Argon gas discharge lamp

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Revision as of 12:25, 27 April 2022 by Kunhee (talk | contribs) (→‎Setup)
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By applying a sufficiently high DC voltage across a gas, the gas atoms/molecules are ionised by the strong electric field. In this project, we construct an Argon-based gas discharge lamp, with adjustable pressure and voltage. The breakdown voltage of Argon gas with respect to pressure changes is observed, and compared with Paschen's law. We also observe changes in the spectroscopic properties of the plasma with varying pressure.

Setup

A small air-tight chamber was evacuated with a rough pump to about Torr (measured with a Pirani gauge). Then, Argon gas was slowly introduced to the chamber via a needle valve, until the chamber reached the pressure of about to Torr. The metallic cylinder that interfaces with the gas lines forms the cathode of the chamber, and is grounded. Another metallic cylinder (anode) was attached to the cathode using a glass pipe.

Schematics for the Argon gas discharge lamp setup

The glass pipe provides an electrical isolation between the cathode and the anode, and provides a viewport for the experimenter to observe glow discharge. The anode was connected to the positive terminal of a high-voltage power supply, which can reach upto 760 V. Epoxy was used to connect the pieces and seal the vacuum chamber. A ballast resistor (33 kΩ) was added in series with the gas discharge lamp in order to limit the current. The electrodes were mechanically held using laser-cut acrylic plates fixed to an optical breadboard using brackets and bolts.

Argon gas discharge lamp setup

Glow Discharge

Spectroscopic Properties