Crookes tube

The shadow cross tube is a form of the electron tube. It was invented by physicist Sir William Crookes in 1879 and is therefore also called Crookes tube.

It is used to study the cathode rays, another name for electron beams.

Construction

The traditional shadow cross tube consists of an aluminum cathode, an anode in the form of a paw Cross or a Maltese cross, often of a fluorescent phosphor screen on which after application of a high electric voltage by the electric field turn accelerated electrons due to fluorescence light produce and thus show the shadow of the cross - anode.

All just mentioned components are in a partially evacuated glass tube, which has a slightly conical shape. Newer versions are often completely evacuated, have a hot cathode and a Wehnelt.

The operating voltage for this type of electron tubes is similar to TV, CRT at approximately 5 to 12 kV.

Function

The shadow cross tube was used to study the gas discharge and the particle beams in vacuum.

A similar construction led to the discovery of cathode rays. Their properties can be studied at the shadow cross tube, about their straight, but deflectable by magnetic propagation or the fluorescence that they cause on the glass or the fluorescent screen.

These properties were originally attributed to a fourth state of matter, the radiation condition. The cathode ray was thereby misinterpreted as atomic beam.

Designs

There are also slightly different designs, but which have the same function as the original. These shapes are often made in single of glassblowers. Can be made ​​of aluminum and use it as the anode instead of the cross also about any other shape.

Gas-filled tubes do not require heated cathode; instead, they show electron emission due to ion bombardment. Polarity they are, respectively, the cathode is in turn a sheet with a hole can be observed canal rays.

Web Links / References

• Examples of individual productions

• Display tube
• Gas discharge lamp