How to draw the depicted contour in tikz?

Question

How may I draw the following image as a tikzpicture?

Answer 1

Here is at least something for you to play with. I haven't added everything from the image, you'll have to figure those out.

\documentclass[tikz,margin=4mm]{standalone}
\usetikzlibrary{calc}
\begin{document}
\begin{tikzpicture}
\def\xEpsilon{1}
  \def\cRadius{5}
  \coordinate (R) at (\cRadius,0);
  \coordinate (mR) at (-\cRadius,0);
  \coordinate (O) at (0,0);
  \coordinate (x) at ($(O)!0.6!(R)$);
  \coordinate (xme) at ($(x)+(-\xEpsilon,0)$);
  \coordinate (xpe) at ($(x)+(\xEpsilon,0)$);
\begin{scope}[red,very thick]
    \draw (R) arc [start angle=0,end angle=180,radius=5]
    -- (O)
    -- (xme) arc [start angle=180,end angle=0,radius=\xEpsilon] node[pos=0.5,above,black] {$\gamma_{\varepsilon}$}
    -- cycle
    ;
  \end{scope}
\draw ($(x)+(0,0.1)$)  -- ++(0,-0.2) node[below] {\strut$x$};
  \draw ($(R)+(0,0.1)$)  -- ++(0,-0.2) node[below] {\strut$R$};
  \draw ($(mR)+(0,0.1)$) -- ++(0,-0.2) node[below] {\strut$-R$};
  \draw ($(mR)+(-0.2,0)$) -- ($(R)+(0.2,0)$);
  \draw ($(O)+(0,-0.2)$) -- ++ (0,\cRadius + 0.4);
\end{tikzpicture}
\end{document}