bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative visualization of steady and unsteady flows using spark velocimetry
Authors: Hansen E. C.
Published: July 2002

This paper describes the usefulness, limitations, and potential applications of spark velocimetry to complex flows in fluid machinery. Spark velocimetry uses high-voltage high-frequency sparks to successively illuminate a column of air particles and thus map out a complex velocity field. This work applied spark velocimetry to a two-dimensional boundary layer, a three-dimensional horseshoe vortex boundary layer, and boundary layers on the suction surface of a rotor blade in steady flow and in rotating stall. Measurements made in a two-dimensional boundary layer compared favorably with measurements taken using a total pressure probe. The measurements in the horseshoe vortex showed the types of primary and secondary flow expected. The velocity profile of the boundary layer on a rotor blade was shown in both unstalled and stalled flow. The spark velocimetry method was shown to be a very useful measurement tool for three-dimensional and unsteady flows with some limitations.
Modular software-controlled electrochemical system
Authors: Hagan D. , Spivey J. , Niculescu V. A.
Published: July 2002

A modular microcomputer-controlled three-electrode potentiostat configured with graphics is presented. The system is designed for metallic surface characterization and is capable of performing in different modes of operation including single sweep voltammetry, cyclic voltammetry, and chronoamperometry. An integrated and flexible software system for control, data taking, data storage, and transfer is described. Data analysis software for the IBM-PC computer including two- and three-dimensional plotting as well as menu-driven theoretical modeling, simulation, and curvefitting has been developed.
Development of a beam probing system for measurement of density, temperature, and magnetic field of RFP plasma
Authors: Kamada Y. , Utsumi M. , Saitoh M. , Morikawa J. , Nihei H. , Yoshida Z. , Inoue N.
Published: July 2002

A hydrogen beam probing system developed for the REPUTE-1 reversed field pinch device is described. With this system, the plasma ion line density, the central ion temperature, and the magnetic field profile can be measured. Before being applied to the REPUTE-1 device, the probing system was tested on the TORIUT-5 tokamak and TORIUT-6 ultralow-q (ULQ) devices. The experimental results show the availability of the system. The measured line density agrees well with that measured by the microwave interferometry. The measurable density ranges from 1019 m−3 to 3×1020 m−3. A new method of magnetic field measurement which is effective and important for RFP plasmas is proposed. The resolution and the accuracy of this measurement have been confirmed by experiments on the TORIUT-5 device. Experimental results agree well with computation.
Pulse radiolysis equipment: A setup for simultaneous multiwavelength kinetic spectroscopy
Authors: Saran Manfred , Vetter Georg , Erben-Russ Michael , Winter Robert , Kruse Alf , Michel Christa , Bors Wolf
Published: July 2002

A setup for pulse radiolysis experiments is described consisting of the following main components: an array of 15 photomultipliers attached to a spectrograph (allowing 4032 spectra to be recorded with a time resolution of 500 ns per spectrum), self-regulating high-voltage supply for the photomultipliers, computer-controlled solution mixing and dispensing system, and provisions for continuous dose variation of the FEBETRON-accelerator electron beam. The general performance of the system is discussed and construction or electronic details are given for special components.
Experimental apparatus for measurements of electron impact excitation
Authors: Lafyatis G. P. , Kohl J. L. , Gardner L. D.
Published: July 2002

An ion beam apparatus for the absolute measurement of collision cross sections in singly and multiply charged ions is described. An inclined electron and ion beams arrangement is used. Emitted photons from the decay of collision produced excited states are collected by a mirror and imaged onto a photomultiplier. Absolute measurements of the electron impact excitation of the 2s–2p transition in C3+ were used to demonstrate the reliability of the apparatus.
Models of formation and erosion of a plasma column in a silicon surface-barrier detector
Authors: Kanno Ikuo
Published: July 2002

Quantitative models of the formation and erosion of the plasma column are presented. With the model of formation, the radius, volume, and surface area of the plasma column and the number and the density of the electron-hole pairs are calculated. In the model of the erosion, the change of the dielectric quality of the plasma column due to the enlargement of its volume is considered to be the cause of the erosion. The internal electric field strength of the plasma column is determined as a function of time. With this model, plasma delays are estimated for alpha particle, 40Ar and 129Xe ions and are compared with other author’s experiments. Ideally the recombination effect should be calculated as a product of the recombination rate and the time interval of the plasma delay. However, it is estimated here using two parameters for the fission fragments from thermal-neutron-induced fission of 235U because of the lack of adequate experimental data.
Optically coupled electrical sampling system with 4-GHz bandwidth
Authors: Samaan S. B. , Pearson L. Wilson , Smith Charles E.
Published: July 2002

A new approach to the design of a fiber-optic interface that links a commercial sampling head to its matching time-domain reflectometer (TDR)/sampler oscilloscope plug-in unit is reported. Three fiber-optic links replace the wired signal paths of the original design that convey the vertical error signal, the feedback signal, and the horizontal sampling command signal between the sampling head and the oscilloscope sampling plug-in. The dielectric fiber pigtails allow the use of the sampling head inside objects that need to be electromagnetically insulated from the instrumentation system. Low-frequency analog links are used to convey the error and feedback signals. The sampling command signal is conveyed via a link where a powerful, fast-rise infrared laser pulse is generated. The laser pulse is used to trigger an avalanche transistor in the strobe generator circuit of the sampling head by directly coupling the optical energy to the transistor chip. This direct method of detection minimizes the time jitter introduced to the strobe signal, resulting in a bandwidth of 4 GHz. Some of the results of the tests which were carried out on the system are reported.
Strain-induced quantum dots by self-organized stressors
Authors: Sopanen M. , Lipsanen H. , Ahopelto J.
Published: July 2002

Novel in situ method to produce quantum dots is reported. Three-dimensional confinement of carriers to a GaInAs/GaAs quantum well dots is observed by photoluminescence. The confinement potential is induced by stressors, formed by self-organizing growth of InP nanoscale islands on top barrier GaAs surface. Two transitions arising from the strain-induced quantum dots produced by two types of InP islands are identified. The luminescence from higher electronic states of the quantum dots having a level splitting of 8 meV is also observed.
Intense blue emission from porous β-SiC formed on C+-implanted silicon
Authors: Liao Liang-Sheng , Bao Xi-Mao , Yang Zhi-Feng , Min Nai-Ben
Published: July 2002

Carbon ions were implanted into crystal silicon wafers at an energy of 50 keV and with a dose of 1017 cm−2 followed by thermal annealing. A layer of polycrystalline β-SiC was formed beneath the sample surface. Porous nanometer structures were prepared by conventional anodization. At room temperature, the samples exhibit a blue luminescence peak at 2.79 eV (445 nm), which is higher than the energy gap of bulk β-SiC (2.2 eV), and its intensity is stronger than that of the reference porous silicon. The results could be explained by the quantum confinement effect.
Measurements of the ion temperature and plasma rotation from Kα emission with the TFTR horizontal x-ray crystal spectrometer
Authors: Hsuan H. , Bitter M. , Rice J. E. , Hill K. W. , Johnson L. , Liew S. L. , Scott S. D. , von Goeler S.
Published: July 2002

The TFTR horizontal x-ray crystal spectrometer has been improved by installation of γ and neutron shielding and is now operating in the TFTR Test Cell up to the presently maximum neutron production rates of 2×1016 neutrons/s. Further optimization by using a modified detector may assure operation of the spectrometer during the DT phase when TFTR is covered by an igloo. The instrument is set up for simultaneous observation of the entire satellite spectrum of Ni xxvii, and it provides data on the time evolution of the central ion temperature and the central plasma rotation velocity. Ion temperatures of 20–30 keV have been measured under ‘‘supershot’’ conditions. The highest rotation velocity observed with unidirectional injection was 1.1×106 m/s.
Neutron imaging of inertial confinement fusion targets at Nova
Authors: Ress D. , Lerche R. A. , Ellis R. J. , Lane S. M. , Nugent K. A.
Published: July 2002

Images of the neutron-emitting region of high-yield inertial confinement fusion targets have been obtained with a penumbral coded-aperture imaging system. The major components of the imaging system are the penumbral aperture, neutron detector, alignment hardware, and image reconstruction software. We describe these components and present an example of the neutron imaging results.
ECE diagnostic for ATF
Authors: Bell G. L. , Gandy R. F. , Wilgen J. B. , Rasmussen D. A.
Published: July 2002

Electron cyclotron emission (ECE) from the Advanced Toroidal Facility (ATF) torsatron will allow measurement of plasma electron temperature. For low-field operation (0.95 T) the second harmonic is cut off at a relatively low density; therefore, third-harmonic emission from 67 to 83 GHz is used to yield central electron temperatures. At high-field operation (1.9 T) second-harmonic emission from 82 to 114 GHz is optically thick and can provide Te(r) information. A vertical view of the saddle-point geometry of the ATF mod B spatial contours provides a line of sight along which the mod B contours are symmetric with respect to flux surfaces. A single horn–lens viewing beam system with a vertical view is designed to cover the entire 67–114-GHz range, providing a spot size on the order of 6 cm. Radiation will be delivered to one of three waveguide mixers by C-band waveguide. Each of the three mixers covers a 16-GHz segment of the emission spectrum, downconverting it to the 2–18-GHz intermediate-frequency band, where it is processed by a 16-channel array of bandpass filters, providing 1-GHz frequency resolution.
Response of charge-coupled devices to direct electron bombardment
Authors: Stearns D. G. , Wiedwald J. D.
Published: July 2002

We report on the response of three scientific charge-coupled devices (CCD), the RCA SID501, the Tektronix TK512M, and the Texas Instruments 4849, to direct electron bombardment. A scanning electron microscope is used to provide a temporally gated, focused electron source of precise energy and current. Both the detection efficiency and the line-spread response of the CCDs have been measured at incident electron energies in the range of 0.3–30 keV. Simple models for the detection process are discussed.
Novel time and two-dimensional space-resolved x-ray imaging technique
Authors: Deeney Christopher , Choi Peter
Published: July 2002

In this note, a novel, but simple system is described which gives both continuous time resolution and limited two-dimensional spatial resolution. This system uses multiple, displaced pinholes in conjunction with a streak camera. As an example of this technique, the thermalization of a plasma focus has been studied.
On the phase-space description of synchrotron x-ray beams
Authors: Suortti P. , Freund A. K.
Published: July 2002

Simple graphic methods for illustrating the transformation of x-ray beams by optical elements such as mirrors, monochromators, and slits are very helpful tools when optimizing synchrotron radiation experiments. They provide guidelines for matching the optical components to the source and to the experiment, and for checking the physical meaning of the more detailed results obtained by subsequent ray-tracing calculations. Phase-space diagrams have been used extensively to describe synchrotron radiation experiments by plotting an angular variable against a positional one with the possibility to add the energy in a third dimension. For neutron scattering, the traditional method consists in parallel representations, in reciprocal and in real space, that can also be considered as another kind of phase-space diagram. In this paper, we show the specific advantages and the complementary character of the above diagrams. The representation of several optical elements and their effect on beam transformation is given first individually and then for some arrangements of two or more beam-defining devices. Finally, a beamline is described and optimized as a demonstration of the usefulness and the limits of these graphic methods.
A virtual phase CCD detector for synchrotron radiation applications
Authors: Rodricks Brian , Clarke Roy , Smither Robert , Fontaine Alain
Published: July 2002

A two-dimensional charge coupled device (CCD) detector, based on the Texas Instruments ‘‘virtual phase’’ CCD, has been developed for synchrotron radiation applications. Simultaneous near-edge and multilayer scattering experiments have been carried out with the detector on an energy-dispersive synchrotron beamline. The detector was used in an optical mode where the CCD element is coupled to a phosphor screen by a pair of focusing and demagnifying lenses. We report on the performance of the detector in this mode.
High resolution monochromatic tomography with x-ray sensing pickup tube
Authors: Hirano Tatsumi , Usami Katsuhisa , Sakamoto Kozoo
Published: July 2002

Using monochromatic synchrotron radiation and a high resolution x-ray sensing pickup tube as a two-dimensional detector, we have improved the spatial resolution of x-ray computed tomographic (CT) images. A quantitative elemental analysis was made based on the difference between two CT images measured just above and below an element’s absorption edge energy. The developed CT imaging system has been used to observe nondestructive fine structures, such as cracks, in a ceramic material. High resolution of 10 μm was obtained. The differential CT value, which was seen as the shading intensity in the differential CT image, was proportional to the concentration of the specific element.
Fabricating rectangular internal cooling channels in silicon x-ray monochromator optics
Authors: Bilderback D. H.
Published: July 2002

Internally cooled monochromator crystals have been successfully fabricated and tested with synchrotron radiation. A single block of silicon was parted in the middle and grooves on a mm scale were cut into one half. The two blocks were then bonded back together with a silver-glass die attach paste. After firing in air at 430 °C, the composite crystal was virtually strain free. One version of the composite crystal with cooling channels 0.76 mm beneath the diffracting surface was successfully tested at CHESS with intense undulator radiation.
Status of a beamline for a 60-period soft x-ray undulator in the low emittance operation of the Photon Factory storage ring
Authors: Maezawa Hideki , Toyoshima Akio , Kagoshima Yasushi , Mori Kouichi , Ishikawa Tetsuya
Published: July 2002

Progress in performance of a beamline for a 60-period soft x-ray undulator of the 2.5-GeV Photon Factory storage ring was made by implementation of low emittance operation of the storage ring and improvements of beamline and monochromator units. Monochromated photon flux of up to 1012 photons/s has now been achieved at maximum in ordinary operating conditions of the ring current of ≊200 mA with resolution of 500–1000 over the soft x-ray region from 410 eV to a few keV of photon energy.
Pellet imaging techniques in the ASDEX tokamak
Authors: Wurden G. A. , Büchl K. , Hofmann J. , Lang R. , Loch R. , Rudyj A. , Sandmann W.
Published: July 2002

As part of a USDOE/ASDEX collaboration, a detailed examination of pellet ablation in ASDEX with a variety of diagnostics has allowed a better understanding of a number of features of hydrogen ice pellet ablation in a plasma. In particular, fast-gated photos with an intensified Xybion CCD video camera allow in situ velocity measurements of the pellet as it penetrates the plasma. With time resolution of typically 100 ns and exposures every 50 μs, the evolution of each pellet in a multipellet ASDEX tokamak plasma discharge can be followed. When the pellet cloud track has striations, the light intensity profile through the cloud is hollow (dark near the pellet), whereas at the beginning or near the end of the pellet trajectory the track is typically smooth (without striations) and has a gaussian-peaked light emission profile. New, single pellet Stark broadened Dα, Dβ, and Dγ spectra, obtained with a tangentially viewing scanning mirror/spectrometer with Reticon array readout, are consistent with cloud densities of 2×1017 cm−3 or higher in the regions of strongest light emission. A spatially resolved array of Dα detectors shows that the light variations during the pellet ablation are not caused solely by a modulation of the incoming energy flux as the pellet crosses rational q surfaces, but instead are a result of dynamic, nonstationary, ablation process.
Development of x-ray emission computed tomography for ICF research
Authors: Nakai M. , Shinohara S. , Katayama M. , Chen Y.-W. , Kobayashi S. , Miyanaga N. , Tanaka K. A. , Nishihara K. , Yamanaka M. , Yamanaka T. , Nakai S.
Published: July 2002

A computed tomographic (CT) technique has been developed to diagnose laser-irradiated spherical targets using x-ray emissions. The three-dimensional (3-D) x-ray distribution was reconstructed by using an algebraic reconstruction technique (ART) from x-ray pinhole camera images obtained along different sight directions. 3-D distributions of electron temperature and density were measured by use of an absorption filter technique. Time-resolved 3-D x-ray emission images from an imploding hollow shell target were reconstructed with less than 100 ps temporal resolution by using x-ray multiframing cameras.
Rapid programmable 300 ps optical delay scanner and signal-averaging system for ultrafast measurements
Authors: Edelstein D. C. , Romney R. B. , Scheuermann M.
Published: July 2002

A device is presented that sweeps out programmable optical delays of 300 ps (or less) at 30 Hz, with shorter-delay scans possible at much higher rates. It is compact, vibration-free, linear to within 0.02%, and has a position repeatability of 1 part in 105. With this scanner and a PC-based signal-averaging data acquisition system, ultrafast autocorrelation measurements with very high signal/noise are demonstrated in both the fs and ps domains.
The effect of microchannel plate gain depression on PAPA photon counting cameras
Authors: Sams Bruce J.
Published: July 2002

PAPA (precision analog photon address) cameras are photon counting imagers which employ microchannel plates for image intensification. They have been used extensively in astronomical speckle imaging. The PAPA camera can produce artifacts when light incident on its microchannel plate (MCP) image intensifier is highly concentrated. The effect is exacerbated by adjusting the strobe detection level too low, so that the camera accepts very small MCP pulses. The artifacts can occur even at low total count rates if the image has highly a concentrated bright spot. This paper describes how to optimize PAPA camera electronics, and describes six techniques which can avoid or minimize addressing errors: (1) use the hottest possible MCP so the recharge time is short; (2) use a single plate MCP for a short recharge time; (3) keep the local photon flux low on the MCP input face; (4) avoid setting the strobe channel lower detection threshold too low; (5) optimize the camera by proper electronic adjustment of the strobe channel; (6) build the camera with specially contoured masks for best optimization of the strobe. When the camera operates within these guidelines, it produces photon counting images with minimal errors.
Frequency shift of 1.45 MHz for 337-μm HCN laser beam with a super rotating grating
Authors: Maekawa T. , Minami T. , Makino K. , Tanaka S. , Kubo S. , Iguchi M.
Published: July 2002

A frequency shift of ω1F/2π=1.45 MHz is obtained for a 337-μm HCN laser beam by use of a rotating grating fabricated on the top of the rotor of a turbomolecular pump with a high rotating speed of 43200 rpm (super rotating grating). The frequency shift is one order higher than those with usual rotating gratings. Using this as a local beam, heterodyne detection of low-frequency microturbulence as well as high time resolution interferometry in plasmas becomes possible with a single far-infrared laser. The frequency-shifted beam is slightly frequency modulated (modulation index Mf≂1.2) with a period equal to the rotation period of the grating. This frequency modulation does no harm to these diagnostics.
On the possibility of neutron spectrometry for determination of fuel ion densities in DT plasmas
Authors: Källne J. , Batistoni P. , Gorini G.
Published: July 2002

The fuel density (given by nd+nt and nd/nt) is one of the important parameters to determine and control in burning DT plasmas. Here, we propose that nd and nt be deduced from data on the dd and dt neutron energy distributions to be recorded with a neutron spectrometer having energy selective response to the plasma neutron flux. The potential diagnostic capabilities of the magnetic proton recoil spectrometer system are tested for the measuring conditions to be presented by the next step tokamaks such as ITER.
Specific heat of an epoxi resin below 1 K
Authors: Siqueira M. L. , Rapp R. E.
Published: July 2002

The specific heat as a function of temperature of Stycast 1266 was measured in the range from 0.1 to 1 K. The results are described, within 2%, by the expression c(T)=aT+bT3+cT5, where a=2.91(6) μJ/g K2, b=15.7(5) μJ/g K4, and c=8.98(0) μJ/g K6. The linear and cubic terms were related to the model of two-level systems and to the Debye specific heat, respectively. The origin of the T5 contribution remains unexplained.
3.3-MHz charge sensitive preamplifier
Authors: Kawakami Hajime , Thomas Philip , Bowles Jim
Published: July 2002

An optical monitor for the European Space Agency satellite project XMM is under development at MSSL. One option being investigated is the use of an intensifier with a ‘‘SPAN’’ anode readout. The SPAN anode gives 2048×2048 resolution elements from 6 analog signals each digitized to 8 bits. A count rate of 200 000 counts/s is anticipated for the optical monitor which places major constraints upon the analog signal processing electronics. To accommodate the optical monitor’s requirements a charge sensitive electronic system is being developed. The capacitive coupling (∼100 pF) between anodes, which has already been minimized, causes a cross-coupled signal to be observed in the impulsive phase of the pulse. It is shown both theoretically and experimentally that this cross coupling can be removed with a perfect integrator. The principle of operation is to employ an analog switch after the charge integrator to reject the impulsive phase. To obtain good noise characteristics, a long integration time (∼6 μs) has been chosen. However, this leads to pulse pileup in the feedback capacitor of the integrator. Since the rate of decay will depend upon the number of pulses piled up, switched compensation in the form of an RC circuit is employed in parallel with the signal line. Detailed circuit design and performance characteristics are given.
The use of avalanche photodiodes for the detection of soft x rays
Authors: Palmer J. R. , Morrison G. R.
Published: July 2002

Avalanche photodiodes (APDs) offer an attractive alternative to the gas flow proportional counter (GFPC) for the counting of individual soft x-ray photons. They are reasonably efficient detectors and have the capability of handling higher count rates than a GFPC. With the advent of intense monochromatic x-ray beams from synchrotron radiation sources, the ability to handle high count rates is becoming more important than the need for any energy resolution. Another attraction of using solid-state detectors is the possibility of multielement fabrication of devices: configured detector arrays can then be considered for a number of applications. For example, in the scanning transmission x-ray microscope such a detector system allows much more sophisticated imaging techniques, such as differential phase contrast imaging with a quadrant APD array. In this paper we compare results for several commercially available APDs used as photon counters with a GFPC over the energy range 200–700 eV. APDs operated in the Geiger mode with a simple passive circuit to quench the avalanche current pulses can achieve count rates of the order of 106 s−1, and this can be greatly improved upon with the use of an active quenching circuit.
A high counting rate parallel-plate gas proportional counter for fluorescence extended x-ray-absorption fine structure studies
Authors: Smith A. D. , Padmore H. A. , Buksh P. A.
Published: July 2002

Gas proportional counters (GPCs) are well suited for fluorescence extended x-ray-absorption fine structure (EXAFS) experiments in the soft x-ray (<4 keV) region. They have a near unity detection efficiency and offer good energy resolution. Of the different types of GPC, the parallel-plate device is an attractive option for use with synchrotron radiation beam lines where its intrinsically high count rate permits optimum use of the high photon flux available. The development of a parallel-plate gas proportional counter for use on soft x-ray beam lines at the Daresbury synchrotron source is described. This device is demonstrated to have a counting rate in excess of 1 MHz, and data are presented on its performance including its energy resolution, long-term gain stability, and sample EXAFS spectra.
Development of a Unix/VME data acquisition system
Authors: Miller M. C. , Ahern S. , Clark S. M.
Published: July 2002

The current status of a Unix-based VME data acquisition development project is described. It is planned to use existing Fortran data collection software to drive the existing CAMAC electronics via a VME CAMAC branch driver card and associated Daresbury Unix driving software. The first usable Unix driver has been written and produces single-action CAMAC cycles from test software. The data acquisition code has been implemented in test mode under Unix with few problems and effort is now being directed toward finalizing calls to the CAMAC-driving software and ultimate evaluation of the complete system.
Charge-coupled device as a detector in topography
Authors: Tuomi T. , Partanen J. , Simomaa K.
Published: July 2002

A linear charge-coupled device (CCD) having a picture element size of 7 μm is employed for direct measurement of synchrotron x-ray topographs. Deterioration of the detector is not observed. The intensity distribution of a section topograph of a perfect silicon crystal is measured by both the CCD camera and a high-resolution x-ray film and the results are compared to the theoretical Pendellösung fringe pattern.
Compact sources in Japan and their intended applications (invited)
Authors: Tomimasu T.
Published: July 2002

In these ten years, thirteen compact sources whose electron energy is not higher than 1 GeV have been constructed in Japan. Five sources have been developed by Electrotechnical Laboratory jointly with Sumitomo Electric Industries, Ltd. and Kawasaki Heavy Industries, Ltd. It is worth mentioning that the operations of ten rings (NIJI-II, III, IV, NAR, SuperALIS, SORTEC, AURORA, LUNA, JSR, HITACHI) have started since 1988. Recent status of these sources and their intended applications including visible and ultraviolet free electron laser projects using insertion devices installed in TERAS and NIJI-IV are briefly reported and key technologies needed to realize compact sources for ultralarge scale integration lithography and angiography, such as the electron undulating method and long lived, high-current beam storage at the early stage of commissioning, are discussed.
Synchrotron radiation applications of charge coupled device detectors (invited)
Authors: Clarke Roy , Lowe Walter P. , MacHarrie R. A. , Brizard C. , Rodricks B. G.
Published: July 2002

Scientific charge coupled devices (CCDs) offer many opportunities for high brightness synchrotron radiation applications where good spatial resolution and fast data acquisition are important. We describe the use of virtual-phase CCD pixel arrays as two-dimensional area detectors illustrating the techniques with results from recent x-ray scattering, imaging, and absorption spectroscopy studies at NSLS, CHESS, SRC, and LURE DCI. The virtual phase architecture allows direct frontside illumination of the CCD detector chips giving advantages in the speed and sensitivity of the detector. Combining developments in x-ray optics (dispersive geometry), position sensitive area detectors (CCDs), and fast data acquisition, we have been able to perform time-resolved measurements at the microsecond level. Current developments include faster data transfer rates so that the single bunch timing structure of third generation synchrotron sources can be exploited.
Present status and future plan of soft x-ray microscopy at the Photon Factory
Authors: Kagoshima Yasushi , Miyahara Tsuneaki , Ando Masami , Aoki Sadao
Published: July 2002

At the Photon Factory a project of a transmission soft x-ray microscope using zone plates as imaging elements has been initiated since 1986 at the beam line BL2B which is for the linearly polarized undulator radiation. The prototype version was built and its performance was measured in 1987. In order to proceed with our project we have reconstructed it capable of the spatial resolution better than 100 nm. Further, we have just started a new plan of microscopy at the station BL28 which introduces the circularly polarized soft x-ray/vacuum ultraviolet light emitted from a helical undulator. Both the present status at BL2B and a future plan at BL28 are described.
The EMBL-Hamburg imaging plate scanner (abstract)
Authors: Hendrix Jules
Published: July 2002

At the EMBL outstation in Hamburg, imaging plate scanners have now been operational for the last two years. The success can be called enormous, despite the disadvantage of a ″very slow″ read-out time, which is after all not longer than for scientific charge coupled devices. We will discuss the principles of operation of our scanner and illustrate its characteristics by measured results. Some important features of the Hamburg scanner are (i) From its characteristics it can be said that this system combines an excellent spatial resolution with the high sensitivity of a single photon counter, and negligible intrinsic noise. (ii) The virtually constant sensitivity at short wavelengths, down to 0.5 Å, makes this detection system ideal for protein work. The lack of absorption reduces radiation damage to a minimum and makes absorption corrections unnecessary. (iii) The exposure times are reduced by typically a factor of 20–50 as compared to photographic film. (iv) These short exposure times demand for the shortest possible read-out times. The handling of plates at a synchrotron source would become quite cumbersome. Our scanner has been optimized for a minimum read-out time without spoiling the accuracy of the data. (v) A single computer collects, stores, displays, and processes the crystallographic data. (vi) Its reliability and insensitivity to environmental changes (i.e., temperature) make it an ideal device for long term automatic data collection with only a minimum of servicing required. (vii) The spatial resolution (150 μm×150 μm) does not represent the ultimate intrinsic limit of the imaging plate, but is a common sense choice in order to avoid the need of excessive data storage space. (viii) The large size of the imaging plate matches the dimensions of the reflections obtained with average size crystals and x-ray beams very well. Up to 100 orders can be resolved in practice, at each side of the center of the plate. This limitation is not dictated by the spatial resolution of the scanner, but rather by the actual spot sizes in the patterns.
Absolute spectral sensitivity of linear-photodiode arrays in 7–20 keV energy x-ray range
Authors: Dolbnya I. P. , Kurylo S. G.
Published: July 2002

This paper deals with the study of the absolute spectral sensitivity of linear photodiode arrays (of LF1024-25/2 type) as x-ray one-coordinate detectors within the 7–20 keV energy range. The threshold sensitivity of such detectors was estimated in the indicated range. The measurements were made using synchrotron radiation from the VEPP-3 storage ring.
Bragg–Fresnel lens with the slope zone structure
Authors: Aristov V. V. , Basov Yu. A. , Snigirev A. A. , Yunkin V. A.
Published: July 2002

The effect of the one-dimensional x-ray focusing by a linear Bragg-Fresnel lens (BFL) with the slope zone structure has been found theoretically to exist in a meridional diffraction layout. Optimization of the BFL spatial configuration was carried out. This BFL was fabricated, applying the results of simulations.
Double-crystal monochromator for high-power and high-energy synchrotron radiation
Authors: Iwazumi T. , Sato M. , Kawata H.
Published: July 2002

The performance of the fixed-exit-beam sagittal-focusing double-crystal monochromator installed in the elliptical-multipole wiggler beam line at the 6.5-GeV accumulation ring for the TRISTAN project is reported. The first crystal of the monochromator is directly water cooled. Because of its large size, the crystal deformation made by the cooling water pressure and the mounting method of the crystal is found to be a serious problem. The second bent crystal for sagittal focusing and the adjusting mechanisms must be also cooled to avoid the heating by Compton scattered x rays from the first crystal. It is important for the double-crystal monochromator installed in the high-power and high-energy beam line to cool various components in addition to the first crystal.
Optimization and theoretical performance of an adaptive x-ray mirror
Authors: Susini J. , Förstner G. , Zhang L. , Boyer C. , Ravelet R.
Published: July 2002

The performance of an adaptive mirror strongly depends on the quality of the overall mirror optimization and on the model on which the control algorithm is based. Fundamental parameters entering the mirror design are: mirror function, source and beam parameters, response time, actuator positions and forces. In a case of a wiggler source, we show that it is possible to decrease the thermal deformation generated by 4 kW absorbed power by a segmented mirror of one meter length from 600 μrad to a few μrad. The discussion is based on detailed mechanical analysis and on ray-tracing simulation.
Performance of beryllium crystals exposed to high x-ray power density
Authors: Freund A. K. , Joksch St. , Kawata H. , Marot G. , Ziegler E. , Berman L. E. , Hastings J. B.
Published: July 2002

High quality beryllium single crystals are currently proposed for several applications in synchrotron radiation x-ray optics, in particular as the first element which will have to take the high power of the beam generated by insertion devices. Be has the advantage that much of this incident radiation is transmitted, especially higher energy wiggler radiation. Therefore, it is important to know how Be crystals behave under high x-ray power. For our test measurements we used the focused wiggler beam of the beam line X25 at the National Synchrotron Light Source, Brookhaven, that provides a power of 75 W at 230 mA ring current and a peak power density in excess of 200 W/mm2. A Be crystal was positioned in this white beam and its reflection properties were studied using a perfect silicon analyzer crystal. An ‘‘ideal mosaic’’ type rocking curve 58 arcsec wide was obtained with a strongly attenuated beam increasing to 73 arcsec at 200 W/mm2. No deterioration of the crystal was observed. Much better performance is expected for thinner crystals. It can be concluded that presently available Be single crystals have the properties required for currently proposed applications as first optical element.
Conservation of brightness in undulator beamlines: Tangent errors and their reduction
Authors: Menthel U. , Peatman W. B. , Senf F.
Published: July 2002

Creating and conserving the high brightness of undulator light sources on storage rings of the third generation requires an optimization of (a) undulator design and operation, (b) beamline design, and (c) cooling schemes to minimize the effect of the photons absorbed in the optical components on the performance of those components. For storage rings with electron energies of 1.5–2 GeV, the problems associated with conservation of brightness through the entire system to and including the experiment are surmountable. In the present work the optimization details to points (a) and (b) above as presented in a previous work are summarized, and point (c) is developed in some detail. With the help of the finite element method (FEM) cooling schemes were investigated that minimize the loss of brightness resulting from the heat loading of the optical components. A new concept for external cooling that fulfills the requirements and that appears feasible to build is presented.
URGENT−A computer program for calculating undulator radiation spectral, angular, polarization, and power density properties
Authors: Walker R. P. , Diviacco B.
Published: July 2002

A computer program, URGENT, is described that allows efficient calculation of the main properties of undulator radiation (spectral, angular, polarization, power density), including the effects of electron beam emittance and finite collection angles, for ideal plane, elliptical or helical trajectories, and also for the crossed-undulators scheme.
The JAERI-RIKEN SPring-8 Project
Authors: Kamitsubo H.
Published: July 2002

The Japan Atomic Energy Research Institute (JAERI) and the Institute of Physical and Chemical Research (RIKEN) are building an 8-GeV synchrotron radiation source in Harima Science Garden City, 100 km west of Osaka. The facility consists of an 8-GeV storage ring of 1436-m circumference with a natural emittance of 6.9 nm rad, an injector linac of 1 GeV, and an 8-GeV synchrotron. Sixty-one beam lines will be installed: 38 on insertion devices and 23 on bending magnets. Construction started in 1991 and the first beam is foreseen in 1997.
Combination of fixed focus and higher-order suppression modes in a SX-700-type monochromator
Authors: Erme E.
Published: July 2002

A method for optimization of the SX-700-type monochromator is described. The use of an optimal working curve and a plane grating with variable spacing for simultaneous higher-order suppression and fixed focusing are discussed. An example of new design is presented in which an aberration-corrected variable spacing grating and spherical focusing mirror are used. Effective higher-order suppression and high throughput are provided by proper choice of a monochromator working curve. Ray-tracing results and comparison with some other SX-700-type monochromators are given. The energy resolution of 0.02–0.7 eV is derived from spot pattern FWHM in the region from 83 to 1500 eV.
A mosaic crystal backscattering monochromator for high-resolution powder diffraction
Authors: Wroblewski T. , Ternes W.
Published: July 2002

The resolution function of a powder diffractometer at a synchrotron radiation source increases with increasing Bragg angle of the monochromator. Consequently, a monochromator close to backscattering has been designed and built. Two mosaic crystals of beryllium in nondispersive setting serve as optical elements. They are mounted on goniometer heads inside a tube-like housing which may be evacuated. Fine adjustment of one of the crystals is done with a micro-goniometer driven by a magnetostrictive actuator. The fact that the housing is a tube allows the use of the assembly as part of a multi-purpose monochromator system for powder diffraction.
Cryo-protection of protein crystals in intense x-ray beams
Authors: Gonzalez A. , Thompson A. W. , Nave C.
Published: July 2002

A focused white beam from existing synchrotrons has an intensity comparable with the monochromatic beams available from future undulator beamlines. The beam from station 9.5 on the SRS has therefore been used to examine the radiation damage caused within a protein crystal, cooled to near liquid nitrogen temperature. It was found that observable radiation damage occurred at doses comparable with those which have been observed in cryo-electron microscopy. It would be possible to collect many data sets from the test lysozyme crystal before radiation damage occurred under these conditions. However, it would not be possible to collect a good quality data set from a single protein crystal of a few tens of microns in size, even at liquid nitrogen temperature.
A triple-axis/four-circle diffractometer at the beam line BL-3A of the Photon Factory
Authors: Kawasaki Koichi , Takagi Yasuo , Nose Koichi , Morikawa Hirofumi , Yamazaki Shuichi , Kikuchi Toshiharu , Sasaki Satoshi
Published: July 2002

A triple-axis/four-circle diffractometer was newly designed and installed in the experimental station BL-3A of the Photon Factory. The station is currently used for multipurpose works such as diffraction, scattering, and absorption in the x-ray region both for basic and applied research. The diffractometer consists of three different types of goniometers: (1) a four-circle goniometer having a high-precision ω axis and a large, off-centered χ circle to mount various apparatuses such as an electric furnace and a helium cryostat; (2) a two-circle goniometer for crystal analyzers; and (3) a two-circle goniometer for collimators. ‘‘Dynamic’’ studies at high temperatures and microarea diffraction studies are possible by using a highly focused x-ray beam provided by a mirror-monochromator system in BL-3A. Furthermore, the combination of the high precision diffractometer and the well-collimated beam makes possible such experiments as high energy and/or momentum resolution measurements, ultrasmall angle scattering, and diffuse scattering.
A micropipette force probe suitable for near-field scanning optical microscopy
Authors: Shalom Shmuel , Lieberman Klony , Lewis Aaron , Cohen Sidney R.
Published: July 2002

In this paper it is demonstrated that glass micropipettes have unique applicability as force probes for a variety of imaging conditions and a variety of scanned tip microscopies. These probes are characterized in terms of the parameters that determine their force characteristics. Measurements are presented showing that one can readily achieve force constants of 10 N/m and it is anticipated that a reduction in this force constant by two orders of magnitude can be achieved. Such probes can be produced simply with a variety of geometries that permit a wide range of force imaging requirements to be met. Specifically, the glass micropipette probes reported in this paper are readily produced with apertures at the tip and can thus be applied to near-field scanning optical microscopy (NSOM). This opens the possibility of the long-awaited development of a universal feedback mechanism for NSOM.
Measurements of n
e(r) and T
e(r) in TdeV boundary layer by injection of laser ablated Li and C
Authors: Michaud D. , Ross G. G. , Haddad E. , Mai H. H. , Pospieszczyk A. , St-Germain J. P.
Published: July 2002

Li-atom and C-atom beams with energies of 5 and 15 eV, respectively, have been used to measure the electron density and temperature profiles in the scrape off layer and the plasma edge in TdeV. The beam penetrates into the plasma up to line densities of about nel=3×1017 m−2 and allows an instantaneous (≊250 μs) measurement of ne and Te up to 1.5×1019 m−3 and 100 eV, respectively. A camera with a Si-diode array is used to determine the spatial emissivity of the emitted light. Te(r) and ne(r) are obtained from the different attenuation and emission characteristics over the spatial range from the wall to ≊50 mm within the separatrix.
A phase contrast interferometer on DIII-D
Authors: Coda S. , Porkolab M. , Carlstrom T. N.
Published: July 2002

A novel imaging diagnostic has recently become operational on the DIII-D tokamak for the study of density fluctuations at the outer edge of the plasma. The phase contrast imaging approach overcomes the limitations of conventional scattering techniques in the spectral range of interest for transport-related phenomena, by allowing detection of long-wavelength modes (up to 7.6 cm) with excellent spatial resolution (5 mm) in the radial direction. Additional motivation for the diagnostic is provided by wave-plasma interactions during heating and current drive experiments in the ion cyclotron range of frequencies. Density perturbations of 4×107 cm−3 with a 1-MHz bandwidth can be resolved. The diagnostic employs a 7.6-cm-diam CO2 laser beam launched vertically across the plasma edge. An image of the plasma is then created on a 16-element detector array: the detector signals are directly proportional to the density fluctuations integrated along each chord. Wavelengths and correlation lengths can be inferred from the spatial mapping. The phase contrast method and its application to DIII-D are described and tests and first plasma data are presented.
Hardware for digitally controlled scanned probe microscopes
Authors: Clark S. M. , Baselt D. R. , Spence C. F. , Youngquist M. G. , Baldeschwieler J. D.
Published: July 2002

The design and implementation of a flexible and modular digital control and data acquisition system for scanned probe microscopes (SPMs) is presented. The measured performance of the system shows it to be capable of 14-bit data acquisition at a 100-kHz rate and a full 18-bit output resolution resulting in less than 0.02-Å rms position noise while maintaining a scan range in excess of 1 μm in both the X and Y dimensions. This level of performance achieves the goal of making the noise of the microscope control system an insignificant factor for most experiments. The adaptation of the system to various types of SPM experiments is discussed. Advances in audio electronics and digital signal processors have made the construction of such high performance systems possible at low cost.
An improved higher harmonic rejection system: Investigations on Station 8.1 at the SRS
Authors: Oversluizen M. , Derbyshire G. E. , Morrell C. , Farrow R. , Dobson B. R.
Published: July 2002

The monochromator commissioned on Station 8.1 at the SRS was fitted with a low voltage piezoelectric actuator. The gain in signal to noise ratio obtained with this device is briefly discussed in this article. Further improvements to the servo system on Station 8.1 are also briefly discussed.
Instrumentation and cell design for in situ studies of electrode surfaces using x-ray synchrotron radiation
Authors: Herron M. E. , Doyle S. E. , Roberts K. J. , Robinson J. , Walsh F. C.
Published: July 2002

As an integral part of a program to develop x-ray techniques for in situ structural studies of electrode surfaces, a series of experiments has been carried out using x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) at the Daresbury SRS. These studies, which involve continuous control of the electrode potential and the need to probe the electrode surface with synchrotron radiation, demand careful attention to cell design. Three types of experiment are described in order to illustrate possible approaches to cell design and the versatility of in situ x-ray techniques.