I found this other approach quite appealing. It is a bit tricky to get the coil right, but if it is not too important where the spiral runs exactly, this may be a possible solution:
\documentclass[border=1mm, tikz]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.pathmorphing}
\begin{document}
\begin{tikzpicture}
% base
\draw (-4,-1) node[shift={(.5,.25)}] {$\alpha$} -- (-2,1) --
(4,1) -- (2,-1) -- cycle;
% cylinder
\draw (0,0) ellipse (2cm and .5cm);
\draw (0,5) ellipse (2cm and .5cm);
\draw (-2,0) -- (-2,5) (2,0) -- (2,5);
% axes
\draw[dashed] (0,0) node[above left] {$0$} -- (0,5);
\draw[->] (0,5) -- (0,6) node[right] {$x^3 = a$};;
\draw[->] (0,0) -- (2.25,0) node[right] {$x^2$};
\draw[->] (0,0) -- (-.75,-.75) node[left] {$x^1$};
% spiral
\begin{scope}
\clip (-2,0) rectangle (2,5);
\draw[decoration={coil, aspect=.55, segment length=50mm, amplitude=20mm}, decorate] (0,7.5) -- (0,-2.5);
\end{scope}
\end{tikzpicture}
\end{document}

EDIT
I tried again, this time without using decorative coils but rather by drawing an approximation of the spiral using curved lines. It should actually be possible to draw an exact spiral this way, but I don't know the math behind it, so I leave it like this. I finally used the intersection
and the calc
libraries to compute the coordinates where the different lines intersect.
\documentclass[border=1mm, tikz]{standalone}
\usepackage{tikz}
\usetikzlibrary{intersections, calc}
\begin{document}
\begin{tikzpicture}[coord/.style={fill, circle, inner sep=1pt}]
% base
\draw (-4,-1) -- (-2,1) -- (4,1) -- (2,-1) -- cycle;
% cylinder
\draw[name path=cylinderbase] (-2,0) arc (180:360:2cm and .5cm);
\draw[dashed] (2,0) arc (0:180:2cm and .5cm);
\draw[name path=cylindertop] (0,5) ellipse (2cm and .5cm);
\draw (-2,0) -- (-2,5) (2,0) -- (2,5);
% axes
\draw[dashed] (0,0) node[coord, label=above left:$0$] (null) {} -- (0,5) node[coord] {};
\draw[->] (0,5) -- (0,6) node[right] {$x^3 = a$};
\draw[->] (0,0) -- (2.25,0) node[right] {$x^2$};
\draw[->] (0,0) -- (-.75,-.75) node[left] {$x^1$};
% spiral
\begin{scope}
\clip (-2,0) -- (-2,5) arc (180:360:2cm and .5cm) -- (2,0) arc (360:180:2cm and .5cm) -- cycle;
\draw[name path global=spiralstart] (2,5.175) to[controls=+(270:2) and +(270:.5)] (-2,3.175);
\draw[dashed] (-2,3.175) to[controls=+(90:.5) and +(90:2)] (2,1.175);
\draw[name path global=spiralend] (2,1.175) to[controls=+(270:2) and +(270:.5)] (-2,-.175);
\end{scope}
% nodes
\path[name path=temp1] (null) -- ++(4.5,-1);
\path[name intersections={of=temp1 and cylinderbase}];
\node[coord, label=below:$P_1$] (p1) at (intersection-1) {};
\path[name path=temp2] (p1) -- ++(0,5);
\path[name intersections={of=temp2 and spiralend}];
\node[coord, label=above left:$P$] (p) at (intersection-1) {};
\path[name intersections={of=temp2 and spiralstart}];
\node[coord, label=above:$\bar P$] (pbar) at (intersection-1) {};
\draw[dashed] (null) -- (p1);
\draw[dashed] (p1) -- (pbar);
\draw[dashed] (p) -- +($(null)-(p1)$) node[coord, label=above left:$P_2$] {};
% labels
\node at (-3.45,-.75) {$\alpha$};
\node at (-1,0) {$\gamma$};
\node at (.125,-.25) {$\varphi$};
\end{tikzpicture}
\end{document}

samples=100, samples y=0
. This will smoothen the curve.