bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion sputtering on metal oxides: A source of translationally hot O(3P
J) atoms for chemical studies above 1 eV
Authors: Ferrieri Richard A. , Chu Yung Y.
Published: July 2002

A novel technique is described for generation of translationally ‘‘hot’’ oxygen atoms that can be used for chemical studies. These atoms are produced through ion sputtering on Ta2 O5 targets. Mass-resolved beams of noble gas ions in the kilovolt energy range are generated for this purpose using a 150-cm isotope separator. The technique can yield fluxes of oxygen atoms in the range of 1015 –1016 atoms cm−2  s−1 from a 40-keV argon ion beam with 15-μA intensity. The sputtered atoms are predominantly neutral and reside exclusively in their 3PJ ground electronic state upon ejection. Translational energy profiles, measured for an incident ion beam angle of 30° from the surface normal, were found to be similar in both the forward and backward scattered directions at a 60° angle from the surface normal. These distributions peaked at about 7 eV, but extended beyond 20 eV. Theoretical calculations using a modified Thompson model yielded a similar distribution at this angle. This suggests that kilovolt ion sputtering on Ta2 O5 proceeds predominantly through a collision cascade mechanism. The energy range provided by this technique opens up a new area of hot-atom chemistry for oxygen atoms that has been relatively unexplored until now because of the lack of methods for their generation.
Fourier transform, electromodulated, infrared spectrometer for studies at the electrochemical interface
Authors: Ozanam F. , Chazalviel J-N.
Published: July 2002

We report on a newly built infrared spectrometer to be used for vibrational studies at the electrochemical interface. The usual way to select the weak interface absorption consists in changing the electrode potential and measuring the associated change in absorption. However, up to now it was difficult to benefit from both the advantages of using a lock-in detection and Fourier transform spectroscopy. Our apparatus allows simultaneous use of these two techniques. This is achieved by using a slow scan speed (∼6 μm s−1) for the Michelson interferometer. The electrode potential may be modulated at a frequency as low as 100 Hz. The ultimate sensitivity of our apparatus corresponds to a relative change of transmitted light intensity of ΔI/I∼10−6, for a measuring time of 45 min, in the 800–4200 cm−1 range, with a resolution of 25 cm−1. Our ultimate resolution capability is 0.5 cm−1. Data are presented that have been obtained on the n-Si/acetonitrile interface using an attenuated total reflection geometry, which allows further improvement of the performances by one order of magnitude.
Generation of pressure pulses by impacting an opposed-anvil setup with a low-velocity projectile
Authors: Singh Anil K.
Published: July 2002

It is shown that the pressure pulses of short duration can be generated by dropping a weight (5–10 kg) from a height (≤2 m) on a tungsten carbide opposed-anvil setup with a pyrophyllite gasket and a talc pressure transmitting medium. The amplitude of the pulse depends on the momentum of the drop weight. Typically, a drop-weight momentum of 10 kg m s−1 generates a peak pressure of ∼2 GPa on 12.5-mm-diam anvils. The pulse duration increases from 280 to 380 μs as the drop-weight momentum is increased from 10 to 60 kg m s−1. The highest pressure achieved in these experiments is 6 GPa.
Transport system for 9×12 in. substrates in a laboratory vacuum deposition system
Authors: Pargellis A. N. , Lake T. V.
Published: July 2002

A transport system has been built whereby a printed wiring board (PWB) panel, 22×30 cm (9×12 in.) in size and up to 3 mm (0.12 in) thick, is moved in a vacuum deposition system at speeds of 1.5 to 150 cm/min (0.65 to 60 in./min). The deposition system consists of a series of sputter stations for depositing copper metal at rates of 0.1 to 1.0 μm/min (4 to 40 μin./min). The panel is suspended at the top from a bar that has wheels that roll along a support rail. The bottom of the panel is constrained within a slot defined by two guide rails. Metal shields protect the roller assembly from ‘‘line-of-sight’’ deposition such as is encountered in evaporation and sputtering. Smaller panels can be accommodated either by modifying the suspension system or by mounting them in a frame of the above dimensions.
Low-frequency noise reduction in SQUID measurements using a laser-driven superconducting switch. Part B: Modulated inductance switching
Authors: Anderson J. T. , Cabrera B. , Taber M. A.
Published: July 2002

We describe a technique for substantially decreasing the noise in SQUID measurement applications which are intrinsically low frequency or dc and thus fall below the 1/f knee in the SQUID noise energy spectrum. Direct switching of the SQUID input leads at a frequency above the 1/f knee, a technique detailed in the preceding article [Anderson et al., Rev. Sci. Instrum. 60, xxx (1989)], extends white-noise floor to much lower frequencies with an accompanying loss of slew rate. For those applications where the loss of slew rate is unacceptable, we present in this article an alternate chopping technique which can preserve the original SQUID slew rate with a loss in the low-frequency signal-to-noise energy ratio of about a factor of four.
Ultrashort light pulses
Authors: Simon John D.
Published: July 2002

This article reviews the generation and amplification of ultrashort laser light pulses, τp≤10−12 s. Current methods for generating optical pulses in the ultraviolet, visible, and infrared regions of the spectrum are described. Devices based on mode-locking techniques, as well as various novel sources for ultrashort light pulses, are examined. In addition, recent advances in using fiber optics to shape and compress optical pulses are presented. Optical amplifiers that have been developed to generate kilowatt and higher peak powers at a variety of repetition rates are described and compared. In the last section of the paper, various nonlinear optical techniques that have been developed to extend the tuning range of ultrashort laser pulses are briefly discussed.
Time-resolved x-ray measurement system for studying the lattice deformation of semiconductor crystals under laser irradiation
Authors: Kawado S. , Kojima S. , Ishikawa T. , Takahashi T. , Kikuta S.
Published: July 2002

This article describes the outline of a time-resolved x-ray measurement system developed at the Photon Factory to study the pulsed laser annealing of silicon crystals. This system consists of a triple-crystal diffractometer, Q-switched Nd:YAG laser, and two fast detector electronics using a plastic scintillation counter, and enables us to examine the time-change behavior of nearly intrinsic rocking curves under laser irradiation with a time resolution of about 50 ns. The difference in the recovery from lattice deformation between 1.06-μm laser annealing and 0.53-μm laser annealing is clarified.
6-m TGM implementation at the Wisconsin Synchrotron Radiation Center (SRC)
Authors: Cole R. K. , Perkins F. K. , Brodsky E. L. , Filipponi A. , Korpella E. , Mancini D. C. , Pruett C. H. , Wallace D. J. , Welnak J. T. , Zanini F.
Published: July 2002

We recently commissioned the SRC/Vanderbilt University 6-m toroidal grating monochromator beamline. The problems with mirror heating, signal normalization, monochromator control, and scattered light reduction have led to several innovations on this line, making for a better user interface and adding to the stability and reliability of the final image. We discuss these innovations, and how they affect the user. They include a built-in laser alignment system, a sapphire windowed gate valve, entrance mirror temperature stabilization, computer automation and control, a beam-chopper, and the capability of real-time monitoring of the photon flux during the experiment. We have used noble gas resonance lines to carefully characterize the wavelength resolution of the beamline as a function of energy over a range of beamline parameters. The results demonstrate that by limiting the horizontal width of the image at the slits, and by masking outer portions of the gratings, the flux/bandwidth ratio can be improved at the points where the exit slit location does not coincide with the Rowland circle. These same resonance lines, in conjunction with accurate measurements of the grating rotation angle as a function of scan-drive displacement, are used to correct for imperfections in the surface of the drive-flat and thus obtain a precise and accurate determination of wavelength versus scan-drive displacement.
Construction and operation of the multipole wiggler, MPW♯16, at the Photon Factory
Authors: Shioya T. , Yamamoto S. , Sasaki S. , Katoh M. , Kamiya Y. , Kitamura H.
Published: July 2002

A high-field multipole wiggler (MPW♯16), which was composed of hybrid-configured permanent magnets, was completed and installed in the 2.5-GeV Photon Factory (PF) storage ring as the third insertion device. Compared to the synchrotron radiation from the bending magnet on the PF ring, the radiation from the MPW♯16 has two orders higher brilliance in the x-ray region and three orders higher in the vacuum ultraviolet region. The stable operation of the storage ring coupled with the MPW♯16 has been confirmed through various machine studies.
First observations of phonon dispersion curves with inelastic x-ray scattering (invited)
Authors: Burkel E. , Dorner B. , Illini Th. , Peisl J.
Published: July 2002

The first direct observations of phonon excitations with x rays were carried out with the inelastic x-ray scattering spectrometer ‘‘INELAX’’ at HASYLAB of DESY, Hamburg. A Be single crystal and a diamond were used to measure the dispersions of longitudinal phonons in the acoustic and optical range in the [00ξ] direction.
High power microwave line with arbitrary impedance matching capability for plasma applications
Authors: Ganguli A. , Baskaran R. , Naidu P. A. , Raju G. V. R.
Published: July 2002

The details of a high power microwave transmission line developed for plasma applications are presented. The line operates at 2.45 GHz and can handle about ≲1 kW of cw microwave power with about 15%–20% insertion loss. A special feature of the line is its wide range impedance matching capability for operating under different load conditions. A coaxial triple stub tuner capable of handling high power cw microwaves was especially developed for this purpose. Detailed design considerations for the tuner and other critical components like the high power vacuum seal are presented.
An improved gas puff design for a Z-pinch x-ray source
Authors: Badaye M. , Stemprok R. , Gupta R. P.
Published: July 2002

An analysis of the magnetically induced, compression gas puff has led to a new design which greatly enhances the performance of the Z-pinch, soft x-ray source incorporating this concept. It is shown that the improved gas puff design has resolved the problems related to the nonuniformity of the annular slit opening in the gas puff nozzle and to the poor coupling of the induction coil current with the gas in the nozzle plenum. Suggestions are made to further improve the design in order to reduce nozzle erosion due to arcing from the high-current Z-pinch discharge.
Construction of a liquid He cryostat insert for high spatial resolution photoluminescence experiments on GaAs
Authors: Visser E. P. , Giling L. J.
Published: July 2002

A high-spatial resolution focusing and translation mechanism for photoluminescence experiments at 4.2 K on GaAs is demonstrated. The restrictions posed on the obtainable spatial resolution of conventional setups, where the focusing lenses are situated outside a liquid He cryostat, were circumvented by building the microscope objective and the translation stage into the cryostat. The objective and the translation stage are functioning at 4.2 K and are controlled from outside the cryostat. A spatial resolution of 1 μm was obtained. Up to eight crystals can be mounted and interchanged during an experiment without returning to room temperature. A horizontal translation table was constructed based on two separate spring systems for each direction of translation. Thermal leakages were minimized so that a hold time of 20 h for a conventional liquid-He-bath cryostat was reached.
Fully automated manipulator for Sanger dideoxy sequencing reaction
Authors: Sakabe Munechika , Kobayasi Kiyosi , Segawa Osamu , Saitoh Masamitsu , Soeda Eiichi , Wada Akiyoshi
Published: July 2002

We have succeeded in developing a fully automated machine to handle the Sanger dideoxy sequencing reactions. The robot is constructed of a pipetter unit, reaction unit, tip storage unit, and reagent storage unit. The pipetting precision is found to be 0.037 in terms of standard deviation at the dispensing volume of 0.95 μℓ, and the cross contamination between different sample solutions in the course of pipetting is reduced to 0.005 μℓ. Satisfactory results are obtained in temperature control and in the suppression of liquid evaporation, and a precision equivalent to a high level of manual manipulation is realized in DNA sequencing analysis.
Microfabricated nonoptical chemical sensors
Authors: Zemel Jay N.
Published: July 2002

In the past two decades, there has been growing interest in new types of chemically sensitive devices based on the photolithographic batch processing employed by the semiconductor industry. This article reviews several classes of chemical sensors including electrochemical devices based on potentiometry and amperometry, chemical sensors based on thermal processes, and acoustic wave devices. Devices based on dielectric property variation, the core of spectroscopy, are not treated here since many reviews of these topics are available. The article touches on the device principles and reviews some of the more recent developments in each class.
High sensitivity photoacoustic spectrometer for variable temperature solution studies
Authors: Beitz James V. , Doxtader M. M. , Maroni V. A. , Okajima S. , Reed D. T.
Published: July 2002

A single beam, dual cell, photoacoustic spectrometer has been developed for use with solutions from ambient temperature to the boiling point of the liquid. The optical absorbance sensitivity of the apparatus is 3×10−7 absorbance units per cm (base 10 logarithm, 1000 pulse average, 13 mJ/pulse) for solutes in aqueous solution at 90 °C, using an excimer-pumped dye laser as the light source. The cell assembly is designed to thermally isolate the acoustic detector and prevent evaporative loss of the solvent. High accuracy subtraction of solvent optical absorption is achieved using preamplifiers with continuously variable gain, matched electrical bandpass filters, and a high common mode rejection ratio differential amplifier. Design constraints resulting from factors such as the temperature dependence of solute photoacoustic signal amplitude are discussed and results of experimental tests probing some limits of the identified constraints are presented. A data analysis method is described which substantially reduces the effect of transient acoustic interference from suspended particles in sample solutions.
A top loading, very low-temperature, X-band, microwave spectrometer
Authors: Lin M. Z. , Zhao Z. , Shen Y. H. , Ketterson J. B. , Qian Y. J. , Sarma Bimal K.
Published: July 2002

We describe modifications to an Oxford Model TLE 400 dilution refrigerator permitting measurements of microwave response at X-band. Coupling to the cavity is accomplished with a Gordon coupler involving a 1/4-in. access hole and a 1/4-in. dielectric rod running coaxial with the circular waveguide which feeds the microwave cavity. The rod extends through a vacuum load lock and may be removed. A stainless-steel sample insertion rod may then be inserted allowing top loading of specimens directly into the cavity; the samples themselves are attached to a copper fixture, involving a combination of left- and right-hand threads which may be reversibly screwed into and out of the bottom of the cavity. Preliminary surface impedance studies of s-wave superconductors (Sn, Zn, and In) and the heavy fermion UPt3 superconductor have been performed with this spectrometer.
Characteristics of the negative ion beam extracted from an LBL multicusp volume source
Authors: Debiak T. W. , Solensten L. , Sredniawski J. J. , Ng Y. C. , Heuer R.
Published: July 2002

This work encompasses a study of the beam position, profile, and emittance of a Lawrence Berkeley Lab (LBL) multicusp volume source. The study includes a comparison of different extraction geometries with single- and multiple-hole apertures. Our work is currently based on single-gap extraction and acceleration. These experiments are the first of a planned series of studies with various extractor geometries. The beam profile full width at half-maximum ranged from 5.7 to 10.2 mm at a position 69 mm from the emission aperture. Measurements of profile and position in the vertical direction indicate that the beam is significantly bent in the direction expected due to the field of the electron separation magnet. Phase space contour plots in the horizontal plane have been obtained for circular extraction apertures with a diameter of 1.0 and 2.0 mm, and a multiple-hole aperture with an overall diameter of 2.46 mm. Emittances were calculated to be as low as 0.0010 π cm mrad for the 1-mm aperture and 0.0014 π cm mrad for the 2-mm aperture. Emittances are not reported for the multiple-hole aperture due to the shape of the phase space contours; however, analysis of the data is in progress to provide a meaningful comparison of the single-hole and multiple-hole beam characteristics.
An area x-ray detector system based on a commercially available CCD-unit
Authors: Fuchs Heribert F. , Wu Dan Q. , Chu Benjamin
Published: July 2002

A two-dimensional x-ray detector has been developed by combining a fiber-optic face plate (FOFP) which was deposited with a thin layer of phosphor (Y2O2S:Tb), a high-quality camera lens, and a slow-scan fiber-optics (FO) bonded charge-coupled device (CCD) camera system. The detector showed good linearity of response to the incident x-ray intensity and good spatial linearity. It had an effective area on the phosphor screen of 31.5 mm× 47.2 mm. Low CCD dark count allowed up to about 30 min of continuous measurement. No radiation damage was detected, even for measurements of the synchrotron x-ray main beam. However, the detector quantum efficiency was low (∼25%), and the bonding between the FO and the CCD was very fragile, so that the chicken wire pattern produced by the bonded FO introduced a 5% error in detector sensitivity which was difficult to correct. However, such a detector with a non-FO-bonded CCD camera system instead of the FO-bonded CCD system should be ideal for extended x-ray absorption of fine structure (EXAFS) experiments.
Reproducible memory effect in the leakage current of epitaxial ferroelectric/conductive perovskite heterostructures
Authors: Watanabe Yukio
Published: July 2002

Leakage currents in epitaxial ferroelectric/perovskite-conductor heterostructures reproducibly show diode properties having hysteresis. The hysteresis appears in forward bias, which is positive for electron (n) type conductors and negative for hole (p) type conductors. The hysteresis is due to the increase of conductivity by the forward bias current, which exhibits the memory retention for more than an hour. The write and erase speeds of the diode and the origin of the effect are discussed.
Digital dielectrophoretic levitation
Authors: Tombs T. N. , Jones T. B.
Published: July 2002

In this article we describe a computer-controlled active feedback dielectrophoretic (DEP) levitator and its measurement capabilities for characterizing single particles and particle chains (20–500 μm in length). Edge detection using a linear array of photodiodes is employed and an adaptive controller updates the voltage required for stable levitation at a rate of 4.7 kHz. Rms voltage fluctuations are typically less than 0.2% of the levitation voltage. The most precise data to date for the effective dipole moment of conducting particle chains up to four in length are presented along with experimental measurements of the effective dipole moment of two particle chains of unequal size as tests of accuracy and precision of the apparatus.
Absolute calibration of a retarding-potential Mott polarimeter
Authors: Oro D. M. , Butler W. H. , Tang F. -C. , Walters G. K. , Dunning F. B.
Published: July 2002

A novel technique for absolute calibration of a Mott polarimeter is described that makes use of electrons of accurately known polarization obtained through chemiionization reactions involving spin polarized He(2 3S) metastable atoms. This technique has been used to calibrate a compact retarding-potential Mott polarimeter and values of the effective asymmetry (Sherman) function Seff are presented for both gold and thorium target foils under a variety of operating conditions.
A 2-m grazing incidence monochromator with a silicon-carbide-based master grating for undulator radiation
Authors: Muramatsu Yasuji , Kato Hiroo , Maezawa Hideki , Harada Tatsuo
Published: July 2002

Performance of a 2-m grazing incidence vacuum ultraviolet (VUV)/soft x-ray monochromator was evaluated with silicon-carbide-based master grating of 1200 lines/mm groove density that was newly developed for use of undulator radiation. Incident power density on the grating surface was as high as 120 mW/mm2. Surface observation of the grating after the test operation showed that the periodic structure and reflective surface of the grooves were well preserved, except for slight degradation of the groove edges, even though no active cooling system was equipped. Photon flux was of the order of 1012 photons/s. Efficiency of second-order diffraction relative to the first-order diffraction was 20%–50%. Resolving power of 2200 was achieved at 244.4 eV for 5-μm exit slit width.
Upgrade and recent performance of 24-m SGM at the Photon Factory
Authors: Masui S. , Shigemasa E. , Yagishita A.
Published: July 2002

Performance of a 24-m spherical grating monochromator is described. This beamline is composed of a prefocusing toroidal mirror, a spherical grating monochromator with a movable exit slit and refocusing mirrors. With a 600-ℓ/mm grating and 50-μm slit openings, the resolving power of 5700 was achieved at 45 eV in good agreement with the theoretical prediction. The second-order contribution was estimated from Ne 2p photoelectron yield to be less than 40% of the first order for the spectral range of 30–90 eV and less than 11% for that of 90–160 eV with the grating of 600 ℓ/mm. As to the grating of 1800 ℓ/mm, it was estimated to be less than 31% for the spectral range of 80–90 eV and less than 11% for that of 90–150 eV. A photon flux of ≂5×1012 photons/s is obtainable at 70 eV for the grating of 600 ℓ/mm and that of ≂1012 photons/s is obtainable at 150 eV for the grating of 1800 ℓ/mm.
Microinterferometer for the hard x-ray range
Authors: Snigirev A. A. , Suvorov A. Yu.
Published: July 2002

The properties of a multibolck microinterferometer (MI) treated as a collimating optic element have been theoretically analyzed. It is shown that under certain conditions the MI rocking curve gets much narrower compared with that of a single crystal. The numerical calculations of the rocking curves for (422) reflection and wavelength λ=0.5 Å are demonstrated. If the number of MI blocks are 20 then the rocking curve contracts by 35 times.
Characterization of platinum–carbon, tungsten–silicon, and tungsten–B4C multilayers
Authors: Yamashita K. , Watanabe M. , Matsudo O. , Yamazaki J. , Hatsukade I. , Ishigami T. , Takahama S. , Tamura K. , Ohtani M.
Published: July 2002

Multilayers of Pt/C, W/Si, and W/B4C have been developed as a reflector and dispersive element to be applied to the beamline optical system of the synchrotron radiation (SR) in 1- to 20-A region. Pt/C(2d=105 A, N=10) overcoated with Pt(d=100 A) is useful in a glazing incidence optics, which makes it possible to extend the wavelength region to the shorter side at the fixed incidence angle. W/Si(2d=53 A, N=200) and W/B4C(2d=31 A, N=300) are utilized as a dispersive element of double-crystal monochromator (DXM). The second order of Bragg reflection of W/Si is matched to the first order of KAP(2d=26.6 A) crystal. The characterization of these multilayers was carried out by using characteristic x rays and monochromatized SR in 1.5–8 keV. DXM was made of a combination of W/Si and KAP and a pair of W/B4C. Multilayers are used as the first crystal to protect the damage of the crystal caused by the strong irradiation of SR. A pair of W/B4C is aimed at getting high throughput. The energy resolution of these combinations was evaluated with Na–K absorption edge of NaCl around 1.07 keV, which was a bit poor compared to a pair of beryl crystals.
X-ray camera for high- and small-angle x-ray diffraction studies of the drawing and annealing of polymers at Daresbury Synchrotron Radiation Source
Authors: Mahendrasingam A. , Fuller W. , Forsyth V. T. , Oldman R. J. , MacKerron D. , Blundell D. J.
Published: July 2002

A purpose-designed x-ray fiber diffraction camera has been constructed in the Keele University Physics Department to be used at the SERC Daresbury Laboratory Synchrotron Radiation Source. The camera allows time-resolved studies of the change in both the high- and low-angle diffraction patterns during drawing and annealing of polymer films to be recorded. Drawing of the films is achieved by two opposed stepper motors which allow films to be drawn uniaxially in both directions. The temperature of the sample environment can be controlled to within 1 °C by a radio spares proportional, integral, and derivative (PID) controller. Diffraction patterns can be recorded on the Enraf-Nonius TV FAST detector or on photographic film. Exposure times using the FAST detector are typically 5 s, representing a gain of approximately a factor of 5 over photographic film. The FAST detector has a further advantage over photographic film in that essentially an unlimited number of diffraction patterns can be recorded end-to-end while a structural transition is being followed. A video camera is incorporated to allow the variation in the gross appearance of the specimen to be recorded during drawing and annealing and to be related to the variation in the diffraction pattern. The application of the camera in the study of drawing and annealing of poly (aryl-ether-ether-ketone) (PEEK) is described.
High-energy resolution in x-ray scattering for inelastic studies of excitations in condensed matter
Authors: Burkel E.
Published: July 2002

Very-high-energy resolution measurements using x rays can be achieved by extreme backreflection (Bragg angle close to 90°) from perfect crystals. This technique, combined with the high intensity of x rays emitted by the HARWI wiggler at DORIS, DESY Hamburg, allowed the development of the instrument INELAX for inelastic scattering experiments. Recently, the high-energy resolution of 9 meV could be achieved and the instrument proved to be an excellent tool to investigate collective excitations in condensed matter. Energy transfers from 10 meV to 5 eV and wavevectors over the whole reciprocal space are accessible.
Performance of an x-ray optical time delay line with synchrotron radiation
Authors: Joksch Stefan , Graeff Walter , Hastings Jerome B. , Siddons D. Peter
Published: July 2002

We describe pump-probe experiments in the x-ray region using synchrotron radiation to supply both the pump and probe beams. The time between pump and probe is adjustable on the nanosecond time scale by means of an optical delay line operating in the x-ray region. With the ‘‘third generation’’ sources presently under construction around the world it should be practicable to study optical excitations using similar techniques to those described here. The initial studies we describe were carried out at the National Synchrotron Light Source. A 30-μm-thick silicon [110] crystal was irradiated by white light from a bending magnet. The radiation passing through this sample was monochromated by two silicon [660] reflections in such a way that the monochromatic beam was directed onto the first surface of the thin crystal sample. The surface of this thin crystal was probed by recording the symmetric (220) reflexion 2.78 ns after illumination by the white beam. Techniques for overcoming the background problem resulting from scattering of the white beam by the sample crystal are discussed.
X-ray beam sheet deflection for liquid surface spectrometry
Authors: Wulff M. , Als-Nielsen J.
Published: July 2002

An x-ray beam incident on a liquid surface at glancing angles may be specularly reflected (XR), diffracted (GID), or yield fluorescent radiation (GIF). The three mechanisms, encompassing liquid surface x-ray spectrometry, give complementary information about the liquid surface structure. In common is the incident monochromatic beam: It has the shape of a downward sloping thin sheet with the sheet normal and the propagation direction ideally spanning a vertical plane. Methods to produce such a beam from a horizontal, polychromatic synchrotron radiation beam are discussed. For a high brilliance undulator source the simplest solution turns out to be Bragg reflection from a single tilted monochromator crystal in Laue geometry.
A shutter design for time domain studies using synchrotron radiation at the Advanced Photon Source
Authors: Norris J. R. , Bowman M. K. , Chen L. , Tang J. , Thurnauer M. C. , Knapp G. S. , Montano P. A.
Published: July 2002

In general, a variable repetition rate of the x-ray bunches is needed to explore time domain problems using x-rays. In some instances, the results of several hundreds or thousands of x-ray pulses must be averaged requiring the sample to be in the same time-dependent state each time the monitoring pulse strikes. The important point is that before a second x-ray pulse hits the sample, the system must return to its initial relaxed ground state prior to another spectrum pulse in order to prepare the same excited state again. Our key design principle employs a subsonic, rotating mirror whose period is slaved to the synchrotron intrapulse period. The synchrotron x-ray bunches will be reflected a distance of about 2 m to a narrow 0.5-mm slit just in front of the sample. A mirror rotating at a low 7500 rpm (125 Hz) is sufficient to select a single synchrotron pulse for the Advanced Photon Source. The very precise phase stability required by this method is currently available in rotating mirror devices for laser scanning.
Polarization analysis in magnetic x-ray scattering using 45° linearly polarized x-ray incident beam (abstract)
Authors: Mori Koichi , Namikawa Kazumichi , Funahashi Yoshisato , Higashi Yasuo , Ando Masami
Published: July 2002

An instrument for polarization analysis in magnetic x-ray scattering is now being commissioned. Its side view is shown in Fig. 1, and inserts in the figure show the polarization state of x rays at various spots. This system adopts no flipping of the magnetic field over a hard magnetic material which needs large saturation magnetization. Its basic components are (a) a polarizer monochromator which converts the horizontal polarization into 45° one, (b) a two-axis diffractometer having a magnet for a sample, and (c) a polarization analyzer crystal. Furthermore, the magnet accommodates a cryostat for cooling a sample and a solid state detector covered with a magnetic shield cap for measuring fluorescent x rays. The electric vector of linearly polarized x rays is rotated through scattering from a magnetic sample because both magnetic scattering amplitudes, σ0 to σf and π0 to πf, are different from those of the electric one. It will be therefore possible to investigate the spin-resolved unoccupied density of states by analyzing polarization of the magnetically scattered x rays. Polarization analysis of a Gd metal at L edges is now under way.
Analytical corrections for dead time effects in the measurement of time-interval distributions
Authors: Coates P. B.
Published: July 2002

Corrections for the effects of instrumental dead time in the measurement of time-interval distributions are presented for the idealized cases of paralyzable and nonparalyzable detection systems. It is assumed that signal pulses occurring within the measurement cycle following each initial stimulus applied to the system under study, referred to as the source, are random and uncorrelated. Usually the total number n of pulses from the source in each measurement cycle is also random and is given by a Poisson distribution. However, correction equations are also developed for those cases where the source distribution S(n) may be represented by an arbitrary but known probability distribution. An example of their application in the field of time-of-flight mass spectrometry, where the distribution consists of peaks corresponding to different masses, is given. The limitation of the method arising from the increase in statistical noise at high count rates is analyzed.
New possibilities of the x-ray standing wave method in multiple diffraction of synchrotron radiation
Authors: Kazimirov A. Yu. , Kovalchuk M. V. , Kharitonov I. Yu. , Samoilova L. V. , Ishikawa T. , Kikuta S.
Published: July 2002

Results of measurements of the reflected beam intensity and photoelectron yield under conditions of dynamical 111/220 diffraction of synchrotron x-ray radiation are presented. The experiments were carried out on beam lines 15C and 14B at the Photon Factory. Two possible multicrystal arrangements were used for the preprocessing of the incident beam. In the first one, a double-crystal Si (111) monochromator was used for monochromation and collimation of the x-ray beam in the vertical plane and a Si (220) channel-cut crystal was used for collimation in the horizontal plane. The second crystal arrangement is based on a (111)-oriented Si crystal adjusted for a six-beam Laue diffraction condition. The anomalously transmitted (μt/γ0 ≊ 40) beam was used as an incident beam in the x-ray standing wave measurements. The angular dependence of the total photoelectron yield was measured using a gas flow proportional counter.
Calculation of surface x-ray diffraction patterns in total external reflection conditions
Authors: Casalis L. , Lenardi C.
Published: July 2002

The high brilliance of the new generation of synchrotron radiation sources improves the grazing incidence x-ray diffraction techniques and leads to great advances in the determination of crystal surface structures. The evaluation of the diffraction pattern intensity can be obtained in the distorted-wave approximation introduced by Vineyard. In conditions of total reflection, typical penetration depths are about 50 Å and only the atoms in the near-surface layers interact with the electric field and produce the diffraction pattern. This model is the ground for a simulation code developed in order to calculate the diffracted peaks intensity of reconstructed and/or relaxed surfaces. An example of application, the Au (110) (1×2) reconstructed surface, is given. The intensity and the position of the diffraction peaks are determined for different values of the azimuthal angle and for different diffraction orders. The program takes into account the parameters of the beamline Advanced Line for Overlayer Interface and Surface Analysis (ALOISA) which will be available at the storage ring ELETTRA in Trieste.
Small-angle x-ray scattering/diffraction system for studies of biological and other materials at the Stanford Synchrotron Radiation Laboratory (abstract)a)
Authors: Wakatsuki S. , Hodgson K. O. , Eliezer D. , Rice M. , Hubbard S. , Gillis N. , Doniach S. , Spann U.
Published: July 2002

A versatile small-angle x-ray diffraction/scattering system has been developed at Stanford Synchrotron Radiation Laboratory for studies of biological and other materials. The system includes two sets of collimation slits separated by an ionization chamber, a sample holder cooled by a circulation bath, a vacuum/He scattering path after the sample holder and a detector, either a linear one-dimensional position-sensitive proportional counter or a position-sensitive quadrant detector. Data aquisition is controlled by a VAXstation through a CAMAC interface. Menu-driven data acquisition and on-line analysis software has been developed. The system can be used to collect small- to intermediate-angle x-ray scattering and diffraction data. Monochromatic, anomalous, and time-resolved diffraction/scattering experiments are possible. A time-resolved spectrophotometer using photodiode arrays has also been developed for simultaneous measurements of optical absorption spectra and x-ray scattering/diffraction.
High-temperature/ultrahigh vacuum compatible probe station
Authors: Santos Edval J. P.
Published: July 2002

This note describes the design and testing of a simple ultrahigh vacuum (UHV) compatible probe station, which also works as a substrate heater. This probe station has been tested up to temperatures as high as 650 °C inside a UHV chamber, whose base pressure is better than 2×10−10 Torr.
E-plane horn excitation of slow wave structures for obtaining high-density electron cyclotron resonance plasmas
Authors: Baskaran R. , Jain S. K. , Ramamurthi S. S.
Published: July 2002

This paper describes a new method of exciting slow wave structures (SWS) for obtaining high-density electron cyclotron resonance plasmas. The electric field component corresponding to the slow wave mode (SWM) of SWS is excited by an E-plane horn antenna. The special features of the microwave transmission line are the stable tuning for a given antenna and no requirement for water cooling on any of the components. Two types of SWS, a helical coil and a slotted line antenna, are studied, and the experiments are carried out in nitrogen and argon. The plasma producing capability is examined for these systems in the region wce,wpe≳wrf, where wce, wpe, and wrf correspond to electron cyclotron, plasma, and microwave frequencies, respectively. A high-density, large-diameter plasma (n0∼5×1011 cm−3; diameter ∼8.0 cm) could be obtained and the plasma could be maintained in the region 1≤wce/wrf≤2.
A rheometer with two-dimensional area detection for light scattering studies of polymer melts and solutions
Authors: Nakatani Alan I. , Waldow Dean A. , Han Charles C.
Published: July 2002

A combined rheometer and light scattering photometer has been constructed to examine the light scattering behavior of polymer melts and solutions under the influence of a simple shear field. The device utilizes a special lens system and a two-dimensional charge-coupled device array detector which has not been used previously in an apparatus of this type to quantitatively measure the scattering intensity as a function of shear rate. The accessible q range of the instrument is from 3.75×10−4 to 3.0×10−3 nm−1 (2.2°–17.4° scattering angle, with λ=632.8 nm). The rheometer utilizes a cone and plate geometry to generate the shear gradient and is capable of measuring torque (1.8 N m maximum) and normal forces (50 N maximum). An 8% solution of a 50:50 polystyrene/polybutadiene blend in dioctyl phthalate was used to test the apparatus. This sample shows a shear-induced mixing behavior which is consistent with previous measurements by other investigators.
Implementation of a dual linear image sensor for measurements of transient absorption spectra in the picosecond time regime
Authors: Nagamura T. , Nakamura N. , Ibuki K. , Nakayama T. , Hamanoue K.
Published: July 2002

In order to enhance the picosecond absorption spectroscopy, a dual linear image sensor was used for simultaneous intensity measurements of the probing and reference lights by a single polychromator. This detector enabled us to record a fairly well stabilized transient absorption spectrum, and its signal-to-noise (S/N) ratio was much improved. Although the base line spectrum (not averaged) recorded by using a broadband continuum (a self-phase modulation light generated by focusing the fundamental light pulse from a ruby laser into a BK-7 glass block) revealed that the base line fluctuation and drift were less than ±0.04 absorbance units, the five-times spectral average gave rise to the base line fluctuation and drift of less than ±0.01 absorbance units. For an absorption spectrum recorded at a slit width of ≤0.2 mm, the spectral resolution was found to be better than that recorded by a commercial spectrophotometer with a bandwidth of 1.0 nm.
Primary electron drift in a volume hybrid multicusp H− ion source
Authors: Courteille C. , Bruneteau J. , Valckx F. P. G. , Sledziewski Z. , Bacal M.
Published: July 2002

A new, large, hybrid volume negative ion source is described. Observations of curvature and grad B primary electron drift in the multicusp magnetic field are reported. The direction of the electron drift changes from one filament to the neighboring one, because of the change in the direction of the magnetic field. For a given discharge current the extracted negative ion current and the plasma density at the center of the extraction region are affected by the direction of the primary electron drift of the active filaments. It was shown, however, that the negative ion current is controlled by the plasma density at the center of the extraction region. A trajectory calculation, effected in the guiding center approximation, allows to estimate the average drift velocity.
High rate dry etching of InGaP in BCl3 plasma chemistries
Authors: Ren F. , Hobson W. S. , Lothian J. R. , Lopata J. , Caballero J. A. , Pearton S. J. , Cole M. W.
Published: July 2002

A remarkable increase in InGaP etch rate in electron cyclotron resonance BCl3 discharges is observed as the microwave power is increased from 250 W (etch rate ∼500 Å/min) to 1000 W (etch rate ∼8000 Å/min). The surface roughness measured by atomic force microscopy decreases from 36 nm at 250 W to 2 nm at 1000 W. The high ion flux incident on the InGaP at high microwave powers appears to remove InClx species by sputter-assisted desorption and prevents formation of the nonstoichiometric In-rich surfaces generally observed with Cl2-based dry etching using conventional reactive ion etching.
Modeling of the electron cyclotron resonance sulphur source
Authors: Baskaran R. , Heurtier J. M. , Hill C. E.
Published: July 2002

A MINIMAFIOS-type electron cyclotron resonance ion source is being used for S12+ injection into the CERN injector chain for physics experiments at the Super Proton Synchrotron. In this article, charge state distribution spectra obtained from the source are studied and, in addition, the possibility of improving the source performance by various methods is explored.
Operational characteristics of the impregnated-electrode-type liquid-metal ion source with multiple tip and reservoirs
Authors: Gotoh Y. , Yoshida K. , Kawai T. , Fukayama N. , Ogata Y. , Tsuji H. , Ishikawa J.
Published: July 2002

A new type of impregnated-electrode-type liquid-metal ion source, which eliminated the heating problem in the previous source, has been developed with multiple tip and reservoirs (TAR’s). In the present ion source, the TAR’s are connected electrically in series by modifying the TAR holding system. In order to achieve uniform heating of the TAR’s, the materials of the knife-edged electrodes, which introduce the heating current to the TAR’s, were examined. Tantalum electrodes exhibited better results as compared with the conventional Mo electrodes. Both of the two TAR’s could be heated up to 700 °C with a heating power of 200 W. The maximum indium ion current of 9.1 mA was obtained from the four-TAR source with 40 emission points. Since the present ion current was limited by the current capacity of the extraction power supply, an ion current of more than 10 mA will be expected with a larger power supply. The results indicated that an ion current approximately proportional to the number of the emission points was obtained. This kind of ion source could be used as a general ion source in materials science.
Role of a biased electrode in the first stage of electron cyclotron resonance multicharge ion source
Authors: Matsumoto K.
Published: July 2002

The fundamental physics of the beneficial effect of a biased electrode, positioned in the first stage, on the output ion currents have been investigated on the basis of the measurements of plasma parameters. Conventional Langmuir probes were used for diagnostics in both stages. It was found that the plasma space potential in the first stage changes with the variation of disk potential and consequently a potential difference occurs between the first stage and the second one. Without the first stage plasma, the beneficial effect was also obtained when negative potential was directly applied to the first stage chamber wall. Probe measurements showed that the electron density and temperature in the second stage increased with the application of negative potential. It was suggested that the beneficial effect is mainly caused by the improvement of the electron confinement in the second stage.
Parametric study of an x-ray preionizer with plasma cathode
Authors: Bollanti S. , Di Lazzaro P. , Flora F. , Giordano G. , Letardi T. , Schina G. , Zheng C. E.
Published: July 2002

The construction characteristics and the performances of an x-ray diode working at 200 Hz are described. The temporal behavior of both the plasma cathode emission and the diode discharge has been studied, including the measurements of vacuum effects on the repetition rate and lifetime capability, preionization versus electrical features, and ionization density versus dosage. This simple and low-cost x-ray diode has been used to uniformly preionize a half-liter XeCl laser, delivering an output laser energy of 800 mJ/shot at a 100 Hz repetition rate.
Falling cylinder viscometer end correction factor
Authors: Park N. A. , Irvine T. F.
Published: July 2002

A simple superposition technique is utilized to account for the end effects of a flat ends falling cylinder viscometer. The technique is only applicable for Newtonian fluids. The method consists of adding the pressure and shear forces and wall correction factor of a falling disc to the sidewall shear solution of a cylinder of infinite length. The results agree within 0.6% with a recently reported numerical solution which considered the total flow field around the cylinder and whose calculated end correction factor was determined by experiment to be accurate within 0.5%.
Scanning polarization force microscopy: A technique for imaging liquids and weakly adsorbed layers
Authors: Hu Jun , Xiao Xu-Dong , Salmeron Miquel
Published: July 2002

The atomic force microscope is used to measure dielectric polarization forces on surfaces induced by a charged tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using polarization forces we have been able to image liquid films, droplets, and other weakly adsorbed material.
Lasers and light-emitting diodes as sources for fixed-wavelength magneto-optical phase modulated ellipsometry
Authors: Callegaro Luca , Puppin Ezio
Published: July 2002

Fixed-wavelength magneto-optical measurements of hysteresis loops based on phase modulation techniques is a standard method of investigation for thin ferromagnetic films and multilayers. We show that the most common light source employed, i.e., the multimode 632.8 nm HeNe laser, has very poor stability properties which strongly limit the overall sensitivity. Solid state diode lasers constitute a good alternative for immediate replacement. New generation, high luminosity light-emitting diodes are an excellent alternative which requires only minor adjustments in existing setups.