bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and design of a nonmagnetic and nonconducting interferometer optical system
Authors: Burns S. R. , Peebles W. A. , Brooksby C. A. , Rice B. W.
Published: July 2002

The use of a 0.185-mm far-infrared (FIR) laser interferometer on MTX required the design and development of optical components which are nonmagnetic and nonconducting. This arose from the requirement that the path length of the FIR interferometer not change by more than (1)/(50) of a wavelength during the half-second plasma pulse. The time-dependent stray magnetic fields, 7000–400 G over the optical table area, generate strong eddy current forces which would produce path length changes greater than the design criteria if the components were metallic. Thus, the optical tower which supports the optical tables, one above and one below the tokamak, is a composite structure of 304 stainless steel and G-10 fiberglass. Also, the optical table and components are made of G-10 with a minimum of 304 stainless-steel parts to avoid eddy current forces and maintain structural rigidity. The design criteria of the optical components are discussed with a comparison of suitable materials. A discussion of the process which was developed to fabricate plastic parabolic beam expanding and focusing mirrors with a metallized reflective surface is presented. The mixer and electronics enclosure design minimizes eddy current forces by use of printed circuit board material while maintaining excellent EMI/RFI shielding.
A correction algorithm for particle size distribution measurements made with the forward-scattering spectrometer probe
Authors: Lock James A. , Hovenac Edward A.
Published: July 2002

Multiparticle coincidence events in the scattering volume of the forward-scattering spectrometer probe (FSSP) cause the instrument to bias the measurement of the particle size distribution of atmospheric aerosols toward large diameters. We employ a probabilistic model based on Poisson statistics to determine the average diameter and rms width of the actual size distribution as functions of the average diameter and rms width of the measured distribution. We compare our predictions to a Monte Carlo simulation of the FSSP operation
Double-resonance 14N nuclear-magnetic-resonance probe for single-crystal studies
Authors: Naito Akira , McDowell Charles A.
Published: July 2002

A double-resonance 14N nuclear-magnetic-resonance (NMR) probe suitable for single-crystal studies is described. The 14N and 1H sample coils are wound as coaxial solenoids and used instead of a doubly tuned single coil to tune over the required frequency range of the 14N channel. The choice of materials for the probe body and the wire size for the sample and impedance matching coils were chosen carefully to minimize spurious ringing phenomena, which is troublesome in probe designs for solid-state NMR. The probe has a very accurate goniometer since the resolution of 14N NMR signals is high.
Determining the integrated cavity emissivity of blackbody furnaces
Authors: Wu Quansheng , Chen Yinghang , Chu Zaixiang , Li Bijuan
Published: July 2002

An apparatus has been constructed for determining the integrated cavity emissivity of blackbody furnace simulators near 500 K and for calibrating infrared detectors. A difference-ratio method is described for measuring the radiant emission characteristics of the simulator by using a high-quality heat-pipe blackbody as a standard radiant source operated at 500 K and a water-immersed cavity as a reference source operated at a lower temperature. It is verified that the total uncertainties of the method are less than 0.6% for determining the integrated cavity emissivity and 0.5% for determining irradiance from the 500-K standard blackbody on the detectors.
Photoelectron-counting electronics for a microchannel-plate-intensified integrated diode array
Authors: Parkinson Murray
Published: July 2002

A multichannel photoelectron-counting system employing a Reticon 1024-element linear silicon photodiode array with fiber optic window has been developed. The fiber optic window may be used to couple a microchannel-plate intensifier which provides a front-end gain of photons to the photodiode array. With sufficient front-end gain, the cascade of photons which results from a single photodetection by the microchannel plate will produce a number of charge carriers in the photodiode array comparable to its saturation level. Thus, low-resolution pulse-counting circuits are required to interrogate the array and approach the ideal of single-photon-counting shot-limited performance. Details of the intrinsic functions and properties of photodiode arrays and microchannel plates have been reported elsewhere. The intent of this paper is to elucidate simple electronics designed specifically for operating photodiode arrays in the intensified single-photon recording mode. Although a microchannel plate was not available during the term of this work, performance of the system was illustrated by some simple optical experiments.
Design considerations and performance characteristics of a dual mode time-of-flight mass spectrometer system for surface reactivity studies
Authors: Eldridge Benjamin N.
Published: July 2002

We have designed a reflectron type time-of-flight mass spectrometer (TOFMS) system with both SIMS and electron impact (EI) ion optics. The system was designed to study the interaction of solid surfaces with reactive species initially in the gas phase. In the EI mode, the main TOFMS assembly, which consists of the flight tubes, reflectron, and a channel plate detector, is fitted with the EI ion source. The entire TOFMS is mounted in a rotatable cage permitting 270° of rotation about the sample center. Reactive species are supplied by a pulsed molecular beam source. The EI source has an unobstructed view of the target throughout most of the 2π solid angle defined by the plane of the sample. Angular and time-resolved detection of scattered beam species and desorbed reaction products to a limiting partial pressure of ∼10−13 Pa is possible in this configuration. In the SIMS detection configuration, the main TOFMS assembly is refitted with SIMS extraction optics and repositioned on the sample axis. The pulsed molecular beam source is again used to supply reactive species. By controlling the timing relationship between the arrival of the pulsed molecular beam and the pulsed ion beam used to sputter the target, time-resolved detection of transient surface species is possible. A 50% mass resolution of ∼1400 has been demonstrated in both operating modes. The feasibility of time-resolved detection in both operating modes has also been demonstrated.
Piezoelectric bimorph-based translation device for two-dimensional, remote micropositioning
Authors: Peters D. J. , Blackford B. L.
Published: July 2002

We describe a two-dimensional, remote micropositioning device that uses the bending mode of a piezoelectric bimorph for walking in the forward/reverse direction of motion. For this mode of operation step sizes range from ∼50 to 5000 nm, with a voltage sensitivity of ∼10 nm/V. Speeds of about 1 mm/s are possible. In the lateral direction of motion, the linear extension mode of the bimorph is used, giving step sizes from ∼50 to 1000 nm, with a sensitivity of ∼2 nm/V. For the walking sequence, anodized aluminum feet are electrostatically clamped to an anodized aluminum baseplate. When used as the coarse positioner in a scanning tunneling microscope, the device requires less than 100 V operating voltage, thus eliminating the high-voltage supply needed for previous piezoelectric walking devices. A circuit diagram for ‘‘joystick’’ control of the micropositioner is also described.
Use of a helical resonator as a capacitive transducer in vibrating reed measurements
Authors: Xiang X.-D. , Brill J. W. , Fuqua W. L.
Published: July 2002

A new design of the vibrating reed apparatus for studying the high-resonant overtones of very small samples is described. Using the high Q (∼103) helical rf resonator as a capacitive transducer, great sensitivity has been obtained. The theoretical sensitivity of the detector is investigated with transmission-line theory, and the result shows that the Johnson-noise-limited sensitivity is proportional to the Q of the resonator instead of Q1/2, as is the case of lumped LC-tuned circuit analyses. For a nonsuperconducting resonator, the Johnson-noise-limited minimum detectable displacement (Δdmin) at room temperature, with bandwidth B, is about 10−7 Å (B/Hz)1/2, if the rf electrical field level is only limited by vacuum breakdown. An application of the apparatus in studying the temperature-dependent changes in the Young’s modulus of single crystals of TaS3 is shown.
A simple optoelectronic device for controlling an electrophoresis apparatus
Authors: Paul A-L. , Ferl R. J. , Boudreaux G. S. , Meisel M. W.
Published: July 2002

The details of a simple optoelectronic cut-off device for controlling an electrophoresis apparatus are given. The device monitors the progress of the colored indicator dye as it passes through a point in the gel matrix and terminates an electrophoretic run by turning off the power supply when the indicator dye arrives at a location predetermined by the researcher. This switch frees the worker from having to constantly monitor the terminal stages of the experiment.
Low pump power performance of optoacoustic discriminator for CH3OH FIR laser
Authors: Wallace T. L. , Ventrice C. A.
Published: July 2002

The resonance enhancement of an optoacoustic signal is used to obtain a reliable discriminator in order to stabilize the output frequency of a CO2 laser. The CO2 laser is maintained on the 9P(36) emission line, the methyl alcohol vapor pressure within the acoustic cell is maintained at a value pg =1 Torr, and the chopper frequency is fixed at the fundamental longitudinal resonant frequency of the cylindrical resonator throughout the experiment. Utilizing a back electret condenser microphone to detect the optoacoustic signal, a reliable discriminator is obtained for a value of pump power as low as 10 mW.
New machining method for making precise and very smooth mirror surfaces made from Cu and Al alloys for synchrotron radiation optics
Authors: Higashi Y. , Meike T. , Suzuki J. , Mori Y. , Yamauchi K. , Endo K. , Namba H.
Published: July 2002

A combined machining method of diamond turning and numerically controlled elastic emission machining has been developed for finishing metal mirror surfaces made from Cu and Al alloys. A mirror surface can be polished without any stress by this method. Shape and roughness of the mirror surface examined in different machining methods are compared and discussed. A precisely shaped mirror with a roughness less than 2-nm Rmax was obtained. A copper mirror was installed in a VUV beamline of the Photon Factory. It is confirmed that the metal mirror finished by the present method has good optical characteristics for synchrotron radiation beamlines.
Optical design of a 200 eV–2.5 keV cylindrical element monochromator for the 1.3-GeV storage ring of SRRC
Authors: Chang Chu-Nan , Tseng Ping-Chung , Song Yunn-Fang
Published: July 2002

Separate focus-function mirrors in combination with a simple-scanning spherical/cylindrical grating are to be used for an extreme grazing-incidence beamline design in the photon energy range of 200 eV–2.5 keV at the ARC synchrotron radiation of the TBA lattice of SRRC. Three mechanically ruled gratings are used to cover the spectral wavelength range of the extreme VUV and soft x rays. Both the throughput and the resolution of this optical system have been carefully calculated and compromised against the grazing angle, arm length, grating size, etc. The proper parameters of the optical elements as well as their geometrical arrangements are proposed. A resolving power of at least 2000 is obtainable at the high-energy end of the spectrum around 2 keV. At the low-energy end, the resolving power can be as high as 8000, comparable to a grazing-incidence Rowland circle type of monochromator. The overall resolving power has been found to be superior to that of either the plane grating monochromator (PGM) or the 10-m toroidal grazing monochromator (TGM) in the same spectral wavelength range.
Examination of thermally induced deformation of a synchrotron radiation mirror using finite element analysis
Authors: Lenardi C. , Vecile C. , Vitali R. , Rosei R.
Published: July 2002

A synchrotron radiation mirror is subjected to high thermal loads that cause thermal gradients and surface distortions. The thermally induced deformations can strongly affect the transmission and the energy resolution of insertion device beamlines. We have performed heat transfer calculations and mechanical analyses in order to evaluate surface slope errors of a grazing-incidence mirror. The parameters for these calculations have been chosen according to what will be a typical working situation at the synchrotron radiation facility of Trieste, presently under design. The analysis has been carried out by using the finite element method.
Magnetic measurements on insertion devices at NSLS
Authors: Decker Glenn , Galayda John , Solomon L. , Kitamura M.
Published: July 2002

Magnetic measurements on three insertion devices for use in the National Synchrotron Light Source (NSLS) x-ray ring are described. Hall probes were used for field mapping, and rotating long coils were used to determine integrated multipole coefficients. Results are presented for an iron pole-REC hybrid indulator, a vanadium permendur pole-REC hybrid wiggler, and a 5 T superconducting wiggler.
New possibilities and some construction problems of low emittance rings at an energy of 8–10 GeV (invited) (abstract)
Authors: Kulipanov G. N.
Published: July 2002

The fields of using a new generation of synchrotron radiation sources storage rings at an energy of 8–10 GeV are discussed. Much attention is paid to the problems whose solution opens the basically new possibilities: generation of pulsed beams of slow high brightness positrons, obtaining of powerful pulsed fluxes of neutrons, generation of quasimonochromatic gamma quanta. The ways and the bounds of further improving of such storage rings are considered.
Review of synchrotron beam stability and stabilizing systems (invited)
Authors: Hettel R.
Published: July 2002

Fluctuations of the stored beam orbit, together with the vibration and thermal distortion of beamline optical components, introduce photon beam position and angle instabilities at distant experimental stations and degrade data quality for many experiments. Systems employing sensitive photon beam position monitors have been devised to reduce the magnitude of these disturbances to tolerable levels. Desired stability levels for the vertical plane, in which the beam is highly collimated, are 10 μm in position and 1 μrad in angle. Horizontal stabilizing systems are also being developed for certain undulator and horizontally focused beams that are likewise adversely influenced by small motions. An order of magnitude increase in stability requirements is expected for the next generation of very low emittance and small aperture beam sources. Achieving this stability will depend on the combined efforts of storage ring mechanical, electrical, and lattice designers as well as on the development of improved position monitoring and beamline optical systems.
Beam position stabilization at the Photon Factory (invited)
Authors: Katsura T. , Kamiya Y. , Haga K. , Mitsuhashi T. , Nakamura N. , Katoh M. , Abe I.
Published: July 2002

To obtain position-stabilized photon beams from the Photon Factory storage ring, our efforts were concentrated on two directions, one to minimize any disturbances causing the stored beam to move, and the other to suppress undesired beam motion by using feedback systems. This paper concerns one of the most disturbing cases, the diurnal beam position drift. The drift motion was suppressed with a global orbit feedback system, so that photon beam position was kept stable at all the beamlines. At the same time, some disturbances were reduced by investigating the cause and the mechanism of beam motion. The fact that the beam drift motion was closely correlated to the outdoor temperature variations led us to make a model simulation by taking account of the meteorological conditions around the building. It was proved that the building distortion due to the external thermal stress resulted in the diurnal beam motion. To minimize such distortion, it is suggested that one should insulate the building on the rooftop rather than underneath it as is usually done.
Multiply adjustable point-contact system
Authors: Hoevers H. F. C. , Hermsen J. G. H. , van Kempen H.
Published: July 2002

We have constructed a double point-contact system for use at liquid-helium temperatures which is adjustable from the outside. Both point-contact wires can be independently displaced vertically with a travel of 5 mm and horizontally with a travel of 4 mm. Displacements of 5 μm can be achieved. The sample table is rotatable over 360° and can be translated over 2 mm, which implies that point-contact wires can be placed at any desired position of a sample. Moreover, the point-contact wires and the sample can be viewed from the outside to check positions and a magnetic field up to 1.2 T can be applied. The point contacts obtained with this system are both mechanically and electrically stable, also in a magnetic field. The instrument is of great use for transverse electron focusing studies of transport properties of metals, surfaces, and interfaces. Because of versatility, the instrument is also suitable for single point-contact experiments to study interfaces of normal metals and superconductors or to perform point-contact spectroscopy experiments.
Core level photoelectron microscopy with synchrotron radiation (invited)
Authors: Pianetta P. , Lindau I. , King P. L. , Keenlyside M. , Knapp G. , Browning R.
Published: July 2002

The capabilities of a direct imaging photoelectron microscope (MicroESCA from Surface Science Instruments) have been demonstrated in a set of experiments carried out at the Stanford Synchrotron Radiation Laboratory (SSRL) using a torroidal grating monochromator in the photon energy range 20–170 eV. Photoelectrons from a 300×300 μm2 sample area are projected in the diverging magnetic field of a superconducting solenoid and an image reflecting the variation in photoelectron yield is recorded digitally with a resistive anode imaging detector. Lateral resolution is better than 5 μm. A retarding field analyzer located in front of the imaging detector acts as a high-pass filter and allows us to obtain a series of spectrally resolved images which can be processed to give a spot XPS analysis of areas as small as 5×5 μm2. Images from a sample of patterned aluminum on silicon are presented to demonstrate the potential of the instrument.
Signal processing for an infrared array detector
Authors: Young M. A. , Smith G. E. , Pimentel G. C.
Published: July 2002

A broadband detection scheme for a time-resolved infrared absorption spectrometer, based on a multielement mercury-cadmium-telluride (MCT) array, has been successfully implemented. The spectrometer achieves a resolution on the 10-ns time scale despite the much larger time constant characteristic of the MCT elements. Our signal-collection circuitry takes advantage of the slow decay by integrating the detector response to pulsed IR radiation. The dynamic range is 100–1 and the resultant noise level is near the detector limit. Data acquisition for the 120 elements is fast enough to allow scan rates of 30–40 Hz. The completed electronics are sufficiently compact to be situated local to the array detector, and the design is relatively inexpensive to construct using commonly found electronic components.
Lasing in visible and ultraviolet regions in an optical klystron installed on the VEPP-3 storage ring (invited)
Authors: Vinokurov N. A. , Drobyazko I. B. , Kulipanov G. N. , Litvinenko V. N. , Pinayev I. V.
Published: July 2002

Since 1979, experiments on the storage ring VEPP-3 with an optical klystron (OK) have been performed at the INP Academy of Sciences of the USSR. In 1979, 1981, and 1983, three different OK magnetic systems based on SmCo permanent magnets undulators were installed at the VEPP-3 straight section at 6300-A wavelength. The following gains per pass have been obtained: 0.5% in 1980, 1% in 1982, and 2%–2.5% in 1984. In late 1985, we decided to improve the storage ring VEPP-3 and develop a dc bypass, a special straight section dedicated for OK operation. The bypass allowed us to install an OK magnetic system of 7.8 m length and significantly increase the gain per pass in March of 1988. The bypass was installed at the storage ring VEPP-3 on 3 June 1988. We obtained lasing in the red and yellow light spectral range from 5800 to 6900 A with 5%–10% gain per pass. After changing mirrors for new ones with minimum losses at 4150 A, lasing in the violet and near UV spectral range with 3%–6% gain per pass from 4500 to 3750 A was obtained on 8 July. All work is being carried out at an energy of 350 MeV. Threshold currents for lasing are 1–10 mA depending on the optical cavity mirror conditions. The maximum current is 80 mA at present. A set of measurements on studying lasing in various conditions is underway.
Measurements of the length of intense electron bunches using a capacitive probe and a 20-GHz sampling oscilloscope
Authors: Van der Meer A. F. G. , Bakker R. J. , Van der Geer C. A. J. , Van Amersfoort P. W.
Published: July 2002

Measurements of the longitudinal profile of intense electron bunches with an energy of 100 keV, using a button monitor and a 20-GHz sampling oscilloscope, are presented in this paper. At this energy, which is intermediate between nonrelativistic and relativistic, the button response is quite different from the response in either of the two extreme cases. An analytical model of the response is presented. The resolution derived from this model is 80 ps at 100-keV beam energy. For more relativistic beams, a resolution of about 40 ps appears to be feasible. Great care has to be taken in avoiding resonances.
Compact radio-frequency glow-discharge atomic hydrogen beam source
Authors: Hodgson John A. B. , Haasz Anthony A.
Published: July 2002

An atomic hydrogen beam source, compatible with ultrahigh vacuum and clean surface conditions, has been developed. Hydrogen atoms (H0) of thermal energy distribution are produced by dissociation of hydrogen molecules in a radio-frequency (rf) glow discharge. The resulting mixture of atoms and molecules is allowed to flow from the discharge vessel to the vacuum test chamber through a capillary, resulting in the formation of a beam. Dissociation fractions [ 1/2  H0/(H2+ 1/2  H0)] of >0.5 and H0 fluxes of >2×1017 H0/s were achieved. Locating the rf power source adjacent to the discharge vessel resulted in a compact device which is easy to maintain and operate.
A simple and reliable method of thermoelectic effect spectroscopy for semi-insulating III-V semiconductors
Authors: Huang Z. C. , Xie K. , Wie C. R.
Published: July 2002

We have developed a simpler and more reliable method of thermoelectric effect spectroscopy (TEES), eliminating the second heater in the technique. We have applied this method to the deep level studies in the semi-insulating undoped or Cr-doped GaAs materials and in the GaAs epitaxial layers grown at a low temperature by molecular beam epitaxy. We have found that the electrical contacts made on front and back surfaces of the sample are more reliable for the TEES measurement than both contacts made on the same surface. In this contact arrangement, the temperature difference of about 1–2 K between the back and front surfaces is enough to produce a clear and reliable TEES data, without the need for a second heater. The results obtained by TEES are consistent with the results obtained by photoinduced transient spectroscopy (PITS) and by thermally stimulated current (TSC) measurements. The TEES results clearly distinguish between the electron traps and the hole traps. We discuss the results on the various semi-insulating GaAs samples and the advantages and limitations of the TEES technique.
Portable i
n s
i
t
u wall-rock thermal conductivity meter for mine pits
Authors: Shen Xian-jie , Yang Shu-zhen , Zhang Wen-ren
Published: July 2002

A novel ring heat source probe based on three-dimensional transient heat conduction from a point heat source is applied to measure in situ wall-rock thermal conductivity in mine pits. The calibration is based on two reference materials. The data are processed digitally, using an acoustically controlled channel selector. The application of a fully automatic control technique by a microcomputer program results in successful establishment of a quick and portable one-button triggering, in situ wall-rock thermal conductivity meter for mine pits.
The Stableflow Pump−a low-noise and drift-free pump for high performance liquid chromatography
Authors: LeBlanc Jacques C.
Published: July 2002

The Stableflow Pumpb) is a novel pump being developed for isocratic elution in high performance liquid chromatography (HPLC). The pump is characterized by low flow noise whose level has a standard deviation of 0.030% over a period of 4 min, and a wander of ±0.02%; the flow is drift free, and is accurate to within ±0.10%. With the present design, the flow range is from 0.1 to 100 mL/min, and the maximum pressure rating is 6800 kPa (1000 psi). The flow characteristics of three commercially available pumps were also tested with a Thermalpulse flowmeter, which was calibrated using the Stableflow Pump to control the flow rate. The Stableflow Pump has a great advantage with flow-sensitive detectors and for molecular weight determinations, and would be especially useful in certain HPLC applications where low detection limits are required.
Cooling device for low-temperature thermal analysis studies
Authors: Dworkin Ary , Jaffre Joël , Szwarc Henri
Published: July 2002

The exhaust gas of a liquid nitrogen tank is pumped to force evaporation of the liquid in a chamber thermally linked to the measuring heads of a thermal analysis device (Perkin Elmer DSC 2C):cooling down to 80 K and long thermal treatments are currently performed.
The design and calibration of a very fast current probe for short pulse measurements
Authors: Calico Steve E. , Crawford Mark T. , Kristiansen M. , Krompholz H.
Published: July 2002

The design, construction, and calibration of a probe to measure fast rise, short pulse currents is described. This probe is a 60° section of a Rogowski coil that is designed to behave as a slow wave structure. The device described has nanosecond response and the output is proportional to the excitation current for approximately 70 ns.
A diamond anvil cell for high-pressure NMR investigations
Authors: Bertani R. , Mali M. , Roos J. , Brinkmann D.
Published: July 2002

A diamond anvil cell suitable for high-pressure NMR experiments in a cryostat is described. Inside a rhenium gasket pressures up to 8.3 GPa could be generated. With this apparatus the pressure dependence of the Knight shift and of the self-diffusion coefficient in metallic lithium and sodium has been measured (as published elsewhere).
Photon-beam-feedback system and mirror-alignment mechanism
Authors: Tsang King-Long , Chung Shinchun , Song Yen-Fang , Tseng Ping-Chung , Chen Ching-Iue , Lin Hsueh-Feng , Huang Liang-Ren , Dann Tang-Eh , Chang Chu-Nan
Published: July 2002

A feedback system is designed and built to automatically correct the long-term instability of the photon beam generated from the synchrotron radiation storage ring. This feedback system is composed of a stepping motor-controlled mirror-alignment mechanism, a photon-beam-position monitor, a high precision current amplifier, and a PC-controlled CAMAC interface system. The details of the system design as well as the motorized mirror-alignment mechanism are presented in this article.
The Exxon microtomography beam line at the National Synchrotron Light Source (invited)
Authors: D’Amico K. L. , Dunsmuir J. H. , Ferguson S. R. , Flannery B. P. , Deckman H. W.
Published: July 2002

Instrumentation for beam line X2 at the National Synchrotron Light Source is described. The beam line is configured as a dedicated experimental station whose design has been optimized for carrying out both microtomography and microradiography. The facility has proven to be a reliable three-dimensional microscope for imaging the interior structure of heterogeneous materials.
X-ray optics for ESRF beamlines: Problems and projects (invited)
Authors: Freund Andreas K.
Published: July 2002

Third generation, dedicated synchrotron radiation sources will produce x-ray beams of unprecedented quality and power. This calls for substantial research and development of adequate instrumentation. In particular, the unprecedented properties of the new sources must be followed up by a complete review of the optical devices which constitute the first part of the beamline after the beryllium window. This article gives a short account of where and what the problems are in x-ray optics for the European Synchrotron Radiation Facility and what is presently going on and being envisaged to solve these. This review is divided into problems concerning conservation of the low source emittance such as the optical quality of mirror surfaces and high crystalline perfection of monochromators, and the important problem of how to preserve the very high brilliance resulting in unprecedented x-ray total power and power density generated by wigglers and undulators. Finally, a brief presentation of the ESRF optics laboratory is given.
Design of 10-T superconducting wiggler for angiography
Authors: Sugiyama S. , Ohgaki H. , Mikado M. , Noguchi T. , Yamada K. , Chiwaki M. , Suzuki R. , Koike M. , Yamazaki T. , Tomimasu T. , Keishi T. , Usami H. , Hosoda Y.
Published: July 2002

The design of a 10-T superconducting wiggler as a synchrotron radiation source for angiography has been carried out to be installed in an 800-MeV electron storage ring, TERAS, at Electrotechnical Laboratory (ETL). Synchrotron radiation generated by the wiggler has a critical photon energy of 4.47 keV and the radiation spectrum identical to that from a 2.5-GeV storage ring with a bending radius of 8.3 m. The magnet of the wiggler consists of three pairs of iron-cored superconducting coils designed to provide a peak field of 10.5 T on the beam trajectory. The effect of the wiggler on the storage ring has been investigated and a pair of quadrupole doublets on both sides of the wiggler can compensate a large deviation of the betatron tune.
Intentional and unintentional generation of integrated multipoles by insertion devices (abstract)
Authors: Halbach K.
Published: July 2002

Basic concepts and use of a general and rather simple theory will be presented that allows one to calculate quantitatively and with very little effort the strength of the integrated multipoles that are generated when one disturbs virtually any aspect of a (three-dimensional!) insertion device. This type of information can be used both to assess the required tolerances that have to be achieved in order to incorporate an insertion device into an accelerator-like structure without degrading that structure, or to design corrections into an insertion device.
Perspectives on variable-period/polarizing insertion devices in synchrotron radiation science and technology: Recent developments at SSRL (abstract)
Authors: Tatchyn Roman
Published: July 2002

Insertion devices that are tuned by electrical period variation, in contrast to the conventional method of mechanically varying the field strength, offer a number of advantages for the successful development of the next generation of higher-brightness storage rings and associated experimental techniques [R. Tatchyn, Nucl. Instrum. Methods A 275, 430 (1989); J. Appl. Phys. 65, 4107 (1989); R. Tatchyn and T. Cremer, IEEE Trans. Mag. 26, 3102 (1990)]. for example, due to the inherently low total output power levels of variable-period devices, their use can do more to relax power loading constraints on beamline optics at existing and future facilities than many of the alternative approaches explored in recent years, such as, e.g., gallium-cooled optics, multilayer premonochromator structures, or adaptive/deformable optics. With regard to machine optics, variable-period structures can be operated without varying the tune of the host machine lattice, enabling the design and flexible operation of ultralarge, yet reliable and versatile multiuser facilities. In the area of synchrotron radiation (SR) science, variable-period fields can be naturally configure in a literally infinite number of ways, permitting, e.g., fully flexible polarizing field profiles, dynamical field profiles, and multicolor field configurations, all of which serve to expand the possible modes and means of SR experimentation. In this paper we report on recent results obtained at SSRL in the development of variable-period insertion devices that indicate the possibility of extending this technology into short-period (<10 cm), high-field (≳0.05 T) regimes, i.e., into parameter ranges presently occupied by conventional variable-gap, permanent magnet structures. General theoretical arguments, specific designs and their projected performance, as well as an outline of current activities related to the implementation of polarizing and nonpolarizing prototypes on Beam Line V at SSRL, are summarized.
Impedance measurements at the Photon Factory storage ring
Authors: Izawa M. , Kiuchi T. , Tokumoto S. , Hori Y. , Sakanaka S. , Kobayashi M. , Kobayakawa H.
Published: July 2002

The loss parameters of the ducts in the Photon Factory (PF) storage ring were evaluated using the wire method and the code tbci. Both the measurement and the calculation were done for different bunch length σ ranging from 25 to 80 ps. The ring impedance was estimated to be ‖Z/n‖=3.19 Ω using the broadband impedance model. The measurements in frequency domain were also carried out to investigate the resonances of some duct components such as the gate valves without rf shield and the flange gaps. The results are presented.
High T
c superconducting switch
Authors: Dhali Shirshak K. , Mohsin Mohammad
Published: July 2002

We report the results of an experimental and modeling investigation of a high-temperature superconducting opening switch using optical and current switching. The switch was fabricated using a thin film of YBaCuO on a SrTiO3 substrate. A Nd:YAG pulsed laser, operating at the fundamental frequency, and the signal current was used as a triggered source. The results of optical switching indicates that the switching is due to the heating of the superconductor by the laser from its superconducting to the normal state. Switching using current pulses shows a thermal hysterisis effect. The dependence of the switching characteristics (rise time and delay) on the bias (temperature and current) and trigger intensity is discussed. Also, the results of a model based on heat equations is presented.
A versatile microcomputer interface and peripheral devices: An application in deuterium lamp background correction graphite furnace atomic absorption spectrometry
Authors: Gökmen A. , Yalcin S.
Published: July 2002

A versatile interface card for Apple IIe computer and various peripheral devices are designed to control instruments which generates transient signals like in graphite furnace atomic spectrometer. The interface card consists of a multiplexed analog-to-digital converter, a digital-to-analog converter, and a timer/counter chip. The timer/counter chip with 16 built-in registers can be programmed in many modes which provides a time base for real-time measurements. A stepper motor runs under the control of timer/counter chip independent of computer. A light chopper connected to the stepper motor is controlled easily by computer. A dual high-voltage switch can modulate dc light sources under computer control. This system is applied to D2-lamp background correction graphite furnace atomic absorption spectrometer. The D2 lamp is chopped by a mechanical chopper driven by a stepper motor and a hollow cathode lamp is modulated electronically. The data acquisition program is written in machine language and synchronization between light sources and computer is provided by chopper position signal through the interrupts. A sampling rate of 16 during a signal period at 50-Hz chopping frequency is found to be the optimum value. A large number of data collected during atomization period is compressed in machine code. This saved storage space and analysis time.
New scanning device for scanning tunneling microscope applications
Authors: Koops R. , Sawatzky G. A.
Published: July 2002

A small, single piezo XYZ translator has been developed. The device has been used as a scanner for a scanning tunneling microscope and has been tested successfully in air and in UHV. Its simple design results in a rigid and compact scanning unit which permits high scanning rates.
A flexible foil, gravity-driven mixer for preparation of gas mixtures
Authors: Brugge H. B. , Holste J. C. , Hall K. R.
Published: July 2002

A flexible foil mixer is described which is gravity driven and which assists in the preparation of gas mixtures of accurately known composition. This mixer, which is simple, inexpensive, and easy to construct, does not limit the operating temperature and pressure ranges of the containment vessel.
Alpha-CHERS: A spectroscopic experiment to detect nonthermal alpha particles on TFTR
Authors: Stratton B. C. , Fonck R. J. , Kim Y. J. , McKee G. , Thorson T.
Published: July 2002

A spectroscopic diagnostic for measurement of slowing-down alpha particles is under development and will be implemented for D–T operation of the Tokamak Fusion Test Reactor. The visible 468.6 nm He+ line (n=3–4) is excited by charge exchange recombination of alphas with a heating neutral beam (55 keV/amu), and the distortion of the line profile caused by alphas with energies up to 0.5–1.0 MeV is observed. Expected intensities are 0.1%–10% of the bremsstrahlung background for D–T discharges with Q=0.2–1.0. Because the signal is small, a high-throughput optical system is needed to achieve the desired signal-to-noise ratio of 10–100. Vertical and horizontal arrays of sightlines with five spatial channels will be used. Initially, two spatial channels will be coupled via fiber optics to an f/3.8 spectrometer equipped with a low-noise charge coupled device detector, with expansion to 5–10 spatial channels planned for D–T operation.
Paramagnetic resonance in GaN-based light emitting diodes
Authors: Carlos W. E. , Glaser E. R. , Kennedy T. A. , Nakamura S.
Published: July 2002

Significant advances in GaN-based materials and devices have prompted intense interest in the group III nitrides. In this letter, we report electroluminescence-detected magnetic resonance (ELDMR) and electrically detected magnetic resonance (EDMR) results on InGaN/AlGaN double heterostructures which have an intense blue emission. The dominant feature detected by either technique is a broad resonance (ΔB∼21 mT) at g≊2.00. Our ELDMR measurements show that this is associated with the blue emission and we ascribe this resonance signal to a deep Zn-related acceptor. A second resonance, resolved in EDMR, is tentatively identified as a deep donor trap. Based on our results we propose a model for the blue emission from these diodes.
A Fourier transform microscope for x-ray imaging
Authors: Wood K. S. , Feldman U. , Becker P. A. , Nemiroff R. J. , Kania D. R.
Published: July 2002

This is a progress report on development of a new x-ray imaging system, called a Fourier transform microscope, intended for use with x-ray emitting targets in laser fusion experiments. It is being built by Naval Research Laboratory and Lawrence Livermore National Laboratory. The system works at energies from 3 to 7 keV. We describe the development of the design, which utilizes fine etched grids to extract Fourier amplitudes for the source brightness distribution at selected spatial frequencies. The finest grids in the prototype system will have rib dimensions of 2 μm. The prototype system is expected to achieve position resolution of 4 μm in 3–7 keV. Simulations of the expected imaging performance are presented.
Small-angle Thomson scattering system for current density and electron distribution function measurements on T-10
Authors: Grek B. , Sannikov V. , Bartolick J. , Gorshkov A. , Lhor J.
Published: July 2002

As part of a US–USSR collaboration on electron cyclotron heating and current drive, a small-angle Thomson scattering system has been designed and installed on the T-10 tokamak at the Kurchatov Institute of Atomic Energy. The system makes use of a 20-J Nd-glass laser, provided by Kurchatov, that can deliver up to four pulses at energies greater than 20 J. The detection system uses an axicon-based collection optics and high quantum efficiency avalanche photodiodes. The combination of high laser power, high quantum efficiency of the photodiodes, and the small scattering angle geometry make it possible to observe either the perpendicular or parallel (to the tokamak magnetic field) electron distribution function to energies greater than three times the electron thermal energy, at plasma densities of 1013/cm3.
Synthesis of oriented textured diamond films on silicon via hot filament chemical vapor deposition
Authors: Chen Qijin , Yang Jie , Lin Zhangda
Published: July 2002

Oriented diamond films were achieved on Si(001) and Si(111) substrates via hot filament chemical vapor deposition (HFCVD) with the orientation relationship of dia〈110〉//Si〈110〉 and dia(001)//Si(001) for Si(001), and of dia〈11̄0〉//Si〈11̄0〉 and dia(111)//Si(111) for Si(111). The substrates were negatively biased relative to the filament during the nucleation stage. The as-grown films were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. The role of negative bias is discussed in light of the differences between HFCVD and microwave plasma CVD. In conclusion, the importance of the electron emission from the diamond coating on the substrate holder is highlighted, while the ion bombardment is eliminated as a main factor based on our experiments.
Fast bolometric diagnostic in the RFX reversed field pinch experiment
Authors: Mast K. F. , Gadani G. , Gaggini P. , Giubbilei M. , Guatieri R. , Martin P. , Murari A. , Parini A. , Perdon E.
Published: July 2002

Bolometric measurements are performed in the RFX reversed field pinch experiment by means of a low noise miniaturized multichannel metal resistor bolometer module. The first tests on RFX, an experiment with geometrical dimensions comparable with those of large tokamaks but characterized by a much faster plasma dynamics, show that this thin film bolometer can be operated with high bandwidth and high time resolution in very different fusion experiments. A new data analysis technique, which allows the derivation of the power absorbed by the bolometer at a high time resolution (Δt=3×10−5 s) for the study of fast phenomena is presented.
Modeling fast alpha-particle distributions
Authors: Schivell J. , Monticello D. A. , Zweben S. J.
Published: July 2002

We have developed a code for following the radial diffusion and slowing down of alpha particles from DT fusion. The partial differential equation is solved by a finite-difference method. Ion as well as electron drag is included. Any given source function of radius, time, and energy width can be handled correctly. The code has been used to examine time waveforms, radial distributions, and energy spectra. The results can be used to model signals expected from the alpha charge exchange recombination spectroscopy and collective Thomson (‘‘gyrotron’’) scattering diagnostics. The code has also been used to calculate, as a function of diffusion coefficient, the flux of escaping fast ions that enters a lost-ion detector, and thus to deduce from measurements an upper limit for the diffusion of fast charged fusion products.
Phenomenology of intense electron cyclotron emission bursts during high power neutral beam heating on TFTR (abstract)
Authors: Taylor G. , Bush C. E. , Fredrickson E. , Park H. K. , Ramsey A. T.
Published: July 2002

A 20-channel grating polychromator has been used to study intense bursts of electron cyclotron emission (ECE) from TFTR deuterium plasmas predominantly heated by 90–110-keV neutral beams (Pinj/Poh≳30). The ECE bursts have a duration of 20–150 μs and are usually seen 300–500 ms after the start of neutral beam injection, when the stored energy and neutron production are collapsing or rolling over. In most cases the ECE bursts have Δf/f∼0.2–0.5, if this frequency spread is due entirely to relativistic broadening it implies an electron energy of 10–100 keV (Core electron temperatures in these plasmas are typically 7–12 keV). The ECE bursts are often correlated with ELM activity during limiter H modes and appear to occur at the beginning of the rise in the Dα signal. In some instances the spectral width of the ECE burst is narrow enough (Δf/f∼0.1) to allow identification of the origin of the emission, in these cases the source appears to be within 0.2 m of the plasma edge and the ECE burst exhibits a delay characteristic of an outwardly directed velocity of 2–3×103 m/s. This work is supported by U.S. Department of Energy Contract No. DE-AC02-76-CHO-3073.
Runaway electrons as a diagnostic of magnetic fluctuations (abstract)
Authors: Bengtson Roger D. , Wang P. W. , Freeman M. , Wootton A. J. , Catto Peter J. , Myra J. R.
Published: July 2002

The transport of runaway electrons in a hot plasma can be comparatively easily measured by perturbation experiments. The runaway electron diffusion coefficient is determined by intrinsic magnetic fluctuations rather than electrostatic fluctuations because of the high energies involved. The results presented here demonstrate the efficacy of using runaway transport techniques for determining intrinsic magnetic fluctuations. This work was supported in part by U. S. Department of Energy under grant DE-FG05-88ER-53267 and the Texas Advanced Research Program.
Method to reduce local permeability variations in magnets
Authors: Wollnik H.
Published: July 2002

Since the achieved magnetic flux density in steel depends on the excitation history of the steel, precision magnets often suffer from local changes in permeability in the steel of the pole pieces. These effects can be reduced by once fully saturating the pole pieces of the magnet. For high field magnets this can easily be done, but also in low field magnets such a saturation can be achieved by temporarily introducing a bar of steel into the magnet air gap.
Cell design for low-temperature time-domain reflectance measurements
Authors: Berberian J. G. , Cole R. H.
Published: July 2002

The design and construction of a dielectric cell, used in time-domain reflectance measurements at low temperature and high frequencies, are presented. Criteria are developed for cell construction, based on a transmission line model of bilinear form, and are applied to the physical construction of the cell. Bilinear parameters are derived for the cell model and compared with parameters calculated from short circuit measurements of two cells differing in design.
Observation of alloy solidification using high-speed video
Authors: Bassler B. T. , Hofmeister W. H. , Bayuzick R. J. , Gorenflo R. , Bergman T. , Stockum L.
Published: July 2002

A high-speed video instrumentation system was used to observe solidification of undercooled Ti-51 at. % Al. The camera system developed by Battelle is capable of operation at rates up to 12 000 frames per second. The system digitizes and stores video images acquired by a 64×64 pixel silicon photodiode array. In a joint effort with Vanderbilt University the camera was used to observe three transformations of the undercooled alloys using containerless processing by electromagnetic levitation. The first was solidification where nucleation was induced at an undercooling of 9% Tl, where Tl is the liquidus temperature of the alloy, and the second was solidification where nucleation was spontaneous at an undercooling of 15% Tl. The third event was a solid-state nucleation and growth transformation following the solidification at an undercooling of 15% Tl.