• J.D. Jarvis, H.L. Andrews, C.A. Brau, B.K. Choi, J.L. Davidson, W.P. Kang, C.L. Stewart, Y.M. Wong
  Vanderbilt University, Nashville

We present new results in the measured electron energy spectrum from diamond field emitters. The energy spectrum from a clean diamond surface has been measured and is comparable in shape and width to that of metal emitters. The results suggest that the emitted spectrum is sensitive to the presence of adsorbed species on the emitter surface. Electrons significantly below the cathode’s Fermi level are emitted by resonant tunneling. Furthermore, these resonant surface states can increase the total emitted current by more than an order of magnitude while maintaining a narrow spectral width (~0.5 eV). Experiments are also being performed with individual multiwall carbon nanotubes (MWCNTs). We have observed beams emitted from individual residual gas molecules that approach the quantum-degenerate limit of electron-beam brightness. This limit has profound consequences for the behavior of an electron. Tightly bound designer adsorbates may greatly enhance the emission properties and improve performance in electron injector systems.

• J.D. Jarvis, H.L. Andrews, C.A. Brau, B.K. Choi, J.L. Davidson, B.L. Ivanov, W.P. Kang, C.L. Stewart, Y.M. Wong
  Vanderbilt University, Nashville

We present recent advances in the uniformity conditioning of diamond field-emitter arrays (DFEAs), and new results from emittance measurements of their emitted electron beams. DFEAs have shown considerable promise as potential cathodes for free-electron lasers. They have demonstrated their rugged nature by providing high per-tip currents, excellent temporal stability, and significant resistance to back-bombardment damage during poor vacuum, close-diode DC operation. Until now, the successful conditioning of high-density arrays has been precluded by thermal damage to the anode. We report successful uniformity conditioning of densely packed DFEAs using microsecond-pulsed high-current conditioning (HCC). A high degree of spatial uniformity was confirmed in low-current DC testing following these HCC procedures. The conditioned arrays will be used to refine previous measurements of the normalized transverse emittance of the emitted electron beams.