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Using the open-source code SMILEI [J. Derouillat et al., Comput. Phys. Commun. 222, 351-373 (2018)], we perform one-dimensional full-f particle-in-cell (PIC) simulations of parasitic electrostatic wave excitation in the Ion Cyclotron Range of Frequencies (ICRF) and High Harmonic Fast Wave (HHFW) regimes in an inhomogeneous plasma. We first study direct coupling from the fast wave to electrostatic waves at the lower hybrid (LH) resonance (S=0). In the ICRF regime, we show that the fast wave can couple to the Ion Bernstein Wave (IBW), which propagates beyond the LH resonance layer. On the other hand, in the HHFW regime, no direct coupling to the IBW is observed, but electrostatic waves, likely to be Hot Ion Plasma Waves (HIPW or HPW), are seen on the low-density side of the LH resonance layer. The coupling efficiency to electrostatic waves is seen to increase with ion temperature. Parametric decay instabilities (PDIs) are then investigated in both regimes. In the ICRF regime, both resonant and non-resonant decay channels are observed and compared with theory. In the HHFW regime, we observe multiple sidebands separated by the ion cyclotron frequency, as measured experimentally on NSTX [J. R. Wilson et al., AIP Conf. Proc. 787, 66 (2005)]. The nature of these waves is discussed. Perpendicular ion heating is also found in the region where PDIs occur, consistent with experimental observations. [ABSTRACT FROM AUTHOR]

This paper reports the recent progress towards a whole-device scale RF actuator simulation. Our approach is to combine progresses made by open source scientific and math software communities for meshing, FEM assembly, and linear solvers to construct an integrated FEM fullwave simulation framework (the Petra-M FEM framework). The goal is to bring in engineering CAD level geometrical detail to our wave simulation capability, and advanced RF wave physics models, such as RF rectified sheath models and non-local hot plasma effects. In Petra-M, the high harmonic fast wave (HHFW) propagation was fully resolved in a 3D NSTX-U torus. In the NSTX-U simulation, the ratio between wavelength to the device size reaches 15, which is in the range required for resolving the ICRF wave fields in ITER. Verification and validation of the RF wave field computed by Petra-M through the international/multi-institutional efforts has been a major research focus, which yields an excellent code benchmark agreement between Petra-M, TOPICA and RAPLCIASOL. The spectral analysis of 3D wave field has been performed to interrogate the wave field behavior, which shows the consistency with the wave theory. RF rectified potential model was incorporated in our wave field solver. We developed a new non-linear iteration algorithm, which allows for using both the thick sheath (asymptotic) model and non-linear sheath impedance models seamlessly. The 3D RF sheath simulation on the WEST ICRF antenna indicates that the sheath potential tends to concentrate near the corner of antenna box, which is consistent with experimental observation of RF induced heat load pattern. [ABSTRACT FROM AUTHOR]

Effects of ion collision in collisional radiative (CR) processes are investigated using a newly developed CR model for hydrogen atom. Population density is systematically investigated. Significance on ion collision is quantitatively clarified. Tradi- tional CR model overestimate population density more than 10% compared to the CR model with ion collision for high density, high temperature plasma. Using the ion temperature dependence of Balmer line intensity ratios, ion temperature measurement is possible. High temperature ion superimposed to recombining plasma also affects population density but quantitatively limited in practical cases. [ABSTRACT FROM AUTHOR]

In a thermonuclear reactor plasma interacts with the divertor walls in the form of periodic heat pulses as well as constant heat load. As a result, residual plastic deformations and mechanical stresses can occur, which cause destruction of the divertor material. However, these residual deformations and stresses can be relieved under the influence of constant flux of plasma and the consequential high temperature of the material. The goal of this work was the study of residual stresses dynamics in a heated material. Residual deformations and stresses were measured using X-ray diffractometry. The measurements were conducted on tungsten samples that were irradiated with an electron beam on the BETA facility with the purpose of simulating plasma heat loads. Synchrotron radiation scattering station "Anomalous scattering" on the beam line 2 of VEPP-3 was used to measure diffractograms from which scattering angle – sample tilt angle dependencies were obtained. The experimental data was used for calculation of deformation and stress tensor components. To compare heat load and residual stress profiles the measurements were conducted with spatial resolution. Synchrotron radiation scattering station "Diffraction movie" was used for measuring the dynamics of residual stresses during heating. As a result of these experiments scattering angle – temperature dependencies were obtained. Residual stresses relaxation was measured, the result has met our expectations. [ABSTRACT FROM AUTHOR]

A simplified, flat, plasma-loaded, ion-cyclotron antenna has been simulated using three different modeling approaches and a comparison of simulation outputs is presented in this paper. Several plasma profiles with different density gradients and distances between the antenna and the cutoff density have been used as benchmark for the numerical simulations, which have been run at 30 MHz by means of two tools. The one is the TOrino Polythecnic Ion-Cyclotron Antenna (TOPICA) code that has been repeatedly used and validated for this type of problems. The other tool is the finite-element method (FEM) of a commercial software, where inhomogeneous anisotropic materials can be defined and the perfectly matched layer technique can be adopted. In this tool, two models of antenna load have been implemented: an equivalent dielectric, locally matching the perpendicular propagation constant of the fast wave in the plasma, and a cold plasma model. The simulation results by such models are compared with the results by TOPICA, which relies on a 1-D inhomogeneous, hot plasma. [ABSTRACT FROM AUTHOR]

Using the example of a solenoid in a coaxial cylindrical screen, the possibility of development of a quasiforce- free double-layer coil that is balanced along the entire length is shown. It has been shown previously that such magnet is characterized by significantly reduced mechanical stresses. In particular, it has been demonstrated by means of axisymmetric computations that the mentioned stresses are about an order less than the magnetic pressure of the generated field. However, the strength of actually manufactured multi-turn coils is inevitably less than predicted by axisymmetric simulations due to the inter-turn gaps filled with dielectric medium and due to the effect of magnetic flux density components that are normal to the coil. It is shown in the paper that application of high-modulus dielectrics and field correction by split screens allow one to reduce the role of these factors and to develop a magnet in which the stresses do not exceed 1 GPa. That opens up possibilities of using such field for the confinement of hot dense plasma in controlled thermonuclear fusion reactors. [ABSTRACT FROM AUTHOR]

An electric explosion occurs when a micron-scale metal film, such as a copper film, is stimulated by a shorttime current pulse, while generating high temperature and high-pressure plasma. In this paper, the electric explosion process is divided into two stages, namely, the energy deposition stage and the quasi-isentropic expansion stage, and a dynamic EOS of the plasma considering the energy replenishment is established. On this basis, a flyer driven by plasma is studied numerically, and the pressure and the internal energy of plasma are obtained based on the simulation result which has been validated by experimental result. The influence of the backplane material on flyer velocity is analyzed. [ABSTRACT FROM AUTHOR]

The development of the fourth generation light sources based on the X-ray free electron laser (XFEL) opens new perspectives in the investigation of high-energy-density plasmas. The properties of these tunable X-ray laser sources permit to consider an active spectroscopy experiments to improve the understanding of hot and dense plasmas. In this work, we present prospective calculations of spectral line shapes and redistribution functions of the neon-like aluminum 1s2s22p6nl - 1s22s22p5nl, (n = 3, 4, 5, ..) and 1s2s22p63l - 1s22s22p6 lines at 1490 eV and 1572 eV, respectively, for typical laser-plasma conditions. These calculations are based on a theoretical model for calculating the redistribution function in hot and dense plasmas. It relies on an extension of the Frequency Fluctuation of Model. This model takes into account the complexity of the atomic structure of ionic emitters and the various line broadening mechanisms including effects of the emitter environment fluctuations. [ABSTRACT FROM AUTHOR]

The broadening of lines by Stark effect is widely used for inferring electron density and temperature in plasmas. Starkeffect calculations often rely on atomic data (transition rates, energy levels,...) not always exhaustive and/or valid only for isolated atoms. In this work, we first present a recent development in the detailed opacity code SCO-RCG for K-shell spectroscopy. The approach is adapted from the work of Gilles and Peyrusse. Neglecting non-diagonal terms in dipolar and collision operators, the line profile is expressed as a sum of Voigt functions associated to the Stark components. The formalism relies on the use of parabolic coordinates and the relativistic fine structure of Lyman lines is included by diagonalizing the Hamiltonian matrix associated to quantum states having the same principal quantum number n. The SCO-RCG code enables one to investigate plasma environment effects, the impact of the microfield distribution, the decoupling between electron and ion temperatures and the role of satellite lines (such as Li-like 1snℓn'ℓ' - 1s2nℓ, Be-like, etc.). Atomic structure calculations have reached levels of accuracy which require evaluation of Breit interaction and many-electron quantum electro-dynamics (QED) contributions. Although much work was done for QED effects (self-energy and vacuum polarization) in hydrogenic atoms, the case of an arbitrary number of electrons is more complicated. Since exact analytic solutions do not exist, a number of heuristic methods have been used to approximate the screening of additional electrons in the self-energy part. We compare different ways of including such effects in atomic-structure codes (Slater-Condon, Multi-Configuration Dirac-Fock, etc.). [ABSTRACT FROM AUTHOR]

The study of spectra of gamma-ray burst is certainly a very promising part of the GRB studies. More and more data are available for GRBs and with time-sequence analysis it is possible also to propose a link with the other set of data represented by the light curves. Consequently, the explanation of the spectra requires both the local physical condition of the engine as well as the dynamic of the explosion process. In this view, we have analysed the GRB spectra with a specific model: black-body + thermal Bremsstrahlung. Our results show that this model is consistent with the observed GRB spectra. We can derive the temperature of the hot plasma needed to reproduce this spectrum consistent with the core of a very hot star ~ 109 K. We have also found a correlation between the variation in time of this temperature and the variation of the spikes in luminosity of the light curves. This time profile each spike could be the correct fingerprint of the GRB physical process. Each spike, as a fingerprint, could keep the memory of the GRB physical process. If this model find a confirmation for other GRBs, this idea will ask us to open a new paradigm in GRB physics. [ABSTRACT FROM AUTHOR]

Superconducting ECR ion source incorporated with the cutting edge techniques provides the ultimate conditions for highly charged ion beam production. In the last 12 years (since ICIS2005 in Caen, France), ECR ion source performance has got remarkable improvement, most of the typical ion beam intensity records have been renewed almost every year, with the great efforts in superconducting ECR ion source development. SECRAL and recently built SECRAL II ion sources are both high performance 3rd generation ECR ion sources developed at IMP. Technical advancement has obviously helped to boost the yield of high charge state ion beams. For instance, only 8.5 eμA Ar17+ has been produced in 2007 with SECRAL, and up to 130 eμA Ar17+ has been recently made with SECRAL II during a high microwave power test. Similar improvement also applies to many other highly charged heavy ion beams. These promising results owe to the continuous technical modification and optimization for dense hot plasma buildup, highly charged ion production, intense beam extraction and high efficiency transmission with reasonable beam quality. This paper will summarize the achievements made with both SECRAL and SECRAL II. The technical solutions to make very intense highly charged ion beams will be discussed and presented. [ABSTRACT FROM AUTHOR]

In this paper we report the first observation of x-ray radiation from the new Clemson University Electron Beam Ion Trap (CUEBIT). The analysis of the emitted dielectronic recombination x-ray photons from highly charged argon ions allowed us to probe parameters specific to the ion cloud inside the machine. Argon dielectronic resonances could provide a standard method to cross-compare the electron beam and ion cloud characteristics of different devices. [ABSTRACT FROM AUTHOR]

The review is made of the problems of ITER optical diagnostics. Most of these problems will be related to the intensive neutron radiation from hot plasma. At a high level of radiation loads the most types of materials gradually change their properties. This effect is most critical for optical diagnostics because of degradation of optical glasses and mirrors. The degradation of mirrors, that collect the light from plasma, basically will be induced by impurity deposition and (or) sputtering by charge exchange atoms. Main attention is paid to the search of glasses for vacuum windows and achromatic lens which are stable under ITER irradiation conditions. The last results of irradiation tests in nuclear reactor of candidate silica glasses KU-1, KS-4V and TF 200 are presented. An additional problem is discussed that deals with the stray light produced by multiple reflections from the first wall of the intense light emitted in the divertor plasma. [ABSTRACT FROM AUTHOR]

A Synthetic Aperture Microwave Imaging (SAMI) system has been designed and built to obtain 2-D images at several frequencies from fusion plasmas. SAMI uses a phased array of linearly polarised antennas. The array configuration has been optimised to achieve maximum synthetic aperture beam efficiency. The signals received by antennas are down-converted to the intermediate frequency range and then recorded in a full vector form. Full vector signals allow beam focusing and image reconstruction in both real time and a post-processing mode. SAMI can scan over 16 pre-programmed frequencies in the range of 10-35GHz with a switching time of 300ns. The system operates in 2 different modes simultaneously: both a 'passive' imaging of plasma emission and also an 'active' imaging of the backscattered signal of the radiation launched by one of the antennas from the same array. This second mode is similar to socalled Doppler backscattering (DBS) reflectometry with 2-D resolution of the propagation velocity of turbulent structures. Both modes of operation show good performance in fusion plasma experiments on Mega Amp Spherical Tokamak (MAST). We have obtained the first ever 2-D images of BXO mode conversion windows. With active probing, first ever turbulence velocity maps have been obtained. We present an overview of the diagnostic and discuss recent results. In contrast to quasi-optical microwave imaging systems SAMI requires neither big aperture viewing ports nor large 2-D detector arrays to achieve the desired imaging resolution. The number of effective 'pixels' of the synthesized image is proportional to the number of receiving antennas squared. Thus only a small number of optimised antennas is sufficient for the majority of applications. Possible implementation of SAMI on ITER and DEMO is discussed. [ABSTRACT FROM AUTHOR]

Various active control strategies of the Neoclassical tearing modes are being studied in present tokamaks using established detection techniques which exploit the measurements of the fluctuations of the magnetic field and of the electron temperature. The extrapolation of such techniques to the fusion reactor scale is made problematic by the neutron fluence and by the physics conditions related to the high plasma temperature and density which degrade the spatial resolution of such measurements. [ABSTRACT FROM AUTHOR]

The effective viscosity of a homogeneous magnetized shear flow is calculated for the two-dimensional case of hot plasma without rotation and for large Reynolds numbers. The general magnetohydrodynamic equations are solved in the wave-vector space and the spectral density of slow magnetosonic waves (SMWs) is numerically calculated. The analytical solution of SMWs amplification for evanescent dissipation gives the basis of the Kraichnan wave turbulence. [ABSTRACT FROM AUTHOR]

An increasing number of physics experiments require low background materials for their construction. The presence of Uranium and Thorium and their progeny in these materials present a variety of unwanted background sources for these experiments. The sensitivity of the experiments continues to drive the necessary levels of detection ever lower as well. This requirement for greater sensitivity has rendered direct radioassay impractical in many cases requiring large quantities of material, frequently many kilograms, and prolonged counting times, often months. Other assay techniques have been employed such as Neutron Activation Analysis but this requires access to expensive facilities and instrumentation and can be further complicated and delayed by the formation of unwanted radionuclides. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is a useful tool and recent advancements have increased the sensitivity particularly in the elemental high mass range of U and Th. Unlike direct radioassay, ICP-MS is a destructive technique since it requires the sample to be in liquid form which is aspirated into a high temperature plasma. But it benefits in that it usually requires a very small sample, typically about a gram. This paper discusses how a variety of low background materials such as copper, polymers, and fused silica are made amenable to ICP-MS assay and how the arduous task of maintaining low backgrounds of U and Th is achieved. [ABSTRACT FROM AUTHOR]

We present spectra of highly charged iron, gadolinium, and tungsten ions obtained with electron beam ion traps. Spectroscopic studies of these ions are important to diagnose and control hot plasmas in several areas. For iron ions, the electron density dependence of the line intensity ratio in extreme ultraviolet spectra is investigated for testing the model calculation used in solar corona diagnostics. Soft x-ray spectra of gadolinium are studied to obtain atomic data required in light source development for future lithography. Tungsten is considered to be the main impurity in the ITER plasma, and thus visible and soft x-ray spectra of tungsten have been observed to explore the emission lines useful for the spectroscopic diagnostics of the ITER plasma. [ABSTRACT FROM AUTHOR]

We study the various physical processes and their timescales involved in the excitation of wakefields in relativistically hot plasma. This has relevance to the design of a high repetition-rate plasma wakefield collider in which the plasma has not had time to cool between bunches in addition to understanding the physics of cosmic jets in relativistically hot astrophysical plasmas. When the plasma is relativistically hot (plasma temperature near mec2), the thermal pressure competes with the restoring force of ion space charge and can reduce or even eliminate the accelerating field of a wake. We will investigate explicitly the case where the hot plasma is created by a preceding Wakefield drive bunch 10's of picoseconds to many nanoseconds ahead of the next drive bunch. The relativistically hot plasma is created when the excess energy (not coupled to the driven e- bunch) in the wake driven by the drive e- bunch is eventually converted into thermal energy on 10's of picosecond timescale. We will investigate the thermalization and diffusion processes of this non-equilibrium plasma on longer time scales, including the effects of ambi-polar diffusion of ions driven by hot electron expansion, possible Columbic explosion of ions producing higher ionization states and ionization of surrounding neutral atoms via collisions with hot electrons. Preliminary results of the transverse and longitudinal wakefields at different timescales of separation between a first and second bunch are presented and a possible experiment to study this topic at the FACET facility is described. [ABSTRACT FROM AUTHOR]

Strong ablative shock waves were generated on a highly oriented pyrolytic graphite surface by intense IR femtosecond laser pulses in a broad fluence range and their basic parameters (pressure, velocity) were acquired by means of a non-contact broadband ultrasonic technique. At moderate laser fluences (F ≥ 0.3 J/cm2), ultrafast formation of a dense, strongly-heated (supercritical) carbon phase is expected, which expands on a fluence-dependent picosecond timescale in the form of a point-like three-dimensional explosion, driving a multi-GPa shock wave both in ambient air and the graphite target. At higher laser fluences (F > 5 J/cm2), critical electron-ion plasma is formed instantaneously during the exciting femtosecond laser pulse, with its strong plasma absorption initiating a TPa-level shock wave (the maximum shock wave pressure ≈ 3 TPa is more than twice the previous maximum for carbon). Because of the ablative removal of the laser-heated surface carbon layer, the following time-integrated structural studies indicate the formation of a mixture of diamond and graphite nanocrystallites or, in other words, glassy carbon only in the redeposition products. [ABSTRACT FROM AUTHOR]

In the last few years significant progress on technological, experimental and numerical studies on fusion process in high density and high temperature plasmas produced by a high intensity laser pulse interaction with clusters in a high external applied magnetic field, enable us to propose a compact photo-fusion magnetic device for high neutron production. For the purpose of the project a pulsed magnetic field driver with values up to 110 Tesla has been developed which allows increasing the trapping time of the high density plasma in the device and improving the neutron yield. Numerical simulations show that the proposed device is capable of producing up to 109-1010 neutrons per laser shot with an external magnetic field of 150 Tesla. The proposed device can be used for experiments and numerical code validation concerning different conventional and (or) exotic fusion fuels. [ABSTRACT FROM AUTHOR]

Fourier analysis in the poloidal direction is a standard ingredient in present-day 2D wave equation solvers describing radio frequency waves in hot tokamak plasmas. Although a powerful and elegant technique, Fourier analysis has the disadvantage that a large number of modes is needed to describe the field pattern on a magnetic surface if a short wavelength mode exists on any - even very small - subpart of the particle trajectory. The present paper examines the potential of a method that does not suffer from this drawback: a finite element technique relying on simple linear or cubic area base functions that are defined on irregular elementary surfaces of triangular shape. The wave equation is solved in its weak Galerkin variational form and for realistic 2D tokamak geometry, accounting for the toroidal curvature but assuming the toroidal angle is ignorable, allowing to study the wave pattern for each of the independent toroidal modes excited by the antenna individually. The locally uniform full hot plasma dielectric tensor to all orders in finite Larmor radius was adopted. As the main intended application is the study of fast wave behavior (heating and current drive) at arbitrary harmonics, the wave vector complex amplitude appearing in the dielectric tensor is determined through a local dispersion root evaluation. High frequency fast wave propagation and damping is provided as an illustration in view of possible application of this type of current drive in future high density reactor-like tokamaks. [ABSTRACT FROM AUTHOR]

ECRIS-Electron Cyclotron Resonance Ion Sources are able to feed accelerators with intense currents of highly charged ions. In ECRIS a high density-high temperature plasma is generated by means of the Electron Cyclotron Resonance Heating inside a B-min, MHD stable trap. The state of the art about the principal heating mechanisms will be given. The paper will specially discuss the most critical and still open issues concerning the influence of the magnetic field and of the RF frequency on the plasma heating, as well as the impact of possible non-linear pumping wave-to-plasma interactions. The contribution of INFN-LNS will be specifically underlined. A short review on the future perspectives for the design of new generation ion sources will be given in conclusion. [ABSTRACT FROM AUTHOR]

In previous work I have discussed how and to what extent the thermodynamic concepts and the thermodynamic formalism can be extended to the description of high temperature states of the plasma not necessarily associated with a Boltzmann distribution and with thermal equilibrium. The present paper is a compressed version of this work, focused on the essential assumptions and on the essential results and emphasizing the conceptual unity that the thermodynamic approach reveals in the description of some general properties of different magnetic and electrostatic plasma states. For the derivation of the results and the discussion of critical aspects of the theory, see the original work: and the discussion of critical aspects of the theory, see the original work: http-sol/www.mdpi.com/1099[sharp/mesh/hash_synonym]1F7E18 and the last version improved in many respects of the FP09/05 report: http://www.ifp.cnr.it/publications/2009.html[sharp/mesh/hash_synonym]MINOR7 [ABSTRACT FROM AUTHOR]

Extreme ultra-violet (EUV) emission spectra from highly charged tin, xenon and tungsten ions have been measured in optically thin high-temperature plasmas produced in the Large Helical Device (LHD) at the National Institute for Fusion Science by using a grazing incidence spectrometer and a tracer-encapsulated solid pellet (TESPEL) injector. Quasi-continuous spectral features arising from unresolved transition array (UTA) of open 4d subshell ions were observed for tin, xenon and tungsten around 13.5, 11, and 5 nm, respectively, when edge plasma was cooled sufficiently. The spectral appearance obviously depends on edge electron temperature and atomic number. In the case of intermediate edge temperature, sharp discrete lines from highly charged open 4s or 4p subshell ions are clearly observed for tin and xenon in the longer wavelength side of the UTAs but not the case for tungsten. Assignments of the strong discrete lines have been performed by comparison with other experimental data and the theoretical calculations generated using the Cowan code. In order to interpret the tungsten spectra it was necessary to include the contribution of open 4f subshell ions. [ABSTRACT FROM AUTHOR]

Thermodynamics of a model system where a group of cold charged particles locally confined in a volume VP within a warm plasma of temperature T and fixed volume V (VP<

The interaction of the fast particles from the hot plasma of a magnetic confinement fusion experiment with the first wall is one of the most challenging problems toward the realization of a fusion power plant. The erosion of the first wall by the fast particles leads to life time limitations and the radiative cooling of the plasma by the eroded impurity species lowers the energy confinement. Apart from these obvious consequences also the trapping of large quantities of the fuelling species (deuterium and tritium) in re-deposited layers of the eroded species poses a problem due to accumulation of large radiative inventories and plasma fuelling inefficiency. The source of all these challenges is the erosion of first wall components due to physical sputtering, chemical erosion and radiation enhanced sublimation. This paper will give an overview about the physical principles behind these erosion channels. [ABSTRACT FROM AUTHOR]

The magnetic confinement of a hot plasma is the most promising concept to realize controlled thermonuclear fusion on earth. In the last years of intense research activities in the frame of broad international collaboration, it became clear that on the way to a stationary operating fusion reactor not only questions of plasma heating, transport and stability but also the problems associated with the choice of plasma facing materials are decisive. These issues cannot be decoupled from each other [1]. It is demonstrated that both sides, the plasma and the wall, exhibit mutual dependences. Burning conditions will not be achieved without careful adaptation of the chosen materials to the developed plasma scenarios and vice versa. Integrated concepts are required. [ABSTRACT FROM AUTHOR]

Different aspects of the plasma generated in a gas contained in a tube due to detonation of a small explosive charge located at one end of the tube are presented. The motion of the charged particles within the plasma is monitored using Rogowski coils. Using time-resolved emission spectroscopy the temperature and species in the detonation products and compressed gas behind the shock wave are recorded. From the spectral lines of the emission profiles the temperatures and electron density were evaluated to be in the vicinity of 7,000 K and 5×1022 m-3. An ultra fast wave traveling down the guide tube ahead of the hydrodynamic shock and causing any charged particles there to move fast enough to be detected by the Rogowski coils was recorded. From the measurements the phase velocity of the wave was calculated at 525 km/s when krypton filled the tube, and 1300 km/s in the case of argon. The temperature and density measurements are consistent with the data reported in the literature for similar tests. The electrostatic pulse measurements are a new phenomena not previously observed. [ABSTRACT FROM AUTHOR]

The paper pays the main attention to the LHCD efficiency in experiments on the FT-2 tokamak. LH wave spectra P(Nz) excited by the grill computed by GRILL3D code are presented. Physical processes responsible for termination of the CD with density rise are discussed for lower and higher plasma currents that are for relatively cold and relatively hot plasmas. A role of parametric processes and additional impurity influx for CD switching-off in the plasma are considered for those conditions. [ABSTRACT FROM AUTHOR]

LHCD on Alcator C-Mod is being used in plasmas with parameters similar to those expected on ITER for the purpose of tailoring the plasma current profile. LHCD experiments have also produced intriguing results related to momentum transport and edge pedestal physics that affect the toroidal rotation profile and the temperature and density profiles. Quantitative comparisons between local measurements and theory/simulation have been performed, confirming the off-axis localization of the current drive, as well as its magnitude and location dependence on the launched n| spectrum and electron temperature. Applying LHCD during the current ramp saves volt-seconds and delays the peaking of the current profile. Counter current toroidal rotation during LHCD has been observed in both L and H-mode plasmas. In H-mode plasmas the edge pedestal collisionality is reduced while the overall pressure in the pedestal increases slightly. [ABSTRACT FROM AUTHOR]

An ICRF discharge cleaning and a plasma heating experiment were performed in KSTAR toka-mak. For an automated operation and the diagnostics of the ICRF system, the ICRF local network was designed and implemented. This internal network provides monitoring, RF protection, remote control and RF diagnostics. All the functions of the control system were realized by customized DSP units. The DSP units were tied by a local network in parallel. For RF diagnostics, a detector based on digital I/Q demodulation technique was fabricated. The I/Q detector collects the RF amplitude and phase at the same time without errors from I/Q imbalance inherent in an analog counterpart. During the first experimental campaign of the KSTAR tokamak, the control system was operated as expected without any major problems such as affecting the tokamak operation. The transmitter was protected from the harmful over-voltage events through a reliable operation of the system. Details of ICRF control system and RF detecting technique with a brief experimental result will be presented. [ABSTRACT FROM AUTHOR]

Comparisons have been made between TOPLHA and ALOHA, two codes for Lower Hybrid antenna coupling to cold inhomogeneous plasmas, on the Tore-Supra C2 multi-junction and an ITER relevant Passive-Active Multi-junction (PAM). Calculation for several plasma scenarios of reflexion coefficients and launched spectra are in good agreement. [ABSTRACT FROM AUTHOR]

Essential for modeling heating and transport of fusion plasma is determining the distribution function of the plasma species. Characteristic for RF-heating is creation of particle distributions with a high energy tail. In the high energy region the deviation from a Maxwellian distribution is large while in the low energy region the distribution is close to a Maxwellian due to the velocity dependency of the collision frequency. Because of geometry and orbit topology Monte Carlo methods are frequently used. To avoid simulating the thermal part, δf methods are beneficial. Here we present a new δf Monte Carlo method with an adaptive scheme for reducing the total variance and sources, suitable for calculating the distribution function for RF-heating. [ABSTRACT FROM AUTHOR]

We report recent experiments which have been conducted at reduced field (B0(0)∼2T) in the Tore Supra tokamak. Up to∼7MW of combined ICRF and LH power have been coupled to deuterium plasmas containing ∼5–12% of hydrogen, resulting in values of normalized toroidal beta reaching βN∼1. For this confinement field, the second harmonic layer of the hydrogen ions resonance is located in the vicinity of the magnetic axis by setting the ICRF generator frequency at∼63MHz. The ICRF power is thus expected to be mostly absorbed by second harmonic cyclotron damping, a scenario known to be prone to the development of fast ion tails. Analysis of plasma measurements and preliminary associated modeling are presented, together with plans regarding forthcoming experiments. [ABSTRACT FROM AUTHOR]

Alcator C-Mod uses ICRF for the bulk auxiliary heating and relies primarily on hydrogen minority heating scenarios. Measuring the resulting hydrogen ion distribution provides an opportunity to validate upgraded ICRF simulation capability that includes non-Maxwellian ions. The Compact Neutral Particle Analyzer (CNPA) is a diagnostic employed on Alcator C-Mod to measure this fast ion distribution function. The diagnostic can measure the energy distribution of the fast ion tail, serving as a benchmark for simulation results and allowing for an assessment of the simulation algorithm and physics kernel. In this poster, we will present results from the detector in the most recent campaigns. We will discuss the calculation of the fast ion distribution from the measured CNPA distribution and the resulting effective temperature from applying a Stix fit to this distribution. [ABSTRACT FROM AUTHOR]

An integrated experimental approach is presented for processing the optical emission produced from electric arc plasma. The method is based on chromatic modulation techniques to provide a holistic measurement of the persistence of particle decays within the environment of high power circuit breakers. Chromaticity changes in a number of chromatic parameters are related to changes in physical electric arc plasma environment (e.g. particle concentration). The results are in the form of chromatic maps which show how the overall electric arc plasma and its environment behave and respond. Such maps show the totality of information which can be accessed about the arcing event and the level of monitoring discrimination which is achievable with the chromatic methodology in a simple and easy to understand manner. The suggested method provides easier data analysis and high levels of data compression. [ABSTRACT FROM AUTHOR]

Pressure gradients, or more widely, density gradients and/or temperature gradients can be free energy sources of various instabilities in a magnetically confined high-temperature plasmas. In the framework of magnetohydrodynamics (MHD), such an instability is essentially the same as Rayleigh Taylor instability that leads to Rayleigh Bénard convection of a charge-neutral fluid in a gravitational field. In this article, nonlinear evolution of such instabilities and transition mechanisms to fully developed turbulence are discussed. [ABSTRACT FROM AUTHOR]

The paper reports on experimental studies of processes of the interaction of pulsed streams of fast deuterium ions (Ei∼100 keV) and dense deuterium plasma (vpl>107 cm/s) with samples made of carbon and tungsten. Experiments were performed in the large PF-1000 plasma-focus facility with the charging energy of 481 kJ and with the pure deuterium filling. Power flux density of plasma/ions streams was q = 107–1010 W/cm2 and the pulse length was from 10-7 s to 10-6 s, whereas the duration of heat pulses (due to a secondary plasma at the target's surface) was 10-4 s. The stainless steel, tungsten and carbon-tungsten samples were placed in the zone of their strong melting and evaporation or in the zone without their melting. Each sample was exposed to 1 through 10 discharges, and the irradiated samples were investigated with optical-, electron- and atomic-force-microscopes. The interaction of intense plasma-ion pulses with the carbon-tungsten samples caused the formation of a wave-like relief on sample surfaces, the evident erosion of the sample material, and the creation of numerous micro-cracks. It was also found that about 200-nm-thick layer of the irradiated tungsten sample contained many melted fragments of nm-dimensions. The results might be useful for estimations of tungsten behavior in extreme situations (e.g. disruptions) expected in fusion reactors with magnetic plasma confinement. [ABSTRACT FROM AUTHOR]

Emission lines in X-ray spectra of clusters of galaxies reveal the presence of heavy elements in the diffuse hot plasma (the Intra Cluster Medium, or ICM) in virial equilibrium in the dark matter potential well. The relatively simple physical state of the ICM allows us to estimate, with good accuracy, its thermodynamical properties and chemical abundances. These measures put strong constraints on the interaction processes between the galaxies and the surrounding medium, and have significant impact on models of galaxy formation as well. This field is rapidly evolving thanks to the X-ray satellites Chandra and XMM-Newton. Among the most relevant progresses in the last years, we briefly discuss the nature of cool cores and the measure of the Iron abundance in high redshift clusters. Future X-ray missions with bolometers promise to provide a substantial step forward to a more comprehensive understanding of the complex physics of the ICM. [ABSTRACT FROM AUTHOR]

State-of-the-art spectroscopic models of the radiative transitions of interest for Earth re-entry and ground-based diagnostic facilities for aerospace applications are reviewed. The spectral range considered extends from the vacuum ultraviolet to the mid-infrared range (80 nm to 5.5 μm). The modeling results are compared with absolute intensity measurements of the ultraviolet-visible-infrared emission of a well-characterized high-temperature air plasma produced with a 50 kW inductively coupled radio-frequency plasma torch, and with high-resolution absorption spectra from the Center for Astrophysics in the vacuum ultraviolet. The Spectroscopic data required to better model the spectral features of interest for aerospace applications are discussed. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The idea presented here is to use the neutrons released from a thermonuclear plasma to drive currents by the thermomagnetic Nernst effect through neutron-induced nuclear reactions in a light nuclei containing plasma corona surrounding the thermonuclear plasma. To increase the nuclear cross section for the neutron-induced nuclear reactions, the neutrons are slowed down in a hydrogen-rich neutron moderator, separated from the zone where these reactions occur. Of special interest are the neutron induced fission reactions for B10 and Li6, and it is shown that the thermomagnetic currents can become large enough to confine the fusion plasma. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The idea of use the Capillary-Pore System (CPS) as material of tokamak limiter is discussed. The results of CPS Li limiter tests in T-11M tokamak have shown that the Li erosion in temperature interval 200 –700°C can not be a serious obstacle for tokamak operations. The sorption of deuterium ions by Li wall can be excluded by its heating up to 400–500°C. The idea of combined lithium limiter with thin (1-0,6mm) Li CPS coating as a solution of heat removal problem was realized. The quasi steady state tokamak regime with duration up to 0.2–0.3s and clean (Zeff≈1) deuterium plasma has been achieved. The measurements of plasma radiation showed up to 90 % of total non-coronal radiation losses located in a relatively thin (5cm) boundary layer. A version of Li CPS limiter of DEMO reactor and Li CPS limiter experiment in ITER are suggested. The concept of “emitter-collector” tokamak limiter is discussed. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Voyager and Cassini plasma probe observations suggest that there are at least three fundamentally different plasma regimes in Saturn: the hot outer magnetosphere, the extended plasma sheet, and the inner plasma torus. At the outer regions of the inner torus some ions have been accelerated to reach energies of the order of 43 keV. Protons are the dominant species outside about 9 Rs, whereas inside, the plasma consists primarily of a corotating comet-like mix of water-derived ions with ∼3% N+. Over the A and B rings, an ionosphere —dominated by O2+ and O+ — can be observed. The energies of magnetospheric particles range from hundreds of keV to several MeV. Possible explanations to the observed high-energy population of particles involve the release of magnetic energy which heats the ion component of the plasma and then accelerates electrons to energies of some MeV. In this work we develop a model that calculates the acceleration of charged particles in the Saturn’s magnetosphere. We propose that the stochastic electric field associated to the observed magnetic field fluctuations is responsible of such acceleration. A random electric field is derived from the fluctuating magnetic field —via a Monte Carlo simulation— which then is applied to the momentum equation of charged particles seeded in the magnetosphere. Taking different initial conditions, like the source of charged particles and the distribution function of their velocities, we find that particles injected with very low energies (0.103 eV to 558.35 eV) can be strongly accelerated to reach much higher energies (8.79 eV to 9.189 keV) as a result of 200,000 hitting events. The components of the final velocity in the perpendicular direction to the corotation velocity (z-axis) show a bimodal behavior in their distribution. A possible consequence of this acceleration is the radial transport of the particles due to their gain of kinetic energy. It is, when the particle’s final energy surpasses the escape energy (in Saturn it ranges from 6.57 eV for protons to 91.33 eV for N+) the particle is able to be radially transported to the outer regions of the magnetosphere. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Real-time control will play an important role in the operation and scientific exploitation of the new generation fusion devices. This paper summarizes the real-time systems and diagnostics developed by the Portuguese Fusion Euratom Association based on digital signal processors and field programmable gate arrays. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

There are two well-known motivations for theoretical studies of fast particle interaction with waves in magnetic confinement devices. One is the challenge of avoiding strong collective losses of alpha particles and beam ions in future burning plasma experiments. The other one is the compelling need to quantitatively interpret the large amount of experimental data from JET, TFTR, JT-60U, DIII-D, and other machines. Such interpretation involves unique diagnostic opportunities offered by MHD spectroscopy. This report discusses how the present theory responds to the stated challenges and what theoretical and computational advances are required to address the outstanding problems. More specifically, this paper deals with the following topics: predictive capabilities of linear theory and simulations; theory of Alfvén cascades; diagnostic opportunities based on linear and nonlinear properties of unstable modes; interplay of kinetic and fluid nonlinearities; fast chirping phenomena for non-perturbative modes; and global transport of fast particles. Recent results are presented on some of the listed topics, although the main goal is to identify critical issues for future work. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A plasma lens based on a short hydrogen-filled alumina capillary discharge is experimentally characterized. For a plasma length of about 5mm, the focal length, measured from the plasma entrance, was ∼ 11 to 8mm for on axis densities of ∼ 2.5 to 5 × 1018cm-3, respectively. The plasma temperature away from the walls of the 1/2mm diameter capillary was estimated to be ∼ 8eV indicating that the plasma is fully ionized. Such a lens should thus be suitable for focusing very high intensity pulses. Comparisons of the measured focusing strength to that predicted by a first-order fluid model [N. A. Bobrova, et al., Phys. Rev. E 65, 016407 (2002)] shows reasonable agreement given that some of the observed plasma parameters are not predicted by this model. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Plasma-Focus (PF) devices, which are based on high-voltage high-current pulse discharges, belong to the non-cylindrical Z-pinches. They can produce high-temperature dense magnetized plasma and intense radiation pulses (of X-rays, electrons, ion beams and fusion products). The paper reports on numerical modeling of different phases of high-current pulse discharges in a PF-type device. The numerical results concerning the breakdown and collapse phases are presented and discussed. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

There is strong interest in many laboratories worldwide in utilizing less expensive, longer rise-time (> 200 ns) pulsed power to drive x-ray producing z-pinches. Based on the idea of a magnetically-driven annular implosion, the emission of K-shell photons requires high energy per ion (implosion velocity above 43 cm/μs for argon) to strip the atoms to the helium-like and hydrogen-like states. This high velocity must be combined with high density in the final hot plasma to produce significant x-ray yield. To first order, implosion velocity correlates with the initial diameter of the z-pinch load in proportion to the implosion time. Thus some effort has been made in the last few years to develop larger diameter z-pinch loads suitable for use with the longer rise-time drivers. Advancing from the <4 cm diameter loads (used for 100 ns implosions) of a decade ago, progress with 8 cm loads was reported at the last DZP meeting. Here we review further progress with 12 cm loads as used to date at peak currents of 3.5 MA to almost 6 MA with >200 ns implosion times. The most interesting result is that implosions from 12 cm diameter have not proven hopelessly unstable. High quality pinches with few millimeter K-shell emitting diameters, <5 ns pulse widths, electron temperatures above 1.7 keV and ion densities >4*1019/cm3 have been achieved. The observed argon K yield has equaled simple scaling estimates that ignore the expected increase in instabilities for large initial diameters. This more stable result probably occurs because we are using radial mass distributions that are “snowplow” stabilized, i.e., they are not shell-like but rather have smoothly varying mass with the radial density gradient, dρ/dr small or negative over much of the gas flow. Data on yield as a function of the radial distribution suggest that a near or on-axis peak in the initial gas density is probably optimal. Work remains to be done to establish the details of the “best” mass distribution. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A capacitor bank is fabricated to drive (JXB) Plasma gun to generate hot plasma (target) for liner plasma investigation. The bank will also be used for driving other pintch experiments. The bank consists of 8 capacitors connected in parallel, each having capacitance of 178 μF giving a total of 1424uF. The bank is charged at 15 kV using a 28 kV power supply charging the capacitors in 65 seconds utilizing full wave charging technique. The total energy of the bank is 160kJ at 15kV. A modeling of power supply was done so that all the components involved are utilized to their operating limit safely. Moreover to give fault protection to the capacitor bank we have implemented the neutral control technique in the power supply. The capacitor bank is discharged to the inductive load through an ignitron switch of very high coulomb rating and capable of withstanding high voltages at its electrodes. The cables used for connecting capacitor bank with ignitron switch are used in parallel to give them collective capability of bearing capacitor discharge currents. These cables are capable of holding high DC voltages (40kV), which appear at the time of charging of the bank. The bank is tested and is operational. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]