\documentclass[a4]{standalone}
\standaloneconfig{border=20pt}
\usepackage{tikz}
\usepackage{graphicx}
\usepackage[a4paper,top=3cm, bottom=2.5cm, left=1cm, right=2cm ]{geometry}
\begin{document}
\begin{tikzpicture}
\draw  [dashed] ( 0.0 , 2.8 )   --  ( 0.0 , 0 )  ;

\node [rotate=-90] at (0.0,0) {{\verb#   0#}};
\draw  [dashed] ( 0.0 , 2.8 )   --  ( 0 , 2.8 )  ;

\node [left] at (0,2.8) {{\verb#TPC_inner_radius#}};
\draw  [dashed] ( 0.0 , 15.3872340426 )   --  ( 0 , 15.3872340426 )  ;

\node [left] at (0,15.3872340426) {{\verb#TPC_outer_radius#}};
\draw  [dashed] ( 20.0 , 15.3872340426 )   --  ( 20.0 , 0 )  ;

\node [rotate=-90] at (20.0,0) {{\verb#                 TPC_half_length#}};
\draw  [ultra thick] ( 0.0 , 2.8 )   --  ( 0.0 , 15.3872340426 )   --  ( 20.0 , 15.3872340426 )   --  ( 20.0 , 2.8 )   --  ( 0.0 , 2.8 )  ;

\draw  [<->,thick] ( 0 , 19.2340425532 )   --  ( 0 , 0 )   --  ( 25.0 , 0 )  ;

\end{tikzpicture}
\end{document}
