bluuebunny/crossref_metadata_2025 huggingface dataset:
Review of accelerator based sources (invited) (abstract)
Authors: Hofmann A.
Published: July 2002

The development of storage rings for synchrotron radiation have now arrived at so-called third-generation and have straight sections with optical functions optimized for undulators and electron beams of very small emittances. The beam optics of the ring is chosen so as to minimize the quantum excitation of betatron oscillations which determine the emittance. This can be achieved with a ring containing many cells with a small bending angle and with strong focusing in each cell. The first point results in large and expensive rings and both points require strong sextupole magnets for the chromaticity correction which can limit the dynamic acceptance. The optimization of storage rings with these points in mind lead to lattices which have achromatic cells with two, three, or more bending magnets. Studies for future rings consider further methods like the use of wigglers, combined function magnets, increased transverse damping partitions, etc. in order to obtain even smaller emittances which approach the diffraction limit.
Design of x-ray undulator beamline and experimental station for the feasibility study at Tristan Main Ring (abstract)
Authors: Sugiyama Hiroshi , Zhang Xiaowei , Ando Masami
Published: July 2002

A feasibility study will be carried out for synchrotron radiation (SR) experiments using the Tristan Main Ring (MR) as a superbrilliant x-ray source in the autumn of 1995. A test beamline BL-BW-TL is under construction for that purpose. It is a very long x-ray undulator beamline designed for superbrilliant radiation in the x-ray region with high heat load. The SR experimental station is located 4.5 m lower than the MR. The beam path line is kicked down to the SR experimental station by a double crystal monochromator. The first crystal of the monochromator is cooled by liquid nitrogen in order to prevent the SR beam from deteriorating.
Thermomechanical analysis of the white-beam slits for a wiggler/undulator beamline at the Advanced Photon Source
Authors: Nian H. L. Thomas , Kuzay Tuncer M. , Shu D. , Tcheskidov V. , Sheng A.
Published: July 2002

A set of precision, vertical, white-beam slits has been designed for an undulator/wiggler beamline at the Advanced Photon Source (APS). The slit, a knife-edge-type precision device, is required to have very small thermal distortion during operation with beam. The traditional slit consists of a cooling block and an OFHC cooling channel inside the block. The design consists of one large block and an OFHC cooling tube (filled with copper mesh) brazed inside the large block. This design will accommodate the x-ray source from both undulators and wigglers. Due to the powerful x-ray heat flux coming from APS Undulator A, it is an exceedingly difficult problem to reduce the thermal distortion to less than 50 μm as required by some users.
Faster magnet sorting with a threshold acceptance algorithm
Authors: Lidia Steve , Carr Roger
Published: July 2002

We introduce here a new technique for sorting magnets to minimize the field errors in permanent magnet insertion devices. Simulated annealing has been used in this role, but we find the technique of threshold acceptance produces results of equal quality in less computer time. Threshold accepting would be of special value in designing very long insertion devices, such as long free electron lasers (FELs). Our application of threshold acceptance to magnet sorting showed that it converged to equivalently low values of the cost function, but that it converged significantly faster. We present typical cases showing time to convergence for various error tolerances, magnet numbers, and temperature schedules.
Insertion devices at the ESRF
Authors: Chavanne Joel , Elleaume Pascal
Published: July 2002

Fifteen undulators and wigglers are now installed on the ESRF. They have been designed and measured in-house. The magnetic field has been corrected using iron shims which remove all multipoles and fully corrects the radiation spectrum. The measured spectra confirm the expected low emittance of the beam resulting in an unprecedented high brilliance above 10 keV of photon energy. The observed interaction with the electron beam is negligible.
Performance of the soft x-ray double crystal monochromator on beamline 4.2 at the SRS, Daresbury Laboratory
Authors: Robinson A. W. , D’Addato S. , Dhanak V. R. , Finetti P. , Thornton G.
Published: July 2002

The performance of a new beamline, designated BL4.2, at the SRS, Daresbury Laboratory is described. This beamline covers the energy range 640≥hν≥10 keV, using a double crystal monochromator. The performance of the beamline is illustrated by reference to two S K-edge studies. One is a near edge x-ray absorption fine structure (NEXAFS) study of thiophenecarboxylate (C4H3SCO−2) on Cu(110); the second is a surface extended x-ray absorption fine structure (SEXAFS) study of Ni(110)c(2×2)S. A resolution of ≤1 eV (FWHM) at a photon energy of 2470 eV is indicated by the NEXAFS data, which is sufficient to resolve the two leading resonances associated with the thiophene ring. The SEXAFS data extend to a k range of 13 Å−1, which corresponds to a photon energy range of 650 eV.
Performance of a materials science facility at the Photon Factory: Soft x-ray beamline BL 13C coupled with multipurpose analytical apparatus
Authors: Shimada H. , Matsubayashi N. , Imamura M. , Sato T. , Yoshimura Y. , Hayakawa T. , Takehira K. , Toyoshima A. , Tanaka K. , Nishijima A.
Published: July 2002

The performance data of an undulator soft x-ray beamline based on the cylindrical element monochromator concept are described. Photon fluxes over 1012 photon/s 0.1% b.w. are achieved with the slit width of 100 μm at the harmonic peaks of a 13-period undulator. The maximum resolution obtained at the N K edge (E/ΔE) is ≊5000 with the slit width of 10 μm. The beamline is equipped with a multipurpose analytical instrument having a hemispherical electron analyzer and other detectors. The system is used for both x-ray photoelectron spectroscopy and x-ray absorption fine structure analyses for surface and materials science.
SR instrumentation for optimized anomalous scattering and high resolution structure studies of proteins and nucleic acids (invited)
Authors: Deacon A. , Habash J. , Harrop S. J. , Helliwell J. R. , Hunter W. N. , Leonard G. A. , Peterson M. , Hadener A. , Kalb (Gilboa) A. J. , Allinson N. M. , Castelli C. , Moon K. , McSweeney S. , Gonzalez A. , Thompson A. W. , Ealick S. , Szebenyi D. M. , Walter R.
Published: July 2002

Crystal structure solution by anomalous dispersion methods has been greatly facilitated using the rapidly tunable station 9.5 at the Daresbury SRS. Both SIROAS and MAD techniques, with IP data, have been used in the phasing of a brominated nucleotide and a seleno deaminase, respectively. The electron density maps in each case are interpretable. Throughput of projects could be improved upon with a better duty cycle detector. Another category of data collection is that at very high resolution. Detailed structure refinement pushes the limits of resolution and data quality. Station 9.5 has been used to collect high resolution (1.4 Å) native data for the protein concanavalin A. This utilized very short wavelengths (0.7 Å), the image plate, and crystal freezing. A total of 155 407 measurements from two crystals benefited from the on-line nature of the IP detector device, but a slow and quick pass are required to capture the full dynamic range of the data. There are data seen to 1.2 Å and beyond for a pure Mn substituted form of the protein, but a higher intensity still is required to actually record these data. By comparison, trials at CHESS, on a multipole wiggler (station A1) with a CCD (without image intensifier) system, yield native concanavalin A data to 0.98 Å and beyond. This demonstrates that the combination of yet higher intensity and the ease of use of a CCD offers worthwhile improvements; in this case an increase in the data by a factor of (1.4/0.98)3, thus at least doubling the data to parameter ratio for protein structure model refinement and potentially opening up direct structure determination of proteins of the size of concanavalin A (25 kDa).

Finally, possibilities at ESRF and further detector developments, such as mosaic CCDs and scintillator coatings, offer further impetus for the field. These include more intense rapidly tunable beams for anomalous dispersion-based structure solution and ‘‘ideal’’ higher resolution data collection and reactivity studies. ESRF BL19 is described; facilities on BL19 will include a system for freezing and storing crystals at cryogenic temperatures, so that data can be recorded from the same crystal on different runs. Overall, there have been tremendous strides made in this field in the last 15 years, and yet further improvements are to come.
All-in-one spectrometer—A simple experimental setup for measuring transport characteristics in semiconductors
Authors: Oettinger K. , Meyer B. K.
Published: July 2002

The characterization of semiconductor heterostructures requires different measurement techniques such as photoluminescence, Shubnikov–de Haas, and cyclotron resonance. We present a simple experimental setup which allows to make use of all these techniques without changing the equipment. There is no need for electrical contacts. The performance is demonstrated on InxGa1−xAs/InP quantum wells.
A transputer-based measuring system for decentralized signal processing, applied to two-phase flow
Authors: Schmitt A. , Hoffmann K. , Loth R.
Published: July 2002

An innovative concept for decentralized processing of the signals of multiple sensors is presented. The basic idea is to connect every sensor via an analog-to-digital converter with a high-performance microprocessor, a transputer, that exclusively collects and processes its signal. The transputers are linked to a powerful network. Exemplarily, a measuring system based on this concept was used for the determination of local parameters of liquid–gas two-phase flows (e.g., local void fraction and bubble frequency). Up to six fiber-optical probes were utilized simultaneously to demonstrate the efficiency of the system. The signal processing under that special application may include on-line evaluation of flow parameters and on-line correction of errors of measurement due to sensor-induced effects. The concept of the new system, however, is basically independent of the number and type of sensors, as well as of the method of signal processing. The transputer-based measuring system thus provides a flexible, efficient tool for applications in which great amounts of data have to be evaluated or manipulated quickly.
A passive scheme for ID end correction
Authors: Vasserman I. , Moog E. R.
Published: July 2002

A passive end correction scheme used on a prototype undulator is described. This scheme allows the integrated field requirements to be met at all gaps from 11.5 to 200 mm, with no active correction. The main parameters that need to be adjusted are the strength of the end magnets and the height of the next-to-last poles. The first field integral remains constant over the entire gap range, to within 25 G cm in the vertical direction and 50 G cm in the horizontal direction. The second field integral remains constant to within 10 000 G cm2. Results of magnetic measurements are presented.
High frequency intensity modulation of a CO2 waveguide laser by mode-locking techniques
Authors: Tulip John , Simard Jean-Robert
Published: July 2002

Mode-locking techniques are well known for the generation of short pulses. However, little work has been done to evaluate the use of this technique with long wavelength (10.6 μm) CO2 waveguide lasers. For this region of the spectrum, mode locking has the advantage of requiring smaller modulation voltage than other conventional modulation techniques which makes possible the generation of pulses at a frequency higher than 100 MHz. The efficient generation of pulses at these frequencies makes this type of laser attractive for active imaging at long wavelengths. In this paper, the design of a mode-locked waveguide CO2 laser is reported and its characteristics of operation are compared with an existing model. Significant depth of modulation is observed at 190 MHz with an applied modulation voltage lower than 50 V. From the comparison between the experimental results and the theoretical model, improvements are proposed.
Novel light gas gun with minimal timing jitter
Authors: Laabs Gary W. , Funk David J. , Asay Blaine W.
Published: July 2002

We have designed a gas gun capable of delivering a projectile on target within a time window of 60 μs, and up to velocities of 182 m/s. The gun uses a prepressurized brass projectile held in place with a glass rod in compression. The glass rod is fractured at a precise time using an explosive detonator. Performance calculations were conducted using a simplified model, and the predictions compare favorably with experimental data.
A detector for charged particle counting in the presence of strong electromagnetic noise
Authors: Sekine Shigeyuki , Ichimura Shingo
Published: July 2002

An electron/ion pulse counting system was used for a high-counting-rate application under strong electromagnetic noise. The number of photoelectrons produced by a nonresonant multiphoton ionization of gaseous molecules was counted as a function of gas pressure in vacuum. The system was successfully operated under electromagnetic noise originated from a pulsed laser. The detector acted as a gated, accumulating counter with a capacity of 300 cps. A maximum counting rate of 2×1010 cps was experimentally achieved when laser-produced photoelectrons arrived within a gate of 15 ns.
A simple apparatus for measuring electrical resistance of materials at high temperatures
Authors: Rao G. V. Narasimha , Sastry V. S. , Radhakrishnan T. S. , Seshagiri V.
Published: July 2002

Electrical resistance measurements in a wide temperature range are very important for understanding the physical properties of materials. It is often difficult to carry out the measurements at high temperatures since taking electrical leads reliably from specimens is a nontrivial problem. In this note we describe in detail a simple apparatus which can be used for studying any foil or pellet-shaped sample at temperatures up to 800 °C in vacuum or in an inert atmosphere. The apparatus uses spring loaded pins for electrical contact, obviating the need for silver paint or spot welding, thus avoiding any possible change in the properties of the sample. The springs used for loading are far removed from the high temperature zone; the load, therefore, remains unchanged during the experiment and the contacts remain uniformly reliable.
Control of plasma parameters in sheet-shaped electron cyclotron resonance heating plasma supplemented with radio frequency discharge
Authors: Shibata Kanetoshi , Yugami Noboru , Nishida Yasushi , Miyazaki Tadaomi
Published: July 2002

Production and parameter control techniques of sheet-shaped electron cyclotron resonance heating (ECRH) plasma are described. When rf power (f≂13.56 MHz) is supplemented by the sheet-shaped ECR plasma, the ion temperature, Ti, ion fluxes, nb/n0, and high energy component, εi, of ions deposited to the substrate can be controlled arbitrarily within the range of 0.3 eV≤Ti≤10.0 eV, 0≤nb/n0≤30%, and 0≤εi≤60 eV, respectively, in the neutral Ar gas pressure, 4×10−4≤p≤3×10−3 Torr. Furthermore, the ion energy and/or the ion flux flowing onto the substrate could be well controlled by changing the bias voltage supplied to the substrate holder. We can expect that the present experimental technique could be applied to the material processing in a well-defined manner.
Crossed-beams arrangement for the investigation of charge-changing collisions between multiply charged ions
Authors: Meuser S. , Melchert F. , Krüdener S. , Pfeiffer A. , von Diemar K. , Salzborn E.
Published: July 2002

A crossed-beams experiment designed to study charge-changing collisions between singly charged ions has been modified to extend its applicability to collisions between multiply charged ions in a broader range of collision energies. Computer simulations of the beam transport system and the new electrostatic analyzing units are presented. The ion-optical predictions are tested experimentally. A data acquisition system that allows measurements of angular differential cross sections in ion–ion collisions is described.
Growth of La–Ca–Mn–O films by ozone-assisted molecular beam epitaxy
Authors: Achutharaman V. S. , Kraus P. A. , Vas’ko V. A. , Nordman C. A. , Goldman A. M.
Published: July 2002

We have grown very high quality epitaxial thin films of La–Ca–Mn–O on SrTiO3 and LaAlO3 using ozone-assisted molecular beam epitaxy and the block-by-block deposition technique. Films of thicknesses of at least 600 Å are fully strained and are tetragonal on both SrTiO3 (100) and LaAlO3 (100) substrates, and are single phase with extremely low rocking curve widths (about 0.067°), suggesting a high degree of structural perfection. Magnetoresistance values of 900% at an applied field of 5.5 T have been obtained for as-deposited La0.58Ca0.33MnO3 films.
A compact frequency domain fluorometer with a directly modulated deuterium light source
Authors: Morgan C. G. , Hua Y. , Mitchell A. K , Murray J. G. , Boardman A. D.
Published: July 2002

A phase fluorometer based on a low-cost and versatile high-frequency modulated light source and a fast gain-modulated photomultiplier is described. The apparatus is particularly well-suited to high-sensitivity frequency-domain fluorescence measurements requiring ultraviolet excitation. The system is very compact since it features a directly modulated light source, a miniature photomultiplier tube, and an rf synthesizer on a PC board. Equipped with a suitable fiber optic probe sensor, the device has potential as a portable unit for a wide range of remote sensing applications. The lamp can be modulated at frequencies up to 120 MHz and the phase fluorometer has been tested at up to 70 MHz with a range of fluorescent lifetime standards containing quinine sulfate quenched with sodium chloride.
Transport measurements at low temperatures in a diamond anvil cell with helium as pressure medium
Authors: Thomasson J. , Dumont Y. , Griveau J.-C. , Ayache C.
Published: July 2002

We report the development of a technique to measure transport properties using a new diamond anvil cell and helium as pressure transmitting medium to ensure hydrostatic conditions. The chamber pressure is measured at any working temperature below 300 K by the ruby fluorescence method. This technique has been used to pressures up to 3 GPa at T=5 K to measure the effect of hydrostatic pressure and magnetic field on the superconducting transition temperature of a single crystal of the anisotropic cuprate superconductor Bi2.1Sr1.9−yLayCuO6+δ.
Effect of scanning force microscope scanner geometry on probe-sample contact force
Authors: Chen X. , Davies M. C. , Roberts C. J. , Tendler S. J. B. , Williams P. M.
Published: July 2002

In a scanning force microscopy (SFM, or atomic force microscopy) system, a simultaneous recording of the probe cantilever deflection and the corresponding probe-sample distance yields a so-called force-distance curve. When the SFM probe is away from the sample surface, there is no significant interaction between the probe and the sample and hence the deflection angle is constant. This results in a zero force change in the force-distance curve. However, in SFM probe-scanning geometry as opposed to sample scanning, a nonzero force change in a force-distance curve before probe-sample contact is usually observed. This article discusses the reasons for this phenomenon and its implications for contact mode SFM imaging and complementary measurements. It is found that such a slope is directly related to the minimum probe-sample contact force and the force uniformity that the microscope can achieve during contact imaging. Possible solutions, including a “variable set-point” scheme, are proposed.
He
3
immersion cell for ultralow temperature study of amorphous solids
Authors: Rogge Sven , Natelson Douglas , Osheroff D. D.
Published: July 2002

We have constructed a He3 immersion cell for dielectric measurements of insulating amorphous solids in a nuclear demagnetization cryostat at temperatures between 500 μK and 150 mK. The samples are directly immersed in He3 with two heat exchangers per electrode which are thermally isolated from each other and have a very low capacitance to ground. The cell incorporates a Pt195 pulsed NMR thermometer with a novel superconducting magnet and a He3 viscometer for calibration.
A computer driven crystal spectrometer with charge coupled device detectors for x-ray spectroscopy of laser plasmas
Authors: Koenig Michel , Boudenne Jean Michel , Legriel P. , Benuzzi A. , Grandpierre T. , Batani Dimitri , Bossi Simone , Nicolella Sonia , Benattar René
Published: July 2002

A completely automated crystal spectrometer has been realized. It is computer driven by a Macintosh computer using the LabVIEW graphical interfacing and driving software. The spectrometer uses charge coupled device detectors for online read out of collected x-ray spectra. It may work under vacuum conditions and it has been tested with a Nd laser-plasma x-ray source using Al targets.
Design for a 10 picometer magnetic actuator
Authors: Gauthier-Manuel B. , Garnier L.
Published: July 2002

Scanning probe microscopies need actuators to produce controlled displacements of surfaces in the nanoscale range. Usually piezoelectric ceramics are used for this function. In this article, we describe a magnetic way to produce a similar movement without the use of high voltage. The position is obtained with a precision lower than 10 pm in the range of a hundred micrometers and a bandwidth of 1 kHz. All the parameters of this system can be accurately and easily determined. The knowledge of an analytical form of the transient response of the actuator makes the calibration of the position sensor needless. The direct measurement of the position of the magnet gives entirely reliable results. This actuator could be, for example, applied to atomic force microscopy where a good precision in displacement is required to get force/distance curves or surface images.
Construction of a subpicosecond double-beam laser photolysis system utilizing a femtosecond Ti:sapphire oscillator and three Ti:sapphire amplifiers (a regenerative amplifier and two double passed linear amplifiers), and measurements of the transient absorption spectra by a pump-probe method
Authors: Nakayama Toshihiro , Amijima Yutaka , Ibuki Kazuyasu , Hamanoue Kumao
Published: July 2002

A double-beam Ti:sapphire laser photolysis system has been constructed for measurements of the subpicosecond transient absorption spectra by a pump-probe method. Although the spectroscopic characteristics tested for the practical availability are satisfactory enough, the transient absorption spectrum thus obtained exhibits an artificial time-dependent spectral change owing to the group velocity dispersion of the probing light pulse. Hence, its wavelength-dependent arrival time to the sample cell is determined utilizing the optical Kerr effect induced in carbon tetrachloride and the true transient absorption spectrum (the corrected spectrum) at a given delay-line setting is calculated by a microcomputer using a great number of uncorrected transient absorption spectra obtained at different delay-line settings. Interestingly, the corrected singlet-singlet absorption band (band C with a lifetime of 0.8 ps) obtained for the lowest excited singlet state of 9-nitroanthracene in cyclohexane really shifts with time. This can be interpreted in terms of the wide wavelength-range superposition of band C and an absorption band which increases and then decreases with rise and decay times of 0.8 and 1.8 ps, respectively; the latter band is ascribed to the absorption of 9-nitrite (or its precursor) or that of a higher excited triplet state of 9-nitroanthracene. By 400 nm biphotonic excitation of the neat solvents (cyclohexane and n-heptane), furthermore, population of their higher excited singlet states with a very short lifetime of 0.4 ps can be seen.
Single-input double-tuned circuit for double resonance nuclear magnetic resonance experiments
Authors: Hu Sanlin , Reimer Jeffrey A. , Bell Alexis T.
Published: July 2002

A single-input double-tuned probe was designed for double resonance nuclear magnetic resonance (NMR) experiments, in which high radio frequency power irradiations were achieved at two closely spaced frequencies (such as 26.1 MHz for Al27 and 28.4 MHz for Cu65). The efficiency of the probe for both nuclei was determined to be about 80%, compared to that obtained with a single-tuned probe. The probe was used successfully for Al–6527Cu SEDOR experiments to derive the internuclear distance between Al and Cu in Cu-ZSM-5 zeolite. The circuit is ideal for SEDOR-type double resonance NMR experiments, when high power irradiation is required for nuclei with closely spaced resonance frequencies.
Low-cost monochromatic microsecond flash microbeam apparatus for single-cell photolysis of rhodopsin or other photolabile pigments
Authors: Sullivan Jack M.
Published: July 2002

Delivery of intense, brief flashes of monochromatic light are required in single-cell physiological experiments to photolyze cellular chromophores or pigments. In the xenon flash instrument constructed, flashes are collimated, made monochromatic with selectable bandpass filters and imaged into a small-core fiber. The flash is transmitted over meters to the epiflourescent port of a microscope where additional optics again collimate the beam. The objective lens of the microscope functions to condense flash energy into a microbeam in the specimen (field) plane and to image the cell under parafocal conditions. Spot diameters are 228 and 166 μm (full width half maximum) for 40× and 60× objectives. Flash intensities can be measured with this instrument during experiments using the microscope phase/differential interference contrast condenser to couple the microbeam to a calibrated photodiode. Flash intensities between 108 and 109 photons/μm2 were achieved across the near-ultraviolet/visible spectrum. Flash durations were under 20 μs with a short-arc 7 J flash tube. Shielding and fiber transfer permit delivery of intense flashes without electromagnetic noise to the electrophysiological recording apparatus. Flashes generated with this instrument activated intramolecular charge motions (early receptor currents) in the visual pigment, rhodopsin, expressed from transgenes in single cultured cells.
A plasma window for vacuum–atmosphere interface and focusing lens of sources for nonvacuum ion material modification (invited)
Authors: Hershcovitch Ady
Published: July 2002

Material modifications by ion implantation, dry etching, and microfabrication are widely used technologies, all of which are performed in vacuum, since ion beams at energies used in these applications are completely attenuated by foils or by long differentially pumped sections, which are currently used to interface between vacuum and atmosphere. A novel plasma window, which utilizes a short arc for vacuum–atmosphere interface, has been developed. This window provides for sufficient vacuum atmosphere separation, as well as for ion beam propagation through it, thus facilitating nonvacuum ion material modification.
High current H− ion sources for the large helical device neutral beam injector
Authors: Oka Y. , Tsumori K. , Takeiri Y. , Kaneko O. , Osakabe M. , Asano E. , Kawamoto T. , Akiyama R.
Published: July 2002

Two large helical device–neutral beam injector (LHD–NBI) ion sources were fabricated and tested in the test stand for producing a beam of 180 keV×40 A with H− ions. They are Cesiated multicusp ion sources with a rectangular discharge chamber and a single stage multihole accelerator. These are scaled up from the 16 A H− ion sources in the National Institute for Fusion Science (NIFS). A plasma source with a high aspect ratio was operated stably with an arc power up to ∼300 kW for 10 s, after balancing of the electron emission from the filaments was made. A satisfactorily dense and uniform plasma without mode flip was produced. Electrons accompanied by H− ions were reduced by an extraction grid with the electron trap, instead of straight holes. The electron beam component caused by the stripping of electrons from H− ions was detected with an array of calorimeters at the bottom of the connecting duct. At the first stage of the test, one of the five segment grids of the accelerator was installed. An H− ion current of 5.5 A with a current density of 27.5 mA/cm2 for 0.6 s was obtained with an arc power of 135 kW with Cs introduction. A high arc power efficiency for H− ions was observed. The intense cusp field is considered to be the important factor to improve this. The beam divergence angle at 10.4 m downstream was ∼10 mrad. Since these results satisfied our design, a full segment accelerator was tested in the next stage. Beam conditioning for five segment grids is underway. So far, an H− current of 21.0 A has been obtained at 106 keV for 0.6 s. As a result, we had good prospects for achieving the full specification of LHD–NBI ion sources, especially for achieving higher current and focused beam as well as for long pulse. The neutral beam injection experiment for the LHD is scheduled to start in the middle of 1998.
Selective method of the separation of the isobars of the alkali and rare-earth elements products in nuclear reactions
Authors: Demyanov A. V.
Published: July 2002

A technique for the isolation and spatial separation of the nuclear isobars of alkaline and rare-earth elements, products of nuclear reactions, including short-lived ones, is proposed to investigate their spectrometric properties on-line. For this purpose a surface ionization method is used employing a distinction in the ionization potentials of these elements, in the electronic work function and the temperatures of two ionizers, made of different materials and placed in magnetic and electric fields.
Further development for the TRIUMF H−/D− multicusp source
Authors: Kuo T. , Yuan D. , Jayamanna K. , McDonald M. , Baartman R. , Gelbart W. Z. , Stevenson N. , Schmor P. , Dutto G.
Published: July 2002

We have reported a 15 mA dc H− multicusp source at the sixth International Ion Source Conference in 1995 at Whistler. Since then, the H− beam has been further upgraded to 20 mA for 25 kV dc extraction. The D− beam output of the new cusp source has also been measured at 25 and 12.5 kV energies. An 8 mA D− peak current at 25 kV with 0.5 π mm mrad normalized 4 rms emittance has been obtained. Special attention was given to the effects of gas flow, pumping speed, and neutralization on the 12.5 kV operation which is used for the D− injection into a 15 MeV D− cyclotron. At present, we are making an effort to test the effect of injecting Cs in the vicinity of the plasma aperture. On the other hand, a hybrid of filament plus LaB6 cathode mechanism has been tested for filament lifetime issue. The results from these tests are reported. In particular, the experience in operating this new source for the Triumf/Nordion TR30 cyclotron is summarized.
Radial distribution of space-charge force in compensated positive-ion beams (invited)
Authors: Dölling R. , Pozimski J. , Gross P.
Published: July 2002

The space-charge compensated state of drifting dc beams of He+ ions of 10 keV ion energy and 0.14 and 1.5 mA current was determined with an electron beam probe, a rf resonance probe, the analysis of residual gas ion energies, and emittance measurement. The results are compatible with a basic model describing a two-dimensional multiplicity of possible self-consistent radial density distributions of beam ions, residual gas ions, and compensating electrons. The effects of electron drainage and beam current oscillations on space-charge compensation are pointed out.
Production and control of high current ion beams in plasma-optical systems
Authors: Goncharov A.
Published: July 2002

A brief review of investigations carried out in the Institute of Physics is presented along with an analysis of processes determining production of ions as well as formation and transport of intense ion beams in plasma-optical systems. All these systems have a common mechanism of space charge equipotentialization. When a noncompensated beam’s self-potential exceeds significantly an external potential, a charge compensation is mainly provided by secondary electron emission. Two systems are considered, a magnetically isolated diode gap (MDG) operating in the plasma-optical regime, and a high-current electrostatic plasma lens. It is demonstrated that a MDG can be used for production of hydrogen ions with unique parameters (current 6 A, density of current 6 A/cm2, energy up to 20 keV, pulse duration up to 100 μs). An effective method of intense ion beam low pressure transport is proposed.
A novel sensitive method of surface impedance measurement for small samples
Authors: Chin C. C.
Published: July 2002

We propose a novel sensitive method of surface impedance measurement for small samples utilizing a YIG delay line. We will give a full analysis of the relationship between the phase and amplitude of the signals to surface impedance. The sensitivity of this method will be fully addressed. The dispersion relations of magnetostatic waves guided by lossy ground planes will also be given as byproducts of the above analysis.
Automated gate valve operation for pressure control
Authors: Barshilia Harish C. , Kalmar Balazs , Windsor Norman R. , Kershmann Gordon , O’Brien James J.
Published: July 2002

An automated pressure control system is described. The components consist of a reversible, geared, ac motor, a gate valve, a Granville–Phillips Stabil-ion pressure gauge with set-points and an electronics switching unit. The reversible motor is attached to the adjustment shaft of the gate valve and the system is operated in conjunction with a diffusion pump. The orifice of the gate valve is varied so that the chamber pressure is maintained between two selected set-points fixed on the control unit of the Stabil-ion pressure gauge. The system is used to control the operating pressure in a chemical vapor deposition process. It has been found to work satisfactorily for both gas and liquid phase precursor materials. The simplicity of the system together with its low cost allows for its use in a variety of low-pressure processes.
Development of a portable time-of-flight membrane inlet mass spectrometer for environmental analysis
Authors: White A. J. , Blamire M. G. , Corlett C. A. , Griffiths B. W. , Martin D. M. , Spencer S. B. , Mullock S. J.
Published: July 2002

The benefits of on-site analysis of environmental pollutants are well known, with such techniques increasing sample throughput and reducing the overall cost of pollution level monitoring. This article describes a transportable time-of-flight (TOF) mass spectrometer, based upon a converging, annular TOF (CAT) arrangement. The instrument, the transportable CAT or T-CAT is battery powered and self-contained. The vacuum chamber is never vented and is kept at a very low pressure, even during analysis. Sample gases are admitted to the mass spectrometer via a membrane inlet system. Data collection and analysis are accomplished via a portable PC. The T-CAT is capable of detection limits approaching those of more conventional, nonportable design. The device shows reasonable linearity over wide concentration ranges. Initial results indicate that the T-CAT will be capable of use in a wide range of applications, particularly for environmental monitoring. This article describes the features of the T-CAT, and presents initial results from the membrane inlet/T-CAT system.
An inductive position sensor for the measurement of large displacements at low temperature
Authors: Backes K. A. , Brisson J. G.
Published: July 2002

An inductive position sensor used to measure centimeter displacements with a typical sensitivity of 140 mV/m at 4.2 K is described. The sensor’s outer housing is constructed of brass and stainless steel tubing, with two inset linear bearings that support a surface ground carbon steel drive rod. The sensitivity of the device increases with excitation frequency and with operating temperature. The displacement range for which the sensor output is linear is 1.4 cm. The resolution of the device is better than 12 μm. The sensor is robust in design and in operation, and is insensitive to thermal cycling.
Parametric decay of electron cyclotron waves and its influence on the ion transport in an electron cyclotron resonance ion source
Authors: Meyer D. , Bolshukhin D. , Wiesemann K.
Published: July 2002

When measuring the rf emission spectra of an electron cyclotron resonance plasma by a shielded antenna under different discharge conditions, a parametric decay of electron cyclotron waves was detected. Above a certain threshold of the launched microwave power, the pump wave at ω0/2π=9.733 GHz decays into two different wave modes following the condition ω2=ω0±ω1, where ω1 is in the ion cyclotron resonance frequency range. Thus heating of ions is possible. Light ions are preferably heated. We consider this mechanism a possible candidate for explaining the isotope anomaly detected by A. Drentje et al. [Rev. Sci. Instrum. 67, 3 (1996)], which indicates that the heavier isotope of the same ion species is preferentially enriched in the discharge, whereas the lighter one is more easily transported out of the plasma. Experimental results are discussed with respect to this hypothesis.
A tensile stage to study thin polymer films in an environmental scanning electron microscope
Authors: Thomas V. , Wolfenden A.
Published: July 2002

An economical and easily constructed tensile stage to study thin polymer films in an environmental scanning electron microscope has been developed. Surface features of the film and the morphology in the vicinity of a crack tip while under stress may be studied using this stage. The construction, sample mounting technique, and some of the photomicrographs obtained using this tensile stage have been illustrated and described.
A novel thick-layer electrochemical cell for in situ x-ray diffraction
Authors: Scherb G. , Kazimirov A. , Zegenhagen J.
Published: July 2002

In this article we describe an electrochemical cell allowing x-ray diffraction from the working electrode in situ. The key feature of our novel design is a hemispherical fused silica dome serving as the x-ray window. The electrode is covered with a thick layer of electrolyte during the x-ray measurement, avoiding mass transport limitations inherent to common setups, where the thickness of the electrolyte layer is strongly reduced for the diffraction experiment. This allows in particular the monitoring of electrode processes which are associated with the consumption of species from solution and/or generation of a significant amount of reaction products. All solid angles in the hemisphere above the sample surface are accessible for the incoming and outgoing x-ray beam at a constant path length in the electrolyte. Thus, our cell is perfectly suitable for in situ surface x-ray diffraction, truncation rod scattering, and specular reflectivity measurements. We demonstrate the performance of the new cell by monitoring the electrochemical stripping of a 50 nm thick amorphous As layer on GaAs(001) in 0.5 M H2SO4 in situ with x rays.
Experimental methods in radioactive ion beam target/ion source development and characterization (abstract)
Authors: Welton R. F. , Alton G. D. , Cui B. , Murray S. N.
Published: July 2002

We have developed off-line experimental techniques and apparatuses that permit direct measurement of effusive-flow delay-times and ionization efficiencies for nearly any chemically reactive element in high-temperature target/ion sources (TISs) commonly used for on-line radioactive ion beam (RIB) generation. The apparatuses include a hot Ta valve for effusive-flow delay-time measurements, a cooled molecular-injection system for determination of ionization efficiencies and a gas-flow measurement/control system for introducing very low, well-defined molecular flows into the TIS. Measurements are performed on a test stand using molecular feed compounds containing stable complements of the radioactive nuclei of interest delivered to the TIS at flow rates commensurate with on-line RIB generation. In this article, the general techniques are described and effusive-flow delay-times and ionization efficiency measurements are reported for fluorine in an electron-beam-plasma target/ion source (EBPTIS) developed for RIB generation and operated in both positive and negative ion extraction modes.
Ion charge state distributions of pulsed vacuum arc plasmas in strong magnetic fields
Authors: Anders André , Yushkov George , Oks Efim , Nikolaev Alexey , Brown Ian
Published: July 2002

Vacuum arc plasmas with discharge currents of 300 A and duration 250 μs have been produced in strong magnetic fields up to 4 T. Ion charge state distributions have been measured for C, Al, Ag, Ta, Pt, Ho, and Er with a time-of-flight charge-mass spectrometer. Our previous measurements have been confirmed which show that ion charge states can be considerably enhanced when increasing the magnetic field up to about 1 T. The new measurements address the question of whether or not the additional increase continues at even higher magnetic field strength. It has been found that the increase becomes insignificant for field strengths greater than 1 T. Ion charge state distributions are almost constant for magnetic field strengths between 2 and 4 T. The results are explained by comparing the free expansion length with the freezing length. The most significant changes of charge state distributions are observed when these lengths are similar.
A microbeam Cs ion source for accelerator mass spectrometry
Authors: Sie S. H. , Niklaus T. R. , Suter G. F. , Bruhn F.
Published: July 2002

A negative ion sputter source incorporating a microbeam Cs+ source intended for application in accelerator mass spectrometry (AMS) has been developed from a General Ionex HICONEX 834™ source. (HICONEX is a trade mark of High Voltage Engineering Europa.) The source is part of a microbeam AMS system, designed for in situ microanalysis of geological samples known as AUSTRALIS (AMS for UltraSensitive TRAce eLement and Isotopic Studies) recently developed at the Heavy Ion Analytical Facility laboratory. With requirements of precise beam positioning on mineralogical samples, a high magnification sample viewing system is a vital part of the source, enabling live observation of the sputtering process and visual tuning of the primary beam. Microbeam of Cs+ of 30 μm in diameter can be produced routinely with adequate intensity for a number of applications. The “screen” electrode in the secondary ion extraction system facilitates steering of the primary beam affected by the extraction field, back into the geometric center of the sample. The injector system includes high resolution electric and magnetic analyzers, improving the background suppression before injection into the accelerator.
Ion decelerator for creation of dense low-energy ion beams (abstract)
Authors: Gontcharov L. A. , Qbukhov V. A.
Published: July 2002

In recent years new processes of ion-plasma technology of thin-film coating in which rather dense mono-kinetic ion flows on processable substrates are used have been developed. In the processing of optical film coating, e.g., ion beams of argon, oxygen, and other heavy gases with a cross section of up to 100 mm in diameter, with a current density of up to 2 mA/cm2 and energy 50–70 eV are required. Such beams are difficult for receiving in “classical” ion sources because of restriction on ion space charge. The new approach to resolve this problem consists of the application of decelerating the ions. In this method a broad ion beam is formed in an ion source of known type with the ion energy 500–1000 eV, and then the ions are decelerated in a specially developed ion decelerator. Devices on breaking of ion—ion decelerators based on the discharge with closed electron drift in crossed EXE fields were proposed and technological decelerators of ions, intended for processing of substrates with a diameter of up to 100 mm, were developed. The properties of the system consisting of an ion source and an ion decelerator, were investigated. It was shown that the researched system effectively produces ion beams with above-mentioned parameters. But in case of submission of breaking potential on DE, positive in relation to the output electrode of a source, potential of a beam also grows. The increase of the beam potential causes the reduction of the axial component of the ions’ velocity and preservation of their transversal velocity component constant. The divergency of a beam thus increases, and the ion current density on DE falls. Essential influence of a decelerating degree is shown at deep (more than 50%) decelerating of ions on the ion current density distribution and on the plasma potential of the beam body. Probe measurements of the local plasma properties and ion beam parameters in the space of ion beam transportation were done and show that the change of the beam potential is observed in wide area of the beam, and only 30%–40% of the potential drop is concentrated in a short layer near DE. The analysis of balances of currents of ions and electrons in the investigated system are brought forward for cases, when no special means were used for the ion beam space charge compensation and when on the source output there a neutralizer in kind of a heated filament was applied.
A compact, intense, monochromatic, atmospheric pressure, extreme ultraviolet light source
Authors: Scime Earl E. , Balkey Matthew M.
Published: July 2002

An intense, monochromatic, extreme ultraviolet (121.6 nm) light source has been constructed for testing extreme ultraviolet light rejecting filters. The source and detection system operates at atmospheric pressure, is physically compact, and is relatively inexpensive to build. A calibrated neutral density filter with a transmission of 1×10−6 is used as a reference. The light source has been used to measure transmissions as small as 9×10−6 quickly (in less than 1 min) with negligible background levels.
New sample preparation for quantitative laser desorption mass spectrometry and optical spectroscopy
Authors: Haefliger Olivier P. , Zenobi Renato
Published: July 2002

Several analytical mass spectrometric and optical spectroscopic methods require a step during which a nonvolatile substance is desorbed by a laser pulse. It is, however, very difficult to use these methods for quantitative measurements because an accurate control over the amount desorbed by the laser pulse is generally not possible, especially when mixtures of several substances are used. We report a new fast and convenient sample preparation procedure that solves these problems. A solution of the analytes is mixed with a solution of poly(vinyl chloride) to obtain a homogeneous and vacuum-stable thin polymer membrane after the solvent has evaporated. Laser ablation is then performed directly from this membrane, allowing an accurate control of the amount of ablated analytes and excellent reproducibility. Quantitative laser desorption mass spectrometry over three orders of magnitude as well as optical spectroscopic measurements using this sample preparation method are demonstrated for polycyclic aromatic hydrocarbons.
A new design for study on reactivity of clusters
Authors: Gao Zhen , Liu Peng
Published: July 2002

This article reports on a new apparatus, called the laser double ablation reactor, for studies on the reactivity of clusters. Structure and operative principle of the apparatus were presented. With this apparatus reactions between manganese/carbon clusters and sulfur clusters, and between silver and sulfur clusters were studied. The experiments indicate that manganese/carbon clusters appear inert when they react with sulfur clusters, while for reactions between silver and sulfur clusters, the products [AgS4]+, [AgS8]+, [AgS12]+, and [AgS16]+, mainly are obtained. In comparison to the results obtained by Fourier transform ion cyclotron resonance, it shows that the new apparatus is very efficient for study on reactions between clusters.