An apparatus for magnetic field compression includes a plurality of tubes of different dimensions. Each smaller tube extends within a larger tube and each tube includes an electrically conductive material for generating a magnetic field in response to electric current flowing in the conductive material. A longitudinal slot is formed in each tube. The longitudinal slot in each tube is aligned to form an aperture in which the magnetic field is compressed or has a highest magnetic flux in the aperture in response to the electric current flowing in the conductive material of each tube.