In the last 30 days

• Open/close Hazardous gas treatment using atmospheric pressure microwave discharges

  Jerzy Mizeraczyk et al  2005 Plasma Phys. Control. Fusion 47 B589 Tag this article

  Article References Full text PDF (1.03 MB)

  Atmospheric pressure microwave discharge methods and devices used for producing non-thermal plasmas for control of gaseous pollutants are described in this paper. The main part of the paper is concerned with microwave torch discharges (MTDs). Results of laboratory experiments on plasma abatement of several volatile organic compounds (VOCs) in their mixtures with either synthetic air or nitrogen in low (~100 W) and moderate (200–400 W) microwave torch plasmas at atmospheric pressure are presented. Three types of MTD generators, i.e. low-power coaxial-line-based MTDs, moderate-power waveguide-based coaxial-line MTDs and moderate-power waveguide-based MTDs were used. The gas flow rate and microwave (2.45 GHz) power delivered to the discharge were in the range of 1–3 litre min ⁻¹ and 100–400 W, respectively. The concentrations of the processed gaseous pollutants were from several to several tens of per cent. The results showed that the MTD plasmas fully decomposed the VOCs at a relatively low energy cost. The energy efficiency of decomposition of several gaseous pollutants reached 1000 g (kW-h) ⁻¹. This suggests that MTD plasmas can be useful tools for decomposition of highly concentrated VOCs.

• Open/close A 3D multi-mode geometry-independent RMP optimization method and its application to TCV

  J X Rossel et al  2010 Plasma Phys. Control. Fusion 52 035006 Tag this article

  Article References Full text PDF (5.66 MB)

  Resonant magnetic perturbation (RMP) and error field correction (EFC) produced by toroidally and poloidally distributed coil systems can be optimized if each coil is powered with an independent power supply. A 3D multi-mode geometry-independent Lagrange method has been developed and appears to be an efficient way to minimize the parasitic spatial modes of the magnetic perturbation and the coil current requirements while imposing the amplitude and phase of a number of target modes. A figure of merit measuring the quality of a perturbation spectrum with respect to RMP independently of the considered coil system or plasma equilibrium is proposed. To ease the application of the Lagrange method, a spectral characterization of the system, based on a generalized discrete Fourier transform applied in current space, is performed to determine how spectral degeneracy and side-band creation limit the set of simultaneously controllable target modes. This characterization is also useful to quantify the efficiency of the coil system in each toroidal mode number and to know whether optimization is possible for a given number of target modes.

  The efficiency of the method is demonstrated in the special case of a multi-purpose saddle coil system proposed as part of a future upgrade of Tokamak à Configuration Variable (TCV). This system consists of three rows of eight internal coils, each coil having independent power supplies, and provides simultaneously EFC, RMP and fast vertical position control.

• Open/close Progress in the study of warm dense matter

  M Koenig et al  2005 Plasma Phys. Control. Fusion 47 B441 Tag this article

  Article References Full text PDF (553 KB)

  In the last few years, high power lasers have demonstrated the possibility to explore a new state of matter, the so-called warm dense matter. Among the possible techniques utilized to generate this state, we present the dynamic compression technique using high power lasers. Applications to planetary cores material (iron) will be discussed. Finally new diagnostics such as proton and hard-x-ray radiography of a shock propagating in a solid target will be presented.

• Open/close Simulation of a collisionless planar electrostatic shock in a proton–electron plasma with a strong initial thermal pressure change

  M E Dieckmann et al  2010 Plasma Phys. Control. Fusion 52 025001 Tag this article

  Article References Full text PDF (1.89 MB)

  The localized deposition of the energy of a laser pulse, as it ablates a solid target, introduces high thermal pressure gradients in the plasma. The thermal expansion of this laser-heated plasma into the ambient medium (ionized residual gas) triggers the formation of non-linear structures in the collisionless plasma. Here an electron–proton plasma is modelled with a particle-in-cell simulation to reproduce aspects of this plasma expansion. A jump is introduced in the thermal pressure of the plasma, across which the otherwise spatially uniform temperature and density change by a factor of 100. The electrons from the hot plasma expand into the cold one and the charge imbalance drags a beam of cold electrons into the hot plasma. This double layer reduces the electron temperature gradient. The presence of the low-pressure plasma modifies the proton dynamics compared with the plasma expansion into a vacuum. The jump in the thermal pressure develops into a primary shock. The fast protons, which move from the hot into the cold plasma in the form of a beam, give rise to the formation of phase space holes in the electron and proton distributions. The proton phase space holes develop into a secondary shock that thermalizes the beam.

• Open/close Physics and applications of atmospheric non-thermal air plasma with reference to environment

  E Marode et al  2009 Plasma Phys. Control. Fusion 51 124002 Tag this article

  Article References Full text PDF (748 KB)

  Since air is a natural part of our environment, special attention is given to the study of plasmas in air at atmospheric pressure and their applications. This fact promoted the study of electrical conduction in air-like mixtures, i.e. mixtures containing an electronegative gas component. If the ionization growth is not limited its temporal evolution leads to spark formation, i.e. a thermal plasma of several thousand kelvins in a quasi-local thermodynamic equilibrium state. But before reaching such a thermal state, a plasma sets up where the electrons increase their energy characterized by an electron temperature T _e much higher than that of heavy species T or T ₊ for the ions. Since the plasma is no longer characterized by only one temperature T, it is said to be in a non-thermal plasma (NTP) state. Practical ways are listed to prevent electron ionization from going beyond the NTP states. Much understanding of such NTP may be gathered from the study of the simple paradigmatic case of a discharge induced between a sharp positively stressed point electrode facing a grounded negative plane electrode. Some physical properties will be gathered from such configurations and links underlined between these properties and some associated applications, mostly environmental. Aerosol filtration and electrostatic precipitators, pollution control by removal of hazardous species contained in flue gas exhaust, sterilization applications for medical purposes and triggering fuel combustion in vehicle motors are among such applications nowadays.

• Open/close Active and passive spectroscopic imaging in the DIII-D tokamak

  M A Van Zeeland et al  2010 Plasma Phys. Control. Fusion 52 045006 Tag this article

  Article References Full text PDF (1.86 MB)

  Wide-angle, 2D imaging of Doppler-shifted, Balmer alpha ( D _α) emission from high energy injected neutrals, charge exchange recombination (CER) emission from neutral beam interaction with thermal ions and fully stripped impurity ions and visible bremsstrahlung (VB) from the core of DIII-D plasmas has been carried out. Narrowband interference filters were used to isolate the specific wavelength ranges of visible radiation for detection by a tangentially viewing, fast-framing camera. Measurements of the D _α emission from fast neutrals injected into the plasma from the low field side reveal the vertical distribution of the beam, its divergence and the variation in its radial penetration with density. Modeling of this emission using both a full Monte Carlo collisional radiative code as well as a simple beam attenuation code coupled to Atomic Data and Analysis Structure emissivity lookup tables yields qualitative agreement, however the absolute magnitudes of the emissivities in the predicted distribution are larger than those measured. Active measurements of carbon CER brightness are in agreement with those made independently along the beam midplane using DIII-D's multichordal, CER spectrometer system, confirming the potential of this technique for obtaining 2D profiles of impurity density. Passive imaging of VB, which can be inverted to obtain local emissivity profiles, is compared with measurements from both a calibrated filter/photomultiplier array and the standard multichordal CER spectrometer system.

• Open/close Reviews of Plasma Physics 22

  V D Shafranov  2002 Plasma Phys. Control. Fusion 44 293 Tag this article

  Article References

  This new release of Reviews of Plasma Physics is somewhat different from the previous volumes, as it actually contains two reviews. The first one, due to the late B B Kadomtsev, is a general presentation of `Cooperative Effects in Plasmas'. The second Review is a collective work by different authors, and deals with recent results on `Relativistic interactions of laser-pulses with plasmas'.

  The first part of the book is based on B B Kadomtsev's written lectures for students of the Moscow Institute of Physics and Technology. Although it begins with very general aspects of basic effects in plasmas such as Landau damping, waves, plasma echoes, two fluid MHD, it contains the more specialised material necessary to grasp the physical subtleties of laser-plasma interaction: nonlinear waves, solitons, self-focusing, three-wave processes with Manley-Rowe relations, wave-particle interaction, etc.

  In connection with the first part, the second review is an exhaustive presentation of recent works on the physics of laser-plasma interaction, and covers a wide range of nonlinear relativistic topics on plasmas interacting with high-intensity laser pulses. The various subjects are presented from a theoretical point of view, with special emphasis on the use of numerical simulations. The matter covered includes relativistically strong electromagnetic waves propagating in underdense plasmas, stimulated Raman scattering, filamentation and self-focusing, charged particle acceleration as well as photon acceleration. A special paragraph is devoted to the interaction of an ultra-short ultra-intense laser pulse with an overdense plasma.

  Although the first part can be read with profit by students, or physicists unfamiliar with nonlinear plasma physics, the second one is significantly more specialised. It is a systematic review of several areas of current research, with a concise presentation of the main results and exhaustive bibliographical references, rather than a detailed study of a few selected topics. The plasma physicist should find in it a valuable contribution for an exhaustive overview of laser-plasma phenomena. Students and physicists from other disciplines may profit from a more elementary introduction before addressing the second part of this book.

  Pierre Bertrand and Giovanni Manfredi
  

• Open/close Analytical description of poloidally diverted tokamak equilibrium with linear stream functions

  R Srinivasan et al  2010 Plasma Phys. Control. Fusion 52 035007 Tag this article

  Article References Full text PDF (212 KB)

  The tokamak plasmas in most of the present experiments and those considered for the future reactors are up–down asymmetric in nature. This asymmetry arises due to external coils and conducting structures which surround the plasma. The analytical description of these equilibria using mathematically simpler methods is useful for the theoretical study of stability and transport. Such a tokamak equilibrium has been constructed analytically for arbitrary aspect ratios. The asymmetric nature arises through the homogeneous part of the exact solution of the Grad–Shafranov equation with a choice of pressure and toroidal function as linear in poloidal flux. These solutions can describe both single- and double-null divertor plasmas with an appropriate choice of plasma boundary. This has been used to construct DIII-D and ITER-like equilibrium and compared with those computed numerically.

• Open/close Comparison of MHD-induced rotation damping with NTV predictions on MAST

  M-D Hua et al  2010 Plasma Phys. Control. Fusion 52 035009 Tag this article

  Article References Full text PDF (554 KB)

  Plasma rotation in tokamaks is of special interest for its potential stabilizing effect on micro- and macro-instabilities, leading to increased confinement. In MAST, the torque from neutral beam injection can spin the plasma to a core velocity ~300 km s ⁻¹ (Alfvén Mach number ~0.3). Low density plasmas often exhibit a weakly non-monotonic safety factor profile just above unity. Theory predicts that such equilibria are prone to magneto-hydro-dynamic (MHD) instabilities, which was confirmed by recent observations. The appearance of the mode is accompanied by strong damping of core rotation on a timescale much faster than the momentum confinement time.

  The mode's saturated structure is estimated using the CASTOR code together with soft x-ray measurements, enabling the calculation of the plasma braking by the MHD mode according to neoclassical toroidal viscosity (NTV) theory. The latter exhibits strong similarities with the torque measured experimentally.

• Open/close Laser driven inertial fusion: the physical basis of current and recently proposed ignition experiments

  S Atzeni  2009 Plasma Phys. Control. Fusion 51 124029 Tag this article

  Article References Full text PDF (491 KB)

  A brief overview of the inertial fusion principles and schemes is presented. The bases for the laser driven ignition experiments programmed for the near future at the National Ignition Facility are outlined. These experiments adopt indirect-drive and aim at central ignition. The principles of alternate approaches, based on direct-drive and different routes to ignition (fast ignition and shock ignition) are also discussed. Gain curves are compared and discussed.