An apparatus for accelerating and compressing plasma (10, 1000), comprising: a plasma accelerator (100, 1100) comprising a tubular outer electrode and a tubular inner electrode (115, 1015) extending inside the outer electrode such that an annular plasma propagation channel (118, 1118) is defined therebetween for accelerating and compressing a plasma torus (13, 1013) therethrough, the accelerator (100, 1100) having an inlet (112, 1112) for receiving the plasma torus (13, 1012) from a plasma generator (12, 1012), an outlet (140, 1140) for discharging an accelerated and compressed plasma torus (13, 1013), the plasma propagation channel (118, 1118) having a lengthwise elongated section (120, 1120) with an upstream end (114a, 1114a) in fluid communication with the inlet and a downstream end in fluid communication with the outlet (140, 1140), and wherein a cross-sectional annular gap defined as a radial distance between the inner (115, 1015) and outer electrodes decreases non linearly in a downstream direction along the length of the elongated section (120, 1120); and a power source (24, 1024) electrically coupled to the accelerator (100, 1100) and configured to provide an electrical acceleration pulse that produces a current that flows in the accelerator (100, 1100) and generates a magnetic pushing flux behind the plasma torus (13, 1013) that is sufficient to push the plasma torus from the upstream end and through the elongated section (120, 1120) to the downstream end and the outlet (140, 1140) of the accelerator; wherein the apparatus is configured to have a predetermined inductance before the elongated section (120, 1120) such that the plasma torus (13, 1013) is accelerated and compressed throughout the elongated section (120, 1120) by an expansion of the magnetic pushing flux, and wherein the dimensions of the plasma propagation channel (118, 1118) are selected such that for a selected inductance of the elongated section (120, 1120) and selected inductance before the elongated section (120, 1120), the current flowing in the elongated section (120, 1120) at the downstream end is smaller than at the upstream end (114a, 1114a) of the elongated section (120, 1120) and a plasma torus pressure is greater at the downstream end (140, 1140) of the elongated section (120, 1120) than at the upstream end (114a, 1114a) of the elongated section (120, 1120). a plasma accelerator (100, 1100) comprising a tubular outer electrode and a tubular inner electrode (115, 1015) extending inside the outer electrode such that an annular plasma propagation channel (118, 1118) is defined therebetween for accelerating and compressing a plasma torus (13, 1013) therethrough, the accelerator (100, 1100) having an inlet (112, 1112) for receiving the plasma torus (13, 1012) from a plasma generator (12, 1012), an outlet (140, 1140) for discharging an accelerated and compressed plasma torus (13, 1013), the plasma propagation channel (118, 1118) having a lengthwise elongated section (120, 1120) with an upstream end (114a, 1114a) in fluid communication with the inlet and a downstream end in fluid communication with the outlet (140, 1140), and wherein a cross-sectional annular gap defined as a radial distance between the inner (115, 1015) and outer electrodes decreases non linearly in a downstream direction along the length of the elongated section (120, 1120); and a power source (24, 1024) electrically coupled to the accelerator (100, 1100) and configured to provide an electrical acceleration pulse that produces a current that flows in the accelerator (100, 1100) and generates a magnetic pushing flux behind the plasma torus (13, 1013) that is sufficient to push the plasma torus from the upstream end and through the elongated section (120, 1120) to the downstream end and the outlet (140, 1140) of the accelerator; wherein the apparatus is configured to have a predetermined inductance before the elongated section (120, 1120) such that the plasma torus (13, 1013) is accelerated and compressed throughout the elongated section (120, 1120) by an expansion of the magnetic pushing flux, and wherein the dimensions of the plasma propagation channel (118, 1118) are selected such that for a selected inductance of the elongated section (120, 1120) and selected inductance before the elongated section (120, 1120), the current flowing in the elongated section (120, 1120) at the downstream end is smaller than at the upstream end (114a, 1114a) of the elongated section (120, 1120) and a plasma torus pressure is greater at the downstream end (140, 1140) of the elongated section (120, 1120) than at the upstream end (114a, 1114a) of the elongated section (120, 1120).