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  • 1.
    Bergsåker, Henric
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brunsell, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Drake, James R.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Metal impurity fluxes and plasma-surface interactions in EXTRAP T2R2008In: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY, 2008, Vol. 100Conference paper (Refereed)
    Abstract [en]

    The EXTRAP T2R is a large aspect ratio Reversed Field Pinch device. The main focus of interest for the experiments is the active feedback control of resistive wall modes [1]. With feedback it has been possible to prolong plasma discharges in T2R from about 20 ms to nearly 100 ms. In a series of experiments in T2R, in H- and D- plasmas with and without feedback, quantitative spectroscopy and passive collector probes have been used to study the flux of metal impurities. Time resolved spectroscopic measurements of Cr and Mo lines showed large metal release towards discharge termination without feedback. Discharge integrated fluxes of Cr, Fe, Ni and Mo were also measured with collector probes at wall position. Reasonable quantitative agreement was found between the spectroscopic and collector probe measurements. The roles of sputtering, thermal evaporation and arcing in impurity production are evaluated based on the composition of the measured impurity flux.

  • 2.
    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.

  • 3.
    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.

  • 4.
    Brunsell, Per
    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.
    Yadikin, Dmitriy
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Cecconello, Marco
    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.
    Drake, James Robert
    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.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Zanca, P.
    Active control of multiple resistive wall modes2005In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 47, no 12 B, p. B25-B36Article in journal (Refereed)
    Abstract [en]

     A two-dimensional array of saddle coils at M-c poloidal and N-c toroidal positions is used on the EXTRAP T2R reversed-field pinch (Brunsell P R et al 2001 Plasma Phys. Control. Fusion 43 1457) to study active control of resistive wall modes (RWMs). Spontaneous growth of several RWMs with poloidal mode number m = 1 and different toroidal mode number n is observed experimentally, in agreement with linear MHD modelling. The measured plasma response to a controlled coil field and the plasma response computed using the linear circular cylinder MHD model are in quantitive agreement. Feedback control introduces a linear coupling of modes with toroidal mode numbers n, n' that fulfil the condition vertical bar n - n'vertical bar = N-c. Pairs of coupled unstable RWMs are present in feedback experiments with an array of Mc x Nc = 4 x 16 coils. Using intelligent shell feedback, the coupled modes are generally not controlled even though the field is suppressed at the active coils. A better suppression of coupled modes may be achieved in the case of rotating modes by using the mode control feedback scheme with individually set complex gains. In feedback with a larger array of Mc x Nc = 4 x 32 coils, the coupling effect largely disappears, and with this array, the main internal RWMs n = -11, -10, +5, +6 are all simultaneously suppressed throughout the discharge (7-8 wall times). With feedback there is a two-fold extension of the pulse length, compared to discharges without feedback.

  • 5.
    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)
  • 6.
    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.

  • 7.
    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)
  • 8.
    Frassinetti, Lorenzo
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brunsell, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Cecconello, Marco
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Drake, James R.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Khan, Muhammad Waqas Mehmood
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Olofsson, Erik
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Active feedback control of QSH in EXTRAP-T2R2008Conference paper (Refereed)
  • 9.
    Frassinetti, Lorenzo
    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.
    Brunsell, Per
    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.
    Drake, James Robert
    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.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Cecconello, Marco
    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.
    Spontaneous QSH in the EXTRAP T2R reversed-field pinch2007In: 34th EPS Conference on Plasma Physics 2007, EPS 2007 - Europhysics Conference Abstracts, 2007, p. 579-582Conference paper (Refereed)
  • 10.
    Frassinetti, Lorenzo
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Fridström, Richard
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brunsell, Per R.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    The tearing mode locking-unlocking mechanism to an external resonant field in EXTRAP T2R2014In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 56, no 10, p. 104001-Article in journal (Refereed)
    Abstract [en]

    The tearing mode (TM) locking and unlocking process due to an external resonant magnetic perturbation (RMP) is experimentally studied in EXTRAP T2R. The RMP produces a reduction of the natural TM velocity and ultimately the TM locking if a threshold in the RMP amplitude is exceeded. During the braking process, the TM slows down via a mechanism composed of deceleration and acceleration phases. During the acceleration phases, the TM can reach velocities higher than the natural velocity. Once the TM locking occurs, the RMP must be reduced to a small amplitude to obtain the TM unlocking, showing that the unlocking threshold is significantly smaller than the locking threshold and that the process is characterized by hysteresis. Experimental results are in qualitative agreement with a model that describes the locking-unlocking process via the balance of the electromagnetic torque produced by the RMP that acts to brake the TM and the viscous torque that tends to re-establish the unperturbed velocity.

  • 11.
    Frassinetti, Lorenzo
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Izzo, V.
    Olofsson, Erik
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    Brunsell, Per R.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Screening effect of plasma flow on resonant magnetic perturbations in EXTRAP T2R2012In: EPS Conf. Plasma Phys., EPS Int. Congr. Plasma Phys., 2012, p. 365-368Conference paper (Refereed)
  • 12.
    Frassinetti, Lorenzo
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brunsell, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Resonant magnetic perturbation penetration and locking threshold in EXTRAP T2R2013In: 40th EPS Conference on Plasma Physics: Espoo, Finland, 1-5 July, 2013, 2013Conference paper (Refereed)
    Abstract [en]

    In a tokamak or reversed field pinch plasma with rotating tearing modes (TM), the penetration of resonant magnetic perturbations (RMPs) and/or error-fields can lead to braking of the TM rotation velocity and eventually to wall locking of the TM. The TM rotation braking may occur via the electromagnetic torque that acts locally near the rational surface [1, 2, 3]. At a critical RMP amplitude, a transition from a fast rotating TM to a slowly rotating or wall locked TM occurs. This critical RMP amplitude is referred to as the error-field penetration threshold or the TM locking threshold. In this work, the threshold is experimentally studied in the EXTRAP T2R reversed-field pinch. The experimental results are compared with a model for the non-linear TM dynamics, which incorporates the balance between the electromagnetic braking torque and the viscous drag of the rotating plasma [3].

  • 13.
    Frassinetti, Lorenzo
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Khan, Waqas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Olofsson, Erik
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brunsell, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    The effect of external control fields on tearing mode dynamics2011In: Proceedings of the 38th European Physical Society Conference on Plasma Physics, 2011, p. 1220-1223Conference paper (Refereed)
  • 14.
    Frassinetti, Lorenzo
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Olofsson, K. Erik J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brunsell, Per R.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tearing mode velocity braking due to resonant magnetic perturbations2012In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 52, no 10, p. 103014-Article in journal (Refereed)
    Abstract [en]

    The effect of resonant magnetic perturbations (RMPs) on the tearing mode (TM) velocity is studied in EXTRAP T2R. Experimental results show that the RMP produces TM braking until a new steady velocity or wall locking is reached. The braking is initially localized at the TM resonance and then spreads to the other TMs and to the rest of the plasma producing a global velocity reduction via the viscous torque. The process has been used to experimentally estimate the kinematic viscosity profile, in the range 2-40 m 2 s -1, and the electromagnetic torque produced by the RMP, which is strongly localized at the TM resonance. Experimental results are then compared with a theoretical model which gives a reasonable qualitative explanation of the entire process.

  • 15.
    Frassinetti, Lorenzo
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Olofsson, K. Erik. J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Khan, Muhammad Waqas Mehmood
    Brunsell, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Experimental Studies of the Plasma Response to Applied Nonaxisymmetric External Magnetic Perturbations in EXTRAP T2R2012In: 24th IAEA Fusion Energy Conference, 2012, p. EX/P4-21-Conference paper (Refereed)
  • 16.
    Frassinetti, Lorenzo
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Sun, Y.
    Fridström, Richard
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Olofsson, K. E. J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brunsell, Per R.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Khan, M. W. M.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Liang, Y.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Braking due to non-resonant magnetic perturbations and comparison with neoclassical toroidal viscosity torque in EXTRAP T2R2015In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 11, article id 112003Article in journal (Refereed)
    Abstract [en]

    The non-resonant magnetic perturbation (MP) braking is studied in the EXTRAP T2R reversed-field pinch (RFP) and the experimental braking torque is compared with the torque expected by the neoclassical toroidal viscosity (NTV) theory. The EXTRAP T2R active coils can apply magnetic perturbations with a single harmonic, either resonant or non-resonant. The non-resonant MP produces velocity braking with an experimental torque that affects a large part of the core region. The experimental torque is clearly related to the plasma displacement, consistent with a quadratic dependence as expected by the NTV theory. The work show a good qualitative agreement between the experimental torque in a RFP machine and NTV torque concerning both the torque density radial profile and the dependence on the non-resonant MP harmonic.

  • 17.
    Frassinetti, Lorenzo
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Sun, Y.
    Khan, Muhammad Waqas Mehmood
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Olofsson, K. Erik J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brunsell, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Flow braking due to non-resonant external perturbations in EXTRAP T2R and comparison   with neoclassical toroidal viscosity torque2012In: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics, 2012, p. 1190-1193Conference paper (Refereed)
  • 18.
    Frassinetti, Lorenzo
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Sun, Y
    Khan, Muhammad Waqas Mehmood
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Olofsson, K. Erik J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brunsell, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Screening effect of plasma flow on RMPs in EXTRAP T2R2012In: 39th European Physical Society (EPS) Conference on Plasma Physics, 2012, p. P1.067-Conference paper (Refereed)
  • 19. Günther, S.
    et al.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Zohm, H.
    et al.,
    Overview of ASDEX Upgrade results - development of integrated operating scenarios for ITER2005In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 45, no 10, p. S98-S108Article in journal (Refereed)
    Abstract [en]

    Significant progress has been made on ASDEX Upgrade during the last two years in the basic understanding of transport, in the extension of the improved H-mode in parameter space and towards an integrated operating scenario and in the development of control methods for major performance limiting instabilities. The important features were the understanding of particle transport and the control of impurity accumulation based on it, the satisfactory operation with predominantly tungsten-clad walls, the improved H-mode operation over density ranges and for temperature ratios covering (non-simultaneously) the ITER requirements on v*, n/n(GW) and T(e)/T(i), the ELM frequency control by pellet injection and the optimization of NTM suppression by DC-ECCD through variation of the launching angle. From these experiments an integrated scenario has emerged which extrapolates to a 50% improvement in n T tau or a 30% reduction of the required current when compared with the ITER base-line assumptions, with moderately peaked electron and controllable high-Z density profiles.

  • 20.
    Khan, Muhammad Waqas Mehmood
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brunsell, Per
    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 Electrical Engineering (EES), Fusion Plasma Physics.
    Olofsson, Erik
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Braking of Plasma Rotation by Non-axisymmetric Magnetic Fields in EXTRAP T2R2011In: Proceedings of the 38th European Physical Society Conference on Plasma Physics, 2011, p. 841-844Conference paper (Refereed)
  • 21. Krieger, K.
    et al.
    Brezinsek, S.
    Jachmich, S.
    Lisgo, S.
    Stamp, M.
    Esser, H. G.
    Kreter, A.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Mertens, Ph.
    Philipps, V.
    Sundelin, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Be wall sources and migration in L-mode discharges after Be evaporation in the JET tokamak2009In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 390-91, p. 110-114Article in journal (Refereed)
    Abstract [en]

    First wall material erosion and migration after fresh Be evaporation in the JET tokamak were studied in a series of consecutive identical L-mode discharges. The evolution of Be and C wall and divertor sources towards steady state conditions after deposition of a finite amount of Be at the carbon first wall of JET by the beryllium evaporation procedure provides a data set for benchmarking impurity transport simulations. Furthermore the experiment serves as a reference case for comparison of Be erosion to that of the planned ITER-like wall experiment with mainly Be plasma facing components (PFCs) in the main chamber. The experimental results confirm the migration pattern obtained by campaign integrated accounting of impurity sources and sinks, which is characterised by the main chamber wall and outer divertor as erosion dominated zones and migration of eroded material predominantly to the inner divertor where the material is finally deposited at the target plates.

  • 22.
    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.

  • 23.
    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.

  • 24.
    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)
  • 25.
    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)
  • 26. Lawson, K. D.
    et al.
    Groth, M.
    Belo, P.
    Brezinsek, S.
    Corrigan, G.
    Czarnecka, A. A.
    Delabie, E.
    Drewelow, P.
    Harting, D.
    Ksiazek, I.
    Maggi, C. F.
    Marchetto, C.
    Meigs, A. G.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stamp, M. F.
    Wiesen, S.
    Improved EDGE2D-EIRENE simulations of JET ITER-like wall L-mode discharges utilising poloidal VUV/visible spectral emission profiles2015In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, p. 582-585Article in journal (Refereed)
    Abstract [en]

    A discrepancy in the divertor radiated powers between EDGE2D-EIRENE simulations, both with and without drifts, and JET-ILW experiments employing a set of NBI-heated L-mode discharges with step-wise density variation is investigated. Results from a VUV/visible poloidally scanning spectrometer are used together with bolometric measurements to determine the radiated power and its composition. The analysis shows the importance of D line radiation in contributing to the divertor radiated power, while contributions from D radiative recombination are smaller than expected. Simulations with W divertor plates underestimate the Be content in the divertor, since no allowance is made for Be previously deposited on the plates being re-eroded. An improved version of EDGE2D-EIRENE is used to test the importance of the deposited layer in which the sputtering yield from supposed pure Be divertor plates is reduced to match the spectroscopic signals, while keeping the sputtering yield for the Be main chamber walls unchanged.

  • 27.
    Martin, P.
    et al.
    Consorzio RFX.
    Adamek, J.
    Agostinetti, P.
    Agostini, M.
    Alfier, A.
    Angioni, C.
    Antoni, V.
    Apolloni, L.
    Auriemma, F.
    Barana, O.
    Barison, S.
    Baruzzo, M.
    Bettini, P.
    Boldrin, M.
    Bolzonella, T.
    Bonfiglio, D.
    Bonomo, F.
    Boozer, A. H.
    Brombin, M.
    Brotankova, J.
    Buffa, A.
    Canton, A.
    Cappello, S.
    Carraro, L.
    Cavazzana, R.
    Cavinato, M.
    Chacon, L.
    Chitarin, G.
    Cooper, W. A.
    Bello, S. D.
    Dalla Palma, M.
    Delogu, R.
    De Lorenzi, A.
    De Masi, G.
    Dong, J. Q.
    Drevlak, M.
    Escande, D. F.
    Fantini, F.
    Fassina, A.
    Fellin, F.
    Ferro, A.
    Fiameni, S.
    Fiorentin, A.
    Franz, P.
    Gaio, E.
    Garbet, X.
    Gazza, E.
    Giudicotti, L.
    Gnesotto, F.
    Gobbin, M.
    Grando, L.
    Guo, S. C.
    Hirano, Y.
    Hirshman, S. P.
    Ide, S.
    Igochine, V.
    In, Y.
    Innocente, P.
    Kiyama, S.
    Liu, S. F.
    Liu, Y. Q.
    Lòpez Bruna, D.
    Lorenzini, R.
    Luchetta, A.
    Manduchi, G.
    Mansfield, D. K.
    Marchiori, G.
    Marcuzzi, D.
    Marrelli, L.
    Martini, S.
    Matsunaga, G.
    Martines, E.
    Mazzitelli, G.
    McCollam, K.
    Menmuir, Sheena
    Assoc EURATOM ENEA Fus, Consorzio RFX, I-35137 Padua, Italy .
    Milani, F.
    Momo, B.
    Moresco, M.
    Munaretto, S.
    Novello, L.
    Okabayashi, M.
    Ortolani, S.
    Paccagnella, R.
    Pasqualotto, R.
    Pavei, M.
    Perverezev, G. V.
    Peruzzo, S.
    Piovan, R.
    Piovesan, P.
    Piron, L.
    Pizzimenti, A.
    Pomaro, N.
    Pomphrey, N.
    Predebon, I.
    Puiatti, M. E.
    Rigato, V.
    Rizzolo, A.
    Rostagni, G.
    Rubinacci, G.
    Ruzzon, A.
    Sakakita, H.
    Sanchez, R.
    Sarff, J. S.
    Sattin, F.
    Scaggion, A.
    Scarin, P.
    Schneider, W.
    Serianni, G.
    Sonato, P.
    Spada, E.
    Soppelsa, A.
    Spagnolo, S.
    Spolaore, M.
    Spong, D. A.
    Spizzo, G.
    Takechi, M.
    Taliercio, C.
    Terranova, D.
    Toigo, V.
    Valisa, M.
    Veranda, M.
    Vianello, N.
    Villone, F.
    Wang, Z.
    White, R. B.
    Yadikin, D.
    Zaccaria, P.
    Zamengo, A.
    Zanca, P.
    Zaniol, B.
    Zanotto, L.
    Zilli, E.
    Zollino, G.
    Zuin, M.
    Overview of the RFX fusion science program2011In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 51, no 9, p. 094023-Article in journal (Refereed)
    Abstract [en]

    This paper summarizes the main achievements of the RFX fusion science program in the period between the 2008 and 2010 IAEA Fusion Energy Conferences. RFX-mod is the largest reversed field pinch in the world, equipped with a system of 192 coils for active control of MHD stability. The discovery and understanding of helical states with electron internal transport barriers and core electron temperature >1.5 keV significantly advances the perspectives of the configuration. Optimized experiments with plasma current up to 1.8 MA have been realized, confirming positive scaling. The first evidence of edge transport barriers is presented. Progress has been made also in the control of first-wall properties and of density profiles, with initial first-wall lithization experiments. Micro-turbulence mechanisms such as ion temperature gradient and micro-tearing are discussed in the framework of understanding gradient-driven transport in low magnetic chaos helical regimes. Both tearing mode and resistive wall mode active control have been optimized and experimental data have been used to benchmark numerical codes. The RFX programme also provides important results for the fusion community and in particular for tokamaks and stellarators on feedback control of MHD stability and on three-dimensional physics. On the latter topic, the result of the application of stellarator codes to describe three-dimensional reversed field pinch physics will be presented.

  • 28.
    Melero Garcia, Emilio
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Alvarez Ruiz, Jesus
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Rachlew, Elisabet
    KTH, School of Engineering Sciences (SCI), Physics.
    Erman, Peter
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Kivimäki et al., Antti
    Fluorescence study of doubly excited states of molecular hydrogen2006In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 39, no 2, p. 205-213Article in journal (Refereed)
    Abstract [en]

    Photodissociation of molecular hydrogen has been investigated by means of fluorescence spectroscopy using synchrotron radiation. Balmer-alpha emission from atomic hydrogen photofragments was collected in the 20-55 eV excitation energy range. Experimental data are interpreted in terms of excitation and fragmentation of neutral doubly excited states and excited ionic states with the aid of recent theoretical model calculation.

  • 29.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Visible spectroscopic diagnostics: application and development in fusion plasmas2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Diagnostic measurements play a vital role in experiments. Without them we would be in the dark with no way of knowing what was happening; of understanding the processes and behaviour occurring; or even of judging the success or failure of our experiments. The development of fusion plasma devices is no different. In this thesis we concentrate on visible spectroscopy based diagnostics: examining the techniques for measurement and analysis; the breadth of plasma parameters that can be extracted from the spectroscopic data; and how the application of these diagnostic techniques gives us a broader picture of the plasma and the events taking place within. Techniques are developed and applied to plasmas in three fusion experiments, EXTRAP T2R, ASDEX Upgrade and JET. The diagnostic techniques exploit different features of the measurements of the emitted photons to obtain various useful plasma parameters.

    Determination of the ion temperature and rotation velocity of oxygen impurity ions in the EXTRAP T2R plasma is achieved through measurement and analysis of, respectively, the Doppler broadening and the Doppler wavelength shift of visible wavelength atomic spectral lines. The evolution of the temperature and rotation is studied as a function of the discharge parameters, in particular looking at the effect of applying active feedback control schemes to the resistive wall modes and/or pulsed poloidal current drive. Measurements of multiple ionisation stages are used to estimate radial profiles of the toroidal rotation and the ion temperature and correlations between the ion rotations and the rotation velocities of tearing modes are also established.

    Radial profiles of the emissivity and density (or concentration) of the oxygen ions are obtained by means of measurements of the spectral line intensities on a small array of linesof- sight through the plasma. Changes to the profiles for different plasma schemes and the implications for particle transport are investigated. The derived emissivity profiles are used in the analysis for some of the other spectroscopic diagnostics. Spectral line intensity measurements (in this case of neutral ions) are also the basis for calculations of both the electron temperature and the particle fluxes at the plasma edge. The latter is an indicator of the degree and type of interaction between the plasma and the surrounding surfaces. Particle fluxes of the operating gas hydrogen and of chromium and molybdenum impurities are investigated in EXTRAP T2R for different operating scenarios, in particular changes in the metallic influx with the application of active feedback mode control are examined along with the correspondence between spectroscopic and collector probe results. In the ASDEX Upgrade divertor estimates of the particle flux of the deuterium operating gas are also made through analysis of spectral intensities. Molecular D2 band structure is explored in addition to the Balmer Dα spectral line intensity to acquire both atomic and molecular particle fluxes, investigate the contribution of the dissociating D2 to the Dα line and study the effect of changes in the divertor.

    Analysis of the D2 molecular band structure (the relative intensities of the rotational lines and vibrational bands) also enables calculation of the upper state rotational and ground state vibrational temperatures. The locations of emitting atomic ions in JET are estimated from Zeeman splitting analysis of the structure of their spectral lines.

    The measurement and analysis of visible wavelength light is demonstrated to be a sensitive diagnostic tool in the quest for increased knowledge about fusion plasmas and their operating scenarios.

  • 30.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Visible spectroscopy as a sensitive diagnostic tool for fusion plasmas2005Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    To further the understanding and knowledge about fusion plasmas and their behaviour during different conditions, it is important to be able to collect information about the plasma and the processes occurring within it. Visible spectroscopy, or the study of the visible wavelength light emitted by the plasma, is a useful tool in this search for knowledge.

    This thesis is based on experiments where visible wavelength light has been measured and analysed in order to determine quantities about the emitting source. Doppler shift measurements of spectral lines have been utilised to determine the toroidal rotation velocities of plasma impurity ions and to study the correlation with mode rotation and the effect of active feedback control of the resistive wall modes. Information on the impurities present in the plasma has been determined and the calibrated intensities of spectral lines has yielded impurity concentrations, particle fluxes and electron temperature and densities. Ion temperatures have been determined from Doppler broadening measurements.

    The measured vibrational and rotational band structure of deuterium molecular spectra has been analysed in order to calculate rotational and vibrational temperatures, relative populations and molecular particle fluxes. The effect of the molecular flux on simple calculations of atomic flux has also been studied. Specific molecular states and transitions of deuterium have also been probed with synchrotron radiation to study the level and transition energies.

    The measurement and analysis of visible wavelength light has been demonstrated to be a sensitive diagnostic tool in the quest for increased knowledge about fusion plasmas and molecular structure.

  • 31.
    Menmuir, Sheena
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics. EURATOM-VR Association, Denmark .
    Bergsåker, Henric
    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.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics. EURATOM-VR Association, Denmark .
    Brunsell, Per
    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. EURATOM-VR Association, Denmark .
    Frassinetti, Lorenzo
    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. EURATOM-VR Association, Denmark .
    Drake, James Robert
    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. EURATOM-VR Association, Denmark .
    Particle flux and surface interaction in EXTRAP T2R2007In: 34th EPS Conference on Plasma Physics 2007, EPS 2007 - Europhysics Conference Abstracts, European Physical Society , 2007, p. 347-350Conference paper (Refereed)
  • 32.
    Menmuir, Sheena
    et al.
    Consorzio RFX.
    Carraro, L.
    Consorzio RFX.
    Agostini, M.
    Consorzio RFX.
    Innocente, P.
    Consorzio RFX.
    Munaretto, S.
    Consorzio RFX.
    Puiatti, M.E.
    Consorzio RFX.
    Scarin, P.
    Consorzio RFX.
    Edge spectroscopic characterization of RFX-mod after Li wall conditioning2010In: 37th EPS Conference on Plasma Physics, 2010, Vol. 52, no 9, p. P2.149-Conference paper (Refereed)
  • 33.
    Menmuir, Sheena
    et al.
    Consorzio RFX.
    Carraro, L.
    Consorzio RFX.
    Alfier, A.
    Consorzio RFX.
    Bonomo, F.
    Consorzio RFX.
    Fassina, A.
    Consorzio RFX.
    Spizzo, G.
    Consorzio RFX.
    Vianello, N.
    Consorzio RFX.
    Impurity transport studies in RFX-mod multiple helicity and enhanced confinement QSH regimes2010In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 52, no 9, p. 095001-Article in journal (Refereed)
    Abstract [en]

    The transport of intrinsic and artificially introduced impurities is investigated in the multiple helicity (MH) and quasi-single helicity (QSH) plasma regimes of the RFX-mod reversed-field pinch. Impurities are introduced through Ni laser blow-off and Ne gas puffing in both magnetic confinement scenarios. Simulation of experimental spectroscopic measurements, including line and soft x-ray emission, electron density and radiated power is carried out with a one-dimensional collisional-radiative model. For both QSH and MH an outwardly directed pinch velocity with a large barrier in the edge and no reversal is determined, accompanied by a diffusion coefficient that is an order of magnitude greater in the core than at the edge. The established transport parameters are similar for the Ni and Ne injected impurities with the transition region and barrier less external and stronger in the QSH regime.

  • 34.
    Menmuir, Sheena
    et al.
    Consorzio RFX.
    Carraro, L.
    Consorzio RFX.
    Fassina, A.
    Consorzio RFX.
    Alfier, A.
    Consorzio RFX.
    Auriemma, F.
    Consorzio RFX.
    Franz, P.
    Consorzio RFX.
    Puiatti, M.E.
    Consorzio RFX.
    Valisa, M.
    Consorzio RFX.
    Impurity transport studies in multiple helicity and enhanced confinement QSH regimes in RFX-mod2009In: 36th EPS Conference on Plasma Physics, 2009, Vol. 52, no 9, p. P2.184-Conference paper (Refereed)
  • 35.
    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)
  • 36.
    Menmuir, Sheena
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brunsell, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Khan, Muhammad Waqas Mehmood
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Olofsson, Erik
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Response of EXTRAP T2R plasma velocity and ion temperature profiles to varying plasma conditions2011In: 38th EPS Conference on Plasma Physics 2011, EPS 2011 - Europhysics Conference Abstracts, 2011, p. 1216-1219Conference paper (Refereed)
  • 37.
    Menmuir, Sheena
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Giroud, C.
    Biewer, T. M.
    Coffey, I. H.
    Delabie, E.
    Hawkes, N. C.
    Sertoli, M.
    Carbon charge exchange analysis in the ITER-like wall environment2014In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, no 11, p. 11E412-Article in journal (Refereed)
    Abstract [en]

    Charge exchange spectroscopy has long been a key diagnostic tool for fusion plasmas and is well developed in devices with Carbon Plasma-Facing Components. Operation with the ITER-like wall at JET has resulted in changes to the spectrum in the region of the Carbon charge exchange line at 529.06 nm and demonstrates the need to revise the core charge exchange analysis for this line. An investigation has been made of this spectral region in different plasma conditions and the revised description of the spectral lines to be included in the analysis is presented.

  • 38.
    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)
  • 39.
    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.

  • 40.
    Menmuir, Sheena
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Fantz, U.
    Institute of Plasma Physics, Augsburg University.
    Pugno, R.
    IPP, EURATOM Association, MPI, Garching, Germany.
    Dux, R.
    IPP, EURATOM Association, MPI, Garching, Germany.
    Molecular contribution to the D alpha emission in the divertor of the ASDEX Upgrade experiment2007In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 105, no 3, p. 425-437Article in journal (Refereed)
    Abstract [en]

    Spectral line emission from the deuterium Balmer alpha line and from molecular deuterium in the Fulcher band, d(3)Pi(u)-> a(3)Sigma(+)(g), was studied in the outer divertor region of the ASDEX Upgrade plasma with a pair of relatively calibrated spectrometers. A dependence of the signals on the proximity of the plasma strike point and on divertor gas puffing was noted. The rotational spectrum of the lowest diagonal vibrational molecular bands indicated rotational temperatures of ca. 1000 K and hence, through calculation of relative upper state populations, a ground state vibrational temperature of ca. 4000 K. Calculating the particle fluxes, the molecular deuterium was found to contribute up to 1% of the D alpha intensity, the relative importance of the molecules at some divertor heights was affected by the position of the strike point.

  • 41.
    Puiatti, M. E.
    et al.
    Consorzio RFX.
    Alfier, A.
    Auriemma, F.
    Cappello, S.
    Carraro, L.
    Cavazzana, R.
    Dal Bello, S.
    Fassina, A.
    Escande, D. F.
    Franz, P.
    Gobbin, M.
    Innocente, P.
    Lorenzini, R.
    Marrelli, L.
    Martin, P.
    Piovesan, P.
    Predebon, I.
    Sattin, F.
    Spizzo, G.
    Terranova, D.
    Valisa, M.
    Zaniol, B.
    Zanotto, L.
    Zuin, M.
    Agostini, M.
    Antoni, V.
    Apolloni, L.
    Baruzzo, M.
    Bolzonella, T.
    Bonfiglio, D.
    Bonomo, F.
    Boozer, A.
    Brombin, M.
    Canton, A.
    Delogu, R.
    De Masi, G.
    Gaio, E.
    Gazza, E.
    Giudicotti, L.
    Grando, L.
    Guo, S. C.
    Manduchi, G.
    Marchiori, G.
    Martines, E.
    Martini, S.
    Menmuir, Sheena
    Momo, B.
    Moresco, M.
    Munaretto, S.
    Novello, L.
    Paccagnella, R.
    Pasqualotto, R.
    Piovan, R.
    Piron, L.
    Pizzimenti, A.
    Pomphrey, N.
    Scarin, P.
    Serianni, G.
    Spada, E.
    Soppelsa, A.
    Spagnolo, S.
    Spolaore, M.
    Taliercio, C.
    Vianello, N.
    Zamengo, A.
    Zanca, P.
    Helical equilibria and magnetic structures in the reversed field pinch and analogies to the tokamak and stellarator2009In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 51, no 12, p. 124031-Article in journal (Refereed)
    Abstract [en]

    The reversed field pinch configuration is characterized by the presence of magnetic structures both in the core and at the edge: in the core, at high plasma current the spontaneous development of a helical structure is accompanied by the appearance of internal electron transport barriers; at the edge strong pressure gradients, identifying an edge transport barrier, are observed too, related to the position of the field reversal surface. The aim of this paper is the experimental characterization of both the internal and edge transport barriers in relation to the magnetic topology, discussing possible analogies and differences with other confinement schemes.

  • 42.
    Puiatti, M. E.
    et al.
    Consorzio RFX.
    Valisa, M.
    Agostini, M.
    Auriemma, F.
    Bonomo, F.
    Carraro, L.
    Fassina, A.
    Gobbin, M.
    Lorenzini, R.
    Momo, B.
    Scaggion, A.
    Zaniol, B.
    Alfier, A.
    Apolloni, L.
    Baruzzo, M.
    Bolzonella, T.
    Bonfiglio, D.
    Canton, A.
    Cappello, S.
    Cavazzana, R.
    Dal Bello, S.
    De Masi, G.
    Escande, D. F.
    Franz, P.
    Gazza, E.
    Guo, S.
    Innocente, P.
    Marchiori, G.
    Marrelli, L.
    Martin, P.
    Martines, E.
    Martini, S.
    Menmuir, Sheena
    Novello, L.
    Paccagnella, R.
    Piovesan, P.
    Piron, L.
    Predebon, I.
    Ruzzon, A.
    Sattin, F.
    Scarin, P.
    Soppelsa, A.
    Spizzo, G.
    Spagnolo, S.
    Spolaore, M.
    Terranova, D.
    Veranda, M.
    Vianello, N.
    Zanca, P.
    Zanotto, L.
    Zuin, M.
    Internal and external electron transport barriers in the RFX-mod reversed field pinch2011In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 51, no 7, p. 073038-Article in journal (Refereed)
    Abstract [en]

    An interesting result of magnetic chaos reduction in RFX-mod high current discharges is the development of strong electron transport barriers. An internal heat and particle transport barrier is formed when a bifurcation process changes the magnetic configuration into a helical equilibrium and chaos reduction follows, together with the formation of a null in the q shear. Strong temperature gradients develop, corresponding to a decreased thermal and particle transport. Turbulence analysis shows that the large electron temperature gradients are limited by the onset of micro-tearing modes, in addition to residual magnetic chaos. A new type of electron transport barrier with strong temperature gradients develops more externally (r/a = 0.8) accompanied by a 30% improvement of the global confinement time. The mechanism responsible for the formation of such a barrier is still unknown but it is likely associated with a local reduction of magnetic chaos. These external barriers develop primarily in situations of well-conditioned walls so that they might be regarded as attempts towards an L-H transition. Both types of barriers occur in high-current low-collisionality regimes. Analogies with tokamak and stellarators are discussed. © 2011 IAEA, Vienna.

  • 43. Romanelli, F.
    et al.
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brzozowski, Jerzy
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Chernyshova, M.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Drake, James Robert
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Emmoth, Birger
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Johnson, Thomas J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Laxåback, Martin
    KTH, School of Electrical Engineering (EES), Fusion Plasma 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.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Overview of the JET results with the ITER-like wall2013In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 53, no 10, p. 104002-Article in journal (Refereed)
    Abstract [en]

    Following the completion in May 2011 of the shutdown for the installation of the beryllium wall and the tungsten divertor, the first set of JET campaigns have addressed the investigation of the retention properties and the development of operational scenarios with the new plasma-facing materials. The large reduction in the carbon content (more than a factor ten) led to a much lower Z(eff) (1.2-1.4) during L- and H-mode plasmas, and radiation during the burn-through phase of the plasma initiation with the consequence that breakdown failures are almost absent. Gas balance experiments have shown that the fuel retention rate with the new wall is substantially reduced with respect to the C wall. The re-establishment of the baseline H-mode and hybrid scenarios compatible with the new wall has required an optimization of the control of metallic impurity sources and heat loads. Stable type-I ELMy H-mode regimes with H-98,H-y2 close to 1 and beta(N) similar to 1.6 have been achieved using gas injection. ELM frequency is a key factor for the control of the metallic impurity accumulation. Pedestal temperatures tend to be lower with the new wall, leading to reduced confinement, but nitrogen seeding restores high pedestal temperatures and confinement. Compared with the carbon wall, major disruptions with the new wall show a lower radiated power and a slower current quench. The higher heat loads on Be wall plasma-facing components due to lower radiation made the routine use of massive gas injection for disruption mitigation essential.

  • 44.
    Ström, Petter
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Bergsåker, Henric
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tholerus, Simon
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Rachlew, Elisabeth
    KTH, Superseded Departments (pre-2005), Physics. KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Johnson, T.
    Stefanikova, E.
    Zhou, Y.
    Zychor, I.
    et al.,
    Analysis of deposited layers with deuterium and impurity elements on samples from the divertor of JET with ITER-like wall2019In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 516, p. 202-213Article in journal (Refereed)
    Abstract [en]

    Inconel-600 blocks and stainless steel covers for quartz microbalance crystals from remote corners in the JET-ILW divertor were studied with time-of-flight elastic recoil detection analysis and nuclear reaction analysis to obtain information about the areal densities and depth profiles of elements present in deposited material layers. Surface morphology and the composition of dust particles were examined with scanning electron microscopy and energy-dispersive X-ray spectroscopy. The analyzed components were present in JET during three ITER-like wall campaigns between 2010 and 2017. Deposited layers had a stratified structure, primarily made up of beryllium, carbon and oxygen with varying atomic fractions of deuterium, up to more than 20%. The range of carbon transport from the ribs of the divertor carrier was limited to a few centimeters, and carbon/deuterium co-deposition was indicated on the Inconel blocks. High atomic fractions of deuterium were also found in almost carbon-free layers on the quartz microbalance covers. Layer thicknesses up to more than 1 micrometer were indicated, but typical values were on the order of a few hundred nanometers. Chromium, iron and nickel fractions were less than or around 1% at layer surfaces while increasing close to the layer-substrate interface. The tungsten fraction depended on the proximity of the plasma strike point to the divertor corners. Particles of tungsten, molybdenum and copper with sizes less than or around 1 micrometer were found. Nitrogen, argon and neon were present after plasma edge cooling and disruption mitigation. Oxygen-18 was found on component surfaces after injection, indicating in-vessel oxidation. Compensation of elastic recoil detection data for detection efficiency and ion-induced release of deuterium during the measurement gave quantitative agreement with nuclear reaction analysis, which strengthens the validity of the results.

  • 45. Tamain, P.
    et al.
    Joffrin, E.
    Bufferand, H.
    Jarvinen, A.
    Brezinsek, S.
    Ciraolo, G.
    Delabie, E.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Giroud, C.
    Groth, M.
    Lipschultz, B.
    Lomas, P.
    Marsen, S.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Oberkofler, M.
    Stamp, M.
    Wiesen, S.
    Investigation of the influence of divertor recycling on global plasma confinement in JET ITER-like wall2015In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, p. 450-454Article in journal (Refereed)
    Abstract [en]

    The impact of the divertor geometry on global plasma confinement in type I ELMy H-mode has been investigated in the JET tokamak equipped with ITER-Like Wall. Discharges have been performed in which the position of the strike-points was changed while keeping the bulk plasma equilibrium essentially unchanged. Large variations of the global plasma confinement have been observed, the H-98 factor changing from typically 0.7 when the outer strike-point is on the vertical or horizontal targets to 0.9 when it is located in the pump duct entrance. Profiles are mainly impacted in the pedestal but core gradient lengths, especially for the density, are also modified. Although substantial differences are observed in the divertor conditions, none seem to correlate directly with the confinement. Modelling with the EDGE2D-EIRENE and SOLEDGE2D-EIRENE transport codes exhibits differences in the energy losses due to neutrals inside the separatrix, but orders of magnitude are too low to explain simply the impact on the confinement.

  • 46.
    Terranova, D.
    et al.
    Consorzio RFX.
    Bonfiglio, D.
    Boozer, A. H.
    Cooper, A. W.
    Gobbin, M.
    Hirshman, S. P.
    Lorenzini, R.
    Marrelli, L.
    Martines, E.
    Momo, B.
    Pomphrey, N.
    Predebon, I.
    Sanchez, R.
    Spizzo, G.
    Agostini, M.
    Alfier, A.
    Apolloni, L.
    Auriemma, F.
    Baruzzo, M.
    Bolzonella, T.
    Bonomo, F.
    Brombin, M.
    Canton, A.
    Cappello, S.
    Carraro, L.
    Cavazzana, R.
    Dal Bello, S.
    Delogu, R.
    De Masi, G.
    Drevlak, M.
    Fassina, A.
    Ferro, A.
    Franz, P.
    Gaio, E.
    Gazza, E.
    Giudicotti, L.
    Grando, L.
    Guo, S. C.
    Innocente, P.
    Lòpez-Bruna, D.
    Manduchi, G.
    Marchiori, G.
    Martin, P.
    Martini, S.
    Menmuir, Sheena
    Munaretto, S.
    Novello, L.
    Paccagnella, R.
    Pasqualotto, R.
    Pereverzev, G. V.
    Piovan, R.
    Piovesan, P.
    Piron, L.
    Puiatti, M. E.
    Recchia, M.
    Sattin, F.
    Scarin, P.
    Serianni, G.
    Soppelsa, A.
    Spagnolo, S.
    Spolaore, M.
    Taliercio, C.
    Valisa, M.
    Vianello, N.
    Wang, Z.
    Zamengo, A.
    Zaniol, B.
    Zanotto, L.
    Zanca, P.
    Zuin, M.
    A 3D approach to equilibrium, stability and transport studies in RFX-mod improved regimes2010In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 52, no 12, p. 124023-Article in journal (Refereed)
    Abstract [en]

    The full three-dimensional (3D) approach is now becoming an important issue for all magnetic confinement configurations. It is a necessary condition for the stellarator but also the tokamak and the reversed field pinch (RFP) now cannot be completely described in an axisymmetric framework. For the RFP the observation of self-sustained helical configurations with improved plasma performances require a better description in order to assess a new view on this configuration. In this new framework plasma configuration studies for RFX-mod have been considered both with tools developed for the RFP as well as considering codes originally developed for the stellarator and adapted to the RFP. These helical states are reached through a transition to a very low/reversed shear configuration leading to internal electron transport barriers. These states are interrupted by MHD reconnection events and the large Te gradients at the barriers indicate that both current and pressure driven modes are to be considered. Furthermore the typically flat Te profiles in the helical core have raised the issue of the role of electrostatic and electromagnetic turbulence in these reduced chaos regions, so that a stability analysis in the correct 3D geometry is required to address an optimization of the plasma setup. In this viewtheVMECcode proved to be an effectiveway to obtain helical equilibria to be studied in terms of stability and transport with a suite of well tested codes. In this work, the equilibrium reconstruction technique as well as the experimental evidence of 3D effects and their first interpretation in terms of stability and transport are presented using both RFP and stellarator tools.

  • 47.
    Vall-llosera, Gemma
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Álvarez Ruiz, Jesús
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Erman, Peter
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Melero García, Emilio
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Stankiewicz, Marek
    Instytut Fizyki, Jageillonian University.
    The npσ,π to EF emission systems in D2 studied by selective excitation2005In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 38, no 6, p. 659-664Article in journal (Refereed)
    Abstract [en]

    The np sigma 1 Sigma(u)(+) and np pi (1)Pi(u) states in D-2 have been selectively excited using monoenergetic synchrotron light in the range of 13.97-15.84 eV and the subsequent dispersed emission to the EF (1)Sigma(g)(+) state was observed using a grating spectrometer. In total, 18 emission bands from the levels n = 3-6 were studied and rotationally analysed. The intensities of the P and R branches relative to the Q branch were found to vary strongly in the np pi (1)Pi(u)(+)-EF(1)Sigma(g)(+) bands indicating the existence of predissociations of np pi (1)Pi(u)(+) levels above the dissociation limit D(1s) + D(2l).

1 - 47 of 47
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