scispace - formally typeset
Search or ask a question

Showing papers in "Review of Scientific Instruments in 1986"


Journal ArticleDOI
TL;DR: In this article, a three-dimensional mechanical scanner fabricated from a single piezoelectric tube is presented, with a typical response of 5 nm/V in each orthogonal direction and mechanical resonances at 8 kHz and 40 kHz, respectively.
Abstract: We report a new type of three‐dimensional mechanical scanner fabricated from a single piezoelectric tube. It has a typical response of 5 nm/V in each orthogonal direction and mechanical resonances at 8 kHz (bending perpendicular to the tube axis) and 40 kHz (motion parallel to the tube axis). When used in a scanning tunneling microscope it is the higher frequency mode which is most critical since it corresponds to motion perpendicular to the sample surface. We show an image of the atomic surface of graphite taken in air using a tube scanner incorporated into a scanning tunneling microscope. The tube scanner allows the development of smaller, simpler, and faster scanning tunneling microscopes.

580 citations


Journal ArticleDOI
TL;DR: In this article, the authors derived theoretical limits on the ability to locate signal position by applying maximum likelihood estimation to this problem and showed that the limiting error in position measurement is a simple function of the instrument resolution, the density of sample points, and the signal-to-noise ratio of the data.
Abstract: A common problem in experimental data analysis is to locate the position of a signal to an accuracy which is substantially less than the actual signal width. By applying maximum likelihood estimation to this problem, this paper derives theoretical limits on the ability to locate signal position. The limiting error in position measurement is shown to be a simple function of the instrument resolution, the density of sample points, and the signal‐to‐noise ratio of the data. An interesting conclusion is that position information on a much finer scale than the minimum instrument sampling interval is contained in data of modest signal‐to‐noise ratio. The common procedure of excluding the portion of the data lying below an amplitude threshold to guard against background fluctuations is incorporated in the maximum likelihood analysis. It is shown that selection of the optimum amplitude threshold level depends on the type of noise present in the data, and can be an important factor in position accuracy. The analytical results exhibit close agreement with Monte Carlo simulations of position accuracy in the presence of noise.

409 citations


Journal ArticleDOI
TL;DR: In this article, a frequency-domain fluorometer was developed, which operates from 4 to 2000 MHz with the modulated excitation provided by the harmonic content of a laser pulse train (3.76 MHz, 5 ps).
Abstract: We developed a frequency‐domain fluorometer which operates from 4 to 2000 MHz. The modulated excitation is provided by the harmonic content of a laser pulse train (3.76 MHz, 5 ps) from a synchronously pumped and cavity dumped dye laser. The phase angle and modulation of the emission are measured with a microchannel‐plate photomultiplier (PMT). Cross‐correlation detection is performed outside the PMT. The high‐frequency signals for cross correlation were obtained by multiplication of the output from a 500‐MHz frequency synthesizer. The performance was verified in several ways, including measurement of known time delays and examination of standard fluorophores. The detector displayed no detectable color effect, with the 300–600‐nm difference being less than 5 ps. The precision of the measurements is adequate to detect differences of 20 ps for decay times of 500 ps. A correlation time of 53 ps was found for indole in water at 20 °C. The shortest correlation time we measured was 15 ps for indole in methanol/water (75/25) at 40 °C. Also, the 2‐GHz data reveal the time‐dependent ((t)1/2) terms found in the presence of collisional quenching. The degree of random error is about 0.3° of phase and 0.005 in modulation throughout the frequency range.

218 citations


Journal ArticleDOI
Ch. Gerber1, G. Binnig1, Harald Fuchs1, Othmar Marti1, Heinrich Rohrer1 
TL;DR: In this paper, a small scanning tunneling microscope (STM) is incorporated into a scanning electron microscope (SEM) to achieve tunnel-gap stability of about 1 A at atmospheric air pressure without additional sound protection.
Abstract: We have developed a small scanning tunneling microscope (STM) to be incorporated into a scanning electron microscope (SEM). Vibration isolation and damping is achieved solely with Viton dampers. As a stand-alone unit, a tunnel-gap stability of about 1 A is reached at atmospheric air pressure without additional sound protection. Stability improves by at least an order of magnitude when incorporated into a SEM.

206 citations


Journal ArticleDOI
TL;DR: In this paper, the authors made absolute measurements of x-ray spectra from 0.1-1.5 keV produced by plasmas from targets irradiated by the Lawrence Livermore National Laboratory Nova laser.
Abstract: We have made absolute measurements of x‐ray spectra from 0.1–1.5 keV produced by plasmas from targets irradiated by the Lawrence Livermore National Laboratory Nova laser. These measurements were made using a 15‐channel K‐ and L‐edge filtered x‐ray diode system. Valid interpretation of the results from this type of diagnostic requires some care in eliminating the effect of channel response at photon energies higher than the absorption edge. Significant errors can occur if this is disregarded. We will discuss the techniques used and the magnitude of the effects observed. Integrated x‐ray energy in the 1.5–3‐keV region is inferred from the results.

192 citations


Journal ArticleDOI
TL;DR: In this paper, the development of a microcomputer-controlled electrostatic probe as a diagnostic technique is described, which uses cylindrical probes and the definitive theory of Laframboise to give rapid measurements of the plasma parameters in a medium density (1010 to 1012 cm−3) plasma including the fast electron density and temperature.
Abstract: The development of a microcomputer‐controlled electrostatic probe as a diagnostic technique is described. The technique uses cylindrical probes and the definitive theory of Laframboise to give rapid measurements of the plasma parameters in a medium density (1010 to 1012 cm−3) plasma including the fast electron density and temperature. The iterative technique described overcomes many of the problems associated with established methods of Langmuir probe analysis.

181 citations


Journal ArticleDOI
TL;DR: In this paper, a high-current ion source is described in which a metal vapor vacuum arc is used to create the plasma from which the ion beam is extracted, and an ion beam current of up to about 1 A has been measured at an extraction voltage of 25 kV for a range of metallic species spanning the periodic table.
Abstract: A high‐current ion source is described in which a metal vapor vacuum arc is used to create the plasma from which the ion beam is extracted. An ion beam current of up to about 1 A has been measured at an extraction voltage of 25 kV for a range of metallic species spanning the periodic table from lithium to uranium. Multiply ionized charge states are seen up to as high as Q=6+ in the case of uranium. In the metal vapor vacuum arc, regions of intense current concentration are formed at the cathode, and it is at these regions, the cathode spots, that the cathode material is vaporized and ionized to form a dense, quasi‐neutral plasma which plumes away from the cathode surface. The plasma plume is caused to impinge upon a set of extractor grids, and the ion beam is extracted from the streaming metal plasma. A preliminary survey of the performance of the source has been made. We describe here the principle of operation of the source, the source design, and the results of those measurements that we have made to date.

176 citations


Journal ArticleDOI
TL;DR: The recently activated Nova laser facility as discussed by the authors is capable of irradiating complex targets with laser wavelengths of 0.53 and 0.35 μm and pulse widths that range from 0.09 to >5 ns, and peak powers greater than several terrawatts per beam line.
Abstract: The goals of the recently activated Nova laser facility are to address critical issues for evaluating the feasibility of inertial confinement fusion, to implode DT to densities exceeding 200 g/cm3 and pressures greater than 1011 atm, and to perform a wide range of high energy density plasma physics experiments in the areas of XUV/x‐ray lasers, hydrodynamics, and radiation generation and transport. An extremely flexible and sophisticated facility is required to successfully perform such a variety of tasks. The ten‐arm Nova laser is capable of irradiating complex targets with laser wavelengths of 0.53 and 0.35 μm and pulse widths that range from 0.09 to >5 ns, and peak powers greater than several terrawatts per beam line. A sophisticated, variable impedance, transmission line driven Pockels cell allows for complex temporal shaping of the laser pulse. Synchronized oscillators allow for different pulses to be propagated down the beam lines for experiments that require long‐pulse or short‐pulse x‐ray backlight...

141 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that it is possible to deposit positrons (e+) in a tokamak plasma by injecting bursts of neutral positronium atoms (e+e−), which are then ionized by the plasma.
Abstract: It now appears feasible to deposit positrons (e+) in a tokamak plasma by injecting bursts of neutral positronium atoms (e+e−), which are then ionized by the plasma The annihilation time of these positrons in the plasma is long compared with typical particle containment times Thus the subsequent transport of the positrons can be studied by monitoring the time dependence of the annihilation, gamma radiation produced when the positrons strike a limiter This paper discusses the design of such an experiment, the kinds of data which can be obtained, and the physics questions which this experiment might address This diagnostic technique could also be useful in studying transport in other magnetic confinement devices such as reversed‐field pinches and magnetic mirrors

140 citations


Journal ArticleDOI
TL;DR: The poloidal magnetic field distribution in a tokamak can be determined by probing the plasma with an array of FIR laser beams perpendicular to BT and measuring the Faraday rotation ψ of their plane of polarization as mentioned in this paper.
Abstract: The poloidal magnetic field distribution in a tokamak can be determined by probing the plasma with an array of FIR laser beams perpendicular to BT and measuring the Faraday rotation ψ of their plane of polarization. A concomitant detection of the phase shifts Δφ provides sufficient information to take the electron density profile properly into account. For the TEXTOR tokamak (R=1.75 m, a=0.5 m, BT =2 T) a nine‐channel Veron‐type interferometer has been upgraded to allow simultaneous measurements of Δφ and ψ with sensitivities of about 0.01×2π and 0.15° and time resolutions of 0.1 and 3 ms, respectively. The number of channels and their distribution are sufficient to reconstruct the local poloidal field and hence the current density profile with an accuracy of about ±5%–10% at half the plasma radius. For the central current density an accuracy of ±15%–20% is achieved by slowly moving the plasma across the probe beams and thereby multiplying the number of chords especially near the magnetic axis. For rapid ...

138 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the finite response time of the plasma synthesizes an inductance that serves to decouple the negative resistance of the plasmas from the rest of the circuit, and that oscillation is prevented if the circuit RC time constant is shorter than that which the plasma can follow.
Abstract: Stable operation of a corona excited supersonic expansion for the production of cold radicals or ions requires control of the geometry, chemistry, and electrical parameters. The nozzle must taper rapidly on the high‐pressure side to a throat that opens up into a free expansion on the vacuum side. Optimum radical and ion production is obtained with only a few percent of precursor in an inert carrier gas. Capacitive loading must be kept to a minimum to prevent oscillation. It is shown that the finite response time of the plasma synthesizes an inductance that serves to decouple the negative resistance of the plasma from the rest of the circuit. Practically, oscillation is prevented if the circuit RC time constant is shorter than that which the plasma can follow.

Journal ArticleDOI
TL;DR: In this article, a spin analyzer based on low-energy diffuse scattering from a high-Z target, for example, an evaporated polycrystalline Au film opaque to the incident electron beam, is described.
Abstract: A new, compact (approximately fist sized), efficient electron‐spin analyzer is described. It is based on low‐energy (150 eV) diffuse scattering from a high‐Z target, for example, an evaporated polycrystalline Au film opaque to the incident electron beam. By collecting a large solid angle of scattered electrons, a figure of merit S2I/I0=10−4 is achieved with an analyzing power S=0.11. The figure of merit degrades only marginally (<10%) for beams with an energy width of 40 eV or after one month of operation at 10−8 Torr. The electron optical acceptance is of order 100 mm2 sr eV. The details of the design and construction are discussed and its performance is compared to six other spin analyzers. Illustrative results are presented from an application to scanning electron microscopy with polarization analysis (SEMPA) to image magnetic microstructure.

Journal ArticleDOI
TL;DR: In this article, a new apparatus for measuring vapor-liquid equilibria of mixture has been designed to work up to 10 MPa and 423 K. This apparatus makes it possible to take reproducible and representative samples and inject them directly into a chromatographic circuit.
Abstract: A new apparatus to measure vapor–liquid equilibria of mixture has been designed to work up to 10 MPa and 423 K. This apparatus makes it possible to take reproducible and representative samples and inject them directly into a chromatographic circuit {the same requirements were already satisfied by another apparatus described in a previous paper [P. Figuiere, J. F. Hom, S. Laugier, H. Renon, D. Richon, and H. Szwarc, AIChE J. 26, 872 (1980)]}. The use of the new apparatus is very simple. Comparisons with data from Kay and Albert [Ind. Eng. Chem. 48, 422 (1956)] reveal a strong similarity in the whole pressure range. Measurements in the critical region do not involve significant experimental difficulty.

Journal ArticleDOI
TL;DR: In this article, a double-sided, high-frequency response heat-flux gauge was developed which allows measurement of heat flux from dc to 100 kHz, at temperatures up to 400°C.
Abstract: A double‐sided, high‐frequency response heat‐flux gauge has been developed which allows measurement of heat flux from dc to 100 kHz. The instrument is designed for heat‐flux magnitudes ranging from one to several hundred kW/m2 at temperatures up to 400 °C and is independent of the test article material. The gauges consist of a metal film (1500 A) resistance thermometers sputtered on both sides of a thin (25 μm) polyimide sheet. The sheet, which can contain many gauges, is then adhesively bonded to a test article. The temperature difference across the polyimide is a direct measure of the heat flux at low frequencies, while a quasi‐1D analysis is used to infer the high‐frequency heat flux from the upper surface temperature history. The design criteria, construction and application techniques, and a novel, ratiometric calibration procedure are discussed in detail.

Journal ArticleDOI
TL;DR: In this paper, a spectrometer for measuring the fluorescence emission from a single trapped aerosol particle is described, which consists of a particle generator, an electrodynamic levitator, an excitation source, and detection optics and electronics.
Abstract: A spectrometer for measuring the fluorescence emission from a single trapped aerosol particle is described. This device consists of a particle generator, an electrodynamic levitator, an excitation source, and detection optics and electronics. Provision is made to cool the sample chamber, and spectra can be obtained in real time. Typical spectra from particles containing organic laser dyes are presented.

Journal ArticleDOI
TL;DR: In this paper, a multipinhole-plate ultrasonic atomizer was experimentally optimized, employing a bender bimorph vibrator structure made up of a thin pinhole plate and a circular ring piezoelectric element.
Abstract: A multipinhole‐plate ultrasonic atomizer was experimentally optimized, employing a bender bimorph vibrator structure made up of a thin pinhole plate and a circular ring piezoelectric element. Effects of the vibration mode upon the performance were studied in terms of the sound pressure generation and the behavior of bubbles caused by cavitation. The performance was also examined with regard to the number of pinholes and the shape of the pinhole plate. As a result, the atomizer was proved to be able to jet and nebulize ordinary liquid most efficiently by the second harmonic vibration mode if the vibrating system is supported along the circumference of the ring piezoelectric element. It was also proved that the maximum atomizing rate is approximately proportional to the number of pinholes and that the spray pattern can easily be controlled by changing the shape of the pinhole plate.

Journal ArticleDOI
TL;DR: In this article, a 6.5m normal incidence monochromator installed at the storage ring BESSY was optimized for a high throughput of circularly polarized off-plane radiation at moderate resolution.
Abstract: A 6.5‐m normal incidence monochromator installed at the storage ring BESSY, which is optimized for a high throughput of circularly polarized off‐plane radiation at moderate resolution is described. The monochromator employs two exit slits and is specially designed and used for low‐signal experiments such as spin‐ and angle‐resolved photoelectron spectroscopy on solids, adsorbates, free atoms, and molecules. The Monk–Gillieson mounting (plane grating in a convergent light beam) allows for large apertures with relatively little astigmatism. With two gratings, a flux of more than 1011 photons s−1 bandwidth−1 (0.2–0.5 nm) with a circular polarization of more than 90% in the wavelength range from 35 to 675 nm is achieved.

Journal ArticleDOI
TL;DR: In this paper, the effects of RF on plasma potential measurements with electron emitting probes and methods for interpreting data are presented, corresponding to the floating and inflection point methods of single-emitting and differential emitting probes, respectively.
Abstract: Investigations of the effects of RF on plasma potential measurements with electron emitting probes and methods for interpreting data are presented. Techniques correspond to the floating and inflection point methods of single-emitting and differential emitting probes, respectively. A simple method of measurement of plasma potential fluctuations is given which makes use of time-averaged emitting probe I-V characteristics.

Journal ArticleDOI
TL;DR: A tunneling microscope that is a hybrid between IBM Zurich designs and squeezable tunnel junctions has been operated in air, oil, and liquid nitrogen as discussed by the authors, achieving maximum rigidity and minimum thermal drift.
Abstract: A tunneling microscope that is a hybrid between IBM Zurich designs and squeezable tunnel junctions has been operated in air, oil, and liquid nitrogen. Key design goals were (1) maximum rigidity and (2) minimum thermal drift. Images of individual atoms in a close packed layer have been obtained under liquid nitrogen.

Journal ArticleDOI
TL;DR: In this paper, a feedback charge measurement circuit is used to reduce the effect of several significant error terms, which has the advantages of higher signal-to-noise ratio at the frequencies of interest, independence of signal size from measurement time, and ease of distinction of signal charge from error currents at the time of measurement.
Abstract: A method is described for the measurement of quasistatic CV characteristics in semiconductors which offers significant advantages over previous methods. Using a small voltage step across the device under test, a displacement charge is stimulated and measured. A feedback charge measurement circuit is used, reducing the effect of several significant error terms. This technique has the advantages of higher signal‐to‐noise ratio at the frequencies of interest, independence of signal size from measurement time, and ease of distinction of signal charge from error currents at the time of measurement. Results consistent with those of previous techniques have been obtained on silicon MOS capacitors and other devices using steps from 10 to 100 mV and delays between step and measurement of up to 200 s. Furthermore, the method has been extended to provide additional information useful in determining whether an equilibrium measurement is obtained and in diagnosing and correcting for errors due to dc leakage currents. ...

Journal ArticleDOI
TL;DR: In this article, a Wien filter was combined with a dedicated scanning transmission electron microscope (STEM) to obtain an energy resolution of 140 meV with a specimen collection semiangle of 25 mR at 100 keV.
Abstract: A Wien Filter electron spectrometer has been successfully combined with a dedicated scanning transmission electron microscope (STEM) to obtain an energy resolution of 140 meV with a specimen collection semiangle of 25 mR at 100 keV. A cold‐field emission electron source is used to produce a 0.35–10‐nm‐size electron beam which has a spread in energy of about 0.25 eV. Because this energy spread is much larger than the spectrometer energy resolution, deconvolution techniques may be applied under appropriate conditions to yield a spectroscopic energy resolution of about 70 meV at a 12.5‐mR collection semiangle. The Wien Filter is a conventional design, but is immersed in a high‐voltage electrode of asymmetric design to facilitate control of prespectrometer electron trajectories. A doublet quadrupole lens is used to match the spectrometer angular acceptance range with that of scattered electrons at the specimen. A weak sextupole lens is used to reduce the second‐order angular aberrations.

Journal ArticleDOI
TL;DR: In this article, a scanning tunneling microscope is described for graphite at room and liquid-helium temperatures, which can resolve the atomic structure of graphite with high accuracy.
Abstract: We describe a scanning tunneling microscope which is extremely compact and rigid. Neither springs nor stacks of metal plates and rubber are necessary for vibration isolation. It can resolve the atomic structure of graphite at room and liquid‐helium temperatures. Its small size permits it to be dipped into a standard liquid‐helium storage Dewar.

Journal ArticleDOI
TL;DR: The use of position-sensitive detectors (PSDs) has become common in many spectroscopies as mentioned in this paper, and the increased signal provided by the parallel detection of many spectral elements affords increases in sensitivity and/or time resolution.
Abstract: The use of position‐sensitive detectors (PSDs) has become common in many spectroscopies. The increased signal provided by the parallel detection of many spectral elements affords increases in sensitivity and/or time resolution. Recently, the use of a PSD to increase the temporal resolution of an electron energy loss (EEL) spectrometer has been demonstrated in our laboratory. This article summarizes the present development of EEL spectrometers and then presents a detailed review of four classes of PSDs in the context of their potential application to EEL spectroscopy (EELS). The four classes considered are (a) discrete channel detectors, (b) coincidence array detectors, (c) charge division detectors, and (d) optical detectors imaging phosphor screens. All four designs, as typically implemented, utilize microchannel plates (MCPs) as spatially imaging electron multipliers. The performance of MCPs is reviewed and the constraints that MCP behavior at the high count rates achievable in EELS places on acceptable...

Journal ArticleDOI
TL;DR: In this paper, a soft flash x-ray (FX) apparatus with a new type of FX tube for biomedical use is described, which may be used for condenser charging voltages of 50-90 kV and peak currents of 20-40 kA. The electric pulse width of the FX waveforms was almost constant and its value was about 0.3 μs.
Abstract: The construction of a soft flash x‐ray (FX) apparatus with a new type of FX tube for biomedical use is described. The FX apparatus may be used for condenser charging voltages of 50–90 kV and peak currents of 20–40 kA. The electric pulse width of the FX waveforms was almost constant and its value was about 0.3 μs. The effective focal spot varied according to the condenser charging voltage, the anode–cathode (A–C) distance, etc., ranging from 0.2–3.0 mm in diameter. We selected two combinations of electrodes: (a) for normal focusing and a high dose rate; (b) for fine focusing and a low dose rate. The FX intensity was determined by the condenser charging voltage and the A–C distance, while the FX quality (average spectrum distribution) was determined by the average voltage of the FX tube and insertion of metal filters. The average voltage of the FX tube varied according to the condenser charging voltage and the A–C gap impedance. Various clear FX images were obtained by controlling the FX intensity, quality, and the focal spot size. We used Fuji Computed Radiography (FCR) in conjunction with our FX radiography, and by controlling the FX quality and the focal spot size, we obtained some interesting biomedical radiograms.

Journal ArticleDOI
TL;DR: In this paper, a soft x-ray spectrometer designed for use with photon excitation from synchrotron light sources is described and characterized, including a close-spaced input slit, large toroidal gratings, and a two-dimensional charge-coupled device array based detector system, providing exceptional measuring efficiency in a 5m Rowland circle design.
Abstract: A new soft x‐ray spectrometer designed for use with photon excitation from synchrotron light sources is described and characterized. Special design features, including a close‐spaced input slit, large toroidal gratings, and a two‐dimensional charge‐coupled‐device array based detector system, provide exceptional measuring efficiency in a 5‐m Rowland circle design. Descriptions are given of the spectrometer’s mechanical and detector design, and of calibration and alignment procedures. The beam line providing photon excitation from a synchrotron light source is described. Typical electron beam and/or photon excited emission spectra of Al, Si, and LiF are presented and compared with those produced by other instruments.

Journal ArticleDOI
TL;DR: In this paper, the upper frequency for loop-gap resonators intended for use in electron spin resonance spectroscopy was extended to the Q band (35 GHz) and a practical structure was described containing sample support, frequency tuning, and variable coupling.
Abstract: The upper frequency for loop‐gap resonators intended for use in electron‐spin‐resonance spectroscopy has been extended to Q band (35 GHz). A practical structure is described containing sample support, frequency tuning, and variable coupling. A typical sample volume is 39 nL. High‐energy densities (15 GW−1/2) were achieved. As found previously at X band, Q‐band loop‐gap resonators permit observation of the dispersion with minimal demodulation of phase noise originating in the klystron. Theoretical calculations of the resonant frequency, Q, and the filling factor are found to be in good agreement with experiment.

Journal ArticleDOI
TL;DR: In this paper, a conceptual basis for the technique of time delay photothermal wave spectroscopy is presented and the signal generation and appropriate system functions in the time delay and frequency domains are introduced and discussed from the point of view of correlation and spectral analysis and processing.
Abstract: A conceptual basis for the technique of time delay photothermal wave spectroscopy is presented. The signal generation and appropriate system functions in the time delay and frequency domains are introduced and discussed from the point of view of correlation and spectral analysis and processing.

Journal ArticleDOI
TL;DR: In this article, a high-resolution apparatus for the study of elastic and inelastic scattering of thermal helium atoms from crystal surfaces is presented, which allows for a nondestructive nearly exhaustive characterization of the thermodynamics, structure, and dynami...
Abstract: A high‐resolution apparatus designed for the study of elastic and inelastic scattering of thermal helium atoms from crystal surfaces is presented. The highly expanded He nozzle beam has an energy spread ΔE/E of about 1.4% and is collimated to 0.2°. The angle subtended by the detector opening as seen from the sample is also 0.2°. Beam intensities as low as 10−6 of the specular beam intensity from a low‐temperature clean Pt(111) surface are detectable. Pseudorandom chopping with a resolution of 2.5 μs (flight path 790 mm) is used for time‐of‐flight (TOF) analysis of the scattered helium. The base pressure in the sample chamber is in the low 10−11 mbar. The capabilities of the apparatus are demonstrated for physisorbed Xe adlayers on Pt(111). The results presented are obtained by using He scattering in various modes: coherent inelastic, coherent elastic, and incoherent (diffuse) elastic. This technique allows for a nondestructive nearly exhaustive characterization of the thermodynamics, structure, and dynami...

Journal ArticleDOI
TL;DR: In this paper, the authors measured the time response of the classical photomultipliers 56DUVP and XP2020 in time correlated single-photon counting at several wavelengths between 257 and 630 nm with a best result of 235 ps FWHM.
Abstract: The time response of the classical photomultipliers 56DUVP and XP2020 in time‐correlated single‐photon counting has been measured at several wavelengths between 257 and 630 nm with a best result of 235 ps FWHM. Also, the time response has been measured of the microchannel‐plate photomultiplier R1564U‐01 and the crossed‐field photomultiplier VPM‐154M at the two wavelengths 273 and 546 nm. The best result was 47 ps at λ=273 nm. The use of a fast constant‐fraction discriminator was crucial. The origin of after pulses in the time response curve of photomultipliers is discussed.

Journal ArticleDOI
TL;DR: In this paper, an instrument was developed to spectroscopically measure ion temperature and rotation speed spatial profiles in neutral-beam-heated tokamak plasmas.
Abstract: An instrument has been developed to spectroscopically measure ion temperature and rotation speed spatial profiles in neutral‐beam‐heated tokamak plasmas. Up to eight spatial chords of data can be obtained for 32 time slices during a single discharge with selectable resolution times as short as 2 ms. A special arrangement of fiber optics allows simultaneous data acquisition from all chords without the use of scanning mirrors or other moving parts. Techniques used to analyze the data from the system are discussed.