Analysis of Hydrocarbons in the Exhaust Gas of a Fusion Test Device Using Infrared Absorption Spectroscopy

Abstract

To investigate the behavior of hydrogen isotopes in a large fusion test device, a new technique using infrared absorption spectroscopy is applied for the monitoring of hydrocarbons in exhaust gas. Fourier transform infrared (FT-IR) spectroscopy combined with a gas cell, which has an optical path length of 16 m, was installed at the plasma exhaust line. In this configuration, the detection limit of CH 4 , C 2 H 6 , C 2 H 4 , and CO is at the level of sub-ppm. The exhaust gas observations were conducted during hydrogen glow discharge and during the regeneration operation of cryosorption pumps during the hydrogen plasma phase. As a result, hydrocarbons and carbon monoxide were detected in the exhaust gas, and the exhaust behavior and the ratio of gas components were determined. It is also demonstrated that light and the heavy hydrocarbons can be discriminated by the FT-IR system. Our infrared absorption spectroscopy study provides positive prospects for its application to exhaust gas analyses.

Detection of Ammonia and Deuterated Hydrocarbons in Exhaust Gas by Infrared Absorption Spectroscopy during Wall Conditioning

“…In the unstable operation region, acetylene, which was not detected during the glow discharge operation in a previous study [18], was observed. Additionally, the ratio of hydrogen atoms in the produced hydrocarbons, C x Q y , was higher.…”

“…Hydrocarbons are produced by chemical sputtering of carbon tiles during the hydrogen isotope glow discharge operation. In a previous study [18], however, deuterated hydrocarbons (C x H y D z ) were not detected during D 2 glow discharge between LHD plasma experiments. Thus, the vacuum vessel is cleaned by the plasma experiments and wall conditioning operations, lowering impurity components such as water vapor.…”

“…In a previous study, extremely low concentrations of hydrocarbons, on the order of sub-ppm, were successfully detected using an FTIR spectroscopy system (Perkin Elmer, Frontier FTIR) with a long optical path gas cell (PIKE Technologies, PN: 163-1674). Details of the analytical system and the measurement conditions of the FTIR spectroscopy system combined with a long optical path gas cell are described in a previous article [18]. In this study, the measured wavenumber range was 650 to 3500 cm −1 , the scan number was set to 50, the wavenumber resolution was set to 1 cm −1 , and the optical path length in the gas cell was fixed to 16 m. The Atmospheric Vapor Compensation algorithm, which is an advanced digital filtering algorithm designed to compensate for H 2 O absorption [19], was used while obtaining measurements.…”

“…Figure 2 shows FTIR absorption spectrum during D 2 glow discharge and wall baking at 368 K. CO, CO 2 , and deuterated hydrocarbons are observed. CO and CO 2 are known to be produced and observed during the glow discharge operation [18,22]. Hydrocarbons are produced by chemical sputtering of carbon tiles during the hydrogen isotope glow discharge operation.…”