![]() Potential mechanisms at the origin of the different outgassing behavior for D and He in W plasma facing components are discussed in light of a systematic analysis of the He and D gas balance and a macroscopic rate equation modeling of the D outgassing from the divertor strike points. These striking differences should be related to different retention and outgassing from WEST plasma facing components, presently constituted of actively-cooled ITER-like W units and inertially cooled W-coated graphite. On the other hand, D outgassing can reach a maximum up to several tens of seconds after the termination of the plasma and this outgassing can last for about 10 min. ![]() On one hand, He outgassing is instantaneous and decays within 60 s until the He signal gets below detection level. It is found that the time evolutions for He and D outgassing in the post-discharge are markedly different. The first results obtained with TIMS during consecutive D and He plasma discharges in the full tungsten (W) tokamak WEST are reported. upon plasma breakdown and plasma termination, are discussed. Commercial He mass spectrometer leak detectors usually do not provide sufficient sensitivity to perform accurate measurements of the permeation rate of He. The calibration method of TIMS using a D plasma discharge is presented while the uncertainties related to TIMS during rapid pressure variations, i.e. For elements with no stable isotopes, the mass number of the isotope with the longest half-life is in parentheses. This method has been tested with sub-second temporal resolution in WEST during its first He plasma discharges in the so-called He changeover experimental campaign. We present the first demonstration of another potential application of TIMS in a tokamak environment, namely, the analysis of deuterium (D) and He outgassing following a plasma discharge i.e. The technique can resolve tritium concentrations in waters of the pre-nuclear era.Threshold ionization mass spectrometry (TIMS) is one of two methods envisioned in ITER to quantify the helium (He) fusion product in the exhaust pumping lines during plasma discharges. Even when atmospheric tritium concentrations have become rather uniform, tritium provides water ages if 3He data are taken concurrently. One of the things this means is that a mole of Helium has a mass of 4.003 grams. ![]() To date, we have measured more than 15,000 samples for tritium and 23,000 for helium isotopes and neon, mostly in the context of oceanographic and hydrologic work. These achievements are enabled, among other features, by automation of the measurement procedure and by elaborate calibration, assisted by continual development in detail. Positive-ion helium DART mass spectrum showing. ![]() Sample throughputs can reach some thousands per year. Some compounds with molecular weights in excess of 2000 can be detected if they are sufficiently volatile. Tritium precision is typically☓ % and the detection limit 10 mTU (≈ 1.2♱0 −3 Bq/kg of pure water). For water samples in a near-equilibrium with atmospheric air, the facility achieves precision for 3He/ 4He ratios of☐.4% or better, and☐.8 % or better for helium and neon concentrations. We describe the mass spectrometric facility for measuring helium isotopes, neon, and tritium that has been operative at this institute since 1989, and also the sampling and sample preparation steps that precede the mass spectrometric analysis. ![]()
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