Special Lamps
Special applications and Spectral lamps
On the right is a Super high pressure Xenon arc lamps are used in cinema projectors and search lights. This is a 3kW XBO lamp. The xenon pressure in the lamp is many times atmospheric, making these lamps dangerous to handle as they can literally explode if stressed.
Re-lamping is carried out with a ballistic jacket around the lamp and the operator wearing leather gauntlets and eye and body protection. They produce an intense discharge similar in colour to daylight. While the arc voltage is around 20V DC once struck, 30kV
is required to initiate an arc. The cathode is thoriated and runs in thermionic emission due to the high current
This is an old specialist vapour lamps used in education and spectroscopy. Manufactured by GEC this is an early example of a low-pressure Cadmium vapour lamp.
Next is an example of a Deuterium lamp. These lamps produce an almost continual spectrum in the UV range making them an important lamp in UV spectroscopy. They often have quartz envelopes or windows to allow the transmission of the wide UV spectrum. These lamps use a heated cathode with a DC supply and require a warm up sequence before ignition. Once struck the discharge current is often enough to maintain the cathode temperature and the DC heater current can be reduced or removed. The visible Spectral line image is shown below.
A selection of educational, Spectral tubes. These tubes operate like short neon sign tubes and require high operating voltages. Gasses shown are starting from the left; Hydrogen, Neon, Krypton, and Helium. Some of the spectral line images for these tubes are shown below.
