bluuebunny/crossref_metadata_2025 huggingface dataset:
High performance charge-coupled-device imager technology for plasma diagnostics
Authors: Reich R. K. , McGonagle W. M. , Gregory J. A. , Mountain R. W. , Kosicki B. B. , Savoye E. D.
Published: July 2002

High-sensitivity, low-noise, and high-frame-rate charge-coupled-devices (CCD) and camera system electronics have been developed for imaging applications in the visible and near infrared spectra. Back-illuminated CCD imagers are used in the camera system for sensitive signal detection. A fabrication technology, using a refractory process, has been developed for CCD back-illumination that has quantum efficiencies as high as 90% from 500 to 700 nm and 50% from 200 to 400 nm. The CCD imagers use multiple output ports, with single-port pixel rates up to 5 MHz, for low-noise operation at high frame rates. An electronic shutter has been integrated into the pixel structure that has switching times of approximately 50 ns and an extinction ratio value of 104 (signal detected shutter opened to shutter closed) at wavelengths below 540 nm. A flexible electronic board set, providing various operating modes, has been designed to run the CCD at high frame rates while maintaining the detection sensitivity of the imager.
Laser induced fluorescence diagnostic for measuring small magnetic fields
Authors: Noonan W. A. , Jones T. G. , Ottinger P. F.
Published: July 2002

A novel, spatially and temporally resolved diagnostic is being developed to measure small B fields by detecting Zeeman shifts much smaller than the transition linewidth. This diagnostic technique will be used to measure magnetic fields associated with intense ion beam propagation through a low-pressure gas, as envisioned for particle beam fusion. High sensitivity is achieved by a variation on the Babcock technique using laser-induced fluorescence (LIF) spectroscopy. The LIF from a J=1→0 transition in a probe species is viewed parallel to B. In this direction, ΔM=0 fluorescence is not observed, while ΔM=±1 fluorescence is right- and left-circularly polarized and can be measured separately using polarization filters. If a narrow-band pump laser is tuned to a half-maximum point of the unsplit transition line, the presence of the magnetic field shifts one of the ΔM=±1 absorption transitions into resonance with the laser and shifts the other transition further out of resonance. For small field strengths, the difference in the fluorescence signals is proportional to the Zeeman split.
Radial profiles of 2p-1s heliumlike oxygen lines measured from the compact helical system using a vacuum crystal spectrometer
Authors: Muto Sadatsugu , Morita Shigeru , Kondo Katsumi
Published: July 2002

The vacuum crystal spectrometer (Johann type; RAP crystal) has been designed and developed to measure soft x-ray lines in the vicinity of 20 Å. A photodiode array and a two-stage multichannel plate were used as a detector. Radial profiles of heliumlike oxygen lines were successfully obtained from NBI plasmas in the compact helical system with a spectral resolution of 525 (=λ/Δλ). The radial profile in the intensity ratio of Y(3P1→1S0) to W(1P1→1S0) was also obtained. The intensity ratio among 2l-1l transitions of the heliumlike oxygen are calculated as a function of the electron temperature and the electron temperature profile was obtained from the ratio. The obtained electron temperature was compared with one from a Thomsom scattering measurement. As a result, the comparison showed a good agreement.
Nuclear magnetic resonance probe for supercritical water and aqueous solutions
Authors: Hoffmann Markus M. , Conradi Mark S.
Published: July 2002

A nuclear magnetic resonance (NMR) probe for high pressure, high temperature studies is presented. While applicable to many physical systems, the device is optimized for the study of the physics and chemistry of supercritical water and its solutions. The design is modular and is particularly simple, using readily available parts and materials. A new approach is presented for elimination of the magnetic field from the heater currents. The probe has been used to 600 °C and 400 bar. The rf performance is quite good; the NMR linewidth is about 0.1 ppm full width at half-height at any pressure and temperature.
Waveform transformation using shaped superconducting films
Authors: Badri Narayana T. , Satyam M.
Published: July 2002

This article describes a procedure to arrive at a current controlled resistor, based on superconducting films for converting a sinusoidal current waveform of a certain magnitude into a triangular voltage waveform. As an example, it describes a resistor for converting a current of 180 μA into a triangular voltage of 22 mV. It is also shown that this resistor can be used to obtain voltage waveforms which are very close to triangular waveforms for input currents in the range 18 to 180 μA up to a frequency of 1.0 MHz. Corresponding peak output voltages of the triangular waveform are 1.4 to 22 mV, respectively.
A Rutherford scattering diagnostic for intense pulsed proton beams transported in low-pressure gases
Authors: Young F. C. , Hinshelwood D. D. , Stephanakis S. J.
Published: July 2002

Rutherford scattering of pulsed 1 MeV proton beams is developed as a time-resolved fluence diagnostic for proton transport experiments. The incident beam is scattered from a thin aluminum target and recorded with a silicon PIN detector. For a pinched-beam diode, fluences of protons transported in 1 Torr air are consistent with fluences determined with calorimeters, provided the proton energy is smaller than expected from the measured ion current and voltage. Beam bunching is observed as the flight path increases, consistent with reduced proton energy at the head of the beam.
A fast charge coupled device detector for charge exchange recombination spectroscopy on the DIII-D Tokamak (abstract)
Authors: Thomas D. M. , Burrell K. H. , Groebner R. J. , Gohil P. , Kaplan D. , Makariou C. , Seraydarian R. P.
Published: July 2002

Charge exchange recombination (CER) spectroscopy has become a standard diagnostic for Tokamaks. CER measurements have been used to determine spatially and temporally resolved ion temperature, toroidal and poloidal ion rotation speed, impurity density, and radial electric field. Knowledge of the spatial profile and temporal evolution of the electric field shear in the plasma edge is crucial to understanding the physics of the L to H transition. High speed CER measurements are also valuable for edge localized mode studies. Since the 0.52 ms minimum time resolution of our present system is barely adequate to study the time evolution of these phenomena, we have developed a new charge coupled device (CCD) detector system with about a factor of 2 better time resolution. In addition, our existing system detects sufficient photons to utilize the shortest time resolution only under exceptional conditions. The new CCD detector has a quantum efficiency of about 0.65, which is a factor of 7 better than our previous image intensifier-silicon photodiode detector systems. We have also equipped the new system with spectrometers of lower f/number. This combination should allow more routine operation at the minimum integration time, as well as improving data quality for measurements in the divertor-relevant region outside of the separatrix. Construction details, benchmark data, and initial Tokamak measurements for the new system will be presented.
High-resolution tomographic imaging of vacuum magnetic surfaces in the H-1 heliac
Authors: Blackwell B. D. , Tumlos R. B. , Howard J.
Published: July 2002

A new, high-precision rotating wire grid apparatus for vacuum magnetic surface mapping of current-free toroidal plasma confinement geometries is described. This full-scaled version of the prototype apparatus1 developed on the SHEILA heliac has been tested and permanently installed on the H-1 heliac. Data of high quality are obtained with low electron energy (<20 eV) to avoid drift errors, with submillimeter resolution and accuracy, within a 700 mm circular field of view. The apparatus avoids pixcell resolution limits and optical distortion, and is shown to be highly suited to precise comparison of computed and experimental magnetic surfaces, and after tomographic inversion, can produce useful images of the magnetic surfaces.
Equilibrium reconstructions of reversed-shear discharges based on motional Stark effect measurements
Authors: Batha S. H. , Levinton F. M. , Wieland R. M. , Hirshman S. P.
Published: July 2002

Internal magnetic field measurements are now routinely made in tokamak discharges with a motional Stark effect polarimeter. Using these measurements, free-boundary equilibrium reconstructions of the temporal evolution of tokamak discharges can be made. The variational moments equilibrium code (VMEC) has been upgraded with an improved plasma boundary positioning algorithm and an improved spline representation of the pressure and q profiles. The uncertainty of the reconstruction is assessed for discharges with reversed magnetic shear where q(0)≫qmin>1.
High precision mechanical approach mechanism for a low temperature scanning tunneling microscope
Authors: Rust H.-P. , Buisset J. , Schweizer E. K. , Cramer L.
Published: July 2002

A novel mechanical micropositioner has been developed for producing exact linear displacements in the nm range. Incorporated in a low temperature scanning tunneling microscope (STM), it is used as a coarse approach mechanism for the tunneling tip. The advantage of the design is the high accuracy of the linear motion and the absence of backlash. The design principle is discussed and its positioning accuracy and stability for STM imaging are demonstrated.
Neutron activation measurements over an extremely wide dynamic range (invited) (abstract)
Authors: Barnes Cris W.
Published: July 2002

The DT program at the Tokamak Fusion Test Reactor (TFTR) created requirements on 14 MeV neutron measurements to measure from ∼106 n/cm2 (for triton burnup and Ohmic tritium plasmas) to >1012 n/cm2 (characteristic of >10 MW DT plasmas) with an accuracy of 7% (one-sigma).1 To maintain an absolute calibration over this dynamic range with active neutron detectors required one to go from some absolute standard at one fluence level to a measurement at a much higher fluence. Maintaining accuracy requires an extremely linear set of measurements not systematically affected over this dynamic range. Neutron activation can provide such linearity when care is taken with a number of effects such as gamma-ray detection efficiency and sample contamination.2 Absolutely calibrated neutron yield measurements using dosimetric (well-known cross section) reactions with thin (low-mass) elemental foils will be described. This technique makes the detector comparison to an absolute standard of gamma-ray activity correspond to all neutron fluences by reducing the sample mass while keeping the activation detectors operating in a linear counting mode; that is, one always uses low count rates to minimize pileup effects. The International Thermonuclear Experimental Reactor is projected to have 1000 s burn durations at fluxes of few 1013 n/cm2 s, or more neutron fluence per second than entire TFTR discharges. Extrapolating neutron activation to these higher fluences will require yet more care. Some of the issues at such high fluences will be discussed.3 The National Ignition Facility (NIF) is projected to yield 10 MJ of fusion energy, or up to 1012 n/cm2 at the vacuum vessel wall, similar to TFTR DT conditions. However, it is expected that much interesting physics will be performed at yields far less than those from ignition, possibly covering an even greater dynamic range than needed on TFTR. Thin foil techniques do not have the sensitivity required at low fluences. Absolutely calibrated neutron yield measurements using associated particle calibrations of thick (large mass) foils on accelerators4 will be compared. Using both thin and thick foil approaches can cover the dynamic range required for NIF.
Diagnostics for studies of absorption and energy transfer process features in low-density porous targets irradiated with powerful laser pulses
Authors: Burdonsky I. N. , Bugrov A. E. , Gavrilov V. V. , Goltsov A. Yu. , Kovalsky N. G. , Pergament M. I. , Zhuzhukalo E. V.
Published: July 2002

A diagnostic methodology for studies of powerful laser pulse interaction with a porous material of low average density in conditions of interest for advanced inertial confinement fusion targets is discussed. These diagnostics were used in experiments with a powerful 1 μm Nd:laser beam incident upon “agar-agar” targets (C14H18O7)n of different average density from 1×10−3 to 5×10−3 g/cm3 and thickness from 100 to 1000 μm with and without thin aluminium layers (0.5–6 μm) on the front and rear surfaces. Intensity at the focal spot area 100 μm in diameter ranged from 1013 to 1014 W/cm2. It is shown that it is possible to estimate the longitudinal and transverse dimensions of the laser–plasma interaction region and to obtain the plasma dynamics data by recording: the visible and IR radiation at the rear side of illuminated targets with streak camera; x-ray images with filtered pin holes; and multiframe shlieren- and shadowgraphy snapshots (0.3 ns laser pulses at 0.53 μm wavelength have been used).
Radio frequency-driven energetic tritium ion tail measurements in the Tokamak Fusion Test Reactor using the pellet charge exchange diagnostic
Authors: Duong H. H. , Fisher R. K. , McChesney J. M. , Parks P. B. , Medley S. S. , Mansfield D. K. , Roquemore A. L. , Petrov M. P.
Published: July 2002

Charge exchange interactions of ions with the ablation cloud of an injected low-Z impurity pellet can be used to measure the energy spectrum and radial profile of confined fast ions in a fusion plasma. On the Tokamak Fusion Test Reactor we use this technique to directly measure energetic alphas from D–T reactions, tritons from D–D reactions, and radio frequency (rf)-driven minority tail ions (e.g., H, He3, T). We describe the status of the pellet charge exchange (PCX) diagnostic including a brief description of the measurement technique and discussion of operational experience. PCX measurements of the energy spectrum, radial density distribution, and heating deposition profile of rf-driven tritium ions during 2ΩT heating of L-mode plasmas are presented.
Long-pulse operation of a cesium-seeded high-current large negative ion source
Authors: Takeiri Y. , Osakabe M. , Oka Y. , Tsumori K. , Kaneko O. , Takanashi T. , Asano E. , Kawamoto T. , Akiyama R. , Kuroda T.
Published: July 2002

A high-power large negative ion source has been operated for a long pulse duration. A three-grid single-stage accelerator is used, where the extraction grid is shaped so that the secondary electrons generated on the extraction grid would be prevented from leaking into the acceleration gap. A stable long-pulse arc discharge with an arc power of 100 kW has been obtained over 15 s by balancing an individual arc current flowing through each filament. The cesium-seeded operation is not influenced by a temperature rise over 100 °C of the plasma grid during the long-pulse arc discharge. As a result, 330 kW (91 keV–3.6 A) of the negative ion beam was produced stably for 10 s from an area of 25 cm×26 cm, where the current density was 21 mA/cm2 and the negative ion power density was 1.9 kW/cm2. The neutralization efficiency of accelerated negative ions has been measured including the residual positive and negative ion ratios by the water calorimetry of the beam dumps. The result agrees well with the calculation result.
New method to analyze fast metastable atomic beams
Authors: Hecht T. , Winter H. , McCullough R. W.
Published: July 2002

By making use of effects of the image charge on projectile trajectories in scattering of a fast beam of metastable He-atoms with keV energies from an Al (111) surface under a glancing angle of incidence, we have developed a new method to analyze fast atomic beams with respect to relative populations of excited metastable states. Based on our experimental studies we propose the construction of a corresponding detector.
Kerr hysteresis loop tracer with alternate driving magnetic field up to 10 kHz
Authors: Callegaro Luca , Fiorini Carlo , Triggiani Giacomo , Puppin Ezio
Published: July 2002

A magneto-optical Kerr loop tracer for hysteresis loop measurements in thin films with field excitation frequency f0 from 10 mHz to 10 kHz is described. A very high sensitivity is obtained by using an ultrabright light-emitting diode as a low-noise light source and a novel acquisition process. The field is generated with a coil driven by an audio amplifier connected to a free-running oscillator. The conditioned detector output constitutes the magnetization signal (M); the magnetic field (H) is measured with a fast Hall probe. The acquisition electronics are based on a set of sample-and-hold amplifiers which allow the simultaneous sampling of M, H, and dH/dt. Acquisition is driven by a personal computer equipped with a multifunction I/O board. Test results on a 120 nm Fe film on Si substrate are shown. The coercive field of the film increases with frequency and nearly doubles at 10 kHz with respect to dc.
Pulsed laser induced mode-mismatched crossed-beam thermal lens measurements
Authors: Li Bin-cheng , Zhang Shu-yi , Fang Jian-wen , Shui Xiu-ji
Published: July 2002

In this article, an accurate Fresnel diffraction model for a pulsed laser induced thermal lens effect in mode-mismatched crossed-beam configuration is presented. The effect of a lateral offset between the two beams is included in the model. This model is used to calculate the diffraction field of the probe beam at the detection plane from the very near- to the far-field, therefore the evolution of the intensity profile of the probe beam from the near- to the far-field is clearly illustrated. Numerical calculations predict and experimental results demonstrate that the thermal lens (TL) signal maximum is obtained when the probe beam propagates about a characteristic distance away from the sample position, while the characteristic distance is determined by the radius of the excitation beam in the sample and the wavelength of the probe beam. At large size mismatch of two beams and near-field detection cases, the TL signal is approximately independent on the sample location relative to the waist of the probe beam. The theoretical and experimental results are of great importance to configuration optimization of an extremely sensitive and compact TL instrument, which is the trend in the development of analytical instruments.
Cryostat for in situ scanning tunneling microscopy studies of film growth at low temperatures
Authors: Ekinci K. L. , Valles J. M.
Published: July 2002

This article describes a low temperature scanning tunneling microscope (STM) system which is designed to study film growth at very low substrate temperatures (4 K<TS<77 K). A simple tripod design with the addition of a sample manipulator, is implemented as the STM head. In this system, a metal film can be thermally deposited on a conducting or an insulating substrate held at cryogenic temperatures and be probed in situ by STM. In situ and room temperature images of a Pb film grown on a 4 K substrate are presented.
Wide-dynamic-range digital correlator using field programmable gate arrays
Authors: Kinoshita Junji , Matsumoto Midori , Aoki Tadashi
Published: July 2002

A new digital correlator was developed. The one-bit-clipped digital correlator used so far is simple and sensitive enough to detect one photon. The clipping circuits, however, tend to distort the temporal characteristics. In order to alleviate the distortion, we extended the clipping points of counters and multipliers to two bits and three bits, respectively. The novel correlator has the dynamic range ten times wider than that of one-bit-clipped correlator. Here we report the 130 channel correlator that uses seven chips of field programmable gate array.
Diagnosis of relativistic electron beams using a free electron laser amplifier
Authors: Ciocci F. , Dattoli G.
Published: July 2002

The potential use of a free electron laser (FEL) amplifier as a diagnostic tool for relativistic electron beams is investigated. It is in fact shown that a simple relation exists between electron bunch length, energy spread, and the gain of a FEL resonant amplification. It is also discussed how the beam qualities can be derived from an actual experimental configuration. Finally, the possibility of combining the present methods to other techniques, like nondestructive diagnosis with short undulators, is also analyzed.
Analytical and numerical computation of multipole components of magnetic deflectors
Authors: Lenc Michal , Lencová Bohumila
Published: July 2002

This article presents an analytical expression of the first, the third, and the fifth harmonic component for axial field of magnetic deflectors made of straight or tapered saddle coils or straight toroidal coils in air. In particular, the expressions for the tapered saddle coils and also for the fifth components for straight saddle and toroidal coils have not been derived so far. The existence of the analytical expressions for the simple but important problems of magnetic deflectors in free space is quite advantageous for the check of the correct mesh layout for the more general problems. The axial field functions are compared with those computed with the first order finite element method for the same geometry, with very good agreement of the results.
An ultrahigh vacuum surface analysis instrument incorporating a Fourier transform mass spectrometer and a Fourier transform infrared spectrometer
Authors: Abdelrehim Ihab M. , Thornburg Nick A. , Land Donald P.
Published: July 2002

An ultrahigh vacuum chamber equipped with Fourier transform reflection absorption infrared spectroscopy, Fourier transform mass spectrometry, laser-induced thermal desorption, Auger electron spectroscopy, and low energy electron diffraction is described. The marriage of the various techniques has led to novel designs for sample manipulation and incorporation of the instrumentation. A new ion deflection technique is also described. Some results from studies of hydrocarbon reactions on Pd(111) surfaces, such as desorption kinetics for propene and the kinetics and mechanisms of acetylene cyclization to benzene and thiophene, are discussed, as are analyses of oxidized Ti foils exposed to the ambient environment. The performance of this instrument is thus evaluated.
Optimized compact secondary electron collector with 100% collection efficiency for focused ion beam systems
Authors: Wang Li , Keckley Dave , Bui Dan
Published: July 2002

This article describes the optimization procedure to design a compact scintillator which has a maximum secondary electron collection efficiency without the need of a bias voltage for a focused ion beam (FIB) system. The optimized scintillator design was proven to be very effective for focused ion beam systems. By doing design optimization theoretically and experimentally, a 100% collection was realized for a simple, compact and robust scintillator structure without the bias voltage. So far our experimental study is within the scope of FIB imaging, but we have reasons to believe that the optimized designs or the optimization methodology discussed in this article should be useful in other charged particle applications such as scanning electron microscopy or wherever a scintillator is used to collect secondary electrons.
Fast mixing device for time-resolved synchrotron x-ray scattering studies of radiation sensitive proteins
Authors: Dı́az José Fernando , Strobbe Rik , Engelborghs Yves , Chacón Pablo , Andreu José Manuel , Diakun Greg
Published: July 2002

A fast mixing device apparatus has been constructed to study the kinetic structural reactions of radiation sensitive proteins by time-resolved small angle x-ray scattering. The sample cell has a volume of 0.75 ml and is translated through the synchrotron x-ray beam as the experiment progresses. The dead time of the device is 50 ms, and it is able to mix viscous liquids with ratios ranging from 1:1 to 1:250 with a measured precision of 0.1 μl. The device uses two motor driven syringes that are individually controlled. The whole instrument is thermostated and is remotely controlled. Cleaning of the cell is carried out remotely, removing the need to enter the x-ray hutch between each measurement. Commissioning of the apparatus was carried out by following the assembly of the radiation sensitive protein tubulin into microtubules induced by two different chemical jumps.
A modified shear cell for mass transport measurements in melts
Authors: Griesche A. , Kraatz K. H. , Frohberg G.
Published: July 2002

A graphite shear cell had been developed to measure diffusion coefficients in metal or semiconductor melts. The usable temperature range reaches from the melting point of the material to limits like chemical reaction temperatures with the graphite crucible, respectively, to the vaporization temperature of the liquid. As opposed to existing cells the improvement is in the simple initial shear to start diffusion and the “comb-shearing” process to terminate the diffusion experiment. These mechanisms minimize convection in the melt initialized by the shear movement itself. The reliability of the cell had been verified in diffusion experiments in the system In–Sn, for which microgravity data (without an additional contribution due to gravity-driven natural convection) are present. In addition the mass transport of the pure shearing process had been measured. It was found to be negligible for typical diffusion experiments with t>10 000 s.
The effect of high magnetic fields on junction field effect transistor device performance
Authors: Bodart J. R. , Garcia B. M. , Phelps L. , Sullivan N. S. , Moulton W. G. , Kuhns P.
Published: July 2002

We report measurements of the characteristics of a junction field effect transistor (JFET) in applied magnetic fields up to 30 T. For orientations parallel to the applied field, the device maintained a high transconductance (gfs) close to 80% of the zero field value. For field orientations perpendicular to the plane of current transport, gfs decreased by a factor of 6 at 30 T. This field dependence can be understood quantitatively in terms of the magnetoresistance associated with the cyclotron motion of current carriers within the conductive channels of the JFET. The results show that for suitable orientations the JFET may be used “in situ” for applications in very high fields.
Two methods for a first order hardware gradiometer using two high temperature superconducting quantum interference devices
Authors: Espy M. A. , Kraus R. H. , Flynn E. R. , Matlashov A.
Published: July 2002

Two different systems for noise cancellation (first order gradiometers) have been developed using two similar high temperature superconducting quantum interference devices (SQUIDs). “Analog” gradiometry is accomplished in hardware by either (1) subtracting the signals from the sensor and background SQUIDs at a summing amplifier (parallel technique) or (2) converting the inverted background SQUID signal to a magnetic field at the sensor SQUID (series technique). Balance levels (ability to reject a uniform background magnetic field) achieved are 2×103 and 1×103 at 20 Hz for the parallel and series methods, respectively. The balance level as a function of frequency is also presented. The effects which time delays (phase differences) in the two sets of SQUID electronics have on these balance levels are presented and discussed. It is shown that these delays, along with geometrical considerations, are the limiting factor for balance level for any electronic gradiometer system using two (or more) SQUIDs, a very different situation from the case with wire-wound gradiometers. Results using a dipole field to study the performance of both the parallel and series devices functioning as gradiometers in an unshielded laboratory are presented and compared with theory.
Companding through shaped superconductors
Authors: Badri Narayana T. , Satyam M.
Published: July 2002

Companding has been performed through the use of a shaped superconductor and a design procedure for arriving at the required profile of the superconductor to obtain the required law of companding as described.
Constraints due to the production of radioactive ion beams in the SPIRAL project
Authors: Leroy R. , Huguet Y. , Jardin P. , Marry C. , Pacquet J. Y. , Villari A. C. C.
Published: July 2002

The radioactive ion beams that will be delivered by the SPIRAL facility will be produced by the interaction of a stable high energy (95 MeV/A) and high intensity (2×1013 particle/s) primary ion beam delivered by the GANIL cyclotrons with a carbon target heated to 2000 °C. During this interaction, some radioactive atoms will be created and will diffuse out of the target before entering into an electron cyclotron resonance (ECR) ion source where they will be ionized and extracted. The production of radioactive ion beams with this method implies high radiation fields that activate and can damage materials located in the neighborhood of the target. Therefore, the production system which is composed of the permanent magnet ECR ion source coupled to a graphite target will be changed after two weeks of irradiation. As this ensemble will be very radioactive, this operation has to be supervised by remote control. The radiation levels around the target–ion source system and a detailed description of the different precautions that have been taken for safety and for prevention of contamination and irradiation are presented.
Development of compact microwave ion source for low-energy application
Authors: Gotoh Y. , Fujimori Y. , Kubo H. , Tsuji H. , Ishikawa J.
Published: July 2002

A compact microwave ion source for the research of low-energy ion beam application such as ion beam assisted deposition or ion beam sputtering has been developed. The developed ion source is based on the previously reported compact microwave ion source, which was developed for higher-energy extraction. In order to extract the ions with a lower energy, it is necessary to lower the plasma density. The present ion source possesses a plasma expansion cup in order to make the plasma thinner. As a consequence of the thinner plasma, the extractable current becomes lower than that of the thicker plasma, thus the source has multiple extraction apertures. Current–voltage characteristics of the ion source were measured with an extraction system with 37 apertures and the extraction gap of 1.5 mm. At the voltage of 500 V, the current of the extraction electrode decreased rapidly and it was shown that at this voltage, an optimum ion optics was achieved. The argon ion current of 0.4 mA with the energy of 500 eV was extracted. The gas pressure in the processing chamber could be reduced to 5×10−4 Pa.
Report on the Thirteenth International Electron Cyclotron Resonance Ion Source Workshop (invited)
Authors: May D. P.
Published: July 2002

The 13th International Electron Cyclotron Resonance Ion Source Workshop was hosted by the Cyclotron Institute of Texas A&M University in College Station, Texas from the 26th to the 28th of February 1997. The workshop was devoted to ECRIS design, construction, operation, and applications. Workshop topics covered the methods used in ECRIS technology, ECRIS behavior and physics, and atomic physics applications for ECR ion sources. Some high points were the report on the PIAFE Project where an ECRIS is used to decelerate, catch, and further ionize a low-charge-state radioactive ion beam, the report on the two-frequency ECRIS of Berkeley producing beams of ions such as Au60+197, the report on ECRIS behavior incorporating realistic modeling of the absorption of the rf by the plasma, and the report on the recent completion of SERSE, a superconducting, high B mode, high-frequency ECRIS, which promises the next major advance in the field. The balance and scope of all the presentations and discussions gave an overview of a rapidly advancing field where major avenues for improvement and for new applications are available.
Ion charge state distribution in plasma of electron cyclotron resonance discharge sustained by powerful millimeter wave radiation
Authors: Golubev S. V. , Razin S. V. , Zorin V. G.
Published: July 2002

An essential increase of operation efficiency of electron cyclotron resonance (ECR) multiply charged ion (MCI) sources (that is the increase of the average charge number and current of ion beams) is related to the possibility of achieving more dense plasma and transferring to the so-called quasi-gas dynamic regime of the plasma confinement in mirror traps by pumping with higher frequency. The first results of this experimental investigation of ion charge state distribution in a pulsed ECR source of MCI with pumping by millimeter wave radiation of a powerful gyrotron are presented in the article. Millimeter wave radiation with maximum power W=130 kW, frequency f=37.5 GHz, and pulse duration up to 1.5 ms is used for the experiments. The charge state distribution maximum corresponded to argon charge (+11)-(+12). Total ion saturation current density of the probe achieved 2 A/cm2.
Beam bunching of the radioactive nuclear beam in a 6.4 GHz electron cyclotron resonance ion source
Authors: Oyaizu M. , Ishiyama H. , Jeong S. C. , Kawakami H. , Miyatake H. , Tanaka J. , Tojo E. , Wada M. , Katayama I. , Nomura T. , Fujita M. , Tanigaki M. , Shinozuka T. , Fujioka M.
Published: July 2002

A single stage 6.4 GHz ECR ion source for an isotope separator on-line based radioactive nuclear beam facility at KEK-Tanashi, is under an on-line test for the effective production of Ne2+19 ions by using alpha beams from a cyclotron. Synchronized with the pulsed operation of heavy ion linacs, the millisecond beam bunching is now being performed to reduce the loss of radioactive ions in acceleration by using a pulsed-gating potential method. The highest beam intensity at 100 Hz and 20% duty factor reaches 60% of that obtained in a continuous-wave mode.
Pulse height analysis using Si-pin diode of x-ray irradiated from a 2.45 GHz electron cyclotron resonance multicharged ion source
Authors: Kato Yushi , Kubo Yoshiyuki , Ishii Shigeyuki
Published: July 2002

Production of multicharged ions is experimentally studied on an electron cyclotron resonance (ECR) source. The ECR zone for a microwave frequency of 2.45 GHz is formed at the bottom of a mirror trap. The x-ray spectra are measured by Si-pin diode detector in the various operating conditions. Available energy range of the x-ray measurement is several keV approximately several tens keV. Measurements are carried out at either line of sight including the ECR zone along the geometrical axis or at off-ECR zone from the side wall. The temperatures determined at both positions are about 2–3 keV from the observed spectrum with assuming nonrelativistic maxwellian plasma. The intensities of Ar Kα and bremsstrahlung radiation correlate to pressure and microwave power dependence of multicharged-ion production. But the dependence of the temperature is not clear. Therefore the multicharged-ion production largely depends on an abundance of high energy electrons rather than the change of the temperature of them in this energy region; and it is suggested that the emission profiles of the x-ray radiation peaks at the center of the mirror at the low pressure.
Precision Bragg reflectors obtained by molecular beam epitaxy under in situ tunable dynamic reflectometry control
Authors: Bardinal V. , Legros R. , Fontaine C.
Published: July 2002

Highly accurate layer thicknesses are required for multilayers involved in photonic devices, such as Bragg reflectors. In this letter, we demonstrate that precise, real-time monitoring of molecular beam epitaxy growing layers can be achieved by near-normal incidence dynamic reflectometry with a tunable sapphire–titanium laser used as a source. The advantage of this new technique lies in the possibility of synchronizing the material changes and the reflectivity extrema by selecting adequate analysis wavelengths. This technique is shown to provide 885 nm GaAs–AlAs Bragg reflectors with a layer thickness accuracy in excess of 1%.
A hydrothermal atomic force microscope for imaging in aqueous solution up to 150 °C
Authors: Higgins Steven R. , Eggleston Carrick M. , Knauss Kevin G. , Boro Carl O.
Published: July 2002

We present the design of a contact atomic force microscope (AFM) that can be used to image solid surfaces in aqueous solution up to 150 °C and 6 atm. The main features of this unique AFM are: (1) an inert gas pressurized microscope base containing stepper motor for coarse advance and the piezoelectric tube scanner; (2) a chemically inert membrane separating these parts from the fluid cell; (3) a titanium fluid cell with fluid inlet–outlet ports, a thermocouple port, and a sapphire optical window; (4) a resistively heated ceramic booster heater for the fluid cell to maintain the temperature of solutions sourced from a hydrothermal bomb; and (5) mass flow control. The design overcomes current limitations on the temperature and pressure range accessible to AFM imaging in aqueous solutions. Images taken at temperature and pressure are presented, demonstrating the unit-cell scale (<1 nm) vertical resolution of the AFM under hydrothermal conditions.
A stopped-flow apparatus with a push–pull coupler for the study of fast reactions in solution under high pressure
Authors: Ishihara Koji , Kondo Yuichi , Koizumi Mitsuo
Published: July 2002

A new high-pressure stopped-flow apparatus equipped with a push–pull coupler has been developed which enables one to monitor fast reactions in various organic solvents as well as in strongly acidic media under pressure up to 200 MPa. Sample solutions come into contact only with chemically inert materials: Daiflon, quartz, and a Teflon-coated O-ring. The reactant-syringe and receiver-syringe pistons are driven at the same time with the aid of a push–pull coupler and an actuator. The dead time of this apparatus is ∼2 ms.
Linac-based free electron lasers and e-beam energy modulation
Authors: Bizzarri U. , Dattoli G. , Ottaviani P. L.
Published: July 2002

We discuss the effect of the energy modulation over the macropulse of an e-beam driving a free electron lasers oscillator. It is shown that this modulation produces an efficient cavity depletion and provides an output optical beam, chopped at the same frequency of the beam energy modulation. The advantages offered by this method are discussed, with particular reference to the case of intracavity harmonic generation. The effective realization of an electron beam energy modulating device is finally discussed.
18 GHz upgrading of the superconducting electron cyclotron resonance ion source SERSE
Authors: Gammino S. , Ciavola G. , Celona L. , Castro M. , Chines F. , Marletta S.
Published: July 2002

The superconducting electron cyclotron resonance ion source SERSE of INFN-Laboratori Nazionali del Sud has been recently upgraded with an 18 GHz generator which takes the place of the 14.5 GHz generator, used up to now. In order to further extend the validation of high B mode to higher frequency, some comparative tests have also been carried out, aimed at understanding the role of the magnetic field and frequency on the ion yield at higher levels than were ever done before. The results at the frequencies of 14.5 and 18 GHz are compared and the trend already observed elsewhere is here confirmed. Preliminary observations of the “two frequency heating” have contributed to increase further the currents of the highest charge states.
Detectivity comparison between thin-film Pd/PVDF photopyroelectric interferometric and optical reflectance hydrogen sensors
Authors: Wang Chinhua , Mandelis Andreas , Garcia Jose A.
Published: July 2002

A novel dual photopyroelectric interference (PPEI)/optical reflectance (OR) solid-state hydrogen sensor system has been developed and demonstrated. Based on the recently developed PPE-interference technique and the variations of optical and electronic properties of Pd metal in the presence of hydrogen, simultaneous signal responses were obtained from a polyvinylidene fluoride (PVDF) thin-film detector and an optical photodiode. The dual measurement of PPEI and OR channels provides not only a more reliable sensor system, but also a powerful tool to identify the operating mechanism(s) in the process of Pd/PVDF/hydrogen interaction. The experimental results show that the detectivity and the signal dynamic range of the PPEI method are much higher than those of the OR method due to the suppression of the large base-line signal and the signal noise. The comparison of PPEI and OR results reveals that both signals are mainly due to the same electronic mechanism.
Proton injector operational results on a high-power continuous-wave radio-frequency quadrupole accelerator
Authors: Sherman Joseph D. , Bolme Gerald O. , Hansborough Lash D. , Hardek Thomas W. , Kerstiens Debora M. , Meyer Earl A. , Schneider J. David , Smith H. Vernon , Stettler Matthew W. , Stevens Ralph R. , Thuot Michael E. , Zaugg Thomas J. , Arvin Adrian A. , Bolt Alvin S. , Hegler Patrick H. , Richards Mitchell C. , Boers Jack E. , Kamperschroer James H. , Figueroa Terry L.
Published: July 2002

A 50 keV proton injector utilizing a dc microwave source has been used to operate a 1.25 MeV continuous wave (cw) radio-frequency quadrupole (RFQ) accelerator. RFQ injection places stringent requirements on beam properties including centroid control, emittance, and phase-space matching. The ion source chosen for these applications is based on a microwave discharge operating at 2.45 GHz with an on-axis magnetic field near 875 G. The injector employs a space-charge-neutralized, two-solenoid-lens, low-energy beam transport (LEBT) system. Proton injector development with a 1.25 MeV RFQ has resulted in meeting the RFQ 75 mA design current specification in cw mode. Details of the ion source and LEBT operation are presented, and simulations for ion beam extraction and transport are compared with the injector measurements. The proton injector has been converted to 75 keV beam operation for injecting into a 6.7 MeV cw RFQ.
Fundamental aspects of electron cyclotron resonance ion sources: From classical to large superconducting devices (invited)
Authors: Hitz Denis , Melin Gérard , Girard Alain
Published: July 2002

Electron cyclotron resonance ion sources (ECRIS) of highly charged ions are widely used for many applications. Depending on the application, ECRIS now have to cope with new beam requirements: intense flux of medium charge states and/or very high charge states are demanded by users. In addition, these sources have to be stable and reliable. These requirements lead to large volume/high magnetic field devices. Through a discussion of the main parameters of an ECRIS, we deal with the present state of the art of ECRIS in this article. The evolution from “classical” sources to superconducting devices is presented.
Monte Carlo simulation of negative ion production in the negative hydrogen ion source
Authors: Uematsu M. , Morishita T. , Hatayama A. , Sakurabayashi T. , Ogasawara M.
Published: July 2002

Two Monte Carlo simulation codes: (a) neutral transport code and (b) negative ion (H−) transport code, have been developed to understand transport phenomena in negative ion sources. In the neutral transport code, Boltzmann equations for hydrogen molecules (H2) and atoms (H) are solved. Three dimensional (3D) spatial distributions of H2, H, and H− production are obtained for a tandem negative ion source. The volume production of H− is limited to the area around the gas inlet in the first chamber and near the plasma grid in the second chamber. On the other hand, distribution of H− surface production is shown to be almost uniform over all the plasma grid surface. In the negative ion code, H− trajectories are calculated by numerically solving the 3D equation of motion for H− ions. The effects of the magnetic filter on the extraction probability of surface produced H− ions are mainly studied. The dependence of the extraction probability on the field strength is small.
Design of an electron cyclotron resonance ion source for the isotope separator and accelerator at TRIUMF
Authors: Yuan D. , Jayamanna K. , Dombsky M. , Louie D. , Kadantsev S. , Keitel R. , Kuo T. , McDonald M. , Olivo M. , Schmor P.
Published: July 2002

A 2.45 GHz electron cyclotron resonance ion source has been designed and built to ionize radioactive atoms and produce single charged ion beams for the isotope separator and accelerator at TRIUMF. The source is characterized by its short axial length (8 cm) and the small pair of magnetic coils (diam=φ26 cm) placed adjacent to the source cavity. A small diameter quartz tube is inserted in the cavity to confine the plasma to a small volume and to shorten total ion transient time for the exotic gaseous elements with short and intermediate half life. The computer code POISSON is used to design the magnetic coils. A three-electrode extraction system simulated with the code IGUNE is used to study the beam extraction efficiency. In this article the design of the source, extraction system, and the preliminary results on beam emittance and energy spread are presented; the results on ion transient time, ionization efficiency, and beam extraction efficiency are presented in a separate article.
The electron cyclotron resonance (1+n+) systems and the ISOL radioactive beam facilities (invited)
Authors: Geller R.
Published: July 2002

Short life radioactive beams presently need charge breeders either for continuous or pulsed postaccelerators. Until recently these charge breeders were mainly based on stripper foils and or electron beam ion source projects associated with ion trap bunching devices. In 1995 however, we demonstrated the feasibility of radioactive electron cyclotron resonance ion source (ECRIS) charge breeders with rather good efficiencies working in continuous regime and well adapted for continuous postaccelerators. In 1998, we demonstrated also the feasibility of pulsed ECR ion traps (ECRITs) which are well adapted for pulsed postaccelerators with short life radioactive ion bunches. In this article, we explain the basic principles of these devices shortly named (1+n+) ECR systems and compare their characteristics with other systems. More precise results are given in companion articles at this meeting.
Time resolved experiments at the Frankfurt 14 GHz electron cyclotron resonance ion source
Authors: Runkel S. , Hohn O. , Stiebing K. E. , Schempp A. , Schmidt-Böcking H. , Mironov V. , Shirkov G.
Published: July 2002

Time resolved measurements of the extracted ion currents at the Frankfurt 14 GHz electron cyclotron resonance ion source (ECRIS) are reported. These measurements were performed to provide more detailed information on the “biased disk effect” in an ECRIS. From a first series of measurements with pulsed biased disk voltage it was concluded that the “biased disk effect” is mainly due to improvements of the extraction conditions and the enhanced transport of highly charged ions into the extraction area. In this article we present new measurements with an improved setup allowing for a faster pulsing of the biased disk voltage. We also present data for the injection of neutral particles from laser ablated plasmas and Bremsstrahlung spectra for different dc biased disk voltages. All results from these measurements support our previous conclusion.