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\begin{document}
\title{Remote demonstration of the GOLEM tokamak\\
\thanks{The project was partially supported by the CTU RVO68407700 grant, by the FUSENET association and by the Grant Agency of the Czech Technical University in Prague, grant No. SGS17/138/OHK4/2T/14, Research of the Magnetic Field Confinement in Tokamak. Additional support has been granted from IAEA research contract F13019, entitled ‘Network of Small and Medium Size Magnetic Confinement Fusion Devices for Fusion Research’. The opinions expressed by authors do not necessarily represent the positions of the European Commission neither IAEA.}
}
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\begin{abstract}
The GOLEM tokamak serves as an educational device in the field of tokamak physics, technology, diagnostics and operation in the scope of the wider field of thermonuclear fusion. The typical scenario of a remote demonstration of the GOLEM tokamak is described. The new remote control and live status web interface in its mobile-ready form is presented.
\end{abstract}
\begin{IEEEkeywords}
Tokamak technology and control\sep online experimentation\sep remote participation\sep education
\end{IEEEkeywords}
\section{Introduction}
%\epigraph{\it First of all, we would like to express our gratitude for this remarkable opportunity. To perform a remote measurement on a tokamak, and to be part of such an international operation for the first time in our life, is way beyond our earlier expectations as physics students. We wish you luck for the future, and lots of plasma :)}{\textit{Andras Karman, Gergely Klujber, \\ Mate Ferenczy, Peter Nemetvarga }}
%\GWip{Tokamak/BasicDescription/Introduction}{\EXPATMadeira}
The GOLEM tokamak, a.k.a. the grandfather of all tokamaks \cite{ITERgrandfatherGOLEM}, currently serves as an educational device at the Faculty of Nuclear Sciences and Physical Engineering of the Czech Technical University in Prague (FNSPE, CTU) with the aim of training domestic as well as foreign students and young physicists in the field of tokamak physics, technology, diagnostics and operation in the scope of the wider field of thermonuclear fusion.
\def\GWigpw#1#2{\includegraphics[width=#1\textwidth]{figs/#2}}
The reinstalled tokamak \cite{EPSDublin2010} (major and minor radius of the vessel is $R_0=0.4$ m and $r_0 = 0.1$ m, respectively) with circular limiter geometry operates in a modest range of parameters: toroidal magnetic field $B_t < 0.5$ T, plasma current $I_p < 8$ kA, discharge duration
$\tau_p < 25$ ms, Hydrogen or Helium as a working gas.
%It is equipped with a basic set of diagnostics i) a coil around the transformer core for the loop voltage ($U_l$) measurement; ii) a Rogowski coil around the vessel for the plasma current measurement $I_p$; iii) a small coil for the toroidal magnetic field $B_t$ measurement; %and iv) a photodiode measuring the visible radiation intensity.
%Advanced diagnostics include a fast camera for imaging of a poloidal slice of the plasma, interferometer for electron density $n_e$ measurement, a set of 20 aligned AXUV detectors (bolometers) for measurements of the radiated power profile, scintillators for hard X-ray radiation measurement, various set of coils for monitoring magnetohydrodynamic activity in the plasma, and arrays of various electric probes.
%All measurements are stored in a database. A pulse summary with the main plasma parameters is displayed on the experiment web page. The data can be also retrieved as files for further analysis. For an overview of this experimental setup see \cite{Grover2016}.
\par
One of the ways in which its educational mission is fulfilled are remote demonstrations during various training courses, winter or summer plasma physics and technology events.
The aim of such a remote demonstration is to provide participants (typically students) with a reasonable understanding of the relationship between the achieved plasma quantities and the adjustable technological parameters of such a complex device. This is often accompanied by a competition among participants to achieve the longest discharge duration or the highest plasma current or the highest electron temperature.
\par
%This contribution describes the online experimentation procedure in detail: From the discharge request specification, through the live stream of the current status of the device, to the discharge results access.
\section{Typical remote demonstration scenario}
A typical remote demonstration lasting \aprx 2 hours for an audience consisting
mostly of non-experts or lay people is described here. With a repetition rate of
\aprx 1 discharge per 2 minutes, nearly all (active) participants typically have
a chance to configure their own discharge during the demonstration.
Such a remote demonstration event is lead by a qualified ``performer'', typically a researcher or a
teacher from the GOLEM tokamak staff or a trained PhD student. The remote
performer typically communicates with an operator on the tokamak side through
a video conference or text chat technology (whichever is available or most
convenient).
The demonstration usually starts by a short presentation by the
performer, during which the motivation of achieving thermonuclear fusion in a
tokamak is introduced, then the tokamak technology is briefly described
sub-system by sub-system. Each sub-system is illustrated by an engineering
schematic and labelled pictures of the system as seen at the GOLEM tokamak. A
sufficiently qualified performer may even demonstrate the activation of some of these sub-systems
during the presentation, e.g. initiate the vacuum pump-down.
Then the performer explains step-by-step the discharge procedure how the steps relate to the adjustable parameters in the remote control interface.
Finally, the performer displays a QR code page which participants can scan with their mobile phones and access the remote control interface themselves.
The performer then shows the participants how to configure a real discharge request and then submits it. He then guides the participants through the live real-time view of the experiment status during the execution of the configured discharge request. Afterwards the participants can submit their requests and watch as they are processed through the live status view.
The whole system is essentially offered free of charge. The only ``fee'' is that the remote participants send a postcard from the venue of the remote operation.
\section{Remote control interface}
\label{sec:RemoteControlInterface}
While the GOLEM tokamak has for long been known to have remote operation capabilities \cite{FusenEngDes11,Grover2016}, the recently developed new virtual remote control interface offers a better experience for such remote demonstrations. Specifically, the new virtual control room interface a) offers a wizard-like experience in order to better explain the necessary steps to students and prevent the omission of an important setup step, b) improves cross-browser and cross-platform compatibility in order to enable a operation by a wider audience (including mobile-phone or tablet users). The new live real-time overview of the experiment aimed to add up-to date information on the machine status to the existing IP camera views.
The new web application is built with modern (but tested and reliable), cross-browser-compatible, responsive technologies such as JQuery, Bootstrap. The responsive design
of the web application enables even mobile (smart-)phone users (the majority during remote demonstrations) to easily
participate, the typical view on an iPhone screen is shown in Figure~\ref{fig:remote_control}.
% Each of view is actually composed from 2 columns
% displayed side-by-side only on a wide, desktop-like
%display, but responsively stacked
%vertically on a narrow mobile-like display.
%The URL address of this web interface is \url{http://golem.fjfi.cvut.cz/remote/control_room}
%However,it is recommended to use the URL provided by the remote experiment personnel,
%because it will likely include the necessary access token.
The system is protected with an access token provided by the operators for the particular event. For such remote demonstration events the access token gives access for typically 30 minutes and is typically encoded in the link represented by the QR code displayed for participants. Therefore, when the participants visit the
control interface for the first time, a form is displayed asking only for the
``Identification'' which is a user-name by which the current user wishes his
discharges to be identified in the database.
\begin{figure}[tb]
\centering
\GWigpw{0.5}{{remote_responsive.pdf}}
\caption{Remote control and live status interface of the GOLEM tokamak as viewed on a mobile smartphone. The control room
interface at the electric field setup step is shown on the left. The live real-time view of the experiment during the preaparatory phase of the discharge is shown on the right.
}
\label{fig:remote_control}
\end{figure}
\par
The remote control room interface shown in the left part of Figure~\ref{fig:remote_control} consists
of 2 main panels. The first panel contains 6 tabs, each tab
corresponds to a step in the discharge setup procedure configuring a given
tokamak sub-system.
The second panel contains a rendering of the 3D
model which dynamically changes according to the currently selected tab.
\par
Each tab contains brief information about the setup step,
an engineering schematic of the
tokamak sub-systems with the one currently being configured highlighted, slider and checkbox widgets for configuring discharge parameters, a ``Next'' button which switches to the next tab (configuration step)
and a ``Set recommended value'' button.
All the settable parameters are completely safe, therefore, participants can freely choose their parameters without any fear of destroying any part of the device.
%\subsection{Live real-time view of the experiment}
%\GWip{Handling/Controll/StandardUser/RemoteControl/Tabs/vOG/ControllRoom_Live}{\ControlRoomLive}
%\label{sec:live}
The live real-time overview of the machine status in the right part of Figure~\ref{fig:remote_control} shows the experiment during the preparatory phase of the discharge. The gauges over the engineering scheme show the gradual charging of capacitors and filling of the chamber with the selected working gas. The wide-angle room camera shows the general surroundings of the device, while the chamber camera shows the pre-ionization filament activation inside the chamber. The queue of discharge requests with the most important basic parameters is also shown to give remote participants an idea of when their requests will be
executed.
The chamber camera with a sampling rate of 1/30 s usually captures the flash of
plasma (living only several tens of ms) at least on a portion of a frame. This
moment gives the remote participants visual confirmation of plasma in near-real-time and is
particularly popular during remote demonstrations.
\section{Summary}
\label{sec:summary}
The remote demonstration of the GOLEM tokamak enables remote participants to gain basic understanding of tokamak technology and its use for achieving controlled thermonuclear fusion. The new remote control interface enables participants to easily use their mobile devices to control the tokamak. Readers interested in a remote demonstration at their venue are very welcome to exploit the system
%\footnote{send an e-mail to \href{mailto:vojtech.svoboda@fjfi.cvut.cz}{vojtech.svoboda@fjfi.cvut.cz}}.
\footnote{send an e-mail to XYZ}.
%\GWip{Handling/Controll/StandardUser/RemoteControl/Tabs/vOG/ControllRoom_Introduction}{\EXPAT19}
% \subsection{Remote data access}
% While the database of GOLEM discharge results remains the same as was described in \cite{Grover2016} remains the same, what has evolved since then are high-level libraries which make reading, manipulating and plotting data accessible over HTTP much easier then before. Therefore, the GOLEM team has greatly benefited from having a clear HTTP API for accessing all the data. For example, the Pandas Python library \cite{mckinney-proc-scipy-2010} for high-level table data structures makes plotting the basic discharge evolution overview much simpler: Whereas previously one had to use several libraries and their low-level functions to separately download, read, parse, slice and plot the data, this library hides all this in a well-designed and convenient API which enables students to focus on data analysis and less on programming.
% The following Python code example using only a few high-level functions, downloads, parses and displays the discharge evolution as measured by basic diagnostics as shown in Figure~\ref{fig:python-output}.
% \inputminted[fontsize=\footnotesize]{python}{plot_shot.py}
% \begin{figure}
% \centering
% \includegraphics[width=\linewidth]{plot_shot_out.png}
% \caption{Figure created by the simple example Python code which displays an overview of the discharge evolution as measured by basic diagnostics.}
% \label{fig:python-output}
% \end{figure}
% \subsection{Level 1 ``basic''}
% %\TheItem{Education/ExperimentMenu/BreakdownStudies}
% \EduTopic{Breakdown studies}{Investigate probability of the plasma breakdown (creation of plasma), mainly the role of the working gas (Hydrogen or Helium) and its pressure $p_{WG}$, breakdown electric field controlled by the $U_{E_t}$ and its orientation. A dependency similar to the Paschen Curve can be obtained.}{wiki:paschenlaw}
% %\TheItem{Education/ExperimentMenu/ElectronEnergyConfinementTime}
% \EduTopic{Energy confinement time $\tau_E$}{Under the assumption of a simplified power balance, the heating power $P_H$ is partially absorbed in the plasma and leads to an increase of the plasma energy $W_p$ and the rest is lost as the loss power $P_L$. The energy confinement time is defined as the characteristic time scale of the exponential decay of the plasma energy $W_p$ due to the loss power $P_L$. Choosing the quasistationary phase of the plasma discharge gives: $\tau_E(t)=\frac{W_{p}(t)}{P_H(t)}$}{}
% \EduTopic{$\mathbf{q=2}$ disruptions}{When the plasma current $I_p$ grows so strong that the edge safety factor $q$, see \cite{wiki:safetyfactor}, reaches the
% value of 2, a plasma instability resonant to the q = 2 rational surface destabilizes, and a discharge
% terminating disruption occurs. The aim is to reach this limit of tokamak operation.}{}
% \subsection{Level 1.5 ``data mining``}
% All of the results obtained in Level 1 can be statistically analyzed in greater detail with the help of the enormous database of past GOLEM discharges. These topics may devote more time to analysis than experimentation alone.
% \EduTopic{Neo-Alcator confinement scaling law}{To compare the plasma behaviour (in particular the confinement time) in the GOLEM tokamak with the so-called Neo-Alcator confinement scaling law, see \cite{Goldston_1984}.}{}
% \EduTopic{Machine learning}{The large database of discharges with their associated breakdown success or disruption termination can be used to train machine learning algorithms to predict the breakdown \cite{MOdstrcil} or disruption probability.}{}
% \subsection{Level 2 ``advanced''}
% \EduTopic{Isotopic studies}{Comparison of tokamak discharges in H$_2$ and He$_2$ working gas, for en exemplary report see \cite{Svoboda2016}. Differences between discharges (for example turbulence properties observed by probes) in H$_2$ and He$_2$ as the working gas can be analyzed and explained. Which plasma parameters are influenced by higher mass of the main species particles and which are influenced by much higher
% ionization energy of He can be also investigated.}{}
%\references
\bibliographystyle{unsrt}\bibliography{golem,others}
\end{document}
