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A novel spectroscopy diagnostic for measuring internal magnetic fields in high temperature magnetized plasmas has been developed. It involves spectrally resolving the Balmer-α (656 nm) neutral beam radiation split by the motional Stark effect with a spatial heterodyne spectrometer (SHS). The unique combination of high optical throughput (3.7 mm2sr) and spectral resolution (δλ ∼ 0.1 nm) allows these measurements to be made with time resolution ≪1 ms. The high throughput is effectively utilized by incorporating a novel geometric Doppler broadening compensation technique in the spectrometer. The technique significantly reduces the spectral resolution penalty inherent to using large area, high-throughput optics while still collecting the large photon flux provided by such optics. In this work, fluxes of order 1010 s−1 support the measurement of deviations of < 5 mT (ΔλStark ∼ 10−4 nm) in the local magnetic field with 50 µs time resolution. Example high time resolution measurements of the pedestal magnetic field throughout the ELM cycle of a DIII-D tokamak plasma are presented. Local magnetic field measurements give access to the dynamics of the edge current density, which is essential to understanding stability limits, edge localized mode generation and suppression, and predicting performance of H-mode tokamaks. [ABSTRACT FROM AUTHOR]

Thomson scattered light is polarized in the same orientation as the incident laser beam at low electron temperatures (Te). At high Te, part of the spectrum begins to become randomly polarized due to relativistic reasons. First measurements of the depolarized Thomson scattering spectrum were obtained from Joint European Torus (JET) pulses in 2016. This paper builds upon these initial measurements with the data obtained during 2021. These new measurements improve upon first results, in particular, by obtaining spectral measurements of the depolarized spectrum. The recent JET campaign was well suited to these measurements with long and hot plasmas. The resulting data are averaged over many plasmas and laser pulses to obtain a measurement of the amount of "p" and "s" scattered light as a function of Te. This experimentally obtained d(p/s)/dTe is then fitted and found to show reasonable agreement with the theoretically predicted depolarized fraction. Error estimates on the measured "p/s" have been obtained and show that the measurements are meaningful. This is good news for ITER for which the intention is to use this measurement as a check on Te determined by the core plasma Thomson scattering diagnostic by using conventional spectral measurement techniques. [ABSTRACT FROM AUTHOR]

A laboratory-scale experiment was conducted to reproduce plasma with properties similar to re-entry plasma and measure the plasma density using a microwave reflectometer system. To reproduce a similar re-entry plasma, a high-temperature refractory anode vacuum arc plasma method was used among arc plasma discharge methods, and arc plasma having high temperature, high speed, and high-density plasma characteristics was discharged inside a vacuum chamber. A hot refractory anode made of tungsten was used to show high-temperature plasma characteristics, and high-density plasma characteristics were demonstrated using re-evaporation around the anode. In addition, high-speed plasma characteristics were exhibited using a brass cathode. This kind of arc plasma discharge has a high temperature and is characterized by high fluctuation. It was determined that a microwave reflectometer system with good spatial resolution and non-invasiveness would be suitable to measure plasma with these characteristics. The reflection coefficient was measured using a reflector system by comparing the voltage between the traveling wave applied to the plasma and the reflected wave reflected by the plasma, and the technique of analyzing the plasma density using the difference between these reflection coefficients was used. In this study, the plasma density according to the pressure change was typically measured as 1012–1013 cm−3, which showed a similar tendency to the result of measuring the actual re-entry plasma density. [ABSTRACT FROM AUTHOR]

A novel approach for density measurements at the edge of a hot plasma device is presented—Microwave Interferometer in the Limiter Shadow (MILS). The diagnostic technique is based on measuring the change in phase and power of a microwave beam passing tangentially through the edge plasma, perpendicular to the background magnetic field. The wave propagation involves varying combinations of refraction, phase change, and further interference of the beam fractions. A 3D model is constructed as a synthetic diagnostic for MILS and allows exploring this broad range of wave propagation regimes. The diagnostic parameters, such as its dimensions, frequency, and configuration of the emitter and receiver antennas, should be balanced to meet the target range and location of measurements. It can be therefore adjusted for various conditions, and here, the diagnostic concept is evaluated on a chosen example, which was taken as suitable to cover densities of ∼1015 to 1019 m−3 on the edge of the ASDEX Upgrade tokamak. Based on a density profile with a fixed radial shape, appropriate for experimental density approximation, a database of synthetic diagnostic measurements is built. The developed genetic algorithm genMILS of density profile reconstruction using the constructed database has quite low errors. It is estimated as ∼5% to 15% for density ≥ 1017 m−3. Therefore, the new diagnostic technique (with a dedicated data processing algorithm) has a large potential in practical applications in a wide range of densities, with low errors in the numerical model and in the method of density reconstruction, so the total error and the density estimation accuracy are expected to be defined mostly by experimental uncertainties. [ABSTRACT FROM AUTHOR]

The measurement of gigagauss magnetic fields using Zeeman broadening of Ne-like transitions in highly charged ions in high energy density plasmas is investigated. The transition in Xe44+ from the (2p51/23d3/2)J=1 level to the (2p6)J=0 ground level, designated 3C and having 4.858 keV transition energy, is considered in detail. Ne-like Xe spectra were previously recorded from compressed Xe-filled capsules, and the plasma conditions were determined from spectral line ratios and atomic code modeling. Using the Paschen–Back expression for Zeeman broadening produced by strong magnetic fields and the plasma conditions from the compressed Xe-filled capsule experiments to estimate the competing Stark, Doppler, and turbulence broadenings, it is found that >0.34 GG fields can be determined from spectra recorded by a high-resolution spectrometer having 1 eV resolution (5000 resolving power). By scaling the plasma conditions to higher temperatures and densities, the minimum detectable magnetic field is determined for Zeeman broadening of the 3C transition in Ne-like ions up to U82+. Recently developed transmission-crystal spectrometers, employing a cylindrically bent crystal in the Cauchois configuration, have sufficient resolution to determine gigagauss magnetic fields from Zeeman broadening of Ne-like transitions in the 4–18 keV range in Xe44+ to U82+. [ABSTRACT FROM AUTHOR]

In this paper, we used radio frequency (RF) full wave simulation to explore the feasibility of generating a density beat oscillation formed by high harmonic fast waves (HHFWs) in the National Spherical Tokamak Experiment-Upgrade (NSTX-U) and of measuring it numerically with 2D beam emission spectroscopy (BES). This oscillation is of interest as it can be used to determine the injected RF fields. We began by computing HHFW fields in NSTX-U under a variety of experimental conditions and antenna configurations with Petra-M, a 3D RF wavefield solver. These fields were then used to evaluate the amplitude of δne,beat/ne0 in the volume of measurement, which we predict to be between 5 × 10−10 and 10−9, although it is highly dependent on plasma parameters. Trends in magnetic field, core temperature, core density, and antenna phasing are presented, and the parameters most suitable to this measurement are identified. Finally, we developed a synthetic BES diagnostic to compare the experimental BES signal against. [ABSTRACT FROM AUTHOR]

Great strides have been made in improving the quality of x-ray radiographs in high energy density plasma experiments, enabled in part by innovations in engineering and manufacturing of integrated circuits and materials. As a consequence, the radiographs of today are filled with a great deal of detail, but few of these features are extracted in a systematic way. Analysis techniques familiar to plasma physicists tend toward brittle 1D lineout or Fourier transform type analyses. The techniques applied to process our data have not kept pace with improvements in the quality of our data. Fortunately, the field of computer vision has a wealth of tools to offer, which have been widely used in industrial imaging and, more recently, adopted in biological imaging. We demonstrate the application of computer vision techniques to the analysis of x-ray radiographs from high energy density plasma experiments, as well as give a brief tutorial on the computer vision techniques themselves. These tools robustly extract 2D contours of shocks, boundaries of inhomogeneities, and secondary flows, thereby allowing for increased automation of analysis, as well as direct and quantitative comparisons with simulations. [ABSTRACT FROM AUTHOR]

Scientific instruments continue to be the foundation of exceptional developments and innovations in the field of plasma physics. Scientists and engineers from around the world met to present the latest advancements in instrumentation at the 24th edition of the biennial Topical Conference on High-Temperature Plasma Diagnostics (HTPD) held in Rochester, New York, on May 15-19, 2022. Manuscripts from the conference are being published in this special issue of Review of Scientific Instruments to present the recent, innovative, and exciting diagnostic advances in plasma physics. [Extracted from the article]

The direct measurements of high-frequency electric fields in a plasma bring about significant advances in the physics and engineering of various waves. We have developed an electro-optic sensor system based on the Pockels effect. Since the signal is transmitted through an optical fiber, the system has high tolerance for electromagnetic noises. To demonstrate its applicability to plasma experiments, we report the first result of measurement of the ion-cyclotron wave excited in the RT-1 magnetosphere device. This study compares the results of experimental field measurements with simulation results of electric fields in plasmas. [ABSTRACT FROM AUTHOR]

The soft X-ray (SXR) emission provides valuable insight into processes happening inside of hightemperature plasmas. A standard method for deriving the local emissivity profiles of the plasma from the line-of-sight integrals measured by pinhole cameras is the tomographic inversion. Such an inversion is challenging due to its ill-conditioned nature and because the reconstructed profiles depend not only on the quality of the measurements but also on the inversion algorithm used. This paper provides a detailed description of several tomography algorithms, which solve the inversion problem of Tikhonov regularization with linear computational complexity in the number of basis functions. The feasibility of combining these methods with the minimum Fisher information regularization is demonstrated, and various statistical methods for the optimal choice of the regularization parameter are investigated with emphasis on their reliability and robustness. Finally, the accuracy and the capability of the methods are demonstrated by reconstructions of experimental SXR profiles, featuring poloidal asymmetric impurity distributions as measured at the ASDEX Upgrade tokamak. [ABSTRACT FROM AUTHOR]

The elliptical spectrometer described by Cahill et al. [Rev. Sci. Instrum. 85, 103114 (2014)] is designed to enable absorption X-ray spectroscopy under circumstances in which the object plasma is, itself, a relatively bright X-ray emitter. An implementation of this design was developed using a doubly curved mica crystal for X-ray dispersion. The geometry of the spectrometer was verified by ray tracing calculations assuming Bragg reflection from mica in the second order. Control of X-ray reflections from other orders was an anticipated challenge and has been attempted by means of filtering and control of the source spectrum. These efforts have been found to be insufficient to allow the spectrometer to operate as designed because of the strong fifth order reflection of source radiation by the mica crystal. Potential solutions are presented that may enable a successful implementation of this novel crystal spectrometer design. [ABSTRACT FROM AUTHOR]

Understanding stellar interiors, inertial confinement fusion, and Z pinches depends on opacity models for mid-Z plasmas in the 100–300 eV temperature range. These models are complex and experimental validation is crucial. In this paper we describe the diagnosis of the first experiments to measure iron plasma opacity at a temperature high enough to produce the charge states and electron configurations that exist in the solar interior. The dynamic Hohlraum x-ray source at Sandia National Laboratories’ Z facility was used to both heat and backlight Mg/Fe CH tamped foils. The backlighter equivalent brightness temperature was estimated to be Tr∼314 eV±8% using time-resolved x-ray power and imaging diagnostics. This high brightness is significant because it overwhelms the sample self-emission. The sample transmission in the 7–15.5 Å range was measured using two convex potassium acid phthalate crystal spectrometers that view the backlighter through the sample. The average spectral resolution over this range was estimated to be λ/δλ∼700 by comparing theoretical crystal resolution calculations with measurements at 7.126, 8.340, and 12.254 Å. The electron density was determined to be ne=6.9±1.7×1021 cm-3 using the Stark-broadened Mg Heβ, Heγ, and Heδ lines. The temperature inferred from the H-like to He-like Mg line ratios was Te=156±6 eV. Comparisons with three different spectral synthesis models all have normalized χ2 that is close to unity, indicating quantitative consistency in the inferred plasma conditions. This supports the reliability of the results and implies the experiments are suitable for testing iron opacity models. [ABSTRACT FROM AUTHOR]

Microchannel plates (MCPs) are a standard detector for fast-framing x-ray imaging and spectroscopy of high-temperature plasmas. The MCP is coated with conductive striplines that carry short duration voltage pulses to control the timing and amplitude of the signal gain. This gain depends on the voltage to a large exponent so that small reflections or impedance losses along the striplines can have a significant impact on the position-dependent amplitude and pulse width of the gain. Understanding the pulsed gain response therefore requires careful measurements of the position- and time-dependent surface voltage coupled with detailed modeling of the resulting electron cascade. We present measurements and modeling of the time- and space-dependent gain response of MCP detectors designed for use at Sandia National Laboratories’ Z facility. The pulsed gain response is understood through measurements using a high impedence probe to determine the voltage pulse propagating along the stripline surface. Coupling the surface voltage measurements with Monte Carlo calculations of the electron cascade in the MCP provides a prediction of the time- and position-dependent gain that agrees with measurements made on a subpicosecond UV laser source to within the 25% uncertainty in the simulations. [ABSTRACT FROM AUTHOR]

Charge exchange recombination spectroscopy on Alcator C-Mod relies on the use of the diagnostic neutral beam injector as a source of neutral particles which penetrate deep into the plasma. It employs the emission resulting from the interaction of the beam atoms with fully ionized impurity ions. To interpret the emission from a given point in the plasma as the density of emitting impurity ions, the density of beam atoms must be known. Here, an analysis of beam propagation is described which yields the beam density profile throughout the beam trajectory from the neutral beam injector to the core of the plasma. The analysis includes the effects of beam formation, attenuation in the neutral gas surrounding the plasma, and attenuation in the plasma. In the course of this work, a numerical simulation and an analytical approximation for beam divergence are developed. The description is made sufficiently compact to yield accurate results in a time consistent with between-shot analysis. [ABSTRACT FROM AUTHOR]

A near-infrared laser phase contrast optical system incorporating a folded beam was developed in order to measure the distribution of density fluctuations in a high-temperature plasma. The coherent light source used was an yttrium aluminum garnet laser stabilized by a ring oscillator. The probe beam system separates and reflects the incident and exiting beams with a polarizer and a fully reflective mirror with a waveplate. This system was employed with a compact helical system to detect fluctuations at the plasma edge. [ABSTRACT FROM AUTHOR]

A novel mathematical model for the investigations of a cluster formation process in a gas jet is presented, which enables us to obtain the detailed description of the spatial and temporal distributions of all cluster target parameters. In this model, a cluster target is considered as a two-phase medium, consisting of the continuous gas phase and the discrete condensed phase (clusters). The detailed nozzle geometry is also taken into account in this model. In order to confirm the advantage of the present model over a conventional model, a considerable amount of numerical computations has been carried out and the results are compared with the data obtained from Hagena’s theory [Rev. Sci. Instrum. 63, 2374 (1992)]. Based on the developed modeling, a three-staged nozzle, which cannot be modeled using the conventional model, is designed for the purpose of producing a sufficient amount of micron-sized clusters. The generation of unprecedented amount of keV x rays from the laser-cluster interaction experiments with this nozzle and their accurate intensity dependences on various experimental parameters support the adequateness of the nozzle design. [ABSTRACT FROM AUTHOR]

A continuous-mode H- ion source has been developed in SNU by using rf transformer coupled plasma source for long lifetime. Recently, its plasma confinement has been improved by modifying the main cusp magnet system that covers rf antenna and plasma electrode regions. The extraction system has also been upgraded to triode extraction system, where permanent magnets in dipole configuration are embedded in extraction electrode to provide additional magnetic field for filtering out fast electrons. Electrode shape, extraction hole size, and gap distance are optimized for high beam currents with low emittance by using PBGUNS code. With new configuration, H- beam currents of up to 1.67 mA with 1.7 kW, 13.56 MHz rf power are extracted in a continuous mode. Low e/H- ratios down to 8 are achieved by increasing total filtering field strength up to 190 G. [ABSTRACT FROM AUTHOR]

The transient internal probe (TIP) is a diagnostic for local internal field measurements in high temperature plasmas. A verdet material, which rotates the polarization angle of the laser light under magnetic fields, is launched into a plasma at about 1.8 km/s. A linearly polarized Ar+ laser illuminates the probe in transit and the light retroreflected from the probe is analyzed to determine the local magnetic field profiles. The TIP has been used for magnetic field measurements on the helicity injected torus where electron temperature Te<=80 eV. In order to apply the TIP in higher temperature plasmas, refractory clad probes have been developed utilizing a sapphire tube, rear disc, and a MgO window on the front. The high melting points of these refractory materials should allow probe operation at plasma electron temperatures up to Te∼300 eV. A retroreflecting probe has also been developed using “catseye” optics. The front window is replaced with a plano-convex MgO lens, and the back surface of the probe is aluminized. This approach reduces spurious polarization effects and provides refractory cladding for the probe entrance face. In-flight measurements of a static magnetic field demonstrate the ability of the clad probes to withstand gun-launch acceleration, and provide high accuracy measurements of magnetic field. [ABSTRACT FROM AUTHOR]

Since volume-produced negative ions were found in 1977 at the Ecole Polytechnique in France, H- volume sources have been developed in North America, Europe, and Asia. There are sources for continuous wave, high (5%) and low (0.01%) duty factors. Currents up to 120 mA have been reached. Several techniques have been applied. Plasma heating has been done with filaments and later also with radio frequency (rf) power. The rf frequency has been varied over a wide frequency range. Different types of rf coupling have been used. Also gas mixing, cesiation, and several extraction methods have been tested. The report gives a survey with emphasis on new developments. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A method of measuring the temperature of the fast electrons produced in ultraintense laser-plasma interactions is described by inducing photonuclear reactions, in particular (γ,n) and (γ,3n) reactions in tantalum. Analysis of the γ rays emitted by the daughter nuclei of these reactions using a germanium counter enables a relatively straightforward near real-time temperature measurement to be made. This is especially important for high temperature plasmas where alternative diagnostic techniques are usually difficult and time consuming. This technique can be used while other experiments are being conducted. [ABSTRACT FROM AUTHOR]

Measurements of the flux of fusion products from high temperature plasmas provide valuable insights into the ion energy distribution, as the fusion reaction rate is a very sensitive function of ion energy. In C-2, where field reversed configuration plasmas are formed by the collision of two compact toroids and partially sustained by high power neutral beam injection [M. Binderbauer et al., Phys. Rev. Lett. 105, 045003 (2010); M. Tuszewski et al., Phys. Rev. Lett. 108, 255008 (2012)], measurements of DD fusion neutron flux are used to diagnose ion temperature and study fast ion confinement and dynamics. In this paper, we will describe the development of a new 3 MeV proton detector that will complement 2 existing neutron detectors. The detector is a large area (50 cm ), partially depleted, ion implanted silicon diode operated in a pulse counting regime. While the scintillator-based neutron detectors allow for high time resolution measurements (~100 kHz), they have no spatial or energy resolution. The proton detector will provide 10 cm spatial resolution, allowing us to determine if the axial distribution of fast ions is consistent with classical fast ion theory or whether anomalous scattering mechanisms are active. We will describe in detail the diagnostic design and present initial data from a neutral beam test chamber. [ABSTRACT FROM AUTHOR]

Explores the possibility of determining the plasma electron temperature by measuring the depolarization of the radiation scattered by the high temperature fusion reactor plasma. Relationship between plasma electron temperature and depolarization; Wavelength and energy of the incident radiation pulse.

Focuses on the electron cyclotron emission diagnostic of high temperature electron cyclotron resonance heated plasmas on Frascati tokamak upgrade. Accuracy of the electron temperature measurements; Comparison the accomplished measurements with Thomson scattering and observations of x-ray spectra from highly stripped molybdenum ions.

Describes a high resolution multiposition Thomson scattering setup to measure the electron temperature and density of a hot plasma. Operation of the system at the Rijnhuizen Tokamak Project; Scattering of light from a high power pulsed ruby laser by the free plasma electrons and relayed to a Littrow polychromator for spectral analysis.

Describes the properties of a number of diagnostics developed at the Los Alamos National Laboratory in Los Alamos, New Mexico, that utilize the radiation emitted from high-temperature plasmas. X-ray diodes; Silicon photodiodes; Curved crystal spectrometer; Bolometers.

Discusses the use of thin wall hohlraums to observe the physical location of hot, dense, laser produced hohlraum plasmas. Thin wall imaging experiments with the Nova and Shiva lasers; Limits of the technique; Other applications.

Demonstrates the capability of the transient internal probe diagnostic technique for measuring magnetic fields in hot plasmas and verifies its compatibility with plasma vacuum requirements. Probe survivability; System of operation; Determination of the amount of muzzle gas entering the simulated plasma chamber.

Describes a two-millimeter scattering diagnostic used to study density fluctuations of the electron cyclotron resonance heated plasma in the Advanced Toroidal Facility (ATF). Antenna layout in the minor cross section of the ATF plasma; Analysis of the microwaves propagation; Noise analysis.

Describes a transient internal probe diagnostic designed to permit internal magnetic field measurements in hot, high density plasmas. Probe acceleration; Optical detection system; Sabot removal; Magneto-optic probe; Magnetic field measurement.

A high-resolution spectrometer has been developed and used to measure simultaneously impurity ion temperatures and flow velocities in high temperature plasmas with 10 μs temporal resolution (limited by digitization rate). This device is actually a duo-spectrometer: measurements from two different chordal views of the plasma can be made simultaneously via two separate quartz input fiber optic bundles coupled to the entrance slits which are tilted to compensate for line curvature. The dispersed spectra on the exit plane of the duo-spectrometer are coupled via quartz fiber optics to two arrays of 16 photomultiplier tubes each. Measurements made by recording the Doppler broadened and shifted 227.091 nm emission from the C v impurity ions in the Madison Symmetric Torus (MST) reversed-field pinch (RFP) plasma have achieved precisions of <6 eV for temperatures of 150 eV and <0.7 km/s for flow velocities of 6 km/s. Representative results from the MST RFP indicate that the toroidal flow velocity drops and ion temperature increase during sawtooth events in MST. [ABSTRACT FROM AUTHOR]

The transport of runaway electrons in a hot plasma can be comparatively easily measured by perturbation experiments which provide a runaway electron diffusivity D. The diffusion can be interpreted in terms of a magnetic fluctuation level, from which an electron thermal diffusivity can be deduced. We find the runaway electron diffusion coefficient is determined by intrinsic magnetic fluctuations rather than electrostatic fluctuations because of the high energies involved. The results presented here demonstrate the efficacy of using runaway transport techniques for determining intrinsic magnetic fluctuations. [ABSTRACT FROM AUTHOR]

A high-power, power-modulated transversely excited atmosphere (TEA) CO2 laser system is developed with the intention of applying it to high-temperature plasmas for diagnostic purpose. Two-mode pulse injection locking is adopted to obtain the required output pulses of the TEA CO2 laser. Together with the power modulation, the gain-switched spike of the output pulses are also suppressed by the adopted method, resulting in pulse lengthening. Two feedback loops are incorporated for reliable power modulation. The power-modulated output so obtained is used to excite electrostatic plasma waves in laboratory plasmas. [ABSTRACT FROM AUTHOR]

Particle beams have been developed at the Culham Laboratory for many years, mainly for application to the production of high-temperature plasmas. These developments included demonstration of fundamental plasma physics such as particle trapping, heating, and current drive coupled to continuous advances in the physics and technology of ion beam production and transport. This work reached its zenith in production of multimegawatt high-proton fraction sources for the neutral beam injectors for JET. A new initiative is now coming for the development of negative ion based injectors. This wide ranging base of physics and technology provided a springboard for exploitation of beams in areas other than fusion. The last few years have seen increasing R and D at Culham in areas such as space, defense, surface treatment, and implantation. The applications have ranged from beams of H[sup +] or H[sup -] to Xe[sup +], from currents of less than 1 mA to currents of amperes and from energies of 50 eV to energies of hundreds of kilovolts. This paper describes some examples of these activities and relates them to the physics and technology base. Future areas of interest are also discussed. [ABSTRACT FROM AUTHOR]

Application of a double-crystal Bragg device with the one crystal swiveling additionally around the x-ray optical axis between the two crystals allows continuous spatial scanning of x-ray line emission from high-temperature plasmas. The main components and physical properties of the monochromator are described, and first results of measurements of spatial profiles of the emission shells of several nickel ionization stages at JET are given. [ABSTRACT FROM AUTHOR]

A Monte Carlo simulation has been used to study the fusion-product spectral line shape in high temperature thermonuclear and beam-driven plasmas in order to determine whether line-shape measurements are a viable technique to determine the reacting ion speed distribution and its mean energy. Specific reactions considered include D(d,n), T(d,n), and ³He(d,p). Several speed distributions characteristic of "mirror-confined" and beam-driven plasmas were assumed, including Maxwellian, monoenergetic, three-component Gaussian (characteristic of injected neutrals), and an injected beam reacting with Maxwellian targets. Mean energies in these distributions were varied over the range 1-100 keV. Results indicate that symmetrical Gaussian spectral lines are generated for isotropic plasmas regardless of ion energy or speed-distribution form. However, the location and width of the Gaussian depends not only on the mean ion energy, but also on the form of the ion speed distribution and its angular distribution. Generally, the linewidth is proportional to the square root of the mean ion energy, but the proportionality constant varies significantly among the speed and angular distributions considered. Thus the angular distribution and functional form of the reacting ion speed distribution must be known before measured Doppler width in the product spectrum may be used to infer the mean ion energy of the reacting plasma. [ABSTRACT FROM AUTHOR]

It has been previously suggested that crossed-sightline correlation of electron cylotron emission might be used to measure magnetic fluctuations in high-temperature plasmas. Reported here are the results of a continuing project to determine under what conditions (if any) this measurement will be feasible. An initial conceptual design for the device hardware has been completed. Large portions of the numerical simulation are working, including ray-tracing and emission/absorption packages. An initial discussion of data analysis for the experimental data is presented, and an analysis of the uncertainty in the line center (magnetic field) measurement in terms of the experimental uncertainties is given. [ABSTRACT FROM AUTHOR]

A knowledge of the spatial distribution of the x rays emitted by the hot plasma region is a key element in the study of the physical processes occurring in laser-produced plasmas and complements other diagnostics such as spectroscopy and temporal studies. X-ray microscopy with reflection microscopes offers the most direct means of obtaining this information. Until recently, the two types of microscopes that had been developed for this purpose, the KirkpatrickBaez and the Wolter, operated at relatively low energies (about 4-5 keV) and had very little spectral selectivity, relying on filters for coarse spectral resolution. With the development of x-ray reflecting multilayer mirrors, the energy response of such microscopes can be extended to 10 kev or higher, with good spectral selectivity. In addition, it is possible to reduce some of the optical aberrations to obtain improved spatial resolution. This paper describes some of the recent progress in making and evaluating x-ray reflectors, and outlines the optical design considerations for multilayer-coated microscopes. Results from a prototype multilayer K-B microscope are presented. [ABSTRACT FROM AUTHOR]

We present a collimator configuration for measuring energy resolved x-ray plasma volume bremsstrahlung emitted, e.g., by an ECRIS. Special attention we paid to shielding the detector against interfering Compton scattered radiation and wall bremsstrahlung stemming from the collimator entrance aperture. We estimate the efficiency for shielding of Compton scattered radiation at least attainable by this arrangement. [ABSTRACT FROM AUTHOR]

An x-ray pinhole camera and a monochromatic Kα imager are used to measure the interactions of intense femtosecond laser pulses with Cu foil targets. The two diagnostics give different features in the spot size and the laser energy scaling, which are resulted from different physical processes. Under our experimental conditons, the Kα emission is mainly excited by the fast electrons transporting inside the cold bulk target. In contrast, the x-ray pinhole signals are dominated by the broadband thermal x-ray emission from the hot plasma at the front target surface. [ABSTRACT FROM AUTHOR]

The Zeeman effect has been used for measurement of magnetic fields in low-temperature plasma, but the diagnostic technique is difficult to implement in a high-temperature plasma. This paper describes new instrumentation and methodology for simultaneous measurement of the entire Doppler-broadened left and right circularly polarized Zeeman spectra in high-temperature plasmas. Measurements are made using spectra emitted parallel to the magnetic field by carbon impurities in high-temperature plasma. The Doppler-broadened width is much larger than the magnitude of the Zeeman splitting, thus simultaneous recording of the two circularly polarized Zeeman line profiles is key to accurate measurement of the magnetic field in the ZaP Z-pinch plasma device. Spectral data are collected along multiple chords on both sides of the symmetry axis of the plasma. This enables determination of the location of the current axis of the Z-pinch and of lower-bound estimates of the local magnetic field at specific radial locations in the plasma. [ABSTRACT FROM AUTHOR]

Two dimensional (2D) plasma image analysis is useful to study the improvement of plasma confinement in magnetically confined fusion plasmas. We have constructed a 2D interferometer system with phase imaging method for studying 2D plasma density distribution and its fluctuation measurement in the tandem mirror GAMMA 10. 2D profiles of electron density and its fluctuation have been successfully obtained by using this 2D phase imaging system. We show that 2D plasma density and fluctuation profiles clearly depends on the axial confining potential formation with application of plug electron cyclotron heating in GAMMA 10. [ABSTRACT FROM AUTHOR]

In Large Helical Device (LHD) experiments, an electron temperature (Te) more than 15 keV has been observed by the yttrium-aluminum-garnet (YAG) laser Thomson scattering diagnostic. Since the LHD Thomson scattering system has been optimized for the temperature region, 50 eV≤Te≤10 keV, the data quality becomes worse in the higher Te region exceeding 10 keV. In order to accurately determine Te in the LHD high-Te experiments, we tried to increase the laser pulse energy by simultaneously firing three lasers. The technique enables us to decrease the uncertainties in the measured Te. Another signal accumulation method was also tested. In addition, we estimated the influence of high-energy electrons on Te obtained by the LHD Thomson scattering system. [ABSTRACT FROM AUTHOR]

A 2400 lines/mm variable-spaced grating spectrometer has been used to measure soft x-ray emission (8-22 Å) from laser-produced plasma experiments at Lawrence Livermore National Laboratory's Compact Multipulse Terrawatt (COMET) Laser Facility. The spectrometer was coupled to a Kentech x-ray streak camera to study the temporal evolution of soft x rays emitted from the back of the Mylar and the copper foils irradiated at 1015 W/cm2. The instrument demonstrated a resolving power of ∼120 at 19 Å with a time resolution of 31 ps. The time-resolved copper emission spectrum was consistent with a photodiode monitoring the laser temporal pulse shape and indicated that the soft x-ray emission follows the laser heating of the target. The time and spectral resolutions of this diagnostic make it useful for studies of high temperature plasmas. [ABSTRACT FROM AUTHOR]

Quantum microcalorimeters show promise in being able to fully resolve x-ray spectra from heavy highly charged ions, such as would be found in hot plasmas with temperatures in excess of 50 keV. Quantum microcalorimeter arrays are able to achieve this as they have a high-resolving power and good effective quantum efficiency for hard x-ray photons up to 60 keV. To demonstrate this, we present a measurement using an array of thin HgTe quantum microcalorimeters to measure the K-shell spectrum of hydrogenlike through carbonlike praseodymium (Z=57). With this device we are able to attain a resolving power, E/ΔE, of 1000 at a photon energy of 37 keV. [ABSTRACT FROM AUTHOR]

Diagnostic of high-temperature M-shell W plasmas is challenging because of contribution of numerous ionization stages in a relatively narrow x-ray spectral region. A method using LLNL EBIT data generated at different electron beam energies has been established for the identification of prominent spectral features and for the determination of charge balance in x-ray M-shell W spectra between 3.5 and 8.5 Å. It extends previous work [A. S. Safronova et al., Can. J. Phys. 86, 267 (2008)] which used only Ni-like lines to include the neighboring ionization stages. This diagnostic procedure was tested with results from Z-pinch plasmas produced on the 1 MA pulse power generator Zebra at UNR. These results are of particular importance for fusion research. [ABSTRACT FROM AUTHOR]

Dust varies from a few nanometers to a fraction of a millimeter in size. Dust also offers essentially unlimited choices in material composition and structure. The potential of dust for high-temperature plasma diagnostic is largely unfulfilled yet. The principles of dust spectroscopy to measure internal magnetic field, microparticle tracer velocimetry to measure plasma flow, and dust photometry to measure heat flux are described. Two main components of the different dust diagnostics are a dust injector and a dust imaging system. The dust injector delivers a certain number of dust grains into a plasma. The imaging system collects and selectively detects certain photons resulted from dust-plasma interaction. One piece of dust gives the local plasma quantity, a collection of dust grains together reveals either two-dimensional (using only one or two imaging cameras) or three-dimensional (using two or more imaging cameras) structures of the measured quantity. A generic conceptual design suitable for all three types of dust diagnostics is presented. [ABSTRACT FROM AUTHOR]

Z-pinches can produce intense fluxes of argon K-shell (3 keV) radiation, but typically only a fraction of the load mass near the axis of the pinch radiates in this spectral range. The majority of the mass does not get hot or dense enough to radiate efficiently in the K-shell. We have designed, built, and tested an instrument to image pinch emission, specifically the radial emission profile, at energies below the K-shell in order to track the location of the cooler mass. A gold mirror provides a high-energy cut-off at 2 keV while a transmission grating disperses the incoming radiation and provides a low-energy cutoff at 0.1 keV. A vertical slit images the pinch radiation in the radial direction and the emission profile is recorded with either an extreme ultraviolet-sensitive charge-coupled device camera (time-integrated) or a linear photodiode array (∼1 ns time resolution). We present results for the mirror, grating, and system characterization obtained at the Advanced Light Source synchrotron located at Lawrence Berkeley National Laboratory (Berkeley, CA). [ABSTRACT FROM AUTHOR]

In study of hot and dense plasma, a high spatial resolution (a few microns) x-ray imaging is very important to observe these plasmas. The Fresnel phase zone plate (FPZP) consists of alternately material and transparent circular annuli placed concentrically, which image x rays using diffraction x rays from all annuli. FPZP have imaged 4.7–4.77 keV x rays with 2.2 μm spatial resolution. However FPZP has a problem that background level is comparable to signal level. In subtraction of background, the error of 10% is caused. For the accurate background subtraction, we designed new FPZP, which consist of three β layers of a transparent zone and two material zones. The new design FPZP parameters (thickness of material zones, each zone width) have been optimized, and in that optimum design signal-to-background ratio is 4 times better than conventional two layers FPZP. [ABSTRACT FROM AUTHOR]

Makes observations on the characteristics of x-rays and electron energy distribution function in anisotropical hot plasmas. Production characteristic of x-ray lines; Line intensity ratios; Estimation of anisotropy for electron energy distribution function.

The recently developed technique of beam emission spectroscopy (BES) provides a tool to study long-wavelength density turbulence (coherence length » ion gyroradius) in hot tokamak plasmas. To provide an accurate conversion of the measured light intensity fluctuations to a local ñ/n density fluctuation and to assess the influence of density fluctuations in the neutral beam induced by large edge turbulence, a multistate neutral beam excitation/transport code for realistic experimental geometries has been written. Results from this code show that the attenuation of the beam density induced by edge turbulence can give rise to significant levels of common-mode fluctuation power in signals from the plasma core and that the derivation of quantitative values of ñ/n from experimental measurements depends weakly on the radial extent of the density fluctuations. [ABSTRACT FROM AUTHOR]