bluuebunny/crossref_metadata_2025 huggingface dataset:
Scanning polarimeter for measurement of the poloidal magnetic field in a tokamak
Authors: Wróblewski D. , Huang L. K. , Moos H. W.
Published: July 2002

The internal magnetic field in a magnetically confined plasma may be deduced from the analysis of circular polarization of spectral lines emitted by the plasma. The theory of the measurement and a detailed design of a polarimeter constructed to measure the poloidal field profile in the Texas Experimental Tokamak (TEXT) are presented. The instrument measures the difference between left-hand and right-hand circularly polarized line profiles, a quantity directly proportional to the magnetic field component in the direction of observation. The high throughput of the Fabry–Perot interferometer employed in this design, combined with efficient light-collecting optics and lock-in detection of the polarization signal, allows measurement of the fractional circular polarization of the magnetic dipole line Ti xvii 3834 Å with an accuracy on the order of 10−3. The line-of-sight averaged poloidal field is determined with uncertainty as small as 50 G. The line emission used in the present measurement is not well localized in the plasma, necessitating the use of a spatial inversion procedure to obtain the local values of the field.
Design and performance of an UHV beamline to produce low and hyperthermal energy ion beams
Authors: Adler D. L. , Cooper B. H.
Published: July 2002

We have constructed and tested an UHV beamline to produce beams of alkali metal and noble gas ions over the energy range <20 eV to 10 keV with energy resolution ΔE/E of 1% or better. At the sample position, we have attained tens of nanoamps of current for keV energy beams in a 1–2-mm beam spot with about ±1° angular divergence, and nanoamps of current at 25 eV in a 4-mm beam spot with ±2° angular divergence. By applying Liouville’s theorem to the beam’s emittance and using waist-to-waist transport through the beam optics, the current on the sample is maximized while limiting the spot size and angular divergence. To achieve useful current at the lowest energies, special attention was paid to minimizing space-charge effects. Beam emittances measured at the sample position are consistent with Liouville’s theorem. Equations for waist-to-waist transport are derived in the Appendix.
Measurements with vertically viewing charge exchange analyzers during ion cyclotron range of frequencies heating in TFTR
Authors: Kaita R. , Hammett G. W. , Gammel G. , Goldston R. J. , Medley S. S. , Scott S. D. , Young K. M.
Published: July 2002

The utility of charge exchange neutral particle analyzers for studying energetic ion distributions in high-temperature plasmas has been demonstrated in a variety of tokamak experiments. Power deposition profiles have been estimated in the Princeton large torus (PLT) from particle measurements as a function of energy and angle during heating in the ion cyclotron range of frequencies (ICRF) and extensive studies of this heating mode are planned for the upcoming operational period in the tokamak fusion test reactor (TFTR). Unlike the horizontally scanning analyzer on PLT, the TFTR system consists of vertical sightlines intersecting a poloidal cross section of the plasma. A bounce-averaged Fokker–Planck program, which includes a quasilinear operator to calculate ICRF-generated energetic ions, is used to simulate the charge exchange flux expected during fundamental hydrogen heating. These sightlines also cross the trajectory of a diagnostic neutral beam (DNB), and it may be possible to observe the fast ion tail during 3He minority heating, if the DNB is operated in helium for double charge exchange neutralization.
Poloidal field measurements using laser-enhanced attenuation of an energetic lithium beam
Authors: West W. P. , Thomas D. M. , Thomas M. P.
Published: July 2002

The current density profile diagnostic system presently operating on the Texas Experimental Tokamak (TEXT) employs a cw dye laser system to induce fluorescence in a lithium beam injected into the discharge. Systematic effects due to the finite lifetime of the excited state and enhancement of the beam attenuation during laser excitation limit the application of this technique to plasma densities ≲1×1013 cm−3. Laser enhancement of beam attenuation results from the large collisional ionization cross sections of the excited Li 2P state compared to the 2S ground state. This effect is exploited in a new diagnostic scheme which uses the polarization modulation of the present technique, but monitors the enhanced attenuation as opposed to the fluorescence. Detailed modeling indicates that a collinear beams configuration, with a short pulse laser and time-of-flight signal analysis, will provide a measurement of the complete poloidal field profile on TEXT at plasma densities up to 3×1013 cm−3 with 16-ms averaging times.
Corrections to charge exchange spectroscopic measurements in TFTR due to energy-dependent excitation rates
Authors: Howell R. B. , Fonck R. J. , Knize R. J. , Jaehnig K. P.
Published: July 2002

The use of charge exchange spectroscopy to determine plasma rotation speeds and ion temperature is complicated by the energy dependence of the excitation cross sections. The Doppler-broadened spectral line shape is distorted by the relative velocity between the neutral hydrogen atoms of the injected beam and impurity ions. The asymmetric nature of the energy dependence of this cross section causes a nonmotional shift of the line center and a nonthermal change in the linewidth. These effects vary with the angles between the beam direction, rotation velocity direction, and direction of the viewing sightline. When viewing two neutral beams at different angles on TFTR, the two measurements of vφ(r) show discrepancies of about 20%–30% with each other. The calculation of the spectral intensity profiles using the available excitation rates overcorrects these discrepancies and indicates the need for better excitation coefficients.
Nanoradian sensitivity Kerr effect apparatus
Authors: Shelton D. P. , Cameron Ruth E.
Published: July 2002

The shot-noise limit to the sensitivity of ellipsometric phase shift measurements with a laser beam power of a few mW is of the order of 10−9 rad. An apparatus is described that realizes shot-noise-limited performance for dc Kerr effect birefringence measurements.
Multifunctional pulse sequence generator for pulse NMR
Authors: Wang Dongsheng
Published: July 2002

A new multifunctional pulse sequence generator has been designed and constructed. It can conveniently generate various pulse sequences used in nuclear-magnetic resonance (NMR) to measure the spin-lattice relaxation time T1, the spin–spin relaxation time T2, and the spin-locking relaxation time T1 ρ. It can also be used in pulse Fourier transform NMR and double resonance. The intervals of pulses can increase automatically with sequence repetitions and the generator can be used in two-dimensional spectrum measurement and spin-density imaging research. The sequences can be generated through four different triggering methods and there are two synchronous pulse outputs and fifteen auxiliary pulse outputs, so the generator can be conveniently interfaced with a computer or other instruments. The circuitry, functions, and features of the generator are described in this article.
A simple method of impurity injection into tokamak plasmas
Authors: Hildebrandt D. , Bakos J. S. , Petravich G. , Badalec H. , Jakubka K.
Published: July 2002

Injection of test impurities into the edge plasma of tokamak discharges by erosion probes containing these impurities is described. By applying a short bias pulse to the probe inserted into the sol-plasma, the plasma density and temperature at the probe location can be deduced and the time of injection during the discharge can be controlled. By locating the probe at an appropriate position it is possible to release defined quantities of the material and to influence the fraction which penetrates into the core plasma. The injection of Li into hydrogen discharges of the small-sized tokamaks Castor and MT-1 is demonstrated. The nature of the main erosion process (ion sputtering or arcing) has been found to depend on the radial position of the probe and the probe potential. The lithium amount released by sputtering is determined, while in the case of arcing only an estimate can be given. The temporal evolution and the radial penetration of the Li influx into the plasma have been observed by monitoring the neutral emission line using a grating spectrometer and a CCD camera. In addition, Li transported through the plasma was collected on solid samples. An estimate is given on the fraction of the impurity efflux from the core plasma which is collected on the samples.
Laser beat mapping with a Nipkow disk
Authors: Giusfredi G. , Hostetler R.
Published: July 2002

We describe a simple system displaying the intensity profile of specific frequency components of a pulsating light beam. This device employs a spiral pattern of small apertures on a rotating wheel (Nipkow disk), which provides a two-dimensional scanning of the beam. A phototube ac-coupled with standard one-channel electronics is used to analyze the light sampled by the wheel. These elements allow for homodyne, heterodyne, and phase-detection techniques yielding pictures of the whole mode-beating profile on an oscilloscope monitor. A demonstration application to the study of the transverse modes of a single-line argon laser is given.
Randomization of the start pulse in time-of-arrival correlators
Authors: Basano L. , Ottonello P.
Published: July 2002

Correlators based on the measurement of the time of arrival of photoelectron pulses are subject to a start-pulse bias related to the method according to which the pulse that triggers the count sequence is selected. For the bias to be negligible, the count rate must be low or the coherence time of the fluctuating signal must be short. In this work we point out a new start-pulse selection method that considerably broadens the useful range of time-of-arrival correlators. Results of tests conducted on laser light scattered by a ground-glass disk are reported.
Using correlated photometers to measure the average velocity of pyrotechnic exhaust particles
Authors: Cohen D. L.
Published: July 2002

The problem of measuring the average velocity of exhaust particles coming from vacuum-burning flares is solved by mounting two narrow-field-of-view photometers at two different positions downstream from the burning flare. The naturally occurring, high-frequency fluctuations in the flare’s unstable burning rate send hot, luminous particles down the exhaust plume in clumps rather than a smooth distribution; by cross-correlating fluctuations in the two photometer signals, we can measure the exhaust particles’ time of flight and thus their average velocity. These measurements are confirmed using an approximate formula connecting the particle velocity to the infrared radiance emitted by the flare’s exhaust plume.
A coaxial electrostatic lens design for a low-energy electron-spin detector
Authors: Woods J. , Tobise M. , O’Handley R. C.
Published: July 2002

A novel coaxial electrostatic lens is employed to focus low-energy electrons through a thin-film low-energy electron-spin polarization analyzer. The coaxial lens consists of an axial electrode suspended through a cylinder or an aperture. Electron transmission is measured as a function of the voltage applied to the central and outer conductors. Surface magnetic hysteresis loops are obtained by plotting the spin polarization of secondary electrons emitted from a ferromagnetic surface as a function of the applied magnetic field.
High-pressure, low-temperature, demountable, compact, and simple seal
Authors: Lee Sam-Hyeon
Published: July 2002

A new seal using a circular ring of D-shaped cross section wrapped with Teflon tape is described. This demountable and space-saving seal works with little initial tightening even for large bore cylinders. No prepressurization is required. The seal works at least from 10−5 mm Hg vacuum to 2 kbar and at temperatures from 4 to 300 K.
Secondary electron multiplier for a retarding field energy analyzer with coaxial cylindrical electrodes
Authors: Inaba Seiki
Published: July 2002

A secondary electron multiplier has been developed for a retarding field energy analyzer with coaxial cylindrical electrodes. In this multiplier, whole electrons emitted at right angles for the incident beam can be multiplied.
A compact thermal lithium-beam source using a solid Al/Li alloy for Li sublimation
Authors: Schorn R. P. , Hintz E. , Musso S. , Schweer B.
Published: July 2002

Thermal lithium beams are widely used in physics for different purposes. To overcome certain disadvantages of conventional liquid-lithium ovens concerning handling, conditioning, and lifetime of the Li filling, a solid Li-evaporation device was constructed. An aluminum-based alloy, which contains about 9 at. % of lithium, is employed. The oven can easily be mounted in any position, and Li atoms can be injected in any desired direction. The parameters of the beam (axial and radial flux profiles) have been measured as a function of temperature and time. At a distance of 100 mm from the oven, Li flux densities of more than 2×1014 cm−2 s−1 have been achieved, lasting for more than 16 days of continued operation. The full beam divergence at half maximum is 8°. As a typical application of the device in plasma diagnostics, radial electron density profiles have been measured in the scrape-off layer of the TEXTOR tokamak.
Stable current supply with protection circuits for a lead-salt laser diode
Authors: Cafferty Michael S. , Thompson Eric D.
Published: July 2002

A high-stability, high-level (1.3-A) current source circuit of modest cost is described, suitable for powering lead-salt laser diodes or other semiconductor devices, especially expensive, delicate, or rare experimental samples requiring the protection features this current supply offers. The supply features circuits to shut off current to the laser or other device smoothly and quickly (in less than 90 μs) if there is an overvoltage, overcurrent, main battery supply failure, or elevated temperature condition, to protect the laser or device from any of these potentially damaging conditions. Spectral data of a lead-salt laser emitting in the 1840-cm−1 region are presented to demonstrate the use of the current supply.
Surfactants in Si(111) homoepitaxy
Authors: Horn-von Hoegen M. , Falta J. , Copel M. , Tromp R. M.
Published: July 2002

Si epitaxy is strongly affected by the presence of an adsorbate (surfactant). We have examined both film quality and dopant incorporation in homoepitaxy for Sb, As, and Ga terminated Si(111). The efficency of site exchange between Si and adsorbate depends sensitively on binding energy and binding geometry of the adsorbate. For a weakly bound adsorbate (Ga or Sb), there is no inhibition of epitaxy, but a strongly bound adsorbate (As) kinetically inhibits growth.
Boxcar photography
Authors: Greene G. J. , Cutsogeorge G. , Ono M.
Published: July 2002

A simple, inexpensive diagnostic has been developed for time-resolved imaging of repetitive self-luminescent phenomena. An electro-optic birefringent ceramic shutter is employed to perform photographic sampling and has demonstrated time resolution of 60 μs. Photographic film was used for image detection in this system, and methods of image enhancement in the presence of background light from a finite-contrast shutter are discussed. The system has been applied to the study of plasma evolution in the CDX plasma confinement device.
LSU Center for Advanced Microstructures and Devices
Authors: Craft B. C. , Findley A. M. , Findley G. L. , McGlynn S. P. , Scott J. D. , Watson F. H.
Published: July 2002

The LSU Center for Advanced Microstructures and Devices (CAMD) is a DOE-funded materials science and engineering laboratory which will include a normal-conducting compact electron storage ring optimized for the production of soft x rays. The focus of CAMD is the fundamental study of processing and analysis technologies—including x-ray lithography—important to microstructure fabrication and electronic device development. Design details of the storage ring, which is being acquired commercially, are presented in this article.
Synchrotron radiation stimulated semiconductor processes: Chemical vapor deposition and etching
Authors: Urisu Tsuneo , Kyuragi Hakaru , Utsumi Yuichi , Takahashi Jun-ichi , Kitamura Mamoru
Published: July 2002

A synchrotron radiation beamline and reaction chamber were constructed for the study of synchrotron radiation excited photochemical reactions, especially for their application to semiconductor processes. Characteristics of this experiment and experimental results with chemical vapor deposition and etching in this beamline are described. The potential of this new application is discussed.
Role of misfit dislocations on pseudomorphic high electron mobility transistors
Authors: Meshkinpour M. , Goorsky M. S. , Chu G. , Streit D. C. , Block T. R. , Wojtowicz M.
Published: July 2002

The relationship between structural defects and device performance of In0.21Ga0.79As/(Al,Ga)As high electron mobility transistors with different In0.21Ga0.79As channel thicknesses (75–300 Å) was analyzed. Using triple axis x-ray diffraction and transmission electron microscopy, we determined that the presence of misfit dislocations along only one of the 〈110〉 directions did not impair device performance. In fact, the sample with the highest cutoff frequency possessed the misfit dislocations along one 〈110〉 direction. However, for thicker samples, with an orthogonal array of misfit dislocations, the device parameters were significantly degraded. We also determined that x-ray diffuse scattering correlates strongly with device performance, making this nondestructive technique useful for device performance evaluation.
Upgrades and recent performance of the grating/crystal monochromator
Authors: Rife J. C. , Sadeghi H. R. , Hunter W. R.
Published: July 2002

Upgrades to the 5 to 2000 eV grating/crystal monochromator are reported. Operating equations are outlined. Paraboloidal mirror quality, mechanical and encoding systems, in situ diffraction element exchange, and diffraction grating performance are discussed.
Double-tilt wide-aperture two-crystal monochromator for x-ray absorption spectroscopy (abstract)
Authors: Diakun G. P. , Dobson B. R. , Greaves G. N. , Moore P. R. , Hart M.
Published: July 2002

A water-cooled double-crystal monochromator for x-ray absorption spectroscopy is described. It has a wide aperture (3 mrad) and is attached to a linear slide through a twin axis goniometer to a large Huber rotary table for accurate alignment of the crystal planes to the incident beam. The center of rotation of the goniometers has been chosen as the geometric center at the surface of the first crystal. The linear slide adjusts the monochromator vertically so that the axis of rotation intercepts the synchrotron radiation. The two goniometers provide the monochromator with a transverse and longitudinal tilt with respect to the x-ray beam. Water cooling is incorporated in the first crystal to dissipate the expected heat loading of 120 W from the SRS wiggler. The second crystal is supported by three Inchworms which control the yaw and tilt. Then adjustments are required to optimize spectral purity across the beam alignment and harmonic rejection, respectively, with respect to the first crystal. The performance of the monochromator is discussed.
Characterization of undulator radiation from a high-field BL-16 multipole wiggler/undulator at the Photon Factory
Authors: Maezawa Hideki , Muramatsu Yasuji , Shioya Tatsuro , Yamamoto Shigeru , Kitamura Hideo
Published: July 2002

Spectral characterization was made on undulator radiation from a 26-period high-field permanent magnet multipole wiggler/undulator at the 2.5-GeV Photon Factory storage ring. In an undulator mode of a weaker field version of the insertion device, the K parameter was tuned up to 5.8. Absolute spectral measurement showed source brightness of the first harmonic peak in the order of 1015 photons/s mrad2 100 mA 0.1% bandwidth over the full tunable range of the first peak from 40 to 400 eV. As for the higher harmonics, spectral profile, the peak brightness, and quasimonochromaticity were obtained in this transition region where the K parameter increased beyond unity.
A substrate temperature measurement system for use during rf diode sputtering
Authors: Snyder J. E. , Kryder M. H.
Published: July 2002

A substrate temperature measurement system is described, which has proved useful for measuring substrate temperature in situ in an rf diode sputtering system. This temperature measurement system mimics the true deposition materials, geometry, and thermal contact as much as possible. The measurement electronics are quite insensitive to rf interference and allow for cancellation of lead resistance and thermoelectric voltages.
Transportation system for 11CO2
Authors: McKinney C. J. , Fares Y. , Musser R. L. , Goeschl J. D. , Magnuson C. E. , Need J. L.
Published: July 2002

A transportation system for safe movement of up to 1.0 Ci of 11CO2 from a production facility to an experimental facility 800 m away is described. This development allows plant physiological tracer kinetic studies to be performed in a remote laboratory location which is more suitable for plant growth. It also has the potential to allow field studies to be performed in nearby outdoor field plots.
Minimization of discrimination jitter in time-correlated single photon counting
Authors: Anfinrud Philip A. , Struve Walter S.
Published: July 2002

Instrument function widths in time-correlated single photon counting are minimized by adapting a commercial constant-fraction discriminator for essentially jitter-free processing of anode pulses from a Hamamatsu R1564U microchannel plate photomultiplier. This modification yields an instrument function with 47 ps FWHM, limited chiefly by photomultiplier transit-time spread.
An automated imaging and control system for the continuous determination of size and relative mass of single compositionally dynamic droplets
Authors: Maloney D. J. , Fasching G. E. , Lawson L. O. , Spann J. F.
Published: July 2002

A novel droplet imaging system (DIS) has been developed which, when interfaced with an electrodynamic balance (EDB), offers unique capabilities for characterizing size, mass, density, and composition of single, compositionally dynamic droplets. The DIS employs a standard closed-circuit video camera as a droplet sensor. Real-time hardware image processing techniques are employed to extract cross-sectional area and position information from the video signals. The position information is used to generate a control signal which is proportional to the droplet mass. The DIS capabilities are demonstrated for evaporating water and coal-water slurry droplets. The results presented clearly demonstrate that this system can be applied to easily detect compositional variations from one droplet to another. Accurate estimates of droplet composition can be obtained with little knowledge of the starting composition. The DIS has a wide range of applications and is particularly valuable when applied to the study of multicomponent droplets where the physical and chemical behavior often times depends on the droplet composition.
A tilted-plate capacitance displacement sensor
Authors: Genossar Jan , Steinitz Michael
Published: July 2002

We have developed a capacitance displacement sensor whose novel design greatly simplifies its construction and use. It is small, compact, extremely simple, and capable of angstrom resolution. It can be used with samples of any shape, size, or dielectric constant. One variant of the design allows its use at high temperatures, where such resolution has been unattainable until now. It may also be used to detect small changes in angle.
Multiple reflection high-energy electron diffraction beam intensity measurement system
Authors: Resh J. S. , Jamison K. D. , Strozier J. , Ignatiev A.
Published: July 2002

A video-based analysis system for reflection high-energy electron diffraction (RHEED) is described which simultaneously measures the intensities and profiles of multiple diffraction beams. This system is used to record real-time RHEED intensity oscillations for layer-by-layer epitaxial growth. Fast Fourier transform analysis of the oscillation data is used to directly determine the growth rate and to accurately obtain phase information about the oscillations. This system is demonstrated and compared to other methods of recording RHEED oscillation data.
The effect of space charge on beams extracted from the room temperature electron cyclotron resonance ion source
Authors: Xie Z. Q. , Antaya T. A.
Published: July 2002

We have obtained excellent agreement between BEAM-3D calculations and beam profile and emittance measurements of the total extracted beam from the room temperature electron cyclotron resonance (RTECR), when a low degree of beam neutralization is assumed in the calculations, as will be presented in this paper. The beam envelope has approximately a quadratic dependence on drift distance, and space-charge effects dominate the early beam formation and beamline optics matching process.
A technique for measurement of electrical potential of a balloon-borne gondola
Authors: Narayan A. , Acharya Y. B. , Gupta S. P.
Published: July 2002

During electrical conductivity measurements using balloon-borne probes, the gondola was observed to acquire an electrical potential of the order of a few tens of volts. Such an effect was found to occur mainly during balloon ascent and also to a lesser extent during balloon float and descent periods. A technique has been developed at the Physical Research Laboratory (Ahmedabad, India) for the direct measurement of potential acquired by the gondola during the course of its flight. Such measurement has relevance when we interpret the data obtained from the balloon-borne conductivity and electric field probes.
An amplifier for use with large-area photodiodes
Authors: Dyer G. R. , Uckan T.
Published: July 2002

We describe a high-gain (∼107) amplifier for use with large-area silicon photodiodes for monitoring the intensity of plasma light from fusion experiments. To achieve the necessary gain without saturating the output signal, the amplifier design incorporates a bootstrap technique and capacitive coupling between amplifier stages. This design eliminates voltage offset at the amplifier output due to detector leakage, while retaining desirable low-frequency response characteristics.
New cross-beam technique for charge transfer cross section measurement using a pulsed ion beam produced by laser photoionization
Authors: Sakabe Shuji , Izawa Yasukazu , Hashida Masaki , Naka Toshihiro , Sudo Tomokazu , Mochizuki Takayasu , Yamanaka Tatsuhiko , Nakai Sadao , Yamanaka Chiyoe
Published: July 2002

A new cross-beam technique has been developed to measure the charge transfer cross sections of metallic atoms which have not been experimentally investigated previously. Two high-density atomic beams were produced by the vaporization of a metal heated with an electron beam gun. A pulsed ion beam produced from one atomic beam by laser photoionization was collided with another atomic beam. By colliding the pulsed ion beam produced in this manner with the second atomic beam, the apparatus was simplified in comparison with conventional one; additionally, only a single pulsed laser shot is required to obtain the data necessary to determine a cross section. By using repetitive laser pulses it is possible to acquire in a short time a more accurate cross section as a function of impact energy. The apparatus was successfully applied to the measurement of the charge transfer cross section of gadolinium, a metallic atom with a relatively high ionization potential and high melting point.
Constraints on escaping alpha particle detectors for ignited tokamaks
Authors: Zweben S. J. , Boivin R. , Liew S. L. , Owens D. K. , Strachan J. D. , Ulrickson M.
Published: July 2002

Several modifications to existing escaping alpha scintillation detectors in TFTR will be needed before they could be used on ignited tokamaks such as CIT or ITER. The main difficulties are the large heat flux at the desired detector locations and the accumulated radiation damage to the scintillator itself. Constraints imposed by these problems can probably be overcome by using remotely movable (and removable) detectors.
DIII-D physics analysis database
Authors: Bramson G. , Schissel D. P. , DeBoo J. C. , St. John H.
Published: July 2002

Since June 1986 the DIII-D tokamak has had over 16 000 discharges accumulating more than 250 Gbytes of raw data (currently over 30 Mbytes per discharge). The centralized DIII-D databases and the associated support software described earlier provide the means to extract, analyze, store, and display reduced sets of data for specific physics issues. The confinement, stability, transition, and cleanliness databases consist of more than 7500 records of basic reduced diagnostic data datasets. Each database record corresponds to a specific snapshot in time for a selected discharge. Recently some profile datasets have been implemented. Diagnostic data are fit by a cubic spline or a parabola by the in-house energy code to provide density, temperature, radiated power, effective charge (Zeff), and rotation velocity profiles. These fits are stored in the profile datasets which are inputs for the onetwo code which computes transport data.
Ultra high vacuum compatible metal ion beam surface modification system
Authors: Mori Yuzo , Wang Hui , Endo Katsuyoshi , Yamauchi Kazuto , Ide Takashi , Goto Hidekazu
Published: July 2002

A high current ion system for surface modification has been developed. It consists of a liquid metal ion source, a focusing lens system, deflection plates, a mass separator, and a deceleration electrode system. It can produce a high purity metal ion beam with an energy in the range of 10 eV to 10 keV and ion current up to 20 μA in a vacuum as low as 10−9 Torr.
Scattering of radiation by alpha particle induced fluctuations
Authors: Aamodt R. E. , Russell D. A.
Published: July 2002

Motivated by the possibility of diagnosing alpha particles in a burning fusion plasma by scattering radiation off of the fluctuations that they induce, we model the linear Maxwell–Vlasov theory of the scattering in a homogeneous plasma consisting of electrons, deuterium ions, and alpha particles. The fluctuating electric field is driven by the undressed particle current so that the problem of finding the power spectrum of the scattered radiation amounts to solving a system of linear algebraic equations ‘‘driven’’ by the power spectrum of the undressed current density fluctuations; a coefficient matrix contains the dielectric tensor. Scattering off of field fluctuations is included in the model in addition to the usual scattering off of electron density fluctuations. The model is solved numerically and we compare our results to earlier studies that neglected scattering off field fluctuations and assumed electrostatic shielding.
Confined alpha particle diagnostics in JT-60U
Authors: Kusama Y. , Tobita K. , Itoh T. , Nemoto M. , Tsukahara Y. , Kimura H. , Takeuchi H.
Published: July 2002

In reactor-grade tokamaks, it is important to investigate confinement properties of alpha particles. A double charge-exchange method using a high-energy probing beam is considered to be the most reliable one in diagnostic methods proposed for the measurement. In JT-60U, an alpha particle production experiment by D-3He ICRF heating will be performed to study the behavior of fusion product alphas. The alpha particle measurement is planned using a helium diagnostic beam (200 keV) and a mass-resolved neutral particle energy analyzer. The expected flux and spectral shape were evaluated by taking into account multistep ionization of helium beam atoms and neutralized alphas. The beam energy is lower than desirable for measuring fast confined alphas near the birth energy. However, by using the beam system, it has been found from the evaluation that we can investigate the confinement properties of fusion product alphas from the spectral shape. And also such a system using a present-day He beam is useful to diagnose behavior of confined alphas in reactor-grade tokamak such as ITER.
Calibration of the neutron yield measurement system on FTU tokamak (abstract)
Authors: Angelone M. , Batistoni P. , Bertalot L. , Esposito B. , Martone M. , Podda S. , Pillon M. , Rapisarda M. , Rollet S.
Published: July 2002

This paper describes the in situ calibration of the BF3 detector system used for measuring the total neutron yield from the FTU tokamak. Two different neutron sources, 252Cf (7.23×107 n/s) and AmBe (2.18×106 n/s), were used. The calibration was performed by placing the two sources at different radial and toroidal positions inside the vacuum vessel. Data on the response of the different detectors as a function of the source position are presented. The effect of the different spectra of the neutron sources is pointed out. Finally, the procedure for the computation of the relationship between the local flux at the detectors and the total neutron yield from an extended plasma is presented.
Development of holographic interferometry techniques for application to PBFA-II ion source and target experiments (abstract)
Authors: Noack D. D. , Perry F. C.
Published: July 2002

We report on a second-generation pulsed laser holographic interferometry system (PLHIS) and its applications to the recording and measurement of light-ion diode and target plasmas on the Particle Beam Fusion Accelerator (PBFA II). Known as the Optical Diagnostics System (ODS), it combines an actively mode-locked and Q-switched, 0.15 ns, pulsed Nd:YAG laser with a 76 m pathlength Mach–Zehnder interferometer. This produces multiple, time-resolved holographic interferograms and shadowgrams from which we can obtain density, velocity, and qualitative information on diode and target plasmas. Background information on the first-generation PLHIS is presented to show the evolution of this diagnostic. The development in the laboratory and installation of the ODS at PBFA II is described, emphasizing the mechanical, optical, electrical, and safety engineering aspects. Included are some of the unique optical engineering problems with regard to current and proposed experiments as well as the limitations of this type of ‘‘long stand-off’’ diagnostic system. This work was supported by U. S. DOE contract No. DE-AC04-76DP00789.
Collector probe measurement of fusion tritons in TFTR
Authors: Bastasz Robert , Buchenauer Dean , Zweben Stewart
Published: July 2002

The production of fusion tritons in the Tokamak Fusion Test Reactor (TFTR) has been measured using Si collector probes. Four probes at two toroidal and two poloidal positions were exposed to about 1200 plasma discharges over a six month period and subsequently analyzed using high-sensitivity secondary-ion mass spectrometry (SIMS). SIMS depth profiles show that the incident tritons had an average projected range of about 10 μm in the Si, which is characteristic of 1 MeV tritons produced by DD fusion. The triton fluences observed at the various sample locations ranged from 5×1011 to 5×1012 T/cm2. First-orbit loss code calculations, scaled by the measured total neutron production during the exposure period, were used to predict the expected triton fluence to the samples. The predicted and observed triton fluences agree to within an order of magnitude.
Compact and wide-range charge-exchange neutral particle analyzer with an acceleration tube
Authors: Kusama Y. , Nemoto M. , Tobita K. , Takeuchi H.
Published: July 2002

An E//B type neutral particle analyzer with an acceleration tube between a stripping cell and a deflection magnet has been developed to measure ion energy distributions in a wide energy range from thermal ions to fast ions up to several hundred kiloelectron volts simultaneously without making the analyzer size large. In the acceleration tube, ions are accelerated up to the detectable energy before coming into the deflection magnetic field. The acceleration method enables us to detect low-energy ions even for a strong deflection magnetic field to measure high-energy ions. Calibration experiments confirmed that ions were well accelerated according to expectation without degrading the abilities of the analyzer. The energy dynamic range Emax/Emin was improved up to 100 by the acceleration method. Using the analyzer, ion energy distributions have been measured in various heating experiments of JT-60.
High-fluence large-area MeV proton-beam diagnostics
Authors: Young F. C. , Stephanakis S. J. , Scherrer V. E. , Mosher D. , Richter S. H.
Published: July 2002

The spatial distribution of intense MeV pulsed proton beams over 100 cm2 area is measured with two techniques. An array of carbon-activation samples gives fluences of 100–400 J/cm2 with 1–2 cm resolution. Continuous distributions with 3–4 mm resolution are obtained by imaging proton-induced Al K-line x rays.
A 15 MeV proton diagnostic for DIII-D
Authors: Duong Hau H. , Heidbrink W. W.
Published: July 2002

A 15 MeV proton diagnostic that is patterned after the ASDEX proton probe is presently being fabricated for the DIII-D tokamak. A bellows assembly inserts a silicon detector into the vacuum for plasma operation and retracts it for baking. The detector preamplifier is situated in a reentrant tube (at atmosphere) beside the detector; electrically, the whole assembly is referenced to vessel potential. Orbit calculations in realistic magnetic field geometries predict a proton detection efficiency of O(10−7). The diagnostic will be used for burnup studies at high β and particle transport studies in the H mode.
Fast multiline low-Z impurity imaging diagnostic for fluctuation and particle confinement studies
Authors: Boody F. P. , Prelas M. A.
Published: July 2002

A system for imaging complete tokamak edge cross sections using radiation from intrinsic low-Z impurities, such as carbon, with a frequency response of 500 kHz and a spatial resolution of 1–4 cm (depending on the thickness of the radiating region) is being developed. The noise level is determined by the electronics and is ≤2% for the full 500 kHz bandwidth and ≤1% for a 100 kHz subset of that bandwidth. Photon noise is 0.3% for the full 500 kHz bandwidth. This diagnostic can be used for studying fluctuations in Prad(λ), Γz, and Te. Additionally it may be useful for studying marfes and detached plasmas, transport and oscillations during pellet injection, and as a fast disruption precursor monitor.
Cyclotron maser radiation from planetary magnetospheres (abstract)
Authors: Gurnett Donald A.
Published: July 2002

For over 20 years it has been known that the Earth is an intense radio emitter in the frequency range from about 100 to 500 kHz. This radiation is generated at altitudes of about one Earth radius over the northern and southern auroral zones, and is closely correlated with the occurrence of discrete auroral arcs. During active periods, the total radiated power is very large, averaging from 107 to 108 W, with peaks possibly as high as 109 W. It is now widely believed that this radiation is generated by a process known as a cyclotron maser instability. This process involves a Doppler-shifted cyclotron resonance interaction between the free-space R-X mode and the auroral electrons. The most recent data, from the Viking satellite, indicate that the free-energy source driving the instability is produced by electrons trapped by the magnetic mirror force and the electric field response for the auroral particle acceleration. In addition to the Earth, it is now known that four other planetary magnetospheres, at Jupiter, Saturn, Uranus, and Neptune, all have similar types of radio emissions. Also, it has been suggested that certain types of microwave emissions from the Sun, and from binary star systems may also be produced by this same mechanism. Thus, in addition to being a relatively new, interesting plasma physics phenomenon, the cyclotron maser mechanism appears to be important for a broad range of astronomical radio sources.
UCLA FIR diagnostic systems on TEXT and developments for TEXT Upgrade (abstract)
Authors: Peebles W. A. , Brower D. L. , Burns S. , Luhmann N. C. , Yu C. X.
Published: July 2002

A multipurpose multiview far-infrared diagnostic system is being designed and constructed for the TEXT Upgrade. The system’s capabilities, designed to enhance the applications of the present FIR system on TEXT, will include two-view interferometry, polarimetry, and collective scattering in order to measure the plasma density profile, current profile, and density fluctuation distribution. The interferometer/polarimeter system will possess high spatial (Δx=1.5 cm) and high-density (≤5×1010 cm−3) resolution. Tomographic reconstruction techniques will be employed to investigate both the equilibrium and perturbed profiles of plasma density. This represents an extension of the present work on TEXT where MHD effects such as sawteeth, Mirnov oscillations, and disruptions have been studied. Two-view multichannel collective scattering (1≤k⊥≤20 cm−1) will allow the kr and kθ spectra to be measured simultaneously. Heterodyne detection permits the wave propagation direction and multiple modes to be resolved unambiguously. Cross correlation of signals from each view may produce significant improvement in the scattering system spatial resolution. A reflectometry system will also be installed to study fluctuations and provide more localized measurement. This work was supported by U.S. DOE contract No. DE-FG03-86ER-53225 and DE-FG03-88ER-53267.
Broadband reflectometry for the density profile and fluctuation measurements in the JT-60 tokamak (abstract)
Authors: Fukuda T. , Nagashima K. , Konoshima S. , Haraguchi K. , Takahashi T. , Nagashima A. , Matoba T.
Published: July 2002

A broadband reflectometric system in O-mode operation has been developed for the density profile determination, MHD and turbulent fluctuation measurement, and evaluation of the particle diffusion coefficient in the JT-60 tokamak. For the profile determination, full Ka-Q band frequencies of BWOs have been swept in 750 μs, in order to minimize the effect of Doppler shift due to the fluctuation of reflection layers. The heterodyne fixed-frequency reflectometer has unveiled its effectiveness to probe MHD activities, diagnosing the m=1 tearing mode oscillations. It has also enabled the observation of the dramatic suppression of edge plasma density fluctuations at the L to H-mode transition in the LHCD limiter plasma. Furthermore, the propagation delay of density pulses has been observed by different fixed-frequency channels during a series of sawteeth, from which the particle diffusion coefficient was evaluated, with a newly proposed method applicable to fully diffusive plasmas.
Arcjet plasma plume effect on a microwave reflector antenna
Authors: Birkner B. W. , Hallock G. A. , Kim H. , Ling H.
Published: July 2002

A configuration is described to measure the effect of the plasma produced by an arcjet thruster on a reflector antenna. The diagnostic consists of a small movable rf probe coupled to a Hewlett–Packard 8510 network analyzer. Because the perturbation is expected to be small (<10° phase shift), wall reflections are an important consideration. To minimize their effect we use Fourier transform gating techniques.
Advances in laser-pumped helium magnetometers for space applications (abstract)
Authors: Slocum R. E.
Published: July 2002

Recently tunable lasers have been developed which are suitable for use as pumping sources in optically pumped helium magnetometers. This advance in laser technology is leading to a new generation of improved laser-pumped resonance magnetometers for use in geophysical and space applications. The history of optically pumped resonance magnetometers in space exploration will be reviewed, in order to describe the anticipated benefits of laser pumping. Experiments will be described which have demonstrated signal strengths in laser-pumped helium magnetometers which are 45 times greater than those observed in the same sensor pumped with a conventional rf electrodeless discharge helium lamp. This was a collaborative effort with the Magnetics Group at the Jet Propulsion Laboratory and Professor L. D. Schearer’s group at the University of Missouri at Rolla. The impact of the laser pumping technique on sensitivity, accuracy, and versatility of space magnetometers will be discussed. Proposed laser-pumped magnetometers will be described including the vector helium magnetometer for interplanetary field measurement, the scalar helium magnetometer for earth orbital applications, and the vector/scalar hybrid magnetometer for planetary and cometary encounters. Recent developments in miniaturized turnable laser sources will be presented. This was supported by the Jet Propulsion Laboratory/NASA.
Ion trajectory simulations for the TEXT upgrade 2 MeV heavy ion beam probe (abstract)
Authors: Schwelberger J. , Connor K. A. , Crowley T. P. , Hickok R. L. , Lewis J. F. , Bhavnagarwala A. J.
Published: July 2002

Ion trajectory calculations play a key role in the design of a heavy ion beam probe system and the interpretation of its measurements. In the case of the HIBP for TEXT Upgrade presently under construction, ion trajectory simulations showed that ions with energies up to 2 MeV have to be injected and detected at two different locations in order to make measurements over the whole plasma cross section. Trajectory calculations also provide essential guidelines for the construction of system components such as energy analyzers. In order to measure fluctuation-induced transport (ñ, φ̃, phase, k), the analyzers will have multiple slits. The distance of the apertures that gives reasonable distances of the sample volumes in the plasma was determined, and examples for sample volumes sizes and shapes, which determine the quality of the measurements, are presented. Another issue involving the quality and the understanding of HIBP measurements is ion beam attenuation. The trajectory code has been used to estimate the signal strength that can be expected from the 2 MeV HIBP. This work was supported by DOE.
Retarding grided energy analyzer for plasma-wall interaction study for ITER (abstract)
Authors: Yang T. F. , Bankhead W. , Peng S. Y. , Wan A. S.
Published: July 2002

A retarding energy analyzer, JANUS [A. S. Wan, T. F. Yang, B. Lipschultz, and B. LeBonbard, Rev. Sci. Instrum. 57, 1542 (1986)], has been developed at MIT which has the capability of measuring the local electron temperature, ion temperature, and sheath potential in the scrape-off layer of a plasma. This offers a useful tool in the study of material development for the divertor target to be considered for ITER. The radial profile of sheath potential (φw) on tungsten surfaces has been measured in the boundary layer of Alcator C plasma using this analyzer. Simultaneous measurement of the electron temperature (Te) and ion temperature (Ti) profiles were also made. The retarding grids of the JANUS analyzer were made of fine screens, which made it difficult to determine the absolute values of the ion and electron current. A new analyzer under development replaces the screen with slits, making determination of the absolute currents, ne, and ni easier. This analyzer will be calibrated and tested on a compact tandem mirror machine, the PPEX, that is currently operational at MIT. This work was supported by U.S. DOE contract No. DE-AC02-78ET51053, AFOSR, and NASA/JPL.
Proposal to measure the q profile on JET by Thomson scattering
Authors: Carolan P. G. , Forrest M. J. , Gowers C. W. , Nielsen P.
Published: July 2002

The existing single point Thomson scattering apparatus on JET has been modified to allow measurements of local magnetic fields. Multiviewing access will be provided by axicone optics, giving a scattering angle of about 4°, and should provide an accuracy of better than 10% in measuring Bpol over most of the plasma radius. A Fabry–Perot spectrometer will detect the scattered spectra, modulated at the electron gyrofrequency, using a gated image intensifier and a cooled CCD camera. The location of an interference partial fringe will give the magnetic field vector at a particular position in the plasma. From the locus of such partial fringes, the q profile may be determined.