The electrode attachment was made of nylon. The profile diagram of the electrode attachment and the experimental electrode setup are shown in Fig. 1a, b, respectively. Temperaturecontrolandmeasureunitswereused.Thelow temperature thermometer used was DTM-280, with a resolution of ±1 °C and an accuracy of 0.1 °C, which ranges from −200 to 200 °C, Fig. 2a shows DTM-280, and Fig. 1a shows the setup of the thermometer. The temperature sensor was covered with a layer of stainless steel. Thus, the tip of the sensor should not contact the electrode; otherwise, the high frequency voltage might damage the sensor.