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N Gierse,
S Brezinsek,
T F Giesen,
A Huber,
M Laengner,
R Leyte-Gonzales,
L Marot,
E Meyer,
S Möller,
M Naiim-Habib,
V Philipps,
A Pospieszczyk,
B Schweer,
G Sergienko,
M Zlobinski, U Samm,
the TEXTOR team
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A. Kirschner,
P. Wienhold,
D. Borodin,
C. Björkas,
O. Van Hoey,
D. Matveev,
S. Brezinsek,
A. Kreter,
M. Laengner,
K. Ohya,
V. Philipps,
A. Pospieszczyk, U. Samm,
B. Schweer
[show abstract]
[hide abstract]
ABSTRACT: Tracer experiments have been carried out by injection 13C marked methane through test limiters exposed to the scrape-off-layer in TEXTOR. The influence of impact energy and flux on depositing 13C species has been studied. One experiment has been performed with biased test limiter (−300 V) in order to increase energy of positively charged ions and the other one with 10 times reduced 13CH4 injection rate compared to previously used injection rate. Biasing of the test limiter increases the resulting 13C deposition by a factor of ∼6 – post-mortem analysis yields a 13C deposition efficiency of ∼1.7% compared to ∼0.3% without biasing. Reducing the injection rate increases 13C deposition efficiency to ∼0.7%, which is more than two times larger compared to experiments with previously used injection rate. ERO modelling shows that enhanced re-erosion of redeposits is still necessary to reproduce measured 13C deposition efficiencies.
Journal of Nuclear Materials 01/2013; · 2.05 Impact Factor
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A Huber,
S Brezinsek,
Ph Mertens,
B Schweer,
G Sergienko,
A Terra,
G Arnoux,
N Balshaw,
M Clever,
T Edlingdon, [......],
C Morlock,
A Murari,
M Reindl,
V Riccardo, U Samm,
S Sanders,
M Stamp,
J Williams,
K D Zastrow,
C Zauner
[show abstract]
[hide abstract]
ABSTRACT: A new endoscope with optimised divertor view has been developed in order to survey and monitor the emission of specific impurities such as tungsten and the remaining carbon as well as beryllium in the tungsten divertor of JET after the implementation of the ITER-like wall in 2011. The endoscope is a prototype for testing an ITER relevant design concept based on reflective optics only. It may be subject to high neutron fluxes as expected in ITER. The operating wavelength range, from 390 nm to 2500 nm, allows the measurements of the emission of all expected impurities (W I, Be II, C I, C II, C III) with high optical transmittance (≥30% in the designed wavelength range) as well as high spatial resolution that is ≤2 mm at the object plane and ≤3 mm for the full depth of field (±0.7 m). The new optical design includes options for in situ calibration of the endoscope transmittance during the experimental campaign, which allows the continuous tracing of possible transmittance degradation with time due to impurity deposition and erosion by fast neutral particles. In parallel to the new optical design, a new type of possibly ITER relevant shutter system based on pneumatic techniques has been developed and integrated into the endoscope head. The endoscope is equipped with four digital CCD cameras, each combined with two filter wheels for narrow band interference and neutral density filters. Additionally, two protection cameras in the λ > 0.95 μm range have been integrated in the optical design for the real time wall protection during the plasma operation of JET.
The Review of scientific instruments 10/2012; 83(10):10D511. · 1.52 Impact Factor
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[show abstract]
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ABSTRACT: A supersonic helium beam diagnostic, based on the line-ratio technique for high resolution electron density and temperature measurements in the plasma edge (r/a > 0.9) was designed, built, and optimised at TEXTOR (Torus Experiment for Technology Oriented Research). The supersonic injection system, based on the Campargue skimmer-nozzle concept, was developed and optimised in order to provide both a high neutral helium beam density of n(0) = 1.5 × 10(18) m(-3) and a low beam divergence of ±1° simultaneously, achieving a poloidal resolution of Δ(poloidal) = 9 mm. The setup utilises a newly developed dead volume free piezo valve for operation in a high magnetic field environment of up to 2 T with a maximum repetition rate of 80 Hz. Gas injections are realised for a duration of 120 ms at a repetition rate of 2 Hz (duty cycle 1/3). In combination with a high sensitivity detection system, consisting of three 32 multi-channel photomultipliers (PMTs), measurements of edge electron temperature and density with a radial resolution of Δ(radial) = 2 mm and a maximum temporal resolution of Δt ≃ 2 μs (470 kHz) are possible for the first time. The diagnostic setup at TEXTOR is presented. The newly developed injection system and its theoretical bases are discussed. The applicability of the stationary collisional-radiative model as basis of the line-ratio technique is shown. Finally, an example of a fluctuation analysis demonstrating the unique high temporal and spatial resolution capabilities of this new diagnostic is presented.
The Review of scientific instruments 06/2012; 83(6):065107. · 1.52 Impact Factor
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M. Laengner,
S. Brezinsek,
J. W. Coenen,
A. Pospieszczyck,
D. Kondratyev,
D. Borodin,
H. Stoschus,
O. Schmitz,
V. Philipps, U. Samm,
the TEXTOR Team
20th International Conference on Plasma Surface Interaction in Fusion Devices, to be published in Journal of Nuclear Materials. 01/2012;
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R. Laengner,
S. Brezinsek,
J. W. Coenen,
T. Eich,
M. Freisinger,
A. Kirschner,
A. Kreter,
S. Moeller,
M. Laengner,
V. Philipps,
A. Pospieszczyck,
H. Reimer, U. Samm,
O. Schmitz,
P. Wienhold,
the TEXTOR Team
20th International Conference on Plasma Surface Interaction in Fusion Devices, to be published in Journal of Nuclear Materials. 01/2012;
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O. Schmitz,
T.E. Evans,
M.E. Fenstermacher,
M. Lehnen,
H. Stoschus,
E.A. Unterberg,
J. W. Coenen,
H. Frerichs,
M.W. Jakubowski,
R. Laengner,
C.L. Lasnier,
S. Mordijck,
R.A. Moyer,
T.H. Osborne,
H. Reimerdes,
D. Reiter, U. Samm,
B. Unterberg,
the DIII-D,
TEXTOR teams
Nuclear Fusion. 01/2012; 52(4):043005.
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J. W. Coenen,
B Bazylev,
S Brezinsek,
V Philipps,
T Hirai,
A Kreter,
J Linke,
G Pintsuk,
Sergienko G,
A. Pospieszczyck,
T Tanabe,
Y. Ueda, U Samm,
the TEXTOR Team
Fusion Science and Technology 01/2012; 61(2):129-135. · 1.12 Impact Factor
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ABSTRACT: In future fusion devices such as ITER tritium retention due to tritium co-deposition in mixed material layers can be a serious safety problem. Laser induced desorption spectroscopy (LIDS) can measure the hydrogen content of hydrogenic carbon layers locally on plasma-facing components, while hydrogen is used as a tritium substitute. For several years, this method has been applied in the TEXTOR tokamak in situ during plasma operation to monitor the hydrogen content in space and time. This work shows the LIDS signal reproducibility and studies the effects of different plasma conditions, desorption distances from the plasma and different laser energies using a dedicated sample with constant hydrogen amount. Also the LIDS signal evaluation procedure is described in detail and the detection limits for different conditions in the TEXTOR tokamak are estimated.
Physica Scripta 12/2011; 2011(T145):014027. · 1.20 Impact Factor
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D Borodin,
A Kirschner,
S Carpentier-Chouchana,
R A Pitts,
S Lisgo,
C Björkas,
P C Stangeby,
J D Elder,
A Galonska,
D Matveev,
V Philipps, U Samm
[show abstract]
[hide abstract]
ABSTRACT: Previous studies (Carpentier et al 2011 J. Nucl. Mater. 415 S165–S169) carried out with the LIM code of the ITER first wall (FW) on beryllium (Be) erosion, re-deposition and tritium retention by co-deposition under steady-state burning plasma conditions have shown that, depending on input plasma parameter assumptions and sputtering yields, the erosion lifetime and fuel retention on some parts of the FW can be a serious concern. The importance of the issue is such that a benchmark of this previous work is sought and has been provided by the ERO code (Pitts et al 2011 J. Nucl. Mater. 415 S957–S964) simulations described in this paper. Provided that inputs to the codes are carefully matched, excellent agreement is found between the erosion/deposition profiles from both codes for a given ITER-shaped FW panel. Issues regarding the difficult problem of the correct treatment of Be sputtering are discussed in relation to the simulations. The possible influence of intrinsic Be impurity is investigated.
Physica Scripta 12/2011; 2011(T145):014008. · 1.20 Impact Factor
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N Gierse,
S Brezinsek,
T F Giesen,
A Huber,
M Laengner,
R Leyte-Gonzales,
L Marot,
E Meyer,
S Möller,
M Naiim-Habib,
V Philipps,
A Pospieszczyk,
B Schweer,
G Sergienko,
M Zlobinski, U Samm,
the TEXTOR team
[show abstract]
[hide abstract]
ABSTRACT: Laser-based methods are investigated for the development of an in situ diagnostic for spatially and temporally resolved characterization of the first wall in fusion devices. Here we report on the first systematic laser-induced ablation spectroscopy (LIAS) measurements carried out on various surface layers in the TEXTOR tokamak. These materials include a-C:D, mixed W/C/Al/D2, Oerlikon Balzers 'Balinit' diamond-like carbon layers and EK98 fine-grain graphite. In LIAS, the bulk or deposited material is evaporated during the plasma discharge by intense laser radiation. The light emitted by particles entering the edge of the ionizing tokamak plasma is then observed by optical spectroscopy. In the measurements taken, it was found that the studied layers can be identified by their characteristic line emission. A good correlation between the observed line intensity and layer thickness is found. The observed plumes show target material dependence. To analyze layers formed during tokamak operation, further investigation of the ablation process and reference materials for cross calibration is required.
Physica Scripta 12/2011; 2011(T145):014026. · 1.20 Impact Factor
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A Huber,
B Schweer,
V Philipps,
R Leyte-Gonzales,
N Gierse,
M Zlobinski,
S Brezinsek,
V Kotov,
P Mertens, U Samm,
G Sergienko
[show abstract]
[hide abstract]
ABSTRACT: This paper presents a feasibility study of laser-induced breakdown spectroscopy (LIBS) for the development of an in-situ diagnostic for the characterization of deposition layers on plasma-facing components in fusion devices. Preferentially, LIBS would be applied in the presence of a toroidal magnetic field and under high vacuum conditions. The impact of the laser-energy densities on the laser-induced plasma parameters and correspondingly on the number of emitted photons and on the reproducibility of the LIBS method has been studied in laboratory experiments and in TEXTOR on fine-grain graphite (EK98) as well as on bulk W samples coated with carbon and metallic-containing deposits. The effect of magnetic fields and of ambient pressures in the range from 2×10–4 Pa to 10 Pa on the carbon plasma plume produced by the LIBS technique has been studied on TEXTOR between plasma pulses. The possibility of applying this method to ITER is discussed.
Physica Scripta 12/2011; 2011(T145):014028. · 1.20 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Deposition of impurities can drastically change optical properties of metallic mirrors used for diagnostics of fusion plasmas. Specifically in ITER, this can become critical for the reactor operation by affecting the quality and reliability of detected signals. A series of experiments was performed in TEXTOR where local gas feeding was used for mitigation of carbon deposition on the mirror surface. A prototype of a diagnostic duct with molybdenum mirrors equipped with a gas feeding system was exposed in scrape-off layer plasma under deposition-dominated conditions. In the case of helium feeding, suppression of deposition was observed, while feeding of deuterium not only demonstrated full suppression of deposition but even favored complete removal of initially pre-deposited a-C:D layers. This paper presents results of experiments along with dedicated modeling of plasma–gas interaction inside the diagnostic duct.
Physica Scripta 12/2011; 2011(T145):014072. · 1.20 Impact Factor
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A Kirschner,
H G Esser,
D Matveev,
O Van Hoey,
D Borodin,
A Galonska,
K Ohya,
V Philipps,
A Pospieszczyk, U Samm,
O Schmitz,
P Wienhold
[show abstract]
[hide abstract]
ABSTRACT: To analyse the impurity transport in plasma-shadowed, remote areas, methane CD4 has been injected into the far scrape-off layer of TEXTOR through a cylinder equipped with a quartz micro balance (QMB). CD4 transport including break-up and resulting deposition on the QMB (shot-resolved) and on the cylinder top surface (shot-integrated) has been modelled with the codes ERO and 3D-GAPS. The modelling shows good agreement with the observations if reflection coefficients based on molecular dynamics simulations are used. In contrast to plasma-wetted areas, no enhanced erosion has to be applied.
Physica Scripta 12/2011; · 1.20 Impact Factor
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J.W. Coenen,
V. Philipps,
S. Brezinsek,
G. Pintsuk,
I. Uytdenhouwen,
M. Wirtz,
A. Kreter,
K. Sugiyama,
H. Kurishita,
Y. Torikai,
Y. Ueda, U. Samm,
the TEXTOR-Team
[show abstract]
[hide abstract]
ABSTRACT: The behaviour of tungsten (W) plasma-facing components (PFCs) has been investigated in the plasma edge of the TEXTOR tokamak to study melt-layer ejection, macroscopic tungsten erosion from the melt layer as well as the changes of material properties such as grain-size and abundance of voids or bubbles. The parallel heat flux at the radial position of the exposed tungsten tile in the plasma ranges around q|| ~ 45 MW m−2 causing samples to be exposed at an impact angle of 35° to 20–30 MW m−2. Locally the temperature reached up to 6000 K, high levels of evaporation and boiling are causing significant erosion in the form of continuous fine spray or droplet ejection. The amount of fine-spray tungsten emission depends strongly on the material properties: in the case of the tungsten–tantalum alloy the effect of spraying and droplet emission is significantly higher at even low temperatures when compared with regular tungsten or even ultra-high purity tungsten which shows almost no spraying at all. Differences in the material composition, grain structure and size may be related to the different evolution of macroscopic erosion. In addition the re-solidified material is studied and strong differences in terms of re-crystallized grain size and evolution of the grain structure and grain orientation are observed. The build up of large voids has been observed.
Nuclear Fusion 11/2011; 51(11):113020. · 4.09 Impact Factor
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B. Unterberg,
R. Jaspers,
R. Koch,
V. Massaut,
J. Rapp,
D. Reiter,
S. Kraus,
A. Kreter,
V. Philipps,
H. Reimer, [......],
W. Melissen,
M. van de Pol,
G.J. van Rooij,
P. Smeets,
J. Scholten,
D.C. Schram,
G. De Temmerman,
W. Vijvers,
P.A. Zeijlmans van Emmichoven,
J.J. Zielinski
Fusion Engineering and Design 10/2011; 86(9–11):1797-1800. · 1.49 Impact Factor
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J.W. Coenen,
V. Philipps,
S. Brezinsek,
B. Bazylev,
A. Kreter,
T. Hirai,
M. Laengner,
T. Tanabe,
Y. Ueda, U. Samm,
the TEXTOR Team
[show abstract]
[hide abstract]
ABSTRACT: Behaviour and characteristics of W plasma-facing components under impinging high heat fluxes are investigated in view of the material choices for the divertor in future devices such as ITER and DEMO. Experiments have been carried out in the plasma edge of the TEXTOR tokamak to study melt-layer motion, macroscopic tungsten erosion from the melt layer as well as the changes in material properties such as grain size and abundance of voids or bubbles. The parallel heat flux at the radial position of the plasma-facing components (PFCs) in the plasma ranges around q|| ~ 45 MW m−2 allowing samples to be exposed at an impact angle of 35° to 20–30 MW m−2. Melt-layer motion perpendicular to the magnetic field is observed following a Lorentz force originating from thermoelectric emission of the hot sample. Up to 3 g of molten W are redistributed forming mountain-like structures at the edge of the sample. The typical melt-layer thickness is 1–1.5 mm. Those hills are, due to the changes in the local geometry, particularly susceptible to even higher heat fluxes of up to the full q||. Locally the temperature can reach up to 6000 K, high levels of evaporation are causing significant erosion in the form of continuous fine-spray (~1 × 1024 atoms m−2 s−1). Strong evaporation cooling is observed hindering the further heating of the samples. In addition, the formation of ligaments and splashes occurs several times during the melt phase ejecting droplets in the order of several 10 µm up to 100 µm probably caused by an instability evolving in the melt. In terms of material degradation several aspects are considered: formation of leading edges by redistributed melt, bubble formation and recrystallization. Bubbles are occurring in sizes between 1 and 200 µm while recrystallization increases the grain size up to 1.5 mm. The power-handling capabilities are thus severely degraded. Melting of tungsten (W) in future devices is highly unfavourable and needs to be avoided especially in light of uncontrolled transients and possible unshaped PFCs
Nuclear Fusion 07/2011; 51(8):083008. · 4.09 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: In this paper the results of a systematic experimental assessment of the plasma edge rotation and radial electric field with application of resonant magnetic perturbation (RMP) are presented. The results are based on the radially resolved measurement of the poloidal (v pol) and toroidal (v tor) rotation. It is shown that the radial electric field E r can be deduced from the radial force balance when small amplitude resonant magnetic perturbations are applied to the plasma boundary (B r /B tor ∼ 10 −4). Both v pol and v tor spin-up in the ion-diamagnetic-drift and co-current direction, respectively, with increasing external perturbation field (v pol ∼ 15 km s −1 , v tor ∼ 2–5 km s −1) yielding an increase in E r by E r,max = 9 kV m −1 . The toroidal rotation increases over the whole radius while the poloidal rotation shows distinct local features driving the evolution of the E r -profiles. Depending on the edge safety factor a local (at the q = 5/2 rational surface) increase in the shear rate E×B (q=5/2 = 1.4 × 10 5 s −1) or reduced shearing can occur. Increased shearing is correlated with an improved particle confinement with an increase in the particle confinement time by τ p = +40% . Increasing the local resonant amplitude by 30% induces a reduced density level, the so-called RMP induced pump-out. At this confinement stage the shear rate decreases by 15% correlated with a significant drop in particle confinement (τ p = −30%). Field line tracing in the vacuum approximation gives indications towards explaining the threshold behaviour connecting the shearing rate, confinement stages and magnetic topology to the amount of applied RMP. However, this basic approach does not account for plasma response and the results presented are linked in the discussion section to recent results on the link between rotation and plasma response as well as on the transport features of RMP. (Some figures in this article are in colour only in the electronic version)
Nuclear Fusion 06/2011; 51(6):63030-13. · 4.09 Impact Factor
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R Laengner,
B Unterberg,
A Lyssoivan,
M Paul,
V Philipps,
A Pospieszczyk, U Samm,
O Schmitz,
B Schweer,
G Sergienko,
M Vervier
[show abstract]
[hide abstract]
ABSTRACT: a b s t r a c t In this contribution, we report on the application of Li beam emission spectroscopy to determine electron density and temperature in ion cyclotron wall conditioning plasmas with the help of a collisional-radiative model. Intensity ratios of atomic line emission at 670 nm, 610 nm and 460 nm have been chosen. The overall range of n e and T e in ICWC plasmas measured with the Li beam is 10 16 m À3 to a few 10 17 m À3 for the electron density and 1.5–15 eV for the electron temperature. With the application of oscillating vertical and horizontal magnetic fields in the range of 0.01 T the plasma extends towards the bottom of the TEXTOR vessel, providing a wider distribution of particle fluxes to the vessel walls.
Journal of Nuclear Materials 03/2011; · 2.05 Impact Factor
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A Litnovsky,
V Philipps,
P Wienhold,
M Matveeva,
A Pospieszczyk,
G Sergienko,
O Schmitz, U Samm,
H Stoschus,
C Schulz,
L Marot,
A Romanyuk,
G De Temmerman,
M Laengner,
U Breuer,
A Stärk,
Textor Team
[show abstract]
[hide abstract]
ABSTRACT: a b s t r a c t In future fusion devices like ITER deposition of impurities will likely occur in areas, remote from plasma and on the sensitive components of optical diagnostics, like mirrors and windows. Deposition in remote areas may lead to the tritium retention and therefore represent a safety issue. Deposition on optical com-ponents will severely deteriorate their optical properties potentially leading to the shutdown of the respective diagnostic systems. An active control over deposition is therefore highly desirable. The paper contains an overview of experiments on active control over carbon deposition undertaken in TEXTOR tokamak. A prototype of diagnostic duct was exposed in the scrape-off layer plasmas of TEXTOR where several techniques were applied to mitigate carbon deposition on diagnostic mirrors located inside this prototype. The complete suppression of carbon deposition on the surface of diagnostic mirror was achieved by feeding the deuterium gas inside the diagnostic duct.
Journal of Nuclear Materials 01/2011; · 2.05 Impact Factor
