Tritium concentration measurements in the JET divertor by optical spectroscopy of a Penning discharge

Technical Report · Mon Jun 01 04:00:00 EDT 1998

DOI:https://doi.org/10.2172/658453· OSTI ID:658453

Hillis, D L ^[1]; Morgan, P D; Ehrenberg, J K; Groth, M; Stamp, M F; Hellermann, M von ^[2]; Kumar, V ^[3]

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1. Oak Ridge National Lab., TN (United States)
2. JET Joint Undertaking, Abingdon (United Kingdom)
3. Inst. for Plasma Research, Bhat (India)

Obtaining precision measurements of the relative concentrations of hydrogen, deuterium, tritium, and helium in the divertor of a tokamak are an important task for nuclear fusion research. Control of the deuterium-tritium isotopic ratio while limiting the helium ash content in a fusion plasma are key factors for optimizing the fuel burn in a fusion reactor, like the International Tokamak Experimental Reactor (ITER). A diagnostic technique has been developed to measure the deuterium-tritium isotopic ratio in the divertor of the Joint European Torus (JET) with a species-selective Penning vacuum gauge. The Penning discharge provides a source of electrons to excite the neutral hydrogen isotopes in the pumping duct. Subsequently, the visible light from the hydrogen isotopes is collected in an optical fiber bundle, transferred away from the tokamak into a low radiation background area, and analyzed in a high resolution Czerny-Turner spectrometer, which is equipped with a fast charge coupled device (CCD) camera for optical detection. The intensity of the observed line emission (D{sub {alpha}} -- 6561.03 {angstrom}; and T{sub {alpha}} -- 6560.44 {angstrom}) is directly proportional to the partial pressure of each gas found in the divertor. The line intensity of each isotope is calibrated as a function of pressure. The ratio of the line intensities thus provides a direct measurement of the deuterium-tritium isotopic ratio. The lower limit for the determination of the deuterium-tritium isotopic ratio is about 0.5%. The applicable pressure range for this system is from 10{sup {minus}5} mbar to a few times 10{sup {minus}3} mbar.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: USDOE Office of Energy Research, Washington, DC (United States)
• DOE Contract Number: AC05-96OR22464
• OSTI ID: 658453
• Report Number(s): ORNL/CP--98498; CONF-980605--; ON: DE98003585; BR: AT5010701
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DEUTERIUM
EXPERIMENTAL DATA
HELIUM ASH
IONIC COMPOSITION
ISOTOPE RATIO
JET TOKAMAK
MEASURING METHODS
PENNING DISCHARGES
PLASMA DIAGNOSTICS
TRITIUM