Aluminum wire x‐pinch and z‐pinch experiments were conducted using the XP pulsed power generator at Cornell University. Time resolved measurements of plasma expansion and sausage instability growth along the wires were made using a sub‐nanosecond pulsed nitrogen laser and x‐ray backlighting. Rapid (0.9 to 2.9 cm/&mgr;s) unstable expansion of a coronal plasma formed around both x‐pinch and z‐pinch wires was observed, while a dense core plasma expanded more slowly (0.1 to 0.8 cm/&mgr;s) and uniformly. The x‐pinch cross point is an intense, compact L‐shell and K‐shell radiation source. The cross region imploded to a minimum radius just before the intense emission of soft x‐rays. Time resolved characteristics of the K‐shell radiation implied electron densities as high as 1022cm−3and temperatures of a few hundred eV for 12 to 75 &mgr;m wires and 185 to 360 kA peak current. Z‐pinches showed pinch points along the full wire length.