Focusing of shock waves upon explosion of annular charges in air

The pressure field near the focus and at the axis of an annular charge for the case of its explosion in air is studied experimentally; the detonation is initiated at one point of the ring and propagates simultaneously along its two sides. It is found that, for different ways of detonation propagation, the pressure in the shock-wave front at the axis of annular charges is almost identical at distances greater than three radii of the ring. At distances up to two radii from the plane of the annular charge, the pressure at the focus center is much greater than the pressure at the charge axis.