## 2 Material and Methods
### Experimental Setup of a Nitrate Production System Using Plasma Technology  
The plasma system designed for nitrate production from water consists of two main components. The first component is a high-voltage generator that supplies 100 W of power to the electrodes, creating an electric field that directs electrons toward the positive electrode, generating an electric current between the electrodes. The second component is a series of five sawtooth-shaped electrode emitters, each arranged in parallel with a positive charge characteristic. The cathode is a rectangular aluminum ground plate positioned parallel to the sawtooth electrode lines.  
Selecting the appropriate electrode materials is crucial for efficient plasma generation, as they must exhibit excellent electrical conductivity. Among the materials evaluated, copper (Cu) proved to be the most suitable for the anode electrode due to its high electrical conductivity (5.96 \(\times\) 10\({}^{7}\) S/m). The ground plane is made of aluminum, which, while having a slightly lower conductivity than copper (3.5 \(\times\) 10\({}^{7}\) S/m), offers the advantages of being lightweight and cost-effective, making it ideal for use in ground planes and reducing construction costs for industrial applications.  
The block diagram of the plasma system used for nitrate production from water is shown in Figure 1. The system consists of a high-voltage power source (100 W) with a voltage range of 2-30 kV and a control system to supply power to the discharge electrode. The discharge electrode is designed to generate a high-intensity electric field within a plasma state. The system also includes a fan to direct steam through the electrodes, which are exposed to high electric field stress, and an ultrasonic head to facilitate the conversion of water into steam.  
Figure 1: Plasma system for nitrate production from water: (**a**) block diagram; (**b**) plasma-based nitrate fertilizer production system.  
The electrodes are designed with a pointed tip, using copper for the tip and aluminum for the ground plane component, to optimize electrode size and geometry. To evaluate the electric field intensity between the sharp-tipped electrode and the plate, a tungsten needle with a 1.5 mm diameter was used as the electrode. The distance between the electrodes was maintained at a constant 21 mm, and the voltage applied during the experiments ranged from 2 to 30 kV. The primary objective of this investigation was to determine the intensity of the electric field during the streamer formation phase, which occurs at voltages between 13 and 23 kV. The field intensity was calculated using Equations (1) and (2).  
\[E_{\text{max}}=\frac{V}{d\eta^{*}} \tag{1}\]  
\[\eta^{*}=\frac{E_{av}}{E_{\text{max}}}\ ;\ 0\leq\eta^{*}\leq 1 \tag{2}\]  
where \(\eta^{*}\) is the field utilization factor, \(E_{av}\) is the average of the electric field intensity, and \(d\) is the distance between the electrodes.  
The analysis and design of a nitrate production system from water using electric field technology involve the implementation of electromagnetic technology in the form of plasma, utilizing an electric field intensity of 6.31 \(\times\) 10\({}^{5}\) V/m, as applied in the experiments.