bluuebunny/crossref_metadata_2025 huggingface dataset:
The Advanced Photon Source Metrology Laboratory
Authors: Bresloff Cynthia , Mills Dennis M.
Published: July 2002

The Advanced Photon Source (APS) Metrology Laboratory is now operational in its permanent location in a cleanroom environment on the Experiment Hall floor of the APS site. The Metrology Laboratory will provide characterization of the figure and finish of x-ray optical surfaces for the user community using visible light instrumentation. Three noncontact instruments are now available for measuring surface features with lateral resolution from less than a micron to lengths of 2 meters and with a vertical resolution as small as an Angstrom. This paper gives a brief description of the three instruments used to cover this spatial frequency range and other associated issues, such as the environment and cleanliness of the laboratory.
Beamline diagnostics for protein crystallography using synchrotron radiation
Authors: Buth Gernot , Kölln Ingo , Bartunik Hans D.
Published: July 2002

Beam diagnostics devices are described for the monitoring of all basic parameters relevant to protein data collection using synchrotron radiation. The parameters include the total power in the white beam, the positions and directions of the incident white and monochromatic beams, and the intensity, wavelength, and polarization in the incident monochromatic beam. Such devices have been installed on a doubly focusing wiggler beamline, BW6, at DORIS. They assure high quality in protein data collection despite fluctuations in the beam, facilitate rapid alignment of the entire beamline, and provide a basis for automatic realignment of the diffraction setup and the x-ray optics.
A beamline for 1–4 keV microscopy and coherence experiments at the Advanced Photon Source
Authors: McNulty I. , Khounsary A. , Feng Y.P. , Qian Y. , Barraza J. , Benson C. , Shu D.
Published: July 2002

The third-generation Advanced Photon Source will open up dramatic new opportunities for experiments requiring coherent x-rays, such as scanning x-ray microscopy, interferometry, and coherent scattering. We are building a beamline at the Advanced Photon Source to exploit the potential of coherent x-ray applications in the 1–4 keV energy region. A high brightness 5.5-cm-period undulator supplies the coherent x-rays. The beamline uses horizontally deflecting grazing-incidence optical elements to preserve the coherence of the undulator beam. The optics have multilayer coatings for operation at energies above 1.5 keV. This paper discusses the beamline design and its expected performance.
Design of a dedicated beamline for x-ray microfocusing- and coherence-based techniques at the Advanced Photon Source
Authors: Yun W. , Lai B. , Shu D. , Khounsary A. , Cai Z. , Barraza J. , Legnini D.
Published: July 2002

A dedicated insertion-device beamline has been designed and is being constructed at the Advanced Photon Source (APS) for development of x-ray microfocusing- and coherence-based techniques and applications. Important parameters considered in this design include preservation of source brilliance and coherence, selectable transverse coherence length and energy bandwidth, high beam angular stability, high order harmonic suppression, quick x-ray energy scan, and accurate and stable x-ray energy. The overall design of this beamline layout and the major beamline components are described. The use of a horizontally deflecting mirror as the first optical component is one of the main features of this beamline design, and the resulting advantages are briefly discussed.
TGM-to-SGM conversion at NSLS beamline U7A: Recyclying of beamline components (abstract)
Authors: Hulbert Steven L. , Dong Q.-Y.
Published: July 2002

The U7A bending magnet toroidal grating monochromator (TGM) beamline has been converted into a spherical grating monochromator (SGM) type, without constructing any new vacuum components. That is, the mirror, slit, and grating chambers have been recycled. The inherited optical arrangement and the recycling concept prevented the use of ‘‘standard’’ SGM Kirkpatrick-Baez collecting and focusing mirrors at the front end. We show that this modification is not a serious detriment to the optical properties of the resulting beamline. Specifically, the resolution is completely unaffected and the throughput is approximately 2/3 of the ‘‘standard’’ SGM value. The flux and photon energy resolution of the U7A beamline throughout its 200–1000 eV operating photon energy range will be presented. Three end stations are being constructed for this beamline, featuring soft x-ray absorption and photoemission chambers optimized for operation in the carbon K-, oxygen K-, and transition metal L-edge ranges. Two of these end stations will be preceded by refocusing mirrors that will focus the soft x-rays to <1 mm spot size onto their samples.
Grazing-angle characterization of photosynthetic oxygen evolution protein monolayers
Authors: Yu Eileen Y. , Penner-Hahn James E. , Yocum Charles F. , Mayer Robert H. , Pickering Ingrid J.
Published: July 2002

Variable-period x-ray standing wave (XSW) spectroscopy has been shown to be a practical probe for studying metalloproteins. The photosynthetic oxygen evolving complex (OEC) is a transmembrane multipolypeptide complex that catalyzes the oxidation of water to dioxygen. The OEC contains Mn, Ca, and Cl and is potentially amenable to study by XSW. In this feasibility study, preliminary results on OEC samples deposited on Au mirrors are discussed. First XSW measurements from the SSRL grazing-incidence setup are presented.
X-ray standing wave study of strain in a buried heterostructure (abstract)
Authors: Lee T.L.
Published: July 2002

The structure of 1 ML InAs on GaAsw (001) capped with 25 Å GaAs was examined by the x-ray standing wave (XSW) method. By monitoring the In L fluorescence while scanning through the GaAs (004) Bragg reflection, the perpendicular strain within the InAs heterolayer was directly measured to be 7.7%, which is in good agreement with the macroscopic elasticity theory (7.3%) and the previously reported local density approximation calculation (7.8%). In this work, we also demonstrated that, combined with the evanescent-wave emission effect, XSW can be used to measure the strain-induced cap displacement in the growth direction relative to the bulk (004) diffraction plane. This result is consistent with our directly measured strain of the InAs layer. The XSW measurements were performed at the NSLS X15A beamline.
Polarization characteristics of silicon photodiodes and their dependence on oxide thickness
Authors: Saito Terubumi , Hughey Lanny R. , Proctor James E. , O’Brian Thomas R.
Published: July 2002

We have studied the polarization dependence of silicon photodiode responsivity as a function of wavelength, the angle of incidence, and the thickness of the silicon dioxide overlayer. The experimental results in the spectral region where there is no absorption in the silicon dioxide are explained well by a purely optical model. The responsivity dependence on polarization in the VUV is found to be smaller than that predicted and to be explainable by the presence of charge injection from the silicon dioxide layer.
Inelastic x-ray scattering at the National Synchrotron Light Source (invited)
Authors: Kao C.-C. , Caliebe W. A. , Hastings J. B. , Hämäläinen K. , Krisch M. H.
Published: July 2002

The research program at the inelastic x-ray scattering beamline at the National Synchrotron Light Source is focused on the study of elementary excitations in condensed matter with total energy resolution on the order of 0.1 eV to 1.0 eV. Results from selected experiments are reported to demonstrate the capability of the beamline as well as the information that can be obtained from inelastic x-ray scattering experiments.
A simple pressure cell and delivery system for the preparation of Xe derivatives for protein crystallography
Authors: Stowell Michael H. B. , Soltis S. Michael , Kisker Caroline , Peters John W. , Schindelin Hermann , Rees D. C. , Cascio Duilio , Beamer Lesa , Hart John , Whitby Frank G.
Published: July 2002

We have developed a simple device for preparing Xe derivatives under moderate gaseous pressure (1–100 atm). The device employs a Cajon ultra-torr fitting to ensure a gas-tight seal around a standard x-ray capillary. As such, the cell can accommodate standard x-ray capillaries up to 1.5 mm in diameter without any modification. The device is straightforward to utilize, and samples can be mounted and pressurized in a matter of seconds. In addition, a simple and safe purging and pressurization system has been designed and constructed for the use at beamline 7-1 at the Stanford Synchrotron Radiation Laboratory (SSRL). We describe the construction of both the pressure cell and the delivery system and present results on the cells use in the preparation of xenon derivatives.
Design criteria for beamline protection systems at the Advanced Photon Source
Authors: Quintana J.P. , Jemian P.
Published: July 2002

Designing and building beamlines at third-generation sources force beamline designers to place a high emphasis on the beamline equipment protection system (EPS). This work presents a set of design criteria as well as a prototype system that UNI-CAT and DND-CAT will use for the basis of their EPSs at the Advanced Photon Source. These criteria balance hardware and manpower costs in the design as well as the reusability of already existing software protocols (e.g., World Wide Web and EPICS) to report conditions to the beamline staff.
Designing a Beamline Equipment Protection System Using a Programmable Logic Controller
Authors: Minich James M.
Published: July 2002

As part of the Synchrotron Radiation Instrumentation Collaborative Access Team (SRI-CAT), a new beamline equipment protection system was designed, implemented and installed. The beamline equipment protection system is designed to assure the safe operation of bending magnet and insertion device beamline components, such as white-beam slits, user filters, shutters and stops, mirrors and monochromators. Design goals of the equipment protection system were to improve equipment safety performance, reduce nuisance trips and incorporate additional system functions with minimal cost. To meet the requirements of such a safety system, it was configured to use a programmable controller, remote block input/output (I/O), local interfaces and a serial communication link known as remote I/O (RIO). Aspects about the design requirements, functionality and constraints are presented, as well as specifics on programmable ladder logic design, hardware selection, testing and interfacing requirements.
Innovations in the design of mechanical components for a beamline—The SRI’95 Workshop 2 Summary (invited)
Authors: Kuzay T.M. , Warwick T.
Published: July 2002

The Synchrotron Radiation Instrumentation 1995 Conference (SRI’95) was hosted by the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). Of the many workshops within the conference, the SRI’95 Workshop 2 was ‘‘Innovations in the Design of Mechanical Components of a Beamline.’’ The workshop was well attended with over 140 registrants. The following topics were discussed. Industry’s perspective on the status and future was provided by Huber Diffraktionstechnik GMBH on goniometers/diffractometers, Oxford Instruments on advanced manufacturing technique of high heat load components, such as the APS photon shutter, and Kohzu Seiki Co. Ltd. on the specialties of monochromators provided to the third-generation synchrotrons. This was followed by a description of the engineering of a dual function monochromator design for water-cooled diamond or cryogenically cooled silicon monochromators by CMC CAT/APS. Another category was the nagging problem of sensitivity of the photon beam position monitors (XBPM) to bending magnet radiation (‘‘BM contamination’’) and the undulator magnet gap changes. Problem descriptions and suggested solutions were provided by both the Advanced Light Source (ALS) and the APS. Other innovative ideas were the cooling schemes (enhanced cooling of beamline components using metallic porous meshes including cryo-cooled applications); Glidcop photon shutter design using microchannels at the ALS; and window/filter design, manufacture and operational experiences at CHESS and PETRA/HASYLAB. Additional discussions were held on designing for micromotions and precision in the optical support systems and smart user filter schemes. This is a summary of the presentations at the Workshop.
Design of the Structural Biology Center beamlines at the APS (abstract)
Authors: Rosenbaum Gerd , Westrbrook Edwin M.
Published: July 2002

The Structural Biology Center-CAT will develop and operate a sector of the APS as a user facility for studies in macromolecular crystallography. The techniques applied will include multiple-energy anomalous dispersion (MAD) phasing and polychromatic (Laue) data collection. Data will be recorded on a high resolution CCD-area detector. The SBC is constructing two beamlines, one for radiation from an undulator and one for radiation from a bending magnet. The x ray optics of both beamlines are designed to produce a highly demagnified image of the source in order to match the focal size with the sizes of the sample and the resolution element of the detector. Vertical focusing is achieved by a flat, cylindrically bent mirror. Horizontal focusing is achieved by sagittally bending the second crystal of a double crystal-monochromator. The double-crystal monochromators of both beamlines have a constant exit height output beam. On the undulator beamline, two double-crystal monochromators are installed in series—one with Si-111 crystals and the second with Si-220 crystals—in order to facilitate quick change between high flux and narrow bandwidth. For the heat-loaded first crystals, the liquid-nitrogen-cooled, thin-web design being developed by the APS has been adopted. On the bending magnet beamline, three crystals (Si-111, Si-220, Si-400) are mounted side-by-side on the first crystal stage and translated into the beam is required.
Special manufacturing/joining techniques used in the manufacture of the Advanced Photon Source (APS) front-end and beamline components
Authors: Townsend M. C.
Published: July 2002

The front ends and beamlines of the Advanced Photon Source (APS) are designed to control, define, and/or confine the x-ray beam. Power densities of the order of 500 watts/mm2 are generated by the intense undulator beams, thus conventional materials and cooling techniques for beam stops, slits and masks are inadequate. Extensive use of Glidcop®, tungsten and molybdenum has been made in the design of these components; this has resulted in the need to develop and use specialized manufacturing/joining techniques. Experience gained using these techniques for the fabrication of APS front-end and beamline components is presented.
Plasma mass density, species mix, and fluctuation diagnostics using a fast Alfvén wave
Authors: Ikezi H. , deGrassie J. S. , Pinsker R. I. , Snider R. T.
Published: July 2002

We propose use of a fast Alfvén wave interferometer and reflectometer as a tokamak diagnostic to measure the plasma mass density, D–T species mix profile, and density fluctuations. Utilizing the property that the phase velocity of the fast wave propagating across the magnetic field is the Alfvén speed with thermal correction, this fast wave interferometer on the DIII-D tokamak was successfully used to obtain the line integrated density. Since the position of the ion–ion hybrid cutoff in tokamaks is uniquely determined by the species mix ratio and wave frequency, the reflectometer arrangement finds the species mix profile. The inversion method of reflectometry is discussed. The multiple chord interferometer also measures the mass density fluctuation profile.
Design of luminescent detectors for the TJ-II device
Authors: Zurro B. , Burgos C. , McCarthy K. J. , Rodriguez Barquero L.
Published: July 2002

We outline designs for several rare-earth-based phosphor powder detector systems for monitoring the broadband VUV plasma radiation in the TJ-II torsatron device. These include a global radiation detector, a detector with temporal and spectral resolution, and a third with radial scanning capabilities. We describe the selection of a phosphor powder for this application having good response from the soft x ray to the VUV, a fast response time, and the capability of operation at high temperatures. In addition, we give details of a method developed in-house for depositing thin uniform layers of powder on glass substrates for use as phosphor screens. Finally, we present some detector test results obtained in the plasma of the TJ-I U torsatron.
In situ plume-emission monitoring during pulsed-laser deposition of YBa2Cu3O7−δ and yttria-stabilized zirconia thin films
Authors: Göres Jörn , Kung Pang-Jen , Fenner D. B. , Budnick J. I.
Published: July 2002

A visible (optical) emission spectroscopy system has been developed as an in situ monitor for pulsed-laser deposition (PLD) of metal-oxide thin films, including YBa2Cu3O7−δ and yttria-stabilized zirconia, onto various substrates including silicon wafers. The spectrometer consists of a fiber-optic transfer to a diffraction grating and charge-coupled device (CCD) array, that provides spectroscopy with about 1.3 nm of resolution from 410 to 640 nm. The optical-emission spectral-refresh rate is limited to about 2 Hz, due to the operational requirements of the CCD and the digital converter. This is, however, sufficiently fast relative to film deposition rates that the quality of the plume can be usefully assessed during the complete film-deposition period, i.e., an in situ process monitor for PLD. Dependence of the emission plume spectra on distance from the target, laser energy density, ambient oxygen pressure, and in one case, target cation composition have all been measured.
Application of a species-selective Penning gauge to the measurement of neon and hydrogen-isotope partial pressures in the plasma boundary
Authors: Klepper C. C. , Hillis D. L. , Wade M. R. , Maingi R. , McKee G. R.
Published: July 2002

A species-selective Penning gauge, previously applied to He partial pressures, is now applied to the detection of small concentrations of Ne in a D2 gas. This is important for the study of Ne in the boundary region of magnetic fusion devices, where this impurity is deliberately injected to enhance the radiated power in that region. The application of the technique to the detection of the partial pressure of a minority hydrogen isotope is also examined. In this latter application, the detection system and the data analysis are more complex, because of the proximity of the spectral lines of the isotopes. In both applications, it is found that use of a proper detection scheme permits reliable measurements of concentrations as low as 0.5% of the minority neutral species, without requiring changes to the standard commercial Penning gauge setup.
Oblique electron cyclotron emission for electron distribution studies (invited)
Authors: Preische S. , Efthimion P. C. , Kaye S. M.
Published: July 2002

Electron cyclotron emission (ECE) at an oblique angle to the magnetic field provides a means of probing the electron distribution function both in energy and physical space through changes in and constraints on the relativistic electron cyclotron resonance condition. Diagnostics based on this Doppler shifted resonance are able to study a variety of electron distributions through changes in the location of the resonance in physical or energy space accomplished by changes in the viewing angle and frequency, and the magnetic field. For the case of observation across a changing magnetic field, such as across the tokamak midplane, the constraint on the resonance condition for real solutions to the dispersion relation can constrain the physical location of optically thin emission. A new Oblique ECE diagnostic was installed and operated on the PBX-M tokamak for the study of energetic electrons during lower hybrid current drive. It has a view 33° with respect to perpendicular in the tokamak midplane, receives second harmonic X-mode emission, and is constrained to receive single pass emission by SiC viewing dumps on the tokamak walls. Spatial localization of optically thin emission from superthermal electrons (50–100 keV) was obtained by observation of emission upshifted from a thermal cyclotron harmonic. The localized measurements of the electron energy distribution and the superthermal density profile made by this diagnostic demonstrate its potential to study the spatial transport of energetic electrons on fast magnetohydrodynamic time scales or anomalous diffusion time scales. Oblique ECE can also be used to study electron distributions that may have a slight deviation from a Maxwellian by localizing the emission in energy space. In “near-Maxwellian” plasmas, the Doppler broadening of the resonance means that observed oblique ECE from optically thick harmonics will originate from electrons with energies near or slightly above the thermal energy [(1–2)vth for example, depending on the observation angle and spatial gradients]. This is different from observed perpendicular ECE from optically thick harmonics that originate from electrons below the thermal energy. Experiments are presently being performed on the Tore Supra tokamak with two oblique views of ECE in equal and opposite toroidal directions (approximately 25° with respect to perpendicular) using two Michelson interferometers capable of observing second and third harmonic emission in X mode.
Experimental device for studying the magnetocaloric effect in pulse magnetic fields
Authors: Dan’kov S. Yu. , Tishin A. M. , Pecharsky V. K. , Gschneidner K. A.
Published: July 2002

A device for studying the magnetocaloric effect in pulsed magnetic fields up to 8 T is described. Data on magnetocaloric effect in gadolinium metal obtained by this technique was compared to that obtained by other experimental methods.
Continuous highly charged ion beams from the National Institute of Standards and Technology electron-beam ion trap
Authors: Ratliff L. P. , Bell E. W. , Parks D. C. , Pikin A. I. , Gillaspy J. D.
Published: July 2002

We describe our newly modified beam line and present its performance in conjunction with the National Institute of Standards and Technology electron-beam ion trap. We find that, contrary to previously reported results from similar ion sources, the highest intensity time-averaged ion fluxes are achieved by letting the ions boil out of the trap in a continuous stream rather than periodically dumping the trap to produce a pulsed beam. We produced continuous beams of 3.0(6)×106 Xe44+ ions per second and lower flux beams of charge states up to Xe49+. Also, in pulsed mode, we created beams with very high peak flux, over 1010 Xe44+ ions per second.
Photoinduced intersubband absorption in Si/SiGe quantum wells
Authors: Boucaud P. , Gao L. , Moussa Z. , Visocekas F. , Julien F. H. , Lourtioz J.-M. , Sagnes I. , Campidelli Y. , Badoz P.-A.
Published: July 2002

We have investigated photoinduced infrared absorption in p-doped Si/SiGe quantum wells. The absorption spectra exhibit two distinct features: free-carrier absorption and intersubband absorption in the valence band. The photoinduced absorption in both p and s polarizations is found to depend on the carrier density and strongly differs from the original absorption of the doped quantum wells. Photoinduced intersubband absorption is attributed to carriers away from the Brillouin zone center. We show that photoinduced intersubband absorption spectroscopy can provide useful information on valence band mixing effects in Si/SiGe quantum wells.
Instrument for the in situ measurement of depositing particles
Authors: Tsuchiya Masayoshi , Takami Katsumi
Published: July 2002

Contaminant particles peculiar to a type of equipment emanate inside and around a semiconductor, or thin-film-transistor–liquid-crystal-display device fabrication front-end equipment. To analyze such deposition phenomena and implement contamination control measures, it is necessary to observe in situ deposition behavior over a long period. This article describes a measuring instrument for this purpose. Deposition and tearing off of particles or mist take place on the surface of a transparent plate (of glass or quartz) and Mie scattering occurs when a laser beam is irradiated onto the particles or mist from below. The scattered light is detected in situ while the detection signals are accumulated and kept track of. In this instrument, a semiconductor laser with beam focusing optics and an ellipsoidal mirror are integrated into a small, portable unit. The laser beam is scanned onto the glass surface over a maximum area of 250 by 250 mm in one or two dimensions. It is possible to adjust the scanned area, scanning speed, and laser beam diameter. One-spot, fixed irradiation is also possible for detection of particle flow or tearing on the surface. The minimum detectable particle size was about 0.3–0.4 μm for polystyrene latex sphere (PSL) particles deposited on the glass surface with a beam diameter of 35 μm and a scanning speed of 0.3 m/s (0.14 μm for a silicon wafer surface). Two kinds of experiments were carried out by the use of one glass with PSL particles deposited on the surface and another glass on whose surface PSL particles were spouted so they would roll without deposition. By using this instrument, it became clear that the response curve for the rolling of the particles agreed well with the Mie equation, whereas the curve for the deposited particles deviated from the equation, but only in the range of minute particle sizes. Another phenomenon clarified through in situ measurement was that once deposited, real-world particles were subjected to the influence of the down flow of clean air (0.3 m/s), and some were torn off in a time period on the order of hours. A comparison of the real-world particle deposition rate was made between the grounded and ungrounded states using a glass plate with a transparent conductive thin film. An increase in the deposition rate was observed for the ungrounded state, while a remarkable tearing-off rate was seen for the grounded state.
A high resolution multiposition Thomson scattering system for the Rijnhuizen Tokamak Project
Authors: Barth C. J. , Beurskens M. N. A. , Chu C. C. , Donné A. J. H. , Lopes Cardozo N. J. , Herranz J. , Meiden H. J. v. d. , Pijper F. J.
Published: July 2002

A high resolution multiposition Thomson scattering setup to measure the electron temperature (Te) and density (ne) of a hot plasma is described. The system is operational at the Rijnhuizen Tokamak Project. Light from a high power pulsed ruby laser is scattered by the free plasma electrons and relayed to a Littrow polychromator for spectral analysis. The spectrally and spatially resolved light is detected by a GaAsP photocathode. The two-dimensional image is intensified and recorded with a charge-coupled device camera. Te in the range of 50 eV–6 keV can be measured at 115 spatial elements of 2.6 mm length along the laser beam. The observation error is <6% at ne=2×1019  m−3 and smaller for higher ne. The high resolution and accuracy enabled the observation of small scale structures in Te and ne.
Rapid acquisition, analysis, and display of fluorescence lifetime-resolved images for real-time applications
Authors: Schneider Peter C. , Clegg Robert M.
Published: July 2002

Fluorescence lifetime-resolved imaging (FLI) is a relatively new technique of fluorescence imaging whereby the spatial distribution of fluorescence decay times can be determined directly at every pixel of an image simultaneously. The fluorescence decay times of many chromophores can act as sensitive gauges of their molecular environments. By employing measurement techniques that are quantitatively related to the radiative dynamics of the dye molecules (in the nanosecond time range), additional physical parameters are available for discerning different fluorophores with disparate lifetimes, or for characterizing a single fluorophore in different surroundings. Many physical processes such as molecular aggregation, binding of dyes to macromolecular species, inclusion of chromophores in specific cellular organwelles, fluorescence resonance energy transfer, and dynamic quenching determine the excited-state lifetime of a fluorophore. The FLI technique provides a way to measure these processes directly at 103–106 pixels in an image. In addition, if image domains differ with respect to the mean fluorescence lifetime, FLI can be used to improve the contrast of a fluorescence image. By measuring the fluorescence lifetime one can determine whether fluorescence intensity differences from different locations in an image can be attributed to differences in dye concentration or whether physical spectroscopic effects such as local differences in the rate of dynamic quenching are responsible. All the above applications provide new possibilities for biology and medical diagnostics. However the speed of data acquisition and analysis in current FLI instrumentation is limited in general to several minutes; for real-time applications (in order to follow rapid changes of microscopic samples or make in vivo endoscopic medical diagnosis) the present instruments are too slow. We present here a FLI apparatus that is capable of acquiring, processing, and displaying fluorescence lifetime-resolved images in quasi-real time. We also present rapid algorithms for analyzing the data in real time.
A stroboscopic scanning solid immersion lens microscope
Authors: Stotz J. A. H. , Freeman M. R.
Published: July 2002

A high resolution scanning optical microscope for stroboscopic time-resolved studies is presented. High optical efficiency is the prime motivation in selecting a solid immersion lens to surpass conventional diffraction limited resolution. A microscope design including details concerning the fabrication, mounting, and operation of both the hemispherical and the truncated-sphere solid immersion lenses is discussed. A thin-film magnetic recording head is used as a convenient, planar test specimen with well-defined optically reflective and magnetic features on a submicrometer length scale that allows characterization of the lateral spatial resolution of the instrument. In addition, the versatility of the microscope is demonstrated through examples of time-resolved magneto-optic imaging of the head. Further enhancement of the spatial resolution through the incorporation of confocal imaging is also described. The tradeoffs governing the selection of a particular style of microscope for specific circumstances are outlined.
Compact electron cyclotron resonance plasma source
Authors: Gaudin C. , Hay L. , Buzzi J. M. , Bacal M. , Lamoureux M.
Published: July 2002

A compact electron cyclotron resonance plasma source has been built and is being investigated in view of ion and x-ray production. A method recently developed to deduce the energetic electron temperature parameter from the bremsstrahlung spectra emitted by the plasma is adapted to the present plasma case and shows that this temperature parameter can reach a dozen keV. We show that the high-energy electrons are localized on a ring in the mirror midplane by obtaining the image of the x-ray emitters on the chamber walls with a pinhole camera. It indeed appears that the emitters are two rings, due to the hot electrons leaking towards the magnets from the midplane ring where they are located inside the plasma.
Methods for the analysis and design of a solid state nuclear magnetic resonance probe
Authors: Stringer John A. , Drobny Gary P.
Published: July 2002

Methods for the analysis and design of solid state nuclear magnetic resonance (NMR) probes are presented. These techniques have been applied to a 200 MHz (1H Larmor frequency) H1–19F–13C cross polarization magic angle spinning probe. Transmission lines have been used throughout the design enabling the production of a highly power efficient probe (1H-22%, F19-17%, and C13-33%) capable of detecting F19 NMR signals while applying proton decoupling fields of 250 kHz. These techniques have proven very useful in designing the probe discussed within the text but are not confined to such a triple resonant design. In fact the techniques are sufficiently general to be useful to all radio frequency design efforts including deuterium wide-line probes and multiresonant high resolution NMR probes. A series of simple but useful design concepts are presented which are used to predict the efficiencies of the design presented.
A two color millimeter-wave interferometer for the measurement of line integral electron density on large helical device
Authors: Kawahata K. , Tanaka K. , Ito Y. , Ejiri A. , Wylde R. J.
Published: July 2002

In the National Institute for Fusion Science, the large helical device (LHD) (R=3.9 m, ap=0.65 m, B=3–4 T) was constructed in Toki City on January, 1998. The LHD is a torsatron/heliotron type device with a superconducting helical winding of pitch parameters of l/m=2/10 and three sets of superconducting poloidal coils. A two color millimeter-wave interferometer has been developed for the measurement of line integral electron density on the horizontal midplane of the LHD. To overcome the effects of the change in the transmission path length (∼100 m) during long pulse plasmas (10–1800 s), we have applied two color interferometry at 140 and 285 GHz.
Multipulse Thomson scattering system for the National Spherical Torus Experiment
Authors: Johnson D. , Bretz N. , LeBlanc B. , Palladino R. , Long D. , Parsells R.
Published: July 2002

A design using a backscattering geometry is presented, which emphasizes high sensitivity and high spatial resolution at the outer edge of the National Spherical Torus Experiment, while providing full profile capability with a moderate number of channels. The design is based on Nd:YAG lasers and avalanche photodiode detectors to allow for high repetition rate measurements.
Measurement and simulation of apertures on Z hohlraums
Authors: Chrien R. E. , Matuska W. , Idzorek G. , Swenson F. J. , Peterson D. L. , Wilde B. H. , Porter J. L. , Breeze S. P. , Ruggles L. E. , Simpson W. W. , Vargas M.
Published: July 2002

We have performed aperture measurements and simulations for vacuum hohlraums heated by wire array implosions. A low-Z plastic coating is often applied to the aperture to create a high ablation pressure which retards the expansion of the gold hohlraum wall. However this interface is unstable and may be subject to the development of highly nonlinear perturbations (“jets”) as a result of shocks converging near the edge of the aperture. These experiments have been simulated using Lagrangian and Eulerian radiation hydrodynamics codes.
New dc magnetic sensor
Authors: Schaffer M. J.
Published: July 2002

A new concept is proposed to measure a dc magnetic induction vector B whose magnitude is sufficiently large to saturate a small ferro- or ferrimagnetic sphere and align its magnetization vector M parallel to B. The direction of M is measured by modulating B locally at a convenient ac frequency by one or more small exciter coils near the sphere and using separate detector coils to measure components of the modulated induction due to the ac perturbed orientation of M. Equations are derived to relate the perturbed quantities to the original induction B. Several combinations of exciter and detector coils are possible, especially if distinct frequencies are used for each direction component. All three vector components of B can be calculated from the raw data. Because the proposed sensor has neither moving parts nor semiconductor components, it should be suitable for measurements in ionizing radiation environments, such as long pulse or steady state magnetically confined fusion power reactors.
High precision pick-up (Mirnov) coils for disruption studies in the T-11M and TCABR tokamaks
Authors: Semenov I. , Mirnov S. , Nascimento I. C. , Galvao R. M. O. , Kuznetsov Yu. , Belov A. , Vannucci A.
Published: July 2002

Newly developed methods of visualization and determination of widths of internal magnetic islands are based on measurements of the perturbed magnetic fields near the plasma border. Reliable analysis of pick-up (Mirnov) coils data is rather complicated and measurement errors have to be minimized. Plasma wall interaction, electrical sparks in the discharge chamber, and resonances in the measurement systems could be main sources of errors but, also, the design of coils should take into account that the typical frequency band of the disruptive processes is in the range of ∼100 kHz–1.5 MHz. A double Faraday coaxial screening with a symmetrically input system of pick-up coils was developed for disruption studies in the TCABR tokamak in São Paulo. The main design features of this high precision pick-up coil system are discussed.
A low cost PCI-VME controller for control and data acquisition systems on fusion experiments
Authors: Carvalho B. B. , Sousa J. , Varandas C. A. F.
Published: July 2002

A universal hardware interface system that allows the transparent use of digital instrumentation of different buses has been developed using the VMEbus as the host platform. In this article a new controller for the VME system, based on a desktop-type PCI Pentium motherboard and a locally developed PCI-VME interconnector is described. This interconnector is composed of two boards, which are connected by an ac-terminated flexible cable and inserted into slots of the PCI motherboard and VME crate. This system decreases the cost of the global system and permits low priced and modular upgradeability. The software drivers have been developed for a UNIX environment using the LINUX-LAB project in a user-friendly approach.
A multipoint Thomson scattering diagnostic for the tokamak ISTTOK
Authors: Alonso M. P. , Wilcock P. D. , Varandas C. A. F.
Published: July 2002

This article describes the conventional Thomson scattering diagnostic that has been developed for multipoint measurements of the electron temperature and plasma density of the tokamak ISTTOK plasma. The design is based on a single laser pulse, two multi-input three channel spectrometers, one digital oscilloscope, and a time-delay technique. Special collection optics, optimized detectors, and high transmission monofibers with large numerical aperture have been used to increase the sensitivity and spatial resolution. The number of measurement points can be extended by increasing the number of fibers without altering the collection optics or light relay system. Results are in good agreement with those determined with other diagnostics.
Development of microwave diagnostic simulator
Authors: Hojo H. , Kurosawa Y. , Mase A.
Published: July 2002

Two-dimensional simulator models are presented for microwave diagnostics. The models assume the Maxwell wave equation coupled with the equation of plasma current density in a cold magnetized plasma, which can describe propagation, reflection, and cross polarization scattering of the ordinary and extraordinary modes. The effects of waveguide for the microwave launcher and wall boundary of the vacuum vessel are included in the models. The simulations of ultrashort-pulse reflectometry with the use of incident subcyclic ordinary modes in the models are performed to test the problem of density profile reconstruction.
Geometrical optics interpretation of the phase runaway in microwave reflectometry
Authors: Brañas B. , Hirsch M. , Sánchez J. , Zhuravlev V.
Published: July 2002

In this article we present experimental results obtained with a heterodyne/amplitude modulated (AM) reflectometer at W7-AS and simulations [two-dimensional (2D) (WKB)] of reflection on a rotating cutoff layer corrugated by turbulence for the W7-AS conditions. When the turbulence has a large amplitude and a small size relative to the illuminated spot, the calculations show the existence of a phase runaway and reproduce the typical behavior of the measured phase and amplitude signals. It is not possible to deduce the plasma rotation from the phase runaway value at “close to normal” incidence, as this value depends on the turbulence characteristics. When the illuminated cutoff surface is smooth, no runaway occurs, amplitude and phase signals are coherent and in certain poloidal wavelength ranges (∼1 to 2 cm for W7-AS conditions) their relative phase is π/2, conditions that have been observed experimentally during H mode. The phase runaway can affect the ne(r) measurements. However, the comparison between the measured carrier and AM phases shows that its effect is canceled by differential measurements of ne(r).
Tokamak fusion test reactor poloidal rotation diagnostic (invited)
Authors: Bell R. E. , Dudek L. E. , Grek B. , Johnson D. W. , Palladino R. W.
Published: July 2002

A new spectroscopic diagnostic was developed to measure poloidal velocity profiles of Tokamak fusion test reactor (TFTR) plasmas. Carbon poloidal velocities were measured using the Doppler shift of the C VI 5291 Å impurity line of both intrinsic emission and charge exchange emission from neutral beams. Poloidal velocities are typically small (vθ⩽104 m/s) requiring small wavelength shifts (Δλ⩽0.2 Å) to be measured. However, the high central ion temperatures in TFTR required the use of a low dispersion spectrometer to view the entire linewidth (full width at half maximum ⩽25 Å). A very high throughput spectrometer/detector system was assembled to achieve the necessary precision in vθ. Statistical errors in the chord-averaged poloidal velocity less than 100 m/s have been obtained. The short focal length spectrometer features f/1.8 input optics, a transmission grating, and refractive optics. A thinned back-illuminated charge coupled device detector provided a high quantum efficiency (QE=75%). The diagnostic had 20 ms time resolution and a radial resolution of ⩽3.5 cm after an inversion. Two symmetric up/down views were used to eliminate atomic physics effects that would otherwise distort the measured rotation velocity. This diagnostic complemented the measurements of Ti, vφ, and ni from a charge exchange spectroscopy system, allowing the determination of radial electric field profiles using the force balance equation.
Edge x-ray imaging measurements of plasma edge in Alcator C-Mod
Authors: Sunn Pedersen T. , Granetz R. S.
Published: July 2002

Recent results from the high resolution edge x-ray imaging diagnostic at Alcator C-Mod are presented. The diagnostic measures the soft x-ray emissivity using an array of 38 photodiodes viewing the plasma through a narrow aperture. A 10 μm beryllium foil located in the aperture filters away photons below 600 eV and has close to 100% transmission above 2 keV photon energy. The viewing chords are separated by about 1 mm in the plasma region and have minimal overlap. The absolute position of the chords with respect to the vessel has been determined within 1 mm. The chord integrated data are inverted into emissivity as a function of midplane radius assuming that the emissivity is constant on a flux surface. The full three-dimensional geometry is used in the inversion. The emissivity profiles have a radial resolution of 1.7 mm at the midplane and a temporal resolution of 12 μs. Results show that L-mode discharges have very low edge x-ray emission. During H mode, the edge x-ray emissivity is an order of magnitude higher than in the L mode, and has a pronounced pedestal shape with widths in the range 1.5–8 mm. The width is determined as a function of time by fitting a modified tanh function to each profile. Results for width scalings with local parameters such as ρpi and ρi, as well as time resolved edge localized mode data will be presented.
Launched wave packets in an ion beam-plasma system
Authors: Lee S. G. , Diebold D. A. , Hershkowitz N.
Published: July 2002

A generation mechanism of wave packets and measurement of the launched wave packets using Langmuir probes in an ion beam-plasma system are presented. The origin of the wave packets appears to be the Johnson noise of a resistor in a simple amplifying circuit. The measured wave packets were found to propagate on the slow beam mode.
Analysis of an asymmetric resonant cavity as a beam monitor
Authors: Whittum David H. , Kolomensky Yury
Published: July 2002

We analyze the excitation of an arbitrary, externally coupled resonant structure by a charged particle beam, providing a rigorous formulation of the effect of spurious modes and intrinsic mode nonlinearity on inferred beam coordinates. Results are illustrated for a two-cavity system employed for beam-position monitoring with an idealized front-end signal processor.
Development of magnetization measurement under high pressure and pulsed high magnetic field
Authors: Endo S. , Yamada J. , Imada S. , Ishizuka M. , Kindo K. , Miyamoto S. , Ono F.
Published: July 2002

A method for measuring magnetization under high pressure and pulsed high magnetic field was developed for a Drickamer-type cell using diamond anvils and an insulator gasket. As the first test, the magnetization of invar alloy Fe0.65Ni0.35 was measured at room temperature up to 8 GPa in a pulsed field of 10 T with a width of 4 ms. The magnetization decreased with increasing pressure, indicating a transition to a paramagnetic state at 5–6 GPa, in accordance with the results of previous experiments using conventional methods such as ac susceptibility measurement.
Columnar focal lens
Authors: Scholfield David W. , Gahl John M. , Shimomura Naoyuki
Published: July 2002

The concept of utilizing a plasma generated by laser guided electric discharges in the atmosphere as the conducting element of an antenna was introduced in 1968. The principal objective was the development of an antenna with no physical structure, but with a large effective area. The goal of producing an ionized column of atmosphere for use as a practical antenna, or to direct lighting strikes, has proved to be elusive. The main difficulty in the production of a viable plasma antenna lies in the tendency of the plasma initially created to block the radiation required to maintain the plasma in a columnar geometry. Various strategies have been used to overcome this difficulty. We present the design of a novel lens with a focal column at a right angle to the principal plane. The design of the lens allows incident radiation to travel around any existing plasma, thereby limiting the blockage incurred by previous methods. Such a lens has application in the fields of plasma antennas and directed lighting strikes.
Calibration procedures for charge-coupled device x-ray detectors
Authors: Barna S. L. , Tate M. W. , Gruner S. M. , Eikenberry E. F.
Published: July 2002

Calibration procedures are described for use with electronic x-ray detectors, with an emphasis on detectors based on fiber-optically coupled charge-coupled devices. Methods are detailed for removing spurious events, pixel pedestals, dark-current, spatial distortion, and intensity response variations for both small-angle and wide-angle applications. The accuracy of the calibration procedures is discussed.
Contact angles and wetting velocity measured electrically
Authors: Verheijen H. J. J. , Prins M. W. J.
Published: July 2002

We describe two new measurement techniques for studying the wetting behavior of a liquid on a surface. First, we measure the contact angle of a droplet, by measuring the capacitance between a conducting droplet and a subsurface counter electrode. The estimated error in the measured contact angle is 2% for contact angles in the range between 60° and 120°. In the second measurement technique, we detect the current as a function of time, which provides information about the dynamics of a droplet wetting the substrate. The time-integrated current is related to the base area of the droplet. Consequently, we can derive the radial velocity of the three-phase line of the droplet. The time resolution of the measurement technique is limited by the charging time of the initial capacitance, in our case approximately 0.5 ms.