Application Cases

Application of High-Voltage Amplifiers in the Study of Discharge Characteristics of Rod-Ring Jets

Test Equipment: High-voltage amplifier, Signal generator, Oscilloscope, Voltage probe, Camera, etc.

Experimental Process:

Figure 1: Experimental setup diagram of Type I rod-ring jet

Figure 2: Experimental setup diagram of Type II rod-ring jet

Figure 1 shows the setup of the Type I rod-ring jet device, where the rod electrode is placed inside the gas guide tube. A tungsten rod (length 12 cm, diameter 1.5 mm) is coaxially placed inside a glass gas guide tube (inner diameter 7.0 mm, outer diameter 9.0 mm), with the rod tip aligned with the tube orifice. A ring electrode (inner diameter 4.0 cm) made from 1.0 mm diameter copper wire is coaxially placed at the tube orifice, ensuring the rod tip coincides with the center of the ring. It should be noted that the ring diameter is much larger than the tube diameter to avoid spark discharge between the electrodes and allow a wider range of applied voltage adjustment. Figure 2 shows the Type II rod-ring jet setup, where the rod electrode is placed outside the gas guide tube. A tungsten rod (length 12 cm, diameter 1.0 mm) and a copper ring (inner diameter 5.0 cm, outer diameter 5.2 cm) are arranged coaxially, with the rod tip fixed at the ring's center. The distance from the gas guide tube orifice (inner diameter 1.5 mm, outer diameter 3.0 mm) to the rod tip is approximately 3.0 mm. The angle α between the rod electrode (electric field direction) and the gas guide tube (flow field direction) can be adjusted between 5° and 85°. For both discharge setups, argon gas (purity 99.99%) is used as the working gas and flows from the tube orifice into the ambient air. The argon flow rate is controlled by a flow meter. A signal generator produces signals of different waveforms (DC, sine, triangular, and square waves), which are then amplified 2000 times by a high-voltage amplifier to serve as the high-voltage signal. This high-voltage signal is connected to the ring electrode. The tungsten rod electrode is grounded. The circuit current is measured using either a small resistor (100 Ω) voltage divider method or a current probe. The applied voltage between the rod-ring electrodes is measured using a voltage probe. Light emission from the discharge region is detected by a photomultiplier tube via a lens. An oscilloscope simultaneously observes and records the applied voltage, current, and light emission signals. Discharge images are captured using a digital camera and an ICCD (Intensified Charge-Coupled Device). Emission spectra from the discharge region are collected by a spectrometer via an optical fiber.

Experimental Results:

Figure 3: Schematic diagram of the discharge filament velocity measurement principle

Measurement Method of Bullet Propagation Velocity: High-speed photographs of the plasma plume taken by an ICCD with nanosecond exposure time reveal that the plasma plume consists of a series of rapidly propagating plasma bullets. The propagation speed of these plasma bullets can be measured using these high-speed photographs; the measurement principle is shown in Figure 3. The figure shows two high-speed photographs taken at different times. Assuming the bullet does not move forward during the exposure time, the propagation speed of the plasma bullet can be obtained by dividing the propagation distance difference (D) of the bullet in the two images by the time difference (t₂ - t₁) between the two images.

High-Voltage Amplifier Recommendation: ATA-7100

Figure: ATA-7100 High-Voltage Amplifier Specifications

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