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Energy efficient louver and blind. Final technical progress report

Description: In the month of July, the authors completed the energy testing at Lawrence Berkeley Labs. The final testing was done with blinds in 15 degree position. This is a comfortable blind angle that allows for view of the outside while allowing for natural light to enter the room. It was found that the energy savings are much higher at this angle. At zero degree blind angle the savings were 150 W/sq. meter, in the 15 degree the heat gain is cut by 225 W/sq. meter. During the same period the heat gain in control chamber was 500 W. The heat gain reduction achieved in tests if used in commercial blinds, would result in an energy pay back period or one year and nine months.
Date: October 14, 1996
Creator: Khajavi, S.
Partner: UNT Libraries Government Documents Department

Measurement of bidirectional optical properties of complex shading devices

Description: A new method of predicting the solar heat gain through complex fenestration systems involving nonspecular layers such as shades or blinds has been examined in a project jointly sponsored by ASHRAE and DOE. In this method, a scanning radiometer is used to measure the bidirectional radiative transmittance and reflectance of each layer of a fenestration system. The properties of systems containing these layers are then built up computationally from the measured layer properties using a transmission/multiple-reflection calculation. The calculation produces the total directional-hemispherical transmittance of the fenestration system and the layer-by-layer absorptances. These properties are in turn combined with layer-specific measurements of the inward-flowing fractions of absorbed solar energy to produce the overall solar heat gain coefficient. This paper describes the method of measuring the spatially averaged bidirectional optical properties using an automated, large-sample gonioradiometer/photometer, termed a ``Scanning Radiometer.`` Property measurements are presented for one of the most optically complex systems in common use, a venetian blind. These measurements will form the basis for optical system calculations used to test the method of determining performance.
Date: January 1995
Creator: Klems, J. H. & Warner, J. L.
Partner: UNT Libraries Government Documents Department

Development of a Fast X-ray Shutter System. Final Technical Report

Description: The objective of the project was to develop a fast shutter mechanism to allow separation of a single pulse of x-rays out of the given time structure of the APS. Technological challenges in developing this device range from engineering of ultra high strength alloys, mechanical shape development for optimal strength, coupling such materials to motorized shafts, magnetic suspension of high velocity rotors in combination with phase pick up and excursion monitoring, resonance control and jitter-free electronics. The pulse selector was delivered, integrated into the x-ray diffraction environment and tested. The researchers developed an acoustic delay line as protection against air inrushes and associated failure of the rotor and thin diamond windows for maximum x-ray transparency. Design goals were reached or exceeded and practical experience with the device began in March 2000.
Date: February 28, 2000
Creator: Schildkamp, Wilfried
Partner: UNT Libraries Government Documents Department

Monolithic geared-mechanisms driven by a polysilicon surface-micromachined on-chip electrostatic microengine

Description: We have previously described a practical micromachined power source: the polysilicon, surface-micromachined, electrostatically actuated microengine. Here we report on 3 aspects of implementing the microengine. First, we discuss demonstrations of the first-generation microengine actuating geared micromechanisms including gear trains with elements having dimensions comparable to the drive gear (about 50 {mu}m) and a relatively large (1600-{mu}m-diameter) rotating optical shutter element. These configurations span expected operating extremes for the microengine and address the coupling and loading issues for very-low-aspect-ratio micromechanisms which are common to the design of surface-micromachined devices. Second, we report on a second-generation of designs that utilize improved gear teeth design, a gear speed-reduction unit, and higher force-per-unit-area electrostatic comb drives. The speed-reduction unit produces an overall angular speed reduction of 9.63 and requires dual-level compound gears. Third, we discuss a dynamics model developed to accomplish 3 objectives: drive inertial loads in a controlled fashion, minimize stress and frictional forces during operation, and determine as a function of time the forces associated with the drive gear (eg load torque on drive gear from friction).
Date: May 1, 1996
Creator: Sniegowski, J.J.; Miller, S.L.; LaVigne, G.F.; Rodgers, M.S. & McWhorter, P.J.
Partner: UNT Libraries Government Documents Department

An integrated bremsstrahlung safety shutter and collimator designed for the APS front end operating in the top-up mode

Description: The Bremsstrahlung safety shutter is an important device for synchrotron radiation facility personal safety. The APS front ends have double redundant safety shutter assemblies (as per PSAR requirements) that are located about 22.6 m from the source, just upstream of the ratchet wall. These assemblies are needed to guard against an accidental positron beam loss during injection and normal operation, which then can result in high energy Bremsstrahlung radiation being directed down the front end into the First Optics Enclosure (FOE) and the experimental station. In the APS top-up mode of operation, the positron injection will be continued during the normal operation. Therefore, it is necessary to have special Bremsstrahlung shielding to protect the downstream experimental area. There are many ways to do this, but the most economical way is to design a special long Bremsstrahlung collimator in the front-end area. The better the collimation in the front end, the less the shielding material needed in the beamline. The major difficulty in designing the front-end special Bremsstrahlung collimator is the space problem. In the APS, the total length available for the APS ID front end is only about 7.6 m; there is not extra space for additional collimators. To solve this problem, we propose here a novel integrated design that will provide the functions of both a Bremsstrahlung collimator and a safety shutter.
Date: April 14, 1992
Creator: Shu, D.; Sanchez, T. & Kuzay, T.
Partner: UNT Libraries Government Documents Department

Wide-angle monochromatic x-ray beam shutter : a design study.

Description: A novel design of a wide-angle monochromatic x-ray beam shutter is discussed. The shutter is designed as a compact unit capable of providing users with the means of shutting off the beam in secondary beamlines that are at an angle to the primary beamline and to each other. The single-unit design used the fact that all the secondary beamlines will be closed at the same time. The main challenge was to fit the shutter in the limited space of the existing Advanced Photon Source IMMW-CAT hutch. Space limitations led to the change in position of the actuator subassembly as compared to the standard shutter design. Although the actuator subassembly is placed underneath the shutter, fail-safe shutting is achieved by placing tungsten blocks above the beam while the shutter is open and using gravity to close the shutter in case of pneumatic failure. Redundancy required by safety concerns was achieved by duplicating the tungsten block/actuator subunits. Tungsten blocks of uneven length were used to counteract the increase in the center-to-center distance among secondary beamlines due to their angular offset. A special support table was designed to facilitate assembly and adjustability of the shutter position in the available space. To provide a radiation-tight hutch, a non-standard guillotine system was designed. In this paper, the design, specifications and optical ray tracing of the shutter assembly are presented.
Date: July 9, 2002
Creator: Brajuskovic, B.; Chang, J.; Carrera, F.; Lourio, L.; Pelletier, J.F. & Shu, D.
Partner: UNT Libraries Government Documents Department

The LSST Camera Overview

Description: The LSST camera is a wide-field optical (0.35-1um) imager designed to provide a 3.5 degree FOV with better than 0.2 arcsecond sampling. The detector format will be a circular mosaic providing approximately 3.2 Gigapixels per image. The camera includes a filter mechanism and, shuttering capability. It is positioned in the middle of the telescope where cross-sectional area is constrained by optical vignetting and heat dissipation must be controlled to limit thermal gradients in the optical beam. The fast, f/1.2 beam will require tight tolerances on the focal plane mechanical assembly. The focal plane array operates at a temperature of approximately -100 C to achieve desired detector performance. The focal plane array is contained within an evacuated cryostat, which incorporates detector front-end electronics and thermal control. The cryostat lens serves as an entrance window and vacuum seal for the cryostat. Similarly, the camera body lens serves as an entrance window and gas seal for the camera housing, which is filled with a suitable gas to provide the operating environment for the shutter and filter change mechanisms. The filter carousel can accommodate 5 filters, each 75 cm in diameter, for rapid exchange without external intervention.
Date: January 10, 2007
Creator: Gilmore, Kirk; Kahn, Steven A.; Nordby, Martin; Burke, David; O'Connor, Paul; Oliver, John et al.
Partner: UNT Libraries Government Documents Department

Speeding up the Raster Scanning Methods used in theX-Ray Fluorescence Imaging of the Ancient Greek Text of Archimedes

Description: Progress has been made at the Stanford Linear Accelerator Center (SLAC) toward deciphering the remaining 10-20% of ancient Greek text contained in the Archimedes palimpsest. The text is known to contain valuable works by the mathematician, including the ''Method of Mechanical Theorems, the Equilibrium of Planes, On Floating Bodies'', and several diagrams as well. The only surviving copy of the text was recycled into a prayer book in the Middle Ages. The ink used to write on the goat skin parchment is partly composed of iron, which is visible by x-ray radiation. To image the palimpsest pages, the parchment is framed and placed in a stage that moves according to the raster method. When an x-ray beam strikes the parchment, the iron in the ink is detected by a germanium detector. The resulting signal is converted to a gray-scale image on the imaging program, Rasplot. It is extremely important that each line of data is perfectly aligned with the line that came before it because the image is scanned in two directions. The objectives of this experiment were to determine the best parameters for producing well-aligned images and to reduce the scanning time. Imaging half a page of parchment during previous beam time for this project was achieved in thirty hours. Equations were produced to evaluate count time, shutter time, and the number of pixels in this experiment. On Beamline 6-2 at the Stanford Synchrotron Radiation Laboratory (SSRL), actual scanning time was reduced by one fourth. The remaining pages were successfully imaged and sent to ancient Greek experts for translation.
Date: August 24, 2006
Creator: Turner, Manisha & U., /Norfolk State
Partner: UNT Libraries Government Documents Department

The Physics Analysis of a Gas Attenuator with Argon as a Working Gas

Description: A gas attenuator is an important element of the LCLS facility. The attenuator has to operate in a broad range of x-ray energies, provide attenuation coefficient between 1 and 10{sup 4} with the accuracy of 1% and, at the same time, be reliable and allow for many months of un-interrupted operation. A detailed design study of the attenuator based on the use of nitrogen as a working gas has been recently carried out by S. Shen et al [1]. In this note we assess the features of the attenuator based on the use of argon. We concentrate on the physics issues; the design features will probably be not that different from the aforementioned nitrogen attenuator. Although specific results obtained in our note pertain to argon, the general framework (and many equations obtained) are applicable also to the nitrogen attenuator. In the past, an analysis of the attenuator based on the use of a noble gas has already been carried out [2]. This analysis was performed for an extremely stringent set of specifications. In particular, a very large diameter for the unobstructed x-ray beam was set (1 cm) to accommodate the spontaneous radiation; the attenuator was supposed to cover the whole range of energies of the coherent radiation, from 800 eV to 8000 eV; the maximum attenuation was set at the level of 10{sup 4}; the use of solid attenuators was not allowed, as well as the use of rotating shutters. The need to reach a sufficient absorption at the high-energy end of the spectrum predetermined the choice of Xe as the working gas (in order to have a reasonable absorption at a not-too-high pressure). A sophisticated differential pumping system that included a Penning-type ion pump was suggested in order to minimize the gas leak into the undulator/accelerator part of the ...
Date: December 19, 2005
Creator: Ryutov, D D; Bionta, R M; McKernan, M A; Shen, S & Trent, J W
Partner: UNT Libraries Government Documents Department

Top-Off Safety Analysis for NSLS-II

Description: Top-off injection will be adopted in NSLS-II. To ensure no injected beam can pass into experimental beamlines with open photon shutters during top-off injection, simulation studies for possible machine fault scenarios are required. We compare two available simulation methods, backward (H. Nishimura-LBL) and forward tracking (A. Terebilo-SLAC). We also discuss the tracking settings, fault scenarios, apertures and interlocks considered in the analysis.
Date: May 4, 2009
Creator: Li,Y.; Casey, B.; Heese, R.; Hseuh, H.; Job, O.; Krinsky, S. et al.
Partner: UNT Libraries Government Documents Department

Fenestration System Performance Research, Testing, and Evaluation

Description: The US DOE was and is instrumental to NFRC's beginning and its continued success. The 2005 to 2009 funding enables NFRC to continue expanding and create new, improved ratings procedures. Research funded by the US DOE enables increased fenestration energy rating accuracy. International harmonization efforts supported by the US DOE allow the US to be the global leader in fenestration energy ratings. Many other governments are working with the NFRC to share its experience and knowledge toward development of their own national fenestration rating process similar to the NFRC's. The broad and diverse membership composition of NFRC allows anyone with a fenestration interest to come forward with an idea or improvement to the entire fenestration community for consideration. The NFRC looks forward to the next several years of growth while remaining the nation's resource for fair, accurate, and credible fenestration product energy ratings. NFRC continues to improve its rating system by considering new research, methodologies, and expanding to include new fenestration products. Currently, NFRC is working towards attachment energy ratings. Attachments are blinds, shades, awnings, and overhangs. Attachments may enable a building to achieve significant energy savings. An NFRC rating will enable fair competition, a basis for code references, and a new ENERGY STAR product category. NFRC also is developing rating methods to consider non specular glazing such as fritted glass. Commercial applications frequently use fritted glazing, but no rating method exists. NFRC is testing new software that may enable this new rating and contribute further to energy conservation. Around the world, many nations are seeking new energy conservation methods and NFRC is poised to harmonize its rating system assisting these nations to better manage and conserve energy in buildings by using NFRC rated and labeled fenestration products. As this report has shown, much more work needs to be done ...
Date: November 30, 2009
Creator: Benney, Jim
Partner: UNT Libraries Government Documents Department

Combined photonics and MEMs function demonstration

Description: The authors have recently demonstrated two prototypes where photonics and microelectromechanical system (MEMs) technologies have been integrated to show proof-of-principle functionality for weapon surety functions. These activities are part of a program which is exploring the miniaturization of electromechanical components for making weapon systems safer. Such miniaturization can lead to a low-cost, small, high-performance ``systems-on-a-chip``, and have many applications ranging from advanced military systems to large-volume commercial markets like automobiles, rf or land-based communications networks and equipment, or commercial electronics. One of the key challenges in realization of the microsystem is integration of several technologies including digital electronics; analog and rf electronics, optoelectronics (light emitting and detecting devices and circuits), sensors and actuators, and advanced packaging technologies. In this work the authors describe efforts in integrating MEMs and photonic functions and the fabrication constraints on both system components. Here, they discuss two examples of integration of MEMs and a photonic device. In the first instance, a MEMs locking device pin is driven by a voltage generated by photovoltaic cells connected in series, which are driven by a laser. In the second case, a VCSEL emitting at 1.06 {micro}m is packaged together with a metallized MEMs shutter. By appropriate alignment to the opening in the shutter, the VCSEL is turned on and off by the movement of the Si chopper wheel.
Date: January 1, 1998
Creator: Blum, O.; Warren, M.E.; Hou, H.Q.; Choquette, K.D.; Rogers, M.S.; Sniegowski, J.J. et al.
Partner: UNT Libraries Government Documents Department

Real time pulse width monitor for Intensified Charge Coupled Device (ICCD) electro-optic shutters

Description: A method is described or controlling and measuring the pulse width of electrical gate pulses used for optical shuttering of image intensifier. The intensifiers are coupled to high frame rate Charge-Coupled-Devices (CCD) or Focus-Projection Scan (FPS) vidicon TV cameras for readout and telemetry of time resolved image sequences. The shutter duration or gate width of individual shutters is measured in real time and encoded in the video frame corresponding to a given shutter interval. The shutter information is updated once catch video frame by strobing new data with each TV camera vertical sync pulse. This circuitry is used in conjunction with commercial video insertion/annotation equipment to provide die shutter width information in alpha numeric text form along with the time resolved video image on a frame-by-frame basis. The measurement technique and circuitry involving a combination of high speed digital counters and analog integrators for measurements in the Ins to 1024 ns range are described. The accuracy obtained is compared with measurements obtained using batch speed DSOs. The measured data are provided in 10-bit Binary (Bi) and four decades of Binary Coded Decimal (BCD) and also displayed on four digit seven segment displays. The control circuitry including digital and analog input means for gate width selection are described. The implementation of both measurement and control circuitry into an Intensified Shuttered CCD (ISCCD) radiometric system for recording fast shuttered images at RS-170 to 4 KHz frame rates is presented.
Date: December 1, 1996
Creator: Yates, G.J.
Partner: UNT Libraries Government Documents Department

Design and performance of an integrated envelope/lighting system

Description: Dynamic envelope/lighting systems offer the potential to achieve a near optimum energy-efficient environment meeting occupant needs throughout the year by adapting to dynamic meteorological conditions and changing occupant preferences in real time. With the dramatic increased functionality of the microprocessor, there is an untapped potential to make dynamic envelop/lighting systems easier to use, diagnose, and monitor, and to integrate them as part of a sophisticated building-wide control system. This study addresses the complex relationship between this energy-efficiency technology and many of the non-energy issues related to its potential acceptance by the building industry, architects, owners, and users. The authors demonstrate the concept of integrated dynamic systems with a prototype motorized venetian blind operated in synchronization with electric lighting and daylighting controls via an intelligent control system. Research work conducted with simulation software and reduced-scale and full-scale field tests is summarized. Much of this work is directly relevant to other active shading and daylighting systems on the market today and to state-of-the-art window systems yet to come (i.e., electrochromics).
Date: April 1, 1997
Creator: Lee, E.S. & Selkowitz, S.E.
Partner: UNT Libraries Government Documents Department

Radiation transport analyses in support of the SNS Target Station Neutron Beam Line Shutters Title I Design

Description: A detailed radiation transport analysis of the Spallation Neutron Source (SNS) shutters is important for the construction of the SNS because of its impact on conventional facility design, normal operation of the facility, and maintenance operations. Thus far the analysis of the SNS shutter travel gaps has been completed. This analysis was performed using coupled Monte Carlo and multi-dimensional discrete ordinates calculations.
Date: December 1, 2000
Creator: Miller, T.M.; Pevey, R.E.; Lillie, R.A. & Johnson, J.O.
Partner: UNT Libraries Government Documents Department

In vivo argon laser vascular welding using thermal feedback: open and closed loop patency and collagen crosslinking

Description: An in vivo study of vascular welding with a fiber-delivered argon laser was conducted using a canine model. Longitudinal arteriotomies and venotomies were treated on femoral vein and artery. Laser energy was delivered to the vessel wall via a 400 {micro}m optical fiber. The surface temperature at the center of the laser spot was monitored in real time using a hollow glass optical fiber-based two-color infrared thermometer. The surface temperature was limited by either a room-temperature saline drip or direct feedback control of the laser using a mechanical shutter to alternately pass and block the laser. Acute patency was evaluated either visually (leak/no leak) or by in vivo burst pressure measurements. Biochemical assays were performed to investigate the possible laser-induced formation or destruction of enzymatically mediated covalent crosslinks between collagen molecules. Viable welds were created both with and without the use of feedback control. Tissues maintained at 50 C using feedback control had an elevated crosslink count compared to controls, while those irradiated without feedback control experienced a decrease. Differences between the volumetric heating associated with open and closed loop protocols may account for the different effects on collagen crosslinks. Covalent mechanisms may play a role in argon laser vascular fusion.
Date: February 28, 1997
Creator: Small, W., LLNL
Partner: UNT Libraries Government Documents Department

Control of the heavy-ion beam line gas pressure and density in the HYLIFE thick-liquid chamber

Description: Controlling the density and pressure of the background gas in the beam lines of thick-liquid heavy-ion fusion chambers is of paramount importance for the beams to focus and propagate properly. Additionally, transport and deposition of debris material onto metal beam-tube surfaces may reduce the breakdown voltage and permit arcing with the beam. The strategy to control the gas pressure and the rate of debris deposition is twofold. First, the cool thick-liquid jet structures will mitigate the venting to the beam tubes. The ablation and venting of debris through thick-liquid structures must be modeled to predict the quantities of debris reaching the beam ports. TSUNAMI calculations have been performed to estimate the mass and energy flux histories at the entrance of the beam ports in a 9x9 HYLIFE pocket geometry. Secondly, additional renewable shielding will be interposed in the beam tubes themselves. Thick-liquid vortexes are planned to coat the inside of the beam tubes and provide a quasi-continuous protection of the beam-tube walls up to the final focus magnets. A three-component molten salt, flinabe, with a low melting temperature and vapor pressure, has been identified as a candidate liquid for the vortexes. The use of flinabe may actually eliminate the necessity of mechanical shutters to rapidly close the beam tubes after target ignition.
Date: February 26, 2002
Creator: Debonnel, Christophe D.; Fukuda, Grant T.; Bardet, Philippe M. & Peterson, Per F.
Partner: UNT Libraries Government Documents Department

Thermomechanical analysis of high-heat-load components for the canted-undulator front end.

Description: With the canted undulators operating at 200 mA at closed gap at the Advanced Photon Source in the future, the front end will receive 20.4 kW of total power and 281 kW/mrad{sup 2} of peak power density. Thermal analysis of the front-end high-heat-load components becomes an essential part of the front-end design. An extensive study has been conducted on the thermal design of the photon shutters and fixed masks. A unique dog-bone-shaped cross-section design for the photon shutters was derived to relieve high stress in the corners. The dual-undulator x-ray beams were simulated at several locations on the fixed mask to ensure the worst possible case is considered. Stress analysis on the fixed mask revealed that the maximum stress occurs when beam hits the intersection between the horizontal surface and the corner surface. The details of the analysis procedure are presented, and the failure criteria are discussed.
Date: September 20, 2002
Creator: Jaski, Y.; Trakhtenberg, E.; Collins, J.; Benson, C.; Brajuskovic, B. & Den Hartog, P.
Partner: UNT Libraries Government Documents Department

The LCLS Gas Attenuator Revisited

Description: In the report ''X-ray attenuation cell'' [1] a preliminary analysis of the gas attenuator for the Linac Coherent Light Source (LCLS) was presented. This analysis was carried out for extremely stringent set of specifications. In particular, a very large diameter for the unobstructed beam was set (1 cm) to accommodate the spontaneous radiation; the attenuator was supposed to cover the whole range of energies of the coherent radiation, from 800 eV to 8000 eV; the maximum attenuation was set at the level of 10{sup 4}; the use of solid attenuators was not allowed, as well as the use of rotating shutters. The need to reach a sufficient absorption at the high-energy end of the spectrum predetermined the choice of Xe as the working gas (in order to have a reasonable absorption at a not-too-high pressure). A sophisticated differential pumping system that included a Penning-type ion pump was suggested in order to minimize the gas leak into the undulator/accelerator part of the facility. A high cost of xenon meant also that an efficient (and expensive) gas-recovery system would have to be installed. The main parameter that determined the high cost and the complexity of the system was a large radius of the orifice. The present viewpoint allows for much smaller size of the orifice, r{sub 0} = 1.5 mm. (1) The use of solid attenuators is also allowed (R.M. Bionta, private communication). It is, therefore, worthwhile to reconsider various parameters of the gas attenuator for these much less stringent conditions. This brief study should be considered as a physics input for the engineering design. As a working gas we consider now the argon, which, on the one hand, provides a reasonable absorption lengths and, on the other hand, is inexpensive enough to be exhausted into the atmosphere (no recovery). The absorption ...
Date: June 7, 2005
Creator: Ryutov, D
Partner: UNT Libraries Government Documents Department

The Physics Analysis of a Gas Attenuator with Argon as a Working Gas (Rev. 1)

Description: A gas attenuator is an important element of the LCLS facility. The attenuator has to operate in a broad range of x-ray energies, provide attenuation coefficient between 1 and 10{sup 4} with the accuracy of 1% and, at the same time, be reliable and allow for many months of un-interrupted operation. A detailed design study of the attenuator based on the use of nitrogen as a working gas has been recently carried out by S. Shen [1]. In this note we assess the features of the attenuator based on the use of argon. We concentrate on the physics issues; the design features will probably be not that different from the aforementioned nitrogen attenuator. Although specific results obtained in our note pertain to argon, the general framework (and many equations obtained) are applicable also to the nitrogen attenuator. In the past, an analysis of the attenuator based on the use of a noble gas has already been carried out [2]. This analysis was performed for an extremely stringent set of specifications. In particular, a very large diameter for the unobstructed x-ray beam was set (1 cm) to accommodate the spontaneous radiation; the attenuator was supposed to cover the whole range of energies of the coherent radiation, from 800 eV to 8000 eV; the maximum attenuation was set at the level of 10{sup 4}; the use of solid attenuators was not allowed, as well as the use of rotating shutters. The need to reach a sufficient absorption at the high-energy end of the spectrum predetermined the choice of Xe as the working gas (in order to have a reasonable absorption at a not-too-high pressure). A sophisticated differential pumping system that included a Penning-type ion pump was suggested in order to minimize the gas leak into the undulator/accelerator part of the facility. A ...
Date: January 3, 2006
Creator: Ryutov, D D; Bionta, R M; McKernan, M A; Shen, S & Trent, J W
Partner: UNT Libraries Government Documents Department

Caution -- Beam Crossing Ahead

Description: There are times when a laser beam needs to cross between tables or even go from one room to another. This presents an interesting traffic-flow and safety challenge to both the laser safety officer and laser user. Fortunately it is a challenge that has several solutions But the simplest solution may not be the best one. For example, the simplest way to get a beam from one optical table to another is just to put a sturdy tube around it. That's a permanent solution, and it completely contains the laser beam. While this is laser safe, there can be egress issues if it blocks a walkway. One comment this author often hears is, 'We can just duck under the tube.' The fire marshal, as well as the laser safety officer, might have issues with this. Especially in the case of a darkened lab, a blocked walkway can present a hazard of its own. One good solution is to transport the beam from Point A to Point B through a fiberoptic cable, when that is possible. One should easily be able to run the fiber up and over any walkway or down through a conduit on the floor. An important concern often overlooked with fibers is a label at the termination end indicating disconnection may expose one to laser radiation. Suppose there's an experiment that is usually confined to a single optical table, but sometimes needs to expand to a second table. It's inconvenient to install a permanent tube between the tables, so some sort of temporary arrangement is desirable. I have often seen people casually lay a beam tube across support arms, and remove it when it's not needed. The problem with this approach is that there's no mechanism to prevent the beam from crossing if somebody's forgotten the tube, ...
Date: April 2, 2008
Creator: Barat, Kenneth L.
Partner: UNT Libraries Government Documents Department

Spheromak Formation and Sustainment Studies at the Sustained Spheromak Physics Experiment Using High-Speed Imaging and Magnetic Diagnostics

Description: A high-speed imaging system with shutter speeds as fast as 2 ns and double frame capability has been used to directly image the formation and evolution of the Sustained Spheromak Physics Experiment (SSPX). Reproducible plasma features have been identified with this diagnostic and divided in three groups, according to the stage in the discharge at which they occur: (1) breakdown and ejection, (2) sustainment, and (3) decay. During the first stage, plasma descends into the flux conserver shortly after breakdown and a transient plasma column is formed. The column then rapidly bends and simultaneously becomes too dim to photograph a few microseconds after formation. We conjecture that this rapid bending precedes the transfer of toroidal to poloidal flux. During sustainment, a stable plasma column different from the transient one is observed. It has been possible to measure the column diameter and compare it to CORSICA, an MHD equilibrium reconstruction code which showed good agreement with the measurements. Elongation and velocity measurements were made of cathode patterns also seen during this stage, possibly caused by pressure gradients or E x B drifts. The patterns elongate in a toroidal-only direction which depends on the magnetic field polarity. During the decay stage the column diameter expands as the current ramps down, until it eventually dissolves into filaments. With the use of magnetic probes inserted in the gun region, a X-point which moved axially depending on current level and toroidal mode number, was observed in all the stages of the SSPX plasma discharge.
Date: November 9, 2005
Creator: Romero-Talamas, C A; Holcomb, C; Bellan, P M & Hill, D N
Partner: UNT Libraries Government Documents Department

High Resolution Imaging of Satellites with Ground-Based 10-m Astronomical Telescopes

Description: High resolution imaging of artificial satellites can play an important role in current and future space endeavors. One such use is acquiring detailed images that can be used to identify or confirm damage and aid repair plans. It is shown that a 10-m astronomical telescope equipped with an adaptive optics system (AO) to correct for atmospheric turbulence using a natural guide star can acquire high resolution images of satellites in low-orbits using a fast shutter and a near-infrared camera even if the telescope is not capable of tracking satellites. With the telescope pointing towards the satellite projected orbit and less than 30 arcsec away from a guide star, multiple images of the satellite are acquired on the detector using the fast shutter. Images can then be shifted and coadded by post processing to increase the satellite signal to noise ratio. Using the Keck telescope typical Strehl ratio and anisoplanatism angle as well as a simple diffusion/reflection model for a satellite 400 km away observed near Zenith at sunset or sunrise, it is expected that such system will produced > 10{sigma} K-band images at a resolution of 10 cm inside a 60 arcsec diameter field of view. If implemented, such camera could deliver the highest resolution satellite images ever acquired from the ground.
Date: January 4, 2007
Creator: Marois, C
Partner: UNT Libraries Government Documents Department

Detection of Off-normal Images for NIF Automatic Alignment

Description: One of the major purposes of National Ignition Facility at Lawrence Livermore National Laboratory is to accurately focus 192 high energy laser beams on a nanoscale (mm) fusion target at the precise location and time. The automatic alignment system developed for NIF is used to align the beams in order to achieve the required focusing effect. However, if a distorted image is inadvertently created by a faulty camera shutter or some other opto-mechanical malfunction, the resulting image termed ''off-normal'' must be detected and rejected before further alignment processing occurs. Thus the off-normal processor acts as a preprocessor to automatic alignment image processing. In this work, we discuss the development of an ''off-normal'' pre-processor capable of rapidly detecting the off-normal images and performing the rejection. Wide variety of off-normal images for each loop is used to develop the criterion for rejections accurately.
Date: July 11, 2005
Creator: Candy, J V; Awwal, A S; McClay, W A; Ferguson, S W & Burkhart, S C
Partner: UNT Libraries Government Documents Department