CODEX Entry 8501: Making Plasma Gun
DIY which can be made using items available in many large hardware stores. To generate the energy for a plasma discharge, a high current, high voltage source and a large capacitor bank are used. The capacitor is loaded with as high a voltage as possible, then discharged. The gap between the electrodes ionizes, turning the selected medium into a superheated conductive plasma. With the right ionizing environment and butane this plasma can be propelled forward at high velocity.
A High Voltage Inverter for converting from low to high voltage for charging the primary capacitor by pulsing a high voltage ignition coil. Pulsing the spark coil steps up the voltage which is then used to charge the main capacitor. This capacitor is later discharged into the primary coil of a Tesla Coil to further increase the voltage.
It is necessary to add a high voltage diode to the output of the ignition coil so that a capacitor can be charged. For this, the rubber end of the ignition coil was removed, and the diode connected to the spring inside the tip. The tip is then filled with epoxy resin so that the high voltage does not flash over the body of the diode. The cathode wire is connected to a small inductor. This inductor serves as a choke to protect the diode from the high frequency currents in the primary circuit.
A Primary Tank Circuit for storing energy in a resonant circuit to be rapidly discharged in pulses. This is made up of a high voltage capacitor, spark gap, and the primary coil. When the capacitor becomes charged to a high enough voltage, the air between the terminals of the spark gap will break down with a loud bang and a bright flash. During this very brief flash, the energy in the capacitor will be moved into the primary coil and then back again 1,000,000 times per second. This frequency of 1MHz is determined by the sizes of the capacitor and the coil and is the resonant frequency. Use a quality polypropelene capacitor with a low ESR and low ESL.
A Secondary Coil to use as a self-resonant circuit, which magnifies the primary voltage so that it can discharge as plasma streams. Use 0.25mm wire to wrap around 700 times onto the primary coil. Without a discharge terminal, the resonant frequency is around 1100kHz, so to reduce this a larger topload is added. The toroid used brings it down to 900kHz. Due to the high electrical stresses, it is important to insulate the coil well with multiple layers of varnish.
A Breakout Electrode is used for concentrating the electrical discharge in a focused place. By using a large topload, the electrical field is spread over a large area and will not break out in to arcs until the voltage is very high. While this is advantageous for increasing arc length, it also increases the chances of the arc discharging back towards the coils. The breakout point creates a localised area of intense electric field which will ionise the air more easily and force the discharge away from the end of the plasma gun. The electrode is fitted with a pipe so that gas can be ejected from the tip. Some gasses such as Argon or Carbon Dioxide will ionise more easily than air, but butane is suggested as it will ignite and conduct the currents. When ionised it will provide a conductive path, allowing the plasma to reach further from the coil.
There are two resonant circuits in the Tesla coil part of the plasma gun which must be tuned to the same frequency. If the frequencies are not matched, the energy transfer will be very poor. To make small adjustments to the secondary coil’s resonant frequency by changing the size of the topload or by adjusting the number of turns of the primary coil.