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Accelerator Subsystems
Published in Volker Ziemann, ®, 2019
The composition of the gas in a vacuum system—or the partial pressures—is measured with a residual gas analyzer. One operating principle is based on accelerating ionized gas molecules or atoms and passing them through a long electro-static quadrupole that is excited by a sinusoidal voltage on top of a constant voltage. The motion of the gas ions with a specific mass is only stable for certain excitation frequencies and measuring the current exiting from the quadrupole as a function of the frequency contains information about the gas composition.
In-Situ Metrology
Published in Robert Doering, Yoshio Nishi, Handbook of Semiconductor Manufacturing Technology, 2017
In addition to the optical methods previously described, gases can also be analyzed by mass spectroscopy of the molecular species and their fragmented parts. The in-situ mass spectrometric sensor for gas analysis is commonly known as a residual gas analyzer.
Monte Carlo Analysis of the Performance of the ITER Diagnostic Residual Gas Analyzer
Published in Fusion Science and Technology, 2021
The diagnostic residual gas analyzer (DRGA) is a key diagnostic system, particularly for the burning plasma phase of ITER, as it provides the critical measurement of the evolution of fuel cycle components and helium ash at timescales relevant to plasma and plasma-wall–interaction dynamics.
Monitoring and Recovery of Tritium in a Fusion Test Facility
Published in Fusion Science and Technology, 2020
Masahiro Tanaka, Naoyuki Suzuki, Hiromi Kato, Chie Iwata, Naofumi Akata, Hiroshi Hayashi, Hitoshi Miyake
Tritium is produced in the fusion test device and then exhausted via a vacuum pumping system. The vacuum pumping gas is fed with dry N2 gas at the rate of about 4 Nm3/h to prevent hydrogen explosion. To determine the tritium activity in the exhaust gas and the tritium recovery rate of the EDS, an active tritium sampler system using a water bubbler9 was developed and installed at the inlet and the outlet of the EDS. The water bubbler system at the inlet can distinguish the chemical forms of tritium. The sampling period is 1 week, and then the collected tritium is measured by an LSC for 50 min (10 min × five repeats). The detection limit is less than 10−7 Bq/cm3. The ionization chamber (Y221G0300, Ohkura Electric Co., Ltd.) was also installed at the inlet of the EDS for real-time tritium monitoring. In addition, to determine and clarify the gas species in the exhaust gas, several gas analytical instruments were installed at the inlet of the EDS. As for the measurement of hydrocarbons and inorganic gas, such as hydrogen isotopes, helium, neon, xenon, oxygen, nitrogen, and so on, a micro-gas chromatography (GC) system (490 Micro GC QUAD, Agilent Technology Ltd.) was prepared in accordance with Ref. 10. The GC had three separation columns. The first column was an 8-m molecular sieve 5A column for inorganic gas and noble gases of He and Ne. The second column was a 10-m PoraPLOT Q column for CO2,; water vapor; noble gases of Kr and Xe; ethylene; acetylene; and ethane. The third column was an 8-m Sil 5CB column for higher hydrocarbon analysis. The detector was a thermal conductivity detector (TCD) and the detection limit was about 10 ppm. To observe the hydrogen isotope gases (H2, D2) in helium gas, a quadrupole residual gas analyzer (qRGA, Hiden Analytical Ltd.) operating in threshold ionization mass spectrometry11 (TIMS) mode was installed at the inlet of the EDS. The gas sampling was applied with a differential pumping system using gas-regulating valves (RVC300 and RME005, Pfeiffer-vacuum). The detection limit of the deuterium gas in the helium gas was about 0.1% in the system. In addition, the Fourier transform infrared spectroscopy (FTIR) (Frontier FTIR, Perkin Elmer) with a 16-m-optical-path-length gas cell (volume: 2 L, PIKE Technologies) was proposed for the observation of hydrocarbons. Infrared absorption spectrometry by the long-optical-path-length gas cell can detect extremely low concentrations of hydrocarbons. The gas sampling system for the FTIR gas analysis is shown in Fig. 1. The sampling procedures are based on the following: (1) gas evacuation operation in the gas cell by a scroll pump for 6 min, (2) sample gas-filling operation in the gas cell until atmospheric pressure for 8 min, and (3) measurement by FTIR (detector: DTGS, number of scans: 80, resolution: 1 cm−1). The valves for gas sampling were automatically opened and closed by a program logic controller. The total measurement interval was 36 min. The background absorption spectrum was measured before the plasma experiment in 1 day. The specifications of the exhaust gas monitoring instruments are summarized in Table I.