bluuebunny/crossref_metadata_2025 huggingface dataset:
High intensity luminescence from pulsed laser annealed europium implanted sapphire
Authors: Can N. , Townsend P. D. , Hole D. E. , Afonso C. N.
Published: July 2002

Sapphire samples (Al2O3) were implanted with 400-keV ions at a dose of 1×1016 ions cm−2. A comparison was made between furnace annealing and pulsed laser annealing of the implanted samples. Furnace annealing to 1200 °C, followed by excimer laser anneals, resulted in an increase of the cathodoluminescence emission intensity of the implanted europium by a factor of ∼20. This enhanced intensity is ∼50 times that of the signal prior to any form annealing treatment. It is proposed that the laser anneals dissociate Eu related clusters. The Eu 622-nm lifetime reached 1.53 ms compared with an original postimplant value of 0.14 ms.
Prospects for truly blue ZnSe/Zn1−uMguSvSe1−v/Zn1−xMgxSy Se1−y semiconductor diode lasers
Authors: Mensz P. M.
Published: July 2002

The electrical and optical operation of separate confinement heterostructure quantum-well lasers of ZnSe/Zn1−uMguSvSe1−v/Zn1−xMgxSy Se1−y (blue laser) and Zn0.8Cd0.2Se/ZnS0.06Se0.94/ Zn1−zMgzSuSe1−u (blue-green laser) was studied by numerical simulation. The physical model was based on the self-consistent solution of Poisson’s equation, the current continuity equation, the photon rate equation, and the scalar wave equation. The band structure of strained quantum well was calculated using k⋅p theory, and the gain model was based on the interband electron-hole pair recombination without including excitonic effects. Good agreement was obtained between the experimental and the calculated output characteristics of Zn0.8Cd0.2Se/ZnSe0.06Se0.94/ Zn1−zMgzSuSe1−u blue-green lasers over a wide temperature range from 85 to 394 K. Further extension of these calculations to the ZnSe/Zn1−uMguSvSe1−v/Zn1−xMgxSy Se1−y structures demonstrated a considerable increase in threshold current density of blue lasers, due to the insufficient level of doping in wide-band p-Zn1−xMgxSySe1−y cladding layers. This would likely impose more stringent conditions for realization of continuous blue laser emission compared to their blue-green laser counterparts.
Micromechanical radiation dosimeter
Authors: Thundat T. , Sharp S. L. , Fisher W. G. , Warmack R. J. , Wachter E. A.
Published: July 2002

We demonstrate the use of microcantilevers coated with ultraviolet cross-linking polymers as optical radiation dosimeters. Upon exposure to radiation, a treated cantilever bends due to stress and its resonance frequency increases due to stiffening. These phenomena can be used to develop sensitive radiation dosimeters which respond to radiation affecting the mechanical properties of the selected coating.
Application of optical phase conjugation to plasma diagnostics (invited)
Authors: Jahoda F. C. , Anderson B. T. , Forman P. R. , Weber P. G.
Published: July 2002

Several possibilities for plasma diagnostics provided by optical phase conjugation and, in particular, self-pumped phase conjugation in barium titanate (BaTiO3) are discussed. These include placing a plasma within a dye laser cavity equipped with a phase conjugate mirror for intracavity absorption measurements, time differential refractometry with high spatial resolution, and simplified real-time holographic interferometry. The principles of phase conjugation with particular reference to photorefractive media and the special advantages of self-pumped phase conjugation are reviewed prior to the discussion of the applications. Distinctions are made in the applications between those for which photorefractive conjugators are essential and those for which they only offer experimental simplification relative to other types of phase conjugators.
Measurement of the fluorescent decay time of GaAs under x-ray excitation (abstract)
Authors: Lowry M. E. , Kilkenny J. D.
Published: July 2002

Cooled GaAs is potentially useful as an x-ray fluor with a very fast response time. We present measurements of the decay time of the near-infrared emission from cooled intrinsic GaAs under excitation by a 200-ps pulse of ∼1-keV x rays. The x-ray pulse was produced by focusing the Janus laser onto a Cu target. An x-ray diode array and an x-ray crystal spectrometer characterized the x-ray pulse. The linearity and decay time of the optical fluorescence from GaAs was measured by varying the distance of the sample from the laser plasma.
Two-dimensional space-resolved soft x-ray spectroscopy of hot dense plasmas (abstract)
Authors: Kiuttu G. F. , Degnan J. H. , Richter-Sand R. J. , Woodall D. M.
Published: July 2002

Two-dimensional spatially resolved K shell spectra from hot (Te≂40–400 eV) dense (ne≂1019–1021 cm−3) aluminum plasmas have been recorded using a convex curved KAP crystal spectrograph in a dispersion mapping mode1 with an orthogonal imaging slit. The approximately 1-cm-diameter, 2-cm-long cylindrical source was viewed on end, yielding axially and temporally integrated spectra. The relative intensities of the lines and recombination continua were used to estimate local temperatures and densities. The measurement technique is reviewed and representative analysis and results presented in this paper.
Intensified CCD camera system for plasma diagnostics (abstract)
Authors: Smith J. , Chase R. , Garcia J. , Hsieh C. , Vaslow D.
Published: July 2002

It is possible to put together an intensified imaging system which has about the same sensitivity as photomultiplier tubes. Such a camera system, which utilizes a combination of image intensifiers and CCD image sensor, was constructed recently for the multipoint Thomson scattering diagnostic on Doublet III. In our case, the incoming image is first gated and amplified in the intensifier stages, then lens coupled to a CCD camera cooled to LN2 temperature. The camera contains a RCA back-illuminated CCD of 320×512 pixels, has a good quantum efficiency (≂85% at 550 nm), and has a noise level per pixel of about 60 electrons. The system is controlled through CAMAC with a photometric camera controller which allows a number of pictures to be taken and stored on the CCD chip for later readout. The multipicture capability is convenient for use with a multipulse Thomson scattering diagnostic to provide ne and Te profile measurements at several time points in a plasma shot. It is also conceivable that the camera system can be utilized to directly view the two-dimensional spatial distribution of plasma radiation at a particular energy in the range from near-infrared to soft x rays for information relating to plasma activities on flux surfaces.
Rapid synthesis of indium phosphide
Authors: Adamski Joseph A. , Ahern Brian S.
Published: July 2002

A method for the high-pressure synthesis (440 psi) of InP is investigated. Independent temperature control of a three-zone furnace incorporating a heat pipe provides a stable temperature profile throughout the synthesis cycle. Internal/external pressure control of the quartz ampoule is maintained by use of a water-cooled baffle and a temperature/pressure balancing program. Complete synthesis is achieved in less than 5 h.
Extraction of volume-produced H− ions from a hybrid magnetic multicusp source
Authors: Bacal M. , Hillion F.
Published: July 2002

The negative ion density n− is studied using the photodetachment technique in the extraction region of a 5.7-l hybrid magnetic multicusp source, and is correlated with the extracted negative ion current I−. It is found that biasing positive the plasma electrode (PE) of the extractor affects in a similar way both n− and I−: both attain a maximum for a PE bias of +1.5 V, while the electron density ne and extracted current Ie exhibit a monotonic reduction. At optimum PE bias, n−/ne attains a value of 0.7. Ie is found to be comparable to the electron thermal flux through the extraction slit; this indicates that there is no potential barrier for the negative particles at the plasma border in front of the extraction slit. At optimum PE bias both Ie and I− vary in proportion to n0.8e. Two regimes characterize the variation of I− vs n−; at high density I− varies in proportion to n1− and appears to be larger than the thermal negative ion flux through the extraction slit, calculated under the assumption that the negative ion temperature is close to the neutral molecule temperature. The discrepancy is the largest (a factor of ten) at the lowest gas pressure.
Computer-controlled, small sample ac calorimetry at low temperatures and in high magnetic fields
Authors: Schmiedeshoff G. M. , Fortune N. A. , Brooks J. S. , Stewart G. R.
Published: July 2002

We describe a computer based ac calorimetry technique for small samples (m<100 mg) at low temperatures (T<2 K) and in high magnetic fields (B≤20 T). We have found this technique suitable for relative calorimetry in noisy environments. Extension of this technique to absolute calorimetry is also discussed.
Improved rectangular cavity for EPR in TE102 mode
Authors: De S. K.
Published: July 2002

Usually the side walls of a rectangular cavity are less than one skin depth thick at the field-modulation frequency. Eddy current creates an opposing magnetic field to the incoming modulation field, which tends to reduce the field at the center of the cavity. Moreover if the walls of the cavity are kept thin, interaction of eddy currents and the static magnetic field will create mechanical vibrations that will modulate the microwave frequency, thus generating spurious signals at the output of the amplifier. In this note a cavity for X band (in 9–10 GHz) is described in which the above problems have been overcome by corrugating the cavity walls in a precise manner. In comparison with a thin sidewall, the EMF that drives the eddy currents remains unchanged, but because the resistance increases, the eddy currents decrease.
Interface for data exchange between a parallel and the IEEE-488 bus
Authors: Grubic M.
Published: July 2002

Low-cost talker and listener interfaces between the IEEE-488 bus and a BCD instrument parallel data bus are described. The circuits do not employ any microprocessor at all. Their versatile handshake lines enable simple connection to numerous devices.
Timed source of slow protons
Authors: Mills A. P.
Published: July 2002

Alpha particle bombardment of a Si surface-barrier detector in vacuum causes the release of several species of ions from the contaminant layer on the detector surface. The mass-to-charge ratios of the ions are determined by time-of-flight spectroscopy. A significant fraction of the ions are H+ with a yield of 4×10−5 H+ per alpha particle and an emission energy of less than 70 eV. This ion source could be useful for testing slow μ+ collection optics and possibly for studying the diffusion of H atoms in liquid He.
Microsecond time resolution on a conventional EPR spectrometer using 200-kHz magnetic field modulation and phase-sensitive detection
Authors: de Jager P. A. , van Wijk F. G. H.
Published: July 2002

A method is developed to detect electron paramagnetic resonance (EPR) transient signals with frequency components in the range from dc to 1 MHz and a low initial signal-to-noise ratio (e.g., 0.1 after one sweep). This method uses 200-kHz magnetic field modulation on a conventional EPR spectrometer, using a modified lock-in detector: the tuned amplifier is replaced by a broadband preamplifier with a high-pass filter and the low-pass filter of the lock-in detector is replaced by a broadband amplifier. The transients are generated incoherently from the magnetic field modulation, and subsequently averaged. The function of the (removed) low-pass filter is taken over by the averaging. An instrumental response time of less than 1 μs is obtained. This was determined by measuring the rise time of the triplet state of the photosynthetic reaction center of Rhodopseudomonas sphaeroides R-26 at 165 K. This method, direct detection, and high-frequency (1–2 MHz) modulation are discussed. The S/N ratio of the method described in this paper is similar to that of the other two methods. However, when large linewidths (>0.5 mT) are met, it gives a superior S/N ratio as compared to high-frequency (1–2 MHz) modulation methods, due to the higher maximum modulation amplitude. When the transients of interest contain frequency components in the low-frequency noise regime (dc–50 kHz), the described method is to be preferred over direct detection because of its better S/N ratio.
Calibration of pulsed x-ray spectra
Authors: Anderson J. A. , Collins C. B.
Published: July 2002

A new technique has recently been described for the absolute calibration of intense sources of pulsed radiation in the 0.2–1-MeV range of photon energies. An x-ray activation technique, it depended upon the storage of samples of the irradiating spectrum in the form of populations of nuclei excited to isomeric states with lifetimes of seconds to hours. Accuracy was dependent upon the precision assumed for tabulated values of nuclear parameters. Described here is an extension of this technique to the larger range of photon energies, 0.2–1.5 MeV and to intensities from 1012 keV/keV to 1016 keV/keV using the target nuclei 79Br and 77Se. In this work self-consistency of the nuclear parameters was directly determined. Important changes were found to be necessary for improved accuracy, particularly over the larger ranges of experimental variables being considered. Values of the now-consistent set of nuclear parameters are reported.
A new method for i
n s
i
t
u dynamic calibration of temperature sensors
Authors: Budwig R. , Quijano C.
Published: July 2002

A new method for in situ dynamic calibration of temperature sensors has been developed. The method is nonintrusive and can be used on a variety of sensors mounted in a variety of configurations. Chopped laser heating is used to generate a step change in sensor temperature so that dynamic calibration may be accomplished. Results on the dynamic response of a thermistor in air flow are presented as an application. A procedure for estimating time constants using data from existing heat transfer correlations has also been described.
Photodetachment technique for measuring H− velocities in a hydrogen plasma
Authors: Devynck P. , Auvray J. , Bacal M. , Berlemont P. , Bruneteau J. , Leroy R. , Stern R. A.
Published: July 2002

This article reports work in progress on laser diagnostics of negative-ion transport velocity in H−-ion volume sources. The plasma dynamics after the laser shot is discussed in detail, and the effect of the potential perturbation on the H− velocities is evaluated. A method of evaluation of the H− transport velocity from single-laser-beam photodetachment experiments is proposed. To substantiate this method, two-laser-beam photodetachment experiments have been effected. The velocities thus determined are pressure dependent; they correspond to H− energies in the range 0.23–0.08 eV.
Continuous level sensors for cryogenic liquids using high-T
c superconductors
Authors: Siegmann St. , Frey T. , Ramseyer J. P. , Güntherodt H.-J.
Published: July 2002

We have developed a new device using high-temperature superconducting sensors for the continuous detection and control of the level of cryogenic liquids with boiling temperatures of up to 90 K. The sensors contain material of La-(Ba,Sr)-Cu or Y-Ba-Cu oxides with superconducting transition temperatures between 20 and 90 K. For the first time, continuous level measurements become possible in open cryostats of, e.g., liquid nitrogen over a length of 1 m. Conventional methods are usually limited due to ice formation.
Electrostatic beam blanking systems
Authors: Grigorov Grigor Nikolov
Published: July 2002

Electrostatic beam blanking systems are widely used in beam optics. Their characteristics (speed, damped oscillations, and position with respect to the optical axis) determine the optical and technological parameters of the beam-handling system. The proposed configuration of the blanking system uses signals which have rise times smaller than 10−10 to 10−9 s and amplitudes 10–102 V. Moreover, the screening of the blanking system is ensured by the cylindrical form of one of the electrodes.
Photoluminescence measurement system using fiber optics
Authors: Srivastava A. K. , Bandyopadhyay A.
Published: July 2002

We describe a novel photoluminescence measurement apparatus which incorporates an optical fiber for carrying both the excitation beam and the luminescence from the sample. The advantages of the optical fiber makes the system very versatile and suitable for sensitive measurements. The collection efficiency of the setup is demonstrated to be the same as that of a conventional setup. Several photoluminescence spectra of III-V compounds recorded using the apparatus are also included to demonstrate its applicability over a wide wavelength range (0.8–2.0 μm).
Diagnostic beamline for a third generation storage ring
Authors: Perera R. C. C. , Melczer M. E. , Warwick A. , Jackson A. , Kincaid B. M.
Published: July 2002

A knowledge of the position, size, and stability of the source and the angle of emission of synchrotron radiation (SR) from the storage ring are essential for optimizing the operation of storage ring, insertion devices and monochromators. Berkeley’s Advanced Light Source (ALS) has a natural emittance of 3.4×10−9 mrad, and has beam sizes σh and σv (assuming a 10% emittance ratio into the vertical direction) in bending magnet 1 (BM1) of 44 and 83 μm, respectively. Simple diffractive optical calculations show that imaging this beam using visible light optics is not feasible and imaging must be performed using photon energies greater than 50 eV. This will be the same for all third generation low emittance storage rings. The synchrotron radiation diagnostics at ALS will consist of an imaging system for 200 eV photons and a ‘‘white beam’’ port with a streak camera to obtain the timing information. The imaging system will employ two crossed spherical mirrors in a Kirkpatrick–Baez configuration, to eliminate astigmatism. Use of 1:1 imaging will eliminate coma, resulting in an image of the source which is only limited by the residual aberrations of the optics. Real time imaging of the beam is deemed feasible by the use of a high resolution charged coupled device (CCD), and the associated electronics necessary to read the CCD. The design of the imaging system of the diagnostic beamline for ALS and the detection system will be discussed with a view toward applications in other third generation SR sources.
High spatial resolution infrared emission thermal measurement of laser-induced chemical vapor deposition
Authors: Dupuy C. G. , Hurst J. E.
Published: July 2002

Infrared emission radiometry was used as a noncontact temperature probe with a tens of micron spatial resolution for monitoring laser-induced chemical vapor deposition (LCVD). With appropriate calibration of the emissivity, a temperature of 255±15 °C was measured during gold LCVD from dimethylhexafluoroacetylacetonate gold (III). Equivalent deposition temperatures were calculated for both continuous and modulated laser illumination. Depending on the deposition conditions, material deposited with a modulated laser beam varied from notably worse (due to stress cracking) to notably better (more uniform growth morphology) than material deposited with continuous laser illumination.
A novel small-period wiggler for free-electron lasers
Authors: Feng Bibo , Wang Mingchang , Wang Zhijiang , Lu Zaitong , Zhang Lifeng
Published: July 2002

A novel small-period wiggler constructed of edgy-wound bifilar-helical conducting sheets with ferromagnetic cores, intended for free-electron lasers (FELs), is presented, and the performance characteristics of the wiggler prototype with 10-mm period are measured. A field as high as 500–1000 G has been obtained. It is feasible to make a Raman FELs with this type of wiggler operating in the wavelength range of millimeters and submillimeters with a low electron energy (<500 keV) beam.
High-speed infrared camera
Authors: Garcia J. P. , Dereniak E. L. , Shepard S. M.
Published: July 2002

We have developed a staring-mode, high-speed infrared camera based on a RCA 160×244 PtSi Schottky-barrier charge-coupled device image sensor. The camera uses a unique method to achieve greater temporal resolution of rapidly varying thermal phenomena in the 3–5 μm band. Rather than increase the imager’s frame rate, we decrease the image integration time while maintaining a frame rate that is compatible with standard RS-170 video. This technique allows us to display and record repetitive events that occur at frequencies up to 5 kHz with conventional video equipment. In this article we describe the theory and operation of this system.
Improved calibration of the neutron yield measurement system on the FTU tokamak
Authors: Bertalot L. , Esposito B. , Podda S. , Rollet S.
Published: July 2002

The neutron yield measurement system on FTU was initially composed of six BF3 proportional chambers for the start-up phase. The present reliable operations in deuterium, at higher plasma current, produce higher temperature discharges with higher neutron yields, therefore requiring less sensitive detectors: three fission chambers were chosen. We report the results of the new detector system calibration performed in September 1990. The BF3 detectors were also recalibrated as large scattering masses had been added around the machine since the previous calibration (November 1989). The calibration was performed by placing a 252Cf source (5.81×107 n/s) at different radial and toroidal positions inside the vacuum vessel; an increased number of points on the torus axis, with the inclusion of some off-port positions, represents the improvement with respect to the previous calibration campaign. Data on the response of the different detectors as a function of the source position are presented. The computation procedures of the relationship between the counts of a single detector and the total neutron yield from an extended plasma are discussed. A comparison between the two detection systems is carried out and, for the BF3 chambers, the data of the ’89 calibration are compared with the present ones. Finally, preliminary results of the neutron emission from FTU ohmic discharges (campaign 1991) are presented.
Correlation between measured undulator magnetic fields and x-ray spectraa)
Authors: Carr Roger , Kincaid Brian , Hassenzahl William
Published: July 2002

Electron storage ring insertion devices, especially undulators, are designed using ideal device theory and the resulting x-ray spectra are reasonably close to predictions in most cases. However, magnetic field errors result in nonideal x-ray spectra. These effects can be calculated theoretically, and may also be measured. Here we present a study of an undulator whose magnetic fields and x-ray spectra have been measured carefully. We compare experiment and theory and explain the deviation from ideal of the shape of the undulator’s spectral peaks in terms of magnet errors.
Optical switching mechanism based on charge accumulation effects in resonant tunneling diodes
Authors: Park Pyong Woon , Chu Hye Yong , Han Seon Gyu , Choi Young Wan , Kim Gyungock , Lee El-Hang
Published: July 2002

We have identified the charge accumulation effects in a resonant tunneling diode for the application of optical switching by observing the hole tunneling peak under illumination with a Ti:sapphire laser. Two mechanisms, photocurrent and charge accumulation, are rigorously examined to determine which one is the dominant effect for optical switching by comparing the current–voltage (I–V) characteristics for forward biases and reverse biases. It is believed that the hole accumulation effect in the depletion region, which results in the hole tunneling current, is responsible for the shift of the I–V curves.
Superconducting resonator and a cryogenic GaAs field-effect transistor amplifier as a single-ion detection system
Authors: Jefferts S. R. , Heavner T. , Hayes P. , Dunn G. H.
Published: July 2002

A current measuring system capable of detecting single ions is described. The detector operates at a frequency of nominally 900 kHz and utilizes a superconducting inductor with high Q(Q≊8500) and a cryogenic GaAs field-effect transistor (FET) amplifier with noise temperature less than 0.3 K. Noise measurements of the FET are presented along with details of the construction of the superconducting inductor.
Measurement of the shape of a liquid-liquid interface by the method of light reflection
Authors: Chan C. K. , Liang N. Y. , Liu W. C.
Published: July 2002

An apparatus has been developed to measure the shape of the liquid-liquid interface of a phase-separated binary mixture after a temperature quench. The working principle of the apparatus is to measure the shape of the interface by using the reflection of a scanning light beam to find out the slope of the interface at various positions, and then the shape of the interface is obtained by a numerical integration. A real-time display sensitive to the shape of the interface is also provided to facilitate alignment of the optics. Results from calibrations show that a vertical resolution of 1 μm over a horizontal distance of 5 cm can easily be attained.
Optical design of a fast multiframe holographic interferometry system for transient plasma diagnostics
Authors: Chuaqui H. , Soto L. , Moreno M. , Favre M. , Wyndham E.
Published: July 2002

The design of a fast multiframe holographic interferometry system for rapidly evolving transparent objects is described. Essential elements to the configuration are a multipulse laser, an electro-optic deflector (EOD), and a concave spherical mirror. The hologram, EOD and concave mirror are in a circle whose radius is the same as the spherical mirror. The different frames are superimposed on the same area of the hologram. On reconstruction separation of multiple images is achieved on the Fourier plane of a lens which is used to image the reconstruction of the hologram. The total number of optical components is kept to a minimum and only two of these are used in transmission. Due to the low component count the quality of interferograms obtained is very high.
Image and sample geometry effects in SQUID magnetometers
Authors: Zie̢ba Andrzej
Published: July 2002

This review concerns the interpretation of the signal provided by SQUID magnetometers designed for measurements of magnetization and magnetic susceptibility. ‘‘Image effect’’ refers to the influence of superconducting elements in the vicinity of the sample and detection coil. Several exact and approximate methods are presented for calculation of how the device sensitivity G(r) varies with position r of a unit dipole sample in the presence of a superconducting shielding tube. In particular, the relative decrease of G(r) is approximately given by the third power of the ratio of the detection coil and shield diameters, and the effect of the shield’s finite length is found to be negligible in practical situations. A survey of complex detection coils (Helmholtz, saddle-type, gradiometer, and second derivative coil) includes calculation of the optimum spacing of the Helmholtz pair in the presence of a superconducting cylinder. The image effects due to the properties of the SQUID circuit and the field-dependent effects in high-field SQUID magnetometers are also discussed. Change in the instrument calibration due to sample size, shape, and location is considered for arbitrary samples as well as for specific cases of small, medium, and very long samples. A spherical harmonic expansion of G(r) makes it possible to derive simple formulas describing sample geometry effects for medium-sized samples with regular geometries (thin rod, cylinder, and rectangular parallelepiped). The results are compared to published experimental data.
A fluorescent plastic optical fiber sensor for the detection of corona discharges in high voltage electrical equipment
Authors: Farenc J. , Mangeret R. , Boulanger A. , Destruel P. , Lescure M.
Published: July 2002

The reliability of electrical equipment in high voltage systems can be affected by certain defaults (metallic particles, roughness, etc.) inside the device enclosure. These anomalies may cause a local glow discharge which propagates progressively inside the insulator and which can lead to electrical breakdown. To avoid this end result, corona discharges have to be detected with a system which satisfies some requirements. Actual methods are not well adapted to industrial constraints. An optoelectronic setup, consisting of a fluorescent plastic optical fiber as a light sensor, connected to a simple, low-cost amplifier, is proposed. Measurements were first carried out in air to demonstrate the feasibility of this detection method, then air was replaced by SF6. Results lead to the delineation of a sensor made of the fluorescent fiber and the associated amplifier.
Temperature measurement in rapid thermal processing using acoustic techniques
Authors: Lee Y. J. , Khuri-Yakub B. T. , Saraswat K. C.
Published: July 2002

Acoustic techniques are used to monitor the temperature of silicon wafers during rapid thermal processing from room temperature to 1000 °C with ±5 °C accuracy. Acoustic transducers are mounted at the bases of the quartz pins that hold up the silicon wafer during rapid thermal processing. An electrical pulse applied across a transducer generates an extensional mode acoustic wave guided by the quartz pins. The extensional mode is converted into Lamb waves in the silicon wafer which acts as a plate waveguide. The Lamb waves propagate across the length of the silicon wafer and are converted back into an extensional mode in the opposite pin. The time of flight of the extensional mode in the quartz pins is measured using pulse echo techniques and is subtracted from the total time of flight to obtain the Lamb wave time of flight across the wafer. Because the velocity of Lamb waves in the silicon wafer is systematically affected by temperature, the measurement of the time of flight of the Lamb wave provides the accurate temperature of the silicon wafer.
Magnetoresistance probe of spatial current variations in high-T
c YBa2Cu3O7–SrRuO3–YBa2Cu3O7 Josephson junctions
Authors: Gausepohl S. C. , Lee Mark , Antognazza L. , Char K.
Published: July 2002

The low frequency current–voltage characteristics of YBa2Cu3O7–SrRuO3–YBa2Cu3O7 Josephson junctions show an increasing resistance and phase shift in fields of 0 to 8 T. A critical current is also evident up to 8 T. Data are analyzed in terms of field-induced perturbations of the current paths through the junction. Results indicate a highly inhomogeneous interface where the mean width of spatial variations in both normal and supercurrent is of order 50 to 100 Å.
A near-infrared Fourier-transform planar supersonic jet spectrometer for rovibrational studies of weakly bound dimers and trimers
Authors: Hartz C. , Wofford B. A. , Meads R. F. , Lucchese R. R. , Bevan J. W.
Published: July 2002

A high-resolution FTIR supersonic slit jet absorption spectrometer is described for the investigation of weakly bound dimers and trimers in the near-infrared spectral region. The spectrometer is demonstrated to conservatively have a sensitivity of 6×108 molecules/cc/state and can be operated at an apodized resolution of 0.004 cm−1. To illustrate the performance of the spectrometer, it has been applied to the rovibrational analysis of the band spectra of three weakly bound species in the near infrared: ν1 OC–HF, ν1 N2–HCl, and ν5 (H35Cl)3. The recorded spectra of these species are compared with corresponding investigations using state-of-the-art tunable infrared laser supersonic jet or molecular-beam spectrometers to illustrate the capabilities and limitations of the current FTIR supersonic jet spectrometer.
Ultrahigh sensitivity single-photon detector using a Si avalanche photodiode for the measurement of ultraweak biochemiluminescence
Authors: Isoshima Takashi , Isojima Yasushi , Hakomori Katsuhiko , Kikuchi Kazuro , Nagai Katsuya , Nakagawa Hachiro
Published: July 2002

A single-photon detector using a Si avalanche photodiode (APD) has been constructed. A trans-impedance type front-end circuit was employed in order to achieve a high signal-to-noise ratio. The APD and front-end circuit were cooled in liquid nitrogen to reduce dark count rate and circuit noise. The system performances were measured, and the achieved dark count rate and total quantum efficiency were 0.08 count/s and 5%, respectively. The sensitivity was evaluated to be of the order of 10−19 W. The APD single-photon detector was demonstrated to be available for measurement of the ultraweak biochemiluminescence at the order of 10−19 W/mm2 from brain slices, i.e., hippocampal slices. It was shown that the addition of tetrodotoxin to the hippocampal slice caused a decrease in the intensity of biochemiluminescence.
Application of hydrostatic weighing to density determination of tiny porous samples
Authors: Wolf B.
Published: July 2002

The sinter density of small superconducting BSCCO samples (Bi2Sr2Can−1CunOy; n=1, 2, or 3; y about 7) was determined by hydrostatic weighing using a special technique to correct the mass data for penetration of immersion liquid. A discontinuity in the reevaporation curve permits one to distinguish between liquid, penetrated into the sample, and that adhering to the surface of the specimen. This allows one to calibrate by wiping away of excess liquid without fluid extraction out of sample pores.
Fluorescent-based lifetime measurement thermometer for use at subroom temperatures (200–300 K)
Authors: Anghel F. , Iliescu C. , Grattan K. T. V. , Palmer A. W. , Zhang Z. Y.
Published: July 2002

The development, construction, and evaluation of a simple ruby-based fiber optic thermometer, for use over the region 200–300 K, are described. The results are compared with those obtained from a simple theoretical model, which may be used for system calibration, and with those of previously published work, and good agreement is seen. The application of such a sensor to the food processing industry and environmental monitoring is indicated.
The penta-prism LTP: A long-trace-profiler with stationary optical head and moving penta prisma)
Authors: Qian Shinan , Jark Werner , Takacs Peter Z.
Published: July 2002

Metrology requirements for optical components for third-generation synchrotron sources are taxing the state of the art in manufacturing technology. We have investigated a number of error sources in a commercial figure measurement instrument, the Long-Trace-Profiler II, and have demonstrated that, with some simple modifications, we can significantly reduce the effect of error sources and improve the accuracy and reliability of the measurement. By keeping the optical head stationary and moving a penta prism along the translation stage, as in the original pencil-beam interferometer design of von Bieren, the stability of the optical system is greatly improved, and the remaining error signals can be corrected by a simple reference beam subtraction. We illustrate the performance of the modified system by investigating the distortion produced by gravity on a typical synchrotron mirror and demonstrate the repeatability of the instrument despite relaxed tolerances on the translation stage.
Applications of wavefront division interferometers in soft x rays
Authors: Polack F. , Joyeux D. , Svatoš J. , Phalippou D.
Published: July 2002

The development of soft x-ray interferometry demands high quality optical elements and high brightness sources. However, the balance between these two requirements depends on the exact nature of the interferometer setups. Generally speaking, amplitude division interferometers require beam splitters, the optical quality of which remain a big technological issue. On the contrary, the high brightness sources needed by wavefront division interferometers are readily available, and will progress in the near future. Examples of such interferometers are given for various applications in development or in project.
A new apparatus for photon- and ion-beam-assisted deposition
Authors: Wengenmair H. , Stritzker B. , Rauschenbach B.
Published: July 2002

Over the last decade ion-beam-assisted deposition (IBAD) has become a well-known technique for deposition of thin films because of its ability to control properties of coatings. A new IBAD system is introduced which includes a facility to illuminate samples by UV light during the deposition process in order to enhance motion of deposited atoms and interfacial reactions between substrate and coating. The IBAD system consists of two vacuum chambers, the preparation chamber and the analysis chamber, which are connected by a straight tube for sample transfer. Samples may be moved through the tube between the two chambers by a linear feedthrough. The preparation chamber includes a filamentless rf ion source, an electron-beam evaporator, and a tube with a nozzle delivering reactive gases near the sample during deposition. In addition to the ion-assisted deposition process, a technique based on photon irradiation has been employed to obtain significant improvements of structure and properties of deposited metal layers. As these films reflect a large fraction of light in the visible range, we use UV-light illumination. The samples are irradiated by UV light with a mercury arc lamp during deposition. To achieve the high degree of process automation most process parameters are controlled with a computer system. The analysis chamber includes a reverse view LEED/AES system, which is used to analyze composition and surface structure of thin the films.
SPA-RHEED—A novel method in reflection high-energy electron diffraction with extremely high angular and energy resolution
Authors: Müller B. , Henzler M.
Published: July 2002

A new instrument for spot profile analysis of reflection high-energy electron diffraction (SPA-RHEED) has been developed. The system works either in the conventional mode with a fluorescent screen or in the new high-resolution mode with a channeltron for the registration of the diffraction pattern. The unique properties (a transfer width of 0.2 μm, perfect linearity, high dynamic range, insensitivity to ambient light, low beam current, and energy filtering better than 4 eV) are described in detail. The results show that SPA-RHEED offers new additional applications such as quantitative spot profile analysis for the determination of the surface morphology and lattice constant measurements with an accuracy better than 0.001.
Thermal emission decay Fourier transform infrared spectroscopy
Authors: Imhof R. E. , McKendrick A. D. , Xiao P.
Published: July 2002

We present a new technique, thermal emission decay Fourier transform infrared spectroscopy, designed to perform noninvasive, noncontacting absorption spectrum measurements on unprepared, arbitrary surfaces. It uses pulsed optical heating of the near-surface region of the sample to produce transient thermal emission spectra in the midinfrared spectral region for room temperature samples. The raw data of intensity versus path difference versus time after excitation can be processed in two ways; (1) to yield time-resolved spectra for depth profiling of layered samples; and (2) to yield decay-associated spectra for absolute absorbance measurements of homogeneous samples.
Laboratory characterization of Wölter x-ray optics
Authors: Remington B. A. , Morales R. I.
Published: July 2002

We have conducted characterization measurements of a Wölter grazing incidence x-ray microscope. The measurements were carried out on 5% sectors of a Wölter x-ray optic in a laboratory utilizing a new, very versatile, high brightness x-ray source. Absolute reflectance measurements as a function of x-ray energy were made with Si(Li) detectors to acquire continuum spectra prior to and after reflecting off the Wölter optic. Spatial resolution characteristics of the Wölter were mapped out using backilluminated pinholes or grids imaged onto film or an x-ray charge-coupled device camera. The implications of the asymmetric point spread function are considered.
Apparatus for measuring the curvature of spherical and cylindrical surfaces
Authors: Shiue S. G. , Liao T. S. , Chang S. T. , Kao C. F. , Chen Y. F.
Published: July 2002

An apparatus, which is comprised of four equal ball feet forming a square on the same plane of the support plate and a plunger in the square and acts as a probe for determining the sagittal depth, can be used to measure the curvature of spherical as well as cylindrical surfaces.
Isotope separation in a magneto-optical trap
Authors: Noh H. R. , Kim J. O. , Nam D. S. , Jhe W.
Published: July 2002

We demonstrate simultaneous trapping and spatial separation of the two stable rubidium isotopes in a magneto-optical trap. To realize this novel type of isotope separation, we have built a compact diode laser which is frequency-stabilized by optical feedback from a diffraction grating, and frequency-modulated by a direct microwave modulation of the bias current from a yittrium iron garnet tuned oscillator. Use of the single diode laser with microwave sidebands provides much ease and flexibility in the applications of a magneto-optical trap.
Use of ion sources for highly charged ions in studies of atomic and ion–solid collisions (invited)a)
Authors: Winter H.
Published: July 2002

Collisions of slow multicharged and highly charged ions, i.e., ions with kinetic energies up to some 10 keV, with atoms in the gas phase and with solids have been studied in detail over the last few years. A brief review is presented on some typical experiments and their results which make use of the specific features of highly charged ions in the fields of atomic spectroscopy, ion–atom collisions, and ion–solid interactions. In particular recent progress in the understanding of the interaction mechanisms of highly charged ions with solid surfaces will be discussed.
A solenoidal and monocusp ion source (SAMIS)a),b)
Authors: Burns E. J. T. , Brainard J. P. , Draper C. H. , Ney R. H. , Leung K. N. , Perkins L. T. , Williams M. D. , Wilde S. B.
Published: July 2002

We have developed a new magnetic monocusp ion source for single aperture applications such as neutron generators. Coupling solenoidal magnetic fields on both sides of a monocusp magnetic field has generated over 70% atomic deuterium ions at pressures as low as 0.4 Pa (3 mTorr). This article describes the performance and characteristics of the solenoidal and monocusp ion source.
A cryogenic xenon droplet generator for use in a compact laser plasma x-ray source
Authors: Gouge Michael J. , Fisher Paul W.
Published: July 2002

A research instrument has been designed, fabricated, and tested that produces ∼25–100 μm diameter, liquid xenon droplets on demand at variable repetition rates of 1–100 Hz. Drops have been produced with low spatial dispersion which allows consistent interception by a high power laser beam to produce x-rays for advanced lithography systems. Experimental sequences of up to 42 min in length have been conducted at 30 Hz, producing over 75 000 xenon drops. This technology allows significant debris reduction from the laser-target interaction. The mass-limited, cryogenic droplets are vaporized, producing no fragments, and the resulting gas can be collected preferentially on a cold surface for later recycling.
Bipolar programmable current supply for superconducting nuclear magnetic resonance magnets
Authors: Koivuniemi Jaakko , Luusalo Reeta , Hakonen Pertti
Published: July 2002

In high resolution continuous-wave nuclear magnetic resonance (NMR) work well-reproducible, linear sweeps of current are needed. We have developed a microcontroller based programmable current supply, tested with superconducting magnets with inductance of 10 mH and 10 H. We achieved a resolution and noise of 4 ppm. The supply has an internal sweep with programmable ramping rate and a possibility for remote operation from a computer with either GPIB or RS232 interface. It is based on an 18-bit D/A converter. The maximum output current is ±10 A, the sweep rate can be set between 1 μA/s–140 mA/s, and the maximum output voltage is ±2.5 V. In work at ultralow temperatures, especially in superconducting quantum interference device NMR, all rf interference to the experiment should be avoided. One of the sources of this kind of unwanted input is the digital switching noise of fast logic devices. We discuss this problem in the context of our design.
Derivation of local impurity transport quantities from soft-x radiation evolution during tracer injection at W7-AS
Authors: Burhenn R. , Weller A. ,   W7-AS Team,   NI Group,   The ECRH Group
Published: July 2002

A frequently used method for determination of impurity transport coefficients is the analysis of the radial and temporal time evolution of the impurity density of injected tracer impurities. In cases when the impurity density cannot be measured directly, e.g., by active charge exchange recombination spectroscopy, the impurity density has to be reconstructed from impurity radiation as measured, e.g., by the soft-x camera. Due to the energy integrated information, assumption about the spatial ionization state distribution, e.g., coronal equilibrium, is necessary. This might not be valid in cases of large transport. Consequently, the transport quantities, derived under the preliminary assumption of radial coronal distribution, are used again in an iterative way to improve the density reconstruction in order to approach more realistic transport quantities. The procedure was applied to plasma discharges in the stellarator Wendelstein 7-AS.
Requirements for an active spectroscopy diagnostic with neutral beams on the RFX reversed field pinch
Authors: Carraro L. , Puiatti M. E. , Sattin F. , Scarin P. , Valisa M.
Published: July 2002

The conceptual feasibility of an active spectroscopic diagnostic on reversed field experiment (RFX) to measure the radial profiles of ion temperature, toroidal and poloidal drift velocities, and main impurity densities is examined. In particular a charge exchange recombination spectroscopy experiment is simulated for carbon and helium impurities. The motional Stark effect on the beam atoms injected into RFX is estimated as a means to measure the magnetic field pitch and intensity. A modulated beam injector (500 Hz) with 2 A of equivalent current and an energy of 50 keV/amu appears to be adequate to perform the measurements over a reasonable range of operational regimes.
Temperature stabilized effusion cell evaporation source for thin film deposition and molecular-beam epitaxy
Authors: Tiedje H. F. , Brodie D. E.
Published: July 2002

A simple effusion cell evaporation source for thin film deposition and molecular-beam epitaxy is described. The source consists of a crucible with a thermocouple temperature sensor heated by a resistive crucible heater. Radiation heat transfer from the crucible to the thermocouple produces a consistent and reproducible thermocouple temperature for a given crucible temperature, without direct contact between the thermocouple and the crucible. The thermocouple temperature is somewhat less than the actual crucible temperature because of heat flow from the thermocouple junction along the thermocouple lead wires. In a typical case, the thermocouple temperature is 1007 °C while the crucible is at 1083 °C. The crucible temperature stability is estimated from the measured sensitivity of the evaporation rate of indium to temperature, and the observed variations in the evaporation rate for a fixed thermocouple temperature. The crucible temperature peak-to-peak variation over a one hour period is 1.2 °C. Machined molybdenum crucibles were used in the indium and copper sources for depositing CuInSe2 thin films for solar cells.
A novel thermal desorption spectroscopy apparatus
Authors: Castro Facundo J. , Meyer Gabriel
Published: July 2002

We present a new experimental setup designed to perform measurements of thermal desorption spectroscopy of hydrogen released from metallic samples. The distinctive features of the proposed arrangement are a compact reactor and the use of a mass flow meter to measure the flux of gas desorbed from the sample. A complete set of hydrogen desorption spectra from Pd samples has been recorded to test the equipment. The spectra show very good reproducibility, a high signal-to-noise ratio, and agree very well with results reported in the literature obtained using more sophisticated equipment. These features encourage the use of this low cost setup to perform a fast and reliable characterization of the processes controling hydrogen desorption from metallic compounds.