# Units

We use cylindrical coordinates \((r, \varphi, \xi)\) for the axisymmetric geometry and Cartesian coordinates \((x, y, \xi)\) for the 3d geometry. The beam propagates in positive \(\xi\)-direction.

The code works with dimensionless quantities. Units of measure depend on some basic plasma density \(n_0\). It is recommended to use the initial unperturbed plasma density as \(n_0\). All times are in units of \(\omega_p^{-1}\), where \(\omega_p = \sqrt{4 \pi n_0 e^2/m}\) is the electron plasma frequency, \(e\) is the elementary charge, and \(m\) is the electron mass. All distances are in units of \(c/\omega_p\). The unit velocity is \(c\). The notation used and units of measure for various quantities are given in old manual, p. 3.