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  • 1.
    Brunsell, Per
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Olofsson, K. Erik J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Cecconello, Marco
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Yadikin, D.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Kuldkepp, Mattias
    KTH, School of Engineering Sciences (SCI), Physics.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabethth
    KTH, School of Engineering Sciences (SCI), Physics.
    Resistive wall mode feedback control experiments in EXTRAP T2R2007In: 34th EPS Conference on Plasma Physics 2007, EPS 2007 - Europhysics Conference Abstracts, 2007, p. 544-547Conference paper (Refereed)
    Abstract [en]

    Experiments in EXTRAP T2R on RWM stabilization using intelligent shell feedback with a P-controller showed that mode suppression improves with increasing gain up to the system stability limit. A PD-controller gives faster response and allows operation with higher gain. The PI-controller is useful for suppression of modes driven by external resonant field error. Best mode suppression was in the present study achieved with a PID-controller.

  • 2.
    Brunsell, Per R.
    et al.
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Kuldkepp, Mattias
    KTH, School of Engineering Sciences (SCI), Physics.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Cecconello, Marco
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Hedqvist, Anders
    KTH, School of Engineering Sciences (SCI), Physics.
    Yadikin, Dimitry
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Reversed field pinch operation with intelligent shell feedback control in EXTRAP T2R2006In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 46, no 11, p. 904-913Article in journal (Refereed)
    Abstract [en]

    Discharges in the thin shell reversed field pinch (RFP) device EXTRAP T2R without active feedback control are characterized by growth of non-resonant m = 1 unstable resistive wall modes (RWMs) in agreement with linear MHD theory. Resonant m = 1 tearing modes (TMs) exhibit initially fast rotation and the associated perturbed radial fields at the shell are small, but eventually TMs wall-lock and give rise to a growing radial field. The increase in the radial field at the wall due to growing RWMs and wall-locked TMs is correlated with an increase in the toroidal loop voltage, which leads to discharge termination after 3-4 wall times. An active magnetic feedback control system has been installed in EXTRAP T2R. A two-dimensional array of 128 active saddle coils (pair-connected into 64 independent m = 1 coils) is used with intelligent shell feedback control to suppress the m = 1 radial field at the shell. With feedback control, active stabilization of the full toroidal spectrum of 16 unstable m = 1 non-resonant RWMs is achieved, and TM wall locking is avoided. A three-fold extension of the pulse length, up to the power supply limit, is observed. Intelligent shell feedback control is able to maintain the plasma equilibrium for 10 wall times, with plasma confinement parameters sustained at values comparable to those obtained in thick shell devices of similar size.

  • 3.
    Cecconello, Marco
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Kuldkepp, Mattias
    KTH, School of Engineering Sciences (SCI), Physics.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Hedqvist, Anders
    KTH, School of Engineering Sciences (SCI), Physics.
    Brunsell, Per R.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Current profile modifications with active feedback stabilization of resistive wall modes in a reversed field pinch2006In: Proceedings of the 33rd European Physical Society Conference on Plasma Physics, 2006, p. 1680-1683Conference paper (Refereed)
  • 4.
    Cecconello, Marco
    et al.
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Brunsell, Per R.
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Kuldkepp, Mattias
    KTH, School of Engineering Sciences (SCI), Physics.
    Rotation in a reversed field pinch with active feedback stabilization of resistive wall modes2006In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 48, no 9, p. 1311-1331Article in journal (Refereed)
    Abstract [en]

    Active feedback stabilization of multiple resistive wall modes (RWMs) has been successfully proven in the EXTRAP T2R reversed field pinch. One of the features of plasma discharges operated with active feedback stabilization, in addition to the prolongation of the plasma discharge, is the sustainment of the plasma rotation. Sustained rotation is observed both for the internally resonant tearing modes (TMs) and the intrinsic impurity oxygen ions. Good quantitative agreement between the toroidal rotation velocities of both is found: the toroidal rotation is characterized by an acceleration phase followed, after one wall time, by a deceleration phase that is slower than in standard discharges. The TMs and the impurity ions rotate in the same poloidal direction with also similar velocities. Poloidal and toroidal velocities have comparable amplitudes and a simple model of their radial profile reproduces the main features of the helical angular phase velocity. RWMs feedback does not qualitatively change the TMs behaviour and typical phenomena such as the dynamo and the `slinky' are still observed. The improved sustainment of the plasma and TMs rotation occurs also when feedback only acts on internally non- resonant RWMs. This may be due to an indirect positive effect, through non- linear coupling between TMs and RWMs, of feedback on the TMs or to a reduced plasma- wall interaction affecting the plasma flow rotation. Electromagnetic torque calculations show that with active feedback stabilization the TMs amplitude remains well below the locking threshold condition for a thick shell. Finally, it is suggested that active feedback stabilization of RWMs and current profile control techniques can be employed simultaneously thus improving both the plasma duration and its confinement properties.

  • 5.
    Drake, James Robert
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brunsell, Per R.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Yadikin, Dmitriy
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Cecconello, Marco
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hedqvist, Anders
    KTH, School of Engineering Sciences (SCI), Physics.
    Kuldkepp, Mattias
    KTH, School of Engineering Sciences (SCI), Physics.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Experiments on feedback control of multiple resistive wall modes comparing different active coil arrays and sensor types2006In: IAEA-F1-CN-149, 2006, p. Paper EX/P8-11-Conference paper (Refereed)
  • 6.
    Kuldkepp, Matias
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Hawkes, N. C.
    Schunke, B.
    Accurate polarization measurements with a dual photoelastic modulator2005In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 44, no 28, p. 5899-5904Article in journal (Refereed)
    Abstract [en]

    Measurements of the polarization effects in multimirror experiments by using a dual photoelastic modulator are described. The effect of single and multiple mirrors in polarization measurements in two and three dimensions is discussed, and experimental results show how symmetrical placement of mirrors in three-dimensional geometry can eliminate changes in the polarization. Calibration procedures for a dual photoelastic modulator and potential error sources such as misalignment of analyzer, signal dc offset, and neglect of aperture size are presented. Mirror-surface evolution and how it can disturb the polarization measurement are also addressed.

  • 7.
    Kuldkepp, Matias
    et al.
    KTH, Superseded Departments, Physics.
    Rachlew, Elisabeth
    KTH, Superseded Departments, Physics.
    Hawkes, N.C.
    Schunke, B.
    First mirror contamination studies for polarimetry motional Stark effect measurements for ITER2004In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 75, p. 3446-3448Article in journal (Refereed)
    Abstract [en]

    The motional Stark effect (MSE) diagnostic on the International Thermonuclear Experimental Reactor will need to guide the light through a labyrinth of mirrors to provide neutron shielding. Knowledge of how the mirrors change the polarization is essential for accurate determination of the q profile. The optical properties of the plasma facing mirror are also expected to change with time due to deposition/erosion. For the purpose of examining this experimentally a detector system, identical to the JET MSE system, using twin photoelastic modulators was constructed. Measurements have been performed on freshly prepared mirrors, on mirrors after exposure to plasmas in Tore Supra, and labyrinth designs. The result shows a significant effect on the optical properties and demonstrate the need for in situ monitoring. The measured properties of the labyrinth closely follow the Mueller matrix formalism. With a correct choice of material the angle change introduced by the four mirrors furthest away from the plasma will be below 1 degrees.

  • 8.
    Kuldkepp, Matias
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Walsh, M.J.
    Carolan, P. G.
    Conway, N. J.
    Hawkes, N. C.
    McCone, J.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Wearing, G.
    Motional Stark effect diagnostic pilot experiment for MAST2006In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 77, no 10, p. 10E905-Article in journal (Refereed)
    Abstract [en]

    Exploiting the motional Stark effect (MSE) in the low magnetic fields of spherical tokamaks such as MAST is complicated by the Doppler smearing of the relatively closely spaced Stark components. Extensive modeling of MSE spectra and the subsequent polarized fraction (similar to 20%) of spectrally filtered light and signal to noice ratios have been performed taking account of real experimental conditions including neutral beam parameters, port sizes, optical losses, filter characteristics, etc. A design is selected which uses high throughput interference filters (0.1 nm bandpass ) for separation of the spectral components. An accuracy of similar to 0.5 degrees S compared with typically 15 degrees is estimated for field angle measurements. The design allows for early implementation, starting with a pilot two chord system, and for an economic expansion to a multiplicity of chords. Matching the Doppler shifted D-alpha from the beam neutrals will be accomplished by a combination of filter selection and fine-tuning of the beam voltage. Avoiding filter tuning in the design greatly simplifies the diagnostic. Calibration results of the diagnostic support the calculations.

  • 9.
    Kuldkepp, Mattias
    KTH, School of Engineering Sciences (SCI), Physics.
    Diagnostics for advanced fusion plasma scenarios2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Over the past decade, fusion research has showed the potential of being a main candidate for energy production for future generations. Further advances in improved fusion performance are therefore vital. This thesis focuses on advanced fusion plasma scenarios and their diagnostic requirements. In particular the design of a motional Stark effect (MSE) diagnostic at the MAST spherical tokamak and the analysis of magneto-hydrodynamic mode feedback control and pulsed poloidal current drive (PPCD) at the reversed field pinch (RFP) experiment EXTRAP T2R are discussed.

    The MSE diagnostic is important for the determination of the plasma current profile, information that is necessary for studies in advanced confinement scenarios like reversed shear profiles or current holes. The MAST MSE system has two channels and selects the spectral components using 1Å FWHM interference filters. The diagnostic has been commissioned during the fall of 2006 and the results show the feasibility of the technique with rms-noise ~0.5° using a time resolution of 1 ms. Investigations of mirror labyrinths for the future ITER MSE diagnostic highlight the need for careful calibration considerations.

    Feedback control and PPCD are techniques for improved confinement. Feedback control dramatically decreases impurity influx at the end of discharges while transport in the bulk plasma is largely unaffected. During PPCD the transport is seen to decrease and it is demonstrated that PPCD and feedback control can be employed simultaneously.

    New and innovative techniques for fusion spectroscopy are furthermore described. This includes the use of correlations in line integrated signals to determine ion emission profiles in poloidally symmetric environments. Good agreement with other diagnostic methods is obtained. The assessment of electron temperature profiles using measured differences between Thomson scattering and vacuum ultra-violet spectroscopy is also shown.

  • 10.
    Kuldkepp, Mattias
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Radial profiling using local and line integrated spectroscopic measurements2005Licentiate thesis, comprehensive summary (Other scientific)
  • 11.
    Kuldkepp, Mattias
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Brunsell, Per R.
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Cecconello, Marco
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Dux, R.
    Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Measurements and modeling of transport and impurity radial profiles in the EXTRAP T2R reversed field pinch2006In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 13, no 9, p. 092506-Article in journal (Refereed)
    Abstract [en]

    Radial impurity profiles of oxygen in the rebuilt reversed field pinch EXTRAP T2R [P. R. Brunsell , Plasma Phys. Control. Fusion 43, 1457 (2001)] have been measured with a multichannel spectrometer. Absolute ion densities for oxygen peak between 1-4x10(10) cm(-3) for a central electron density of 1x10(13) cm(-3). Transport simulations with the one-dimensional transport code STRAHL with a diffusion coefficient of 20 m(2) s(-1) yield density profiles similar to those measured. Direct measurement of the ion profile evolution during pulsed poloidal current drive suggests that the diffusion coefficient is reduced by a factor similar to 2 in the core but remains unaffected toward the edge. Core transport is not significantly affected by the radial magnetic field growth seen at the edge in discharges without feedback control. This indicates that the mode core amplitude remains the same while the mode eigenfunction increases at the edge.

  • 12.
    Kuldkepp, Mattias
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Brunsell, Per R.
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Drake, James
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Method for measuring radial impurity emission profiles using correlations of line integrated signals2006In: Review of scientific instruments, ISSN 0034-6748, Vol. 77, no 4, p. 043508-Article in journal (Refereed)
    Abstract [en]

    A method of determining radial impurity emission profiles is outlined. The method uses correlations between line integrated signals and is based on the assumption of cylindrically symmetric fluctuations. Measurements at the reversed field pinch EXTRAP T2R show that emission from impurities expected to be close to the edge is clearly different in raw as well as analyzed data to impurities expected to be more central. Best fitting of experimental data to simulated correlation coefficients yields emission profiles that are remarkably close to emission profiles determined using more conventional techniques. The radial extension of the fluctuations is small enough for the method to be used and bandpass filtered signals indicate that fluctuations below 10 kHz are cylindrically symmetric. The novel method is not sensitive to vessel window attenuation or wall reflections and can therefore complement the standard methods in the impurity emission reconstruction procedure.

  • 13.
    Kuldkepp, Mattias
    et al.
    KTH, Superseded Departments, Physics.
    Gravestijn, Robert
    KTH, Superseded Departments, Physics.
    Cecconello, Marco
    KTH, Superseded Departments, Alfvén Laboratory.
    Rachlew, E.lisabeth
    KTH, Superseded Departments, Physics.
    A Spectroscopic Method To Determine Changes In The Temperature Profile2003In: 30th EPS Conference on Contr. Fusion and Plasma Phys / [ed] R. Koch, S. Lebedev, Mulhouse: European Physical Society , 2003Conference paper (Refereed)
  • 14.
    Kuldkepp, Mattias
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Brunsell, Per
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Cecconello, Marco
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    First Results The Radial 5-Channel Spectrometer On EXTRAP T2RManuscript (preprint) (Other academic)
  • 15.
    Kuldkepp, Mattias
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Corre, Yann
    Brunsell, Per
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Cecconello, Marco
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Oxygen impurity profile studies in the EXTRAP T2R reversed field pinch2005In: 32nd EPS Conference on Plasma Physics 2005, EPS 2005, Held with the 8th International Workshop on Fast Ignition of Fusion Targets: Europhysics Conference Abstracts, 2005, p. 413-416Conference paper (Refereed)
  • 16. Lloyd, B.
    et al.
    Akers, R. J.
    Alladio, F.
    Andrew, Y.
    Appel, L. C.
    Applegate, D.
    Axon, K. B.
    Ben Ayed, N.
    Bunting, C.
    Buttery, R. J.
    Carolan, P. G.
    Chapman, I.
    Ciric, D.
    Connor, J. W.
    Conway, N. J.
    Cox, M.
    Counsell, G. F.
    Cunningham, G.
    Darke, A.
    Delchambre, E.
    Dendy, R. O.
    Dowling, J.
    Dudson, B.
    Dunstan, M.
    Field, A. R.
    Foster, A.
    Gee, S.
    Garzotti, L.
    Gryaznevich, M. P.
    Gurchenko, A.
    Gusakov, E.
    Hawkes, N. C.
    Helander, P.
    Hender, T. C.
    Hnat, B.
    Howell, D. F.
    Joiner, N.
    Keeling, D.
    Kirk, A.
    Koch, B.
    Kuldkepp, Mattias
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Lisgo, S.
    Lott, F.
    Maddison, G. P.
    Maingi, R.
    Mancuso, A.
    Manhood, S. J.
    Martin, R.
    McArdle, G. J.
    McCone, J.
    Meyer, H.
    Micozzi, P.
    Morris, A. W.
    Muir, D. G.
    Nelson, M.
    O'Brien, M. R.
    Patel, A.
    Pinches, S.
    Preinhaelter, J.
    Price, M. N.
    Rachlew, Elisabeth
    Roach, C. M.
    Rozhansky, V.
    Saarelma, S.
    Saveliev, A.
    Scannell, R.
    Sharapov, S. E.
    Shevchenko, V.
    Shibaev, S.
    Stammers, K.
    Storrs, J.
    Surkov, A.
    Sykes, A.
    Tallents, S.
    Taylor, D.
    Thomas-Davies, N.
    Turnyanskiy, M. R.
    Urban, J.
    Valovic, M.
    Vann, R. G. L.
    Volpe, F.
    Voss, G.
    Walsh, M. J.
    Warder, S. E. V.
    Watkins, R.
    Wilson, H. R.
    Wisse, M.
    Overview of physics results from MAST2007In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 47, no 10, p. S658-S667Article in journal (Refereed)
    Abstract [en]

    Substantial advances have been made on the Mega AmpÚre Spherical Tokamak (MAST). The parameter range of the MAST confinement database has been extended and it now also includes pellet-fuelled discharges. Good pellet retention has been observed in H-mode discharges without triggering an ELM or an H/L transition during peripheral ablation of low speed pellets. Co-ordinated studies on MAST and DIII-D demonstrate a strong link between the aspect ratio and the beta scaling of H-mode energy confinement, consistent with that obtained when MAST data were merged with a subset of the ITPA database. Electron and ion ITBs are readily formed and their evolution has been investigated. Electron and ion thermal diffusivities have been reduced to values close to the ion neoclassical level. Error field correction coils have been used to determine the locked mode threshold scaling which is comparable to that in conventional aspect ratio tokamaks. The impact of plasma rotation on sawteeth has been investigated and the results have been well-modelled using the MISHKA-F code. Alfvén cascades have been observed in discharges with reversed magnetic shear. Measurements during off-axis NBCD and heating are consistent with classical fast ion modelling and indicate efficient heating and significant driven current. Central electron Bernstein wave heating has been observed via the O-X-B mode conversion process in special magnetically compressed plasmas. Plasmas with low pedestal collisionality have been established and further insight has been gained into the characteristics of filamentary structures at the plasma edge. Complex behaviour of the divertor power loading during plasma disruptions has been revealed by high resolution infra-red measurements.

  • 17. Malaquias, A
    et al.
    von Hellermann, M
    Tugarinov, S
    Lotte, P
    Hawkes, N
    Kuldkepp, Mattias
    KTH, Superseded Departments, Physics.
    Rachlew, Elisabeth
    KTH, Superseded Departments, Physics.
    Gorshkov, A
    Walker, C
    Costley, A
    Vayakis, G
    Active beam spectroscopy diagnostics for ITER: Present status (invited)2004In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 75, no 10, p. 3393-3398Article in journal (Refereed)
    Abstract [en]

    An overview is given of the present design of the active beam spectroscopy diagnostics for the ITER. Present spatial resolution and signal-to-noise indicate that, in principle, all proposed measurements are possible covering the entire plasma minor radius. Calculations show that the mirror based periscopes and the impurity coating of the first mirror affect the signal strength and the polarization characteristics of the measured spectra having an impact in the measurement accuracy. On-line calibration techniques and methods to access the first mirror status are addressed.

  • 18.
    Menmuir, Sheena
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Cecconello, Marco
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Kuldkepp, Mattias
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Brunsell, Per
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Ion and mode rotation in the EXTRAP T2R device during discharges with and without the application of feedback control2005Conference paper (Refereed)
  • 19.
    Menmuir, Sheena
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Hedqvist, Anders
    KTH, School of Engineering Sciences (SCI), Physics.
    Kuldkepp, Mattias
    KTH, School of Engineering Sciences (SCI), Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Brunsell, Per R.
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Large periodic fluctuations of plasma signals in EXTRAP T2R2007In: Proceedings of the 34th European Physical Society Conference on Plasma Physics, 2007Conference paper (Refereed)
  • 20.
    Menmuir, Sheena
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Kuldkepp, Mattias
    KTH, School of Engineering Sciences (SCI), Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Impurity identifications, concentrations and particle fluxes from spectral measurements of the EXTRAP T2R plasma2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 74, no 4, p. 439-448Article in journal (Refereed)
    Abstract [en]

    An absolute intensity calibrated 0.5m spectrometer with optical multi-channel analyser detector was used to observe the visible-UV radiation from the plasma in the EXTRAP T2R reversed field pinch experiment. Spectral lines were identified indicating the presence of oxygen, chromium, iron and molybdenum impurities in the hydrogen plasma. Certain regions of interest were examined in more detail and at different times in the plasma discharge. Impurity concentration calculations were made using the absolute intensities of lines of OIV and OV measured at 1-2 ms into the discharge generating estimates of the order of 0.2% of ne in the central region rising to 0.7% of ne at greater radii for OIV and 0.3% rising to 0.6% for OV. Edge electron temperatures of 0.5-5 eV at electron densities of 5-10 x 10(11) cm(-3) were calculated from the measured relative intensities of hydrogen Balmer lines. The absolute intensities of hydrogen lines and of multiplets of neutral chromium and molybdenum were used to determine particle fluxes (at 4-5 ms into the plasma) of the order 1 x 10(16), 7 x 1013 and 3 x 10(13) particles cm(-2) s(-1), respectively.

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