## 3 Testing of Marx Generator  
The Marx generator was tested using a resistive load. First, a single stage of the generator was examined. Figure 4a shows the output voltage across the 50 \(\Omega\) load when the capacitor of capacitance 0.1 \(\mu\)F is charged to 300 V. The resistance of the load is characteristic of the cuvettes (VWR International, Taiwan) with buffer liquid used in biological experiments. The trigger pulse formed with a thyristor driver is also shown in the inset of this figure. According to the datasheet for this type of thyristor, the gate trigger current should be higher than 300 mA, and the chosen design of the thyristor driver fully meets this requirement.  
As for the voltage drops across the load, it is clear that the maximum load voltage (about 230 V) is lower than the charged voltage of the capacitor. To understand the reason for this discrepancy, voltage measurements were made across both the capacitor and the thyristor (see Figure 4b). It was found that the switching time of the thyristor was about 1 \(\mu\)s, and during this time, the voltage was divided between the load and the thyristor. The voltage across the load becomes equal to the voltage across the capacitor only when the thyristor is fully open. However, the capacitor is partially discharged at this point, and the maximum voltage across the load is lower. This is confirmed by the graph, showing the result of summing the voltage across the load and the thyristor (see Figure 4b). As can be seen, the summed voltage is the same as the voltage across the capacitor. Therefore, we can conclude that the lower maximum voltage at the load is not so much caused by the inductance of the circuit, which could also lower the maximum voltage but rather by the opening rate of the thyristor. It should be noted that the use of capacitors with higher capacitance or with higher load resistance reduces this effect due to the slower discharge of the capacitor.  
Figure 5 presents the output voltage (V\({}_{\text{out}}\)) across the active load of 416 \(\Omega\) for the 12-stage Marx generator at different charging voltages. Such a load was chosen to become as close as possible to the impedance of the test cell suspension used in electroporation experiments with milk casein (see Section 4.2). As can be seen from this figure, charging the capacitors up to 1.2 kV using a module with a capacitance of 0.25 \(\mu\)F (module 1) generated a peak voltage of about 10 kV with a pulse duration at 37% of maximal amplitude at about 14 \(\mu\)s. When using the second module with a capacitance of 1 \(\mu\)F, a peak voltage of around 12.5 kV with a half amplitude pulse duration of around 47 \(\mu\)s was generated. However, it should be noted that the internal impedance of the generator consisted not only of the reactance of the capacitors but also has an inductive component caused by the wires connecting the thyristors and capacitors. In addition, we also considered the contribution  
Figure 4: The general shape of the output voltage across the 50 \(\Omega\) load of one stage of the Marx generator (**a**). The gate current of the thyristor is shown in the inset. Waveforms of the voltage across the thyristor V\({}_{\text{Thyr}}\), the load V\({}_{\text{R}}\), the capacitor V\({}_{\text{C}}\), and the sum voltage of V\({}_{\text{R}}\) and V\({}_{\text{Thyr}}\). (**b**).  
of inductor coils (L2 and L3) and resistors (R2 and R3) connected in series with the load, which served to reduce the effects of a short circuit in the load. In this case, the maximum voltage and the pulse duration could be different.  
The main advantages of this design are a high output voltage, a wide range of repetition rates, and two ranges of pulse duration.