commit 99741d0f2217bc8b8b9e98139fe4f2c79863a6cd Author: Georg Schlisio Date: Fri May 12 17:43:10 2023 +0200 current status of manuscript diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..66827c8 --- /dev/null +++ b/.gitignore @@ -0,0 +1,10 @@ +~* +*~ +*.aux +*.bbl +*.out +*.log +*.swp +*.blg +*.gz +*eps-converted-to.pdf diff --git a/Manuscript_outline.docx b/Manuscript_outline.docx new file mode 100644 index 0000000..cdb7693 Binary files /dev/null and b/Manuscript_outline.docx differ diff --git a/img/gauge_range_plot_draft.png b/img/gauge_range_plot_draft.png new file mode 100644 index 0000000..397b865 Binary files /dev/null and b/img/gauge_range_plot_draft.png differ diff --git a/manuscript.pdf b/manuscript.pdf new file mode 100644 index 0000000..8518337 Binary files /dev/null and b/manuscript.pdf differ diff --git a/manuscript.tex b/manuscript.tex new file mode 100644 index 0000000..2bd14cf --- /dev/null +++ b/manuscript.tex @@ -0,0 +1,375 @@ +\documentclass[% +superscriptaddress, +% aip, +iop, +% jmp, +% bmf, +% sd, +% rsi, +amsmath,amssymb, +preprint,% +% reprint,% +%author-year,% +author-numerical,% +% Conference Proceedings +]{revtex4-2} + +\usepackage{graphicx}% Include figure files +\usepackage{dcolumn}% Align table columns on decimal point +\usepackage{bm}% bold math +%\usepackage{filecontents} + +\usepackage[utf8]{inputenc} +\usepackage[T1]{fontenc} +\usepackage{mathptmx} +\usepackage{gensymb} +\usepackage{amsmath} +\usepackage[colorlinks=true,allcolors=black]{hyperref} +\usepackage{multirow} +\usepackage{booktabs} +\usepackage[exponent-product=\cdot]{siunitx} + + +\begin{document} + +\preprint{PREPRINT: DRAFT} + +\title[Calibration of the neutral gas systems of Wendelstein 7-X]{Calibration of the neutral gas systems of Wendelstein 7-X} + +\author{G. Schlisio} +\email{georg.schlisio@ipp.mpg.de} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{H. Viebke} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{T. Bräuer} +\affiliation{ +Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{D. Naujoks} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{O. Volzke} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{V. Rohde} +\affiliation{ +Max-Planck-Institut für Plasmaphysik,Boltzmannstra{\ss}e 1, Garching, Germany +} +\author{B. Jagielski} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{T. Kreyemer} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{P. McNeely} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{} +\affiliation{ + Max-Planck-Institut für Plasmaphysik, Wendelsteinstra{\ss}e 1, 17491 Greifswald, Germany +} +\author{the W7-X team\footnote{See author list of T. Klinger et al., Nuclear Fusion 59 (2019) 112004}} + +\date{\today}% It is always \today, today + +\begin{abstract} +Fusion plasmas heavily rely on the surrounding neutral reservoir for fueling and exhaust, hence precise knowledge of it is basis for many detailed diagnostic and physics investigations. +The observed pressures range from UHV (O(1e-6 Pa)) surrounding the main plasma to medium vacuum (O(1 Pa)) in the plasma-compressed exhaust stream, so a wide range of precise measurement is required. + +We present the calibration effort of all neutral-reservoir related systems, such as gauges, valves, and pumps, with respect to their relevant quantities: +The pumping system, consisting of turbomolecular pumps and cryo vacuum pumps, was characterized for pumping speed. +The gas injection systems were characterized for gas injection rates. +The pressure measurement systems were calibrated to a common standard. +The plasma vessel volume was determined. +The NBI box volume and internal getter pump pumping speed were determined. + + +\end{abstract} + +\maketitle + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +\section{\label{sec:intro}Introduction} +The optimized modular stellarator Wendelstein 7-X (W7X) recently went into operation with a water-cooled divertor [reference]. +With the change from the previously utilized inertially cooled divertor [reference] the components in the plasma vessel (PV) changed dramatically, amongst other things a cryo vacuum pump (CVP) was installed in the subdivertor space [reference?]. + +This changed the effective volume available for gas to expand into from the previously estimated value + +The following sections are organized as follows: +First, we + +\section{Vacuum system of W7X} +The Plasma Vessel (PV) of W7X is equipped with 30 turbo-molecular pumps (TMPs), individually separatable from the PV by a gate valve. +These 30 TMPs are located in receded positions to safeguard from magnetic field, and a evenly distributed around the machine. +For details refer to \cite{Grote2003}. + +Additionally, starting from OP2.1, the low iota sub-divertor space is equipped with a cryo vacuum pump (CVP). +Details on this device can be found in [reference]. +The CVPs cannot be decoupled from the PV and can only controlled by their temperature determined by the circulated fluid temperature. + +The neutral beam injection system (NBI) consists of two identical boxes (NI20, NI21), equipped with a large Titanium getter pump and a smaller TMP. +Each box is separated from the PV with a large gate valve. + + +\section{Pressure measurement} + +The torus pressure is observed by various systems serving different purposes. + +The main operational pressure monitoring consists of combinations of commercial Penning (cold cathode) and Pirani (conductance) gauges observing the pressure over the full range at low time resolution (1 Hz). +This system is operational throughout the entire campaign and collects total pressures pre-calibrated for N2. +The measurement positions are close to the TMPs in a low-magnetic-field area. + +It is supplemented with two sets of capacitance manometers with overlapping range, providing gas-type-independent measurement of pressure in the high and medium pressure range. These are also sampled at 1 Hz time-resolution and are mounted in similar locations as the main operational pressure monitoring. + +For further precise measurement at pressures from 1e-4 Pa to 10 Pa an additional capacitance manometer with a full range of 0.1 Torr has been installed and outfitted with an automated zeroing system. +This serves as total pressure reference for calibration of all other systems. +For observation of fast pressure changes in different positions inside the vessel, two systems exist: +The crystal cathode pressure gauges (CCPG) are hot cathode gauges adapted for use in high magnetic field \cite{Haas1998,Wenzel2019} and measure in up to 18 positions inside the PV. +They are sampled with minimum 1 kHz and provide gas-type-dependent ion currents, which have to be calibrated to be interpreted as total pressure. + +There also exist WISP gauges (Wisconsin In-Situ-Penning) \cite{Kremeyer2020}, which are spectroscopically enhanced cold cathode gauges capable of measuring gas-type dependent total pressure as well as, with help of the observed line intensities, partial pressures – typically for He and H2. +An overview of all described systems can be found in figure \ref{fig:gaugeranges} with additional details in table \ref{tab:gauges}. + +\begin{figure} + \includegraphics[width=0.6\columnwidth]{img/gauge_range_plot_draft.png} +\caption{\label{fig:gaugeranges} + Overview of the gauge systems available on W7-X. + For more details see table \ref{tab:gauges}. + (color online) +} +\end{figure} + +\begin{table} + \begin{tabular}{ccccccc} + \textbf{System} & \textbf{sensor type} & \textbf{\shortstack{range\\(mbar)}} & \textbf{\shortstack{sampling rate\\(Hz)}} & \textbf{\shortstack{toroidal\\coverage}} & \textbf{\shortstack{distance\\from PV}} & \textbf{reference} \\ + \hline + op. Pirani & Pfeiffer RPT100 & \num{1e-3}…\num{1200} & 1 & full & \SI{4}{\meter} & - \\ + op. Penning & Pfeiffer IKR070 & \num{1e-11}…\num{5e-3} & 1 & full & \SI{4}{\meter} & - \\ + op. CM & MKS Baratron & \num{1e-5}…\num{100} & 1 & 2 pos. & \SI{5}{\meter} & - \\ + fine CM & MKS Baratron AA06 0.1 & \num{1e-6}…\num{1e-1} & 3 & 1 pos. & \SI{5}{\meter} & - \\ + CCPG & hot cathode ionization gauge & \num{1e-7}…\num{1e-2} & 1000/2000 & 18 pos. & in-vessel & \cite{Wenzel2019} \\ + WISP & in-situ Penning & \num{1e-4}…\num{1e-2} & 1000 & 3 pos. & in-vessel & \cite{Kremeyer2020} \\ % TODO verify values + \end{tabular} + \caption{\label{tab:gauges} + Details of the available pressure gauge systems at W7-X. + } +\end{table} + +\section{Gas inlet systems} +There are a number of plasma fueling systems: +The main gas valves are toroidally symmetric on the inboard midplane of the torus. +The divertor gas inlet system [reference] is located in each of the 10 divertor modules in the low iota section of the divertor. +The steady-state pellet injector (SSPI) [reference] +Additionally, there are a few diagnostics puffing small amounts of gases for technical or diagnostic purposes: +The gas-puff imaging (GPI) diagnostics injects small amounts of super-sonic H2 and He into the PV [reference]. +The ion-cyclotron-resonance-heating (ICRH) antenna is equipped with a gas inlet system to facilitate favourable coupling conditions in front of the antenna [reference]. +The endoscopes [reference] use H2 venting of their optical components and inject upto XX mbarl/s into the vessel. +The neutral beam injection system (NBI) [reference] also acts a particle source, by both the beam and parasitic gas injection from other sources, e.g. dragged-on neutralizer gas and beam duct outgassing. + +\section{Calibrated pressure standard} +An externally calibrated pressure standard (MKS Baratron AA06 0.1Torr) was used as a reference to calibrate the operational gauges. +To counter inevitable sensor drift an automatic zeroing was applied daily, if the observed pressure in the Penning system was below \SI{1e-7}{\milli\bar}. + + +\section{Vessel volume determination} +The PV volume was determined with two independent methods, first a gas expansion from a well-known volume (“expansion method”) and second a well-defined gas inlet (“injection method”). Both methods were conducted with the TMP gate valves closed and the CVP warmed up, to ensure no pumping on the plasma vessel. +Uncertainty propagation was performed for each single measurement, all results are combined in a weighted average for a final value. +With the individual measurement results $\nu_i$ and their corresponding uncertainties $\delta_i$ the final value $V$ with uncertainty $\Delta$ is given by +\begin{align} + \Delta^2 &= \left( \sum_i \frac{1}{\delta_i}\right)^{-1} \\ + V &= \Delta^2 \sum_i \frac{\nu_i}{\delta_i} \, . +\end{align} +The result of each measurement and the weighted average are given in table \ref{table:pvvolume} + +\subsection{Expansion method} +From the ideal gas law we get the volume $V$ with the pressure difference $p$ and the injected gas amount $n k_b T$: +\begin{align} + V = \frac{n k_b T}{p} . +\end{align} +A well characterized test volume with \SI{0.392116}{\liter} was filled with Argon gas up to a pressure of \SI{00}{\milli\bar} and left for temperature equilibration. %TODO value +Subsequently the test volume, attached to the DRGA diagnostic, was expanded into the diagnostic and, through the open gate valve, into the PV, where the resulting pressure was observed with a capacitance manometer. + +% volume temperature was checked with a IR camera\footnote{Bosch Professional GTC400 C} + +For the expansion method, a well characterized test volume of was filled with Nitrogen gas up to a pressure of \SI{1000}{\pascal} and subsequently expanded into the vessel. % TODO correct value + +% Due to the availability of vacuum access, the expansion process was performed in two steps. +% A first expansion from the test volume into the DRGA, which is not as well equipped for total pressure measurement and thus has limited precision in the resulting DRGA volume. +% The second expansion from the DRGA to the PV. +% Due to the relatively small DRGA volume compared to the PV the less precise volume determination of the former still results in a small increase of uncertainty of the PV volume. +% The statistical method employed assumes the dominance of statistical errors, which + +% The result + +\subsection{Injection method} + +For the injection method, a mass flow controller (MFC, MKS GE50A) with a fullscale of \SI{5000}{sccm} was used at an injection rate of 9 mbar l / s for 120s, resulting in a pressure increase of about 1 Pa. The PV volume is then calculated by +\begin{align} + \nu = Q \cdot \frac{T}{p} +\end{align} +with the injection rate Q, injection time T and pressure difference p. +The measured pressure was corrected for the leak rate, which was assumed to be linear and measured to be \SI{2.8}{\milli\bar\per\second}. %TODO value%. + +\begin{table}\label{table:pvvolume} + \begin{tabular}{ccccc} + \textbf{method} & \textbf{W7-X program} & \textbf{Gas type} & \textbf{volume (l)} & \textbf{uncertainty (l)} \\ + \hline + expansion \\ + expansion \\ + expansion total & & & xxx & xxx \\ + \hline + injection & DCH\_20230414-event2 & N2 & 109 672 & 2036 \\ + injection & DCH\_20230414-event3 & N2 & 107 780 & 167 \\ + injection & DCH\_20230414-event4 & N2 & 107 786 & 251 \\ + injection & DCH\_20230419-event1 & He & 110 697 & 319 \\ + injection & DCH\_20230419-event2 & H2 & 107 307 & 132 \\ + injection total & & & 107 795 & 92 \\ + \hline + Grand total & & & & + + \end{tabular} +\caption{} +\end{table} + + +\section{Neutral gas manometers and WISP gauges} +Pressure steps to compare against known reference gauges, conducted with and without magnetic field for He, H2 and – for the WISP gauges – in gas mixtures with 5\%, 10\%, 20\%, and 50\% He in H2. +The obtained data was averaged over the plateau time of 10 s and individually fitted for each gauge with the orthogonal distance regression algorithm [reference https://doi.org/10.6028/nist.ir.89-4197] to obtain a model for conversion from raw ion current to absolute pressure. + +\section{NBI box volume and pumping speed} +The W7X NBI consists of two practically identical systems, NI20 and NI21, [reference] which feature a large UHV volume with included Titanium getter pump. +The box volume was determined in an expansion experiment, where the PV was filled with He up to a pressure of 9.7621e-03 mbar and subsequently expanded into the NI20 system by opening the gate valve. +After equilibration, a pressure of 7.7213e-03 mbar was measured, yielding an NBI box volume $V_{NBI} = 0.2643 * V_{PV} = \SI{28.4910}{\cubic \meter}$. +The getter pump pumping speed was determined with a similar experiment, but with Hydrogen instead of Helium. +The pressure drop after opening the gate valve was fitted with +\begin{align} +p(t) = p_0 e^{-\frac{S}{V} \cdot t} + p_{base} +\end{align} +Where P0 is the initial pressure, S the pumping speed, V the total volume of the system, and $p_{base}$ the observed base pressure after equilibration. + +\section{TMP pumping speed} +The TMP pumping speed was determined by a number of gas inj experiments… + +\section{CVP pumping speed} +The CVP pumping speed was determined by a number of experiments for a set of gases: H2, He, N2, Ar, both with and without TMP. + +\section{QRT02 endoscope flushing} + +The QRT02 endoscopes employ mirrors inside the PV, which are expected to receive some degree of material deposition. +To minimize the deposition and keep reflectivity high, the endoscope in AEA31 was equipped with a hydrogen flushing system which constantly feeds a small stream of hydrogen over the mirrors into the PV. +As of OP2.1, this leak rate was measured to be \SI{3.63}{\milli\bar\liter\per\second} (QRT\_20230424-event3) by running the flushing system in an unpumped PV. +Due to the small injection rate, the measured pressure increase had to be corrected for the leak rate + + + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%\section{\label{sec:concepts}Concepts, methodology, and assumptions} + +%\begin{figure} +% \includegraphics[width=0.5\columnwidth]{img/gasbalance_sketch.eps} +% \caption{\label{fig:concept} +% Schematic view of the reservoir model. +% The outer contour symbolizes the plasma vessel, subdivision of the particle content according to equation (\ref{eq:gbalance}). +% Arrows indicate migration between reservoirs and are annotated with the main mechanisms. +% The role of NBI is left out for simplicity. +% (color online) +% } +%\end{figure} + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +\section{\label{sec:summary}Conclusions} + +\begin{table} + % sorry for the hacky table… + \begin{tabular}{ccccccc} + scenario & \shortstack{experiment\\ID} & \shortstack{plasma\\duration} & \shortstack{total\\injected} & \shortstack{total\\removed} & \shortstack{net\\wall} & removed/injected \\ + \toprule + \shortstack{Simple plasma \\ (section \ref{sec:basicplasma})} & 20180829.6 & \SI{4}{\second} & \num{ 3.23 } & \num{ 25.9 } & \num{ -22.7 } & 8.02 \\ + \midrule + \multirow{2}*{ + \shortstack{short term retention \\ (section \ref{sec:retention})} + } & 20180816.9 & \SI{15}{\second} & \num{ 37.6 } & \num{ 30.0 } & \num{ 7.60 } & 0.80 \\ + & 20180816.10 & \SI{15}{\second} & \num{ 10.5 } & \num{ 47.3 } & \num{ -36.8 } & 4.50 \\ + \midrule + \multirow{4}*{ + \shortstack{long term retention \\ (section \ref{sec:100s})} + } & 20181017.15 & \SI{40}{\second} & \num{ 103 } & \num{ 95.9 } & \num{ 7.10 } & 0.93 \\ + & 20181017.16 & \SI{53}{\second} & \num{ 89.2 } & \num{ 287 } & \num{ -198 } & 3.22 \\ + & 20181017.17 & \SI{78}{\second} & \num{ 99.9 } & \num{ 344 } & \num{ -244 } & 3.44 \\ + & 20181017.19 & \SI{100}{\second} & \num{ 129 } & \num{ 402 } & \num{ -273 } & 3.12 \\ + \bottomrule + \end{tabular} + \caption{\label{tab:inout} + Overview of total injected and removed particles as well as net wall result, for all discussed experiments. + All particle numbers are given as \num{e20} $H_2$ molecules. + Last column shows ratio of injected and removed particle count for easier comparison. + } +\end{table} + + +\begin{acknowledgments} + This work has been carried out within the framework of the EUROfusion + Consortium and has received funding from the Euratom research and + training programme 2014-2018 and 2019-2020 under grant agreement No + 633053. The views and opinions expressed herein do not necessarily + reflect those of the European Commission. +\end{acknowledgments} + +\appendix + +\nocite{*} +\bibliography{aipsamp}% Produces the bibliography via BibTeX. + +\begin{thebibliography}{10} + +%\bibitem{loarer2005} % no DOI found, see https://inis.iaea.org/search/search.aspx?orig_q=RN:36078348 +%T. Loarer, et al., 20th IAEA fusion energy conference proceedings (2005): 36078348. + +\bibitem{Grote2003} % DOI https://doi.org/10.1016/S0022-3115(02)01503-9 +H. Grote, et al., J.Nuc.Mat. Volumes 313–316, March 2003, Pages 1298-1303 + +\bibitem{Haas1998} +G. Haas, H.-S. Bosch, Vacuum 51.1 (1998): 39-46. % DOI https://doi.org/10.1016/S0042-207X(98)00131-6 + +\bibitem{Wenzel2019} +U. Wenzel, et al., RSI (2019) % DOI https://doi.org/10.1063/1.5121203 + +\bibitem{Kremeyer2020} +T. Kremeyer, et al., RSI (2020) % https://doi.org/10.1063/1.5125863 + +\end{thebibliography} + +\end{document} \ No newline at end of file diff --git a/manuscriptNotes.bib b/manuscriptNotes.bib new file mode 100644 index 0000000..8f3dc15 --- /dev/null +++ b/manuscriptNotes.bib @@ -0,0 +1,2 @@ +@CONTROL{REVTEX42Control} +@CONTROL{apsrev42Control,author="08",editor="1",pages="0",title="0",year="1"}