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Title: Evaluation of electropolished stainless steel electrodes for use in DC high voltage photoelectron guns

Abstract

DC high voltage photoelectron guns are used to produce polarized electron beams for accelerator-based nuclear and high-energy physics research. Low-level field emission (∼nA) from the cathode electrode degrades the vacuum within the photogun and reduces the photoelectron yield of the delicate GaAs-based photocathode used to produce the electron beams. High-level field emission (>μA) can cause significant damage the photogun. To minimize field emission, stainless steel electrodes are typically diamond-paste polished, a labor-intensive process often yielding field emission performance with a high degree of variability, sample to sample. As an alternative approach and as comparative study, the performance of electrodes electropolished by conventional commercially available methods is presented. Our observations indicate the electropolished electrodes exhibited less field emission upon the initial application of high voltage, but showed less improvement with gas conditioning compared to the diamond-paste polished electrodes. In contrast, the diamond-paste polished electrodes responded favorably to gas conditioning, and ultimately reached higher voltages and field strengths without field emission, compared to electrodes that were only electropolished. The best performing electrode was one that was both diamond-paste polished and electropolished, reaching a field strength of 18.7 MV/m while generating less than 100 pA of field emission. The authors speculate that the combinedmore » processes were the most effective at reducing both large and small scale topography. However, surface science evaluation indicates topography cannot be the only relevant parameter when it comes to predicting field emission performance.« less

Authors:
;  [1]; ; ; ; ;  [2]; ;  [3];  [4]
  1. Department of Mechanical Engineering, Old Dominion University, Norfolk, Virginia 23529 (United States)
  2. Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)
  3. The College of William and Mary, Williamsburg, Virginia 23187 (United States)
  4. NASA Langley, Hampton, Virginia 23681 (United States)
Publication Date:
OSTI Identifier:
22392195
Resource Type:
Journal Article
Journal Name:
Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films
Additional Journal Information:
Journal Volume: 33; Journal Issue: 4; Other Information: (c) 2015 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0734-2101
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; ACCELERATORS; COMPARATIVE EVALUATIONS; DIAMONDS; ELECTRIC POTENTIAL; ELECTRON BEAMS; FIELD EMISSION; GALLIUM ARSENIDES; PHOTOCATHODES; STAINLESS STEELS; SURFACES

Citation Formats

BastaniNejad, Mahzad, Elmustafa, Abdelmageed A., Forman, Eric, Covert, Steven, Hansknecht, John, Hernandez-Garcia, Carlos, Poelker, Matthew, Das, Lopa, Kelley, Michael, and Williams, Phillip. Evaluation of electropolished stainless steel electrodes for use in DC high voltage photoelectron guns. United States: N. p., 2015. Web. doi:10.1116/1.4920984.
BastaniNejad, Mahzad, Elmustafa, Abdelmageed A., Forman, Eric, Covert, Steven, Hansknecht, John, Hernandez-Garcia, Carlos, Poelker, Matthew, Das, Lopa, Kelley, Michael, & Williams, Phillip. Evaluation of electropolished stainless steel electrodes for use in DC high voltage photoelectron guns. United States. https://doi.org/10.1116/1.4920984
BastaniNejad, Mahzad, Elmustafa, Abdelmageed A., Forman, Eric, Covert, Steven, Hansknecht, John, Hernandez-Garcia, Carlos, Poelker, Matthew, Das, Lopa, Kelley, Michael, and Williams, Phillip. 2015. "Evaluation of electropolished stainless steel electrodes for use in DC high voltage photoelectron guns". United States. https://doi.org/10.1116/1.4920984.
@article{osti_22392195,
title = {Evaluation of electropolished stainless steel electrodes for use in DC high voltage photoelectron guns},
author = {BastaniNejad, Mahzad and Elmustafa, Abdelmageed A. and Forman, Eric and Covert, Steven and Hansknecht, John and Hernandez-Garcia, Carlos and Poelker, Matthew and Das, Lopa and Kelley, Michael and Williams, Phillip},
abstractNote = {DC high voltage photoelectron guns are used to produce polarized electron beams for accelerator-based nuclear and high-energy physics research. Low-level field emission (∼nA) from the cathode electrode degrades the vacuum within the photogun and reduces the photoelectron yield of the delicate GaAs-based photocathode used to produce the electron beams. High-level field emission (>μA) can cause significant damage the photogun. To minimize field emission, stainless steel electrodes are typically diamond-paste polished, a labor-intensive process often yielding field emission performance with a high degree of variability, sample to sample. As an alternative approach and as comparative study, the performance of electrodes electropolished by conventional commercially available methods is presented. Our observations indicate the electropolished electrodes exhibited less field emission upon the initial application of high voltage, but showed less improvement with gas conditioning compared to the diamond-paste polished electrodes. In contrast, the diamond-paste polished electrodes responded favorably to gas conditioning, and ultimately reached higher voltages and field strengths without field emission, compared to electrodes that were only electropolished. The best performing electrode was one that was both diamond-paste polished and electropolished, reaching a field strength of 18.7 MV/m while generating less than 100 pA of field emission. The authors speculate that the combined processes were the most effective at reducing both large and small scale topography. However, surface science evaluation indicates topography cannot be the only relevant parameter when it comes to predicting field emission performance.},
doi = {10.1116/1.4920984},
url = {https://www.osti.gov/biblio/22392195}, journal = {Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films},
issn = {0734-2101},
number = 4,
volume = 33,
place = {United States},
year = {Wed Jul 15 00:00:00 EDT 2015},
month = {Wed Jul 15 00:00:00 EDT 2015}
}

Works referencing / citing this record:

Dark Matter Detection Using Helium Evaporation and Field Ionization
journal, November 2017


Dark Matter Detection Using Helium Evaporation and Field Ionization
text, January 2017