bluuebunny/crossref_metadata_2025 huggingface dataset:
A drop-tube apparatus to promote spherically symmetric evaporation and combustion of unsupported droplets
Authors: Wang D. F. , Woo J. S. , Shaw B. D.
Published: July 2002

Fluid-mechanical aspects of a unique drop-tube apparatus to promote spherically symmetric evaporation and combustion of freely falling droplets are discussed. Design of the apparatus is based upon the principle that gravitationally induced pressure gradients in gases may be significantly reduced by accelerating the gases with properly contoured tubes. Droplets traveling with the gases will experience greatly reduced buoyancy and forced convection environments, promoting spherical symmetry. For specification of tube contours, the Navier–Stokes and continuity equations are recast into a vorticity-stream function formulation and solved numerically with pseudospectral methods. Axisymmetric tube contours which produce desired velocity and pressure fields are found, and implications for designs and limits of experimental apparatus are discussed.
Cryostat to provide a solid deuterium layer in a plastic shell for the Gekko XII glass laser system
Authors: Norimatsu T. , Ito H. , Chen C. , Yasumoto M. , Tsukamoto M. , Tanaka K. A. , Yamanaka T. , Nakai S.
Published: July 2002

A system to provide a liquid or solid deuterium shell target with a plastic ablator for laser implosion experiments was developed. The system is capable of filling a plastic capsule with deuterium gas of 11 MPa at room temperature at the firing position in the target chamber. Then, the target is cooled down to a cryogenic temperature to form a uniform liquid or solid fuel layer inside without exposing it to the atmosphere. Details of the system, tensile strength of polystyrene shells at low temperature, and the residual vapor pressure in the central void of the target at the laser irradiation are described.
Process of optimization of the ECR CAPRICE sources (abstract)
Authors: Delaunay M. , Jacquot B. , Pontonnier M.
Published: July 2002

Axial exploration of the plasma in a multicharged electron cyclotron resonance (ECR) CAPRICE ion source was performed with a Langmuir probe and a thermocouple. Hot electron density profile is hollow at the center and the peaks of density are found near the electron cyclotron resonance zones. When the plasma density increases, the microwave heating occurs between the ECR zone and the upper-hybrid resonance. The axial electron density profiles appear to be modulated in space and the gaps between two current peaks equal to 1/2 of the injected wavelength. The CAPRICE ion source performances are achieved when the resonance zones coincide with the peaks of modulation of the electric field distribution in the plasma chamber. This process enables us to rationally optimize all the CAPRICE sources. These results could be explained by the presence of standing waves in the plasma cavity and the dominance of the transverse electromagnetic mode (TEM) when the plasma density increases. This article has been printed in its entirety (9 pages) in Nucl. Instrum. Methods Phys. Res. A 305, 223 (1991) in July and in the French patent No. B 10847.3 BM.
Optimization of the cyclotron arc ion source mode control
Authors: Kutner V. B. , Tretyakov Yu. P. , Sukhov A. M. , Subbotin V. G. , Kasyanov A. A. , Rybin V. M.
Published: July 2002

Formulation and solution of the problem of the U-400 cyclotron arc ion source mode control optimization are considered. The optimization criterion is formulated as follows: to get the preset or maximum beam current in a limited range of the discharge and sputtering parameters. The ion source mode control is fulfilled by six input parameters variation. The algorithms of control are realized on the basis of CAMAC crate microprocessor controller and microcomputer compatible with IBM PC/XT/AT.
Secondary emission effects in an ion injector beam transportation system
Authors: Lobanov N. R. , Glazkov A. A.
Published: July 2002

Beam transportation evokes various secondary effects caused by beam-internal surfaces interaction. A number of effects connected with secondary emission of ion-electron type is considered. The cylindrical device is described which neutralizes beam spatial charge by the secondary electrons captured in the potential well of an ion beam. The conditions are discovered which lead to the following effect: secondary emitted electrons after drifting to the ion source form a virtual source of ions created due to the residual gas molecules ionization. These secondary low-energy ions drift together with the primary ions. The output part of the optical system where virtual ion source is localized works as a diverging lens, so at some distance the increased image of the local surface is formed and easily observed.
Development of the method to calculate duoplasmatron-type injectors using special nomogramms
Authors: Lobanov N. R. , Glazkov A. A.
Published: July 2002

Duoplasmatrons as injectors are widely used in various fields of science and technology. The method for calculation of duoplasmatron injectors based on analysis and generalization of theoretical and experimental data and provided with special nomogramms has been developed. Optimizing calculations of the main gas discharge and emission parameters of injectors allows quick determination of duoplasmatron and extractor dimensions starting with initial data on required ion beam properties. This method allows us to vary the working mode and to define the operational conditions. Nomogramms are presented for the determination of injector parameters when the working gas is hydrogen. The comparison of calculated and experimentally measured data reveals good agreement.
Laser-plasma ion sources (invited)(abstract)
Authors: Bykovsky J. A.
Published: July 2002

Basic principles of the operation of laser-plasma multicharged ion sources are given. Specific features of the interaction of high-intensity laser beams with solids are discussed, together with formation and main characteristics of multicharged ion beams, such as charge state distribution, angular distribution, emittance and time structure, and the influence of magnetic fields. Laser ion sources constructed for linear accelerators, synchrotrons, and cyclotrons are presented and experimental data are compared with theoretical considerations.
Laser ion sources for ion implantation (invited)(abstract)
Authors: Nevolin V. N.
Published: July 2002

The further progress in the employment of ion beams in technology depends on the improvement of the ion beam formation and transport systems. The range of the devices constructed now includes both weak current devices focusing the beam to less than 0.01 μm for the purpose of microelectronics, and powerful high current multibeam plants to modify metals and alloys. Among the wide range of such equipment are the universal devices able to generate the ion beams of different species without constructive changes. For these devices the laser plasma ion source is particularly helpful. This report presents a review of the 20-year study of the laser plasma, the parameters of laser plasma ion components, the means of the ion beam formation from laser plasma, as well as the results concerning the employment of laser plasma ion sources in analytical and technological equipment.
A chemically selective laser ion source for on-line mass separation
Authors: Scheerer F. , Fedoseyev V. N. , Kluge H.-J. , Mishin V. I. , Lethokov V. S. , Ravn H. L. , Shirakabe Y. , Sundell S. , Tengblad O.
Published: July 2002

Laser resonance ionization has been applied to ionize radioactive atoms released from thick ISOLDE/CERN targets. Laser light from pulsed dye lasers with a high repetition rate (10 kHz) was used for stepwise excitation and ionization. By this method, efficiency as well as the selectivity of the target/ion source system could be improved. In a series of off-line and on-line studies, the resonance ionization of elements with different ionization potentials, such as Yb (Ei=6.2 eV), Tm (Ei=5.8 eV) and Sn (Ei=7.3 eV), was investigated. For Yb, photoionization efficiencies of up to 15% have been measured. An efficiency of 0.2% was obtained for Sn at the on-line separator ISOLDE-3. However, this value can be improved by about two orders of magnitude using a transition to an autoionizing state at 59 375.9 cm−1.
Laser plasma ion source for intense heavy ion beams (abstract)
Authors: Shumshurov A. , Belajev G. , Dubenkov V. , Golubev A. , Henkelmann T. , Korschinek G. , Wolf B. , Hoffmann D. H. H. , Sharkov B.
Published: July 2002

In a series of experiments a laser plasma ion source for TA ions has been investigated. The main components were a 3-J CO2 laser, the laser ion source, a 3.2-m beamline, a 90° analyzing magnet, and an ion detector. The FWHM of the CO2 laser pulse was approximately 100 ns, the full duration was about 1 μs. The spot diameter was about 0.2 mm. The charge state distribution has been measured up to 10+. The plasma temperature has been calculated; recombination has been observed. The results will be shown and discussed in detail.
Development of negative heavy ion sources for plasma potential measurement
Authors: Sasao M. , Okabe Y. , Fujisawa A. , Fujita J. , Yamaoka H. , Wada M.
Published: July 2002

A plasma sputter negative ion source was evaluated for its applicability for measuring the plasma potentials in fusion devices. Both the beam current density and the beam energy spread are key issues for this application. The energy spectra of self-extracted Au− beams from the source were measured under the condition of a constant work function of the production surface. The FWHM increases from 3 to 9 eV monotonically as the target voltage increases from 50 to 300 V, independently from the target surface work function of 2.2–3 eV.
A bucket ion source with microwave plasma generator
Authors: Isaia G. , Becker R. , Leung K.
Published: July 2002

For the injection of a low-current (100 μA) high-brightness ion beam into an EBIS for subsequent ionization to very high-charge states, we have constructed a bucket-type ion source with the following specific features: a) microwave discharge plasma generator for long lifetime, b) isolated end flanges to allow for versatile ion species production by sputtering, c) SmCo magnets in 90° easy-axis rotation for the magnetic cusp fields, and d) large diameter for reduction of gas load to the UHV beamline of the EBIS. The extraction system has been optimized for maximum brilliance at an emission current density of about 2 mA/cm2. The extraction electrode consists of a spent washer of the sputtered material and of the long-lasting complex shaped main part. The design provides almost unchanged extraction optics until the washer is sputtered away.
Study of a microwave plasma cathode
Authors: Sun B. H. , Zhao W.
Published: July 2002

A microwave plasma cathode which will be used in CHORDIS source has been developed. In this paper, the structure and the working property of the cathode are described.
Inert gas ion beam formation at the tandem accelerator in Alma-Ata (abstract)
Authors: Arzumanov A. A. , Lysukhin S. N.
Published: July 2002

At the Cockroft–Walton-type 2×1 MV tandem accelerator in Alma-Ata, a method of obtaining inert gas ion beams by means of injection of neutral particles into a first accelerating tube has been developed. The procedure of injected beam intensity control is described. The neutralization cross section of He+ and Ar+ ions on the various gaseous targets has been estimated. Recently obtained results in comparison with analogous data obtained elsewhere are presented.
A 2.45 GHz multicusp ECR-ion source for neutral–beam diagnostics at the tokamak TEXTOR
Authors: Mank G. , Schorn R. P. , Hintz E. , Papenbreer R. , Keller H. M. , Korzec D. , Bansky J. , Engemann J.
Published: July 2002

In order to implement a new setup for neutral–beam activated impact excitation spectroscopy at the nuclear fusion experiment ‘‘TEXTOR’’ (Tokamak Experiment for Technology Oriented Research) a 2.45 GHz ECR multicusp ion source was built. Special emphasis was given to extract an intense He+-ion beam, which will be used in the forthcoming experiment. After neutralization the slow (2.2 × 107 cm/s, 1 keV) He atoms are injected into the tokamak plasma. Necessarily the atom beam has to have a small divergence. To optimize the extraction optics, calculations concerning the multihole extraction aperture have been made, taking different ECR-plasma parameters into account. The divergence shows a strong dependence on the extracted beam current density (≳5 mA/cm2) and the chosen optics. The ion source has to be operated in a pulsed mode (max. 5 kHz, duty cycle 50%) due to experimental requirements.
Performance of the rf-ion sources RIM for reactive and nonreactive gases
Authors: Freisinger J. , Heland J. , Krämer D. , Löb H. , Scharmann A.
Published: July 2002

A family of rf-ion sources for material processing RIM with ionizer diameters between 4 and 15 cm have been developed. Contrary to dc-ion sources, no filaments are needed in rf-discharges. By that, rf-ion sources are excellently suited to operate with reactive (and nonreactive) gases. The performance data of RIM sources for Ar, O2, and N2 are presented. The ion energies can be varied between 25 eV and 2.5 keV. The loss powers (by dissociation, eddy currents, radiation, etc.) have been determined. Probe measurements in the ion beam show the dependency of the beam divergence on the ion energy. Furthermore, ion beam effects (like charge exchange, beam neutralization by admission of electrons at ion energies <500 eV, etc.) were investigated.
An ECR microwave plasma cathode for ion sources with electrostatic reflex containment
Authors: Aubert J. , Farchi A. , Wartski L.
Published: July 2002

Ion sources for industrial reactors are used in a lot of applications such as ion beam sputtering or etching, ion assisted thin-film deposition, and surface treatment. They must satisfy several conditions; three of them are most important for reactive, especially oxygen, ion beams: (1) a lifetime longer than 100 h, (2) no deposition of an insulating film on the electrodes, (3) the electron energy must be chosen in a given range in order to control the fragmentation of the injected neutrals. The aim of this work was to compare the behavior of two ion sources having the same microwave plasma cathode, where the plasma is created by a microwave field (2.45 GHz) under an ECR condition: an electrostatic reflex ion source (ERIS) and a multipolar electrostatic reflex ion source (MERIS). Typically, we have produced an oxygen beam current of 83 mA with the ERIS structure and 118 mA with the MERIS structure, in 84 mm diameter for an extracted energy of 1200 eV. We have obtained broad uniform oxygen beams during about 100 h with both sources. A comparison between figures of the two structures is given, concerning the discharge characteristics, the extracted current, the yield, and finally, the extracted beam profile.
Ge+ ion extraction from a microwave ion source
Authors: Sakudo N. , Matsuo T. , Seki T. , Koike H. , Usami Y.
Published: July 2002

Preamorphization of a silicon substrate by Ge+ ion implantation is required for shallow doping of boron, which, in turn, is the key process to realize highly integrated semiconductor devices. However, Ge+ ions have not been stably extracted by conventional methods. Several chemical compounds of germanium, GeO, GeS, GeCl4, and GeF4, were supplied to a microwave ion source and the characteristics of their ion extractions were compared. The conditions for obtaining mass-separated Ge+ ions of more than 1 mA were found.
A plasma reactor based on the forced constricted type dc plasma jet and its application to thermal plasma processing in low pressure
Authors: Sakiyama Satoshi , Hirabaru Tetuya , Fukumasa Osamu
Published: July 2002

A reactor consisting of a forced constricted type dc plasma jet generator and a feed ring has been developed. In order to demonstrate the application feasibility of this reactor to low pressure plasma processing, the characteristics of the forced constricted arc in low pressure, and production of ultrafine particles of refractory materials (Al2O3, ZrC, TiC) are studied.
Field escalation effect in the pulsed ion beam sources based on the pseudospark discharge
Authors: Jiang X. L. , Han L. J.
Published: July 2002

The great potential of the pseudospark has resulted in a significant extension of the applications of the intense pulsed particle beam sources, the high-power switching technology, and film deposition with pulsed electron beam ablation, etc. The discharge mechanism of the pseudospark multiplate chamber has been successfully explained by using the field escalation effect. The pseudospark takes place in the left-hand region of Paschen’s breakdown curve under low-pressure gas. The positive space charge accumulation in the initial glow-like discharge phase leads to the rapid local field enhancement near the protrusion surface of the cathode hole. The intense pulsed electron beams, as well as the ion beams with high charge states and high current density, have been extracted from both the anode hole and the cathode hole.
High resolution and symmetry resolved core-level spectroscopy using soft x-ray undulator (invited)
Authors: Yagishita A. , Shigemasa E.
Published: July 2002

The performance of a soft x-ray undulator beamline equipped with a 10 m grazing incidence monochromator is described. Several experimental results are presented to exemplify the good performance. The decomposition of photoabsorption spectra of CO and O2 into their component molecular symmetries has been achieved by our new experimental technique of angle-resolved photoion spectroscopy. Two Rydberg series converging to the K-shell ionization limits of O2 have been revealed in a high resolution spectrum.
On comparison of spectroscopically deduced central ion temperatures and plasma rotation at JET
Authors: Danielsson M. , von Hellermann M. G. , Källne E. , Mandl W. , Morsi H. W. , Summers H. P. , Zastrow K.-D.
Published: July 2002

It is shown that a significant increase in the consistency of charge exchange spectroscopy and x-ray spectroscopy data for central ion temperature and plasma rotation is obtained when allowance is made for the following: (i) The charge exchange cross-section dependence on the impact energy of the neutral beam atoms in the frame-of-reference of the C+6 nuclei. In this paper we have experimentally verified the predicted cross-section effects on plasma rotation measurements using charge exchange spectroscopy by comparing to passive x-ray spectroscopy. The effect increases with lighter species. It should be emphasized that this effect is important for the rotation measurements only, while for the ion temperature measurements the effect is small compared to other error sources. (ii) The precise position of the radiating ion shell in line-of-sight averaged measurements using x-ray spectroscopy. For high-temperature plasmas with broad emission profiles the uncertainty in central ion temperature is reduced from up to 60% to the order of 20%.
Computer-controlled thermoelectric power measurement for bulk high T
c superconductors
Authors: Xin Y. , Ford D. , Sheng Z. Z.
Published: July 2002

We have established a quick and easy, modified dc method to measure thermoelectric power for bulk high transition-temperature (Tc) superconductors. The temperature range investigated is from 300 to 50 K. The apparatus was developed on the basis of our already-existing commercial APD (APD CRYOGENICS INC, Allentown, Pennsylvania) superconductor characterization cryostat with a limited amount of extra instrumentation. The thermoelectric power is measured continuously within the temperature range by the control of a computer, a real time Seebeck coefficient S(T) versus temperature curve is plotted on the computer screen during the measurement, and the data can be saved to a disk. The entire processing period for each sample takes less than 2 h. This apparatus was calibrated with pure lead. By measuring on high Tc superconductors which are well known in thermoelectric power, the system has been shown to have high accuracy and reliability.
Diamond force microscope tips fabricated by chemical vapor deposition
Authors: Germann G. J. , McClelland G. M. , Mitsuda Y. , Buck M. , Seki H.
Published: July 2002

A chemical vapor deposition method is described for fabricating force microscope cantilevers with single-crystal diamond tips. The ≂1-μm-diam diamond tips have corner radii of 30 nm, and have been used to study diamond–diamond friction on well-characterized surfaces in UHV. The tip size and orientation can be determined by electron microscopy without altering the surface atomic structure.
A 14.6-GHz ECR ion source for atomic physics and materials research with highly charged slow ions (abstract)
Authors: Zschornack G. , Birke U. , Hofmann D. , Mühle C. , Musiol G. , Schmidt-Böcking H. , Schneider M. , Stiebing K. E. , Streitz H. , Zippe C.
Published: July 2002

A 14.6-GHz electron cyclotron resonance ion source has been designed and will be installed at the TU Dresden. Contrary to other ECR sources some features are foreseen for atomic physics experiments to study the source plasma. Beside the description of source construction and computer-aided source control first physical experiments on the source are discussed.
An intelligent radiological instrument for field samples and contamination measurements
Authors: Drndarevic Vujo R. , Djuric Danko J.
Published: July 2002

A new intelligent radiological instrument for fast and accurate measurements of mass α and β activities of samples of human and animal food and other materials and for the detection of surface contamination of different objects have been developed. The original concept of an iterative dialogue operator–instrument, based on the built-in intelligence into the instrument—has reduced to a minimum the chance of obtaining an erroneous result. The built-in intelligence specifies: the sequence of the measurements, the subsequence of selecting the necessary absorber for mass β activity measurement, the algorithms for all necessary calculations. Minimum detectable β activity of measured samples (40K) is 0.17 Bq/g with an error not exceeding ±30% and measurement time 1000 s. The sensitivity of α activity measurement is related to the method of sample preparation; it ranges from 0.04 up to 10 Bq/g, with a selectivity with respect to β activity exceeding 104.
High-intensity low tube-voltage x-ray source for laboratory extended x-ray absorption fine structure measurements
Authors: Sakurai Kenji , Sakurai Hitoshi
Published: July 2002

A new high-intensity x-ray source equipped with an electron gun for low tube-voltage operation has been developed. Lowering the tube voltage is highly effective in eliminating higher order harmonics from the monochromator, which degrade the spectrum in extended x-ray absorption fine structure measurements. The present x-ray generator provides a narrow line focal spot with a high tube current of 900 mA even at a low tube voltage of 20 kV. Extremely intense monochromatic x-rays, which are completely free from higher order reflections, are now available in a laboratory.
High resolution in the soft x-ray range from a toroidal grating monochromator
Authors: Reich T. , Hussain Z. , Moler E. , Blackwell M. , Kaindl G. , Shirley D. A. , Howells M. R.
Published: July 2002

A resolving power, E/ΔE, of ≥13 000 has been achieved with the modified 6 m/160° toroidal grating monochromator (TGM) installed on Beam Line 8-1 at the Stanford Synchrotron Radiation Laboratory. The resolving power of the TGM was increased by replacing the entrance and exit slits with high-precision slits, masking the horizontal part (short radius) of the grating, and improving the TGM scanning mechanisms. To determine the performance of the monochromator, we measured the dependences of resolution and photon flux on the entrance- and exit-slit widths, the exit-slit position, and the masking of the grating. The monochromator resolution in the energy range of 25–65 eV was derived from photoionization measurements of extremely narrow core-excitation resonances in He and Ne. With 10-μm vertical entrance- and exit-slit widths and 32% mask opening of the grating, the monochromator has a resolution (full-width at half maximum) of 5.0±0.7 meV at a photon energy of 64.5 eV and a flux of 2×107 photons/s/100 mA. The results suggest a simple procedure for converting a TGM with moderate resolution into a high-resolution monochromator with a moderate reduction in photon flux due to masking the grating, beyond the reduction attributable to the slit widths.
A numerical procedure to determine near midgap level defect parameters in Schottky diodes with significant leakage current densities
Authors: Dmowski K. , Losson E. , Lepley B.
Published: July 2002

The conventional deep-level transient spectroscopy (DLTS) analysis for Schottky diodes is based on the assumption that the relaxation processes in the space-charge layer are governed by the thermal emission processes of majority carriers from deep-level defects. It is shown in this article that this assumption cannot be justified for near midgap level defects in Schottky diodes with relatively low barrier heights, i.e., with high leakage current densities. In such cases, three thermal processes in the depletion layer have to be taken into account: the majority- and minority-carrier emission processes and the majority-carrier capture processes. It is shown that the conventional analysis of DLTS spectra based on the peak data leads to significant errors in the calculated deep-level defect parameters. A numerical procedure for analysis of the DLTS spectra including the three above mentioned processes is proposed to determine the accurate values of near midgap level defect parameters.
rf plasma source using a magnetic line-cusp field
Authors: Yamauchi Kazuo , Takahashi Keiji , Yabe Eiji
Published: July 2002

A large volume cylindrical radio frequency (rf) plasma source using a magnetic line-cusp field has been developed for use in large scale plasma processing. In this type of plasma source, a capacitively coupled 13.56 MHz rf plasma is produced in the presence of a magnetic line-cusp field. Three versions of the plasma source have been constructed and tested. The first version has a pair of peripheral rf electrodes placed outside the ionization chamber and is suitable for preparing a large volume uniform plasma. This plasma source can attain a useful area of plasma with 10% uniformity over a 30-cm-diam region. The second version is featured by parallel doughnut-plate electrodes which form part of the chamber wall and serve as a high current source, where the electron density is proportional to the rf power, being equal to 4×1010 cm−3 at 400 W. The third version is a slab-plasma source, which has a rectangular ionization chamber, a pair of rectangular magnetic coils, and a pair of rectangular rf electrodes, yielding an electron density of the order of 109 cm−3 for a 25 W rf power.
Disktron accelerator
Authors: Shoji M. , Takahashi K. , Hanamoto K. , Tsuji H. , Tsubakihara M. , Nakabayashi T. , Tsuchida K. , Okada N. , Nakano H. , Furuta K. , Ono R. , Nakayama Y. , Miyake Y.
Published: July 2002

A new type of low-energy ion accelerator has been developed. It includes an eight-storied Disktron generator, newly developed accelerating tubes which hold up to 4 MV/m, both single and tandem acceleration capability, and a compound negative ion source. The Disktron generates 3.2 MV with a dummy load and 2.2 MV with ion beams, and has a voltage stability better than 10−3 at around 1 MV with a corona feedback stabilizer or a generating voltmeter feedback stabilizer only. The highly stabilized voltage of the Disktron has particularly been allowed to form an ion microbeam of about 1-μm diameter.
Nanosecond time-resolved vacuum ultraviolet spectrometer for ion diode spectroscopy
Authors: Nash T. , Noack D. , Filuk A. B.
Published: July 2002

A 1-m normal incidence spectrometer has been modified for use as a diagnostic of ion diode plasmas. To improve instrumental sensitivity, an elliptical mirror images an anode surface plasma onto the entrance slit of an f/10 normal incidence spectrometer. The detector is a time-resolving copper iodide coated microchannel plate stripline framing camera with 60-μm resolution, limiting instrumental resolution to 1 Å with a 600 ℓ/mm grating in first order. Reflectivity of optics and photoelectron efficiency limit the spectral range from 400 to 2000 Å. With a 600-ℓ/mm grating the detector spans a 600-Å range. Applications of the instrument may include ion source divergence measurements from Doppler broadening, electric field measurements from Stark splittings or shifts, electron temperature from mean ionization state, and magnetic field measurements on high-power Z pinches from Zeeman splitting.
Vertical two-dimensional piezoelectric inertial slider for scanning tunneling microscope
Authors: Libioulle L. , Ronda A. , Derycke I. , Vigneron J. P. , Gilles J. M.
Published: July 2002

To achieve both high stability during scanning tunneling microscopy (STM) measurements at atomic resolution and long-range imaging of nonhomogeneous samples, we have developed a fully 2D vertical inertial nanopositioner which allows tunneling tip displacements in the 0.01–1000 μm range while keeping high-resolution STM conditions. The inertial sliding of the tip is obtained by overriding the static friction criterion between the tip and its support. By controlling the expansion of the piezotubes and the direction of the applied acceleration, one can obtain displacements as small as 100 Å in the vertical direction. The same piezotubes are also used to scan the sample during conventional STM measurements. Increasing the resonance frequency of the scanner above 10 kHz was essential to ensure good operation. The complete device has not altered the mechanical stability of the microscope; it works in air as well as in ultra-high vacuum conditions. Its reliability is demonstrated by the possibility of obtaining STM images of adjacent areas.
Active control of a balanced two-stage pendulum vibration isolation system and its application to laser interferometric gravity wave detectors
Authors: Veitch P. J. , Robertson N. A. , Cantley C. A. , Hough J.
Published: July 2002

The investigation of the servo control of the position of the bottom mass in a balanced two-stage pendulum vibration isolation system is reported. Experimental results for a simple prototype system and predictions based on a model presented in this paper are in good agreement. The application of such a system to a high-sensitivity laser interferometric gravity wave detector is discussed.
A method of measurement of thermal conductivity: Application to free-standing diamond sheet
Authors: Kosky Philip G.
Published: July 2002

Self-supporting diamond sheets, made by the metastable chemical vapor deposition (CVD) technique, have been reported to have a range of properties, presumably dependent on the morphological details and the impurity burden of the particular sample. CVD diamonds are typically in the form of large area (i.e., many square cm) sheets averaging a few hundred microns in thickness. For this form of matter, a novel method of thermal conductivity measurement is reported based upon the well-known principle of the phase lag of a traveling thermal wave. In the present variation of this technique, the traveling wave traverses the diamond sheet from its leading edge (which was pulsed with an infrared diode laser) through the point of measurement. The average thermal diffusivity of the sheet was calculated. The equipment is relatively simple and the sample preparation minimal. Both theoretical and experimental details are given. The random error in thermal diffusivity measurements is estimated to be about 7% due mainly to uncertainties in estimating the delay time lag of the thermal wave as it travels along the length of the diamond sheet.
Quantization error of slit-grid emittance measurement devices
Authors: Ludwig T. , Volk K. , Barth W. , Klein H.
Published: July 2002

Slit-grid emittance measurement devices usually do not scan the beam continously but in fixed linear (x) and angular (x′) steps. Thus in an emittance measurement performed with a slit-grid system, the beam is represented by a number of phase space boxes with a constant area or volume determined by the linear and angular resolution. Considering the emittance as the area in the two-dimensional subspace (x,x′) covered by the beam, the quantization error and its dependence on the resolution (linear and angular) as well as the influence of the beam parameters is discussed. Measuring the very low emittance of the high efficiency source (HIEFS) proved that the quantization error can be unacceptably high (≫100%). With an optimized measuring device, the normalized emittance came down from 10−1 to 3.6×10−3 π mm mrad. Finally, a typical misleading result of an emittance measurement, caused by the quantization error, is presented.
A dual optically pumped polarized negative deuterium ion source
Authors: Kinsho Michikazu , Mori Yoshiharu
Published: July 2002

An optically pumped polarized H− source (OPPIS), which is based on the charge exchange between H+ ions and electron-spin polarized alkali atoms has been developed at KEK. Just by applying this scheme to a deuteron beam, it is difficult to obtain a highly vector polarized deuteron beam. To obtain highly vector polarized D− ions, we have developed a ‘‘dual optical pumping type’’ of polarized D− source. With this scheme, a 100% vector nuclear-spin polarization for D− ions is possible in principle. In a preliminary experiment, a 60% vector nuclear-spin polarized D− ion was obtained.
Josephson vortex flow in superconducting single-crystal Bi2Sr2CaCu2Ox
Authors: Lee Ji Ung , Nordman James E. , Hohenwarter Gert
Published: July 2002

Using various size rectangular mesas formed by photolithographically patterning and etching on single-crystal Bi2Sr2Ca1Cu2Ox superconductors, we have obtained c-axis volt-ampere characteristics as a function of magnetic field applied parallel to the a-b planes. Enhanced sensitivity with field perpendicular to the long side was observed even in mesas with dimensions smaller than the magnetic penetration depth λc. This can be explained in terms of viscous flow of Josephson vortices. The measurements are in good quantitative agreement with theoretical models for Josephson vortex motion in layered superconductors. Vortex flow coexists with the multiple hysteretic structure previously presented as evidence that this material behaves as a stack of underdamped intrinsic Josephson junctions.
Intense negative ion sources at Culham Laboratory (invited)
Authors: Holmes A. J. T. , McAdams R. , Proudfoot G. , Cox S. , Surrey E. , King R.
Published: July 2002

Over the past 20 years, Culham Laboratory has been involved in the development of ion sources. Initially these were positive ion systems using magnetic multipole sources for neutral beam heating in the fusion program. However, the development of high proton yield sources with a magnetic filter at Culham has led to a major program in negative ion sources based on the so-called volume-type source which has a similar design. This work has been the basis of a range of negative ion sources for industrial, defence, and fusion applications, all of which are described. A significant part of this work lies in the basic physics of these sources, both for modeling and ion beam acceleration. Numerical models of these are presented. Recently the effects of catalysts such as cesium on the discharge has been shown to cause considerable enhancement in H− and D− yield. The cesium itself also acts as a discharge component and a large source and accelerator for a pure cesium diagnostic beam has been developed. This technique is applicable to other vapors.
A laser-aided prealigned pinhole collimator for synchrotron x rays
Authors: Chu Benjamin , Harney Paul J. , Li Yingjie , Linliu Kung , Yeh Fengji , Hsiao Benjamin S.
Published: July 2002

A pinhole small-angle x-ray scattering (SAXS) instrument was constructed at the SUNY X3A2 beamline, National Synchrotron Light Source, Brookhaven National Laboratory. The three pinholes were mounted in a thick-walled stainless steel pipe and prealigned by using a portable laser source and a charge-coupled device (CCD) area detector. After the prealignment, incorporation of the collimator to the synchrotron x-ray source required only maximization of the incident x-ray intensity passing through the pinholes, which could be done easily by using a scintillation counter after proper attenuation. The entire synchrotron SAXS instrument setup took only a few hours even without stepping motor control for the pinhole collimator unit. By combining this collimator with a CCD-based x-ray area detector which could be assembled by using commercially available components, the SAXS instrument showed good performance for structural scales up to an order of 100 nm. The CCD-based x-ray area detector used a computer- (or manually) controlled intensified unit with a variable gain setting in order to accommodate the changing x-ray flux and to protect the detector from over exposure, a necessary feature for operation of an area detector at a synchrotron light source.
Micromagnetic scanning microprobe system
Authors: Thompson C. A. , Cross R. W. , Kos A. B.
Published: July 2002

We describe the apparatus, instrumentation, and data acquisition techniques which make up the micromagnetic scanning microprobe system (MSMS). This system was developed to study magnetoresistive (MR) thin films used in magnetic recording read heads. It uses a dc, four-probe resistance measurement coupled with two pairs of orthogonal field sources. Voltage contacts to the thin film are made with microprobe tips 0.1 μm in diameter on local edge and central regions of the film. Horizontal and vertical microscopes are used to verify tip placement. Results from magnetoresistance measurements of the dynamic response of a MR read head film are shown to demonstrate system operation and performance. The bulk and local magnetoresistance of a 10 μm×10 μm NiFe thin film was measured as a function of applied field and angle. Significant variations in MR responses were seen across the width of the device because of local domain formation. The MSMS is an effective tool for characterizing the effects of domain formation on the output of a MR read head.
Micro-pellet injection into tokamak plasma by laser acceleration
Authors: Zoletnik S. , Kálvin S. , Bürger G.
Published: July 2002

Different methods are tested for the injection of small (<100 μm) pellets into tokamak plasmas using laser acceleration. In one type of method the pellets are formed in the random fragmentation process of a foil, while in another series of experiments aluminum granules were accelerated. In the first case pellet velocities up to 4 km/s were achieved, but the reproducibility was found to be poor. In the second case the reproducibility was much better, and pellets with diameters in the ten micron range were accelerated to 200–300 m/s velocity. With some further improvements, this technique may become a simple source of impurities for transport studies in fusion plasmas.
Multimass thermal desorption spectroscopy as a monitoring device for chemical reaction products
Authors: Zagatta G. , Müller H. , Böwering N. , Heinzmann U.
Published: July 2002

To observe the products of surface reaction mechanisms we combined a standard quadrupole mass spectrometer featuring high-speed scanning options with fast data acquisition and a computer-controlled sample heating system. This combination served to obtain a general view (like a ‘‘fingerprint’’) of the reaction occurring on a Pt(100) crystal upon heating the adsorbate covered surface, as well as to allow for a detailed analysis of the gas compounds leaving the surface within a single measurement. The method is denoted by multimass thermal desorption spectroscopy (MTDS). The MTDS device is capable of recording 850 amu/s providing up to 15 complete mass spectra per second of 50 amu width while heating the surface linearly. The data contain the ion currents of both the reaction products and their fractions (cracking patterns) generated in the spectrometer. Thus it is possible to distinguish between gas species with equal mass numbers by subsequent numerical evaluation.
Highly sensitive method for simultaneous measurements of thermal conductivity and thermoelectric power: Fe and Al examples
Authors: Bougrine H. , Ausloos M.
Published: July 2002

The main purpose of this work is to present a highly sensitive method for measuring simultaneously thermal conductivity and thermoelectric power in a 4.2–300 K temperature range, and to discuss the errors made in measurements of such quantities due to radiation and convection losses. An experimental setup is presented in detail and discussed. It is emphasized how in this quasi-steady-state method, the residual heat flow and temperature difference between various components are taken into account. Measurements of the thermal conductivity and thermoelectric power of Fe are presented for such a setup with and without radiation shields, and for high or low vacuum in the range 70–300 K. The best conditions are then used for measuring these properties in Al. Brief comparison is made to existing data.
Effects of finite absorption depth and infrared detector nonlinearity on thermal diffusivity measurement of thin films using the flash method
Authors: Tang D. W. , He G. H. , Zhou B. L. , Zhang H.
Published: July 2002

The flash method including the single- and double-ended method has gained widespread acceptance for measuring thermal diffusivity of thick foils (in millimeters) as well as thin films (in microns). However when the method is employed, some basic experimental conditions are assumed. In this paper, two of the assumptions, the finite absorption depth effect and the nonlinearity of the detector, are discussed in the situation of thin film samples. For the first one, the deviation of the factor ω1/2 (=π2αt1/2/L2) from 1.37 and the corresponding errors in deriving thermal diffusivity from t1/2 are discussed for various relative absorption depth δ. The result indicates criteria for the method to be available, that is, L≳10δ and L≳14δ for the double- and the single-ended method. For the second one, by considering the errors in voltage output of a (Hg, Cd)Te IR detector, how the factor ω1/2 deviates from 1.37 and the corresponding errors in thermal diffusivity measurement under various initial temperature conditions are discussed. The results are shown graphically and tabulated.
A static Fourier-transform spectrometer based on Wollaston prisms
Authors: Padgett M. J. , Harvey A. R.
Published: July 2002

A static Fourier-transform spectrometer has been designed based on Wollaston prisms. It produces an interferogram in the spatial domain which is recorded using a 2D camera. A combination of two Wollaston prisms localizes the interference fringes coincident with the plane of the detector, thereby facilitating an extremely compact design. A personal computer is used to calculate the wavelength spectrum of the input light from the Fourier transform of the interferogram. In addition to its use as a compact and efficient spectrometer, the instrument’s use as a laser wavemeter has also been demonstrated.
In situ oxidation cell for the high-voltage electron microscope
Authors: Blümchen Th. , Messerschmidt U.
Published: July 2002

An environmental cell has been designed for in situ oxidation experiments in the high-voltage electron microscope. The gas around the specimen is separated from the microscope vacuum by two apertures on both sides and a differential pumping system operating between the inner and outer apertures. The cell allows gas pressures between 10−3 and about 150 Pa and specimen temperatures above 1000 °C. To adjust appropriate imaging conditions, the specimen can be tilted around two axes. First experiments were carried out on Fe–22Cr–5Al and Ni–Al polycrystals.
Self-calibrating magnetic field diagnostics in beam emission spectroscopy
Authors: Voslamber D.
Published: July 2002

Magnetic field diagnostics in tokamaks using the motional Stark effect in fast neutral beams have been based on two kinds of polarimetry which we call ‘‘static’’ and ‘‘dynamic.’’ A detailed analysis shows that static polarimetry presents a number of advantages over dynamic polarimetry, provided it is made complete in the sense that a sufficient number of polarization analyzers are installed and different parts of the spectrum are explored to yield full information on the set of unknowns inherent in the problem. A detailed scheme of complete static polarimetry is proposed, including the case where an in-vessel mirror with changing characteristics (coating by impurities) is placed in front of the optical detection system. The main merit of this scheme relies on the fact that it is self-calibrating with respect to both the characteristics of the mirror and the transmission of the different polarization channels, the latter item implying that it is uniquely based on relative measurements of spectra. Further advantages are a greater flexibility with regard to different kinds of diagnostics and the circumstance that the technical equipment is less involved. The above scheme is based on a detection system of moderate etendue exploiting a large spectral domain, which is the regime where static polarimetry usually operates. It is also possible, however, to work with large etendue and a small spectral domain, such as commonly adopted in dynamic polarimetry. Using such a regime, static polarimetry loses the advantages mentioned above but gains, as a new advantage, the benefit of a comparatively lower level of photon noise.
A rheo-light-scattering instrument for the study of the phase behavior of polymer blends under simple-shear flow
Authors: Wu R. , Shaw M. T. , Weiss R. A.
Published: July 2002

A rheo-light-scattering instrument for investigating the influence of shear on the phase behavior of polymer blends was constructed from a commercial parallel-plate rheometer. Laser light scattering from the sample plane formed by the flow and vorticity directions was projected on a screen, and a combination of a camera lens and a charge-coupled device detector was used to record the scattering pattern. The rheometer, which can generate angular velocities of up to 100 rad/s and measure torque and normal forces up to 9.8×103 N m and 9.8×105 N, respectively, is suitable for studying polymer melts at stresses up to 9.1 kPa. The maximum accessible q range was from 5.72×10−4 to 7.11×10−3 nm−1 (3°–42° scattering angle and a laser wavelength of λ=632.8 nm). The performance of the light-scattering instrumentation and the accuracy of the correction algorithms were tested with a Ronchi ruling diffraction grating and a colloid of monodisperse polystyrene spheres. Example rheo-light-scattering measurements were made with a 50/50 blend of polystyrene and polyisobutylene oligomers and a 40/60 blend of polybutadiene and polyisoprene. All components had narrow molecular weight distributions. The first blend exhibits an upper critical solution temperature while the second blend shows a lower critical solution temperature.