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High resolution K-shell emission from Ni solid and near solid density nanowire arrays was measured at the ALEPH laser facility using a newly commissioned high resolution x-ray spectrometer. The spectrometer consists of a spherically bent Ge crystal coupled to a CCD. The targets were irradiated with high contrast laser pulses using the 400nm second harmonic beamline which operates at highly relativistic intensities, ao ~ 20. The ion and electron density of the plasmas were varied using arrays of 100nm diameter nanowire arrays with different wire spacings which varied from 7% of solid density to 24%. This parametrizes the collisional and radiative properties of the plasma as well as the temperature. The time integrated, high resolution K-shell spectra, coupled with moderate resolution, time resolved x ray emission reveal that the lower density nanowire arrays reach higher temperatures and radiate for longer durations of time (~25 ps) whereas the higher density nanowire arrays radiate for less than 10 ps, converging with the x-ray emission of the solid density Ni foil. Overall, the x-ray yield of the lower density nanowire arrays exceeds that of the solid density foil by a factor of ~5x. In contrast to this, the average charge state of the solid density foils is greater than that of the nanowire arrays due to the larger collisional ionization rates which occur at solid density. The experimental results will be compared to detailed transient atomic physics computations coupled with radiative hydrodynamic simulations with initial conditions provided by three-dimensional particle in cell simulations.

Ion-electron equilibration drives plasma dynamics but is challenging to model at high plasma densities, where thermalization is fast and correlation effects are significant. Experimental benchmarks in this regime have been rare due to a lack of precision diagnostics for electron or ion temperatures at high density. We present simultaneous measurements of electron and ion temperatures in solid-density titanium based on high-resolution x-ray emission spectra and newly applied advances in Stark lineshape modeling. The measurements imply an ion temperature significantly lower than the electron temperature, despite short Spitzer equilibration times. X-ray lineshapes are emitted from buried layer targets heated with a short-pulse, high-intensity laser. Titanium tracer layers heat to 1 keV electron temperatures, as inferred from x-ray line intensity ratios, while remaining at solid density due to the high temporal contrast of the laser. Observed x-ray lineshapes are double-peaked and redshifted, both of which are hallmarks of Stark broadening that are influenced differently by the electron density and the ion temperature. A new lineshape model that abandons the common assumption of dipole interactions for electron broadening can model both redshifts and line broadening self consistently. Comparing the data with this model strongly constrains both the ion temperature (700 eV) and the electron density (1.2×10 24 cm -3 ). Measured plasmas are near solid density and support a significant temperature differential between hot electrons and cooler ions. The lack of equilibration suggests that either (1) the equilibration rate is substantially slower than theorized or (2) ion heat transport plays an important role in the system.

$\mathrm{He}\ensuremath{\beta}$ spectral line shapes are important for diagnosing temperature and density in many dense plasmas. This work presents $\mathrm{He}\ensuremath{\beta}$ line shapes measured with high spectral resolution from solid-density plasmas with minimized gradients. The line shapes show hallmark features of Stark broadening, including quantifiable redshifts and double-peaked structure with a significant dip between the peaks; these features are compared to models through a Markov chain Monte Carlo framework. Line shape theory using the dipole approximation can fit the width and peak separation of measured line shapes, but it cannot resolve an ambiguity between electron density ${n}_{e}$ and ion temperature ${T}_{i}$, since both parameters influence the strength of quasistatic ion microfields. Here a line shape model employing a full Coulomb interaction for the electron broadening computes self-consistent line widths and redshifts through the monopole term; redshifts have different dependence on plasma parameters and thus resolve the ${n}_{e}\ensuremath{-}{T}_{i}$ ambiguity. The measured line shapes indicate densities that are 80--100% of solid, identifying a regime of highly ionized but well-tamped plasma. This analysis also provides the first strong evidence that dense ions and electrons are not in thermal equilibrium, despite equilibration times much shorter than the duration of x-ray emission; cooler ions may arise from nonclassical thermalization rates or anomalous energy transport. The experimental platform and diagnostic technique constitute a promising new approach for studying ion-electron equilibration in dense plasmas.

Fine-structure x-ray spectra have been measured from foils with embedded tracer layers at two laser facilities. A suite of layered foils with thin Ti tracers under varied tamper layers was studied at both the Titan and the ALEPH 400 nm laser facilities, where Ti Heα emission was recorded using a high-resolution Bragg crystal spectrometer. Several indicators of plasma parameters are examined in the spectra, including temperature- and density-dependent line ratios and line broadening from Stark and opacity effects. Spectra indicate that (1) the plasma density at ALEPH is significantly higher than at Titan and (2) the electron temperature is high for near-surface layers at both facilities but drops more quickly with depth at ALEPH. These inferences of plasma conditions are consistent with differing levels of temporal contrast at each laser facility.

A novel high-resolution x-ray spectrometer for point-like emission sources has been developed using a crystal shape having both a variable major and a variable minor radius of curvature. This variable-radii sinusoidal spiral spectrometer (VR-Spiral) allows three common spectrometer design goals to be achieved simultaneously: 1. reduction of aberrations and improved spectral (energy) resolution, 2. reduction of source size broadening, and 3. use of large crystals to improve total throughput. The VR-Spiral concept and its application to practical spectrometer design are described in detail. This concept is then used to design a spectrometer for an extreme extended x-ray absorption fine structure experiment at the National Ignition Facility looking at the Pb L3 absorption edge at 13.0352 keV. The expected performance of this VR-Spiral spectrometer, both in terms of energy resolution and spatial resolution, is evaluated through the use of a newly developed raytracing tool, xicsrt. Finally, the expected performance of the VR-Spiral concept is compared to that of spectrometers based on conventional toroidal and variable-radii toroidal crystal geometries showing a greatly improved energy resolution.

A multi-energy soft x-ray pinhole camera has been designed, built, and deployed at the Madison Symmetric Torus to aid the study of particle and thermal transport, as well as MHD stability physics. This novel imaging diagnostic technique employs a pixelated x-ray detector in which the lower energy threshold for photon detection can be adjusted independently on each pixel. The detector of choice is a PILATUS3 100 K with a 450 μm thick silicon sensor and nearly 100 000 pixels sensitive to photon energies between 1.6 and 30 keV. An ensemble of cubic spline smoothing functions has been applied to the line-integrated data for each time-frame and energy-range, obtaining a reduced standard-deviation when compared to that dominated by photon-noise. The multi-energy local emissivity profiles are obtained from a 1D matrix-based Abel-inversion procedure. Central values of Te can be obtained by modeling the slope of the continuum radiation from ratios of the inverted radial emissivity profiles over multiple energy ranges with no a priori assumptions of plasma profiles, magnetic field reconstruction constraints, high-density limitations, or need of shot-to-shot reproducibility. In tokamak plasmas, a novel application has recently been tested for early detection, 1D imaging, and study of the birth, exponential growth, and saturation of runaway electrons at energies comparable to 100 × Te,0; thus, early results are also presented.

We report the development of a high-resolution spectrometer for extended x-ray absorption fine structure (EXAFS) studies of materials under extreme conditions. A curved crystal and detector in the spectrometer are replaceable such that a single body is employed to perform EXAFS measurements at different x-ray energy intervals of interest. Two configurations have been implemented using toroidal crystals with Ge 311 reflection set to provide EXAFS at the Cu K-edge (energy range 8.9-9.8 keV) and Ge 400 reflection set to provide EXAFS at the Ta L3-edge (9.8-10.7 keV). Key performance characteristics of the spectrometer were found to be consistent with design parameters. The data generated at the National Ignition Facility have shown an ≃3 eV spectral resolution for the Cu K-edge configuration and ≃6 eV for the Ta L3-edge configuration.

This paper describes a new class of focusing crystal forms for the x-ray Bragg crystal spectroscopy of small, point-like, x-ray sources. These new crystal forms are designed with the aid of sinusoidal spirals, a family of curves, whose shapes are defined by only one parameter, which can assume any real value. The potential of the sinusoidal spirals for the design x-ray crystal spectrometers is demonstrated with the design of a toroidally bent crystal of varying major and minor radii for measurements of the extended x-ray absorption fine structure near the Ta-L3 absorption edge at the National Ignition Facility.

We have proposed, designed and built a dual-channel x-ray imaging crystal spectrometer (XICS) for spectrally- and spatially-resolved x-ray Thomson scattering (XRTS) measurements in the Matter in Extreme Conditions (MEC) end station at the Linac Coherent Light Source (LCLS). This spectrometer employs two spherically-bent germanium (Ge) 220 crystals, which are combined to form a large aperture dispersive element with a spectral bandwidth of ~300 eV that enables both the elastic and inelastic x-ray scattering peaks to be simultaneously measured. The apparatus and its characterization are described. A resolving power of ~1900 was demonstrated and a spatial resolution of ~12 μm was achieved in calibration tests. For XRTS measurements, a narrow-bandwidth (ΔE/E

Newly developed large-area pixelated two-dimensional detector and two-crystal assemblies were deployed for the first time on tokamaks to enable time-resolved Bragg-diffracted x-ray imaging with good framing rate and water-cooling capabilities for in-vacuum long-pulse operations. High-quality helium-like (He-like) and hydrogen-like (H-like) argon spectra have been observed simultaneously for the first time on a single detector for a wide range of plasma parameters to infer both ion temperature and rotation profiles and support studies on spontaneous rotation, impurity transport, and RF physics. Since tokamak plasmas rotate in both the poloidal (θ) and toroidal (ϕ) directions, a reliable wavelength calibration is needed to account for the correct Doppler shift as well as to compute the spectrometer's instrumental function. Lyα lines emitted from Cd x-ray tubes are proposed to be used as "markers" to provide an in situ calibration of the EAST's X-ray imaging crystal spectrometer systems measuring He- and H-like argon spectra. The first lab test indicated that the X-ray tube can excite strong Lyα lines at 15 kV voltage and 1 mA current when the crystal is shined for 10 min. Other indirect calibration methods using locked-mode discharge scenarios were also studied as complementary methods.

The here-described spectrometer was developed for the extended x-ray absorption fine structure spectroscopy of high-density plasmas at the National Ignition Facility. It employs as the Bragg reflecting element a new type of toroidally bent crystal with a constant and very large major radius R and a much smaller, locally varying, minor radius r. The focusing properties of this crystal and the experimental arrangement of the source and detector make it possible to (a) fulfill the conditions for a perfect imaging of an ideal point source for each wavelength, (b) obtain a high photon throughput, (c) obtain a high spectral resolution by eliminating the effects of source-size broadening, and (d) obtain a one-dimensional spatial resolution with a high magnification perpendicular to the main dispersion plane.

RF-heated H-mode plasmas are readily achieved with lower hybrid current drive and ICRF heating on experimental advanced superconducting tokamak (EAST). Characteristics of H-mode plasma rotation are studied, including the behaviors for non-stationary and stationary H-mode discharges. Experimental results indicate that substantial co-current core rotation increment is observed at L-H transition. For non-stationary discharges with multiple L-H transitions, central plasma rotation varies as the plasma enters and exits the H-mode phase. Rotation increase over L-H transition is linearly correlated with plasma stored energy for both edge localized mode (ELM)-free phases and phases with type-III ELMs. For stationary H-mode discharges with type-III ELMs, core plasma rotation profile is elevated and remains stable during the H-mode phase, although the occurrence of ELMs tends to slow down the core rotation, especially for type-I ELMs where the entire core profiles are affected. Evolution of plasma rotation is fitted with a source-free transport equation and it is found that the momentum transport is dominated by diffusion and explains the flat profile in the core. Based on the Rice scaling and for the same stored energy increase, smaller increase in the core rotation is observed for H-mode discharges with type-III ELMs than for ELM-free discharges. A linear fit indicates that the slope is 75% larger for the ELM-free discharges data.

A new x-ray imaging crystal spectrometer is developed for time-resolved measurements of x-ray line spectra. One of the main advantages is that it produces perfect images of a point source for each wavelength in a selectable spectral range. The other advantage is that the detector plane can have an arbitrary orientation with respect to the crystal surface. These unique imaging properties are obtained by bending the crystal into a certain shape, which is generated by arranging multiple cones from different aperture angles on a common nodal line. The test results were presented from optical tests of the multi-cone and single-cone structures. The numerical results on the deteriorations of the spectral and spatial resolutions are obtained due to the potential misalignments of the source. The concept of the configuration is considered to be particularly useful for high-power laser experiments where the size of the source is small and a wide spectral range would be diagnosed.

This paper describes a new objective for EUV lithography, EUV-microscopy, and 2D x-ray imaging, which similar to the well-known Schwarzschild objective and which consists of two concentric, convex and concave, spherical reflectors. Its essentially new feature is that it satisfies the Bragg condition for the wavelength of interest at every point on the surfaces of both reflectors. The reflectors would be spherical multi-layer structures with a uniform 2d-spacing, in the case of EUV radiation, and spherically bent crystals, in the case of x-rays. Thanks to this new feature, it is possible to obtain two-dimensional EUV or x-ray images from a large area, at once. The advantage for EUV lithography would be that an entire mask could be imaged onto a wafer, at once, and that a scanning of the mask by a narrow beam of EUV radiation – which is being used with present systems because the Bragg condition can only locally be satisfied - would no longer be necessary.

In inertial confinement fusion (ICF) experiments on the National Ignition Facility (NIF), measurements of average ion temperature using DT neutron time of flight broadening and of DD neutrons do not show the same apparent temperature. Some of this may be due to time and space dependent temperature profiles in the imploding capsule which are not taken into account in the analysis. As such, we are attempting to measure the electron temperature by recording the free-free electron-ion scattering-spectrum from the tail of the Maxwellian temperature distribution. This will be accomplished with the new NIF Continuum Spectrometer (ConSpec) which spans the x-ray range of 20 keV to 30 keV (where any opacity corrections from the remaining mass of the ablator shell are negligible) and will be sensitive to temperatures between ∼ 3 keV and 6 keV. The optical design of the ConSpec is designed to be adaptable to an x-ray streak camera to record time resolved free-free electron continuum spectra for direct measurement of the dT/dt evolution across the burn width of a DT plasma. The spectrometer is a conically bent Bragg crystal in a focusing geometry that allows for the dispersion plane to be perpendicular to the spectrometer axis. Additionally, to address the spatial temperature dependence, both time integrated and time resolved pinhole and penumbral imaging will be provided along the same polar angle. The optical and mechanical design of the instrument is presented along with estimates for the dispersion, solid angle, photometric sensitivity, and performance.

Soft x-ray detection with the new "multi-energy" PILATUS3 detector systems holds promise as a magnetically confined fusion (MCF) plasma diagnostic for ITER and beyond. The measured x-ray brightness can be used to determine impurity concentrations, electron temperatures, ne2Zeff products, and to probe the electron energy distribution. However, in order to be effective, these detectors which are really large arrays of detectors with photon energy gating capabilities must be precisely calibrated for each pixel. The energy-dependence of the detector response of the multi-energy PILATUS3 system with 100 K pixels has been measured at Dectris Laboratory. X-rays emitted from a tube under high voltage bombard various elements such that they emit x-ray lines from Zr-Lα to Ag-Kα between 1.8 and 22.16 keV. Each pixel on the PILATUS3 can be set to a minimum energy threshold in the range from 1.6 to 25 keV. This feature allows a single detector to be sensitive to a variety of x-ray energies, so that it is possible to sample the energy distribution of the x-ray continuum and line-emission. PILATUS3 can be configured for 1D or 2D imaging of MCF plasmas with typical spatial energy and temporal resolution of 1 cm, 0.6 keV, and 5 ms, respectively.

A compact multi-energy soft x-ray camera has been developed for time, energy and space-resolved measurements of the soft-x-ray emissivity in magnetically confined fusion plasmas. Multi-energy soft x-ray imaging provides a unique opportunity for measuring, simultaneously, a variety of important plasma properties (Te, nZ, ΔZeff, and ne,fast). The electron temperature can be obtained by modeling the slope of the continuum radiation from ratios of the available brightness and inverted radial emissivity profiles over multiple energy ranges. Impurity density measurements are also possible using the line-emission from medium- to high-Z impurities to separate the background as well as transient levels of metal contributions. This technique should be explored also as a burning plasma diagnostic in-view of its simplicity and robustness.

A high spatial resolution of a few μm is often required for probing small-scale high-energy-density plasmas using high resolution x-ray imaging spectroscopy. This resolution can be achieved by adjusting system magnification to overcome the inherent limitation of the detector pixel size. Laboratory experiments on investigating the relation between spatial resolution and system magnification for a spherical crystal spectrometer are presented. Tungsten Lβ2 rays from a tungsten-target micro-focus x-ray tube were diffracted by a Ge 440 crystal, which was spherically bent to a radius of 223 mm, and imaged onto an x-ray CCD with 13-μm pixel size. The source-to-crystal (p) and crystal-to-detector (q) distances were varied to produce spatial magnifications (M = q/p) ranging from 2 to 10. The inferred instrumental spatial width reduces with increasing system magnification M. However, the experimental measurement at each M is larger than the theoretical value of pixel size divided by M. Future work will focus on investigating possible broadening mechanisms that limit the spatial resolution.

During the past two years, key parts of poloidal and tangential x-ray imaging crystal spectrometers (PXCSs and TXCSs) have been upgraded. For poloidal XCSs, double-crystals of ArXVII and FeXXV were deployed. For fulfilling in situ alignment of a poloidal XCS, the beryllium window must be flexibly removed. By utilizing a design, where the beryllium window was installed in the vacuum chamber of the double-crystal, and between the double-crystal and wall of this chamber, an in situ alignment for the two spectrometers was fulfilled. Also, a new holder for the double-crystal was installed to allow for precise adjustments of azimuth angle and vertical height of the double-crystal. In order to facilitate these adjustments of double-crystal and installation of beryllium window, the chamber of the double-crystal for PXCS was upgraded from a cylinder to a cuboid. The distance between double-crystal and magnetic axis was extended from 8936 mm to 9850 mm in order to improve spatial resolution for PXCS, which is currently in the range from 1.237 mm to 4.80 mm at magnetic axis. Furthermore, a new pixelated detector (PILATUS 900K), which has a large sensitive area of 83.8 × 325.3 mm2 and which is vacuum compatible, is being implemented on the PXCS. This detector is mounted on a rail, so that its position can be changed by 50 mm to effectively record spectra of He-like argon and He-like iron (ArXVII and FeXXV). Similarly, a rail, which allows detector movement by 50 mm, was also installed in TXCS to alternatively record spectra of ArXVII and ArXVIII. Presently, the operation duration of PXCS and TXCS has been upgraded to hundreds of seconds in one shot. Ti- and uϕ-profiles measured by TXCS and charge exchange recombination spectroscopy (CXRS) were compared and found to be in good agreement.

A high-resolving-power x-ray spectrometer has been developed for the OMEGA EP Laser System based on a spherically bent Si [220] crystal with a radius of curvature of 330 mm and a Spectral Instruments (SI) 800 Series charge-coupled device. The instrument measures time-integrated x-ray emission spectra in the 7.97- to 8.11-keV range, centered on the Cu Kα1 line. To demonstrate the performance of the spectrometer under high-power conditions, Kα1,2 emission spectra were measured from Cu foils irradiated by the OMEGA EP laser with 100-J, 1-ps pulses at focused intensities above 1018 W/cm2. The ultimate goal is to couple the spectrometer to a picosecond x-ray streak camera and measure temperature-equilibration dynamics inside rapidly heated materials. The plan for these ultrafast streaked x-ray spectroscopy studies is discussed.

A two-crystal X-ray spectrometer system has been implemented in the EAST tokamak to simultaneously diagnose high- and low-temperature plasmas using He- and H-like argon spectra. But for future fusion devices like ITER and Chinese Fusion Engineering Test Reactor (CFETR), argon ions become fully stripped in the core and the intensity of the H-like lines will be significantly at high temperatures (Te > 5 keV). With increasing auxiliary heating power on EAST, the core plasma temperature could also reach 5 keV and higher. In such conditions, the use of a xenon puff becomes an appropriate choice for both ion-temperature and flow-velocity measurements. A new two-crystal system using a quartz 110 crystal (2d = 4.913 A) to view He-like argon lines and a quartz 011 crystal (2d = 6.686 A) to view Ne-like xenon spectra has been deployed on a poloidal X-ray crystal spectrometer. While the He-like argon spectra will be used to measure the plasma temperature in the edge plasma region, the Ne-like xenon spectra will be used for measurement in the hot core. The new crystal arrangement allows a wide temperature measurement ranging from 0.5 to 10 keV or even higher, being the first tests for burning plasmas like ITER and CFETR. The preliminary result of lab-tests, Ne-like xenon lines measurement will be presented.

A high resolution, Diagnostic Instrument Manipulator (DIM)-based x-ray Bragg crystal spectrometer has been calibrated for and deployed at the National Ignition Facility (NIF) to diagnose plasma conditions in ignition capsules near stagnation times. The spectrometer has two conical crystals in the Hall geometry focusing rays from the Kr Heα, Lyα, and Heβ complexes onto a streak camera, with the physics objectives of measuring time-resolved electron density and temperature through observing Stark broadening and the relative intensities of dielectronic satellites. A third von Hamos crystal that time-integrates the Kr Heα, Heβ and intervening energy range provides in situ calibration for the streak camera signals. The spectrometer has been absolutely calibrated using a microfocus x-ray source, an array of CCD and single-photon-counting detectors, and multiple K- and L-absorption edge filters at the Princeton Plasma Physics Laboratory (PPPL) x-ray laboratory. Measurements of the integrated reflectivity, energy range, and energy resolution for each crystal are discussed. These calibration data provide absolute x-ray signal levels for NIF measurements, enabling precise filter selection and comparisons to simulations.

An in situ wavelength calibration system for the X-ray Imaging Crystal Spectrometer (XICS) on W7-X has been developed to provide routine calibration between plasma shots. XICS is able to determine plasma flow profiles by measuring the Doppler shift of x-ray line emission from highly charged impurity species. A novel design is described that uses an x-ray tube with a cadmium anode placed in front of the diffracting spherically bent crystal. This arrangement provides calibration lines over the full detector extent for both the Ar16+ and Ar17+/Fe24+ spectrometer channels. This calibration system can provide a relative wavelength accuracy of 3 × 10-7 A across the full spatial extent of the detector, which corresponds to 50 m/s in the W7-X system. An absolute wavelength calibration of 1 × 10-5 A is expected, corresponding to 1 km/s, based on the current known accuracy of the calibration wavelength and the achievable measurement of the absolute positioning of the hardware. This calibration system can be used to independently calibrate XICS systems on both stellarators and tokamaks, without the need for special plasma conditions often used for calibration, such as locked modes on tokamaks. Experimental and simulated results are shown along with expected results, and the complete design of the calibration hardware that is to be installed in the W7-X XICS system.

A new simple method is presented for the wavelength calibration and measurement of poloidal rotation velocities with X-ray imaging crystal spectrometer (XICS) in magnetic fusion devices. In this method, the toroidal rotation of plasma is applied for high precise alignment and wavelength calibration of the poloidal XICS. The measurement threshold of poloidal rotation velocity can be lowered to 1–3 km/s with this method.

An attempt was made to improve the spatio-temporal resolution of the tangential X-ray crystal spectrometer (XCS) on the Experimental Advanced Superconducting Tokamak (EAST) by evaluating experimentally the applicability of a novel X-ray photon detection technology for measuring the satellite spectra of Ar XVII with a high counting rate. High-resolution experimental data on the profiles of ion temperature and plasma rotation velocity facilitate the studies of the mechanisms underlining important physical phenomena, such as plasma heating, L-H transition and momentum transport. Based on silicon diode array and single-photon counting technology, a relatively small area (83.8?33.5 mm2) two-dimensional detector was successfully installed and tested in the recent EAST campaign. X-ray photon counting rate higher than 20 MHz was observed for the first time, and high quality satellite spectra were recorded for ion temperature and plasma rotation measurement, indicating that the new technology is suitable for the next-step high-resolution XCS on EAST, and the deployment of a detector array with a much larger X-ray sensing area is planned for better plasma coverage.

An analysis of the radial electric field and heat transport, both for ions and electrons, is presented for a high-$${ {T}_{\text{e}}}$$ electron cyclotron heated (ECH) discharge on the large helical device (LHD). Transport analysis is done using the task3d transport suite utilizing experimentally measured profiles for both ions and electrons. Ion temperature and perpendicular flow profiles are measured using the recently installed x-ray imaging crystal spectrometer diagnostic (XICS), while electron temperature and density profiles are measured using Thomson scattering. The analysis also includes calculated ECH power deposition profiles as determined through the travis ray-tracing code. This is the first time on LHD that this type of integrated transport analysis with measured ion temperature profiles has been performed without NBI, allowing the heat transport properties of plasmas with only ECH heating to be more clearly examined. For this study, a plasma discharge is chosen which develops a high central electron temperature ($${ {T}_{\text{eo}}}=9$$ keV) at moderately low densities ($${ {n}_{\text{eo}}}=1.5\times { {10}^{19}}$$ m-3). The experimentally determined transport properties from task3d are compared to neoclassical predictions as calculated by the gsrake and fortec-3d codes. The predicted electron fluxes are seen to be an order of magnitude less than the measured fluxes, indicating that electron transport is largely anomalous, while the neoclassical and measured ion heat fluxes are of the same magnitude. Neoclassical predictions of a strong positive ambipolar electric field ($${ {E}_{\text{r}}}$$ ) in the plasma core are validated through comparisons to perpendicular flow measurements from the XICS diagnostic. Furthermore, this provides confidence that the predictions are producing physically meaningful results for the particle fluxes and radial electric field, which are a key component in correctly predicting plasma confinement.

A new high-resolution tangential imaging X-ray crystal spectrometer (TXCS) is described for implementation on the Experimental Advanced Superconducting Tokamak (EAST) to provide spatially and temporally resolved data on the toroidal plasma rotation velocity and on the ion and the electron temperature. These data are derived from observations of the satellite spectra of heliumlike argon (Ar XVII). The TXCS will provide data for all experimental conditions, which include ohmically heated discharges as well as plasmas with radio-frequency (RF) waves and neutral-beam heating. The latest experimental results show that lower hybrid waves (LHW) induce a co-current change in a toroidal rotation of up to 45 km/s in the L-mode plasma core region. A modification of the toroidal rotation develops on the extended plasma region and a long time scale (≥1 s). The experimental setup and the initial experimental results are presented.

Major developments on the Mega Amp Spherical Tokamak (MAST) have enabled important advances in support of ITER and the physics basis of a spherical tokamak (ST) based component test facility (CTF), as well as providing new insight into underlying tokamak physics. For example, L–H transition studies benefit from high spatial and temporal resolution measurements of pedestal profile evolution (temperature, density and radial electric field) and in support of pedestal stability studies the edge current density profile has been inferred from motional Stark effect measurements. The influence of the q-profile and E × B flow shear on transport has been studied in MAST and equilibrium flow shear has been included in gyro-kinetic codes, improving comparisons with the experimental data. H-modes exhibit a weaker q and stronger collisionality dependence of heat diffusivity than implied by IPB98(y,2) scaling, which may have important implications for the design of an ST-based CTF. ELM mitigation, an important issue for ITER, has been demonstrated by applying resonant magnetic perturbations (RMPs) using both internal and external coils, but full stabilization of type-I ELMs has not been observed. Modelling shows the importance of including the plasma response to the RMP fields. MAST plasmas with q > 1 and weak central magnetic shear regularly exhibit a long-lived saturated ideal internal mode. Measured plasma braking in the presence of this mode compares well with neo-classical toroidal viscosity theory. In support of basic physics understanding, high resolution Thomson scattering measurements are providing new insight into sawtooth crash dynamics and neo-classical tearing mode critical island widths. Retarding field analyser measurements show elevated ion temperatures in the scrape-off layer of L-mode plasmas and, in the presence of type-I ELMs, ions with energy greater than 500 eV are detected 20 cm outside the separatrix. Disruption mitigation by massive gas injection has reduced divertor heat loads by up to 70%.

The results from the investigation of neoclassical core transport and the role of the radial electric field profile (Er) in the first operational phase of the Wendelstein 7-X (W7-X) stellarator are presented. In stellarator plasmas, the details of the Er profile are expected to have a strong effect on both the particle and heat fluxes. Investigation of the radial electric field is important in understanding neoclassical transport and in validation of neoclassical calculations. The radial electric field is closely related to the perpendicular plasma flow (u⊥) through the force balance equation. This allows the radial electric field to be inferred from measurements of the perpendicular flow velocity, which can be measured using the x-ray imaging crystal spectrometer and correlation reflectometry diagnostics. Large changes in the perpendicular rotation, on the order of Δu⊥∼ 5 km/s (ΔEr ∼ 12 kV/m), have been observed within a set of experiments where the heating power was stepped down from 2 MW to 0.6 MW. The...

Spectroscopy of radiation emitted by impurities and hydrogen isotopes plays an important role in the study of magnetically confined fusion plasmas, both in determining the effects of impurities on ...

The paper reviews the results from tokamak experiments and measurements on electron beam ion traps for the line ratios x/w, y/w, and z/w in the spectra of helium-like ions with Z in the range from 14 to 28. With the exception of the DITE experiments, where these line ratios were found to be in agreement with theoretical predictions, all other tokamak experiments yielded values that were significantly greater than predicted. The reasons for these discrepancies are not yet understood. It is possible that radial profile effects were not properly taken into account in the majority of the tokamak experiments. The paper also gives a short historical review of the X-ray diagnostic developments and presents very recent data from a new type of X-ray imaging crystal spectrometer, which records spatially resolved spectra with a spatial resolution of about 1 cm in the plasma. These new data can be Abel inverted, so that it will be possible to determine line ratios at each radial position in the plasma. Effects of radial profiles, which may have affected the chord-integrated measurements of the past, will thus be eliminated in the future. PACS Nos.: 52.55.Fa, 32.30.Rj

Electron beam ion traps are uniquely well suited for laboratory astrophysics because they can produce nearly any charge state of any element in a collisionally excited plasma that is comparable in density and temperature to many astronomical sources. The Lawrence Livermore EBIT facility has been optimized for laboratory astrophysics with a suite of dedicated instruments and has made significant advances in this field. This paper reviews some of the work performed at LLNL in compiling comprehensive spectral catalogues, discovery of a magnetic field line diagnostic in the EUV and soft X-ray regimes, and density diagnostics on EBIT and at the NSTX tokamak.PACS Nos.: 95.30.Ky, 32.30.Rj, 95.75.–z, 95.85.Nv, 97.10.Ex, 95.55.Ka, 95.85.Mt, 52.55.Fa

This paper describes a new type of x-ray crystal spectrometer, which can be used in combination with gated x-ray detectors to obtain spectra from laser-produced plasmas with a high (sub-ns) time resolution. The spectrometer consists of a convex, spherically bent crystal, which images individual spectral lines as perfectly straight lines across multiple, sequentially gated, strip detectors. Since the Bragg-reflected rays are divergent, the distance between detector and crystal is arbitrary, so that this distance can be appropriately chosen to optimize the experimental arrangement with respect to the detector parameters. The spectrometer concept was verified in proof-of-principle experiments by imaging the Lβ1- and Lβ2-lines of tungsten, at 9.6735 and 9.96150 keV, from a micro-focus x-ray tube with a tungsten target onto a two-dimensional pixilated Pilatus detector, using a convex, spherically bent Si-422 crystal with a radius of curvature of 500 mm.

A high resolution 1D imaging x-ray spectrometer concept comprising a spherically bent crystal and a 2D pixelated detector is being optimized for diagnostics of small sources such as high energy density physics (HEDP) and synchrotron radiation or x-ray free electron laser experiments. This instrument is used on tokamak experiments for Doppler measurements of ion temperature and plasma flow velocity profiles. Laboratory measurements demonstrate a resolving power, E/ΔE of order 10 000 and spatial resolution better than 10 μm. Initial tests of the high resolution instrument on HEDP plasmas are being performed.

The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high βT in order to advance the spherical torus (ST) concept. In order to do this, NSTX utilizes up to 7.5 MW of neutral beam injection, up to 6 MW of high harmonic fast waves (HHFWs), and it operates with plasma currents up to 1.5 MA and elongations of up to 2.6 at a toroidal field up to 0.45 T. New facility, and diagnostic and modelling capabilities developed over the past two years have enabled the NSTX research team to make significant progress towards establishing this physics basis for future ST devices. Improvements in plasma control have led to more routine operation at high elongation and high βT (up to ~40%) lasting for many energy confinement times. βT can be limited by either internal or external modes. The installation of an active error field (EF) correction coil pair has expanded the operating regime at low density and has allowed for initial resonant EF amplification experiments. The determination of the confinement and transport properties of NSTX plasmas has benefitted greatly from the implementation of higher spatial resolution kinetic diagnostics. The parametric variation of confinement is similar to that at conventional aspect ratio but with values enhanced relative to those determined from conventional aspect ratio scalings and with a BT dependence. The transport is highly dependent on details of both the flow and magnetic shear. Core turbulence was measured for the first time in an ST through correlation reflectometry. Non-inductive start-up has been explored using PF-only and transient co-axial helicity injection techniques, resulting in up to 140 kA of toroidal current generated by the latter technique. Calculated bootstrap and beam-driven currents have sustained up to 60% of the flat-top plasma current in NBI discharges. Studies of HHFW absorption have indicated parametric decay of the wave and associated edge thermal ion heating. Energetic particle modes, most notably toroidal Alfven eigenmodes and fishbone-like modes result in fast particle losses, and these instabilities may affect fast ion confinement on devices such as ITER. Finally, a variety of techniques has been developed for fuelling and power and particle control.

Enhanced confinement regimes with steep gradients of density profiles and the need to place rotation velocity profiles call for maximum spatial resolution in the tokamak plasma. It is proposed to achieve such a resolution by using X-ray spectroscopy with double reflections in single crystals.

An overview of the research capabilities and the future plans on the MA-class National Spherical Torus Experiment (NSTX) at Princeton is presented. NSTX research is exploring the scientific benefits of modifying the field line structure from that in more conventional aspect ratio devices, such as the tokamak. The relevant scientific issues pursued on NSTX include energy confinement, MHD stability at high beta, non-inductive sustainment, solenoid-free start-up, and power and particle handling. In support of the NSTX research goal, research tools are being developed by the NSTX team. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a high beta Demo device based on the ST, are being considered. For these, it is essential to develop high performance (high beta and high confinement), steady-state (non-inductively driven) ST operational scenarios and an efficient solenoid-free start-up concept. We will also briefly describe the Next-Step-ST (NSST) device being designed to address these issues in fusion-relevant plasma conditions.

A new type of high-resolution x-ray imaging crystal spectrometer is being developed to measure ion and electron temperature profiles in tokamak plasmas. The instrument is particularly valuable for diagnosing plasmas with purely ohmic heating and rf heating, since it does not require the injection of a neutral beam—although it can also be used for the diagnosis of neutral-beam heated plasmas. The spectrometer consists of a spherically bent quartz crystal and a two-dimensional position-sensitive detector. It records spectra of helium-like argon (or krypton) from multiple sightlines through the plasma and projects a de-magnified image of a large plasma cross section onto the detector. The spatial resolution in the plasma is solely determined by the height of the crystal, its radius of curvature, and the Bragg angle. This new x-ray imaging crystal spectrometer may also be of interest for the diagnosis of ion temperature profiles in future large tokamaks, the Korea Superconducting Tokamak Advanced Research tok...

The L-shell emission spectrum of Fe XVII is measured in high-temperature laboratory plasmas, and the inferred intensities of the 3s → 2p transitions relative to those of the dominant 3d → 2p transition are compared to solar observations, as well as to observations of Capella, Procyon, Castor C, II Pegassi, and NGC 4636 with the Chandra and XMM-Newton X-ray observatories. The results from laboratory and astrophysical plasmas are in very good agreement, indicating that the collisional line formation processes found in low-density, high-temperature laboratory plasmas are a good description of those found in astrophysical plasmas. The laboratory observations disagree, however, to varying degrees with spectral modeling calculations. A review of existing laboratory measurements suggests that the intensity of the dominant 3d → 2p transition is overestimated by spectral modeling predications. By calibrating spectral models with laboratory data, especially by decreasing the strength of the dominant 3d → 2p transition, spectral models can be brought into agreement with the majority of solar and astrophysical observations. Without doing so, opacity effects may be grossly overestimated.

A major research goal of the national spherical torus experiment is establishing long-pulse, high beta, high confinement operation and its physics basis. This research has been enabled by facility capabilities developed during 2001 and 2002, including neutral beam (up to 7?MW) and high harmonic fast wave (HHFW) heating (up to 6?MW), toroidal fields up to 6?kG, plasma currents up to 1.5?MA, flexible shape control, and wall preparation techniques. These capabilities have enabled the generation of plasmas with of up to 35%. Normalized beta values often exceed the no-wall limit, and studies suggest that passive wall mode stabilization enables this for H mode plasmas with broad pressure profiles. The viability of long, high bootstrap current fraction operations has been established for ELMing H mode plasmas with toroidal beta values in excess of 15% and sustained for several current relaxation times. Improvements in wall conditioning and fuelling are likely contributing to a reduction in H mode power thresholds. Electron thermal conduction is the dominant thermal loss channel in auxiliary heated plasmas examined thus far. HHFW effectively heats electrons, and its acceleration of fast beam ions has been observed. Evidence for HHFW current drive is obtained by comparision of the loop voltage evolution in plasmas with matched density and temperature profiles but varying phases of launched HHFW waves. Studies of emissions from electron Bernstein waves indicate a density scale length dependence of their transmission across the upper hybrid resonance near the plasma edge that is consistent with theoretical predictions. A peak heat flux to the divertor targets of 10?MW?m?2 has been measured in the H mode, with large asymmetries being observed in the power deposition between the inner and outer strike points. Non-inductive plasma startup studies have focused on coaxial helicity injection. With this technique, toroidal currents up to 400?kA have been driven, and studies to assess flux closure and coupling to other current drive techniques have begun.

This article describes an efficient method for the simultaneous measurement of the integrated reflectivity of a crystal in multiple orders of reflection at a predefined Bragg angle by using the bremsstrahlung continuum from an x-ray tube in combination with an energy-sensitive detector. The technique is demonstrated with a mica crystal for Bragg angles of 43°, 47°, and 50°. The measured integrated reflectivity for Bragg reflections up to the 24th order is compared with theoretical predictions, which are also presented in this article.

Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta (?), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values ?T of up to 35% with a near unity central ?T have been obtained. NSTX will be exploring advanced regimes where ?T up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction (~60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fast wave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX to test the method up to Ip ~ 500?kA. In parallel, start-up using a RF current drive and only external poloidal field coils are being developed on NSTX. The area of power and particle handling is expected to be challenging because of the higher power density expected in the ST relative to that in conventional aspect-ratio tokamaks. Due to its promise for power and particle handling, liquid lithium is being studied in CDX-U as a potential plasma-facing surface for a fusion reactor.

High harmonic fast wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [M. Ono, S. M. Kaye, S. Neumeyer et al., in Proceedings of the 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999 (IEEE, Piscataway, NJ, 1999), p. 53] is such a device. An rf heating system has been installed on the NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the ST concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to ...

A high-resolution x-ray crystal spectrometer has recently been installed at the National Spherical Torus Experiment to record the satellite spectra of helium-like argon, Ar XVII, in the wavelength range from 3.94 to 4.00 A for measurements of ion and electron temperatures, and measurements of the ionization equilibrium of argon, which is of interest for studies of ion transport. The instrument presently consists of a spherically bent quartz crystal and a conventional one-dimensional position-sensitive multiwire proportional counter, but it will soon be upgraded to a new type of x-ray imaging crystal spectrometer by the installation of a large size (10 cm×30 cm) two-dimensional position-sensitive detector that will allow us to obtain temporally and spatially resolved spectra from a 80 cm high cross-section of the plasma. In its present configuration, the spectrometer has been optimized for high throughput so that it is possible to record spectra with small statistical errors with a time resolution of 10 ms...