Dielectric-breakdown tests of water at 6 MV

We have conducted dielectric-breakdown tests on water subject to a single unipolar pulse. The peak voltages used for the tests range from 5.8 to 6.8 MV; the effective pulse widths range from 0.60 to 1.1 mu s; and the effective areas tested range from 1.8 X 10(5) to 3.6 X 10(6) cm(2). The tests were conducted on water-insulated coaxial capacitors. The two electrodes of each capacitor have outer and inner radii of 99 and 56 cm, respectively. Results of the tests are consistent with predictions of the water-dielectric-breakdown relation developed in [Phys. Rev. ST Accel. Beams 9, 070401 (2006)].