What is hollow cathode glow discharge?
A hollow cathode discharge may be used as a reservoir of sputtered atoms for spectroscopic investigations. The negative glow from the opposite walls of the inner surface of hollow cathode merge to produce a high density of neutral and excited atoms as well as of ions at the center of the hollow cathode.
How do hollow cathodes work?
Hollow cathodes typically employ a conductive tube with a low work function insert. Due to its low work function, the insert thermionically emits electrons at relatively low operating temperatures (1000-1700 C) and at high current densities (up to 20 A/cm2), while maintaining a long operational lifetime.
How the sputtering process occurs in a hollow cathode lamp?
The fill gas allows the sputtering of the cathode material. The gas is ionized when a high voltage is applied. These ions are accelerated towards the cathode. When they hit the cathode they knock metals atoms loose.
Why is a hollow cathode lamp used in AAS?
A hollow cathode lamp is used as a spectral line source for Atomic Absorption (AA) instruments. AAS lamps utilize the hollow cathode effect to generate light at wavelengths for the element of interest. The emission line selected must avoid wavelength overlaps, and have good intensity with low noise.
What is hollow cathode plasma?
Hollow Cathodes are high-density plasma sources that are non-equilibrium from their principle. They are characterized by high activation and ionization degrees and can work in a broad range of parameters – pressures, powers and gas flows. They are scalable, versatile and cost effective.
How can intensity of radiation be increased in hollow cathode?
How can the intensity of radiation be increased in Hollow cathode lamp? Explanation: The intensity of radiation is increased in Hollow cathode lamp by the addition of a non-conductive protective shield of mica. The protective shield can be made of glass too.
What is the disadvantage of hollow cathode discharge lamp?
The only disadvantage of such lamps is that the useful life of some elements can get shortened as higher current can be passed but this single disadvantage far outweighs the advantages over conventional lamps.
Why does the hollow cathode lamp have a low pressure instead of a high pressure of argon filler gas?
A low pressure of argon in the lamp insures that the line width from the hollow cathode lamp is less than the line width of the absorbing species.
What is the key requirement of a hollow cathode lamp?
The key requirement for the hollow cathode lamp is to generate a narrow emission line for the element being determined. The emission line should be of sufficient spectral purity and intensity to achieve a good calibration (preferably linear) with low noise.