NDLI: Evaluation of niobium as candidate electrode material for dc high voltage photoelectron guns

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Evaluation of niobium as candidate electrode material for dc high voltage photoelectron guns

Content Provider	NASA Technical Reports Server (NTRS)
Author	Elmustafa, A. A. Mohamed, Abdullah Hansknecht, J. Covert, S. Surles-Law, K. Adderley, P. Poelker, M. Mammei, R. Williams, P. BastaniNejad, M. Clark, J. Hernandez-Garcia, C.
Copyright Year	2012
Description	The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirror-like finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain, and two fine-grain) that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and field strength. In all cases, field emission from electrodes (stainless steel and/or niobium) could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (< 10 pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a field strength of 18:7 MV/m.
File Size	2760039
Page Count	11
File Format	PDF
Alternate Webpage(s)	http://archive.org/details/NASA_NTRS_Archive_20120016801
Archival Resource Key	ark:/13960/t2x39s992
Language	English
Publisher Date	2012-08-17
Access Restriction	Open
Subject Keyword	Electronics And Electrical Engineering Field Strength Electrodes Single Crystals Electric Potential Vacuum Chambers Direct Current Photoelectrons Field Emission High Voltages Electric Fields Niobium Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science
Content Type	Text
Resource Type	Article

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