The LIDAR Thomson scattering diagnostic on JET (invited)

The performance of the 'hybrid' H-mode regime (long pulse operation with high neutron fluency) has been extensively investigated in JET during the [2005][2006][2007] experimental campaign up to normalized pressure β N = 3, toroidal magnetic field B t = 1.7 T, with type I ELMs plasma edge conditions. The optimized external current drive sources, self-generated non-inductive bootstrap current and plasma core stability properties provide a good prospect of achieving a high fusion gain at reduced plasma current for long durations in ITER.One of the remaining issues is the erosion of the divertor target plates associated with the type I ELM regime. regime with a normalized pressure β N = 2.6 (P NBI ∼ 20-22 MW) and a thermal confinement factor of H * 98 (y, 2) ∼ 0.83 has been recently successfully developed on JET with nitrogen seeding. This scenario shows good plasma edge condition (compatible with the future ITER-like wall on JET) and moderate MHD activity. In this paper, we report on the experimental development of the scenario (with plasma current I p = 1.7 MA and magnetic field B t = 1.7 T) and the trade-off between heat load reduction at the target plates and global confinement due to nitrogen seeding and type III ELM working conditions.

show abstract

“…A slightly higher temperature is observed for the electron with the core and edge LIDAR Thomson scattering measurements [23] ( figure 9(a)). …”

Section: Edge Pedestalmentioning

confidence: 95%

Hybrid H-mode scenario with nitrogen seeding and type III ELMs in JET

Corre

Joffrin

Monier‐Garbet

et al. 2008

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…The LIDAR (light detection and ranging) diagnostic is described in detail in [5]. It uses a ruby laser to obtain density profile information across the mid plane, as shown schematically in Fig.…”

Section: Density Profile Measurements On Jetmentioning

confidence: 99%

Reconstruction of tokamak density profiles using feedforward networks

Bishop

Strachan

O’Rourke

et al. 1993

Neural Comput & Applic

View full text Add to dashboard Cite

“…Thus, the T e and n e profiles are not only important factors of the development and the efficiency of the fusion process but indicators as well of the dynamic plasma state. So far, the most appropriate approach to their simultaneous express determination in a remote contactless way is the Thomson scattering (TS) lidar approach [1][2][3] . It allows one to obtain the T e and n e profiles along a line of sight through the torus core.…”

Section: Introductionmentioning

confidence: 99%

Statistical modeling of deconvolution procedures for improving the resolution of measuring electron temperature profiles in tokamak plasmas by Thomson scattering lidar

Dreischuh¹,

Gurdev²,

Stoyanov³

2010

SPIE Proceedings

View full text Add to dashboard Cite

The potentialities are investigated, by statistical modeling, of deconvolution techniques for high-resolution restoration of electron temperature profiles in fusion plasma reactors like Joint European Torus (JET) measured by Thomson scattering lidar using the center-of-mass wavelength approach. The sensing laser pulse shape and the receiving-system response function are assumed to be exponentially-shaped. The plasma light background influence is taken into account as well as the Poisson fluctuations of the photoelectron number after the photocathode enhanced in the process of cascade multiplying in the employed microchannel photomultiplier tube. It is shown that the Fourier-deconvolution of the measured long-pulse (lidar-response-convolved) lidar profiles, at relatively high and low signal-to-noise ratios, ensures a higher accuracy of recovering the electron temperature profiles with three times higher range resolution compared to the case without deconvolution. The final resolution scale is determined by the width of the window of an optimum monotone sharp-cutoff digital noise-suppressing (noise-controlling) filter applied to the measured lidar profiles.Keywords: Thomson scattering lidar, fusion plasma diagnostics, electron temperature profiles INTRODUCTIONThe electron temperature T e and density n e distributions in the torus are basic characteristics of the tokamak fusion plasma. They are conditioned by the modes of heating and confinement of the high-temperature plasma as well as by the different oscillatory movements of the plasma particles sometimes leading to the appearance of crucial instabilities. Thus, the T e and n e profiles are not only important factors of the development and the efficiency of the fusion process but indicators as well of the dynamic plasma state. So far, the most appropriate approach to their simultaneous express determination in a remote contactless way is the Thomson scattering (TS) lidar approach 1-3 . It allows one to obtain the T e and n e profiles along a line of sight through the torus core. The minimum range resolution interval achievable by the contemporary core TS lidars 3 is about 12-15 cm. Such a resolution is relatively good in general, but is insufficient for resolving small-scale inhomogeneities and the edge pedestal areas of T e and n e profiles in the so-called high-confinement mode (H-mode) of operation of the tokamak reactors.A way of improving the range resolution of the TS lidars is based on the use of deconvolution techniques 4 for recovering the high-resolution lidar profiles. The deconvolution procedures, however, increase the influence of the noise. Therefore, to achieve acceptable recovered profiles one should apply a final filtering that lowers the sensing resolution to some compromise extent.The main purpose of the present work is to outline by statistical modeling some optimal conditions under which the deconvolution techniques lead to satisfactory high-resolution restoration of the T e profiles measured by the center-ofmass wavelength (CMW) method 5-6 ....

show abstract

The LIDAR Thomson scattering diagnostic on JET (invited)

Cited by 94 publications

References 7 publications

Hybrid H-mode scenario with nitrogen seeding and type III ELMs in JET

Hybrid H-mode scenario with nitrogen seeding and type III ELMs in JET

Reconstruction of tokamak density profiles using feedforward networks

Statistical modeling of deconvolution procedures for improving the resolution of measuring electron temperature profiles in tokamak plasmas by Thomson scattering lidar

Contact Info

Product

Resources

About