Hollow cathode lampThe structure of the lamp is composed of a cathode, an anode, and a shielding layer. The cathode is mostly made of pure metal or alloy. For some precious metals, it is made into thin sheets and lined on the supporting electrode. The cathode is in the shape of an empty barrel in the middle, hence the name hollow cathode lamp. The anode is a tungsten rod welded with tantalum or titanium wire, which has a gas absorbing effect and can absorb a small amount of harmful gases (such as H2) at high temperatures. A shielding layer is installed between the anode and cathode to prevent breakdown.
The function of hollow cathode lamp
1. Hollow cathode lamp is a special form of low-pressure gas discharge light source, where the discharge is concentrated in the cathode cavity. When a voltage of 200V-500V is applied between the two poles, glow discharge occurs. Under the action of an electric field, electrons collide with carrier gas atoms on their way to the anode and ionize them, releasing secondary electrons and increasing the number of electrons and positive ions to maintain discharge. Positive ions obtain kinetic energy from an electric field. If the kinetic energy of positive ions is sufficient to overcome the lattice energy of the metal cathode surface, when they collide with the cathode surface, atoms can be sputtered out of the lattice, so hollow cathode lamps have the function of sputtering atoms out.
2. During the heating process of the cathode, the surface elements of the cathode also undergo thermal evaporation. The sputtered and evaporated atoms enter the cavity and collide with electrons, atoms, ions, etc. to be excited, emitting resonance radiation characteristic of the corresponding elements. At the same time, the spectral lines emitted by the hollow cathode lamp also include internal gas filling, cathode material, and impurity elements.
When using hollow cathode lamps, be careful not to reverse the polarity. In order to stabilize the luminous intensity of the lamp, preheat it for 10-30 minutes at the working current. If the lamp is not used for a long time, it should be ignited regularly, usually for one hour at the working current. If there are impurities in the lamp after long-term storage, the reverse connection method can be used to remove the gas, invert the electrodes, and light the lamp with high current for 30 minutes. Because hollow cathode lamps are a special form of low-pressure gas discharge light source, they must be operated according to specifications to avoid affecting the cathode.