Diffusing light probing of aged wet foams

NASA Astrophysics Data System (ADS)

Slavnetskov, I. O.; Kalacheva, A. V.; Yuvchenko, S. A.; Markova, N. S.; Zimnyakov, D. A.

2018-04-01

Features of diffusing light probes of aged liquid foams are discussed. These probes were carried out using broadband and laser radiation with the wavelength of 532 nm. Experimental data were obtained for aged samples of Gillette shaving cream as a model foamed substance. The coefficients of diffusion and collimated transmittance were applied for characterization of the structural changes in the aged wet foams. Also, the changes in the liquid fraction due to gravitational drainage were monitored using volumometric measurements in the course of the foam aging. Obtained empirical data on the diffuse and collimated transmittance were used as the reference values for correction of the spectral measurements in the visible range with a broadband source of probe light. The problem of correction of the collimated transmittance partially corrupted by the diffusing component of multiply scattered light is discussed.

In-situ spectrophotometric probe

DOEpatents

Prather, William S.

1992-01-01

A spectrophotometric probe for in situ absorption spectra measurements comprising a first optical fiber carrying light from a remote light source, a second optical fiber carrying light to a remote spectrophotometer, the proximal ends of the first and second optical fibers parallel and coterminal, a planoconvex lens to collimate light from the first optical fiber, a reflecting grid positioned a short distance from the lens to reflect the collimated light back to the lens for focussing on the second optical fiber. The lens is positioned with the convex side toward the optical fibers. A substrate for absorbing analyte or an analyte and reagent mixture may be positioned between the lens and the reflecting grid.

TU-EF-304-11: Therapeutic Benefits of Collimation in Spot Scanning Proton Therapy in the Treatment of Brain Cancer

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

Moignier, A; Gelover, E; Wang, D

Purpose: A dynamic collimation system (DCS) based on two orthogonal pairs of mobile trimmer blades has recently been proposed to reduce the lateral penumbra in spot scanning proton therapy (SSPT). The purpose of this work is to quantify the therapeutic benefit of using the DCS for SSPT of brain cancer by comparing un-collimated and collimated treatment plans. Methods: Un-collimated and collimated brain treatment plans were created for five patients, previously treated with SSPT, using an in-house treatment planning system capable of modeling collimated and un-collimated beamlets. Un-collimated plans reproduced the clinically delivered plans in terms of target coverage and organ-at-riskmore » (OAR) sparing, whereas collimated plans were re-optimized to improve the organ-at-risk sparing while maintaining target coverage. Physical and biological comparison metrics such as dose distribution conformity, mean and maximum doses, normal tissue complication probability (NTCP) and risk of secondary brain cancer were used to evaluate the plans. Results: The DCS systematically improved the dose distribution conformity while preserving the target coverage. The average reduction of the mean dose to the 10-mm ring surrounding the target and the healthy brain were 7.1% (95% CI: 4.2%–9.9%; p<0.01) and 14.3% (95% CI: 7.8%–20.8%; p<0.01), respectively. This yielded an average reduction of 12.0% (95% CI: 8.2%–15.7%; p<0.01) for the brain necrosis NTCP using the Flickinger model, and 14.2% (95% CI: 7.7%–20.8%; p<0.01) for the risk of secondary brain cancer. The average maximum dose reductions for the brainstem, chiasm, optic nerves, cochleae and pituitary gland when comparing un-collimated and collimated plans were 14.3%, 10.4%, 11.2%, 13.0%, 12.9% and 3.4%, respectively. Evaluating individual plans using the Lyman-Kutcher-Burman NTCP model also yielded improvements. Conclusion: The lateral penumbra reduction performed by the DCS increases the normal tissue sparing capabilities of SSPT for brain tumor treatment while preserving the target coverage. This research was financially supported by Ion Beam Applications S.A. (IBA, Louvain-La-Neuve, Belgium)« less

In-situ spectrophotometric probe

DOEpatents

Prather, W.S.

1992-12-15

A spectrophotometric probe is described for in situ absorption spectra measurements comprising a first optical fiber carrying light from a remote light source, a second optical fiber carrying light to a remote spectrophotometer, the proximal ends of the first and second optical fibers parallel and co-terminal, a planoconvex lens to collimate light from the first optical fiber, a reflecting grid positioned a short distance from the lens to reflect the collimated light back to the lens for focusing on the second optical fiber. The lens is positioned with the convex side toward the optical fibers. A substrate for absorbing analyte or an analyte and reagent mixture may be positioned between the lens and the reflecting grid. 5 figs.

Solar concentrator with integrated tracking and light delivery system with summation

DOEpatents

Maxey, Lonnie Curt

2015-05-05

A solar light distribution system includes a solar light concentrator that is affixed externally to a light transfer tube. Solar light waves are processed by the concentrator into a collimated beam of light, which is then transferred through a light receiving port and into the light transfer tube. A reflector redirects the collimated beam of light through the tube to a light distribution port. The interior surface of the light transfer tube is highly reflective so that the light transfers through the tube with minimal losses. An interchangeable luminaire is attached to the light distribution port and provides light inside of a structure. A sun tracking device rotates the concentrator and the light transfer tube to optimize the receiving of solar light by the concentrator throughout the day. The system provides interior lighting that uses only renewable energy sources, and releases no carbon dioxide emissions into the atmosphere.

Toward improved target conformity for two spot scanning proton therapy delivery systems using dynamic collimation

PubMed Central

Moignier, Alexandra; Gelover, Edgar; Smith, Blake R.; Wang, Dongxu; Flynn, Ryan T.; Kirk, Maura L.; Lin, Liyong; Solberg, Timothy D.; Lin, Alexander; Hyer, Daniel E.

2016-01-01

Purpose: To quantify improvement in target conformity in brain and head and neck tumor treatments resulting from the use of a dynamic collimation system (DCS) with two spot scanning proton therapy delivery systems (universal nozzle, UN, and dedicated nozzle, DN) with median spot sizes of 5.2 and 3.2 mm over a range of energies from 100 to 230 MeV. Methods: Uncollimated and collimated plans were calculated with both UN and DN beam models implemented within our in-house treatment planning system for five brain and ten head and neck datasets in patients previously treated with spot scanning proton therapy. The prescription dose and beam angles from the clinical plans were used for both the UN and DN plans. The average reduction of the mean dose to the 10-mm ring surrounding the target between the uncollimated and collimated plans was calculated for the UN and the DN. Target conformity was analyzed using the mean dose to 1-mm thickness rings surrounding the target at increasing distances ranging from 1 to 10 mm. Results: The average reductions of the 10-mm ring mean dose for the UN and DN plans were 13.7% (95% CI: 11.6%–15.7%; p < 0.0001) and 11.5% (95% CI: 9.5%–13.5%; p < 0.0001) across all brain cases and 7.1% (95% CI: 4.4%–9.8%; p < 0.001) and 6.3% (95% CI: 3.7%–9.0%; p < 0.001), respectively, across all head and neck cases. The collimated UN plans were either more conformal (all brain cases and 60% of the head and neck cases) than or equivalent (40% of the head and neck cases) to the uncollimated DN plans. The collimated DN plans offered the highest conformity. Conclusions: The DCS added either to the UN or DN improved the target conformity. The DCS may be of particular interest for sites with UN systems looking for a more economical solution than upgrading the nozzle to improve the target conformity of their spot scanning proton therapy system. PMID:26936726

Integrated RGB laser light module for autostereoscopic outdoor displays

NASA Astrophysics Data System (ADS)

Reitterer, Jörg; Fidler, Franz; Hambeck, Christian; Saint Julien-Wallsee, Ferdinand; Najda, Stephen; Perlin, Piotr; Stanczyk, Szymon; Czernecki, Robert; McDougall, Stewart D.; Meredith, Wyn; Vickers, Garrie; Landles, Kennedy; Schmid, Ulrich

2015-02-01

We have developed highly compact RGB laser light modules to be used as light sources in multi-view autostereoscopic outdoor displays and projection devices. Each light module consists of an AlGaInP red laser diode, a GaInN blue laser diode, a GaInN green laser diode, as well as a common cylindrical microlens. The plano-convex microlens is a so-called "fast axis collimator", which is widely used for collimating light beams emitted from high-power laser diode bars, and has been optimized for polychromatic RGB laser diodes. The three light beams emitted from the red, green, and blue laser diodes are collimated in only one transverse direction, the so-called "fast axis", and in the orthogonal direction, the so-called "slow axis", the beams pass the microlens uncollimated. In the far field of the integrated RGB light module this produces Gaussian beams with a large ellipticity which are required, e.g., for the application in autostereoscopic outdoor displays. For this application only very low optical output powers of a few milliwatts per laser diode are required and therefore we have developed tailored low-power laser diode chips with short cavity lengths of 250 μm for red and 300 μm for blue. Our RGB laser light module including the three laser diode chips, associated monitor photodiodes, the common microlens, as well as the hermetically sealed package has a total volume of only 0.45 cm³, which to our knowledge is the smallest RGB laser light source to date.

Performance optimization of a bendable parabolic cylinder collimating X-ray mirror for the ALS micro-XAS beamline 10.3.2

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

Yashchuk, Valeriy V.; Morrison, Gregory Y.; Marcus, Matthew A.

The Advanced Light Source (ALS) beamline (BL) 10.3.2 is an apparatus for X-ray microprobe spectroscopy and diffraction experiments, operating in the energy range 2.4–17 keV. The performance of the beamline, namely the spatial and energy resolutions of the measurements, depends significantly on the collimation quality of light incident on the monochromator. In the BL 10.3.2 end-station, the synchrotron source is imaged 1:1 onto a set of roll slits which form a virtual source. The light from this source is collimated in the vertical direction by a bendable parabolic cylinder mirror. Details are presented of the mirror design, which allows formore » precision assembly, alignment and shaping of the mirror, as well as for extending of the mirror operating lifetime by a factor of ~10. Assembly, mirror optimal shaping and preliminary alignment were performed ex situ in the ALS X-ray Optics Laboratory (XROL). Using an original method for optimal ex situ characterization and setting of bendable X-ray optics developed at the XROL, a root-mean-square (RMS) residual surface slope error of 0.31 µrad with respect to the desired parabola, and an RMS residual height error of less than 3 nm were achieved. Once in place at the beamline, deviations from the designed optical geometry ( e.g. due to the tolerances for setting the distance to the virtual source, the grazing incidence angle, the transverse position) and/or mirror shape ( e.g. due to a heat load deformation) may appear. Due to the errors, on installation the energy spread from the monochromator is typically a few electron-volts. Here, a new technique developed and successfully implemented for at-wavelength ( in situ) fine optimal tuning of the mirror, enabling us to reduce the collimation-induced energy spread to ~0.05 eV, is described.« less

Performance optimization of a bendable parabolic cylinder collimating X-ray mirror for the ALS micro-XAS beamline 10.3.2

PubMed Central

Yashchuk, Valeriy V.; Morrison, Gregory Y.; Marcus, Matthew A.; Domning, Edward E.; Merthe, Daniel J.; Salmassi, Farhad; Smith, Brian V.

2015-01-01

The Advanced Light Source (ALS) beamline (BL) 10.3.2 is an apparatus for X-ray microprobe spectroscopy and diffraction experiments, operating in the energy range 2.4–17 keV. The performance of the beamline, namely the spatial and energy resolutions of the measurements, depends significantly on the collimation quality of light incident on the monochromator. In the BL 10.3.2 end-station, the synchrotron source is imaged 1:1 onto a set of roll slits which form a virtual source. The light from this source is collimated in the vertical direction by a bendable parabolic cylinder mirror. Details are presented of the mirror design, which allows for precision assembly, alignment and shaping of the mirror, as well as for extending of the mirror operating lifetime by a factor of ∼10. Assembly, mirror optimal shaping and preliminary alignment were performed ex situ in the ALS X-ray Optics Laboratory (XROL). Using an original method for optimal ex situ characterization and setting of bendable X-ray optics developed at the XROL, a root-mean-square (RMS) residual surface slope error of 0.31 µrad with respect to the desired parabola, and an RMS residual height error of less than 3 nm were achieved. Once in place at the beamline, deviations from the designed optical geometry (e.g. due to the tolerances for setting the distance to the virtual source, the grazing incidence angle, the transverse position) and/or mirror shape (e.g. due to a heat load deformation) may appear. Due to the errors, on installation the energy spread from the monochromator is typically a few electron-volts. Here, a new technique developed and successfully implemented for at-wavelength (in situ) fine optimal tuning of the mirror, enabling us to reduce the collimation-induced energy spread to ∼0.05 eV, is described. PMID:25931083

Performance optimization of a bendable parabolic cylinder collimating X-ray mirror for the ALS micro-XAS beamline 10.3.2

DOE PAGES

Yashchuk, Valeriy V.; Morrison, Gregory Y.; Marcus, Matthew A.; ...

2015-04-08

The Advanced Light Source (ALS) beamline (BL) 10.3.2 is an apparatus for X-ray microprobe spectroscopy and diffraction experiments, operating in the energy range 2.4–17 keV. The performance of the beamline, namely the spatial and energy resolutions of the measurements, depends significantly on the collimation quality of light incident on the monochromator. In the BL 10.3.2 end-station, the synchrotron source is imaged 1:1 onto a set of roll slits which form a virtual source. The light from this source is collimated in the vertical direction by a bendable parabolic cylinder mirror. Details are presented of the mirror design, which allows formore » precision assembly, alignment and shaping of the mirror, as well as for extending of the mirror operating lifetime by a factor of ~10. Assembly, mirror optimal shaping and preliminary alignment were performed ex situ in the ALS X-ray Optics Laboratory (XROL). Using an original method for optimal ex situ characterization and setting of bendable X-ray optics developed at the XROL, a root-mean-square (RMS) residual surface slope error of 0.31 µrad with respect to the desired parabola, and an RMS residual height error of less than 3 nm were achieved. Once in place at the beamline, deviations from the designed optical geometry ( e.g. due to the tolerances for setting the distance to the virtual source, the grazing incidence angle, the transverse position) and/or mirror shape ( e.g. due to a heat load deformation) may appear. Due to the errors, on installation the energy spread from the monochromator is typically a few electron-volts. Here, a new technique developed and successfully implemented for at-wavelength ( in situ) fine optimal tuning of the mirror, enabling us to reduce the collimation-induced energy spread to ~0.05 eV, is described.« less

Conjugation of both on-axis and off-axis light in Nipkow disk confocal microscope to increase availability of incoherent light source.

PubMed

Saito, Kenta; Arai, Yoshiyuki; Zhang, Jize; Kobayashi, Kentaro; Tani, Tomomi; Nagai, Takeharu

2011-01-01

Laser-scanning confocal microscopy has been employed for exploring structures at subcellular, cellular and tissue level in three dimensions. To acquire the confocal image, a coherent light source, such as laser, is generally required in conventional single-point scanning microscopy. The illuminating beam must be focused onto a small spot with diffraction-limited size, and this determines the spatial resolution of the microscopy system. In contrast, multipoint scanning confocal microscopy using a Nipkow disk enables the use of an incoherent light source. We previously demonstrated successful application of a 100 W mercury arc lamp as a light source for the Yokogawa confocal scanner unit in which a microlens array was coupled with a Nipkow disk to focus the collimated incident light onto a pinhole (Saito et al., Cell Struct. Funct., 33: 133-141, 2008). However, transmission efficiency of incident light through the pinhole array was low because off-axis light, the major component of the incident light, was blocked by the non-aperture area of the disk. To improve transmission efficiency, we propose an optical system in which off-axis light is able to be transmitted through pinholes surrounding the pinhole located on the optical axis of the collimator lens. This optical system facilitates the use of not only the on-axis but also the off-axis light such that the available incident light is considerably improved. As a result, we apply the proposed system to high-speed confocal and multicolor imaging both with a satisfactory signal-to-noise ratio.

Variable magnification with Kirkpatrick-Baez optics for synchrotron X-ray microscopy

DOE PAGES

Jach, Terrence; Bakulin, Alex S.; Durbin, Stephen M.; ...

2006-05-01

In this study, we describe the distinction between the operation of a short focal length x-ray microscope forming a real image with a laboratory source (convergent illumination) and with a highly collimated intense beam from a synchrotron light source (Kohler illumination).

Effects of source shape on the numerical aperture factor with a geometrical-optics model.

PubMed

Wan, Der-Shen; Schmit, Joanna; Novak, Erik

2004-04-01

We study the effects of an extended light source on the calibration of an interference microscope, also referred to as an optical profiler. Theoretical and experimental numerical aperture (NA) factors for circular and linear light sources along with collimated laser illumination demonstrate that the shape of the light source or effective aperture cone is critical for a correct NA factor calculation. In practice, more-accurate results for the NA factor are obtained when a linear approximation to the filament light source shape is used in a geometric model. We show that previously measured and derived NA factors show some discrepancies because a circular rather than linear approximation to the filament source was used in the modeling.

Collimation study for LCLS

DOE PAGES

Marin, E.; Raubenhaimer, T.; Welch, J.; ...

2017-06-13

In this study we investigate the power deposition along the undulator section of the SLAC Linac Coherent Light Source (LCLS) due to the primary e¯ -beam but also due to potential secondary particles. The expected beam distribution after the LCLS injector is deliberately broadened as an approximated representation of the beam halo. Secondary particles, as e +, e¯ and photons, are generated as a result of tracking the intercepted beam through a dense material. This process is carried out by means of GEANT-4, which has been convoluted into our main tracking engine, LUCRETIA. Simulations show no losses along the undulatormore » section when assuming the nominal primary beam and collimator gaps. However when opening the gaps of collimators located at the first collimator section, by 25%, the fattened beam is partially intercepted by the second collimator section, which is aligned to the undulators. Secondary particles, mostly photons generated at the second collimator section, deposit their energy along the undulator section, at a rate of the order of a milliwatt.« less

Collimation study for LCLS

NASA Astrophysics Data System (ADS)

Marin, E.; Raubenhaimer, T.; Welch, J.; White, G.

2017-09-01

In this paper we investigate the power deposition along the undulator section of the SLAC Linac Coherent Light Source (LCLS) due to the primary e--beam but also due to potential secondary particles. The expected beam distribution after the LCLS injector is deliberately broadened as an approximated representation of the beam halo. Secondary particles, as e+, e- and photons, are generated as a result of tracking the intercepted beam through a dense material. This process is carried out by means of GEANT-4, which has been convoluted into our main tracking engine, LUCRETIA. Simulations show no losses along the undulator section when assuming the nominal primary beam and collimator gaps. However when opening the gaps of collimators located at the first collimator section, by 25%, the fattened beam is partially intercepted by the second collimator section, which is aligned to the undulators. Secondary particles, mostly photons generated at the second collimator section, deposit their energy along the undulator section, at a rate of the order of a milliwatt.

40 CFR 1033.525 - Smoke testing.

Code of Federal Regulations, 2010 CFR

2010-07-01

... rectangular duct), you may align the beam to have a different path length and correct it to be equivalent to a... that maximum response below 430 nanometers and above 680 nanometers). (4) Attach a collimating tube to... light. (6) You may use an air curtain across the light source and detector window assemblies to minimize...

Multi-angle nuclear imaging apparatus and method

DOEpatents

Anger, Hal O. [Berkeley, CA

1980-04-08

Nuclear imaging apparatus for obtaining multi-plane readouts of radioactive material in a human or animal subject. A probe disposed in the vicinity of the subject is provided for receiving radiation from radiating sources in the subject and for forming a probe radiation image. The probe has a collimator with different portions thereof having holes disposed at different angles. A single scintillation crystal overlies the collimator for receiving radiation passing through the collimator and producing scintillations to provide the probe image. An array of photomultiplier tubes overlie the single crystal for observing the probe image and providing electrical outputs. Conversion apparatus is provided for converting the electrical outputs representing the probe image into optical images displayed on the screen of a cathode ray tube. Divider apparatus is provided for dividing the probe radiation image into a plurality of areas with the areas corresponding to different portions of the collimator having holes disposed at different angles. A light sensitive medium is provided for receiving optical images. Apparatus is provided for causing relative movement between the probe and the subject. Apparatus is also provided for causing relative movement between the optical image on the screen and the light sensitive medium which corresponds to the relative movement between the probe and the subject whereby there is produced on the light sensitive medium a plurality of images that portray the subject as seen from different angles corresponding to the portions of the collimator having holes at different angles.

Multi-angle nuclear imaging apparatus and method

DOEpatents

Anger, H.O.

1980-04-08

A nuclear imaging apparatus is described for obtaining multi-plane readouts of radioactive material in a human or animal subject. A probe disposed in the vicinity of the subject is provided for receiving radiation from radiating sources in the subject and for forming a probe radiation image. The probe has a collimator with different portions having holes disposed at different angles. A single scintillation crystal overlies the collimator for receiving radiation passing through the collimator and producing scintillations to provide the probe image. An array of photomultiplier tubes overlie the single crystal for observing the probe image and providing electrical outputs. Conversion apparatus is provided for converting the electrical outputs representing the probe image into optical images displayed on the screen of a cathode ray tube. Divider apparatus is provided for dividing the probe radiation image into a plurality of areas with the areas corresponding to different portions of the collimator having holes disposed at different angles. A light sensitive medium is provided for receiving optical images. Apparatus is provided for causing relative movement between the probe and the subject. Apparatus is also provided for causing relative movement between the optical image on the screen and the light sensitive medium which corresponds to the relative movement between the probe and the subject whereby there is produced on the light sensitive medium a plurality of images that portray the subject as seen from different angles corresponding to the portions of the collimator having holes at different angles. 11 figs.

Development of multiwavelength excitation light source for autofluorescence and photodynamic diagnosis systems

NASA Astrophysics Data System (ADS)

Kenar, Necla; Lim, H. S.; Mirzaaghasi, Amin

2014-02-01

New design of the excitation light source that can stably generate light with center wavelengths of 450nm, 530nm, 632.8nm and white light for auto-fluorescence(AF) and photodynamic diagnosis(PDD) of cancer in clinics in a single system is presented in this study. The light source consists of Xenon Lamp (300W), light guide module including motorize filter wheel equipped with optical filters with corresponding to wavelength bands, servo motor, motorize iris, a cooling system, power supply and optical transmission part for the output light. The transmission part of the light source was developed to collimate the light with desired wavelength into input of fiber optic. Output powers are obtained average 99.91 mW for 450+/-40 nm, 111.01 mW for 530+/-10nm, and 78.50 mW for 632.8+/-10nm.

Direction-division multiplexed holographic free-electron-driven light sources

NASA Astrophysics Data System (ADS)

Clarke, Brendan P.; MacDonald, Kevin F.; Zheludev, Nikolay I.

2018-01-01

We report on a free-electron-driven light source with a controllable direction of emission. The source comprises a microscopic array of plasmonic surface-relief holographic domains, each tailored to direct electron-induced light emission at a selected wavelength into a collimated beam in a prescribed direction. The direction-division multiplexed source is tested by driving it with the 30 kV electron beam of a scanning electron microscope: light emission, at a wavelength of 800 nm in the present case, is switched among different output angles by micron-scale repositioning of the electron injection point among domains. Such sources, with directional switching/tuning possible at picosecond timescales, may be applied to field-emission and surface-conduction electron-emission display technologies, optical multiplexing, and charged-particle-beam position metrology.

Exploiting Auto-Collimation for Real-Time Onboard Monitoring of Space Optical Camera Geometric Parameters

NASA Astrophysics Data System (ADS)

Liu, W.; Wang, H.; Liu, D.; Miu, Y.

2018-05-01

Precise geometric parameters are essential to ensure the positioning accuracy for space optical cameras. However, state-of-the-art onorbit calibration method inevitably suffers from long update cycle and poor timeliness performance. To this end, in this paper we exploit the optical auto-collimation principle and propose a real-time onboard calibration scheme for monitoring key geometric parameters. Specifically, in the proposed scheme, auto-collimation devices are first designed by installing collimated light sources, area-array CCDs, and prisms inside the satellite payload system. Through utilizing those devices, the changes in the geometric parameters are elegantly converted into changes in the spot image positions. The variation of geometric parameters can be derived via extracting and processing the spot images. An experimental platform is then set up to verify the feasibility and analyze the precision index of the proposed scheme. The experiment results demonstrate that it is feasible to apply the optical auto-collimation principle for real-time onboard monitoring.

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.

Virtual-source diffusion approximation for enhanced near-field modeling of photon-migration in low-albedo medium.

PubMed

Jia, Mengyu; Chen, Xueying; Zhao, Huijuan; Cui, Shanshan; Liu, Ming; Liu, Lingling; Gao, Feng

2015-01-26

Most analytical methods for describing light propagation in turbid medium exhibit low effectiveness in the near-field of a collimated source. Motivated by the Charge Simulation Method in electromagnetic theory as well as the established discrete source based modeling, we herein report on an improved explicit model for a semi-infinite geometry, referred to as "Virtual Source" (VS) diffuse approximation (DA), to fit for low-albedo medium and short source-detector separation. In this model, the collimated light in the standard DA is analogously approximated as multiple isotropic point sources (VS) distributed along the incident direction. For performance enhancement, a fitting procedure between the calculated and realistic reflectances is adopted in the near-field to optimize the VS parameters (intensities and locations). To be practically applicable, an explicit 2VS-DA model is established based on close-form derivations of the VS parameters for the typical ranges of the optical parameters. This parameterized scheme is proved to inherit the mathematical simplicity of the DA approximation while considerably extending its validity in modeling the near-field photon migration in low-albedo medium. The superiority of the proposed VS-DA method to the established ones is demonstrated in comparison with Monte-Carlo simulations over wide ranges of the source-detector separation and the medium optical properties.

Lighting system combining daylight concentrators and an artificial source

DOEpatents

Bornstein, Jonathan G.; Friedman, Peter S.

1985-01-01

A combined lighting system for a building interior includes a stack of luminescent solar concentrators (LSC), an optical conduit made of preferably optical fibers for transmitting daylight from the LSC stack, a collimating lens set at an angle, a fixture for receiving the daylight at one end and for distributing the daylight as illumination inside the building, an artificial light source at the other end of the fixture for directing artifical light into the fixture for distribution as illumination inside the building, an automatic dimmer/brightener for the artificial light source, and a daylight sensor positioned near to the LSC stack for controlling the automatic dimmer/brightener in response to the daylight sensed. The system also has a reflector positioned behind the artificial light source and a fan for exhausting heated air out of the fixture during summer and for forcing heated air into the fixture for passage into the building interior during winter.

Variable Magnification With Kirkpatrick-Baez Optics for Synchrotron X-Ray Microscopy

PubMed Central

Jach, Terrence; Bakulin, Alex S.; Durbin, Stephen M.; Pedulla, Joseph; Macrander, Albert

2006-01-01

We describe the distinction between the operation of a short focal length x-ray microscope forming a real image with a laboratory source (convergent illumination) and with a highly collimated intense beam from a synchrotron light source (Köhler illumination). We demonstrate the distinction with a Kirkpatrick-Baez microscope consisting of short focal length multilayer mirrors operating at an energy of 8 keV. In addition to realizing improvements in the resolution of the optics, the synchrotron radiation microscope is not limited to the usual single magnification at a fixed image plane. Higher magnification images are produced by projection in the limit of geometrical optics with a collimated beam. However, in distinction to the common method of placing the sample behind the optical source of a diverging beam, we describe the situation in which the sample is located in the collimated beam before the optical element. The ultimate limits of this magnification result from diffraction by the specimen and are determined by the sample position relative to the focal point of the optic. We present criteria by which the diffraction is minimized. PMID:27274930

SU-E-T-187: Collimation Methods in Spot Scanning Proton Therapy: A Treatment Plan Comparison Between a Fixed Aperture and a Dynamic Collimation System

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

Smith, B; Gelover, E; Wang, D

2015-06-15

Purpose: Low-energy treatments during spot scanning proton therapy (SSPT) suffer from poor conformity due to increased spot size. Collimation devices can reduce the lateral penumbra of a proton therapy dose distribution and improve the overall plan quality. The purpose of this work was to study the advantages of individual energy-layer collimation, which is unique to a recently proposed Dynamic Collimation System (DCS), in comparison to a standard, fixed aperture that allows only a single shape for all energy layers. Methods: Three brain patients previously planned and treated with SSPT were re-planned using an in-house treatment planning system capable of modelingmore » collimated and un-collimated proton beamlets. The un-collimated plans, which served as a baseline for comparison, reproduced the target coverage of the clinically delivered plans. The collimator opening for the aperture based plans included a 0.6 cm expansion of the largest cross section of the target in the Beam’s Eye View, while the DCS based plans were created by optimizing the collimator position for beam spots near the periphery of the target in each energy layer. Results: The reduction of mean dose to normal tissue adjacent to the target, as defined by a 10 mm ring, averaged 9.13% and 3.48% for the DCS and aperture plans, respectively. The conformity index, as defined by the ratio of the volume of the 50% isodose line to the target volume, yielded an average improvement of 16.42% and 8.16% for the DCS and aperture plans, respectively. Conclusion: Collimation reduces the dose to normal tissue adjacent to the target and increases dose conformity to the target region for low-energy SSPT. The ability of the DCS to provide collimation to each energy layer yields better conformity in comparison to fixed aperture plans. This work was partially funded by IBA (Ion Beam Applications S.A.)« less

Hybrid algorithm for simulating the collimated transmittance of homogeneous stratified turbid media

PubMed Central

Cruzado, Beatriz Morales; Atencio, José Alberto Delgado; Vázquez y Montiel, Sergio; Gómez, Erick Sarmiento

2015-01-01

In this work we describe the development of a program that simulates the propagation of photons through refractive and reflecting optical components such as lenses, mirrors and stops that includes a biological tissue sample as the main issue to be investigated in order to get a simulated value of light distribution, in particular, of the unscattered light. The analysis of the photons that travel through the sample is based on the program Monte Carlo Multi-Layered with some modifications that consider a Gaussian beam as initial source of light. Position, directional cosines and weight of photons exiting the turbid media are used to propagate them through an optical system. As a mean of validation of the program, we selected a typical optical system for measurement of collimated transmittance. Therefore, several tests were carried out to find the optical system that gives the theoretical collimated transmittance at different values of the optical properties of the turbid media. Along this validation, the optimal experimental configuration is found. Using this results, a comparison between the simulated optimal configuration and the experimental set-up was done, by using a colloidal suspension as a turbid media. PMID:26137375

Optimisation of a polygon mirror-based spectral filter for swept source optical coherence tomography (SS-OCT)

NASA Astrophysics Data System (ADS)

Everson, Michael; Duma, Virgil-Florin; Dobre, George

2018-03-01

Medical imaging using Optical Coherence Tomography (OCT) provides clinicians with 3D, high resolution reconstructions of microscopic structures, in depth. It has been initially developed for ophthalmology, in order to scan the retinas of patients to diagnose illness. The quality of the images depends upon their axial and lateral resolutions and the properties of the light being used. Research using a polygon mirror (PM) as a spectral filter in Swept Source OCT (SS-OCT) has resulted in a variety of different experimental arrangements. Although the application of PM-based SS-OCT sources has been successfully demonstrated, the combination of their components' fundamental properties and the overall impact they have on imaging performance is rarely reported. A more detailed examination of these properties would lead to a full description of their operation and to the best methods to employ if system performance is to be maximised. This work presents our current findings of on-going research into the optimisation of PM-based SS-OCT systems. A swept source spectral filter, consisting of a collimator, a transmission grating, a two-lens telescope and an off-axis PM with an end reflector mirror has been evaluated experimentally and compared with theoretical predictions. The system's performance has been compared for two different fibre collimators. Although the beam width on the grating is different for each of the two collimators, the spot size at the PM facet is made the same by selecting appropriate focal lengths. An improvement in the signal roll-off at the interferometer output of 1.0 dB/mm was obtained when using a 3.4 mm collimator compared to a 1.5 mm collimator.

A simple quality assurance test tool for the visual verification of light and radiation field congruent using electronic portal images device and computed radiography

PubMed Central

2012-01-01

Background The radiation field on most megavoltage radiation therapy units are shown by a light field projected through the collimator by a light source mounted inside the collimator. The light field is traditionally used for patient alignment. Hence it is imperative that the light field is congruent with the radiation field. Method A simple quality assurance tool has been designed for rapid and simple test of the light field and radiation field using electronic portal images device (EPID) or computed radiography (CR). We tested this QA tool using Varian PortalVision and Elekta iViewGT EPID systems and Kodak CR system. Results Both the single and double exposure techniques were evaluated, with double exposure technique providing a better visualization of the light-radiation field markers. The light and radiation congruency could be detected within 1 mm. This will satisfy the American Association of Physicists in Medicine task group report number 142 recommendation of 2 mm tolerance. Conclusion The QA tool can be used with either an EPID or CR to provide a simple and rapid method to verify light and radiation field congruence. PMID:22452821

A prototype optical-CT system for PRESAGE 3D dosimeter readout

NASA Astrophysics Data System (ADS)

Miles, Devin; Yoon, Paul; Kodra, Jacob; Adamovics, John; Oldham, Mark

2017-05-01

This work introduces the Duke Integrated-lens Optical Scanner (DIOS), a prototype optical-CT system designed for convenient and low-cost readout of PRESAGE 3D dosimeters. A key novelty of the DIOS is the incorporation of a multi-purpose light-collimating tank (the LC-tank). The LC-tank collimates light from a point source, maintains parallel ray geometry through a dosimeter mounted inside the tank, and refocuses emergent light onto a CCD detector. A second purpose is to dramatically reduce the amount of refractive matched fluid required in prior optical-CT scanners. This is achieved by substituting large quantities of refractive-matched fluid with solid RI-matched polyurethane. The advantages of DIOS include eliminating the need for expensive telecentric lenses, and eliminating the impracticality of large volumes of RI matched fluid. The DIOS is potentially more susceptible to stray-light artifacts. Preliminary phantom testing shows promising agreement between PRESAGE/DIOS readout and prior commissioned optical-CT scanners, as well as with Eclipse dose calculations.

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

PubMed

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

2012-06-10

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

Apparatus and method for combining light from two or more fibers into a single fiber

DOEpatents

Klingsporn, Paul Edward

2007-02-20

An apparatus and method for combining light signals carried on a plurality of input fibers onto a single receiving fiber with a high degree of efficiency. The apparatus broadly comprises the receiving fiber and a plurality of input fiber-lens assemblies, with each fiber lens assembly including an input fiber; a collimating lens interposed between the input fiber and the receiving fiber and adapted to collimate the light signal; and a focusing lens interposed between the collimating lens and the receiving fiber and adapted to focus the collimated light signal onto the face of the receiving fiber. The components of each fiber-lens assembly are oriented along an optic axis that is inclined relative to the receiving fiber, with the inclination angle depending at least in part on the input fiber's numerical aperture and the focal lengths and diameters of the collimating and focusing lenses.

Apparatus and method for combining light from two or more fibers into a single fiber

DOEpatents

Klingsporn, Paul Edward

2006-03-14

An apparatus and method for combining light signals carried on a plurality of input fibers onto a single receiving fiber with a high degree of efficiency. The apparatus broadly comprises the receiving fiber and a plurality of input fiber-lens assemblies, with each fiber lens assembly including an input fiber; a collimating lens interposed between the input fiber and the receiving fiber and adapted to collimate the light signal; and a focusing lens interposed between the collimating lens and the receiving fiber and adapted to focus the collimated light signal onto the face of the receiving fiber. The components of each fiber-lens assembly are oriented along an optic axis that is inclined relative to the receiving fiber, with the inclination angle depending at least in part on the input fiber's numerical aperture and the focal lengths and diameters of the collimating and focusing lenses.

Microbial UV fluence-response assessment using a novel UV-LED collimated beam system.

PubMed

Bowker, Colleen; Sain, Amanda; Shatalov, Max; Ducoste, Joel

2011-02-01

A research study has been performed to determine the ultraviolet (UV) fluence-response of several target non-pathogenic microorganisms to UV light emitting diodes (UV-LEDs) by performing collimated beam tests. UV-LEDs do not contain toxic mercury, offer design flexibility due to their small size, and have a longer operational life than mercury lamps. Comsol Multiphysics was utilized to create an optimal UV-LED collimated beam design based on number and spacing of UV-LEDs and distance of the sample from the light source while minimizing the overall cost. The optimized UV-LED collimated beam apparatus and a low-pressure mercury lamp collimated beam apparatus were used to determine the UV fluence-response of three surrogate microorganisms (Escherichia coli, MS-2, T7) to 255 nm UV-LEDs, 275 nm UV-LEDs, and 254 nm low-pressure mercury lamps. Irradiation by low-pressure mercury lamps produced greater E. coli and MS-2 inactivation than 255 nm and 275 nm UV-LEDs and similar T7 inactivation to irradiation by 275 nm UV-LEDs. The 275 nm UV-LEDs produced more efficient T7 and E. coli inactivation than 255 nm UV-LEDs while both 255 nm and 275 nm UV-LEDs produced comparable microbial inactivation for MS-2. Differences may have been caused by a departure from the time-dose reciprocity law due to microbial repair mechanisms. Copyright © 2010 Elsevier Ltd. All rights reserved.

Speckle Free, Low Coherency, High Brightness, and High Pulse Speed Infrared Collimated Light Sources for Mid-IR Target Designator and Hyperspectral Imaging

DTIC Science & Technology

2007-10-31

designator and hyperspectral imaging 6. AUfHOR(S) Yee-LoyLam 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION DenseLight...DenseLight Semiconductors CONTENTS 1. Introduction 3 1.1 Overview of Project 3 1.2 Organization of Project 4 1.3 Target...Performance 4 2. SLED Chip Design and Fabrication Development 5 2.1 Organization of Design Stages 5 2.2 SLED Chip Design 6 2.3

Continuous wavelength tunable laser source with optimum positioning of pivot axis for grating

DOEpatents

Pushkarsky, Michael; Amone, David F.

2010-06-08

A laser source (10) for generating a continuously wavelength tunable light (12) includes a gain media (16), an optical output coupler (36F), a cavity collimator (38A), a diffraction grating (30), a grating beam (54), and a beam attacher (56). The diffraction grating (30) is spaced apart from the cavity collimator (38A) and the grating (30) cooperates with the optical output coupler (36F) to define an external cavity (32). The grating (30) includes a grating face surface (42A) that is in a grating plane (42B). The beam attacher (56) retains the grating beam (54) and allows the grating beam (54) and the grating (30) to effectively pivot about a pivot axis (33) that is located approximately at an intersection of a pivot plane (50) and the grating plane (42B). As provided herein, the diffraction grating (30) can be pivoted about the unique pivot axis (33) to move the diffraction grating (30) relative to the gain media (16) to continuously tune the lasing frequency of the external cavity (32) and the wavelength of the output light (12) so that the output light (12) is mode hop free.

A time-domain fluorescence diffusion optical tomography system for breast tumor diagnosis

NASA Astrophysics Data System (ADS)

Zhang, Wei; Gao, Feng; Wu, LinHui; Ma, Wenjuan; Yang, Fang; Zhou, Zhongxing; Zhang, Limin; Zhao, Huijuan

2011-02-01

A prototype time-domain fluorescence diffusion optical tomography (FDOT) system using near-infrared light is presented. The system employs two pulsed light sources, 32 source fibers and 32 detection channels, working separately for acquiring the temporal distribution of the photon flux on the tissue surface. The light sources are provided by low power picosecond pulsed diode lasers at wavelengths of 780 nm and 830 nm, and a 1×32-fiber-optic-switch sequentially directs light sources to the object surface through 32 source fibers. The light signals re-emitted from the object are collected by 32 detection fibers connected to four 8×1 fiber-optic-switch and then routed to four time-resolved measuring channels, each of which consists of a collimator, a filter wheel, a photomultiplier tube (PMT) photon-counting head and a time-correlated single photon counting (TCSPC) channel. The performance and efficacy of the designed multi-channel PMT-TCSPC system are assessed by reconstructing the fluorescent yield and lifetime images of a solid phantom.

System and Method for Scan Range Gating

NASA Technical Reports Server (NTRS)

Lindemann, Scott (Inventor); Zuk, David M. (Inventor)

2017-01-01

A system for scanning light to define a range gated signal includes a pulsed coherent light source that directs light into the atmosphere, a light gathering instrument that receives the light modified by atmospheric backscatter and transfers the light onto an image plane, a scanner that scans collimated light from the image plane to form a range gated signal from the light modified by atmospheric backscatter, a control circuit that coordinates timing of a scan rate of the scanner and a pulse rate of the pulsed coherent light source so that the range gated signal is formed according to a desired range gate, an optical device onto which an image of the range gated signal is scanned, and an interferometer to which the image of the range gated signal is directed by the optical device. The interferometer is configured to modify the image according to a desired analysis.

Design of axisymmetrical tailored concentrators for LED light source applications

NASA Astrophysics Data System (ADS)

Van Giel, Bart; Meuret, Youri; Thienpont, Hugo

2006-04-01

In our contribution we present a solution to an important question in the design of a LED-based illumination engine for projection systems: the collimation of the LED light. We tested the principle in the modification of a common device in non-imaging optics, the compound Parabolic Concentrator. This CPC-like achieves a collection of 72% (ideal reflective coating presumed). This CPC-like was tailored by numerically solving an differential equation. This approach has some serious drawbacks. For a compact collection device with high collimation, an other approach is required. A more elegant design strategy will rely fully on geometrical principles. The result of our work is a compound collection lens that achieves a collection efficiency of 87%, assuming an ideal reflective coating and neglecting Fresnel losses. We study the performance of this device in detail. Further enhancements are suggested.

Multiple wavelength light collimator and monitor

NASA Technical Reports Server (NTRS)

Gore, Warren J. (Inventor)

2011-01-01

An optical system for receiving and collimating light and for transporting and processing light received in each of N wavelength ranges, including near-ultraviolet, visible, near-infrared and mid-infrared wavelengths, to determine a fraction of light received, and associated dark current, in each wavelength range in each of a sequence of time intervals.

Opacity meter for monitoring exhaust emissions from non-stationary sources

DOEpatents

Dec, John Edward

2000-01-01

Method and apparatus for determining the opacity of exhaust plumes from moving emissions sources. In operation, a light source is activated at a time prior to the arrival of a diesel locomotive at a measurement point, by means of a track trigger switch or the Automatic Equipment Identification system, such that the opacity measurement is synchronized with the passage of an exhaust plume past the measurement point. A beam of light from the light source passes through the exhaust plume of the locomotive and is detected by a suitable detector, preferably a high-rate photodiode. The light beam is well-collimated and is preferably monochromatic, permitting the use of a narrowband pass filter to discriminate against background light. In order to span a double railroad track and provide a beam which is substantially stronger than background, the light source, preferably a diode laser, must provide a locally intense beam. A high intensity light source is also desirable in order to increase accuracy at the high sampling rates required. Also included is a computer control system useful for data acquisition, manipulation, storage and transmission of opacity data and the identification of the associated diesel engine to a central data collection center.

Performance characterization of a new CZT-based preclinical SPECT system: a comparative study of different collimators

NASA Astrophysics Data System (ADS)

Yu, A. R.; Park, S.-J.; Choi, Y. Y.; Kim, K. M.; Kim, H.-J.

2015-09-01

Triumph X-SPECT is a newly released CZT-based preclinical small-animal SPECT system with interchangeable collimators. The purpose of this work was to evaluate and systematically compare the imaging performances of three different collimators in the CZT-based preclinical small-animal system: a single-pinhole collimator (SPH), a multi-pinhole collimator (MPH) and a parallel-hole collimator. We measured the spatial resolutions and sensitivities of the three collimators with 99mTc sources, considering three distinct energy window widths (5, 10, and 20%), and used the NEMA NU4-2008 Image Quality phantom to test the imaging performance of the three collimators in terms of uniformity and spill-over ratio (SOR) for each energy window. With a 10% energy window width at a radius of rotation (ROR) of 30 mm, the system resolution of the SPH, MPH and parallel-hole collimators was 0.715, 0.855 and 3.270 mm FWHM, respectively. For the same energy window, the sensitivity of the system with SPH, MPH and parallel-hole collimators was 32.860, 152.514 and 49.205 counts/sec/MBq at a 100 mm source-to-detector distance and 6.790, 33.376 and 49.038 counts/sec/MBq at a 130 mm source-to-detector distance, respectively. The image noise and SORair for the three collimators were 20.137, 12.278 and 11.232 (%STDunif) and 0.106, 0.140 and 0.161, respectively. Overall, the results show that the SPH had better spatial resolution than the other collimators. The MPH had the highest sensitivity at 100 mm source-to-collimator distance, and the parallel-hole collimator had the highest sensitivity at 130 mm-source-to-detector distance. Therefore, the proper collimator for Triumph X-SPECT system must be determined by the task. These results provide valuable reference data and insight into the imaging performance of various collimators in CZT-based preclinical small-animal SPECT.

Ion source with improved primary arc collimation

DOEpatents

Dagenhart, W.K.

1983-12-16

An improved negative ion source is provided in which a self-biasing, molybdenum collimator is used to define the primary electron stream arc discharge from a filament operated at a negative potential. The collimator is located between the anode and the filament. It is electrically connected to the anode by means of an appropriate size resistor such that the collimator is biased at essentially the filament voltage during operation. Initially, the full arc voltage appears across the filament to collimator until the arc discharge strikes. Then the collimator biases itself to essentially filament potential due to current flow through the resistor thus defining the primary electron stream without intercepting any appreciable arc power. The collimator aperture is slightly smaller than the anode aperture to shield the anode from the arc power which, in the past, has caused overheating and erosion of the anode collimator during extended time pulsed-beam operation of the source. With the self-biasing collimator of this invention, the ion source may be operated from short pulse periods to steady-state without destroying the anode.

Ion source with improved primary arc collimation

DOEpatents

Dagenhart, William K.

1985-01-01

An improved negative ion source is provided in which a self-biasing, molybdenum collimator is used to define the primary electron stream arc discharge from a filament operated at a negative potential. The collimator is located between the anode and the filament. It is electrically connected to the anode by means of an appropriate size resistor such that the collimator is biased at essentially the filament voltage during operation. Initially, the full arc voltage appears across the filament to collimator until the arc discharge strikes. Then the collimator biases itself to essentially filament potential due to current flow through the resistor thus defining the primary electron stream without intercepting any appreciable arc power. The collimator aperture is slightly smaller than the anode aperture to shield the anode from the arc power, thereby preventing the exposure of the anode to the full arc power which, in the past, has caused overheating and erosion of the anode collimator during extended time pulsed-beam operation of the source. With the self-biasing collimator of this invention, the ion source may be operated from short pulse periods to steady-state without destroying the anode.

Angular dependence of source-target-detector in active mode standoff infrared detection

NASA Astrophysics Data System (ADS)

Pacheco-Londoño, Leonardo C.; Castro-Suarez, John R.; Aparicio-Bolaños, Joaquín. A.; Hernández-Rivera, Samuel P.

2013-06-01

Active mode standoff measurement using infrared spectroscopy were carried out in which the angle between target and the source was varied from 0-70° with respect to the surface normal of substrates containing traces of highly energetic materials (explosives). The experiments were made using three infrared sources: a modulated source (Mod-FTIR), an unmodulated source (UnMod-FTIR) and a scanning quantum cascade laser (QCL), part of a dispersive mid infrared (MIR) spectrometer. The targets consisted of PENT 200 μg/cm2 deposited on aluminum plates placed at 1 m from the sources. The evaluation of the three modalities was aimed at verifying the influence of the highly collimated laser beam in the detection in comparison with the other sources. The Mod-FTIR performed better than QCL source in terms of the MIR signal intensity decrease with increasing angle.

Fiber optic engine for micro projection display.

PubMed

Arabi, Hesam Edin; An, Sohee; Oh, Kyunghwan

2010-03-01

A novel compact optical engine for a micro projector display is experimentally demonstrated, which is composed of RGB light sources, a tapered 3 x 1 Fiber Optic Color Synthesizer (FOCS) along with a fiberized ball-lens, and a two dimensional micro electromechanical scanning mirror. In the proposed optical engine, we successfully employed an all-fiber beam shaping technique combining optical fiber taper and fiberized ball lens that can render a narrow beam and enhance the resolution of the screened image in the far field. Optical performances of the proposed device assembly are investigated in terms of power loss, collimating strength of the collimator assembly, and color gamut of the output.

Light scattering regimes along the optical axis in turbid media

NASA Astrophysics Data System (ADS)

Campbell, S. D.; O'Connell, A. K.; Menon, S.; Su, Q.; Grobe, R.

2006-12-01

We inject an angularly collimated laser beam into a scattering medium of a nondairy creamer-water solution and examine the distribution of the scattered light along the optical axis as a function of the source-detector spacing. The experimental and simulated data obtained from a Monte Carlo simulation suggest four regimes characterizing the transition from unscattered to diffusive light. We compare the data also with theoretical predictions based on a first-order scattering theory for regions close to the source, and with diffusionlike theories for larger source-detector spacings. We demonstrate the impact of the measurement process and the effect of the unavoidable absorption of photons by the detection fiber on the light distribution inside the medium. We show that the range of validity of these theories can depend on the experimental parameters such as the diameter and acceptance angle of the detection fiber.

Monte Carlo simulation for coherent backscattering with diverging illumination (Conference Presentation)

NASA Astrophysics Data System (ADS)

Wu, Wenli; Radosevich, Andrew J.; Eshein, Adam; Nguyen, The-Quyen; Backman, Vadim

2016-03-01

Diverging beam illumination is widely used in many optical techniques especially in fiber optic applications and coherence phenomenon is one of the most important properties to consider for these applications. Until now, people have used Monte Carlo simulations to study the backscattering coherence phenomenon in collimated beam illumination only. We are the first one to study the coherence phenomenon under the exact diverging beam geometry by taking into account the impossibility of the existence for the exact time-reversed path pairs of photons, which is the main contribution to the backscattering coherence pattern in collimated beam. In this work, we present a Monte Carlo simulation that considers the influence of the illumination numerical aperture. The simulation tracks the electric field for the unique paths of forward path and reverse path in time-reversed pairs of photons as well as the same path shared by them. With this approach, we can model the coherence pattern formed between the pairs by considering their phase difference at the collection plane directly. To validate this model, we use the Low-coherence Enhanced Backscattering Spectroscopy, one of the instruments looking at the coherence pattern using diverging beam illumination, as the benchmark to compare with. In the end, we show how this diverging configuration would significantly change the coherent pattern under coherent light source and incoherent light source. This Monte Carlo model we developed can be used to study the backscattering phenomenon in both coherence and non-coherence situation with both collimated beam and diverging beam setups.

Diode-laser-pump module with integrated signal ports for pumping amplifying fibers and method

DOEpatents

Savage-Leuchs,; Matthias, P [Woodinville, WA

2009-05-26

Apparatus and method for collimating pump light of a first wavelength from laser diode(s) into a collimated beam within an enclosure having first and second optical ports, directing pump light from the collimated beam to the first port; and directing signal light inside the enclosure between the first and second port. The signal and pump wavelengths are different. The enclosure provides a pump block having a first port that emits pump light to a gain fiber outside the enclosure and that also passes signal light either into or out of the enclosure, and another port that passes signal light either out of or into the enclosure. Some embodiments use a dichroic mirror to direct pump light to the first port and direct signal light between the first and second ports. Some embodiments include a wavelength-conversion device to change the wavelength of at least some of the signal light.

Compact collimators designed with a modified point approximation for light-emitting diodes

NASA Astrophysics Data System (ADS)

Luo, Tao; Wang, Gang

2017-09-01

We present a novel freeform lens design method for an application to LED collimating illumination. The method is derived from a basic geometric-optics analysis and construction approach. By using this method, a compact collimated lenses with Aspect Ratio = 0.219 is presented. Moreover, the utility efficiency (UE) inside the angle defined by ideal concentrator hypothesis with different lens-to-LED size ratios for both this lens and TIR lens are presented. A prototype of the collimator lens is also made to verify the practical performance of the lens, which has light distribution very compatible with the simulation results.

Collimator of multiple plates with axially aligned identical random arrays of apertures

NASA Technical Reports Server (NTRS)

Hoover, R. B.; Underwood, J. H. (Inventor)

1973-01-01

A collimator is disclosed for examining the spatial location of distant sources of radiation and for imaging by projection, small, near sources of radiation. The collimator consists of a plurality of plates, all of which are pierced with an identical random array of apertures. The plates are mounted perpendicular to a common axis, with like apertures on consecutive plates axially aligned so as to form radiation channels parallel to the common axis. For near sources, the collimator is interposed between the source and a radiation detector and is translated perpendicular to the common axis so as to project radiation traveling parallel to the common axis incident to the detector. For far sources the collimator is scanned by rotating it in elevation and azimuth with a detector to determine the angular distribution of the radiation from the source.

Beam shaping to improve the free-electron laser performance at the Linac Coherent Light Source

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

Ding, Y.; Bane, K. L. F.; Colocho, W.

2016-10-27

A new operating mode has been developed for the Linac Coherent Light Source (LCLS) in which we shape the longitudinal phase space of the electron beam. This mode of operation is realized using a horizontal collimator located in the middle of the first bunch compressor to truncate the head and tail of the beam. With this method, the electron beam longitudinal phase space and current profile are reshaped, and improvement in lasing performance can be realized. As a result, we present experimental studies at the LCLS of the beam shaping effects on the free-electron laser performance.

TH-CD-201-05: Characterization of a Novel Light-Collimating Tank Optical-CT System for 3D Dosimetry

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

Miles, D; Yoon, S; Adamovics, J

Purpose: Comprehensive 3D dosimetry is highly desirable for advanced clinical QA, but costly optical readout techniques have hindered widespread implementation. Here, we present the first results from a cost-effective Integrated-lens Dry-tank Optical Scanner (IDOS), designed for convenient 3D dosimetry readout of radiochromic plastic dosimeters (e.g. PRESAGE). Methods: The scanner incorporates a novel transparent light-collimating tank, which collimates a point light source into parallel-ray CT geometry. The tank was designed using an in-house Monte-Carlo optical ray-tracing simulation, and was cast in polyurethane using a 3D printed mould. IDOS spatial accuracy was evaluated by imaging a set of custom optical phantoms, withmore » comparison to x-ray CT images. IDOS dose measurement performance was assessed by imaging PRESAGE dosimeters irradiated with simple known dose distributions (e.g., 4 field box 6MV treatment with Varian Linac). Direct comparisons were made to images from our gold standard DLOS scanner and calculated dose distributions from a commissioned Eclipse planning system. Results: All optical CT images were reconstructed at 1mm isotropic resolution. Comparison of IDOS and x-ray CT images of the geometric phantom demonstrated excellent IDOS geometric accuracy (sub-mm) throughout the dosimeter. IDOS measured 3D dose distribution agreed well with prediction from Eclipse, with 95% gamma pass rate at 3%/3mm. Cross-scanner dose measurement gamma analysis shows >90% of pixels passing at 3%/3mm. Conclusion: The first prototype of the IDOS system has demonstrated promising performance, with accurate dosimeter readout and negligible spatial distortion. The use of optical simulations and 3D printing to create a light collimating-tank has dramatically increased convenience and reduced costs by removing the need for expensive lenses and large volumes of refractive matching fluids.« less

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.

An underwater optical wireless communication system based on LED source

NASA Astrophysics Data System (ADS)

Rao, Jionghui; Wei, Wei; Wang, Feng; Zhang, Xiaohui

2011-11-01

Compared with other communication methods, optical wireless communication (OWC) holds the merits of higher transmitting rate and sufficient secrecy. So it is an efficacious communicating measure for data transmitting between underwater carriers. However, due to the water attenuation and the transmitter & the receiver (TX/RX) collimation, this application is restrained in underwater mobile carriers. A prototype for underwater OWC was developed, in which a high-powered green LED array was used as the light source which partly raveled the TX/RX collimation out. A small pumped-multiple-tube (PMT) was used as the detector to increase the communicating range, and FPGA chips were employed to code and decode the communicating data. The data rate of the prototype approached to 4 Mb/s at 8.4m and 1 Mb/s at 22m where voice and Morse communications were achieved in a scope of 30 degree TX/RX angle.

High-power LED light sources for optical measurement systems operated in continuous and overdriven pulsed modes

NASA Astrophysics Data System (ADS)

Stasicki, Bolesław; Schröder, Andreas; Boden, Fritz; Ludwikowski, Krzysztof

2017-06-01

The rapid progress of light emitting diode (LED) technology has recently resulted in the availability of high power devices with unprecedented light emission intensities comparable to those of visible laser light sources. On this basis two versatile devices have been developed, constructed and tested. The first one is a high-power, single-LED illuminator equipped with exchangeable projection lenses providing a homogenous light spot of defined diameter. The second device is a multi-LED illuminator array consisting of a number of high-power LEDs, each integrated with a separate collimating lens. These devices can emit R, G, CG, B, UV or white light and can be operated in pulsed or continuous wave (CW) mode. Using an external trigger signal they can be easily synchronized with cameras or other devices. The mode of operation and all parameters can be controlled by software. Various experiments have shown that these devices have become a versatile and competitive alternative to laser and xenon lamp based light sources. The principle, design, achieved performances and application examples are given in this paper.

Optical manifold

DOEpatents

Falicoff, Waqidi; Chaves, Julio C.; Minano, Juan Carlos; Benitez, Pablo; Dross, Oliver; Parkyn, Jr., William A.

2010-02-23

Optical systems are described that have at least one source of a beam of blue light with divergence under 15.degree.. A phosphor emits yellow light when excited by the blue light. A collimator is disposed with the phosphor and forms a yellow beam with divergence under 15.degree.. A dichroic filter is positioned to transmit the beam of blue light to the phosphor and to reflect the beam of yellow light to an exit aperture. In different embodiments, the beams of blue and yellow light are incident upon said filter with central angles of 15.degree., 22.degree., and 45.degree.. The filter may reflect all of one polarization and part of the other polarization, and a polarization rotating retroreflector may then be provided to return the unreflected light to the filter.

Intramural Comparison of NIST Laser and Optical Fiber Power Calibrations.

PubMed

Lehman, John H; Vayshenker, Igor; Livigni, David J; Hadler, Joshua

2004-01-01

The responsivity of two optical detectors was determined by the method of direct substitution in four different NIST measurement facilities. The measurements were intended to demonstrate the determination of absolute responsivity as provided by NIST calibration services at laser and optical-communication wavelengths; nominally 633 nm, 850 nm, 1060 nm, 1310 nm, and 1550 nm. The optical detectors have been designated as checks standards for the purpose of routine intramural comparison of our calibration services and to meet requirements of the NIST quality system, based on ISO 17025. The check standards are two optical-trap detectors, one based on silicon and the other on indium gallium arsenide photodiodes. The four measurement services are based on: (1) the laser optimized cryogenic radiometer (LOCR) and free field collimated laser light; (2) the C-series isoperibol calorimeter and free-field collimated laser light; (3) the electrically calibrated pyroelectric radiometer and fiber-coupled laser light; (4) the pyroelectric wedge trap detector, which measures light from a lamp source and monochromator. The results indicate that the responsivity of the check standards, as determined independently using the four services, agree to within the published expanded uncertainty ranging from approximately 0.02 % to 1.24 %.

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

Koren, S; Kindler, J; Reich, E

Purpose: We propose the use of a HDR X-ray source collimator to apply a conformal, relatively small, radiation suitable for a single fraction with short delivery time. In addition, this technique can be applied using a radioactive source. Methods: We have built a stainless steel 1.5 mm thick applicator, to accommodate the needle applicator of the Intra-Beam X-ray source. Additional cavity is created in the applicator to allow the hosting/nesting/positioning of a LED diode. This LED is allowing a pre-irradiation beam marking on the tissue. The visible light emitted from the opening of the collimated applicator will delineate/verify the aperturemore » of the kV beam to be applied, as well as serve as distance indicator and will assist in the determination of dose to be delivered. For the evaluation of the collimated spatial dose distribution we have performed water tank measurements using (IBA Dosimetry) with a 0.4 cc ion chamber (IBA Dosimetry). We have scanned a two dimensional array with 1mm pitch in depth and 0.3 mm step size laterally. Additional verifications were conducted using Gaf-Chromic film for PDD measurements and Optical Stimulated Luminescence Dosimetry (OSLD, Landauer inc.) for absolute dosimetry. Results: The collimated applicator enables a conformal irradiated cross-section of about 3 mm square at the applicator surface was used in this study. A 180 seconds of 50 kVp delivery yielded 29 Gy, 20.6 Gy and 14.5 Gy at 5, 10 and 15 mm depths respectively. These results are in good agreement with the needle applicator depth dose curve published data. Conclusion: We have demonstrated the feasibility of focal HDR brachytherapy for conjunctival and ocular tumors, using the Intra-Beam needle applicator with in-house developed collimator. The delivery time was found to be several minutes- suitable for an intra-operative procedure and will allow dose fractionation deliveries.« less

Method and apparatus for enhanced sensitivity filmless medical x-ray imaging, including three-dimensional imaging

DOEpatents

Parker, S.

1995-10-24

A filmless X-ray imaging system includes at least one X-ray source, upper and lower collimators, and a solid-state detector array, and can provide three-dimensional imaging capability. The X-ray source plane is distance z{sub 1} above upper collimator plane, distance z{sub 2} above the lower collimator plane, and distance z{sub 3} above the plane of the detector array. The object to be X-rayed is located between the upper and lower collimator planes. The upper and lower collimators and the detector array are moved horizontally with scanning velocities v{sub 1}, v{sub 2}, v{sub 3} proportional to z{sub 1}, z{sub 2} and z{sub 3}, respectively. The pattern and size of openings in the collimators, and between detector positions is proportional such that similar triangles are always defined relative to the location of the X-ray source. X-rays that pass through openings in the upper collimator will always pass through corresponding and similar openings in the lower collimator, and thence to a corresponding detector in the underlying detector array. Substantially 100% of the X-rays irradiating the object (and neither absorbed nor scattered) pass through the lower collimator openings and are detected, which promotes enhanced sensitivity. A computer system coordinates repositioning of the collimators and detector array, and X-ray source locations. The computer system can store detector array output, and can associate a known X-ray source location with detector array output data, to provide three-dimensional imaging. Detector output may be viewed instantly, stored digitally, and/or transmitted electronically for image viewing at a remote site. 5 figs.

Method and apparatus for enhanced sensitivity filmless medical x-ray imaging, including three-dimensional imaging

DOEpatents

Parker, Sherwood

1995-01-01

A filmless X-ray imaging system includes at least one X-ray source, upper and lower collimators, and a solid-state detector array, and can provide three-dimensional imaging capability. The X-ray source plane is distance z.sub.1 above upper collimator plane, distance z.sub.2 above the lower collimator plane, and distance z.sub.3 above the plane of the detector array. The object to be X-rayed is located between the upper and lower collimator planes. The upper and lower collimators and the detector array are moved horizontally with scanning velocities v.sub.1, v.sub.2, v.sub.3 proportional to z.sub.1, z.sub.2 and z.sub.3, respectively. The pattern and size of openings in the collimators, and between detector positions is proportional such that similar triangles are always defined relative to the location of the X-ray source. X-rays that pass through openings in the upper collimator will always pass through corresponding and similar openings in the lower collimator, and thence to a corresponding detector in the underlying detector array. Substantially 100% of the X-rays irradiating the object (and neither absorbed nor scattered) pass through the lower collimator openings and are detected, which promotes enhanced sensitivity. A computer system coordinates repositioning of the collimators and detector array, and X-ray source locations. The computer system can store detector array output, and can associate a known X-ray source location with detector array output data, to provide three-dimensional imaging. Detector output may be viewed instantly, stored digitally, and/or transmitted electronically for image viewing at a remote site.

Design of a fast multileaf collimator for radiobiological optimized IMRT with scanned beams of photons, electrons, and light ions.

PubMed

Svensson, Roger; Larsson, Susanne; Gudowska, Irena; Holmberg, Rickard; Brahme, Anders

2007-03-01

Intensity modulated radiation therapy is rapidly becoming the treatment of choice for most tumors with respect to minimizing damage to the normal tissues and maximizing tumor control. Today, intensity modulated beams are most commonly delivered using segmental multileaf collimation, although an increasing number of radiation therapy departments are employing dynamic multileaf collimation. The irradiation time using dynamic multileaf collimation depends strongly on the nature of the desired dose distribution, and it is difficult to reduce this time to less than the sum of the irradiation times for all individual peak heights using dynamic leaf collimation [Svensson et al., Phys. Med. Biol. 39, 37-61 (1994)]. Therefore, the intensity modulation will considerably increase the total treatment time. A more cost-effective procedure for rapid intensity modulation is using narrow scanned photon, electron, and light ion beams in combination with fast multileaf collimator penumbra trimming. With this approach, the irradiation time is largely independent of the complexity of the desired intensity distribution and, in the case of photon beams, may even be shorter than with uniform beams. The intensity modulation is achieved primarily by scanning of a narrow elementary photon pencil beam generated by directing a narrow well focused high energy electron beam onto a thin bremsstrahlung target. In the present study, the design of a fast low-weight multileaf collimator that is capable of further sharpening the penumbra at the edge of the elementary scanned beam has been simulated, in order to minimize the dose or radiation response of healthy tissues. In the case of photon beams, such a multileaf collimator can be placed relatively close to the bremsstrahlung target to minimize its size. It can also be flat and thin, i.e., only 15-25 mm thick in the direction of the beam with edges made of tungsten or preferably osmium to optimize the sharpening of the penumbra. The low height of the collimator will minimize edge scatter from glancing incidence. The major portions of the collimator leafs can then be made of steel or even aluminum, so that the total weight of the multileaf collimator will be as low as 10 kg, which may even allow high-speed collimation in real time in synchrony with organ movements. To demonstrate the efficiency of this collimator design in combination with pencil beam scanning, optimal radiobiological treatments of an advanced cervix cancer were simulated. Different geometrical collimator designs were tested for bremsstrahlung, electron, and light ion beams. With a 10 mm half-width elementary scanned photon beam and a steel collimator with tungsten edges, it was possible to make as effective treatments as obtained with intensity modulated beams of full resolution, i.e., here 5 mm resolution in the fluence map. In combination with narrow pencil beam scanning, such a collimator may provide ideal delivery of photons, electrons, or light ions for radiation therapy synchronized to breathing and other organ motions. These high-energy photon and light ion beams may allow three-dimensional in vivo verification of delivery and thereby clinical implementation of the BioArt approach using Biologically Optimized three-dimensional in vivo predictive Assay based adaptive Radiation Therapy [Brahme, Acta Oncol. 42, 123-126 (2003)].

Optimal design of a high accuracy photoelectric auto-collimator based on position sensitive detector

NASA Astrophysics Data System (ADS)

Yan, Pei-pei; Yang, Yong-qing; She, Wen-ji; Liu, Kai; Jiang, Kai; Duan, Jing; Shan, Qiusha

2018-02-01

A kind of high accuracy Photo-electric auto-collimator based on PSD was designed. The integral structure composed of light source, optical lens group, Position Sensitive Detector (PSD) sensor, and its hardware and software processing system constituted. Telephoto objective optical type is chosen during the designing process, which effectively reduces the length, weight and volume of the optical system, as well as develops simulation-based design and analysis of the auto-collimator optical system. The technical indicators of auto-collimator presented by this paper are: measuring resolution less than 0.05″; a field of view is 2ω=0.4° × 0.4° measuring range is +/-5' error of whole range measurement is less than 0.2″. Measuring distance is 10m, which are applicable to minor-angle precise measuring environment. Aberration analysis indicates that the MTF close to the diffraction limit, the spot in the spot diagram is much smaller than the Airy disk. The total length of the telephoto lens is only 450mm by the design of the optical machine structure optimization. The autocollimator's dimension get compact obviously under the condition of the image quality is guaranteed.

Optical design of a light-emitting diode lamp for a maritime lighthouse.

PubMed

Jafrancesco, D; Mercatelli, L; Sansoni, P; Fontani, D; Sani, E; Coraggia, S; Meucci, M; Francini, F

2015-04-10

Traffic signaling is an emerging field for light-emitting diode (LED) applications. This sustainable power-saving illumination technology can be used in maritime signaling thanks to the recently updated norms, where the possibility to utilize LED sources is explicitly cited, and to the availability of high-power white LEDs that, combined with suitable lenses, permit us to obtain well-collimated beams. This paper describes the optical design of a LED-based lamp that can replace a traditional lamp in an authentic marine lighthouse. This source recombines multiple separated LEDs realizing a quasi-punctual localized source. Advantages can be lower energy consumption, higher efficiency, longer life, fewer faults, slower aging, and minor maintenance costs. The proposed LED source allows us to keep and to utilize the old Fresnel lenses of the lighthouse, which very often have historical value.

Investigation of attenuation coefficients of some stainless steel and aluminum alloys

NASA Astrophysics Data System (ADS)

Caner, Zafer; Tufan, Mustafa ćaǧatay

2018-02-01

In this study, attenuation coefficients of two different stainless steel alloys (AISI 304 and AISI 310), which have a wide range of applications from home appliances to the automotive sector, and two different aluminum alloys (6013 and 5083), which have a high mechanical strength and a light weight structure and are used in many fields from aviation to military vehicles, has been determined. For this purpose, we used gamma spectrometer system with NaI(Tl) detector. In our measurements, we used Eu-152, Ra-226 and Co-60 as gamma ray sources. To narrow the beam of gamma rays, we designed the new steel based collimator. We also investigated the effect of using collimator. Obtained results were compared with the NIST XCOM values.

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

Cifuentes, A.; Departamento de Física Aplicada I, Escuela Técnica Superior de Ingeniería, Universidad del País Vasco UPV/EHU, Alameda Urquijo s/n, 48013 Bilbao; Alvarado, S.

Here, we present a novel application of the shadowgraph technique for obtaining the thermal diffusivity of an opaque solid sample, inspired by the orthogonal skimming photothermal beam deflection technique. This new variant utilizes the shadow projected by the sample when put against a collimated light source. The sample is then heated periodically by another light beam, giving rise to thermal waves, which propagate across it and through its surroundings. Changes in the refractive index of the surrounding media due to the heating distort the shadow. This phenomenon is recorded and lock-in amplified in order to determine the sample's thermal diffusivity.

Visualization of fluid turbulence and acoustic cavitation during phacoemulsification.

PubMed

Tognetto, Daniele; Sanguinetti, Giorgia; Sirotti, Paolo; Brezar, Edoardo; Ravalico, Giuseppe

2005-02-01

To describe a technique for visualizing fluid turbulence and cavitational energy created by ultrasonic phaco tips. University Eye Clinic of Trieste, Trieste, Italy. Generation of cavitational energy by the phaco tip was visualized using an optical test bench comprising several components. The technique uses a telescope system to expand a laser light source into a coherent, collimated beam of light with a diameter of approximately 50.0 mm. The expanded laser beam shines on the test tube containing the tip activated in a medium of water or ophthalmic viscosurgical device (OVD). Two precision optical collimators complete the optical test bench and form the system used to focus data onto a charge-coupled device television camera connected to a recorder. Images of irrigation, irrigation combined with aspiration, irrigation/aspiration, and phacosonication were obtained with the tip immersed in a tube containing water or OVD. Optical image processing enabled acoustic cavitation to be visualized during phacosonication. The system is a possible means of evaluating a single phaco apparatus power setting and comparing phaco machines and techniques.

Free-form surface design method for a collimator TIR lens.

PubMed

Tsai, Chung-Yu

2016-04-01

A free-form (FF) surface design method is proposed for a general axial-symmetrical collimator system consisting of a light source and a total internal reflection lens with two coupled FF boundary surfaces. The profiles of the boundary surfaces are designed using a FF surface construction method such that each incident ray is directed (refracted and reflected) in such a way as to form a specified image pattern on the target plane. The light ray paths within the system are analyzed using an exact analytical model and a skew-ray tracing approach. In addition, the validity of the proposed FF design method is demonstrated by means of ZEMAX simulations. It is shown that the illumination distribution formed on the target plane is in good agreement with that specified by the user. The proposed surface construction method is mathematically straightforward and easily implemented in computer code. As such, it provides a useful tool for the design and analysis of general axial-symmetrical optical systems.

Planar concentrators near the étendue limit.

PubMed

Winston, Roland; Gordon, Jeffrey M

2005-10-01

Recently proposed aplanatic imaging designs are integrally combined with nonimaging flux boosters to produce an ultracompact planar glass-filled concentrator that performs near the étendue limit. Such optical devices are attractive for high-efficiency multijunction photovoltaics at high flux, with realistic power generation of 1 W from a 1 mm2 cell. When deployed in reverse, our designs provide collimation even for high-numerical-aperture light sources.

Planar concentrators near the étendue limit

NASA Astrophysics Data System (ADS)

Winston, Roland; Gordon, Jeffrey M.

2005-10-01

Recently proposed aplanatic imaging designs are integrally combined with nonimaging flux boosters to produce an ultracompact planar glass-filled concentrator that performs near the étendue limit. Such optical devices are attractive for high-efficiency multijunction photovoltaics at high flux, with realistic power generation of 1 W from a 1 mm² cell. When deployed in reverse, our designs provide collimation even for high-numerical-aperture light sources.

Portable biochip scanner device

DOEpatents

Perov, Alexander; Sharonov, Alexei; Mirzabekov, Andrei D.

2002-01-01

A portable biochip scanner device used to detect and acquire fluorescence signal data from biological microchips (biochips) is provided. The portable biochip scanner device employs a laser for emitting an excitation beam. An optical fiber delivers the laser beam to a portable biochip scanner. A lens collimates the laser beam, the collimated laser beam is deflected by a dichroic mirror and focused by an objective lens onto a biochip. The fluorescence light from the biochip is collected and collimated by the objective lens. The fluorescence light is delivered to a photomultiplier tube (PMT) via an emission filter and a focusing lens. The focusing lens focuses the fluorescence light into a pinhole. A signal output of the PMT is processed and displayed.

Normalization of a collimated 14.7 MeV neutron source in a neutron spectrometry system for benchmark experiments

NASA Astrophysics Data System (ADS)

Ofek, R.; Tsechanski, A.; Shani, G.

1988-05-01

In the present study a method used to normalize a collimated 14.7 MeV neutron beam is introduced. It combined a measurement of the fast neutron scalar flux passing through the collimator, using a copper foil activation, with a neutron transport calculation of the foil activation per unit source neutron, carried out by the discrete-ordinates transport code DOT 4.2. The geometry of the collimated neutron beam is composed of a D-T neutron source positioned 30 cm in front of a 6 cm diameter collimator, through a 120 cm thick paraffin wall. The neutron flux emitted from the D-T source was counted by an NE-213 scintillator, simultaneously with the irradiation of the copper foil. Thus, the determination of the normalization factor of the D-T source is used for an absolute flux calibration of the NE-213 scintillator. The major contributions to the uncertainty in the determination of the normalization factor, and their origins, are discussed.

Instruments for Reading Direct-Marked Data-Matrix Symbols

NASA Technical Reports Server (NTRS)

Schramm, Harry F.; Corder, Eric L.

2006-01-01

Improved optoelectronic instruments (specially configured digital cameras) for reading direct-marked data-matrix symbols on the surfaces of optically reflective objects (including specularly reflective ones) are undergoing development. Data-matrix symbols are two-dimensional binary patterns that are used, like common bar codes, for automated identification of objects. The first data-matrix symbols were checkerboard-like patterns of black-and-white rectangles, typically existing in the forms of paint, ink, or detachable labels. The major advantage of direct marking (the marks are more durable than are painted or printed symbols or detachable labels) is offset by a major disadvantage (the marks generated by some marking methods do not provide sufficient contrast to be readable by optoelectronic instruments designed to read black-and-white data-matrix symbols). Heretofore, elaborate lighting, lensing, and software schemes have been tried in efforts to solve the contrast problem in direct-mark matrix- symbol readers. In comparison with prior readers based on those schemes, the readers now undergoing development are expected to be more effective while costing less. All of the prior direct-mark matrix-symbol readers are designed to be aimed perpendicularly to marked target surfaces, and they tolerate very little angular offset. However, the reader now undergoing development not only tolerates angular offset but depends on angular offset as a means of obtaining the needed contrast, as described below. The prototype reader (see Figure 1) includes an electronic camera in the form of a charge-coupled-device (CCD) image detector equipped with a telecentric lens. It also includes a source of collimated visible light and a source of collimated infrared light for illuminating a target. The visible and infrared illumination complement each other: the visible illumination is more useful for aiming the reader toward a target, while the infrared illumination is more useful for reading symbols on highly reflective surfaces. By use of beam splitters, the visible and infrared collimated lights are introduced along the optical path of the telecentric lens, so that the target is illuminated and viewed from the same direction.

Ion beam collimating grid to reduce added defects

DOEpatents

Lindquist, Walter B.; Kearney, Patrick A.

2003-01-01

A collimating grid for an ion source located after the exit grid. The collimating grid collimates the ion beamlets and disallows beam spread and limits the beam divergence during transients and steady state operation. The additional exit or collimating grid prevents beam divergence during turn-on and turn-off and prevents ions from hitting the periphery of the target where there is re-deposited material or from missing the target and hitting the wall of the vessel where there is deposited material, thereby preventing defects from being deposited on a substrate to be coated. Thus, the addition of a collimating grid to an ion source ensures that the ion beam will hit and be confined to a specific target area.

Suite of three protein crystallography beamlines with single superconducting bend magnet as the source.

PubMed

MacDowell, Alastair A; Celestre, Rich S; Howells, Malcolm; McKinney, Wayne; Krupnick, James; Cambie, Daniella; Domning, Edward E; Duarte, Robert M; Kelez, Nicholas; Plate, David W; Cork, Carl W; Earnest, Thomas N; Dickert, Jeffery; Meigs, George; Ralston, Corie; Holton, James M; Alber, Tom; Berger, James M; Agard, David A; Padmore, Howard A

2004-11-01

At the Advanced Light Source, three protein crystallography beamlines have been built that use as a source one of the three 6 T single-pole superconducting bending magnets (superbends) that were recently installed in the ring. The use of such single-pole superconducting bend magnets enables the development of a hard X-ray program on a relatively low-energy 1.9 GeV ring without taking up insertion-device straight sections. The source is of relatively low power but, owing to the small electron beam emittance, it has high brightness. X-ray optics are required to preserve the brightness and to match the illumination requirements for protein crystallography. This was achieved by means of a collimating premirror bent to a plane parabola, a double-crystal monochromator followed by a toroidal mirror that focuses in the horizontal direction with a 2:1 demagnification. This optical arrangement partially balances aberrations from the collimating and toroidal mirrors such that a tight focused spot size is achieved. The optical properties of the beamline are an excellent match to those required by the small protein crystals that are typically measured. The design and performance of these new beamlines are described.

High-speed imaging with endoscopic optical coherence tomography using bending vibration of optical fiber

NASA Astrophysics Data System (ADS)

Isago, Ryoichi; Nakamura, Kentaro

2009-10-01

In this report, we propose an endoscopic scanner head for optical coherence tomography (OCT) using bending vibration of an optical fiber. The optical fiber is attached to the center of a cylindrical piezoelectric actuator with four outer electrodes, and the voltages with the phase shift of π/2 are applied to the electrodes to excite a circular vibration of the fiber end. The output light from the fiber end is collimated by a lens, and deflected by 90 degrees using a cone mirror. The collimated light is scanned along the circumference of the endoscope due to the vibration of the optical fiber end. We made a prototype scanner head of 7.0 mm in outer diameter, and demonstrated tomographic imaging of tubular objects. The circumferential scan is carried out at 1 kHz which is the frequency of the fiber vibration, while the radial (depth) scan is performed at 20 kHz by the wavelength sweep of the light source. Two-dimensional OCT images were obtained in a short measuring time of 5 ms (flame rate of 200 fps), and three-dimensional dynamic imaging were demonstrated.

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

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

Fong, G; Kapadia, A

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

Exploiting Photo-induced Reactions in Polymer Blends to Create Hierarchically Ordered, Defect-free Materials

ScienceCinema

Balazs, Anna [University of Pittsburgh, Pittsburgh, Pennsylvania, United States

2017-12-09

Computer simulations reveal how photo-induced chemical reactions can be exploited to create long-range order in binary and ternary polymeric materials. The process is initiated by shining a spatially uniform light over a photosensitive AB binary blend, which undergoes both a reversible chemical reaction and phase separation. We then introduce a well-collimated, higher-intensity light source. Rastering this secondary light over the sample locally increases the reaction rate and causes formation of defect-free, spatially periodic structures. These binary structures resemble either the lamellar or hexagonal phases of microphase-separated di-block copolymers. We measure the regularity of the ordered structures as a function of the relative reaction rates for different values of the rastering speed and determine the optimal conditions for creating defect-free structures in the binary systems. We then add a non-reactive homo-polymer C, which is immiscible with both A and B. We show that this component migrates to regions that are illuminated by the secondary, higher-intensity light, allowing us to effectively write a pattern of C onto the AB film. Rastering over the ternary blend with this collimated light now leads to hierarchically ordered patterns of A, B, and C. The findings point to a facile, non-intrusive process for manufacturing high-quality polymeric devices in a low-cost, efficient manner.

Method and apparatus for a multibeam beacon laser assembly for optical communications

NASA Technical Reports Server (NTRS)

Biswas, Abhijit (Inventor); Sanji, Babak (Inventor); Wright, Malcolm W. (Inventor); Page, Norman Alan (Inventor)

2005-01-01

An optical beacon is comprised of a telescope having a primary focal plane or Coud? focal plane, a plurality of fiber coupled laser sources for generating a plurality of beams, a collimator for collimating the plurality of beams, and optics for combining and focusing the plurality of collimated beams onto the primary or Coud? focal plane of the telescope. The telescope propagates the optical beacon, which is arranged into a ring of incoherent plurality of collimated beams. The apparatus further comprises fiber splitters coupled to each laser source to provide at least eight beams from at least four laser sources. The optics comprises a prism assembly, a combiner lens, a focusing lens and a field lens for focusing the plurality of collimated beams onto the primary focal plane or Coud? focal plane of the telescope.

Radiative Energy Budgets of Phototrophic Surface-Associated Microbial Communities and their Photosynthetic Efficiency Under Diffuse and Collimated Light

PubMed Central

Lichtenberg, Mads; Brodersen, Kasper E.; Kühl, Michael

2017-01-01

We investigated the radiative energy budgets of a heterogeneous photosynthetic coral reef sediment and a compact uniform cyanobacterial biofilm on top of coastal sediment. By combining electrochemical, thermocouple and fiber-optic microsensor measurements of O2, temperature and light, we could calculate the proportion of the absorbed light energy that was either dissipated as heat or conserved by photosynthesis. We show, across a range of different incident light regimes, that such radiative energy budgets are highly dominated by heat dissipation constituting up to 99.5% of the absorbed light energy. Highest photosynthetic energy conservation efficiency was found in the coral sediment under low light conditions and amounted to 18.1% of the absorbed light energy. Additionally, the effect of light directionality, i.e., diffuse or collimated light, on energy conversion efficiency was tested on the two surface-associated systems. The effects of light directionality on the radiative energy budgets of these phototrophic communities were not unanimous but, resulted in local spatial differences in heat-transfer, gross photosynthesis, and light distribution. The light acclimation index, Ek, i.e., the irradiance at the onset of saturation of photosynthesis, was >2 times higher in the coral sediment compared to the biofilm and changed the pattern of photosynthetic energy conservation under light-limiting conditions. At moderate to high incident irradiances, the photosynthetic conservation of absorbed energy was highest in collimated light; a tendency that changed in the biofilm under sub-saturating incident irradiances, where higher photosynthetic efficiencies were observed under diffuse light. The aim was to investigate how the physical structure and light propagation affected energy budgets and light utilization efficiencies in loosely organized vs. compact phototrophic sediment under diffuse and collimated light. Our results suggest that the optical properties and the structural organization of phytoelements are important traits affecting the photosynthetic efficiency of biofilms and sediments. PMID:28400749

Radiative Energy Budgets of Phototrophic Surface-Associated Microbial Communities and their Photosynthetic Efficiency Under Diffuse and Collimated Light.

PubMed

Lichtenberg, Mads; Brodersen, Kasper E; Kühl, Michael

2017-01-01

We investigated the radiative energy budgets of a heterogeneous photosynthetic coral reef sediment and a compact uniform cyanobacterial biofilm on top of coastal sediment. By combining electrochemical, thermocouple and fiber-optic microsensor measurements of O 2 , temperature and light, we could calculate the proportion of the absorbed light energy that was either dissipated as heat or conserved by photosynthesis. We show, across a range of different incident light regimes, that such radiative energy budgets are highly dominated by heat dissipation constituting up to 99.5% of the absorbed light energy. Highest photosynthetic energy conservation efficiency was found in the coral sediment under low light conditions and amounted to 18.1% of the absorbed light energy. Additionally, the effect of light directionality, i.e., diffuse or collimated light, on energy conversion efficiency was tested on the two surface-associated systems. The effects of light directionality on the radiative energy budgets of these phototrophic communities were not unanimous but, resulted in local spatial differences in heat-transfer, gross photosynthesis, and light distribution. The light acclimation index, E k , i.e., the irradiance at the onset of saturation of photosynthesis, was >2 times higher in the coral sediment compared to the biofilm and changed the pattern of photosynthetic energy conservation under light-limiting conditions. At moderate to high incident irradiances, the photosynthetic conservation of absorbed energy was highest in collimated light; a tendency that changed in the biofilm under sub-saturating incident irradiances, where higher photosynthetic efficiencies were observed under diffuse light. The aim was to investigate how the physical structure and light propagation affected energy budgets and light utilization efficiencies in loosely organized vs. compact phototrophic sediment under diffuse and collimated light. Our results suggest that the optical properties and the structural organization of phytoelements are important traits affecting the photosynthetic efficiency of biofilms and sediments.

Space and time resolved representation of a vacuum arc light emission

NASA Astrophysics Data System (ADS)

Georgescu, N.; Sandolache, G.; Zoita, V.

1999-04-01

An optoelectronic multichannel detection system for the study of the visible light emission of a vacuum circuit breaker arc is described. The system consists of two multiple slit collimator assemblies coupled directly to the arc discharge chamber and an electronic detection part. The light emitted by the arc is collected by the two collimator assemblies and is transmitted through optical fibres to the electronic detection part. By using a new, simple computational method two-dimensional plots of the vacuum arc light emission at different times are obtained.

Highly improved operation of monolithic BGO-PET blocks

NASA Astrophysics Data System (ADS)

Gonzalez-Montoro, A.; Sanchez, F.; Majewski, S.; Zanettini, S.; Benlloch, J. M.; Gonzalez, A. J.

2017-11-01

In PET scanners both scintillation crystals and photosensors are key components defining the system's performance and cost. Original PET systems used BGO or NaI(Tl) scintillators but achieved limited performance due to its slow decay and relatively low light output. Moreover, NaI(Tl) has low stopping power for 511 keV annihilation photons. In this study we report the possibility to reintroduce BGO crystals, and in particular in the form of monolithic blocks, especially suitable for low-dose large-size PET scanners, offering significantly improved sensitivity at a highly reduced cost compared to LYSO type fast scintillators. We have studied the performance of a monolithic BGO block as large as 50 × 50 × 15 mm3 with black-painted lateral walls to reduce lights spread, enabling accurate photon depth of interaction (DOI) measurements. A directional optical layer, called retro-reflector, was coupled to the entrance face bouncing back the scintillation light in the direction of the emission source and, therefore, adding to the light signal while preserving the narrow light cone distribution. Four configurations namely 12 × 12 and 16 × 16 SiPM arrays (3 mm × 3 mm each) as photosensors, with or without a nanopattern treatment at the crystal exit face, have been studied. This structure consisted of a thin layer of a specific high refractive index material shaped with a periodic nanopattern, increasing the scintillation light extraction. The readout returned information for each SiPM row and column, characterizing the X-Y light distribution projections. We have studied the detector spatial resolution using collimated 22Na sources at normal incidence. The DOI resolution was evaluated using collimated gamma beams with lateral incidence. The overall best detector performance was obtained for the 16× 16 SiPM array offering higher readout granularity. We have determined the spatial resolution for 3 separated DOI layers, obtaining the best results for the DOI region near to the photosensor.

Method and apparatus for assaying wood pulp fibers

DOEpatents

Gustafson, Richard [Bellevue, WA; Callis, James B [Seattle, WA; Mathews, Jeffrey D [Neenah, WI; Robinson, John [Issaquah, WA; Bruckner, Carsten A [San Mateo, CA; Suvamakich, Kuntinee [Seattle, WA

2009-05-26

Paper pulp is added to a stain solution. The stain solution and pulp fibers are mixed to form a slurry. Samples are removed from the slurry and are admixed with dilution water and a bleach. Then, the fibers are moved into a flow cell where they are subjected to a light source adapted to stimulate fluorescence from the stained pulp fiber. Before the fiber slurry enters the flow cell it is mixed with a dilution water of bleach to reduce background fluorescence. The fluorescent light is collimated and directed through a dichroic filter onto a fluorescence splitting dichroic filter.

Slit-Slat Collimator Equipped Gamma Camera for Whole-Mouse SPECT-CT Imaging

NASA Astrophysics Data System (ADS)

Cao, Liji; Peter, Jörg

2012-06-01

A slit-slat collimator is developed for a gamma camera intended for small-animal imaging (mice). The tungsten housing of a roof-shaped collimator forms a slit opening, and the slats are made of lead foils separated by sparse polyurethane material. Alignment of the collimator with the camera's pixelated crystal is performed by adjusting a micrometer screw while monitoring a Co-57 point source for maximum signal intensity. For SPECT, the collimator forms a cylindrical field-of-view enabling whole mouse imaging with transaxial magnification and constant on-axis sensitivity over the entire axial direction. As the gamma camera is part of a multimodal imaging system incorporating also x-ray CT, five parameters corresponding to the geometric displacements of the collimator as well as to the mechanical co-alignment between the gamma camera and the CT subsystem are estimated by means of bimodal calibration sources. To illustrate the performance of the slit-slat collimator and to compare its performance to a single pinhole collimator, a Derenzo phantom study is performed. Transaxial resolution along the entire long axis is comparable to a pinhole collimator of same pinhole diameter. Axial resolution of the slit-slat collimator is comparable to that of a parallel beam collimator. Additionally, data from an in-vivo mouse study are presented.

Near-field collimation of light carrying orbital angular momentum with bull's-eye-assisted plasmonic coaxial waveguides.

PubMed

Pu, Mingbo; Ma, Xiaoliang; Zhao, Zeyu; Li, Xiong; Wang, Yanqin; Gao, Hui; Hu, Chenggang; Gao, Ping; Wang, Changtao; Luo, Xiangang

2015-07-10

The orbital angular momentum (OAM) of light, as an emerging hotspot in optics and photonics, introduces many degrees of freedom for applications ranging from optical communication and quantum processing to micromanipulation. To achieve a high degree of integration, optical circuits for OAM light are essential, which are, however, challenging in the optical regime owing to the lack of well-developed theory. Here we provide a scheme to guide and collimate the OAM beam at the micro- and nano-levels. The coaxial plasmonic slit was exploited as a naturally occurring waveguide for light carrying OAM. Concentric grooves etched on the output surface of the coaxial waveguide were utilized as a plasmonic metasurface to couple the OAM beam to free space with greatly increased beam directivity. Experimental results at λ = 532 nm validated the novel transportation and collimating effect of the OAM beam. Furthermore, dynamic tuning of the topological charges was demonstrated by using a liquid crystal spatial light modulator (SLM).

Near-field collimation of light carrying orbital angular momentum with bull’s-eye-assisted plasmonic coaxial waveguides

NASA Astrophysics Data System (ADS)

Pu, Mingbo; Ma, Xiaoliang; Zhao, Zeyu; Li, Xiong; Wang, Yanqin; Gao, Hui; Hu, Chenggang; Gao, Ping; Wang, Changtao; Luo, Xiangang

2015-07-01

The orbital angular momentum (OAM) of light, as an emerging hotspot in optics and photonics, introduces many degrees of freedom for applications ranging from optical communication and quantum processing to micromanipulation. To achieve a high degree of integration, optical circuits for OAM light are essential, which are, however, challenging in the optical regime owing to the lack of well-developed theory. Here we provide a scheme to guide and collimate the OAM beam at the micro- and nano-levels. The coaxial plasmonic slit was exploited as a naturally occurring waveguide for light carrying OAM. Concentric grooves etched on the output surface of the coaxial waveguide were utilized as a plasmonic metasurface to couple the OAM beam to free space with greatly increased beam directivity. Experimental results at λ = 532 nm validated the novel transportation and collimating effect of the OAM beam. Furthermore, dynamic tuning of the topological charges was demonstrated by using a liquid crystal spatial light modulator (SLM).

Near-field collimation of light carrying orbital angular momentum with bull’s-eye-assisted plasmonic coaxial waveguides

PubMed Central

Pu, Mingbo; Ma, Xiaoliang; Zhao, Zeyu; Li, Xiong; Wang, Yanqin; Gao, Hui; Hu, Chenggang; Gao, Ping; Wang, Changtao; Luo, Xiangang

2015-01-01

The orbital angular momentum (OAM) of light, as an emerging hotspot in optics and photonics, introduces many degrees of freedom for applications ranging from optical communication and quantum processing to micromanipulation. To achieve a high degree of integration, optical circuits for OAM light are essential, which are, however, challenging in the optical regime owing to the lack of well-developed theory. Here we provide a scheme to guide and collimate the OAM beam at the micro- and nano-levels. The coaxial plasmonic slit was exploited as a naturally occurring waveguide for light carrying OAM. Concentric grooves etched on the output surface of the coaxial waveguide were utilized as a plasmonic metasurface to couple the OAM beam to free space with greatly increased beam directivity. Experimental results at λ = 532 nm validated the novel transportation and collimating effect of the OAM beam. Furthermore, dynamic tuning of the topological charges was demonstrated by using a liquid crystal spatial light modulator (SLM). PMID:26159423

Scanned Image Projection System Employing Intermediate Image Plane

NASA Technical Reports Server (NTRS)

DeJong, Christian Dean (Inventor); Hudman, Joshua M. (Inventor)

2014-01-01

In imaging system, a spatial light modulator is configured to produce images by scanning a plurality light beams. A first optical element is configured to cause the plurality of light beams to converge along an optical path defined between the first optical element and the spatial light modulator. A second optical element is disposed between the spatial light modulator and a waveguide. The first optical element and the spatial light modulator are arranged such that an image plane is created between the spatial light modulator and the second optical element. The second optical element is configured to collect the diverging light from the image plane and collimate it. The second optical element then delivers the collimated light to a pupil at an input of the waveguide.

Development and deployment of the Collimated Directional Radiation Detection System

NASA Astrophysics Data System (ADS)

Guckes, Amber L.; Barzilov, Alexander

2017-09-01

The Collimated Directional Radiation Detection System (CDRDS) is capable of imaging radioactive sources in two dimensions (as a directional detector). The detection medium of the CDRDS is a single Cs2LiYCl6:Ce3+ scintillator cell enriched in 7Li (CLYC-7). The CLYC-7 is surrounded by a heterogeneous high-density polyethylene (HDPE) and lead (Pb) collimator. These materials make-up a coded aperture inlaid in the collimator. The collimator is rotated 360° by a stepper motor which enables time-encoded imaging of a radioactive source. The CDRDS is capable of spectroscopy and pulse shape discrimination (PSD) of photons and fast neutrons. The measurements of a radioactive source are carried out in discrete time steps that correlate to the angular rotation of the collimator. The measurement results are processed using a maximum likelihood expectation (MLEM) algorithm to create an image of the measured radiation. This collimator design allows for the directional detection of photons and fast neutrons simultaneously by utilizing only one CLYC-7 scintillator. Directional detection of thermal neutrons can also be performed by utilizing another suitable scintillator. Moreover, the CDRDS is portable, robust, and user friendly. This unit is capable of utilizing wireless data transfer for possible radiation mapping and network-centric applications. The CDRDS was tested by performing laboratory measurements with various gamma-ray and neutron sources.

Bending self-collimated one-way light by using gyromagnetic photonic crystals

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

Li, Qing-Bo; Jiangsu Key Construction Laboratory of Modern Measurement Technology and Intelligent System, Huaiyin Normal University, Huaian 223300; Li, Zhen

2015-12-14

We theoretically demonstrate that electromagnetic waves can self-collimate and propagate unidirectionally in photonic crystals fabricated using semicylindrical ferrite rods in magnetized states. The parity and time-reversal symmetries of such photonic crystals are broken, resulting in a self-collimated one-way body wave within the photonic crystals. By applying the bias magnetic field in a complex configuration, the self-collimated one-way wave beam can be bent into arbitrary trajectories within the photonic crystal, providing an avenue for controlling wave beams.

Fiber optic laser-induced breakdown spectroscopy sensor for molten material analysis

DOEpatents

Zhang, Hansheng; Rai, Awadesh K.; Singh, Jagdish P.; Yueh, Fang-Yu

2004-07-13

A fiber optic laser-induced breakdown spectroscopy (LIBS) sensor, including a laser light source, a harmonic separator for directing the laser light, a dichroic mirror for reflecting the laser light, a coupling lens for coupling the laser light at an input of a multimode optical fiber, a connector for coupling the laser light from an output of the multimode optical fiber to an input of a high temperature holder, such as a holder made of stainless steel, and a detector portion for receiving emission signal and analyzing LIBS intensities. In one variation, the multimode optical fiber has silica core and silica cladding. The holder includes optical lenses for collimating and focusing the laser light in a molten alloy to produce a plasma, and for collecting and transmitting an emission signal to the multimode optical fiber.

Anti-spoof touchless 3D fingerprint recognition system using single shot fringe projection and biospeckle analysis

NASA Astrophysics Data System (ADS)

Chatterjee, Amit; Bhatia, Vimal; Prakash, Shashi

2017-08-01

Fingerprint is a unique, un-alterable and easily collected biometric of a human being. Although it is a 3D biological characteristic, traditional methods are designed to provide only a 2D image. This touch based mapping of 3D shape to 2D image losses information and leads to nonlinear distortions. Moreover, as only topographic details are captured, conventional systems are potentially vulnerable to spoofing materials (e.g. artificial fingers, dead fingers, false prints, etc.). In this work, we demonstrate an anti-spoof touchless 3D fingerprint detection system using a combination of single shot fringe projection and biospeckle analysis. For fingerprint detection using fringe projection, light from a low power LED source illuminates a finger through a sinusoidal grating. The fringe pattern modulated because of features on the fingertip is captured using a CCD camera. Fourier transform method based frequency filtering is used for the reconstruction of 3D fingerprint from the captured fringe pattern. In the next step, for spoof detection using biospeckle analysis a visuo-numeric algorithm based on modified structural function and non-normalized histogram is proposed. High activity biospeckle patterns are generated because of interaction of collimated laser light with internal fluid flow of the real finger sample. This activity reduces abruptly in case of layered fake prints, and is almost absent in dead or fake fingers. Furthermore, the proposed setup is fast, low-cost, involves non-mechanical scanning and is highly stable.

Solar simulator for concentrator photovoltaic systems.

PubMed

Domínguez, César; Antón, Ignacio; Sala, Gabriel

2008-09-15

A solar simulator for measuring performance of large area concentrator photovoltaic (CPV) modules is presented. Its illumination system is based on a Xenon flash light and a large area collimator mirror, which simulates natural sun light. Quality requirements imposed by the CPV systems have been characterized: irradiance level and uniformity at the receiver, light collimation and spectral distribution. The simulator allows indoor fast and cost-effective performance characterization and classification of CPV systems at the production line as well as module rating carried out by laboratories.

Cone penetrometer fiber optic raman spectroscopy probe assembly

DOEpatents

Kyle, Kevin R.; Brown, Steven B.

2000-01-01

A chemically and mechanically robust optical Raman spectroscopy probe assembly that can be incorporated in a cone penetrometer (CPT) for subsurface deployment. This assembly consists of an optical Raman probe and a penetrometer compatible optical probe housing. The probe is intended for in-situ chemical analysis of chemical constituents in the surrounding environment. The probe is optically linked via fiber optics to the light source and the detection system at the surface. A built-in broadband light source provides a strobe method for direct measurement of sample optical density. A mechanically stable sapphire window is sealed directly into the side-wall of the housing using a metallic, chemically resistant, hermetic seal design. This window permits transmission of the interrogation light beam and the resultant signal. The spectroscopy probe assembly is capable of accepting Raman, Laser induced Fluorescence, reflectance, and other optical probes with collimated output for CPT deployment.

Integral freeform illumination lens design of LED based pico-projector.

PubMed

Zhao, Shuang; Wang, Kai; Chen, Fei; Qin, Zong; Liu, Sheng

2013-05-01

In this paper, an illumination lens design for a LED-based pico-projector is presented. Different from the traditional illumination systems composed by lens group, the integral illumination lens consists of a total internal reflector (TIR) and a freeform surface. TIR acts as collimation lens and its top surface formed by a freeform surface reshapes the nonuniform circular light pattern generated by TIR to be rectangular and uniform. Diameter and height of the lens are 16 and 10 mm, respectively. An optimization method to deal with the problem of extended light source is also presented in detail in this paper. According to the simulation results of the final optimized lens, 77% (neglecting the effect of polarization) of the power of light source is collected on liquid crystal on silicon panel with a 16∶9 ratio and illumination uniformity achieves 92%.

Un-collimated single-photon imaging system for high-sensitivity small animal and plant imaging.

PubMed

Walker, Katherine L; Judenhofer, Martin S; Cherry, Simon R; Mitchell, Gregory S

2015-01-07

In preclinical single-photon emission computed tomography (SPECT) system development the primary objective has been to improve spatial resolution by using novel parallel-hole or multi-pinhole collimator geometries. However, such high-resolution systems have relatively poor sensitivity (typically 0.01-0.1%). In contrast, a system that does not use collimators can achieve very high-sensitivity. Here we present a high-sensitivity un-collimated detector single-photon imaging (UCD-SPI) system for the imaging of both small animals and plants. This scanner consists of two thin, closely spaced, pixelated scintillator detectors that use NaI(Tl), CsI(Na), or BGO. The performance of the system has been characterized by measuring sensitivity, spatial resolution, linearity, detection limits, and uniformity. With (99m)Tc (140 keV) at the center of the field of view (20 mm scintillator separation), the sensitivity was measured to be 31.8% using the NaI(Tl) detectors and 40.2% with CsI(Na). The best spatial resolution (FWHM when the image formed as the geometric mean of the two detector heads, 20 mm scintillator separation) was 19.0 mm for NaI(Tl) and 11.9 mm for CsI(Na) at 140 keV, and 19.5 mm for BGO at 1116 keV, which is somewhat degraded compared to the cm-scale resolution obtained with only one detector head and a close source. The quantitative accuracy of the system's linearity is better than 2% with detection down to activity levels of 100 nCi. Two in vivo animal studies (a renal scan using (99m)Tc MAG-3 and a thyroid scan with (123)I) and one plant study (a (99m)TcO4(-) xylem transport study) highlight the unique capabilities of this UCD-SPI system. From the renal scan, we observe approximately a one thousand-fold increase in sensitivity compared to the Siemens Inveon SPECT/CT scanner. UCD-SPI is useful for many imaging tasks that do not require excellent spatial resolution, such as high-throughput screening applications, simple radiotracer uptake studies in tumor xenografts, dynamic studies where very good temporal resolution is critical, or in planta imaging of radioisotopes at low concentrations.

Un-collimated single-photon imaging system for high-sensitivity small animal and plant imaging

DOE PAGES

Walker, Katherine L.; Judenhofer, Martin S.; Cherry, Simon R.; ...

2014-12-12

In preclinical single-photon emission computed tomography (SPECT) system development the primary objective has been to improve spatial resolution by using novel parallel-hole or multi-pinhole collimator geometries. Furthermore, such high-resolution systems have relatively poor sensitivity (typically 0.01% to 0.1%). In contrast, a system that does not use collimators can achieve very high-sensitivity. Here we present a high-sensitivity un-collimated detector single-photon imaging (UCD-SPI) system for the imaging of both small animals and plants. This scanner consists of two thin, closely spaced, pixelated scintillator detectors that use NaI(Tl), CsI(Na), or BGO. The performance of the system has been characterized by measuring sensitivity, spatialmore » resolution, linearity, detection limits, and uniformity. With 99mTc (140 keV) at the center of the field of view (20 mm scintillator separation), the sensitivity was measured to be 31.8% using the NaI(Tl) detectors and 40.2% with CsI(Na). The best spatial resolution (FWHM when the image formed as the geometric mean of the two detector heads, 20 mm scintillator separation) was 19.0 mm for NaI(Tl) and 11.9 mm for CsI(Na) at 140 keV, and 19.5 mm for BGO at 1116 keV, which is somewhat degraded compared to the cm-scale resolution obtained with only one detector head and a close source. The quantitative accuracy of the system’s linearity is better than 2% with detection down to activity levels of 100 nCi. Two in vivo animal studies (a renal scan using 99mTc MAG-3 and a thyroid scan with 123I) and one plant study (a 99mTcO 4- xylem transport study) highlight the unique capabilities of this UCD-SPI system. From the renal scan, we observe approximately a one thousand-fold increase in sensitivity compared to the Siemens Inveon SPECT/CT scanner. In conclusion, UCD-SPI is useful for many imaging tasks that do not require excellent spatial resolution, such as high-throughput screening applications, simple radiotracer uptake studies in tumor xenografts, dynamic studies where very good temporal resolution is critical, or in planta imaging of radioisotopes at low concentrations.« less

Un-collimated single-photon imaging system for high-sensitivity small animal and plant imaging

NASA Astrophysics Data System (ADS)

Walker, Katherine L.; Judenhofer, Martin S.; Cherry, Simon R.; Mitchell, Gregory S.

2015-01-01

In preclinical single-photon emission computed tomography (SPECT) system development the primary objective has been to improve spatial resolution by using novel parallel-hole or multi-pinhole collimator geometries. However, such high-resolution systems have relatively poor sensitivity (typically 0.01-0.1%). In contrast, a system that does not use collimators can achieve very high-sensitivity. Here we present a high-sensitivity un-collimated detector single-photon imaging (UCD-SPI) system for the imaging of both small animals and plants. This scanner consists of two thin, closely spaced, pixelated scintillator detectors that use NaI(Tl), CsI(Na), or BGO. The performance of the system has been characterized by measuring sensitivity, spatial resolution, linearity, detection limits, and uniformity. With 99mTc (140 keV) at the center of the field of view (20 mm scintillator separation), the sensitivity was measured to be 31.8% using the NaI(Tl) detectors and 40.2% with CsI(Na). The best spatial resolution (FWHM when the image formed as the geometric mean of the two detector heads, 20 mm scintillator separation) was 19.0 mm for NaI(Tl) and 11.9 mm for CsI(Na) at 140 keV, and 19.5 mm for BGO at 1116 keV, which is somewhat degraded compared to the cm-scale resolution obtained with only one detector head and a close source. The quantitative accuracy of the system’s linearity is better than 2% with detection down to activity levels of 100 nCi. Two in vivo animal studies (a renal scan using 99mTc MAG-3 and a thyroid scan with 123I) and one plant study (a 99mTcO4- xylem transport study) highlight the unique capabilities of this UCD-SPI system. From the renal scan, we observe approximately a one thousand-fold increase in sensitivity compared to the Siemens Inveon SPECT/CT scanner. UCD-SPI is useful for many imaging tasks that do not require excellent spatial resolution, such as high-throughput screening applications, simple radiotracer uptake studies in tumor xenografts, dynamic studies where very good temporal resolution is critical, or in planta imaging of radioisotopes at low concentrations.

Mini-beam collimator applications at the Advanced Photon Source

NASA Astrophysics Data System (ADS)

Xu, Shenglan; Keefe, Lisa J.; Mulichak, Anne; Yan, Lifen; Alp, Ercan E.; Zhao, Jiyong; Fischetti, Robert F.

2011-09-01

In 2007, the General Medicine and Cancer Institutes Collaborative Access Team (GM/CA CAT, Sector 23, Advanced Photon Source) began providing mini-beam collimators to its users. These collimators contained individual, 5- or 10-μm pinholes and were rapidly exchangeable, thereby allowing users to tailor the beam size to their experimental needs. The use of these collimators provided a reduction in background noise, and thus improved the signal-to-noise ratio [1,2]. Recent improvements in the collimator design include construction of the device from a monolithic piece of molybdenum with multiple pinholes mounted inside [3]. This allows users to select from various size options from within the beamline control software without the realignment that was previously necessary. In addition, a new, 20-μm pinhole has been added to create a "quad-collimator", resulting in greater flexibility for the users. The mini-beam collimator is now available at multiple crystallographic beamlines and also is a part of the first Mössbauer Microscopic system at sector 3-ID.

Aberration-free intraocular lenses - What does this really mean?

PubMed

Langenbucher, Achim; Schröder, Simon; Cayless, Alan; Eppig, Timo

2017-09-01

So-called aberration-free intraocular lenses (IOLs) are well established in modern cataract surgery. Usually, they are designed to perfectly refract a collimated light beam onto the focal point. We show how much aberration can be expected with such an IOL in a convergent light beam such as that found anterior to the human cornea. Additionally, the aberration in a collimated beam is estimated for an IOL that has no aberrations in the convergent beam. The convergent beam is modelled as the pencil of rays corresponding to the spherical wavefront resulting from a typical corneal power of 43m -1 . The IOLs are modelled as infinitely thin phase plates with 20m -1 optical power placed 5mm behind the cornea. Their aberrations are reported in terms of optical path length difference and longitudinal spherical aberration (LSA) of the marginal rays, as well as nominal spherical aberration (SA) calculated based on a Zernike representation of the wavefront-error at the corneal plane within a 6mm aperture. The IOL designed to have no aberrations in a collimated light beam has an optical path length difference of -1.8μm, and LSA of 0.15m -1 in the convergent beam of a typical eye. The corresponding nominal SA is 0.065μm. The IOL designed to have no aberrations in a convergent light beam has an optical path length difference of 1.8μm, and LSA of -0.15m -1 in the collimated beam. An IOL designed to have no aberrations in a collimated light beam will increase the SA of a patient's eye after implantation. Copyright © 2017. Published by Elsevier GmbH.

Evaluation of radiation exposure with Tru-Align intraoral rectangular collimation system using OSL dosimeters.

PubMed

Goren, Arthur D; Bonvento, Michael J; Fernandez, Thomas J; Abramovitch, Kenneth; Zhang, Wenjian; Roe, Nadine; Seltzer, Jared; Steinberg, Mitchell; Colosi, Dan C

2011-03-01

A pilot study to compare radiation exposure with the Tru-Align rectangular collimation system to round collimation exposures was undertaken. Radiation exposure at various points within the cross sections of the collimators and entrance, intraoral and exit dose measurements were measured using InLight OSL dosimeters. Overall dose reduction with the use of the rectangular collimation system was estimated by taking into account the ratios of collimator openings and the average radiation exposure at the measurement points. Use of the Tru-Align system resulted in an average radiation exposure within the perimeter of the projected outline of the rectangular collimator of 36.1 mR, compared to 148.5 mR with the round collimator. Our calculations indicate a dose reduction by a factor of approximately 3.2 in the case of the Tru-Align system compared to round collimation. The Tru-Align system was easy to use, but in some situations failed to allow Xray coverage of the entire surface of the image receptor, leading to cone cuts.

Microfocus/Polycapillary-Optic Crystallographic X-Ray System

NASA Technical Reports Server (NTRS)

Joy, Marshall; Gubarev, Mikhail; Ciszak, Ewa

2005-01-01

A system that generates an intense, nearly collimated, nearly monochromatic, small-diameter x-ray beam has been developed for use in macromolecular crystallography. A conventional x-ray system for macromolecular crystallography includes a rotating-anode x-ray source, which is massive (.500 kg), large (approximately 2 by 2 by 1 m), and power-hungry (between 2 and 18 kW). In contrast, the present system generates a beam of the required brightness from a microfocus source, which is small and light enough to be mounted on a laboratory bench, and operates at a power level of only tens of watts. The figure schematically depicts the system as configured for observing x-ray diffraction from a macromolecular crystal. In addition to the microfocus x-ray source, the system includes a polycapillary optic . a monolithic block (typically a bundle of fused glass tubes) that contains thousands of straight or gently curved capillary channels, along which x-rays propagate with multiple reflections. This particular polycapillary optic is configured to act as a collimator; the x-ray beam that emerges from its output face consists of quasi-parallel subbeams with a small angular divergence and a diameter comparable to the size of a crystal to be studied. The gap between the microfocus x-ray source and the input face of the polycapillary optic is chosen consistently with the focal length of the polycapillary optic and the need to maximize the solid angle subtended by the optic in order to maximize the collimated x-ray flux. The spectrum from the source contains a significant component of Cu K (photon energy is 8.08 keV) radiation. The beam is monochromatized (for Cu K ) by a nickel filter 10 m thick. In a test, this system was operated at a power of 40 W (current of 897 A at an accelerating potential of 45 kV), with an anode x-ray spot size of 41+/-2 microns. Also tested, in order to provide a standard for comparison, was a commercial rotating-anode x-ray crystallographic system with a pyrolytic graphite monochromator and a 250-micron pinhole collimator, operating at a power of 3.15 kW (current of 70 mA at an accelerating potential of 45 kV). The flux of collimated Cu K radiation in this system was found to be approximately 16 times that in the rotatinganode system. Data on x-ray diffraction from crystals of tetragonal form of lysozyme (protein) in this system were found to be of high quality and to be reducible by use of standard crystallographic software.

Parallel detecting, spectroscopic ellipsometers/polarimeters

DOEpatents

Furtak, Thomas E.

2002-01-01

The parallel detecting spectroscopic ellipsometer/polarimeter sensor has no moving parts and operates in real-time for in-situ monitoring of the thin film surface properties of a sample within a processing chamber. It includes a multi-spectral source of radiation for producing a collimated beam of radiation directed towards the surface of the sample through a polarizer. The thus polarized collimated beam of radiation impacts and is reflected from the surface of the sample, thereby changing its polarization state due to the intrinsic material properties of the sample. The light reflected from the sample is separated into four separate polarized filtered beams, each having individual spectral intensities. Data about said four individual spectral intensities is collected within the processing chamber, and is transmitted into one or more spectrometers. The data of all four individual spectral intensities is then analyzed using transformation algorithms, in real-time.

A quality assurance program for clinical PDT

NASA Astrophysics Data System (ADS)

Dimofte, Andreea; Finlay, Jarod; Ong, Yi Hong; Zhu, Timothy C.

2018-02-01

Successful outcome of Photodynamic therapy (PDT) depends on accurate delivery of prescribed light dose. A quality assurance program is necessary to ensure that light dosimetry is correctly measured. We have instituted a QA program that include examination of long term calibration uncertainty of isotropic detectors for light fluence rate, power meter head intercomparison for laser power, stability of the light-emitting diode (LED) light source integrating sphere as a light fluence standard, laser output and calibration of in-vivo reflective fluorescence and absorption spectrometers. We examined the long term calibration uncertainty of isotropic detector sensitivity, defined as fluence rate per voltage. We calibrate the detector using the known calibrated light fluence rate of the LED light source built into an internally baffled 4" integrating sphere. LED light sources were examined using a 1mm diameter isotropic detector calibrated in a collimated beam. Wavelengths varying from 632nm to 690nm were used. The internal LED method gives an overall calibration accuracy of +/- 4%. Intercomparison among power meters was performed to determine the consistency of laser power and light fluence rate measured among different power meters. Power and fluence readings were measured and compared among detectors. A comparison of power and fluence reading among several power heads shows long term consistency for power and light fluence rate calibration to within 3% regardless of wavelength. The standard LED light source is used to calibrate the transmission difference between different channels for the diffuse reflective absorption and fluorescence contact probe as well as isotropic detectors used in PDT dose dosimeter.

Matrix light and pixel light: optical system architecture and requirements to the light source

NASA Astrophysics Data System (ADS)

Spinger, Benno; Timinger, Andreas L.

2015-09-01

Modern Automotive headlamps enable improved functionality for more driving comfort and safety. Matrix or Pixel light headlamps are not restricted to either pure low beam functionality or pure high beam. Light in direction of oncoming traffic is selectively switched of, potential hazard can be marked via an isolated beam and the illumination on the road can even follow a bend. The optical architectures that enable these advanced functionalities are diverse. Electromechanical shutters and lens units moved by electric motors were the first ways to realize these systems. Switching multiple LED light sources is a more elegant and mechanically robust solution. While many basic functionalities can already be realized with a limited number of LEDs, an increasing number of pixels will lead to more driving comfort and better visibility. The required optical system needs not only to generate a desired beam distribution with a high angular dynamic, but also needs to guarantee minimal stray light and cross talk between the different pixels. The direct projection of the LED array via a lens is a simple but not very efficient optical system. We discuss different optical elements for pre-collimating the light with minimal cross talk and improved contrast between neighboring pixels. Depending on the selected optical system, we derive the basic light source requirements: luminance, surface area, contrast, flux and color homogeneity.

Optical pulling of airborne absorbing particles and smut spores over a meter-scale distance with negative photophoretic force

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

Lin, Jinda; Hart, Adam G.; Li, Yong-qing, E-mail: liy@ecu.edu

2015-04-27

We demonstrate optical pulling of single light-absorbing particles and smut spores in air over a meter-scale distance using a single collimated laser beam based on negative photophoretic force. The micron-sized particles are pulled towards the light source at a constant speed of 1–10 cm/s in the optical pulling pipeline while undergoing transverse rotation at 0.2–10 kHz. The pulled particles can be manipulated and precisely positioned on the entrance window with an accuracy of ∼20 μm, and their chemical compositions can be characterized with micro-Raman spectroscopy.

High transmittance optical films based on quantum dot doped nanoscale polymer dispersed liquid crystals

NASA Astrophysics Data System (ADS)

Gandhi, Sahil Sandesh; Chien, Liang-Chy

2016-04-01

We propose a simple way to fabricate highly transparent nanoscale polymer dispersed liquid crystal (nano-PDLC) films between glass substrates and investigate their incident angle dependent optical transmittance properties with both collimated and Lambertian intensity distribution light sources. We also demonstrate that doping nano-PDLC films with 0.1% InP/ZnS core/shell quantum dots (QD) results in a higher optical transmittance. This work lays the foundation for such nanostructured composites to potentially serve as roll-to-roll coatable light extraction or brightness enhancement films in emissive display applications, superior to complex nanocorrugation techniques proposed in the past.

Computer controlled fluorometer device and method of operating same

DOEpatents

Kolber, Z.; Falkowski, P.

1990-07-17

A computer controlled fluorometer device and method of operating same, said device being made to include a pump flash source and a probe flash source and one or more sample chambers in combination with a light condenser lens system and associated filters and reflectors and collimators, as well as signal conditioning and monitoring means and a programmable computer means and a software programmable source of background irradiance that is operable according to the method of the invention to rapidly, efficiently and accurately measure photosynthetic activity by precisely monitoring and recording changes in fluorescence yield produced by a controlled series of predetermined cycles of probe and pump flashes from the respective probe and pump sources that are controlled by the computer means. 13 figs.

Computer controlled fluorometer device and method of operating same

DOEpatents

Kolber, Zbigniew; Falkowski, Paul

1990-01-01

A computer controlled fluorometer device and method of operating same, said device being made to include a pump flash source and a probe flash source and one or more sample chambers in combination with a light condenser lens system and associated filters and reflectors and collimators, as well as signal conditioning and monitoring means and a programmable computer means and a software programmable source of background irradiance that is operable according to the method of the invention to rapidly, efficiently and accurately measure photosynthetic activity by precisely monitoring and recording changes in fluorescence yield produced by a controlled series of predetermined cycles of probe and pump flashes from the respective probe and pump sources that are controlled by the computer means.

Fabrication of polymer microlenses on single mode optical fibers for light coupling

NASA Astrophysics Data System (ADS)

Zaboub, Monsef; Guessoum, Assia; Demagh, Nacer-Eddine; Guermat, Abdelhak

2016-05-01

In this paper, we present a technique for producing fibers optics micro-collimators composed of polydimethylsiloxane PDMS microlenses of different radii of curvature. The waist and working distance values obtained enable the optimization of optical coupling between optical fibers, fibers and optical sources, and fibers and detectors. The principal is based on the injection of polydimethylsiloxane (PDMS) into a conical micro-cavity chemically etched at the end of optical fibers. A spherical microlens is then formed that is self-centered with respect to the axis of the fiber. Typically, an optimal radius of curvature of 10.08 μm is obtained. This optimized micro-collimator is characterized by a working distance of 19.27 μm and a waist equal to 2.28 μm for an SMF 9/125 μm fiber. The simulation and experimental results reveal an optical coupling efficiency that can reach a value of 99.75%.

Development of two-channel prototype ITER vacuum ultraviolet spectrometer with back-illuminated charge-coupled device and microchannel plate detectors.

PubMed

Seon, C R; Choi, S H; Cheon, M S; Pak, S; Lee, H G; Biel, W; Barnsley, R

2010-10-01

A vacuum ultraviolet (VUV) spectrometer of a five-channel spectral system is designed for ITER main plasma impurity measurement. To develop and verify the system design, a two-channel prototype system is fabricated with No. 3 (14.4-31.8 nm) and No. 4 (29.0-60.0 nm) among the five channels. The optical system consists of a collimating mirror to collect the light from source to slit, two holographic diffraction gratings with toroidal geometry, and two different electronic detectors. For the test of the prototype system, a hollow cathode lamp is used as a light source. To find the appropriate detector for ITER VUV system, two kinds of detectors of the back-illuminated charge-coupled device and the microchannel plate electron multiplier are tested, and their performance has been investigated.

Introduction of a novel ultrahigh sensitivity collimator for brain SPECT imaging

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

Park, Mi-Ae, E-mail: miaepark@bwh.harvard.edu; Kij

Purpose: Noise levels of brain SPECT images are highest in central regions, due to preferential attenuation of photons emitted from deep structures. To address this problem, the authors have designed a novel collimator for brain SPECT imaging that yields greatly increased sensitivity near the center of the brain without loss of resolution. This hybrid collimator consisted of ultrashort cone-beam holes in the central regions and slant-holes in the periphery (USCB). We evaluated this collimator for quantitative brain imaging tasks. Methods: Owing to the uniqueness of the USCB collimation, the hole pattern required substantial variations in collimator parameters. To utilize themore » lead-casting technique, the authors designed two supporting plates to position about 37 000 hexagonal, slightly tapered pins. The holes in the supporting plates were modeled to yield the desired focal length, hole length, and septal thickness. To determine the properties of the manufactured collimator and to compute the system matrix, the authors prepared an array of point sources that covered the entire detector area. Each point source contained 32 μCi of Tc-99m at the first scan time. The array was imaged for 5 min at each of the 64 shifted locations to yield a 2-mm sampling distance, and hole parameters were calculated. The sensitivity was also measured using a point source placed along the central ray at several distances from the collimator face. High-count projection data from a five-compartment brain phantom were acquired with the three collimators on a dual-head SPECT/CT system. The authors calculated Cramer-Rao bounds on the precision of estimates of striatal and background activity concentration. In order to assess the new collimation system to detect changes in striatal activity, the authors evaluated the precision of measuring a 5% decrease in right putamen activity. The authors also reconstructed images of projection data obtained by summing data from the individual phantom compartments. Results: The sensitivity of the novel cone-beam collimator varied with distance from the detector face; it was higher than that of the fan-beam collimator by factors ranging from 2.7 to 162. Examination of the projections of the point sources revealed that only a few holes were distorted or partially blocked, indicating that the intensive manual fabrication process was very successful. Better reconstructed phantom images were obtained from the USCB+FAN collimator pair than from either LEHR or FAN collimation. For the left caudate, located near the center of the brain, the detected counts were 9.8 (8.3) times higher for UCSB compared with LEHR (FAN), averaged over 60 views. The task-specific SNR for detecting a 5% decrease in putamen uptake was 7.4 for USCB and 3.2 for LEHR. Conclusions: The authors have designed and manufactured a novel collimator for brain SPECT imaging. The sensitivity is much higher than that of a fan-beam collimator. Because of differences between the manufactured collimator and its design, reconstruction of the data requires a measured system matrix. The authors have demonstrated the potential of USCB collimation for improved precision in estimating striatal uptake. The novel collimator may be useful for early detection of Parkinson’s disease, and for monitoring therapy response and disease progression.« less

Plasma devices to guide and collimate a high density of MeV electrons.

PubMed

Kodama, R; Sentoku, Y; Chen, Z L; Kumar, G R; Hatchett, S P; Toyama, Y; Cowan, T E; Freeman, R R; Fuchs, J; Izawa, Y; Key, M H; Kitagawa, Y; Kondo, K; Matsuoka, T; Nakamura, H; Nakatsutsumi, M; Norreys, P A; Norimatsu, T; Snavely, R A; Stephens, R B; Tampo, M; Tanaka, K A; Yabuuchi, T

2004-12-23

The development of ultra-intense lasers has facilitated new studies in laboratory astrophysics and high-density nuclear science, including laser fusion. Such research relies on the efficient generation of enormous numbers of high-energy charged particles. For example, laser-matter interactions at petawatt (10(15) W) power levels can create pulses of MeV electrons with current densities as large as 10(12) A cm(-2). However, the divergence of these particle beams usually reduces the current density to a few times 10(6) A cm(-2) at distances of the order of centimetres from the source. The invention of devices that can direct such intense, pulsed energetic beams will revolutionize their applications. Here we report high-conductivity devices consisting of transient plasmas that increase the energy density of MeV electrons generated in laser-matter interactions by more than one order of magnitude. A plasma fibre created on a hollow-cone target guides and collimates electrons in a manner akin to the control of light by an optical fibre and collimator. Such plasma devices hold promise for applications using high energy-density particles and should trigger growth in charged particle optics.

Efficient dielectric metasurface collimating lenses for mid-infrared quantum cascade lasers.

PubMed

Arbabi, Amir; Briggs, Ryan M; Horie, Yu; Bagheri, Mahmood; Faraon, Andrei

2015-12-28

Light emitted from single-mode semiconductor lasers generally has large divergence angles, and high numerical aperture lenses are required for beam collimation. Visible and near infrared lasers are collimated using aspheric glass or plastic lenses, yet collimation of mid-infrared quantum cascade lasers typically requires more costly aspheric lenses made of germanium, chalcogenide compounds, or other infrared-transparent materials. Here we report mid-infrared dielectric metasurface flat lenses that efficiently collimate the output beam of single-mode quantum cascade lasers. The metasurface lenses are composed of amorphous silicon posts on a flat sapphire substrate and can be fabricated at low cost using a single step conventional UV binary lithography. Mid-infrared radiation from a 4.8 μm distributed-feedback quantum cascade laser is collimated using a polarization insensitive metasurface lens with 0.86 numerical aperture and 79% transmission efficiency. The collimated beam has a half divergence angle of 0.36° and beam quality factor of M2=1.02.

Efficient dielectric metasurface collimating lenses for mid-infrared quantum cascade lasers

DOE PAGES

Arbabi, Amir; Briggs, Ryan M.; Horie, Yu; ...

2015-01-01

Light emitted from single-mode semiconductor lasers generally has large divergence angles, and high numerical aperture lenses are required for beam collimation. Visible and near infrared lasers are collimated using aspheric glass or plastic lenses, yet collimation of mid-infrared quantum cascade lasers typically requires more costly aspheric lenses made of germanium, chalcogenide compounds, or other infrared-transparent materials. We report mid-infrared dielectric metasurface flat lenses that efficiently collimate the output beam of single-mode quantum cascade lasers. The metasurface lenses are composed of amorphous silicon posts on a flat sapphire substrate and can be fabricated at low cost using a single step conventionalmore » UV binary lithography. Mid-infrared radiation from a 4.8 μm distributed-feedback quantum cascade laser is collimated using a polarization insensitive metasurface lens with 0.86 numerical aperture and 79% transmission efficiency. The collimated beam has a half divergence angle of 0.36° and beam quality factor of M² =1.02.« less

Ion source for high-precision mass spectrometry

DOEpatents

Todd, Peter J.; McKown, Henry S.; Smith, David H.

1984-01-01

The invention is directed to a method for increasing the precision of positive-ion relative abundance measurements conducted in a sector mass spectrometer having an ion source for directing a beam of positive ions onto a collimating slit. The method comprises incorporating in the source an electrostatic lens assembly for providing a positive-ion beam of circular cross section for collimation by the slit.

Far-field self-focusing and -defocusing radiation behaviors of the electroluminescent light sources due to negative refraction.

PubMed

Yin, Yu-Feng; Lin, Yen-Chen; Tsai, Tsung-Han; Shen, Yi-Chun; Huang, Jianjang

2013-01-15

In recent years, researchers have demonstrated negative refraction theoretically and experimentally by pumping optical power into photonic crystal (PhC) or waveguide structures. The concept of negative refraction can be used to create a perfect lens that focuses an object smaller than the wavelength. By inserting two-dimensional PhCs into the peripheral of a semiconductor light emitting structure, this study presents an electroluminescent device with negative refraction in the visible wavelength range. This approach produces polarization dependent collimation behavior in far-field radiation patterns. The modal dispersion of negative refraction results in strong group velocity modulation, and self-focusing and -defocusing behaviors are apparent from light extraction. This study further verifies experimental results by using theoretic calculations based on equifrequency contours.

Near field of an oscillating electric dipole and cross-polarization of a collimated beam of light: Two sides of the same coin

NASA Astrophysics Data System (ADS)

Aiello, Andrea; Ornigotti, Marco

2014-09-01

We address the question of whether there exists a hidden relationship between the near-field distribution generated by an oscillating electric dipole and the so-called cross-polarization of a collimated beam of light. We find that the answer is affirmative by showing that the complex field distributions occurring in both cases have a common physical origin: the requirement that the electromagnetic fields must be transverse.

White light photothermal lens spectrophotometer for the determination of absorption in scattering samples.

PubMed

Marcano, Aristides; Alvarado, Salvador; Meng, Junwei; Caballero, Daniel; Moares, Ernesto Marín; Edziah, Raymond

2014-01-01

We developed a pump-probe photothermal lens spectrophotometer that uses a broadband arc-lamp and a set of interference filters to provide tunable, nearly monochromatic radiation between 370 and 730 nm as the pump light source. This light is focused onto an absorbing sample, generating a photothermal lens of millimeter dimensions. A highly collimated monochromatic probe light from a low-power He-Ne laser interrogates the generated lens, yielding a photothermal signal proportional to the absorption of light. We measure the absorption spectra of scattering dye solutions using the device. We show that the spectra are not affected by the presence of scattering, confirming that the method only measures the absorption of light that results in generation of heat. By comparing the photothermal spectra with the usual absorption spectra determined using commercial transmission spectrophotometers, we estimate the quantum yield of scattering of the sample. We discuss applications of the device for spectroscopic characterization of samples such as blood and gold nanoparticles that exhibit a complex behavior upon interaction with light.

Evaluation of an adaptive detector collimation for prospectively ECG-triggered coronary CT angiography with third-generation dual-source CT.

PubMed

Messerli, Michael; Dewes, Patricia; Scholtz, Jan-Erik; Arendt, Christophe; Wildermuth, Simon; Vogl, Thomas J; Bauer, Ralf W

2018-05-01

To investigate the impact of an adaptive detector collimation on the dose parameters and accurateness of scan length adaption at prospectively ECG-triggered sequential cardiac CT with a wide-detector third-generation dual-source CT. Ideal scan lengths for human hearts were retrospectively derived from 103 triple-rule-out examinations. These measures were entered into the new scanner operated in prospectively ECG-triggered sequential cardiac scan mode with three different detector settings: (1) adaptive collimation, (2) fixed 64 × 0.6-mm collimation, and (3) fixed 96 × 0.6-mm collimation. Differences in effective scan length and deviation from the ideal scan length and dose parameters (CTDIvol, DLP) were documented. The ideal cardiac scan length could be matched by the adaptive collimation in every case while the mean scanned length was longer by 15.4% with the 64 × 0.6 mm and by 27.2% with the fixed 96 × 0.6-mm collimation. While the DLP was almost identical between the adaptive and the 64 × 0.6-mm collimation (83 vs. 89 mGycm at 120 kV), it was 62.7% higher with the 96 × 0.6-mm collimation (135 mGycm), p < 0.001. The adaptive detector collimation for prospectively ECG-triggered sequential acquisition allows for adjusting the scan length as accurate as this can only be achieved with a spiral acquisition. This technique allows keeping patient exposure low where patient dose would significantly increase with the traditional step-and-shoot mode. • Adaptive detector collimation allows keeping patient exposure low in cardiac CT. • With novel detectors the desired scan length can be accurately matched. • Differences in detector settings may cause 62.7% of excessive dose.

Design of smartphone-based spectrometer to assess fresh meat color

NASA Astrophysics Data System (ADS)

Jung, Youngkee; Kim, Hyun-Wook; Kim, Yuan H. Brad; Bae, Euiwon

2017-02-01

Based on its integrated camera, new optical attachment, and inherent computing power, we propose an instrument design and validation that can potentially provide an objective and accurate method to determine surface meat color change and myoglobin redox forms using a smartphone-based spectrometer. System is designed to be used as a reflection spectrometer which mimics the conventional spectrometry commonly used for meat color assessment. We utilize a 3D printing technique to make an optical cradle which holds all of the optical components for light collection, collimation, dispersion, and a suitable chamber. A light, which reflects a sample, enters a pinhole and is subsequently collimated by a convex lens. A diffraction grating spreads the wavelength over the camera's pixels to display a high resolution of spectrum. Pixel values in the smartphone image are translated to calibrate the wavelength values through three laser pointers which have different wavelength; 405, 532, 650 nm. Using an in-house app, the camera images are converted into a spectrum in the visible wavelength range based on the exterior light source. A controlled experiment simulating the refrigeration and shelving of the meat has been conducted and the results showed the capability to accurately measure the color change in quantitative and spectroscopic manner. We expect that this technology can be adapted to any smartphone and used to conduct a field-deployable color spectrum assay as a more practical application tool for various food sectors.

Active implant for optoacoustic natural sound enhancement

NASA Astrophysics Data System (ADS)

Mohrdiek, S.; Fretz, M.; Jose James, R.; Spinola Durante, G.; Burch, T.; Kral, A.; Rettenmaier, A.; Milani, R.; Putkonen, M.; Noell, W.; Ortsiefer, M.; Daly, A.; Vinciguerra, V.; Garnham, C.; Shah, D.

2017-02-01

This paper summarizes the results of an EU project called ACTION: ACTive Implant for Optoacoustic Natural sound enhancement. The project is based on a recent discovery that relatively low levels of pulsed infrared laser light are capable of triggering activity in hair cells of the partially hearing (hearing impaired) cochlea and vestibule. The aim here is the development of a self-contained, smart, highly miniaturized system to provide optoacoustic stimuli directly from an array of miniature light sources in the cochlea. Optoacoustic compound action potentials (oaCAP) are generated by the light source fully inserted into the unmodified cochlea. Previously, the same could only be achieved with external light sources connected to a fiber optic light guide. This feat is achieved by integrating custom made VCSEL arrays at a wavelength of about 1550 nm onto small flexible substrates. The laser light is collimated by a specially designed silicon-based ultra-thin lens (165 um thick) to get the energy density required for the generation of oaCAP signals. A dramatic miniaturization of the packaging technology is also required. A long term biocompatible and hermetic sapphire housing with a size of less than a 1 cubic millimeter and miniature Pt/PtIr feedthroughs is developed, using a low temperature laser assisted process for sealing. A biofouling thin film protection layer is developed to avoid fibrinogen and cell growth on the system.

Wavelength independent interferometer

NASA Technical Reports Server (NTRS)

Hochberg, Eric B. (Inventor); Page, Norman A. (Inventor)

1991-01-01

A polychromatic interferometer utilizing a plurality of parabolic reflective surfaces to properly preserve the fidelity of light wavefronts irrespective of their wavelengths as they pass through the instrument is disclosed. A preferred embodiment of the invention utilizes an optical train which comprises three off-axis parabolas arranged in conjunction with a beam-splitter and a reference mirror to form a Twyman-Green interferometer. An illumination subsystem is provided and comprises a pair of lasers at different preselected wavelengths in the visible spectrum. The output light of the two lasers is coaxially combined by means of a plurality of reflectors and a grating beam combiner to form a single light source at the focal point of the first parabolic reflection surface which acts as a beam collimator for the rest of the optical train. By using visible light having two distinct wavelengths, the present invention provides a long equivalent wavelength interferogram which operates at visible light wherein the effective wavelength is equal to the product of the wavelengths of the two laser sources divided by their difference in wavelength. As a result, the invention provides the advantages of what amounts to long wavelength interferometry but without incurring the disadvantage of the negligible reflection coefficient of the human eye to long wavelength frequencies which would otherwise defeat any attempt to form an interferogram at that low frequency using only one light source.

Comparison of fan beam, slit-slat and multi-pinhole collimators for molecular breast tomosynthesis.

PubMed

van Roosmalen, Jarno; Beekman, Freek J; Goorden, Marlies C

2018-05-16

Recently, we proposed and optimized dedicated multi-pinhole molecular breast tomosynthesis (MBT) that images a lightly compressed breast. As MBT may also be performed with other types of collimators, the aim of this paper is to optimize MBT with fan beam and slit-slat collimators and to compare its performance to that of multi-pinhole MBT to arrive at a truly optimized design. Using analytical expressions, we first optimized fan beam and slit-slat collimator parameters to reach maximum sensitivity at a series of given system resolutions. Additionally, we performed full system simulations of a breast phantom containing several tumours for the optimized designs. We found that at equal system resolution the maximum achievable sensitivity increases from pinhole to slit-slat to fan beam collimation with fan beam and slit-slat MBT having on average a 48% and 20% higher sensitivity than multi-pinhole MBT. Furthermore, by inspecting simulated images and applying a tumour-to-background contrast-to-noise (TB-CNR) analysis, we found that slit-slat collimators underperform with respect to the other collimator types. The fan beam collimators obtained a similar TB-CNR as the pinhole collimators, but the optimum was reached at different system resolutions. For fan beam collimators, a 6-8 mm system resolution was optimal in terms of TB-CNR, while with pinhole collimation highest TB-CNR was reached in the 7-10 mm range.

Ion source for high-precision mass spectrometry

DOEpatents

Todd, P.J.; McKown, H.S.; Smith, D.H.

1982-04-26

The invention is directed to a method for increasing the precision of positive-ion relative abundance measurements conducted in a sector mass spectrometer having an ion source for directing a beam of positive ions onto a collimating slit. The method comprises incorporating in the source an electrostatic lens assembly for providing a positive-ion beam of circular cross section for collimation by the slit. 2 figures, 3 tables.

Improved self-reliance shearing interferometric technique for collimation testing

NASA Astrophysics Data System (ADS)

Zhao, Mingshan; Li, Guohua; Wang, Zhaobing; Jing, Yaling; Li, Yi

1995-06-01

Self-reference single plate shearing interferometric technique used for collimation testing of light beams are briefly reviewed. Two improved configurations of this self-reference interferometry with an inclined screen and matched half-field interferograms are described in detail. Sensitivity of these configurations is analyzed and compared with that of the existing ones.

Applications of Elpasolites as a Multimode Radiation Sensor

NASA Astrophysics Data System (ADS)

Guckes, Amber

This study consists of both computational and experimental investigations. The computational results enabled detector design selections and confirmed experimental results. The experimental results determined that the CLYC scintillation detector can be applied as a functional and field-deployable multimode radiation sensor. The computational study utilized MCNP6 code to investigate the response of CLYC to various incident radiations and to determine the feasibility of its application as a handheld multimode sensor and as a single-scintillator collimated directional detection system. These simulations include: • Characterization of the response of the CLYC scintillator to gamma-rays and neutrons; • Study of the isotopic enrichment of 7Li versus 6Li in the CLYC for optimal detection of both thermal neutrons and fast neutrons; • Analysis of collimator designs to determine the optimal collimator for the single CLYC sensor directional detection system to assay gamma rays and neutrons; Simulations of a handheld CLYC multimode sensor and a single CLYC scintillator collimated directional detection system with the optimized collimator to determine the feasibility of detecting nuclear materials that could be encountered during field operations. These nuclear materials include depleted uranium, natural uranium, low-enriched uranium, highly-enriched uranium, reactor-grade plutonium, and weapons-grade plutonium. The experimental study includes the design, construction, and testing of both a handheld CLYC multimode sensor and a single CLYC scintillator collimated directional detection system. Both were designed in the Inventor CAD software and based on results of the computational study to optimize its performance. The handheld CLYC multimode sensor is modular, scalable, low?power, and optimized for high count rates. Commercial?off?the?shelf components were used where possible in order to optimize size, increase robustness, and minimize cost. The handheld CLYC multimode sensor was successfully tested to confirm its ability for gamma-ray and neutron detection, and gamma?ray and neutron spectroscopy. The sensor utilizes wireless data transfer for possible radiation mapping and network?centric deployment. The handheld multimode sensor was tested by performing laboratory measurements with various gamma-ray sources and neutron sources. The single CLYC scintillator collimated directional detection system is portable, robust, and capable of source localization and identification. The collimator was designed based on the results of the computational study and is constructed with high density polyethylene (HDPE) and lead (Pb). The collimator design and construction allows for the directional detection of gamma rays and fast neutrons utilizing only one scintillator which is interchangeable. For this study, a CLYC-7 scintillator was used. The collimated directional detection system was tested by performing laboratory directional measurements with various gamma-ray sources, 252Cf and a 239PuBe source.

VUV-soft x-ray beamline for spectroscopy and calibration

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

Bartlett, R.J.; Trela, W.J.; Southworth, S.H.

1986-01-01

We describe the design and performance of the Los Alamos VUV synchrotron radiation beamline, U3C, on the VUV ring of the National Synchrotron Light Source at Brookhaven National Laboratory. The beamline uses separate function optics to collect and focus the horizontally and vertically diverging beam. The monochromator is a grazing incidence Roland circle instrument of the extended grasshopper design (ERG). A post monochromator refocusing mirror is used to focus or collimate the diverging beam from the monochromator. The beamline control and diagnostics systems are also discussed.

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

PubMed

Khorshidi, Abdollah; Ashoor, Mansour

2014-05-01

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

Neutron range spectrometer

DOEpatents

Manglos, S.H.

1988-03-10

A neutron range spectrometer and method for determining the neutron energy spectrum of a neutron emitting source are disclosed. Neutrons from the source are colliminated along a collimation axis and a position sensitive neutron counter is disposed in the path of the collimated neutron beam. The counter determines positions along the collimation axis of interactions between the neutrons in the neutron beam and a neutron-absorbing material in the counter. From the interaction positions, a computer analyzes the data and determines the neutron energy spectrum of the neutron beam. The counter is preferably shielded and a suitable neutron-absorbing material is He-3. 1 fig.

Note: Detector collimators for the nanoscale ordered materials diffractometer instrument at the Spallation Neutron Source

DOE PAGES

Tamalonis, A.; Weber, J. K. R.; Neuefeind, J. C.; ...

2015-09-09

We constructed and tested five neutron collimator designs using the nanoscale ordered materials diffractometer (NOMAD) instrument. Collimators were made from High Density PolyEthylene (HDPE) or 5% borated HDPE. In all cases, collimators improved the signal to background ratio and reduced detection of secondary scattering. Moreover, in the Q-range 10-20 Å -1, signal to background ratio improved by factors of approximately 1.6 and 2.0 for 50 and 100 mm deep collimators, respectively. In the Q-range 40-50 Å -1, the improvement factors were 1.8 and 2.7. Secondary scattering as measured at Q similar to 9.5 Å -1 was significantly decreased when themore » collimators were installed.« less

Comparison of fan beam, slit-slat and multi-pinhole collimators for molecular breast tomosynthesis

NASA Astrophysics Data System (ADS)

van Roosmalen, Jarno; Beekman, Freek J.; Goorden, Marlies C.

2018-05-01

Recently, we proposed and optimized dedicated multi-pinhole molecular breast tomosynthesis (MBT) that images a lightly compressed breast. As MBT may also be performed with other types of collimators, the aim of this paper is to optimize MBT with fan beam and slit-slat collimators and to compare its performance to that of multi-pinhole MBT to arrive at a truly optimized design. Using analytical expressions, we first optimized fan beam and slit-slat collimator parameters to reach maximum sensitivity at a series of given system resolutions. Additionally, we performed full system simulations of a breast phantom containing several tumours for the optimized designs. We found that at equal system resolution the maximum achievable sensitivity increases from pinhole to slit-slat to fan beam collimation with fan beam and slit-slat MBT having on average a 48% and 20% higher sensitivity than multi-pinhole MBT. Furthermore, by inspecting simulated images and applying a tumour-to-background contrast-to-noise (TB-CNR) analysis, we found that slit-slat collimators underperform with respect to the other collimator types. The fan beam collimators obtained a similar TB-CNR as the pinhole collimators, but the optimum was reached at different system resolutions. For fan beam collimators, a 6–8 mm system resolution was optimal in terms of TB-CNR, while with pinhole collimation highest TB-CNR was reached in the 7–10 mm range.

Performance characteristics of UV imaging instrumentation for diffusion, dissolution and release testing studies.

PubMed

Jensen, Sabrine S; Jensen, Henrik; Goodall, David M; Østergaard, Jesper

2016-11-30

UV imaging is capable of providing spatially and temporally resolved absorbance measurements, which is highly beneficial in drug diffusion, dissolution and release testing studies. For optimal planning and design of experiments, knowledge about the capabilities and limitations of the imaging system is required. The aim of this study was to characterize the performance of two commercially available UV imaging systems, the D100 and SDI. Lidocaine crystals, lidocaine containing solutions, and gels were applied in the practical assessment of the UV imaging systems. Dissolution of lidocaine from single crystals into phosphate buffer and 0.5% (w/v) agarose hydrogel at pH 7.4 was investigated to shed light on the importance of density gradients under dissolution conditions in the absence of convective flow. In addition, the resolution of the UV imaging systems was assessed by the use of grids. Resolution was found to be better in the vertical direction than the horizontal direction, consistent with the illumination geometry. The collimating lens in the SDI imaging system was shown to provide more uniform light intensity across the UV imaging area and resulted in better resolution as compared to the D100 imaging system (a system without a lens). Under optimal conditions, the resolution was determined to be 12.5 and 16.7 line pairs per mm (lp/mm) corresponding to line widths of 40μm and 30μm in the horizontal and vertical direction, respectively. Overall, the performance of the UV imaging systems was shown mainly to depend on collimation of light, the light path, the positioning of the object relative to the line of 100μm fibres which forms the light source, and the distance of the object from the sensor surface. Copyright © 2016 Elsevier B.V. All rights reserved.

A SPECT Scanner for Rodent Imaging Based on Small-Area Gamma Cameras

NASA Astrophysics Data System (ADS)

Lage, Eduardo; Villena, José L.; Tapias, Gustavo; Martinez, Naira P.; Soto-Montenegro, Maria L.; Abella, Mónica; Sisniega, Alejandro; Pino, Francisco; Ros, Domènec; Pavia, Javier; Desco, Manuel; Vaquero, Juan J.

2010-10-01

We developed a cost-effective SPECT scanner prototype (rSPECT) for in vivo imaging of rodents based on small-area gamma cameras. Each detector consists of a position-sensitive photomultiplier tube (PS-PMT) coupled to a 30 x 30 Nal(Tl) scintillator array and electronics attached to the PS-PMT sockets for adapting the detector signals to an in-house developed data acquisition system. The detector components are enclosed in a lead-shielded case with a receptacle to insert the collimators. System performance was assessed using 99mTc for a high-resolution parallel-hole collimator, and for a 0.75-mm pinhole collimator with a 60° aperture angle and a 42-mm collimator length. The energy resolution is about 10.7% of the photopeak energy. The overall system sensitivity is about 3 cps/μCi/detector and planar spatial resolution ranges from 2.4 mm at 1 cm source-to-collimator distance to 4.1 mm at 4.5 cm with parallel-hole collimators. With pinhole collimators planar spatial resolution ranges from 1.2 mm at 1 cm source-to-collimator distance to 2.4 mm at 4.5 cm; sensitivity at these distances ranges from 2.8 to 0.5 cps/μCi/detector. Tomographic hot-rod phantom images are presented together with images of bone, myocardium and brain of living rodents to demonstrate the feasibility of preclinical small-animal studies with the rSPECT.

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

Flechsig, U.; Nolting, F.; Fraile Rodriguez, A.

The Surface/Interface: Microscopy beamline of the Swiss Light Source started operation in 2001. In 2007 the beamline has been significantly upgraded with a second refocusing section and a blazed grating optimized for high photon flux. Two Apple II type undulators with a plane grating monochromator using the collimated light scheme deliver photons with an energy from 90eV to about 2keV with variable polarization for the photoemission electron microscope (PEEM) as the primary user station. We measured a focus of (45x60) {mu}m({nu}xh) and a photon flux > 10{sup 12} photon/s for all gratings. Polarization switching within a few seconds is realizedmore » with the small bandpass of the monochromator and a slight detuning of the undulator.« less

PIGE-PIXE analysis of human milk

NASA Astrophysics Data System (ADS)

Olabanji, S. O.; Buoso, M. C.; Ceccato, D.; Haque, A. M. I.; Cherubini, R.; Moschini, G.

1996-04-01

PIGE-PIXE nuclear techniques were employed for the determination of the elemental composition of human breast milk which is the main source of nutrients to babies in Nigeria. Samples were collected from 32 healthy lactating mothers from Obafemi Awolowo Teaching University Hospital, Ile-Ife, Nigeria. The samples were homogenized and immediately frozen, and then freeze-dried. Pellets were made using a Perkin Elmer instrument and its accessory the 13 mm die. PIGE measurements of light elements were performed using 3.5 MeV collimated protons from the 7 MV CN Van de Graaff accelerator of INFN, LNL, Legnaro (Padova) Italy while PIXE analysis was carried out using 1.8 MeV collimated proton beam from the 2.5 MV AN 2000 Van de Graaff accelerator of the same Institute. The results show the presence of important elements that are essential for growth and development of babies. We searched for certain toxic elements which include As, Cd, Hg, Pb, etc. because of their negative roles in enhancing infant mortality rates, but none of them was detected except Pb.

Optimising in situ gamma measurements to identify the presence of radioactive particles in land areas.

PubMed

Rostron, Peter D; Heathcote, John A; Ramsey, Michael H

2014-12-01

High-coverage in situ surveys with gamma detectors are the best means of identifying small hotspots of activity, such as radioactive particles, in land areas. Scanning surveys can produce rapid results, but the probabilities of obtaining false positive or false negative errors are often unknown, and they may not satisfy other criteria such as estimation of mass activity concentrations. An alternative is to use portable gamma-detectors that are set up at a series of locations in a systematic sampling pattern, where any positive measurements are subsequently followed up in order to determine the exact location, extent and nature of the target source. The preliminary survey is typically designed using settings of detector height, measurement spacing and counting time that are based on convenience, rather than using settings that have been calculated to meet requirements. This paper introduces the basis of a repeatable method of setting these parameters at the outset of a survey, for pre-defined probabilities of false positive and false negative errors in locating spatially small radioactive particles in land areas. It is shown that an un-collimated detector is more effective than a collimated detector that might typically be used in the field. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Evaluation of dual γ-ray imager with active collimator using various types of scintillators.

PubMed

Lee, Wonho; Lee, Taewoong; Jeong, Manhee; Kim, Ho Kyung

2011-10-01

The performance of a specialized dual γ-ray imager using both mechanical and electronic collimation was evaluated by Monte Carlo simulation (MCNP5). The dual imager consisted of an active collimator and a planar detector that were made from scintillators. The active collimator served not only as a coded aperture for mechanical collimation but also as a first detector for electronic collimation. Therefore, a single system contained both mechanical and electronic collimation. Various types of scintillators were tested and compared with each other in terms of their angular resolution, efficiency, and background noise. In general, a BGO active collimator had the best mechanical collimation performance, and an LaCl₃(Ce) active collimator provided the best electronic collimation performance. However, for low radiation energies, the mechanical collimation images made from both scintillators showed the same quality, and, for high radiation energies, electronic collimation images made from both scintillators also show similar quality. Therefore, if mechanical collimation is used to detect low-energy radiation and electronic collimation is applied to reconstruct a high-energy source, either LaCl₃(Ce) or BGO would be appropriate for the active collimator of a dual γ-ray imager. These results broaden the choice of scintillators for the active collimator of the dual γ-ray imager, which makes it possible to consider other factors, such as machinability and cost, in making the imager. As a planar detector, BGO showed better performance than other scintillators since its radiation detection efficiency was highest of all. Copyright © 2011 Elsevier Ltd. All rights reserved.

Holographic memory using beam steering

NASA Technical Reports Server (NTRS)

Chao, Tien-Hsin (Inventor); Hanan, Jay C. (Inventor); Reyes, George F. (Inventor); Zhou, Hanying (Inventor)

2007-01-01

A method, apparatus, and system provide the ability for storing holograms at high speed. A single laser diode emits a collimated laser beam to both write to and read from a photorefractice crystal. One or more liquid crystal beam steering spatial light modulators (BSSLMs) steer a reference beam, split from the collimated laser beam, at high speed to the photorefractive crystal.

Optimization of a Scintillator for the Measurement of Positrons from Trapped, Polarized 37K

NASA Astrophysics Data System (ADS)

France, Erin; Melconian, Dan

2011-10-01

Precision beta decay experiments can be used to test the Standard Model via their value of correlation parameters. The TRINAT Collaboration is performing such an experiment using a source of polarized 37K from a magneto optical trap. The momentum of an emitted positron will be detected using a Silicon strip detector backed by a plastic scintillator. The goal of my research was to optimize the readout of the scintillator by testing different experimental setups. The front face and sides of the scintillator and light guide were wrapped with various reflective materials to find which maximized the light output. We found that one layer of Teflon tape on the front face with a loose wrapping of 3M-ESR (Enhanced Spectral Reflector) on the sides was optimal. We then tested the position dependence of this detector by moving a collimated source of betas across the front face, showing only a (5.9 +/- 0.5)% reduction in light collection at the edge compared to the center. The product of this work will be used in the upcoming TRINAT experiment measuring the beta asymmetry of 37K.

Thermal analysis and cooling structure design of the primary collimator in CSNS/RCS

NASA Astrophysics Data System (ADS)

Zou, Yi-Qing; Wang, Na; Kang, Ling; Qu, Hua-Min; He, Zhe-Xi; Yu, Jie-Bing

2013-05-01

The rapid cycling synchrotron (RCS) of the China Spallation Neutron Source (CSNS) is a high intensity proton ring with beam power of 100 kW. In order to control the residual activation to meet the requirements of hands-on maintenance, a two-stage collimation system has been designed for the RCS. The collimation system consists of one primary collimator made of thin metal to scatter the beam and four secondary collimators as absorbers. Thermal analysis is an important aspect in evaluating the reliability of the collimation system. The calculation of the temperature distribution and thermal stress of the primary collimator with different materials is carried out by using ANSYS code. In order to control the temperature rise and thermal stress of the primary collimator to a reasonable level, an air cooling structure is intended to be used. The mechanical design of the cooling structure is presented, and the cooling efficiency with different chin numbers and wind velocity is also analyzed. Finally, the fatigue lifetime of the collimator under thermal shocks is estimated.

Development of ultra-precision micro-cavity measurement technique in HIT-UOI

NASA Astrophysics Data System (ADS)

Cui, Jiwen; Li, Lei; Tan, Jiubin

2010-08-01

Micro cavities with high aspect ratio are widely used in different fields including aerospace and defense industries with the development of manufacturing technology. So how to measure the dimension of these cavities has become one of the major research subjects in the field of measurement and instrument. This paper describes some activities of the precision micro cavity measurement technique in Center of Ultra-precision Optoelectronic Instrument (UOI), Harbin Institute of Technology (HIT). The key issue of micro cavity measurement in UOI is called touch-trigger measurement method. The first scheme is double optical fiber coupling, in which light coming from the incident optical fiber is transmitted in the reversal direction via the optical fiber coupling into the effluent optical fiber, the lateral displacement of the touch-trigger sensor is transformed into the deflexion of light coming out from the effluent optical fiber, and the deflexion is transformed into an image signal by the object lens and CCD capturing system. And the second scheme is micro focal-length collimation, in which a fiber stem with a ball mounted on its end is used as a probe and a small segment of it is used as a cylindrical lens to collimate a point light source and image it to a camera, the deflection of the fiber stem can be inferred from the change in image acquired by the camera with ultrahigh displacement sensitivity. Experiments for these activities will be given with a focus on the measurement results and repeatability uncertainty.

Method and system for determining depth distribution of radiation-emitting material located in a source medium and radiation detector system for use therein

DOEpatents

Benke, Roland R.; Kearfott, Kimberlee J.; McGregor, Douglas S.

2003-03-04

A method, system and a radiation detector system for use therein are provided for determining the depth distribution of radiation-emitting material distributed in a source medium, such as a contaminated field, without the need to take samples, such as extensive soil samples, to determine the depth distribution. The system includes a portable detector assembly with an x-ray or gamma-ray detector having a detector axis for detecting the emitted radiation. The radiation may be naturally-emitted by the material, such as gamma-ray-emitting radionuclides, or emitted when the material is struck by other radiation. The assembly also includes a hollow collimator in which the detector is positioned. The collimator causes the emitted radiation to bend toward the detector as rays parallel to the detector axis of the detector. The collimator may be a hollow cylinder positioned so that its central axis is perpendicular to the upper surface of the large area source when positioned thereon. The collimator allows the detector to angularly sample the emitted radiation over many ranges of polar angles. This is done by forming the collimator as a single adjustable collimator or a set of collimator pieces having various possible configurations when connected together. In any one configuration, the collimator allows the detector to detect only the radiation emitted from a selected range of polar angles measured from the detector axis. Adjustment of the collimator or the detector therein enables the detector to detect radiation emitted from a different range of polar angles. The system further includes a signal processor for processing the signals from the detector wherein signals obtained from different ranges of polar angles are processed together to obtain a reconstruction of the radiation-emitting material as a function of depth, assuming, but not limited to, a spatially-uniform depth distribution of the material within each layer. The detector system includes detectors having different properties (sensitivity, energy resolution) which are combined so that excellent spectral information may be obtained along with good determinations of the radiation field as a function of position.

Design requirements for a stand alone EUV interferometer

NASA Astrophysics Data System (ADS)

Michallon, Ph.; Constancias, C.; Lagrange, A.; Dalzotto, B.

2008-03-01

EUV lithography is expected to be inserted for the 32/22 nm nodes with possible extension below. EUV resist availability remains one of the main issues to be resolved. There is an urgent need to provide suitable tools to accelerate resist development and to achieve resolution, LER and sensitivity specifications simultaneously. An interferometer lithography tool offers advantages regarding conventional EUV exposure tool. It allows the evaluation of resists, free from the deficiencies of optics and mask which are limiting the achieved resolution. Traditionally, a dedicated beam line from a synchrotron, with limited access, is used as a light source in EUV interference lithography. This paper identifies the technology locks to develop a stand alone EUV interferometer using a compact EUV source. It will describe the theoretical solutions adopted and especially look at the feasibility according to available technologies. EUV sources available on the market have been evaluated in terms of power level, source size, spatial coherency, dose uniformity, accuracy, stability and reproducibility. According to the EUV source characteristics, several optic designs were studied (simple or double gratings). For each of these solutions, the source and collimation optic specifications have been determined. To reduce the exposure time, a new grating technology will also be presented allowing to significantly increasing the transmission system efficiency. The optical grating designs were studied to allow multi-pitch resolution print on the same exposure without any focus adjustment. Finally micro mechanical system supporting the gratings was studied integrating the issues due to vacuum environment, alignment capability, motion precision, automation and metrology to ensure the needed placement control between gratings and wafer. A similar study was carried out for the collimation-optics mechanical support which depends on the source characteristics.

Mapping algorithm for freeform construction using non-ideal light sources

NASA Astrophysics Data System (ADS)

Li, Chen; Michaelis, D.; Schreiber, P.; Dick, L.; Bräuer, A.

2015-09-01

Using conventional mapping algorithms for the construction of illumination freeform optics' arbitrary target pattern can be obtained for idealized sources, e.g. collimated light or point sources. Each freeform surface element generates an image point at the target and the light intensity of an image point is corresponding to the area of the freeform surface element who generates the image point. For sources with a pronounced extension and ray divergence, e.g. an LED with a small source-freeform-distance, the image points are blurred and the blurred patterns might be different between different points. Besides, due to Fresnel losses and vignetting, the relationship between light intensity of image points and area of freeform surface elements becomes complicated. These individual light distributions of each freeform element are taken into account in a mapping algorithm. To this end the method of steepest decent procedures are used to adapt the mapping goal. A structured target pattern for a optics system with an ideal source is computed applying corresponding linear optimization matrices. Special weighting factor and smoothing factor are included in the procedures to achieve certain edge conditions and to ensure the manufacturability of the freefrom surface. The corresponding linear optimization matrices, which are the lighting distribution patterns of each of the freeform surface elements, are gained by conventional raytracing with a realistic source. Nontrivial source geometries, like LED-irregularities due to bonding or source fine structures, and a complex ray divergence behavior can be easily considered. Additionally, Fresnel losses, vignetting and even stray light are taken into account. After optimization iterations, with a realistic source, the initial mapping goal can be achieved by the optics system providing a structured target pattern with an ideal source. The algorithm is applied to several design examples. A few simple tasks are presented to discussed the ability and limitation of the this mothed. It is also presented that a homogeneous LED-illumination system design, in where, with a strongly tilted incident direction, a homogeneous distribution is achieved with a rather compact optics system and short working distance applying a relatively large LED source. It is shown that the lighting distribution patterns from the freeform surface elements can be significantly different from the others. The generation of a structured target pattern, applying weighting factor and smoothing factor, are discussed. Finally, freeform designs for much more complex sources like clusters of LED-sources are presented.

Design Studies of a CZT-based Detector Combined with a Pixel-Geometry-Matching Collimator for SPECT Imaging.

PubMed

Weng, Fenghua; Bagchi, Srijeeta; Huang, Qiu; Seo, Youngho

2013-10-01

Single Photon Emission Computed Tomography (SPECT) suffers limited efficiency due to the need for collimators. Collimator properties largely decide the data statistics and image quality. Various materials and configurations of collimators have been investigated in many years. The main thrust of our study is to evaluate the design of pixel-geometry-matching collimators to investigate their potential performances using Geant4 Monte Carlo simulations. Here, a pixel-geometry-matching collimator is defined as a collimator which is divided into the same number of pixels as the detector's and the center of each pixel in the collimator is a one-to-one correspondence to that in the detector. The detector is made of Cadmium Zinc Telluride (CZT), which is one of the most promising materials for applications to detect hard X-rays and γ -rays due to its ability to obtain good energy resolution and high light output at room temperature. For our current project, we have designed a large-area, CZT-based gamma camera (20.192 cm×20.192 cm) with a small pixel pitch (1.60 mm). The detector is pixelated and hence the intrinsic resolution can be as small as the size of the pixel. Materials of collimator, collimator hole geometry, detection efficiency, and spatial resolution of the CZT detector combined with the pixel-matching collimator were calculated and analyzed under different conditions. From the simulation studies, we found that such a camera using rectangular holes has promising imaging characteristics in terms of spatial resolution, detection efficiency, and energy resolution.

Effects of detector-source distance and detector bias voltage variations on time resolution of general purpose plastic scintillation detectors.

PubMed

Ermis, E E; Celiktas, C

2012-12-01

Effects of source-detector distance and the detector bias voltage variations on time resolution of a general purpose plastic scintillation detector such as BC400 were investigated. (133)Ba and (207)Bi calibration sources with and without collimator were used in the present work. Optimum source-detector distance and bias voltage values were determined for the best time resolution by using leading edge timing method. Effect of the collimator usage on time resolution was also investigated. Copyright © 2012 Elsevier Ltd. All rights reserved.

Relativistic jets in SS 433

NASA Astrophysics Data System (ADS)

Margon, B.

1982-01-01

A variety of recent optical, radio, and X-ray observations have confirmed the hypothesis that the peculiar star SS 433 is ejecting two narrow, opposed, highly collimated jets of matter at one-quarter the speed of light. This unique behavior is probably driven by mass exchange between a relatively normal star and a compact companion, either a neutron star or a black hole. However, numerous details regarding the energetics, radiation, acceleration, and collimation of the jets remain to be understood. This phenomenon may well be a miniature example of similar collimated ejection of gas by active extragalactic objects such as quasars and radio galaxies.

Nonradial and nonpolytropic astrophysical outflows. X. Relativistic MHD rotating spine jets in Kerr metric

NASA Astrophysics Data System (ADS)

Chantry, L.; Cayatte, V.; Sauty, C.; Vlahakis, N.; Tsinganos, K.

2018-04-01

Context. High-resolution radio imaging of active galactic nuclei (AGN) has revealed that the jets of some sources present superluminal knots and transverse stratification. Recent observational projects, such as ALMA and γ-ray telescopes, such as HESS and HESS2 have provided new observational constraints on the central regions of rotating black holes in AGN, suggesting that there is an inner- or spine-jet surrounded by a disk wind. This relativistic spine-jet is likely to be composed of electron-positron pairs extracting energy from the black hole and will be explored by the future γ-ray telescope CTA. Aims: In this article we present an extension to and generalization of relativistic jets in Kerr metric of the Newtonian meridional self-similar mechanism. We aim at modeling the inner spine-jet of AGN as a relativistic light outflow emerging from a spherical corona surrounding a Kerr black hole and its inner accretion disk. Methods: The model is built by expanding the metric and the forces with colatitude to first order in the magnetic flux function. As a result of the expansion, all colatitudinal variations of the physical quantities are quantified by a unique parameter. Unlike previous models, effects of the light cylinder are not neglected. Results: Solutions with high Lorentz factors are obtained and provide spine-jet models up to the polar axis. As in previous publications, we calculate the magnetic collimation efficiency parameter, which measures the variation of the available energy across the field lines. This collimation efficiency is an integral part of the model, generalizing the classical magnetic rotator efficiency criterion to Kerr metric. We study the variation of the magnetic efficiency and acceleration with the spin of the black hole and show their high sensitivity to this integral. Conclusions: These new solutions model collimated or radial, relativistic or ultra-relativistic outflows in AGN or γ-ray bursts. In particular, we discuss the relevance of our solutions to modeling the M 87 spine-jet. We study the efficiency of the central black hole spin to collimate a spine-jet and show that the jet power is of the same order as that determined by numerical simulations.

Optical Materials Characterization, Final Technical Report February 1, 1978-September 30, 1978

DTIC Science & Technology

1979-02-01

FIGURES PAGE Figure 1. (a) Schematic of spectrometer used for visible region refractometry . (b) Schematic of spectrometer used for non-,visible...region refractometry . Symbols: A = source, B = divided circle, C = prism table, D = collimator, E = telescope, F = collimating mirror, G = movable... refractometry . (b) Schematic of spectrometer used for non- visible region refractometry . Symbols: A = source, B = divided circle, C = prism table

Biocular vehicle display optical designs

NASA Astrophysics Data System (ADS)

Chu, H.; Carter, Tom

2012-06-01

Biocular vehicle display optics is a fast collimating lens (f / # < 0.9) that presents the image of the display at infinity to both eyes of the viewer. Each eye captures the scene independently and the brain merges the two images into one through the overlapping portions of the images. With the recent conversion from analog CRT based displays to lighter, more compact active-matrix organic light-emitting diodes (AMOLED) digital image sources, display optical designs have evolved to take advantage of the higher resolution AMOLED image sources. To maximize the field of view of the display optics and fully resolve the smaller pixels, the digital image source is pre-magnified by relay optics or a coherent taper fiber optics plate. Coherent taper fiber optics plates are used extensively to: 1. Convert plano focal planes to spherical focal planes in order to eliminate Petzval field curvature. This elimination enables faster lens speed and/or larger field of view of eye pieces, display optics. 2. Provide pre-magnification to lighten the work load of the optics to further increase the numerical aperture and/or field of view. 3. Improve light flux collection efficiency and field of view by collecting all the light emitted by the image source and guiding imaging light bundles toward the lens aperture stop. 4. Reduce complexity of the optical design and overall packaging volume by replacing pre-magnification optics with a compact taper fiber optics plate. This paper will review and compare the performance of biocular vehicle display designs without and with taper fiber optics plate.

NSLS-II beamline scattered gas bremsstrahlung radiation shielding calculation

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

Popescu, Razvan; Xia, Zhenghua, E-mail: xiazhenghuacn@hotmail.com; Job, Panakkal

2016-07-27

National Synchrotron Light Source II (NSLS-II) is a new state-of-the-art 3rd generation synchrotron. The NSLS-II facility is shielded up to 3 GeV electron beam energy at 500 mA. When the gas bremsstrahlung (GB) from the storage ring is scattered by the beamline components in the first optical enclosure (FOE), the scattered radiation will pose additional radiation hazard (bypassing primary GB collimators and stops) and challenge the FOE shielding. The scattered GB radiation hazard can be mitigated by supplementary shielding or with an exclusion zone downstream of the FOE.

Note: Detector collimators for the nanoscale ordered materials diffractometer instrument at the Spallation Neutron Source

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

Tamalonis, A.; Weber, J. K. R.; Neuefeind, J. C.

2015-09-01

Five neutron collimator designs were constructed and tested at the nanoscale ordered materials diffractometer (NOMAD) instrument. Collimators were made from High Density PolyEthylene (HDPE) or 5% borated HDPE. In all cases, collimators improved the signal to background ratio and reduced detection of secondary scattering. In the Q-range 10-20 (angstrom) -1, signal to background ratio improved by factors of approximately 1.6 and 2.0 for 50 and 100 mm deep collimators, respectively. In the Q-range 40-50 angstrom -1, the improvement factors were 1.8 and 2.7. Secondary scattering as measured at Q similar to 9.5 angstrom -1 was significantly decreased when the collimatorsmore » were installed.« less

Refractive-index determination of solids from first- and second-order critical diffraction angles of periodic surface patterns

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

Meichner, Christoph, E-mail: christoph.meichner@uni-bayreuth.de; Kador, Lothar, E-mail: lothar.kador@uni-bayreuth.de; Schedl, Andreas E.

2015-08-15

We present two approaches for measuring the refractive index of transparent solids in the visible spectral range based on diffraction gratings. Both require a small spot with a periodic pattern on the surface of the solid, collimated monochromatic light, and a rotation stage. We demonstrate the methods on a polydimethylsiloxane film (Sylgard{sup ®} 184) and compare our data to those obtained with a standard Abbe refractometer at several wavelengths between 489 and 688 nm. The results of our approaches show good agreement with the refractometer data. Possible error sources are analyzed and discussed in detail; they include mainly the linewidthmore » of the laser and/or the angular resolution of the rotation stage. With narrow-band light sources, an angular accuracy of ±0.025{sup ∘} results in an error of the refractive index of typically ±5 ⋅ 10{sup −4}. Information on the sample thickness is not required.« less

Low-level laser therapy of acute and chronic pain: results of the trials and light delivery optimization

NASA Astrophysics Data System (ADS)

Stoykova, Elena V.; Roeva, Tatiana

2003-09-01

The work presents the results of the low-level laser therapy (LLLT) of two groups of volunteers with a variety of conditions performed with a GaAs-system. The volunteers were randomly selected among the patients who were usually treated by conventional therapy that included massage and acupuncture needles. The LLLT was proposed to the first group as extension of conventional treatment. The second group underwent only the LLLT. The effectiveness of the therapy was graded under four categories. Short-term and long-term side effects as well as conditions responding only to LLLT were recorded. The successful treatments were up to 70% for both groups, which coincided with the result of the control group treated by the conventional therapy. For optimization of the light delivery, the spatial maps of the absorbed dose in a homogeneous medium, both in the proximity of the light source and at a distance from it, were compared for collimated and divergent light beams using a reduced variance Monte-Carlo code.

Light pollution and solid-state lighting: reducing the carbon dioxide footprint is not enough

NASA Astrophysics Data System (ADS)

Bará, Salvador

2013-11-01

Public and private lighting account for a relevant share of the overall electric power consumption worldwide. The pressing need of reducing the carbon dioxide emissions as well as of lowering the lumen•hour price tag has fostered the search for alternative lighting technologies to substitute for the incandescent and gas-discharge based lamps. The most successful approach to date, solid-state lighting, is already finding its way into the public lighting market, very often helped by substantial public investments and support. LED-based sources have distinct advantages: under controlled coditions their efficacy equals or surpasses that of conventional solutions, their small source size allows for an efficient collimation of the lightbeam (delivering the photons where they are actually needed and reducing lightspill on the surrounding areas), and they can be switched and/or dimmed on demand at very high rates, thus allowing for a taylored schedule of lighting. However, energy savings and carbon dioxide reduction are not the only crucial issues faced by present day lighting. A growing body of research has shown the significance of the spectral composition of light when it comes to assess the detrimental effects of artificial light-at-night (ALAN). The potential ALAN blueshift associated to the deployment of LED-based lighting systems has raised sensible concerns about its scientific, cultural, ecological and public health consequences, which can be further amplified if an increased light consumption is produced due to the rebound effect. This contribution addresses some of the challenges that these issues pose to the Optics and Photonics community.

Numerical convergence and validation of the DIMP inverse particle transport model

DOE PAGES

Nelson, Noel; Azmy, Yousry

2017-09-01

The data integration with modeled predictions (DIMP) model is a promising inverse radiation transport method for solving the special nuclear material (SNM) holdup problem. Unlike previous methods, DIMP is a completely passive nondestructive assay technique that requires no initial assumptions regarding the source distribution or active measurement time. DIMP predicts the most probable source location and distribution through Bayesian inference and quasi-Newtonian optimization of predicted detector re-sponses (using the adjoint transport solution) with measured responses. DIMP performs well with for-ward hemispherical collimation and unshielded measurements, but several considerations are required when using narrow-view collimated detectors. DIMP converged well to themore » correct source distribution as the number of synthetic responses increased. DIMP also performed well for the first experimental validation exercise after applying a collimation factor, and sufficiently reducing the source search vol-ume's extent to prevent the optimizer from getting stuck in local minima. DIMP's simple point detector response function (DRF) is being improved to address coplanar false positive/negative responses, and an angular DRF is being considered for integration with the next version of DIMP to account for highly collimated responses. Overall, DIMP shows promise for solving the SNM holdup inverse problem, especially once an improved optimization algorithm is implemented.« less

Holographic memory using beam steering

NASA Technical Reports Server (NTRS)

Chao, Tien-Hsin (Inventor); Hanan, Jay C. (Inventor); Reyes, George F. (Inventor); Zhou, Hanying (Inventor)

2006-01-01

A method, apparatus, and system provide the ability for storing holograms at high speed. A single laser diode emits a collimated laser beam to both write to and read from a photorefractice crystal. One or more liquid crystal beam steering spatial light modulators (BSSLMs) or Micro-Electro-Mechanical Systems (MEMS) mirrors steer a reference beam, split from the collimated laser beam, at high speed to the photorefractive crystal.

Proof of Principle for Electronic Collimation of a Gamma Ray Detector

DTIC Science & Technology

2016-01-01

complete the Environmental Baseline Survey mission for soldiers. The monitoring of radioactive waste handling, as well as other sources of radioactive ...electronic collimation of a gamma ray spectroscopic detector will include identifying and characterizing environmentally hazardous radioactivity to

Design and dosimetry of small animal radiation facilities

NASA Astrophysics Data System (ADS)

Rodriguez, Manuel R.

The aim of this work was to develop an irradiation system for radiobiology studies. We designed a novel image-guided micro-irradiator capable of partial-body zebrafish embryo irradiation. The radiation source is a 50 kV photon beam from a miniature x-ray source (Xoft Inc., CA). The source is inserted in a cylindrical brass collimator, 3 cm in diameter and 3 cm in length. The collimator has a 1 mm-diameter pinhole along the longitudinal axis, which provides a well-focused beam with a sharp penumbra. A photodiode is installed at one exit of the pinhole collimator to monitor the photon dose rate. The source with the collimator is attached under a movable table. A video camera, connected to the computer, is placed above the movable table to record position of the specimens in relation to the pinhole collimator. The captured images are analyzed, and the relative distances between the specimens and the pinhole are calculated. The coordinates are sent to the computer-controlled movable table to accurately position the specimens in the beam. Monte Carlo simulations were performed to characterize dosimetric properties of the system, to determine dosimetric sensitivity, and to help in the design. The image-guidance and high precision of the movable table enable very accurate specimen position. The beam monitoring system provides accurate, fast and easy dose determination. Portability and self-shielding make this system suitable for any radiobiology laboratory. This novel micro-irradiator is appropriate for partial irradiation of zebrafish embryos; however its potential use is much wider like irradiation of cell cultures or other small specimens.

Characterization of the Shielded Neutron Source at Triangle Universities Nuclear Laboratory

NASA Astrophysics Data System (ADS)

Hobson, Chad; Finch, Sean; Howell, Calvin; Malone, Ron; Tornow, Wernew

2016-09-01

In 2015, Triangle Universities Nuclear Laboratory rebuilt its shielded neutron source (SNS) with the goal of improving neutron beam collimation and reducing neutron and gamma-ray backgrounds. Neutrons are produced via the 2H(d,n)3He reaction and then collimated by heavy shielding to form a beam. The SNS has the ability to produce both a rectangular and circular neutron beam through use of two collimators with different beam apertures. Our work characterized both the neutron beam profiles as well as the neutron and gamma-ray backgrounds at various locations around the SNS. This characterization was performed to provide researchers who use the SNS with beam parameters necessary to plan and conduct an experiment. Vertical and horizontal beam profiles were measured at two different distances from the neutron production cell by scanning a small plastic scintillator across the face of the beam at various energies for each collimator. Background neutron and gamma-ray intensities were measured using time-of-flight techniques at 10 MeV and 16 MeV with the rectangular collimator. We present results on the position and size of neutron beam as well as on the structure and magnitude of the backgrounds.

Source holder collimator for encapsulating radioactive material and collimating the emanations from the material

DOEpatents

Laurer, G.R.

1974-01-22

This invention provides a transportable device capable of detecting normal levels of a trace element, such as lead in a doughnutshaped blood sample by x-ray fluorescence with a minimum of sample preparation in a relatively short analyzing time. In one embodiment, the blood is molded into a doughnut-shaped sample around an annular array of low-energy radioactive material that is at the center of the doughnut-shaped sample but encapsulated in a collimator, the latter shielding a detector that is close to the sample and facing the same so that the detector receives secondary emissions from the sample while the collimator collimates ths primary emissions from the radioactive material to direct these emissions toward the sample around 360 deg and away from the detector. (Official Gazette)

Alignment reference device

DOEpatents

Patton, Gail Y.; Torgerson, Darrel D.

1987-01-01

An alignment reference device provides a collimated laser beam that minimizes angular deviations therein. A laser beam source outputs the beam into a single mode optical fiber. The output end of the optical fiber acts as a source of radiant energy and is positioned at the focal point of a lens system where the focal point is positioned within the lens. The output beam reflects off a mirror back to the lens that produces a collimated beam.

Development of a 0.5m clear aperture Cassegrain type collimator telescope

NASA Astrophysics Data System (ADS)

Ekinci, Mustafa; Selimoǧlu, Özgür

2016-07-01

Collimator is an optical instrument used to evaluate performance of high precision instruments, especially space-born high resolution telescopes. Optical quality of the collimator telescope needs to be better than the instrument to be measured. This requirement leads collimator telescope to be a very precise instrument with high quality mirrors and a stable structure to keep it operational under specified conditions. In order to achieve precision requirements and to ensure repeatability of the mounts for polishing and metrology, opto-mechanical principles are applied to mirror mounts. Finite Element Method is utilized to simulate gravity effects, integration errors and temperature variations. Finite element analyses results of deformed optical surfaces are imported to optical domain by using Zernike polynomials to evaluate the design against specified WFE requirements. Both mirrors are aspheric and made from Zerodur for its stability and near zero CTE, M1 is further light-weighted. Optical quality measurements of the mirrors are achieved by using custom made CGHs on an interferometric test setup. Spider of the Cassegrain collimator telescope has a flexural adjustment mechanism driven by precise micrometers to overcome tilt errors originating from finite stiffness of the structure and integration errors. Collimator telescope is assembled and alignment methods are proposed.

DUHOCAMIS: a dual hollow cathode ion source for metal ion beams.

PubMed

Zhao, W J; Müller, M W O; Janik, J; Liu, K X; Ren, X T

2008-02-01

In this paper we describe a novel ion source named DUHOCAMIS for multiply charged metal ion beams. This ion source is derived from the hot cathode Penning ion gauge ion source (JINR, Dubna, 1957). A notable characteristic is the modified Penning geometry in the form of a hollow sputter electrode, coaxially positioned in a compact bottle-magnetic field along the central magnetic line of force. The interaction of the discharge geometry with the inhomogeneous but symmetrical magnetic field enables this device to be operated as hollow cathode discharge and Penning discharge as well. The main features of the ion source are the very high metal ion efficiency (up to 25%), good operational reproducibility, flexible and efficient operations for low charged as well as highly charged ions, compact setup, and easy maintenance. For light ions, e.g., up to titanium, well-collimated beams in the range of several tens of milliamperes of pulsed ion current (1 ms, 10/s) have been reliably performed in long time runs.

Violet laser diodes as light sources for cytometry.

PubMed

Shapiro, H M; Perlmutter, N G

2001-06-01

Violet laser diodes have recently become commercially available. These devices emit 5-25 mW in the range of 395-415 nm, and are available in systems that incorporate the diodes with collimating optics and regulated power supplies in housing incorporating thermoelectric coolers, which are necessary to maintain stable output. Such systems now cost several thousand dollars, but are expected to drop substantially in price. Materials and Methods A 4-mW, 397-nm violet diode system was used in a laboratory-built flow cytometer to excite fluorescence of DAPI and Hoechst dyes in permeabilized and intact cells. Forward and orthogonal light scattering were also measured. DNA content histograms with good precision (G(0)/G(1) coefficient of variation 1.7%) were obtained with DAPI staining; precision was lower using Hoechst 33342. Hoechst 34580, with an excitation maximum nearer 400 nm, yielded the highest fluorescence intensity, but appeared to decompose after a short time in solution. Scatter signals exhibited relatively broad distributions. Violet laser diodes are relatively inexpensive, compact, efficient, and quiet light sources for DNA fluorescence measurement using DAPI and Hoechst dyes; they can also excite several other fluorescent probes. Copyright 2001 Wiley-Liss, Inc.

Gamma ray camera

DOEpatents

Perez-Mendez, V.

1997-01-21

A gamma ray camera is disclosed for detecting rays emanating from a radiation source such as an isotope. The gamma ray camera includes a sensor array formed of a visible light crystal for converting incident gamma rays to a plurality of corresponding visible light photons, and a photosensor array responsive to the visible light photons in order to form an electronic image of the radiation therefrom. The photosensor array is adapted to record an integrated amount of charge proportional to the incident gamma rays closest to it, and includes a transparent metallic layer, photodiode consisting of a p-i-n structure formed on one side of the transparent metallic layer, and comprising an upper p-type layer, an intermediate layer and a lower n-type layer. In the preferred mode, the scintillator crystal is composed essentially of a cesium iodide (CsI) crystal preferably doped with a predetermined amount impurity, and the p-type upper intermediate layers and said n-type layer are essentially composed of hydrogenated amorphous silicon (a-Si:H). The gamma ray camera further includes a collimator interposed between the radiation source and the sensor array, and a readout circuit formed on one side of the photosensor array. 6 figs.

Gamma ray camera

DOEpatents

Perez-Mendez, Victor

1997-01-01

A gamma ray camera for detecting rays emanating from a radiation source such as an isotope. The gamma ray camera includes a sensor array formed of a visible light crystal for converting incident gamma rays to a plurality of corresponding visible light photons, and a photosensor array responsive to the visible light photons in order to form an electronic image of the radiation therefrom. The photosensor array is adapted to record an integrated amount of charge proportional to the incident gamma rays closest to it, and includes a transparent metallic layer, photodiode consisting of a p-i-n structure formed on one side of the transparent metallic layer, and comprising an upper p-type layer, an intermediate layer and a lower n-type layer. In the preferred mode, the scintillator crystal is composed essentially of a cesium iodide (CsI) crystal preferably doped with a predetermined amount impurity, and the p-type upper intermediate layers and said n-type layer are essentially composed of hydrogenated amorphous silicon (a-Si:H). The gamma ray camera further includes a collimator interposed between the radiation source and the sensor array, and a readout circuit formed on one side of the photosensor array.

Large area soft x-ray collimator to facilitate x-ray optics testing

NASA Technical Reports Server (NTRS)

Espy, Samuel L.

1994-01-01

The first objective of this program is to design a nested conical foil x-ray optic which will collimate x-rays diverging from a point source. The collimator could then be employed in a small, inexpensive x-ray test stand which would be used to test various x-ray optics and detector systems. The second objective is to demonstrate the fabrication of the x-ray reflectors for this optic using lacquer-smoothing and zero-stress electroforming techniques.

Apparatus and method for detecting gamma radiation

DOEpatents

Sigg, Raymond A.

1994-01-01

A high efficiency radiation detector for measuring X-ray and gamma radiation from small-volume, low-activity liquid samples with an overall uncertainty better than 0.7% (one sigma SD). The radiation detector includes a hyperpure germanium well detector, a collimator, and a reference source. The well detector monitors gamma radiation emitted by the reference source and a radioactive isotope or isotopes in a sample source. The radiation from the reference source is collimated to avoid attenuation of reference source gamma radiation by the sample. Signals from the well detector are processed and stored, and the stored data is analyzed to determine the radioactive isotope(s) content of the sample. Minor self-attenuation corrections are calculated from chemical composition data.

Lens design of LED searchlight of high brightness and distant spot.

PubMed

Zhao, Shuang; Wang, Kai; Chen, Fei; Wu, Dan; Liu, Sheng

2011-05-01

The study related in this paper is the design of a ship-mounted LED of high brightness and distant spot. The freeform lens design obeying the edge ray principle and Snell's law is presented first. Then, to fit the illumination requirement of the searchlight, we designed a freeform lens to collimate all the light rays coming from the LED. However, theoretical analysis proves that there is a critical angle for incident rays beyond which the rays cannot be collimated, and 55% is the light-efficiency limit for polymethyl methacrylate freeform lens. We then designed a combination of a freeform lens-coupled parabolic reflector that improved light efficiency to 70%. In this paper, the design of the freeform lens-coupled parabolic reflector is given in detail. In addition, tolerance analysis and the effect of manufacturing defect are presented.

Multiple window spatial registration error of a gamma camera: 133Ba point source as a replacement of the NEMA procedure.

PubMed

Bergmann, Helmar; Minear, Gregory; Raith, Maria; Schaffarich, Peter M

2008-12-09

The accuracy of multiple window spatial resolution characterises the performance of a gamma camera for dual isotope imaging. In the present study we investigate an alternative method to the standard NEMA procedure for measuring this performance parameter. A long-lived 133Ba point source with gamma energies close to 67Ga and a single bore lead collimator were used to measure the multiple window spatial registration error. Calculation of the positions of the point source in the images used the NEMA algorithm. The results were validated against the values obtained by the standard NEMA procedure which uses a liquid 67Ga source with collimation. Of the source-collimator configurations under investigation an optimum collimator geometry, consisting of a 5 mm thick lead disk with a diameter of 46 mm and a 5 mm central bore, was selected. The multiple window spatial registration errors obtained by the 133Ba method showed excellent reproducibility (standard deviation < 0.07 mm). The values were compared with the results from the NEMA procedure obtained at the same locations and showed small differences with a correlation coefficient of 0.51 (p < 0.05). In addition, the 133Ba point source method proved to be much easier to use. A Bland-Altman analysis showed that the 133Ba and the 67Ga Method can be used interchangeably. The 133Ba point source method measures the multiple window spatial registration error with essentially the same accuracy as the NEMA-recommended procedure, but is easier and safer to use and has the potential to replace the current standard procedure.

Spectral radiance source based on supercontinuum laser and wavelength tunable bandpass filter: the spectrally tunable absolute irradiance and radiance source.

PubMed

Levick, Andrew P; Greenwell, Claire L; Ireland, Jane; Woolliams, Emma R; Goodman, Teresa M; Bialek, Agnieszka; Fox, Nigel P

2014-06-01

A new spectrally tunable source for calibration of radiometric detectors in radiance, irradiance, or power mode has been developed and characterized. It is termed the spectrally tunable absolute irradiance and radiance source (STAIRS). It consists of a supercontinuum laser, wavelength tunable bandpass filter, power stabilization feedback control scheme, and output coupling optics. It has the advantages of relative portability and a collimated beam (low étendue), and is an alternative to conventional sources such as tungsten lamps, blackbodies, or tunable lasers. The supercontinuum laser is a commercial Fianium SC400-6-02, which has a wavelength range between 400 and 2500 nm and a total power of 6 W. The wavelength tunable bandpass filter, a PhotonEtc laser line tunable filter (LLTF), is tunable between 400 and 1000 nm and has a bandwidth of 1 or 2 nm depending on the wavelength selected. The collimated laser beam from the LLTF filter is converted to an appropriate spatial and angular distribution for the application considered (i.e., for radiance, irradiance, or power mode calibration of a radiometric sensor) with the output coupling optics, for example, an integrating sphere, and the spectral radiance/irradiance/power of the source is measured using a calibration optical sensor. A power stabilization feedback control scheme has been incorporated that stabilizes the source to better than 0.01% for averaging times longer than 100 s. The out-of-band transmission of the LLTF filter is estimated to be < -65 dB (0.00003%), and is sufficiently low for many end-user applications, for example the spectral radiance calibration of earth observation imaging radiometers and the stray light characterization of array spectrometers (the end-user optical sensor). We have made initial measurements of two end-user instruments with the STAIRS source, an array spectrometer and ocean color radiometer.

Spectral resolution control of acousto-optical cells operating with collimated and divergent beams

NASA Astrophysics Data System (ADS)

Voloshinov, Vitaly B.; Mishin, Dimitry D.

1994-01-01

The paper is devoted to theoretical and experimental investigations of acousto-optical interactions in crystals which may be used for spectral filtration of light in tunable acousto- optical filters. Attention is paid to spectral resolution control during operation with divergent or collimated noncoherent optical beams. In all examined cases spectral bands of anisotropic Bragg diffraction were regulated by means of novel electronical methods. Resolution control was achieved in paratellurite cells with non-collinear and quasi-collinear regimes of the diffraction. Filtration spectral bandwidths for visible light were electronically changed by a factor of 10 divided by 20 by drive electrical signals switching and drive electrical power regulations.

Holographic Waveguide Array Rollable Display.

DTIC Science & Technology

1997-04-01

scale lithography for fabrication. Projection systems offer large images, in the range of 40 - 60 inches diagonal, and both front-view and rear-view...Boulder, CO, and a l-D array of digital micromirrors ( DMD ) from Texas Instruments. The linear format permits simple driving electronics and high...TI’s DMD , or a CMOS-SLM. A collimated laser beaming (combine three colors) or a collimated white light beam from a high intensity halogen lamp can be

Solution-processed nanoparticle super-float-gated organic field-effect transistor as un-cooled ultraviolet and infrared photon counter.

PubMed

Yuan, Yongbo; Dong, Qingfeng; Yang, Bin; Guo, Fawen; Zhang, Qi; Han, Ming; Huang, Jinsong

2013-01-01

High sensitivity photodetectors in ultraviolet (UV) and infrared (IR) range have broad civilian and military applications. Here we report on an un-cooled solution-processed UV-IR photon counter based on modified organic field-effect transistors. This type of UV detectors have light absorbing zinc oxide nanoparticles (NPs) sandwiched between two gate dielectric layers as a floating gate. The photon-generated charges on the floating gate cause high resistance regions in the transistor channel and tune the source-drain output current. This "super-float-gating" mechanism enables very high sensitivity photodetectors with a minimum detectable ultraviolet light intensity of 2.6 photons/μm(2)s at room temperature as well as photon counting capability. Based on same mechansim, infrared photodetectors with lead sulfide NPs as light absorbing materials have also been demonstrated.

Analysis of a color-matching backlight system using a blazed grating and a lenticular lens array.

PubMed

Son, Chang-Gyun; Gwag, Jin Seok; Lee, Jong Hoon; Kwon, Jin Hyuk

2012-12-20

A high efficiency LCD employing a color-matching backlight system that consists of a collimation lenticular lens sheet, a blazed grating, and a focusing lenticular lens array is proposed and analyzed. The RGB lights that are collimated and dispersed from the collimation lenticular lens sheet and the blazed grating are incident on the RGB color filters by the focusing lenticular lens array. The color-matched transmittance was increased 183% and 121% for divergence angles of 2° and 11°, respectively, compared to a conventional backlight that does not use a blazed grating. The design, simulation, and experimental results for the prototype color-matching backlight system are presented.

Use of thermal sieve to allow optical testing of cryogenic optical systems.

PubMed

Kim, Dae Wook; Cai, Wenrui; Burge, James H

2012-05-21

Full aperture testing of large cryogenic optical systems has been impractical due to the difficulty of operating a large collimator at cryogenic temperatures. The Thermal Sieve solves this problem by acting as a thermal barrier between an ambient temperature collimator and the cryogenic system under test. The Thermal Sieve uses a set of thermally controlled baffles with array of holes that are lined up to pass the light from the collimator without degrading the wavefront, while attenuating the thermal background by nearly 4 orders of magnitude. This paper provides the theory behind the Thermal Sieve system, evaluates the optimization for its optical and thermal performance, and presents the design and analysis for a specific system.

Design of a setup for 252Cf neutron source for storage and analysis purpose

NASA Astrophysics Data System (ADS)

Hei, Daqian; Zhuang, Haocheng; Jia, Wenbao; Cheng, Can; Jiang, Zhou; Wang, Hongtao; Chen, Da

2016-11-01

252Cf is a reliable isotopic neutron source and widely used in the prompt gamma ray neutron activation analysis (PGNAA) technique. A cylindrical barrel made by polymethyl methacrylate contained with the boric acid solution was designed for storage and application of a 5 μg 252Cf neutron source. The size of the setup was optimized with Monte Carlo code. The experiments were performed and the results showed the doses were reduced with the setup and less than the allowable limit. The intensity and collimating radius of the neutron beam could also be adjusted through different collimator.

A new variable parallel holes collimator for scintigraphic device with validation method based on Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Trinci, G.; Massari, R.; Scandellari, M.; Boccalini, S.; Costantini, S.; Di Sero, R.; Basso, A.; Sala, R.; Scopinaro, F.; Soluri, A.

2010-09-01

The aim of this work is to show a new scintigraphic device able to change automatically the length of its collimator in order to adapt the spatial resolution value to gamma source distance. This patented technique replaces the need for collimator change that standard gamma cameras still feature. Monte Carlo simulations represent the best tool in searching new technological solutions for such an innovative collimation structure. They also provide a valid analysis on response of gamma cameras performances as well as on advantages and limits of this new solution. Specifically, Monte Carlo simulations are realized with GEANT4 (GEometry ANd Tracking) framework and the specific simulation object is a collimation method based on separate blocks that can be brought closer and farther, in order to reach and maintain specific spatial resolution values for all source-detector distances. To verify the accuracy and the faithfulness of these simulations, we have realized experimental measurements with identical setup and conditions. This confirms the power of the simulation as an extremely useful tool, especially where new technological solutions need to be studied, tested and analyzed before their practical realization. The final aim of this new collimation system is the improvement of the SPECT techniques, with the real control of the spatial resolution value during tomographic acquisitions. This principle did allow us to simulate a tomographic acquisition of two capillaries of radioactive solution, in order to verify the possibility to clearly distinguish them.

A beamline for high-pressure studies at the Advanced Light Source with a superconducting bending magnet as the source.

PubMed

Kunz, Martin; MacDowell, Alastair A; Caldwell, Wendel A; Cambie, Daniella; Celestre, Richard S; Domning, Edward E; Duarte, Robert M; Gleason, Arianna E; Glossinger, James M; Kelez, Nicholas; Plate, David W; Yu, Tony; Zaug, Joeseph M; Padmore, Howard A; Jeanloz, Raymond; Alivisatos, A Paul; Clark, Simon M

2005-09-01

A new facility for high-pressure diffraction and spectroscopy using diamond anvil high-pressure cells has been built at the Advanced Light Source on beamline 12.2.2. This beamline benefits from the hard X-radiation generated by a 6 T superconducting bending magnet (superbend). Useful X-ray flux is available between 5 keV and 35 keV. The radiation is transferred from the superbend to the experimental enclosure by the brightness-preserving optics of the beamline. These optics are comprised of a plane parabola collimating mirror, followed by a Kohzu monochromator vessel with Si(111) crystals (E/DeltaE approximately equal 7000) and W/B4C multilayers (E/DeltaE approximately equal 100), and then a toroidal focusing mirror with variable focusing distance. The experimental enclosure contains an automated beam-positioning system, a set of slits, ion chambers, the sample positioning goniometry and area detector (CCD or image-plate detector). Future developments aim at the installation of a second endstation dedicated to in situ laser heating and a dedicated high-pressure single-crystal station, applying both monochromatic and polychromatic techniques.

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

Reininger, Ruben; Dhesi, Sarnjeet

The main requirement of the Nanoscience Beamline at Diamond is to deliver the highest possible flux at the sample position of a PEEM with a resolving power of about 5000 in the energy range 80-2000 eV. The source of the beamline is a couple of APPLE II helical undulators in tandem that can also be used separately to allow for faster switching of the circular polarization. Based on its versatility, a collimated plane grating monochromator using sagittally focusing elements was chosen to cover the required energy range with three gratings. The operation of this monochromator requires a collimated beam incidentmore » on the grating along the dispersion direction. This can be achieved either with a toroid, focusing with its major radius along the non-dispersive direction at the exit slit, or with a sagittal cylinder. The former option uses a sagittal cylinder after the grating to focus the collimated beam at the exit slit. In the latter case, a toroid after the grating is used to focus in both directions at the exit slit. The advantage of the toroid downstream the grating is the higher horizontal demagnification. This configuration fulfills the Nanoscience Beamline's required resolving power but cannot be used to achieve very high resolution due to the astigmatic coma aberration of the toroidal mirror. The focusing at the sample position is performed with a KB pair of plane elliptical mirrors. Assuming achievable values for the errors on all the optical surfaces, the expected spots FWHW in the horizontal and vertical directions are 10 {mu}m and 3 {mu}m, respectively. The calculated photon flux at this spot at 5000 resolving power is >1012 photons/sec between 80 and 1600 eV for linearly polarized light and between 106 and 1200 eV for circularly polarized light. The beamline is expected to be operational in January 2007.« less

SU-F-T-425: Head-Scatter Off-Axis for FFF Megavoltage Photon Beams

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

Zhu, T; Penjweini, R; Dimofte, A

Purpose: Head-scatter photons inside a clinical accelerator cause the output to change with collimator setting. On the central-axis, this contribution is well-described by output factor in air (or head-scatter factor). However, a few studies have examined this component at off-axis points. Methods: We define the head-scatter off-axis ratio, HOA, as the ratio of the water kerma in air due to head-scatter photons at the off-axis position x to the water kerma from direct primary photons on the central axis: HOA(cx,cy,xy) = (Q(cx,cy,x) – QP(cx,cy,x))/QP(cx,cy,0), where Q(cx, cy,x), QP(cx,cy,x) are charges measured by an ionization chamber in a miniphantom for collimatormore » setting cx × cy and cx × 3 cm, respectively, at off-axis point x. “Direct primary” is those photons that come from the source without interactions in the intervening structures. Results: We measured HOA for two energies (6XFFF and 6X) along X and Y jaw directions for various collimator settings. The shape of HOA has well defined penumbra for collimator setting larger than 10 × 10 cm2. Conclusion: The narrow gaussian component is interpreted as the source of photons scattered in the flattening filter and the primary collimator. The broad component is attributed to photons scattered in the secondary (variable) collimators. By a direct comparison between 6X and 6XFFF beams, we can confirm that the second component is indeed coming from collimator jaws and identify the parts coming from the primary collimator and the flattening filter, respectively.« less

Design of optimal collimation for dedicated molecular breast imaging systems

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

Weinmann, Amanda L.; Hruska, Carrie B.; O'Connor, Michael K.

2009-03-15

Molecular breast imaging (MBI) is a functional imaging technique that uses specialized small field-of-view gamma cameras to detect the preferential uptake of a radiotracer in breast lesions. MBI has potential to be a useful adjunct method to screening mammography for the detection of occult breast cancer. However, a current limitation of MBI is the high radiation dose (a factor of 7-10 times that of screening mammography) associated with current technology. The purpose of this study was to optimize the gamma camera collimation with the aim of improving sensitivity while retaining adequate resolution for the detection of sub-10-mm lesions. Square-hole collimatorsmore » with holes matched to the pixilated cadmium zinc telluride detector elements of the MBI system were designed. Data from MBI patient studies and parameters of existing dual-head MBI systems were used to guide the range of desired collimator resolutions, source-to-collimator distances, pixel sizes, and collimator materials that were examined. General equations describing collimator performance for a conventional gamma camera were used in the design process along with several important adjustments to account for the specialized imaging geometry of the MBI system. Both theoretical calculations and a Monte Carlo model were used to measure the geometric efficiency (or sensitivity) and resolution of each designed collimator. Results showed that through optimal collimation, collimator sensitivity could be improved by factors of 1.5-3.2, while maintaining a collimator resolution of either {<=}5 or {<=}7.5 mm at a distance of 3 cm from the collimator face. These gains in collimator sensitivity permit an inversely proportional drop in the required dose to perform MBI.« less

Influence of detector collimation on SNR in four different MDCT scanners using a reconstructed slice thickness of 5 mm.

PubMed

Verdun, F R; Noel, A; Meuli, R; Pachoud, M; Monnin, P; Valley, J-F; Schnyder, P; Denys, A

2004-10-01

The purpose of this paper is to compare the influence of detector collimation on the signal-to-noise ratio (SNR) for a 5.0 mm reconstructed slice thickness for four multi-detector row CT (MDCT) units. SNRs were measured on Catphan test phantom images from four MDCT units: a GE LightSpeed QX/I, a Marconi MX 8000, a Toshiba Aquilion and a Siemens Volume Zoom. Five-millimetre-thick reconstructed slices were obtained from acquisitions performed using detector collimations of 2.0-2.5 mm and 5.0 mm, 120 kV, a 360 degrees tube rotation time of 0.5 s, a wide range of mA and pitch values in the range of 0.75-0.85 and 1.25-1.5. For each set of acquisition parameters, a Wiener spectrum was also calculated. Statistical differences in SNR for the different acquisition parameters were evaluated using a Student's t-test (P<0.05). The influence of detector collimation on the SNR for a 5.0-mm reconstructed slice thickness is different for different MDCT scanners. At pitch values lower than unity, the use of a small detector collimation to produce 5.0-mm thick slices is beneficial for one unit and detrimental for another. At pitch values higher than unity, using a small detector collimation is beneficial for two units. One manufacturer uses different reconstruction filters when switching from a 2.5- to a 5.0-mm detector collimation. For a comparable reconstructed slice thickness, using a smaller detector collimation does not always reduce image noise. Thus, the impact of the detector collimation on image noise should be determined by standard deviation calculations, and also by assessing the power spectra of the noise. Copyright 2004 Springer-Verlag

LETTER TO THE EDITOR: Combined optical and single photon emission imaging: preliminary results

NASA Astrophysics Data System (ADS)

Boschi, Federico; Spinelli, Antonello E.; D'Ambrosio, Daniela; Calderan, Laura; Marengo, Mario; Sbarbati, Andrea

2009-12-01

In vivo optical imaging instruments are generally devoted to the acquisition of light coming from fluorescence or bioluminescence processes. Recently, an instrument was conceived with radioisotopic detection capabilities (Kodak in Vivo Multispectral System F) based on the conversion of x-rays from the phosphorus screen. The goal of this work is to demonstrate that an optical imager (IVIS 200, Xenogen Corp., Alameda, USA), designed for in vivo acquisitions of small animals in bioluminescent and fluorescent modalities, can even be employed to detect signals due to radioactive tracers. Our system is based on scintillator crystals for the conversion of high-energy rays and a collimator. No hardware modifications are required. Crystals alone permit the acquisition of photons coming from an in vivo 20 g nude mouse injected with a solution of methyl diphosphonate technetium 99 metastable (Tc99m-MDP). With scintillator crystals and collimators, a set of measurements aimed to fully characterize the system resolution was carried out. More precisely, system point spread function and modulation transfer function were measured at different source depths. Results show that system resolution is always better than 1.3 mm when the source depth is less than 10 mm. The resolution of the images obtained with radioactive tracers is comparable with the resolution achievable with dedicated techniques. Moreover, it is possible to detect both optical and nuclear tracers or bi-modal tracers with only one instrument.

3D-printed focused collimator for intra-operative gamma-ray detection

NASA Astrophysics Data System (ADS)

Holdsworth, David W.; Nikolov, Hristo N.; Pollmann, Steven I.

2017-03-01

Recent developments in targeted radiopharmaceutical labels have increased the need for sensitive, real-time gamma detection during cancer surgery and biopsy. Additive manufacturing (3D printing) in metal has now made it possible to design and fabricate complex metal collimators for compact gamma probes. We describe the design and implementation of a 3D-printed focused collimator that allows for real-time detection of gamma radiation from within a small volume of interest, using a single-crystal large-area detector. The collimator was fabricated using laser melting of powdered stainless steel (316L), using a commercial 3D metal printer (AM125, Renishaw plc). The prototype collimator is 20 mm thick, with hexagonal close-packed holes designed to focus to a point 35 mm below the surface of the collimator face. Tests were carried out with a low-activity (<1 μCi) 241 Am source, using a conventional gamma-ray detector probe, incorporating a 2.5 cm diameter, 2.5 cm thick NaI crystal coupled to a photomultiplier. The measured full-width half maximum (FWHM) was less than 5.6 mm, and collimator detection efficiency was 44%. The ability to fabricate fine features in solid metal makes it possible to develop optimized designs for high-efficiency, focused gamma collimators for real-time intraoperative imaging applications.

Freeform étendue-preserving optics for light and color mixing

NASA Astrophysics Data System (ADS)

Sorgato, Simone; Mohedano, Rubén.; Chaves, Julio; Cvetkovic, Aleksandra; Hernández, Maikel; Benítez, Pablo; Miñano, Juan C.; Thienpont, Hugo; Duerr, Fabian

2015-09-01

Today's SSL illumination market shows a clear trend towards high flux packages with higher efficiency and higher CRI, realized by means of multiple color chips and phosphors. Such light sources require the optics to provide both near- and far-field color mixing. This design problem is particularly challenging for collimated luminaries, since traditional diffusers cannot be employed without enlarging the exit aperture and reducing brightness (so increasing étendue). Furthermore, diffusers compromise the light output ratio (efficiency) of the lamps to which they are applied. A solution, based on Köhler integration, consisting of a spherical cap comprising spherical microlenses on both its interior and exterior sides was presented in 2012. When placed on top of an inhomogeneous multichip Lambertian LED, this so-called Shell-Mixer creates a homogeneous (both spatially and angularly) virtual source, also Lambertian, where the images of the chips merge. The virtual source is located at the same position with essentially the same size of the original source. The diameter of this optics was 3 times that of the chip-array footprint. In this work, we present a new version of the Shell-Mixer, based on the Edge Ray Principle, where neither the overall shape of the cap nor the surfaces of the lenses are constrained to spheres or rotational Cartesian ovals. This new Shell- Mixer is freeform, only twice as large as the original chip-array and equals the original model in terms of brightness, color uniformity and efficiency.

Apparatus and method for detecting gamma radiation

DOEpatents

Sigg, R.A.

1994-12-13

A high efficiency radiation detector is disclosed for measuring X-ray and gamma radiation from small-volume, low-activity liquid samples with an overall uncertainty better than 0.7% (one sigma SD). The radiation detector includes a hyperpure germanium well detector, a collimator, and a reference source. The well detector monitors gamma radiation emitted by the reference source and a radioactive isotope or isotopes in a sample source. The radiation from the reference source is collimated to avoid attenuation of reference source gamma radiation by the sample. Signals from the well detector are processed and stored, and the stored data is analyzed to determine the radioactive isotope(s) content of the sample. Minor self-attenuation corrections are calculated from chemical composition data. 4 figures.

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.

On the use of an analytic source model for dose calculations in precision image-guided small animal radiotherapy.

PubMed

Granton, Patrick V; Verhaegen, Frank

2013-05-21

Precision image-guided small animal radiotherapy is rapidly advancing through the use of dedicated micro-irradiation devices. However, precise modeling of these devices in model-based dose-calculation algorithms such as Monte Carlo (MC) simulations continue to present challenges due to a combination of very small beams, low mechanical tolerances on beam collimation, positioning and long calculation times. The specific intent of this investigation is to introduce and demonstrate the viability of a fast analytical source model (AM) for use in either investigating improvements in collimator design or for use in faster dose calculations. MC models using BEAMnrc were developed for circular and square fields sizes from 1 to 25 mm in diameter (or side) that incorporated the intensity distribution of the focal spot modeled after an experimental pinhole image. These MC models were used to generate phase space files (PSFMC) at the exit of the collimators. An AM was developed that included the intensity distribution of the focal spot, a pre-calculated x-ray spectrum, and the collimator-specific entrance and exit apertures. The AM was used to generate photon fluence intensity distributions (ΦAM) and PSFAM containing photons radiating at angles according to the focal spot intensity distribution. MC dose calculations using DOSXYZnrc in a water and mouse phantom differing only by source used (PSFMC versus PSFAM) were found to agree within 7% and 4% for the smallest 1 and 2 mm collimator, respectively, and within 1% for all other field sizes based on depth dose profiles. PSF generation times were approximately 1200 times faster for the smallest beam and 19 times faster for the largest beam. The influence of the focal spot intensity distribution on output and on beam shape was quantified and found to play a significant role in calculated dose distributions. Beam profile differences due to collimator alignment were found in both small and large collimators sensitive to shifts of 1 mm with respect to the central axis.

Design of laser monitoring and sound localization system

NASA Astrophysics Data System (ADS)

Liu, Yu-long; Xu, Xi-ping; Dai, Yu-ming; Qiao, Yang

2013-08-01

In this paper, a novel design of laser monitoring and sound localization system is proposed. It utilizes laser to monitor and locate the position of the indoor conversation. In China most of the laser monitors no matter used in labor in an instrument uses photodiode or phototransistor as a detector at present. At the laser receivers of those facilities, light beams are adjusted to ensure that only part of the window in photodiodes or phototransistors received the beams. The reflection would deviate from its original path because of the vibration of the detected window, which would cause the changing of imaging spots in photodiode or phototransistor. However, such method is limited not only because it could bring in much stray light in receivers but also merely single output of photocurrent could be obtained. Therefore a new method based on quadrant detector is proposed. It utilizes the relation of the optical integral among quadrants to locate the position of imaging spots. This method could eliminate background disturbance and acquired two-dimensional spots vibrating data pacifically. The principle of this whole system could be described as follows. Collimated laser beams are reflected from vibrate-window caused by the vibration of sound source. Therefore reflected beams are modulated by vibration source. Such optical signals are collected by quadrant detectors and then are processed by photoelectric converters and corresponding circuits. Speech signals are eventually reconstructed. In addition, sound source localization is implemented by the means of detecting three different reflected light sources simultaneously. Indoor mathematical models based on the principle of Time Difference Of Arrival (TDOA) are established to calculate the twodimensional coordinate of sound source. Experiments showed that this system is able to monitor the indoor sound source beyond 15 meters with a high quality of speech reconstruction and to locate the sound source position accurately.

WE-DE-BRA-10: Development of a Novel Scanning Beam Low-Energy Intraoperative Radiation Therapy (SBIORT) System for Pancreatic Cancer

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

Wears, B; Mohiuddin, I; Flynn, R

2016-06-15

Purpose: Developing a compact collimator system and validating a 3D surface imaging module for a scanning beam low-energy x-ray radiation therapy (SBIORT) system that enables delivery of non-uniform radiation dose to targets with irregular shapes intraoperatively. Methods: SBIORT consists of a low energy x-ray source, a custom compact collimator module, a robotic arm, and a 3D surface imaging module. The 3D surface imaging system (structure sensor) is utilized for treatment planning and motion monitoring of the surgical cavity. SBIORT can deliver non-uniform dose distributions by dynamically moving the x-ray source assembly along optimal paths with various collimator apertures. The compactmore » collimator utilizes a dynamic shutter mechanism to form a variable square aperture. The accuracy and reproducibility of the collimator were evaluated using a high accuracy encoder and a high resolution camera platform. The dosimetrical characteristics of the collimator prototype were evaluated using EBT3 films with a Pantak Therapax unit. The accuracy and clinical feasibility of the 3D imaging system were evaluated using a phantom and a cadaver cavity. Results: The SBIORT collimator has a compact size: 66 mm diameter and 10 mm thickness with the maximum aperture of 20 mm. The mechanical experiment indicated the average accuracy of leaf position was 0.08 mm with a reproducibility of 0.25 mm at 95% confidence level. The dosimetry study indicated the collimator had a penumbra of 0.35 mm with a leaf transmission of 0.5%. 3D surface scans can be acquired in 5 seconds. The average difference between the acquired 3D surface and the ground truth is 1 mm with a standard deviation of 0.6 mm. Conclusion: This work demonstrates the feasibility of the compact collimator and 3D scanning system for the SBIORT. SBIORT is a way of delivering IORT with a compact system that requires minimum shielding of the procedure room. This research is supported by the University of Iowa Internal Funding Initiatives.« less

High energy collimating fine grids for HESP program

NASA Technical Reports Server (NTRS)

Eberhard, Carol D.; Frazier, Edward

1993-01-01

There is a need to develop fine pitch x-ray collimator grids as an enabling technology for planned future missions. The grids consist of an array of thin parallel strips of x-ray absorbing material, such as tungsten, with pitches ranging from 34 microns to 2.036 millimeters. The grids are the key components of a new class of spaceborne instruments known as 'x-ray modulation collimators.' These instruments are the first to produce images of celestial sources in the hard x-ray and gamma-ray spectral regions.

Hollow Electron Beam Collimation for HL-LHC - Effects on the Beam Core

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

Fitterer, M.; Stancari, G.; Valishev, A.

2017-06-13

Collimation with hollow electron beams is currently one of the most promising concepts for active halo control in the High Luminosity Large Hadron Collider (HL-LHC). To ensure the successful operation of the hollow beam collimator the unwanted effects on the beam core, which might arise from the operation with a pulsed electron beam, must be minimized. This paper gives a summary of the effect of hollow electron lenses on the beam core in terms of sources, provides estimates for HL-LHC and discusses the possible mitigation methods.

Proposed US Contributions to LOFT

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen

2013-01-01

Proposed US Enhancements include:Tantalum X -ray collimator, Additional ground station, Large Observatory for X-Ray Timing (LOFT) instrument team participation, US science support center & data archive, and Science enabled by US hardware. High-Z material with excellent stopping power. Fabricated using a combination of laser micromachining and chemical etching. Known technology capable of producing high-aspect ratio holes and large open fractions. Reduces LOFT LAD background by a factor of 3. Telemetry formats for LOFT based upon RXTE/EDS experience. Ground system software and strategies for WFM based upon RXTE/ASM automated pipeline software. MSFC engineering trade studies supporting the Ta collimator. Burst alert triggers based upon Fermi/GBM and HETE-2. Science Enhancements Enabled by US Hardware include: Tantalum collimator: Reduces background by factor of 3. Improves sensitivity to faint sources such as AGN. Eliminates contamination by bright/variable sources. outside the LAD field of view. US Ground Station: Enables continuous telemetry of all events from the WFM. Allows LAD to observe very bright >500 mCrab sources with full event resolution.

The analysis of optical-electro collimated light tube measurement system

NASA Astrophysics Data System (ADS)

Li, Zhenhui; Jiang, Tao; Cao, Guohua; Wang, Yanfei

2005-12-01

A new type of collimated light tube (CLT) is mentioned in this paper. The analysis and structure of CLT are described detail. The reticle and discrimination board are replaced by a optical-electro graphics generator, or DLP-Digital Light Processor. DLP gives all kinds of graphics controlled by computer, the lighting surface lies on the focus of the CLT. The rays of light pass through the CLT, and the tested products, the image of aim is received by variant focus objective CCD camera, the image can be processed by computer, then, some basic optical parameters will be obtained, such as optical aberration, image slope, etc. At the same time, motorized translation stage carry the DLP moving to simulate the limited distance. The grating ruler records the displacement of the DLP. The key technique is optical-electro auto-focus, the best imaging quality can be gotten by moving 6-D motorized positioning stage. Some principal questions can be solved in this device, for example, the aim generating, the structure of receiving system and optical matching.

High-efficiency directional backlight design for an automotive display.

PubMed

Chen, Bo-Tsuen; Pan, Jui-Wen

2018-06-01

We propose a high-efficiency directional backlight module (DBM) for automotive display applications. The DBM is composed of light sources, a light guide plate (LGP), and an optically patterned plate (OPP). The LGP has a collimator on the input surface that serves to control the angle of the light emitted to be in the horizontal direction. The OPP has an inverse prism to adjust the light emission angle in the vertical direction. The DBM has a simple structure and high optical efficiency. Compared with conventional backlight systems, the DBM has higher optical efficiency and a suitable viewing angle. This is an improvement in normalized on-axis luminous intensity of 2.6 times and a twofold improvement in optical efficiency. The viewing angles are 100° in the horizontal direction and 35° in the vertical direction. The angle of the half-luminous intensity is 72° in the horizontal direction and 20° in the vertical direction. The uniformity of the illuminance reaches 82%. The DBM is suitable for use in the center information displays of automobiles.

Recent developments in optical detection methods for microchip separations.

PubMed

Götz, Sebastian; Karst, Uwe

2007-01-01

This paper summarizes the features and performances of optical detection systems currently applied in order to monitor separations on microchip devices. Fluorescence detection, which delivers very high sensitivity and selectivity, is still the most widely applied method of detection. Instruments utilizing laser-induced fluorescence (LIF) and lamp-based fluorescence along with recent applications of light-emitting diodes (LED) as excitation sources are also covered in this paper. Since chemiluminescence detection can be achieved using extremely simple devices which no longer require light sources and optical components for focusing and collimation, interesting approaches based on this technique are presented, too. Although UV/vis absorbance is a detection method that is commonly used in standard desktop electrophoresis and liquid chromatography instruments, it has not yet reached the same level of popularity for microchip applications. Current applications of UV/vis absorbance detection to microchip separations and innovative approaches that increase sensitivity are described. This article, which contains 85 references, focuses on developments and applications published within the last three years, points out exciting new approaches, and provides future perspectives on this field.

Partial polarization: a comprehensive student exercise

NASA Astrophysics Data System (ADS)

Topasna, Gregory A.; Topasna, Daniela M.

2015-10-01

We present a comprehensive student exercise in partial polarization. Students are first introduced to the concept of partial polarization using Fresnel Equations. Next, MATHCAD is used to compute and graph the reflectance for dielectrics materials. The students then design and construct a simple, easy to use collimated light source for their experiment, which is performed on an optical breadboard using optical components typically found in an optics lab above the introductory level. The students obtain reflection data that is compared with their model by a nonlinear least square fit using EXCEL. Sources of error and uncertainty are discussed and students present a final written report. In this one exercise students learn how an experiment is constructed "from the ground up". They gain practical experience on data modeling and analysis, working with optical equipment, machining and construction, and preparing a final presentation.

Vehicle and cargo inspection system

NASA Astrophysics Data System (ADS)

Verbinski, Victor V.; Orphan, Victor J.

1997-02-01

Vehicle and Cargo Inspection System (VACIS) is comprised of a 1 Curie 137Cs gamma-ray source in a shield and collimator which produces a fan-shaped beam designed to intercept a vertical array of gama-ray detectors contained in a tower structure. The source and detector modules straddle the vehicle or container being inspected and are mounted on self-propelled trolleys which travel in synchronization along two parallel tracks covering the length of the scanned object. The signals from the gamma-ray detector array are processed and displayed so as to produce a 2D gamma-radiographic image of the object. Testing of the system on a variety of empty and lightly-loaded vehicles and containers has demonstrated the effectiveness of VACIS in detecting hidden contraband. For example, a small sample of cocaine only 1.5 inches thick was readily detected in a container.

A radio counterpart to a neutron star merger.

PubMed

Hallinan, G; Corsi, A; Mooley, K P; Hotokezaka, K; Nakar, E; Kasliwal, M M; Kaplan, D L; Frail, D A; Myers, S T; Murphy, T; De, K; Dobie, D; Allison, J R; Bannister, K W; Bhalerao, V; Chandra, P; Clarke, T E; Giacintucci, S; Ho, A Y Q; Horesh, A; Kassim, N E; Kulkarni, S R; Lenc, E; Lockman, F J; Lynch, C; Nichols, D; Nissanke, S; Palliyaguru, N; Peters, W M; Piran, T; Rana, J; Sadler, E M; Singer, L P

2017-12-22

Gravitational waves have been detected from a binary neutron star merger event, GW170817. The detection of electromagnetic radiation from the same source has shown that the merger occurred in the outskirts of the galaxy NGC 4993, at a distance of 40 megaparsecs from Earth. We report the detection of a counterpart radio source that appears 16 days after the event, allowing us to diagnose the energetics and environment of the merger. The observed radio emission can be explained by either a collimated ultrarelativistic jet, viewed off-axis, or a cocoon of mildly relativistic ejecta. Within 100 days of the merger, the radio light curves will enable observers to distinguish between these models, and the angular velocity and geometry of the debris will be directly measurable by very long baseline interferometry. Copyright © 2017, American Association for the Advancement of Science.

COLLIMATION AND SCATTERING OF THE ACTIVE GALACTIC NUCLEUS EMISSION IN THE SOMBRERO GALAXY

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

Menezes, R. B.; Steiner, J. E.; Ricci, T. V., E-mail: robertobm@astro.iag.usp.br

2013-03-10

We present an analysis of a data cube of the central region of M104, the Sombrero galaxy, obtained with the GMOS-IFU of the Gemini-South telescope, and report the discovery of collimation and scattering of the active galactic nucleus (AGN) emission in the circumnuclear region of this galaxy. Analysis with PCA Tomography and spectral synthesis revealed the existence of collimation and scattering of the AGN featureless continuum and also of a broad component of the H{alpha} emission line. The collimation and scattering of this broad H{alpha} component was also revealed by fitting the [N II] {lambda}{lambda}6548, 6583 and H{alpha} emission linesmore » as a sum of Gaussian functions. The spectral synthesis, together with a V-I image obtained with the Hubble Space Telescope, showed the existence of circumnuclear dust, which may cause the light scattering. We also identify a dusty feature that may be interpreted as a torus/disk structure. The existence of two opposite regions with featureless continuum (P.A. = -18 Degree-Sign {+-} 13 Degree-Sign and P.A. = 162 Degree-Sign {+-} 13 Degree-Sign ) along a direction perpendicular to the torus/disk (P.A. = 72 Degree-Sign {+-} 14 Degree-Sign ) suggests that this structure is approximately edge-on and collimates the AGN emission. The edge-on torus/disk also hides the broad-line region. The proposed scenario is compatible with the unified model and explains why only a weak broad component of the H{alpha} emission line is visible and also why many previous studies detected no broad H{alpha}. The technique used here proved to be an efficient method not only for detecting scattered light, but also for testing the unified model in low-luminosity AGNs.« less

Protocol for Determining Ultraviolet Light Emitting Diode (UV-LED) Fluence for Microbial Inactivation Studies.

PubMed

Kheyrandish, Ataollah; Mohseni, Madjid; Taghipour, Fariborz

2018-06-15

Determining fluence is essential to derive the inactivation kinetics of microorganisms and to design ultraviolet (UV) reactors for water disinfection. UV light emitting diodes (UV-LEDs) are emerging UV sources with various advantages compared to conventional UV lamps. Unlike conventional mercury lamps, no standard method is available to determine the average fluence of the UV-LEDs, and conventional methods used to determine the fluence for UV mercury lamps are not applicable to UV-LEDs due to the relatively low power output, polychromatic wavelength, and specific radiation profile of UV-LEDs. In this study, a method was developed to determine the average fluence inside a water suspension in a UV-LED experimental setup. In this method, the average fluence was estimated by measuring the irradiance at a few points for a collimated and uniform radiation on a Petri dish surface. New correction parameters were defined and proposed, and several of the existing parameters for determining the fluence of the UV mercury lamp apparatus were revised to measure and quantify the collimation and uniformity of the radiation. To study the effect of polychromatic output and radiation profile of the UV-LEDs, two UV-LEDs with peak wavelengths of 262 and 275 nm and different radiation profiles were selected as the representatives of typical UV-LEDs applied to microbial inactivation. The proper setup configuration for microorganism inactivation studies was also determined based on the defined correction factors.

Wide-Field Optic for Autonomous Acquisition of Laser Link

NASA Technical Reports Server (NTRS)

Page, Norman A.; Charles, Jeffrey R.; Biswas, Abhijit

2011-01-01

An innovation reported in Two-Camera Acquisition and Tracking of a Flying Target, NASA Tech Briefs, Vol. 32, No. 8 (August 2008), p. 20, used a commercial fish-eye lens and an electronic imaging camera for initially locating objects with subsequent handover to an actuated narrow-field camera. But this operated against a dark-sky background. An improved solution involves an optical design based on custom optical components for the wide-field optical system that directly addresses the key limitations in acquiring a laser signal from a moving source such as an aircraft or a spacecraft. The first challenge was to increase the light collection entrance aperture diameter, which was approximately 1 mm in the first prototype. The new design presented here increases this entrance aperture diameter to 4.2 mm, which is equivalent to a more than 16 times larger collection area. One of the trades made in realizing this improvement was to restrict the field-of-view to +80 deg. elevation and 360 azimuth. This trade stems from practical considerations where laser beam propagation over the excessively high air mass, which is in the line of sight (LOS) at low elevation angles, results in vulnerability to severe atmospheric turbulence and attenuation. An additional benefit of the new design is that the large entrance aperture is maintained even at large off-axis angles when the optic is pointed at zenith. The second critical limitation for implementing spectral filtering in the design was tackled by collimating the light prior to focusing it onto the focal plane. This allows the placement of the narrow spectral filter in the collimated portion of the beam. For the narrow band spectral filter to function properly, it is necessary to adequately control the range of incident angles at which received light intercepts the filter. When this angle is restricted via collimation, narrower spectral filtering can be implemented. The collimated beam (and the filter) must be relatively large to reduce the incident angle down to only a few degrees. In the presented embodiment, the filter diameter is more than ten times larger than the entrance aperture. Specifically, the filter has a clear aperture of about 51 mm. The optical design is refractive, and is comprised of nine custom refractive elements and an interference filter. The restricted maximum angle through the narrow-band filter ensures the efficient use of a 2-nm noise equivalent bandwidth spectral width optical filter at low elevation angles (where the range is longest), at the expense of less efficiency for high elevations, which can be tolerated because the range at high elevation angles is shorter. The image circle is 12 mm in diameter, mapped to 80 x 360 of sky, centered on the zenith.

Feasibility of Shipboard Laser-Attenuation Measurements With a Portable Transmissometer.

DTIC Science & Technology

1979-02-26

Aerosol Extinction The transmittance of monochromatic, single-scattered light through aerosol is given by - S the Bouguer .-Beer law, (1) o where is the...of Applicability of the Bouguer Law in Scattering Media for Collimated Light Beams,” (English trans.), Izu. Atm. and Oceanic Phys. 3, 724-732 (1967

Assessing the effectiveness of low-pressure ultraviolet light for inactivating Mycobacterium avium complex (MAC) micro-organisms

EPA Science Inventory

Aims: To assess low-pressure ultraviolet light (LP-UV) inactivation kinetics of Mycobacterium avium complex (MAC) strains in a water matrix using collimated beam apparatus. Methods and Results: Strains of M. avium (n = 3) and Mycobacterium intracellulare (n = 2) were exposed t...

Development of gamma-photon/Cerenkov-light hybrid system for simultaneous imaging of I-131 radionuclide

NASA Astrophysics Data System (ADS)

Yamamoto, Seiichi; Suzuki, Mayumi; Kato, Katsuhiko; Watabe, Tadashi; Ikeda, Hayato; Kanai, Yasukazu; Ogata, Yoshimune; Hatazawa, Jun

2016-09-01

Although iodine 131 (I-131) is used for radionuclide therapy, high resolution images are difficult to obtain with conventional gamma cameras because of the high energy of I-131 gamma photons (364 keV). Cerenkov-light imaging is a possible method for beta emitting radionuclides, and I-131 (606 MeV maximum beta energy) is a candidate to obtain high resolution images. We developed a high energy gamma camera system for I-131 radionuclide and combined it with a Cerenkov-light imaging system to form a gamma-photon/Cerenkov-light hybrid imaging system to compare the simultaneously measured images of these two modalities. The high energy gamma imaging detector used 0.85-mm×0.85-mm×10-mm thick GAGG scintillator pixels arranged in a 44×44 matrix with a 0.1-mm thick reflector and optical coupled to a Hamamatsu 2 in. square position sensitive photomultiplier tube (PSPMT: H12700 MOD). The gamma imaging detector was encased in a 2 cm thick tungsten shield, and a pinhole collimator was mounted on its top to form a gamma camera system. The Cerenkov-light imaging system was made of a high sensitivity cooled CCD camera. The Cerenkov-light imaging system was combined with the gamma camera using optical mirrors to image the same area of the subject. With this configuration, we simultaneously imaged the gamma photons and the Cerenkov-light from I-131 in the subjects. The spatial resolution and sensitivity of the gamma camera system for I-131 were respectively 3 mm FWHM and 10 cps/MBq for the high sensitivity collimator at 10 cm from the collimator surface. The spatial resolution of the Cerenkov-light imaging system was 0.64 mm FWHM at 10 cm from the system surface. Thyroid phantom and rat images were successfully obtained with the developed gamma-photon/Cerenkov-light hybrid imaging system, allowing direct comparison of these two modalities. Our developed gamma-photon/Cerenkov-light hybrid imaging system will be useful to evaluate the advantages and disadvantages of these two modalities.

High spatial resolution X-ray and gamma ray imaging system using diffraction crystals

DOEpatents

Smither, Robert K [Hinsdale, IL

2011-05-17

A method and a device for high spatial resolution imaging of a plurality of sources of x-ray and gamma-ray radiation are provided. The device comprises a plurality of arrays, with each array comprising a plurality of elements comprising a first collimator, a diffracting crystal, a second collimator, and a detector.

Calibration techniques and results in the soft X-ray and extreme ultraviolet for components of the Extreme Ultraviolet Explorer Satellite

NASA Technical Reports Server (NTRS)

Malina, Roger F.; Jelinsky, Patrick; Bowyer, Stuart

1986-01-01

The calibration facilities and techniques for the Extreme Ultraviolet Explorer (EUVE) from 44 to 2500 A are described. Key elements include newly designed radiation sources and a collimated monochromatic EUV beam. Sample results for the calibration of the EUVE filters, detectors, gratings, collimators, and optics are summarized.

Demonstration of Laser Plasma X-Ray Source with X-Ray Collimator Final Report CRADA No. TC-1564-99

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

Lane, S. M.; Forber, R. A.

2017-09-28

This collaborative effort between the University of California, Lawrence Livermore National Laboratory (LLNL) and JMAR Research, Inc. (JRI), was to demonstrate that LLNL x-ray collimators can effectively increase the wafer throughput of JRI's laser based x-ray lithography systems. The technical objectives were expected to be achieved by completion of the following tasks, which are separated into two task lists by funding source. The organization (LLNL or JMAR) having primary responsibility is given parenthetically for each task.

High-power LED package requirements

NASA Astrophysics Data System (ADS)

Wall, Frank; Martin, Paul S.; Harbers, Gerard

2004-01-01

Power LEDs have evolved from simple indicators into illumination devices. For general lighting applications, where the objective is to light up an area, white LED arrays have been utilized to serve that function. Cost constraints will soon drive the industry to provide a discrete lighting solution. Early on, that will mean increasing the power densities while quantum efficiencies are addressed. For applications such as automotive headlamps & projection, where light needs to be tightly collimated, or controlled, arrays of die or LEDs will not be able to satisfy the requirements & limitations defined by etendue. Ultimately, whether a luminaire requires a small source with high luminance, or light spread over a general area, economics will force the evolution of the illumination LED into a compact discrete high power package. How the customer interfaces with this new package should be an important element considered early on in the design cycle. If an LED footprint of adequate size is not provided, it may prove impossible for the customer, or end user, to get rid of the heat in a manner sufficient to prevent premature LED light output degradation. Therefore it is critical, for maintaining expected LED lifetime & light output, that thermal performance parameters be defined, by design, at the system level, which includes heat sinking methods & interface materials or methdology.

The HEAO-1 Scanning Modulation Collimator

NASA Astrophysics Data System (ADS)

Schwartz, Daniel A.

2013-01-01

My niche on this panel seems to be the High Energy Astronomy Observatory-1 Scanning Modulation Collimator experiment. Our chair, Hale Bradt, and the late Herb Gursky each proposed a different version modulation collimator, which was condensed by NASA via "forced marriage," to the SMC. I worked as Project Scientist under Herb, later inheriting the PI role. The MIT Project Scientist, the late Rodger Doxsey, and I were told "this is your experiment," and "we are a seamless team regardless of institution." Rodger and I were young enough to believe this, and we made it happen (and not always with the best results vis a vis higher internal management). I was never interested in astronomy, and allegedly am still not. Why do an astro-metrical job of measuring and reporting the coordinates of X-ray sources? In fact we participated widely in the identification of the sources with astronomical object, and making each paper a discussion of the physics of the emission. An enjoyable way to learn some astronomy. The stated purpose of the Gursky/Bradt experiment was to enable optical identifications so that more detailed study could be done. I remember meeting with John Whelan to discuss his collaboration in making the optical identifications. He said he only wanted to study sources after they were identified. For many milliseconds I became very angry - "who is going to to the work to MAKE those identifications," but luckily before speaking I realized how satisfying it was that astronomers indeed wanted to study X-ray sources in other wavebands. The second biggest excitement in the HEAO-1 program was the "glitches" that appeared in the gyro data during final functional testing. This took some high-powered politics by all the PI's to convince MSFC to delay for 4 months, replacing the "funny" unit with one from HEAO-2 (Einstein) and later refurbishing that unit. Third biggest excitement was when a computer failed and final checkout during countdown at the Cape was done by looking at lights on gound support equipment. Biggest excitement was cancellation of the entire HEAO program late on a Friday afternoon in January 1971. It took a year of study and re-configuration as a series of 3, instead of 4, satellites to reinstate.

Collimation, Acceleration, and Recollimation Shock in the Jet of Gamma-Ray Emitting Radio-loud Narrow-line Seyfert 1 Galaxy 1H0323+342

NASA Astrophysics Data System (ADS)

Hada, Kazuhiro; Doi, Akihiro; Wajima, Kiyoaki; D’Ammando, Filippo; Orienti, Monica; Giroletti, Marcello; Giovannini, Gabriele; Nakamura, Masanori; Asada, Keiichi

2018-06-01

We investigated the detailed radio structure of the jet of 1H 0323+342 using high-resolution multifrequency Very Long Baseline Array observations. This source is known as the nearest γ-ray emitting radio-loud narrow-line Seyfert 1 (NLS1) galaxy. We discovered that the morphology of the inner jet is well characterized by a parabolic shape, indicating that the jet is continuously collimated near the jet base. On the other hand, we found that the jet expands more rapidly at larger scales, resulting in a conical shape. The location of the “collimation break” is coincident with a bright quasi-stationary feature at 7 mas from core (corresponding to a deprojected distance on the order of ∼100 pc), where the jet width locally contracts together with highly polarized signals, suggesting a recollimation shock. We found that the collimation region is coincident with the region where the jet speed gradually accelerates, suggesting a coexistence of the jet acceleration and collimation zone, ending up with the recollimation shock, which could be a potential site of high-energy γ-ray flares detected by the Fermi-LAT. Remarkably, these observational features of the 1H 0323+342 jet are overall very similar to those of the nearby radio galaxy M87 and HST-1 as well as some blazars, suggesting that a common jet formation mechanism might be at work. Based on the similarity of the jet profile of the two sources, we also briefly discuss the mass of the central black hole of 1H 0323+342, which is also still highly controversial in this source and NLS1s in general.

Relationship between the Kubelka-Munk scattering and radiative transfer coefficients.

PubMed

Thennadil, Suresh N

2008-07-01

The relationship between the Kubelka-Munk (K-M) and the transport scattering coefficient is obtained through a semi-empirical approach. This approach gives the same result as that given by Gate [Appl. Opt.13, 236 (1974)] when the incident beam is diffuse. This result and those given by Star et al. [Phys. Med. Biol.33, 437 (1988)] and Brinkworth [Appl. Opt.11, 1434 (1972)] are compared with the exact solution of the radiative transfer equation over a large range of optical properties. It is found that the latter expressions, which include an absorption component, do not give accurate results over the range considered. Using the semi-empirical approach, the relationship between the K-M and the transport scattering coefficient is derived for the case where the incident light is collimated. It is shown that although the K-M equation is derived based on diffuse incident light, it can also represent very well the reflectance from a slab of infinite thickness when the incident light is collimated. However, in this case the relationship between the coefficients has to include a function that is dependent on the anisotropy factor. Analysis indicates that the K-M transform achieves the objective of obtaining a measure that gives the ratio of absorption to scattering effects for both diffuse and collimated incident beams over a large range of optical properties.

Simultaneous calculation of three optical surfaces in the 3D SMS freeform RXI optic

NASA Astrophysics Data System (ADS)

Sorgato, Simone; Chaves, Julio; Mohedano, Rubén.; Hernández, Maikel; Blen, José; Benitez, Pablo; Miñano, Juan C.; Grabovickic, Dejan; Thienpont, Hugo; Duerr, Fabian

2016-09-01

The Freeform RXI collimator is a remarkable example of advanced nonimaging device designed with the 3D Simultaneous Multiple Surface (SMS) Method. In the original design, two (the front refracting surface and the back mirror) of the three optical surfaces of the RXI are calculated simultaneously and one (the cavity surrounding the source) is fixed by the designer. As a result, the RXI perfectly couples two input wavefronts (coming from the edges of the extended LED source) with two output wavefronts (defining the output beam). This allows for LED lamps able to produce controlled intensity distributions, which can and have been successfully applied to demanding applications like high- and low-beams for Automotive Lighting. Nevertheless, current trends in this field are moving towards smaller headlamps with more shape constraints driven by car design. We present an improved version of the 3D RXI in which also the cavity surface is computed during the design, so that there are three freeform surfaces calculated simultaneously and an additional degree of freedom for controlling the light emission: now the RXI can perfectly couple three input wavefronts with three output wavefronts. The enhanced control over ray beams allows for improved light homogeneity and better pattern definition.

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.

Characterization of diffraction gratings scattering in uv and ir for space applications

NASA Astrophysics Data System (ADS)

Achour, Sakina; Kuperman-Le Bihan, Quentin; Etcheto, Pierre

2017-09-01

The use of Bidirectional Scatter Distribution Function (BSDF) in space industry and especially when designing telescopes is a key feature. Indeed when speaking about space industry, one can immediately think about stray light issues. Those important phenomena are directly linked to light scattering. Standard BSDF measurement goniophotometers often have a resolution of about 0.1° and are mainly working in or close to the visible spectrum. This resolution is far too loose to characterize ultra-polished surfaces. Besides, wavelength range of BSDF measurements for space projects needs to be done far from visible range. How can we measure BSDF of ultra-polished surfaces and diffraction gratings in the UV and IR range with high resolution? We worked on developing a new goniophometer bench in order to be able to characterize scattering of ultra-polished surfaces and diffraction gratings used in everyday space applications. This ten meters long bench was developed using a collimated beam approach as opposed to goniophotometer using focused beam. Sources used for IR characterization were CO2 (10.6?m) and Helium Neon (3.39?m) lasers. Regarding UV sources, a collimated and spatially filtered UV LED was used. The detection was ensure by a photomultiplier coupled with synchronous detection as well as a MCT InSb detector. The so-built BSDF measurement instrument allowed us to measure BSDF of ultra-polished surfaces as well as diffraction gratings with an angular resolution of 0.02° and a dynamic of 1013 in the visible range. In IR as well as in UV we manage to get 109 with same angular resolution of 0.02°. The 1m arm and translation stages allows us to measure samples up to 200mm. Thanks to such a device allowing ultra-polished materials as well as diffraction gratings scattering characterization, it is possible to implement those BSDF measurements into simulation software and predict stray light issues. This is a big help for space industry engineers to apprehend stray light due to surface finishes and to delete those effects before the whole project is done. We are now thinking of possible improvement on our optical bench to try to get dynamic in IR and UV similar to what we have in visible range (e.g. 1013).

Observation of valley-dependent beams in photonic graphene.

PubMed

Deng, Fusheng; Sun, Yong; Wang, Xiao; Xue, Rui; Li, Yuan; Jiang, Haitao; Shi, Yunlong; Chang, Kai; Chen, Hong

2014-09-22

Valley-dependent propagation of light in an artificial photonic hexagonal lattice, akin to electrons in graphene, is investigated in microwave regime. Both numerical and experimental results show that the valley degeneracy in the photonic graphene is broken when the frequency is away from the Dirac point. The peculiar anisotropic wave transport property due to distinct valleys is analyzed using the equifrequency contours. More interestingly, the valley-dependent self-collimation and beam splitting phenomena are experimentally demonstrated with the armchair and zigzag interfaces, respectively. Our results confirm that there are two inequivalent Dirac points that lead to two distinct valleys in photonic graphene, which could be used to control the flow of light and might be used to carry information in valley polarized beam splitter, collimator or guiding device.

Three-dimensional collimation of in-plane-propagating light using silicon micromachined mirror

NASA Astrophysics Data System (ADS)

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

2014-03-01

We demonstrate light collimation of single-mode optical fibers using deeply-etched three-dimensional curved micromirror on silicon chip. The three-dimensional curvature of the mirror is controlled by a process combining deep reactive ion etching and isotropic etching of silicon. The produced surface is astigmatic with out-of-plane radius of curvature that is about one half the in-plane radius of curvature. Having a 300-μm in-plane radius and incident beam inplane inclined with an angle of 45 degrees with respect to the principal axis, the reflected beam is maintained stigmatic with about 4.25 times reduction in the beam expansion angle in free space and about 12-dB reduction in propagation losses, when received by a limited-aperture detector.

A remote acceptance probe and illumination configuration for spectral assessment of internal attributes of intact fruit

NASA Astrophysics Data System (ADS)

Greensill, Colin V.; Walsh, Kerry B.

2000-12-01

Near infrared spectroscopy can be employed in the non-invasive assessment of intact fruit for eating quality attributes such as soluble solid content (SSC). Rapid sorting is dependent on a suitable non-contact geometry of fruit, light source and detector assembly, optimized for a given fruit commodity. An optical system was designed with reference to distribution of SSC and light penetration into rockmelon fruit. SSC of mesocarp tissue was not significantly different over the greater part of the proximal-distal axis of the fruit, particularly in the vicinity of the fruit equator. There was also no consistent variation in SSC of mesocarp tissue with respect to radial position of sampling. Mesocarp SSC was higher (~3% w/v) closer to the seed cavity. The optical sampling system was therefore designed to assess an equatorial position on the fruit. Light penetrating a rockmelon fruit was empirically assessed to be diffuse at a depth of <15 mm from the fruit surface. Signal decreased in an exponential proportionality with depth into the fruit, but was still detectable at depths in excess of the seed cavity of rockmelons. A partial transmittance optical design was employed, with a collimated light source interrupted by a central light stop, and a detector viewing the shadowed region of the sample. This system did not physically contact the sample. It was compared to a system with a light excluding `contacting' shroud between the detector and the fruit surface. The performance of calibrations generated using the non-contact configuration was not significantly different than for the configuration requiring contact.

High stability wavefront reference source

DOEpatents

Feldman, M.; Mockler, D.J.

1994-05-03

A thermally and mechanically stable wavefront reference source which produces a collimated output laser beam is disclosed. The output beam comprises substantially planar reference wavefronts which are useful for aligning and testing optical interferometers. The invention receives coherent radiation from an input optical fiber, directs a diverging input beam of the coherent radiation to a beam folding mirror (to produce a reflected diverging beam), and collimates the reflected diverging beam using a collimating lens. In a class of preferred embodiments, the invention includes a thermally and mechanically stable frame comprising rod members connected between a front end plate and a back end plate. The beam folding mirror is mounted on the back end plate, and the collimating lens mounted to the rods between the end plates. The end plates and rods are preferably made of thermally stable metal alloy. Preferably, the input optical fiber is a single mode fiber coupled to an input end of a second single mode optical fiber that is wound around a mandrel fixedly attached to the frame of the apparatus. The output end of the second fiber is cleaved so as to be optically flat, so that the input beam emerging therefrom is a nearly perfect diverging spherical wave. 7 figures.

High stability wavefront reference source

DOEpatents

Feldman, Mark; Mockler, Daniel J.

1994-01-01

A thermally and mechanically stable wavefront reference source which produces a collimated output laser beam. The output beam comprises substantially planar reference wavefronts which are useful for aligning and testing optical interferometers. The invention receives coherent radiation from an input optical fiber, directs a diverging input beam of the coherent radiation to a beam folding mirror (to produce a reflected diverging beam), and collimates the reflected diverging beam using a collimating lens. In a class of preferred embodiments, the invention includes a thermally and mechanically stable frame comprising rod members connected between a front end plate and a back end plate. The beam folding mirror is mounted on the back end plate, and the collimating lens mounted to the rods between the end plates. The end plates and rods are preferably made of thermally stable metal alloy. Preferably, the input optical fiber is a single mode fiber coupled to an input end of a second single mode optical fiber that is wound around a mandrel fixedly attached to the frame of the apparatus. The output end of the second fiber is cleaved so as to be optically flat, so that the input beam emerging therefrom is a nearly perfect diverging spherical wave.

Reshaping Light-Emitting Diodes To Increase External Efficiency

NASA Technical Reports Server (NTRS)

Rogowski, Robert; Egalon, Claudio

1995-01-01

Light-emitting diodes (LEDs) reshaped, according to proposal, increasing amount of light emitted by decreasing fraction of light trapped via total internal reflection. Results in greater luminous output power for same electrical input power; greater external efficiency. Furthermore, light emitted by reshaped LEDs more nearly collimated (less diffuse). Concept potentially advantageous for conventional red-emitting LEDs. More advantageous for new "blue" LEDs, because luminous outputs and efficiencies of these devices very low. Another advantage, proposed conical shapes achieved relatively easily by chemical etching of semiconductor surfaces.

Development of a hemispherical rotational modulation collimator system for imaging spatial distribution of radiation sources

NASA Astrophysics Data System (ADS)

Na, M.; Lee, S.; Kim, G.; Kim, H. S.; Rho, J.; Ok, J. G.

2017-12-01

Detecting and mapping the spatial distribution of radioactive materials is of great importance for environmental and security issues. We design and present a novel hemispherical rotational modulation collimator (H-RMC) system which can visualize the location of the radiation source by collecting signals from incident rays that go through collimator masks. The H-RMC system comprises a servo motor-controlled rotating module and a hollow heavy-metallic hemisphere with slits/slats equally spaced with the same angle subtended from the main axis. In addition, we also designed an auxiliary instrument to test the imaging performance of the H-RMC system, comprising a high-precision x- and y-axis staging station on which one can mount radiation sources of various shapes. We fabricated the H-RMC system which can be operated in a fully-automated fashion through the computer-based controller, and verify the accuracy and reproducibility of the system by measuring the rotational and linear positions with respect to the programmed values. Our H-RMC system may provide a pivotal tool for spatial radiation imaging with high reliability and accuracy.

SU-E-T-366: Estimation of Whole Body Dose From Cranial Irradiation From C and Perfexion Series Gamma Knife Units

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

Srivastava, S; Indiana University School of Medicine, Indianapolis, IN, University Hospitals Case Medical Center, Cleaveland, OH; Andersen, A

2015-06-15

Purpose: The Leksell Gamma Knife (GK) B & C series contains 201 Cobalt-60 sources with a helmet. The new model, Perfexion uses 192 Cobalt-60 sources without a helmet; using IRIS system for collimation and stereotactic guidance to deliver SRS to brain tumors. Relative dose to extracranial organs at risk (OARs) is measured in phantom in this study for Perfexion and C-series GK. Materials & Methods: Measurements were performed in a Rando anthropomorphic phantom on both systems using a large ion chamber (Keithley-175) for each collimator. The Keithley-175 cc ion chamber was sandwiched between phantom slices at various locations in themore » phantom to correspond to different extracranial OARs (thyroid, heart, kidney, ovary and testis, etc.) The dose measurement was repeated with OSL detectors for each position and collimator. Results: A large variation is observed in the normalized dose between these two systems. The dose beyond the housing falls off exponentially for Perfexion. Dose beyond the C-series GK housing falls off exponentially from 0–20cm then remains relatively constant from 20–40cm and again falls off with distance but less rapidly. The variation of extracranial dose with distance for each collimator is found to be parallel to each other for both systems. Conclusion: Whole body dose is found to vary significantly between these systems. It is important to measure the extracranial dose, especially for young patients. It is estimated that dose falls off exponentially from the GK housing and is about 1% for large collimators at 75 cm. The dose is two-orders of magnitude smaller for the 4mm collimator. However, this small dose for patient may be significant radiologically.« less

A Monte Carlo study on the performance evaluation of a parallel hole collimator for a HiReSPECT: A dedicated small-animal SPECT.

PubMed

Abbaspour, Samira; Tanha, Kaveh; Mahmoudian, Babak; Assadi, Majid; Pirayesh Islamian, Jalil

2018-04-22

Collimator geometry has an important contribution on the image quality in SPECT imaging. The purpose of this study was to investigate the effect of parallel hole collimator hole-size on the functional parameters (including the spatial resolution and sensitivity) and the image quality of a HiReSPECT imaging system using SIMIND Monte Carlo program. To find a proper trade-off between the sensitivity and spatial resolution, the collimator with hole diameter ranges of 0.3-1.5 mm (in steps of 0.3 mm) were used with a fixed septal and hole thickness values (0.2 mm and 34 mm, respectively). Lead, Gold, and Tungsten as the LEHR collimator material were also investigated. The results on a 99m Tc point source scanning with the experimental and also simulated systems were matched to validate the simulated imaging system. The results on the simulation showed that decreasing the collimator hole size, especially in the Gold collimator, improved the spatial resolution to 18% and 3.2% compared to the Lead and the Tungsten, respectively. Meanwhile, the Lead collimator provided a good sensitivity in about of 7% and 8% better than that of Tungsten and Gold, respectively. Overall, the spatial resolution and sensitivity showed small differences among the three types of collimator materials assayed within the defined energy. By increasing the hole size, the Gold collimator produced lower scatter and penetration fractions than Tungsten and Lead collimator. The minimum detectable size of hot rods in micro-Jaszczak phantom on the iterative maximum-likelihood expectation maximization (MLEM) reconstructed images, were determined in the sectors of 1.6, 1.8, 2.0, 2.4 and 2.6 mm for scanning with the collimators in hole sizes of 0.3, 0.6, 0.9, 1.2 and 1.5 mm at a 5 cm distance from the phantom. The Gold collimator with hole size of 0.3 mm provided a better image quality with the HiReSPECT imaging. Copyright © 2018 Elsevier Ltd. All rights reserved.

Design a freeform microlens array module for any arbitrary-shape collimated beam shaping and color mixing

NASA Astrophysics Data System (ADS)

Chen, Enguo; Wu, Rengmao; Guo, Tailiang

2014-06-01

Collimated beam shaping with freeform surface usually employs a predefined mapping to tailor one or multiple freeform surfaces. Limitation on those designs is that the source, the freeform optics and the target are in fixed one-to-one correspondence with each other. To overcome this drawback, this paper presents a kind of freeform microlens array module integrated with an ultra-thin freeform microlens array and a condenser lens to reshape any arbitrary-shape collimated beam into a prescribed uniform rectangular illumination and achieve color mixing. The design theory is explicitly given, and some key issues are addressed. Several different application examples are given, and the target is obtained with high uniformity and energy efficiency. This freeform microlens array module, which shows better flexibility and practicality than the regular designs, can be used not only to reshape any arbitrary-shape collimated beam (or a collimated beam integrated with several sub-collimated beams), but also most importantly to achieve color mixing. With excellent optical performance and ultra-compact volume, this optical module together with the design theory can be further introduced into other applications and will have a huge market potential in the near future.

Neutron source

DOEpatents

Cason, J.L. Jr.; Shaw, C.B.

1975-10-21

A neutron source which is particularly useful for neutron radiography consists of a vessel containing a moderating media of relatively low moderating ratio, a flux trap including a moderating media of relatively high moderating ratio at the center of the vessel, a shell of depleted uranium dioxide surrounding the moderating media of relatively high moderating ratio, a plurality of guide tubes each containing a movable source of neutrons surrounding the flux trap, a neutron shield surrounding one part of each guide tube, and at least one collimator extending from the flux trap to the exterior of the neutron source. The shell of depleted uranium dioxide has a window provided with depleted uranium dioxide shutters for each collimator. Reflectors are provided above and below the flux trap and on the guide tubes away from the flux trap.

APPARATUS FOR PRODUCING IONS OF VAPORIZABLE MATERIALS

DOEpatents

Wright, B.T.

1958-01-28

a uniform and copious supply of ions. The source comprises a hollow arc- block and means for establishing a magnetic field through the arc-block. Vaporization of the material to be ionized is produced by an electric heated filament. The arc producing structure within the arc-block consists of a cathode disposed between a pair of collimating electrodes along with an anode adjacent each collimating electrode on the side opposite the cathode. A positive potential applied to the anodes and collimating electrodes, with respect to the cathode, and the magnetic field act to accelerate the electrons from the cathode through a slit in each collimating clectrode towards the respective anode. In this manner a pair of collinear arc discharges are produced in the gas region which can be tapped for an abundant supply of ions of the material being analyzed.

Experimental results from magnetized-jet experiments executed at the Jupiter Laser Facility

NASA Astrophysics Data System (ADS)

Manuel, M. J.-E.; Kuranz, C. C.; Rasmus, A. M.; Klein, S. R.; MacDonald, M. J.; Trantham, M. R.; Fein, J. R.; Belancourt, P. X.; Young, R. P.; Keiter, P. A.; Drake, R. P.; Pollock, B. B.; Park, J.; Hazi, A. U.; Williams, G. J.; Chen, H.

2015-12-01

Recent experiments at the Jupiter Laser Facility investigated magnetization effects on collimated plasma jets. Laser-irradiated plastic-cone-targets produced collimated, millimeter-scale plasma flows as indicated by optical interferometry. Proton radiography of these jets showed no indication of strong, self-generated magnetic fields, suggesting a dominantly hydrodynamic collimating mechanism. Targets were placed in a custom-designed solenoid capable of generating field strengths up to 5 T. Proton radiographs of the well-characterized B-field, without a plasma jet, suggested an external source of trapped electrons that affects proton trajectories. The background magnetic field was aligned with the jet propagation direction, as is the case in many astrophysical systems. Optical interferometry showed that magnetization of the plasma results in disruption of the collimated flow and instead produces a hollow cavity. This result is a topic of ongoing investigation.

Stellar physics. Observing the onset of outflow collimation in a massive protostar.

PubMed

Carrasco-González, C; Torrelles, J M; Cantó, J; Curiel, S; Surcis, G; Vlemmings, W H T; van Langevelde, H J; Goddi, C; Anglada, G; Kim, S-W; Kim, J-S; Gómez, J F

2015-04-03

The current paradigm of star formation through accretion disks, and magnetohydrodynamically driven gas ejections, predicts the development of collimated outflows, rather than expansion without any preferential direction. We present radio continuum observations of the massive protostar W75N(B)-VLA 2, showing that it is a thermal, collimated ionized wind and that it has evolved in 18 years from a compact source into an elongated one. This is consistent with the evolution of the associated expanding water-vapor maser shell, which changed from a nearly circular morphology, tracing an almost isotropic outflow, to an elliptical one outlining collimated motions. We model this behavior in terms of an episodic, short-lived, originally isotropic ionized wind whose morphology evolves as it moves within a toroidal density stratification. Copyright © 2015, American Association for the Advancement of Science.

Multi-pinhole collimator design for small-object imaging with SiliSPECT: a high-resolution SPECT

NASA Astrophysics Data System (ADS)

Shokouhi, S.; Metzler, S. D.; Wilson, D. W.; Peterson, T. E.

2009-01-01

We have designed a multi-pinhole collimator for a dual-headed, stationary SPECT system that incorporates high-resolution silicon double-sided strip detectors. The compact camera design of our system enables imaging at source-collimator distances between 20 and 30 mm. Our analytical calculations show that using knife-edge pinholes with small-opening angles or cylindrically shaped pinholes in a focused, multi-pinhole configuration in combination with this camera geometry can generate narrow sensitivity profiles across the field of view that can be useful for imaging small objects at high sensitivity and resolution. The current prototype system uses two collimators each containing 127 cylindrically shaped pinholes that are focused toward a target volume. Our goal is imaging objects such as a mouse brain, which could find potential applications in molecular imaging.

T Pyxidis: The First Cataclysmic Variable with a Collimated Jet

NASA Technical Reports Server (NTRS)

Shahbaz, T.; Livio, M.; Southwell, K. A.; Charles, P. A.

1997-01-01

We present the first observational evidence for a collimated jet in a cataclysmic variable system; the recurrent nova T Pyxidis. Optical spectra show bipolar components of H(alpha) with velocities approx. 1400 km/s, very similar to those observed in the supersoft X-ray sources and in SS 433. We argue that a key ingredient of the formation of jets in the supersoft X-ray sources and T Pyx (in addition to an accretion disk threaded by a vertical magnetic field), is the presence of nuclear burning on the surface of the white dwarf.

1×3 optical drop splitter in a rod-type silicon photonic crystal

NASA Astrophysics Data System (ADS)

Zhuang, Dongxia; Chen, Xiyao; Li, Junjun; Lin, Guimin; Qiang, Zexuan; Qiu, Yishen; Li, Hui

2011-12-01

We report an 1×3 optical drop splitter (ODS) based on a self-collimation ring resonator (SCRR) in a rod-type silicon photonic crystal. The proposed 1×3 ODS consists of four beam splitters which are formed by changing the radius of one row of silicon rods. When the self-collimated light with resonance frequency is launched into the ODS, the light beam can be split into three parts come out from three drop ports while no light coming out from the through port. The splitting ratio of the three drop beams can be controlled by tuning the radii of the beam splitters. The FDTD method is employed to calculate the transmission of the 1×3 ODS. For the drop wavelength of 1550 nm, the free spectral range is 28.7 nm, which almost covers the whole optical communication C-band window. This 1×3 ODS may have applications in photonic integrated circuits.

Optical design of the PEPSI high-resolution spectrograph at LBT

NASA Astrophysics Data System (ADS)

Andersen, Michael I.; Spano, Paolo; Woche, Manfred; Strassmeier, Klaus G.; Beckert, Erik

2004-09-01

PEPSI is a high-resolution, fiber fed echelle spectrograph with polarimetric capabilities for the LBT. In order to reach a maximum resolution R=120.000 in polarimetric mode and 300.000 in integral light mode with high efficiency in the spectral range 390-1050~nm, we designed a white-pupil configuration with Maksutov collimators. Light is dispersed by an R4 31.6 lines/mm monolithic echelle grating mosaic and split into two arms through dichroics. The two arms, optimized for the spectral range 390-550~nm and 550-1050~nm, respectively, consist of Maksutov transfer collimators, VPH-grism cross dispersers, optimized dioptric cameras and 7.5K x 7.5K 8~μ CCDs. Fibers of different core sizes coupled to different image-slicers allow a high throughput, comparable to that of direct feed instruments. The optical configuration with only spherical and cylindrical surfaces, except for one aspherical surface in each camera, reduces costs and guarantees high optical quality. PEPSI is under construction at AIP with first light expected in 2006.

Design and performance of a multi-pinhole collimation device for small animal imaging with clinical SPECT and SPECT-CT scanners

PubMed Central

DiFilippo, Frank P.

2008-01-01

A multi-pinhole collimation device is developed that uses the gamma camera detectors of a clinical SPECT or SPECT-CT scanner to produce high resolution SPECT images. The device consists of a rotating cylindrical collimator having 22 tungsten pinholes with 0.9 mm diameter apertures and an animal bed inside the collimator that moves linearly to provide helical or ordered-subsets axial sampling. CT images also may be acquired on a SPECT-CT scanner for purposes of image co-registration and SPECT attenuation correction. The device is placed on the patient table of the scanner without attaching to the detectors or scanner gantry. The system geometry is calibrated in-place from point source data and is then used during image reconstruction. The SPECT imaging performance of the device is evaluated with test phantom scans. Spatial resolution from reconstructed point source images is measured to be 0.6 mm full width at half maximum or better. Micro-Derenzo phantom images demonstrate the ability to resolve 0.7 mm diameter rod patterns. The axial slabs of a Micro-Defrise phantom are visualized well. Collimator efficiency exceeds 0.05% at the center of the field of view, and images of a uniform phantom show acceptable uniformity and minimal artifact. The overall simplicity and relatively good imaging performance of the device make it an interesting low-cost alternative to dedicated small animal scanners. PMID:18635899

Design and performance of a multi-pinhole collimation device for small animal imaging with clinical SPECT and SPECT CT scanners

NASA Astrophysics Data System (ADS)

Di Filippo, Frank P.

2008-08-01

A multi-pinhole collimation device is developed that uses the gamma camera detectors of a clinical SPECT or SPECT-CT scanner to produce high-resolution SPECT images. The device consists of a rotating cylindrical collimator having 22 tungsten pinholes with 0.9 mm diameter apertures and an animal bed inside the collimator that moves linearly to provide helical or ordered-subsets axial sampling. CT images also may be acquired on a SPECT-CT scanner for purposes of image co-registration and SPECT attenuation correction. The device is placed on the patient table of the scanner without attaching to the detectors or scanner gantry. The system geometry is calibrated in-place from point source data and is then used during image reconstruction. The SPECT imaging performance of the device is evaluated with test phantom scans. Spatial resolution from reconstructed point source images is measured to be 0.6 mm full width at half maximum or better. Micro-Derenzo phantom images demonstrate the ability to resolve 0.7 mm diameter rod patterns. The axial slabs of a Micro-Defrise phantom are visualized well. Collimator efficiency exceeds 0.05% at the center of the field of view, and images of a uniform phantom show acceptable uniformity and minimal artifact. The overall simplicity and relatively good imaging performance of the device make it an interesting low-cost alternative to dedicated small animal scanners.

Characteristic of laser diode beam propagation through a collimating lens.

PubMed

Xu, Qiang; Han, Yiping; Cui, Zhiwei

2010-01-20

A mathematical model of a laser diode beam propagating through a collimating lens is presented. Wave propagation beyond the paraxial approximation is studied. The phase delay of the laser diode wave in passing through the lens is analyzed in detail. The propagation optical field after the lens is obtained from the diffraction integral by the stationary phase method. The model is employed to predict the light intensity at various beam cross sections, and the computed intensity distributions are in a good agreement with the corresponding measurements.

Method for obtaining a collimated near-unity aspect ratio output beam from a DFB-GSE laser with good beam quality.

PubMed

Liew, S K; Carlson, N W

1992-05-20

A simple method for obtaining a collimated near-unity aspect ratio output beam from laser sources with extremely large (> 100:1) aspect ratios is demonstrated by using a distributed-feedback grating-surfaceemitting laser. Far-field power-in-the-bucket measurements of the laser indicate good beam quality with a high Strehl ratio.

Wavefront Compensation Segmented Mirror Sensing and Control

NASA Technical Reports Server (NTRS)

Redding, David C.; Lou, John Z.; Kissil, Andrew; Bradford, Charles M.; Woody, David; Padin, Stephen

2012-01-01

The primary mirror of very large submillimeter-wave telescopes will necessarily be segmented into many separate mirror panels. These panels must be continuously co-phased to keep the telescope wavefront error less than a small fraction of a wavelength, to ten microns RMS (root mean square) or less. This performance must be maintained continuously across the full aperture of the telescope, in all pointing conditions, and in a variable thermal environment. A wavefront compensation segmented mirror sensing and control system, consisting of optical edge sensors, Wavefront Compensation Estimator/Controller Soft ware, and segment position actuators is proposed. Optical edge sensors are placed two per each segment-to-segment edge to continuously measure changes in segment state. Segment position actuators (three per segment) are used to move the panels. A computer control system uses the edge sensor measurements to estimate the state of all of the segments and to predict the wavefront error; segment actuator commands are computed that minimize the wavefront error. Translational or rotational motions of one segment relative to the other cause lateral displacement of the light beam, which is measured by the imaging sensor. For high accuracy, the collimator uses a shaped mask, such as one or more slits, so that the light beam forms a pattern on the sensor that permits sensing accuracy of better than 0.1 micron in two axes: in the z or local surface normal direction, and in the y direction parallel to the mirror surface and perpendicular to the beam direction. Using a co-aligned pair of sensors, with the location of the detector and collimated light source interchanged, four degrees of freedom can be sensed: transverse x and y displacements, as well as two bending angles (pitch and yaw). In this approach, each optical edge sensor head has a collimator and an imager, placing one sensor head on each side of a segment gap, with two parallel light beams crossing the gap. Two sets of optical edge sensors are used per segment-to-segment edge, separated by a finite distance along the segment edge, for four optical heads, each with an imager and a collimator. By orienting the beam direction of one edge sensor pair to be +45 away from the segment edge direction, and the other sensor pair to be oriented -45 away from the segment edge direction, all six degrees of freedom of relative motion between the segments can be measured with some redundancy. The software resides in a computer that receives each of the optical edge sensor signals, as well as telescope pointing commands. It feeds back the edge sensor signals to keep the primary mirror figure within specification. It uses a feed-forward control to compensate for global effects such as decollimation of the primary and secondary mirrors due to gravity sag as the telescope pointing changes to track science objects. Three segment position actuators will be provided per segment to enable controlled motions in the piston, tip, and tilt degrees of freedom. These actuators are driven by the software, providing the optical changes needed to keep the telescope phased.

NGST/XRCF Design and Build Wavescope System Pallet

NASA Technical Reports Server (NTRS)

Geary, Joe

1999-01-01

Based on the successful Wavescope demonstration at MSFC at the end of March, the decision was made by the optical testing team to purchase an upgraded Wavescope from AOA. The MSFC version would include: a higher resolution camera (1000 x 1000 pixels); a higher density lenslet array (150 x 150); updated software; and longer cables (to accommodate the remote operation of the Wavescope optical head which was resident in the Beam Guide Tube). The AOA proposal for the new instrument was received in mid-April, and delivered to MSFC in mid-July. A considerable amount of effort was expended to provide the infrastructure needed for Wavescope operation, and to incorporate it into the overall test system. This was provided by the Wavescope System Pallet (WSP) built by UAH. The WSP is illustrated. Several instruments are incorporated on this pallet. These include the: Wavescope optical head; a PDI wavefront sensor; a point spread function sensor; a Leica light-based distance measuring sensor. In addition there is a single mode fiber point source (fed from a separate source pallet) which serves both as a reference for the Wavescope and as a source point for the test mirror. There is a dual function lens which both collimates the beam from the test image point, and images the test mirror onto the lenslet array. There is a high quality Collimator which can provide a flat input wavefront directly into the Wavescope. There are also various aids such as an alignment laser, an alignment telescope, alignment sticks and apertures. The WSP was delivered to MSFC on 7/28/99. An picture shows the WSP installed in the Guide Tube at the X-Ray Calibration Facility (XRCF).

Experimentally enhanced model-based deconvolution of propagation-based phase-contrast data

NASA Astrophysics Data System (ADS)

Pichotka, M.; Palma, K.; Hasn, S.; Jakubek, J.; Vavrik, D.

2016-12-01

In recent years phase-contrast has become a much investigated modality in radiographic imaging. The radiographic setups employed in phase-contrast imaging are typically rather costly and complex, e.g. high performance Talbot-Laue interferometers operated at synchrotron light sources. In-line phase-contrast imaging states the most pedestrian approach towards phase-contrast enhancement. Utilizing small angle deflection within the imaged sample and the entailed interference of the deflected and un-deflected beam during spatial propagation, in-line phase-contrast imaging only requires a well collimated X-ray source with a high contrast & high resolution detector. Employing high magnification the above conditions are intrinsically fulfilled in cone-beam micro-tomography. As opposed of 2D imaging, where contrast enhancement is generally considered beneficial, in tomographic modalities the in-line phase-contrast effect can be quite a nuisance since it renders the inverse problem posed by tomographic reconstruction inconsistent, thus causing reconstruction artifacts. We present an experimentally enhanced model-based approach to disentangle absorption and in-line phase-contrast. The approach employs comparison of transmission data to a system model computed iteratively on-line. By comparison of the forward model to absorption data acquired in continuous rotation strong local deviations of the data residual are successively identified as likely candidates for in-line phase-contrast. By inducing minimal vibrations (few mrad) to the sample around the peaks of such deviations the transmission signal can be decomposed into a constant absorptive fraction and an oscillating signal caused by phase-contrast which again allows to generate separate maps for absorption and phase-contrast. The contributions of phase-contrast and the corresponding artifacts are subsequently removed from the tomographic dataset. In principle, if a 3D handling of the sample is available, this method also allows to track discontinuities throughout the volume and therefore states a powerful tool in 3D defectoscopy.

ODERACS 2 White Spheres Optical Calibration Report

NASA Technical Reports Server (NTRS)

Culp, Robert D.; Gravseth, Ian; Gloor, Jason; Wantuch, Todd

1995-01-01

This report documents the status of the Orbital Debris Radar Calibration Spheres (ODERACS) 2 white spheres optical calibration study. The purpose of this study is to determine the spectral reflectivity and scattering characteristics in the visible wavelength region for the white spheres that were added to the project in the fall, 1994. Laboratory measurements were performed upon these objects and an analysis of the resulting data was conducted. These measurements are performed by illuminating the objects with a collimated beam of light and measuring the reflected light versus the phase angle. The phase angle is defined as the angle between the light source and the sensor, as viewed from the object. By measuring the reflected signal at the various phase angles, one is able to estimate the reflectance properties of the object. The methodology used in taking the measurements and reducing the data are presented. The results of this study will be used to support the calibration of ground-based optical instruments used in support of space debris research. Visible measurements will be made by the GEODDS, NASA and ILADOT telescopes.

Micro-Optic Color Separation Technology for Efficient Projection Displays

NASA Technical Reports Server (NTRS)

Gunning, W. J.; Boehmer, E.

1997-01-01

Phase 1 of this project focused on development of an overall optical concept which incorporated a single liquid crystal spatial light modulator. The system achieved full color by utilizing an echelon grating, which diffracted the incident light into three orders with different color spectra, in combination with a microlens array, which spatially separated RGB bands and directed the light of the appropriate wavelength to the appropriate color dot. Preliminary echelon grating designs were provided by MIT/LL and reviewed by Rockwell. Additional Rockwell activities included the Identification of microlens designs, light sources (ILC), and projection optics to fulfill the overall design requirements. An Internal subcontract was established with Rockwell's Collins Avionics and Communications Division (CACD) which specified the liquid crystal SLM (Sharp Model No. LQ 46EO2) and built the projection display baseline projector. Full Color projected video images were produced and shown at the 1995 HDS meeting in Washington. Analysis of the luminance performance of the projector and detailed parameter trade studies helped define the dependence of overall display efficiency on lamp collimation, and indicated that a lamp with very small arc dimension is required for the optical concept to be viable.

An optical fiber guided ultrasonic excitation and sensing system for online monitoring of nuclear power plants

NASA Astrophysics Data System (ADS)

Yang, J.; Lee, H.; Sohn, H.

2012-05-01

This study presents an embedded laser ultrasonic system for pipeline monitoring under high temperature environment. Recently, laser ultrasonics is becoming popular because of their advantageous characteristics such as (a) noncontact inspection, (b) immunity against electromagnetic interference (EMI), and (c) applicability under high temperature. However, the performance of conventional laser ultrasonic techniques for pipeline monitoring has been limited because many pipelines are covered by insulating materials and target surfaces are inaccessible. To overcome the problem, this study designs an embeddable optical fibers and fixing devices that deliver laser beams from laser sources to a target pipe using embedded optical fibers. For guided wave generation, an optical fiber is furnished with a beam collimator for irradiating a laser beam onto a target structure. The corresponding response is measured based on the principle of laser interferometry. Light from a monochromatic source is colliminated and delivered to a target surface by another optical with a focusing module, and reflected light is transmitted back to the interferometer through the same fiber. The feasibility of the proposed system for embedded ultrasonic measurement has been experimentally verified using a pipe specimen under high temperature.

Study of neutron shielding collimators for curved beamlines at the European Spallation Source

NASA Astrophysics Data System (ADS)

Santoro, V.; DiJulio, D. D.; Ansell, S.; Cherkashyna, N.; Muhrer, G.; Bentley, P. M.

2018-06-01

The European Spallation Source is being constructed in Lund, Sweden and is planned to be the world’s brightest pulsed spallation neutron source for cold and thermal neutron beams (≤ 1 eV). The facility uses a 2 GeV proton beam to produce neutrons from a tungsten target. The neutrons are then moderated in a moderator assembly consisting of both liquid hydrogen and water compartments. Surrounding the moderator are 22 beamports, which view the moderator’s outside surfaces. The beamports are connected to long neutron guides that transport the moderated neutrons to the sample position via reflections. As well as the desired moderated neutrons, fast neutrons coming directly from the target can find their way down the beamlines. These can create unwanted sources of background for the instruments. To mitigate such a kind of background, several instruments will use curved guides to lose direct line-of-sight (LoS) to the moderator and the target. In addition instruments can also use shielding collimators to reduce the amount of fast neutrons further traveling down the guide due to albedo reflections or streaming. Several different materials have been proposed for this purpose. We present the results of a study of different options for collimators and identify the optimal choices that balance cost, background and activation levels.

Experimental results from magnetized-jet experiments executed at the Jupiter Laser Facility

DOE PAGES

Manuel, M. J. -E.; Kuranz, C. C.; Rasmus, A. M.; ...

2014-08-20

Recent experiments at the Jupiter Laser Facility investigated magnetization effects on collimated plasma jets. Laser-irradiated plastic-cone-targets produced collimated, millimeter-scale plasma flows as indicated by optical interferometry. Proton radiography of these jets showed no indication of strong, self-generated magnetic fields, suggesting a dominantly hydrodynamic collimating mechanism. Targets were placed in a custom-designed solenoid capable of generating field strengths up to 5 T. Proton radiographs of the well-characterized B-field, without a plasma jet, suggested an external source of trapped electrons that affects proton trajectories. The background magnetic field was aligned with the jet propagation direction, as is the case in many astrophysicalmore » systems. Optical interferometry showed that magnetization of the plasma results in disruption of the collimated flow and instead produces a hollow cavity. Furthermore, this result is a topic of ongoing investigation.« less

Experimental results from magnetized-jet experiments executed at the Jupiter Laser Facility

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

Manuel, M. J. -E.; Kuranz, C. C.; Rasmus, A. M.

Recent experiments at the Jupiter Laser Facility investigated magnetization effects on collimated plasma jets. Laser-irradiated plastic-cone-targets produced collimated, millimeter-scale plasma flows as indicated by optical interferometry. Proton radiography of these jets showed no indication of strong, self-generated magnetic fields, suggesting a dominantly hydrodynamic collimating mechanism. Targets were placed in a custom-designed solenoid capable of generating field strengths up to 5 T. Proton radiographs of the well-characterized B-field, without a plasma jet, suggested an external source of trapped electrons that affects proton trajectories. The background magnetic field was aligned with the jet propagation direction, as is the case in many astrophysicalmore » systems. Optical interferometry showed that magnetization of the plasma results in disruption of the collimated flow and instead produces a hollow cavity. Furthermore, this result is a topic of ongoing investigation.« less

System for determining position of normal shock in supersonic flow

NASA Technical Reports Server (NTRS)

Iverson, Jr., Donald G. (Inventor); Daiber, Troy D. (Inventor)

1991-01-01

Light from a plurality of light emitting diodes is transmitted through optical cables (12) to a lens system. The lenses (56, 58) expand and collimate the light and project it in a sheet (16) across the supersonic inlet of an aircraft power plant perpendicular to incoming airflow. A normal shock bends a portion of the sheet of light (16). A linear array of a multiplicity of optical fiber ends collects discrete samples of light. The samples are processed and compared to a predetermined profile to determine the shock location.

A comparison between using incoherent or coherent sources to align and test an adaptive optical telescope

NASA Technical Reports Server (NTRS)

Anderson, Richard

1994-01-01

The concept in the initial alignment of the segmented mirror adaptive optics telescope called the phased array mirror extendable large aperture telescope (Pamela) is to produce an optical transfer function (OTF) which closely approximates the diffraction limited value which would correspond to a system pupil function that is unity over the aperture and zero outside. There are differences in the theory of intensity measurements between coherent and incoherent radiation. As a result, some of the classical quantities which describe the performance of an optical system for incoherent radiation can not be defined for a coherent field. The most important quantity describing the quality of an optical system is the OTF and for a coherent source the OTF is not defined. Instead a coherent transfer function (CTF) is defined. The main conclusion of the paper is that an incoherent collimated source and not a collimated laser source is preferred to calibrate the Hartmann wavefront sensor (WFS) of an aligned adaptive optical system. A distant laser source can be used with minimum problems to correct the system for atmospheric turbulence. The collimation of the HeNe laser alignment source can be improved by using a very small pin hole in the spatial filter so only the central portion of the beam is transmitted and the beam from the filter is nearly constant in amplitude. The size of this pin hole will be limited by the sensitivity of the lateral effect diode (LEDD) elements.

Documentation of Apollo 15 samples

NASA Technical Reports Server (NTRS)

Sutton, R. L.; Hait, M. H.; Larson, K. B.; Swann, G. A.; Reed, V. S.; Schaber, G. G.

1972-01-01

A catalog is presented of the documentation of Apollo 15 samples using photographs and verbal descriptions returned from the lunar surface. Almost all of the Apollo 15 samples were correlated with lunar surface photographs, descriptions, and traverse locations. Where possible, the lunar orientations of rock samples were reconstructed in the lunar receiving laboratory, using a collimated light source to reproduce illumination and shadow characteristics of the same samples shown in lunar photographs. In several cases, samples were not recognized in lunar surface photographs, and their approximate locations are known only by association with numbered sample bags used during their collection. Tables, photographs, and maps included in this report are designed to aid in the understanding of the lunar setting of the Apollo 15 samples.

Wide Field Collimator 2 (WFC2) for GOES Imager and Sounder

NASA Technical Reports Server (NTRS)

Etemad, Shahriar; Bremer, James C.; Zukowski, Barbara J.; Pasquale, Bert A.; zukowski, Tmitri J.; Prince, Robert E.; O'Neill, Patrick A.; Ross, Robert W.

2004-01-01

Two of the GOES instruments, the Imager and the Sounder, perform scans of the Earth to provide a full disc picture of the Earth. To verify the entire scan process, an image of a target that covers an 18 deg. circular field-of-view is collimated and projected into the field of regard of each instrument. The Wide Field Collimator 2 (WFC2) has many advantages over its predecessor, WFC1, including lower thermal dissipation higher fir field MTF, smaller package, and a more intuitive (faster) focusing process. The illumination source is an LED array that emits in a narrow spectral band centered at 689 nm, within the visible spectral bands of the Imager and Sounder. The illumination level can be continuously adjusted electronically. Lower thermal dissipation eliminates the need for forced convection cooling and minimizes time to reach thermal stability. The lens system has been optimized for the illumination source spectral output and athernalized to remain in focus during bulk temperature changes within the laboratory environment. The MTF of the lens is higher than that of the WFC1 at the edge of FOV. The target is focused in three orthogonal motions, controlled by an ergonomic system that saves substantial time and produces a sharper focus. Key words: Collimator, GOES, Imager, Sounder, Projector

System and process for detecting and monitoring surface defects

NASA Technical Reports Server (NTRS)

Mueller, Mark K. (Inventor)

1994-01-01

A system and process for detecting and monitoring defects in large surfaces such as the field joints of the container segments of a space shuttle booster motor. Beams of semi-collimated light from three non-parallel fiber optic light panels are directed at a region of the surface at non-normal angles of expected incidence. A video camera gathers some portion of the light that is reflected at an angle other than the angle of expected reflectance, and generates signals which are analyzed to discern defects in the surface. The analysis may be performed by visual inspection of an image on a video monitor, or by inspection of filtered or otherwise processed images. In one alternative embodiment, successive predetermined regions of the surface are aligned with the light source before illumination, thereby permitting efficient detection of defects in a large surface. Such alignment is performed by using a line scan gauge to sense the light which passes through an aperture in the surface. In another embodiment a digital map of the surface is created, thereby permitting the maintenance of records detailing changes in the location or size of defects as the container segment is refurbished and re-used. The defect detection apparatus may also be advantageously mounted on a fixture which engages the edge of a container segment.

Giant collimated gamma-ray flashes

NASA Astrophysics Data System (ADS)

Benedetti, Alberto; Tamburini, Matteo; Keitel, Christoph H.

2018-06-01

Bright sources of high-energy electromagnetic radiation are widely employed in fundamental research, industry and medicine1,2. This motivated the construction of Compton-based facilities planned to yield bright gamma-ray pulses with energies up to3 20 MeV. Here, we demonstrate a novel mechanism based on the strongly amplified synchrotron emission that occurs when a sufficiently dense ultra-relativistic electron beam interacts with a millimetre-thickness conductor. For electron beam densities exceeding approximately 3 × 1019 cm-3, electromagnetic instabilities occur, and the ultra-relativistic electrons travel through self-generated electromagnetic fields as large as 107-108 gauss. This results in the production of a collimated gamma-ray pulse with peak brilliance above 1025 photons s-1 mrad-2 mm-2 per 0.1% bandwidth, photon energies ranging from 200 keV to gigaelectronvolts and up to 60% electron-to-photon energy conversion efficiency. These findings pave the way to compact, high-repetition-rate (kilohertz) sources of short (≲30 fs), collimated (milliradian) and high-flux (>1012 photons s-1) gamma-ray pulses.

Instrument and method for X-ray diffraction, fluorescence, and crystal texture analysis without sample preparation

NASA Technical Reports Server (NTRS)

Gendreau, Keith (Inventor); Martins, Jose Vanderlei (Inventor); Arzoumanian, Zaven (Inventor)

2010-01-01

An X-ray diffraction and X-ray fluorescence instrument for analyzing samples having no sample preparation includes a X-ray source configured to output a collimated X-ray beam comprising a continuum spectrum of X-rays to a predetermined coordinate and a photon-counting X-ray imaging spectrometer disposed to receive X-rays output from an unprepared sample disposed at the predetermined coordinate upon exposure of the unprepared sample to the collimated X-ray beam. The X-ray source and the photon-counting X-ray imaging spectrometer are arranged in a reflection geometry relative to the predetermined coordinate.

Ultra-directional source of longitudinal acoustic waves based on a two-dimensional solid/solid phononic crystal

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

Morvan, B.; Tinel, A.; Sainidou, R.

2014-12-07

Phononic crystals (PC) can be used to control the dispersion properties of acoustic waves, which are essential to direct their propagation. We use a PC-based two-dimensional solid/solid composite to demonstrate experimentally and theoretically the spatial filtering of a monochromatic non-directional wave source and its emission in a surrounding water medium as an ultra-directional beam with narrow angular distribution. The phenomenon relies on square-shaped equifrequency contours (EFC) enabling self-collimation of acoustic waves within the phononic crystal. Additionally, the angular width of collimated beams is controlled via the EFC size-shrinking when increasing frequency.

Design of a radiation facility for very small specimens used in radiobiology studies

NASA Astrophysics Data System (ADS)

Rodriguez, Manuel; Jeraj, Robert

2008-06-01

A design of a radiation facility for very small specimens used in radiobiology is presented. This micro-irradiator has been primarily designed to irradiate partial bodies in zebrafish embryos 3-4 mm in length. A miniature x-ray, 50 kV photon beam, is used as a radiation source. The source is inserted in a cylindrical brass collimator that has a pinhole of 1.0 mm in diameter along the central axis to produce a pencil photon beam. The collimator with the source is attached underneath a computer-controlled movable table which holds the specimens. Using a 45° tilted mirror, a digital camera, connected to the computer, takes pictures of the specimen and the pinhole collimator. From the image provided by the camera, the relative distance from the specimen to the pinhole axis is calculated and coordinates are sent to the movable table to properly position the samples in the beam path. Due to its monitoring system, characteristic of the radiation beam, accuracy and precision of specimen positioning, and automatic image-based specimen recognition, this radiation facility is a suitable tool to irradiate partial bodies in zebrafish embryos, cell cultures or any other small specimen used in radiobiology research.

Primary Beam Air Kerma Dependence on Distance from Cargo and People Scanners

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

Strom, Daniel J.; Cerra, Frank

The distance dependence of air kerma or dose rate of the primary radiation beam is not obvious for security scanners of cargo and people in which there is relative motion between a collimated source and the person or object being imaged. To study this problem, one fixed line source and three moving-source scan-geometry cases are considered, each characterized by radiation emanating perpendicular to an axis. The cases are 1) a stationary line source of radioactive material, e.g., contaminated solution in a pipe; 2) a moving, uncollimated point source of radiation that is shuttered or off when it is stationary; 3)more » a moving, collimated point source of radiation that is shuttered or off when it is stationary; and 4) a translating, narrow “pencil” beam emanating in a flying-spot, raster pattern. Each case is considered for short and long distances compared to the line source length or path traversed by a moving source. The short distance model pertains mostly to dose to objects being scanned and personnel associated with the screening operation. The long distance model pertains mostly to potential dose to bystanders. For radionuclide sources, the number of nuclear transitions that occur a) per unit length of a line source, or b) during the traversal of a point source, is a unifying concept. The “universal source strength” of air kerma rate at a meter from the source can be used to describe x-ray machine or radionuclide sources. For many cargo and people scanners with highly collimated fan or pencil beams, dose varies as the inverse of the distance from the source in the near field and with the inverse square of the distance beyond a critical radius. Ignoring the inverse square dependence and using inverse distance dependence is conservative in the sense of tending to overestimate dose.« less

Primary Beam Air Kerma Dependence on Distance from Cargo and People Scanners.

PubMed

Strom, Daniel J; Cerra, Frank

2016-06-01

The distance dependence of air kerma or dose rate of the primary radiation beam is not obvious for security scanners of cargo and people in which there is relative motion between a collimated source and the person or object being imaged. To study this problem, one fixed line source and three moving-source scan-geometry cases are considered, each characterized by radiation emanating perpendicular to an axis. The cases are 1) a stationary line source of radioactive material, e.g., contaminated solution in a pipe; 2) a moving, uncollimated point source of radiation that is shuttered or off when it is stationary; 3) a moving, collimated point source of radiation that is shuttered or off when it is stationary; and 4) a translating, narrow "pencil" beam emanating in a flying-spot, raster pattern. Each case is considered for short and long distances compared to the line source length or path traversed by a moving source. The short distance model pertains mostly to dose to objects being scanned and personnel associated with the screening operation. The long distance model pertains mostly to potential dose to bystanders. For radionuclide sources, the number of nuclear transitions that occur a) per unit length of a line source or b) during the traversal of a point source is a unifying concept. The "universal source strength" of air kerma rate at 1 m from the source can be used to describe x-ray machine or radionuclide sources. For many cargo and people scanners with highly collimated fan or pencil beams, dose varies as the inverse of the distance from the source in the near field and with the inverse square of the distance beyond a critical radius. Ignoring the inverse square dependence and using inverse distance dependence is conservative in the sense of tending to overestimate dose.

Device to color modulate a stationary light beam gives high intensity

NASA Technical Reports Server (NTRS)

Gantz, W. A.

1966-01-01

Signal controlled system color modulates a beam of light while also providing high intensity and a stationary beam, either collimated or focused. The color modulation acquired by the presented system can be compatible with any color film by employing color filters formed to provide a color wedge having a color distribution compatible with the films color sensitivity.

Minibeam therapy with protons and light ions: physical feasibility and potential to reduce radiation side effects and to facilitate hypofractionation.

PubMed

Dilmanian, F Avraham; Eley, John G; Krishnan, Sunil

2015-06-01

Despite several advantages of proton therapy over megavoltage x-ray therapy, its lack of proximal tissue sparing is a concern. The method presented here adds proximal tissue sparing to protons and light ions by turning their uniform incident beams into arrays of parallel, small, or thin (0.3-mm) pencil or planar minibeams, which are known to spare tissues. As these minibeams penetrate the tissues, they gradually broaden and merge with each other to produce a solid beam. Broadening of 0.3-mm-diameter, 109-MeV proton pencil minibeams was measured using a stack of radiochromic films with plastic spacers. Monte Carlo simulations were used to evaluate the broadening in water of minibeams of protons and several light ions and the dose from neutron generated by collimator. A central parameter was tissue depth, where the beam full width at half maximum (FWHM) reached 0.7 mm, beyond which tissue sparing decreases. This depth was 22 mm for 109-MeV protons in a film stack. It was also found by simulations in water to be 23.5 mm for 109 MeV proton pencil minibeams and 26 mm for 116 MeV proton planar minibeams. For light ions, all with 10 cm range in water, that depth increased with particle size; specifically it was 51 mm for Li-7 ions. The ∼2.7% photon equivalent neutron skin dose from the collimator was reduced 7-fold by introducing a gap between the collimator and the skin. Proton minibeams can be implemented at existing particle therapy centers. Because they spare the shallow tissues, they could augment the efficacy of proton therapy and light particle therapy, particularly in treating tumors that benefit from sparing of proximal tissues such as pediatric brain tumors. They should also allow hypofractionated treatment of all tumors by allowing the use of higher incident doses with less concern about proximal tissue damage. Copyright © 2015 Elsevier Inc. All rights reserved.

All-reflective optical target illumination system with high numerical aperture

DOEpatents

Thomas, Carlton E.; Sigler, Robert D.; Hoeger, John G.

1979-01-01

An all-reflective optical system for providing illumination of a target focal region at high numerical aperture from a pair of confluent collimated light beams. The collimated beams are each incident upon an associated concave eccentric pupil paraboloidal reflective surface, and thereby each focused through an opening in an associated outer ellipsoidal reflective surface onto a plane reflector. Each beam is reflected by its associated plane reflector onto the opposing concave surface of the outer ellipsoids to be focused through an opening in the plane surface onto an opposing inner concave ellipsoidal reflective surface, and thence onto the target region.

Measuring spatially varying, multispectral, ultraviolet bidirectional reflectance distribution function with an imaging spectrometer

NASA Astrophysics Data System (ADS)

Li, Hongsong; Lyu, Hang; Liao, Ningfang; Wu, Wenmin

2016-12-01

The bidirectional reflectance distribution function (BRDF) data in the ultraviolet (UV) band are valuable for many applications including cultural heritage, material analysis, surface characterization, and trace detection. We present a BRDF measurement instrument working in the near- and middle-UV spectral range. The instrument includes a collimated UV light source, a rotation stage, a UV imaging spectrometer, and a control computer. The data captured by the proposed instrument describe spatial, spectral, and angular variations of the light scattering from a sample surface. Such a multidimensional dataset of an example sample is captured by the proposed instrument and analyzed by a k-mean clustering algorithm to separate surface regions with same material but different surface roughnesses. The clustering results show that the angular dimension of the dataset can be exploited for surface roughness characterization. The two clustered BRDFs are fitted to a theoretical BRDF model. The fitting results show good agreement between the measurement data and the theoretical model.

A new transportable instrument for in-situ void and corrosion imaging in thick structural sections by three dimensional Compton scatter imaging

NASA Astrophysics Data System (ADS)

Bridge, B.

2000-05-01

When X Gamma or other kinds of subatomic particle radiation are being used for NDE, measurements are almost always made on the primary beam after transmission through the object under test. Cases are described where better results, i.e., image quality or cost effectiveness can be obtained from measurements on scattered radiation rather than the primary beam. Compton imaging of high volume resolution in thick structures has previously been achieved only by fixed laboratory installations involving massive primary beam shields (collimators) between source and detectors. Here the design of a relatively portable collimator (98 kg mass) for a cobalt 60 source is given. It permits three dimensional material density imaging, with voxel (3-dimensional pixel) volumes small enough to permit the detection of voids down to 10 cubic mm in up to 30 mm thickness of steel or 250 mm of wood (for example, a 500 mm diameter tree trunk). Using a 370 GBq source, typical results of thickness measurements to a precision of 1 mm over cross sections down to 10 square mm are presented. The collimator mass is reducible to about 68 kg with the use of depleted uranium instead of lead. The means of deploying such a collimator in a mobile way are discussed. A typical in-situ application is the detection of inner wall corrosion and flooding of tubular members of underwater offshore oil platforms and ship hulls without the need to remove hard marine growth. Another case is the detection of telegraph pole and tree rot below ground level.

Fluorescence molecular imaging based on the adjoint radiative transport equation

NASA Astrophysics Data System (ADS)

Asllanaj, Fatmir; Addoum, Ahmad; Rodolphe Roche, Jean

2018-07-01

A new reconstruction algorithm for fluorescence diffuse optical tomography of biological tissues is proposed. The radiative transport equation in the frequency domain is used to model light propagation. The adjoint method studied in this work provides an efficient way for solving the inverse problem. The methodology is applied to a 2D tissue-like phantom subjected to a collimated laser beam. Indocyanine Green is used as fluorophore. Reconstructed images of the spatial fluorophore absorption distribution is assessed taking into account the residual fluorescence in the medium. We show that illuminating the tissue surface from a collimated centered direction near the inclusion gaves a better reconstruction quality. Two closely positioned inclusions can be accurately localized. Additionally, their fluorophore absorption coefficients can be quantified. However, the algorithm failes to reconstruct smaller or deeper inclusions. This is due to light attenuation in the medium. Reconstructions with noisy data are also achieved with a reasonable accuracy.

Electron beam collimation with a photon MLC for standard electron treatments

NASA Astrophysics Data System (ADS)

Mueller, S.; Fix, M. K.; Henzen, D.; Frei, D.; Frauchiger, D.; Loessl, K.; Stampanoni, M. F. M.; Manser, P.

2018-01-01

Standard electron treatments are currently still performed using standard or molded patient-specific cut-outs placed in the electron applicator. Replacing cut-outs and electron applicators with a photon multileaf collimator (pMLC) for electron beam collimation would make standard electron treatments more efficient and would facilitate advanced treatment techniques like modulated electron radiotherapy (MERT) and mixed beam radiotherapy (MBRT). In this work, a multiple source Monte Carlo beam model for pMLC shaped electron beams commissioned at a source-to-surface distance (SSD) of 70 cm is extended for SSDs of up to 100 cm and validated for several Varian treatment units with field sizes typically used for standard electron treatments. Measurements and dose calculations agree generally within 3% of the maximal dose or 2 mm distance to agreement. To evaluate the dosimetric consequences of using pMLC collimated electron beams for standard electron treatments, pMLC-based and cut-out-based treatment plans are created for a left and a right breast boost, a sternum, a testis and a parotid gland case. The treatment plans consist of a single electron field, either alone (1E) or in combination with two 3D conformal tangential photon fields (1E2X). For each case, a pMLC plan with similar treatment plan quality in terms of dose homogeneity to the target and absolute mean dose values to the organs at risk (OARs) compared to a cut-out plan is found. The absolute mean dose to an OAR is slightly increased for pMLC-based compared to cut-out-based 1E plans if the OAR is located laterally close to the target with respect to beam direction, or if a 6 MeV electron beam is used at an extended SSD. In conclusion, treatment plans using cut-out collimation can be replaced by plans of similar treatment plan quality using pMLC collimation with accurately calculated dose distributions.

APPARATUS FOR PRODUCING IONS OF VAPORIZABLE MATERIALS

DOEpatents

Starr, C.

1957-11-19

This patent relates to electronic discharge devices used as ion sources, and in particular describes an ion source for application in a calutron. The source utilizes two cathodes disposed at opposite ends of a longitudinal opening in an arc block fed with vaporized material. A magnetic field is provided parallel to the length of the arc block opening. The electrons from the cathodes are directed through slits in collimating electrodes into the arc block parallel to the magnetic field and cause an arc discharge to occur between the cathodes, as the arc block and collimating electrodes are at a positive potential with respect to the cathode. The ions are withdrawn by suitable electrodes disposed opposite the arc block opening. When such an ion source is used in a calutron, an arc discharge of increased length may be utilized, thereby increasing the efficiency and economy of operation.

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

Walker, Katherine L.; Judenhofer, Martin S.; Cherry, Simon R.

In preclinical single-photon emission computed tomography (SPECT) system development the primary objective has been to improve spatial resolution by using novel parallel-hole or multi-pinhole collimator geometries. Furthermore, such high-resolution systems have relatively poor sensitivity (typically 0.01% to 0.1%). In contrast, a system that does not use collimators can achieve very high-sensitivity. Here we present a high-sensitivity un-collimated detector single-photon imaging (UCD-SPI) system for the imaging of both small animals and plants. This scanner consists of two thin, closely spaced, pixelated scintillator detectors that use NaI(Tl), CsI(Na), or BGO. The performance of the system has been characterized by measuring sensitivity, spatialmore » resolution, linearity, detection limits, and uniformity. With 99mTc (140 keV) at the center of the field of view (20 mm scintillator separation), the sensitivity was measured to be 31.8% using the NaI(Tl) detectors and 40.2% with CsI(Na). The best spatial resolution (FWHM when the image formed as the geometric mean of the two detector heads, 20 mm scintillator separation) was 19.0 mm for NaI(Tl) and 11.9 mm for CsI(Na) at 140 keV, and 19.5 mm for BGO at 1116 keV, which is somewhat degraded compared to the cm-scale resolution obtained with only one detector head and a close source. The quantitative accuracy of the system’s linearity is better than 2% with detection down to activity levels of 100 nCi. Two in vivo animal studies (a renal scan using 99mTc MAG-3 and a thyroid scan with 123I) and one plant study (a 99mTcO 4- xylem transport study) highlight the unique capabilities of this UCD-SPI system. From the renal scan, we observe approximately a one thousand-fold increase in sensitivity compared to the Siemens Inveon SPECT/CT scanner. In conclusion, UCD-SPI is useful for many imaging tasks that do not require excellent spatial resolution, such as high-throughput screening applications, simple radiotracer uptake studies in tumor xenografts, dynamic studies where very good temporal resolution is critical, or in planta imaging of radioisotopes at low concentrations.« less

Wireless Synchronization of a Multi-Pinhole Small Animal SPECT Collimation Device With a Clinical Scanner

NASA Astrophysics Data System (ADS)

DiFilippo, Frank P.; Patel, Sagar

2009-06-01

A multi-pinhole collimation device for small animal single photon emission computed tomography (SPECT) uses the gamma camera detectors of a standard clinical SPECT scanner. The collimator and animal bed move independently of the detectors, and therefore their motions must be synchronized. One approach is manual triggering of the SPECT acquisition simultaneously with a programmed motion sequence for the device. However, some data blurring and loss of image quality result, and true electronic synchronization is preferred. An off-the-shelf digital gyroscope with integrated Bluetooth interface provides a wireless solution to device synchronization. The sensor attaches to the SPECT gantry and reports its rotational speed to a notebook computer controlling the device. Software processes the rotation data in real-time, averaging the signal and issuing triggers while compensating for baseline drift. Motion commands are sent to the collimation device with minimal delay, within approximately 0.5 second of the start of SPECT gantry rotation. Test scans of a point source demonstrate an increase in true counts and a reduction in background counts compared to manual synchronization. The wireless rotation sensor provides robust synchronization of the collimation device with the clinical SPECT scanner and enhances image quality.

MCNP simulation of a Theratron 780 radiotherapy unit.

PubMed

Miró, R; Soler, J; Gallardo, S; Campayo, J M; Díez, S; Verdú, G

2005-01-01

A Theratron 780 (MDS Nordion) 60Co radiotherapy unit has been simulated with the Monte Carlo code MCNP. The unit has been realistically modelled: the cylindrical source capsule and its housing, the rectangular collimator system, both the primary and secondary jaws and the air gaps between the components. Different collimator openings, ranging from 5 x 5 cm2 to 20 x 20 cm2 (narrow and broad beams) at a source-surface distance equal to 80 cm have been used during the study. In the present work, we have calculated spectra as a function of field size. A study of the variation of the electron contamination of the 60Co beam has also been performed.

Particle generator

DOEpatents

Hess, Wayne P.; Joly, Alan G.; Gerrity, Daniel P.; Beck, Kenneth M.; Sushko, Peter V.; Shlyuger, Alexander L.

2005-06-28

Energy tunable solid state sources of neutral particles are described. In a disclosed embodiment, a halogen particle source includes a solid halide sample, a photon source positioned to deliver photons to a surface of the halide, and a collimating means positioned to accept a spatially defined plume of hyperthermal halogen particles emitted from the sample surface.

NLC Special Projects

Science.gov Websites

Measurement (with NLC RF group) LCLS and related technologies (LCLS work related to NLC work) Collimation Systems (with Beam Delivery group) Combined Laser System (with NLC sources group) Polarized Positron Sources (with NLC sources group) Crab Cavity Phase Control System Timing and RF distribution System (with

3D visualization of optical ray aberration and its broadcasting to smartphones by ray aberration generator

NASA Astrophysics Data System (ADS)

Hellman, Brandon; Bosset, Erica; Ender, Luke; Jafari, Naveed; McCann, Phillip; Nguyen, Chris; Summitt, Chris; Wang, Sunglin; Takashima, Yuzuru

2017-11-01

The ray formalism is critical to understanding light propagation, yet current pedagogy relies on inadequate 2D representations. We present a system in which real light rays are visualized through an optical system by using a collimated laser bundle of light and a fog chamber. Implementation for remote and immersive access is enabled by leveraging a commercially available 3D viewer and gesture-based remote controlling of the tool via bi-directional communication over the Internet.

N, S co-doped-TiO2/fly ash beads composite material and visible light photocatalytic activity

NASA Astrophysics Data System (ADS)

Lv, Jun; Sheng, Tong; Su, Lili; Xu, Guangqing; Wang, Dongmei; Zheng, Zhixiang; Wu, Yucheng

2013-11-01

Using TiCl4 as the titanium source, urea as the precipitating agent, nano-TiO2/fly ash beads composite materials were prepared by hydrolysis-precipitation method. Using (NH2)2CO and (NH2)2SC as the N and S source respectively, N and S co-doped TiO2/fly ash beads composite materials were prepared by grinding them together according to a certain proportion and calcined at 500 °C for 2 h. The composite materials were characterized by SEM, EDS, XPS, and UV-vis spectrophotometer methods. The UV-vis absorption spectra results show that the absorption edge of un-doped composites is 390 nm while that of doped composites red-shifts to 500 nm. The photocatalytic activity of composite materials was evaluated by degradation of methyl orange under visible light irradiation (halogen lamp, 250 W). The results showed that after irradiation for 1 h, degradation rate of N, S co-doped-TiO2/fly ash beads composite material can reach 65%, while the degradation rate of un-doped sample and P25 were just 10% and 6%, respectively. The composite material also showed excellent recycling properties.

Laser Applications in Orthodontics

PubMed Central

Heidari, Somayeh; Torkan, Sepideh

2013-01-01

A laser is a collimated single wavelength of light which delivers a concentrated source of energy. Soon after different types of lasers were invented, investigators began to examine the effects of different wavelengths of laser energy on oral tissues, routine dental procedures and experimental applications. Orthodontists, along with other specialist in different fields of dentistry, can now benefit from several different advantages that lasers provide during the treatment process, from the beginning of the treatment, when separators are placed, to the time of resin residues removal from the tooth surface at the end of orthodontic treatment. This article outlines some of the most common usages of laser beam in orthodontics and also provides a comparison between laser and other conventional method that were the standard of care prior to the advent of laser in this field. PMID:25606324

Techniques in Broadband Interferometry

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

Erskine, D J

2004-01-04

This is a compilation of my patents issued from 1997 to 2002, generally describing interferometer techniques that modify the coherence properties of broad-bandwidth light and other waves, with applications to Doppler velocimetry, range finding, imaging and spectroscopy. Patents are tedious to read in their original form. In an effort to improve their readability I have embedded the Figures throughout the manuscript, put the Figure captions underneath the Figures, and added section headings. Otherwise I have resisted the temptation to modify the words, though I found many places which could use healthy editing. There may be minor differences with the officialmore » versions issued by the US Patent and Trademark Office, particularly in the claims sections. In my shock physics work I measured the velocities of targets impacted by flyer plates by illuminating them with laser light and analyzing the reflected light with an interferometer. Small wavelength changes caused by the target motion (Doppler effect) were converted into fringe shifts by the interferometer. Lasers having long coherence lengths were required for the illumination. While lasers are certainly bright sources, and their collimated beams are convenient to work with, they are expensive. Particularly if one needs to illuminate a wide surface area, then large amounts of power are needed. Orders of magnitude more power per dollar can be obtained from a simple flashlamp, or for that matter, a 50 cent light bulb. Yet these inexpensive sources cannot practically be used for Doppler velocimetry because their coherence length is extremely short, i.e. their bandwidth is much too wide. Hence the motivation for patents 1 & 2 is a method (White Light Velocimetry) for allowing use of these powerful but incoherent lamps for interferometry. The coherence of the illumination is modified by passing it through a preparatory interferometer.« less

Proximal design for a multimodality endoscope with multiphoton microscopy, optical coherence microscopy and visual modalities

NASA Astrophysics Data System (ADS)

Kiekens, Kelli C.; Talarico, Olivia; Barton, Jennifer K.

2018-02-01

A multimodality endoscope system has been designed for early detection of ovarian cancer. Multiple illumination and detection systems must be integrated in a compact, stable, transportable configuration to meet the requirements of a clinical setting. The proximal configuration presented here supports visible light navigation with a large field of view and low resolution, high resolution multiphoton microscopy (MPM), and high resolution optical coherence microscopy (OCM). All modalities are integrated into a single optical system in the endoscope. The system requires two light sources: a green laser for visible light navigation and a compact fiber based femtosecond laser for MPM and OCM. Using an inline wavelength division multiplexer, the two sources are combined into a single mode fiber. To accomplish OCM, a fiber coupler is used to separate the femtosecond laser into a reference arm and signal arm. The reflected reference arm and the signal from the sample are interfered and wavelength separated by a reflection grating and detected using a linear array. The MPM signal is collimated and goes through a series of filters to separate the 2nd and 3rd harmonics as well as twophoton excitation florescence (2PEF) and 3PEF. Each signal is independently detected on a photo multiplier tube and amplified. The visible light is collected by multiple high numerical aperture fibers at the endoscope tip which are bundled into one SMA adapter at the proximal end and connected to a photodetector. This integrated system design is compact, efficient and meets both optical and mechanical requirements for clinical applications.

Realization of rapid debugging for detection circuit of optical fiber gas sensor: Using an analog signal source

NASA Astrophysics Data System (ADS)

Tian, Changbin; Chang, Jun; Wang, Qiang; Wei, Wei; Zhu, Cunguang

2015-03-01

An optical fiber gas sensor mainly consists of two parts: optical part and detection circuit. In the debugging for the detection circuit, the optical part usually serves as a signal source. However, in the debugging condition, the optical part can be easily influenced by many factors, such as the fluctuation of ambient temperature or driving current resulting in instability of the wavelength and intensity for the laser; for dual-beam sensor, the different bends and stresses of the optical fiber will lead to the fluctuation of the intensity and phase; the intensity noise from the collimator, coupler, and other optical devices in the system will also result in the impurity of the optical part based signal source. In order to dramatically improve the debugging efficiency of the detection circuit and shorten the period of research and development, this paper describes an analog signal source, consisting of a single chip microcomputer (SCM), an amplifier circuit, and a voltage-to-current conversion circuit. It can be used to realize the rapid debugging detection circuit of the optical fiber gas sensor instead of optical part based signal source. This analog signal source performs well with many other advantages, such as the simple operation, small size, and light weight.

Stokes polarimetry probe for skin lesion evaluation: preliminary results

NASA Astrophysics Data System (ADS)

Louie, Daniel C.; Tchvialeva, Lioudmilla; Kalia, Sunil; Lui, Harvey; Lee, Tim K.

2018-02-01

This paper reports on the design of a prototype in-vivo Stokes polarimetry probe for skin lesion evaluation, and preliminary results from skin phantom and clinical trials of this device. The probe releases a single millisecond-long pulse from a laser diode with either linear or circular polarization. It then captures the resulting backscattered far-field polarization speckle and calculates the Stokes parameters. This probe was designed with three novel innovations in mind. First, the Stokes vector is captured quickly, using low-cost components without the use of moving parts. Second, a compact collimated laser diode was used as the light source. Third, the device and detector geometry were designed to produce and capture a uniform speckle field. In the first clinical trial of this device, measurements were taken from a variety of skin lesions, both cancerous and benign. The Stokes vector was measured and used to calculate the degree of polarization (DOP), the azimuth angle, and the ellipticity angle of the polarization ellipse for two input light polarizations. Among other findings, the DOP for circular polarized input light was consistently lower than the DOP for linear polarized input light. These findings indicate the potential for a fast and low-cost in-vivo skin cancer screening tool, and encourages the continuing development of this probe's techniques.

PLEIADES: High Peak Brightness, Subpicosecond Thomson Hard-X-ray source

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

Kuba, J; Anderson, S G; Barty, C J

2003-12-15

The Picosecond Laser-Electron Inter-Action for the Dynamic Evaluation of Structures (PLEIADES) facility, is a unique, novel, tunable (10-200 keV), ultrafast (ps-fs), hard x-ray source that greatly extends the parameter range reached by existing 3rd generation sources, both in terms of x-ray energy range, pulse duration, and peak brightness at high energies. First light was observed at 70 keV early in 2003, and the experimental data agrees with 3D codes developed at LLNL. The x-rays are generated by the interaction of a 50 fs Fourier-transform-limited laser pulse produced by the TW-class FALCON CPA laser and a highly focused, relativistic (20-100 MeV),more » high brightness (1 nC, 0.3-5 ps, 5 mm.mrad, 0.2% energy spread) photo-electron bunch. The resulting x-ray brightness is expected to exceed 10{sup 20} ph/mm{sup 2}/s/mrad{sup 2}/0.1% BW. The beam is well-collimated (10 mrad divergence over the full spectrum, 1 mrad for a single color), and the source is a unique tool for time-resolved dynamic measurements in matter, including high-Z materials.« less

Dual-head gamma camera system for intraoperative localization of radioactive seeds

NASA Astrophysics Data System (ADS)

Arsenali, B.; de Jong, H. W. A. M.; Viergever, M. A.; Dickerscheid, D. B. M.; Beijst, C.; Gilhuijs, K. G. A.

2015-10-01

Breast-conserving surgery is a standard option for the treatment of patients with early-stage breast cancer. This form of surgery may result in incomplete excision of the tumor. Iodine-125 labeled titanium seeds are currently used in clinical practice to reduce the number of incomplete excisions. It seems likely that the number of incomplete excisions can be reduced even further if intraoperative information about the location of the radioactive seed is combined with preoperative information about the extent of the tumor. This can be combined if the location of the radioactive seed is established in a world coordinate system that can be linked to the (preoperative) image coordinate system. With this in mind, we propose a radioactive seed localization system which is composed of two static ceiling-suspended gamma camera heads and two parallel-hole collimators. Physical experiments and computer simulations which mimic realistic clinical situations were performed to estimate the localization accuracy (defined as trueness and precision) of the proposed system with respect to collimator-source distance (ranging between 50 cm and 100 cm) and imaging time (ranging between 1 s and 10 s). The goal of the study was to determine whether or not a trueness of 5 mm can be achieved if a collimator-source distance of 50 cm and imaging time of 5 s are used (these specifications were defined by a group of dedicated breast cancer surgeons). The results from the experiments indicate that the location of the radioactive seed can be established with an accuracy of 1.6 mm  ±  0.6 mm if a collimator-source distance of 50 cm and imaging time of 5 s are used (these experiments were performed with a 4.5 cm thick block phantom). Furthermore, the results from the simulations indicate that a trueness of 3.2 mm or less can be achieved if a collimator-source distance of 50 cm and imaging time of 5 s are used (this trueness was achieved for all 14 breast phantoms which were used in this study). Based on these results we conclude that the proposed system can be a valuable tool for (real-time) intraoperative breast cancer localization.

Enhanced PET resolution by combining pinhole collimation and coincidence detection

NASA Astrophysics Data System (ADS)

DiFilippo, Frank P.

2015-10-01

Spatial resolution of clinical PET scanners is limited by detector design and photon non-colinearity. Although dedicated small animal PET scanners using specialized high-resolution detectors have been developed, enhancing the spatial resolution of clinical PET scanners is of interest as a more available alternative. Multi-pinhole 511 keV SPECT is capable of high spatial resolution but requires heavily shielded collimators to avoid significant background counts. A practical approach with clinical PET detectors is to combine multi-pinhole collimation with coincidence detection. In this new hybrid modality, there are three locations associated with each event, namely those of the two detected photons and the pinhole aperture. These three locations over-determine the line of response and provide redundant information that is superior to coincidence detection or pinhole collimation alone. Multi-pinhole collimation provides high resolution and avoids non-colinearity error but is subject to collimator penetration and artifacts from overlapping projections. However the coincidence information, though at lower resolution, is valuable for determining whether the photon passed near a pinhole within the cone acceptance angle and for identifying through which pinhole the photon passed. This information allows most photons penetrating through the collimator to be rejected and avoids overlapping projections. With much improved event rejection, a collimator with minimal shielding may be used, and a lightweight add-on collimator for high resolution imaging is feasible for use with a clinical PET scanner. Monte Carlo simulations were performed of a 18F hot rods phantom and a 54-pinhole unfocused whole-body mouse collimator with a clinical PET scanner. Based on coincidence information and pinhole geometry, events were accepted or rejected, and pinhole-specific crystal-map projections were generated. Tomographic images then were reconstructed using a conventional pinhole SPECT algorithm. Hot rods of 1.4 mm diameter were resolved easily in a simulated phantom. System sensitivity was 0.09% for a simulated 70-mm line source corresponding to the NEMA NU-4 mouse phantom. Higher resolution is expected with further optimization of pinhole design, and higher sensitivity is expected with a focused and denser pinhole configuration. The simulations demonstrate high spatial resolution and feasibility of small animal imaging with an add-on multi-pinhole collimator for a clinical PET scanner. Further work is needed to develop geometric calibration and quantitative data corrections and, eventually, to construct a prototype device and produce images with physical phantoms.

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

Senaratne, Ruwan, E-mail: rsenarat@physics.ucsb.edu; Rajagopal, Shankari V.; Geiger, Zachary A.

We present a simple and inexpensive design for a multichannel effusive oven nozzle which provides improved atomic beam collimation and thus extended oven lifetimes. Using this design, we demonstrate an atomic lithium source suitable for trapped-atom experiments. At a nozzle temperature of 525 °C, the collimated atomic beam flux directly after the nozzle is 1.2 × 10{sup 14} atoms/s with a peak beam intensity greater than 5.0 × 10{sup 16} atoms/s/sr. This suggests an oven lifetime of several decades of continuous operation.

Non-contact continuous-wave diffuse optical tomographic system to capture vascular dynamics in the foot

NASA Astrophysics Data System (ADS)

Hoi, Jennifer W.; Kim, Hyun K.; Khalil, Michael A.; Fong, Christopher J.; Marone, Alessandro; Shrikhande, Gautam; Hielscher, Andreas H.

2015-03-01

Dynamic optical tomographic imaging has shown promise in diagnosing and monitoring peripheral arterial disease (PAD), which affects 8 to 12 million in the United States. PAD is the narrowing of the arteries that supply blood to the lower extremities. Prolonged reduced blood flow to the foot leads to ulcers and gangrene, which makes placement of optical fibers for contact-based optical tomography systems difficult and cumbersome. Since many diabetic PAD patients have foot wounds, a non-contact interface is highly desirable. We present a novel non-contact dynamic continuous-wave optical tomographic imaging system that images the vasculature in the foot for evaluating PAD. The system images at up to 1Hz by delivering 2 wavelengths of light to the top of the foot at up to 20 source positions through collimated source fibers. Transmitted light is collected with an electron multiplying charge couple device (EMCCD) camera. We demonstrate that the system can resolve absorbers at various locations in a phantom study and show the system's first clinical 3D images of total hemoglobin changes in the foot during venous occlusion at the thigh. Our initial results indicate that this system is effective in capturing the vascular dynamics within the foot and can be used to diagnose and monitor treatment of PAD in diabetic patients.

Modulus design multiwavelength polarization microscope for transmission Mueller matrix imaging

NASA Astrophysics Data System (ADS)

Zhou, Jialing; He, Honghui; Chen, Zhenhua; Wang, Ye; Ma, Hui

2018-01-01

We have developed a polarization microscope based on a commercial transmission microscope. We replace the halogen light source by a collimated LED light source module of six different colors. We use achromatic polarized optical elements that can cover the six different wavelength ranges in the polarization state generator (PSG) and polarization state analyzer (PSA) modules. The dual-rotating wave plate method is used to measure the Mueller matrix of samples, which requires the simultaneous rotation of the two quarter-wave plates in both PSG and PSA at certain angular steps. A scientific CCD detector is used as the image receiving module. A LabView-based software is developed to control the rotation angels of the wave plates and the exposure time of the detector to allow the system to run fully automatically in preprogrammed schedules. Standard samples, such as air, polarizers, and quarter-wave plates, are used to calibrate the intrinsic Mueller matrix of optical components, such as the objectives, using the eigenvalue calibration method. Errors due to the images walk-off in the PSA are studied. Errors in the Mueller matrices are below 0.01 using air and polarizer as standard samples. Data analysis based on Mueller matrix transformation and Mueller matrix polarization decomposition is used to demonstrate the potential application of this microscope in pathological diagnosis.

Optical trapping, pulling, and Raman spectroscopy of airborne absorbing particles based on negative photophoretic force

NASA Astrophysics Data System (ADS)

Chen, Gui-hua; He, Lin; Wu, Mu-ying; Yang, Guang; Li, Y. Q.

2017-08-01

Optical pulling is the attraction of objects back to the light source by the use of optically induced "negative forces". The light-induced photophoretic force is generated by the momentum transfer between the heating particles and surrounding gas molecules and can be several orders of magnitude larger than the radiation force and gravitation force. Here, we demonstrate that micron-sized absorbing particles can be optically pulled and manipulated towards the light source over a long distance in air with a collimated Gaussian laser beam based on a negative photophoretic force. A variety of airborne absorbing particles can be pulled by this optical pipeline to the region where they are optically trapped with another focused laser beam and their chemical compositions are characterized with Raman spectroscopy. We found that micron-sized particles are pulled over a meter-scale distance in air with a pulling speed of 1-10 cm/s in the optical pulling pipeline and its speed can be controlled by changing the laser intensity. When an aerosol particle is optically trapped with a focused Gaussian beam, we measured its rotation motion around the laser propagation direction and measured its Raman spectroscopy for chemical identification by molecular fingerprints. The centripetal acceleration of the trapped particle as high as 20 times the gravitational acceleration was observed. Optical pulling over large distances with lasers in combination with Raman spectroscopy opens up potential applications for the collection and identification of atmospheric particles.

Supernova 1987A Interpreted through the SLIP Pulsar Model

NASA Astrophysics Data System (ADS)

Middleditch, John

2010-01-01

The model of pulsar emission through superluminally induced polarization currents (SLIP) predicts that pulsations produced by such currents, induced by a rotating, magnetized body at many light cylinder radii, as would be the case for a neutron star born within any star of >1.5 solar masses, will drive pulsations close to the axis of rotation. Such highly collimated pulsations (<= 1 in 10,000), and the similarly collimated jets of particles which it drove, including 1e-6 solar masses with velocities of up to 0.95 c, were responsible for the features of its very early light curve (days 3 - 20), the "Mystery Spot," observed slightly later (days 30 - 50 and >), and later, in less collimated form, the bipolarity of SN 1987A itself. The pulsations and jet interacted with circumstellar material (CM), to produce features observed in the very early light curve which correspond to: 1) the entry of the pulsed beam into the CM; 2) the entry of the 0.95 c particles into the CM; 3) the exit of the pulsed beam from the CM (with contributions in the B and I bands -- the same as later inferred/observed for its 2.14 ms pulsations); and 4) the exit of the fastest particles from the CM. Because of the energy requirements of the jet in these early stages, the spindown required of its pulsar could exceed 1e-5 Hz/s at a rotation rate of 500 Hz. There is no reason to suggest that this mechanism is not universally applicable to all SNe with gaseous remnants remaining, and thus SN 1987A is the Rosetta Stone for 99% of SNe, gamma-ray bursts, and millisecond pulsars. This work was supported in part by the Department of Energy through the Los Alamos Directed Research Grant DR20080085.

Geometric Characterization of Multi-Axis Multi-Pinhole SPECT

PubMed Central

DiFilippo, Frank P.

2008-01-01

A geometric model and calibration process are developed for SPECT imaging with multiple pinholes and multiple mechanical axes. Unlike the typical situation where pinhole collimators are mounted directly to rotating gamma ray detectors, this geometric model allows for independent rotation of the detectors and pinholes, for the case where the pinhole collimator is physically detached from the detectors. This geometric model is applied to a prototype small animal SPECT device with a total of 22 pinholes and which uses dual clinical SPECT detectors. All free parameters in the model are estimated from a calibration scan of point sources and without the need for a precision point source phantom. For a full calibration of this device, a scan of four point sources with 360° rotation is suitable for estimating all 95 free parameters of the geometric model. After a full calibration, a rapid calibration scan of two point sources with 180° rotation is suitable for estimating the subset of 22 parameters associated with repositioning the collimation device relative to the detectors. The high accuracy of the calibration process is validated experimentally. Residual differences between predicted and measured coordinates are normally distributed with 0.8 mm full width at half maximum and are estimated to contribute 0.12 mm root mean square to the reconstructed spatial resolution. Since this error is small compared to other contributions arising from the pinhole diameter and the detector, the accuracy of the calibration is sufficient for high resolution small animal SPECT imaging. PMID:18293574

High collimated coherent illumination for reconstruction of digitally calculated holograms: design and experimental realization

NASA Astrophysics Data System (ADS)

Morozov, Alexander; Dubinin, German; Dubynin, Sergey; Yanusik, Igor; Kim, Sun Il; Choi, Chil-Sung; Song, Hoon; Lee, Hong-Seok; Putilin, Andrey; Kopenkin, Sergey; Borodin, Yuriy

2017-06-01

Future commercialization of glasses-free holographic real 3D displays requires not only appropriate image quality but also slim design of backlight unit and whole display device to match market needs. While a lot of research aimed to solve computational issues of forming Computer Generated Holograms for 3D Holographic displays, less focus on development of backlight units suitable for 3D holographic display applications with form-factor of conventional 2D display systems. Thereby, we report coherent backlight unit for 3D holographic display with thickness comparable to commercially available 2D displays (cell phones, tablets, laptops, etc.). Coherent backlight unit forms uniform, high-collimated and effective illumination of spatial light modulator. Realization of such backlight unit is possible due to holographic optical elements, based on volume gratings, constructing coherent collimated beam to illuminate display plane. Design, recording and measurement of 5.5 inch coherent backlight unit based on two holographic optical elements are presented in this paper.

Radiative transport produced by oblique illumination of turbid media with collimated beams

NASA Astrophysics Data System (ADS)

Gardner, Adam R.; Kim, Arnold D.; Venugopalan, Vasan

2013-06-01

We examine the general problem of light transport initiated by oblique illumination of a turbid medium with a collimated beam. This situation has direct relevance to the analysis of cloudy atmospheres, terrestrial surfaces, soft condensed matter, and biological tissues. We introduce a solution approach to the equation of radiative transfer that governs this problem, and develop a comprehensive spherical harmonics expansion method utilizing Fourier decomposition (SHEFN). The SHEFN approach enables the solution of problems lacking azimuthal symmetry and provides both the spatial and directional dependence of the radiance. We also introduce the method of sequential-order smoothing that enables the calculation of accurate solutions from the results of two sequential low-order approximations. We apply the SHEFN approach to determine the spatial and angular dependence of both internal and boundary radiances from strongly and weakly scattering turbid media. These solutions are validated using more costly Monte Carlo simulations and reveal important insights regarding the evolution of the radiant field generated by oblique collimated beams spanning ballistic and diffusely scattering regimes.

Benchmarking the MCNP code for Monte Carlo modelling of an in vivo neutron activation analysis system.

PubMed

Natto, S A; Lewis, D G; Ryde, S J

1998-01-01

The Monte Carlo computer code MCNP (version 4A) has been used to develop a personal computer-based model of the Swansea in vivo neutron activation analysis (IVNAA) system. The model included specification of the neutron source (252Cf), collimators, reflectors and shielding. The MCNP model was 'benchmarked' against fast neutron and thermal neutron fluence data obtained experimentally from the IVNAA system. The Swansea system allows two irradiation geometries using 'short' and 'long' collimators, which provide alternative dose rates for IVNAA. The data presented here relate to the short collimator, although results of similar accuracy were obtained using the long collimator. The fast neutron fluence was measured in air at a series of depths inside the collimator. The measurements agreed with the MCNP simulation within the statistical uncertainty (5-10%) of the calculations. The thermal neutron fluence was measured and calculated inside the cuboidal water phantom. The depth of maximum thermal fluence was 3.2 cm (measured) and 3.0 cm (calculated). The width of the 50% thermal fluence level across the phantom at its mid-depth was found to be the same by both MCNP and experiment. This benchmarking exercise has given us a high degree of confidence in MCNP as a tool for the design of IVNAA systems.

The journey from proton to gamma knife.

PubMed

Ganz, Jeremy C

2014-01-01

It was generally accepted by the early 1960s that proton beam radiosurgery was too complex and impractical. The need was seen for a new machine. The beam design had to be as good as a proton beam. It was also decided that a static design was preferable even if the evolution of that notion is no longer clear. Complex collimators were designed that using sources of cobalt-60 could produce beams with characteristics adequately close to those of proton beams. The geometry of the machine was determined including the distance of the sources from the patient the optimal distance between the sources. The first gamma unit was built with private money with no contribution from the Swedish state, which nonetheless required detailed design information in order to ensure radiation safety. This original machine was built with rectangular collimators to produce lesions for thalamotomy for functional work. However, with the introduction of dopamine analogs, this indication virtually disappeared overnight.

A Monte Carlo simulation study for the gamma-ray/neutron dual-particle imager using rotational modulation collimator (RMC).

PubMed

Kim, Hyun Suk; Choi, Hong Yeop; Lee, Gyemin; Ye, Sung-Joon; Smith, Martin B; Kim, Geehyun

2018-03-01

The aim of this work is to develop a gamma-ray/neutron dual-particle imager, based on rotational modulation collimators (RMCs) and pulse shape discrimination (PSD)-capable scintillators, for possible applications for radioactivity monitoring as well as nuclear security and safeguards. A Monte Carlo simulation study was performed to design an RMC system for the dual-particle imaging, and modulation patterns were obtained for gamma-ray and neutron sources in various configurations. We applied an image reconstruction algorithm utilizing the maximum-likelihood expectation-maximization method based on the analytical modeling of source-detector configurations, to the Monte Carlo simulation results. Both gamma-ray and neutron source distributions were reconstructed and evaluated in terms of signal-to-noise ratio, showing the viability of developing an RMC-based gamma-ray/neutron dual-particle imager using PSD-capable scintillators.

Beam Loss Simulation and Collimator System Configurations for the Advanced Photon Source Upgrade

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

Xiao, A.; Borland, M.

The proposed multi-bend achromat lattice for the Advanced Photon Source upgrade (APS-U) has a design emittance of less than 70 pm. The Touschek loss rate is high: compared with the current APS ring, which has an average beam lifetime ~ 10 h, the simulated beam lifetime for APS-U is only ~2 h when operated in the high flux mode (I=200 mA in 48 bunches). An additional consequence of the short lifetime is that injection must be more frequent, which provides another potential source of particle loss. In order to provide information for the radiation shielding system evaluation and to avoidmore » particle loss in sensitive locations around the ring (for example, insertion device straight sections), simulations of the detailed beam loss distribution have been performed. Several possible collimation configurations have been simulated and compared.« less

Characterization of X-Ray Diffraction System with a Microfocus X-Ray Source and a Polycapillary Optic

NASA Technical Reports Server (NTRS)

Gubarev, Mikhail; Marshall, Joy K.; Ciszak, Ewa; Ponomarev, Igor

2000-01-01

We present here an optimized microfocus x-ray source and polycapillary optic system designed for diffraction of small protein crystals. The x-ray beam is formed by a 5.5mm focal length capillary collimator coupled with a 40 micron x-ray source operating at 46Watts. Measurements of the x-ray flux, the divergence and the spectral characteristics of the beam are presented, This optimized system provides a seven fold greater flux than our recently reported configuration [M. Gubarev, et al., J. of Applied Crystallography (2000) 33, in press]. We now make a comparison with a 5kWatts rotating anode generator (Rigaku) coupled with confocal multilayer focusing mirrors (Osmic, CMF12- 38Cu6). The microfocus x-ray source and polycapillary collimator system delivers 60% of the x-ray flux from the rotating anode system. Additional ways to improve our microfocus x-ray system, and thus increase the x-ray flux will be discussed.

Photonics and Optoelectronics

DTIC Science & Technology

2013-03-07

Distribution Outline/Agenda • Nanophotonics: plasmonics, nanostructures, metasurfaces etc • Integrated Nanophotonics & Silicon Photonics...Highlights Nanophotonics Nanophotonics: metasurfaces , nanostructures, plasmonics etc • Shalaev – Broadband Light Bending with Plasmonic...solitons, slot waveguide, “ Metasurface ” collimator etc " World Changing Ideas 2012” Electronic Tattoos, sciencemag , J. Rogers UICU P

Using Light Curves to Characterize Size and Shape of Pseudo-Debris

NASA Technical Reports Server (NTRS)

Rodriquez, Heather M.; Abercromby, Kira J.; Jarvis, Kandy S.; Barker, Edwin

2006-01-01

Photometric measurements were collected for a new study aimed at estimating orbital debris sizes based on object brightness. To obtain a size from optical measurements the current practice is to assume an albedo and use a normalized magnitude to calculate optical size. However, assuming a single albedo value may not be valid for all objects or orbit types; material type and orientation can mask an object s true optical cross section. This experiment used a CCD camera to record data, a 300 W Xenon, Ozone Free collimated light source to simulate solar illumination, and a robotic arm with five degrees of freedom to move the piece of simulated debris through various orientations. The pseudo-debris pieces used in this experiment originate from the European Space Operations Centre s ESOC2 ground test explosion of a mock satellite. A uniformly illuminated white ping-pong ball was used as a zero-magnitude reference. Each debris piece was then moved through specific orientations and rotations to generate a light curve. This paper discusses the results of five different object-based light curves as measured through an x-rotation. Intensity measurements, from which each light curve was generated, were recorded in five degree increments from zero to 180 degrees. Comparing light curves of different shaped and sized pieces against their characteristic length establishes the start of a database from which an optical size estimation model will be derived in the future.

Minibeam Therapy With Protons and Light Ions: Physical Feasibility and Potential to Reduce Radiation Side Effects and to Facilitate Hypofractionation

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

Dilmanian, F. Avraham, E-mail: avraham.dilmanian@stonybrook.edu; Eley, John G.; Krishnan, Sunil

2015-06-01

Purpose: Despite several advantages of proton therapy over megavoltage x-ray therapy, its lack of proximal tissue sparing is a concern. The method presented here adds proximal tissue sparing to protons and light ions by turning their uniform incident beams into arrays of parallel, small, or thin (0.3-mm) pencil or planar minibeams, which are known to spare tissues. As these minibeams penetrate the tissues, they gradually broaden and merge with each other to produce a solid beam. Methods and Materials: Broadening of 0.3-mm-diameter, 109-MeV proton pencil minibeams was measured using a stack of radiochromic films with plastic spacers. Monte Carlo simulationsmore » were used to evaluate the broadening in water of minibeams of protons and several light ions and the dose from neutron generated by collimator. Results: A central parameter was tissue depth, where the beam full width at half maximum (FWHM) reached 0.7 mm, beyond which tissue sparing decreases. This depth was 22 mm for 109-MeV protons in a film stack. It was also found by simulations in water to be 23.5 mm for 109 MeV proton pencil minibeams and 26 mm for 116 MeV proton planar minibeams. For light ions, all with 10 cm range in water, that depth increased with particle size; specifically it was 51 mm for Li-7 ions. The ∼2.7% photon equivalent neutron skin dose from the collimator was reduced 7-fold by introducing a gap between the collimator and the skin. Conclusions: Proton minibeams can be implemented at existing particle therapy centers. Because they spare the shallow tissues, they could augment the efficacy of proton therapy and light particle therapy, particularly in treating tumors that benefit from sparing of proximal tissues such as pediatric brain tumors. They should also allow hypofractionated treatment of all tumors by allowing the use of higher incident doses with less concern about proximal tissue damage.« less

Collimation testing using slit Fresnel diffraction

NASA Astrophysics Data System (ADS)

Luo, Xiaohe; Hui, Mei; Wang, Shanshan; Hou, Yinlong; Zhou, Siyu; Zhu, Qiudong

2018-03-01

A simple collimation testing method based on slit Fresnel diffraction is proposed. The method needs only a CMOS and a slit with no requirement in dimensional accuracy. The light beam to be tested diffracts across the slit and forms a Fresnel diffraction pattern received by CMOS. After analysis, the defocusing amount and the distance between the primary peak point and secondary peak point of diffraction pattern fulfill an expression relationship and then the defocusing amount can be deduced from the expression. The method is applied to both the coherent beam and partially coherent beam, and these two beams are emitted from a laser and light-emitting diode (LED) with a spectrum width of about 50 nm in this paper. Simulations show that the wide spectrum of LED has the effect of smooth filtering to provide higher accuracy. Experiments show that the LED with a spectrum width of about 50 nm has a lower limitation error than the laser and can achieve up to 58.1601 μm with focal length 200 mm and slit width 15 mm.

The realuminizing of the 7-meter-diameter solar simulator collimating mirror

NASA Technical Reports Server (NTRS)

Noller, E. W.

1994-01-01

This paper describes the modification of a three-electron-beam (EB) gun system for vacuum depositing a highly reflective aluminum coating on a 7.01-m (23-ft) -diam nickel-plated aluminum collimating mirror. The mirror is part of the JPL 7.62-m space simulator that was recently modernized with a new high vacuum pumping system, solar lamp power supplies, solar optic lens system, and refurbished collimating mirror. The 7.01-m 12,700-kg (14-ton) spherical collimating mirror was removed from this facility for replating with 381 micron (0.015 in.) of electroless nickel and polished to a specular finish for realuminizing. The space chamber served as the vacuum coating vessel for the realuminizing coating process. The mirror is the primary reflector for the solar simulation system and the aluminized reflective surface is its most critical performance element. The uniformity of thickness and high reflectivity of the coating in visible and near-ultraviolet (UV) light governs the accuracy of the beam for solar testing. The uniformity of the thin-film thickness also controls the durability of the mirror over time. The mirror was polished to a 64-percent reflectivity with a uniformity of 1.5 percent. The performance goal for the aluminizing was 89 percent with +/- 0.5-percent variation over the mirror.

Modified optical fiber daylighting system with sunlight transportation in free space.

PubMed

Vu, Ngoc-Hai; Pham, Thanh-Tuan; Shin, Seoyong

2016-12-26

We present the design, optical simulation, and experiment of a modified optical fiber daylighting system (M-OFDS) for indoor lighting. The M-OFDS is comprised of three sub-systems: concentration, collimation, and distribution. The concentration part is formed by coupling a Fresnel lens with a large-core plastic optical fiber. The sunlight collected by the concentration sub-system is propagated in a plastic optical fiber and then collimated by the collimator, which is a combination of a parabolic mirror and a convex lens. The collimated beam of sunlight travels in free space and is guided to the interior by directing flat mirrors, where it is diffused uniformly by a distributor. All parameters of the system are calculated theoretically. Based on the designed system, our simulation results demonstrated a maximum optical efficiency of 71%. The simulation results also showed that sunlight could be delivered to the illumination destination at distance of 30 m. A prototype of the M-OFDS was fabricated, and preliminary experiments were performed outdoors. The simulation results and experimental results confirmed that the M-OFDS was designed effectively. A large-scale system constructed by several M-OFDSs is also proposed. The results showed that the presented optical fiber daylighting system is a strong candidate for an inexpensive and highly efficient application of solar energy in buildings.

Optical switch

DOEpatents

Reedy, R.P.

1985-01-18

An optical switching device is provided whereby light from a first glass fiber or a second glass fiber may be selectively transmitted into a third glass fiber. Each glass fiber is provided with a focusing and collimating lens system. In one mode of operation, light from the first glass fiber is reflected by a planar mirror into the third glass fiber. In another mode of operation, light from the second glass fiber passes directly into the third glass fiber. The planar mirror is attached to a rotatable table which is rotated to provide the optical switching.

Optical switch

DOEpatents

Reedy, R.P.

1987-11-10

An optical switching device is provided whereby light from a first glass fiber or a second glass fiber may be selectively transmitted into a third glass fiber. Each glass fiber is provided with a focusing and collimating lens system. In one mode of operation, light from the first glass fiber is reflected by a planar mirror into the third glass fiber. In another mode of operation, light from the second glass fiber passes directly into the third glass fiber. The planar mirror is attached to a rotatable table which is rotated to provide the optical switching. 3 figs.

Broadband, Achromatic Twyman-Green Interferometer

NASA Technical Reports Server (NTRS)

Steimle, Lawrence J.

1991-01-01

Improved Twyman-Green interferometer used in wave-front testing optical components at wavelengths from 200 to 1,100 nm, without having to readjust focus when changing wavelength. Built to measure aberrations of light passing through optical filters. Collimating and imaging lenses of classical Twyman-Green configuration replaced by single spherical mirror. Field lens replaced by field mirror. Mirrors exhibit no axial chromatic aberration and made to reflect light efficiently over desired broad range of wavelengths.

Thermal Neutron Point Source Imaging using a Rotating Modulation Collimator (RMC)

DTIC Science & Technology

2010-03-01

Source Details.........................................................................................37 3.5 Simulation of RMC in MCNP ...passed through the masks at each rotation angle. ................................. 42 19. Figure 19: MCNP Generate Modulation Profile for Cadmium. The...Cadmium. The multi-energetic neutron source simulation from MCNP is used for this plot. The energy is values are shown per energy bin. The

Monte Carlo study for designing a dedicated “D”-shaped collimator used in the external beam radiotherapy of retinoblastoma patients

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

Mayorga, P. A.; Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada; Brualla, L.

2014-01-15

Purpose: Retinoblastoma is the most common intraocular malignancy in the early childhood. Patients treated with external beam radiotherapy respond very well to the treatment. However, owing to the genotype of children suffering hereditary retinoblastoma, the risk of secondary radio-induced malignancies is high. The University Hospital of Essen has successfully treated these patients on a daily basis during nearly 30 years using a dedicated “D”-shaped collimator. The use of this collimator that delivers a highly conformed small radiation field, gives very good results in the control of the primary tumor as well as in preserving visual function, while it avoids themore » devastating side effects of deformation of midface bones. The purpose of the present paper is to propose a modified version of the “D”-shaped collimator that reduces even further the irradiation field with the scope to reduce as well the risk of radio-induced secondary malignancies. Concurrently, the new dedicated “D”-shaped collimator must be easier to build and at the same time produces dose distributions that only differ on the field size with respect to the dose distributions obtained by the current collimator in use. The scope of the former requirement is to facilitate the employment of the authors' irradiation technique both at the authors' and at other hospitals. The fulfillment of the latter allows the authors to continue using the clinical experience gained in more than 30 years. Methods: The Monte Carlo codePENELOPE was used to study the effect that the different structural elements of the dedicated “D”-shaped collimator have on the absorbed dose distribution. To perform this study, the radiation transport through a Varian Clinac 2100 C/D operating at 6 MV was simulated in order to tally phase-space files which were then used as radiation sources to simulate the considered collimators and the subsequent dose distributions. With the knowledge gained in that study, a new, simpler, “D”-shaped collimator is proposed. Results: The proposed collimator delivers a dose distribution which is 2.4 cm wide along the inferior-superior direction of the eyeball. This width is 0.3 cm narrower than that of the dose distribution obtained with the collimator currently in clinical use. The other relevant characteristics of the dose distribution obtained with the new collimator, namely, depth doses at clinically relevant positions, penumbrae width, and shape of the lateral profiles, are statistically compatible with the results obtained for the collimator currently in use. Conclusions: The smaller field size delivered by the proposed collimator still fully covers the planning target volume with at least 95% of the maximum dose at a depth of 2 cm and provides a safety margin of 0.2 cm, so ensuring an adequate treatment while reducing the irradiated volume.« less

Self-collimating photonic crystal polarization beam splitter.

PubMed

Zabelin, V; Dunbar, L A; Le Thomas, N; Houdré, R; Kotlyar, M V; O'Faolain, L; Krauss, T F

2007-03-01

We present theoretical and experimental results of a polarization splitter device that consists of a photonic crystal (PhC) slab, which exhibits a large reflection coefficient for TE and a high transmission coefficient for TM polarization. The slab is embedded in a PhC tile operating in the self-collimation mode. Embedding the polarization-discriminating slab in a PhC with identical lattice symmetry suppresses the in-plane diffraction losses at the PhC-non-PhC interface. The optimization of the PhC-non-PhC interface is thereby decoupled from the optimization of the polarizing function. Transmissions as high as 35% for TM- and 30% for TE-polarized light are reported.

Planetary X ray experiment

NASA Technical Reports Server (NTRS)

Anderson, K. A.

1972-01-01

Design studies for an X-ray experiment using solid state detectors and for an experiment using a proportional counter for investigating Jovian and Saturnian magnetospheres are reported. Background counting rates through the forward aperture and leakage fluxes are discussed for each design. It is concluded that the best choice of instrument appears to have following the characteristics: (1) two separate multiwire proportional counters for redundancy; (2) passive collimation to restrict the field to about 5 deg, wiregrid modulation collimation to about 0.1 deg angular resolution; (3) no active shielding system around the counter body; and (4) light passive shielding around any portion of the counter body exposed to space to absorb most of the cosmic X-ray background.

Improvement of the prompt-gamma neutron activation facility at Brookhaven National Laboratory.

PubMed

Dilmanian, F A; Lidofsky, L J; Stamatelatos, I; Kamen, Y; Yasumura, S; Vartsky, D; Pierson, R N; Weber, D A; Moore, R I; Ma, R

1998-02-01

The prompt-gamma neutron activation facility at Brookhaven National Laboratory was upgraded to improve both the precision and accuracy of its in vivo determinations of total body nitrogen. The upgrade, guided by Monte Carlo simulations, involved elongating and modifying the source collimator and its shielding, repositioning the system's two NaI(Tl) detectors, and improving the neutron and gamma shielding of these detectors. The new source collimator has a graphite reflector around the 238PuBe neutron source to enhance the low-energy region of the neutron spectrum incident on the patient. The gamma detectors have been relocated from positions close to the upward-emerging collimated neutron beam to positions close to and at the sides of the patient. These modifications substantially reduced spurious counts resulting from the capture of small-angle scattered neutrons in the NaI detectors. The pile-up background under the 10.8 MeV 14N(n, gamma)15N spectral peak has been reduced so that the nitrogen peak-to-background ratio has been increased by a factor of 2.8. The resulting reduction in the coefficient of variation of the total body nitrogen measurements from 3% to 2.2% has improved the statistical significance of the results possible for any given number of patient measurements. The new system also has a more uniform composite sensitivity.

Converting sunlight into audible sound by means of the photoacoustic effect: The Heliophone.

PubMed

Roozen, N B; Glorieux, C; Liu, L; Rychtáriková, M; Van der Donck, T; Jacobs, A

2016-09-01

One hundred and thirty-five years after Alexander Graham Bell and his assistant Charles Sumner Tainter explored the photoacoustic effect, and about 40 years after Rosencwaig and Gersho modeled the effect in a photoacoustic cell configuration, the phenomenon is revisited in a "Heliophone" device that converts sunlight into sound. The light is focused on a carbon blackened copper coated Kapton foil in an acoustic cell by means of a compound parabolic collimator, and its intensity is modulated by a mechanical chopper. A horn is employed to make the sound audible without electronic amplification. The description of the photoacoustic effect that was introduced by Rosencwaig and Gersho is extended to a cell-horn configuration, in which the periodically heated air above the foil acts as an oscillating piston, driving acoustic waves in the horn. The pressure in the cavity-horn assembly is calculated by considering the air layer piston as an equivalent volume velocity source. The importance of the carbon black (soot) layer to enhance light absorption, but above all to enhance the photothermal excitation efficiency, is elucidated by means of an experimentally supported physical model.

In Situ Aerosol Detector

NASA Technical Reports Server (NTRS)

Vakhtin, Andrei; Krasnoperov, Lev

2011-01-01

An affordable technology designed to facilitate extensive global atmospheric aerosol measurements has been developed. This lightweight instrument is compatible with newly developed platforms such as tethered balloons, blimps, kites, and even disposable instruments such as dropsondes. This technology is based on detection of light scattered by aerosol particles where an optical layout is used to enhance the performance of the laboratory prototype instrument, which allows detection of smaller aerosol particles and improves the accuracy of aerosol particle size measurement. It has been determined that using focused illumination geometry without any apertures is advantageous over using the originally proposed collimated beam/slit geometry (that is supposed to produce uniform illumination over the beam cross-section). The illumination source is used more efficiently, which allows detection of smaller aerosol particles. Second, the obtained integral scattered light intensity measured for the particle can be corrected for the beam intensity profile inhomogeneity based on the measured beam intensity profile and measured particle location. The particle location (coordinates) in the illuminated sample volume is determined based on the information contained in the image frame. The procedure considerably improves the accuracy of determination of the aerosol particle size.

Smartphone instrument for portable enzyme-linked immunosorbent assays

PubMed Central

Long, Kenneth D.; Yu, Hojeong; Cunningham, Brian T.

2014-01-01

We demonstrate the utilization of a smartphone camera as a spectrometer that is capable of measuring Enzyme Linked Immunosorbent Assays (ELISA) at biologically-relevant concentrations with the aid of a custom cradle that aligns a diffraction grating and a collimating lens between a light source and the imaging sensor. Two example biomarkers are assayed using conventional ELISA protocols: IL-6, a protein used diagnostically for several types of cancer, and Ara h 1, one of the principle peanut allergens. In addition to the demonstration of limits of detection at medically-relevant concentrations, a screening of various cookies was completed to measure levels of peanut cross-contamination in local bakeries. The results demonstrate the utility of the instrument for quantitatively performing broad classes of homogeneous colorimetric assays, in which the endpoint readout is the color change of a liquid sample. PMID:25426311

Optical effects module. [housing instruments used to measure degradation of optical samples from contamination during orbital operations

NASA Technical Reports Server (NTRS)

1978-01-01

The possible degradation of optical samples exposed to the effluent gases and particulate matter emanating from the payload of the space transportation system during orbital operations may be determined by measuring two optical parameters for five samples exposed to this environment, namely transmittance and diffuse reflectance. Any changes detected in these parameters as a function of time during the mission are then attributable to surface contamination or to increased material absorption. These basic functions are attained in the optical effects module by virtue of the following subsystems which are described: module enclosure; light source with collimator and modulator; sample wheel with holders and rotary drive; photomultipliers for radiation detection; processing and sequencing electronic circuitry; and power conditioning interfaces. The functions of these subsystems are reviewed and specified.

Neutron range spectrometer

DOEpatents

Manglos, Stephen H.

1989-06-06

A neutron range spectrometer and method for determining the neutron energy spectrum of a neutron emitting source are disclosed. Neutrons from the source are collimnated along a collimation axis and a position sensitive neutron counter is disposed in the path of the collimated neutron beam. The counter determines positions along the collimation axis of interactions between the neutrons in the neutron beam and a neutron-absorbing material in the counter. From the interaction positions, a computer analyzes the data and determines the neutron energy spectrum of the neutron beam. The counter is preferably shielded and a suitable neutron-absorbing material is He-3. The computer solves the following equation in the analysis: ##EQU1## where: N(x).DELTA.x=the number of neutron interactions measured between a position x and x+.DELTA.x, A.sub.i (E.sub.i).DELTA.E.sub.i =the number of incident neutrons with energy between E.sub.i and E.sub.i +.DELTA.E.sub.i, and C=C(E.sub.i)=N .sigma.(E.sub.i) where N=the number density of absorbing atoms in the position sensitive counter means and .sigma. (E.sub.i)=the average cross section of the absorbing interaction between E.sub.i and E.sub.i +.DELTA.E.sub.i.

Small angle light scattering characterization of single micrometric particles in microfluidic flows

NASA Astrophysics Data System (ADS)

Dannhauser, David; Romeo, Giovanni; Causa, Filippo; Netti, Paolo A.

2013-04-01

A CCD-camera based small angle light scattering (SALS) apparatus has been used to characterize single micrometric particles flowing in a micro-channel. The measured scattering vector spans the range 2x10-2 - 6:8x101μm-1. The incident laser light is collimated to a spot of about 50 μm in diameter at the sample position with a divergence lower than 0.045 rad. Such small collimated laser beam opens the possibility to perform on-line SALS of micron-sized particles flowing in micro-channels. By properly designing the micro-channel and using a viscoelastic liquid as suspending medium we are able to realize a precise 3D focusing of the target particles. The forward scattering emitted from the particle is collected by a lens with high numerical aperture. At the focal point of that lens a homemade beam stop is blocking the incident light. Finally, a second lens maps the scattered light on the CCD sensor, allowing to obtain far field images on short distances. Measurements with mono-disperse polystyrene particles, both in quiescent and in-flow conditions have been realized. Experiments in-flow allow to measure the single particle scattering. Results are validated by comparison with calculations based on the Lorenz-Mie theory. The quality of the measured intensity profiles confirms the possibility to use our apparatus in real multiplex applications, with particles down to 1 μm in radius.

Optimization of physiological parameter for macroscopic modeling of reacted singlet oxygen concentration in an in-vivo model

NASA Astrophysics Data System (ADS)

Wang, Ken Kang-Hsin; Busch, Theresa M.; Finlay, Jarod C.; Zhu, Timothy C.

2009-02-01

Singlet oxygen (1O2) is generally believed to be the major cytotoxic agent during photodynamic therapy (PDT), and the reaction between 1O2 and tumor cells define the treatment efficacy. From a complete set of the macroscopic kinetic equations which describe the photochemical processes of PDT, we can express the reacted 1O2 concentration, [1O2]rx, in a form related to time integration of the product of 1O2 quantum yield and the PDT dose rate. The production of [1O2]rx involves physiological and photophysical parameters which need to be determined explicitly for the photosensitizer of interest. Once these parameters are determined, we expect the computed [1O2]rx to be an explicit dosimetric indicator for clinical PDT. Incorporating the diffusion equation governing the light transport in turbid medium, the spatially and temporally-resolved [1O2]rx described by the macroscopic kinetic equations can be numerically calculated. A sudden drop of the calculated [1O2]rx along with the distance following the decrease of light fluence rate is observed. This suggests that a possible correlation between [1O2]rx and necrosis boundary may occur in the tumor subject to PDT irradiation. In this study, we have theoretically examined the sensitivity of the physiological parameter from two clinical related conditions: (1) collimated light source on semi-infinite turbid medium and (2) linear light source in turbid medium. In order to accurately determine the parameter in a clinical relevant environment, the results of the computed [1O2]rx are expected to be used to fit the experimentally-measured necrosis data obtained from an in vivo animal model.

Apparatus for and method of performing spectroscopic analysis on an article

DOEpatents

Powell, George Louis; Hallman, Jr., Russell Louis

1999-01-01

An apparatus for and method of analyzing an article having an entrance and an exit in communication with the entrance. The apparatus comprises: a spectrometer having an emission source with a focal point; a plurality of mirrors; and a detector connected to the spectroscope. The emission source is positioned so that its focal point is substantially coextensive with the entrance of the article. The mirrors comprise: a first mirror positionable adjacent the exit of the article and a second mirror positioned relative to the other of said plurality of mirrors. The first mirror receives scattered emissions exiting the article and substantially collimates the scattered emissions. The second mirror substantially focuses the collimated emissions into a focused emission. The detector receives the focused emission from the mirrors.

Apparatus for and method of performing spectroscopic analysis on an article

DOEpatents

Powell, G.L.; Hallman, R.L. Jr.

1999-04-20

An apparatus and method are disclosed for analyzing an article having an entrance and an exit in communication with the entrance. The apparatus comprises: a spectrometer having an emission source with a focal point; a plurality of mirrors; and a detector connected to the spectroscope. The emission source is positioned so that its focal point is substantially coextensive with the entrance of the article. The mirrors comprise: a first mirror positionable adjacent the exit of the article and a second mirror positioned relative to the other of said plurality of mirrors. The first mirror receives scattered emissions exiting the article and substantially collimates the scattered emissions. The second mirror substantially focuses the collimated emissions into a focused emission. The detector receives the focused emission from the mirrors. 6 figs.

Maskless Lithography Using Surface Plasmon Enhanced Illumination

DTIC Science & Technology

2007-04-30

Dale Larson Figure 1. Nanohole array probes exhibiting extraordinary optical transmission of light with a high degree of collimation. Left: a bull’s...Technol. B 22, 3552-3556 (2004). 2. Stark, P., Halleck, A. E. & Larson, D. N. Short order nanohole arrays in metals for highly sensitive probing of local

Rarefaction acceleration of ultrarelativistic magnetized jets in gamma-ray burst sources

NASA Astrophysics Data System (ADS)

Komissarov, Serguei S.; Vlahakis, Nektarios; Königl, Arieh

2010-09-01

When a magnetically dominated superfast-magnetosonic long/soft gamma-ray burst (GRB) jet leaves the progenitor star, the external pressure support will drop and the jet may enter the regime of ballistic expansion, during which additional magnetic acceleration becomes ineffective. However, recent numerical simulations by Tchekhovskoy et al. have suggested that the transition to this regime is accompanied by a spurt of acceleration. We confirm this finding numerically and attribute the acceleration to a sideways expansion of the jet, associated with a strong magnetosonic rarefaction wave that is driven into the jet when it loses pressure support, which induces a conversion of magnetic energy into kinetic energy of bulk motion. This mechanism, which we dub rarefaction acceleration, can only operate in a relativistic outflow because in this case the total energy can still be dominated by the magnetic component even in the superfast-magnetosonic regime. We analyse this process using the equations of relativistic magnetohydrodynamics and demonstrate that it is more efficient at converting internal energy into kinetic energy when the flow is magnetized than in a purely hydrodynamic outflow, as was found numerically by Mizuno et al. We show that, just as in the case of the magnetic acceleration of a collimating jet that is confined by an external pressure distribution - the collimation-acceleration mechanism - the rarefaction-acceleration process in a magnetized jet is a consequence of the fact that the separation between neighbouring magnetic flux surfaces increases faster than their cylindrical radius. However, whereas in the case of effective collimation-acceleration the product of the jet opening angle and its Lorentz factor does not exceed ~1, the addition of the rarefaction-acceleration mechanism makes it possible for this product to become >>1, in agreement with the inference from late-time panchromatic breaks in the afterglow light curves of long/soft GRBs.

Near-Infrared Spectroscopy Using a Supercontinuum Laser: Application to Long Wavelength Transmission Spectra of Barley Endosperm and Oil.

PubMed

Ringsted, Tine; Dupont, Sune; Ramsay, Jacob; Jespersen, Birthe Møller; Sørensen, Klavs Martin; Keiding, Søren Rud; Engelsen, Søren Balling

2016-07-01

The supercontinuum laser is a new type of light source, which combines the collimation and intensity of a laser with the broad spectral region of a lamp. Using such a source therefore makes it possible to focus the light onto small sample areas without losing intensity and thus facilitate either rapid or high-intensity measurements. Single seed transmission analysis in the long wavelength (LW) near-infrared (NIR) region is one area that might benefit from a brighter light source such as the supercontinuum laser. This study is aimed at building an experimental spectrometer consisting of a supercontinuum laser source and a dispersive monochromator in order to investigate its capability to measure the barley endosperm using transmission experiments in the LW NIR region. So far, barley and wheat seeds have only been studied using NIR transmission in the short wavelength region up to 1100 nm. However, the region in the range of 2260-2380 nm has previously shown to be particularly useful in differentiating barley phenotypes using NIR spectroscopy in reflectance mode. In the present study, 350 seeds (consisting of 70 seeds from each of five barley genotypes) in 1 mm slices were measured by NIR transmission in the range of 2235-2381 nm and oils from the same five barley genotypes were measured in a cuvette with a 1 mm path length in the range of 2003-2497 nm. The spectra of the barley seeds could be classified according to genotypes by principal component analysis; and spectral covariances with reference analysis of moisture, β-glucan, starch, protein and lipid were established. The spectral variations of the barley oils were compared to the fatty acid compositions as measured using gas chromotography-mass spectrometry (GC-MS). © The Author(s) 2016.

SeHCAT retention values as measured with a collimated and an uncollimated gamma camera: a method comparison study.

PubMed

Wright, James W; Lovell, Lesley A; Gemmell, Howard G; McKiddie, Fergus; Staff, Roger T

2013-07-01

TauroH-23-(Se) selena-25-homocholic acid retention values are used in the diagnosis of bile acid malabsorption. The standard method for measuring values is with an uncollimated gamma camera, which can create some logistic difficulties, with other background sources of activity, which are irrelevant when a collimator is used, becoming significant. In this study we compare the retention values obtained with a collimated and an uncollimated gamma camera in phantoms and in 23 patients. Bland-Altman plots were created using the data, which showed a mean bias in retention of 0.10% in the phantom study and 0.55% in the patient study between methods. A Wilcoxon signed-rank test with the null hypothesis of zero median difference between uncollimated and collimated methods was not statistically significant to P values less than 0.05 in the patient and phantom studies. In the patient study, on using a fixed boundary of retention (10%) between positive and negative status, the status of one patient was changed from negative (12%) to positive (9%). We conclude that measurement of retention with a collimated gamma camera is similar but not identical to that of uncollimated values. The clinical significance of this shift is unclear, as the threshold of significance and the method of integrating this measure with other clinical factors into management remain unclear.

High flux table-top ultrafast soft X-ray source generated by high harmonic generation

NASA Astrophysics Data System (ADS)

Thiré, Nicolas; Schmidt, Bruno E.; Fourmeaux, Sylvain; Beaulieu, Samuel; Cardin, Vincent; Negro, Matteo; Kieffer, Jean-Claude; Vozzi, Caterina; Legare, François

2014-05-01

Generation of ultrafast soft X-ray pulses is a major challenge for conventional laboratories. Using the process of HHG enables generation of such short wavelength photons. Intense laser sources in the infrared are necessary to reach the soft X-ray spectral range as the HHG cut-off scales with Iλ2. However, in the limit of the single atom response, increasing the laser wavelength leads to a significant decrease of the HHG flux. To compensate, one has to increase the number of emitters with high ionization potential. At the Advanced Laser Light Source, we have addressed this challenge by using a new gas cell design and developing a 10 mJ - 30 fs source at 1.8 μm. Using this setup, we have been able to generate harmonics in the water window spectral range for neon and helium with short time duration (<30 fs) in a conventional laboratory. A flux measurement has been performed showing ~ 2 × 105 photons/shot between 280 and 540 eV, making it possible to see the carbon k-edge at 280eV in a single shot manner. This soft X-ray beam is also extremely well collimated (0.1 mrad) making it this table-top beamline ideal for a number of applications.

Scattered light in a DMD based multi-object spectrometer

NASA Astrophysics Data System (ADS)

Fourspring, Kenneth D.; Ninkov, Zoran; Kerekes, John P.

2010-07-01

The DMD (Digital Micromirror Device) has an important future in both ground and space based multi-object spectrometers. A series of laboratory measurements have been performed to determine the scattered light properties of a DMD. The DMD under test had a 17 μm pitch and 1 μm gap between adjacent mirrors. Prior characterization of this device has focused on its use in DLP (TI Digital Light Processing) projector applications in which a whole pixel is illuminated by a uniform collimated source. The purpose of performing these measurements is to determine the limiting signal to noise ratio when utilizing the DMD as a slit mask in a spectrometer. The DMD pixel was determined to scatter more around the pixel edge and central via, indicating the importance of matching the telescope point spread function to the DMD. Also, the generation of DMD tested here was determined to have a significant mirror curvature. A maximum contrast ratio was determined at several wavelengths. Further measurements are underway on a newer generation DMD device, which has a smaller mirror pitch and likely different scatter characteristics. A previously constructed instrument, RITMOS (RIT Multi-Object Spectrometer) will be used to validate these scatter models and signal to noise ratio predications through imaging a star field.

3 GeV Booster Synchrotron Conceptual Design Report

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

Wiedemann, Helmut

2009-06-02

Synchrotron light cna be produced from a relativistic particle beam circulating in a storage ring at extremely high intensity and brilliance over a large spectral region reaching from the far infrared regime to hard x-rays. The particles, either electrons or positrons, radiate as they are deflected in the fields of the storage ring bending magnets or of magnets specially optimized for the production of synchrotron light. The synchrotron light being very intense and well collimated in the forward direction has become a major tool in a large variety of research fields in physics, chemistry, material science, biology, and medicine.

Modulus design multiwavelength polarization microscope for transmission Mueller matrix imaging.

PubMed

Zhou, Jialing; He, Honghui; Chen, Zhenhua; Wang, Ye; Ma, Hui

2018-01-01

We have developed a polarization microscope based on a commercial transmission microscope. We replace the halogen light source by a collimated LED light source module of six different colors. We use achromatic polarized optical elements that can cover the six different wavelength ranges in the polarization state generator (PSG) and polarization state analyzer (PSA) modules. The dual-rotating wave plate method is used to measure the Mueller matrix of samples, which requires the simultaneous rotation of the two quarter-wave plates in both PSG and PSA at certain angular steps. A scientific CCD detector is used as the image receiving module. A LabView-based software is developed to control the rotation angels of the wave plates and the exposure time of the detector to allow the system to run fully automatically in preprogrammed schedules. Standard samples, such as air, polarizers, and quarter-wave plates, are used to calibrate the intrinsic Mueller matrix of optical components, such as the objectives, using the eigenvalue calibration method. Errors due to the images walk-off in the PSA are studied. Errors in the Mueller matrices are below 0.01 using air and polarizer as standard samples. Data analysis based on Mueller matrix transformation and Mueller matrix polarization decomposition is used to demonstrate the potential application of this microscope in pathological diagnosis. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Study on Dynamic Alignment Technology of COIL Resonator

NASA Astrophysics Data System (ADS)

Xiong, M. D.; Zou, X. J.; Guo, J. H.; Jia, S. N.; Zhang2, Z. B.

2006-10-01

The performance of great power chemical oxygen-iodine laser (COIL) beam is decided mostly by resonator mirror maladjustment and environment vibration. To improve the performance of light beam, an auto-alignment device is used in COIL resonator, the device can keep COIL resonator collimating by adjusting the optical components of resonator. So the coupling model of COIL resonator is present. The multivariable self study fuzzy uncoupling arithmetic and six-dimensional micro drive technology are used to design a six-input-three-output uncoupling controller, resulting in the realization of the high precision dynamic alignment. The experiments indicate that the collimating range of this system is 8 mrad, precision is 5 urad and frequency response is 20Hz, which meet the demand of resonator alignment system.

The optical design and simulation of the collimated solar simulator

NASA Astrophysics Data System (ADS)

Zhang, Jun; Ma, Tao

2018-01-01

The solar simulator is a lighting device that can simulate the solar radiation. It has been widely used in the testing of solar cells, satellite space environment simulation and ground experiment, test and calibration precision of solar sensor. The solar simulator mainly consisted of short—arc xenon lamp, ellipsoidal reflectors, a group of optical integrator, field stop, aspheric folding mirror and collimating reflector. In this paper, the solar simulator's optical system basic size are given by calculation. Then the system is optically modeled with the Lighttools software, and the simulation analysis on solar simulator using the Monte Carlo ray -tracing technique is conducted. Finally, the simulation results are given quantitatively by diagrammatic form. The rationality of the design is verified on the basis of theory.

Illumination design for semiconductor backlight inspection and application extensions

NASA Astrophysics Data System (ADS)

Zhou, Wei; Rutherford, Todd; Hart, Darcy

2013-09-01

High speed strobe based illumination scheme is one of the most critical factors for high throughput semiconductor defect inspection applications. HB LEDs are always the first and best options for such applications due to numerous unique advantages such as excellent spatial and temporal stability, fast responding time, large and linear intensity dynamic range and no heat issue for the extremely low duty cycle applications. For some applications where a large area is required to be illuminated simultaneously, it remains a great challenge to efficiently package a large amount of HB-LEDs in a highly confined 3D space, to generate a seamless illuminated area with high luminance efficiency and spatial uniformity. A novel 3D structured collimation lens is presented in this paper. The non-circular edge shape reduces the intensity drop at the channel boundaries, while the secondary curvatures on the top of the collimator lens efficiently guides the light into desired angular space. The number of the edges and the radius of the top surface curvature are control parameters for the system level performance and the manufacture cost trade-off. The proposed 3D structured LED collimation lens also maintains the benefits of traditional LED collimation lens such as coupling efficiency and mold manufacture capability. The applications can be extended into other non-illumination area like parallelism measurement and solar panel concentrator etc.

Time-Resolved Hot Electron Transport in Electronic Devices

DTIC Science & Technology

1988-12-01

fluctuations of any given spectral portion of the continuum are about 8-12% rms. The white light is collimated by a 38-mm achromatic lens after the glycol jet...due to GVD in the glycol jet, lenses , and filters between the red and blue portions of the probe spectrum can be significant. This temporal shift can be...microjoule level at kilohertz repetition rates. At this energy level a light continuum can be produced. This laser system allowed us to study both in

Time-resolved forward-light-scattering monitoring of protein–lysozyme aggregation in precrystalline solutions

NASA Astrophysics Data System (ADS)

Wakamatsu, Takashi; Onoda, Takashi; Ogata, Makoto

2018-05-01

An in situ measurement method of monitoring protein aggregation in precrystalline solutions is presented. The method is based on a small-angle forward static light scattering (F-SLS) technique. This technique uses an accurate optical arrangement of a combination of a collimating lens and a CCD to obtain an F-SLS pattern from an aggregate-containing protein solution in one shot. The real-time observation of a crystallizing lysozyme captured the formation of fractal aggregates in the initial formation stage.

Scientific investigations with the data base HEAO-1 scanning modulator collimator

NASA Technical Reports Server (NTRS)

Schwartz, Daniel A.

1992-01-01

The hardware specification for the Scanning Modulation Collimator (MC) experiment on HEAO-1 was to measure positions of bright (greater than 10(exp -11) ergs/cm(exp 2)s), hard (1 to 15 keV) x-ray sources to 5-10 arcsec, and to measure their size and structure in three energy bands down to 10 arcsec resolution. The scientific purpose of this specification was to enable the identification of these x-ray sources with optical and radio objects in order to elucidate the x-ray emission mechanism and the nature of the candidate astronomical system. The experiment was an outstanding success. Hardware systems functioned perfectly although loss of one (out of eight) proportional counters degraded our sensitivity by about 10 percent. Our aspect solution of 7 arcsec precision, allowed us to achieve statistic-limited location precision for all but the strongest sources. We vigorously pursued a strategy of determining the scientific importance of each identification, and of publishing each scientific result as it came along.

Compton backscattered collimated x-ray source

DOEpatents

Ruth, R.D.; Huang, Z.

1998-10-20

A high-intensity, inexpensive and collimated x-ray source is disclosed for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications. 4 figs.

Compton backscattered collimated x-ray source

DOEpatents

Ruth, Ronald D.; Huang, Zhirong

1998-01-01

A high-intensity, inexpensive and collimated x-ray source for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications.

Plasma surface reflectance spectroscopy for non-invasive and continuous monitoring of extracellular component of blood

NASA Astrophysics Data System (ADS)

Sakota, Daisuke; Takatani, Setsuo

2012-04-01

To achieve the quantitative optical non-invasive diagnosis of blood during extracorporeal circulation therapies, the instrumental technique to extract extracellular spectra from whole blood was developed. In the circuit, the continuous blood flow was generated by a centrifugal blood pump. The oxygen saturation was maintained 100% by an oxygenator. The developed glass optical flow cell was attached to the outlet tubing of the oxygenator. The halogen lamp including the light from 400 to 900 nm wavelength was used for the light source. The light was guided into an optical fiber. The light emitted by the fiber was collimated and emitted to the flow cell flat surface at the incident angle of 45 degrees. The light just reflected on the boundary between inner surface of the flow cell and plasma at 45 degrees was detected by the detection fiber. The detected light was analyzed by a spectral photometer. The obtained spectrum from 400 to 600nm wavelength was not changed with respect to the hematocrit. In contrast, the signal in the spectral range was changed when the plasma free hemoglobin increased. By using two spectral range, 505+/-5 nm and 542.5+/-2.5 nm, the differential spectrum was correlated with the free hemoglobin at R2=0.99. On the other hand, as for the hematocrit, the differential spectrum was not correlated at R2=0.01. Finally, the plasma free hemoglobin was quantified with the accuracy of 22+/-19mg/dL. The result shows that the developed plasma surface reflectance spectroscopy (PSRS) can extract the plasma spectrum from flowing whole blood.

Infrared emission in Seyfert 2 galaxies - Reprocessed radiation from a dusty torus?

NASA Technical Reports Server (NTRS)

Storchi-Bergmann, Thaisa; Mulchaey, John S.; Wilson, Andrew S.

1992-01-01

New and existing data for a sample of nine Seyfert 2 galaxies with known 'ionization cones' are combined in order to test whether collimation results from shadowing of radiation from a small isotropic nuclear source by a thick dusty torus. The number of ionizing photons emitted by the compact nucleus is calculated from the emission-line ratios measured for gas within the cones. On the assumption that this compact nuclear source radiates isotropically, the optical-UV power incident on the torus, which is expected to be reradiated in the IR, is determined. It is found that the observed IRAS luminosities are consistent with the torus model in eight of the nine objects with sufficient data to perform the calculation. It is concluded that the data are generally consistent with collimation and reradiation by a dusty torus.

Missouri University Multi-Plane Imager (MUMPI): A high sensitivity rapid dynamic ECT brain imager

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

Logan, K.W.; Holmes, R.A.

1984-01-01

The authors have designed a unique ECT imaging device that can record rapid dynamic images of brain perfusion. The Missouri University Multi-Plane Imager (MUMPI) uses a single crystal detector that produces four orthogonal two-dimensional images simultaneously. Multiple slice images are reconstructed from counts recorded from stepwise or continuous collimator rotation. Four simultaneous 2-d image fields may also be recorded and reviewed. The cylindrical sodium iodide crystal and the rotating collimator concentrically surround the source volume being imaged with the collimator the only moving part. The design and function parameters of MUMPI have been compared to other competitive tomographic head imagingmore » devices. MUMPI's principal advantages are: 1) simultaneous direct acquisition of four two-dimensional images; 2) extremely rapid project set acquisition for ECT reconstruction; and 3) instrument practicality and economy due to single detector design and the absence of heavy mechanical moving components (only collimator rotation is required). MUMPI should be ideal for imaging neutral lipophilic chelates such as Tc-99m-PnAO which passively diffuses across the intact blood-brain-barrier and rapidly clears from brain tissue.« less

Conceptual development of the Laser Beam Manifold (LBM)

NASA Technical Reports Server (NTRS)

Campbell, W.; Owen, R. B.

1979-01-01

The laser beam manifold, a device for transforming a single, narrow, collimated beam of light into several beams of desired intensity ratios is described. The device consists of a single optical substrate with a metallic coating on both optical surfaces. By changing the entry point, the number of outgoing beams can be varied.

Summary of the 2014 Beam-Halo Monitoring Workshop

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

Fisher, Alan

2015-09-25

Understanding and controlling beam halo is important for high-intensity hadron accelerators, for high-brightness electron linacs, and for low-emittance light sources. This can only be achieved by developing suitable diagnostics. The main challenge faced by such instrumentation is the high dynamic range needed to observe the halo in the presence of an intense core. In addition, measurements must often be made non-invasively. This talk summarizes the one-day workshop on Beam-Halo Monitoring that was held at SLAC on September 19 last year, immediately following IBIC 2014 in Monterey. Workshop presentations described invasive techniques using wires, screens, or crystal collimators, and non-invasive measurementsmore » with gas or scattered electrons. Talks on optical methods showed the close links between observing halo and astronomical problems like observing the solar corona or directly observing a planet orbiting another star.« less

Plasmonic beaming and active control over fluorescent emission.

PubMed

Jun, Young Chul; Huang, Kevin C Y; Brongersma, Mark L

2011-01-01

Nanometallic optical antennas are rapidly gaining popularity in applications that require exquisite control over light concentration and emission processes. The search is on for high-performance antennas that offer facile integration on chips. Here we demonstrate a new, easily fabricated optical antenna design that achieves an unprecedented level of control over fluorescent emission by combining concepts from plasmonics, radiative decay engineering and optical beaming. The antenna consists of a nanoscale plasmonic cavity filled with quantum dots coupled to a miniature grating structure that can be engineered to produce one or more highly collimated beams. Electromagnetic simulations and confocal microscopy were used to visualize the beaming process. The metals defining the plasmonic cavity can be utilized to electrically control the emission intensity and wavelength. These findings facilitate the realization of a new class of active optical antennas for use in new optical sources and a wide range of nanoscale optical spectroscopy applications.

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

NASA Astrophysics Data System (ADS)

Kawashima, Natsumi; Hosono, Satsuki; Ishimaru, Ichiro

2016-05-01

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

Highly Collimated Jets and Wide-angle Outflows in HH 46/47: New Evidence from Spitzer Infrared Images

NASA Technical Reports Server (NTRS)

Velusamy, T.; Langer, William D.; Marsh, Kenneth. A.

2007-01-01

We present new details of the structure and morphology of the jets and outflows in HH 46/47 as seen in Spitzer infrared images from IRAC and MIPS, reprocessed using the 'HiRes' deconvolution technique. HiRes improves the visualization of spatial morphology by enhancing resolution (to subarcsecond levels in IRAC bands) and removing the contaminating side lobes from bright sources. In addition to sharper views of previously reported bow shocks, we have detected (1) the sharply delineated cavity walls of the wide-angle biconical outflow, seen in scattered light on both sides of the protostar, (2) several very narrow jet features at distances approximately 400 AU to approximately 0.1 pc from the star, and (3) compact emissions at MIPS 24 m with the jet heads, tracing the hottest atomic/ionic gas in the bow shocks. Together the IRAC and MIPS images provide a more complete picture of the bow shocks, tracing both the molecular and atomic/ionic gases, respectively. The narrow width and alignment of all jet-related features indicate a high degree of jet collimation and low divergence (width of approximately 400 AU increasing by only a factor of 2.3 over 0.2 pc). The morphology of this jet, bow shocks, wide-angle outflows, and the fact that the jet is nonprecessing and episodic, constrain the mechanisms for producing the jet's entrained molecular gas, and origins of the fast jet, and slower wide-angle outflow.

Line defects on As2Se3-Chalcogenide photonic crystals for the design of all-optical power splitters and digital logic gates

NASA Astrophysics Data System (ADS)

Saghaei, Hamed; Zahedi, Abdulhamid; Karimzadeh, Rouhollah; Parandin, Fariborz

2017-10-01

In this paper, a triangular two-dimensional photonic crystal (PhC) of As2Se3-chalcogenide rods in air is presented and its photonic band diagram is calculated by plane wave method. In this structure, an optical waveguide is obtained by creating a line defect (eliminating rods) in diagonal direction of PhC. Numerical simulations based on finite difference time domain method show that when self-collimated beams undergo total internal reflection at the PhC-air interface, a total reflection of 90° occurs for the output beams. We also demonstrate that by decreasing the radius of As2Se3-chalcogenide instead of eliminating a diagonal line, a two-channel optical splitter will be designed. In this case, incoming self-collimated beams can be divided into the reflected and transmitted beams with arbitrary power ratio by adjusting the value of their radii. Based on these results, we propose a four-channel optical splitter using four line defects. The power ratio among output channels can be controlled systematically by varying the radius of rods in the line defects. We also demonstrate that by launching two optical sources with the same intensity and 90° phase difference from both perpendicular faces of the PhC, two logic OR and XOR gates will be achieved at the output channels. These optical devices have some applications in photonic integrated circuits for controlling and steering (managing) the light as desired.

SHIELDING CONSIDERATIONS FOR THE SMALL ANIMAL RADIATION RESEARCH PLATFORM (SARRP)

PubMed Central

Sayler, Elaine; Dolney, Derek; Avery, Stephen; Koch, Cameron

2014-01-01

The Small Animal Radiation Research Platform (SARRP) is a commercially available platform designed to deliver conformal, image-guided radiation to small animals using a dual-anode kV x-ray source. At the University of Pennsylvania, a free-standing 2 m3 enclosure was designed to shield the SARRP according to federal code regulating cabinet x-ray systems. The initial design consisted of 4.0-mm-thick lead for all secondary barriers and proved wholly inadequate. Radiation levels outside the enclosure were 15 times higher than expected. Additionally, the leakage appeared to be distributed broadly within the enclosure, so concern arose that a subject might receive significant doses outside the intended treatment field. Thus, a detailed analysis was undertaken to identify and block all sources of leakage. Leakage sources were identified by Kodak X-OmatV (XV) film placed throughout the enclosure. Radiation inside the enclosure was quantified using Gafchromic film. Outside the enclosure, radiation was measured using a survey meter. Sources of leakage included (1) an unnecessarily broad beam exiting the tube, (2) failure of the secondary collimator to confine the primary beam entirely, (3) scatter from the secondary collimator, (4) lack of beam-stop below the treatment volume, and (5) incomplete shielding of the x-ray tube. The exit window was restricted, and a new collimator was designed to address problems (1–3). A beam-stop and additional tube shielding were installed. These modifications reduced internal scatter by more than 100-fold. Radiation outside the enclosure was reduced to levels compliant with federal regulations, provided the SARRP is operated using tube potentials of 175 kV or less. In addition, these simple and relatively inexpensive modifications eliminate the possibility of exposing a larger animal (such as a rat) to significant doses outside the treatment field. PMID:23532076

Single surface barrier detectors for neutron dosimetry and associated light-ion fluxes

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

Treado, P.A.; Allas, R.G.; Eman, B.

1981-04-01

In this paper the authors have attempted to perfect a simple, compact and inexpensive single surface barrier detection system to measure both the intensities and approximate spectral shape of continuous neutron and light ion fluxes. They have measured such fluxes for three known collimated and uncollimated neutron beams with two geometrical configurations and with at least two different thicknesses of CH/sub 2/ and CD/sub 2/ radiators. All neutron flux data were obtained with a Au shield in front of the detector; this was removed for LIF measurements. The known shapes of the impinging neutron beams were used to calculate themore » expected recoil-particle spectra and such predictions have been compared with the experimental data. Also, data have been obtained with telescopes, with carbon foil and thin detector-grade silicon foil radiators. These data allow the authors to estimate contributions to the higher-energy portion of the recoil-particle spectra from reactions due to the carbon in the CH/sub 2/ and CD/sub 2/ radiators and due to the silicon in the detector. Corrections for rim effects in the detector and multiple scattering in the radiator are calculable. The precipitous decrease in the number of observed events, expected at the maximum energy that can be deposited by a recoil particle from the radiator, was observed for each of the radiator/detector combinations studied. The data agree reasonably well with both the intensity and spectral shape predictions for recoil-particle energies above about 300 keV. The telescope data confirm the single-detector data and add significant information about the LIFs created by the collimation of the neutron beams. In fact, both the single-detector and telescope data indicate that (n,p) reactions in collimation and target-backing materials contribute significant proton components to the light-ion fluxes.« less

SU-E-T-24: Development and Implementation of an Automated Algorithm to Determine Radiation Isocenter, Radiation vs. Light Field Coincidence, and Analyze Strip Tests.

PubMed

Hyer, D; Mart, C

2012-06-01

The aim of this study was to develop a phantom and analysis software that could be used to quickly and accurately determine the location of radiation isocenter using the Electronic Portal Imaging Device (EPID). The phantom could then be used as a static reference point for performing other tests including: radiation vs. light field coincidence, MLC and Jaw strip tests, and Varian Optical Guidance Platform (OGP) calibration. The solution proposed uses a collimator setting of 10×10 cm to acquire EPID images of the new phantom constructed from LEGO® blocks. Images from a number of gantry and collimator angles are analyzed by the software to determine the position of the jaws and center of the phantom in each image. The distance between a chosen jaw and the phantom center is then compared to the same distance measured after a 180 degree collimator rotation to determine if the phantom is centered in the dimension being investigated. The accuracy of the algorithm's measurements were verified by independent measurement to be approximately equal to the detector's pitch. Light versus radiation field as well as MLC and Jaw strip tests are performed using measurements based on the phantom center once located at the radiation isocenter. Reproducibility tests show that the algorithm's results were objectively repeatable. Additionally, the phantom and software are completely independent of linac vendor and this study presents results from two major linac manufacturers. An OGP calibration array was also integrated into the phantom to allow calibration of the OGP while the phantom is positioned at radiation isocenter to reduce setup uncertainty contained in the calibration. This solution offers a quick, objective method to perform isocenter localization as well as laser alignment, OGP calibration, and other tests on a monthly basis. © 2012 American Association of Physicists in Medicine.

Compact 2100 nm laser diode module for next-generation DIRCM

NASA Astrophysics Data System (ADS)

Dvinelis, Edgaras; Greibus, Mindaugas; TrinkÅ«nas, Augustinas; NaujokaitÄ--, Greta; Vizbaras, Augustinas; Vizbaras, Dominykas; Vizbaras, Kristijonas

2017-10-01

Compact high-power 2100 nm laser diode module for next-generation directional infrared countermeasure (DIRCM) systems is presented. Next-generation DIRCM systems require compact, light-weight and robust laser modules which could provide intense IR light emission capable of disrupting the tracking sensor of heat-seeking missile. Currently used solid-state and fiber laser solutions for mid-IR band are bulky and heavy making them difficult to implement in smaller form-factor DIRCM systems. Recent development of GaSb laser diode technology greatly improved optical output powers and efficiencies of laser diodes working in 1900 - 2450 nm band [1] while also maintaining very attractive size, weight, power consumption and cost characteristics. 2100 nm laser diode module presented in this work performance is based on high-efficiency broad emitting area GaSb laser diode technology. Each laser diode emitter is able to provide 1 W of CW output optical power with working point efficiency up to 20% at temperature of 20 °C. For output beam collimation custom designed fast-axis collimator and slow-axis collimator lenses were used. These lenses were actively aligned and attached using UV epoxy curing. Total 2 emitters stacked vertically were used in 2100 nm laser diode module. Final optical output power of the module goes up to 2 W at temperature of 20 °C. Total dimensions of the laser diode module are 35 x 25 x 16 mm (L x W x H) with a weight of 28 grams. Finally output beam is bore-sighted to mechanical axes of the module housing allowing for easy integration into next-generation DIRCM systems.

CT radiation profile width measurement using CR imaging plate raw data

PubMed Central

Yang, Chang‐Ying Joseph

2015-01-01

This technical note demonstrates computed tomography (CT) radiation profile measurement using computed radiography (CR) imaging plate raw data showing it is possible to perform the CT collimation width measurement using a single scan without saturating the imaging plate. Previously described methods require careful adjustments to the CR reader settings in order to avoid signal clipping in the CR processed image. CT radiation profile measurements were taken as part of routine quality control on 14 CT scanners from four vendors. CR cassettes were placed on the CT scanner bed, raised to isocenter, and leveled. Axial scans were taken at all available collimations, advancing the cassette for each scan. The CR plates were processed and raw CR data were analyzed using MATLAB scripts to measure collimation widths. The raw data approach was compared with previously established methodology. The quality control analysis scripts are released as open source using creative commons licensing. A log‐linear relationship was found between raw pixel value and air kerma, and raw data collimation width measurements were in agreement with CR‐processed, bit‐reduced data, using previously described methodology. The raw data approach, with intrinsically wider dynamic range, allows improved measurement flexibility and precision. As a result, we demonstrate a methodology for CT collimation width measurements using a single CT scan and without the need for CR scanning parameter adjustments which is more convenient for routine quality control work. PACS numbers: 87.57.Q‐, 87.59.bd, 87.57.uq PMID:26699559

Point kernel calculations of skyshine exposure rates

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

Roseberry, M.L.; Shultis, J.K.

1982-02-01

A simple point kernel model is presented for the calculation of skyshine exposure rates arising from the atmospheric reflection of gamma radiation produced by a vertically collimated or a shielded point source. This model is shown to be in good agreement with benchmark experimental data from a /sup 60/Co source for distances out to 700 m.

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.

SU-C-BRE-04: Microbeam-Radiation-Therapy (MRT): Characterizing a Novel MRT Device Using High Resolution 3D Dosimetry

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

Li, Q; Juang, T; Bache, S

2014-06-15

Purpose: The feasibility of MRT has recently been demonstrated utilizing a new technology of Carbon-Nano-Tube(CNT) field emission x-ray sources.This approach can deliver very high dose(10's of Gy) in narrow stripes(sub-mm) of radiation which enables the study of novel radiation treatment approaches. Here we investigate the application of highresolution (50um isotropic) PRESAGE/Optical-CT 3D dosimetry techniques to characterize the radiation delivered in this extremely dosimetrically challenging scenario. Methods: The CNT field emission x-ray source irradiator comprises of a linear cathode array and a novel collimator alignment system. This allows a precise delivery of high-energy small beams up to 160 kVp. A cylindricalmore » dosimeter (∼2.2cm in height ∼2.5cm in diameter) was irradiated by CNT MRT delivering 3 strips of radiation with a nominal entrance dose of 32 Gy.A second dosimeter was irradiated with similar entrance dose, with a regular x-ray irradiator collimated to microscopical strip-beams. 50um (isotropic) 3D dosimetry was performed using an in-house optical-CT system designed and optimized for high resolution imaging (including a stray light deconvolution correction).The percentage depth dose (PDD), peak-to-valley ratio (PVR) and beam width (FWHM) data were obtained and analyzed in both cases. Results: High resolution 3D images were successfully achieved with the prototype system, enabling extraction of PDD and dose profiles. The PDDs for the CNT irradiation showed pronounced attenuation, but less build-up effect than that from the multibeam irradiation. The beam spacing between the three strips has an average value of 0.9mm while that for the 13 strips is 1.5 mm at a depth of 16.5 mm. The stray light corrected image shows line profiles with reduced noise and consistent PVR values. Conclusion: MRT dosimetry is extremely challenging due to the ultra small fields involved.This preliminary application of a novel, ultra-high resolution, optical-CT 3D dosimetry system shows promise, but further work is required to validate and investigate accuracy and artifacts. This work was supported by NIH R01CA100835.« less

Optical switch

DOEpatents

Reedy, Robert P.

1987-01-01

An optical switching device (10) is provided whereby light from a first glass fiber (16) or a second glass fiber (14) may be selectively transmitted into a third glass fiber (18). Each glass fiber is provided with a focusing and collimating lens system (26, 28, 30). In one mode of operation, light from the first glass fiber (16) is reflected by a planar mirror (36) into the third glass fiber (18). In another mode of operation, light from the second glass fiber (14) passes directly into the third glass fiber (18). The planar mirror (36) is attached to a rotatable table (32) which is rotated to provide the optical switching.

Multibeam collimator uses prism stack

NASA Technical Reports Server (NTRS)

Minott, P. O.

1981-01-01

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

Efficient color mixing through étendue conservation using freeform optics

NASA Astrophysics Data System (ADS)

Sorgato, Simone; Mohedano, Rubén.; Chaves, Julio; Cvetkovic, Aleksandra; Hernández, Maikel; Benitez, Pablo; Miñano, Juan C.; Thienpont, Hugo; Duerr, Fabian

2015-08-01

Today's SSL illumination market shows a clear trend to high flux packages with higher efficiency and higher CRI, realized by means of multiple color chips and phosphors. Such light sources require the optics to provide both near- and far-field color mixing. This design problem is particularly challenging for collimated luminaries, since traditional diffusers cannot be employed without enlarging the exit aperture and reducing brightness. Furthermore, diffusers compromise the light output ratio (efficiency) of the lamps to which they are applied. A solution, based on Köhler integration, consisting of a spherical cap comprising spherical microlenses on both its interior and exterior sides was presented in 2012. The diameter of this so-called Shell-Mixer was 3 times that of the chip array footprint. A new version of the Shell-Mixer, based on the Edge Ray Principle and conservation of etendue, where neither the outer shape of the cap nor the surfaces of the lenses are constrained to spheres or 2D Cartesian ovals will be shown in this work. The new shell is freeform, only twice as large as the original chip-array and equals the original model in terms of color uniformity, brightness and efficiency.

Off-axis low coherence digital holographic interferometry for quantitative phase imaging with an LED

NASA Astrophysics Data System (ADS)

Guo, Rongli; Wang, Fan; Hu, Xiaoying; Yang, Wenqian

2017-11-01

Off-axis digital holographic interferometry with the light source of a light emitting diode (LED) is presented and its application for quantitative phase imaging in a large range with low noise is demonstrated. The scheme is implemented in a grating based Mach-Zehnder interferometer. To achieve off-axis interferometry, firstly, the collimated beam emitted from an LED is diffracted into multiple orders by a grating and they are split into two copies by a beam splitter; secondly, in the object arm the zero order of one copy is filtered in the Fourier plane and is reshaped to illuminate the sample, while in the reference arm one of its first order of another copy is selected to serve as the reference beam, and then an off-axis hologram can be obtained at the image plane. The main advantage stemming from an LED illumination is its high spatial phase resolution, due to the subdued speckle effect. The off-axis geometry enables one-shot recording of the hologram in the millisecond scale. The utility of the proposed setup is illustrated with measurements of a resolution target and part of a wing of green-lacewing, and dynamic evaporation process of an ethanol film.

A compactly integrated laser-induced fluorescence detector for microchip electrophoresis.

PubMed

Li, Hai-Fang; Lin, Jin-Ming; Su, Rong-Guo; Uchiyama, Katsumi; Hobo, Toshiyuki

2004-06-01

A simple and easy-to-use integrated laser-induced fluorescence detector for microchip electrophoresis was constructed and evaluated. The fluid channels and optical fiber channels in the glass microchip were fabricated using standard photolithographic techniques and wet chemical etching. A 473 nm diode-pumped laser was used as the excitation source, and the collimation and collection optics and mirrors were discarded by using a multimode optical fiber to couple the excitation light straight into the microchannel and placing the microchip directly on the top of the photomultiplier tube. A combination of filter systems was incorporated into a poly(dimethylsiloxane) layer, which was reversibly sealed to the bottom of the microchip to eliminate the scattering excitation light reaching to the photomultiplier tube. Fluorescein/calcein samples were taken as model analytes to evaluate the performance with respect to design factors. The detection limits were 0.05 microM for fluorescein and 0.18 microM for calcein, respectively. The suitability of this simple detector for fluorescence detection was demonstrated by baseline separation of fluorescein isothiocyanate (FITC)-labeled arginine, phenylalanine, and glycine and FITC within 30 s at separation length of 3.8 cm and electrical field strength of 600 V/cm.

Polarization characteristics of radiation in both 'light' and conventional undulators

NASA Astrophysics Data System (ADS)

Potylitsyn, A. P.; Kolchuzhkin, A. M.; Strokov, S. A.

2017-07-01

As a rule, an intensity spectrum of undulator radiation (UR) is calculated by using the classical approach, even for electron energy higher than 10 GeV. Such a spectrum is determined by an electron trajectory in an undulator while neglecting radiation loss. Using Planck's law, the UR photon spectrum can be calculated from the obtained intensity spectrum, for both linear and nonlinear regimes. The electron radiation process in a field of strong electromagnetic waves is considered within the quantum electrodynamics framework, using the Compton scattering process or radiation in a 'light' undulator. A comparison was made of the results from using these two approaches, for UR spectra generated by 250-GeV electrons in an undulator with a 11.5-mm period; this comparison shows that they coincide with high accuracy. The characteristics of the collimated UR beam (i.e. spectrum and circular polarization) were simulated while taking into account the discrete process of photon emission along an electron trajectory in both undulator types. Both spectral photon distributions and polarization dependence on photon energy are 'smoothed', in comparison to that expected for a long undulator-the latter of which considers the ILC positron source (ILC Technical Design Report).

SU-E-J-104: Single Photon Image From PET with Insertable SPECT Collimator for Boron Neutron Capture Therapy: A Feasibility Study

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

Jung, J; Yoon, D; Suh, T

2014-06-01

Purpose: The aim of our proposed system is to confirm the feasibility of extraction of two types of images from one positron emission tomography (PET) module with an insertable collimator for brain tumor treatment during the BNCT. Methods: Data from the PET module, neutron source, and collimator was entered in the Monte Carlo n-particle extended (MCNPX) source code. The coincidence events were first compiled on the PET detector, and then, the events of the prompt gamma ray were collected after neutron emission by using a single photon emission computed tomography (SPECT) collimator on the PET. The obtaining of full widthmore » at half maximum (FWHM) values from the energy spectrum was performed to collect effective events for reconstructed image. In order to evaluate the images easily, five boron regions in a brain phantom were used. The image profiles were extracted from the region of interest (ROI) of a phantom. The image was reconstructed using the ordered subsets expectation maximization (OSEM) reconstruction algorithm. The image profiles and the receiver operating characteristic (ROC) curve were compiled for quantitative analysis from the two kinds of reconstructed image. Results: The prompt gamma ray energy peak of 478 keV appeared in the energy spectrum with a FWHM of 41 keV (6.4%). On the basis of the ROC curve in Region A to Region E, the differences in the area under the curve (AUC) of the PET and SPECT images were found to be 10.2%, 11.7%, 8.2% (center, Region C), 12.6%, and 10.5%, respectively. Conclusion: We attempted to acquire the PET and SPECT images simultaneously using only PET without an additional isotope. Single photon images were acquired using an insertable collimator on a PET detector. This research was supported by the Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, Information and Communication Technologies (ICT) and Future Planning (MSIP)(Grant No.2009 00420) and the Radiation Technology R and D program (Grant No.2013M2A2A7043498), Republic of Korea.« less

SU-F-T-670: From the OR to the Radiobiology Lab: The Journey of a Small X-Ray Source

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

Lehmann, J; The University of Sydney, Sydney, NSW; The University of Newcastle, Newcastle, NSW

Purpose: Irradiation of small animal tumor models within laboratories is vital to radiobiological experiments. Often the animals are not able to be brought back into the lab after being taken out for irradiation. Cell biology laboratories benefit from irradiation capability available around the clock without regard to patient load in an associated radiotherapy clinic. Commercial systems are available, but bulky and expensive. Methods: An intraoperative kV irradiation system (IntraBeam™) designed to deliver spherical dose distributions to surgical cavities has been repurposed for the irradiation of cell plates and small laboratory animals. An applicator has been altered to allow for simple,more » open fields. Special collimators are being developed. BEAMnrc Monte Carlo simulations with the “NRC swept BEAM” source model have been performed to characterize the dose distributions, to develop optimal collimators and as basis for dose prescription. Measurements with radiochromic film and with an ionization chamber were performed to characterize the beam and to validate the simulations. Results: Using its highest setting (50 kV and 40 µA) the x-ray unit is capable of delivering dose rates over 1 Gy/min homogeneously to standard cell plates even without an optimized collimator. Smaller areas (tumors in animals) can be irradiated with significantly higher dose rates (> 20 Gy/min) depending on distance of the source to the tumor. The HVL was found to be 0.21 mm Al which means the shielding requirements for the device are easily achievable in the lab. Conclusion: A mobile irradiation facility is feasible. It will allow easier access to radiation for radiobiology experiments. The modified system is versatile in that for cell plates homogenous irradiations can be achieved through distance from the source, while for high dose rate small field irradiations the source can be brought in close proximity to the target.« less

Systematic studies of small scintillators for new sampling calorimeter

NASA Astrophysics Data System (ADS)

Jacosalem, E. P.; Iba, S.; Nakajima, N.; Ono, H.; Sanchez, A. L. C.; Bacala, A. M.; Miyata, H.

2007-12-01

A new sampling calorimeter using very thin scintillators and the multi-pixel photon counter (MPPC) has been proposed to produce better position resolution for the international linear collider (ILC) experiment. As part of this R&D study, small plastic scintillators of different sizes, thickness and wrapping reflectors are systematically studied. The scintillation light due to beta rays from a collimated ^{90}Sr source are collected from the scintillator by wavelength-shifting (WLS) fiber and converted into electrical signals at the PMT. The wrapped scintillator that gives the best light yield is determined by comparing the measured pulse height of each 10 × 40 × 2 mm strip scintillator covered with 3M reflective mirror film, teflon, white paint, black tape, gold, aluminum and white paint+teflon. The pulse height dependence on position, length and thickness of the 3M reflective mirror film and teflon wrapped scintillators are measured. Results show that the 3M radiant mirror film-wrapped scintillator has the greatest light yield with an average of 9.2 photoelectrons. It is observed that light yield slightly increases with scintillator length, but increases to about 100% when WLS fiber diameter is increased from 1.0 mm to 1.6 mm. The position dependence measurement along the strip scintillator showed the uniformity of light transmission from the sensor to the PMT. A dip across the strip is observed which is 40% of the maximum pulse height. The block type scintillator pulse height, on the other hand, is found to be almost proportional to scintillator thickness.

Light beam frequency comb generator

DOEpatents

Priatko, G.J.; Kaskey, J.A.

1992-11-24

A light beam frequency comb generator uses an acousto-optic modulator to generate a plurality of light beams with frequencies which are uniformly separated and possess common noise and drift characteristics. A well collimated monochromatic input light beam is passed through this modulator to produce a set of both frequency shifted and unshifted optical beams. An optical system directs one or more frequency shifted beams along a path which is parallel to the path of the input light beam such that the frequency shifted beams are made incident on the modulator proximate to but separated from the point of incidence of the input light beam. After the beam is thus returned to and passed through the modulator repeatedly, a plurality of mutually parallel beams are generated which are frequency-shifted different numbers of times and possess common noise and drift characteristics. 2 figs.

Light beam frequency comb generator

DOEpatents

Priatko, Gordon J.; Kaskey, Jeffrey A.

1992-01-01

A light beam frequency comb generator uses an acousto-optic modulator to generate a plurality of light beams with frequencies which are uniformly separated and possess common noise and drift characteristics. A well collimated monochromatic input light beam is passed through this modulator to produce a set of both frequency shifted and unshifted optical beams. An optical system directs one or more frequency shifted beams along a path which is parallel to the path of the input light beam such that the frequency shifted beams are made incident on the modulator proximate to but separated from the point of incidence of the input light beam. After the beam is thus returned to and passed through the modulator repeatedly, a plurality of mutually parallel beams are generated which are frequency-shifted different numbers of times and possess common noise and drift characteristics.

Multisite silicon neural probes with integrated silicon nitride waveguides and gratings for optogenetic applications.

PubMed

Shim, Euijae; Chen, Yu; Masmanidis, Sotiris; Li, Mo

2016-03-04

Optimal optogenetic perturbation of brain circuit activity often requires light delivery in a precise spatial pattern that cannot be achieved with conventional optical fibers. We demonstrate an implantable silicon-based probe with a compact light delivery system, consisting of silicon nitride waveguides and grating couplers for out-of-plane light emission with high spatial resolution. 473 nm light is coupled into and guided in cm-long waveguide and emitted at the output grating coupler. Using the direct cut-back and out-scattering measurement techniques, the propagation optical loss of the waveguide is measured to be below 3 dB/cm. The grating couplers provide collimated light emission with sufficient irradiance for neural stimulation. Finally, a probe with multisite light delivery with three output grating emitters from a single laser input is demonstrated.

A study of optical design and optimization of laser optics

NASA Astrophysics Data System (ADS)

Tsai, C.-M.; Fang, Yi-Chin

2013-09-01

This paper propose a study of optical design of laser beam shaping optics with aspheric surface and application of genetic algorithm (GA) to find the optimal results. Nd: YAG 355 waveband laser flat-top optical system, this study employed the Light tools LDS (least damped square) and the GA of artificial intelligence optimization method to determine the optimal aspheric coefficient and obtain the optimal solution. This study applied the aspheric lens with GA for the flattening of laser beams using collimated laser beam light, aspheric lenses in order to achieve best results.

Cesium Absorption Spectrum Perturbed by Argon: Observation of Non-Lorentzian Wing Properties

DTIC Science & Technology

2012-03-01

vapor phase Cs contained in a heat pipe in order to observe the absorption lines. Two lenses were used to collimate the light through the heat pipe...After passing through the heat pipe, a mirror was used to direct light around a 90 degree turn and then through an f/# matched lens into a monochromator...pipe used here was built by Charles Fox as part of [19]. Brewster’s angle windows were attached to either end of a pipe approximately 1 inch in diameter

SU-E-T-59: Calculations of Collimator Scatter Factors (Sc) with and Without Custom-Made Build-Up Caps for CyberKnife

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

Wokoma, S; Yoon, J; Jung, J

2014-06-01

Purpose: To investigate the impact of custom-made build-up caps for a diode detector in robotic radiosurgery radiation fields with variable collimator (IRIS) for collimator scatter factor (Sc) calculation. Methods: An acrylic cap was custom-made to fit our SFD (IBA Dosimetry, Germany) diode detector. The cap has thickness of 5 cm, corresponding to a depth beyond electron contamination. IAEA phase space data was used for beam modeling and DOSRZnrc code was used to model the detector. The detector was positioned at 80 cm source-to-detector distance. Calculations were performed with the SFD, with and without the build-up cap, for clinical IRIS settingsmore » ranging from 7.5 to 60 mm. Results: The collimator scatter factors were calculated with and without 5 cm build-up cap. They were agreed within 3% difference except 15 mm cone. The Sc factor for 15 mm cone without buildup was 13.2% lower than that with buildup. Conclusion: Sc data is a critical component in advanced algorithms for treatment planning in order to calculate the dose accurately. After incorporating build-up cap, we discovered differences of up to 13.2 % in Sc factors in the SFD detector, when compared against in-air measurements without build-up caps.« less

Ideal engine durations for gamma-ray-burst-jet launch

NASA Astrophysics Data System (ADS)

Hamidani, Hamid; Takahashi, Koh; Umeda, Hideyuki; Okita, Shinpei

2017-08-01

Aiming to study gamma-ray-burst (GRB) engine duration, we present numerical simulations to investigate collapsar jets. We consider typical explosion energy (1052 erg) but different engine durations, in the widest domain to date from 0.1 to 100 s. We employ an adaptive mesh refinement 2D hydrodynamical code. Our results show that engine duration strongly influences jet nature. We show that the efficiency of launching and collimating relativistic outflow increases with engine duration, until the intermediate engine range where it is the highest, past this point to long engine range, the trend is slightly reversed; we call this point where acceleration and collimation are the highest 'sweet spot' (˜10-30 s). Moreover, jet energy flux shows that variability is also high in this duration domain. We argue that not all engine durations can produce the collimated, relativistic and variable long GRB jets. Considering a typical progenitor and engine energy, we conclude that the ideal engine duration to reproduce a long GRB is ˜10-30 s, where the launch of relativistic, collimated and variable jets is favoured. We note that this duration domain makes a good link with a previous study suggesting that the bulk of Burst and Transient Source Experiment's long GRBs is powered by ˜10-20 s collapsar engines.

An MCNP-based model of a medical linear accelerator x-ray photon beam.

PubMed

Ajaj, F A; Ghassal, N M

2003-09-01

The major components in the x-ray photon beam path of the treatment head of the VARIAN Clinac 2300 EX medical linear accelerator were modeled and simulated using the Monte Carlo N-Particle radiation transport computer code (MCNP). Simulated components include x-ray target, primary conical collimator, x-ray beam flattening filter and secondary collimators. X-ray photon energy spectra and angular distributions were calculated using the model. The x-ray beam emerging from the secondary collimators were scored by considering the total x-ray spectra from the target as the source of x-rays at the target position. The depth dose distribution and dose profiles at different depths and field sizes have been calculated at a nominal operating potential of 6 MV and found to be within acceptable limits. It is concluded that accurate specification of the component dimensions, composition and nominal accelerating potential gives a good assessment of the x-ray energy spectra.

Performance evaluation for pinhole collimators of small gamma camera by MTF and NNPS analysis: Monte Carlo simulation study

NASA Astrophysics Data System (ADS)

Jeon, Hosang; Kim, Hyunduk; Cha, Bo Kyung; Kim, Jong Yul; Cho, Gyuseong; Chung, Yong Hyun; Yun, Jong-Il

2009-06-01

Presently, the gamma camera system is widely used in various medical diagnostic, industrial and environmental fields. Hence, the quantitative and effective evaluation of its imaging performance is essential for design and quality assurance. The National Electrical Manufacturers Association (NEMA) standards for gamma camera evaluation are insufficient to perform sensitive evaluation. In this study, modulation transfer function (MTF) and normalized noise power spectrum (NNPS) will be suggested to evaluate the performance of small gamma camera with changeable pinhole collimators using Monte Carlo simulation. We simulated the system with a cylinder and a disk source, and seven different pinhole collimators from 1- to 4-mm-diameter pinhole with lead. The MTF and NNPS data were obtained from output images and were compared with full-width at half-maximum (FWHM), sensitivity and differential uniformity. In the result, we found that MTF and NNPS are effective and novel standards to evaluate imaging performance of gamma cameras instead of conventional NEMA standards.

A simplified model of the source channel of the Leksell GammaKnife tested with PENELOPE.

PubMed

Al-Dweri, Feras M O; Lallena, Antonio M; Vilches, Manuel

2004-06-21

Monte Carlo simulations using the code PENELOPE have been performed to test a simplified model of the source channel geometry of the Leksell GammaKnife. The characteristics of the radiation passing through the treatment helmets are analysed in detail. We have found that only primary particles emitted from the source with polar angles smaller than 3 degrees with respect to the beam axis are relevant for the dosimetry of the Gamma Knife. The photon trajectories reaching the output helmet collimators at (x, v, z = 236 mm) show strong correlations between rho = (x2 + y2)(1/2) and their polar angle theta, on one side, and between tan(-1)(y/x) and their azimuthal angle phi, on the other. This enables us to propose a simplified model which treats the full source channel as a mathematical collimator. This simplified model produces doses in good agreement with those found for the full geometry. In the region of maximal dose, the relative differences between both calculations are within 3%, for the 18 and 14 mm helmets, and 10%, for the 8 and 4 mm ones. Besides, the simplified model permits a strong reduction (larger than a factor 15) in the computational time.

Fast interaction of atoms with crystal surfaces: coherent lighting

NASA Astrophysics Data System (ADS)

Gravielle, M. S.

2017-11-01

Quantum coherence of incident waves results essential for the observation of interference patterns in grazing incidence fast atom diffraction (FAD). In this work we investigate the influence of the impact energy and projectile mass on the transversal length of the surface area that is coherently illuminated by the atomic beam, after passing through a collimating aperture. Such a transversal coherence length controls the general features of the interference structures, being here derived by means of the Van Cittert-Zernike theorem. The coherence length is then used to build the initial coherent wave packet within the Surface Initial Value Representation (SIVR) approximation. The SIVR approach is applied to fast He and Ne atoms impinging grazingly on a LiF(001) surface along a low-indexed crystallographic direction. We found that with the same collimating setup, by varying the impact energy we would be able to control the interference mechanism that prevails in FAD patterns, switching between inter-cell and unit-cell interferences. These findings are relevant to use FAD spectra adequately as a surface analysis tool, as well as to choose the appropriate collimating scheme for the observation of interference effects in a given collision system.

Optical design of a robotic TV camera probe for minimally invasive abdominal surgery

NASA Astrophysics Data System (ADS)

Todaro, Susanna; He, Weiyi; Killinger, Dennis

2011-03-01

Minimally invasive techniques are a promising new field of surgery; however, they limit the surgeon's access points and maneuverability. In order to increase the number of access points in minimally invasive abdominal surgery, a proposed implantable medical probe braces to the abdominal wall and provides illumination and video signal. The probe is cylindrical, about 25 mm long and 10 mm in diameter. A ring of LEDs on the end of the probe illuminates the tissue, and the resulting image is focused onto an HD video detector. It was necessary to apply beam-shaping reflectors to collimate the light onto a small target area, to avoid illuminating areas not picked up by the video. These reflectors were designed and simulated using the optical ray tracing software TracePro. Two LED chip geometries and three types of reflector geometries were analyzed, and the parameters for each geometry were optimized. For the straight-edged reflectors, the intensity patterns and optimization were compared to experimental results. Although parabolic reflectors produced the best collimation, cone reflectors with a 20-degree half-angle produced significant collimation at a much cheaper price. This work was supported by NSF REU program (award No DMR-1004873).

Status of NSLS-II Storage Ring Vacuum Systems

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

Doom,L.; Hseuh,H.; Ferreira, M.

2009-05-04

National Synchrotron Light Source II (NSLS-II), being constructed at Brookhaven National Laboratory, is a 3-GeV, high-flux and high- brightness synchrotron radiation facility with a nominal current of 500 mA. The storage ring vacuum system will have extruded aluminium chambers with ante-chamber for photon fans and distributed NEG strip pumping. Discrete photon absorbers will be used to intercept the un-used bending magnet radiation. In-situ bakeout will be implemented to achieve fast conditioning during initial commissioning and after interventions.

An Undulator-Based Laser Wakefield Accelerator Electron Beam Diagnostic

NASA Astrophysics Data System (ADS)

Bakeman, Michael S.

Currently particle accelerators such as the Large Hadron Collider use RF cavities with a maximum field gradient of 50-100 MV/m to accelerate particles over long distances. A new type of plasma based accelerator called a Laser Plasma Accelerator (LPA) is being investigated at the LOASIS group at Lawrence Berkeley National Laboratory which can sustain field gradients of 10-100 GV/m. This new type of accelerator offers the potential to create compact high energy accelerators and light sources. In order to investigate the feasibility of producing a compact light source an undulator-based electron beam diagnostic for use on the LOASIS LPA has been built and calibrated. This diagnostic relies on the principal that the spectral analysis of synchrotron radiation from an undulator can reveal properties of the electron beam such as emittance, energy and energy spread. The effects of electron beam energy spread upon the harmonics of undulator produced synchrotron radiation were derived from the equations of motion of the beam and numerically simulated. The diagnostic consists of quadrupole focusing magnets to collimate the electron beam, a 1.5 m long undulator to produce the synchrotron radiation, and a high resolution high gain XUV spectrometer to analyze the radiation. The undulator was aligned and tuned in order to maximize the flux of synchrotron radiation produced. The spectrometer was calibrated at the Advanced Light Source, with the results showing the ability to measure electron beam energy spreads at resolutions as low as 0.1% rms, a major improvement over conventional magnetic spectrometers. Numerical simulations show the ability to measure energy spreads on realistic LPA produced electron beams as well as the improvements in measurements made with the quadrupole magnets. Experimentally the quadrupoles were shown to stabilize and focus the electron beams at specific energies for their insertion into the undulator, with the eventual hope of producing an all optical Free Electron Laser operating in the XUV and soft x-ray regimes.

A new method and device of aligning patient setup lasers in radiation therapy.

PubMed

Hwang, Ui-Jung; Jo, Kwanghyun; Lim, Young Kyung; Kwak, Jung Won; Choi, Sang Hyuon; Jeong, Chiyoung; Kim, Mi Young; Jeong, Jong Hwi; Shin, Dongho; Lee, Se Byeong; Park, Jeong-Hoon; Park, Sung Yong; Kim, Siyong

2016-01-08

The aim of this study is to develop a new method to align the patient setup lasers in a radiation therapy treatment room and examine its validity and efficiency. The new laser alignment method is realized by a device composed of both a metallic base plate and a few acrylic transparent plates. Except one, every plate has either a crosshair line (CHL) or a single vertical line that is used for alignment. Two holders for radiochromic film insertion are prepared in the device to find a radiation isocenter. The right laser positions can be found optically by matching the shadows of all the CHLs in the gantry head and the device. The reproducibility, accuracy, and efficiency of laser alignment and the dependency on the position error of the light source were evaluated by comparing the means and the standard deviations of the measured laser positions. After the optical alignment of the lasers, the radiation isocenter was found by the gantry and collimator star shots, and then the lasers were translated parallel to the isocenter. In the laser position reproducibility test, the mean and standard deviation on the wall of treatment room were 32.3 ± 0.93 mm for the new method whereas they were 33.4 ± 1.49 mm for the conventional method. The mean alignment accuracy was 1.4 mm for the new method, and 2.1 mm for the conventional method on the walls. In the test of the dependency on the light source position error, the mean laser position was shifted just by a similar amount of the shift of the light source in the new method, but it was greatly magnified in the conventional method. In this study, a new laser alignment method was devised and evaluated successfully. The new method provided more accurate, more reproducible, and faster alignment of the lasers than the conventional method.

Long path monitoring of tropospheric O3, NO2, H2CO and SO2

NASA Technical Reports Server (NTRS)

Vandaele, A. C.; Carleer, M.; Colin, R.; Simon, P. C.

1994-01-01

Concentrations of tropospheric O3, NO2, H2CO, and SO2 have been measured on the Campus of the 'Universite Libre de Bruxelles' on a routine basis since October 1990. The long path system consists of a source lamp, a first 30 cm f/8 Cassegrain type telescope which collimates the light onto a slightly parabolic mirror placed on the roof of a building situated 394 m away from the laboratory. The light is sent back into a second 30 cm Cassegrain telescope. This telescope has been modified so that the output beam is a 5 cm diameter parallel beam. This beam is then focused onto the entrance aperture of the BRUKER IFS120HR fourier transform spectrometer. The two telescopes are mounted on alignment devices and the external mirror is equipped with a driving system operated from the laboratory. The choice of the light source (either a 1000 W high pressure 'ozone free' xenon lamp or a 250 W tungsten filament) and of the detector (either a solar blind UV-diode or a silicon diode) depended on the spectral region studied. These regions lie respectively from 26,000 cm(exp -1) to 30,000 cm(exp -1) (260-380 nm) and from 14,000 cm(exp -1) to 30,000 cm(exp -1) (330-700 nm). The spectra have been recorded at the resolution of 16 cm(exp -1) and with a dispersion of 7.7 cm(exp -1). They have been measured during the forward and the backward movements of the mobile mirror, in double sided mode; each spectrum is an average of 2000 scans. The time required to record a spectrum is about 45 minutes. The shape of the raw spectra in the two investigated regions are represented.

High-resolution soft X-ray beamline ADRESS at the Swiss Light Source for resonant inelastic X-ray scattering and angle-resolved photoelectron spectroscopies

PubMed Central

Strocov, V. N.; Schmitt, T.; Flechsig, U.; Schmidt, T.; Imhof, A.; Chen, Q.; Raabe, J.; Betemps, R.; Zimoch, D.; Krempasky, J.; Wang, X.; Grioni, M.; Piazzalunga, A.; Patthey, L.

2010-01-01

The concepts and technical realisation of the high-resolution soft X-ray beamline ADRESS operating in the energy range from 300 to 1600 eV and intended for resonant inelastic X-ray scattering (RIXS) and angle-resolved photoelectron spectroscopy (ARPES) are described. The photon source is an undulator of novel fixed-gap design where longitudinal movement of permanent magnetic arrays controls not only the light polarization (including circular and 0–180° rotatable linear polarizations) but also the energy without changing the gap. The beamline optics is based on the well established scheme of plane-grating monochromator operating in collimated light. The ultimate resolving power E/ΔE is above 33000 at 1 keV photon energy. The choice of blazed versus lamellar gratings and optimization of their profile parameters is described. Owing to glancing angles on the mirrors as well as optimized groove densities and profiles of the gratings, the beamline is capable of delivering high photon flux up to 1 × 1013 photons s−1 (0.01% BW)−1 at 1 keV. Ellipsoidal refocusing optics used for the RIXS endstation demagnifies the vertical spot size down to 4 µm, which allows slitless operation and thus maximal transmission of the high-resolution RIXS spectrometer delivering E/ΔE > 11000 at 1 keV photon energy. Apart from the beamline optics, an overview of the control system is given, the diagnostics and software tools are described, and strategies used for the optical alignment are discussed. An introduction to the concepts and instrumental realisation of the ARPES and RIXS endstations is given. PMID:20724785

A New Electron Source for Laboratory Simulation of the Space Environment

NASA Technical Reports Server (NTRS)

Krause, Linda Habash; Everding, Daniel; Bonner, Mathew; Swan, Brian

2012-01-01

We have developed a new collimated electron source called the Photoelectron Beam Generator (PEBG) for laboratory and spaceflight applications. This technology is needed to replace traditional cathodes because of serious fundamental weaknesses with the present state of the art. Filament cathodes suffer from numerous practical problems, even if expertly designed, including the dependence of electron emission on filament temperature, short lifetimes (approx 100 hours), and relatively high power (approx 10s of W). Other types of cathodes have solved some of these problems, but they are plagued with other difficult problems, such as the Spindt cathode's extreme sensitivity to molecular oxygen. None to date have been able to meet the demand of long lifetime, robust packaging, and precision energy and flux control. This new cathode design avoids many common pitfalls of traditional cathodes. Specifically, there are no fragile parts, no sensitivity to oxygen, no intrinsic emission dependencies on device temperature, and no vacuum requirements for protecting the source from contamination or damage. Recent advances in high-brightness Light Emitting Diodes (LEDs) have provided the key enabling technology for this new electron source. The LEDs are used to photoeject electrons off a target material of a low work-function, and these photoelectrons are subsequently focused into a laminar beam using electrostatic lenses. The PEBG works by illuminating a target material and steering photoelectrons into a laminar beam using electrostatic lenses

Lithographically-fabricated channel arrays for confocal x-ray fluorescence microscopy and XAFS

NASA Astrophysics Data System (ADS)

Woll, Arthur R.; Agyeman-Budu, David; Choudhury, Sanjukta; Coulthard, Ian; Finnefrock, Adam C.; Gordon, Robert; Hallin, Emil; Mass, Jennifer

2014-03-01

Confocal X-ray Fluorescence Microscopy (CXRF) employs overlapping focal regions of two x-ray optics—a condenser and collector—to directly probe a 3D volume. The minimum-achievable size of this probe volume is limited by the collector, for which polycapillaries are generally the optic of choice. Recently, we demonstrated an alternative collection optic for CXRF, consisting of an array of micron-scale collimating channels, etched in silicon, and arranged like spokes of a wheel directed towards a single source position. The optic, while successful, had a working distance of only 0.2 mm and exhibited relatively low total collection efficiency, limiting its practical application. Here, we describe a new design in which the collimating channels are formed by a staggered array of pillars whose side-walls taper away from the channel axis. This approach improves both collection efficiency and working distance, while maintaining excellent spatial resolution. We illustrate these improvements with confocal XRF data obtained at the Cornell High Energy Synchrotron Source (CHESS) and the Advanced Photon Source (APS) beamline 20-ID-B.

THE NATURE AND FREQUENCY OF OUTFLOWS FROM STARS IN THE CENTRAL ORION NEBULA CLUSTER

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

O’Dell, C. R.; Ferland, G. J.; Henney, W. J.

Recent Hubble Space Telescope images have allowed the determination with unprecedented accuracy of motions and changes of shocks within the inner Orion Nebula. These originate from collimated outflows from very young stars, some within the ionized portion of the nebula and others within the host molecular cloud. We have doubled the number of Herbig–Haro objects known within the inner Orion Nebula. We find that the best-known Herbig–Haro shocks originate from relatively few stars, with the optically visible X-ray source COUP 666 driving many of them. While some isolated shocks are driven by single collimated outflows, many groups of shocks aremore » the result of a single stellar source having jets oriented in multiple directions at similar times. This explains the feature that shocks aligned in opposite directions in the plane of the sky are usually blueshifted because the redshifted outflows pass into the optically thick photon-dominated region behind the nebula. There are two regions from which optical outflows originate for which there are no candidate sources in the SIMBAD database.« less

Monte Carlo study of a 60Co calibration field of the Dosimetry Laboratory Seibersdorf.

PubMed

Hranitzky, C; Stadtmann, H

2007-01-01

The gamma radiation fields of the reference irradiation facility of the Dosimetry Laboratory Seibersdorf with collimated beam geometry are used for calibrating radiation protection dosemeters. A close-to-reality simulation model of the facility including the complex geometry of a 60Co source was set up using the Monte Carlo code MCNP. The goal of this study is to characterise the radionuclide gamma calibration field and resulting air-kerma distributions inside the measurement hall with a total of 20 m in length. For the whole range of source-detector-distances (SDD) along the central beam axis, simulated and measured relative air-kerma values are within +/-0.6%. Influences on the accuracy of the simulation results are investigated, including e.g., source mass density effects or detector volume dependencies. A constant scatter contribution from the lead ring-collimator of approximately 1% and an increasing scatter contribution from the concrete floor for distances above 7 m are identified, resulting in a total air-kerma scatter contribution below 5%, which is in accordance to the ISO 4037-1 recommendations.

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

NASA Astrophysics Data System (ADS)

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

2016-11-01

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

Maui Space Surveillance System Satellite Categorization Laboratory

NASA Astrophysics Data System (ADS)

Deiotte, R.; Guyote, M.; Kelecy, T.; Hall, D.; Africano, J.; Kervin, P.

The MSSS satellite categorization laboratory is a fusion of robotics and digital imaging processes that aims to decompose satellite photometric characteristics and behavior in a controlled setting. By combining a robot, light source and camera to acquire non-resolved images of a model satellite, detailed photometric analyses can be performed to extract relevant information about shape features, elemental makeup, and ultimately attitude and function. Using the laboratory setting a detailed analysis can be done on any type of material or design and the results cataloged in a database that will facilitate object identification by "curve-fitting" individual elements in the basis set to observational data that might otherwise be unidentifiable. Currently the laboratory has created, an ST-Robotics five degree of freedom robotic arm, collimated light source and non-focused Apogee camera have all been integrated into a MATLAB based software package that facilitates automatic data acquisition and analysis. Efforts to date have been aimed at construction of the lab as well as validation and verification of simple geometric objects. Simple tests on spheres, cubes and simple satellites show promising results that could lead to a much better understanding of non-resolvable space object characteristics. This paper presents a description of the laboratory configuration and validation test results with emphasis on the non-resolved photometric characteristics for a variety of object shapes, spin dynamics and orientations. The future vision, utility and benefits of the laboratory to the SSA community as a whole are also discussed.

Full-field fan-beam x-ray fluorescence computed tomography system design with linear-array detectors and pinhole collimation: a rapid Monte Carlo study

NASA Astrophysics Data System (ADS)

Zhang, Siyuan; Li, Liang; Li, Ruizhe; Chen, Zhiqiang

2017-11-01

We present the design concept and initial simulations for a polychromatic full-field fan-beam x-ray fluorescence computed tomography (XFCT) device with pinhole collimators and linear-array photon counting detectors. The phantom is irradiated by a fan-beam polychromatic x-ray source filtered by copper. Fluorescent photons are stimulated and then collected by two linear-array photon counting detectors with pinhole collimators. The Compton scatter correction and the attenuation correction are applied in the data processing, and the maximum-likelihood expectation maximization algorithm is applied for the image reconstruction of XFCT. The physical modeling of the XFCT imaging system was described, and a set of rapid Monte Carlo simulations was carried out to examine the feasibility and sensitivity of the XFCT system. Different concentrations of gadolinium (Gd) and gold (Au) solutions were used as contrast agents in simulations. Results show that 0.04% of Gd and 0.065% of Au can be well reconstructed with the full scan time set at 6 min. Compared with using the XFCT system with a pencil-beam source or a single-pixel detector, using a full-field fan-beam XFCT device with linear-array detectors results in significant scanning time reduction and may satisfy requirements of rapid imaging, such as in vivo imaging experiments.

3-D Spatial Resolution of 350 μm Pitch Pixelated CdZnTe Detectors for Imaging Applications.

PubMed

Yin, Yongzhi; Chen, Ximeng; Wu, Heyu; Komarov, Sergey; Garson, Alfred; Li, Qiang; Guo, Qingzhen; Krawczynski, Henric; Meng, Ling-Jian; Tai, Yuan-Chuan

2013-02-01

We are currently investigating the feasibility of using highly pixelated Cadmium Zinc Telluride (CdZnTe) detectors for sub-500 μ m resolution PET imaging applications. A 20 mm × 20 mm × 5 mm CdZnTe substrate was fabricated with 350 μ m pitch pixels (250 μ m anode pixels with 100 μ m gap) and coplanar cathode. Charge sharing among the pixels of a 350 μ m pitch detector was studied using collimated 122 keV and 511 keV gamma ray sources. For a 350 μ m pitch CdZnTe detector, scatter plots of the charge signal of two neighboring pixels clearly show more charge sharing when the collimated beam hits the gap between adjacent pixels. Using collimated Co-57 and Ge-68 sources, we measured the count profiles and estimated the intrinsic spatial resolution of 350 μ m pitch detector biased at -1000 V. Depth of interaction was analyzed based on two methods, i.e., cathode/anode ratio and electron drift time, in both 122 keV and 511 keV measurements. For single-pixel photopeak events, a linear correlation between cathode/anode ratio and electron drift time was shown, which would be useful for estimating the DOI information and preserving image resolution in CdZnTe PET imaging applications.

3-D Spatial Resolution of 350 μm Pitch Pixelated CdZnTe Detectors for Imaging Applications

PubMed Central

Yin, Yongzhi; Chen, Ximeng; Wu, Heyu; Komarov, Sergey; Garson, Alfred; Li, Qiang; Guo, Qingzhen; Krawczynski, Henric; Meng, Ling-Jian; Tai, Yuan-Chuan

2016-01-01

We are currently investigating the feasibility of using highly pixelated Cadmium Zinc Telluride (CdZnTe) detectors for sub-500 μm resolution PET imaging applications. A 20 mm × 20 mm × 5 mm CdZnTe substrate was fabricated with 350 μm pitch pixels (250 μm anode pixels with 100 μm gap) and coplanar cathode. Charge sharing among the pixels of a 350 μm pitch detector was studied using collimated 122 keV and 511 keV gamma ray sources. For a 350 μm pitch CdZnTe detector, scatter plots of the charge signal of two neighboring pixels clearly show more charge sharing when the collimated beam hits the gap between adjacent pixels. Using collimated Co-57 and Ge-68 sources, we measured the count profiles and estimated the intrinsic spatial resolution of 350 μm pitch detector biased at −1000 V. Depth of interaction was analyzed based on two methods, i.e., cathode/anode ratio and electron drift time, in both 122 keV and 511 keV measurements. For single-pixel photopeak events, a linear correlation between cathode/anode ratio and electron drift time was shown, which would be useful for estimating the DOI information and preserving image resolution in CdZnTe PET imaging applications. PMID:28250476

Automatic targeting of plasma spray gun

DOEpatents

Abbatiello, Leonard A.; Neal, Richard E.

1978-01-01

A means for monitoring the material portion in the flame of a plasma spray gun during spraying operations is provided. A collimated detector, sensitive to certain wavelengths of light emission, is used to locate the centroid of the material with each pass of the gun. The response from the detector is then relayed to the gun controller to be used to automatically realign the gun.

Hemispherical-field-of-view, nonimaging narrow-band spectral filter

NASA Technical Reports Server (NTRS)

Miles, R. B.; Webb, S. G.; Griffith, E. L.

1981-01-01

Two compound parabolic concentrators are used to create a 180-deg-field-of-view spectral filter. The collection optics are reflective and are designed to collimate the light through a multilayer interference filter and then to refocus it onto an optical detector. Assuming unit reflectance and no loss through the optical filter, this device operates at the thermodynamic collection limit.

Hemispherical-field-of-view, nonimaging narrow-band spectral filter.

PubMed

Miles, R B; Webb, S G; Griffith, E L

1981-12-01

Two compound parabolic concentrators are used to create a 180 degrees -field-of-view spectral filter. The collection optics are reflective and are designed to collimate the light through a multilayer interference filter and then to refocus it onto an optical detector. Assuming unit reflectance and no loss through the optical filter, this device operates at the thermodynamic collection limit.

A cylindrical SPECT camera with de-centralized readout scheme

NASA Astrophysics Data System (ADS)

Habte, F.; Stenström, P.; Rillbert, A.; Bousselham, A.; Bohm, C.; Larsson, S. A.

2001-09-01

An optimized brain single photon emission computed tomograph (SPECT) camera is being designed at Stockholm University and Karolinska Hospital. The design goal is to achieve high sensitivity, high-count rate and high spatial resolution. The sensitivity is achieved by using a cylindrical crystal, which gives a closed geometry with large solid angles. A de-centralized readout scheme where only a local environment around the light excitation is readout supports high-count rates. The high resolution is achieved by using an optimized crystal configuration. A 12 mm crystal plus 12 mm light guide combination gave an intrinsic spatial resolution better than 3.5 mm (140 keV) in a prototype system. Simulations show that a modified configuration can improve this value. A cylindrical configuration with a rotating collimator significantly simplifies the mechanical design of the gantry. The data acquisition and control system uses early digitization and subsequent digital signal processing to extract timing and amplitude information, and monitors the position of the collimator. The readout system consists of 12 or more modules each based on programmable logic and a digital signal processor. The modules send data to a PC file server-reconstruction engine via a Firewire (IEEE-1394) network.

Comparison of collimated blue-light generation in 85Rb atoms via the D1 and D2 lines

NASA Astrophysics Data System (ADS)

Prajapati, Nikunj; Akulshin, Alexander M.; Novikova, Irina

2018-05-01

We experimentally studied the characteristics of the collimated blue light (CBL) produced in ${}^{85}$Rb vapor by two resonant laser fields exciting atoms into the $5D_{3/2}$ state, using either the $5P_{1/2}$ or the $5P_{3/2}$ intermediate state. We compared the CBL output at different values of frequency detunings, powers, and polarizations of the pump lasers in these two cases, and confirmed the observed trends using a simple theoretical model. We also demonstrated that the addition of the repump laser, preventing the accumulation of atomic population in the uncoupled hyperfine ground state, resulted in nearly an order of magnitude increase in CBL power output. Overall, we found that the $5S_{1/2} - 5P_{1/2} - 5D_{3/2}$ excitation pathway results in stronger CBL generation, as we detected up to $4.25~\\mu$W using two pumps of the same linear polarization. The optimum CBL output for the $5S_{1/2} - 5P_{3/2} - 5D_{3/2}$ excitation pathway required the two pump lasers to have the same circular polarization, but resulted only in a maximum CBL power of $450$~nW.

From optics testing to micro optics testing

NASA Astrophysics Data System (ADS)

Brock, Christian; Dorn, Ralf; Pfund, Johannes

2017-10-01

Testing micro optics, i.e. lenses with dimensions down to 0.1mm and less, with high precision requires a dedicated design of the testing device, taking into account propagation and wave-optical effects. In this paper, we discuss testing methods based on Shack-Hartmann wavefront technology for functional testing in transmission and for the measurement of surface shape in reflection. As a first example of more conventional optics testing, i.e. optics in the millimeter range, we present the measurement of binoculars in transmission, and discuss the measured wave aberrations and imaging quality. By repeating the measurement at different wavelengths, information on chromatic effects is retrieved. A task that is often tackled using Shack-Hartman wavefront sensors is the alignment of collimation optics in front of a light source. In case of a micro-optical collimation unit with a 1/e² beam diameter of ca. 1mm, we need adapted relay optics for suitable beam expansion and well-defined imaging conditions. In this example, we will discuss the alignment process and effects of the relay optics magnification, as well as typical performance data. Oftentimes, micro optics are fabricated not as single pieces, but as mass optics, e.g. by lithographic processes. Thus, in order to reduce tooling and alignment time, an automated test procedure is necessary. We present an approach for the automated testing of wafer- or tray-based micro optics, and discuss transmission and reflection measurement capabilities. Exemplary performance data is shown for a sample type with 30 microns in diameter, where typical repeatabilities of a few nanometers (rms) are reached.

Variable two-crystal cascade for conical refraction.

PubMed

Peet, V

2015-05-15

The cascade conical refraction occurs when a collimated light beam is passed consequently along the optic axes of several biaxial crystals arranged in a series. For commonly used optical arrangements, the general structure of light emerging from such a cascade is rigorously determined by the used crystals, leaving few possibilities for the variations of the established light pattern. A simple modification of a two-crystal arrangement where one of the two crystals is placed beyond the imaging lens is reported. This modification adds an extreme versatility to the effect and allows one to tune continuously the actual cascade parameters. As a result, practically any pattern of two-crystal cascade conical refraction can be obtained for any pair of biaxial crystals.

Biconcave micro-optofluidic lens with low-refractive-index liquids.

PubMed

Song, Chaolong; Nguyen, Nam-Trung; Asundi, Anand Krishna; Low, Cassandra Lee-Ngo

2009-12-01

One of the current problems of micro-optofluidics is the choice of a suitable liquid with a high refractive index (RI). We report the use of a low-RI liquid in a biconcave liquid-core liquid-cladding lens for focusing light. For the characterization of the lens, a telescope system was constructed from polydimethylsiloxane lenses to collimate and expand a light beam emitted from an optical fiber. The tunable optofluidic biconcave lens focuses the parallel beam. Fluorescent dye diluted in an index-matching liquid was used for the visualization of the light rays in a beam-tracing chamber. The focused beam is tuned by adjusting the flow rate ratio between core and cladding streams.

SKYDOSE: A code for gamma skyshine calculations using the integral line-beam method

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

Shultis, J.K.; Faw, R.E.; Brockhoff, R.C.

1994-07-01

SKYDOS evaluates skyshine dose from an isotropic, monoenergetic, point photon source collimated by three simple geometries: (1) a source in a silo; (2) a source behind an infinitely long, vertical, black wall; and (3) a source in a rectangular building. In all three geometries, an optical overhead shield may be specified. The source energy must be between 0.02 and 100 MeV (10 MeV for sources with an overhead shield). This is a user`s manual. Other references give more detail on the integral line-beam method used by SKYDOSE.

Monte Carlo design of optimal wire mesh collimator for breast tumor imaging process

NASA Astrophysics Data System (ADS)

Saad, W. H. M.; Roslan, R. E.; Mahdi, M. A.; Choong, W.-S.; Saion, E.; Saripan, M. I.

2011-08-01

This paper presents the modeling of breast tumor imaging process using wire mesh collimator gamma camera. Previous studies showed that the wire mesh collimator has a potential to improve the sensitivity of the tumor detection. In this paper, we extend our research significantly, to find an optimal configuration of the wire mesh collimator specifically for semi-compressed breast tumor detection, by looking into four major factors: weight, sensitivity, spatial resolution and tumor contrast. The numbers of layers in the wire mesh collimator is varied to optimize the collimator design. The statistical variations of the results are studied by simulating multiple realizations for each experiment using different starting random numbers. All the simulation environments are modeled using Monte Carlo N-Particle Code (MCNP). The quality of the detection is measured directly by comparing the sensitivity, spatial resolution and tumor contrast of the images produced by the wire mesh collimator and benchmarked that with a standard multihole collimator. The proposed optimal configuration of the wire mesh collimator is optimized by selecting the number of layers in wire mesh collimator, where the tumor contrast shows a relatively comparable value to the multihole collimator, when it is tested with uniformly semi-compressed breast phantom. The wire mesh collimator showed higher number of sensitivity because of its loose arrangement while the spatial resolution of wire mesh collimator does not shows much different compared to the multihole collimator. With a relatively good tumor contrast and spatial resolution, and increased in sensitivity, a new proposed wire mesh collimator gives a significant improvement in the wire mesh collimator design for breast cancer imaging process. The proposed collimator configuration is reduced to 44.09% from the total multihole collimator weight.

Optical system

NASA Technical Reports Server (NTRS)

Breckinridge, J. B.; Page, N. A.; Shack, R. V.; Shannon, R. R. (Inventor)

1985-01-01

Disclosed is an otpical system used in a spacecraft to observe a remote surface and provide a spatial and spectral image of this surface. The optical system includes aspheric and spherical mirrors aligned to focus at a first focal plane an image of the surface, and a mirror at this first focal plane which reflects light back on to the spherical mirror. This spherical mirror collimates the light and directs it through a prism which disperses it. The dispersed light is then focused on an array of light responsive elements disposed at a second focal plane. The prism is designed such that it disperses light into components of different wavelengths, with the components of shorter wavelengths being dispersed more than the components of longer wavelengths to present at the second focal plane a distribution pattern in which preselected groupings of the components are dispersed over essentially equal spacing intervals.

The Effect of Hawking Radation on Fermion Re-Inflation of a Schwartszchild Kugelblitz

NASA Astrophysics Data System (ADS)

Lee, J. S.

The implementation of laser-created subatomic black holes (Schwarzschild Kugelblitzes or SKs) as propulsive and power sources for interstellar starships has been presented in the literature [l]. SKs with life expectancies of only several years resulting from petawatt Hawking Radiation suggest the appeal of a mechanism to "re-inflate" the SK. This paper calculates the absorption cross-sections and absorption probabilities of attometer Schwarzschild Kugelblitzes, and demonstrates the need for incoming inflating particles to have an energy in the TeV-PeV range. The interaction between collimated re-inflating fermions and the instantaneous spectrum of Hawking radiation, and the challenges associated with subnuclear-scale beam collimation are examined.

Apparatus and method for variable angle slant hole collimator

DOEpatents

Lee, Seung Joon; Kross, Brian J.; McKisson, John E.

2017-07-18

A variable angle slant hole (VASH) collimator for providing collimation of high energy photons such as gamma rays during radiological imaging of humans. The VASH collimator includes a stack of multiple collimator leaves and a means of quickly aligning each leaf to provide various projection angles. Rather than rotate the detector around the subject, the VASH collimator enables the detector to remain stationary while the projection angle of the collimator is varied for tomographic acquisition. High collimator efficiency is achieved by maintaining the leaves in accurate alignment through the various projection angles. Individual leaves include unique angled cuts to maintain a precise target collimation angle. Matching wedge blocks driven by two actuators with twin-lead screws accurately position each leaf in the stack resulting in the precise target collimation angle. A computer interface with the actuators enables precise control of the projection angle of the collimator.

Impact of imaging approach on radiation dose and associated cancer risk in children undergoing cardiac catheterization

PubMed Central

Einstein, Andrew J.; Januzis, Natalie; Nguyen, Giao; Li, Jennifer S.; Fleming, Gregory A.; Yoshizumi, Terry K.

2016-01-01

Objectives To quantify the impact of image optimization on absorbed radiation dose and associated risk in children undergoing cardiac catheterization. Background Various imaging and fluoroscopy system technical parameters including camera magnification, source-to-image distance, collimation, anti-scatter grids, beam quality, and pulse rates, all affect radiation dose but have not been well studied in younger children. Methods We used anthropomorphic phantoms (ages: newborn and 5-years-old) to measure surface radiation exposure from various imaging approaches and estimated absorbed organ doses and effective doses (ED) using Monte Carlo simulations. Models developed in the National Academies’ Biological Effects of Ionizing Radiation VII report were used to compare an imaging protocol optimized for dose reduction versus suboptimal imaging (+20cm source-to-image-distance, +1 magnification setting, no collimation) on lifetime attributable risk (LAR) of cancer. Results For the newborn and 5-year-old phantoms respectively ED changes were as follows: +157% and +232% for an increase from 6-inch to 10-inch camera magnification; +61% and +59% for a 20cm increase in source-to-image-distance; −42% and −48% with addition of 1-inch periphery collimation; −31% and −46% with removal of the anti-scatter grid. Compared to an optimized protocol, suboptimal imaging increased ED by 2.75-fold (newborn) and 4-fold (5-year-old). Estimated cancer LAR from 30-minutes of postero-anterior fluoroscopy using optimized versus sub-optimal imaging respectively was: 0.42% versus 1.23% (newborn female), 0.20% vs 0.53% (newborn male), 0.47% versus 1.70% (5-year-old female) and 0.16% vs 0.69% (5-year-old male). Conclusions Radiation-related risks to children undergoing cardiac catheterization can be substantial but are markedly reduced with an optimized imaging approach. PMID:27315598

Impact of imaging approach on radiation dose and associated cancer risk in children undergoing cardiac catheterization.

PubMed

Hill, Kevin D; Wang, Chu; Einstein, Andrew J; Januzis, Natalie; Nguyen, Giao; Li, Jennifer S; Fleming, Gregory A; Yoshizumi, Terry K

2017-04-01

To quantify the impact of image optimization on absorbed radiation dose and associated risk in children undergoing cardiac catheterization. Various imaging and fluoroscopy system technical parameters including camera magnification, source-to-image distance, collimation, antiscatter grids, beam quality, and pulse rates, all affect radiation dose but have not been well studied in younger children. We used anthropomorphic phantoms (ages: newborn and 5 years old) to measure surface radiation exposure from various imaging approaches and estimated absorbed organ doses and effective doses (ED) using Monte Carlo simulations. Models developed in the National Academies' Biological Effects of Ionizing Radiation VII report were used to compare an imaging protocol optimized for dose reduction versus suboptimal imaging (+20 cm source-to-image-distance, +1 magnification setting, no collimation) on lifetime attributable risk (LAR) of cancer. For the newborn and 5-year-old phantoms, respectively ED changes were as follows: +157% and +232% for an increase from 6-inch to 10-inch camera magnification; +61% and +59% for a 20 cm increase in source-to-image-distance; -42% and -48% with addition of 1-inch periphery collimation; -31% and -46% with removal of the antiscatter grid. Compared with an optimized protocol, suboptimal imaging increased ED by 2.75-fold (newborn) and fourfold (5 years old). Estimated cancer LAR from 30-min of posteroanterior fluoroscopy using optimized versus suboptimal imaging, respectively was 0.42% versus 1.23% (newborn female), 0.20% versus 0.53% (newborn male), 0.47% versus 1.70% (5-year-old female) and 0.16% versus 0.69% (5-year-old male). Radiation-related risks to children undergoing cardiac catheterization can be substantial but are markedly reduced with an optimized imaging approach. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Adaptors for radiation detectors

DOEpatents

Livesay, Ronald Jason

2014-04-22

Described herein are adaptors and other devices for radiation detectors that can be used to make accurate spectral measurements of both small and large bulk sources of radioactivity, such as building structures, soils, vessels, large equipment, and liquid bodies. Some exemplary devices comprise an adaptor for a radiation detector, wherein the adaptor can be configured to collimate radiation passing through the adapter from an external radiation source to the radiation detector and the adaptor can be configured to enclose a radiation source within the adapter to allow the radiation detector to measure radiation emitted from the enclosed radiation source.

Adaptors for radiation detectors

DOEpatents

Livesay, Ronald Jason

2015-07-28

Described herein are adaptors and other devices for radiation detectors that can be used to make accurate spectral measurements of both small and large bulk sources of radioactivity, such as building structures, soils, vessels, large equipment, and liquid bodies. Some exemplary devices comprise an adaptor for a radiation detector, wherein the adaptor can be configured to collimate radiation passing through the adapter from an external radiation source to the radiation detector and the adaptor can be configured to enclose a radiation source within the adapter to allow the radiation detector to measure radiation emitted from the enclosed radiation source.

NOTE: Implementation of angular response function modeling in SPECT simulations with GATE

NASA Astrophysics Data System (ADS)

Descourt, P.; Carlier, T.; Du, Y.; Song, X.; Buvat, I.; Frey, E. C.; Bardies, M.; Tsui, B. M. W.; Visvikis, D.

2010-05-01

Among Monte Carlo simulation codes in medical imaging, the GATE simulation platform is widely used today given its flexibility and accuracy, despite long run times, which in SPECT simulations are mostly spent in tracking photons through the collimators. In this work, a tabulated model of the collimator/detector response was implemented within the GATE framework to significantly reduce the simulation times in SPECT. This implementation uses the angular response function (ARF) model. The performance of the implemented ARF approach has been compared to standard SPECT GATE simulations in terms of the ARF tables' accuracy, overall SPECT system performance and run times. Considering the simulation of the Siemens Symbia T SPECT system using high-energy collimators, differences of less than 1% were measured between the ARF-based and the standard GATE-based simulations, while considering the same noise level in the projections, acceleration factors of up to 180 were obtained when simulating a planar 364 keV source seen with the same SPECT system. The ARF-based and the standard GATE simulation results also agreed very well when considering a four-head SPECT simulation of a realistic Jaszczak phantom filled with iodine-131, with a resulting acceleration factor of 100. In conclusion, the implementation of an ARF-based model of collimator/detector response for SPECT simulations within GATE significantly reduces the simulation run times without compromising accuracy.

Optical manifold for light-emitting diodes

DOEpatents

Chaves, Julio C.; Falicoff, Waqidi; Minano, Juan C.; Benitez, Pablo; Parkyn, Jr., William A.; Alvarez, Roberto; Dross, Oliver

2008-06-03

An optical manifold for efficiently combining a plurality of blue LED outputs to illuminate a phosphor for a single, substantially homogeneous output, in a small, cost-effective package. Embodiments are disclosed that use a single or multiple LEDs and a remote phosphor, and an intermediate wavelength-selective filter arranged so that backscattered photoluminescence is recycled to boost the luminance and flux of the output aperture. A further aperture mask is used to boost phosphor luminance with only modest loss of luminosity. Alternative non-recycling embodiments provide blue and yellow light in collimated beams, either separately or combined into white.

The Current Performance of the Wide Range (90-2500 eV) Soft X-ray Beamline at the Australian Synchrotron

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

Cowie, B. C. C.; Tadich, A.; Thomsen, L.

2010-06-23

The Soft X-ray beamline at the Australian synchrotron has been constructed around a collimated light Plane Grating Monochromator taking light from an Elliptically Polarized Undulator (EPU). The beamline covers a wide photon energy range between 90 to 2500 eV, using two gratings of 250 l/mm and 1200 l/mm. At present the output from the monochromator is directed into one branchline with a dedicated UHV endstation. The measured performance of the beamline in flux and resolution is shown to be very close to that of theoretical calculations.

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

Shen, S; Meredith, R; Azure, M

Purpose: To support the phase I trial for toxicity, biodistribution and pharmacokinetics of intra-peritoneal (IP) 212Pb-TCMC-trastuzumab in patients with HER-2 expressing malignancy. A whole body gamma camera imaging method was developed for estimating amount of 212Pb-TCMC-trastuzumab left in the peritoneal cavity. Methods: {sup 212}Pb decays to {sup 212}Bi via beta emission. {sup 212}Bi emits an alpha particle at an average of 6.1 MeV. The 238.6 keV gamma ray with a 43.6% yield can be exploited for imaging. Initial phantom was made of saline bags with 212Pb. Images were collected for 238.6 keV with a medium energy general purpose collimator. Theremore » are other high energy gamma emissions (e.g. 511keV, 8%; 583 keV, 31%) that penetrate the septae of the collimator and contribute scatter into 238.6 keV. An upper scatter window was used for scatter correction for these high energy gammas. Results: A small source containing 212Pb can be easily visualized. Scatter correction on images of a small 212Pb source resulted in a ∼50% reduction in the full width at tenth maximum (FWTM), while change in full width at half maximum (FWHM) was <10%. For photopeak images, substantial scatter around phantom source extended to > 5 cm outside; scatter correction improved image contrast by removing this scatter around the sources. Patient imaging, in the 1st cohort (n=3) showed little redistribution of 212Pb-TCMC-trastuzumab out of the peritoneal cavity. Compared to the early post-treatment images, the 18-hour post-injection images illustrated the shift to more uniform anterior/posterior abdominal distribution and the loss of intensity due to radioactive decay. Conclusion: Use of medium energy collimator, 15% width of 238.6 keV photopeak, and a 7.5% upper scatter window is adequate for quantification of 212Pb radioactivity inside peritoneal cavity for alpha radioimmunotherapy of ovarian cancer. Research Support: AREVA Med, NIH 1UL1RR025777-01.« less

SU-F-T-657: In-Room Neutron Dose From High Energy Photon Beams

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

Christ, D; Ding, G

Purpose: To estimate neutron dose inside the treatment room from photodisintegration events in high energy photon beams using Monte Carlo simulations and experimental measurements. Methods: The Monte Carlo code MCNP6 was used for the simulations. An Eberline ESP-1 Smart Portable Neutron Detector was used to measure neutron dose. A water phantom was centered at isocenter on the treatment couch, and the detector was placed near the phantom. A Varian 2100EX linear accelerator delivered an 18MV open field photon beam to the phantom at 400MU/min, and a camera captured the detector readings. The experimental setup was modeled in the Monte Carlomore » simulation. The source was modeled for two extreme cases: a) hemispherical photon source emitting from the target and b) cone source with an angle of the primary collimator cone. The model includes the target, primary collimator, flattening filter, secondary collimators, water phantom, detector and concrete walls. Energy deposition tallies were measured for neutrons in the detector and for photons at the center of the phantom. Results: For an 18MV beam with an open 10cm by 10cm field and the gantry at 180°, the Monte Carlo simulations predict the neutron dose in the detector to be 0.11% of the photon dose in the water phantom for case a) and 0.01% for case b). The measured neutron dose is 0.04% of the photon dose. Considering the range of neutron dose predicted by Monte Carlo simulations, the calculated results are in good agreement with measurements. Conclusion: We calculated in-room neutron dose by using Monte Carlo techniques, and the predicted neutron dose is confirmed by experimental measurements. If we remodel the source as an electron beam hitting the target for a more accurate representation of the bremsstrahlung fluence, it is feasible that the Monte Carlo simulations can be used to help in shielding designs.« less

Development and Validation of a Monte Carlo Simulation Tool for Multi-Pinhole SPECT

PubMed Central

Mok, Greta S. P.; Du, Yong; Wang, Yuchuan; Frey, Eric C.; Tsui, Benjamin M. W.

2011-01-01

Purpose In this work, we developed and validated a Monte Carlo simulation (MCS) tool for investigation and evaluation of multi-pinhole (MPH) SPECT imaging. Procedures This tool was based on a combination of the SimSET and MCNP codes. Photon attenuation and scatter in the object, as well as penetration and scatter through the collimator detector, are modeled in this tool. It allows accurate and efficient simulation of MPH SPECT with focused pinhole apertures and user-specified photon energy, aperture material, and imaging geometry. The MCS method was validated by comparing the point response function (PRF), detection efficiency (DE), and image profiles obtained from point sources and phantom experiments. A prototype single-pinhole collimator and focused four- and five-pinhole collimators fitted on a small animal imager were used for the experimental validations. We have also compared computational speed among various simulation tools for MPH SPECT, including SimSET-MCNP, MCNP, SimSET-GATE, and GATE for simulating projections of a hot sphere phantom. Results We found good agreement between the MCS and experimental results for PRF, DE, and image profiles, indicating the validity of the simulation method. The relative computational speeds for SimSET-MCNP, MCNP, SimSET-GATE, and GATE are 1: 2.73: 3.54: 7.34, respectively, for 120-view simulations. We also demonstrated the application of this MCS tool in small animal imaging by generating a set of low-noise MPH projection data of a 3D digital mouse whole body phantom. Conclusions The new method is useful for studying MPH collimator designs, data acquisition protocols, image reconstructions, and compensation techniques. It also has great potential to be applied for modeling the collimator-detector response with penetration and scatter effects for MPH in the quantitative reconstruction method. PMID:19779896

Multicenter evaluation of a synthetic single-crystal diamond detector for CyberKnife small field size output factors.

PubMed

Russo, Serenella; Masi, Laura; Francescon, Paolo; Frassanito, Maria Cristina; Fumagalli, Maria Luisa; Marinelli, Marco; Falco, Maria Daniela; Martinotti, Anna Stefania; Pimpinella, Maria; Reggiori, Giacomo; Verona Rinati, Gianluca; Vigorito, Sabrina; Mancosu, Pietro

2016-04-01

The aim of the present work was to evaluate small field size output factors (OFs) using the latest diamond detector commercially available, PTW-60019 microDiamond, over different CyberKnife systems. OFs were measured also by silicon detectors routinely used by each center, considered as reference. Five Italian CyberKnife centers performed OFs measurements for field sizes ranging from 5 to 60mm, defined by fixed circular collimators (5 centers) and by Iris(™) variable aperture collimator (4 centers). Setup conditions were: 80cm source to detector distance, and 1.5cm depth in water. To speed up measurements two diamond detectors were used and their equivalence was evaluated. MonteCarlo (MC) correction factors for silicon detectors were used for comparing the OF measurements. Considering OFs values averaged over all centers, diamond data resulted lower than uncorrected silicon diode ones. The agreement between diamond and MC corrected silicon values was within 0.6% for all fixed circular collimators. Relative differences between microDiamond and MC corrected silicon diodes data for Iris(™) collimator were lower than 1.0% for all apertures in the totality of centers. The two microDiamond detectors showed similar characteristics, in agreement with the technical specifications. Excellent agreement between microDiamond and MC corrected silicon diode detectors OFs was obtained for both collimation systems fixed cones and Iris(™), demonstrating the microDiamond could be a suitable detector for CyberKnife commissioning and routine checks. These results obtained in five centers suggest that for CyberKnife systems microDiamond can be used without corrections even at the smallest field size. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Ultrashort Laser Retinal Damage Threshold Mechanisms

DTIC Science & Technology

2010-01-15

epithelium . Below one nanosecond both stress-confinement in melanosomes and self-focusing reduce the threshold for damage as measured in corneal radiant... epithelium (RPE). Below 1 ns, both stress confinement in melanosomes and self-focusing reduce the threshold for damage as measured in corneal radiant...collimated laser light is focused to a very small spot on the retina. The retinal pigment epithelium (RPE) contains melanosomes, which are the primary

Holographic Optical Elements Formed in Light of Reduced Coherence.

DTIC Science & Technology

1986-02-27

providing low noise optical elements by interferometric means, including gratings, lenses, beam combiners, corrector plates, and other *. special...collimators have become increasingly widespread. The study of aberrations and noise of HOEs are two important topics of research. In this paper we discuss...techniques for analysis and construction of low noise , zone plate HOEs. Low noise HOEs have been created by reducing the spatial coherence of the

Design of a multilayer-based collimated plane-grating monochromator for tender X-ray range.

PubMed

Yang, Xiaowei; Wang, Hongchang; Hand, Matthew; Sawhney, Kawal; Kaulich, Burkhard; Kozhevnikov, Igor V; Huang, Qiushi; Wang, Zhanshan

2017-01-01

Collimated plane-grating monochromators (cPGMs), consisting of a plane mirror and plane diffraction grating, are essential optics in synchrotron radiation sources for their remarkable flexibility and good optical characteristics in the soft X-ray region. However, the poor energy transport efficiency of a conventional cPGM (single-layer-coated) degrades the source intensity and leaves reduced flux at the sample, especially for the tender X-ray range (1-4 keV) that covers a large number of K- and L-edges of medium-Z elements, and M-edges of high-Z elements. To overcome this limitation, the use of a multilayer-based cPGM is proposed, combining a multilayer-coated plane mirror with blazed multilayer gratings. With this combination, the effective efficiency of cPGMs can be increased by an order of magnitude compared with the conventional single-layer cPGMs. In addition, higher resolving power can be achieved with improved efficiency by increasing the blaze angle and working at higher diffraction order.

Design of a multilayer-based collimated plane-grating monochromator for tender X-ray range

PubMed Central

Yang, Xiaowei; Wang, Hongchang; Hand, Matthew; Sawhney, Kawal; Kaulich, Burkhard; Kozhevnikov, Igor V.; Huang, Qiushi; Wang, Zhanshan

2017-01-01

Collimated plane-grating monochromators (cPGMs), consisting of a plane mirror and plane diffraction grating, are essential optics in synchrotron radiation sources for their remarkable flexibility and good optical characteristics in the soft X-ray region. However, the poor energy transport efficiency of a conventional cPGM (single-layer-coated) degrades the source intensity and leaves reduced flux at the sample, especially for the tender X-ray range (1–4 keV) that covers a large number of K- and L-edges of medium-Z elements, and M-edges of high-Z elements. To overcome this limitation, the use of a multilayer-based cPGM is proposed, combining a multilayer-coated plane mirror with blazed multilayer gratings. With this combination, the effective efficiency of cPGMs can be increased by an order of magnitude compared with the conventional single-layer cPGMs. In addition, higher resolving power can be achieved with improved efficiency by increasing the blaze angle and working at higher diffraction order. PMID:28009556

Laboratory Plasma Source as an MHD Model for Astrophysical Jets

NASA Technical Reports Server (NTRS)

Mayo, Robert M.

1997-01-01

The significance of the work described herein lies in the demonstration of Magnetized Coaxial Plasma Gun (MCG) devices like CPS-1 to produce energetic laboratory magneto-flows with embedded magnetic fields that can be used as a simulation tool to study flow interaction dynamic of jet flows, to demonstrate the magnetic acceleration and collimation of flows with primarily toroidal fields, and study cross field transport in turbulent accreting flows. Since plasma produced in MCG devices have magnetic topology and MHD flow regime similarity to stellar and extragalactic jets, we expect that careful investigation of these flows in the laboratory will reveal fundamental physical mechanisms influencing astrophysical flows. Discussion in the next section (sec.2) focuses on recent results describing collimation, leading flow surface interaction layers, and turbulent accretion. The primary objectives for a new three year effort would involve the development and deployment of novel electrostatic, magnetic, and visible plasma diagnostic techniques to measure plasma and flow parameters of the CPS-1 device in the flow chamber downstream of the plasma source to study, (1) mass ejection, morphology, and collimation and stability of energetic outflows, (2) the effects of external magnetization on collimation and stability, (3) the interaction of such flows with background neutral gas, the generation of visible emission in such interaction, and effect of neutral clouds on jet flow dynamics, and (4) the cross magnetic field transport of turbulent accreting flows. The applicability of existing laboratory plasma facilities to the study of stellar and extragalactic plasma should be exploited to elucidate underlying physical mechanisms that cannot be ascertained though astrophysical observation, and provide baseline to a wide variety of proposed models, MHD and otherwise. The work proposed herin represents a continued effort on a novel approach in relating laboratory experiments to astrophysical jet observation. There exists overwhelming similarity among these flows that has already produced some fascinating results and is expected to continue a high pay off in future flow similarity studies.

TU-H-BRC-09: Validation of a Novel Therapeutic X-Ray Array Source and Collimation System

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

Trovati, S; King, GJ; Loo, BW

2016-06-15

Purpose: We have experimentally characterized and simulated the dosimetric properties and spatial fidelity of a novel X-ray array source and collimation system called SPHINX that has the potential to generate complex intensity modulated X-ray beams by varying the electron beam intensity only, and without any moving parts like in multi-leaf collimators. Methods: We investigated the spatial fidelity and the X-ray performances of a SPHINX prototype in tungsten, using a Cyber Knife and the experimental high-energy electron beam line at XTA at SLAC National Laboratory. Dose distributions were recorded with gafchromic films, placed at the distal end of SPHINX and atmore » several depths in a solid water phantom. The geometry of SPHINX and of the experimental set-ups was also modeled in Monte Carlo (MC) simulations with the FLUKA code, used to reproduce the experimental results and, after validation, to predict and optimize the performance and design of the SPHINX. Results: The results indicate significant particle leakage through the channels during a single-channel irradiation for high incident energies, followed by a rapid decrease for energies of clinical interest. When the collimator channels are used as target, the photon production increases, however at expense of the beam size that is also enlarged. The illumination of all channels simultaneously shows a fairly even transmission of the beam. Conclusion: With the measurements we have verified the MC models and the uniformity of beam transmission through SPHINX, and we have evaluated the importance of particle leakage through adjacent channels. These results can be used to optimize SPHINX design through the validated MC simulations. Funding: Weston Havens Foundation, Office of the Dean of Medical School and Office of the Provost (Stanford University). Loo, Maxim, Borchard, Tantawi are co-founders of TibaRay Inc. Loo and Tantawi are TibaRay Inc. board members. Loo and Maxim received grants from Varian Medical Systems and RaySearch Laboratory.« less

A simplified model of the source channel of the Leksell GammaKnife® tested with PENELOPE

NASA Astrophysics Data System (ADS)

Al-Dweri, Feras M. O.; Lallena, Antonio M.; Vilches, Manuel

2004-06-01

Monte Carlo simulations using the code PENELOPE have been performed to test a simplified model of the source channel geometry of the Leksell GammaKnife®. The characteristics of the radiation passing through the treatment helmets are analysed in detail. We have found that only primary particles emitted from the source with polar angles smaller than 3° with respect to the beam axis are relevant for the dosimetry of the Gamma Knife. The photon trajectories reaching the output helmet collimators at (x, y, z = 236 mm) show strong correlations between rgr = (x2 + y2)1/2 and their polar angle thgr, on one side, and between tan-1(y/x) and their azimuthal angle phgr, on the other. This enables us to propose a simplified model which treats the full source channel as a mathematical collimator. This simplified model produces doses in good agreement with those found for the full geometry. In the region of maximal dose, the relative differences between both calculations are within 3%, for the 18 and 14 mm helmets, and 10%, for the 8 and 4 mm ones. Besides, the simplified model permits a strong reduction (larger than a factor 15) in the computational time.

Demonstrating H- beam focusing using an elliptical einzel lens

NASA Astrophysics Data System (ADS)

Lawrie, S. R.; Faircloth, D. C.; Letchford, A. P.; Whitehead, M. O.; Wood, T.

2017-08-01

H- ion source research is being performed at the ISIS spallation neutron and muon facility on a dedicated Vessel for Extraction and Source Plasma Analyses (VESPA). The ion extraction and optics system presently being used on ISIS is centered on a combined-function sector dipole magnet. This traps cesium vapor escaping the ion source; mass-separates co-extracted electrons and stripped neutrals, and weak-focusses the highly asymmetric slit-shaped ion beam. Unfortunately the added drift length through the magnet under strong space-charge forces means up to 50% of the beam is collimated on the magnet. The VESPA has shown that the ISIS ion source actually produces 80 mA of beam current at standard settings, but because of magnet collimation only 55 mA is injected into the solenoid Low Energy Beam Transport (LEBT). A new purely electrostatic post-extraction system incorporating an einzel lens with an elliptical aperture is currently under test. This allows much greater flexibility of perveance and phase space matching for injection into the LEBT and Radio Frequency Quadrupole (RFQ). This paper discusses high voltage breakdown mitigation strategies and presents the first results of the novel elliptical transport system. So far, 70 mA of beam has been transported through the new system with a normalized transverse RMS emittance of 0.2 π mm mrad.

Low Level (Sub Threshold), Large Spot Laser Irradiations of the Foveas of Macaca Mulatta.

DTIC Science & Technology

1981-11-01

light period of the light-dark cycle. GrUn (1980) reported that in adult larval Xenopus and the larvae of the fish, Tilapia , 24 hours of continuous...pulses. Exp. Eye Res. 21 : 457 - 469. 1975. GrUn, G. Developmental dynamic in synaptic ribbons of retinal receptor cells. ( Tilapia , Xenopus). Cell

Application of fiber tapers in astronomy

NASA Astrophysics Data System (ADS)

Marcel, Jaclyn; Haynes, Roger; Bland-Hawthorn, Joss

2006-06-01

Fiber tapers have the potential to significantly advance instrument technology into the realm of fully integrated optical systems. Our initial investigation was directed at the use of fiber tapers as f-ratio transformation devices. Using a technique developed for testing focal ratio degradation (FRD), a collimated light source was injected at different angles into various fiber taper samples and the far-field profile of the fiber output was observed. We compare the FRD present in the optical fiber tapers with conventional fibers and determine how effectively fiber tapers perform as image converters. We demonstrate that while silica fiber tapers may have slightly more intrinsic FRD than conventional fibers they still show promise as adiabatic mode transformers and are worth investigating further for their potential use in astronomical instruments. In this paper we present a brief review of the current status of fiber tapers with particular focus on the astronomical applications. We demonstrate the conservation of etendue in the taper transformation process and present the experimental results for a number of different taper profiles and manufacturers.

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

NASA Astrophysics Data System (ADS)

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

2008-08-01

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

Maxi/gsc

NASA Astrophysics Data System (ADS)

Mihara, T.; Maxi Team

2010-12-01

Gas Slit Camera (GSC) is the instrument in the MAXI mission. The GSC utilizes twelve large area proportional counters (PC), a slit and slats collimator. The energy range is 2-30 keV. The GSC has two FOVs of 160 x 3 degrees. One is toward forward direction of ISS and the other is the zenithal direction. Two arches of FOV scans the sky in every 92 minutes with ISS rotation. The slats collimator makes the narrow arc FOV, and the one-dimensional position-resolution of the PC resolves the X-ray sources within the FOV. Thus the position resolution is determined by the slats collimator and a combination of the slit and the position resolution of the detector. These make the point spread function of 1.5 x 1.5 degrees. The background is 1.2 × 10^-4 c/s/cm2 /keV, which is almost the same level with Ginga/LAC. The 5-sigma sensitivity is 15 mCrab/day, which is improved to with the sqrt (t) law. It will reach the 5 sigma confusion limit of 0.5 mCrab in 900 days, if the particle-background estimation is accurate enough.

Model-Based Normalization of a Fractional-Crystal Collimator for Small-Animal PET Imaging

PubMed Central

Li, Yusheng; Matej, Samuel; Karp, Joel S.; Metzler, Scott D.

2017-01-01

Previously, we proposed to use a coincidence collimator to achieve fractional-crystal resolution in PET imaging. We have designed and fabricated a collimator prototype for a small-animal PET scanner, A-PET. To compensate for imperfections in the fabricated collimator prototype, collimator normalization, as well as scanner normalization, is required to reconstruct quantitative and artifact-free images. In this study, we develop a normalization method for the collimator prototype based on the A-PET normalization using a uniform cylinder phantom. We performed data acquisition without the collimator for scanner normalization first, and then with the collimator from eight different rotation views for collimator normalization. After a reconstruction without correction, we extracted the cylinder parameters from which we generated expected emission sinograms. Single scatter simulation was used to generate the scattered sinograms. We used the least-squares method to generate the normalization coefficient for each LOR based on measured, expected and scattered sinograms. The scanner and collimator normalization coefficients were factorized by performing two normalizations separately. The normalization methods were also verified using experimental data acquired from A-PET with and without the collimator. In summary, we developed a model-base collimator normalization that can significantly reduce variance and produce collimator normalization with adequate statistical quality within feasible scan time. PMID:29270539

Model-Based Normalization of a Fractional-Crystal Collimator for Small-Animal PET Imaging.

PubMed

Li, Yusheng; Matej, Samuel; Karp, Joel S; Metzler, Scott D

2017-05-01

Previously, we proposed to use a coincidence collimator to achieve fractional-crystal resolution in PET imaging. We have designed and fabricated a collimator prototype for a small-animal PET scanner, A-PET. To compensate for imperfections in the fabricated collimator prototype, collimator normalization, as well as scanner normalization, is required to reconstruct quantitative and artifact-free images. In this study, we develop a normalization method for the collimator prototype based on the A-PET normalization using a uniform cylinder phantom. We performed data acquisition without the collimator for scanner normalization first, and then with the collimator from eight different rotation views for collimator normalization. After a reconstruction without correction, we extracted the cylinder parameters from which we generated expected emission sinograms. Single scatter simulation was used to generate the scattered sinograms. We used the least-squares method to generate the normalization coefficient for each LOR based on measured, expected and scattered sinograms. The scanner and collimator normalization coefficients were factorized by performing two normalizations separately. The normalization methods were also verified using experimental data acquired from A-PET with and without the collimator. In summary, we developed a model-base collimator normalization that can significantly reduce variance and produce collimator normalization with adequate statistical quality within feasible scan time.

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

Arcadi, Giorgio; Ghosh, Pradipta; Centre de Physique Théorique, Ecole polytechnique, CNRS, Université Paris-Saclay, 91128 Palaiseau Cedex

We investigate a simple setup in which an excess in the di-photon invariant mass distribution around 750 GeV, as seen by the ATLAS and CMS collaborations, is originated through a pair of collimated photon pairs. In this framework a scalar state s decays into two light pseudo-Goldstone bosons a, each of which subsequently decays into a pair of collimated photons which are misidentified as a single photon. In a minimal context of spontaneous symmetry breaking, we show that coupling a complex scalar field Φ=(s+ia)/√2 to a fermionic dark matter candidate χ, also responsible for generating its mass, allows for themore » correct relic density in a large region of the parameter space, while not being excluded by the direct or indirect detection experiments. Moreover, the correct relic abundance can naturally co-exist with a relatively large width for the resonant field s.« less

Ultra-thin metasurface microwave flat lens for broadband applications

DOE PAGES

Azad, Abul K.; Efimov, Anatoly V.; Ghosh, Shuprio; ...

2017-05-31

In this paper, we demonstrate a metasurface-based ultrathin flat lens operating at microwave frequencies. A series of subwavelength metallic split-ring resonators, which are sandwiched between two cross-polarized metallic gratings, are defined to obtain a radially symmetric parabolic phase distribution, covering relative phase differences ranging from 0 to 2.5π radians to create a lens. The tri-layer lens exhibits focusing/collimating of broadband microwaves from 7.0 to 10.0 GHz, with a gain enhancement of 17 dBi at a central wavelength 9.0 GHz while fed by a rectangular horn antenna. The measured focal length agrees reasonably well with design, achieving a 3 dB directionalitymore » <4.5° and confirming high-quality beam collimation along the propagation direction. Finally, the demonstrated metasurface flat lens enables light-weight, low-cost, and easily deployable flat transceivers for microwave communication, detection, and imaging applications.« less

Ultra-thin metasurface microwave flat lens for broadband applications

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

Azad, Abul K.; Efimov, Anatoly V.; Ghosh, Shuprio

In this paper, we demonstrate a metasurface-based ultrathin flat lens operating at microwave frequencies. A series of subwavelength metallic split-ring resonators, which are sandwiched between two cross-polarized metallic gratings, are defined to obtain a radially symmetric parabolic phase distribution, covering relative phase differences ranging from 0 to 2.5π radians to create a lens. The tri-layer lens exhibits focusing/collimating of broadband microwaves from 7.0 to 10.0 GHz, with a gain enhancement of 17 dBi at a central wavelength 9.0 GHz while fed by a rectangular horn antenna. The measured focal length agrees reasonably well with design, achieving a 3 dB directionalitymore » <4.5° and confirming high-quality beam collimation along the propagation direction. Finally, the demonstrated metasurface flat lens enables light-weight, low-cost, and easily deployable flat transceivers for microwave communication, detection, and imaging applications.« less

Ultra-thin metasurface microwave flat lens for broadband applications

PubMed Central

Azad, Abul K.; Efimov, Anatoly V.; Ghosh, Shuprio; Singleton, John; Taylor, Antoinette J.

2017-01-01

We demonstrate a metasurface-based ultrathin flat lens operating at microwave frequencies. A series of subwavelength metallic split-ring resonators, which are sandwiched between two cross-polarized metallic gratings, are defined to obtain a radially symmetric parabolic phase distribution, covering relative phase differences ranging from 0 to 2.5π radians to create a lens. The tri-layer lens exhibits focusing/collimating of broadband microwaves from 7.0 to 10.0 GHz, with a gain enhancement of 17 dBi at a central wavelength 9.0 GHz while fed by a rectangular horn antenna. The measured focal length agrees reasonably well with design, achieving a 3 dB directionality <4.5° and confirming high-quality beam collimation along the propagation direction. The demonstrated metasurface flat lens enables light-weight, low-cost, and easily deployable flat transceivers for microwave communication, detection, and imaging applications. PMID:29104299

Expanded beam non-imaging fiber optic connector

DOEpatents

Jannson, T.; Jannson, J.; Yeung, P.

1990-02-06

There is disclosed an expanded beam fiber to fiber connector, based on non-imaging optic principles for coupling light beams from one optical fiber to another. The system consists of two identical connector parts, referred to herein as a collimating part and a concentrating part, each having a preferred partially curved reflective boundary surface for minimizing power loss and surrounding either a hollow space or a space filled with a uniform transparent medium. In one embodiment the boundary is metallic while in a second embodiment the boundary is in the form of an interface allowing total internal reflection. In both the hollow and filled case a lens may be located at the expanded end of both the collimator part and the concentrator part forming the connector. The connector is preferably located in a housing in order to protect and preserve the mechanical stability of the coupler. 13 figs.

Ultra-thin metasurface microwave flat lens for broadband applications.

PubMed

Azad, Abul K; Efimov, Anatoly V; Ghosh, Shuprio; Singleton, John; Taylor, Antoinette J; Chen, Hou-Tong

2017-05-29

We demonstrate a metasurface-based ultrathin flat lens operating at microwave frequencies. A series of subwavelength metallic split-ring resonators, which are sandwiched between two cross-polarized metallic gratings, are defined to obtain a radially symmetric parabolic phase distribution, covering relative phase differences ranging from 0 to 2.5π radians to create a lens. The tri-layer lens exhibits focusing/collimating of broadband microwaves from 7.0 to 10.0 GHz, with a gain enhancement of 17 dBi at a central wavelength 9.0 GHz while fed by a rectangular horn antenna. The measured focal length agrees reasonably well with design, achieving a 3 dB directionality <4.5° and confirming high-quality beam collimation along the propagation direction. The demonstrated metasurface flat lens enables light-weight, low-cost, and easily deployable flat transceivers for microwave communication, detection, and imaging applications.

An efficient self-collimating photonic crystal coupling technique in the RF regime

NASA Astrophysics Data System (ADS)

Sabas, Jerico N.; Mirza, Iftekhar O.; Shi, Shouyuan; Prather, Dennis W.

2010-02-01

In this paper, we present both numerical and experimental results for the waveguiding of light using a low-index-contrast (LIC) self-collimating photonic crystal (SCPhC) in the RF frequency regime. This waveguiding structure utilizes the unique interactions of light with the periodic structure of the photonic crystal (PhC) to propagate a beam of light without divergence. This design also employs materials with a low index contrast (LIC), which reduces the electromagnetic signature of the PhC. This SCPhC was designed by extracting its dispersion contours and numerically simulating it using HFSS, a commercial 3-D, full-wave FEM software. In particular, we addressed the issue of coupling the PhC to a coaxial medium by designing an input/output (I/O) coupler consisting of a coaxial-to-waveguide transition, a rectangular waveguide and a tapered dielectric transition. We fabricated the SCPhC with a rigid polyurethane foam slab and Rexolite polystyrene rods using an automated CNC router to drill the periodic lattice in the slab. We also fabricated the dielectric segments of the I/O couplers with Rexolite slabs using an automated milling machine. Using these I/O couplers and SCPhC slab, we simulated and subsequently measured experimentally an insertion loss, for the entire system, of -3.3 dB through a 24" PhC slab, and a coupling loss of -0.95 dB at each coupler-PhC interface.

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

NASA Technical Reports Server (NTRS)

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

1990-01-01

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

Korean "-(n)un," Salience, and Information Structure

ERIC Educational Resources Information Center

Kim, Ilkyu

2013-01-01

A Korean particle "-(n)un" is widely known as a topic and/or contrast marker. Despite this seemingly well-established view on the meaning/function of "-(n)un," however, its exact nature is far from clearly understood. The main purpose of this dissertation is to shed light on the meaning of "-(n)un," by looking at it…

Estimation of bone mineral content using gamma camera: A real possibility

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

Levy, L.M.; Hoory, S.; Bandyopadhyay, D.

1985-05-01

Osteopenia and Osteoporosis are the diseases related to loss of bone minerals. At present, dual photon absorptiometry using a dedicated specially built scanner along with a very high source of Gd-153 is being used as a diagnostic tool for the early detection of bone loss. The present study was undertaken to explore the possibility that gamma cameras which are widely available in all Nuclear Medicine departments could be used successfully to evaluate bone mineral content. A Siemens LFOV gamma camera equipped with a converging collimator was used for this purpose. A fixed source (100 mCi) of Gd-153 was placed atmore » the focal point of the collimator. A series of calcium chloride solutions of varying concentrations in plastic vials were placed near the center of the collimator and imaged both in air and water. Both 44 Kev and 100 Kev images were digitized in 128 x 128 matrices and processed in a CD and A Delta system attached to a VAX 11-750 computer. Uniformity corrections for each field of view were applied and the attenuation coefficients of calcium chloride for both peaks of Gd-153 were evaluated. In addition, due to the high count rate, corrections for the dead time losses were also found to be essential. An excellent concordance between the estimated Calcium contents and that actually present were obtained by this technic. In conclusion, use of gamma camera for the routine evaluation of Osteoporosis appears to be highly promising and worth pursuing.« less

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

Kim, Jungho; Shi, Xianbo; Casa, Diego

Advances in resonant inelastic X-ray scattering (RIXS) have come in lockstep with improvements in energy resolution. Currently, the best energy resolution at the IrL 3-edge stands at ~25 meV, which is achieved using a diced Si(844) spherical crystal analyzer. However, spherical analyzers are limited by their intrinsic reflection width. A novel analyzer system using multiple flat crystals provides a promising way to overcome this limitation. For the present design, an energy resolution at or below 10 meV was selected. Recognizing that the angular acceptance of flat crystals is severely limited, a collimating element is essential to achieve the necessary solid-anglemore » acceptance. For this purpose, a laterally graded, parabolic, multilayer Montel mirror was designed for use at the IrL 3-absorption edge. It provides an acceptance larger than 10 mrad, collimating the reflected X-ray beam to smaller than 100 µrad, in both vertical and horizontal directions. The performance of this mirror was studied at beamline 27-ID at the Advanced Photon Source. X-rays from a diamond (111) monochromator illuminated a scattering source of diameter 5 µm, generating an incident beam on the mirror with a well determined divergence of 40 mrad. A flat Si(111) crystal after the mirror served as the divergence analyzer. From X-ray measurements, ray-tracing simulations and optical metrology results, it was established that the Montel mirror satisfied the specifications of angular acceptance and collimation quality necessary for a high-resolution RIXS multi-crystal analyzer system.« less

Measurement of bow tie profiles in CT scanners using a real-time dosimeter

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

Whiting, Bruce R., E-mail: whitingbrucer@gmail.com; Evans, Joshua D.; Williamson, Jeffrey F.

2014-10-15

Purpose: Several areas of computed tomography (CT) research require knowledge about the intensity profile of the x-ray fan beam that is introduced by a bow tie filter. This information is considered proprietary by CT manufacturers, so noninvasive measurement methods are required. One method using real-time dosimeters has been proposed in the literature. A commercially available dosimeter was used to apply that method, and analysis techniques were developed to extract fan beam profiles from measurements. Methods: A real-time ion chamber was placed near the periphery of an empty CT gantry and the dose rate versus time waveform was recorded as themore » x-ray source rotated about the isocenter. In contrast to previously proposed analysis methods that assumed a pointlike detector, the finite-size ion chamber received varying amounts of coverage by the collimated x-ray beam during rotation, precluding a simple relationship between the source intensity as a function of fan beam angle and measured intensity. A two-parameter model for measurement intensity was developed that included both effective collimation width and source-to-detector distance, which then was iteratively solved to minimize the error between duplicate measurements at corresponding fan beam angles, allowing determination of the fan beam profile from measured dose-rate waveforms. Measurements were performed on five different scanner systems while varying parameters such as collimation, kVp, and bow tie filters. On one system, direct measurements of the bow tie profile were collected for comparison with the real-time dosimeter technique. Results: The data analysis method for a finite-size detector was found to produce a fan beam profile estimate with a relative error between duplicate measurement intensities of <5%. It was robust over a wide range of collimation widths (e.g., 1–40 mm), producing fan beam profiles that agreed with a relative error of 1%–5%. Comparison with a direct measurement technique on one system produced agreement with a relative error of 2%–6%. Fan beam profiles were found to differ for different filter types on a given system and between different vendors. Conclusions: A commercially available real-time dosimeter probe was found to be a convenient and accurate instrument for measuring fan beam profiles. An analysis method was developed that could handle a wide range of collimation widths by explicitly considering the finite width of the ion chamber. Relative errors in the profiles were found to be less than 5%. Measurements of five different clinical scanners demonstrate the variation in bow tie designs, indicating that generic bow tie models will not be adequate for CT system research.« less

Modeling of a multileaf collimator

NASA Astrophysics Data System (ADS)

Kim, Siyong

A comprehensive physics model of a multileaf collimator (MLC) field for treatment planning was developed. Specifically, an MLC user interface module that includes a geometric optimization tool and a general method of in- air output factor calculation were developed. An automatic tool for optimization of MLC conformation is needed to realize the potential benefits of MLC. It is also necessary that a radiation therapy treatment planning (RTTP) system is capable of modeling MLC completely. An MLC geometric optimization and user interface module was developed. The planning time has been reduced significantly by incorporating the MLC module into the main RTTP system, Radiation Oncology Computer System (ROCS). The dosimetric parameter that has the most profound effect on the accuracy of the dose delivered with an MLC is the change in the in-air output factor that occurs with field shaping. It has been reported that the conventional method of calculating an in-air output factor cannot be used for MLC shaped fields accurately. Therefore, it is necessary to develop algorithms that allow accurate calculation of the in-air output factor. A generalized solution for an in-air output factor calculation was developed. Three major contributors of scatter to the in-air output-flattening filter, wedge, and tertiary collimator-were considered separately. By virtue of a field mapping method, in which a source plane field determined by detector's eye view is mapped into a detector plane field, no additional dosimetric data acquisition other than the standard data set for a range of square fields is required for the calculation of head scatter. Comparisons of in-air output factors between calculated and measured values show a good agreement for both open and wedge fields. For rectangular fields, a simple equivalent square formula was derived based on the configuration of a linear accelerator treatment head. This method predicts in-air output to within 1% accuracy. A two-effective-source algorithm was developed to account for the effect of source to detector distance on in-air output for wedge fields. Two effective sources, one for head scatter and the other for wedge scatter, were dealt with independently. Calculations provided less than 1% difference of in-air output factors from measurements. This approach offers the best comprehensive accuracy in radiation delivery with field shapes defined using MLC. This generalized model works equally well with fields shaped by any type of tertiary collimator and have the necessary framework to extend its application to intensity modulated radiation therapy.

Evaluation of Large Volume SrI2(Eu) Scintillator Detectors

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

Sturm, B W; Cherepy, N J; Drury, O B

2010-11-18

There is an ever increasing demand for gamma-ray detectors which can achieve good energy resolution, high detection efficiency, and room-temperature operation. We are working to address each of these requirements through the development of large volume SrI{sub 2}(Eu) scintillator detectors. In this work, we have evaluated a variety of SrI{sub 2} crystals with volumes >10 cm{sup 3}. The goal of this research was to examine the causes of energy resolution degradation for larger detectors and to determine what can be done to mitigate these effects. Testing both packaged and unpackaged detectors, we have consistently achieved better resolution with the packagedmore » detectors. Using a collimated gamma-ray source, it was determined that better energy resolution for the packaged detectors is correlated with better light collection uniformity. A number of packaged detectors were fabricated and tested and the best spectroscopic performance was achieved for a 3% Eu doped crystal with an energy resolution of 2.93% FWHM at 662keV. Simulations of SrI{sub 2}(Eu) crystals were also performed to better understand the light transport physics in scintillators and are reported. This study has important implications for the development of SrI{sub 2}(Eu) detectors for national security purposes.« less

Modeling of Diffuse-Diffuse Photon Coupling via a Nonscattering Region: a Comparative Study

NASA Astrophysics Data System (ADS)

Lee, Jae Hoon; Kim, Seunghwan; Kim, Youn Tae

2004-06-01

It is well established that diffusion approximation is valid for light propagation in highly scattering media, but it breaks down in nonscattering regions. The previous methods that manipulate nonscattering regions are essentially boundary-to-boundary coupling (BBC) methods through a nonscattering void region based on the radiosity theory. We present a boundary-to-interior coupling (BIC) method. BIC is based on the fact that the collimated pencil beam incident on the medium can be replaced by an isotropic point source positioned at one reduced scattering length inside the medium from an illuminated point. A similar replacement is possible for the nondiffuse lights that enter the diffuse medium through the void, and it is formulated as the BIC method. We implemented both coupling methods using the finite element method (FEM) and tested for the circle with a void gap and for a four-layer adult head model. For mean time of flight, the BIC shows better agreement with Monte Carlo (MC) simulation results than BBC. For intensity, BIC shows a comparable match with MC data compared with that of BBC. The effect of absorption of the clear layer in the adult head model was investigated. Both mean time and intensity decrease as absorption of the clear layer increases.

Modeling of diffuse-diffuse photon coupling via a nonscattering region: a comparative study.

PubMed

Lee, Jae Hoon; Kim, Seunghwan; Kim, Youn Tae

2004-06-20

It is well established that diffusion approximation is valid for light propagation in highly scattering media, but it breaks down in nonscattering regions. The previous methods that manipulate nonscattering regions are essentially boundary-to-boundary coupling (BBC) methods through a nonscattering void region based on the radiosity theory. We present a boundary-to-interior coupling (BIC) method. BIC is based on the fact that the collimated pencil beam incident on the medium can be replaced by an isotropic point source positioned at one reduced scattering length inside the medium from an illuminated point. A similar replacement is possible for the nondiffuse lights that enter the diffuse medium through the void, and it is formulated as the BIC method. We implemented both coupling methods using the finite element method (FEM) and tested for the circle with a void gap and for a four-layer adult head model. For mean time of flight, the BIC shows better agreement with Monte Carlo (MC) simulation results than BBC. For intensity, BIC shows a comparable match with MC data compared with that of BBC. The effect of absorption of the clear layer in the adult head model was investigated. Both mean time and intensity decrease as absorption of the clear layer increases.

Synchronized parameter optimization of the double freeform lenses illumination system used for the CF-LCoS pico-projectors

NASA Astrophysics Data System (ADS)

Chen, Enguo; Liu, Peng; Yu, Feihong

2012-10-01

A novel synchronized optimization method of multiple freeform surfaces is proposed and applied to double lenses illumination system design of CF-LCoS pico-projectors. Based on Snell's law and the energy conservation law, a series of first-order partial differential equations are derived for the multiple freeform surfaces of the initial system. By assigning the light deflection angle to each freeform surface, multiple surfaces can be obtained simultaneously by solving the corresponding equations, meanwhile the restricted angle on CF-LCoS is guaranteed. In order to improve the spatial uniformity, the multi-surfaces are synchronously optimized by using simplex algorithm for an extended LED source. Design example shows that the double lenses based illumination system, which employs a single 2 mm×2 mm LED chip and a CF-LCoS panel with a diagonal of 0.59 inches satisfies the needs of pico-projector. Moreover, analytical result indicates that the design method represents substantial improvement and practical significance over traditional CF-LCoS projection system, which could offer outstanding performance with both portability and low cost. The synchronized optimization design method could not only realize collimating and uniform illumination, but also could be introduced to other specific light conditions.

Self-assembly of Nano-rods in Photosensitive Phase Separation

NASA Astrophysics Data System (ADS)

Liu, Ya; Kuksenok, Olga; Maresov, Egor; Balazs, Anna

2012-02-01

Computer simulations reveal how photo-induced chemical reactions in polymeric mixtures can be exploited to create long-range order in materials whose features range from the sub-micron to the nanoscale. The process is initiated by shining a spatially uniform light on a photosensitive AB binary blend, which thereby undergoes both a reversible chemical reaction and phase separation. When a well-collimated, higher intensity light is rastered over the sample, the system forms defect-free, spatially periodic structures. We now build on this approach by introducing nanorods that have a preferential affinity for one the phases in a binary mixture. By rastering over the sample with the higher intensity light, we can create ordered arrays of rods within periodically ordered materials in essentially one processing step.

Common path point diffraction interferometer using liquid crystal phase shifting

NASA Technical Reports Server (NTRS)

Mercer, Carolyn R. (Inventor)

1997-01-01

A common path point diffraction interferometer uses dyed, parallel nematic liquid crystals which surround an optically transparent microsphere. Coherent, collimated and polarized light is focused on the microsphere at a diameter larger than that of the microsphere. A portion of the focused light passes through the microsphere to form a spherical wavefront reference beam and the rest of the light is attenuated by the dyed liquid crystals to form an object beam. The two beams form an interferogram which is imaged by a lens onto an electronic array sensor and into a computer which determines the wavefront of the object beam. The computer phase shifts the interferogram by stepping up an AC voltage applied across the liquid crystals without affecting the reference beam.

Note: Laser beam scanning using a ferroelectric liquid crystal spatial light modulator

NASA Astrophysics Data System (ADS)

Das, Abhijit; Boruah, Bosanta R.

2014-04-01

In this work we describe laser beam scanning using a ferroelectric liquid crystal spatial light modulator. Commercially available ferroelectric liquid crystal spatial light modulators are capable of displaying 85 colored images in 1 s using a time dithering technique. Each colored image, in fact, comprises 24 single bit (black and white) images displayed sequentially. We have used each single bit image to write a binary phase hologram. For a collimated laser beam incident on the hologram, one of the diffracted beams can be made to travel along a user defined direction. We have constructed a beam scanner employing the above arrangement and demonstrated its use to scan a single laser beam in a laser scanning optical sectioning microscope setup.

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

Mutaf, Yildirim D.; Yi, Byong Yong; Prado, Karl

Purpose: A dedicated stereotactic gamma irradiation device, the GammaPod Trade-Mark-Sign from Xcision Medical Systems, was developed specifically to treat small breast cancers. This study presents the first evaluation of dosimetric and geometric characteristics from the initial prototype installed at University of Maryland Radiation Oncology Department. Methods: The GammaPod Trade-Mark-Sign stereotactic radiotherapy device is an assembly of a hemi-spherical source carrier containing 36 {sup 60}Co sources, a tungsten collimator, a dynamically controlled patient support table, and the breast immobilization system which also functions as a stereotactic frame. The source carrier contains the sources in six columns spaced longitudinally at 60 Degree-Signmore » intervals and it rotates together with the variable-size collimator to form 36 noncoplanar, concentric arcs focused at the isocenter. The patient support table enables motion in three dimensions to position the patient tumor at the focal point of the irradiation. The table moves continuously in three cardinal dimensions during treatment to provide dynamic shaping of the dose distribution. The breast is immobilized using a breast cup applying a small negative pressure, where the immobilization cup is embedded with fiducials also functioning as the stereotactic frame for the breast. Geometric and dosimetric evaluations of the system as well as a protocol for absorbed dose calibration are provided. Dosimetric verifications of dynamically delivered patient plans are performed for seven patients using radiochromic films in hypothetical preop, postop, and target-in-target treatment scenarios. Results: Loaded with 36 {sup 60}Co sources with cumulative activity of 4320 Ci, the prototype GammaPod Trade-Mark-Sign unit delivers 5.31 Gy/min at the isocenter using the largest 2.5 cm diameter collimator. Due to the noncoplanar beam arrangement and dynamic dose shaping features, the GammaPod Trade-Mark-Sign device is found to deliver uniform doses to targets with good conformity. The spatial accuracy of the device to locate the radiation isocenter is determined to be less than 1 mm. Single shot profiles with 2.5 cm collimator are measured with radiochromic film and found to be in good agreement with respect to the Monte Carlo based calculations (congruence of FWHM less than 1 mm). Dosimetric verifications corresponding to all hypothetical treatment plans corresponding to three target scenarios for each of the seven patients demonstrated good agreement with gamma index pass rates of better than 97% (99.0%{+-} 0.7%). Conclusions: Dosimetric evaluation of the first GammaPod Trade-Mark-Sign stereotactic breast radiotherapy unit was performed and the dosimetric and spatial accuracy of this novel technology is found to be feasible with respect to clinical radiotherapy standards. The observed level of agreement between the treatment planning system calculations and dosimetric measurements has confirmed that the system can deliver highly complex treatment plans with remarkable geometric and dosimetric accuracy.« less

Wide Field Lyman alpha Geocoronal Simulator (WFLaGS) for the Far-uv Off Rowland-circle Telescope for Imaging and Spectroscopy (FORTIS)

NASA Astrophysics Data System (ADS)

Carter, Anna; McCandliss, Stephan R.; Redwine, Keith; Pelton, Russell

2017-01-01

At 23:52 on 17 December 2015 FORTIS (36.312 UG) was launched from the White Sands Missile Range in New Mexico on a mission to observe hydrogen emission and absorption features superimposed on the stellar continua of hot star formation regions in the spiral galaxy NGC 1365. Unfortunately scattered geocoronal Lyα from well outside our nominal (1/2 degree)2 field-of-view (FOV) overwhelmed the signal from the target. Post-flight analysis of the observed scattered light levels, in comparison to a wide-FOV model of the light scattered from various surfaces in the optical train, produced good agreement. Suppression of this scatter is the highest priority for the FORTIS return to flight effort. Our analysis pointed to the need for development of a Wide Field Lyα Geocoronal Simulator (WFLaGS) with a 10○ FOV to fully characterize the end-to-end response of FORTIS to off-axis illumination. Previous end-to-end testing was performed with a vacuum UV collimator with only a limited FOV, ≈ 100”. The development of WFLaGS will allow us to validate our scattered light model and verify our mitigation strategies, which will incorporate low scatter materials, and possibly 3-d printed light traps, covering exposed scatter centers. The design of WFLaGs, consisting of a 50mm diameter F/1 aluminum parabolic collimator and a hydrogen discharge lamp with an ~ 80mm clear MgF2 window is described, along with our initial turn-on tests. This work is supported by NASA grants to John Hopkins University, NNX11AG54G and NNX14AI78G.

Prospects for compact high-intensity laser synchrotron x-ray and gamma sources

NASA Astrophysics Data System (ADS)

Pogorelsky, I. V.

1997-03-01

A laser interacting with a relativistic electron beam behaves like a virtual wiggler of an extremely short period equal to half of the laser wavelength. This approach opens a route to relatively compact, high-brightness x-ray sources alternative or complementary to conventional synchrotron light sources. Although not new, the laser synchrotron source (LSS) concept is still waiting for a convincing demonstration. Available at the BNL Accelerator Test Facility (ATF), a high-brightness electron beam and the high-power CO2 laser may be used for prototype LSS demonstration. In a feasible demonstration experiment, 10-GW, 100-ps CO2 laser beam will be brought to a head-on collision with a 10-ps, 0.5-nC, 50 MeV electron bunch. Flashes of collimated 4.7 keV (2.6 Å) x-rays of 10-ps pulse duration, with a flux of ˜1019photons/sec, will be produced via linear Compton backscattering. The x-ray spectrum is tunable proportionally to the e-beam energy. A rational short-term extension of the proposed experiment would be further enhancement of the x-ray flux to the 1022 photons/sec level, after the ongoing ATF CO2 laser upgrade to 5 TW peak power and electron bunch shortening to 3 ps is realized. In the future, exploiting the promising approach of a high-gradient laser wake field accelerator, a compact "table-top" LSS of monochromatic gamma radiation may become feasible.

Objective comparison of lesion detectability in low and medium-energy collimator iodine-123 mIBG images using a channelized Hotelling observer

NASA Astrophysics Data System (ADS)

Gregory, Rebecca A.; Murray, Iain; Gear, Jonathan; Aldridge, Matthew D.; Levine, Daniel; Fowkes, Lucy; Waddington, Wendy A.; Chua, Sue; Flux, Glenn

2017-01-01

Iodine-123 mIBG imaging is widely regarded as a gold standard for diagnostic studies of neuroblastoma and adult neuroendocrine cancer although the optimal collimator for tumour imaging remains undetermined. Low-energy (LE) high-resolution (HR) collimators provide superior spatial resolution. However due to septal penetration of high-energy photons these provide poorer contrast than medium-energy (ME) general-purpose (GP) collimators. LEGP collimators improve count sensitivity. The aim of this study was to objectively compare the lesion detection efficiency of each collimator to determine the optimal collimator for diagnostic imaging. The septal penetration and sensitivity of each collimator was assessed. Planar images of the patient abdomen were simulated with static scans of a Liqui-Phil™ anthropomorphic phantom with lesion-shaped inserts, acquired with LE and ME collimators on 3 different manufacturers’ gamma camera systems (Skylight (Philips), Intevo (Siemens) and Discovery (GE)). Two-hundred normal and 200 single-lesion abnormal images were created for each collimator. A channelized Hotelling observer (CHO) was developed and validated to score the images for the likelihood of an abnormality. The areas under receiver-operator characteristic (ROC) curves, Az, created from the scores were used to quantify lesion detectability. The CHO ROC curves for the LEHR collimators were inferior to the GP curves for all cameras. The LEHR collimators resulted in statistically significantly smaller Azs (p  <  0.05), of on average 0.891  ±  0.004, than for the MEGP collimators, 0.933  ±  0.004. In conclusion, the reduced background provided by MEGP collimators improved 123I mIBG image lesion detectability over LEHR collimators that provided better spatial resolution.

LOR-interleaving image reconstruction for PET imaging with fractional-crystal collimation

NASA Astrophysics Data System (ADS)

Li, Yusheng; Matej, Samuel; Karp, Joel S.; Metzler, Scott D.

2015-01-01

Positron emission tomography (PET) has become an important modality in medical and molecular imaging. However, in most PET applications, the resolution is still mainly limited by the physical crystal sizes or the detector’s intrinsic spatial resolution. To achieve images with better spatial resolution in a central region of interest (ROI), we have previously proposed using collimation in PET scanners. The collimator is designed to partially mask detector crystals to detect lines of response (LORs) within fractional crystals. A sequence of collimator-encoded LORs is measured with different collimation configurations. This novel collimated scanner geometry makes the reconstruction problem challenging, as both detector and collimator effects need to be modeled to reconstruct high-resolution images from collimated LORs. In this paper, we present a LOR-interleaving (LORI) algorithm, which incorporates these effects and has the advantage of reusing existing reconstruction software, to reconstruct high-resolution images for PET with fractional-crystal collimation. We also develop a 3D ray-tracing model incorporating both the collimator and crystal penetration for simulations and reconstructions of the collimated PET. By registering the collimator-encoded LORs with the collimator configurations, high-resolution LORs are restored based on the modeled transfer matrices using the non-negative least-squares method and EM algorithm. The resolution-enhanced images are then reconstructed from the high-resolution LORs using the MLEM or OSEM algorithm. For validation, we applied the LORI method to a small-animal PET scanner, A-PET, with a specially designed collimator. We demonstrate through simulated reconstructions with a hot-rod phantom and MOBY phantom that the LORI reconstructions can substantially improve spatial resolution and quantification compared to the uncollimated reconstructions. The LORI algorithm is crucial to improve overall image quality of collimated PET, which can have significant implications in preclinical and clinical ROI imaging applications.

Optimal Shape of a Gamma-ray Collimator: single vs double knife edge

NASA Astrophysics Data System (ADS)

Metz, Albert; Hogenbirk, Alfred

2017-09-01

Gamma-ray collimators in nuclear waste scanners are used for selecting a narrow vertical segment in activity measurements of waste vessels. The system that is used by NRG uses tapered slit collimators of both the single and double knife edge type. The properties of these collimators were investigated by means of Monte Carlo simulations. We found that single knife edge collimators are highly preferable for a conservative estimate of the activity of the waste vessels. These collimators show much less dependence on the angle of incidence of the radiation than double knife edge collimators. This conclusion also applies to cylindrical collimators of the single knife edge type, that are generally used in medical imaging spectroscopy.

Evaluating the influence of laser wavelength and detection stage geometry on optical detection efficiency in a single-particle mass spectrometer

NASA Astrophysics Data System (ADS)

Marsden, Nicholas; Flynn, Michael J.; Taylor, Jonathan W.; Allan, James D.; Coe, Hugh

2016-12-01

Single-particle mass spectrometry (SPMS) is a useful tool for the online study of aerosols with the ability to measure size-resolved chemical composition with a temporal resolution relevant to atmospheric processes. In SPMS, optical particle detection is used for the effective temporal alignment of an ablation laser pulse with the presence of a particle in the ion source, and it gives the option of aerodynamic sizing by measuring the offset of particle arrival times between two detection stages. The efficiency of the optical detection stage has a strong influence on the overall instrument performance. A custom detection laser system consisting of a high-powered fibre-coupled Nd:YAG solid-state laser with a collimated beam was implemented in the detection stage of a laser ablation aerosol particle time-of-flight (LAAP-TOF) single-particle mass spectrometer without major modifications to instrument geometry. The use of a collimated laser beam permitted the construction of a numerical model that predicts the effects of detection laser wavelength, output power, beam focussing characteristics, light collection angle, particle size, and refractive index on the effective detection radius (R) of the detection laser beam. We compare the model predictions with an ambient data set acquired during the Ice in Clouds Experiment - Dust (ICE-D) project. The new laser system resulted in an order-of-magnitude improvement in instrument sensitivity to spherical particles in the size range 500-800 nm compared to a focussed 405 nm laser diode system. The model demonstrates that the limit of detection in terms of particle size is determined by the scattering cross section (Csca) as predicted by Mie theory. In addition, if light is collected over a narrow collection angle, oscillations in the magnitude of Csca with respect to particle diameter result in a variation in R, resulting in large particle-size-dependent variation in detection efficiency across the particle transmission range. This detection bias is imposed on the aerodynamic size distributions measured by the instrument and accounts for some of the detection bias towards sea salt particles in the ambient data set.

Results from Solar Reflective Band End-to-End Testing for VIIRS F1 Sensor Using T-SIRCUS

NASA Technical Reports Server (NTRS)

McIntire, Jeff; Moyer, David; McCarthy, James K.; DeLuccia, Frank; Xiong, Xiaoxiong; Butler, James J.; Guenther, Bruce

2011-01-01

Verification of the Visible Infrared Imager Radiometer Suite (VIIRS) End-to-End (E2E) sensor calibration is highly recommended before launch, to identify any anomalies and to improve our understanding of the sensor on-orbit calibration performance. E2E testing of the Reflective Solar Bands (RSB) calibration cycle was performed pre-launch for the VIIRS Fight 1 (F1) sensor at the Ball Aerospace facility in Boulder CO in March 2010. VIIRS reflective band calibration cycle is very similar to heritage sensor MODIS in that solar illumination, via a diffuser, is used to correct for temporal variations in the instrument responsivity. Monochromatic light from the NIST T-SIRCUS was used to illuminate both the Earth View (EV), via an integrating sphere, and the Solar Diffuser (SD) view, through a collimator. The collimator illumination was cycled through a series of angles intended to simulate the range of possible angles for which solar radiation will be incident on the solar attenuation screen on-orbit. Ideally, the measured instrument responsivity (defined here as the ratio of the detector response to the at-sensor radiance) should be the same whether the EV or SD view is illuminated. The ratio of the measured responsivities was determined at each collimator angle and wavelength. In addition, the Solar Diffuser Stability Monitor (SDSM), a ratioing radiometer designed to track the temporal variation in the SD BRF by direct comparison to solar radiation, was illuminated by the collimator. The measured SDSM ratio was compared to the predicted ratio. An uncertainty analysis was also performed on both the SD and SDSM calibrations.

An excess noise measurement system for weak responsivity avalanche photodiodes

NASA Astrophysics Data System (ADS)

Qiao, Liang; Dimler, Simon J.; Baharuddin, Aina N. A. P.; Green, James E.; David, John P. R.

2018-06-01

A system for measuring, with reduced photocurrent, the excess noise associated with the gain in avalanche photodiodes (APDs), using a transimpedance amplifier front-end and based on phase-sensitive detection is described. The system can reliably measure the excess noise power of devices, even when the un-multiplied photocurrent is low (~10 nA). This is more than one order of magnitude better than previously reported systems and represents a significantly better noise signal to noise ratio. This improvement in performance has been achieved by increasing the value of the feedback resistor and reducing the op-amp bandwidth. The ability to characterise APD performance with such low photocurrents enables the use of low power light sources such as light emitting diode rather than lasers to investigate the APD noise performance.

Inspection of feasible calibration conditions for UV radiometer detectors with the KI/KIO3 actinometer.

PubMed

Qiang, Zhimin; Li, Wentao; Li, Mengkai; Bolton, James R; Qu, Jiuhui

2015-01-01

UV radiometers are widely employed for irradiance measurements, but their periodical calibrations not only induce an extra cost but also are time-consuming. In this study, the KI/KIO3 actinometer was applied to calibrate UV radiometer detectors at 254 nm with a quasi-collimated beam apparatus equipped with a low-pressure UV lamp, and feasible calibration conditions were identified. Results indicate that a washer constraining the UV light was indispensable, while the size (10 or 50 mL) of a beaker containing the actinometer solution had little influence when a proper washer was used. The absorption or reflection of UV light by the internal beaker wall led to an underestimation or overestimation of the irradiance determined by the KI/KIO3 actinometer, respectively. The proper range of the washer internal diameter could be obtained via mathematical analysis. A radiometer with a longer service time showed a greater calibration factor. To minimize the interference from the inner wall reflection of the collimating tube, calibrations should be conducted at positions far enough away from the tube bottom. This study demonstrates that after the feasible calibration conditions are identified, the KI/KIO3 actinometer can be applied readily to calibrate UV radiometer detectors at 254 nm. © 2014 The American Society of Photobiology.

SRXRF analysis with spatial resolution of dental calculus

NASA Astrophysics Data System (ADS)

Sánchez, Héctor Jorge; Pérez, Carlos Alberto; Grenón, Miriam

2000-09-01

This work presents elemental-composition studies of dental calculus by X-ray fluorescence analysis using synchrotron radiation. The intrinsic characteristics of synchrotron light allow for a semi-quantitative analysis with spatial resolution. The experiments were carried out in the high-vacuum station of the XRF beamline at the Synchrotron Light National Laboratory (Campinas, Brazil). All the measurements were performed in conventional geometry (45°+45°) and the micro-collimation was attained via a pair of orthogonal slits mounted in the beamline. In this way, pixels of 50 μm×50 μm were obtained keeping a high flux of photons on the sample. Samples of human dental calculus were measured in different positions along their growing axis, in order to determine variations of the compositions in the pattern of deposit. Intensity ratios of minor elements and traces were obtained, and linear profiles and surface distributions were determined. As a general summary, we can conclude that μXRF experiments with spatial resolution on dental calculus are feasible with simple collimation and adequate positioning systems, keeping a high flux of photon. These results open interesting perspectives for the future station of the line, devoted to μXRF, which will reach resolutions of the order of 10 μm.

The telecommunications and data acquisition report

NASA Technical Reports Server (NTRS)

Renzetti, N. A. (Editor)

1982-01-01

Developments in Earth-based radio technology are reported. The Deep Space Network is discussed in terms of its advanced systems, network and facility engineering and implementation, operations, and energy sources. Problems in pulse communication and radio frequency interference are addressed with emphasis on pulse position modulation and laser beam collimation.

10 CFR 34.3 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... stop, “J” tube and collimator when it is used as an exposure head. Becquerel (Bq) means one... (Projection sheath) means a flexible or rigid tube (i.e., “J” tube) for guiding the source assembly and the... materials by nondestructive methods, utilizing ionizing radiation to make radiographic images. Lay-barge...

10 CFR 34.3 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... stop, “J” tube and collimator when it is used as an exposure head. Becquerel (Bq) means one... (Projection sheath) means a flexible or rigid tube (i.e., “J” tube) for guiding the source assembly and the... materials by nondestructive methods, utilizing ionizing radiation to make radiographic images. Lay-barge...

10 CFR 34.3 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... stop, “J” tube and collimator when it is used as an exposure head. Becquerel (Bq) means one... (Projection sheath) means a flexible or rigid tube (i.e., “J” tube) for guiding the source assembly and the... materials by nondestructive methods, utilizing ionizing radiation to make radiographic images. Lay-barge...

Cleaning Insertions and Collimation Challenges

NASA Astrophysics Data System (ADS)

Redaelli, S.; Appleby, R. B.; Bertarelli, A.; Bruce, R.; Jowett, J. M.; Lechner, A.; Losito, R.

High-performance collimation systems are essential for operating efficiently modern hadron machine with large beam intensities. In particular, at the LHC the collimation system ensures a clean disposal of beam halos in the superconducting environment. The challenges of the HL-LHC study pose various demanding requests for beam collimation. In this paper we review the present collimation system and its performance during the LHC Run 1 in 2010-2013. Various collimation solutions under study to address the HL-LHC requirements are then reviewed, identifying the main upgrade baseline and pointing out advanced collimation concept for further enhancement of the performance.

Radiography by selective detection of scatter field velocity components

NASA Technical Reports Server (NTRS)

Dugan, Edward T. (Inventor); Jacobs, Alan M. (Inventor); Shedlock, Daniel (Inventor)

2007-01-01

A reconfigurable collimated radiation detector, system and related method includes at least one collimated radiation detector. The detector has an adjustable collimator assembly including at least one feature, such as a fin, optically coupled thereto. Adjustments to the adjustable collimator selects particular directions of travel of scattered radiation emitted from an irradiated object which reach the detector. The collimated detector is preferably a collimated detector array, where the collimators are independently adjustable. The independent motion capability provides the capability to focus the image by selection of the desired scatter field components. When an array of reconfigurable collimated detectors is provided, separate image data can be obtained from each of the detectors and the respective images cross-correlated and combined to form an enhanced image.

Application of ion thruster technology to a 30-cm multipole sputtering ion source

NASA Technical Reports Server (NTRS)

Robinson, R. S.; Kaufman, H. R.

1976-01-01

A 30-cm electron-bombardment ion source has been designed and fabricated for micromachining and sputtering applications. This source has a multipole magnetic field that employs permanent magnets between permeable pole pieces. An average ion current density of 1 ma/sq cm with 500-eV argon ions was selected as a design operating condition. The ion beam at this operating condition was uniform and well collimated, with an average variation of + or -5 percent over the center 20 cm of the beam at a distance up to 30 cm from the ion source.

Linac head scatter factor for asymmetric radiation field

NASA Astrophysics Data System (ADS)

Soubra, Mazen Ahmed

1997-11-01

The head scatter factor, Sh is an important dosimetric quantity used in radiation therapy dose calculation. It is empirically determined and its field size dependence reflects changes in photon scatter from components in the linac treatment head. In this work a detailed study of the physical factors influencing the determination of Sh was performed with particular attention given to asymmetric field geometries. Ionization measurements for 6 and 18 MV photon beams were made to examine the factors which determine Sh. These include: phantom size and material, collimator backscatter, non-lateral electronic equilibrium (LEE) conditions, electron contamination, collimator-exchange, photon energy, flattening filter and off-axis distance (OAD). Results indicated that LEE is not required for Sh measurements if electron contamination is minimized. Brass caps or polystyrene miniphantoms can both be used in Sh measurements provided the phantom thickness is large enough to stop contaminant electrons. Backscatter radiation effects into the monitor chamber were found to be negligible for the Siemens linac. It was found that the presence and shape of the flattening filter had a significant effect on the empirically determined value of Sh was also shown to be a function of OAD, particularly for small fields. For fields larger than 12×12 cm2/ Sh was independent of OAD. A flattening filter mass model was introduced to explain qualitatively the above results. A detailed Monte Carlo simulation of the Siemens KD2 linac head in 6 MV mode was performed to investigate the sources of head scatter which contribute to the measured Sh. The simulated head components include the flattening filter, the electron beam stopper, the primary collimator, the photon monitor chamber and the secondary collimators. The simulations showed that the scatter from the head of the Siemens linac is a complex function of the head components. On the central axis the flattening filter played the dominant role in the contributing to scatter. However this role was significantly reduced off- axis and other head components, such as the electron beam stopper and the primary collimator, became more important. The role of the mirror and ion chamber was relatively minor. Scatter from the secondary collimators was shown to be a function of the filed size and the position of the collimators in the treatment head. They were also found to play a dual role, both as a scatter source and as an attenuator for scatter produced upstream in the linac head. A closed form model, based on the work of Yu and Slobada, was developed to estimate head scatter factors for on- and off-axis asymmetric fields. The model requires three parameters to fit the measured data. The first, a constant c, has a physical significance and is independent of energy and off-axis distance. The second, g, shows a small variation with the energy and OAD while the third parameter, the primary-to-scatter ratio, is strongly dependent on energy and off-axis distance. Comparison of Sh, predicted by the model, to measurement for a large range of symmetric and asymmetric fields showed excellent agreement. A maximum of 0.7% discrepancy was observed at 12 cm OAD.

Monte Carlo simulation of a compact microbeam radiotherapy system based on carbon nanotube field emission technology.

PubMed

Schreiber, Eric C; Chang, Sha X

2012-08-01

Microbeam radiation therapy (MRT) is an experimental radiotherapy technique that has shown potent antitumor effects with minimal damage to normal tissue in animal studies. This unique form of radiation is currently only produced in a few large synchrotron accelerator research facilities in the world. To promote widespread translational research on this promising treatment technology we have proposed and are in the initial development stages of a compact MRT system that is based on carbon nanotube field emission x-ray technology. We report on a Monte Carlo based feasibility study of the compact MRT system design. Monte Carlo calculations were performed using EGSnrc-based codes. The proposed small animal research MRT device design includes carbon nanotube cathodes shaped to match the corresponding MRT collimator apertures, a common reflection anode with filter, and a MRT collimator. Each collimator aperture is sized to deliver a beam width ranging from 30 to 200 μm at 18.6 cm source-to-axis distance. Design parameters studied with Monte Carlo include electron energy, cathode design, anode angle, filtration, and collimator design. Calculations were performed for single and multibeam configurations. Increasing the energy from 100 kVp to 160 kVp increased the photon fluence through the collimator by a factor of 1.7. Both energies produced a largely uniform fluence along the long dimension of the microbeam, with 5% decreases in intensity near the edges. The isocentric dose rate for 160 kVp was calculated to be 700 Gy∕min∕A in the center of a 3 cm diameter target. Scatter contributions resulting from collimator size were found to produce only small (<7%) changes in the dose rate for field widths greater than 50 μm. Dose vs depth was weakly dependent on filtration material. The peak-to-valley ratio varied from 10 to 100 as the separation between adjacent microbeams varies from 150 to 1000 μm. Monte Carlo simulations demonstrate that the proposed compact MRT system design is capable of delivering a sufficient dose rate and peak-to-valley ratio for small animal MRT studies.

SU-D-206-07: CBCT Scatter Correction Based On Rotating Collimator

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

Yu, G; Feng, Z; Yin, Y

2016-06-15

Purpose: Scatter correction in cone-beam computed tomography (CBCT) has obvious effect on the removal of image noise, the cup artifact and the increase of image contrast. Several methods using a beam blocker for the estimation and subtraction of scatter have been proposed. However, the inconvenience of mechanics and propensity to residual artifacts limited the further evolution of basic and clinical research. Here, we propose a rotating collimator-based approach, in conjunction with reconstruction based on a discrete Radon transform and Tchebichef moments algorithm, to correct scatter-induced artifacts. Methods: A rotating-collimator, comprising round tungsten alloy strips, was mounted on a linear actuator.more » The rotating-collimator is divided into 6 portions equally. The round strips space is evenly spaced on each portion but staggered between different portions. A step motor connected to the rotating collimator drove the blocker to around x-ray source during the CBCT acquisition. The CBCT reconstruction based on a discrete Radon transform and Tchebichef moments algorithm is performed. Experimental studies using water phantom and Catphan504 were carried out to evaluate the performance of the proposed scheme. Results: The proposed algorithm was tested on both the Monte Carlo simulation and actual experiments with the Catphan504 phantom. From the simulation result, the mean square error of the reconstruction error decreases from 16% to 1.18%, the cupping (τcup) from 14.005% to 0.66%, and the peak signal-to-noise ratio increase from 16.9594 to 31.45. From the actual experiments, the induced visual artifacts are significantly reduced. Conclusion: We conducted an experiment on CBCT imaging system with a rotating collimator to develop and optimize x-ray scatter control and reduction technique. The proposed method is attractive in applications where a high CBCT image quality is critical, for example, dose calculation in adaptive radiation therapy. We want to thank Dr. Lei Xing and Dr. Yong Yang in the Stanford University School of Medicine for this work. This work was jointly supported by NSFC (61471226), Natural Science Foundation for Distinguished Young Scholars of Shandong Province (JQ201516), and China Postdoctoral Science Foundation (2015T80739, 2014M551949).« less

Smartphone application for mechanical quality assurance of medical linear accelerators

NASA Astrophysics Data System (ADS)

Kim, Hwiyoung; Lee, Hyunseok; In Park, Jong; Choi, Chang Heon; Park, So-Yeon; Kim, Hee Jung; Kim, Young Suk; Ye, Sung-Joon

2017-06-01

Mechanical quality assurance (QA) of medical linear accelerators consists of time-consuming and human-error-prone procedures. We developed a smartphone application system for mechanical QA. The system consists of two smartphones: one attached to a gantry for obtaining real-time information on the mechanical parameters of the medical linear accelerator, and another displaying real-time information via a Bluetooth connection with the former. Motion sensors embedded in the smartphone were used to measure gantry and collimator rotations. Images taken by the smartphone’s high-resolution camera were processed to evaluate accuracies of jaw-positioning, crosshair centering and source-to-surface distance (SSD). The application was developed using Android software development kit and OpenCV library. The accuracy and precision of the system was validated against an optical rotation stage and digital calipers, prior to routine QA measurements of five medical linear accelerators. The system accuracy and precision in measuring angles and lengths were determined to be 0.05  ±  0.05° and 0.25  ±  0.14 mm, respectively. The mean absolute errors (MAEs) in QA measurements of gantry and collimator rotation were 0.05  ±  0.04° and 0.05  ±  0.04°, respectively. The MAE in QA measurements of light field was 0.39  ±  0.36 mm. The MAEs in QA measurements of crosshair centering and SSD were 0.40  ±  0.35 mm and 0.41  ±  0.32 mm, respectively. In conclusion, most routine mechanical QA procedures could be performed using the smartphone application system with improved precision and within a shorter time-frame, while eliminating potential human errors.

Significant and variable linear polarization during the prompt optical flash of GRB 160625B.

PubMed

Troja, E; Lipunov, V M; Mundell, C G; Butler, N R; Watson, A M; Kobayashi, S; Cenko, S B; Marshall, F E; Ricci, R; Fruchter, A; Wieringa, M H; Gorbovskoy, E S; Kornilov, V; Kutyrev, A; Lee, W H; Toy, V; Tyurina, N V; Budnev, N M; Buckley, D A H; González, J; Gress, O; Horesh, A; Panasyuk, M I; Prochaska, J X; Ramirez-Ruiz, E; Lopez, R Rebolo; Richer, M G; Román-Zúñiga, C; Serra-Ricart, M; Yurkov, V; Gehrels, N

2017-07-26

Newly formed black holes of stellar mass launch collimated outflows (jets) of ionized matter that approach the speed of light. These outflows power prompt, brief and intense flashes of γ-rays known as γ-ray bursts (GRBs), followed by longer-lived afterglow radiation that is detected across the electromagnetic spectrum. Measuring the polarization of the observed GRB radiation provides a direct probe of the magnetic fields in the collimated jets. Rapid-response polarimetric observations of newly discovered bursts have probed the initial afterglow phase, and show that, minutes after the prompt emission has ended, the degree of linear polarization can be as high as 30 per cent-consistent with the idea that a stable, globally ordered magnetic field permeates the jet at large distances from the central source. By contrast, optical and γ-ray observations during the prompt phase have led to discordant and often controversial results, and no definitive conclusions have been reached regarding the origin of the prompt radiation or the configuration of the magnetic field. Here we report the detection of substantial (8.3 ± 0.8 per cent from our most conservative simulation), variable linear polarization of a prompt optical flash that accompanied the extremely energetic and long-lived prompt γ-ray emission from GRB 160625B. Our measurements probe the structure of the magnetic field at an early stage of the jet, closer to its central black hole, and show that the prompt phase is produced via fast-cooling synchrotron radiation in a large-scale magnetic field that is advected from the black hole and distorted by dissipation processes within the jet.

Significant and variable linear polarization during the prompt optical flash of GRB 160625B.

NASA Astrophysics Data System (ADS)

Troja, E.; Lipunov, V. M.; Mundell, C. G.; Butler, N. R.; Watson, A. M.; Kobayashi, S.; Cenko, S. B.; Marshall, F. E.; Ricci, R.; Fruchter, A.; Wieringa, M. H.; Gorbovskoy, E. S.; Kornilov, V.; Kutyrev, A.; Lee, W. H.; Toy, V.; Tyurina, N. V.; Budnev, N. M.; Buckley, D. A. H.; González, J.; Gress, O.; Horesh, A.; Panasyuk, M. I.; Prochaska, J. X.; Ramirez-Ruiz, E.; Rebolo Lopez, R.; Richer, M. G.; Roman-Zuniga, C.; Serra-Ricart, M.; Yurkov, V.; Gehrels, N.

2017-07-01

Newly formed black holes of stellar mass launch collimated outflows (jets) of ionized matter that approach the speed of light. These outflows power prompt, brief and intense flashes of γ-rays known as γ-ray bursts (GRBs), followed by longer-lived afterglow radiation that is detected across the electromagnetic spectrum. Measuring the polarization of the observed GRB radiation provides a direct probe of the magnetic fields in the collimated jets. Rapid-response polarimetric observations of newly discovered bursts have probed the initial afterglow phase, and show that, minutes after the prompt emission has ended, the degree of linear polarization can be as high as 30 per cent - consistent with the idea that a stable, globally ordered magnetic field permeates the jet at large distances from the central source. By contrast, optical and γ-ray observations during the prompt phase have led to discordant and often controversial results, and no definitive conclusions have been reached regarding the origin of the prompt radiation or the configuration of the magnetic field. Here we report the detection of substantial (8.3 ± 0.8 per cent from our most conservative simulation), variable linear polarization of a prompt optical flash that accompanied the extremely energetic and long-lived prompt γ-ray emission from GRB 160625B. Our measurements probe the structure of the magnetic field at an early stage of the jet, closer to its central black hole, and show that the prompt phase is produced via fast-cooling synchrotron radiation in a large-scale magnetic field that is advected from the black hole and distorted by dissipation processes within the jet.

Smartphone application for mechanical quality assurance of medical linear accelerators.

PubMed

Kim, Hwiyoung; Lee, Hyunseok; Park, Jong In; Choi, Chang Heon; Park, So-Yeon; Kim, Hee Jung; Kim, Young Suk; Ye, Sung-Joon

2017-06-07

Mechanical quality assurance (QA) of medical linear accelerators consists of time-consuming and human-error-prone procedures. We developed a smartphone application system for mechanical QA. The system consists of two smartphones: one attached to a gantry for obtaining real-time information on the mechanical parameters of the medical linear accelerator, and another displaying real-time information via a Bluetooth connection with the former. Motion sensors embedded in the smartphone were used to measure gantry and collimator rotations. Images taken by the smartphone's high-resolution camera were processed to evaluate accuracies of jaw-positioning, crosshair centering and source-to-surface distance (SSD). The application was developed using Android software development kit and OpenCV library. The accuracy and precision of the system was validated against an optical rotation stage and digital calipers, prior to routine QA measurements of five medical linear accelerators. The system accuracy and precision in measuring angles and lengths were determined to be 0.05  ±  0.05° and 0.25  ±  0.14 mm, respectively. The mean absolute errors (MAEs) in QA measurements of gantry and collimator rotation were 0.05  ±  0.04° and 0.05  ±  0.04°, respectively. The MAE in QA measurements of light field was 0.39  ±  0.36 mm. The MAEs in QA measurements of crosshair centering and SSD were 0.40  ±  0.35 mm and 0.41  ±  0.32 mm, respectively. In conclusion, most routine mechanical QA procedures could be performed using the smartphone application system with improved precision and within a shorter time-frame, while eliminating potential human errors.

Particle-Image Velocimeter Having Large Depth of Field

NASA Technical Reports Server (NTRS)

Bos, Brent

2009-01-01

An instrument that functions mainly as a particle-image velocimeter provides data on the sizes and velocities of flying opaque particles. The instrument is being developed as a means of characterizing fluxes of wind-borne dust particles in the Martian atmosphere. The instrument could also adapted to terrestrial use in measuring sizes and velocities of opaque particles carried by natural winds and industrial gases. Examples of potential terrestrial applications include monitoring of airborne industrial pollutants and airborne particles in mine shafts. The design of this instrument reflects an observation, made in field research, that airborne dust particles derived from soil and rock are opaque enough to be observable by use of bright field illumination with high contrast for highly accurate measurements of sizes and shapes. The instrument includes a source of collimated light coupled to an afocal beam expander and an imaging array of photodetectors. When dust particles travel through the collimated beam, they cast shadows. The shadows are magnified by the beam expander and relayed to the array of photodetectors. Inasmuch as the images captured by the array are of dust-particle shadows rather of the particles themselves, the depth of field of the instrument can be large: the instrument has a depth of field of about 11 mm, which is larger than the depths of field of prior particle-image velocimeters. The instrument can resolve, and measure the sizes and velocities of, particles having sizes in the approximate range of 1 to 300 m. For slowly moving particles, data from two image frames are used to calculate velocities. For rapidly moving particles, image smear lengths from a single frame are used in conjunction with particle- size measurement data to determine velocities.

Hybrid Parallel-Slant Hole Collimators for SPECT Imaging

NASA Astrophysics Data System (ADS)

Bai, Chuanyong; Shao, Ling; Ye, Jinghan; Durbin, M.; Petrillo, M.

2004-06-01

We propose a new collimator geometry, the hybrid parallel-slant (HPS) hole geometry, to improve sensitivity for SPECT imaging with large field of view (LFOV) gamma cameras. A HPS collimator has one segment with parallel holes and one or more segments with slant holes. The collimator can be mounted on a conventional SPECT LFOV system that uses parallel-beam collimators, and no additional detector or collimator motion is required for data acquisition. The parallel segment of the collimator allows for the acquisition of a complete data set of the organs-of-interest and the slant segments provide additional data. In this work, simulation studies of an MCAT phantom were performed with a HPS collimator with one slant segment. The slant direction points from patient head to patient feet with a slant angle of 30/spl deg/. We simulated 64 projection views over 180/spl deg/ with the modeling of nonuniform attenuation effect, and then reconstructed images using an MLEM algorithm that incorporated the hybrid geometry. It was shown that sensitivity to the cardiac region of the phantom was increased by approximately 50% when using the HPS collimator compared with a parallel-hole collimator. No visible artifacts were observed in the myocardium and the signal-to-noise ratio (SNR) of the myocardium walls was improved. Compared with collimators with other geometries, using a HPS collimator has the following advantages: (a) significant sensitivity increase; (b) a complete data set obtained from the parallel segment that allows for artifact-free image reconstruction; and (c) no additional collimator or detector motion. This work demonstrates the potential value of hybrid geometry in collimator design for LFOV SPECT imaging.

An automatic alignment system for measuring optical path of transmissometer based on light beam scanning

NASA Astrophysics Data System (ADS)

Zhou, Shudao; Ma, Zhongliang; Wang, Min; Peng, Shuling

2018-05-01

This paper proposes a novel alignment system based on the measurement of optical path using a light beam scanning mode in a transmissometer. The system controls both the probe beam and the receiving field of view while scanning in two vertical directions. The system then calculates the azimuth angle of the transmitter and the receiver to determine the precise alignment of the optical path. Experiments show that this method can determine the alignment angles in less than 10 min with errors smaller than 66 μrad in the azimuth. This system also features high collimation precision, process automation and simple installation.

Dose characteristics of in-house-built collimators for stereotactic radiotherapy with a linear accelerator.

PubMed

Norrgård, F S; Sipilä, P M; Kulmala, J A; Minn, H R

1998-06-01

Dose characteristics of a stereotactic radiotherapy unit based on a standard Varian Clinac 4/100 4 MV linear accelerator, in-house-built Lipowitz collimators and the SMART stereotactic radiotherapy treatment planning software have been determined. Beam collimation is constituted from the standard collimators of the linear accelerator and a tertiary collimation consisting of a replaceable divergent Lipowitz collimator. Four collimators with isocentre diameters of 15, 25, 35 and 45 mm, respectively, were constructed. Beam characteristics were measured in air, acrylic or water with ionization chamber, photon diode, electron diode, diamond detector and film. Monte Carlo simulation was also applied. The radiation leakage under the collimators was less than 1% at 50 mm depth in water. Specific beam characteristics for each collimator were imported to SMART and dose planning with five non-coplanar converging 140 degrees arcs separated by 36 degrees angles was performed for treatment of a RANDO phantom. Dose verification was made with TLD and radiochromic film. The in-house-built collimators were found to be suitable for stereotactic radiotherapy and patient treatments with this system are in progress.

Neutron collimator design of neutron radiography based on the BNCT facility

NASA Astrophysics Data System (ADS)

Yang, Xiao-Peng; Yu, Bo-Xiang; Li, Yi-Guo; Peng, Dan; Lu, Jin; Zhang, Gao-Long; Zhao, Hang; Zhang, Ai-Wu; Li, Chun-Yang; Liu, Wan-Jin; Hu, Tao; Lü, Jun-Guang

2014-02-01

For the research of CCD neutron radiography, a neutron collimator was designed based on the exit of thermal neutron of the Boron Neutron Capture Therapy (BNCT) reactor. Based on the Geant4 simulations, the preliminary choice of the size of the collimator was determined. The materials were selected according to the literature data. Then, a collimator was constructed and tested on site. The results of experiment and simulation show that the thermal neutron flux at the end of the neutron collimator is greater than 1.0×106 n/cm2/s, the maximum collimation ratio (L/D) is 58, the Cd-ratio(Mn) is 160 and the diameter of collimator end is 10 cm. This neutron collimator is considered to be applicable for neutron radiography.

SU-F-T-671: Effects of Collimator Material On Proton Minibeams

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

Lee, E; Sandison, G; Cao, N

2016-06-15

Purpose: To investigate the dosimetric effects of collimator material on spatially modulated proton minibeams (pMBRT). Methods: pMBRT holds promise to exhibit shallow depth normal-tissue sparing effects similar to synchrotron based microbeams while also retaining potential for uniform dose distributions for tumor targets. TOPAS Monte Carlo simulations were performed for a 5cm thick multislit collimator with 0.3mm slits and 1mm center-to-center spacing for a 50.5MeV proton minibeam while varying collimator material between brass, tungsten, and iron. The collimator was placed both “flush” at the water phantom surface and at 5cm distance to investigate the effects on surface dose, peak-to-valley-dose-ratio (PVDR) andmore » neutron contribution. Results: For flush placement, the neutron dose at the phantom surface for the tungsten collimator was approximately 20% higher than for brass and iron. This was not reflected in the overall surface dose, which was comparable for all materials due to the relatively low neutron contribution of <0.1%. When the collimator was retracted, the overall neutron contribution was essentially identical for all three collimators. Surface dose dropped by ∼40% for all collimator materials with air gap compared to being flush with the phantom surface. This surface dose reduction was at the cost of increase in valley dose for all collimator materials due to increased angular divergence of the mini-beams at the surface and their consequent geometric penumbra at depth. When the collimator was placed at distance from the phantom surface the PVDR decreased. The peak-to-entrance-dose ratio was highest for the iron collimator with 5cm air gap. Conclusion: The dosimetric difference between the collimator materials is minimal despite the relatively higher neutron contribution at the phantom surface for the tungsten collimator when placed flush. The air gap between the collimator and phantom surface strongly influences all dosimetry parameters due to the influence of scatter on the narrow spatial modulation.« less

Radiation beam collimation system and method

DOEpatents

Schmidt, Oliver A.; Ramanathan, Mohan

2015-08-18

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

Sci-Thur PM – Brachytherapy 05: Surface Collimation Applied to Superficial Flap High Dose-Rate Brachytherapy

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

Liu, Derek; Sabondjian, Eric; Lawrence, Kailin

Purpose: To apply surface collimation for superficial flap HDR skin brachytherapy utilizing common clinical resources and to demonstrate the potential for OAR dose reduction within a clinically relevant setting. Methods: Two phantom setups were used. 3 mm lead collimation was applied to a solid slab phantom to determine appropriate geometries relating to collimation and dwell activation. The same collimation was applied to the temple of an anthropomorphic head phantom to demonstrate lens dose reduction. Each setup was simulated and planned to deliver 400 cGy to a 3 cm circular target to 3 mm depth. The control and collimated irradiations weremore » sequentially measured using calibrated radiochromic films. Results: Collimation for the slab phantom attenuated the dose beyond the collimator opening, decreasing the fall-off distances by half and reducing the area of healthy skin irradiated. Target coverage can be negatively impacted by a tight collimation margin, with the required margin approximated by the primary beam geometric penumbra. Surface collimation applied to the head phantom similarly attenuated the surrounding normal tissue dose while reducing the lens dose from 84 to 68 cGy. To ensure consistent setup between simulation and treatment, additional QA was performed including collimator markup, accounting for collimator placement uncertainties, standoff distance verification, and in vivo dosimetry. Conclusions: Surface collimation was shown to reduce normal tissue dose without compromising target coverage. Lens dose reduction was demonstrated on an anthropomorphic phantom within a clinical setting. Additional QA is proposed to ensure treatment fidelity.« less

Diamond-anvil high-pressure cell with improved X-ray collimation system

DOEpatents

Schiferl, David; Olinger, Barton W.; Livingston, Robert W.

1986-01-01

An adjustable X-ray collimation system for a diamond-anvil high-pressure cell of the type including a cooperable piston and cylinder and a pair of opposing diamonds located between the head of the piston and the head of the cylinder. The X-ray collimation system includes a tubular insert which contains an X-ray collimator. The insert is engageable in the bore of the piston. The collimator is mounted within the insert by means of an elastomeric O-ring at the end closest the opposed diamonds, and by means of a set of adjustable set screws at the opposite end. By adjustment of the set screws the collimator can be pivoted about the O-ring and brought into alignment with the opposed diamonds and the sample contained therein. In the preferred embodiment there is further provided a set of plugs which are insertable in the bore of the collimator. The plugs have bores of different diameters. By successively inserting plugs of progressively smaller bore diameters and adjusting the alignment of the collimator with each plug, the collimator can be quickly brought into accurate alignment with the diamonds. The collimation system allows alignment of the collimator either before or after the cell has been loaded and pressurized.