RSI Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Feb 2001

Volume 72, Issue 2, pp. 1270-1601

Page 1 of 3 Pages Next Page | Jump to Page
back to top
RSS Feeds

The birth and development of laser heating in diamond anvil cells

William A. Bassett

Rev. Sci. Instrum. 72, 1270 (2001); http://dx.doi.org/10.1063/1.1343861 (3 pages) | Cited 18 times

Full Text: | Download PDF

Show Abstract
In 1968 Taro Takahashi and I observed a phase transition that resulted from laser heating under pressure in a diamond anvil cell. Using a ruby laser, we successfully converted graphite to diamond. We soon realized that the ruby laser had such limited capabilities that we acquired a yttrium–aluminum–garnet (YAG) laser that could be used in both continuous and pulsed modes. The road to successfully applying the technique was not without a few bumps. Thirty years later, these seem more amusing than they did at the time. It was with the YAG laser that Ming and Liu investigated a number of silicate phase transitions important to our understanding of the earth’s mantle. Since then it has been gratifying to watch as others have adopted the technique and made many important contributions with it. © 2001 American Institute of Physics.
Show PACS
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
62.50.-p High-pressure effects in solids and liquids
64.70.K- Solid-solid transitions
42.62.-b Laser applications

Laser heated diamond cell system at the Advanced Photon Source for in situ x-ray measurements at high pressure and temperature

Guoyin Shen, Mark L. Rivers, Yanbin Wang, and Stephen R. Sutton

Rev. Sci. Instrum. 72, 1273 (2001); http://dx.doi.org/10.1063/1.1343867 (10 pages) | Cited 99 times

Full Text: | Download PDF

Show Abstract
We describe a laser heated diamond anvil cell system at the GeoSoilEnviroCARS sector at the Advanced Photon Source. The system can be used for in situ x-ray measurements at simultaneously ultrahigh pressures (to >150 GPa) and ultrahigh temperatures (to >4000 K). Design goals of the laser heating system include generation of a large heating volume compared to the x-ray beam size, minimization of the sample temperature gradients both radially and axially in the diamond anvil cell, and maximization of heating stability. The system is based on double-sided laser heating technique and consists of two Nd:YLF lasers with one operating in TEM00 mode and the other in TEM01∗ mode, optics to heat the sample from both sides, and two spectroradiometric systems for temperature measurements on both sides. When combined with an x-ray microbeam (3–10 μm) technique, a temperature variation of less than 50 K can be achieved within an x-ray sampled region for longer than 10 min. The system has been used to obtain in situ structural data and high temperature equations of state on metals, oxides, and silicates to 3500 K and 160 GPa. © 2001 American Institute of Physics.
Show PACS
07.85.Qe Synchrotron radiation instrumentation
61.05.cp X-ray diffraction
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
07.20.Ka High-temperature instrumentation; pyrometers
42.62.-b Laser applications
07.85.Jy Diffractometers

Synchrotron radiation and laser heating in a diamond anvil cell

Denis Andrault and Guillaume Fiquet

Rev. Sci. Instrum. 72, 1283 (2001); http://dx.doi.org/10.1063/1.1343866 (6 pages) | Cited 23 times

Full Text: | Download PDF

Show Abstract
The last decade has seen the development of very bright third generation x-ray synchrotron sources that have significantly improved x-ray diffraction experiments at high pressure and high temperature. In the same time, focusing optics as well as detectors have been improved in such a way that x-ray diffraction experiments can be routinely carried out on samples in laser-heated diamond anvil-cell, i.e., under extreme static pressure and temperature conditions. It is now possible to obtain from a laser heated sample in a diamond anvil cell (DAC) very high quality powder patterns, needed for accurate in situ phase boundary and pressure-volume-temperature equation of state determinations, as well as for structural refinements. The setup for in situ x-ray investigation at simultaneous high pressure and temperature is complex, since perfect alignment of x-ray path, infrared-laser hot spot, and optical temperature measurement is required. It provides, however, the most accurate information on the structural behavior with step by step increases of pressure and temperature. In addition, a range of experiments can also be realized at room temperature after laser annealing of DAC samples, which has been shown very efficient in releasing stresses build on compression, and/or overcoming phase transitions kinetic barriers. © 2001 American Institute of Physics.
Show PACS
61.05.cp X-ray diffraction
07.85.Qe Synchrotron radiation instrumentation
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
07.20.Ka High-temperature instrumentation; pyrometers
42.62.-b Laser applications

Construction of laser-heated diamond anvil cell system for in situ x-ray diffraction study at SPring-8

Tetsu Watanuki, Osamu Shimomura, Takehiko Yagi, Tadashi Kondo, and Maiko Isshiki

Rev. Sci. Instrum. 72, 1289 (2001); http://dx.doi.org/10.1063/1.1343869 (4 pages) | Cited 42 times

Full Text: | Download PDF

Show Abstract
A double-sided laser heated diamond anvil cell (DAC) system was constructed at a high brilliance, undulator beamline (BL10XU) at SPring-8 a third generation synchrotron radiation facility, for performing in situ angle-dispersive x-ray diffraction experiments under high temperature and high pressure. The design of this system puts emphasis on reliable data collection for the structural analysis. With this system, the adjustment of the optical systems for both x-ray and laser beams can be done easily, and high quality diffraction data can be obtained typically within several minutes. A system for temperature measurement of ten points in a sample area at the same time was also developed. The performance of the laser heated DAC system was tested by observing phase transitions of natural olivine. © 2001 American Institute of Physics.
Show PACS
61.05.cp X-ray diffraction
07.85.Qe Synchrotron radiation instrumentation
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
07.20.Ka High-temperature instrumentation; pyrometers
42.62.-b Laser applications

Laser heated diamond anvil apparatus at the Photon Factory and SPring-8: Problems and improvements

Takehiko Yagi, Tadashi Kondo, Tetsu Watanuki, Osamu Shimomura, and Takumi Kikegawa

Rev. Sci. Instrum. 72, 1293 (2001); http://dx.doi.org/10.1063/1.1343868 (5 pages) | Cited 22 times

Full Text: | Download PDF

Show Abstract
Two high pressure high temperature in situ x-ray diffraction systems constructed at the Photon Factory and at SPring-8 are described. Both systems consist of a laser heated diamond anvil cell, CO2 or YAG laser heating systems, and an angle dispersive powder x-ray diffraction system with an imaging plate detector. CO2 laser heating has an advantage in that the sample can be heated stably and uniformly due to stable absorption of the sample. Use of type-IIa diamond, however, caused plastic deformation of the anvils. YAG laser heating, compared to CO2 laser heating, can be used to much higher pressures and temperatures, although a good control system is required for stable heating. Various problems encountered during construction are discussed. © 2001 American Institute of Physics.
Show PACS
07.85.Qe Synchrotron radiation instrumentation
61.05.cp X-ray diffraction
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
07.20.Ka High-temperature instrumentation; pyrometers
07.85.Jy Diffractometers
42.62.-b Laser applications

A diamond gasket for the laser-heated diamond anvil cell

Guangtian Zou, Yanzhang Ma, Ho-kwang Mao, Russell J. Hemley, and Stephen A. Gramsch

Rev. Sci. Instrum. 72, 1298 (2001); http://dx.doi.org/10.1063/1.1343864 (4 pages) | Cited 16 times

Full Text: | Download PDF

Show Abstract
Advances in laser heating techniques with diamond anvil cells have enabled direct investigations of materials under extreme pressure-temperature conditions. The success of uniform heating to the maximum temperatures at megabar pressures relies critically on maximizing the gasket thickness which in turn depends upon the shear strength of the gasket. We have used diamond powder, the strongest possible material, to formulate a gasket for in situ x-ray diffraction with double-sided laser heating. The increase in gasket thickness allows increases in sample and insulator thickness, thereby improving the quality and pressure-temperature range of the measurement. We did not observe any pressure difference within 40 μm of the center of the sample chamber and the temperature distribution across the sample itself is within ±47 K. These improvements as well as the fact that the diamond gasket can allow the sample to remain in good condition after high P–T processing make it an extremely useful technique in diamond cell laser-heating experiments. As an example of the technique, we present in situ x-ray diffraction results for FeO to above 86 GPa and 3500 K. © 2001 American Institute of Physics.
Show PACS
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
42.62.-b Laser applications
07.20.Ka High-temperature instrumentation; pyrometers
61.05.cp X-ray diffraction

Two-dimensional energy dispersive x-ray diffraction at high pressures and temperatures

Yanzhang Ma, Ho-kwang Mao, Russell J. Hemley, Stephen A. Gramsch, Guoyin Shen, and Maddury Somayazulu

Rev. Sci. Instrum. 72, 1302 (2001); http://dx.doi.org/10.1063/1.1343865 (4 pages) | Cited 9 times

Full Text: | Download PDF

Show Abstract
Diffraction studies at extreme pressure-temperature conditions encounter intrinsic difficulties due to the small access angle of the diamond anvil cell and the high background of the diffraction peaks. Energy-dispersive x-ray diffraction is ideal for overcoming these difficulties and allows the collection and display of diffracted signals on the order of seconds, but is limited to one-dimensional information. Materials at high pressures in diamond anvil cells, particularly during simultaneous laser heating to temperatures greater than 3000 K often form coarse crystals and develop preferred orientation, and thus require information in a second dimension for complete analysis. We have developed and applied a diamond cell rotation method for in situ energy-dispersive x-ray diffraction at high pressures and temperatures in solving this problem. With this method, we can record the x-ray diffraction as a function of χ angle over 360°, and we can acquire sufficient information for the determination of high P–T phase diagrams, structural properties, and equations of state. Technical details are presented along with experimental results for iron and boron. © 2001 American Institute of Physics.
Show PACS
61.05.cp X-ray diffraction
07.85.Jy Diffractometers
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
07.20.Ka High-temperature instrumentation; pyrometers
07.85.Qe Synchrotron radiation instrumentation

The effect of sample thickness and insulation layers on the temperature distribution in the laser-heated diamond cell

Wendy R. Panero and Raymond Jeanloz

Rev. Sci. Instrum. 72, 1306 (2001); http://dx.doi.org/10.1063/1.1343863 (3 pages) | Cited 9 times

Full Text: | Download PDF

Show Abstract
The temperature gradients in the laser-heated diamond anvil cell can be modeled through the solution of the steady-state heat equation. For a given laser, the width of the hotspot is dependent on the thickness and thermal conductivity of the sample and of any thermal-insulation layers between the sample and the diamonds. For a given sample, insulation and peak temperature, thicker samples will have broader hotspots than thinner ones. Therefore, increasing the pressure on a sample will thin the gasket, sample and insulation, producing a narrower hotspot and increasing temperature gradients. © 2001 American Institute of Physics.
Show PACS
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
07.20.-n Thermal instruments and apparatus
44.10.+i Heat conduction
42.62.-b Laser applications

Laser-heated diamond anvil cell system for photochemical reaction measurements

H. Yusa

Rev. Sci. Instrum. 72, 1309 (2001); http://dx.doi.org/10.1063/1.1343862 (4 pages)

Full Text: | Download PDF

Show Abstract
A laser heating system constructed for photochemical reaction within a diamond anvil cell features a tunable pulsed laser and an excimer laser ranging from ultraviolet to infrared in a continuous-wave Nd:yttrium–aluminum–garnet laser heating system. Pulse duration is measured during experiments using a high-speed photoreceiver and pulse modes are measured by a beam profiler. High-purity synthetic diamond with high ultraviolet transmittance are used to avoid damaging the anvils. Decomposition of silver iodide by an excimer laser irradiation is confirmed under high pressure. This laser technology will, combined with high-pressure experiments, open up avenues in photochemical reaction processes. © 2001 American Institute of Physics.
Show PACS
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
42.62.-b Laser applications
82.50.Hp Processes caused by visible and UV light
07.20.Ka High-temperature instrumentation; pyrometers
back to top
RSS Feeds
back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY

BACH, the beamline for advanced dichroic and scattering experiments at ELETTRA

M. Zangrando, M. Finazzi, G. Paolucci, G. Comelli, B. Diviacco, R. P. Walker, D. Cocco, and F. Parmigiani

Rev. Sci. Instrum. 72, 1313 (2001); http://dx.doi.org/10.1063/1.1334626 (7 pages) | Cited 43 times

Full Text: | Download PDF

Show Abstract
A beamline for advanced dichroism (BACH), to perform light polarization dependent experiments in the 35–1600 eV photon energy range is under construction at the ELETTRA Synchrotron Radiation Source in Trieste, Italy. The radiation source, based on two APPLE-II helical undulators, is designed for high photon flux and high resolving powers. The photons dispersion system is based on a Padmore variable angle spherical grating monochromator with a typical resolving power of 20 000–6000, 20 000–6000, and 15 000–5000 in the energy ranges 35–200 eV, 200–500 eV, and 500–1600 eV, respectively. Two separate branches after the monochromator allow setting two independent experimental chambers. The photon flux in the experimental chamber(s), calculated at the best resolutions achievable and with the aperture of the slits set at 10 μm, is expected to be above 1011 photons’s with linearly or circularly polarized light. In addition, a fourth grating operates in the 400–1600 eV range to provide a higher flux, 1012 photons’s with smaller resolving power (10 000–2000), allowing fluorescence and x-ray scattering experiments. The refocusing section(s), based on plane elliptical mirrors in a Kirkpatrick–Baez scheme, will provide on the sample, a nearly free-aberration spot(s), whose dimensions are expected to be 200×10 μm2 (horizontal×vertical). In the following, the general layout of the beamline is reported and the characteristics of the optical elements, as well as the optical performances (resolving powers and efficiencies of the monochromator, flux, and spot dimensions) are described in detail. © 2001 American Institute of Physics.
Show PACS
07.85.Qe Synchrotron radiation instrumentation
29.20.db Storage rings and colliders
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
41.60.Ap Synchrotron radiation
41.50.+h X-ray beams and x-ray optics

Very high spectral resolution obtained with SU5: A vacuum ultraviolet undulator-based beamline at Super-ACO

Laurent Nahon, Christian Alcaraz, Jean-Louis Marlats, Bruno Lagarde, François Polack, Roland Thissen, Didier Lepère, and Kenji Ito

Rev. Sci. Instrum. 72, 1320 (2001); http://dx.doi.org/10.1063/1.1337073 (10 pages) | Cited 41 times

Full Text: | Download PDF

Show Abstract
In this article we wish to report on the commissioning of the SU5 undulator-based beamline, whose primary scientific goal deals with high-resolution spectroscopy and photon-induced dynamics in the vacuum ultraviolet range on dilute species. In order to achieve such a scientific program, we have conceived an original optical design, centered around a 6.65 m off-plane Eagle monochromator equipped with two gratings (2400 and 4300 l/mm) illuminated by an astigmatic prefocusing optical system. The different components of the actual beamline, such as the optical elements, their holders/manipulators and the monochromator are described, with a special emphasis on critical aspects such as the mechanical resolution and stability, the vibrations limitations, and the thermal stability. Then, a spectral calibration procedure of the monochromator is described, followed by the presentation of the measured performances of the beamline in terms of ultimate resolution and flux. Owing to a gas phase ion yield experiment on rare gases, we have been able to measure a raw linewidth of 184 μeV at 21.61 eV (18s′ line of Ne) corresponding to a resolving power of 117 000 and a raw (respectively, lifetime-deconvoluted) linewidth of 119 μeV (respectively, 76 μeV) at 15.82 eV (13s′ line of Ar) corresponding to a raw resolving power of 133 000 (respectively, 208 000). The ultimate targeted 105 resolving power is therefore observed on most of the VUV range, which corresponds to an unprecedented performance. The measured photon flux in a 1/50 000 bandwidth is in reasonable agreement with the expected values lying in the 1010–109 photon/s range over the VUV range. These very satisfactory performances, with a slit-limited resolution down to about 15 μm slits aperture, are due to the special care which has been paid at both the conception and construction stages concerning critical issues such as the optical and mechanical design, the vibrations, the driving/encoding system, and the slope errors of the gratings. © 2001 American Institute of Physics.
Show PACS
42.72.Bj Visible and ultraviolet sources
07.60.Rd Visible and ultraviolet spectrometers
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
07.85.Qe Synchrotron radiation instrumentation
41.85.Si Particle beam collimators, monochromators

Theoretical study of space focusing in linear time-of-flight mass spectrometers

D. P. Seccombe and T. J. Reddish

Rev. Sci. Instrum. 72, 1330 (2001); http://dx.doi.org/10.1063/1.1336824 (9 pages) | Cited 6 times

Full Text: | Download PDF

Show Abstract
In response to continued improvements in the production of “cold” atoms, molecular beams, and in electronic timing resolution, the issue of space focusing in linear time-of-flight (TOF) mass spectrometers is reevaluated. Starting with the Wiley–McLaren [W. C. Wiley and I. H. McLaren, Rev. Sci. Instrum. 26, 1150 (1955)] condition for first-order space focusing in the conventional two-field system, we extend the approach to higher orders in more complicated situations. A general, solvable, set of equations for satisfying n-order space focusing in an m-field regime is derived. We demonstrate quantitatively that if higher orders of space focus are employed, then provided the initial velocity distribution of the ions is sufficiently narrow, a significant improvement in the mass resolution can be achieved. The conclusions drawn have important implications for the design of the next generation of TOF instruments. © 2001 American Institute of Physics.
Show PACS
07.75.+h Mass spectrometers

Laser pointing stabilization and control in the submicroradian regime with neural networks

F. Breitling, R. S. Weigel, M. C. Downer, and T. Tajima

Rev. Sci. Instrum. 72, 1339 (2001); http://dx.doi.org/10.1063/1.1334624 (4 pages) | Cited 5 times

Full Text: | Download PDF

Show Abstract
The possibility of controling the pointing stability of a slowly pulsed Ti:Sapphire laser system by lowpass filters and artificial neural networks (NN) is investigated by performing time series analysis and computer simulations on experimentally measured datasets. The simulations show that at pulse repetition rates of 20 Hz it is possible to use a feedforward algorithm to reduce the angular standard deviation from 0.7 to 0.3 μrad. The properties and advantages of NN methods such as automatic adaptation characteristics of a time series are discussed. © 2001 American Institute of Physics.
Show PACS
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
07.05.Mh Neural networks, fuzzy logic, artificial intelligence
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.55.Rz Doped-insulator lasers and other solid state lasers

Versatile cavity for optically pumped molecular lasers

J. Padma Nilaya and Dhruba J. Biswas

Rev. Sci. Instrum. 72, 1343 (2001); http://dx.doi.org/10.1063/1.1338488 (3 pages)

Full Text: | Download PDF

Show Abstract
We describe here an optically pumped molecular laser cavity configuration which allows near total transmission of pump radiation into the cavity maintaining, at the same time, a high Q value at the lasing wavelength. This also has built into it the capability of elimination of unabsorbed pump radiation, isolation of pump cavity, and suppression of self-focusing effect. The efficient performance of this versatile cavity has been demonstrated in the pulsed operation of a NH3 laser pumped by a transversely excited atmospheric CO2 laser. The low lasing threshold observed here suggests that this cavity can also be employed for the continuous operation of such lasers. © 2001 American Institute of Physics.
Show PACS
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Lt Gas lasers including excimer and metal-vapor lasers

Diode-pumped Nd:YAG laser intensity noise suppression using a current shunt

R. S. Abbott and P. J. King

Rev. Sci. Instrum. 72, 1346 (2001); http://dx.doi.org/10.1063/1.1334627 (4 pages) | Cited 10 times

Full Text: | Download PDF

Show Abstract
A current shunt actuator has been used to stabilize the intensity of a 10 W cw Nd3+:YAG laser. The current shunt developed exhibited a better actuator response than the pump diode current adjust actuator provided with the laser. Using the current shunt actuator, the relative intensity noise was suppressed from ∼ 10−51 / math to below ∼ 5 × 10−71 / math. © 2001 American Institute of Physics.
Show PACS
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Mi Dynamical laser instabilities; noisy laser behavior
42.55.Xi Diode-pumped lasers

Theoretical consideration of x-ray transmission through cylinder capillaries

Baozhen Chen

Rev. Sci. Instrum. 72, 1350 (2001); http://dx.doi.org/10.1063/1.1331324 (4 pages)

Full Text: | Download PDF

Show Abstract
A new model for calculating the transmission efficiency of x rays through a cylinder capillary is proposed. Based on some reasonable physical and mathematical assumptions the model can give a simple, straightforward procedure for the calculation of transmission efficiency. The calculation results given by the model can get a better fit to the experimental results than the results given by the previous model with taking some factors into account which affect the transmission of x rays through a capillary. © 2001 American Institute of Physics.
Show PACS
41.50.+h X-ray beams and x-ray optics
07.85.-m X- and γ-ray instruments
back to top PARTICLE SOURCES, OPTICS and ACCELERATION

Calibration facility for solar wind plasma instrumentation

Adrian Marti, Reto Schletti, Peter Wurz, and Peter Bochsler

Rev. Sci. Instrum. 72, 1354 (2001); http://dx.doi.org/10.1063/1.1340020 (7 pages) | Cited 8 times

Full Text: | Download PDF

Show Abstract
Space-borne analysis of the composition of the solar wind offers the unique possibility of direct measurement of material originating from the sun. For development, testing, and calibration of solar wind particle instrumentation, particle beams of highly charged ions for all elements from hydrogen up to iron are needed. Although sources for these ions have been available for some time, the special demands of space instrumentation made it necessary to build a dedicated facility. We built an electron-cyclotron-resonance ion source operating at 2.45 GHz. The ion source is installed on a high voltage platform allowing for postacceleration potentials of up to 100 kV. Ions are produced from elements in gaseous and solid phase; the latter from vapor emitted from a high temperature furnace closely attached to the ion source. © 2001 American Institute of Physics.
Show PACS
95.55.Ev Solar instruments
96.20.Br Origin and evolution
06.20.F- Units and standards
07.77.Ka Charged-particle beam sources and detectors
52.72.+v Laboratory studies of space- and astrophysical-plasma processes

Development of a microstrip gas chamber to study the effect of drift gap on its performance

V. Radhakrishna, K. Rajanna, S. S. Desai, and A. M. Shaikh

Rev. Sci. Instrum. 72, 1361 (2001); http://dx.doi.org/10.1063/1.1336820 (5 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
We present a new microstrip gas chamber design and a detailed experimental study of the effect of drift gap on its performance. The chamber has the provision to vary the drift gap in situ which enables one to carry out the performance study without altering the other set operating parameters such as gas pressure, anode voltage, and drift voltage. The effect of drift gap on detector gain and energy resolution is discussed here. The importance of optimization of drift gap is highlighted. The maximum gain obtained with P10 (Ar90%+CH410%) gas is ∼750 and the best resolution achieved is ∼19% for 5.9 keV x rays. © 2001 American Institute of Physics.
Show PACS
29.40.Cs Gas-filled counters: ionization chambers, proportional, and avalanche counters
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
back to top NUCLEAR PHYSICS, FUSION and PLASMAS

Microwave reflectometry for turbulence studies on ASDEX Upgrade

T. T. Ribeiro, F. Serra, G. D. Conway, M. E. Manso, F. Ryter, L. Cupido, B. Kurzan, A. Silva, W. Suttrop, and S. Vergamota

Rev. Sci. Instrum. 72, 1366 (2001); http://dx.doi.org/10.1063/1.1337071 (6 pages) | Cited 8 times

Full Text: | Download PDF

Show Abstract
We study the evolution of turbulence at several radial plasma locations in the Axially Symmetric Divertor Experiment (ASDEX) Upgrade tokamak, using microwave reflectometry. We analyze two types of scenarios: H-mode plasmas with improved performance and plasmas with electron cyclotron resonance heating modulation. Profound modifications of the turbulence spectra, occurring at specific plasma regions, have been found in both cases, indicating the relation between turbulence changes and confinement. The results demonstrate the ability of the reflectometry system on ASDEX Upgrade to make localized measurements. Mapping the radial distribution of turbulence can help us to understand the links between plasma rotation, shear, E×B flows, and the plasma turbulence behavior. © 2001 American Institute of Physics.
Show PACS
52.70.Gw Radio-frequency and microwave measurements
52.55.Fa Tokamaks, spherical tokamaks
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
52.35.Ra Plasma turbulence

Ultrafast soft x-ray two-dimensional plasma imaging system based on gas electron multiplier detector with pixel readout

D. Pacella, G. Pizzicaroli, L. Gabellieri, M. Leigheb, R. Bellazzini, A. Brez, G. Gariano, L. Latronico, N. Lumb, G. Spandre, M. M. Massai, and S. Reale

Rev. Sci. Instrum. 72, 1372 (2001); http://dx.doi.org/10.1063/1.1340026 (7 pages) | Cited 10 times

Full Text: | Download PDF

Show Abstract
In the present article a new diagnostic device in the soft x-ray range, for magnetic fusion plasmas, is proposed based on a gas electron multiplier detector with 2.5×2.5 cm active area, equipped with a true two-dimensional readout system. The readout printed circuit board, designed for these experiments, has 128 pads. Each pad is 2 mm square and covers a roughly circular area. The operational conditions of the detector are settled to work in the x-ray range 3–15 keV at very high counting rates, with a linear response up to 2 MHz/pixel. This limitation is due to the electronic dead time. Images of a wrench and two pinholes were done at rates of 2.5 MHz/pixel with a powerful x-ray laboratory source showing an excellent imaging capability. Finally preliminary measurements of x-ray emission from a magnetic fusion plasma were performed on the Frascati tokamak upgrade experiment. The system was able to image the plasma with a wide dynamic range (more than a factor of 100), with a sampling frequency of 20 kHz and with counting rates up to 4 MHz/pixel, following the changes of the x-ray plasma emissivity due to additional radio frequency heating. The spatial resolution and imaging properties of this detector have been studied in this work for conditions of high counting rates and high gain, with the detector fully illuminated by very intense x-ray sources (laboratory tube and tokamak plasma). © 2001 American Institute of Physics.
Show PACS
52.70.La X-ray and γ-ray measurements
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
29.40.Gx Tracking and position-sensitive detectors

Robust Langmuir probe circuitry for fusion research

J. Boedo, G. Gunner, D. Gray, and R. Conn

Rev. Sci. Instrum. 72, 1379 (2001); http://dx.doi.org/10.1063/1.1340023 (4 pages)

Full Text: | Download PDF

Show Abstract
Langmuir probes attached to the plasma facing components of fusion experiments are biased with constant or swept voltages to obtain measurements of plasma parameters such as electron temperature and density. The circuitry used must be rugged and protect the power supplies and electronics against generally harsh conditions and sudden discharge terminations, or disruptions. Modularity, ease of repair and expandability are important because short-lived radiation from neutron activation is often present after the discharges, preventing access to the circuitry. We report the implementation of modular probe circuitry featuring robust protection, remote testing and reset and easy maintenance and expandability, achieved by using DIN-rail modules. © 2001 American Institute of Physics.
Show PACS
52.70.Ds Electric and magnetic measurements
28.52.Lf Components and instrumentation

A novel Y-type reactor for selective excitation of atmospheric pressure glow discharge plasma

Guan-Guang Xia, Jin-Yun Wang, Aimin Huang, Steven L. Suib, Yuji Hayashi, and Hiroshige Matsumoto

Rev. Sci. Instrum. 72, 1383 (2001); http://dx.doi.org/10.1063/1.1340557 (8 pages)

Full Text: | Download PDF

Show Abstract
A novel Y-type atmospheric pressure ac glow discharge plasma reactor has been designed and tested in CO reduction with hydrogen and the reverse water–gas shift reaction. The reactor consists of a Y-type quartz tube with an angle of 120°–180° between the two long arms, two metal rod electrodes serving as high voltage terminals and two pieces of aluminum foil which were wrapped outside of the quartz tubes as a ground electrode. Different combinations of input power applied on this three- electrode system can lead to selective plasmas on one side, two sides, or can also generate a stable arc between the two high voltage terminal electrodes. The ability to selectively activate different species with this type of apparatus can help to minimize side reactions in plasmas to obtain desirable products. The Y-type reactor may provide a novel means to study fundamental problems regarding radical reactions. © 2001 American Institute of Physics.
Show PACS
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.80.Hc Glow; corona
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions

The method of ion current measurement on capacitive-coupled plasma

Yasushi Iseki, Kazuo Hayashi, and Etsuo Noda

Rev. Sci. Instrum. 72, 1391 (2001); http://dx.doi.org/10.1063/1.1340022 (4 pages)

Full Text: | Download PDF

Show Abstract
A small device, the conduction current probe, has been developed for the multi-point observation of ion currents. The probes are mounted on an electrode of a capacitive-coupled rf plasma source. The probe obtains the conduction current entering the electrode as a function of time by shielding the rf displacement current. The conduction current consists of the ion current as well as the electron one. The ion current is nearly constant although the electron one synchronizes with the rf electric field and flows in the short time of a rf cycle. Therefore, the ion current is obtained from the constant region of the conduction current. The experiments on a rf magnetron have revealed that the probe is a useful device for studying the parametric properties of the plasma source. © 2001 American Institute of Physics.
Show PACS
52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties

Characterization of internal MHD modes in Princeton beta experiment modification by ECE fluctuation radiometry

A. M. Zolfaghari, P. P. Woskov, S. Luckhardt, and R. Kaita

Rev. Sci. Instrum. 72, 1395 (2001); http://dx.doi.org/10.1063/1.1309007 (5 pages)

Full Text: | Download PDF

Show Abstract
Localized measurements of internal magnetohydrodynamic (MHD) activity in the Princeton Beta Experiment-Modification (PBX-M) have been made using a heterodyne radiometer. The radiometer measures third harmonic optically gray electron cyclotron emission (ECE) from the center to the outer edge of the plasma on eight radially localized frequency channels from 112–128 GHz. The radiometer uses a focusing Gaussian optics system, which provides a vertical resolution of approximately 6 cm throughout the plasma. The radial resolution of the diagnostics is limited by the relativistic broadening to approximately 2–3 cm. Long wavelength (k<0.5 cm−1) temperature and density fluctuations can therefore be detected using this diagnostic. A MHD mode’s characteristics such as pressure fluctuations and mode amplitude can be derived from the coherent fluctuations it causes in the ECE signal using an analytical theory developed by Luckhardt et al. (MIT Plasma Fusion Center Report No. PFC-JA/91-16, 1991). Using this analysis, pressure fluctuations (δP/P) have been calculated for high n-number MHD modes in high-βp PBX-M plasmas. © 2001 American Institute of Physics.
Show PACS
52.70.Gw Radio-frequency and microwave measurements
52.30.-q Plasma dynamics and flow
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
52.25.Gj Fluctuation and chaos phenomena
52.55.Fa Tokamaks, spherical tokamaks

Real-time extraction of plasma equilibrium parameters in KSTAR tokamak using statistical methods

Yong-Su Na, Young-Mu Jeon, S. H. Hong, and Y. S. Hwang

Rev. Sci. Instrum. 72, 1400 (2001); http://dx.doi.org/10.1063/1.1315639 (6 pages) | Cited 5 times

Full Text: | Download PDF

Show Abstract
To improve inherent shortcomings of statistical methods and apply them to the extraction of plasma equilibrium parameters in a fast timescale for real-time plasma control, new concepts of statistical methods such as principal component analysis-based neural network (NN), functional parametrization (FP)-based NN and double network are introduced by modifying NN and FP. These new methods are benchmarked and compared with the conventional techniques of NN and FP in a simple single-filament system. As a result of their applications to identification of plasma equilibrium parameters in the Korea Superconducting Tokamak Advanced Research tokamak, particularly, the double network concept among them has successfully achieved the improvement of drawbacks in the conventional methods. It is shown that more reliable results from the double network method can be obtained by combining several different statistical treatments as a primary network. Even in the case of nonoptimized methods united as a primary network, quite acceptable results can be achieved in the double network method. © 2001 American Institute of Physics.
Show PACS
52.55.Fa Tokamaks, spherical tokamaks
02.50.-r Probability theory, stochastic processes, and statistics
07.05.Mh Neural networks, fuzzy logic, artificial intelligence
52.70.Ds Electric and magnetic measurements
Page 1 of 3 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close