Plasma in a Syringe

Introduction

This demonstration uses a sealed plastic syringe as a small low-pressure discharge chamber. A metal nail is fitted into the outlet, sealed by heating and hot-melt adhesive, and the plunger is pulled out fully before the rear side is sealed.

Experiment

Approximately 10 kV AC is applied to the nail. After a short time, a visible discharge forms inside the reduced-pressure volume. The effect is related to gas-discharge tubes: electrons are accelerated by the electric field and excite the remaining gas molecules.

I also experimented with deflecting the discharge using a magnet, in a way loosely comparable to electron-beam deflection in a CRT. The syringe eventually became hot and deformed, so this is only a brief demonstration and not a device intended for continuous operation.

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