bluuebunny/crossref_metadata_2025 huggingface dataset:
Scanning-laser microscope for cryogenic applications
Authors: Kittel A. , Stagge P. , Parisi J.
Published: July 2002

We present a new concept of a scanning-laser microscope that is integrated inside an encapsulated cryogenic sample stage. All the components of the microscope, i.e., a laser diode, the deflection unit, and the focusing optics, are cooled to the temperature of the sample under investigation. Furthermore, unwanted excitation of the sample, like excitation due to background radiation, is suppressed. Our technical solution meets the challenging experimental claims of a perfect shielding and low-temperature applicability further enables the sample to be exposed to strong magnetic fields.
Improved apparatus and procedures for isopiestic studies at elevated temperatures
Authors: Hefter Glenn , May Peter M. , Marshall Simon L. , Cornish John , Kron Ivan
Published: July 2002

A significantly improved apparatus for the isopiestic measurement of thermodynamic activities at elevated temperatures is described. Details of the new design and of an analysis of the propagation of the experimental errors are presented. The apparatus was tested by measurements of calcium chloride against sodium chloride at 353.15 K. Accuracies of better than 0.1% in the osmotic coefficient are routinely achieved. Data are also given for the osmotic coefficient of aqueous sodium hydroxide solutions at 353.15 K as a function of molality (up to 13 mol/kg), measured with respect to both sodium chloride and calcium chloride solutions as reference electrolytes.
Novel method of realizing metal freezing points by induced solidification
Authors: Ma C. K.
Published: July 2002

The freezing point of a pure metal, tf, is the temperature at which the solid and liquid phases are in equilibrium. The purest metal available is actually a dilute alloy. Normally, the liquidus point of a sample, tl, at which the amount of the solid phase in equilibrium with the liquid phase is minute, provides the closest approximation to tf. Thus the experimental realization of tf is a matter of realizing tl. The common method is to cool a molten sample continuously so that it supercools and recalesces. The highest temperature after recalescence is normally the best experimental value of tl. In the realization, supercooling of the sample at the sample container and the thermometer well is desirable for the formation of dual solid–liquid interfaces to thermally isolate the sample and the thermometer. However, the subsequent recalescence of the supercooled sample requires the formation of a certain amount of solid, which is not minute. Obviously, the plateau temperature is not the liquidus point. In this article we describe a method that minimizes supercooling. The condition that provides tl is closely approached so that the latter may be measured. As the temperature of the molten sample approaches the anticipated value of tl, a small solid of the same alloy is introduced into the sample to induce solidification. In general, solidification does not occur as long as the temperature is above or at tl, and occurs as soon as the sample supercools minutely. Thus tl can be obtained, in principle, by observing the temperature at which induced solidification begins. In case the solid is introduced after the sample has supercooled slightly, a slight recalescence results and the subsequent maximum temperature is a close approximation to tl. We demonstrate that the principle of induced solidification is indeed applicable to freezing point measurements by applying it to the design of a copper-freezing-point cell for industrial applications, in which a supercooled sample is reheated and then induced to solidify by the solidification of an auxiliary sample. Further experimental studies are necessary to assess the practical advantages and disadvantages of the induction method.
A steady-state high-temperature apparatus for measuring thermal conductivity of ceramics
Authors: Filla B. James
Published: July 2002

A one-sided very-high-temperature guarded hot plate has been built to measure thermal conductivity of monolithic ceramics, ceramic composites, thermal barrier coatings, functional graded materials, and high-temperature metal alloys. It is an absolute, steady-state measurement device with an operational temperature range of 400–1400 K. Measurements are made in an atmosphere of low-pressure helium. Specimens examined in this apparatus are 70 mm in diameter, with thicknesses ranging between 1 and 8 mm. Optimal specimen thermal conductivities fall in the range of 0.5–30 W/(mK). Internal heated components are composed entirely of high-purity aluminum oxide, boron nitride, beryllium oxide, and fibrous alumina insulation board. Pure nickel and thermocouple-grade platinum-based alloys are the only metals used in the system. Apparatus design, modeling, and operation are described, along with the methods of data analysis that are unique to this system. An analysis of measurement uncertainty yields a combined measurement uncertainty of ±5%. Experimental measurements on several materials are presented to illustrate the precision and bias of the apparatus.
30 Hz–10 kHz hysteresis loop tracer with field up to 0.1 T for high-Tc superconductors
Authors: Ji Z. M. , Wang H. B. , Zhou J. , Zhou G. D. , Xu W. W. , Cheng Q. H. , Yang S. Z. , Wu P. H. , Jin X.
Published: July 2002

A hysteresis loop tracer to measure the ac magnetization of high-Tc superconductors in the frequency range of 30 Hz–10 kHz is described, with driving field amplitudes up to 0.1 T. Due to the high frequency of the magnetic field, the hysteresis loops could be displayed on an oscilloscope and their details could be observed. The demagnetization factor, the stability, and the frequency characteristics of the tracer were tested. The ac magnetization of granular high-Tc superconductors was studied as a function of field amplitude and frequency.
Detection of deeply buried thin oxide layer by means of Auger depth profiling
Authors: Sulyok A. , Menyhard M.
Published: July 2002

Using our dedicated Auger depth profiling device (applying a grazing angle of incidence 84° and low ion energy 1 keV of Ar and specimen rotation), we could detect a thin oxide layer buried by about a 180 nm thick layer. Due to the good depth resolution achieved, the oxide layer could be localized to the interface. The oxide layer thickness was determined for two independent specimens to be about 2 and 3 ML.
Apparatus for materials testing in high-pressure hydrogen at low temperatures
Authors: Han Gang , He Jianhong , Fukuyama Seiji , Yokogawa Kiyoshi
Published: July 2002

A new type of apparatus for materials testing in high-pressure hydrogen up to 10 MPa at low temperatures down to 20 K was developed. The apparatus consists of the pressure vessel, cooled by a two-step external cooling method, and the hydraulic loading system. In the first cooling step the specimen in the pressure vessel is cooled to 84 K using a cooling tube between the coolant shroud filled with liquid nitrogen and the pressure vessel. In the second cooling step the specimen is cooled to 20 K using a helium refrigerator. The apparatus is designed to measure the actual load on the specimen with an external load cell irrespective of the axial load caused by high pressure and friction at the sliding seals. As an example of the application of the apparatus, the tensile properties of type 304L stainless steel in 1 MPa hydrogen and helium at low temperature are measured and hydrogen environment embrittlement of the steel is briefly discussed.
High-contrast piezoelectric fiber resonance detection for near-field optical microscopy
Authors: Débarre A. , Richard A. , Tchénio P.
Published: July 2002

We describe a simple, piezoelectric shear-force detection for controlling the tip–sample distance in near-field optical microscopes. The fiber is glued to a V-shaped piezoelectric cantilever and the assembly is fixed to a piezoelectric plate. The piezoelectric plate excites the fiber at resonance, while the piezoelectric cantilever of small mass detects the fiber motion with a high sensitivity. When the fiber approaches within, typically, 10–20 nm above the sample, shear forces cause the signal to reduce. The only signal processing before injecting it into the feedback loop is demodulation by a lock-in amplifier. The high signal-to-background allows the fiber resonance to be identified easily. We demonstrate the performance of our system with shear-force images of two test patterns.
Magnetic resonance imaging of vibrating granular beds by spatial scanning
Authors: Caprihan Arvind , Fukushima Eiichi , Rosato Anthony D. , Kos Miha
Published: July 2002

Nuclear magnetic resonance is becoming an important experimental technique to study the behavior of moving granular materials because of its unique ability to measure concentration, velocity, and dissipation within the bulk granular materials rather than only on the surface. Of all the common motions of such assemblies of particles, the most difficult to measure is the vibrating bed because of the unsteady motion. This paper demonstrates a nuclear magnetic resonance imaging method to study highly energetic vibrating granular beds by spatial scanning. In contrast to Fourier imaging, spatial scanning prevents scattering of image intensities caused by unsteady motion. Two-dimensional images of a vibrating bed undergoing period doubling were obtained. A band of high shear was identified by reduced image intensity. It traveled back and forth across the bed with each cycle of up and down motion of the bed. Further studies of vibrating beds with the sequence modified for velocity encoding and velocity compensation should provide additional useful information.
Improved sample-holder design for specific-heat measurements in magnetic fields up to 17.5 T
Authors: Klaasse J. C. P. , Hagmusa I. H. , Brück E.
Published: July 2002

By the use of a gold-plated silver sample holder, and a RuO2-Cernox combination thermometer, low-temperature specific-heat measurements in the temperature range from 0.35 to 90 K, and in magnetic fields up to 17.5 T, have become possible with remarkably improved accuracy. At 500 mK, the lower limit for the heat capacity that can be measured amounts to 0.02 mJ/K. The sensitivity in that case is about 0.3 μJ/K. The error margin is 1% for large heat capacities (larger than twice the sample-holder contribution) at higher temperatures, increasing to 3% for small heat capacities (half of the sample-holder contribution) around 500 mK. In high fields, for accurate measurements (error <3%) the temperature range is restricted to above 0.5 K.
Development of a 2.45 GHz electron cyclotron resonance ion source for ion-implanter application
Authors: Sekiguchi M. , Matsushita H. , Jonoshita I. , Kabasawa M.
Published: July 2002

A compact electron cyclotron resonance (ECR) ion source has been designed at 2.45 GHz microwave frequency for ion implanter and is being tested. The design is based on a straightforward application of the method adopted for conventional ECR ion sources for multiply charged ions: a closed ECR surface completely contained in the plasma chamber. Initial tests have shown a promising indication: a total current of about 7 mA of Ar ions has been extracted at 25 kV extraction voltage. Design features and preliminary performance are reported.
Status of the development of electron beam ion sources at Frankfurt
Authors: Kleinod M. , Becker R. , Höltermann H. , Mücke M. , Rao R. , Weidenmüller M. , Zipfel B.
Published: July 2002

The Frankfurt superconducting electron beam ion source (EBIS) is under reconstruction for higher ion yield by employing an immersed gun with a 2-mm-diam cathode for a 3 A electron beam. The trap electrode construction is as simple as possible to avoid any rf production. The ion extraction will be similar to the one applied in our MEDEBIS, using tapered electrodes to create a high axial extraction gradient. Research was continued on the use of oscillating electrons to reduce the power requirements of the beam, investigating the formation of a virtual cathode by decelerating the beam at full magnetic field strength while operating the gun under immersed flow conditions with adjustable compression. The MEDEBIS has proven its quality and reliability for the application as an injector for a medically dedicated synchrotron. To improve its yield of bare nuclei, better vacuum conditions are provided by drilling out the inner windings of the warm solenoid to allow for the installation of higher vacuum conductance. After the successful presentation of our XEBIST principle that delivers highly charged ions as Ar18+ and Ba46+ we have now shown its application for the production of singly charged ions as an injector of metallic ions. Finally, an EBIS/T with an internal Penning trap has been constructed to prepare selected ion species and charge states inside the ionization region. This new device will allow the study of electron–ion interactions in well-defined initial and final charge states, i.e., to be able to distinguish between single and multiple step ionization. If the homogeneity of the magnetic field in the trap region will reach 10−9, the determination of binding energies of highly charged ions may be better than a 1 eV accuracy.
Ion source requirements for a radio frequency high-energy ion implanter
Authors: Saadatmand Kourosh
Published: July 2002

Over the last several years, high-energy (in MeV range) ion implantation has become an integral part of mainstream semiconductor device manufacturing. The rapid growth in use of high-energy implanters has been driven by process and performance requirements for sub 0.25 μm device nodes. At Eaton, we have developed an rf linac based high-energy implanter, NV-GSD/VHE, capable of delivering in excess of one particle mA of B+ beam current at energies approaching 1.7 MeV. The Linac’s output energy is almost doubled if B++ ions are used. However, for fixed implanter throughput an ion source capable of sourcing ∼5 particle mA of B++ is required. The 90% un-normalized emittance at 90 keV should be less than 150 π mm mrad. We are investigating three completely different ion source technologies, hot cathode, rf-driven bucket, and electron cyclotron resonance ion sources as candidates. The present performance and the future expectation from each of these ion source technologies will be discussed.
Ion sources for industrial applications (invited)
Authors: Ishikawa Junzo
Published: July 2002

The ion-source and beam-transport characteristics required for industrial application are discussed. Currently, a high-current broad ion beam extracted from multiapertures is most commonly used for large area surface modification and ion beam assisted deposition. The beam quality strongly depends on the space-charge neutrality of the ion beam and nonuniformity of plasma density as well as beam emittance. To produce selective ion species without mass separation, the electron energy for ionization or electron temperature must be controlled. Applications for negative and molecular ions are also discussed. A charging-less ion implantation technique can be realized using negative ions. With molecular ions, ultra-low-energy ion implantation is possible, as is same-depth implantation of multielements.
Numerical simulation of the effect of Cs volume reaction in an H− ion source
Authors: Ogasawara M. , Morishita T. , Miura M. , Shibayama N. , Hatayama A.
Published: July 2002

Effects of cesium related reactions are investigated using a simulation code for H− ion sources. Effects begin to appear when cesium density is 1011 cm−3, but are still small and become large when the cesium density is greater than 1012 cm−3. The H− density decreases due to electron detachment. Decreasing the plasma potential by cesium seeding results in 12% smaller H− density. The minimum of the plasma potential shown experimentally by Bacal is found to correspond to a cesium coverage of 50% with the use of Langmuir adsorption isotherm. Surface production is effective only when the cesium density is around 1011 cm−3. For cesium density greater than 1012 cm−3, the effect of the cesium related volume reaction becomes larger.
Temperature control of plasma grid for continuous operation in cesium-seeded volume negative ion source
Authors: Fujiwara Y. , Miyamoto N. , Okumura Y.
Published: July 2002

A new-concept plasma grid, named frame-cooling-type plasma grid, was developed for a long pulse operation of a cesium-seeded volume H− ion source. The frame-cooling-type plasma grid was tested using a long pulse H− ion source. The grid has a kind of bellows structure that acts as thermal insulator to keep the surface temperature at an optimum value for H− ion production. It was confirmed that the temperature was kept at over 250 °C, an optimum temperature for the cesium effect, in steady-state operations with the plasma grid cooled by room-temperature water. Using the plasma grid, a maximum H− ion beam of 40 keV, 600 mA (16 mA/cm2) for a long pulse operation of 90 s was generated successfully.
Direct measurement of refractive-index dispersion using a time-delayed technique
Authors: Lin Shawn-Yu , Wang Li , Zubrzycki Walt
Published: July 2002

We describe a new way to measure the refractive index of dielectric materials using a time-resolved correlation method. By measuring the time delay of femtosecond pulse trains through a dielectric material, we obtain the refractive index of the material. This technique is direct, less surface sensitive, and precise to four digits. Consequently, it gives a true bulk index value. We apply this technique to measure the refractive index of fused silica, InP, and GaAs in the near infrared spectral regime.
Averaging and recording of digital deep-level transient spectroscopy transient signals
Authors: Kolev P. V. , Deen M. J. , Alberding N.
Published: July 2002

A new approach to the signal processing in digital deep-level transient spectroscopy (DLTS) systems is introduced. The problems of signal recovery from noise and efficient data storage are addressed separately from the transient signal analysis. As a result of this approach, an improved digital averaging scheme for DLTS signal recovery from noise and transient data storage is proposed. We have shown that the combined action of two complementary digital averaging techniques can improve the DLTS digital signal processing. Pseudologarithmic time averaging is efficient in reducing the number of processed data points and improving the signal-to-noise ratio for the high frequency noise components and in the transient tail. We demonstrate that the normalized errors in the magnitude measurements introduced by this type of averaging remain below 1% for pure logarithmic and below 0.1% provided that the logarithmic averaging intervals are further divided into five or more equal parts. Continuous time averaging is well suited for improving overall signal-to-noise ratio, for continuous display and processing of data, and it is more efficient in using the computer resources. The described combination of hardware and software tools for the implementation of these techniques supplies continuously fresh data and does not require any synchronization with the main computer program. Compared to other digital DLTS systems, this new approach offers an improved short delay time resolution, improved signal-to-noise ratio, and more efficient data storage. At the same time it offers real-time observation of essentially noise-free transients and, like analog systems, a real-time display of the DLTS scan. The real-time display means that the displayed transient and DLTS scan can be updated on the computer screen after each pulse even for a very large number of averaged pulses, and the result can be predicted well before the acquisition process reaches this number. The proposed techniques allow one to combine the powerful transient analysis of the digital DLTS methods with the sensitivity and the convenience of the analog methods. The described averaging and data reduction techniques are intended primarily for DLTS data processing, but the same principles can be useful for many other physical experiments involving transient data analysis.
Evaporation through a capillary allows electrically determined rate
Authors: Lawson Lawrence R.
Published: July 2002

Using a capillary to suppress diffusion allowed construction of an electrically calibrated vapor dispenser for organic solvent vapors. The rate of flow was essentially the applied electric power divided by the heat of vaporization.
Polarization of porous silicon luminescence
Authors: Gaponenko S. V. , Kononenko V. K. , Petrov E. P. , Germanenko I. N. , Stupak A. P. , Xie Y. H.
Published: July 2002

The polarization characteristics of light emitting porous Si films is investigated. The degree of polarization increases to well over 20% when the excitation wavelength is at the blue edge of the emission band and decreases with decreasing excitation wavelength. The steady-state value of the degree of polarization is established in less than 1 μs. The experimental results bear qualitative agreement with a quantum-wire model.
Heavy ion beam probe diagnostic system on JFT-2M
Authors: Ido T. , Hamada Y. , Nishizawa A. , Kawasumi Y. , Miura Y. , Kamiya K.
Published: July 2002

Heavy ion beam probe (HIBP) on JFT-2M has been installed. The diagnostic system is described briefly alone with a detailed description of planned calibration experiments. Two sets of poloidal and toroidal sweepers are used, one set at the entrance port and the other set at the exit port. These are used to measure a potential profile from the edge to the core of the plasma and to reduce the error due to the change of the angle to the energy analyzer. The calibration of the required voltages on electrodes of these sweepers for the potential profile measurement will be performed by the ionization of the injected beams with the neutral gas puffed into the tokamak chamber, with special emphasis on the effects of peculiar behaviors of the double sample volumes and sample volume divergence. It is found that in JFT-2M HIBP these phenomena do not disturb the calibration of the potential measurement. These peculiar behaviors will be useful for accurately determining the location of the observation point.
Observations of a dynamical percolating network in dense Z-pinch plasmas
Authors: Kukushkin A. B. , Rantsev-Kartinov V. A.
Published: July 2002

The method of multilevel dynamical contrasting [A. B. Kukushkin and V. A. Rantsev-Kartinov, Laser Part. Beams 16, 445 (1998)] is applied to analyzing earlier Z-pinch experiments. The results suggest Z-pinch plasmas to be a dynamical percolating network formed by the long-living filaments of electric current. The probable role of filamentation and networking of filaments is analyzed for the following phenomena: (1) formation of a “stocking” woven by the individual filaments, from the very beginning of discharge; (2) formation of an electric current precursor on axis, in advance of the convergence of the major current sheath; (3) fine structuring of the Z-pinch’s main body and halo at stagnation stage; (4) development and saturation of the magnetically driven Rayleigh–Taylor instability in the filamentary current sheath; (5) disruption of the necks in the filamentary Z pinch; (6) fine structure of “hot spots.”
Uniaxial single shot autocorrelator
Authors: Collier J. , Danson C. , Johnson C. , Mistry C.
Published: July 2002

An optical pulse autocorrelator for single or multiple pulses is described that has the novel feature of being essentially uniaxial and offers a number of distinct benefits over traditional designs. The uniaxial nature of the device, coupled with a small number of degrees of freedom means that there is an inherent simplicity of alignment. A fixed and equal group delay in each arm guarantees the necessary temporal overlap of the optical pulses. Calibration is fixed and easily determined and it is extremely compact and transportable. We have verified its performance over three time ranges and have demonstrated that it is capable of measuring pulse lengths ranging from 100 fs to tens of picoseconds.
Collimation of plasma-produced x-rays by spherical crystals: Ray-tracing simulations and experimental results
Authors: Sanchez del Rio M. , Fraenkel M. , Zigler A. , Faenov A. Ya. , Pikuz T. A.
Published: July 2002

Ray-tracing simulations, validated by experimental results, demonstrate that high intensity collimated x-ray beams can be produced from an isotropic x-ray source. A spherically bent mica crystal was used to collimate and monochromatize x rays emitted by a femtosecond laser-produced plasma. The result is a short pulse x-ray beam with a high degree of collimation (less than 1 mrad divergence), good spectral resolution (10−2<Δλ/λ<10−4), and tunability over a wide spectral range. The role of the experimental parameters in the resulting beam divergence is thoroughly analyzed by ray-tracing modeling. These simulations are validated by test experiments. The ray-tracing calculations define a set of boundaries in the experimental parameters, which will guarantee the achievement of collimated beams better than 1 mrad in further experiments.
A new method for determining polymer optical anisotropy using two wavelengths
Authors: Osaki Shigeyoshi , Mori Masahiro
Published: July 2002

A new method is developed for determining the optical anisotropy of transparent polymer films using two wavelengths. The method allows the retardation, orientation angle, and minimum-to-maximum intensity ratio to be accurately determined without help of a second measurement by a Berek compensator. The retardation is determined by selecting a pair of retardations whose difference should be the smallest between a number of retardations derived from the angular dependencies of transmitted light intensity through the film at two different wavelengths. The retardation determined by our method agrees well with that by the conventional method of a polarizing microscope equipped with the Berek compensator.
Real time chemical vapor detection and enhancement utilizing aerosol adsorption
Authors: Novick V. J. , Johnson S. A. , Hisgen H. A. , Reyes V. J.
Published: July 2002

A new trace gas detection system, using the high surface area properties of an aerosol to adsorb specific gas species and the high sensitivity and near real time capabilities of the infrared aerosol analyzer, has been successfully demonstrated. A new technique is described that allows certain chemical vapor species to be detected in time frames on the order of 2 min. The technique uses aerosols of selected materials to adsorb the vapor from an air sample, concentrating the vapor onto the surface of the aerosol, then depositing the particles onto a substrate for infrared analysis. For 1 min sample collection times, discernable signals were observed for SO2 levels as low as 2.3 ppm and NH3 concentrations as low as 1.5 ppm. Dimethyl methyl phosphonate (DMMP) vapors from a room temperature container were also detected. Preliminary results indicate that the measured absorbance is a monotonic function of the quantity of the trace gas injected, which gives encouraging evidence that a quantitative determination of the amounts of trace gases present in the atmosphere can be made in many cases. Trace gas detection is dependent upon the aerosol material chosen as the absorbent. For this work, copper (II) chloride and copper (II) sulfate were found to adsorb NH3, SO2, and DMMP. The copper compounds did not absorb NO or NO2. This enables the system to reduce the myriad potential interferences that can exist when sampling the atmosphere. The ammonia complex detected by this technique could be one of many such complexes that can be formed by properly matching the aerosol material and trace gas. As such, the process could be tailored to specific gas/aerosol combinations that could be used to unambiguously identify gaseous effluents of interest.
A new measuring device for measuring valve lift
Authors: Marčič Milan
Published: July 2002

The injection system is the main unit of diesel engines, having a major impact on proper operation of the engines. The delivery valve as an important element of the injection system assures its smooth functioning. In order to learn as much as possible about the movement of the delivery valve during the operation of the injection system, an inductive displacement transducer has been designed. The results of the measurements clearly indicate that the movements of the delivery valve are in agreement with the other measured parameters of the injection and that the proposed method for measuring the delivery valve lift can be successfully used with certain types of delivery valves.
Preliminary experiment of total reflection x-ray fluorescence using two glancing x-ray beams excitation
Authors: Tsuji Kouichi , Sato Tasaku , Wagatsuma Kazuaki , Claes Martine , Van Grieken René
Published: July 2002

In conventional total reflection x-ray fluorescence (TXRF), one glancing x-ray beam irradiates the sample carrier for excitation of x-ray fluorescence. However, it is also possible to excite x-ray fluorescence by multiple x-ray beams. We performed a preliminary TXRF experiment excited by two independent glancing x-ray beams. The two x-ray beams excitation would be effective to enhance the intensity of x-ray fluorescence and to improve the detection limit in TXRF. X rays from both a rotating Mo anode x-ray tube and a glow discharge x-ray tube with an Fe target irradiated a Cr thin film sample on a quartz glass. The x-ray fluorescence of Cr Kα from the sample was slightly enhanced compared with the intensity measured by one x-ray beam excitation.
Locking the cavity of a pulsed periodically poled lithium niobate optical parametric oscillator to the wavelength of a continuous-wave injection seeder by an “intensity-dip” method
Authors: He Y. , Baxter G. W. , Orr B. J.
Published: July 2002

Injection seeding by a single-mode continuous-wave (cw) laser provides a convenient way to achieve narrowband tunable operation of a laser with a broad spectral gain profile, or of an optical parametric oscillator (OPO). Continuous single-mode tunability of the laser or OPO output usually requires the length of the optical cavity to be controlled as the injection-seeding wavelength is scanned. We report a novel variant on established methods of locking the optical cavity length to the seed wavelength. Our approach takes advantage of the resonance properties of an optical cavity. When the cavity is in resonance with the cw seed radiation, the total intensity of that radiation reflected off the cavity displays a pronounced dip; this intensity dip can be used as a locking signal to reset the cavity length piezoelectrically during each interval between the pump pulses that excite the laser or OPO. Our active cavity-locking scheme is realized in the case of a ring-cavity OPO, incorporating periodically poled lithium niobate (PPLN), pumped at 1.064 μm by a single-mode pulsed Nd:yttrium–aluminum–garnet laser and injection-seeded at its signal wavelength by a 1.55 μm single-mode tunable diode laser. The coherent infrared output of this injection-seeded PPLN OPO is shown to be continuously tunable, with an optical bandwidth of ∼130 MHz (0.0045 cm−1) and excellent spatial beam quality.
The generation of a tunable laser emission in the vacuum ultraviolet and its application to supersonic jet/multiphoton ionization mass spectrometry
Authors: Uchimura Tomohiro , Onoda Takayuki , Lin Cheng-Huang , Imasaka Totaro
Published: July 2002

An optical parametric oscillator and a Ti:sapphire laser are used as a pump source for the generation of high-order vibrational stimulated Raman emission in the vacuum ultraviolet region. This tunable laser is employed as an excitation/ionization source in a supersonic jet/multiphoton ionization/time-of-flight mass spectrometric study of benzene. The merits and potential advantages of this approach are discussed in this study.
The characteristics of the newly designed microchannel plate detector in a strong magnetic field
Authors: Katsuki Y. , Ishii K. , Ono Y. , Kikuno N. , Goto T. , Goi Y. , Nagasaki M. , Ishibashi N. , Tamano T. , Yatsu K.
Published: July 2002

A gold neutral beam probe system which uses a microchannel plate (MCP) as a beam detector is being constructed in order to measure the electrostatic potential at the inner mirror throat (IMT) of the plug/barrier cell in the tandem mirror. The MCP detector was newly designed so as to be able to be used in the IMT strong magnetic field. The characteristics of the MCP gain were measured on a test stand with the strong magnetic field. The characteristic curves of the relative MCP gain were described as functions of the magnetic field strength, the MCP bias voltage, and the angle between the magnetic field and the capillary axis of the MCP. It was found that the newly designed MCP detector was useful for the potential measurement at the IMT region.
An inductively coupled, doubly tuned resonator for in vivo nuclear magnetic resonance spectroscopy
Authors: McNichols Roger J. , Wright Steven M. , Wasser Jeremy S. , Coté Gerard L.
Published: July 2002

We present a coil designed for in vivo P31 and H1 nuclear magnetic resonance spectroscopy which consists of a doubly tuned resonator inductively coupled to separate H1 and P31 feed coils. The advantages of the resonator include the ability to H1 shim over the same volume from which P31 spectra are extracted by using a single sample coil, elimination of coupling problems between separate H1 and P31 coils, ease of design and tuning over conventional double-tuned coils, and reduced match/tune sensitivity to coil loading, which is important in in vivo applications. We have used this coil to collect phosphorus spectra from the in situ heart of the western painted turtle (Chrysemys picta bellii) at 2 T. The total heart volume was less than 1 mL and acquisition time was just under 10 min.
The discovery of new transuranic elements and the role of the electron cyclotron resonance ion sources
Authors: Geller R.
Published: July 2002

The recent successes in the production of superheavy (and near superheavy) elements have been made possible due to the availability of extremely high beam currents of heavy ions from electron cyclotron resonance ion sources (ECRIS). This letter points out the importance of the ECRIS in these recent exciting results and discusses the ion source features which have made this breakthrough possible.
Time-correlated photon counting technique robust against multiple photon events using a multianode photomultiplier tube
Authors: Ohsuka Shinji , Ohsugi Akira , Takamoto Hisayoshi
Published: July 2002

A time-correlated photon counting technique which is robust against multiple photon events has been developed. Utilizing a 16 channel multianode photomultiplier tube, both the time interval between the excitation and the first detection of a fluorescence photon and the number of detected fluorescence photons are measured simultaneously. Based on the time and the number data fluorescence decay parameters can be estimated by maximizing the log likelihood. Results of computer simulations and experiments show that this technique can be successfully applicable at high detection rates of >0.9 fluorescence photon detection event per excitation on average.
Nuclear magnetic resonance spectrometer with a frequency range extended below the megahertz region
Authors: Sitnikov R. , Furó I. , Henriksson U. , Tóth F.
Published: July 2002

A conventional nuclear magnetic resonance (NMR) spectrometer with an original low-frequency limit of 2 MHz and equipped with an electromagnet is rebuilt to allow performing NMR experiments at resonance frequencies down to 100 kHz. The instrument is intended for accurate field-dependent spin relaxation studies. The preamplifier and the duplexer are completely replaced by new designs that provide low noise figure, large gain and fast recovery. The receiver, the transmitter, and the magnet power supply are modified to operate at low frequency (receiver and transmitter) and at low current (power supply). The performance of the instrument is demonstrated by H2 NMR experiments in the 500 kHz–2 MHz region and is compared to that of instruments based on direct current-superconducting quantum interference device and operated on room-temperature samples.
Thermal scanning alternating current susceptometry with multiple pick-up coils for ranging local phenomena in high Tc superconductors
Authors: Laiho R. , Lähderanta E. , Bódi A. C.
Published: July 2002

We describe a new experimental technique where ac susceptibility is measured simultaneously with three pick-up coils in three different regions along a YBCO ceramic sample, in the presence of strong thermal gradient. Each of the pick-up coils “feels” the shielding currents from the entire sample but with different weight due to geometrical factors. The multiple coil system permits the localization of any particularities (here a local avalanche-like decrease of the susceptibility function). Using this technique we observed experimental evidence of adiabatic flux change in a sintered high Tc superconductive material.
Long-path monitoring of atmospheric aerosol extinction with an automated laser positioning system
Authors: Widada Wahyu , Kuze Hiroaki , Xue Yanqun , Maeda Kazuhito , Takeuchi Nobuo
Published: July 2002

An automated laser-beam positioning system has been developed and applied to long-path (700 m) monitoring of atmospheric aerosols. The system is based on a piezoelectric-driven mirror mount whose vertical and horizontal positioning is precisely controlled so as to maximize the return beam intensity. By optimizing the direction of the transmitted beam every 5–10 min, the change in aerosol extinction can be measured to an accuracy of better than 2×10−5 m−1 without interference from beam displacement due to the temperature change. This positioning method allows one to use relatively small detectors and optical components which are easier to operate and maintain when compared with the previous method for the long-path measurement.
Measuring the Hall weighting function for square and cloverleaf geometries
Authors: Scherschligt Julia K. , Koon Daniel W.
Published: July 2002

We have directly measured the Hall weighting function—the sensitivity of a four-wire Hall measurement to the position of macroscopic inhomogeneities in Hall angle—for both a square shaped and a cloverleaf specimen. Comparison with the measured resistivity weighting function for a square geometry [D. W. Koon and W. K. Chan, Rev. Sci. Instrum. 69, 12 (1998)] proves that the two measurements sample the same specimen differently. For Hall measurements on both a square and a cloverleaf, the function is nonnegative with its maximum in the center and its minimum of zero at the edges of the square. Converting a square into a cloverleaf is shown to dramatically focus the measurement process onto a much smaller portion of the specimen. While our results agree qualitatively with theory, details are washed out, owing to the finite size of the magnetic probe used.
Characteristics of ion beams extracted from a compact powdery sample ion source
Authors: Wada M. , Kasuya T. , Sasao M. , Kawano H.
Published: July 2002

Spatial distributions of the current density of the ion beams extracted from an electron-stimulated-desorption-type powdery sample ion source have been measured. The vertical profile showed an asymmetry which can be attributable to the localized ion emission at the powder surface. The deflection of the beam in the horizontal direction caused by the magnetic field for guiding the electron’s motion to hit the powder surface was also confirmed. Despite the presence of this inhomogeneity which may degrade the beam quality, the positive and negative oxygen ion beams produced from BaO powder with the beam energy as low as 2 kV were focused to about 2 mm diameter.
Electron energy distribution function in a Hall-type thruster (abstract)
Authors: Bacal M. , Fedotov V. Yu. , Guerrini G. , Ivanov A. A. , Vesselovzorov A. N.
Published: July 2002

The electron energy distribution function measured at the channel exit of a small Hall-type thruster is interpreted as a beam-plasma electron distribution function with electron beam energy of several tens of electron volts. Although unstable, the distribution function does not correspond to the completely quasilinear relaxed beam function. Comparison with the measured function in the vicinity of the channel exit shows that the electron beam energy is about 30 eV for the total voltage applied ≅200 V. The contribution of the electron beam is shown to be essential in the ionization of the working gas, even when single ionization processes only are considered.
Status report on electron cyclotron resonance ion source operation at the Flerov Laboratory of Nuclear Reactions (Joint Institute for Nuclear Research) cyclotrons
Authors: Kutner V. B. , Bogomolov S. L. , Efremov A. A. , Lebedev A. N. , Loginov V. N. , Yazvitsky N. Yu.
Published: July 2002

Two electron cyclotron resonance (ECR) sources, DECRIS-14-2 and ECR4M, are presently in permanent operation at the Flerov Laboratory of Nuclear Reactions cyclotrons, U400M and U400, respectively. A wide range of ions of gases from He up to Xe was delivered by the sources and accelerated in the cyclotrons. Major efforts were made in the production of high current stable ion beams of solids with relatively low melting points in mass ranges from Li up to Bi. Both the evaporator and the MIVOC technique were used. Among the solids a beam as exotic as Ca48 was produced at the U400 cyclotron with high efficiency. The main results on production of ion beams of gases and solids are reported. For further development of ECR ion sources a test bench was designed and built. The test bench is equipped with the new DECRIS-3 ion source. The parameters of the test bench and ECR source are described.
A plan for on-line production and acceleration of radioactive isotope beams by use of electron cyclotron resonance ion source NANOGAN
Authors: Matsuta K. , Fukuda M. , Mihara M. , Minamisono T. , Mizobuchi A. , Kitagawa A. , Hattori T. , Sasaki M. , Kaminaka S. , Hashimoto K. , Tsubota T. , Kobayashi Y. , Sakamoto M. , Sakurai T.
Published: July 2002

For the precise low background experiments on β decay and material sciences, we are planning to build a new ISOL-type facility to accelerate various β-radioactive nuclei utilizing the existing 5 MV Van de Graaff accelerator and an RFQ linac. Present status of the designing work is reported. In the present work, optical elements of the 41-m-long beam transport line to connect Van de Graaff accelerator and an RFQ linac were designed. Using two dipole magnets, two electric quadrupole doublets and six electric quadrupole triplets, low energy radioactive nuclear beams can be transported with sufficient efficiency.
High current and high intensity pulsed ion-beam sources for combined treatment of materials
Authors: Ryabchikov A. I. , Petrov A. V. , Stepanov I. B. , Shulepov I. A. , Tolmachjeva V. G.
Published: July 2002

The complex installation for combined materials treatment with accelerated ion beams of different peak power and metallic plasma flows is described. The installation comprises the high-current repetitively pulsed vacuum arc ion source, high-intensity pulsed ion beam source, and direct-current vacuum arc plasma source combined with the plasma filter for plasma cleaning from the microparticle fraction. It has been found that the preliminary treatment of stainless steel samples with the high-power ion beam of nanosecond pulse duration results in the reduction of ion sputtering coefficient at the implantation of tungsten ions. It has been shown that the increase of maximum implanted tungsten concentration is influenced by changing the surface morphology and element structure of the samples affected by the high-power ion beam.
Status and new developments of the high intensity electron cyclotron resonance source light ion continuous wave, and pulsed mode (invited)
Authors: Lagniel J.-M. , Beauvais P.-Y. , Bogard D. , Bourdelle G. , Charruau G. , Delferrière O. , De Menezes D. , France A. , Ferdinand R. , Gauthier Y. , Gobin R. , Harrault F. , Jannin J.-L. , Leroy P.-A. , Yao I. , Ausset P. , Pottin B. , Rouvière N. , Celona L. , Gammino S.
Published: July 2002

The high intensity light ion source (SILHI) is the electron cyclotron resonance (ECR) source constructed and tested at CEA-Saclay. The first aim is to produce up to 100 mA cw proton beams at 95 keV for the proton injection high intensity (IPHI) beams [5 MeV radio frequency quadrupole (RFQ) and 10 MeV drift tube linac (DTL)]. This prototype is developed by a CEA–CNRS-IN2P3 collaboration for applications such as accelerator driven systems for nuclear waste transmutation, production of radioactive ion beams or secondary particles. SILHI is also used to study the production of deuteron and H− beams for the International Fusion Material Irradiation Facility and European spallation source projects, respectively. The present status of SILHI and the experiments planned for the near future in both cw and pulsed modes are presented in this article. 80 mA cw proton beams are now currently produced at 95 keV with a high availability (∼1 spark/day). The proton fraction is around 90% and the typical r–r′ rms normalized emittance after transport through a single solenoid low energy beam transport (LEBT) without beam losses is 0.3 πmm mrad. The best beam characteristics are obtained when an ECR zone is created at the frontier between the plasma chamber and the rf ridged transition. Extensive emittance measurements performed with different gas injection in the LEBT have shown a factor of three emittance reduction. Space charge compensation measurements in cw mode will be undertaken with a four-grid analyzer to understand this behavior. Time resolved space charge compensation measurements in pulsed mode are also discussed. The highest total beam current of 120 mA (240 mA/cm2) can be extracted with two ECR zones located at the plasma chamber extremities. Nevertheless a new electrode design must be done for this configuration to avoid excessive beam losses in the extraction system.
Dynamic simulations of the interchange instability, ion production, and electron heating processes in an electron cyclotron resonance ion source plasma
Authors: Niimura M. , Lamoureux M. , Goto A. , Yano Y.
Published: July 2002

Simulations hitherto performed with electron cyclotron resonance (ECR) ion sources (ECRIS) were mostly to predict physical quantities in their steady states. This article explores the time-dependent phenomena such as: interchange instability, ion production, and electron heating in order to simulate the time variations of hot-electron density, ion-trapping potential well, and core-electron temperature. This study has identified that the oscillations of around 1 Hz observable for these plasma parameters are a consequence of the interchange instability suffered by the hot electrons in the outer radial edge of an ECR shell. A pulsation of the ion-trapping potential well was found to take place under the unstable regime, thereby increasing the extractable ion current whenever the depth of the well is reduced due to the instability-triggered loss of electrons from the confinement. This finding may be exploited as a new method to obtain pulsed ion beams without pulsing the rf power. This article presents a formula for the best operating condition to achieve the highest steady ion beam currents out of an ECRIS. A self-consistent core-electron temperature was also predicted as a function of time.