%
% Copyright (C) 2015-2022 The ESPResSo project
%
% This file is part of ESPResSo.
%
% ESPResSo is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% ESPResSo is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program.  If not, see <http://www.gnu.org/licenses/>.
%

\documentclass[tikz]{standalone}
\usepackage{tikz-3dplot}
\tikzset{
  dot/.style = {draw,fill,circle,inner sep=1pt}
}
\begin{document}
\tdplotsetmaincoords{80}{15}
\tdplotsetthetaplanecoords{-90}
\begin{tikzpicture}
  \node at ( 0,2) {\textsf{(a)}};
  \node at (12,2) {\textsf{(b)}};
  \begin{scope}[tdplot_main_coords]
    \tdplotdrawarc[tdplot_rotated_coords]{(0,0,0)}{1}{0}{360}{}{}
    \tdplotdrawarc[tdplot_rotated_coords]{(0,0,10)}{1}{0}{360}{}{}
    \draw (0,0,1) -- (10,0,1);
    \draw (0,0,-1) -- (10,0,-1);

    \tdplotdrawarc[tdplot_rotated_coords,help lines]{(0,0,1)}{1}{0}{360}{}{}
    \tdplotdrawarc[tdplot_rotated_coords,help lines]{(0,0,9)}{1}{0}{360}{}{}
    \draw (1,-2,-2) -- (1,2,-2) -- (1,2,2) -- (1,-2,2) -- cycle;
    \draw (9,-2,-2) -- (9,2,-2) -- (9,2,2) -- (9,-2,2) -- cycle;

    \tdplotdrawarc[tdplot_rotated_coords]{(0,0,4)}{1.5}{0}{360}{}{}
    \tdplotdrawarc[tdplot_rotated_coords]{(0,0,6)}{ .8}{0}{360}{}{}
    \tdplotdrawarc[tdplot_rotated_coords]{(0,0,4)}{1.2}{0}{360}{}{}
    \tdplotdrawarc[tdplot_rotated_coords]{(0,0,6)}{ .5}{0}{360}{}{}
    \draw (4,0, 1.5) -- (6,0, .8);
    \draw (4,0,-1.5) -- (6,0,-.8);
    \draw (4,0, 1.2) -- (6,0, .5);
    \draw (4,0,-1.2) -- (6,0,-.5);
  \end{scope}
  \begin{scope}[shift={(12,0)}]
    \node[dot] (p) {};
    \draw (p) -- node[left] {$r_i$} +(0,-1);
    \draw (p) -- node[above left] {$r_o$} +(30:2) coordinate (c);
    \draw[<->] (c) +(30+90:.25) -- node[right] {$u$} +(30+90:-.25);
    \draw[help lines] (p) -- +({2*cos(30)},0);
    \draw[->] (p) +(1,0) arc(0:30:1);
    \node at (15:.7) {$\alpha$};
  \end{scope}
\end{tikzpicture}
\end{document}
