Ingot niobium as candidate electrode material for Jefferson Lab 200 kV inverted electron photogun

Conference · Tue Dec 01 00:00:00 EST 2015 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.4935329· OSTI ID:1969516

BastaniNejad, Mahzad; Suleiman, Riad

This contribution describes the field emission characterization of niobium electrodes using a DC high voltage field emission test apparatus. A total of six electrodes were evaluated: two large-grain, two single-crystal, and two fine-grain that were chemically polished using a buffered-chemical acid solution. Field emission from niobium electrodes could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode is 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. Motivated by these results, an inverted electron photogun operated at Jefferson Lab injector test facility was equipped with a large-grain niobium cathode electrode and it has been successfully conditioned to 225?kV without field emission. This photogun was used to study strained superlattice GaAs and K2CsSb photocathodes at high beam currents.

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1969516
• Report Number(s): JLAB-ACC-15-2216; DOE/OR/23177-6018
• Journal Information: AIP Conference Proceedings, Vol. 1687, Issue 1; Conference: AIP Conference Proceedings, SCIENCE AND TECHNOLOGY OF INGOT NIOBIUM FOR SUPERCONDUCTING RADIO FREQUENCY APPLICATIONS, 4 December 2015, Virginia, USA; ISSN 0094-243X
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English