A series of observations using soft X-rays and optical techniques diagnose key plasma parameters in a low inductance large aspect ratio fast capillary discharge. The capillary discharge is operated with less than 1 Joule of stored electrical energy and is designed for fast repetition rate operation. Peak current is between 5 and 8 kA with a quarter period between 8 and 11 ns. The energy storage capacitor is directly charged during 1µs. Gas is fed into the hollow cathode volume and extracted at the anode, establishing a pressure gradient, which is found to be essential. The pre-breakdown phase is characterized by transient hollow cathode physics, where optical emission from the hollow cathode and measurements of the electron beams that propagate through the cathode orifice and are collimated along the capillary axis to emerge at the anode. The discharges are performed in Xe, Ar, N with admixtures of He. The capillary is of 1.6 mm diameter, either a smooth bore or is segmented with a length of 21 or 16 mm respectively.