bluuebunny/crossref_metadata_2025 huggingface dataset:
Compact hard x-ray source based on the photon storage ring
Authors: Yamada Hironari , Tsutsui Hiroshi , Amano Daizou , Masui Shin , Toba Yosiyuki , Mima Kunioki , Shimoda Koichi
Published: July 2002

A compact synchrotron light source, which is composed of an exactly circular electron storage ring, features not only soft x-ray generation but also laser emission as well as hard x-ray generation. An insertion device is not applicable for the exact circular storage ring, since it has no straight section. However an optical resonator installed around the electron orbit functions like an optical undulator. The photon storage ring (PhSR) so named is essentially a free-electron laser. A use of the Compton back scattering enables the PhSR to generate hard x rays. Sizable amount of hard x rays is expected from calculation.
Development of compact synchrotron light source LUNA for x-ray lithography
Authors: Takahashi M. , Mandai S. , Hoshi Y. , Kohno Y.
Published: July 2002

A compact synchrotron light source LUNA has been developed by Ishikawajima-Harima Heavy Industries Co., Ltd. (IHI), especially for x-ray lithography. It consists of a 45-MeV linac as an electron injector and an 800-MeV synchrotron. The peak wavelength of synchrotron radiation is around 10 Å. The installation of LUNA was completed in April 1989 at the Tsuchiura Facility of IHI. The synchrotron radiation was first observed in December 1989. A stored beam current of 50 mA at 800 MeV and a lifetime over 1 h have been achieved. At present, experiments are still continuing to increase the stored current and the lifetime. X-ray lithography testing is scheduled to begin in a clean room in this facility. This paper describes the outline of LUNA and the present status.
A new proposal on use of the dual beam produced by an elliptic-MPW (EMPW) for angiography (abstract)
Authors: Hyodo Kazuyuki , Shiwaku Hideaki , Yamamoto Shigeru , Kitamura Hideo , Ando Masami
Published: July 2002

We have been developing a two-dimensional imaging system for K-edge subtraction angiography with a large size monochromatic SR beam by using asymmetrical reflection from a crystal and a two-dimensional detector system [M. Akisada et al., Nucl. Instrum. Methods A 246, 713 (1987); K. Hyodo et al., KEK-Preprint 89–181 (1990)]. Through our preliminary experiments, the advantages in the two-dimensional imaging system with real-time image aquisition were confirmed. However, taking account of a clinical application, it needs a faster energy switching system between above and below the K-edge energy and the incident x-ray intensity onto a patient should be more than 1011 photons mm2/s to attain subtracted images with high S/N ratio. If the dual SR beam produced by an EMPW would be used, we can overcome those problems. The EMPW installed at the accumulation ring (AR) primarily designed to produce elliptically polarized SR also naturally yields dual and very intense linearly polarized SR [S. Yamamoto et al., Phys. Rev. Lett. 62, 2672 (1989)]. Their angle separation is described as Ψ=2×Kx/γ(rad), where Kx=0.834Bxeλu, Bxe is the value of the horizontal magnetic field, λu is the periodicity of the magnet array, and γ is the ratio of the acceleration energy over the rest energy of an electron. In the case of the current device, its maximum separation is about 0.48 mrad.

The advantages of use of these beams are as follows: (a) They will cause no resonant vibration of a crystal which deteriorates x-ray energy resolution because only a mechanical switch of the incident x-ray energy is needed in the current imaging system [K. Hyodo et al., KEK-Preprint 89–181 (1990)]. (b) The x-ray intensity is large enough for clinical application. Two asymmetrical cut Si(311) crystals were set to attain each linearly polarized SR beam, which corresponds to the x-ray energy at above and below the K edge, respectively. Both beams were introduced to an II-TV detector system after a vessel phantom filled with iodine concentration of 15% in weight. The spatial and concentration resolution of the x-ray images were evaluated. The possibility of this new imaging method for angiography was successfully demonstrated.
Development of an x-ray microscopy and microtomography station at the VEPP-3 storage ring
Authors: Dolbnya I. P. , Gavrilov N. G. , Mezentsev N. A. , Pindyurin V. F.
Published: July 2002

The current status of the experimental station for x-ray scanning transmission subtraction microscopy and microtomography using synchrotron radiation produced by a wiggler-magnet installed at the storage ring VEPP-3 (2 GeV, 100–200 mA, 2 T) is described. The working x-radiation energies range from 5 to 35 keV. The results are presented concerning the achievement of 1-μm spatial resolution in this spectral range.
A topography measurement instrument based on the scanning electron microscope
Authors: Thong J. T. L. , Breton B.C.
Published: July 2002

A technique for in situ measurement of surface height variations in the scanning electron microscope (SEM) has been developed. Based on the comparison of images of microscopic areas obtained by tilting the electron beam, cross correlation is used to determine the image shift between like features in the stereo pair which is then used to dynamically correct the height of the tilt axis and lens focus in a feedback loop. This paper describes the principle of the method and its implementation using a commercial electron-optical column. Experimental determination of measurement accuracy and examples of line scan profiling and three-dimensional mapping are presented. Developments in instrumentation to further improve both accuracy and measurement speed are also discussed.
A beam line for radiant power measurements of vacuum ultraviolet and ultraviolet sources in the wavelength range 40–400 nm
Authors: Hollandt J. , Jans W. , Kühne M. , Lindenlauf F. , Wende B.
Published: July 2002

The Physikalisch-Technische Bundesanstalt (PTB) is operating a radiometric laboratory at the Berlin electron storage ring BESSY. In this laboratory a new instrumentation has been set up for the characterization of sources in the wavelength range from 40 to 400 nm. The spectral radiant power of the storage ring can be calculated from the knowledge of the storage ring parameters, allowing the use of BESSY as a primary radiometric standard source. The unknown spectral radiant power of a source under investigation is determined by comparison with the calculable spectral radiant power of BESSY. A concave mirror is imaging either the tangent point of the storage ring, or the vacuum ultraviolet source under investigation, into the entrance slit of a 1-m, 15° McPherson-type monochromator. In order to account for the polarization property the complete optical instrumentation can be rotated around its optical axis. Measurements have been performed with the optical plane of the instrumentation parallel and perpendicular to the plane of the electron storage ring. The performance of this new beam line will be described. The polarization property, the influence of higher order radiation, and the spectral responsivity of the instrumentation are presented.
The materials science and Laue diffraction beamlines at the European Synchrotron Radiation Facility
Authors: Kvick Å. , Wulff M.
Published: July 2002

This article presents the design of two diffraction beamlines, BL2 and BL3, at the European Synchrotron Radiation Facility. The materials science beamline will produce a monochromatic beam tunable in the energy range 5<E<60 keV and provide an energy resolution of 10−4 < ΔE/E < 3 × 10−4 below ∼40 keV. The radiation is generated by a 24 pole wiggler with critical energy εc = 28.8 keV and K=14.0. It produces 4.9 kW of power over a horizontal fan of 1.5 mrad. The heat load on the first monochromator crystal is controlled by an adaptive premirror set to reflect an energy band exceeding the desired monochromator energy by 20% or by low energy absorbing filters. The first monochromator crystal will be cryogenically cooled. The premirror and a symmetric postmirror will collimate and refocus in the vertical plane. Horizontal focusing will be done by sagittal bending of a rib enforced second monochromator crystal. The white beam station BL3 is optimized for Laue diffraction in the energy range 5<E <60 keV. The source is a 44 pole wiggler with εc = 17.2 keV and K=4.7. It produces a power of 1.8 kW and an integrated flux ∼ 6 × 1017 ph/s. over a horizontal fan of 0.5 mrad. The radiation is focused by a toroidal mirror with fixed sagittal radius.
A novel multichord spectrometer for plasma velocity measurements
Authors: Hawkes N. , Peacock N.
Published: July 2002

A diagnostic has been designed to study edge plasma velocities in (JET) with good space and time resolution. To eliminate ambiguities in the measurement arising from atomic physics effects opposing views are provided. Each viewing direction incorporates ten fibers imaged on the path of a neutral heating beam with a channel spacing of 1.5 cm. The chord views are imaged onto a spectrometer with 20 individual entrance slits arranged in a rectangular array. The dispersed spectra from adjacent slits form linear images 25 mm long that are recorded using four fast optical multichannel analyzers. To prevent crosstalk of signals from adjacent slits the instrument incorporates a low dispersion spectrometer to limit the bandpass of the system. The principal advantage of this design is the ability to match the f number of the fiber optic arrays. This results from the rectangular arrangement of the slits which allows for a 4× magnification of the fiber images without requiring an exceptionally long (70 mm) entrance slit. This matching optimises the light collection efficiency of the complete diagnostic which ultimately sets the shortest time resolution. The minimum readout time for all 20 channels is 0.5 ms, although longer integration times are generally needed in JET.
Compact ion beam source for feedback control of plasma instabilities
Authors: Sekiguchi A. , Sen A. K. , Tham P. , Navratil G. A. , Greaves R. G.
Published: July 2002

A compact ion beam source has been constructed for use in the Columbia Linear Machine for feedback control of plasma instabilities. This source has been used in a feedback configuration to stabilize the collisionless trapped particle instability [Phys. Rev. Lett. 67, 204 (1991)]. The source was based on an E×B hot cathode, magnetron-type design. It utilized the background magnetic field and a radial discharge voltage to obtain the azimuthal E×B drifts. The pressure inside the discharge chamber was maintained in the mTorr range via differential pumping. The source had a stable operating window in gas pressure of over 50% about the chosen operating parameters. Typical source plasma parameters were a plasma potential of 100 V, an electron temperature of 10 eV, and a plasma density of 109–1010 cm−3. The power dissipated was around 30 W. The ion beam energy was typically 100 eV with an energy spread of 20 eV and it could be modulated 100%. In addition, external control of the ion beam energy was provided via the anode bias.
Dispersive EXAFS apparatus at Frascati
Authors: D’Acapito F. , Boscherini F. , Marcelli A. , Mobilio S.
Published: July 2002

We report the successful design and test of a dispersive extended x-ray absorption fine structure (EXAFS) apparatus at Frascati. This technique is capable of measuring x-ray absorption spectra in fractions of a second and makes time-resolved structural studies possible. We describe the design of the instrument and compare the experimental performance with theoretical predictions. An energy resolution of 2–3×10−4, an energy dispersion ranging from 350 to 870 eV (at 7 to 11 keV), a spot size between 0.5 to 1 mm, and a flux of the order of 106 photons/s/pixel/100 mA was achieved. EXAFS spectra with good signal-to-noise ratio can be obtained in 100 to 600 ms on concentrated samples.
A dynamic focusing x-ray monochromator for a wiggler beam line at the SRS of the SERC Daresbury Laboratory (abstract)
Authors: De Bruijn D. , Van Zuylen P. , Kruizinga G.
Published: July 2002

A Si(220) double-crystal monochromator for the energy range 10–30 keV is presented. It will be used for EXAFS as well as powder diffraction measurements. To determine the requirements for this monochromator we looked, apart from mean considerations, at the requirements dictated by EXAFS in transmission mode. For good data analyses the proper shape, amplitude, and location at the energy axis of each wiggle is required. Moreover it is essential to separate the wiggles from background and noise. For the latter a high flux through the sample is desirable, which can be achieved by horizontal focusing of the beam. For that we have chosen to bend the second crystal sagitally. The sagittal bending radius is adjustable between 50 and 0.8 m, because for different energies different sagittal radii are necessary to focus the beam on the sample. The mean meridional radius of the second crystal is fixed at 130 m, which is an optimization for 20 keV. The meridional radius of the first crystal can be tuned between 100 and 500 m. When this radius is set to 130 m the energy resolution is calculated to be 6, 3, and 35 eV for 10, 20, and 30 keV (for perfectly bent crystals). By changing the meridional radius of the first crystal, future users of this monochromator can make the trade off between resolution and intensity. Movement of the monochromator exit beam, during a scan, will occur due to the monochromator geometry, but is reduced as much as possible by using an asymmetrically cut second crystal, with an asymmetry angle of 2.5°. The average exit beam movement of the monochromator for a 1-keV scan is 20 μm. For 40% of the energy range (10–30 keV) the exit beam position remains within 10 μm. For the second crystal no translation stage is used. When using a translation stage it is difficult to keep the change in flux within acceptable limits, because an alignment error of 0.01 arcsec at 30 keV will result in a change in intensity of 1%.
Horizontal acceptance of a double-crystal (n,−n) monochromator with sagittally bent second crystal
Authors: Hrdy Jaromir
Published: July 2002

A simple formula for the horizontal divergence which is accepted by a double-crystal (n,−n) monochromator with sagittally bent second crystal is derived.
An investigation into the use of filters as a means of enhancing the performance of solid state detectors for extended x-ray absorption fine structure
Authors: Bilsborrow Robert L.
Published: July 2002

Selectively absorbing x-ray filters have been widely used with scintillation detectors to provide some degree of energy discrimination and hence improve the signal/noise ratio [E. Stern and S. Heald, Rev. Sci. Instrum. 50, 1579 (1979); J. Baines, D. Garner, S. Hasnain, and C. Morrell, Nucl. Instrum. Methods A 266, 565 (1988)]. Solid state detectors, with their intrinsic high resolution, do not require filtration for energy discrimination as pulses can be collected solely from a window set on the energy of interest. However, these detectors have maximum count rates, limited by the signal processing electronics, typically a decade smaller than those for scintillators, which severely limits their ability to exploit the high intensities provided by synchrotron radiation sources. This limitation can be minimized by increasing the number of detector elements [S. Cramer, O. Tench, M. Yocum, and G. George, Nucl. Instrum. Methods A 266, 586 (1988)], by faster signal processing [G. Derbyshire, R. Farrow, R. Bilsborrow, C. Morrell, N. Greaves, and B. Dobson, Adv. X-Ray Anal. 34], or a combination of both. The first solution eventually becomes both unwieldy and prohibitively expensive and there is a limit to the improvements that can be made to the second, which is still likely to be below the intensities provided by the next generation of synchrotron sources. A filter in combination with a multielement solid state detector array can significantly enhance its performance at negligible cost.
X-ray Couette shear cell for nonequilibrium structural studies of complex fluids under flow
Authors: Plano R. J. , Safinya C. R. , Sirota E. B. , Wenzel L. J.
Published: July 2002

We have designed and constructed a sealed, temperature-controlled Couette-type shear cell which allows us to carry out in situ synchrotron x-ray scattering studies of the nonequilibrium structures of complex fluids under flow, probing lengths ranging from the nanometer to the semimacroscopic micron scale. The sealed design allows the cell to be tilted, facilitating the scanning of all directions in reciprocal space. In contrast to existing neutron shear cells, we access the shear plane containing the velocity and the velocity gradient. The temperature control of the cell enables us to carry out phase transition studies far from equilibrium. The complex fluid systems which may be studied with this cell include thermotropic and lyotropic liquid crystals, microemulsions, and polymeric fluids. Recent results on the nematic and smectic-A phases of a liquid crystal, and the disordered bicontinuous L3 phases of surfactant membranes in the vicinity of the ordered lamellar Lα phase under flow, are presented.
Dual time to digital converter for delay-line readout of position-sensitive gas-filled detectors
Authors: Berry Andrew
Published: July 2002

A new dual channel time digitizer has been designed. It is based on the coarse counter and interpolation method. A new technique of interpolation has been employed which gives a FWHM resolution of 50 ps and a differential nonlinearity of ±2%, at a master oscillator frequency of 200 MHz. The module has a dynamic measurement range of 10 bits with a fixed dead time of 30 ns. It is a single width C size VXI format. Presented is a description of the new interpolation method and typical performance results.
Scanned-cantilever atomic force microscope
Authors: Baselt David R. , Baldeschwieler John D.
Published: July 2002

We have developed a 3.6 μm scan range atomic force microscope that scans the cantilever instead of the sample, while the optical-lever detection apparatus remains stationary. The design permits simpler, more adaptable sample mounting, and generally improves ease of use. Software workarounds alleviate the minor effects of spurious signal variations that arise as a result of scanning the cantilever. The performance of the microscope matches that of scanned-sample instruments.
A robust particle position controller for an electrodynamic chamber
Authors: Baum David , Har-Nov Yosef , Guterman Hugo , Bar-Ziv Ezra
Published: July 2002

A novel scheme for robust feedback control of a charged particle in an electrodynamic chamber has been designed and applied. The determination of the particle position is based on photodiode array (PDA) shadowgraphy. A 128 linear PDA is used to measure the trace of the particle. The PDA trace is transferred to a PC computer by a special purpose digitizer. Analog-to-digital conversion is realized by feeding the signal through a hard limiter and measuring the time that corresponds to the shadow and light zones. The designed hardware allows a high sampling rate (7.8 kHz). The obtained position value is used by a PID algorithm to control the particle position. The one-to-one correspondence between the calculated and experimental trajectories allows one to study the system performance by simulation rather than by experiments and to assign the proper controller to the specific application. It is shown that the system is insensitive to extreme variations in particle size.
Improved multipass optics for diode laser spectroscopy
Authors: Hu T. A. , Chappell E. L. , Munley J. T. , Sharpe S. W.
Published: July 2002

Feedback between optical elements can be a major source of noise when trying to attain high sensitivity in infrared absorption experiments. We find that a conventional White-cell optical arrangement introduces étaloning fringes that modulate the peak-to-peak amplitude of our signals by 1 part in 16 666, a fractional change of 6×10−5. Although relatively small, this ‘‘noise’’ is systematic and adds coherently with averaging, obscuring interesting absorption features. An easily constructed multipass optical system suited for performing high-resolution infrared spectroscopy in molecular beams is described. The design is based on a variation of the White cell and has been optimized for use with lead salt diode lasers. One of the key components in the improved design is the addition of an oscillating mirror for spoiling optical feedback generated by laser scatter and/or poor mode coupling of the laser to the multipass optics.
Heterodyn interferometer for the detection of electric and thermal signals in integrated circuits through the substrate
Authors: Goldstein M. , Sölkner G. , Gornik E.
Published: July 2002

A laser diode based probing system for the interferometric detection of charge density modulations and temperature changes which accompany electric signals in integrated circuits has been developed. Measurements are performed through the substrate of the device under test. Compared to previously introduced measuring schemes the system offers the advantage of a versatile and inexpensive positioning system of the probing and the reference laser beam, noise reduction due to the use of heterodyn techniques, and the absence of polarizing elements. The temporal resolution is limited by the width of the laser diode pulse to 500 ps. The probe beam can be focused to a diameter of 1.5 μm through a 400-μm-thick silicon substrate which determines the spatial resolution of our measurement system. It should be stressed that probing through the substrate provides the only access to internal measurement nodes for a growing number of highly integrated circuits the front side of which is masked by multilevel wiring, bonding wires, or lead frames.
Micro-Raman at variable low-temperature and very high pressure
Authors: Chervin J. C. , Canny B. , Gauthier M. , Pruzan Ph.
Published: July 2002

A setup for micro-Raman investigation at low temperature in a membrane diamond anvil cell is described. This setup allows investigations at variable temperature from room temperature down to 10 K. For a given temperature the system permits a continuous variation in pressure. Performance of the system is illustrated with investigations on benzene and deuterated ice which required pressure cycling (at low temperature) or temperature cycling (at high pressure).
An automated test system for measuring x-ray transmission through glass polycapillaries
Authors: Rath B. K. , Youngman R. , MacDonald C. A.
Published: July 2002

To support the development of the recently invented capillary-based x-ray optics technology, it is necessary to have quick and repeatable precision measurements of x-ray transmission. A novel fully automated measurement system has been built for this purpose. Measurements are reproducible within half a percent.
Highly efficient microwave coupling devices for remote plasma applications
Authors: Dupret C. , Supiot P. , Dessaux O. , Goudmand P.
Published: July 2002

Microwave resonant cavities running at 2.45 GHz are now being investigated for use in the high power remote plasma processings. The present paper deals with the design of two coupling devices, e.g., one coaxial cavity and one TM012 mode cylindrical cavity, using an antenna coupling. Their main attractive feature is the ability to run at powers as high as 3 and 6 kW, respectively. A basic model used to describe the wave–plasma interaction is developed and leads to the main consequences for the cavities conception thanks to the deduced equivalent electrical circuits. Their high efficiency is experimentally demonstrated for nitrogen, oxygen, air, and argon.
A new data reduction procedure in the flash method of measuring thermal diffusivity
Authors: Gembarovič J. , Taylor R. E.
Published: July 2002

This article presents a new way to reduce data in the flash method of measuring thermal diffusivity. Experimental temperature versus time data are first periodized, then transformed by using the discrete Fourier transformation (DFT), and the real part of the second term of the transformed temperature is then fitted with a theoretical formula derived in this article. The main advantage of this procedure is that the thermal diffusivity calculation actually does not depend on the temperature level before the flash, and can also be applied in the case when the measured temperature signal of the sample is superimposed with an arbitrary linearly rising or falling signal, with no need to know the parameters of this imposed signal. This is a unique, completely new feature of this procedure, which has no analog among the other methods of data reduction. Practically, it means that the thermal diffusivity of the sample can be measured by the flash method under an arbitrary dynamically (linearly) changing condition of temperature. The proposed procedure allows the treatment of perturbed signals, even in the case when the data are partly statistically correlated, i.e., the noise is not Gaussian. Experimentally, the data reduction procedure has been tested for a correction of the effect of an electronic noise imposed on the temperature versus time signal in the flash method. The results show that the reproducibility of our procedure is favorable, and the accuracy is comparable with other data reduction methods.
Low-temperature two-axis goniometer with accurate temperature control
Authors: Herzog R. , Evetts J. E.
Published: July 2002

We have designed a probe to rotate a sample around two independent axes in a magnetic field of up to 8 T and at temperatures varying from 3 K to room temperature. The sample is in very good thermal contact with a thermometer and a regulated heater, enabling precise temperature control. Pogo pins enable quick electrical connections to the sample. Two computer-controlled stepper motors rotate the sample around the two independent axes. This probe was primarily designed to investigate the anisotropy of the critical currents of superconducting thin films in a magnetic field.
Fluoride salts as supersonic nozzle materials for hot fluorine
Authors: Ericson Tommy , Copeland Kyle , Keil Mark , Apelblat Y. , Fan Y. B.
Published: July 2002

An intense supersonic beam of atomic fluorine has been generated using nozzles fabricated from single-crystal CaF2 and MgF2. The latter material has been tested up to 1000 °C with no observable damage. This is ≳250 °C hotter than previously achieved, increasing the atomic beam intensity by ≳5×.
Sampled waveform measurement in integrated circuits using heterodyne electrostatic force microscopy
Authors: Bridges G. E. , Said R. A. , Mittal M. , Thomson D. J.
Published: July 2002

A high-resolution noncontact scanned probe technique has been developed for sampling the internal signals of an operating integrated circuit. The signal waveform is extracted by sensing the localized electrostatic force between a small probe and point on the circuit being measured. A heterodyne approach is used to enable the sampled measurement of high-frequency digital or analog waveforms. In conjunction with a nulling method, the technique is capable of accurate signal measurement without complex calibration or probe positioning, and can be performed over passivated structures. Measurement of digital and analog signals is demonstrated with a voltage accuracy of less than 100 mV.
Characterization of a purely thermal wave based photopyroelectric gas sensor for hydrogen detection
Authors: Munidasa Mahendra , Mandelis Andreas , Katz Arrin , Do Do V. , Luong Viet K.
Published: July 2002

A study towards the characterization of a new photopyroelectric gas sensor with an operating mechanism based purely on thermal waves is performed. It has been found that by restricting the gas flow over the sensor to a thin layer, sensitivity of the phase of the photopyroelectric signal to hydrogen is greatly enhanced. The phase of the signal has been shown to be more stable than the amplitude. Furthermore, the thinner the pyroelectric film, the better the sensitivity. Hydrogen concentrations as low as 1% in air have been detected using a 9 μm film.
High-resolution tritium calorimetry based on inertial temperature control
Authors: Hemmerich J. L. , Serio L. , Milverton P.
Published: July 2002

A reassessment of the basic equation governing calorimetry shows the crucial importance of temperature stability in the calorimeter environment. Following the principles derived, we have developed a new temperature control method and demonstrated it in a prototype calorimeter over a wide dynamic range (5 μW–2 W). Temperature control is achieved by using a metal block of high thermal inertia, surrounded by heat flow sensing thermopile arrays, which is embedded in an isothermal environment. Any temperature fluctuations in this environment are detected by the heat flow sensors and can be corrected by conventional feedback control. The advantage of this method is its high sensitivity to temperature changes: whereas conventional thermometers typically provide signals in the order of 1×10−3 V/K−1, a correctly selected combination of inertial mass and thermopile arrays can provide signals in the order of 1 V K−1, thus permitting an improvement of temperature control by three orders of magnitude. A commercially available thermoelectric calorimeter in an isothermal environment controlled by the new method permitted measurement of sample powers with ±10 μW accuracy (long-term, short-term noise ∼±1 μW), whereas in a conventional thermostatic bath (temperature stability ±0.02 K h−1) its resolution was limited to ±3 mW.
Junction temperature measurements in reverse-biased PIN diodes
Authors: Leifer Mark C.
Published: July 2002

Designers using reverse-biased PIN diodes at high power levels (to thousands of watts) have always faced a complex problem in choosing the optimal reverse bias voltage. Because the conservative approach of using bias voltage equal to the peak applied rf voltage can lead to excessive cost and complexity, operation with reduced or weak bias where the diode makes excursions into the forward bias direction is attractive if heat dissipation can be controlled. A method is presented here for measuring temperature rise in the PIN diode under weak reverse bias. The measurement of junction temperature under actual operating conditions provides an important tool both for choosing the appropriate bias voltage and for evaluating the reliability of the design. For diodes operating in the capacitive (nonconductive) regime, it is further shown that temperature rise at high bias voltages and high rf power levels can be predicted accurately from low power data.
High-pressure quasielastic and static light scattering apparatus
Authors: Richards C. J. , Fisch M. R.
Published: July 2002

We describe an apparatus for multiangle light scattering studies of samples that are under hydrostatic pressures. The mean hydrodynamic radius and mean radius of gyration can be determined using quasielastic and static light scattering at temperatures between 5 and 85 °C and pressures between 0.1 and 100 MPa.
Tandem time-of-flight mass spectrometer for cluster–surface scattering experiments
Authors: Beck Rainer D. , Weis Patrick , Bräuchle Götz , Rockenberger Jörg
Published: July 2002

A new tandem time-of-flight mass spectrometer is described which is designed to study the mass-, velocity-, and angle-resolved scattering of cluster ions from solid surfaces. Clusters are produced in a supersonic jet laser desorption/vaporization source, ionized either directly in the formation step or by subsequent photoionization of neutrals, mass selected in a primary time-of-flight region, and decelerated to the impact energy (50–1000 eV) close to the target surface. Cluster–surface collisions take place in a field-free region in order to determine both velocity and angular distributions of the scattered clusters and fragments with an independently pulsed, rotatable secondary time-of-flight mass spectrometer. Several surface targets can be mounted in the UHV scattering chamber (10−10 Torr base pressure) on a five-axis manipulator which, together with the rotatable secondary TOF, allows for independent variation of incident and scattering angles. Target surfaces can be cleaned by direct current heating and sputtering with an argon-ion gun. Surface structure and composition are assessed by low-energy electron diffraction (LEED) and Auger spectroscopy with a four grid reverse view LEED/Auger system. Surface collision experiments of fullerenes (C+60, C+70, C+76, C+84, ...) and metallofullerenes (La@C+82) with highly oriented pyrolitic graphite (HOPG) surfaces are described as examples for the performance of the instrument. Effects of surface contamination in the scattering of fullerenes from HOPG are described to demonstrate the need for thorough cleaning procedures in order to obtain reproducible results. © 1995 American Institute of Physics.
Space-resolved extreme ultraviolet (XUV) spectroscopy using a toroidal mirror
Authors: Shin Hyun-Joon , Kim Dong-Eon , Lee Tong-Nyong
Published: July 2002

In order to collect radiation from a distant light source and to compensate astigmatism, a toroidal mirror is often placed in front of a grazing-incidence spectrograph. In this study, characteristics of space-resolved spectra obtained with such a system have been investigated using a ray-tracing analysis. The following was found: in the stigmatic focal region of the spectrum, the spatial resolution along the sagittal direction is excellent but that along the meridional direction is poor; on the other hand, in the astigmatic wavelength region, the trend is reversed, i.e., the spatial resolution along the sagittal direction is poor but that along the meridional direction is good, particularly in the wavelength region which is far from the stigmatic focus. The method was successfully applied to the space-resolved spectroscopic study of a capillary discharge plasma.
Thermal diffusivity of solids by photoacoustic cell rotation and phase lag measurement
Authors: Thomas Sheenu , Isaac Johney , Philip J.
Published: July 2002

A single-beam photoacoustic phase lag measurement is demonstrated for determining the thermal diffusivity α of solid samples. The method involves measurement of the phase difference of the photoacoustic signal between front and rear surface illuminations at a single chopping frequency with the same light beam. Results on representative samples, with widely different thermal properties, show very good agreement with literature values. Temperature variation of α can also be measured with the setup.
An intensity interferometer for soft x rays
Authors: Yang L. , McNulty I. , Gluskin E.
Published: July 2002

We designed and built an intensity interferometer to characterize the spatial coherence of a soft x-ray undulator beam. The beam source size and shape can be determined from the measured coherence function. The instrument is 400 mm long and is mounted on a standard 204-mm diameter flange. This compact design is readily adaptable to other beamlines with sources of sufficient spectral brightness. Details of the interferometer design and performance are presented. We anticipate that when this technique is mature, it will provide a useful diagnostic for high brightness x-ray beams.
Dead-time correction and I0 normalization in germanium solid-state detector systems using an incoming count rate monitor (abstract)
Authors: Dent A. J. , Derbyshire G. E. , Derst G. , Farrow R. C.
Published: July 2002

The rate limitation of a photon counting germanium solid-state detector system is largely determined by the shaping time of the amplifier, which is in turn set by the required system resolution. This rate limitation arises because when an event passes into the shaping amplifier, it is paralyzed for a time referred to as the dead time, which is a function of the shaping time. If any further events pass into the shaping amplifier during this time, one or both events may be corrupted or lost. This phenomenon is known as pulse pileup. However, if one uses an incident count rate monitor (ICR) which gives an accurate indication of the incident photon rate but no energy information, one can correct for any pulses lost in the shaping amplifier due to pileup. This allows one to run the detector system at higher rates and still retain throughput linearity. This has been shown by the work of Zhang et al. The authors also showed that with respect to EXAFS, the loss of linearity due to pulse pileup at high rates has two main effects: (1) The EXAFS oscillations and edge step height are reduced and (2) noise and glitches present in I0 do not normalize out. This work has been extended to higher input count rates and in addition to using the paralyzable model to correct for the loss of throughput linearity as the input rate increases, was also used the ICR monitor to give an I0 value which when itself corrected can give improvements over an ion chamber I0 in normalizing noise and glitches out. Data has been taken with station 9.3 on the SRS at Daresbury Laboratory using 18 mM CuNO3 solution at ICR values of 20, 47, 84, 120, and 180 kHz. In addition, data has also been taken for 0.02 at. % As implanted to 1 μm depth in a-Si using reflexafs. This data was collected at 120 kHz as opposed to the usual 40 kHz and normalized using these techniques. It will be shown using this data that using pileup correction and an ICR I0, the linearity of the system can be retained at higher count rates and thus significant improvements in the signal-to-noise ratio can be gained.
Recent developments in the avalanche photodiode x-ray detector for timing and fast counting measurements
Authors: Kishimoto Shunji
Published: July 2002

An avalanche photodiode (APD) detector using a new silicon device has been developed for x-ray timing measurements. The device, Model No. S5343 (Hamamatsu Photonics), has an excellent time resolution of 0.10 ns and has only a short tail, or a full width of 1.41 ns at 10−5 maximum, in the response function for the time spectrum. Measurements of the purity between the main and second bunches to the order of 10−9 were successfully executed in observing the bunch structure of the Photon Factory ring with the detector as an application to the bunch-purity monitor. The APD detector also has a property for fast counting up to the order of 108 counts per second by using its output width, shorter than several nanoseconds. The count-rate property has been examined with the pulsed beams of synchrotron radiation and with an APD device Model No. C30817E (EG&G Optoelectronics), which has a depletion layer about 100 μm thick. The results show that the count-rate response can almost be expressed by a counting model for the pulsed beam.
Importance of wave-optical corrections to geometrical ray tracing for high brilliance beamlines
Authors: Miyahara Tsuneaki , Kagoshima Yasushi
Published: July 2002

It is demonstrated that wave-optical corrections to geometrical ray tracing is important especially when light beam with emittance close to the diffraction limit is transported. Even in the Gaussian beam approximation the difference between the geometrical and the wave-optical focal points is not negligible for high brilliance beamlines. In order to make wave-optical corrections based on the uncertainty principle of light the brightness function should be modified to give non-negative values, because it is directly related to the Bose degeneracy of the radiation field.
Synchrotron radiation time gate quartz device for nuclear resonant scattering
Authors: Suzuki Carlos K. , Zhang Xiao W. , Ando Masami , Yoda Yoshitaka , Ishikawa Tetsuya , Kikuta Seishi , Harami Taikan , Shiwaku Hideaki , Ohno Hideo
Published: July 2002

A synchrotron radiation time gate with X-cut quartz resonator has been constructed for use on nuclear resonant scattering at ultrahigh brilliance beam lines. The purpose is to discriminate the electronic scattered prompt (zero time) from the time delayed nuclear scattered photons. The special feature of this device is the possibility of adjusting the time modulation width of the gate without changing the frequency.
X-ray optics research and development for SPring-8 beamlines
Authors: Uruga Tomoya , Kimura Hiroaki , Kohmura Yoshiki , Kuroda Masanori , Nagasawa Hisao , Ohtomo Kiyotaka , Yamaoka Hitoshi , Ishikawa Tetsuya , Ueki Tatzuo , Iwasaki Hitoshi , Hashimoto Shinya , Kashihara Yasuharu , Okui Kazumori
Published: July 2002

X-ray optics research and development for SPring-8 beamlines are described. These include standard developments of monochromators, high-heat load optics, wide energy-range monochromators for bending beamlines, long x-ray mirrors, and single and graded d-spacing synthetic multilayers.
Liquid-metal, pin-fin pressure drop by correlation in cross flow
Authors: Wang Zhibi , Kuzay Tuncer M. , Assoufid Lahsen
Published: July 2002

The pin-fin configuration is widely used in high-heat-flux applications. Recently, the pin-fin design with liquid-metal coolant was also applied to synchrotron-radiation beamline devices. This article investigates the pressure drop in a pin-post crystal with liquid gallium as the coolant. Because the pin-post configuration is a relatively new concept, information in the literature on pin-post mirrors or crystals is rare, and information on the pressure drop in pin-post mirrors with liquid metal as the coolant is even rarer. Because the cross flow in cylinder-array geometry is very similar to that of the pin post, the pressure drop correlation data for the cross flow of fluid with various fluid characteristics or properties through a tube bank are studied so that the results can be scaled to the pin-fin geometry with liquid metal as the coolant. The emphasis of this article is on the influence of two variables on the pressure drop: viscosity and density of fluid. The difference and correlation of the pressure drop between long and short posts and the predication of the pressure drop of liquid metal in the pin-post mirror and comparison with an existing experiment are addressed.
Microbeam generation with capillary optics (invited)
Authors: Bilderback Donald H. , Thiel Daniel J.
Published: July 2002

Grazing incidence x-ray optics for microbeam generation can be classified into five types: ellipsoidal mirror, Wolter mirror, monocapillary concentrator, microchannel array, and polycapillary concentrator. These components each have their own properties, yet they are closely related. Each optical component is at a different stage of development. Ellipsoidal mirrors are based on a mature technology and at 1/10 magnification should yield 10-μm-diam beams. Optics based on replicate Wolter mirrors are capable of producing beams on a 1–10 μm scale with high gain. Monocapillary concentrators are producing beam sizes of less than 0.1 μm. On a larger scale, polycapillary concentrators, and microchannel arrays are promising microbeam components. Ray tracing programs exist in different forms for some of these components. Prototype capillary optics have been tested, but as a whole, the manufacturing methods could be significantly improved with further investments in time and effort. All of these optical designs show great promise for intensifying a beam in a small area if they can be adequately perfected. This is the great challenge before us.
Reflectometer end station for synchrotron calibrations of Advanced X-ray Astrophysics Facility flight optics and for spectrometric research applications
Authors: Graessle D. E. , Fitch J. J. , Ingram R. , Zhang Juda J. , Blake R. L.
Published: July 2002

Preparations have been underway to construct and test a facility for grazing incidence reflectance calibrations of flat mirrors at the National Synchrotron Light Source. The purpose is to conduct calibrations on witness flats to the coating process of the flight mirrors for NASA’s Advanced X-ray Astrophysics Facility (AXAF). The x-ray energy range required is 50 eV–12 keV. Three monochromatic beamlines (X8C, X8A, U3A) will provide energy tunability over this entire range. The goal is to calibrate the AXAF flight mirrors with uncertainties approaching 1%. A portable end station with a precision-positioning reflectometer has been developed for this work. We have resolved the vacuum cleanliness requirements to preserve the coating integrity of the flats with the strict grazing-angle certainty requirements placed on the rotational control system of the reflectometer. A precision positioning table permits alignment of the system to the synchrotron beam to within 10 arcsec; the reflectometer’s rotational control system can then produce grazing angle accuracy to within less than 2 arcsec, provided that the electron orbit is stable. At 10–12 keV, this degree of angular accuracy is necessary to achieve the calibration accuracy required for AXAF. However the most important energy regions for the synchrotron calibration are in the 2000–3200 eV range, where the M-edge absorption features of the coating element, iridium, appear, and the 300–700 eV range of the Ir N edges. The detail versus energy exhibited in these features cannot be traced adequately without a tunable energy source, which necessitates a synchrotron for this work. We present the mechanical designs, motion control systems, detection and measurement capabilities, and selected procedures for our measurements, as well as reflectance data.
Beam stability in the third-generation SR sources (invited)
Authors: Mülhaupt G.
Published: July 2002

After recapitulation of the principal sources for beam instability, the different ways to minimize beam instability at the design stage and during operation are discussed. The achieved beam stability data (presently a few percent of the beam sizes at the ESRF) and the limitations of beam position measurements are presented.
Preserving the high source brightness with x-ray beam line optics (invited)
Authors: Berman Lonny E.
Published: July 2002

A first-order challenge facing developers of x-ray beam line optics at synchrotron sources lies in producing optics that faithfully deliver the brightness of the source, especially in the presence of adverse power loads. Once overcome, continued use of beam line optics in experiments often reveals a second-order challenge, that of preservation of the source brightness over time, especially as conditions such as the storage ring current change. This requires maintaining stability, with beam line optics, of the peaks, widths, and centroid positions of the various parameters that contribute to the brightness, the wavelength, position, and angle distributions of the delivered photon beam. Some ideas on the use of x-ray monochromators, mirrors, apertures, and position-sensitive monitors to sense and stabilize the brightness parameter distributions, as well as methods to avoid or minimize transients in the first place, are presented. Examples based on experiences at the X25 wiggler beam line at the National Synchrotron Light Source are given.
Performance evaluation of a soft x-ray quadruple reflection circular polarizer
Authors: Höchst Hartmut , Bulicke Peter , Nelson Tom , Middleton Fred
Published: July 2002

We built a quadruple reflection polarizer which can be used in the energy range hν=8–130 eV to convert linearly polarized synchrotron radiation into circularly polarized light of either left or right handedness. The design permits independent adjustment of the angle of reflection θ as well as the angle of rotation α along the light axis. These adjustments allow us to operate the polarizer at any given energy in a mode where either the degree of circular polarization Pcirc or the figure of merit TP2circ is maximized. We tested the optical performance and phase shifting properties of a prototype polarizer using a bending magnet beamline. The data verify our model calculations of the conversion efficiency and the optimum operating parameters to maintain the highest degree of circular polarization.