Geissler's tube
The Geissler tube or geißlersche tube is a cold cathode - gas discharge tube for examination and demonstration of gas discharges .
It was invented in the 19th century by the instrument maker Heinrich Geißler , who was also a glassblower.
Layout and function
The Geissler tube consists of two electrodes (mostly made of aluminum ), a cathode and an anode . These are usually shaped the same.
The two electrode feedthroughs in the inside of the tube are made of thin platinum wire in old tubes, as this has a very similar coefficient of thermal expansion to glass. The electrodes are fused in a partially evacuated glass tube filled with gases (e.g. neon , air , argon , hydrogen ), vapors ( water , alcohol ) or aerosols , which can have a wide variety of shapes. There are also screw-shaped tubes with a fluorescent liquid jacket or those made of uranium glass . Different gases lead to different colors and spectral lines of the fillings that are excited to glow.
The operating voltage of the tubes is approx. 0.5 to 20 kV, it depends on the internal pressure, the distance between the electrodes and the gas filling. Depending on the operating voltage and internal pressure, X-rays can occur during operation . A series of such tubes with different internal pressures are used in physics lessons to demonstrate the processes involved in a gas discharge . The cross-section of the discharge channel decreases with increasing pressure until it becomes a spark discharge at normal pressure.
Geissler tubes are usually fed with a spark inductor .
literature
- August Scherl: The big book of technology. Publishing house for knowledge and education, Gütersloh 1972.
Web links
- Peter Schnetzer: The fascination: glass - high voltage - vacuum - light. Retrieved on May 6, 2009 (pictures of glowing Geissler tubes).
- Overview of historical Geissler tubes (eng)
