A code to compute the action-angle transformation for a particle in an arbitrary potential well

For a Vlasov treatment of longitudinal stability under an arbitrary wake field with the solution of the Haissinski equation as the unperturbed distribution, it is important to have the action-angle transformation for the distorted potential well in a convenient form. We have written a code that gives the transformation q, p→J, φ, with q(J, φ) as a Fourier series in φ, the Fourier coefficients and the Hamiltonian H(J) being spline functions of J in C² (having continuous second derivatives)