bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency response of a supported thermocouple wire: Effects of axial conduction
Authors: Fralick G. C. , Forney L. J.
Published: July 2002

Theoretical expressions are derived for the steady-state frequency response of a supported thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a supported one material wire and a two material wire with unequal material properties across the junction. For the case of a one material supported wire, an exact solution is derived which compares favorably with an approximate expression that only matches temperatures at the support junction. Moreover, for the case of a two material supported wire, an analytical expression is derived that closely correlates numerical results.
Electron cyclotron resonance plasma in multicusp magnets with axial magnetic plugging
Authors: Maeda Mitsuru , Amemiya Hiroshi
Published: July 2002

An electron cyclotron resonance plasma source is built by arranging SmCo magnets to form a multicusp magnetic field with axial magnetic plugging. The source is tested in H2, N2, and Ar by the microwave of 2.45 GHz in the range from 10−2 to 10−3 Pa. The discharge sustaining power is measured as a function of pressure. The plasma density, the average electron energy, and the electron energy distribution are measured by using a Langmuir probe. Plasma is obtained at pressures as low as 10−3 Pa in Ar. The average electron energy and the ion density increase with the feed microwave power. The electron energy distribution shows depletion at the low-energy part. Ion spectra obtained in Ar show a multicharged state up to Ar8+.
An X–Y scan generator for a scanning tunneling microscope
Authors: Valenzuela-Benavides J.
Published: July 2002

The design and construction of a digital X–Y scan generator used in conjunction with a scanning tunneling microscope and a data acquisition card for the purpose of digitizing images are presented here. The unit generates triangular waveform voltages for the piezoelectric elements and equally spaced pulses in the X and Y directions. The ‘‘n×n’’ triggering pulses are used to initiate digital to analog conversions in a data acquisition card thus obtaining a symmetrical digitized image. The generator is well suited as a scan generator for any lab-built tunneling microscope.
An ultrahigh vacuum chamber for simultaneous Fourier transform infrared spectroscopy and microgravimetric measurements
Authors: Zhuang Guorong , Chottiner Gary , Bae In Tae , Hwang Euijin , Scherson Daniel A.
Published: July 2002

A small UHV chamber that fits in the sample compartment of a commercial Fourier transform infrared spectrometer (IBM-98, Brucker) has been designed and constructed to acquire reflection/absorption spectra of species adsorbed and/or condensed on metal films vapor deposited in situ on the surface of a quartz-crystal microbalance (QCM). The QCM is mounted on a variable-temperature Au-plated Cu block, which houses a second (reference) QCM, attached in turn to a liquid-He cold finger. The unique capabilities of this apparatus make it possible to correlate quantitatively various spectral characteristics, including peak widths and intensities, with the absolute mass of adsorbed and/or condensed material per unit area m, or coverage, over a wide range of m and temperatures. Results obtained using tetrahydrofuran (THF) condensed on freshly vapor deposited gold films have shown that the sensitivity of the instrument is sufficient to detect mTHF on the order of a single monolayer. Plots of the intensity of the most prominent THF peak at 1064 cm−1 as a function of mTHF were found to deviate significantly from linearity in the range 0.1<mTHF<2.8 μg/cm2. In addition, the relative intensities of the most prominent THF peaks for even the largest mTHF examined differed markedly from those of bulk-like THF, an effect that can be attributed to a preferential orientation of THF microcrystals with respect to the underlying substrate. In the case of coverages on the order of one monolayer, such spectral behavior may arise from specific adsorbate/substrate interactions, which can cause a lowering in the molecular symmetry and/or distortions in the structure of the adsorbate. Evidence in support of a Au-induced THF activation was obtained from independent temperature programmed desorption (TPD) measurements involving perdeuterated THF (TDF) performed in a separate UHV system. In particular, for exposures of about 1.5 L, the TPD spectra for the largest m/e features, i.e., 80, 48, and 30, revealed the presence of a peak centered at a higher temperature (∼180 K) than that found for much larger exposures (120 K).
A compact laser interferometer with a piezodriven scanner for metrological measurements in regular SEMs
Authors: Hatsuzawa Takeshi , Tanimura Yoshihisa , Toyoda Kouji , Nara Makoto , Toyonaga Syuuji , Hara Shin-ya , Iwasaki Hirotaka , Kondou Kazuhiko
Published: July 2002

A compact laser interferometer combined with a mechanical scanner has been developed for precise microlinewidth measurements in regular scanning electron microscopes (SEMs). Optical components and a piezodriven mechanical table are integrated on a small disk 130 mm in diameter. The device is so compact that it can be installed in the vacuum chamber of regular SEMs, and useful for accurate and precise measurements based on the laser wavelength—a practical length standard. An optical multipath technique and a differential arrangement of prisms in the interferometer, as well as electrical sensitized technique, realized a high resolution of 0.4 nm (λ/1600). By using the device and a SEM, an absolute linewidth measurement system has been constructed for microlinewidth measurements. To evaluate the system performance, a comparison has been made between a metrological SEM and the system by using a silicon test artifact. The result shows a good agreement between the two systems within an uncertainty of several nanometers. This device can be applied for various types of microscopes such as optical and scanning probing microscopes, and useful as an important scaling device for the calibration of measurement systems.
An ultrahigh-vacuum system for STM studies
Authors: Wörtge M. , Dey S. , Grafström S. , Hagen T. , Kowalski J. , Neumann R. , Probst O.
Published: July 2002

An ultrahigh-vacuum (UHV) system for STM studies is described where a home-built STM is combined with a novel facility for in situ exchange of samples and tips. Technical details concerning the design of the sample and tip holders and the manipulation and storage equipment are given. For the preparation of organic films a compact evaporation source comprising two ovens with an excellent thermal insulation was constructed. First STM results of a coronene film on graphite and of tungsten diselenide are presented.
Modulated microwave surface impedance of superconducting films
Authors: Chen H. J. , Owliaei J. , Sridhar S.
Published: July 2002

We present details of an experimental method to measure the field modulated surface resistance (dRs/dH) of superconducting films accurately, which enables both field and temperature sweep experiments and is particularly useful for low-field or near Tc measurements. The complex surface impedance Zs(H,T)=Rs(H,T)+iXs(H,T) can also be simultaneously measured. This technique utilizes specially built circuitry to lock the microwave source to the cavity and keep the input power of the cavity constant, even as the resonant frequency or Q value of the cavity changes with changing temperature or applied field. With the above circuitry, we were able to measure (dRs/dH) directly rather than (dP/dH) as in some modulated microwave absorption measurements. With the high accuracy offered by the modulation technique and the high Q of the cavity, important information about the magnetic-field response of superconducting films, such as dynamics of vortices and low-field properties of weak links can be obtained. The technique can also be employed to measure any possible spontaneously induced internal fields in two-dimensional high-Tc superconductors.
Linear polarization and the effects of metal reflectors used to redirect the beam in microwave radiometers
Authors: Cortiglioni S.
Published: July 2002

Problems concerning the response of microwave radiometers to the polarization of incident radiation are examined. Particular attention is given to their consequences in experiments measuring the intensity anisotropy of the cosmic background radiation. Considered in detail are instrumental configurations in which metal reflectors are used to redirect the antenna beam. Some effects introduced by such reflectors are calculated and modelled for different values of some relevant parameters, in order to evaluate their contribution to instrumental errors. The analysis of a real experiment is then considered. It is shown that such mechanisms, if ignored, can seriously affect the measurements.
A flow reactor system for catalytic reaction studies, allowing time- and space-resolved measurements of gas composition and temperature around the catalyst
Authors: Lundgren S. , Keck K.-E. , Kasemo B.
Published: July 2002

A flow reactor system for catalytic reaction studies is described. The system is equipped with a movable gas sampling device and on-line mass spectrometry (MS), allowing time- and space-resolved measurements of gas composition and temperature. Results from H2 oxidation on Pt are used to illustrate the system performance. Spatial variations of H2, O2, and H2O concentrations can be measured, e.g., during mass transport limited conditions. Temporal variations in H2, O2, and H2O during chemical oscillations are well resolved close to the catalyst, but successively smeared away at increasing distance. The special design of the gas sampling probe allows quantible MS measurement even of H2O and other ‘‘difficult’’ gases, and of gas temperature variations.
Impedance-corrected carrier lifetime measurements in semiconductor lasers
Authors: Shtengel G. E. , Ackerman D. A. , Morton P. A. , Flynn E. J. , Hybertsen M. S.
Published: July 2002

Differential carrier lifetime as a function of subthreshold bias current in 1.3 m bulk active lasers is obtained by measurement of small-signal modulation of amplified spontaneous emission together with careful characterization of frequency- and current-dependent device impedance. The strong influence of rapidly varying device impedance upon these measurements is illustrated. In contrast to other studies, neither saturation of differential lifetime at low currents nor linear dependence of spontaneous emission on carrier density is observed. Recombination parameters, fit from current versus carrier density, along with consistent fits of spontaneous emission versus carrier density, are presented.
Vacuum arc bismuth ion source with film cathode
Authors: Vasilyev A.
Published: July 2002

A new variant of vacuum arc ion source is described whereby the problems of short cathode lifetime and low charge states, commonly found for low boiling point cathode materials, are avoided. This novel source embodiment has been operated using bismuth as the wanted ionic species. It was found that the ion charge state spectrum can be improved (i.e., increased) significantly, with the charge state of maximum amplitude being increased from Bi1+ to Bi3+, and the number of pulses that were obtained before the cathode needed changing was 108.
Efficient low-energy beam transport for intense, high-brightness H− beams in high energy accelerators: Perspectives and a solution using ESQ lensesa)
Authors: Guharay S. K. , Allen C. K. , Reiser M. , Saadatmand K. , Chang C. R.
Published: July 2002

The characteristics of a 30 mA, 35 kV H− beam from a volume source have been determined using emittance measurements. A low energy-beam transport (LEBT) system consisting of six electrostatic quadrupole lenses and a short (about 5 cm long) single-stage einzel lens is designed with the aim of transporting the beam over a distance of about 30 cm and focusing a clean, matched beam into a radio-frequency quadrupole accelerator of the Superconducting Super Collider. The system parameters are chosen on the basis of simulation of beam dynamics. The emittance growth in the LEBT section is within a factor of about 1.5 and this satisfies the requirement of the emittance budget. The LEBT system is designed to be mechanically rugged.
Production of negative lithium ions from powdery LiH by ion stimulated desorptiona)
Authors: Wada Motoi , Tsuda Hiroshi , Sasao Mamiko , Kawano Hiroyuki
Published: July 2002

Production characteristics of Li− from powdery LiH immersed in argon and hydrogen discharges were investigated. The surface of the LiH powder was covered with a Mo mesh and a negative bias potential was applied to the mesh to bombard LiH powder with plasma ions. The amount of Li− current produced at the surface of the LiH powder was an increasing function of the bombarding ion energy. The decomposition of LiH by the ion bombardment accompanied the production of hydrogen gas, and the H− current was also extracted from the ion source plasma. The addition of Cs into a discharge showed little enhancement of Li− production.
PIN photodiode-based miniature gamma radiation detector for multiple applications including positron emission tomography radioisotopes
Authors: McKinney Collin J.
Published: July 2002

A method for using inexpensive PIN photodiodes for applications involving gamma radiation detection over several orders of magnitude in intensity is discussed. A description of the response characteristics of the PIN diode and its associated electronics is presented. Application of the detector to a radioactivity transporter, radioisotope delivery system, radiochemical processor, and radio-high pressure liquid chromatograph is discussed.
A tunable microwave frequency alternating current scanning tunneling microscope
Authors: Stranick S. J. , Weiss P. S.
Published: July 2002

By modulating the scanning tunneling microscope junction bias voltage at microwave frequencies, imaging and spectroscopy of insulating surfaces have become possible. In order to explore the spectroscopic capabilities of this instrument, we have developed a tunable microwave frequency alternating current scanning tunneling microscope. We combine the reliable beetle-style sample approach with coaxial sample and tip contacts. This provides us with a stable microwave-frequency-compatible scanning tunneling microscope. This alternating current scanning tunneling microscope design is compatible with ultrahigh vacuum and low-temperature operation.
An electronic pepper pot
Authors: Peters J.
Published: July 2002

An electronic pepper pot has been developed at DESY for analyzing the H− beam. It consists of a number of slits in front of a harp with a high wire density. Multiplexing of the harp signals is done in the vacuum. The number of slits and the distance between the harp and the slits can be varied according to the beam parameters. The first version consists of a harp with 484 wires which are 0.1 mm wide with a spacing of 0.1 mm. They are printed on a board. The storage and readout is done using three chips in the vacuum. External transfer of the analog signals is done with a few lines. One may measure the current distribution and the emittance within one shot of the beam and is free to choose the time for the sample. This is of special interest for sources with a low repetition rate such as the HERA H− source. The present arrangement is only a first step. Further designs are discussed.
Extraction of C60 cluster ion beam
Authors: Chuanchen Sun , Haibin Gao , Dufei Fang
Published: July 2002

A C+60 ion beam was extracted from a hollow cathode ion source (model 911A). The mass spectra of 6 keV C60 and its fragments have been measured. Only those clusters with an even number of C atoms were observed and the largest one was C84. The result shows that the fragment ion beam has an exponential distribution, which is similar to that of C+60–H2(He) collision experiments. We also have extracted C-cluster negative-ion beams from a Middleton 860 sputtering source. With a graphite cathode, we have observed many cluster ions which were not previously reported. For a C60/C70 cathode, we have obtained a stable C−60 ion beam with current of about 1 nA. The spectra of the negative ions are complicated due to the existence of the Cs–Cn clusters.
TAMEK—Sources and techniques for high-dose implantation, ion beam mixing, and ion-beam assisted deposition of metal ions
Authors: Tolopa A. M.
Published: July 2002

Unlike widely published sources MEVVA, since 1984 we have constructed vacuum arc ion sources of any hard electroconductive materials (like metal or composites type—TiC, TiSiC, NiCrAlY, MoS, TiMoSi, WAlB, TiBNi) for modification of materials. The principle of Technological Accelerator of Metal ion and Electron Kit—source TAMEK, provides realization of regimes mentioned in the title in each (or in any series) of a sequence of f=50 Hz pulses: t=300 μs, Ii<1 A, Ei<200 keV, dDi=1016 ion/cm2/min for implantation and t=1000 μs, Iarc<2000 A, dh=50–200 nm/min for deposition and so realized, if you wish, ion implantation, deposition, mixing, ion-beam-assisted deposition of the same ions without switching off the source. The experimental data demonstrate the possibility of obtaining mutual mixed (10×90 at %) alloyed layers up to 3 μm for time in t=15 min at T=100 °C temperature surface, with structure improving (microhardness) inner layer up to 50 μm in depth and possibility of further coating growth on the surface. This report presents a brief review of TAMEK principle design and its application for modification of constructed materials.
Performance of an inertially coupled, three-mode gravitational wave antenna prototype
Authors: Marchese Linda E. , Bocko Mark F. , Zhang Guizhen , Karim Munawar
Published: July 2002

A prototype three-mode gravitational wave antenna which employs a two-mode torsional transducer has been constructed and tested. For the torsional transducer the coupling from one stage to the next is via inertial forces, whereas in a conventional transducer the stage-to-stage coupling is proportional to the relative displacements via the springs. Experiments with our antenna-torsional transducer prototype demonstrate a maximum antenna bandwidth of 260 Hz (29% of the antenna resonant frequency of 900 Hz) and a mechanical amplification factor of 40. A mathematical model for the three-mode antenna has been developed and predictions of the system transfer functions and transient response are in close agreement with the measurements. Through the optimization of the transducer parameters we find that maximum fractional antenna bandwidths near 30% may be simultaneously achieved with mechanical amplification factors of 100 or more. Furthermore, the torsional transducer has a larger mechanical gain-antenna bandwidth product than a linear transducer with similar masses.
A simple and efficient external gas filtration and trapping system for excimer lasers
Authors: Stevens R. E. , Kung C. Y. , Kittrell C. , Kinsey J. L.
Published: July 2002

Excimer lasers are excellent sources of coherent light in the ultraviolet range of the spectrum. However, they have the drawback of requiring significant maintenance due to the corrosive gases, generation of dust, and contamination of the laser chamber optics which occur during normal operation. Improvements which are generally applicable to any excimer laser system are specifically described in terms of the two Questek (Lambda Physik, Acton, MA) model 2860 lasers in our lab. The same basic procedures are currently being implemented in two Lambda lasers in other research groups at our university. A novel gas triple filtration system, a simple cold trap with a counter-flow heat exchanger, and a careful selection of valves have been added to minimize dust contamination of the optics, to decrease contamination and leakage of the gas fill, to provide safe and easy dust removal, and to reduce maintenance downtime.
Third harmonic generation through shaped superconductors
Authors: Narayana T. Badri , Satyam M.
Published: July 2002

This paper describes a methodology of obtaining only third harmonic along with the fundamental using shaped superconductors. It also indicates how one can design a nonlinear superconducting resistor with the required current versus resistance variation.
A simple technique to measure stress in ultrathin films during growth
Authors: Sander D. , Enders A. , Kirschner J.
Published: July 2002

We demonstrate an easy implementation of the cantilever bending beam approach to measure stress during film growth in ultrahigh vacuum. Using a simple and compact optical deflection technique, film stress with sub-monolayer sensitivity can be detected. A stress measurement during FeSi2 formation on Si(111) is presented.
A probe for magnetization measurements of thin superconducting films in pulsed high magnetic fields
Authors: Lagutin A. S. , Vanacken J. , Harrison N. , Herlach F.
Published: July 2002

This paper describes an inductive magnetization sensor, designed to measure thin superconducting films (of order 3000 Å) in very strong magnetic fields. For magnetic fields in the range 250–500 kG, the sensitivity of the probe is 10−2 emu. Accuracy and high sensitivity were obtained by combining a sample extraction system, vibration isolation, and an inductive sensor with optimized flux coupling geometry. The magnetic flux coupling to the sensor was verified to exceed 70%, both by calculation and experimental calibration.
Tabletop linear accelerator for massive molecules
Authors: Hendell E. , Even U.
Published: July 2002

A simple, tabletop, linear accelerator based on low duty factor square wave pulses has been developed to accelerate very heavy molecular ions (100–10 000 a.m.u.) to energies of tens of keV. The accelerator can be added to existing mass spectrometers to improve the detection efficiency (secondary electron yield) of both positive and negatively charged clusters.
Apparatus for chemical vapor deposition of polyimide films
Authors: Hutchings C. W. , Grunze Michael
Published: July 2002

We describe the design, construction, and calibration of Knudsen cell evaporators for the chemical vapor deposition of organic films. The evaporators can easily be constructed using equipment and materials available in most labs. We employed them to codeposit monomers for polyimide formation. The vapor deposition process of polyimide and other polymeric materials can be controlled to form ultrathin films suitable for the investigation of the interaction between the overlayer and the substrate. We describe a deposition system used to produce polyimide films from 2 nm to more than 1000 nm thick on 1- to 2-cm-diam substrates at growth rates from ∼1 nm/min to more than 10 nm/min.
An optical capillary flow viscometer
Authors: Teboul V. , St-Arnaud J. M. , Bose T. K. , Gelinas I.
Published: July 2002

A new capillary flow viscometer is presented, based on optical measurements of the refractive index. The apparatus consisting mainly of two pressure vessels, a capillary, and a Michelson interferometer for refractive index measurements is described together with the experimental procedure. The viscosity is computed with the Poiseuille formula tacking into account perfect gas variations. The accuracy of the viscometer is then evaluated and tested using three different gases: carbon dioxide, methane, and sulfur hexafluoride. As this technique can easily be automated we think that it will be interesting for practical purposes. Moreover, this technique can be improved to produce results of higher accuracy and it can also be applied with a few modifications to other media like supercritical fluids.
A tunable, double-wavelength heterodyne detection interferometer with frequency-locked diode-pumped Nd:YAG sources for absolute measurements
Authors: Gelmini E. , Minoni U. , Docchio F.
Published: July 2002

A double heterodyne interferometric instrument using a tunable synthetic wavelength for the absolute measurements of distance and position is presented. The optical synthetic wavelength is generated by a pair of PZT-tunable diode-pumped Nd:YAG lasers operating at 1.064 μm. Based on a closed-loop scheme, a suitable electronic circuit has been developed to implement the frequency locking of the two lasers. A digital frequency comparator provides an error signal, used to control the slave laser, by comparing the laser beat frequency to a reference oscillator. Demodulation of the superheterodyne signals is obtained by a rf detector followed by low-pass filtering. Distance measurements are obtained by a digital phase meter gauging the phase difference between the demodulated signals from a measuring interferometer and from a reference interferometer. The paper presents the optical and the electronic layouts of the instrument as well as experimental results from a laboratory prototype.
A power-stable CO2 laser with ceramic resonator frame
Authors: Bartosch T. , März M.
Published: July 2002

A CO2 laser with a resonator frame made of low expansion ceramics has been developed to provide superior passive stability properties. High stiffness, low specific weight, and very good electric insulation properties recommend ceramic as an attractive material for many laser applications. The long-term power stability of a first prototype was better than ±0.44% measured over 15 min, the short-term stability was better than ±0.24%. Both values were achieved without any active stabilization technique, without damping of external vibrations, and with a non-temperature-controlled coolant. With a new switch mode power supply without ballast resistor a wall-plug efficiency of about 14% has been achieved under quasi-sealed-off conditions. The specific laser output power was about 20 W/m at a gas pressure of 18.5 mbar and a gas mixture He:N2:CO2=75:15:10+5.5% Xe.
Low-temperature micro-photoluminescence using confocal microscopy
Authors: Kasai Jun-ichi , Katayama Yoshifumi
Published: July 2002

We describe an optical setup for low-temperature micro-photoluminescence measurements using confocal microscopy. The spatial resolution of the setup was estimated by observing photoluminescence images of a luminescent line formed in a cleaved face of a quantum-well crystal. A high spatial resolution of 0.55 μm was obtained at a 457.9 nm excitation wavelength. Measurements of photoluminescence excitation spectra are also possible with a high spatial resolution of less than 1 μm. As an application of low-temperature micro-photoluminescence measurements, photoluminescence images of a dot array comprising buried quantum wells have been obtained. These images show the distribution due to emissions from single dots with diameters down to 0.3 μm.
Automatic temperature-controlled helium-vapor cryostat for atom-probe field-ion microscopy studies
Authors: Van Bakel G. P. E. M. , Shashkov D. A. , Seidman D. N.
Published: July 2002

An automatic temperature control mechanism was fabricated from readily available components and installed on an existing continuous flow helium-vapor cryostat as part of an atom-probe field-ion microscope. This control system eliminates tedious manual adjustment of the vapor flow rate. It is shown that the time needed to cool the cryostat from room temperature to a cryogenic temperature is reduced from 3 to 1 h. Within the 40–80 K range changes in the setpoint temperature are accommodated within 10 min. The temperature stability is better than 0.1 K.
Mammography exposure standard: Design and characterization of free-air ionization chamber
Authors: Coletti J. G. , Pearson D. W. , DeWerd L. A.
Published: July 2002

The University of Wisconsin-Madison Accredited Dosimetry Calibration Laboratory has designed and constructed an Attix style variable-length free-air ionization chamber for application in mammographic energy x-ray beams. The chamber is designed to enable absolute in-air exposure measurements. A unique feature of this design is that the variation in plate separation is accomplished by use of two stepping motor controlled translation stages. This paper details the characterization of this instrument and presents some preliminary exposure measurement results.
Measurement of thickness of plate materials by infrared scanning
Authors: Malik S. , Hsieh C. K. , Lin Z.
Published: July 2002

A procedure is described to determine the thickness of a plate material by infrared scanning. It consists of heating the material with a moving heat source and measuring the temperature of the plate by infrared scanning when the material has reached a quasisteady state. At that time, the initial temperature has been damped out, and the plate temperature becomes invariant with time in the moving coordinates of the heat source. The plate thickness can thus be determined independent of the initial temperature of the plate, and the infrared image can be analyzed more conveniently for an accurate determination of the plate thickness. This paper covers the analysis and experiment for infrared scanning. The uncertainty in the measurement is found to be within one gauge size of the plate thickness tested.
Compact low-pass electrical filters for cryogenic detectors
Authors: Freund M. M. , Hirao T. , Hristov V. , Chegwidden S. , Matsumoto T. , Lange A. E.
Published: July 2002

We describe the design and performance of compact, low-pass electrical filters, suitable for operation at cryogenic temperatures. The filters are two pole LC filters with a cutoff at ≊100 kHz, an attenuation of −24 dB/octave, and a stop band rejection of −80 dB between 5 and 20 MHz. Their function is to suppress rf voltage noise to sensitive cryogenic detectors. The low-pass filters are realized using surface mounted devices on thin PC boards which can be stacked for maximum packing density. Compact modules containing 14 and 35 filters have been developed and installed in the Infrared Telescope in Space.
An in situ gamma ray spectrometer with CsI/p-i-n detector
Authors: Xu Clarke X. , Williams Ron R.
Published: July 2002

The development of a portable gamma ray spectrometer based on a CsI(Tl) scintillator (1.8 cm×1.8 cm×4 cm) with integral p-i-n diode (1.8 cm×4 cm) is described. A single board computer containing the MC68HC11 microcontroller, a single-chip self-contained computer system, is used for system control. The total size of the instrument is only 12 in×7 in. including the spectrometer and power supply. The system provides a low cost, low power gamma ray spectrometer as compared to the more common PMT-based devices. Spectra can be collected in daily intervals for up to 1 week. Special software which monitors the proper working of the spectrometer insures long term stability. This spectrometer can be used for routine monitoring and detection of gamma ray emitting radio nuclides. Performance of the spectrometer as well as gamma ray spectra are presented. The qualitative and quantitative reliability have shown its potential as a stand alone field monitoring instrument due to its low power consumption and intelligence.
Low cost, simple gate valve
Authors: Alonso E. V. , Jiménez-Rodríguez J. J. , Martínez-Albertos J. L.
Published: July 2002

A straight-through high vacuum gate valve with Conflat(R) type flanges, well within the manufacturing capabilities of small workshops is described. The valve is based on the translational displacement of only one part provided with a grove for a standard Viton O ring. Other sealings are performed with Viton and Teflon gaskets. The valve requires relatively small space in the pipeline direction, and is bakeable to 150 °C, open.
Correction factors for reflectance and transmittance measurements of scattering samples in focusing Coblentz spheres and integrating spheres
Authors: Rönnow Daniel , Roos Arne
Published: July 2002

The detector signals from a total integrated scatter (TIS) instrument, which uses a focusing Coblentz sphere, have been evaluated. Models for the calculation of correct reflectance and transmittance values for both scattering and nonscattering samples are presented. In particular, the correction for multiple reflections between sample and detector, the detector efficiency versus angle of incidence, and the symmetry properties of the Coblentz sphere have been investigated. Experimental results are compared with results obtained with an integrating sphere using a model for the correction of sphere asymmetry. The results show that the transmittance and reflectance values obtained with the TIS instrument and the integrating sphere agree only when the presented correction factors are properly taken into account.
Fourier transform infrared absorption spectroscopy of jet-cooled radicals
Authors: Rohrs Henry W. , Wickham-Jones C. Tom , Ellison G. Barney , Berry David , Argrow Brian M.
Published: July 2002

We describe an experiment that couples a high-resolution Fourier transform spectrometer (FTS) to a supersonic jet of radicals. A 1-mm-i.d. cylindrical SiC nozzle is resistively heated to 1500 K in order to decompose organic precursors and generate expansions of jet-cooled radicals. We have used this apparatus to pyrolyze alkyl nitrites to make alkoxy and nitric oxide radicals. The residence time of radicals in this hot nozzle is roughly 20 μs RONO→ΔRO+NO. We use the FTS to detect the IR absorption of the product NO (ν0=1876.1 cm−1) at resolutions as fine as 0.005 cm−1 FWHM. We observe the product NO from the pyrolysis of CH3CH2ONO to be rotationally cooled to roughly 50 K. The IR spectra indicate that the optical path length is about 3/4 cm and that the nitrites pyrolyze to produce approximately 1014 NO radicals cm−3 some 9 mm downstream from the nozzle. Our spectrometer is capable of detecting an absorption signal of 0.1% over a bandwidth of 100 cm−1 at 0.005 cm−1 resolution. Depending on the infrared cross section of the radical, this implies that we are able to monitor diatomic radical densities of roughly 5×1012 cm−3 (quantum state)−1.
Modular filter design for the white-beam undulator/wiggler beamlines at the Advanced Photon Source
Authors: Brite C. , Nian T. , Shu D. , Wang Z. , Haeffner D. , Alp E. , Kuzay T.
Published: July 2002

A new filter has been designed at Argonne National Laboratory that is intended for the use in undulator/wiggler beamlines at the Advanced Photon Source. The water-cooled frame allows up to four individual filter foil banks simultaneously in the beam path. Additionally, the bottom of each frame holds two thin (20 μm) uncooled carbon filters in tandem for low-energy filtering. Therefore a maximum of 625 filter selection combinations is theoretically possible. The design is compact and modular, with great flexibility for the users. To prevent accidental movement of the filter, effort has been taken to provide a mechanically locked, fail-safe actuator system. Programming aspects are under development as part of the general personnel and equipment protection system to provide an intelligent control system. Aspects of the design and operational principles of the filter are presented in this paper.
A critical assessment of the QEXAFS method (abstract)
Authors: Wong Joe , Fröba Michael , Frahm R.
Published: July 2002

The idea of recording an x-ray-absorption spectrum ‘‘on the fly’’ when a mechanically stable monochromator is being slewed smoothly and continuously over a given energy range has been proposed and successfully demonstrated in 1988 [R. Frahm, HASYLAB Annual Report (unpublished), 1987, p. 374; Nucl. Instrum. Methods A 270, 578 (1988)]. This procedure constitutes what is now known as the QEXAFS method. The question ‘‘How quick is QEXAFS?’’ has been examined in some detail at the Kobe conference [R. Frahm and Joe Wong, Jpn. J. Appl. Phys. 32, 188 (1993)]. Thus the QEXAFS technique provides a novel characterization tool to study the bonding and local atomic structure in materials with a time resolution of the order of seconds. In the present paper, a critical assessment of this technique is provided in terms of spectral quality and resolution as a function of various QEXAFS experimental parameters such as scan rate, integration time, type of monochromator used, as well as an experimentally definiable energy window over which a QEXAFS data point is collected. Model compounds with well defined shape preedge XANES and white line features and long k-range EXAFS are used as test systems to arrive at a set of practical experimental parameters. The versatility, application, and limitations of this time-resolved spectroscopic tool will be discussed.
Electron and x-ray fluorescence yield measurements of the Cu L2,3-edge x-ray absorption fine structures: A comparative study
Authors: Hiraya A. , Watanabe M. , Sham T. K.
Published: July 2002

The Cu L2,3-edge x-ray absorption fine structures (XAFS) of a series of Cu samples have been recorded at the BL1A beamline of UVSOR using both electron yield and x-ray fluorescence yield techniques. XAFS measurements were simultaneously recorded in three modes: total electron yield (TEY) with specimen current, total electron yield with a channeltron electron multiplier and x-ray fluorescence yield (FLY) with an Ar/CH4 gas proportional counter. While both TEY measurements produce essentially identical spectra, a comparison between TEY and FLY results shows a drastic difference in the sensitivity of the techniques towards sampling depth. These results and their implications are discussed.
A spectrometer for high-resolution resonant inelastic x-ray scattering (abstract)a)
Authors: Schülke W. , Kaprolat A. , Fischer Th. , Höppner K. , Wohlert F.
Published: July 2002

The requirements on the radiation source, the monochromator/mirror, the diffractometer, and the crystal dispersive analyzer for an optimum instrumentation dedicated to high-resolution resonant inelastic-scattering experiments are formulated. The possibility for the application of dispersion compensation is stressed. A provisional instrumentation at the HARWI-Compton beamline is described and test measurements of the resonant inelastic-scattering cross section of Cu for incident photon energies scanning across the K threshold and for scattered photon energies near the Kα1 line are reported. By means of model calculation the important role of correct absorption correction of resonant inelastic-scattering data is emphasized.
Direct measurement of magnetic circular dichroism and Kerr rotation spectra in vacuum ultraviolet using four-mirror polarizer
Authors: Suzuki M. , Hanmura K. , Kotani T. , Yamaguchi N. , Kobayashi M. , Misu A.
Published: July 2002

A reflection-type four-mirror polarizer has been constructed and used in magnetocircular dichroism and Kerr rotation studies in the vacuum ultraviolet region. Geometrical properties and polarization characteristics were measured. The polarizer is sufficient to convert linearly polarized synchrotron radiation into circularly polarized light. Magneto-optical measurements were performed using magnetization modulation technique, and measured magnetocircular dichroism and Kerr rotation spectra in yttrium iron garnet were shown to satisfy the Kramers–Kronig relation. It is concluded that the reflection-type four-mirror polarizer together with the synchrotron radiation can be used in magneto-optical studies with high precision.
Dielectric resonators in a TE102 X-band rectangular cavity
Authors: Del Monaco S. , Brivati J. , Gualtieri G. , Sotgiu A.
Published: July 2002

A method for simply coupling a dielectric resonator (DR) to a standard TE102 rectangular cavity is described. The DR/TE102 resonator is easily realized with minor changes to existing rectangular cavities. In comparison with other resonant structures based on dielectric resonators, coupling of the microwave power to the dielectric is much easier. Its use in electron paramagnetic resonance spectroscopy results in a high filling factor and a high value of the H1 field inside the resonator. It can be particularly useful for pulsed application, where high filling factors are required.
Atomic force microscope using optical heterodyne detection incorporated in an optical microscope
Authors: Kikuta Hisao , Nasu Kosuke , Kato Nobuhiro , Iwata Koichi
Published: July 2002

An atomic force microscope has been constructed which enables us to observe sample surfaces through a metallurgical optical microscope. The cantilever deflection is detected by a polarization common-path interferometer with optical heterodyne technique. The optical system of the interferometer is incorporated in the commercial optical microscope. The common-path interferometer is rather insensitive to the effects of environmental disturbance such as thermal drift and mechanical vibration. The sample surface and the cantilever are observed by a microscopic objective of ×20. We can adjust the interferometer easily by observing both the cantilever and laser beams. The detection system has a total rms noise of 0.35 Å in a frequency bandwidth of 0.5–200 Hz on a free Si3N4 cantilever of 0.1 N/m spring constant.
A neutron spectrometer for ITER
Authors: Elevant T. , Garis N. , Chakarova R. , Linden P.
Published: July 2002

A study of energy resolution and efficiency of a self-contained time-of-flight energy spectrometer has been performed by means of Monte Carlo calculations. For 14-MeV neutrons, the instrument provides an energy resolution of 225 keV, an efficiency of 10−3 cm2 and a neutron flux operating range from 5×106 to 1010 n/(cm2 s). For diagnostics of deuterium–tritium plasmas in ITER, measurements of ion temperatures ranging from 3 to 50 keV, with an accuracy better than 10%, a time resolution better than 100 ms and a radial resolution better than 5 cm are feasible. Usage of scintillating fiber detectors permits operation with background radiation levels well above those estimated for the diagnostic areas of the ITER experiment.
New neutron spectrometer for high power DT experiments on JET (abstract)
Authors: Kallne J. , Conroy S. , Frenje J. , Ericsson G. , Traneus E. , Renberg P. U. , Enge H. , King N.
Published: July 2002

A high resolution neutron spectrometer, based on the magnetic proton recoil (MPR) technique, is under construction for use on JET. It is designed for the planned high power DT experiments to make use of the very high neutron fluxes (up to a few times 1010 n/cm s) obtainable at vantage points close to the plasma. This will be used to operate at highest possible neutron count rates (Cn) to facilitate plasma measurements of maximum (statistical) accuracy without need of excessive integration times. The JET experimental conditions will permit operation in the MHz range (Cn≤0.5 MHz compared to Cn≤10 MHz on ITER). Prototype tests are planned to be performed with the MPR spectrometer besides diagnostic studies of the JET plasmas. We will describe the principles of the spectrometer and the research plans.
Absolute calibration of tokamak fusion test reactor neutron detectors for D-T plasma operation
Authors: Jassby D. L. , Barnes Cris W. , Johnson L. C. , Roquemore A. L. , Strachan J. D. , Johnson D. W. , Medley S. S. , Young K. M.
Published: July 2002

The two most sensitive TFTR fission-chamber detectors were absolutely calibrated in situ by a D-T neutron generator (∼5×107 n/s) rotated once around the torus in each direction, with data taken at about 45 positions. The combined uncertainty for determining fusion neutron rates, including the uncertainty in the total neutron generator output (±9%), counting statistics, the effect of coil coolant, detector stability, cross calibration to the current mode or log Campbell mode and to other fission chambers, and plasma position variation, is about ±13%. The NE-451 (ZnS) scintillators and 4He proportional counters that view the plasma in up to 10 collimated sightlines were calibrated by scanning the neutron generator radially and toroidally in the horizontal midplane across the flight tubes of 7 cm diam. Spatial integration of the detector responses using the calibrated signal per unit chord-integrated neutron emission gives the global neutron source strength with an overall uncertainty of ±14% for the scintillators and ±15% for the 4He counters.
Absolute calibration of TFTR helium proportional counters (abstract)a)
Authors: Strachan J. D. , Barnes Cris W. , Diesso M. , Jassby D. , Johnson L. , Loughlin M. , McCauley S. , Munsat T. , Roquemore A. L.
Published: July 2002

The TFTR helium proportional counters are located in the central five (5) channels of the TFTR multichannel neutron collimator. These detectors were absolutely calibrated using a 14 MeV neutron generator positioned at the horizontal midplane of the TFTR vacuum vessel. The neutron generator position was scanned in centimeter steps to determine the collimator aperture width to 14 MeV neutrons and the absolute sensitivity of each channel. Neutron profiles were measured for TFTR plasmas with time resolution between 5 and 50 ms depending upon count rates. The He detectors were used to measure the burnup of 1 MeV tritons in deuterium plasmas, the transport of tritium in trace tritium experiments, and the residual tritium levels in plasmas following 50:50 DT experiments.
Performance of the upgraded multichannel neutron collimator
Authors: Roquemore A. L. , Johnson L. C. , von Goeler S.
Published: July 2002

The original ZnS based NE451 detectors become saturated at the highest levels of D-D operation. A new less sensitive detector configuration, also based on ZnS crystals, was designed and tested at PPPL in order to extend the collimator capabilities to D-T plasma operation. The new detector design is composed of a thin layer of ZnS powder uniformly deposited between two layers of Plexiglas. The detector capabilities are further extended by upgraded signal processing electronics for a total enhancement of ∼1000× compared to the original detector system. An array of these detectors has been installed on TFTR in tandem with the original detector system. The current mode is presently being implemented on the original NE451 detectors. This will extend their capabilities and allow for greater overlap in data taken in the crossover region between the two detector systems. The performance of the collimator system will be illustrated by neutron data obtained during D-T operation.
High-pressure position-sensitive proportional counter
Authors: Vogel David , Beiersdorfer P. , Decaux V. , Widmann K.
Published: July 2002

A gas-filled position-sensitive proportional counter was constructed for the detection and analysis of x rays in the 8–20 keV range. The detector’s active volume is 9.5×3×0.4 cm3. Based on an earlier design, the cathode incorporates a 160-ns delay line, etched using printed-circuit techniques. The detector operates at an 80-psig gas pressure and achieves a spatial resolution as low as 80 μm and linearity better than 25 μm. The counting efficiency ranges from 80% at 8 keV to 37% at 20 keV. The new detector allowed efficient recording of high-resolution spectra of the K emission lines from heliumlike Ge30+ and Kr34+.
Magnetic fluctuation induced transport in MST (abstract)a)
Authors: Stoneking M. R. , Fiksel G. , Hokin S. A. , Prager S. C. , Ji H.
Published: July 2002

We made local measurements of the magnetic fluctuation induced transport of particles and energy in the outer region (r/a≳0.75) of the MST reversed field pinch plasma. These measurements allow comparison with the Rochester–Rosenbluth stochastic diffusion coefficients. An electrostatic electron energy analyzer and fast pyrobolometer were employed in combination with magnetic pickup coils to directly measure the correlated products 〈J̃θB̃r〉 and 〈q̃∥B̃r〉, respectively. Magnetic fluctuation induced transport of both particles and energy is negligible at the extreme edge of MST (r/a≳0.9), but increases to a level consistent with estimates of the entire particle and energy flux as the core is approached (5×1021 m−2 s−1 and 105 W m−2). Stochastic particle transport is limited by an apparent ambipolar electric field to the ion stochastic diffusion rate (D=50 m2 s−1), the electron transport being dominated by the energetic component of the distribution (E≳50 eV). The measured heat transport is consistent with the convective energy transport carried by the fast electron component (Teffective=100 eV).