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

Journal Article · Thu Mar 15 00:00:00 EDT 2012 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3689770· OSTI ID:22072258

Brunner, D; LaBombard, B ^[1]

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1. MIT PSFC, Cambridge, Massachusetts 02139 (United States)

A novel set of thermocouple sensors has 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 {approx}10 MW/m{sup 2} over an {approx}1 s pulse. Thermoelectric EMF signals are produced across a non-standard bimetallic junction: a 50 {mu}m 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 1D thermal heat transport model. For an incident heat flux of 10 MW/m{sup 2}, surface temperatures rise {approx}1000 deg. C/s, corresponding to a heat flux flowing along the local magnetic field of {approx}200 MW/m{sup 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.

• OSTI ID: 22072258
• Journal Information: Review of Scientific Instruments, Vol. 83, Issue 3; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ALCATOR DEVICE
BIMETALS
CALORIMETERS
DIVERTORS
HEAT FLUX
HEAT TRANSFER
INTERFERENCE
LANGMUIR PROBE
MAGNETIC CONFINEMENT
MAGNETIC FIELDS
MOLYBDENUM
PLASMA
PLASMA SHEATH
PULSES
RHENIUM
SENSORS
SIGNALS
SURFACES
THERMOCOUPLES
TUNGSTEN