High-temperature Plasma Diagnostics Research Articles

Optimization of optical components of spectrometers based on multilayer mirrors for soft x-ray radiation

Abstract The basic principles in the development of the multilayer mirrors (MLM)-based spectrometers for the diagnostics of high temperature plasma and some recent data on the MLM characteristics are given. A two-channel adjustable spectrometer of soft X-ray radiation is described.

Advance in diagnostics for high temperature plasmas based on the analytical result for the ion dynamical broadening of hydrogen spectral lines (abstract)

It is well known that the ion dynamics is very important for Stark broadening of spectral lines in high-temperature plasmas. However, it was usually assumed that with the increase of the plasma density N and/or of the principal quantum number n of the upper level of the radiator, the ionic contribution to the impact width (ICIW) tends to zero. In distinction to that paradigm, by finding an analytical result for the ion dynamical broadening of hydrogen spectral lines, we show here that with the increase of N and/or n, the ICIW does not decrease. Moreover, for practically important ranges of T, N, and n, this “residual” ICIW, being virtually independent of n, can be comparable to the standard electron impact width. This novel result leads to: (1) a substantial revision of the past diagnostic conclusions for a variety of high-temperature plasma experiments; (2) a much better possibility to deduce from experimental, Stark-broadened line profiles not only the plasma density but also the plasma temperature; (3) a significant enhancement of the accuracy of N and T obtained from experimental line profiles. The consequences are especially important for tokamak plasmas, where the diagnostics based on experimental profiles of high Balmer and Paschen lines is frequently used.

Pellet Technologies for Plasma Fuelling and Diagnostics

The paper reviews recent results in fueling and diagnostics of high temperature plasmas of tokamaks and stellarators by means of pellet injection. Physical and engineering problems of the pellet technologies are considered. The technologies developed can be applied for fueling and diagnostics of open systems.

High repetition rate probing laser for Thomson scattering diagnostics

A new laser based on a multipass intracavity probing system for Thomson scattering diagnostics is presented in the article. The laser system provides a considerable gain in both repetition rate of laser pulses and the diagnostics sensitivity. These capabilities have their origin in a highly effective pumping-to-probing energy conversion which is intrinsic to the system suggested. Main factors affecting the performance of the system are considered. The application of the system in high temperature plasma diagnostics is tested experimentally, and the results are discussed in this article.

Present Status of Hanbit Magnetic Mirror Device

The Hanbit magnetic mirror device, which is operated as a joint plasma research facility, has been constructed at Korea Basic Science Institute for basic study and technology development of high temperature plasma confinement, plasma heating and diagnostics, and plasma applications, such as high-temperature material testing for tokamak divertors. A 500-kW RF transmitter and a 100-kW RF transmitter for ICRF heating are major heating sources in operation, and a few gyrotron-based ECRH systems are in preparation. The target plasma parameters at the central cell are 1-keV ion temperature, 200-eV electron temperature, and 5 × 1012 cm−3 electron density with 500-ms plasma duration. The present status of the Hanbit device, which includes the system overview and recent experimental result, is described in this paper, and future plans will be discussed.

Short-period X-ray multilayers based on Cr/Sc, W/Sc

New experimental results on fabrication and investigations of X-ray properties of multilayer X-ray mirrors based on Cr/Sc and W/Sc for close-to-normal and Brewster's angles of incidence are presented. It is experimentally shown that the peak reflection coefficient of the mirrors Cr/Sc with the periods of 1.6–1.7 nm for the wavelength 3.14 nm reaches 10% at the resolution λ Δλ up to 175. The reflection coefficient of the mirrors at the Brewster's angle reaches 10–12%. The high reflectivity of the mirrors allows to use them for creation of multi-mirror schemes for the X-ray microscopy and astronomy, X-ray diagnostics of high-temperature plasma.

Short-period X-ray multilayers based on [formula omitted

New experimental results on fabrication and investigations of the X-ray properties of multilayer X-ray mirrors based on Cr Sc for close-to-normal and Brewster's angles of incidence are presented. It is experimentally shown that the peak reflection coefficient of mirrors with periods of 1.6–1.7 nm for the wavelength 3.14 nm reaches 10% at a resolution λ Δλ up to 175. The reflection coefficient of the mirrors at the Brewster's angle reaches 10–12%. The high reflectivity of the mirrors allows to use them for the creation of multi-mirror schemes for X-ray microscopy and astronomy and X-ray diagnostics of high-temperature plasma.

New optical methods for short wavelength hot plasma diagnostics

We have developed new types of experimental methods for high-temperature plasma diagnostics based on both glass capillary converters (GCCs) and multilayer mirrors (MLMs), where the optical GCC device provides guiding, focusing, and polarization analysis of short wavelength radiation with a large bandwidth, and the MLM elements are used for dispersing, focusing, and polarization sensitive studies of radiation within a narrow bandwidth. In particular, we report here for the first time, to the best of our knowledge, the development and testing of such new optical diagnostic devices for: (i) pinhole chamber with GCC, (ii) GCC converter for time-resolved x-ray measurements, (iii) polarimeters–spectrometers with GCC and MLM for measurements of polarization and spectral characteristics of short wavelength radiation, and (iv) high sensitivity extreme ultraviolet spectrometers.

Spectra of dielectronic satellites due to 2 → 1 transitions and line polarization used for high-temperature plasma diagnostics

Atomic data calculated using the ‘MZ’ program were used to construct synthetic spectra of dielectronic satellites to resonance line 1s2p 1P 1−1s 2 1S 0 . The contribution of Li-, Be-, B-, C-, N-, O-like ions were taken into account. The inclusion of various amount of the levels of the ground state of the preceding isoelectronic sequence relevant to the formation of upper (autoionizing) levels in the calculation of autoionization rates and intensity factors leads to various theoretical synthetic spectra. Polarization of B-like dielectronic satellite lines was calculated and the most polarized lines from all intense lines were determined which is important in diagnostics of hot electrons in high-temperature plasma.

The 2p 53l Configurations of Highly Stripped Ne-like Ions: Possibility of X-Ray Laser Emission

The 2{ital p}{sup 5}3{ital l} ({ital l}=0,1,2) singlet configurations of highly stripped Ne-like ions from Ar{sup 8+} to Kr{sup 26+} have been calculated using time-dependent coupled Hartree-Fock theory, and their transition schemes are analyzed. Many of these lines are observed from laser-produced plasmas of the respective atoms and are useful for high-temperature plasma diagnostics and in stellar opacity projects. The data are very useful for understanding and modeling of laser action at short wavelengths, particularly in the X-ray region. The lasing action usually occurs from transitions with the levels 2{ital p}{sup 5}3{ital p}{r_arrow}2{ital p}{sup 5}3{ital s}. Transition energies, oscillator strengths, and dipolar and quadrupolar transition probabilities have been estimated for all the excitations studied. Results agree well with experimental and theoretical data wherever available. {copyright} {ital 1995 The American Astronomical Society.}

Precision measurements and identification of laser plasma emission spectra due to transitions from doubly excited levels of the sodium-like selenium ion

The spectrum of dielectronic satellites of resonance lines of the neon-like selenium ion was analyzed experimentally and theoretically. The satellite line spectrum resulting from stabilizing radiative transitions from doubly excited states of the sodium-like selenium ion to nonautoionizing states was obtained using a laser plasma and a record spectral resolution of λ/Δλ ≈ 5000–8000. A detailed analysis is given of the laser plasma x-ray emission spectrum in the range 7.2–8.8 A, more than 300 lines or compact groups of spectral lines were identified, and their wavelengths were measured with an error of ±5−10−4 A.The good agreement between the modeled and experimental spectra indicates that the emission spectrum of Na-like ions shows promise for use in high-temperature plasma diagnostics.

Circular polarization of the Fe XXV x-ray lines following collisional excitation by longitudinally polarized electrons.

The circular polarization of x-ray lines emitted by heliumlike iron collisionally excited by a longitudinally polarized electron beam has been investigated theoretically. The required collision strengths for excitation of the different n=2 and 3 magnetic sublevels from the 1${\mathit{s}}^{2}$ ground level have been calculated by two different distorted-wave methods and compared with each other. The agreement is generally good. One of these methods is semirelativistic, and the other is fully relativistic with QED effects included in the atomic structure part of the calculations. A high degree of circular polarization is obtained for the magnetic dipole 1 $^{1}$${\mathit{S}}_{0--}$2 $^{3}$${\mathit{S}}_{1}$ and quadrupole 1 $^{1}$${\mathit{S}}_{0--}$2 $^{3}$${\mathit{P}}_{2}$ lines, while the intercombination line 1 $^{1}$${\mathit{S}}_{0--}$2 $^{3}$${\mathit{P}}_{1}$ is found to be almost completely circularly polarized in the near-threshold region. In addition to being of intrinsic interest for atomic collision physics, the reported results might have useful applications in future diagnostics of high-temperature plasmas with a view to providing information on the possible polarization of suprathermal electron beams.

Density sensitive line ratios for highly ionized atoms of the Cu i and Na i isoelectronic sequences

We discuss extreme ultraviolet and x-ray spectral lines emitted by ions of the Cu i and Na i isoelectronic sequences and show that certain intensity ratios of these lines are sensitive to electron density in the range from about 1018 to 1022 cm−3. These lines therefore provide density diagnostics for high-temperature plasmas. We illustrate the density dependence for four ions of the Cu i sequence (Z=60, 71, 82, 92) and seven ions of the Na i sequence (Z=32, 42, 52, 62, 72, 82, 92). We also show that the dependence of the ratios on electron temperature is not strong, and demonstrate that opacity can be kept small by employing the spot spectroscopy technique.

Test particle diagnostics for high-temperature plasmas (abstract)

A new type of tagging diagnostic which employs ballistic modes to follow particle orbits is introduced. ‘‘Vlasov tagging’’ is accomplished by the selective excitation of small amplitude ballistic modes either by the resonant Landau or cyclotron resonant absorption of incident waves or by spatially localized nonresonant nonlinear interactions. Subsequent detection of ballistic modes may be accomplished by laser fluorescence (for ions) or by changes in the transmission of a probe beam. Results demonstrating ion Vlasov tagging will be presented. Electron Vlasov tagging appears most attractive by means of the cyclotron resonance. Transmission measurements with a search beam may be made at the harmonics. Vlasov tagging may be used to directly measure transport in both velocity and coordinate space.

New tilted-poles Wien filter with enhanced performance

The Wien filter is an E×B deflecting analyzer with the electrostatic field perpendicular to the magnetostatic field. The twofold functions of the Wien filter are as an energy analyzer as well as a mass analyzer. It has very high resolution for paraxial charged-particle beams with V=E/B, the Wien velocity. Two Wien filters, a tilted-poles Wien filter, and a classical parallel-rectangular-poles Wien filter were built and tested for electrons up to 3.5 keV and protons beams of 200 eV. (The tilted-poles Wien filter is a new diagnostic developed by the authors.) The performance of the two is compared, and the tilted-poles Wien filter has superior resolution to the classical Wien filter. Both Wien filters appear to have features useful for high-temperature plasma diagnostics, including simultaneous measurement of energy and mass spectra, and high resolution.

X-ray response of AlGaAs/GaAs radiation-hardened double-heterostructure photodiode compared to Si:p-i-n photodiodes

Requirements for continuous operation of photodiodes in the presence of nuclear radiation has led to the development of a novel AlGaAs/GaAs photodiode. Device structure and semiconductor properties of this design were optimized to balance the need for photodetection at λ=820 nm against unwanted excess photocurrents induced by ionizing radiation. To achieve radiation hardness the photodiode employs a double-heterojunction device structure. The spectral response of this detector, 1 keV–10 MeV, may offer unique opportunities for use in high-temperature plasma diagnostics compared to typical bare Si:p-i-n x-ray photodiode characteristics. Application of this AlGaAs/GaAs detector in a fiber-optic link will be reviewed. Also, use of this detector in simple atomic-absorption-edge filtered x-ray detector channels is presented.

E×B Wien analyzers (abstract)

The Wien filter is an E×B deflecting analyzer with the electrostatic field perpendicular to the magnetostatic field. The twofold functions of the Wien filter are as an energy analyzer as well as a mass analyzer. It has very high resolution for paraxial charged particle beams with V=E/B, the Wien velocity. Two Wien filters were built and tested for electrons up to 3.5 keV and protons beams of 200 eV. The performance of the two is compared and appears to have features useful for high-temperature plasma diagnostics including simultaneous measurement of energy and mass spectra and high resolution.

Diagnostics of High Temperature Plasma

Diagnostics of High Temperature Plasma

文部省科学研究費補助金(昭和58〜60年度)エネルギー特別研究(核融合)研究成果報告会の概要

The Summary Meeting on Nuclear Fusion Research by Grant-in-Aid (1983-1985) of Monbusho has been held on Aug. 25-27, 1986 at Gakushikaikan in Tokyo. More than 300 papers, including the research activities in the following subjects have been presented.I. Reactor Materials and Plasma-Wall Interactions1. Heavy irradiation effects, 2. Plasma-wall interactions, 3. Compatibility of non-metal materials including ceramicsII. Science, Technology and Biological Effects of Tritium1. Science and technology of tritium, 2. Dynamics of tritium in environment, 3. Biological effects of tritiumIII. Fundamentals of Reactor Plasma Control1. Diagnostics of high-temperature plasma, 2. Fundamentals of implosion engineering for inertial confinement, 3. Fundamentals of plasma heating, 4. Physics of new schemes for plasma confinementIV. Technology of Superconducting Magnet1. Superconducting magnet materials, 2. Fundamental phenomena of superconductivity, 3. Magnet technologyV. Fusion Reactor Blanket Engineering1. Fusion neutronics, 2. Heat transfer, fluid dynamics and structural engineeringVI. Design and Evaluation of Fusion Reactor1. System design, 2. Technological assessment of fusion energy, 3. Fusion theory.

Space- and time-resolving spectrograph for high-temperature plasma diagnostics

Construction of an EUV (60 –370 Å) space- and time-resolving, grazing incidence spectrograph (STRS) is described. The simultaneous spectral coverage of the instrument ranges from 40 to 75 Å, depending on the wavelength region. The spectral resolution is about 1 Å. The spatial resolution, accomplished by using the pinhole camera effect and the inherent astigmatism of a concave grating in grazing incidence, is about 2 cm, with a total field of view of 60 cm at a distance of 2 m from the plasma. The detector consists of a 75-mm MCP image intensifier optically coupled to three CCD area array detectors. Time resolution of up to 2 ms is achieved with high-speed readout electronics. A PDP 11/73 minicomputer controls the spectrograph and collects and reduces 3.0 Mbyte of data per shot.