Speaker
Description
Highly-alloyed chrome-nickel stainless steel is the most important material in vacuum technology. Especially in high and ultra-high vacuum technology it is used for vacuum chambers and components. One of the main research focuses before 2005 [1] was the study of parasitic field emission (FE) of specially treated stainless-steel surfaces for applications in accelerator technology. The measured threshold field strength is about 25…30 V/µm for 1 nA [2]. An important cause of field emission enhancement is the grain boundary structure. Therefore, stainless steel (ASTM 304 or 1.4301) was wet-chemical micro-structured and investigated with respect to field-emission properties. Some selected results are:
1. Threshold field strengths of micro-structured stainless steel are in the range of 7 V/µm for 1 mA (is better than [3], but CNT field emitter has 1…2 V/µm [4]).
2. For application as FE cathodes in vacuum components (cylindrical surfaces [1]), very large cathode arrays of a few cm² can be produced cost efficiently.
3. Very large cathode arrays with lower current density (≤ 30µA/cm²) are field emitter with long-term stability.
However, the main objective is the substitution of thermionic cathodes in vacuum electronic applications.
References
[1] W. Knapp, M. Wüest: “Vacuum measuring gauge”, patent WO 2006/094687, priority data 04.03.2005.
[2] B.M. Cox, W. T. Williams: “Field-emission sites on unpolished stainless steel”, J. Phys. D: Appl. Phys. 10 L5 (1977).
[3] A.K. Singh, D. Shinde, M.A. More, S. Shina.: “Enhanced field emission from nanosecond laser based surface micro-structured stainless steel”, Appl. Surf. Sci. 357, 1313-1318 (2015).
[4] W. Knapp, D. Schleussner, “Field-emission characteristics of carbon buckypaper”, JVST B 21 557-561 (2003).
