Investigation of the high voltage vacuum discharge characteristics − current derivative (di/dt), current, voltage, and soft as well as hard X-rays − versus time has been carried out. Recorded traces indicate pinching of the interelectrode discharge column two or three times during which the voltage increases to values as high as the initial voltage or even higher. X-ray radiation of high penetration power is emitted during these events. In addition, sausage instabilities have been observed during the pinch giving rise to extreme penetrating X-rays caused partly by the pinch voltage and partly by the sausage voltage. Visible electrode studies show the fact that the discharge is restricted to a narrow column. Finally, a theoretical treatment of the discharge mechanism that seems to be in good agreement with the experimental result is also presented.