Wave-Particle Studies in the Ion Cyclotron and Lower Hybrid Ranges of Frequencies in Alcator C-Mod

Bonoli, P. T.; Parker, R.; Wukitch, S.; Lin, Y.; Porkoláb, M.; Wright, J. C.; Edlund, E.; Graves, T. P.; Lin, L.; Liptac, J.; Parisot, A.; Schmidt, Andréa; Tang, V.; Beck, W.; Childs, R.; Grimes, M.; Gwinn, D.; Johnson, D.; Irby, J.; Kanojia, A.; Koert, P.; Marazita, S.; Marmar, E.; Terry, D.R.; Vieira, R.; Wallace, G.; Zaks, J.; Bernabei, S.; Brunkhorse, C.; Ellis, R.; Fredd, E.; Greenough, N.; Hosea, J.; Kung, C. C.; Loesser, G. D.; Rushinski, J.; Schilling, G.; Phillips, C. K.; Wilson, J. R.; Harvey, R. W.; Fiore, C. L.; Granetz, R.; Greenwald, M.; Hubbard, A.; Hutchinson, I. H.; LaBombard, B.; Lipschultz, B.; Rice, J. E.; Snipes, J. A.; Terry, J. L.; Wolfe, S.; Team, Alcator C‐Mod

doi:10.13182/fst07-a1430

Cited by 75 publications

(45 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ion Cyclotron Range of Frequencies (ICRF) heating is the sole auxiliary heating method used in these experiments [17]. Fundamental hydrogen (H)-minority ICRF at 78-80.5 MHz up to 5.5 MW is used for central heating of deuterium (D) majority plasmas at typical magnetic field B ~ 5.4.…”

Section: Methodsmentioning

confidence: 99%

“…For the purposes of this study, and consistent with previous reports [5], 80% absorption efficiency is assumed for fundamental H-minority heating. In addition, the study includes a campaign at reduced B field (~3-3.4 T) which primarily uses central ICRF H-minority 50 MHz heating, and some additional 80 MHz 2 nd harmonic H-minority heating (although the absorption efficiency of 2 nd harmonic heating is uncertain [17]). …”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

I-mode: an H-mode energy confinement regime with L-mode particle transport in Alcator C-Mod

Whyte

Hubbard

Hughes³

et al. 2010

Nucl. Fusion

Self Cite

275

370

View full text Add to dashboard Cite

An improved energy confinement regime, I-mode is studied in Alcator C-Mod, a compact high-field divertor tokamak using Ion Cyclotron Range of Frequencies (ICRF) auxiliary heating. I-mode features an edge energy transport barrier without an accompanying particle barrier, leading to several performance benefits. H-mode energy confinement is obtained without core impurity accumulation, resulting in reduced impurity radiation with a high-Z metal wall and ICRF heating. I-mode has a stationary temperature pedestal with Edge Localized Modes (ELMs) typically absent, while plasma density is controlled using divertor cryopumping. I-mode is a confinement regime that appears distinct from both L-mode and H-mode, combining the most favorable elements of both. The I-mode regime is obtained predominately with ion ∇B drift away from the active X-point. The transition from L-mode to I-mode is primarily identified by the formation of a high temperature edge pedestal, while the edge density profile remains nearly identical to Lmode. Laser blowoff injection shows that I-mode core impurity confinement times are nearly identical with those in L-mode, despite the enhanced energy confinement. In addition a weakly coherent edge MHD mode is apparent at high frequency ~ 100-300 kHz which appears to increase particle transport in the edge. The I-mode regime has been obtained over a wide parameter space (B=3-6 T, I p =0.7-1.3 MA, q 95 =2.5-5). In general the I-mode exhibits the strongest edge T pedestal and normalized energy confinement (H 98 >1) at low q 95 (<3.5) and high heating power (P heat > 4 MW). I-mode significantly expands the operational space of ELM-free, stationary pedestals in C-Mod to T ped~1 keV and low collisionality ν* ped~0 .1, as compared to EDA H-mode with T ped < 0.6 keV, ν* ped >1. The I-mode global energy confinement has a relatively weak degradation with heating power; W th ~ I p P heat 0.7 leading to increasing H 98 with heating power.2

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

I-mode: an H-mode energy confinement regime with L-mode particle transport in Alcator C-Mod

Whyte

Hubbard

Hughes³

et al. 2010

Nucl. Fusion

Self Cite

275

370

View full text Add to dashboard Cite

show abstract

“…Details of the ICRF systems are reviewed in Ref. [21]. CMod has a Lower Hybrid (LH) system [21], but this is not used in these experiments.…”

Section: Experimental Results From Alcator C-modmentioning

confidence: 99%

Survey of the TS-ECE Discrepancy and recent investigations in ICRF heated plasmas at Alcator C-Mod

White

Hubbard

Hughes

et al. 2012

EPJ Web of Conferences

Self Cite

View full text Add to dashboard Cite

Abstract. This paper reports on a new investigation of the long-standing, unresolved discrepancy between Thomson Scattering (TS) and Electron Cyclotron Emission (ECE) measurements of electron temperature in high temperature tokamak plasmas. At the Alcator C-Mod tokamak, ion cyclotron range of frequency (ICRF) heating is used to produce high temperature conditions where the TS-ECE discrepancy, as observed in the past at JET and TFTR, should appear. Plasmas with T e (0) up to 8 keV are obtained using three different heating scenarios: Ion Cyclotron Resonance Heating (ICRH), ICRF mode conversion heating and a combination of the two heating methods. This is done in order to explore the hypothesis that ICRH-generated fast ions may be related to the discrepancy. In all high temperature cases at C-Mod, we find no evidence for the type of discrepancy reported at JET and TFTR. Here we present the C-Mod results along with a summary of past work on the TS-ECE discrepancy.

show abstract

“…The lack of a temperature change at the thermojunction between the surface thermocouple and its stainless steel mount is also confirmed by the QFLUX_1D thermal simulations that use the surface temperature to calculate heat flux. pick-up seen during operation of lower hybrid heating or lower-hybrid current drive [16] (both at 4.6 GHz), allowing surface thermocouple analysis to be performed in these discharges. Measurements of surface heat flux during a plasma disruption, i.e.…”

Section: Performancementioning

confidence: 99%

Surface thermocouples for measurement of pulsed heat flux in the divertor of the Alcator C-Mod tokamak

Brunner¹,

LaBombard²

2012

Review of Scientific Instruments

Self Cite

View full text Add to dashboard Cite

A novel set of thermocouple sensors have been developed to measure heat fluxes arriving at divertor surfaces in the Alcator C-Mod tokamak, a magnetic confinement fusion experiment. These sensors operate in direct contact with the divertor plasma, which deposits heat fluxes in excess of ~10 MW/m 2 over a ~1 second pulse. Thermoelectric EMF is produced across a non-standard bimetallic junction: a 50 µm thick 74% tungsten-26% rhenium ribbon embedded in a 6.35 mm diameter molybdenum cylinder. The unique coaxial geometry of the sensor combined with its single-point electrical ground contact minimizes interference from the plasma/magnetic environment. Incident heat fluxes are inferred from surface temperature evolution via a 1-D thermal heat transport model. For an incident heat flux of 10 MW/m 2 , surface temperatures rise ~1000 °C/s, corresponding to a heat flux flowing along the local magnetic field of ~200 MW/m 2 . Separate calorimeter sensors are used to independently confirm the derived heat fluxes by comparing total energies deposited during a plasma pulse. Langmuir probes in close proximity to the surface thermocouples are used to test plasma-sheath heat transmission theory and to identify potential sources of discrepancies among physical models.

show abstract

Wave-Particle Studies in the Ion Cyclotron and Lower Hybrid Ranges of Frequencies in Alcator C-Mod

Cited by 75 publications

References 61 publications

I-mode: an H-mode energy confinement regime with L-mode particle transport in Alcator C-Mod

I-mode: an H-mode energy confinement regime with L-mode particle transport in Alcator C-Mod

Survey of the TS-ECE Discrepancy and recent investigations in ICRF heated plasmas at Alcator C-Mod

Surface thermocouples for measurement of pulsed heat flux in the divertor of the Alcator C-Mod tokamak

Contact Info

Product

Resources

About