Experimental verification of the method for detection of water microleakages in plasma vacuum chambers by using the hydr
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Experimental Verification of the Method for Detection of Water Microleakages in Plasma Vacuum Chambers by Using the Hydroxyl Spectrum A. B. Antipenkova, O. N. Afoninb, V. N. Ochkinb, S. Yu. Savinovb, and S. N. Tskhaib a
b
ITER Organization, Route de VinonsurVerdon, St. PaullezDurance, 13115 France Lebedev Physical Institute, Russian Academy of Sciences, Leninskii pr. 53, Moscow, 119991 Russia Received July 5, 2011
Abstract—Experimental determination of the sensitivity of the method for detection of water microleakages in the cooling systems of the plasma vacuum chambers of complex electrophysical devices (such as tokamaks, fuel elements of nuclear reactors, and plasmachemical reactors) is considered. It was shown that the spectro scopic method for detection of water microleakages by using the hydroxyl radiation spectrum makes it possi ble to detect leakages at a level of 10–5 Pa m3 s–1. The spatial resolution of the method allows one to localize defects with an accuracy of several centimeters. DOI: 10.1134/S1063780X12020018
1. INTRODUCTION Micronsize leakages in the walls of vacuum and hermetic chambers can be detected using conven tional diagnostics [1]. However, these diagnostics fail to provide rapid detection of microleakages, especially in largevolume chambers of complex devices. As a rule, microleakages practically do not influence the performance of such devices, because the rate of gas leakage through them is usually comparable with the flux of adsorbed molecules from the chamber wall, so such leakages may not manifest themselves in quiet conditions. However, the problem of detection of microleakages is rather challenging for such devices as tokamaks, fuel elements of nuclear reactors, plasma chemical reactors, and spacecraft. The chamber walls of these devices undergo enormous stresses; as a result, the existing microleakages can widen and new ones may appear, thereby leading to emergency conditions. The problem of rapid detection of microleakages in plasma vacuum chambers was noticed in the ITER Final Design Report [2] as one of the important tasks to be resolved. In [2], microleakages through which water vapor can leak into the chamber from the cool ing system were discussed. The idea of spectroscopic method for detection of water leakages is as follows. When a plasma (or an electron) flow interacts with the chamber wall, water vapor is decomposed and radia tion of its components (H2O, H, O, OH, or a marker) is excited, the characteristic spectral region of which can be detected against the minimal noise back ground. If the plasma parameters are appropriate for efficient excitation, then a halo radiating within the wavelength range Δλ appears around the leakage. In this case, the problem is reduced to the choice of the
detected component and optimization of its excitation conditions and spectrum measurements. It is more convenient to do this during the conditioning of the inner surface of the chamber wall with an auxiliary dis charge, although it is also possible to continuously mo
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