\begin{tikzpicture}[]
  \draw (0,0) circle (2);
  \draw[color=blue,fill=blue!20] (-1,-0.4) rectangle (1,-0.6);
  \draw[color=gray!20,fill=gray!20] (-1,0.4) rectangle (1,0.6);
  \path (0, -1) node[] {\normalsize{1$^\text{st.}$ dynode down}};
  \path (0, 1) node[] {\normalsize{2$^\text{nd.}$ dynode}};
  %% \draw[thick,->] (1,-1) to (0.15, 0);
  \path (2,2.) node[] {\huge{$\uparrow$}\large{$\vec{B}$}};  
  \path (0,-2.5) node[text=blue] {\large{PMT Front View}};  
\end{tikzpicture}


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