined with PBT, would enable the delivery of a highly specific dose of radiation that is monitored and guided in real time.

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.

Ponderomotive phase plate for transmission electron microscopes

DOEpatents

Reed, Bryan W [Livermore, CA

2012-07-10

A ponderomotive phase plate system and method for controllably producing highly tunable phase contrast transfer functions in a transmission electron microscope (TEM) for high resolution and biological phase contrast imaging. The system and method includes a laser source and a beam transport system to produce a focused laser crossover as a phase plate, so that a ponderomotive potential of the focused laser crossover produces a scattering-angle-dependent phase shift in the electrons of the post-sample electron beam corresponding to a desired phase contrast transfer function.

Raman beam combining for laser brightness enhancement

DOEpatents

Dawson, Jay W.; Allen, Graham S.; Pax, Paul H.; Heebner, John E.; Sridharan, Arun K.; Rubenchik, Alexander M.; Barty, Chrisopher B. J.

2015-10-27

An optical source capable of enhanced scaling of pulse energy and brightness utilizes an ensemble of single-aperture fiber lasers as pump sources, with each such fiber laser operating at acceptable pulse energy levels. Beam combining involves stimulated Raman scattering using a Stokes' shifted seed beam, the latter of which is optimized in terms of its temporal and spectral properties. Beams from fiber lasers can thus be combined to attain pulses with peak energies in excess of the fiber laser self-focusing limit of 4 MW while retaining the advantages of a fiber laser system of high average power with good beam quality.

Quantitative analysis of artifacts in 4D DSA: the relative contributions of beam hardening and scatter to vessel dropout behind highly attenuating structures

NASA Astrophysics Data System (ADS)

Hermus, James; Szczykutowicz, Timothy P.; Strother, Charles M.; Mistretta, Charles

2014-03-01

When performing Computed Tomographic (CT) image reconstruction on digital subtraction angiography (DSA) projections, loss of vessel contrast has been observed behind highly attenuating anatomy, such as dental implants and large contrast filled aneurysms. Because this typically occurs only in a limited range of projection angles, the observed contrast time course can potentially be altered. In this work, we have developed a model for acquiring DSA projections that models both the polychromatic nature of the x-ray spectrum and the x-ray scattering interactions to investigate this problem. In our simulation framework, scatter and beam hardening contributions to vessel dropout can be analyzed separately. We constructed digital phantoms with large clearly defined regions containing iodine contrast, bone, soft issue, titanium (dental implants) or combinations of these materials. As the regions containing the materials were large and rectangular, when the phantoms were forward projected, the projections contained uniform regions of interest (ROI) and enabled accurate vessel dropout analysis. Two phantom models were used, one to model the case of a vessel behind a large contrast filled aneurysm and the other to model a vessel behind a dental implant. Cases in which both beam hardening and scatter were turned off, only scatter was turned on, only beam hardening was turned on, and both scatter and beam hardening were turned on, were simulated for both phantom models. The analysis of this data showed that the contrast degradation is primarily due to scatter. When analyzing the aneurysm case, 90.25% of the vessel contrast was lost in the polychromatic scatter image, however only 50.5% of the vessel contrast was lost in the beam hardening only image. When analyzing the teeth case, 44.2% of the vessel contrast was lost in the polychromatic scatter image and only 26.2% of the vessel contrast was lost in the beam hardening only image.

Tissue Equivalent Phantom Design for Characterization of a Coherent Scatter X-ray Imaging System

NASA Astrophysics Data System (ADS)

Albanese, Kathryn Elizabeth

Scatter in medical imaging is typically cast off as image-related noise that detracts from meaningful diagnosis. It is therefore typically rejected or removed from medical images. However, it has been found that every material, including cancerous tissue, has a unique X-ray coherent scatter signature that can be used to identify the material or tissue. Such scatter-based tissue-identification provides the advantage of locating and identifying particular materials over conventional anatomical imaging through X-ray radiography. A coded aperture X-ray coherent scatter spectral imaging system has been developed in our group to classify different tissue types based on their unique scatter signatures. Previous experiments using our prototype have demonstrated that the depth-resolved coherent scatter spectral imaging system (CACSSI) can discriminate healthy and cancerous tissue present in the path of a non-destructive x-ray beam. A key to the successful optimization of CACSSI as a clinical imaging method is to obtain anatomically accurate phantoms of the human body. This thesis describes the development and fabrication of 3D printed anatomical scatter phantoms of the breast and lung. The purpose of this work is to accurately model different breast geometries using a tissue equivalent phantom, and to classify these tissues in a coherent x-ray scatter imaging system. Tissue-equivalent anatomical phantoms were designed to assess the capability of the CACSSI system to classify different types of breast tissue (adipose, fibroglandular, malignant). These phantoms were 3D printed based on DICOM data obtained from CT scans of prone breasts. The phantoms were tested through comparison of measured scatter signatures with those of adipose and fibroglandular tissue from literature. Tumors in the phantom were modeled using a variety of biological tissue including actual surgically excised benign and malignant tissue specimens. Lung based phantoms have also been printed for future testing. Our imaging system has been able to define the location and composition of the various materials in the phantom. These phantoms were used to characterize the CACSSI system in terms of beam width and imaging technique. The result of this work showed accurate modeling and characterization of the phantoms through comparison of the tissue-equivalent form factors to those from literature. The physical construction of the phantoms, based on actual patient anatomy, was validated using mammography and computed tomography to visually compare the clinical images to those of actual patient anatomy.

Scattering apodizer for laser beams

DOEpatents

Summers, Mark A.; Hagen, Wilhelm F.; Boyd, Robert D.

1985-01-01

A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

Scattering apodizer for laser beams

DOEpatents

Summers, M.A.; Hagen, W.F.; Boyd, R.D.

1984-01-01

A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

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

EXPERIMENTAL STUDIES OF IBS (INTRA-BEAM SCATTERING) IN RHIC AND COMPARISON WITH THEORY.

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

FEDOTOV, A.V.; FISCHER, W.; TEPIKIAN, S.

A high-energy electron cooling system is presently being developed to overcome emittance growth due to Intra-beam Scattering (IBS) in RHIC. A critical item for choosing appropriate parameters of the cooler is an accurate description of the IBS. The analytic models were verified vs dedicated IBS measurements. Analysis of the 2004 data with the Au ions showed very good agreement for the longitudinal growth rates but significant disagreement with exact IBS models for the transverse growth rates. Experimental measurements were improved for the 2005 run with the Cu ions. Here, we present comparison of the 2005 data with theoretical models.

SU-F-I-06: Evaluation of Imaging Dose for Modulation Layer Based Dual Energy Cone-Beam CT

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

Ju, Eunbin; Ahn, SoHyun; Cho, Samju

Purpose: Dual energy cone beam CT system is finding a variety of promising applications in diagnostic CT, both in imaging of endogenous materials and exogenous materials across a range of body sites. Dual energy cone beam CT system to suggest in this study acquire image by rotating 360 degree with half of the X-ray window covered using copper modulation layer. In the region that covered by modulation layer absorb the low energy X-ray by modulation layer. Relative high energy X-ray passes through the layer and contributes to image reconstruction. Dose evaluation should be carried out in order to utilize suchmore » an imaging acquirement technology for clinical use. Methods: For evaluating imaging dose of modulation layer based dual energy cone beam CT system, Prototype cone beam CT that configured X-ray tube (D054SB, Toshiba, Japan) and detector (PaxScan 2520V, Varian Medical Systems, Palo Alto, CA) is used. A range of 0.5–2.0 mm thickness of modulation layer is implemented in Monte Carlo simulation (MCNPX, ver. 2.6.0, Los Alamos National Laboratory, USA) with half of X-ray window covered. In-house phantom using in this study that has 3 cylindrical phantoms configured water, Teflon air with PMMA covered for verifying the comparability the various material in human body and is implemented in Monte Carlo simulation. The actual dose with 2.0 mm copper covered half of X-ray window is measured using Gafchromic EBT3 film with 5.0 mm bolus for compared with simulative dose. Results: Dose in phantom reduced 33% by copper modulation layer of 2.0 mm. Scattering dose occurred in modulation layer by Compton scattering effect is 0.04% of overall dose. Conclusion: Modulation layer of that based dual energy cone beam CT has not influence on unnecessary scatter dose. This study was supported by the Radiation Safety Research Programs (1305033) through the Nuclear Safety and Security Commission.« less

New beam line for time-of-flight medium energy ion scattering with large area position sensitive detector

NASA Astrophysics Data System (ADS)

Linnarsson, M. K.; Hallén, A.; Åström, J.; Primetzhofer, D.; Legendre, S.; Possnert, G.

2012-09-01

A new beam line for medium energy ion mass scattering (MEIS) has been designed and set up at the Ångström laboratory, Uppsala University, Sweden. This MEIS system is based on a time-of-flight (ToF) concept and the electronics for beam chopping relies on a 4 MHz function generator. Repetition rates can be varied between 1 MHz and 63 kHz and pulse widths below 1 ns are typically obtained by including beam bunching. A 6-axis goniometer is used at the target station. Scattering angle and energy of backscattered ions are extracted from a time-resolved and position-sensitive detector. Examples of the performance are given for three kinds of probing ions, 1H+, 4He+, and 11B+. Depth resolution is in the nanometer range and 1 and 2 nm thick Pt layers can easily be resolved. Mass resolution between nearby isotopes can be obtained as illustrated by Ga isotopes in GaAs. Taking advantage of the large size detector, a direct imaging (blocking pattern) of crystal channels are shown for hexagonal, 4H-SiC. The ToF-MEIS system described in this paper is intended for use in semiconductor and thin film areas. For example, depth profiling in the sub nanometer range for device development of contacts and dielectric interfaces. In addition to applied projects, fundamental studies of stopping cross sections in this medium energy range will also be conducted.

Ambient dose equivalent and effective dose from scattered x-ray spectra in mammography for Mo/Mo, Mo/Rh and W/Rh anode/filter combinations.

PubMed

Künzel, R; Herdade, S B; Costa, P R; Terini, R A; Levenhagen, R S

2006-04-21

In this study, scattered x-ray distributions were produced by irradiating a tissue equivalent phantom under clinical mammographic conditions by using Mo/Mo, Mo/Rh and W/Rh anode/filter combinations, for 25 and 30 kV tube voltages. Energy spectra of the scattered x-rays have been measured with a Cd(0.9)Zn(0.1)Te (CZT) detector for scattering angles between 30 degrees and 165 degrees . Measurement and correction processes have been evaluated through the comparison between the values of the half-value layer (HVL) and air kerma calculated from the corrected spectra and measured with an ionization chamber in a nonclinical x-ray system with a W/Mo anode/filter combination. The shape of the corrected x-ray spectra measured in the nonclinical system was also compared with those calculated using semi-empirical models published in the literature. Scattered x-ray spectra measured in the clinical x-ray system have been characterized through the calculation of HVL and mean photon energy. Values of the air kerma, ambient dose equivalent and effective dose have been evaluated through the corrected x-ray spectra. Mean conversion coefficients relating the air kerma to the ambient dose equivalent and to the effective dose from the scattered beams for Mo/Mo, Mo/Rh and W/Rh anode/filter combinations were also evaluated. Results show that for the scattered radiation beams the ambient dose equivalent provides an overestimate of the effective dose by a factor of about 5 in the mammography energy range. These results can be used in the control of the dose limits around a clinical unit and in the calculation of more realistic protective shielding barriers in mammography.

Plasma characterization using ultraviolet Thomson scattering from ion-acoustic and electron plasma waves (invited).

PubMed

Follett, R K; Delettrez, J A; Edgell, D H; Henchen, R J; Katz, J; Myatt, J F; Froula, D H

2016-11-01

Collective Thomson scattering is a technique for measuring the plasma conditions in laser-plasma experiments. Simultaneous measurements of ion-acoustic and electron plasma-wave spectra were obtained using a 263.25-nm Thomson-scattering probe beam. A fully reflective collection system was used to record light scattered from electron plasma waves at electron densities greater than 10 21 cm -3 , which produced scattering peaks near 200 nm. An accurate analysis of the experimental Thomson-scattering spectra required accounting for plasma gradients, instrument sensitivity, optical effects, and background radiation. Practical techniques for including these effects when fitting Thomson-scattering spectra are presented and applied to the measured spectra to show the improvements in plasma characterization.

Scattering and propagation of a Laguerre-Gaussian vortex beam by uniaxial anisotropic bispheres

NASA Astrophysics Data System (ADS)

Qu, Tan; Wu, Zhensen; Shang, Qingchao; Li, Zhengjun; Wu, Jiaji; Li, Haiying

2018-04-01

Within the framework of the generalized multi-particle Mie (GMM) theory, analytical solution to electromagnetic scattering of two interacting homogeneous uniaxial anisotropic spheres by a Laguerre-Gaussian (LG) vortex beam is investigated. The particles with different size and dielectric parameter tensor elements are arbitrarily configured. Based on the continuous boundary conditions at each sphere surface, the interactive scattering coefficients are derived. The internal and near-surface field is investigated to describe the propagation of LG vortex beam through the NaCl crystal. In addition, the far fields of some typical anisotropic medium such as LiNbO3, TiO2 bispheres illuminated by an LG vortex beam are numerically presented in detail to analyze the influence of the anisotropic parameters, sphere positions, separation distance and topological charge etc. The results show that LG vortex beam has a better recovery after interacting with a spherical particle compared with Gaussian beam. The study in the paper are useful for the further research on the scattering and propagation characteristics of arbitrary vortex beam in anisotropic chains and periodic structure.

Stimulated Rayleigh-Bragg scattering in two-photon absorbing media

NASA Astrophysics Data System (ADS)

He, Guang S.; Lu, Changgui; Zheng, Qingdong; Prasad, Paras N.; Zerom, Petros; Boyd, Robert W.; Samoc, Marek

2005-06-01

The origin and mechanism of backward stimulated Rayleigh scattering in two-photon absorbing media are studied theoretically and experimentally. This type of stimulated scattering has the unusual features of no frequency shift and low pump threshold requirement compared to all other known stimulated scattering effects. This frequency-unshifted stimulated Rayleigh scattering effect can be well explained by a two-photon-excitation-enhanced Bragg grating reflection model. The reflection of the forward pump beam from this stationary Bragg grating may substantially enhance the backward Rayleigh scattering beam, providing a positive feedback mechanism without causing any frequency shift. A two-counterpropagating-beam-formed grating experiment in a two-photon absorbing dye solution is conducted. The measured dynamic behavior of Bragg grating formation and reflectivity properties are basically consistent with the predictions from the proposed model.

Development study of the X-ray scattering properties of a group of optically polished flat samples

NASA Technical Reports Server (NTRS)

Froechtenigt, J. F.

1973-01-01

A group of twelve optically polished flat samples were used to study the scattering of X-rays. The X-ray beam reflected from the twelve optical flat samples was analyzed by means of a long vacuum system of special design for these tests. The scattering measurements were made at 8.34A and 0.92 deg angle of incidence. The results for ten of the samples are comparable, the two exceptions being the fire polished samples.

A 300 GHz collective scattering diagnostic for low temperature plasmas.

PubMed

Hardin, Robert A; Scime, Earl E; Heard, John

2008-10-01

A compact and portable 300 GHz collective scattering diagnostic employing a homodyne detection scheme has been constructed and installed on the hot helicon experiment (HELIX). Verification of the homodyne detection scheme was accomplished with a rotating grooved aluminum wheel to Doppler shift the interaction beam. The HELIX chamber geometry and collection optics allow measurement of scattering angles ranging from 60 degrees to 90 degrees. Artificially driven ion-acoustic waves are also being investigated as a proof-of-principle test for the diagnostic system.

Dust-concentration measurement based on Mie scattering of a laser beam

PubMed Central

Yu, Xiaoyu; Shi, Yunbo; Wang, Tian; Sun, Xu

2017-01-01

To realize automatic measurement of the concentration of dust particles in the air, a theory for dust concentration measurement was developed, and a system was designed to implement the dust concentration measurement method based on laser scattering. In the study, the principle of dust concentration detection using laser scattering is studied, and the detection basis of Mie scattering theory is determined. Through simulation, the influence of the incident laser wavelength, dust particle diameter, and refractive index of dust particles on the scattered light intensity distribution are obtained for determining the scattered light intensity curves of single suspended dust particles under different characteristic parameters. A genetic algorithm was used to study the inverse particle size distribution, and the reliability of the measurement system design is proven theoretically. The dust concentration detection system, which includes a laser system, computer circuitry, air flow system, and control system, was then implemented according to the parameters obtained from the theoretical analysis. The performance of the designed system was evaluated. Experimental results show that the system performance was stable and reliable, resulting in high-precision automatic dust concentration measurement with strong anti-interference ability. PMID:28767662

Comparisons between GRNTRN simulations and beam measurements of proton lateral broadening distributions

NASA Astrophysics Data System (ADS)

Mertens, Christopher; Moyers, Michael; Walker, Steven; Tweed, John

Recent developments in NASA's High Charge and Energy Transport (HZETRN) code have included lateral broadening of primary ion beams due to small-angle multiple Coulomb scattering, and coupling of the ion-nuclear scattering interactions with energy loss and straggling. The new version of HZETRN based on Green function methods, GRNTRN, is suitable for modeling transport with both space environment and laboratory boundary conditions. Multiple scattering processes are a necessary extension to GRNTRN in order to accurately model ion beam experiments, to simulate the physical and biological-effective radiation dose, and to develop new methods and strategies for light ion radiation therapy. In this paper we compare GRNTRN simulations of proton lateral scattering distributions with beam measurements taken at Loma Linda Medical University. The simulated and measured lateral proton distributions will be compared for a 250 MeV proton beam on aluminum, polyethylene, polystyrene, bone, iron, and lead target materials.

Spin Filtering in Storage Rings

NASA Astrophysics Data System (ADS)

Nikolaev, N. N.; Pavlov, F. F.

The spin filtering in storage rings is based on a multiple passage of a stored beam through a polarized internal gas target. Apart from the polarization by the spin-dependent transmission, a unique geometrical feature of interaction with the target in such a filtering process, pointed out by H.O. Meyer,1 is a scattering of stored particles within the beam. A rotation of the spin in the scattering process affects the polarization buildup. We derive here a quantum-mechanical evolution equation for the spin-density matrix of a stored beam which incorporates the scattering within the beam. We show how the interplay of the transmission and scattering within the beam changes from polarized electrons to polarized protons in the atomic target. After discussions of the FILTEX results on the filtering of stored protons,2 we comment on the strategy of spin filtering of antiprotons for the PAX experiment at GSI FAIR.3.

A new measurement of electron transverse polarization in polarized nuclear β-decay

NASA Astrophysics Data System (ADS)

Kawamura, H.; Akiyama, T.; Hata, M.; Hirayama, Y.; Ikeda, M.; Ikeda, Y.; Ishii, T.; Kameda, D.; Mitsuoka, S.; Miyatake, H.; Nagae, D.; Nakaya, Y.; Ninomiya, K.; Nitta, M.; Ogawa, N.; Onishi, J.; Seitaibashi, E.; Tanaka, S.; Tanuma, R.; Totsuka, Y.; Toyoda, T.; Watanabe, Y. X.; Murata, J.

2017-03-01

The Mott polarimetry for T-violation (MTV) experiment tests time-reversal symmetry in polarized nuclear β-decay by measuring an electron’s transverse polarization as a form of angular asymmetry in Mott scattering using a thin metal foil. A Mott scattering analyzer system developed using a tracking detector to measure scattering angles offers better event selectivity than conventional counter experiments. In this paper, we describe a pilot experiment conducted at KEK-TRIAC using a prototype system with a polarized 8Li beam. The experiment confirmed the sound performance of our Mott analyzer system to measure T-violating triple correlation (R correlation), and therefore recommends its use in higher-precision experiments at the TRIUMF-ISAC.

Immersive Visual Analytics for Transformative Neutron Scattering Science

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

Steed, Chad A; Daniel, Jamison R; Drouhard, Margaret

The ORNL Spallation Neutron Source (SNS) provides the most intense pulsed neutron beams in the world for scientific research and development across a broad range of disciplines. SNS experiments produce large volumes of complex data that are analyzed by scientists with varying degrees of experience using 3D visualization and analysis systems. However, it is notoriously difficult to achieve proficiency with 3D visualizations. Because 3D representations are key to understanding the neutron scattering data, scientists are unable to analyze their data in a timely fashion resulting in inefficient use of the limited and expensive SNS beam time. We believe a moremore » intuitive interface for exploring neutron scattering data can be created by combining immersive virtual reality technology with high performance data analytics and human interaction. In this paper, we present our initial investigations of immersive visualization concepts as well as our vision for an immersive visual analytics framework that could lower the barriers to 3D exploratory data analysis of neutron scattering data at the SNS.« less

Beam Diagnostics of the Compton Scattering Chamber in Jefferson Lab's Hall C

NASA Astrophysics Data System (ADS)

Faulkner, Adam; I&C Group Collaboration

2013-10-01

Upcoming experimental runs in Hall C will utilize Compton scattering, involving the construction and installation of a rectangular beam enclosure. Conventional cylindrical stripline-style Beam Position Monitors (BPMs) are not appropriate due to their form factor; therefore to facilitate measurement of position, button-style BPMs are being considered due to the ease of placement within the new beam enclosure. Button BPM experience is limited at JLAB, so preliminary measurements are needed to characterize the field response, and guide the development of appropriate algorithms for the Analog to Digital receiver systems. -field mapping is performed using a Goubau Line (G-Line), which employs a surface wave to mimic the electron beam, helping to avoid problems associated with vacuum systems. Potential algorithms include simplistic 1/r modeling (-field mapping), look-up-tables, as well as a potential third order power series fit. In addition, the use of neural networks specifically the multi-layer Perceptron will be examined. The models, sensor field maps, and utility of the neural network will be presented. Next steps include: modification of the control algorithm, as well as to run an in-situ test of the four Button electrodes inside of a mock beam enclosure. The analysis of the field response using Matlab suggests the button BPMs are accurate to within 10 mm, and may be successful for beam diagnostics in Hall C. More testing is necessary to ascertain the limitations of the new electrodes. The National Science Foundation, Old Dominion University, The Department of Energy, and Jefferson Lab.

On radiation forces acting on a transparent nanoparticle in the field of a focused laser beam

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

Afanas'ev, A A; Rubinov, A N; Gaida, L S

2015-10-31

Radiation forces acting on a transparent spherical nanoparticle in the field of a focused Gaussian laser beam are studied theoretically in the Rayleigh scattering regime. Expressions are derived for the scattering force and Cartesian components of the gradient force. The resultant force acting on a nanoparticle located in the centre of a laser beam is found. The parameters of the focused beam and optical properties of the nanoparticle for which the longitudinal component of the gradient force exceeds the scattering force are determined. Characteristics of the transverse gradient force are discussed. (nanophotonics)

Atmospheric aerosol profiling with a bistatic imaging lidar system.

PubMed

Barnes, John E; Sharma, N C Parikh; Kaplan, Trevor B

2007-05-20

Atmospheric aerosols have been profiled using a simple, imaging, bistatic lidar system. A vertical laser beam is imaged onto a charge-coupled-device camera from the ground to the zenith with a wide-angle lens (CLidar). The altitudes are derived geometrically from the position of the camera and laser with submeter resolution near the ground. The system requires no overlap correction needed in monostatic lidar systems and needs a much smaller dynamic range. Nighttime measurements of both molecular and aerosol scattering were made at Mauna Loa Observatory. The CLidar aerosol total scatter compares very well with a nephelometer measuring at 10 m above the ground. The results build on earlier work that compared purely molecular scattered light to theory, and detail instrument improvements.

Hyperspectral microscopic imaging by multiplex coherent anti-Stokes Raman scattering (CARS)

NASA Astrophysics Data System (ADS)

Khmaladze, Alexander; Jasensky, Joshua; Zhang, Chi; Han, Xiaofeng; Ding, Jun; Seeley, Emily; Liu, Xinran; Smith, Gary D.; Chen, Zhan

2011-10-01

Coherent anti-Stokes Raman scattering (CARS) microscopy is a powerful technique to image the chemical composition of complex samples in biophysics, biology and materials science. CARS is a four-wave mixing process. The application of a spectrally narrow pump beam and a spectrally wide Stokes beam excites multiple Raman transitions, which are probed by a probe beam. This generates a coherent directional CARS signal with several orders of magnitude higher intensity relative to spontaneous Raman scattering. Recent advances in the development of ultrafast lasers, as well as photonic crystal fibers (PCF), enable multiplex CARS. In this study, we employed two scanning imaging methods. In one, the detection is performed by a photo-multiplier tube (PMT) attached to the spectrometer. The acquisition of a series of images, while tuning the wavelengths between images, allows for subsequent reconstruction of spectra at each image point. The second method detects CARS spectrum in each point by a cooled coupled charged detector (CCD) camera. Coupled with point-by-point scanning, it allows for a hyperspectral microscopic imaging. We applied this CARS imaging system to study biological samples such as oocytes.

The design of the optical Thomson scattering diagnostic for the National Ignition Facility.

PubMed

Datte, P S; Ross, J S; Froula, D H; Daub, K D; Galbraith, J; Glenzer, S; Hatch, B; Katz, J; Kilkenny, J; Landen, O; Manha, D; Manuel, A M; Molander, W; Montgomery, D; Moody, J; Swadling, G F; Weaver, J

2016-11-01

The National Ignition Facility (NIF) is a 192 laser beam facility designed to support the Stockpile Stewardship, High Energy Density and Inertial Confinement Fusion (ICF) programs. We report on the design of an Optical Thomson Scattering (OTS) diagnostic that has the potential to transform the community's understanding of NIF hohlraum physics by providing first principle, local, time-resolved measurements of under-dense plasma conditions. The system design allows operation with different probe laser wavelengths by manual selection of the appropriate beam splitter and gratings before the shot. A deep-UV probe beam (λ 0 -210 nm) will be used to optimize the scattered signal for plasma densities of 5 × 10 20 electrons/cm 3 while a 3ω probe will be used for experiments investigating lower density plasmas of 1 × 10 19 electrons/cm 3 . We report the phase I design of a two phase design strategy. Phase I includes the OTS telescope, spectrometer, and streak camera; these will be used to assess the background levels at NIF. Phase II will include the design and installation of a probe laser.

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.

Robert R. Wilson Prize III: Applications of Intrabeam Scattering Formulae to a Myriad of Accelerator Systems

NASA Astrophysics Data System (ADS)

Mtingwa, Sekazi K.

2017-01-01

We discuss our entree into accelerator physics and the problem of intrabeam scattering in particular. We focus on the historical importance of understanding intrabeam scattering for the successful operation of Fermilab's Accumulator and Tevatron and the subsequent hunt for the top quark, and its importance for successful operation of CERN's Large Hadron Collider that discovered the Higgs boson. We provide details on intrabeam scattering formalisms for hadron and electron beams at high energies, concluding with an Ansatz by Karl Bane that has applications to electron damping rings and synchrotron light sources.

High-frequency fluctuation measurements by far-infrared laser Faraday-effect polarimetry-interferometry and forward scattering system on MST.

PubMed

Ding, W X; Lin, L; Duff, J R; Brower, D L

2014-11-01

Magnetic fluctuation-induced transport driven by global tearing modes has been measured by Faraday-effect polarimetry and interferometry (phase measurements) in the MST reversed field pinch. However, the role of small-scale broadband magnetic and density turbulence in transport remains unknown. In order to investigate broadband magnetic turbulence, we plan to upgrade the existing detector system by using planar-diode fundamental waveguide mixers optimized for high sensitivity. Initial tests indicate these mixers have ×10 sensitivity improvement compared to currently employed corner-cube Schottky-diode mixers and ×5 lower noise. Compact mixer design will allow us to resolve the wavenumbers up to k ∼ 1-2 cm(-1) for beam width w = 1.5 cm and 15 cm(-1) for beam width w = 2 mm. The system can also be used to measure the scattered signal (amplitude measurement) induced by both plasma density and magnetic fluctuations.

Characterization of Compton-scatter imaging with an analytical simulation method

PubMed Central

Jones, Kevin C; Redler, Gage; Templeton, Alistair; Bernard, Damian; Turian, Julius V; Chu, James C H

2018-01-01

By collimating the photons scattered when a megavoltage therapy beam interacts with the patient, a Compton-scatter image may be formed without the delivery of an extra dose. To characterize and assess the potential of the technique, an analytical model for simulating scatter images was developed and validated against Monte Carlo (MC). For three phantoms, the scatter images collected during irradiation with a 6 MV flattening-filter-free therapy beam were simulated. Images, profiles, and spectra were compared for different phantoms and different irradiation angles. The proposed analytical method simulates accurate scatter images up to 1000 times faster than MC. Minor differences between MC and analytical simulated images are attributed to limitations in the isotropic superposition/convolution algorithm used to analytically model multiple-order scattering. For a detector placed at 90° relative to the treatment beam, the simulated scattered photon energy spectrum peaks at 140–220 keV, and 40–50% of the photons are the result of multiple scattering. The high energy photons originate at the beam entrance. Increasing the angle between source and detector increases the average energy of the collected photons and decreases the relative contribution of multiple scattered photons. Multiple scattered photons cause blurring in the image. For an ideal 5 mm diameter pinhole collimator placed 18.5 cm from the isocenter, 10 cGy of deposited dose (2 Hz imaging rate for 1200 MU min−1 treatment delivery) is expected to generate an average 1000 photons per mm2 at the detector. For the considered lung tumor CT phantom, the contrast is high enough to clearly identify the lung tumor in the scatter image. Increasing the treatment beam size perpendicular to the detector plane decreases the contrast, although the scatter subject contrast is expected to be greater than the megavoltage transmission image contrast. With the analytical method, real-time tumor tracking may be possible through comparison of simulated and acquired patient images. PMID:29243663

Characterization of Compton-scatter imaging with an analytical simulation method

NASA Astrophysics Data System (ADS)

Jones, Kevin C.; Redler, Gage; Templeton, Alistair; Bernard, Damian; Turian, Julius V.; Chu, James C. H.

2018-01-01

By collimating the photons scattered when a megavoltage therapy beam interacts with the patient, a Compton-scatter image may be formed without the delivery of an extra dose. To characterize and assess the potential of the technique, an analytical model for simulating scatter images was developed and validated against Monte Carlo (MC). For three phantoms, the scatter images collected during irradiation with a 6 MV flattening-filter-free therapy beam were simulated. Images, profiles, and spectra were compared for different phantoms and different irradiation angles. The proposed analytical method simulates accurate scatter images up to 1000 times faster than MC. Minor differences between MC and analytical simulated images are attributed to limitations in the isotropic superposition/convolution algorithm used to analytically model multiple-order scattering. For a detector placed at 90° relative to the treatment beam, the simulated scattered photon energy spectrum peaks at 140-220 keV, and 40-50% of the photons are the result of multiple scattering. The high energy photons originate at the beam entrance. Increasing the angle between source and detector increases the average energy of the collected photons and decreases the relative contribution of multiple scattered photons. Multiple scattered photons cause blurring in the image. For an ideal 5 mm diameter pinhole collimator placed 18.5 cm from the isocenter, 10 cGy of deposited dose (2 Hz imaging rate for 1200 MU min-1 treatment delivery) is expected to generate an average 1000 photons per mm2 at the detector. For the considered lung tumor CT phantom, the contrast is high enough to clearly identify the lung tumor in the scatter image. Increasing the treatment beam size perpendicular to the detector plane decreases the contrast, although the scatter subject contrast is expected to be greater than the megavoltage transmission image contrast. With the analytical method, real-time tumor tracking may be possible through comparison of simulated and acquired patient images.

Elastic scattering of 8He on 4He and 4 n system

NASA Astrophysics Data System (ADS)

Wolski, R.; Sidorchuk, S. I.; Ter-Akopian, G. M.; Fomichev, A. S.; Rodin, A. M.; Stepantsov, S. V.; Mittig, W.; Roussel-Chomaz, P.; Savajols, H.; Alamanos, N.; Auger, F.; Lapoux, V.; Raabe, R.; Tchuvil'sky, Yu. M.; Rusek, K.

2003-07-01

Elastic scattering of a 26A MeV beam of 8He on a gaseous helium target has been studied. In spite of efforts made for the observation of backward angle enhancement only upper limits could be obtained for the elastic scattering cross section at backward angles. The angular distribution of 8He nuclei scattered to CM 20°-80° was was analyzed in terms of a phenomenological Optical Model. Possible contributions from transfer reactions were estimated. The DWBA calculations indicate that the two step 2n transfer is more important than the one step 4n transfer. The transfer reaction d( 8He, 6Li)4n is discussed in terms of possible tests of a four-neutron system.

Optical method and apparatus for detection of defects and microstructural changes in ceramics and ceramic coatings

DOEpatents

Ellingson, William A.; Todd, Judith A.; Sun, Jiangang

2001-01-01

Apparatus detects defects and microstructural changes in hard translucent materials such as ceramic bulk compositions and ceramic coatings such as after use under load conditions. The beam from a tunable laser is directed onto the sample under study and light reflected by the sample is directed to two detectors, with light scattered with a small scatter angle directed to a first detector and light scattered with a larger scatter angle directed to a second detector for monitoring the scattering surface. The sum and ratio of the two detector outputs respectively provide a gray-scale, or "sum" image, and an indication of the lateral spread of the subsurface scatter, or "ratio" image. This two detector system allows for very high speed crack detection for on-line, real-time inspection of damage in ceramic components. Statistical image processing using a digital image processing approach allows for the quantative discrimination of the presence and distribution of small flaws in a sample while improving detection reliability. The tunable laser allows for the penetration of the sample to detect defects from the sample's surface to the laser's maximum depth of penetration. A layered optical fiber directs the incoming laser beam to the sample and transmits each scattered signal to a respective one of the two detectors.

Control and automation of the Pegasus multi-point Thomson scattering system

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

Bodner, G. M., E-mail: gbodner@wisc.edu; Bongard, M. W.; Fonck, R. J.

A new control system for the Pegasus Thomson scattering diagnostic has recently been deployed to automate the laser operation, data collection process, and interface with the system-wide Pegasus control code. Automation has been extended to areas outside of data collection, such as manipulation of beamline cameras and remotely controlled turning mirror actuators to enable intra-shot beam alignment. Additionally, the system has been upgraded with a set of fast (∼1 ms) mechanical shutters to mitigate contamination from background light. Modification and automation of the Thomson system have improved both data quality and diagnostic reliability.

Control and automation of the Pegasus multi-point Thomson scattering system

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

Bodner, Grant M.; Bongard, Michael W.; Fonck, Raymond J.

A new control system for the Pegasus Thomson scattering diagnostic has recently been deployed to automate the laser operation, data collection process, and interface with the system-wide Pegasus control code. Automation has been extended to areas outside of data collection, such as manipulation of beamline cameras and remotely controlled turning mirror actuators to enable intra-shot beam alignment. In addition, the system has been upgraded with a set of fast (~1 ms) mechanical shutters to mitigate contamination from background light. Modification and automation of the Thomson system have improved both data quality and diagnostic reliability.

Control and automation of the Pegasus multi-point Thomson scattering system

DOE PAGES

Bodner, Grant M.; Bongard, Michael W.; Fonck, Raymond J.; ...

2016-08-12

A new control system for the Pegasus Thomson scattering diagnostic has recently been deployed to automate the laser operation, data collection process, and interface with the system-wide Pegasus control code. Automation has been extended to areas outside of data collection, such as manipulation of beamline cameras and remotely controlled turning mirror actuators to enable intra-shot beam alignment. In addition, the system has been upgraded with a set of fast (~1 ms) mechanical shutters to mitigate contamination from background light. Modification and automation of the Thomson system have improved both data quality and diagnostic reliability.

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.

SU-E-T-441: Comparison of Dose Distributions for Spot-Scanned Pencil-Beam and Scattered-Beam Proton Treatments of Ocular Tumors

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

Deisher, A; Whitaker, T; Kruse, J

2014-06-01

Purpose: To study the cross-field and depth dose profiles of spot-scanned pencil beam configurations for the treatment of ocular tumors and to compare their performance to a simulated scattered beam. Methods: Dose distributions in a cubic water phantom were compared for beams that passed through a final 24mm diameter aperture to deposit maximum dose at 2.4cm depth. The pencil-beam spots formed a hexagonally-packed ring with a center-to-center spacing of 4mm. The protons exited the nozzle with energy 95.5MeV, traversed a 4.5cm water-equivalent range shifter, and travelled either 42.5cm or 100cm to the phantom surface. The aperture-to-phantom distance (APD) was 5.7cmmore » to allow room for eye-tracking hardware. A configuration with APD=0 was also tested. The scattered beam was generated with energy 159MeV, passed through 127mm of Lexan, exited the final aperture, and travelled 5.7cm to the phantom surface. This latter configuration is comparable to the MGH single scattered beamline. All beams were modelled with TOPAS1.0-beta6 compiled with GEANT4.9.6p2. Results: The modeled scattered beam produced a distal fall-off along the central axis of zd90%-zd10%=3.6mm. For the pencil beam, the zd90%-zd10% was 1.6mm in all configurations. The scattered beam's cross-field penumbra at depth of maximum dose was r90%- r10%=1.9mm. For the spot-scanned configuration with the range-shifter-tophantom distance (RsPD) of 100cm, similar cross-field profiles were achieved with r90%-r10%=2.0mm. At shorter RsPD of 42.5cm, the crossfield penumbras were 5.6mm and 7.7mm for APD=0cm and APD=5.7cm, respectively. Conclusion: For proton treatments employing a range shifter, the cross-field and central axis dose profiles depend on the quality of the original beam, the size of the range shifter, the distance from the range shifter exit to the patient, and the distance from the final aperture to the patient. A spot-scanned pencil beam configuration can achieve cross-field penumbras equal to a scattered beam and superior distal gradients.« less

Computational study of scattering of a zero-order Bessel beam by large nonspherical homogeneous particles with the multilevel fast multipole algorithm

NASA Astrophysics Data System (ADS)

Yang, Minglin; Wu, Yueqian; Sheng, Xinqing; Ren, Kuan Fang

2017-12-01

Computation of scattering of shaped beams by large nonspherical particles is a challenge in both optics and electromagnetics domains since it concerns many research fields. In this paper, we report our new progress in the numerical computation of the scattering diagrams. Our algorithm permits to calculate the scattering of a particle of size as large as 110 wavelengths or 700 in size parameter. The particle can be transparent or absorbing of arbitrary shape, smooth or with a sharp surface, such as the Chebyshev particles or ice crystals. To illustrate the capacity of the algorithm, a zero order Bessel beam is taken as the incident beam, and the scattering of ellipsoidal particles and Chebyshev particles are taken as examples. Some special phenomena have been revealed and examined. The scattering problem is formulated with the combined tangential formulation and solved iteratively with the aid of the multilevel fast multipole algorithm, which is well parallelized with the message passing interface on the distributed memory computer platform using the hybrid partitioning strategy. The numerical predictions are compared with the results of the rigorous method for a spherical particle to validate the accuracy of the approach. The scattering diagrams of large ellipsoidal particles with various parameters are examined. The effect of aspect ratios, as well as half-cone angle of the incident zero-order Bessel beam and the off-axis distance on scattered intensity, is studied. Scattering by asymmetry Chebyshev particle with size parameter larger than 700 is also given to show the capability of the method for computing scattering by arbitrary shaped particles.

Design and performance of the spin asymmetries of the nucleon experiment

DOE PAGES

Maxwell, J. D.; Armstrong, W. R.; Choi, S.; ...

2018-03-01

The Spin Asymmetries of the Nucleon Experiment (SANE) performed inclusive, double-polarized electron scattering measurements of the proton at the Continuous Electron Beam Facility at Jefferson Lab. A novel detector array observed scattered electrons of four-momentum transfer 2.5 < Q 2 < 6.5 GeV 2 and Bjorken scaling 0.3 < x < 0.8 from initial beam energies of 4.7 and 5.9 GeV. Employing a polarized proton target which could be rotated with respect to the incident electron beam, both parallel and near perpendicular spin asymmetries were measured, allowing model-independent access to transverse polarization observables A 1, A 2, g 1, gmore » 2 and moment d 2 of the proton. This article summarizes the operation and performance of the polarized target, polarized electron beam, and novel detector systems used during the course of the experiment, and describes analysis techniques utilized to access the physics observables of interest.« less

Design and performance of the spin asymmetries of the nucleon experiment

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

Maxwell, J. D.; Armstrong, W. R.; Choi, S.

The Spin Asymmetries of the Nucleon Experiment (SANE) performed inclusive, double-polarized electron scattering measurements of the proton at the Continuous Electron Beam Facility at Jefferson Lab. A novel detector array observed scattered electrons of four-momentum transfer 2.5 < Q 2 < 6.5 GeV 2 and Bjorken scaling 0.3 < x < 0.8 from initial beam energies of 4.7 and 5.9 GeV. Employing a polarized proton target which could be rotated with respect to the incident electron beam, both parallel and near perpendicular spin asymmetries were measured, allowing model-independent access to transverse polarization observables A 1, A 2, g 1, gmore » 2 and moment d 2 of the proton. This article summarizes the operation and performance of the polarized target, polarized electron beam, and novel detector systems used during the course of the experiment, and describes analysis techniques utilized to access the physics observables of interest.« less

Analysis of EM penetration into and scattering by electrically large open waveguide cavities using Gaussian beam shooting

NASA Technical Reports Server (NTRS)

Burkholder, Robert J.; Pathak, Prabhakar H.

1991-01-01

Gaussian beam (GB) representation methods are used to analyze the electromagnetic coupling into and the scattering by a large nonuniform cavity. The aperture field in the cavity is decomposed into beams using the Gabor expansion, and shooting techniques are then employed. The method is illustrated only for the two-dimensional (2-D) case. The GBs are tracked axially using the rules of beam optics which ignore any beam distortion upon reflection at the walls. The effects of beam distortion are not significant for relatively slowly varying waveguide cavities. The field scattered into the exterior by the termination within the cavity is found using a reciprocity integral formulation which requires a knowledge of the beam fields near the termination. Numerical results based on this GB approach are presented and compared with results based on an independent reference solution.

Study of Fabry-Perot Etalon Stability and Tuning for Spectroscopic Rayleigh Scattering

NASA Technical Reports Server (NTRS)

Clem, Michelle M.; Mielke-Fagan, Amy F.; Elam, Kristie A.

2010-01-01

The Fabry-Perot interferometer is a commonly employed instrument for resolving the spectrum of molecular Rayleigh scattered light for the purpose of evaluating flow properties such as gas velocity and temperature. Rayleigh scattered light from a focused laser beam can be directly imaged through a solid Fabry-Perot etalon onto a CCD detector to provide the spectral content of the scattered light. The spatial resolution of the measurements is governed by the locations of interference fringes. The location of the fringes can be changed by altering the etalon?s physical characteristics, such as thickness and index of refraction. For a fused silica solid etalon the physical properties can be adjusted by changing the etalon temperature; hence changing the order of the interference pattern and the physical fringe locations. Controlling the temperature of the etalon can provide for a slow time-response spatial scanning method for this type of etalon system. A custom designed liquid crystal Fabry-Perot (LCFP) can provide for a fast time-response method of scanning the etalon system. Voltage applied to the liquid crystal interface sets the etalon?s properties allowing Rayleigh measurements to be acquired at varying spatial locations across the image of the laser beam over a very short time period. A standard fused silica etalon and a tunable LCFP etalon are characterized to select the system that is best suited for Rayleigh scattering measurements in subsonic and supersonic flow regimes. A frequency-stabilized laser is used to investigate the apparent frequency stability and temperature sensitivity of the etalon systems. Frequency stability and temperature sensitivity data of the fused silica and LCFP etalon systems are presented in this paper, along with measurements of the LCFP etalon?s tuning capabilities. Rayleigh scattering velocity measurements with both etalon systems are presented, in an effort to determine which etalon is better suited to provide optical flow measurements of velocity, temperature, and density.

Propagation and scattering of optical light beams in free space, in atmosphere and in biological media

NASA Astrophysics Data System (ADS)

Sahin, Serkan

With their first production implemented around 1960's, lasers have afterwards proven to be excellent light sources in building the technology. Subsequently, it has been shown that the extraordinary properties of lasers are related to their coherence properties. Recent developments in optics make it possible to synthesize partially coherent light beams from fully coherent ones. In the last several decades it was seen that using partially coherent light sources may be advantageous, in the areas such as laser surface processing, fiber and free-space optical communications, and medical diagnostics. In this thesis, I study extensively the generation, the propagation in different media, and the scattering of partially coherent light beams with respect to their spectral polarization and coherence states. For instance, I analyze the evolution of recently introduced degree of cross-polarization of light fields in free space; then develop a novel partially coherent light source which acquires and keeps a flat intensity profile around the axis at any distance in the far field; and investigate the interaction of electromagnetic random light with the human eye lens. A part of the thesis treats the effect of atmospheric turbulence on random light beams. Due to random variations in the refractive index, atmospheric turbulence modulates all physical and statistical properties of propagating beams. I have explored the possibility of employing the polarimetric domain of the beam for scintillation reduction, which positively affects the performance of free-space communication systems. I also discuss novel techniques for the sensing of rough targets in the turbulent atmosphere by polarization and coherence properties of light. The other contribution to the thesis is the investigation of light scattering from deterministic or random collections of particles, within the validity of first Born approximation. In the case of a random collection, I introduce and model the new quantity (named pair-structure function) describing correlations among particles, the knowledge of which is necessary for the rigorous predictions of scattered radiation's statistics. Also, by introducing the multi-Gaussian family of functions for scattering potentials, we demonstrate a realistic model for semi-hard edges of particles and bubblelike particles.

A new dump system design for stray light reduction of Thomson scattering diagnostic system on EAST

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

Xiao, Shumei; Zang, Qing, E-mail: zangq@ipp.ac.cn; Han, Xiaofeng

Thomson scattering (TS) diagnostic is an important diagnostic for measuring electron temperature and density during plasma discharge. However, the measurement of Thomson scattering signal is disturbed by the stray light easily. The stray light sources in the Experimental Advanced Superconducting Tokamak (EAST) TS diagnostic system were analyzed by a simulation model of the diagnostic system, and simulation results show that the dump system is the primary stray light source. Based on the optics theory and the simulation analysis, a novel dump system including an improved beam trap was proposed and installed. The measurement results indicate that the new dump systemmore » can reduce more than 60% of the stray light for the diagnostic system, and the influence of stray light on the error of measured density decreases.« less

Correlation between Satellite-Derived Aerosol Characteristics and Oceanic Dimethylsulfide (DMS)

DTIC Science & Technology

1988-12-01

intensity gained by multiple scattering into the beam from all directions and the beam addition term accounting for single scattering events. The physical...the extinction and scattering coefficients are the integracion over radius of the product of the cross sectional area of aerosol particles, the...the same photon more than once is small. Therefore, the multiple interaction term can be neglected and a single scattering approximation is made. The

Measurement of the modulation transfer function of x-ray scintillators via heterodyne speckles (Conference Presentation)

NASA Astrophysics Data System (ADS)

Manfredda, Michele; Giglio, Marzio

2016-09-01

The approach can be seen as the optical transposition of what is done in electronics, when a system is fed with a white noise (the input signal autocorrelation is a Diract-delta) and the autocorrelation of the the output signal is then taken, thus yielding the Point Spread Function (PSF) of the system (which is the Fourier Transform of the MTF). In the realm of optics, the tricky task consists in the generation and handling of such a suitable random noise, which must be produced via scattering. Ideally, pure 2D white noise (random superposition of sinusoidal intensity modulation at all spatial frequencies in all the diractions) would be produced by ideal point-like scatterers illuminated with completely coherent radiation: interference between scattered waves would generate high-frequency fringes, realizing the sought noise signal. Practically, limited scatterer size and limited coherence properties of radiation introduce a limitation in the spatial bandwidth of the illuminating field. Whereas information about particle-size effect can be promptly obtained from the form factor of the sample used, which is very well known in the case of spherical particles, the information about beam coherence, in general, is usally not known with adequate accuracy, especially at the x-ray wavelengths. In the particular configuration used, speckles are produced by interfering the scattered waves with the strong transmitted beam, (heterodyne speckles), contrarily to the very common case where speckles are produced by the mutual interference between scattered waves (without any transmitted beam acting as local oscillator) (homodyne speckles). In the end the use of an heterodyne speckle field, thanks to its self-referencing scheme, allows to gather, at a fixed distance, response curves spanning a wide range of wavevectors. By crossing the info from curves acquired at few distances (e.g. 2-3) , it is possible to experimentally separate the contribution of spurious effects (such as limited coherence), in order to identify the spectral component, due to the response of the test system, which is the responsible of the broadening of the optical input signal.

Negative radiation forces and the asymmetry of scattered radiation: spheres in Bessel beams

NASA Astrophysics Data System (ADS)

Marston, Philip L.; Zhang, Likun

2011-11-01

The discovery that acoustical and optical, radiation forces computed on spheres placed on the axis of acoustical and optical Bessel beams may be opposite the direction of beam propagation makes it appropriate to reexamine the relationship between radiation forces and the asymmetry of the scattered radiation. For all of the previously identified acoustical cases in which the force was negative and the scattering pattern was also computed, it was found that the backscattering was suppressed and the forward scattering relatively enhanced (see e.g.). In the present research the acoustic radiation force on an arbitrary isotropic sphere is related to the asymmetry in the scattering and the extinction introduced by the sphere for the case of a helical Bessel beam of arbitrary order. The analysis confirms that conditions are more favorable for generating negative forces when the asymmetry is such that the backscattering is suppressed relative to the forward scattering. It is also found, however, that absorption of power by the sphere gives rise to a positive force contribution, a term which has been neglected in the corresponding optical analysis.

Biophysical characteristics of HIMAC clinical irradiation system for heavy-ion radiation therapy.

PubMed

Kanai, T; Endo, M; Minohara, S; Miyahara, N; Koyama-ito, H; Tomura, H; Matsufuji, N; Futami, Y; Fukumura, A; Hiraoka, T; Furusawa, Y; Ando, K; Suzuki, M; Soga, F; Kawachi, K

1999-04-01

The irradiation system and biophysical characteristics of carbon beams are examined regarding radiation therapy. An irradiation system was developed for heavy-ion radiotherapy. Wobbler magnets and a scatterer were used for flattening the radiation field. A patient-positioning system using X ray and image intensifiers was also installed in the irradiation system. The depth-dose distributions of the carbon beams were modified to make a spread-out Bragg peak, which was designed based on the biophysical characteristics of monoenergetic beams. A dosimetry system for heavy-ion radiotherapy was established to deliver heavy-ion doses safely to the patients according to the treatment planning. A carbon beam of 80 keV/microm in the spread-out Bragg peak was found to be equivalent in biological responses to the neutron beam that is produced at cyclotron facility in National Institute Radiological Sciences (NIRS) by bombarding 30-MeV deuteron beam on beryllium target. The fractionation schedule of the NIRS neutron therapy was adapted for the first clinical trials using carbon beams. Carbon beams, 290, 350, and 400 MeV/u, were used for a clinical trial from June of 1994. Over 300 patients have already been treated by this irradiation system by the end of 1997.

Contribution of High-Order Rainbows to the Scattering of a Gaussian Laser Beam by a Spherical Particle

NASA Technical Reports Server (NTRS)

Lock, James A.

1993-01-01

I review the theory of the scattering of a Gaussian laser beam by a dielectric spherical particle and give the details for constructing a computer program to implement the theory. Computational results indicate that if the width of the laser beam is much less than the diameter of the particle and if the axis of the beam is incident near the edge of the particle, the fifth-, sixth-, and ninth-order rainbows should be evident in the far-field scattered intensity. I performed an experiment that yielded tentative evidence for the presence of the sixth- order rainbow.

Plasma characterization using ultraviolet Thomson scattering from ion-acoustic and electron plasma waves (invited)

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

Follett, R. K., E-mail: rfollett@lle.rochester.edu; Delettrez, J. A.; Edgell, D. H.

2016-11-15

Collective Thomson scattering is a technique for measuring the plasma conditions in laser-plasma experiments. Simultaneous measurements of ion-acoustic and electron plasma-wave spectra were obtained using a 263.25-nm Thomson-scattering probe beam. A fully reflective collection system was used to record light scattered from electron plasma waves at electron densities greater than 10{sup 21} cm{sup −3}, which produced scattering peaks near 200 nm. An accurate analysis of the experimental Thomson-scattering spectra required accounting for plasma gradients, instrument sensitivity, optical effects, and background radiation. Practical techniques for including these effects when fitting Thomson-scattering spectra are presented and applied to the measured spectra tomore » show the improvements in plasma characterization.« less

Application of the diagnostic radiological index of protection to protective garments

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

Pasciak, Alexander S.; Jones, A. Kyle, E-mail: kyle.jones@mdanderson.org; Wagner, Louis K.

2015-02-15

Purpose: Previously, the diagnostic radiological index of protection (DRIP) was proposed as a metric for quantifying the protective value of radioprotective garments. The DRIP is a weighted sum of the percent transmissions of different radiation beams through a garment. Ideally, the beams would represent the anticipated stray radiation encountered during clinical use. However, it is impractical to expect a medical physicist to possess the equipment necessary to accurately measure transmission of scattered radiation. Therefore, as a proof of concept, the authors tested a method that applied the DRIP to clinical practice. Methods: Primary beam qualities used in interventional cardiology andmore » radiology were observed and catalogued. Based on the observed range of beam qualities, five representative clinical primary beam qualities, specified by kV and added filtration, were selected for this evaluation. Monte Carlo simulations were performed using these primary beams as source definitions to generate scattered spectra from the clinical primary beams. Using numerical optimization, ideal scatter mimicking primary beams, specified by kV and added aluminum filtration, were matched to the scattered spectra according to half- and quarter-value layers and spectral shape. To within reasonable approximation, these theoretical scatter-mimicking primary beams were reproduced experimentally in laboratory x ray beams and used to measure transmission through pure lead and protective garments. For this proof of concept, the DRIP for pure lead and the garments was calculated by assigning equal weighting to percent transmission measurements for each of the five beams. Finally, the areal density of lead and garments was measured for consideration alongside the DRIP to assess the protective value of each material for a given weight. Results: The authors identified ideal scatter mimicking primary beams that matched scattered spectra to within 0.01 mm for half- and quarter-value layers in copper and within 5% for the shape function. The corresponding experimental scatter-mimicking primary beams matched the Monte Carlo generated scattered spectra with maximum deviations of 6.8% and 6.6% for half- and quarter-value layers. The measured DRIP for 0.50 mm lead sheet was 2.0, indicating that it transmitted, on average, 2% of incident radiation. The measured DRIP for a lead garment and one lead-alternative garment closely matched that for pure lead of 0.50 mm thickness. The DRIP for other garments was substantially higher than 0.50 mm lead (3.9–5.4), indicating they transmitted about twice as much radiation. When the DRIP was plotted versus areal density, it was clear that, of the garments tested, none were better than lead on a weight-by-weight basis. Conclusions: A method for measuring the DRIP for protective garments using scatter-mimicking primary beams was developed. There was little discernable advantage in protective value per unit weight for lead-alternative versus lead-only garments. Careful consideration must be given to the balance of protection and weight when choosing a lead-alternative protective garment with a lower specified “lead equivalence,” e.g., 0.35 mm. The DRIP has the potential to resolve this dilemma. Reporting the DRIP relative to areal density is an ideal metric for objective comparisons of protective garment performance, considering both protective value in terms of transmission of radiation and garment weight.« less

Characterization and correction of cupping effect artefacts in cone beam CT

PubMed Central

Hunter, AK; McDavid, WD

2012-01-01

Objective The purpose of this study was to demonstrate and correct the cupping effect artefact that occurs owing to the presence of beam hardening and scatter radiation during image acquisition in cone beam CT (CBCT). Methods A uniform aluminium cylinder (6061) was used to demonstrate the cupping effect artefact on the Planmeca Promax 3D CBCT unit (Planmeca OY, Helsinki, Finland). The cupping effect was studied using a line profile plot of the grey level values using ImageJ software (National Institutes of Health, Bethesda, MD). A hardware-based correction method using copper pre-filtration was used to address this artefact caused by beam hardening and a software-based subtraction algorithm was used to address scatter contamination. Results The hardware-based correction used to address the effects of beam hardening suppressed the cupping effect artefact but did not eliminate it. The software-based correction used to address the effects of scatter resulted in elimination of the cupping effect artefact. Conclusion Compensating for the presence of beam hardening and scatter radiation improves grey level uniformity in CBCT. PMID:22378754

Rutherford forward scattering and elastic recoil detection (RFSERD) as a method for characterizing ultra-thin films

DOE PAGES

Lohn, Andrew J.; Doyle, Barney L.; Stein, Gregory J.; ...

2014-04-03

We present a novel ion beam analysis technique combining Rutherford forward scattering and elastic recoil detection (RFSERD) and demonstrate its ability to increase efficiency in determining stoichiometry in ultrathin (5-50 nm) films as compared to Rutherford backscattering. In the conventional forward geometries, scattering from the substrate overwhelms the signal from light atoms but in RFSERD, scattered ions from the substrate are ranged out while forward scattered ions and recoiled atoms from the thin film are simultaneously detected in a single detector. Lastly, the technique is applied to tantalum oxide memristors but can be extended to a wide range of materialsmore » systems.« less

Optimal spectral structure for simultaneous Stimulated Brillouin Scattering suppression and coherent property preservation in high power coherent beam combination system

NASA Astrophysics Data System (ADS)

Han, Kai; Xu, Xiaojun; Liu, Zejin

2013-05-01

Based on the spectral manipulation technique, the Stimulated Brillouin Scattering (SBS) suppression effect and the coherent beam combination (CBC) effect in multi-tone CBC system are researched theoretically and experimentally. To get satisfactory SBS suppression, the frequency interval of the multi-tone seed laser should be large enough, at least larger than the SBS gain bandwidth. In order to attain excellent CBC effect, the spectra of the multi-tone seed laser need to be matched with the optical path differences among the amplifier chains. Hence, a sufficiently separated matching spectrum is capable at both SBS mitigation and coherent property preservation. By comparing the SBS suppression effect and the CBC effect at various spectra, the optimal spectral structure for simultaneous SBS suppression and excellent CBC effect is found.

Elastic scattering and total reaction cross section for the {sup 6}He+{sup 58}Ni system

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

Morcelle, V.; Lichtenthäler, R.; Lépine-Szily, A.

2014-11-11

Elastic scattering measurements of {sup 6}He + {sup 58}Ni system have been performed at the laboratory energy of 21.7 MeV. The {sup 6}He secondary beam was produced by a transfer reaction {sup 9}Be ({sup 7}Li, {sup 6}He) and impinged on {sup 58}Ni and {sup 197}Au targets, using the Radioactive Ion Beam (RIB) facility, RIBRAS, installed in the Pelletron Laboratory of the Institute of Physics of the University of São Paulo, Brazil. The elastic angular distribution was obtained in the angular range from 15° to 80° in the center of mass frame. Optical model calculations have been performed using a hybridmore » potential to fit the experimental data. The total reaction cross section was derived.« less

The Qweak experimental apparatus

NASA Astrophysics Data System (ADS)

Allison, T.; Anderson, M.; Androić, D.; Armstrong, D. S.; Asaturyan, A.; Averett, T.; Averill, R.; Balewski, J.; Beaufait, J.; Beminiwattha, R. S.; Benesch, J.; Benmokhtar, F.; Bessuille, J.; Birchall, J.; Bonnell, E.; Bowman, J. D.; Brindza, P.; Brown, D. B.; Carlini, R. D.; Cates, G. D.; Cavness, B.; Clark, G.; Cornejo, J. C.; Dusa, S. Covrig; Dalton, M. M.; Davis, C. A.; Dean, D. C.; Deconinck, W.; Diefenbach, J.; Dow, K.; Dowd, J. F.; Dunne, J. A.; Dutta, D.; Duvall, W. S.; Echols, J. R.; Elaasar, M.; Falk, W. R.; Finelli, K. D.; Finn, J. M.; Gaskell, D.; Gericke, M. T. W.; Grames, J.; Gray, V. M.; Grimm, K.; Guo, F.; Hansknecht, J.; Harrison, D. J.; Henderson, E.; Hoskins, J. R.; Ihloff, E.; Johnston, K.; Jones, D.; Jones, M.; Jones, R.; Kargiantoulakis, M.; Kelsey, J.; Khan, N.; King, P. M.; Korkmaz, E.; Kowalski, S.; Kubera, A.; Leacock, J.; Leckey, J. P.; Lee, A. R.; Lee, J. H.; Lee, L.; Liang, Y.; MacEwan, S.; Mack, D.; Magee, J. A.; Mahurin, R.; Mammei, J.; Martin, J. W.; McCreary, A.; McDonald, M. H.; McHugh, M. J.; Medeiros, P.; Meekins, D.; Mei, J.; Michaels, R.; Micherdzinska, A.; Mkrtchyan, A.; Mkrtchyan, H.; Morgan, N.; Musson, J.; Mesick, K. E.; Narayan, A.; Ndukum, L. Z.; Nelyubin, V.; Nuruzzaman; van Oers, W. T. H.; Opper, A. K.; Page, S. A.; Pan, J.; Paschke, K. D.; Phillips, S. K.; Pitt, M. L.; Poelker, M.; Rajotte, J. F.; Ramsay, W. D.; Roberts, W. R.; Roche, J.; Rose, P. W.; Sawatzky, B.; Seva, T.; Shabestari, M. H.; Silwal, R.; Simicevic, N.; Smith, G. R.; Sobczynski, S.; Solvignon, P.; Spayde, D. T.; Stokes, B.; Storey, D. W.; Subedi, A.; Subedi, R.; Suleiman, R.; Tadevosyan, V.; Tobias, W. A.; Tvaskis, V.; Urban, E.; Waidyawansa, B.; Wang, P.; Wells, S. P.; Wood, S. A.; Yang, S.; Zhamkochyan, S.; Zielinski, R. B.

2015-05-01

The Jefferson Lab Qweak experiment determined the weak charge of the proton by measuring the parity-violating elastic scattering asymmetry of longitudinally polarized electrons from an unpolarized liquid hydrogen target at small momentum transfer. A custom apparatus was designed for this experiment to meet the technical challenges presented by the smallest and most precise e → p asymmetry ever measured. Technical milestones were achieved at Jefferson Lab in target power, beam current, beam helicity reversal rate, polarimetry, detected rates, and control of helicity-correlated beam properties. The experiment employed 180 μA of 89% longitudinally polarized electrons whose helicity was reversed 960 times per second. The electrons were accelerated to 1.16 GeV and directed to a beamline with extensive instrumentation to measure helicity-correlated beam properties that can induce false asymmetries. Møller and Compton polarimetry were used to measure the electron beam polarization to better than 1%. The electron beam was incident on a 34.4 cm liquid hydrogen target. After passing through a triple collimator system, scattered electrons between 5.8° and 11.6° were bent in the toroidal magnetic field of a resistive copper-coil magnet. The electrons inside this acceptance were focused onto eight fused silica Cherenkov detectors arrayed symmetrically around the beam axis. A total scattered electron rate of about 7 GHz was incident on the detector array. The detectors were read out in integrating mode by custom-built low-noise pre-amplifiers and 18-bit sampling ADC modules. The momentum transfer Q2=0.025 GeV2 was determined using dedicated low-current (~ 100 pA) measurements with a set of drift chambers before (and a set of drift chambers and trigger scintillation counters after) the toroidal magnet.

X-ray scattering study

NASA Technical Reports Server (NTRS)

Wriston, R. S.; Froechtenigt, J. F.

1972-01-01

A soft X-ray glancing incidence telescope mirror and a group of twelve optical flat samples were used to study the scattering of X-rays. The mirror was made of Kanigen coated beryllium and the images produced were severely limited by scattering of X-rays. The best resolution attained was about fifteen arc seconds. The telescope efficiency was found to be 0.0006. The X-ray beam reflected from the twelve optical flat samples was analyzed by means of a long vacuum system of special design for these tests. The scattering then decreased with increasing angle of incidence until a critical angle was passed. At larger angles the scattering increased again. The samples all scattered more at 44 A than at 8 A. Metal samples were found to have about the same scattering at 44 A but greater scattering at 8 A than glass samples.

154 GHz collective Thomson scattering in LHD

NASA Astrophysics Data System (ADS)

Tanaka, K.; Nishiura, M.; Kubo, S.; Shimozuma, T.; Saito, T.; Moseev, D.; Abramovic, I.

2018-01-01

Collective Thomson scattering (CTS) was developed by using a 154 GHz gyrotron, and the first data has been obtained. Already, 77 GHz CTS has worked successfully. However, in order to access higher density region, 154 GHz option enhances the usability that reduces the refraction effect, which deteriorates in the local measurements. The system in the down converted frequency was almost identical to the system for 77 GHz. Probing beam, a notch filter, a mixer, and a local oscillator in the receiver system for 77 GHz option were replaced to those for the 154 GHz option. 154 GHz gyrotron was originally prepared for the second harmonic electron cyclotron heating (ECRH) at 2.75 T. However, scattering signal was masked by the second harmonic electron cyclotron emission (ECE) at 2.75 T. Therefore, 154 GHz CTS was operated at 1.375 T with fourth harmonic ECE, and an acceptable signal to noise ratio was obtained. There is a signature of fast ion components with neutral beam (NB) injection. In addition, the CTS spectrum became broader in hydrogen discharge than in deuterium discharge, as the theoretical CTS spectrum expects. This observation indicates a possibility to identify ion species ratio by the 154 GHz CTS diagnostic.

Comparison of Head Scatter Factor for 6MV and 10MV flattened (FB) and Unflattened (FFF) Photon Beam using indigenously Designed Columnar Mini Phantom.

PubMed

Ashokkumar, Sigamani; Nambi Raj, N Arunai; Sinha, Sujit Nath; Yadav, Girigesh; Thiyagarajan, Rajesh; Raman, Kothanda; Mishra, Manindra Bhushan

2014-07-01

To measure and compare the head scatter factor for flattened (FB) and unflattened (FFF) of 6MV and 10MV photon beam using indigenously designed mini phantom. A columnar mini phantom was designed as recommended by AAPM Task Group 74 with low and high atomic number materials at 10 cm (mini phantom) and at approximately twice the depth of maximum dose water equivalent thickness (brass build-up cap). Scatter in the accelerator (Sc) values of 6MV-FFF photon beams are lesser than that of the 6MV-FB photon beams (0.66-2.8%; Clinac iX, 2300CD) and (0.47-1.74%; True beam) for field sizes ranging from 10 × 10 cm(2) to 40 × 40 cm(2). Sc values of 10MV-FFF photon beams are lesser (0.61-2.19%; True beam) than that of the 10MV-FB photons beams for field sizes ranging from 10 × 10 cm(2) to 40 × 40 cm(2). The SSD had no influence on head scatter for both flattened and unflattened beams and irrespective of head design of the different linear accelerators. The presence of field shaping device influences the Sc values. The collimator exchange effect reveals that the opening of the upper jaw increases Sc irrespective of FB or FFF photon beams and different linear accelerators, and it is less significant in FFF beams. Sc values of 6MV-FB square field were in good agreement with that of AAPM, TG-74 published data for Varian (Clinac iX, 2300CD) accelerator. Our results confirm that the removal of flattening filter decreases in the head scatter factor compared to flattened beam. This could reduce the out-of-field dose in advanced treatment delivery techniques.

Comparison of Head Scatter Factor for 6MV and 10MV flattened (FB) and Unflattened (FFF) Photon Beam using indigenously Designed Columnar Mini Phantom

PubMed Central

Ashokkumar, Sigamani; Nambi Raj, N Arunai; Sinha, Sujit Nath; Yadav, Girigesh; Thiyagarajan, Rajesh; Raman, Kothanda; Mishra, Manindra Bhushan

2014-01-01

To measure and compare the head scatter factor for flattened (FB) and unflattened (FFF) of 6MV and 10MV photon beam using indigenously designed mini phantom. A columnar mini phantom was designed as recommended by AAPM Task Group 74 with low and high atomic number materials at 10 cm (mini phantom) and at approximately twice the depth of maximum dose water equivalent thickness (brass build-up cap). Scatter in the accelerator (Sc) values of 6MV-FFF photon beams are lesser than that of the 6MV-FB photon beams (0.66-2.8%; Clinac iX, 2300CD) and (0.47-1.74%; True beam) for field sizes ranging from 10 × 10 cm2 to 40 × 40 cm2. Sc values of 10MV-FFF photon beams are lesser (0.61-2.19%; True beam) than that of the 10MV-FB photons beams for field sizes ranging from 10 × 10 cm2 to 40 × 40 cm2. The SSD had no influence on head scatter for both flattened and unflattened beams and irrespective of head design of the different linear accelerators. The presence of field shaping device influences the Sc values. The collimator exchange effect reveals that the opening of the upper jaw increases Sc irrespective of FB or FFF photon beams and different linear accelerators, and it is less significant in FFF beams. Sc values of 6MV-FB square field were in good agreement with that of AAPM, TG-74 published data for Varian (Clinac iX, 2300CD) accelerator. Our results confirm that the removal of flattening filter decreases in the head scatter factor compared to flattened beam. This could reduce the out-of-field dose in advanced treatment delivery techniques. PMID:25190997

Fast analytical scatter estimation using graphics processing units.

PubMed

Ingleby, Harry; Lippuner, Jonas; Rickey, Daniel W; Li, Yue; Elbakri, Idris

2015-01-01

To develop a fast patient-specific analytical estimator of first-order Compton and Rayleigh scatter in cone-beam computed tomography, implemented using graphics processing units. The authors developed an analytical estimator for first-order Compton and Rayleigh scatter in a cone-beam computed tomography geometry. The estimator was coded using NVIDIA's CUDA environment for execution on an NVIDIA graphics processing unit. Performance of the analytical estimator was validated by comparison with high-count Monte Carlo simulations for two different numerical phantoms. Monoenergetic analytical simulations were compared with monoenergetic and polyenergetic Monte Carlo simulations. Analytical and Monte Carlo scatter estimates were compared both qualitatively, from visual inspection of images and profiles, and quantitatively, using a scaled root-mean-square difference metric. Reconstruction of simulated cone-beam projection data of an anthropomorphic breast phantom illustrated the potential of this method as a component of a scatter correction algorithm. The monoenergetic analytical and Monte Carlo scatter estimates showed very good agreement. The monoenergetic analytical estimates showed good agreement for Compton single scatter and reasonable agreement for Rayleigh single scatter when compared with polyenergetic Monte Carlo estimates. For a voxelized phantom with dimensions 128 × 128 × 128 voxels and a detector with 256 × 256 pixels, the analytical estimator required 669 seconds for a single projection, using a single NVIDIA 9800 GX2 video card. Accounting for first order scatter in cone-beam image reconstruction improves the contrast to noise ratio of the reconstructed images. The analytical scatter estimator, implemented using graphics processing units, provides rapid and accurate estimates of single scatter and with further acceleration and a method to account for multiple scatter may be useful for practical scatter correction schemes.

Coronagraphic Notch Filter for Raman Spectroscopy

NASA Technical Reports Server (NTRS)

Cohen, David; Stirbl, Robert

2004-01-01

A modified coronagraph has been proposed as a prototype of improved notch filters in Raman spectrometers. Coronagraphic notch filters could offer alternatives to both (1) the large and expensive double or triple monochromators in older Raman spectrometers and (2) holographic notch filters, which are less expensive but are subject to environmental degradation as well as to limitations of geometry and spectral range. Measurement of a Raman spectrum is an exercise in measuring and resolving faint spectral lines close to a bright peak: In Raman spectroscopy, a monochromatic beam of light (the pump beam) excites a sample of material that one seeks to analyze. The pump beam generates a small flux of scattered light at wavelengths slightly greater than that of the pump beam. The shift in wavelength of the scattered light from the pump wavelength is known in the art as the Stokes shift. Typically, the flux of scattered light is of the order of 10 7 that of the pump beam and the Stokes shift lies in the wave-number range of 100 to 3,000 cm 1. A notch filter can be used to suppress the pump-beam spectral peak while passing the nearby faint Raman spectral lines. The basic principles of design and operation of a coronagraph offer an opportunity for engineering the spectral transmittance of the optics in a Raman spectrometer. A classical coronagraph may be understood as two imaging systems placed end to end, such that the first system forms an intermediate real image of a nominally infinitely distant object and the second system forms a final real image of the intermediate real image. If the light incident on the first telescope is collimated, then the intermediate image is a point-spread function (PSF). If an appropriately tailored occulting spot (e.g., a Gaussian-apodized spot with maximum absorption on axis) is placed on the intermediate image plane, then the instrument inhibits transmission of light from an on-axis source. However, the PSFs of off-axis light sources are formed off axis - that is, away from the occulting spot - so that they become refocused onto the final image plane.

Characterization of random scattering media and related information retrieval

NASA Astrophysics Data System (ADS)

Wang, Zhenyu

There has been substantial interest in optical imaging in and through random media in applications as diverse as environmental sensing and tumor detection. The rich scatter environment also leads to multiple paths or channels, which may provide higher capacity for communication. Coherent light passing through random media produces an intensity speckle pattern when imaged, as a result of multiple scatter and the imaging optics. When polarized coherent light is used, the speckle pattern is sensitive to the polarization state, depending on the amount of scatter, and such measurements provide information about the random medium. This may form the basis for enhanced imaging of random media and provide information on the scatterers themselves. Second and third order correlations over laser scan frequency are shown to lead to the ensemble averaged temporal impulse response, with sensitivity to the polarization state in the more weakly scattering regime. A new intensity interferometer is introduced that provides information about two signals incident on a scattering medium. The two coherent beams, which are not necessarily overlapping, interfere in a scattering medium. A sinusoidal modulation in the second order intensity correlation with laser scan frequency is shown to be related to the relative delay of the two incident beams. An intensity spatial correlation over input position reveals that decorrelation occurs over a length comparable to the incident beam size. Such decorrelation is also related to the amount of scatter. Remarkably, with two beams incident at different angles, the intensity correlation over the scan position has a sinusoidal modulation that is related to the incidence angle difference between the two input beams. This spatial correlation over input position thus provides information about input wavevectors.

Extension of geometrical-optics approximation to on-axis Gaussian beam scattering. I. By a spherical particle.

PubMed

Xu, Feng; Ren, Kuan Fang; Cai, Xiaoshu

2006-07-10

The geometrical-optics approximation of light scattering by a transparent or absorbing spherical particle is extended from plane wave to Gaussian beam incidence. The formulas for the calculation of the phase of each ray and the divergence factor are revised, and the interference of all the emerging rays is taken into account. The extended geometrical-optics approximation (EGOA) permits one to calculate the scattering diagram in all directions from 0 degrees to 180 degrees. The intensities of the scattered field calculated by the EGOA are compared with those calculated by the generalized Lorenz-Mie theory, and good agreement is found. The surface wave effect in Gaussian beam scattering is also qualitatively analyzed by introducing a flux ratio factor. The approach proposed is particularly important to the further extension of the geometrical-optics approximation to the scattering of large spheroidal particles.

Rayleigh scattering of twisted light by hydrogenlike ions

NASA Astrophysics Data System (ADS)

Peshkov, A. A.; Volotka, A. V.; Surzhykov, A.; Fritzsche, S.

2018-02-01

The elastic Rayleigh scattering of twisted light and, in particular, the polarization (transfer) of the scattered photons have been analyzed within the framework of second-order perturbation theory and Dirac's relativistic equation. Special attention was paid hereby to the scattering on three different atomic targets: single atoms, a mesoscopic (small) target, and a macroscopic (large) target, which are all centered with regard to the beam axis. Detailed calculations of the polarization Stokes parameters were performed for C5 + ions and for twisted Bessel beams. It is shown that the polarization of scattered photons is sensitive to the size of an atomic target and to the helicity, the opening angle, and the projection of the total angular momentum of the incident Bessel beam. These computations indicate more that the Stokes parameters of the (Rayleigh) scattered twisted light may significantly differ from their behavior for an incident plane-wave radiation.

SU-F-T-160: Commissioning of a Single-Room Double-Scattering Proton Therapy System

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

Jin, H; Ahmad, S; Chen, Y

2016-06-15

Purpose: To report the detailed commissioning experience for a compact double-scattering Mevion S250 proton therapy system at a University Cancer Center site. Methods: The commissioning of the proton therapy system mainly consisted of ensuring integrity of mechanical and imaging system, beam data collection, and commissioning of a treatment planning system (TPS). First, mechanical alignment and imaging were tested including safety, interlocks, positional accuracy of couch and gantry, image quality, mechanical and imaging isocenter and so on. Second, extensive beam data (outputs, PDDs, and profiles) were collected and analyzed through effective sampling of range (R) and modulation width (M) from 24more » beam options. Three different output (cGy/MU) prediction models were also commissioned as primary and secondary MU calculation tool. Third, the Varian Eclipse TPS was commissioned through five sets of data collections (in-water Bragg peak scans, in-air longitudinal fluence scans, in-air lateral profiles, in-air half-beam profiles, and an HU-to-stopping-power conversion curve) and accuracy of TPS calculation was tested using in-water scans and dose measurements with a 2D array detector with block and range compensator. Finally, an anthropomorphic phantom was scanned and heterogeneity effects were tested by inserting radiochromic films in the phantom and PET activation scans for range verification in conjunction with end-to-end test. Results: Beam characteristics agreed well with the vendor specifications; however, minor mismatches in R and M were found in some measurements during the beam data collection. These were reflected into the TPS commissioning such that the TPS could accurately predict the R and M within tolerance levels. The output models had a good agreement with measured outputs (<3% error). The end-to-end test using the film and PET showed reasonably the TPS predicted dose, R and M in heterogeneous medium. Conclusion: The proton therapy system was successfully commissioned and was released for clinical use.« less

Data consistency-driven scatter kernel optimization for x-ray cone-beam CT

NASA Astrophysics Data System (ADS)

Kim, Changhwan; Park, Miran; Sung, Younghun; Lee, Jaehak; Choi, Jiyoung; Cho, Seungryong

2015-08-01

Accurate and efficient scatter correction is essential for acquisition of high-quality x-ray cone-beam CT (CBCT) images for various applications. This study was conducted to demonstrate the feasibility of using the data consistency condition (DCC) as a criterion for scatter kernel optimization in scatter deconvolution methods in CBCT. As in CBCT, data consistency in the mid-plane is primarily challenged by scatter, we utilized data consistency to confirm the degree of scatter correction and to steer the update in iterative kernel optimization. By means of the parallel-beam DCC via fan-parallel rebinning, we iteratively optimized the scatter kernel parameters, using a particle swarm optimization algorithm for its computational efficiency and excellent convergence. The proposed method was validated by a simulation study using the XCAT numerical phantom and also by experimental studies using the ACS head phantom and the pelvic part of the Rando phantom. The results showed that the proposed method can effectively improve the accuracy of deconvolution-based scatter correction. Quantitative assessments of image quality parameters such as contrast and structure similarity (SSIM) revealed that the optimally selected scatter kernel improves the contrast of scatter-free images by up to 99.5%, 94.4%, and 84.4%, and of the SSIM in an XCAT study, an ACS head phantom study, and a pelvis phantom study by up to 96.7%, 90.5%, and 87.8%, respectively. The proposed method can achieve accurate and efficient scatter correction from a single cone-beam scan without need of any auxiliary hardware or additional experimentation.

Scatter in Cargo Radiography

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

Miller, Erin A.; Caggiano, Joseph A.; Runkle, Robert C.

As a complement to passive detection systems, radiographic inspection of cargo is an increasingly important tool for homeland security because it has the potential to detect highly attenuating objects associated with special nuclear material or surrounding shielding. Detecting such objects relies on high image contrast between regions of different density and atomic number (Z). Threat detection is affected by scatter of the interrogating beam, both in the cargo and surrounding objects, which degrades image contrast. Here, we work to determine the extent to which scatter plays a role in radiographic imaging of cargo containers.

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

Enhancements to the Low-Energy Ion Facility at SUNY Geneseo

NASA Astrophysics Data System (ADS)

Barfield, Zachariah; Kostick, Steven; Nagasing, Ethan; Fletcher, Kurt; Padalino, Stephen

2017-10-01

The Low Energy Ion Facility at SUNY Geneseo is used for detector development and characterization for inertial confinement fusion diagnostics. The system has been upgraded to improve the ion beam quality by reducing contaminant ions. In the new configuration, ions produced by the Peabody Scientific duoplasmatron ion source are accelerated through a potential, focused into a new NEC analyzing magnet and directed to an angle of 30°. A new einzel lens on the output of the magnet chamber focuses the beam into a scattering chamber with a water-cooled target mount and rotatable detector mount plates. The analyzing magnet has been calibrated for deuteron, 4He+, and 4He2+ ion beams at a range of energies, and no significant hysteresis has been observed. The system can accelerate deuterons to energies up to 25 keV to initiate d-d fusion using a deuterated polymer target. Charged particle spectra with protons, tritons, and 3He ions from d-d fusion have been measured at scattering angles ranging from 55° to 135°. A time-of-flight beamline has been designed to measure the energies of ions elastically scattered at 135°. CEM detectors initiate start and stop signals from secondary electrons produced when low energy ions pass through very thin carbon foils. Funded in part by the U.S. Department of Energy through the Laboratory for Laser Energetics.

Forward scattering in two-beam laser interferometry

NASA Astrophysics Data System (ADS)

Mana, G.; Massa, E.; Sasso, C. P.

2018-04-01

A fractional error as large as 25 pm mm-1 at the zero optical-path difference has been observed in an optical interferometer measuring the displacement of an x-ray interferometer used to determine the lattice parameter of silicon. Detailed investigations have brought to light that the error was caused by light forward-scattered from the beam feeding the interferometer. This paper reports on the impact of forward-scattered light on the accuracy of two-beam optical interferometry applied to length metrology, and supplies a model capable of explaining the observed error.

Instrument for underwater high-angular resolution volume scattering function measurements

NASA Astrophysics Data System (ADS)

Dueweke, Paul W.; Bolstad, Jay; Leonard, Donald A.; Sweeney, Harold E.; Boyer, Philip A.; Winkler, Erik M.

1997-02-01

A prototype instrument for in situ measurements of the volume scattering function (VSF) and the beam attenuation of water has been built and tested in the EOO laboratory. The intended application of the instrument is the enhancement of Navy operational optical systems for finding and imaging underwater objects such as mines. A description of the apparatus that was built and preliminary laboratory data will be presented. The instrument measures the VSF, (beta) ((theta) ), near the optical axis in both the forward and back directions from approximately 0.2 degrees off axis to approximately 5 degrees in 0.1 degree steps and at side angles of 45 degrees, 90 degrees, and 135 degrees. A diode- pumped, frequency-doubled, Nd:YAG laser provides the 532 nm light. This is the most used wavelength for underwater optical systems. The forward and back scattered light is collected and focused to a plane where scattering angles in the water are mapped onto concentric rings. At this focal plane, a conical reflector compresses the annular optical data onto a line along the cone axis where it is read by a MOS linear image array providing over 500 separate angular measurements. The beam attenuation coefficient, c, is also measured by means of a unique dual path configuration.

The influence of current neutralization and multiple Coulomb scattering on the spatial dynamics of resistive sausage instability of a relativistic electron beam propagating in ohmic plasma

NASA Astrophysics Data System (ADS)

Kolesnikov, E. K.; Manuilov, A. S.; Petrov, V. S.; Klyushnikov, G. N.; Chernov, S. V.

2017-06-01

The influence of the current neutralization process, the phase mixing of the trajectories of electrons and multiple Coulomb scattering of electrons beam on the atoms of the background medium on the spatial increment of the growth of sausage instability of a relativistic electron beam propagating in ohmic plasma channel has been considered. It has been shown that the amplification of the current neutralization leads to a significant increase in this instability, and phase mixing and the process of multiple scattering of electrons beam on the atoms of the background medium are the stabilizing factor.

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

Yokosawa, A.

Structures appearing in various experimental data (particularly those with polarized beams) in nucleon-nucleon systems are reviewed. A number of candidates are presented for dibaryon resonances which can couple to nucleon-nucleon systems. The present status of experimental data in the nucleon-nucleon system is discussed. Details of N-N scattering are written elsewhere, and here relatively new aspects are presented.

Physical-geometric optics method for large size faceted particles.

PubMed

Sun, Bingqiang; Yang, Ping; Kattawar, George W; Zhang, Xiaodong

2017-10-02

A new physical-geometric optics method is developed to compute the single-scattering properties of faceted particles. It incorporates a general absorption vector to accurately account for inhomogeneous wave effects, and subsequently yields the relevant analytical formulas effective and computationally efficient for absorptive scattering particles. A bundle of rays incident on a certain facet can be traced as a single beam. For a beam incident on multiple facets, a systematic beam-splitting technique based on computer graphics is used to split the original beam into several sub-beams so that each sub-beam is incident only on an individual facet. The new beam-splitting technique significantly reduces the computational burden. The present physical-geometric optics method can be generalized to arbitrary faceted particles with either convex or concave shapes and with a homogeneous or an inhomogeneous (e.g., a particle with a core) composition. The single-scattering properties of irregular convex homogeneous and inhomogeneous hexahedra are simulated and compared to their counterparts from two other methods including a numerically rigorous method.

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.

Airborne Polarized Lidar Detection of Scattering Layers in the Ocean

NASA Astrophysics Data System (ADS)

Vasilkov, Alexander P.; Goldin, Yury A.; Gureev, Boris A.; Hoge, Frank E.; Swift, Robert N.; Wright, C. Wayne

2001-08-01

A polarized lidar technique based on measurements of waveforms of the two orthogonal-polarized components of the backscattered light pulse is proposed to retrieve vertical profiles of the seawater scattering coefficient. The physical rationale for the polarized technique is that depolarization of backscattered light originating from a linearly polarized laser beam is caused largely by multiple small-angle scattering from particulate matter in seawater. The magnitude of the small-angle scattering is determined by the scattering coefficient. Therefore information on the vertical distribution of the scattering coefficient can be derived potentially from measurements of the timedepth dependence of depolarization in the backscattered laser pulse. The polarized technique was verified by field measurements conducted in the Middle Atlantic Bight of the western North Atlantic Ocean that were supported by in situ measurements of the beam attenuation coefficient. The airborne polarized lidar measured the timedepth dependence of the backscattered laser pulse in two orthogonal-polarized components. Vertical profiles of the scattering coefficient retrieved from the timedepth depolarization of the backscattered laser pulse were compared with measured profiles of the beam attenuation coefficient. The comparison showed that retrieved profiles of the scattering coefficient clearly reproduce the main features of the measured profiles of the beam attenuation coefficient. Underwater scattering layers were detected at depths of 2025 m in turbid coastal waters. The improvement in dynamic range afforded by the polarized lidar technique offers a strong potential benefit for airborne lidar bathymetric applications.

Edge Thomson scattering diagnostic on COMPASS tokamak: Installation, calibration, operation, improvements

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

Bohm, P., E-mail: bohm@ipp.cas.cz; Bilkova, P.; Melich, R.

2014-11-15

The core Thomson scattering diagnostic (TS) on the COMPASS tokamak was put in operation and reported earlier. Implementation of edge TS, with spatial resolution along the laser beam up to ∼1/100 of the tokamak minor radius, is presented now. The procedure for spatial calibration and alignment of both core and edge systems is described. Several further upgrades of the TS system, like a triggering unit and piezo motor driven vacuum window shutter, are introduced as well. The edge TS system, together with the core TS, is now in routine operation and provides electron temperature and density profiles.

WE-F-16A-03: 3D Printer Application in Proton Therapy: A Novel Method to Deliver Passive-Scattering Proton Beams with a Fixed Range and Modulation for SRS and SRT

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

Ding, X; Witztum, A; Liang, X

2014-06-15

Purpose: To present a novel technique to deliver passive-scattering proton beam with fixed range and modulation using a 3D printed patient-specific bolus for proton stereotactic radiosurgery and radiotherapy. Methods: A CIRS head phantom was used to simulate a patient with a small brain lesion. A custom bolus was created in the Eclipse Treatment Planning System (TPS) to compensate for the different water equivalent depths from the patient surface to the target from multiple beam directions. To simulate arc therapy, a plan was created on the initial CT using three passive-scattering proton beams with a fixed range and modulations irradiating frommore » different angles. The DICOM-RT structure file of the bolus was exported from the TPS and converted to STL format for 3D printing. The phantom was rescanned with the printed custom bolus and head cup to verify the dose distribution comparing to the initial plan. EBT3 films were placed in the sagital plane of the target to verify the delivered dose distribution. The relative stopping power of the printing material(ABSplus-P430) was measured using the Zebra multi-plate ion chamber. Results: The relative stopping power of the 3D printing material, ABSplus-P430 was 1.05 which is almost water equivalent. The dose difference between verification CT and Initial CT is almost negligible. Film measurement also confirmed the accuracy for this new proton delivery technique. Conclusion: Our method using 3D printed range modifiers simplify the treatment delivery of multiple passive-scattering beams in treatment of small lesion in brain. This technique makes delivery of multiple beam more efficient and can be extended to allow arc therapy with proton beams. The ability to create and construct complex patient specific bolus structures provides a new dimension in creating optimized quality treatment plans not only for proton therapy but also for electron and photon therapy.« less

Optical Sensors Using Stimulated Brillouin Scattering

NASA Technical Reports Server (NTRS)

Christensen, Caleb A (Inventor); Zavriyev, Anton (Inventor)

2017-01-01

A method for enhancing a sensitivity of an optical sensor having an optical cavity counter-propagates beams of pump light within the optical cavity to produce scattered light based on Stimulated Brillouin Scattering (SBS). The properties of the pump light are selected to generate fast-light conditions for the scattered light, such that the scattered light includes counter-propagating beams of fast light. The method prevents the pump light from resonating within the optical cavity, while allowing the scattered light to resonate within the optical cavity. At least portions of the scattered light are interfered outside of the optical cavity to produce a beat note for a measurement of the optical sensor. The disclosed method is particularly applicable to optical gyroscopes.

Neutron beam flux monitors in coaxial and planar geometry for neutron scattering instruments at Dhruva reactor

NASA Astrophysics Data System (ADS)

Desai, Shraddha S.; Devan, Shylaja; Das, Amrita; Patkar, S. M.; Rao, Mala N.

2018-04-01

Neutron scattering instruments at Dhruva reactor are equipped with in house developed neutron beam flux monitors. Measurements of variations in intensity are essential to normalize the scattered neutron spectra against the reactor power fluctuations, energy of monochromatic beam, and various other factors. Two different beam monitor geometries are considered as per the beam size and optics. These detectors are fabricated with tailor-made designs to suit individual beam size and neutron flux. Pencil size beam monitors for integral intensity measurement are fabricated with coaxial geometry and BF3 fill gas for high n-gamma discrimination and count rate capability. Brass cathode design is modified to SS based rugged design, considering beam transmission. Coaxial beam monitor partially intercepts the collimated beam and gives relative magnitude of the flux with time. For certain experiments, size of beam varies due to use of focusing monochromator. Thus a beam monitor with square sensitive region covering entire beam is essential. Multiwire based planar detector for use in transmission mode is designed. Negligible absorption of neutron beam intensity within the detector hardware is ensured. Design of detectors is tailor made for beam geometry. Both these types of beam monitors are fabricated and characterized at G2 beam line and Triple Axis Spectrometer at Dhruva reactor. Performance of detector is suitable for the beam monitoring up to neutron flux ˜ 106 n/cm2/sec. Design aspects and performance details of these beam monitors are mentioned in the paper.

Applications of an Energy Transfer Model to Three Problems in Planetary Regoliths: The Solid-State Greenhouse, Thermal Beaming, and Emittance Spectra

NASA Technical Reports Server (NTRS)

Hapke, Bruce

1996-01-01

Several problems of interest in planetary infrared remote sensing are investigated using a new radiative-conductive model of energy transfer in regoliths: the solid-state greenhouse effect, thermal beaming, and reststrahlen spectra. The results of the analysis are as follows: (1) The solid-state greenhouse effect is self-limiting to a rise of a few tens of degrees in bodies of the outer solar system. (2) Non-Lambertian directional emissivity can account for only about 20% of the observed thermal beaming factor. The remainder must have another cause, presumably surface roughness effects. (3) The maximum in a reststrahlen emissivity spectrum does not occur exactly at the Christiansen wavelength where, by definition, the real part of the refractive index equals one, but rather at the first transition minimum in reflectance associated with the transition from particle scattering being dominated by volume scattering to that dominated by strong surface scattering. The transparency feature is at the second transition minimum and does not require the presence of a second band at longer wavelength for its occurance. Subsurface temperature gradients have only a small effect on emissivity bands.

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.

Spot Scanning and Passive Scattering Proton Therapy: Relative Biological Effectiveness and Oxygen Enhancement Ratio in Cultured Cells.

PubMed

Iwata, Hiromitsu; Ogino, Hiroyuki; Hashimoto, Shingo; Yamada, Maho; Shibata, Hiroki; Yasui, Keisuke; Toshito, Toshiyuki; Omachi, Chihiro; Tatekawa, Kotoha; Manabe, Yoshihiko; Mizoe, Jun-etsu; Shibamoto, Yuta

2016-05-01

To determine the relative biological effectiveness (RBE), oxygen enhancement ratio (OER), and contribution of the indirect effect of spot scanning proton beams, passive scattering proton beams, or both in cultured cells in comparison with clinically used photons. The RBE of passive scattering proton beams at the center of the spread-out Bragg peak (SOBP) was determined from dose-survival curves in 4 cell lines using 6-MV X rays as controls. Survival of 2 cell lines after spot scanning and passive scattering proton irradiation was then compared. Biological effects at the distal end region of the SOBP were also investigated. The OER of passive scattering proton beams and 6 MX X rays were investigated in 2 cell lines. The RBE and OER values were estimated at a 10% cell survival level. The maximum degree of protection of radiation effects by dimethyl sulfoxide was determined to estimate the contribution of the indirect effect against DNA damage. All experiments comparing protons and X rays were made under the same biological conditions. The RBE values of passive scattering proton beams in the 4 cell lines examined were 1.01 to 1.22 (average, 1.14) and were almost identical to those of spot scanning beams. Biological effects increased at the distal end of the SOBP. In the 2 cell lines examined, the OER was 2.74 (95% confidence interval, 2.56-2.80) and 3.08 (2.84-3.11), respectively, for X rays, and 2.39 (2.38-2.43) and 2.72 (2.69-2.75), respectively, for protons (P<.05 for both cells between X rays and protons). The maximum degree of protection was significantly higher for X rays than for proton beams (P<.05). The RBE values of spot scanning and passive scattering proton beams were almost identical. The OER was lower for protons than for X rays. The lower contribution of the indirect effect may partly account for the lower OER of protons. Copyright © 2016 Elsevier Inc. All rights reserved.

IBS simulation with different RF configurations in RHIC

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

Liu, C.; Fedotov, A.; Minty, M.

It is a crucial task to understand the beam emittance growth during RHIC cycle and the underlying causes. One would benefit not just for the current operation of RHIC, also for the design of eRHIC. This report focuses on the Intra-Beam Scattering (IBS) contribution to the emittance growth of the proton beam with two different configurations of RF system. The answers to these questions will be given in the end of the report; can IBS explain the emittance growth all alone? What’s the difference of IBS growth rates for different RF configurations?

Differential pencil beam dose computation model for photons.

PubMed

Mohan, R; Chui, C; Lidofsky, L

1986-01-01

Differential pencil beam (DPB) is defined as the dose distribution relative to the position of the first collision, per unit collision density, for a monoenergetic pencil beam of photons in an infinite homogeneous medium of unit density. We have generated DPB dose distribution tables for a number of photon energies in water using the Monte Carlo method. The three-dimensional (3D) nature of the transport of photons and electrons is automatically incorporated in DPB dose distributions. Dose is computed by evaluating 3D integrals of DPB dose. The DPB dose computation model has been applied to calculate dose distributions for 60Co and accelerator beams. Calculations for the latter are performed using energy spectra generated with the Monte Carlo program. To predict dose distributions near the beam boundaries defined by the collimation system as well as blocks, we utilize the angular distribution of incident photons. Inhomogeneities are taken into account by attenuating the primary photon fluence exponentially utilizing the average total linear attenuation coefficient of intervening tissue, by multiplying photon fluence by the linear attenuation coefficient to yield the number of collisions in the scattering volume, and by scaling the path between the scattering volume element and the computation point by an effective density.

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

Iwata, Hiromitsu, E-mail: h-iwa-ncu@nifty.com; Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya; Ogino, Hiroyuki

Purpose: To determine the relative biological effectiveness (RBE), oxygen enhancement ratio (OER), and contribution of the indirect effect of spot scanning proton beams, passive scattering proton beams, or both in cultured cells in comparison with clinically used photons. Methods and Materials: The RBE of passive scattering proton beams at the center of the spread-out Bragg peak (SOBP) was determined from dose-survival curves in 4 cell lines using 6-MV X rays as controls. Survival of 2 cell lines after spot scanning and passive scattering proton irradiation was then compared. Biological effects at the distal end region of the SOBP were also investigated. Themore » OER of passive scattering proton beams and 6 MX X rays were investigated in 2 cell lines. The RBE and OER values were estimated at a 10% cell survival level. The maximum degree of protection of radiation effects by dimethyl sulfoxide was determined to estimate the contribution of the indirect effect against DNA damage. All experiments comparing protons and X rays were made under the same biological conditions. Results: The RBE values of passive scattering proton beams in the 4 cell lines examined were 1.01 to 1.22 (average, 1.14) and were almost identical to those of spot scanning beams. Biological effects increased at the distal end of the SOBP. In the 2 cell lines examined, the OER was 2.74 (95% confidence interval, 2.56-2.80) and 3.08 (2.84-3.11), respectively, for X rays, and 2.39 (2.38-2.43) and 2.72 (2.69-2.75), respectively, for protons (P<.05 for both cells between X rays and protons). The maximum degree of protection was significantly higher for X rays than for proton beams (P<.05). Conclusions: The RBE values of spot scanning and passive scattering proton beams were almost identical. The OER was lower for protons than for X rays. The lower contribution of the indirect effect may partly account for the lower OER of protons.« less

Lateral scattered light used to study laser light propagation in turbid media phantoms

NASA Astrophysics Data System (ADS)

Valdes, Claudia; Solarte, Efrain

2010-02-01

Laser light propagation in soft tissues is important because of the growing biomedical applications of lasers and the need to optically characterize the biological media. Following previous developments of the group, we have developed low cost models, Phantoms, of soft tissue. The process was developed in a clean room to avoid the medium contamination. Each model was characterized by measuring the refractive index, and spectral reflectance and transmittance. To study the laser light propagation, each model was illuminated with a clean beam of laser light, using sources such as He-Ne (632nm) and DPSSL (473 nm). Laterally scattered light was imaged and these images were digitally processed. We analyzed the intensity distribution of the scattered radiation in order to obtain details of the beam evolution in the medium. Line profiles taken from the intensity distribution surface allow measuring the beam spread, and to find expressions for the longitudinal (along the beam incident direction) and transversal (across the beam incident direction) intensities distributions. From these behaviors, the radiation penetration depth and the total coefficient of extinction have been determined. The multiple scattering effects were remarkable, especially for the low wavelength laser beam.

Understanding and eliminating artifact signals from diffusely scattered pump beam in measurements of rough samples by time-domain thermoreflectance (TDTR).

PubMed

Sun, Bo; Koh, Yee Kan

2016-06-01

Time-domain thermoreflectance (TDTR) is a pump-probe technique frequently applied to measure the thermal transport properties of bulk materials, nanostructures, and interfaces. One of the limitations of TDTR is that it can only be employed to samples with a fairly smooth surface. For rough samples, artifact signals are collected when the pump beam in TDTR measurements is diffusely scattered by the rough surface into the photodetector, rendering the TDTR measurements invalid. In this paper, we systemically studied the factors affecting the artifact signals due to the pump beam leaked into the photodetector and thus established the origin of the artifact signals. We find that signals from the leaked pump beam are modulated by the probe beam due to the phase rotation induced in the photodetector by the illumination of the probe beam. As a result of the modulation, artifact signals due to the leaked pump beam are registered in TDTR measurements as the out-of-phase signals. We then developed a simple approach to eliminate the artifact signals due to the leaked pump beam. We verify our leak-pump correction approach by measuring the thermal conductivity of a rough InN sample, when the signals from the leaked pump beam are significant. We also discuss the advantages of our new method over the two-tint approach and its limitations. Our new approach enables measurements of the thermal conductivity of rough samples using TDTR.

Understanding and eliminating artifact signals from diffusely scattered pump beam in measurements of rough samples by time-domain thermoreflectance (TDTR)

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

Sun, Bo; Koh, Yee Kan, E-mail: mpekyk@nus.edu.sg; Centre of Advanced 2D Materials, National University of Singapore, Singapore 117542

Time-domain thermoreflectance (TDTR) is a pump-probe technique frequently applied to measure the thermal transport properties of bulk materials, nanostructures, and interfaces. One of the limitations of TDTR is that it can only be employed to samples with a fairly smooth surface. For rough samples, artifact signals are collected when the pump beam in TDTR measurements is diffusely scattered by the rough surface into the photodetector, rendering the TDTR measurements invalid. In this paper, we systemically studied the factors affecting the artifact signals due to the pump beam leaked into the photodetector and thus established the origin of the artifact signals.more » We find that signals from the leaked pump beam are modulated by the probe beam due to the phase rotation induced in the photodetector by the illumination of the probe beam. As a result of the modulation, artifact signals due to the leaked pump beam are registered in TDTR measurements as the out-of-phase signals. We then developed a simple approach to eliminate the artifact signals due to the leaked pump beam. We verify our leak-pump correction approach by measuring the thermal conductivity of a rough InN sample, when the signals from the leaked pump beam are significant. We also discuss the advantages of our new method over the two-tint approach and its limitations. Our new approach enables measurements of the thermal conductivity of rough samples using TDTR.« less

Brookhaven highlights, October 1978-September 1979. [October 1978 to September 1979

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

Not Available

1979-01-01

These highlights present an overview of the major research and development achievements at Brookhaven National Laboratory from October 1978 to September 1979. Specific areas covered include: accelerator and high energy physics programs; high energy physics research; the AGS and improvements to the AGS; neutral beam development; heavy ion fusion; superconducting power cables; ISABELLE storage rings; the BNL Tandem accelerator; heavy ion experiments at the Tandem; the High Flux Beam Reactor; medium energy physics; nuclear theory; atomic and applied physics; solid state physics; neutron scattering studies; x-ray scattering studies; solid state theory; defects and disorder in solids; surface physics; the Nationalmore » Synchrotron Light Source ; Chemistry Department; Biology Department; Medical Department; energy sciences; environmental sciences; energy technology programs; National Center for Analysis of Energy Systems; advanced reactor systems; nuclear safety; National Nuclear Data Center; nuclear materials safeguards; Applied Mathematics Department; and support activities. (GHT)« less

Radar - ARL Wind Profilerwith RASS, Boardman - Raw Data

DOE Data Explorer

Gottas, Daniel

2017-10-23

**Winds** A radar wind profiler measures the Doppler shift of electromagnetic energy scattered back from atmospheric turbulence and hydrometeors along 3-5 vertical and off-vertical point beam directions. Back-scattered signal strength and radial-component velocities are remotely sensed along all beam directions and combined to derive the horizontal wind field over the radar. These data typically are sampled and averaged hourly and usually have 6-m and/or 100-m vertical resolutions up to 4 km for the 915 MHz and 8 km for the 449 MHz systems. **Temperature** To measure atmospheric temperature, a radio acoustic sound system (RASS) is used in conjunction with the wind profile. These data typically are sampled and averaged for five minutes each hour and have a 60-m vertical resolution up to 1.5 km for the 915 MHz and 60-m up to 3.5k m for the 449 MHz.

Radar - ANL Wind Profiler with RASS, Yakima - Raw Data

DOE Data Explorer

Gottas, Daniel

2017-10-23

**Winds** A radar wind profiler measures the Doppler shift of electromagnetic energy scattered back from atmospheric turbulence and hydrometeors along 3-5 vertical and off-vertical point beam directions. Back-scattered signal strength and radial-component velocities are remotely sensed along all beam directions and combined to derive the horizontal wind field over the radar. These data typically are sampled and averaged hourly and usually have 6-m and/or 100-m vertical resolutions up to 4 km for the 915 MHz and 8 km for the 449 MHz systems. **Temperature** To measure atmospheric temperature, a radio acoustic sound system (RASS) is used in conjunction with the wind profile. These data typically are sampled and averaged for five minutes each hour and have a 60-m vertical resolution up to 1.5 km for the 915 MHz and 60-m up to 3.5k m for the 449 MHz.

Radar - ESRL Wind Profiler with RASS, Condon - Raw Data

DOE Data Explorer

Gottas, Daniel

2017-10-23

**Winds** A radar wind profiler measures the Doppler shift of electromagnetic energy scattered back from atmospheric turbulence and hydrometeors along 3-5 vertical and off-vertical point beam directions. Back-scattered signal strength and radial-component velocities are remotely sensed along all beam directions and combined to derive the horizontal wind field over the radar. These data typically are sampled and averaged hourly and usually have 6-m and/or 100-m vertical resolutions up to 4 km for the 915 MHz and 8 km for the 449 MHz systems. **Temperature** To measure atmospheric temperature, a radio acoustic sound system (RASS) is used in conjunction with the wind profile. These data typically are sampled and averaged for five minutes each hour and have a 60-m vertical resolution up to 1.5 km for the 915 MHz and 60-m up to 3.5k m for the 449 MHz.

Radar - ANL Wind Profiler with RASS, Walla Walla - Raw Data

DOE Data Explorer

Gottas, Daniel

2017-10-23

**Winds** A radar wind profiler measures the Doppler shift of electromagnetic energy scattered back from atmospheric turbulence and hydrometeors along 3-5 vertical and off-vertical point beam directions. Back-scattered signal strength and radial-component velocities are remotely sensed along all beam directions and combined to derive the horizontal wind field over the radar. These data typically are sampled and averaged hourly and usually have 6-m and/or 100-m vertical resolutions up to 4 km for the 915 MHz and 8 km for the 449 MHz systems. **Temperature** To measure atmospheric temperature, a radio acoustic sound system (RASS) is used in conjunction with the wind profile. These data typically are sampled and averaged for five minutes each hour and have a 60-m vertical resolution up to 1.5 km for the 915 MHz and 60-m up to 3.5k m for the 449 MHz.

Radar - ESRL Wind Profiler with RASS, Prineville - Raw Data

DOE Data Explorer

Gottas, Daniel

2017-10-23

**Winds** A radar wind profiler measures the Doppler shift of electromagnetic energy scattered back from atmospheric turbulence and hydrometeors along 3-5 vertical and off-vertical point beam directions. Back-scattered signal strength and radial-component velocities are remotely sensed along all beam directions and combined to derive the horizontal wind field over the radar. These data typically are sampled and averaged hourly and usually have 6-m and/or 100-m vertical resolutions up to 4 km for the 915 MHz and 8 km for the 449 MHz systems. **Temperature** To measure atmospheric temperature, a radio acoustic sound system (RASS) is used in conjunction with the wind profile. These data typically are sampled and averaged for five minutes each hour and have a 60-m vertical resolution up to 1.5 km for the 915 MHz and 60-m up to 3.5k m for the 449 MHz.

Radar - ESRL Wind Profiler with RASS, Troutdale - Raw Data

DOE Data Explorer

Gottas, Daniel

2017-10-23

**Winds** A radar wind profiler measures the Doppler shift of electromagnetic energy scattered back from atmospheric turbulence and hydrometeors along 3-5 vertical and off-vertical point beam directions. Back-scattered signal strength and radial-component velocities are remotely sensed along all beam directions and combined to derive the horizontal wind field over the radar. These data typically are sampled and averaged hourly and usually have 6-m and/or 100-m vertical resolutions up to 4 km for the 915 MHz and 8 km for the 449 MHz systems. **Temperature** To measure atmospheric temperature, a radio acoustic sound system (RASS) is used in conjunction with the wind profile. These data typically are sampled and averaged for five minutes each hour and have a 60-m vertical resolution up to 1.5 km for the 915 MHz and 60-m up to 3.5k m for the 449 MHz.

Radar - ANL Wind Profiler with RASS, Goldendale - Raw Data

DOE Data Explorer

Gottas, Daniel

2017-10-23

**Winds** A radar wind profiler measures the Doppler shift of electromagnetic energy scattered back from atmospheric turbulence and hydrometeors along 3-5 vertical and off-vertical point beam directions. Back-scattered signal strength and radial-component velocities are remotely sensed along all beam directions and combined to derive the horizontal wind field over the radar. These data typically are sampled and averaged hourly and usually have 6-m and/or 100-m vertical resolutions up to 4 km for the 915 MHz and 8 km for the 449 MHz systems. **Temperature** To measure atmospheric temperature, a radio acoustic sound system (RASS) is used in conjunction with the wind profile. These data typically are sampled and averaged for five minutes each hour and have a 60-m vertical resolution up to 1.5 km for the 915 MHz and 60-m up to 3.5k m for the 449 MHz.

Radar - ESRL Wind Profiler with RASS, Wasco Airport - Raw Data

DOE Data Explorer

Gottas, Daniel

2017-10-23

**Winds** A radar wind profiler measures the Doppler shift of electromagnetic energy scattered back from atmospheric turbulence and hydrometeors along 3-5 vertical and off-vertical point beam directions. Back-scattered signal strength and radial-component velocities are remotely sensed along all beam directions and combined to derive the horizontal wind field over the radar. These data typically are sampled and averaged hourly and usually have 6-m and/or 100-m vertical resolutions up to 4 km for the 915 MHz and 8 km for the 449 MHz systems. **Temperature** To measure atmospheric temperature, a radio acoustic sound system (RASS) is used in conjunction with the wind profile. These data typically are sampled and averaged for five minutes each hour and have a 60-m vertical resolution up to 1.5 km for the 915 MHz and 60-m up to 3.5k m for the 449 MHz.

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

PubMed

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

2013-08-01

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

Dose and scatter characteristics of a novel cone beam CT system for musculoskeletal extremities

NASA Astrophysics Data System (ADS)

Zbijewski, W.; Sisniega, A.; Vaquero, J. J.; Muhit, A.; Packard, N.; Senn, R.; Yang, D.; Yorkston, J.; Carrino, J. A.; Siewerdsen, J. H.

2012-03-01

A novel cone-beam CT (CBCT) system has been developed with promising capabilities for musculoskeletal imaging (e.g., weight-bearing extremities and combined radiographic / volumetric imaging). The prototype system demonstrates diagnostic-quality imaging performance, while the compact geometry and short scan orbit raise new considerations for scatter management and dose characterization that challenge conventional methods. The compact geometry leads to elevated, heterogeneous x-ray scatter distributions - even for small anatomical sites (e.g., knee or wrist), and the short scan orbit results in a non-uniform dose distribution. These complex dose and scatter distributions were investigated via experimental measurements and GPU-accelerated Monte Carlo (MC) simulation. The combination provided a powerful basis for characterizing dose distributions in patient-specific anatomy, investigating the benefits of an antiscatter grid, and examining distinct contributions of coherent and incoherent scatter in artifact correction. Measurements with a 16 cm CTDI phantom show that the dose from the short-scan orbit (0.09 mGy/mAs at isocenter) varies from 0.16 to 0.05 mGy/mAs at various locations on the periphery (all obtained at 80 kVp). MC estimation agreed with dose measurements within 10-15%. Dose distribution in patient-specific anatomy was computed with MC, confirming such heterogeneity and highlighting the elevated energy deposition in bone (factor of ~5-10) compared to soft-tissue. Scatter-to-primary ratio (SPR) up to ~1.5-2 was evident in some regions of the knee. A 10:1 antiscatter grid was found earlier to result in significant improvement in soft-tissue imaging performance without increase in dose. The results of MC simulations elucidated the mechanism behind scatter reduction in the presence of a grid. A ~3-fold reduction in average SPR was found in the MC simulations; however, a linear grid was found to impart additional heterogeneity in the scatter distribution, mainly due to the increase in the contribution of coherent scatter with increased spatial variation. Scatter correction using MC-generated scatter distributions demonstrated significant improvement in cupping and streaks. Physical experimentation combined with GPU-accelerated MC simulation provided a sophisticated, yet practical approach in identifying low-dose acquisition techniques, optimizing scatter correction methods, and evaluating patientspecific dose.

Progress on the Development of the Next Generation X-ray Beam Position Monitors at the Advanced Photon Source

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

Lee, S.H.; Yang, B.X.; Decker, G.

Accurate and stable x-ray beam position monitors (XBPMs) are ke y elements in obtaining the desired user beam stability in the Advanced Photon Source (APS). The next generat ion XBPMs for high heat load front ends (HHL FEs) have been designed to meet these requirements by utilizing Cu K-edge x-ray fluorescence (XRF) from a pair of copper absorbers and have been installed at the front ends (FEs) of the APS. Com missioning data showed a significant performance improvement over the existing photoemission-based XBPMs. While a similar design concept can be applied for the canted undulator front ends, where two undulatormore » beams are separated by 1.0-mrad, the lower beam power (< 10 kW) per undulator allows us to explore lower-cost solutions based on Compton scat tering from the diamond blades placed edge-on to the x- ray beam. A prototype of the Compton scattering XBPM system was i nstalled at 24-ID-A in May 2015. In this report, the design and test results for XRF-based XBPM and Compton scattering based XBPM are presented. Ongoing research related to the development of the next generation XBPMs on thermal contac t resistance of a joint between two solid bodies is also discussed« less

Assessment of beryllium and molybdenum nuclear data files with the RPI neutron scattering system in the energy region from 0.5 to 20 MeV

NASA Astrophysics Data System (ADS)

Daskalakis, Adam; Blain, Ezekiel; Leinweber, Gregory; Rapp, Michael; Barry, Devin; Block, Robert; Danon, Yaron

2017-09-01

A series of neutron scattering benchmark measurements were performed on beryllium and molybdenum with the Rensselaer Polytechnic Institute's Neutron Scattering System. The pulsed neutron source was produced by the Rensselaer Polytechnic Institute's Linear Accelerator and a well collimated neutron beam was incident onto the samples located at a distance of 30.07 m. Neutrons that scattered from the sample were measured using the time-of-flight by eight EJ-301 liquid scintillator detectors positioned 0.5 m from the sample of interest. A total of eight experiments were performed with two sample thicknesses each, measured by detectors placed at two sets of angles. All data were processed using pulse shape analysis that separated the neutron and gamma ray events and included a gamma misclassification correction to account for erroneously identified gamma rays. A detailed model of the neutron scattering system simulated each experiment with several current evaluated nuclear data libraries and their predecessors. Results for each evaluation were compared to the experimental data using a figure-of-merit. The neutron scattering system has been used as a means to quantify a library's performance.

Single-Pulse Multi-Point Multi-Component Interferometric Rayleigh Scattering Velocimeter

NASA Technical Reports Server (NTRS)

Bivolaru, Daniel; Danehy, Paul M.; Lee, Joseph W.; Gaffney, Richard L., Jr.; Cutler, Andrew D.

2006-01-01

A simultaneous multi-point, multi-component velocimeter using interferometric detection of the Doppler shift of Rayleigh, Mie, and Rayleigh-Brillouin scattered light in supersonic flow is described. The system uses up to three sets of collection optics and one beam combiner for the reference laser light to form a single collimated beam. The planar Fabry-Perot interferometer used in the imaging mode for frequency detection preserves the spatial distribution of the signal reasonably well. Single-pulse multi-points measurements of up to two orthogonal and one non-orthogonal components of velocity in a Mach 2 free jet were performed to demonstrate the technique. The average velocity measurements show a close agreement with the CFD calculations using the VULCAN code.

Precision Møller Polarimetry

NASA Astrophysics Data System (ADS)

Henry, William; Jefferson Lab Hall A Collaboration

2017-09-01

Jefferson Lab's cutting-edge parity-violating electron scattering program has increasingly stringent requirements for systematic errors. Beam polarimetry is often one of the dominant systematic errors in these experiments. A new Møller Polarimeter in Hall A of Jefferson Lab (JLab) was installed in 2015 and has taken first measurements for a polarized scattering experiment. Upcoming parity violation experiments in Hall A include CREX, PREX-II, MOLLER and SOLID with the latter two requiring <0.5% precision on beam polarization measurements. The polarimeter measures the Møller scattering rates of the polarized electron beam incident upon an iron target placed in a saturating magnetic field. The spectrometer consists of four focusing quadrapoles and one momentum selection dipole. The detector is designed to measure the scattered and knock out target electrons in coincidence. Beam polarization is extracted by constructing an asymmetry from the scattering rates when the incident electron spin is parallel and anti-parallel to the target electron spin. Initial data will be presented. Sources of systematic errors include target magnetization, spectrometer acceptance, the Levchuk effect, and radiative corrections which will be discussed. National Science Foundation.

SERODS optical data storage with parallel signal transfer

DOEpatents

Vo-Dinh, Tuan

2003-09-02

Surface-enhanced Raman optical data storage (SERODS) systems having increased reading and writing speeds, that is, increased data transfer rates, are disclosed. In the various SERODS read and write systems, the surface-enhanced Raman scattering (SERS) data is written and read using a two-dimensional process called parallel signal transfer (PST). The various embodiments utilize laser light beam excitation of the SERODS medium, optical filtering, beam imaging, and two-dimensional light detection. Two- and three-dimensional SERODS media are utilized. The SERODS write systems employ either a different laser or a different level of laser power.

SERODS optical data storage with parallel signal transfer

DOEpatents

Vo-Dinh, Tuan

2003-06-24

Surface-enhanced Raman optical data storage (SERODS) systems having increased reading and writing speeds, that is, increased data transfer rates, are disclosed. In the various SERODS read and write systems, the surface-enhanced Raman scattering (SERS) data is written and read using a two-dimensional process called parallel signal transfer (PST). The various embodiments utilize laser light beam excitation of the SERODS medium, optical filtering, beam imaging, and two-dimensional light detection. Two- and three-dimensional SERODS media are utilized. The SERODS write systems employ either a different laser or a different level of laser power.

Development of dual-beam system using an electrostatic accelerator for in-situ observation of swift heavy ion irradiation effects on materials

NASA Astrophysics Data System (ADS)

Matsuda, M.; Asozu, T.; Sataka, M.; Iwase, A.

2013-11-01

We have developed the dual beam system which accelerates two kinds of ion beams simultaneously especially for real-time ion beam analysis. We have also developed the alternating beam system which can efficiently change beam species in a short time in order to realize efficient ion beam analysis in a limited beam time. The acceleration of the dual beam is performed by the 20 UR Pelletron™ tandem accelerator in which an ECR ion source is mounted at the high voltage terminal [1,2]. The multi-charged ions of two or more elements can be simultaneously generated from the ECR ion source, so dual-beam irradiation is achieved by accelerating ions with the same charge to mass ratio (for example, 132Xe11+ and 12C+). It enables us to make a real-time beam analysis such as Rutherford Back Scattering (RBS) method, while a target is irradiated with swift heavy ions. For the quick change of the accelerating ion beam, the program of automatic setting of the optical parameter of the accelerator has been developed. The switchover time for changing the ion beam is about 5 min. These developments have been applied to the study on the ion beam mixing caused by high-density electronic excitation induced by swift heavy ions.

An investigation of accelerator head scatter and output factor in air.

PubMed

Ding, George X

2004-09-01

Our purpose in this study was to investigate whether the Monte Carlo simulation can accurately predict output factors in air. Secondary goals were to study the head scatter components and investigate the collimator exchange effect. The Monte Carlo code, BEAMnrc, was used in the study. Photon beams of 6 and 18 MV were from a Varian Clinac 2100EX accelerator and the measurements were performed using an ionization chamber in a mini-phantom. The Monte Carlo calculated in air output factors was within 1% of measured values. The simulation provided information of the origin and the magnitude of the collimator exchange effect. It was shown that the collimator backscatter to the beam monitor chamber played a significant role in the beam output factors. However the magnitude of the scattered dose contributions from the collimator at the isocenter is negligible. The maximum scattered dose contribution from the collimators was about 0.15% and 0.4% of the total dose at the isocenter for a 6 and 18 MV beam, respectively. The scattered dose contributions from the flattening filter at the isocenter were about 0.9-3% and 0.2-6% of the total dose for field sizes of 4x4 cm2-40x40 cm2 for the 6 and 18 MV beam, respectively. The study suggests that measurements of head scatter factors be done at large depth well beyond the depth of electron contamination. The insight information may have some implications for developing generalized empirical models to calculate the head scatter.

A model of primary and scattered photon fluence for mammographic x-ray image quantification

NASA Astrophysics Data System (ADS)

Tromans, Christopher E.; Cocker, Mary R.; Brady, Michael, Sir

2012-10-01

We present an efficient method to calculate the primary and scattered x-ray photon fluence component of a mammographic image. This can be used for a range of clinically important purposes, including estimation of breast density, personalized image display, and quantitative mammogram analysis. The method is based on models of: the x-ray tube; the digital detector; and a novel ray tracer which models the diverging beam emanating from the focal spot. The tube model includes consideration of the anode heel effect, and empirical corrections for wear and manufacturing tolerances. The detector model is empirical, being based on a family of transfer functions that cover the range of beam qualities and compressed breast thicknesses which are encountered clinically. The scatter estimation utilizes optimal information sampling and interpolation (to yield a clinical usable computation time) of scatter calculated using fundamental physics relations. A scatter kernel arising around each primary ray is calculated, and these are summed by superposition to form the scatter image. Beam quality, spatial position in the field (in particular that arising at the air-boundary due to the depletion of scatter contribution from the surroundings), and the possible presence of a grid, are considered, as is tissue composition using an iterative refinement procedure. We present numerous validation results that use a purpose designed tissue equivalent step wedge phantom. The average differences between actual acquisitions and modelled pixel intensities observed across the adipose to fibroglandular attenuation range vary between 5% and 7%, depending on beam quality and, for a single beam quality are 2.09% and 3.36% respectively with and without a grid.

Optical probe for porosity defect detection on inner diameter surfaces of machined bores

NASA Astrophysics Data System (ADS)

Kulkarni, Ojas P.; Islam, Mohammed N.; Terry, Fred L.

2010-12-01

We demonstrate an optical probe for detection of porosity inside spool bores of a transmission valve body with diameters down to 5 mm. The probe consists of a graded-index relay rod that focuses a laser beam spot onto the inner surface of the bore. Detectors, placed in the specular and grazing directions with respect to the incident beam, measure the change in scattered intensity when a surface defect is encountered. Based on the scattering signatures in the two directions, the system can also validate the depth of the defect and distinguish porosity from bump-type defects coming out of the metal surface. The system can detect porosity down to a 50-μm lateral dimension and ~40 μm in depth with >3-dB contrast over the background intensity fluctuations. Porosity detection systems currently use manual inspection techniques on the plant floor, and the demonstrated probe provides a noncontact technique that can help automotive manufacturers meet high-quality standards during production.

Multi-Point Thomson Scattering Diagnostic for the Helicity Injected Torus

NASA Astrophysics Data System (ADS)

Liptac, J. E.; Smith, R. J.; Hoffman, C. S.; Jarboe, T. R.; Nelson, B. A.; Leblanc, B. P.; Phillips, P.

1999-11-01

The multi-point Thomson scattering system on the Helicity Injected Torus--II can determine electron temperature and density at 11 radial positions at a single time during the plasma discharge. The system includes components on loan from both PPPL and from the University of Texas. The collection optics and Littrow spectrometer from Princeton, and the 1 GW laser and multi-anode microchannel plate detector from Texas have been integrated into a compact structure, creating a mobile and reliable diagnostic. The mobility of the system allows alignment to occur in a room adjacent to the experiment, greatly reducing the disturbance to normal machine operation. The four main parts of the Thomson scattering system, namely, the laser, the beam line, the collection optics, and the mobile structure are presented and discussed.

Radiation force of an arbitrary acoustic beam on an elastic sphere in a fluid

PubMed Central

Sapozhnikov, Oleg A.; Bailey, Michael R.

2013-01-01

A theoretical approach is developed to calculate the radiation force of an arbitrary acoustic beam on an elastic sphere in a liquid or gas medium. First, the incident beam is described as a sum of plane waves by employing conventional angular spectrum decomposition. Then, the classical solution for the scattering of a plane wave from an elastic sphere is applied for each plane-wave component of the incident field. The net scattered field is expressed as a superposition of the scattered fields from all angular spectrum components of the incident beam. With this formulation, the incident and scattered waves are superposed in the far field to derive expressions for components of the radiation stress tensor. These expressions are then integrated over a spherical surface to analytically describe the radiation force on an elastic sphere. Limiting cases for particular types of incident beams are presented and are shown to agree with known results. Finally, the analytical expressions are used to calculate radiation forces associated with two specific focusing transducers. PMID:23363086

Geometries and focal properties of two electron-lens systems useful in low-energy electron or ion scattering

NASA Technical Reports Server (NTRS)

Chutjian, A.

1979-01-01

Geometries and focal properties are given for two types of electron-lens system commonly needed in electron scattering. One is an electron gun that focuses electrons from a thermionic emitter onto a fixed point (target) over a wide range of final energies. The other is an electron analyzer system that focuses scattered electrons of variable energy onto a fixed position (e.g., the entrance plane of an analyzer) at fixed energy with a zero final beam angle. Analyzer-system focusing properties are given for superelastically, elastically, and inelastically scattered electrons. Computer calculations incorporating recent accurate tube-lens focal properties are used to compute lens voltages, locations and diameters of all pupils and windows, filling factors, and asymptotic rays throughout each lens system. Focus voltages as a function of electron energy and energy change are given, and limits of operation of each system discussed. Both lens systems have been in routine use for several years, and good agreement has been consistently found between calculated and operating lens voltages.

a Search for Lower-Hybrid Drift Fluctuations in a Field-Reversed Configuration by Means of Carbon Dioxide Heterodyne Scattering.

NASA Astrophysics Data System (ADS)

Carlson, Arthur William

A measurement is reported which sets an upper bound on LHD-like density fluctuations in an FRC which is two orders of magnitude below the predicted levels. Particle loss from FRC's is known to occur anomalously fast, and this is usually attributed to effects of the LHD instability. If LHD waves are present, they can be measured using heterodyne detection of CO(,2) laser light scattered from the associated density fluctuations. In the present case, the usual scattering system was successfully modified to compensate for severe refraction of the beams by the plasma. This system was calibrated by detection of an electrooptically modulated CO(,2) laser beam, and by detection of light scattered from acoustic waves in salt. The plasma measurements made on the TRX-2 field-reversed theta-pinch covered all parameters at which LHD fluctuations might be expected to occur, namely wavenumbers from 30 to 240 cm('-1), frequencies from 10 to 300 MHz, and radii from one centimeter inside the separatrix to two centimeters outside. The lack of detectable scattered light under any of these conditions indicates ((delta)n/n) < 1 x 10('-4), compared to predictions of ((delta)n/n) ('(TURN)) 1 x 10('-2) based on mode coupling theory, ion -trapping theory, and observed transport rates. Several mechanisms are discussed which may stabilize LHD in these plasmas. Several alternate explanations of the observed anomalous transport rates in FRC's are also discussed.

Coupling of Multiple Coulomb Scattering with Energy Loss and Straggling in HZETRN

NASA Technical Reports Server (NTRS)

Mertens, Christopher J.; Wilson, John W.; Walker, Steven A.; Tweed, John

2007-01-01

The new version of the HZETRN deterministic transport code based on Green's function methods, and the incorporation of ground-based laboratory boundary conditions, has lead to the development of analytical and numerical procedures to include off-axis dispersion of primary ion beams due to small-angle multiple Coulomb scattering. In this paper we present the theoretical formulation and computational procedures to compute ion beam broadening and a methodology towards achieving a self-consistent approach to coupling multiple scattering interactions with ionization energy loss and straggling. Our initial benchmark case is a 60 MeV proton beam on muscle tissue, for which we can compare various attributes of beam broadening with Monte Carlo simulations reported in the open literature.

Resonant scattering experiments with radioactive nuclear beams - Recent results and future plans

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

Teranishi, T.; Sakaguchi, S.; Uesaka, T.

2013-04-19

Resonant scattering with low-energy radioactive nuclear beams of E < 5 MeV/u have been studied at CRIB of CNS and at RIPS of RIKEN. As an extension to the present experimental technique, we will install an advanced polarized proton target for resonant scattering experiments. A Monte-Carlo simulation was performed to study the feasibility of future experiments with the polarized target. In the Monte-Carlo simulation, excitation functions and analyzing powers were calculated using a newly developed R-matrix calculation code. A project of a small-scale radioactive beam facility at Kyushu University is also briefly described.

Method and apparatus for measuring micro structures, anisotropy and birefringence in polymers using laser scattered light

DOEpatents

Grek, Boris; Bartolick, Joseph; Kennedy, Alan D.

2000-01-01

A method and apparatus for measuring microstructures, anistropy and birefringence in polymers using laser scattered light includes a laser which provides a beam that can be conditioned and is directed at a fiber or film which causes the beam to scatter. Backscatter light is received and processed with detectors and beam splitters to obtain data. The data is directed to a computer where it is processed to obtain information about the fiber or film, such as the birefringence and diameter. This information provides a basis for modifications to the production process to enhance the process.

Monte Carlo simulation of inverse geometry x-ray fluoroscopy using a modified MC-GPU framework

PubMed Central

Dunkerley, David A. P.; Tomkowiak, Michael T.; Slagowski, Jordan M.; McCabe, Bradley P.; Funk, Tobias; Speidel, Michael A.

2015-01-01

Scanning-Beam Digital X-ray (SBDX) is a technology for low-dose fluoroscopy that employs inverse geometry x-ray beam scanning. To assist with rapid modeling of inverse geometry x-ray systems, we have developed a Monte Carlo (MC) simulation tool based on the MC-GPU framework. MC-GPU version 1.3 was modified to implement a 2D array of focal spot positions on a plane, with individually adjustable x-ray outputs, each producing a narrow x-ray beam directed toward a stationary photon-counting detector array. Geometric accuracy and blurring behavior in tomosynthesis reconstructions were evaluated from simulated images of a 3D arrangement of spheres. The artifact spread function from simulation agreed with experiment to within 1.6% (rRMSD). Detected x-ray scatter fraction was simulated for two SBDX detector geometries and compared to experiments. For the current SBDX prototype (10.6 cm wide by 5.3 cm tall detector), x-ray scatter fraction measured 2.8–6.4% (18.6–31.5 cm acrylic, 100 kV), versus 2.1–4.5% in MC simulation. Experimental trends in scatter versus detector size and phantom thickness were observed in simulation. For dose evaluation, an anthropomorphic phantom was imaged using regular and regional adaptive exposure (RAE) scanning. The reduction in kerma-area-product resulting from RAE scanning was 45% in radiochromic film measurements, versus 46% in simulation. The integral kerma calculated from TLD measurement points within the phantom was 57% lower when using RAE, versus 61% lower in simulation. This MC tool may be used to estimate tomographic blur, detected scatter, and dose distributions when developing inverse geometry x-ray systems. PMID:26113765

Monte Carlo simulation of inverse geometry x-ray fluoroscopy using a modified MC-GPU framework.

PubMed

Dunkerley, David A P; Tomkowiak, Michael T; Slagowski, Jordan M; McCabe, Bradley P; Funk, Tobias; Speidel, Michael A

2015-02-21

Scanning-Beam Digital X-ray (SBDX) is a technology for low-dose fluoroscopy that employs inverse geometry x-ray beam scanning. To assist with rapid modeling of inverse geometry x-ray systems, we have developed a Monte Carlo (MC) simulation tool based on the MC-GPU framework. MC-GPU version 1.3 was modified to implement a 2D array of focal spot positions on a plane, with individually adjustable x-ray outputs, each producing a narrow x-ray beam directed toward a stationary photon-counting detector array. Geometric accuracy and blurring behavior in tomosynthesis reconstructions were evaluated from simulated images of a 3D arrangement of spheres. The artifact spread function from simulation agreed with experiment to within 1.6% (rRMSD). Detected x-ray scatter fraction was simulated for two SBDX detector geometries and compared to experiments. For the current SBDX prototype (10.6 cm wide by 5.3 cm tall detector), x-ray scatter fraction measured 2.8-6.4% (18.6-31.5 cm acrylic, 100 kV), versus 2.1-4.5% in MC simulation. Experimental trends in scatter versus detector size and phantom thickness were observed in simulation. For dose evaluation, an anthropomorphic phantom was imaged using regular and regional adaptive exposure (RAE) scanning. The reduction in kerma-area-product resulting from RAE scanning was 45% in radiochromic film measurements, versus 46% in simulation. The integral kerma calculated from TLD measurement points within the phantom was 57% lower when using RAE, versus 61% lower in simulation. This MC tool may be used to estimate tomographic blur, detected scatter, and dose distributions when developing inverse geometry x-ray systems.

Rectangular Relief Diffraction Gratings for Coherent Lidar Beam Deflection

NASA Technical Reports Server (NTRS)

Cole, H. J.; Dixit, S. N.; Shore, B. W.; Chambers, D. M.; Britten, J. A.; Kavaya, M. J.

1999-01-01

LIDAR systems require a light transmitting system for sending a laser light pulse into space and a receiving system for collecting the retro-scattered light, separating it from the outgoing beam and analyzing the received signal for calculating wind velocities. Currently, a shuttle manifested coherent LIDAR experiment called SPARCLE (SPAce Readiness Coherent Lidar Experiment) includes a silicon wedge (or prism) in its design in order to deflect the outgoing beam 30 degrees relative to the incident direction. The intent of this paper is to present two optical design approaches that may enable the replacement of the optical wedge component (in future, larger aperture, post-SPARCLE missions) with a surface relief transmission diffraction grating. Such a grating could be etched into a lightweight, flat, fused quartz substrate. The potential advantages of a diffractive beam deflector include reduced weight, reduced power requirements for the driving scanning motor, reduced optical sensitivity to thermal gradients, and increased dynamic stability.

Multi-aperture laser transmissometer system for long-path aerosol extinction rate measurement.

PubMed

Wu, Chensheng; Rzasa, John R; Ko, Jonathan; Paulson, Daniel A; Coffaro, Joseph; Spychalsky, Jonathan; Crabbs, Robert F; Davis, Christopher C

2018-01-20

We present the theory, design, simulation, and experimental evaluations of a new laser transmissometer system for aerosol extinction rate measurement over long paths. The transmitter emits an ON/OFF modulated Gaussian beam that does not require strict collimation. The receiver uses multiple point detectors to sample the sub-aperture irradiance of the arriving beam. The sparse detector arrangement makes our transmissometer system immune to turbulence-induced beam distortion and beam wander caused by the atmospheric channel. Turbulence effects often cause spatial discrepancies in beam propagation and lead to miscalculation of true power loss when using the conventional approach of measuring the total beam power directly with a large-aperture optical concentrator. Our transmissometer system, on the other hand, combines the readouts from distributed detectors to rule out turbulence-induced temporal power fluctuations. As a result, we show through both simulation and field experiments that our transmissometer system works accurately with turbulence strength Cn2 up to 10 -12   m -2/3 over a typical 1-km atmospheric channel. In application, our turbulence- and weather-resistant laser transmissometer system has significant advantages for the measurement and study of aerosol concentration, absorption, and scattering properties, which are crucial for directed energy systems, ground-level free-space optical communication systems, environmental monitoring, and weather forecasting.

Scattering of Gaussian Beams by Disordered Particulate Media

NASA Technical Reports Server (NTRS)

Mishchenko, Michael I.; Dlugach, Janna M.

2016-01-01

A frequently observed characteristic of electromagnetic scattering by a disordered particulate medium is the absence of pronounced speckles in angular patterns of the scattered light. It is known that such diffuse speckle-free scattering patterns can be caused by averaging over randomly changing particle positions and/or over a finite spectral range. To get further insight into the possible physical causes of the absence of speckles, we use the numerically exact superposition T-matrix solver of the Maxwell equations and analyze the scattering of plane-wave and Gaussian beams by representative multi-sphere groups. We show that phase and amplitude variations across an incident Gaussian beam do not serve to extinguish the pronounced speckle pattern typical of plane-wave illumination of a fixed multi-particle group. Averaging over random particle positions and/or over a finite spectral range is still required to generate the classical diffuse speckle-free regime.

Free space optical communications system performance under atmospheric scattering and turbulence for 850 and 1550  nm operation.

PubMed

El-Wakeel, Amr S; Mohammed, Nazmi A; Aly, Moustafa H

2016-09-10

In this work, a free space optical communication (FSO) link is proposed and utilized to explore and evaluate the FSO link performance under the joint occurrence of the atmospheric scattering and turbulence phenomena for 850 and 1550 nm operation. Diffraction and nondiffraction-limited systems are presented and evaluated for both wavelengths' operation, considering far-field conditions under different link distances. Bit error rate, pointing error angles, beam divergence angles, and link distance are the main performance indicators that are used to evaluate and compare the link performance under different system configurations and atmospheric phenomena combinations. A detailed study is performed to provide the merits of this work. For both far-field diffraction-limited and nondiffraction-limited systems, it is concluded that 1550 nm system operation is better than 850 nm for the whole presented joint occurrences of atmospheric scattering and turbulence.

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

PubMed

Mitri, F G

2017-11-01

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

Final Report - X-ray Studies of Highly Correlated Systems

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

Burns, Clement

2017-11-27

The overall goal of the research was to improve the capabilities of x-ray synchrotron instrumentation to enable cutting-edge research in condensed matter physics. The main goal of the current grant cycle was to find a method to measure the polarization of the scattered x-ray in resonant inelastic x-ray scattering. To do this, we developed a polarization analysis apparatus using a thin, toroidally bent single crystal, which could be set to reflect one or the other of the two polarization components in the scattered x-ray beam. Resonant x-ray scattering measurements were also carried out on interfaces and the charge density wavemore » in high temperature superconducting materials.« less

Laser Light Scattering with Multiple Scattering Suppression Used to Measure Particle Sizes

NASA Technical Reports Server (NTRS)

Meyer, William V.; Tin, Padetha; Lock, James A.; Cannell, David S.; Smart, Anthony E.; Taylor, Thomas W.

1999-01-01

Laser light scattering is the technique of choice for noninvasively sizing particles in a fluid. The members of the Advanced Technology Development (ATD) project in laser light scattering at the NASA Lewis Research Center have invented, tested, and recently enhanced a simple and elegant way to extend the concentration range of this standard laboratory particle-sizing technique by several orders of magnitude. With this technique, particles from 3 nm to 3 mm can be measured in a solution. Recently, laser light scattering evolved to successfully size particles in both clear solutions and concentrated milky-white solutions. The enhanced technique uses the property of light that causes it to form tall interference patterns at right angles to the scattering plane (perpendicular to the laser beam) when it is scattered from a narrow laser beam. Such multiple-scattered light forms a broad fuzzy halo around the focused beam, which, in turn, forms short interference patterns. By placing two fiber optics on top of each other and perpendicular to the laser beam (see the drawing), and then cross-correlating the signals they produce, only the tall interference patterns formed by singly scattered light are detected. To restate this, unless the two fiber optics see the same interference pattern, the scattered light is not incorporated into the signal. With this technique, only singly scattered light is seen (multiple-scattered light is rejected) because only singly scattered light has an interference pattern tall enough to span both of the fiber-optic pickups. This technique is simple to use, easy to align, and works at any angle. Placing a vertical slit in front of the signal collection fibers enhanced this approach. The slit serves as an optical mask, and it significantly shortens the time needed to collect good data by selectively masking out much of the unwanted light before cross-correlation is applied.

Enhanced backscattering through a deep random phase screen

NASA Astrophysics Data System (ADS)

Jakeman, E.

1988-10-01

The statistical properties of radiation scattered by a system consisting of a plane mirror placed in the Fresnel region behind a smoothly varying deep random-phase screen with off-axis beam illumination are studied. It is found that two mechanisms cause enhanced scattering around the backward direction, according to the mirror position with respect to the focusing plane of the screen. In all of the plane mirror geometries considered, the scattered field remains a complex Gaussian process with a spatial coherence function identical to that expected for a single screen, and a speckle size smaller than the width of backscatter enhancement.

Binary moving-blocker-based scatter correction in cone-beam computed tomography with width-truncated projections: proof of concept.

PubMed

Lee, Ho; Fahimian, Benjamin P; Xing, Lei

2017-03-21

This paper proposes a binary moving-blocker (BMB)-based technique for scatter correction in cone-beam computed tomography (CBCT). In concept, a beam blocker consisting of lead strips, mounted in front of the x-ray tube, moves rapidly in and out of the beam during a single gantry rotation. The projections are acquired in alternating phases of blocked and unblocked cone beams, where the blocked phase results in a stripe pattern in the width direction. To derive the scatter map from the blocked projections, 1D B-Spline interpolation/extrapolation is applied by using the detected information in the shaded regions. The scatter map of the unblocked projections is corrected by averaging two scatter maps that correspond to their adjacent blocked projections. The scatter-corrected projections are obtained by subtracting the corresponding scatter maps from the projection data and are utilized to generate the CBCT image by a compressed-sensing (CS)-based iterative reconstruction algorithm. Catphan504 and pelvis phantoms were used to evaluate the method's performance. The proposed BMB-based technique provided an effective method to enhance the image quality by suppressing scatter-induced artifacts, such as ring artifacts around the bowtie area. Compared to CBCT without a blocker, the spatial nonuniformity was reduced from 9.1% to 3.1%. The root-mean-square error of the CT numbers in the regions of interest (ROIs) was reduced from 30.2 HU to 3.8 HU. In addition to high resolution, comparable to that of the benchmark image, the CS-based reconstruction also led to a better contrast-to-noise ratio in seven ROIs. The proposed technique enables complete scatter-corrected CBCT imaging with width-truncated projections and allows reducing the acquisition time to approximately half. This work may have significant implications for image-guided or adaptive radiation therapy, where CBCT is often used.

Binary moving-blocker-based scatter correction in cone-beam computed tomography with width-truncated projections: proof of concept

NASA Astrophysics Data System (ADS)

Lee, Ho; Fahimian, Benjamin P.; Xing, Lei

2017-03-01

This paper proposes a binary moving-blocker (BMB)-based technique for scatter correction in cone-beam computed tomography (CBCT). In concept, a beam blocker consisting of lead strips, mounted in front of the x-ray tube, moves rapidly in and out of the beam during a single gantry rotation. The projections are acquired in alternating phases of blocked and unblocked cone beams, where the blocked phase results in a stripe pattern in the width direction. To derive the scatter map from the blocked projections, 1D B-Spline interpolation/extrapolation is applied by using the detected information in the shaded regions. The scatter map of the unblocked projections is corrected by averaging two scatter maps that correspond to their adjacent blocked projections. The scatter-corrected projections are obtained by subtracting the corresponding scatter maps from the projection data and are utilized to generate the CBCT image by a compressed-sensing (CS)-based iterative reconstruction algorithm. Catphan504 and pelvis phantoms were used to evaluate the method’s performance. The proposed BMB-based technique provided an effective method to enhance the image quality by suppressing scatter-induced artifacts, such as ring artifacts around the bowtie area. Compared to CBCT without a blocker, the spatial nonuniformity was reduced from 9.1% to 3.1%. The root-mean-square error of the CT numbers in the regions of interest (ROIs) was reduced from 30.2 HU to 3.8 HU. In addition to high resolution, comparable to that of the benchmark image, the CS-based reconstruction also led to a better contrast-to-noise ratio in seven ROIs. The proposed technique enables complete scatter-corrected CBCT imaging with width-truncated projections and allows reducing the acquisition time to approximately half. This work may have significant implications for image-guided or adaptive radiation therapy, where CBCT is often used.

Analysis of Neutron Production in Passively Scattered Ion-Beam Therapy.

PubMed

Heo, Seunguk; Yoo, Seunghoon; Song, Yongkeun; Kim, Eunho; Shin, Jaeik; Han, Soorim; Jung, Wongyun; Nam, Sanghee; Lee, Rena; Lee, Kitae; Cho, Sungho

2017-07-01

A new treatment facility for heavy ion therapy since 2010 was constructed. In the broad beam, a range shifter, ridge filter and multi leaf collimator (MLC) for the generation of the spread-out Bragg peak is used. In this case, secondary neutrons produced by the interactions of the ion field with beam-modifying devices (e.g. double-scattering system, beam shaping collimators and range compensators) are very important for patient safety. Therefore, these components must be carefully examined in the context of secondary neutron yield and associated secondary cancer risk. In this article, Monte Carlo simulation has been carried out with the FLUktuierende KAskade particle transport code, the fluence and distribution of neutron generation and the neutron dose equivalent from the broad beam components are compared using carbon and proton beams. As a result, it is confirmed that the yield of neutron production using a carbon beam from all components of the broad beam was higher than using a proton beam. The ambient dose by neutrons per heavy ion and proton ion from the MLC surface was 0.12-0.18 and 0.0067-0.0087 pSv, respectively, which shows that heavy ions generate more neutrons than protons. However, ambient dose per treatment 2 Gy, which means physical dose during treatment by ion beam, is higher than carbon beam because proton therapy needs more beam flux to make 2-Gy prescription dose. Therefore, the neutron production from the MLC, which is closed to the patient, is a very important parameter for patient safety. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Problems in nonlinear acoustics: Scattering of sound by sound, parametric receiving arrays, nonlinear effects in asymmetric sound beams and pulsed finite amplitude sound beams

NASA Astrophysics Data System (ADS)

Hamilton, Mark F.

1989-08-01

Four projects are discussed in this annual summary report, all of which involve basic research in nonlinear acoustics: Scattering of Sound by Sound, a theoretical study of two nonconlinear Gaussian beams which interact to produce sum and difference frequency sound; Parametric Receiving Arrays, a theoretical study of parametric reception in a reverberant environment; Nonlinear Effects in Asymmetric Sound Beams, a numerical study of two dimensional finite amplitude sound fields; and Pulsed Finite Amplitude Sound Beams, a numerical time domain solution of the KZK equation.

Theoretical and Experimental Studies in Reactive Scattering.

DTIC Science & Technology

1986-08-11

dynamics 3. Three-dimensional reaction dynamics 4. Anisotropic potentials for He + C02, OCS, CS2 .. 5. Production of a high intensity-high energy beam of...involving beams of He atoms, H atoms and metastable H molecules aimed at the determination of potential energy surfaces involving these systems. 2... energy of 0.3 ’, Kcal/mole below the top of the barrier, the reaction probability from ground S"t vibrational state reagent to ground vibrational

Interaction of doughnut-shaped laser pulses with glasses

DOE PAGES

Zhukov, Vladimir P.; Rubenchik, Alexander M.; Fedoruk, Mikhail P.; ...

2017-01-26

Non-Gaussian laser beams can open new opportunities for microfabrication, including ultrashort laser direct writing. By using a model based on Maxwell’s equations, we investigate the dynamics of doughnut-shaped laser beams focused inside fused silica glass, in comparison with Gaussian pulses of the same energy. The laser propagation dynamics reveals intriguing features of beam splitting and sudden collapse toward the beam axis, overcoming the intensity clamping effect. The resulting structure of light absorption represents a very hot, hollow nanocylinder, which can lead to an implosion process that brings matter to extreme thermodynamic states. Furthermore, by monitoring the simulations of the lasermore » beam scattering we see a considerable difference in both the blueshift and the angular distribution of scattered light for different laser energies, suggesting that investigations of the spectra of scattered radiation can be used as a diagnostic of laser-produced electron plasmas in transparent materials.« less

Studies on ion scattering and sputtering processes relevant to ion beam sputter deposition of multicomponent thin films

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

Auciello, O.; Ameen, M.S.; Kingon, A.I.

1989-01-01

Results from computer simulation and experiments on ion scattering and sputtering processes in ion beam sputter deposition of high Tc superconducting and ferroelectric thin films are presented. It is demonstrated that scattering of neutralized ions from the targets can result in undesirable erosion of, and inert gas incorporation in, the growing films, depending on the ion/target atom ass ratio and ion beam angle of incidence/target/substrate geometry. The studies indicate that sputtering Kr{sup +} or Xe{sup +} ions is preferable to the most commonly used Ar{sup +} ions, since the undesirable phenomena mentioned above are minimized for the first two ions.more » These results are used to determine optimum sputter deposition geometry and ion beam parameters for growing multicomponent oxide thin films by ion beam sputter-deposition. 10 refs., 5 figs.« less

A 3 MV Pelletron at Fudan University

NASA Astrophysics Data System (ADS)

Sun, Chuan-Chen; Lu, Cheng-Rong; Fe, Zhi-Yu; Yuan, Dao-Sheng; Yang, Fujia

1989-04-01

A 3 MV Pelletron tandem, model 9SDH-2, the fourth machine manufactured by NEC was installed and has been operating at Fudan University since 1987. The operating experiences obtained during the past year are described. Three beam lines have been established: one is for Auger-ESCA and RBS in an ultrahigh-vacuum chamber in which Al(100) clean surfaces have been studied; the second beam line is used as a mubeam analysis system using a 2 μ proton beam for resonant prefitting studies. The third is a general purpose beam line, for studies of the effect of nuclear resonance on K X-ray yield. At present, the third beam line is also used for ion beam analysis studies of 8.8 MeV He 2+ non-Rutherford scattering on high Tc superconductors.

SU-E-T-486: In Vivo Skin Dosimetry Using the Exradin W1 Plastic Scintillation Detector for Passively Scattered Proton Beam Therapy

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

Alsanea, F; Kudchadker, R; Usama, M

Purpose: To evaluate the accuracy and usefulness of plastic scintillation detectors used for skin dosimetry of patients undergoing passive scatter proton therapy. Methods: Following an IRB approved protocol, six patients undergoing passively scattered proton beam therapy for prostate cancer were selected for in vivo skin dosimetry using the Exradin W1 plastic scintillator. The detector was calibrated on a Cobalt-60 unit, and phantom measurements in the proton beam with the W1 and a calibrated parallel plate ion chamber were used to account for the under-response due to high LET at energies used for treatment. Measurements made in a heated water tankmore » were used to account for temperature dependence. For in vivo measurements, the W1 is fixed to the patient’s skin with medical tape in the center of each of two laterally opposed treatment fields. Measurements will be performed once per week for each patient for the duration of treatment, for a total of thirty six measurements. The measured dose will be compared to the expected dose, extracted from the Eclipse treatment planning system. The average difference over all measurements and per-patient will be computed, as well as standard deviations. Results: The calibrated detector exhibited a 7% under-response in 225 and 250 MeV beams, and a 4% under-response when used at 37 °C (relative to the response at the calibration temperature of 20 °C). Patient measurements are ongoing. Conclusion: The Exradin W1 plastic scintillator detector is a strong candidate for in vivo skin dosimetry in passively scattered proton beams as PSDs are water equivalent and very small (2mm in diameter), permitting accurate measurements that do not perturb the delivered dose. This project was supported in part by award number CA182450 from the National Cancer Institute.« less

Active probing of cloud multiple scattering, optical depth, vertical thickness, and liquid water content using wide-angle imaging lidar

NASA Astrophysics Data System (ADS)

Love, Steven P.; Davis, Anthony B.; Rohde, Charles A.; Tellier, Larry; Ho, Cheng

2002-09-01

At most optical wavelengths, laser light in a cloud lidar experiment is not absorbed but merely scattered out of the beam, eventually escaping the cloud via multiple scattering. There is much information available in this light scattered far from the input beam, information ignored by traditional 'on-beam' lidar. Monitoring these off-beam returns in a fully space- and time-resolved manner is the essence of our unique instrument, Wide Angle Imaging Lidar (WAIL). In effect, WAIL produces wide-field (60-degree full-angle) 'movies' of the scattering process and records the cloud's radiative Green functions. A direct data product of WAIL is the distribution of photon path lengths resulting from multiple scattering in the cloud. Following insights from diffusion theory, we can use the measured Green functions to infer the physical thickness and optical depth of the cloud layer, and, from there, estimate the volume-averaged liquid water content. WAIL is notable in that it is applicable to optically thick clouds, a regime in which traditional lidar is reduced to ceilometry. Here we present recent WAIL data on various clouds and discuss the extension of WAIL to full diurnal monitoring by means of an ultra-narrow magneto-optic atomic line filter for daytime measurements.

Commissioning a passive-scattering proton therapy nozzle for accurate SOBP delivery.

PubMed

Engelsman, M; Lu, H M; Herrup, D; Bussiere, M; Kooy, H M

2009-06-01

Proton radiotherapy centers that currently use passively scattered proton beams do field specific calibrations for a non-negligible fraction of treatment fields, which is time and resource consuming. Our improved understanding of the passive scattering mode of the IBA universal nozzle, especially of the current modulation function, allowed us to re-commission our treatment control system for accurate delivery of SOBPs of any range and modulation, and to predict the output for each of these fields. We moved away from individual field calibrations to a state where continued quality assurance of SOBP field delivery is ensured by limited system-wide measurements that only require one hour per week. This manuscript reports on a protocol for generation of desired SOBPs and prediction of dose output.

Measurements of Classical Transport of Fast Ions in the LAPD

NASA Astrophysics Data System (ADS)

Zhao, L.; Boehmer, H.; Edrich, D.; Heidbrink, W. W.; McWilliams, R.; Zimmerman, D.; Lenenman, D.; Vincena, S.

2004-11-01

To study fast ion transport in a well controlled background plasma, a 3cm diameter RF ion gun launches a pulsed, 400 eV ribbon shape argon ion beam in the LArge Plasma Device (LAPD) at UCLA. The beam velocity distribution is calibrated by Laser Induced Fluorescence (LIF) on the Mirror of UCI and the beam energy is also measured by a two-grid energy analyzer at different axial locations (z=0.3-6.0 m) from the source on LAPD. Slowing down of the ion beam is observed when the beam is launched parallel or at 15 degrees to the 0.85 kG magnetic field. Using Langmuir probe measurements of the plasma parameters, the observed energy deceleration rate is consistent with classical Coulomb scattering theory. The radial beam profile is also measured by the energy analyzer when the beam is launched at 15 degrees to the magnetic field. The beam follows the expected helical trajectory and its contour has the shape predicted by Monte Carlo simulations. The diffusion measurements are performed at different axial locations where the ion beam has the same gyro-phase to eliminate the peristaltic effect. The spatial spreading of the beam is compared with classical scattering and neutral scattering theory.

High-k Scattering Receiver Mixer Performance for NSTX-U

NASA Astrophysics Data System (ADS)

Barchfeld, Robert; Riemenschneider, Paul; Domier, Calvin; Luhmann, Neville; Ren, Yang; Kaita, Robert

2016-10-01

The High-k Scattering system detects primarily electron-scale turbulence k θ spectra for studying electron thermal transport in NSTX-U. A 100 mW, 693 GHz probe beam passes through plasma, and scattered power is detected by a 4-pixel quasi optical, mixer array. Remotely controlled receiving optics allows the scattering volume to be located from core to edge with a k θ span of 7 to 40 cm-1. The receiver array features 4 RF diagonal input horns, where the electric field polarization is aligned along the diagonal of a square cross section horn, at 30 mm channel spacing. The local oscillator is provided by a 14.4 GHz source followed by a x48 multiplier chain, giving an intermediate frequency of 1 GHz. The receiver optics receive 4 discreet scattering angles simultaneously, and then focus the signals as 4 parallel signals to their respective horns. A combination of a steerable probe beam, and translating receiver, allows for upward or downward scattering which together can provide information about 2D turbulence wavenumber spectrum. IF signals are digitized and stored for later computer analysis. The performance of the receiver mixers is discussed, along with optical design features to enhance the tuning and performance of the mixers. Work supported in part by U.S. DOE Grant DE-FG02-99ER54518 and DE-AC02-09CH1146.

Controlling Light Transmission Through Highly Scattering Media Using Semi-Definite Programming as a Phase Retrieval Computation Method.

PubMed

N'Gom, Moussa; Lien, Miao-Bin; Estakhri, Nooshin M; Norris, Theodore B; Michielssen, Eric; Nadakuditi, Raj Rao

2017-05-31

Complex Semi-Definite Programming (SDP) is introduced as a novel approach to phase retrieval enabled control of monochromatic light transmission through highly scattering media. In a simple optical setup, a spatial light modulator is used to generate a random sequence of phase-modulated wavefronts, and the resulting intensity speckle patterns in the transmitted light are acquired on a camera. The SDP algorithm allows computation of the complex transmission matrix of the system from this sequence of intensity-only measurements, without need for a reference beam. Once the transmission matrix is determined, optimal wavefronts are computed that focus the incident beam to any position or sequence of positions on the far side of the scattering medium, without the need for any subsequent measurements or wavefront shaping iterations. The number of measurements required and the degree of enhancement of the intensity at focus is determined by the number of pixels controlled by the spatial light modulator.

Scattered radiation from dental metallic crowns in head and neck radiotherapy.

PubMed

Shimozato, T; Igarashi, Y; Itoh, Y; Yamamoto, N; Okudaira, K; Tabushi, K; Obata, Y; Komori, M; Naganawa, S; Ueda, M

2011-09-07

We aimed to estimate the scattered radiation from dental metallic crowns during head and neck radiotherapy by irradiating a jaw phantom with external photon beams. The phantom was composed of a dental metallic plate and hydroxyapatite embedded in polymethyl methacrylate. We used radiochromic film measurement and Monte Carlo simulation to calculate the radiation dose and dose distribution inside the phantom. To estimate dose variations in scattered radiation under different clinical situations, we altered the incident energy, field size, plate thickness, plate depth and plate material. The simulation results indicated that the dose at the incident side of the metallic dental plate was approximately 140% of that without the plate. The differences between dose distributions calculated with the radiation treatment-planning system (TPS) algorithms and the data simulation, except around the dental metallic plate, were 3% for a 4 MV photon beam. Therefore, we should carefully consider the dose distribution around dental metallic crowns determined by a TPS.

Scattered radiation from dental metallic crowns in head and neck radiotherapy

NASA Astrophysics Data System (ADS)

Shimozato, T.; Igarashi, Y.; Itoh, Y.; Yamamoto, N.; Okudaira, K.; Tabushi, K.; Obata, Y.; Komori, M.; Naganawa, S.; Ueda, M.

2011-09-01

We aimed to estimate the scattered radiation from dental metallic crowns during head and neck radiotherapy by irradiating a jaw phantom with external photon beams. The phantom was composed of a dental metallic plate and hydroxyapatite embedded in polymethyl methacrylate. We used radiochromic film measurement and Monte Carlo simulation to calculate the radiation dose and dose distribution inside the phantom. To estimate dose variations in scattered radiation under different clinical situations, we altered the incident energy, field size, plate thickness, plate depth and plate material. The simulation results indicated that the dose at the incident side of the metallic dental plate was approximately 140% of that without the plate. The differences between dose distributions calculated with the radiation treatment-planning system (TPS) algorithms and the data simulation, except around the dental metallic plate, were 3% for a 4 MV photon beam. Therefore, we should carefully consider the dose distribution around dental metallic crowns determined by a TPS.

The Born approximation, multiple scattering, and the butterfly algorithm

NASA Astrophysics Data System (ADS)

Martinez, Alejandro F.

Radar works by focusing a beam of light and seeing how long it takes to reflect. To see a large region the beam is pointed in different directions. The focus of the beam depends on the size of the antenna (called an aperture). Synthetic aperture radar (SAR) works by moving the antenna through some region of space. A fundamental assumption in SAR is that waves only bounce once. Several imaging algorithms have been designed using that assumption. The scattering process can be described by iterations of a badly behaving integral. Recently a method for efficiently evaluating these types of integrals has been developed. We will give a detailed implementation of this algorithm and apply it to study the multiple scattering effects in SAR using target estimates from single scattering algorithms.

Accurate Monte Carlo simulations for nozzle design, commissioning and quality assurance for a proton radiation therapy facility.

PubMed

Paganetti, H; Jiang, H; Lee, S Y; Kooy, H M

2004-07-01

Monte Carlo dosimetry calculations are essential methods in radiation therapy. To take full advantage of this tool, the beam delivery system has to be simulated in detail and the initial beam parameters have to be known accurately. The modeling of the beam delivery system itself opens various areas where Monte Carlo calculations prove extremely helpful, such as for design and commissioning of a therapy facility as well as for quality assurance verification. The gantry treatment nozzles at the Northeast Proton Therapy Center (NPTC) at Massachusetts General Hospital (MGH) were modeled in detail using the GEANT4.5.2 Monte Carlo code. For this purpose, various novel solutions for simulating irregular shaped objects in the beam path, like contoured scatterers, patient apertures or patient compensators, were found. The four-dimensional, in time and space, simulation of moving parts, such as the modulator wheel, was implemented. Further, the appropriate physics models and cross sections for proton therapy applications were defined. We present comparisons between measured data and simulations. These show that by modeling the treatment nozzle with millimeter accuracy, it is possible to reproduce measured dose distributions with an accuracy in range and modulation width, in the case of a spread-out Bragg peak (SOBP), of better than 1 mm. The excellent agreement demonstrates that the simulations can even be used to generate beam data for commissioning treatment planning systems. The Monte Carlo nozzle model was used to study mechanical optimization in terms of scattered radiation and secondary radiation in the design of the nozzles. We present simulations on the neutron background. Further, the Monte Carlo calculations supported commissioning efforts in understanding the sensitivity of beam characteristics and how these influence the dose delivered. We present the sensitivity of dose distributions in water with respect to various beam parameters and geometrical misalignments. This allows the definition of tolerances for quality assurance and the design of quality assurance procedures.

Muon energy estimate through multiple scattering with the MACRO detector

NASA Astrophysics Data System (ADS)

Ambrosio, M.; Antolini, R.; Auriemma, G.; Bakari, D.; Baldini, A.; Barbarino, G. C.; Barish, B. C.; Battistoni, G.; Becherini, Y.; Bellotti, R.; Bemporad, C.; Bernardini, P.; Bilokon, H.; Bloise, C.; Bower, C.; Brigida, M.; Bussino, S.; Cafagna, F.; Calicchio, M.; Campana, D.; Candela, A.; Carboni, M.; Caruso, R.; Cassese, F.; Cecchini, S.; Cei, F.; Chiarella, V.; Choudhary, B. C.; Coutu, S.; Cozzi, M.; de Cataldo, G.; de Deo, M.; Dekhissi, H.; de Marzo, C.; de Mitri, I.; Derkaoui, J.; de Vincenzi, M.; di Credico, A.; Dincecco, M.; Erriquez, O.; Favuzzi, C.; Forti, C.; Fusco, P.; Giacomelli, G.; Giannini, G.; Giglietto, N.; Giorgini, M.; Grassi, M.; Gray, L.; Grillo, A.; Guarino, F.; Gustavino, C.; Habig, A.; Hanson, K.; Heinz, R.; Iarocci, E.; Katsavounidis, E.; Katsavounidis, I.; Kearns, E.; Kim, H.; Kyriazopoulou, S.; Lamanna, E.; Lane, C.; Levin, D. S.; Lindozzi, M.; Lipari, P.; Longley, N. P.; Longo, M. J.; Loparco, F.; Maaroufi, F.; Mancarella, G.; Mandrioli, G.; Margiotta, A.; Marini, A.; Martello, D.; Marzari-Chiesa, A.; Mazziotta, M. N.; Michael, D. G.; Monacelli, P.; Montaruli, T.; Monteno, M.; Mufson, S.; Musser, J.; Nicolo, D.; Nolty, R.; Orth, C.; Osteria, G.; Palamara, O.; Patera, V.; Patrizii, L.; Pazzi, R.; Peck, C. W.; Perrone, L.; Petrera, S.; Pistilli, P.; Popa, V.; Raino, A.; Reynoldson, J.; Ronga, F.; Rrhioua, A.; Satriano, C.; Scapparone, E.; Scholberg, K.; Sciubba, A.; Serra, P.; Sioli, M.; Sirri, G.; Sitta, M.; Spinelli, P.; Spinetti, M.; Spurio, M.; Steinberg, R.; Stone, J. L.; Sulak, L. R.; Surdo, A.; Tarle, G.; Tatananni, E.; Togo, V.; Vakili, M.; Walter, C. W.; Webb, R.; MACRO Collaboration

2002-10-01

Muon energy measurement represents an important issue for any experiment addressing neutrino-induced up-going muon studies. Since the neutrino oscillation probability depends on the neutrino energy, a measurement of the muon energy adds an important piece of information concerning the neutrino system. We show in this paper how the MACRO limited streamer tube system can be operated in drift mode by using the TDCs included in the QTPs, an electronics designed for magnetic monopole search. An improvement of the space resolution is obtained, through an analysis of the multiple scattering of muon tracks as they pass through our detector. This information can be used further to obtain an estimate of the energy of muons crossing the detector. Here we present the results of two dedicated tests, performed at CERN PS-T9 and SPS-X7 beam lines, to provide a full check of the electronics and to exploit the feasibility of such a multiple scattering analysis. We show that by using a neural network approach, we are able to reconstruct the muon energy for E μ<40 GeV. The test beam data provide an absolute energy calibration, which allows us to apply this method to MACRO data.

Propagation stability of self-reconstructing Bessel beams enables contrast-enhanced imaging in thick media.

PubMed

Fahrbach, Florian O; Rohrbach, Alexander

2012-01-17

Laser beams that can self-reconstruct their initial beam profile even in the presence of massive phase perturbations are able to propagate deeper into inhomogeneous media. This ability has crucial advantages for light sheet-based microscopy in thick media, such as cell clusters, embryos, skin or brain tissue or plants, as well as scattering synthetic materials. A ring system around the central intensity maximum of a Bessel beam enables its self-reconstruction, but at the same time illuminates out-of-focus regions and deteriorates image contrast. Here we present a detection method that minimizes the negative effect of the ring system. The beam's propagation stability along one straight line enables the use of a confocal line principle, resulting in a significant increase in image contrast. The axial resolution could be improved by nearly 100% relative to the standard light-sheet techniques using scanned Gaussian beams, while demonstrating self-reconstruction also for high propagation depths.

Scatter correction for cone-beam computed tomography using self-adaptive scatter kernel superposition

NASA Astrophysics Data System (ADS)

Xie, Shi-Peng; Luo, Li-Min

2012-06-01

The authors propose a combined scatter reduction and correction method to improve image quality in cone beam computed tomography (CBCT). The scatter kernel superposition (SKS) method has been used occasionally in previous studies. However, this method differs in that a scatter detecting blocker (SDB) was used between the X-ray source and the tested object to model the self-adaptive scatter kernel. This study first evaluates the scatter kernel parameters using the SDB, and then isolates the scatter distribution based on the SKS. The quality of image can be improved by removing the scatter distribution. The results show that the method can effectively reduce the scatter artifacts, and increase the image quality. Our approach increases the image contrast and reduces the magnitude of cupping. The accuracy of the SKS technique can be significantly improved in our method by using a self-adaptive scatter kernel. This method is computationally efficient, easy to implement, and provides scatter correction using a single scan acquisition.

Observation of the Second Harmonic in Thomson Scattering from Relativistic Electrons

NASA Astrophysics Data System (ADS)

Babzien, Marcus; Ben-Zvi, Ilan; Kusche, Karl; Pavlishin, Igor V.; Pogorelsky, Igor V.; Siddons, David P.; Yakimenko, Vitaly; Cline, David; Zhou, Feng; Hirose, Tachishige; Kamiya, Yoshio; Kumita, Tetsuro; Omori, Tsunehiko; Urakawa, Junji; Yokoya, Kaoru

2006-02-01

A free relativistic electron in an electromagnetic field is a pure case of a light-matter interaction. In the laboratory environment, this interaction can be realized by colliding laser pulses with electron beams produced from particle accelerators. The process of single photon absorption and reemission by the electron, so-called linear Thomson scattering, results in radiation that is Doppler shifted into the x-ray and γ-ray regions. At elevated laser intensity, nonlinear effects should come into play when the transverse motion of the electrons induced by the laser beam is relativistic. In the present experiment, we achieved this condition and characterized the second harmonic of Thomson x-ray scattering using the counterpropagation of a 60 MeV electron beam and a subterawatt CO2 laser beam.

Observation of the second harmonic in Thomson scattering from relativistic electrons.

PubMed

Babzien, Marcus; Ben-Zvi, Ilan; Kusche, Karl; Pavlishin, Igor V; Pogorelsky, Igor V; Siddons, David P; Yakimenko, Vitaly; Cline, David; Zhou, Feng; Hirose, Tachishige; Kamiya, Yoshio; Kumita, Tetsuro; Omori, Tsunehiko; Urakawa, Junji; Yokoya, Kaoru

2006-02-10

A free relativistic electron in an electromagnetic field is a pure case of a light-matter interaction. In the laboratory environment, this interaction can be realized by colliding laser pulses with electron beams produced from particle accelerators. The process of single photon absorption and reemission by the electron, so-called linear Thomson scattering, results in radiation that is Doppler shifted into the x-ray and gamma-ray regions. At elevated laser intensity, nonlinear effects should come into play when the transverse motion of the electrons induced by the laser beam is relativistic. In the present experiment, we achieved this condition and characterized the second harmonic of Thomson x-ray scattering using the counterpropagation of a 60 MeV electron beam and a subterawatt CO2 laser beam.

Method and apparatus for measuring lung density by Compton backscattering

DOEpatents

Loo, B.W.; Goulding, F.S.

1988-03-11

The density of the lung of a patient suffering from pulmonary edema is monitored by irradiating the lung by a single collimated beam of monochromatic photons and measuring the energies of photons compton back-scattered from the lung by a single high-resolution, high-purity germanium detector. A compact system geometry and a unique data extraction scheme are utilized to minimize systematic errors due to the presence of the chestwall and multiple scattering. 11 figs., 1 tab.

Apparatus and method for generating partially coherent illumination for photolithography

DOEpatents

Sweatt, William C.

2001-01-01

The present invention introduces a novel scatter plate into the optical path of source light used for illuminating a replicated object. The scatter plate has been designed to interrupt a focused, incoming light beam by introducing between about 8 to 24 diffraction zones blazed onto the surface of the scatter plate which intercept the light and redirect it to a like number of different positions in the condenser entrance pupil each of which is determined by the relative orientation and the spatial frequency of the diffraction grating in each of the several zones. Light falling onto the scatter plate, therefore, generates a plurality of unphased sources of illumination as seen by the back half of the optical system. The system comprises a high brightness source, such as a laser, creating light which is taken up by a beam forming optic which focuses the incoming light into a condenser which in turn, focuses light into a field lens creating Kohler illumination image of the source in a camera entrance pupil. The light passing through the field lens illuminates a mask which interrupts the source light as either a positive or negative image of the object to be replicated. Light passing by the mask is focused into the entrance pupil of the lithographic camera creating an image of the mask onto a receptive media.

Observation of stimulated Mie-Bragg scattering from large-size-gold-nanorod suspension in water

NASA Astrophysics Data System (ADS)

He, Guang S.; Yong, Ken-Tye; Zhu, Jing; Prasad, P. N.

2012-04-01

Highly directional backward stimulated scattering has been observed from large-size-gold nanorods suspended in water, pumped with ˜816 nm and ˜10 ns laser pulses. In comparison with other known stimulated scattering effects, the newly observed effect exhibits the following features. (i) The scattering centers are impurity particles with a size comparable in order of magnitude to the incident wavelength. (ii) There is no frequency shift between the pump wavelength and the stimulated scattering wavelength. (iii) The pump threshold can be significantly lower than that of stimulated Brillouin scattering in pure water. The nonfrequency shift can be explained by the formation of a standing-wave Bragg grating induced by the interference between the forward pump beam and the backward Mie-scattering beam. The low pump threshold results from stronger initial Mie-scattering (seed) signals and the intensity-dependent refractive-index change of the scattering medium enhanced by metallic nanoparticles.

Laser scattering induced holograms in lithium niobate. [observation of diffraction cones

NASA Technical Reports Server (NTRS)

Magnusson, R.; Gaylord, T. K.

1974-01-01

A 3.0-mm thick poled single crystal of lithium niobate doped with 0.1 mole% iron was exposed to a single beam and then to two intersecting beams of an argon ion laser operating at 515-nm wavelength. Laser scattering induced holograms were thus written and analyzed. The presence of diffraction cones was observed and is shown to result from the internally recorded interference pattern resulting from the interference of the original incident laser beam with light scattered from material inhomogeneities. This phenomenon is analyzed using Ewald sphere construction techniques which reveal the geometrical relationships existing for the diffraction cones.

Refractive Index Seen by a Probe Beam Interacting with a Laser-Plasma System

NASA Astrophysics Data System (ADS)

Turnbull, D.; Goyon, C.; Kemp, G. E.; Pollock, B. B.; Mariscal, D.; Divol, L.; Ross, J. S.; Patankar, S.; Moody, J. D.; Michel, P.

2017-01-01

We report the first complete set of measurements of a laser-plasma optical system's refractive index, as seen by a second probe laser beam, as a function of the relative wavelength shift between the two laser beams. Both the imaginary and real refractive index components are found to be in good agreement with linear theory using plasma parameters measured by optical Thomson scattering and interferometry; the former is in contrast to previous work and has implications for crossed-beam energy transfer in indirect-drive inertial confinement fusion, and the latter is measured for the first time. The data include the first demonstration of a laser-plasma polarizer with 85 %- 87 % extinction for the particular laser and plasma parameters used in this experiment, complementing the existing suite of high-power, tunable, and ultrafast plasma-based photonic devices.

Refractive Index Seen by a Probe Beam Interacting with a Laser-Plasma System.

PubMed

Turnbull, D; Goyon, C; Kemp, G E; Pollock, B B; Mariscal, D; Divol, L; Ross, J S; Patankar, S; Moody, J D; Michel, P

2017-01-06

We report the first complete set of measurements of a laser-plasma optical system's refractive index, as seen by a second probe laser beam, as a function of the relative wavelength shift between the two laser beams. Both the imaginary and real refractive index components are found to be in good agreement with linear theory using plasma parameters measured by optical Thomson scattering and interferometry; the former is in contrast to previous work and has implications for crossed-beam energy transfer in indirect-drive inertial confinement fusion, and the latter is measured for the first time. The data include the first demonstration of a laser-plasma polarizer with 85%-87% extinction for the particular laser and plasma parameters used in this experiment, complementing the existing suite of high-power, tunable, and ultrafast plasma-based photonic devices.

A line scanned light-sheet microscope with phase shaped self-reconstructing beams.

PubMed

Fahrbach, Florian O; Rohrbach, Alexander

2010-11-08

We recently demonstrated that Microscopy with Self-Reconstructing Beams (MISERB) increases both image quality and penetration depth of illumination beams in strongly scattering media. Based on the concept of line scanned light-sheet microscopy, we present an add-on module to a standard inverted microscope using a scanned beam that is shaped in phase and amplitude by a spatial light modulator. We explain technical details of the setup as well as of the holograms for the creation, positioning and scaling of static light-sheets, Gaussian beams and Bessel beams. The comparison of images from identical sample areas illuminated by different beams allows a precise assessment of the interconnection between beam shape and image quality. The superior propagation ability of Bessel beams through inhomogeneous media is demonstrated by measurements on various scattering media.

Beam position monitoring system at CESR

NASA Astrophysics Data System (ADS)

Billing, M. G.; Bergan, W. F.; Forster, M. J.; Meller, R. E.; Rendina, M. C.; Rider, N. T.; Sagan, D. C.; Shanks, J.; Sikora, J. P.; Stedinger, M. G.; Strohman, C. R.; Palmer, M. A.; Holtzapple, R. L.

2017-09-01

The Cornell Electron-positron Storage Ring (CESR) has been converted from a High Energy Physics electron-positron collider to operate as a dedicated synchrotron light source for the Cornell High Energy Synchrotron Source (CHESS) and to conduct accelerator physics research as a test accelerator, capable of studying topics relevant to future damping rings, colliders and light sources. Some of the specific topics that were targeted for the initial phase of operation of the storage ring in this mode, labeled CESRTA (CESR as a Test Accelerator), included 1) tuning techniques to produce low emittance beams, 2) the study of electron cloud development in a storage ring and 3) intra-beam scattering effects. The complete conversion of CESR to CESRTA occurred over a several year period and is described elsewhere. As a part of this conversion the CESR beam position monitoring (CBPM) system was completely upgraded to provide the needed instrumental capabilities for these studies. This paper describes the new CBPM system hardware, its function and representative measurements performed by the upgraded system.

Monte Carlo-based parametrization of the lateral dose spread for clinical treatment planning of scanned proton and carbon ion beams.

PubMed

Parodi, Katia; Mairani, Andrea; Sommerer, Florian

2013-07-01

Ion beam therapy using state-of-the-art pencil-beam scanning offers unprecedented tumour-dose conformality with superior sparing of healthy tissue and critical organs compared to conventional radiation modalities for external treatment of deep-seated tumours. For inverse plan optimization, the commonly employed analytical treatment-planning systems (TPSs) have to meet reasonable compromises in the accuracy of the pencil-beam modelling to ensure good performances in clinically tolerable execution times. In particular, the complex lateral spreading of ion beams in air and in the traversed tissue is typically approximated with ideal Gaussian-shaped distributions, enabling straightforward superimposition of several scattering contributions. This work presents the double Gaussian parametrization of scanned proton and carbon ion beams in water that has been introduced in an upgraded version of the worldwide first commercial ion TPS for clinical use at the Heidelberg Ion Beam Therapy Center (HIT). First, the Monte Carlo results obtained from a detailed implementation of the HIT beamline have been validated against available experimental data. Then, for generating the TPS lateral parametrization, radial beam broadening has been calculated in a water target placed at a representative position after scattering in the beamline elements and air for 20 initial beam energies for each ion species. The simulated profiles were finally fitted with an idealized double Gaussian distribution that did not perfectly describe the nature of the data, thus requiring a careful choice of the fitting conditions. The obtained parametrization is in clinical use not only at the HIT center, but also at the Centro Nazionale di Adroterapia Oncologica.

Monte Carlo-based parametrization of the lateral dose spread for clinical treatment planning of scanned proton and carbon ion beams

PubMed Central

Parodi, Katia; Mairani, Andrea; Sommerer, Florian

2013-01-01

Ion beam therapy using state-of-the-art pencil-beam scanning offers unprecedented tumour-dose conformality with superior sparing of healthy tissue and critical organs compared to conventional radiation modalities for external treatment of deep-seated tumours. For inverse plan optimization, the commonly employed analytical treatment-planning systems (TPSs) have to meet reasonable compromises in the accuracy of the pencil-beam modelling to ensure good performances in clinically tolerable execution times. In particular, the complex lateral spreading of ion beams in air and in the traversed tissue is typically approximated with ideal Gaussian-shaped distributions, enabling straightforward superimposition of several scattering contributions. This work presents the double Gaussian parametrization of scanned proton and carbon ion beams in water that has been introduced in an upgraded version of the worldwide first commercial ion TPS for clinical use at the Heidelberg Ion Beam Therapy Center (HIT). First, the Monte Carlo results obtained from a detailed implementation of the HIT beamline have been validated against available experimental data. Then, for generating the TPS lateral parametrization, radial beam broadening has been calculated in a water target placed at a representative position after scattering in the beamline elements and air for 20 initial beam energies for each ion species. The simulated profiles were finally fitted with an idealized double Gaussian distribution that did not perfectly describe the nature of the data, thus requiring a careful choice of the fitting conditions. The obtained parametrization is in clinical use not only at the HIT center, but also at the Centro Nazionale di Adroterapia Oncologica. PMID:23824133

The effects of scattering on the relative LPI performance of optical and mm-wave systems

NASA Astrophysics Data System (ADS)

Oetting, John; Hampton, Jerry

1988-01-01

Previous results comparing the LPI performance of optical and millimeter-wave satellite systems is extended to include the effects of scattering on optical LPI performance. The LPI figure of merit used to compare the two media is the circular equivalent vulnerability radius (CEVR). The CEVR is calculated for typical optical and spread spectrum millimeter-wave systems, and the LPI performance tradeoffs available with each medium are compared. Attention is given to the possibility that light will be scattered into the interceptor's FOV and thereby enable detection in geometries in which interception of the main beam is impossible. The effects of daytime vs. nighttime operation of the optical LPI system are also considered. Some illustrative results for the case of a ground-to-space uplink to a low earth orbit satellite are presented, along with some conclusions and unresolved issues for further study.

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).

Collective effects in the Thomson back-scattering between a laser pulse and a relativistic electron beam

NASA Astrophysics Data System (ADS)

Bacci, A.; Maroli, C.; Petrillo, V.; Serafini, L.

2006-08-01

Collective effects in the radiation emission via Thomson back-scattering of an intense optical laser pulse by high brightness electron beams are analyzed. The micro-bunching of the electron beam on the scale of the wavelength of the emitted radiation and the consequent free-electron-laser instability may significantly enhance the number of photons emitted. Scaling-laws of the radiation properties, both in the collective and incoherent spontaneous regimes versus laser and electron beam parameters are discussed in the framework of the one-dimensional model.

Beam energy spread in FERMI@elettra gun and linac induced by intrabeam scattering

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

Zholents, Alexander A; Zholents, Alexander A; Zolotorev, Max S.

Intrabeam scattering (IBS) of electrons in the pre-cathode area in the electron guns know in the literature as Boersh effect is responsible for a growth of the electron beam energy spread there. Albeit most visible within the electron gun where the electron beam density is large and the energy spread is small, the IBS acts all along the entire electron beam pass through the Linac. In this report we calculate the energy spread induced by IBS in the FERMI@elettra electron gun.

Influence of scatter reduction method and monochromatic beams on image quality and dose in mammography.

PubMed

Moeckli, Raphaël; Verdun, Francis R; Fiedler, Stefan; Pachoud, Marc; Bulling, Shelley; Schnyder, Pierre; Valley, Jean-François

2003-12-01

In mammography, the image contrast and dose delivered to the patient are determined by the x-ray spectrum and the scatter to primary ratio S/P. Thus the quality of the mammographic procedure is highly dependent on the choice of anode and filter material and on the method used to reduce the amount of scattered radiation reaching the detector. Synchrotron radiation is a useful tool to study the effect of beam energy on the optimization of the mammographic process because it delivers a high flux of monochromatic photons. Moreover, because the beam is naturally flat collimated in one direction, a slot can be used instead of a grid for scatter reduction. We have measured the ratio S/P and the transmission factors for grids and slots for monoenergetic synchrotron radiation. In this way the effect of beam energy and scatter rejection method were separated, and their respective importance for image quality and dose analyzed. Our results show that conventional mammographic spectra are not far from optimum and that the use of a slot instead of a grid has an important effect on the optimization of the mammographic process. We propose a simple numerical model to quantify this effect.

Narrow bandwidth Laser-Plasma Accelerator driven Thomson photon source development

NASA Astrophysics Data System (ADS)

Geddes, C. G. R.; Tsai, H.-E.; Otero, G.; Liu, X.; van Tilborg, J.; Toth, Cs.; Vay, J.-L.; Lehe, R.; Schroeder, C. B.; Esarey, E.; Friedman, A.; Grote, D. P.; Leemans, W. P.

2017-10-01

Compact, high-quality photon sources at MeV energies can be provided by Thomson scattering of a laser from the electron beam of a Laser-Plasma Accelerator (LPA). Recent experiments and simulations demonstrate controllable LPAs in the energy range appropriate to MeV sources. Simulations indicate that high flux with narrow energy spread can be achieved via control of the scattering laser pulse shape and laser guiding, and that undesired background bremsstrahlung can be mitigated by plasma based deceleration of the electron beam after photon production. Construction of experiments and laser capabilities to combine these elements will be presented, along with initial operations, towards a compact photon source system. Work supported by US DOE NNSA DNN R&D and by Sc. HEP under contract DE-AC02-05CH11231.

5 MeV Mott Polarimeter Development at Jefferson Lab

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

Price, J. S.; Sinclair, C. K.; Cardman, L. S.

1997-01-01

Low energy (E{sub k}=100 keV) Mott scattering polarimeters are ill- suited to support operations foreseen for the polarized electron injector at Jefferson Lab. One solution is to measure the polarization at 5 MeV where multiple and plural scattering are unimportant and precision beam monitoring is straightforward. The higher injector beam current offsets the lower cross-sections. Recent improvements in the CEBAF injector polarimeter scattering chamber have improved signal to noise.

Measuring the Contribution of Atmospheric Scatter to Laser Eye Dazzle

DTIC Science & Technology

2015-09-01

alignment of the detector was then fine tuned to ensure that the reflected beam traveled perfectly back through the aperture, thus indicating normal...spanning June and July 2014. A narrow acceptance angle detector was used to measure scattered laser radiation within the laser beam at different... scatter does not make a significant contribution to laser eye dazzle for short-range laser engagements in atmospheres of good to moderate air quality

Novel micro-reactor flow cell for investigation of model catalysts using in situ grazing-incidence X-ray scattering

PubMed Central

Kehres, Jan; Pedersen, Thomas; Masini, Federico; Andreasen, Jens Wenzel; Nielsen, Martin Meedom; Diaz, Ana; Nielsen, Jane Hvolbæk; Hansen, Ole

2016-01-01

The design, fabrication and performance of a novel and highly sensitive micro-reactor device for performing in situ grazing-incidence X-ray scattering experiments of model catalyst systems is presented. The design of the reaction chamber, etched in silicon on insulator (SIO), permits grazing-incidence small-angle X-ray scattering (GISAXS) in transmission through 10 µm-thick entrance and exit windows by using micro-focused beams. An additional thinning of the Pyrex glass reactor lid allows simultaneous acquisition of the grazing-incidence wide-angle X-ray scattering (GIWAXS). In situ experiments at synchrotron facilities are performed utilizing the micro-reactor and a designed transportable gas feed and analysis system. The feasibility of simultaneous in situ GISAXS/GIWAXS experiments in the novel micro-reactor flow cell was confirmed with CO oxidation over mass-selected Ru nanoparticles. PMID:26917133

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.

Precise optical dosimetry in low-level laser therapy of soft tissues in oral cavity

NASA Astrophysics Data System (ADS)

Stoykova, Elena V.; Sabotinov, O.

2004-06-01

The new low level laser therapy (LLLT) is widely applied for treatment of diseases of the oral mucosa and parodont. Depending on indication, different optical tips and light-guides are used to create beams with a required shape. However, to the best of our knowledge, the developed irradiation geometries are usually proposed assuming validity of Bouger-Lambert law. This hardly corresponds to the real situation because of the dominating multiple scattering within 600-1200 nm range that destroys correlation between the emitted laser beam and the spatial distribution of the absorbed dose inside the tissue. The aim of this work is to base the dosimetry of the LLLT procedures of periodontal tissues on radiation transfer theory using a flexible Monte-Carlo code. We studied quantitatively the influence of tissue optical parameters (absorption and scattering coefficients, tissue refraction index, anisotropy factor) on decreasing of correlation between the emitted beam and the energy deposition for converging or diverging beams. We evaluated energy deposition for the developed by us LLLT system in a 3-D model of periodontal tissues created using a cross-sectional image of this region with internal structural information on the gingival and the tooth. The laser source is a CW diode laser emitting elliptical beam within 650-675 nm at output power 5-30 mW. To determine the geometry of the irradiating beam we used CCD camera Spiricon LBA 300.

The design of the optical Thomson scattering diagnostic for the National Ignition Facility [The preliminary design of the optical Thomson scattering diagnostic for the National Ignition Facility

DOE PAGES

Datte, P. S.; Ross, J. S.; Froula, D. H.; ...

2016-09-21

Here, the National Ignition Facility (NIF) is a 192 laser beam facility designed to support the Stockpile Stewardship, High Energy Density and Inertial Confinement Fusion (ICF) programs. We report on the design of an Optical Thomson Scattering (OTS) diagnostic that has the potential to transform the community’s understanding of NIF hohlraum physics by providing first principle, local, time-resolved measurements of under-dense plasma conditions. The system design allows operation with different probe laser wavelengths by manual selection of the appropriate beam splitter and gratings before the shot. A deep-UV probe beam (λ 0-210 nm) will be used to optimize the scatteredmore » signal for plasma densities of 5 × 10 20 electrons/cm 3 while a 3ω probe will be used for experiments investigating lower density plasmas of 1 × 10 19 electrons/cm 3. We report the phase I design of a two phase design strategy. Phase I includes the OTS telescope, spectrometer, and streak camera; these will be used to assess the background levels at NIF. Phase II will include the design and installation of a probe laser.« less

The design of the optical Thomson scattering diagnostic for the National Ignition Facility [The preliminary design of the optical Thomson scattering diagnostic for the National Ignition Facility

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

Datte, P. S.; Ross, J. S.; Froula, D. H.

Here, the National Ignition Facility (NIF) is a 192 laser beam facility designed to support the Stockpile Stewardship, High Energy Density and Inertial Confinement Fusion (ICF) programs. We report on the design of an Optical Thomson Scattering (OTS) diagnostic that has the potential to transform the community’s understanding of NIF hohlraum physics by providing first principle, local, time-resolved measurements of under-dense plasma conditions. The system design allows operation with different probe laser wavelengths by manual selection of the appropriate beam splitter and gratings before the shot. A deep-UV probe beam (λ 0-210 nm) will be used to optimize the scatteredmore » signal for plasma densities of 5 × 10 20 electrons/cm 3 while a 3ω probe will be used for experiments investigating lower density plasmas of 1 × 10 19 electrons/cm 3. We report the phase I design of a two phase design strategy. Phase I includes the OTS telescope, spectrometer, and streak camera; these will be used to assess the background levels at NIF. Phase II will include the design and installation of a probe laser.« less

Development of online automatic detector of hydrocarbons and suspended organic matter by simultaneously acquisition of fluorescence and scattering.

PubMed

Mbaye, Moussa; Diaw, Pape Abdoulaye; Gaye-Saye, Diabou; Le Jeune, Bernard; Cavalin, Goulven; Denis, Lydie; Aaron, Jean-Jacques; Delmas, Roger; Giamarchi, Philippe

2018-03-05

Permanent online monitoring of water supply pollution by hydrocarbons is needed for various industrial plants, to serve as an alert when thresholds are exceeded. Fluorescence spectroscopy is a suitable technique for this purpose due to its sensitivity and moderate cost. However, fluorescence measurements can be disturbed by the presence of suspended organic matter, which induces beam scattering and absorption, leading to an underestimation of hydrocarbon content. To overcome this problem, we propose an original technique of fluorescence spectra correction, based on a measure of the excitation beam scattering caused by suspended organic matter on the left side of the Rayleigh scattering spectral line. This correction allowed us to obtain a statistically validated estimate of the naphthalene content (used as representative of the polyaromatic hydrocarbon contamination), regardless of the amount of suspended organic matter in the sample. Moreover, it thus becomes possible, based on this correction, to estimate the amount of suspended organic matter. By this approach, the online warning system remains operational even when suspended organic matter is present in the water supply. Copyright © 2017 Elsevier B.V. All rights reserved.

Geometrical correction of the e-beam proximity effect for raster scan systems

NASA Astrophysics Data System (ADS)

Belic, Nikola; Eisenmann, Hans; Hartmann, Hans; Waas, Thomas

1999-06-01

Increasing demands on pattern fidelity and CD accuracy in e- beam lithography require a correction of the e-beam proximity effect. The new needs are mainly coming from OPC at mask level and x-ray lithography. The e-beam proximity limits the achievable resolution and affects neighboring structures causing under- or over-exposion depending on the local pattern densities and process settings. Methods to compensate for this unequilibrated does distribution usually use a dose modulation or multiple passes. In general raster scan systems are not able to apply variable doses in order to compensate for the proximity effect. For system of this kind a geometrical modulation of the original pattern offers a solution for compensation of line edge deviations due to the proximity effect. In this paper a new method for the fast correction of the e-beam proximity effect via geometrical pattern optimization is described. The method consists of two steps. In a first step the pattern dependent dose distribution caused by back scattering is calculated by convolution of the pattern with the long range part of the proximity function. The restriction to the long range part result in a quadratic sped gain in computing time for the transformation. The influence of the short range part coming from forward scattering is not pattern dependent and can therefore be determined separately in a second step. The second calculation yields the dose curve at the border of a written structure. The finite gradient of this curve leads to an edge displacement depending on the amount of underground dosage at the observed position which was previously determined in the pattern dependent step. This unintended edge displacement is corrected by splitting the line into segments and shifting them by multiples of the writers address grid to the opposite direction.

Effect of secondary electron generation on dose enhancement in Lipiodol with and without a flattening filter.

PubMed

Kawahara, Daisuke; Ozawa, Shuichi; Saito, Akito; Kimura, Tomoki; Suzuki, Tatsuhiko; Tsuneda, Masato; Tanaka, Sodai; Nakashima, Takeo; Ohno, Yoshimi; Murakami, Yuji; Nagata, Yasushi

2018-03-01

Lipiodol, which was used in transcatheter arterial chemoembolization before liver stereotactic body radiation therapy (SBRT), remains in SBRT. Previous we reported the dose enhancement in Lipiodol using 10 MV (10×) FFF beam. In this study, we compared the dose enhancement in Lipiodol and evaluated the probability of electron generation (PEG) for the dose enhancement using flattening filter (FF) and flattening filter free (FFF) beams. FF and FFF for 6 MV (6×) and 10× beams were delivered by TrueBeam. The dose enhancement factor (DEF), energy spectrum, and PEG was calculated using Monte Carlo (MC) code BEAMnrc and heavy ion transport code system (PHITS). DEFs for FF and FFF 6× beams were 7.0% and 17.0% at the center of Lipiodol (depth, 6.5 cm). DEFs for FF and FFF 10× beams were 8.2% and 10.5% at the center of Lipiodol. Spectral analysis revealed that the FFF beams contained more low-energy (0-0.3 MeV) electrons than the FF beams, and the FF beams contained more high-energy (>0.3 MeV) electrons than the FFF beams in Lipiodol. The difference between FFF and FF beam DEFs was larger for 6× than for 10×. This occurred because the 10× beams contained more high-energy electrons. The PEGs for photoelectric absorption and Compton scattering for the FFF beams were higher than those for the FF beams. The PEG for the photoelectric absorption was higher than that for Compton scattering. FFF beam contained more low-energy photons and it contributed to the dose enhancement. Energy spectra and PEGs are useful for analyzing the mechanisms of dose enhancement. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

A nonlinear OPC technique for laser beam control in turbulent atmosphere

NASA Astrophysics Data System (ADS)

Markov, V.; Khizhnyak, A.; Sprangle, P.; Ting, A.; DeSandre, L.; Hafizi, B.

2013-05-01

A viable beam control technique is critical for effective laser beam transmission through turbulent atmosphere. Most of the established approaches require information on the impact of perturbations on wavefront propagated waves. Such information can be acquired by measuring the characteristics of the target-scattered light arriving from a small, preferably diffraction-limited, beacon. This paper discusses an innovative beam control approach that can support formation of a tight laser beacon in deep turbulence conditions. The technique employs Brillouin enhanced fourwave mixing (BEFWM) to generate a localized beacon spot on a remote image-resolved target. Formation of the tight beacon doesn't require a wavefront sensor, AO system, or predictive feedback algorithm. Unlike conventional adaptive optics methods which allow wavefront conjugation, the proposed total field conjugation technique is critical for beam control in the presence of strong turbulence and can be achieved by using this non-linear BEFWM technique. The phase information retrieved from the established beacon beam can then be used in conjunction with an AO system to propagate laser beams in deep turbulence.

Physics and applications of positron beams in an integrated PET/MR.

PubMed

Watson, Charles C; Eriksson, Lars; Kolb, Armin

2013-02-07

In PET/MR systems having the PET component within the uniform magnetic field interior to the MR, positron beams can be injected into the PET field of view (FOV) from unshielded emission sources external to it, as a consequence of the action of the Lorentz force on the transverse components of the positron's velocity. Such beams may be as small as a few millimeters in diameter, but extend 50 cm or more axially without appreciable divergence. Larger beams form 'phantoms' of annihilations in air that can be easily imaged, and that are essentially free of γ-ray attenuation and scatter effects, providing a unique tool for characterizing PET systems and reconstruction algorithms. Thin targets intersecting these beams can produce intense annihilation sources having the thickness of a sheet of paper, which are very useful for high resolution measurements, and difficult to achieve with conventional sources. Targeted beams can provide other point, line and surface sources for various applications, all without the need to have radioactivity within the FOV. In this paper we discuss the physical characteristics of positron beams in air and present examples of their applications.

Modeling of beam customization devices in the pencil-beam splitting algorithm for heavy charged particle radiotherapy.

PubMed

Kanematsu, Nobuyuki

2011-03-07

A broad-beam-delivery system for radiotherapy with protons or ions often employs multiple collimators and a range-compensating filter, which offer complex and potentially useful beam customization. It is however difficult for conventional pencil-beam algorithms to deal with fine structures of these devices due to beam-size growth during transport. This study aims to avoid the difficulty with a novel computational model. The pencil beams are initially defined at the range-compensating filter with angular-acceptance correction for upstream collimation followed by stopping and scattering. They are individually transported with possible splitting near the aperture edge of a downstream collimator to form a sharp field edge. The dose distribution for a carbon-ion beam was calculated and compared with existing experimental data. The penumbra sizes of various collimator edges agreed between them to a submillimeter level. This beam-customization model will be used in the greater framework of the pencil-beam splitting algorithm for accurate and efficient patient dose calculation.

Upgraded divertor Thomson scattering system on DIII-D

NASA Astrophysics Data System (ADS)

Glass, F.; Carlstrom, T. N.; Du, D.; McLean, A. G.; Taussig, D. A.; Boivin, R. L.

2016-11-01

A design to extend the unique divertor Thomson scattering system on DIII-D to allow measurements of electron temperature and density in high triangularity plasmas is presented. Access to this region is selectable on a shot-by-shot basis by redirecting the laser beam of the existing divertor Thomson system inboard — beneath the lower floor using a moveable, high-damage threshold, in-vacuum mirror — and then redirecting again vertically. The currently measured divertor region remains available with this mirror retracted. Scattered light is collected from viewchords near the divertor floor using in-vacuum, high temperature optical elements and relayed through the port window, before being coupled into optical fiber bundles. At higher elevations from the floor, measurements are made by dynamically re-focusing the existing divertor system collection optics. Nd:YAG laser timing, analysis of the scattered light spectrum via polychromators, data acquisition, and calibration are all handled by existing systems or methods of the current multi-pulse Thomson scattering system. Existing filtered polychromators with 7 spectral channels are employed to provide maximum measurement breadth (Te in the range of 0.5 eV-2 keV, ne in the range of 5 × 1018-1 × 1021 m3) for both low Te in detachment and high Te measurement up beyond the separatrix.

Upgraded divertor Thomson scattering system on DIII-D.

PubMed

Glass, F; Carlstrom, T N; Du, D; McLean, A G; Taussig, D A; Boivin, R L

2016-11-01

A design to extend the unique divertor Thomson scattering system on DIII-D to allow measurements of electron temperature and density in high triangularity plasmas is presented. Access to this region is selectable on a shot-by-shot basis by redirecting the laser beam of the existing divertor Thomson system inboard - beneath the lower floor using a moveable, high-damage threshold, in-vacuum mirror - and then redirecting again vertically. The currently measured divertor region remains available with this mirror retracted. Scattered light is collected from viewchords near the divertor floor using in-vacuum, high temperature optical elements and relayed through the port window, before being coupled into optical fiber bundles. At higher elevations from the floor, measurements are made by dynamically re-focusing the existing divertor system collection optics. Nd:YAG laser timing, analysis of the scattered light spectrum via polychromators, data acquisition, and calibration are all handled by existing systems or methods of the current multi-pulse Thomson scattering system. Existing filtered polychromators with 7 spectral channels are employed to provide maximum measurement breadth (T e in the range of 0.5 eV-2 keV, n e in the range of 5 × 10 18 -1 × 10 21 m 3 ) for both low T e in detachment and high T e measurement up beyond the separatrix.

Effect of the magnetic field on coexisting stimulated Raman and Brillouin backscattering of an extraordinary mode

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

Vyas, Ashish, E-mail: ashishvyas.optics@gmail.com; Singh, Ram Kishor, E-mail: ram007kishor@gmail.com; Sharma, R. P., E-mail: rpsharma@ces.iitd.ernet.in

2016-01-15

This paper presents a model to study the interplay between the stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) in the presence of background magnetic field. This formalism is applicable to laser produced plasma as well as to heating mechanism in toroidal system by an extraordinary electromagnetic wave. In the former case, the magnetic field is self-generated, while in the latter case (toroidal plasmas) magnetic field is applied externally. The behavior of one scattering process is explicitly dependent on the coexisting scattering process as well as on the magnetic field. Explicit expressions for the back-reflectivity of scattered beams (SRSmore » and SBS) are presented. It has been demonstrated that due to the magnetic field and coexistence of the scattering processes (SRS and SBS) the back-reflectivity gets modified significantly. Results are also compared with the three wave interaction case (isolated SRS or SBS case)« less

Nuclear rainbow in elastic scattering of {sup 9}Be nuclei

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

Glukhov, Yu. A., E-mail: gloukhov@inbox.ru; Ogloblin, A. A.; Artemov, K. P.

2010-01-15

A systematic investigation of the elastic scattering of the {sup 9}Be nucleus, which is among themost loosely bound stable nuclei was performed.Differential cross sections for elastic {sup 9}Be + {sup 16}O scattering were measured at a c.m. energy of 47.5 MeV (beam of 132-MeV {sup 16}O nuclei). Available data at different energy values and data for neighboring nuclei were included in our analysis. As a result, the very fact of rainbow scattering was reliably established for the first time in systems involving {sup 9}Be. In addition, the analysis in question made it possible to identify Airy minima and to determinemore » unambiguously the nucleus-nucleus potential with a high probability.« less

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

Kyriakou, Ioanna; Emfietzoglou, Dimitris; Nojeh, Alireza

A systematic study of electron-beam penetration and backscattering in multi-walled carbon nanotube (MWCNT) materials for beam energies of {approx}0.3 to 30 keV is presented based on event-by-event Monte Carlo simulation of electron trajectories using state-of-the-art scattering cross sections. The importance of different analytic approximations for computing the elastic and inelastic electron-scattering cross sections for MWCNTs is emphasized. We offer a simple parameterization for the total and differential elastic-scattering Mott cross section, using appropriate modifications to the Browning formula and the Thomas-Fermi screening parameter. A discrete-energy-loss approach to inelastic scattering based on dielectric theory is adopted using different descriptions of themore » differential cross section. The sensitivity of electron penetration and backscattering parameters to the underlying scattering models is examined. Our simulations confirm the recent experimental backscattering data on MWCNT forests and, in particular, the steep increase of the backscattering yield at sub-keV energies as well as the sidewalls escape effect at high-beam energies.« less

Beam production of 18Ne with in-flight method for alpha scattering at CRIB

NASA Astrophysics Data System (ADS)

Duy, N. N.; Chae, K. Y.; Cha, S. M.; Yamaguchi, H.; Abe, K.; Bae, S. H.; Binh, D. N.; Choi, S. H.; Hahn, K. I.; Hayakawa, S.; Hong, B.; Iwasa, N.; Kahl, D.; Khiem, L. H.; Kim, A.; Kim, D. H.; Kim, E. J.; Kim, G. W.; Kim, M. J.; Kwak, K.; Kwag, M. S.; Lee, E. J.; Lim, S. I.; Moon, B.; Moon, J. Y.; Park, S. Y.; Phong, V. H.; Shimizu, H.; Yang, L.; Ge, Z.; Hao, T. V. Nhan

2018-07-01

We conducted a measurement of 18Ne + α scattering in inverse kinematics, in order to search for experimental evidence of α-cluster structure in 22Mg above the alpha threshold (Ethr = 8 . 14 MeV) and determine the astrophysical rates of the 18Ne(α, p)21Na reaction under the conditions of break-out from the Hot-CNO cycle. A high intensity 18Ne beam at 2.54 AMeV was successfully produced at CRIB (CNS Radioactive Ion Beam separator) of the Center for Nuclear Study, the University of Tokyo. This paper presents the in-flight production of the radioactive 18Ne beam by using the production reaction 3He(16O, 18Ne)n with a windowed cryogenic gas target, which was employed in the mentioned resonant α-scattering experiment.

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.

Ultraviolet laser beam monitor using radiation responsive crystals

DOEpatents

McCann, Michael P.; Chen, Chung H.

1988-01-01

An apparatus and method for monitoring an ultraviolet laser beam includes disposing in the path of an ultraviolet laser beam a substantially transparent crystal that will produce a color pattern in response to ultraviolet radiation. The crystal is exposed to the ultraviolet laser beam and a color pattern is produced within the crystal corresponding to the laser beam intensity distribution therein. The crystal is then exposed to visible light, and the color pattern is observed by means of the visible light to determine the characteristics of the laser beam that passed through crystal. In this manner, a perpendicular cross sectional intensity profile and a longitudinal intensity profile of the ultraviolet laser beam may be determined. The observation of the color pattern may be made with forward or back scattered light and may be made with the naked eye or with optical systems such as microscopes and television cameras.

Return Current Electron Beams and Their Generation of "Raman" Scattering

NASA Astrophysics Data System (ADS)

Simon, A.

1998-11-01

For some years, we(A. Simon and R. W. Short, Phys. Rev. Lett. 53), 1912 (1984). have proposed that the only reasonable explanation for many of the observations of "Raman" scattering is the presence of an electron beam in the plasma. (The beam creates a bump-on-tail instability.) Two major objections to this picture have been observation of Raman when no n_c/4 surface was present, with no likely source for the electron beam, and the necessity for the initially outward directed beam to bounce once to create the proper waves. Now new observations on LLE's OMEGA(R. Petrasso et al), this conference. and at LULI(C. Labaune et al)., Phys. Plasma 5, 234 (1998). have suggested a new origin for the electron beam. This new scenario answers the previous objections, maintains electron beams as the explanation of the older experiments, and may clear up puzzling observations that have remained unexplained. The new scenario is based on two assumptions: (1) High positive potentials develop in target plasmas during their creation. (2) A high-intensity laser beam initiates spark discharges from nearby surfaces to the target plasma. The resulting return current of electrons should be much more delta-like, is initially inwardly directed, and no longer requires the continued presence of a n_c/4 surface. Scattering of the interaction beam from the BOT waves yields the observed Raman signal. Experimental observations that support this picture will be cited. ``Pulsation'' of the scattering and broadband ``flashes'' are a natural part of this scenario. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460.

Thermal management and prototype testing of Compton scattering X-ray beam position monitor for the Advanced Photon Source Upgrade

NASA Astrophysics Data System (ADS)

Lee, S. H.; Yang, B. X.; Collins, J. T.; Ramanathan, M.

2017-02-01

Accurate and stable x-ray beam position monitors (XBPMs) are key elements in obtaining the desired user beam stability in the Advanced Photon Source Upgrade. In the next-generation XBPMs for the canted-undulator front ends, where two undulator beams are separated by 1.0 mrad, the lower beam power (<10 kW) per undulator allows us to explore lower-cost solutions based on Compton scattering from a diamond placed edge-on to the x-ray beam. Because of the high peak power density of the x-ray beams, this diamond experiences high temperatures and has to be clamped to a water-cooled heat spreader using thermal interface materials (TIMs), which play a key role in reducing the temperature of the diamond. To evaluate temperature changes through the interface via thermal simulations, the thermal contact resistance (TCR) of TIMs at an interface between two solid materials under even contact pressure must be known. This paper addresses the TCR measurements of several TIMs, including gold, silver, pyrolytic graphite sheet, and 3D graphene foam. In addition, a prototype of a Compton-scattering XBPM with diamond blades was installed at APS Beamline 24-ID-A in May 2015 and has been tested. This paper presents the design of the Compton-scattering XBPM, and compares thermal simulation results obtained for the diamond blade of this XBPM by the finite element method with in situ empirical measurements obtained by using reliable infrared technology.

Thermal management and prototype testing of Compton scattering X-ray beam position monitor for the Advanced Photon Source Upgrade.

PubMed

Lee, S H; Yang, B X; Collins, J T; Ramanathan, M

2017-02-01

Accurate and stable x-ray beam position monitors (XBPMs) are key elements in obtaining the desired user beam stability in the Advanced Photon Source Upgrade. In the next-generation XBPMs for the canted-undulator front ends, where two undulator beams are separated by 1.0 mrad, the lower beam power (<10 kW) per undulator allows us to explore lower-cost solutions based on Compton scattering from a diamond placed edge-on to the x-ray beam. Because of the high peak power density of the x-ray beams, this diamond experiences high temperatures and has to be clamped to a water-cooled heat spreader using thermal interface materials (TIMs), which play a key role in reducing the temperature of the diamond. To evaluate temperature changes through the interface via thermal simulations, the thermal contact resistance (TCR) of TIMs at an interface between two solid materials under even contact pressure must be known. This paper addresses the TCR measurements of several TIMs, including gold, silver, pyrolytic graphite sheet, and 3D graphene foam. In addition, a prototype of a Compton-scattering XBPM with diamond blades was installed at APS Beamline 24-ID-A in May 2015 and has been tested. This paper presents the design of the Compton-scattering XBPM, and compares thermal simulation results obtained for the diamond blade of this XBPM by the finite element method with in situ empirical measurements obtained by using reliable infrared technology.

SU-E-T-375: Passive Scattering to Pencil-Beam-Scanning Comparison for Medulloblastoma Proton Therapy: LET Distributions and Radiobiological Implications

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

Giantsoudi, D; MacDonald, S; Paganetti, H

2014-06-01

Purpose: To compare the linear energy transfer (LET) distributions between passive scattering and pencil beam scanning proton radiation therapy techniques for medulloblastoma patients and study the potential radiobiological implications. Methods: A group of medulloblastoma patients, previously treated with passive scattering (PS) proton craniospinal irradiation followed by prosterior fossa or involved field boost, were selected from the patient database of our institution. Using the beam geometry and planning computed tomography (CT) image sets of the original treatment plans, pencil beam scanning (PBS) treatment plans were generated for the cranial treatment for each patient, with average beam spot size of 8mm (sigmamore » in air at isocenter). 3-dimensional dose and LET distributions were calculated by Monte Carlo methods (TOPAS) both for the original passive scattering and new pencil beam scanning treatment plans. LET volume histograms were calculated for the target and OARs and compared for the two delivery methods. Variable RBE weighted dose distributions and volume histograms were also calculated using a variable dose and LET-based model. Results: Better dose conformity was achieved with PBS planning compared to PS, leading to increased dose coverage for the boost target area and decreased average dose to the structures adjacent to it and critical structures outside the whole brain treatment field. LET values for the target were lower for PBS plans. Elevated LET values for OARs close to the boosted target areas were noticed, due to end of range of proton beams falling inside these structures, resulting in higher RBE weighted dose for these structures compared to the clinical RBE value of 1.1. Conclusion: Transitioning from passive scattering to pencil beam scanning proton radiation treatment can be dosimetrically beneficial for medulloblastoma patients. LET–guided treatment planning could contribute to better decision making for these cases, especially for critical structures at close proximity to the boosted target area.« less

Experimental electron energy-loss spectra and cross sections for the 4/2/S - 4/2/P transition in Zn II

NASA Technical Reports Server (NTRS)

Chutjian, A.; Newell, W. R.

1982-01-01

Electron energy-loss spectra and differential cross sections are reported for inelastic scattering from Zn II. Measurements were carried out in a crossed electron beam-ion beam apparatus, at incident electron energies of 30, 40, 50, 60, 75, 85, and 100 eV, and at a scattering angle of 14 deg. The present results are the first reported measurements of inelastic electron scattering from an ion.

Experimental study: Underwater propagation of polarized flat top partially coherent laser beams with a varying degree of spatial coherence

NASA Astrophysics Data System (ADS)

Avramov-Zamurovic, S.; Nelson, C.

2018-10-01

We report on experiments where spatially partially coherent laser beams with flat top intensity profiles were propagated underwater. Two scenarios were explored: still water and mechanically moved entrained salt scatterers. Gaussian, fully spatially coherent beams, and Multi-Gaussian Schell model beams with varying degrees of spatial coherence were used in the experiments. The main objective of our study was the exploration of the scintillation performance of scalar beams, with both vertical and horizontal polarizations, and the comparison with electromagnetic beams that have a randomly varying polarization. The results from our investigation show up to a 50% scintillation index reduction for the case with electromagnetic beams. In addition, we observed that the fully coherent beam performance deteriorates significantly relative to the spatially partially coherent beams when the conditions become more complex, changing from still water conditions to the propagation through mechanically moved entrained salt scatterers.

Coherent backscattering of singular beams

NASA Astrophysics Data System (ADS)

Schwartz, Chaim; Dogariu, Aristide

2006-02-01

The phenomenon of coherent backscattering depends on both the statistical characteristics of a random scattering medium and the correlation features of the incident field. Imposing a wavefront singularity on the incident field offers a unique and very attractive way to modify the field correlations in a deterministic manner. The field correlations are found to act as a path-length filter which modifies the distribution of different contributions to the enhancement cone. This effect is thoroughly discussed and demonstrated experimentally for the case of single scale scattering systems.

Biological cell classification by multiangle light scattering

DOEpatents

Salzman, G.C.; Crowell, J.M.; Mullaney, P.F.

1975-06-03

The specification is directed to an apparatus and method for detecting light scattering from a biological cell. Light, preferably from a coherent source of radiation, intercepts an individual biological cell in a stream of cells passing through the beam. Light scattered from the cell is detected at a selected number of angles between 0 and 90/sup 0/ to the longitudinal axis of the beam with a circular array of light responsive elements which produce signals representative of the intensity of light incident thereon. Signals from the elements are processed to determine the light-scattering pattern of the cell and therefrom its identity.

First measurement of time evolution of electron temperature profiles with Nd:YAG Thomson scattering system on Heliotron J.

PubMed

Kenmochi, N; Minami, T; Takahashi, C; Tei, S; Mizuuchi, T; Kobayashi, S; Nagasaki, K; Nakamura, Y; Okada, H; Kado, S; Yamamoto, S; Ohshima, S; Konoshima, S; Shi, N; Zang, L; Ohtani, Y; Kasajima, K; Sano, F

2014-11-01

A Nd:YAG Thomson scattering system has been developed for Heliotron J. The system consists of two 550 mJ 50 Hz lasers, large collection optics, and 25 radial channel (∼1 cm spatial resolution) interference polychromators. This measurement system achieves a S/N ratio of ∼50 for low-density plasma (ne ∼ 0.5 × 10(19) m(-3)). A time evolution of electron temperature profiles was measured with this system for a high-intensity gas-puff (HIGP) fueling neutral-beam-injection plasma. The peripheral temperature of the higher-density phase after HIGP recovers to the low-density pre-HIGP level, suggesting that improving particle transport in the HIGP plasma may be possible.

Electron scattering by highly polar molecules. III - CsCl

NASA Technical Reports Server (NTRS)

Vuskovic, L.; Srivastava, S. K.

1981-01-01

Utilizing a crossed electron-beam-molecular-beam scattering geometry, relative values of differential electron scattering cross sections for cesium chloride at 5 and 20 eV electron impact energies and at scattering angles between 10 and 120 deg have been measured. These relative cross sections have been normalized to the cross section at 15 deg scattering angle calculated by the hybrid S-matrix technique. In the angular range between 0 and 10 deg and between 120 and 180 deg extrapolations have been made to obtain integral and momentum transfer cross sections. An energy-loss spectrum is also presented which gives various spectral features lying between the 4 and 10 eV regions in CsCl.

Plasmon-enhanced scattering and charge transfer in few-layer graphene interacting with buried printed 2D-pattern of silver nanoparticles

NASA Astrophysics Data System (ADS)

Carles, R.; Bayle, M.; Bonafos, C.

2018-04-01

Hybrid structures combing silver nanoparticles and few-layer graphene have been synthetized by combining low-energy ion beam synthesis and stencil techniques. A single plane of metallic nanoparticles plays the role of an embedded plasmonic enhancer located in dedicated areas at a controlled nanometer distance from deposited graphene layers. Optical imaging, reflectance and Raman scattering mapping are used to measure the enhancement of electronic and vibrational properties of these layers. In particular electronic Raman scattering is shown as notably efficient to analyze the optical transfer of charge carriers between the systems and the presence of intrinsic and extrinsic defects.

Plasmon-enhanced scattering and charge transfer in few-layer graphene interacting with buried printed 2D-pattern of silver nanoparticles.

PubMed

Carles, R; Bayle, M; Bonafos, C

2018-04-27

Hybrid structures combing silver nanoparticles and few-layer graphene have been synthetized by combining low-energy ion beam synthesis and stencil techniques. A single plane of metallic nanoparticles plays the role of an embedded plasmonic enhancer located in dedicated areas at a controlled nanometer distance from deposited graphene layers. Optical imaging, reflectance and Raman scattering mapping are used to measure the enhancement of electronic and vibrational properties of these layers. In particular electronic Raman scattering is shown as notably efficient to analyze the optical transfer of charge carriers between the systems and the presence of intrinsic and extrinsic defects.

Soft x-ray scattering facility at the Advanced Light Source with real-time data processing and analysis

NASA Astrophysics Data System (ADS)

Gann, E.; Young, A. T.; Collins, B. A.; Yan, H.; Nasiatka, J.; Padmore, H. A.; Ade, H.; Hexemer, A.; Wang, C.

2012-04-01

We present the development and characterization of a dedicated resonant soft x-ray scattering facility. Capable of operation over a wide energy range, the beamline and endstation are primarily used for scattering from soft matter systems around the carbon K-edge (˜285 eV). We describe the specialized design of the instrument and characteristics of the beamline. Operational characteristics of immediate interest to users such as polarization control, degree of higher harmonic spectral contamination, and detector noise are delineated. Of special interest is the development of a higher harmonic rejection system that improves the spectral purity of the x-ray beam. Special software and a user-friendly interface have been implemented to allow real-time data processing and preliminary data analysis simultaneous with data acquisition.

Commissioning a passive-scattering proton therapy nozzle for accurate SOBP delivery

PubMed Central

Engelsman, M.; Lu, H.-M.; Herrup, D.; Bussiere, M.; Kooy, H. M.

2009-01-01

Proton radiotherapy centers that currently use passively scattered proton beams do field specific calibrations for a non-negligible fraction of treatment fields, which is time and resource consuming. Our improved understanding of the passive scattering mode of the IBA universal nozzle, especially of the current modulation function, allowed us to re-commission our treatment control system for accurate delivery of SOBPs of any range and modulation, and to predict the output for each of these fields. We moved away from individual field calibrations to a state where continued quality assurance of SOBP field delivery is ensured by limited system-wide measurements that only require one hour per week. This manuscript reports on a protocol for generation of desired SOBPs and prediction of dose output. PMID:19610306

Computation of tightly-focused laser beams in the FDTD method

PubMed Central

Çapoğlu, İlker R.; Taflove, Allen; Backman, Vadim

2013-01-01

We demonstrate how a tightly-focused coherent TEMmn laser beam can be computed in the finite-difference time-domain (FDTD) method. The electromagnetic field around the focus is decomposed into a plane-wave spectrum, and approximated by a finite number of plane waves injected into the FDTD grid using the total-field/scattered-field (TF/SF) method. We provide an error analysis, and guidelines for the discrete approximation. We analyze the scattering of the beam from layered spaces and individual scatterers. The described method should be useful for the simulation of confocal microscopy and optical data storage. An implementation of the method can be found in our free and open source FDTD software (“Angora”). PMID:23388899

Computation of tightly-focused laser beams in the FDTD method.

PubMed

Capoğlu, Ilker R; Taflove, Allen; Backman, Vadim

2013-01-14

We demonstrate how a tightly-focused coherent TEMmn laser beam can be computed in the finite-difference time-domain (FDTD) method. The electromagnetic field around the focus is decomposed into a plane-wave spectrum, and approximated by a finite number of plane waves injected into the FDTD grid using the total-field/scattered-field (TF/SF) method. We provide an error analysis, and guidelines for the discrete approximation. We analyze the scattering of the beam from layered spaces and individual scatterers. The described method should be useful for the simulation of confocal microscopy and optical data storage. An implementation of the method can be found in our free and open source FDTD software ("Angora").

Binary collision rates of relativistic thermal plasmas. I Theoretical framework

NASA Technical Reports Server (NTRS)

Dermer, C. D.

1985-01-01

Binary collision rates for arbitrary scattering cross sections are derived in the case of a beam of particles interacting with a Maxwell-Boltzmann (MB) plasma, or in the case of two MB plasmas interacting at generally different temperatures. The expressions are valid for all beam energies and plasma temperatures, from the nonrelativistic to the extreme relativistic limits. The calculated quantities include the reaction rate, the energy exchange rate, and the average rate of change of the squared transverse momentum component of a monoenergetic particle beam as a result of scatterings with particles of a MB plasma. Results are specialized to elastic scattering processes, two-temperature reaction rates, or the cold plasma limit, reproducing previous work.

Optimization of Compton Source Performance through Electron Beam Shaping

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

Malyzhenkov, Alexander; Yampolsky, Nikolai

2016-09-26

We investigate a novel scheme for significantly increasing the brightness of x-ray light sources based on inverse Compton scattering (ICS) - scattering laser pulses off relativistic electron beams. The brightness of ICS sources is limited by the electron beam quality since electrons traveling at different angles, and/or having different energies, produce photons with different energies. Therefore, the spectral brightness of the source is defined by the 6d electron phase space shape and size, as well as laser beam parameters. The peak brightness of the ICS source can be maximized then if the electron phase space is transformed in a waymore » so that all electrons scatter off the x-ray photons of same frequency in the same direction, arriving to the observer at the same time. We describe the x-ray photon beam quality through the Wigner function (6d photon phase space distribution) and derive it for the ICS source when the electron and laser rms matrices are arbitrary.« less

An upgrade beamline for combined wide, small and ultra small-angle x-ray scattering at the ESRF

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

Van Vaerenbergh, Pierre; Léonardon, Joachim; Sztucki, Michael

2016-07-27

This contribution presents the main design features of the upgraded beamline ID02 (TRUSAXS). The beamline combines different small-angle X-ray scattering techniques in one unique instrument. The key component of this instrument is an evacuated (5×10{sup −3} mbar) stainless steel detector tube of length 34 m and diameter 2 m. Three different detectors (Rayonix MX170, Pilatus 300 K and FReLoN 4M) are housed inside a motorized wagon which travels along a rail system with very low parasitic lateral movements (± 0.3 mm). This system allows automatically changing the sample-to-detector distance from about 1 m to 31 m and selecting the desiredmore » detector. In addition, a wide angle detector (Rayonix LX170) is installed just above the entrance cone of the tube for optional wide-angle X-ray scattering measurements. The beamstop system enables monitoring of the X-ray beam intensity in addition to blocking the primary beam, and automated insertion of selected masks behind the primary beamstop. The focusing optics and collimation system permit to cover a scattering vector (q) range of 0.002 nm{sup −1} ≤ q ≤ 50 nm{sup −1} with one unique setting using 0.1 nm X-ray wavelength for moderate flux (5×10{sup 12} photons/sec). However, for higher flux (6x10{sup 13} photons/sec) or higher resolution (minimum q < 0.001 nm{sup −1}), focusing and collimation, respectively need to be varied. For a sample-to-detector distance of 31 m and 0.1 nm wavelength, two dimensional ultra small-angle X-ray scattering patterns can be recorded down to q≈0.001 nm{sup −1} with far superior quality as compared to one dimensional profiles obtained with a Bonse-Hart instrument.« less

Scatter correction, intermediate view estimation and dose characterization in megavoltage cone-beam CT imaging

NASA Astrophysics Data System (ADS)

Sramek, Benjamin Koerner

The ability to deliver conformal dose distributions in radiation therapy through intensity modulation and the potential for tumor dose escalation to improve treatment outcome has necessitated an increase in localization accuracy of inter- and intra-fractional patient geometry. Megavoltage cone-beam CT imaging using the treatment beam and onboard electronic portal imaging device is one option currently being studied for implementation in image-guided radiation therapy. However, routine clinical use is predicated upon continued improvements in image quality and patient dose delivered during acquisition. The formal statement of hypothesis for this investigation was that the conformity of planned to delivered dose distributions in image-guided radiation therapy could be further enhanced through the application of kilovoltage scatter correction and intermediate view estimation techniques to megavoltage cone-beam CT imaging, and that normalized dose measurements could be acquired and inter-compared between multiple imaging geometries. The specific aims of this investigation were to: (1) incorporate the Feldkamp, Davis and Kress filtered backprojection algorithm into a program to reconstruct a voxelized linear attenuation coefficient dataset from a set of acquired megavoltage cone-beam CT projections, (2) characterize the effects on megavoltage cone-beam CT image quality resulting from the application of Intermediate View Interpolation and Intermediate View Reprojection techniques to limited-projection datasets, (3) incorporate the Scatter and Primary Estimation from Collimator Shadows (SPECS) algorithm into megavoltage cone-beam CT image reconstruction and determine the set of SPECS parameters which maximize image quality and quantitative accuracy, and (4) evaluate the normalized axial dose distributions received during megavoltage cone-beam CT image acquisition using radiochromic film and thermoluminescent dosimeter measurements in anthropomorphic pelvic and head and neck phantoms. The conclusions of this investigation were: (1) the implementation of intermediate view estimation techniques to megavoltage cone-beam CT produced improvements in image quality, with the largest impact occurring for smaller numbers of initially-acquired projections, (2) the SPECS scatter correction algorithm could be successfully incorporated into projection data acquired using an electronic portal imaging device during megavoltage cone-beam CT image reconstruction, (3) a large range of SPECS parameters were shown to reduce cupping artifacts as well as improve reconstruction accuracy, with application to anthropomorphic phantom geometries improving the percent difference in reconstructed electron density for soft tissue from -13.6% to -2.0%, and for cortical bone from -9.7% to 1.4%, (4) dose measurements in the anthropomorphic phantoms showed consistent agreement between planar measurements using radiochromic film and point measurements using thermoluminescent dosimeters, and (5) a comparison of normalized dose measurements acquired with radiochromic film to those calculated using multiple treatment planning systems, accelerator-detector combinations, patient geometries and accelerator outputs produced a relatively good agreement.

Conditional-sampling spectrograph detection system for fluorescence measurements of individual airborne biological particles

NASA Astrophysics Data System (ADS)

Nachman, Paul; Pinnick, R. G.; Hill, Steven C.; Chen, Gang; Chang, Richard K.; Mayo, Michael W.; Fernandez, Gilbert L.

1996-03-01

We report the design and operation of a prototype conditional-sampling spectrograph detection system that can record the fluorescence spectra of individual, micrometer-sized aerosols as they traverse an intense 488-nm intracavity laser beam. The instrument's image-intensified CCD detector is gated by elastic scattering or by undispersed fluorescence from particles that enter the spectrograph's field of view. It records spectra only from particles with preselected scattering-fluorescence levels (a fiber-optic-photomultiplier subsystem provides the gating signal). This conditional-sampling procedure reduces data-handling rates and increases the signal-to-noise ratio by restricting the system's exposures to brief periods when aerosols traverse the beam. We demonstrate these advantages by reliably capturing spectra from individual fluorescent microspheres dispersed in an airstream. The conditional-sampling procedure also permits some discrimination among different types of particles, so that spectra may be recorded from the few interesting particles present in a cloud of background aerosol. We demonstrate such discrimination by measuring spectra from selected fluorescent microspheres in a mixture of two types of microspheres, and from bacterial spores in a mixture of spores and nonfluorescent kaolin particles.

Edge roughness evaluation method for quantifying at-size beam blur in electron-beam lithography

NASA Astrophysics Data System (ADS)

Yoshizawa, Masaki; Moriya, Shigeru

2000-07-01

At-size beam blur at any given pattern size of an electron beam (EB) direct writer, HL800D, was quantified using the new edge roughness evaluation (ERE) method to optimize the electron-optical system. We characterized the two-dimensional beam-blur dependence on the electron deflection length of the EB direct writer. The results indicate that the beam blur ranged from 45 nm to 56 nm in a deflection field 2520 micrometer square. The new ERE method is based on the experimental finding that line edge roughness of a resist pattern is inversely proportional to the slope of the Gaussian-distributed quasi-beam-profile (QBP) proposed in this paper. The QBP includes effects of the beam blur, electron forward scattering, acid diffusion in chemically amplified resist (CAR), the development process, and aperture mask quality. The application the ERE method to investigating the beam-blur fluctuation demonstrates the validity of the ERE method in characterizing the electron-optical column conditions of EB projections such as SCALPEL and PREVAIL.

Effects of Coherence and Polarization in Radiation and in Scattering Processes

DTIC Science & Technology

2012-02-08

Beams in the Space-time and Space-frequency Domains”, Opt. Lett. 34, 2936- 2938 , (2009). 11. Lahiri and E. Wolf, “Beam Condition for Scattering on...in the space- time and space-frequency domains”, Opt. Lett. 34, 2936- 2938 , (2009). Although the theories of polarization in the space-time and space

Study of the effect of scattering from turbid water on the polarization of a laser beam

NASA Technical Reports Server (NTRS)

Henderson, R. G.; Hovanlou, A. H.

1978-01-01

A Monte Carlo simulation method was used to determine the effect of scattering from turbid water on the polarization of a backscattered beam of laser light. The relationship between the polarization and the type and amount of suspended particulates in the water was investigated.

A Mo-anode-based in-house source for small-angle X-ray scattering measurements of biological macromolecules

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

Bruetzel, Linda K.; Fischer, Stefan; Salditt, Annalena

2016-02-15

We demonstrate the use of a molybdenum-anode-based in-house small-angle X-ray scattering (SAXS) setup to study biological macromolecules in solution. Our system consists of a microfocus X-ray tube delivering a highly collimated flux of 2.5 × 10{sup 6} photons/s at a beam size of 1.2 × 1.2 mm{sup 2} at the collimation path exit and a maximum beam divergence of 0.16 mrad. The resulting observable scattering vectors q are in the range of 0.38 Å{sup −1} down to 0.009 Å{sup −1} in SAXS configuration and of 0.26 Å{sup −1} up to 5.7 Å{sup −1} in wide-angle X-ray scattering (WAXS) mode. Tomore » determine the capabilities of the instrument, we collected SAXS data on weakly scattering biological macromolecules including proteins and a nucleic acid sample with molecular weights varying from ∼12 to 69 kDa and concentrations of 1.5–24 mg/ml. The measured scattering data display a high signal-to-noise ratio up to q-values of ∼0.2 Å{sup −1} allowing for an accurate structural characterization of the samples. Moreover, the in-house source data are of sufficient quality to perform ab initio 3D structure reconstructions that are in excellent agreement with the available crystallographic structures. In addition, measurements for the detergent decyl-maltoside show that the setup can be used to determine the size, shape, and interactions (as characterized by the second virial coefficient) of detergent micelles. This demonstrates that the use of a Mo-anode based in-house source is sufficient to determine basic geometric parameters and 3D shapes of biomolecules and presents a viable alternative to valuable beam time at third generation synchrotron sources.« less

Two particle tracking and detection in a single Gaussian beam optical trap.

PubMed

Praveen, P; Yogesha; Iyengar, Shruthi S; Bhattacharya, Sarbari; Ananthamurthy, Sharath

2016-01-20

We have studied in detail the situation wherein two microbeads are trapped axially in a single-beam Gaussian intensity profile optical trap. We find that the corner frequency extracted from a power spectral density analysis of intensity fluctuations recorded on a quadrant photodetector (QPD) is dependent on the detection scheme. Using forward- and backscattering detection schemes with single and two laser wavelengths along with computer simulations, we conclude that fluctuations detected in backscattering bear true position information of the bead encountered first in the beam propagation direction. Forward scattering, on the other hand, carries position information of both beads with substantial contribution from the bead encountered first along the beam propagation direction. Mie scattering analysis further reveals that the interference term from the scattering of the two beads contributes significantly to the signal, precluding the ability to resolve the positions of the individual beads in forward scattering. In QPD-based detection schemes, detection through backscattering, thereby, is imperative to track the true displacements of axially trapped microbeads for possible studies on light-mediated interbead interactions.

Performance of traffic-alert collision avoidance (TCAS) antennas in the presence of scatterers

NASA Technical Reports Server (NTRS)

Sampath, K. S.; Rojas, R. G.; Burnside, W. D.

1993-01-01

The performance of two TCAS systems is studied in the presence of electromagnetic scatterers. TCAS is an aircraft mounted angle of arrival (AOA) system, which estimates the bearing of a signal transmitted from a mode-S transponder on another nearby aircraft (intruder). Two systems are studied: (1) Comparison of Relative Amplitude system (CRA), and (2) Spiral Phase Antenna (SPA). The CRA antenna receives the reply via four switched beams. The bearing is estimated by comparing the amplitudes of the received signal. The SPA is based on the phase interferometer, which utilizes the received phase via sum and difference beams. The AOA is computed by comparing the reply with similar values on a calibration table, which is generated by modeling the TCAS antenna on the bare fuselage of a Boeing 727-200. The antenna patterns for the TCAS are found via high frequency methods based on the Uniform Geometric theory of Diffraction (UTD). By minimizing the standard deviation of the bearing error in a specified angular sector, optimal locations for top and bottom mounted TCAS antennas are found on the Boeing 727-200, 737-300 and 747-200 airframes. It will be shown that the overall bearing errors of the amplitude system are consistently smaller than the spiral phase TCAS. The effect of two types of nearby scatterers--antennas, and engine inlets--is studied. The AT741 L-band blade, DMC60-1 VHF Communication antenna were chosen as being representative antenna interference examples. Models are derived for the blades via a moment method analysis followed by a least squares procedure to synthesize the scattering patterns. Studies were conducted to estimate the minimum separation between the two antennas for acceptable operation. It will be shown that the spiral phase TCAS is adversely affected by the presence of a blade antenna. The amplitude system does not suffer from this limitation, especially for the forward look angles which are of most interest here. A model to represent the inlet scattering is based on the multiple scattering method and UTD. The engine on top of the B727-200 fuselage is modeled by a terminated circular waveguide. Then, the effect of moving the antenna forward on the fuselage is studied. It is again shown that the performance of the amplitude system is superior.

A system to track skin dose for neuro-interventional cone-beam computed tomography (CBCT)

NASA Astrophysics Data System (ADS)

Vijayan, Sarath; Xiong, Zhenyu; Rudin, Stephen; Bednarek, Daniel R.

2016-03-01

The skin-dose tracking system (DTS) provides a color-coded illustration of the cumulative skin-dose distribution on a closely-matching 3D graphic of the patient during fluoroscopic interventions in real-time for immediate feedback to the interventionist. The skin-dose tracking utility of DTS has been extended to include cone-beam computed tomography (CBCT) of neurointerventions. While the DTS was developed to track the entrance skin dose including backscatter, a significant part of the dose in CBCT is contributed by exit primary radiation and scatter due to the many overlapping projections during the rotational scan. The variation of backscatter inside and outside the collimated beam was measured with radiochromic film and a curve was fit to obtain a scatter spread function that could be applied in the DTS. Likewise, the exit dose distribution was measured with radiochromic film for a single projection and a correction factor was determined as a function of path length through the head. Both of these sources of skin dose are added for every projection in the CBCT scan to obtain a total dose mapping over the patient graphic. Results show the backscatter to follow a sigmoidal falloff near the edge of the beam, extending outside the beam as far as 8 cm. The exit dose measured for a cylindrical CTDI phantom was nearly 10 % of the entrance peak skin dose for the central ray. The dose mapping performed by the DTS for a CBCT scan was compared to that measured with radiochromic film and a CTDI-head phantom with good agreement.

Laser beam alignment and profilometry using diagnostic fluorescent safety mirrors

NASA Astrophysics Data System (ADS)

Lizotte, Todd E.

2011-03-01

There are a wide range of laser beam delivery systems in use for various purposes; including industrial and medical applications. Virtually all such beam delivery systems for practical purposes employ optical systems comprised of mirrors and lenses to shape, focus and guide the laser beam down to the material being processed. The goal of the laser beam delivery is to set the optimum parameters and to "fold" the beam path to reduce the mechanical length of the optical system, thereby allowing a physically compact system. In many cases, even a compact system can incorporate upwards of six mirrors and a comparable number of lenses all needing alignment so they are collinear. One of the major requirements for use of such systems in industry is a method of safe alignment. The alignment process requires that the aligner determine where the beam strikes each element. The aligner should also preferably be able to determine the shape or pattern of the laser beam at that point and its relative power. These alignments are further compounded in that the laser beams generated are not visible to the unaided human eye. Such beams are also often of relatively high power levels, and are thereby a significant hazard to the eyes of the aligner. Obvious an invisible beam makes it nearly impossible to align laser system without some form of optical assistance. The predominant method of visually aligning the laser beam delivery is the use of thermal paper, paper cards or fluorescing card material. The use of paper products which have limited power handling capability or coated plastics can produce significant debris and contaminants within the beam line that ultimately damage the optics. The use of the cards can also create significant laser light scatter jeopardizing the safety of the person aligning the system. This paper covers a new safety mirror design for use with at various UV and Near IR wavelengths (193 nm to 1064 nm) within laser beam delivery systems and how its use can provide benefits covering eye safety, precise alignment and beam diagnostics.

SU-E-T-535: Proton Dose Calculations in Homogeneous Media.

PubMed

Chapman, J; Fontenot, J; Newhauser, W; Hogstrom, K

2012-06-01

To develop a pencil beam dose calculation algorithm for scanned proton beams that improves modeling of scatter events. Our pencil beam algorithm (PBA) was developed for calculating dose from monoenergetic, parallel proton beams in homogeneous media. Fermi-Eyges theory was implemented for pencil beam transport. Elastic and nonelastic scatter effects were each modeled as a Gaussian distribution, with root mean square (RMS) widths determined from theoretical calculations and a nonlinear fit to a Monte Carlo (MC) simulated 1mm × 1mm proton beam, respectively. The PBA was commissioned using MC simulations in a flat water phantom. Resulting PBA calculations were compared with results of other models reported in the literature on the basis of differences between PBA and MC calculations of 80-20% penumbral widths. Our model was further tested by comparing PBA and MC results for oblique beams (45 degree incidence) and surface irregularities (step heights of 1 and 4 cm) for energies of 50-250 MeV and field sizes of 4cm × 4cm and 10cm × 10cm. Agreement between PBA and MC distributions was quantified by computing the percentage of points within 2% dose difference or 1mm distance to agreement. Our PBA improved agreement between calculated and simulated penumbral widths by an order of magnitude compared with previously reported values. For comparisons of oblique beams and surface irregularities, agreement between PBA and MC distributions was better than 99%. Our algorithm showed improved accuracy over other models reported in the literature in predicting the overall shape of the lateral profile through the Bragg peak. This improvement was achieved by incorporating nonelastic scatter events into our PBA. The increased modeling accuracy of our PBA, incorporated into a treatment planning system, may improve the reliability of treatment planning calculations for patient treatments. This research was supported by contract W81XWH-10-1-0005 awarded by The U.S. Army Research Acquisition Activity, 820 Chandler Street, Fort Detrick, MD 21702-5014. This report does not necessarily reflect the position or policy of the Government, and no official endorsement should be inferred. © 2012 American Association of Physicists in Medicine.

Measurement of two-photon exchange effect by comparing elastic e ± p cross sections

DOE PAGES

Rimal, D.; Adikaram, D.; Raue, B. A.; ...

2017-06-01

Here, the electromagnetic form factors of the proton measured by unpolarized and polarized electron scattering experiments show a significant disagreement that grows with the squared four momentum transfer (more » $$Q^{2}$$). Calculations have shown that the two measurements can be largely reconciled by accounting for the contributions of two-photon exchange (TPE). TPE effects are not typically included in the standard set of radiative corrections since theoretical calculations of the TPE effects are highly model dependent, and, until recently, no direct evidence of significant TPE effects has been observed. We measured the ratio of positron-proton to electron-proton elastic-scattering cross sections in order to determine the TPE contribution to elastic electron-proton scattering and thereby resolve the proton electric form factor discrepancy. We produced a mixed simultaneous electron-positron beam in Jefferson Lab's Hall B by passing the 5.6 GeV primary electron beam through a radiator to produce a bremsstrahlung photon beam and then passing the photon beam through a convertor to produce electron/positron pairs. The mixed electron-positron (lepton) beam with useful energies from approximately 0.85 to 3.5 GeV then struck a 30-cm long liquid hydrogen (LH$$_2$$) target located within the CEBAF Large Acceptance Spectrometer (CLAS). By detecting both the scattered leptons and the recoiling protons we identified and reconstructed elastic scattering events and determined the incident lepton energy. A detailed description of the experiment is presented.« less

Multi-Point Interferometric Rayleigh Scattering using Dual-Pass Light Recirculation

NASA Technical Reports Server (NTRS)

Bivolaru, Daniel; Danehy, Paul M.; Cutler, Andrew D.

2008-01-01

This paper describes for the first time an interferometric Rayleigh scattering system using dual-pass light recirculation (IRS-LR) capable of simultaneously measuring at multiple points two orthogonal components of flow velocity in combustion flows using single shot laser probing. An additional optical path containing the interferometer input mirror, a quarter-wave plate, a polarization dependent beam combiner, and a high reflectivity mirror partially recirculates the light that is rejected by the interferometer. Temporally- and spatially-resolved acquisitions of Rayleigh spectra in a large-scale combustion-heated supersonic axi-symmetric jet were performed to demonstrate the technique. Recirculating of Rayleigh scattered light increases the number of photons analyzed by the system up to a factor of 1.8 compared with previous configurations. This is equivalent to performing measurements with less laser energy or performing measurements with the previous system in gas flows at higher temperatures.

Photoelastic Analysis of Three-dimensional Stress Systems Using Scattered Light

NASA Technical Reports Server (NTRS)

Weller, R; Bussey, J K

1939-01-01

A method has been developed for making photoelastic analyses of three-dimensional stress systems by utilizing the polarization phenomena associated with the scattering of light. By this method, the maximum shear and the directions of the three principal stresses at any point within a model can be determined, and the two principal stresses at a free-bounding surface can be separately evaluated. Polarized light is projected into the model through a slit so that it illuminates a plane section. The light is continuously analyzed along its path by scattering and the state of stress in the illuminated section is obtained. By means of a series of such sections, the entire stress field may be explored. The method was used to analyze the stress system of a simple beam in bending. The results were found to be in good agreement with those expected from elementary theory.

Production of thin targets by implantation for the measurement of the 16O + 16O elastic scattering below the Coulomb barrier

NASA Astrophysics Data System (ADS)

Silva, H.; Cruz, J.; Sánchez-Benítez, A. M.; Santos, C.; Luís, H.; Fonseca, M.; Jesus, A. P.

2017-09-01

In recent decades, the processes of fusion of 16O were studied both theoretically and experimentally. However, the theoretical calculations are unable to fit both elastic scattering cross sections and fusion S-factors. The use of 16O thin transmission targets is required to measure the elastic forward scattering 16O + 16O reaction. The areal density of the target must be high to maximize the reaction products yields, but not so high as to allow a correct calculation of the effective beam energy. Besides this, the target must withstand beam interactions without noticeable deterioration, and contaminants must be minimal. In this study, the production of thin targets is performed with an innovative technique. Beam characterization and preliminary spectrum for the elastic scattering are also presented, showing the suitability of these targets for the proposed reaction.

Video-based beam position monitoring at CHESS

NASA Astrophysics Data System (ADS)

Revesz, Peter; Pauling, Alan; Krawczyk, Thomas; Kelly, Kevin J.

2012-10-01

CHESS has pioneered the development of X-ray Video Beam Position Monitors (VBPMs). Unlike traditional photoelectron beam position monitors that rely on photoelectrons generated by the fringe edges of the X-ray beam, with VBPMs we collect information from the whole cross-section of the X-ray beam. VBPMs can also give real-time shape/size information. We have developed three types of VBPMs: (1) VBPMs based on helium luminescence from the intense white X-ray beam. In this case the CCD camera is viewing the luminescence from the side. (2) VBPMs based on luminescence of a thin (~50 micron) CVD diamond sheet as the white beam passes through it. The CCD camera is placed outside the beam line vacuum and views the diamond fluorescence through a viewport. (3) Scatter-based VBPMs. In this case the white X-ray beam passes through a thin graphite filter or Be window. The scattered X-rays create an image of the beam's footprint on an X-ray sensitive fluorescent screen using a slit placed outside the beam line vacuum. For all VBPMs we use relatively inexpensive 1.3 Mega-pixel CCD cameras connected via USB to a Windows host for image acquisition and analysis. The VBPM host computers are networked and provide live images of the beam and streams of data about the beam position, profile and intensity to CHESS's signal logging system and to the CHESS operator. The operational use of VBPMs showed great advantage over the traditional BPMs by providing direct visual input for the CHESS operator. The VBPM precision in most cases is on the order of ~0.1 micron. On the down side, the data acquisition frequency (50-1000ms) is inferior to the photoelectron based BPMs. In the future with the use of more expensive fast cameras we will be able create VBPMs working in the few hundreds Hz scale.

Beam-target double-spin asymmetry in quasielastic electron scattering off the deuteron with CLAS

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

Mayer, M.; Kuhn, S. E.; Adhikari, K. P.

Background: The deuteron plays a pivotal role in nuclear and hadronic physics, as both the simplest bound multi-nucleon system and as an ``effective neutron target''. Quasi-elastic electron scattering on the deuteron is a benchmark reaction to test our understanding of deuteron structure and the properties and interactions of the two nucleons bound in the deuteron. Purpose: The experimental data presented here test state-of-the-art models of the deuteron and the two-nucleon interaction in the final state after two-body breakup of the deuteron. Focusing on polarization degrees of freedom, we gain information on the limits of the Impulse Approximation (IA) picture andmore » put the interpretation of spin structure measurements with deuterium on a firmer footing. Information on this reaction can also be used to improve the determination of the deuteron polarization through quasi-elastic electron scattering. Method: We measured the beam-target double spin asymmetry (A||) for quasi-elastic electron scattering off the deuteron at several beam energies (1.6-1.7 GeV, 2.5 GeV, 4.2 GeV and 5.6-5.8 GeV), using the CEBAF Large Acceptance Spectrometer (CLAS) at Thomas Jefferson National Accelerator Facility. The deuterons were polarized along (or opposite to) the beam direction. The double spin asymmetries were measured as a function of photon virtuality Q2 (0.13-3.17 (GeV/c)2), missing momentum (pm = 0.0 - 0.5 GeV/c), and the angle between the (inferred) ``spectator'' neutron and the momentum transfer direction (θnq). Results: The results are compared with a recent model that includes Final State Interactions (FSI) using a complete parameterization of nucleon-nucleon scattering, as well as a simplified model using the Plane Wave Impulse Approximation (PWIA). We find overall good agreement with both the PWIA and FSI expectations at low to medium missing momenta (pm ≤ 0.25 GeV/c), including the change of the asymmetry due to the contribution of the deuteron D-state at higher momenta. At the highest missing momenta, our data clearly agree better with the calculations including FSI. Conclusions: Final state interactions seem to play a lesser role for polarization observables in deuteron two-body electro-disintegration than for absolute cross sections. Our data, while limited in statistical power, indicate that PWIA models work reasonably well to understand the asymmetries at lower missing momenta. In turn, this information can be used to extract the product of beam and target polarization (PbPt) from quasi-elastic electron-deuteron scattering, which is useful for measurements of spin observables in electron-neutron inelastic scattering. However, at the highest missing (neutron) momenta, FSI effects become important and must be accounted for.« less

Ultracompact beam splitters based on plasmonic nanoslits

PubMed Central

Zhou, Chuanhong; Kohli, Punit

2011-01-01

An ultracompact plasmonic beam splitter is theoretically and numerically investigated. The splitter consists of a V-shaped nanoslit in metal films. Two groups of nanoscale metallic grooves inside the slit (A) and at the small slit opening (B) are investigated. We show that there are two energy channels guiding light out by the splitter: the optical and the plasmonic channels. Groove A is used to couple incident light into the plasmonic channel. Groove B functions as a plasmonic scatter. We demonstrate that the energy transfer through plasmonic path is dominant in the beam splitter. We find that more than four times the energy is transferred by the plasmonic channel using structures A and B. We show that the plasmonic waves scattered by B can be converted into light waves. These light waves redistribute the transmitted energy through interference with the field transmitted from the nanoslit. Therefore, different beam splitting effects are achieved by simply changing the interference conditions between the scattered waves and the transmitted waves. The impact of the width and height of groove B are also investigated. It is found that the plasmonic scattering of B is changed into light scattering with increase of the width and the height of B. These devices have potential applications in optical sampling, signal processing, and integrated optical circuits. PMID:21647248

Geometry Survey of the Time-of-Flight Neutron-Elastic Scattering (Antonella) Experiment

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

Oshinowo, Babatunde O.; Izraelevitch, Federico

The Antonella experiment is a measurement of the ionization efficiency of nuclear recoils in silicon at low energies [1]. It is a neutron elastic scattering experiment motivated by the search for dark matter particles. In this experiment, a proton beam hits a lithium target and neutrons are produced. The neutron shower passes through a collimator that produces a neutron beam. The beam illuminates a silicon detector. With a certain probability, a neutron interacts with a silicon nucleus of the detector producing elastic scattering. After the interaction, a fraction of the neutron energy is transferred to the silicon nucleus which acquiresmore » kinetic energy and recoils. This kinetic energy is then dissipated in the detector producing ionization and thermal energy. The ionization produced is measured with the silicon detector electronics. On the other hand, the neutron is scattered out of the beam. A neutron-detector array (made of scintillator bars) registers the neutron arrival time and the scattering angle to reconstruct the kinematics of the neutron-nucleus interaction with the time-of-flight technique [2]. In the reconstruction equations, the energy of the nuclear recoil is a function of the scattering angle with respect to the beam direction, the time-of-flight of the neutron and the geometric distances between components of the setup (neutron-production target, silicon detector, scintillator bars). This paper summarizes the survey of the different components of the experiment that made possible the off-line analysis of the collected data. Measurements were made with the API Radian Laser Tracker and I-360 Probe Wireless. The survey was completed at the University of Notre Dame, Indiana, USA in February 2015.« less

Acoustic scattering by arbitrary distributions of disjoint, homogeneous cylinders or spheres.

PubMed

Hesford, Andrew J; Astheimer, Jeffrey P; Waag, Robert C

2010-05-01

A T-matrix formulation is presented to compute acoustic scattering from arbitrary, disjoint distributions of cylinders or spheres, each with arbitrary, uniform acoustic properties. The generalized approach exploits the similarities in these scattering problems to present a single system of equations that is easily specialized to cylindrical or spherical scatterers. By employing field expansions based on orthogonal harmonic functions, continuity of pressure and normal particle velocity are directly enforced at each scatterer using diagonal, analytic expressions to eliminate the need for integral equations. The effect of a cylinder or sphere that encloses all other scatterers is simulated with an outer iterative procedure that decouples the inner-object solution from the effect of the enclosing object to improve computational efficiency when interactions among the interior objects are significant. Numerical results establish the validity and efficiency of the outer iteration procedure for nested objects. Two- and three-dimensional methods that employ this outer iteration are used to measure and characterize the accuracy of two-dimensional approximations to three-dimensional scattering of elevation-focused beams.

Simulated performance of the optical Thomson scattering diagnostic designed for the National Ignition Facility.

PubMed

Ross, J S; Datte, P; Divol, L; Galbraith, J; Froula, D H; Glenzer, S H; Hatch, B; Katz, J; Kilkenny, J; Landen, O; Manuel, A M; Molander, W; Montgomery, D S; Moody, J D; Swadling, G; Weaver, J

2016-11-01

An optical Thomson scattering diagnostic has been designed for the National Ignition Facility to characterize under-dense plasmas. We report on the design of the system and the expected performance for different target configurations. The diagnostic is designed to spatially and temporally resolve the Thomson scattered light from laser driven targets. The diagnostic will collect scattered light from a 50 × 50 × 200 μm volume. The optical design allows operation with different probe laser wavelengths. A deep-UV probe beam (λ 0 = 210 nm) will be used to Thomson scatter from electron plasma densities of ∼5 × 10 20 cm -3 while a 3ω probe will be used for plasma densities of ∼1 × 10 19 cm -3 . The diagnostic package contains two spectrometers: the first to resolve Thomson scattering from ion acoustic wave fluctuations and the second to resolve scattering from electron plasma wave fluctuations. Expected signal levels relative to background will be presented for typical target configurations (hohlraums and a planar foil).

Evaluation of dosimetric properties of 6 MV & 10 MV photon beams from a linear accelerator with no flattening filter

NASA Astrophysics Data System (ADS)

Pearson, David

A linear accelerator manufactured by Elekta, equipped with a multi leaf collimation (MLC) system has been modelled using Monte Carlo simulations with the photon flattening filter removed. The purpose of this investigation was to show that more efficient and more accurate Intensity Modulated Radiation Therapy (IMRT) treatments can be delivered from a standard linear accelerator with the flattening filter removed from the beam. A range of simulations of 6 MV and 10 MV photon were studied and compared to a model of a standard accelerator which included the flattening filter for those beams. Measurements using a scanning water phantom were also performed after the flattening filter had been removed. We show here that with the flattening filter removed, an increase to the dose on the central axis by a factor of 2.35 and 4.18 is achieved for 6 MV and 10 MV photon beams respectively using a standard 10x 10cm2 field size. A comparison of the dose at points at the field edges led to the result that, removal of the flattening filter reduced the dose at these points by approximately 10% for the 6 MV beam over the clinical range of field sizes. A further consequence of removing the flattening filter was the softening of the photon energy spectrum leading to a steeper reduction in dose at depths greater than dmax. Also studied was the electron contamination brought about by the removal of the filter. To reduce this electron contamination and thus reduce the skin dose to the patient we consider the use of an electron scattering foil in the beam path. The electron scattering foil had very little effect on dmax. From simulations of a standard 6MV beam, a filter-free beam and a filter-free beam with electron scattering foil, we deduce that the proportion of electrons in the photon beam is 0.35%, 0.28% and 0.27%, consecutively. In short, higher dose rates will result in decreased treatment times and the reduced dose outside of the field is indicative of reducing the dose to the surrounding tissue. Electron contamination was found to be comparable with conventional IMRT treatments carried out with a flattening filter.

Space-time windowing of angle-beam wavefield data to characterize scattering from defects

NASA Astrophysics Data System (ADS)

Weng, Yu; Michaels, Jennifer E.

2018-04-01

The primary focus of ultrasonic nondestructive evaluation is defect detection and characterization. In particular, fatigue cracks emanating from fastener holes are commonly found in aerospace structures. Therefore, scattering of ultrasonic waves from crack-like notches is of practical interest. Here, angle-beam shear waves are used to interrogate notches in aluminum plates. In prior work, notch-scattering was characterized and quantified in the frequency-wavenumber domain, which has the undesirable effect of lumping all scattered shear wave energy from notches into a single energy curve. This present work focuses on developing space-time windowing methods to quantify notch-scattered energy directly in the time-space domain. Two strategies are developed. The first is to indirectly characterize notch-scattering via the change in scattering as compared to the undamaged through-hole. The second strategy is to directly track notch-scattered waves in the time-space domain and then quantify scattered energy by constructing energy-versus-direction curves. Both strategies provide a group of energy difference curves, which show how notch-scattering evolves as time progresses. Notch-scattering quantification results for different notch lengths are shown and discussed.

5 MeV Mott polarimeter for rapid precise electron beam polarization measurements

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

Price, J.S.; Poelker, B.M.; Sinclair, C.K.

1997-11-01

Low energy (E{sub k} = 100 keV) Mott scattering polarimeters are ill-suited to support operations foreseen for the polarized electron injector at Jefferson Lab. One solution is to measure the polarization at 5 MeV where multiple and plural scattering are unimportant and precision beam monitoring is straightforward. The higher injector beam current offsets the lower cross-sections; measured rates scale to 1 kHz/{mu}A with a 1 {mu}m thick gold target foil.

High flux, narrow bandwidth compton light sources via extended laser-electron interactions

DOEpatents

Barty, V P

2015-01-13

New configurations of lasers and electron beams efficiently and robustly produce high flux beams of bright, tunable, polarized quasi-monoenergetic x-rays and gamma-rays via laser-Compton scattering. Specifically, the use of long-duration, pulsed lasers and closely-spaced, low-charge and low emittance bunches of electron beams increase the spectral flux of the Compton-scattered x-rays and gamma rays, increase efficiency of the laser-electron interaction and significantly reduce the overall complexity of Compton based light sources.

Treatment vault shielding for a flattening filter-free medical linear accelerator

NASA Astrophysics Data System (ADS)

Kry, Stephen F.; Howell, Rebecca M.; Polf, Jerimy; Mohan, Radhe; Vassiliev, Oleg N.

2009-03-01

The requirements for shielding a treatment vault with a Varian Clinac 2100 medical linear accelerator operated both with and without the flattening filter were assessed. Basic shielding parameters, such as primary beam tenth-value layers (TVLs), patient scatter fractions, and wall scatter fractions, were calculated using Monte Carlo simulations of 6, 10 and 18 MV beams. Relative integral target current requirements were determined from treatment planning studies of several disease sites with, and without, the flattening filter. The flattened beam shielding data were compared to data published in NCRP Report No. 151, and the unflattened beam shielding data were presented relative to the NCRP data. Finally, the shielding requirements for a typical treatment vault were determined for a single-energy (6 MV) linac and a dual-energy (6 MV/18 MV) linac. With the exception of large-angle patient scatter fractions and wall scatter fractions, the vault shielding parameters were reduced when the flattening filter was removed. Much of this reduction was consistent with the reduced average energy of the FFF beams. Primary beam TVLs were reduced by 12%, on average, and small-angle scatter fractions were reduced by up to 30%. Head leakage was markedly reduced because less integral target current was required to deliver the target dose. For the treatment vault examined in the current study, removal of the flattening filter reduced the required thickness of the primary and secondary barriers by 10-20%, corresponding to 18 m3 less concrete to shield the single-energy linac and 36 m3 less concrete to shield the dual-energy linac. Thus, a shielding advantage was found when the linac was operated without the flattening filter. This translates into a reduction in occupational exposure and/or the cost and space of shielding.

Treatment vault shielding for a flattening filter-free medical linear accelerator.

PubMed

Kry, Stephen F; Howell, Rebecca M; Polf, Jerimy; Mohan, Radhe; Vassiliev, Oleg N

2009-03-07

The requirements for shielding a treatment vault with a Varian Clinac 2100 medical linear accelerator operated both with and without the flattening filter were assessed. Basic shielding parameters, such as primary beam tenth-value layers (TVLs), patient scatter fractions, and wall scatter fractions, were calculated using Monte Carlo simulations of 6, 10 and 18 MV beams. Relative integral target current requirements were determined from treatment planning studies of several disease sites with, and without, the flattening filter. The flattened beam shielding data were compared to data published in NCRP Report No. 151, and the unflattened beam shielding data were presented relative to the NCRP data. Finally, the shielding requirements for a typical treatment vault were determined for a single-energy (6 MV) linac and a dual-energy (6 MV/18 MV) linac. With the exception of large-angle patient scatter fractions and wall scatter fractions, the vault shielding parameters were reduced when the flattening filter was removed. Much of this reduction was consistent with the reduced average energy of the FFF beams. Primary beam TVLs were reduced by 12%, on average, and small-angle scatter fractions were reduced by up to 30%. Head leakage was markedly reduced because less integral target current was required to deliver the target dose. For the treatment vault examined in the current study, removal of the flattening filter reduced the required thickness of the primary and secondary barriers by 10-20%, corresponding to 18 m(3) less concrete to shield the single-energy linac and 36 m(3) less concrete to shield the dual-energy linac. Thus, a shielding advantage was found when the linac was operated without the flattening filter. This translates into a reduction in occupational exposure and/or the cost and space of shielding.

Experimental setup for Single Event Effects at the São Paulo 8UD Pelletron Accelerator

NASA Astrophysics Data System (ADS)

Aguiar, V. A. P.; Added, N.; Medina, N. H.; Macchione, E. L. A.; Tabacniks, M. H.; Aguirre, F. R.; Silveira, M. A. G.; Santos, R. B. B.; Seixas, L. E.

2014-08-01

In this work we present an experimental setup mounted in one of the beam lines at the São Paulo 8UD Pelletron Accelerator in order to study Single Event Effects in electronic devices. The basic idea is to use elastic scattering collisions to achieve a low-flux with a high-uniformity ion beam to irradiate several devices. 12C, 16O, 28Si, 35Cl and 63Cu beams were used to test the experimental setup. In this system it is possible to use efficiently LET values of 17 MeV/mg/cm2 for an external beam arrangement and up to 32 MeV/mg/cm2 for in-vacuum irradiation.

Acoustics of finite asymmetric exotic beams: Examples of Airy and fractional Bessel beams

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2017-12-01

The purpose of this investigation is to examine the properties of finite asymmetric exotic scalar (acoustic) beams with unusual properties using the angular spectrum decomposition in plane waves. Such beams possess intrinsic uncommon characteristics that make them attractive from the standpoint of particle manipulation, handling and rotation, and possibly other applications in particle clearing and separation. Assuming a specific apodization function at the acoustic source, the angular spectrum function is calculated and used to synthesize the radiated pressure field (i.e., excluding evanescent waves that decay away from the source) in the forward direction of wave motion (i.e., away from the source). Moreover, a generalized hybrid method combining the angular spectrum approach with the multipole expansion formalism in spherical coordinates is developed, which is applicable to any finite beam of arbitrary wavefront. The improved approach allows adequate computation of the resonance scattering, radiation force, and spin torque components on an object of arbitrary shape, located on or off the axis of the incident beam in space. Considering the illustrative example of a viscous fluid sphere submerged in a non-viscous liquid and illuminated by finite asymmetric beams such as the Airy and the Bessel vortex beam with fractional order, numerical computations for the scattering, radiation force, and torque components are performed with an emphasis on the distance from the source, the arbitrary location of the particle ,and the asymmetric nature of the incident field. Moreover, beamforming calculations are presented with supplementary animations for the pressure field distribution in space, with an emphasis on the intrinsic properties of the selected beams. The numerical predictions illustrate the scattering, radiation force, and spin torque properties depending on the beam parameters and the distance separating the sphere from the source. This study provides a generalized hybrid method to analyze quantitatively the scattering, radiation force, and spin torque by any finite asymmetric (or symmetric) acoustic beam with potential applications in various fields of applied physics (such as beam-forming, imaging, and mechanical effects of asymmetric sound beams).

Surface and adsorbate structural analysis from time-of-flight scattering and recoiling spectrometry (TOF-SARS)

NASA Astrophysics Data System (ADS)

Rabalais, J. W.; Bu, H.; Roux, C.

1992-02-01

The methods of obtaining surface structural information from low energy ion scattering spectrometry are described. These methods include measurements of backscattering, forwardscattering, and recoiling intensities vs beam incident α, beam exit β, crystal azimuthal δ, and scattering Θ angles. References are provided which give examples of each different kind of measurement. The technique of time-of-flight scattering and recoiling spectrometry (TOF-SARS), which collects both scattered.and recoiled neutrals and ions simultaneously, is described. TOF-SARS data for the three surface phases, clean Ni{110}-(1 × 1), Ni{110}-(1 × 2)-H missing row, and Ni{110}-(2 × 1)-O missing row, are used to illustrate some of the structural measurements.

ISTC projects devoted to improving laser beam quality

NASA Astrophysics Data System (ADS)

Malakhov, Yu. I.

2007-05-01

Short overview is done about the activity of ISTC in a direction concerned with improving powerful laser beam quality by means of nonlinear and linear adaptive optics methods. Completed projects #0591 and #1929 resulted in the development of a stimulated Brillouin scattering (SBS) phase conjugation mirror of superhigh fidelity employing the kinoform optical elements (rasters of small lenses) of new generation designed for pulsed or pulse-periodic lasers with nanosecond scale pulse duration. Project #2631 is devoted to development of an adaptive optical system for phase registration and correction of laser beams with wave front vortices. The principles of operation of conventional adaptive systems are based on the assumption that the phase is a smooth continuous function in space. Therefore the solution of the Project tasks will assume a new step in adaptive optics.

Advanced TIL system for laser beam focusing in a turbulent regime

NASA Astrophysics Data System (ADS)

Sprangle, Phillip A.; Ting, Antonio C.; Kaganovich, Dmitry; Khizhnyak, Anatoliy I.; Tomov, Ivan V.; Markov, Vladimir B.; Korobkin, Dmitriy V.

2014-10-01

This paper discusses an advanced target in the loop (ATIL) system with its performance based on a nonlinear phase conjugation scheme that performs rapid adjustment of the laser beam wavefront to mitigate effects associated with atmospheric turbulence along the propagation path. The ATIL method allows positional control of the laser spot (the beacon) on a remote imaged-resolved target. The size of this beacon is governed by the reciprocity of two counterpropagating beams (one towards the target and another scattered by the target) and the fidelity of the phase conjugation scheme. In this presentation we will present the results of the thorough analysis of ATIL operation, factors that affect its performance, its focusing efficiency and the comparison of laboratory experimental validation and computer simulation results.

Neutron-neutron quasifree scattering in nd breakup at 10 MeV

NASA Astrophysics Data System (ADS)

Malone, R. C.; Crowe, B.; Crowell, A. S.; Cumberbatch, L. C.; Esterline, J. H.; Fallin, B. A.; Friesen, F. Q. L.; Han, Z.; Howell, C. R.; Markoff, D.; Ticehurst, D.; Tornow, W.; Witała, H.

2016-03-01

The neutron-deuteron (nd) breakup reaction provides a rich environment for testing theoretical models of the neutron-neutron (nn) interaction. Current theoretical predictions based on rigorous ab-initio calculations agree well with most experimental data for this system, but there remain a few notable discrepancies. The cross section for nn quasifree (QFS) scattering is one such anomaly. Two recent experiments reported cross sections for this particular nd breakup configuration that exceed theoretical calculations by almost 20% at incident neutron energies of 26 and 25 MeV [1, 2]. The theoretical values can be brought into agreement with these results by increasing the strength of the 1S0 nn potential matrix element by roughly 10%. However, this modification of the nn effective range parameter and/or the 1S0 scattering length causes substantial charge-symmetry breaking in the nucleon-nucleon force and suggests the possibility of a weakly bound di-neutron state [3]. We are conducting new measurements of the cross section for nn QFS in nd breakup. The measurements are performed at incident neutron beam energies below 20 MeV. The neutron beam is produced via the 2H(d, n)3He reaction. The target is a deuterated plastic cylinder. Our measurements utilize time-of-flight techniques with a pulsed neutron beam and detection of the two emitted neutrons in coincidence. A description of our initial measurements at 10 MeV for a single scattering angle will be presented along with preliminary results. Also, plans for measurements at other energies with broad angular coverage will be discussed.

The optimal balance between quality and efficiency in proton radiography imaging technique at various proton beam energies: A Monte Carlo study.

PubMed

Biegun, A K; van Goethem, M-J; van der Graaf, E R; van Beuzekom, M; Koffeman, E N; Nakaji, T; Takatsu, J; Visser, J; Brandenburg, S

2017-09-01

Proton radiography is a novel imaging modality that allows direct measurement of the proton energy loss in various tissues. Currently, due to the conversion of so-called Hounsfield units from X-ray Computed Tomography (CT) into relative proton stopping powers (RPSP), the uncertainties of RPSP are 3-5% or higher, which need to be minimized down to 1% to make the proton treatment plans more accurate. In this work, we simulated a proton radiography system, with position-sensitive detectors (PSDs) and a residual energy detector (RED). The simulations were built using Geant4, a Monte Carlo simulation toolkit. A phantom, consisting of several materials was placed between the PSDs of various Water Equivalent Thicknesses (WET), corresponding to an ideal detector, a gaseous detector, silicon and plastic scintillator detectors. The energy loss radiograph and the scattering angle distributions of the protons were studied for proton beam energies of 150MeV, 190MeV and 230MeV. To improve the image quality deteriorated by the multiple Coulomb scattering (MCS), protons with small angles were selected. Two ways of calculating a scattering angle were considered using the proton's direction and position. A scattering angle cut of 8.7mrad was applied giving an optimal balance between quality and efficiency of the radiographic image. For the three proton beam energies, the number of protons used in image reconstruction with the direction method was half the number of protons kept using the position method. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

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

Barada, K., E-mail: kshitish@ucla.edu; Rhodes, T. L.; Crocker, N. A.

We present new measurements of internal magnetic fluctuations obtained with a novel eight channel cross polarization scattering (CPS) system installed on the DIII-D tokamak. Measurements of internal, localized magnetic fluctuations provide a window on an important physics quantity that we heretofore have had little information on. Importantly, these measurements provide a new ability to challenge and test linear and nonlinear simulations and basic theory. The CPS method, based upon the scattering of an incident microwave beam into the opposite polarization by magnetic fluctuations, has been significantly extended and improved over the method as originally developed on the Tore Supra tokamak.more » A new scattering geometry, provided by a unique probe beam, is utilized to improve the spatial localization and wavenumber range. Remotely controllable polarizer and mirror angles allow polarization matching and wavenumber selection for a range of plasma conditions. The quasi-optical system design, its advantages and challenges, as well as important physics validation tests are presented and discussed. Effect of plasma beta (ratio of kinetic to magnetic pressure) on both density and magnetic fluctuations is studied and it is observed that internal magnetic fluctuations increase with beta. During certain quiescent high confinement operational regimes, coherent low frequency modes not detected by magnetic probes are detected locally by CPS diagnostics.« less

SU-E-T-279: A Novel Electron-Beam Combined with Magnetic Field Application for Radiotherapy.

PubMed

Alezra, D; Nardi, E; Koren, S; Bragilovski, D; Orion, I

2012-06-01

The new beam and delivery system consists of an electron accelerator and a system of magnets (one or more). Introducing a transverse magnetic field in and near the tumor, causes the electrons to spiral in this region, thereby producing an effective peak in the depth dose distribution, within the tumor volume. Although the basic idea is not new, we suggest here for the first time, a viable as well as a workable, magnetic field configuration, which in addition to focusing the beam does not interfere with its propagation to the target. The electron accelerator: can be a linear accelerator or any other type electron accelerator, capable of producing different electron energies for different depths and dose absorption accumulation. The Field size can be as small as a pencil beam and as big as any of the other standard field sizes that are used in radiotherapy. The scatter filter can be used or removed. The dose rate accumulation can be as higher as possible.The magnets are able to produce magnetic fields. The order, direction, width, place, shape and number of the magnetic fields define the shape and the Percentage Depth Dose (PDD) curve of the electron beam. Prototypes were successfully tested by means of computer simulation, using:COMSOL-Multiphsics for magnetic fields calculations. FLUKA package, for electron beam MC simulation. Our results suggest that by using an electron beam at different energies, combined with magnetic fields, we could modify the delivered dose. This is caused by manipulating the electron motion via the Lorentz force. The applied magnetic field, will focus the electron beam at a given depth and deposit the energy in a given volume and depth, where otherwise the electron energy will have spread deeper. The direction and magnitude of the magnetic fields will prevent the scattering of the electron beam and its absorption in remote volumes. In practice, we get a pseudo Bragg peak depth dose distribution, applying a relatively low cost system. The therapeutic efficiency induced by the system is of similar efficiency as the ion beam therapy techniques. Our novel concept demonstrates treatment that is almost similar to proton therapy and in some parameters even better performance.Unlike the current high-energy electron therapy, our system's beam deposit almost all of its energy on its target, with a low amount of radiation deposited in tissues from the surface of the skin to the front of tumor, and almost no "exit dose" beyond the tumor. This property will enables to hit tumors with higher, potentially more effective radiation doses, while being considerably less expensive. © 2012 American Association of Physicists in Medicine.

SU-F-T-149: Development of the Monte Carlo Simulation Platform Using Geant4 for Designing Heavy Ion Therapy Beam Nozzle

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

Shin, Jae-ik; Yoo, SeungHoon; Cho, Sungho

Purpose: The significant issue of particle therapy such as proton and carbon ion was a accurate dose delivery from beam line to patient. For designing the complex delivery system, Monte Carlo simulation can be used for the simulation of various physical interaction in scatters and filters. In this report, we present the development of Monte Carlo simulation platform to help design the prototype of particle therapy nozzle and performed the Monte Carlo simulation using Geant4. Also we show the prototype design of particle therapy beam nozzle for Korea Heavy Ion Medical Accelerator (KHIMA) project in Korea Institute of Radiological andmore » Medical Science(KIRAMS) at Republic of Korea. Methods: We developed a simulation platform for particle therapy beam nozzle using Geant4. In this platform, the prototype nozzle design of Scanning system for carbon was simply designed. For comparison with theoretic beam optics, the beam profile on lateral distribution at isocenter is compared with Mont Carlo simulation result. From the result of this analysis, we can expected the beam spot property of KHIMA system and implement the spot size optimization for our spot scanning system. Results: For characteristics study of scanning system, various combination of the spot size from accerlator with ridge filter and beam monitor was tested as simple design for KHIMA dose delivery system. Conclusion: In this report, we presented the part of simulation platform and the characteristics study. This study is now on-going in order to develop the simulation platform including the beam nozzle and the dose verification tool with treatment planning system. This will be presented as soon as it is become available.« less

Thermal management and prototype testing of Compton scattering X-ray beam position monitor for the Advanced Photon Source Upgrade

DOE PAGES

Lee, S. H.; Yang, B. X.; Collins, J. T.; ...

2017-02-07

Accurate and stable x-ray beam position monitors (XBPMs) are key elements in obtaining the desired user beam stability in the Advanced Photon Source Upgrade. In the next-generation XBPMs for the canted-undulator front ends, where two undulator beams are separated by 1.0 mrad, the lower beam power (<10 kW) per undulator allows us to explore lower-cost solutions based on Compton scattering from a diamond placed edge-on to the x-ray beam. Because of the high peak power density of the x-ray beams, this diamond experiences high temperatures and has to be clamped to a water-cooled heat spreader using thermal interface materials (TIMs),more » which play a key role in reducing the temperature of the diamond. To evaluate temperature changes through the interface via thermal simulations, the thermal contact resistance (TCR) of TIMs at an interface between two solid materials under even contact pressure must be known. This paper addresses the TCR measurements of several TIMs, including gold, silver, pyrolytic graphite sheet, and 3D graphene foam. In addition, a prototype of a Compton-scattering XBPM with diamond blades was installed at APS Beamline 24-ID-A in May 2015 and has been tested. This study presents the design of the Compton-scattering XBPM, and compares thermal simulation results obtained for the diamond blade of this XBPM by the finite element method with in situ empirical measurements obtained by using reliable infrared technology.« less

Acousto-Optic Beam Sampler, Part 2. Green’s Function Solution to Acousto-Optic Interaction Problem.

DTIC Science & Technology

This part of the ’ Acousto - Optic Beam Sampler,’ series lays down the formalism behind the Green’s function integral approach to solving the acousto ... optic scattering problem. The advantage of this formulation which is applicable to gases is shown through developing the solution to the scattering

Determination of the scalar polarizabilities of the proton using beam asymmetry $$\\Sigma_{3}$$ in Compton scattering

DOE PAGES

Sokhoyan, V.; Downie, E. J.; Mornacchi, E.; ...

2017-01-01

The scalar dipole polarizabilities, α E1 and β M1, are fundamental properties related to the internal dynamics of the nucleon. The currently accepted values of the proton polarizabilities were determined by fitting to unpolarized proton Compton scattering cross section data. The measurement of the beam asymmetry Σ 3 in a certain kinematical range provides an alternative approach to the extraction of the scalar polarizabilities. At the Mainz Microtron (MAMI) the beam asymmetry was measured for Compton scattering below pion photoproduction threshold for the first time. Finally, the results are compared with model calculations and the influence of the experimental datamore » on the extraction of the scalar polarizabilities is determined.« less

Effects of Carrier Confinement and Intervalley Scattering on Photoexcited Electron Plasma in Silicon.

PubMed

Sieradzki, A; Kuznicki, Z T

2013-01-01

The ultrafast reflectivity of silicon, excited and probed with femtosecond laser pulses, is studied for different wavelengths and energy densities. The confinement of carriers in a thin surface layer delimited by a nanoscale Si-layered system buried in a Si heavily-doped wafer reduces the critical density of carriers necessary to create the electron plasma by a factor of ten. We performed two types of reflectivity measurements, using either a single beam or two beams. The plasma strongly depends on the photon energy density because of the intervalley scattering of the electrons revealed by two different mechanisms assisted by the electron-phonon interaction. One mechanism leads to a negative differential reflectivity that can be attributed to an induced absorption in X valleys. The other mechanism occurs, when the carrier population is thermalizing and gives rise to a positive differential reflectivity corresponding to Pauli-blocked intervalley gamma to X scattering. These results are important for improving the efficiency of Si light-to-electricity converters, in which there is a possibility of multiplying carriers by nanostructurization of Si.

Potential Elevation Biases for Laser Altimeters from Subsurface Scattered Photons: Laboratory and Model Exploration of Green Light Scattering in Snow

NASA Astrophysics Data System (ADS)

Greeley, A.; Neumann, T.; Markus, T.; Kurtz, N. T.; Cook, W. B.

2015-12-01

Existing visible light laser altimeters such as MABEL (Multiple Altimeter Beam Experimental Lidar) - a single photon counting simulator for ATLAS (Advanced Topographic Laser Altimeter System) on NASA's upcoming ICESat-2 mission - and ATM (Airborne Topographic Mapper) on NASA's Operation IceBridge mission provide scientists a view of Earth's ice sheets, glaciers, and sea ice with unprecedented detail. Precise calibration of these instruments is needed to understand rapidly changing parameters like sea ice freeboard and to measure optical properties of surfaces like snow covered ice sheets using subsurface scattered photons. Photons travelling into snow, ice, or water before scattering back to the altimeter receiving system (subsurface photons) travel farther and longer than photons scattering off the surface only, causing a bias in the measured elevation. We seek to identify subsurface photons in a laboratory setting using a flight-tested laser altimeter (MABEL) and to quantify their effect on surface elevation estimates for laser altimeter systems. We also compare these estimates with previous laboratory measurements of green laser light transmission through snow, as well as Monte Carlo simulations of backscattered photons from snow.

Carbon contamination analysis and its effect on extreme ultra violet mask imaging performance using coherent scattering microscopy/in-situ accelerated contamination system.

PubMed

Jeong, Chang Young; Lee, Sangsul; Doh, Jong Gul; Lee, Jae Uk; Cha, Han-sun; Nichols, William T; Lee, Dong Gun; Kim, Seong Sue; Cho, Han Ku; Rah, Seung-yu; Ahn, Jinho

2011-07-01

The coherent scattering microscopy/in-situ accelerated contamination system (CSM/ICS) is a developmental metrology tool designed to analyze the impact of carbon contamination on the imaging performance. It was installed at 11B EUVL beam-line of the Pohang Accelerator Laboratory (PAL). Monochromatized 13.5 nm wavelength beam with Mo/Si multilayer mirrors and zirconium filters was used. The CSM/ICS is composed of the CSM for measuring imaging properties and the ICS for implementing acceleration of carbon contamination. The CSM has been proposed as an actinic inspection technique that records the coherent diffraction pattern from the EUV mask and reconstructs its aerial image using a phase retrieval algorithm. To improve the CSM measurement accuracy, optical and electrical noises of main chamber were minimized. The background noise level measured by CCD camera was approximately 8.5 counts (3 sigma) when the EUV beam was off. Actinic CD measurement repeatability was <1 A (3 sigma) at 17.5 nm line and space pattern. The influence of carbon contamination on the imaging properties can be analyzed by transferring EUV mask to CSM imaging center position after executing carbon contamination without a fine alignment system. We also installed photodiode and ellipsometry for in-situ reflectivity and thickness measurement. This paper describes optical design and system performance observed during the first phase of integration, including CSM imaging performance and carbon contamination analysis results.

Prior image constrained image reconstruction in emerging computed tomography applications

NASA Astrophysics Data System (ADS)

Brunner, Stephen T.

Advances have been made in computed tomography (CT), especially in the past five years, by incorporating prior images into the image reconstruction process. In this dissertation, we investigate prior image constrained image reconstruction in three emerging CT applications: dual-energy CT, multi-energy photon-counting CT, and cone-beam CT in image-guided radiation therapy. First, we investigate the application of Prior Image Constrained Compressed Sensing (PICCS) in dual-energy CT, which has been called "one of the hottest research areas in CT." Phantom and animal studies are conducted using a state-of-the-art 64-slice GE Discovery 750 HD CT scanner to investigate the extent to which PICCS can enable radiation dose reduction in material density and virtual monochromatic imaging. Second, we extend the application of PICCS from dual-energy CT to multi-energy photon-counting CT, which has been called "one of the 12 topics in CT to be critical in the next decade." Numerical simulations are conducted to generate multiple energy bin images for a photon-counting CT acquisition and to investigate the extent to which PICCS can enable radiation dose efficiency improvement. Third, we investigate the performance of a newly proposed prior image constrained scatter correction technique to correct scatter-induced shading artifacts in cone-beam CT, which, when used in image-guided radiation therapy procedures, can assist in patient localization, and potentially, dose verification and adaptive radiation therapy. Phantom studies are conducted using a Varian 2100 EX system with an on-board imager to investigate the extent to which the prior image constrained scatter correction technique can mitigate scatter-induced shading artifacts in cone-beam CT. Results show that these prior image constrained image reconstruction techniques can reduce radiation dose in dual-energy CT by 50% in phantom and animal studies in material density and virtual monochromatic imaging, can lead to radiation dose efficiency improvement in multi-energy photon-counting CT, and can mitigate scatter-induced shading artifacts in cone-beam CT in full-fan and half-fan modes.

Extension of DQE to include scatter, grid, magnification, and focal spot blur: a new experimental technique and metric

NASA Astrophysics Data System (ADS)

Ranger, N. T.; Mackenzie, A.; Honey, I. D.; Dobbins, J. T., III; Ravin, C. E.; Samei, E.

2009-02-01

In digital radiography, conventional DQE evaluations are performed under idealized conditions that do not reflect typical clinical operating conditions. For this reason, we have developed and evaluated an experimental methodology for measuring theeffective detective quantum efficiency (eDQE) of digital radiographic systems and its utility in chest imaging applications.To emulate the attenuation and scatter properties of the human thorax across a range of sizes, the study employed pediatric and adult geometric chest imaging phantoms designed for use in the FDA/CDRH Nationwide Evaluation of X-Ray Trends (NEXT) program and a third phantom configuration designed to represent the bariatric population. The MTF for each phantom configuration was measured using images of an opaque edge device placed at the nominal surface of each phantom and at a common reference point. For each phantom, the NNPS was measured in a uniform region within the phantom image acquired at an exposure level determined from a prior phototimed acquisition. Scatter measurements were made using a beam-stop technique. These quantities were used along with measures of phantom attenuation and estimates of x-ray flux, to compute the eDQE at the beam-entrance surface of the phantoms, reflecting the presence of scatter, grid, magnification, and focal spot blur. The MTF results showed notable degradation due to focal spot blurring enhanced by geometric magnification, with increasing phantom size. Measured scatter fractions were 33%, 34% and 46% for the pediatric, adult, and bariatric phantoms, respectively. Correspondingly, the measured narrow beam transmission fractions were 16%, 9%, and 3%. The eDQE results for the pediatric and adult phantoms correlate well at low spatial frequencies but show degradation in the eDQE at increasing spatial frequencies for the adult phantom in comparison to the pediatric phantom. The results for the bariatric configuration showed a marked decrease in eDQE in comparison to the adult phantom results, across all spatial frequencies, attributable to the combined differences in geometric magnification, and scatter. The eDQE metric has been demonstrated to be sensitive to body habitus suggesting its usefulness in assessing system response across a range of chest sizes and potentially making it a useful factor in protocol assessment and optimization.

Pulsed holographic system for imaging through spatially extended scattering media

NASA Astrophysics Data System (ADS)

Kanaev, A. V.; Judd, K. P.; Lebow, P.; Watnik, A. T.; Novak, K. M.; Lindle, J. R.

2017-10-01

Imaging through scattering media is a highly sought capability for military, industrial, and medical applications. Unfortunately, nearly all recent progress was achieved in microscopic light propagation and/or light propagation through thin or weak scatterers which is mostly pertinent to medical research field. Sensing at long ranges through extended scattering media, for example turbid water or dense fog, still represents significant challenge and the best results are demonstrated using conventional approaches of time- or range-gating. The imaging range of such systems is constrained by their ability to distinguish a few ballistic photons that reach the detector from the background, scattered, and ambient photons, as well as from detector noise. Holography can potentially enhance time-gating by taking advantage of extra signal filtering based on coherence properties of the ballistic photons as well as by employing coherent addition of multiple frames. In a holographic imaging scheme ballistic photons of the imaging pulse are reflected from a target and interfered with the reference pulse at the detector creating a hologram. Related approaches were demonstrated previously in one-way imaging through thin biological samples and other microscopic scale scatterers. In this work, we investigate performance of holographic imaging systems under conditions of extreme scattering (less than one signal photon per pixel signal), demonstrate advantages of coherent addition of images recovered from holograms, and discuss image quality dependence on the ratio of the signal and reference beam power.

Electromagnetic radiation from beam-plasma instabilities

NASA Technical Reports Server (NTRS)

Pritchett, P. L.; Dawson, J. M.

1983-01-01

A computer simulation is developed for the generation of electromagnetic radiation in an electron beam-plasma interaction. The plasma is treated as a two-dimensional finite system, and effects of a continuous nonrelativistic beam input are accounted for. Three momentum and three field components are included in the simulation, and an external magnetic field is excluded. EM radiation generation is possible through interaction among Langmuir oscillations, ion-acoustic waves, and the electromagnetic wave, producing radiation perpendicular to the beam. The radiation is located near the plasma frequency, and polarized with the E component parallel to the beam. The scattering of Langmuir waves caused by ion-acoustic fluctuations generates the radiation. Comparison with laboratory data for the three-wave interactions shows good agreement in terms of the radiation levels produced, which are small relative to the plasma thermal energy.

First measurement of time evolution of electron temperature profiles with Nd:YAG Thomson scattering system on Heliotron J

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

Kenmochi, N., E-mail: kemmchi.naoki.62r@st.kyoto-u.ac.jp; Tei, S.; Zang, L.

2014-11-15

A Nd:YAG Thomson scattering system has been developed for Heliotron J. The system consists of two 550 mJ 50 Hz lasers, large collection optics, and 25 radial channel (∼1 cm spatial resolution) interference polychromators. This measurement system achieves a S/N ratio of ∼50 for low-density plasma (n{sub e} ∼ 0.5 × 10{sup 19} m{sup −3}). A time evolution of electron temperature profiles was measured with this system for a high-intensity gas-puff (HIGP) fueling neutral-beam-injection plasma. The peripheral temperature of the higher-density phase after HIGP recovers to the low-density pre-HIGP level, suggesting that improving particle transport in the HIGP plasma maymore » be possible.« less

SU-F-T-146: Comparing Monte Carlo Simulations with Commissioning Beam Data for Mevion S250 Proton Therapy System

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

Prusator, M; Jin, H; Ahmad, S

2016-06-15

Purpose: To evaluate the Monte Carlo simulated beam data with the measured commissioning data for the Mevion S250 proton therapy system. Method: The Mevion S250 proton therapy system utilizes a passive double scattering technique with a unique gantry mounted superconducting accelerator and offers effective proton therapy in a compact design concept. The field shaping system (FSS) includes first scattering foil, range modulator wheel (RMW), second scattering foil and post absorber and offers two field sizes and a total of 24 treatment options from proton range of 5 cm to 32 cm. The treatment nozzle was modeled in detail using TOPASmore » (TOolkit for PArticle Simulation) Monte Carlo code. The timing feathers of the moving modulator wheels were also implemented to generate the Spread Out Bragg Peak (SOBP). The simulation results including pristine Bragg Peak, SOBP and dose profiles were compared with the data measured during beam commissioning. Results: The comparison between the measured data and the simulation data show excellent agreement. For pristine proton Bragg Peaks, the simulated proton range (depth of distal 90%) values agreed well with the measured range values within 1 mm accuracy. The differences of the distal falloffs (depth from distal 80% to 20%) were also found to be less than 1 mm between the simulations and measurements. For the SOBP, the widths of modulation (depth of proximal 95% to distal 90%) were also found to agree with the measurement within 1 mm. The flatness of the simulated and measured lateral profiles was found to be 0.6 % and 1.1 %, respectively. Conclusion: The agreement between simulations and measurements demonstrate that TOPAS could be used as a viable platform to proton therapy applications. The matched simulation results offer a great tool and open opportunity for variety of applications.« less

Designing a range modulator wheel to spread-out the Bragg peak for a passive proton therapy facility

NASA Astrophysics Data System (ADS)

Jia, S. Bijan; Romano, F.; Cirrone, Giuseppe A. P.; Cuttone, G.; Hadizadeh, M. H.; Mowlavi, A. A.; Raffaele, L.

2016-01-01

In proton beam therapy, a Spread-Out Bragg peak (SOBP) is used to establish a uniform dose distribution in the target volume. In order to create a SOBP, several Bragg peaks of different ranges, corresponding to different entrance energies, with certain intensities (weights) should be combined each other. In a passive beam scattering system, the beam is usually extracted from a cyclotron at a constant energy throughout a treatment. Therefore, a SOBP is produced by a range modulator wheel, which is basically a rotating wheel with steps of variable thicknesses, or by using the ridge filters. In this study, we used the Geant4 toolkit to simulate a typical passive scattering beam line. In particular, the CATANA transport beam line of INFN Laboratori Nazionali del Sud (LNS) in Catania has been reproduced in this work. Some initial properties of the entrance beam have been checked by benchmarking simulations with experimental data. A class dedicated to the simulation of the wheel modulators has been implemented. It has been designed in order to be easily modified for simulating any desired modulator wheel and, hence, any suitable beam modulation. By using some auxiliary range-shifters, a set of pristine Bragg peaks was obtained from the simulations. A mathematical algorithm was developed, using the simulated pristine dose profiles as its input, to calculate the weight of each pristine peak, reproduce the SOBP, and finally generate a flat dose distribution. Therefore, once the designed modulator has been realized, it has been tested at CATANA facility, comparing the experimental data with the simulation results.

Effect of molecular anisotropy on beam scattering measurements

NASA Technical Reports Server (NTRS)

Goldflam, R.; Green, S.; Kouri, D. J.; Monchick, L.

1978-01-01

Within the energy sudden approximation, the total integral and total differential scattering cross sections are given by the angle average of scattering cross sections computed at fixed rotor orientations. Using this formalism the effect of molecular anisotropy on scattering of He by HCl and by CO is examined. Comparisons with accurate close coupling calculations indicate that this approximation is quite reliable, even at very low collision energies, for both of these systems. Comparisons are also made with predictions based on the spherical average of the interaction. For HCl the anisotropy is rather weak and its main effect is a slight quenching of the oscillations in the differential cross sections relative to predictions of the spherical averaged potential. For CO the anisotropy is much stronger, so that the oscillatory pattern is strongly quenched and somewhat shifted. It appears that the sudden approximation provides a simple yet accurate method for describing the effect of molecular anisotropy on scattering measurements.

Computational model for simulation of sequences of helicity and angular momentum transfer in turbid tissue-like scattering medium (Conference Presentation)

NASA Astrophysics Data System (ADS)

Doronin, Alexander; Meglinski, Igor

2017-02-01

Current report considers development of a unified Monte Carlo (MC) -based computational model for simulation of propagation of Laguerre-Gaussian (LG) beams in turbid tissue-like scattering medium. With a primary goal to proof the concept of using complex light for tissue diagnosis we explore propagation of LG beams in comparison with Gaussian beams for both linear and circular polarization. MC simulations of radially and azimuthally polarized LG beams in turbid media have been performed, classic phenomena such as preservation of the orbital angular momentum, optical memory and helicity flip are observed, detailed comparison is presented and discussed.

Soft x-ray scattering facility at the Advanced Light Source with real-time data processing and analysis.

PubMed

Gann, E; Young, A T; Collins, B A; Yan, H; Nasiatka, J; Padmore, H A; Ade, H; Hexemer, A; Wang, C

2012-04-01

We present the development and characterization of a dedicated resonant soft x-ray scattering facility. Capable of operation over a wide energy range, the beamline and endstation are primarily used for scattering from soft matter systems around the carbon K-edge (∼285 eV). We describe the specialized design of the instrument and characteristics of the beamline. Operational characteristics of immediate interest to users such as polarization control, degree of higher harmonic spectral contamination, and detector noise are delineated. Of special interest is the development of a higher harmonic rejection system that improves the spectral purity of the x-ray beam. Special software and a user-friendly interface have been implemented to allow real-time data processing and preliminary data analysis simultaneous with data acquisition. © 2012 American Institute of Physics

Simplified Formulae System for Resonant Inverse Compton Scattering of a Fast Electron in an Intense Magnetic Field

NASA Technical Reports Server (NTRS)

You, J. H.; Chen, W. P.; Zhang, S. N.; Chen, L.; Liu, D.; Chou, C. K.

2003-01-01

We present simple analytical formulae for the emission spectrum and total power of a special kind of resonant inverse Compton scattering (RICS) of a relativistic electron in an intense magnetic field. In contrast with the available formulae system, we obtain a markedly simplified one based on the semiclassical quantum theory, which is more understandable for people who are unfamiliar with quantum electrodynamics. We show that the RICS process, under an appropriate 'accommodation condition' derived in this paper, is predominantly much more efficient than the coexistent ordinary inverse Compton scattering, and produces highly beamed high-frequency radiation with moderately good monochromaticity. Our formulae are simple to use - thus offering a lucid physical intuition for the theory - and may find wide applications in hard X-ray and gamma-ray astrophysics.

Momentum Flux Determination Using the Multi-beam Poker Flat Incoherent Scatter Radar

NASA Technical Reports Server (NTRS)

Nicolls, M. J.; Fritts, D. C.; Janches, Diego; Heinselman, C. J.

2012-01-01

In this paper, we develop an estimator for the vertical flux of horizontal momentum with arbitrary beam pointing, applicable to the case of arbitrary but fixed beam pointing with systems such as the Poker Flat Incoherent Scatter Radar (PFISR). This method uses information from all available beams to resolve the variances of the wind field in addition to the vertical flux of both meridional and zonal momentum, targeted for high-frequency wave motions. The estimator utilises the full covariance of the distributed measurements, which provides a significant reduction in errors over the direct extension of previously developed techniques and allows for the calculation of an error covariance matrix of the estimated quantities. We find that for the PFISR experiment, we can construct an unbiased and robust estimator of the momentum flux if sufficient and proper beam orientations are chosen, which can in the future be optimized for the expected frequency distribution of momentum-containing scales. However, there is a potential trade-off between biases and standard errors introduced with the new approach, which must be taken into account when assessing the momentum fluxes. We apply the estimator to PFISR measurements on 23 April 2008 and 21 December 2007, from 60-85 km altitude, and show expected results as compared to mean winds and in relation to the measured vertical velocity variances.

Polarisation in spin-echo experiments: Multi-point and lock-in measurements

NASA Astrophysics Data System (ADS)

Tamtögl, Anton; Davey, Benjamin; Ward, David J.; Jardine, Andrew P.; Ellis, John; Allison, William

2018-02-01

Spin-echo instruments are typically used to measure diffusive processes and the dynamics and motion in samples on ps and ns time scales. A key aspect of the spin-echo technique is to determine the polarisation of a particle beam. We present two methods for measuring the spin polarisation in spin-echo experiments. The current method in use is based on taking a number of discrete readings. The implementation of a new method involves continuously rotating the spin and measuring its polarisation after being scattered from the sample. A control system running on a microcontroller is used to perform the spin rotation and to calculate the polarisation of the scattered beam based on a lock-in amplifier. First experimental tests of the method on a helium spin-echo spectrometer show that it is clearly working and that it has advantages over the discrete approach, i.e., it can track changes of the beam properties throughout the experiment. Moreover, we show that real-time numerical simulations can perfectly describe a complex experiment and can be easily used to develop improved experimental methods prior to a first hardware implementation.

On the importance of full-dimensionality in low-energy molecular scattering calculations

PubMed Central

Faure, Alexandre; Jankowski, Piotr; Stoecklin, Thierry; Szalewicz, Krzysztof

2016-01-01

Scattering of H2 on CO is of great importance in astrophysics and also is a benchmark system for comparing theory to experiment. We present here a new 6-dimensional potential energy surface for the ground electronic state of H2-CO with an estimated uncertainty of about 0.6 cm−1 in the global minimum region, several times smaller than achieved earlier. This potential has been used in nearly exact 6-dimensional quantum scattering calculations to compute state-to-state cross-sections measured in low-energy crossed-beam experiments. Excellent agreement between theory and experiment has been achieved in all cases. We also show that the fully 6-dimensional approach is not needed with the current accuracy of experimental data since an equally good agreement with experiment was obtained using only a 4-dimensional treatment, which validates the rigid-rotor approach widely used in scattering calculations. This finding, which disagrees with some literature statements, is important since for larger systems full-dimensional scattering calculations are currently not possible. PMID:27333870

Evaluation of dual polarization scattering matrix radar rain backscatter measurements in the X- and Q-bands

NASA Astrophysics Data System (ADS)

Agrawal, A. P.; Carnegie, D. W.; Boerner, W.-M.

This paper presents an evaluation of polarimetric rain backscatter measurements collected with coherent dual polarization radar systems in the X (8.9 GHz) and Q (45GHz) bands, the first being operated in a pulsed mode and the second being a FM-CW system. The polarimetric measurement data consisted for each band of fifty files of time-sequential scattering matrix measurements expressed in terms of a linear (H, V) antenna polarization state basis. The rain backscattering takes place in a rain cell defined by the beam widths and down range distances of 275 ft through 325 ft and the scattering matrices were measured far below the hydrometeoric scattering center decorrelation time so that ensemble averaging of time-sequential scattering matrices may be applied. In the data evaluation great care was taken in determining: (1) polarimetric Doppler velocities associated with the motion of descending oscillating raindrops and/or eddies within the moving swaths of coastal rain showers, and (2) also the properties of the associated co/cross-polarization rain clutter nulls and their distributions on the Poincare polarization sphere.

HISCAT: A proposed new scatter facility in Northern Scandinavia

NASA Technical Reports Server (NTRS)

Bostrom, R.; Thide, B.

1986-01-01

It is proposed that a new versatile ionospheric and atmospheric scatter radar be constructed in northern Scandavia through a multinational collaborative effort. The new facility tentatively named HISCAT (High frequency, High power, High latitude, Heating and Ionospheric Scatter facility), should be used for scientific investigations of: the physics of the neutral (middle) atmosphere; fundamental plasma phenomena, natural or artificially induced in the ionosphere; electrodynamic conditions at high altitudes above the auroral region and in the polar cap ionosphere; plasma waves in the solar atmosphere. The system should thus be able to operate as a mesosphere-stratosphere-troposphere (MST) radar, a so-called ionospheric modification facility, incoherent-scatter radar, coherent-scatter radar, and solar radar. Basically, the new facility should be a device that can operate simultaneously on several frequencies in the frequency range 5 to 50 MHz not covered by other instruments. It should comprise: powerful transmitters, capable of delivering a total average power of several megawatts; an advanced phased antenna array of high gain forming one or two steerable and well collimated beams; and an advanced data collection and analysis system.

Upgraded divertor Thomson scattering system on DIII-D

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

Glass, F., E-mail: glassf@fusion.gat.com; Carlstrom, T. N.; Du, D.

2016-11-15

A design to extend the unique divertor Thomson scattering system on DIII-D to allow measurements of electron temperature and density in high triangularity plasmas is presented. Access to this region is selectable on a shot-by-shot basis by redirecting the laser beam of the existing divertor Thomson system inboard — beneath the lower floor using a moveable, high-damage threshold, in-vacuum mirror — and then redirecting again vertically. The currently measured divertor region remains available with this mirror retracted. Scattered light is collected from viewchords near the divertor floor using in-vacuum, high temperature optical elements and relayed through the port window, beforemore » being coupled into optical fiber bundles. At higher elevations from the floor, measurements are made by dynamically re-focusing the existing divertor system collection optics. Nd:YAG laser timing, analysis of the scattered light spectrum via polychromators, data acquisition, and calibration are all handled by existing systems or methods of the current multi-pulse Thomson scattering system. Existing filtered polychromators with 7 spectral channels are employed to provide maximum measurement breadth (T{sub e} in the range of 0.5 eV–2 keV, n{sub e} in the range of 5 × 10{sup 18}–1 × 10{sup 21} m{sup 3}) for both low T{sub e} in detachment and high T{sub e} measurement up beyond the separatrix.« less

Lidar instruments proposed for Eos

NASA Technical Reports Server (NTRS)

Grant, William B.; Browell, Edward V.

1990-01-01

Lidar, an acronym for light detection and ranging, represents a class of instruments that utilize lasers to send probe beams into the atmosphere or onto the surface of the Earth and detect the backscattered return in order to measure properties of the atmosphere or surface. The associated technology has matured to the point where two lidar facilities, Geodynamics Laser Ranging System (GLRS), and Laser Atmospheric Wind Sensor (LAWS) were accepted for Phase 2 studies for Eos. A third lidar facility Laser Atmospheric Sounder and Altimeter (LASA), with the lidar experiment EAGLE (Eos Atmospheric Global Lidar Experiment) was proposed for Eos. The generic lidar system has a number of components. They include controlling electronics, laser transmitters, collimating optics, a receiving telescope, spectral filters, detectors, signal chain electronics, and a data system. Lidar systems that measure atmospheric constituents or meteorological parameters record the signal versus time as the beam propagates through the atmosphere. The backscatter arises from molecular (Rayleigh) and aerosol (Mie) scattering, while attenuation arises from molecular and aerosol scattering and absorption. Lidar systems that measure distance to the Earth's surface or retroreflectors in a ranging mode record signals with high temporal resolution over a short time period. The overall characteristics and measurements objectives of the three lidar systems proposed for Eos are given.

Using an intense laser beam in interaction with muon/electron beam to probe the noncommutative QED

NASA Astrophysics Data System (ADS)

Tizchang, S.; Batebi, S.; Haghighat, M.; Mohammadi, R.

2017-02-01

It is known that the linearly polarized photons can partly transform to circularly polarized ones via forward Compton scattering in a background such as the external magnetic field or noncommutative space time. Based on this fact we explore the effects of the NC-background on the scattering of a linearly polarized laser beam from an intense beam of charged leptons. We show that for a muon/electron beam flux {overline{ɛ}}_{μ, e}˜ 1{0}^{12}/{10}^{10} TeV cm-2 sec-1 and a linearly polarized laser beam with energy k 0 ˜1 eV and average power {overline{P}}_{laser}˜eq 1{0}^3 KW, the generation rate of circularly polarized photons is about R V ˜ 104 /sec for noncommutative energy scale ΛNC ˜ 10 TeV. This is fairly large and can grow for more intense beams in near future.

Status of the AFP project in the ATLAS experiment

NASA Astrophysics Data System (ADS)

Taševský, Marek

2015-04-01

Status of the AFP project in the ATLAS experiment is summarized. The AFP system is composed of a tracker to detect intact, diffractively scattered protons, and of a time-of-flight detector serving to suppress background from pile-up interactions. The whole system, located around 210 m from the main ATLAS detector, is placed in Roman Pots which move detectors from and to the incident proton beams. A typical distance of the closest approach of the tracker to these beams is 2-3 mm. The main physics motivation lies in measuring diffractive processes in runs with not a very high amount of pile-up.

SU-F-J-149: Beam and Cryostat Scatter Characteristics of the Elekta MR-Linac

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

Duglio, M; Towe, S; Roberts, D

2016-06-15

Purpose: The Elekta MR-Linac combines a digital linear accelerator system with a 1.5T Philips MRI machine. This study aimed to determine key characteristic information regarding the MR-Linac beam and in particular it evaluated the effect of the MR cryostat on the out of field scatter dose. Methods: Tissue phantom ratios, profiles and depth doses were acquired in plastic water with an IC-profiler or with an MR compatible water tank using multiple system configurations (Full (B0= 1.5T), Full (B0=0T) and No cryostat). Additionally, an in-house CAD based Monte Carlo code based on Penelope was used to provide comparative data. Results: Withmore » the cryostat in place and B0=0T, the measured TPR for the MR Linac system was 0.702, indicating an energy of around 7MV. Without the cryostat, the measured TPR was 0.669. For the Full (B0=0T) case, out of field dose at a depth of 10 cm in the isocentric plane, 5 cm from the field edge was 0.8%, 3.1% and 5.4% for 3×3 cm{sup 2}, 10×10 cm{sup 2} and 20×20 cm{sup 2} fields respectively.The out of field dose (averaged between 5 cm and 10 cm beyond the field edges) in the “with cryostat” case is 0.78% (absolute difference) higher than without the cryostat for clinically relevant field sizes (i.e. 10×10 cm{sup 2}) and comparable to measured conventional 6MV treatment beams at a depth of 10 cm (within 0.1% between 5 cm and 6 cm from field edge). At dose maximum and at 5 cm from the field edge, the “with cryostat” out of field scatter for a 10×10 cm{sup 2} field is 1.5% higher than “without cryostat', with a modest increase (0.9%) compared to Agility 6MV in the same conditions. Conclusion: The study has presented typical characteristics of the MR-Linac beam and determined that out of field dose is comparable to conventional treatment beams. All authors are employed by Elekta Ltd., who are developing an MR-Linac.« less

Validation of the MCNP6 electron-photon transport algorithm: multiple-scattering of 13- and 20-MeV electrons in thin foils

NASA Astrophysics Data System (ADS)

Dixon, David A.; Hughes, H. Grady

2017-09-01

This paper presents a validation test comparing angular distributions from an electron multiple-scattering experiment with those generated using the MCNP6 Monte Carlo code system. In this experiment, a 13- and 20-MeV electron pencil beam is deflected by thin foils with atomic numbers from 4 to 79. To determine the angular distribution, the fluence is measured down range of the scattering foil at various radii orthogonal to the beam line. The characteristic angle (the angle for which the max of the distribution is reduced by 1/e) is then determined from the angular distribution and compared with experiment. Multiple scattering foils tested herein include beryllium, carbon, aluminum, copper, and gold. For the default electron-photon transport settings, the calculated characteristic angle was statistically distinguishable from measurement and generally broader than the measured distributions. The average relative difference ranged from 5.8% to 12.2% over all of the foils, source energies, and physics settings tested. This validation illuminated a deficiency in the computation of the underlying angular distributions that is well understood. As a result, code enhancements were made to stabilize the angular distributions in the presence of very small substeps. However, the enhancement only marginally improved results indicating that additional algorithmic details should be studied.

Subsurface Scattered Photons: Friend or Foe? Improving visible light laser altimeter elevation estimates, and measuring surface properties using subsurface scattered photons

NASA Astrophysics Data System (ADS)

Greeley, A.; Kurtz, N. T.; Neumann, T.; Cook, W. B.; Markus, T.

2016-12-01

Photon counting laser altimeters such as MABEL (Multiple Altimeter Beam Experimental Lidar) - a single photon counting simulator for ATLAS (Advanced Topographical Laser Altimeter System) - use individual photons with visible wavelengths to measure their range to target surfaces. ATLAS, the sole instrument on NASA's upcoming ICESat-2 mission, will provide scientists a view of Earth's ice sheets, glaciers, and sea ice with unprecedented detail. Precise calibration of these instruments is needed to understand rapidly changing parameters such as sea ice freeboard, and to measure optical properties of surfaces like snow covered ice sheets using subsurface scattered photons. Photons that travel through snow, ice, or water before scattering back to an altimeter receiving system travel farther than photons taking the shortest path between the observatory and the target of interest. These delayed photons produce a negative elevation bias relative to photons scattered directly off these surfaces. We use laboratory measurements of snow surfaces using a flight-tested laser altimeter (MABEL), and Monte Carlo simulations of backscattered photons from snow to estimate elevation biases from subsurface scattered photons. We also use these techniques to demonstrate the ability to retrieve snow surface properties like snow grain size.

Anomalous time delays and quantum weak measurements in optical micro-resonators

PubMed Central

Asano, M.; Bliokh, K. Y.; Bliokh, Y. P.; Kofman, A. G.; Ikuta, R.; Yamamoto, T.; Kivshar, Y. S.; Yang, L.; Imoto, N.; Özdemir, Ş.K.; Nori, F.

2016-01-01

Quantum weak measurements, wavepacket shifts and optical vortices are universal wave phenomena, which originate from fine interference of multiple plane waves. These effects have attracted considerable attention in both classical and quantum wave systems. Here we report on a phenomenon that brings together all the above topics in a simple one-dimensional scalar wave system. We consider inelastic scattering of Gaussian wave packets with parameters close to a zero of the complex scattering coefficient. We demonstrate that the scattered wave packets experience anomalously large time and frequency shifts in such near-zero scattering. These shifts reveal close analogies with the Goos–Hänchen beam shifts and quantum weak measurements of the momentum in a vortex wavefunction. We verify our general theory by an optical experiment using the near-zero transmission (near-critical coupling) of Gaussian pulses propagating through a nano-fibre with a side-coupled toroidal micro-resonator. Measurements demonstrate the amplification of the time delays from the typical inverse-resonator-linewidth scale to the pulse-duration scale. PMID:27841269

Improved cross-calibration of Thomson scattering and electron cyclotron emission with ECH on DIII-D.

PubMed

Brookman, M W; Austin, M E; McLean, A G; Carlstrom, T N; Hyatt, A W; Lohr, J

2016-11-01

Thomson scattering produces n e profiles from measurement of scattered laser beam intensity. Rayleigh scattering provides a first calibration of the relation n e ∝ I TS , which depends on many factors (e.g., laser alignment and power, optics, and measurement systems). On DIII-D, the n e calibration is adjusted against an absolute n e from the density-driven cutoff of the 48 channel 2nd harmonic X-mode electron cyclotron emission system. This method has been used to calibrate Thomson n e from the edge to near the core (r/a > 0.15). Application of core electron cyclotron heating improves the quality of cutoff and depth of its penetration into the core, and also changes underlying MHD activity, minimizing crashes which confound calibration. Less fueling is needed as "ECH pump-out" generates a plasma ready to take up gas. On removal of gyrotron power, cutoff penetrates into the core as channels fall successively and smoothly into cutoff.

Proton Lateral Broadening Distribution Comparisons Between GRNTRN, MCNPX, and Laboratory Beam Measurements

NASA Technical Reports Server (NTRS)

Mertens, Christopher J.; Moyers, Michael F.; Walker, Steven A.; Tweed, John

2010-01-01

Recent developments in NASA s deterministic High charge (Z) and Energy TRaNsport (HZETRN) code have included lateral broadening of primary ion beams due to small-angle multiple Coulomb scattering, and coupling of the ion-nuclear scattering interactions with energy loss and straggling. This new version of HZETRN is based on Green function methods, called GRNTRN, and is suitable for modeling transport with both space environment and laboratory boundary conditions. Multiple scattering processes are a necessary extension to GRNTRN in order to accurately model ion beam experiments, to simulate the physical and biological-effective radiation dose, and to develop new methods and strategies for light ion radiation therapy. In this paper we compare GRNTRN simulations of proton lateral broadening distributions with beam measurements taken at Loma Linda University Proton Therapy Facility. The simulated and measured lateral broadening distributions are compared for a 250 MeV proton beam on aluminum, polyethylene, polystyrene, bone substitute, iron, and lead target materials. The GRNTRN results are also compared to simulations from the Monte Carlo MCNPX code for the same projectile-target combinations described above.

Diffusing Wave Spectroscopy Used to Study Foams

NASA Technical Reports Server (NTRS)

Zimmerli, Gregory A.; Durian, Douglas J.

2000-01-01

The white appearance of familiar objects such as clouds, snow, milk, or foam is due to the random scattering of light by the sample. As we all know, pure water is clear and easily passes a beam of light. However, tiny water droplets, such as those in a cloud, scatter light because the air and water droplet have different indexes of refraction. When many droplets, or scattering sites, are present, the incident light is scattered in random directions and the sample takes on a milky white appearance. In a glass of milk, the scattering is due to small colloidal particles. The white appearance of shaving cream, or foam, is due to the scattering of light at the water-bubble interface. Diffusing wave spectroscopy (DWS) is a laser light-scattering technique used to noninvasively probe the particle dynamics in systems that strongly scatter light. The technique takes advantage of the diffuse nature of light, which is reflected or transmitted from samples such as foams, dense colloidal suspensions (such as paint and milk), emulsions, liquid crystals, sandpiles, and even biological tissues.

Virtual edge illumination and one dimensional beam tracking for absorption, refraction, and scattering retrieval

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

Vittoria, Fabio A., E-mail: fabio.vittoria.12@ucl.ac.uk; Diemoz, Paul C.; Research Complex at Harwell, Harwell Oxford Campus, OX11 0FA Didcot

2014-03-31

We propose two different approaches to retrieve x-ray absorption, refraction, and scattering signals using a one dimensional scan and a high resolution detector. The first method can be easily implemented in existing procedures developed for edge illumination to retrieve absorption and refraction signals, giving comparable image quality while reducing exposure time and delivered dose. The second method tracks the variations of the beam intensity profile on the detector through a multi-Gaussian interpolation, allowing the additional retrieval of the scattering signal.

DESIGN OF A GAMMA-RAY SOURCE BASED ON INVERSE COMPTON SCATTERING AT THE FAST SUPERCONDUCTING LINAC

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

Mihalcea, D.; Jacobson, B.; Murokh, A.

2016-10-10

A watt-level average-power gamma-ray source is currently under development at the Fermilab Accelerator Science & Technology (FAST) facility. The source is based on the Inverse Compton Scattering of a high-brightness 300-MeV beam against a high-power laser beam circulating in an optical cavity. The back scattered gamma rays are expected to have photon energies up to 1.5 MeV. This paper discusses the optimization of the source, its performances, and the main challenges ahead.

SU-F-T-372: Surface and Peripheral Dose in Compensator-Based FFF Beam IMRT

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

Zhang, D; Feygelman, V; Moros, E

2016-06-15

Purpose: Flattening filter free (FFF) beams produce higher dose rates. Combined with compensator IMRT techniques, the dose delivery for each beam can be much shorter compared to the flattened beam MLC-based or compensator-based IMRT. This ‘snap shot’ IMRT delivery is beneficial to patients for tumor motion management. Due to softer energy, surface doses in FFF beam treatment are usually higher than those from flattened beams. Because of less scattering due to no flattening filter, peripheral doses are usually lower in FFF beam treatment. However, in compensator-based IMRT using FFF beams, the compensator is in the beam pathway. Does it introducemore » beam hardening effects and scattering such that the surface dose is lower and peripheral dose is higher compared to FFF beam MLC-based IMRT? Methods: This study applied Monte Carlo techniques to investigate the surface and peripheral doses in compensator-based IMRT using FFF beams and compared it to the MLC-based IMRT using FFF beams and flattened beams. Besides various thicknesses of copper slabs to simulate various thicknesses of compensators, a simple cone-shaped compensator was simulated to mimic a clinical application. The dose distribution in water phantom by the cone-shaped compensator was then simulated by multiple MLC defined FFF and flattened beams with various openings. After normalized to Dmax, the surface and peripheral dose was compared between the FFF beam compensator-based IMRT and FFF/flattened beam MLC-based IMRT. Results: The surface dose at the central 0.5mm depth was close between the compensator and 6FFF MLC dose distributions, and about 8% (of Dmax) higher than the flattened 6MV MLC dose. At 8cm off axis at dmax, the peripheral dose between the 6FFF and flattened 6MV MLC demonstrated similar doses, while the compensator dose was about 1% higher. Conclusion: Compensator does not reduce the surface doses but slightly increases the peripheral doses due to scatter inside compensator.« less

Room scatter effects in Total Skin Electron Irradiation: Monte Carlo simulation study.

PubMed

Nevelsky, Alexander; Borzov, Egor; Daniel, Shahar; Bar-Deroma, Raquel

2017-01-01

Total Skin Electron Irradiation (TSEI) is a complex technique which usually involves the use of large electron fields and the dual-field approach. In this situation, many electrons scattered from the treatment room floor are produced. However, no investigations of the effect of scattered electrons in TSEI treatments have been reported. The purpose of this work was to study the contribution of floor scattered electrons to skin dose during TSEI treatment using Monte Carlo (MC) simulations. All MC simulations were performed with the EGSnrc code. Influence of beam energy, dual-field angle, and floor material on the contribution of floor scatter was investigated. Spectrum of the scattered electrons was calculated. Measurements of dose profile were performed in order to verify MC calculations. Floor scatter dependency on the floor material was observed (at 20 cm from the floor, scatter contribution was about 21%, 18%, 15%, and 12% for iron, concrete, PVC, and water, respectively). Although total dose profiles exhibited slight variation as functions of beam energy and dual-field angle, no dependence of the floor scatter contribution on the beam energy or dual-field angle was found. The spectrum of the scattered electrons was almost uniform between a few hundred KeV to 4 MeV, and then decreased linearly to 6 MeV. For the TSEI technique, dose contribution due to the electrons scattered from the room floor may be clinically significant and should be taken into account during design and commissioning phases. MC calculations can be used for this task. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Coherent beam control through inhomogeneous media in multi-photon microscopy

NASA Astrophysics Data System (ADS)

Paudel, Hari Prasad

Multi-photon fluorescence microscopy has become a primary tool for high-resolution deep tissue imaging because of its sensitivity to ballistic excitation photons in comparison to scattered excitation photons. The imaging depth of multi-photon microscopes in tissue imaging is limited primarily by background fluorescence that is generated by scattered light due to the random fluctuations in refractive index inside the media, and by reduced intensity in the ballistic focal volume due to aberrations within the tissue and at its interface. We built two multi-photon adaptive optics (AO) correction systems, one for combating scattering and aberration problems, and another for compensating interface aberrations. For scattering correction a MEMS segmented deformable mirror (SDM) was inserted at a plane conjugate to the objective back-pupil plane. The SDM can pre-compensate for light scattering by coherent combination of the scattered light to make an apparent focus even at a depths where negligible ballistic light remains (i.e. ballistic limit). This problem was approached by investigating the spatial and temporal focusing characteristics of a broad-band light source through strongly scattering media. A new model was developed for coherent focus enhancement through or inside the strongly media based on the initial speckle contrast. A layer of fluorescent beads under a mouse skull was imaged using an iterative coherent beam control method in the prototype two-photon microscope to demonstrate the technique. We also adapted an AO correction system to an existing in three-photon microscope in a collaborator lab at Cornell University. In the second AO correction approach a continuous deformable mirror (CDM) is placed at a plane conjugate to the plane of an interface aberration. We demonstrated that this "Conjugate AO" technique yields a large field-of-view (FOV) advantage in comparison to Pupil AO. Further, we showed that the extended FOV in conjugate AO is maintained over a relatively large axial misalignment of the conjugate planes of the CDM and the aberrating interface. This dissertation advances the field of microscopy by providing new models and techniques for imaging deeply within strongly scattering tissue, and by describing new adaptive optics approaches to extending imaging FOV due to sample aberrations.

Laser pulsing in linear Compton scattering

DOE PAGES

Krafft, G. A.; Johnson, E.; Deitrick, K.; ...

2016-12-16

Previous work on calculating energy spectra from Compton scattering events has either neglected considering the pulsed structure of the incident laser beam, or has calculated these effects in an approximate way subject to criticism. In this paper, this problem has been reconsidered within a linear plane wave model for the incident laser beam. By performing the proper Lorentz transformation of the Klein-Nishina scattering cross section, a spectrum calculation can be created which allows the electron beam energy spread and emittance effects on the spectrum to be accurately calculated, essentially by summing over the emission of each individual electron. Such anmore » approach has the obvious advantage that it is easily integrated with a particle distribution generated by particle tracking, allowing precise calculations of spectra for realistic particle distributions in collision. The method is used to predict the energy spectrum of radiation passing through an aperture for the proposed Old Dominion University inverse Compton source. In addition, as discussed in the body of the paper, many of the results allow easy scaling estimates to be made of the expected spectrum. A misconception in the literature on Compton scattering of circularly polarized beams is corrected and recorded.« less