High resolution electron cyclotron emission temperature profile and fluctuation diagnostic for Alcator C-Mod

Heard, J. W.; Watts, Christopher; Gandy, R. F.; Phillips, P. E.; Cima, Greg; Chatterjee, Rajdeep Mohan; Blair, A. P.; Hubbard, A.; Domier, Calvin; Luhmann, Neville C.

doi:10.1063/1.1149368

Cited by 31 publications

(28 citation statements)

References 5 publications

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“…Grating-polychromator ECE (GPC ECE) diagnostics [4] provide a total of 28 core and edge T e channels with instrument-limited imaging sizes of ∼ 9 mm, digitized at 20 kHz. Additionally, a high-resolution 32-channel heterodyne ECE (HRECE) diagnostic [21] provides plasma coverage with sub-centimeter spot sizes in the edge. Both have sufficient spatial resolution to distinguish edge T e (though they cannot resolve the temperature pedestal structure), along with the time resolution necessary to track ELM crashes.…”

Section: Diagnosticsmentioning

confidence: 99%

Characterization of the pedestal in Alcator C-Mod ELMing H-modes and comparison with the EPED model

Walk¹,

Snyder²,

Hughes³

et al. 2012

Nucl. Fusion

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Abstract. A dedicated series of ELMing H-Mode discharges on Alcator C-Mod spanning a broad range of plasma parameters, including plasma current (400-1000kA), magnetic field (3.5-8T), and plasma shaping, are presented with experimental scalings of the plasma pedestal with bulk plasma and engineering parameters. The H-modes presented achieve pedestals with densities spanning 5 × 10 19 − 2.5 × 10 20 m −3 and temperatures of 150 − 1000 eV (corresponding to 5 − 40 kPa in the pressure pedestal), over a width of 3 − 5% of poloidal flux. The observed pedestal structure is compared with the most recent iteration of the EPED class of models, which uniquely predict the pedestal width and height for a set of scalar input parameters via a combination of stability calculations for peeling-ballooning MHD modes and kinetic ballooning modes (KBM).

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Section: Diagnosticsmentioning

confidence: 99%

Characterization of the pedestal in Alcator C-Mod ELMing H-modes and comparison with the EPED model

Walk¹,

Snyder²,

Hughes³

et al. 2012

Nucl. Fusion

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“…For the first time, experimental measurements demonstrate a direct dynamic relation between LHCD generated fast electrons and a fishbone-like mode. A time history of the central electron temperature inferred by the slow electron cyclotron emission (ECE) grating polychromator (GPC) 18 shows that the mode growth begins at the maximum of the inferred core T e , which falls to a minimum by the disappearance of the mode [see dotted lines in Fig. 5-a)].…”

mentioning

confidence: 99%

Non-resonant destabilization of (1/1) internal kink mode by suprathermal electron pressure

Delgado‐Aparicio

Sugiyama²,

Shiraiwa

et al. 2015

Phys. Plasmas

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New experimental observations are reported on the structure and dynamics of short-lived periodic (1, 1) "fishbone"-like oscillations that appear during radio frequency heating and current-drive experiments in tokamak plasmas. For the first time, measurements can directly relate changes in the high energy electrons to the mode onset, saturation, and damping. In the relatively high collisionality of Alcator C-Mod with lower hybrid current drive, the instability appears to be destabilized by the non-resonant suprathermal electron pressure -rather than by wave-particle resonance, rotates toroidally with the plasma and grows independently of the (1, 1) sawtooth crash driven by the thermal plasma pressure. The economic feasibility of a fusion reactor can be measured in terms of β ≡ p/ B 2 /2µ 0 , where p is the plasma pressure and B 2 /2µ 0 is the magnetic field energy density. The presence of magnetohydrodynamic (MHD) instabilities can distort the orbits of fast ions and electrons compared to the equilibrium, causing an off-axis redistribution of the fusion heating and current density to the detriment of the central β, reducing the fusion power and the production of fast neutrons for tritium breeding. Therefore, understanding the stability and behavior of 3D helical modes in the core of an axisymmetric toroidal configuration remains one of the challenges of fusion research 1-6 . It is doubly significant for burning plasmas such as ITER, where the q = 1 radius that bounds these instabilities may reach half the minor radius.A helical internal kink-like mode 7-9 with dominant poloidal and toroidal mode numbers m = 1, n = 1 has recently been observed in the Alcator C-Mod tokamak 10

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“…To measure electron heating in the mode conversion regime, a second harmonic heterodyne electron cyclotron emission radiometer (FRC-ECE) 53 was used. poloidal Larmor radius, a: radial scale length).…”

Section: Introductionmentioning

confidence: 99%

Measurements of ion cyclotron range of frequencies mode converted wave intensity with phase contrast imaging in Alcator C-Mod and comparison with full-wave simulations

et al. 2012

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Radio frequency waves in the ion cyclotron range of frequencies (ICRF) are widely used to heat tokamak plasmas. In ICRF heating schemes involving multiple ion species, the launched fast waves convert to ion cyclotron waves or ion Bernstein waves at the two-ion hybrid resonances. Mode converted waves are of interest as actuators to optimise plasma performance through current drive and flow drive. In order to describe these processes accurately in a realistic tokamak geometry, numerical simulations are essential, and it is important that these codes be validated against experiment. In this study, the mode converted waves were measured using a phase contrast imaging technique in D-H and D-3 He plasmas. The measured mode converted wave intensity in the D-3 He mode conversion regime was found to be a factor of ∼50 weaker than the full-wave predictions. The discrepancy was reduced in the hydrogen minority heating regime, where mode conversion is weaker.a)

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High resolution electron cyclotron emission temperature profile and fluctuation diagnostic for Alcator C-Mod

Cited by 31 publications

References 5 publications

Characterization of the pedestal in Alcator C-Mod ELMing H-modes and comparison with the EPED model

Characterization of the pedestal in Alcator C-Mod ELMing H-modes and comparison with the EPED model

Non-resonant destabilization of (1/1) internal kink mode by suprathermal electron pressure

Measurements of ion cyclotron range of frequencies mode converted wave intensity with phase contrast imaging in Alcator C-Mod and comparison with full-wave simulations

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