bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic field mapping using an image-intensifying fluorescent probe
Authors: Tou T. Y. , Blackwell B. D. , Sharp L. E.
Published: July 2002

A simple, cost-effective image-intensifying fluorescent probe designed for mapping the magnetic surfaces in the heliac sheila is described. It consists of a phosphor-coated metal plate which is enclosed in a grounded U-channel that provides electrostatic shielding. An adjustable accelerating voltage is applied to the metal plate to greatly increase the cathodoluminescence produced by the directed electron beam from an electron gun, and the visible electron-beam image is recorded by a CCD camera. The gain in the image brightness allows significant reduction of the electron-beam energy to minimize the deviation of the measured drift surfaces from the true magnetic surfaces, and to improve resolution for detailed studies of surfaces in the newer stellarator experiments. This technique is particularly suited to electron energies below the phosphor activation threshold, when external image intensifying systems are likely to be very inefficient. Up to 36 toroidal rotations have been observed, limited mainly by the effective cross sections of the fluorescent probe and the electron gun. Mapping at low magnetic field strengths allows detection of small fixed amplitude field errors. Measurements of the gain characteristics and resolution are presented, with an example of the electrically variable resolution achievable with this design. The effect of electron energy on drift surfaces of a heliac is demonstrated.
Beam emittance growth caused by a nonuniform ion density
Authors: Holmes Andrew J. T. , Surrey Elizabeth
Published: July 2002

An expression for the root-mean-square emittance of an ion beam is derived in terms of the distribution of particle density at the plasma boundary. Three distributions are considered: a uniform plasma, a linear variation due to B×v effects, and a quadratic variation. It is shown that for the nonuniform distributions additional terms enter the expression for beam emittance causing emittance growth. Experimental data, in agreement with the model, are presented for both positive and negative ion beam systems. Applying the model to the data provides values of ion temperature within the ion source and the degree of nonuniformity across the plasma boundary for several different ion source systems.
Estimation methods for the angle of divergence of low energy ion beams
Authors: Maniv S.
Published: July 2002

Three estimation methods for the determination of the angle of divergence β for low energy ion beams are described. A Kaufman-type argon ion source of 11 cm beam diameter, 150 to 2000 eV beam energy, and 0.1 to 1 mA/cm2 ion current density is used. The first method is based on the etching morphology of a 12-μm-thick HgCdTe sample that is overlayed by a 3-μm-thick photoresist pattern. The second method makes use of the halfwidth of the ion current density profile measured along the diameter of the ion beam cross-section at different distances z, from the grid. The third method employs a variable angle collimator to profile the ion current density along a diameter of the ion beam cross section; the angle of divergence is then extracted by fitting a mathematical model to the data. The angle of divergence that is obtained by using the above three measurement methods indicates that β decreases from 16° to 4° as the ion beam energy is increased from 150 to 900 eV, respectively.
An apparatus to measure charges on particles of three different size categories under a rainshower
Authors: Kamra A. K.
Published: July 2002

An apparatus has been developed that can separate various particles near the ground surface under a rainshower into three different size categories and can measure the electric charge of each category. The apparatus consists of three stages. In the first stage, raindrops of millimeter size are collected by their gravitational fall in a funnel. In the second stage, air containing smaller particles is circulated through a helical tube so that particles of the size of cloud droplet (∼100 μm) are collected by centrifugal force acting on them. In the third stage air is passed through an absolute filter that entraps particles larger than 0.3 μm with 99.97% efficiency. The three stages are insulated from each other and from the ground. The signal received from each stage is amplified and recorded on a strip chart recorder. Laboratory tests and preliminary measurements made with the apparatus under rainshowers are discussed.
Current deep-level transient spectroscopy in MOS structures with a boxcar integrator and an arbitrary gate-width-data analysis
Authors: Dmowski K. , Bethge K.
Published: July 2002

New formulas are given describing the current correlation signals of bulk traps and interface states in metal-oxide-semiconductor structures. The presented formulas describe the correlation signals for analog measurement systems utilizing a single-channel or a two-channel boxcar integrator. These formulas take into account both the so-called Lambda effect and an arbitrarily chosen gate width of a boxcar integrator. A comparative analysis has been made of a potential sensitivity and selectivity of these systems as a function of a gate width.
Reduction of radiation errors in thermal conductivity measurements above 100 K
Authors: Talpe Juan H. , Bekeris Victoria I. , Sanchez Maria J. , Simonelli Gabriela
Published: July 2002

A steady-state method for thermal conductivity measurements above 100 K on poor conductors is described. Radiation errors are made negligible using a closely fitting shield with a temperature profile matched along its length to that of the sample. Calculations show that for a typical geometry, the radiation error at room temperature is two or three orders of magnitude lower than for a shield kept at the sink temperature. The experimental setup is described and measurements on PMMA are reported. The results agree with measurements reported by other authors who use completely different methods.
Experimental study of a hot wire, sonic nozzle probe for concentration measurements
Authors: Maroteaux Damien , Maroteaux Fadila , Murat Michel
Published: July 2002

A hot wire sampling probe for instantaneous concentration measurements is described. The sensitivity of the probe to concentration, pressure, and temperature variations is studied on a simple experimental facility designed for steady-state experiments. The probe sensitivity to methane concentration, measured in methane-nitrogen mixtures, is 0.024% CH4/mV for the low methane mole fractions. It is shown that this type of probe can be used to measure concentrations in a pressure and temperature varying environment, provided that these parameters are known by another means. Simple calculations with a proper heat transfer correlation allow us to avoid a complete calibration of the probe. The probe resolution is shown to depend strongly on the platinum-iridium wire operating temperature, which must be as high as possible (usually 830 K in our experiments).
A data collection system for protein crystallography with area-sensitive proportional counters
Authors: Nienhaus G. U. , Hartmann H. , Parak F.
Published: July 2002

To take full advantage of the capabilities of an area-sensitive electronic detector for x-ray crystallography, data analysis and reduction has to be performed in parallel to the data collection. A data collection system is described that makes extensive use of computer modules for the VME bus. The data acquisition electronics is embedded in the computer system that analyzes the diffraction pictures so as to keep data transfer time short. It is based on an intelligent computer module allowing us to add the electronic hardware necessary for our specific application. Using a fast FIFO buffer we can collect 24-bit-wide data words at an average rate of almost 300 kHz with a dead time τD of 100 ns between successive events.
H− temperature measurements by a slit diagnostic technique
Authors: Sherman Joseph D. , Smith H. Vernon , Geisik Carl , Allison Paul
Published: July 2002

H− ion beams are extracted at 5–25 kV from a long, narrow slit on a Penning surface-plasma source (the 8X source). The extraction geometry produces negligible transverse electric fields (focusing effects) along the slit length. Therefore, the ion angular spread reflects the distribution of ion energies at the plasma surface. The angular distributions are measured with an electric-sweep emittance scanner whose slits are oriented normal to the long dimension of the emission slit. The nearly Maxwellian angular distributions measured over the central portions of the ribbon beam give kTH− of 0.1–0.2 eV for a 2-A dc discharge and 0.8–1.0 eV for 350–500 A pulsed discharges. This diagnostic technique has sufficient position resolution to allow measurement of the kTH− spatial distributions. It also allows study of the kTH− dependencies on ion source parameters (e.g., increasing the H2 gas flow lowers kTH−).
Technique for covering large apertures in ion optics with electroformed metal mesh
Authors: Noll Robert J. , Ochalla Lloyd L. , Weisshaar James C.
Published: July 2002

We describe a method for covering large apertures of nearly arbitrary size and shape in ion optics with uniformly taut, flat, electroformed metal mesh. An O-ring trapped between two plates in a specially cut, beveled groove provides uniform radial tensioning of the mesh as the plates are bolted together.
Plasma properties in the open-ended region of a coaxial-type microwave cavity
Authors: Yoshida Yoshikazu
Published: July 2002

A sputtering source utilizing both microwave and dc planar magnetron plasmas is described. Microwave power is introduced into the plasma by a coaxial-type cavity. The magnetron target is placed on the open end of the inner conductor. This source produces a plasma which is well matched, stable, and can operate continuously at gas pressures from 3×10−4 to 2×10−2 Torr. Plasmas with densities greater than 1011 cm−3 are obtained at gas pressure of 10−4 Torr using a microwave power of 100 W. The deposition rate of Cu is more than 0.13 μm/min for an argon gas pressure of 3×10−4 Torr, and microwave and dc powers of 100 W, respectively. This new source has many potential uses such as sputtering, etching, and chemical vapor deposition.
Jig for high-T
c superconductor bulk wigglers
Authors: Ishibashi Yoshiharu , Ariizumi Masato , Saegusa Hiroshi , Mizukami Shinzo , Matsuzawa Hidenori
Published: July 2002

A jig is described that was used to form high Tc superconductor bulk wigglers (undulators) for intense electron beams. The wigglers are one of novel applications of Supertrons (lenses for charged particle beams) that were previously proposed and demonstrated by the authors.
GYRAC-D-O: Relativistic plasma accumulator and ion accelerator
Authors: Andreev V. V. , Apraksin A. A. , Umnov A. M.
Published: July 2002

Plasma heating and relativistic plasma accumulation are realized in the GYRAC-D-O installation. Relativistic plasma accumulation is a result of plasma heating under synchrotron gyromagnetic autoresonance (SGA) and subsequent throwing of the SGA plasma into the central region of the magnetic mirror trap in the regime of the SGA-pulse packet. The optimum of the initial plasma pulsed injection is found. The obtained plasma is e-vortex filled with ions. Major parameters of the plasma are as follows: n ≂ 8 × 109 cm−3: average energy of electrons W≂200 keV; lifetime τ≂40 ms. The problem of the plasma ejection out of the trap after the accumulation cycle completion is discussed. It is shown that effective plasma ejection and ion acceleration are possible in case of a relatively dense plasma which is feasible only in the accumulation regime.
Laser ion source for heavy ion accelerators
Authors: Sharkov B. Yu. , Shumshurov A. V. , Dubenkow V. P. , Shamaev O. B. , Golubev A. A.
Published: July 2002

The development, construction, and operation of laser ion sources for different types of heavy ion accelerators at ITEP are presented. A number of general physical problems connected with the special plasma heating regime by means of a powerful CO2 laser were under consideration. The results of experimental measurements show that the currents up to ≂103 mA per pulses about 5–15 μs and emittance ≤3 πcm mrad have been achieved for multicharged ions of a large number of elements. The recent results of laser ion source operation on the ITEP Van-de-Graaf facility and on the 2-MV heavy ion synchrotron injector are reported.
Ion sources at the cooler synchrotron COSY
Authors: Beuscher H.
Published: July 2002

A short survey of the existing and future ion sources at the cooler synchrotron COSY is given. The performance of an adapted H2+ source is discussed and results from first stage studies on the 14 GHz ECR source are presented.
Beam extraction from ion sources with electrostatic containment
Authors: Coste Ph. , Aubert J. , Farchi A. , Lejeune C. , Wartski L.
Published: July 2002

Ion sources with electrostatic containment of the primary electrons are very attractive since they possess an upgraded ionization efficiency and are simple to realize. However, their plasma potential is quite different from the potential of the plasma electrode, which supports extraction apertures, resulting in a non-negligible space-charge sheath between the plasma and the extraction plane. An experimental comparative study of the extraction of an ion beam with and without electrostatic containment shows the influence of the space-charge sheath on the extracted ion beam characteristics. For the same extraction potential condition, the ion beam current is lowered when the ion source uses the electrostatic containment. For monoaperture applications, an improvement of the ERIS structure in which the anode is the extraction aperture itself has been tested. In this case, space-charge sheath effects in the extraction area are negligible and the matching conditions are much better than with a standard reflex structure. For multiaperture applications, space-charge sheath effects in the extraction area are reduced when the plasma grid is positively biased with respect to the cathode potential. Experimental results prove that this polarization permits to upgrade transmission of beamlets.
Investigation of extraction systems with low aberrations
Authors: Wituschek H. , Rück D. M. , Spädtke P.
Published: July 2002

The extraction of ions from a plasma source suffers from the aberrations due to the fact that electrodes are not infinitely thin and/or the aspect ratio is not correct. These aberrations are shown by experiment and computer simulation using the interactive axcel-gsi code. The experiments are made using a pepperpot device for the emittance measurement. This device is ideally suited for making measurements that can be compared with emittances calculated by computer simulations.
The thermophysical characteristics of the ionizer in cesium sputter-type negative ion sources
Authors: Rao Yusheng , Xi Boling , Chen Houpeng , Dong Beidou
Published: July 2002

The thermophysical characteristics of the ionizer in cesium sputter-type negative ion sources is studied by means of the heat transfer theory in this paper. A heat transfer model is given and theoretical calculations are performed. The theoretical calculations are in good agreement with experimental results. Based on the theoretical analysis the configuration of the source is improved and the calorific efficiency is increased, so that the temperature of the ionizer can reach up to 1300 K and the lifetime of the heater core of the ionizer is prolonged. The theoretical model can serve as the basis for the ionizer design of the cesium sputter-type negative ion sources. In addition, the study is also helpful for the design of the heater in the similar ion sources.
Improving ion beam quality by its interaction with electron beam
Authors: Abdelaziz M. E. , Zakhary S. G. , Abdelghaffar A. M.
Published: July 2002

The influence of electrons interaction with ion beams extracted from rf source on the behavior of ion beam optics has been studied. Both theoretical and experimental studies show decrease of beam emittance and beam radius due to decrease of space-charge effect produced by partial neutralization of ion beams. Decrease of neutralization percentage and increase of the beam angular divergence occur with increasing the plasma intensity of the source.
Oxygen and carbon ions from a reflex discharge ion source
Authors: Hentschel R. , Henke D.
Published: July 2002

Intense beams of oxygen and carbon ions are of interest for applications in microelectronics and material modification. However, it is often impossible to produce them with usual arc discharge ion sources for a sufficiently long time because of the corrosion or covering of the cathode. The paper shows how the lifetime difficulties can be overcome using a strontium oxide platinum cathode in connection with oxygen or carbon dioxide as working gas. Beams in the 50 mA range with a share of 40% O+ or 30% C+ are steadily obtained from a compact reflex discharge ion source. A cathode lifetime of more than 60 h has been reached at a discharge current of 8 A.
A modified electrostatic ion source
Authors: Abdelaziz M. E. , Abdel-Salam F. W. , Helal A. G. , El-Khabeary T. H.
Published: July 2002

The oscillating electron ion source has been modified to obtain an improved form by extracting more low-energy ions from it. It has been found that biasing of the oscillating ions by applying a negative potential to the cathodes would increase the output beam current to about three times its value for the same ion source plasma parameters, whereas applying the same negative potential on the screens and Faraday cups, while the cathodes connected to earth will increase the beam current five times its value. The discharge starts at lower values of discharge voltage, or higher values of beam current are obtained at the same value of discharge voltage as the applied negative potential is increased. It is concluded that the electrode configuration constitutes a convergent lens when the negative potential on the screens and Faraday cups is only one-ninth as large as that of the positive anode electrode.
The new BNL polarized negative ion source
Authors: Hershcovitch A. I. , Alessi J. G. , DeVito B. , Kponou A. E.
Published: July 2002

A new ground state source of negative hydrogen ions with polarized nuclei (H−) is being developed at BNL. Extensive developmental research has been aimed at improving each element of (H−) production: cold H° beam, spin selection and focusing magnets, and ionizer. These elements have recently been integrated into a source. A first test with the accommodator nozzle cooled only to liquid nitrogen temperatures resulted in 5 μA of H−. Tests at liquid helium temperatures are now beginning.
Study on the mechanism of negative ion formation in cesium sputter-type negative ion sources
Authors: Rao Yusheng , Chen Houpeng , Xi Boling , Dong Beidou , Xia Baihua
Published: July 2002

The mechanism of forming negative ions in cesium sputter negative ion sources is studied by means of a modified dipole layer model and quantum theory. Formulas of the change of work function on the metal surface adsorbing cesium layer and the electron transfer probability are given. The formation probabilities of the negative ions are derived using a quantum tunneling model. The negative ion yield is also calculated. The calculated results are in essential agreement with the experimental data. The philosophy described in this paper may offer a useful theoretical model for the mechanism study of cesium sputter negative ion sources.
Negative ions generated by laser-material interaction (invited)
Authors: Korschinek G. , Henkelmann T.
Published: July 2002

Different applications and results in the generation of laser-induced negative ions are reviewed. Emphasis is put on analytical achievements as well as recent developments in very high negative ion currents. Yields up to 4 mA have been observed. The production mechanism is discussed. Three-body collisions in the extremely dense laser plasma are considered to be the origin of the strong yields observed. Already, a dedicated source has been constructed, but, e.g., a conventional cesium-beam sputter source is also well suited to serve as a laser ion source.
Mass spectra of alloy liquid metal ion sources (abstract)
Authors: Machalett F. , Mühle R.
Published: July 2002

Liquid metal ion sources are widely used in focused ion beam systems with applications such as maskless ion implantation and microfabrication. For these applications a variety of technologically important ions are required. Alloys with a eutectic composition as source feed materials are generally used and the desired ions are selected by means of a mass separating system. This paper presents the results of mass spectrometric investigations on Pd-Ge, Cu-Ge, Au-Si-Be, Au-Si-Sb, Au-Ge-Sb, and Pt-Sb-P-Au-Si alloys using tungsten as needle material. The suitable atomic alloy composition was deduced from the corresponding phase diagrams and the temperature range of melting of the employed alloys was determined by differential thermal analysis. Relative intensities of the main ion species in dependence on the total source current were investigated.
Ion source with rf autogenerating beam-plasma discharge
Authors: Vizgalov I. V. , Dimitrov S. K. , Chernyatjev Yu. V.
Published: July 2002

An ion source was developed to meet such contradictory requirements as a high-perveance at a low-beam energy, ion selection, and a possibility to produce metal and multicharged ions. An electron beam in a magnetic field is used to produce and heat plasma in a discharge chamber to form an ion emitter. The particular feature of the source is generation of rather powerful rf auto-oscillations in the contour coupled with a special electrode system, the first harmonic being tuned in a wide frequency range up to 100 MHz. Provided rf power is used for an auxiliary plasma heating in a discharge chamber with a magnetic nozzle configuration, an additional longitudinal ion acceleration to the emissive electrode and a significant (by a factor of 2–3) increase of an ion yield at a lowered gas pressure are observed. When rf power is loaded onto a resonance structure installed behind an emissive electrode, an ion selective acceleration takes place.
A multisample, high-intensity Cs sputter negative ion source for accelerator mass spectrometry applications
Authors: Houzhi Si , Weizhong Zhang , Jinhua Zhu , Guangtian Du , Tiaorong Zhang
Published: July 2002

The development of a high-intensity Cs sputter negative ion source has been completed. The source is equipped with a spherical tungsten ionizer and a target wheel with 18 sample positions. The wheel is separated from the hot sputter region by a gate valve in order to change the samples rapidly and reduce cross contamination. A drive system can push the selected sample into the sputter position and pull it back to the wheel. A metal-ceramic bonded ring is used to support all the parts at sputter potential. The ring is protected from vapor depositions by a specially designed shielding structure, resulting in reliable insulation between the ionizer and the sputter samples. No insulation trouble has occurred during the work for over one year. Beams of 10-μA BeO−, 5-μA Al−, 4.5-μA Fe−, and 350-μA C−, etc. have been delivered. The normalized beam emittance ranges from (2–4) πmm mrad MeV1/2. The memory effect has been evaluated. More than 1000 and 500 times of attenuation for C− and BeO− are observed, respectively, in 10 min after a sample change. The ionization efficiency for 12C− is higher than 5.4% for a graphite sample.
Technical considerations in the design of the Chalk River high temperature helium-jet ion source
Authors: Watson M. J. , Koslowsky V. T. , Hagberg E. , Hardy J. C. , Steer M. G. , Schmeing H. , Perry W. L.
Published: July 2002

A second-generation helium-jet-coupled ion source of the Bernas–Nier type has been developed for the Chalk River on-line isotope separator. The source features improvements to the anode-cylinder heating system, which enables the anode to reach temperatures exceeding 2000 °C. The source suspension has been redesigned to accommodate the effects of operation at increased temperature in order to maintain critical anode alignment at all power levels, thus assuring a consistent high-resolution ion beam.
Improving the Coherent CR-699-29 Autoscan(t
m) interface box
Authors: Erickson M. G. , Basinger W. H.
Published: July 2002

A simple floating input differential amplifier circuit is described for enhancing both the performance and the reliability of the Coherent CR-699-29 Autopscan(tm) system. The circuit eliminates ground loops, incorporates again, and eliminates polarity problems presented by instruments with negative output voltages.
Surface modification by ion bombardment
Authors: Bisten M. , Freisinger J. , Löb H. , Neumann P. , Scharmann A.
Published: July 2002

In recent years the production of thin high-quality films has become more and more important. At the University of Giessen, radiofrequency ion sources for material treatment (RIM) had been designed and optimized. The presented results show some of our analyses of RIM-produced thin films and RIM-modified surfaces. By means of an oscillating quartz crystal, the distribution of sputtered atoms and the properties of the growing thin film were measured. Furthermore, the formation of seed textures on the sputtered surfaces were analyzed.
Investigation of a 2.45 GHz ECR plasma for ion etching
Authors: Eichelberger M. , Friedrich L. , Huttel E. , Wiss L.
Published: July 2002

Reactive ion-stream etching of SiO2 by CF4 ECR plasma has been investigated using different magnetic configurations. Whereas a permanent multipole field yielded the best results concerning the homogeneity over a large area, the highest etching rates were achieved with a longitudinally gradient field.
Performance investigation of a focused ion beam for sputter deposition
Authors: Yuan-Zhu Kuang , Jun Yan
Published: July 2002

Recently, focused ion beam sources have been widely used in various film deposition. This paper introduces the performance investigation of a focused ion beam source for sputter deposition. A 3.5-cm-diam ion source was used in the experiments. The results of the tests show that (1) at given ion beam energy there is an optimum value of ion beam current which gives the maximum value of ion beam current density; (2) at higher beam energy the peak of ion beam current density is higher and is obtained at larger beam current; (3) the ion beam current density increases with increasing magnetic flux density but there is an optimum value of magnetic flux density, and (4) the ion beam current density increases with increasing discharge voltage and gas flow rate, decreases with increasing accelerator voltage. Finally, these results are analyzed and discussed.
ALLIGATOR−An apparatus for ion beam assisted deposition with a broad-beam ion source
Authors: Wituschek H. , Barth M. , Ensinger W. , Frech G. , Rück D. M. , Leible K. D. , Wolf G. K.
Published: July 2002

Ion beam assisted deposition is a versatile technique for preparing thin films and coatings for various applications. Up to now a prototype setup for research purposes has been used in our laboratory. Processing of industrial standard workpieces requires a high current ion source with broad beam and high uniformity for homogeneous bombardment. In this contribution a new apparatus for large area samples will be described. It is named ALLIGATOR (German acronym of facility for ion assisted evaporation on transverse movable or rotary targets). In order to have a wide energy range available two ion sources are used. One delivers a beam energy up to 1.3 keV. The other is suitable for energies from 5 keV up to 40 keV. The ‘‘high-energy’’ ion source is a multicusp multiaperture source with 180-mA total current and a beam diameter of 280 mm at the target position.
Pulsed laser deposition and characterization of optical waveguiding (Pb,La)(Zr,Ti)O3 thin films
Authors: Xiong S. B. , Liu Z. G. , Chen X. Y. , Guo X. L. , Liu X. , Zhu S. N.
Published: July 2002

The ferroelectric (Pb,La)(Zr,Ti)O3 optical waveguiding thin films have been prepared on MgO coated (100)LiF substrates by pulsed laser deposition. X-ray θ-2θ scans revealed that the films are single-phase pseudocubic perovskite and highly 〈100〉 textured. The surface chemical composition of the as-grown films was determined by x-ray photoelectron spectroscopy. The ferroelectric properties of the films as grown on Pt/Ti coated silicon were demonstrated by using a modified Sawyer–Tower circuit, and the optical waveguiding properties of the films were characterized by using a rutile prism coupling method. The as-grown films have an average transmittance of 75% in the wavelength range of 400–2000 nm and a refractive index of 2.2 at 632.8 nm close to the bulk PLZT. The distinct m lines of the guided TM and TE modes of the films as grown on MgO coated LiF substrates have been observed.
Coherence measurement technique for short-wavelength light sources
Authors: Nugent K. A. , Trebes J. E.
Published: July 2002

This paper proposes and analyzes a technique that will allow the spatial coherence properties of short-wavelength radiation sources to be measured. The technique is based on the analysis of the partially coherent diffraction patterns produced by a uniformly redundant array.
Substrate temperature measurements using ultrasonically bonded Platinel II thermocouples
Authors: Westerheim A. C. , Anderson Alfredo C. , Cima M. J.
Published: July 2002

The accurate measurement of substrate temperature is important for thin-film deposition processes. In this paper, we report a simple and reproducible method to bond thermocouples directly to a substrate, thus circumventing many difficulties of other temperature measurement techniques. We have ultrasonically bonded 25-μm-diam wires of two different Au-Pt-Pd alloys (14%-31%-55% and 65%-0%-35%), commercially known as Platinel II, to gold bonding pads evaporated onto several surfaces: stainless steel, LaAlO3, Al2O3, and YBa2Cu3O7−x (YBCO) thin films. The ultrasonic bonding process does not change the thermal emf of the thermocouple from the bulk value, and the resultant bond is able to withstand temperature cycling from room temperature to at least 800 °C without detachment of the thermocouple from the surface or change in its thermal emf. We have used these thermocouples to measure the surface temperature of a LaAlO3 substrate and a 2000-Å YBCO film on a LaAlO3 substrate in order to evaluate the effectiveness of silver paste as a thermal contact to anchor substrates to a heater block during the sputter deposition of YBCO thin films. Silver paste is found to provide an excellent contact. At a heater temperature of 750 °C, the temperature difference between the surface of the LaAlO3 substrate and the surface of the heater was 348 °C without silver paste and only 2 °C with silver paste.
A line beam electron gun for rapid thermal processing
Authors: Pauli M. , Müller J. , Hartkopf K. , Barth T.
Published: July 2002

A line beam electron gun based on the Pierce gun type was developed. The line cathode was realized by a directly heated tungsten rod. The temperature distribution along the tungsten rod was simulated numerically. The simulation shows a flat temperature across 2/3 of the cathode length and it agrees with appropriate measurable parameters. The beam profiles of the electron gun perpendicular to the line direction were examined as a function of electrical and geometrical parameters: The space-charge distribution in front of the cathode was found to be responsible for the shape of the beam profile. The shape of the beam profile is weakly influenced by the acceleration to the anode. The heating current induced voltage drop along the cathode was found to be responsible for the nonuniform emission in line direction. A model for the emission behavior of the line beam electron gun was developed. The model is based on the results of the measurements and on a numerical simulation of the potential distribution in the area between Pierce reflectors and anode. The emission model shows a solution to homogenize the emission by a suitable variation of geometrical parameters in line direction. A linear variation was realized in experiment which enables a uniform emission across 2/3 of the cathode length. The beam profile is adjustable by a bias voltage between the cathode and the Pierce reflectors.
A new furnace for thin-film stress experiments
Authors: von Preissig F. J.
Published: July 2002

A specialized furnace that is compatible with the optical-lever method of thin-film stress measurement has been developed. Its design is geared toward experiments in which changes in stress at constant temperature are to be monitored. Important capabilities include a maximum temperature of over 700 °C, good temperature control, hot-furnace sample insertion, lack of interference with stress measurement, and the use of inert gas or steam as ambients. Application of the furnace to the study of thermally activated material processes is demonstrated in experiments involving water sorption in phosphosilicate glass and crystallization of amorphous silicon.
A new method for x-ray powder diffraction studies
Authors: Beno M. A. , Knapp G. S. , Jennings G.
Published: July 2002

A new method has been developed which results in a major improvement in count rate of Bragg–Brentano-type diffractometers. The method uses a focusing exit beam monochromator and a multichannel detector to achieve this improvement. The method is very efficient in eliminating background and can have very high resolution. Existing diffractometers can be easily modified to take advantage of this technique.
Cathodoluminescence studies of growth and process-induced defects in bulk gallium antimonide
Authors: Méndez B. , Dutta P. S. , Piqueras J. , Dieguez E.
Published: July 2002

The homogeneity and luminescence properties of undoped bulk GaSb have been studied by the cathodoluminescence (CL) technique in the scanning electron microscope. CL images have revealed a nonuniform distribution of native defects in GaSb wafers prepared from as-grown single crystals. Postgrowth annealing in vacuum, gallium, and antimony atmospheres has been performed to obtain more accurate information about the defect structure in this material. In general, on annealing, homogeneous distribution of impurities is observed throughout the wafers. CL spectra show that a luminescence band (centered at 756 meV) is enhanced by annealing in a gallium atmosphere, suggesting that Ga atoms play an important role in the formation of this acceptor center. The 756 meV peak has been attributed to a transition from conduction band to an acceptor center comprised of GaSb or a related complex. Interestingly, localized crystallization at the subgrain boundaries seems to occur by annealing in Ga atmosphere.
An ion detector for imaging two-dimensional velocity distributions
Authors: Corr D. , Jacobs D. C.
Published: July 2002

The design and performance of a novel ion detector is described. The detector produces a two-dimensional image which displays the time-of-flight distribution of a pulsed packet of ions. Pulse sequencing within the detector allows for simultaneous mass and velocity resolution of the detected ions. The image capturing hardware combines long-term signal integration with single-ion detection in order to provide a wide dynamic range in ion sensitivity.
Absolute calibration of a total yield indium activation detector for DD and DT neutrons
Authors: Ruiz C. L. , Leeper R. J. , Schmidlapp F. A. , Cooper G. , Malbrough D. J.
Published: July 2002

Progress in Z-pinch experiments at Sandia’s Saturn facility have underscored a need for an absolute yield measurement for DD fusion neutrons. The technique chosen for making this absolute yield measurement was neutron activation of indium metal samples. To calibrate the technique, a 175-keV deuteron beam was allowed to impinge on a 3.0-μm-thick erbium deuteride target, producing neutrons through the 2H(d,n)3He fusion reaction. The neutron flux produced at 0° and incident on nominal 5-g indium samples was determined by the associated particle method. This method employed protons measured from the 2H(d,p)3H reaction to infer the neutron flux produced. After neutron irradiation, the activity of the indium samples was measured with a Ge gamma-ray detector. The total activity of the metastable state 115mIn (336.23 keV) was measured, compared with the total incident flux, and a calibration factor (indium counts/neutron/gram of indium) determined. For completeness, a calibration factor for DT neutrons from the 3H(d,n)4He fusion reaction was also obtained through the measured activity of the metastable state 114mIn(190.29 keV). The experiment and the measured calibration factors for both reactions are described in the paper.
Ultrasonic time-of-flight monitoring of the position of the liquid/solid interface during the Bridgman growth of germanium
Authors: Carter John N. , Lam Alex , Schleich Donald M.
Published: July 2002

Ultrasound has been used to track the movement of the solid/liquid interface during the vertical Bridgman growth of germanium. Digitally processed data representing the received ultrasonic signal indicated a time lag prior to crystal growth, and showed a growth rate close to the pulling rate of the furnace. We observed no effect of the ultrasonic energy on the growth of the crystal or on the formation of defects. We have been able to locate the interface to within 0.3 mm in the presence of substantial temperature gradients. An extension of the work presented could lead to a tomographic reconstruction of the interface shape.
Absolute measurements of elastic-wave phase and group velocities in lossy materials
Authors: Fortunko C. M. , Peterson G. L. , Chick B. B. , Renken M. C. , Preis A. L.
Published: July 2002

Traditional methods of determining phase and group velocities are often inadequate for many thick-section materials that exhibit greater than 30 dB, frequency-dependent propagation losses across the passband of the transducer. This article describes a measurement method that addresses this problem. Our method is mechanized as a pulsed, swept-frequency interferometer. The method’s accuracy and reliability are enhanced by a combination of circuit-design improvements, which increase the signal-to-noise ratio and linearity, and signal-processing methods, which remove circuit-related measurement errors and compensate for diffraction. First we describe the foundations of our measurement method and its mechanization. Then we describe the signal-processing procedures, used to calibrate the instrumentation and to determine the absolute phase and group velocities. To illustrate the method, we determine the phase velocities in a very lossy, 50-mm-thick, glass/epoxy specimen in the 0.3–1.2-MHz region.
Optical tweezers using a diode laser
Authors: Afzal Robert S. , Treacy E. Brian
Published: July 2002

Simple modifications were made to a commercial microscope to enable injection of light from a diode laser, and demonstrate optical tweezers action. The basic properties of microscope optics are presented together with discussion of principles to be followed in arranging the external optics for achieving useful tweezers. Procedures using a single-mode diode laser along with experimental results are presented in enough detail to permit readers to make their own system for trapping and manipulating single cells. It is surprisingly easy to demonstrate tweezers action once some basic concepts are understood.
A single quartz crystal to measure dynamic elastic moduli at several ultrasonic frequencies
Authors: Thomas V. , Giacomin A. J. , Wolfenden A.
Published: July 2002

An instrument for measuring the elastic moduli at several ultrasonic frequencies, using a single quartz crystal, has been developed. In the past an array of pairs of oscillators was used as part of the piezoelectric ultrasonic composite oscillator technique to measure the dynamic Young’s modulus and shear modulus at several ultrasonic frequencies. Experimentation was done using the conventional composite and the new single crystal systems at 40, 80, and 160 kHz on brass and aluminum samples, both in the longitudinal and torsional modes. The good agreement between these systems is indicative of the validity and applicability of the new design.
Optical and structural investigation of stain-etched silicon
Authors: Kalem Ş. , Rosenbauer M.
Published: July 2002

We report on optical and vibrational properties of porous silicon (por-Si) layers grown on p-type Si wafers by electroless etching technique. The results indicate a correlation between the photoluminescence (PL) intensity and the multihydride complexes (SiHn with n≥2). However, similar correlation was also found for monohydride species from the layers containing no multihydrides. It is shown that the increase in the amount of oxidation is responsible for broadening of the PL emission band. Furthermore, a new IR absorption band is observed at 710 cm−1 and assigned to multihydrides suggesting a new local bonding environment for hydrogen atoms in these layers.
Bistable locking of single-electron tunneling elements for digital circuitry
Authors: Kiehl R. A. , Ohshima T.
Published: July 2002

Bistable phase locking of single-electron tunneling oscillations is proposed as the basis for digital logic circuitry. A simple model of single-electron tunneling is used to examine the locking of capacitively coupled junctions pumped at twice the tunneling frequency and activated by clocking the dc bias. The locking to sinusoidal input signals and the locking between coupled junctions is examined. It is shown that bistable locking exhibits an input amplitude threshold and phase noise margin and that junctions rapidly lock in antiphase due to a strong interaction between tunneling events. Conditions under which the operation is potentially useful for digital circuitry are identified.
(InAs)n/(InxGa1−xSb)m superlattice structures for optimal miniband-edge absorption
Authors: Loehr John P.
Published: July 2002

We present effective bond orbital model calculations of the cutoff wavelengths and oscillator strengths of strained type-II (InAs)n/(InxGa1−xSb)m superlattice structures lattice mismatched to (001) GaSb substrates. The monolayer numbers n and m giving the maximal miniband-edge oscillator strength are determined for fixed wavelengths λ ranging from 5 to 30 μm, and for all values of the indium mole fraction x. At the longer wavelengths, the superlattice miniband gap is extremely sensitive to submonolayer fluctuations in n and m.
A versatile microwave plasma source and its application for a CO2 laser
Authors: März M. , Oestreicher W.
Published: July 2002

A single ridged waveguide with nonconstant ridge height, operated with a traveling wave has been proven to be a versatile microwave plasma applicator. Easy dimensioning, inexpensive production, and compatibility to standard rectangular waveguide components are the main advantages compared to other designs. The described plasma source is especially suitable for any applications where an exceptionally uniform plasma is required. Design equations are given for easy adaption of the applicator to individual requirements. The applicator has been investigated for microwave excitation of a diffusion-cooled CO2 laser. With a nonoptimized system, laser output power of 9 W could be achieved in a quasi-cw mode. A traveling discharge operating mode is described which is useful for plasma diagnostics and for pulsed laser applications.
Determination of neutral-beam-power profiles: Divergences and power fractions of the species from measurements inside the torus of TEXTOR
Authors: Euringer H. , Verplancke Ph.
Published: July 2002

A set of experiments was carried out with TEXTOR neutral beams inside the torus to obtain detailed knowledge about the beam for later use in experiments such as charge exchange recombination spectroscopy and for energy deposition calculations. A segmented graphite plate and an infrared camera were used to gain information about the total beam power profile for different beams (H, D, He) and particle energies. Spatially resolved measurements of Doppler-shifted Hα line intensities were used to calculate the relative widths and fractional powers of the three beam species (for H and D) at different energies (this report mainly deals with this method). By these measurements the beams are fully characterized so that charge exchange spectroscopy could be employed to yield impurity concentration profiles in spite of an extended beam and lines of sight not tangential to the plasma surfaces. The results for a 50 keV hydrogen beam are also taking into account the calorimetric measurements inside the injector box. The beamlets are composed of two Gaussian profiles. The broader profile (divergence of 3° and a power fraction of 30%) is mainly scraped off in the injector itself. The composition of the smaller profile, which almost exclusively determines the power to TEXTOR, is calculated from the measured results. The power fractions for the three species (E, E/2, E/3) are 50%, 37.6% and 12.4% respectively. The divergences horizontally are 0.87, 0.92, 0.95 degrees and vertically 0.91, 0.98, 1.02 degrees respectively. The exact position of the beam inside TEXTOR and its direction are determined as well.
Dual beam spectrometer for optical studies of spread monolayers at the air-water interface
Authors: Wang Yicheng , Wang Yi-Ming , Patterson L. K.
Published: July 2002

An optical spectrometer for the study of low level optical absorption and reflection of spread monolayers at the air-water interface is described. This spectrometer is suitable for measurements at wavelengths from ∼350 to 800 nm and has a precision of ∼2×10−5 in terms of effective optical density. It employs a dual beam design utilizing fiber optic bundles to guide light and a multichannel photodiode array detection system. Instrumental control and data gathering are designed within Labwindows software. Representative spectral absorption data from chlorophyll a degradation kinetics are presented by way of illustration. Comparison of chlorophyll a reflection and absorption is also given.
An improved transient hot-wire method for studying thermal transport in condensed matter
Authors: Takahashi H. , Hiki Y. , Kogure Y.
Published: July 2002

The transient hot-wire method for simultaneously measuring the thermal conductivity and thermal diffusivity of materials has been modified to improve the accuracy of the measurements. In this new experimental method, called the multicurrent method, several constant current values are used for heating the hot wire in order to determine accurately the thermal transport quantities. The details of the multicurrent method are precisely described, and examples of experiments using the method with pure water, electrolytic solution, and ionic conducting glasses are given. It is shown that this method can be used both for liquid and solid materials; a relatively small amount of the specimen material is sufficient for each experiment; the material can be insulating as well as highly ionic-conductive; the accuracies of the determined thermal conductivity and the thermal diffusivity values are, respectively, around ±1% and ±5%.