抄録
We previously measured discharge currents due to collision of the hand-held metal piece of a charged human through a 50 Ω SMA connector with a 6 GHz or 12 GHz digital oscilloscope, and then proposed an equivalent circuit model to calculate the discharge current. This model enables one to derive a discharge voltage across the spark gap from the measured discharge current, which revealed that at charge voltages bellow 600 V the estimated breakdown fields from the discharge voltages are almost kept constant (2-3×107 [V/m]) regardless of the different approach speeds of the metal piece. In this study, with a 12 GHz wide-band digital oscilloscope, we measured the discharge currents through a commercially available IEC calibration current target in order to estimate breakdown fields at different charge voltages from 200 V to 8,000 V. As a result, we confirmed that at charge voltages below 400 V, the breakdown fields show an almost constant value of (2-3)×107 V/m. It was also found that the breakdown fields at charge voltages from 600 V to 1,000 V decrease with charge voltages, and approximately agree with the Pachen's law, while at 2,000 V to 8,000 V they are smaller compared to the results calculated from the Pachen's law.
