skip to main content

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

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 K{sub 2}CsSb photocathodes at high beam currents.
Authors:
 [1] ;  [2]
  1. Christopher Newport University, Newport News VA (United States)
  2. Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)
Publication Date:
OSTI Identifier:
22492695
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1687; Journal Issue: 1; Conference: Ingot niobium summary workshop, Newport News, VA (United States), 4 Dec 2015; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANODES; BEAM CURRENTS; BUFFERS; CEBAF ACCELERATOR; ELECTRIC POTENTIAL; ELECTRONS; FIELD EMISSION; GALLIUM ARSENIDES; KRYPTON; MONOCRYSTALS; NIOBIUM; PHOTOCATHODES; STRAINS; SUPERLATTICES; TEST FACILITIES