Comments on "Dielectric breakdown characteristics of cryogenic nitrogen gas above liquid nitrogen surface" [with reply]

For the original article see ibid., vol. 1, no. 3, p. 538-43 (1994). In the commenter´s experience, a needle electrode in mist, just over the surface of the liquid, collects liquid droplets especially under voltage stress, which cause the test results to be very variable. This situation has been found not only with liquid nitrogen, liquid hydrogen and especially liquid helium, but also in air close to the surface of a layer of oil. It is also noted that all the data in the original paper were taken as the voltage was rising at a rate of 0.5 kV/s, while during the commenter´s tests the voltage was held steady for a long enough time to observe the liquid droplets collecting on the needle. It is surmised that whatever the true reason for the difference between data of Goshima et al. and the commenter´s, the method of voltage application can have very significant effects, not only on the scatter but also on the mean. Finally, caution is suggested in the use of Styrofoam containers to hold cryogenic liquids for electrical tests, as an explosion is possible under certain conditions. In reply, the author clarifies the conditions under which the data were collected and agrees that the difference in the two sets of results may well arise from the voltage application method. In regards to the caution needed in the use of Styrofoam containers, the author states that he and his co-authors were already aware of this and acted accordingly.<>